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Sample records for characteristic diffusion length

  1. Characteristic length of glass transition

    NASA Astrophysics Data System (ADS)

    Donth, E.

    1996-03-01

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

  2. 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.

  3. 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.

  4. Decoupled length scales for diffusivity and viscosity in glass-forming liquids

    NASA Astrophysics Data System (ADS)

    Peng, H. L.; Voigtmann, Th.

    2016-10-01

    The growth of the characteristic length scales both for diffusion and viscosity is investigated by molecular dynamics utilizing the finite-size effect in a binary Lennard-Jones mixture. For those quantities relevant to the diffusion process (e.g., the hydrodynamic value and the spatial correlation function), a strong system-size dependence is found. In contrast, it is weak or absent for the shear relaxation process. Correlation lengths are estimated from the decay of the spatial correlation functions. We find the length scale for viscosity decouples from the one of diffusivity, featured by a saturated length even in high supercooling. This temperature-independent behavior of the length scale is reminiscent of the unapparent structure change upon supercooling, implying the manifestation of configuration entropy. Whereas for the diffusion process, it is manifested by relaxation dynamics and dynamic heterogeneity. The Stokes-Einstein relation is found to break down at the temperature where the decoupling of these lengths happens.

  5. 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.

  6. Thirty years since diffuse sound reflection by maximum length

    NASA Astrophysics Data System (ADS)

    Cox, Trevor J.; D'Antonio, Peter

    2005-09-01

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

  7. Long Spin Diffusion Length in Few-Layer Graphene Flakes

    NASA Astrophysics Data System (ADS)

    Yan, W.; Phillips, L. C.; Barbone, M.; Hämäläinen, S. J.; Lombardo, A.; Ghidini, M.; Moya, X.; Maccherozzi, F.; van Dijken, S.; Dhesi, S. S.; Ferrari, A. C.; Mathur, N. D.

    2016-09-01

    We report a spin valve with a few-layer graphene flake bridging highly spin-polarized La0.67Sr0.33MnO3 electrodes, whose surfaces are kept clean during lithographic definition. Sharp magnetic switching is verified using photoemission electron microscopy with x-ray magnetic circular dichroism contrast. A naturally occurring high interfacial resistance ˜12 M Ω facilitates spin injection, and a large resistive switching (0.8 M Ω at 10 K) implies a 70 - 130 μ m spin diffusion length that exceeds previous values obtained with sharp-switching electrodes.

  8. Beyond the mixing-length theory - A turbulent diffusivity approach

    NASA Astrophysics Data System (ADS)

    Unno, W.

    The use of single mode theory and Xiong's (1979, 1981) theory is considered for approximating the dynamics of convection. In the largest eddy limit, the simulation of turbulent convection is reduced to Xiong's nonlocal mixing-length theory, with application to the construction of stellar convection zones. The spectral theory is valid for large wave numbers and provides correct estimates for the eddy diffusivities. Using nonlinear convection theory, the single mode simulation with an effective Reynolds number of about 10 is shown to correctly simulate the dynamics of large scale flow. It is noted that the single mode simulation also has application to the study of the hydrodynamical properties of steller convection zones.

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

    PubMed

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

    2006-05-09

    The conformation and dynamics of circular polymers is a subject of considerable theoretical and experimental interest. DNA is an important example because it occurs naturally in different topological states, including linear, relaxed circular, and supercoiled circular forms. A fundamental question is how the diffusion coefficients of isolated polymers scale with molecular length and how they vary for different topologies. Here, diffusion coefficients D for relaxed circular, supercoiled, and linear DNA molecules of length L ranging from approximately 6 to 290 kbp were measured by tracking the Brownian motion of single molecules. A topology-independent scaling law D approximately L(-nu) was observed with nu(L) = 0.571 +/- 0.014, nu(C) = 0.589 +/- 0.018, and nu(S) = 0.571 +/- 0.057 for linear, relaxed circular, and supercoiled DNA, respectively, in good agreement with the scaling exponent of nu congruent with 0.588 predicted by renormalization group theory for polymers with significant excluded volume interactions. Our findings thus provide evidence in support of several theories that predict an effective diameter of DNA much greater than the Debye screening length. In addition, the measured ratio D(Circular)/D(Linear) = 1.32 +/- 0.014 was closer to the value of 1.45 predicted by using renormalization group theory than the value of 1.18 predicted by classical Kirkwood hydrodynamic theory and agreed well with a value of 1.31 predicted when incorporating a recently proposed expression for the radius of gyration of circular polymers into the Zimm model.

  10. Exciton diffusion lengths of organic semiconductor thin films measured by spectrally resolved photoluminescence quenching

    NASA Astrophysics Data System (ADS)

    Lunt, Richard R.; Giebink, Noel C.; Belak, Anna A.; Benziger, Jay B.; Forrest, Stephen R.

    2009-03-01

    We demonstrate spectrally resolved photoluminescence quenching as a means to determine the exciton diffusion length of several archetype organic semiconductors used in thin film devices. We show that aggregation and crystal orientation influence the anisotropy of the diffusion length for vacuum-deposited polycrystalline films. The measurement of the singlet diffusion lengths is found to be in agreement with diffusion by Förster transfer, whereas triplet diffusion occurs primarily via Dexter transfer.

  11. Patient and hospital characteristics associated with average length of stay.

    PubMed

    Shi, L

    1996-01-01

    This article examines the relationship between patient, hospital characteristics, and hospital average length of stay controlling for major disease categories. A constellation of patient and physician factors were found to be significantly associated with average hospital length of stay.

  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 μm as compared to that of visible illumination measured at 90 μm. 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. Surface recombination velocity and diffusion length of minority carriers in heavily doped silicon layers

    NASA Technical Reports Server (NTRS)

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

    1977-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Reid, Elliott G

    1953-01-01

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

  15. Studies of minority carrier diffusion length increase in p-type ZnO:Sb

    SciTech Connect

    Lopatiuk-Tirpak, O.; Chernyak, L.; Xiu, F. X.; Liu, J. L.; Jang, S.; Ren, F.; Pearton, S. J.; Gartsman, K.; Feldman, Y.; Osinsky, A.; Chow, P.

    2006-10-15

    Minority electron diffusion length was measured in p-type, Sb-doped ZnO as a function of temperature using the electron beam induced current technique. A thermally induced increase of electron diffusion length was determined to have an activation energy of 184{+-}10 meV. Irradiation with a low energy (5 kV) electron beam also resulted in an increase of diffusion length with a similar activation energy (219{+-}8 meV). Both phenomena are suggested to involve a Sb{sub Zn}-2V{sub Zn} acceptor complex. Saturation and relaxation dynamics of minority carrier diffusion length are explored. Details of a possible mechanism for diffusion length increase are presented.

  16. Characterization of photonic amorphous structures with different characteristic lengths

    NASA Astrophysics Data System (ADS)

    Wen, Cheng-Chi; Hung, Yu-Chueh

    2016-04-01

    Photonic amorphous structure (PAS) has attracted increasing research attention due to their interesting characteristics, such as noniridescent structural colors and isotropic photonic band gap. In this work, we present PAS with different characteristic lengths and analyze their structural and topological properties. First, a Fourier spectral method was used to solve Cahn-Hilliard equation and generate a spinodal binary phase structure. By changing the time of the evolution of phase field, mobility, and standard deviation, the characteristic length of amorphous structures can be adjusted. We present the numerical analysis based on finite-difference time-domain (FDTD) method to characterize the density of state (DOS) of PAS based on different time of the evolution of phase field. The corresponding spatial Fourier spectrum of PAS is calculated to examine the characteristic length, and the photonic band gap properties will be discussed in association with the characteristic length. These results are crucial for design of new optical materials display devices base on dielectric amorphous photonic structures.

  17. First working group meeting on the minority carrier diffusion length/lifetime measurement: Results of the round robin lifetime/diffusion length tests

    SciTech Connect

    Cudzinovic, M; Sopori, B

    1995-11-01

    As was noted in the cover letter that accompanied the samples, the eleven bare silicon samples were from various manufacturers. Table I lists the codes for the samples and the manufacturer of each sample. It also notes if the sample was single or poly-crystalline. The samples had been polished on one side before being sent out for measurements, but no further processing was done. The participants of the study were asked to measure either the lifetime or diffusion length of each of the samples using their standard procedure. Table II shows the experimental conditions used by the groups who measured diffusion length. All the diffusion length measurements were performed using the Surface Photovoltage method (SPV). Table M shows the experimental conditions for the lifetime measurements. All the lifetime measurements were made using the Photoconductance Decay method (PCD) under low level injection. These tables show the diameter of the spot size used during the measurement (the effective sampling area), the locations where measurements were taken, and the number of measurements taken at each location. Table N shows the results of the measurements. The table is divided into diffusion length and lifetime measurements for each sample. The values listed are the average values reported by each group. One of the immediate artifacts seen in the data is the large variation in the lifetime measurements. The values from MIT and Mobil are generally close. However, the measurements from NCSU are typically an order of magnitude lower.

  18. Variable helium diffusion characteristics in fluorite

    NASA Astrophysics Data System (ADS)

    Wolff, R.; Dunkl, I.; Kempe, U.; Stockli, D.; Wiedenbeck, M.; von Eynatten, H.

    2016-09-01

    Precise analysis of the diffusion characteristics of helium in fluorite is crucial for establishing the new fluorite (U-Th-Sm)/He thermochronometer (FHe), which potentially provides a powerful tool for dating ore deposits unsuitable for the application of conventional geochronometers. Incremental helium outgassing experiments performed on fluorites derived from a spectrum of geological environments suggest a thermally activated volume diffusion mechanism. The diffusion behaviour is highly variable and the parameters range between log D0/a2 = 0.30 ± 0.27-7.27 ± 0.46 s-1 and Ea = 96 ± 3.5-182 ± 3.8 kJ/mol. Despite the fact that the CaF2 content of natural fluorites in most cases exceeds 99 weight percent, the closure temperature (Tc) of the fluorite (U-Th-Sm)/He thermochronometer as calculated from these diffusion parameters varies between 46 ± 14 °C and 169 ± 9 °C, considering a 125 μm fragment size. Here we establish that minor substitutions of calcium by rare earth elements and yttrium (REE + Y) and related charge compensation by sodium, fluorine, oxygen and/or vacancies in the fluorite crystal lattice have a significant impact on the diffusivity of helium in the mineral. With increasing REE + Y concentrations F vacancies are reduced and key diffusion pathways are narrowed. Consequently, a higher closure temperature is to be expected. An empirical case study confirms this variability: two fluorite samples from the same deposit (Horni Krupka, Czech Republic) with ca. 170 °C and ca. 43 °C Tc yield highly different (U-Th-Sm)/He ages of 290 ± 10 Ma and 79 ± 10 Ma, respectively. Accordingly, the fluorite sample with the high Tc could have quantitatively retained helium since the formation of the fluorite-bearing ores in the Permian, despite subsequent Mesozoic burial and associated regional hydrothermal heating. In contrast, the fluorite with the low Tc yields a Late Cretaceous age close to the apatite fission track (AFT) and apatite (U-Th)/He ages (AHe

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

    PubMed

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

    2015-09-14

    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.

  20. Diffusion characteristics of pediatric pineal tumors

    PubMed Central

    Whitehead, Matthew T; Siddiqui, Adeel; Klimo, Paul; Boop, Frederick A

    2015-01-01

    Background Diffusion weighted imaging (DWI) has been shown to be helpful in characterizing tumor cellularity, and predicting histology. Several works have evaluated this technique for pineal tumors; however studies to date have not focused on pediatric pineal tumors. Objective We evaluated the diffusion characteristics of pediatric pineal tumors to confirm if patterns seen in studies using mixed pediatric and adult populations remain valid. Materials and methods This retrospective study was performed after Institutional Review Board approval. We retrospectively evaluated all patients 18 years of age and younger with pineal tumors from a single institution where preoperative diffusion weighted imaging as well as histologic characterization was available. Results Twenty patients (13 male, 7 female) with pineal tumors were identified: seven with pineoblastoma, four with Primitive Neuroectodermal Tumor (PNET), two with other pineal tumors, and seven with germ cell tumors including two germinomas, three teratomas, and one mixed germinoma-teratoma. The mean apparent diffusion coefficient (ADC) values in pineoblastoma (544 ± 65 × 10–6 mm2/s) and pineoblastoma/PNET (595 ± 144 × 10–6 mm2/s) was lower than that of the germ cell tumors (1284 ± 334 × 10–6 mm2/s; p < 0.0001 vs pineoblastoma). One highly cellular germinoma had an ADC value of 694 × 10–6 mm2/s. Conclusion ADC values can aid in differentiation of pineoblastoma/PNET from germ cell tumors in a population of children with pineal masses. PMID:25963154

  1. The Length and Characteristics of Women's Lifetime Work Experience.

    ERIC Educational Resources Information Center

    Gwartney-Gibbs, Patricia A.

    A study examined the length and characteristics of women's lifetime work experience. The principal data source for the survey was a set of detailed work, educational, marital, and fertility histories that were collected in the fall of 1979 from 314 couples in the Detroit metropolitan area. While prior researchers had relied upon measures of the…

  2. 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.

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

    PubMed Central

    Jones, J D; Luby-Phelps, K

    1996-01-01

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

  4. 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.

  5. Excitation and temperature dependent exciton-carrier transport in CVD diamond: Diffusion coefficient, recombination lifetime and diffusion length

    NASA Astrophysics Data System (ADS)

    Ščajev, Patrik

    2017-04-01

    Time-resolved induced absorption (IA) and light induced transient grating (LITG) techniques were applied for the investigation of nonequilibrium exciton-carrier diffusion and recombination processes in a high-purity CVD diamond. Injection range from 1015 to 1020 cm-3 carrier density was achieved by combining one photon and two photon excitations. The measurements were performed in the 10-750 K temperature range. The LITG diffusion coefficient peaked at 44 cm2/s value at room temperature under low injection conditions. At lower temperatures it transferred to much lower exciton diffusion coefficient. A strong decrease of diffusion coefficient under higher injection conditions was explained by exciton formation with a low diffusion coefficient and many body effects, as polyexciton and electron-hole droplet formation. High temperature phonon-limited diffusion coefficient was weakly injection dependent. Low excitation carrier lifetime was about 700 ns above 200 K. At lower temperatures, the decay time reduced by two orders of magnitude, which was explained by the formation of biexcitons. At lowest temperatures, an increase of the carrier recombination rate at high injection was attributed to Auger recombinations of polyexcitons and electron-hole droplets. While at high temperatures, the increase of the recombination rate with 490 meV activation energy was observed. The combination of IA and LITG measurements provided effective diffusion lengths in a 0.3-50 μm range, being strongly dependent on the excess carrier density and temperature.

  6. 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.

  7. Laser interferometric method for determining the carrier diffusion length in semiconductors

    SciTech Connect

    Manukhov, V. V.; Fedortsov, A. B.; Ivanov, A. S.

    2015-09-15

    A new laser interferometric method for measuring the carrier diffusion length in semiconductors is proposed. The method is based on the interference–absorption interaction of two laser radiations in a semiconductor. Injected radiation generates additional carriers in a semiconductor, which causes a change in the material’s optical constants and modulation of the probing radiation passed through the sample. When changing the distance between carrier generation and probing points, a decrease in the carrier concentration, which depends on the diffusion length, is recorded. The diffusion length is determined by comparing the experimental and theoretical dependences of the probe signal on the divergence of the injector and probe beams. The method is successfully tested on semiconductor samples with different thicknesses and surface states and can be used in scientific research and the electronics industry.

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

    SciTech Connect

    Zhang, Wei; Pearson, John E.; Hoffmann, Axel; Vlaminck, Vincent; Divan, Ralu; Bader, Samuel D.

    2013-12-09

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

  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. Histological characteristics of diffuse idiopathic skeletal hyperostosis.

    PubMed

    Kuperus, Jonneke S; Westerveld, L Anneloes; Rutges, Joost P H J; Alblas, Jacqueline; van Rijen, Mattie H P; Bleys, Ronald L A W; Öner, F Cumhur; Verlaan, Jorrit-Jan

    2017-01-01

    Diffuse idiopathic skeletal hyperostosis (DISH) is a predominantly radiographic diagnosis and histological knowledge of DISH is limited. The aim of this study was to describe the histological characteristics of DISH in the spinal column and to study the relation between DISH and intervertebral disc (IVD) degeneration. Therefore, 10 human cadaveric spines with fluoroscopic evidence of DISH were compared with 10 controls. Plain radiographs and computed tomography (CT) scans were obtained and tissue blocks were resected from three predefined levels of all specimens. The microscopic sections were scored by two blinded observers using a newly developed scoring system specific for characteristics of DISH and a validated scoring system for IVD degeneration. Maximum IVD height was measured on the CT scans. Analyses were performed using Fisher's exact test and Student's t-test. When compared to controls, the right sided sections from DISH specimens showed partial or complete bone bridges, consisting of cortical woven bone, accompanied by morphological changes in the adjoining part of the IVD. Using the histological scoring system for DISH, all parameters were significantly different between the DISH and control group (p < 0.01). The contralateral location did not show differences between the groups. The overall degree of IVD degeneration and height of IVD was comparable for the two groups. The histopathological changes observed in spines with DISH corresponded to the fluoroscopic images and CT scans. The degree of IVD degeneration and IVD height was comparable for both groups, suggesting a limited role for IVD degeneration in the pathogenesis of DISH. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:140-146, 2017.

  11. Determination of the spin diffusion length in germanium by spin optical orientation and electrical spin injection

    NASA Astrophysics Data System (ADS)

    Rinaldi, C.; Bertoli, S.; Asa, M.; Baldrati, L.; Manzoni, C.; Marangoni, M.; Cerullo, G.; Bianchi, M.; Sordan, R.; Bertacco, R.; Cantoni, M.

    2016-10-01

    The measurement of the spin diffusion length and/or lifetime in semiconductors is a key issue for the realisation of spintronic devices, exploiting the spin degree of freedom of carriers for storing and manipulating information. In this paper, we address such parameters in germanium (0 0 1) at room temperature (RT) by three different measurement methods. Exploiting optical spin orientation in the semiconductor and spin filtering across an insulating MgO barrier, the dependence of the resistivity on the spin of photo-excited carriers in Fe/MgO/Ge spin photodiodes (spin-PDs) was electrically detected. A spin diffusion length of 0.9  ±  0.2 µm was obtained by fitting the photon energy dependence of the spin signal by a mathematical model. Electrical techniques, comprising non-local four-terminal and Hanle measurements performed on CoFeB/MgO/Ge lateral devices, led to spin diffusion lengths of 1.3  ±  0.2 µm and 1.3  ±  0.08 µm, respectively. Despite minor differences due to experimental details, the order of magnitude of the spin diffusion length is the same for the three techniques. Although standard electrical methods are the most employed in semiconductor spintronics for spin diffusion length measurements, here we demonstrate optical spin orientation as a viable alternative for the determination of the spin diffusion length in semiconductors allowing for optical spin orientation.

  12. Contemplating Transport Characteristics by Augmenting the Length of Molecule

    NASA Astrophysics Data System (ADS)

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

    2013-11-01

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

  13. Two Birds with One Stone: Tailoring Singlet Fission for Both Triplet Yield and Exciton Diffusion Length.

    PubMed

    Zhu, Tong; Wan, Yan; Guo, Zhi; Johnson, Justin; Huang, Libai

    2016-09-01

    By direct imaging of singlet and triplet populations with ultrafast microscopy, it is shown that the triplet diffusion length and singlet fission yield can be simultaneously optimized for tetracene and its derivatives, making them ideal structures for application in bilayer solar cells.

  14. Two Birds with One Stone: Tailoring Singlet Fission for Both Triplet Yield and Exciton Diffusion Length

    SciTech Connect

    Zhu, Tong; Wan, Yan; Guo, Zhi; Johnson, Justin; Huang, Libai

    2016-06-27

    By direct imaging of singlet and triplet populations with ultrafast microscopy, it is shown that the triplet diffusion length and singlet fission yield can be simultaneously optimized for tetracene and its derivatives, making them ideal structures for application in bilayer solar cells.

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

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

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

  16. Effective defect diffusion lengths in Ar-ion bombarded 3C-SiC

    SciTech Connect

    Bayu Aji, L. B.; Wallace, J. B.; Shao, L.; Kucheyev, S. O.

    2016-04-14

    Above room temperature, SiC exhibits pronounced processes of diffusion and interaction of radiation-generated point defects. Here, we use the recently developed pulsed ion beam method to measure effective defect diffusion lengths in 3C-SiC bombarded in the temperature range of 25–200 °C with 500 keV Ar ions. Results reveal a diffusion length of ~10 nm, which exhibits a weak temperature dependence, changing from 9 to 13 nm with increasing temperature. Lastly, these results have important implications for understanding and predicting radiation damage in SiC and for the development of radiation-resistant materials via interface-mediated defect reactions.

  17. Determination of the diffusion length and surface recombination velocity: Two simple methods

    SciTech Connect

    Duran, J.C.; Venier, G.L.; Tamasi, M.J.L.; Bolzi, C.G.; Pla, J.C.; Godfrin, E.M.

    1997-12-31

    The present paper analyzes two new methods for the estimation of the diffusion length (L{sub d}) and surface recombination velocity (S) through simple and inexpensive equipment. The first one is based on the behavior of the short circuit current (J{sub sc}) under rear illumination, as a function of the cell width (d). In a general case, this model allows one to determine L{sub d} and the effective rear S by a numerical fitting. The second method uses crystalline silicon cells with localized diffusions. A geometry with linear diffusions is considered and the dependence of J{sub sc} with the distance between those diffusions is analyzed by means of a one dimensional model. The second method is applied to n{sup +}pp{sup +} solar cells fabricated in the Argentine Atomic Energy Commission (CNEA).

  18. Diffuse and specular characteristics of leaf reflectance

    NASA Technical Reports Server (NTRS)

    Grant, Lois

    1987-01-01

    In this paper, the evolution of current understanding of the mechanisms of leaf reflectance is reviewed. The use of measurements of polarized reflectance to separate leaf reflectance into diffuse and specular components is discussed. A section on the factors influencing leaf reflectance - leaf structure and physiological disturbances - is included along with discussion on the manner in which these influences are manifested.

  19. Diffusion length measurements of thin GaAs solar cells by means of energetic electrons

    NASA Technical Reports Server (NTRS)

    Vonross, O.

    1980-01-01

    A calculation of the short circuit current density (j sub sc) of a thin GaAs solar cell induced by fast electrons is presented. It is shown that in spite of the disparity in thickness between the N-type portion of the junction and the P-type portion of the junction, the measurement of the bulk diffusion length L sub p of the N-type part of the junction is seriously hampered due to the presence of a sizable contribution to the j sub sc from the P-type region of the junction. Corrections of up to 50% had to be made in order to interpret the data correctly. Since these corrections were not amenable to direct measurements it is concluded that the electron beam method for the determination of the bulk minority carrier diffusion length, which works so well for Si solar cells, is a poor method when applied to thin GaAs cells.

  20. Length distributions of nanowires: Effects of surface diffusion versus nucleation delay

    NASA Astrophysics Data System (ADS)

    Dubrovskii, Vladimir G.

    2017-04-01

    It is often thought that the ensembles of semiconductor nanowires are uniform in length due to the initial organization of the growth seeds such as lithographically defined droplets or holes in the substrate. However, several recent works have already demonstrated that most nanowire length distributions are broader than Poissonian. Herein, we consider theoretically the length distributions of non-interacting nanowires that grow by the material collection from the entire length of their sidewalls and with a delay of nucleation of the very first nanowire monolayer. The obtained analytic length distribution is controlled by two parameters that describe the strength of surface diffusion and the nanowire nucleation rate. We show how the distribution changes from the symmetrical Polya shape without the nucleation delay to a much broader and asymmetrical one for longer delays. In the continuum limit (for tall enough nanowires), the length distribution is given by a power law times an incomplete gamma-function. We discuss interesting scaling properties of this solution and give a recipe for analyzing and tailoring the experimental length histograms of nanowires which should work for a wide range of material systems and growth conditions.

  1. Minority carrier diffusion length measurements - A review and comparison of techniques

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

    A review of the major techniques for measuring minority carrier diffusion lengths in solar cells is given. Limits of applicability are indicated for each method, as relevant to indirect bandgap materials such as silicon, and direct bandgap materials like gallium arsenide. A discussion and bibliography is presented for the following techniques: uniform generation, electron beam induced current, Schottky barrier (and other steady-state) photocurrent, surface photovoltage, transient decay, and luminescence.

  2. 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.

  3. Near Field Imaging for the Characterization of Diffusion Length and Waveguiding in Zinc Oxide Nanowires

    DTIC Science & Technology

    2012-06-01

    searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments...raster scan of the nanowire featured . Some diffusion length data are lost by starting the probe tip far away from the cathodoluminescence... featured . By placing the probe tip close to the electron beam, the chances of incidental contact increase. The risk increases that photons would

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

  5. Acid Diffusion Length Corresponding to Post Exposure Bake Time and Temperature

    NASA Astrophysics Data System (ADS)

    Park, Jin-Back; Kim, Sung-Hyuck; Kim, Sung-Jin; Cho, Jung-Hyuk; Oh, Hye-Keun

    2007-01-01

    The post exposure bake (PEB) step in lithography is important for fabricating good patterns when a chemically amplified resist is used. Hydrogen ions or acid is generated by a photoacid generator through light exposure. The generated acid diffuses and acts as a catalyst for chemical amplification during the PEB step. Acid diffusion length (ADL) affects the deprotection of a resist polymer, such that linewidth is affected by ADL. The common parameter that determines ADL is the acid diffusion coefficient D; thus, we must determine D accurately in order to obtain the actual linewidth. However, D cannot be unambiguously determined for the actual PEB temperature and time. ADL has become a critical factor for 100 nm patterns and below. Thus, the accurate ADL determination becomes an important issue for better linewidth prediction by simulation. To match ADL and PEB time and temperature, we attempted to determine the relationship between the PEB parameters and ADL. As a result, we obtained a reasonable ADL.

  6. 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.

  7. Diffusion of Nanoparticles in Semidilute Polymer Solutions: The Effect of Different Length Scales.

    NASA Astrophysics Data System (ADS)

    Kohli, Indermeet; Mukhopadhyay, Ashis

    2012-10-01

    Gold nanoparticles (Au NPs) were used to investigate the length-scale dependent dynamics in semidilute poly(ethylene glycol) (PEG)-water solutions. Fluctuation correlation spectroscopy was used to measure the diffusion coefficients (D) of the NPs as a function of their radius, Ro (2.5-10 nm), PEG volume fraction, φ (0-0.37) and molecular weight, Mw (5 kg/mol and 35 kg/mol). Our results indicate that the radius of gyration, Rg of the polymer chain is the crossover length scale for the NPs experiencing nanoviscosity or macroviscosity. The reduced diffusivity can be plotted on a single master curve as Do/D= exp (α(Ro/ξ)^δ) for Rg > Ro and as Do/D= exp (α(Rg/ξ)^δ) for Rg <= Ro, where Do is diffusion coefficient in the neat solvent, ξ is the correlation length, α = 1.63 and δ = 0.89. In the intermediate size regime, ξ < Ro < a(φ), where `a(φ)' is the tube diameter for entangled polymer liquid, we found that D ˜ φ-1.45 and independent of Mw. For Ro > a(φ), D˜φ-4 was obtained. The results were compared with currently available theories.

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

    DOEpatents

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

    1983-07-12

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

  9. 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

    2013-08-23

    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 μs 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 μm 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.

  10. 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).

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

    PubMed

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

    2015-06-18

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

  12. 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.

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

    DOE PAGES

    Zaikowski, Lori; Mauro, Gina; Bird, Matthew; ...

    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

  14. A novel diffusion-tensor MRI approach for skeletal muscle fascicle length measurements.

    PubMed

    Oudeman, Jos; Mazzoli, Valentina; Marra, Marco A; Nicolay, Klaas; Maas, Mario; Verdonschot, Nico; Sprengers, Andre M; Nederveen, Aart J; Strijkers, Gustav J; Froeling, Martijn

    2016-12-01

    Musculoskeletal (dys-)function relies for a large part on muscle architecture which can be obtained using Diffusion-Tensor MRI (DT-MRI) and fiber tractography. However, reconstructed tracts often continue along the tendon or aponeurosis when using conventional methods, thus overestimating fascicle lengths. In this study, we propose a new method for semiautomatic segmentation of tendinous tissue using tract density (TD). We investigated the feasibility and repeatability of this method to quantify the mean fascicle length per muscle. Additionally, we examined whether the method facilitates measuring changes in fascicle length of lower leg muscles with different foot positions. Five healthy subjects underwent two DT-MRI scans of the right lower leg, with the foot in 15° dorsiflexion, neutral, and 30° plantarflexion positions. Repeatability of fascicle length measurements was assessed using Bland-Altman analysis. Changes in fascicle lengths between the foot positions were tested using a repeated multivariate analysis of variance (MANOVA). Bland-Altman analysis showed good agreement between repeated measurements. The coefficients of variation in neutral position were 8.3, 16.7, 11.2, and 10.4% for soleus (SOL), fibularis longus (FL), extensor digitorum longus (EDL), and tibialis anterior (TA), respectively. The plantarflexors (SOL and FL) showed significant increase in fascicle length from plantarflexion to dorsiflexion, whereas the dorsiflexors (EDL and TA) exhibited a significant decrease. The use of a tract density for semiautomatic segmentation of tendinous structures provides more accurate estimates of the mean fascicle length than traditional fiber tractography methods. The method shows moderate to good repeatability and allows for quantification of changes in fascicle lengths due to passive stretch.

  15. Electron beam induced current study of minority carrier diffusion length in homoepitaxial GaN (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Talin, A. Alec; Collins, Kimberlee C.; Armstrong, Andrew M.; Allerman, Andrew A.; Léonard, François

    2016-09-01

    GaN is a promising material for a range of high power, high frequency, and high temperature device applications. The wide bandgap of GaN leads to high breakdown voltages and low switching losses. Recently, large HVPE grown GaN substrates have become available for homoepitaxial growth leading to 103 reduction in dislocation density compared to similarly grown heteroepitaxial films. Device performance, however, is ultimately limited by the transport properties of minority carriers. Measured values for minority carrier diffusion lengths and lifetimes in GaN vary widely1-3, and a recent report suggests flaws in the commonly adopted electron beam induced current (EBIC) method in the planar-collection geometry.1 Here we report on EBIC measurements performed on 8 micrometer thick GaN grown by MOCVD on 2 inch GaN substrates with a n-type dopant density of 5×1016 cm-3. We determine the carrier diffusion length using both the conventional EBIC method by varying the electron beam-to-contact lateral distance as well as by varying the electron beam penetration depth and find the extracted values differ by 10×, with the latter technique yielding the lower diffusion length. We rationalize these results in light of other materials characteristics including Raman and photoluminescence. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

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

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

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

  17. 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.

  18. Lab on a chip Canada--rapid diffusion over large length scales.

    PubMed

    Juncker, David; Wheeler, Aaron R; Sinton, David

    2013-07-07

    The roots of lab on a chip in Canada are deep, comprising of some of the earliest contributions and first demonstrations of the potential of microfluidic chips. In an editorial leading off this special issue, Jed Harrison of University of Alberta reflects on these early days and Canada's role in the field's development (DOI: 10.1039/c3lc50522g). Over the last decade, microfluidics and lab-on-a-chip research efforts grew exponentially - rapidly diffusing across the vast Canadian length scales.

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

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

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

  20. Diffusion length and grain boundary recombination activity determination by means of induced current methods

    NASA Astrophysics Data System (ADS)

    Shabelnikova, Yana; Yakimov, Eugene

    2016-11-01

    The application of induced current methods for a quantitative description of multicrystalline silicon solar cell properties is demonstrated. For the minority carriers' diffusion length (L) and grain boundary recombination velocity (Vs) determination three types of measurements were used. They included the measurement of EBIC signal dependence on electron beam energy and of EBIC and XBIC grain boundary contrast profiles. The L and Vs values obtained by means of minimization the residual function between measured and model induced current curves are presented. The inaccuracy of obtained parameters is discussed for each of three types of measurements.

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

    DOEpatents

    Moore, Arnold R.

    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.

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

    DOEpatents

    Moore, Arnold R.

    1984-01-01

    Method and apparatus are provided for determining the diffusion length of minority carriers in semiconductor material, particularly amorphous silicon which has a significantly small minority carrier diffusion length using the constant magnitude surface-photovoltage (SPV) method. Steady or modulated illumination at several wavelengths provides the light excitation on the surface of the material to generate the SPV. A manually controlled or automatic servo system maintains a constant predetermined value of the SPV for each wavelength. A drop of a transparent electrolyte solution containing redox couples (preferably quinhydrone) having an oxidation-reduction potential (E) in the order of +0.6 to -1.65 volts couples the SPV to a measurement system. The drop of redox couple solution functions to create a liquid Schottky barrier at the surface of the material. Illumination light is passed through a transparent rod supported over the surface and through the drop of transparent electrolyte. The drop is held in the gap between the rod and the surface. Steady red light is also used as an optical bias to reduce deleterious space-charge effects that occur in amorphous silicon.

  3. 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.

  4. Soundproof characteristics of finite length orthotropic honeycomb shells

    NASA Astrophysics Data System (ADS)

    Chonan, S.

    1989-01-01

    Acoustic radiation emanating from the walls of orthotropic honeycomb shells is studied analytically for the case of axisymmetric acoustic mode transmission within the shell. The shell has a finite vibrating length and is mounted on an infinite rigid baffle in a free field. The problem is studied on the basis of a shell theory in which it is assumed that the honeycomb core resists only transverse shear forces and that the facings resist only bending moments. The sound transmission loss through the shell wall, TL, is derived and calculated for various values of the physical parameters involved.

  5. Fractal Theory and Field Cover Experiments: Implications for the Fractal Characteristics and Radon Diffusion Behavior of Soils and Rocks.

    PubMed

    Tan, Wanyu; Li, Yongmei; Tan, Kaixuan; Duan, Xianzhe; Liu, Dong; Liu, Zehua

    2016-12-01

    Radon diffusion and transport through different media is a complex process affected by many factors. In this study, the fractal theories and field covering experiments were used to study the fractal characteristics of particle size distribution (PSD) of six kinds of geotechnical materials (e.g., waste rock, sand, laterite, kaolin, mixture of sand and laterite, and mixture of waste rock and laterite) and their effects on radon diffusion. In addition, the radon diffusion coefficient and diffusion length were calculated. Moreover, new formulas for estimating diffusion coefficient and diffusion length functional of fractal dimension d of PSD were proposed. These results demonstrate the following points: (1) the fractal dimension d of the PSD can be used to characterize the property of soils and rocks in the studies of radon diffusion behavior; (2) the diffusion coefficient and diffusion length decrease with increasing fractal dimension of PSD; and (3) the effectiveness of final covers in reducing radon exhalation of uranium tailings impoundments can be evaluated on the basis of the fractal dimension of PSD of materials.

  6. 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.

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

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

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

  8. Role of impurities in determining the exciton diffusion length in organic semiconductors

    NASA Astrophysics Data System (ADS)

    Curtin, Ian J.; Blaylock, D. Wayne; Holmes, Russell J.

    2016-04-01

    The design and performance of organic photovoltaic cells is dictated, in part, by the magnitude of the exciton diffusion length (LD). Despite the importance of this parameter, there have been few investigations connecting LD and materials purity. Here, we investigate LD for the organic small molecule N,N'-bis(naphthalen-1-yl)-N,N'-bis(phenyl)-benzidine as native impurities are systematically removed from the material. Thin films deposited from the as-synthesized material yield a value for LD, as measured by photoluminescence quenching, of (3.9 ± 0.5) nm with a corresponding photoluminescence efficiency (ηPL) of (25 ± 1)% and thin film purity of (97.1 ± 1.2)%, measured by high performance liquid chromatography. After purification by thermal gradient sublimation, the value of LD is increased to (4.7 ± 0.5) nm with a corresponding ηPL of (33 ± 1)% and purity of (98.3 ± 0.8)%. Interestingly, a similar behavior is also observed as a function of the deposition boat temperature. Films deposited from the purified material at a high temperature give LD = (5.3 ± 0.8) nm with ηPL = (37 ± 1)% for films with a purity of (99.0 ± 0.3)% purity. Using a model of diffusion by Förster energy transfer, the variation of LD with purity is predicted as a function of ηPL and is in good agreement with measurements. The removal of impurities acts to decrease the non-radiative exciton decay rate and increase the radiative decay rate, leading to increases in both the diffusivity and exciton lifetime. The results of this work highlight the role of impurities in determining LD, while also providing insight into the degree of materials purification necessary to achieve optimized exciton transport.

  9. A multi-resolution analysis of lidar-DTMs to identify geomorphic processes from characteristic topographic length scales

    NASA Astrophysics Data System (ADS)

    Sangireddy, H.; Passalacqua, P.; Stark, C. P.

    2013-12-01

    Characteristic length scales are often present in topography, and they reflect the driving geomorphic processes. The wide availability of high resolution lidar Digital Terrain Models (DTMs) allows us to measure such characteristic scales, but new methods of topographic analysis are needed in order to do so. Here, we explore how transitions in probability distributions (pdfs) of topographic variables such as (log(area/slope)), defined as topoindex by Beven and Kirkby[1979], can be measured by Multi-Resolution Analysis (MRA) of lidar DTMs [Stark and Stark, 2001; Sangireddy et al.,2012] and used to infer dominant geomorphic processes such as non-linear diffusion and critical shear. We show this correlation between dominant geomorphic processes to characteristic length scales by comparing results from a landscape evolution model to natural landscapes. The landscape evolution model MARSSIM Howard[1994] includes components for modeling rock weathering, mass wasting by non-linear creep, detachment-limited channel erosion, and bedload sediment transport. We use MARSSIM to simulate steady state landscapes for a range of hillslope diffusivity and critical shear stresses. Using the MRA approach, we estimate modal values and inter-quartile ranges of slope, curvature, and topoindex as a function of resolution. We also construct pdfs at each resolution and identify and extract characteristic scale breaks. Following the approach of Tucker et al.,[2001], we measure the average length to channel from ridges, within the GeoNet framework developed by Passalacqua et al.,[2010] and compute pdfs for hillslope lengths at each scale defined in the MRA. We compare the hillslope diffusivity used in MARSSIM against inter-quartile ranges of topoindex and hillslope length scales, and observe power law relationships between the compared variables for simulated landscapes at steady state. We plot similar measures for natural landscapes and are able to qualitatively infer the dominant geomorphic

  10. Performance characteristics according to the channel length and magnetic fields of cylindrical Hall thrusters

    NASA Astrophysics Data System (ADS)

    Lee, Jongsub; Seo, Mihui; Seon, Jongho; June Lee, Hae; Choe, Wonho

    2011-09-01

    Performance characteristics of low power cylindrical Hall thrusters are investigated in terms of the length of the discharge channel. Thrust, efficiency, discharge current, and propellant utilization are evaluated for different channel lengths of 19, 22, and 25 mm. It is found that the propellant utilization and ion energy distribution function are strongly associated with the channel length. Increase of thrust and efficiency are also found with increasing channel lengths. These characteristics of the thruster are interpreted with possible generation of multi-charged ions due to increased residing time within the extended space inside the channel.

  11. Studies of deep level centers determining the diffusion length in epitaxial layers and crystals of undoped n-GaN

    NASA Astrophysics Data System (ADS)

    Lee, In-Hwan; Polyakov, A. Y.; Smirnov, N. B.; Yakimov, E. B.; Tarelkin, S. A.; Turutin, A. V.; Shemerov, I. V.; Pearton, S. J.

