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Sample records for aids-related diffuse mixed

  1. mTOR activity in AIDS-related diffuse large B-cell lymphoma

    PubMed Central

    Diaz-Perez, Julio A.; Preziosi, Michael; King, Charles C.; Jones, George A.; Jain, Sonia; Sun, Xiaoying; Reid, Erin G.; VandenBerg, Scott; Wang, Huan-You

    2017-01-01

    Background Patients infected with HIV have a significantly increased risk of developing non–Hodgkin lymphomas despite the widespread use of HAART. To investigate mTOR pathway activity in acquired immunodeficiency syndrome (AIDS) related diffuse large B-cell lymphoma AR-DLBCL, we used immunohistochemistry to examine the presence of the phosphorylated 70 ribosomal S6 protein-kinase (p70S6K), an extensively studied effector of mTOR Complex 1 (mTORC1) and the phosphorylated phosphatase and tensin homolog (pPTEN), a negative regulator of mTORC1 pathway. Materials and methods We evaluated tissue samples from 126 patients with AR-DLBCL. Among them, 98 samples were from tissue microarrays (TMAs) supplied by the Aids and Cancer Specimen Resource (ACSR), the remaining 28 samples were from cases diagnosed and treated at the University of California, San Diego (UCSD). The presence of p70S6K was evaluated with two antibodies directed against the combined epitopes Ser235/236 and Ser240/244, respectively; and additional monoclonal anti-bodies were used to identify pPTEN and phosphorylated proline-rich Akt substrate of 40kDa (pPRAS40). The degree of intensity and percentage of cells positive for p70S6K and pPTEN were assessed in all the samples. In addition, a subgroup of 28 patients from UCSD was studied to assess the presence of pPRAS40, an insulin-regulated activator of the mTORC1. The expression of each of these markers was correlated with clinical and histopathologic features. Results The majority of the patients evaluated were males (88%); only two cases (1.6%) were older than 65 years of age. We found high levels of both p70S6K-paired epitopes studied, 48% positivity against Ser235/236 (44% in ACSR and 64% in UCSD group), and 86% positivity against Ser240/244 (82% in ACSR and 100% in UCSD group). We observed more positive cells and stronger intensity with epitope Ser240/244 in comparison to Ser235/236 (p<0.0001). The degree of intensity and percentage of cells positive

  2. Gene Therapy and Combination Chemotherapy in Treating Patients With AIDS-Related Non-Hodgkin Lymphoma

    ClinicalTrials.gov

    2017-02-23

    AIDS-Related Burkitt Lymphoma; AIDS-Related Diffuse Large B-cell Lymphoma; AIDS-Related Plasmablastic Lymphoma; AIDS-Related Primary Effusion Lymphoma; HIV Infection; AIDS Related Non-Hodgkin Lymphoma

  3. Diffusive mixing and Tsallis entropy

    DOE PAGES

    O'Malley, Daniel; Vesselinov, Velimir V.; Cushman, John H.

    2015-04-29

    Brownian motion, the classical diffusive process, maximizes the Boltzmann-Gibbs entropy. The Tsallis q-entropy, which is non-additive, was developed as an alternative to the classical entropy for systems which are non-ergodic. A generalization of Brownian motion is provided that maximizes the Tsallis entropy rather than the Boltzmann-Gibbs entropy. This process is driven by a Brownian measure with a random diffusion coefficient. In addition, the distribution of this coefficient is derived as a function of q for 1 < q < 3. Applications to transport in porous media are considered.

  4. Diffusion in mixed solvents. II - The heat of mixing parameter

    NASA Technical Reports Server (NTRS)

    Carapellucci, P. A.

    1975-01-01

    Correlation of second-order rate constants for many reactions involving electron transfer between organic molecules, solvated electron reactions, iodine diffusion coefficients, and triplet state electron transfer reactions has been made with the heat of mixing parameter (HMP) for the aqueous binary solvent systems. The aqueous binary solvents studied are those containing methanol or ethanol (type I solvent); 1-propanol or tert-butyl alcohol (type II solvent); or sucrose or glycerol (type III solvent). A plot of the HMP vs. the diffusion parameter for each reaction yields superimposable curves for these reactions in a particular solvent mixture over the entire solvent mixture range, irrespective of the value of the reaction's rate constant or diffusion coefficient in water.

  5. A Mapping method for mixing with diffusion

    NASA Astrophysics Data System (ADS)

    Schlick, Conor P.; Christov, Ivan C.; Umbanhowar, Paul B.; Ottino, Julio M.; Lueptow, Richard M.

    2012-11-01

    We present an accurate and efficient computational method for solving the advection-diffusion equation in time-periodic chaotic flows. The method uses operator splitting which allows advection and diffusion steps to be treated independently. Taking advantage of flow periodicity, the advection step is solved with a mapping method, and diffusion is added discretely after each iteration of the advection map. This approach allows for a ``composite'' mapping matrix to be constructed for an entire period of a chaotic advection-diffusion process, which provides a natural approach to the spectral analysis of mixing. To test the approach, we consider the two-dimensional time-periodic sine flow. When compared to the exact solution for this simple velocity field, the operator splitting method exhibits qualitative agreement (overall concentration structure) for large time steps and is quantitatively accurate (average and maximum error) for small time steps. We extend the operator splitting approach to three-dimensional chaotic flows. Funded by NSF Grant CMMI-1000469. Present affiliation: Princeton University. Supported by NSF Grant DMS-1104047.

  6. Statistical mixing and aggregation in Feller diffusion

    NASA Astrophysics Data System (ADS)

    Anteneodo, C.; Duarte Queirós, S. M.

    2009-10-01

    We consider Feller mean-reverting square-root diffusion, which has been applied to model a wide variety of processes with linearly state-dependent diffusion, such as stochastic volatility and interest rates in finance, and neuronal and population dynamics in the natural sciences. We focus on the statistical mixing (or superstatistical) process in which the parameter related to the mean value can fluctuate—a plausible mechanism for the emergence of heavy-tailed distributions. We obtain analytical results for the associated probability density function (both stationary and time-dependent), its correlation structure and aggregation properties. Our results are applied to explain the statistics of stock traded volume at different aggregation scales.

  7. Mixing and diffusion in intermittent overturning turbulence

    NASA Astrophysics Data System (ADS)

    Redondo, Jose M.; Mahjoub, Otman B.; Gonzalez-Nieto, Pilar L.; Lawry, Andrew

    2014-05-01

    The improvements in experimental methods and high resolution image analysis are nowadays able to detect subtle changes in the structure of the turbulence over a wide range of temporal and spatial scales [1], we compare the scaling shown by different mixing fronts driven by buoyancy that form a Rayleigh-Taylor mixing front. We use PIV and density front tracking in several experimental configurations akin to geophysical overturning [2-7]. We parametrize the role of unstable stratification by means of the Atwood number and compare both the scaling and the multifractal and the maximum local fractal structure functions of the different markers used to visualize the front. Both reactive and passive scalar tracers are used to investigate the mixing structure and the intermittency of the flow. Different initial conditions are compared and the mixing efficiency of the overal turbulent process evaluated [6-7]. An interesting approach, relating the Multi-Fractal dimension spectra, the intermittency and the spectral exponent is to find relationships that may be used to parameterise the sub-grid turbulence in terms of generalized diffusivities [4 ] that take into account the topology and the self-similarity of the Mixing RT and RM flows. As an example, a relationship between the diffusivity, the exponent β, the intermittency μ, and D(i), may be found for the volume fraction or the concentration, at the same time other locally measured parameters such as the enstrophy or the gradient alignment as well as their multi-fractal structures may turn out to be physically relevant indicators of the local turbulence and the mixing. Several methods of deriving local eddy diffusivity and local entrainment should give more realistic estimates of the spatial/temporal non-homogeneities (and intermittencies in the Kolmogorov 62 sense obtained as spatial correlations of the turbulent dissipation, or from structure functions) and these values may be used to parameterise turbulence at a variety

  8. Treatment Option Overview (AIDS Related-Lymphoma)

    MedlinePlus

    ... Childhood Hodgkin Lymphoma Treatment Childhood NHL Treatment Research AIDS-Related Lymphoma Treatment (PDQ®)–Patient Version General Information About AIDS-Related Lymphoma Go to Health Professional Version Key ...

  9. Stages of AIDS-Related Lymphoma

    MedlinePlus

    ... Childhood Hodgkin Lymphoma Treatment Childhood NHL Treatment Research AIDS-Related Lymphoma Treatment (PDQ®)–Patient Version General Information About AIDS-Related Lymphoma Go to Health Professional Version Key ...

  10. Treatment Options for AIDS-Related Lymphoma

    MedlinePlus

    ... Childhood Hodgkin Lymphoma Treatment Childhood NHL Treatment Research AIDS-Related Lymphoma Treatment (PDQ®)–Patient Version General Information About AIDS-Related Lymphoma Go to Health Professional Version Key ...

  11. General Information about AIDS-Related Lymphoma

    MedlinePlus

    ... Childhood Hodgkin Lymphoma Treatment Childhood NHL Treatment Research AIDS-Related Lymphoma Treatment (PDQ®)–Patient Version General Information About AIDS-Related Lymphoma Go to Health Professional Version Key ...

  12. Diffusive mixing through velocity profile variation in microchannels

    NASA Astrophysics Data System (ADS)

    Yakhshi-Tafti, Ehsan; Cho, Hyoung J.; Kumar, Ranganathan

    2011-03-01

    Rapid mixing does not readily occur at low Reynolds number flows encountered in microdevices; however, it can be enhanced by passive diffusive mixing schemes. This study of micromixing of two miscible fluids is based on the principle that (1) increased velocity at the interface of co-flowing fluids results in increased diffusive mass flux across their interface, and (2) diffusion interfaces between two liquids progress transversely as the flow proceeds downstream. A passive micromixer is proposed that takes advantage of the peak velocity variation, inducing diffusive mixing. The effect of flow variation on the enhancement of diffusive mixing is investigated analytically and experimentally. Variation of the flow profile is confirmed using micro-Particle Image Velocimetry (μPIV) and mixing is evaluated by color variations resulting from the mixing of pH indicator and basic solutions. Velocity profile variations obtained from μPIV show a shift in peak velocities. The mixing efficiency of the Σ-micromixer is expected to be higher than that for a T-junction channel and can be as high as 80%. The mixing efficiency decreases with Reynolds number and increases with downstream length, exhibiting a power law.

  13. Diffusive Mixing in Strongly Coupled Plasmas

    NASA Astrophysics Data System (ADS)

    Diaw, Abdourahmane; Murillo, Michael

    2016-10-01

    A multispecies hydrodynamic model based on moments of the Born-Bogolyubov-Green-Kirkwood-Yvon (BBGKY) hierarchy is developed for physical conditions relevant to astrophysical plasmas. The modified transport equations incorporate strong correlations through a density functional theory closure, while fluctuations enters through a mixture BGK operator. This model extends the usual Burgers equations for a dilute gas to strongly coupled and isothermal plasmas mixtures. The diffusive currents for these strongly coupled plasmas is self-consistently derived. The settling of impurities and its impact on cooling of white dwarfs and neutron stars can be greatly affected by strong Coulomb coupling, which we show can be quantified using the direct-correlation function. This work was supported by the Air Force Office of Scientific Research (Grant No. FA9550-12-1-0344).

  14. 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.

  15. Structure and Mixing of a Turbulent Meandering Plume Part 2: Turbulent Mixing and Eddy-Diffusivity

    NASA Astrophysics Data System (ADS)

    Webster, D. R.; Young, D. L.; Larsson, A. I.

    2016-11-01

    Turbulent mixing in a meandering non-buoyant chemical plume is far less understood than in a straight plume - partially due to the difficulty separating the plume meander fluctuations from the turbulent fluctuations. In this study we present high resolution measurements of the covariance of the turbulent fluctuations of velocity and concentration in a phase-locked meandering plume, acquired by combining simultaneous PTV velocity and LIF concentration measurements. The effectiveness of the eddy-diffusivity model for predicting the turbulent flux is assessed. Analysis of the data reveals that the spatial distribution of the turbulent flux is governed by the large-scale alternating-sign vortices that induce the plume meander. Further, regions of high turbulent flux are co-located with areas of large phase-averaged concentration gradients. As a result, the eddy-diffusivity framework models the turbulent flux effectively. As expected from turbulent mixing theory, the eddy-diffusivity coefficient plateaus at a constant value once the plume width reaches the size of the largest eddies (i.e., the scale of the water depth in this open channel flow). However, when the plume width is less than the water depth the eddy-diffusivity coefficient scales with the plume width to the 3/4 power. This differs from the theoretical 4/3 scaling that results from the assumption of an inertial subrange. The extent of the inertial subrange is extremely limited in the current moderate-Re open channel flow.

  16. Design and performance of family of diffusing scrolls with mixed-flow impeller and vaneless diffuser

    NASA Technical Reports Server (NTRS)

    Brown, W Byron; Bradshaw, Guy R

    1949-01-01

    A family of diffusing scrolls was designed for use with a mixed-flow impeller and a small-diameter vaneless diffuser. The design theory, intended to maintain a uniform pressure around the scroll inlet, permits determination of the position of scroll cross sections of preassigned area by considering the radial variation in fluid density and the effects of friction along the scroll. Inasmuch as the design method leaves the cross-sectional shape undetermined, the effect of certain variations in scroll shape was investigated by studying scrolls having angles of divergence (of the scroll walls downstream of the entrance section) of 24 degrees, 40 degrees, and 80 degrees. A second 80 degree scroll was of asymmetrical construction and a third was plaster-cast instead of sand-cast. Each scroll was tested as a compressor component at actual impeller tip speeds of 700 to 1300 feet per second from full throttle to surge.

  17. Subgrid models for mass and thermal diffusion in turbulent mixing

    SciTech Connect

    Sharp, David H; Lim, Hyunkyung; Li, Xiao - Lin; Gilmm, James G

    2008-01-01

    We are concerned with the chaotic flow fields of turbulent mixing. Chaotic flow is found in an extreme form in multiply shocked Richtmyer-Meshkov unstable flows. The goal of a converged simulation for this problem is twofold: to obtain converged solutions for macro solution features, such as the trajectories of the principal shock waves, mixing zone edges, and mean densities and velocities within each phase, and also for such micro solution features as the joint probability distributions of the temperature and species concentration. We introduce parameterized subgrid models of mass and thermal diffusion, to define large eddy simulations (LES) that replicate the micro features observed in the direct numerical simulation (DNS). The Schmidt numbers and Prandtl numbers are chosen to represent typical liquid, gas and plasma parameter values. Our main result is to explore the variation of the Schmidt, Prandtl and Reynolds numbers by three orders of magnitude, and the mesh by a factor of 8 per linear dimension (up to 3200 cells per dimension), to allow exploration of both DNS and LES regimes and verification of the simulations for both macro and micro observables. We find mesh convergence for key properties describing the molecular level of mixing, including chemical reaction rates between the distinct fluid species. We find results nearly independent of Reynolds number for Re 300, 6000, 600K . Methodologically, the results are also new. In common with the shock capturing community, we allow and maintain sharp solution gradients, and we enhance these gradients through use of front tracking. In common with the turbulence modeling community, we include subgrid scale models with no adjustable parameters for LES. To the authors' knowledge, these two methodologies have not been previously combined. In contrast to both of these methodologies, our use of Front Tracking, with DNS or LES resolution of the momentum equation at or near the Kolmogorov scale, but without resolving the

  18. Aids-Related Cancers in Africa

    NASA Astrophysics Data System (ADS)

    Mbulaiteye, Sam M.

    2014-07-01

    Thank you Professor Zichichi for inviting me to give a talk about AIDS-related cancers in Africa. Let me begin by congratulating the team that organized the 46th Session of the Erice International Seminar Series, whose theme is THE ROLE OF SCIENCE IN THE THIRD MILLENIUM. I also congratulate the scientists from 38 countries who are attending these seminars. They are perpetuating the principle of SCIENCE WITHOUT SECRETS in the true spirit espoused by Archimedes, Galileo, and Fermi. It is a wonderful honor for me to be here to shed some light on the health impacts of the HIV epidemic in the area of cancer...

  19. Parameterization of large-scale turbulent diffusion in the presence of both well-mixed and weakly mixed patchy layers

    NASA Astrophysics Data System (ADS)

    Osman, M. K.; Hocking, W. K.; Tarasick, D. W.

    2016-06-01

    Vertical diffusion and mixing of tracers in the upper troposphere and lower stratosphere (UTLS) are not uniform, but primarily occur due to patches of turbulence that are intermittent in time and space. The effective diffusivity of regions of patchy turbulence is related to statistical parameters describing the morphology of turbulent events, such as lifetime, number, width, depth and local diffusivity (i.e., diffusivity within the turbulent patch) of the patches. While this has been recognized in the literature, the primary focus has been on well-mixed layers, with few exceptions. In such cases the local diffusivity is irrelevant, but this is not true for weakly and partially mixed layers. Here, we use both theory and numerical simulations to consider the impact of intermediate and weakly mixed layers, in addition to well-mixed layers. Previous approaches have considered only one dimension (vertical), and only a small number of layers (often one at each time step), and have examined mixing of constituents. We consider a two-dimensional case, with multiple layers (10 and more, up to hundreds and even thousands), having well-defined, non-infinite, lengths and depths. We then provide new formulas to describe cases involving well-mixed layers which supersede earlier expressions. In addition, we look in detail at layers that are not well mixed, and, as an interesting variation on previous models, our procedure is based on tracking the dispersion of individual particles, which is quite different to the earlier approaches which looked at mixing of constituents. We develop an expression which allows determination of the degree of mixing, and show that layers used in some previous models were in fact not well mixed and so produced erroneous results. We then develop a generalized model based on two dimensional random-walk theory employing Rayleigh distributions which allows us to develop a universal formula for diffusion rates for multiple two-dimensional layers with

  20. Attached and lifted diffusion flames in a mixing layer

    NASA Astrophysics Data System (ADS)

    Matalon, Moshe; Lu, Zhanbin

    2016-11-01

    Many practical combustion devices are concerned with the stabilization of diffusion flames that are formed by injecting gaseous fuels into a co-flowing stream containing an oxidizer. A primary concern of these configurations is the attachment and lift-off characteristics of the diffusion flame relative to the rim of the injector. In such circumstances, the edge of the flame, which possesses a distinct structure that combines characteristics of both premixed an diffusion flames, is found to play a crucial role in determining the stabilization of the diffusion flame. In this study, we examine the effect of streams of unequal flow rates on the structural and dynamical properties of the edge flame. We show that, depending on the stoichiometric conditions and the diffusive properties of the fuel and oxidizer, the diffusion flame may either be attached to the rim of the injector, lifted and stabilized at a downstream equilibrium position, or blown off by the flow. Under certain conditions the diffusion flame may undergo spontaneous oscillations, whereby the edge of the flame exhibits a back and forth motion along a direction that coincides with the diffusion flame surface.

  1. Estimating diffusivity from the mixed layer heat and salt balances in the North Pacific

    NASA Astrophysics Data System (ADS)

    Cronin, M. F.; Pelland, N.; Emerson, S. R.; Crawford, W. R.

    2015-12-01

    Data from two National Oceanographic and Atmospheric Administration (NOAA) surface moorings in the North Pacific, in combination with data from satellite, Argo floats and glider (when available), are used to evaluate the residual diffusive flux of heat across the base of the mixed layer from the surface mixed layer heat budget. The diffusion coefficient (i.e., diffusivity) is then computed by dividing the diffusive flux by the temperature gradient in the 20-m transition layer just below the base of the mixed layer. At Station Papa in the NE Pacific subpolar gyre, this diffusivity is 1×10-4 m2/s during summer, increasing to ~3×10-4 m2/s during fall. During late winter and early spring, diffusivity has large errors. At other times, diffusivity computed from the mixed layer salt budget at Papa correlate with those from the heat budget, giving confidence that the results are robust for all seasons except late winter-early spring and can be used for other tracers. In comparison, at the Kuroshio Extension Observatory (KEO) in the NW Pacific subtropical recirculation gyre, somewhat larger diffusivity are found based upon the mixed layer heat budget: ~ 3×10-4 m2/s during the warm season and more than an order of magnitude larger during the winter, although again, wintertime errors are large. These larger values at KEO appear to be due to the increased turbulence associated with the summertime typhoons, and weaker wintertime stratification.

  2. A mapping method for distributive mixing with diffusion: Interplay between chaos and diffusion in time-periodic sine flow

    NASA Astrophysics Data System (ADS)

    Schlick, Conor P.; Christov, Ivan C.; Umbanhowar, Paul B.; Ottino, Julio M.; Lueptow, Richard M.

    2013-05-01

    We present an accurate and efficient computational method for solving the advection-diffusion equation in time-periodic chaotic flows. The method uses operator splitting, which allows the advection and diffusion steps to be treated independently. Taking advantage of flow periodicity, the advection step is solved using a mapping method, and diffusion is "added" discretely after each iteration of the advection map. This approach results in the construction of a composite mapping matrix over an entire period of the chaotic advection-diffusion process and provides a natural framework for the analysis of mixing. To test the approach, we consider two-dimensional time-periodic sine flow. By comparing the numerical solutions obtained by our method to reference solutions, we find qualitative agreement for large time steps (structure of concentration profile) and quantitative agreement for small time steps (low error). Further, we study the interplay between mixing through chaotic advection and mixing through diffusion leading to an analytical model for the evolution of the intensity of segregation with time. Additionally, we demonstrate that our operator splitting mapping approach can be readily extended to three dimensions.

  3. Gravity induced diffusive mixing between fluids of different densities in a vertical tube

    NASA Astrophysics Data System (ADS)

    Lefaucheur, E.; Souche, M.; Salin, D.; Hulin, J. P.; Allouche, M.; Daccord, G.; Hinch, E. J.

    2000-11-01

    Gravity induced mixing is studied experimentally between two fluids of different densities initially separated in an unstable configuration inside a transparent vertical tube (4m height, 20 mm diameter). Spatiotemporal diagrams of the concentration profile along the tube are realized optically. For large density contrasts (Δ ρ = 10-40%), the mixing zone displays an erf like concentration profile with a width increasing diffusively as √t. The corresponding diffusion coefficient D is of order 10-4m^2/s (10^5 times larger than molecular diffusion) and varies slowly with the Δ ρ. This "diffusive mixing" is due to random tubulent motions in the mixing zone over distances of the order of the diameter and with velocities of a few cm/s. At lower contrasts Δ ρ = 0.05-1% and long times, the concentration profile remains diffusive at all distances, with D strongly increasing at low Δ ρ. At short times, Rayleigh-Tayor like fingers develop and get unstable : the concentration profile is diffusive only at short distances and terminates by a sharp front of roughly constant convection velocity.

  4. Mixing in Billow Turbulence and Stratospheric Eddy Diffusion

    DTIC Science & Technology

    1979-04-10

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  5. Sensitivity of mix in Inertial Confinement Fusion simulations to diffusion processes

    NASA Astrophysics Data System (ADS)

    Melvin, Jeremy; Cheng, Baolian; Rana, Verinder; Lim, Hyunkyung; Glimm, James; Sharp, David H.

    2015-11-01

    We explore two themes related to the simulation of mix within an Inertial Confinement Fusion (ICF) implosion, the role of diffusion (viscosity, mass diffusion and thermal conduction) processes and the impact of front tracking on the growth of the hydrodynamic instabilities. Using the University of Chicago HEDP code FLASH, we study the sensitivity of post-shot simulations of a NIC cryogenic shot to the diffusion models and front tracking of the material interfaces. Results of 1D and 2D simulations are compared to experimental quantities and an analysis of the current state of fully integrated ICF simulations is presented.

  6. Prediction of Air Mixing From High Sidewall Diffusers in Cooling Mode: Preprint

    SciTech Connect

    Ridouane, E. H.; Gawlik, K.

    2011-02-01

    Computational fluid dynamics modeling was used to evaluate the performance of high sidewall air supply in cooling mode. The research focused on the design, placement, and operation of air supply diffusers located high on a sidewall and return grilles located near the floor on the same sidewall. Parameters of the study are the supply velocity, supply temperature, diffuser dimensions and room dimensions. Thermal loads characteristic of high performance homes were applied at the walls and room temperature was controlled via a thermostat. The results are intended to provide information to guide the selection of high sidewall supply diffusers to provide proper room mixing for cooling of high performance homes.

  7. Turbulent mix or ion diffusion? Hypothesis testing in ICF capsule implosions

    NASA Astrophysics Data System (ADS)

    Hoffman, N. M.; Zimmerman, G. B.; Vander Wiel, S. A.; Herrmann, H. W.; Kim, Y. H.

    2016-10-01

    Turbulent mixing at a contact surface combines materials that are initially separated across the contact. While the mixing layer may contain the initially separate materials (each assumed to be composed of a number of distinct ion species) in a range of concentrations, from zero to 100%, the concentration of individual ion species within each material, relative to one another, is not altered by turbulent mixing alone. Ion diffusion likewise causes mixing at a contact, but does alter the relative concentration of ion species within each material, since the relative diffusivity of ions, in a fixed background plasma, varies as A 1 / 2/Z2. Recent hydrodynamically equivalent capsule implosions allow a test of the influence of these processes on observed capsule behavior. We use numerical simulations and hypothesis-testing methods to show quantitatively that turbulent mixing with ion diffusion is a better explanation of observed behavior than turbulent mixing alone (subject to the assumptions inherent in the computational models of these processes.) Research supported by US DOE under contract DE-AC52-06NA25396.

  8. Thermodynamic calculations of oxygen self-diffusion in mixed-oxide nuclear fuels

    DOE PAGES

    Parfitt, David C.; Cooper, Michael William; Rushton, Michael J.D.; ...

    2016-07-29

    Mixed-oxide fuels containing uranium with thorium and/or plutonium may play an important part in future nuclear fuel cycles. There are, however, significantly less data available for these materials than conventional uranium dioxide fuel. In the present study, we employ molecular dynamics calculations to simulate the elastic properties and thermal expansivity of a range of mixed oxide compositions. These are then used to support equations of state and oxygen self-diffusion models to provide a self-consistent prediction of the behaviour of these mixed oxide fuels at arbitrary compositions.

  9. Numerical investigation of sensitivity of the Black Sea mixed layer to vertical turbulent diffusion processes

    NASA Astrophysics Data System (ADS)

    Kvaratskhelia, Diana; Demetrashvili, Demuri

    2015-04-01

    The upper mixed-layer of seas and oceans is one of the important water areas, the thermodynamic state of which defines many important physical, chemical or biological processes in the sea- atmosphere environment. The same can be note concerning the Black Sea turbulent mixed layer, which represents the object of our investigation. It is well known that the depth of the mixed layer is generaly determined by measurements of water properties: temperature and sigma-t (density) but here the depth of the mixed layer and its variability are investigated by using of the basin-scale numerical model of the Black Sea dynamics of M. Nodia Institute of Geophysics (BSM-IG, Tbilisi, Georgia). The main object of this study is to investigate the Black Sea upper mixed-layer generation and its evolution in connection with the nonstationarity atmospheric circulation and thermohaline action in the inner-annual time scale. Besides, how the temperature and salinity fields of the Black Sea upper layer are substantially reacted by the vertical diffusion coefficient are the centre of our attention. Therefore, the coefficient of vertical turbulent diffusion for heat and salt are tested as constant equal to 10 cm2s-1 and it was parameterized by modified Oboukhov's formula. The results of the numerical investigations show that: in wintertime for any choosing of this vertical diffusion coefficient the intense wind-driven turbulence promotes mixing aproximetly till 16-26 m in deep layers of the Black Sea. Except for that, cold fluxes through the surface and precipitation-evapuration system play aditionally role on the mixed layer forming as well. During the transitive spring season (in difference from the cold season), when the depth of the mixed layer is aproxometly 2-4 m., the role of vertical turbulent viscosity insignificantly grows. In the warm season (summer), when the mixed layer does not observe in the upper layer of the Black Sea, the role of the vertical diffusion coefficient is more

  10. Flow reversal of fully developed double diffusive mixed convection in a vertical channel

    NASA Astrophysics Data System (ADS)

    Makhatar, Nur Asiah Mohd; Saleh, Habibis; Hashim, Ishak

    2015-10-01

    The mixed convection flow within a vertical channel having internal heat generation at a rate proportional to a power of the temperature difference is considered. The analysis is concerning the studies of occurrence of flow reversal and the effects of three dimensionless parameters, identified as the internal heat parameter (G), a mixed convection parameter (λ) and the exponent (p) in the local heating term on the fully developed double diffusive mixed convection flow in a vertical channel. The governing equations are solved numerically via MAPLE. It was found that flow reversal occurs with larger values of internal heat parameter and mixed convection parameter, but smaller values of local-heating exponent. They also show that, unlike the internal heat parameter and the local-heating exponent, the mixed convection parameter do not give any significant effect on the temperature.

  11. Lognormality of gradients of diffusive scalars in homogeneous, two-dimensional mixing systems

    NASA Astrophysics Data System (ADS)

    Kerstein, A. R.; Ashurst, W. T.

    1984-12-01

    Kolmogorov's third hypothesis, as extended by Gurvich and Yaglom, is found to be obeyed by a diffusive scalar for a class of homogeneous, two-dimensional mixing models. The mixing models all involve the advection of fluid by discrete vortices distributed in a square region with periodic boundary conditions. By computer simulation, it is found that the squared gradient of a diffusive scalar so advected is lognormally distributed, obeys the predicted scaling when a spatial smoothing is applied, and exhibits a power-law range in the spatial autocorrelation. In addition, it is found that the scaling property cuts off at the Batchelor length, as predicted by Gibson. Since the mixing models employed do not incorporate the dynamical features of high-Reynolds-number turbulence, these results suggest that scalar lognormality and associated scaling behavior may be more robust or persistent than the scaling laws of the flow field.

  12. Precipitation of calcium carbonate and calcium phosphate under diffusion controlled mixing

    SciTech Connect

    Tsigabu Gebrehiwet; James R. Henriksen; Luanjing Guo; Don T. Fox; Hai Huang; Lee Tu; Yoshiko Fujita; Robert W. Smith; George Redden

    2014-07-01

    Multi-component mineral precipitation in porous, subsurface environments is challenging to simulate or engineer when in situ reactant mixing is controlled by diffusion. In contrast to well-mixed systems, the conditions that favor mineral precipitation in porous media are distributed along chemical gradients, which evolve spatially due to concurrent mineral precipitation and modification of solute transport in the media. The resulting physical and chemical characteristics of a mixing/precipitation zone are a consequence of coupling between transport and chemical processes, and the distinctive properties of individual chemical systems. We examined the spatial distribution of precipitates formed in “double diffusion” columns for two chemical systems, calcium carbonate and calcium phosphate. Polyacrylamide hydrogel was used as a low permeability, high porosity medium to maximize diffusive mixing and minimize pressure- and density-driven flow between reactant solutions. In the calcium phosphate system, multiple, visually dense and narrow bands of precipitates were observed that were reminiscent of previously reported Liesegang patterns. In the calcium carbonate system, wider precipitation zones characterized by more sparse distributions of precipitates and a more open channel structure were observed. In both cases, formation of precipitates inhibited, but did not necessarily eliminate, continued transport and mixing of the reactants. A reactive transport model with fully implicit coupling between diffusion, chemical speciation and precipitation kinetics, but where explicit details of nucleation processes were neglected, was able to qualitatively simulate properties of the precipitation zones. The results help to illustrate how changes in the physical properties of a precipitation zone depend on coupling between diffusion-controlled reactant mixing and chemistry-specific details of precipitation kinetics.

  13. Mixed waste storage facility CDR review, Paducah Gaseous Diffusion Plant; Solid waste landfill CDR review, Paducah Gaseous Diffusion Plant

    SciTech Connect

    1998-08-01

    This report consists of two papers reviewing the waste storage facility and the landfill projects proposed for the Paducah Gaseous Diffusion Plant complex. The first paper is a review of DOE`s conceptual design report for a mixed waste storage facility. This evaluation is to review the necessity of constructing a separate mixed waste storage facility. The structure is to be capable of receiving, weighing, sampling and the interim storage of wastes for a five year period beginning in 1996. The estimated cost is assessed at approximately $18 million. The review is to help comprehend and decide whether a new storage building is a feasible approach to the PGDP mixed waste storage problem or should some alternate approach be considered. The second paper reviews DOE`s conceptual design report for a solid waste landfill. This solid waste landfill evaluation is to compare costs and the necessity to provide a new landfill that would meet State of Kentucky regulations. The assessment considered funding for a ten year storage facility, but includes a review of other facility needs such as a radiation detection building, compactor/baler machinery, material handling equipment, along with other personnel and equipment storage buildings at a cost of approximately $4.1 million. The review is to help discern whether a landfill only or the addition of compaction equipment is prudent.

  14. Oxygen diffusion model of the mixed (U,Pu)O2 ± x: Assessment and application

    NASA Astrophysics Data System (ADS)

    Moore, Emily; Guéneau, Christine; Crocombette, Jean-Paul

    2017-03-01

    The uranium-plutonium (U,Pu)O2 ± x mixed oxide (MOX) is used as a nuclear fuel in some light water reactors and considered for future reactor generations. To gain insight into fuel restructuring, which occurs during the fuel lifetime as well as possible accident scenarios understanding of the thermodynamic and kinetic behavior is crucial. A comprehensive evaluation of thermo-kinetic properties is incorporated in a computational CALPHAD type model. The present DICTRA based model describes oxygen diffusion across the whole range of plutonium, uranium and oxygen compositions and temperatures by incorporating vacancy and interstitial migration pathways for oxygen. The self and chemical diffusion coefficients are assessed for the binary UO2 ± x and PuO2 - x systems and the description is extended to the ternary mixed oxide (U,Pu)O2 ± x by extrapolation. A simulation to validate the applicability of this model is considered.

  15. New Grid of Models for ELM WDs Including Element Diffusion and Rotational Mixing

    NASA Astrophysics Data System (ADS)

    Istrate, A. G.

    2017-03-01

    We present our latest results for the modelling of extremely low-mass white dwarfs (ELM WDs) in which, for the first time, we study the combined effects of rotational mixing and element diffusion. In particular, we investigate how their general properties, such as their evolutionary timescales, the hydrogen envelope mass and their surface composition are affected compared to the case when just element diffusion is included. The formation of ELM WDs through the LMXB channel in environments with different metallicities is modelled using the state-of-the-art stellar evolution code MESA. Rotational mixing is found to counteract the effect of gravitational settling in the surface of young, bloated ELM proto-WDs suggesting that it is the key process needed to explain the observed metals (especially calcium) abundances in their atmospheres.

  16. Patterns of gallium-67 scintigraphy in patients with acquired immunodeficiency syndrome and the AIDS related complex

    SciTech Connect

    Bitran, J.; Bekerman, C.; Weinstein, R.; Bennett, C.; Ryo, U.; Pinsky, S.

    1987-07-01

    Thirty-two patients with AIDS related complex (ARC) or acquired immunodeficiency syndrome (AIDS) underwent /sup 67/Ga scans as part of their evaluation. Three patterns of /sup 67/Ga biodistribution were found: lymph node uptake alone; diffuse pulmonary uptake; normal scan. Gallium-67 scans were useful in identifying clinically occult Pneumocystis carinii pneumonia in seven of 15 patients with ARC who were asymptomatic and had normal chest radiographs. Gallium scans are a useful ancillary procedure in the evaluation of patients with ARC or AIDS.

  17. The arbitrary order mixed mimetic finite difference method for the diffusion equation

    DOE PAGES

    Gyrya, Vitaliy; Lipnikov, Konstantin; Manzini, Gianmarco

    2016-05-01

    Here, we propose an arbitrary-order accurate mimetic finite difference (MFD) method for the approximation of diffusion problems in mixed form on unstructured polygonal and polyhedral meshes. As usual in the mimetic numerical technology, the method satisfies local consistency and stability conditions, which determines the accuracy and the well-posedness of the resulting approximation. The method also requires the definition of a high-order discrete divergence operator that is the discrete analog of the divergence operator and is acting on the degrees of freedom. The new family of mimetic methods is proved theoretically to be convergent and optimal error estimates for flux andmore » scalar variable are derived from the convergence analysis. A numerical experiment confirms the high-order accuracy of the method in solving diffusion problems with variable diffusion tensor. It is worth mentioning that the approximation of the scalar variable presents a superconvergence effect.« less

  18. The arbitrary order mixed mimetic finite difference method for the diffusion equation

    SciTech Connect

    Gyrya, Vitaliy; Lipnikov, Konstantin; Manzini, Gianmarco

    2016-05-01

    Here, we propose an arbitrary-order accurate mimetic finite difference (MFD) method for the approximation of diffusion problems in mixed form on unstructured polygonal and polyhedral meshes. As usual in the mimetic numerical technology, the method satisfies local consistency and stability conditions, which determines the accuracy and the well-posedness of the resulting approximation. The method also requires the definition of a high-order discrete divergence operator that is the discrete analog of the divergence operator and is acting on the degrees of freedom. The new family of mimetic methods is proved theoretically to be convergent and optimal error estimates for flux and scalar variable are derived from the convergence analysis. A numerical experiment confirms the high-order accuracy of the method in solving diffusion problems with variable diffusion tensor. It is worth mentioning that the approximation of the scalar variable presents a superconvergence effect.

  19. Primal-mixed formulations for reaction-diffusion systems on deforming domains

    NASA Astrophysics Data System (ADS)

    Ruiz-Baier, Ricardo

    2015-10-01

    We propose a finite element formulation for a coupled elasticity-reaction-diffusion system written in a fully Lagrangian form and governing the spatio-temporal interaction of species inside an elastic, or hyper-elastic body. A primal weak formulation is the baseline model for the reaction-diffusion system written in the deformed domain, and a finite element method with piecewise linear approximations is employed for its spatial discretization. On the other hand, the strain is introduced as mixed variable in the equations of elastodynamics, which in turn acts as coupling field needed to update the diffusion tensor of the modified reaction-diffusion system written in a deformed domain. The discrete mechanical problem yields a mixed finite element scheme based on row-wise Raviart-Thomas elements for stresses, Brezzi-Douglas-Marini elements for displacements, and piecewise constant pressure approximations. The application of the present framework in the study of several coupled biological systems on deforming geometries in two and three spatial dimensions is discussed, and some illustrative examples are provided and extensively analyzed.

  20. Enhanced nonlinear inspection of diffusion bonded interfaces using reflected non-collinear ultrasonic wave mixing

    NASA Astrophysics Data System (ADS)

    Zhang, Ziyin; Nagy, Peter B.; Hassan, Waled

    2016-02-01

    Ultrasonic wave mixing has shown promising potential for assessing otherwise hidden subtle imperfections in imperfect diffusion bonds between Ti-6Al-4V components. When interrogating a diffusion bonded specimen using non-collinear shear wave mixing, both bulk and interface nonlinearity will contribute to the transmitted nonlinear signal. Although a recent study has shown that changing the transducer alignment can suppress the intrinsic nonlinearity of the surrounding material to some extent so that the interface nonlinearity could be detected more selectively, it is still difficult to distinguish different levels of bond quality based on the detected transmitted signal only. Analytical and numerical studies showed that an imperfect interface generates the same amount of nonlinear displacement in the reflected and transmitted fields. In this study, we used the reflected nonlinear interface signature to characterize diffusion bonded interfaces. Our results indicate that it is better to use the reflected nonlinear interface signature to assess the bond quality, which is in agreement with our previous analytical and numerical predictions. However, the observed random phase of the reflected signature indicates that existing nonlinear interface models are insufficient for accurately describing the nonlinear interaction of shear incident waves with high-quality diffusion bonded interfaces.

  1. Horizontal mixing of Great Barrier Reef waters: Offshore diffusivity determined from radium isotope distribution

    NASA Astrophysics Data System (ADS)

    Hancock, Gary J.; Webster, Ian. T.; Stieglitz, Thomas C.

    2006-12-01

    The Great Barrier Reef (GBR), northern Australia, is the largest coral reef system in the world and provides habitat for highly diverse tropical marine ecosystems. Mixing in the coastal waters of the GBR is an important parameter influencing the health of these ecosystems. We have used the distribution of the four naturally occurring radium isotopes to determine the rate of mixing of nearshore waters of the central part of the GBR lagoon with water from the Coral Sea. The observed radium distribution is modeled using a one-dimensional diffusion model. The model improves on previous radium offshore mixing models by incorporating the benthic flux of radium diffusing across the sediment-water interface and offshore changes in water column depth. We find that the inner lagoon diffusivity (<20 km offshore) is best estimated using the short-lived isotopes 224Ra and 223Ra. The concordance of Kx estimated using the two different isotopes and the apparent consistency between measured riverine inflows to the lagoon and inflows inferred from the modeled salinity distribution provide confidence in the results. The mean value of Kx for the inner lagoon region of the southern central zone between latitudes 15.8°S and 19.0°S (265 ± 36 m2 s-1) is more than twice that in the northern central zone (14.3°S to 15.8°S). This difference likely reflects the different reef matrix density in the two zones. The distribution of the longer-lived isotope 228Ra indicates more rapid mixing in the middle and outer lagoon. These results indicate that central GBR water within 20 km of coast is flushed with outer lagoon water on a timescale of 18-45 days, with the flushing time increasing northward.

  2. Unity and diversity in mixing: Stretching, diffusion, breakup, and aggregation in chaotic flows

    SciTech Connect

    Ottino, J.M. )

    1991-05-01

    Experiments and theory have produced a reasonably good qualitative understanding of the evolution of chaotic mixing of passive tracers, especially in two-dimensional time-periodic flow fields. Such an understanding forms a fabric for the evolution of breakup, aggregation, and diffusion-controlled reactions in more complex flows. These systems can be viewed as a population of microstructures'' whose behavior is dictated by iterations of a chaotic flow; microstructures break, diffuse, and aggregate, causing the population to evolve in space and time. This paper presents simple physical models for such processes. Self-similarity is common to all the problems; examples arise in the context of the distribution of stretchings within chaotic flows, in the asymptotic evolution of diffusion-reaction processes at striation thickness scales, in the equilibrium distribution of drop sizes generated upon mixing of immiscible fluids, in the equations describing mean-field kinetics of coagulation, in the sequence of actions necessary for the destruction of islands in two-dimensional flow, and in the fractal structure of clusters produced upon aggregation in chaotic flows.

  3. Understanding the mixing process in 3D microfluidic nozzle/diffuser systems: simulations and experiments

    NASA Astrophysics Data System (ADS)

    Sayah, Abdeljalil; Gijs, Martin A. M.

    2016-11-01

    We characterise computationally and experimentally a three-dimensional (3D) microfluidic passive mixer for various Reynolds numbers ranging from 1 to 100, corresponding to primary flow rates of 10-870 µl min-1. The 3D mixing channel is composed of multiple curved segments: circular arcs situated in the substrate plane and curved nozzle/diffuser elements normal to the substrate plane. Numerical simulation provides a detailed understanding of the mixing mechanism resulting from the geometrical topology of the mixer. These Comsol software-based simulations reveal the development of two secondary flows perpendicular to the primary flow: a swirling flow resulting from tangential injection of the flow into the nozzle holes and Dean vortices present in the circular arcs. These phenomena are particularly important at a Reynolds number larger than 30, where mixing occurs by chaotic advection. Experimentally, the 3D mixer is fabricated in a monolithic glass substrate by powder blasting machining, exploiting eroding powder beams at various angles of impact with respect to the substrate plane. Experimental mixing was characterised using two coloured dyes, showing nearly perfect mixing for a microfluidic footprint of the order of a few mm2, in good agreement with the simulations.

  4. ATOMIC DIFFUSION AND MIXING IN OLD STARS. III. ANALYSIS OF NGC 6397 STARS UNDER NEW CONSTRAINTS

    SciTech Connect

    Nordlander, T.; Korn, A. J.; Richard, O.; Lind, K.

    2012-07-01

    We have previously reported on chemical abundance trends with evolutionary state in the globular cluster NGC 6397 discovered in analyses of spectra taken with FLAMES at the Very Large Telescope. Here, we reinvestigate the FLAMES-UVES sample of 18 stars, ranging from just above the turnoff point to the red giant branch below the bump. Inspired by new calibrations of the infrared flux method, we adopt a set of hotter temperature scales. Chemical abundances are determined for six elements (Li, Mg, Ca, Ti, Cr, and Fe). Signatures of cluster-internal pollution are identified and corrected for in the analysis of Mg. On the modified temperature scales, evolutionary trends in the abundances of Mg and Fe are found to be significant at the 2{sigma} and 3{sigma} levels, respectively. The detailed evolution of abundances for all six elements agrees with theoretical isochrones, calculated with effects of atomic diffusion and a weak to moderately strong efficiency of turbulent mixing. The age of these models is compatible with the external determination from the white dwarf cooling sequence. We find that the abundance analysis cannot be reconciled with the strong turbulent-mixing efficiency inferred elsewhere for halo field stars. A weak mixing efficiency reproduces observations best, indicating a diffusion-corrected primordial lithium abundance of log {epsilon}(Li) = 2.57 {+-} 0.10. At 1.2{sigma}, this value agrees well with Wilkinson Microwave Anisotropy Probe calibrated big bang nucleosynthesis predictions.

  5. Electrokinetic mixing at high zeta potentials: ionic size effects on cross stream diffusion.

    PubMed

    Ahmadian Yazdi, Alireza; Sadeghi, Arman; Saidi, Mohammad Hassan

    2015-03-15

    The electrokinetic phenomena at high zeta potentials may show several unique features which are not normally observed. One of these features is the ionic size (steric) effect associated with the solutions of high ionic concentration. In the present work, attention is given to the influences of finite ionic size on the cross stream diffusion process in an electrokinetically actuated Y-shaped micromixer. The method consists of a finite difference based numerical approach for non-uniform grid which is applied to the dimensionless form of the governing equations, including the modified Poisson-Boltzmann equation. The results reveal that, neglecting the ionic size at high zeta potentials gives rise to the overestimation of the mixing length, because the steric effects retard liquid flow, thereby enhancing the mixing efficiency. The importance of steric effects is found to be more intense for channels of smaller width to height ratio. It is also observed that, in sharp contrast to the conditions that the ions are treated as point charges, increasing the zeta potential improves the cross stream diffusion when incorporating the ionic size. Moreover, increasing the EDL thickness decreases the mixing length, whereas the opposite is true for the channel aspect ratio.

  6. Structure and ionic diffusion of alkaline-earth ions in mixed cation glasses

    SciTech Connect

    Konstantinou, Konstantinos; Sushko, Petr; Duffy, Dorothy M.

    2015-08-15

    A series of mixed cation silicate glasses of the composition A2O – 2MO – 4SiO2, with A=Li,Na,K and M=Ca,Sr,Ba has been investigated by means of molecular dynamics simulations in order to understand the effect of the nature of the cations on the mobility of the alkaline-earth ions within the glass network. The size of the alkaline-earth cation was found to affect the inter-atomic distances, the coordination number distributions and the bond angle distributions , whereas the medium-range order was almost unaffected by the type of the cation. All the alkaline-earth cations contribute to lower vibrational frequencies but it is observed that that there is a shift to smaller frequencies and the vibrational density of states distribution gets narrower as the size of the alkaline-earth increases. The results from our modeling for the ionic diffusion of the alkaline-earth cations are in a qualitative agreement with the experimental observations in that there is a distinct correlation between the activation energy for diffusion of alkaline earth-ions and the cation radii ratio. An asymmetrical linear behavior in the diffusion activation energy with increasing size difference is observed. The results can be described on the basis of a theoretical model that relates the diffusion activation energy to the electrostatic interactions of the cations with the oxygens and the elastic deformation of the silicate network.

  7. Effect of mixing on reaction-diffusion kinetics for protein hydrogel-based microchips.

    PubMed

    Zubtsov, D A; Ivanov, S M; Rubina, A Yu; Dementieva, E I; Chechetkin, V R; Zasedatelev, A S

    2006-03-09

    Protein hydrogel-based microchips are being developed for high-throughput evaluation of the concentrations and activities of various proteins. To shorten the time of analysis, the reaction-diffusion kinetics on gel microchips should be accelerated. Here we present the results of the experimental and theoretical analysis of the reaction-diffusion kinetics enforced by mixing with peristaltic pump. The experiments were carried out on gel-based protein microchips with immobilized antibodies under the conditions utilized for on-chip immunoassay. The dependence of fluorescence signals at saturation and corresponding saturation times on the concentrations of immobilized antibodies and antigen in solution proved to be in good agreement with theoretical predictions. It is shown that the enhancement of transport with peristaltic pump results in more than five-fold acceleration of binding kinetics. Our results suggest useful criteria for the optimal conditions for assays on gel microchips to balance high sensitivity and rapid fluorescence saturation kinetics.

  8. A coupling strategy for nonlocal and local diffusion models with mixed volume constraints and boundary conditions

    SciTech Connect

    D'Elia, Marta; Perego, Mauro; Bochev, Pavel B.; Littlewood, David John

    2015-12-21

    We develop and analyze an optimization-based method for the coupling of nonlocal and local diffusion problems with mixed volume constraints and boundary conditions. The approach formulates the coupling as a control problem where the states are the solutions of the nonlocal and local equations, the objective is to minimize their mismatch on the overlap of the nonlocal and local domains, and the controls are virtual volume constraints and boundary conditions. When some assumptions on the kernel functions hold, we prove that the resulting optimization problem is well-posed and discuss its implementation using Sandia’s agile software components toolkit. As a result, the latter provides the groundwork for the development of engineering analysis tools, while numerical results for nonlocal diffusion in three-dimensions illustrate key properties of the optimization-based coupling method.

  9. A coupling strategy for nonlocal and local diffusion models with mixed volume constraints and boundary conditions

    DOE PAGES

    D'Elia, Marta; Perego, Mauro; Bochev, Pavel B.; ...

    2015-12-21

    We develop and analyze an optimization-based method for the coupling of nonlocal and local diffusion problems with mixed volume constraints and boundary conditions. The approach formulates the coupling as a control problem where the states are the solutions of the nonlocal and local equations, the objective is to minimize their mismatch on the overlap of the nonlocal and local domains, and the controls are virtual volume constraints and boundary conditions. When some assumptions on the kernel functions hold, we prove that the resulting optimization problem is well-posed and discuss its implementation using Sandia’s agile software components toolkit. As a result,more » the latter provides the groundwork for the development of engineering analysis tools, while numerical results for nonlocal diffusion in three-dimensions illustrate key properties of the optimization-based coupling method.« less

  10. Shell Model for Atomistic Simulation of Lithium Diffusion in Mixed Mn/Ti Oxides

    SciTech Connect

    Kerisit, Sebastien N.; Chaka, Anne M.; Droubay, Timothy C.; Ilton, Eugene S.

    2014-10-23

    Mixed Mn/Ti oxides present attractive physicochemical properties such as their ability to accommodate Li for application in Li-ion batteries. In this work, atomic parameters for Mn were developed to extend an existing shell model of the Li-Ti-O system and allow simulations of pure and lithiated Mn and mixed Mn/Ti oxide polymorphs. The shell model yielded good agreement with experimentally-derived structures (i.e. lattice parameters and inter-atomic distances) and represented an improvement over existing potential models. The shell model was employed in molecular dynamics (MD) simulations of Li diffusion in the 1×1 c direction channels of LixMn1 yTiyO2 with the rutile structure, where 0 ≤ x ≤ 0.25 and 0 ≤ y ≤ 1. In the infinite dilution limit, the arrangement of Mn and Ti ions in the lattice was found to have a significant effect on the activation energy for Li diffusion in the c channels due to the destabilization of half of the interstitial octahedral sites. Anomalous diffusion was demonstrated for Li concentrations as low as x = 0.125, with a single Li ion positioned in every other c channel. Further increase in Li concentration showed not only the substantial effect of Li-Li repulsive interactions on Li mobility but also their influence on the time dependence of Li diffusion. The results of the MD simulations can inform intrinsic structure-property relationships for the rational design of improved electrode materials for Li-ion batteries.

  11. [Component analysis of complex mixed solution based on multidimensional diffuse reflectance spectroscopy].

    PubMed

    Li, Gang; Xiong, Chan; Zhao, Li-ying; Lin, Ling; Tong, Ying; Zhang, Bao-ju

    2012-02-01

    In the present paper, the authors proposed a method for component analysis of complex mixed solutions based on multidimensional diffuse reflectance spectroscopy by analyzing the information carried by spectrum signals from various optical properties of various components of the analyte. The experiment instrument was designed with supercontinuum laser source, the motorized precision translation stage and the spectrometer. The Intralipid-20% was taken as an analyte, and was diluted over a range of 1%-20% in distilled water. The diffuse reflectance spectrum signal was measured at 24 points within the distance of 1.5-13 mm (at an interval of 0.5 mm) above the incidence point. The partial least squares algorithm model was used to perform a modeling and forecasting analysis for the spectral analysis data collected from single-point and multi-point. The results showed that the most accurate calibration model was created by the spectral data acquired from the nearest 1-13 points above the incident point; the most accurate prediction model was created by the spectral signal acquired from the nearest 1-7 points above the incident point. It was proved that multidimensional diffuse reflectance spectroscopy can improve the spectral signal to noise ratio. Compared with the traditional spectrum technology using a single optical property such as absorbance or reflectance, this method increased the impact of scattering characteristics of the analyte. So the use of a variety of optical properties of the analytes can make an improvement of the accuracy of the modeling and forecasting, and also provide a basis for component analysis of the complex mixed solution based on multidimensional diffuse reflectance spectroscopy.

  12. Evaluation of molten lead mixing in sodium coolant by diffusion for application to PAHR. [LMFBR

    SciTech Connect

    Chawla, T.C.; Pedersen, D.R.; Leaf, G.; Minkowycz, W.J.

    1983-01-01

    In post-accident heat removal (PAHR) applications the use of a lead slab is being considered for protecting a porous bed of steel shots in ex-vessel cavity from direct impingement of molten steel or fuel upon vessel failure following a hypothetical core dissembly accident in an LMFBR. The porous bed is provided to increase coolability of the fuel debris by the sodium coolant. The objectives of the present study are (1) to determine melting rates of lead slabs of various thicknesses in contact with sodium coolant and (2) to evaluate the extent of penetration and mixing rates of molten lead into sodium coolant by molecular diffusion alone.

  13. Clouding tracing: Visualization of the mixing of fluid elements in convection-diffusion systems

    NASA Technical Reports Server (NTRS)

    Ma, Kwan-Liu; Smith, Philip J.

    1993-01-01

    This paper describes a highly interactive method for computer visualization of the basic physical process of dispersion and mixing of fluid elements in convection-diffusion systems. It is based on transforming the vector field from a traditionally Eulerian reference frame into a Lagrangian reference frame. Fluid elements are traced through the vector field for the mean path as well as the statistical dispersion of the fluid elements about the mean position by using added scalar information about the root mean square value of the vector field and its Lagrangian time scale. In this way, clouds of fluid elements are traced and are not just mean paths. We have used this method to visualize the simulation of an industrial incinerator to help identify mechanisms for poor mixing.

  14. Epigenetic regulation of HIV, AIDS, and AIDS-related malignancies.

    PubMed

    Verma, Mukesh

    2015-01-01

    Although epigenetics is not a new field, its implications for acquired immunodeficiency syndrome (AIDS) research have not been explored fully. To develop therapeutic and preventive approaches against the human immunodeficiency virus (HIV) and AIDS, it is essential to understand the mechanisms of interaction between the virus and the host, involvement of genetic and epigenetic mechanisms, characterization of viral reservoirs, and factors influencing the latency of the virus. Both methylation of viral genes and histone modifications contribute to initiating and maintaining latency and, depending on the context, triggering viral gene repression or expression. This chapter discusses progress made at the National Institutes of Health (NIH), recommendations from the International AIDS Society Scientific Working Group on HIV Cure, and underlying epigenetic regulation. A number of epigenetic inhibitors have shown potential in treating AIDS-related malignancies. Epigenetic drugs approved by the US Food and Drug Administration and their implications for the eradication of HIV/AIDS and AIDS-related malignancies also are discussed.Past and current progress in developing treatments and understanding the molecular mechanisms of AIDS and HIV infection has greatly improved patient survival. However, increased survival has been coupled with the development of cancer at higher rates than those observed among the HIV/AIDS-negative population. During the early days of the AIDS epidemic, the most frequent AIDS-defining malignancies were Kaposi's sarcoma and non-Hodgkin lymphoma (NHL). Now, with increased survival as the result of widespread use in the developed world of highly active antiretroviral therapy (HAART), non-AIDS defining cancers (i.e., anal, skin, and lung cancers, and Hodgkin disease) are on the increase in HIV-infected populations. The current status of AIDS-related malignancies also is discussed.

  15. Microstructure Imaging of Crossing (MIX) White Matter Fibers from diffusion MRI

    PubMed Central

    Farooq, Hamza; Xu, Junqian; Nam, Jung Who; Keefe, Daniel F.; Yacoub, Essa; Georgiou, Tryphon; Lenglet, Christophe

    2016-01-01

    Diffusion MRI (dMRI) reveals microstructural features of the brain white matter by quantifying the anisotropic diffusion of water molecules within axonal bundles. Yet, identifying features such as axonal orientation dispersion, density, diameter, etc., in complex white matter fiber configurations (e.g. crossings) has proved challenging. Besides optimized data acquisition and advanced biophysical models, computational procedures to fit such models to the data are critical. However, these procedures have been largely overlooked by the dMRI microstructure community and new, more versatile, approaches are needed to solve complex biophysical model fitting problems. Existing methods are limited to models assuming single fiber orientation, relevant to limited brain areas like the corpus callosum, or multiple orientations but without the ability to extract detailed microstructural features. Here, we introduce a new and versatile optimization technique (MIX), which enables microstructure imaging of crossing white matter fibers. We provide a MATLAB implementation of MIX, and demonstrate its applicability to general microstructure models in fiber crossings using synthetic as well as ex-vivo and in-vivo brain data. PMID:27982056

  16. Older female caregivers and HIV/AIDS-related secondary stigma in rural South Africa.

    PubMed

    Ogunmefun, Catherine; Gilbert, Leah; Schatz, Enid

    2011-03-01

    South Africa's HIV/AIDS epidemic poses a major public health threat with multi-faceted harmful impacts and 'socially complex' outcomes. While some outcomes relate to structural issues, others stem from society's attitudinal milieu. Due to negative attitudes toward People Living with HIV/AIDS, stigmatisation mars their own experience and often extends to those close to them, in particular their caregivers. Many of the caregivers in South Africa are older women; thus, older women are the focus of this paper, which aims to examine HIV/AIDS-related stigma from their perspective. This paper explores secondary stigma as a socio-cultural impact of HIV/AIDS through repeated semistructured interviews with 60 women aged 50-75 in the MRC/Wits Rural Public Health and Health Transitions Unit research site (Agincourt), many of whom had cared for a family member with HIV/AIDS. Respondents' narratives reveal that many older persons attribute high rates of death in their community to young persons' lack of respect for societal norms and traditions. The findings illustrate the forms and expressions of HIV/AIDS-related secondary stigma and their impacts on older female caregivers. The types of secondary stigma experienced by the respondents include physical stigma in the form of isolation and separation from family members; social stigma in the form of voyeurism and social isolation; and verbal stigma in the form of being gossiped about, finger-pointing and jeering at them. Despite mixed reports about community responses toward infected and affected people, HIV/AIDS-related stigma remains a cause for concern, as evidenced by the reports of older women in this study.

  17. Relative role of convective and diffusive mixing in the miscible Rayleigh-Taylor instability in porous media

    NASA Astrophysics Data System (ADS)

    Gopalakrishnan, S. S.; Carballido-Landeira, J.; De Wit, A.; Knaepen, B.

    2017-01-01

    The relative role of convection and diffusion is characterized both numerically and experimentally for porous media flows due to a Rayleigh-Taylor instability of a horizontal interface between two miscible solutions in the gravity field. We show that, though globally convection dominates over diffusion during the nonlinear regime, diffusion can locally be as important as convection and even dominates over lateral convection far away from the fingertips. Our experimental and numerical computations of the temporal evolution of the mixing length, the width of the fingers, and their wavelength are in good agreement and show that the lateral evolution of fingers is governed by diffusion.

  18. Photodynamic therapy for treatment of AIDS-related mucocutaneous Kaposi's sarcoma (Invited Paper)

    NASA Astrophysics Data System (ADS)

    Schweitzer, Vanessa G.

