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Sample records for aids-related diffuse mixed

  1. Gene Therapy After Frontline Chemotherapy in Treating Patients With AIDS-Related Non-Hodgkin Lymphoma

    ClinicalTrials.gov

    2016-03-14

    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 Small Noncleaved Cell Lymphoma; HIV Infection

  2. Treatment outcomes in AIDS-related diffuse large B-cell lymphoma in the setting roll-out of combination antiretroviral therapy in South Africa

    PubMed Central

    de Witt, Pieter; Maartens, Deborah J; Uldrick, Thomas S; Sissolak, Gerhard

    2013-01-01

    Background Long term survival for patients with AIDS-related diffuse large B-cell lymphoma (DLBCL) is feasible in settings with available combination antiretroviral therapy (cART). However, given limited oncology resources, outcomes for AIDS-associated DLBCL in South Africa are unknown. Methods We performed a retrospective analysis of survival in patients with newly diagnosed AIDS-related diffuse large B-cell lymphoma (DLBCL) treated at a tertiary teaching hospital in Cape Town, South Africa with CHOP or CHOP-like chemotherapy (January 2004 until Dec 2010). HIV and lymphoma related prognostic factors were evaluated. Results 36 patients evaluated; median age 37.3 years, 52.8% men, and 61.1% black South Africans. Median CD4 count 184 cells/μl (in 27.8% this was < 100 cells/μl), 80% high-risk according to the age-adjusted International Prognostic Index. Concurrent Mycobacterium tuberculosis in 25%. Two-year overall survival (OS) was 40.5% (median OS 10.5 months, 95%CI 6.5 – 31.8). ECOG performance status of 2 or more (25.4% versus 50.0%, p = 0.01) and poor response to cART (18.0% versus 53.9%, p = 0.03) predicted inferior 2-year OS. No difference in 2-year OS was demonstrated in patients co-infected with Mycobacterium tuberculosis (p = 0.87). Conclusions Two-year OS for patients with AIDS-related DLBCL treated with CHOP like regimens and cART is comparable to that seen in the US and Europe. Important factors effecting OS in AIDS-related DLBCL in South Africa include performance status at presentation and response to cART. Patients with co-morbid Mycobacterium tuberculosis or hepatitis B seropositivity appear to tolerate CHOP in our setting. Additional improvements in outcomes are likely possible. PMID:23797692

  3. Immunophenotypic Analysis of AIDS-Related Diffuse Large B-Cell Lymphoma and Clinical Implications in Patients From AIDS Malignancies Consortium Clinical Trials 010 and 034

    PubMed Central

    Chadburn, Amy; Chiu, April; Lee, Jeannette Y.; Chen, Xia; Hyjek, Elizabeth; Banham, Alison H.; Noy, Ariela; Kaplan, Lawrence D.; Sparano, Joseph A.; Bhatia, Kishor; Cesarman, Ethel

    2009-01-01

    Purpose Diffuse large B-cell lymphoma (DLBCL) represents a clinically heterogeneous disease. Models based on immunohistochemistry predict clinical outcome. These include subdivision into germinal center (GC) versus non-GC subtypes; proliferation index (measured by expression of Ki-67), and expression of BCL-2, FOXP1, or B-lymphocyte-induced maturation protein (Blimp-1)/PRDM1. We sought to determine whether immunohistochemical analyses of biopsies from patients with DLBCL having HIV infection are similarly relevant for prognosis. Patients and Methods We examined 81 DLBCLs from patients with AIDS in AMC010 (cyclophosphamide, doxorubicin, vincristine, and prednisone [CHOP] v CHOP-rituximab) and AMC034 (etoposide, doxorubicin, vincristine, prednisone, and dose-adjusted cyclophosphamide plus rituximab concurrent v sequential) clinical trials and compared the immunophenotype with survival data, Epstein-Barr virus (EBV) positivity, and CD4 counts. Results The GC and non-GC subtypes of DLBCL did not differ significantly with respect to overall survival or CD4 count at cancer presentation. EBV could be found in both subtypes of DLBCL, although less frequently in the GC subtype, and did not affect survival. Expression of FOXP1, Blimp-1/PRDM1, or BCL-2 was not correlated with the outcome in patients with AIDS-related DLBCL. Conclusion These data indicate that with current treatment strategies for lymphoma and control of HIV infection, commonly used immunohistochemical markers may not be clinically relevant in HIV-infected patients with DLBCL. The only predictive immunohistochemical marker was found to be Ki-67, where a higher proliferation index was associated with better survival, suggesting a better response to therapy in patients whose tumors had higher proliferation rates. PMID:19752343

  4. Diffusive mixing and Tsallis entropy

    DOE PAGESBeta

    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.

  5. 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.

  6. 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

  7. General Information about AIDS-Related Lymphoma

    MedlinePlus

    ... AIDS-Related Lymphoma Treatment (PDQ®)–Patient Version General Information About AIDS-Related Lymphoma Go to Health Professional ... the PDQ Adult Treatment Editorial Board . Clinical Trial Information A clinical trial is a study to answer ...

  8. Double-diffusive layering and mixing in Patagonian fjords

    NASA Astrophysics Data System (ADS)

    Pérez-Santos, Iván; Garcés-Vargas, José; Schneider, Wolfgang; Ross, Lauren; Parra, Sabrina; Valle-Levinson, Arnoldo

    2014-12-01

    Double-diffusive layering was quantified for the first time in the Chilean Patagonian fjords region (41.5-56°S). Approximately 600 temperature and salinity profiles collected during 1995-2012 were used to study water masses, quantify diffusive layering and compute the vertical diffusivity of heat. Development of 'diffusive-layering' or simply 'layering' was favored by relatively fresh-cold waters overlying salty-warm waters. Fresh waters are frequently derived from glacial melting that influences the fjord either directly or through rivers. Salty waters are associated with Modified Subantarctic (MSAAW) and Subantarctic Water (SAAW). Double-diffusive convection occurred as layering in 40% of the year-round data and as salt fingering in <1% of the time. The most vigorous layering, was found at depths between 20 and 70 m, as quantified by (a) Turner angles, (b) density ratios, and (c) heat diffusivity (with maximum values of 5 × 10-5 m2 s-1). Diffusive-layering events presented a meridional gradient with less layering within the 41-47°S northern region, relative to the southern region between 47° and 56°S. Layering occupied, on average, 27% and 56% of the water column in the northern and southern regions, respectively. Thermohaline staircases were detected with microprofile measurements in Martinez and Baker channels (48°S), showing homogeneous layers (2-4 m thick) below the pycnocline (10-40 m). Also in this area, increased vertical mixing coincided with the increased layering events. High values of Thorpe scale (LT ∼ 7 m), dissipation rate of TKE (ε = 10-5-10-3 W kg-1) and diapycnal eddy diffusivity (Kρ = 10-6-10-3 m-2 s-1) were associated with diffusive layering. Implications of these results are that diffusive layering should be taken into account, together with other mixing processes such as shear instabilities and wind-driven flows, in biological and geochemical studies.

  9. Effects of microscopic diffusion and rotational mixing on stellar models

    NASA Astrophysics Data System (ADS)

    Chaboyer, Brian Charles

    1993-01-01

    We have calculated evolutionary tracks for halo stars and constructed isochrones with alpha-enhanced compositions which cover the entire globular cluster metallicity range and include the effects of the diffusion of He-4. We find that including the effects of helium diffusion has a negligible effect (less than 0.5 Gyr) on the derived ages of globular clusters. Regardless of the inclusion of helium diffusion, we find a significant age spread of 5 Gyr among the globular clusters. The oldest globular cluster studied was M92 with an age of 17 +/- 2 Gyr old. The stellar models may be tested by comparing the Li-7 depletion and surface rotation rates to observations in young clusters stars. The observed Li-7 abundances clearly indicate that standard or diffusive models do not deplete enough Li-7. Instabilities induced by rotation provide an additional mixing mechanism. For this reason the stellar evolution code was modified to include the combined effects of diffusion and rotational mixing of H-1, He-4 and the trace elements He-3, Li-7 and Be-9. The calibrated solar models have a convection zone depth of 0.709-0.714 solar radius, in excellent agreement with the observed depth of (0.713 +/- 0.003) solar radius. The rotational mixing inhibits the diffusion in the outer parts of the models, leading to a decrease in the envelope diffusion by 50-80 percent. These models are able to reproduce the Li-7 abundances and rotation velocities observed in young cluster stars. Observations of Li-7 abundances in extremely metal poor halo stars provide another test of the stellar models. Standard models do a good job of fitting the observed Li-7 abundances and predict a primordial Li-7 abundance of log N(Li) = 2.24 +/- 0.03. Models of hot stars which include microscopic diffusion, but not rotational mixing, deplete too much Li-7. The (Fe/H) = 2.28 stellar models which include both diffusion and rotational mixing provide an excellent match to the observations, and predict a primordial Li-7

  10. Diffusion in mixed solvents - On the viscosity question

    NASA Technical Reports Server (NTRS)

    Carapellucci, P. A.

    1975-01-01

    Linear plots of reaction rate vs reciprocal of solvent viscosity are generally used as the classifying criteria for diffusion controlled reactions in fluid solutions and to determine reaction mechanisms in mixed hydroxylic solvents like glycerol and water. This paper presents data which shows that the above-mentioned criteria are insufficient in many cases where nonideal mixed solvent systems are used to increase solvent viscosity. Data correlations suggest that the excess functions determine the variation in reaction rate constants. Kinetic parameters are presented for sucrose-water and methanol-water solvent systems for a reaction involving Fe(CN)6 and zinc uroporphyrin.

  11. Pricing turbo warrants under mixed-exponential jump diffusion model

    NASA Astrophysics Data System (ADS)

    Yu, Jianfeng; Xu, Weidong

    2016-06-01

    Turbo warrant is a special type of barrier options in which the rebate is calculated as another exotic option. In this paper, using Laplace transforms we obtain the valuation of turbo warrant under the mixed-exponential jump diffusion model, which is able to approximate any jump size distribution. The numerical Laplace inversion examples verify that the analytical solutions are accurate. The results of simulation confirm the argument that jump risk should not be ignored in the valuation of turbo warrants.

  12. Effects of Microscopic Diffusion and Rotational Mixing on Stellar Models

    NASA Astrophysics Data System (ADS)

    Chaboyer, Brian

    1994-02-01

    Evolutionary tracks and isochrones were calculated with alpha-enhanced compositions which cover the entire globular cluster metallicity range and include the effects of the diffusion of ^4He. Including the effects of helium diffusion has a negligible effect (< 0.5 Gyr) on the derived ages of globular clusters. Regardless of the inclusion of helium diffusion, a significant age spread of ~5$ Gyr exists among the globular clusters. The oldest globular cluster studied was M92 with an age of 17 +/- 2 Gyr old. The stellar models may be tested by comparing the Li depletion and surface rotation rates to observations in young clusters stars. The observed Li abundances clearly indicate that standard or diffusive models do not deplete enough Li. Instabilities induced by rotation provide an additional mixing mechanism. For this reason the stellar evolution code was modified to include the combined effects of diffusion and rotational mixing on ^1H, ^4He and the trace elements ^3He, ^6Li, ^7Li, and ^9Be. The calibrated solar models have a convection zone depth of 0.709 - 0.714~R_odot, in excellent agreement with the observed depth of (0.713 +/- 0.003)~R_odot. The rotational mixing inhibits the diffusion in the outer parts of the models, leading to a decrease in the envelope diffusion by 30 - 50%. The combined models are able to simultaneously match the Li abundances observed in the Pleiades, UMaG, Hyades, NGC 752 and M67. They also match the observed rotation periods in the Hyades. However, these models are unable to explain the presence of the rapidly rotating G and K stars in the Pleiades. Observations of Li abundances in extremely metal poor halo stars provide another test of the stellar models. All models which use Kurucz (1992) model atmospheres to determine the surface boundary conditions are unable to match the observed Li depletion in cool halo stars. Models which use the gray atmosphere approximation provide a much better fit to the data. Standard models do a good job

  13. A Mixed-Culture Biofilm Model with Cross-Diffusion.

    PubMed

    Rahman, Kazi A; Sudarsan, Rangarajan; Eberl, Hermann J

    2015-11-01

    We propose a deterministic continuum model for mixed-culture biofilms. A crucial aspect is that movement of one species is affected by the presence of the other. This leads to a degenerate cross-diffusion system that generalizes an earlier single-species biofilm model. Two derivations of this new model are given. One, like cellular automata biofilm models, starts from a discrete in space lattice differential equation where the spatial interaction is described by microscopic rules. The other one starts from the same continuous mass balances that are the basis of other deterministic biofilm models, but it gives up a simplifying assumption of these models that has recently been criticized as being too restrictive in terms of ecological structure. We show that both model derivations lead to the same PDE model, if corresponding closure assumptions are introduced. To investigate the role of cross-diffusion, we conduct numerical simulations of three biofilm systems: competition, allelopathy and a mixed system formed by an aerobic and an anaerobic species. In all cases, we find that accounting for cross-diffusion affects local distribution of biomass, but it does not affect overall lumped quantities such as the total amount of biomass in the system. PMID:26582360

  14. 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...

  15. Photoionized Mixing Layer Models of the Diffuse Ionized Gas

    NASA Astrophysics Data System (ADS)

    Binette, Luc; Flores-Fajardo, Nahiely; Raga, Alejandro C.; Drissen, Laurent; Morisset, Christophe

    2009-04-01

    It is generally believed that O stars, confined near the galactic midplane, are somehow able to photoionize a significant fraction of what is termed the "diffuse ionized gas" (DIG) of spiral galaxies, which can extend up to 1-2 kpc above the galactic midplane. The heating of the DIG remains poorly understood, however, as simple photoionization models do not reproduce the observed line ratio correlations well or the DIG temperature. We present turbulent mixing layer (TML) models in which warm photoionized condensations are immersed in a hot supersonic wind. Turbulent dissipation and mixing generate an intermediate region where the gas is accelerated, heated, and mixed. The emission spectrum of such layers is compared with observations of Rand of the DIG in the edge-on spiral NGC 891. We generate two sequence of models that fit the line ratio correlations between [S II]/Hα, [O I]/Hα, [N II]/[S II], and [O III]/Hβ reasonably well. In one sequence of models, the hot wind velocity increases, while in the other, the ionization parameter and layer opacity increase. Despite the success of the mixing layer models, the overall efficiency in reprocessing the stellar UV is much too low, much less than 1%, which compels us to reject the TML model in its present form.

  16. Thymostimulin treatment in AIDS-related complex.

    PubMed

    Palmisano, L; Chisesi, T; Galli, M; Gritti, F M; Ielasi, G; Lazzarin, A; Mezzaroma, I; Moroni, M; Raise, E; Vaglia, A

    1988-06-01

    Thirty-four patients with AIDS-related complex (ARC) were treated for 6 months with thymostimulin, a thymic hormone. Clinical and immunological findings after a 1-year follow-up were compared with those in 24 age- and sex-matched controls receiving no immunotherapy. Statistical evaluation after 6 and 12 months showed significant differences in the two groups. The thymostimulin-treated group had higher leukocyte and lymphocyte counts, more positivity in intradermal tests with multiple recall antigens, and less lymphadenopathy and weight loss. The number of OKT3+ and OKT4+ lymphocytes decreased significantly in the control group, but did not change in the thymostimulin-treated patients. Finally, after 18 months of follow-up, no progression to AIDS was seen among the treated subjects, whereas 3 of the controls developed the disease. We conclude that thymostimulin, alone or in combination with antiviral drugs, may be helpful in the management of ARC patients. PMID:3259480

  17. Analysis of a mixed space-time diffusion equation

    NASA Astrophysics Data System (ADS)

    Momoniat, Ebrahim

    2015-06-01

    An energy method is used to analyze the stability of solutions of a mixed space-time diffusion equation that has application in the unidirectional flow of a second-grade fluid and the distribution of a compound Poisson process. Solutions to the model equation satisfying Dirichlet boundary conditions are proven to dissipate total energy and are hence stable. The stability of asymptotic solutions satisfying Neumann boundary conditions coincides with the condition for the positivity of numerical solutions of the model equation from a Crank-Nicolson scheme. The Crank-Nicolson scheme is proven to yield stable numerical solutions for both Dirichlet and Neumann boundary conditions for positive values of the critical parameter. Numerical solutions are compared to analytical solutions that are valid on a finite domain.

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

    NASA Astrophysics Data System (ADS)

    Lim, H.; Yu, Y.; Glimm, J.; Li, X.-L.; Sharp, D. H.

