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Sample records for characteristic diffusion length

  1. Correlation of hole mobility, exciton diffusion length, and solar cell characteristics in phthalocyanine/fullerene organic solar cells

    NASA Astrophysics Data System (ADS)

    Terao, Yuhki; Sasabe, Hiroyuki; Adachi, Chihaya

    2007-03-01

    The authors investigated heterojunction organic solar cells composed of different metal phthalocyanines (MPcs, M =Fe, Co, Ni, Cu, and H2)/fullerene (C60) and compared the solar cell characteristics with the field-effect hole mobilities (?h) and exciton diffusion length (Lex) of the different MPcs. They observed that the short circuit current (JSC) is linearly dependent on the ?h of the MPcs, except for ZnPc. They also estimated the Lex of the MPcs by creating a line of best fit using the action spectra of the external quantum efficiency in the solar cells and found that JSC is closely correlated with the Lex of the MPcs.

  2. Characteristics of combustor diffusers

    NASA Astrophysics Data System (ADS)

    Klein, A.

    Combustor diffusers in aircraft engines are required to maintain stable and efficient combustion, to provide the turbine nozzles with an acceptable temperature profile as well as with sufficient cooling air and to minimise total pressure losses. Their importance is growing as compressor discharge velocities increase and combustion requirements become more challenging. In spite of the progress of computational fluid dynamics (CFD) in recent years, the development of combustor diffusers is still mainly based on experimental work. This review deals in a general fashion with flow phenomena in diffusers, explains problems the designer is confronted with and then discusses results of tests conducted on various combustor diffusers. In addition to the evidence available in the open literature, unpublished material of extensive research work carried out at MTU Motoren und Turbinen-Union München is presented and future developments are outlined. A short summary of CFD methods is included.

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

    PubMed

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

    2013-07-19

    Connecting molecular structure and exciton diffusion length in rubrene derivatives demonstrates how the diffusion length of rubrene can be enhanced through targeted functionalization aiming to enhance self-Förster energy transfer. Functionalization adds steric bulk, forcing the molecules farther apart on average, and leading to increased photoluminescence efficiency. A diffusion length enhancement greater than 50% is realized over unsubstituted rubrene. PMID:23754475

  4. 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.

  5. Characteristic lengths affecting evaporative drying of porous media.

    PubMed

    Lehmann, Peter; Assouline, Shmuel; Or, Dani

    2008-05-01

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

  6. 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.

  7. Long Minority Carrier Diffusion Lengths in Bridged Silicon Nanowires

    NASA Astrophysics Data System (ADS)

    Yu, Dong; Triplett, Mark; Yang, Yiming; Leonard, Francois; Talin, Alec; Islam, Saif

    2015-03-01

    Nanowires have large surface areas which create new challenges for their optoelectronic applications. Lithographic processes involved in device fabrication and substrate interfaces can lead to surface defects and substantially reduce charge carrier lifetimes and diffusion lengths. Here, we show that using a bridging method to suspend pristine nanowires allows for circumventing detrimental fabrication steps and interfacial effects associated with planar device architectures. We report electron diffusion lengths up to 2.7 ?m in bridged silicon nanowire devices, much longer than previously reported values for silicon nanowires with a diameter of 100 nm. Strikingly, electron diffusion lengths are reduced to only 45 nm in planar devices incorporating nanowires grown under the same conditions. The highly scalable and low-cost silicon nano-bridge devices with the demonstrated long diffusion lengths may find exciting applications in photovoltaics, image sensing and photodetectors. DMR-1310678, CMMI-1235592, DEAC01-94-AL85000.

  8. Long minority carrier diffusion lengths in bridged silicon nanowires.

    PubMed

    Triplett, M; Yang, Y; Léonard, F; Talin, A Alec; Islam, M Saif; Yu, D

    2015-01-14

    Nanowires have large surface areas that create new challenges for their optoelectronic applications. Lithographic processes involved in device fabrication and substrate interfaces can lead to surface defects and substantially reduce charge carrier lifetimes and diffusion lengths. Here, we show that using a bridging method to suspend pristine nanowires allows for circumventing detrimental fabrication steps and interfacial effects associated with planar device architectures. We report electron diffusion lengths up to 2.7 ?m in bridged silicon nanowire devices, much longer than previously reported values for silicon nanowires with a diameter of 100 nm. Strikingly, electron diffusion lengths are reduced to only 45 nm in planar devices incorporating nanowires grown under the same conditions. The highly scalable silicon nanobridge devices with the demonstrated long diffusion lengths may find exciting applications in photovoltaics, sensing, and photodetectors. PMID:25541642

  9. EBIC measurements of small diffusion length in semiconductor structures

    SciTech Connect

    Yakimov, E. B. Borisov, S. S.; Zaitsev, S. I.

    2007-04-15

    The problems arising under submicron diffusion-length measurements by EBIC are discussed. As an example, the results of diffusion-length measurements in GaN are presented. It is shown that fitting the collection efficiency dependence on beam energy is the most reliable method for this purpose. The depth-dose dependence for GaN is calculated by the Monte-Carlo method and its analytical approximation is presented. This expression was verified experimentally by simultaneous fitting of the collected current dependence on beam energy for a few applied bias values.

  10. Direct imaging of anisotropic exciton diffusion and triplet diffusion length in rubrene single crystals.

    PubMed

    Irkhin, Pavel; Biaggio, Ivan

    2011-07-01

    We visualize exciton diffusion in rubrene single crystals using localized photoexcitation and spatially resolved detection of excitonic luminescence. We show that the exciton mobility in this material is strongly anisotropic with long-range diffusion by several micrometers associated only with the direction of molecular stacking in the crystal, along the b axis. We determine a triplet exciton diffusion length of 4.0 ± 0.4 ?m from the spatial exponential decay of the photoluminescence that originates from singlet excitons formed by triplet-triplet fusion. PMID:21797572

  11. 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

  12. 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.

  13. Microrheology and characteristic lengths in wormlike micelles made of a zwitterionic surfactant and SDS in brine.

    PubMed

    Sarmiento-Gomez, Erick; Lopez-Diaz, David; Castillo, Rolando

    2010-09-30

    We study the Brownian motion of probe particles embedded in a wormlike micellar fluid made of a zwitterionic surfactant N-tetradecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (TDPS), sodium dodecyl sulfate (SDS), and salty water to get structural and dynamical information of the micellar network. The motion of the probe particles was tracked with diffusing wave spectroscopy, and the mean square displacement as a function of time for the particles was obtained. This allowed us to obtain the long-time diffusion coefficient for microspheres moving in the micellar network and the cage size where each particle is harmonically bound at short times in that network. The bulk mechanical susceptibility of the fluid determines the response of the probe particles excited by the thermal stochastic forces. As a consequence, the mean square displacement curves allowed us to calculate the elastic (storage) and the viscous (loss) moduli as a function of the frequency. From these curves, spanning a wide frequency range, we estimated the characteristic lengths as the mesh size, the entanglement length, the persistence length, and the contour length for micellar solutions of different zwitterionic surfactant concentration, surfactant ratio ([SDS]/[TDPS]), salt concentration, and temperature. Mesh size, entanglement length, and persistence length are almost insensitive to the change of these variables. In contrast, the contour length changes in an important way. The contour length becomes shorter as the temperature increases, and it presents a peak at a surfactant ratio of ?0.50-0.55. When salt is added to the solution, the contour length presents a peak at a salt concentration of ?0.225 M, and in some solutions, this length can reach values of ?12 ?m. Scission energies help us to understand why the contour length first increases and then decreases when salt is added. PMID:20825212

  14. 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.

  15. 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.

  16. 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.

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

    NASA Astrophysics Data System (ADS)

    Horn, G. L.; Ouwersloot, H. G.; Vilà-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.

  18. Isotropic soft-core potentials with two characteristic length scales and anomalous behaviour

    E-print Network

    Pol Vilaseca; Giancarlo Franzese

    2010-05-07

    Isotropic soft-core potentials with two characteristic length scales have been used since 40 years to describe systems with polymorphism. In the recent years intense research is showing that these potentials also display polyamorphism and several anomalies, including structural, diffusion and density anomaly. These anomalies occur in a hierarchy that resembles the anomalies of water. However, the absence of directional bonding in these isotropic potentials makes them different from water. Other systems, such as colloidal suspensions, protein solutions or liquid metals, can be well described by these family of potentials, opening the possibility of studying the mechanism generating the polyamorphism and anomalies in these complex liquids.

  19. Spin Diffusion Characteristics in Magnesium Nanowires Hiroshi Idzuchi1

    E-print Network

    Otani, Yoshichika

    Spin Diffusion Characteristics in Magnesium Nanowires Hiroshi Idzuchi1Ã , Yasuhiro Fukuma2 , Le diffusion characteristics of magnesium have been investigated by using lateral spin-valve structures consisting of permalloy spin injector and detector electrodes bridged by a magnesium-nanowire. Large spin

  20. 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.

  1. 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

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

    PubMed Central

    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

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  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.

    2015-02-01

    Paleoclimatic 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 (PSD) of the record of a single isotope species can be biased and is therefore not a reliable proxy for past temperature reconstruction. 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 proofs to be a good alternative for the PSD method as it yields equal or somewhat higher precision 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. Additional to application to synthetic data the two methods are tested on stable isotope records from the EPICA 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. 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.

  9. 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.

  10. 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.

  11. 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

  12. Disconnected Glass-Glass Transitions and Diffusion Anomalies in a Model with Two Repulsive Length Scales

    E-print Network

    Stanley, H. Eugene

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

  13. 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.

  14. 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.

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

    DOEpatents

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

    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.

  16. 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 program’s 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.

  17. 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 400°C. This improvement of the diffusion length is very important for application to solar cells, and Al2O3 deposited by ALD is a promising passivation material for a structure with high aspect ratio such as SiNW arrays. PMID:23968156

  18. 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 400°C. This improvement of the diffusion length is very important for application to solar cells, and Al2O3 deposited by ALD is a promising passivation material for a structure with high aspect ratio such as SiNW arrays. PMID:23968156

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

    NASA Astrophysics Data System (ADS)

    Piotrowski, T.; W?grzecki, M.; Stolarski, M.; Krajewski, T.

    2015-12-01

    One of the key parameters determining detection properties of silicon PIN detector structures (p+-?-n+ or n+-?-p+) is minority carrier diffusion length in p-n junction regions p-n (p+-? or n+-?). 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 ?m) with monochromatic radiation of two wavelengths ?1 = 500 nm (silicon penetration depth of around 0.9 ?m) and ?2 = 900 nm (silicon penetration depth of around 33 ?m). The value of diffusion length was determined by analysing the spatial distribution of optical carrier generation and values of photoelectric currents.

  20. 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.

  1. 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).

  2. Effect of fiber volume fraction and length on the wear characteristics of glass fiber-reinforced

    E-print Network

    Vaziri, Ashkan

    Effect of fiber volume fraction and length on the wear characteristics of glass fiber the fiber weight percent added to the matrix as well as fiber length. Methods. Dental specimens with glass by mixing an activated dental resin with commercial glass fibers. The specimens were then tested on a pin

  3. 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

  4. 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.

  5. 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.

  6. 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

  7. Self-Consciousness and Body Image: Length and Accuracy of Self-Reports of Physical Characteristics.

    ERIC Educational Resources Information Center

    Turner, Robert G.; Gilliland, LuNell

    The extent to which private self-consciousness (as defined by Fenigstein, Scheier, and Buss, 1975) is related to the length and accuracy of self-reports concerning physical characteristics was investigated. In the first phase of the experiment subjects (N=87) listed their physical characteristics that they liked, disliked, or toward which they…

  8. 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.

  9. Measurement of diffusion length, lifetime, and surface recombination velocity in thin semiconductor layers

    NASA Astrophysics Data System (ADS)

    Gonzalez, F. N.; Neugroschel, A.

    1984-04-01

    A small-signal admittance method is developed for the determination of two important parameters affecting the performance of several semiconductor devices with thin layers such as integrated-injection-logic and MOS transistors, OCHI-HLE, BSF and TJ solar cells. These parameters, the minority-carrier diffusion length (or the minority-carrier lifetime) and the surface recombination velocity, are found using a combination of low-frequency and high-frequency admittance measurements. The theoretical base of the method and experimental results showing its application and usefulness are presented.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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).

  4. 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.

  5. A new method of determination of minority carrier diffusion length in the base region of silicon solar cells

    SciTech Connect

    Basu, P.K.; Singh, S.N.; Arora, N.K.; Chakravarty, B.C. )

    1994-03-01

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

  6. 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.

  7. Quantitative analysis along the pyramidal tract by length-normalized parameterization based on diffusion tensor tractography

    E-print Network

    Jiang,Tianzi

    on diffusion tensor tractography: Application to patients with relapsing neuromyelitis optica Fuchun Lin,a,1 the pyramidal tract (PYT) of relapsing neuromyelitis optica (RNMO) patients without visible brain lesions-normalized parameterization; Diffusion indices; Pyramidal tract; Relapsing neuromyelitis optica Introduction Diffusion tensor

  8. 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.

  9. Lateral diffusion of molecules partitioned into silica-bound alkyl chains:? influence of chain length and bonding density.

    PubMed

    Hansen, R L; Harris, J M

    1996-09-01

    Lateral diffusion of a hydrophobic fluorescent molecule partitioned into monomeric alkyl chains bound to a planar silica substrate was measured as a function of chain density and chain length. Measurement of fluorescence recovery after patterned photobleaching was used to observe the diffusional relaxation of a concentration profile of probe molecules over distances of micrometers. The diffusion rate of the probe molecule partitioned into C-18 chains decreased with decreasing chain coverage. As the chain length was reduced from C-18 to C-8 and C-4, the rate of diffusion also decreased. These results, when combined with results from a previous study of the effect of overlaying solvent on diffusion rate (Hansen, R. L.; Harris, J. M. Anal. Chem. 1995, 67, 492-498), are consistent with a domain model for long-range transport of partitioned molecules through the bound ligands. Fluorescence recovery experiments in which diffusion is monitored over a distance of micrometers offer a unique means to probe long-range structure of surface-immobilized alkyl chains. PMID:21619357

  10. 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. ...

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  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. NOx emission characteristics of counterflow syngas diffusion flames with airstream dilution

    E-print Network

    Aggarwal, Suresh K.

    NOx emission characteristics of counterflow syngas diffusion flames with airstream dilution Daniel, biomass, organic waste, and refinery residual. Although, its composition may vary significantly. There are, however, gaps in the fundamental understanding of syngas combustion and emissions, as most

  17. 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.

  18. 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.

  19. 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.

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

    E-print Network

    the governing partial differential equations (PDEs) into an approximate inertial manifold (AIM) system, for i [1, N], (1) where Yi RN is a vector of mass fractions, jm i RN is a vector of diffusive mass manifold (AIM) [5]. To accomplish this, we assume a spectral decomposition of zi(x, t) = m=0 zi

  1. 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.

  2. 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).

  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. Photoluminescence-based measurements of the energy gap and diffusion length of Zn3P2

    E-print Network

    Kimball, Gregory

    into polycrystalline boules that were 1 cm in diameter and 4 cm in length, with grain sizes of 1­5 mm2 and hole:v Br2 in CH3OH, rinsed in CH3OH, dried under a stream of N2, and used promptly thereafter

  5. 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.

  6. 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

  7. Chemical diffusion characteristics of Al-Si alloy melts under a transverse magnetic field

    NASA Astrophysics Data System (ADS)

    Zhang, Kai; Bian, Xiufang; Li, Yumin; Liu, Yang; Yang, Chuncheng; Zhao, Xiaolin

    2015-07-01

    Effect of a transverse magnetic field on the chemical diffusion (interdiffusion) characteristics between Al-10 at.% Si metallic melts and pure Al melts has been investigated experimentally. Results show that the application of a weak transverse magnetic field has evidently decreased the diffusivity of solute atoms and retarded the interdiffusion process. This effect can be attributed to the combined suppression action of interior Hall Effect and Lorentz force on the atoms mobility.

  8. 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.

  9. 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.

  10. 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 427°C, 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.

  11. 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

  12. 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.

  13. The relationship between telomere length and clinicopathologic characteristics in colorectal cancers among Tunisian patients.

    PubMed

    Mzahma, Raja; Kharrat, Maher; Fetiriche, Fadhel; Bouasker; Ben Moussa, Mounir; Ben Safta, Zoubeir; Dziri, Chadli; Zaouche, AbdelJelil; Chaabouni-Bouhamed, Habiba

    2015-11-01

    Alterations in telomere dynamics have emerged as having a causative role in carcinogenesis. Both the telomere attrition contribute to tumor initiation via increasing chromosomal instability and that the telomere elongation induces cell immortalization and leads to tumor progression. The objectives of this study are to investigate the dynamics of telomere length in colorectal cancer (CRC) and the clinicopathological parameters implicated. We measured the relative telomere length (RTL) in cancerous tissues and in corresponding peripheral blood leukocytes (PBL) using quantitative PCR (Q-PCR) from 94 patients with CRC. Telomere length correlated significantly in cancer tissues and corresponding PBL (r?=?0.705). Overall, cancer tissue had shorter telomeres than PBL (p?=?0.033). In both cancer tissue and PBL, the RTL was significantly correlated with age groups (p?=?0.008 and p?=?0.012, respectively). The RTL in cancer tissue was significantly longer in rectal tumors (p?=?0.04) and in the late stage of tumors (p?=?0.01). In PBL, the RTL was significantly correlated with the macroscopic aspect of tumors (p?=?0.02). In addition, the telomere-length ratio of cancer to corresponding PBL increased significantly with late-stage groups. Shortening of the telomere was detected in 44.7 %, elongation in 36.2 %, and telomeres were unchanged in 19.1 % of 94 tumors. Telomere shortening occurred more frequently in the early stage of tumors (p?=?0.01). This study suggests that the telomere length in PBL is affected by the macroscopic aspect of tumors and that telomere length in cancer tissues is a marker for progression of CRC and depends on tumor-origin site. PMID:26047604

  14. 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.

  15. 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.

  16. Deformation and strain characteristics along the length of the anterior band of the inferior glenohumeral ligament.

    PubMed

    McMahon, P J; Dettling, J R; Sandusky, M D; Lee, T Q

    2001-01-01

    Efficacious surgical treatment of anterior glenohumeral instability often requires repair of the anteroinferior capsulolabral structures, including the glenoid origin of the anterior band of the inferior glenohumeral ligament. Rupture in this location, the Bankart lesion, may be accompanied by nonrecoverable stretching of the anterior band. The purpose of this study was to evaluate the amount and location of nonrecoverable stretching with tensile testing. Twelve glenoid-soft tissue-humerus complexes from fresh-frozen glenohumeral joints were studied by means of a custom jig, an Instron machine, and a video digitizing system. The joints were positioned to simulate that known to cause apprehension for anterior instability. Nonrecoverable deformation differed along the length of the anterior band but was slight in all locations. For those that failed at the glenoid insertion region, the mean nonrecoverable deformation was 0.10 +/- 0.16 mm (mean +/- SEM) at the bone-labral junction of the glenoid insertion region and 0.38 +/- 0.23 mm at the labral-ligament junction of the glenoid insertion region. It was 0.53 +/- 0.23 mm at the ligament midsubstance and 0.04 +/- 0.10 mm at the humeral insertion region. For those that failed at the glenoid insertion region, the nonrecoverable stretching was 1.4% +/- 1.9% at the bone-labral junction of the glenoid insertion region and 3.5% +/- 2.0% at the labral-ligament junction of the glenoid insertion region. It was 2.3% +/- 1.1% at the ligament midsubstance and 0.0% +/- 1.4% at the humeral insertion region. Rupture of the anterior band resulted in little nonrecoverable stretching at both the site of failure and elsewhere along the length, remote from the failure site. Surgical repairs after initial dislocation may restore the length of the anterior band of the inferior glenohumeral ligament with little shortening. PMID:11641708

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

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

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

  18. 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.

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

    NASA Astrophysics Data System (ADS)

    Gapinski, Jacek; Nägele, 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. 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.

  20. Multiscaling for Systems with a Broad Continuum of Characteristic Lengths and Times: Structural Transitions in Nanocomposites

    E-print Network

    Pankavich, Stephen

    2010-01-01

    The multiscale approach to N-body systems is generalized to address the broad continuum of long time and length scales associated with collective behaviors. A technique is developed based on the concept of an uncountable set of time variables and of order parameters (OPs) specifying major features of the system. We adopt this perspective as a natural extension of the commonly used discrete set of timescales and OPs which is practical when only a few, widely-separated scales exist. The existence of a gap in the spectrum of timescales for such a system (under quasiequilibrium conditions) is used to introduce a continuous scaling and perform a multiscale analysis of the Liouville equation. A functional-differential Smoluchowski equation is derived for the stochastic dynamics of the continuum of Fourier component order parameters. A continuum of spatially non-local Langevin equations for the OPs is also derived. The theory is demonstrated via the analysis of structural transitions in a composite material, as occu...

  1. Effects of Characteristic Length Scales on the Exciton Dynamics in Rubrene Single Crystals

    E-print Network

    Gieseking, Björn; Müller, Benjamin; Deibel, Carsten; Engels, Bernd; Dyakonov, Vladimir; Pflaum, Jens

    2013-01-01

    As for its inorganic counterparts the future developments in organic electronics are driven by an advanced device miniaturization. Therefore, the opto-electronic behavior of up-to-date devices is progressively governed by the local structural environment. However, there is a lack of organic semiconductor materials providing access to the fundamental structure-functionality relation, either due to limitations by their inherent growth or their optical characteristics. In this work we present a systematic investigation of the optical states, so-called excitons, and their temporal evolution in the prototypical organic semiconductor rubrene by means of time and temperature dependent photoluminescence studies. This material offers the unique possibility of preparing well-defined morphologies with adjustable degree of confinement. By this approach we are able to confirm the direct influence on the temperature dependent optical processes with picosecond resolution already for a spatial localization of excitation on t...