    2016-05-01

    A wide variety of parameters were measured for undoped n-GaN grown by hydride vapor phase epitaxy and compared to n-GaN films grown by conventional and lateral overgrowth metalorganic chemical vapor deposition. The parameters included deep level electron and hole trap spectra, microcathodoluminescence, electron beam induced current, diffusion length, and electron capture cross section from the dependence of the low temperature persistent photocapacitance on forward bias injection pulse duration. The results show a prominent role of electron traps with levels near Ec-0.56 eV in limiting the lifetime and diffusion length values in all these materials.

  12. Characteristics of donkey spermatozoa along the length of the epididymis.

    PubMed

    Contri, A; Gloria, A; Robbe, D; De Amicis, I; Carluccio, A

    2012-01-01

    In mammals, the epididymis has numerous interrelated functions including absorptive and secretory activity that affect luminal environment and cell membrane, and the maturation and storage of sperm. Spermatozoa acquire their motility and fertilizing ability during their passage through the epididymis and the motility of epididymal spermatozoa should be a balance between the maturation of flagellum and the inhibition of the flagellar machinery. In this study maturational change in sperm characteristics were evaluated in the epididymis of donkey. Spermatozoa collected from four portions of the epididymis (head, cranial corpus, caudal corpus, tail) were compared before and after ejaculation for viability, mitochondrial activity, kinetic parameters, and morphology. A significant increase in the mitochondrial activity along the epididymis was reported, suggesting a possible involvement in the motion mechanism. This should be corroborated by the significant correlation between mitochondrial activity and the total and progressive motility and the increase in velocities of spermatozoa recorded by computer-assisted sperm analysis. The percentage of most of the abnormal spermatozoa were similar in all tracts, with a great variability between jackasses. Only the bent midpiece percentage decreased significantly along epididymis. A significant increase in the percentage of distal cytoplasmic droplets (DCD), and a simultaneous decrease in the proximal cytoplasmic droplets (PCD), was found. The DCD fell down after ejaculation suggesting the late loss of the cytoplasmic residual (DCD) in the donkey, as hypothesized in the stallion. Because the prevalence of PCD were similar in both tail epididymal and ejaculated spermatozoa, a defect of the maturative process in the PCD sperm should be speculated.

  13. Enhancing electron collection efficiency and effective diffusion length in dye-sensitized solar cells.

    PubMed

    Wong, Daniel Kwan-Pang; Ku, Chen-Hao; Chen, Yen-Ru; Chen, Guan-Ren; Wu, Jih-Jen

    2009-10-19

    Intensity-modulated photocurrent spectroscopy and intensity-modulated photovoltage spectroscopy are employed to measure the dynamics of electron transport and recombination in the ZnO nanowire (NW) array-ZnO/layered basic zinc acetate (LBZA) nanoparticle (NP) composite dye-sensitized solar cells (DSSCs). The roles of the vertical ZnO NWs and insulating LBZA in the electron collection and transport in DSSCs are investigated by comparing the results to those in the TiO(2)-NP, horizontal TiO(2)-NW and vertical ZnO-NW-array DSSCs. The electron transport rate and electron lifetime in the ZnO NW/NP composite DSSC are superior to those in the conventional TiO(2)-NP cell due to the existence of the vertical ZnO NWs and insulating LBZA. It indicates that the ZnO NW/NP composite anode is able to sustain efficient electron collection over much greater thickness than the TiO(2)-NP cell does. Consequently, a larger effective electron diffusion length is available in the ZnO composite DSSC.

  14. Spin-Diffusion Lengths in Ag(4%Sn) and Cu(2%Ge) alloys

    NASA Astrophysics Data System (ADS)

    Sharma, Amit; Richard, Brandon; Fowler, Quinton; Loloee, Reza; Pratt, William, Jr.; Bass, Jack

    2008-03-01

    Alloying Ag with a little Sn, or Cu with a little Ge, greatly increases elastic scattering of electrons---i.e., greatly decreases the electron mean-free-path (mfp), but does not produce much spin-flipping---i.e., leaves the electron spin-diffusion length, l, relatively long. Thus, dilute AgSn and CuGe alloys were used to study effects of changing the mfp on current-perpendicular-to-plane (CPP) magnetoresistance [1] and current-induced magnetization switching (CIMS) [2], while leaving spin-flipping weak. Published transport data in dilute AgSn and CuGe alloys give only lower bounds for l [3-5]. We find l = 34 ± 4 nm for Ag(4%Sn) and l = 125 ± 10 nm for Cu(2%Ge). [1] K. Eid et al., J. Magn. Magn. Mat. 224, L205 (2001). [2] N. Theodoropoulou et al., Phys. Rev. B (rapid comm.) in press. [3] S.-F.Lee et al., J. Magn. Magn. Mat. 118, L1 (993). [4] J. Bass et al, Mat. Sci. and Eng. B31, 77 (1995). [5] J. Bass and W.P. Pratt Jr., J. Phys. Cond. Matt. 19, 183201 (2007).

  15. Roughness distribution of multiple hit and long surface diffusion length noise reduced discrete growth models

    NASA Astrophysics Data System (ADS)

    Disrattakit, P.; Chanphana, R.; Chatraphorn, P.

    2016-11-01

    Conventionally, the universality class of a discrete growth model is identified via the scaling of interface width. This method requires large-scale simulations to minimize finite-size effects on the results. The multiple hit noise reduction techniques (m > 1 NRT) and the long surface diffusion length noise reduction techniques (ℓ > 1 NRT) have been used to promote the asymptotic behaviors of the growth models. Lately, an alternative method involving comparison of roughness distribution in the steady state has been proposed. In this work, the roughness distribution of the (2 +1)-dimensional Das Sarma-Tamborenea (DT), Wolf-Villain (WV), and Larger Curvature (LC) models, with and without NRTs, are calculated in order to investigate effects of the NRTs on the roughness distribution. Additionally, effective growth exponents of the noise reduced (2 +1)-dimensional DT, WV and LC models are also calculated. Our results indicate that the NRTs affect the interface width both in the growth and the saturation regimes. In the steady state, the NRTs do not seem to have any impact on the roughness distribution of the DT model, but it significantly changes the roughness distribution of the WV and LC models to the normal distribution curves.

  16. Characteristic length of phonon transport within periodic nanoporous thin films and two-dimensional materials

    NASA Astrophysics Data System (ADS)

    Hao, Qing; Xiao, Yue; Zhao, Hongbo

    2016-08-01

    In the past two decades, phonon transport within nanoporous thin films has attracted enormous attention for their potential applications in thermoelectrics and thermal insulation. Various computational studies have been carried out to explain the thermal conductivity reduction within these thin films. Considering classical phonon size effects, the lattice thermal conductivity can be predicted assuming diffusive pore-edge scattering of phonons and bulk phonon mean free paths. Following this, detailed phonon transport can be simulated for a given porous structure to find the lattice thermal conductivity [Hao et al., J. Appl. Phys. 106, 114321 (2009)]. However, such simulations are intrinsically complicated and cannot be used for the data analysis of general samples. In this work, the characteristic length Λ P o r e of periodic nanoporous thin films is extracted by comparing the predictions of phonon Monte Carlo simulations and the kinetic relationship using bulk phonon mean free paths modified by Λ P o r e . Under strong ballistic phonon transport, Λ P o r e is also extracted by the Monte Carlo ray-tracing method for graphene with periodic nanopores. The presented model can be widely used to analyze the measured thermal conductivities of such nanoporous structures.

  17. Optical characteristics of the filamentary and diffuse modes in surface dielectric barrier discharge

    NASA Astrophysics Data System (ADS)

    Zhang, Ying; Li, Jie; Jiang, Nan; Shang, Ke-Feng; Lu, Na; Wu, Yan

    2016-11-01

    Surface dielectric barrier discharge (DBD) plasmas generally exhibits filamentary and diffuse discharges at atmospheric air. The focus of this investigation is on the different optical characteristics and quantitative research about morphological features of two discharge modes. The temporally and spatially resolved characteristics of discharge phenomenon together with the gas temperature are presented with microsecond time scale. Discharge area is estimated by the sum of pixels that equal to "1" in MATLAB software. The formation of diffuse plasma mainly depends on an increase of the ionization coefficient and a creation of sufficient seed electrons by the Penning effect at low electric fields. Accordingly, experimental measurements show that diffuse discharge during the negative half cycle has good uniformity and stability compared with filamentary discharge during the positive half cycle. The rotational temperatures of plasma are determined by comparing the experimental spectra with the simulated spectra that have been investigated. The plasma gas temperature keeps almost constant in the filamentary discharge phase and subsequently increased by about 115 K during the diffuse discharge. In addition, it is shown to be nearly identical in the axial direction. Non-uniform temperature distribution can be observed in the radial direction with large fluctuations. The plasma length is demonstrated almost the same between two discharge modes.

  18. 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.

  19. Creep and the characteristic length scale of strain-energy dissipation in polycrystalline ice; implications for tidal dissipation

    NASA Astrophysics Data System (ADS)

    Caswell, T. E.; Cooper, R. F.; Goldsby, D. L.

    2015-12-01

    Many outer planet satellites possess thick, icy crusts over an ocean of liquid water. Maintaining an ocean over geologic time requires internal heating by tidal dissipation, but the mechanisms of tidal dissipation in ice are poorly resolved. The physics of dissipation in the geological context (the "high temperature background") are dominated by stress-induced chemical diffusion, which has a distinct length-scale dependence that is frequently cited as the grain size. The experiments of McCarthy [2009], however, measured attenuation simultaneously with steady-state creep in polycrystalline ice and showed distinctly grain size-insensitive dissipation. These data can instead be normalized by the steady-state creep stress, implying that the deformation-induced microstructure dominates the length scale of diffusion. Thus, the relationship between deformation-induced microstructure and dissipation is critical to understanding how tidal dissipation affects (or, perhaps, effects) the geodynamics of icy satellites. To characterize the role of deformation microstructure in strain-energy dissipation, we conducted creep and stress-reduction experiments on polycrystalline ice. The stress (0.5-5 MPa), grain size (30 & 245 μm) and temperature (233K) of the experiments place our specimens in the rheological regimes of grain boundary sliding (geometrically accommodated by basal glide) or dislocation creep, both of which accrue significant plastic strain by the motion of lattice dislocations. Stress-reductions allow a specific deformation-induced microstructure—that produced in steady-state creep—to be probed for its effective viscosity (or "hardness") at a variety of stresses. This "constant-hardness creep compliance" is affected by deviatoric stress, but not by grain size, confirming a characteristic length scale for relaxation that is dictated by deformation. The microstructures of deformed samples, analyzed via cryogenic electron backscatter diffraction (EBSD) and reflected

  20. Levitation effect: role of symmetry and dependence of diffusivity on the bond length of homonuclear and heteronuclear diatomic species.

    PubMed

    Sharma, Manju; Yashonath, S

    2011-04-07

    Molecular dynamics investigation of model diatomic species confined to the α-cages of zeolite NaY is reported. The dependence of self-diffusivity on the bond length of the diatomic species has been investigated. Three different sets of runs have been carried out. In the first set, the two atoms of the diatomic molecule interact with the zeolite atoms with equal strength (example, O(2), the symmetric case). In the second and third sets which correspond to asymmetric cases, the two atoms of the diatomic molecule interact with unequal strengths (example, CO). The result for the symmetric case exhibits a well-defined maximum in self-diffusivity for an intermediate bond length. In contrast to this, the intermediate asymmetry leads to a less pronounced maximum. For the large asymmetric case, the maximum is completely absent. These findings are analyzed by computing a number of related properties. These results provide a direct confirmation at the microscopic level of the suggestion by Derouane that the supermobility observed experimentally by Kemball has its origin in the mutual cancellation of forces. The maximum in diffusivity from molecular dynamics is seen at the value predicted by the levitation effect. Further, these findings suggest a role for symmetry in the existence of a diffusivity maximum as a function of diameter of the diffusant often referred to as the levitation effect. The nature of the required symmetry for the existence of anomalous diffusivity is interaction symmetry which is different from that normally encountered in crystallography.

  1. Method to extract diffusion length from solar cell parameters—Application to polycrystalline silicon

    NASA Astrophysics Data System (ADS)

    Taretto, K.; Rau, U.; Werner, J. H.

    2003-05-01

    A closed form, analytical expression for the interdependence of the effective diffusion length Leff and the open-circuit voltage of solar cells is derived for the parallel connection of recombination in the space-charge region and in the neutral base region. This expression allows for the calculation of Leff from the open-circuit voltage, the short-circuit current, and the base doping of the solar cell as the only quantities that need to be determined experimentally. Values of Leff calculated with our method match with an accuracy of 35% values that are determined experimentally by quantum-efficiency measurements of silicon solar cells. The agreement holds in a range 0.3 μm

  2. Tracer counterpermeation analysis of diffusivity in finite-length nanopores with and without single-file dynamics

    NASA Astrophysics Data System (ADS)

    Ackerman, David M.; Evans, James W.

    2017-01-01

    We perform a tracer counterpermeation (TCP) analysis for a stochastic model of diffusive transport through a narrow linear pore where passing of species within the pore is inhibited or even excluded (single-file diffusion). TCP involves differently labeled but otherwise identical particles from two decoupled infinite reservoirs adsorbing into opposite ends of the pore, and desorbing from either end. In addition to transient behavior, we assess steady-state concentration profiles, spatial correlations, particle number fluctuations, and diffusion fluxes through the pore. From the profiles and fluxes, we determine a generalized tracer diffusion coefficient Dtr(x ) , at various positions x within the pore. Dtr(x ) has a plateau value in the pore center scaling inversely with the pore length, but it is enhanced near the pore openings. The latter feature reflects the effect of fluctuations in adsorption and desorption, and it is also associated with a nontrivial scaling of the concentration profiles near the pore openings.

  3. Measurement of minority carrier lifetime, mobility and diffusion length in heavily doped silicon

    NASA Technical Reports Server (NTRS)

    Swirhun, S. E.; Swanson, R. M.

    1986-01-01

    Carrier transport and recombination parameters in heavily doped silicon were examined. Data were presented for carrier diffusivity in both p- and n-type heavily doped silicon covering a broad range of doping concentrations from 10 to the 15th power to 10 to the 20th power atoms/cu cm. One of the highlights of the results showed that minority carrier diffusivities are higher by a factor of 2 in silicon compared to majority carrier diffusivities.

  4. Exciton diffusion length in complex quantum systems: the effects of disorder and environmental fluctuations on symmetry-enhanced supertransfer.

    PubMed

    Abasto, D F; Mohseni, M; Lloyd, S; Zanardi, P

    2012-08-13

    Symmetric couplings among aggregates of n chromophores increase the transfer rate of excitons by a factor n(2), a quantum-mechanical phenomenon called 'supertransfer'. In this work, we demonstrate how supertransfer effects induced by geometrical symmetries can enhance the exciton diffusion length by a factor n along cylindrically symmetric structures, consisting of arrays of rings of chromophores, and along spiral arrays. We analyse both closed-system dynamics and open quantum dynamics, modelled by combining a random bosonic bath with static disorder. In the closed-system case, we use the symmetries of the system within a short-time approximation to obtain a closed analytical expression for the diffusion length that explicitly reveals the supertransfer contribution. When subject to disorder, we show that supertransfer can enhance excitonic diffusion lengths for small disorders and characterize the crossover from coherent to incoherent motion. Owing to the quasi-one-dimensional nature of the model, disorder ultimately localizes the excitons, diminishing but not destroying the effects of supertransfer. When dephasing effects are included, we study the scaling of diffusion with both time and number of chromophores and observe that the transition from a coherent, ballistic regime to an incoherent, random-walk regime occurs at the same point as the change from supertransfer to classical scaling.

  5. 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

  6. Measurement of diffusion length and surface recombination velocity in Interdigitated Back Contact (IBC) and Front Surface Field (FSF) solar cells

    NASA Astrophysics Data System (ADS)

    Verlinden, Pierre; Van de Wiele, Fernand

    1985-03-01

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

  7. 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.

  8. Direct determination of minority carrier diffusion lengths at axial GaAs nanowire p-n junctions.

    PubMed

    Gutsche, Christoph; Niepelt, Raphael; Gnauck, Martin; Lysov, Andrey; Prost, Werner; Ronning, Carsten; Tegude, Franz-Josef

    2012-03-14

    Axial GaAs nanowire p-n diodes, possibly one of the core elements of future nanowire solar cells and light emitters, were grown via the Au-assisted vapor-liquid-solid mode, contacted by electron beam lithography, and investigated using electron beam induced current measurements. The minority carrier diffusion lengths and dynamics of both, electrons and holes, were determined directly at the vicinity of the p-n junction. The generated photocurrent shows an exponential decay on both sides of the junction and the extracted diffusion lengths are about 1 order of magnitude lower compared to bulk material due to surface recombination. Moreover, the observed strong diameter-dependence is well in line with the surface-to-volume ratio of semiconductor nanowires. Estimating the surface recombination velocities clearly indicates a nonabrupt p-n junction, which is in essential agreement with the model of delayed dopant incorporation in the Au-assisted vapor-liquid-solid mechanism. Surface passivation using ammonium sulfide effectively reduces the surface recombination and thus leads to higher minority carrier diffusion lengths.

  9. Study on flow instability in a diffuser with swirling flow under several conditions of pipe length and swirl intensity

    NASA Astrophysics Data System (ADS)

    Matsuzaka, R.; Nakashima, T.; Miyagawa, K.

    2016-11-01

    A swirling flow in a diffuser such as a draft tube of a hydro turbine may induce the flow instabilities accompanied by pressure fluctuations known as vortex rope behaviour and cavitation surge. Cavitation surge is the self-excited oscillation, which induces the large flow rate fluctuation that results from the change of the cavity volume. In this research, the investigation of the effect of the pipe length and the swirl intensity on the flow instabilities in a diffuser was performed by experiments and numerical analyses using the draft tube component experimental facility. The length of the pipe was modified by up to about 25 times as long as the diameter of the throat in order to validate the one-dimensional analyses. In addition, the swirl intensity was changed by replacing another swirl generator. The frequency of cavitation surge was changed with regard to the swirl intensity as the one-dimensional analyses in the previous study has predicted it. Unsteady numerical simulations of the swirling flow with cavitation in the diffuser was performed. The results of experiments and numerical analyses correspond qualitatively with the result of the one-dimensional analyses, which suggested that the coupling with the experiments, CFD analyses and the one-dimensional analyses is the more effective way in order to predict the flow instabilities in the diffuser.

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

    PubMed Central

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

    2012-01-01

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

  11. Penetration and lateral diffusion characteristics of polycrystalline graphene barriers.

    PubMed

    Yoon, Taeshik; Mun, Jeong Hun; Cho, Byung Jin; Kim, Taek-Soo

    2014-01-07

    We report penetration and lateral diffusion behavior of environmental molecules on synthesized polycrystalline graphene. Penetration occurs through graphene grain boundaries resulting in local oxidation. However, when the penetrated molecules diffuse laterally, the oxidation region will expand. Therefore, we measured the lateral diffusion rate along the graphene-copper interface for the first time by the environment-assisted crack growth test. It is clearly shown that the lateral diffusion is suppressed due to the high van der Waals interaction. Finally, we employed bilayer graphene for a perfect diffusion barrier facilitated by decreased defect density and increased lateral diffusion path.

  12. Increase in the diffusion length of minority carriers in Al{sub x}Ga{sub 1–x}N alloys ({sub x} = 0–0.1) fabricated by ammonia molecular beam epitaxy

    SciTech Connect

    Malin, T. V. Gilinsky, A. M.; Mansurov, V. G.; Protasov, D. Yu.; Kozhuhov, A. S.; Yakimov, E. B.; Zhuravlev, K. S.

    2015-10-15

    The room-temperature diffusion length of minority carriers in n-Al{sub 0.1}Ga{sub 0.9}N layers grown by ammonia molecular beam epitaxy on sapphire (0001) substrates used in structures for ultraviolet photodetectors is studied. Measurements were performed using the spectral dependence of the photocurrent recorded in a built-in p–n junction for thin samples and using the induced electron-current procedure for films up to 2 µm thick. The results show that the hole diffusion length in n-AlGaN films is 120–150 nm, which is larger than in GaN films grown under similar growth conditions by a factor of 3–4. This result can be associated with the larger lateral sizes characteristic of hexagonal columns in AlGaN layers grown by molecular beam epitaxy. No increase in the hole diffusion length is observed for thicker films.

  13. Improvement of oxygen diffusion characteristic in gas diffusion layer with planar-distributed wettability for polymer electrolyte fuel cell

    NASA Astrophysics Data System (ADS)

    Koresawa, Ryo; Utaka, Yoshio

    2014-12-01

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

  14. Amide Proton Transfer Imaging of Diffuse Gliomas: Effect of Saturation Pulse Length in Parallel Transmission-Based Technique

    PubMed Central

    Hiwatashi, Akio; Keupp, Jochen; Yamashita, Koji; Kikuchi, Kazufumi; Yoshiura, Takashi; Yoneyama, Masami; Kruiskamp, Marijn J.; Sagiyama, Koji; Takahashi, Masaya; Honda, Hiroshi

    2016-01-01

    In this study, we evaluated the dependence of saturation pulse length on APT imaging of diffuse gliomas using a parallel transmission-based technique. Twenty-two patients with diffuse gliomas (9 low-grade gliomas, LGGs, and 13 high-grade gliomas, HGGs) were included in the study. APT imaging was conducted at 3T with a 2-channel parallel transmission scheme using three different saturation pulse lengths (0.5 s, 1.0 s, 2.0 s). The 2D fast spin-echo sequence was used for imaging. Z-spectrum was obtained at 25 frequency offsets from -6 to +6 ppm (step 0.5 ppm). A point-by-point B0 correction was performed with a B0 map. Magnetization transfer ratio (MTRasym) and ΔMTRasym (contrast between tumor and normal white matter) at 3.5 ppm were compared among different saturation lengths. A significant increase in MTRasym (3.5 ppm) of HGG was found when the length of saturation pulse became longer (3.09 ± 0.54% at 0.5 s, 3.83 ± 0.67% at 1 s, 4.12 ± 0.97% at 2 s), but MTRasym (3.5 ppm) was not different among the saturation lengths in LGG. ΔMTRasym (3.5 ppm) increased with the length of saturation pulse in both LGG (0.48 ± 0.56% at 0.5 s, 1.28 ± 0.56% at 1 s, 1.88 ± 0.56% at 2 s and HGG (1.72 ± 0.54% at 0.5 s, 2.90 ± 0.49% at 1 s, 3.83 ± 0.88% at 2 s). In both LGG and HGG, APT-weighted contrast was enhanced with the use of longer saturation pulses. PMID:27227746

  15. Penetration and lateral diffusion characteristics of polycrystalline graphene barriers

    NASA Astrophysics Data System (ADS)

    Yoon, Taeshik; Mun, Jeong Hun; Cho, Byung Jin; Kim, Taek-Soo

    2013-12-01

    We report penetration and lateral diffusion behavior of environmental molecules on synthesized polycrystalline graphene. Penetration occurs through graphene grain boundaries resulting in local oxidation. However, when the penetrated molecules diffuse laterally, the oxidation region will expand. Therefore, we measured the lateral diffusion rate along the graphene-copper interface for the first time by the environment-assisted crack growth test. It is clearly shown that the lateral diffusion is suppressed due to the high van der Waals interaction. Finally, we employed bilayer graphene for a perfect diffusion barrier facilitated by decreased defect density and increased lateral diffusion path.We report penetration and lateral diffusion behavior of environmental molecules on synthesized polycrystalline graphene. Penetration occurs through graphene grain boundaries resulting in local oxidation. However, when the penetrated molecules diffuse laterally, the oxidation region will expand. Therefore, we measured the lateral diffusion rate along the graphene-copper interface for the first time by the environment-assisted crack growth test. It is clearly shown that the lateral diffusion is suppressed due to the high van der Waals interaction. Finally, we employed bilayer graphene for a perfect diffusion barrier facilitated by decreased defect density and increased lateral diffusion path. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr03849a

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

  17. 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.

  18. 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.

  19. Clinicopathological characteristics of TERT promoter mutation and telomere length in hepatocellular carcinoma

    PubMed Central

    Lee, Hye Won; Park, Tae In; Jang, Se Young; Park, Soo Young; Park, Won-Jin; Jung, Soo-Jung; Lee, Jae-Ho

    2017-01-01

    Abstract Promoter mutations in telomerase reverse transcriptase (TERT) and telomere length have been studied in various tumors. In the present study, the frequency and clinical characteristics of TERT promoter mutation and telomere length were studied in hepatocellular carcinoma (HCC). TERT promoter mutation and telomere length were analyzed in 162 tumor samples of the patients with HCC by sequencing and real-time PCR, respectively. The TERT promoter mutation rate was 28.8% (46/160) in HCC and was associated with males (P = 0.027). The telomere length was not significantly different in the presence of a TERT promoter mutation but was shorter in high-grade tumor stages (P = 0.048). Survival analyses showed that poor overall survival was associated with longer telomere length (P = 0.013). However, the TERT promoter mutation did not have a prognostic value for HCC. Multivariate survival analyses demonstrated that the telomere length was an independent prognostic marker for poor overall survival (hazard ratio = 1.75, 95% confidence interval: 1.046–2.913, P = 0.033). These data demonstrated that TERT promoter mutation is a frequent event in HCC; however, telomere length, but not the presence of a TERT promoter mutation, might have potential value as a prognostic indicator of HCC. PMID:28151853

  20. Clinicopathological characteristics of TERT promoter mutation and telomere length in hepatocellular carcinoma.

    PubMed

    Lee, Hye Won; Park, Tae In; Jang, Se Young; Park, Soo Young; Park, Won-Jin; Jung, Soo-Jung; Lee, Jae-Ho

    2017-02-01

    Promoter mutations in telomerase reverse transcriptase (TERT) and telomere length have been studied in various tumors. In the present study, the frequency and clinical characteristics of TERT promoter mutation and telomere length were studied in hepatocellular carcinoma (HCC). TERT promoter mutation and telomere length were analyzed in 162 tumor samples of the patients with HCC by sequencing and real-time PCR, respectively. The TERT promoter mutation rate was 28.8% (46/160) in HCC and was associated with males (P = 0.027). The telomere length was not significantly different in the presence of a TERT promoter mutation but was shorter in high-grade tumor stages (P = 0.048). Survival analyses showed that poor overall survival was associated with longer telomere length (P = 0.013). However, the TERT promoter mutation did not have a prognostic value for HCC. Multivariate survival analyses demonstrated that the telomere length was an independent prognostic marker for poor overall survival (hazard ratio = 1.75, 95% confidence interval: 1.046-2.913, P = 0.033). These data demonstrated that TERT promoter mutation is a frequent event in HCC; however, telomere length, but not the presence of a TERT promoter mutation, might have potential value as a prognostic indicator of HCC.

  1. Determination of diffusion coefficients and diffusion characteristics for chlorferon and diethylthiophosphate in Ca-alginate gel beads.

    PubMed

    Ha, Jiyeon; Engler, Cady R; Lee, Seung Jae

    2008-07-01

    Diffusion characteristics of chlorferon and diethylthiophosphate (DETP) in Ca-alginate gel beads were studied to assist in designing and operating bioreactor systems. Diffusion coefficients for chlorferon and DETP in Ca-alginate gel beads determined at conditions suitable for biodegradation studies were 2.70 x 10(-11) m(2)/s and 4.28 x 10(-11) m(2)/s, respectively. Diffusivities of chlorferon and DETP were influenced by several factors, including viscosity of the bulk solution, agitation speed, and the concentrations of diffusing substrate and immobilized cells. Diffusion coefficients increased with increasing agitation speed, probably due to poor mixing at low speed and some attrition of beads at high speeds. Diffusion coefficients also increased with decreasing substrate concentration. Increased cell concentration in the gel beads caused lower diffusivity. Theoretical models to predict diffusivities as a function of cell weight fraction overestimated the effective diffusivities for both chlorferon and DETP, but linear relations between effective diffusivity and cell weight fraction were derived from experimental data. Calcium-alginate gel beads with radii of 1.65-1.70 mm used in this study were not subject to diffusional limitations: external mass transfer resistances were negligible based on Biot number calculations and effectiveness factors indicated that internal mass transfer resistance was negligible. Therefore, the degradation rates of chlorferon and DETP inside Ca-alginate gel beads were reaction-limited.

  2. 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.

  3. Characteristics of Cluster Implantation and Low Diffusion Annealing

    SciTech Connect

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

    2008-11-03

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

  4. Diffusion length of photo-generated charge carriers in layers and powders of CH3NH3PbI3 perovskite

    NASA Astrophysics Data System (ADS)

    Dittrich, Th.; Lang, F.; Shargaieva, O.; Rappich, J.; Nickel, N. H.; Unger, E.; Rech, B.

    2016-08-01

    The diffusion or transport lengths of photo-generated charge carriers in CH3NH3PbI3 layers (thickness up to 1 μm) and powders have been directly measured with high accuracy by modulated surface photovoltage after Goodman. The values of the diffusion lengths of photo-generated charge carriers ranged from 200 nm to tenths of μm. In thin CH3NH3PbI3 layers, the transport lengths corresponded to the layer thickness whereas in thicker layers and in crystallites of CH3NH3PbI3 powders the grain size limited the diffusion length. For grains, the diffusion length of photo-generated charge carriers depended on the measurement conditions.

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

    PubMed

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

    2014-10-22

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

  6. Electrochemical measurement of lateral diffusion coefficients of ubiquinones and plastoquinones of various isoprenoid chain lengths incorporated in model bilayers.

    PubMed Central

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

    1998-01-01

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

  7. Tracer counterpermeation analysis of diffusivity in finite-length nanopores with and without single-file dynamics

    DOE PAGES

    Ackerman, David M.; Evans, James W.

    2017-01-19

    Here, we perform a tracer counterpermeation (TCP) analysis for a stochastic model of diffusive transport through a narrow linear pore where passing of species within the pore is inhibited or even excluded (single-file diffusion). TCP involves differently labeled but otherwise identical particles from two decoupled infinite reservoirs adsorbing into opposite ends of the pore, and desorbing from either end. In addition to transient behavior, we assess steady-state concentration profiles, spatial correlations, particle number fluctuations, and diffusion fluxes through the pore. From the profiles and fluxes, we determine a generalized tracer diffusion coefficient Dtr(x), at various positions x within the pore.more » Dtr(x) has a plateau value in the pore center scaling inversely with the pore length, but it is enhanced near the pore openings. The latter feature reflects the effect of fluctuations in adsorption and desorption, and it is also associated with a nontrivial scaling of the concentration profiles near the pore openings.« less

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

  9. 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.

  10. 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.

  11. 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).

  12. 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).

  13. Identifying ergodicity breaking for fractional anomalous diffusion: Criteria for minimal trajectory length

    NASA Astrophysics Data System (ADS)

    Loch-Olszewska, Hanna; Sikora, Grzegorz; Janczura, Joanna; Weron, Aleksander

    2016-11-01

    In this paper, we study ergodic properties of α -stable autoregressive fractionally integrated moving average (ARFIMA) processes which form a large class of anomalous diffusions. A crucial practical question is how long trajectories one needs to observe in an experiment in order to claim that the analyzed data are ergodic or not. This will be solved by checking the asymptotic convergence to 0 of the empirical estimator F (n ) for the dynamical functional D (n ) defined as a Fourier transform of the n -lag increments of the ARFIMA process. Moreover, we introduce more flexible concept of the ɛ -ergodicity.

  14. Factors affecting gestation length and estrus cycle characteristics in Spanish donkey breeds reared in southern Spain.

    PubMed

    Galisteo, J; Perez-Marin, C C

    2010-08-01

    This paper investigated gestation length and estrus cycle characteristics in three different Spanish donkey breeds (Andalusian, Zamorano-Leones, and Catalonian) kept on farm conditions in southern Spain, using data for ten consecutive breeding seasons. Gestation length was measured in 58 pregnancies. Ovarian ultrasonography was used to detect the ovulation, in order to ascertain true gestation length (ovulation-parturition). Pregnancy was diagnosed approximately 14-18 d after ovulation and confirmed on approximately day 60. Average gestation length was 362 +/-15.3 (SD) d, and no significant differences were observed between the three different breeds. Breeding season had a significant effect (P < 0.01), with longer gestation lengths when jennies were covered during the early period. Breed, age of jenny, year of birth, foal gender, month of breeding, and type of gestation had no significant effect on gestation length. After parturition, foal-heat was detected in 53.8% of the postpartum cycles studied (n = 78), and ovulation occurred on day 13.2 +/- 2.7. The duration of foal-heat was 4.7 +/-1.7 d, with a pregnancy rate of 40.5%. When subsequent estrus cycles were analyzed, the interovulatory interval (n = 68) and estrus duration (n = 258) were extended to a mean 23.8 +/- 3.5 and 5.7 +/- 2.2 d, respectively. Both variables were influenced by the year of study (P < 0.03 and P < 0.001), whereas month and season of ovulation (P < 0.005 and P < 0.009, respectively) affected only interovulatory intervals. Estrus duration was significantly longer than that observed at the foal-heat (P < 0.006), and the pregnancy rate was 65.8%. This study provides reference values for true gestation length and estrus cycle characteristics in Spanish jennies. Breeding season affected gestation length in farm conditions. Also, seasonal influence was observed on the length of the estrus cycle (i.e., interovulatory interval), although foal-heat was not affected by environmental factors.

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

    NASA Astrophysics Data System (ADS)

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

    2000-02-01

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

  16. 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.

  17. Terahertz Conductivity within Colloidal CsPbBr3 Perovskite Nanocrystals: Remarkably High Carrier Mobilities and Large Diffusion Lengths.

    PubMed

    Yettapu, Gurivi Reddy; Talukdar, Debnath; Sarkar, Sohini; Swarnkar, Abhishek; Nag, Angshuman; Ghosh, Prasenjit; Mandal, Pankaj

    2016-08-10

    Colloidal CsPbBr3 perovskite nanocrystals (NCs) have emerged as an excellent light emitting material in last one year. Using time domain and time-resolved THz spectroscopy and density functional theory based calculations, we establish 3-fold free carrier recombination mechanism, namely, nonradiative Auger, bimolecular electron-hole recombination, and inefficient trap-assisted recombination in 11 nm sized colloidal CsPbBr3 NCs. Our results confirm a negligible influence of surface defects in trapping charge carriers, which in turn results into desirable intrinsic transport properties, from the perspective of device applications, such as remarkably high carrier mobility (∼4500 cm(2) V(-1) s(-1)), large diffusion length (>9.2 μm), and high luminescence quantum yield (80%). Despite being solution processed and possessing a large surface to volume ratio, this combination of high carrier mobility and diffusion length, along with nearly ideal photoluminescence quantum yield, is unique compared to any other colloidal quantum dot system.

  18. 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.

  19. Characteristics of Li diffusion on silicene and zigzag nanoribbon

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

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

  20. Measuring the Minority-Carrier Diffusion Length of n-Type In0.53Ga0.47As Epilayers Using Surface Photovoltage

    NASA Astrophysics Data System (ADS)

    Li, Ping; Tang, Hengjing; Li, Tao; Li, Xue; Shao, Xiumei; Pavelka, Tibor; Huang, Li; Gong, Haimei

    2017-04-01

    We report measurements of the minority-carrier diffusion length of n-type In0.53Ga0.47As epilayer samples using the surface photovoltage (SPV) method, and the minority-carrier lifetime of the same samples obtained by the microwave photoconductivity decay ( μ-PCD) method. The minority-carrier diffusion length was determined from the surface photovoltage and the optical absorption coefficient of the material. By scanning the SPV probe over the sample, the difference in surface photovoltage could be measured, as well as enabling surface photovoltage mapping. Samples having two different doping concentrations were used: sample A with 3 × 1016 cm-3 and sample B with 1 × 1016 cm-3, having minority-carrier diffusion length at room temperature of 5.59 μm and 6.3 μm, respectively. Meanwhile, sample uniformity was investigated using SPV for the first time. Lifetime measurements were performed on the n-type In0.53Ga0.47As epilayer samples using the μ-PCD technique, obtaining the minority-carrier diffusion length indirectly. Comparison of the minority-carrier diffusion length values obtained from SPV versus μ-PCD showed good consistency. Therefore, the presented method could be useful for characterization of the minority-carrier diffusion length of wafers.

  1. 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.

  2. Average Path-Length Parameter of Diffuse Light in Scattering Media

    NASA Astrophysics Data System (ADS)

    Arancibia-Bulnes, Camilo A.; Ruiz-Suárez, Jesús C.

    1999-03-01

    We use Monte Carlo simulations to study in detail the propagation of light in a plane-parallel medium containing scattering particles. In particular, we compute the forward and backward average path-length parameters (FAPP and BAPP, respectively) of four-flux radiative transfer models as functions of the optical depth. Strong dependence on the single scattering albedo and phase function asymmetry is found for both quantities. In general the values of the FAPP decrease with increasing absorption, whereas the opposite occurs for the BAPP. A similar effect is produced when changing from isotropic phase functions to phase functions with a large asymmetry in the forward direction. We present analytical results for the asymptotic values of the FAPP and BAPP as functions of albedo for the particular case of isotropic scattering. Our results differ markedly from the predictions obtained recently with two multiple-scattering models by Vargas and Niklasson J. Opt. Soc. Am. A 14, 2243 (1997); Appl. Opt. 36, 3735 (1997) . The differences found point out the intrinsic limitations of these models.

  3. Diffusion, Perfusion, and Histopathologic Characteristics of Desmoplastic Infantile Ganglioglioma

    PubMed Central

    Ho, Chang Y; Gener, Melissa; Bonnin, Jose; Kralik, Stephen F

    2016-01-01

    We present a case series of a rare tumor, the desmoplastic infantile ganglioglioma (DIG) with MRI diffusion and perfusion imaging quantification as well as histopathologic characterization. Four cases with pathologically-proven DIG had diffusion weighted imaging (DWI) and two of the four had dynamic susceptibility contrast imaging. All four tumors demonstrate DWI findings compatible with low-grade pediatric tumors. For the two cases with perfusion imaging, a higher relative cerebral blood volume was associated with higher proliferation index on histopathology for one of the cases. Our results are discussed in conjunction with a literature review. PMID:27761184

  4. Modular interference characteristics and beat length of a two-hole photonic crystal fiber

    NASA Astrophysics Data System (ADS)

    Lu, Xin; Liu, Ying; Guo, Xuan

    2016-10-01

    We show the mode propagation characteristics of fundamental and second-order modes in a two-mode highly birefringent photonics crystal fiber (HB-PCF) under a longitudinal strain. The two-mode operation range in HB-PCF is researched. Within this range, the modular interference beat length LMB in each Eigen polarization are simulated with respect to wavelength λ , and the fitting equations between LMB and λ are presented. We also measure LMB at λ = 532nm , respectively. The results show that the theoretical simulation is basically in accordance with the experimental data.

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

    SciTech Connect

    Mohammadi, V. Nihtianov, S.

    2016-02-15

    The lateral gas phase diffusion length of boron atoms, L{sub B}, along silicon and boron surfaces during chemical vapor deposition (CVD) using diborane (B{sub 2}H{sub 6}) is reported. The value of L{sub B} is critical for reliable and uniform boron layer coverage. The presented information was obtained experimentally and confirmed analytically in the boron deposition temperature range from 700 °C down to 400 °C. For this temperature range the local loading effect of the boron deposition is investigated on the micro scale. A L{sub B} = 2.2 mm was determined for boron deposition at 700 °C, while a L{sub B} of less than 1 mm was observed at temperatures lower than 500 °C.