    2010-12-01

    We propose a new method for the large eddy simulation (LES) of turbulent mixing flows. The method yields convergent probability distribution functions (PDFs) for temperature and concentration and a chemical reaction rate when applied to reshocked Richtmyer-Meshkov (RM) unstable flows. Because such a mesh convergence is an unusual and perhaps original capability for LES of RM flows, we review previous validation studies of the principal components of the algorithm. The components are (i) a front tracking code, FronTier, to control numerical mass diffusion and (ii) dynamic subgrid scale (SGS) models to compensate for unresolved scales in the LES. We also review the relevant code comparison studies. We compare our results to a simple model based on 1D diffusion, taking place in the geometry defined statistically by the interface (the 50% isoconcentration surface between the two fluids). Several conclusions important to physics could be drawn from our study. We model chemical reactions with no closure approximations beyond those in the LES of the fluid variables itself, and as with dynamic SGS models, these closures contain no adjustable parameters. The chemical reaction rate is specified by the joint PDF for temperature and concentration. We observe a bimodal distribution for the PDF and we observe significant dependence on fluid transport parameters.

  19. 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.

  20. 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

  1. Turbulent Diapycnal Mixing In Stratified Shear Flows: Parameterizations of Mixing Efficiency and Diapycnal Diffusivity

    NASA Astrophysics Data System (ADS)

    Salehipour, Hesam; Peltier, W. Richard

    2014-11-01

    Motivated by the importance of diapycnal mixing in geophysical fluids, we study the inhomogeneously stratified and sheared turbulence that is engendered by the breaking of a Kelvin-Helmholtz wave and will direct connections to the homogeneously stratified case. We employ DNS method to focus on the high- Re regime and investigate a wide range of Ri and Pr . This talk will consist of three related topics: (1) linear stability analysis of the transition process to understand the sequence of secondary instabilities that govern transition at increasing values of Pr at a fixed high- Re . (2) A ``recipe'' for irreversible mixing which illuminates the fundamental physical mechanisms that are involved in rising the background potential energy and represents mixing as being composed of both (i) turbulent buoyancy flux and (ii) flow anisotropy due to energy-containing coherent eddies. (3) The precise derivation of diapycnal diffusivity, Kρ, with no simplifying assumptions which depends on an exact definition of mixing efficiency (rather than approximating it in terms of the flux Richardson number). We will propose robust parameterizations in terms of buoyancy Reynolds number, Reb , Ri and Pr for a wide range of these parameters extending Reb = O (103) .

  2. Pancreatic abnormalities and AIDS related sclerosing cholangitis.

    PubMed Central

    Teare, J P; Daly, C A; Rodgers, C; Padley, S P; Coker, R J; Main, J; Harris, J R; Scullion, D; Bray, G P; Summerfield, J A

    1997-01-01

    OBJECTIVES: Biliary tract abnormalities are well recognised in AIDS, most frequently related to opportunistic infection with Cryptosporidium, Microsporidium, and cytomegalovirus. We noted a high frequency of pancreatic abnormalities associated with biliary tract disease. To define these further we reviewed the clinical and radiological features in these patients. METHODS: Notes and radiographs were available from two centres for 83 HIV positive patients who had undergone endoscopic retrograde cholangiopancreatography for the investigation of cholestatic liver function tests or abdominal pain. RESULTS: 56 patients had AIDS related sclerosing cholangitis (ARSC); 86% of these patients had epigastric or right upper quadrant pain and 52% had hepatomegaly. Of the patients with ARSC, 10 had papillary stenosis alone, 11 had intra- and extrahepatic sclerosing cholangitis alone, and 35 had a combination of the two. Ampullary biopsies performed in 24 patients confirmed an opportunistic infection in 16. In 15 patients, intraluminal polyps were noted on the cholangiogram. Pancreatograms were available in 34 of the 45 patients with papillary stenosis, in which 29 (81%) had associated pancreatic duct dilatation, often with associated features of chronic pancreatitis. In the remaining 27 patients, final diagnoses included drug induced liver disease, acalculous cholecystitis, gall bladder empyema, chronic B virus hepatitis, and alcoholic liver disease. CONCLUSION: Pancreatic abnormalities are commonly seen with ARSC and may be responsible for some of the pain not relieved by biliary sphincterotomy. The most frequent radiographic biliary abnormality is papillary stenosis combined with ductal sclerosis. Images PMID:9389948

  3. 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

  4. One-Way Diffusion of Ionic Liquids in a Mixing Process with Water

    NASA Astrophysics Data System (ADS)

    Oikawa, Noriko; Tahara, Daiki; Kurita, Rei

    2016-09-01

    In contrast to the usual diffusive mixing process between two miscible liquids, the ionic liquid [Cnmim][PF6] forms a droplet in water while mixing. The droplet retains a sharp interface with surface tension, gradually decreasing in size until completely mixed with water. This peculiar behavior in the mixing process accompanies one-way diffusion, in which ions diffuse in one direction only from the bulk IL droplet into the bulk continuum of water. The activation energy of the one-way diffusion at the [Cnmim][PF6]/water interface increases with increasing length of the hydrophobic alkyl chains attached to the cation molecules of [Cnmim][PF6]. It is considered that the hydrophobic nanoscale structure observed in [C4mim][PF6] plays an important role in the generation of the droplet and the mixing dynamics.

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

    NASA Astrophysics Data System (ADS)

    Cronin, Meghan F.; Pelland, Noel A.; Emerson, Steven R.; Crawford, William R.

    2015-11-01

    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 diffusivities 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.

  6. 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.

  7. Stellar models with microscopic diffusion and rotational mixing. 1: Application to the Sun

    NASA Technical Reports Server (NTRS)

    Chaboyer, Brian; Demarque, P.; Pinsonneault, M. H.

    1995-01-01

    The Yale stellar evolution code has been modified to include the combined effects of diffusion and rotational mixing on H-1, H-4, and the trace elements He, Li-6, Li-7, and Be-9. The interaction between rotational mixing and diffusion is studied by calculating a number of calibrated solar models. The rotational mixing inhibits the diffusion in the outer parts of the models, leading to a decrease in the envelope diffusion by 25%-50%. Conversely, diffusion leads to gradients in mean molecular weight which can inhibit the rotational mixing. The degree to which gradients in mean molecular weight inhibit the rotational mixing is somewhat uncertain. A comparison with the observed solar oblateness suggests that gradients in the mean molecular weight play a smaller role in inhibiting the rotational mixing than previously believed. This is reinforced by the fact that the model with the standard value for the inhibiting effect of mean molecular weight on the rotational mixing depletes no Li on the main sequence. This is clear in contrast to the observations. A reduction in the inhibiting effect of mean molecular weight gradients by a factor of 10 loads to noticeable main-sequence Li depletion.

  8. Anomalous Diffusion and Mixing of Chaotic Orbits in Hamiltonian Dynamical Systems

    NASA Astrophysics Data System (ADS)

    Ishizaki, R.; Horita, T.; Mori, H.

    1993-05-01

    Anomalous behaviors of the diffusion and mixing of chaotic orbits due to the intermittent sticking to the islands of normal tori and accelerator-mode tori in a widespread chaotic sea are studied numerically and theoretically for Hamiltonian systems with two degrees of freedom. The probability distribution functions for the coarse-grained velocity (characterizing the diffusion) and the coarse-grained expansion rate (characterizing the mixing) turn out to obey an anomalous scaling law which is quite different from the Gaussian. The scaling law is confirmed for both diffusion and mixing by numerical experiments on the heating map introduced by Karney, which exhibits remarkable statistical properties more clearly than the standard map. Its scaling exponents for the two cases, however, are found to be different from each other.

  9. Psychological Consequences of AIDS-Related Bereavement among Gay Men.

    ERIC Educational Resources Information Center

    Martin, John L.

    1988-01-01

    Interviewed 745 homosexual men to examine relation between Acquired Immune Deficiency Syndrome (AIDS)-related bereavement and psychological distress. Loss of lover or close friend to AIDS was reported by 27 percent of sample. Found direct relation between number of bereavements and symptoms of traumatic stress response, demoralization, sleep…

  10. Cation Diffusivity and the Mixed Network Former Effect in Borosilicate Glasses.

    PubMed

    Smedskjaer, Morten M; Mauro, John C; Yue, Yuanzheng

    2015-06-11

    Understanding the structural origins of cationic diffusion processes in silicate glasses is important for high-tech applications of silicate glasses. For glasses with more than one network former, transport properties such as diffusivity are often nonlinear functions of the particular distribution of these network formers, a phenomenon known as the mixed network former effect. Here, we investigate the sodium-potassium interdiffusion (D̅Na-K) and the calcium inward diffusion (DCa) in soda lime borosilicate glasses with varying silica/borate ratio but constant modifier content. Indeed, the structural organization of borosilicate glasses results in a pronounced nonlinear composition dependence of D̅Na-K and DCa (i.e., the mixed network former effect). Initial addition of B2O3 to the glass system results in a significant decrease in both diffusivities, whereas the change in diffusivity per mole of added B2O3 decreases with increasing B2O3 concentration. Besides the influences of water content and atomic packing degree, we find that 99% of the composition dependence of log D̅Na-K can be ascribed to the change in concentration of tetrahedral boron groups. This indicates that the formation of BO4/2 groups slows down diffusion processes of alkali and alkaline earth ions. Therefore, the mixed network former effect of the studied glass series is linked with the change of the concentration of tetrahedral boron groups, which is caused by the interactions between the different types of network formers. PMID:25978700

  11. 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.

  12. 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.

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

    DOE PAGESBeta

    Parfitt, David C.; Cooper, Michael William; Rushton, Michael J.D.; Christopoulos, S. R.; Fitzpatrick, M. E.; Chroneos, A.

    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.

  14. 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.

  15. 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

  16. Design Optimization of Mixed-flow Pump Impellers and Diffusers in a Fixed Meridional Shape

    NASA Astrophysics Data System (ADS)

    Kim, Sung; Choi, Young-Seok; Lee, Kyoung-Yong

    2010-06-01

    In this paper, design optimization for mixed-flow pump impellers and diffusers has been studied by using a commercial CFD code and DOE(design of experiments). We also discussed how to improve the performance of the mixed-flow pump by designing the impeller and diffuser in the mixed-flow pump. Geometric design variables were defined by the vane plane development which indicates the blade-angle distributions and length of the impeller and the diffusers. The vane plane development was controlled by using blade-angle in a fixed meridional shape. First the design optimization of the defined impeller geometric variables was done, and then the flow characteristics were analyzed in the point of incidence angle at the diffuser leading edge for the optimized impeller. Then design optimizations of the defined diffuser shape variables were performed. The importance of the geometric design variables was analyzed by using 2k factorial designs, and the design optimization of the geometric variables were determined using the response surface method. The objective functions are defined as the total head and the total efficiency at the design flow-rate. From the comparison of CFD results between optimized pump and base design model, the reason for the performance improvement was discussed.

  17. 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.

  18. 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.

  19. A numerical study of the effects of heat diffusion through the base of the mixed layer

    NASA Technical Reports Server (NTRS)

    Posmentier, E. S.

    1980-01-01

    In the present paper, a simple numerical model is used to study the warming of the mixed layer during the early summer. It is shown that the springtime temperature increase in the layer below the mixed layer (for example, in the cold pool on a continental shelf) has a maximum value which occurs for a limiting value of the surface heat flux. This is a result of the positive feedback at large Richardson numbers between stability and vertical diffusion of heat. The springtime temperature increase in the mixed layer increases nonlinearly with surface heat flux, because of the same positive feedback. The effects of interseasonal fluctuations of the surface heat flux on the spring and summer mixed layer and deeper temperature increases can be as great as the effect of interseasonal fluctuations of the average heat flux.

  20. Pore-Scale Simulation of Intragranular Diffusion: Effects of Incomplete Mixing on Macroscopic Manifestations

    SciTech Connect

    Scheibe, Timothy D.; Hou, Zhangshuan; Palmer, Bruce J.; Tartakovsky, Alexandre M.

    2013-07-01

    Diffusive mass transfer into and out of intragranular micropores ("intragranular diffusion") plays an important role in the large-scale transport of some groundwater contaminants. We are interested in understanding the combined effect of pore-scale advection and intragranular diffusion on solute transport at the effective porous medium scale. To study this problem, we have developed a three-dimensional pore-scale model of fluid flow and solute transport that incorporates diffusion into and out of intragranular pore spaces. Our model is based on the Smoothed Particle Hydrodynamics (SPH) simulation method, which represents fluid and solid phases by a mesh-free particle discretization. In the pore spaces, fluid flow is simulated by discretizing the Navier-Stokes equations using the SPH approach. Solute transport is represented by advection, diffusion within the fluid phase, and diffusion between the fluid and solid phases. Our model is implemented on large-scale parallel computing hardware, allowing us to simulate millions of computational particles and represent fully three-dimensional systems of pores and grains with arbitrarily complex physical geometry. We have used this model system to perform numerical experiments using various model porous media systems, which allows us to draw comparisons between macroscopic measures computed from the pore-scale simulations (such as breakthrough curves) and those predicted by macroscopic formulations that assume complete mixing over the representative volume. In this paper we present results of 3D simulations of pore-scale flow and transport, including cases with and without intragranular diffusion, in two model porous media, one with randomly-packed uniform spherical grains and a second with randomly-packed spheres drawn from a binary grain size distribution. Breakthrough curves were computed from the 3D simulations at various transport distances. Comparable breakthrough curves were computed using 1D macroscopic models with

  1. 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.

  2. Errors associated with standard nodal diffusion methods as applied to mixed oxide fuel problems

    SciTech Connect

    Brantley, P. S., LLNL

    1998-07-24

    The evaluation of the disposition of plutonium using light water reactors is receiving increased attention. However, mixed-oxide (MOX) fuel assemblies possess much higher absorption and fission cross- sections when compared to standard UO2 assemblies. Those properties yield very high thermal flux gradients at the interfaces between MOX and UO2 assemblies. It has already been reported that standard flux reconstruction methods (that recover the homogeneous intranodal flux shape using the converged nodal solution) yield large errors in the presence of MOX assemblies. In an accompanying paper, we compare diffusion and simplified PN calculations of a mixed-oxide benchmark problem to a reference transport calculation. In this paper, we examine the errors associated with standard nodal diffusion methods when applied to the same benchmark problem. Our results show that a large portion of the error is associated with the quadratic leakage approximation (QLA) that is commonly used in the standard nodal codes.

  3. DOUBLE-DIFFUSIVE MIXING IN STELLAR INTERIORS IN THE PRESENCE OF HORIZONTAL GRADIENTS

    SciTech Connect

    Medrano, M.; Garaud, P.; Stellmach, S.

    2014-09-10

    We have identified a potentially important source of mixing in stellar radiation zones which would arise whenever two conditions are satisfied: (1) the presence of an inverse vertical compositional gradient, and (2) the presence of density-compensating horizontal gradients of temperature and composition. The former can be caused by off-center nuclear burning, atomic diffusion, or surface accretion. The latter could be caused by rotation, tides, meridional flows, etc. The linear instability and its nonlinear development have been studied in an oceanographic context. It is known to drive the formation of stacks of fingering layers separated by diffusive interfaces, called intrusions. Using three-dimensional numerical simulations of the process in the astrophysically relevant region of parameter space, we find similar results and demonstrate that the material transport in the intrusive regime can be highly enhanced compared with pure diffusion, even in systems which would otherwise be stable to fingering (thermohaline) convection.

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

    DOE PAGESBeta

    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

  5. 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.

  6. HIV/AIDS-related stigma in Kumasi, Ghana

    PubMed Central

    Ulasi, Chijioke I; Preko, Peter O; Baidoo, Joseph A.; Bayard, Budry; Ehiri, John E; Jolly, Curtis M; Jolly, Pauline E

    2009-01-01

    Objective To assess HIV/AIDS-related stigma and discrimination of people living with HIV/AIDS (PLWHA) in Kumasi, Ghana. Methods A cross-sectional survey of 104 adults from the four sub-districts in Kumasi was conducted. Results Four stigma constructs, employment-based discrimination, screening and identification of HIV positive people, revelation of HIV status and social contact stigma were determined based on reliability measures from responses to the questionnaire. Regression analysis showed that participants with higher educational attainment were more likely to favor policies denying employment to PLWHA (p<0.05), but disapproved of revealing HIV sero-status (p<0.05). Muslims were more likely than Christians to agree with identifying PLWHA (p<0.05) and more likely to advocate revealing HIV sero-status (p<0.05). Males were more likely to favor revealing HIV status (p<0.05). Employed persons were more likely to have social contact with PLWHA (p<0.05). Conclusions These findings are useful in guiding the design of interventions against HIV/AIDS-related stigma in Kumasi. PMID:18632302

  7. 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.

  8. 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.

  9. Atomic Diffusion and Mixing in Old Stars. III. Analysis of NGC 6397 Stars under New Constraints

    NASA Astrophysics Data System (ADS)

    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 2σ and 3σ 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 ɛ(Li) = 2.57 ± 0.10. At 1.2σ, this value agrees well with Wilkinson Microwave Anisotropy Probe calibrated big bang nucleosynthesis predictions.

  10. 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.

  11. 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.

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

    DOE PAGESBeta

    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,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

  13. 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.