    1992-06-01

    Since 1975, Phase I/II studies have demonstrated the successfulness of hematoporphyrin derivative photodynamic therapy (PDT) in the treatment of various malignancies of the skin, eye, bladder, lung, and head and neck. Moreover, in 1981 two cases of traditional Western cutaneous Kaposi's sarcoma (TKS) have been treated with photodynamic therapy with both early and late complete response. To date, attempts to cure and palliation of the more aggressive AIDS-related oral Kaposi's sarcoma with conventional radiation, chemotherapy or immunotherapy, or surgical excision have been limited and often associated with debilitating mucositis and further immunosuppression. Certain aspects of photodynamic therapy may be efficacious for treatment of mucocutaneous Kaposi's sarcoma: (1) the selective retention of hematoporphyrin derivative by neoplastic lesions (endothelial cell tumors); (2) a tumor- specific cytotoxic agent (i.e., free oxygen radical); (3) absence of systemic toxicity from immunosuppression; (4) the potential for retreatment without increasing side effects; and (5) porphyrin-mediated photoinactivation of enveloped viruses. Herein presented are seven cases of AIDS-related KS (EKS) with diffuse, superficial, and nodular mucocutaneous lesions treated with dihematoporphyrin derivative and photodynamic therapy with subsequent dramatic early partial and complete responses.

  19. Vortex-scalar element calculations of a diffusion flame stabilized on a plane mixing layer

    NASA Technical Reports Server (NTRS)

    Ghoniem, Ahmed F.; Givi, Peyman

    1987-01-01

    The vortex-scalar element method, a scheme which utilizes vortex elements to discretize the region of high vorticity and scalar elements to represent species or temperature fields, is utilized in the numerical simulations of a two-dimensional reacting mixing layer. Computations are performed for a diffusion flame at high Reynolds and Peclet numbers without resorting to turbulence models. In the nonreacting flow, the mean and fluctuation profiles of a conserved scalar show good agreement with experimental measurements. Results for the reacting flow indicate that for temperature independent kinetics, the chemical reaction begins immediately downstream of the splitter plate where mixing starts. Results for the reacting flow with Arrhenius kinetics show an ignition delay, which depends on reactant temperature, before significant chemical reaction occurs. Harmonic forcing changes the structure of the layer, and concomitantly the rates of mixing and reaction, in accordance with experimental results. Strong stretch within the braids in the nonequilibrium kinetics case causes local flame quenching due to the temperature drop associated with the large convective fluxes.

  20. The Impact of Multiple AIDS-Related Bereavement in the Gay Male Population.

    ERIC Educational Resources Information Center

    Springer, Carrie A.; Lease, Suzanne H.

    2000-01-01

    Discusses the issue of AIDS-related loss and the correlative epidemic of AIDS-related bereavement. Notes that individuals are considered particularly susceptible to such bereavement when loss is multiple, as is often the case in the gay male population. Reviews the research exploring the impact of AIDS-related loss and suggests counseling…

  1. On the role of mass diffusion and fluid dynamics in the dissipation of chunk mix

    SciTech Connect

    Cloutman, L D

    1999-03-01

    When numerically simulating multicomponent turbulent flows, subgrid-scale diffusion of chemical species requires closure. This mixing of chemical species at the molecular level dissipates concentration uctuations, which limits possible demixing and affects other pro- cesses such as energy transport and reaction rates at the subgrid level. We discuss some of the physical processes that reduce small chunks of a heavy material in a light gas or plasma to a mixture at the atomic level. Preliminary direct numerical simulations of these processes are presented using the dissipation of small spheres of heavy gas in a light gas as an archetypal process in turbulent micromixing in multicomponent ows, including classical uid instabilities and shock ejecta. We use a detailed approach for the diffusion process, directly solving the Stefan-Maxwell equations for the mass fluxes. We discuss the dissipa- tion of a 24µm sphere of xenon in helium in three different flow regimes, and we present suggestions for future work intended as input to improved subgrid-scale turbulence models.

  2. Verification of high-order mixed FEM solution of transient Magnetic diffusion problems

    SciTech Connect

    Rieben, R; White, D A

    2005-05-12

    We develop and present high order mixed finite element discretizations of the time dependent electromagnetic diffusion equations for solving eddy current problems on 3D unstructured grids. The discretizations are based on high order H(grad), H(curl) and H(div) conforming finite element spaces combined with an implicit and unconditionally stable generalized Crank-Nicholson time differencing method. We develop three separate electromagnetic diffusion formulations, namely the E (electric field), H (magnetic field) and the A-{phi} (potential) formulations. For each formulation, we also provide a consistent procedure for computing the secondary variables F (current flux density) and B (magnetic flux density), as these fields are required for the computation of electromagnetic force and heating terms. We verify the error convergence properties of each formulation via a series of numerical experiments on canonical problems with known analytic solutions. The key result is that the different formulations are equally accurate, even for the secondary variables J and B, and hence the choice of which formulation to use depends mostly upon relevance of the Natural and Essential boundary conditions to the problem of interest. In addition, we highlight issues with numerical verification of finite element methods which can lead to false conclusions on the accuracy of the methods.

  3. Diffusion-flame ignition by shock-wave impingement on a supersonic mixing layer

    NASA Astrophysics Data System (ADS)

    Sanchez, Antonio L.; Huete, Cesar; Williams, Forman A.; Urzay, Javier

    2015-11-01

    Ignition in a supersonic mixing layer interacting with an oblique shock wave is investigated analytically and numerically under conditions such that the post-shock flow remains supersonic. The study requires consideration of the structure of the post-shock ignition kernel that is found to exist around the point of maximum temperature, which may be located either near the edge of the mixing layer or in its interior. The ignition kernel displays a balance between the rates of chemical reaction and of post-shock flow expansion, including the acoustic interactions of the chemical heat release with the shock wave, leading to increased front curvature. The analysis, which adopts a one-step chemistry model with large activation energy, indicates that ignition develops as a fold bifurcation, the turning point in the diagram of the peak perturbation induced by the chemical reaction as a function of the Damköhler number providing the critical conditions for ignition. Subsequent to ignition the lead shock will rapidly be transformed into a thin detonation on the fuel side of the ignition kernel, and, under suitable conditions, a deflagration may extend far downstream, along with the diffusion flame that must separate the rich and lean reaction products.

  4. Mixed variational potentials and inherent symmetries of the Cahn–Hilliard theory of diffusive phase separation

    PubMed Central

    Miehe, C.; Hildebrand, F. E.; Böger, L.

    2014-01-01

    This work shows that the Cahn–Hilliard theory of diffusive phase separation is related to an intrinsic mixed variational principle that determines the rate of concentration and the chemical potential. The principle characterizes a canonically compact model structure, where the two balances involved for the species content and microforce appear as the Euler equations of a variational statement. The existence of the variational principle underlines an inherent symmetry in the two-field representation of the Cahn–Hilliard theory. This can be exploited in the numerical implementation by the construction of time- and space-discrete incremental potentials, which fully determine the update problems of typical time-stepping procedures. The mixed variational principles provide the most fundamental approach to the finite-element solution of the Cahn–Hilliard equation based on low-order basis functions, leading to monolithic symmetric algebraic systems of iterative update procedures based on a linearization of the nonlinear problem. They induce in a natural format the choice of symmetric solvers for Newton-type iterative updates, providing a speed-up and reduction of data storage when compared with non-symmetric implementations. In this sense, the potentials developed are believed to be fundamental ingredients to a deeper understanding of the Cahn–Hilliard theory. PMID:24711722

  5. Atomic diffusion and mixing in old stars. VI. The lithium content of M30

    NASA Astrophysics Data System (ADS)

    Gruyters, Pieter; Lind, Karin; Richard, Olivier; Grundahl, Frank; Asplund, Martin; Casagrande, Luca; Charbonnel, Corinne; Milone, Antonino; Primas, Francesca; Korn, Andreas J.

    2016-05-01

    Context. The prediction of the Planck-constrained primordial lithium abundance in the Universe is in discordance with the observed Li abundances in warm Population II dwarf and subgiant stars. Among the physically best motivated ideas, it has been suggested that this discrepancy can be alleviated if the stars observed today had undergone photospheric depletion of lithium. Aims: The cause of this depletion is investigated by accurately tracing the behaviour of the lithium abundances as a function of effective temperature. Globular clusters are ideal laboratories for such an abundance analysis as the relative stellar parameters of their stars can be precisely determined. Methods: We performed a homogeneous chemical abundance analysis of 144 stars in the metal-poor globular cluster M30, ranging from the cluster turnoff point to the tip of the red giant branch. Non-local thermal equilibrium (NLTE) abundances for Li, Ca, and Fe were derived where possible by fitting spectra obtained with VLT/FLAMES-GIRAFFE using the quantitative-spectroscopy package SME. Stellar parameters were derived by matching isochrones to the observed V vs. V-I colour-magnitude diagram. Independent effective temperatures were obtained from automated profile fitting of the Balmer lines and by applying colour-Teff calibrations to the broadband photometry. Results: Li abundances of the turnoff and early subgiant stars form a thin plateau that is broken off abruptly in the middle of the SGB as a result of the onset of Li dilution caused by the first dredge-up. Abundance trends with effective temperature for Fe and Ca are observed and compared to predictions from stellar structure models including atomic diffusion and ad hoc additional mixing below the surface convection zone. The comparison shows that the stars in M30 are affected by atomic diffusion and additional mixing, but we were unable to determine the efficiency of the additional mixing precisely. This is the fourth globular cluster (after NGC

  6. Solution processable broadband transparent mixed metal oxide nanofilm optical coatings via substrate diffusion doping

    NASA Astrophysics Data System (ADS)

    Glynn, Colm; Aureau, Damien; Collins, Gillian; O'Hanlon, Sally; Etcheberry, Arnaud; O'Dwyer, Colm

    2015-11-01

    Devices composed of transparent materials, particularly those utilizing metal oxides, are of significant interest due to increased demand from industry for higher fidelity transparent thin film transistors, photovoltaics and a myriad of other optoelectronic devices and optics that require more cost-effective and simplified processing techniques for functional oxides and coatings. Here, we report a facile solution processed technique for the formation of a transparent thin film through an inter-diffusion process involving substrate dopant species at a range of low annealing temperatures compatible with processing conditions required by many state-of-the-art devices. The inter-diffusion process facilitates the movement of Si, Na and O species from the substrate into the as-deposited vanadium oxide thin film forming a composite fully transparent V0.0352O0.547Si0.4078Na0.01. Thin film X-ray diffraction and Raman scattering spectroscopy show the crystalline component of the structure to be α-NaVO3 within a glassy matrix. This optical coating exhibits high broadband transparency, exceeding 90-97% absolute transmission across the UV-to-NIR spectral range, while having low roughness and free of surface defects and pinholes. The production of transparent films for advanced optoelectronic devices, optical coatings, and low- or high-k oxides is important for planar or complex shaped optics or surfaces. It provides opportunities for doping metal oxides to ternary, quaternary or other mixed metal oxides on glass, encapsulants or other substrates that facilitate diffusional movement of dopant species.Devices composed of transparent materials, particularly those utilizing metal oxides, are of significant interest due to increased demand from industry for higher fidelity transparent thin film transistors, photovoltaics and a myriad of other optoelectronic devices and optics that require more cost-effective and simplified processing techniques for functional oxides and coatings

  7. Intravenous Chemotherapy or Oral Chemotherapy in Treating Patients With Previously Untreated Stage III-IV HIV-Associated Non-Hodgkin Lymphoma

    ClinicalTrials.gov

    2016-09-29

    AIDS-related Diffuse Large Cell Lymphoma; AIDS-related Diffuse Mixed Cell Lymphoma; AIDS-related Diffuse Small Cleaved Cell Lymphoma; AIDS-related Immunoblastic Large Cell Lymphoma; AIDS-related Lymphoblastic Lymphoma; AIDS-related Peripheral/Systemic Lymphoma; AIDS-related Small Noncleaved Cell Lymphoma; Stage III AIDS-related Lymphoma; Stage IV AIDS-related Lymphoma

  8. Mixed cellulose ester filter as a separator for air-diffusion cathode microbial fuel cells.

    PubMed

    Wang, Zejie; Lim, Bongsu

    2017-04-01

    Separator is important to prevent bio-contamination of the catalyst layer of air-diffusion cathode microbial fuel cells (MFCs). Mixed cellulose ester filter (MCEF) was examined as a separator for an air-cathode MFC in the present study. The MCEF-MFC produced a maximum power density of 780.7 ± 18.7 mW/m(2), which was comparable to 770.9 ± 35.9 mW/m(2) of MFC with Nafion membrane (NFM) as a separator. Long-term examination demonstrated a more stable performance of the MCEF-MFC than NFM-MFC. After 25 cycles, the maximum voltage of the MCEF-MFC decreased by only 1.3% from 425.1 ± 4.3 mV (initial 5 cycles) to 419.5 ± 2.3 mV (last 5 cycles). However, it was decreased by 9.1% from 424.8 ± 5.7 to 386 ± 2.5 mV for the NFM-MFC. The coulombic efficiency (CE) of the MCEF-MFC did not change (from 3.11 ± 0.09% to 3.13 ± 0.02%), while it decreased by 9.12% from 3.18 ± 0.04% to 2.89 ± 0.02% for the NFM-MFC. The MCEF separator was with less biofouling than the NFM separator over 60 days' operation, which might be the reason for the more table long-term performance of the MCEF-MFC. The results demonstrated that MCEF was feasible as a separator to set up good-performing and cost-effective air-diffusion cathode MFC.

  9. Solution processable broadband transparent mixed metal oxide nanofilm optical coatings via substrate diffusion doping.

    PubMed

    Glynn, Colm; Aureau, Damien; Collins, Gillian; O'Hanlon, Sally; Etcheberry, Arnaud; O'Dwyer, Colm

    2015-12-21

    Devices composed of transparent materials, particularly those utilizing metal oxides, are of significant interest due to increased demand from industry for higher fidelity transparent thin film transistors, photovoltaics and a myriad of other optoelectronic devices and optics that require more cost-effective and simplified processing techniques for functional oxides and coatings. Here, we report a facile solution processed technique for the formation of a transparent thin film through an inter-diffusion process involving substrate dopant species at a range of low annealing temperatures compatible with processing conditions required by many state-of-the-art devices. The inter-diffusion process facilitates the movement of Si, Na and O species from the substrate into the as-deposited vanadium oxide thin film forming a composite fully transparent V0.0352O0.547Si0.4078Na0.01. Thin film X-ray diffraction and Raman scattering spectroscopy show the crystalline component of the structure to be α-NaVO3 within a glassy matrix. This optical coating exhibits high broadband transparency, exceeding 90-97% absolute transmission across the UV-to-NIR spectral range, while having low roughness and free of surface defects and pinholes. The production of transparent films for advanced optoelectronic devices, optical coatings, and low- or high-k oxides is important for planar or complex shaped optics or surfaces. It provides opportunities for doping metal oxides to ternary, quaternary or other mixed metal oxides on glass, encapsulants or other substrates that facilitate diffusional movement of dopant species.

  10. Surface tensions, viscosities, and diffusion constants in mixed component single aerosol particles

    NASA Astrophysics Data System (ADS)

    Bzdek, Bryan; Marshall, Frances; Song, Young-Chul; Haddrell, Allen; Reid, Jonathan

    2016-04-01

    Surface tension and viscosity are important aerosol properties but are challenging to measure on individual particles owing to their small size and mass. Aerosol viscosity impacts semivolatile partitioning from the aerosol phase, molecular diffusion in the bulk of the particle, and reaction kinetics. Aerosol surface tension impacts how particles activate to serve as cloud condensation nuclei. Knowledge of these properties and how they change under different conditions hinders accurate modelling of aerosol physical state and atmospheric impacts. We present measurements made using holographic optical tweezers to directly determine the viscosity and surface tension of optically trapped droplets containing ~1-4 picolitres of material (corresponding to radii of ~5-10 micrometres). Two droplets are captured in the experimental setup, equilibrated to a relative humidity, and coalesced through manipulation of the relative trap positions. The moment of coalescence is captured using camera imaging as well as from elastically backscattered light connected to an oscilloscope. For lower viscosity droplets, the relaxation in droplet shape to a sphere follows the form of a damped oscillator and gives the surface tension and viscosity. For high viscosity droplets, the relaxation results in a slow merging of the two droplets to form a sphere and the timescale of that process permits determination of viscosity. We show that droplet viscosity and surface tension can be quantitatively determined to within <10% of the expected value for low viscosity droplets and to better than 1 order of magnitude for high viscosity droplets. Examples illustrating how properties such as surface tension can change in response to environmental conditions will be discussed. Finally, a study of the relationship between viscosity, diffusion constants, vapour pressures, and reactive uptake coefficients for a mixed component aerosol undergoing oxidation and volatilisation will be discussed.

  11. Self-diffusion of ions in Nafion-117 membrane having mixed ionic composition.

    PubMed

    Chaudhury, Sanhita; Agarwal, Chhavi; Pandey, A K; Goswami, A

    2012-02-09

    The self-diffusion coefficients (SDCs) of Na(+), Cs(+), and Ba(2+) have been determined in Nafion-117 membrane having mixed cationic compositions. Membranes with different proportions of Na(+)-Cs(+), Cs(+)-Ba(2+), Na(+)-Ba(2+), and Ag(+)-Ba(2+) cations have been prepared by equilibrating with solutions containing different ratios of these cations. The SDCs of the cations (D(Na), D(Cs), D(Ba)) and the ionic compositions of the membrane have been determined using a radiotracer method. For the Na-Cs and Cs-Ba systems, the SDCs of the cations have been found to be independent of the ionic compositions of the membrane. In the case of the Na-Ba system, D(Na) does not change with ionic composition, while D(Ba) has been found to be strongly dependent on the ionic composition of the membrane and decreases continuously with increasing Na(+) content in the membrane. Similar results have also been obtained for D(Ba) in the case of the Ag-Ba system. The specific conductivities (κ(imp)) of the membrane in mixed cationic forms have also been obtained from ac impedance measurement and compared with that (κ(cal)) calculated from the SDC data. For the Na-Ba system, the increment of κ(imp) with increase in the Na(+) content of the membrane has been found to be parabolic, whereas for the Na-Cs system the increment is linear. The reason behind the different behaviors for different types of ionic systems has been qualitatively explained based on different transport pathways of the cations in the membrane.

  12. Electron Energization and Mixing Observed by MMS in the Vicinity of an Electron Diffusion Region During Magnetopause Reconnection

    NASA Technical Reports Server (NTRS)

    Chen, Li-Jen; Hesse, Michael; Wang, Shan; Gershman, Daniel; Ergun, Robert; Pollock, Craig; Torbert, Roy; Bessho, Naoki; Daughton, William; Dorelli, John; Giles, Barbara; Moore, Thomas

    2016-01-01

    Measurements from the Magnetospheric Multiscale (MMS) mission are reported to show distinct features of electron energization and mixing in the diffusion region of the terrestrial magnetopause reconnection. At the ion jet and magnetic field reversals, distribution functions exhibiting signatures of accelerated meandering electrons are observed at an electron out-of-plane flow peak. The meandering signatures manifested as triangular and crescent structures are established features of the electron diffusion region (EDR). Effects of meandering electrons on the electric field normal to the reconnection layer are detected. Parallel acceleration and mixing of the inflowing electrons with exhaust electrons shape the exhaust flow pattern. In the EDR vicinity, the measured distribution functions indicate that locally, the electron energization and mixing physics is captured by two-dimensional reconnection, yet to account for the simultaneous four-point measurements, translational invariant in the third dimension must be violated on the ion-skin-depth scale.

  13. [Successful treatment with hyper-CVAD and highly active anti-retroviral therapy (HAART) for AIDS-related Burkitt lymphoma].

    PubMed

    Suzuki, Kazuhito; Nakazato, Tomonori; Sanada, Yukinari; Mihara, Ai; Tachikawa, Natsuo; Kurai, Hanako; Yoshimura, Yukihiro; Hayashi, Hiroyuki; Yoshida, Sachiko; Kakimoto, Tsunayuki

    2010-03-01

    A 38-year-old man was admitted to our hospital because of continuous fever and right facial palsy. He was diagnosed as HIV positive. Abdominal CT scan showed a large mass in the ascending colon. Gallium scintigraphy demonstrated increased uptake in the ascending colon. Colonoscopy was performed and histological examination of the colon tumor revealed Burkitt's lymphoma (BL). He received highly active anti-retroviral therapy (HAART) and his facial palsy improved. Because CD4 count was significantly low at 31/microl, he was treated with dose-adjusted EPOCH (DA-EPOCH) combined with HAART. Although the tumor was decreased in size by DA-EPOCH, we changed to the combination of hyper-CVAD/MTX-Ara-C alternating therapy with HAART in order to increase dose intensity. Six cycles of hyper-CVAD/MTX-Ara-C were performed and complete remission was obtained. In the HAART era, the survival of patients with AIDS-related diffuse large cell lymphoma (DLCL) improved dramatically, whereas the survival of similarly treated patients with AIDS-related BL remained poor. Our case suggests that intensive chemotherapy with hyper-CVAD/MTX-Ara-C combined with HAART may be well tolerated and effective in AIDS-related BL.

  14. 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.

  15. Measurements of exciton diffusion by degenerate four-wave mixing in CdS1-xSex

    NASA Astrophysics Data System (ADS)

    Schwab, H.; Pantke, K.-H.; Hvam, J. M.; Klingshirn, C.

    1992-09-01

    We performed transient-grating experiments to study the diffusion of excitons in CdS1-xSex mixed crystals. The decay of the initially created exciton density grating is well described for t<=1 ns by a stretched-exponential function. For later times this decay changes over to a behavior that is well fitted by a simple exponential function. During resonant excitation of the localized states, we find the diffusion coefficient (D) to be considerably smaller than in the binary compounds CdSe and CdS. At 4.2 K, D is below our experimental resolution which is about 0.025 cm2/s. With increasing lattice temperature (Tlattice) the diffusion coefficient increases. It was therefore possible to prove, in a diffusion experiment, that at Tlattice<=5 K the excitons are localized, while the exciton-phonon interaction leads to a delocalization and thus to the onset of diffusion. It was possible to deduce the diffusion coefficient of the extended excitons as well as the energetic position of the mobility edge.

  16. Diffusion of major and trace elements in natural silicate melts as a tool to investigate timescales in magma mixing

    NASA Astrophysics Data System (ADS)

    González-García, Diego; Zezza, Angela; Behrens, Harald; Vetere, Francesco; Petrelli, Maurizio; Morgavi, Daniele; Perugini, Diego

    2016-04-01

    New melt injection into a shallow magma chamber is regarded as one of the potential triggers for explosive volcanic eruptions. Chemical diffusion occurring between the two mixing melts is a time-dependent process, and thus has the potential to shed light on the timescales involved in magma mixing events leading to an eruption. In order to achieve this, a complete database of diffusion coefficients in natural melts is a necessary prerequisite. We have carried out a set of 12 diffusion couple experiments in order to determine diffusion coefficients (D) of major and trace elements in two natural silicate melts. Two end-members from the Vulcano island (Aeolian archipelago, Italy) have been chosen for the experiments: a shoshonite (Vulcanello lava platform) and a rhyolitic obsidian (Pietre Cotte lava flow, La Fossa cone). Glasses from each end-member with added water contents of 0 wt%, 1 wt% and 2 wt% were produced in an Internally Heated Pressure Vessel (IHPV). Two glass cylinders with similar water content but different base composition are inserted in Au-Pd capsules and experiments are run in the IHPV at 1200° C with pressure from 0.5 to 3 kbar. Experiment capsules are rapidly quenched and analyzed by FTIR, EPMA and LA-ICP-MS for H2O, major and trace elements, respectively, along 2 mm linear profiles extending across the interface. A Boltzmann-Matano approach is used to obtain concentration-dependent diffusivities. The obtained concentration-distance profiles are asymmetric and extend deeper into the shoshonite relative to the rhyolite, indicating that diffusion is slower in the latter. Results show that diffusivities are notably accelerated by the presence of H2O in the melt. Experiments performed by using water-free glass show diffusivities one order of magnitude lower compared to glasses containing up to 2 wt% H2O. The effect of pressure, in the investigated range, is negligible and falls within measurement error. Among major elements, Si and Ti are the slowest

  17. Measuring HIV/AIDS-Related Stigma across South Africa: A Versatile and Multidimensional Scale

    ERIC Educational Resources Information Center

    Smith, Edward A.; Miller, Jacqueline A.; Newsome, Valerie; Sofolahan, Yewande A.; Airhihenbuwa, Collins O.

    2014-01-01

    Reducing HIV/AIDS-related stigma is critical in the fight against HIV/AIDS. Although national campaigns and prevention programs have been implemented across South Africa to address this critical concern, assessing the impact of these initiatives is difficult as it requires that measurement of HIV/AIDS-related stigma is uniform and comparable…

  18. Atomic diffusion and mixing in old stars. V. A deeper look into the globular cluster NGC 6752

    NASA Astrophysics Data System (ADS)

    Gruyters, Pieter; Nordlander, Thomas; Korn, Andreas J.

    2014-07-01

    Context. Abundance trends in heavier elements with evolutionary phase have been shown to exist in the globular cluster NGC 6752 ([Fe / H] = -1.6). These trends are a result of atomic diffusion and additional (non-convective) mixing. Studying such trends can provide us with important constraints on the extent to which diffusion modifies the internal structure and surface abundances of solar-type, metal-poor stars. Aims: Taking advantage of a larger data sample, we investigate the reality and the size of these abundance trends and address questions and potential biases associated with the various stellar populations that make up NGC 6752. Methods: We perform an abundance analysis by combining photometric and spectroscopic data of 194 stars located between the turnoff point and the base of the red giant branch. Stellar parameters are derived from uvby Strömgren photometry. Using the quantitative-spectroscopy package SME, stellar surface abundances for light elements such as Li, Na, Mg, Al, and Si as well as heavier elements such as Ca, Ti, and Fe are derived in an automated way by fitting synthetic spectra to individual lines in the stellar spectra, obtained with the VLT/FLAMES-GIRAFFE spectrograph. Results: Based on uvby Strömgren photometry, we are able to separate three stellar populations in NGC 6752 along the evolutionary sequence from the base of the red giant branch down to the turnoff point. We find weak systematic abundance trends with evolutionary phase for Ca, Ti, and Fe which are best explained by stellar-structure models including atomic diffusion with efficient additional mixing. We derive a new value for the initial lithium abundance of NGC 6752 after correcting for the effect of atomic diffusion and additional mixing which falls slightly below the predicted standard BBN value. Conclusions: We find three stellar populations by combining photometric and spectroscopic data of 194 stars in the globular cluster NGC 6752. Abundance trends for groups of

  19. Study of HIV/AIDS-related knowledge among junior high-school students in Shanghai, China.

    PubMed

    Cai, Y; Shi, R; Li, S; Xu, G; Huang, H

    2012-03-01

    The aim of this study was to assess the HIV/AIDS-related knowledge among junior high-school students in Shanghai, China, and the factors influencing this knowledge. A cross-sectional study was conducted in 20 middle schools of two districts by a cluster-stratified selection procedure in Shanghai, China. The 2432 sampled students, aged from 11.1 to 16.7 years, completed a self-administered questionnaire of HIV/AIDS prevention. The results showed that the overall correct rate of HIV/AIDS-related knowledge was 62%. Using multivariable logistic regression analysis, we found that the main factors influencing HIV/AIDS-related knowledge among junior high school students were the type of school (odds ratio [OR] = 1.641), age (OR = 1.727), whether the student was a single child in the family (OR = 1.389), whether the student had previous HIV/AIDS-related education experience (OR = 2.003) and whether the student had ever discussed HIV/AIDS with their parents (OR = 1.282). The results indicate that HIV/AIDS-related knowledge among Shanghai junior high school students is not high enough, and more attention needs to be paid to enhance HIV/AIDS-related knowledge, especially among younger students from common type schools without HIV/AIDS-related education experience. We encourage Chinese parents to get involved in their children's HIV/AIDS prevention education.

  20. [AIDS related lymphomas: Histopathological subtypes and association with Epstein Barr virus and Human Herpes virus type-8].

    PubMed

    Corti, Marcelo; de Dios Soler, Marcela; Bare, Patricia; Villafañe, María F; De Tezanos Pinto, Miguel; Perez Bianco, Raúl; Narbaitz, Marina

    2010-01-01

    Non-Hodgkin lymphomas (NHL) of the B-cell type are the second most common neoplasm among patients with human immunodeficiency virus (HIV) infection and AIDS. Here, we evaluated 48 cases of AIDS-related lymphomas (ARL) diagnosed at the Histopathological Division of the Instituto de Investigaciones Hematológicas of the National Academy of Medicine. Five were females and 43 were males with a median of age of 37 years at the time of the diagnosis. Micrometer sections were prepared and stained with hematoxilin-eosin; immunohistochemical examination for the presence of Epstein-Barr virus (EBV) was carried out in 48/48 cases. Additionally, biotinilated oligonucleotides were used to determine the presence of DNA of the Human Herpes virus type-8 (HHV-8) in 14/14 biopsy smears corresponding to plasmablastic lymphomas (PL). All were fenotype B cell lymphomas with an aggressive course and advanced neoplasm disease at the time of diagnosis. Virological findings showed the strong association between EBV and AIDS-related NHL. According to the histopathological subtype, the EBV genome was detected in 16/21 (76%) diffuse large B cell lymphomas, 1/3 Burkitt lymphoma and 3/4 (75%) of primary central nervous system lymphomas. Globally, EBV genome was detected in 20/28 NHL of this series. Detection of HHV-8 was negative in all cases of PL. Hodgkin lymphoma were more frequent in males 18/20 (90%), with an aggressive clinical course and a significant predominance of the subtypes associated with worse prognosis (90% of cases). We detected a significant association between EBV and HL (90% of cases). We consider that all cases of AIDS related lymphomas should be assessed for the presence of EBV because its presence may play a role in the prognosis.

  1. Drift-Diffusion Studies of Compositional Morphology in Bulk Heterojunctions: The Role of the Mixed Phase in Photovoltaic Performance

    NASA Astrophysics Data System (ADS)

    Finck, Benjamin Y.; Schwartz, Benjamin J.

    2016-11-01

    The active layers of most organic photovoltaic (OPV) devices are constructed from a blend of two organic compounds. The two materials spontaneously segregate into pure-component phases during device fabrication, creating a bicontinuous network of conduction pathways that are selective for electron or hole charge carriers. The morphological distribution of these materials within the active layer has long been known to influence charge transport and resulting device performance. In addition to the two pure-component phases present in these devices, a third, mixed-composition phase exists at the interface between the two pure phases. The exact effects of this mixed-composition phase on OPV device performance are not well understood, although it is argued that the presence of a mixed phase is necessary for optimal device operation. In this paper, we probe the effects of having a mixed-composition interfacial phase on the performance and charge-transport characteristics of OPV devices through a series of drift-diffusion model simulations. We start with set of model morphologies with only pure-component phases and then introduce an interfacial mixed phase in a controllable fashion. Our simulations show that a modest amount of mixing initially improves device efficiency by reducing the tortuosity of the device's conduction pathways and easing morphological traps. However, an excessive amount of mixing can actually degrade high-conductivity pathways, reducing photovoltaic performance. The point at which mixing switches from being beneficial to detrimental to OPV performance depends on the average domain size of a device's morphology. Devices with smaller feature sizes are more susceptible to the debilitating effects of overmixing, so that the presence of a mixed phase may either raise power-conversion efficiency by as much as 100% or lower it by as much as 50%, depending on the average domain size and the extent of mixing. These trends suggest that variations in the amount

  2. An experimental study iof the diffusion of C and O in calcite in mixed Co2-H2O fluids.

    SciTech Connect

    Labotka, Theodore C.; Cole, David; Fayek, Mostafa; Chacko, Thomas {nmn}

    2011-01-01

    The diffusivity of C and O in calcite in mixed CO2-H2O fluid was determined over the range in xCO2 from 1.0 to about 0.2 at 700 C, 100 MPa, with selected experiments conducted at pressures to 250 MPa and temperatures of 600 and 800 C. The diffusivity of C, DC, varies little with xCO2, although there is some evidence for a slight increase in DC from 5 10 18 to 5 10 17 cm2/s with decreasing xCO2. Our data and those of others are consistent with a model for DC 1/fCO2. Despite the large uncertainty, we observed that the diffusivity of O, DO, increases from 2 10 16 to 5 10 14 cm2/s with xCO2 decreasing from 1.0 to 0. There is a good correlation at 700 C between log DO and log fH2O regardless of the total pressure, matching the observations of previous workers. The data are consistent with a simple two-component model for the diffusion of O in calcite, one component for diffusion in the presence of CO2 and one in the presence of H2O: DO = DOCO2 + DOH2O aH2O. The activity of H2O is relative to the fugacity at 100 MPa, 700 C. DOCO2 is 3.45 10 16, and DOH2O is 3.8 10 14 cm2/s. The data indicate that the rate of diffusion of C and O in calcite is controlled by reactions at the surface of calcite. Adsorption of H2O and the creation of vacancies at the surface account for the dependence of the diffusivity on the fugacity of the fluid components. There is little evidence that H itself diffuses into calcite. With this model and the values of DO in pure CO2 (Labotka et al. 2000) and in pure H2O (Farver 1994), the value of DO is predicted over the temperature range 600 800 C and pH2O up to 300 MPa, the range of the data. Calculated closure temperatures for diffusive exchange of O between calcite and fluid are reduced by about 150 C in the presence of an aqueous fluid.

  3. Oxygen self-diffusion in polycrystalline uranium-plutonium mixed oxide U0.55Pu0.45O2

    NASA Astrophysics Data System (ADS)

    Vauchy, Romain; Robisson, Anne-Charlotte; Bienvenu, Philippe; Roure, Ingrid; Hodaj, Fiqiri; Garcia, Philippe

    2015-12-01

    Atomic transport properties in uranium-plutonium mixed oxides U1-yPuyO2 are of essential concern because they impact numerous aspects of their physicochemical behavior at all stages of the fuel cycle. In this paper, we report oxygen tracer diffusion coefficients in homogeneous U0.55Pu0.45O2 mixed oxide. The study is based on tracer diffusion coefficient measurements obtained using Secondary Ion Mass Spectrometry (SIMS) following diffusion annealing involving gas-solid 18O/16O isotopic exchange. As for other fundamental material properties governed by the nature and behavior of point defects, we show that a careful study of tracer diffusion coefficients as a function of oxygen partial pressure and temperature is liable to provide insight into prevailing diffusion mechanisms. Under the conditions studied in this work, it appears that oxygen diffusion is vacancy mediated.

  4. Ignition and structure of a laminar diffusion flame in a compressible mixing layer with finite rate chemistry

    NASA Technical Reports Server (NTRS)

    Grosch, C. E.; Jackson, T. L.

    1991-01-01

    The ignition and structure of a reacting compressible mixing layer is considered using finite rate chemistry lying between two streams of reactants with different freestream speeds and temperatures. Numerical integration of the governing equations show that the structure of the reacting flow can be quite complicated depending on the magnitude of the Zeldovich number. An analysis of both the ignition a diffusion flame regimes is presented using a combination of large Zeldovich number asymptotics and numerics. This allows to analyze the behavior of these regimes as a function of the parameters of the problem.

  5. Ignition and structure of a laminar diffusion flame in a compressible mixing layer with finite rate chemistry

    NASA Technical Reports Server (NTRS)

    Grosch, C. E.; Jackson, T. L.

    1991-01-01

    The ignition and structure of a reacting compressible mixing layer is considered using finite rate chemistry lying between two streams of reactants with different freestream speeds and temperatures. Numerical integration of the governing equations show that the structure of the reacting flow can be quite complicated depending on the magnitude of the Zeldovich number. An analysis of both the ignition and diffusion flame regimes is presented using a combination of large Zeldovich number asymptotics and numerics. This allows to analyze the behavior of these regimes as a function of the parameters of the problem.

  6. Shear, dilation, and swap: Mixing in the limit of fast diffusion

    NASA Astrophysics Data System (ADS)

    Brassart, Laurence; Liu, Qihan; Suo, Zhigang

    2016-11-01

    Molecules of different species mix by local rearrangement and long-range migration. Under certain conditions, the molecules are partially jammed: they rearrange slowly, but migrate fast. Here we formulate a theory of mixing when the long-range migration of molecules is fast, and the local rearrangement of molecules sets the time needed for mixing. In this limit, the time needed for mixing is independent of the length scale of inhomogeneity. We identify three modes of local rearrangement: shear, dilation, and swap. All three modes break and form intermolecular bonds. We place the three modes on equal footing, as distinct, concurrent, nonequilibrium processes. Our theory thus removes the bias that assumes local chemical equilibrium but allows the nonequilibrium process of shear. We propose a kinetic model of four independent viscosity-like coefficients, and a thermodynamic model of ideal mixing of molecules of unequal sizes and nonzero volume of mixing. We illustrate the theory with several examples, including the development of growth stress, the homogenization of a bilayer, and the disappearance of an inclusion in a matrix.

  7. Morphologic studies of lymphocyte nuclei in follicular and diffuse mixed small- and large-cell (lymphocytic-histiocytic) lymphoma.

    PubMed

    Dardick, I; Caldwell, D R; Moher, D; Jabi, M

    1988-08-01

    Twelve examples of mixed small- and large-cell lymphoma (eight follicular, one follicular and diffuse, and three diffuse) were investigated morphometrically using plastic-embedded tissue in order to study nuclear characteristics of lymphocyte populations in this form of non-Hodgkin's lymphoma (NHL) and to test morphologic bases for current NHL classification systems. This study illustrates that there are many inaccuracies, illusions, and misconceptions in the morphologic criteria currently used to classify mixed small- and large-cell lymphoma. A principal finding was that lymphocyte nuclear profiles in mixed-cell lymphomas tend to be smaller in size (P less than .005) and more irregular in shape (P = .0001) than the morphologically similar counterparts in germinal centers of lymph nodes with reactive hyperplasia. Intercase comparison of mixed small- and large-cell lymphomas revealed a considerable range of mean nuclear area values, some of which were within the size range of normal, small lymphocytes. At the magnifications used for morphometric assessment, a high proportion of lymphocyte nuclear profiles had shallow invaginations, but only a limited number of profiles (4% to 14%) had deep (cleaved) indentations. Contrary to current definitions for this subtype of NHL, lymphocytes with "small" nuclei had the same proportion of the nuclear diameter occupied by nuclear invaginations as lymphocytes with "large" nuclei and, in fact, mean nuclear invagination depth was shallower in "small" nuclei than in "large" nuclei. Furthermore, regardless of whether it is nuclear area or shape that is evaluated, lymphocytes in mixed-cell lymphoma do not separate into two populations of small-cleaved and large noncleaved cells. Morphometry reveals that only four of the 12 examples of mixed small- and large-cell lymphoma had a proportion of the lymphocytes in the size range of fully transformed germinal center lymphocytes that exceeded 25%, and none of the cases approached 50% even

  8. Raman measurement of mixing and finite-rate chemistry in a supersonic hydrogen-air diffusion flame

    SciTech Connect

    Cheng, T.S.; Wehrmeyer, J.A.; Pitz, R.W. . Dept. of Mechanical Engineering); Jarrett, O. Jr.; Northam, G.B. . Langley Research Center)

    1994-10-01

    Ultraviolet (UV) spontaneous vibrational Raman scattering and laser-induced predissociative fluorescence (LIPF) from a KrF excimer laser are combined to simultaneously measure temperature, major species concentrations (H[sub 2], O[sub 2], N[sub 2], H[sub 2]O), and OH radical concentration in a supersonic lifted co-flowing hydrogen-air diffusion flame. The axisymmetric flame is formed when a sonic jet of hydrogen mixes with a Mach 2 annular jet of vitiated air. Mean and rms profiles of temperature, species concentrations, and mixture fraction are obtained throughout the supersonic flame. Simultaneous measurements of the chemical species and temperature are compared with frozen chemistry and equilibrium chemistry limits to assess the local state of the mixing and chemistry. Upstream of the lifted flame base, a very small amount of reaction occurs form mixing with hot vitiated air. Downstream of the lifted flame base, strong turbulent mixing leads to sub equilibrium values of temperature and OH concentration. Due to the interaction of velocity and temperature in supersonic compressible flames, the fluctuations of temperature and species concentrations are found to be higher than subsonic flames. Farther downstream, slow three-body recombination reactions result in super equilibrium OH concentrations that depress temperatures below their equilibrium values.

  9. Properties of polyethylene glycol (23) lauryl ether with cetyltrimethylammonium bromide in mixed aqueous solutions studied by self-diffusion coefficient NMR.

    PubMed

    Gao, HongChang; Zhu, RongXian; Yang, XiaoYan; Mao, ShiZhen; Zhao, Sui; Yu, JiaYong; Du, YouRu

    2004-05-15

    NMR self-diffusion coefficient measurements have been used to study the properties of polyethylene glycol (23) lauryl ether (Brij-35) with cetyltrimethylammonium bromide (CTAB) in the mixed aqueous solutions with different mole fractions of CTAB. By fitting the self-diffusion coefficients to the two-state exchange model, the critical micelle concentrations of the two solutes in the mixed solutions (cmc*1 and cmc*2) were obtained. The critical mixed micelle concentrations (cmc*) were then evaluated by the sum of cmc*1 and cmc*2, which are in good agreement with the results measured by the surface tension method. The cmc* values are lower than those of the ideal case of mixing, which indicates that the behavior of the CTAB/Brij-35 system is nonideal. Moderate interactions between CTAB and Brij-35 in their mixtures can be deduced from the interaction parameters (betaM) based on the cmc* obtained by the NMR self-diffusion method. The compositions (x1) of the mixed micelles at different total surfactant concentrations were also evaluated. By using these results, a possible mechanism of mixed micellar formation and a picture of the formation of nonsimultaneous CTAB/Brij-35 binary mixed micelle were proposed. In contrast to the case of CTAB/TX-100 system, Brij-35 molecules have a tendency to form micelles first at any mole fraction of CTAB. The mixed micellar self-diffusion coefficients (Dm) increase slightly at lower CTAB molar ratios, and then speed up with increasing CTAB mole fraction.

  10. A novel approach for blood purification: mixed-matrix membranes combining diffusion and adsorption in one step.

    PubMed

    Tijink, Marlon S L; Wester, Maarten; Sun, Junfen; Saris, Anno; Bolhuis-Versteeg, Lydia A M; Saiful, Saiful; Joles, Jaap A; Borneman, Zandrie; Wessling, Matthias; Stamatialis, Dimitris F

    2012-07-01

    Hemodialysis is a commonly used blood purification technique in patients requiring kidney replacement therapy. Sorbents could increase uremic retention solute removal efficiency but, because of poor biocompatibility, their use is often limited to the treatment of patients with acute poisoning. This paper proposes a novel membrane concept for combining diffusion and adsorption of uremic retention solutes in one step: the so-called mixed-matrix membrane (MMM). In this concept, adsorptive particles are incorporated in a macro-porous membrane layer whereas an extra particle-free membrane layer is introduced on the blood-contacting side of the membrane to improve hemocompatibility and prevent particle release. These dual-layer mixed-matrix membranes have high clean-water permeance and high creatinine adsorption from creatinine model solutions. In human plasma, the removal of creatinine and of the protein-bound solute para-aminohippuric acid (PAH) by single and dual-layer membranes is in agreement with the removal achieved by the activated carbon particles alone, showing that under these experimental conditions the accessibility of the particles in the MMM is excellent. This study proves that the combination of diffusion and adsorption in a single step is possible and paves the way for the development of more efficient blood purification devices, excellently combining the advantages of both techniques.

  11. Direct molecular diffusion and micro-mixing for rapid dewatering of LiBr solution

    SciTech Connect

    Bigham, S; Isfahani, RN; Moghaddam, S

    2014-03-01

    A slow molecular diffusion rate often limits the desorption process of an absorbate molecule from a liquid absorbent. To enhance the desorption rate, the absorbent is often boiled to increase the liquid vapor interfacial area. However, the growth of bubbles generated during the nucleate boiling process still remains mass-diffusion limited. Here, it is shown that a desorption rate higher than that of boiling can be achieved, if the vapor absorbent interface is continuously replenished with the absorbate-rich solution to limit the concentration boundary layer growth. The study is conducted in a LiBr-water-solution, in which the water molecules' diffusion rate is quite slow. The manipulation of the vapor solution interface concentration distribution is enabled by the mechanical confinement of the solution flow within microchannels, using a hydrophobic vapor-venting membrane and the implementation of microstructures on the flow channel's bottom wall. The microstructures stretch and fold the laminar streamlines within the solution film and produce vortices. The vortices continuously replace the concentrated solution at the vapor solution interface with the water-rich solution brought from the bottom and middle of the flow channel. The physics of the process is described using a combination of experimental and numerical studies. Published by Elsevier Ltd.

  12. Passive scalars: Mixing, diffusion, and intermittency in helical and nonhelical rotating turbulence

    NASA Astrophysics Data System (ADS)

    Imazio, P. Rodriguez; Mininni, P. D.

    2017-03-01

    We use direct numerical simulations to compute structure functions, scaling exponents, probability density functions, and effective transport coefficients of passive scalars in turbulent rotating helical and nonhelical flows. We show that helicity affects the inertial range scaling of the velocity and of the passive scalar when rotation is present, with a spectral law consistent with ˜k⊥-1.4 for the passive scalar variance spectrum. This scaling law is consistent with a phenomenological argument [P. Rodriguez Imazio and P. D. Mininni, Phys. Rev. E 83, 066309 (2011), 10.1103/PhysRevE.83.066309] for rotating nonhelical flows, which follows directly from Kolmogorov-Obukhov scaling and states that if energy follows a E (k ) ˜k-n law, then the passive scalar variance follows a law V (k ) ˜k-nθ with nθ=(5 -n ) /2 . With the second-order scaling exponent obtained from this law, and using the Kraichnan model, we obtain anomalous scaling exponents for the passive scalar that are in good agreement with the numerical results. Multifractal intermittency models are also considered. Intermittency of the passive scalar is stronger than in the nonhelical rotating case, a result that is also confirmed by stronger non-Gaussian tails in the probability density functions of field increments. Finally, Fick's law is used to compute the effective diffusion coefficients in the directions parallel and perpendicular to rotation. Calculations indicate that horizontal diffusion decreases in the presence of helicity in rotating flows, while vertical diffusion increases. A simple mean field argument explains this behavior in terms of the amplitude of velocity fluctuations.

  13. Traditional beliefs about the cause of AIDS and AIDS-related stigma in South Africa.

    PubMed

    Kalichman, S C; Simbayi, L

    2004-07-01

    AIDS-related stigmas are pervasive in some segments of South African society and stigmas can impede efforts to promote voluntary counselling and testing and other HIV-AIDS prevention efforts. The current study examined associations among the belief that AIDS is caused by spirits and supernatural forces, AIDS-related knowledge and AIDS-related stigmas. A street intercept survey with 487 men and women living in a Black township in Cape Town, South Africa showed that 11% (n=54) believed that AIDS is caused by spirits and supernatural forces, 21% (n=105) were unsure if AIDS is caused by spirits and the supernatural, and 68% (n=355) did not believe that AIDS is caused by spirits and supernatural forces. Multiple logistic regression analyses controlling for participant age, gender, years of education and survey venue showed that people who believed HIV-AIDS is caused by spirits and the supernatural demonstrated significantly more misinformation about AIDS and were significantly more likely to endorse repulsion and social sanction stigmatizing beliefs against people living with HIV-AIDS. However, nearly all associations between beliefs that AIDS is caused by spirits and AIDS stigmas were non-significant when logistic regressions were repeated with AIDS-related knowledge included as a control variable. This finding suggests that relationships between traditional beliefs about the cause of HIV-AIDS and AIDS stigmas are mediated by AIDS-related knowledge. AIDS education efforts are urgently needed to reach people who hold traditional beliefs about AIDS to remedy AIDS stigmas.

  14. Unsteady magnetohydrodynamics mixed convection flow in a rotating medium with double diffusion

    SciTech Connect

    Jiann, Lim Yeou; Ismail, Zulkhibri; Khan, Ilyas; Shafie, Sharidan

    2015-05-15

    Exact solutions of an unsteady Magnetohydrodynamics (MHD) flow over an impulsively started vertical plate in a rotating medium are presented. The effects of thermal radiative and thermal diffusion on the fluid flow are also considered. The governing equations are modelled and solved for velocity, temperature and concentration using Laplace transforms technique. Expressions of velocity, temperature and concentration profiles are obtained and their numerical results are presented graphically. Skin friction, Sherwood number and Nusselt number are also computed and presented in tabular forms. The determined solutions can generate a large class of solutions as special cases corresponding to different motions with technical relevance. The results obtained herein may be used to verify the validation of obtained numerical solutions for more complicated fluid flow problems.

  15. New Insights into Tree Height Distribution Based on Mixed Effects Univariate Diffusion Processes

    PubMed Central

    Rupšys, Petras

    2016-01-01

    The aim of this paper is twofold: to introduce the mathematics of stochastic differential equations (SDEs) for forest dynamics modeling and to describe how such a model can be applied to aid our understanding of tree height distribution corresponding to a given diameter using the large dataset provided by the Lithuanian National Forest Inventory (LNFI). Tree height-diameter dynamics was examined with Ornstein-Uhlenbeck family mixed effects SDEs. Dynamics of a tree height, volume and their coefficients of variation, quantile regression curves of the tree height, and height-diameter ratio were demonstrated using newly developed tree height distributions for a given diameter. The parameters were estimated by considering a discrete sample of the diameter and height and by using an approximated maximum likelihood procedure. All models were evaluated using a validation dataset. The dataset provided by the LNFI (2006–2010) of Scots pine trees is used in this study to estimate parameters and validate our modeling technique. The verification indicated that the newly developed models are able to accurately capture the behavior of tree height distribution corresponding to a given diameter. All of the results were implemented in a MAPLE symbolic algebra system. PMID:28002500

  16. Child Abuse and Aids-Related Knowledge, Attitudes and Behavior among Adolescents in Zambia

    ERIC Educational Resources Information Center

    Slonim-Nevo, Vered; Mukuka, Lawrence

    2007-01-01

    Objective: To research the correlation between physical and sexual abuse by family members and AIDS-related knowledge, attitudes, self-efficacy and behavior among urban and rural adolescents in Zambia. Sample: The sample comprises 3,360 adolescents, aged 10-19, from urban and rural Zambia; 2,160 of them attended school, while 1,200 of them did…

  17. Exploring AIDS-Related Knowledge, Attitudes, and Behaviors of Female Mexican Migrant Workers.

    ERIC Educational Resources Information Center

    Organista, Pamela Balls; Organista, Kurt C.; Soloff, Pearl R.

    1998-01-01

    AIDS-related knowledge, attitudes, and behaviors were assessed among female migrant laborers (N=32). Results are reported regarding knowledge and beliefs about AIDS transmission, knowledge and beliefs about condom use, and actual use of condoms. Needs for health education and services, sexual power, and other implications of findings are…

  18. Confocal-based method for quantification of diffusion kinetics in microwell plates and its application for identifying a rapid mixing method for high-content/throughput screening.

    PubMed

    Song, Ok Ryul; Kim, Tae-Hee; Perrodon, Xavier; Lee, Changbok; Jeon, Hee Kyoung; Seghiri, Zahir; Kwon, Ho Jeong; Cechetto, Jonathan; Christophe, Thierry

    2010-02-01

    Rapid mixing in microplates is still an underappreciated challenge in screening assay development, particularly with the use of noncontact nanoliter liquid handlers. In high-content/throughput screening (HC/TS), fast and efficient mixing between compounds and cell culture medium is even more critical as biological kinetics dictates speed of mixing, usually within a few minutes. Moreover, mixing in HC/TS should be gentle enough to avoid any negative disruption in cell layer. Here the authors introduce a method to accurately quantify drop diffusion into a microplate well, independently of buffer, liquid handler, or dispensing protocol. This method was used to determine the effect of various mixing methods on the diffusion of a nanoliter drop of pure DMSO in aqueous buffer in 384-well plates. Rapid plate shaking and additional buffer addition were shown to be the most efficient and effective mixing methods for HC/TS. However, efficient mixing by plate shaking is limited by assay volume. Bulk addition shows fast and efficient mixing, without negative effects on cells. Moreover, this simple, fast, and inexpensive method can be easily adapted on any platform.

  19. Models of low-mass helium white dwarfs including gravitational settling, thermal and chemical diffusion, and rotational mixing

    NASA Astrophysics Data System (ADS)

    Istrate, A. G.; Marchant, P.; Tauris, T. M.; Langer, N.; Stancliffe, R. J.; Grassitelli, L.

    2016-10-01

    A large number of extremely low-mass helium white dwarfs (ELM WDs) have been discovered in recent years. The majority of them are found in close binary systems suggesting they are formed either through a common-envelope phase or via stable mass transfer in a low-mass X-ray binary (LMXB) or a cataclysmic variable (CV) system. Here, we investigate the formation of these objects through the LMXB channel with emphasis on the proto-WD evolution in environments with different metallicities. We study for the first time the combined effects of rotational mixing and element diffusion (e.g. gravitational settling, thermal and chemical diffusion) on the evolution of proto-WDs and on the cooling properties of the resulting WDs. We present state-of-the-art binary stellar evolution models computed with MESA for metallicities of Z = 0.02, 0.01, 0.001 and 0.0002, producing WDs with masses between 0.16-0.45 M⊙. Our results confirm that element diffusion plays a significant role in the evolution of proto-WDs that experience hydrogen shell flashes. The occurrence of these flashes produces a clear dichotomy in the cooling timescales of ELM WDs, which has important consequences e.g. for the age determination of binary millisecond pulsars. In addition, we confirm that the threshold mass at which this dichotomy occurs depends on metallicity. Rotational mixing is found to counteract the effect of gravitational settling in the surface layers of young, bloated ELM proto-WDs and therefore plays a key role in determining their surface chemical abundances, i.e. the observed presence of metals in their atmospheres. We predict that these proto-WDs have helium-rich envelopes through a significant part of their lifetime. This is of great importance as helium is a crucial ingredient in the driving of the κ-mechanism suggested for the newly observed ELM proto-WD pulsators. However, we find that the number of hydrogen shell flashes and, as a result, the hydrogen envelope mass at the beginning of

  20. Deep Pacific ventilation ages during the last deglaciation: Evaluating the influence of diffusive mixing and source region reservoir age

    NASA Astrophysics Data System (ADS)

    Lund, David C.

    2013-11-01

    Enhanced ventilation of the deep ocean during the last deglaciation may have caused the rise in atmospheric carbon dioxide that drove Earth's climate from a glacial to interglacial state. Recent results based on the projection age method, however, suggest the ventilation rate of the deep Pacific slowed during the deglaciation, opposite the expected pattern (Lund et al., 2011). Because the projection age method does not account for tracer diffusion (Adkins and Boyle, 1997) it can yield spurious results and therefore requires validation with alternative techniques. Here ventilation ages are determined using the transit-time equilibration-time distribution (TTD-ETD) method which explicitly accounts for diffusive mixing in the ocean interior (DeVries and Primeau, 2010). The overall time history of deep Pacific TTD-ETD and projection ages is very similar; both show a 1000-yr increase in ventilation age during Heinrich Stadial 1 (HS1; 14.5-17.5 kyr BP) and a 500-yr increase during the Younger Dryas (YD). The similarity is due in part to the use of projection age error estimates that take into account uncertainty in both calendar age and benthic 14C age. Centennial-scale offsets between the TTD-ETD and projection ages are due primarily to the different approaches used to estimate surface ocean radiocarbon content. Both the TTD-ETD and projection age results imply that the ventilation rate of the deep Pacific decreased during the deglaciation, opposite the pattern expected if Southern Ocean upwelling and enhanced meridional overturning drove outgassing of CO2 from the abyss. Variations in surface water reservoir age could cause an apparent shift in deep Pacific ventilation age but existing proxy records from the Southern Ocean appear to be inconsistent with such a driver.

  1. The sediment-water flux of HOCs due to "diffusion" or is there a well-mixed layer? If there is, does it matter?

    PubMed

    Lick, Wilbert

    2006-09-15

    In most present modeling of the sediment-water flux of hydrophobic organic chemicals (HOCs), the flux due to sediment erosion/deposition is described explicitly by means of a sediment transport model, while the remaining components of the flux (molecular diffusion, bioturbation, and groundwater flow) are lumped together and modeled as a "diffusive" flux. This diffusive flux is usually described by means of a mass transfer approximation with the implicit assumption of a well-mixed contaminant layer of thickness h in the sediments. On the basis of recent experiments and theoretical modeling, the justification forthis assumption and the quantification of this diffusive flux are discussed here. In particular, for HOCs with large partition coefficients, it is argued that a well-mixed layer often may not exist, and, when it does, it is slow to form; that h is difficult to define and even harder to quantify; and that, as far as long-term predictions (up to 100 years) of this diffusive flux are concerned, the exact value for h probably does not matter. What does matter are the magnitudes and time dependencies of each of the components of the flux and the interactions between the diffusive flux and the flux due to erosion/deposition.

  2. Investigation of the 4-Quadrant behaviour of a mixed flow diffuser pump with CFD-methods and test rig evaluation

    NASA Astrophysics Data System (ADS)

    Höller, S.; Benigni, H.; Jaberg, H.

    2016-11-01

    The complete pump characteristics including its 4-quadrant behaviour are of essential interest for off-design operations such as a pump trip. At this exceptional load case the pump enters the dissipation mode and moves further into the turbine mode while the direction of rotation and the flow direction will change. The time-consuming and expensive experimental investigation of the 4-quadrant behaviour requires a specific test rig, allowing the flow direction as well as the rotational direction of the investigated pump to be reverted. By measuring the pump performance (head and efficiency) at variable positive and negative discharge and rotation the complete pump characteristics are evaluated. Nowadays CFD- analysis allows for the reliable prediction of the hydraulic performance of a pump near the design point. However, abnormal operating conditions lead to complex and unsteady flow phenomena inside the pump. Besides steady-state calculations in the normal operating conditions quite comprehensive transient CFD-investigations are required to simulate the whole pump characteristics accurately. The present study focuses on the comparison of the results obtained on the test rig and by numerical methods and shows a remarkably good agreement between them. It can be shown that it is possible to reliably simulate the 4-quadrant behaviour of a mixed flow diffuser pump based on CFD-methods. Furthermore an exemplary waterhammer calculation shows the successful application of the numerically calculated 4- quadrant behaviour.

  3. Acculturation, alcohol consumption and AIDS-related risky sexual behavior among African American women.

    PubMed

    Hines, A M; Snowden, L R; Graves, K L

    1998-01-01

    The present study examined the relationship between acculturation, alcohol consumption and AIDS-related risky sexual behavior in a national probability sample of 533 African American women. Results indicated that women who were the heaviest drinkers were also the least acculturated. However, women most likely to engage in risky sexual behavior, including having multiple partners, being nonmonogamous or in a nonmonogamous relationship, and being nonmonogamous or in a nonmonogamous relationship and not using a condom consistently, were high in acculturation rather than low. Alcohol use proved related to risky sexual behavior when considered in conjunction with respondents' level of acculturation. Women at risk for contracting AIDS were not low acculturated African American women who drank heavily, but high acculturated African American women. Findings from this study extend our understanding of risk and contain implications for research and prevention efforts in the area of alcohol use and AIDS-related sexual behavior among African American women.

  4. Mirtazapine and mefloquine therapy for non-AIDS-related progressive multifocal leukoencephalopathy.

    PubMed

    Epperla, Narendranath; Medina-Flores, Rafael; Mazza, Joseph J; Yale, Steven H

    2014-12-01

    Progressive multifocal leukoencephalopathy (PML) is an opportunistic infection of the human nervous system caused by the JC virus. We report what is, to the best of our knowledge, the second reported case using a combination of mefloquine and mirtazapine in a patient with non-AIDS-related PML with a good clinical outcome. Conversely, the recent trial of mefloquine in 21 patients with AIDS and 3 without AIDS failed to show a reduction of JC viral DNA levels in the cerebral spinal fluid. However, the positive clinical response seen in our patient after the initiation of this combination therapy suggests that further studies in the form of randomized controlled trials for the treatment of non-AIDS-related PML are warranted.

  5. Social disparities, communication inequalities, and HIV/AIDS-related knowledge and attitudes in India.

    PubMed

    Ackerson, Leland K; Ramanadhan, Shoba; Arya, Monisha; Viswanath, Kasisomayajula

    2012-10-01

    Promoting awareness, increasing knowledge, and eliminating stigma is important for stopping the spread of HIV/AIDS. The relation of social determinants and communication inequalities with HIV/AIDS-related cognitive processes has not been studied previously in India. Gender-stratified Poisson regression models of 123,459 women and 73,908 men in the 2005-2006 National Family Health Survey were used to calculate relative risk estimates and 95% confidence intervals for these associations. Results indicated that there are significant inequalities in mass media use among different social classes. Education and wealth are strongly and positively associated with awareness of HIV/AIDS and knowledge about prevention and transmission of AIDS and negatively associated with HIV/AIDS-related stigma. These associations attenuated when use of various mass media types were added to the models with television showing the strongest effect. Mass media may be helpful in reducing social disparities in HIV/AIDS outcomes.

  6. Trends in AIDS incidence and AIDS-related mortality in British Columbia between 1981 and 2013

    PubMed Central

    Lima, Viviane D.; Lourenço, Lillian; Yip, Benita; Hogg, Robert S.; Phillips, Peter; Montaner, Julio S.G.