  6. Spin Torque Study of the Spin Hall Conductivity and Spin Diffusion Length in Platinum Thin Films with Varying Resistivity

    NASA Astrophysics Data System (ADS)

    Nguyen, Minh-Hai; Ralph, D. C.; Buhrman, R. A.

    2016-03-01

    We report measurements of the spin torque efficiencies in perpendicularly magnetized Pt /Co bilayers where the Pt resistivity ρPt is strongly dependent on thickness tPt . The dampinglike spin Hall torque efficiency per unit current density ξDLj varies significantly with tPt , exhibiting a peak value ξDLj=0.12 at tPt=2.8 - 3.9 nm . In contrast, ξDLj/ρPt increases monotonically with tPt and saturates for tPt>5 nm , consistent with an intrinsic spin Hall effect mechanism, in which ξDLj is enhanced by an increase in ρPt . Assuming the Elliott-Yafet spin scattering mechanism dominates, we estimate that the spin diffusion length λs=(0.77 ±0.08 )×10-15 Ω .m2/ρPt .

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  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. Temperature dependence of the magnon spin diffusion length and magnon spin conductivity in the magnetic insulator yttrium iron garnet

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

    We present a systematic study of the temperature dependence of diffusive magnon spin transport using nonlocal devices fabricated on a 210-nm yttrium iron garnet film on a gadolinium gallium garnet substrate. In our measurements, we detect spin signals arising from electrical and thermal magnon generation, and we directly extract the magnon spin diffusion length λm for temperatures from 2 to 293 K. Values of λm obtained from electrical and thermal generation agree within the experimental error with λm=9.6 ±0.9 μ m at room temperature to a minimum of λm=5.5 ±0.7 μ m at 30 K. Using a two-dimensional finite element model to fit the data obtained for electrical magnon generation we extract the magnon spin conductivity σm as a function of temperature, which is reduced from σm=3.7 ±0.3 ×105S /m at room temperature to σm=0.9 ±0.6 ×104S /m at 5 K. Finally, we observe an enhancement of the signal originating from thermally generated magnons for low temperatures where a maximum is observed around T =7 K . An explanation for this low-temperature enhancement is however still missing and requires additional investigation.

  10. Some polarization characteristics of magnesium oxide and other diffuse reflectors.

    PubMed

    Carmer, D C; Bair, M E

    1969-08-01

    Measurements were made with a laser at a wavelength of 6328 A to determine the effects of polarization on the reflection properties of "diffuse" reflectors. Bidirectional reflectance, with the polarization plane of the laser source and the plane of a polarization analyzer at the receiver as parameters, was measured in the incidence plane for smoke-deposited magnesium oxide, pressed magnesium oxide powder, a diffusely reflecting white paint, and Fiberfrax ceramic insulating felt. It is shown that the bidirectional reflectance, rho', of these samples and the extent to which it departs from Lambert's cosine law are definitely functions of source and receiver polarization. The percentage polarization of reflected radiation is also given for both polarized and unpolarized sources.

  11. Improvement of mechanical characteristics and performances with Ni diffusion mechanism throughout Bi-2223 superconducting matrix

    NASA Astrophysics Data System (ADS)

    Sarıtekin, N. K.; Bilge, H.; Kahraman, M. F.; Zalaoǧlu, Y.; Pakdil, M.; Doǧruer, M.; Yıldırım, G.; Oz, M.

    2016-03-01

    This study is interested in the role of diffusion annealing temperature (650-850°C) on the mechanical characteristics and performance of pure and Ni diffused Bi-2223 superconducting materials by means of standard compression tests and Vickers hardness measurements at performed different applied loads in the range of 0.245-2.940N and theoretical calculations. Based on the experimental findings, the mechanical performances improve with increasing annealing temperature up to 700 °C beyond which they degrade drastically due to the increased artificial disorders, cracks and irregular grain orientation distribution. In other words, the penetration of excess Ni inclusions accelerates both the dislocation movement and especially the cracks and voids propagation as a result of the decrement in the Griffith critical crack length. Further, it is to be mentioned here that all the sample exhibit typical indentation size effect (ISE) behavior. In this respect, both the plastic (irreversible) and elastic (reversible) deformations have dominant role on the superconducting structures as a result of the enhancement in the elastic recovery. At the same time elastic modulus, yield strength and fracture toughness parameters are theoretically extracted from the microhardness values. Moreover, the elastic modulus parameters are compared with the experimental values. It is found that the differentiation between the comparison results enhances hastily with the increment in the applied indentation test loads due to the existence of the increased permanent disorders, lattice defects and strains in the stacked layers. Namely, the error level increases away from the actual crystal structure. Additionally, the microhardness values are theoretically analyzed for the change of the mechanical behaviors with the aid of Meyer's law, elastic/plastic deformation and Hays-Kendall approaches for the first time.

  12. Cow characteristics and their association with production performance with different dry period lengths.

    PubMed

    Steeneveld, W; van Knegsel, A T M; Remmelink, G J; Kemp, B; Vernooij, J C M; Hogeveen, H

    2014-01-01

    Shortening or omitting the dry period (DP) has been proposed as a management strategy to improve energy balance of dairy cows in early lactation. Both shortening and complete omission of the DP reduces milk production in the subsequent lactation compared with a conventional DP length of 60d. Some cows have less milk production loss than other cows after applying no DP or a short DP. The aim of this study is to evaluate which cow characteristics are associated with the amount of milk production losses following no DP or a short DP (30d). Daily production information from the lactation before and after the DP was available from 161 dairy cows (54 cows with a 0-d DP, 51 cows with a 30-d DP, and 56 cows with a 60-d DP) from a research herd. Daily production (milk, fat, and protein) until 305d in milk was estimated for all cows. Subsequently, total fat- and protein-corrected milk yield from 60d before the expected calving date until 305d in the following lactation (FPCMtotal) was estimated. A statistical analysis was performed to evaluate which cow characteristics were associated with limited or no production losses following no DP or a short DP, compared with a conventional DP length of 60d. Average FPCMtotal was 9,341, 10,499, and 10,795kg for cows with no DP, a 30-d DP, and a 60-d DP, respectively. The cow characteristics parity, daily milk production at 12wk before the expected calving date, and reduction in daily milk production between 16 and 12wk before the expected calving date were associated with production loss due to a short (30d) or no DP. Compared with 60d DP, multiparous cows had less production loss (987kg) following no DP than primiparous cows (2,132kg). The difference in FPCMtotal between the 3DP groups was largest for cows with a low milk production (e.g., 10kg/d) at 12wk before the expected calving date. The greater the reduction in milk production between 16 and 12wk before the expected calving date, the larger the difference in FPCMtotal between

  13. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    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 jph 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 jph ≠ 0) charge-carrier diffusion length ld eff as a function of jph for jph → 0 inferred from our experimental data proved to be consistent with the behavior of ld eff vs jph 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. Maternal Characteristics, Short Mid-Trimester Cervical Length, and Preterm Delivery

    PubMed Central

    Cho, Soo-Hyun; Jung, Eun Young; Joo, Jung Kyung; Jang, Ji Ae; Yoo, Ha-Na

    2017-01-01

    We aimed to determine the maternal characteristics (demographics, an obstetric history, and prior cervical excisional procedure) associated with a short mid-trimester cervical length (CL, defined as a CL of ≤ 25 mm) and whether having a short cervix explains the association between these maternal characteristics and spontaneous preterm delivery (SPTD, defined as a delivery before 34 weeks). This is a single-center retrospective cohort study of 3,296 consecutive women with a singleton pregnancy who underwent routine CL measurement between 20 and 24 weeks. Data were collected on maternal age, weight, height, parity, obstetric history (nulliparity; a history of at least 1 SPTD; and at least 1 term birth and no preterm birth [low-risk history group]), and prior cervical excisional procedure. In the multivariate regression analysis, an obstetric history, prior cervical excisional procedure, and gestational age at measurement were the variables significantly associated with short CL. In contrast, maternal weight, height, age, and parity were not significantly associated with short CL. By using the likelihood of SPTD as an outcome variable, logistic regression indicated that short CL and obstetric history, but not prior cervical excisional procedure, were significantly associated with SPTD after adjustment for potential confounders. A history of SPTD and prior cervical excisional procedure were associated with an increased risk of a short mid-trimester CL. A history of SPTD, but not prior cervical excisional procedure, is associated with an increased risk of SPTD, independent of a short CL. PMID:28145653

  16. Graded functional diffusion map-defined characteristics of apparent diffusion coefficients predict overall survival in recurrent glioblastoma treated with bevacizumab.

    PubMed

    Ellingson, Benjamin M; Cloughesy, Timothy F; Lai, Albert; Mischel, Paul S; Nghiemphu, Phioanh L; Lalezari, Shadi; Schmainda, Kathleen M; Pope, Whitney B

    2011-10-01

    Diffusion imaging has shown promise as a predictive and prognostic biomarker in glioma. We assessed the ability of graded functional diffusion maps (fDMs) and apparent diffusion coefficient (ADC) characteristics to predict overall survival (OS) in recurrent glioblastoma multiforme (GBM) patients treated with bevacizumab. Seventy-seven patients with recurrent GBMs were retrospectively examined. MRI scans were obtained before and approximately 6 weeks after treatment with bevacizumab. Graded fDMs were created by registering datasets to each patient's pretreatment scan and then performing voxel-wise subtraction between post- and pretreatment ADC maps. Voxels were categorized according to the degree of change in ADC within pretreatment fluid-attenuated inversion recovery (FLAIR) and contrast-enhancing regions of interest (ROIs). We found that the volume of tissue showing decreased ADC within both FLAIR and contrast-enhancing regions stratified OS (log-rank, P < .05). fDMs applied to contrast-enhancing ROIs more accurately predicted OS compared with fDMs applied to FLAIR ROIs. Graded fDMs (showing voxels with decreased ADC between 0.25 and 0.4 µm(2)/ms) were more predictive of OS than traditional (single threshold) fDMs, and the predictive ability of graded fDMs could be enhanced even further by adding the ADC characteristics from the fDM-classified voxels to the analysis (log-rank, P < .001). These results demonstrate that spatially resolved diffusion-based tumor metrics are a powerful imaging biomarker of survival in patients with recurrent GBM treated with bevacizumab.

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

    DOE PAGES

    Dong, Qingfeng; Fang, Yanjun; Shao, Yuchuan; ...

    2015-02-27

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

  18. 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

    --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.

  19. National Seminar on the Diffusion of New Instructional Materials and Practices. 5.0 Characteristics of the Communications Network: What are the Mechanisms Within the Diffusion System That Encourage or Discourage the Diffusion of Innovation?

    ERIC Educational Resources Information Center

    Social Science Education Consortium, Inc., Boulder, CO.

    In this document conference participants consider characteristics of the communications network for diffusion of new instructional materials and practices. Responses to these questions are presented: What are the communication mechanisms within the diffusion system that encourage or discourage the diffusion of innovation? What role do journal…

  20. Effect of diffusion and surface recombination on the frequency-dependent characteristics of an OPFET

    NASA Astrophysics Data System (ADS)

    Singh, Vinaya K.

    1993-02-01

    Analytical studies have been made on the effect of diffusion and surface recombination on the frequency dependent characteristics of an ion-implanted GaAs optical field effect transistor. Modulated optical generation and voltage dependent depletion layer width in the active region have been considered whereas photovoltaic effect is ignored in this analysis. Result shows that drain-source current decreases with the increases of modulated signal frequency but diffusion effect increases the modulating frequency range from c.m. to m.m. wavelength. Moreover, I- V changes significantly with the trap center density only when Nr >= 1023/m2 with diffusion effect and >= 1020/m2 without diffusion effect at a particular dimension of the device. This model may be very much useful to measure the sensitivity of the device in terms of trap center density and modulating frequency.

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

    SciTech Connect

    Damle, Ashok S; Cole, J Vernon

    2008-12-01

    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

  2. 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.

  3. Ceruminal diffusion activities and ceruminolytic characteristics of otic preparations – an in-vitro study

    PubMed Central

    2013-01-01

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

  4. 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.

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

    PubMed Central

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

    2016-01-01

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

  6. Muscle-specific changes in length-force characteristics of the calf muscles in the spastic Han-Wistar rat.

    PubMed

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

    2014-11-01

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

  7. Evaluation of a multimode fiber optic low coherence interferometer for path length resolved Doppler measurements of diffuse light

    NASA Astrophysics Data System (ADS)

    Varghese, Babu; Rajan, Vinayakrishnan; Van Leeuwen, Ton G.; Steenbergen, Wiendelt

    2007-12-01

    The performance of a graded index multimode fiber optic low coherence Mach-Zehnder interferometer with phase modulation is analyzed. Investigated aspects were its ability to measure path length distributions and to perform path length resolved Doppler measurements of multiple scattered photons in a turbid suspension of particles undergoing Brownian and translational motion. The path length resolution of this instrument is compared with a system using single mode fibers for illumination and detection. The optical path lengths are determined from the zero order moment of the phase modulation peak in the power spectrum. The weighted first moment, which is equal to the average Doppler shift, shows a linear response for different mean flow velocities within the physiological range.

  8. 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.

  9. DEPENDENCE OF LASER SINGLE-PULSE CHARACTERISTICS ON ACTIVE ROD LENGTH,

    DTIC Science & Technology

    The dependence of population inversion on rod length in the case of ruby and neodymium glass laser rods was investigated. The required pumping rates...switching, provided the dependence of emitted power on the coefficient of useful losses is investigated and the position of its maximum is determined.

  10. The effect of gate length variation on InAlGaN/GaN HFET device characteristics

    NASA Astrophysics Data System (ADS)

    Ketteniss, N.; Behmenburg, H.; Lecourt, F.; Defrance, N.; Hoel, V.; De Jaeger, J. C.; Heuken, M.; Kalisch, H.; Vescan, A.

    2012-03-01

    InAlGaN/GaN heterostructure field effect transistors (HFETs) with a nearly lattice-matched barrier layer (thickness tbar = 8.3 nm) are investigated. The focus is set on resolving the systematic dependence of device characteristics on the gate length LG. Therefore, five different gate length devices with LG ranging from 75 nm to 2 µm have been realized. Peak values of 460 mS mm-1 and 100 GHz for transconductance gm and unity current gain cut-off frequency fT are obtained for the 75 nm device. DC characteristics as well as the cut-off frequency fT show systematic scaling with the gate length LG. Nevertheless, short-channel effects appear for the short gate length devices in both DC and RF operation, and a critical minimum aspect ratio LG/tbar of 27 is identified for the investigated barrier composition of xIn = 0.11; yAl = 0.63 and zGa = 0.26.

  11. Which patient characteristics influence length of hospital stay after primary total hip arthroplasty in a 'fast-track' setting?

    PubMed

    den Hartog, Y M; Mathijssen, N M C; Hannink, G; Vehmeijer, S B W

    2015-01-01

    After implementation of a 'fast-track' rehabilitation protocol in our hospital, mean length of hospital stay for primary total hip arthroplasty decreased from 4.6 to 2.9 nights for unselected patients. However, despite this reduction there was still a wide range across the patients' hospital duration. The purpose of this study was to identify which specific patient characteristics influence length of stay after successful implementation of a 'fast-track' rehabilitation protocol. A total of 477 patients (317 female and 160 male, mean age 71.0 years; 39.3 to 92.6, mean BMI 27.0 kg/m(2);18.8 to 45.2) who underwent primary total hip arthroplasty between 1 February 2011 and 31 January 2013, were included in this retrospective cohort study. A length of stay greater than the median was considered as an increased duration. Logistic regression analyses were performed to identify potential factors associated with increased durations. Median length of stay was two nights (interquartile range 1), and the mean length of stay 2.9 nights (1 to 75). In all, 266 patients had a length of stay ≤ two nights. Age (odds ratio (OR) 2.46; 95% confidence intervals (CI) 1.72 to 3.51; p < 0.001), living situation (alone vs living together with cohabitants, OR 2.09; 95% CI 1.33 to 3.30; p = 0.002) and approach (anterior approach vs lateral, OR 0.29; 95% CI 0.19 to 0.46; p < 0.001) (posterolateral approach vs lateral, OR 0.24; 95% CI 0.10 to 0.55; p < 0.001) were factors that were significantly associated with increased length of stay in the multivariable logistic regression model.

  12. A Study of the Correlation Between Dislocations and Diffusion Length in In(49)Ga(51)P Solar Cells

    DTIC Science & Technology

    2008-12-01

    Length in In49Ga51P 6. AUTHOR(S) Scott Edward Williams 5 . FUNDING NUMBERS 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Naval Postgraduate...1 B. PURPOSE OF THESIS................................................................................... 5 C. MILITARY...RELEVANCE............................................................................. 5 D. THESIS OVERVIEW

  13. Observational Estimates of the Horizontal Eddy Diffusivity and Mixing Length in the Low-Level Region of Intense Hurricanes

    DTIC Science & Technology

    2011-11-01

    372 statistical analysis (t- test ) shows that the difference between the mean mixing length and 373 energy/flux containing scale is significantly...and R. W. Burpee , 2008: Structure of the eye and 521 eyewall of Hurricane Hugo (1989). Mon. Wea. Rev., 136, 1237-1259. 522 Montgomery, T. M., and R

  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. A Technique for Mapping Characteristic Lengths to Preserve Energy Dissipated via Strain Softening in a Multiscale Analysis

    NASA Technical Reports Server (NTRS)

    Pineda, Evan J.; Bednarcyk, Brett A.; Arnold, Steven M.

    2014-01-01

    It is often advantageous to account for the microstructure of the material directly using multiscale modeling. For computational tractability, an idealized repeating unit cell (RUC) is used to capture all of the pertinent features of the microstructure. Typically, the RUC is dimensionless and depends only on the relative volume fractions of the different phases in the material. This works well for non-linear and inelastic behavior exhibiting a positive-definite constitutive response. Although, once the material exhibits strain softening, or localization, a mesh objective failure theories, such as smeared fracture theories, nodal and element enrichment theories (XFEM), cohesive elements or virtual crack closure technique (VCCT), can be utilized at the microscale, but the dimensions of the RUC must then be defined. One major challenge in multiscale progressive damage modeling is relating the characteristic lengths across the scales in order to preserve the energy that is dissipated via localization at the microscale. If there is no effort to relate the size of the macroscale element to the microscale RUC, then the energy that is dissipated will remain mesh dependent at the macroscale, even if it is regularized at the microscale. Here, a technique for mapping characteristic lengths across the scales is proposed. The RUC will be modeled using the generalized method of cells (GMC) micromechanics theory, and local failure in the matrix constituent subcells will be modeled using the crack band theory. The subcell characteristic lengths used in the crack band calculations will be mapped to the macroscale finite element in order to regularize the local energy in a manner consistent with the global length scale. Examples will be provided with and without the regularization, and they will be compared to a baseline case where the size and shape of the element and RUC are coincident (ensuring energy is preserved across the scales).

  16. Comparison of the electron work function, hole concentration and exciton diffusion length for P3HT and PT prepared by thermal or acid cleavage

    NASA Astrophysics Data System (ADS)

    Toušek, J.; Toušková, J.; Ludvík, J.; Liška, A.; Remeš, Z.; Kylián, O.; Kousal, J.; Chomutová, R.; Heckler, I. M.; Bundgaard, E.; Krebs, F. C.

    2016-02-01

    The electron work function, hole concentration and diffusion length were compared for poly(3-hexylthiophene) polymer (P3HT) that is commonly used for construction of solar cells, and two types of native polythiophene (PT) samples which are prospective candidates for this purpose. The polythiophene samples were prepared from 2 different precursors by thermal or chemical treatment at room temperature. Cyclic voltammetry and work function measurements were used for estimating the concentration of holes. The measured data were evaluated assuming the validity of band theory based on the tight-binding model. Published data on the valence bandwidth were used for calculating the value of the overlap integral which is related to the hole effective mass. Energy band diagrams were constructed for all 3 materials. Finally, the exciton diffusion length, which is a critical parameter for the application of conjugated polymer materials in solar cells, was measured by a modified surface photovoltage method. The approach allowed us to identify the differences in the material properties related to the processing method. Morphology of the samples determined by AFM was another tool showing these differences. It is stated that a native polythiophene prepared by treatment with acids is a prospective material for solar cells and shows a similar quality as that produced by a thermal process.

  17. Mass transfer characteristics of eggplant slices during length of continuous band dryer

    NASA Astrophysics Data System (ADS)

    Kaveh, Mohammad; Amiri Chayjan, Reza; Nikbakht, Ali Mohammad

    2016-12-01

    This study presents a mathematical modeling of eggplant slice drying process in a continuous band dryer. The experiments for drying of eggplant slices were conducted at three air temperature levels of 45, 60, and 75 °C, inlet air velocities of 1, 1.5, and 2 m/s, and belt linear speeds of 2.5, 6.5, and 10.5 mm/s. To estimate the drying kinetics of eggplant slices, different mathematical models were utilized to fit the empirical data of thin layer drying. The models were compared based on their coefficients of determination (R 2), reduced Chi squares (χ 2) and root mean square errors (RMSE) between the experimental and predicted moisture ratios (MR). A feed and cascade forward with back-propagation algorithm was employed to predict the moisture ratio (MR) and drying rate (DR). The effective moisture diffusivity varied from 3.40 × 10-9 to 1.13 × 10-8 m2/s. The activation energy varied from 14.18 to 25.09 kJ/mol. The obtained results show that the feed forward back-propagation network with training algorithm of Levenberg-Marquardt, 4-5-5-2 topology, threshold functions of tansig-tansig-tansig can able to predict the moisture content and drying rate with R2 values of 0.9992 and 0.9726, respectively. Comparison of ANN results with mathematical models revealed that mathematical modeling yields better accuracy to predict the moisture content and drying rate of eggplant.

  18. Single vessel air injection estimates of xylem resistance to cavitation are affected by vessel network characteristics and sample length.

    PubMed

    Venturas, Martin D; Rodriguez-Zaccaro, F Daniela; Percolla, Marta I; Crous, Casparus J; Jacobsen, Anna L; Pratt, R Brandon

    2016-10-01

    Xylem resistance to cavitation is an important trait that is related to the ecology and survival of plant species. Vessel network characteristics, such as vessel length and connectivity, could affect the spread of emboli from gas-filled vessels to functional ones, triggering their cavitation. We hypothesized that the cavitation resistance of xylem vessels is randomly distributed throughout the vessel network. We predicted that single vessel air injection (SVAI) vulnerability curves (VCs) would thus be affected by sample length. Longer stem samples were predicted to appear more resistant than shorter samples due to the sampled path including greater numbers of vessels. We evaluated the vessel network characteristics of grapevine (Vitis vinifera L.), English oak (Quercus robur L.) and black cottonwood (Populus trichocarpa Torr. & A. Gray), and constructed SVAI VCs for 5- and 20-cm-long segments. We also constructed VCs with a standard centrifuge method and used computer modelling to estimate the curve shift expected for pathways composed of different numbers of vessels. For all three species, the SVAI VCs for 5 cm segments rose exponentially and were more vulnerable than the 20 cm segments. The 5 cm curve shapes were exponential and were consistent with centrifuge VCs. Modelling data supported the observed SVAI VC shifts, which were related to path length and vessel network characteristics. These results suggest that exponential VCs represent the most realistic curve shape for individual vessel resistance distributions for these species. At the network level, the presence of some vessels with a higher resistance to cavitation may help avoid emboli spread during tissue dehydration.

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

    SciTech Connect

    Diallo, S. O.

    2015-07-16

    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 (similar to 12 and 18 angstrom, 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. Suppression, we found, is accompanied by a systematic dependence of the average translational diffusion coefficient D-r and relaxation time [tau(0)] of the restricted water on pore size and temperature. We observed D-r values and tested against a proposed scaling law, in which the translational diffusion coefficient D-r of water within a porous matrix was found to depend solely on two single parameters, a temperature-independent translational diffusion coefficient D-c associated with the water bound to the pore walls and the ratio 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.

  20. 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 <τ0> 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 θ 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.

  1. Diffuse characteristics study of laser target board using Monte Carlo simulation

    NASA Astrophysics Data System (ADS)

    Yang, Pengling; Wu, Yong; Wang, Zhenbao; Tao, Mengmeng; Wu, Junjie; Wang, Ping; Yan, Yan; Zhang, Lei; Feng, Gang; Zhu, Jinghui; Feng, Guobin

    2013-05-01

    In this paper, Torrance-Sparrow and Oren-Nayar model is adopt to study diffuse characteristics of laser target board. The model which based on geometric optics, assumes that rough surfaces are made up of a series of symmetric V-groove cavities with different slopes at microscopic level. The distribution of the slopes of the V-grooves are modeled as beckman distribution function, and every microfacet of the V-groove cavity is assumed to behave like a perfect mirror, which means the reflected ray follows Fresnel law at the microfacet. The masking and shadowing effects of rough surface are also taken into account through geometric attenuation factor. Monte Carlo method is used to simulate the diffuse reflectance distribution of the laser target board with different materials and processing technology, and all the calculated results are verified by experiment. It is shown that the profile of bidirectional reflectance distribution curve is lobe-shaped with the maximum lies along the mirror reflection direction. The width of the profile is narrower for a lower roughness value, and broader for a higher roughness value. The refractive index of target material will also influence the intensity and distribution of diffuse reflectance of laser target surface.

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

    DOE PAGES

    Diallo, S. O.

    2015-07-16

    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 (similar to 12 and 18 angstrom, 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. Suppression, we found, is accompanied by a systematic dependence of the average translational diffusion coefficient D-r and relaxation timemore » [tau(0)] of the restricted water on pore size and temperature. We observed D-r values and tested against a proposed scaling law, in which the translational diffusion coefficient D-r of water within a porous matrix was found to depend solely on two single parameters, a temperature-independent translational diffusion coefficient D-c associated with the water bound to the pore walls and the ratio 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.« less

  3. 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.

  4. Investigation of Three-Dimensional Unsteady Flow Characteristics in Transonic Diffusers

    NASA Astrophysics Data System (ADS)

    Proshchanka, Dzianis; Yonezawa, Koichi; Tsujimoto, Yoshinobu

    Three-dimensional characteristics of unsteady flow in supercritical transonic diffuser are investigated. For various pressure ratios three-dimensional flow containing a normal shock/turbulent boundary layer interaction regions with shockwave and pseudo-shockwaves fluctuating in longitudinal and spanwise directions is observed. Experimental and numerical investigations show details of the flowfield in the vicinity of terminal shock, interaction regions and downstream turbulent unsteady flow. Spectral analysis of pressure fluctuations reveals existence of two characteristic frequencies attributed to the shockwave fluctuation in longitudinal direction for the lower frequency case and acoustic resonance in spanwise direction for the higher one. Vortices appear at each corner in transversal sections modifying the core flow. As a result, size and depth of longitudinal and vertical penetration of separation regions impelled by the terminal shock is either increased or decreased.

  5. Night and Day in the VA: Associations between Night Shift Staffing, Nurse Workforce Characteristics, and Length of Stay

    PubMed Central

    de Cordova, Pamela B.; Phibbs, Ciaran S.; Schmitt, Susan; Stone, Patricia W.

    2014-01-01

    In hospitals, nurses provide patient care around the clock, but the impact of night staff characteristics on patient outcomes is not well understood. The aim of this study was to examine the association between night nurse staffing and workforce characteristics and the length of stay (LOS) in 138 Veterans Affairs (VA) hospitals using panel data from 2002 through 2006. Staffing in hours per patient day was higher during the day than at night. The day nurse workforce had more educational preparation than the night workforce. Nurses’ years of experience at the unit, facility, and VA level were greater at night. In multivariate analyses controlling for confounding variables, higher night staffing and a higher skill mix were associated with reduced LOS. PMID:24403000

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

    PubMed

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

    2014-11-15

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

  7. The influence of institutional characteristics on length of stay for psychiatric patients: a national database study in South Korea.

    PubMed

    Chung, Woojin; Cho, Woo Hyun; Yoon, Chung Won

    2009-03-01

    The institutionalization of psychiatric patients has put a tremendous burden on many societies, but few studies have examined the effects of institutional characteristics on patient length of stay (LOS). This paper investigated the association between institutional characteristics and LOS for 160,517 psychiatric patients in South Korea by applying a two-level modeling technique to administrative claims databases covering the entire patient population. Patient LOS, expressed in terms of days, was analyzed by taking account of institutional type, ownership, location, inpatient capacity, staffing, and patient demographics. The characteristics of inpatients were used as control variables and consisted of gender, age, sub-diagnosis, and the type of national health security program. The main findings of this study are: (1) patient LOS was 69% longer at psychiatric hospitals than at tertiary-care hospitals; (2) neither location nor inpatient capacity was associated with LOS; (3) larger staffs reduced LOS; and (4), LOS increased with a higher proportion of male inpatients, inpatients > or =65 years old, or inpatients diagnosed with organic or schizophrenic disorders, possibly through contextual effects. The results of this study suggest that researchers and policy makers could improve their assessment of psychiatric patient LOS and its association with health outcome by taking into account institutional characteristics and using multi-level analyses.

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

    NASA Astrophysics Data System (ADS)

    Karatas, Ahmet Emre

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

  9. 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.

  10. Time-domain diffuse optical tomography using analytic statistical characteristics of photon trajectories

    SciTech Connect

    Konovalov, Aleksandr B; Vlasov, V V; Kalintsev, A G; Lyubimov, Vladimir V; Kravtsenyuk, Olga V

    2006-11-30

    The inverse problem of diffuse optical tomography (DOT) is reduced by the method of photon average trajectories (PAT) to the solution of the integral equation integrated along the conditional mean statistical photon trajectory. The PAT bending near the flat boundary of a scattering medium is estimated analytically. These estimates are used to determine the analytic statistical characteristics of photon trajectories for the flat layer geometry. The inverse DOT problem is solved by using the multiplicative algebraic algorithm modified to improve the convergence of the iteration reconstruction process. The numerical experiment shows that the modified PAT method permits the reconstruction of near-surface optical inhomogeneities virtually without distortions. (special issue devoted to multiple radiation scattering in random media)

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

    SciTech Connect

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

    2014-04-21

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

  12. 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

  13. 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.

  14. Elastic and length-force characteristics of the gastrocnemius of the hopping mouse (Notomys alexis) and the rat (Rattus norvegicus).

    PubMed

    Ettema, G J

    1996-06-01

    The aim of this study was to compare the contractile and series elastic properties of terrestrial mammals that use bipedal versus quadrupedal gaits. The gastrocnemius muscle of the hopping mouse (body mass 30.2 +/- 2.4 g, mean +/- S.D.) and the rat (313 +/- 10.7 g) were compared with data from the literature for the wallaby and the kangaroo rat to distinguish scaling effects and locomotion-related effects on muscle properties. Contractile length-force properties and series elastic stiffness were measured in situ during maximal tetanic contractions. The rat had a larger muscle-fibre-to-tendon-length ratio. The rat and hopping mouse showed similar normalised length-force characteristics of the gastrocnemius. Normalised stiffness in the hopping mouse was higher. The hopping mouse showed a higher capacity to store elastic energy per unit of contractile work capacity, as well as per unit of body mass. Accounting for body size differences, the rat had a smaller relative muscle mass and thus smaller work capacity than the three hopping animals considered. This is an agreement with a quadrupedal versus bipedal locomotion style. The differences in contractile and elastic properties of the gastrocnemius of the rat and hopping mouse seem to be closely related to locomotion patterns. Small animals seem to be able to utilise the storage and release of elastic energy to a far lesser extent than larger animals. However, even in animals as small as hopping mice, the storage and utilisation of elastic energy during locomotion is of functional significance and probably depends on locomotor behaviour.

  15. Quantifying the effect of metal-rich precipitates on minority carrier diffusion length in multicrystalline silicon using synchrotron-based spectrally resolved x-ray beam-induced current

    NASA Astrophysics Data System (ADS)

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

    2005-07-01

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

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

    NASA Astrophysics Data System (ADS)

    Shuster, Jason R.

    How does magnetic reconnection happen in a collisionless plasma? Knowledge of electron-scale dynamics is necessary to answer this outstanding question of plasma physics. Based on fully kinetic particle-in-cell (PIC) simulations of symmetric reconnection, the spatiotemporal evolution of velocity distribution functions in and around the electron diffusion region (EDR) elucidates how electrons are accelerated and heated by the cooperating reconnection electric and normal magnetic fields. The discrete, triangular structures characteristic of EDR distributions rotate and gyrotropize in velocity space as electrons remagnetize, forming multicomponent arc and ring structures. Further downstream, exhaust electrons are found to exhibit highly structured, time-dependent anisotropies that can be used to infer the temporal stage of reconnection. Cluster spacecraft measurements from a magnetotail reconnection exhaust region agree with these simulation predictions. In PIC simulations of asymmetric reconnection, EDR distributions acquire crescent-shaped populations, indicative of accelerated magnetosheath electrons mixing with electrons of magnetospheric origin. NASA's successfully launched Magnetospheric Multiscale (MMS) mission caught an EDR at the magnetopause and confirmed the signature crescent electron populations. A virtual spacecraft trajectory through the PIC domain is determined quantitatively by inputting MMS magnetic field measurements into an algorithm that outputs a trajectory along which the input measurements are matched. The crescent structures observed by MMS in the EDR are consistent with the simulation distributions at the corresponding time along the computed trajectory. This work demonstrates that electron characteristics can serve as "smoking-gun" observables of the EDR at the heart of the magnetic reconnection mystery.

  17. Novel distance dependence of diffusion constants in hyaluronan aqueous solution resulting from its characteristic nano-microstructure.

    PubMed

    Masuda, A; Ushida, K; Koshino, H; Yamashita, K; Kluge, T

    2001-11-21

    Material transports in hyaluronan (HA) aqueous solution were investigated applying two different techniques, i.e., pulsed field gradient NMR (PFG-NMR) and photochemical quenching, to the measurement of diffusion constants to show a sharp contrast resulting from the difference of the spectroscopic observation time while the same probe molecules were commonly used in two experiments. The value from PFG-NMR reflects the relatively long transport along which the majority of the molecules are retarded by the mesh structure of HA solution. In such inhomogeneous fluids, the observable diffusion constant should generally depend on the observation time and, i.e., the averaged distance of diffusion. Quantitative discussion, which compares the obtained characteristic distance of diffusion with the pore size, clarifies the role of the nano-microstructure of HA solution forming small pores surrounded by the polymer chain networks.

  18. Effect of alkyl chain length on the rotational diffusion of nonpolar and ionic solutes in 1-alkyl-3-methylimidazolium-bis(trifluoromethylsulfonyl)imides.

    PubMed

    Gangamallaiah, V; Dutt, G B

    2013-10-10

    Rotational diffusion of a nonpolar solute 9-phenylanthracene (9-PA) and a cationic solute rhodamine 110 (R110) has been examined in a series of 1-alkyl-3-methylimidazolium (alkyl = octyl, decyl, dodecyl, tetradecyl, hexadecyl, and octadecyl) bis(trifluoromethylsulfonyl)imides to understand the influence of alkyl chain length on solute rotation. In this study, reorientation times (τr) have been measured as a function of viscosity (η) by varying the temperature (T) of the solvents. These results have been analyzed using the Stokes-Einstein-Debye (SED) hydrodynamic theory along with the ones obtained for the same solutes in 1-alkyl-3-methylimidazolium (alkyl = methyl, ethyl, propyl, butyl, and hexyl) bis(trifluoromethylsulfonyl)imides (Gangamallaiah and Dutt, J. Phys. Chem. B 2012, 116, 12819-12825). It has been noticed that the data for 9-PA and R110 follows the relation τr = A(η/T)(n) with A being the ratio of hydrodynamic volume of the solute to the Boltzmann constant and n = 1 as envisaged by the SED theory. However, upon increasing the alkyl chain length from methyl to octadecyl significant deviations from the SED theory have been observed especially from the octyl derivative onward. From methyl to octadecyl derivatives, the value of A decreases by a factor of 3 for both the solutes and n by a factor of 1.4 and 1.6 for 9-PA and R110, respectively. These observations have been rationalized by taking into consideration the organized structure of the ionic liquids, whose influence appears to be pronounced when the number of carbon atoms in the alkyl chain attached to the imidazolium cation exceeds eight.

  19. 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...

  20. Solid-State Mesostructured Perovskite CH3NH3PbI3 Solar Cells: Charge Transport, Recombination, and Diffusion Length.

    PubMed

    Zhao, Yixin; Nardes, Alexandre M; Zhu, Kai

    2014-02-06

    We report on the effect of TiO2 film thickness on charge transport and recombination in solid-state mesostructured perovskite CH3NH3PbI3 (via one-step coating) solar cells using spiro-MeOTAD as the hole conductor. Intensity-modulated photocurrent/photovoltage spectroscopies show that the transport and recombination properties of solid-state mesostructured perovskite solar cells are similar to those of solid-state dye-sensitized solar cells. Charge transport in perovskite cells is dominated by electron conduction within the mesoporous TiO2 network rather than from the perovskite layer. Although no significant film-thickness dependence is found for transport and recombination, the efficiency of perovskite cells increases with TiO2 film thickness from 240 nm to about 650-850 nm owing primarily to the enhanced light harvesting. Further increasing film thickness reduces cell efficiency associated with decreased fill factor or photocurrent density. The electron diffusion length in mesostructured perovskite cells is longer than 1 μm for over four orders of magnitude of light intensity.

  1. 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.

  2. [Cloning of full-length coding sequence of tree shrew CD4 and prediction of its molecular characteristics].

    PubMed

    Tian, Wei-Wei; Gao, Yue-Dong; Guo, Yan; Huang, Jing-Fei; Xiao, Chang; Li, Zuo-Sheng; Zhang, Hua-Tang

    2012-02-01

    The tree shrews, as an ideal animal model receiving extensive attentions to human disease research, demands essential research tools, in particular cellular markers and monoclonal antibodies for immunological studies. In this paper, a 1 365 bp of the full-length CD4 cDNA encoding sequence was cloned from total RNA in peripheral blood of tree shrews, the sequence completes two unknown fragment gaps of tree shrews predicted CD4 cDNA in the GenBank database, and its molecular characteristics were analyzed compared with other mammals by using biology software such as Clustal W2.0 and so forth. The results showed that the extracellular and intracellular domains of tree shrews CD4 amino acid sequence are conserved. The tree shrews CD4 amino acid sequence showed a close genetic relationship with Homo sapiens and Macaca mulatta. Most regions of the tree shrews CD4 molecule surface showed positive charges as humans. However, compared with CD4 extracellular domain D1 of human, CD4 D1 surface of tree shrews showed more negative charges, and more two N-glycosylation sites, which may affect antibody binding. This study provides a theoretical basis for the preparation and functional studies of CD4 monoclonal antibody.

  3. [Analysis of the molecular characteristics and cloning of full-length coding sequence of interleukin-2 in tree shrews].

    PubMed

    Huang, Xiao-Yan; Li, Ming-Li; Xu, Juan; Gao, Yue-Dong; Wang, Wen-Guang; Yin, An-Guo; Li, Xiao-Fei; Sun, Xiao-Mei; Xia, Xue-Shan; Dai, Jie-Jie

    2013-04-01

    While the tree shrew (Tupaia belangeri chinensis) is an excellent animal model for studying the mechanisms of human diseases, but few studies examine interleukin-2 (IL-2), an important immune factor in disease model evaluation. In this study, a 465 bp of the full-length IL-2 cDNA encoding sequence was cloned from the RNA of tree shrew spleen lymphocytes, which were then cultivated and stimulated with ConA (concanavalin). Clustal W 2.0 was used to compare and analyze the sequence and molecular characteristics, and establish the similarity of the overall structure of IL-2 between tree shrews and other mammals. The homology of the IL-2 nucleotide sequence between tree shrews and humans was 93%, and the amino acid homology was 80%. The phylogenetic tree results, derived through the Neighbour-Joining method using MEGA5.0, indicated a close genetic relationship between tree shrews, Homo sapiens, and Macaca mulatta. The three-dimensional structure analysis showed that the surface charges in most regions of tree shrew IL-2 were similar to between tree shrews and humans; however, the N-glycosylation sites and local structures were different, which may affect antibody binding. These results provide a fundamental basis for the future study of IL-2 monoclonal antibody in tree shrews, thereby improving their utility as a model.