  2. Poroelastic response of articular cartilage by nanoindentation creep tests at different characteristic lengths.

    PubMed

    Taffetani, M; Gottardi, R; Gastaldi, D; Raiteri, R; Vena, P

    2014-07-01

    Nanoindentation is an experimental technique which is attracting increasing interests for the mechanical characterization of articular cartilage. In particular, time dependent mechanical responses due to fluid flow through the porous matrix can be quantitatively investigated by nanoindentation experiments at different penetration depths and/or by using different probe sizes. The aim of this paper is to provide a framework for the quantitative interpretation of the poroelastic response of articular cartilage subjected to creep nanoindentation tests. To this purpose, multiload creep tests using spherical indenters have been carried out on saturated samples of mature bovine articular cartilage achieving two main quantitative results. First, the dependence of indentation modulus in the drained state (at equilibrium) on the tip radius: a value of 500 kPa has been found using the large tip (400 ?m radius) and of 1.7 MPa using the smaller one (25 ?m). Secon, the permeability at microscopic scale was estimated at values ranging from 4.5×10(-16) m(4)/N s to 0.1×10(-16) m(4)/N s, from low to high equivalent deformation. Consistently with a poroelastic behavior, the size-dependent response of the indenter displacement disappears when characteristic size and permeability are accounted for. For comparison purposes, the same protocol was applied to intrinsically viscoelastic homogeneous samples of polydimethylsiloxane (PDMS): both indentation modulus and time response have been found size-independent. PMID:24814573

  3. 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.

  4. Critical assessment of diffusion coefficients in semidilute to concentrated solutions of polystyrene in toluene

    NASA Astrophysics Data System (ADS)

    Pollak, T.; Köhler, W.

    2009-03-01

    We have measured collective diffusion coefficients of dilute, semidilute, and concentrated solutions of polystyrene in toluene up to a polymer concentration of 0.832 mass fractions at T =25 °C. The three employed experimental techniques of photon correlation spectroscopy, thermal diffusion forced Rayleigh scattering, and optical beam deflection cover four orders of magnitude with respect to their characteristic diffusion lengths (200 nm-2.9 mm), corresponding to more than 8 decades of the diffusion time constants. Contrary to existing literature data, which suggest a length scale dependent anomalous diffusion at high concentrations, all our techniques yield identical diffusion coefficients and purely Fickian diffusion, irrespective of their characteristic length scale.

  5. 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.

  6. 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.

  7. 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 Å, 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.

  8. Pore-size dependence and characteristics of water diffusion in slit-like micropores

    E-print Network

    S. O. Diallo

    2015-04-10

    The temperature dependence of the dynamics of water inside microporous activated carbon fibers (ACF) is investigated by means of incoherent elastic and quasi- elastic 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 (\\sim 12 and 18 {\\AA}, 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 nanoporous 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 {\\theta} 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.

  9. 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.

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

    PubMed

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

    2013-01-01

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

  11. Experimental study and analytical modeling of the channel length influence on the electrical characteristics of small-molecule thin-film transistors

    NASA Astrophysics Data System (ADS)

    Boukhili, W.; Mahdouani, M.; Bourguiga, R.; Puigdollers, J.

    2015-07-01

    Bottom-contact p-type small-molecule copper phthalocyanine (CuPc) thin film transistors (TFTs) with different channel lengths have been fabricated by thermal evaporation. The influence of the channel length on the current-voltage characteristics of the fabricated transistors were investigated in the linear and saturation regimes. The devices exhibit excellent p-type operation characteristics. Results show that devices with smaller channel length (L = 2.5 ?m and 5 ?m) present the best electrical performance, in terms of drain current value, field effect mobility and subthreshold slope. Saturation field-effect mobilities of 1.7 × 10-3 cm2 V-1 s-1 and 1 × 10-3 cm2 V-1 s-1 were obtained for TFTs with channel lengths of L = 2.5 ?m and L = 5 ?m, respectively. Transmission line method was used to study the dependence of the contact resistance with the channel length. Contact resistance becomes dominant with respect to the channel resistance only in the case of short channel devices (L = 2.5 ?m and 5 ?m). It was also found that the field effect mobility is extremely dependent on the channel length dimension. Finally, an analytical model has been developed to reproduce the dependence of the transfer characteristics with the channel length and the obtained data are in good agreement with the experimental results for all fabricated devices.

  12. 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.

  13. 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??m, which accords with the simulation results.

  14. 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.

  15. 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 ?m. A transverse cross section that exhibits relatively equiaxed grains with an average grain diameter of 10 ?m. Chemical banding, in some areas more than 100 ?m 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 ?m. A visible UZr2 bearing layer with a thickness of 1-2 ?m. 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.

  16. 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.

  17. The length dependence of translational diffusion, free solution electrophoretic mobility, and electrophoretic tether force of rigid rod-like model duplex DNA.

    PubMed Central

    Allison, S; Chen, C; Stigter, D

    2001-01-01

    In this work, boundary element modeling is used to study the transport of highly charged rod-like model polyions of various length under a variety of different aqueous salt conditions. Transport properties considered include free solution electrophoretic mobility, translational diffusion, and the components of the "tether force" tensor. The model parameters are chosen to coincide with transport measurements of duplex DNA carried out under six different salt/temperature conditions. The focus of the analysis is on the length dependence of the free solution electrophoretic mobility. In a solution containing 0.04 M Tris-acetate buffer at 25 degrees C, calculated mobilities using straight rod models show a stronger dependence on fragment length than that observed experimentally. By carrying out model studies on curved rod models, it is concluded that the "leveling off" of mobility with fragment length is due, in part at least, to the finite curvature of DNA. Experimental mobilities of long duplex DNA in monovalent alkali salts are reasonably well explained once account is taken of long-range bending and the simplifying assumptions of the model studies. PMID:11606270

  18. 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.

  19. Effects of thermal annealing on deep-level defects and minority-carrier electron diffusion length in Be-doped InGaAsN

    SciTech Connect

    Xie, S.Y.; Yoon, S.F.; Wang, S.Z.

    2005-04-01

    We report the effects of ex situ thermal annealing on the deep-level defects and the minority-carrier electron diffusion length in Be-doped, p-type In{sub 0.03}Ga{sub 0.97}As{sub 0.99}N{sub 0.01} grown by solid source molecular-beam epitaxy. Deep-level transient spectroscopy measurements reveal two majority-carrier hole traps, HT1 (0.18 eV) and HT4 (0.59 eV), and two minority-carrier electron traps, ET1 (0.09 eV) and ET3 (0.41 eV), in the as-grown sample. For the sample with postgrowth thermal annealing, the overall deep-level defect-concentration is decreased. Two hole traps, HT2 (0.39 eV) and HT3 (0.41 eV), and one electron trap, ET2 (0.19 eV), are observed. We found that the minority-carrier electron diffusion length increases by {approx}30% and the leakage current of the InGaAsN/GaAs p-n junction decreases by 2-3 orders after thermal annealing. An increase of the net acceptor concentration after annealing is also observed and can be explained by a recently proposed three-center-complex model.

  20. 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

  1. 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...

  2. 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...

  3. Characteristics and barriers impacting the diffusion of e-extension among Texas Cooperative Extension County Extension agents 

    E-print Network

    Harder, Amy Marie

    2009-05-15

    Characteristics and Barriers Impacting the Diffusion of E-Extension among Texas Cooperative Extension County Extension Agents. (August 2007) Amy Marie Harder, B.S., Colorado State University; M.Agr., Colorado State University Chair of Advisory........................................................................................................... 121 APPENDIX A ......................................................................................................... 132 APPENDIX B ......................................................................................................... 138...

  4. Characteristics and variability of structural networks derived from diffusion tensor imaging

    PubMed Central

    Cheng, Hu; Wang, Yang; Sheng, Jinhua; Kronenberger, William G.; Mathews, Vincent P.; Hummer, Tom A.; Saykin, Andrew J.

    2012-01-01

    Structural brain networks were constructed based on diffusion tensor imaging (DTI) data of 59 young healthy male adults. The networks had 68 nodes, derived from FreeSurfer parcellation of the cortical surface. By means of streamline tractography, the edge weight was defined as the number of streamlines between two nodes normalized by their mean volume. Specifically, two weighting schemes were adopted by considering various biases from fiber tracking. The weighting schemes were tested for possible bias toward the physical size of the nodes. A novel thresholding method was proposed using the variance of number of streamlines in fiber tracking. The backbone networks were extracted and various network analyses were applied to investigate the features of the binary and weighted backbone networks. For weighted networks, a high correlation was observed between nodal strength and betweenness centrality. Despite similar small-worldness features, binary networks and weighted networks are distinctive in many aspects, such as modularity and nodal betweenness centrality. Inter-subject variability was examined for the weighted networks, along with the test–retest reliability from two repeated scans on 44 of the 59 subjects. The inter-/intra-subject variability of weighted networks was discussed in three levels — edge weights, local metrics, and global metrics. The variance of edge weights can be very large. Although local metrics show less variability than the edge weights, they still have considerable amounts of variability. Weighting scheme one, which scales the number of streamlines by their lengths, demonstrates stable intra-class correlation coefficients against thresholding for global efficiency, clustering coefficient and diversity. The intra-class correlation analysis suggests the current approach of constructing weighted network has a reasonably high reproducibility for most global metrics. PMID:22450298

  5. 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.

  6. 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

  7. 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

  8. 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.

  9. Moisture diffusion and permeability characteristics of hydroxypropylmethylcellulose and hard gelatin capsules.

    PubMed

    Barham, Ahmad S; Tewes, Frederic; Healy, Anne Marie

    2015-01-30

    The primary objective of this paper is to compare the sorption characteristics of hydroxypropylmethylcellulose (HPMC) and hard gelatin (HG) capsules and their ability to protect capsule contents. Moisture sorption and desorption isotherms for empty HPMC and HG capsules have been investigated using dynamic vapour sorption (DVS) at 25°C. All sorption studies were analysed using the Young-Nelson model equations which distinguishes three moisture sorption types: monolayer adsorption moisture, condensation and absorption. Water vapour diffusion coefficients (D), solubility (S) and permeability (P) parameters of the capsule shells were calculated. ANOVA was performed with the Tukey comparison test to analyse the effect of %RH and capsule type on S, P, and D parameters. The moisture uptake of HG capsules were higher than HPMC capsules at all %RH conditions studied. It was found that values of D and P across HPMC capsules were greater than for HG capsules at 0-40 %RH; whereas over the same %RH range S values were higher for HG than for HPMC capsules. S values decreased gradually as the %RH was increased up to 60% RH. To probe the effect of moisture ingress, spray dried lactose was loaded into capsules. Phase evolution was characterised by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), and differential scanning calorimetry (DSC). The capsules under investigation are not capable of protecting spray dried lactose from induced solid state changes as a result of moisture uptake. For somewhat less moisture sensitive formulations, HPMC would appear to be a better choice than HG in terms of protection of moisture induced deterioration. PMID:25526672

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

    PubMed Central

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

    2013-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

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

  12. 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.

  13. 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

  14. 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 subject’s 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

  15. 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

  16. 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.; Gružinskis, 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.

  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. Diffusion length and junction spectroscopy analysis of low-temperature annealing of electron irradiation-induced deep levels in 4H-SiC

    SciTech Connect

    Castaldini, A.; Cavallini, A.; Rigutti, L.; Pizzini, S.; Le Donne, A.; Binetti, S.

    2006-02-01

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

  19. 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/µm 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/µm 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 µA/µm. These results suggest the possibility that the CAAC-IGZO transistor can be applied to an LSI in a deep submicron region.

  20. Microstructural White Matter Tissue Characteristics Are Modulated by Homocysteine: A Diffusion Tensor Imaging Study

    PubMed Central

    Hsu, Jung-Lung; Chen, Wei-Hung; Bai, Chyi-Huey; Leu, Jyu-Gang; Hsu, Chien-Yeh; Viergever, Max A.; Leemans, Alexander

    2015-01-01

    Homocysteine level can lead to adverse effects on the brain white matter through endothelial dysfunction, microstructural inflammation, and neurotoxin effects. Despite previously observed associations between elevated homocysteine and macroscopic structural brain changes, it is still unknown whether microstructural associations of homocysteine on brain tissue properties can be observed in healthy subjects with routine MRI. To this end, we investigated potential relationships between homocysteine levels and microstructural measures computed with diffusion tensor imaging (DTI) in a cohort of 338 healthy participants. Significant positive correlations were observed between homocysteine levels and diffusivity measures in the bilateral temporal WM, the brainstem, and the bilateral cerebellar peduncle. This is the first study demonstrating that DTI is sufficiently sensitive to relate microstructural WM properties to homocysteine levels in healthy subjects. PMID:25693199

  1. Microstructural white matter tissue characteristics are modulated by homocysteine: a diffusion tensor imaging study.

    PubMed

    Hsu, Jung-Lung; Chen, Wei-Hung; Bai, Chyi-Huey; Leu, Jyu-Gang; Hsu, Chien-Yeh; Viergever, Max A; Leemans, Alexander

    2015-01-01

    Homocysteine level can lead to adverse effects on the brain white matter through endothelial dysfunction, microstructural inflammation, and neurotoxin effects. Despite previously observed associations between elevated homocysteine and macroscopic structural brain changes, it is still unknown whether microstructural associations of homocysteine on brain tissue properties can be observed in healthy subjects with routine MRI. To this end, we investigated potential relationships between homocysteine levels and microstructural measures computed with diffusion tensor imaging (DTI) in a cohort of 338 healthy participants. Significant positive correlations were observed between homocysteine levels and diffusivity measures in the bilateral temporal WM, the brainstem, and the bilateral cerebellar peduncle. This is the first study demonstrating that DTI is sufficiently sensitive to relate microstructural WM properties to homocysteine levels in healthy subjects. PMID:25693199

  2. 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

  3. 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 ?m ridge stripe and a 1000 ?m 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.

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

    PubMed Central

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

    2013-01-01

    Diffusion-tensor imaging can be used to observe the microstructure of brain tissue. Fractional sotropy reflects the integrity of white matter fibers. Fractional anisotropy of a young adult brain is low in gray matter, high in white matter, and highest in the splenium of the corpus callosum. Thus, we selected the anterior and posterior limbs of the internal capsule, head of the caudate nucleus, semioval center, thalamus, and corpus callosum (splenium and genu) as regions of interest when using diffusion-tensor imaging to observe fractional anisotropy of major white matter fiber tracts and the deep gray matter of healthy rhesus monkeys aged 4–8 years. Results showed no laterality ferences in fractional anisotropy values. Fractional anisotropy values were low in the head of date nucleus and thalamus in gray matter. Fractional anisotropy values were highest in the splenium of corpus callosum in the white matter, followed by genu of the corpus callosum and the posterior limb of the internal capsule. Fractional anisotropy values were lowest in the semioval center and posterior limb of internal capsule. These results suggest that fractional anisotropy values in major white matter fibers and the deep gray matter of 4–8-year-old rhesus monkeys are similar to those of healthy young people. PMID:25206616

  5. Interface characteristics in diffusion bonding of Fe3Al with Cr18-Ni8 stainless steel.

    PubMed

    Wang, Juan; Li, Yajiang; Yin, Yansheng

    2005-05-01

    Fe3Al and Cr18-Ni8 stainless steel were diffusion-bonded in vacuum and a Fe3Al/Cr18-Ni8 interface with reaction layer was formed. Microstructure in the reaction layer at Fe3Al/Cr18-Ni8 interface was analyzed by means of scanning electron microscope (SEM) and electron probe micro-analyzer (EPMA). The growth of reaction layer with heating temperature (T) and holding time (t) was researched. The results indicate that FeAl, Fe3Al, Ni3Al, and alpha-Fe (Al) solid solution are formed in the reaction layer. These phases are favorable to promote the element diffusion and to accelerate the formation of the reaction layer at Fe3Al/Cr18-Ni8 interface. The growth of reaction layer obeys the parabolic law and its thickness (X) is expressed by X2 = 7.5 x 10(-4)exp(-83.59/RT)(t - t0). PMID:15797414

  6. 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.

  7. 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.

  8. 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.

  9. 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

  10. 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.

  11. Diffusion MRI of complex tissue structure

    E-print Network

    Tuch, David Solomon, 1973-

    2002-01-01

    Magnetic resonance diffusion imaging provides an exquisitely sensitive probe of tissue microstructure. Owing to the microscopic length scale of diffusion in biological tissues, diffusion imaging can reveal histological ...

  12. 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

  13. 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.

  14. 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.

  15. 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

  16. 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.

  17. 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 ...

  18. 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

  19. Intravoxel Incoherent Motion MR Imaging: Comparison of Diffusion and Perfusion Characteristics for Differential Diagnosis of Soft Tissue Tumors

    PubMed Central

    Du, Jun; Li, Kun; Zhang, Weisheng; Wang, Shaowu; Song, Qingwei; Liu, Ailian; Miao, Yanwei; Lang, Zhijin; Zhang, Lina; Zheng, Minting

    2015-01-01

    Abstract We used intravoxel incoherent motion (IVIM) magnetic resonance imaging (MRI) to explore the possibility of preoperative diagnosis of soft tissue tumors (STTs). This prospective study enrolled 23 patients. Conventional MRI and IVIM examinations were performed on a 3.0T MR imager. Eight (35%) hemangiomas, 11 (47%) benign soft tissue tumors excluding hemangiomas (BSTTEHs) and 4 soft tissue sarcomas (STSs) were assessed. The mean tumor size was about 1652.36?±?233.66?mm2. Ten b values (0–800?s/mm2) were used to evaluate diffusion and perfusion characteristics of IVIM. IVIM parameters (ADCstandard, ADCslow, ADCfast, and f) of STTs were measured and evaluated for differentiating hemangiomas, BSTTEHs, and STSs. ADCslow and ADCfast value were different for hemangiomas, BSTTEHs, and STSs separately (P?

  20. 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.

  1. 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.

  2. 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...

  3. 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.

  4. 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

  5. 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 4.2–356 mg/dl, while the p(HEMA-co-AM) sensors had a higher sensitivity [14.9%/(mg/dl)] and a narrower analytical range (17.6–70.5 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

  6. 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.

  7. 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.

  8. 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.

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

    PubMed

    Küker, Wilhelm; Weise, Jens; Krapf, Hilmar; Schmidt, Friederike; Friese, Sigrid; Bähr, 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

  10. 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.

  11. 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.

  12. 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

  13. 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

  14. Diffusion Geometry Diffusion Geometry

    E-print Network

    Hirn, Matthew

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

  15. 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.

  16. 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 ? 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.

  17. 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

  18. 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.

  19. Clinical characteristics and outcomes in diffuse large B cell lymphoma patients aged 70 years and older: a single-center experience with a literature review

    PubMed Central

    Jung, Yun Hwa; Woo, In Sook; Han, Chi Wha

    2015-01-01

    Background/Aims: Among diffuse large B cell lymphoma (DLBCL) patients, determining the appropriate dose and chemotherapy schedule to balance toxicity and efficacy is harder in elderly than in younger patients. Moreover, there are no currently available clinical factors that consistently identify patients who are unfit to receive chemotherapy. Therefore, the clinical characteristics and outcomes of elderly patients with DLBCL and the causes of treatment-related death were investigated in this study. Methods: The clinical characteristics and outcomes of 44 elderly (? 70 years of age) patients diagnosed with DLBCL between January 2005 and June 2013 were evaluated. Variable clinical data along with the response rate, overall survival (OS), and causes of treatment-related death or treatment interruption were investigated. Results: The median OS was 18.6 months, and 19 patients completed curative treatment. The mean average relative dose intensity of adriamycin in patients who completed chemotherapy was 0.617, and of these patients, 16 achieved complete remission. Chemotherapy incompletion, infectious complications, ex tranoda l involvement, high lactate dehydrogenase, poor performance status, and low albumin level at diagnosis were related to a shorter OS. However, multivariate analysis revealed that only infections and chemotherapy incompletion were significantly related to poor prognosis. The most common cause of treatment-related death was infection, and patients who had experienced infectious complications tended to have lower albumin levels than those of patients without such complications. Conclusions: In the treatment of elderly lymphoma patients, the dose intensity of adriamycin is not as important as it is in young patients. However, in elderly patients, infections are particularly dangerous, especially in patients with low albumin levels. PMID:26354063

  20. 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.

  1. 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

  2. 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.

  3. 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.

  4. Lateral diffusion in an archipelago. Dependence on tracer size.

    PubMed Central

    Saxton, M J

    1993-01-01

    In a pure fluid-phase lipid, the dependence of the lateral diffusion coefficient on the size of the diffusing particle may be obtained from the Saffman-Delbrück equation or the free-volume model. When diffusion is obstructed by immobile proteins or domains of gel-phase lipids, the obstacles yield an additional contribution to the size dependence. Here this contribution is examined using Monte Carlo calculations. For random point and hexagonal obstacles, the diffusion coefficient depends strongly on the size of the diffusing particle, but for fractal obstacles--cluster-cluster aggregates and multicenter diffusion-limited aggregates--the diffusion coefficient is independent of the size of the diffusing particle. The reason is that fractals have no characteristic length scale, so a tracer sees on average the same obstructions, regardless of its size. The fractal geometry of the excluded area for tracers of various sizes is examined. Percolation thresholds are evaluated for a variety of obstacles to determine how the threshold depends on tracer size and to compare the thresholds for compact and extended obstacles. Images FIGURE 3 PMID:8494970

  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. Invariant lengths using existing Special Relativity

    E-print Network

    Christopher D. Burton

    2009-12-14

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

  7. Skin characteristics in newborns

    MedlinePLUS

    Newborn skin characteristics; Infant skin characteristics ... the first few weeks of the baby's life. Newborn skin will vary, depending on the length of the pregnancy. Premature infants have thin, transparent skin. The skin of a ...

  8. 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…

  9. 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.

  10. 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

  11. 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.

  12. 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

  13. An investigation on parallel, divergent and convergent acetylene dual jet diffusion flames

    SciTech Connect

    Abdalla, V.R.; Carvalho, J.A. Jr.; Ferreira, M.A.

    1999-11-01

    Turbulent jet diffusion flames are quite common in industrial applications. Because of the large flow rates involved, usually the fuel gas is discharged through multiple burners and the mutual interaction between the jets determines flame shape, length, and general characteristics. Results are presented and discussed of an experimental investigation on acetylene turbulent dual jet diffusion flames. The study includes parameters of flames in parallel, divergent and convergent configurations. Tests with two parallel jets with addition of helium in the fuel stream were also performed and analyzed. The variation of overall flame length and of other flame physical characteristics, such as width, volume and conditions for lifting, are presented as functions of burner tip Reynolds number, jet distance from each other and inclination angle. The effects of diluent concentration in the fuel gas stream are presented for single and two parallel jets.