    2015-01-01

    Background Appropriate use of highly active antiretroviral therapy (HAART) can markedly decrease the risk of progression to acquired immunodeficiency syndrome (AIDS) and of premature mortality. We aimed to characterize the trends between 1981 and 2013 in AIDS-defining illnesses (ADIs) and in the number AIDS-related deaths in British Columbia (BC), Canada. Methods We included data of 3550 HIV-positive individuals, aged 19 years or older, from different administrative databases in BC. We estimated the relative risk of developing an ADI over time using a Negative Binomial model, and we investigated trends in the percentage of all deaths associated with AIDS using generalized additive models. Findings The number of ADIs has decreased dramatically to its lowest level in 2013. The peak of the AIDS epidemic in BC happened in 1994 with 696 ADIs being reported (rate 42 ADIs per 100 person-years). Since 1997, the number of ADIs decreased from 253 (rate 7 per 100 person-years) to 84 cases in 2013 (rate 1 per 100 person-years) (p-value equals to zero for the trend in the number of ADIs). We have also shown that out of 22 ADIs considered, only PCP maintained its prominent ranking (albeit with much reduced overall prevalence). Finally, we observed that over time very few deaths were related to AIDS-related causes, especially in the most recent years. Interpretation We showed that the number of new ADIs and AIDS-related mortality have been decreasing rapidly over time in BC. These results provide further evidence that integrated comprehensive free programs that facilitate testing, and deliver treatment and care to this population can be effective in markedly decreasing AIDS-related morbidity and mortality, thus suggesting that controlling and eventually ending AIDS is possible. Funding The British Columbia Ministry of Health, the US National Institutes of Health, the US National Institute on Drug Abuse, the Canadian Institutes of Health Research, and the Michael Institute for

  7. The parallel-antiparallel signal difference in double-wave-vector diffusion-weighted MR at short mixing times: A phase evolution perspective

    NASA Astrophysics Data System (ADS)

    Finsterbusch, Jürgen

    2011-01-01

    Experiments with two diffusion weightings applied in direct succession in a single acquisition, so-called double- or two-wave-vector diffusion-weighting (DWV) experiments at short mixing times, have been shown to be a promising tool to estimate cell or compartment sizes, e.g. in living tissue. The basic theory for such experiments predicts that the signal decays for parallel and antiparallel wave vector orientations differ by a factor of three for small wave vectors. This seems to be surprising because in standard, single-wave-vector experiments the polarity of the diffusion weighting has no influence on the signal attenuation. Thus, the question how this difference can be understood more pictorially is often raised. In this rather educational manuscript, the phase evolution during a DWV experiment for simple geometries, e.g. diffusion between parallel, impermeable planes oriented perpendicular to the wave vectors, is considered step-by-step and demonstrates how the signal difference develops. Considering the populations of the phase distributions obtained, the factor of three between the signal decays which is predicted by the theory can be reproduced. Furthermore, the intermediate signal decay for orthogonal wave vector orientations can be derived when investigating diffusion in a box. Thus, the presented “phase gymnastics” approach may help to understand the signal modulation observed in DWV experiments at short mixing times.

  8. Kinetics of Sr and Nd exchange in silicate liquids: Theory, experiments, and applications to uphill diffusion, isotopic equilibration, and irreversible mixing of magmas

    SciTech Connect

    Lesher, C.E.

    1994-05-10

    Diffusion coefficients that govern chemical and isotopic exchange of Sr and Nd were determined from compositional profiles developed between juxtaposed anhydrous basaltic and rhyolitic liquids. Analysis of simple diffusion couples involving isotopically enriched and normal tholeiitic basalt and metaluminous rhyolite recover Sr and Nd self-diffusion coefficients (D{sup *}) in the end-member compositions of contrasting polymerization. Self-diffusion of Sr is 7 times faster in basaltic melt than rhyolitic melt at 1255{degrees}C and 1 GPa, while self-diffusion of Nd is more than 1 order of magnitude greater in basalt than rhyolite. Also, at these conditions, D{sub Sr}{sup *} is a factor of 3 greater than D{sub Nd}{sup *} in basalt and an order of magnitude greater than D{sub Nd}{sup *} in rhyolite. The results of a Botlzmann-Matano analysis of {sup 87}Sr/{Sigma}Sr and {sup 144}Nd/{Sigma}Nd profiles of complex diffusion couples composed of isotopically normal basalt and enriched rhyolite yield diffusion coefficients for intermediate bulk compositions in agreement with interpolated values given by the relationships above. An important feature of the interdiffusion of basaltic and rhyolitic liquids is the equilibration of isotopic composition in advance of chemical homogenization. This behavior is best displayed by Sr in the present experiments and predicted for Nd. These results are considered in a magmatic context, where intimate blending of magmas during mixing is frustrated by large rheological contrasts and/or insufficient exposure time. Time-dependent diffusional exchange between mingling magmas leads to covariations in chemical and isotopic compositions that differ markedly from the expectations of bulk mixing. Examples presented offer alternative interpretations for the compositional relationships found among magmatic rocks of hybrid origin. 63 refs., 14 figs., 4 tabs.

  9. Is the surface oxygen exchange rate linked to bulk ion diffusivity in mixed conducting Ruddlesden-Popper phases?

    PubMed

    Tomkiewicz, Alex C; Tamimi, Mazin A; Huq, Ashfia; McIntosh, Steven

    2015-01-01

    The possible link between oxygen surface exchange rate and bulk oxygen anion diffusivity in mixed ionic and electronic conducting oxides is a topic of great interest and debate. While a large body of experimental evidence and theoretical analyses support a link, observed differences between bulk and surface composition of these materials are hard to reconcile with this observation. This is further compounded by potential problems with simultaneous measurement of both parameters. Here we utilize separate techniques, in situ neutron diffraction and pulsed isotopic surface exchange, to examine bulk ion mobility and surface oxygen exchange rates of three Ruddlesden-Popper phases, general form A(n-1)A(2)'B(n)O(3n+1), A(n-1)A(2)'B(n)X(3n+1); LaSrCo(0.5)Fe(0.5)O(4-δ) (n = 1), La(0.3)Sr(2.7)CoFeO(7-δ) (n = 2) and LaSr3Co(1.5)Fe(1.5)O(10-δ) (n = 3). These measurements are complemented by surface composition determination via high sensitivity-low energy ion scattering. We observe a correlation between bulk ion mobility and surface exchange rate between materials. The surface exchange rates vary by more than one order of magnitude with high anion mobility in the bulk of an oxygen vacancy-rich n = 2 Ruddlesden-Popper material correlating with rapid oxygen exchange. This is in contrast with the similar surface exchange rates which we may expect due to similar surface compositions across all three samples. We conclude that experimental limitations lead to inherent convolution of surface and bulk rates, and that surface exchange steps are not likely to be rate limiting in oxygen incorporation.

  10. Is the surface oxygen exchange rate linked to bulk ion diffusivity in mixed conducting Ruddlesden–Popper phases?

    DOE PAGES

    Tomkiewicz, Alex C.; Tamimi, Mazin A.; Huq, Ashfia; ...

    2015-03-02

    There is a possible link between oxygen surface exchange rate and bulk oxygen anion diffusivity in mixed ionic and electronic conducting oxides; it is a topic of great interest and debate. While a large body of experimental evidence and theoretical analyses support a link, observed differences between bulk and surface composition of these materials are hard to reconcile with this observation. This is further compounded by potential problems with simultaneous measurement of both parameters. Here we utilize separate techniques, in situ neutron diffraction and pulsed isotopic surface exchange, to examine bulk ion mobility and surface oxygen exchange rates of threemore » Ruddlesden-Popper phases, general form An-1A2'BnO3n+1, An-1A2'BnX3n+1; LaSrCo0.5Fe0.5O4-δ (n = 1), La0.3Sr2.7CoFeO7-δ (n = 2) and LaSr3Co1.5Fe1.5O10-δ (n = 3). These measurements are complemented by surface composition determination via high sensitivity-low energy ion scattering. We observe a correlation between bulk ion mobility and surface exchange rate between materials. The surface exchange rates vary by more than one order of magnitude with high anion mobility in the bulk of an oxygen vacancy-rich n = 2 Ruddlesden-Popper material correlating with rapid oxygen exchange. Furthermore this is in contrast with the similar surface exchange rates which we may expect due to similar surface compositions across all three samples. This paper conclude that experimental limitations lead to inherent convolution of surface and bulk rates, and that surface exchange steps are not likely to be rate limiting in oxygen incorporation.« less

  11. Equivalence of on-Lattice Stochastic Chemical Kinetics with the Well-Mixed Chemical Master Equation in the Limit of Fast Diffusion.

    PubMed

    Stamatakis, Michail; Vlachos, Dionisios G

    2011-12-14

    Well-mixed and lattice-based descriptions of stochastic chemical kinetics have been extensively used in the literature. Realizations of the corresponding stochastic processes are obtained by the Gillespie stochastic simulation algorithm and lattice kinetic Monte Carlo algorithms, respectively. However, the two frameworks have remained disconnected. We show the equivalence of these frameworks whereby the stochastic lattice kinetics reduces to effective well-mixed kinetics in the limit of fast diffusion. In the latter, the lattice structure appears implicitly, as the lumped rate of bimolecular reactions depends on the number of neighbors of a site on the lattice. Moreover, we propose a mapping between the stochastic propensities and the deterministic rates of the well-mixed vessel and lattice dynamics that illustrates the hierarchy of models and the key parameters that enable model reduction.

  12. Solid state diffusion in the lubricious film formation on iron by mixed tertiary butyl phenyl phosphates under static conditions

    NASA Astrophysics Data System (ADS)

    Shaeffer, Steven Kent

    The reaction between vaporous aryl phosphate esters and iron is known to yield a lubricious product film at high temperatures. The rate law exhibited in the growth of this film is consistent with a diffusion controlled process. In this work the actual movement of elements during this growth process was characterized using laminated metal foil samples consisting of a 1,000 A iron film deposited on a platinum substrate. The interface between the platinum and iron served as a reference datum against which the movement of the elements was observed. Iron was found to be the lone mobile element that diffuses through the product layer where it reacts with the vapor at the exposed surface generating more product. The change in the concentration profiles of the iron within the product served as a means to evaluate the diffusivity of the iron during the product growth. In this case the diffusivity of iron was found to be greater than its self diffusivity and within the range of values typical of iron oxide. This data in combination with the estimated activation energy for the process suggested that the diffusion was of a nature similar to the vacancy diffusion displayed in the oxidation of iron. The data suggests that the diffusion of iron through the product is the rate controlling step in the product growth process.

  13. Is the surface oxygen exchange rate linked to bulk ion diffusivity in mixed conducting Ruddlesden–Popper phases?

    SciTech Connect

    Tomkiewicz, Alex C.; Tamimi, Mazin A.; Huq, Ashfia; McIntosh, Steven

    2015-03-02

    There is a possible link between oxygen surface exchange rate and bulk oxygen anion diffusivity in mixed ionic and electronic conducting oxides; it is a topic of great interest and debate. While a large body of experimental evidence and theoretical analyses support a link, observed differences between bulk and surface composition of these materials are hard to reconcile with this observation. This is further compounded by potential problems with simultaneous measurement of both parameters. Here we utilize separate techniques, in situ neutron diffraction and pulsed isotopic surface exchange, to examine bulk ion mobility and surface oxygen exchange rates of three Ruddlesden-Popper phases, general form An-1A2'BnO3n+1, An-1A2'BnX3n+1; LaSrCo0.5Fe0.5O4-δ (n = 1), La0.3Sr2.7CoFeO7-δ (n = 2) and LaSr3Co1.5Fe1.5O10-δ (n = 3). These measurements are complemented by surface composition determination via high sensitivity-low energy ion scattering. We observe a correlation between bulk ion mobility and surface exchange rate between materials. The surface exchange rates vary by more than one order of magnitude with high anion mobility in the bulk of an oxygen vacancy-rich n = 2 Ruddlesden-Popper material correlating with rapid oxygen exchange. Furthermore this is in contrast with the similar surface exchange rates which we may expect due to similar surface compositions across all three samples. This paper conclude that experimental limitations lead to inherent convolution of surface and bulk rates, and that surface exchange steps are not likely to be rate limiting in oxygen incorporation.

  14. Fungal infections in patients with AIDS and AIDS-related complex.

    PubMed

    Holmberg, K; Meyer, R D

    1986-01-01

    Persons with AIDS are predisposed to a variety of previously rare bacterial and fungal infections. Improvement in the quality and duration of survival of AIDS patients depends on the efficacy of treatment for these infections. Between 58-81% of AIDS patients contract fungal infections at some time, and 10-20% of AIDS patients die as a direct consequence of such infections. Oral candidiasis, commonly known as thrush, is the most common fungal infection among AIDS and AIDS Related Complex patients, occurring in 80-90% of cases. In a recent U.S. study, 59% of persons with oral candidiasis who were at high risk of contracting AIDS went on to develop Kaposi's sarcoma and other life- threatening infections. The most common life-threatening fungal infection experienced by AIDS patients is cryptococcosis, a disease occurring among 6% of American AIDS patients and having a mortality rate of 17% during initial infections and 75-100% on relapse. Other opportunistic infections associated with AIDS and AIDS Related Complex are bronchial candidiasis, invasive aspergillosis, disseminated histoplasmosis, and disseminated coccidioidomycosis. All are treatable but eradication i s difficult and relapse common.

  15. Molecular dynamics insights into the structural and diffusive properties of ZIF-8/PDMS mixed matrix membranes in the n-butanol/water pervaporation process

    NASA Astrophysics Data System (ADS)

    Sun, Tao; Fang, Manquan; Wu, Zhen; Yu, Lixin; Li, Jiding

    2017-04-01

    Molecular dynamics (MD) simulation was used to study the structural and diffusive properties of zeolitic imidazolate framework-8 (ZIF-8)/polydimethylsiloxane (PDMS), a novel alcohol-permselective mixed matrix membrane (MMM). Simulation models of one pure PDMS membrane and three ZIF-8/PDMS MMMs with increasing loadings were successfully constructed. Non-bond energy turned out to be a strong attractive interaction between the PDMS matrix and ZIF-8 cells. The morphology and mobility of PDMS chains were characterized by mean square displacement (MSD). The fraction of free volume (FFV) of the pure membrane and MMMs was calculated and showed declining trends with increasing ZIF-8 loadings. The diffusion coefficients of n-butanol and water molecules were calculated by the Einstein relation. {D}n-\\text{butanol} first increased then decreased, while {D}{{water}} decreased with the increasing loadings. The mechanism of selective diffusion behaviour was investigated and it was found that the inner channels of ZIF-8 provided selective pathways for n-butanol. Diffusion coefficients were correlated with FFV and the results showed that the logarithm of {D}{{water}} demonstrated a good linear relation with the inverse FFV and was in agreement with the free volume theory, while {D}n-\\text{butanol} showed a significant deviation in the case of MMM-1 due to the selective diffusion channels provided by ZIF-8.

  16. Transient Liquid Phase Diffusion Bonding of 6061Al-15 wt.% SiC p Composite Using Mixed Cu-Ag Powder Interlayer

    NASA Astrophysics Data System (ADS)

    Roy, Pallab; Pal, Tapan Kumar; Maity, Joydeep

    2016-08-01

    Microstructure and shear strength of transient liquid phase diffusion bonded (560 °C, 0.2 MPa) 6061Al-15 wt.% SiCp extruded composite using a 50-µm-thick mixed Cu-Ag powder interlayer have been investigated. During isothermal solidification that took 2 h for completion, a ternary liquid phase formed due to diffusion of Cu and Ag in Al. Subsequent cooling formed a ternary phase mixture (α-Al + CuAl2 + Ag2Al) upon eutectic solidification. With mixed Cu-Ag powder interlayer, isothermal solidification was faster than for pure Al joints made using a 50-µm-thick Cu foil interlayer and for the composite joints made using a 50-µm-thick Cu foil/powder interlayer under similar conditions. The presence of brittle eutectic phase mixture (CuAl2 + Ag2Al) led to poor joint strength at short TLP bonding times. The mixture disappeared upon isothermal solidification with a 2-h hold yielding improved joint strength even with solidification shrinkage in the joint. Increased holding time (6 h) erased shrinkage via solid state diffusion and yielded the highest joint strength (87 MPa) and fair joint efficiency (83%).

  17. Orphanhood by AIDS-Related Causes and Child Mental Health: A Developmental Psychopathology Approach

    PubMed Central

    Sharp, Carla; Jardin, Charles; Marais, Lochner; Boivin, Michael

    2016-01-01

    While the number of new HIV infections has declined, the number of orphans as a result of AIDS-related deaths continues to increase. The aim of this paper was to systematically review empirical research on the mental health of children affected by HIV/AIDS in the developing world, specifically with an eye on developing a theoretical framework to guide intervention and research. Articles for review were gathered by following the Preferred Reporting Items for Systemic Reviews and Meta Analyses (PRISMA standards), reviewed and then organized and synthesized with a Developmental Psychopathology framework. Results showed that the immediate and longterm effects of AIDS orphanhood are moderated by a number of important risk and protective factors that may serve as strategic targets for intervention. Research and clinical implications are discussed. PMID:27668289

  18. Understanding and Addressing AIDS-Related Stigma: From Anthropological Theory to Clinical Practice in Haiti

    PubMed Central

    Castro, Arachu; Farmer, Paul

    2005-01-01

    For the past several years, diverse and often confused concepts of stigma have been invoked in discussions on AIDS. Many have argued compellingly that AIDS-related stigma acts as a barrier to voluntary counseling and testing. Less compelling are observations regarding the source of stigma or its role in decreasing interest in HIV care. We reviewed these claims as well as literature from anthropology, sociology, and public health. Preliminary data from research in rural Haiti suggest that the introduction of quality HIV care can lead to a rapid reduction in stigma, with resulting increased uptake of testing. Rather than stigma, logistic and economic barriers determine who will access such services. Implications for scale-up of integrated AIDS prevention and care are explored. PMID:15623859

  19. Effects of Smoking on Non-AIDS-Related Morbidity in HIV-Infected Patients

    PubMed Central

    Shirley, Daniel K.; Kaner, Robert J.; Glesby, Marshall J.

    2013-01-01

    Tobacco smoking has many adverse health consequences. Patients with human immunodeficiency virus (HIV) infection smoke at very high rates, and many of the comorbidities associated with smoking in the general population are more prevalent in this population. It is likely that a combination of higher smoking rates along with an altered response to cigarette smoke throughout the body in persons with HIV infection leads to increased rates of the known conditions related to smoking. Several AIDS-defining conditions associated with smoking have been reviewed elsewhere. This review aims to summarize the data on non-AIDS-related health consequences of smoking in the HIV-infected population and explore evidence for the potential compounding effects on chronic systemic inflammation due to HIV infection and smoking. PMID:23572487

  20. Understanding Internalized HIV/AIDS-Related Stigmas in the Dominican Republic: A Short Report

    PubMed Central

    Hampanda, Karen

    2016-01-01

    HIV/AIDS-related stigmas can become internalized, resulting in declines in physical and mental health. Pathways to internalized HIV-related stigma (IS), characterized by persistently negative, self-abasing thoughts, are not well established among women living with HIV/AIDS (WLWHA) in the Dominican Republic (DR). Identifying factors involved in self-directed shaming and blaming is important, given the high HIV prevalence in the DR’s most vulnerable populations. The present study sheds light on factors involved in negative and self-abasing thoughts in WLWHA in the DR by examining the relationship between depression, perceived HIV-related stigma from the community (PSC), perceived HIV-related stigma from family (PSF) and IS. The Internalized AIDS-Related Stigma Scale (IA-RSS), the Center for Epidemiologic Studies Short Depression Scale (CES-D 10), and an instrument designed to measure perceived HIV-related stigma from the community and family was administered to 233 WLWHA in Puerto Plata, DR. Data were analyzed using descriptive statistics and ordered multiple logistic regression. Results showed that depression (OR=1.60; p<0.05), PSC (OR=3.68; p<0.001), and PSF (OR=1.60; p<0.01) were positively associated with IS. These findings indicate that IS-reducing interventions should address HIV-related depression. Additionally, HIV-related treatment and care services should work with WLWHA to adopt healthier attitudes about how community members view people living with HIV/AIDS in the Dominican Republic. PMID:26466239

  1. Circulating Mediators of Inflammation and Immune Activation in AIDS-Related Non-Hodgkin Lymphoma

    PubMed Central

    Nolen, Brian M.; Breen, Elizabeth Crabb; Bream, Jay H.; Jenkins, Frank J.; Kingsley, Lawrence A.; Rinaldo, Charles R.; Lokshin, Anna E.

    2014-01-01

    Background Non-Hodgkin lymphoma (NHL) is the most common AIDS-related malignancy in developed countries. An elevated risk of developing NHL persists among HIV-infected individuals in comparison to the general population despite the advent of effective antiretroviral therapy. The mechanisms underlying the development of AIDS-related NHL (A-NHL) are not fully understood, but likely involve persistent B-cell activation and inflammation. Methods This was a nested case-control study within the ongoing prospective Multicenter AIDS Cohort Study (MACS). Cases included 47 HIV-positive male subjects diagnosed with high-grade B-cell NHL. Controls were matched to each case from among participating HIV-positive males who did not develop any malignancy. Matching criteria included time HIV+ or since AIDS diagnosis, age, race and CD4+ cell count. Sera were tested for 161 serum biomarkers using multiplexed bead-based immunoassays. Results A subset of 17 biomarkers, including cytokines, chemokines, acute phase proteins, tissue remodeling agents and bone metabolic mediators was identified to be significantly altered in A-NHL cases in comparison to controls. Many of the biomarkers included in this subset were positively correlated with HIV viral load. A pathway analysis of our results revealed an extensive network of interactions between current and previously identified biomarkers. Conclusions These findings support the current hypothesis that A-NHL develops in the context of persistent immune stimulation and inflammation. Further analysis of the biomarkers identified in this report should enhance our ability to diagnose, monitor and treat this disease. PMID:24922518

  2. Double-diffusive mixed convection boundary layer flow from a vertical flat plate embedded in a porous medium filled by a nanofluid

    NASA Astrophysics Data System (ADS)

    Yasin, Mohd Hafizi Mat; Ishak, Anuar

    2016-11-01

    The objective of this study is to investigate the effects of mass suction on double diffusive mixed convection boundary layer flow from a vertical flat plate embedded in a porous medium filled by a nanofluid using Buongiorno's model. The appropriate similarity transformation is used to reduce the partial differential equations into a system of ordinary differential equation, which is then solved numerically using a shooting method. The effects of mass suction parameter on the flow field and heat transfer characteristics are presented and discussed.

  3. Tight asteroseismic constraints on core overshooting and diffusive mixing in the slowly rotating pulsating B8.3V star KIC 10526294

    NASA Astrophysics Data System (ADS)

    Moravveji, E.; Aerts, C.; Pápics, P. I.; Triana, S. A.; Vandoren, B.

    2015-08-01

    Context. KIC 10526294 was recently discovered to be a very slowly rotating and slowly pulsating late B-type star. Its 19 consecutive dipole gravity modes constitute a series with almost constant period spacing. This unique collection of identified modes probes the near-core environment of this star and holds the potential to reveal the size and structure of the overshooting zone above the convective core, as well as the mixing properties of the star. Aims: We revisit the asteroseismic modelling of this star with specific emphasis on the properties of the core overshooting, while considering additional diffusive mixing throughout the radiative envelope of the star. Methods: We pursued forward seismic modelling based on adiabatic eigenfrequencies of equilibrium models for eight extensive evolutionary grids tuned to KIC 10526294 by varying the initial mass, metallicity, chemical mixture, and the extent of the overshooting layer on top of the convective core. We examined models for both OP and OPAL opacities and tested the occurrence of extra diffusive mixing throughout the radiative interior. Results: We find a tight mass-metallicity relation within the ranges M ∈ [ 3.13,3.25 ] M⊙ and Z ∈ [ 0.014,0.028 ]. We deduce that an exponentially decaying diffusive core overshooting prescription describes the seismic data better than a step function formulation and derive a value of fov between 0.017 and 0.018. Moreover, the inclusion of extra diffusive mixing with a value of log Dmix between 1.75 and 2.00 dex (with Dmix in cm2 s-1) improves the goodness-of-fit based on the observed and modelled frequencies by a factor ~11 compared to the case where no extra mixing is considered, irrespective of the (M,Z) combination within the allowed seismic range. Conclusions: The inclusion of diffusive mixing in addition to core overshooting is essential to explain the structure in the observed period spacing pattern of this star. Moreover, for the input physics and chemical mixtures

  4. Effect of the 5E Model on Prospective Teachers' Conceptual Understanding of Diffusion and Osmosis: A Mixed Method Approach

    ERIC Educational Resources Information Center

    Artun, Huseyin; Costu, Bayram

    2013-01-01

    The aim of this study was to explore a group of prospective primary teachers' conceptual understanding of diffusion and osmosis as they implemented a 5E constructivist model and related materials in a science methods course. Fifty prospective primary teachers' ideas were elicited using a pre- and post-test and delayed post-test survey consisting…

  5. A prospective microstructure imaging study in mixed-martial artists using geometric measures and diffusion tensor imaging: methods and findings.

    PubMed

    Mayer, Andrew R; Ling, Josef M; Dodd, Andrew B; Meier, Timothy B; Hanlon, Faith M; Klimaj, Stefan D

    2016-04-12

    Although diffusion magnetic resonance imaging (dMRI) has been widely used to characterize the effects of repetitive mild traumatic brain injury (rmTBI), to date no studies have investigated how novel geometric models of microstructure relate to more typical diffusion tensor imaging (DTI) sequences. Moreover, few studies have evaluated the sensitivity of different registration pipelines (non-linear, linear and tract-based spatial statistics) for detecting dMRI abnormalities in clinical populations. Results from single-subject analyses in healthy controls (HC) indicated a strong negative relationship between fractional anisotropy (FA) and orientation dispersion index (ODI) in both white and gray matter. Equally important, only moderate relationships existed between all other estimates of free/intracellular water volume fractions and more traditional DTI metrics (FA, mean, axial and radial diffusivity). These findings suggest that geometric measures provide differential information about the cellular microstructure relative to traditional DTI measures. Results also suggest greater sensitivity for non-linear registration pipelines that maximize the anatomical information available in T1-weighted images. Clinically, rmTBI resulted in a pattern of decreased FA and increased ODI, largely overlapping in space, in conjunction with increased intracellular and free water fractions, highlighting the potential role of edema following repeated head trauma. In summary, current results suggest that geometric models of diffusion can provide relatively unique information regarding potential mechanisms of pathology that contribute to long-term neurological damage.

  6. Evaluation of a hybrid kinetics/mixing-controlled combustion model for turbulent premixed and diffusion combustion using KIVA-II

    NASA Technical Reports Server (NTRS)

    Nguyen, H. Lee; Wey, Ming-Jyh

    1990-01-01

    Two-dimensional calculations were made of spark ignited premixed-charge combustion and direct injection stratified-charge combustion in gasoline fueled piston engines. Results are obtained using kinetic-controlled combustion submodel governed by a four-step global chemical reaction or a hybrid laminar kinetics/mixing-controlled combustion submodel that accounts for laminar kinetics and turbulent mixing effects. The numerical solutions are obtained by using KIVA-2 computer code which uses a kinetic-controlled combustion submodel governed by a four-step global chemical reaction (i.e., it assumes that the mixing time is smaller than the chemistry). A hybrid laminar/mixing-controlled combustion submodel was implemented into KIVA-2. In this model, chemical species approach their thermodynamics equilibrium with a rate that is a combination of the turbulent-mixing time and the chemical-kinetics time. The combination is formed in such a way that the longer of the two times has more influence on the conversion rate and the energy release. An additional element of the model is that the laminar-flame kinetics strongly influence the early flame development following ignition.

  7. Evaluation of a hybrid kinetics/mixing-controlled combustion model for turbulent premixed and diffusion combustion using KIVA-2

    NASA Technical Reports Server (NTRS)

    Nguyen, H. Lee; Wey, Ming-Jyh

    1990-01-01

    Two dimensional calculations were made of spark ignited premixed-charge combustion and direct injection stratified-charge combustion in gasoline fueled piston engines. Results are obtained using kinetic-controlled combustion submodel governed by a four-step global chemical reaction or a hybrid laminar kinetics/mixing-controlled combustion submodel that accounts for laminar kinetics and turbulent mixing effects. The numerical solutions are obtained by using KIVA-2 computer code which uses a kinetic-controlled combustion submodel governed by a four-step global chemical reaction (i.e., it assumes that the mixing time is smaller than the chemistry). A hybrid laminar/mixing-controlled combustion submodel was implemented into KIVA-2. In this model, chemical species approach their thermodynamics equilibrium with a rate that is a combination of the turbulent-mixing time and the chemical-kinetics time. The combination is formed in such a way that the longer of the two times has more influence on the conversion rate and the energy release. An additional element of the model is that the laminar-flame kinetics strongly influence the early flame development following ignition.

  8. Macromolecular crowding effect upon in vitro enzyme kinetics: mixed activation-diffusion control of the oxidation of NADH by pyruvate catalyzed by lactate dehydrogenase.

    PubMed

    Balcells, Cristina; Pastor, Isabel; Vilaseca, Eudald; Madurga, Sergio; Cascante, Marta; Mas, Francesc

    2014-04-17

    Enzyme kinetics studies have been usually designed as dilute solution experiments, which differ substantially from in vivo conditions. However, cell cytosol is crowded with a high concentration of molecules having different shapes and sizes. The consequences of such crowding in enzymatic reactions remain unclear. The aim of the present study is to understand the effect of macromolecular crowding produced by dextran of different sizes and at diverse concentrations in the well-known reaction of oxidation of NADH by pyruvate catalyzed by L-lactate dehydrogenase (LDH). Our results indicate that the reaction rate is determined by both the occupied volume and the relative size of dextran obstacles with respect to the enzyme present in the reaction. Moreover, we analyzed the influence of macromolecular crowding on the Michaelis-Menten constants, vmax and Km. The obtained results show that only high concentrations and large sizes of dextran reduce both constants suggesting a mixed activation-diffusion control of this enzymatic reaction due to the dextran crowding action. From our knowledge, this is the first experimental study that depicts mixed activation-diffusion control in an enzymatic reaction due to the effect of crowding.

  9. 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

  10. HIV/AIDS related knowledge among school-going adolescents from the Middle East and North Africa.

    PubMed

    Boneberger, Anja; Rückinger, Simon; Guthold, Regina; Kann, Laura; Riley, Leanne

    2012-05-01

    The aim of this secondary analysis was to present cross-national data about HIV/AIDS related knowledge among 13- to 15-year-old school-going adolescents from the Middle East and North Africa. Data from 23673 school-going adolescents from seven countries (Jordan, Lebanon, Libyan Arab Jamahiriya, Morocco, Oman, Tunisia and United Arab Emirates) that undertook the Global School-Based Student Health Survey between 2004 and 2008 were analysed. HIV/AIDS related knowledge varied significantly between countries and gender. Research for this sensitive topic is scarce in this region. In addition, schools could be among the many key players for HIV/AIDS education.

  11. Women's voices: attitudes and behaviors of female Ghanaian sex workers regarding HIV prevention and AIDS-related stigma.

    PubMed

    Raingruber, Bonnie; Uwazie, Ernest; Bowie, Sylvester

    2010-08-01

    Attitudes and behaviors of sex workers have a pivotal influence on the spread of AIDS. A qualitative descriptive study was undertaken to elicit Ghanaian female sex workers' perspectives regarding effective methods of HIV prevention, sources of AIDS-related stigma, and challenges associated with sex work. Women described that: (1) sex work is hard; (2) they felt God would protect their health; (3) staying safe is both a gift and a priority; (4) sex work allows for autonomy; and (5) AIDS-related stigma is very real. To design effective prevention programs it is necessary to consider the culture and perspectives of those who will be served.

  12. An Experimental Investigation of Forced Mixing of a Turbulent Boundary Layer in an Annular Diffuser. Ph.D. Thesis - Ohio State Univ.; [for boundary layer control

    NASA Technical Reports Server (NTRS)

    Shaw, R. J.

    1979-01-01

    The forced mixing process of a turbulent boundary layer in an axisymmetric annular diffuser using conventional wing-like vortex generators was studied. Flow field measurements were made at four axial locations downstream of the vortex generators. At each axial location, a total of 25 equally spaced profiles were measured behind three consecutive vortex generators which formed two pairs of vortex generators. Hot film anemometry probes measured the boundary layer turbulence structure at the same locations where pressure measurements were made. Both single and cross film probes were used. The diffuser turbulence data was teken only for a nominal inlet Mach number of 0.3. Three vortex generator configurations were tested. The differences between configurations involved changes in size and relative vortex generator positions. All three vortex generator configurations tested provided increases in diffuser performance. Distinct differences in the boundary layer integral properties and skin friction levels were noted between configurations. The axial turbulence intensity and Reynolds stress profiles measured displayed similarities in trends but differences in levels for the three configurations.

  13. [Successful discontinuation of antifungal secondary prophylaxis in AIDS-related cryptococcosis].

    PubMed

    Negroni, R; Helou, S H; López Daneri, G; Robles, A M; Arechavala, A I; Bianchi, M H

    2004-01-01

    The clinical and laboratory data of 22 patients with AIDS related cryptococcosis who were able to interrupt antifungal secondary prophylaxis after HAART administration, are presented. They were 14 males and 8 females, between 15 and 50 years old (X: 34 years old). All patients presented fever and severe deterioration of their general health status, and 19 exhibited a meningeal syndrome. At the start of antifungal treatment, 59% of the cases presented < 50 CD4+ cells/microl, the median viral burden was 134,804 RNA copies/ml and the median titer of serum cryptococcal antigen was 1/3,000. Amphotericin B by intravenous route, (0.7 mg/kg/day) or fluconazole (600 to 800 mg/day) were given as a treatment of the initial episode, up to CSF cultures negativization. Oral fluconazole (200 mg/day) or intravenous amphotericin B, 50 mg twice a week, were given as a secondary prophylaxis. The secondary prophylaxis was interrupted when the patients had received HAART for an average lapse of 19 months (6 to 36 months) and the median CD4+ cell count was 249/microl. The follow up after secondary prophylaxis discontinuation lasted for a median lapse of 22 months. These data seem to show that secondary prophylaxis is not necessary when the patient are clinically asymptomatic and the CD4+ cell counts are above 150/microl.

  14. AIDS as social construction: text mining of AIDS-related information in the Italian press.

    PubMed

    Caputo, Andrea; Giacchetta, Agnese; Langher, Viviana

    2016-09-01

    Given the relevance of AIDS as a public health problem in the Italian context and of the role of mass media in the social construction of the phenomenon, the aim of the present study is twofold: (1) to explore the main AIDS-related themes in the Italian popular press; (2) to analyse the temporal trends of AIDS representations over the last decades. For the research, we decided to consult Italian newspaper articles produced between 1985 and 1990 and between 2005 and 2010 using the archives of the main two national newspapers (La Repubblica and Corriere della Sera), resulting in an overall sample of 446 newspaper articles. A computer-aided content analysis allowed the detection of five different thematic domains (clusters), respectively focused on: Medical care (7.47%), Family support (37.03%), Science and religion debate (27%), Social exclusion (17.6%) and Healthcare policies (10.9%). These thematic domains are conceived along two main latent dimensions (factors) which explain 72.47% of the data variance which respectively deal with: (1) Attitudes towards people with AIDS (care versus avoidance) and (2) Social mandate on AIDS (powerlessness versus control). The study results also reveal the potential evolution of representations of people with AIDS over time: from stigmatised subjects who represent a risk for the entire society within a climate of social control to people progressively symbolised as frail subjects that need to be taken care of.

  15. AIDS-related illness trajectories in Mexico: findings from a qualitative study in two marginalized communities.

    PubMed

    Castro, R; Orozco, E; Eroza, E; Manca, M C; Hernández, J J; Aggleton, P

    1998-10-01

    This paper describes findings from a recent study examining how people affected directly and indirectly by the HIV/AIDS epidemic cope with HIV-related illness in Mexico. One-hundred-and-thirteen in-depth interviews were conducted with key informants in two contrasting communities: Ciudad Netzahualcóyotl (an economically marginalized community) and the gay community in Mexico City (a sexually marginalized community). This paper describes the AIDS-related wellness/illness careers or trajectories followed by individuals in both communities, and identifies critical points for material and emotional intervention. This career comprises four stages: (1) life before infection; (2) life surrounding the discovery of seropositivity; (3) living as an HIV-positive person; and (4) facing death. Comparisons are drawn between the processes of adjustment and coping found in both communities. In Ciudad Netzahualcóyotl, wellness/illness careers are closely linked to prevailing poverty and oppression, as well as the sense of urgency in which local people live their lives. In the case of the gay community, wellness/illness careers are associated with the intolerance and social repression faced by homosexual men. The paper concludes by suggesting possible interventions to improve the lives of people with HIV/AIDS in Mexico today.

  16. Kaposi's sarcoma-associated herpesvirus in non-AIDS related lymphomas occurring in body cavities.

    PubMed Central

    Cesarman, E.; Nador, R. G.; Aozasa, K.; Delsol, G.; Said, J. W.; Knowles, D. M.

    1996-01-01

    DNA sequences belonging to the recently discovered Kaposi's sarcoma-associated herpesvirus (KSHV), now provisionally designated human herpesvirus 8, have been previously identified in an uncommonly occurring subset of AIDS-related lymphomas, referred to as body-cavity-based lymphomas (BCBLs), which present as lymphomatous effusions. Pyothorax-associated lymphomas (PALS) are non-Hodgkin's lymphomas that arise in the pleural cavity after long-standing pleural inflammation resulting from therapeutic artificial pneumothorax or from tuberculosis pleuritis. Although PALs present as solid tumor masses, they are otherwise similar to BCBLs in that they also are B cell lymphomas, usually exhibit immunoblastic morphology, and contain Epstein-Barr virus. We investigated whether KSHV sequences are present in 2 BCBLs in patients without AIDS and 12 in Japanese and 2 French PALs. The 2 BCBLs were positive for KSHV sequences, whereaas all 14 PALs were KSHV negative. This finding strongly suggests that BCBLs and PALs are distinct clinicopathological entities and further strengthens the association between the presence of KSHV and an effusion phenotype. Based on these findings, we propose replacing the term body-cavity-based lymphoma with the term primary effusion lymphoma, which describes these non-Hodgkin's lymphomas more accurately and avoids confusion with other lymphomas that may occur in the body cavities, such as the PALs. Images Figure 1 Figure 2 PMID:8686762

  17. Double Diffusive Magnetohydrodynamic (MHD) Mixed Convective Slip Flow along a Radiating Moving Vertical Flat Plate with Convective Boundary Condition

    PubMed Central

    Rashidi, Mohammad M.; Kavyani, Neda; Abelman, Shirley; Uddin, Mohammed J.; Freidoonimehr, Navid

    2014-01-01

    In this study combined heat and mass transfer by mixed convective flow along a moving vertical flat plate with hydrodynamic slip and thermal convective boundary condition is investigated. Using similarity variables, the governing nonlinear partial differential equations are converted into a system of coupled nonlinear ordinary differential equations. The transformed equations are then solved using a semi-numerical/analytical method called the differential transform method and results are compared with numerical results. Close agreement is found between the present method and the numerical method. Effects of the controlling parameters, including convective heat transfer, magnetic field, buoyancy ratio, hydrodynamic slip, mixed convective, Prandtl number and Schmidt number are investigated on the dimensionless velocity, temperature and concentration profiles. In addition effects of different parameters on the skin friction factor, , local Nusselt number, , and local Sherwood number are shown and explained through tables. PMID:25343360

  18. Double diffusive magnetohydrodynamic (MHD) mixed convective slip flow along a radiating moving vertical flat plate with convective boundary condition.

    PubMed

    Rashidi, Mohammad M; Kavyani, Neda; Abelman, Shirley; Uddin, Mohammed J; Freidoonimehr, Navid

    2014-01-01

    In this study combined heat and mass transfer by mixed convective flow along a moving vertical flat plate with hydrodynamic slip and thermal convective boundary condition is investigated. Using similarity variables, the governing nonlinear partial differential equations are converted into a system of coupled nonlinear ordinary differential equations. The transformed equations are then solved using a semi-numerical/analytical method called the differential transform method and results are compared with numerical results. Close agreement is found between the present method and the numerical method. Effects of the controlling parameters, including convective heat transfer, magnetic field, buoyancy ratio, hydrodynamic slip, mixed convective, Prandtl number and Schmidt number are investigated on the dimensionless velocity, temperature and concentration profiles. In addition effects of different parameters on the skin friction factor, [Formula: see text], local Nusselt number, [Formula: see text], and local Sherwood number [Formula: see text] are shown and explained through tables.

  19. HIV/AIDS Related Stigma and Discrimination against PLWHA in Nigerian Population

    PubMed Central

    Bulgiba, Awang; Oche, Oche Mansur; Adekunjo, Felix Oluyemi

    2015-01-01

    Background HIV/AIDS remain a major public health concern in Nigeria. People living with HIV/AIDS (PLWHA) face not only personal medical problems but also social problems associated with the disease such as stigma and discriminatory attitudes. This study provides an insight into HIV/AIDS related stigma and discrimination against PLWHA in Nigeria. Methods The data for this study was extracted from the 2013 Nigeria Demographic and Health Survey conducted by the National Population Commission. All men and women aged 15–49 years, permanent residents and visitors of the households were eligible for the interview. Several questionnaires were used in the survey, some covering questions on HIV/AIDS. Results A total of 56 307 men and women aged 15–49 years participated in this national survey. About half of the population in Nigeria have HIV stigma. Younger persons, men, those without formal education and those within poor wealth index are more likely to have stigma towards PLWHA. In addition, married people are more likely to have stigma on PLWHA and are more likely to blame PLWHA for bringing the disease to the community. Also about half of the population discriminates against PLWHA. However, those with higher levels of education and those from higher wealth index seem to be more compassionate towards PLWHA. About 70% in the population are willing to care for relative with AIDS, even more so among those with higher level of education. Conclusion There is a high level of HIV stigma and discrimination against PLWHA in the Nigerian population. Education seems to play a major role in the society with respect to HIV stigma and discrimination against PLWHA. Educating the population with factual information on HIV/AIDS is needed to reduce stigma and discrimination towards PLWHA in the community. PMID:26658767

  20. Knowledge, attitude, and practice of HIV/AIDS-related stigma and discrimination reduction among nursing students in southwest Nigeria

    PubMed Central

    Farotimi, Adekunbi A; Nwozichi, Chinomso Ugochukwu; Ojediran, Tolulope D

    2015-01-01

    Background: One of the reported obstacles to the achievement of universal access to Human Immunodeficiency Virus (HIV) prevention, treatment, care, and support programs includes stigma and discrimination from health workers, particularly nurses. Since nursing students would become future practising nurses and are most likely exposed to caring for people living with HIV/AIDS (PL WHA) during their training, it is of great importance to assess the knowledge, attitude, and practice of student nurses toward the reduction of HIV/AIDS-related stigma and discrimination. Materials and Methods: A descriptive survey research design was used. A total of 150 nursing students were selected using the simple random sampling technique of fish bowl method with replacement. Data were obtained using a self-administered (33-item) validated questionnaire to assess the knowledge, attitude, and practice of student nurses with regard to HIV/AIDS-related stigma and discrimination reduction strategies. Reliability of the tool was tested using Cronbach alpha (R) yielding a reliability value of 0.72. Data collected were analyzed with descriptive statistics of frequencies and percentages. Results: Majority (76.0%) of the respondents were females and 82.7% were married. Respondents were found to have high knowledge (94.0%) of strategies for reducing HIV/AIDS-related stigma and discrimination. Also, 64% had moderate discriminatory attitude, 74% engaged in low discriminatory practice, while 26% engaged in high discriminatory practice. Conclusions: Student nurses had adequate knowledge about strategies for reducing HIV/AIDS-related stigma and discrimination; negative discriminatory attitude toward PLWHA and some form of discriminatory practices exist in participants’ training schools. It is, therefore, recommended that an educational package on reduction of HIV/AIDS-related stigma and discrimination be developed and implemented for the participants. PMID:26793257

  1. Detection of polyomavirus simian virus 40 tumor antigen DNA in AIDS-related systemic non-Hodgkin lymphoma

    NASA Technical Reports Server (NTRS)

    Vilchez, Regis A.; Lednicky, John A.; Halvorson, Steven J.; White, Zoe S.; Kozinetz, Claudia A.; Butel, Janet S.

    2002-01-01

    Systemic non-Hodgkin lymphoma (S-NHL) is a common malignancy during HIV infection, and it is hypothesized that infectious agents may be involved in the etiology. Epstein-Barr virus DNA is found in <40% of patients with AIDS-related S-NHL, suggesting that other oncogenic viruses, such as polyomaviruses, may play a role in pathogenesis. We analyzed AIDS-related S-NHL samples, NHL samples from HIV-negative patients, peripheral blood leukocytes from HIV-infected and -uninfected patients without NHL, and lymph nodes without tumors from HIV-infected patients. Specimens were examined by polymerase chain reaction analysis with use of primers specific for an N-terminal region of the oncoprotein large tumor antigen ( T-ag ) gene conserved among all three polyomaviruses (simian virus 40 [SV40], JC virus, and BK virus). Polyomavirus T-ag DNA sequences, proven to be SV40-specific, were detected more frequently in AIDS-related S-NHL samples (6 of 26) than in peripheral blood leukocytes from HIV-infected patients (6 of 26 vs. 0 of 69; p =.0001), NHL samples from HIV-negative patients (6 of 26 vs. 0 of 10; p =.09), or lymph nodes (6 of 26 vs. 0 of 7; p =.16). Sequences of C-terminal T-ag DNA from SV40 were amplified from two AIDS-related S-NHL samples. Epstein-Barr virus DNA sequences were detected in 38% (10 of 26) AIDS-related S-NHL samples, 50% (5 of 10) HIV-negative S-NHL samples, and 57% (4 of 7) lymph nodes. None of the S-NHL samples were positive for both Epstein-Barr virus DNA and SV40 DNA. Further studies of the possible role of SV40 in the pathogenesis of S-NHL are warranted.

  2. Development of a multicomponent film diffusion controlled mixed bed ion exchange column model applicable to variable influent systems

    NASA Astrophysics Data System (ADS)

    Hussey, Dennis Frank

    2000-10-01

    Scope and method of study. The purpose of this study was to develop a generalized rate model to handle multicomponent mixed-bed ion exchange (MBIE) with multivalent dissociative species and variable influent conditions. To achieve this goal, mass transfer mechanisms of weak electrolytes in ion exchange column have been studied; and based on which, rate expressions for weak electrolyte transfer have been proposed. In addition, the column material balance has been derived in terms of the constituent species concentrations only. Finally, generalized dissociation equilibrium equations for several types of weak electrolyte constituents were implemented, and the effluent concentrations were determined by solving column material balance equations along with the rate expressions. Findings and conclusions. The mixed bed ion exchange column model has been successfully programmed into a computer program and is capable of predicting the effluent concentration histories, dynamic resin loading, solution, and rate profiles. The column material balance has been satisfied to within 1% for all chemistries studied. The model is capable of simulating variable influent contaminant concentrations and flow rates by sequentially using the loading profiles of previous simulations. The model maintains electroneutrality at all times. Dissociative species transfer is adequate for many systems, but additional work is required to incorporate molecular constituent mass transfer.

  3. 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.

  4. Cation Mixing Properties toward Co Diffusion at the LiCoO2 Cathode/Sulfide Electrolyte Interface in a Solid-State Battery.

    PubMed

    Haruyama, Jun; Sodeyama, Keitaro; Tateyama, Yoshitaka

    2017-01-11

    All-solid-state Li-ion batteries (ASS-LIBs) are expected to be the next-generation battery, however, their large interfacial resistance hinders their widespread application. To understand and resolve the possible causes of this resistance, we examined mutual diffusion properties of the cation elements at LiCoO2 (LCO) cathode/β-Li3PS4 (LPS) solid electrolyte interface as a representative system as well as the effect of a LiNbO3 buffer layer by first-principles calculations. Evaluating energies of exchanging ions between the cathode and the electrolyte, we found that the mixing of Co and P is energetically preferable to the unmixed states at the LCO/LPS interface. We also demonstrated that the interposition of the buffer layer suppresses such mixing because the exchange of Co and Nb is energetically unfavorable. Detailed analyses of the defect levels and the exchange energies by using the individual bulk crystals as well as the interfaces suggest that the lower interfacial states in the energy gap can make a major contribution to the stabilization of the Co ↔ P exchange, although the anion bonding preference of Co and P as well as the electrostatic interactions may have effects as well. Finally, the Co ↔ P exchanges induce interfacial Li sites with low chemical potentials, which enhance the growth of the Li depletion layer. These atomistic understandings can be meaningful for the development of ASS-LIBs with smaller interfacial resistances.

  5. An Integrated Intervention for Increasing Clinical Nurses' Knowledge of HIV/AIDS-Related Occupational Safety.

    PubMed

    He, Liping; Lu, Zhiyan; Huang, Jing; Zhou, Yiping; Huang, Jian; Bi, Yongyi; Li, Jun

    2016-11-07

    Background: Approximately 35 new HIV (Human Immunodeficiency Virus, HIV) cases and at least 1000 serious infections are transmitted annually to health care workers. In China, HIV prevalence is increasing and nursing personnel are encountering these individuals more than in the past. Contaminated needle-stick injuries represent a significant occupational burden for nurses. Evidence suggests that nurses in China may not fully understand HIV/AIDS (Acquired immunodeficiency syndrome, AIDS) and HIV-related occupational safety. At this time, universal protection precautions are not strictly implemented in Chinese hospitals. Lack of training may place nurses at risk for occupational exposure to blood-borne pathogens. Objectives: To assess the effectiveness of integrated interventions on nurses' knowledge improvement about reducing the risk of occupationally acquired HIV infection. Methods: We audited integrated interventions using 300 questionnaires collected from nurses at the Affiliated Hospital of Xiangnan University, a public polyclinic in Hunan Province. The intervention studied was multifaceted and included appropriate and targeted training content for hospital, department and individual levels. After three months of occupational safety integrated interventions, 234 participants who completed the program were assessed. Results: Of the subjects studied, 94.3% (283/300) were injured one or more times by medical sharp instruments or splashed by body fluids in the last year and 95.3% considered their risk of occupational exposure high or very high. After the intervention, awareness of HIV/AIDS-related knowledge improved significantly (χ² = 86.34, p = 0.00), and correct answers increased from 67.9% to 82.34%. Correct answers regarding risk perception were significantly different between pre-test (54.4%) and post-test (66.6%) (χ² = 73.2, p = 0.00). When coming into contact with patient body fluids and blood only 24.0% of subjects used gloves regularly. The pre

  6. Effect of the 5E Model on Prospective Teachers' Conceptual Understanding of Diffusion and Osmosis: A Mixed Method Approach

    NASA Astrophysics Data System (ADS)

    Artun, Hüseyin; Coştu, Bayram

    2013-02-01

    The aim of this study was to explore a group of prospective primary teachers' conceptual understanding of diffusion and osmosis as they implemented a 5E constructivist model and related materials in a science methods course. Fifty prospective primary teachers' ideas were elicited using a pre- and post-test and delayed post-test survey consisting of ten two-tier questions of which an explanatory part was integral. Individual interviews were conducted with six prospective teachers at the end of the implementation of the unit using four questions. Test scores were analyzed quantitatively and qualitatively. Post-instructional interviews were analyzed qualitatively. Statistical analysis using one-way ANOVA of student test scores pointed to statistically significant differences between pre- and post- and delayed post-test ( p < 0.05). A qualitative analysis of the prospective teachers' explanations in the two-tier questions revealed changes in their ideas overtime. Both quantitative and qualitative analyses suggest that the teaching activities promoted students' conceptual understanding. No statistically significant differences were found between post-test and delayed post-test scores, suggesting that the teaching activities based on 5E model enabled students to retain their new conceptual understanding.

  7. Direct and indirect effects of enablers on HIV testing, initiation and retention in antiretroviral treatment and AIDS related mortality

    PubMed Central

    2017-01-01

    Background An enabling environment is believed to have significant and critical effects on HIV and AIDS program implementation and desired outcomes. This paper estimates the paths, directionality, and direct and indirect associations between critical enablers with antiretroviral treatment (ART) coverage and to AIDS-related mortality. Methods Frameworks that consider the role of enablers in HIV and AIDS programs were systematically reviewed to develop a conceptual model of interaction. Measurements for constructs of the model were pooled from the latest publicly available data. A hypothetical model, including latent/unobserved factors and interaction of enablers, program activities and outcomes, was analyzed cross-sectionally with structural equation modeling. Coefficients of the model were used to estimate the indirect associations of enablers to treatment coverage and the subsequent associated impact on AIDS related mortality. Findings The model’s fit was adequate (RMSEA = 0·084, 90% CI [0·062, 0·104]) and the indirect effects of enablers on outcomes were measured. Enablers having significant associations with increased ART coverage were social/financial protection, governance, anti-discrimination, gender equality, domestic AIDS spending, testing service delivery, and logistics. Interpretation Critical enablers are significantly correlated to outcomes like ART coverage and AIDS related mortality. Even while this model does not allow inference on causality, it provides directionality and magnitude of the significant associations. PMID:28225790

  8. Creating Social Spaces to Tackle AIDS-Related Stigma: Reviewing the Role of Church Groups in Sub-Saharan Africa

    PubMed Central

    Skovdal, M.; Gibbs, A.

    2012-01-01

    An expanding body of literature explores the role of African church groups in facilitating or hindering the support of people living with AIDS and challenging or contributing to HIV/AIDS-related stigma. Treating church groups as social spaces in which HIV/AIDS-related stigma may potentially be challenged, we systematically review this literature, identifying five themes that highlight the complex and contradictory role of the church as a potential agent of health-enhancing social change. In many ways the church perpetuates HIV/AIDS-related stigma through (i) moralistic attitudes and (ii) its reinforcement of conservative gender ideologies. However some churches have managed move towards action that makes a more positive contribution to HIV/AIDS management through (iii) promoting various forms of social control for HIV prevention, (iv) contributing to the care and support of the AIDS-affected and (v) providing social spaces for challenging stigmatising ideas and practices. We conclude that church groups, including church leadership, can play a key role in facilitating or hindering the creation of supportive social spaces to challenge stigma. Much work remains to be done in developing deeper understandings of the multi-layered factors that enable some churches, but not others, to respond effectively to HIV/AIDS. PMID:20668927

  9. Sub-inertial Gravity Modes in the B8V Star KIC 7760680 Reveal Moderate Core Overshooting and Low Vertical Diffusive Mixing

    NASA Astrophysics Data System (ADS)

    Moravveji, Ehsan; Townsend, Richard H. D.; Aerts, Conny; Mathis, Stéphane

    2016-06-01

    Thus far, KIC 7760680 is the richest slowly pulsating B star, exhibiting 36 consecutive dipole (ℓ = 1) gravity (g-) modes. The monotonically decreasing period spacing of the series, in addition to the local dips in the pattern, confirm that KIC 7760680 is a moderate rotator with clear mode trapping in chemically inhomogeneous layers. We employ the traditional approximation of rotation to incorporate rotational effects on g-mode frequencies. Our detailed forward asteroseismic modeling of this g-mode series reveals that KIC 7760680 is a moderately rotating B star with mass ˜3.25 M ⊙. By simultaneously matching the slope of the period spacing and the number of modes in the observed frequency range, we deduce that the equatorial rotation frequency of KIC 7760680 is 0.4805 day-1, which is 26% of its Roche break up frequency. The relative deviation of the model frequencies and those observed is less than 1%. We succeed in tightly constraining the exponentially decaying convective core overshooting parameter to f ov ≈ 0.024 ± 0.001. This means that convective core overshooting can coexist with moderate rotation. Moreover, models with exponentially decaying overshoot from the core outperform those with the classical step-function overshoot. The best value for extra diffusive mixing in the radiatively stable envelope is confined to {log}{D}{{ext}}≈ 0.75+/- 0.25 (with D ext in cm2 s-1), which is notably smaller than theoretical predictions.

  10. Salvage Therapy for Refractory Aids-Related Primary Central Nervous System Lymphoma

    PubMed Central

    Ferro, Hugo; Parino, Eduardo

    2012-01-01

    A 27-year-old male patient presented with speech disorders and multiple brain masses on MRI evaluation. He tested positive for HIV. A sterotactic biopsy diagnosed primary central nervous system lymphoma (diffuse large B-cell lymphoma). After two cycles of high-dose metotrexate (HD-MTX-)-based chemotherapy, the tumor progressed. He underwent whole brain radiotherapy achieving complete response. Six cycles of consolidating immunochemotherapy with rituximab-temozolomide were administered after radiation. Forty-three months after remission, he has not recurred and his neurological status is optimal. Younger HIV patients with refractory PCNSL and preserved immune function can face salvage therapy successfully achieving long term remissions with no remarkable neurotoxicity. PMID:23029628

  11. Salvage therapy for refractory AIDS-related primary central nervous system lymphoma.

    PubMed

    Ferro, Hugo; Parino, Eduardo

    2012-01-01

    A 27-year-old male patient presented with speech disorders and multiple brain masses on MRI evaluation. He tested positive for HIV. A sterotactic biopsy diagnosed primary central nervous system lymphoma (diffuse large B-cell lymphoma). After two cycles of high-dose metotrexate (HD-MTX-)-based chemotherapy, the tumor progressed. He underwent whole brain radiotherapy achieving complete response. Six cycles of consolidating immunochemotherapy with rituximab-temozolomide were administered after radiation. Forty-three months after remission, he has not recurred and his neurological status is optimal. Younger HIV patients with refractory PCNSL and preserved immune function can face salvage therapy successfully achieving long term remissions with no remarkable neurotoxicity.

  12. Clinical Analysis of Five Cases of AIDS-related Non-Hodgkin Lymphoma

    PubMed Central

    Zuo, Shubo; Xu, Na; Li, Zhongkun; Li, Na; Xia, Hong; Ren, Hongtao; Bao, Huizheng

    2016-01-01

    Objective: Secondary malignancy is a major life-threatening complication facing patients afflicted with acquired immunodeficiency syndrome (AIDS). This study aimed to retrospectively review clinical features and treatment course of five patients with AIDS-associated non-Hodgkin lymphoma (A-NHL) in Jilin Tumor Hospital. Methods: Five A-NHL patients were retrospectively and consecutively hospitalized at our oncological unit between January 2012 and June 2014. All patients received pre-emptive highly active antiretroviral therapy (HAART) and chemotherapy, and were subsequently followed up at the outpatient clinic. All five patients were male, aged 27–53 years, and afflicted with A-NHL involving upper jaw, right inguinal region, right-side gingiva, mediastinum, or right-side neck. Histology showed diffuse large B-cell lymphoma (n = 3) or plasmablastic lymphoma (n = 2). Results: Two patients achieved complete remission after HAART and chemotherapy, whereas other three patients required a second-line treatment, with two achieving stable disease and one dying within a follow-up period of 0.5−2 years. Conclusion: The findings of the present study showed that A-NHL is a disease often diagnosed in the middle-to-late stages, with diverse clinical manifestations and short overall survival. In the cases reviewed in this study, HAART in combination with standard dose or high-dose chemotherapy, HAART and molecular targeted chemotherapy was administered, and these treatments proved to be effective for improving the prognosis of these patients. Moreover, the CD4+ cell count was important for determining the prognosis of patients. PMID:28083067

  13. Framing, agenda setting, and disease phobia of AIDS-related coverage in the South Korean mass media.

    PubMed

    Jung, Minsoo

    2013-01-01

    There has been little research on the concrete role of the press in discourses on AIDS. This study investigated the AIDS discourses created by the major media. In particular, from the perspective of the agenda-setting theory, it examines differences in the framing of AIDS-related news depending on the political orientation and news sources of the press. This study analyzed the thematic frames and news sources implied by AIDS-related coverage. The 2 major media representing conservatism and progressivism were selected as the objects of analysis. As for the search engine for content analysis, the Korean Integrated Newspaper Database System was used, and 151 articles containing "AIDS" or "HIV" over 5 years from January 2005 to December 2010 were analyzed. According to the results of the analysis, there were the 6 following frames: aid/support, accident, human rights, risk, prevention, and biomedicine. Whereas the conservative press in South Korea continued to frame AIDS in the traditional way, the progressive press tended relatively more often to attempt new agenda setting, from the perspective of human rights and inequality. However, both newspaper companies tended mostly to select experts as the sources of AIDS news, thus continuing to exclude infectees and civil and society organizations.

  14. Ethnobotanical Study of Plants Used in the Management of HIV/AIDS-Related Diseases in Livingstone, Southern Province, Zambia

    PubMed Central

    Chinsembu, Kazhila C.