  4. [Factors affecting benzene diffusion from contaminated soils to the atmosphere and flux characteristics].

    PubMed

    Du, Ping; Wang, Shi-Jie; Zhao, Huan-Huan; Wu, Bin; Han, Chun-Mei; Fang, Ji-Dun; Li, Hui-Ying; Hosomi, Masaaki; Li, Fa-Sheng

    2013-12-01

    The influencing factors of benzene diffusion fluxes from sand and black soil to atmosphere were investigated using a flux chamber (30.0 cm x 17.5 cm x 29.0 cm). In this study, the benzene diffusion fluxes were estimated by measuring the benzene concentrations both in the headspace of the chamber and in the soils of different layers. The results indicated that the soil water content played an important role in benzene diffusion fluxes. The diffusion flux showed positive correlation with the initial benzene concentration and the benzene dissolution concentration for both soil types. The changes of air flow rate from 300 to 900 mL x min(-1) and temperature from 20 degrees C to 40 degrees C resulted in increases of the benzene diffusion flux. Our study of benzene diffusion fluxes from contaminated soils will be beneficial for the predicting model, and emergency management and precautions.

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

    PubMed Central

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

    2014-01-01

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

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

    PubMed

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

    2014-01-01

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

  7. The effect of personal characteristics on the relationship between diffusion and adoption of telecentre with value creation

    NASA Astrophysics Data System (ADS)

    Dahalin, Zulkhairi Md.

    2016-08-01

    This paper examines personal characteristics of respondents in the rural areas and the extent of its effect on the diffusion and adoption of the telecentre. Understanding the personal characteristics of the participants is needed in order to encourage better participation. A survey was conducted among participants of telecentres situated in rural areas in the northern states of Malaysia. Results showed that whilst family size had a significant effect on the relationships between diffusion and adoption with value creation, other personal characteristics were found not to affect the relationships. The results have important implications to sustainability of the telecentre, in which focus should be placed in small-sized families rather than based on background and other demographic profile of participants.

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

    SciTech Connect

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

    2015-02-27

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

  9. Patient characteristics associated with increased postoperative length of stay and readmission after elective laminectomy for lumbar spinal stenosis

    PubMed Central

    Basques, Bryce A.; Varthi, Arya G.; Golinvaux, Nicholas S.; Bohl, Daniel D.; Grauer, Jonathan N.

    2014-01-01

    Study Design Retrospective cohort. Objective To identify factors that were independently associated with increased postoperative length of stay (LOS) and readmission in patients who underwent elective laminectomy for lumbar spinal stenosis (LSS). Summary of Background Data LSS is a common pathology that is traditionally treated with decompressive laminectomy. Risk factors associated with increased LOS and readmission have not been fully characterized for laminectomy. Methods Patients who underwent laminectomy for LSS during 2011 and 2012 were identified from the American College of Surgeons National Surgical Quality Improvement Program (ACS-NSQIP) database. Patient characteristics were tested for association with LOS and readmission using bivariate and multivariate analyses. Patients with LOS > 10 days were excluded from the readmission analysis as the ACS-NSQIP only captures readmissions within 30 postoperative days, and the window for potential readmission was deemed too short for patients staying longer than 10 days. Results A total of 2,358 laminectomy patients met inclusion criteria. The average age was 66.4 ± 11.7 years (mean ± standard deviation). Average postoperative LOS was 2.1 ± 2.6 days. Of those meeting criteria for readmission analysis, 3.7% of patients (86 of 2,339) were readmitted within 30 days postoperatively. Independent risk factors for prolonged LOS were increased age (p < 0.001), increased body mass index (p = 0.004), American Society of Anesthesiologists class 3–4 (p = 0.005), and preoperative hematocrit < 36.0 (p = 0.001). Independent risk factors for readmission were increased age (p = 0.013), increased body mass index (p = 0.040), ASA class 3–4 (p < 0.001), and steroid use (p = 0.001). The most common reason for readmission was surgical site-related infections (25.0% of patients readmitted in 2012). Conclusion The identified factors associated with LOS and readmission following lumbar laminectomy may be useful for optimizing patient

  10. 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.

  11. An Experimental Study of Polymer Drag Reduction and Boundary Layer Diffusion Characteristics for Incompressible Flow Over a Flat Plate.

    DTIC Science & Technology

    1979-08-15

    dimensional turbulent mixing of amonia gas from a line source near a wall. They envisioned a four-zone diffusion process that is worthy of descripcion...Frieche and Schmartz (1969) have shown that hot-element sensors are difficult to calibrate because polymer additives alter the heat transfer...characteristics of the medium and collect on the sensors . It is pointed out that the calibration drift problem is particularly severe in dilute polymer solutions

  12. Edge effects on the characteristics of uranium diffusion on graphene and graphene nanoribbons

    NASA Astrophysics Data System (ADS)

    Cheng, Cheng; Han, Han; Ren, Cui-Lan; Wang, Chang-Ying; Shao, Kuan; Huai, Ping

    2016-08-01

    The first principles density-functional theoretical calculations of U adatom adsorption and diffusion on a planar graphene and quasi-one-dimensional graphene nanoribbons (GNRs) are performed. An energetic preference is found for U adatom diffusing to the hollow sites of both graphene and GNRs surface. A number of U distinctive diffusion paths either perpendicular or parallel to the ribbon growth direction are examined. The edge effects are evidenced by the calculated energy barriers of U adatom diffusion on armchair and zigzag nanoribbons surfaces. The calculation results indicate that the diffusion of U adatom from the inner site toward the edge site is a feasible process, particularly in zigzag GNR. It is viable to control the initial morphology of nuclear carbon material to retard the diffusion and concentration of nuclides. Project supported by the International S & T Cooperation Program of China (Grant No. 2014DFG60230), the National Natural Science Foundation of China (Grant Nos. 91326105, 21306220, and 21501189), and the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDA02040104).

  13. Impact of water dilution and cation tail length on ionic liquid characteristics: Interplay between polar and non-polar interactions

    NASA Astrophysics Data System (ADS)

    Hegde, Govind A.; Bharadwaj, Vivek S.; Kinsinger, Corey L.; Schutt, Timothy C.; Pisierra, Nichole R.; Maupin, C. Mark

    2016-08-01

    The recalcitrance of lignocellulosic biomass poses a major challenge that hinders the economical utilization of biomass for the production of biofuel, plastics, and chemicals. Ionic liquids have become a promising solvent that addresses many issues in both the pretreatment process and the hydrolysis of the glycosidic bond for the deconstruction of cellulosic materials. However, to make the use of ionic liquids economically viable, either the cost of ionic liquids must be reduced, or a less expensive solvent (e.g., water) may be added to reduce the overall amount of ionic liquid used in addition to reducing the viscosity of the binary liquid mixture. In this work, we employ atomistic molecular dynamics simulations to investigate the impact of water dilution on the overall liquid structure and properties of three imidazolium based ionic liquids. It is found that ionic liquid-water mixtures exhibit characteristics that can be grouped into two distinct regions, which are a function of the ionic liquid concentration. The trends observed in each region are found to correlate with the ordering in the local structure of the ionic liquid that arises from the dynamic interactions between the ion pairs. Simulation results suggest that there is a high level of local ordering in the molecular structure at high concentrations of ionic liquids that is driven by the aggregation of the cationic tails and the anion-water interactions. It is found that as the concentration of ionic liquids in the binary mixture is decreased, there is a point at which the competing self and cross interaction energies between the ionic liquid and water shifts away from a cation-anion dominated regime, which results in a significant change in the mixture properties. This break point, which occurs around 75% w/w ionic liquids, corresponds to the point at which water molecules percolate into the ionic liquid network disrupting the ionic liquids' nanostructure. It is observed that as the cationic alkyl

  14. The relationship between shear force, compression, collagen characteristics, desmin degradation and sarcomere length in lamb biceps femoris.

    PubMed

    Starkey, Colin P; Geesink, Geert H; van de Ven, Remy; Hopkins, David L

    2017-04-01

    This study aimed to identity the relationships between known variants of tenderness (collagen content (total and soluble), desmin degradation and sarcomere length) and shear force and compression in the biceps femoris aged for 14days from 112 mixed sex lambs. Desmin degradation was related to compression (P<0.05) such that as desmin degradation increased compression decreased. Sarcomere length (SL) was related to shear force (P<0.05), such that as SL increased shear force declined. Shear force was also related to compression (P<0.05), and soluble collagen (P<0.05), with male lambs producing higher shear force values than females (4.4±1.72N: P<0.05) when adjusted for compression, sarcomere length and soluble collagen. The findings from this experiment indicate that the known variants (soluble collagen, sarcomere length and desmin degradation) are related to shear force and compression in ovine biceps femoris.

  15. Characteristics of reactively sputtered niobium nitride thin films as diffusion barriers for Cu metallization

    NASA Astrophysics Data System (ADS)

    Huang, Cheng-Lin; Lai, Chih-Huang; Tsai, Po-Hao; Huang, Hsing-An; Lin, Jing-Cheng; Lee, Chiapyng

    2013-09-01

    NbN films were prepared by radio frequency reactive magnetron sputtering and then employed as diffusion barriers between Cu and Si. The microstructure of the NbN films was an assembly of very small columnar crystallites with a cubic structure. To investigate the properties as diffusion barriers, we performed metallurgical reactions of Cu/NbN0.8/Si, Cu/Nb/Si and Cu/TaN0.7/Si for comparisons. The sheet resistance increased dramatically after annealing above 750°C for Cu/NbN0.80/Si, and above 500°C for both Cu/Nb/Si and Cu/TaN0.7/Si. The interfaces were deteriorated seriously and formation of Cu3Si was observed when the sheet resistance was significantly increased. The diffusion coefficient of Cu in NbN barrier films was estimated by using the change of resistance (Δ R s / R s %). Compared with TaN0.7, NbN0.8 films possess larger grain size and lower Cu diffusion coefficient. Our results suggest that the NbN film can be used as a diffusion barrier for Cu metallization as compared to the well-known TaN film.

  16. A study of the characteristics of scintillation detectors with a diffuse reflector

    NASA Astrophysics Data System (ADS)

    Baranov, V. A.; Filchenkov, V. V.; Konin, A. D.; Zhuk, V. V.

    1996-02-01

    The process of light collection in a scintillation counter with a diffuse reflector is studied using the Monte-Carlo codes "PHOTON" and "LIGHT". The results obtained are compared with the simple model estimations and employed to describe the time shape of the signal for several different detectors including the full absorption neutron spectrometer, and reanalyze the previous NE-213 transparency measurements.

  17. CFD analysis of a rocket exhaust diffuser

    NASA Astrophysics Data System (ADS)

    Bose, Tarit K.; Thanawala, R. H.; Annamalai, K.

    1992-11-01

    The nature of the complex shock structure responsible for the pressure recovery phenomenon in supersonic diffusers is investigated by means of a theoretical CFD analysis using a newly developed computer program for Navier-Stokes solution of an ejector system, and the Prandtl mixing length to model the turbulent boundary layer. The pressure recovery characteristics of an ejector diffuser system was studied for various geometric and flow conditions. A comparison of the results with those of pressure measurements along the diffuser length in an experimental facility showed discrepancies, which are attributed to the boundary conditions imposed.

  18. Effects of maternal and infant characteristics on birth weight and gestation length in a colony of rhesus macaques (Macaca mulatta).

    PubMed

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

    2008-12-01

    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.

  19. Model studies of spectral and photophysical characteristics of a series of donor acceptor polyenes of different length

    NASA Astrophysics Data System (ADS)

    El-Gezawy, Hani; Rettig, Wolfgang

    2006-09-01

    The photophysical behaviour of a series of donor-acceptor-polyenes of different length: 4-dimethylamino-4'-cyanostilbene (DCS), 4-dimethylamino-4'-cyano-1,4-diphenylbutadiene (DCB) and 4-dimethylamino-4'-cyano-1,4-diphenylhexatriene (DCH) has been studied by means of steady state and time resolved fluorescence and low temperature measurements. Quantum chemical calculations were performed for comparison. For all three dyes, the fluorescence quantum yields show a maximum in the most polar solvents. A pronounced solvatochromic behaviour is only observed for the emission spectra whereas the absorption spectra remain nearly unaffected. The nonradiative decay decreases in the order DCS > DCB > DCH. Similarly, the radiative rate constant decreases in this order, contrary to the usual behaviour for a lengthening of the π-system. The chain-length dependence of the dipole moments of the relaxed excited state μe is better described by the Onsager radius derived from molecular length rather than from the density approach. Both calculations and experiments support the conclusion that the emissive state is not a TICT state.

  20. Scale-Up of flat plate photobioreactors considering diffuse and direct light characteristics.

    PubMed

    Quinn, Jason C; Turner, Chris W; Bradley, Thomas H

    2012-02-01

    This study investigates the scaling of photobioreactor productivity based on the growth of Nannochloropsis salina incorporating the effects of direct and diffuse light. The scaling and optimization of photobioreactor geometry was analyzed by determining the growth response of a small-scale system designed to represent a core sample of a large-scale photobioreactor. The small-scale test apparatus was operated at a variety of light intensities on a batch time scale to generate a photosynthetic irradiance (PI) growth dataset, ultimately used to inform a PI growth model. The validation of the scalability of the PI growth model to predict productivity in large-scale systems was done by comparison with experimental growth data collected from two geometrically different large-scale photobioreactors operated at a variety of light intensities. For direct comparison, the small-scale and large-scale experimental systems presented were operated similarly and in such a way to incorporate cultivation relevant time scales, light intensities, mixing, and nutrient loads. Validation of the scalability of the PI growth model enables the critical evaluation of different photobioreactor geometries and design optimization incorporating growth effects from diffuse and direct light. Discussion focuses on the application of the PI growth model to assess the effect of diffuse light growth compared to direct light growth for the evaluation of photobioreactors followed by the use of the model for photobioreactor geometry optimization on the metric of areal productivity.

  1. Clinical characteristics and pathophysiological mechanisms of focal and diffuse traumatic brain injury.

    PubMed

    Andriessen, Teuntje M J C; Jacobs, Bram; Vos, Pieter E

    2010-10-01

    Traumatic brain injury (TBI) is a frequent and clinically highly heterogeneous neurological disorder with large socioeconomic consequences. TBI severity classification, based on the hospital admission Glasgow Coma Scale (GCS) score, ranges from mild (GCS 13-15) and moderate (GCS 9-12) to severe (GCS ≤ 8). The GCS reflects the risk of dying from TBI, which is low after mild (∼1%), intermediate after moderate (up to 15%) and high (up to 40%) after severe TBI. Intracranial damage can be focal, such as epidural and subdural haematomas and parenchymal contusions, or diffuse, for example traumatic axonal injury and diffuse cerebral oedema, although this distinction is somewhat arbitrary. Study of the cellular and molecular post-traumatic processes is essential for the understanding of TBI pathophysiology but even more to find therapeutic targets for the development of neuroprotective drugs to be eventually used in human beings. To date, studies in vitro and in vivo, mainly in animals but also in human beings, are unravelling the pathological TBI mechanisms at high pace. Nevertheless, TBI pathophysiology is all but completely elucidated. Neuroprotective treatment studies in human beings have been disappointing thus far and have not resulted in commonly accepted drugs. This review presents an overview on the clinical aspects and the pathophysiology of focal and diffuse TBI, and it highlights several acknowledged important events that occur on molecular and cellular level after TBI.

  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. Survey: calculation of the characteristics of oral diffusion-controlled release dosage forms related to the drug.

    PubMed

    Rosca, I D; Vergnaud, J M

    2010-09-01

    Oral dosage forms with controlled release exhibit various advantages over their immediate release counterparts, but they must be built adequately by dispersing the drug through the well-defined polymer matrix. This study is concerned with diffusion-controlled dosage forms to resolve the problems that appear: in vitro tests generally used for determining the kinetics of drug release do not take into account the nature of the drug. On the contrary, the plasma drug profiles obtained through in vivo tests strongly depend on the nature of the drug, through their typical pharmacokinetic parameters. Moreover, the effect of the stirring rate is difficult to evaluate. Following the demand from the FDA concerned with the in vitro/in vivo correlation, a numerical model was built so as to evaluate the plasma drug profile obtained with any drug delivered from a diffusion-controlled release dosage form. The results are expressed by connecting the half-life times of the drugs obtained either with bolus injection or with the dosage forms, for various values of the parameters of interest: the diffusivity of the matrix polymer and the size of the dosage form. Thus, these diagrams make it possible to promptly determine the characteristics of the dosage forms able to give the desired plasma drug profile for any drug. Of course, for each drug being defined by its pharmacokinetic parameters, the polymer matrix should be selected as a function of its diffusivity. Finally, the evaluation of the plasma drug profile is of effective help to determine quantitatively the effect of the intervariability of the patients as well as the effect of the patient's noncompliance.

  4. Experiments on the low frequency barrier characteristics of cellular metamaterial panels in a diffuse sound field.

    PubMed

    Varanasi, Srinivas; Bolton, J Stuart; Siegmund, Thomas

    2017-01-01

    The metamaterial under investigation here consists of a periodic arrangement of unit plates in a grid-like frame such that there is a contrast in the local areal mass between cell interior and cell wall. In the low frequency range and under normal incidence this metamaterial panel exhibits a sound transmission loss significantly larger than the transmission loss of an unstructured panel with the same homogeneous mass per unit area. However, when the incident sound field is diffuse, the relative advantage of the metamaterial barrier is reduced or eliminated. A sequence of experiments is documented to demonstrate that the relative advantage of the metamaterial barrier can be realized even in a diffuse sound field by creating a hybrid barrier system which embeds the metamaterial layer between a normalizing waveguide layer on the incident side and an absorbing layer on the transmitted side. The sound normalizing waveguide layer is a lattice structure, and the absorbing layer is high performance glass fiber mat. By using measurements of the transmission loss of a 1.2 m square panel system the role of each of these components is demonstrated.

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

    NASA Astrophysics Data System (ADS)

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

    2010-02-01

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

  6. Griffith diffusers

    NASA Technical Reports Server (NTRS)

    Yang, T.-T.; Nelson, C. D.

    1979-01-01

    Contoured wall diffusers are designed by using an inverse method. The prescribed wall velocity distribution(s) was taken from the high lift airfoil designed by A. A. Griffith in 1938; therefore, such diffusers are named Griffith diffusers. First the formulation of the inverse problem and the method of solution are outlined. Then the typical contour of a two-dimensional diffuser and velocity distributions across the flow channel at various stations are presented. For a Griffith diffuser to operate as it is designed, boundary layer suction is necessary. Discussion of the percentage of through-flow required to be removed for the purpose of boundary layer control is given. Finally, reference is made to the latest version of a computer program for a two-dimensional diffuser requiring only area ratio, nondimensional length and suction percentage as inputs.

  7. Characteristic length scale of the magnon accumulation in Fe3O4/Pt bilayer structures by incoherent thermal excitation

    NASA Astrophysics Data System (ADS)

    Anadón, A.; Ramos, R.; Lucas, I.; Algarabel, P. A.; Morellón, L.; Ibarra, M. R.; Aguirre, M. H.

    2016-07-01

    The dependence of Spin Seebeck effect (SSE) with the thickness of the magnetic materials is studied by means of incoherent thermal excitation. The SSE voltage signal in Fe3O4/Pt bilayer structure increases with the magnetic material thickness up to 100 nm, approximately, showing signs of saturation for larger thickness. This dependence is well described in terms of a spin current pumped in the platinum film by the magnon accumulation in the magnetic material. The spin current is generated by a gradient of temperature in the system and detected by the Pt top contact by means of inverse spin Hall effect. Calculations in the frame of the linear response theory adjust with a high degree of accuracy the experimental data, giving a thermal length scale of the magnon accumulation (Λ) of 17 ± 3 nm at 300 K and Λ = 40 ± 10 nm at 70 K.

  8. The relative diffusive transport rate of SrI2 in water changes over the nanometer length scale as measured by coherent quasielastic neutron scattering.

    PubMed

    Rubinson, Kenneth A; Faraone, Antonio

    2016-05-14

    X-ray and neutron scattering have been used to provide insight into the structures of ionic solutions for over a century, but the probes have covered distances shorter than 8 Å. For the non-hydrolyzing salt SrI2 in aqueous solution, a locally ordered lattice of ions exists that scatters slow neutrons coherently down to at least 0.1 mol L(-1) concentration, where the measured average distance between scatterers is over 18 Å. To investigate the motions of these scatterers, coherent quasielastic neutron scattering (CQENS) data on D2O solutions with SrI2 at 1, 0.8, 0.6, and 0.4 mol L(-1) concentrations was obtained to provide an experimental measure of the diffusive transport rate for the motion between pairs of ions relative to each other. Because CQENS measures the motion of one ion relative to another, the frame of reference is centered on an ion, which is unique among all diffusion measurement methods. We call the measured quantity the pairwise diffusive transport rate Dp. In addition to this ion centered frame of reference, the diffusive transport rate can be measured as a function of the momentum transfer q, where q = (4π/λ)sin θ with a scattering angle of 2θ. Since q is related to the interion distance (d = 2π/q), for the experimental range 0.2 Å(-1)≤q≤ 1.0 Å(-1), Dp is, then, measured over interion distances from 40 Å to ≈6 Å. We find the measured diffusional transport rates increase with increasing distance between scatterers over the entire range covered and interpret this behavior to be caused by dynamic coupling among the ions. Within the model of Fickian diffusion, at the longer interionic distances Dp is greater than the Nernst-Hartley value for an infinitely dilute solution. For these nm-distance diffusional transport rates to conform with the lower, macroscopically measured diffusion coefficients, we propose that local, coordinated counter motion of at least pairs of ions is part of the transport process.

  9. EFFECT OF FLOW CHARACTERISTICS ON DO DISTRIBUTION IN A FULL SCALE OXIDATION DITCH WITH DIFFUSED AERATION AND VERTICAL FLOW BOOSTERS

    NASA Astrophysics Data System (ADS)

    Nakamachi, Kazuo; Fujiwara, Taku; Kawaguchi, Yukio; Tsuno, Hiroshi

    The high loading rate oxidation ditch (OD) system with dual dissolved oxygen (DO) control has been developed for the purpose of advanced wastewater treatment and cost saving. For the purpose of scale-up to the real scale, the clean water experiments were conducted, with the full scale oxidation ditch with diffused aeration and vertical flow boosters, to examine the effect to the dual DO control by the design and operational factors, which include a flow characteristics and a oxygen supply capability. In this study, the flow characteristics of the OD channel were analyzed using a tank number and circulation ratio as the parameters. The analysis showed the complicated flow characteristics of the OD channel, which changed from the plug flow to the completely mixing transiently. Based on the tank number N =65~100 which were obtained from the tracer tests, a model of DO mass balance was constructed, then the accurate method for estimate the overall oxygen transfer coefficients was proposed. The potential error of the conventional method in the specific conditions was indicated. In addition, the effect of the flow characteristics on the design and operational parameters of the dual DO control, which include the circulation time or the DO profile, was clarified.

  10. A Poisson model for identifying characteristic size effects in frequency data: Application to frequency-size distributions for global earthquakes, "starquakes", and fault lengths

    NASA Astrophysics Data System (ADS)

    Leonard, Thomas; Papasouliotis, Orestis; Main, Ian G.

    2001-01-01

    The standard Gaussian distribution for incremental frequency data requires a constant variance which is independent of the mean. We develop a more general and appropriate method based on the Poisson distribution, which assumes different unknown variances for the frequencies, equal to the means. We explicitly include "empty bins", and our method is quite insensitive to the choice of bin width. We develop a maximum likelihood technique that minimizes bias in the curve fits, and penalizes additional free parameters by objective information criteria. Various data sets are used to test three different physical models that have been suggested for the density distribution: the power law; the double power law; and the "gamma" distribution. For the CMT catalog of global earthquakes, two peaks in the posterior distribution are observed at moment magnitudes m* = 6.4 and 6.9 implying a bimodal distribution of seismogenic depth at around 15 and 30 km, respectively. A similar break at a characteristic length of 60 km or so is observed in moment-length data, but this does not outperform the simpler power law model. For the earthquake frequency-moment data the gamma distribution provides the best overall fit to the data, implying a finite correlation length and a system near but below the critical point. In contrast, data from soft gamma ray repeaters show that the power law is the best fit, implying infinite correlation length and a system that is precisely critical. For the fault break data a significant break of slope is found instead at characteristic scale of 44 km, implying a typical seismogenic thickness of up to 22 km or so in west central Nevada. The exponent changes from 1.5 to -2.1, too large to be accounted for by changes in sampling for an ideal, isotropic fractal set.

  11. Investigation of Diffusion Characteristics through Microfluidic Channels for Passive Drug Delivery Applications

    PubMed Central

    Ghuman, Alyssa P.; Collins, Stephanie B.; Handa, Hitesh

    2016-01-01

    Microfluidics has many drug delivery applications due to the ability to easily create complex device designs with feature sizes reaching down to the 10s of microns. In this work, three different microchannel designs for an implantable device are investigated for treatment of ocular diseases such as glaucoma, age-related macular degeneration (AMD), and diabetic retinopathy. Devices were fabricated using polydimethylsiloxane (PDMS) and soft lithography techniques, where surface chemistry of the channels was altered using 2-[methoxy(polyethyleneoxy)propyl]trimethoxysilane (PEG-silane). An estimated delivery rate for a number of common drugs was approximated for each device through the ratio of the diffusion coefficients for the dye and the respective drug. The delivery rate of the model drugs was maintained at a physiological condition and the effects of channel design and surface chemistry on the delivery rate of the model drugs were recorded over a two-week period. Results showed that the surface chemistry of the device had no significant effect on the delivery rate of the model drugs. All designs were successful in delivering a constant daily dose for each model drug. PMID:27313895

  12. The Evolutionary and Pulsational Characteristics of Alpha Virginis Including Turbulent Diffusive Mixing

    NASA Astrophysics Data System (ADS)

    Pesnell, W. D.; Odell, A. P.

    The best-observed star (besides the sun) for comparison to stellar evolution and pulsation theory is Alpha Virginis, a double-line spectroscopic and "visual" binary which shows apsidal motion and Beta Cephei-type pulsation. Unfortunately, it is impossible to fit simultaneously all of the observed properties of this star with one model that also exhibits an unstable pulsation mode of the correct period (see Odell and Pesnell, 32nd Liege Colloquium 1995 procedings), even with new opacities computed by the OPAL group of Rogers and Iglesias (Ap. J. Suppl. 79, 507, 1992).Lyubimkov et al. (Astronomicheskii Zhurnal 72, 212, 1995) have observed that the composition of Alpha Vir A differs from Alpha Vir B in that the helium abundance in the atmosphere of the primary star is significantly higher than the secondary, by approximately a factor of two. Denissenkov (A&A 287, 113, 1994) has suggested that this and other abundance anomolies (CN-cycle processed material) can be explained by Turbulent Diffusive Mixing in early B-stars near the main sequence. Thus it is of interest to determine the effects of this helium abundance change on the properties and stability of models of Alpha Virginis.

  13. Lasing and thermal characteristics of Yb:YAG/YAG composite with atomic diffusion bonding

    NASA Astrophysics Data System (ADS)

    Sankar Nagisetty, Siva; Severova, Patricie; Miura, Taisuke; Smrž, Martin; Kon, Hitoe; Uomoto, Miyuki; Shimatsu, Takehito; Kawasaki, Masato; Higashiguchi, Takeshi; Endo, Akira; Mocek, Tomáš

    2017-01-01

    We demonstrated the laser performance of an Yb:YAG/YAG composite ceramic laser medium mounted on an aluminium heatsink via atomic diffusion bonding (ADB) technique using nanocrystalline metal films at room temperature in air. The surface temperature rise of the ADB bonded laser medium was linear with 57 °C lower than that of the commercially available soldered Yb:YAG thin disk at the pump power of 280 W. Moreover, the ADB disk was pumped 1.5 times higher (7.3 kW cm-2) than the typical damage threshold of the soldered disk without any sign of damage. The undoped capping may be effective for the suppression of ASE heating; however, according to the in situ OPD measurement it induces strong thermal lensing. The CW laser output power of 177 W was obtained at the pump power of 450 W with the optical-to-optical efficiency of 40% using V-shape cavity.

  14. 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.

  15. 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.

  16. 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.

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

    PubMed Central

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

    2014-01-01

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

  18. Head rotational acceleration characteristics influence behavioral and diffusion tensor imaging outcomes following concussion.

    PubMed

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

    2015-05-01

    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/s(2) 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.

  19. A submicrometer lifted diffused-layer MOSFET

    NASA Astrophysics Data System (ADS)

    Inokawa, Hiroshi; Kobayashi, Toshio; Kiuchi, Kazuhide

    1987-03-01

    A new lifted diffused-layer (LID) MOSFET has been devised and fabricated, where the major portions of the source/drain (S/D) diffused layers are placed on top of the field insulator to reduce S/D parasitic capacitances. The primary feature of this MOSFET is that the structure and processing are especially developed for submicrometer gate lengths. The fabricated LID MOSFET with a 0.5-micron gate length and a 10-nm gate oxide thickness showed good electrical characteristics, such as a maximum transconductance of 115 mS/mm and an inverter delay time of 59 ps/stage.

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

    SciTech Connect

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

    2014-04-14

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

  1. Data mining of molecular dynamics data reveals Li diffusion characteristics in garnet Li7La3Zr2O12

    NASA Astrophysics Data System (ADS)

    Chen, Chi; Lu, Ziheng; Ciucci, Francesco

    2017-01-01

    Understanding Li diffusion in solid conductors is essential for the next generation Li batteries. Here we show that density-based clustering of the trajectories computed using molecular dynamics simulations helps elucidate the Li diffusion mechanism within the Li7La3Zr2O12 (LLZO) crystal lattice. This unsupervised learning method recognizes lattice sites, is able to give the site type, and can identify Li hopping events. Results show that, while the cubic LLZO has a much higher hopping rate compared to its tetragonal counterpart, most of the Li hops in the cubic LLZO do not contribute to the diffusivity due to the dominance of back-and-forth type jumps. The hopping analysis and local Li configuration statistics give evidence that Li diffusivity in cubic LLZO is limited by the low vacancy concentration. The hopping statistics also shows uncorrelated Poisson-like diffusion for Li in the cubic LLZO, and correlated diffusion for Li in the tetragonal LLZO in the temporal scale. Further analysis of the spatio-temporal correlation using site-to-site mutual information confirms the weak site dependence of Li diffusion in the cubic LLZO as the origin for the uncorrelated diffusion. This work puts forward a perspective on combining machine learning and information theory to interpret results of molecular dynamics simulations.

  2. Data mining of molecular dynamics data reveals Li diffusion characteristics in garnet Li7La3Zr2O12.

    PubMed

    Chen, Chi; Lu, Ziheng; Ciucci, Francesco

    2017-01-17

    Understanding Li diffusion in solid conductors is essential for the next generation Li batteries. Here we show that density-based clustering of the trajectories computed using molecular dynamics simulations helps elucidate the Li diffusion mechanism within the Li7La3Zr2O12 (LLZO) crystal lattice. This unsupervised learning method recognizes lattice sites, is able to give the site type, and can identify Li hopping events. Results show that, while the cubic LLZO has a much higher hopping rate compared to its tetragonal counterpart, most of the Li hops in the cubic LLZO do not contribute to the diffusivity due to the dominance of back-and-forth type jumps. The hopping analysis and local Li configuration statistics give evidence that Li diffusivity in cubic LLZO is limited by the low vacancy concentration. The hopping statistics also shows uncorrelated Poisson-like diffusion for Li in the cubic LLZO, and correlated diffusion for Li in the tetragonal LLZO in the temporal scale. Further analysis of the spatio-temporal correlation using site-to-site mutual information confirms the weak site dependence of Li diffusion in the cubic LLZO as the origin for the uncorrelated diffusion. This work puts forward a perspective on combining machine learning and information theory to interpret results of molecular dynamics simulations.

  3. Data mining of molecular dynamics data reveals Li diffusion characteristics in garnet Li7La3Zr2O12

    PubMed Central

    Chen, Chi; Lu, Ziheng; Ciucci, Francesco

    2017-01-01

    Understanding Li diffusion in solid conductors is essential for the next generation Li batteries. Here we show that density-based clustering of the trajectories computed using molecular dynamics simulations helps elucidate the Li diffusion mechanism within the Li7La3Zr2O12 (LLZO) crystal lattice. This unsupervised learning method recognizes lattice sites, is able to give the site type, and can identify Li hopping events. Results show that, while the cubic LLZO has a much higher hopping rate compared to its tetragonal counterpart, most of the Li hops in the cubic LLZO do not contribute to the diffusivity due to the dominance of back-and-forth type jumps. The hopping analysis and local Li configuration statistics give evidence that Li diffusivity in cubic LLZO is limited by the low vacancy concentration. The hopping statistics also shows uncorrelated Poisson-like diffusion for Li in the cubic LLZO, and correlated diffusion for Li in the tetragonal LLZO in the temporal scale. Further analysis of the spatio-temporal correlation using site-to-site mutual information confirms the weak site dependence of Li diffusion in the cubic LLZO as the origin for the uncorrelated diffusion. This work puts forward a perspective on combining machine learning and information theory to interpret results of molecular dynamics simulations. PMID:28094317

  4. Effective diffusivity in active Brownian suspensions

    NASA Astrophysics Data System (ADS)

    Burkholder, Eric; Brady, John

    2016-11-01

    We study the single-particle diffusion of a Brownian probe of size R in a suspension comprised of a Newtonian solvent and a dilute dispersion of active Brownian particles (ABPs) with size a, characteristic swim velocity U0, and a reorientation time τR. These ABPs, or "swimmers," have a run length l =U0τR , and a mechanical activity ksTs =ζaU02τR / 6 , where ζa is the Stokes drag coefficient of a swimmer. When the swimmers are inactive, collisions between the probe and the swimmers sterically hinder the probe's diffusive motion. When the activity of the swimmers is greater than the Boltzmann energy, ksTs >kB T , rather than being sterically hindered, the probe diffusivity is actually greater than its Stokes-Einstein-Sutherland diffusivity due to the mechanical energy imparted to the probe upon collisions with the swimmers. The active contribution to the effective diffusivity is a non-monotonic function of the swimmers' run length compared to the contact length between the probe and a swimmer: l / (R + a) . Comparisons are made to previous theoretical and experimental investigations of the hydrodynamic diffusion of a colloidal particle in a dilute suspension of swimming bacteria. NSF Grant No. CBET 1437570.

  5. 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.

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

    PubMed

    Kim, Dae-Yeon; Seo, Jong-Wook

    2015-01-26

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

  7. 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.

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

    DOEpatents

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

    1988-06-28

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

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

    DOEpatents

    Christophorou, Loucas G.; Hunter, Scott R.

    1990-01-01

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

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

    DOEpatents

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

    1990-06-26

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

  11. Generalized Drift-Diffusion Model In Semiconductors

    SciTech Connect

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

    2008-09-23

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

  12. Diffusion archeology for diffusion progression history reconstruction.

    PubMed

    Sefer, Emre; Kingsford, Carl

    2016-11-01

    Diffusion through graphs can be used to model many real-world processes, such as the spread of diseases, social network memes, computer viruses, or water contaminants. Often, a real-world diffusion cannot be directly observed while it is occurring - perhaps it is not noticed until some time has passed, continuous monitoring is too costly, or privacy concerns limit data access. This leads to the need to reconstruct how the present state of the diffusion came to be from partial diffusion data. Here, we tackle the problem of reconstructing a diffusion history from one or more snapshots of the diffusion state. This ability can be invaluable to learn when certain computer nodes are infected or which people are the initial disease spreaders to control future diffusions. We formulate this problem over discrete-time SEIRS-type diffusion models in terms of maximum likelihood. We design methods that are based on submodularity and a novel prize-collecting dominating-set vertex cover (PCDSVC) relaxation that can identify likely diffusion steps with some provable performance guarantees. Our methods are the first to be able to reconstruct complete diffusion histories accurately in real and simulated situations. As a special case, they can also identify the initial spreaders better than the existing methods for that problem. Our results for both meme and contaminant diffusion show that the partial diffusion data problem can be overcome with proper modeling and methods, and that hidden temporal characteristics of diffusion can be predicted from limited data.

  13. A case of mass-forming splenic tuberculosis: MRI findings with emphasis of diffusion-weighted imaging characteristics.

    PubMed

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

    2011-03-01

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

  14. [Characteristics of diffuse attenuation coefficient of underwater irradiance in the lakes in the middle and lower reaches of Yangtze river ].

    PubMed

    Shi, Zhi-Qiang; Zhang, Yun-Lin; Wang, Ming-Zhu; Liu, Xiao-Han

    2013-02-01

    Based on the underwater irradiance profile measurement and water samples collection in September, October 2007 in Lake Donghu, Lake Liangzi and Lake Honghu, and in April in 2010 in Lake Kuileihu, the diffuse attenuation coefficient and the dominant attenuation factors were analyzed. The ranges of diffuse attenuation coefficient and total suspended solid (TSS), organic suspended solid (OSS), inorganic suspended solid (ISS), chlorophyll a (Chla), and dissolved organic carbon (DOC) concentration varied less in Lake Donghu and Lake Kuileihu than in Lake liangzi and Lake Honghu. The regression analysis showed that ISS was the dominant affecting factor of transparency in Lake Donghu and Lake Kuileihu, but ISS and OSS jointly controlled the transparency in Lake Liangzi and Lake Honghu. The diffuse attenuation coefficient minimum occurred near 580 nm. At around 675 nm, the diffuse attenuation coefficient peak was due to phytoplankton absorption, especially at sites with high pigment concentration. The euphotic depth was less than the mean water depth in Lake Donghu, suggesting that the submerged aquatic vegetation (SAV) can not grow in the present underwater light climate. However, the euphotic depth was larger than the mean water depth in other three lakes showing that the underwater light climate can meet the light requirements for the growth of SAV. The regression analysis showed that ISS was the dominant affecting factor of PAR attenuation in Lake Donghu and Lake Kuileihu, but ISS, OSS and Chla jointly controlled PAR attenuation in lake Liangzi and lake Honghu. The significant correlation between the beam attenuatin coefficient at 750 nm and PAR difffuse attenuation coefficient showed that the particles scattering significantly contributed to underwater irradiance attenuation.

  15. The epidemiological and clinical characteristics of diarrhea associated with enteropathogenic, enteroaggregative and diffuse-adherent Escherichia coli in Egyptian children.

    PubMed

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

    2014-10-01

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

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

    PubMed

    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.

  17. Characterization of a novel hemagglutinin of diarrhea-associated Escherichia coli that has characteristics of diffusely adhering E. coli and enteroaggregative E. coli.