  14. [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. PMID:22512196

  15. Mixed-order phase transition in a minimal, diffusion-based spin model

    NASA Astrophysics Data System (ADS)

    Fronczak, Agata; Fronczak, Piotr

    2016-07-01

    In this paper we exactly solve, within the grand canonical ensemble, a minimal spin model with the hybrid phase transition. We call the model diffusion based because its Hamiltonian can be recovered from a simple dynamic procedure, which can be seen as an equilibrium statistical mechanics representation of a biased random walk. We outline the derivation of the phase diagram of the model, in which the triple point has the hallmarks of the hybrid transition: discontinuity in the average magnetization and algebraically diverging susceptibilities. At this point, two second-order transition curves meet in equilibrium with the first-order curve, resulting in a prototypical mixed-order behavior.

  16. Mixed-order phase transition in a minimal, diffusion-based spin model.

    PubMed

    Fronczak, Agata; Fronczak, Piotr

    2016-07-01

    In this paper we exactly solve, within the grand canonical ensemble, a minimal spin model with the hybrid phase transition. We call the model diffusion based because its Hamiltonian can be recovered from a simple dynamic procedure, which can be seen as an equilibrium statistical mechanics representation of a biased random walk. We outline the derivation of the phase diagram of the model, in which the triple point has the hallmarks of the hybrid transition: discontinuity in the average magnetization and algebraically diverging susceptibilities. At this point, two second-order transition curves meet in equilibrium with the first-order curve, resulting in a prototypical mixed-order behavior. PMID:27575073

  17. 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.

  18. Coupling mixed and finite volume discretizations of convection-diffusion-reaction equations on non-matching grids

    SciTech Connect

    Lazarov, R; Pasciaic, J; Vassilevski, P

    1999-07-01

    In this paper, we consider approximation of a second order convection- diffusion problem by coupled mixed and finite volume methods. Namely, the domain is partitioned into two subdomains, and in one of them we apply the mixed jinite element method while on the other subdomain we use the finite volume element approximation. We prove the stability of this discretization and derive an error estimate.

  19. AIDS-related apprehensions among nursing students of Delhi.

    PubMed

    Kumar, A; Lal, P; Ingle, G K; Gulati, N

    1999-12-01

    Students from a nursing school of Delhi were surveyed anonymously using a self-administered questionnaire to explore various AIDS-related apprehensions and their possible reasons. The observations revealed that, majority of the students and their families/friends feared that these students were at risk of contracting HIV infection while providing routine patient care. A large number of students also opined that they would feel uncomfortable while talking, hugging, shaking hands, and sharing a room with an HIV positive person. The main reasons for their apprehensions were unsatisfactory anti-AIDS campaigning by the government, non-availability of sufficient protective measures in the health care settings, inadequate professional education related to prevention of HIV infection, and increase in HIV transmission following false sense of security due to excessive condom promotion. Findings of the study imply imparting factual knowledge addressing the concerns and removing misconceptions which influence attitudes and willingness of the nursing students to provide care to the HIV positives/AIDS patients, facts regarding efficacy of various preventive measures, and provision of counselling services in the event of exposure. PMID:10937297

  20. The tumor virus landscape of AIDS-related lymphomas.

    PubMed

    Arvey, Aaron; Ojesina, Akinyemi I; Pedamallu, Chandra Sekhar; Ballon, Gianna; Jung, Joonil; Duke, Fujiko; Leoncini, Lorenzo; De Falco, Giulia; Bressman, Eric; Tam, Wayne; Chadburn, Amy; Meyerson, Matthew; Cesarman, Ethel

    2015-05-14

    Immunodeficiency dramatically increases susceptibility to cancer as a result of reduced immune surveillance and enhanced opportunities for virus-mediated oncogenesis. Although AIDS-related lymphomas (ARLs) are frequently associated with known oncogenic viruses, many cases contain no known transforming virus. To discover novel transforming viruses, we profiled a set of ARL samples using whole transcriptome sequencing. We determined that Epstein-Barr virus (EBV) was the only virus detected in the tumor samples of this cohort, suggesting that if unidentified pathogens exist in this disease, they are present in <10% of cases or undetectable by our methods. To evaluate the role of EBV in ARL pathogenesis, we analyzed viral gene expression and found highly heterogeneous patterns of viral transcription across samples. We also found significant heterogeneity of viral antigen expression across a large cohort, with many patient samples presenting with restricted type I viral latency, indicating that EBV latency proteins are under increased immunosurveillance in the post-combined antiretroviral therapies era. Furthermore, EBV infection of lymphoma cells in HIV-positive individuals was associated with a distinct host gene expression program. These findings provide insight into the joint host-virus regulatory network of primary ARL tumor samples and expand our understanding of virus-associated oncogenesis. Our findings may also have therapeutic implications, as treatment may be personalized to target specific viral and virus-associated host processes that are only present in a subset of patients. PMID:25827832

  1. 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.

  2. Numerical study of diffusion on a random-mixed-bond lattice.

    PubMed

    Holder, Devora; Scher, Harvey; Berkowitz, Brian

    2008-03-01

    Diffusion on lattices with random mixed bonds in two and three dimensions is reconsidered using a random walk (RW) algorithm, which is equivalent to the master equation. In this numerical study the main focus is on the simple case of two different transition rates W(1),W(2) along bonds between sites. Although analysis of diffusion and transport on this type of disordered medium, especially for the case of one-bond pure percolation (i.e., W(1)=0 ), comprises a sizable subliterature, we exhibit additional basic results for the two-bond case: When the probability p of W(2) replacing W(1) in a lattice of W(1) bonds is below the percolation threshold p(c) , the mean square displacement r(2) is a nonlinear function of time t . A best fit to the lnr[(2) vs ln t plot is a straight line with the value of the slope varying with p,Delta,d , where Delta identical with W(2)/W(1) and d is the dimension, i.e., r(2) proportional, variant t(1+eta(p,Delta,d)) with eta>0 for Delta>1 . In other terms, all the diffusion (D identical with(r)(2)/2t proportional, variant t(eta)) is anomalous superdiffusion for p1 for d=2,3 . Previous work in the literature for d=2 with a different RW algorithm established an effective diffusion constant D(eff) , which was shown to scale as (p(c)-p)(1/2) . However, the anomalous nature (time dependence) of D(t) becomes manifest with an expanded regime of t , increased range of Delta , and the use of our algorithm. The nature of the superdiffusion is related to the percolation cluster geometry and Lévy walks. PMID:18517341

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

    ClinicalTrials.gov

    2016-06-09

    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

  4. Chemical diffusion of CO in mixed CO + O adlayers and reaction-front propagation in CO oxidation on Pd(100).

    PubMed

    Liu, Da-Jiang; Evans, J W

    2006-08-01

    Within the framework of a realistic atomistic lattice-gas model, we present the theoretical formulation and simulation procedures for precise analysis of the chemical diffusion flux of highly mobile CO within a nonuniform interacting mixed CO + O adlayer on a Pd(100) surface. The approach applies in both regimes of relatively immobile unequilibrated and fairly mobile near-equilibrated O adlayer distributions. Spatiotemporal behavior in surface reactions is controlled by chemical diffusion in mixed adlayers. Thus, we naturally integrate the above analysis with a previously developed multiscale modeling strategy to describe mesoscale reaction front propagation in CO oxidation on Pd(100). This treatment avoids using a simplified prescription of chemical diffusion and reaction kinetics as in traditional mean-field reaction-diffusion equation approaches. PMID:16942243

  5. Stellar models with microscopic diffusion and rotational mixing. 2: Application to open clusters

    NASA Technical Reports Server (NTRS)

    Chaboyer, B.; Demarque, P.; Pinsonneault, M. H.

    1995-01-01

    Stellar models with masses ranging from 05.5 to 1.3 solar mass were constructed for comparison with young cluster observations of Li and of rotation velocities. The amount of Li depletion in cool stars is sensitive to the amount of overshoot at the base of the surface convection zone, and the exact metallicity of the models. Even when this is taken into account, the Li observations are a severe constraint for the models and rule out standard models and pure diffusion models. Stellar models which include diffusion and rotational mixing in the radiative regions of stars are able to simultaneously match the Li abundances observed in the Pleiades, the UMa Group, The Hyades, Praesepe, NGC 752, and M67. They also match the observed rotation periods in the Hyades. However, these models are unable to simultaneously explain the presence of the rapidly rotating late G and K stars in the Pleiades and the absence of rapidly rotating late F and early G stars.

  6. 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.

  7. 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.

  8. 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.

  9. 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

  10. Effect of a deep breath on gas mixing and diffusion in the lung.

    PubMed

    Prabhu, M B; Mink, J T; Graham, B L; Cotton, D J

    1990-03-01

    We examined the effect of a previous deep breath on both inert gas mixing and the single breath diffusing capacity (DLCOSB) during submaximal single breath maneuvers in normal subjects. Single breath washouts were performed either immediately after a deep breath or after breathing tidally for 10 min. Maneuvers consisted of inhaling test gas from functional residual capacity to 50% inspiratory capacity and, after either 0 or 6 s of breath holding, exhaling slowly back to residual volume. We measured the Fowler dead space, the Phase III slope of the alveolar plateau of the He washout (delta He/L), the amplitude of the cardiogenic oscillations (Oc), closing capacity, mixing efficiency (Emix) and DLCOSB using the three equation method. For maneuvers immediately after a deep breath we found that delta He/L was steeper and the Oc were larger for washouts with 6 s but not 0 s of breath holding, while Emix was significantly lower and DLCOSB significantly higher for both the 0 s and the 6 s breath holding maneuvers. We conclude that a deep breath increases DLCOSB but simultaneously also increases convective-dependent inhomogeneity in the lung. PMID:2356360

  11. 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.

    2016-04-01

    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

  12. 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

  13. 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…

  14. 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

  15. 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. PMID:26575987

  16. 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.

  17. Field-scale tests for determining mixing patterns associated with coarse-bubble air diffuser configurations, Egan Quarry, Illinois

    USGS Publications Warehouse

    Hornewer, N.J.; Johnson, G.P.; Robertson, D.M.; Hondzo, Miki

    1997-01-01

    The U.S. Geological Survey in cooperation with the U.S. Army Corps of Engineers, Chicago District did field-scale tests in August-September 1996 to determine mixing patterns associated with different configurations of coarse-bubble air diffusers. The tests were done in an approximately 13-meter deep quarry near Chicago, Ill. Three-dimensional velocity, water-temperature, dissolved oxygen concentration, and specific-conductivity profiles were collected from locations between approximately 2 to 30 meters from the diffusers for two sets of five test configurations; one set for stratified and one set for destratified conditions in the quarry. The data-collection methods and instrumentation used to characterize mixing patterns and interactions of coarse-bubble diffusers were successful. An extensive data set was collected and is available to calibrate and verify aeration and stratification models, and to characterize basic features of bubble-plume interaction.

  18. Electron energization and mixing observed by MMS in the vicinity of an electron diffusion region during magnetopause reconnection

    NASA Astrophysics Data System (ADS)

    Chen, Li-Jen; Hesse, Michael; Wang, Shan; Gershman, Daniel; Ergun, Robert; Pollock, Craig; Torbert, Roy; Bessho, Naoki; Daughton, William; Dorelli, John; Giles, Barbara; Strangeway, Robert; Russell, Christopher; Khotyaintsev, Yuri; Burch, Jim; Moore, Thomas; Lavraud, Benoit; Phan, Tai; Avanov, Levon

    2016-06-01

    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.

  19. Expression of immunohistochemical markers in patients with AIDS-related lymphoma.

    PubMed

    Barreto, Luciana; Azambuja, Denize; Morais, José Carlos de

    2012-01-01

    AIDS-related lymphomas (ARL) present high biological heterogeneity. For better characterization of this type of lymphoma, the objectives of the present study were to evaluate the expression of immunohistochemical markers of cell differentiation (CD10, Bcl-6, MUM-1) and determine cell origin profile according to Hans' classification of diffuse large B-cell lymphoma in AIDS patients. This study included 72 consecutive patients with ARL diagnosed at the University Hospital, Universidade Federal do Rio de Janeiro (UFRJ) and at the Brazilian Instituto Nacional de Câncer (INCA) from 2000 to 2006. The morphologic distribution of the lymphomas was the following: 61% were diffuse large B-cell lymphomas (DLBCLs), 15% were Burkitt's lymphomas, 13% were plasmablastic lymphomas, 10% were high-grade lymphomas and 1% was follicular lymphoma. The positivity for each immunohistochemical marker in DLBCLs, Burkitt's lymphoma and plasmablastic lymphoma was respectively: CD20, 84%, 100%, and 0; CD10, 55%, 100%, and 0; Bcl-6, 45%, 80%, and 0; MUM-1, 41%, 20%, and 88%. A higher positivity of CD20 (84% x 56%, p = 0.01) was found in DLBCL compared to non-DLBCL; in Burkitt's lymphomas a higher positivity of CD10 (100% x 49%, p = 0.04) and Bcl-6 (80% x 39%, p = 0.035) were found compared to non-Burkitt's lymphomas. Germinal center (GC) profile was detected in 60% of DLBCLs. Our study suggests particular findings in ARL, as the most frequent phenotype was GC, different from HIV-negative patients. PMID:22358360

  20. FDLBM simulation of double-diffusive mixed convection of shear-thinning fluids between two-square concentric duct annuli

    NASA Astrophysics Data System (ADS)

    Kefayati, GH. R.

    2015-11-01

    Double-diffusive mixed convection of pseudoplastic fluids between two-square concentric duct annuli has been analyzed by FDLBM. Results indicate that the augmentation of Richardson number decreases heat and mass transfer. The fall of the power law index declines heat and mass transfer at Ri = 0.00062 and 0.01. The increase in the size of the adiabatic body enhances the heat and mass transfer in the lid-driven enclosure generally.

  1. 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

  2. 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

  3. Endoscopic appearance of AIDS-related gastrointestinal lymphoma with c-MYC rearrangements: Case report and literature review

    PubMed Central

    Tanaka, Shohei; Nagata, Naoyoshi; Mine, Sohtaro; Igari, Toru; Kobayashi, Taiichiro; Sugihara, Jun; Honda, Haruhito; Teruya, Katsuji; Kikuchi, Yoshimi; Oka, Shinichi; Uemura, Naomi

    2013-01-01

    Acquired immune deficiency syndrome (AIDS)-related lymphoma (ARL) remains the main cause of AIDS-related deaths in the highly active anti-retroviral therapy (HAART) era. Recently, rearrangement of MYC is associated with poor prognosis in patients with diffuse large B-cell lymphoma. Here, we report a rare case of gastrointestinal (GI)-ARL with MYC rearrangements and coinfected with Epstein-Barr virus (EBV) infection presenting with various endoscopic findings. A 38-year-old homosexual man who presented with anemia and was diagnosed with an human immunodeficiency virus infection for the first time. GI endoscopy revealed multiple dish-like lesions, ulcerations, bloody spots, nodular masses with active bleeding in the stomach, erythematous flat lesions in the duodenum, and multiple nodular masses in the colon and rectum. Magnified endoscopy with narrow band imaging showed a honeycomb-like pattern without irregular microvessels in the dish-like lesions of the stomach. Biopsy specimens from the stomach, duodenum, colon, and rectum revealed diffuse large B-cell lymphoma concomitant with EBV infection that was detected by high tissue EBV-polymerase chain reaction levels and Epstein-Barr virus small RNAs in situ hybridization. Fluorescence in situ hybridization analysis revealed a fusion between the immunoglobulin heavy chain (IgH) and c-MYC genes, but not between the IgH and BCL2 loci. After 1-mo of treatment with HAART and R-CHOP, endoscopic appearance improved remarkably, and the histological features of the biopsy specimens revealed no evidence of lymphoma. However, he died from multiple organ failure on the 139th day after diagnosis. The cause of his poor outcome may be related to MYC rearrangement. The GI tract involvement in ARL is rarely reported, and its endoscopic findings are various and may be different from those in non-AIDS GI lymphoma; thus, we also conducted a literature review of GI-ARL cases. PMID:23922484

  4. Endoscopic appearance of AIDS-related gastrointestinal lymphoma with c-MYC rearrangements: case report and literature review.