    2016-01-01

    Faced with critical shortages of staff, long queues, and stigma at public health facilities in Livingstone, Zambia, persons who suffer from HIV/AIDS-related diseases use medicinal plants to manage skin infections, diarrhoea, sexually transmitted infections, tuberculosis, cough, malaria, and oral infections. In all, 94 medicinal plant species were used to manage HIV/AIDS-related diseases. Most remedies are prepared from plants of various families such as Combretaceae, Euphorbiaceae, Fabaceae, and Lamiaceae. More than two-thirds of the plants (mostly leaves and roots) are utilized to treat two or more diseases related to HIV infection. Eighteen plants, namely, Achyranthes aspera L., Lannea discolor (Sond.) Engl., Hyphaene petersiana Klotzsch ex Mart., Asparagus racemosus Willd., Capparis tomentosa Lam., Cleome hirta Oliv., Garcinia livingstonei T. Anderson, Euclea divinorum Hiern, Bridelia cathartica G. Bertol., Acacia nilotica Delile, Piliostigma thonningii (Schumach.) Milne-Redh., Dichrostachys cinerea (L.) Wight and Arn., Abrus precatorius L., Hoslundia opposita Vahl., Clerodendrum capitatum (Willd.) Schumach., Ficus sycomorus L., Ximenia americana L., and Ziziphus mucronata Willd., were used to treat four or more disease conditions. About 31% of the plants in this study were administered as monotherapies. Multiuse medicinal plants may contain broad-spectrum antimicrobial agents. However, since widely used plants easily succumb to the threats of overharvesting, they need special protocols and guidelines for their genetic conservation. There is still need to confirm the antimicrobial efficacies, pharmacological parameters, cytotoxicity, and active chemical ingredients of the discovered plants. PMID:27069489

  15. Recruiting Chinese American adolescents to HIV/AIDS-related research: a lesson learned from a cross-sectional study.

    PubMed

    Lee, Yi-Hui; Salman, Ali; Wang, Fan

    2012-02-01

    The purpose of this article was to report identified barriers and challenges experienced in the recruiting process of Chinese American adolescents to a cross-sectional HIV/AIDS-related study. Snowball sampling method was used to recruit Chinese American adolescents from Chinese American communities in a U.S. Midwestern state. Barriers and challenges to recruitment were reviewed and analyzed from Chinese cultural perspectives in the hope of aiding researchers and health care providers understand and facilitate future recruitment of Chinese Americans for HIV/AIDS prevention studies. Barriers to recruitment were found related to the taboo topic of sexual issues in Chinese culture, unawareness and denial of HIV/AIDS risks, authoritarian parenting style in Chinese culture, and the required active consents. Facilitating factors of recruiting Chinese American adolescents to future HIV/AIDS prevention research or intervention programs are discussed. Information provided in this article may increase nurses' awareness of various barriers that they might encounter when they conduct research or address HIV/AIDS-related topics of Chinese American adolescents.

  16. Eradication of HCV and non-liver-related non-AIDS-related events in HIV/HCV coinfection.

    PubMed

    Berenguer, Juan; Rodríguez-Castellano, Elena; Carrero, Ana; Von Wichmann, Miguel A; Montero, Marta; Galindo, María J; Mallolas, Josep; Crespo, Manuel; Téllez, María J; Quereda, Carmen; Sanz, José; Barros, Carlos; Tural, Cristina; Santos, Ignacio; Pulido, Federico; Guardiola, Josep M; Rubio, Rafael; Ortega, Enrique; Montes, María L; Jusdado, Juan J; Gaspar, Gabriel; Esteban, Herminia; Bellón, José M; González-García, Juan

    2017-01-21

    We assessed non-liver-related non-AIDS-related (NLR-NAR) events and mortality in a cohort of HIV/HCV-coinfected patients treated with interferon and ribavirin between 2000 and 2008. The censoring date was May 31, 2014. Cox regression analysis was performed to assess the adjusted hazard rate (HR) of overall death in responders and non-responders. Fine and Gray regression analysis was conducted to determine the adjusted sub-hazard rate (sHR) of NLR deaths and NLR-NAR events considering death as the competing risk. The NLR-NAR events analyzed included diabetes mellitus, chronic renal failure, cardiovascular events, NLR-NAR cancer, bone events, and non-AIDS-related infections. The variables for adjustment were age, sex, prior AIDS, HIV-transmission category, nadir CD4+ T-cell count, antiretroviral therapy, HIV-RNA, liver fibrosis, HCV genotype, and exposure to specific anti-HIV drugs. Of the 1,625 patients included, 592 (36%) had a sustained viral response (SVR). After a median five-year follow-up, SVR was found to be associated with a significant decrease in the hazard of diabetes mellitus (sHR 0.57 [95% CI, 0.35 - 0.93] P= .024) and decline in the hazard of chronic renal failure close to the threshold of significance (sHR 0.43 [95% CI, 0.17 - 1.09], P=.075).

  17. AIDS-Related Stigma and Mental Disorders among People Living with HIV: A Cross-Sectional Study in Cambodia

    PubMed Central

    Yi, Siyan; Chhoun, Pheak; Suong, Samedy; Thin, Kouland; Brody, Carinne; Tuot, Sovannary

    2015-01-01

    Background AIDS-related stigma and mental disorders are the most common conditions in people living with HIV (PLHIV). We therefore conducted this study to examine the association of AIDS-related stigma and discrimination with mental disorders among PLHIV in Cambodia. Methods A two-stage cluster sampling method was used to select 1,003 adult PLHIV from six provinces. The People Living with HIV Stigma Index was used to measure stigma and discrimination, and a short version of general health questionnaire (GHQ-12) was used to measure mental disorders. Multivariate logistic regression analysis was conducted. Results The reported experiences of discrimination in communities in the past 12 months ranged from 0.8% for reports of being denied health services to 42.3% for being aware of being gossiped about. Internal stigma was also common ranging from 2.8% for avoiding going to a local clinic and/or hospital to 59.6% for deciding not to have (more) children. The proportions of PLHIV who reported fear of stigma and discrimination ranged from 13.9% for fear of being physically assaulted to 34.5% for fear of being gossiped about. The mean score of GHQ-12 was 3.2 (SD = 2.4). After controlling for several potential confounders, higher levels of mental disorders (GHQ-12≥ 4) remained significantly associated with higher levels of experiences of stigma and discrimination in family and communities (AOR = 1.9, 95% CI = 1.4–2.6), higher levels of internal stigma (AOR = 1.7, 95% CI = 1.2–2.3), and higher levels of fear of stigma and discrimination in family and communities (AOR = 1.5, 95% CI = 1.1–2.2). Conclusions AIDS-related stigma and discrimination among PLHIV in Cambodia are common and may have potential impacts on their mental health conditions. These findings indicate a need for community-based interventions to reduce stigma and discrimination in the general public and to help PLHIV to cope with this situation. PMID:25806534

  18. Specificity of anti-lymphocyte antibodies in sera from patients with AIDS-related complex (ARC) and healthy homosexuals.

    PubMed Central

    Warren, R Q; Johnson, E A; Donnelly, R P; Lavia, M F; Tsang, K Y

    1988-01-01

    The presence and specificity of anti-lymphocyte antibodies (ALA) was investigated in sera from male homosexuals with AIDS-Related Complex (ARC) as well as healthy homosexuals. Individuals in the healthy homosexual group had no detectable antibodies to human immunodeficiency virus (HIV). Antibodies reactive with normal peripheral blood mononuclear cells were detected by Western blot analysis in sera from both groups of homosexuals. Of those individuals whose sera contained ALA, 71% of ARC patients and 83% of healthy homosexuals had antibodies recognizing a 73 kilodalton (kD) molecule. ALA present in ARC sera reacted with CD3+, CD4+ and CD8+ lymphocytes while little reactivity with B cells was observed. Our results indicate that ALA appear in homosexuals prior to HIV infection and are reactive primarily with T lymphocytes. A 73 kD structure associated with the T cell membrane is frequently the target for these antibodies. Images Fig. 1 Fig. 2 Fig. 3 PMID:3052941

  19. Altered natural history of AIDS-related opportunistic infections in the era of potent combination antiretroviral therapy.

    PubMed

    Jacobson, M A; French, M

    1998-01-01

    Since potent HIV protease inhibitor drugs became widely available in early 1996, many HIV clinical specialists have noted a marked decrease in the occurrence of AIDS-related opportunistic infections, and some specialists have reported unusual clinical presentations and manifestations of previously common opportunistic infections. In this article, we will review (1) the available data regarding recent trends in AIDS-related opportunistic infections incidence and manifestations, (2) clinical and immunologic evidence that potent combination antiretroviral therapy can alter the natural history of these opportunistic infections, and (3) the implications of these findings for current patient management practice and future clinical and immunologic research. As a preface to this review, however, it is important to acknowledge that any evaluation of the potential benefit of potent combination antiretroviral therapy in reducing the risk of serious opportunistic infections can be confounded by the concomitant use of prophylactic antimicrobial agents co-administered to prevent specific opportunistic infections. For example, it is standard clinical practice to administer trimethoprim-sulfamethoxazole (or another agent if trimethoprim-sulfamethoxazole cannot be tolerated) to patients with an absolute CD4 lymphocyte count < 200 cells/microliters, unexplained chronic fever or a history of oropharyngeal candidiasis. Similarly, specific antimicrobial prophylaxis to prevent disseminated Mycobacterium avium complex (MAC) infection in patients with absolute CD4 counts < 50 cells/microliters is also a widely recommended guideline. Although the relative efficacies of specific antimicrobial prophylaxis regimens in preventing the most common life- and sight-threatening opportunistic infectious complications of AIDS [Pneumocystis carinii pneumonia (PCP), disseminated MAC infection, and cytomegalovirus (CMV) retinitis] are now well established, these relative efficacies were established in

  20. Topotecan Hydrochloride in Treating Children With Meningeal Cancer That Has Not Responded to Previous Treatment

    ClinicalTrials.gov

    2013-02-20

    AIDS-related Diffuse Large Cell Lymphoma; AIDS-related Diffuse Mixed Cell Lymphoma; AIDS-related Diffuse Small Cleaved Cell Lymphoma; AIDS-related Immunoblastic Large Cell Lymphoma; AIDS-related Lymphoblastic Lymphoma; AIDS-related Peripheral/Systemic Lymphoma; AIDS-related Primary CNS Lymphoma; AIDS-related Small Noncleaved Cell Lymphoma; Childhood Diffuse Large Cell Lymphoma; Childhood Immunoblastic Large Cell Lymphoma; HIV-associated Hodgkin Lymphoma; Leptomeningeal Metastases; Recurrent Childhood Acute Lymphoblastic Leukemia; Recurrent Childhood Acute Myeloid Leukemia; Recurrent Childhood Large Cell Lymphoma; Recurrent Childhood Lymphoblastic Lymphoma; Recurrent Childhood Medulloblastoma; Recurrent Childhood Small Noncleaved Cell Lymphoma; Recurrent/Refractory Childhood Hodgkin Lymphoma; Unspecified Childhood Solid Tumor, Protocol Specific

  1. Population Density and AIDS-Related Stigma in Large-Urban, Small-Urban, and Rural Communities of the Southeastern USA.

    PubMed

    Kalichman, Seth; Katner, Harold; Banas, Ellen; Kalichman, Moira

    2017-02-11

    AIDS stigmas delay HIV diagnosis, interfere with health care, and contribute to mental health problems among people living with HIV. While there are few studies of the geographical distribution of AIDS stigma, research suggests that AIDS stigmas are differentially experienced in rural and urban areas. We conducted computerized interviews with 696 men and women living with HIV in 113 different zip code areas that were classified as large-urban, small-urban, and rural areas in a southeast US state with high-HIV prevalence. Analyses conducted at the individual level (N = 696) accounting for clustering at the zip code level showed that internalized AIDS-related stigma (e.g., the sense of being inferior to others because of HIV) was experienced with greater magnitude in less densely populated communities. Multilevel models indicated that after adjusting for potential confounding factors, rural communities reported greater internalized AIDS-related stigma compared to large-urban areas and that small-urban areas indicated greater experiences of enacted stigma (e.g., discrimination) than large-urban areas. The associations between anticipated AIDS-related stigma (e.g., expecting discrimination) and population density at the community-level were not significant. Results suggest that people living in rural and small-urban settings experience greater AIDS-related internalized and enacted stigma than their counterparts living in large-urban centers. Research is needed to determine whether low-density population areas contribute to or are sought out by people who experienced greater AIDS-related stigma. Regardless of causal directions, interventions are needed to address AIDS-related stigma, especially among people in sparsely populated areas with limited resources.

  2. HIV/AIDS-related knowledge and behaviors among rural married migrant women in Shandong Province, China: a comparison study.

    PubMed

    Song, Yapei; Kang, Dianmin; Wang, Guoyong; Wei, Chongyi; Tao, Xiaorun; Huang, Tao; Qian, Yuesheng; Zhu, Tiwen; Yang, Shan; Yu, Shaoqi; Wang, Hong; Ma, Wei

    2015-02-01

    Migrant women in China are disproportionately affected by HIV/AIDS. This study described HIV/AIDS-related knowledge and behaviors among married migrant women in Shandong province in comparison to non-migrant local women and identified factors associated with HIV testing history and extramarital sex among married migrant women. A probability-based sample of 1,076 migrant and 1,195 local women were included in the analyses. Compared to local women, married migrant women had lower levels of HIV/AIDS knowledge and were more likely to have had premarital sex, extramarital sex, history of sexually transmitted diseases, and drug use. Less than a quarter of migrant women used condoms consistently in extramarital sex. Only 31.0 % of married migrant women had ever tested for HIV, and the rate of premarital HIV testing was very low. Multivariable analysis showed that married migrant women with a history of extramarital sex were more likely to be from Yunnan province, be living in Yantai city, be in their first marriage, have lower family income, have poor relationship with spouses, use drug, have a history of sexually transmitted diseases, and have lower social support. Our findings provide further evidence that married migrant women are at higher risk for HIV infection and that targeted interventions need to be developed for this population.

  3. Enthalpy Diffusion in Multicomponent Flows

    SciTech Connect

    Cook, A W

    2008-11-12

    The enthalpy diffusion flux in the multicomponent energy equation is a well known yet frequently neglected term. It accounts for energy changes, associated with compositional changes, resulting from species diffusion. Enthalpy diffusion is important in flows where significant mixing occurs between species of dissimilar molecular weight. The term plays a critical role in preventing local violations of the entropy condition. In simulations of nonpremixed combustion, omission of the enthalpy flux can lead to anomalous temperature gradients, which may cause mixing regions to exceed ignition conditions. The term can also play a role in generating acoustic noise in turbulent mixing layers. Euler solvers that rely on numerical diffusion to mix fluids cannot accurately predict the temperature in mixed regions. On the other hand, Navier-Stokes solvers that incorporate enthalpy diffusion can provide much more accurate results.

  4. Longitudinal Effects of Coping on Outcome in a Randomized Controlled Trial of a Group Intervention for HIV-Positive Adults with AIDS-Related Bereavement

    ERIC Educational Resources Information Center

    Hansen, Nathan B.; Tarakeshwar, Nalini; Ghebremichael, Musie; Zhang, Heping; Kochman, Arlene; Sikkema, Kathleen J.

    2006-01-01

    This study examined the longitudinal effects of coping on outcome one year following completion of a randomized, controlled trial of a group coping intervention for AIDS-related bereavement. Bereaved HIV-positive participants (N = 267) were administered measures of grief, psychiatric distress, quality of life, and coping at baseline,…

  5. The Unfinished Nature of Rights-Informed HIV- and AIDS-Related Education: An Analysis of Three School-Based Initiatives

    ERIC Educational Resources Information Center

    Miedema, Esther; Maxwell, Claire; Aggleton, Peter

    2015-01-01

    Over the past 25 years, there has been growing investment in concepts of rights in the areas of HIV prevention, care and treatment, including HIV- and AIDS-related education delivered in schools. Despite this increasing commitment to the notion of rights, few efforts appear to have been made to understand the varying conceptions of rights that…

  6. With and With"out": The Bereavement Experiences of Gay Men Who Have Lost a Partner to Non-AIDS-Related Causes

    ERIC Educational Resources Information Center

    Hornjatkevyc, Nina L.; Alderson, Kevin G.

    2011-01-01

    This study gives voice to the experiences of gay men who have lost a partner to non-AIDS-related causes, a subject that has received little attention in the psychological literature. Interviews were conducted with 8 gay men. An analysis informed by hermeneutic phenomenology generated themes and contextualized meanings regarding the participants'…

  7. Efficacy and safety of Stealth liposomal doxorubicin in AIDS-related Kaposi's sarcoma. The International SL-DOX Study Group.

    PubMed Central

    Goebel, F. D.; Goldstein, D.; Goos, M.; Jablonowski, H.; Stewart, J. S.

    1996-01-01

    The utility of current chemotherapeutic regimens in the treatment of AIDS-related Kaposi's sarcoma (AIDS-KS) is often compromised by both limited efficacy and substantial toxicity. Pegylated (Stealth) liposomal doxorubicin hydrochloride (SL-DOX) has been demonstrated specifically to deliver high concentrations of doxorubicin to Kaposi's sarcoma (KS) lesions. This phase II study was performed to evaluate the efficacy and safety of SL-DOX in the treatment of moderate to severe AIDS-KS. Patients were treated biweekly with 10, 20, or 40 mg m-2 SL-DOX. Tumour response was assessed according to AIDS Clinical Trials Groups (ACTG) criteria before each cycle. Best response was determined for 238 patients and was achieved after a mean of 2.3 cycles (range 1-20). Fifteen patients (6.3%) had a complete response to SL-DOX, 177 (74.4%) had a partial response, 44 (18.5%) had stable disease and two (0.8%) had disease progression. SL-DOX was well tolerated: ten patients discontinued therapy because of adverse events, in four cases because of neutropenia. Grade 3 or 4 neutropenia occurred after 281 of 2023 cycles (13.9%) but involved 137 of 240 patients (57.1%) for whom data were available. SL-DOX has substantial activity in AIDS-KS. Best response is typically seen after fewer than three cycles of chemotherapy and in some cases may be prolonged. The most important adverse event is neutropenia, which occurs after a minority of cycles but which may occur in over half of all patients. PMID:8611437

  8. HIV/AIDS-related stigma and discrimination: accounts of HIV-positive Caribbean people in the United Kingdom.

    PubMed

    Anderson, Moji; Elam, Gillian; Gerver, Sarah; Solarin, Ijeoma; Fenton, Kevin; Easterbrook, Philippa

    2008-09-01

    This paper explores the effects of HIV/AIDS-related stigma and discrimination (HASD) on HIV-positive Caribbean people in the Caribbean and the UK. In-depth, semi-structured interviews were held with a purposively selected group of 25 HIV-positive people of Caribbean origin, using primary selection criteria of sex, age, sexuality and country of birth. Interviews with respondents revealed that they are keenly aware of the stigma surrounding HIV/AIDS, which some attribute to a particularly Caribbean combination of fear of contamination, homophobia, and ignorance, reinforced by religious beliefs. In fact, religion serves a double role: underpinning stigma and assisting in coping with HIV. HASD has usually occurred where respondents have lost or do not have control over disclosure. Compared to UK-born respondents, the accounts of Caribbean-born respondents, most of whom were born in Jamaica, include more reports of severe HASD, particularly violence and employment discrimination. All respondents mobilise a variety of strategies in order to avoid HASD, which have implications for their social interactions and emotional well being. While some manage to avoid the "spoiled identity" of the stigmatised, thereby creating their own understandings of HIV infection, these may remain individual-level negotiations. HASD affects HIV-positive Caribbean people at home and in the diaspora in a variety of ways: emotionally, mentally, financially, socially and physically. Interventions specifically addressing stigma and discrimination must be formulated for the UK's Caribbean population. Tackling stigma and discrimination requires more than education; it requires "cultural work" to address deeply entrenched notions of sexuality.

  9. High titer anti-HIV antibody reactivity associated with a paraprotein spike in a homosexual male with AIDS related complex.

    PubMed

    Ng, V L; Hwang, K M; Reyes, G R; Kaplan, L D; Khayam-Bashi, H; Hadley, W K; McGrath, M S

    1988-05-01

    We observed a human immunodeficiency virus (HIV)-infected homosexual male with AIDS related complex (ARC) who had a serum globulin level of 80 g/L. Serum protein electrophoresis revealed a gamma globulin fraction of 40 g/L, of which 50% (20 g/L) was contained within a paraprotein spike, comprised predominantly of IgG kappa. This patient also had high titer anti-HIV antibodies in his serum, which were Western blot reactive at a final dilution of 1:500,000, and recognized gp120env, p66pol, p55gag, p53pol, p41gag, and p24gag. Because paraproteins in the past have been shown to be directed against specific antigens, we purified this patient's paraprotein using a modified high performance liquid chromatography (HPLC)-hydroxylapatite procedure and tested the purified paraprotein for anti-HIV antibody activity. The purified paraprotein retained anti-HIV antibody activity to a final dilution of 1:100,000, and recognized p66pol, p55gag, p53pol, p41gag, and p24gag. The recognition of both "gag" and "pol" gene products suggested that the purified paraprotein might not be monoclonal in origin. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) demonstrated that the purified paraprotein contained at least two immunoglobulin light chain species (Mol wt 30 to 33 Kd). Affinity chromatography of the purified paraprotein using a p24-Sepharose 4B matrix separated the "gag" and "pol" antibody activities. Immunoglobulin gene rearrangement analysis of a bone marrow aspirate (which contained 15% plasma cells) failed to reveal a clonal population of immunoglobulin producing cells. We conclude that this patient's paraprotein accounted for most of the anti-HIV activity present in whole serum, and that this paraprotein was not monoclonal in origin.

  10. Ecological effects of diffuse mixed pollution are site-specific and require higher-tier risk assessment to improve site management decisions: a discussion paper.

    PubMed

    Leo, Posthuma; Eijsackers, Herman J P; Koelmans, Albert A; Vijver, Martina G

    2008-12-01

    Many Dutch ecosystems, whether terrestrial, aquatic or sediment-based, are diffusely polluted by mixtures of contaminants, whose concentrations often exceed regulatory Safe Values or other generic quality criteria. This situation has unclear consequences, especially when local authorities are confronted with such pollution. Water managers are frequently in doubt whether their water systems satisfy the criteria for 'Good Ecological Status' as defined in the EU's Water Framework Directive. In case of soils, soil users may wonder whether the soil is 'fit for use'. In case of nature conservation, the problem is that protected species might suffer from toxic stress. Official regulations in these cases call for appropriate action, but it is unclear whether the diffuse exposure causes adverse effects, and what the action should be. This paper proposes and discusses a site-oriented approach in the risk assessment of diffusely contaminated sites that can be used in addition to the compound-oriented policies from which the abovementioned generic quality criteria were derived. The site-oriented approach can be of help in reducing site-specific risks of diffuse contamination. Reflecting on the results of a large Dutch research effort in systems-oriented ecotoxicological effects, the conclusion is drawn that exposure and effects of diffuse pollution are site-specific in kind and magnitude, determined by the local combination of source-pathway-receptor issues, and often not clearly detectable (though often present). To assist in risk management, higher-tier methods can address various aspects, like addressing local mixture composition, bioavailability, and sensitivity of local species groups. Higher-tier risk assessment methods have as yet been developed mainly for cases of serious contamination, like for pesticide management and Risk-Based Land Management. For diffuse pollution, site-specific information can also be used to obtain site-specific exposure and impact information

  11. Vorinostat and Combination Chemotherapy With Rituximab in Treating Patients With HIV-Related Diffuse Large B-Cell Non-Hodgkin Lymphoma or Other Aggressive B-Cell Lymphomas

    ClinicalTrials.gov

    2017-01-31

    AIDS-Related Diffuse Large Cell Lymphoma; AIDS-Related Plasmablastic Lymphoma; AIDS-Related Primary Effusion Lymphoma; Grade 3b Follicular Lymphoma; HIV Infection; Plasmablastic Lymphoma; Primary Effusion Lymphoma; Recurrent Adult Diffuse Large Cell Lymphoma; Recurrent Grade 3 Follicular Lymphoma; Stage I Adult Diffuse Large Cell Lymphoma; Stage I Grade 3 Follicular Lymphoma; Stage II Contiguous Adult Diffuse Large Cell Lymphoma; Stage II Grade 3 Contiguous Follicular Lymphoma; Stage II Grade 3 Non-Contiguous Follicular Lymphoma; Stage II Non-Contiguous Adult Diffuse Large Cell Lymphoma; Stage III Adult Diffuse Large Cell Lymphoma; Stage III Grade 3 Follicular Lymphoma; Stage IV Adult Diffuse Large Cell Lymphoma; Stage IV Grade 3 Follicular Lymphoma

  12. Study on effectiveness of gemcitabine, dexamethasone, and cisplatin (GDP) for relapsed or refractory AIDS-related non-Hodgkin's lymphoma.

    PubMed

    Zhong, Dong Ta; Shi, Chun Mei; Chen, Qiang; Huang, Jing Ze; Liang, Jian Gang

    2012-11-01

    Non-Hodgkin's lymphoma (NHL) remains the second most common malignant complication in patients with human immunodeficiency virus (HIV) infection. Even though NHL is commonly chemosensitive to primary treatment, failure or relapse still occurs in a large number of patients. We conducted this retrospective study to evaluate the efficacy and safety of gemcitabine, dexamethasone, and cisplatin (GDP) for relapsed or refractory AIDS-related NHL (AIDS-NHL). Forty-eight patients with relapsed or refractory AIDS-NHL were treated with intravenous combination chemotherapy with GDP. The overall objective response rate was 54.1% (95% confidence interval, CI, 40.1-68.3%), with 10 complete responses and 16 partial responses. The 2-year overall survival rate (OS) was 70.8% (95% CI 58.0-83.7%), and the 5-year OS was 41.7% (95% CI 27.7-55.6%). The 2-year progression-free survival rate (PFS) was 37.5% (95% CI 23.8-51.2%), and the 5-year PFS was 25.0% (95% CI 12.8-37.3%). The median progression-free survival was 8.8 months (95% CI 0-20.3 months), and the median overall survival was 40.6 months (95% CI 22.6-58.6 months). Patients with B cell tumors who relapsed but had no B symptoms were clinical stage I/II, had infiltration fewer than two extranodal sites, had CD4⁺ counts >200 cells/μL, and had lactate dehydrogenase (LDH) less than the upper limit of normal benefited from GDP. The level of LDH had a significant impact on the response rate to chemotherapy with GDP (P = 0.015). Myelosuppression was the main side effect; the incidence of grade 3-4 anemia was 8.3%; leukopenia, 37.5%; and thrombocytopenia, 48.3%. Univariate and multivariate analyses were performed to determine variables for OS and PFS. This study confirms that GDP is an effective and safe salvage regimen in relapsed or refractory AIDS-NHL, was associated with modest declines in CD4⁺ lymphocyte counts, and did not promote HIV-1 viral replication.

  13. Autograft HIV-DNA load predicts HIV-1 peripheral reservoir after stem cell transplantation for AIDS-related lymphoma patients.

    PubMed

    Zanussi, Stefania; Bortolin, Maria Teresa; Pratesi, Chiara; Tedeschi, Rosamaria; Basaglia, Giancarlo; Abbruzzese, Luciano; Mazzucato, Mario; Spina, Michele; Vaccher, Emanuela; Tirelli, Umberto; Rupolo, Maurizio; Michieli, Mariagrazia; Di Mascio, Michele; De Paoli, Paolo

    2015-01-01

    Autologous stem cell transplantation (ASCT) is a widely used procedure for AIDS-related lymphomas, and it represents an opportunity to evaluate strategies curing HIV-1 infection. The association of autograft HIV-DNA load with peripheral blood HIV-1 reservoir before ASCT and its contribution in predicting HIV-1 reservoir size and stability during combination antiretroviral therapy (cART) after transplantation are unknown. Aiming to obtain information suggesting new functional cure strategies by ASCT, we retrospectively evaluated HIV-DNA load in autograft and in peripheral blood before and after transplantation in 13 cART-treated HIV-1 relapse/refractoring lymphoma patients. Among them seven discontinued cART after autograft infusion. HIV-DNA was evaluated by a sensitive quantitative real-time polymerase chain reaction (PCR). After debulking chemotherapy/mobilization, the autograft HIV-1 reservoir was higher than and not associated with the peripheral HIV-1 reservoir at baseline [median 215 HIV-DNA copies/10(6) autograft mononuclear cells, range 13-706 vs. 82 HIV-DNA copies/10(6) peripheral blood mononuclear cells (PBMCs), range 13-479, p = 0.03]. After high dose chemotherapy and autograft infusion, HIV-DNA levels reached a plateau between month 6 and 12 of follow-up. No association was found between peripheral HIV-DNA levels at baseline and after infusion in both cART interrupting and not interrupting patients. Only in the last subgroup, a stable significant linear association between autograft and peripheral blood HIV-1 reservoir emerged from month 1 (R(2) = 0.84, p = 0.01) to month 12 follow-up (R(2) = 0.99, p = 0.0005). In summary, autograft HIV-1 reservoir size could be influenced by the mobilization phase and predicts posttransplant peripheral HIV-1 reservoir size in patients on continuous cART. These findings could promote new research on strategies reducing the HIV-1 reservoir by using the ASCT procedure.

  14. Mixed weak-perturbative solution method for Maxwell's equations of diffusion with Müller's partial stress tensor in the low velocity limit

    NASA Astrophysics Data System (ADS)

    Faliagas, A. C.

    2016-03-01

    Maxwell's theory of multicomponent diffusion and subsequent extensions are based on systems of mass and momentum conservation equations. The partial stress tensor, which is involved in these equations, is expressed in terms of the gradients of velocity fields by statistical and continuum mechanical methods. We propose a method for the solution of Maxwell's equations of diffusion coupled with Müller's expression for the partial stress tensor. The proposed method consists in a singular perturbation process, followed by a weak (finite element) analysis of the resulting PDE systems. The singularity involved in the obtained equations was treated by a special technique, by which lower-order systems were supplemented by proper combinations of higher-order equations. The method proved particularly efficient for the solution of the Maxwell-Müller system, eventually reducing the number of unknown fields to that of the classical Navier-Stokes/Fick system. It was applied to the classical Stefan tube problem and the Hagen-Poiseuille flow in a hollow-fiber membrane tube. Numerical results for these problems are presented, and compared with the Navier-Stokes/Fick approximation. It is shown that the 0-th order term of the Maxwell-Müller equations differs from a properly formulated Navier-Stokes/Fick system, by a numerically insignificant amount. Numerical results for 1st-order terms indicate a good agreement of the classical approximation (with properly formulated Navier-Stokes and Fick's equations) with the Maxwell-Müller system, in the studied cases.

  15. Nanoparticle volume fraction with heat and mass transfer on MHD mixed convection flow in a nanofluid in the presence of thermo-diffusion under convective boundary condition

    NASA Astrophysics Data System (ADS)

    Kandasamy, R.; Jeyabalan, C.; Sivagnana Prabhu, K. K.

    2016-02-01

    This article examines the influence of thermophoresis, Brownian motion of the nanoparticles with variable stream conditions in the presence of magnetic field on mixed convection heat and mass transfer in the boundary layer region of a semi-infinite porous vertical plate in a nanofluid under the convective boundary conditions. The transformed boundary layer ordinary differential equations are solved numerically using Maple 18 software with fourth-fifth order Runge-Kutta-Fehlberg method. Numerical results are presented both in tabular and graphical forms illustrating the effects of these parameters with magnetic field on momentum, thermal, nanoparticle volume fraction and solutal concentration boundary layers. The numerical results obtained for the velocity, temperature, volume fraction, and concentration profiles reveal interesting phenomenon, some of these qualitative results are presented through plots. It is interesting to note that the magnetic field plays a dominant role on nanofluid flow under the convective boundary conditions.

  16. A NEW MODEL FOR MIXING BY DOUBLE-DIFFUSIVE CONVECTION (SEMI-CONVECTION). II. THE TRANSPORT OF HEAT AND COMPOSITION THROUGH LAYERS

    SciTech Connect

    Wood, T. S.; Garaud, P.; Stellmach, S.

    2013-05-10

    Regions of stellar and planetary interiors that are unstable according to the Schwarzschild criterion, but stable according to the Ledoux criterion, are subject to a form of oscillatory double-diffusive (ODD) convection often called ''semi-convection''. In this series of papers, we use an extensive suite of three-dimensional (3D) numerical simulations to quantify the transport of heat and composition by ODD convection, and ultimately propose a new 1D prescription that can be used in stellar and planetary structure and evolution models. The first paper in this series demonstrated that under certain conditions ODD convection spontaneously transitions from an initial homogeneous state of weak wave-breaking turbulence into a staircase of fully convective layers, which results in a substantial increase in the transport of heat and composition. Here, we present simulations of ODD convection in this layered regime, we describe the dynamical behavior of the layers, and we derive empirical scaling laws for the transport through layered convection.

  17. Rotational diffusion of ionic and neutral solutes in mixed micelles: Effect of surfactant to block copolymer mole ratio on solute rotation

    NASA Astrophysics Data System (ADS)

    Mali, K. S.; Dutt, G. B.; Mukherjee, T.

    2007-10-01

    Rotational diffusion of an ionic solute rhodamine 110 and a neutral solute 2,5-dimethyl-1,4-dioxo-3,6-diphenylpyrrolo[3,4-c]pyrrole (DMDPP) has been investigated in aqueous mixtures of cetyltrimethylammonium chloride (CTAC) and poly(ethyleneoxide)20-poly(propyleneoxide)70-poly(ethyleneoxide)20 (P123). The purpose of this work is to understand how an increase in the mole ratio of surfactant to block copolymer from low to high influences the dynamics of ionic and neutral solute molecules. The variation in the mole ratio of CTAC to P123 from low to high has resulted in a drastic increase in the average reorientation time of rhodamine 110. In contrast, an exactly opposite trend has been noticed in the case of DMDPP. In the low mole ratio regime, rhodamine 110 and DMDPP are located at the interface and palisade layer, respectively, of P123 micelle-CTAC complexes. On the other hand, in the high mole ratio regime, both the probes are located in the Stern layer of CTAC-P123 complexes. The enhancement in the average reorientation time of rhodamine 110 with an increase in the mole ratio of surfactant to block copolymer has been rationalized on the basis of formation of rhodamine 110-Cl ion pair, which in turn associates with the cationic head groups of CTAC-P123 complexes. The observed decrease in the average reorientation time of DMDPP with an increase in the mole ratio of CTAC to P123 is a consequence of lower microviscosity of the Stern layer of CTAC-P123 complexes compared to the palisade layer of P123 micelle-CTAC complexes.

  18. Magnetically driven surface mixing

    NASA Astrophysics Data System (ADS)

    Belkin, M.; Snezhko, A.; Aranson, I. S.; Kwok, W.-K.

    2009-07-01

    Magnetic microparticles suspended on the surface of liquid and energized by vertical alternating magnetic field exhibit complex collective behavior. Various immobile and self-propelled self-assembled structures have been observed. Here, we report on experimental studies of mixing and surface diffusion processes in this system. We show that the pattern-induced surface flows have properties of quasi-two-dimensional turbulence. Correspondingly, the surface advection of tracer particle exhibits properties of Brownian diffusion.

  19. Individual attitudes and perceived social norms: Reports on HIV/AIDS-related stigma among service providers in China

    PubMed Central

    Li, Li; Liang, Li-Jung; Wu, Zunyou; Lin, Chunqing; Wen, Yi

    2009-01-01

    This study examined HIV/AIDS-related stigma among Chinese service providers by comparing their personal attitudes toward people living with HIV/AIDS with their perception of social norms related to people living with HIV/AIDS. We randomly selected three provincial hospitals, four city/prefecture hospitals, 10 county hospitals, 18 township health clinics, and 54 village clinics from Yunnan, China. Doctors and nurses were randomly sampled proportionally to the doctor-nurse ratio of each hospital or clinic. Lab technicians were over-sampled in order to include an adequate representation in the analysis. A total of 1,101 service providers participated in a voluntary, anonymous survey where demographic characteristics, individual attitude and perceived social norms toward people living with HIV/AIDS, discrimination intent at work, general prejudicial attitude and knowledge on HIV/AIDS were measured. A majority of the sample demonstrated a similarity between their personal views and what they thought most people in society believe. Multiple logistic regressions revealed that participants who were younger or reported personal contact with people living with HIV/AIDS were significantly more likely to report personal attitudes toward the population that were more liberal than their perceived social norms. Holding a more liberal personal attitude toward people living with HIV/AIDS than perceived social norms was significantly and negatively related to the level of discrimination intent at work, perceived discrimination at interpersonal level and the level of general prejudicial attitude toward people living with HIV/AIDS. Results underscored the importance of understanding social norms and personal attitudes in studying HIV-related stigma and called for the incorporation of existing human capital into future HIV stigma reduction programs. Cette étude a examiné le VIH/SIDA lié à stigmatisation parmi les agences chinoises fournissant des soins en comparant leurs attitudes

  20. Effect of media use on HIV/AIDS-related knowledge and condom use in sub-Saharan Africa: a cross-sectional study.

    PubMed

    Jung, Minsoo; Arya, Monisha; Viswanath, Kasisomayajula

    2013-01-01

    It is known that the level of HIV/AIDS-related knowledge and the degree of condom use varies by socioeconomic status (SES). However, there is limited research on the effect of mass media use on HIV/AIDS-related cognitive and behavioral outcomes in low-income countries and how it might influence the association between SES and HIV-related outcomes. We investigated the moderating effect of media use on the relationship between SES and HIV/AIDS-related knowledge and condom use in sub-Saharan Africa in terms of communication inequalities. Cross-sectional data from the Demographic Health Surveys from 13 sub-Saharan countries (2004-10) were pooled. Gender-stratified multivariable poisson regression of 151,209 women and 68,890 men were used to calculate adjusted relative ratios and 95% confidence intervals for the associations between SES, media use, HIV-related outcomes, and condom use. We found significant disparities in mass media use among people from different SES groups as well as among countries. Education and wealth are strongly and positively associated with awareness of HIV/AIDS and knowledge about transmission and prevention of HIV/AIDS and are significantly associated with condom use. These associations are attenuated when the use of various types of mass media is added to the models, with newspapers showing the strongest effect. The findings of this study suggest that media use has the potential to blunt the impact of socioeconomic status though not completely eliminate it. Thus, we need to pay attention to reducing communication inequalities among social groups and countries to moderate the effect of wealth and SES on HIV/AIDS.

  1. 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

  2. The effects of two AIDS risk-reduction interventions on heterosexual college women's AIDS-related knowledge, attitudes and condom use.

    PubMed

    Ploem, C; Byers, E S

    1997-01-01

    An intervention combining AIDS information with condom eroticization, condom normalization, and communication skills training was found to increase both AIDS-related knowledge and condom use among Canadian college students. 112 unmarried female undergraduates (mean age, 18 years) were randomly assigned to this combination intervention (n = 49), an information-only intervention (n = 44), or a pre-test/post-test control group (n = 19). 80% of students had engaged in vaginal intercourse and 14% in anal intercourse. 84% of coitally active women had engaged in unprotected intercourse in the past year and 48% had not used condoms consistently with any sexual partner. Condom use in the pre-intervention period was associated with positive attitudes toward the method and the perception that condom use was normative among peers. One month after the interventions, both the combination and information groups, but not controls, showed an increase over baseline in AIDS-related knowledge. However, among the 36 students who were coitally active in the 1-month periods before and after the intervention, only the combination intervention was associated with increased condom use. In the combination group, the percentage of episodes of intercourse protected by condoms increased from an average of 21.8% in the month preceding the study to 50% during the 4-week follow-up period. Due to the small sample size and design of the study, it was not possible to determine which component of the multifaceted educational intervention was most responsible for this change.

  3. 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.

  4. Monitoring HIV and AIDS Related Policy Reforms: A Road Map to Strengthen Policy Monitoring and Implementation in PEPFAR Partner Countries.

    PubMed

    Lane, Jeffrey; Verani, Andre; Hijazi, Mai; Hurley, Erin; Hagopian, Amy; Judice, Nicole; MacInnis, Ron; Sanford, Sallie; Zelek, Sarah; Katz, Aaron

    2016-01-01

    Achieving an AIDS-free generation will require the adoption and implementation of critical health policy reforms. However, countries with high HIV burden often have low policy development, advocacy, and monitoring capacity. This lack of capacity may be a significant barrier to achieving the AIDS-free generation goals. This manuscript describes the increased focus on policy development and implementation by the United States President's Emergency Plan for AIDS Relief (PEPFAR). It evaluates the curriculum and learning modalities used for two regional policy capacity building workshops organized around the PEPFAR Partnership Framework agreements and the Road Map for Monitoring and Implementing Policy Reforms. A total of 64 participants representing the U.S. Government, partner country governments, and civil society organizations attended the workshops. On average, participants responded that their policy monitoring skills improved and that they felt they were better prepared to monitor policy reforms three months after the workshop. When followed-up regarding utilization of the Road Map action plan, responses were mixed. Reasons cited for not making progress included an inability to meet or a lack of time, personnel, or governmental support. This lack of progress may point to a need for building policy monitoring systems in high HIV burden countries. Because the success of policy reforms cannot be measured by the mere adoption of written policy documents, monitoring the implementation of policy reforms and evaluating their public health impact is essential. In many high HIV burden countries, policy development and monitoring capacity remains weak. This lack of capacity could hinder efforts to achieve the ambitious AIDS-free generation treatment, care and prevention goals. The Road Map appears to be a useful tool for strengthening these critical capacities.

  5. Monitoring HIV and AIDS Related Policy Reforms: A Road Map to Strengthen Policy Monitoring and Implementation in PEPFAR Partner Countries

    PubMed Central

    2016-01-01

    Achieving an AIDS-free generation will require the adoption and implementation of critical health policy reforms. However, countries with high HIV burden often have low policy development, advocacy, and monitoring capacity. This lack of capacity may be a significant barrier to achieving the AIDS-free generation goals. This manuscript describes the increased focus on policy development and implementation by the United States President’s Emergency Plan for AIDS Relief (PEPFAR). It evaluates the curriculum and learning modalities used for two regional policy capacity building workshops organized around the PEPFAR Partnership Framework agreements and the Road Map for Monitoring and Implementing Policy Reforms. A total of 64 participants representing the U.S. Government, partner country governments, and civil society organizations attended the workshops. On average, participants responded that their policy monitoring skills improved and that they felt they were better prepared to monitor policy reforms three months after the workshop. When followed-up regarding utilization of the Road Map action plan, responses were mixed. Reasons cited for not making progress included an inability to meet or a lack of time, personnel, or governmental support. This lack of progress may point to a need for building policy monitoring systems in high HIV burden countries. Because the success of policy reforms cannot be measured by the mere adoption of written policy documents, monitoring the implementation of policy reforms and evaluating their public health impact is essential. In many high HIV burden countries, policy development and monitoring capacity remains weak. This lack of capacity could hinder efforts to achieve the ambitious AIDS-free generation treatment, care and prevention goals. The Road Map appears to be a useful tool for strengthening these critical capacities. PMID:26914708

  6. Enthalpy Diffusion in Multicomponent Flows

    SciTech Connect

    Cook, A W

    2009-01-20

    The conclusions of this paper are: (1) Enthalpy diffusion preserves the second law. (2) Euler solvers will not produce correct temperatures in mixing regions. (3) Navier-Stokes solvers will only produce correct temperatures if q{sub d} is included. (4) Errors from neglecting enthalpy diffusion are most severe when differences in molecular weights are large. (5) In addition to temperature, enthalpy diffusion affects density, dilatation and other fields in subtle ways. (6) Reacting flow simulations that neglect the term are a dubious proposition. (7) Turbulence models for RANS and LES closures should preserve consistency between energy and species diffusion.

  7. Microfluidic Mixing: A Review

    PubMed Central

    Lee, Chia-Yen; Chang, Chin-Lung; Wang, Yao-Nan; Fu, Lung-Ming

    2011-01-01

    The aim of microfluidic mixing is to achieve a thorough and rapid mixing of multiple samples in microscale devices. In such devices, sample mixing is essentially achieved by enhancing the diffusion effect between the different species flows. Broadly speaking, microfluidic mixing schemes can be categorized as either “active”, where an external energy force is applied to perturb the sample species, or “passive”, where the contact area and contact time of the species samples are increased through specially-designed microchannel configurations. Many mixers have been proposed to facilitate this task over the past 10 years. Accordingly, this paper commences by providing a high level overview of the field of microfluidic mixing devices before describing some of the more significant proposals for active and passive mixers. PMID:21686184

  8. Successful administration of aggressive chemotherapy concomitant to tuberculostatic and highly active antiretroviral therapy in a patient with AIDS-related Burkitt's lymphoma.

    PubMed

    Lehmann, C; Wyen, C; Hoffmann, C; Fätkenheuer, G

    2005-01-01

    Treatment of AIDS-related malignant lymphoma (ARL) remains a therapeutic challenge. There are concerns not only about infectious and haematological complications in HIV-infected patients during intensive chemotherapy, but also about potential interactions between chemotherapy and highly active antiretroviral therapy (HAART). Current data on patients treated concomitantly with intensive chemotherapy and HAART are limited, and no data exist on patients with ARL suffering from active opportunistic infections. We report the case of a 38-year-old man with advanced HIV-1 infection, pulmonary tuberculosis and Burkitt's lymphoma. Intensive chemotherapy was administered in parallel with tuberculostatic therapy and HAART. Six months later, the patient achieved not only a complete remission of Burkitt's lymphoma and sustained viral suppression, but also a full recovery from tuberculosis. This case report provides some useful observations on the successful application of intensive chemotherapy in addition to tuberculostatic therapy and HAART in HIV-infected patients.

  9. 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.

  10. Epstein-Barr virus-negative, CD5-positive diffuse large B-cell lymphoma developing after treatment with oral tacrolimus for mixed connective tissue disease : a case report and review of the literature.

    PubMed

    Sekiguchi, Yasunobu; Shimada, Asami; Imai, Hidenori; Wakabayashi, Mutsumi; Sugimoto, Keiji; Nakamura, Noriko; Sawada, Tomonori; Komatsu, Norio; Noguchi, Masaaki

    2012-01-01

    A 69-year-old woman, who had been diagnosed as having Sjögren's syndrome at 37 years old and mixed connective tissue disease at 42 years old, was under treatment with oral prednisolone. In 2009, she was diagnosed as having active systemic lupus erythematosus, and started on treatment with tacrolimus at 3 mg/day. In 2010, para-aortic lymphadenopathy and superficial multiple lymphadenopathy were detected. Tacrolimus was discontinued. Axillary lymph node biopsy revealed Epstein-Barr (EB) virus-negative CD5-positive diffuse large B-cell lymphoma (DLBCL). The patient was classified into clinical stage IIIA and as being at high risk according to the international prognostic index. After the discontinuation of tacrolimus, the lymph nodes reduced temporarily in size. In January 2011, the lymphadenopathy increased again, and the patient received a total of 8 courses of therapy with rituximab, pirarubicin, vincristine, cyclophosphamide and prednisolone, followed by intrathecal injection to prevent central nervous system infiltration, which was followed by complete remission. In February 2012, fluorodeoxyglucose positron emission tomography showed relapse in multiple lymph nodes and central nervous system infiltration. The patient was considered to have iatrogenic lymphoproliferative disorder classified as "other iatrogenic immunodeficiency-associated lymphoproliferative disorders" by the WHO, and this is the first reported case of CD5-positive DLBCL and central nervous system infiltration following administration of the drug. The patient was considered to have a poor prognosis as EB virus was negative, discontinuation of tacrolimus was ineffective and there was evidence of central nervous system infiltration.

  11. Evaluation and application of the diffusive gradients in thin films technique using a mixed-binding gel layer for measuring inorganic arsenic and metals in mining impacted water and soil.

    PubMed

    Huynh, Trang; Zhang, Hao; Noller, Barry

    2012-11-20

    The diffusive gradients in thin films (DGT) equipped with a Chelex or ferrihydrite binding gel has been designed to enable the measurement of either labile metal species or inorganic arsenic, respectively. In the mine impacted environment, metals and metalloids commonly coexist in a variety of species. This study, for the first time reports the performance of the DGT with a mixed-binding layer (MBL), consisting of Chelex and ferrihydrite for measurements of both metals and arsenic in a single assay. The MBL that consists of a combination of Chelex and ferrihydrite at a ratio of 1:2 has the greatest binding capacity for arsenic (As), cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn). The elemental concentrations measured by using MBL-DGT (C(DGT)) were comparable (92-104%) with the original test solution concentrations (C(SOL)). The measurement of As by using MBL-DGT was consistent across a wide pH range (3-8) and ionic strength (0.001-0.1 M). At high pH (9), As measurement was slightly affected (∼80%). The measurements of Cd, Pb, and Zn were affected at low pH (<3) and high pH (9). Measurements of Cd, Cu, and Pb were affected at low ionic strength (0.001 M). At high ionic strength (0.1 M), measurements of Cd; Cu and Pb were slightly affected. The capacity of MBL-DGT for quantitative measurement in a multielements solution is effectively limited to 15 μg for As and 70 μg for metals per MBL-DGT device. Good correlations (p < 0.01) between MBL-DGT measurements and ferrihydrite or Chelex DGT were obtained for As, Cd, Cu, Pb, and Zn in water and soil with exception for Cd and Cu (p < 0.05) when deployed in soil.

  12. Mixed cryoglobulinemia

    PubMed Central

    Ferri, Clodoveo

    2008-01-01

    Mixed cryoglobulinemia (MC), type II and type III, refers to the presence of circulating cryoprecipitable immune complexes in the serum and manifests clinically by a classical triad of purpura, weakness and arthralgias. It is considered to be a rare disorder, but its true prevalence remains unknown. The disease is more common in Southern Europe than in Northern Europe or Northern America. The prevalence of 'essential' MC is reported as approximately 1:100,000 (with a female-to-male ratio 3:1), but this term is now used to refer to a minority of MC patients only. MC is characterized by variable organ involvement including skin lesions (orthostatic purpura, ulcers), chronic hepatitis, membranoproliferative glomerulonephritis, peripheral neuropathy, diffuse vasculitis, and, less frequently, interstitial lung involvement and endocrine disorders. Some patients may develop lymphatic and hepatic malignancies, usually as a late complication. MC may be associated with numerous infectious or immunological diseases. When isolated, MC may represent a distinct disease, the so-called 'essential' MC. The etiopathogenesis of MC is not completely understood. Hepatitis C virus (HCV) infection is suggested to play a causative role, with the contribution of genetic and/or environmental factors. Moreover, MC may be associated with other infectious agents or immunological disorders, such as human immunodeficiency virus (HIV) infection or primary Sjögren's syndrome. Diagnosis is based on clinical and laboratory findings. Circulating mixed cryoglobulins, low C4 levels and orthostatic skin purpura are the hallmarks of the disease. Leukocytoclastic vasculitis involving medium- and, more often, small-sized blood vessels is the typical pathological finding, easily detectable by means of skin biopsy of recent vasculitic lesions. Differential diagnoses include a wide range of systemic, infectious and neoplastic disorders, mainly autoimmune hepatitis, Sjögren's syndrome, polyarthritis, and B

  13. HIV and AIDS related knowledge, sources of information, and reported need for further education among dental students in Sudan- a cross sectional study

    PubMed Central

    Nasir, Elwalid Fadul; Åstrøm, Anne Nordrehaug; David, Jamil; Ali, Rouf Wahab

    2008-01-01

    Background Information on the HIV and AIDS-related knowledge among dental students provides a crucial foundation for efforts aimed at developing an appropriate dental curriculum on HIV and AIDS, and for attracting the attention of dental school educators towards the subject. Purposes Focusing on a census of dental students attending their 3rd, 4th and 5th study year at publicly – and privately funded dental faculties in Khartoum, this study aimed to assess the prevalence and socio-economic correlates of dental students' knowledge, sources of information and reported need for further education related to HIV and AIDS. Methods At the time of the survey (March–May 2007), the total number of dental students registered was 782 of which 642 (response rate 82%, mean age 21.7 year, 72% girls) completed anonymous self-administered questionnaires in supervised class room settings. Results A total of 49% and 86% had correct sum scores with respect to knowledge of transmission through contamination and through shaking hands and eating, respectively. About half the dental students recognized a need for further education across HIV related issues, varying from 75% (basic HIV/AIDS related issues) to 84% (patient management). Only 38% of the students had correct sum scores regarding various occupational groups at risk for contacting HIV and AIDS. Multiple logistic regression analysis revealed that compared to privately funded dental school students, publicly funded dental school students were less likely to have correct knowledge about modes of HIV transmission (OR = 0.6) and occupational risk groups (OR = 0.6) and to have received information from lectures/health care workers (OR = 0.5). Conclusion Students attending privately funded schools were more knowledgeable about various HIV related issues than students from publicly funded schools. About half of the students investigated had received HIV/AIDS information from various sources and reported need for further education

  14. 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.

  15. 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.

  16. The dynamics of the production of AIDS-related stigma among pregnant women living with HIV/AIDS in Rio de Janeiro, Brazil.

    PubMed

    Monteiro, Simone; Villela, Wilza; Fraga, Livia; Soares, Priscilla; Pinho, Adriana

    2016-12-15

    The study analyses the relationship between AIDS-related stigma and the processes of discrimination prior to diagnosis among pregnant women living with HIV/AIDS. The fieldwork involved interviews about the life trajectories of 29 pregnant women living with HIV/AIDS, recruited at two AIDS services in Rio de Janeiro, Brazil. The analysis revealed that before HIV diagnosis, social and gender inequalities experienced by these women reduced their access to material and symbolic goods that could have enhanced educational and career prospects and their ability and autonomy to exercise sexual and reproductive rights. Being diagnosed with HIV triggered fear of moral judgment and of breakdown in social and family support networks. Given these fears, pregnant women living with HIV/AIDS opt for concealment of the diagnosis. It is necessary for health services, NGOs and government agencies to work together to face the factors that fuel stigma, such as socioeconomic and gender inequalities, taboos and prejudices related to sexuality, and also develop actions to enable women to redefine the meaning of the disease.

  17. Anomalous Sediment Mixing by Bioturbation

    NASA Astrophysics Data System (ADS)

    Roche, K. R.; Aubeneau, A. F.; Xie, M.; Packman, A. I.

    2013-12-01

    Bioturbation, the reworking of sediments by animals and plants, is the dominant mode of sediment mixing in low-energy environments, and plays an important role in sedimentary biogeochemical processes. Mixing resulting from bioturbation has historically been modeled as a diffusive process. However, diffusion models often do not provide a sufficient description of sediment mixing due to bioturbation. Stochastic models, such as the continuous time random walk (CTRW) model, provide more general descriptions of mixing behavior that are applicable even when regular diffusion assumptions are not met. Here we present results from an experimental investigation of anomalous sediment mixing by bioturbation in freshwater sediments. Clean and heavy-metal-contaminated sediments were collected from Lake DePue, a backwater lake of the Illinois River. The burrowing worm species Lumbriculus variegatus was introduced to homogenized Lake DePue sediments in aerated aquaria. We then introduced inert fine fluorescent particles to the sediment-water interface. Using time-lapse photography, we observed the mixing of the fluorescent particles into the sediment bed over a two-week period. We developed image analysis software to characterize the concentration distribution of the fluorescent particles as a function of sediment depth, and applied this to the time-series of images to evaluate sediment mixing. We fit a one-dimensional CTRW model to the depth profiles to evaluate the underlying statistical properties of the mixing behavior. This analysis suggests that the sediment mixing caused by L. variegatus burrowing is subdiffusive in time and superdiffusive in space. We also found that heavy metal contamination significantly reduces L. variegatus burrowing, causing increasingly anomalous sediment mixing. This result implies that there can be important feedbacks between sediment chemistry, organism behavior, and sediment mixing that are not considered in current environmental models.

  18. The Turbulent Diffusivity of Convective Overshoot

    NASA Astrophysics Data System (ADS)

    Lecoanet, Daniel; Schwab, Josiah; Quataert, Eliot; Bildsten, Lars; Timmes, Frank; Burns, Keaton; Vasil, Geoffrey; Oishi, Jeffrey; Brown, Benjamin

    2016-11-01

    There are many natural systems with convectively unstable fluid adjacent to stably stratified fluid; including the Earth's atmosphere, most stars, and perhaps even the Earth's liquid core. The convective motions penetrating into the stable region can enhance mixing, leading to changes in transport within the stable region. This work describes convective overshoot simulations. To study the extra mixing due to overshoot, we evolve a passive tracer field. The horizontal average of the passive tracer quickly approaches a self-similar state. The self-similar state is the solution to a diffusion equation with a spatially dependent turbulent diffusivity. We find the extra mixing due to convection can be accurately modeled as a turbulent diffusivity, and discuss implications of this turbulent diffusivity for the astrophysical problem of mixing in convectively bounded carbon flames.

  19. Mixing in polymeric microfluidic devices.

    SciTech Connect

    Schunk, Peter Randall; Sun, Amy Cha-Tien; Davis, Robert H.; Brotherton, Christopher M. (University of Colorado at Boulder, Boulder, CO)

    2006-04-01

    This SAND report describes progress made during a Sandia National Laboratories sponsored graduate fellowship. The fellowship was funded through an LDRD proposal. The goal of this project is development and characterization of mixing strategies for polymeric microfluidic devices. The mixing strategies under investigation include electroosmotic flow focusing, hydrodynamic focusing, physical constrictions and porous polymer monoliths. For electroosmotic flow focusing, simulations were performed to determine the effect of electroosmotic flow in a microchannel with heterogeneous surface potential. The heterogeneous surface potential caused recirculations to form within the microchannel. These recirculations could then be used to restrict two mixing streams and reduce the characteristic diffusion length. Maximum mixing occurred when the ratio of the mixing region surface potential to the average channel surface potential was made large in magnitude and negative in sign, and when the ratio of the characteristic convection time to the characteristic diffusion time was minimized. Based on these results, experiments were performed to evaluate the manipulation of surface potential using living-radical photopolymerization. The material chosen to manipulate typically exhibits a negative surface potential. Using living-radical surface grafting, a positive surface potential was produced using 2-(Dimethylamino)ethyl methacrylate and a neutral surface was produced using a poly(ethylene glycol) surface graft. Simulations investigating hydrodynamic focusing were also performed. For this technique, mixing is enhanced by using a tertiary fluid stream to constrict the two mixing streams and reduce the characteristic diffusion length. Maximum mixing occurred when the ratio of the tertiary flow stream flow-rate to the mixing streams flow-rate was maximized. Also, like the electroosmotic focusing mixer, mixing was also maximized when the ratio of the characteristic convection time to the

  20. Cation diffusion in titanomagnetites

    NASA Astrophysics Data System (ADS)

    Aragon, R.; McCallister, R. H.; Harrison, H. R.

    1984-02-01

    Interdiffusion couple experiments were performed with titanomagnetite single crystals at 1,000°C, 1,100° C and 1,200° C in various buffered atmospheres. The dependence of the interdiffusion coefficient on oxygen fugacity, composition and temperature was interpreted in terms of point defect structure. Estimates of the cation tracer diffusivities indicate that Fe migrates via a point defect mechanism, involving mixed tetrahedral-octahedral site jumps, with an activation energy of 33 Kcal/mole; whereas Ti migration is one to two orders of magnitude slower, is restricted to octahedral sites and has an activation energy of 60 Kcal/mole.

  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. Plasma kinetic effects on interfacial mix

    NASA Astrophysics Data System (ADS)

    Yin, L.; Albright, B. J.; Taitano, W.; Vold, E. L.; Chacon, L.; Simakov, A. N.

    2016-11-01

    Mixing at interfaces in dense plasma media is a problem central to inertial confinement fusion and high energy density laboratory experiments. In this work, collisional particle-in-cell simulations are used to explore kinetic effects arising during the mixing of unmagnetized plasma media. Comparisons are made to the results of recent analytical theory in the small Knudsen number limit and while the bulk mixing properties of interfaces are in general agreement, some differences arise. In particular, "super-diffusive" behavior, large diffusion velocity, and large Knudsen number are observed in the low density regions of the species mixing fronts during the early evolution of a sharp interface prior to the transition to a slow diffusive process in the small-Knudsen-number limit predicted by analytical theory. A center-of-mass velocity profile develops as a result of the diffusion process and conservation of momentum.

  4. Expandable mixing section gravel and cobble eductor

    DOEpatents

    Miller, Arthur L.; Krawza, Kenneth I.

    1997-01-01

    In a hydraulically powered pump for excavating and transporting slurries in hich it is immersed, the improvement of a gravel and cobble eductor including an expandable mixing section, comprising: a primary flow conduit that terminates in a nozzle that creates a water jet internal to a tubular mixing section of the pump when water pressure is applied from a primary supply flow; a tubular mixing section having a center line in alignment with the nozzle that creates a water jet; a mixing section/exit diffuser column that envelopes the flexible liner; and a secondary inlet conduit that forms an opening at a bas portion of the column and adjacent to the nozzle and water jet to receive water saturated gravel as a secondary flow that mixes with the primary flow inside of the mixing section to form a combined total flow that exits the mixing section and decelerates in the exit diffuser.