    PubMed Central

    Yamamoto, T; Wakisaka, N; Nakae, T; Kamano, T; Serichantalergs, O; Echeverria, P

    1996-01-01

    Escherichia coli 73-1 (serotype O73:H33) and 5-2 (serotype O89:H-) isolated from patients with diarrhea adhered to tissue culture cells (HeLa and HEp-2) as well as coverslips (plastic and glass) in a diffuse pattern. Adherence of strain 73-1 was mediated by a 110-kbp plasmid designated pEDA1 and correlated with D-mannose-resistant hemagglutinin (MRHA) detected with bovine, sheep, or human erythrocytes. The MRHA region was duplicated on pEDA1 and mediated the production of the 57-kDa outer membrane protein whose N-terminal amino acid sequence was hydrophobic. In accordance with MRHA and adherence, the 57-kDa outer membrane protein was observed best at 37 degrees C and to a lesser extent at 25 degrees C. In human intestine, adherence to mucus and colonic epithelium was obvious. No detectable pili were observed. The enteroaggregative E. coli heat-stable enterotoxin 1 (EAST1) gene, whose nucleotide sequence was 99.1% homologous to that of enteroaggregative E. coli, was present adjacent to the MRHA region on pEDA1. Strain 5-2 also exhibited MRHA activities and adherence and had sequences corresponding to those of the MRHA region and EAST1 gene. The data suggest that strain 73-1 (and strain 5-2), which has characteristics of both diffusely adhering E. coli and enteroaggregative E. coli, possesses a novel hemagglutinin associated with diffuse adherence. PMID:8751919

  18. Outer membrane and porin characteristics of Serratia marcescens grown in vitro and in rat intraperitoneal diffusion chambers.

    PubMed Central

    Malouin, F; Campbell, G D; Halpenny, M; Becker, G W; Parr, T R

    1990-01-01

    The composition and antibiotic permeability barrier of the outer membrane of Serratia marcescens were assessed in cells grown in vivo and in vitro. Intraperitoneal diffusion chambers implanted in rats were used for the in vivo cultivation of bacteria. Outer membranes isolated from log-phase bacterial cells recovered from these chambers were compared with membranes isolated from cells grown in vitro. Analysis revealed that the suspected 41-kilodalton porin and the OmpA protein were recovered on sodium dodecyl sulfate-polyacrylamide gels in equal quantities. Several high-molecular-weight proteins, thought to be iron starvation induced, appeared in the diffusion chamber-grown cells. The outer membrane permeability barriers to cephaloridine were similar in in vivo- and in vitro-grown cells based on permeability coefficient calculations. The permeability coefficient of cephaloridine in S. marcescens cells (30.3 x 10(-5) to 38.9 x 10(-5) cm s-1) was greater than that obtained for an Escherichia coli strain expressing only porin OmpC but smaller than those obtained for the E. coli wild type and a strain expressing only porin OmpF. Functional characterization of the suspected porin was performed by using the planar lipid bilayer technology. The sodium dodecyl sulfate-0.4 M NaCl-soluble porin from both in vitro- and in vivo-grown cells showed an average single-channel conductance in 1 M KCl of 1.6. A partial amino acid sequence (19 residues) was obtained for the S. marcescens porin. The sequence showed a very high homology to the E. coli OmpC porin. These data identified the S. marcescens outer membrane 41-kilodalton protein as a porin by both functional and amino acid analyses. Also, the methodology used allowed for efficient growth and recovery of diffusion chamber-grown bacterial cells and permitted identification of specific in vivo-induced changes in bacterial cell membrane composition. Images PMID:2157667

  19. Influence of polyethylene glycol chain length on compatibility and release characteristics of ternary solid dispersions of itraconazole in polyethylene glycol/hydroxypropylmethylcellulose 2910 E5 blends.

    PubMed

    Janssens, Sandrien; Denivelle, Samgar; Rombaut, Patrick; Van den Mooter, Guy

    2008-10-02

    The present study aims to elucidate the influence of the polyethylene glycol chain length on the miscibility of PEG/HPMC 2910 E5 polymer blends, the influence of polymer compatibility on the degree of molecular dispersion of itraconazole, and in vitro dissolution. PEG 2000, 6000, 10,000 and 20,000 were included in the study. Solid dispersions were prepared by spray drying and characterized with MDSC, XRPD and in vitro dissolution testing. The polymer miscibility increased with decreasing chain length due to a decrease in the Gibbs free energy of mixing. Recrystallization of itraconazole occurred as soon as a critical temperature of ca. 75 degrees C was reached for the glass transition that represents the ternary amorphous phase. Due to the lower miscibility degree between the longer PEG types and HPMC 2910 E5, the ternary amorphous phase was further separated, leading to a more rapid decrease of the ternary amorphous phase glass transition as a function of PEG and itraconazole weight percentage and hence, itraconazole recrystallization. In terms of release, an advantage of the shorter chain length PEG types (2000, 6000) over the longer chain length PEG types (10,000, 20,000) was observed for the polymer blends with 5% of PEG with respect to the binary itraconazole/HPMC 2910 E5 solid dispersion. Among the formulations with a 15/85 (w/w) PEG/HPMC 2910 E5 ratio on the other hand, there was no difference in the release profile.

  20. Finite-element solution for a combined radiative-conductive analysis with mixed diffuse-specular surface characteristics. [of spaceborne telescope

    NASA Technical Reports Server (NTRS)

    Lee, H.-P.; Jackson, C. E., Jr.

    1975-01-01

    The finite-element method has been applied to solve a combined radiative-conductive heat transfer problem for a large space telescope similar to those used in orbiting satellites. The derivation of the underlying matrices and associated solution algorithm for a 2-D triangular element is presented in detail. The resulting expressions for this triangular element typify such an analysis, which yields constitutive matrices when the heat equation is cast in the matrix form. The relevant matrices include those pertaining to thermal conductance, internal heat generation, radiative exchanges, and all possible external thermal loadings. Emphasis is placed on the treatment of non-linear radiative interchange between surfaces in an enclosure having mixed diffuse-specular surface characteristics. Essential differences in governing equations describing these distinctive surface characteristics are identified. Concluding remarks are drawn from an example simulating a Cassegrainian space telescope.

  1. 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.

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

    NASA Technical Reports Server (NTRS)

    Whitlow, J. B., Jr.

    1976-01-01

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

  3. Hydrodynamic length-scale selection in microswimmer suspensions

    NASA Astrophysics Data System (ADS)

    Heidenreich, Sebastian; Dunkel, Jörn; Klapp, Sabine H. L.; Bär, Markus

    2016-08-01

    A universal characteristic of mesoscale turbulence in active suspensions is the emergence of a typical vortex length scale, distinctly different from the scale invariance of turbulent high-Reynolds number flows. Collective length-scale selection has been observed in bacterial fluids, endothelial tissue, and active colloids, yet the physical origins of this phenomenon remain elusive. Here, we systematically derive an effective fourth-order field theory from a generic microscopic model that allows us to predict the typical vortex size in microswimmer suspensions. Building on a self-consistent closure condition, the derivation shows that the vortex length scale is determined by the competition between local alignment forces, rotational diffusion, and intermediate-range hydrodynamic interactions. Vortex structures found in simulations of the theory agree with recent measurements in Bacillus subtilis suspensions. Moreover, our approach yields an effective viscosity enhancement (reduction), as reported experimentally for puller (pusher) microorganisms.

  4. Hydrodynamic length-scale selection in microswimmer suspensions.

    PubMed

    Heidenreich, Sebastian; Dunkel, Jörn; Klapp, Sabine H L; Bär, Markus

    2016-08-01

    A universal characteristic of mesoscale turbulence in active suspensions is the emergence of a typical vortex length scale, distinctly different from the scale invariance of turbulent high-Reynolds number flows. Collective length-scale selection has been observed in bacterial fluids, endothelial tissue, and active colloids, yet the physical origins of this phenomenon remain elusive. Here, we systematically derive an effective fourth-order field theory from a generic microscopic model that allows us to predict the typical vortex size in microswimmer suspensions. Building on a self-consistent closure condition, the derivation shows that the vortex length scale is determined by the competition between local alignment forces, rotational diffusion, and intermediate-range hydrodynamic interactions. Vortex structures found in simulations of the theory agree with recent measurements in Bacillus subtilis suspensions. Moreover, our approach yields an effective viscosity enhancement (reduction), as reported experimentally for puller (pusher) microorganisms.

  5. Phase singularity diffusion.

    PubMed

    Cheng, Xiaojun; Lockerman, Yitzchak; Genack, Azriel Z

    2014-06-01

    We follow the trajectories of phase singularities at nulls of intensity in the speckle pattern of waves transmitted through random media as the frequency of the incident radiation is scanned in microwave experiments and numerical simulations. Phase singularities are observed to diffuse with a linear increase of the square displacement 〈R2〉 with frequency shift. The product of the diffusion coefficient of phase singularities in the transmitted speckle pattern and the photon diffusion coefficient through the random medium is proportional to the square of the effective sample length. This provides the photon diffusion coefficient and a method for characterizing the motion of dynamic material systems.

  6. White matter characteristics of idiopathic normal pressure hydrocephalus: a diffusion tensor tract-based spatial statistic study.

    PubMed

    Koyama, Tetsuo; Marumoto, Kohei; Domen, Kazuhisa; Miyake, Hiroji

    2013-01-01

    Using magnetic resonance-diffusion tensor imaging (DTI), we examined white matter changes within the brains of patients diagnosed with idiopathic normal pressure hydrocephalus (INPH). We analyzed data for 24 INPH patients who were presented with typical clinical symptoms (gait disturbance, dementia, and/or urinary incontinence) and Evans index > 0.3, and compared these with the control data from 21 elderly persons (≥ 60 years). DTI brain images were obtained with a 3T scanner. Fractional anisotropy (FA) brain maps were generated using a computer-automated method, and tract-based spatial statistics (TBSS) were then applied to compare the FA brain maps of the INPH and control groups in standard space. The TBSS data were further investigated using region-of-interest (ROI) analyses. ROIs were set within the corpus callosum, the posterior limb of the internal capsule (PLIC), and the cerebral peduncle in reference to a standard brain template. Compared with the control group, FA values in the INPH group were significantly lower in the corpus callosum and just significantly higher in the PLIC, but no significant differences were evident in the cerebral peduncle. The much lower FA values in the corpus callosum, but not the slightly higher FA values in the PLIC, were associated with more severe clinical symptoms such as gait disturbance. The lower FA values in the corpus callosum may offer a clue to solve the pathophysiology of INPH.

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

    PubMed

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

    2014-01-01

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

  8. Quantitative assessment of hemodynamic and structural characteristics of in vivo brain tissue using total diffuse reflectance spectrum measured in a non-contact fashion

    PubMed Central

    Song, Yinchen; Garcia, Sarahy; Frometa, Yisel; Ramella-Roman, Jessica C.; Soltani, Mohammad; Almadi, Mohamed; Riera, Jorge J.; Lin, Wei-Chiang

    2016-01-01

    Here we present a new methodology that investigates the intrinsic structural and hemodynamic characteristics of in vivo brain tissue, in a non-contact fashion, and can be easily incorporated in an intra-operative environment. Within this methodology, relative total diffuse reflectance spectra (RTD(λ)) were acquired from targets using a hybrid spectroscopy imaging system. A spectral interpretation algorithm was subsequently applied to RTD(λ) to retrieve optical properties related to the compositional and structural characteristics of each target. Estimation errors of the proposed methodology were computationally evaluated using a Monte Carlo simulation model for photon migration under various conditions. It was discovered that this new methodology could handle moderate noise and achieve very high accuracy, but only if the refractive index of the target is known. The accuracy of the technique was also validated using a series of tissue phantom studies, and consistent and accurate estimates of μs’(λ)/μa(λ) were obtained from all the phantoms tested. Finally, a small-scale animal study was conducted to demonstrate the clinical utility of the reported method, wherein a forepaw stimulation model was utilized to induce transient hemodynamic responses in somatosensory cortices. With this approach, significant stimulation-related changes (p < 0.001) in cortical hemodynamic and structural characteristics were successfully measured. PMID:28101403

  9. Quantitative assessment of hemodynamic and structural characteristics of in vivo brain tissue using total diffuse reflectance spectrum measured in a non-contact fashion.

    PubMed

    Song, Yinchen; Garcia, Sarahy; Frometa, Yisel; Ramella-Roman, Jessica C; Soltani, Mohammad; Almadi, Mohamed; Riera, Jorge J; Lin, Wei-Chiang

    2017-01-01

    Here we present a new methodology that investigates the intrinsic structural and hemodynamic characteristics of in vivo brain tissue, in a non-contact fashion, and can be easily incorporated in an intra-operative environment. Within this methodology, relative total diffuse reflectance spectra (RTD(λ)) were acquired from targets using a hybrid spectroscopy imaging system. A spectral interpretation algorithm was subsequently applied to RTD(λ) to retrieve optical properties related to the compositional and structural characteristics of each target. Estimation errors of the proposed methodology were computationally evaluated using a Monte Carlo simulation model for photon migration under various conditions. It was discovered that this new methodology could handle moderate noise and achieve very high accuracy, but only if the refractive index of the target is known. The accuracy of the technique was also validated using a series of tissue phantom studies, and consistent and accurate estimates of μs'(λ)/μa(λ) were obtained from all the phantoms tested. Finally, a small-scale animal study was conducted to demonstrate the clinical utility of the reported method, wherein a forepaw stimulation model was utilized to induce transient hemodynamic responses in somatosensory cortices. With this approach, significant stimulation-related changes (p < 0.001) in cortical hemodynamic and structural characteristics were successfully measured.

  10. Noise characteristics of centrifugal blower with low solidity cascade diffuser (Noise reduction by means of small groove located at LSD blade leading tip)

    NASA Astrophysics Data System (ADS)

    Murakami, Tengen; Ishida, Masahiro; Sakaguchi, Daisaku; Koba, Yu

    2009-12-01

    This paper deals with the effect of the blade tip-groove of the low solidity cascade diffuser (LSD) on the blower characteristic and the noise generated by the LSD. The small grooves were set up at the root and/or tip near the leading edge of the LSD blade. In order to clarify the mechanism of noise increase due to LSD and also to reduce the noise, the relationships between the noise increase based on the LSD, the LSD performance and the secondary flow formed additionally by the tip-groove were investigated experimentally as well as numerically, especially analyzing flow behaviors in the LSD in view points of flow separation on the suction surface of the LSD blade and the secondary flow on the side walls. By reducing the stagnation region smaller near the root and/or tip of the LSD blade leading edge, the secondary flow behavior changes remarkably around the LSD blade, as a result, the noise level and the blower characteristics vary. It can be concluded that, by means of a small tip-groove located only at the shroud side near the LSD blade leading edge, the noise generated by the LSD can be reduced without deteriorations of the LSD performance and the blower characteristics as well.

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

    PubMed

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

    2015-07-01

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

  12. Experimental Magnus and Static Stability Characteristics of Ballistic Projectiles with Various Boattail Angles and Lengths at Mach Numbers from 0.5 Through 2.5

    DTIC Science & Technology

    1975-08-01

    BOATTAIL ANGLES AND LENGTHS AT MACH NUMBERS FROM 0.5 THROUGH 2.5 I m m I PROPULSION WIND TUNNEL FACILITY ARNOLD ENGINEERING DEVELOPMENT CENTER AIR... Wind T u n n e l ( 4 T ) , P r o p u l s i o n Wind T u n n e l F a c i l i t y (PWT). The t e s t s w e r e p a r t o f a c o n t i n u i...with a variable stagnation pressure from 2.1 to 23.6 psia at all Mach numbers. The test section is 4 ft square and 12.5 ft long with variable ~orosity

  13. 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.

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

    PubMed

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

    2014-11-07

    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.

  15. Combustor diffuser interaction program

    NASA Technical Reports Server (NTRS)

    Srinivasan, Ram; Thorp, Daniel

    1986-01-01

    Advances in gas turbine engine performance are achieved by using compressor systems with high stage loading and low part count, which result in high exit Mach numbers. The diffuser and combustor systems in such engines should be optimized to reduce system pressure loss and to maximize the engine thrust-to-weight ratio and minimize length. The state-of-the-art combustor-diffuser systems do not meet these requirements. Detailed understanding of the combustor-diffuser flow field interaction is required for designing advanced gas turbine engines. An experimental study of the combustor-diffuser interaction (CDI) is being conducted to obtain data for the evaluation and improvement of analytical models applicable to a wide variety of diffuser designs. The CDI program consists of four technical phases: Literature Search; Baseline Configuration; Parametric Configurations; and Performance Configurations. Phase 2 of the program is in progress.

  16. The diffusive idealization of charged particle transport in random magnetic fields

    NASA Technical Reports Server (NTRS)

    Earl, J. A.

    1974-01-01

    The transport of charged particles diffusing in a random magnetic field parallel to a relatively large guiding field is presented. The same coefficient of diffusion is obtained by three methods. Two corrections must be added to the expression in which the diffusive flux is proportional to the gradient of the density. Explicit expressions are given for a characteristic time and a characteristic length which describe the corrections. The well known divergence of the coefficient of diffusion, which is implied by the quasilinear analysis of pitch angle scattering, does not occur if the scattering rate is finite at 90 deg pitch angle. This effect is illustrated by formulas which give the coefficient of diffusion when the quasilinear expression is perturbed by a variable amount of isotropic scattering.

  17. Charged Particle Diffusion in Isotropic Random Static Magnetic Fields

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

  18. Charged Particle Diffusion in Isotropic Random Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Subedi, P.; Sonsrettee, W.; Blasi, P.; Ruffolo, D.; Matthaeus, W. H.; Montgomery, D.; Chuychai, P.; Dmitruk, P.; Wan, M.; Parashar, T. N.; Chhiber, R.

    2017-03-01

    The investigation of the diffusive transport of charged particles in a turbulent magnetic field remains a subject of considerable interest. Research has most frequently concentrated on determining the diffusion coefficient in the presence of a mean magnetic field. Here we consider the diffusion of charged particles in fully three-dimensional isotropic turbulent magnetic fields with no mean field, which may be pertinent to many astrophysical situations. We identify different ranges of particle energy depending upon the ratio of Larmor radius to the characteristic outer length scale of turbulence. Two different theoretical models are proposed to calculate the diffusion coefficient, each applicable to a distinct range of particle energies. The theoretical results are compared to those from computer simulations, showing good agreement.

  19. 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.

  20. Investigation of a 1000-MW smoke plume by means of a 1.064 μm lidar—II. Determination of diffusion characteristics of the plume particles

    NASA Astrophysics Data System (ADS)

    Benech, B.; Van Dinh, Pham; Ezcurra, A.; Lesne, J. L.

    A mobile 1.064-μm monostatic lidar was used to study the carbon aerosol particles from a 1000-MW oil-burning system. After part I, describing the lidar calibration procedure from airborne measurements and lidar vertical shots on the ambient aerosol, this paper presents the determination of the field of C particle concentrations in order to study the plume characteristics, such as particle concentration, plume trajectography and dispersion parameters … The method proposed allows the retrieval of particle concentrations in amounts comparable with those measured by direct instrumentation and the verification of the classical diffusion laws as established by, for example, Briggs, in nearly neutral meteorological conditions. In particular, for maximum concentration zone as revealed by the automatic scanning procedure of the lidar system, the plume height Z is related to the ambient wind speed U and the horizontal distance X from the source by the expression Z = C 1 F 1/30Ū-1X 1/3. Finally, the high particle concentration zone, localized upwind, is revealed as the most active one both dynamically and thermodynamically, where more than 80% of the vertical transfer fluxes are accomplished.

  1. 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.

  2. Novel Diffusivity Measurement Technique

    NASA Technical Reports Server (NTRS)

    Rashidnia, Nasser

    2001-01-01

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

  3. 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.

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

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

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

  5. Investigation of High-Subsonic Performance Characteristics of a 12 Degree 21-Inch Conical Diffuser, Including the Effects of Change in Inlet-Boundary-Layer Thickness

    NASA Technical Reports Server (NTRS)

    Copp, Martin R.; Klevatt, Paul L.

    1950-01-01

    Investigations were conducted of a 12 degree 21-inch conical diffuser of 2:l area ratio to determine the interrelation of boundary layer growth and performance characteristics. surveys were made of inlet and exit from, longitudinal static pressures were recorded, and velocity profiles were obtained through an inlet Reynolds number range, determined From mass flows and based on inlet diameter of 1.45 x 10(exp 6) to 7.45 x 10(exp 6) and a Mach number range of 0.11 to approximately choking. These investigations were made to two thicknesses of inlet boundary layer. The mean value, over the entire range of inlet velocities, of the displacement thickness of the thinner inlet boundary layer was approximately 0.035 inch and that of the thicker inlet boundary layer was approximately six times this value. The loss coefficient in the case of the thinner inlet boundary layer had a value between 2 to 3 percent of the inlet impact pressure over most of the air-flow range. The loss coefficient with the thicker inlet boundary layer was of the order of twice that of the thinner inlet boundary layer at low speeds and approximately three times at high speeds. In both cases the values were substantially less than those given in the literature for fully developed pipe flow. The static-pressure rise for the thinner inlet boundary layer was of the order of 95 percent of that theoretically possible over the entire speed range. For the thicker inlet boundary layer the static pressure rise, as a percentage of that theoretically possible, ranged from 82 percent at low speeds to 68 percent at high speeds.

  6. Diffusion MRI

    NASA Astrophysics Data System (ADS)

    Fukuyama, Hidenao

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

  7. 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…

  8. Effects of spatially heterogeneous porosity on matrix diffusion as investigated by X-ray absorption imaging

    NASA Astrophysics Data System (ADS)

    Tidwell, Vincent C.; Meigs, Lucy C.; Christian-Frear, Tracy; Boney, Craig M.

    2000-03-01

    High-resolution X-ray absorption imaging was used to investigate the effects of spatially heterogeneous porosity on matrix diffusion. Experiments were performed on four, centimeter-scale slabs of Culebra dolomite taken from the Waste Isolation Pilot Plant (WIPP) site. These tests involved the diffusion of potassium iodide into a single edge of each brine-saturated rock slab, while X-ray absorption imaging was used to measure the two-dimensional relative concentration distribution at different times during the experiment. X-ray imaging was also used to measure the heterogeneous, two-dimensional porosity distribution of each rock slab. The resulting high-resolution data provide unique insight into the spatially varying diffusion characteristics of each heterogeneous rock sample, which traditional methods such as through-diffusion experiments cannot. In these tests, significant variations in the diffusion coefficient were calculated over the relatively small length (centimeter) and time scales (months) investigated. Results also indicated that these variations were related to the heterogeneous porosity characteristics of each rock sample. Not only were the diffusion coefficients found to depend on the magnitude of the porosity but also on its spatial distribution. Specifically, the geometry, position, and orientation of the heterogeneous porosity features populating each rock slab appeared to influence the diffusion characteristics.

  9. 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.

  10. Diffusion tensor imaging of the human calf muscle: distinct changes in fractional anisotropy and mean diffusion due to passive muscle shortening and stretching.

    PubMed

    Schwenzer, Nina F; Steidle, Günter; Martirosian, Petros; Schraml, Christina; Springer, Fabian; Claussen, Claus D; Schick, Fritz

    2009-12-01

    The influence of passive shortening and stretching of the calf muscles on diffusion characteristics was investigated. The diffusion tensor was measured in transverse slices through the lower leg of eight healthy volunteers (29 +/- 7 years) on a 3 T whole-body MR unit in three different positions of the foot (40 degrees plantarflexion, neutral ankle position (0 degrees ), and -10 degrees dorsiflexion in the ankle). Maps of the mean diffusivity, the three eigenvalues of the tensor and fractional anisotropy (FA) were calculated. Results revealed a distinct dependence of the mean diffusivity and FA on the foot position and the related shortening and stretching of the muscle groups. The tibialis anterior muscle showed a significant increase of 19% in FA with increasing dorsiflexion, while the FA of the antagonists significantly decreased ( approximately 20%). Regarding the mean diffusivity of the diffusion tensor, the muscle groups showed an opposed response to muscle elongation and shortening. Regarding the eigenvalues of the diffusion tensor, lambda(2) and lambda(3) showed significant changes in relation to muscle length. In contrast, no change in lambda(1) could be found. This work reveals significant changes in diffusional characteristics induced by passive muscle shortening and stretching.

  11. 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

  12. Characteristics of WN{sub x}C{sub y} films deposited using remote plasma atomic layer deposition with ({sup Me}Cp)W(CO){sub 2}(NO) for Cu diffusion barrier

    SciTech Connect

    Kim, Hyunjung; Park, Jingyu; Jeon, Heeyoung; Jang, Woochool; Jeon, Hyeongtag; Yuh, Junhan

    2015-09-15

    Diffusion barrier characteristics of tungsten–nitride–carbide (WN{sub x}C{sub y}) thin films interposed between Cu and SiO{sub 2} layers were studied. The WN{sub x}C{sub y} films were deposited by remote plasma atomic layer deposition (RPALD) using a metal organic source, ({sup Me}Cp)W(CO){sub 2}(NO), and ammonia. Auger electron spectroscopy analysis indicated the WN{sub x}C{sub y} films consisted of tungsten, nitrogen, carbon, and oxygen. X-ray diffraction (XRD) analysis showed that the film deposited at 350 °C was nanocrystalline. The resistivity of WN{sub x}C{sub y} film deposited by RPALD was very low compared to that in previous research because of the lower nitrogen content and different crystal structures of the WN{sub x}C{sub y}. To verify the diffusion barrier characteristics of the WN{sub x}C{sub y} film, Cu films were deposited by physical vapor deposition after WN{sub x}C{sub y} film was formed by RPALD on Si substrate. The Cu/WN{sub x}C{sub y}/Si film stack was annealed in a vacuum by rapid thermal annealing at 500 °C. Cu diffusion through the barrier layer was verified by XRD. Stable film properties were observed up to 500 °C, confirming that WN{sub x}C{sub y} film is suitable as a Cu diffusion barrier in microelectronic circuits.

  13. 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 λ{sub mfp}, the diffusion coefficients of field lines D{sub FL}, and the collisional diffusion coefficients, χ{sub ⊥} are studied. Based on these numerical data and the heuristic arguments, the empirical formula, D{sub r}=χ{sub ⊥}+v{sub ||}D{sub FL}/(1+L{sub c}/λ{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}=πqR{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.

  14. Welding arc length control system

    NASA Technical Reports Server (NTRS)

    Iceland, William F. (Inventor)

    1993-01-01

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

  15. 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.

  16. Characteristic-Galerkin and Galerkin/Least-Squares Space-Time Formulations for the Advection-Diffusion Equation with Time-Dependent Domains

    DTIC Science & Technology

    1992-01-01

    formulations for the advection- diffusion equation with time-dependent domains 0. Pironneau Universite Paris 6. Analyse Numerique . T 55-65/5. 4 place...solution of the advection- dissipation equation, Correspondence to: Dr. 0. Pironneau, Universit6 Paris 6, Analyse Numerique . T 55-65/5, 4 place...for Partial Differential Equations (Cambridize Univ. Press. Cambridge. 1989). 1121 TE. Tezduvar. .I. Behr and J. Liou. A new strategy for finite

  17. Diffusion barriers

    NASA Technical Reports Server (NTRS)

    Nicolet, M. A.

    1983-01-01

    The choice of the metallic film for the contact to a semiconductor device is discussed. One way to try to stabilize a contact is by interposing a thin film of a material that has low diffusivity for the atoms in question. This thin film application is known as a diffusion barrier. Three types of barriers can be distinguished. The stuffed barrier derives its low atomic diffusivity to impurities that concentrate along the extended defects of a polycrystalline layer. Sacrificial barriers exploit the fact that some (elemental) thin films react in a laterally uniform and reproducible fashion. Sacrificial barriers have the advantage that the point of their failure is predictable. Passive barriers are those most closely approximating an ideal barrier. The most-studied case is that of sputtered TiN films. Stuffed barriers may be viewed as passive barriers whose low diffusivity material extends along the defects of the polycrystalline host.

  18. 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.

  19. 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.

  20. Knudsen Diffusion in Silicon Nanochannels

    NASA Astrophysics Data System (ADS)

    Gruener, Simon; Huber, Patrick

    2008-02-01

    Measurements on helium and argon gas flow through an array of parallel, linear channels of 12 nm diameter and 200μm length in a single crystalline silicon membrane reveal a Knudsen diffusion type transport from 102 to 107 in Knudsen number Kn. The classic scaling prediction for the transport diffusion coefficient on temperature and mass of diffusing species, DHe∝T, is confirmed over a T range from 40 K to 300 K for He and for the ratio of DHe/DAr∝mAr/mHe. Deviations of the channels from a cylindrical form, resolved with electron microscopy down to subnanometer scales, quantitatively account for a reduced diffusivity as compared to Knudsen diffusion in ideal tubular channels. The membrane permeation experiments are described over 10 orders of magnitude in Kn, encompassing the transition flow regime, by the unified flow model of Beskok and Karniadakis.

  1. Myofilament length dependent activation.

    PubMed

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

    2010-05-01

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

  2. Coefficients of Effective Length.

    ERIC Educational Resources Information Center

    Edwards, Roger H.

    1981-01-01

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

  3. Myofilament length dependent activation

    SciTech Connect

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

    2010-05-25

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

  4. 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)

  5. Normal and Anomalous Diffusion: An Analytical Study Based on Quantum Collision Dynamics and Boltzmann Transport Theory.

    PubMed

    Mahakrishnan, Sathiya; Chakraborty, Subrata; Vijay, Amrendra

    2016-09-15

    Diffusion, an emergent nonequilibrium transport phenomenon, is a nontrivial manifestation of the correlation between the microscopic dynamics of individual molecules and their statistical behavior observed in experiments. We present a thorough investigation of this viewpoint using the mathematical tools of quantum scattering, within the framework of Boltzmann transport theory. In particular, we ask: (a) How and when does a normal diffusive transport become anomalous? (b) What physical attribute of the system is conceptually useful to faithfully rationalize large variations in the coefficient of normal diffusion, observed particularly within the dynamical environment of biological cells? To characterize the diffusive transport, we introduce, analogous to continuous phase transitions, the curvature of the mean square displacement as an order parameter and use the notion of quantum scattering length, which measures the effective interactions between the diffusing molecules and the surrounding, to define a tuning variable, η. We show that the curvature signature conveniently differentiates the normal diffusion regime from the superdiffusion and subdiffusion regimes and the critical point, η = ηc, unambiguously determines the coefficient of normal diffusion. To solve the Boltzmann equation analytically, we use a quantum mechanical expression for the scattering amplitude in the Boltzmann collision term and obtain a general expression for the effective linear collision operator, useful for a variety of transport studies. We also demonstrate that the scattering length is a useful dynamical characteristic to rationalize experimental observations on diffusive transport in complex systems. We assess the numerical accuracy of the present work with representative experimental results on diffusion processes in biological systems. Furthermore, we advance the idea of temperature-dependent effective voltage (of the order of 1 μV or less in a biological environment, for example

  6. Length of Stay

    PubMed Central

    Gustafson, David H.

    1968-01-01

    Five methodologies for predicting hospital length of stay were developed and compared. Two—a subjective Bayesian forecaster and a regression forecaster—also measured the relative importance of the symptomatic and demographic factors in predicting length of stay. The performance of the methodologies was evaluated with several criteria of effectiveness and one of cost. The results should provide encouragement for those interested in computer applications to utilization review and to scheduling inpatient admissions. PMID:5673664

  7. 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.

  8. Observations on oesophageal length.

    PubMed Central

    Kalloor, G J; Deshpande, A H; Collis, J L

    1976-01-01

    The subject of oesophageal length is discussed. The great variations in the length of the oesophagus in individual patients is noted, and the practical use of its recognition in oesophageal surgery is stressed. An apprasial of the various methods available for this measurement is made; this includes the use of external chest measurement, endoscopic measurement, and the measurement of the level of the electrical mucosal potential change. Correlative studies of these various methods are made, and these show a very high degree of significance. These studies involved simultaneous measurement of external and internal oesophageal length in 26 patients without a hiatal hernia or gastro-oesophageal length in 26 patients without a hiatal hernia or gastro-oesophageal reflux symptoms, 42 patients with sliding type hiatal hernia, and 17 patients with a peptic stricture in association with hiatal hernia. The method of measuring oesophageal length by the use of the external chest measurement, that is, the distance between the lower incisor teeth and the xiphisternum, measured with the neck fully extended and the patient lying supine, is described in detail, its practical application in oesophageal surgery is illustrated, and its validity tested by internal measurements. The findings of this study demonstrate that the external chest measurement provides a mean of assessing the true static length of the oesophagus, corrected for the size of the individual. Images PMID:941114

  9. 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.

  10. Degradation of bulk diffusion length in CZ silicon solar cells

    SciTech Connect

    Reiss, J.H.; King, R.R.; Mitchell, K.W.

    1995-08-01

    Commercially-produced, unencapsulated, CZ silicon solar cells can lose 3 to 4% of their initial efficiency after exposure to light. After this initial, rapid ( < 30 min.) decrease, the cell power output remains stable. The cell performance recovers in a matter of hours in the dark at room temperature, and degrades again under light exposure. The different conditions under which CZ silicon cells degrade, and the reverse process, annealing, are characterized with the methods of spectral response and current-voltage (I-V) measurements. Iron impurities are a possible cause of this effect.

  11. Correlated Diffusion of Colloidal Particles near a Liquid-Liquid Interface

    PubMed Central

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

    2014-01-01

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

  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.

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

    SciTech Connect

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

    1996-04-01

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

  14. Slow-release of methanogenic inhibitors derived from encapsulated calcium carbide using paraffin wax and/or rosin: matrix optimization and diffusion characteristics.

    PubMed

    Tiantao, Zhao; Youcai, Zhao; Lijie, Zhang; Haoquan, Chen; Feng, Shi; Haiyan, Zhou

    2011-11-01

    Acetylene has been found to significantly inhibit biological activity of methanogens and thus might be applicable for reducing the generation and emission of methane from municipal solid waste landfills. However, acetylene is gaseous and so it is considered physically infeasible to directly apply this gas to waste in landfill conditions. In the present study, a novel acetylene release mechanism was tested, using a matrix of acetylene entrapped in high hydrophobic paraffin wax and/or rosin and calcium carbide capsules with a ratio of 1.0 g g(-1) matrix and a diameter of 10 mm to facilitate the gradual release of acetylene. A diffusion mechanism model (Q = &b.gamma; × t (0.5)) for the matrix was derived based on the T. Higuchi equation, and the effective diffusion coefficients (D(e)) were acquired by linear fitting. Additionally, it was found that D(e) remained constant when the rosin content was up to more than 20% g g(-1) matrix.

  15. 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.

  16. Upper Extremity Length Equalization

    PubMed Central

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

    1992-01-01

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

  17. 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.

  18. Power output uniformity and power output capabilities of a guidewire-compatible cylindrical light-diffusing catheter

    NASA Astrophysics Data System (ADS)

    Anderson, Steven C.; Narciso, Hugh L., Jr.; Mai, David; Doiron, Daniel R.

    1994-07-01

    Cardiovascular Photodynamic Therapy requires the uniform application of laser energy over the length of an atherosclerotic lesion, thus ensuring equal treatment to all parts of the lesion. The total amount of laser energy delivered to the lesion also affects the results of the treatment. Uniform light distribution both radially and axially of a cylindrical diffuser during Photodynamic Therapy prevents miscalculated dosimetry and uneven treatment. Maximizing the amount of laser power delivered to the cylindrical diffuser tip (without inducing temperature elevation) minimizes the exposure time thus reducing the overall treatment time. Power output uniformity and power output capabilities are thus crucial factors in the design of a cardiovascular cylindrical diffuser. This paper will discuss the output characteristics and performance of six guidewire compatible cylindrical diffusers. Each diffuser consists of an array of fiber optics surrounding an inner guidewire lumen. This assembly is covered by an outer sheath. The fibers launch into an elastomer which contains a scattering medium. In this way a light diffusing tip is created. The total length of the fiber system is 3.0 meters. The total length of the difffuser tip is 2.0 cm.

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

    DOE PAGES

    Aguayo, E.; Amman, M.; Avignone, F. T.; ...

    2012-11-09

    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. Furthermore, experiments that operate germanium detectors with a verymore » low energy threshold may benefit from the methods presented herein.« less

  20. 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.; 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.

    2012-11-09

    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. Furthermore, experiments that operate germanium detectors with a very low energy threshold may benefit from the methods presented herein.

  1. 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…

  2. 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)

  3. Correlation of Minimum Apparent Diffusion Coefficient and Maximum Standardized Uptake Value of the Primary Tumor with Clinicopathologic Characteristics in Endometrial Cancer

    PubMed Central

    Sürer Budak, Evrim; Toptaş, Tayfun; Aydın, Funda; Öner, Ali Ozan; Çevikol, Can; Şimşek, Tayup

    2017-01-01

    Objective: To explore the correlation of the primary tumor’s maximum standardized uptake value (SUVmax) and minimum apparent diffusion coefficient (ADCmin) with clinicopathologic features, and to determine their predictive power in endometrial cancer (EC). Methods: A total of 45 patients who had undergone staging surgery after a preoperative evaluation with 18F-fluorodeoxyglucose (FDG) positron emission tomography/computerized tomography (PET/CT) and diffusion-weighted magnetic resonance imaging (DW-MRI) were included in a prospective case-series study with planned data collection. Multiple linear regression analysis was used to determine the correlations between the study variables. Results: The mean ADCmin and SUVmax values were determined as 0.72±0.22 and 16.54±8.73, respectively. A univariate analysis identified age, myometrial invasion (MI) and lymphovascular space involvement (LVSI) as the potential factors associated with ADCmin while it identified age, stage, tumor size, MI, LVSI and number of metastatic lymph nodes as the potential variables correlated to SUVmax. In multivariate analysis, on the other hand, MI was the only significant variable that correlated with ADCmin (p=0.007) and SUVmax (p=0.024). Deep MI was best predicted by an ADCmin cutoff value of ≤0.77 [93.7% sensitivity, 48.2% specificity, and 93.0% negative predictive value (NPV)] and SUVmax cutoff value of >20.5 (62.5% sensitivity, 86.2% specificity, and 81.0% NPV); however, the two diagnostic tests were not significantly different (p=0.266). Conclusion: Among clinicopathologic features, only MI was independently correlated with SUVmax and ADCmin. However, the routine use of 18F-FDG PET/CT or DW-MRI cannot be recommended at the moment due to less than ideal predictive performances of both parameters. PMID:28291007

  4. Surface Roughness Lengths

    DTIC Science & Technology

    1993-08-01

    m trees 110 - 170 Thom 1972 Pine forest - 20 m trees 128 DeBruin and Moore 1985 Forested plateau, rolling 120 - 130 Ming et al. 1983 Rolling terrain...H. A. R., and C. J. Moore , 1985 , "Zero-Plane Displacement and Roughness Length for Tall Vegetation, Derived from a Simple Mass Conservation

  5. 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…

  6. Characterizing non-Gaussian diffusion by using generalized diffusion tensors.

    PubMed

    Liu, Chunlei; Bammer, Roland; Acar, Burak; Moseley, Michael E

    2004-05-01

    Diffusion tensor imaging (DTI) is known to have a limited capability of resolving multiple fiber orientations within one voxel. This is mainly because the probability density function (PDF) for random spin displacement is non-Gaussian in the confining environment of biological tissues and, thus, the modeling of self-diffusion by a second-order tensor breaks down. The statistical property of a non-Gaussian diffusion process is characterized via the higher-order tensor (HOT) coefficients by reconstructing the PDF of the random spin displacement. Those HOT coefficients can be determined by combining a series of complex diffusion-weighted measurements. The signal equation for an MR diffusion experiment was investigated theoretically by generalizing Fick's law to a higher-order partial differential equation (PDE) obtained via Kramers-Moyal expansion. A relationship has been derived between the HOT coefficients of the PDE and the higher-order cumulants of the random spin displacement. Monte-Carlo simulations of diffusion in a restricted environment with different geometrical shapes were performed, and the strengths and weaknesses of both HOT and established diffusion analysis techniques were investigated. The generalized diffusion tensor formalism is capable of accurately resolving the underlying spin displacement for complex geometrical structures, of which neither conventional DTI nor diffusion-weighted imaging at high angular resolution (HARD) is capable. The HOT method helps illuminate some of the restrictions that are characteristic of these other methods. Furthermore, a direct relationship between HOT and q-space is also established.