    PubMed

    Tanaka, Shohei; Nagata, Naoyoshi; Mine, Sohtaro; Igari, Toru; Kobayashi, Taiichiro; Sugihara, Jun; Honda, Haruhito; Teruya, Katsuji; Kikuchi, Yoshimi; Oka, Shinichi; Uemura, Naomi

    2013-08-01

    Acquired immune deficiency syndrome (AIDS)-related lymphoma (ARL) remains the main cause of AIDS-related deaths in the highly active anti-retroviral therapy (HAART) era. Recently, rearrangement of MYC is associated with poor prognosis in patients with diffuse large B-cell lymphoma. Here, we report a rare case of gastrointestinal (GI)-ARL with MYC rearrangements and coinfected with Epstein-Barr virus (EBV) infection presenting with various endoscopic findings. A 38-year-old homosexual man who presented with anemia and was diagnosed with an human immunodeficiency virus infection for the first time. GI endoscopy revealed multiple dish-like lesions, ulcerations, bloody spots, nodular masses with active bleeding in the stomach, erythematous flat lesions in the duodenum, and multiple nodular masses in the colon and rectum. Magnified endoscopy with narrow band imaging showed a honeycomb-like pattern without irregular microvessels in the dish-like lesions of the stomach. Biopsy specimens from the stomach, duodenum, colon, and rectum revealed diffuse large B-cell lymphoma concomitant with EBV infection that was detected by high tissue EBV-polymerase chain reaction levels and Epstein-Barr virus small RNAs in situ hybridization. Fluorescence in situ hybridization analysis revealed a fusion between the immunoglobulin heavy chain (IgH) and c-MYC genes, but not between the IgH and BCL2 loci. After 1-mo of treatment with HAART and R-CHOP, endoscopic appearance improved remarkably, and the histological features of the biopsy specimens revealed no evidence of lymphoma. However, he died from multiple organ failure on the 139(th) day after diagnosis. The cause of his poor outcome may be related to MYC rearrangement. The GI tract involvement in ARL is rarely reported, and its endoscopic findings are various and may be different from those in non-AIDS GI lymphoma; thus, we also conducted a literature review of GI-ARL cases. PMID:23922484

  5. Semantic organisation and handedness: mixed-handedness is associated with more diffuse activation of ambiguous word associates.

    PubMed

    Sontam, Varalakshmi; Christman, Stephen D

    2012-01-01

    Research indicates that there are individual differences in the flexibility and ease with which one retrieves and uses concepts stored in memory. Based on prior research suggesting that mixed-handedness is associated with greater cognitive flexibility, it was hypothesised that mixed-handers have access to a relatively diffuse associative network, where link strengths for closely related and distantly related concepts are not as disparate as in the case of strong-handers. This idea was explored using ambiguous words for stimuli, as ambiguous words are known to have both strong (concepts related via dominant meaning) and weak associates (concepts related via subordinate meaning). Consistent with the prediction, mixed-handers showed equal ease in accessing both strongly and weakly related concepts. In Experiment 1 mixed-handers exhibited equivalent priming for dominant and subordinate associates, while strong-handers exhibited priming for dominant associates only. In Experiment 2 ratings of strength of association for dominant versus subordinate associates were examined. Mixed-handedness was associated with lesser disparity of dominant and subordinate association ratings. PMID:21598173

  6. Professionalisation and social attitudes: a protocol for measuring changes in HIV/AIDS-related stigma among healthcare students

    PubMed Central

    Ahmadi, Keivan; Reidpath, Daniel D; Allotey, Pascale; Hassali, Mohamed Azmi Ahmad

    2013-01-01

    Introduction HIV/AIDS-related stigma affects the access and utilisation of health services. Although HIV/AIDS-related stigma in the health services has been studied, little work has attended to the relationship between professional development and stigmatising attitudes. Hence, in this study, we will extend earlier research by examining the relationship between the stage of professional development and the kinds of stigmatising attitudes held about people living with HIV/AIDS. Methods and analysis A serial cross-sectional design will be combined with a two-point in time longitudinal design to measure the levels of stigma among healthcare students from each year of undergraduate and graduate courses in Malaysia and Australia. In the absence of suitable measures, we will carry out a sequential mixed methods design to develop such a tool. The questionnaire data will be analysed using mixed effects linear models to manage the repeated measures. Ethics and dissemination We have received ethical approval from the Monash MBBS executive committee as well as the Monash University Human Research Ethics Committee. We will keep the data in a locked filing cabinet in the Monash University (Sunway campus) premises for 5 years, after which the information will be shredded and disposed of in secure bins, and digital recordings will be erased in accordance with Monash University's regulations. Only the principal investigator and the researcher will have access to the filing cabinet. We aim to present and publish the results of this study in national and international conferences and peer-reviewed journals, respectively. PMID:23793653

  7. 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.

  8. 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.

  9. 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.

  10. Charge collected by diffusion from an ion track under mixed boundary conditions

    NASA Technical Reports Server (NTRS)

    Edmonds, Larry D.

    1991-01-01

    Charge-carrier diffusion from an ion track in a silicon substrate at least a few hundred microns thick is analyzed. The substrate upper surface is treated as reflective except for a small section, intended to represent a reverse-biased junction, which is treated as a sink. Total charge collected by the sink is calculated by assuming transport to be governed by an ambipolar diffusion equation with temporally constant and spatially uniform carrier lifetime and diffusion coefficient. Present results apply to a normally incident track but could easily be generalized to arbitrary track direction. The collected charge is found to depend on track length and on the electrostatic capacitance, rather than the area, of the sink. Theoretical predictions are compared to the results of a numerical simulation called the Poisson and Continuity Equation Solver (PISCES) for three cases and are found to agree within a factor of two in the worst case.

  11. Noncontact measurement of the thermal diffusivity of IR semi-transparent and semiconducting n-CdMgSe mixed crystals by means of the photothermal radiometry

    NASA Astrophysics Data System (ADS)

    Pawlak, M.; Maliński, M.

    2014-05-01

    In this paper we present results of noncontact measurements of the thermal diffusivity of infrared semi-transparent n-CdMgSe mixed semiconductor crystals by means of the photothermal radiometry (PTR) in a transmission configuration. In order to overcome an influence of the infrared semi-transparency and plasma waves on the PTR signal from n-CdMgSe mixed crystals the samples were covered by thin aluminum foils on both sides. The thermal diffusivities of n-CdMgSe mixed crystals were estimated from PTR phase frequency characteristics using a well-known formula. It was found that the obtained results are underestimated in comparison to thermal diffusivities estimated from the PPE (photopyro-electric) measurements. A three layer model of a PTR signal was applied in order to estimate an error in determination of the thermal diffusivity of a sample caused by aluminum foils.

  12. Diffusion coefficients and heats of mixing in aqueous alkanolamines. Annual report, January-December 1992

    SciTech Connect

    Rowley, R.L.; Oscarson, J.L.

    1993-01-01

    The objective of the work is to provide accurate data on diffusion coefficients and heats of absorption of acid gases in aqueous amine solutions to assist in the design of economical new amine treating systems and to improve the efficiency of existing plants. Specifically covered in the report are measurements of the mutual diffusion coefficient of methyldiethanolamine(MDEA) and diethanolamine in water. Measurements have been made at 25, 50 and 75C and at 0, 20, 35 and 50 wt% amine. Heats of absorption of CO2 into aqueous mixtures of MDEA have also been measured calorimetrically. Results are reported at temperatures of 120 and 260F and pressures of 500 and 1000 psia at total MDEA concentrations of 20, 35 and 50%.

  13. 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.

  14. Diffusion-induced grain boundary migration during ion beam mixing of Au/Cu bilayers

    SciTech Connect

    Alexander, D.E.; Baldo, P.M.; Rehn, L.E.

    1992-09-01

    Experiments were performed to evaluate the effect of 1.5 MeV Kr irradiation on diffusion-induced grain boundary migration (DIGM) in Au/Cu bilayers in the temperature range of 300{le}T{le}050K. The experimental results were consistent with DIGM occurring in bilayers both during irradiation and during annealing treatments. Rutherford backscattering spectrometry showed a nearly uniform distribution of Cu present through the entire thickness of appropriately prepared polycrystalline Au films irradiated or annealed at temperatures {ge}400K. No parallel effect was seen in similarly treated single-crystal films. In each polycrystalline sample studied, irradiation resulted in greater amounts of Cu present uniformly in the Au compared to annealing-only. The magnitudes of measured Cu compositions were substantially greater than that expected solely from grain boundary diffusion. A simple analysis of the process indicated that ion irradiation affects DIGM by increasing the composition of Cu present in alloyed zones and/or by increasing the grain boundary velocity in the Au.

  15. Brief Report: Role of Thymic Reconstitution in the Outcome of AIDS-Related PML.

    PubMed

    Chalkias, Spyridon G; Gheuens, Sarah; Bord, Evelyn; Batson, Stephanie; Koralnik, Igor J

    2015-12-01

    Implications of thymopoiesis in AIDS-related opportunistic infections remain unexplored. We used progressive multifocal leukoencephalopathy (PML), caused by JC virus (JCV), as an opportunistic infection model, and we simultaneously investigated thymic output and T-cell responses against JCV in 22 patients with PML treated with combined antiretroviral therapy. Thymic output was significantly associated with JCV-specific CD4⁺ and CD8⁺ T-cell responses and improved survival. Our data suggest that patients with AIDS-related PML and impaired thymopoiesis are less likely to develop a robust JCV-specific cellular immune response and consequently are at an increased risk for a poor clinical outcome. PMID:26181821

  16. Effect of grossular on garnet-biotite, Fe Mg exchange reactions: evidence from garnet with mixed growth and diffusion zoning

    NASA Astrophysics Data System (ADS)

    Alcock, J.

    1996-07-01

    Garnets that exhibit mixed growth and diffusion zoning are used to evaluate the effect of grossular content on garnet Fe Mg exchange reactions. These garnets from the uppermost amphibolite-facies to granulite-facies gneiss of the Wissahickon Group, southeastern Pennsylvania, show variation in grossular content (0.035< X Ca<0.14) but nearly constant Mg? ( X Mg/( X Mg+ X Fe) and X Mn through the interior indicating re-equilibration of garnet and matrix minerals with respect to iron, magnesium, and manganese. Mg? is not correlated with calcium content, evidence that the effect of calcium on garnet Fe Mg exchange reactions is small or is offset by other interactions in almandine-rich garnets. In either case, the data presented here indicate that correction for calcium content of garnets in the application of garnet-biotite geothermometry to high-grade metapelites is unnecessary and may lead to an overestimate of peak temperature.

  17. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

    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.

  19. Predicting AIDS-related events using CD4 percentage or CD4 absolute counts

    PubMed Central

    Pirzada, Yasmin; Khuder, Sadik; Donabedian, Haig

    2006-01-01

    Background The extent of immunosuppression and the probability of developing an AIDS-related complication in HIV-infected people is usually measured by the absolute number of CD4 positive T-cells. The percentage of CD4 positive cells is a more easily measured and less variable number. We analyzed sequential CD4 and CD8 numbers, percentages and ratios in 218 of our HIV infected patients to determine the most reliable predictor of an AIDS-related event. Results The CD4 percentage was an unsurpassed predictor of the occurrence of AIDS-related events when all subsets of patients are considered. The CD4 absolute count was the next most reliable, followed by the ratio of CD4/CD8 percentages. The value of CD4 percentage over the CD4 absolute count was seen even after the introduction of highly effective HIV therapy. Conclusion The CD4 percentage is unsurpassed as a parameter for predicting the onset of HIV-related diseases. The extra time and expense of measuring the CD4 absolute count may be unnecessary. PMID:16916461

  20. AIDS-Related Factors Predictive of Suicidal Ideation of Low and High Intent among Gay and Bisexual Men.

    ERIC Educational Resources Information Center

    Schneider, Stephen G.; And Others

    1991-01-01

    Studied Acquired Immune Deficiency Syndrome (AIDS)-related stressors and suicidal ideation/intent among 778 gay and bisexual men (none with AIDS). Compared to those who reported no suicidal ideation over past six months, those who reported ideation (n=212) were more likely to report recent bereavement of partner, AIDS-Related Disorder (ARC)…

  1. Transient Liquid-Phase Diffusion Bonding of Aluminum Metal Matrix Composite Using a Mixed Cu-Ni Powder Interlayer

    NASA Astrophysics Data System (ADS)

    Maity, Joydeep; Pal, Tapan Kumar

    2012-07-01

    In the present study, the transient liquid-phase diffusion bonding of an aluminum metal matrix composite (6061-15 wt.% SiCp) has been investigated for the first time using a mixed Cu-Ni powder interlayer at 560 °C, 0.2 MPa, for different holding times up to 6 h. The microstructure of the isothermally solidified zone contains equilibrium precipitate CuAl2, metastable precipitate Al9Ni2 in the matrix of α-solid solution along with the reinforcement particles (SiC). On the other hand, the microstructure of the central bond zone consists of equilibrium phases such as NiAl3, Al7Cu4Ni and α-solid solution along with SiC particles (without any segregation) and the presence of microporosities. During shear test, the crack originates from microporosities and propagates along the interphase interfaces resulting in poor bond strength for lower holding times. As the bonding time increases, with continual diffusion, the structural heterogeneity is diminished, and the microporosities are eliminated at the central bond zone. Accordingly, after 6-h holding, the microstructure of the central bond zone mainly consists of NiAl3 without any visible microporosity. This provides a joint efficiency of 84% with failure primarily occurring through decohesion at the SiC particle/matrix interface.

  2. Case management for dementia in primary health care: a systematic mixed studies review based on the diffusion of innovation model

    PubMed Central

    Khanassov, Vladimir; Vedel, Isabelle; Pluye, Pierre

    2014-01-01

    Background The purpose of this study was to examine factors associated with the implementation of case management (CM) interventions in primary health care (PHC) and to develop strategies to enhance its adoption by PHC practices. Methods This study was designed as a systematic mixed studies review (including quantitative and qualitative studies) with synthesis based on the diffusion of innovation model. A literature search was performed using MEDLINE, PsycInfo, EMBASE, and the Cochrane Database (1995 to August 2012) to identify quantitative (randomized controlled and nonrandomized) and qualitative studies describing the conditions limiting and facilitating successful CM implementation in PHC. The methodological quality of each included study was assessed using the validated Mixed Methods Appraisal Tool. Results Twenty-three studies (eleven quantitative and 12 qualitative) were included. The characteristics of CM that negatively influence implementation are low CM intensity (eg, infrequent follow-up), large caseload (more than 60 patients per full-time case manager), and approach, ie, reactive rather than proactive. Case managers need specific skills to perform their role (eg, good communication skills) and their responsibilities in PHC need to be clearly delineated. Conclusion Our systematic review supports a better understanding of factors that can explain inconsistent evidence with regard to the outcomes of dementia CM in PHC. Lastly, strategies are proposed to enhance implementation of dementia CM in PHC. PMID:24959072

  3. Successful treatment with autologous peripheral blood stem cell transplantation for acquired immunodeficiency syndrome (AIDS)-related malignant lymphoma.

    PubMed

    NAGAI, Yuya; MORI, Minako; INOUE, Daichi; KIMURA, Takaharu; SHIMOJI, Sonoko; TOGAMI, Katsuhiro; TABATA, Sumie; MATSUSHITA, Akiko; NAGAI, Kenichi; Imai, Yukihiro; Takafuta, Toshiro; Takahashi, Takayuki

    2009-11-01

    A 62-year-old man was diagnosed with human immunodeficiency virus (HIV) infection while suffering from recurrent herpes zoster infection. Laboratory examination revealed CD4(+) lymphocyte count 16 cells/mul and HIV loading 150,000 copies/ml at presentation. In addition, he had multiple lymph node swelling. Histologic diagnosis of a biopsied lymph node was diffuse, large, B cell-type malignant lymphoma. The karyotype of the lymphoma cells was t(8;14)(q24;q32), which was confirmed by G-banding and fluorescent in situ hybridization. Positron emission tomography (PET)-combined CT scanning revealed systemic extranodal tumors involving the gastrointestinal tract, pancreas, and bone marrow. The clinical stage of the lymphoma was IVB and the international prognosis index was categorized as high. Complete remission (CR) of the lymphoma was obtained after 2 courses of CHOP (cyclophosphamide, adriamycin, vincristine, prednisolone) chemotherapy and 4 subsequent courses of rituximab-combined CHOP (R-CHOP). Highly active antiretroviral therapy (HAART) was started at the initiation of CHOP. Because of the poor prognosis of AIDS-related lymphoma, he received autologous peripheral blood stem cell transplantation with the MEAM protocol (ranimustine, etoposide, cytarabine, melphalan) as a conditioning procedure without a severe infectious episode. He remains in CR 24 months after the transplantation. PMID:20009441

  4. Productive human immunodeficiency virus infection levels correlate with AIDS-related manifestations in the patient

    SciTech Connect

    Mathez, D.; Paul, D.; de Belilovsky, C.; Sultan, Y.; Deleuze, J.; Gorin, I.; Saurin, W.; Decker, R.; Leibowitch, J. )

    1990-10-01

    Mononuclear cells were obtained from 71 human immunodeficiency virus type 1 (HIV-1) seropositive subjects presenting and first visit either as asymptomatic or with minor symptoms and with CD4 lymphocytes greater than 550 per mm3 (group A, 35 patients) or as patients with AIDS, AIDS-related illnesses, or CD4 lymphocytes less than 400 per mm3 (group B, 36 patients). After 1-5 years of follow-up, 13 patients of group A had essentially retained their initial status (asymptomatics); the 22 others had suffered clinical or immunological deterioration (progressors). Frozen cells were thawed and submitted to lethal gamma-irradiation in vitro (4500 rads; 1 rad = 0.01 Gy) before they were cultured with normal phytohemagglutinin-stimulated lymphocytes to determine radiation-resistant HIV expression ex vivo (R-HEV). HIV antigenemia correlated with R-HEV values in 142 samples (r = 0.92, P less than 0.001) but was a less sensitive predictor of disease than R-HEV. R-HEV was detected in all specimens from patients with major AIDS-related illnesses or HIV-associated CD4 lymphopenia. In 77% of the progressors from group A, R-HEV detection preceded the onset of AIDS-associated disease or CD4 lymphopenia by 1 year (average). Conversely, R-HEV was low or was not detected in 36 sequential specimens from the 13 patients who remained asymptomatic over the following 2-5 years. Thus, persistently low HIV expression in vivo predicted a nondiseased state, whereas higher HIV expression levels seemed necessary for disease to occur. These data indicate that R-HEV is related to productive HIV infection in vivo, the latter acting as a determinant of AIDS-related illnesses. In view of this, measurement of HIV expression levels in the patient should be useful in antiviral efficacy trials.