  5. Re-validation of the Van Rie HIV/AIDS-related stigma scale for use with people living with HIV in the United States.

    PubMed

    Kipp, Aaron M; Audet, Carolyn M; Earnshaw, Valerie A; Owens, Jared; McGowan, Catherine C; Wallston, Kenneth A

    2015-01-01

    There is little consensus about which of the many validated human immunodeficiency virus (HIV) stigma scales should be regularly used, with few being re-validated in different contexts or evaluated for how they compare to other, existing HIV stigma scales. The purpose of this exploratory study was to re-validate the Van Rie HIV/AIDS-Related Stigma Scale, originally validated in Thailand and using a third-person wording structure, for use with people living with HIV in the United States. Adult HIV clinic patients completed a survey including the Berger and Van Rie scales, and measures of social support and depression. Eighty-five of 211 (40%) eligible participants provided data for both stigma scales. Exploratory factor analyses identified three factors to the Van Rie scale: Loss of Social Relationships (new subscale), Managing HIV Concealment (new subscale), and Perceived Community Stigma (original subscale). These subscales were moderately inter-related (r = 0.51 to 0.58) with acceptable to excellent reliability (Cronbach's alpha = 0.69 to 0.90). The Van Rie subscales were also moderately inter-correlated with the Berger subscales (r = 0.44 to 0.76), had similar construct validity, and tended to have higher mean stigma scores when compared with Berger subscales that were conceptually most similar. The revised Van Rie HIV-related Stigma Scale demonstrates good validity and internal consistency, offering a valid measure of HIV stigma with a three-factor structure. The third-person wording may be particularly suitable for measuring stigmatizing attitudes during an individual's transition from at-risk and undergoing HIV testing to newly diagnosed, a time when experiences of discrimination and processing issues of disclosure have not yet occurred. The stigma mechanisms for individuals making this transition have not been well explored. These scenarios, combined with the observed non-response to the Berger Enacted Stigma subscale items (a surprise finding), highlight

  6. 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.

  7. 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)

  8. Mixed Dementia

    MedlinePlus

    ... with Lewy bodies , What Is Alzheimer's? NIA-Funded Memory & Aging Project Reveals Mixed Dementia Common Data from ... commonly with Alzheimer's disease. For example, in the Memory and Aging Project study involving long-term cognitive ...

  9. Ion mixing

    NASA Technical Reports Server (NTRS)

    Matteson, S.; Nicolet, M.-A.

    1983-01-01

    Recent experimental studies of the ion-mixing phenomenon are summarized. Ion mixing is differentiated from ion implantation and shown to be a useful technique for overcoming the sputter-dependent limitations of implantation processes. The fundamental physical principles of ion/solid interactions are explored. The basic experimental configurations currently in use are characterized: bilayered samples, multilayered samples, and samples with a thin marker layer. A table listing the binary systems (metal-semiconductor or metal-metal) which have been investigated using each configuration is presented. Results are discussed, and some sample data are plotted. The prospects for future application of ion mixing to the alteration of solid surface properties are considered. Practical applications are seen as restricted by economic considerations to the production of small, expensive components or to fields (such as the semiconductor industry) which already have facilities for ion implantation.

  10. Microfluidic mixing using contactless dielectrophoresis.

    PubMed

    Salmanzadeh, Alireza; Shafiee, Hadi; Davalos, Rafael V; Stremler, Mark A

    2011-09-01

    The first experimental evidence of mixing enhancement in a microfluidic system using contactless dielectrophoresis (cDEP) is presented in this work. Pressure-driven flow of deionized water containing 0.5 μm beads was mixed in various chamber geometries by imposing a dielectrophoresis (DEP) force on the beads. In cDEP the electrodes are not in direct contact with the fluid sample but are instead capacitively coupled to the mixing chamber through thin dielectric barriers, which eliminates many of the problems encountered with standard DEP. Four system designs with rectangular and circular mixing chambers were fabricated in PDMS. Mixing tests were conducted for flow rates from 0.005 to 1 mL/h subject to an alternating current signal range of 0-300 V at 100-600 kHz. When the time scales of the bulk fluid motion and the DEP motion were commensurate, rapid mixing was observed. The rectangular mixing chambers were found to be more efficient than the circular chambers. This approach shows potential for mixing low diffusivity biological samples, which is a very challenging problem in laminar flows at small scales.

  11. Modeling Mix in ICF Implosions

    NASA Astrophysics Data System (ADS)

    Weber, C. R.; Clark, D. S.; Chang, B.; Eder, D. C.; Haan, S. W.; Jones, O. S.; Marinak, M. M.; Peterson, J. L.; Robey, H. F.

    2014-10-01

    The observation of ablator material mixing into the hot spot of ICF implosions correlates with reduced yield in National Ignition Campaign (NIC) experiments. Higher Z ablator material radiatively cools the central hot spot, inhibiting thermonuclear burn. This talk focuses on modeling a ``high-mix'' implosion from the NIC, where greater than 1000 ng of ablator material was inferred to have mixed into the hot spot. Standard post-shot modeling of this implosion does not predict the large amounts of ablator mix necessary to explain the data. Other issues are explored in this talk and sensitivity to the method of radiation transport is found. Compared with radiation diffusion, Sn transport can increase ablation front growth and alter the blow-off dynamics of capsule dust. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  12. CO DIFFUSION INTO AMORPHOUS H{sub 2}O ICES

    SciTech Connect

    Lauck, Trish; Karssemeijer, Leendertjan; Cuppen, Herma M.; Shulenberger, Katherine; Rajappan, Mahesh; Öberg, Karin I. E-mail: koberg@cfa.harvard.edu

    2015-03-10

    The mobility of atoms, molecules, and radicals in icy grain mantles regulates ice restructuring, desorption, and chemistry in astrophysical environments. Interstellar ices are dominated by H{sub 2}O, and diffusion on external and internal (pore) surfaces of H{sub 2}O-rich ices is therefore a key process to constrain. This study aims to quantify the diffusion kinetics and barrier of the abundant ice constituent CO into H{sub 2}O-dominated ices at low temperatures (15–23 K), by measuring the mixing rate of initially layered H{sub 2}O(:CO{sub 2})/CO ices. The mixed fraction of CO as a function of time is determined by monitoring the shape of the infrared CO stretching band. Mixing is observed at all investigated temperatures on minute timescales and can be ascribed to CO diffusion in H{sub 2}O ice pores. The diffusion coefficient and final mixed fraction depend on ice temperature, porosity, thickness, and composition. The experiments are analyzed by applying Fick’s diffusion equation under the assumption that mixing is due to CO diffusion into an immobile H{sub 2}O ice. The extracted energy barrier for CO diffusion into amorphous H{sub 2}O ice is ∼160 K. This is effectively a surface diffusion barrier. The derived barrier is low compared to current surface diffusion barriers in use in astrochemical models. Its adoption may significantly change the expected timescales for different ice processes in interstellar environments.

  13. Genetically Modified Peripheral Blood Stem Cell Transplant in Treating Patients With HIV-Associated Non-Hodgkin or Hodgkin Lymphoma

    ClinicalTrials.gov

    2015-05-06

    Adult Nasal Type Extranodal NK/T-cell Lymphoma; AIDS-related Diffuse Large Cell Lymphoma; AIDS-related Diffuse Mixed Cell Lymphoma; AIDS-related Diffuse Small Cleaved Cell Lymphoma; AIDS-related Immunoblastic Large Cell Lymphoma; AIDS-related Lymphoblastic Lymphoma; AIDS-related Peripheral/Systemic Lymphoma; AIDS-related Small Noncleaved Cell Lymphoma; Anaplastic Large Cell Lymphoma; Angioimmunoblastic T-cell Lymphoma; Cutaneous B-cell Non-Hodgkin Lymphoma; Extranodal Marginal Zone B-cell Lymphoma of Mucosa-associated Lymphoid Tissue; Hepatosplenic T-cell Lymphoma; HIV-associated Hodgkin Lymphoma; Intraocular Lymphoma; Nodal Marginal Zone B-cell Lymphoma; Noncutaneous Extranodal Lymphoma; Peripheral T-cell Lymphoma; Recurrent Adult Burkitt Lymphoma; Recurrent Adult Diffuse Large Cell Lymphoma; Recurrent Adult Diffuse Mixed Cell Lymphoma; Recurrent Adult Diffuse Small Cleaved Cell Lymphoma; Recurrent Adult Grade III Lymphomatoid Granulomatosis; Recurrent Adult Hodgkin Lymphoma; Recurrent Adult Immunoblastic Large Cell Lymphoma; Recurrent Adult Lymphoblastic Lymphoma; Recurrent Adult T-cell Leukemia/Lymphoma; Recurrent Cutaneous T-cell Non-Hodgkin Lymphoma; Recurrent Grade 1 Follicular Lymphoma; Recurrent Grade 2 Follicular Lymphoma; Recurrent Grade 3 Follicular Lymphoma; Recurrent Mantle Cell Lymphoma; Recurrent Marginal Zone Lymphoma; Recurrent Mycosis Fungoides/Sezary Syndrome; Recurrent Small Lymphocytic Lymphoma; Refractory Hairy Cell Leukemia; Small Intestine Lymphoma; Splenic Marginal Zone Lymphoma; Stage I AIDS-related Lymphoma; Stage II AIDS-related Lymphoma; Stage III AIDS-related Lymphoma; Stage IV AIDS-related Lymphoma; T-cell Large Granular Lymphocyte Leukemia; Testicular Lymphoma; Waldenström Macroglobulinemia

  14. Fluid dynamics of double diffusive systems

    SciTech Connect

    Koseff, J.R.

    1989-04-07

    A study of mixing processes in doubly diffusive systems is being conducted. Continuous gradients of two diffusing components (heat and salinity in our case) are being used as initial conditions, and forcing is introduced by lateral heating and surface shear. The goals of the proposed work include: (1) quantification of the effects of finite amplitude disturbances on stable, double diffusive systems, particularly with respect to lateral heating, (2) development of an improved understanding of the physical phenomena present in wind-driven shear flows in double diffusive stratified environments, (3) increasing our knowledge-base on turbulent flow in stratified environments and how to represent it, and (4) formulation of a numerical code for such flows. The work is being carried out in an experimental facility which is located in the Stanford Environmental Fluid Mechanics Laboratory, and on laboratory minicomputers and CRAY computers. In particular we are focusing on the following key issues: (1) the formation and propagation of double diffusive intrusions away from a heated wall and the effects of lateral heating on the double diffusive system; (2) the interaction between the double diffusively influenced fluxes and the turbulence induced fluxes; (3) the measurement of heat and mass fluxes; and (4) the influence of double diffusive gradients on mixed layer deepening. 1 fig.

  15. 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.

  16. Lateral Mixing

    DTIC Science & Technology

    2013-09-30

    apl.uw.edu/dasaro LONG-TERM GOALS I seek to understand the processes controlling lateral mixing in the ocean, particularly at the submesoscale ...APPROACH During AESOP, Lee and D’Asaro pioneered an innovative approach to measuring submesoscale structure in strong fronts. An adaptive measurement...injection of potential vorticity and scalars is predicted to create an intense ‘ submesoscale soup’ of high small-scale variance. The combination of small

  17. Lateral Mixing

    DTIC Science & Technology

    2012-11-08

    to mesoscale forcing. APPROACH Figure 1: MVP system deployed from stern of R/V Endeavor in Sargasso Sea . 1 DISTRIBUTION STATEMENT A. Approved for...integrative efforts with other sea -going investigators and numerical modelers. The Lateral Mixing Experiment project was an ideal opportunity to...2011 I also participated in the sea -going part of this project, taking my group on the R/V Endeavor in June 2011. Our role was to sample around the

  18. Lateral Mixing

    DTIC Science & Technology

    2011-09-30

    ocean as it responds to mesoscale forcing. APPROACH Figure 1: MVP system deployed from stern of R/V Endeavor in Sargasso Sea . My approach for...therefore requires integrative efforts with other sea -going investigators and numerical modelers. The Lateral Mixing Experiment project was an ideal...also participated in the sea -going part of this project, taking my group on the R/V Endeavor in June 2011. Our role was to sample around the center of

  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. 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.

  3. 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.

  4. 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

  5. Image-based color ink diffusion rendering.

    PubMed

    Wang, Chung-Ming; Wang, Ren-Jie

    2007-01-01

    This paper proposes an image-based painterly rendering algorithm for automatically synthesizing an image with color ink diffusion. We suggest a mathematical model with a physical base to simulate the phenomenon of color colloidal ink diffusing into absorbent paper. Our algorithm contains three main parts: a feature extraction phase, a Kubelka-Munk (KM) color mixing phase, and a color ink diffusion synthesis phase. In the feature extraction phase, the information of the reference image is simplified by luminance division and color segmentation. In the color mixing phase, the KM theory is employed to approximate the result when one pigment is painted upon another pigment layer. Then, in the color ink diffusion synthesis phase, the physically-based model that we propose is employed to simulate the result of color ink diffusion in absorbent paper using a texture synthesis technique. Our image-based ink diffusing rendering (IBCIDR) algorithm eliminates the drawback of conventional Chinese ink simulations, which are limited to the black ink domain, and our approach demonstrates that, without using any strokes, a color image can be automatically converted to the diffused ink style with a visually pleasing appearance.

  6. Overexpression of MicroRNAs from the miR-17-92 Paralog Clusters in AIDS-Related Non-Hodgkin's Lymphomas

    PubMed Central

    Thapa, Dharma R.; Li, Xinmin; Jamieson, Beth D.; Martínez-Maza, Otoniel

    2011-01-01

    Background Individuals infected by HIV are at an increased risk for developing non-Hodgkin's lymphomas (AIDS-NHL). In the highly active antiretroviral therapy (HAART) era, there has been a significant decline in the incidence of AIDS-associated primary central nervous system lymphoma (PCNSL). However, only a modest decrease in incidence has been reported for other AIDS-NHL subtypes. Thus, AIDS-NHLs remain a significant cause of morbidity and mortality in HIV infected individuals. Recently, much attention has been directed toward the role of miRNAs in cancer, including NHL. Several miRNAs, including those encoded by the miR-17-92 polycistron, have been shown to play significant roles in B cell tumorigenesis. However, the role of miRNAs in NHL in the setting of HIV infection has not been defined. Methodology/Principal Findings We used quantitative realtime PCR to assess the expression of miRNAs from three different paralog clusters, miR-17-92, miR-106a-363, and miR-106b-25 in 24 cases of AIDS-NHLs representing four tumor types, Burkitt's lymphoma (BL, n = 6), diffuse large B-cell lymphoma (DLBCL, n = 8), primary central nervous system lymphoma (PCNSL, n = 5), and primary effusion lymphoma (PEL, n = 5). We also used microarray analysis to identify a differentiation specific miRNA signature of naïve, germinal center, and memory B cell subsets from tonsils (n = 4). miRNAs from the miR-17-92 paralog clusters were upregulated by B cells, specifically during the GC differentiation stage. We also found overexpression of these miRNA clusters in all four AIDS-NHL subtypes. Finally, we also show that select miRNAs from these clusters (miR-17, miR-106a, and miR-106b) inhibited p21 in AIDS-BL and DLBCL cases, thus providing a mechanistic role for these miRNAs in AIDS-NHL pathogenesis. Conclusion Dysregulation of miR-17-92 paralog clusters is a common feature of AIDS-associated NHLs. PMID:21698185

  7. A Stratospheric Mixing and Transport Sampler

    NASA Technical Reports Server (NTRS)

    Sparling, Lynn

    1999-01-01

    The mixing and transport of stratospheric chemical species occurs by a variety of physical mechanisms on a range of length and time scales. Slow vertical diffusion resembles Taylor diffusion in pipe flow, while rapid stirring by chaotic advection is essentially a "baker's transformation", via the stretching and folding of material lines in the flow. Other examples include global scale transport by large organized flow structures, such as the winter stratospheric "eggbeater" that brings tropical air to the north pole. This presentation is a survey of these different mixing and transport phenomena and how we see their signatures in observations of chemical tracers.

  8. 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.

  9. Transition mixing study

    NASA Technical Reports Server (NTRS)

    Reynolds, R.; White, C.

    1986-01-01

    A computer model capable of analyzing the flow field in the transition liner of small gas turbine engines is developed. A FORTRAN code has been assembled from existing codes and physical submodels and used to predict the flow in several test geometries which contain characteristics similar to transition liners, and for which experimental data was available. Comparisons between the predictions and measurements indicate that the code produces qualitative results but that the turbulence models, both K-E and algebraic Reynolds Stress, underestimate the cross-stream diffusion. The code has also been used to perform a numerical experiment to examine the effect of a variety of parameters on the mixing process in transition liners. Comparisons illustrate that geometries with significant curvature show a drift of the jet trajectory toward the convex wall and weaker wake region vortices and decreased penetration for jets located on the convex wall of the liner, when compared to jets located on concave walls. Also shown were the approximate equivalency of angled slots and round holes and a technique by which jet mixing correlations developed for rectangular channels can be used for can geometries.

  10. 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.

  11. Crystal structure, diffusion path, and oxygen permeability of a Pr(2)NiO(4)-based mixed conductor (Pr(0.9)La(0.1))(2)(Ni(0.74)Cu(0.21)Ga(0.05))O(4+delta).

    PubMed

    Yashima, Masatomo; Sirikanda, Nuansaeng; Ishihara, Tatsumi

    2010-02-24

    We have investigated in situ the crystal structure, oxygen diffusion path, oxygen permeation rate, and electrical conductivity of a doped praseodymium nickel oxide, Pr(2)NiO(4)-based mixed conductor, (Pr(0.9)La(0.1))(2)(Ni(0.74)Cu(0.21)Ga(0.05))O(4+delta) (PLNCG) in air between 27 degrees C and 1015.6 degrees C. The PLNCG has a tetragonal I4/mmm K(2)NiF(4)-type structure which consists of a (Pr(0.9)La(0.1))(Ni(0.74)Cu(0.21)Ga(0.05))O(3) perovskite unit and a (Pr(0.9)La(0.1))O rock salt unit in the whole temperature range. Both experimental and theoretical electron density maps indicated two-dimensional networks of (Ni(0.74)Cu(0.21)Ga(0.05))-O covalent bonds in PLNCG. Highest occupied molecular orbitals (HOMO) in PLNCG demonstrate that the electron-hole conduction occurs via Ni and Cu atoms in the (Ni(0.74)Cu(0.21)Ga(0.05))-O layer. The bulk oxygen permeation rate was high (137 mumol cm(-2) min(-1) at 1000 degrees C), and its activation energy was low (51 kJ mol(-1) at 950 degrees C). The Rietveld method, maximum-entropy method (MEM), and MEM-based pattern fitting analyses of neutron and synchrotron diffraction data indicate a large anisotropic thermal motion of the apical O2 oxygen at the 4e site (0, 0, z; z approximately 0.2) in the (Pr(0.9)La(0.1))(Ni(0.74)Cu(0.21)Ga(0.05))O(3) perovskite unit. Neutron and synchrotron diffraction data and theoretical structural optimization show the interstitial oxygen (O3) atom at (x, 0, z) (x approximately 0.6 and z approximately 0.2). The nuclear density analysis indicates that the bulk oxide-ion diffusion, which is responsible for the high oxygen permeation rate, occurs through the interstitial O3 and anisotropic apical O2 sites. The nuclear density at the bottleneck on the oxygen diffusion path increases with temperature and with the oxygen permeation rate. The activation energy from the nuclear density at the bottleneck decreases with temperature, which is consistent with the decrease of the activation energy from oxygen

  12. Weak Atomic Diffusion Trends in NGC 6752

    NASA Astrophysics Data System (ADS)

    Gruyters, Pieter; Korn, Andreas J.; Barklem, Paul S.

    2014-01-01

    Atomic diffusion (AD) is a slow continuous process that depletes heavy elements such as Fe from the surface layers during the MS lifetime of a star. As the star evolves to the RGB the effect of depletion disappears as its deep outer convection zone restores the original composition in the atmosphere. Mixing processes at work below the outer convection zone reduce the effect of AD as they hinder the downward diffusion of heavy elements, and thus a more efficient mixing will cause flattened diffusion trends. Such additional mixing (AddMix) seems to be needed to reproduce observed abundance trends. Although the inclusion of extra mixing in a layer just below the convective envelope is remarkably successful in describing the observed abundance trends in NGC 6397 ([Fe/H] = -2.1), the description applied is in no way unique or physically satisfying. To better understand the physics and place additional constraints on the possible variation of extra mixing with stellar parameters such as metallicity, we conducted a study, similar to that presented in Korn et al. (2007), of another metal-poor GC NGC 6752 ([Fe/H] = -1.6). In Fig. 1 we show the results, published in Gruyters et al. (2013), which shows weak yet systematic abundance trends with evolutionary phase for Fe, Sc, Ti and Ca. The trends are best explained by stellar structure models including AD with efficient AddMix. As a consequence sub-primordial stellar lithium abundances of the stars on the Spite plateau can be brought up to match the WMAP-calibrated Big Bang nucleosynthesis predictions to within the mutual 1-sigma errors.

  13. Diffusely reflecting paints including polytetrafluoroethylene and method of manufacture

    NASA Technical Reports Server (NTRS)

    Schutt, J. B.; Shai, M. C. (Inventor)

    1985-01-01

    The invention pertains to a high diffuse, reflective paint comprising an alcohol soluble binder, polytetrafluoroethylene (TFE) and an alcohol for coating a substrate and forming an optical reference with a superior Lambertian characteristic. A method for making the paint by first mixing the biner and alcohol, and thereafter by mixing in outgassed TFE is described. A wetting agent may be employed to aid the mixing process.

  14. Molecular simulations and experimental studies of solubility and diffusivity for pure and mixed gases of H2, CO2, and Ar absorbed in the ionic liquid 1-n-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([hmim][Tf2N]).

    PubMed

    Shi, Wei; Sorescu, Dan C; Luebke, David R; Keller, Murphy J; Wickramanayake, Shan

    2010-05-20

    Classical molecular dynamics and Monte Carlo simulations are used to calculate the self-diffusivity and solubility of pure and mixed CO(2), H(2), and Ar gases absorbed in the ionic liquid 1-n-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([hmim][Tf(2)N]). Overall, the computed absorption isotherms, Henry's law constants, and partial molar enthalpies for pure H(2) agree well with the experimental data obtained by Maurer et al. [J. Chem. Eng. Data 2006, 51, 1364] and the experimental values determined in this work. However, the agreement is poor between the simulations and the experimental data by Noble et al. [Ind. Eng. Chem. Res. 2008, 47, 3453] and Costa Gomes [J. Chem. Eng. Data 2007, 52, 472] at high temperatures. The computed H(2) permeability values are in good agreement with the experimental data at 313 K obtained by Luebke et al. [J. Membr. Sci. 2007, 298, 41; ibid, 2008, 322, 28], but about three times larger than the experimental value at 573 K from the same group. Our computed H(2) solubilities using different H(2) potential models have similar values and solute polarizations were found to have a negligible effect on the predicted gas solubilities for both the H(2) and Ar. The interaction between H(2) and the ionic liquid is weak, about three times smaller than between the ionic liquid and Ar and six times smaller than that of CO(2) with the ionic liquid, results that are consistent with a decreasing solubility from CO(2) to Ar and to H(2). The molar volume of the ionic liquid was found to be the determining factor for the H(2) solubility. For mixed H(2) and Ar gases, the solubilities for both solutes decrease compared to the respective pure gas solubilities. For mixed gases of CO(2) and H(2), the solubility selectivity of CO(2) over H(2) decreases from about 30 at 313 K to about 3 at 573 K. For the permeability, the simulated values for CO(2) in [hmim][Tf(2)N] are about 20-60% different than the experimental data by Luebke et al. [J. Membr

  15. 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.

  16. Calculation and application of combined diffusion coefficients in thermal plasmas

    NASA Astrophysics Data System (ADS)

    Murphy, Anthony B.

    2014-03-01

    The combined diffusion coefficient method is widely used to treat the mixing and demixing of different plasma gases and vapours in thermal plasmas, such as welding arcs and plasma jets. It greatly simplifies the treatment of diffusion for many gas mixtures without sacrificing accuracy. Here, three subjects that are important in the implementation of the combined diffusion coefficient method are considered. First, it is shown that different expressions for the combined diffusion coefficients, arising from different definitions for the stoichiometric coefficients that assign the electrons to the two gases, are equivalent. Second, an approach is presented for calculating certain partial differential terms in the combined temperature and pressure diffusion coefficients that can cause difficulties. Finally, a method for applying the combined diffusion coefficients in computational models, which typically require diffusion to be expressed in terms of mass fraction gradients, is given.

  17. Extremely slow intramolecular diffusion in unfolded protein L.

    PubMed

    Waldauer, Steven A; Bakajin, Olgica; Lapidus, Lisa J

    2010-08-03

    A crucial parameter in many theories of protein folding is the rate of diffusion over the energy landscape. Using a microfluidic mixer we have observed the rate of intramolecular diffusion within the unfolded B1 domain of protein L before it folds. The diffusion-limited rate of intramolecular contact is about 20 times slower than the rate in 6 M GdnHCl, and because in these conditions the protein is also more compact, the intramolecular diffusion coefficient decreases 100-500 times. The dramatic slowdown in diffusion occurs within the 250 micros mixing time of the mixer, and there appears to be no further evolution of this rate before reaching the transition state of folding. We show that observed folding rates are well predicted by a Kramers model with a denaturant-dependent diffusion coefficient and speculate that this diffusion coefficient is a significant contribution to the observed rate of folding.

  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. Continuous Microfluidic Mixing Using Pulsatile Micropumps

    NASA Astrophysics Data System (ADS)

    Deshmukh, Ajay; Liepmann, Dorian

    2000-11-01

    For many microfluidic and micro-TAS applications, the mixing of two fluids is required. At small length scales, however, traditional means of mixing, such as turbulence generation, are impossible yet diffusion is often too slow. For laminar mixing, 3 degrees of freedom are required. Since MEMS are normally 2-D, time-dependence is added for the third degree of freedom. This process involves the use of two positive displacement pumps to alternatively deliver two different fluids into a common channel and utilizing Taylor dispersion to mix them. This mixing process was modelled numerically and confirmed via experimental observation of fluorescent dye in a fabricated MEMS mixer. The pumps used in the device are a new design consisting of a bubble-piston and two check valves.

  4. Postglacial matrix diffusion in a boulder sample

    SciTech Connect

    Rasilainen, K.; Suksi, J.; Kulmala, S.; Hellmuth, K.H.; Lindberg, A.

    1996-08-01

    A boulder sample was studied for its unusual U content. Analyses of U-series nuclides within the rock matrix perpendicular to an assumed fracture face show abrupt pulse-like concentration distributions with very low concentrations of U daughters. Both Th-230/U-234 and Pa-231/U-235 activity ratios are low, indicating recent U accumulation into the rock. Matrix diffusion is tested as a possible cause for the experimental observations. The authors assume that the diffusion process was triggered and controlled by rock expansion, strong mixing of different water types and rapid land uplift at the end phase of the last glaciation.

  5. AIDS-related mycoses: the way forward.

    PubMed

    Brown, Gordon D; Meintjes, Graeme; Kolls, Jay K; Gray, Clive; Horsnell, William; Achan, Beatrice; Alber, Gottfried; Aloisi, Maria; Armstrong-James, Darius; Beale, Mathew; Bicanic, Tihana; Black, John; Bohjanen, Paul; Botes, Angela; Boulware, David R; Brown, Gordon; Bunjun, Rubina; Carr, William; Casadevall, Arturo; Chang, Christina; Chivero, Ernest; Corcoran, Craig; Cross, Anna; Dawood, Halima; Day, Jeremy; De Bernardis, Flavia; De Jager, Veronique; De Repentigny, Louis; Denning, David; Eschke, Maria; Finkelman, Malcolm; Govender, Nelesh; Gow, Neil; Graham, Lisa; Gryschek, Ronaldo; Hammond-Aryee, Kenneth; Harrison, Tom; Heard, Neil; Hill, Melanie; Hoving, J Claire; Janoff, Edward; Jarvis, Joseph; Kayuni, Sekeleghe; King, Karin; Kolls, Jay; Kullberg, Bart-Jan; Lalloo, David G; Letang, Emilio; Levitz, Stuart; Limper, Andrew; Longley, Nicky; Machiridza, Tendai Rodney; Mahabeer, Yesholata; Martinsons, Neil; Meiring, Susan; Meya, David; Miller, Robert; Molloy, Sile; Morris, Lynn; Mukaremera, Liliane; Musubire, Abdu K; Muzoora, Conrad; Nair, Amy; Nakiwala Kimbowa, Justine; Netea, Mihai; Nielsen, Kirsten; O'hern, Jennifer; Okurut, Samuel; Parker, Arifa; Patterson, Tom; Pennap, Grace; Perfect, John; Prinsloo, Chrisna; Rhein, Joshua; Rolfes, Melissa A; Samuel, Catherine; Schutz, Charlotte; Scriven, James; Sebolai, Olihile M; Sojane, Katlego; Sriruttan, Charlotte; Stead, David; Steyn, Annica; Thawer, Narjis K; Thienemann, Friedrich; Von Hohenberg, Maximilian; Vreulink, Jo-marie; Wessels, Jeannette; Wood, Kathryn; Yang, Yun-liang

    2014-03-01

    The contribution of fungal infections to the morbidity and mortality of HIV-infected individuals is largely unrecognized. A recent meeting highlighted several priorities that need to be urgently addressed, including improved epidemiological surveillance, increased availability of existing diagnostics and drugs, more training in the field of medical mycology, and better funding for research and provision of treatment, particularly in developing countries.

  6. Mobility aid-related accidents in children.

    PubMed

    2012-02-01

    During the period 1991-2008, more than 63 000 children were examined in US emergency rooms following an accident related to a mobility aid: 40% of the children were less than 10 years old; 60% of the accidents occurred at home; and 4.4% of the children were hospitalised. Wheelchairs were the devices most often involved (67%), followed by crutches and walkers. Most accidents involving children under 10 years old were linked to a walker or wheelchair, and mainly resulted in head injuries. Most of the accidents in older children involved crutches and caused lower-limb sprains. In practice, the correct use of mobility aids should be explained to parents and children, and information given about the circumstances most likely to lead to accidents. Children using these devices should be supervised if necessary.

  7. Diagnosis of AIDS-Related Intestinal Parasites

    DTIC Science & Technology

    1989-01-20

    evaluated, only anecdotal success has been reported. In at least three trials, spiramycin , previously the most promising agent, has now been shown to... spiramycin , were ineffective. The patient received the hyperimmune colostrum by direct duodenal infusion, and during infusion, the patient’s fecal output...J Gastro 1086; 81:456-458. 11. Moskovitz BL, Stanton TL, Kusmierek JJE. Spiramycin therapy for cryptosporidial diarrhoea in imrnunocompromised

  8. Diagnosis of AIDS-Related Intestinal Parasites

    DTIC Science & Technology

    1990-06-20

    nosocomial outbreaks of cryptosporidiosis have been recorded from Italy, South Africa, and Argentina . In the first, six patients on a bone marrow...examination; this was considered consistent with hospital spread (32). in a renal transplant unit in Buenos Aires, Argentina , 11 of 14 patients with acute...Peruvian Per-Urban Shanty Town (Pueblo joven ) (submitted). Significance: In a field setting, ELISA testing offers a cheap, quick and reliable diagnostic

  9. Dentistry and HIV/AIDS related stigma

    PubMed Central

    Elizondo, Jesus Eduardo; Treviño, Ana Cecilia; Violant, Deborah

    2015-01-01

    OBJECTIVE To analyze HIV/AIDS positive individual’s perception and attitudes regarding dental services. METHODS One hundred and thirty-four subjects (30.0% of women and 70.0% of men) from Nuevo León, Mexico, took part in the study (2014). They filled out structured, analytical, self-administered, anonymous questionnaires. Besides the sociodemographic variables, the perception regarding public and private dental services and related professionals was evaluated, as well as the perceived stigma associated with HIV/AIDS, through a Likert-type scale. The statistical evaluation included a factorial and a non-hierarchical cluster analysis. RESULTS Social inequalities were found regarding the search for public and private dental professionals and services. Most subjects reported omitting their HIV serodiagnosis and agreed that dentists must be trained and qualified to treat patients with HIV/AIDS. The factorial analysis revealed two elements: experiences of stigma and discrimination in dental appointments and feelings of concern regarding the attitudes of professionals or their teams concerning patients’ HIV serodiagnosis. The cluster analysis identified three groups: users who have not experienced stigma or discrimination (85.0%); the ones who have not had those experiences, but feel somewhat concerned (12.7%); and the ones who underwent stigma and discrimination and feel concerned (2.3%). CONCLUSIONS We observed a low percentage of stigma and discrimination in dental appointments; however, most HIV/AIDS patients do not reveal their serodiagnosis to dentists out of fear of being rejected. Such fact implies a workplace hazard to dental professionals, but especially to the very own health of HIV/AIDS patients, as dentists will not be able to provide them a proper clinical and pharmaceutical treatment. PMID:26538100

  10. Diagnosis of AIDS-Related Intestinal Parasites

    DTIC Science & Technology

    1988-01-07

    Peru), Claudio F. Lanata (Instituto de Investigacion Nutricional , Lima, Peru) and Irene Perez-Schael (Instituto de Biomedicina, Caracas, Venezuela) (15...above) and Homero Martinez, M.D., Instituto National de la Nutricion , Mexico City. In this study, 53 children with at least one microscopic stool

  11. Matrix-assisted diffusion-ordered spectroscopy: choosing a matrix.

    PubMed

    Gramosa, Nilce V; Ricardo, Nágila M S P; Adams, Ralph W; Morris, Gareth A; Nilsson, Mathias

    2016-06-07

    Diffusion-ordered spectroscopy (DOSY) is an important technique for separating the NMR signals of the components in a mixture, and relies on differences in diffusion coefficient. Standard DOSY experiments therefore struggle when the components of a mixture are of similar size, and hence diffuse at similar rates. Fortunately, the diffusion coefficients of solutes can be manipulated by changing the matrix in which they diffuse, using matrix components that interact differentially with them, a technique known as matrix-assisted DOSY. In the present investigation, we evaluate the performance of a number of new, previously used, and mixed matrices with an informative test mixture: the three positional isomers of dihydroxybenzene. The aim of this work is to present the matrix-assisted DOSY user with information about the potential utility of a set of matrices (and combinations of matrices), including ionic and non-ionic surfactants, complexing agents, polymers, and mixed solvents. A variety of matrices improved the diffusion resolution of the signals of the test system, with the best separation achieved by mixed micelles of sodium dodecyl sulfate and cetyl trimethylammonium bromide. The use of mixed matrices offers great potential for the analyst to tailor the matrix to a particular sample under study. © 2016 The Authors Magnetic Resonance in Chemistry Published by John Wiley & Sons, Ltd.

  12. 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.

  13. Can whales mix the ocean?

    NASA Astrophysics Data System (ADS)

    Lavery, T. J.; Roudnew, B.; Seuront, L.; Mitchell, J. G.; Middleton, J.

    2012-07-01

    Ocean mixing influences global climate and enhances primary productivity by transporting nutrient rich water into the euphotic zone. The contribution of the swimming biosphere to diapycnal mixing in the ocean has been hypothesised to occur on scales similar to that of tides or winds, however, the extent to which this contributes to nutrient transport and stimulates primary productivity has not been explored. Here, we introduce a novel method to estimate the diapycnal diffusivity that occurs as a result of a sperm whale swimming through a pycnocline. Nutrient profiles from the Hawaiian Ocean are used to further estimate the amount of nitrogen transported into the euphotic zone and the primary productivity stimulated as a result. We estimate that the 80 sperm whales that travel through an area of 104 km2 surrounding Hawaii increase diapycnal diffusivity by 10-6 m2 s-1 which results in the flux of 105 kg of nitrogen into the euphotic zone each year. This nitrogen input subsequently stimulates 6 × 105 kg of carbon per year. The nutrient input of swimming sperm whales is modest compared to dominant modes of nutrient transport such as nitrogen fixation but occurs more consistently and thus may provide the nutrients necessary to enable phytoplankton growth and survival in the absence of other seasonal and daily nutrient inputs.

  14. 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.

  15. Diapycnal mixing by meso-scale eddies

    NASA Astrophysics Data System (ADS)

    Eden, Carsten; Greatbatch, Richard J.

    The mean available potential energy released by baroclinic instability into the meso-scale eddy field has to be dissipated in some way and Tandon and Garrett [Tandon, A., Garrett, C., 1996. On a recent parameterization of mesoscale eddies. J. Phys. Oceanogr. 26 (3), 406-416] suggested that this dissipation could ultimately involve irreversible mixing of buoyancy by molecular processes at the small-scale end of the turbulence cascade. We revisit this idea and argue that the presence of dissipation within the thermocline automatically requires that a component of the eddy flux associated with meso-scale eddies must be associated with irreversible mixing of buoyancy within the thermocline. We offer a parameterisation of the implied diapycnal diffusivity based on (i) the dissipation rate for eddy kinetic energy given by the meso-scale eddy closure of Eden and Greatbatch [Eden, C., Greatbatch, R.J., 2008. Towards a meso-scale eddy closure. Ocean Modell. 20, 223-239.] and (ii) a fixed mixing efficiency. The implied eddy-induced diapycnal diffusivity ( κ) is implemented in a coarse resolution model of the North Atlantic. In contrast to the vertical diffusivity given by a standard vertical mixing scheme, large lateral inhomogeneities can be found for κ in the interior of the ocean. In general, κ is large, i.e. up to o(10) cm 2/s, near the western boundaries and almost vanishing in the interior of the ocean.

  16. Efficiency of Metal Mixing in Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Hirai, Yutaka; Saitoh, Takayuki R.

    2017-04-01

    Metal mixing plays a critical role in the enrichment of metals in galaxies. The abundance of elements such as Mg, Fe, and Ba in metal-poor stars helps us understand the metal mixing in galaxies. However, the efficiency of metal mixing in galaxies is not yet understood. Here we report a series of N-body/smoothed particle hydrodynamics simulations of dwarf galaxies with different efficiencies of metal mixing using a turbulence-induced mixing model. We show that metal mixing apparently occurs in dwarf galaxies from Mg and Ba abundances. We find that a scaling factor for metal diffusion larger than 0.01 is necessary to reproduce the measured abundances of Ba in dwarf galaxies. This value is consistent with the value expected from turbulence theory and experiments. We also find that the timescale of metal mixing is less than 40 Myr. This timescale is shorter than the typical dynamical times of dwarf galaxies. We demonstrate that the determination of a degree of scatters of Ba abundance by the observation will help us to better constrain the efficiency of metal mixing.

  17. 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.

  18. 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.

  19. 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.

  20. First principles nonequilibrium plasma mixing

    NASA Astrophysics Data System (ADS)

    Ticknor, C.; Herring, S. D.; Lambert, F.; Collins, L. A.; Kress, J. D.

    2014-01-01

    We have performed nonequilibrium classical and quantum-mechanical molecular dynamics simulations that follow the interpenetration of deuterium-tritium (DT) and carbon (C) components through an interface initially in hydrostatic and thermal equilibrium. We concentrate on the warm, dense matter regime with initial densities of 2.5-5.5 g/cm3 and temperatures from 10 to 100 eV. The classical treatment employs a Yukawa pair-potential with the parameters adjusted to the plasma conditions, and the quantum treatment rests on an orbital-free density functional theory at the Thomas-Fermi-Dirac level. For times greater than about a picosecond, the component concentrations evolve in accordance with Fick's law for a classically diffusing fluid with the motion, though, described by the mutual diffusion coefficient of the mixed system rather than the self-diffusion of the individual components. For shorter times, microscopic processes control the clearly non-Fickian dynamics and require a detailed representation of the electron probability density in space and time.

  1. Laboratory studies of ocean mixing by microorganisms

    NASA Astrophysics Data System (ADS)

    Martinez-Ortiz, Monica; Dabiri, John O.

    2011-11-01

    Ocean mixing plays a major role in nutrient and energy transport and is an important input to climate models. Recent studies suggest that the contribution of fluid transport by swimming microorganisms to ocean mixing may be of the same order of magnitude as winds and tides. An experimental setup has been designed in order to study the mixing efficiency of vertical migration of plankton. To this end, a stratified water column is created to model the ocean's density gradient. The vertical migration of Artemia Salina (brine shrimp) within the water column is controlled via luminescent signals on the top and bottom of the column. By fluorescently labelling portions of the water column, the stirring of the density gradient by the animals is visualized and quantified. Preliminary results show that the vertical movement of these organisms produces enhanced mixing relative to control cases in which only buoyancy forces and diffusion are present.

  2. Improvements in Mixing Time and Mixing Uniformity in Devices Designed for Studies of Protein Folding Kinetics

    SciTech Connect

    Yao, Shuhuai; Bakajin, Olgica

    2007-08-01

    Using a microfluidic laminar flow mixer designed for studies of protein folding kinetics, we demonstrate a mixing time of 1 +/- 1 micros with sample consumption on the order of femtomoles. We recognize two limitations of previously proposed designs: (1) size and shape of the mixing region, which limits mixing uniformity and (2) the formation of Dean vortices at high flow rates, which limits the mixing time. We address these limitations by using a narrow shape-optimized nozzle and by reducing the bend of the side channel streamlines. The final design, which combines both of these features, achieves the best performance. We quantified the mixing performance of the different designs by numerical simulation of coupled Navier-Stokes and convection-diffusion equations and experiments using fluorescence resonance energy-transfer (FRET)-labeled DNA.

  3. 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…

  4. 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

  5. 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…

  6. 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.

  7. 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.

  8. Water vapor diffusion membrane development

    NASA Technical Reports Server (NTRS)

    Tan, M. K.

    1977-01-01

    An application of the water vapor diffusion technique is examined whereby the permeated water vapor is vented to space vacuum to alleviate on-board waste storage and provide supplemental cooling. The work reported herein deals primarily with the vapor diffusion-heat rejection (VD-HR) as it applies to the Space Shuttle. A stack configuration was selected, designed and fabricated. An asymmetric cellulose acetate membrane, used in reverse osmosis application was selected and a special spacer was designed to enhance mixing and promote mass transfer. A skid-mount unit was assembled from components used in the bench unit although no attempt was made to render it flight-suitable. The operating conditions of the VD-HR were examined and defined and a 60-day continuous test was carried out. The membranes performed very well throughout the test; no membrane rupture and no unusual flux decay was observed. In addition, a tentative design for a flight-suitable VD-HR unit was made.

  9. Diffusion in Coulomb crystals

    SciTech Connect

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

    2011-07-15

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

  10. Diffusion in Coulomb crystals.

    PubMed

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

    2011-07-01

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

  11. 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.

  12. Diapycnal mixing in an Arctic coastal polynya

    NASA Astrophysics Data System (ADS)

    Bouruet-Aubertot, P.; Jardon, F.; Vivier, F.; Lourenço, A.; Cuypers, Y.

    2009-12-01

    Ocean mixing plays an important role in climate variability. In Arctic coastal polynyas, which are regions of dense water formation, internal wave activity and turbulent mixing can affect the ice cover through induced ocean-ice heat flux. Mixing can also affect the fate of dense waters once formed. In March 2007, a 60m-long ice tethered mooring, recording temperature and salinity at high frequency, with a relatively fine vertical resolution was deployed in the western part of Storfjorden in the Svalbard archipelago. Estimates of turbulent dissipation rates were derived from isopycnal vertical displacements. Eddy diffusivity was next inferred using a parameterization that depends on the energetics of the stratified turbulent flow. Observed levels of dissipation of turbulent potential energy per unit mass, 1.82 x 10e-7 W/kg, and diapycnal diffusivity, 2.8 x 10e-4 m2/s, were consistent with previous direct measurements in the region. The maximum values were found under the ice-ocean interface and down to 35m with a relative minimum in between, suggesting two differents energy source. As the ice cap limits mixing by the winds, internal ocean dynamics becomes a prominent source of mixing, especially in coastal regions. The influence of tides as a possible energy source for the internal wave field was therefore investigated. Finally, the internal wave field is compared with those at mid-latitudes and reasonable agreement with the Garret-Munk model is found.

  13. Risk of lymph node metastasis in mixed-type early gastric cancer determined by the extent of the poorly differentiated component

    PubMed Central

    Hwang, Chung-Su; Ahn, Sangjeong; Lee, Bong-Eun; Lee, So-Jeong; Kim, Ahrong; Choi, Chang In; Kim, Dae Hwan; Jeon, Tae-Yong; Kim, Gwang Ha; Song, Geum Am; Park, Do Youn

    2016-01-01

    AIM: To predict the rate of lymph node (LN) metastasis in diffuse- and mixed-type early gastric cancers (EGC) for guidelines of the treatment. METHODS: We reviewed 550 cases of EGC with diffuse- and mixed-type histology. We investigated the clinicopathological factors and histopathological components that influence the probability of LN metastasis, including sex, age, site, gross type, presence of ulceration, tumour size, depth of invasion, perineural invasion, lymphovascular invasion, and LN metastasis status. We reviewed all slides and estimated the proportions of each tumour component; pure diffuse type, mixed-predominantly diffuse type (diffuse > intestinal type), mixed-predominantly intestinal type (intestinal > diffuse type), and mixed diffuse = intestinal type. We calculated the extents of the respective components. RESULTS: LN metastasis was observed in 12.9% (71/550) of early gastric cancers cases [15/288 mucosal EGCs (5.2%) and 56/262 submucosal EGCs (21.4%)]. Of 550 cases, 302 were diffuse-type and 248 were mixed-type EGCs. Of 248 mixed-type EGCs, 163 were mixed-predominantly diffuse type, 82 were mixed-predominantly intestinal type, and 3 were mixed diffuse = intestinal type. Mixed-type cases with predominantly diffuse type histology showed a higher frequency of LN metastasis (20.2%) than cases of pure diffuse type (9.3%) and predominantly intestinal type (12.2%) histology. We measured the dimensions of each component (intestinal and diffuse type) to determine the association of the extent of each component with LN metastasis in mixed-type gastric carcinoma. The total tumour size and the extent of poorly differentiated components was associated with LN metastasis, while that of signet ring cell components was not. CONCLUSION: We recommend careful identification and quantitative evaluation of mixed-type early gastric cancer components after endoscopic resection to determine the intensity of the treatment. PMID:27099445

  14. Least-squares streamline diffusion finite element approximations to singularly perturbed convection-diffusion problems

    SciTech Connect

    Lazarov, R D; Vassilevski, P S

    1999-05-06

    In this paper we introduce and study a least-squares finite element approximation for singularly perturbed convection-diffusion equations of second order. By introducing the flux (diffusive plus convective) as a new unknown, the problem is written in a mixed form as a first order system. Further, the flux is augmented by adding the lower order terms with a small parameter. The new first order system is approximated by the least-squares finite element method using the minus one norm approach of Bramble, Lazarov, and Pasciak [2]. Further, we estimate the error of the method and discuss its implementation and the numerical solution of some test problems.

  15. 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

  16. Viscosity and mutual diffusion in strongly asymmetric binary ionic mixtures

    SciTech Connect

    Bastea, Sorin

    2005-05-01

    We present molecular dynamics simulation results for the viscosity and mutual diffusion constant of a strongly asymmetric binary ionic mixture. We compare the results with available theoretical models previously tested for much smaller asymmetries. For the case of viscosity we propose a predictive framework based on the linear mixing rule, while for mutual diffusion we discuss some consistency problems of widely used Boltzmann-equation-based models.

  17. Viscosity and mutual diffusion in strongly asymmetric plasma mixtures

    SciTech Connect

    Bastea, S

    2004-09-07

    The authors present molecular dynamics simulation results for the viscosity and mutual diffusion constant of a strongly asymmetric two-component plasma (TCP). They compare the results with available theoretical models previously tested for much smaller asymmetries. for the case of viscosity they propose a new predictive framework based on the linear mixing rule, while for mutual diffusion they point out some consistency problems of widely used Boltzmann equation based models.

  18. Mixing in colliding, ultrasonically levitated drops.

    PubMed

    Chainani, Edward T; Choi, Woo-Hyuck; Ngo, Khanh T; Scheeline, Alexander

    2014-02-18

    Lab-in-a-drop, using ultrasonic levitation, has been actively investigated for the last two decades. Benefits include lack of contact between solutions and an apparatus and a lack of sample cross-contamination. Understanding and controlling mixing in the levitated drop is necessary for using an acoustically levitated drop as a microreactor, particularly for studying kinetics. A pulsed electrostatic delivery system enables addition and mixing of a desired-volume droplet with the levitated drop. Measurement of mixing kinetics is obtained by high-speed video monitoring of a titration reaction. Drop heterogeneity is visualized as 370 nl of 0.25 M KOH (pH: 13.4) was added to 3.7 μL of 0.058 M HCl (pH: 1.24). Spontaneous mixing time is about 2 s. Following droplet impact, the mixed drop orbits the levitator axis at about 5 Hz during homogenization. The video's green channel (maximum response near 540 nm) shows the color change due to phenolphthalein absorption. While mixing is at least an order of magnitude faster in the levitated drop compared with three-dimensional diffusion, modulation of the acoustic waveform near the surface acoustic wave resonance frequency of the levitated drop does not substantially reduce mixing time.

  19. 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.

  20. Tungsten diffusion in silicon

    SciTech Connect

    De Luca, A.; Texier, M.; Burle, N.; Oison, V.; Pichaud, B.; Portavoce, A.; Grosjean, C.

    2014-01-07

    Two doses (10{sup 13} and 10{sup 15} cm{sup −2}) of tungsten (W) atoms were implanted in different Si(001) wafers in order to study W diffusion in Si. The samples were annealed or oxidized at temperatures between 776 and 960 °C. The diffusion profiles were measured by secondary ion mass spectrometry, and defect formation was studied by transmission electron microscopy and atom probe tomography. W is shown to reduce Si recrystallization after implantation and to exhibit, in the temperature range investigated, a solubility limit close to 0.15%–0.2%, which is higher than the solubility limit of usual metallic impurities in Si. W diffusion exhibits unusual linear diffusion profiles with a maximum concentration always located at the Si surface, slower kinetics than other metals in Si, and promotes vacancy accumulation close to the Si surface, with the formation of hollow cavities in the case of the higher W dose. In addition, Si self-interstitial injection during oxidation is shown to promote W-Si clustering. Taking into account these observations, a diffusion model based on the simultaneous diffusion of interstitial W atoms and W-Si atomic pairs is proposed since usual models used to model diffusion of metallic impurities and dopants in Si cannot reproduce experimental observations.

  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. A multifluid mix model with material strength effects

    SciTech Connect

    Chang, C. H.; Scannapieco, A. J.

    2012-04-23

    We present a new multifluid mix model. Its features include material strength effects and pressure and temperature nonequilibrium between mixing materials. It is applicable to both interpenetration and demixing of immiscible fluids and diffusion of miscible fluids. The presented model exhibits the appropriate smooth transition in mathematical form as the mixture evolves from multiphase to molecular mixing, extending its applicability to the intermediate stages in which both types of mixing are present. Virtual mass force and momentum exchange have been generalized for heterogeneous multimaterial mixtures. The compression work has been extended so that the resulting species energy equations are consistent with the pressure force and material strength.

  4. LDV Measurement of Confined Parallel Jet Mixing

    SciTech Connect

    R.F. Kunz; S.W. D'Amico; P.F. Vassallo; M.A. Zaccaria

    2001-01-31

    Laser Doppler Velocimetry (LDV) measurements were taken in a confinement, bounded by two parallel walls, into which issues a row of parallel jets. Two-component measurements were taken of two mean velocity components and three Reynolds stress components. As observed in isolated three dimensional wall bounded jets, the transverse diffusion of the jets is quite large. The data indicate that this rapid mixing process is due to strong secondary flows, transport of large inlet intensities and Reynolds stress anisotropy effects.

  5. Mixing and Transport in the Surfzone

    DTIC Science & Technology

    2008-01-01

    also sample chlrophyl A ( Omand et al, submitted). The dye sampling jetski and fixed fluorometers were deployed at Huntington Beach, as part of the HB06...field experiment. SIO graduate PhD student David Clark, co- advised with Dr Feddersen, is using these observations to characterize surfzone mixing...the similarity theory of turbulence to atmospheric diffusion. Quart. J. Roy. Meteor. Soc., 76, 133–146, 1950 Clark, D.B., F. Feddersen, M. Omand

  6. Method of making gas diffusion layers for electrochemical cells

    DOEpatents

    Frisk, Joseph William; Boand, Wayne Meredith; Larson, James Michael

    2002-01-01

    A method is provided for making a gas diffusion layer for an electrochemical cell comprising the steps of: a) combining carbon particles and one or more surfactants in a typically aqueous vehicle to make a preliminary composition, typically by high shear mixing; b) adding one or more highly fluorinated polymers to said preliminary composition by low shear mixing to make a coating composition; and c) applying the coating composition to an electrically conductive porous substrate, typically by a low shear coating method.

  7. Mixing in astrophysics

    SciTech Connect

    Fryer, Christopher Lee

    2011-01-07

    Turbulent mixing plays a vital role in many fields in astronomy. Here I review a few of these sites, discuss the importance of this turbulent mixing and the techniques used by astrophysicists to solve these problems.

  8. Mixing in explosions

    SciTech Connect

    Kuhl, A.L.

    1993-12-01

    Explosions always contain embedded turbulent mixing regions, for example: boundary layers, shear layers, wall jets, and unstable interfaces. Described here is one particular example of the latter, namely, the turbulent mixing occurring in the fireball of an HE-driven blast wave. The evolution of the turbulent mixing was studied via two-dimensional numerical simulations of the convective mixing processes on an adaptive mesh. Vorticity was generated on the fireball interface by baroclinic effects. The interface was unstable, and rapidly evolved into a turbulent mixing layer. Four phases of mixing were observed: (1) a strong blast wave phase; (2) and implosion phase; (3) a reshocking phase; and (4) an asymptotic mixing phase. The flowfield was azimuthally averaged to evaluate the mean and r.m.s. fluctuation profiles across the mixing layer. The vorticity decayed due to a cascade process. This caused the corresponding enstrophy parameter to increase linearly with time -- in agreement with homogeneous turbulence calculations of G.K. Batchelor.

  9. Measurements of Molecular Mixing in a High Schmidt Number Rayleigh-Taylor Mixing Layer

    SciTech Connect

    Mueschke, N J; Schilling, O; Youngs, D L; Andrews, M

    2007-12-03

    Molecular mixing measurements are performed for a high Schmidt number (Sc {approx} 10{sup 3}), small Atwood number (A {approx} 7.5 x 10{sup -4}) buoyancy-driven turbulent Rayleigh-Taylor mixing layer in a water channel facility. Salt was added to the top stream to create the desired density difference. The degree of molecular mixing was measured as a function of time by monitoring a diffusion-limited chemical reaction between the two fluid streams. The pH of each stream was modified by the addition of acid or alkali such that a local neutralization reaction occurred as the two fluids molecularly mixed. The progress of this neutralization reaction was tracked by the addition of phenolphthalein - a pH-sensitive chemical indicator - to the acidic stream. Accurately calibrated backlit optical techniques were used to measure the average concentration of the colored chemical indicator. Comparisons of chemical product formation for pre-transitional buoyancy- and shear-driven mixing layers are given. It is also shown that experiments performed at different equivalence ratios (acid/alkali concentration) can be combined to obtain a mathematical relationship between the colored product formed and the density variance. This relationship was used to obtain high-fidelity, quantitative measures of the degree of molecular mixing which are independent of probe resolution constraints. The dependence of such mixing parameters on the Schmidt and Reynolds numbers is examined by comparing the current Sc {approx} 10{sup 3} measurements with Sc = 0.7 gas-phase and Pr = 7 liquid-phase measurements. This comparison indicates that the Schmidt number has a large effect on the bulk quantity of mixed fluid at small Reynolds numbers Re{sub h} < 10{sup 3}. At late times, all mixing parameters indicated a greater degree of molecular mixing and a decreased Schmidt number dependence. Implications for the development and quantitative assessment of turbulent transport and mixing models appropriate for

  10. Geomorphic control of radionuclide diffusion in desert soils

    NASA Astrophysics Data System (ADS)

    Pelletier, Jon D.; Harrington, Charles D.; Whitney, John W.; Cline, Michael; DeLong, Stephen B.; Keating, Gordon; Ebert, K. Teryn

    2005-12-01

    Diffusion is a standard model for the vertical migration of radionuclides in soil profiles. Here we show that diffusivity values inferred from fallout 137Cs profiles in soils on the Fortymile Wash alluvial fan, Nye County, Nevada, have a strong inverse correlation with the age of the geomorphic surface. This result suggests that radionuclide-bound particles are predominantly transported by infiltration rather than by bulk-mixing processes such as wetting/drying, freeze/thaw, and bioturbation. Our results provide a preliminary basis for using soil-geomorphic mapping, point-based calibration data, and the diffusion model to predict radionuclide transport in desert soils within a pedotransfer-function approach.

  11. M558 radioactive tracer diffusion. [diffusion coefficients of Zn-65 in liquid zinc under weightlessness conditions

    NASA Technical Reports Server (NTRS)

    Ukanwa, A. O.

    1974-01-01

    This experiment was performed in Skylab 3 with two objectives in mind. First, the experimental self-diffusion coefficients for liquid zinc were to be determined in a convection-free environment. Secondly the reduction in convective mixing in earth gravity by going into the zero-gravity environment of space was to be estimated. The experiment was designed to utilize high temperatures and linear thermal gradients provided by the M518 Multipurpose Electric Furnace, and the radioactivity of zinc-65 of 245-day half-life to investigate self-diffusion in liquid zinc. The distribution of zinc-65 tracer, after melting, maintaining at soak temperature for 1 hour of soak time and then resolidifying, was obtained by sample sectioning. The concentration of activity of each section (microcurie-gram) was plotted against positions along the sample axial and radial position. Experimental data and theoretical results from solution of Fick's law of diffusion in one dimensional were compared. Samples tested on earth showed very rapid diffusion. Diffusion coefficient in unit gravity was 50 times the zero-gravity diffusion coefficient of Skylab.

  12. 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 ( ...

  13. 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.

  14. 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.

  15. 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

  16. 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.

  17. 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.

  18. Mixed methods research.

    PubMed

    Halcomb, Elizabeth; Hickman, Louise

    2015-04-08

    Mixed methods research involves the use of qualitative and quantitative data in a single research project. It represents an alternative methodological approach, combining qualitative and quantitative research approaches, which enables nurse researchers to explore complex phenomena in detail. This article provides a practical overview of mixed methods research and its application in nursing, to guide the novice researcher considering a mixed methods research project.

  19. Vertical diffusion processes in the Eastern Mediterranean - Black Sea System

    NASA Astrophysics Data System (ADS)

    Kioroglou, Sotiris; Tragou, Elina; Zervakis, Vassilis; Georgopoulos, Dimitris; Herut, Barak; Gertman, Isaak; Kovacevic, Vedrana; Özsoy, Emin; Tutsak, Ersin

    2014-07-01

    The identification and examination of ‘complete' potential density overturns in CTD profiles, within the framework of SESAME project, are employed to assess vertical eddy diffusivities, mostly in the top 100 m of the water column, for a broad area covering the East Mediterranean, the Turkish Straits and the Black Sea. The implementation of this method shows that, mixing induced by mechanical turbulence is enhanced in frontal areas, in the proximity of straits and inside anticyclones; furthermore, that mechanical turbulence is insignificant, down to the scale of CTD resolution, within areas of double diffusive staircases, encountered in deep layers of the water column. Consequently, only laminar theories about double diffusion are applied for assessing diffusivities therein. Susceptibility to different types of double diffusion seems to be related to the interaction of different types of water masses.

  20. 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.

  1. Hydrodynamically induced fluid transfer and non-convective double-diffusion in microgravity sliding solvent diffusion cells

    NASA Technical Reports Server (NTRS)

    Pollmann, Konrad W.; Stodieck, Louis S.; Luttges, Marvin W.