  7. Self-diffusion in liquid interfaces.

    PubMed

    Herth, Simone; Ye, Feng; Eggersmann, Martin; Gutfleisch, Oliver; Würschum, Roland

    2004-03-05

    For studying self-diffusion in liquid interfaces, 59Fe tracer diffusion was measured on ultrafine-grained Nd2Fe14B which undergoes an intergranular melting transition for low Nd excess. The diffusion coefficient in the intergranular liquid layers is found to be lower than in bulk melts indicating a hampered atomic mobility due to confinement. Well above the intergranular melting transition, the diffusivity in the liquid interfaces approaches a value characteristic for bulk melts.

  8. Image Halftoning Using Optimized Dot Diffusion

    DTIC Science & Technology

    1998-01-01

    ppvnath@sys.caltech.edu ABSTRACT The dot diffusion method for digital halftoning has the advantage of parallelism unlike the error diffusion ...digital halftoning : ordered dither [1], error diffusion [2], neural-net based methods [8], and more recently direct binary search (DBS) [7]. Ordered...from periodic patterns. On the other hand error diffused halftones do not suffer from periodicity and offer blue noise characteristic [3] which is

  9. Length scales of mantle heterogeneities and their relationship to ocean island basalt geochemistry

    NASA Astrophysics Data System (ADS)

    Kogiso, Tetsu; Hirschmann, Marc M.; Reiners, Peter W.

    2004-01-01

    The upper mantle is widely considered to be heterogeneous, possibly comprising a "marble-cake" mixture of heterogeneous domains in a relatively well-mixed matrix. The extent to which such domains are capable of producing and expelling melts with characteristic geochemical signatures upon partial melting, rather than equilibrating diffusively with surrounding peridotite, is a critical question for the origin of ocean island basalts (OIB) and mantle heterogeneity, but is poorly constrained. Central to this problem is the characteristic length scale of heterogeneous domains. If radiogenic osmium signatures in OIB are derived from discrete domains, then sub-linear correlations between Os isotopes and other geochemical indices, suggesting melt-melt mixing, may be used to constrain the length scales of these domains. These constraints arise because partial melts of geochemically distinct domains must segregate from their sources without significant equilibration with surrounding peridotite. Segregation of partial melts from such domains in upwelling mantle is promoted by compaction of the domain mineral matrix, and must occur faster than diffusive equilibration between the domain and its surroundings. Our calculations show that the diffusive equilibration time depends on the ratios of partition and diffusion coefficients of the partial melt and surrounding peridotite. Comparison of time scales between diffusion and melt segregation shows that segregation is more rapid than diffusive equilibration for Os, Sr, Pb, and Nd isotopes if the body widths are greater than tens of centimeter to several meters, depending on the aspect ratio of the bodies, on the melt fraction at which melt becomes interconnected in the bodies, and on the diffusivity in the solid. However, because Fe-Mg exchange occurs significantly more rapidly than equilibration of these isotopes under solid-state and partially molten conditions, it is possible that some domains can produce melts with Fe/Mg ratios

  10. Associations of Electrocardiographic P-wave Characteristics with Left Atrial Structure, Function and Diffuse Left Ventricular Fibrosis Defined by Cardiac Magnetic Resonance: the PRIMERI Study

    PubMed Central

    Win, Theingi Tiffany; Venkatesh, Bharath Ambale; Volpe, Gustavo J; Mewton, Nathan; Rizzi, Patricia; Sharma, Ravi K.; Strauss, David G.; Lima, Joao A.; Tereshchenko, Larisa G.

    2014-01-01

    Background Abnormal P-terminal force in V1 (PTFV1) is associated with an increased risk of heart failure, stroke, atrial fibrillation (AF) and death. Objective Our goal was to explore associations of left ventricular (LV) diffuse fibrosis with left atrium (LA) function and ECG measures of LA electrical activity. Methods AF-free patients (n=91, mean age 59.5, 61.5% men, 65.9% Caucasian) with structural heart disease (wide spatial QRS-T angle≥105° ± Selvester QRS score≥5 on ECG) but LV ejection fraction >35% underwent clinical evaluation, cardiac magnetic resonance and resting ECG. LA function indices were obtained by multimodality tissue tracking using 2 and 4-chamber long-axis images. T1 mapping and late gadolinium enhancement were used to assess diffuse LV fibrosis and presence of scar. P-prime in V1 amplitude (PPaV1) and duration (PPdV1), averaged P-duration, PR interval and P-axis were automatically measured using 12SL TM algorithm. PTFV1 was calculated as product of PPaV1 by PPdV1. Results In linear regression after adjustment for demographic, body mass index, LA volumemax index, presence of scar and LV mass index, each decile increase in LV interstitial fibrosis was associated with 0.76mV*ms increase in negative abnormal PTFV1 [(95%CI −1.42 to −0.09), P=0.025], 15.3ms prolongation in PPdV1 [(95%CI 6.9 to 23.8), P=0.001], and 5.4ms widening in averaged P-duration [(95%CI 0.9 to 10.0), P=0.020]. LV fibrosis did not affect LA function. PPaV1 and PTFV1 were associated with an increase in LA volumes, decrease in LAEF and LA reservoir function. Conclusion LV interstitial fibrosis is associated with abnormal PTFV1, prolonged PPdV1 and P-duration, but does not affect LA function. PMID:25267584

  11. Effects of low pressure radio frequency discharge on the physical and mechanical characteristics and chemical composition of diffusion coating on a surface of complex configuration details

    NASA Astrophysics Data System (ADS)

    Ladianov, V. I.; Gilmutdinov, F. Z.; Nikonova, R. M.; Kashapov, N. F.; Shaekhov, M. F.; Khristoliubova, V. I.

    2017-01-01

    The work deals with the influence of low-pressure radio frequency (RF) discharge on the surface properties of metals and their alloys. As objects of research to study the interaction of the jet low pressure RF discharge into the surface of the material the following materials were chosen: tungsten cobalt alloy, high speed steel, structural steel. In the presence of the materials energy parameters of low pressure RF discharge flows in the discharge chamber and the electrode gap were studied. A quantitative assessment of the gas composition inside the chamber to determine the characteristics of the plasma flow, making the major contribution to the modification of the surface was carried out. The influence of the input parameters of the plasma unit on the discharge characteristics was held. Identification of the main processes responsible for the modification of the surface of metals and alloys with the metal sample in the plasma jet and the effect of samples of products complex configuration on its properties is determined. The results of studies of physical and mechanical characteristics and chemical composition of the surface layers of high-speed steels, alloys and steel before and after treatment by low pressure radio frequency discharges with the instrumental indentation methods and X-ray photo-electron spectroscopy. With the help of the quality control system of the inner surfaces tubular products were studied.

  12. Diffusion bonding

    DOEpatents

    Anderson, Robert C.

    1976-06-22

    1. A method for joining beryllium to beryllium by diffusion bonding, comprising the steps of coating at least one surface portion of at least two beryllium pieces with nickel, positioning a coated surface portion in a contiguous relationship with an other surface portion, subjecting the contiguously disposed surface portions to an environment having an atmosphere at a pressure lower than ambient pressure, applying a force upon the beryllium pieces for causing the contiguous surface portions to abut against each other, heating the contiguous surface portions to a maximum temperature less than the melting temperature of the beryllium, substantially uniformly decreasing the applied force while increasing the temperature after attaining a temperature substantially above room temperature, and maintaining a portion of the applied force at a temperature corresponding to about maximum temperature for a duration sufficient to effect the diffusion bond between the contiguous surface portions.

  13. A strong host response and lack of MYC expression are characteristic for diffuse large B cell lymphoma transformed from nodular lymphocyte predominant Hodgkin lymphoma

    PubMed Central

    Schuhmacher, Bianca; Rengstl, Benjamin; Döring, Claudia; Bein, Julia; Newrzela, Sebastian; Brunnberg, Uta; Kvasnicka, Hans Michael; Vornanen, Martine; Küppers, Ralf; Hansmann, Martin-Leo; Hartmann, Sylvia

    2016-01-01

    Nodular lymphocyte predominant Hodgkin lymphoma (NLPHL) is an indolent lymphoma, but can transform into diffuse large B cell lymphoma (DLBCL), showing a more aggressive clinical behavior. Little is known about these cases on the molecular level. Therefore, the aim of the present study was to characterize DLBCL transformed from NLPHL (LP-DLBCL) by gene expression profiling (GEP). GEP revealed an inflammatory signature pinpointing to a specific host response. In a coculture model resembling this host response, DEV tumor cells showed an impaired growth behavior. Mechanisms involved in the reduced tumor cell proliferation included a downregulation of MYC and its target genes. Lack of MYC expression was also confirmed in 12/16 LP-DLBCL by immunohistochemistry. Furthermore, CD274/PD-L1 was upregulated in DEV tumor cells after coculture with T cells or monocytes and its expression was validated in 12/19 cases of LP-DLBCL. Thereby, our data provide new insights into the pathogenesis of LP-DLBCL and an explanation for the relatively low tumor cell content. Moreover, the findings suggest that treatment of these patients with immune checkpoint inhibitors may enhance an already ongoing host response in these patients. PMID:27708232

  14. Revealing mesoscopic structural universality with diffusion.

    PubMed

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

    2014-04-08

    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.

  15. In Situ Electromigration in Cu-Sn and Ni-Sn Critical Solder Length for Three-Dimensional Integrated Circuits

    NASA Astrophysics Data System (ADS)

    Huang, Y. T.; Chen, C. H.; Lee, B. H.; Chen, H. C.; Wang, C. M.; Wu, Albert T.

    2016-12-01

    An in situ electromigration study has been conducted on U-groove Cu/Sn-3.5Ag/Cu and Ni/Sn-3.5Ag/Ni sandwich structures; the results were used to simulate microsolder joints passing current density of 1 × 104 A/cm2 at 150°C. The solder gap was only 15 μm, shorter than the critical length of Sn-3.5Ag solder. Backstress was proved to exist at critical solder lengths and to influence the electromigration mechanism. Theoretical calculations of the diffusivity of Cu and Ni in Sn solder indicated that the degree to which the dominant diffusion species (Cu or Ni atoms) diffused through the solder line is retarded by the backstress effect. The morphologies of intermetallic compounds (IMCs) were observed, and the grain boundaries in Sn solder were measured using electron backscatter diffraction to determine the kinetics of intermetallic growth. The results reveal that the unique electromigration characteristics of microbump joints, including the diffusivity, morphology, and backstress, can be determined. The retardation of atomic migration improves the reliability against electromigration.

  16. Hydrogen diffusion in Zircon

    NASA Astrophysics Data System (ADS)

    Ingrin, Jannick; Zhang, Peipei

    2016-04-01

    Hydrogen mobility in gem quality zircon single crystals from Madagascar was investigated through H-D exchange experiments. Thin slices were annealed in a horizontal furnace flushed with a gas mixture of Ar/D2(10%) under ambient pressure between 900 ° C to 1150 ° C. FTIR analyses were performed on oriented slices before and after each annealing run. H diffusion along [100] and [010] follow the same diffusion law D = D0exp[-E /RT], with log D0 = 2.24 ± 1.57 (in m2/s) and E = 374 ± 39 kJ/mol. H diffusion along [001] follows a slightly more rapid diffusion law, with log D0 = 1.11 ± 0.22 (in m2/s) and E = 334 ± 49 kJ/mol. H diffusion in zircon has much higher activation energy and slower diffusivity than other NAMs below 1150 ° C even iron-poor garnets which are known to be among the slowest (Blanchard and Ingrin, 2004; Kurka et al. 2005). During H-D exchange zircon incorporates also deuterium. This hydration reaction involves uranium reduction as it is shown from the exchange of U5+ and U4+ characteristic bands in the near infrared region during annealing. It is the first time that a hydration reaction U5+ + OH- = U4+ + O2- + 1/2H2, is experimentally reported. The kinetics of deuterium incorporation is slightly slower than hydrogen diffusion, suggesting that the reaction is limited by hydrogen mobility. Hydrogen isotopic memory of zircon is higher than other NAMs. Zircons will be moderately retentive of H signatures at mid-crustal metamorphic temperatures. At 500 ° C, a zircon with a radius of 300 μm would retain its H isotopic signature over more than a million years. However, a zircon is unable to retain this information for geologically significant times under high-grade metamorphism unless the grain size is large enough. Refrences Blanchard, M. and Ingrin, J. (2004) Hydrogen diffusion in Dora Maira pyrope. Physics and Chemistry of Minerals, 31, 593-605. Kurka, A., Blanchard, M. and Ingrin, J. (2005) Kinetics of hydrogen extraction and deuteration in

  17. The Diffusion of Charged Particles in Collisional Plasmas: Free and Ambipolar Diffusion at Low and Moderate Pressures

    PubMed Central

    Phelps, A. V.

    1990-01-01

    The interpretation of measurements of the properties of weakly ionized plasmas in terms of diffusion of electrons and ions is reviewed both critically and tutorially. A particular effort is made to tie together various aspects of charged particle diffusion phenomena in quiescent, partially ionized plasmas. The concepts of diffusion length and effective diffusion coefficient and the treatment of partially reflecting boundaries are developed in the limit of the space-charge-free motion of the electrons or ions. A simplified derivation of the screening length for space charge electric fields is followed by a review of the conventional derivation of diffusion in the ambipolar limit. A discussion of the scaling parameters of the ratio of the diffusion length to the screening length and the ratio of the diffusion length to the ion mean-free-path leads to a map used to correlate published models covering the complete range of these parameters. The models of measurements of the diffusion of electrons, several types of positive ions, and negative ions are reviewed. The role of diffusion in the decay of charged particle densities and wall currents during the afterglow of a discharge is then considered. The effects of collapse of the space charge field and of diffusion cooling are reviewed. Finally, the application of the diffusion models to a number of different discharges is discussed. PMID:28179784

  18. Dependence of Temporal Diffusion Spectra on Microstructural Properties of Biological Tissues

    PubMed Central

    Xu, Junzhong; Does, Mark D.; Gore, John C.

    2010-01-01

    The apparent diffusion coefficient (ADC) measured using magnetic resonance imaging (MRI) methods provides information on micro-structural properties of biological tissues, and thus has found applications as a useful biomarker for assessing changes such as those that occur in ischemic stroke and cancer. Conventional pulsed gradient spin echo (PGSE) methods are in widespread use and provide information on, for example, variations in cell density. The oscillating gradient spin echo (OGSE) method has the additional ability to probe diffusion behaviors more readily at short diffusion times, and the temporal diffusion spectrum obtained by the OGSE method provides a unique tool for characterizing tissues over different length scales, including structural features of intra-cellular spaces. It has previously been reported that several tissue properties can affect ADC measurements significantly, and the precise biophysical mechanisms that account for ADC changes in different situations are still unclear. Those factors may vary in importance depending on the time and length scale over which measurements are made. In the present work, a comprehensive numerical simulation is used to investigate the dependence of the temporal diffusion spectra measured by OGSE methods on different micro-structural properties of biological tissues, including cell size, cell membrane permeability, intracellular volume fraction, intra-nucleus and intra-cytoplasm diffusion coefficients, nuclear size and T2 relaxation times. Some unique characteristics of the OGSE method at relatively high frequencies are revealed. The results presented in the paper offer a framework for better understanding possible causes of diffusion changes and may be useful to assist the interpretation of diffusion data from OGSE measurements. PMID:21129880

  19. 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

  20. DIFFUSION PUMP

    DOEpatents

    Levenson, L.

    1963-09-01

    A high-vacuum diffusion pump is described, featuring a novel housing geometry for enhancing pumping speed. An upright, cylindrical lower housing portion is surmounted by a concentric, upright, cylindrical upper housing portion of substantially larger diameter; an uppermost nozzle, disposed concentrically within the upper portion, is adapted to eject downwardly a conical sheet of liquid outwardly to impinge upon the uppermost extremity of the interior wall of the lower portion. Preferably this nozzle is mounted upon a pedestal rising coaxially from within the lower portion and projecting up into said upper portion. (AEC)

  1. Three-dimensional analysis of MHD generators and diffusers

    SciTech Connect

    Vanka, S P; Ahluwalia, R K; Doss, E D

    1982-03-01

    The three-dimensional flow and heat transfer phenomena in MHD channels and diffusers are analyzed by solving the governing partial differential equations for flow and electrical fields. The equation set consists of the mass continuity equation, the three momentum equations, the equations for enthalpy, turbulence kinetic energy and its dissipation rate, and the Maxwell equations. This set of coupled equations is solved by the use of a finite-difference calculation procedure. The turbulence is represented by a two-equation model of turbulence in which partial differential equations are solved for the turbulence kinetic energy and its dissipation rate. Calculations have been performed for Faraday and diagonally-connected channels. Specifically, the AEDC (Faraday) and the UTSI (diagonal) channels have been analyzed, and the results are compared with experimental data. The agreement is fairly good for all the measured quantities. The effects of channel loading on the three-dimensional flow characteristics of Faraday and diagonally-connected generators have been also analyzed. A simple argument is presented to show qualitatively the role of MHD body forces in generating axial vorticity and hence secondary flows in the cross-stream. Calculations have also been made to study the flow evolution in MHD diffusers. The calculations show that the velocity overshoots and secondary flows decay along the diffusers length. Plots of velocity, skin friction and pressure recovery are presented to illustrate the flow development in MHD diffusers.

  2. Length of stain dosimeter

    NASA Technical Reports Server (NTRS)

    Lueck, Dale E. (Inventor)

    1994-01-01

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

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

    SciTech Connect

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

    2015-06-21

    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-μm. 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 L{sub D} ∼ L{sub n} ∼ 10-μm, 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.

  4. Amosphous diffusion barriers

    NASA Technical Reports Server (NTRS)

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

    1986-01-01

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

  5. Theory of vortices in hybridized ballistic/diffusive-band superconductors

    NASA Astrophysics Data System (ADS)

    Tanaka, K.; Eschrig, M.; Agterberg, D. F.

    2007-06-01

    We study the electronic structure in the vicinity of a vortex in a two-band superconductor in which the quasiparticle motion is ballistic in one band and diffusive in the other. This study is based on a model appropriate for such a case, that we have introduced recently [Tanaka , Phys. Rev. B 73, 220501(R) (2006)]. We argue that in the two-band superconductor MgB2 , such a case is realized. Motivated by the experimental findings on MgB2 , we assume that superconductivity in the diffusive band is “weak,” i.e., mostly induced. We examine intriguing features of the order parameter, the current density, and the vortex core spectrum in the “strong” ballistic band under the influence of hybridization with the “weak” diffusive band. Although the order parameter in the diffusive band is induced, the characteristic length scales in the two bands differ due to Coulomb interactions. The current density in the vortex core is dominated by the contribution from the ballistic band, while outside the core the contribution from the diffusive band can be substantial, or even dominating. The current density in the diffusive band has strong temperature dependence, exhibiting the Kramer-Pesch effect when hybridization is strong. A particularly interesting feature of our model is the possibility of additional bound states near the gap edge in the ballistic band, that are prominent in the vortex center spectra. This contrasts with the single band case, where there is no gap-edge bound state in the vortex center. We find the above-mentioned unique features for parameter values relevant for MgB2 .

  6. Diffuse villous hyperplasia of choroid plexus.

    PubMed

    Iplikcioglu, A C; Bek, S; Gökduman, C A; Bikmaz, K; Cosar, M

    2006-06-01

    Diffuse villous hyperplasia of choroid plexus (DVHCP) is a rare condition which is characterized by the presence of diffuse enlargement of the entire choroid plexus throughout the length of the choroidal fissure and overproduction of CSF. The diagnosis of diffuse villous hyperplasia of choroid plexus can be established by the MR demonstration of diffusely large, contrast enhanced choroid plexus in the cases of overproduction hydrocephalus. Although some authors recommend choroid plexus excision or coagulation, ventriculo-atrial shunt insertion is a simple and effective treatment modality in cases of diffuse villous hyperplasia of the choroid plexus. In this report we present a case of diffuse villous hyperplasia of the choroid plexus and a short review of the literature. To our knowledge, in the CT and MRI era only 5 cases of DVHCP cases have been reported.

  7. Dynamic cross-correlations between entangled biofilaments as they diffuse.

    PubMed

    Tsang, Boyce; Dell, Zachary E; Jiang, Lingxiang; Schweizer, Kenneth S; Granick, Steve

    2017-03-10

    Entanglement in polymer and biological physics involves a state in which linear interthreaded macromolecules in isotropic liquids diffuse in a spatially anisotropic manner beyond a characteristic mesoscopic time and length scale (tube diameter). The physical reason is that linear macromolecules become transiently localized in directions transverse to their backbone but diffuse with relative ease parallel to it. Within the resulting broad spectrum of relaxation times there is an extended period before the longest relaxation time when filaments occupy a time-averaged cylindrical space of near-constant density. Here we show its implication with experiments based on fluorescence tracking of dilutely labeled macromolecules. The entangled pairs of aqueous F-actin biofilaments diffuse with separation-dependent dynamic cross-correlations that exceed those expected from continuum hydrodynamics up to strikingly large spatial distances of ≈15 µm, which is more than 10(4) times the size of the solvent water molecules in which they are dissolved, and is more than 50 times the dynamic tube diameter, but is almost equal to the filament length. Modeling this entangled system as a collection of rigid rods, we present a statistical mechanical theory that predicts these long-range dynamic correlations as an emergent consequence of an effective long-range interpolymer repulsion due to the de Gennes correlation hole, which is a combined consequence of chain connectivity and uncrossability. The key physical assumption needed to make theory and experiment agree is that solutions of entangled biofilaments localized in tubes that are effectively dynamically incompressible over the relevant intermediate time and length scales.

  8. Dynamic cross-correlations between entangled biofilaments as they diffuse

    PubMed Central

    Tsang, Boyce; Dell, Zachary E.; Jiang, Lingxiang; Schweizer, Kenneth S.; Granick, Steve

    2017-01-01

    Entanglement in polymer and biological physics involves a state in which linear interthreaded macromolecules in isotropic liquids diffuse in a spatially anisotropic manner beyond a characteristic mesoscopic time and length scale (tube diameter). The physical reason is that linear macromolecules become transiently localized in directions transverse to their backbone but diffuse with relative ease parallel to it. Within the resulting broad spectrum of relaxation times there is an extended period before the longest relaxation time when filaments occupy a time-averaged cylindrical space of near-constant density. Here we show its implication with experiments based on fluorescence tracking of dilutely labeled macromolecules. The entangled pairs of aqueous F-actin biofilaments diffuse with separation-dependent dynamic cross-correlations that exceed those expected from continuum hydrodynamics up to strikingly large spatial distances of ≈15 µm, which is more than 104 times the size of the solvent water molecules in which they are dissolved, and is more than 50 times the dynamic tube diameter, but is almost equal to the filament length. Modeling this entangled system as a collection of rigid rods, we present a statistical mechanical theory that predicts these long-range dynamic correlations as an emergent consequence of an effective long-range interpolymer repulsion due to the de Gennes correlation hole, which is a combined consequence of chain connectivity and uncrossability. The key physical assumption needed to make theory and experiment agree is that solutions of entangled biofilaments localized in tubes that are effectively dynamically incompressible over the relevant intermediate time and length scales. PMID:28283664

  9. Ambipolar diffusion in complex plasma.

    PubMed

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

    2007-04-01

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

  10. 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.

  11. Primary diffuse alveolar septal amyloidosis.

    PubMed Central

    Poh, S C; Tjia, T S; Seah, H C

    1975-01-01

    The case is reported of a 61-year-old man with primary diffuse alveolar septal pulmonary amyloidosis. Amyloid infiltration of the heart and other organs was also observed. The clinical findings and laboratory investigations reveal features characteristic of defective gas transfer with pulmonary oedema due to left ventricular failure from myocardial involvement. Images PMID:1179316

  12. Probing dark exciton diffusion using photovoltage

    PubMed Central

    Mullenbach, Tyler K.; Curtin, Ian J.; Zhang, Tao; Holmes, Russell J.

    2017-01-01

    The migration of weakly and non-luminescent (dark) excitons remains an understudied subset of exciton dynamics in molecular thin films. Inaccessible via photoluminescence, these states are often probed using photocurrent methods that require efficient charge collection. Here we probe exciton harvesting in both luminescent and dark materials using a photovoltage-based technique. Transient photovoltage permits a real-time measurement of the number of charges in an organic photovoltaic cell, while avoiding non-geminate recombination losses. The extracted exciton diffusion lengths are found to be similar to those determined using photocurrent. For the luminescent material boron subphthalocyanine chloride, the photovoltage determined diffusion length is less than that extracted from photoluminescence. This indicates that while photovoltage circumvents non-geminate losses, geminate recombination at the donor–acceptor interface remains the primary recombination pathway. Photovoltage thus offers a general approach for extracting a device-relevant diffusion length, while also providing insight in to the dominant carrier recombination pathways. PMID:28128206

  13. Probing dark exciton diffusion using photovoltage

    NASA Astrophysics Data System (ADS)

    Mullenbach, Tyler K.; Curtin, Ian J.; Zhang, Tao; Holmes, Russell J.

    2017-01-01

    The migration of weakly and non-luminescent (dark) excitons remains an understudied subset of exciton dynamics in molecular thin films. Inaccessible via photoluminescence, these states are often probed using photocurrent methods that require efficient charge collection. Here we probe exciton harvesting in both luminescent and dark materials using a photovoltage-based technique. Transient photovoltage permits a real-time measurement of the number of charges in an organic photovoltaic cell, while avoiding non-geminate recombination losses. The extracted exciton diffusion lengths are found to be similar to those determined using photocurrent. For the luminescent material boron subphthalocyanine chloride, the photovoltage determined diffusion length is less than that extracted from photoluminescence. This indicates that while photovoltage circumvents non-geminate losses, geminate recombination at the donor-acceptor interface remains the primary recombination pathway. Photovoltage thus offers a general approach for extracting a device-relevant diffusion length, while also providing insight in to the dominant carrier recombination pathways.

  14. 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.

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

  16. 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.

  17. Unified Drift-Diffusion Theory for Transverse Spin Currents in Spin Valves, Domain Walls, and Other Textured Magnets

    NASA Astrophysics Data System (ADS)

    Petitjean, Cyril; Luc, David; Waintal, Xavier

    2012-09-01

    Spins transverse to the magnetization of a ferromagnet only survive over a short distance. We develop a drift-diffusion approach that captures the main features of transverse spin effects in systems with arbitrary spin textures (e.g., vortices and domain walls) and generalizes the Valet-Fert theory. In addition to the standard characteristic lengths (mean free path for majority and minority electrons, and spin diffusion length), the theory introduces two length scales, the transverse spin coherence length ℓ⊥ and the (Larmor) spin precession length ℓL. We show how ℓL and ℓ⊥ can be extracted from ab initio calculations or measured with giant magnetoresistance experiments. In long (adiabatic) domain walls, we provide an analytic formula that expresses the so-called “nonadiabatic” (or fieldlike) torque in terms of these length scales. However, this nonadiabatic torque is no longer a simple material parameter but depends on the actual spin texture: in thin (<10nm) domain walls, we observe very significant deviations from the adiabatic limit.

  18. Molecular dynamics simulations of NMR relaxation and diffusion of bulk hydrocarbons and water

    NASA Astrophysics Data System (ADS)

    Singer, Philip M.; Asthagiri, Dilip; Chapman, Walter G.; Hirasaki, George J.

    2017-04-01

    Molecular dynamics (MD) simulations are used to investigate 1H nuclear magnetic resonance (NMR) relaxation and diffusion of bulk n-C5H12 to n-C17H36 hydrocarbons and bulk water. The MD simulations of the 1H NMR relaxation times T1,2 in the fast motion regime where T1 =T2 agree with measured (de-oxygenated) T2 data at ambient conditions, without any adjustable parameters in the interpretation of the simulation data. Likewise, the translational diffusion DT coefficients calculated using simulation configurations agree with measured diffusion data at ambient conditions. The agreement between the predicted and experimentally measured NMR relaxation times and diffusion coefficient also validate the forcefields used in the simulation. The molecular simulations naturally separate intramolecular from intermolecular dipole-dipole interactions helping bring new insight into the two NMR relaxation mechanisms as a function of molecular chain-length (i.e. carbon number). Comparison of the MD simulation results of the two relaxation mechanisms with traditional hard-sphere models used in interpreting NMR data reveals important limitations in the latter. With increasing chain length, there is substantial deviation in the molecular size inferred on the basis of the radius of gyration from simulation and the fitted hard-sphere radii required to rationalize the relaxation times. This deviation is characteristic of the local nature of the NMR measurement, one that is well-captured by molecular simulations.

  19. NIST Diffusion Data Center

    National Institute of Standards and Technology Data Gateway

    NIST Diffusion Data Center (Web, free access)   The NIST Diffusion Data Center is a collection of over 14,100 international papers, theses, and government reports on diffusion published before 1980.

  20. Parallel flow diffusion battery

    DOEpatents

    Yeh, Hsu-Chi; Cheng, Yung-Sung

    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.

  1. 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.

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

    SciTech Connect

    Alam, Todd M.

    2015-09-01

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

  3. Fluid diffusion in porous silica

    NASA Astrophysics Data System (ADS)

    McCann, Lowell I.

    Fluid motion in porous media has received a great deal of theoretical and experimental attention due to its importance in systems as diverse as ground water aquifers, catalytic processes, and size separation schemes. Often, the motion of interest is the random thermal motion of molecules in a fluid undergoing no net flow. This diffusive motion is particularly important when the size of the pores is nearly the same as the size of the molecules. In this study, fluid diffusion is measured in several varieties of porous silica whose pore structure is determined by the process by which it is made. The samples in this study have porosities (φ, the ratio of the pore volume to the total sample volume) that vary from 0.3 to 0.75 and average pore radii that range from approximately 15 to 120 A. Determining the effect of the pore structure on the diffusion of a liquid in a porous material is complicated by the chemical interactions between the diffusing molecules and the pore surface. In this study, ions in a hydrophilic fluid are used to block the adsorption of the diffusing dye molecules to the hydroxyl groups covering the silica surface. This technique is unlike typical surface treatments of silica in that it does not permanently alter the pore geometry. In this work, fluid diffusion is measured with a transient holographic grating technique where interfering laser beams create a periodic refractive index modulation in the fluid. The diffraction of a third laser off this grating is monitored to determine how quickly the grating relaxes, thereby determining the diffusion coefficient of the molecules in the fluid. Varying the grating periodicity controls the length scale of the diffusion measurement from 1.2 to 100 μm which is much larger than the average pore sizes of the samples. Therefore, over these large scales, we measure 'normal' diffusion, where the mean squared displacement of a diffusing particle varies linearly with time. In one particular type of porous silica

  4. Diffusion in porous crystalline materials.

    PubMed

    Krishna, Rajamani

    2012-04-21

    The design and development of many separation and catalytic process technologies require a proper quantitative description of diffusion of mixtures of guest molecules within porous crystalline materials. This tutorial review presents a unified, phenomenological description of diffusion inside meso- and micro-porous structures. In meso-porous materials, with pore sizes 2 nm < d(p) < 50 nm, there is a central core region where the influence of interactions of the molecules with the pore wall is either small or negligible; meso-pore diffusion is governed by a combination of molecule-molecule and molecule-pore wall interactions. Within micro-pores, with d(p) < 2 nm, the guest molecules are always under the influence of the force field exerted with the wall and we have to reckon with the motion of adsorbed molecules, and there is no "bulk" fluid region. The characteristics and physical significance of the self-, Maxwell-Stefan, and Fick diffusivities are explained with the aid of data obtained either from experiments or molecular dynamics simulations, for a wide variety of structures with different pore sizes and topology. The influence of adsorption thermodynamics, molecular clustering, and segregation on both magnitudes and concentration dependences of the diffusivities is highlighted. In mixture diffusion, correlations in molecular hops have the effect of slowing-down the more mobile species. The need for proper modeling of correlation effects using the Maxwell-Stefan formulation is stressed with the aid of examples of membrane separations and catalytic reactors.

  5. FRACTIONAL PEARSON DIFFUSIONS.

    PubMed

    Leonenko, Nikolai N; Meerschaert, Mark M; Sikorskii, Alla

    2013-07-15

    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.

  6. 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

  7. Turbulence reduces magnetic diffusivity in DTS liquid sodium experiment

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  8. Effects of radial diffuser hydraulic design on a double-suction centrifugal pump

    NASA Astrophysics Data System (ADS)

    Hou, H. C.; Zhang, Y. X.; Xu, C.; Zhang, J. Y.; Li, Z. L.

    2016-05-01

    In order to study effects of radial diffuser on hydraulic performance of crude oil pump, the steady CFD numerical method is applied and one large double-suction oil pump running in long-distance pipeline is considered. The research focuses on analysing the influence of its diffuser vane profile on hydraulic performance of oil pump. The four different types of cylindrical vane have been designed by in-house codes mainly including double arcs (DA), triple arcs (TA), equiangular spiral line (ES) and linear variable angle spiral line (LVS). During design process diffuser vane angles at inlet and outlet are tentatively given within a certain range and then the wrapping angle of the four types of diffuser vanes can be calculated automatically. Under the given inlet and outlet angles, the linear variable angle spiral line profile has the biggest wrapping angle and profile length which is good to delay channel diffusion but bring more friction hydraulic loss. Finally the vane camber line is thickened at the certain uniform thickness distribution and the 3D diffuser models are generated. The whole flow passage of oil pump with different types of diffusers under various flow rate conditions are numerically simulated based on RNG k-ɛ turbulent model and SIMPLEC algorithm. The numerical results show that different types of diffusers can bring about great difference on the hydraulic performance of oil pump, of which the ES profile diffuser with its proper setting angle shows the best hydraulic performance and its inner flow field is improved obviously. Compared with the head data from model sample, all designed diffusers can make a certain improvement on head characteristic. At the large flow rate conditions the hydraulic efficiency increases obviously and the best efficiency point shift to the large flow rate range. The ES profile diffuser embodies the better advantages on pump performance which can be explained theoretically that the diffuser actually acts as a diffusion

  9. In situ experiment to determine advective-diffusive controls on solute transport in a clay-rich aquitard.

    PubMed

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

    2012-04-01

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

  10. 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

  11. Multiport Diffuser as Line Source of Momentum in Shallow Water

    NASA Astrophysics Data System (ADS)

    Lee, Joseph H.; Jirka, Gerhard H.

    1980-08-01

    law, and of lateral turbulent entrainment, described by the entrainment hypothesis of Morton et al. (1956). The far-field model is combined with the inviscid near-field solution, thus superimposing the real fluid effects onto the properties of the contracting slipstream. Two distinctive features characterize the diffuser plume. First, it experiences an exponential loss of fluid momentum through turbulent bottom friction which leads to an ultimate plume stagnation at a characteristic distance ƒ0LD/(16H), where ƒ0 is a quadratic friction coefficient, LD the diffuser length, and H the water depth, and also puts a limit on the total lateral entrainment flow. Second, the initial plume characteristics, and thus its rate of entrainment, are controlled by the accelerating high-velocity slipstream in the vicinity of the line source. Experiments in a shallow laboratory basin corroborate the theoretical results, both as regards the qualitative features of the contracting slipstream and the quantitative observations of induced velocities and flow rates.

  12. Shortened estrous cycle length, increased FSH levels, FSH variance, oocyte spindle aberrations, and early declining fertility in aging senescence-accelerated mouse prone-8 (SAMP8) mice: concomitant characteristics of human midlife female reproductive aging.

    PubMed

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

    2014-06-01

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

  13. Universality of modulation length and time exponents.

    PubMed

    Chakrabarty, Saurish; Dobrosavljević, Vladimir; Seidel, Alexander; Nussinov, Zohar

    2012-10-01

    We study systems with a crossover parameter λ, such as the temperature T, which has a threshold value λ(*) across which the correlation function changes from exhibiting fixed wavelength (or time period) modulations to continuously varying modulation lengths (or times). We introduce a hitherto unknown exponent ν(L) characterizing the universal nature of this crossover and compute its value in general instances. This exponent, similar to standard correlation length exponents, is obtained from motion of the poles of the momentum (or frequency) space correlation functions in the complex k-plane (or ω-plane) as the parameter λ is varied. Near the crossover (i.e., for λ→λ(*)), the characteristic modulation wave vector K(R) in the variable modulation length "phase" is related to that in the fixed modulation length "phase" q via |K(R)-q|[proportionality]|T-T(*)|(νL). We find, in general, that ν(L)=1/2. In some special instances, ν(L) may attain other rational values. We extend this result to general problems in which the eigenvalue of an operator or a pole characterizing general response functions may attain a constant real (or imaginary) part beyond a particular threshold value λ(*). We discuss extensions of this result to multiple other arenas. These include the axial next-nearest-neighbor Ising (ANNNI) model. By extending our considerations, we comment on relations pertaining not only to the modulation lengths (or times), but also to the standard correlation lengths (or times). We introduce the notion of a Josephson time scale. We comment on the presence of aperiodic "chaotic" modulations in "soft-spin" and other systems. These relate to glass-type features. We discuss applications to Fermi systems, with particular application to metal to band insulator transitions, change of Fermi surface topology, divergent effective masses, Dirac systems, and topological insulators. Both regular periodic and glassy (and spatially chaotic behavior) may be found in

  14. Marmot-Fission-Gas-Diffusion

    SciTech Connect

    Andersson, Anders; Matthews, Christopher

    2016-10-22

    The MARMOT-FISSION-GAS-DIFFUSION software solves a coupled set of partial differential equations describing fission gas evolution in UO2 nuclear fuel. It is part of the MARMOT code, which builds on the MOOSE framework. Both the MARMOT code and the MOOSE framework are developed and maintained by Idaho National Laboratory. The model in MARMOT-FISSION-GAS-DIFFUSION consists of a set of continuum reaction-diffusion equations capturing formation and annihilation of defects, reactions between defects, diffusion of defects and segregation of defects to grain boundaries. Defects refer to vacancies and interstitials as well fission gas atoms (Xe) occupying various trap sites such as uranium and oxygen vacancies and interstitials sites. The code can treat a large number of defect types. The model is formulated within the phase field framework to be compatible with other MARMOT kernels. The driving forces for all reactions, diffusion and segregation events are consistently formulated as a variational derivatives of the free energy of the system. The rates of the reactions are controlled by the corresponding kinetic coefficients. The free energy and the kinetic coefficients for UO2 have been parameterized by lower length scale simulations. The code can be used to simulate defect evolution in a prescribed UO2 microstructure as well as to solve defect clustering problems that control effective diffusivities under both thermal and irradiation conditions. It I possible to extend the current UO2 model to other fuel types such as accident tolerant fuels based on the U3Si2 compound. This would obviously require a new set of material properties describing the behavior of defects in U3Si2 rather than UO2. The framework is however designed to be generic.

  15. 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.