  5. AIDS-related knowledge, attitudes, and behaviors among juvenile delinquents in Israel.

    PubMed

    Slonim-Nevo, V

    Fifty-six Israeli adolescents under the care of probation officers were interviewed about their AIDS-related knowledge, attitudes, and behaviors. The results suggest that these adolescents put themselves at risk of HIV infection. A substantial proportion of the sample demonstrated a lack of knowledge on issues relevant for AIDS prevention. The majority held negative attitudes toward condoms but were also sexually active, and some had experienced unprotected sexual intercourse, anal sex, and drug use. Most of the respondents, moreover, showed a lack of competence in handling situations that pressure them to act unsafely. Implications for practice are discussed. PMID:1343361

  6. Laser-Induced Thermal Acoustics (LITA): Four-wave mixing measurement of sound speed, thermal diffusivity, and viscosity

    NASA Astrophysics Data System (ADS)

    Cummings, Eric B.

    1994-08-01

    Laser-induced thermal acoustics (LITA) is a promising optical four-wave mixing technique for gasdynamic measurement. The Chi(3) nonlinear process is a sequence of two opto-acoustic effects, electrostriction and absorption/ rapid-thermalization, and the acousto-optic effect. The evolution of the laser-induced acoustic structures temporally modulates Chi(3) and thereby the LITA signal. Time resolution of the signal provides the sound speed, thermal diffusivity, and acoustic damping rate, along with information about atomic or molecular energy transfer rates. LITA can also measure spectra of both the real and imaginary gas susceptibility. The physics of LITA is discussed and the derivation is sketched of a simple analytical expression that accurately describes both the magnitude and time history of the LITA signal. Early experimental results are presented. Sound speeds accurate to 0.5% and transport properties accurate to 30% have been measured in a single-shot without calibration. More realistic modeling should dramatically improve transport-property measurement. LITA spectra have been taken of weak spectral lines of NO2 in concentrations less than 50 ppb. Signal reflectivities as high as 0.0001 have been estimated. New applications of LITA, including velocimetry, are suggested.

  7. Economic empowerment and AIDS-related stigma in rural Kenya: a double-edged sword?

    PubMed

    Gnauck, Katherine; Ruiz, Jamie; Kellett, Nicole; Sussman, Andrew; Sullivan, Mary Ann; Montoya, Maria; Levin, Nick; Tomedi, Angelo; Mwanthi, Mutuku A

    2013-01-01

    Economic empowerment, HIV risk and AIDS-related stigma appear intricately intertwined for women in Kenya. Their interaction must be understood in order to implement effective economic interventions that also decrease HIV risk and stigma. We conducted a qualitative study amongst women in a rural Kamba-speaking community of southeastern Kenya to pursue whether engagement in an economic empowerment initiative (a basket weaving cooperative) influences women's perspectives and experiences with HIV risk and AIDS-related stigma. We conducted seven women's focus groups: participants in the local basket-weaving cooperative comprised four focus groups and non-participants comprised the remaining three groups. The HIV status of the women was not known. Three dominant themes emerged from the focus groups: empowerment, pervasive vulnerability and unanticipated social paradoxes. Contradictions found in these themes suggest that economic empowerment can become a double-edged sword. Economic empowerment enhanced perceived individual, domestic and social community status. However, this enhancement was not protective of domestic violence and perceived HIV risk. Social perceptions may have paradoxically contributed barriers to HIV testing and treatment putting women at greater HIV risk. In conclusion, economic empowerment initiatives for women in developing countries in the context of the HIV epidemic should be coupled with peer mediated support and HIV-risk education. PMID:23668536

  8. HIV and AIDS-related stigma and discrimination: a conceptual framework and implications for action.

    PubMed

    Parker, Richard; Aggleton, Peter

    2003-07-01

    Internationally, there has been a recent resurgence of interest in HIV and AIDS-related stigma and discrimination, triggered at least in part by growing recognition that negative social responses to the epidemic remain pervasive even in seriously affected communities. Yet, rarely are existing notions of stigma and discrimination interrogated for their conceptual adequacy and their usefulness in leading to the design of effective programmes and interventions. Taking as its starting point, the classic formulation of stigma as a 'significantly discrediting' attribute, but moving beyond this to conceptualize stigma and stigmatization as intimately linked to the reproduction of social difference, this paper offers a new framework by which to understand HIV and AIDS-related stigma and its effects. It so doing, it highlights the manner in which stigma feeds upon, strengthens and reproduces existing inequalities of class, race, gender and sexuality. It highlights the limitations of individualistic modes of stigma alleviation and calls instead for new programmatic approaches in which the resistance of stigmatized individuals and communities is utilized as a resource for social change. PMID:12753813

  9. AIDS related knowledge and behaviours among college students, Gondar, Ethiopia: a comparative study.

    PubMed

    Teka, T

    1997-07-01

    AIDS-related knowledge and behaviours among students at the Gondar College of Medical Sciences, Gondar, Ethiopia were evaluated based on identical surveys conducted in 1990 and 1992. One hundred three second year students provided information in 1992. Analysis indicated that 49% were engaged in sexual intercourse and only a third of these group used condom despite their improved knowledge and belief on condom compared to their previous position in 1990 (p < 0.004). On the other hand, their sexual behaviours regarding sexual contact with high risk individuals decreased compared to 1990 (p < 0.0005). Their general level of AIDS-related preventive knowledge increased over time (p < 0.002), although there was no significant difference in knowledge observed among different sexes and departments. Among the sexually active, a large proportion of students (22%) still had sexual contact with high risk individuals and only 33% of them were using safer methods. Continuing efforts, including peer education, specific health education interventions are still crucially needed to bring a positive change in sexual behaviour. PMID:9558757

  10. 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.

  11. Effects of dielectric permittivity and viscosity on diffusion-controlled e/sub s//sup -/ + S reactions in alcoholwater mixed solvents

    SciTech Connect

    Maham, Y.; Freeman, G.R.

    1988-03-24

    The rate constants k/sub 2/ of nearly diffusion controlled reactions of solvated electrons with solute are related to the electrohydrodynamic properties of the solvent; the viscosity eta and dielectric permittivity epsilon of the bulk solvent. Data for reactions with neutral (polar and nonpolar) and charged solutes in methanolwater and ethanolwater mixed solvents are analyzed to display the effects of eta and epsilon. The data support earlier reports that the diffusion coefficients D(e/sub s//sup -/) approx. = D(RO/sup -/) in alcohol and water, but why this is so remains a question

  12. 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.

  13. Responding to AIDS-related bereavement in the South African context.

    PubMed

    Demmer, Craig

    2007-10-01

    AIDS continues to be a death sentence for many individuals living in South Africa where it remains the leading cause of death. Little is currently known about what it is like to experience the loss of a loved one to AIDS from the South African perspective and how to assist individuals who are living in a context vastly different from similarly bereaved individuals in the West. The purpose of this article is to discuss contextual issues that may affect individuals in South Africa who are grieving AIDS-related deaths and to offer preliminary suggestions on how to help these individuals. The author draws on his experience in the province of KwaZulu-Natal working with people affected by the HIV/AIDS epidemic, as well as discussions with practitioners involved in HIV/AIDS care in this region. PMID:17886413

  14. Gender and AIDS-related psychosocial processes: a study of perceived susceptibility, social distance, and homophobia.

    PubMed

    Schieman, S

    1998-06-01

    Over the past decade, researchers have accumulated evidence that suggests six main factors are associated with AIDS-related risk reduction behavior: (a) perceived susceptibility (Dolcini et al., 1995; van der Plight & Richard, 1994); (b) attitudes toward condoms (Catania et al., 1994; Maticka-Tynadale, 1991); (c) personally knowing someone with HIV/AIDS (Joseph et al., 1987); (d) perceived peer norms about risk-reduction (Maticka-Tyndale, 1991); (e) previous sexual activity (Joseph et al., 1987); and (f) self-efficacy (Aspinwall, Kemeny, Taylor, & Schneider, 1991; van der Plight & Richard, 1994). Furthermore, there is some suggestion that the epidemiology and sociocultural constructions of the disease has led to considerable gender, racial, and class differences in awareness of AIDS, perception of HIV threat, and HIV-relevant behavior (Cohan & Atwood, 1994; Dolcini et al., 1995; Gillies, 1994). PMID:9642424

  15. 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

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

    DOE PAGESBeta

    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 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

  17. 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

  18. Understanding internalized HIV/AIDS-related stigmas in the Dominican Republic: a short report.

    PubMed

    Rael, Christine Tagliaferri; Hampanda, Karen

    2016-03-01

    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 < .05), PSC (OR = 3.68; p < .001), and PSF (OR = 1.60; p < .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 DR. PMID:26466239

  19. 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

  20. The political context of AIDS-related stigma and knowledge in a South African township community.

    PubMed

    Forsyth, Brian; Vandormael, Alain; Kershaw, Trace; Grobbelaar, Janis

    2008-07-01

    The purpose of this study was to examine the presentation of AIDS-related stigma and knowledge within the political context of the South African government's response to the AIDS epidemic. It was during the 2000 - 2004 period that key government officials publicly challenged the orthodox views of HIV/AIDS, with the South African president, Thabo Mbeki, actively positing the primary role of poverty and other socio-economic stressors in the progression of the AIDS epidemic. This discursive position had real-time effects for AIDS policy-making and ultimately delayed the implementation of a national antiretroviral (ARV) rollout programme. Consequently this position was criticised by commentators in the media and elsewhere for contributing to an already widespread climate of AIDS stigmatization and misinformation. To shed more light on these claims we conducted a survey in 2005 in Atteridgeville, a South African township, and compared results with those of a similar survey conducted shortly after ARV medications became available in 2004. Results indicated a reduction in AIDS stigma levels across the 1-year period, and that those participants who endorsed contentious political views (such as those expressed by key government officials) were more likely to have a higher level of AIDS-related stigma than those who disagreed. Nevertheless, this study cautions against drawing a causal relationship between the South African government's position and IDS-stigmatizing attitudes, and suggests that further political and social factors be accounted for in an attempt to gain a fuller understanding of this seemingly complex relationship. PMID:18709210

  1. Mixing it up - Measuring diffusion in supercooled liquid solutions of methanol and ethanol at temperatures near the glass transition

    SciTech Connect

    Matthiesen, Jesper; Smith, R. Scott; Kay, Bruce D.

    2011-03-17

    Do liquid mixtures, cooled to temperatures below their freezing point, behave as normal liquids? We address this question using nanoscale films of methanol and ethanol supercooled liquid solutions of varying composition (7 -93% methanol) at temperatures near their glass transition,Tg. The permeation of Kr through these films is used to determine the diffusivities of the supercooled liquid mixtures. We find that the temperature dependent diffusivities of the mixtures are well-fit by a Vogel-Fulcher-Tamman equation indicating that the mixtures exhibit fragile behavior at temperatures just above their Tg. Further, for a given temperature, the composition dependent diffusivity is well-fit by a Vignes-type equation, i.e. the diffusivity of any mixture can be predicted using an exponential weighting of the diffusion of the pure methanol and ethanol diffusivities. These results show that deeply supercooled liquid mixtures can be used to provide valuable insight into the properties of normal liquid mixtures.

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

    NASA Astrophysics Data System (ADS)

    Lesher, C. E.

    1994-05-01

    effects, the rate of chemical homogenization is slow and approximated by the effective binary diffusion coefficient for silica, that is, ln D B-M/SiO2 = -6.70 - (31195/T) + 12.28(0.52 - X(sub SiO2)). Chemical fluxes of Sr and Nd are calculated using Darken's (1948) equation, that is, D c/i = D */i (1 + (d ln gamma i/d ln x(sub i)), relating the chemical diffusion coefficient for species i(D c/i) defined by Fick's law to the self-diffusion coefficent (D */i) for the species and the variation in the species' activity coefficient, gamma (sub i), with concentration x(sub i) along the diffusional pathway. Parameters of the Darken equation are provided in this study and from the literature. Simulations of interdiffusion of basalt and rhyolite quantitatively reproduce salient features of the present experiments including (1) the initial stage of Sr and Nd uphill diffusion into silica-poor regions of couples followed by back diffusion into silica-rich regions, (2) strong asymmetry in the evolving Sr and Nd isotopic profiles, and (3) equilibration of isotopic composition in advance of bulk chemical composition. These results are considered in a magmatic context, where intimate blending of magmas during mixing is frustrated by large rheological constrasts 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.

  3. Probing the Morphology and Diffusivity of Mixed SOA/Squalane Particles Using Size-resolved Composition and Single-particle Measurements.

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

    We present an analysis of the formation and evaporation of mixed-particles comprised of squalane and SOA. First, we use a two-population smog chamber experiment to test the phase-behavior between isotopically-labeled squalane (D62-squalane) and SOA (from α-pinene + O3). Next, we present mixed-particle experiments where one particle type (squalane or SOA) was prepared first to serve as surface area for condensation of the other material, forming the mixed particles. The mixed particles were then subjected to a heating ramp from 22 to 44 ◦C in the chamber. From these experiments, we were able to determine that: 1) squalane and SOA phase separate; 2) the vast majority of squalane is able to evaporate from the mixed particles on the same timescale regardless of the order of preparation; 3) almost all of the SOA mass is comprised of material less volatile than squalane; 4) AMS collection efficiency in these mixed-particle systems varies widely but systematically the course of these experiments where particle phase is dynamic, and can be parameterized as a function of the mass fraction of squalane; and 5) the evaporation profile of squalane can be used to estimate the diffusion coefficient (Dorg) of squalane through SOA.

  4. Impacts of regional mixing on the temperature structure of the equatorial Pacific Ocean. Part 2: Depth-dependent vertical diffusion

    NASA Astrophysics Data System (ADS)

    Jia, Yanli; Furue, Ryo; McCreary, Julian P.

    2015-07-01

    In this study, we use an ocean model to explore how vertical mixing influences temperature in the eastern equatorial Pacific Ocean. Our approach is to change the background diffusion coefficient from a constant value κb to κb + δκ(z) in various subregions of the tropical Pacific, and then to determine the resulting temperature changes in the near-equilibrium response. In a companion paper (Furue et al., 2015), we consider the impacts of depth-independent κb anomalies. Here, we examine the impacts of depth-dependent anomalies that are confined above, or centered on, the mid-depth of the pycnocline. During the first year of adjustment, solutions develop a local temperature response that results largely from the one-dimensional balance δTt =(δκTz)z = δκzTz + δκTzz, with a similar equation for salinity. At this stage, δκ generates temperature and salinity anomalies that are either associated with a density change (dynamical anomalies) or without one (spiciness anomalies). Subsequently, dynamical and spiciness anomalies spread to remote regions by wave radiation and advection, respectively. For positive δκ anomalies confined above the mid-pycnocline, δκzTz tends to produce positive temperature anomalies, which spread to the equator dynamically (by wave radiation) and are still apparent in near-equilibrium solutions. For δκ anomalies confined within the pycnocline (with monopole, dipole, and tripole profiles), the response is dominated by δκzTz, owing to δκ having a smaller vertical scale than T and to the depth range where δκ is large not overlapping well with that where ∣Tzz∣ is; the resulting temperature anomalies tend to shift the pycnocline vertically (dipole profile) or to alter its thickness (monopole and tripole profiles). Positive anomalies from all subregions contribute to an increase of near-surface(upper 50 m) temperature in the eastern equatorial Pacific, the amplitude and location of the warming depending on the depth range of

  5. Impacts of Regional Mixing on the Temperature Structure of the Equatorial Pacific Ocean. Part 2: Depth-Dependent Vertical Diffusion

    NASA Astrophysics Data System (ADS)

    Furue, R.; Jia, Y.; McCreary, J. P., Jr.