    1994-01-01

    Microgravity can provide a diffusion-dominated environment for double-diffusion and diffusion-reaction experiments otherwise disrupted by buoyant convection or sedimentation. In sliding solvent diffusion cells, a diffusion interface between two liquid columns is achieved by aligning two offset sliding wells. Fluid in contact with the sliding lid of the cavities is subjected to an applied shear stress. The momentum change by the start/stop action of the well creates an additional hydrodynamical force. In microgravity, these viscous and inertial forces are sufficiently large to deform the diffusion interface and induce hydrodynamic transfer between the wells. A series of KC-135 parabolic flight experiments were conducted to characterize these effects and establish baseline data for microgravity diffusion experiments. Flow visualizations show the diffusion interface to be deformed in a sinusoidal fashion following well alignment. After the wells were separated again in a second sliding movement, the total induced liquid transfer was determined and normalized by the well aspect ratio. The normalized transfer decreased linearly with Reynolds number from 3.3 to 4.0% (w/v) for Re = 0.4 (Stokes flow) to a minimum of 1.0% for Re = 23 to 30. Reynolds numbers that provide minimum induced transfers are characterized by an interface that is highly deformed and unsuitable for diffusion measurements. Flat diffusion interfaces acceptable for diffusion measurements are obtained with Reynolds numbers on the order of 7 to 10. Microgravity experiments aboard a sounding rocket flight verified counterdiffusion of different solutes to be diffusion dominated. Ground control experiments showed enhanced mixing by double-diffusive convection. Careful selection of experimental parameters improves initial conditions and minimizes induced transfer rates.

  2. 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

  3. High-Rate Oxygen Reduction in Mixed Nonaqueous Electrolyte Containing Acetonitrile

    SciTech Connect

    Zheng D.; Yang X.; Qu D.

    2011-12-02

    A mixed nonaqueous electrolyte that contains acetonitrile and propylene carbonate (PC) was found to be suitable for a LiO2 battery with a metallic Li anode. Both the concentration and diffusion coefficient for the dissolved O2 are significantly higher in the mixed electrolyte than those in the pure PC electrolyte. A powder microelectrode was used to investigate the O2 solubility and diffusion coefficient. A 10 mA?cm-2 discharge rate on a gas-diffusion electrode is demonstrated by using the mixed electrolyte in a LiO2 cell.

  4. A comparison of experimental, theoretical, and numerical simulation Rayleigh-Taylor mixing rates.

    PubMed

    George, E; Glimm, J; Li, X-L; Marchese, A; Xu, Z-L

    2002-03-05

    We present a Rayleigh-Taylor mixing rate simulation with an acceleration rate falling within the range of experiments. The simulation uses front tracking to prevent interfacial mass diffusion. We present evidence to support the assertion that the lower acceleration rate found in untracked simulations is caused, at least to a large extent, by a reduced buoyancy force due to numerical interfacial mass diffusion. Quantitative evidence includes results from a time-dependent Atwood number analysis of the diffusive simulation, which yields a renormalized mixing rate coefficient for the diffusive simulation in agreement with experiment.

  5. Reaction and diffusion in turbulent combustion

    SciTech Connect

    Pope, S.B.

    1993-12-01

    The motivation for this project is the need to obtain a better quantitative understanding of the technologically-important phenomenon of turbulent combustion. In nearly all applications in which fuel is burned-for example, fossil-fuel power plants, furnaces, gas-turbines and internal-combustion engines-the combustion takes place in a turbulent flow. Designers continually demand more quantitative information about this phenomenon-in the form of turbulent combustion models-so that they can design equipment with increased efficiency and decreased environmental impact. For some time the PI has been developing a class of turbulent combustion models known as PDF methods. These methods have the important virtue that both convection and reaction can be treated without turbulence-modelling assumptions. However, a mixing model is required to account for the effects of molecular diffusion. Currently, the available mixing models are known to have some significant defects. The major motivation of the project is to seek a better understanding of molecular diffusion in turbulent reactive flows, and hence to develop a better mixing model.

  6. Three-dimensional Diffusive Strip Method

    NASA Astrophysics Data System (ADS)

    Martinez-Ruiz, Daniel; Meunier, Patrice; Duchemin, Laurent; Villermaux, Emmanuel

    2016-11-01

    The Diffusive Strip Method (DSM) is a near-exact numerical method developed for mixing computations at large Péclet number in two-dimensions. The method consists in following stretched material lines to compute a-posteriori the resulting scalar field is extended here to three-dimensional flows, following surfaces. We describe its 3D peculiarities, and show how it applies to a simple Taylor-Couette configuration with non-rotating boundary conditions at the top end, bottom and outer cylinder. This flow produces an elaborate, although controlled, steady 3D flow which relies on the Ekman pumping arising from the rotation of the inner cylinder is both studied experimentally, and numerically modeled. A recurrent two-cells structure appears formed by stream tubes shaped as nested tori. A scalar blob in the flow experiences a Lagrangian oscillating dynamics with stretchings and compressions, driving the mixing process, and yielding both rapidly-mixed and nearly pure-diffusive regions. A triangulated-surface method is developed to calculate the blob elongation and scalar concentration PDFs through a single variable computation along the advected blob surface, capturing the rich evolution observed in the experiments.

  7. Effects of temporal fluctuations on mixing

    NASA Astrophysics Data System (ADS)

    Pool, Maria; Dentz, Marco; Post, Vincent E. A.; Simmons, Craig T.

    2016-04-01

    Mixing and dispersion in coastal aquifers are strongly influenced by periodic temporal flow fluctuations on multiple time-scales ranging from days (tides), seasons (pumping and recharge) to glacial cycles (regression and transgressions). Transient forcing effects lead to a complex space- ant time-dependent flow response which induces enhanced spreading and mixing of a dissolved substance. We study effective mixing and solute transport in temporally fluctuating one-dimensional flow for a stable stratification of two fluids of different density. We derive explicit expressions for the concentration distribution and variance to identify the controls and obtain realistic predictions of the coupling between mixing and oscillatory transient flow. We find that the magnitude of transient-driven mixing is mainly controlled by the hydraulic diffusivity, the period and the initial interface location. We also find a spatial dependence of the effective dispersion coefficient which at long times causes the concentration profile to become asymmetric. Sand column experiments under well-controlled laboratory conditions are presented to validate the theoretical effective model defined. The proposed formulation is found to provide very good predictions and correctly reproduces the experimental mixing dynamics.

  8. Lidar observation of marine mixed layer

    NASA Technical Reports Server (NTRS)

    Yamagishi, Susumu; Yamanouchi, Hiroshi; Tsuchiya, Masayuki

    1992-01-01

    Marine mixed layer is known to play an important role in the transportation of pollution exiting ship funnels. The application of a diffusion model is critically dependent upon a reliable estimate of a lid. However, the processes that form lids are not well understood, though considerable progress toward marine boundary layer has been achieved. This report describes observations of the marine mixed layer from the course Ise-wan to Nii-jima with the intention of gaining a better understanding of their structure by a shipboard lidar. These observations were made in the summer of 1991. One interesting feature of the observations was that the multiple layers of aerosols, which is rarely numerically modeled, was encountered. No attempt is yet made to present a systematic analysis of all the data collected. Instead we focus on observations that seem to be directly relevant to the structure of the mixed layer.

  9. 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.

  10. Theoretical analysis of mixing in liquid clouds - Part 3: Inhomogeneous mixing

    NASA Astrophysics Data System (ADS)

    Pinsky, Mark; Khain, Alexander; Korolev, Alexei

    2016-07-01

    An idealized diffusion-evaporation model of time-dependent mixing between a cloud volume and a droplet-free volume is analyzed. The initial droplet size distribution (DSD) in the cloud volume is assumed to be monodisperse. It is shown that evolution of the microphysical variables and the final equilibrium state are unambiguously determined by two non-dimensional parameters. The first one is the potential evaporation parameter R, proportional to the ratio of the saturation deficit to the liquid water content in the cloud volume, that determines whether the equilibrium state is reached at 100 % relative humidity, or is characterized by a complete evaporation of cloud droplets. The second parameter Da is the Damkölher number equal to the ratio of the characteristic mixing time to the phase relaxation time. Parameters R and Da determine the type of mixing.The results are analyzed within a wide range of values of R and Da. It is shown that there is no pure homogeneous mixing, since the first mixing stage is always inhomogeneous. The mixing type can change during the mixing process. Any mixing type leads to formation of a tail of small droplets in DSD and, therefore, to DSD broadening that depends on Da. At large Da, the final DSD dispersion can be as large as 0.2. The total duration of mixing varies from several to 100 phase relaxation time periods, depending on R and Da.The definitions of homogeneous and inhomogeneous types of mixing are reconsidered and clarified, enabling a more precise delimitation between them. The paper also compares the results obtained with those based on the classic mixing concepts. >

  11. Response of radiation belt simulations to different radial diffusion coefficients models

    NASA Astrophysics Data System (ADS)

    Drozdov, Alexander; Baker, Daniel N.; Shprits, Yuri; Kellerman, Adam

    2016-07-01

    Two parameterizations of the resonant wave-particle interactions of electrons with ultra-low frequency waves in the magnetosphere by Brautigam and Albert [2000] and Ozeke et al. [2014] are evaluated using the Versatile Electron Radiation Belt (VERB) diffusion code to estimate the effect of changing a diffusion coefficient on the radiation belt simulation. The period of investigation includes geomagnetically quiet and active time. The simulations take into account wave-particle interactions represented by radial diffusion transport, local acceleration, losses due to pitch-angle diffusion, and mixed diffusion.

  12. Diffusion Influenced Adsorption Kinetics.

    PubMed

    Miura, Toshiaki; Seki, Kazuhiko

    2015-08-27

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

  13. Primary diffuse leptomeningeal gliosarcomatosis.

    PubMed

    Moon, Ju Hyung; Kim, Se Hoon; Kim, Eui Hyun; Kang, Seok-Gu; Chang, Jong Hee

    2015-04-01

    Primary diffuse leptomeningeal gliomatosis (PDLG) is a rare condition with a fatal outcome, characterized by diffuse infiltration of the leptomeninges by neoplastic glial cells without evidence of primary tumor in the brain or spinal cord parenchyma. In particular, PDLG histologically diagnosed as gliosarcoma is extremely rare, with only 2 cases reported to date. We report a case of primary diffuse leptomeningeal gliosarcomatosis. A 68-year-old man presented with fever, chilling, headache, and a brief episode of mental deterioration. Initial T1-weighted post-contrast brain magnetic resonance imaging (MRI) showed diffuse leptomeningeal enhancement without a definite intraparenchymal lesion. Based on clinical and imaging findings, antiviral treatment was initiated. Despite the treatment, the patient's neurologic symptoms and mental status progressively deteriorated and follow-up MRI showed rapid progression of the disease. A meningeal biopsy revealed gliosarcoma and was conclusive for the diagnosis of primary diffuse leptomeningeal gliosarcomatosis. We suggest the inclusion of PDLG in the potential differential diagnosis of patients who present with nonspecific neurologic symptoms in the presence of leptomeningeal involvement on MRI.

  14. Multidimensional diffusion MRI

    NASA Astrophysics Data System (ADS)

    Topgaard, Daniel

    2017-02-01

    Principles from multidimensional NMR spectroscopy, and in particular solid-state NMR, have recently been transferred to the field of diffusion MRI, offering non-invasive characterization of heterogeneous anisotropic materials, such as the human brain, at an unprecedented level of detail. Here we revisit the basic physics of solid-state NMR and diffusion MRI to pinpoint the origin of the somewhat unexpected analogy between the two fields, and provide an overview of current diffusion MRI acquisition protocols and data analysis methods to quantify the composition of heterogeneous materials in terms of diffusion tensor distributions with size, shape, and orientation dimensions. While the most advanced methods allow estimation of the complete multidimensional distributions, simpler methods focus on various projections onto lower-dimensional spaces as well as determination of means and variances rather than actual distributions. Even the less advanced methods provide simple and intuitive scalar parameters that are directly related to microstructural features that can be observed in optical microscopy images, e.g. average cell eccentricity, variance of cell density, and orientational order - properties that are inextricably entangled in conventional diffusion MRI. Key to disentangling all these microstructural features is MRI signal acquisition combining isotropic and directional dimensions, just as in the field of multidimensional solid-state NMR from which most of the ideas for the new methods are derived.

  15. Diffuser for wellhead isolation tool

    SciTech Connect

    Surjaatmadja, J.B.

    1981-04-21

    An improved diffuser for a wellhead isolation tool which employs a combination of angles in its bore. This improvement reduces the incidence of erosion caused by the flow of fluids through the diffuser, in both the well production tubing adjacent the end of the diffuser and in the diffuser itself.

  16. Tracer mixing at fracture intersections

    SciTech Connect

    Li, Guomin

    2001-02-10

    Discrete network models are one of the approaches used to simulate a dissolved contaminant, which is usually represented as a tracer in modeling studies, in fractured rocks. The discrete models include large numbers of individual fractures within the network structure, with flow and transport described on the scale of an individual fracture. Numerical simulations for the mixing characteristics and transfer probabilities of a tracer through a fracture intersection are performed for this study. A random-walk, particle-tracking model is applied to simulate tracer transport in fracture intersections by moving particles through space using individual advective and diffusive steps. The simulation results are compared with existing numerical and analytical solutions for a continuous intersection over a wide range of Peclet numbers. This study attempts to characterize the relative concentration at the outflow branches for a continuous intersection with different flow fields. The simulation results demonstrate that the mixing characteristics at the fracture intersections are a function not only of the Peclet number but also of the flow field pattern.

  17. A simple reaction-rate model for turbulent diffusion flames

    NASA Technical Reports Server (NTRS)

    Bangert, L. H.

    1975-01-01

    A simple reaction rate model is proposed for turbulent diffusion flames in which the reaction rate is proportional to the turbulence mixing rate. The reaction rate is also dependent on the mean mass fraction and the mean square fluctuation of mass fraction of each reactant. Calculations are compared with experimental data and are generally successful in predicting the measured quantities.

  18. Age of stratospheric air and aging by mixing in global models

    NASA Astrophysics Data System (ADS)

    Garny, Hella; Dietmüller, Simone; Plöger, Felix; Birner, Thomas; Bönisch, Harald; Jöckel, Patrick

    2016-04-01

    The Brewer-Dobson circulation is often quantified by the integrated transport measure age of air (AoA). AoA is affected by all transport processes, including transport along the residual mean mass circulation and two-way mixing. A large spread in the simulation of AoA by current global models exists. Using CCMVal-2 and CCMI-1 global model data, we show that this spread can only in small parts be attributed to differences in the simulated residual circulation. Instead, large differences in the "mixing efficiency" strongly contribute to the differences in the simulated AoA. The "mixing efficiency" is defined as the ratio of the two-way mixing mass flux across the subtropical barrier to the net (residual) mass flux, and this mixing efficiency controls the relative increase in AoA by mixing. We derive the mixing efficiency from global model data using the analytical solution of a simplified version of the tropical leaky pipe (TLP) model, in which vertical diffusion is neglected. Thus, it is assumed that only residual mean transport and horizontal two-way mixing across the subtropical barrier controls AoA. However, in global models vertical mixing and numerical diffusion modify AoA, and these processes likely contribute to the differences in the mixing efficiency between models. We explore the contributions of diffusion and mixing on mean AoA by a) using simulations with the tropical leaky pipe model including vertical diffusion and b) explicit calculations of aging by mixing on resolved scales. Using the TLP model, we show that vertical diffusion leads to a decrease in tropical AoA, i.e. counteracts the increase in tropical mean AoA due to horizontal mixing. Thus, neglecting vertical diffusion leads to an underestimation of the mixing efficiency. With explicit calculations of aging by mixing via integration of daily local mixing tendencies along residual circulation trajectories, we explore the contributions of vertical and horizontal mixing for aging by mixing. The

  19. Tunable diffusive lateral inhibition in chemical cells⋆

    PubMed Central

    Li, Ning; Tompkins, Nathan; Gonzalez-Ochoa, Hector; Fraden, Seth

    2015-01-01

    The Belousov-Zhabotinsky (BZ) reaction has become the prototype of nonlinear chemical dynamics. Microfluidic techniques provide a convenient method for emulsifying BZ solutions into monodispersed drops with diameters of tens to hundreds of microns, providing a unique system in which reaction-diffusion theory can be quantitatively tested. In this work, we investigate monolayers of microfluidically generated BZ drops confined in close-packed two-dimensional (2D) arrays through experiments and finite element simulations. We describe the transition from oscillatory to stationary chemical states with increasing coupling strength, controlled by independently varying the reaction chemistry within a drop and diffusive flux between drops. For stationary drops, we studied how the ratio of stationary oxidized to stationary reduced drops varies with coupling strength. In addition, using simulation, we quantified the chemical heterogeneity sufficient to induce mixed stationary and oscillatory patterns. PMID:25795263

  20. Consistent flamelet modeling of differential molecular diffusion for turbulent non-premixed flames

    NASA Astrophysics Data System (ADS)

    Wang, Haifeng

    2016-03-01

    Treating differential molecular diffusion correctly and accurately remains as a great challenge to the modeling of turbulent non-premixed combustion. The aim of this paper is to develop consistent modeling strategies for differential molecular diffusion in flamelet models. Two types of differential molecular diffusion models are introduced, linear differential diffusion models and nonlinear differential diffusion models. A multi-component turbulent mixing layer problem is analyzed in detail to gain insights into differential molecular diffusion and its characteristics, particularly the dependence of differential molecular diffusion on the Reynolds number and the Lewis number. These characteristics are then used to validate the differential molecular diffusion models. Finally, the new models are applied to the modeling of a series of laboratory-scale turbulent non-premixed jet flames with different Reynolds number (Sandia Flames B, C, and D) to further assess the models' performance.

  1. Positron diffusion in Si

    SciTech Connect

    Nielsen, B.; Lynn, K.G.; Vehanen, A.; Schultz, P.J.

    1985-06-01

    Positron diffusion in Si(100) and Si(111) has been studied using a variable energy positron beam. The positron diffusion coefficient is found to be D/sub +/ = 2.7 +- 0.3 cm/sup 2//sec using a Makhov-type positron implantation profile, which is demonstrated to fit the data more reliably than the more commonly applied exponential profile. The diffusion related parameter, E/sub 0/, which results from the exponential profile, is found to be 4.2 +- 0.2 keV, significantly longer than previously reported values. A drastic reduction in E/sub 0/ is found after annealing the sample at 1300 K, showing that previously reported low values of E/sub 0/ are probably associated with the thermal history of the sample.

  2. Cesium diffusion in graphite

    SciTech Connect

    Evans, R.B. III; Davis, W. Jr.; Sutton, A.L. Jr.

    1980-05-01

    Experiments on diffusion of /sup 137/Cs in five types of graphite were performed. The document provides a completion of the report that was started and includes a presentation of all of the diffusion data, previously unpublished. Except for data on mass transfer of /sup 137/Cs in the Hawker-Siddeley graphite, analyses of experimental results were initiated but not completed. The mass transfer process of cesium in HS-1-1 graphite at 600 to 1000/sup 0/C in a helium atmosphere is essentially pure diffusion wherein values of (E/epsilon) and ..delta..E of the equation D/epsilon = (D/epsilon)/sub 0/ exp (-..delta..E/RT) are about 4 x 10/sup -2/ cm/sup 2//s and 30 kcal/mole, respectively.

  3. Apparatus for diffusion separation

    DOEpatents

    Nierenberg, William A.; Pontius, Rex B.

    1976-08-10

    1. The method of testing the separation efficiency of porous permeable membranes which comprises causing a stream of a gaseous mixture to flow into contact with one face of a finely porous permeable membrane under such conditions that a major fraction of the mixture diffuses through the membrane, maintaining a rectangular cross section of the gaseous stream so flowing past said membrane, continuously recirculating the gas that diffuses through said membrane and continuously withdrawing the gas that does not diffuse through said membrane and maintaining the volume of said recirculating gas constant by continuously introducing into said continuously recirculating gas stream a mass of gas equivalent to that which is continuously withdrawn from said gas stream and comparing the concentrations of the light component in the entering gas, the withdrawn gas and the recirculated gas in order to determine the efficiency of said membrane.

  4. Transverse Spin Diffusion

    NASA Astrophysics Data System (ADS)

    Mullin, William

    2014-05-01

    Transverse spin diffusion is a relatively new transport coefficient and a review of its history and physical basis will be presented. In NMR spin diffusion is often measured by spin echo techniques, which involve spin currents perpendicular to the direction of the magnetization, in contrast with the usual longitudinal case where the current is parallel to the magnetization. The first indication that this involved new physics was the Leggett-Rice effect (1970) in which spin waves, new spin-echo behavior, and an altered spin diffusion coefficient were predicted in liquid 3He. This effect gave the possibility of the first measurement of F1a, the parameter of the Landau Fermi-liquid theory mean-field responsible for the effect. In 1982 Lhuillier and Laloe found a transport equation very similar to the Leggett equation, but valid for highly-polarized dilute Boltzmann Bose and Fermi gases, and describing the ``identical spin rotation effect'' (ISRE), the analog of a Landau mean field. Coincidentally Bashkin and Meyerovich had also given equivalent descriptions of transport in polarized Boltzmann gases. That a mean-field effect could exists in dilute Boltzmann gases was theoretically surprising, but was confirmed experimentally. At low polarization the basic transverse diffusion constant D⊥ coincides with the longitudinal value D∥ however Meyerovich first pointed out that they could differ in highly polarized degenerate gases. Indeed detailed calculations (Jeon and Mullin) showed that, while D∥ is proportional to T-2, D⊥ approaches a constant (depending on polarization) at low T. Considerable controversy existed until experimental verification was achieved in 2004. The importance of ISRE again arose in 2008 as the basis of ``anomalous spin-state segregation'' in Duke and JILA experiments. More recently application of the ideas of transverse spin diffusion to strongly interacting Fermi gases has resulted in the observation of the diffusion constants at the quantum

  5. 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

  6. Air sparging and bioremediation: The case for in situ mixing

    SciTech Connect

    Clayton, W.S.; Brown, R.A.; Bass, D.H.

    1995-12-31

    Air sparging has sparked considerable controversy in the remediation industry. Some feel air sparging is a significant advance in remedial technology, whereas others feel that air sparging is a very limited technology. A central question in this debate is the presence (or lack thereof) of groundwater mixing during air sparging. Groundwater mixing is important to overcome the diffusion limitations of sparging caused by air channeling and effectively deliver oxygen for in situ bioremediation. Possible mechanisms of groundwater mixing include physical displacement, capillary interactions of air and water, frictional drag, makeup of evaporative loss, thermal convection, and movement of fines. Physical groundwater displacement and groundwater movement resulting from capillary pressure gradients are the two most likely and most commonly effective mechanisms. An important question is the relative degree of groundwater mixing during nonsteady-state and steady-state sparging. Evidence indicates that mixing occurs primarily during nonsteady-state air sparging. Because groundwater mixing is important to overcome the diffusion limitations of air sparging, it is important to operate sparging systems to maximize mixing. Field data show that pulsed sparging, which emphasizes the nonsteady-state aspects of air sparging, greatly enhances groundwater mixing.

  7. Turbulent vertical diffusivity in the sub-tropical stratosphere

    NASA Astrophysics Data System (ADS)

    Pisso, I.; Legras, B.

    2008-02-01

    Vertical (cross-isentropic) mixing is produced by small-scale turbulent processes which are still poorly understood and paramaterized in numerical models. In this work we provide estimates of local equivalent diffusion in the lower stratosphere by comparing balloon borne high-resolution measurements of chemical tracers with reconstructed mixing ratio from large ensembles of random Lagrangian backward trajectories using European Centre for Medium-range Weather Forecasts analysed winds and a chemistry-transport model (REPROBUS). We focus on a case study in subtropical latitudes using data from HIBISCUS campaign. An upper bound on the vertical diffusivity is found in this case study to be of the order of 0.5 m2 s-1 in the subtropical region, which is larger than the estimates at higher latitudes. The relation between diffusion and dispersion is studied by estimating Lyapunov exponents and studying their variation according to the presence of active dynamical structures.

  8. Turbulent vertical diffusivity in the sub-tropical stratosphere

    NASA Astrophysics Data System (ADS)

    Pisso, I.; Legras, B.

    2007-05-01

    Vertical (cross-isentropic) mixing is produced by small-scale turbulent processes which are still poorly understood and parametrized in numerical models. In this work we provide estimates of local equivalent diffusion in the lower stratosphere by comparing balloon borne high-resolution measurements of chemical tracers with reconstructed mixing ratio from large ensembles of random Lagrangian backward trajectories using European Center for Medium-range Weather Forecasts analysed winds and a chemistry-transport model (REPROBUS). We have investigated cases in subtropical latitudes using data from HIBISCUS campaign. Upper bound on the vertical diffusivity is found to be of the order of 0.5 m2 s-1 in the subtropical region, which is larger than the estimates at higher latitudes. The relation between diffusion and dispersion is studied by estimating Lyapunov exponents and studying their variation according to the presence of active dynamical structures.

  9. Detailed stress tensor measurements in a centrifugal compressor vaneless diffuser

    SciTech Connect

    Pinarbasi, A.; Johnson, M.W.

    1996-04-01

    Detailed flow measurements have been made in the vaneless diffuser of a large low-speed centrifugal compressor using hot-wire anemometry. The three time mean velocity components and full stress tensor distributions have been determined on eight measurement plans within the diffuser. High levels of Reynolds stress result in the rapid mixing out of the blade wake. Although high levels of turbulent kinetic energy are found in the passage wake, they are not associated with strong Reynolds stresses and hence the passage wake mixes out only slowly. Low-frequency meandering of the wake position is therefore likely to be responsible for the high kinetic energy levels. The anisotropic nature of the turbulence suggests that Reynolds stress turbulence models are required for CFD modeling of diffuser flows.

  10. [Microbial diffusion and antibiotherapy].

    PubMed

    Vilain, R

    1982-01-01

    Cleaning leg ulcers depends on tissular and microbial enzymes, the production of which depends on good vascularization. When an aetiological treatment is started, the microbes ensure sufficient cleaning, leading to granulation and epidermization. Antibiotherapy is pointless. Sometimes it can be detrimental, replacing a natural growth with alien strains which cause diffusion. Very exceptionally, a short course of antibiotherapy may be necessary to cope with signs of diffusion, usually signifying a Group A streptococcal infection, with seasonal recrudescence. The Blue Pus Microbe has no special pathological significance. It merely indicates that the case has become chronic.

  11. 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

  12. Influence of diffusion on the stability of equilibria in a reaction-diffusion system modeling cholera dynamic.

    PubMed

    Capone, Florinda; De Cataldis, Valentina; De Luca, Roberta

    2015-11-01

    A reaction-diffusion system modeling cholera epidemic in a non-homogeneously mixed population is introduced. The interaction between population and toxigenic Vibrio cholerae concentration in contaminated water has been taken into account. The existence of biologically meaningful equilibria is investigated together with their linear and nonlinear stability. Using the data collected during the Haiti cholera epidemic, a numerical simulation is performed.

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    Rigorous numerical description of multispecies diffusion requires coupling of species, charge, and aqueous and surface complexation reactions that collectively affect diffusive fluxes. The applicability of a fully coupled diffusion model is, however, often constrained by the availability of species self-diffusion coefficients, as well as by computational complication in imposing charge conservation. In this study, several diffusion models with variable complexity in charge and species coupling were formulated and compared to describe reactive multispecies diffusion in groundwater. Diffusion of uranyl [U(VI)] species was used as an example in demonstrating the effectiveness of the models in describing multispecies diffusion. Numerical simulations found that a diffusion model with a single, common diffusion coefficient for all species was sufficient to describe multispecies U(VI) diffusion under a steady state condition of major chemical composition, but not under transient chemical conditions. Simulations revealed that for multispecies U(VI) diffusion under transient chemical conditions, a fully coupled diffusion model could be well approximated by a component-based diffusion model when the diffusion coefficient for each chemical component was properly selected. The component-based diffusion model considers the difference in diffusion coefficients between chemical components, but not between the species within each chemical component. This treatment significantly enhanced computational efficiency at the expense of minor charge conservation. The charge balance in the component-based diffusion model can be enforced, if necessary, by adding a secondary migration term resulting from model simplification. The effect of ion activity coefficient gradients on multispecies diffusion is also discussed. The diffusion models were applied to describe U(VI) diffusive mass transfer in intragranular domains in two sediments collected from U.S. Department of Energy's Hanford 300A

  14. Kinetic Structure of the Reconnection Diffusion Region

    NASA Astrophysics Data System (ADS)

    Khotyaintsev, Yuri

    2016-04-01

    We present high-resolution multi-spacecraft observations of electromagnetic fields and particle distributions by Magnetospheric Multiscale (MMS) mission throughout a reconnection layer at the sub-solar magnetopause. We study which terms in the generalized Ohm's law balance the observed electric field throughout the region. We also study waves and particle distribution functions in order to identify kinetic boundaries created due to acceleration and trapping of electrons and ions as well as mixing of electron populations from different sides of the reconnecting layer. We discuss the interplay between particles, waves, and DC electric and magnetic fields, which clearly demonstrates kinetic and multi-scale nature of the reconnection diffusion region.

  15. Anomalous diffusion in confined turbulent convection.

    PubMed

    Boffetta, G; De Lillo, F; Musacchio, S

    2012-06-01

    Turbulent convection in quasi-one-dimensional geometry is studied by means of high-resolution direct numerical simulations within the framework of Rayleigh-Taylor turbulence. Geometrical confinement has dramatic effects on the dynamics of the turbulent flow, inducing a transition from superdiffusive to subdiffusive evolution of the mixing layer and arresting the growth of kinetic energy. A nonlinear diffusion model is shown to reproduce accurately the above phenomenology. The model is used to predict, without free parameters, the spatiotemporal evolution of the heat flux profile and the dependence of the Nusselt number on the Rayleigh number.

  16. Configurable lipid membrane gradients quantify diffusion, phase separations and binding densities.

    PubMed

    Liu, Katherine N; Hung, Chen-Min S; Swift, Michael A; Muñoz, Kristen A; Cortez, Jose L; Sanii, Babak

    2015-11-14

    Single-experiment analysis of phospholipid compositional gradients reveals diffusion coefficients, phase separation parameters, and binding densities as a function of localized lipid mixture. Compositional gradients are formed by directed self assembly where rapid-prototyping techniques (i.e., additive manufacturing or laser-cutting) prescribe lipid geometries that self-spread, heal and mix by diffusion.

  17. DNS investigation of differential-diffusion effects on temporarily evolving turbulent diffusion flames

    NASA Astrophysics Data System (ADS)

    Almagro, Antonio; Garcia-Villalba, Manuel; Flores, Oscar; Sanchez, Antonio L.

    2016-11-01

    The peak temperature of nonpremixed flames is known to have a profound effect on kinetically controlled processes with a strong temperature dependence, such as strain-induced extinction and NOx production. Here, the influence of differential diffusion on the flame temperature in diffusion-controlled combustion is investigated by direct numerical simulations of a turbulent diffusion flame in a temporarily evolving mixing layer for non-unity Lewis numbers of the fuel. The problem is formulated in the limit of infinitely fast combustion in terms of Shvab-Zel'dovich conserved scalars, not changed directly by the reactions, obtained through chemistry-free linear combinations of the temperature and reactant mass fractions. A previously developed low-Mach-number code is used in the numerical integrations, which consider values of the thermochemical parameters - characterizing the exothermicity and stoichiometry of diffusion-controlled combustion - and fuel Lewis number typical of hydrogen-air and hydrocarbon-air flames. The results of the simulations are used to asses the effect of turbulence and fuel diffusivity on the flame response. This work was funded by the Spanish MCININ under project CSD2010-00011. The computational resources were provided by the XSEDE program, supported by NSF Grant Number ACI-1053575.

  18. Mixed oxide solid solutions

    DOEpatents

    Magno, Scott; Wang, Ruiping; Derouane, Eric

    2003-01-01

    The present invention is a mixed oxide solid solution containing a tetravalent and a pentavalent cation that can be used as a support for a metal combustion catalyst. The invention is furthermore a combustion catalyst containing the mixed oxide solid solution and a method of making the mixed oxide solid solution. The tetravalent cation is zirconium(+4), hafnium(+4) or thorium(+4). In one embodiment, the pentavalent cation is tantalum(+5), niobium(+5) or bismuth(+5). Mixed oxide solid solutions of the present invention exhibit enhanced thermal stability, maintaining relatively high surface areas at high temperatures in the presence of water vapor.

  19. Cement mixing with vibrator

    SciTech Connect

    Allen, T.E.

    1991-07-09

    This patent describes a method of cementing a casing string in a bore hole of a well. It comprises introducing water and dry cement material into a mixing vessel; mixing the water and dry cement material in the mixing vessel to form a cement slurry, the slurry including lumps of the dry cement material, the mixing including steps of: agitating the slurry; and while agitating the slurry, transmitting vibrational energy into the slurry and thereby aiding disintegration and subsequent wetting of the lumps of the dry cement material in the slurry; and pumping the slurry into an annulus between the casing string and the bore hole.

  20. Characteristics of the mixing volume model with the interactions among spatially distributed particles for Lagrangian simulations of turbulent mixing

    NASA Astrophysics Data System (ADS)

    Watanabe, Tomoaki; Nagata, Koji

    2016-11-01

    The mixing volume model (MVM), which is a mixing model for molecular diffusion in Lagrangian simulations of turbulent mixing problems, is proposed based on the interactions among spatially distributed particles in a finite volume. The mixing timescale in the MVM is derived by comparison between the model and the subgrid scale scalar variance equation. A-priori test of the MVM is conducted based on the direct numerical simulations of planar jets. The MVM is shown to predict well the mean effects of the molecular diffusion under various conditions. However, a predicted value of the molecular diffusion term is positively correlated to the exact value in the DNS only when the number of the mixing particles is larger than two. Furthermore, the MVM is tested in the hybrid implicit large-eddy-simulation/Lagrangian-particle-simulation (ILES/LPS). The ILES/LPS with the present mixing model predicts well the decay of the scalar variance in planar jets. This work was supported by JSPS KAKENHI Nos. 25289030 and 16K18013. The numerical simulations presented in this manuscript were carried out on the high performance computing system (NEC SX-ACE) in the Japan Agency for Marine-Earth Science and Technology.

  1. Mixed waste minimization/mixed waste avoidance

    SciTech Connect

    Todisco, L.R.

    1994-12-31

    This presentation describes methods for the minimization and volume reduction of low-level radioactive and mixed wastes. Many methods are presented including: source reduction, better waste monitoring activities, waste segregation, recycling, administrative controls, and optimization of waste-generating processes.

  2. Nanocrystal diffusion doping.

    PubMed

    Vlaskin, Vladimir A; Barrows, Charles J; Erickson, Christian S; Gamelin, Daniel R

    2013-09-25

    A diffusion-based synthesis of doped colloidal semiconductor nanocrystals is demonstrated. This approach involves thermodynamically controlled addition of both impurity cations and host anions to preformed seed nanocrystals under equilibrium conditions, rather than kinetically controlled doping during growth. This chemistry allows thermodynamic crystal compositions to be prepared without sacrificing other kinetically trapped properties such as shape, size, or crystallographic phase. This doping chemistry thus shares some similarities with cation-exchange reactions, but proceeds without the loss of host cations and excels at the introduction of relatively unreactive impurity ions that have not been previously accessible using cation exchange. Specifically, we demonstrate the preparation of Cd(1-x)Mn(x)Se (0 ≤ x ≤ ∼0.2) nanocrystals with narrow size distribution, unprecedentedly high Mn(2+) content, and very large magneto-optical effects by diffusion of Mn(2+) into seed CdSe nanocrystals grown by hot injection. Controlling the solution and lattice chemical potentials of Cd(2+) and Mn(2+) allows Mn(2+) diffusion into the internal volumes of the CdSe nanocrystals with negligible Ostwald ripening, while retaining the crystallographic phase (wurtzite or zinc blende), shape anisotropy, and ensemble size uniformity of the seed nanocrystals. Experimental results for diffusion doping of other nanocrystals with other cations are also presented that indicate this method may be generalized, providing access to a variety of new doped semiconductor nanostructures not previously attainable by kinetic routes or cation exchange.

  3. Water vapor diffusion membranes

    NASA Technical Reports Server (NTRS)

    Holland, F. F., Jr.; Smith, J. K.

    1974-01-01

    The program is reported, which was designed to define the membrane technology of the vapor diffusion water recovery process and to test this technology using commercially available or experimental membranes. One membrane was selected, on the basis of the defined technology, and was subjected to a 30-day demonstration trial.

  4. Osmosis and Diffusion

    ERIC Educational Resources Information Center

    Sack, Jeff

    2005-01-01

    OsmoBeaker is a CD-ROM designed to enhance the learning of diffusion and osmosis by presenting interactive experimentation to the student. The software provides several computer simulations that take the student through different scenarios with cells, having different concentrations of solutes in them.

  5. Diffusion in random networks

    DOE PAGES

    Zhang, Duan Z.; Padrino, Juan C.

    2017-06-01

    The ensemble averaging technique is applied to model mass transport by diffusion in random networks. The system consists of an ensemble of random networks, where each network is made of pockets connected by tortuous channels. Inside a channel, fluid transport is assumed to be governed by the one-dimensional diffusion equation. Mass balance leads to an integro-differential equation for the pocket mass density. The so-called dual-porosity model is found to be equivalent to the leading order approximation of the integration kernel when the diffusion time scale inside the channels is small compared to the macroscopic time scale. As a test problem,more » we consider the one-dimensional mass diffusion in a semi-infinite domain. Because of the required time to establish the linear concentration profile inside a channel, for early times the similarity variable is xt$-$1/4 rather than xt$-$1/2 as in the traditional theory. We found this early time similarity can be explained by random walk theory through the network.« less

  6. Laminar Jet Diffusion Flame Burning

    NASA Technical Reports Server (NTRS)

    2003-01-01

    Study of the downlink data from the Laminar Soot Processes (LSP) experiment quickly resulted in discovery of a new mechanism of flame extinction caused by radiation of soot. Scientists found that the flames emit soot sooner than expected. These findings have direct impact on spacecraft fire safety, as well as the theories predicting the formation of soot -- which is a major factor as a pollutant and in the spread of unwanted fires. This sequence, using propane fuel, was taken STS-94, July 4 1997, MET:2/05:30 (approximate). LSP investigated fundamental questions regarding soot, a solid byproduct of the combustion of hydrocarbon fuels. The experiment was performed using a laminar jet diffusion flame, which is created by simply flowing fuel-like ethylene or propane -- through a nozzle and igniting it, much like a butane cigarette lighter. The LSP principal investigator was Gerard Faeth, University of Michigan, Arn Arbor. The experiment was part of the space research investigations conducted during the Microgravity Science Laboratory-1R mission (STS-94, July 1-17 1997). LSP results led to a reflight for extended investigations on the STS-107 research mission in January 2003. Advanced combustion experiments will be a part of investigations planned for the International Space Station. (983KB, 9-second MPEG, screen 320 x 240 pixels; downlinked video, higher quality not available) A still JPG composite of this movie is available at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-0300184.html.

  7. Burning Laminar Jet Diffusion Flame

    NASA Technical Reports Server (NTRS)

    2003-01-01

    Study of the downlink data from the Laminar Soot Processes (LSP) experiment quickly resulted in discovery of a new mechanism of flame extinction caused by radiation of soot. Scientists found that the flames emit soot sooner than expected. These findings have direct impact on spacecraft fire safety, as well as the theories predicting the formation of soot -- which is a major factor as a pollutant and in the spread of unwanted fires. This sequence was taken July 15, 1997, MET:14/10:34 (approximate) and shows the ignition and extinction of this flame. LSP investigated fundamental questions regarding soot, a solid byproduct of the combustion of hydrocarbon fuels. The experiment was performed using a laminar jet diffusion flame, which is created by simply flowing fuel -- like ethylene or propane -- through a nozzle and igniting it, much like a butane cigarette lighter. The LSP principal investigator was Gerard Faeth, University of Michigan, Arn Arbor. The experiment was part of the space research investigations conducted during the Microgravity Science Laboratory-1R mission (STS-94, July 1-17 1997). LSP results led to a reflight for extended investigations on the STS-107 research mission in January 2003. Advanced combustion experiments will be a part of investigations planned for the International Space Station. (518KB, 20-second MPEG, screen 160 x 120 pixels; downlinked video, higher quality not available) A still JPG composite of this movie is available at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-0300182.html.

  8. Flow and mixing by small intestine villi.

    PubMed

    Lim, Y F; de Loubens, C; Love, R J; Lentle, R G; Janssen, P W M

    2015-06-01

    Flow and mixing in the small intestine are multi-scale processes. Flows at the scale of the villi (finger-like structures of ≈500 μm length) are poorly understood. We developed a three-dimensional lattice-Boltzmann model to gain insight into the effects of villous movements and the rheology of digesta on flow, mixing and absorption of nutrients at the periphery of the intestinal lumen. Our model simulated the hydrodynamic consequences of villi movements that resulted from folding of the mucosa during longitudinal contractions. We found that cyclic approximation and separation of groups of villi generated laminar eddies at the edges of the group and augmented mass transfers in the radial direction between the inter-villous space and the intestinal lumen which improved the absorption of nutrients and mixing at the periphery of the lumen. This augmentation was greater with highly diffusible nutrients and with high levels of shear-thinning (pseudoplasticity) of the fluid. We compared our results with bulk flows simulations done by previous workers and concluded that villous movements during longitudinal contractions is a major radial mixing mechanism in the small intestine and increases mixing and absorption around the mucosa despite adverse rheology.

  9. Diffusion on Cu surfaces

    NASA Technical Reports Server (NTRS)

    Karimi, Majid

    1993-01-01

    Understanding surface diffusion is essential in understanding surface phenomena, such as crystal growth, thin film growth, corrosion, physisorption, and chemisorption. Because of its importance, various experimental and theoretical efforts have been directed to understand this phenomena. The Field Ion Microscope (FIM) has been the major experimental tool for studying surface diffusion. FIM have been employed by various research groups to study surface diffusion of adatoms. Because of limitations of the FIM, such studies are only limited to a few surfaces: nickel, platinum, aluminum, iridium, tungsten, and rhodium. From the theoretical standpoint, various atomistic simulations are performed to study surface diffusion. In most of these calculations the Embedded Atom Method (EAM) along with the molecular static (MS) simulation are utilized. The EAM is a semi-empirical approach for modeling the interatomic interactions. The MS simulation is a technique for minimizing the total energy of a system of particles with respect to the positions of its particles. One of the objectives of this work is to develop the EAM functions for Cu and use them in conjunction with the molecular static (MS) simulation to study diffusion of a Cu atom on a perfect as well as stepped Cu(100) surfaces. This will provide a test of the validity of the EAM functions on Cu(100) surface and near the stepped environments. In particular, we construct a terrace-ledge-kink (TLK) model and calculate the migration energies of an atom on a terrace, near a ledge site, near a kink site, and going over a descending step. We have also calculated formation energies of an atom on the bare surface, a vacancy in the surface, a stepped surface, and a stepped-kink surface. Our results are compared with the available experimental and theoretical results.

  10. Mixing in Helical Pipes

    NASA Astrophysics Data System (ADS)

    Gratton, Michael B.; Bernoff, Andrew J.

    2001-11-01

    We consider advection and diffusion of a passive scalar in a helical pipe. By assuming that the curvature and torsion are small (equivalent to small Dean number) and the Reynolds number is moderate, we can use a closed form approximation, due to Dean (1927) and Germano (1982), for the induced recirculation. We investigate the problem numerically using a split-step particle method for a variety of localized initial conditions. The problem is governed by two parameters: a nondimensional diffusion constant D (typically small), and the scaled ratio of torsion to curvature λ. At small times, the longitudinal width of the particle distribution, σ, is governed by diffusive effects (σ ∝ √Dt). At large times, Taylor diffusion dominates (σ ∝ √t/D). However, at intermediate times, a ballistic region exists where the width spreads linearly, as postulated by Mezic & Wiggins (1994). We also discuss how these various behaviors scale with the parameters D and λ.

  11. Dilution Zone Mixing

    NASA Technical Reports Server (NTRS)

    Holdeman, J. D.

    1983-01-01

    Studies to characterize dilution zone mixing; experiments on the effects of free-stream turbulence on a jet in crossflow; and the development of an interactive computer code for the analysis of the mixing of jets with a confined crossflow are reviewed.

  12. Chaotic Mixing of Granitic and Basaltic Liquids

    NASA Astrophysics Data System (ADS)

    Decampos, C.; Ingrisch, W. E.; Perugini, D.; Dingwell, D. B.; Poli, G.

    2008-12-01

    , changing with depth, in complex chaotic patterns. The general morphology of experimental flow patterns matches theoretical predictions well. We will present the chemical analytical evaluation of these experiments in the context of the effectiveness of the interplay between convection and diffusion, under chaotic dynamics, in enhancing mixing in silicate melts. The results are strong evidence that the treatment of or testing for mixing based solely on the presence of straight lines on inter-elemental plots is flawed.

  13. Erbium diffusion in silicon dioxide

    SciTech Connect

    Lu Yingwei; Julsgaard, B.; Petersen, M. Christian; Jensen, R. V. Skougaard; Pedersen, T. Garm; Pedersen, K.; Larsen, A. Nylandsted

    2010-10-04

    Erbium diffusion in silicon dioxide layers prepared by magnetron sputtering, chemical vapor deposition, and thermal growth has been investigated by secondary ion mass spectrometry, and diffusion coefficients have been extracted from simulations based on Fick's second law of diffusion. Erbium diffusion in magnetron sputtered silicon dioxide from buried erbium distributions has in particular been studied, and in this case a simple Arrhenius law can describe the diffusivity with an activation energy of 5.3{+-}0.1 eV. Within a factor of two, the erbium diffusion coefficients at a given temperature are identical for all investigated matrices.

  14. Scalar transport in plane mixing layers

    NASA Astrophysics Data System (ADS)

    Vanormelingen, J.; Van den Bulck, E.

    This paper describes the application of the Eulerian, single-point, single-time joint-scalar probability density function (PDF) equation for predicting the scalar transport in mixing layer with a high-speed and a low-speed stream. A finite-volume procedure is applied to obtain the velocity field with the k-ɛ closure being used to describe turbulent transport. The scalar field is represented through the modelled evolution equation for the scalar PDF and is solved using a Monte Carlo simulation. The PDF equation employs gradient transport modelling to represent the turbulent diffusion, and the molecular mixing term is modelled by the LMSE closure. There is no source term for chemical reaction as only an inert mixing layer is considered here. The experimental shear layer data published by Batt is used to validate the computational results despite the fact that comparisons between experiments and computational results are difficult because of the high sensitivity of the shear layer to initial conditions and free stream turbulence phenomena. However, the bimodal shape of the RMS scalar fluctuation as was measured by Batt can be reproduced with this model, whereas standard gradient diffusion calculations do not predict the dip in this profile. In this work for the first time an explanation is given for this phenomenon and the importance of a micromixing model is stressed. Also it is shown that the prediction of the PDF shape by the LMSE model is very satisfactory.

  15. Mixing Diagnostics in Confined, High-Speed Droplet Collisions

    NASA Astrophysics Data System (ADS)

    Carroll, Brian; Hidrovo, Carlos

    2012-11-01

    Fast mixing remains a major challenge in droplet-based microfluidics. The low Reynolds number operating regime of most mixing devices signifies orderly flows that are devoid of any inertial characteristics. To increase droplet mixing rates, a novel technique is under development that uses a high Reynolds number gaseous phase for droplet generation and transport and promotes mixing through binary droplet collisions at velocities near 1m/s. Limitations in existing mixing diagnostic methodologies has persuaded cultivation of a new technique for measuring droplet collision mixing in confined microchannels. The technique employs single fluorophore laser-induced fluorescence, custom image processing, and meaningful statistical analysis for monitoring and quantifying mixing in high-speed droplet collisions. Mixing progress is revealed through two statistics that separate the roles of convective rearrangement and molecular diffusion during the mixing process. The end result is a viewing window into the rich dynamics of droplet collisions with spatial and temporal resolutions of 1 μm and 25 μs, respectively. Experimental results obtained across a decade of Reynolds and Peclet numbers reveal a direct link between droplet mixing time and the collision convective timescale. This work provides valuable insight into the emerging field of two-phase gas-liquid microfluidics and opens the door to fundamental research possibilities not offered by traditional oil-based architectures.

  16. Ion beam mixing of Fe with sapphire and silica

    SciTech Connect

    Sinha, S. K.; Vigen, K. M.; Kothari, D. C.; Som, T.; Kulkarni, V. N.; Nair, K. G. M.

    1999-06-10

    We have studied ion beam mixing of Fe with sapphire, silica, Al and Si using different mass of the ions (Ne{sup +},Ar{sup +}), different doses (5x10{sup 15} to 2x10{sup 17} ions/cm{sup 2}) and different temperatures (273 deg. K, 423 deg. K and 573 deg. K). Thin film of Fe was deposited by thermal evaporation method. Ion energy was chosen from 30 to 110 keV so that F{sub d} is maximum at the interface. All the specimens were analyzed by RBS. It is found that the square of the diffusion length Dt is proportional to the ion dose for both types of the substrates (Al{sub 2}O{sub 3} and SiO{sub 2}) implying that mixing is due to the ballistic effect (i.e. cascade mixing). Also mixing is more when irradiated by Ar{sup +} ions than Ne{sup +} ions. Comparison of Dt's shows that mixing is less in ceramics than in pure-elements Al and Si. In Fe-Al{sub 2}O{sub 3} samples, mixing decreases with increase in irradiation temperatures implying de-mixing in crystalline ionic bonded oxide whereas mixing increases in the covalently bonded oxide SiO{sub 2}. Irradiated annealed samples of Fe/Al{sub 2}O{sub 3} and Fe/SiO{sub 2} show de-mixing and mixing respectively.

  17. MHD turbulent mixing layers

    SciTech Connect

    Esquivel, A.; Lazarian, A.; Benjamin, R.A.; Cho, J.; Leitner, S.N.

    2005-09-28

    Turbulent mixing layers have been proposed to explain observations of line ratios of highly ionized elements in the interstellar medium. We present preliminary results of numerical simulations of turbulent mixing layers in a magnetized medium. We developed a MHD code with radiative cooling. The magnetic field is expected to be a controlling factor by suppressing instabilities that lead to the turbulent mixing. Our results suggest that the difference in turbulent mixing in the unmagnetized case as compared to the case of a weak magnetic field, {beta} = Pgas/Pmag {approx} 10, is insignificant. With a more thorough exploration of parameter space, this work will provide more reliable diagnostics of turbulent mixing layers than those available today.

  18. Gas Diffusion in Polyethylene Terepthalate By Molecular Dynamics

    NASA Astrophysics Data System (ADS)

    Butler, Simon; Adolf, David

    2006-03-01

    Molecular dynamics simulations of the diffusion of small penetrants through PET have been performed utilising the anisotropic united atom model [1] and a virtual liquid technique. [2] The accuracy and reliability of these two approaches has been assessed in terms of the improvement in equation of state behaviour and of diffusion co-efficients and solubilities. The effect of the diffusion of nitrogen, carbon dioxide, and oxygen on the local dynamics of PET have been investigated as a result. Attention has been focused on the dual mode effect [3] observed during mixed gas diffusion. [1] Molecular dynamics calculation of the equation of state of alkanes, J. Chem. Phys. 93, 6 (1990) [2] Kikuchi, Kuwajima, Fukada, Novel method to estimate the solubility of small molecules in cis-polyisoprene by molecular dynamics simulations, J. Chem. Phys, 115, 13 (2001) [3] Lewis, Duckett, Ward, Fairclough, Ryan, The barrier properties of polyethylene terephthalate to mixtures of oxygen, carbon dioxide and nitrogen, Polymer, 1631, 44 (2003)

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

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

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

  20. ADVANCED MIXING MODELS

    SciTech Connect

    Lee, S; Richard Dimenna, R; David Tamburello, D

    2008-11-13

    The process of recovering the waste in storage tanks at the Savannah River Site (SRS) typically requires mixing the contents of the tank with one to four dual-nozzle jet mixers located within the tank. The typical criteria to establish a mixed condition in a tank are based on the number of pumps in operation and the time duration of operation. To ensure that a mixed condition is achieved, operating times are set conservatively long. This approach results in high operational costs because of the long mixing times and high maintenance and repair costs for the same reason. A significant reduction in both of these costs might be realized by reducing the required mixing time based on calculating a reliable indicator of mixing with a suitably validated computer code. The work described in this report establishes the basis for further development of the theory leading to the identified mixing indicators, the benchmark analyses demonstrating their consistency with widely accepted correlations, and the application of those indicators to SRS waste tanks to provide a better, physically based estimate of the required mixing time. Waste storage tanks at SRS contain settled sludge which varies in height from zero to 10 ft. The sludge has been characterized and modeled as micron-sized solids, typically 1 to 5 microns, at weight fractions as high as 20 to 30 wt%, specific gravities to 1.4, and viscosities up to 64 cp during motion. The sludge is suspended and mixed through the use of submersible slurry jet pumps. To suspend settled sludge, water is added to the tank as a slurry medium and stirred with the jet pump. Although there is considerable technical literature on mixing and solid suspension in agitated tanks, very little literature has been published on jet mixing in a large-scale tank. If shorter mixing times can be shown to support Defense Waste Processing Facility (DWPF) or other feed requirements, longer pump lifetimes can be achieved with associated operational cost and

  1. Diffusion in Immiscible Melts

    NASA Technical Reports Server (NTRS)

    Pond, R. B.

    1985-01-01

    The objective of this program is to measure the diffusion coefficients for molten Pb in Zn in the immiscible liquid-phase region. Diffusion couples of pure Pb and Zn were prepared using a shear cell. These have been placed in graphite crucibles and encapsulated in stainless steel cartridges and are awaiting the next Materials Experiment Assembly (MEA) flight opportunity. In flight, one couple will be soaked for 40 minutes at 440 deg C (just above the monotectic temperature) and the second couple will be soaked for 40 minutes 820 deg C (just above the consolute temperature). After the soak both samples will be rapidly quenched by flowing He to minimize redistribution of the immiscible phases. Post flight compositional analysis will be accomplished using X-ray fluorescence in the scanning electron microscopy.

  2. 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.

  3. Nonlocal electrical diffusion equation

    NASA Astrophysics Data System (ADS)

    Gómez-Aguilar, J. F.; Escobar-Jiménez, R. F.; Olivares-Peregrino, V. H.; Benavides-Cruz, M.; Calderón-Ramón, C.

    2016-07-01

    In this paper, we present an analysis and modeling of the electrical diffusion equation using the fractional calculus approach. This alternative representation for the current density is expressed in terms of the Caputo derivatives, the order for the space domain is 0<β≤1 and for the time domain is 0<γ≤2. We present solutions for the full fractional equation involving space and time fractional derivatives using numerical methods based on Fourier variable separation. The case with spatial fractional derivatives leads to Levy flight type phenomena, while the time fractional equation is related to sub- or super diffusion. We show that the mathematical concept of fractional derivatives can be useful to understand the behavior of semiconductors, the design of solar panels, electrochemical phenomena and the description of anomalous complex processes.

  4. Magnetic diffuse scattering

    SciTech Connect

    Cable, J.W.

    1987-01-01

    The diffuse scattering of neutrons from magnetic materials provides unique and important information regarding the spatial correlations of the atoms and the spins. Such measurements have been extensively applied to magnetically ordered systems, such as the ferromagnetic binary alloys, for which the observed correlations describe the magnetic moment fluctuations associated with local environment effects. With the advent of polarization analysis, these techniques are increasingly being applied to study disordered paramagnetic systems such as the spin-glasses and the diluted magnetic semiconductors. The spin-pair correlations obtained are essential in understanding the exchange interactions of such systems. In this paper, we describe recent neutron diffuse scattering results on the atom-pair and spin-pair correlations in some of these disordered magnetic systems. 56 refs.

  5. Fractal model of anomalous diffusion.

    PubMed

    Gmachowski, Lech

    2015-12-01

    An equation of motion is derived from fractal analysis of the Brownian particle trajectory in which the asymptotic fractal dimension of the trajectory has a required value. The formula makes it possible to calculate the time dependence of the mean square displacement for both short and long periods when the molecule diffuses anomalously. The anomalous diffusion which occurs after long periods is characterized by two variables, the transport coefficient and the anomalous diffusion exponent. An explicit formula is derived for the transport coefficient, which is related to the diffusion constant, as dependent on the Brownian step time, and the anomalous diffusion exponent. The model makes it possible to deduce anomalous diffusion properties from experimental data obtained even for short time periods and to estimate the transport coefficient in systems for which the diffusion behavior has been investigated. The results were confirmed for both sub and super-diffusion.

  6. Turbo fluid machinery and diffusers

    NASA Technical Reports Server (NTRS)

    Sakurai, T.

    1984-01-01

    The general theory behind turbo devices and diffusers is explained. Problems and the state of research on basic equations of flow and experimental and measuring methods are discussed. Conventional centrifugation-type compressor and fan diffusers are considered in detail.

  7. ADVANCED MIXING MODELS

    SciTech Connect

    Lee, S; Dimenna, R; Tamburello, D

    2011-02-14

    The process of recovering and processing High Level Waste (HLW) the waste in storage tanks at the Savannah River Site (SRS) typically requires mixing the contents of the tank with one to four mixers (pumps) located within the tank. The typical criteria to establish a mixed condition in a tank are based on the number of pumps in operation and the time duration of operation. To ensure that a mixed condition is achieved, operating times are typically set conservatively long. This approach results in high operational costs because of the long mixing times and high maintenance and repair costs for the same reason. A significant reduction in both of these costs might be realized by reducing the required mixing time based on calculating a reliable indicator of mixing with a suitably validated computer code. The focus of the present work is to establish mixing criteria applicable to miscible fluids, with an ultimate goal of addressing waste processing in HLW tanks at SRS and quantifying the mixing time required to suspend sludge particles with the submersible jet pump. A single-phase computational fluid dynamics (CFD) approach was taken for the analysis of jet flow patterns with an emphasis on the velocity decay and the turbulent flow evolution for the farfield region from the pump. Literature results for a turbulent jet flow are reviewed, since the decay of the axial jet velocity and the evolution of the jet flow patterns are important phenomena affecting sludge suspension and mixing operations. The work described in this report suggests a basis for further development of the theory leading to the identified mixing indicators, with benchmark analyses demonstrating their consistency with widely accepted correlations. Although the indicators are somewhat generic in nature, they are applied to Savannah River Site (SRS) waste tanks to provide a better, physically based estimate of the required mixing time. Waste storage tanks at SRS contain settled sludge which varies in

  8. 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.

  9. [The diffusion of knowledge].

    PubMed

    Ramiro-H, Manuel; Cruz-A, Enrique

    2016-01-01

    Between August 19 and 21, the Feria del Libro de las Ciencias de la Salud (Healthcare Book Fair) took place in the Palacio de Medicina in Mexico City. Archives of Medical Research, Revista Médica del IMSS, and Saber IMSS, three of the main instruments of knowledge diffusion of the Instituto Mexicano del Seguro Social, assisted to this book fair, which was organized by the Facultad de Medicina of UNAM.

  10. Peridynamic thermal diffusion

    SciTech Connect

    Oterkus, Selda; Madenci, Erdogan; Agwai, Abigail

    2014-05-15

    This study presents the derivation of ordinary state-based peridynamic heat conduction equation based on the Lagrangian formalism. The peridynamic heat conduction parameters are related to those of the classical theory. An explicit time stepping scheme is adopted for numerical solution of various benchmark problems with known solutions. It paves the way for applying the peridynamic theory to other physical fields such as neutronic diffusion and electrical potential distribution.

  11. Simulation of radiation driven fission gas diffusion in UO2, ThO2 and PuO2

    NASA Astrophysics Data System (ADS)

    Cooper, M. W. D.; Stanek, C. R.; Turnbull, J. A.; Uberuaga, B. P.; Andersson, D. A.

    2016-12-01

    Below 1000 K it is thought that fission gas diffusion in nuclear fuel during irradiation occurs through atomic mixing due to radiation damage. Here we present a molecular dynamics (MD) study of Xe, Kr, Th, U, Pu and O diffusion due to irradiation. It is concluded that the ballistic phase does not sufficiently account for the experimentally observed diffusion. Thermal spike simulations are used to confirm that electronic stopping remedies the discrepancy with experiment and the predicted diffusivities lie within the scatter of the experimental data. Our results predict that the diffusion coefficients are ordered such that DO* > DKr* > DXe* > DU*. For all species >98.5% of diffusivity is accounted for by electronic stopping. Fission gas diffusivity was not predicted to vary significantly between ThO2, UO2 and PuO2, indicating that this process would not change greatly for mixed oxide fuels.

  12. Mixing dynamics and pattern formation around flow stagnation points

    NASA Astrophysics Data System (ADS)

    Hidalgo, Juan J.; Dentz, Marco

    2016-04-01

    We study the mixing of two reactive fluids in the presence of convective instabilities. Such system is characterized by the formation of unique porosity patterns and mixing dynamics linked to the evolution of vortices and stagnation points. Around them, the fluid-fluid interface is stretched and compressed, which enhances mixing and triggers chemical reactions, and the system can be analyzed using fluid deformation model. We consider velocity fields generated by a double gyre synthetic velocity field and Rayleigh-Bénard and Rayleigh-Taylor instabilities. The different flow structures can be visualized by the strain rate and the finite time Lyapunov exponents. We show that the mixing enhancement given by the scalar dissipation rate is controlled by the equilibrium between interface compression and diffusion, which depends on the velocity field configuration. Furthermore, we establish a quantitative relation between the mixing rate and the evolution of the potential energy of the fluid when convection is driven by density instabilities.