  14. 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

  15. Characteristics of signals originating near the lithium-diffused N+ contact of high purity germanium p-type point contact detectors

    NASA Astrophysics Data System (ADS)

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

    2013-02-01

    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.

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

    E-print Network

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

    2012-07-28

    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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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)

  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. 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.

  4. 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.

  5. Quantum diffusion

    E-print Network

    Roumen Tsekov

    2011-04-20

    Quantum diffusion is studied via dissipative Madelung hydrodynamics. Initially the wave packet spreads ballistically, than passes for an instant through normal diffusion and later tends asymptotically to a sub-diffusive law. It is shown that the apparent quantum diffusion coefficient is not a universal physical parameter since it depends on the initial wave packet preparation. The overdamped quantum diffusion of an electron in the field of a periodic potential is also investigated; in this case the wave packet spreads logarithmically in time. Thermo-quantum diffusion of heavier particles as hydrogen, deuterium and tritium atoms in periodic potentials is studied and a simple estimate of the tunneling effect is obtained in the frames 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.

  6. 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.

  7. 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.

  8. The characteristics of atmospheric ice nuclei measured at the top of Huangshan (the Yellow Mountains) in Southeast China using a newly built static vacuum water vapor diffusion chamber

    NASA Astrophysics Data System (ADS)

    Jiang, Hui; Yin, Yan; Su, Hang; Shan, Yunpeng; Gao, Renjie

    2015-02-01

    A newly built static vacuum water vapor diffusion chamber was built to measure the concentration of ice nuclei (INs) at the top of Huangshan (the Yellow Mountains) in Southeast China. The experiments were conducted under temperatures between - 15 °C and - 23 °C and supersaturations with respect to ice between 4% and 25%. The results show that the average IN concentration was in the range of 0.27 to 7.02 L- 1, when the temperature was varied from - 15 °C to - 23 °C. The changes in IN concentrations with time were correlated with the change of number concentration of the aerosol particles of 0.5-20 ?m in diameter. The square correlation coefficients (R2) between IN and coarse aerosol particles (0.5-20 ?m in diameter) were all higher than 0.60, much higher than that (0.10) between IN and smaller particles (0.01-0.5 ?m). The concentration of ice nuclei at 14:00 LST was significantly higher than that at 08:00 LST, which is correlated with the diurnal variation of the concentration of aerosol particles. A parametric equation was developed based on measurements to represent the variations of IN concentration with temperature and supersaturation.

  9. 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.

  10. Sampling by Length.

    ERIC Educational Resources Information Center

    Handley, John C.

    1991-01-01

    Discussion of sampling methods used in information science research focuses on Fussler's method for sampling catalog cards and on sampling by length. Highlights include simple random sampling, sampling with probability equal to size without replacement, sampling with replacement, and examples of estimating the number of books on shelves in certain…

  11. 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

  12. 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.

  13. Tailoring diffusion in analog spacetimes.

    PubMed

    Smerlak, Matteo

    2012-04-01

    Diffusive transport is characterized by the scaling law (length)^{2}?(time). In this paper we show that this relationship is significantly altered in curved analog spacetimes. This circumstance provides an opportunity to tailor diffusion: by a suitable design of the analog metric, it is possible to create materials where diffusion is either faster or slower than in normal media, as desired. This prediction can, in principle, be tested experimentally with optical analogs, curved graphene sheets, and so on (indeed with any analog spacetime). PMID:22680445

  14. 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.

  15. 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 ?eff. The accuracy of these results is comparable to those obtained with other methods of optical property recovery.

  16. 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

  17. Precision structural diagnostics of layered superconductor/ferromagnet nanosystems V/Fe by reflectometry and diffuse scattering of synchrotron radiation

    SciTech Connect

    Nikitin, A. M.; Borisov, M. M.; Mukhamedzhanov, E. Kh.; Kovalchuk, M. V.; Sajti, S.; Tancziko, F.; Deak, L.; Bottyan, L.; Khaydukov, Yu. N.; Aksenov, V. L.

    2011-09-15

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

  18. 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 Peyronie’s 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 (Spearman’s 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

  19. Adaptive smoothing lengths in SPH

    NASA Astrophysics Data System (ADS)

    Attwood, R. E.; Goodwin, S. P.; Whitworth, A. P.

    2007-03-01

    Context: There is a need to improve the fidelity of SPH simulations of self-gravitating gas dynamics. Aims: We remind users of SPH that, if smoothing lengths are adjusted so as to keep the number of neighbours, N, in the range NNEIB±?NNEIB, the tolerance, ?NNEIB, should be set to zero, as first noted by Nelson & Papaloizou. We point out that this is a very straightforward and computationally inexpensive constraint to implement. Methods: We demonstrate this by simulating acoustic oscillations of a self-gravitating isentropic monatomic gas-sphere (cf. Lucy), using NTOT˜6000 particles and NNEIB=50. Results: We show that there is a marked reduction in the rates of numerical dissipation and diffusion as ?NNEIB is reduced from 10 to zero. Moreover this reduction incurs a very small computational overhead. Conclusions: .We propose that this should become a standard test for codes used in simulating star formation. It is a highly relevant test, because pressure waves generated by the switch from approximate isothermality to approximate adiabaticity play a critical role in the fragmentation of collapsing prestellar cores. Since many SPH simulations in the literature use NNEIB=50 and ?NNEIB?10, their results must be viewed with caution.

  20. Anomalous stress diffusion in earthquake triggering: Correlation length, time

    E-print Network

    . This is consistent with a clock advance on the failure time based on the constitutive rules for subcritical crack with the passage of seismic waves and in static elastic stress, with a spatial distribution whose amplitude decays aftershocks in the immediate vicinity of the main shock (i.e., at a distance of around one source dimension

  1. Fokker-Planck . . . Diffusion . . .

    E-print Network

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

  2. 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

  3. 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.

  4. Public good diffusion limits microbial mutualism.

    PubMed

    Menon, Rajita; Korolev, Kirill S

    2015-04-24

    Standard game theory cannot describe microbial interactions mediated by diffusible molecules. Nevertheless, we show that one can still model microbial dynamics using game theory with parameters renormalized by diffusion. Contrary to expectations, greater sharing of metabolites reduces the strength of cooperation and leads to species extinction via a nonequilibrium phase transition. We report analytic results for the critical diffusivity and the length scale of species intermixing. Species producing slower public good is favored by selection when fitness saturates with nutrient concentration. PMID:25955075

  5. Public Good Diffusion Limits Microbial Mutualism

    NASA Astrophysics Data System (ADS)

    Menon, Rajita; Korolev, Kirill S.

    2015-04-01

    Standard game theory cannot describe microbial interactions mediated by diffusible molecules. Nevertheless, we show that one can still model microbial dynamics using game theory with parameters renormalized by diffusion. Contrary to expectations, greater sharing of metabolites reduces the strength of cooperation and leads to species extinction via a nonequilibrium phase transition. We report analytic results for the critical diffusivity and the length scale of species intermixing. Species producing slower public good is favored by selection when fitness saturates with nutrient concentration.

  6. Parameterization of the eddy diffusivity in a dispersion model over homogeneous terrain in the atmospheric boundary layer

    NASA Astrophysics Data System (ADS)

    Kumar, Pramod; Sharan, Maithili

    2012-03-01

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

  7. Primary length standard adjustment

    NASA Astrophysics Data System (ADS)

    Šev?ík, Robert; Guttenová, Jana

    2007-04-01

    This paper deals with problems and techniques connected with primary length standard adjusting, which includes disassembling of the device and by use of the secondary laser with collimated beam and diffraction laws successively reassembling of the laser. In the reassembling process the device was enhanced with substituting the thermal grease cooling of cold finger by copper socket cooler. This improved external cooling system enables more effective cooling of molecular iodine in the cell, which allows better pressure stability of iodine vapor and easier readjustment of the system.

  8. Influence of phase space localization on the energy diffusion in a quantum chaotic billiard

    E-print Network

    D. A. Wisniacki; E. Vergini

    1998-11-10

    The quantum dynamics of a chaotic billiard with moving boundary is considered in this work. We found a shape parameter Hamiltonian expansion which enables us to obtain the spectrum of the deformed billiard for deformations so large as the characteristic wave length. Then, for a specified time dependent shape variation, the quantum dynamics of a particle inside the billiard is integrated directly. In particular, the dispersion of the energy is studied in the Bunimovich stadium billiard with oscillating boundary. The results showed that the distribution of energy spreads diffusively for the first oscillations of the boundary (${ =2 D t$). We studied the diffusion contant $D$ as a function of the boundary velocity and found differences with theoretical predictions based on random matrix theory. By extracting highly phase space localized structures from the spectrum, previous differences were reduced significantly. This fact provides the first numerical evidence of the influence of phase space localization on the quantum diffusion of a chaotic system.

  9. 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.

  10. Molecular characteristics of diffuse large B-cell lymphoma in human immunodeficiency virus-infected and -uninfected patients in the pre-highly active antiretroviral therapy and pre-rituximab era.

    PubMed

    Morton, Lindsay M; Kim, Clara J; Weiss, Lawrence M; Bhatia, Kishor; Cockburn, Myles; Hawes, Debra; Wang, Sophia S; Chang, Cindy; Altekruse, Sean F; Engels, Eric A; Cozen, Wendy

    2014-03-01

    Human immunodeficiency virus (HIV) infection substantially elevates diffuse large B-cell lymphoma (DLBCL) risk, but its impact on the distinct DLBCL subtypes defined by cell of origin is unclear. We compared DLBCL molecular characteristics and prognosis in 51 HIV-infected and 116 HIV-uninfected cases diagnosed during 1977-2003. Using immunohistochemistry to classify cell of origin based on the Tally algorithm, activated B-cell (ABC)-DLBCL was substantially more common in HIV-infected (83%) than in HIV-uninfected (54%) cases (p < 0.001). Epstein-Barr virus (EBV) was detected in 63% of DLBCLs in HIV-infected cases, occurring almost exclusively in ABC-DLBCL (74% vs. 13% of germinal center B-cell [GCB]-DLBCL, p = 0.002), but was rarely detected in DLBCLs among HIV-uninfected cases (3%). Among HIV-uninfected cases, MYC/IgH [t(8;14)(q24;q32)] and IgH/BCL2 [t(14;18)(q32;q21)] translocations were significantly more common and BCL6/IgH [t(3;14)(q27;q32)] significantly less common in GCB-DLBCL than in ABC-DLBCL (p = 0.010, < 0.001 and = 0.039, respectively). Among HIV-infected cases, translocations other than MYC/IgH [t(8;14)(q24;q32)] (21%) were rare (? 6%) and unrelated to cell of origin. ABC-DLBCL was associated with adverse overall survival compared with GCB-DLBCL regardless of HIV status (pHIV-infected = 0.066; pHIV-uninfected = 0.038). Our data demonstrate key differences in the molecular characteristics, cell of origin and prognosis of DLBCL by HIV status in the pre-highly active antiretroviral therapy (HAART) and pre-rituximab era, supporting biologic differences in lymphomagenesis in the presence of HIV. PMID:23772639

  11. Scaling Behavior and Equilibrium Lengths of Knotted Polymers

    E-print Network

    California at Santa Barbara, University of

    Scaling Behavior and Equilibrium Lengths of Knotted Polymers Eric Rawdon Akos Dobay John C. Kern numerical simulations to investigate how the chain length and topology of freely fluctuating knotted polymer of a characteristic changes with the chain size and how this change depends on the topology of the modeled polymers

  12. 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!

  13. 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

  14. 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

  15. 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

  16. Lateral diffusion in an archipelago. Distance dependence of the diffusion coefficient.

    PubMed Central

    Saxton, M J

    1989-01-01

    An understanding of the distance dependence of the lateral diffusion coefficient is useful in comparing the results of diffusion measurements made over different length scales, and in analyzing the kinetics of mobile redox carriers in organelles. A distance-dependent, concentration-dependent diffusion coefficient is defined, and it is evaluated by Monte Carlo calculations of a random walk by mobile point tracers in the presence of immobile obstacles on a triangular lattice, representing the diffusion of a lipid or a small protein in the presence of immobile membrane proteins. This work confirms and extends the milling crowd model of Eisinger, J., J. Flores, and W. P. Petersen (1986. Biophys J. 49:987-1001). Similar calculations for diffusion of mobile particles interacting by a hard-core repulsion yield the distance dependence of the self-diffusion coefficient. An expression for the range of short-range diffusion is obtained, and the distance scales for various diffusion measurements are summarized. PMID:2790141

  17. 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.

  18. Black-hole entropy and minimal diffusion

    E-print Network

    Michele Arzano; Gianluca Calcagni

    2013-10-11

    The density of states reproducing the Bekenstein-Hawking entropy-area scaling can be modeled via a nonlocal field theory. We define a diffusion process based on the kinematics of this theory and find a spectral dimension whose flow exhibits surprising properties. While it asymptotes four from above in the infrared, in the ultraviolet the spectral dimension diverges at a finite (Planckian) value of the diffusion length, signaling a breakdown of the notion of diffusion on a continuum spacetime below that scale. We comment on the implications of this minimal diffusion scale for the entropy bound in a holographic and field-theoretic context.

  19. 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.

  20. Riemann equation for prime number diffusion

    NASA Astrophysics Data System (ADS)

    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.

  1. Critical Waves and the Length Problem of Biology

    E-print Network

    Laughlin, R 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 reaction-diffusion with a small number substances. Min oscillations in E. coli are cited as precedent resonant length measurement using chemical potential waves analogous to laser detection. Mitotic structures in eucaryotes 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. PNAS Significance Statement: This paper invokes physical principles to address the question of how living things might use reaction-diffusion to measure out and regulate the many thou...

  2. Coaxial atomizer liquid intact lengths

    NASA Technical Reports Server (NTRS)

    Eroglu, Hasan; Chigier, Norman; Farago, Zoltan

    1991-01-01

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

  3. 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.

  4. 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)

  5. 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…

  6. Nonlinear Diffusion. Porous Medium and Fast Diffusion.

    E-print Network

    Moroz, Vitaly

    Nonlinear Diffusion. Porous Medium and Fast Diffusion. From Analysis to Physics and Geometry Juan Swansea, July 2008 Juan L. V´azquez - Nonlinear Diffusion. Porous Medium and Fast Diffusion Equations ­ p. 1/?? #12;Introduction Main topic after 1981: Nonlinear Diffusion Juan L. V´azquez - Nonlinear

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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)

  12. Dispersion length scales within the urban canopy

    NASA Astrophysics Data System (ADS)

    Huq, Pablo; Franzese, Pasquale

    2011-11-01

    We discuss the results of lab experiments on three model urban canopies with small, medium and large building aspect ratios to examine the physics of dispersion within the urban canopy from a near-ground continuous point source of passive scalar. The model urban canopies had aspect ratios of building height to width (H/w) = 0.25, 1, 3. Measurements were taken of the turbulent velocity and scalar fields. Plume spreads, concentrations and distance from the source were non-dimensionalized using urban canopy length, time and velocity scales based on the geometry of the buildings. The scaling collapses the data for all three aspect ratios. A model to describe the results is developed. The model is based on a simple Gaussian formulation where the diffusion coefficients are determined by the theories of Taylor (1921) in the horizontal plane, and Hunt and Weber (1979) to account for the vertically inhomogeneous turbulence. NSF Grant AGS 0849190 and 0849191.

  13. 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 ~?m length scales, expect for polymer transport within nanoporous carbons where additional chemical resolution improves the resolvable heterogeneous length scale to hundreds of nm.

  14. SLOW DIFFUSIVE GRAVITATIONAL INSTABILITY BEFORE DECOUPLING

    SciTech Connect

    Thompson, Todd A.

    2010-02-01

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

  15. 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.

  16. The word-length effect in reading: a review.

    PubMed

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

    2014-01-01

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

  17. Hydrogeomorphology and river impoundment affect food-chain length of diverse Neotropical food webs

    E-print Network

    Hoeinghaus, David J.

    Hydrogeomorphology and river impoundment affect food-chain length of diverse Neotropical food webs-900 Parana´, Brasil. Food-chain length is a central characteristic of ecological communities that affects community structure and ecosystem function. What determines the length of food chains is not well resolved

  18. Diffusion bonding

    NASA Astrophysics Data System (ADS)

    Brown, L. E.

    1993-03-01

    A temperature between 400 and 500 and a pressure between 40 MPa and 160 MPa were indicated by a two-factor, three-level factorial experiment for diffusion bonding of molybdenum sheet substrates. These substrates were sputter ion plated with palladium (0.5 microns) and silver (10 microns) films on the mating surfaces, with the silver used as a bonding interlayer. The palladium acted as an adhesive layer between the silver film and molybdenum substrate. The silver diffusion bonds that resulted were qualitatively characterized at the interfacial regions, and bonds with no visible interface were obtained at 7500X magnification. Correlations were obtained for voids found optically at the silver/silver bonding interface and colored image maps, illustrating bond quality, produced by nondestructive ultrasonic imaging. Above 160 MPa, the bonding process produces samples with a nonuniform load distribution. These samples contained regions with gaps and well-bonded regions at the silver/silver interface, and all had macroscopic deformation of the silver films.

  19. 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.

  20. Strain-Rate-Free Diffusion Flames: Initiation, Properties, and Quenching

    NASA Technical Reports Server (NTRS)

    Fendell, Francis; Rungaldier, Harald; Gokoglu, Suleyman; Schultz, Donald

    1997-01-01

    For about a half century, the stabilization of a steady planar deflagration on a heat-sink-type flat-flame burner has been of extraordinary service for the theoretical modeling and diagnostic probing of combusting gaseous mixtures. However, most engineering devices and most unwanted fire involve the burning of initially unmixed reactants. The most vigorous burning of initially separated gaseous fuel and oxidizer is the diffusion flame. In this useful idealization (limiting case), the reactants are converted to product at a mathematically thin interface, so no interpenetration of fuel and oxidizer occurs. This limit is of practical importance because it often characterizes the condition of optimal performance (and sometimes environmentally objectionable operation) of a combustor. A steady planar diffusion flame is most closely approached in the laboratory in the counterflow apparatus. The utility of this simple-strain-rate flow for the modeling and probing of diffusion flames was noted by Pandya and Weinberg 35 years ago, though only in the last decade or so has its use become internationally common place. However, typically, as the strain rate a is reduced below about 20 cm(exp -1), and the diffusion-flame limit (reaction rate much faster than the flow rate) is approached, the burning is observed to become unstable in earth gravity. The advantageous steady planar flow is not available in the diffusion-flame limit in earth gravity. This is unfortunate because the typical spatial scale in a counterflow is (k/a)(sup 1/2), where k denotes a characteristic diffusion coefficient; thus, the length scale becomes large, and the reacting flow is particularly amenable to diagnostic probing, as the diffusion-flame limit is approached. The disruption of planar symmetry is owing the fact that, as the strain rate a decreases, the residence time (l/a) of the throughput in the counterflow burner increases. Observationally, when the residence time exceeds about 50 msec, the inevitably present convective (Rayleigh-Benard) instabilities, associated with hot-under-cold (flame-under-fresh-reactant) stratification of fluid in a gravitational field, have time to grow to finite amplitude during transit of the burner.

  1. 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 ?-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.

  2. Experimental Evaluation of Rocket Exhaust Diffusers for Altitude Simulation

    NASA Technical Reports Server (NTRS)

    Sivo, Joseph N.; Meyer, Carl L.; Peters, Daniel J.

    1960-01-01

    An experimental investigation of exhaust diffusers has been conducted to evaluate various methods of minimizing the overall pressure ratio (from chamber to ambient pressure) required to establish and maintain full expansion of the nozzle flow (altitude simulation). Exhaust-diffuser configurations investigated were (1) cylindrical diffusers, (2) diffusers with contraction, and (3) diffusers including a right-angle turn. Cylindrical diffusers were evaluated with primary nozzles of various area ratios and types, as well as two clustered configurations; the other diffusers were evaluated with individual nozzles of constant area ratio and varied type. Air was the working fluid, except for two check points obtained with JP-4 fuel and liquid-oxygen rocket engines and cylindrical diffusers. The minimum length-diameter ratio of cylindrical diffusers was about 6 for minimum pressure-ratio requirements. With cylindrical diffusers of adequate length, the pressure-ratio requirements were primarily a function of the ratio of diffuser to nozzle-throat areas and were essentially independent of primary-nozzle type (including two clustered configurations) or area ratio. The two check points obtained with rocket engines indicated the pressure-ratio requirements at given ratios of diffuser to nozzle-throat areas were lowered, as compared with the requirements with air, as a result of the reduced ratio of specific heats. The minimum length-diameter ratio of the contraction throat of convergent-divergent diffusers was also about 6 for minimum pressure-ratio requirements. With adequate contraction-throat length, the pressure-ratio requirements of such diffusers were appreciably below those of comparable cylindrical diffusers when used with conical and cutoff-isentropic nozzles, but not when used with a bell nozzle. Minimum pressure-ratio requirements of a diffuser including a simple long-radius right-angle turn at maximum diffuser area, obtained with the center of radius of the turn a minimum of 2 diffuser diameters downstream of the nozzle exit, were not appreciably above those of a comparable optimum cylindrical diffuser. A diffuser including a long-radius right-angle turn at a contraction minimum area had somewhat lower pressure-ratio requirements than the aforementioned simple turn.

  3. 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.

  4. NONLINEAR DIFFUSION Erkut Erdem

    E-print Network

    Erdem, Erkut

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

  5. LINEAR DIFFUSION Erkut Erdem

    E-print Network

    Erdem, Erkut

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

  6. 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

  7. 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 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

  8. 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.

  9. 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.

  10. 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.

  11. 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…

  12. Screening length in plasma winds

    E-print Network

    Elena Caceres; Makoto Natsuume; Takashi Okamura

    2007-06-04

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

  13. 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.

  14. 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

  15. 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.

  16. Human Factor Analysis of Long Cane Design: Weight and Length

    ERIC Educational Resources Information Center

    Rodgers, Mark D.; Emerson, Robert Wall

    2005-01-01

    In a series of experiments, canes of different lengths, weights, and weight distributions were assessed to determine the effect of these characteristics on various performance measures. The results indicate that the overall weight of a cane and the distribution of weight along a cane's shaft do not affect a person's performance, but accuracy does…

  17. Relativistic Ramsauer-Townsend effect in minimal length framework

    NASA Astrophysics Data System (ADS)

    Jahankohan, K.; Hassanabadi, H.; Zarrinkamar, S.