  16. 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)

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

    PubMed Central

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

    2015-01-01

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

  18. 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

  19. Gestation length in farmed reindeer.

    PubMed

    Shipka, M P; Rowell, J E

    2010-01-01

    Reindeer (Rangifer tarandus tarundus) are the only cervids indigenous to the arctic environment. In Alaska, reindeer are a recognized agricultural species and an economic mainstay for many native populations. Traditionally raised in extensive free-ranging systems, a recent trend toward intensive farming requires a more in-depth knowledge of reproductive management. Reported gestation length in reindeer varies, ranging from 198 to 229 d in studies performed at the University of Alaska Fairbanks. A switchback study that manipulated only breeding date demonstrated a mean increase in gestation length of 8.5 d among females bred early in the season. The negative correlation between conception date and gestation length is consistent with reindeer research at other locations and reports of variable gestation length in a growing number of domestic and non-domestic species. This paper reviews the phenomenon in reindeer and discusses some of the factors known to affect gestation length as well as possible areas for future research.

  20. Morphological, Chemical Surface, and Diffusive Transport Characterizations of a Nanoporous Alumina Membrane

    PubMed Central

    Vázquez, María I.; Romero, Virgina; Vega, Victor; García, Javier; Prida, Victor M.; Hernando, Blanca; Benavente, Juana

    2015-01-01

    Synthesis of a nanoporous alumina membrane (NPAM) by the two-step anodization method and its morphological and chemical surface characterization by analyzing Scanning Electron Microscopy (SEM) micrographs and X-Ray Photoelectron Spectroscopy (XPS) spectra is reported. Influence of electrical and diffusive effects on the NaCl transport across the membrane nanopores is determined from salt diffusion measurements performed with a wide range of NaCl concentrations, which allows the estimation of characteristic electrochemical membrane parameters such as the NaCl diffusion coefficient and the concentration of fixed charges in the membrane, by using an appropriated model and the membrane geometrical parameters (porosity and pore length). These results indicate a reduction of ~70% in the value of the NaCl diffusion coefficient through the membrane pores with respect to solution. The transport number of ions in the membrane pores (Na+ and Cl−, respectively) were determined from concentration potential measurements, and the effect of concentration-polarization at the membrane surfaces was also considered by comparing concentration potential values obtained with stirred solutions (550 rpm) and without stirring. From both kinds of results, a value higher than 0.05 M NaCl for the feed solution seems to be necessary to neglect the contribution of electrical interactions in the diffusive transport. PMID:28347115

  1. Theory of linear sweep voltammetry with diffuse charge: Unsupported electrolytes, thin films, and leaky membranes

    NASA Astrophysics Data System (ADS)

    Yan, David; Bazant, Martin Z.; Biesheuvel, P. M.; Pugh, Mary C.; Dawson, Francis P.

    2017-03-01

    Linear sweep and cyclic voltammetry techniques are important tools for electrochemists and have a variety of applications in engineering. Voltammetry has classically been treated with the Randles-Sevcik equation, which assumes an electroneutral supported electrolyte. In this paper, we provide a comprehensive mathematical theory of voltammetry in electrochemical cells with unsupported electrolytes and for other situations where diffuse charge effects play a role, and present analytical and simulated solutions of the time-dependent Poisson-Nernst-Planck equations with generalized Frumkin-Butler-Volmer boundary conditions for a 1:1 electrolyte and a simple reaction. Using these solutions, we construct theoretical and simulated current-voltage curves for liquid and solid thin films, membranes with fixed background charge, and cells with blocking electrodes. The full range of dimensionless parameters is considered, including the dimensionless Debye screening length (scaled to the electrode separation), Damkohler number (ratio of characteristic diffusion and reaction times), and dimensionless sweep rate (scaled to the thermal voltage per diffusion time). The analysis focuses on the coupling of Faradaic reactions and diffuse charge dynamics, although capacitive charging of the electrical double layers is also studied, for early time transients at reactive electrodes and for nonreactive blocking electrodes. Our work highlights cases where diffuse charge effects are important in the context of voltammetry, and illustrates which regimes can be approximated using simple analytical expressions and which require more careful consideration.

  2. 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.

  3. 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.

  4. 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

  5. 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.

  6. Minimum length-maximum velocity

    NASA Astrophysics Data System (ADS)

    Panes, Boris

    2012-03-01

    We study a framework where the hypothesis of a minimum length in space-time is complemented with the notion of reference frame invariance. It turns out natural to interpret the action of the obtained reference frame transformations in the context of doubly special relativity. As a consequence of this formalism we find interesting connections between the minimum length properties and the modified velocity-energy relation for ultra-relativistic particles. For example, we can predict the ratio between the minimum lengths in space and time using the results from OPERA on superluminal neutrinos.

  7. Length Invisibilization of Tachyonic Neutrinos

    NASA Astrophysics Data System (ADS)

    Estakhr, Ahmad Reza

    2016-09-01

    Faster than the speed of light particle such as tachyonic neutrino due to its superluminal nature disapper and is undetectable. L = iΩ-1Lo where, i =√{ - 1 } is imaginary Number, Ω = 1 /√{βs2 - 1 } is Estakhr's Omega factor, L is the Superluminal Length, Lo is the proper length, βs =Vs / c > 1 is superluminal speed parameter, Vs is Superluminal velocity and c is speed of light.

  8. Microfabricated diffusion source

    DOEpatents

    Oborny, Michael C.; Frye-Mason, Gregory C.; Manginell, Ronald P.

    2008-07-15

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

  9. Mechanobiological induction of long-range contractility by diffusing biomolecules and size scaling in cell assemblies

    PubMed Central

    Dasbiswas, K.; Alster, E.; Safran, S. A.

    2016-01-01

    Mechanobiological studies of cell assemblies have generally focused on cells that are, in principle, identical. Here we predict theoretically the effect on cells in culture of locally introduced biochemical signals that diffuse and locally induce cytoskeletal contractility which is initially small. In steady-state, both the concentration profile of the signaling molecule as well as the contractility profile of the cell assembly are inhomogeneous, with a characteristic length that can be of the order of the system size. The long-range nature of this state originates in the elastic interactions of contractile cells (similar to long-range “macroscopic modes” in non-living elastic inclusions) and the non-linear diffusion of the signaling molecules, here termed mechanogens. We suggest model experiments on cell assemblies on substrates that can test the theory as a prelude to its applicability in embryo development where spatial gradients of morphogens initiate cellular development. PMID:27283037

  10. Mechanobiological induction of long-range contractility by diffusing biomolecules and size scaling in cell assemblies

    NASA Astrophysics Data System (ADS)

    Dasbiswas, K.; Alster, E.; Safran, S. A.

    2016-06-01

    Mechanobiological studies of cell assemblies have generally focused on cells that are, in principle, identical. Here we predict theoretically the effect on cells in culture of locally introduced biochemical signals that diffuse and locally induce cytoskeletal contractility which is initially small. In steady-state, both the concentration profile of the signaling molecule as well as the contractility profile of the cell assembly are inhomogeneous, with a characteristic length that can be of the order of the system size. The long-range nature of this state originates in the elastic interactions of contractile cells (similar to long-range “macroscopic modes” in non-living elastic inclusions) and the non-linear diffusion of the signaling molecules, here termed mechanogens. We suggest model experiments on cell assemblies on substrates that can test the theory as a prelude to its applicability in embryo development where spatial gradients of morphogens initiate cellular development.

  11. Volume Diffuse Dielectric Barrier Discharge Plasma Produced by Nanosecond High Voltage Pulse in Airflow

    NASA Astrophysics Data System (ADS)

    Qi, Haicheng; Gao, Wei; Fan, Zhihui; Liu, Yidi; Ren, Chunsheng

    2016-05-01

    Volume diffuse dielectric barrier discharge (DBD) plasma is produced in subsonic airflow by nanosecond high-voltage pulse power supply with a plate-to-plate discharge cell at 6 mm air gap length. The discharge images, optical emission spectra (OES), the applied voltage and current waveforms of the discharge at the changed airflow rates are obtained. When airflow rate is increased, the transition of the discharge mode and the variations of discharge intensity, breakdown characteristics and the temperature of the discharge plasma are investigated. The results show that the discharge becomes more diffuse, discharge intensity is decreased accompanied by the increased breakdown voltage and time lag, and the temperature of the discharge plasma reduces when airflow of small velocity is introduced into the discharge gap. These phenomena are because that the airflow changes the spatial distribution of the heat and the space charge in the discharge gap. supported by National Natural Science Foundation of China (No. 51437002)

  12. Observation of slow down of polystyrene nanogels diffusivities in contact with swollen polystyrene brushes.

    PubMed

    Michailidou, V N; Loppinet, B; Vo, C D; Rühe, J; Tauer, K; Fytas, G

    2008-01-01

    The diffusion of dilute colloids in contact with swollen polymer brushes has been studied by evanescent wave dynamic light scattering. Two polystyrene nanogels with 16 nm and 42 nm radius were put into contact with three polystyrene brushes with varying grafting densities. Partial penetration of the nanogels within the brushes was revealed by the evanescent wave penetration depth-dependent scattering intensities. The experimental short-time diffusion coefficients of the penetrating particles were measured and found to strongly slow down as the nanoparticles get deeper into the brushes. The slow down is much more marked for the smaller (16 nm) nanogels, suggesting a size exclusion type of mechanism and the existence of a characteristic length scale present in the outer part of the brush.

  13. Diffusion of oxygen in cork.

    PubMed

    Lequin, Sonia; Chassagne, David; Karbowiak, Thomas; Simon, Jean-Marc; Paulin, Christian; Bellat, Jean-Pierre

    2012-04-04

    This work reports measurements of effective oxygen diffusion coefficient in raw cork. Kinetics of oxygen transfer through cork is studied at 298 K thanks to a homemade manometric device composed of two gas compartments separated by a cork wafer sample. The first compartment contains oxygen, whereas the second one is kept under dynamic vacuum. The pressure decrease in the first compartment is recorded as a function of time. The effective diffusion coefficient D(eff) is obtained by applying Fick's law to transient state using a numerical method based on finite differences. An analytical model derived from Fick's law applied to steady state is also proposed. Results given by these two methods are in close agreement with each other. The harmonic average of the effective diffusion coefficients obtained from the distribution of 15 cork wafers of 3 mm thickness is 1.1 × 10(-9) m(2) s(-1) with a large distribution over four decades. The statistical analysis of the Gaussian distribution obtained on a 3 mm cork wafer is extrapolated to a 48 mm cork wafer, which length corresponds to a full cork stopper. In this case, the probability density distribution gives a mean value of D(eff) equal to 1.6 × 10(-9) m(2) s(-1). This result shows that it is possible to obtain the effective diffusion coefficient of oxygen through cork from short time (few days) measurements performed on a thin cork wafer, whereas months are required to obtain the diffusion coefficient for a full cork stopper. Permeability and oxygen transfer rate are also calculated for comparison with data from other studies.

  14. Translational diffusion of proteins in nanochannels

    NASA Astrophysics Data System (ADS)

    Kannam, Sridhar Kumar; Downton, Matthew T.

    2017-02-01

    Hydrodynamic interactions play an important role in the transport of analytes through nanoscale devices. Of particular note is the role that no-slip boundary conditions have on the drag coefficient of confined particles and molecules. In this work, we use a coarse grained molecular dynamics model to measure the diffusion coefficients of proteins confined within cylindrical nanochannels of similar dimension. Finite-size corrected bulk diffusion coefficients are found to agree with experimental data, while in channels, a good match is found between theoretical expressions based on continuum fluid mechanics and the reduction of the translational diffusion coefficient across a range of protein to channel size ratios. These results demonstrate that it is possible to directly use molecular simulation to make quantitative predictions of the effects of hydrodynamics on diffusion at length scales of order 1 nm.

  15. Bounds on the length of magnetic field lines in a two-dimensional plasma.

    PubMed

    Núñez, M

    2001-03-01

    Magnetic field lines in ideal turbulent plasmas tend to become quite complicated and their length to grow in time. Diffusivity allows for reconnection and possible shortening, but this fact has not so far been rigorously quantified. We show that in a two-dimensional diffusive plasma the mean length of field lines stays bounded for all time. Moreover, these estimates are local, in the sense that the mean values of magnetic field and velocity in the neighborhood of a ball determine bounds for length within the ball, without recourse to external magnitudes.

  16. 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.

  17. The Effect of Upstream Vane Wakes on Annular Diffuser Flows

    NASA Astrophysics Data System (ADS)

    Cherry, Erica; Padilla, Angelina; Elkins, Christopher; Eaton, John

    2008-11-01

    Experiments were performed to determine the sensitivity to inlet conditions of the flow in two annular diffusers. One of the diffusers was a conservative design typical of a diffuser directly upstream of the combustor in a jet engine. The other had the same length and inlet shape as the first diffuser but a larger area ratio and was meant to operate on the verge of separation. Each diffuser was connected to two different inlets, one containing a fully-developed channel flow, the other containing wakes from a row of airfoils. Three-component velocity measurements were taken on the flow in each inlet/diffuser combination using Magnetic Resonance Velocimetry. Results will be presented on the 3D velocity fields in the two diffusers and the effect of the airfoil wakes on separation and secondary flows.

  18. Diffusion of tungsten hexafluoride

    NASA Astrophysics Data System (ADS)

    Winkelmann, J.

    This document is part of Subvolume A `Gases in Gases, Liquids and their Mixtures' of Volume 15 `Diffusion in Gases, Liquids and Electrolytes' of Landolt-Börnstein Group IV `Physical Chemistry'. It is part of the chapter of the chapter `Diffusion in Pure Gases' and contains data on diffusion of tungsten hexafluoride

  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. A Student Diffusion Activity

    NASA Astrophysics Data System (ADS)

    Kutzner, Mickey; Pearson, Bryan

    2017-02-01

    Diffusion is a truly interdisciplinary topic bridging all areas of STEM education. When biomolecules are not being moved through the body by fluid flow through the circulatory system or by molecular motors, diffusion is the primary mode of transport over short distances. The direction of the diffusive flow of particles is from high concentration toward low concentration.

  2. Handbook on atmospheric diffusion

    SciTech Connect

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

    1982-01-01

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

  3. 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…

  4. IMF Length Scales and Predictability: The Two Length Scale Medium

    NASA Technical Reports Server (NTRS)

    Collier, Michael R.; Szabo, Adam; Slavin, James A.; Lepping, R. P.; Kokubun, S.

    1999-01-01

    We present preliminary results from a systematic study using simultaneous data from three spacecraft, Wind, IMP 8 (Interplanetary Monitoring Platform) and Geotail to examine interplanetary length scales and their implications on predictability for magnetic field parcels in the typical solar wind. Time periods were selected when the plane formed by the three spacecraft included the GSE (Ground Support Equipment) x-direction so that if the parcel fronts were strictly planar, the two adjacent spacecraft pairs would determine the same phase front angles. After correcting for the motion of the Earth relative to the interplanetary medium and deviations in the solar wind flow from radial, we used differences in the measured front angle between the two spacecraft pairs to determine structure radius of curvature. Results indicate that the typical radius of curvature for these IMF parcels is of the order of 100 R (Sub E). This implies that there are two important IMF (Interplanetary Magnetic Field) scale lengths relevant to predictability: (1) the well-established scale length over which correlations observed by two spacecraft decay along a given IMF parcel, of the order of a few tens of Earth radii and (2) the scale length over which two spacecraft are unlikely to even observe the same parcel because of its curvature, of the order of a hundred Earth radii.

  5. The Diffuse Interstellar Bands: Contributed papers

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

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

  6. CEBAF Upgrade Bunch Length Measurements

    SciTech Connect

    Ahmad, Mahmoud

    2016-05-01

    Many accelerators use short electron bunches and measuring the bunch length is important for efficient operations. CEBAF needs a suitable bunch length because bunches that are too long will result in beam interruption to the halls due to excessive energy spread and beam loss. In this work, bunch length is measured by invasive and non-invasive techniques at different beam energies. Two new measurement techniques have been commissioned; a harmonic cavity showed good results compared to expectations from simulation, and a real time interferometer is commissioned and first checkouts were performed. Three other techniques were used for measurements and comparison purposes without modifying the old procedures. Two of them can be used when the beam is not compressed longitudinally while the other one, the synchrotron light monitor, can be used with compressed or uncompressed beam.

  7. 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.

  8. Continuous lengths of oxide superconductors

    DOEpatents

    Kroeger, Donald M.; List, III, Frederick A.

    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.

  9. 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

  10. 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.

  11. 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.

  12. Anomalous diffusion of poly(ethylene oxide) in agarose gels.

    PubMed

    Brenner, Tom; Matsukawa, Shingo

    2016-11-01

    We report on the effect of probe size and diffusion time of poly(ethylene) oxide in agarose gels. Time-dependence of the diffusion coefficient, reflecting anomalous diffusion, was observed for poly(ethylene) oxide chains with hydrodynamic radii exceeding about 20nm at an agarose concentration of 2%. The main conclusion is that the pore distribution includes pores that are only several nm across, in agreement with scattering reports in the literature. Interpretation of the diffusion coefficient dependence on the probe size based on a model of entangled rigid rods yielded a rod length of 72nm.

  13. Simulations of singlet exciton diffusion in organic semiconductors: a review

    SciTech Connect

    Bjorgaard, Josiah A.; Kose, Muhammet Erkan

    2014-12-22

    Our review describes the various aspects of simulation strategies for exciton diffusion in condensed phase thin films of organic semiconductors. Several methods for calculating energy transfer rate constants are discussed along with procedures for how to account for energetic disorder. Exciton diffusion can be modelled by using kinetic Monte-Carlo methods or master equations. Recent literature on simulation efforts for estimating exciton diffusion lengths of various conjugated polymers and small molecules are introduced. Moreover, these studies are discussed in the context of the effects of morphology on exciton diffusion and the necessity of accurate treatment of disorder for comparison of simulation results with those of experiment.

  14. 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)

  15. Incubation length of dabbling ducks

    USGS Publications Warehouse

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

    2005-01-01

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

  16. Finite length Taylor Couette flow

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

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

  17. Persistent Criminality and Career Length

    ERIC Educational Resources Information Center

    Haapanen, Rudy; Britton, Lee; Croisdale, Tim

    2007-01-01

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

  18. Nanosecond pulsed laser texturing of optical diffusers

    NASA Astrophysics Data System (ADS)

    Alqurashi, Tawfiq; Sabouri, Aydin; Yetisen, Ali K.; Butt, Haider

    2017-02-01

    High-quality optical glass diffusers have applications in aerospace, displays, imaging systems, medical devices, and optical sensors. The development of rapid and accurate fabrication techniques is highly desirable for their production. Here, a micropatterning method for the fast fabrication of optical diffusers by means of nanosecond pulsed laser ablation is demonstrated (λ=1064 nm, power=7.02, 9.36 and 11.7 W and scanning speed=200 and 800 mm s-1). The experiments were carried out by point-to-point texturing of a glass surface in spiral shape. The laser machining parameters, the number of pulses and their power had significant effect on surface features. The optical characteristics of the diffusers were characterized at different scattering angles. The features of the microscale structures influenced average roughness from 0.8 μm to 1.97 μm. The glass diffusers scattered light at angles up to 20° and their transmission efficiency were measured up to ˜97% across the visible spectrum. The produced optical devices diffuse light less but do so with less scattering and energy losses as compared to opal diffusing glass. The presented fabrication method can be applied to any other transparent material to create optical diffusers. It is anticipated that the optical diffusers presented in this work will have applications in the production of LED spotlights and imaging devices.

  19. Quantifying GFP Diffusion in Escherichia coli by Using Continuous Photobleaching with Evanescent Illumination

    PubMed Central

    Slade, Kristin M.; Steele, Bridgett L.; Pielak, Gary J.; Thompson, Nancy L.

    2009-01-01

    Fluorescence recovery after photobleaching and fluorescence correlation spectroscopy are the primary means for studying translational diffusion in biological systems. Both techniques, however, present numerous obstacles for measuring translational mobility in structures only slightly larger than optical resolution. We report a new method using through-prism total internal reflection fluorescence microscopy with continuous photobleaching (TIR-CP) to overcome these obstacles. Small structures, such as prokaryotic cells or isolated eukaryotic organelles, containing fluorescent molecules are adhered to a surface. This surface is continuously illuminated by an evanescent wave created by total internal reflection. The characteristic length describing the decay of the evanescent intensity with distance from the surface is smaller than the structures. The fluorescence decay rate resulting from continuous evanescent illumination is monitored as a function of the excitation intensity. The data at higher excitation intensities provide apparent translational diffusion coefficients for the fluorescent molecules within the structures because the decay results from two competing processes (the intrinsic photobleaching propensity and diffusion in the small structures). We present the theoretical basis for the technique and demonstrate its applicability by measuring the diffusion coefficient, 6.3 ± 1.1 µm2/sec, of green fluorescent protein (GFP) in Escherichia coli cells. PMID:19296673

  20. Altered anatomical network in early blindness revealed by diffusion tensor tractography.

    PubMed

    Shu, Ni; Liu, Yong; Li, Jun; Li, Yonghui; Yu, Chunshui; Jiang, Tianzi

    2009-09-28

    The topological architecture of the cerebral anatomical network reflects the structural organization of the human brain. Recently, topological measures based on graph theory have provided new approaches for quantifying large-scale anatomical networks. Diffusion MRI studies have revealed the efficient small-world properties and modular structure of the anatomical network in normal subjects. However, no previous study has used diffusion MRI to reveal changes in the brain anatomical network in early blindness. Here, we utilized diffusion tensor imaging to construct binary anatomical networks for 17 early blind subjects and 17 age- and gender-matched sighted controls. We established the existence of structural connections between any pair of the 90 cortical and sub-cortical regions using deterministic tractography. Compared with controls, early blind subjects showed a decreased degree of connectivity, a reduced global efficiency, and an increased characteristic path length in their brain anatomical network, especially in the visual cortex. Moreover, we revealed some regions with motor or somatosensory function have increased connections with other brain regions in the early blind, which suggested experience-dependent compensatory plasticity. This study is the first to show alterations in the topological properties of the anatomical network in early blindness. From the results, we suggest that analyzing the brain's anatomical network obtained using diffusion MRI data provides new insights into the understanding of the brain's re-organization in the specific population with early visual deprivation.

  1. 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

  2. Tracer diffusion inside fibrinogen layers

    NASA Astrophysics Data System (ADS)

    Cieśla, Michał; Gudowska-Nowak, Ewa; Sagués, Francesc; Sokolov, Igor M.

    2014-01-01

    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.

  3. 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(ε(2)), where ε 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.

  4. Experimental evidence for two thermodynamic length scales in neutralized polyacrylate gels

    NASA Astrophysics Data System (ADS)

    Horkay, Ferenc; Hecht, Anne-Marie; Grillo, Isabelle; Basser, Peter J.; Geissler, Erik

    2002-11-01

    The small angle neutron scattering (SANS) behavior of fully neutralized sodium polyacrylate gels is investigated in the presence of calcium ions. Analysis of the SANS response reveals the existence of three characteristic length scales, two of which are of thermodynamic origin, while the third length is associated with the frozen-in structural inhomogeneities. This latter contribution exhibits power law behavior with a slope of about -3.6, reflecting the presence of interfaces. The osmotically active component of the scattering signal is defined by two characteristic length scales, a correlation length ξ and a persistence length L.

  5. Polymer Diffusion in the Presence of Nanoparticles

    NASA Astrophysics Data System (ADS)

    Winey, Karen

    2014-03-01

    The center-of-mass diffusion of polymers within a polymer melt proceeds by the mechanism of reptation wherein the polymer is confined to a tube that is defined by neighboring entanglements and moves along its contour. Polymer diffusion is perturbed when the melt contains nanoparticles that are comparable in size to the radius of gyration (Rg) of the polymers. Within this talk, we will present tracer diffusion coefficients (D) results for three types of nanocomposite: spherical nanoparticles with surface functionalization, spherical nanoparticles with brushes, and cylindrical nanoparticles (aspect ratio = 5 to 50). When functionalized spherical nanoparticles have neutral or attractive interactions with the polymer matrix, a monotonic decrease in the diffusion coefficient is observed across a wide range of polymer molecular weight, nanoparticle size, and nanoparticle concentration. These data collapse onto a master curve when plotted as D normalized by the diffusion coefficient into a neat homopolymer (D/Do) versus our confinement parameter defined as the interparticle distance divided by 2Rg (ID/2Rg). Polymer diffusion in systems with grafted spherical nanoparticles exhibit the same D/Do versus ID/2Rg, when ID accounts for the extent to which the tracer polymer penetrates the polymer brush. For various cylindrical nanoparticles D/Do versus nanoparticle concentration exhibits a minimum when 2Rg is both larger than the nanoparticle diameter and smaller than the nanoparticle length. Complimentary molecular dynamics simulations and neutron scattering results will also be presented.

  6. Variable focal length deformable mirror

    DOEpatents

    Headley, Daniel; Ramsey, Marc; Schwarz, Jens

    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.

  7. Robustness of compound Dirichlet priors for Bayesian inference of branch lengths.

    PubMed

    Zhang, Chi; Rannala, Bruce; Yang, Ziheng

    2012-10-01

    We modified the phylogenetic program MrBayes 3.1.2 to incorporate the compound Dirichlet priors for branch lengths proposed recently by Rannala, Zhu, and Yang (2012. Tail paradox, partial identifiability and influential priors in Bayesian branch length inference. Mol. Biol. Evol. 29:325-335.) as a solution to the problem of branch-length overestimation in Bayesian phylogenetic inference. The compound Dirichlet prior specifies a fairly diffuse prior on the tree length (the sum of branch lengths) and uses a Dirichlet distribution to partition the tree length into branch lengths. Six problematic data sets originally analyzed by Brown, Hedtke, Lemmon, and Lemmon (2010. When trees grow too long: investigating the causes of highly inaccurate Bayesian branch-length estimates. Syst. Biol. 59:145-161) are reanalyzed using the modified version of MrBayes to investigate properties of Bayesian branch-length estimation using the new priors. While the default exponential priors for branch lengths produced extremely long trees, the compound Dirichlet priors produced posterior estimates that are much closer to the maximum likelihood estimates. Furthermore, the posterior tree lengths were quite robust to changes in the parameter values in the compound Dirichlet priors, for example, when the prior mean of tree length changed over several orders of magnitude. Our results suggest that the compound Dirichlet priors may be useful for correcting branch-length overestimation in phylogenetic analyses of empirical data sets.

  8. Hereditary Diffuse Infiltrating Retinoblastoma.

    PubMed

    Schedler, Katharina J E; Traine, Peter G; Lohmann, Dietmar R; Haritoglou, Christos; Metz, Klaus A; Rodrigues, Eduardo B

    2016-01-01

    Retinoblastoma is one of the most common childhood cancers. The diffuse infiltrating retinoblastoma is a rare subtype of this neoplasm. The majority of cases of diffuse infiltrating retinoblastoma are unilateral and occur sporadically. Herein we report on a family with three children affected by retinoblastoma, among them one girl with diffuse infiltrating retinoblastoma. This girl was diagnosed at the age of 8 years with a unilateral diffuse infiltrating retinoblastoma. By contrast, the two brothers became clinically apparent in the first 2 years of life with bilateral retinoblastoma. The parents were clinically unremarkable. Genetic analysis of RB1 gene was performed. The girl with diffuse infiltrating RB was found to be heterozygous for an oncogenic mutation in the RB1 gene that was also carried by both brothers and the father of the family. These results show that diffuse infiltrating retinoblastoma can develop on the background of a hereditary predisposition to retinoblastoma.

  9. Critical Length Limiting Superlow Friction

    NASA Astrophysics Data System (ADS)

    Ma, Ming; Benassi, Andrea; Vanossi, Andrea; Urbakh, Michael

    2015-02-01

    Since the demonstration of superlow friction (superlubricity) in graphite at nanoscale, one of the main challenges in the field of nano- and micromechanics was to scale this phenomenon up. A key question to be addressed is to what extent superlubricity could persist, and what mechanisms could lead to its failure. Here, using an edge-driven Frenkel-Kontorova model, we establish a connection between the critical length above which superlubricity disappears and both intrinsic material properties and experimental parameters. A striking boost in dissipated energy with chain length emerges abruptly due to a high-friction stick-slip mechanism caused by deformation of the slider leading to a local commensuration with the substrate lattice. We derived a parameter-free analytical model for the critical length that is in excellent agreement with our numerical simulations. Our results provide a new perspective on friction and nanomanipulation and can serve as a theoretical basis for designing nanodevices with superlow friction, such as carbon nanotubes.

  10. Critical length limiting superlow friction.

    PubMed

    Ma, Ming; Benassi, Andrea; Vanossi, Andrea; Urbakh, Michael

    2015-02-06

    Since the demonstration of superlow friction (superlubricity) in graphite at nanoscale, one of the main challenges in the field of nano- and micromechanics was to scale this phenomenon up. A key question to be addressed is to what extent superlubricity could persist, and what mechanisms could lead to its failure. Here, using an edge-driven Frenkel-Kontorova model, we establish a connection between the critical length above which superlubricity disappears and both intrinsic material properties and experimental parameters. A striking boost in dissipated energy with chain length emerges abruptly due to a high-friction stick-slip mechanism caused by deformation of the slider leading to a local commensuration with the substrate lattice. We derived a parameter-free analytical model for the critical length that is in excellent agreement with our numerical simulations. Our results provide a new perspective on friction and nanomanipulation and can serve as a theoretical basis for designing nanodevices with superlow friction, such as carbon nanotubes.

  11. Gaseous diffusion system

    DOEpatents

    Garrett, George A.; Shacter, John

    1978-01-01

    1. A gaseous diffusion system comprising a plurality of diffusers connected in cascade to form a series of stages, each of said diffusers having a porous partition dividing it into a high pressure chamber and a low pressure chamber, and means for combining a portion of the enriched gas from a succeeding stage with a portion of the enriched gas from the low pressure chamber of each stage and feeding it into one extremity of the high pressure chamber thereof.

  12. 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.

  13. Buoyancy Effects on Flow Transition in Hydrogen Gas Jet Diffusion Flames

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

  14. Thermal Diffusivity of Quartz and its Relation to Structure

    NASA Astrophysics Data System (ADS)

    Hoefer, M.; Schilling, F. R.

    2001-12-01

    Thermal transport properties of minerals are fundamental for an understanding of heat transport in rocks and they are a prerequisite to model temperature distribution within the Earth. Besides its significance for crustal rocks, quartz and its physical properties are of interest in material science. Beyond that, quartz is of elementary importance due to its unique physical behavior, especially during low to high transformation. Quartz is characterized by a high anisotropy in thermal expansion, sound velocity, and thermal diffusivity. During the phase transition from low to high quartz the physical properties vary non-linearly, whereas sound velocity shows a distingued minimum, and average Poisson's ratio becomes negative. Moreover, quartz shows the highest thermal diffusivity and strongest temperature dependence of all silicates. Thermal diffusivity a and thermal conductivity l are interrelated by {l = cP ρ a}. Thermal diffusivity can be expressed by mean phonon (sound) velocity v and mean free path length l by a = 1/3 v l. By combining measured phononic velocity and thermal diffusivity the structure dependent mean free path length can be revealed. To determine thermal diffusivity of quartz especially during the low to high transition in the a- and c-direction we used a high precision transient technique (Schilling 1999) with high temperature resolution up to 800\\deg C. For temperatures below 500 \\deg C a pronounced 1/T dependence of thermal diffusivity is observed and is highest in the c-direction. A minimum in thermal diffusivity is observed during the phase transition. Above the transition thermal diffusivity increases and the highest diffusivity is observed in the a-direction. A similar cross over is observed for the maximum phononic velocity. Between 500\\deg and 800\\deg C velocity and thermal diffusivity show similar behavior. No significant contribution of radiative heat transport is detectable over the examined temperature range. The thermal diffusivity

  15. Inpainting using airy diffusion

    NASA Astrophysics Data System (ADS)

    Lorduy Hernandez, Sara

    2015-09-01

    One inpainting procedure based on Airy diffusion is proposed, implemented via Maple and applied to some digital images. Airy diffusion is a partial differential equation with spatial derivatives of third order in contrast with the usual diffusion with spatial derivatives of second order. Airy diffusion generates the Airy semigroup in terms of the Airy functions which can be rewritten in terms of Bessel functions. The Airy diffusion can be used to smooth an image with the corresponding noise elimination via convolution. Also the Airy diffusion can be used to erase objects from an image. We build an algorithm using the Maple package ImageTools and such algorithm is tested using some images. Our results using Airy diffusion are compared with the similar results using standard diffusion. We observe that Airy diffusion generates powerful filters for image processing which could be incorporated in the usual packages for image processing such as ImageJ and Photoshop. Also is interesting to consider the possibility to incorporate the Airy filters as applications for smartphones and smart-glasses.

  16. Numerical investigation of biogas diffusion flames characteristics under several operation conditions in counter-flow configuration with an emphasis on thermal and chemical effects of CO2 in the fuel mixture

    NASA Astrophysics Data System (ADS)

    Mameri, A.; Tabet, F.; Hadef, A.

    2017-03-01

    This study addresses the influence of several operating conditions (composition and ambient pressure) on biogas diffusion flame structure and NO emissions with particular attention on thermal and chemical effect of CO2. The biogas flame is modeled by a counter flow diffusion flame and analyzed in mixture fraction space using flamelet approach. The GRI Mech-3.0 mechanism that involves 53 species and 325 reactions is adopted for the oxidation chemistry. It has been observed that flame properties are very sensitive to biogas composition and pressure. CO2 addition decreases flame temperature by both thermal and chemical effects. Added CO2 may participate in chemical reaction due to thermal dissociation (chemical effect). Excessively supplied CO2 plays the role of pure diluent (thermal effect). The ambient pressure rise increases temperature and reduces flame thickness, radiation losses and dissociation amount. At high pressure, recombination reactions coupled with chain carrier radicals reduction, diminishes NO mass fraction.

  17. The Effect of the Time of Injection of Intrathecal Analgesia on the Length of Early and Advanced Labor

    DTIC Science & Technology

    1999-10-01

    25 Calculation of Mean Length of Each Stage of Labor........................................................25 The Length of the Stages...Spreadsheet xi LIST OF TABLES Table 1. Mean Values of Various Components of Labor...............................................7 Table 2. Characteristics...30 xii LIST OF FIGURES Figure 1. Mean Length in Minutes of Each Stage of Labor..........................................27 Figure 2. The Length of

  18. Diffusive dynamics on paper matrix

    NASA Astrophysics Data System (ADS)

    Chaudhury, Kaustav; Kar, Shantimoy; Chakraborty, Suman

    2016-11-01

    Writing with ink on a paper and the rapid diagnostics of diseases using paper cartridge, despite their remarkable diversities from application perspective, both involve the motion of a liquid from a source on a porous hydrophilic substrate. Here we bring out a generalization in the pertinent dynamics by appealing to the concerned ensemble-averaged transport with reference to the underlying molecular picture. Our results reveal that notwithstanding the associated complexities and diversities, the resultant liquid transport characteristics on a paper matrix, in a wide variety of applications, resemble universal diffusive dynamics. Agreement with experimental results from diversified applications is generic and validates our unified theory.

  19. Narrow groove welding gas diffuser assembly and welding torch

    DOEpatents

    Rooney, Stephen J.

    2001-01-01

    A diffuser assembly is provided for narrow groove welding using an automatic gas tungsten arc welding torch. The diffuser assembly includes a manifold adapted for adjustable mounting on the welding torch which is received in a central opening in the manifold. Laterally extending manifold sections communicate with a shield gas inlet such that shield gas supplied to the inlet passes to gas passages of the manifold sections. First and second tapered diffusers are respectively connected to the manifold sections in fluid communication with the gas passages thereof. The diffusers extend downwardly along the torch electrode on opposite sides thereof so as to release shield gas along the length of the electrode and at the distal tip of the electrode. The diffusers are of a transverse width which is on the order of the thickness of the electrode so that the diffusers can, in use, be inserted into a narrow welding groove before and after the electrode in the direction of the weld operation.

  20. 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 μ 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.

  1. Length Scale of the Spin Seebeck Effect.

    PubMed

    Kehlberger, Andreas; Ritzmann, Ulrike; Hinzke, Denise; Guo, Er-Jia; Cramer, Joel; Jakob, Gerhard; Onbasli, Mehmet C; Kim, Dong Hun; Ross, Caroline A; Jungfleisch, Matthias B; Hillebrands, Burkard; Nowak, Ulrich; 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  μm 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. How current ginning processes affect fiber length uniformity index

    Technology Transfer Automated Retrieval System (TEKTRAN)

    There is a need to develop cotton ginning methods that improve fiber characteristics that are compatible with the newer and more efficient spinning technologies. A literature search produced recent studies that described how current ginning processes affect HVI fiber length uniformity index. Resul...

  7. 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…

  8. Cooperative Length Scale and Fragility of Polystyrene under Confinement

    NASA Astrophysics Data System (ADS)

    Zhang, Chuan; Guo, Yunlong; Priestley, Rodney

    2012-02-01

    While thin films are an attractive model system to investigate the impact of confinement on glassy behavior, extending studies beyond thin films to geometries of higher dimensionalities is vital from both scientific and technological viewpoints. In this talk, we present the impact of confinement on the characteristic length at the glass transition as well as the fragility for confined polystyrene (PS) nanoparticles under isochoric conditions. We measure the glass transition temperature (Tg), fictive temperature (Tf) and isochoric heat capacity of silica-capped PS nanoparticles as a function of diameter via differential scanning calorimetry. From the measurement of Tf, we obtain the isochoric fragility, and via the fluctuation formula, the characteristic length at the glass transition. We illustrate that confinement under isochoric conditions for PS nanoparticles leads to a significant increase in the isochoric fragility while the characteristic length is reduced with size. At the minimum the results demonstrate a relationship between fragility and the characteristics length of isochorically-confined polymer that is not intuitive from the Adam-Gibbs theory.

  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.

  10. 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.

  11. Diffusion of active chiral particles

    NASA Astrophysics Data System (ADS)

    Sevilla, Francisco J.

    2016-12-01

    The diffusion of chiral active Brownian particles in three-dimensional space is studied analytically, by consideration of the corresponding Fokker-Planck equation for the probability density of finding a particle at position x and moving along the direction v ̂ at time t , and numerically, by the use of Langevin dynamics simulations. The analysis is focused on the marginal probability density of finding a particle at a given location and at a given time (independently of its direction of motion), which is found from an infinite hierarchy of differential-recurrence relations for the coefficients that appear in the multipole expansion of the probability distribution, which contains the whole kinematic information. This approach allows the explicit calculation of the time dependence of the mean-squared displacement and the time dependence of the kurtosis of the marginal probability distribution, quantities from which the effective diffusion coefficient and the "shape" of the positions distribution are examined. Oscillations between two characteristic values were found in the time evolution of the kurtosis, namely, between the value that corresponds to a Gaussian and the one that corresponds to a distribution of spherical shell shape. In the case of an ensemble of particles, each one rotating around a uniformly distributed random axis, evidence is found of the so-called effect "anomalous, yet Brownian, diffusion," for which particles follow a non-Gaussian distribution for the positions yet the mean-squared displacement is a linear function of time.

  12. The NIST Length Scale Interferometer

    PubMed Central

    Beers, John S.; Penzes, William B.

    1999-01-01

    The National Institute of Standards and Technology (NIST) interferometer for measuring graduated length scales has been in use since 1965. It was developed in response to the redefinition of the meter in 1960 from the prototype platinum-iridium bar to the wavelength of light. The history of the interferometer is recalled, and its design and operation described. A continuous program of modernization by making physical modifications, measurement procedure changes and computational revisions is described, and the effects of these changes are evaluated. Results of a long-term measurement assurance program, the primary control on the measurement process, are presented, and improvements in measurement uncertainty are documented.