    2014-12-01

    In this study, we use an ocean model to explore how vertical mixing influences temperature in the eastern equatorial Pacific Ocean (EEPO). Our approach is to change the background diffusion coefficient from a constant value κbkappa_{b} to κb+δκ(z)kappa_{b}+deltakappa(z) in various subregions of the tropical Pacific, and then to determine the resulting temperature changes in the near-equilibrium response. In a companion paper (Furue et al., 2014, submitted), we consider the impacts of depth-independent κbkappa_b anomalies. Here, we examine the impacts of depth-dependent anomalies that are confined above, or centered on, the mid-depth of the pycnocline. During the first year of adjustment, solutions develop a local temperature response that results largely from the one-dimensional balance, δTt=(δκTz)z=δκzTz+δκTzzdelta T_{t} = (deltakappa T_{z})_{z} = deltakappa_{z}T_{z}+deltakappa T_{zz}, with a similar equation for salinity. At this stage, δκdeltakappa generates temperature and salinity anomalies that are either associated with a density change (dynamical anomalies) or without one (spiciness anomalies). Subsequently, dynamical and spiciness anomalies spread to remote regions by wave radiation and advection, respectively. For positive δκdeltakappa anomalies confined above the mid-pycnocline, δκzTzdeltakappa_{z}T_{z} (δκTzzdeltakappa T_{zz}) tends to produce positive (negative) temperature anomalies, which spread to the equator dynamically (by wave radiation) and are still apparent in near-equilibrium solutions. For δκdeltakappa anomalies confined within the pycnocline (with monopole, dipole, and tripole profiles), the response is dominated by δκzTzdeltakappa_{z}T_{z}, owing to δκdeltakappa having a smaller vertical scale than TT and to δκdeltakappa not overlapping well with TzzT_{zz}; the resulting temperature anomalies tend to shift the pycnocline vertically (dipole profile) or to alter its thickness (monopole and tripole profiles

  6. 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.

  7. Recent advances in the treatment of AIDS-related Kaposi's sarcoma.

    PubMed

    Cattelan, Anna M; Trevenzoli, Marco; Aversa, Savina M L

    2002-01-01

    Kaposi's sarcoma (KS) is the most common malignancy associated with HIV infection and is considered an AIDS defining condition by the US Centers of Disease Control Guidelines. Several advances in the treatment of AIDS-related KS have been achieved over the past few years, even though a gold standard therapy for KS has not yet been defined and treatment must be tailored to individual needs. Since the availability of highly active antiretroviral therapy (HAART), a dramatic clinical response has been documented in patients with KS, making HAART an essential approach in the management of KS in most, if not all, patients with AIDS-related KS. However, in case of aggressive, visceral, and/or life-threatening KS, more complex therapeutic schedules have to be taken into account, including chemotherapy, radiotherapy, and/or immunotherapy. In general, systemic treatment for KS is limited to widespread, symptomatic disease, whereas local interventions are indicated for minimal, cosmetically troublesome lesions. Among new cytotoxic agents, liposomal anthracyclines and paclitaxel are highly effective molecules for KS and have been approved by the US Food and Drug Administration (FDA) as first-line and second-line monotherapy, respectively, for advanced KS. Furthermore, a greater understanding of the pathogenesis of KS has lead to the development of an array of new experimental agents. Many antiangiogenic agents such as AGM 1470 (TNP 470), thalidomide, and glufanide disodium (IM 862) have produced encouraging responses in patients with KS and large clinical trials are in progress. Retinoic acids may also block neoangiogenesis as well as proliferation of KS cells in vitro, and they have been used either systemically or topically with a high response rate. Thus, a topical compound 0.1% alitretinoin gel was approved in 1999 by the FDA for the treatment of skin lesions associated with KS. Human chorionic gonadotropin, a hormonal agent, has shown a strong inhibitory activity in KS

  8. 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. PMID:26923156

  9. 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

    2016-06-01

    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%).

  10. Reducing AIDS-related stigma in developing countries: the importance of theory- and evidence-based interventions.

    PubMed

    Bos, Arjan E R; Schaalma, Herman P; Pryor, John B

    2008-08-01

    In many developing countries persons living with HIV and AIDS experience strong stigma and discrimination, and AIDS-related stigma has an enormous negative impact on their social relationships, access to resources, and psychological well being. Moreover, AIDS-related stigma hampers HIV-related health promotion, including voluntary HIV counselling and testing. In this article, we will argue that programs to reduce AIDS-related stigma are most likely to be effective if these programs are based upon thorough needs assessments, theory- and evidence-based intervention strategies and collaborative planning. A protocol for health promotion programs design is outlined. Furthermore, psychosocial correlates of AIDS-related stigma in developing countries, social-psychological theories that might be useful in designing intervention strategies to reduce stigmatisation and successful elements of previous interventions aimed at stigma reduction are discussed. It is concluded that psychological theory does provide guidelines for the development of stigma-reducing intervention programs, but that such programs can only be effective when based upon context-specific needs assessment and collaborative planning. PMID:18825583

  11. HIV/AIDS-Related Knowledge and Behaviors Among Most-at-Risk Populations in Vietnam

    PubMed Central

    Vian, Taryn; Semrau, Katherine; Hamer, Davidson H; Loan, Le Thi Thanh; Sabin, Lora L

    2012-01-01

    The U.S. President’s Emergency Plan for AIDS Relief (PEPFAR) has supported the Vietnamese Ministry of Health (MOH) in implementing behavior change strategies to slow the HIV epidemic. These programs target commercial sex workers (CSW), injection drug users (IDU), and men who have sex with men (MSM). Using data from a program evaluation to assess effectiveness of the PEPFAR intervention, we conducted a sub-analysis of HIV/AIDS knowledge, sexual behaviors, and injection drug risk behaviors among 2,199 Vietnamese respondents, including those reporting recent contact with an outreach worker and those who did not report contact. We found overall high levels of HIV/AIDS knowledge, low rates of needle sharing, and moderate to high rates of inconsistent condom use. Average knowledge scores of IDU were significantly higher than non-IDU for antiretroviral treatment knowledge, while MSM had significantly less knowledge of treatment compared to non-MSM. HIV/AIDS-related knowledge was not significantly associated with needle-sharing practices. Knowledge was modestly but significantly associated with more consistent use of condoms with primary and commercial sex partners, even after controlling for contact with an outreach worker. Contact with an outreach worker was also an independent predictor of more consistent condom use. Outreach programs appear to play a meaningful role in changing sexual behavior, though the effect of outreach on IDU risk behaviors was less clear. More research is needed to understand the relationship between outreach programs and skill development, motivation, and use of referral services by most-at-risk populations in Vietnam. PMID:23173025

  12. 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

  13. 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

  14. 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.

  15. Mixed micelles of Triton X-100, sodium dodecyl dioxyethylene sulfate, and synperonic l61 investigated by NOESY and diffusion ordered NMR spectroscopy.

    PubMed

    Denkova, Pavletta S; Van Lokeren, Luk; Willem, Rudolph

    2009-05-14

    Mixed micelles formed from nonionic surfactant Triton X-100 (TX100), anionic surfactant sodium dodecyl dioxyethylene sulfate (SDP2S), and triblock copolymer Synperonic L61 (SL61) were investigated by 1H NMR spectroscopy. The size and shape of the aggregates were determined by diffusion ordered NMR spectroscopy (DOSY), while 2D nuclear Overhauser enhanced spectroscopy (NOESY) NMR was used to study the mutual spatial arrangement of the surfactant molecules in the aggregated state. An average micellar hydrodynamic radius of 3.6 nm, slightly increasing upon increasing TX100 molar fraction, was found for the mixed systems without additives. Addition of SL61 to the mixed micellar systems results in a slight increase of micellar radii. In the presence of AlCl3, an increase of TX100/SDP2S micellar sizes from 4 to 10 nm was found when increasing the SDP2S molar fraction. The mixed TX100/SDP2S micelles in the presence of both AlCl3 and polymer SL61 are almost spherical, with a radius of 4.5 nm. 2D NOESY data reveal that, as the individual TX100 micelles, mixed TX100/SDP2S and TX100/SDP2S/SL61/AlCl3 micelles also have a multilayer structure, with partially overlapping internal and external layers of TX100 molecules. In these mixed micelles, the SDP2S molecules are located at the level of the external layer of TX100 molecules, whereas the SL61 polymer is partially incorporated inside of the micellar core. PMID:19385612

  16. 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

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

    NASA Astrophysics Data System (ADS)

    Nguyen, H. Lee; Wey, Ming-Jyh

    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.

  18. 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.

  19. 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.

  20. Numerical analysis of reaction-diffusion effects on species mixing rates in turbulent premixed methane-air combustion

    SciTech Connect

    Richardson, E.S.; Grout, R.W.; Chen, J.H.; Sankaran, R.

    2010-03-15

    The scalar mixing time scale, a key quantity in many turbulent combustion models, is investigated for reactive scalars in premixed combustion. Direct numerical simulations (DNS) of three-dimensional, turbulent Bunsen flames with reduced methane-air chemistry have been analyzed in the thin reaction zones regime. Previous conclusions from single step chemistry DNS studies are confirmed regarding the role of dilatation and turbulence-chemistry interactions on the progress variable dissipation rate. Compared to the progress variable, the mixing rates of intermediate species is found to be several times greater. The variation of species mixing rates are explained with reference to the structure of one-dimensional premixed laminar flames. According to this analysis, mixing rates are governed by the strong gradients which are imposed by flamelet structures at high Damkoehler numbers. This suggests a modeling approach to estimate the mixing rate of individual species which can be applied, for example, in transported probability density function simulations. Flame-turbulence interactions which modify the flamelet based representation are analyzed. (author)

  1. Pretransitional diffuse neutron scattering in the mixed perovskite relaxor K1-xLixTaO3

    NASA Astrophysics Data System (ADS)

    Yong, Grace; Toulouse, Jean; Erwin, Ross; Shapiro, Stephen M.; Hennion, Bernard

    2000-12-01

    Several previous studies of K1-xLixTaO3 (KLT) have revealed the presence, above the structural transition, of polar nanoregions. Recently, these have been shown to play an essential role in the relaxor behavior of KLT. In order to characterize these regions, we have performed a neutron-scattering study of KLT crystals with different lithium concentrations, both above and below the critical concentration. This study reveals the existence of diffuse scattering that appears upon formation of these regions. The rodlike distribution of the diffuse scattering along cubic directions indicates that the regions form in the shape of discs in the various cubic planes. From the width of the diffuse scattering we extract values for a correlation length or size of the regions as a function of temperature. Finally, on the basis of the reciprocal lattice points around which the diffuse scattering is most intense, we conclude that the regions have tetragonal symmetry. The large increase in Bragg intensities at the first-order transition suggests that the polar regions freeze to form large structural domains and the transition is triggered by the percolation of strain fields through the crystals.

  2. 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…

  3. A NEW MODEL FOR MIXING BY DOUBLE-DIFFUSIVE CONVECTION (SEMI-CONVECTION). I. THE CONDITIONS FOR LAYER FORMATION

    SciTech Connect

    Mirouh, G. M.; Garaud, P.; Traxler, A. L.; Wood, T. S.; Stellmach, S.

    2012-05-01

    The process referred to as 'semi-convection' in astrophysics and 'double-diffusive convection in the diffusive regime' in Earth and planetary sciences occurs in stellar and planetary interiors in regions which are stable according to the Ledoux criterion but unstable according to the Schwarzschild criterion. In this series of papers, we analyze the results of an extensive suite of three-dimensional (3D) numerical simulations of the process, and ultimately propose a new 1D prescription for heat and compositional transport in this regime which can be used in stellar or planetary structure and evolution models. In a preliminary study of the phenomenon, Rosenblum et al. showed that, after saturation of the primary instability, a system can evolve in one of two possible ways: the induced turbulence either remains homogeneous, with very weak transport properties, or transitions into a thermo-compositional staircase where the transport rate is much larger (albeit still smaller than in standard convection). In this paper, we show that this dichotomous behavior is a robust property of semi-convection across a wide region of parameter space. We propose a simple semi-analytical criterion to determine whether layer formation is expected or not, and at what rate it proceeds, as a function of the background stratification and of the diffusion parameters (viscosity, thermal diffusivity, and compositional diffusivity) only. The theoretical criterion matches the outcome of our numerical simulations very adequately in the computationally accessible 'planetary' parameter regime and can be extrapolated to the stellar parameter regime. Subsequent papers will address more specifically the question of quantifying transport in the layered case and in the non-layered case.

  4. Creating social spaces to tackle AIDS-related stigma: reviewing the role of church groups in Sub-Saharan Africa.

    PubMed

    Campbell, C; Skovdal, M; Gibbs, A

    2011-08-01

    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

  5. 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

  6. 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

  7. Plasma-Enhanced Atomic Layer Deposition of Ruthenium-Titanium Nitride Mixed-Phase Layers for Direct-Plate Liner and Copper Diffusion Barrier Applications

    NASA Astrophysics Data System (ADS)

    Gildea, Adam James

    Current interconnect networks in semiconductor processing utilize a sputtered TaN diffusion barrier, Ta liner, and Cu seed to improve the adhesion, microstructure, and electromigration resistance of electrochemically deposited copper that fills interconnect wires and vias. However, as wire/via widths shrink due to device scaling, it becomes increasingly difficult to have the volume of a wire/via be occupied with ECD Cu which increases line resistance and increases the delay in signal propagation in IC chips. A single layer that could serve the purpose of a Cu diffusion barrier and ECD Cu adhesion promoter could allow ECD Cu to occupy a larger volume of a wire/via, leading to a decrease in line resistance and decrease in signal delay. Previous work has shown RuTaN, RuWCN, and RuCo films can act as Cu diffusion barriers and be directly platable to thickness of 2-3nm. However, other material selections may prove as effective or possibly better. Mixed-phase films of ruthenium titanium nitride grown by atomic layer deposition (ALD) were investigated for their performance as a Cu diffusion barrier and as a surface for the direct plating of ECD Cu. All Ru was deposited by plasma-enhanced atomic layer deposition (PEALD) while TiN was deposited by either thermal ALD or PEALD. RuTiN, films with thermal ALD TiN and a Ru:Ti of 20:1 showed barrier performance comparable to PVD TaN at 3-4 nm thickness and 15 nm planar films were directly platable. Follow up work is certainly needed for this material set, yet initial results indicate RuTiN could serve as an effective direct plate liner for Cu interconnects.

  8. On the spatial coherence in mixed sound fields and its application to signal-to-diffuse ratio estimation.

    PubMed

    Thiergart, Oliver; Del Galdo, Giovanni; Habets, Emanuël A P

    2012-10-01

    Many applications in spatial sound recording and processing model the sound scene as a sum of directional and diffuse sound components. The power ratio between both components, i.e., the signal-to-diffuse ratio (SDR), represents an important measure for algorithms which aim at performing robustly in reverberant environments. This contribution discusses the SDR estimation from the spatial coherence between two arbitrary first-order directional microphones. First, the spatial coherence is expressed as function of the SDR. For most microphone setups, the spatial coherence is a complex function where both the absolute value and phase contain relevant information on the SDR. Secondly, the SDR estimator is derived from the spatial coherence function. The estimator is discussed for different practical microphone setups including coincident setups of arbitrary first-order directional microphones and spaced setups of identical first-order directional microphones. An unbiased SDR estimation requires noiseless coherence estimates as well as information on the direction-of-arrival of the directional sound, which usually has to be estimated. Nevertheless, measurement results verify that the proposed estimator is applicable in practice and provides accurate results. PMID:23039430

  9. 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.

  10. Global Confinement, Sawtooth Mixing, and Stochastic Diffusion Ripple Loss of Fast ICRF-driven H+ Minority Ions in TFTR

    SciTech Connect

    Petrov, M.P.; Bell, R.; Budny, R.V.; Gorelenkov, N.N.; Medley, S.S.; Zweben, S.J., PPPL

    1998-07-01

    This paper presents studies of ICRF-driven H+ minority ions in TFTR (Tokamak Fusion Test Reator) deuterium plasmas using primarily passive Ho flux detection in the energy range of 0.2-1.0 MeV with some corroborating active (lithium pellet charge exchange) measurements. It is shown that in the passive mode the main donors for the neutralization of H+ ions in this energy range are C5+ ions. The measured effective H+ tail temperatures range from 0.15 MeV at an ICRF power of 2 MW to 0.35 MeV at 6 MW. Analysis of the ICRF-driven H+ ion energy balance has been performed on the basis of the dependence of effective H+ temperatures on the plasma parameters. The analysis showed that H+ confinement times are comparable with their slowing-down times and tended to decrease with increasing ICRF power. Radial redistribution of ICRF-driven H+ ions was detected when giant sawtooth crashes occurred during the ICRF heating. The redistribution affected ions with energy below 0.7-0.8 MeV. The sawtooth crashes displace H+ ions outward along the plasma major radius into the stochastic ripple diffusion domain were those ions are lost in about 10 milliseconds. These observations are consistent with the model of the redistribution of energetic particles developed previously to explain the results of deuterium-tritium alpha-particle redistribution due to sawteeth observed in TFTR. The experimental data are also consistent with ORBIT code simulations of H+ stochastic ripple diffusion losses.