    2015-09-01

    We consider the Ramsauer-Townsend effect in the presence of a generalized uncertainty principle (GUP) and within the Dirac equation framework for potential well, step potential and infinite well. The system characteristics are obtained in an exact analytical manner and the effect of minimal length parameter on the spectrum of the system is well-illustrated.

  18. Scaling Behavior and Equilibrium Lengths of Knotted Polymers Eric Rawdon,

    E-print Network

    Bigelow, Stephen

    Scaling Behavior and Equilibrium Lengths of Knotted Polymers Eric Rawdon, Akos Dobay, John C. Kern fluctuating knotted polymer rings affect their various spatial characteristics such as the radius of the smallest sphere enclosing momentary configurations of simulated polymer chains. We describe how the average

  19. Moving contact line dynamics: from diffuse to sharp interfaces

    E-print Network

    Halim Kusumaatmaja; Ewan J. Hemingway; Suzanne M. Fielding

    2015-11-20

    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.

  20. 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.

  1. 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.

  2. 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.

  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. Nanoparticle Diffusion in Polymer Nanocomposites

    SciTech Connect

    Kalathi, Jagannathan; Yamamoto, Umi; Schweizer, Kenneth; Grest, Gary S.; Kumar, Sanat

    2014-01-01

    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.

  6. 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.

  7. 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.

  8. Telomere Length Wildlife Aging Technique

    E-print Network

    Gray, Matthew

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

  9. [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

  10. Symmetry, Levitation Effect and Size Dependent Diffusivity Maximum

    E-print Network

    Manju Sharma; S. Yashonath

    2008-11-24

    Diffusion invariably involves motion within a medium. An universal behavior observed is that self diffusivity exhibits a maximum as a function of the size of the diffusant when the diffusant is confined to a medium, as a result of what is known as the Levitation Effect. Such a maximum in self diffusivity has been seen in widely differing medium : microporous solids, dense liquids and close-packed solids, ions in polar solvents, etc. The effect arises because the forces exerted on the diffusant by the medium in which it is confined is a minimum for the size of the diffusant for which self diffusivity is a maximum. We report here simulations on a diatomic species confined to the cages of zeolite Y. Several different simulations in which the two atoms of the model diatomic species interact with equal strength(example, $O_2$, the symmetric case) and with unequal interaction strengths (example, $CO$, asymmetric case) are modeled here. Further, the bond length of the diatomic species is varied. Our results for the symmetric case shows that self diffusivity is maximum for a large enough bond length which fits snugly into the 12-ring window of zeolite Y. For weakly asymmetric case, a weak maximum is seen as a function of the bond length of the diatomic species. However, for strongly asymmetric case, no maximum in self diffusivity is seen for all the bond lengths studied. This demonstrates close relation between symmetry and the diffusivity maximum and provides a direct evidence for the need of force cancellation to observe the Levitation Effect.

  11. 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; Kläui, 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

  12. 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; Kläui, 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.

  13. Flux saturation length of sediment transport

    NASA Astrophysics Data System (ADS)

    Pähtz, 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.

  14. 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.

  15. Diffusion in correlated random potentials, with applications to DNA Michael Slutsky,1,

    E-print Network

    Mirny, Leonid

    Diffusion in correlated random potentials, with applications to DNA Michael Slutsky,1, * Mehran-dimensional diffusion over a correlated inhomogeneous energy land- scape with a correlation length c. Typical examples) formalism, and find diffusion times which exhibit strong sample to sample fluctuations. For a displacement N

  16. Molecular Dynamics of Diffusive-Ballistic Heat Conduction in Single-Walled Carbon Nanotubes

    E-print Network

    Maruyama, Shigeo

    Molecular Dynamics of Diffusive-Ballistic Heat Conduction in Single-Walled Carbon Nanotubes-3-1 Hongo, Bunkyo-ku Tokyo 113-8656, Japan Diffusive-ballistic heat conduction of finite-length single. A gradual transition from nearly pure ballistic to diffusive-ballistic heat conduction was identified from

  17. Diffusive-Ballistic Heat Conduction of Carbon Nanotubes and Nanographene Junichiro Shiomi and Shigeo Maruyama*

    E-print Network

    Maruyama, Shigeo

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

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

    PubMed

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

    2014-11-01

    Diffusion magnetic resonance imaging (dMRI) is an imaging modality that probes the diffusion characteristics of a sample via the application of magnetic field gradient pulses. The dMRI signal from a heterogeneous sample includes the contribution of the water proton magnetization from all spatial positions in a voxel. If the voxel can be spatially divided into different Gaussian diffusion compartments with inter-compartment exchange governed by linear kinetics, then the dMRI signal can be approximated using the macroscopic Karger model, which is a system of coupled ordinary differential equations (ODEs), under the assumption that the duration of the diffusion-encoding gradient pulses is short compared to the diffusion time (the narrow pulse assumption). Recently, a new macroscopic model of the dMRI signal, without the narrow pulse restriction, was derived from the Bloch-Torrey partial differential equation (PDE) using periodic homogenization techniques. When restricted to narrow pulses, this new homogenized model has the same form as the Karger model. We conduct a numerical study of the new homogenized model for voxels that are made up of periodic copies of a representative volume that contains spherical and cylindrical cells of various sizes and orientations and show that the signal predicted by the new model approaches the reference signal obtained by solving the full Bloch-Torrey PDE in O(?(2)), where ? is the ratio between the size of the representative volume and a measure of the diffusion length. When the narrow gradient pulse assumption is not satisfied, the new homogenized model offers a much better approximation of the full PDE signal than the Karger model. Finally, preliminary results of applying the new model to a voxel that is not made up of periodic copies of a representative volume are shown and discussed. PMID:25314082

  19. The gravel-sand transition: Sediment dynamics in a diffuse extension

    NASA Astrophysics Data System (ADS)

    Venditti, Jeremy G.; Domarad, Natalia; Church, Michael; Rennie, Colin D.

    2015-06-01

    As gravel-bedded rivers fine in the downstream direction, they characteristically exhibit an abrupt transition from gravel- to sand-bedded conditions. The prevailing theory for why abrupt gravel-sand transitions emerge is based on bed load sorting of a bimodal sediment. The abruptness is thought to be a consequence of sand overwhelming the gravel-sand mixture once it reaches a critical coverage on the bed. The role suspension plays in the development of gravel-sand transitions has not been fully appreciated. The Fraser River, British Columbia, is an archetypical abrupt gravel-sand transition with a "diffuse extension" composed of a sand bed with some patches of gravel. We examine flow, shear stress, and suspended sediment flux in the diffuse extension to better understand sediment dynamics where the sand bed emerges. Sand is carried in suspension upstream of the primary abrupt gravel-sand transition, but in the diffuse extension, sand is moved as both bed load and suspended load. We do not observe downstream gradients in shear stress or suspended sand flux through the diffuse extension that would suggest a gradual "rain out" of sand moving downstream, which raises the question, how is the sand bed formed? Sediment advection length scales indicate that with the exception of very fine sand that moves as wash load in the diffuse extension, fractions coarser than the median sand size cannot be carried in suspension for more than one channel width. This suggests that sand is deposited en masse at the beginning of the diffuse extension, forming a sediment slug at low flood flows that is smeared downstream at high flood flows to form the sand reach.

  20. Diffusion, dimensionality and noise in transcriptional regulation

    E-print Network

    Gasper Tkacik; William Bialek

    2007-12-12

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

  1. Dependence on chain length of NMR relaxation times in mixtures of alkanes

    NASA Astrophysics Data System (ADS)

    Freed, Denise E.

    2007-05-01

    Many naturally occurring fluids, such as crude oils, consist of a very large number of components. It is often of interest to determine the composition of the fluids in situ. Diffusion coefficients and nuclear magnetic resonance (NMR) relaxation times can be measured in situ and depend on the size of the molecules. It has been shown [D. E. Freed et al., Phys. Rev. Lett. 94, 067602 (2005)] that the diffusion coefficient of each component in a mixture of alkanes follows a scaling law in the chain length of that molecule and in the mean chain length of the mixture, and these relations were used to determine the chain length distribution of crude oils from NMR diffusion measurements. In this paper, the behavior of NMR relaxation times in mixtures of chain molecules is addressed. The author explains why one would expect scaling laws for the transverse and longitudinal relaxation times of mixtures of short chain molecules and mixtures of alkanes, in particular. It is shown how the power law dependence on the chain length can be calculated from the scaling laws for the translational diffusion coefficients. The author fits the literature data for NMR relaxation in binary mixtures of alkanes and finds that its dependence on chain length agrees with the theory. Lastly, it is shown how the scaling laws in the chain length and the mean chain length can be used to determine the chain length distribution in crude oils that are high in saturates. A good fit is obtained between the NMR-derived chain length distributions and the ones from gas chromatography.

  2. Path length enhancement in disordered media for increased absorption

    NASA Astrophysics Data System (ADS)

    Mupparapu, Rajeshkumar; Vynck, Kevin; Svensson, Tomas; Burresi, Matteo; Wiersma, Diederik S.

    2015-11-01

    We theoretically and numerically investigate the capability of disordered media to enhance the optical path length in dielectric slabs and augment their light absorption efficiency due to scattering. We first perform a series of Monte Carlo simulations of random walks to determine the path length distribution in weakly to strongly (single to multiple) scattering, non-absorbing dielectric slabs under normally incident light and derive analytical expressions for the path length enhancement in these two limits. Quite interestingly, while multiple scattering is expected to produce long optical paths, we find that media containing a vanishingly small amount of scatterers can still provide high path length enhancements due to the very long trajectories sustained by total internal reflection at the slab interfaces. The path length distributions are then used to calculate the light absorption efficiency of media with varying absorption coefficients. We find that maximum absorption enhancement is obtained at an optimal scattering strength, in-between the single-scattering and the diffusive (strong multiple-scattering) regimes. This study can guide experimentalists towards more efficient and potentially low-cost solutions in photovoltaic technologies.

  3. 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.

  4. 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.

  5. Design improvements increase run length

    SciTech Connect

    Wood, J.R. ); Marino, C.K. )

    1991-02-25

    The Hawaiian Independent Refinery (HIRI) visbreaker recently completed 843 stream days of operation before its first heater decoke and major turnaround and inspection. This is believed to be a record and shows that, with proper design criteria, longer run lengths and lower maintenance and operating costs can be achieved than previously thought possible. From this commercial experience it can be seen that it is feasible to design coil-type visbreakers to achieve very long run lengths, and because the coke formation that does occur can be quickly and easily removed, better on-stream time and lower maintenance costs can be achieved. The capital and other costs associated with soaker drums and the difficulty and expense of removing and disposing of the coke are well known, as are the problems of fuel oil degradation with soaker drums without complex internals. This demonstrated improvement in run length and on-stream time, together with other improvements made in the past 10 years, gives modern coil design a definite advantage in most visbreaking applications. Many of the concepts employed are applicable to existing units and other processes where undesirable coke formation is normally a problem.

  6. 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.

  7. Design and construction of instruments for exciton diffusion characterization and for patterning of thin films

    E-print Network

    Mendoza, Hiroshi Antonio

    2012-01-01

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

  8. Diffusion of water in nanoporous NF polyamide membrane

    NASA Astrophysics Data System (ADS)

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

    2009-08-01

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

  9. 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.

  10. Fibreoptic diffuse-light irradiators of biological tissues

    SciTech Connect

    Volkov, Vladimir V; Loshchenov, V B; Konov, Vitalii I; Kononenko, Vitalii V

    2010-10-15

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

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

    E-print Network

    Spiegelman, Marc W.

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

  12. Some characteristics of silicon photocells fabricated by planar technology

    SciTech Connect

    Tkhong, C.; Tyan, K.A.; Khoi, P.V.; Nam, L.K.

    1980-01-01

    It is reported that a method for determining the effective diffusion length on the basis of the spectral distribution curve for the collection coefficient permits a qualitative evaluation of the nonequilibrium distribution of recombination centers in the base layer.

  13. 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.

  14. 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.

  15. 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

  16. 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.

  17. Microfabricated diffusion source

    DOEpatents

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

    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.

  18. Mathematical model of alternative mechanism of telomere length maintenance

    E-print Network

    Kollár, Richard; Nosek, Jozef; Tomaska, Lubomir

    2014-01-01

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

  19. 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.

  20. Remark on pion scattering lengths

    E-print Network

    Deirdre Black; Amir H. Fariborz; Renata Jora; Nae Woong Park; Joseph Schechter; M. Naeem Shahid

    2009-07-29

    First it is shown that the tree amplitude for pion pion scattering in the minimal linear sigma model has an exact expression which is proportional to a geometric series in the quantity (s-$m_\\pi^2$)/($m_B^2-m_\\pi^2$), where $m_B$ is the sigma mass which appears in the Lagrangian and is the only a priori unknown parameter in the model. This induces an infinite series for every predicted scattering length in which each term corresponds to a given order in the chiral perturbation theory counting. It is noted that, perhaps surprisingly, the pattern, though not the exact values, of chiral perturbation theory predictions for both the isotopic spin 0 and isotopic spin 2 s-wave pion-pion scattering lengths to orders $p^2$, $p^4$ and $p^6$ seems to agree with this induced pattern. The values of the $p^8$ terms are also given for comparison with a possible future chiral perturation theory calculation. Further aspects of this approach and future directions are briefly discussed.

  1. 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)

  2. Telomere length and cardiovascular aging.

    PubMed

    Fyhrquist, Frej; Saijonmaa, Outi

    2012-06-01

    Telomeres are located at the end of chromosomes. They are composed of repetitive TTAGGG tandem repeats and associated proteins of crucial importance for telomere function. Telomeric DNA is shortened by each cell division until a critical length is achieved and the cell enters senescence and eventually apoptosis. Telomeres are therefore considered a 'biological clock' of the cell. Telomerase adds nucleotides to telomeric DNA thereby contributing to telomere maintenance, genomic stability, functions, and proliferative capacity of the cell. In certain rare forms of progeria, point mutations within the telomere lead to accelerated telomere attrition and premature aging. Endogenous factors causing telomere shortening are aging, inflammation, and oxidative stress. Leukocyte telomere length (LTL) shortening is inhibited by estrogen and endogenous antioxidants. Accelerated telomere attrition is associated with cardiovascular risk factors such as age, gender, obesity, smoking, sedentary life-style, excess alcohol intake, and even mental stress. Cardiovascular (CV) diseases and CV aging are usually but not invariably associated with shorter telomeres than in healthy subjects. LTL appears to be a biomarker of CV aging, reflecting the cumulative burden of endogenous and exogenous factors negatively affecting LTL. Whether accelerated telomere shortening is cause or consequence of CV aging and disease is not clear. PMID:22713142

  3. 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.

  4. Scaling forms of particle densities for Lévy walks and strong anomalous diffusion

    NASA Astrophysics Data System (ADS)

    Dentz, Marco; Le Borgne, Tanguy; Lester, Daniel R.; de Barros, Felipe P. J.

    2015-09-01

    We study the scaling behavior of particle densities for Lévy walks whose transition length r is coupled with the transition time t as |r | ?t? with an exponent ? >0 . The transition-time distribution behaves as ? (t ) ?t-1 -? with ? >0 . For 1 lengths is heavy tailed. These characteristics give rise to the existence of two scaling forms for the particle density, one that is valid at particle displacements |r | ?t? and one at |r | ?t? . As a consequence, the Lévy walk displays strong anomalous diffusion in the sense that the average absolute moments <|r |q> scale as tq ? (q ) with ? (q ) piecewise linear above and below a critical value qc. We derive explicit expressions for the scaling forms of the particle densities and determine the scaling of the average absolute moments. We find that <|r| q>? tq ? /? for q ? t1 +? q -? for q >qc . These results give insight into the possible origins of strong anomalous diffusion and anomalous behaviors in disordered systems in general.

  5. Effect of ion-chelating chain lengths in thiophene-based monomers on in situ photoelectrochemical polymerization and photovoltaic performances.

    PubMed

    Song, In Young; Kim, Minjun; Park, Taiho

    2015-06-01

    We synthesized thiophene-based monomers (bis-EDOTs) with different ethylene glycol oligomer (EGO) lengths (TBO3, TBO4, and TBO5) and investigated their polymerization characteristics during photoelectrochemical polymerization (PEP) at the surfaces of dye (D205)-sensitized TiO2 nanocrystalline particles. During the PEP reaction, monomers were expected to diffuse toward neighboring dyes through the growing polymer layers to enable continuous chain growth. We found that the less bulky monomer (TBO3) formed a more compact polymer layer with a high molecular weight. Its diffusion to the active sites through the resulting growing polymer layer was, therefore, limited. We deployed layers of the polymers (PTBO3, PTBO4, and PTBO5) in iodine-free solid-state hybrid solar cells to investigate the lithium ion chelating properties of the polymers as a function of the number of oxygen atoms present in the EGOs. PTBO4 and PTBO5 were capable of chelating lithium ions, yielding a photovoltaic performance that was 142% of the performance obtained without the polymer layers (3.0?5.2%). PMID:25977990

  6. Critical Waves and the Length Problem of Biology

    E-print Network

    R. B. Laughlin

    2015-04-17

    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 substances. Min oscillations in E. coli are cited as precedent resonant length measurement using chemical potential waves analogous to laser detection. Mitotic structures in eucaryotes 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. PNAS Significance Statement: This paper invokes physical principles to address the question of how living things might use reaction-diffusion to measure out and regulate the many thousands of lengths required to make their body parts and internal organs. It argues that two ideas have been missing. One is that oscillation is necessary to achieve the necessary design stability and plasticity. The other is that the system must be tuned to criticality to stabilize the propagation velocity, thus enabling clocks to function as meter sticks. The broader significance is twofold: First, a fundamental piece of the machinery of life is probably invisible to present-day biochemical methods because they are too slow. Second, the simplicity of growth and form identified a century ago by D'Arcy Thompson is probably a symptom of biological engineering strategies, not primitive law.

  7. Tracer diffusion inside fibrinogen layers

    E-print Network

    Micha? Cie?la; Ewa Gudowska-Nowak; Francesc Sagués; Igor M. Sokolov

    2014-03-13

    We investigate the obstructed motion of tracer (test) particles in crowded environments by carrying simulations of two-dimensional Gaussian random walk in model fibrinogen monolayers of different orientational ordering. The fibrinogen molecules are significantly anisotropic and therefore they can form structures where orientational ordering, similar to the one observed in nematic liquid crystals, appears. The work focuses on the dependence between level of the orientational order (degree of environmental crowding) of fibrinogen molecules inside a layer and non-Fickian character of the diffusion process of spherical tracer particles moving within the domain. It is shown that in general particles motion is subdiffusive and strongly anisotropic, and its characteristic features significantly change with the orientational order parameter, concentration of fibrinogens and radius of a diffusing probe.

  8. Atomistic Simulation of Polymer Crystallization at Realistic Length Scales

    SciTech Connect

    Gee, R H; Fried, L E

    2005-01-28

    Understanding the dynamics of polymer crystallization during the induction period prior to crystal growth is a key goal in polymer physics. Here we present the first study of primary crystallization of polymer melts via molecular dynamics simulations at physically realistic (about 46 nm) length scales. Our results show that the crystallization mechanism involves a spinodal decomposition microphase separation caused by an increase in the average length of rigid trans segments along the polymer backbone during the induction period. Further, the characteristic length of the growing dense domains during the induction period is longer than predicted by classical nucleation theory. These results indicate a new 'coexistence period' in the crystallization, where nucleation and growth mechanisms coexist with a phase separation mechanism. Our results provide an atomistic verification of the fringed micelle model.

  9. 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

  10. 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

  11. 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

  12. Inherent structure length in metallic glasses: simplicity behind complexity

    NASA Astrophysics Data System (ADS)

    Wu, Yuan; Wang, Hui; Cheng, Yongqiang; Liu, Xiongjun; Hui, Xidong; Nieh, Taigang; Wang, Yandong; Lu, Zhaoping

    2015-08-01

    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.

  13. Characteristics of Yerevan High Transparency Scintillators

    SciTech Connect

    Zorn, Carl; Asryan, Gegham; Egiyan, Kim; Tarverdyan, M.; Amaryan, Moscov; Amaryan, Moskov; Demirchyan, Raphael; Stepanyan, Stepan; Burkert, Volker; Sharabian, Youri

    1992-08-01

    Optical transmission, light output and time characteristics are given for long scintillator strips fabricated at the Yerevan Physics Institute using the extrusion method. It is shown that at 45% relative (to anthracene) light output, good transmission (2.5/2.9 m attenuation length with photomultiplier direct readout and 3/3.5 m attenuation length fiber readout) and time characteristics (average decay time 2.8 nsec) were obtained.

  14. 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.

  15. Signatures of Quantum-Tunneling Diffusion of Hydrogen Atoms on Water Ice at 10 K

    NASA Astrophysics Data System (ADS)

    Kuwahata, K.; Hama, T.; Kouchi, A.; Watanabe, N.

    2015-09-01

    Reported here is the first observation of the tunneling surface diffusion of a hydrogen (H) atom on water ice. Photostimulated desorption and resonance-enhanced multiphoton ionization methods were used to determine the diffusion rates at 10 K on amorphous solid water and polycrystalline ice. H-atom diffusion on polycrystalline ice was 2 orders of magnitude faster than that of deuterium atoms, indicating the occurrence of tunneling diffusion. Whether diffusion is by tunneling or thermal hopping also depends on the diffusion length of the atoms and the morphology of the surface. Our findings contribute to a better understanding of elementary physicochemical processes of hydrogen on cosmic ice dust.

  16. 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.

  17. 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.

  18. Narrow groove welding gas diffuser assembly and welding torch

    DOEpatents

    Rooney, Stephen J. (East Berne, NY)

    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.

  19. 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…

  20. Diffusion Strategy Guide.

    ERIC Educational Resources Information Center

    McCutcheon, James R.; Sanders, John R.

    A methodology is presented for planning and managing the spread of educational innovations. The first portion of the guide develops a theoretical framework for diffusion which summarizes and capitalizes on the latest marketing and on the latest marketing and diffusion research findings. Major stages in the diffusion paradigm discussed include…

  1. 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.

  2. 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.