  13. Timescales of Geological Processes: a Diffuse Spectrum

    NASA Astrophysics Data System (ADS)

    Chakraborty, S.; Costa, F.; Trepmann, C. A.; Dueffels, K.; Dohmen, R.

    2004-12-01

    One of the most significant recent advances in the study of geological processes is the ability to identify and quantify a hierarchy of time scales ranging from days to millions of years. Modeling diffusion related processes provides one of the most versatile tools for studying the lower end of this temporal spectrum. We will demonstrate this versatility with two examples chosen from very different milieus. (1) Volcanic processes in the Chilean Andes: We use somewhat novel modeling techniques to show that magma mixing can cause igneous differentiation in a subduction zone setting over decadal time scales. This provides a link between processes occurring over thousands to millions of years (melt generation and transport) and pre-eruptive processes that occur over days to months. (2) Plutonism and mid-crustal metamorphic processes in the Alps. Here, dike emplacement was triggered over time scales of days, cooling in magma chambers occurred over hundreds of years while metamorphism in the mid crustal level lasted millions of years. The regional distribution of such rates allows us to infer differential uplift across a section of the Alps. Traditionally, diffusion modeling has been plagued by large uncertainties arising from a number of sources. Large extrapolations of diffusion coefficients measured at high temperatures, simplified numerical models and inadequate understanding of diffusion mechanisms are some of these. Technical and theoretical developments now allow us to circumvent many of these problems. For example, the ability to manipulate complex silicate compositions on the nanometer scale through the use of thin film technology (e.g. pulsed laser ablation) allows us to measure diffusion coefficients at conditions that were inaccessible only a few years ago. In addition, these experiments are faster and more accurate. Consequently, it is now possible to determine parameters such as enhancement of diffusion rates in defective crystals or due to reactive

  14. The mixing of fluids

    SciTech Connect

    Ottino, J.M.

    1989-01-01

    What do the eruption of Krakatau, the manufacture of puff pastry and the brightness of stars have in common Each involves some aspect of mixing. Mixing also plays a critical role in modern technology. Chemical engineers rely on mixing to ensure that substances react properly, to produce polymer blends that exhibit unique properties and to disperse drag-reducing agents in pipelines. Yet in spite of its of its ubiquity in nature and industry, mixing is only imperfectly under-stood. Indeed, investigators cannot even settle on a common terminology: mixing is often referred to as stirring by oceanographers and geophysicists, as blending by polymer engineers and as agitation by process engineers. Regardless of what the process is called, there is little doubt that it is exceedingly complex and is found in a great variety of systems. In constructing a theory of fluid mixing, for example, one has to take into account fluids that can be miscible or partially miscible and reactive or inert, and flows that are slow and orderly or very fast and turbulent. It is therefore not surprising that no single theory can explain all aspect of mixing in fluids and that straightforward computations usually fail to capture all the important details. Still, both physical experiments and computer simulations can provide insight into the mixing process. Over the past several years the authors and his colleague have taken both approaches in an effort to increase understanding of various aspect of the process-particularly of mixing involving slow flows and viscous fluids such as oils.

  15. Bounded fractional diffusion in geological media: Definition and Lagrangian approximation

    NASA Astrophysics Data System (ADS)

    Zhang, Yong; Green, Christopher T.; LaBolle, Eric M.; Neupauer, Roseanna M.; Sun, HongGuang

    2016-11-01

    Spatiotemporal fractional-derivative models (FDMs) have been increasingly used to simulate non-Fickian diffusion, but methods have not been available to define boundary conditions for FDMs in bounded domains. This study defines boundary conditions and then develops a Lagrangian solver to approximate bounded, one-dimensional fractional diffusion. Both the zero-value and nonzero-value Dirichlet, Neumann, and mixed Robin boundary conditions are defined, where the sign of Riemann-Liouville fractional derivative (capturing nonzero-value spatial-nonlocal boundary conditions with directional superdiffusion) remains consistent with the sign of the fractional-diffusive flux term in the FDMs. New Lagrangian schemes are then proposed to track solute particles moving in bounded domains, where the solutions are checked against analytical or Eulerian solutions available for simplified FDMs. Numerical experiments show that the particle-tracking algorithm for non-Fickian diffusion differs from Fickian diffusion in relocating the particle position around the reflective boundary, likely due to the nonlocal and nonsymmetric fractional diffusion. For a nonzero-value Neumann or Robin boundary, a source cell with a reflective face can be applied to define the release rate of random-walking particles at the specified flux boundary. Mathematical definitions of physically meaningful nonlocal boundaries combined with bounded Lagrangian solvers in this study may provide the only viable techniques at present to quantify the impact of boundaries on anomalous diffusion, expanding the applicability of FDMs from infinite domains to those with any size and boundary conditions.

  16. Extremely slow intramolecular diffusion in unfolded protein L

    PubMed Central

    Waldauer, Steven A.; Bakajin, Olgica; Lapidus, Lisa J.

    2010-01-01

    A crucial parameter in many theories of protein folding is the rate of diffusion over the energy landscape. Using a microfluidic mixer we have observed the rate of intramolecular diffusion within the unfolded B1 domain of protein L before it folds. The diffusion-limited rate of intramolecular contact is about 20 times slower than the rate in 6 M GdnHCl, and because in these conditions the protein is also more compact, the intramolecular diffusion coefficient decreases 100–500 times. The dramatic slowdown in diffusion occurs within the 250 μs mixing time of the mixer, and there appears to be no further evolution of this rate before reaching the transition state of folding. We show that observed folding rates are well predicted by a Kramers model with a denaturant-dependent diffusion coefficient and speculate that this diffusion coefficient is a significant contribution to the observed rate of folding. PMID:20643973

  17. Double Diffusive Plumes

    NASA Astrophysics Data System (ADS)

    Sutherland, Bruce; Lee, Brace

    2008-11-01

    Sour gas flares attempt to dispose of deadly H2S gas through combustion. What does not burn rises as a buoyant plume. But the gas is heavier than air at room temperature, so as the rising gas cools eventually it becomes negatively buoyant and descends back to the ground. Ultimately, our intent is to predict the concentrations of the gas at ground level in realistic atmospheric conditions. As a first step towards this goal we have performed laboratory experiments examining the structure of a steady state plume of hot and salty water that rises buoyantly near the source and descends as a fountain after it has cooled sufficiently. We call this a double-diffusive plume because its evolution is dictated by the different (turbulent) diffusivities of heat and salt. A temperature and conductivity probe measures both the salinity and temperature along the centreline of the plume. The supposed axisymmetric structure of the salinity concentration as it changes with height is determined by light-attenuation methods. To help interpret the results, a theory has been successfully adapted from the work of Bloomfield and Kerr (2000), who developed coupled equations describing the structure of fountains. Introducing a new empirical parameter for the relative rates of turbulent heat and salt diffusion, the predictions are found to agree favourably with experimental results.

  18. Solute diffusion in liquid metals

    NASA Technical Reports Server (NTRS)

    Bhat, B. N.

    1973-01-01

    A gas model of diffusion in liquid metals is presented. In this model, ions of liquid metals are assumed to behave like the molecules in a dense gas. Diffusion coefficient of solute is discussed with reference to its mass, ionic size, and pair potential. The model is applied to the case of solute diffusion in liquid silver. An attempt was made to predict diffusion coefficients of solutes with reasonable accuracy.

  19. The ThermalDiffusion class

    SciTech Connect

    Dolan, Daniel H.

    2014-10-01

    The ThermalDiffusion class was created to simulate one-dimensional thermal diffusion across one or more material layers. Each layer is assumed to have constant conductivity K and diffusivity κ . Interface conductance between layers may be specified. Internal heating as a function of position and time is also supported. The ThermalDiffusion class is included in the SMASH package [1] as part of the PDE (Partial Differential Equation) subpackage.

  20. A new characterization of the turbulent diapycnal diffusivities of mass and momentum in the ocean

    NASA Astrophysics Data System (ADS)

    Salehipour, H.; Peltier, W. R.; Whalen, C. B.; MacKinnon, J. A.

    2016-04-01

    The diapycnal diffusivity of mass supported by turbulent events in the ocean interior plays a fundamental role in controlling the global overturning circulation. The conventional representation of this diffusivity, due to Osborn (1980), assumes a constant mixing efficiency. We replace this methodology by a generalized-Osborn formula which involves a mixing efficiency that varies nonmonotonically with at least two nondimensional variables. Using these two variables, we propose dynamic parameterizations for mixing efficiency and turbulent Prandtl number (the latter quantifies the ratio of momentum to mass diapycnal diffusivities) based on the first synthesis of an extensive direct numerical simulation of inhomogeneously stratified shear-induced turbulence. Data from Argo floats are employed to demonstrate the extent of the spatial and statistical variability to be expected in both the diapycnal diffusivities of mass and momentum. We therefore suggest that previous estimates of these important characteristics of the global ocean require reconsideration.

  1. Mixing method and apparatus

    DOEpatents

    Green, Norman W.

    1982-06-15

    Method of mixing particulate materials comprising contacting a primary source and a secondary source thereof whereby resulting mixture ensues; preferably at least one of the two sources has enough motion to insure good mixing and the particulate materials may be heat treated if desired. Apparatus for such mixing comprising an inlet for a primary source, a reactor communicating therewith, a feeding means for supplying a secondary source to the reactor, and an inlet for the secondary source. Feeding means is preferably adapted to supply fluidized materials.

  2. Nearly discontinuous chaotic mixing

    SciTech Connect

    Sharp, David Howland; Lim, Hyun K; Yu, Yan; Glimm, James G

    2009-01-01

    A new scientific approach is presented for a broad class of chaotic problems involving a high degree of mixing over rapid time scales. Rayleigh-Taylor and Richtmyer-Meshkov unstable flows are typical of such problems. Microscopic mixing properties such as chemical reaction rates for turbulent mixtures can be obtained with feasible grid resolution. The essential dependence of (some) fluid mixing observables on transport phenomena is observed. This dependence includes numerical as well as physical transport and it includes laminar as well as turbulent transport. A new approach to the mathematical theory for the underlying equations is suggested.

  3. Topographic enhancement of vertical turbulent mixing in the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Mashayek, A.; Ferrari, R.; Merrifield, S.; Ledwell, J. R.; St Laurent, L.; Garabato, A. Naveira

    2017-03-01

    It is an open question whether turbulent mixing across density surfaces is sufficiently large to play a dominant role in closing the deep branch of the ocean meridional overturning circulation. The diapycnal and isopycnal mixing experiment in the Southern Ocean found the turbulent diffusivity inferred from the vertical spreading of a tracer to be an order of magnitude larger than that inferred from the microstructure profiles at the mean tracer depth of 1,500 m in the Drake Passage. Using a high-resolution ocean model, it is shown that the fast vertical spreading of tracer occurs when it comes in contact with mixing hotspots over rough topography. The sparsity of such hotspots is made up for by enhanced tracer residence time in their vicinity due to diffusion toward weak bottom flows. The increased tracer residence time may explain the large vertical fluxes of heat and salt required to close the abyssal circulation.

  4. Topographic enhancement of vertical turbulent mixing in the Southern Ocean

    PubMed Central

    Mashayek, A.; Ferrari, R.; Merrifield, S.; Ledwell, J. R.; St Laurent, L.; Garabato, A. Naveira

    2017-01-01

    It is an open question whether turbulent mixing across density surfaces is sufficiently large to play a dominant role in closing the deep branch of the ocean meridional overturning circulation. The diapycnal and isopycnal mixing experiment in the Southern Ocean found the turbulent diffusivity inferred from the vertical spreading of a tracer to be an order of magnitude larger than that inferred from the microstructure profiles at the mean tracer depth of 1,500 m in the Drake Passage. Using a high-resolution ocean model, it is shown that the fast vertical spreading of tracer occurs when it comes in contact with mixing hotspots over rough topography. The sparsity of such hotspots is made up for by enhanced tracer residence time in their vicinity due to diffusion toward weak bottom flows. The increased tracer residence time may explain the large vertical fluxes of heat and salt required to close the abyssal circulation. PMID:28262808

  5. Atomic transport in ion mixed Pd/Co bilayer

    NASA Astrophysics Data System (ADS)

    Chae, K. H.; Jang, H. G.; Song, J. H.; Woo, J. J.; Choi, B. S.; Jeong, K.; Whang, C. N.

    1993-06-01

    Isotropic and anisotropic atomic transport in an ion beam mixed Pd/Co bilayer have been studied from the shifts of a marker layer in Rutherford backscattering spectroscopy. A thin layer of Au (1 nm) was embedded as a marker at the interface between Pd and Co layers. 80 keV Ar + was used to irradiate the marker sample at 90K. The Pd/Co system shows near isotropic atomic transport ( JPd/ JCo = 0.86) due to the thermal spike effect. We present a simple relationship between the ration of atomic fluxes induced by ion mixing and the activation energies for the normal impurity diffusion of constituents in a bilayer to describe quantitatively the isotropic and anisotropic atomic transport in thermal spike induced ion mixing. Thermal spike induced atomic transport is closely related with the activation energy for normal impurity diffusion.

  6. Guidelines for mixed waste minimization

    SciTech Connect

    Owens, C.

    1992-02-01

    Currently, there is no commercial mixed waste disposal available in the United States. Storage and treatment for commercial mixed waste is limited. Host States and compacts region officials are encouraging their mixed waste generators to minimize their mixed wastes because of management limitations. This document provides a guide to mixed waste minimization.

  7. Chemical Reactions in Turbulent Mixing Flows

    DTIC Science & Technology

    1989-06-01

    liquid mixing layer", J. Fluid Mech. 17C, 83-112. 69 LUNDGREN , T. S. [1982] "Strained Spiral Vortex Model for Turbulent Fine Structure", Phy.- Fluids 25(12...diffusion geometry is one of sheets rolled up around vortex filaments, as assumed by Lundgren (1982,1985), then the vorticity axis Is normal to the maximum...the development of efficient algorithms for vortex dynamics calculations. We should note that this effort is part of a larger effort at the Graduate

  8. Plane mixing layer vortical structure kinematics

    NASA Technical Reports Server (NTRS)

    Leboeuf, Richard L.

    1993-01-01

    The objective of the current project was to experimentally investigate the structure and dynamics of the streamwise vorticity in a plane mixing layer. The first part of this research program was intended to clarify whether the observed decrease in mean streamwise vorticity in the far-field of mixing layers is due primarily to the 'smearing' caused by vortex meander or to diffusion. Two-point velocity correlation measurements have been used to show that there is little spanwise meander of the large-scale streamwise vortical structure. The correlation measurements also indicate a large degree of transverse meander of the streamwise vorticity which is not surprising since the streamwise vorticity exists in the inclined braid region between the spanwise vortex core regions. The streamwise convection of the braid region thereby introduces an apparent transverse meander into measurements using stationary probes. These results corroborated with estimated secondary velocity profiles in which the streamwise vorticity produces a signature which was tracked in time.

  9. Artificial upwelling and mixing

    SciTech Connect

    Not Available

    1989-01-01

    The authors present results related to artificial upwelling and coastal mariculture using deep ocean water and mixing in coastal waters. They discuss the application of research results for marine waste disposal.

  10. Mixed-Media Owls

    ERIC Educational Resources Information Center

    Schultz, Kathy

    2010-01-01

    The fun of creating collages is there are unlimited possibilities for the different kinds of materials one can use. In this article, the author describes how her eighth-grade students created an owl using mixed media.

  11. Asymmetric antiproton debuncher: No bad mixing, more good mixing

    SciTech Connect

    Visnjic, V.

    1994-07-01

    An asymmetric lattice for the Fermilab Antiproton Debuncher is designed. The lattice has zero mixing between the pickups and the kickers (bad mixing) while the mixing in the rest of the machine (good mixing) can be varied (even during the operation of the machine) in order to optimize the stochastic cooling. As an example, a lattice with zero bad mixing and twice the good mixing is presented. The betatron cooling rate in this lattice is twice its present value.

  12. Experiments on differential diffusion of temperature and salinity across a sheared density interface

    NASA Astrophysics Data System (ADS)

    Jackson, P. Ryan; Rehmann, Chris

    2005-11-01

    Differential diffusion of two stably stratified scalars with different molecular diffusivities in a turbulent flow can affect ocean circulation modeling and the interpretation of ocean mixing experiments. In past work we used rapid distortion theory to evaluate the effect of a mean shear on differential diffusion. The present work compares those theoretical results with results from laboratory experiments. In the experiments, an Odell-Kovasnay recirculating flume and disk pump was used to drive a warm, fresh water upper layer over the cold, salty quiescent lower layer. Bulk measurements based on the evolution of the scalar profiles and instantaneous interfacial flux measurements were employed to quantify scalar mixing across the sheared interface. Results from the experiments compare well with predictions of the theory. For weakly turbulent, strongly stratified flows, differential diffusion is found to decrease with increasing shear. However, for more energetic flows, differential diffusion is found to increase with increasing shear.

  13. Mixing dynamics of cutting and shuffling for granular materials

    NASA Astrophysics Data System (ADS)

    Lueptow, Richard M.; Zaman, Zafir; Yu, Mengqi; Park, Paul P.; Ottino, Julio M.; Umbanhowar, Paul B.

    2016-11-01

    Chaotic dynamics has been shown to play a major role in fluid mixing, but the study of its relevance to granular flows has only recently begun. We utilize a simple 3D geometry, a half-filled spherical tumbler rotated alternately by <= π /2 about two perpendicular horizontal axes, to develop a dynamical systems framework for granular mixing and non-mixing. In these systems, mixing can only occur during flow (from stretching due to shear and from collisional diffusion in the flowing layer) or by material separation intrinsic to the rotation protocol resulting from cutting and shuffling. In X-ray subsurface visualization experiments, surprisingly persistent (O(100) iterations) non-mixing elliptical regions and larger non-mixing barriers occur as predicted by both a continuum model and an idealized theoretical model (with an infinitely thin flowing layer) based on the mathematics of piece-wise isometries. In these models, the stretching in the flowing layer vanishes as the flowing layer thickness decreases to reveal the underlying skeleton of the mixing. This dynamical systems perspective provides insight into mixing and non-mixing phenomena unique to granular materials. Funded by NSF Grant CMMI-1435065.

  14. Configurational diffusion of coal macromolecules

    SciTech Connect

    Guin, J.A.; Curtis, C.W.; Tarrer, A.R.

    1990-01-01

    The objective of this project is to investigate the phenomenon of hindered diffusion of coal macromolecules in idealized porous media. Tasks towards this objective include: Construct a diffusion cell with ideal pore structure for determination of diffusion coefficients, prepare and characterize ideal porous membranes, perform model compound experiments to calibrate and test diffusion apparatus and methodology, prepare and characterize coal macromolecules, and analyze data to evaluate the diffusional behavior of coal macromolecules. This report describes work on the hindered diffusion of tetraphenylporphine and asphaltene. 18 refs., 3 figs., 4 tabs.

  15. Magma mixing enhanced by bubble segregation

    NASA Astrophysics Data System (ADS)

    Wiesmaier, S.; Daniele, M.; Renggli, C.; Perugini, D.; De Campos, C.; Hess, K. U.; Ertel-Ingrisch, W.; Lavallée, Y.; Dingwell, D. B.

    2014-12-01

    Rising bubbles may significantly affect magma mixing paths as has been demonstrated by analogue experiments in the past. Here, bubble-advection experiments are performed for the first time employing natural materials at magmatic temperatures. Cylinders of basaltic glass were placed below cylinders of rhyolite glass. Upon melting, interstitial air formed bubbles that rose into the rhyolite melt, thereby entraining tails of basaltic liquid. The formation of plume-like filaments of advected basalt within the rhyolite was characterized by microCT and subsequent high-resolution EMP analyses. Melt entrainment by bubble ascent appears as efficient mechanism to mingle contrasting melt compositions. MicroCT imaging shows bubbles trailing each other and trails of multiple bubbles having converged. Rheological modelling of the filaments yields viscosities of up to 2 orders of magnitude lower than for the surrounding rhyolitic liquid. Such a viscosity contrast implies that subsequent bubbles rising are likely to follow the same pathways that previously ascending bubbles have generated. Filaments formed by multiple bubbles would thus experience episodic replenishment with mafic material. Fundamental implications for the concept of bubble advection in magma mixing are thus a) an acceleration of mixing because of decreased viscous resistance for bubbles inside filaments and b) non-conventional diffusion systematics because of intermittent supply of mafic material (instead of a single pulse) inside a filament. Inside these filaments, the mafic material was variably hybridised to andesitic through rhyolitic composition. Compositional profiles alone are ambiguous, however, to determine whether single or multiple bubbles were involved during formation of a filament. Statistical analysis, employing concentration variance as measure of homogenisation, demonstrates that also filaments appearing as single-bubble filaments are likely to have experienced multiple bubbles passing through

  16. Magma mixing enhanced by bubble segregation

    NASA Astrophysics Data System (ADS)

    Wiesmaier, S.; Morgavi, D.; Renggli, C. J.; Perugini, D.; De Campos, C. P.; Hess, K.-U.; Ertel-Ingrisch, W.; Lavallée, Y.; Dingwell, D. B.

    2015-08-01

    In order to explore the materials' complexity induced by bubbles rising through mixing magmas, bubble-advection experiments have been performed, employing natural silicate melts at magmatic temperatures. A cylinder of basaltic glass was placed below a cylinder of rhyolitic glass. Upon melting, bubbles formed from interstitial air. During the course of the experimental runs, those bubbles rose via buoyancy forces into the rhyolitic melt, thereby entraining tails of basaltic liquid. In the experimental run products, these plume-like filaments of advected basalt within rhyolite were clearly visible and were characterised by microCT and high-resolution EMP analyses. The entrained filaments of mafic material have been hybridised. Their post-experimental compositions range from the originally basaltic composition through andesitic to rhyolitic composition. Rheological modelling of the compositions of these hybridised filaments yield viscosities up to 2 orders of magnitude lower than that of the host rhyolitic liquid. Importantly, such lowered viscosities inside the filaments implies that rising bubbles can ascend more efficiently through pre-existing filaments that have been generated by earlier ascending bubbles. MicroCT imaging of the run products provides textural confirmation of the phenomenon of bubbles trailing one another through filaments. This phenomenon enhances the relevance of bubble advection in magma mixing scenarios, implying as it does so, an acceleration of bubble ascent due to the decreased viscous resistance facing bubbles inside filaments and yielding enhanced mass flux of mafic melt into felsic melt via entrainment. In magma mixing events involving melts of high volatile content, bubbles may be an essential catalyst for magma mixing. Moreover, the reduced viscosity contrast within filaments implies repeated replenishment of filaments with fresh end-member melt. As a result, complex compositional gradients and therefore diffusion systematics can be

  17. On modeling pressure diffusion in non-homogeneous shear flows

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

    New models are proposed for the 'slow and 'rapid' parts of the pressure diffusive transport based on the examination of DNS databases for plane mixing layers and wakes. The model for the 'slow' part is non-local, but requires the distribution of the triple-velocity correlation as a local source. The latter can be computed accurately for the normal component from standard gradient diffusion models, but such models are inadequate for the cross component. More work is required to remedy this situation.

  18. Suppression of Cavity-Driven Flow Separation in a Simulated Mixed Compression Inlet

    NASA Technical Reports Server (NTRS)

    Wendt, Bruce J.

    2000-01-01

    A test facility designed to simulate a bifurcated subsonic diffuser operating within a mixed compression inlet is described. The subsonic diffuser in this facility modeled a bypass cavity feature often used in mixed compression inlets for engine flow matching and normal shock control. A bypass cavity-driven flow separation was seen to occur in the subsonic diffuser without applied flow control. Flow control in the form of vortex generators and/or a partitioned bypass cavity cover plate were used to eliminate this flow separation, providing a 2% increase in area-averaged total pressure recovery, and a 70% reduction in circumferential distortion intensity.

  19. Controlling Exciton Diffusion and Fullerene Distribution in Photovoltaic Blends by Side Chain Modification

    PubMed Central

    2015-01-01

    The influence of crystallinity on exciton diffusion and fullerene distribution was investigated by blending amorphous and semicrystalline copolymers. We measured exciton diffusion and fluorescence quenching in such blends by dispersing fullerene molecules into them. We find that the diffusion length is more than two times higher in the semicrystalline copolymer than in the amorphous copolymer. We also find that fullerene preferentially mixes into disordered regions of the polymer film. This shows that relatively small differences in molecular structure are important for exciton diffusion and fullerene distribution. PMID:26267202

  20. Shaken, not Stirred: Mixing Organic Aerosol

    NASA Astrophysics Data System (ADS)

    Donahue, N. M.; Robinson, E.; Trump, E. R.; Saleh, R.

    2013-12-01

    For organic vapors to condense onto or into existing particles in the atmosphere, the compounds must have a positive thermodynamic driving force. Their activity (saturation ratio) in the gas phase must exceed their activity (modified mole fraction) at the particle surface. Organic-aerosol production rates are generally quite small -- a few μg m-3 per hour at most -- and thus gas-phase saturation ratios are correspondingly small. Most experiments are conducted with far higher production rates and thus far higher saturation ratios. Consequently, experiments may or may not constrain whether organics coat particles in the real world. In addition, surface activity is often assumed to equal bulk activity for most species, meaning that particles are well mixed. However, if particles are viscous and coating rates high, diffusion through the bulk of even 100 nm particles may be slow. Again, matching experimental timescales to real-world timescales is important. Here we describe organic particle mixing experiments in which two organic particle populations are prepared separately and then intermingled by transferring the contents of one preparation chamber into another. Constituents of one population are isotopically labeled, making the mass spectra of the two particle types completely orthogonal. Following the intermingling, single-particle mass spectra allow us to track individual particle composition as the populations mix via gas-phase exchange. This allows us to explore the mixing and coating behavior of organic-aerosol populations under conditions much closer to concentrations found in the real world.

  1. Accelerated stochastic diffusion processes

    NASA Astrophysics Data System (ADS)

    Garbaczewski, Piotr

    1990-07-01

    We give a purely probabilistic demonstration that all effects of non-random (external, conservative) forces on the diffusion process can be encoded in the Nelson ansatz for the second Newton law. Each random path of the process together with a probabilistic weight carries a phase accumulation (complex valued) weight. Random path summation (integration) of these weights leads to the transition probability density and transition amplitude respectively between two spatial points in a given time interval. The Bohm-Vigier, Fenyes-Nelson-Guerra and Feynman descriptions of the quantum particle behaviours are in fact equivalent.

  2. Diffusion in quantum geometry

    NASA Astrophysics Data System (ADS)

    Calcagni, Gianluca

    2012-08-01

    The change of the effective dimension of spacetime with the probed scale is a universal phenomenon shared by independent models of quantum gravity. Using tools of probability theory and multifractal geometry, we show how dimensional flow is controlled by a multiscale fractional diffusion equation, and physically interpreted as a composite stochastic process. The simplest example is a fractional telegraph process, describing quantum spacetimes with a spectral dimension equal to 2 in the ultraviolet and monotonically rising to 4 towards the infrared. The general profile of the spectral dimension of the recently introduced multifractional spaces is constructed for the first time.

  3. Diffusion in silicon isotope heterostructures

    SciTech Connect

    Silvestri, Hughes Howland

    2004-01-01

    The simultaneous diffusion of Si and the dopants B, P, and As has been studied by the use of a multilayer structure of isotopically enriched Si. This structure, consisting of 5 pairs of 120 nm thick natural Si and 28Si enriched layers, enables the observation of 30Si self-diffusion from the natural layers into the 28Si enriched layers, as well as dopant diffusion from an implanted source in an amorphous Si cap layer, via Secondary Ion Mass Spectrometry (SIMS). The dopant diffusion created regions of the multilayer structure that were extrinsic at the diffusion temperatures. In these regions, the Fermi level shift due to the extrinsic condition altered the concentration and charge state of the native defects involved in the diffusion process, which affected the dopant and self-diffusion. The simultaneously recorded diffusion profiles enabled the modeling of the coupled dopant and self-diffusion. From the modeling of the simultaneous diffusion, the dopant diffusion mechanisms, the native defect charge states, and the self- and dopant diffusion coefficients can be determined. This information is necessary to enhance the physical modeling of dopant diffusion in Si. It is of particular interest to the modeling of future electronic Si devices, where the nanometer-scale features have created the need for precise physical models of atomic diffusion in Si. The modeling of the experimental profiles of simultaneous diffusion of B and Si under p-type extrinsic conditions revealed that both species are mediated by neutral and singly, positively charged Si self-interstitials. The diffusion of As and Si under extrinsic n-type conditions yielded a model consisting of the interstitialcy and vacancy mechanisms of diffusion via singly negatively charged self-interstitials and neutral vacancies. The simultaneous diffusion of P and Si has been modeled on the basis of neutral and singly negatively charged self-interstitials and neutral and singly

  4. Characterization of supersonic mixing in a nonreacting Mach 2 combustor

    SciTech Connect

    Hollo, S.D.; Mcdaniel, J.C.; Hartfield, R.J., JR. )

    1992-01-01

    Planar measurements of the injection mole fraction distribution and the velocity field within a nonreacting model SCRAMJET combustor have been made using laser-induced iodine fluorescence. The combustor geometry investigated in this work is staged transverse injection of air into a Mach 2 freestream. A complete three-dimensional survey of the injectant mole fraction distribution has been generated and a single planar velocity measurement has been completed. The measurements reveal the dramatic effect of streamwise vortices on the mixing of the injectant in the near field of the injectors, as well as the rapid mixing generated by staging two field injectors. Analysis of the downstream decay of the maximum injectant mole fraction in this and other nonreacting combustor geometries indicates that the relative rate of injectant mixing well downstream of the injectors is independent of combustor geometry, combustor Mach number, and injectant molecular weight. Mixing within this region of the combustor is dominated by turbulent diffusion within the injectant plume. The transition of the dominant mixing mechanism, from vortex-driven mixing in the near field to turbulent diffusion in the far field, was found to occur in the region between 10 and 20 jet diameters downstream of the injectors. 22 refs.

  5. Mixing of Supersonic Streams

    NASA Technical Reports Server (NTRS)

    Hawk, C. W.; Landrum, D. B.; Muller, S.; Turner, M.; Parkinson, D.

    1998-01-01

    The Strutjet approach to Rocket Based Combined Cycle (RBCC) propulsion depends upon fuel-rich flows from the rocket nozzles and turbine exhaust products mixing with the ingested air for successful operation in the ramjet and scramjet modes. It is desirable to delay this mixing process in the air-augmented mode of operation present during low speed flight. A model of the Strutjet device has been built and is undergoing test to investigate the mixing of the streams as a function of distance from the Strutjet exit plane during simulated low speed flight conditions. Cold flow testing of a 1/6 scale Strutjet model is underway and nearing completion. Planar Laser Induced Fluorescence (PLIF) diagnostic methods are being employed to observe the mixing of the turbine exhaust gas with the gases from both the primary rockets and the ingested air simulating low speed, air augmented operation of the RBCC. The ratio of the pressure in the turbine exhaust duct to that in the rocket nozzle wall at the point of their intersection is the independent variable in these experiments. Tests were accomplished at values of 1.0, 1.5 and 2.0 for this parameter. Qualitative results illustrate the development of the mixing zone from the exit plane of the model to a distance of about 10 rocket nozzle exit diameters downstream. These data show the mixing to be confined in the vertical plane for all cases, The lateral expansion is more pronounced at a pressure ratio of 1.0 and suggests that mixing with the ingested flow would be likely beginning at a distance of 7 nozzle exit diameters downstream of the nozzle exit plane.

  6. Mixing of Supersonic Streams

    NASA Technical Reports Server (NTRS)

    Hawk, C. W.; Landrum, D. B.; Muller, S.; Turner, M.; Parkinson, D.

    1998-01-01

    The Strutjet approach to Rocket Based Combined Cycle (RBCC) propulsion depends upon fuel-rich flows from the rocket nozzles and turbine exhaust products mixing with the ingested air for successful operation in the ramjet and scramjet modes. It is desirable to delay this mixing process in the air-augmented mode of operation present during low speed flight. A model of the Strutjet device has been built and is undergoing test to investigate the mixing of the streams as a function of distance from the Strutjet exit plane during simulated low speed flight conditions. Cold flow testing of a 1/6 scale Strutjet model is underway and nearing completion. Planar Laser Induced Fluorescence (PLIF) diagnostic methods are being employed to observe the mixing of the turbine exhaust gas with the gases from both the primary rockets and the ingested air simulating low speed, air augmented operation of the RBCC. The ratio of the pressure in the turbine exhaust duct to that in the rocket nozzle wall at the point of their intersection is the independent variable in these experiments. Tests were accomplished at values of 1.0, 1.5 and 2.0 for this parameter. Qualitative results illustrate the development of the mixing zone from the exit plane of the model to a distance of about 19 equivalent rocket nozzle exit diameters downstream. These data show the mixing to be confined in the vertical plane for all cases, The lateral expansion is more pronounced at a pressure ratio of 1.0 and suggests that mixing with the ingested flow would be likely beginning at a distance of 7 nozzle exit diameters downstream of the nozzle exit plane.

  7. Compositional Gradients Across Mare and Highlands Contacts: The Importance and Geological Implication of Lateral Mixing

    NASA Astrophysics Data System (ADS)

    Li, L.; Mustard, J. F.

    1997-07-01

    Variation in mare abundance across mare-highland contact depends on the relative importance of vertical and lateral mass transport. Nonlinear spectral mixing analysis of Clementine VIS-NIR data of the Grimaldi basin indicates that the abundance of mare and highland are approximately equal to 50% at the geologic contact and the amount of mare materials transported to the highlands is approximately equal to the amount of highland materials to the mare. Thus, vertical mixing is relatively unimportant except near the contact. There are apparently two mixing zones, a steep mixing gradient near the mare and highland contact and a more diffuse zone that extends some distance from the contact. The net transfer of mare across the geologic contact can be approximated by a diffusion process since the transport is a random process driven by impact cratering. We have developed a diffusion model and the results indicate that a typical profile of mare abundance requires two superimposed diffusion curves to match this compositional gradients. A third curve is found to be statistically invalid. The two diffusion parameters can be related to the geologic processes of regolith reworking and development that created the variations. This suggests that there are at least two superimposed processes at work, the one is the reworking of the surface ejecta debris having a larger diffusion coefficient, the other is the development of new regolith from subsurface layers having smaller diffusion coefficient.

  8. Cosmic Diffuse Analysis

    NASA Technical Reports Server (NTRS)

    Ryan, James M.

    1999-01-01

    The final analysis of the COMPTEL cosmic diffuse flux analysis is summarized in the accompanying figure. It shows the intensity of the cosmic diffuse flux spectrum measured jointly between the Virgo region and the South Galactic pole. This spectrum represents flux per unit solid angle over the range of 0.8 to 30 MeV. It contains the first positive measurement of the flux above 10 MeV. The spectrum merges smoothly with that measured with the EGRET instrument, starting at 30 MeV. It also merges smoothly with the latest results of the HEAO-1 measurements. However, the spectrum below is softer than the spectrum above the COMPTEL energy band. In the COMPTEL energy band there must exist a change in spectral shape as the source objects or processes change from the lower energy regime to the higher energy regime. The details of the analysis and the implications and meanings of the results are spelled out in the thesis of Dr. Cheenu Kappadath which is enclosed.

  9. The diffusion of microfinance.

    PubMed

    Banerjee, Abhijit; Chandrasekhar, Arun G; Duflo, Esther; Jackson, Matthew O

    2013-07-26

    To study the impact of the choice of injection points in the diffusion of a new product in a society, we developed a model of word-of-mouth diffusion and then applied it to data on social networks and participation in a newly available microfinance loan program in 43 Indian villages. Our model allows us to distinguish information passing among neighbors from direct influence of neighbors' participation decisions, as well as information passing by participants versus nonparticipants. The model estimates suggest that participants are seven times as likely to pass information compared to informed nonparticipants, but information passed by nonparticipants still accounts for roughly one-third of eventual participation. An informed household is not more likely to participate if its informed friends participate. We then propose two new measures of how effective a given household would be as an injection point. We show that the centrality of the injection points according to these measures constitutes a strong and significant predictor of eventual village-level participation.

  10. Apparatus for diffusion separation

    DOEpatents

    Nierenberg, William A.

    1976-08-10

    1. A diffuser separator apparatus which comprises a plurality of flow channels in a single stage, each of said channels having an inlet port and an outlet port and a constant cross sectional area between said ports, at least a portion of the defining surface of each of said channels being a diffusion separation membrane, and each of said channels having a different cross sectional area, means for connecting said channels in series so that each successive channel of said series has a smaller cross sectional area than the previous channel of said series, a source of gaseous mixture, individual means for flowing said gaseous mixture to the inlet port of each of said channels, gas receiving and analyzing means, individual means for flowing gas passing from each of said outlet ports and means for flowing gas passing through said membranes to said receiving and analyzing means, and individual means for connecting the outlet port of each channel with the inlet port of the channel having the next smaller cross sectional area.

  11. Diffusing obesity myths.

    PubMed

    Ramos Salas, X; Forhan, M; Sharma, A M

    2014-06-01

    Misinformation or myths about obesity can lead to weight bias and obesity stigma. Counteracting myths with facts and evidence has been shown to be effective educational tools to increase an individuals' knowledge about a certain condition and to reduce stigma.The purpose of this study was to identify common obesity myths within the healthcare and public domains and to develop evidence-based counterarguments to diffuse them. An online search of grey literature, media and public health information sources was conducted to identify common obesity myths. A list of 10 obesity myths was developed and reviewed by obesity experts and key opinion leaders. Counterarguments were developed using current research evidence and validated by obesity experts. A survey of obesity experts and health professionals was conducted to determine the usability and potential effectiveness of the myth-fact messages to reduce weight bias. A total of 754 individuals responded to the request to complete the survey. Of those who responded, 464 (61.5%) completed the survey. All 10 obesity myths were identified to be deeply pervasive within Canadian healthcare and public domains. Although the myth-fact messages were endorsed, respondents also indicated that they would likely not be sufficient to reduce weight bias. Diffusing deeply pervasive obesity myths will require multilevel approaches.

  12. A simple flow analysis of diffuser-getter-diffuser systems

    SciTech Connect

    Klein, J. E.; Howard, D. W.

    2008-07-15

    Tritium clean-up systems typically deploy gas processing technologies between stages of palladium-silver (Pd/Ag) diffusers/permeators. The number of diffusers positioned before and after a gas clean-up process to obtain optimal system performance will vary with feed gas inert composition. A simple method to analyze optimal diffuser configuration is presented. The method assumes equilibrium across the Pd/Ag tubes and system flows are limited by diffuser vacuum pump speeds preceding or following the clean-up process. A plot of system feed as a function of inert feed gas composition for various diffuser configuration allows selection of a diffuser configuration for maximum throughput based on feed gas composition. (authors)

  13. FLOW ANALYSIS OF DIFFUSER-GETTER-DIFFUSER SYSTEMS

    SciTech Connect

    Klein, J; Dave W. Howard, D

    2007-07-24

    Tritium clean-up systems typically deploy gas processing technologies between stages of palladium-silver (Pd/Ag) diffusers/permeators. The number of diffusers positioned before and after a gas clean-up process to obtain optimal system performance will vary with feed gas inert composition. A simple method to analyze optimal diffuser configuration is presented. The method assumes equilibrium across the Pd/Ag tubes and system flows are limited by diffuser vacuum pump speeds preceding or following the clean-up process. A plot of system feed as a function of inert feed gas composition for various diffuser configuration allows selection of a diffuser configuration for maximum throughput based on feed gas composition.

  14. Mixed waste management options

    SciTech Connect

    Owens, C.B.; Kirner, N.P.

    1991-12-31

    Disposal fees for mixed waste at proposed commercial disposal sites have been estimated to be $15,000 to $40,000 per cubit foot. If such high disposal fees are imposed, generators may be willing to apply extraordinary treatment or regulatory approaches to properly dispose of their mixed waste. This paper explores the feasibility of several waste management scenarios and attempts to answer the question: Can mixed waste be managed out of existence? Existing data on commercially generated mixed waste streams are used to identify the realm of mixed waste known to be generated. Each waste stream is evaluated from both a regulatory and technical perspective in order to convert the waste into a strictly low-level radioactive or a hazardous waste. Alternative regulatory approaches evaluated in this paper include a delisting petition, no migration petition, and a treatability variance. For each waste stream, potentially available treatment options are identified that could lead to these variances. Waste minimization methodology and storage for decay are also considered. Economic feasibility of each option is discussed broadly.

  15. Achieving uniform mixing in a microfluidic device: hydrodynamic focusing prior to mixing.

    PubMed

    Park, Hye Yoon; Qiu, Xiangyun; Rhoades, Elizabeth; Korlach, Jonas; Kwok, Lisa W; Zipfel, Warren R; Webb, Watt W; Pollack, Lois

    2006-07-01

    We describe a microfluidic mixer that is well-suited for kinetic studies of macromolecular conformational change under a broad range of experimental conditions. The mixer exploits hydrodynamic focusing to create a thin jet containing the macromolecules of interest. Kinetic reactions are triggered by molecular diffusion into the jet from adjacent flow layers. The ultimate time resolution of these devices can be restricted by premature contact between co-flowing solutions during the focusing process. Here, we describe the design and characterization of a mixer in which hydrodynamic focusing is decoupled from the diffusion of reactants, so that the focusing region is free from undesirable contact between the reactants. Uniform mixing on the microsecond time scale is demonstrated using a device fabricated by imprinting optical-grade plastic. Device characterization is carried out using fluorescence correlation spectroscopy (FCS) and two-photon microscopy to measure flow speeds and to quantify diffusive mixing by monitoring the collisional fluorescence quenching, respectively. Criteria for achieving microsecond time resolution are described and modeled.

  16. Sucrose diffusion in aqueous solution

    PubMed Central

    Murray, Benjamin J.

    2016-01-01

    The diffusion of sugar in aqueous solution is important both in nature and in technological applications, yet measurements of diffusion coefficients at low water content are scarce. We report directly measured sucrose diffusion coefficients in aqueous solution. Our technique utilises a Raman isotope tracer method to monitor the diffusion of non-deuterated and deuterated sucrose across a boundary between the two aqueous solutions. At a water activity of 0.4 (equivalent to 90 wt% sucrose) at room temperature, the diffusion coefficient of sucrose was determined to be approximately four orders of magnitude smaller than that of water in the same material. Using literature viscosity data, we show that, although inappropriate for the prediction of water diffusion, the Stokes–Einstein equation works well for predicting sucrose diffusion under the conditions studied. As well as providing information of importance to the fundamental understanding of diffusion in binary solutions, these data have technological, pharmaceutical and medical implications, for example in cryopreservation. Moreover, in the atmosphere, slow organic diffusion may have important implications for aerosol growth, chemistry and evaporation, where processes may be limited by the inability of a molecule to diffuse between the bulk and the surface of a particle. PMID:27364512

  17. 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.

  18. Apparent diffusion profile estimation from high angular resolution diffusion images

    NASA Astrophysics Data System (ADS)

    Descoteaux, Maxime; Angelino, Elaine; Fitzgibbons, Shaun; Deriche, Rachid

    2006-03-01

    High angular resolution diffusion imaging (HARDI) has recently been of great interest to characterize non-Gaussian diffusion process. In the white matter of the brain, this occurs when fiber bundles cross, kiss or diverge within the same voxel. One of the important goal is to better describe the apparent diffusion process in these multiple fiber regions, thus overcoming the limitations of classical diffusion tensor imaging (DTI). In this paper, we design the appropriate mathematical tools to describe noisy HARDI data. Using a meaningful modified spherical harmonics basis to capture the physical constraints of the problem, we propose a new regularization algorithm to estimate a smoother and closer diffusivity profile to the true diffusivities without noise. We exploit properties of the spherical harmonics to define a smoothing term based on the Laplace-Beltrami for functions defined on the unit sphere. An additional contribution of the paper is the derivation of the general transformation taking the spherical harmonics coefficients to the high order tensor independent elements. This allows the careful study of the state of the art high order anisotropy measures computed from either spherical harmonics or tensor coefficients. We analyze their ability to characterize the underlying diffusion process. We are able to recover voxels with isotropic, single fiber anisotropic and multiple fiber anisotropic diffusion. We test and validate the approach on diffusion profiles from synthetic data and from a biological rat phantom.

  19. Support Operators Method for the Diffusion Equation in Multiple Materials

    SciTech Connect

    Winters, Andrew R.; Shashkov, Mikhail J.

    2012-08-14

    A second-order finite difference scheme for the solution of the diffusion equation on non-uniform meshes is implemented. The method allows the heat conductivity to be discontinuous. The algorithm is formulated on a one dimensional mesh and is derived using the support operators method. A key component of the derivation is that the discrete analog of the flux operator is constructed to be the negative adjoint of the discrete divergence, in an inner product that is a discrete analog of the continuum inner product. The resultant discrete operators in the fully discretized diffusion equation are symmetric and positive definite. The algorithm is generalized to operate on meshes with cells which have mixed material properties. A mechanism to recover intermediate temperature values in mixed cells using a limited linear reconstruction is introduced. The implementation of the algorithm is verified and the linear reconstruction mechanism is compared to previous results for obtaining new material temperatures.

  20. Mixed waste: Proceedings

    SciTech Connect

    Moghissi, A.A.; Blauvelt, R.K.; Benda, G.A.; Rothermich, N.E.

    1993-12-31

    This volume contains the peer-reviewed and edited versions of papers submitted for presentation a the Second International Mixed Waste Symposium. Following the tradition of the First International Mixed Waste Symposium, these proceedings were prepared in advance of the meeting for distribution to participants. The symposium was organized by the Mixed Waste Committee of the American Society of Mechanical Engineers. The topics discussed at the symposium include: stabilization technologies, alternative treatment technologies, regulatory issues, vitrification technologies, characterization of wastes, thermal technologies, laboratory and analytical issues, waste storage and disposal, organic treatment technologies, waste minimization, packaging and transportation, treatment of mercury contaminated wastes and bioprocessing, and environmental restoration. Individual abstracts are catalogued separately for the data base.

  1. Natural convective mixing flows

    NASA Astrophysics Data System (ADS)

    Ramos, Eduardo; de La Cruz, Luis; del Castillo, Luis

    1998-11-01

    Natural convective mixing flows. Eduardo Ramos and Luis M. de La Cruz, National University of Mexico and Luis Del Castillo San Luis Potosi University. The possibility of mixing a fluid with a natural convective flow is analysed by solving numerically the mass, momentum and energy equations in a cubic container. Two opposite vertical walls of the container are assumed to have temperatures that oscillate as functions of time. The phase of the oscillations is chosen in such a way that alternating corrotating vortices are formed in the cavity. The mixing efficiency of this kind of flow is examined with a Lagrangian tracking technique. This work was partially financed by CONACyT-Mexico project number GE0044

  2. Remotely controllable mixing system

    NASA Technical Reports Server (NTRS)

    Belew, Robert R. (Inventor)

    1987-01-01

    A remotely controllable mixing system (210) in which a plurality of mixing assemblies (10a-10e) are arranged in an annular configuration, and wherein each assembly (10) employs a central chamber (16) and two outer, upper and lower, chambers (12, 14). Valves (18, 20) are positioned between chambers, and these valves (18, 20) for a given mixing assembly (10) are operated by upper and lower control rotors (29), which in turn are driven by upper and lower drive rotors (270, 270b). Additionally, a hoop (278) is compressed around upper control rotors (29) and a hoop (278b) is compressed around lower control rotors (29) to thus insure constant frictional engagement between all control rotors (29) and drive rotors (270, 270b). The drive rollers (270, 270b) are driven by a motor (213).

  3. Dilution jet mixing program

    NASA Technical Reports Server (NTRS)

    Srinivasan, R.; Coleman, E.; Johnson, K.

    1984-01-01

    Parametric tests were conducted to quantify the mixing of opposed rows of jets (two-sided injection) in a confined cross flow. Results show that jet penetrations for two sided injections are less than that for single-sided injections, but the jet spreading rates are faster for a given momentum ratio and orifice plate. Flow area convergence generally enhances mixing. Mixing characteristics with asymmetric and symmetric convergence are similar. For constant momentum ratio, the optimum S/H(0) with in-line injections is one half the optimum value for single sided injections. For staggered injections, the optimum S/H(0) is twice the optimum value for single-sided injection. The correlations developed predicted the temperature distributions within first order accuracy and provide a useful tool for predicting jet trajectory and temperature profiles in the dilution zone with two-sided injections.

  4. Control of flow separation and mixing by aerodynamic excitation

    NASA Technical Reports Server (NTRS)

    Rice, Edward J.; Abbott, John M.

    1990-01-01

    The recent research progress in the control of shear flows using unsteady aerodynamic excitation conducted at the NASA Lewis Research Center is reviewed. The program is of fundamental nature concentrating on the physics of the unsteady aerodynamic processes. This field of research is a fairly new development with great promise in the areas of enhanced mixing and flow separation control. Enhanced mixing research reported in this paper include influence of core turbulence, forced pairing of coherent structures, and saturation of mixing enhancement. Separation flow control studies included are for a two-dimensional diffuser, conical diffusers, and single airfoils. Ultimate applications of this research include aircraft engine inlet flow control at high angle of attack, wide angle diffusers, highly loaded airfoils as in turbomachinery, and ejector/suppressor nozzles for the supersonic transport. An argument involving the Coanda Effect is made here that all of the above mentioned application areas really only involve forms of shear layer mixing enhancement. The program also includes the development of practical excitation devices which might be used in aircraft applications.

  5. Control of flow separation and mixing by aerodynamic excitation

    NASA Technical Reports Server (NTRS)

    Rice, Edward J.; Abbott, John M.

    1990-01-01

    The recent research in the control of shear flows using unsteady aerodynamic excitation conducted at the NASA Lewis Research Center is reviewed. The program is of a fundamental nature, concentrating on the physics of the unsteady aerodynamic processes. This field of research is a fairly new development with great promise in the areas of enhanced mixing and flow separation control. Enhanced mixing research includes influence of core turbulence, forced pairing of coherent structures, and saturation of mixing enhancement. Separation flow control studies included are for a two-dimensional diffuser, conical diffusers, and single airfoils. Ultimate applications include aircraft engine inlet flow control at high angle of attack, wide angle diffusers, highly loaded airfoils as in turbomachinery, and ejector/suppressor nozzles for the supersonic transport. An argument involving the Coanda Effect is made that all of the above mentioned application areas really only involve forms of shear layer mixing enhancement. The program also includes the development of practical excitation devices which might be used in aircraft applications.

  6. Iron Diffusivity in Water Saturated Rhyolite Melt

    NASA Astrophysics Data System (ADS)

    Simon, A. C.; Bell, A.

    2007-12-01

    measured diffusion length indicating that the bulk diffusivity of iron is not affected by coupled diffusion with these major elements. The chlorine concentration in the melt, however, increases markedly toward the magnetite-glass interface. This finding suggests that iron and chlorine are associated strongly in the melt and that the presence of iron in the melt, owing to magnetite dissolution increases significantly the chlorine "solubility" in the melt. The new results constrain the growth and dissolution rates of iron-bearing minerals during the evolution of hydrous felsic melt, including magma mixing, and the apparent association of iron and chlorine in the melt provides important constraints on the mass transfer of iron, chlorine and other metals, to an exsolved volatile phase and how this impacts the acidity, hence metal-scavenging potential, of the volatile phase.

  7. Mixing navigation on networks

    NASA Astrophysics Data System (ADS)

    Zhou, Tao

    2008-05-01

    In this article, we propose a mixing navigation mechanism, which interpolates between random-walk and shortest-path protocol. The navigation efficiency can be remarkably enhanced via a few routers. Some advanced strategies are also designed: For non-geographical scale-free networks, the targeted strategy with a tiny fraction of routers can guarantee an efficient navigation with low and stable delivery time almost independent of network size. For geographical localized networks, the clustering strategy can simultaneously increase efficiency and reduce the communication cost. The present mixing navigation mechanism is of significance especially for information organization of wireless sensor networks and distributed autonomous robotic systems.

  8. Atomization and mixing study

    NASA Technical Reports Server (NTRS)

    Ferrenberg, A.; Jaqua, V. W.

    1983-01-01

    The state of the art in atomization and mixing for triplet, pentad, and coaxial injectors is described. Injectors that are applicable for LOX/hydrocarbon propellants and main chamber and fuel rich preburner/gas generator mixture ratios are of special interest. Various applicable correlating equations and parameters as well as test data found in the literature are presented. The validity, utility, and important aspects of these data and correlations are discussed and the measurement techniques used are evaluated. Propellant mixing tests performed are described and summarized, results are reported, and tentative conclusions are included.

  9. Mixed crystal organic scintillators

    DOEpatents

    Zaitseva, Natalia P; Carman, M Leslie; Glenn, Andrew M; Hamel, Sebastien; Hatarik, Robert; Payne, Stephen A; Stoeffl, Wolfgang

    2014-09-16

    A mixed organic crystal according to one embodiment includes a single mixed crystal having two compounds with different bandgap energies, the organic crystal having a physical property of exhibiting a signal response signature for neutrons from a radioactive source, wherein the signal response signature does not include a significantly-delayed luminescence characteristic of neutrons interacting with the organic crystal relative to a luminescence characteristic of gamma rays interacting with the organic crystal. According to one embodiment, an organic crystal includes bibenzyl and stilbene or a stilbene derivative, the organic crystal having a physical property of exhibiting a signal response signature for neutrons from a radioactive source.

  10. Atomization and Mixing Study

    NASA Technical Reports Server (NTRS)

    Ferrenberg, A.; Hunt, K.; Duesberg, J.

    1985-01-01

    The primary objective was the obtainment of atomization and mixing performance data for a variety of typical liquid oxygen/hydrocarbon injector element designs. Such data are required to establish injector design criteria and to provide critical inputs to liquid rocket engine combustor performance and stability analysis, and computational codes and methods. Deficiencies and problems with the atomization test equipment were identified, and action initiated to resolve them. Test results of the gas/liquid mixing tests indicated that an assessment of test methods was required. A series of 71 liquid/liquid tests were performed.

  11. Osmosis and diffusion conceptual assessment.

    PubMed

    Fisher, Kathleen M; Williams, Kathy S; Lineback, Jennifer Evarts

    2011-01-01

    Biology student mastery regarding the mechanisms of diffusion and osmosis is difficult to achieve. To monitor comprehension of these processes among students at a large public university, we developed and validated an 18-item Osmosis and Diffusion Conceptual Assessment (ODCA). This assessment includes two-tiered items, some adopted or modified from the previously published Diffusion and Osmosis Diagnostic Test (DODT) and some newly developed items. The ODCA, a validated instrument containing fewer items than the DODT and emphasizing different content areas within the realm of osmosis and diffusion, better aligns with our curriculum. Creation of the ODCA involved removal of six DODT item pairs, modification of another six DODT item pairs, and development of three new item pairs addressing basic osmosis and diffusion concepts. Responses to ODCA items testing the same concepts as the DODT were remarkably similar to responses to the DODT collected from students 15 yr earlier, suggesting that student mastery regarding the mechanisms of diffusion and osmosis remains elusive.

  12. Apoplastic Diffusion Barriers in Arabidopsis

    PubMed Central

    Schreiber, Lukas; Franke, Rochus Benni; Geldner, Niko; Reina-Pinto, José J.; Kunst, Ljerka

    2013-01-01

    During the development of Arabidopsis and other land plants, diffusion barriers are formed in the apoplast of specialized tissues within a variety of plant organs. While the cuticle of the epidermis is the primary diffusion barrier in the shoot, the Casparian strips and suberin lamellae of the endodermis and the periderm represent the diffusion barriers in the root. Different classes of molecules contribute to the formation of extracellular diffusion barriers in an organ- and tissue-specific manner. Cutin and wax are the major components of the cuticle, lignin forms the early Casparian strip, and suberin is deposited in the stage II endodermis and the periderm. The current status of our understanding of the relationships between the chemical structure, ultrastructure and physiological functions of plant diffusion barriers is discussed. Specific aspects of the synthesis of diffusion barrier components and protocols that can be used for the assessment of barrier function and important barrier properties are also presented. PMID:24465172

  13. Light diffusing fiber optic chamber

    DOEpatents

    Maitland, Duncan J.

    2002-01-01

    A light diffusion system for transmitting light to a target area. The light is transmitted in a direction from a proximal end to a distal end by an optical fiber. A diffusing chamber is operatively connected to the optical fiber for transmitting the light from the proximal end to the distal end and transmitting said light to said target area. A plug is operatively connected to the diffusing chamber for increasing the light that is transmitted to the target area.

  14. Dislocation Diffusion in Metallic Materials

    DTIC Science & Technology

    2011-09-08

    DATES COVERED (From - To) April 1,2007-March 31, 2010 4. TITLE AND SUBTITLE Dislocation Diffusion in Metallic Materials 5a. CONTRACT NUMBER...SUPPLEMENTARY NOTES 14. ABSTRACT The goals of this project were: (1) perform a fundamental study of atomic diffusion along dislocation cores in metals and...alloys, (2) develop new methods for the calculation of dislocation diffusion coefficients as functions of temperature and chemical composition and (3

  15. Effect of silica sand on activation energy for diffusion of sodium ions in montmorillonite and silica sand mixture.

    PubMed

    Liu, Jinhong; Yamada, Hiromichi; Kozaki, Tamotsu; Sato, Seichi; Ohashi, Hiroshi

    2003-03-01

    The effect of silica sand on the diffusion of sodium ions in mixtures of montmorillonite and silica sand was studied by measuring the apparent diffusion coefficients, activation energies for diffusion, and the basal spacing of the mixed samples. These diffusion experiments suggest that the apparent diffusion coefficients of sodium ions in the mixed samples were almost the same as those of pure montmorillonite samples having the same partial dry densities of montmorillonite. The activation energy dependence for diffusion of sodium ions on the partial dry density was different between the mixed samples and the pure montmorillonite samples. The activation energy increased by adding silica sand at the partial dry density of 1.0 Mg m(-3), and decreased by adding silica sand at the partial dry densities higher than 1.2 Mg m(-3). A change in the XRD profile was observed after adding silica sand at the partial dry density of 1.6 Mg m(-3). Here, a three-water-layer hydrate state of montmorillonite was found in the mixed sample whereas only a two-water-layer hydrate state was observed in the pure montmorillonite sample. These experimental results suggest that silica sand changed the montmorillonite microstructure in the mixed samples, which then altered the sodium-ion diffusion process.

  16. Multilane driven diffusive systems

    NASA Astrophysics Data System (ADS)

    Curatolo, A. I.; Evans, M. R.; Kafri, Y.; Tailleur, J.

    2016-03-01

    We consider networks made of parallel lanes along which particles hop according to driven diffusive dynamics. The particles also hop transversely from lane to lane, hence indirectly coupling their longitudinal dynamics. We present a general method for constructing the phase diagram of these systems which reveals that in many cases their physics reduce to that of single-lane systems. The reduction to an effective single-lane description legitimizes, for instance, the use of a single TASEP to model the hopping of molecular motors along the many tracks of a single microtubule. Then, we show how, in quasi-2D settings, new phenomena emerge due to the presence of non-zero transverse currents, leading, for instance, to strong ‘shear localization’ along the network.

  17. Fractional chemotaxis diffusion equations.

    PubMed

    Langlands, T A M; Henry, B I

    2010-05-01

    We introduce mesoscopic and macroscopic model equations of chemotaxis with anomalous subdiffusion for modeling chemically directed transport of biological organisms in changing chemical environments with diffusion hindered by traps or macromolecular crowding. The mesoscopic models are formulated using continuous time random walk equations and the macroscopic models are formulated with fractional order differential equations. Different models are proposed depending on the timing of the chemotactic forcing. Generalizations of the models to include linear reaction dynamics are also derived. Finally a Monte Carlo method for simulating anomalous subdiffusion with chemotaxis is introduced and simulation results are compared with numerical solutions of the model equations. The model equations developed here could be used to replace Keller-Segel type equations in biological systems with transport hindered by traps, macromolecular crowding or other obstacles.

  18. Mixing, segregation, and flow of granular materials

    NASA Astrophysics Data System (ADS)

    McCarthy, Joseph J.