  13. Control of arc length during gas metal arc welding

    SciTech Connect

    Madigan, R.B.; Quinn, T.P.

    1994-12-31

    An arc-length control system has been developed for gas metal arc welding (GMAW) under spray transfer welding conditions. The ability to monitor and control arc length during arc welding allows consistent weld characteristics to be maintained and therefore improves weld quality. Arc length control has only been implemented for gas tungsten arc welding (GTAW), where an automatic voltage control (AVC) unit adjusts torch-to-work distance. The system developed here compliments the voltage- and current-sensing techniques commonly used for control of GMAW. The system consists of an arc light intensity sensor (photodiode), a Hall-effect current sensor, a personal computer and software implementing a data interpretation and control algorithms. Arc length was measured using both arc light and arc current signals. Welding current was adjusted to maintain constant arc length. A proportional-integral-derivative (PID) controller was used. Gains were automatically selected based on the desired welding conditions. In performance evaluation welds, arc length varied from 2.5 to 6.5 mm while welding up a sloped workpiece (ramp in CTWD) without the control. Arc length was maintained within 1 mm of the desired (5 mm ) with the control.

  14. Ecosystem size determines food-chain length in lakes.

    PubMed

    Post, D M; Pace, M L; Hairston, N G

    2000-06-29

    Food-chain length is an important characteristic of ecological communities: it influences community structure, ecosystem functions and contaminant concentrations in top predators. Since Elton first noted that food-chain length was variable among natural systems, ecologists have considered many explanatory hypotheses, but few are supported by empirical evidence. Here we test three hypotheses that predict food-chain length to be determined by productivity alone (productivity hypothesis), ecosystem size alone (ecosystem-size hypothesis) or a combination of productivity and ecosystem size (productive-space hypothesis). The productivity and productive-space hypotheses propose that food-chain length should increase with increasing resource availability; however, the productivity hypothesis does not include ecosystem size as a determinant of resource availability. The ecosystem-size hypothesis is based on the relationship between ecosystem size and species diversity, habitat availability and habitat heterogeneity. We find that food-chain length increases with ecosystem size, but that the length of the food chain is not related to productivity. Our results support the hypothesis that ecosystem size, and not resource availability, determines food-chain length in these natural ecosystems.

  15. [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 10⁻⁵). 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.

  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. Diffusion of Botulinum Toxins

    PubMed Central

    Brodsky, Matthew A.; Swope, David M.; Grimes, David

    2012-01-01

    Background It is generally agreed that diffusion of botulinum toxin occurs, but the extent of the spread and its clinical importance are disputed. Many factors have been suggested to play a role but which have the most clinical relevance is a subject of much discussion. Methods This review discusses the variables affecting diffusion, including protein composition and molecular size as well as injection factors (e.g., volume, dose, injection method). It also discusses data on diffusion from comparative studies in animal models and human clinical trials that illustrate differences between the available botulinum toxin products (onabotulinumtoxinA, abobotulinumtoxinA, incobotulinumtoxinA, and rimabotulinumtoxinB). Results Neither molecular weight nor the presence of complexing proteins appears to affect diffusion; however, injection volume, concentration, and dose all play roles and are modifiable. Both animal and human studies show that botulinum toxin products are not interchangeable, and that some products are associated with greater diffusion and higher rates of diffusion-related adverse events than others. Discussion Each of the botulinum toxins is a unique pharmacologic entity. A working knowledge of the different serotypes is essential to avoid unwanted diffusion-related adverse events. In addition, clinicians should be aware that the factors influencing diffusion may range from properties intrinsic to the drug to accurate muscle selection as well as dilution, volume, and dose injected. PMID:23440162

  18. 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…

  19. The Diffusion of Innovation

    NASA Technical Reports Server (NTRS)

    Earabino, Gerard J.; Heyl, G. Christopher; Percorini, Thomas J.

    1987-01-01

    New ideas encounter obstacles on way to becoming products. Report examines process by which new ideas become products, processes, or accepted standards. Sequence of events called "the diffusion of innovation." Focuses on development of material processing in low gravity as case study in diffusion of innovation.

  20. Cosmology with matter diffusion

    SciTech Connect

    Calogero, Simone; Velten, Hermano E-mail: velten@cce.ufes.br

    2013-11-01

    We construct a viable cosmological model based on velocity diffusion of matter particles. In order to ensure the conservation of the total energy-momentum tensor in the presence of diffusion, we include a cosmological scalar field φ 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 σ. The standard ΛCDM model can be recovered by setting σ = 0. If diffusion takes place (σ > 0) the dynamics of the matter and of the dark energy fields are coupled. We argue that the existence of a diffusion mechanism in the universe may serve as a theoretical motivation for interacting models. We constrain the background dynamics of the diffusion model with Supernovae, H(z) and BAO data. We also perform a perturbative analysis of this model in order to understand structure formation in the universe. We calculate the impact of diffusion both on the CMB spectrum, with particular attention to the integrated Sachs-Wolfe signal, and on the matter power spectrum P(k). The latter analysis places strong constraints on the magnitude of the diffusion mechanism but does not rule out the model.

  1. 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.

  2. Diffusion in Coulomb crystals.

    PubMed

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

    2011-07-01

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

  3. Image Halftoning and Inverse Halftoning for Optimized Dot Diffusion

    DTIC Science & Technology

    1998-01-01

    systems.caltech.edu, ppvnath@sys.caltech.edu ABSTRACT The dot diffusion method for digital halftoning has the advantage of parallelism unlike the error ... halftoning : ordered dither [3], error diffusion [4], neural-net based methods [2], and more recently direct binary search (DBS) [10]. Ordered dithering is a...patterns. On the other hand error diffused halftones do not suffer from periodicity and offer blue noise characteristic [11] which is found to be

  4. Anomalous diffusion in gelatin-surfactant solutions and gels

    NASA Astrophysics Data System (ADS)

    Maity, Saroj; Bohidar, H. B.

    1998-07-01

    A photon correlation spectroscopy study carried out on semidilute 4% (wt./vol) aqueous gelatin sols and gels with the anionic surfactant sodium dodecyl sulphate (SDS) showed three relaxation processes in the dynamic structure factor data. First an exponential process S(q,t)~exp(-Dfq2t) at t<=20 μs, referred to as the collective mode, was observed, followed by an intermediate power-law regime S(q,t)~t-α(q) at 20 μs>=t<=1 ms, and finally a stretched exponential decay S(q,t)~exp-(t/τc)β was observed for t>=1 ms. The power-law exponent α and characteristic time τc in the stretched part were found to be q dependent: α~qx, with x=1.80+/-0.09 in the sol state and x=0.98+/-0.05 in the gel state, and τc~q-y, with y=2.05+/-0.08 and 3.0+/-0.2 in the sol and gel states, respectively, but independently of SDS concentrations. In the fast mode the relaxation time was measured to be the same in the pure gelatin sol and gel states. It is proposed that the different q dependences observed in the gel and sol states with and without SDS indicate the presence of different characteristic length scales. Our results agree with the predictions of the anomalous Gaussian diffusion model in the sol state, but differ significantly in the gel state.

  5. Topological analysis of polymeric melts: Chain-length effects and fast-converging estimators for entanglement length

    NASA Astrophysics Data System (ADS)

    Hoy, Robert S.; Foteinopoulou, Katerina; Kröger, Martin

    2009-09-01

    Primitive path analyses of entanglements are performed over a wide range of chain lengths for both bead spring and atomistic polyethylene polymer melts. Estimators for the entanglement length Ne which operate on results for a single chain length N are shown to produce systematic O(1/N) errors. The mathematical roots of these errors are identified as (a) treating chain ends as entanglements and (b) neglecting non-Gaussian corrections to chain and primitive path dimensions. The prefactors for the O(1/N) errors may be large; in general their magnitude depends both on the polymer model and the method used to obtain primitive paths. We propose, derive, and test new estimators which eliminate these systematic errors using information obtainable from the variation in entanglement characteristics with chain length. The new estimators produce accurate results for Ne from marginally entangled systems. Formulas based on direct enumeration of entanglements appear to converge faster and are simpler to apply.

  6. Testable scenario for relativity with minimum length

    NASA Astrophysics Data System (ADS)

    Amelino-Camelia, G.

    2001-06-01

    I propose a general class of spacetimes whose structure is governed by observer-independent scales of both velocity (/c) and length (Planck length), and I observe that these spacetimes can naturally host a modification of FitzGerald-Lorentz contraction such that lengths which in their inertial rest frame are bigger than a ``minimum length'' are also bigger than the minimum length in all other inertial frames. With an analysis in leading order in the minimum length, I show that this is the case in a specific illustrative example of postulates for relativity with velocity and length observer-independent scales.

  7. Novel light diffusing fiber for use in medical applications

    NASA Astrophysics Data System (ADS)

    Klubben, W. Spencer; Logunov, Stephan L.; Fewkes, Edward J.; Mooney, Jeff; Then, Paul M.; Wigley, Peter G.; Schreiber, Horst; Matias, Kaitlyn; Wilson, Cynthia J.; Ocampo, Manuela

    2016-03-01

    Fiber-based cylindrical light diffusers are often used in photodynamic therapy to illuminate a luminal organ, such as the esophagus. The diffusers are often made of plastic and suffer from short diffusion lengths and low transmission efficiencies over a broad spectrum. We have developed FibranceTM, a glass-based fiber optic cylindrical diffuser which can illuminate a fiber from 0.5 cm to 10 meters over a broad wavelength range. With these longer illumination lengths, a variety of other medical applications are possible beyond photodynamic therapy. We present a number of applications for Fibrance ranging from in situ controllable illumination for Photodynamic Therapy to light guided anatomy highlighting for minimally invasive surgery to mitigating hospital acquired infections and more.

  8. High-power diffusing-tip fibers for interstitial photocoagulation

    NASA Astrophysics Data System (ADS)

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

    1997-05-01

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

  9. Diffusion and surface alloying of gradient nanostructured metals

    PubMed Central

    Lu, Ke

    2017-01-01

    Gradient nanostructures (GNSs) have been optimized in recent years for desired performance. The diffusion behavior in GNS metals is crucial for understanding the diffusion mechanism and relative characteristics of different interfaces that provide fundamental understanding for advancing the traditional surface alloying processes. In this paper, atomic diffusion, reactive diffusion, and surface alloying processes are reviewed for various metals with a preformed GNS surface layer. We emphasize the promoted atomic diffusion and reactive diffusion in the GNS surface layer that are related to a higher interfacial energy state with respect to those in relaxed coarse-grained samples. Accordingly, different surface alloying processes, such as nitriding and chromizing, have been modified significantly, and some diffusion-related properties have been enhanced. Finally, the perspectives on current research in this field are discussed. PMID:28382244

  10. Helium diffusion in carbonates

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    The abundance and large grain size of carbonate minerals make them a potentially attractive target for 4He thermochronology and 3He cosmogenic dating, although the diffusive properties of helium in carbonates remain poorly understood. This work characterizes helium diffusion in calcite and dolomite to better understand the crystal-chemical factors controlling He transport and retentivity. Slabs of cleaved natural calcite and dolomite, and polished sections of calcite cut parallel or normal to c, were implanted with 3He at 3 MeV with a dose of 5x1015/cm2. Implanted carbonates were heated in 1-atm furnaces, and 3He distributions following diffusion anneals were profiled with Nuclear Reaction Analysis using the reaction 3He(d,p)4He. For 3He transport normal to cleavage surfaces in calcite, we obtain the following Arrhenius relation over the temperature range 78-300°C: Dcalcite = 9.0x10-9exp(-55 × 6 kJ mol-1/RT) m2sec-1. Diffusion in calcite exhibits marked anisotropy, with diffusion parallel to c about two orders of magnitude slower than diffusion normal to cleavage faces. He diffusivities for transport normal to the c-axis are similar in value to those normal to cleavage surfaces. Our findings are broadly consistent with helium diffusivities from step-heating measurements of calcite by Copeland et al. (2007); these bulk degassing data may reflect varying effects of diffusional anisotropy. Helium diffusion normal to cleavage surfaces in dolomite is significantly slower than diffusion in calcite, and has a much higher activation energy for diffusion. For dolomite, we obtain the following Arrhenius relation for He diffusion over the temperature range 150-400°C: Ddolomite = 9.0x10-8exp(-92 × 9 kJ mol-1/RT) m2sec-1. The role of crystallographic structure in influencing these differences among diffusivities was evaluated using the maximum aperture approach of Cherniak and Watson (2011), in which crystallographic structures are sectioned along possible diffusion

  11. Thorium Diffusion in Monazite

    NASA Astrophysics Data System (ADS)

    Cherniak, D. J.

    2006-05-01

    Diffusion of thorium has been characterized in synthetic monazite under dry conditions. The synthetic monazites (either pure CePO4, NdPO4, or a mixed LREE phosphate containing Ce, Nd, and Sm) were grown via a Na2CO3-MoO3 flux method. The source of diffusant for the experiments were either synthesized ThSiO4 or CaTh(PO4)2 powders. Experiments were performed by placing source and monazite in Pt capsules and annealing capsules in 1 atm furnaces for times ranging from 10 days to a few hours, at temperatures from 1400 to 1550C. The Th distributions in the monazite were profiled by Rutherford Backscattering Spectrometry (RBS). The following Arrhenius relation was obtained for diffusion in monazite: DSm = 7.2x103 exp(-814 kJ mol-1/RT) m2sec-1 The diffusivity of Th was similar for monazites containing a single REE and the mixed LREE phosphates. Th diffusion was also similar for experiments run using the Th silicate and Ca-Th phosphate sources, suggesting that the substitutional mechanism for Th in monazite, i.e, Th+4 + Si+4 for REE+3 + P+5 with the ThSiO4 source, and Th+4 + Ca+2 for 2REE+3 with the CaTh(PO4)2 source, does not significantly affect Th diffusivities, and that Th is likely the rate-limiting species. Th diffusion in monazite is about 4 orders of magnitude slower than Pb diffusion (Cherniak et al., 2004). This contrasts with findings of Gardes et al. (2005) who determined that Pb, Th and REE diffusivities in monazite are similar. Th diffusion in zircon (Cherniak et al., 1997) is about an order of magnitude slower than in monazite, but with similar activation energy for diffusion. The smaller diffusivities in zircon may be a consequence of the larger disparity in size between Th and the Zr site in zircon as compared with Th and the REE site in monazite. Nonetheless, Th is essentially immobile in monazite with respect to exchange by volume diffusion under most geologic conditions; these findings may have implications for containment of high- level actinide

  12. Reactor core length, externally configured thermionic converter.

    NASA Technical Reports Server (NTRS)

    Shimada, K.; Rouklove, P.

    1971-01-01

    Results of testing a converter having an external emitter configuration for 190 hours using RF induction heating. The converter was assembled with a rhenium emitter, 25.4 cm long, having a 91.2 sq cm emitting area, and a niobium collector with a molybdenum coating to improve its electronic property. The collector was water-cooled. The test included: static power output measurements, dynamic characteristics, and the effects of the temperature distribution along the emitter. The maximum power output achieved from the converter at an emitter temperature of 1942 K was 178 W at 0.48 V output, with a power density of 1.95 W/sq cm and an efficiency of 5.5%. The static characteristics also indicated that, with a constant power input, the converter power output does not vary with the output voltage as a result of self-adjustment of the emitter temperature. An investigation of the effects of the temperature distribution along the emitter length showed a 33% improvement in the converter output power with a flattening of the emitter temperature.

  13. 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.

  14. Anomalous diffusion of brain metabolites evidenced by diffusion-weighted magnetic resonance spectroscopy in vivo

    PubMed Central

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

    2012-01-01

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

  15. a Diffusivity Model for Gas Diffusion in Dry Porous Media Composed of Converging-Diverging Capillaries

    NASA Astrophysics Data System (ADS)

    Wang, Shifang; Wu, Tao; Deng, Yongju; Zheng, Qiusha; Zheng, Qian

    2016-08-01

    Gas diffusion in dry porous media has been a hot topic in several areas of technology for many years. In this paper, a diffusivity model for gas diffusion in dry porous media is developed based on fractal theory and Fick’s law, which incorporates the effects of converging-diverging pores and tortuous characteristics of capillaries as well as Knudsen diffusion. The effective gas diffusivity model is expressed as a function of the fluctuation amplitude of the capillary cross-section size variations, the porosity, the pore area fractal dimension and the tortuosity fractal dimension. The results show that the relative diffusivity decreases with the increase of the fluctuation amplitude and increases with the increase of pore area fractal dimension. To verify the validity of the present model, the relative diffusivity from the proposed fractal model is compared with the existing experimental data as well as two available models of Bruggeman and Shou. Our proposed diffusivity model with pore converging-diverging effect included is in good agreement with reported experimental data.

  16. Clustering method for estimating principal diffusion directions

    PubMed Central

    Nazem-Zadeh, Mohammad-Reza; Jafari-Khouzani, Kourosh; Davoodi-Bojd, Esmaeil; Jiang, Quan; Soltanian-Zadeh, Hamid

    2012-01-01

    Diffusion tensor magnetic resonance imaging (DTMRI) is a non-invasive tool for the investigation of white matter structure within the brain. However, the traditional tensor model is unable to characterize anisotropies of orders higher than two in heterogeneous areas containing more than one fiber population. To resolve this issue, high angular resolution diffusion imaging (HARDI) with a large number of diffusion encoding gradients is used along with reconstruction methods such as Q-ball. Using HARDI data, the fiber orientation distribution function (ODF) on the unit sphere is calculated and used to extract the principal diffusion directions (PDDs). Fast and accurate estimation of PDDs is a prerequisite for tracking algorithms that deal with fiber crossings. In this paper, the PDDs are defined as the directions around which the ODF data is concentrated. Estimates of the PDDs based on this definition are less sensitive to noise in comparison with the previous approaches. A clustering approach to estimate the PDDs is proposed which is an extension of fuzzy c-means clustering developed for orientation of points on a sphere. MDL (Minimum description length) principle is proposed to estimate the number of PDDs. Using both simulated and real diffusion data, the proposed method has been evaluated and compared with some previous protocols. Experimental results show that the proposed clustering algorithm is more accurate, more resistant to noise, and faster than some of techniques currently being utilized. PMID:21642005

  17. 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.

  18. 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.

  19. Ligand chain length conveys thermochromism.

    PubMed

    Ganguly, Mainak; Panigrahi, Sudipa; Chandrakumar, K R S; Sasmal, Anup Kumar; Pal, Anjali; Pal, Tarasankar

    2014-08-14

    Thermochromic properties of a series of non-ionic copper compounds have been reported. Herein, we demonstrate that Cu(II) ion with straight-chain primary amine (A) and alpha-linolenic (fatty acid, AL) co-jointly exhibit thermochromic properties. In the current case, we determined that thermochromism becomes ligand chain length-dependent and at least one of the ligands (A or AL) must be long chain. Thermochromism is attributed to a balanced competition between the fatty acids and amines for the copper(II) centre. The structure-property relationship of the non-ionic copper compounds Cu(AL)2(A)2 has been substantiated by various physical measurements along with detailed theoretical studies based on time-dependent density functional theory. It is presumed from our results that the compound would be a useful material for temperature-sensor applications.

  20. Phase-Length Optical Phase-Locked-Loop Sensor (PLOPS)

    NASA Technical Reports Server (NTRS)

    Heyman, Joseph S.; Rogawski, Robert S.

    1988-01-01

    PLOPS system designed to provide high-resolution measurement of change in optical length from optical-system source to any optical reflector, including diffuse reflector. Serves as adjustable optical ruler, providing high resolution in measurements of small and large changes in distance to target. Use is broad and includes most measurement situations requiring information on length, vibration, and their derivatives. Applications include building dynamics, remote sensing of vibrations in such systems as turbine-based machinery, monitoring of structural dynamics, noncontacting sensing of surface contours, measurement of large strains as in earthquake monitoring, measurement of atmospheric dynamics and turbulence, high-resolution sensing of humidity, detection of surface acoustic waves by optical microscopy, and related areas.

  1. 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.

  2. 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.

  3. Channeling and diffusion in dry-etch damage

    NASA Astrophysics Data System (ADS)

    Rahman, M.

    1997-09-01

    At present channeling is accepted to be the primary mechanism causing defects deep within dry-etched material, with diffusion possibly modifying the final defect distribution. In this article detailed analytic expressions are presented incorporating both these mechanisms. The dominant parameter affecting damage depth is found to be the mean channeling length. We show how enhanced diffusion, e.g., by illumination, may increase the observed damage. We also study the effect of damage on depletion depths and suggest how the channeling length may be inferred from the etch-depth dependence of conductance or Raman spectroscopy measurements.

  4. Diffusion of water in cat ventricular myocardium

    PubMed Central

    1978-01-01

    The rates of diffusion of tritiated water (THO) and [14C]sucrose across cat right ventricular myocardium were studied at 23 degrees C in an Ussing-type diffusion cell, recording the time-course of increase in concentration of tracer in one chamber over 4--6 h after adding tracers to the other. Sucrose data were fitted with a model for a homogeneous sheet of uneven thickness in which the tissue is considered to be an array of parallel independent pathways (parallel pathway model) of varying length. The volume of the sucrose diffusion space, presumably a wholly extracellular pathway, was 23% of the tissue or 27.4 +/-1.7% (mean +/- SEM; n=11) of the tissue water. The effective intramyocardial sucrose diffusion coefficient, D8, was 1.51 +/- 0.19 X 10(-6)cm2.s-1 (n=11). Combining these data with earlier data, D8 was 22.6 +/- 1.1% (n=95) of the free diffusion coefficient in aqueous solution D degrees 8. The parallel pathway model and a dead-end pore model, which might have accounted for intracellular sequestration of water, gave estimates of DW/D degrees W (observed/free) of 15%. Because hindrance to water diffusion must be less than for sucrose (where D8/D degrees 8=22.6%), this showed the inadequacy of these models to account simultaneously for the diffusional resistance and the tissue water content. The third or cell-matrix model, a heterogeneous system of permeable cells arrayed in the extracellular matrix, allowed logical and geometrically reasonable interpretations of the steady-state data and implied estimates of DW in the cellular and extracellular fluid of approximately 25% of the aqueous diffusion coefficient. PMID:722277

  5. 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.

  6. Fractality in the neuron axonal topography of the human brain based on 3-D diffusion MRI

    NASA Astrophysics Data System (ADS)

    Katsaloulis, P.; Ghosh, A.; Philippe, A. C.; Provata, A.; Deriche, R.

    2012-05-01

    In this work the fractal architecture of the neuron axonal topography of the human brain is evaluated, as derived from 3-D diffusion MRI (dMRI) acquisitions. This is a 3D extension of work performed previously in 2D regions of interest (ROIs), where the fractal dimension of the neuron axonal topography was computed from dMRI data. A group study with 18 subjects is here conducted and the fractal dimensions D f of the entire 3-D volume of the brains is estimated via the box counting, the correlation dimension and the fractal mass dimension methods. The neuron axon data is obtained using tractography algorithms on diffusion tensor imaging of the brain. We find that all three calculations of D f give consistent results across subjects, namely, they demonstrate fractal characteristics in the short and medium length scales: different fractal exponents prevail at different length scales, an indication of multifractality. We surmise that this complexity stems as a collective property emerging when many local brain units, performing different functional tasks and having different local topologies, are recorded together.

  7. Diffusion across a layered medium and relation to transport in thermonuclear plasmas

    SciTech Connect

    Lopes Cardozo, N.J.; Peters, M.

    1995-11-01

    The generic characteristics of diffusion in a medium exhibiting strong variations of the diffusivity are considered. The varying diffusivity is parametrized by alternating layers of high and low diffusivity. The limiting case is considered that the insulating layers determine the net transport. Some salient features of tokamak transport, such as the fact that perturbative experiments yield a higher diffusivity than a steady-state power balance, are shown to be a natural result of the inhomogeneity. The importance of a possible inhomogeneous diffusivity for the comparison of measurements with theoretical expressions for the diffusivity is discussed. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  8. 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

  9. The influence of a voltage ramp on the measurement of I-V characteristics of a solar cell

    NASA Technical Reports Server (NTRS)

    Von Roos, O.

    1980-01-01

    For efficiency and convenience the voltage applied to a Si solar cell is often fairly rapidly driven from zero to the open circuit value typically at a common rate of 1 V per millisecond. During this time the values of current are determined as a function of the instantaneous voltage thus producing an I-V characteristic. The present paper shows that the customary expressions for the current as a function of cell parameters still remain valid provided that the diffusion length in the expression for the dark current is changed from its steady state value L to the effective diffusion length L1 given by L1 = L(1 + qV/kT.tau) to the -1/2, where V is the ramp rate considered constant and tau is the lifetime of minority carriers. This result is true to a very good approximation provided that low level injection prevails.

  10. Delta-doping in diffusion studies

    NASA Astrophysics Data System (ADS)

    Bénière, François; Chaplain, René; Gauneau, Marcel; Reddy, Viswanatha; Régrény, André

    1993-12-01

    The δ-doping where the dopant is confined on the length-scale of the lattice constant provides perfectly ideal conditions to study the atomic transport processes. We have studied MBE-grown GaAs samples δ-doped with Si and Al layers. Long time diffusion anneals have been performed in the temperature range 550 800 °C. The distribution profiles are examined by SIMS-profiling. We obtain Si diffusion coefficients in good agreement with the other recent studies using different techniques (rapid thermal annealing, capacitance-voltage profiling, sandwiched diffusion source). This contrasts with the earlier measurements based on diffusion of implanted dopants which were much more widely spread. We conclude that the more accurate data allowed with the δ-doping show that the diffusion coefficient is an intrinsic parameter provided that the amount of dopant and the dislocation density are kept sufficiently small. Le dopage-delta, où le dopant est confiné à l'échelle du paramètre du réseau, fournit les conditions parfaitement idéales pour étudier les processus de transport atomique. Nous avons étudié des échantillons de GaAs obtenus par épitaxie par jet moléculaire dopés par des couches-delta de Si et Al. Des traitements de diffusion de longue durée ont été réalisés dans l'intervalle de température 550 à 800°C. Les profils de distribution sont examinés par spectrométrie d'émission d'ions secondaires. Nous obtenons des coefficients de diffusion de Si en bon accord avec les autres études récentes utilisant des techniques différentes (traitement thermique ultrarapide, profil de distribution par la méthode capacité-voltage, diffusion d'une couche “ sandwich ”). Ceci diffère des mesures antérieures qui, basées sur la diffusion de dopants implantés, étaient beaucoup plus dispersées. Nous concluons que les données plus précises rendues possibles par le dopage-delta montrent que le coefficient de diffusion est un paramètre intrinsèque

  11. Mastocytosis, diffuse cutaneous (image)

    MedlinePlus

    This is a picture of diffuse, cutaneous mastocytosis. Abnormal collections of cells in the skin (mast cells) produce this rash. Unlike bullous mastocytosis, rubbing will not lead to formation of blisters ( ...

  12. Factorized Diffusion Map Approximation.

    PubMed

    Amizadeh, Saeed; Valizadegan, Hamed; Hauskrecht, Milos

    2012-01-01

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

  13. Factorized Diffusion Map Approximation

    PubMed Central

    Amizadeh, Saeed; Valizadegan, Hamed; Hauskrecht, Milos

    2013-01-01

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

  14. Diffusion of eccentric microswimmers.

    PubMed

    Debnath, Debajyoti; Ghosh, Pulak K; Li, Yunyun; Marchesoni, Fabio; Li, Baowen

    2016-02-21

    We model the two-dimensional diffusive dynamics of an eccentric artificial microswimmer in a highly viscous medium. We assume that the swimmer's propulsion results from an effective force applied to a center distinct from its center of mass, both centers resting on a body's axis parallel to its average self-propulsion velocity. Moreover, we allow for angular fluctuations of the velocity about the body's axis. We prove, both analytically and numerically, that the ensuing active diffusion of the swimmer is suppressed to an extent that strongly depends on the model parameters. In particular, the active diffusion constant undergoes a transition from a quadratic to a linear dependence on the self-propulsion speed, with practical consequences on the interpretation of the experimental data. Finally, we extend our model to describe the diffusion of chiral eccentric swimmers.

  15. 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.

  16. Guide tube flow diffuser

    SciTech Connect

    Berringer, R.T.; Myron, D.L.

    1980-11-04

    A nuclear reactor upper internal guide tube has a flow diffuser integral with its bottom end. The guide tube provides guidance for control rods during their ascent or descent from the reactor core. The flow diffuser serves to divert the upward flow of reactor coolant around the outside of the guide tube thereby limiting the amount of coolant flow and turbulence within the guide tube, thus enhancing the ease of movement of the control rods.

  17. Trapped bubbles keep pumice afloat and gas diffusion makes pumice sink

    NASA Astrophysics Data System (ADS)

    Fauria, Kristen E.; Manga, Michael; Wei, Zihan

    2017-02-01

    Pumice can float on water for months to years - long enough for pumice to travel across oceans and facilitate the spread of species. Long-lived pumice floatation is unexpected, however, because pumice pores are highly connected and water wets volcanic glass. As a result, observations of long floating times have not been reconciled with predictions of rapid sinking. We propose a mechanism to resolve this paradox - the trapping of gas bubbles by water within the pumice. Gas trapping refers to the isolation of gas by water within pore throats such that the gas becomes disconnected from the atmosphere and unable to escape. We use X-ray microtomography to image partially saturated pumice and demonstrate that non-condensable gas trapping occurs in both ambient temperature and hot (500 °C) pumice. Furthermore, we show that the size distribution of trapped gas clusters matches predictions of percolation theory. Finally, we propose that diffusion of trapped gas determines pumice floatation time. Experimental measurements of pumice floatation support a diffusion control on pumice buoyancy and we find that floatation time τ scales as τ ∝ L2/Dθ2 where L is the characteristic length of pumice, D is the gas-water diffusion coefficient, and θ is pumice water saturation. A mechanistic understanding of pumice floatation is a step towards understanding how pumice is partitioned into floating and sinking components and provides an estimate for the lifetime of pumice rafts in the ocean.

  18. 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.

  19. Highly transparent sapphire micro-grating structures with large diffuse light scattering.

    PubMed

    Ko, Yeong Hwan; Yu, Jae Su

    2011-08-01

    The highly transparent micro-grating structures (MGSs) of sapphire substrate with large diffuse light scattering were theoretically and experimentally studied. From the finite difference time domain simulation, it was found that the degree of diffuse light scattering is strongly dependent on the size of grating structures. For a highly transparent property, the sapphire MGSs were optimally designed by the theoretical calculations using the rigorous coupled wave analysis method. The order of taper, geometry (i.e., width and height), and pitch length of MGSs were optimized to maximize their average total transmittance over a wide wavelength range of 300-1800 nm. Additionally, the influence of the deposition of low-refractive index material such as SiO2 onto sapphire MGSs on the transmittance characteristics was investigated. To verify experimentally the feasibility, the sapphire MGSs were fabricated by the conventional lithography and dry etching processes. The SiO2 deposited sapphire MGS exhibited a further increase in the total transmittance due to its relatively more graded refractive index profile while maintaining a significantly enhanced diffuse light scattering. The experimental data were in a reasonable agreement with the theoretical results.

  20. Diffusion length improvements in GaAs associated with Zn diffusion during Ga/1-x/Al/x/As growth

    NASA Technical Reports Server (NTRS)

    Hovel, H. J.; Woodall, J. M.

    1975-01-01

    Relatively good GaAs solar cells can be made from poor quality substrates by making the junction deep (more than 1 micron) instead of shallow and by leaching both the p and n GaAs regions during the growth process. Air-mass-zero efficiencies of 14.7% (19% AM1) have been obtained from substrates with starting substrate thickness of 0.6 micron.

  1. [Liver ultrasound: focal lesions and diffuse diseases].

    PubMed

    Segura Grau, A; Valero López, I; Díaz Rodríguez, N; Segura Cabral, J M

    2016-01-01

    Liver ultrasound is frequently used as a first-line technique for the detection and characterization of the most common liver lesions, especially those incidentally found focal liver lesions, and for monitoring of chronic liver diseases. Ultrasound is not only used in the Bmode, but also with Doppler and, more recently, contrast-enhanced ultrasound. It is mainly used in the diagnosis of diffuse liver diseases, such as steatosis or cirrhosis. This article presents a practical approach for diagnosis workup, in which the different characteristics of the main focal liver lesions and diffuse liver diseases are reviewed.

  2. Mathematical modeling of molecular diffusion through mucus

    PubMed Central

    Cu, Yen; Saltzman, W. Mark

    2008-01-01

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

  3. 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.

  4. Normal and anomalous diffusion of Brownian particles on disordered potentials

    NASA Astrophysics Data System (ADS)

    Salgado-García, R.

    2016-07-01

    In this work we study the transition from normal to anomalous diffusion of Brownian particles on disordered potentials. The potential model consists of a series of "potential hills" (defined on a unit cell of constant length) whose heights are chosen randomly from a given distribution. We calculate the exact expression for the diffusion coefficient in the case of uncorrelated potentials for arbitrary distributions. We show that when the potential heights have a Gaussian distribution (with zero mean and a finite variance) the diffusion of the particles is always normal. In contrast, when the distribution of the potential heights is exponentially distributed the diffusion coefficient vanishes when the system is placed below a critical temperature. We calculate analytically the diffusion exponent for the anomalous (subdiffusive) phase by using the so-called "random trap model". Our predictions are tested by means of Langevin simulations obtaining good agreement within the accuracy of our numerical calculations.

  5. 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.

  6. 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

  7. Length of Hospital Stay: Some Administrative Considerations.

    ERIC Educational Resources Information Center

    Stoffelmayr, Bertram E.; And Others

    1984-01-01

    Compared, during a two-year period, lengths of stay of patients on two admission wards that served the same community mental health center. Results showed a significant difference in length of stay for voluntary and involuntary patients. (BH)

  8. Flow Control in a Transonic Diffuser

    NASA Astrophysics Data System (ADS)

    Gartner, Jeremy; Amitay, Michael

    2014-11-01

    In some airplanes such as fighter jets and UAV, short inlet ducts replace the more conventional ducts due to their shorter length. However, these ducts are associated with low length-to-diameter ratio and low aspect ratio and, thus, experience massive separation and the presence of secondary flow structures. These flow phenomena are undesirable as they lead to pressure losses and distortion at the Aerodynamic Interface Plane (AIP), where the engine face is located. It causes the engine to perform with a lower efficiency as it would with a straight duct diffuser. Different flow control techniques were studied on the short inlet duct, with the goal to reattach the flow and minimize the distortions at the AIP. Due to the complex interaction between the separation and the secondary flow structures, the necessity to understand the flow mechanisms, and how to control them at a more fundamental level, a new transonic diffuser with an upper ramp and a straight floor was designed and built. The objective of this project is to explore the effectiveness of different flow control techniques in a high subsonic (up to Mach 0.8) diffuser, so that the quasi two-dimensional separation and the formation of secondary flow structure can be isolated using a canonical flow field. Supported by Northrop Grumman.

  9. Water isotope diffusion in the WAIS Divide ice core during the Holocene and last glacial

    NASA Astrophysics Data System (ADS)

    Jones, T. R.; Cuffey, K. M.; White, J. W. C.; Steig, E. J.; Buizert, C.; Markle, B. R.; McConnell, J. R.; Sigl, M.

    2017-01-01

    We use a high-resolution water isotope record from the West Antarctic Ice Sheet Divide ice core (WDC) to evaluate the effects of water isotope diffusion for the last 29 ka B.P. Using spectral analysis of the data, we determine diffusion lengths in depth and time domains. The diffusion length quantifies the mean cumulative diffusive displacement of water molecules relative to their original location at time of deposition. We simulate the observed signal with models and find that our understanding of processes and conditions in the ice sheet is incomplete. With the effects of ice-deformational thinning removed, portions of the Holocene record show total diffusion lengths smaller than predicted for a lower limit case of diffusion through a single ice crystal. Such reduced diffusion is probably due to structural features such as crusts and tortuous porosity that inhibit vapor transport in the firn. In the late glacial portion of the record, diffusion lengths double between 19.5 and 17 ka B.P. Known dependencies of diffusion on climatic variables do not account for this enhancement in models, and we hypothesize that it could arise from thermal gradients in the firn column, impurity-driven enhancement of solid ice diffusion, or changes in firn grain properties that alter vapor access to open pores. Despite model uncertainties, the WDC diffusion length chronology will be an essential input to future studies of high-frequency variability in the water isotope climate record, as it allows for the effects of diffusion to be removed.

  10. 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.

  11. 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...

  12. 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...

  13. 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...

  14. 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...

  15. 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...

  16. Study on length distribution of ramie fibers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The extra-long length of ramie fibers and the high variation in fiber length has a negative impact on the spinning processes. In order to better study the feature of ramie fiber length, in this research, the probability density function of the mixture model applied in the characterization of cotton...

  17. New Chorus Diffusion Matrix

    NASA Astrophysics Data System (ADS)

    Horne, Richard B.; Kersten, Tobias; Glauert, Sarah A.; Meredith, Nigel P.; Boscher, Daniel; Sicard, Angelica; Maget, Vincent

    2013-04-01

    Whistler mode chorus waves play a major role in the loss and acceleration of electrons in the Earth's radiation belts. While high time resolution satellite data show that these waves are highly structured in frequency and time, at present their effects on the electron distribution can only be assessed on a global scale by using quasi-linear diffusion theory. Here we present new quasi-linear diffusion coefficients for upper and lower band chorus waves for use in global radiation belt models. Using data from DE 1 CRRES, Cluster 1, Double Star TC1 and THEMIS, we have constructed a database of wave properties and used this to construct new diffusion coefficients for L* = 1.5 to 10 in steps of 0.5, 10 latitude bins between 0o and 60o ,8 bins in MLT and 5 levels of geomagnetic activity as measured by Kp. We find that the peak frequency of lower band chorus is close to 0.2 fce, which is lower than that used in previous models. The combined upper and lower band chorus diffusion shows structure that should result in an energy dependent pitch angle anisotropy, particularly between 1 keV and 100 keV. The diffusion rates suggest that wave-particle interactions should still be very important outside geostationary orbit, out to at least L* = 8. We find significant energy diffusion near 1 keV near the loss cone, consistent with wave growth. By including the new chorus diffusion matrix into the BAS radiation belt (BRB) model we compare the effects on the evolution of the radiation belts against previous models.

  18. 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.

  19. Lévy flight with absorption: A model for diffusing diffusivity with long tails

    NASA Astrophysics Data System (ADS)

    Jain, Rohit; Sebastian, K. L.

    2017-03-01

    We consider diffusion of a particle in rearranging environment, so that the diffusivity of the particle is a stochastic function of time. In our previous model of "diffusing diffusivity" [Jain and Sebastian, J. Phys. Chem. B 120, 3988 (2016), 10.1021/acs.jpcb.6b01527], it was shown that the mean square displacement of particle remains Fickian, i.e., ∝T at all times, but the probability distribution of particle displacement is not Gaussian at all times. It is exponential at short times and crosses over to become Gaussian only in a large time limit in the case where the distribution of D in that model has a steady state limit which is exponential, i.e., πe(D ) ˜e-D /D0 . In the present study, we model the diffusivity of a particle as a Lévy flight process so that D has a power-law tailed distribution, viz., πe(D ) ˜D-1 -α with 0 <α <1 . We find that in the short time limit, the width of displacement distribution is proportional to √{T }, implying that the diffusion is Fickian. But for long times, the width is proportional to T1 /2 α which is a characteristic of anomalous diffusion. The distribution function for the displacement of the particle is found to be a symmetric stable distribution with a stability index 2 α which preserves its shape at all times.

  20. 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

    2015-06-03

    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%).