  3. 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 Å × 4.8 Å 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 Å. 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

  4. Curved and diffuse interface effects on the nuclear surface tension

    E-print Network

    V. M. Kolomietz; S. V. Lukyanov; A. I. Sanzhur

    2012-01-30

    We redefine the surface tension coefficient for a nuclear Fermi-liquid drop with a finite diffuse layer. Following Gibbs-Tolman concept, we introduce the equimolar radius R_e of sharp surface droplet at which the surface tension is applied and the radius of tension surface R_s which provides the minimum of the surface tension coefficient \\sigma. This procedure allows us to derive both the surface tension and the corresponding curvature correction (Tolman length) correctly for the curved and diffuse interface. We point out that the curvature correction depends significantly on the finite diffuse interface. This fact is missed in traditional nuclear considerations of curvature correction to the surface tension. We show that Tolman's length \\xi is negative for nuclear Fermi-liquid drop. The value of the Tolman length is only slightly sensitive to the Skyrme force parametrization and equals \\xi=-0.36 fm.

  5. 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:

  6. 7 CFR 51.610 - Midrib length.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ...FRUITS, VEGETABLES AND OTHER PRODUCTS 1,2 (INSPECTION, CERTIFICATION, AND STANDARDS) United States Consumer Standards for Celery Stalks Definitions § 51.610 Midrib length. Midrib length of a branch means the distance between the point of...

  7. 7 CFR 51.610 - Midrib length.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ...FRUITS, VEGETABLES AND OTHER PRODUCTS 1,2 (INSPECTION, CERTIFICATION, AND STANDARDS) United States Consumer Standards for Celery Stalks Definitions § 51.610 Midrib length. Midrib length of a branch means the distance between the point of...

  8. 7 CFR 51.610 - Midrib length.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ...FRUITS, VEGETABLES AND OTHER PRODUCTS 1,2 (INSPECTION, CERTIFICATION, AND STANDARDS) United States Consumer Standards for Celery Stalks Definitions § 51.610 Midrib length. Midrib length of a branch means the distance between the point of...

  9. 7 CFR 51.610 - Midrib length.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ...FRUITS, VEGETABLES AND OTHER PRODUCTS 1,2 (INSPECTION, CERTIFICATION, AND STANDARDS) United States Consumer Standards for Celery Stalks Definitions § 51.610 Midrib length. Midrib length of a branch means the distance between the point of...

  10. 7 CFR 51.610 - Midrib length.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ...FRUITS, VEGETABLES AND OTHER PRODUCTS 1 2 (INSPECTION, CERTIFICATION, AND STANDARDS) United States Consumer Standards for Celery Stalks Definitions § 51.610 Midrib length. Midrib length of a branch means the distance between the point of...

  11. Inheritance of Cotton Fiber Length and Strength 

    E-print Network

    Joy, Kolbyn Seth

    2014-04-23

    ), uniformity index, elongation, micronaire, advanced fiber information system (AFIS) upper quartile length on a weight basis, mean length on a number basis, short fiber content on a number basis, immature fiber content, maturity ratio, and standard fineness...

  12. Inheritance of cotton fiber length and distribution 

    E-print Network

    Braden, Chris Alan

    2006-10-30

    length and to determine the inheritance of length distribution data. Four near-long staple (NLS) upland cotton genotypes and one short-staple genotype were crossed in all combinations, excluding reciprocals. Estimates of general (GCA) and specific...

  13. Analysis of the Fluorescence Correlation Function of Quantum Rods with Different Lengths.

    PubMed

    Lee, Jaeran; Kim, Sok Won

    2015-11-01

    We built a polarization fluorescence correlation spectroscopy system to analyze the variation of the correlation function in rotational diffusion based on the length of rod-like fluorescent particles. Because the rotational diffusion of particles in liquid depends on the relative polarization states of the laser source and particle fluorescence, we compared the amplitudes of the rotational diffusion using the autocorrelation function in different polarization states. For experiments that depend on the length of the fluorescent particles, we prepared three kinds of quantum rod samples with a width of 6.5?±?0.5 nm and lengths of 17?±?3, 40?±?3, and 46?±?3 nm. Through the experiment, we obtained the hydrodynamic radii of each particle using the rotational diffusion coefficient: 10.7?±?0.8, 13.4?±?0.7, and 14.1?±?0.4 nm with the length of the particles. All the obtained values for radii are 3 nm larger than the calculated equivalent radii of spheres with the same volume as the rod samples. Through a fraction analysis by polarization state, we confirmed that the ratio of rotational fraction for polarization increases with the aspect ratio of the actual particle. PMID:26399538

  14. Investigation of Perforated Convergent-divergent Diffusers with Initial Boundary Layer

    NASA Technical Reports Server (NTRS)

    Weinstein, Maynard I

    1950-01-01

    An experimental investigation was made at Mach number 1.90 of the performance of a series of perforated convergent-divergent supersonic diffusers operating with initial boundary layer, which was induced and controlled by lengths of cylindrical inlets affixed to the diffusers. Supercritical mass-flow and peak total-pressure recoveries were decreased slightly by use of the longest inlets (4 inlet diameters in length). Combinations of cylindrical inlets, perforated diffusers, and subsonic diffuser were evaluated as simulated wind tunnels having second throats. Comparisons with noncontracted configurations of similar scale indicated conservatively computed power reductions of 25 percent.

  15. Anomalous diffusion with linear reaction dynamics: From continuous time random walks to fractional reaction-diffusion equations

    E-print Network

    Anomalous diffusion with linear reaction dynamics: From continuous time random walks to fractional at the mesoscopic level using continuous time random walks, to include linear reaction dynamics. If a constantR; the characteristic microscopic diffusion time for encounters between reactants D; the microscopic reaction time R

  16. 28 CFR 551.4 - Hair length.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 2011-07-01 2011-07-01 false Hair length. 551.4 Section 551.4 Judicial...MANAGEMENT MISCELLANEOUS Grooming § 551.4 Hair length. (a) The Warden may not restrict hair length if the inmate keeps it neat and...

  17. 28 CFR 551.4 - Hair length.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 2010-07-01 2010-07-01 false Hair length. 551.4 Section 551.4 Judicial...MANAGEMENT MISCELLANEOUS Grooming § 551.4 Hair length. (a) The Warden may not restrict hair length if the inmate keeps it neat and...

  18. 28 CFR 551.4 - Hair length.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 2013-07-01 2013-07-01 false Hair length. 551.4 Section 551.4 Judicial...MANAGEMENT MISCELLANEOUS Grooming § 551.4 Hair length. (a) The Warden may not restrict hair length if the inmate keeps it neat and...

  19. 28 CFR 551.4 - Hair length.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 2012-07-01 2012-07-01 false Hair length. 551.4 Section 551.4 Judicial...MANAGEMENT MISCELLANEOUS Grooming § 551.4 Hair length. (a) The Warden may not restrict hair length if the inmate keeps it neat and...

  20. 28 CFR 551.4 - Hair length.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 2014-07-01 2014-07-01 false Hair length. 551.4 Section 551.4 Judicial...MANAGEMENT MISCELLANEOUS Grooming § 551.4 Hair length. (a) The Warden may not restrict hair length if the inmate keeps it neat and...

  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, 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...

  3. 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...

  4. 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...

  5. 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...

  6. Exact curvilinear diffusion coefficients in the repton model.

    PubMed

    Buhot, A

    2005-10-01

    The Rubinstein-Duke or repton model is one of the simplest lattice model of reptation for the diffusion of a polymer in a gel or a melt. Recently, a slightly modified model with hardcore interactions between the reptons has been introduced. The curvilinear diffusion coefficients of both models are exactly determined for all chain lengths. The case of periodic boundary conditions is also considered. PMID:16235000

  7. Computational study on entanglement length and pore size of carbon nanotube buckypaper

    NASA Astrophysics Data System (ADS)

    Li, Ying; Kröger, Martin

    2012-01-01

    In this letter, both entanglement length and pore size of carbon nanotube (CNT) buckypaper are studied numerically and found to scale with a characteristic length ?EI /? , where EI and ? denote the bending stiffness and binding energy of a CNT, respectively. For ?EI /? <40 nm, the CNTs in buckypaper are "interwound" with a short entanglement length and a small pore size. However, when ?EI /? >40 nm, CNT "ring"/"racket" structures dominate the buckypaper, exhibiting longer entanglement length and larger pore size. The acquired understanding of microscopic structures allows us to propose that CNT buckypaper with different mechanical properties and pore size can be designed through the choice of ?EI /? values.

  8. Diffusion in confined geometries.

    PubMed

    Burada, P Sekhar; Hänggi, Peter; Marchesoni, Fabio; Schmid, Gerhard; Talkner, Peter

    2009-01-12

    Diffusive transport of particles or, more generally, small objects, is a ubiquitous feature of physical and chemical reaction systems. In configurations containing confining walls or constrictions, transport is controlled both by the fluctuation statistics of the jittering objects and the phase space available to their dynamics. Consequently, the study of transport at the macro- and nanoscales must address both Brownian motion and entropic effects. Herein we report on recent advances in the theoretical and numerical investigation of stochastic transport occurring either in microsized geometries of varying cross sections or in narrow channels wherein the diffusing particles are hindered from passing each other (single-file diffusion). For particles undergoing biased diffusion in static suspension media enclosed by confining geometries, transport exhibits intriguing features such as 1) a decrease in nonlinear mobility with increasing temperature or also 2) a broad excess peak of the effective diffusion above the free diffusion limit. These paradoxical aspects can be understood in terms of entropic contributions resulting from the restricted dynamics in phase space. If, in addition, the suspension medium is subjected to external, time-dependent forcing, rectification or segregation of the diffusing Brownian particles becomes possible. Likewise, the diffusion in very narrow, spatially modulated channels is modified via contact particle-particle interactions, which induce anomalous sub-diffusion. The effective sub-diffusion constant for a driven single file also develops a resonance-like structure as a function of the confining coupling constant. PMID:19025741

  9. Real space mapping of ionic diffusion and electrochemical activity in energy storage and conversion materials

    DOEpatents

    Kalinin, Sergei V; Balke, Nina; Kumar, Amit; Dudney, Nancy J; Jesse, Stephen

    2014-05-06

    A method and system for probing mobile ion diffusivity and electrochemical reactivity on a nanometer length scale of a free electrochemically active surface includes a control module that biases the surface of the material. An electrical excitation signal is applied to the material and induces the movement of mobile ions. An SPM probe in contact with the surface of the material detects the displacement of mobile ions at the surface of the material. A detector measures an electromechanical strain response at the surface of the material based on the movement and reactions of the mobile ions. The use of an SPM tip to detect local deformations allows highly reproducible measurements in an ambient environment without visible changes in surface structure. The measurements illustrate effective spatial resolution comparable with defect spacing and well below characteristic grain sizes of the material.

  10. 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

  11. Aerodynamic roughness length related to non-aggregated tillage ridges

    NASA Astrophysics Data System (ADS)

    Kardous, M.; Bergametti, G.; Marticorena, B.

    2005-11-01

    Wind erosion in agricultural soils is dependent, in part, on the aerodynamic roughness length (z0) produced by tillage ridges. Although previous studies have related z0 to ridge characteristics (ridge height (RH) and spacing (RS)), these relationships have not been tested for tillage ridges observed in the North African agricultural fields. In these regions, due to climate and soil conditions, small plowing tools are largely used. Most of these tools produce non-aggregated and closely-spaced small ridges. Thus, experiments were conducted in a 7-m long wind tunnel to measure z0 for 11 ridge types covering the range of geometric characteristics frequently observed in south Tunisia. Experimental results suggest that RH2/RS is the first order parameter controlling z0. A strong relationship between z0 and RH2/RS is proposed for a wide range of ridge characteristics.

  12. Model of Growth Cone Membrane Polarization via Microtubule Length Regulation.

    PubMed

    Xu, Bin; Bressloff, Paul C

    2015-11-17

    We present a mathematical model of membrane polarization in growth cones. We proceed by coupling an active transport model of cytosolic proteins along a two-dimensional microtubule (MT) network with a modified Dogterom-Leibler model of MT growth. In particular, we consider a Rac1-stathmin-MT pathway in which the growth and catastrophe rates of MTs are regulated by cytosolic stathmin, while the stathmin is regulated by Rac1 at the membrane. We use regular perturbation theory and numerical simulations to determine the steady-state stathmin concentration, the mean MT length distribution, and the resulting distribution of membrane-bound proteins. We thus show how a nonuniform Rac1 distribution on the membrane generates a polarized distribution of membrane proteins. The mean MT length distribution and hence the degree of membrane polarization are sensitive to the precise form of the Rac1 distribution and parameters such as the catastrophe-promoting constant and tubulin association rate. This is a consequence of the fact that the lateral diffusion of stathmin tends to weaken the effects of Rac1 on the distribution of mean MT lengths. PMID:26588578

  13. Diffusion in Solids

    NASA Astrophysics Data System (ADS)

    Wahnström, Göran

    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.

  14. Diffusion of iron, cobalt, and nickel in liquid germanium

    SciTech Connect

    Denisov, V.M.; Beletskii, V.V.

    1988-03-01

    To improve the processes employed for preparing single crystals with fixed electrophysical properties it is necessary to have information about the coefficients of diffusion of the impurities present in the melts. In this paper data on the diffusion of Fe, Co, and Ni in liquid germanium, starting from its melting point up to 1380/degree/K, are presented. The coefficients of diffusion of Fe, Co, and Ni in liquid Ge were determined by the capillary method. It was established that the change in the structure of liquid helium as a function of the temperature is responsible for the characteristic features of diffusion in the systems studied.

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

    E-print Network

    Johnson, Jeremy A.

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

  16. Molecular dynamics simulation of fractal aggregate diffusion

    NASA Astrophysics Data System (ADS)

    Pranami, Gaurav; Lamm, Monica H.; Vigil, R. Dennis

    2010-11-01

    The diffusion of fractal aggregates constructed with the method by Thouy and Jullien [J. Phys. A 27, 2953 (1994)10.1088/0305-4470/27/9/012] comprised of Np spherical primary particles was studied as a function of the aggregate mass and fractal dimension using molecular dynamics simulations. It is shown that finite-size effects have a strong impact on the apparent value of the diffusion coefficient (D) , but these can be corrected by carrying out simulations using different simulation box sizes. Specifically, the diffusion coefficient is inversely proportional to the length of a cubic simulation box, and the constant of proportionality appears to be independent of the aggregate mass and fractal dimension. Using this result, it is possible to compute infinite dilution diffusion coefficients (Do) for aggregates of arbitrary size and fractal dimension, and it was found that Do?Np-1/df , as is often assumed by investigators simulating Brownian aggregation of fractal aggregates. The ratio of hydrodynamic radius to radius of gyration is computed and shown to be independent of mass for aggregates of fixed fractal dimension, thus enabling an estimate of the diffusion coefficient for a fractal aggregate based on its radius of gyration.

  17. Tracer diffusivity and effective temperature in bacterial suspensions

    E-print Network

    Patteson, Alison E; Purohit, Prashant K; Arratia, Paulo E

    2015-01-01

    The dynamics of tracer particles in \\textit{E. coli} suspensions are experimentally investigated as a function of particle size and bacteria concentration. We find that tracer diffusivity is enhanced due to particle-bacteria interactions and varies non-monotonically with particle size, exhibiting a peak at sizes comparable to the bacterial length. The time scale characterizing the transition from ballistic to diffusive regime increases monotonically with \\textit{E. coli} concentration and particle size. Diffusivity measurements are then used to estimate suspension effective temperature, which varies nonlinearly with tracer size, suggesting that measures of activity are probe size dependent.

  18. Germanium nanowire growth controlled by surface diffusion effects

    SciTech Connect

    Schmidtbauer, Jan; Bansen, Roman; Heimburger, Robert; Teubner, Thomas; Boeck, Torsten; Fornari, Roberto

    2012-07-23

    Germanium nanowires (NWs) were grown onto Ge(111) substrates by the vapor-liquid-solid process using gold droplets. The growth was carried out in a molecular beam epitaxy chamber at substrate temperatures between 370 Degree-Sign C and 510 Degree-Sign C. The resulting nanowire growth rate turns out to be highly dependent on the substrate temperature exhibiting the maximum at T = 430 Degree-Sign C. The temperature dependence of growth rate can be attributed to surface diffusion both along the substrate and nanowire sidewalls. Analyzing the diffusive material transport yields a diffusion length of 126 nm at a substrate temperature of 430 Degree-Sign C.

  19. Growth with surface diffusion in d = 1 + 1

    NASA Astrophysics Data System (ADS)

    Hontinfinde, Felix; Krug, Joachim; Touzani, M'hamed

    1997-02-01

    A restricted solid-on-solid model where surface relaxation occurs by atom desorption and by surface diffusion is introduced and studied in 1+1 dimensions. The interface profile is mapped onto a four-vertex model and the kinetic equation describing the moving surface is solved exactly for small samples. In the presence of desorption we classify different growth regimes using the Wilson-Frenkel law. In the presence of surface diffusion with step edge barriers we find evidence for a sharp transition from stable to unstable growth which occurs with increasing diffusion length. Growth modes during the thermal evaporation of the crystal are also discussed.

  20. An Effective Subdivision Algorithm for Diffuse Scattering of Ray Tracing Mingming Gan1

    E-print Network

    Zemen, Thomas

    ) the generation of diffuse scattering tiles, which fully demonstrates the random characteristic of diffuseAn Effective Subdivision Algorithm for Diffuse Scattering of Ray Tracing Mingming Gan1 , Xuhong Li2 scattering mechanisms. The accuracy, supported by a precise description of the environment, is achieved

  1. 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

  2. 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

  3. Comparative Analysis of Connection and Disconnection in the Human Brain Using Diffusion MRI: New Methods and Applications 

    E-print Network

    Clayden, Jonathan D

    2008-01-01

    Diffusion magnetic resonance imaging (dmri) is a technique that can be used to examine the diffusion characteristics of water in the living brain. A recently developed application of this technique is tractography, in ...

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

    E-print Network

    Kazuhiko Seki; Sanoop Ramachandran; Shigeyuki Komura

    2011-07-22

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

  5. Size of diffusion pore of Alcaligenes faecalis.

    PubMed Central

    Ishii, J; Nakae, T

    1988-01-01

    The diffusion pore of the outer membrane of Alcaligenes faecalis was shown to be substantially smaller than the Escherichia coli porin pore. In experiments with intact cells, pentoses and hexoses penetrated into the NaCl-expanded periplasm, whereas saccharides of Mr greater than 342 did not. Cells treated with 0.5 M saccharides of Mr greater than 342 weighed 33 to 38% less than cells treated with isotonic solution, suggesting that these saccharides do not permeate through the outer membrane. The diffusion rates of various solutes through the liposome membranes reconstituted from the Mr-43,000 outer membrane protein showed the following characteristics. (i) The relative diffusion rates of pentoses, hexoses, and methylhexoses appeared to be about 1.0, 0.6, and negligibly small, respectively. (ii) The diffusion rate of glucose appeared to be about 1/10th that with the E. coli B porin. (iii) The diffusion rate of gluconic acid was five to seven times higher than that of glucose. (iv) The diffusion rates of beta-lactam antibiotics appeared to be 40 to less than 10% of those with the E. coli B porin. Images PMID:2835003

  6. 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.

  7. Minimal Length Effects on Schwinger Mechanism

    E-print Network

    Benrong Mu; Peng Wang; Haitang Yang

    2015-01-24

    In this paper, we investigate effects of the minimal length on the Schwinger mechanism using the quantum field theory (QFT) incorporating the minimal length. We first study the Schwinger mechanism for scalar fields in both usual QFT and the deformed QFT. The same calculations are then performed in the case of Dirac particles. Finally, we discuss how our results imply for the corrections to the Unruh temperature and the Hawking temperature due to the minimal length.

  8. 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.

  9. 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)

  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. 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

  12. Buoyancy Effects in Fully-Modulated, Turbulent Diffusion Flames

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

  13. 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.

  14. 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.

  15. 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…

  16. 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…

  17. Alignment techniques required by precise measurement of effective focal length

    NASA Technical Reports Server (NTRS)

    Wise, T. D.

    1980-01-01

    The characteristics of false color imagery produced by instrumentation on earth resource mapping satellites are examined. The spatial fidelity of the imagery is dependent upon the geometric accuracy (GA) and the band-to-band registration (BBR) with which the telescope instrument is assembled. BBR and GA require knowledge of telescope effective focal length (EFL) to one part in 10,000 in order that the next generation of earth mappers be able to carry out their missions. The basis for this level of precision is briefly considered, and a description is given of the means by which such precise EFL measurements have been carried out. Attention is given to accuracy requirements, the technique used to measure effective focal length, possible sources of error in the EFL measurement, approaches for eliminating errors, and the results of the efforts to control measurement errors in EFL determinations.

  18. Growing-season length and climatic variation in Alaska

    SciTech Connect

    Sharratt, B.S.

    1992-03-01

    The growing season has lengthened in the contiguous United States since 1900, coinciding with increasing northern hemispheric air temperatures. Information on growing season trends is needed in arctic regions where projected increases in air temperature are to be more pronounced. The lengths of the growing season at four locations in Alaska were evaluated for characteristic trends between 1917 and 1988. Freeze dates were determined using minimum temperature criteria of O deg and -3 deg C. A shortening of the season was found at Sitka and lengthening of the season at Talkeetna. The growing season shortened at Juneau and Sitka during the period 1940 to 1970, which corresponded with declining northern hemisphere temperature. Change in the growing season length was apparent in the Alaska temperature record, but the regional tendency for shorter or longer season needs further evaluation.

  19. NONLINEAR DIFFUSION PDES Erkut Erdem

    E-print Network

    Erdem, Erkut

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

  20. 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 ?=175 to Coulomb parameters up to ?=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

  1. Diffusion in Coulomb Crystals

    E-print Network

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

    2011-06-07

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

  2. 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.

  3. Viscous diffusion of vorticity in unsteady wall layers using the diffusion velocity concept

    SciTech Connect

    Strickland, J.H.; Kempka, S.N.; Wolfe, W.P.

    1995-03-01

    The primary purpose of this paper is to provide a careful evaluation of the diffusion velocity concept with regard to its ability to predict the diffusion of vorticity near a moving wall. A computer code BDIF has been written which simulates the evolution of the vorticity field near a wall of infinite length which is moving in an arbitrary fashion. The simulations generated by this code are found to give excellent results when compared to several exact solutions. We also outline a two-dimensional unsteady viscous boundary layer model which utilizes the diffusion velocity concept and is compatible with vortex methods. A primary goal of this boundary layer model is to minimize the number of vortices generated on the surface at each time step while achieving good resolution of the vorticity field near the wall. Preliminary results have been obtained for simulating a simple two-dimensional laminar boundary layer.