  11. A New Model for Mixing by Double-diffusive Convection (Semi-convection). III. Thermal and Compositional Transport through Non-layered ODDC

    NASA Astrophysics Data System (ADS)

    Moll, Ryan; Garaud, Pascale; Stellmach, Stephan

    2016-05-01

    Oscillatory double-diffusive convection (ODDC; also known as semi-convection) refers to a type of double-diffusive instability that occurs in regions of planetary and stellar interiors that have a destabilizing thermal stratification and a stabilizing mean molecular weight stratification. In this series of papers, we use an extensive suite of three-dimensional (3D) numerical simulations to quantify the transport of heat and chemical species by ODDC. Rosenblum et al. first showed that ODDC can either spontaneously form layers that significantly enhance the transport of heat and chemical species compared to microscopic transport or remain in a state dominated by large-scale gravity waves, in which there is a more modest enhancement of the turbulent transport rates. Subsequent studies in this series focused on identifying under what conditions layers form and quantifying transport through layered systems. Here we proceed to characterize transport through systems that are unstable to ODDC, but do not undergo spontaneous layer formation. We measure the thermal and compositional fluxes in non-layered ODDC from both two-dimensional (2D) and 3D numerical simulations, and show that 3D simulations are well approximated by similar simulations in a 2D domain. We find that the turbulent mixing rate in this regime is weak and can, to a first-level approximation, be neglected. We conclude by summarizing the findings of papers I through III into a single prescription for transport systems unstable to ODDC.

  12. 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.

  13. With and without: the bereavement experiences of gay men who have lost a partner to non-AIDS-related causes.

    PubMed

    Hornjatkevyc, Nina L

    2011-10-01

    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 contexualized meanings regarding the participants' diverse experiences. The themes identified areas of similarity and difference between the bereavement of these participants from those who have participated in general bereavement studies and from those who have lost a partner to AIDS. Implications for counseling practice and further research are discussed. PMID:24501836

  14. 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. PMID:20974090

  15. 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

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

    PubMed

    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

  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. The Effect of Geochemical Reaction on Convective Mixing in a Gravitationally Unstable Diffusive Boundary Layer in Porous Media: Geological Storage of CO2 in Saline Aquifers

    NASA Astrophysics Data System (ADS)

    Ghesmat, Karim; Hassanzadeh, Hassan; Abedi, Jalal

    2010-11-01

    The storage of carbon dioxide and acid gases in deep geological formations is considered a promising option for mitigation of greenhouse gas emissions. Understanding of the primary mechanisms, such as convective mixing and geochemistry that affect the long-term geostorage process in deep saline aquifers is of prime importance. First, a linear stability analysis of an unstable diffusive boundary layer in porous media is presented, where the instability occurs due to a density difference between the carbon dioxide saturated brine and the resident brine. The linear stability results have revealed that geochemistry stabilizes the boundary layer. A detailed physical discussion is also presented with an examination of vorticity and concentration eigenfunctions and streamlines' contours to reveal how the geochemical reaction may affect these physical terms. Second, nonlinear direct numerical simulations are presented, in which the evolution of density-driven instabilities for different reaction rates are discussed. The results indicate that the boundary layer will be more stable for systems with a higher rate of reaction. However, the quantitative analyses show that more carbon dioxide may be removed from the supercritical free phase as the flux at the boundary is higher for flow systems coupled with stronger geochemical reactions.

  19. 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.

  20. 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

  1. PHASE II AIDS MALIGNANCY CONSORTIUM TRIAL OF TOPICAL HALOFUGINONE IN AIDS-RELATED KAPOSI’S SARCOMA

    PubMed Central

    Koon, Henry B.; Fingleton, Barbara; Lee, Jeannette Y.; Geyer, Julia T.; Cesarman, Ethel; Parise, Robert A.; Egorin, Merrill J.; Dezube, Bruce J.; Aboulafia, David; Krown, Susan E.

    2010-01-01

    Using a novel blinded intra-patient vehicle control design, we conducted a phase II study of topically-administered halofuginone, an angiogenesis inhibitor that inhibits collagen type-I and matrix metalloproteinases (MMPs), in patients with AIDS-related Kaposi’s sarcoma (KS). Serial KS biopsies assessed treatment effects on angiogenic factors and KSHV-LANA. We observed marked heterogeneity of KSHV-LANA expression. Although the small number of subjects whose response could be evaluated precluded definitive assessment of halofuginone’s efficacy, we observed a significant decrease in type-I collagen only in halofuginone-treated lesions, but no effect on MMP-2. The trial design is applicable to future studies of topical agents. PMID:21068672

  2. Help-seeking for AIDS-related concerns: a comparison of gay men with various HIV diagnoses.

    PubMed

    Hays, R B; Catania, J A; McKusick, L; Coates, T J

    1990-10-01

    Examined help-seeking and psychological distress among four groups of gay men (30 AIDS-diagnosed, 107 HIV-seropositive, 149 HIV-seronegative, 244 untested) in the AIDS Behavioral Research Project, a longitudinal survey of San Francisco gay men. The men reported high levels of anxiety, depression, and help-seeking from their social networks. AIDS-diagnosed and HIV-positives reported the most AIDS worry and were the most likely to seek help. High percentages of AIDS-diagnosed men sought help from all sources (peers, professionals, family), whereas nondiagnosed men were more likely to seek help from peers. Regardless of the men's HIV status, peers were perceived to be the most helpful source. Family members were less likely sought and perceived as least helpful. The strengths and limitations of peers as social support providers for AIDS-related concerns are discussed, including implications for the design of community programs to enhance the abilities of peer helpers. PMID:2075900

  3. 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

  4. HIV/AIDS-related stigmatizing and discriminatory attitudes and recent HIV testing among men who have sex with men in Beijing.

    PubMed

    Li, Xuefeng; Lu, Hongyan; Ma, Xiaoyan; Sun, Yanming; He, Xiong; Li, Chunmei; Raymond, H F; McFarland, Willi; Pan, Stephen W; Shao, Yiming; Vermund, Sten H; Xiao, Yan; Ruan, Yuhua; Jia, Yujiang

    2012-04-01

    This study assessed the correlates of recent HIV testing and HIV/AIDS-related stigmatizing and discriminatory attitudes among men who have sex with men (MSM) in Beijing, China. A cross-sectional study probed demographics, sexual and drug use behaviors, HIV testing, and prevention services. Of 500 participants, 39.3% recently received a test for HIV. Recent testing was independently associated with expressing lower levels of HIV/AIDS-related stigmatizing and discriminatory attitudes, more male sex partners, no female sexual partners and knowing HIV status of their last male partner. Expressing lower levels of HIV/AIDS-related stigmatizing and discriminatory attitudes was independently associated with recent testing, younger age, and knowing HIV status of their last male partner. This study revealed that HIV/AIDS-related stigmatizing and discriminatory attitudes were common and inversely associated with recent HIV testing. Low levels of testing highlighted the urgent needs to reduce HIV/AIDS-related stigma and discrimination and expand HIV testing among MSM in Beijing. PMID:22350831

  5. AIDS-related myopathy.

    PubMed

    Sheikh, Rafiq A.; Yasmeen, Shagufta; Munn, Robert; Ruebner, Boris H.; Ellis, William G.

    1999-09-01

    Infection with the human immunodeficiency virus (HIV) is often associated with the acquired immunodeficiency syndrome (AIDS), and wasting is one of the defining clinical features of AIDS. Muscular weakness due to myopathy may develop at any stage of HIV infection. We report two illustrative cases of HIV-associated myopathies. One was due to inflammatory myosits most likely directly related to the HIV infection, and the other was most likely the result of mitochondrial damage due to zidovudine, a nucleoside analogue commonly used in treating HIV infection. Biopsies from both patients showed alterations of myofiber structures, of varying severity, culminating in necrosis, lipid droplets, and lymphoplasmocytic inflammatory response. The zidovudine-treated patient also showed distinctive mitochondrial changes, predominantly enlargement, variation in shape and size, and disorganization of the cristae. These two types of HIV-associated inflammatory myopathies are reviewed, along with other HIV-associated myopathies, including HIV wasting syndrome, nemaline rod myopathy, pyomyositis, rhabdomyolysis, cardiomyopathy, and other miscellaneous myopathies associated with HIV infection. PMID:11810429

  6. HIV/AIDS - Related Knowledge, Attitudes, and Sexual Practices among Migrant Wives in Rural Anhui Province, China

    PubMed Central

    Zou, Huachun; Dai, Xin; Meng, Xiaojun; Wang, Huadong; Jiang, Chao; Wang, Yanchun; Zhang, Lin; Gao, Yongqing; Tang, Song; Xu, Tan; Sun, Wenjie; Wen, Yufeng

    2015-01-01

    Background Migrant wives have been increasing in some poor rural regions of China and they may bridge HIV transmission across regions. This study aimed to assess HIV/AIDS-related knowledge, attitudes and sexual practices among this population in rural Anhui Province, China. Methods A cross-sectional survey was conducted with questionnaire of HIV/AIDS-related knowledge, attitudes, and sexual practices between June 2011 and May 2012. A total of 730 migrant wives and 207 local women were enrolled in this study. Unpaired T-test, Chi-square was utilized to compare the difference of HIV/AIDS knowledge, attitudes and sexual practices between migrant wives and local women. Results Around 80% of the migrant wives were from Yunnan, Guizhou, or Sichuan Provinces. The main sources of HIV/AIDS information were TV/radio, posters, and newspapers/periodicals. HIV/AIDS knowledge level among migrant wives was significantly lower than that among local women (e.g. 47.1% vs 57.0% (p<0.001) answered “Yes” for the question “Can an apparently healthy person be HIV-infected?”), and stigma and prejudice towards HIV/AIDS among migrant wives were more common than those among local women (e.g. 73.2% vs 65.7% (p=0.006) answered “No” for the question “If a shopkeeper or food seller had the HIV, would you buy food from them?”). Compared to local women, migrant wives were more likely to have ever had sex during menstruation (6.8% vs 3.4%, p=0.065) and extramarital sex (17.5% vs 10.1%, p=0.01), and were less likely to consistently use condoms with their husbands (45.8% vs 57.5%, p<0.001) or extramarital sex partners (48.8% vs 58.95, p<0.001). Conclusions Migrant wives in rural China had a low HIV/AIDS knowledge level and high prevalence of stigma and prejudice and risky sexual behaviors. Local HIV/AIDS prevention programs should target this neglected population. PMID:25844269

  7. Toxoplasma gondii Infection in Kyrgyzstan: Seroprevalence, Risk Factor Analysis, and Estimate of Congenital and AIDS-Related Toxoplasmosis

    PubMed Central

    Bodosheva, Aigerim; Kuttubaev, Omurbek; Hehl, Adrian B.; Tanner, Isabelle; Ziadinov, Iskender; Torgerson, Paul R.; Deplazes, Peter

    2013-01-01

    Background HIV-prevalence, as well as incidence of zoonotic parasitic diseases like cystic echinococcosis, has increased in the Kyrgyz Republic due to fundamental socio-economic changes after the breakdown of the Soviet Union. The possible impact on morbidity and mortality caused by Toxoplasma gondii infection in congenital toxoplasmosis or as an opportunistic infection in the emerging AIDS pandemic has not been reported from Kyrgyzstan. Methodology/Principal Findings We screened 1,061 rural and 899 urban people to determine the seroprevalence of T. gondii infection in 2 representative but epidemiologically distinct populations in Kyrgyzstan. The rural population was from a typical agricultural district where sheep husbandry is a major occupation. The urban population was selected in collaboration with several diagnostic laboratories in Bishkek, the largest city in Kyrgyzstan. We designed a questionnaire that was used on all rural subjects so a risk-factor analysis could be undertaken. The samples from the urban population were anonymous and only data with regard to age and gender was available. Estimates of putative cases of congenital and AIDS-related toxoplasmosis in the whole country were made from the results of the serology. Specific antibodies (IgG) against Triton X-100 extracted antigens of T. gondii tachyzoites from in vitro cultures were determined by ELISA. Overall seroprevalence of infection with T. gondii in people living in rural vs. urban areas was 6.2% (95%CI: 4.8–7.8) (adjusted seroprevalence based on census figures 5.1%, 95% CI 3.9–6.5), and 19.0% (95%CI: 16.5–21.7) (adjusted 16.4%, 95% CI 14.1–19.3), respectively, without significant gender-specific differences. The seroprevalence increased with age. Independently low social status increased the risk of Toxoplasma seropositivity while increasing numbers of sheep owned decreased the risk of seropositivity. Water supply, consumption of unpasteurized milk products or undercooked meat, as

  8. AIDS-related knowledge, attitudes and behaviour among South African street youth: reflections on power, sexuality and the autonomous self.

    PubMed

    Swart-Kruger, J; Richter, L M

    1997-09-01

    Street children in South Africa are, in the main, between the ages of 11 and 17 years. Rape, prostitution, sexual bartering and exchange, casual sex and romantic sexual relationships all occur in the experiences of young people who live and work on inner-city streets. In this study, the AIDS-related knowledge, attitudes and behaviour of 141 street youth, living in seven large cities in South Africa, were elicited in focus group discussions. At the time of the study, 79 boys (56%) were living in shelters run by nongovernmental and welfare organisations, while 62 boys (44%) were sleeping "rough". The results, both qualitative and quantitative, indicated that the AIDS knowledge of South African street children was comparable to levels reported for groups of "hard-to-reach" youth in other parts of the world. Fear of HIV infection did not appear in a list of day-to-day priorities constructed by the children, a list dominated by survival concerns with food, money and clothes. However, more than half of the boys conceded that they engaged in sex for money, goods or protection, several boys indicated that they had been raped, and most reported being sexually active with "girlfriends", who themselves frequently engaged in transactional sex. The findings are interpreted in terms of the relationships between power dynamics surrounding race and age, and how they affect self-initiated controls over sexuality and sexual protection. PMID:9255928

  9. 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. PMID:25323941

  10. A systematic review of HIV/AIDS-related stigma and discrimination in India: current understanding and future needs.

    PubMed

    Bharat, Shalini

    2011-01-01

    HIV/AIDS-related stigma is recognised as a major barrier to HIV prevention efforts and an impediment to mitigating its impact on individuals and communities. This paper reviews the existing research literature on AIDS stigma in India with the objective of documenting the current status of research, highlighting major findings and identifying key gaps remaining. Thirty publications were identified through a careful search of which a majority focused on stigma assessment and very few on stigma measurement, conceptual aspects of stigma or stigma reduction interventions. A few standardised stigma measures are available but more are required to assess causes of stigma among general population and compounded and internalised stigma among positive people. Research exploring linkages between stigma and HIV services uptake or the effect of HIV care and treatment programs on stigma levels are largely missing and need to be prioritised. In addition, more research is needed to advance conceptual understanding of stigma within the cultural context of the country including research on the neglected groups such as, transgender people. Context-specific (health care, community) interventions are needed to address various forms of stigma - enacted, perceived, internalised and layered - including structural approaches besides inter-personal and information-based approaches. A major gap relates to meager research on developing and evaluating stigma reduction interventions and needs priority focus. Overall, the review recommends developing a national agenda on AIDS stigma research and interventions to help realise the government's goal of stigma reduction. PMID:23237728

  11. 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

  12. 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,…

  13. 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'…

  14. 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…

  15. Autograft HIV-DNA Load Predicts HIV-1 Peripheral Reservoir After Stem Cell Transplantation for AIDS-Related Lymphoma Patients

    PubMed Central

    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

    Abstract 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/106 autograft mononuclear cells, range 13–706 vs. 82 HIV-DNA copies/106 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 (R2=0.84, p=0.01) to month 12 follow-up (R2=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. PMID:25581618

  16. Risk factors for HIV infection in male sexual contacts of men with AIDS or an AIDS-related condition.

    PubMed

    Coates, R A; Calzavara, L M; Read, S E; Fanning, M M; Shepherd, F A; Klein, M H; Johnson, J K; Soskolne, C L

    1988-10-01

    A total of 246 healthy male sexual contacts of men with either acquired immunodeficiency syndrome (AIDS) or an AIDS-related condition were recruited into a prospective study in Toronto, Canada between July 1984 and July 1985. At induction, data were collected on the sexual relationship between the contact and his primary case, sexual activities with other men, history of sexually transmitted diseases and other diseases, and use of recreational drugs. At recruitment, 144 sexual contacts had antibodies to human immunodeficiency virus (HIV); 102 of the contacts were seronegative at induction and at three months following recruitment. No association between HIV seropositivity and total number of sexual partners could be demonstrated. In univariate and multivariate analyses, receptive and insertive anal intercourse with the primary cases, and activities which either indicated or potentially caused anorectal mucosal injury (rectal douching, perianal bleeding, receipt of objects in ano, and receptive fisting) were strongly associated with HIV seropositivity. In the final multiple logistic regression model, two significant interaction effects were observed: the interaction between receptive anal intercourse and insertive anal intercourse and that between receptive anal intercourse and the anorectal mucosal injury index. These two interaction terms had negative regression coefficients which suggested that change in one sexual activity would not decrementally reduce risk of HIV infection without a comparable modification in the other activity. No association could be demonstrated between oral-genital and oral-anal sexual contact and odds ratios for these sexual activities declined to levels below 1.0 when adjusted for frequency of receptive anal intercourse. PMID:3421239

  17. Fulminant inflammatory leukoencephalopathy associated with HAART-induced immune restoration in AIDS-related progressive multifocal leukoencephalopathy.