    1998-11-01

    This dissertation addresses mixing, segregation, and flow of granular materials with the ultimate goal of providing fundamental understanding and tools for the rational design and optimization of mixing devices. In particular, the paradigm cases of a slowly rotated tumbler mixer and flow down an inclined plane are examined. Computational work, as well as supporting experiments, are used to probe both two and three dimensional systems. In the avalanching regime, the mixing and flow can be viewed either on a global-scale or a local-scale. On the global-scale, material is transported via avalanches whose gross motion can be well described by geometrical considerations. On the local-scale, the dynamics of the particle motion becomes important; particles follow complicated trajectories that are highly sensitive to differences in size/density/morphology. By decomposing the problem in this way, it is possible to study the implications of the geometry and dynamics separately and to add complexities in a controlled fashion. This methodology allows even seemingly difficult problems (i.e., mixing in non-convex geometries, and mixing of dissimilar particles) to be probed in a simple yet methodical way. In addition this technique provides predictions of optimal mixing conditions in an avalanching tumbler, a criterion for evaluating the effect of mixer shape, and mixing enhancement strategies for both two and three dimensional mixers. In the continuous regime, the flow can be divided into two regions: a rapid flow region of the cascading layer at the free surface, and a fixed bed region undergoing solid body rotation. A continuum-based description, in which averages are taken across the layer, generates quantitative predictions about the flow in the cascading layer and agrees well with experiment. Incorporating mixing through a diffusive flux (as well as constitutive expression for segregation) within the cascading layer allows for the determination of optimal mixing conditions

  19. Novel type of chimera spiral waves arising from decoupling of a diffusible component

    SciTech Connect

    Tang, Xiaodong; Yang, Tao; Liu, Yang; Zhao, Yuemin; Gao, Qingyu E-mail: gaoqy@cumt.edu.cn; Epstein, Irving R. E-mail: gaoqy@cumt.edu.cn

    2014-07-14

    Spiral waves composed of coherent traveling waves surrounding a core containing stochastically distributed stationary areas are found in numerical simulations of a three-variable reaction-diffusion system with one diffusible species. In the spiral core, diffusion of this component (w) mediates transitions between dynamic states of the subsystem formed by the other two components, whose dynamics is more rapid than that of w. Diffusive coupling between adjacent sites can be “on” or “off” depending on the subsystem state. The incoherent structures in the spiral core are produced by this decoupling of the slow diffusive component from the fast non-diffusing subsystem. The phase diagram reveals that the region of incoherent behavior in chimera spirals grows drastically, leading to modulation and breakup of the spirals, in the transition zones between 1{sup n-1} and 1{sup n} local mixed-mode oscillations.

  20. Site-specific hydrogen diffusion rates during clinopyroxene dehydration

    NASA Astrophysics Data System (ADS)

    Ferriss, Elizabeth; Plank, Terry; Walker, David

    2016-06-01

    The rate of hydrogen diffusion in clinopyroxene is relevant to interpreting hydrogen ("water") concentrations in xenoliths, phenocrysts, and clinopyroxene-hosted melt inclusions to provide insight into the deep-earth water cycle and volcanic explosivity. Here, we determine bulk and site-specific hydrogen diffusivities in two diopsides and an augite by heating initially homogeneous water-bearing samples in a 1-atm CO/CO2 gas-mixing furnace at 800-1000 °C and oxygen fugacity at the quartz-fayalite-magnetite buffer and observing H-loss profiles. The O-H stretching range between wavenumbers 3000 and 4000 cm-1 in FTIR spectra is resolved into 4-6 peaks, each of which is assumed to represent a distinct defect site for the hydrogen, to determine peak-specific diffusivities using our previously published whole-block method. For the diopside from the Kunlun Mts. in China, Arrhenius relations are reported for peaks at 3645, 3617, 3540, 3443, and 3355 cm-1 based on measurements at 816, 904, and 1000 °C. Bulk and site-specific diffusivities are determined for the same set of peaks at 904 °C for the second diopside (Jaipur). The augite (PMR-53) was a triangular thin slab, and hydrogen diffusivities were determined for bulk hydrogen and peaks at 3620, 3550, 3460, and 3355 cm-1 in the thickness direction at 800 °C. Bulk hydrogen diffusivity in the Jaipur diopside is consistent with previous work, and hydrogen diffusivity in augite PMR-53 is slightly lower than the fast direction diffusivities measured || [100] and [001]* in Jaipur diopside. Both diopsides show 1-2 orders of magnitude differences in the peaks-specific diffusivities, with the fastest diffusivities at 3450 cm-1 and the slowest at 3645 cm-1. However, the hydrogen diffusivities in Jaipur diopside are 2-4 orders of magnitude higher than those in Kunlun diopside for bulk hydrogen and all peaks. Thus, peak-specific differences cannot by themselves adequately explain the 5 orders of magnitude range in hydrogen

  1. Lateral Diffusion in an Archipelago

    PubMed Central

    Saxton, Michael J.

    1982-01-01

    Lateral diffusion of molecules in lipid bilayer membranes can be hindered by the presence of impermeable domains of gel-phase lipid or of proteins. Effective-medium theory and percolation theory are used to evaluate the effective lateral diffusion constant as a function of the area fraction of fluid-phase lipid and the permeability of the obstructions to the diffusing species. Applications include the estimation of the minimum fraction of fluid lipid needed for bacterial growth, and the enhancement of diffusion-controlled reactions by the channeling effect of solid patches of lipid. PMID:7052153

  2. Diffusion in Jammed Particle Packs.

    PubMed

    Bolintineanu, Dan S; Grest, Gary S; Lechman, Jeremy B; Silbert, Leonardo E

    2015-08-21

    Using random walk simulations we explore diffusive transport through monodisperse sphere packings over a range of packing fractions ϕ in the vicinity of the jamming transition at ϕ(c). Various diffusion properties are computed over several orders of magnitude in both time and packing pressure. Two well-separated regimes of normal "Fickian" diffusion, where the mean squared displacement is linear in time, are observed. The first corresponds to diffusion inside individual spheres, while the latter is the long-time bulk diffusion. The intermediate anomalous diffusion regime and the long-time value of the diffusion coefficient are both shown to be controlled by particle contacts, which in turn depend on proximity to ϕ(c). The time required to recover normal diffusion t* scales as (ϕ-ϕ(c))(-0.5) and the long-time diffusivity D(∞)∼(ϕ-ϕ(c))0.5, or D(∞)∼1/t*. It is shown that the distribution of mean first passage times associated with the escape of random walkers between neighboring particles controls both t* and D(∞) in the limit ϕ→ϕ(c).

  3. Geomorphic control of radionuclide diffusion in desert soils

    USGS Publications Warehouse

    Pelletier, J.D.; Harrington, C.D.; Whitney, J.W.; Cline, M.; DeLong, S.B.; Keating, G.; Ebert, T.K.

    2005-01-01

    Diffusion is a standard model for the vertical migration of radionuclides in soil profiles. Here we show that diffusivity values inferred from fallout 137CS profiles in soils on the Fortymile Wash alluvial fan, Nye County, Nevada, have a strong inverse correlation with the age of the geomorphic surface. This result suggests that radionuclide-bound particles are predominantly transported by infiltration rather than by bulk-mixing processes such as wetting/ drying, freeze/thaw, and bioturbation. Our results provide a preliminary basis for using soil-geomorphic mapping, point-based calibration data, and the diffusion model to predict radionuclide trans desert soils within a pedotransfer-function approach. Copyright 2005 by the American Geophysical Union.

  4. An effective diffusivity model based on Koopman mode decomposition

    NASA Astrophysics Data System (ADS)

    Arbabi, Hassan; Mezic, Igor

    2016-11-01

    In the previous work, we had shown that the Koopman mode decomposition (KMD) can be used to analyze mixing of passive tracers in time-dependent flows. In this talk, we discuss the extension of this type of analysis to the case of advection-diffusion transport for passive scalar fields. Application of KMD to flows with complex time-dependence yields a decomposition of the flow into mean, periodic and chaotic components. We briefly discuss the computation of these components using a combination of harmonic averaging and Discrete Fourier Transform. We propose a new effective diffusivity model in which the advection is dominated by mean and periodic components whereas the effect of chaotic motion is absorbed into an effective diffusivity tensor. The performance of this model is investigated in the case of lid-driven cavity flow.

  5. Effects of non-unity Lewis numbers in diffusion flames

    NASA Technical Reports Server (NTRS)

    Linan, A.; Orlandi, P.; Verzicco, R.; Higuera, F. J.

    1994-01-01

    The purpose of this work is to carry out direct numerical simulations of diffusion controlled combustion with non-unity Lewis numbers for the reactants and products, thus accounting for the differential diffusion effects of the temperature and concentration fields. We use a formulation based on combining the conservation equations in a way to eliminate the reaction terms similar to the method used by Burke and Schumann (1928) for unity Lewis numbers. We present calculations for an axisymmetric fuel jet and for a planar, time evolving mixing layer, leaving out the effects of thermal expansion and variations of the transport coefficients due to the heat release. Our results show that the front of the flame shifts toward the fuel or oxygen sides owing to the effect of the differential diffusion and that the location of maximum temperature may not coincide with the flame. The dependence of the distribution of the reaction products on their Lewis number has been investigated.

  6. Effects of g-Jitter on Diffusion in Binary Liquids

    NASA Technical Reports Server (NTRS)

    Duval, Walter M. B.

    1999-01-01

    The microgravity environment offers the potential to measure the binary diffusion coefficients in liquids without the masking effects introduced by buoyancy-induced flows due to Earth s gravity. However, the background g-jitter (vibrations from the shuttle, onboard machinery, and crew) normally encountered in many shuttle experiments may alter the benefits of the microgravity environment and introduce vibrations that could offset its intrinsic advantages. An experiment during STS-85 (August 1997) used the Microgravity Vibration Isolation Mount (MIM) to isolate and introduce controlled vibrations to two miscible liquids inside a cavity to study the effects of g-jitter on liquid diffusion. Diffusion in a nonhomogeneous liquid system is caused by a nonequilibrium condition that results in the transport of mass (dispersion of the different kinds of liquid molecules) to approach equilibrium. The dynamic state of the system tends toward equilibrium such that the system becomes homogeneous. An everyday example is the mixing of cream and coffee (a nonhomogeneous system) via stirring. The cream diffuses into the coffee, thus forming a homogeneous system. At equilibrium the system is said to be mixed. However, during stirring, simple observations show complex flow field dynamics-stretching and folding of material interfaces, thinning of striation thickness, self-similar patterns, and so on. This example illustrates that, even though mixing occurs via mass diffusion, stirring to enhance transport plays a major role. Stirring can be induced either by mechanical means (spoon or plastic stirrer) or via buoyancy-induced forces caused by Earth s gravity. Accurate measurements of binary diffusion coefficients are often inhibited by buoyancy-induced flows. The microgravity environment minimizes the effect of buoyancy-induced flows and allows the true diffusion limit to be achieved. One goal of this experiment was to show that the microgravity environment suppresses buoyancy

  7. Sylgard® Mixing Study

    SciTech Connect

    Bello, Mollie; Welch, Cynthia F.; Goodwin, Lynne Alese; Keller, Jennie

    2014-08-22

    Sylgard® 184 and Sylgard® 186 silicone elastomers form Dow Corning® are used as potting agents across the Nuclear Weapons Complex. A standardized mixing procedure is required for filled versions of these products. The present study is a follow-up to a mixing study performed by MST-7 which established the best mixing procedure to use when adding filler to either 184 or 186 base resins. The most effective and consistent method of mixing resin and curing agent for three modified silicone elastomer recipes is outlined in this report. For each recipe, sample size, mixing type, and mixing time was varied over 10 separate runs. The results show that the THINKY™ Mixer gives reliable mixing over varying batch sizes and mixing times. Hand Mixing can give improved mixing, as indicated by reduced initial viscosity; however, this method is not consistent.

  8. Examining Transformative Faculty Development Factors to Advance Technology Adoption and Diffusion at a Campus-Based Institution

    ERIC Educational Resources Information Center

    McKissic, Stephanie Camille

    2012-01-01

    The purpose of this mixed-method research, in the context of a case study was to examine faculty concerns with integrating technologies and the influences and motivations that lead to technology adoption and diffusion in the classroom. Specifically, the study examined the conceptual frameworks of Rogers' Innovation Diffusion Theory (IDT) and…

  9. Turbulent Chemical Diffusion in Convectively Bounded Carbon Flames

    NASA Astrophysics Data System (ADS)

    Lecoanet, Daniel; Schwab, Josiah; Quataert, Eliot; Bildsten, Lars; Timmes, F. X.; Burns, Keaton J.; Vasil, Geoffrey M.; Oishi, Jeffrey S.; Brown, Benjamin P.

    2016-11-01

    It has been proposed that mixing induced by convective overshoot can disrupt the inward propagation of carbon deflagrations in super-asymptotic giant branch stars. To test this theory, we study an idealized model of convectively bounded carbon flames with 3D hydrodynamic simulations of the Boussinesq equations using the pseudo-spectral code Dedalus. Because the flame propagation timescale is much longer than the convection timescale, we approximate the flame as fixed in space, and only consider its effects on the buoyancy of the fluid. By evolving a passive scalar field, we derive a turbulent chemical diffusivity produced by the convection as a function of height, {D}{{t}}(z). Convection can stall a flame if the chemical mixing timescale, set by the turbulent chemical diffusivity, {D}{{t}}, is shorter than the flame propagation timescale, set by the thermal diffusivity, κ, i.e., when {D}{{t}}\\gt κ . However, we find {D}{{t}}\\lt κ for most of the flame because convective plumes are not dense enough to penetrate into the flame. Extrapolating to realistic stellar conditions, this implies that convective mixing cannot stall a carbon flame and that “hybrid carbon-oxygen-neon” white dwarfs are not a typical product of stellar evolution.

  10. Mixing with applications to inertial-confinement-fusion implosions

    NASA Astrophysics Data System (ADS)

    Rana, V.; Lim, H.; Melvin, J.; Glimm, J.; Cheng, B.; Sharp, D. H.

    2017-01-01

    Approximate one-dimensional (1D) as well as 2D and 3D simulations are playing an important supporting role in the design and analysis of future experiments at National Ignition Facility. This paper is mainly concerned with 1D simulations, used extensively in design and optimization. We couple a 1D buoyancy-drag mix model for the mixing zone edges with a 1D inertial confinement fusion simulation code. This analysis predicts that National Ignition Campaign (NIC) designs are located close to a performance cliff, so modeling errors, design features (fill tube and tent) and additional, unmodeled instabilities could lead to significant levels of mix. The performance cliff we identify is associated with multimode plastic ablator (CH) mix into the hot-spot deuterium and tritium (DT). The buoyancy-drag mix model is mode number independent and selects implicitly a range of maximum growth modes. Our main conclusion is that single effect instabilities are predicted not to lead to hot-spot mix, while combined mode mixing effects are predicted to affect hot-spot thermodynamics and possibly hot-spot mix. Combined with the stagnation Rayleigh-Taylor instability, we find the potential for mix effects in combination with the ice-to-gas DT boundary, numerical effects of Eulerian species CH concentration diffusion, and ablation-driven instabilities. With the help of a convenient package of plasma transport parameters developed here, we give an approximate determination of these quantities in the regime relevant to the NIC experiments, while ruling out a variety of mix possibilities. Plasma transport parameters affect the 1D buoyancy-drag mix model primarily through its phenomenological drag coefficient as well as the 1D hydro model to which the buoyancy-drag equation is coupled.

  11. Mixing and Transport.

    ERIC Educational Resources Information Center

    Ditmars, John D.

    1978-01-01

    Presents a literature review of longitudinal dispersion, mixing and transport in streams, rivers, lakes, reservoirs, estuaries, and oceans. This review covers also: (1) fluid-solid mixtures and (2) oil spill behavior. A list of 189 references published in 1976 and 1977 is presented. (HM)

  12. Mixed-Initiative Clustering

    ERIC Educational Resources Information Center

    Huang, Yifen

    2010-01-01

    Mixed-initiative clustering is a task where a user and a machine work collaboratively to analyze a large set of documents. We hypothesize that a user and a machine can both learn better clustering models through enriched communication and interactive learning from each other. The first contribution or this thesis is providing a framework of…

  13. Stabilizer for mixed fuels

    SciTech Connect

    Yamamura, M.; Igarashi, T.; Ukigai, T.

    1984-03-13

    A stabilizer for mixed fuels containing a reaction product obtained by reacting (1) a polyol having at least 3 hydroxyl groups in the molecule and a molecular weight of 400-10,000 with (2) an epihalohydrin, as the principal component.

  14. True Anonymity Without Mixes

    NASA Astrophysics Data System (ADS)

    Molina-Jimenez, C.; Marshall, L.

    2002-04-01

    Anonymizers based on mix computers interposed between the sender and the receiver of an e-mail message have been used in the Internet for several years by senders of e-mail messages who do not wish to disclose their identity. Unfortunately, the degree of anonymity provided by this paradigm is limited and fragile. First, the messages sent are not truly anonymous but pseudo-anonymous since one of the mixes, at least, always knows the sender's identity. Secondly, the strength of the system to protect the sender's identity depends on the ability and the willingness of the mixes to keep the secret. If the mixes fail, the sender/'s anonymity is reduced to pieces. In this paper, we propose a novel approach for sending truly anonymous messages over the Internet where the anonymous message is sent from a PDA which uses dynamically assigned temporary, non-personal, random IP and MAC addresses. Anonymous E-cash is used to pay for the service.

  15. Radial Mixing in Turbomachines

    DTIC Science & Technology

    1991-03-31

    Belgium March 31, 1991 Final Scientific Report June 1, 1989 - July 31, 1990 VUB -STR -17 Approved for public release; distribution unlimited. - Prepared ...secondary flows and turbulence as sources of mixing was investigated by conducting experiments using hot-wire anemometry and ehtylene tracer gas

  16. Response of radiation belt simulations to different radial diffusion coefficients

    NASA Astrophysics Data System (ADS)

    Drozdov, A.; Shprits, Y.; Subbotin, D.; Kellerman, A. C.

    2013-12-01

    Resonant interactions between Ultra Low Frequency (ULF) waves and relativistic electrons may violate the third adiabatic invariant of motion, which produces radial diffusion in the electron radiation belts. This process plays an important role in the formation and structure of the outer electron radiation belt and is important for electron acceleration and losses in that region. Two parameterizations of the resonant wave-particle interaction of electrons with ULF waves in the magnetosphere by Brautigam and Albert [2000] and Ozeke et al. [2012] are evaluated using the Versatile Electron Radiation Belt (VERB) diffusion code to estimate their relative effect on the radiation belt simulation. The period of investigation includes quiet time and storm time geomagnetic activity and is compared to data based on satellite observations. Our calculations take into account wave-particle interactions represented by radial diffusion transport, local acceleration, losses due to pitch-angle diffusion, and mixed diffusion. We show that the results of the 3D diffusion simulations depend on the assumed parametrization of waves. The differences between the simulations and potential missing physical mechanisms are discussed. References Brautigam, D. H., and J. M. Albert (2000), Radial diffusion analysis of outer radiation belt electrons during the October 9, 1990, magnetic storm, J. Geophys. Res., 105(A1), 291-309, doi:10.1029/1999JA900344 Ozeke, L. G., I. R. Mann, K. R. Murphy, I. J. Rae, D. K. Milling, S. R. Elkington, A. A. Chan, and H. J. Singer (2012), ULF wave derived radiation belt radial diffusion coefficients, J. Geophys. Res., 117, A04222, doi:10.1029/2011JA017463.

  17. Bounded fractional diffusion in geological media: Definition and Lagrangian approximation

    USGS Publications Warehouse

    Zhang, Yong; Green, Christopher T.; LaBolle, Eric M.; Neupauer, Roseanna M.; Sun, HongGuang

    2016-01-01

    Spatiotemporal Fractional-Derivative Models (FDMs) have been increasingly used to simulate non-Fickian diffusion, but methods have not been available to define boundary conditions for FDMs in bounded domains. This study defines boundary conditions and then develops a Lagrangian solver to approximate bounded, one-dimensional fractional diffusion. Both the zero-value and non-zero-value Dirichlet, Neumann, and mixed Robin boundary conditions are defined, where the sign of Riemann-Liouville fractional derivative (capturing non-zero-value spatial-nonlocal boundary conditions with directional super-diffusion) remains consistent with the sign of the fractional-diffusive flux term in the FDMs. New Lagrangian schemes are then proposed to track solute particles moving in bounded domains, where the solutions are checked against analytical or Eularian solutions available for simplified FDMs. Numerical experiments show that the particle-tracking algorithm for non-Fickian diffusion differs from Fickian diffusion in relocating the particle position around the reflective boundary, likely due to the non-local and non-symmetric fractional diffusion. For a non-zero-value Neumann or Robin boundary, a source cell with a reflective face can be applied to define the release rate of random-walking particles at the specified flux boundary. Mathematical definitions of physically meaningful nonlocal boundaries combined with bounded Lagrangian solvers in this study may provide the only viable techniques at present to quantify the impact of boundaries on anomalous diffusion, expanding the applicability of FDMs from infinite do mains to those with any size and boundary conditions.

  18. Drifting localized structures in doubly diffusive convection

    NASA Astrophysics Data System (ADS)

    Knobloch, Edgar; Lo Jacono, David; Bergeon, Alain

    2016-11-01

    We use numerical continuation to compute a multiplicity of spatially localized states in doubly diffusive convection in a vertical slot driven by imposed horizontal temperature and concentration differences. The calculations focus on the so-called opposing case, in which the resulting gradients are in balance. No-slip boundary conditions are used at the sides and periodic boundary conditions with large spatial period are used in the vertical direction. This system exhibits homoclinic snaking of stationary spatially localized structures with point symmetry. In this talk we demonstrate the existence, near threshold, of drifting pulses of spatially localized convection that appear when mixed concentration boundary conditions are used, and use homotopic continuation to identify similar states in the case of fixed concentration boundary conditions. We show that these states persist to large values of the Grasshof number and provide a detailed study of their properties.

  19. Horizontal mixing in the Southern Ocean from Argo float trajectories

    NASA Astrophysics Data System (ADS)

    Roach, Christopher J.; Balwada, Dhruv; Speer, Kevin

    2016-08-01

    We provide the first observational estimate of the circumpolar distribution of cross-stream eddy diffusivity at 1000 m in the Southern Ocean using Argo float trajectories. We show that Argo float trajectories, from the float surfacing positions, can be used to estimate lateral eddy diffusivities in the ocean and that these estimates are comparable to those obtained from RAFOS floats, where they overlap. Using the Southern Ocean State Estimate (SOSE) velocity fields to advect synthetic particles with imposed behavior that is "Argo-like" and "RAFOS-like" diffusivity estimates from both sets of synthetic particles agreed closely at the three dynamically very different test sites, the Kerguelen Island region, the Southeast Pacific Ocean, and the Scotia Sea, and support our approach. Observed cross-stream diffusivities at 1000 m, calculated from Argo float trajectories, ranged between 300 and 2500 m2 s-1, with peaks corresponding to topographic features associated with the Scotia Sea, the Kerguelen Plateau, the Campbell Plateau, and the Southeast Pacific Ridge. These observational estimates agree with previous regional estimates from the Diapycnal and Isopycnal Mixing Experiment in the Southern Ocean (DIMES) near the Drake Passage, and other estimates from natural tracers (helium), inverse modeling studies, and current meter measurements. These estimates are also compared to the suppressed eddy diffusivity in the presence of mean flows. The comparison suggests that away from regions of strong topographic steering suppression explains both the structure and magnitude of eddy diffusivity but that eddy diffusivities in the regions of topographic steering are greater than what would be theoretically expected and the ACC experiences localized enhanced cross-stream mixing in these regions.

  20. Numerical Study of Mixing of Two Fluids Under Low Gravity

    NASA Technical Reports Server (NTRS)

    Duval, Walter M. B.

    1992-01-01

    The mixing characteristics of two fluids inside a cavity due to buoyancy driven flow fields for low gravity conditions is investigated via numerical experiments. The buoyancy driven flow, depending on the parametric region, stretches and deforms the material interface into a wave morphological pattern. The morphological pattern affects the resulting stratification thickness of the mixed region. Three basic mixing regimes occur: convective, diffusive, and chaotic. In the convective regime, an overturning motion occurs which gives rise to a stable wave formation. This wave oscillates and its decay leads to a stable stratification. Whereas, in the diffusive regime, the length of the interface remains constant while mixing occurs. This limiting behavior is very important to materials processing in space, and it admits a closed form solution corresponding to vanishing convective terms which agrees with computational results. Finally, in the chaotic regime, the material interface continuously stretches and folds on itself similar to a horseshoe map. The length of stretch of the interface increases exponentially. Internal wavebreaking occurs for this case. This wavebreaking generates local turbulence, and provides an effective mechanism for mixing.

  1. Samoan Passage Abyssal Mixing Experiment

    NASA Astrophysics Data System (ADS)

    Mickett, J. B.; Voet, G.; Alford, M. H.; Girton, J. B.; Carter, G. S.

    2012-12-01

    The majority of the bottom water entering the North Pacific, about 6 Sv of mostly Antarctic origin, flows northward through the Samoan Passage (SP), where previous hydrographic studies have inferred extremely strong watermass modification as it transits the complicated, narrow passage. Global-scale numerical models at best poorly resolve this critical aspect of the global ocean circulation and the processes that affect it. We are in the midst of conducting a major next-generation experiment, coupling hydrographic/lowered ADCP and microstructure profiler measurements with simultaneous high-resolution profiling moorings and detailed numerical simulations. Our goals are to: (1) quantify the flow and its pathways through the SP, and compare them to measurements made 20 years ago as part of the World Ocean Circulation Experiment (WOCE), 2) quantify, with direct measurements, the turbulence and mixing the flow undergoes and the processes that lead to it, and 3) use the resulting knowledge to determine the best strategy for future monitoring of the SP. Here we present initial results from the first two of the experiment's three cruises, which have provided a detailed view of the flow magnitude, pathways and turbulence as it transits the passage's sills. Bathymetry, stratification, rotation, and inertia all play important roles in selecting the pathways taken by the flow, with the lighter layers siphoning off through the shallower sills to the west and the densest water following the deeper main eastern channel. Flows in this main channel are initially O(0.1 m/s), accelerating to > 0.4 m/s at the northernmost of the two major sills, leading to strong shears and warming of the bottom water from 0.66 to 0.72 C through mixing within the stratified overflow and entrainment of overlying water. Direct microstructure measurements show large vertical diffusivities of 10^{-4}-10^{-3} m^2/s throughout the passage and up to 10^{-2} m^2/s past the northern sill, where the flow

  2. Convection and mixing in magma chambers

    NASA Astrophysics Data System (ADS)

    Turner, J. S.; Campbell, I. H.

    1986-08-01

    This paper reviews advances made during the last seven years in the application of fluid dynamics to problems of igneous petrology, with emphasis on the laboratory work with which the authors have been particularly involved. Attention is focused on processes in magma chambers which produce diversity in igneous rocks, such as fractional crystallization, assimilation and magma mixing. Chamber geometry, and variations in the density and viscosity of the magma within it, are shown to play a major role in determining the dynamical behaviour and the composition of the erupted or solidified products. Various convective processes are first reviewed, and in particular the phenomenon of double-diffusive convection. Two types of double-diffusive interfaces between layers of different composition and temperature are likely to occur in magma chambers. A diffusive interface forms when a layer of hot dense magma is overlain by cooler less dense magma. Heat is transported between the layers faster than composition, driving convection in both layers and maintaining a sharp interface between them. If a layer of hot slightly less dense magma overlies a layer of cooler, denser but compositionally lighter magma, a finger interface forms between them, and compositional differences are transported downwards faster than heat (when each is expressed in terms of the corresponding density changes). Processes leading to the establishment of density, compositional and thermal gradients or steps during the filling of a magma chamber are considered next. The stratification produced, and the extent of mixing between the inflowing and resident magmas, are shown to depend on the flow rate and on the relation between the densities and viscosities of the two components. Slow dense inputs of magma may mix very little with resident magma of comparable viscosity as they spread across the floor of the chamber. A similar pulse injected with high upward momentum forms a turbulent "fountain", which is a

  3. Kubo-Anderson Mixing in the Turbulent Boundary Layer

    NASA Astrophysics Data System (ADS)

    Dekker, H.; de Leeuw, G.; Brink, A. Maassen Van Den

    A novel ab initio analysis of the Reynolds stress is presented in order to model non-local turbulence transport. The theory involves a sample path space and a stochastic hypothesis. A scaling relation maps the path space onto the boundary layer. Analytical sampling rates are shown to model mixing by exchange. Nonlocal mixing involves a scaling exponent ɛ≈0.58 (ɛ→∞ in the diffusion limit). The resulting transport equation represents a nondiffusive (Kubo-Anderson or kangaroo) type stochastic process.

  4. Optical and electrical studies of cerium mixed oxides

    SciTech Connect

    Sherly, T. R.; Raveendran, R.

    2014-10-15

    The fast development in nanotechnology makes enthusiastic interest in developing nanomaterials having tailor made properties. Cerium mixed oxide materials have received great attention due to their UV absorption property, high reactivity, stability at high temperature, good electrical property etc and these materials find wide applications in solid oxide fuel cells, solar control films, cosmetics, display units, gas sensors etc. In this study cerium mixed oxide compounds were prepared by co-precipitation method. All the samples were doped with Zn (II) and Fe (II). Preliminary characterizations such as XRD, SEM / EDS, TEM were done. UV - Vis, Diffuse reflectance, PL, FT-IR, Raman and ac conductivity studies of the samples were performed.

  5. Optical and electrical studies of cerium mixed oxides

    NASA Astrophysics Data System (ADS)

    Sherly, T. R.; Raveendran, R.

    2014-10-01

    The fast development in nanotechnology makes enthusiastic interest in developing nanomaterials having tailor made properties. Cerium mixed oxide materials have received great attention due to their UV absorption property, high reactivity, stability at high temperature, good electrical property etc and these materials find wide applications in solid oxide fuel cells, solar control films, cosmetics, display units, gas sensors etc. In this study cerium mixed oxide compounds were prepared by co-precipitation method. All the samples were doped with Zn (II) and Fe (II). Preliminary characterizations such as XRD, SEM / EDS, TEM were done. UV - Vis, Diffuse reflectance, PL, FT-IR, Raman and ac conductivity studies of the samples were performed.

  6. Selected Dissemination/Diffusion Strategies.

    ERIC Educational Resources Information Center

    Schmitt, Marshall L.

    This analysis of selected diffusion and dissemination methods used by developer-demonstrator projects in the National Diffusion Network discusses strategies under the following headings: managing the project, developing materials, disseminating information, conducting awareness sessions, training personnel, using certified trainers, providing…

  7. Development of a Detonation Diffuser

    DTIC Science & Technology

    2014-03-27

    reflection of the shock would result in a detonation that runs out of reactants when it encounters the combustion front. Rotating the reflecting surface...FEASIBILITY AND PARAMETER STUDY OF A DETONATION DIFFUSER DISSERTATION Christopher A Stevens, CTR AFIT-DS...States Government. iii AFIT-DS-ENY-14-M-05 FEASIBILITY AND PARAMETER STUDY OF A DETONATION DIFFUSER DISSTERTATION

  8. Preliminary Investigation of Supersonic Diffusers

    DTIC Science & Technology

    1945-05-01

    No. L5D20 This pressure was measured with a large mercury manometer . The total ’head after diffusion can be assumed equal to the static pressure at...of the entering kinetic energy. A mercury manometer was used to measure the difference between the total heads before and after diffusion. ‘J!hesetwo

  9. Consequences of Diffusion of Innovations.

    ERIC Educational Resources Information Center

    Goss, Kevin F.

    1979-01-01

    The article traces evolution of diffusion theory; illustrates undesirable consequences in a cross-cultural setting, reviews criticisms of several scholars; considers distributional effects and unanticipated consequences for potential ameliorative impact on diffusion theory; and codifies these factors into a framework for research into consequences…

  10. Demonstrating Diffusion: Why the Confusion?

    ERIC Educational Resources Information Center

    Panizzon, Debra Lee

    1998-01-01

    Examines the principles of diffusion and how it may be confused with convection. Suggests that educators may be misleading students and clouding their understanding of the process. Provides two contemporary examples to explain the process of diffusion and how it differs from convection. (Author/CCM)

  11. Fractional diffusion on bounded domains

    DOE PAGES

    Defterli, Ozlem; D'Elia, Marta; Du, Qiang; ...

    2015-03-13

    We found that the mathematically correct specification of a fractional differential equation on a bounded domain requires specification of appropriate boundary conditions, or their fractional analogue. In this paper we discuss the application of nonlocal diffusion theory to specify well-posed fractional diffusion equations on bounded domains.

  12. Diffusion in jammed particle packs

    NASA Astrophysics Data System (ADS)

    Bolintineanu, Dan S.; Silbert, Leonardo E.; Grest, Gary S.; Lechman, Jeremy B.

    2015-03-01

    Diffusive transport in jammed particle packs is of interest for a number of applications, as well as being a potential indicator of structural properties near the jamming point. To this end, we report stochastic simulations of equilibrium diffusion through monodisperse sphere packs near the jamming point in the limit of a perfectly insulating surrounding medium. The time dependence of various diffusion properties is resolved over several orders of magnitude. Two time regimes of expected Fickian diffusion are observed, separated by an intermediate regime of anomalous diffusion. This intermediate regime grows as the particle volume fraction approaches the critical jamming transition. The diffusion behavior is fully controlled by the extent of the contacts between neighboring particles, which in turn depend on proximity to the jamming point. In particular, the mean first passage time associated with the escape of random walkers between neighboring particles is shown to control both the time to recover Fickian diffusion and the long time diffusivity. Scaling laws are established that relate these quantities to the difference between the actual and critical jamming volume fractions. Sandia National Laboratories is a multiprogram laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's NNSA under Contract DE- AC04-94AL85000.

  13. Osmosis and Diffusion Conceptual Assessment

    ERIC Educational Resources Information Center

    Fisher, Kathleen M.; Williams, Kathy S.; Lineback, Jennifer Evarts

    2011-01-01

    Biology student mastery regarding the mechanisms of diffusion and osmosis is difficult to achieve. To monitor comprehension of these processes among students at a large public university, we developed and validated an 18-item Osmosis and Diffusion Conceptual Assessment (ODCA). This assessment includes two-tiered items, some adopted or modified…

  14. The Diffusion of New Math.

    ERIC Educational Resources Information Center

    Ready, Patricia M.

    The life cycle of "new math" is fertile ground for the study of the diffusion of an innovation. New math arrived in 1958 to save the day for America after the Soviet Union launched Sputnik, the first successful space flight in 1957. In a period of 16 years an entire diffusion cycle was completed throughout the entire educational system…

  15. Diffuse-Illumination Systems for Growing Plants

    NASA Technical Reports Server (NTRS)

    May, George; Ryan, Robert

    2010-01-01

    Agriculture in both terrestrial and space-controlled environments relies heavily on artificial illumination for efficient photosynthesis. Plant-growth illumination systems require high photon flux in the spectral range corresponding with plant photosynthetic active radiation (PAR) (400 700 nm), high spatial uniformity to promote uniform growth, and high energy efficiency to minimize electricity usage. The proposed plant-growth system takes advantage of the highly diffuse reflective surfaces on the interior of a sphere, hemisphere, or other nearly enclosed structure that is coated with highly reflective materials. This type of surface and structure uniformly mixes discrete light sources to produce highly uniform illumination. Multiple reflections from within the domelike structures are exploited to obtain diffuse illumination, which promotes the efficient reuse of photons that have not yet been absorbed by plants. The highly reflective surfaces encourage only the plant tissue (placed inside the sphere or enclosure) to absorb the light. Discrete light sources, such as light emitting diodes (LEDs), are typically used because of their high efficiency, wavelength selection, and electronically dimmable properties. The light sources are arranged to minimize shadowing and to improve uniformity. Different wavelengths of LEDs (typically blue, green, and red) are used for photosynthesis. Wavelengths outside the PAR range can be added for plant diagnostics or for growth regulation

  16. Numerical study of mixing viscous fluids in T-shaped micro-channels with compressibility effects

    NASA Astrophysics Data System (ADS)

    Yang, Junfeng; Matar, Omar; Harrison, Christopher; Sullivan, Matthew

    2015-11-01

    We study numerically the mixing processes of two miscible fluids in T-shaped micro-channels in the presence of compressibility effects. Three mixing modes are considered: `passive' mixing, which relies on the molecular diffusion and chaotic advection; `active' mixing relies on external disturbances, e.g. due to periodic compression; and a combination of these modes. In all cases considered, one of the fluids, fluid `A', is initially present in the dead-end region of the micro-channel. In the `passive' mixing case, the other fluid, fluid `B', flows through the open part of the channel at a constant flow rate. In the `active' case, this fluid is initially at rest but is then set in motion through pressure cycling. The combined case, involves the flow of fluid `B' in the presence of compression-decompression cycles. Numerical simulations are carried out for three different fluids, accounting for their compressibility, and their pressure-dependent e.g. density, viscosity, and diffusivity; a simple mixing rule is used to model the properties of the mixed fluids. Our results indicate that the vortices in the dead-end zone, engendered by the relative motion of the fluids leads to their mixing; the combination of mixing modes is shown to promote mixing efficiency significantly. Schlumberger-Doll Research.

  17. 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.

  18. Diffusion of polymer gel implants.

    PubMed

    Davis, B K

    1974-08-01

    Crosslinked polyacrylamide and polyvinylpyrrolidone gels have been used to subcutaneously implant (125)I-labeled immunoglobulin, (125)I-labeled luteinizing hormone, (125)I-labeled bovine serum albumin, (125)I-labeled insulin, [(3)H]prostaglandin F(2alpha), and Na(125)I into hamsters. From the rates of absorption of the solutes, their diffusion coefficients were determined. The diffusion coefficients showed a logarithmic dependence on implant polymer concentration and solute molecular weight. Release of the solutes from gel preparations incubated 10 mM phosphate buffer (pH 7.2) at 37 degrees revealed a similar relationship between solute diffusion coefficient, molecular weight, and the concentration of polymer. A general equation was derived that gives the expected diffusion coefficient of a substance in a polymer gel from its molecular weight, diffusion coefficient in solvent, and polymer concentration of the gel.

  19. Portable vapor diffusion coefficient meter

    DOEpatents

    Ho, Clifford K.

    2007-06-12

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

  20. Heat transfer, diffusion, and evaporation

    NASA Technical Reports Server (NTRS)

    Nusselt, Wilhelm

    1954-01-01

    Although it has long been known that the differential equations of the heat-transfer and diffusion processes are identical, application to technical problems has only recently been made. In 1916 it was shown that the speed of oxidation of the carbon in iron ore depends upon the speed with which the oxygen of the combustion air diffuses through the core of gas surrounding the carbon surface. The identity previously referred to was then used to calculate the amount of oxygen diffusing to the carbon surface on the basis of the heat transfer between the gas stream and the carbon surface. Then in 1921, H. Thoma reversed that procedure; he used diffusion experiments to determine heat-transfer coefficients. Recently Lohrisch has extended this work by experiment. A technically very important application of the identity of heat transfer and diffusion is that of the cooling tower, since in this case both processes occur simultaneously.

  1. Ammonia diffusion through Nalophan™ bags.

    PubMed

    Sironi, Selena; Eusebio, Lidia; Dentoni, Licinia; Capelli, Laura; Del Rosso, Renato

    2014-01-01

    The aim of the work is to verify the diffusion rate of ammonia through the Nalophan™ film that constitutes the sampling bag, considering storage times ranging from 1 to 26 h. The ammonia decay over time was evaluated using gas-chromatography for the quantification of ammonia concentration inside the bag. The research assesses the roles of both of ammonia and water concentration gradients at the polymeric film interface on the diffusion process. The results show that both the ammonia concentration gradient and, in a less pronounced way, the water concentration gradient are the main 'engines' of ammonia diffusion. Double bags seem to represent a simple solution for preventing ammonia losses during storage. Another interesting result concerns the role of the bag surface on the ammonia diffusion rate: the higher the surface/volume (S/V) ratio, the higher the ammonia diffusion rate through the polymeric film.

  2. Diffuse gamma radiation

    NASA Technical Reports Server (NTRS)

    Fichtel, C. E.; Simpson, G. A.; Thompson, D. J.

    1977-01-01

    An examination of the intensity, energy spectrum, and spatial distribution of the diffuse gamma-radiation observed by SAS-2 satellite away from the galactic plane in the energy range above 35 MeV has shown that it consists of two components. One component is generally correlated with galactic latitudes, the atomic hydrogen column density was deduced from 21 cm measurements, and the continuum radio emission, believed to be synchrotron emission. It has an energy spectrum similar to that in the plane and joins smoothly to the intense radiation from the plane. It is therefore presumed to be of galactic origin. The other component is apparently isotropic, at least on a coarse scale, and has a steep energy spectrum. No evidence is found for a cosmic ray halo surrounding the galaxy in the shape of a sphere or oblate spheroid with galactic dimensions. Constraints for a halo model with significantly larger dimensions are set on the basis of an upper limit to the gamma-ray anisotropy.

  3. Handheld Diffusion Test Cells

    NASA Technical Reports Server (NTRS)

    2001-01-01

    This photo shows the Handheld Diffusion Test Cell (HH-DTC) apparatus flown on the Space Shuttle. Similar cells (inside the plastic box) will be used in the Observable Protein Crystal Growth Apparatus (OPCGA) to be operated aboard the International Space Station (ISS). The principal investigator is Dr. Alex McPherson of the University of California, Irvine. Each individual cell comprises two sample chambers with a rotating center section that isolates the two from each other until the start of the experiment and after it is completed. The cells are made from optical-quality quartz glass to allow photography and interferometric observations. Each cell has a small light-emitting diode and lens to back-light the solution. In protein crystal growth experiments, a precipitating agent such as a salt solution is used to absorb and hold water but repel the protein molecules. This increases the concentration of protein until the molecules nucleate to form crystals. This cell is one of 96 that make up the experiment module portion of the OPCGA.

  4. Hydrogen diffusion fuel cell

    SciTech Connect

    Struthers, R.C.

    1987-08-04

    This patent describes a fuel cell comprising; an elongate case; a thin, flat separator part of non-porous, di-electric, hydrogen-permeable material between the ends of and extending transverse the case and defining anode and cathode chambers; a thin, flat anode part of non-porous, electric conductive, hydrogen-permeable metallic material in the anode chamber in flat contacting engagement with and co-extensive with the separator part; a flat, porous, catalytic cathode part in the cathode chamber in contacting engagement with the separator part; hydrogen supply means supplying hydrogen to the anode part within the anode chamber; oxidant gas supply means supplying oxidant gas to the cathode part within the cathode chamber; and, an external electric circuit connected with and between the anode and cathode parts. The anode part absorbs and is permeated by hydrogen supplied to it and diffuses the hydrogen to hydrogen ions and free electrons; the free electrons in the anode part are conducted from the anode part into the electric circuit to perform useful work. The hydrogen ions in the anode part move from the anode part through the separator part and into the cathode part. Free electrons are conducted by the electric circuit into the cathode part. The hydrogen ions, oxidant gas and free electrons in the cathode part react and generate waste, heat and water.

  5. Diffusion in membranes: Toward a two-dimensional diffusion map

    NASA Astrophysics Data System (ADS)

    Toppozini, Laura; Garcia-Sakai, Victoria; Bewley, Robert; Dalgliesh, Robert; Perring, Toby; Rheinstädter, Maikel C.

    2015-01-01

    For decades, quasi-elastic neutron scattering has been the prime tool for studying molecular diffusion in membranes over relevant nanometer distances. These experiments are essential to our current understanding of molecular dynamics of lipids, proteins and membrane-active molecules. Recently, we presented experimental evidence from X-ray diffraction and quasi-elastic neutron scattering demonstrating that ethanol enhances the permeability of membranes. At the QENS 2014/WINS 2014 conference we presented a novel technique to measure diffusion across membranes employing 2-dimensional quasi-elastic neutron scattering. We present results from our preliminary analysis of an experiment on the cold neutron multi-chopper spectrometer LET at ISIS, where we studied the self-diffusion of water molecules along lipid membranes and have the possibility of studying the diffusion in membranes. By preparing highly oriented membrane stacks and aligning them horizontally in the spectrometer, our aim is to distinguish between lateral and transmembrane diffusion. Diffusion may also be measured at different locations in the membranes, such as the water layer and the hydrocarbon membrane core. With a complete analysis of the data, 2-dimensional mapping will enable us to determine diffusion channels of water and ethanol molecules to quantitatively determine nanoscale membrane permeability.

  6. Spatially heterogeneous diapycnal mixing in the abyssal ocean: A comparison of two parameterizations to observations

    NASA Astrophysics Data System (ADS)

    Decloedt, Thomas; Luther, Douglas S.

    2012-11-01

    The spatial distributions of the diapycnal diffusivity predicted by two abyssal mixing schemes are compared to each other and to observational estimates based on microstructure surveys and large-scale hydrographic inversions. The parameterizations considered are the tidal mixing scheme by Jayne, St. Laurent and co-authors (JSL01) and the Roughness Diffusivity Model (RDM) by Decloedt and Luther. Comparison to microstructure surveys shows that both parameterizations are conservative in estimating the vertical extent to which bottom-intensified mixing penetrates into the stratified water column. In particular, the JSL01 exponential vertical structure function with fixed scale height decays to background values much nearer topography than observed. JSL01 and RDM yield dramatically different horizontal spatial distributions of diapycnal diffusivity, which would lead to quite different circulations in OGCMs, yet they produce similar basin-averaged diffusivity profiles. Both parameterizations are shown to yield smaller basin-mean diffusivity profiles than hydrographic inverse estimates for the major ocean basins, by factors ranging from 3 up to over an order of magnitude. The canonical 10-4 m2 s-1abyssal diffusivity is reached by the parameterizations only at depths below 3 km. Power consumption by diapycnal mixing below 1 km of depth, between roughly 32°S and 48°N, for the RDM and JSL01 parameterizations is 0.40 TW & 0.28 TW, respectively. The results presented here suggest that present-day mixing parameterizations significantly underestimate abyssal mixing. In conjunction with other recently published studies, a plausible interpretation is that parameterizing the dissipation of bottom-generated internal waves is not sufficient to approximate the global spatial distribution of diapycnal mixing in the abyssal ocean.

  7. Mixing efficiency of turbulent patches in stably stratified flows

    NASA Astrophysics Data System (ADS)

    Garanaik, Amrapalli; Venayagamoorthy, Subhas Karan

    2016-11-01

    A key quantity that is essential for estimating the turbulent diapycnal (irreversible) mixing in stably stratified flow is the mixing efficiency Rf*, which is a measure of the amount of turbulent kinetic energy that is irreversibly converted into background potential energy. In particular, there is an ongoing debate in the oceanographic mixing community regarding the utility of the buoyancy Reynolds number (Reb) , particularly with regard to how mixing efficiency and diapycnal diffusivity vary with Reb . Specifically, is there a universal relationship between the intensity of turbulence and the strength of the stratification that supports an unambiguous description of mixing efficiency based on Reb ? The focus of the present study is to investigate the variability of Rf* by considering oceanic turbulence data obtained from microstructure profiles in conjunction with data from laboratory experiments and DNS. Field data analysis has done by identifying turbulent patches using Thorpe sorting method for potential density. The analysis clearly shows that high mixing efficiencies can persist at high buoyancy Reynolds numbers. This is contradiction to previous studies which predict that mixing efficiency should decrease universally for Reb greater than O (100) . Funded by NSF and ONR.

  8. Numerical analysis of mixing enhancement for micro-electroosmotic flow

    NASA Astrophysics Data System (ADS)

    Tang, G. H.; He, Y. L.; Tao, W. Q.

    2010-05-01

    Micro-electroosmotic flow is usually slow with negligible inertial effects and diffusion-based mixing can be problematic. To gain an improved understanding of electroosmotic mixing in microchannels, a numerical study has been carried out for channels patterned with wall blocks, and channels patterned with heterogeneous surfaces. The lattice Boltzmann method has been employed to obtain the external electric field, electric potential distribution in the electrolyte, the flow field, and the species concentration distribution within the same framework. The simulation results show that wall blocks and heterogeneous surfaces can significantly disturb the streamlines by fluid folding and stretching leading to apparently substantial improvements in mixing. However, the results show that the introduction of such features can substantially reduce the mass flow rate and thus effectively prolongs the available mixing time when the flow passes through the channel. This is a non-negligible factor on the effectiveness of the observed improvements in mixing efficiency. Compared with the heterogeneous surface distribution, the wall block cases can achieve more effective enhancement in the same mixing time. In addition, the field synergy theory is extended to analyze the mixing enhancement in electroosmotic flow. The distribution of the local synergy angle in the channel aids to evaluate the effectiveness of enhancement method.

  9. Flow Field Measurement of Mixing Driven by Buoyancy

    NASA Technical Reports Server (NTRS)

    Batur, C.; Zhong, H.

    2003-01-01

    Mixing driven by buoyancy-induced flows inside a cavity consists of stretching and folding of an interface. Measurement of the flow field using particle imaging velocimetry shows that during stretching the flow field has a single elliptic point, thus dominated by a single vortex. However, global bifurcation that results in folding introduces a hyperbolic point whereby the flow field degenerates to multiple vortex interactions. The short-lived coherent structure observed during mixing which results in the Rayleigh- Taylor morphology is attributed to vortex interactions. The mixing characteristics of non-homogeneous fluids driven by buoyancy are important towards understanding transport phenomenon in a microgravity environment. Mixing consists of stretching and folding of an interface due to a flow field whose intensity depends on the body force. For miscible liquids, the characteristic of the flow field determines whether mass transport is governed by diffusion or bulk stirring which induces mixing. For technologically important processes, transport of mass is governed by the coupling of the body force to scalar gradients such as concentration and or temperature' 2 3 . In order to lend insight into these classes of problems we consider a model experimental system to study mixing driven by buoyancy-induced flows. The characteristics of mixing is addressed from detail measurements of the flow field using particle imaging velocimetry (PIV), and its corresponding interface dynamics using image processing techniques.

  10. Mixing by individual swimmers

    NASA Astrophysics Data System (ADS)

    Pushkin, Dmitri; Shum, Henry; Yeomans, Julia

    2012-11-01

    Despite their evolutionary and technological importance, different biomixing mechanisms, their effectiveness and universality remain poorly understood. In this talk we focus on the Lagrangian transport of the surrounding fluid by swimmers. Low Re passive tracers advected by swimmers move in loops that are, in general, almost closed. We analyze the reasons for this behavior and, as non-closedness of the loops is a natural requirement for an efficient mixing, propose a classification of possible mechanisms for biogenic mixing. Next, we discuss the universal (common to all swimmers) and the swimmer-dependent features of the resulting tracer displacements and analyze the Darwin drift, the total fluid volume displaced by a swimmer passing from and to infinity. We show that the Darwin drift is finite for force-free swimmers and can be decomposed into a universal and a swimmer-dependent part. We illustrate our consideration with examples for model swimmers and biological data.

  11. Experiments in mixed reality

    NASA Astrophysics Data System (ADS)

    Krum, David M.; Sadek, Ramy; Kohli, Luv; Olson, Logan; Bolas, Mark

    2010-01-01

    As part of the Institute for Creative Technologies and the School of Cinematic Arts at the University of Southern California, the Mixed Reality lab develops technologies and techniques for presenting realistic immersive training experiences. Such experiences typically place users within a complex ecology of social actors, physical objects, and collections of intents, motivations, relationships, and other psychological constructs. Currently, it remains infeasible to completely synthesize the interactivity and sensory signatures of such ecologies. For this reason, the lab advocates mixed reality methods for training and conducts experiments exploring such methods. Currently, the lab focuses on understanding and exploiting the elasticity of human perception with respect to representational differences between real and virtual environments. This paper presents an overview of three projects: techniques for redirected walking, displays for the representation of virtual humans, and audio processing to increase stress.

  12. A SUB-GRID VOLUME-OF-FLUIDS (VOF) MODEL FOR MIXING IN RESOLVED SCALE AND IN UNRESOLVED SCALE COMPUTATIONS

    SciTech Connect

    VOLD, ERIK L.; SCANNAPIECO, TONY J.

    2007-10-16

    A sub-grid mix model based on a volume-of-fluids (VOF) representation is described for computational simulations of the transient mixing between reactive fluids, in which the atomically mixed components enter into the reactivity. The multi-fluid model allows each fluid species to have independent values for density, energy, pressure and temperature, as well as independent velocities and volume fractions. Fluid volume fractions are further divided into mix components to represent their 'mixedness' for more accurate prediction of reactivity. Time dependent conversion from unmixed volume fractions (denoted cf) to atomically mixed (af) fluids by diffusive processes is represented in resolved scale simulations with the volume fractions (cf, af mix). In unresolved scale simulations, the transition to atomically mixed materials begins with a conversion from unmixed material to a sub-grid volume fraction (pf). This fraction represents the unresolved small scales in the fluids, heterogeneously mixed by turbulent or multi-phase mixing processes, and this fraction then proceeds in a second step to the atomically mixed fraction by diffusion (cf, pf, af mix). Species velocities are evaluated with a species drift flux, {rho}{sub i}u{sub di} = {rho}{sub i}(u{sub i}-u), used to describe the fluid mixing sources in several closure options. A simple example of mixing fluids during 'interfacial deceleration mixing with a small amount of diffusion illustrates the generation of atomically mixed fluids in two cases, for resolved scale simulations and for unresolved scale simulations. Application to reactive mixing, including Inertial Confinement Fusion (ICF), is planned for future work.

  13. Front tracking for characterizing and quantifying reactive mixing

    NASA Astrophysics Data System (ADS)

    Kelley, Douglas; Nevins, Thomas

    2016-11-01

    Mixing in industrial chemical reactors involves complicated interactions between advection, reaction, and diffusion that are difficult to simulate or measure in detail. However, in large-Damköhler-number systems which show sharp fronts between reacted and unreacted regions, reactor dynamics might be more simply and usefully characterized in terms of the reaction fronts themselves. In fact, prior work has already shown that the reaction rate and material diffusivity can be calculated directly if front speed and front thickness are known. We have developed methods to optically track reaction fronts, measuring their speed and thickness throughout space and time. We will present such measurements in both simulation and experiment, consider their statistics, and discuss future efforts to characterize and quantify mixing in chemical reactors.

  14. Diffusive instabilities in hyperbolic reaction-diffusion equations.

    PubMed

    Zemskov, Evgeny P; Horsthemke, Werner

    2016-03-01

    We investigate two-variable reaction-diffusion systems of the hyperbolic type. A linear stability analysis is performed, and the conditions for diffusion-driven instabilities are derived. Two basic types of eigenvalues, real and complex, are described. Dispersion curves for both types of eigenvalues are plotted and their behavior is analyzed. The real case is related to the Turing instability, and the complex one corresponds to the wave instability. We emphasize the interesting feature that the wave instability in the hyperbolic equations occurs in two-variable systems, whereas in the parabolic case one needs three reaction-diffusion equations.

  15. Transdermal diffusion of xenon in vitro using diffusion cells

    NASA Astrophysics Data System (ADS)

    Verkhovsky, A.; Petrov, E.

    2015-11-01

    The aim of this research was to study the diffusion rate of xenon through guinea pig skin and how viscosity of cosmetic component capryl/capric triglyceride (CCT) facilitates to deliver xenon to surface of skin patches. They were placed in Franz cell for 24 hours and diffusion rate and permeability of xenon were calculated. Thus diffusion rate was 0.031 mg/hour*cm2 and permeability was 0.003 cm/hour. Using Brookfield viscometer it was shown that viscosity of CCT decreased upon increasing xenon concentration. Obtained results can be utilized in developing of new xenon containing drugs for topical administration.

  16. Flows, Turbulence, and Mixing

    NASA Astrophysics Data System (ADS)

    Lazarian, Alex

    2003-07-01

    HST and FUSE spectra of distant UV-bright sources reveal interstellar absorption lines of high stages of ionization {O VI, C IV, N V, Si IV} arising in many different astrophysical environments such as superbubbles, interstellar chimneys, high-velocity clouds, galaxy halos and cosmic filaments. Turbulence, always present in the magnetized ISM, must mix the hot { 10^6 K} gas with cooler gas within "turbulent mixing layers". Present theory, based on 1D steady-state flows, suggest the line ratios in these layers differ significantly from photoionized gas, radiative shocks, cooling zones, or conduction fronts. These models are use to infer mass and energy fluxes important to understanding the ISM. We propose to develop a suite of 3D time-dependent models that properly calculate turbulent mixing. We will produce synthetic UV absorption lines and optical emission lines directly relevant to HST observations that use GHRS, STIS, and eventually, COS. These models will allow us to explore the sensitivity of the spectral diagnostics to magnetic field strength, turbulence intensity, and relative velocity of the hot and cold gas. We will publish the resulting grid of spectral diagnostics and make them available through the Web.

  17. Stochastic neutrino mixing mechanism

    NASA Astrophysics Data System (ADS)

    Guzzo, M. M.; de Holanda, P. C.; Peres, O. L. G.; Zavanin, E. M.

    2013-05-01

    We propose a mechanism which provides an explanation of the Gallium and antineutrino reactor anomalies. Differently from original Pontecorvo’s hypothesis, this mechanism is based on the phenomenological assumption in which the admixture of neutrino mass eigenstates in the moments of neutrino creation and detection can assume different configurations around the admixture parametrized by the usual values of the mixing angles θ12, θ23, and θ13. For simplicity, we assume a Gaussian distribution for the mixing angles in such a way that the average value of this distribution is given by the usual values of the mixing angles, and the width of the Gaussian is denoted by α. We show that the proposed mechanism provides a possible explanation for very short-baseline neutrino disappearance, necessary to accommodate Gallium and antineutrino reactor anomalies, which is not allowed in usual neutrino oscillations based on Pontecorvo’s original hypotheses. We also can describe high-energy oscillation experiments, like LSND, Fermi, and NuTeV, assuming a weakly energy dependent width parameter, α(E), that nicely fits all experimental results.

  18. A Simple Scheme to Implement a Nonlocal Turbulent Convection Model for Convective Overshoot Mixing

    NASA Astrophysics Data System (ADS)

    Zhang, Q. S.

    2016-02-01

    Classical “ballistic” overshoot models show some contradictions and are not consistent with numerical simulations and asteroseismic studies. Asteroseismic studies imply that overshoot is a weak mixing process. A diffusion model is suitable to deal with it. The form of diffusion coefficient in a diffusion model is crucial. Because overshoot mixing is related to convective heat transport (i.e., entropy mixing), there should be some similarity between them. A recent overshoot mixing model shows consistency between composition mixing and entropy mixing in the overshoot region. A prerequisite to apply the model is to know the dissipation rate of turbulent kinetic energy. The dissipation rate can be worked out by solving turbulent convection models (TCMs). But it is difficult to apply TCMs because of some numerical problems and the enormous time cost. In order to find a convenient way, we have used the asymptotic solution and simplified the TCM to a single linear equation for turbulent kinetic energy. This linear model is easy to implement in calculations of stellar evolution with negligible extra time cost. We have tested the linear model in stellar evolution, and have found that it can well reproduce the turbulent kinetic energy profile of the full TCM, as well as the diffusion coefficient, abundance profile, and stellar evolutionary tracks. We have also studied the effects of different values of the model parameters and have found that the effect due to the modification of temperature gradient in the overshoot region is slight.

  19. Mixing kaons with mixed action chiral perturbation theory

    NASA Astrophysics Data System (ADS)

    Aubin, Christopher

    2006-12-01

    We calculate the neutral kaon mixing parameter, BK , to next-to-leading order in mixed action (domain-wall valence with staggered sea quarks) chiral perturbation theory. We find the expres- sion for BK in this mixed-action case only differs from the continuum partially quenched expres- sion by an additional analytic term. Additionally, in preparation for a lattice calculation of BK with a mixed action, we discuss quantitatively the effects of the taste violations as well as finite volume effects.

  20. The relevance of ambipolar diffusion for neutron star evolution

    NASA Astrophysics Data System (ADS)

    Passamonti, Andrea; Akgün, Taner; Pons, José A.; Miralles, Juan A.

    2017-03-01

    We study ambipolar diffusion in strongly magnetized neutron stars, with special focus on the effects of neutrino reaction rates and the impact of a superfluid/superconducting transition in the neutron star core. For axisymmetric magnetic field configurations, we determine the deviation from β-equilibrium induced by the magnetic force and calculate the velocity of the slow, quasi-stationary, ambipolar drift. We study the temperature dependence of the velocity pattern and clearly identify the transition to a predominantly solenoidal flow. For stars without superconducting/superfluid constituents and with a mixed poloidal-toroidal magnetic field of typical magnetar strength, we find that ambipolar diffusion proceeds fast enough to have a significant impact on the magnetic field evolution only at low core temperatures, T ≲ 1-2 × 108 K. The ambipolar diffusion time-scale becomes appreciably shorter when fast neutrino reactions are present, because the possibility to balance part of the magnetic force with pressure gradients is reduced. We also find short ambipolar diffusion time-scales in the case of superconducting cores for T ≲ 109 K, due to the reduced interaction between protons and neutrons. In the most favourable scenario, with fast neutrino reactions and superconducting cores, ambipolar diffusion results in advection velocities of several km kyr-1. This velocity can substantially reorganize magnetic fields in magnetar cores, in a way which can only be confirmed by dynamical simulations.