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

    SciTech Connect

    Dayananda, M.A.

    1986-05-23

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

  5. A molecular dynamics simulations study on the relations between dynamical heterogeneity, structural relaxation, and self-diffusion in viscous liquids

    NASA Astrophysics Data System (ADS)

    Henritzi, Patrick; Bormuth, André; Klameth, Felix; Vogel, Michael

    2015-10-01

    We perform molecular dynamics simulations for viscous liquids to study the relations between dynamical heterogeneity, structural (?) relaxation, and self-diffusion. For atomistic models of supercooled water, polymer melts, and an ionic liquid, we characterize the space-time characteristics of dynamical heterogeneity by the degree of deviations from Gaussian displacement statistics (?2), the size of clusters comprising highly mobile particles (Sw), and the length of strings consisting of cooperatively moving particles (Lw). Comparison of our findings with previous simulation results for a large variety of viscous liquids, ranging from monoatomic liquids to silica melt, reveals a nearly universal decoupling between the time scales of maximum non-Gaussian parameter (??2) and the time constant of the ? relaxation (??) upon cooling, explicitly, ? ?2 ? ?? 3 / 4 . Such uniform relation was not observed between the peak times of Sw or Lw and ??. On the other hand, the temperature-dependent time scale of maximum string length (?L) follows the inverse of the self-diffusion coefficient (D) for various systems at sufficiently low temperatures, i.e., ?L ? D-1. These observations are discussed in view of a breakdown of the Stokes-Einstein relation for the studied systems. It is found that the degree of deviation from this relation is correlated with the stretching of the ? relaxation.

  6. A molecular dynamics simulations study on the relations between dynamical heterogeneity, structural relaxation, and self-diffusion in viscous liquids.

    PubMed

    Henritzi, Patrick; Bormuth, André; Klameth, Felix; Vogel, Michael

    2015-10-28

    We perform molecular dynamics simulations for viscous liquids to study the relations between dynamical heterogeneity, structural (?) relaxation, and self-diffusion. For atomistic models of supercooled water, polymer melts, and an ionic liquid, we characterize the space-time characteristics of dynamical heterogeneity by the degree of deviations from Gaussian displacement statistics (?2), the size of clusters comprising highly mobile particles (Sw), and the length of strings consisting of cooperatively moving particles (Lw). Comparison of our findings with previous simulation results for a large variety of viscous liquids, ranging from monoatomic liquids to silica melt, reveals a nearly universal decoupling between the time scales of maximum non-Gaussian parameter (??2 ) and the time constant of the ? relaxation (??) upon cooling, explicitly, ??2 ??? (3/4). Such uniform relation was not observed between the peak times of Sw or Lw and ??. On the other hand, the temperature-dependent time scale of maximum string length (?L) follows the inverse of the self-diffusion coefficient (D) for various systems at sufficiently low temperatures, i.e., ?L ? D(-1). These observations are discussed in view of a breakdown of the Stokes-Einstein relation for the studied systems. It is found that the degree of deviation from this relation is correlated with the stretching of the ? relaxation. PMID:26520522

  7. Current-voltage characteristics of manganite-titanite perovskite junctions.

    PubMed

    Ifland, Benedikt; Peretzki, Patrick; Kressdorf, Birte; Saring, Philipp; Kelling, Andreas; Seibt, Michael; Jooss, Christian

    2015-01-01

    After a general introduction into the Shockley theory of current voltage (J-V) characteristics of inorganic and organic semiconductor junctions of different bandwidth, we apply the Shockley theory-based, one diode model to a new type of perovskite junctions with polaronic charge carriers. In particular, we studied manganite-titanate p-n heterojunctions made of n-doped SrTi1- y Nb y O3, y = 0.002 and p-doped Pr1- x Ca x MnO3, x = 0.34 having a strongly correlated electron system. The diffusion length of the polaron carriers was analyzed by electron beam-induced current (EBIC) in a thin cross plane lamella of the junction. In the J-V characteristics, the polaronic nature of the charge carriers is exhibited mainly by the temperature dependence of the microscopic parameters, such as the hopping mobility of the series resistance and a colossal electro-resistance (CER) effect in the parallel resistance. We conclude that a modification of the Shockley equation incorporating voltage-dependent microscopic polaron parameters is required. Specifically, the voltage dependence of the reverse saturation current density is analyzed and interpreted as a voltage-dependent electron-polaron hole-polaron pair generation and separation at the interface. PMID:26199851

  8. Current–voltage characteristics of manganite–titanite perovskite junctions

    PubMed Central

    Ifland, Benedikt; Peretzki, Patrick; Kressdorf, Birte; Saring, Philipp; Kelling, Andreas; Seibt, Michael

    2015-01-01

    Summary After a general introduction into the Shockley theory of current voltage (J–V) characteristics of inorganic and organic semiconductor junctions of different bandwidth, we apply the Shockley theory-based, one diode model to a new type of perovskite junctions with polaronic charge carriers. In particular, we studied manganite–titanate p–n heterojunctions made of n-doped SrTi1? yNbyO3, y = 0.002 and p-doped Pr1? xCaxMnO3, x = 0.34 having a strongly correlated electron system. The diffusion length of the polaron carriers was analyzed by electron beam-induced current (EBIC) in a thin cross plane lamella of the junction. In the J–V characteristics, the polaronic nature of the charge carriers is exhibited mainly by the temperature dependence of the microscopic parameters, such as the hopping mobility of the series resistance and a colossal electro-resistance (CER) effect in the parallel resistance. We conclude that a modification of the Shockley equation incorporating voltage-dependent microscopic polaron parameters is required. Specifically, the voltage dependence of the reverse saturation current density is analyzed and interpreted as a voltage-dependent electron–polaron hole–polaron pair generation and separation at the interface. PMID:26199851

  9. A Multiphase Solute Diffusion Model for Dendritic Alloy Solidification

    E-print Network

    Beckermann, Christoph

    A Multiphase Solute Diffusion Model for Dendritic Alloy Solidification C.Y. WANG and C. BECKERMANN for dendritic solidification of alloys. The model accounts for the different length scales existing dendritic solidification. Finally, illustrative calculations for equiaxed, columnar, and mixed columnar

  10. NONLINEAR DIFFUSION OF DISLOCATION DENSITY AND SELF-SIMILAR SOLUTIONS

    E-print Network

    Monneau, Régis

    NONLINEAR DIFFUSION OF DISLOCATION DENSITY AND SELF-SIMILAR SOLUTIONS PIOTR BILER, GRZEGORZ KARCH of dislocations in crystals. The long time asymptotics of solutions is described by the self-similar profiles. 1. Introduction Dislocation dynamics. Dislocations are line defects in crystals whose typ- ical length is 10-6 m

  11. DCT-Based Characterization of Milk Products Using Diffuse Reflectance Images

    E-print Network

    DCT-Based Characterization of Milk Products Using Diffuse Reflectance Images Sara Sharifzadeh of diffuse reflectance images of laser illumination on milk products in different wave lengths. Based and discriminate eight different milk products. Comparing this result with the current characteriza tion method

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

    E-print Network

    Fayer, Michael D.

    diffusion. Identifying the relative importance of hydrogen bond length and orientational relaxation dynamicsStructural dynamics of hydrogen bonded methanol oligomers: Vibrational transient hole burning studies of spectral diffusion I. R. Piletic, K. J. Gaffney, and M. D. Fayer Department of Chemistry

  13. The streamline diffusion finite element method for compressible and incompressible fluid flow

    NASA Astrophysics Data System (ADS)

    Johnson, C.

    The streamline diffusion finite element method is applied as a general method for hyperbolic type problems including convection-dominated scalar convection-diffusion problems, the incompressible Euler and Navier-Stokes equations, and the incompressible Euler equations. Results on adaptive forms of the streamline diffusion, based on a priori estimates are included. A form of the streamline diffusion method for time-dependent problems, using space-time finite elements oriented along characteristics, is presented.

  14. Helium Diffusion in Olivine

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  15. Diffusion of sulfuric acid in concentrated solutions

    SciTech Connect

    Umino, S.; Newman, J. )

    1993-08-01

    Aqueous sulfuric acid is an economically important chemical reagent. It is one of the largest volume chemical commodities, finding uses in fertilizer production, petroleum refining, extraction of metals from their ores, production of inorganic pigments, pickling of iron and steel, synthesis of surface-active agents, and as a reactant in the lead-acid storage battery. The restricted diffusion method was used to measure the differential diffusion coefficient of sulfuric acid in water at 25 C for the concentration range from 0.3 to 7.5 molar. The concentration gradients of diffusing species were observed by Rayleigh interferometry. Experimental transport data are analyzed with concentrated solution theory of electrolytes in order to elucidate macroscopic transport characteristics of sulfuric acid in terms of specific binary interactions in solution. Results indicate that the transport properties of sulfuric acid are determined by the hydrogen ion-water molecule.

  16. Diffusion pump oils based on neutral oil

    SciTech Connect

    Artem'eva, V.P.; Gorbacheva, S.G.; Kucheryavaya, N.N.; Orlova, S.N.; Potanina, V.A.

    1983-09-01

    VM-1 and VM-5 mineral oils used as working fluids in high vacuum pumps are obtained by high-vacuum distillation of a pharmaceutical white oil produced in Balkhany lube crude which is in limited supply and therefore must be replaced by a new raw material. An investigation of a napthenic neutral oil containing 90% saturated hydrocarbons demonstrated the feasibility of this oil as a raw material for the production of diffusion oil pumps. The characteristics of the diffusion pump oil VM-8 obtained by this processing scheme are listed. The oil was tested on NVD-015 pumps. The favorable results have made it possible to develop and approve specifications for diffusion pump oils in VM-8 and VM-9.

  17. Finding Maximum Length Tours Under Polyhedral Norms

    E-print Network

    Barvinok, Alexander

    Finding Maximum Length Tours Under Polyhedral Norms Alexander Barvinok \\Lambda David S. Johnson y to a polyhedral norm. We show that for any such norm, the problem of finding a tour of maximum length can in time O(n f+1 ), where f is the number of facets of the polyhedron determining the polyhedral norm. Thus

  18. Linking SNPs to CAG repeat length in

    E-print Network

    Cai, Long

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

  19. 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...

  20. 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...

  1. Environmental Stresses Disrupt Telomere Length Homeostasis

    E-print Network

    Ruppin, Eytan

    Environmental Stresses Disrupt Telomere Length Homeostasis Gal Hagit Romano1,2,3. , Yaniv Harari1, and that a carefully regulated homeostasis may become markedly deregulated in opposing directions in response. (2013) Environmental Stresses Disrupt Telomere Length Homeostasis. PLoS Genet 9(9): e1003721. doi:10

  2. Largemouth Bass Fishery Responses to Length Limits

    E-print Network

    Wilde, Gene

    MANAGEMENT Largemouth Bass Fishery Responses to Length Limits By Gene R. Wilde ABSTRACT I compiled and manipulation of freshwater game fishes. Although various length limits have been used to manage freshwater on the theoretical results Gene R. Wilde is an assistantprofessorin the Depart- ment ofRange, Wildlife, and Fisheries

  3. Self-diffusion of Rod-like Viruses Through Smectic Layer

    E-print Network

    M. Paul Lettinga; Eric Grelet

    2007-10-31

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

  4. 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

  5. Global Optimization by Adapted Diffusion

    E-print Network

    Poliannikov, Oleg V.

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

  6. 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.

  7. Tungsten diffusion in olivine

    NASA Astrophysics Data System (ADS)

    Cherniak, D. J.; Van Orman, J. A.

    2014-03-01

    Diffusion of tungsten has been characterized in synthetic forsterite and natural olivine (Fo90) under dry conditions. The source of diffusant was a mixture of magnesium tungstate and olivine powders. Experiments were prepared by sealing the source material and polished olivine under vacuum in silica glass ampoules with solid buffers to buffer at NNO or IW. Prepared capsules were annealed in 1 atm furnaces for times ranging from 45 min to several weeks, at temperatures from 1050 to 1450 °C. Tungsten distributions in the olivine were profiled by Rutherford Backscattering Spectrometry (RBS). The following Arrhenius relation is obtained for W diffusion in forsterite: D=1.0×10-8exp(-365±28 kJ mol/RT) m s Diffusivities for the synthetic forsterite and natural Fe-bearing olivine are similar, and tungsten diffusion in olivine shows little dependence on crystallographic orientation or oxygen fugacity. The slow diffusivities measured for W in olivine indicate that Hf-W ages in olivine-metal systems will close to diffusive exchange at higher temperatures than other chronometers commonly used in cosmochronology, and that tungsten isotopic signatures will be less likely to be reset by subsequent thermal events.

  8. Diffusion Flame Stabilization

    NASA Technical Reports Server (NTRS)

    Takahashi, Fumiaki; Katta, Viswanath R.

    2007-01-01

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

  9. Diffusion Flame Stabilization

    NASA Technical Reports Server (NTRS)

    Takahashi, Fumiaki; Katta, V. R.

    2006-01-01

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

  10. Instabilities and patterns in coupled reaction-diffusion layers.

    PubMed

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

    2012-02-01

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

  11. Cation Diffusion in Fluorapatite

    NASA Astrophysics Data System (ADS)

    Cherniak, D. J.

    2002-12-01

    Diffusion of manganese and uranium has been characterized in natural and synthetic fluorapatite under dry conditions. The source of diffusant for Mn experiments were mixtures of ground synthetic or natural fluorapatite and MnO powder, heated in sealed silica glass capsules prior to diffusion anneals. Mn experiments were run by sealing source and apatite in silica glass capsules under vacuum, and annealing capsules in 1 atm furnaces for times ranging from thirty minutes to a few months, at temperatures from 650 to 1050°C. The Mn distributions in the apatite were profiled by Rutherford Backscattering Spectrometry (RBS). The following Arrhenius relation is obtained for Mn diffusion in natural Durango fluorapatite, for diffusion parallel to c: DMn = 5.4x10-7exp(-288 kJ mol-1/RT)m2sec-1. Mn diffusion normal to c appears to be similar to diffusion parallel to c, and diffusivities in natural and synthetic fluorapatite are the same within experimental uncertainties. Uranium diffusion experiments were run with a U-doped microcrystalline apatite source, made through solid-state reaction of UO2, CaF2 and Ca3(PO4)2 under buffered (NNO) conditions. The source and apatite specimens were loaded into Pt capsules, then sealed under vacuum in silica glass capsules with a solid buffer (NNO). Preliminary results over the temperature range 1150-1250°C yield the following Arrhenius relation: DU = 1.4x10-2exp(-511 kJ mol-1/RT)m2sec-1. Diffusivities of Mn are comparable to those of Sr (Cherniak and Ryerson, 1993), and slightly slower than Pb (Cherniak et al., 1991) in apatite. The ionic radii for divalent Mn, Sr, and Pb are 0.90, 1.21 and 1.23 Å, respectively, in 7-fold coordination (Shannon, 1976), and 1.00, 1.31, and 1.35 Å in 9-fold. The similar diffusion rates for Sr and Mn, despite their significant differences in cationic radii, suggest that cation size does not exert strong influence on diffusion of divalent cations in apatite, a finding consistent with that observed for the trivalent REE. Cation charge, however, does seem to more significantly influence diffusivities in apatite. U diffusion is about 4 orders of magnitude slower than Mn diffusion, and about 2 orders of magnitude slower than REE diffusion (Cherniak, 2000). Further, these results suggest that the activation energy for U diffusion is significantly higher than those for divalent cations or trivalent REE. Cherniak et al. (1991) GCA 55, 1663-1673; Cherniak and Ryerson (1993) GCA 57, 4653-4662; Cherniak (2000) GCA 64, 3871-3885; Shannon (1976) Acta Cryst. A32, 751-767.

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

    NASA Astrophysics Data System (ADS)

    Machguth, H.; Huss, M.

    2014-09-01

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

  13. Neural Processing of Acoustic Duration and Phonological German Vowel Length: Time Courses of Evoked Fields in Response to Speech and Nonspeech Signals

    ERIC Educational Resources Information Center

    Tomaschek, Fabian; Truckenbrodt, Hubert; Hertrich, Ingo

    2013-01-01

    Recent experiments showed that the perception of vowel length by German listeners exhibits the characteristics of categorical perception. The present study sought to find the neural activity reflecting categorical vowel length and the short-long boundary by examining the processing of non-contrastive durations and categorical length using MEG.…

  14. Load Diffusion in Composite and Smart Structures

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

  15. Research on the aerodynamics of intermediate turbine diffusers

    NASA Astrophysics Data System (ADS)

    Göttlich, Emil

    2011-05-01

    Intermediate turbine diffusers represent the flow path between the high pressure and the low pressure turbine of a high-bypass ratio turbofan aero engine. Caused by the different rotational speeds of high and low pressure spool, these components have to diffuse and guide the flow safely to a larger diameter without disturbances or boundary layer separations. The large radial offset between in- and outlet of intermediate turbine diffusers leads to a pronounced S-shape. The trend for further increased bypass ratios will require more attention to this component since its shape influences the overall weight of engine and nacelle considerably. The complicated aerodynamics of these annular ducts has to be understood to realize short S-shaped diffuser designs. This article tries to review the flow evolution through intermediate turbine diffusers and discusses the influence of the different effects in a systematic way. Investigations by various researchers are presented and test turbine rigs for experiments under engine realistic duct inlet conditions are described. Special focus is laid on different measures for the designer to produce more aggressive diffuser layouts whilst keeping the losses low. The application of flow control, shape optimization and endwall contouring are promising actions to shorten the diffuser length and, furthermore, to gain an engine weight reduction. The paper ends with a discussion of new design concepts for turbine ducts as well as for future engine architectures. It can be concluded that intermediate turbine diffusers will become a key component for keeping the overall engine weight and fuel burn low.

  16. Sexual dimorphism in foot length ratios among North Indian adolescents.

    PubMed

    Krishan, Kewal; Kanchan, Tanuj; Passi, Neelam; DiMaggio, John A

    2015-11-01

    Determination of sex along with other parameters of identification like stature, age and ancestry is one of the foremost criteria in establishing the biological profile of an individual. The present study was conducted to analyze the sex differences in the foot length ratios in a North Indian adolescent population. The study was conducted on 149 females and 154 males aged from 13 to 18 years. Foot length measurements were taken from pternion to the most anterior part of each toe and designated as T1, T2, T3, T4, and T5 respectively for first to fifth toes on both the feet in each participant using standard methods and techniques. A total of ten ratios (T1:T2, T1:T3, T1:T4, T1:T5, T2:T3, T2:T4, T2:T5, T3:T4, T3:T5, and T4:T5) were thus, obtained and the same were analyzed for sex differences using Student's t-test. Stature was measured in each participant and Pearson's correlation coefficients were calculated to find the correlation between various foot length ratios, age and stature. Receiver Operating Characteristic (ROC) curve was employed to test the sexing accuracy of the variables. P-value of less than 0.05 was considered as statistically significant. Foot length dimensions from each toe (T1 to T5) and stature were found to be significantly higher in males than females. The foot length ratios did not show any statistically significant correlation with stature. Statistically significant sex differences were exhibited by ratios between T1 and T2 (p = 0.002), T1 and T3 (p = 0.001), T1 and T4 (p < 0.001), T1 and T5 (p = 0.001), and T2 and T4 (p = 0.014). Maximum sex differences were evident for foot length ratio between T1 and T4 (63.4%), and minimum for the ratio between T2 and T4 (56.5%). Though foot length measurements are significantly larger in males, its utility in sex differentiation may be limited owing to its direct correlation with stature of an individual. It has been observed that the foot length ratios are independent of stature and thus, can be considered a better sex determinant since they are not influenced by the body built of an individual. Apart from ratio between T2 and T4, only the foot length ratios with reference to first toe (T1:T2, T1:T3, T1:T4, T1:T5) were found to exhibit significant sex-differences. The present research concludes that the foot length ratios exhibit sex differences in the study population. However, its utility in forensic investigations may be limited owing to the lower sexing accuracy of foot length ratios. PMID:26414875

  17. Effects of Gas Flow Rate on the Discharge Characteristics of a DC Excited Plasma Jet

    NASA Astrophysics Data System (ADS)

    Li, Xuechen; Jia, Pengying; Di, Cong; Bao, Wenting; Zhang, Chunyan

    2015-09-01

    A direct current (DC) source excited plasma jet consisting of a hollow needle anode and a plate cathode has been developed to form a diffuse discharge plume in ambient air with flowing argon as the working gas. Using optical and electrical methods, the discharge characteristics are investigated for the diffuse plasma plume. Results indicate that the discharge has a pulse characteristic, under the excitation of a DC voltage. The discharge pulse corresponds to the propagation process of a plasma bullet travelling from the anode to the cathode. It is found that, with an increment of the gas flow rate, both the discharge plume length and the current peak value of the pulsed discharge decrease in the laminar flow mode, reach their minima at about 1.5 L/min, and then slightly increase in the turbulent mode. However, the frequency of the pulsed discharge increases in the laminar mode with increasing the argon flow rate until the argon flow rate equals to about 1.5 L/min, and then slightly decreases in the turbulent mode. supported by National Natural Science Foundation of China (Nos. 10805013, 11375051), Funds for Distinguished Young Scientists of Hebei Province, China (No. A2012201045), Department of Education for Outstanding Youth Project of China (No. Y2011120), and Youth Project of Hebei University of China (No. 2011Q14)

  18. Diffusion between evolving interfaces

    E-print Network

    Janne Juntunen; Juha Merikoski

    2010-11-19

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

  19. Adaptive multigroup radiation diffusion

    E-print Network

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

    2005-01-01

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

  20. Hereditary Diffuse Gastric Cancer

    MedlinePLUS

    ... with the syndrome is recommended. What are the estimated cancer risks associated with HDGC? Not everyone who ... the lifetime risk for diffuse gastric cancer is estimated to be 70% to 80% for men and ...

  1. Patterning with Diffusion Barriers.

    PubMed

    Miller, Michael A

    2015-11-23

    Notch signaling instructs equivalent cells to form precise differentiation patterns. In this issue of Developmental Cell, Cinquin et al. (2015) characterize diffusion barriers that enhance Notch patterning within the Caenorhabditis elegans gonad. PMID:26609951

  2. Dislocation nucleation: Diffusive origins

    NASA Astrophysics Data System (ADS)

    Li, Ju

    2015-07-01

    A growing body of evidence suggests that nucleation of a first dislocation in a pristine crystal is associated with a diffusion-controlled process. Understanding this is critical for strain-engineered devices at ultrahigh stresses.

  3. Hydrogen Diffusion in Forsterite

    NASA Astrophysics Data System (ADS)

    Demouchy, S.; Mackwell, S.

    2002-12-01

    Physical and chemical properties of Earth's mantle are readily modified by interaction with volatiles, such as water. Thus, characterization of solubility and kinetics of incorporation for water in nominally anhydrous minerals is important in order to understand the behavior of Earth's interior under hydrous conditions. Experimental studies on the olivine-water system indicate that significant amounts of OH can dissolve within olivine as point defects (Bell and Rossman, 1992; Kohlstedt et al. 1996). Extending Kohlstedt and Mackwell's (1998) work, our study concerns the kinetics of hydrogen transport in the iron-free olivine-water system. This study is based on hydrogenation of forsterite samples during piston-cylinder and TZM cold-seal vessel experiments. We use infrared analyses in order to constrain the speciation of the mobile water-derived defects in forsterite single-crystal sample, and the rates of diffusion of such species under uppermost mantle conditions (0.2 to 1.5 GPa, 900 to 1100° C). Hydrogen defect transport in single crystals of forsterite is investigated for diffusion parallel to each crystallographic axis. Defect diffusivities are obtained by fitting a diffusion law to the OH content as a function of position in the sample. Our current results indicate that incorporation of hydroxyl species into iron-free olivine is a one-stage process with hydrogen diffusion linked to magnesium vacancy self-diffusion DV, such that DV = D~/3 = 10-12 m2/s at 1000° C parallel to [001], where D~ represents the chemical diffusivity. Those diffusion rates are slightly lower than in iron-bearing olivine for the same incorporation mechanism. The different concentration profiles show a clear anisotropy of diffusion, with fastest diffusion parallel to [001] as in iron-bearing olivine. Thus, while hydrogen solubilities are dependent on iron content, the rate of incorporation of water-derived species in olivine is not strongly coupled to the concentration of iron. This study is supported financially by the EU through the Human Potential Programme HPRN-CT-2000-00056: TMR HydroSpec. 1. Bell D. R. and Rossman G. R. (1992). Water in Earth's Mantle. The Role of Nominally Anhydrous Minerals. Science, 255, 1391-1397. 2. Kohlstedt D. L., Keppler H. and Rubie D. C. (1996) Solubility of Water in ?, ? > and ? phases of (Mg,Fe)2=SiO4. Contributions to Mineralogy and Petrology, 123, 345-357. 3. Kohlstedt D. L. and Mackwell S. J. (1998). Diffusion of Hydrogen and Intrinsic Point Defects in Olivine. Zeitschrift f\\x81r Physikalische Chemie, 207,147-162.

  4. Effect of Minimal lengths on Electron Magnetism

    E-print Network

    Khireddine Nouicer

    2007-07-13

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

  5. Scattering lengths of calcium and barium isotopes

    E-print Network

    U. Dammalapati; L. Willmann; S. Knoop

    2011-10-25

    We have calculated the s-wave scattering length of all the even isotopes of calcium (Ca) and barium (Ba), in order to investigate the prospect of Bose-Einstein condensation (BEC). For Ca we have used an accurate molecular potential based on detailed spectroscopic data. Our calculations show that Ca does not provide other isotopes alternative to the recently Bose condensed 40Ca that suffers strong losses because of a very large scattering length. For Ba we show by using a model potential that the even isotopes cover a broad range of scattering lengths, opening the possibility of BEC for at least one of the isotopes.

  6. Scattering lengths of calcium and barium isotopes

    SciTech Connect

    Dammalapati, U.; Willmann, L.; Knoop, S.

    2011-11-15

    We have calculated the s-wave scattering length of all the even isotopes of calcium (Ca) and barium (Ba) in order to investigate the prospect of Bose-Einstein condensation (BEC). For Ca we have used an accurate molecular potential based on detailed spectroscopic data. Our calculations show that Ca does not provide other isotopes alternative to the recently Bose condensed {sup 40}Ca that suffers strong losses because of a very large scattering length. For Ba we show by using a model potential that the even isotopes cover a broad range of scattering lengths, opening the possibility of BEC for at least one of the isotopes.

  7. Sub-picosecond electron bunch length measurement

    SciTech Connect

    Settakorn, C.; Hernandez, M.; Wiedemann, H.

    1997-08-01

    A subpicosecond electron bunch length measuring system has been developed at the SUNSHINE facility. The method is based on an autocorrelation technique in the frequency domain utilizing the coherent radiation emitted from the electron bunch at wavelengths equal and longer than the bunch length. The radiation spectrum is the Fourier transform of the electron bunch distribution and measuring this spectrum in a far-infrared Michelson interferometer allows the determination of the bunch length down to the femto-second regime. The experimental setup and measurement of subpicosecond electron pulses including possible improvements to maximize the bunch information available from an interferogram will be described.

  8. Nodal Diffusion & Transport Theory

    Energy Science and Technology Software Center (ESTSC)

    1992-02-19

    DIF3D solves multigroup diffusion theory eigenvalue, adjoint, fixed source, and criticality (concentration, buckling, and dimension search) problems in 1, 2, and 3-space dimensions for orthogonal (rectangular or cylindrical), triangular, and hexagonal geometries. Anisotropic diffusion theory coefficients are permitted. Flux and power density maps by mesh cell and regionwise balance integrals are provided. Although primarily designed for fast reactor problems, upscattering and internal black boundary conditions are also treated.

  9. Multispecies diffusion models: A study of uranyl species diffusion

    SciTech Connect

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

    2011-12-14

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

  10. Diffusion Maps for Changing Data Diffusion Maps for Changing Data

    E-print Network

    Hirn, Matthew

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

  11. Diffusion: Diffusive initial value problems and how to solve them

    E-print Network

    Spiegelman, Marc W.

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

  12. Diffusion Maps for Changing Data Diffusion Maps for Changing Data

    E-print Network

    Hirn, Matthew

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

  13. Diffusion Maps for Changing Data Diffusion Maps for Changing Data

    E-print Network

    Hirn, Matthew

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

  14. Diffusion Maps for Changing Data Diffusion Maps for Changing Data

    E-print Network

    Hirn, Matthew

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

  15. Diffusion Maps for Changing Data Diffusion Maps for Changing Data

    E-print Network

    Hirn, Matthew

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

  16. Revisiting Key Schedule's Diffusion In Relation With Round Function's Diffusion

    E-print Network

    International Association for Cryptologic Research (IACR)

    Revisiting Key Schedule's Diffusion In Relation With Round Function's Diffusion Jialin Huang that the key schedules poorly distribute key bits in the diffusion path of round function. This reminds us of the importance of the diffusion's relation between key schedule and round function. We present new cryptanalysis

  17. Diffusion Maps for Changing Data Diffusion Maps for Changing Data

    E-print Network

    Hirn, Matthew

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

  18. Diffusion Maps for Changing Data Diffusion Maps for Changing Data

    E-print Network

    Hirn, Matthew

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

  19. Enzyme localization, crowding, and buffers collectively modulate diffusion-influenced signal transduction: Insights from continuum diffusion modeling

    NASA Astrophysics Data System (ADS)

    Kekenes-Huskey, Peter M.; Eun, Changsun; McCammon, J. A.

    2015-09-01

    Biochemical reaction networks consisting of coupled enzymes connect substrate signaling events with biological function. Substrates involved in these reactions can be strongly influenced by diffusion "barriers" arising from impenetrable cellular structures and macromolecules, as well as interactions with biomolecules, especially within crowded environments. For diffusion-influenced reactions, the spatial organization of diffusion barriers arising from intracellular structures, non-specific crowders, and specific-binders (buffers) strongly controls the temporal and spatial reaction kinetics. In this study, we use two prototypical biochemical reactions, a Goodwin oscillator, and a reaction with a periodic source/sink term to examine how a diffusion barrier that partitions substrates controls reaction behavior. Namely, we examine how conditions representative of a densely packed cytosol, including reduced accessible volume fraction, non-specific interactions, and buffers, impede diffusion over nanometer length-scales. We find that diffusion barriers can modulate the frequencies and amplitudes of coupled diffusion-influenced reaction networks, as well as give rise to "compartments" of decoupled reactant populations. These effects appear to be intensified in the presence of buffers localized to the diffusion barrier. These findings have strong implications for the role of the cellular environment in tuning the dynamics of signaling pathways.

  20. Nitrogen diffusion in hafnia and the impact of nitridation on oxygen and hydrogen diffusion: A first-principles study

    SciTech Connect

    Sathiyanarayanan, Rajesh E-mail: rajesh.sathiyanarayanan@gmail.com; Pandey, R. K.; Murali, K. V. R. M.

    2015-01-21

    Using first-principles simulations, we have computed incorporation energies and diffusion barriers of ammonia, the nitrogen molecule and atomic nitrogen in monoclinic hafnia (m-HfO{sub 2}). Our calculations show that ammonia is likely to dissociate into an NH{sub 2} molecular unit, whereas the nitrogen molecule remains as a molecule either in the interstitial space or at an oxygen lattice site. The lowest energy pathway for the diffusion of atomic nitrogen interstitials consists of the hopping of the nitrogen interstitial between neighboring three-coordinated lattice oxygen atoms that share a single Hf atom, and the barrier for such hops is determined by a switching mechanism. The substitutional nitrogen atom shows a preference for diffusion through the doubly positive oxygen vacancy-mediated mechanism. Furthermore, we have investigated the impact of nitrogen atoms on the diffusion barriers of oxygen and hydrogen interstitials in m-HfO{sub 2}. Our results show that nitrogen incorporation has a significant impact on the barriers for oxygen and hydrogen diffusion: nitrogen atoms attract oxygen and hydrogen interstitials diffusing in the vicinity, thereby slowing down (reducing) their diffusion (diffusion length)

  1. Advanced manufacturing: Technology diffusion

    SciTech Connect

    Tesar, A.

    1995-12-01

    In this paper we examine how manufacturing technology diffuses rom the developers of technology across national borders to those who do not have the capability or resources to develop advanced technology on their own. None of the wide variety of technology diffusion mechanisms discussed in this paper are new, yet the opportunities to apply these mechanisms are growing. A dramatic increase in technology diffusion occurred over the last decade. The two major trends which probably drive this increase are a worldwide inclination towards ``freer`` markets and diminishing isolation. Technology is most rapidly diffusing from the US In fact, the US is supplying technology for the rest of the world. The value of the technology supplied by the US more than doubled from 1985 to 1992 (see the Introduction for details). History shows us that technology diffusion is inevitable. It is the rates at which technologies diffuse to other countries which can vary considerably. Manufacturers in these countries are increasingly able to absorb technology. Their manufacturing efficiency is expected to progress as technology becomes increasingly available and utilized.

  2. Transport diffusion in one dimensional molecular systems: Power law and validity of Fick's law

    NASA Astrophysics Data System (ADS)

    Xu, Zhi-cheng; Zheng, Dong-qin; Ai, Bao-quan; Hu, Bambi; Zhong, Wei-rong

    2015-10-01

    The transport diffusion in one-dimensional molecular systems is investigated through non-equilibrium molecular dynamics and Monte Carlo methods. We have proposed the power law relationship of the transport diffusion coefficient with the temperature, the mass and the transport length, D* ? T*m*-1L*?, where ? equals to 0.8 for small systems and zero for large systems. It is found that Fick's law is valid in long transport length but invalid in short transport length. Our results can provide a new perspective for understanding the microscopic mechanism of the molecular transport phenomena in low-dimensional systems.

  3. The synthesis-diffusion-degradation model explains Bicoid gradient formation in unfertilized eggs

    PubMed Central

    Drocco, J.A.; Wieschaus, E.F.; Tank, D.W.

    2012-01-01

    Precise formation of morphogen gradients is essential to the establishment of reproducible pattern in development. Mechanisms proposed for obtaining the requisite precision range from simple models with few parameters to more complex models involving many regulated quantities. The synthesis-diffusion-degradation (SDD) model is a relatively simple model explaining the formation of the Bicoid gradient in Drosophila melanogaster, in which the steady-state characteristic length of the gradient is determined solely by the rates of diffusion and degradation of the morphogen. In this work, we test the SDD model in unfertilized D. melanogaster eggs, which contain a single female pronucleus and lack the nuclear division cycles and other zygotic regulatory processes seen in fertilized eggs. Using two-photon live imaging as well as a novel method for quantitative imaging based on decorrelation of photoswitching waveforms, we find that the Bicoid gradient is longer and shallower in unfertilized eggs as compared to the gradient at the same time points in fertilized eggs. Using a means of measuring the Bicoid lifetime by conjugation to a photoconvertible fluorophore, we find that the lifetime is correspondingly longer in unfertilized eggs, providing qualitative and quantitative agreement with the predictions of the SDD model. PMID:23011646

  4. Substrate-mediated diffusion-induced growth of single-crystal nanowires.

    PubMed

    Mohammad, S Noor

    2009-11-28

    Theoretical investigations of the growth and growth rates of single-crystal nanowires (NWs) by vapor phase mechanisms have been carried out. Substrate-induced processes are assumed to dominate this growth. The modeling for growth takes adsorption, desorption, surface scattering, and diffusion into account. It takes into consideration also the retarding electric field arising from the scattering of the NW vapor species by both the substrate and the NW sidewalls. Growth characteristics under the influence of the retarding electric field have been studied. Competitive roles of adatom diffusivity and the electric field in the NW growth are elucidated. Influence of the growing NW length and the adatom impingement rate on the NW growth rate has been described. The effect of adatom collection area around each NW has been examined. The NW tapering and kinking have been explained. The fundamentals of the substrate induction and details of the growth parameters have been analyzed. The influence of foreign element catalytic agents in the vapor-liquid-solid mechanism has been presented. All these have led to the understanding and resolution of problems, controversies, and contradictions involving substrate-induced NW growths. PMID:19947700

  5. Diffusion in natural ilmenite

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

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

  6. Eddy stirring and horizontal diffusivity from Argo float observations: Geographic and depth variability

    NASA Astrophysics Data System (ADS)

    Cole, Sylvia T.; Wortham, Cimarron; Kunze, Eric; Owens, W. Brechner

    2015-05-01

    Stirring along isopycnals is a significant factor in determining the distribution of tracers within the ocean. Salinity anomalies on density surfaces from Argo float profiles are used to investigate horizontal stirring and estimate eddy mixing lengths. Eddy mixing length and velocity fluctuations from the ECCO2 global state estimate are used to estimate horizontal diffusivity at a 300 km scale in the upper 2000 m with near-global coverage. Diffusivity varies by over two orders of magnitude with latitude, longitude, and depth. In all basins, diffusivity is elevated in zonal bands corresponding to strong current regions, including western boundary current extension regions, the Antarctic Circumpolar Current, and equatorial current systems. The estimated mixing lengths and diffusivities provide an observationally based data set that can be used to test and constrain predictions and parameterizations of eddy stirring.

  7. Heterodyne interferometer with unequal path lengths

    SciTech Connect

    Kumar, Deepak; Bellan, Paul M.

    2006-08-15

    Laser interferometry is an extensively used diagnostic for plasma experiments. Existing plasma interferometers are designed on the presumption that the scene and reference beam path lengths have to be equal, a requirement that is costly in both the number of optical components and the alignment complexity. It is shown here that having equal path lengths is not necessary, instead, what is required is that the path length difference be an even multiple of the laser cavity length. This assertion has been verified in a heterodyne laser interferometer that measures typical line-average densities of {approx}10{sup 21}/m{sup 2} with an error of {approx}10{sup 19}/m{sup 2}.

  8. ULTRASHORT ELECTRON BUNCH LENGTH MEASUREMENTS AT DUVFEL.

    SciTech Connect

    GRAVES, W.S.; CARR, G.L.; DIMAURO, L.F.; DOYURAN, A.; HEESE, R.; JOHNSON, E.D.; NEUMAN, C.; RAKOWSKY, G.; ROSE, J.; RUDATI, J.; SHAFTAN, T.; SHEEHY, B.; SKARITKA, J.; YU, L.H.

    2001-06-18

    The DUVFEL electron linac is designed to produce sub-picosecond, high brightness electron bunches for driving a short wavelength FEL. Four experiments have been commissioned to address the challenge of accurately measuring bunch lengths on this timescale. In the frequency domain, a short 12 period undulator is used to produce both off-axis coherent emission and on-axis incoherent single-shot spectra. The total coherent infrared power scales inversely with bunch length and the spectral cutoff is an indication of bunch length. The density of power spikes in the single-shot visible spectrum may also be used to estimate bunch length. In the time domain, the linac accelerating sections and a bending magnet are used to implement the RF-zero phasing method, and a sub-picosecond streak camera is also installed. Beam measurements and comparisons of these methods are reported.

  9. Method of continuously determining crack length

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

  10. Word lengths are optimized for efficient communication

    E-print Network

    Piantadosi, Steven Thomas

    We demonstrate a substantial improvement on one of the most celebrated empirical laws in the study of language, Zipf's 75-y-old theory that word length is primarily determined by frequency of use. In accord with rational ...

  11. Carbon Nanotubes: Measuring Dispersion and Length

    SciTech Connect

    Fagan, Jeffrey A.; Bauer, Barry J.; Hobbie, Erik K.; Becker, Matthew L.; Hight-Walker, Angela; Simpson, Jeffrey R.; Chun, Jaehun; Obrzut, Jan; Bajpai, Vardhan; Phelan, Fred R.; Simien, Daneesh; Yeon Huh, Ji; Migler, Kalman B.

    2011-03-01

    Advanced technological uses of single-wall carbon nanotubes (SWCNTs) rely on the production of single length and chirality populations that are currently only available through liquid phase post processing. The foundation of all of these processing steps is the attainment of individualized nanotube dispersion in solution; an understanding of the collodial properties of the dispersed SWCNTs can then be used to designed appropriate conditions for separations. In many instances nanotube size, particularly length, is especially active in determining the achievable properties from a given population, and thus there is a critical need for measurement technologies for both length distribution and effective separation techniques. In this Progress Report, we document the current state of the art for measuring dispersion and length populations, including separations, and use examples to demonstrate the desirability of addressing these parameters.

  12. Study of a non-buoyant diffusion flame radiative characteristics 

    E-print Network

    Legros, Guillaume

    2003-12-09

    This study is a contribution to a project aiming to characterize a fire spreading in weightlessness. An ethylene burner across which an air flow leads to boundary layer type conditions is used. First experimental results ...

  13. CHARACTERISTICS OF TWO-DIMENSIONAL PARTICLE EDDY DIFFUSION INOFFICE SPACE

    EPA Science Inventory

    The paper discusses the development of a two-dimensional turbulentkinetic energy - dissipation rate (k-epsilon) turbulence model inthe form of vorticity and stream functions. his turbulence modelprovides the distribution of turbulent kinematic viscosity, used tocalculate the effe...

  14. Surface diffusion in reversed-phase liquid chromatography

    SciTech Connect

    Miyabe, Kanji; Guiochon, Georges A

    2010-01-01

    More than 40 years ago, Giddings pointed out in 'Dynamics of Chromatography' that surface diffusion should become an important research topic in the kinetics of chromatographic phenomena. However, few studies on surface diffusion in adsorbents used in chromatography were published since then. Most scientists use ordinary rate equations to study mass transfer kinetics in chromatography. They take no account of surface diffusion and overlook the significant contributions of this mass transfer process to chromatographic behavior and to column efficiency at high mobile phase flow rate. Only recently did the significance of surface diffusion in separation processes begin to be recognized in connection with the development of new techniques of fast flow, high efficiency chromatography. In this review, we revisit the reports on experimental data on surface diffusion and introduce a surface-restricted molecular diffusion model, derived as a first approximation for the mechanism of surface diffusion, on the basis of the absolute rate theory. We also explain how this model accounts for many intrinsic characteristics of surface diffusion that cannot properly be explained by the conventional models of surface diffusion.

  15. Process for fabricating continuous lengths of superconductor

    DOEpatents

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

    1998-01-01

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

  16. Electron Effective-Attenuation-Length Database

    National Institute of Standards and Technology Data Gateway

    SRD 82 NIST Electron Effective-Attenuation-Length Database (PC database, no charge)   This database provides values of electron effective attenuation lengths (EALs) in solid elements and compounds at selected electron energies between 50 eV and 2,000 eV. The database was designed mainly to provide EALs (to account for effects of elastic-eletron scattering) for applications in surface analysis by Auger-electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS).

  17. Role of pressure diffusion in non-homogeneous shear flows

    NASA Technical Reports Server (NTRS)

    Demuren, A. O.; Lele, S. K.; Durbin, P.

    1994-01-01

    A non-local model is presented for approximating the pressure diffusion in calculations of turbulent free shear and boundary layer flows. It is based on the solution of an elliptic relaxation equation which enables local diffusion sources to be distributed over lengths of the order of the integral scale. The pressure diffusion model was implemented in a boundary layer code within the framework of turbulence models based on both the kappa-epsilon-(bar)upsilon(exp 2) system of equations and the full Reynolds stress equations. Model computations were performed for mixing layers and boundary layer flows. In each case, the pressure diffusion model enabled the well-known free-stream edge singularity problem to be eliminated. There was little effect on near-wall properties. Computed results agreed very well with experimental and DNS data for the mean flow velocity, the turbulent kinetic energy, and the skin-friction coefficient.

  18. White matter changes with age utilizing quantitative diffusion MRI

    PubMed Central

    Laidlaw, David H.; Conturo, Thomas E.; Hogan, Joseph; Zhao, Yi; Luo, Xi; Correia, Stephen; Cabeen, Ryan; Lane, Elizabeth M.; Heaps, Jodi M.; Bolzenius, Jacob; Salminen, Lauren E.; Akbudak, Erbil; McMichael, Amanda R.; Usher, Christina; Behrman, Ashley; Paul, Robert H.

    2014-01-01

    Objective: To investigate the relationship between older age and mean cerebral white matter fiber bundle lengths (FBLs) in specific white matter tracts in the brain using quantified diffusion MRI. Methods: Sixty-three healthy adults older than 50 years underwent diffusion tensor imaging. Tractography tracings of cerebral white matter fiber bundles were derived from the diffusion tensor imaging data. Results: Results revealed significantly shorter FBLs in the anterior thalamic radiation for every 1-year increase over the age of 50 years. Conclusions: We investigated the effects of age on FBL in specific white matter tracts in the brains of healthy older individuals utilizing quantified diffusion MRI. The results revealed a significant inverse relationship between age and FBL. Longitudinal studies of FBL across a lifespan are needed to examine the specific changes to the integrity of white matter. PMID:24928121

  19. Diffusion of water in bentonite clay: Neutron scattering study

    NASA Astrophysics Data System (ADS)

    Sharma, V. K.; Prabhudesai, S. A.; Dessai, R. Raut; Erwin Desa, J. A.; Mitra, S.; Mukhopadhyay, R.

    2013-02-01

    Diffusion of water confined in natural bentonite clay is studied using the quasi-elastic neutron scattering (QENS) technique. X-ray diffraction shows a well-defined crystalline structure of the clay with an interlayer spacing of 13 Å. The QENS experiment has been carried out on hydrated as well as dehydrated clay at 300 K. Significant quasi-elastic broadening was observed in case of hydrated bentonite clay whereas dehydrated clay did not show any broadening over the instrument resolution. Analysis of QENS data reveals that diffusion of water occurs through jump diffusion characterized by random distribution of jump lengths. Diffusion of water in clay is found to be hindered vis a vis bulk water.

  20. Pyrrole copolymers with enhanced ion diffusion rates for lithium batteries

    SciTech Connect

    Calvert, P.; Gardlund, Z.; Huntoon, T.; Hall, H.K.; Padias, A.

    1998-07-01

    Copolymers of pyrrole with a polyether-substituted pyrrole were tested as cathodes for lithium batteries. The charge and discharge characteristics showed that anion transport was much faster in the copolymer than in polypyrrole. As a result these electrodes store and release much more charge at higher current densities but are similar to polypyrrole at low currents. Pulse and relaxation measurements of the ion diffusion showed that this difference was due to a ten-fold increase in the anion diffusion coefficient.

  1. Reduced fetal telomere length in gestational diabetes.

    PubMed

    Xu, Jian; Ye, Junyi; Wu, Yanting; Zhang, Hong; Luo, Qiong; Han, Cong; Ye, Xiaoqun; Wang, Hanzhi; He, Jing; Huang, Hefeng; Liu, Yun; Dong, Minyue

    2014-01-01

    Gestational diabetes mellitus (GDM) is an important complication of pregnancy that poses significant threats to women and their offspring. Telomere length shortens as cellular damage increases and is associated with metabolic diseases. Telomere length in fetal leucocytes was determined in 82 infants of women with GDM (N = 82) and 65 normal pregnant women (N = 65). Women with preeclampsia (N = 45) and gestational hypertension (N = 23) were also studied. In the GDM group, telomere length was significantly shorter than normal pregnancy (P = 0.028), but there were no significant differences in fetal telomere length between preeclampsia and normal pregnancy (P = 0.841) and between gestational hypertension and normal pregnancy (P = 0.561). Regression analysis revealed that fetal telomere length was significantly associated with intrauterine exposure to GDM (P = 0.027 after adjustment for maternal age, gestational age at delivery, birth weight and fetal gender). Shortened telomere length may increase the risk of metabolic diseases in adulthood of GDM offspring. PMID:24465936

  2. Control of cell length in Bacillus subtilis.

    PubMed Central

    Sargent, M G

    1975-01-01

    During inhibition of deoxyribonucleic acid synthesis in Bacillus subtilis 168 Thy-minus Tryp-minus, the rate of length extension is constant. A nutritional shift-up during thymine starvation causes an acceleration in the linear rate of length extension. During a nutritional shift-up in the presence of thymine, the rate of length extension gradually increases, reaching a new steady state at about 50 min before the new steady-state rate of cell division is reached. The steady-state rates of nuclear division and length extension are reached at approximately the same time. The ratio of average cell length to numbers of nuclei per cell in exponential cultures is constant over a fourfold range of growth rates. These observations are consistent with: (i) surface growth zones which operate at a constant rate of length extension under any one growth condition, but which operate at an absolute rate proportional to the growth rate of the culture, (ii) a doubling in number of growth zones at nuclear segregation, and (iii) a requirement for deoxyribonucleic acid replication for the doubling in a number of sites. Images PMID:806582

  3. Dynamical Length-Regulation of Microtubules

    NASA Astrophysics Data System (ADS)

    Melbinger, Anna; Reese, Louis; Frey, Erwin

    2012-02-01

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

  4. Diffusion Driven Combustion Waves in Porous Media

    NASA Technical Reports Server (NTRS)

    Aldushin, A. P.; Matkowsky, B. J.

    2000-01-01

    Filtration of gas containing oxidizer, to the reaction zone in a porous medium, due, e.g., to a buoyancy force or to an external pressure gradient, leads to the propagation of Filtration combustion (FC) waves. The exothermic reaction occurs between the fuel component of the solid matrix and the oxidizer. In this paper, we analyze the ability of a reaction wave to propagate in a porous medium without the aid of filtration. We find that one possible mechanism of propagation is that the wave is driven by diffusion of oxidizer from the environment. The solution of the combustion problem describing diffusion driven waves is similar to the solution of the Stefan problem describing the propagation of phase transition waves, in that the temperature on the interface between the burned and unburned regions is constant, the combustion wave is described by a similarity solution which is a function of the similarity variable x/square root of(t) and the wave velocity decays as 1/square root of(t). The difference between the two problems is that in the combustion problem the temperature is not prescribed, but rather, is determined as part of the solution. We will show that the length of samples in which such self-sustained combustion waves can occur, must exceed a critical value which strongly depends on the combustion temperature T(sub b). Smaller values of T(sub b) require longer sample lengths for diffusion driven combustion waves to exist. Because of their relatively small velocity, diffusion driven waves are considered to be relevant for the case of low heat losses, which occur for large diameter samples or in microgravity conditions, Another possible mechanism of porous medium combustion describes waves which propagate by consuming the oxidizer initially stored in the pores of the sample. This occurs for abnormally high pressure and gas density. In this case, uniformly propagating planar waves, which are kinetically controlled, can propagate, Diffusion of oxidizer decreases the wave velocity. In addition to the reaction and diffusion layers, the uniformly propagating wave structure includes a layer with a pressure gradient, where the gas motion is induced by the production or consumption of the gas in the reaction as well as by thermal expansion of the gas. The width of this zone determines the scale of the combustion wave in the porous medium.

  5. Chiral diffusion of rotary nanomotors

    NASA Astrophysics Data System (ADS)

    Nourhani, Amir; Lammert, Paul E.; Borhan, Ali; Crespi, Vincent H.

    2013-05-01

    Neither a purely deterministic rotary nanomotor nor a purely orientational diffuser exhibits long-term translational motion, but coupling rotation to orientational diffusion yields translational diffusion. We demonstrate that this effective translational diffusion can easily dominate the ordinary thermal translational diffusion for experimentally relevant nanomotors, and that this effective diffusion is chiral. Unpowered chiral particles do not exhibit chiral diffusion, but a nanorotor has both handedness and an instantaneous direction of powered motion, thus—unlike an unpowered particle—its diffusional motion can distinguish left from right.

  6. Diffusion Time-Scale of Porous Pressure-Sensitive Paint

    NASA Technical Reports Server (NTRS)

    Liu, Tianshu; Teduka, Norikazu; Kameda, Masaharu; Asai, Keisuke

    2001-01-01

    Pressure-sensitive paint (PSP) is an optical pressure sensor that utilizes the oxygen quenching of luminescence. PSP measurements in unsteady aerodynamic flows require fast time response of the paint. There are two characteristic time-scales that are related to the time response of PSP. One is the luminescent lifetime representing an intrinsic physical limit for the achievable temporal resolution of PSP. Another is the time-scale of oxygen diffusion across the PSP layer. When the time-scale of oxygen diffusion is much larger than the luminescent lifetime, the time response of PSP is controlled by oxygen diffusion. In a thin homogenous polymer layer where diffusion is Fickian, the oxygen concentration 1021 can be described by the diffusion equation in one-dimension.

  7. Information entropy of diffusion processes on complex networks

    NASA Astrophysics Data System (ADS)

    Zhang, Zhanli

    2014-06-01

    Diffusion processes have been widely investigated to understand some essential features of complex networks, and have attracted much attention from physicists, statisticians and computer scientists. In order to understand the evolution of the diffusion process and design the optimal routing strategy according to the maximal entropic diffusion on networks, we propose the information entropy comprehending the structural characteristics and information propagation on the network. Based on the analysis of the diffusion process, we analyze the coupling impact of the structural factor and information propagating factor on the information entropy, where the analytical results fit well with the numerical ones on scale-free complex networks. The information entropy can better characterize the complex behaviors on networks and provides a new way to deepen the understanding of the diffusion process.

  8. Correlation Length of Energy-Containing Structures in the Base of the Solar Corona

    NASA Astrophysics Data System (ADS)

    Abramenko, V.; Zank, G. P.; Dosch, A. M.; Yurchyshyn, V.

    2013-12-01

    An essential parameter for models of coronal heating and fast solar wind acceleration that relay on the dissipation of MHD turbulence is the characteristic energy-containing length of the squared velocity and magnetic field fluctuations transverse to the mean magnetic field inside a coronal hole (CH) at the base of the corona. The characteristic length scale defines directly the heating rate. Rather surprisingly, almost nothing is known observationally about this critical parameter. Currently, only a very rough estimate of characteristic length was obtained based on the fact that the network spacing is about 30000 km. We attempted estimation of this parameter from observations of photospheric random motions and magnetic fields measured in the photosphere inside coronal holes. We found that the characteristic length scale in the photosphere is about 600-2000 km, which is much smaller than that adopted in previous models. Our results provide a critical input parameter for current models of coronal heating and should yield an improved understanding of fast solar wind acceleration. Fig. 1-- Plotted is the natural logarithm of the correlation function of the transverse velocity fluctuations u^2 versus the spatial lag r for the two CHs. The color code refers to the accumulation time intervals of 2 (blue), 5 (green), 10 (red), and 20 (black) minutes. The values of the Batchelor integral length ? the correlation length ? and the e-folding length L in km are shown. Fig. 2-- Plot of the natural logarithm of the correlation function of magnetic fluctuations b^2 versus the spatial lag r. The insert shows this plot with linear axes.

  9. Characteristics of Microbursts

    NASA Astrophysics Data System (ADS)

    Crew, A. B.; Spence, H. E.

    2012-12-01

    The dynamics of the Earth's radiation belts are governed by the interplay between the various source and loss terms. Electron microbursts represent a particular form of electron loss through precipitation to the atmosphere. The total loss from each individual microburst is relatively small; however microbursts are often seen in very large numbers. Accordingly, the total loss due to electron microbursts is a still unresolved question. Taking advantage of the length and continuity of microburst observations from SAMPEX, I will present analysis of the characteristics of ~685,000 electron (> 1 MeV) microburst events. Examining the event frequency, intensity, and duration I will show that microbursts are typically seen on the dawnside from L of approximately 4 to 7, with event frequencies that track with geomagnetic indices such as AE. Individual microburst intensities typically follow power-law like distributions and peak in power close to dawn, and typical event durations are ~100ms. Using the event characteristics and an epoch analysis of over 200 storm intervals from this period we examine the differences in microburst precipitation across different storms as well as provide estimates and constraints on the total effectiveness of microburst precipitation as a form of radiation belt loss. We hope to use the estimates to contextualize results from the upcoming RBSP mission.

  10. LLNL SMP Light Diffuser Fabrication and Preliminary Data

    SciTech Connect

    Small IV, W

    2006-06-02

    We are developing a cylindrical light diffuser using shape memory polymer (SMP) whose diameter, length, stiffness, and diffusion profile can be tailored to suit a particular application. The cylindrical SMP diffuser is made by casting SMP around the end of a glass optical fiber using a teflon tube as the casting mold, and abrading the cured SMP surface to cause the light to leak radially outward. The inner diameter of the casting tube is slightly larger than the fiber diameter. A smaller teflon tube is positioned over the fiber (between the fiber and the casting tube) to approximately center the fiber tip in the casting tube. As the SMP cures, it bonds with the optical fiber, creating a strong joint without the need for additional adhesives or mechanical fixtures. A close-up of the SMP-fiber joint and the finished SMP diffuser are shown in Fig.1. The SMP formulation (developed in-house) was specifically designed to be optically transparent in the visible and near-infrared regions; the spectral absorption of the SMP is shown in Fig. 2. The low absorption is important because (1) it allows the light to travel the length of the diffuser without suffering excessive loss due to absorption and (2) it permits delivery of up to 7 W (300 {micro}m SMP rod on 100 {micro}m core multimode fiber) of laser power into the diffuser without damaging the diffuser. SMP is a good wave guiding material with a refractive index of approximately 1.5. Also, the SMP stiffness can be tailored from stiff (e.g. acrylic, Ea {approx} 10{sup 9} Pa) to very flexible (e.g. silicon rubber, Ea {approx} 10{sup 6} Pa). Finally, since SMP can self-actuate, the SMP diffuser could be designed to actuate into a shape other than a straight rod (e.g. 2D or 3D coil).

  11. Catastrophe in diffusion-controlled annihilation dynamics: general scaling properties

    NASA Astrophysics Data System (ADS)

    Shipilevsky, Boris M.

    2015-11-01

    We present a systematic analytical and numerical study of the annihilation catastrophe phenomenon which develops in an open system, where species A and B diffuse from the bulk of restricted medium and die on its surface (desorb) by the reaction A + B ? 0. This phenomenon arises in the diffusion-controlled limit as a result of self-organizing explosive growth (drop) of the surface concentrations of, respectively, slow and fast particles (concentration explosion) and manifests itself in the form of an abrupt singular jump of the desorption flux relaxation rate. In the recent work [B.M. Shipilevsky, Phys. Rev. E 76, 031126 (2007)] a closed scaling theory of catastrophe development has been given for the asymptotic limit when the characteristic time scale of explosion becomes much less than the characteristic time scales of diffusion of slow and fast particles at an arbitrary ratio of their diffusivities 0 < p < 1. In this paper we consider the behavior of the system at strong difference of species diffusivities p ? 1 and reveal a rich general pattern of catastrophe development for an arbitrary ratio of the characteristic time scales of explosion and fast particle diffusion. As striking results we find remarkable scaling properties of catastrophe evolution at the crossover between two limiting regimes with radically different dynamics.

  12. Aerodynamic characteristics and thermal structure of nonpremixed reacting swirling wakes at low Reynolds numbers

    SciTech Connect

    Huang, Rong F.; Yen, Shun C.

    2008-12-15

    The aerodynamic characteristics and thermal structure of uncontrolled and controlled swirling double-concentric jet flames at low Reynolds numbers are experimentally studied. The swirl and Reynolds numbers are lower than 0.6 and 2000, respectively. The flow characteristics are diagnosed by the laser-light-sheet-assisted Mie scattering flow visualization method and particle image velocimetry (PIV). The thermal structure is measured by a fine-wire thermocouple. The flame shapes, combined images of flame and flow, velocity vector maps, streamline patterns, velocity and turbulence distributions, flame lengths, and temperature distributions are discussed. The flow patterns of the no-control case exhibit an open-top, single-ring vortex sitting on the blockage disc with a jetlike swirling flow evolving from the central disc face toward the downstream area. The rotation direction and size of the near-disc vortex, as well as the flow properties, change in different ranges of annulus swirl number and therefore induce three characteristic flame modes: weak swirling flame, lifted flame, and turbulent reattached flame. Because the near-disc vortex is open-top, the radial dispersion of the fuel-jet fluids is not significantly enhanced by the annulus swirling flow. The flows of the reacting swirling double-concentric jets at such low swirl and Reynolds numbers therefore present characteristics of diffusion jet flames. In the controlled case, the axial momentum of the central fuel jet is deflected radially by a control disc placed above the blockage disc. This arrangement can induce a large near-disc recirculation bubble and high turbulence intensities. The enhanced mixing hence tremendously shortens the flame length and enlarges the flame width. (author)

  13. Diffuse peripheral odontogenic fibroma: report of 3 cases.

    PubMed

    Weber, A; van Heerden, W F; Ligthelm, A J; Raubenheimer, E J

    1992-02-01

    Since peripheral odontogenic fibroma (POF) is characteristically described as a solitary lesion and no diffuse POF had been reported in the literature, our cases should be considered as extremely unusual. Three diffuse cases of POF are described of which one case was seen in association with ocular and skin lesions. The question arises whether POF should be considered as a true odontogenic tumor rather than a diffuse hamartomatous lesion caused by uncontrolled induction of the gingiva. It is also possible that such lesions could be part of a yet undescribed syndrome. PMID:1556666

  14. [Diffusion Weighted Magnetic Resonance Imaging and its Application in Ophthalmology].

    PubMed

    Lindner, T; Langner, S; Paul, K; Pohlmann, A; Hadlich, S; Niendorf, T; Jünemann, A; Guthoff, R F; Stachs, O

    2015-12-01

    The value of diffusion-weighted magnet resonance imaging (DWI-MRI) has been demonstrated for an ever growing range of clinical indications. DWI is sensitive to the diffusion of water molecules and probes their random displacement within tissue. DWI provides both qualitative and quantitative information on tissue characteristics, e.g. tissue cellularity. This review provides an overview of diffusion-weighted imaging and its emerging applications in ophthalmology. The basic physics and technical foundations of DWI are introduced. The emerging applications of DWI are surveyed, particularly in diseases of the eye, orbit and optical nerve. PMID:26678901

  15. Rationalizing the Spatial Distribution of Mesoscale Eddy Diffusivity in Terms of Mixing Length Theory

    E-print Network

    Bates, Michael

    Observations and theory suggest that lateral mixing by mesoscale ocean eddies only reaches its maximum potential at steering levels, surfaces at which the propagation speed of eddies approaches that of the mean flow. Away ...

  16. Lateral Diffusion Length Changes in HgCdTe Detectors in a Proton Environment

    NASA Technical Reports Server (NTRS)

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

    2007-01-01

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

  17. Diffusion Influenced Adsorption Kinetics.

    PubMed

    Miura, Toshiaki; Seki, Kazuhiko

    2015-08-27

    When the kinetics of adsorption is influenced by the diffusive flow of solutes, the solute concentration at the surface is influenced by the surface coverage of solutes, which is given by the Langmuir-Hinshelwood adsorption equation. The diffusion equation with the boundary condition given by the Langmuir-Hinshelwood adsorption equation leads to the nonlinear integro-differential equation for the surface coverage. In this paper, we solved the nonlinear integro-differential equation using the Grünwald-Letnikov formula developed to solve fractional kinetics. Guided by the numerical results, analytical expressions for the upper and lower bounds of the exact numerical results were obtained. The upper and lower bounds were close to the exact numerical results in the diffusion- and reaction-controlled limits, respectively. We examined the validity of the two simple analytical expressions obtained in the diffusion-controlled limit. The results were generalized to include the effect of dispersive diffusion. We also investigated the effect of molecular rearrangement of anisotropic molecules on surface coverage. PMID:25969862

  18. Anomalous Diffusion Near Resonances

    SciTech Connect

    Sen, Tanaji; /Fermilab

    2010-05-01

    Synchro-betatron resonances can lead to emittance growth and the loss of luminosity. We consider the detailed dynamics of a bunch near such a low order resonance driven by crossing angles at the collision points. We characterize the nature of diffusion and find that it is anomalous and sub-diffusive. This affects both the shape of the beam distribution and the time scales for growth. Predictions of a simplified anomalous diffusion model are compared with direct simulations. Transport of particles near resonances is still not a well understood phenomenon. Often, without justification, phase space motion is assumed to be a normal diffusion process although at least one case of anomalous diffusion in beam dynamics has been reported [1]. Here we will focus on the motion near synchro-betatron resonances which can be excited by several means, including beams crossing at an angle at the collision points as in the LHC. We will consider low order resonances which couple the horizontal and longitudinal planes, both for simplicity and to observe large effects over short time scales. While the tunes we consider are not practical for a collider, nonetheless the transport mechanisms we uncover are also likely to operate at higher order resonances.

  19. Orbital Transfer Vehicle Engine Technology High Velocity Ratio Diffusing Crossover

    NASA Technical Reports Server (NTRS)

    Lariviere, Brian W.

    1992-01-01

    High speed, high efficiency head rise multistage pumps require continuous passage diffusing crossovers to effectively convey the pumped fluid from the exit of one impeller to the inlet of the next impeller. On Rocketdyne's Orbital Transfer Vehicle (OTV), the MK49-F, a three stage high pressure liquid hydrogen turbopump, utilizes a 6.23 velocity ratio diffusing crossover. This velocity ratio approaches the diffusion limits for stable and efficient flow over the operating conditions required by the OTV system. The design of the high velocity ratio diffusing crossover was based on advanced analytical techniques anchored by previous tests of stationary two-dimensional diffusers with steady flow. To secure the design and the analytical techniques, tests were required with the unsteady whirling characteristics produced by an impeller. A tester was designed and fabricated using a 2.85 times scale model of the MK49-F turbopumps first stage, including the inducer, impeller, and the diffusing crossover. Water and air tests were completed to evaluate the large scale turbulence, non-uniform velocity, and non-steady velocity on the pump and crossover head and efficiency. Suction performance tests from 80 percent to 124 percent of design flow were completed in water to assess these pump characteristics. Pump and diffuser performance from the water and air tests were compared with the actual MK49-F test data in liquid hydrogen.

  20. Experimental determination of times, amplitudes, and lengths of cycles of water droplet deformation in air

    NASA Astrophysics Data System (ADS)

    Volkov, R. S.; Vysokomornaya, O. V.; Kuznetsov, G. V.; Strizhak, P. A.

    2015-02-01

    The regularities of deformation of water droplets moving in air at the moderate Weber numbers (We < 7) are experimentally investigated with the use of high-speed cross-correlation recording equipment at frame delays of less than 100 ns. Deformation cycles with characteristic times, amplitude, lengths, and droplet forms are established. The effect of the droplet velocity on the main characteristics of the deformation cycles is determined.