    PubMed

    Vendrely, Aurélie; Bienvenu, Boris; Gasnault, Jacques; Thiebault, Jean Baptiste; Salmon, Dominique; Gray, Françoise

    2005-04-01

    HAART-induced immune restoration is beneficial for patients with AIDS-related progressive multifocal leukoencephalopathy (PML). However, in rare instances, an immune-reconstitution inflammatory syndrome (IRIS) may cause paradoxical clinical deterioration. We report the neuropathological study of an AIDS patient who presented with progressive cognitive deterioration; CD4(+) count was 117 and the HIV viral load >10(4); imaging showed non-enhancing lesions consistent with PML. Following initiation of HAART, CD4(+) was 300 and HIV viral load <10(3), but his neurological symptoms continued to deteriorate. Imaging revealed an increase in the size and number of lesions and enhancement of all the lesions. A stereotactic biopsy showed severe inflammatory and demyelinating lesions with marked infiltration by macrophages and T lymphocytes in the absence of a detectable infectious agent. Despite high doses of steroids, the patient died 3 months after admission. Autopsy showed two types of lesions: (1) active inflammatory PML changes with abundant JC virus, and intraparenchymal and perivascular infiltration by T lymphocytes, and (2) acute perivenous leukoencephalitis devoid of JC virus. Most lymphocytes were CD8(+) lymphocytes; CD4(+) lymphocytes were virtually absent. Two pathological reactions were associated with the paradoxical clinical deterioration related to dysregulation of the immune response characteristic of IRIS in PML: (1) an accentuation of JCV infection, and (2) a nonspecific acute perivenous leukoencephalitis. We suggest that both these types of lesions are due to an imbalance of CD8(+)/CD4(+) T cells, with massive infiltration of the cerebral parenchyma by CD8(+) cytotoxic T lymphocytes in the absence of sufficient CD4(+) response. Better understanding of the mechanisms of the IRIS may enable prevention or cure of this severe, sometimes fatal complication of HAART. PMID:15739098

  18. 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. PMID:25581618

  19. The influence of personality disorder indication, social support, and grief on alcohol and cocaine use among HIV-positive adults coping with AIDS-related bereavement.

    PubMed

    Hansen, Nathan B; Cavanaugh, Courtenay E; Vaughan, Ellen L; Connell, Christian M; Tate, David C; Sikkema, Kathleen J

    2009-04-01

    Substance use is prevalent among HIV-positive adults and linked to a number of adverse health consequences; however little is known about risk and protective factors that influence substance use among HIV-positive adults coping with AIDS-related bereavement. Using structural equation modeling (SEM), male gender, diagnostic indications of antisocial and borderline personality disorders (PD), and grief severity were tested as risk factors, and social support as a protective factor, for alcohol and cocaine use among a diverse sample of 268 HIV-positive adults enrolled in an intervention for AIDS-related bereavement. Results indicated that the hypothesized model fit the study data. Male gender, PD indication, and social support had direct effects on substance use. PD had significant indirect effects on both alcohol and cocaine use, mediated by social support, but not by grief. Finally, both PD and social support had significant, but opposite, effects on grief. Implications for intervention and prevention efforts are discussed. PMID:17846878

  20. A comparison of HIV/AIDS-related stigma in four countries: Negative attitudes and perceived acts of discrimination towards people living with HIV/AIDS☆

    PubMed Central

    Genberg, Becky L.; Hlavka, Zdenek; Konda, Kelika A.; Maman, Suzanne; Chariyalertsak, Suwat; Chingono, Alfred; Mbwambo, Jessie; Modiba, Precious; Van Rooyen, Heidi; Celentano, David D.

    2010-01-01

    HIV/AIDS-related stigma and discrimination have a substantial impact on people living with HIV/AIDS (PLHA). The objectives of this study were: (1) to determine the associations of two constructs of HIV/AIDS-related stigma and discrimination (negative attitudes towards PLHA and perceived acts of discrimination towards PLHA) with previous history of HIV testing, knowledge of antiretroviral therapies (ARVs) and communication regarding HIV/AIDS and (2) to compare these two constructs across the five research sites with respect to differing levels of HIV prevalence and ARV coverage, using data presented from the baseline survey of U.S. National Institute of Mental Health (NIMH) Project Accept, a four-country HIV prevention trial in Sub-Saharan Africa (Tanzania, Zimbabwe and South Africa) and northern Thailand. A household probability sample of 14,203 participants completed a survey including a scale measuring HIV/AIDS-related stigma and discrimination. Logistic regression models determined the associations between negative attitudes and perceived discrimination with individual history of HIV testing, knowledge of ARVs and communication regarding HIV/AIDS. Spearman's correlation coefficients determined the relationships between negative attitudes and perceived discrimination and HIV prevalence and ARV coverage at the site-level. Negative attitudes were related to never having tested for HIV, lacking knowledge of ARVs, and never having discussed HIV/AIDS. More negative attitudes were found in sites with the lowest HIV prevalence (i.e., Tanzania and Thailand) and more perceived discrimination against PLHA was found in sites with the lowest ARV coverage (i.e., Tanzania and Zimbabwe). Programs that promote widespread HIV testing and discussion of HIV/AIDS, as well as education regarding and universal access to ARVs, may reduce HIV/AIDS-related stigma and discrimination. PMID:19427086

  1. Validity and Reliability of Persian Version of HIV/AIDS Related Stigma Scale for People Living With HIV/AIDS in Iran

    PubMed Central

    Pourmarzi, Davoud; Khoramirad, Ashraf; Ahmari Tehran, Hoda; Abedini, Zahra

    2015-01-01

    Objective: To assess the perceived HIV/AIDS related stigma a comprehensive and well developed stigma instrument is necessary. This study aimed to assess validity and reliability of the Persian version of HIV/AIDS related stigma scale which was developed by Kang et al for people living with HIV/AIDS in Iran. Materials and methods: Thescale was forward translatedby two bilingual academic members then both translations were discussed by expert team. Back-translation was done by two other bilingual translators then we carried out discussion with both of them. To evaluate understandability the scale was administered to 10 Persons Living with HIV/AIDS (PLWHA). Final Persian version was administered to 80 PLWHA in Qom, Iran in 2014. Test–retest reliability was assessed in a sample of 20 PLWHA after a week by intra-class correlation coefficient (ICC). Results: Cronbach’s alpha coefficient for overall scale was 0.85. Also Cronbach’s alpha coefficients for the five subscales were as follows: social rejection (9 items, α = 0.84), negative self-worth (4 items, α = 0.70), perceived interpersonal insecurity (2 items, α = 0.57), financial insecurity (3 items, α = 0.70), discretionary disclosure (2 items, α = 0.83). Test–retest reliability was also approved with ICC = 0.78. Correlation between items and their hypothesized subscale is greater than 0.5. Correlation between an item and its own subscale was significantly higher than its correlation with other subscales. Conclusion: This study demonstrate that the Persian version of HIV/AIDS related stigma scale is valid and reliable to assess HIV/AIDS related stigma perceived by people living whit HIV/AIDS in Iran. PMID:27047562

  2. A comparison of HIV/AIDS-related stigma in four countries: negative attitudes and perceived acts of discrimination towards people living with HIV/AIDS.

    PubMed

    Genberg, Becky L; Hlavka, Zdenek; Konda, Kelika A; Maman, Suzanne; Chariyalertsak, Suwat; Chingono, Alfred; Mbwambo, Jessie; Modiba, Precious; Van Rooyen, Heidi; Celentano, David D

    2009-06-01

    HIV/AIDS-related stigma and discrimination have a substantial impact on people living with HIV/AIDS (PLHA). The objectives of this study were: (1) to determine the associations of two constructs of HIV/AIDS-related stigma and discrimination (negative attitudes towards PLHA and perceived acts of discrimination towards PLHA) with previous history of HIV testing, knowledge of antiretroviral therapies (ARVs) and communication regarding HIV/AIDS and (2) to compare these two constructs across the five research sites with respect to differing levels of HIV prevalence and ARV coverage, using data presented from the baseline survey of U.S. National Institute of Mental Health (NIMH) Project Accept, a four-country HIV prevention trial in Sub-Saharan Africa (Tanzania, Zimbabwe and South Africa) and northern Thailand. A household probability sample of 14,203 participants completed a survey including a scale measuring HIV/AIDS-related stigma and discrimination. Logistic regression models determined the associations between negative attitudes and perceived discrimination with individual history of HIV testing, knowledge of ARVs and communication regarding HIV/AIDS. Spearman's correlation coefficients determined the relationships between negative attitudes and perceived discrimination and HIV prevalence and ARV coverage at the site-level. Negative attitudes were related to never having tested for HIV, lacking knowledge of ARVs, and never having discussed HIV/AIDS. More negative attitudes were found in sites with the lowest HIV prevalence (i.e., Tanzania and Thailand) and more perceived discrimination against PLHA was found in sites with the lowest ARV coverage (i.e., Tanzania and Zimbabwe). Programs that promote widespread HIV testing and discussion of HIV/AIDS, as well as education regarding and universal access to ARVs, may reduce HIV/AIDS-related stigma and discrimination. PMID:19427086

  3. A qualitative analysis of barriers to accessing HIV/AIDS-related services among newly diagnosed HIV-positive men who have sex with men in China.

    PubMed

    Li, Haochu Howard; Holroyd, Eleanor; Li, Xiaoming; Lau, Joseph

    2015-01-01

    In China, specific HIV/AIDS-related services have been in place since 2004. However, utilisation of these services remains limited among people living with HIV. We explored barriers to accessing HIV/AIDS-related services from the perspective of newly diagnosed HIV-positive men who have sex with men. We conducted repeated in-depth interviews with 31 newly diagnosed HIV-positive men who have sex with men, using the socio-ecological framework and thematic content analysis. Multiple barriers for utilisation of HIV/AIDS-related services were identified, including perceptions of subjective health and poor quality of services, mental and emotional health problems, lack of trust and understanding of the services on offer, low economic status, lack of insurance, and high medical fees, being refused access to services, and restrictive attendance policies. The findings provide information on potential multi-level obstacles preventing newly diagnosed HIV-positive men who have sex with men to use services that they need. It is recommended that policy makers should create a trustful and non-discriminating environment and services integrating physical and mental healthcare. PMID:24626063

  4. 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.

  5. 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

    2016-09-08

    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

  6. 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

  7. 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. PMID:23874598

  8. 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.

  9. Hybrid LBM-MRT model coupled with finite difference method for double-diffusive mixed convection in rectangular enclosure with insulated moving lid

    NASA Astrophysics Data System (ADS)

    Bettaibi, Soufiene; Kuznik, Frédéric; Sediki, Ezeddine

    2016-02-01

    This paper presents a numerical study of thermosolutal mixed convection in rectangular enclosure with sliding top lid. The fluid flow is solved by the multiple relaxation time (MRT) lattice Boltzmann method (LBM), whereas the temperature and concentration fields are computed by finite difference method (FDM). The main objective of this study is to investigate the accuracy and the effectiveness of such model to predict thermodynamics for heat and mass transfer in a driven cavity. This model is validated with different numerical methods in the current literature. A good agreement is obtained between our results and previous works. The different comparisons demonstrate the robustness and the accuracy of the proposed approach.

  10. 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. PMID:26914708

  11. 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

  12. 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.

  13. 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.

  14. AIDS-related lymphoma. Histopathology, immunophenotype, and association with Epstein-Barr virus as demonstrated by in situ nucleic acid hybridization.

    PubMed Central

    Hamilton-Dutoit, S. J.; Pallesen, G.; Franzmann, M. B.; Karkov, J.; Black, F.; Skinhøj, P.; Pedersen, C.

    1991-01-01

    To investigate the range of pathology shown by acquired immune deficiency syndrome (AIDS)-related lymphomas arising in an epidemiologically well-defined group of patients, all cases of lymphoma recognized in Danish human immunodeficiency virus (HIV)-infected individuals up to the end of 1988 were studied. Twenty-seven cases (26 high-grade non-Hodgkin's lymphoma [NHL], 1 Hodgkin's disease) were found, to give a cumulative incidence rate of 8% among Danish AIDS patients. Morphologically most NHL patients were classified into two groups: 1) high-grade tumors with a predominant population of immunoblasts, either monomorphic or more often polymorphic with plasmacytic differentiation; 2) Burkitt-type. Of 26 NHLs, 22 had a B-cell paraffin-section immunophenotype and 4 were non-B, non-T. Epstein-Barr virus (EBV) DNA was demonstrated in tumor cells of 12 of 24 cases (50%) using in situ nucleic acid hybridization with a 35S-labeled probe in paraffin sections. Epstein-Barr virus DNA was found in 65% of group 1 and 20% of group 2 tumors. This study suggests the existence of two main groups of AIDS-related lymphoma with different pathogeneses. First there are immunoblast-rich lesions, which usually are associated with EBV and morphologically resemble lymphomas described in immunosuppressed organ-transplantation patients. Second there are Burkitt-type tumors in which EBV sequences are less common and that may be pathogenetically analogous to sporadic Burkitt's lymphoma. Images Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 PMID:1846263

  15. Belief in AIDS-Related Conspiracy Theories and Mistrust in the Government: Relationship With HIV Testing Among At-Risk Older Adults

    PubMed Central

    Ford, Chandra L.

    2013-01-01

    Purpose: One in 4 persons living with HIV/AIDS is an older adult (age 50 or older); unfortunately, older adults are disproportionately diagnosed in late stages of HIV disease. Psychological barriers, including belief in AIDS-related conspiracy theories (e.g., HIV was created to eliminate certain groups) and mistrust in the government, may influence whether adults undergo HIV testing. We examined relationships between these factors and recent HIV testing among at-risk, older adults. Design and Methods: This was a cross-sectional study among older adults enrolled in a large venue–based study. None had a previous diagnosis of HIV/AIDS; all were seeking care at venues with high HIV prevalence. We used multiple logistic regression to estimate the associations between self-reported belief in AIDS-related conspiracy theories, mistrust in the government, and HIV testing performed within the past 12 months. Results: Among the 226 participants, 30% reported belief in AIDS conspiracy theories, 72% reported government mistrust, and 45% reported not undergoing HIV testing within the past 12 months. Belief in conspiracy theories was positively associated with recent HIV testing (adjusted odds ratio [OR] = 1.94, 95% confidence interval [CI] = 1.05–3.60), whereas mistrust in the government was negatively associated with testing (OR = 0.43, 95% CI = 0.26–0.73). Implications: Psychological barriers are prevalent among at-risk older adults seeking services at venues with high HIV prevalences and may influence HIV testing. Identifying particular sources of misinformation and mistrust would appear useful for appropriate targeting of HIV testing strategies. PMID:23362210

  16. HIV and/or AIDS-related deaths and modifiable risk factors: A descriptive study of medical admissions at Oshakati Intermediate Hospital in Northern Namibia

    PubMed Central

    Mgori, N.K.

    2015-01-01

    Background High rates of HIV infection have decreased life expectancy in many African countries. Regardless of worldwide efforts to escalate treatment, care and prevention strategies, the number of deaths due to AIDS-related disorders is still high. Local healthcare workers suspect that there are modifiable factors in the care of HIV and/or AIDS patients which can be identified and improved. Aim To describe the HIV and/or AIDS-related causes of adult mortality and identify modifiable factors amongst patients admitted to Oshakati Intermediate Hospital, northern Namibia. Methods Data was extracted retrospectively and coded using the modified CoDe protocol for AIDS. Modifiable factors relating to the patient, health system or clinical care were identified using a standardised data collection tool. Results A total of 177 HIV and/or AIDS patients were identified, 94 (53.1%) were male and 120 (68%) had a CD4 count of less than 200 cells/mL. The common HIV-related causes of death were tuberculosis (25.9%), renal failure (15.8%), Pneumocystis jirovecii pneumonia (11.3%), cryptococcal meningitis (9%), HIV wasting syndrome (7.9%) and AIDS-defining malignancy (7.9%). The analysis revealed 281 modifiable factors; patient-related factors were the most common (153 [54.4%]), followed by health system factors (97 [34.5%]) and healthcare personnel factors (31 [11%]). Conclusion Our findings have highlighted the challenges in overall HIV and/or AIDS inpatient care and surrounding primary care facilities. The identification of specific modifiable factors can be used to reduce mortality by providing training as well as rational monitoring, planning and resource allocation.

  17. 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

  18. 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

  19. Museum lighting for golden artifacts, with low correlated color temperature, high color uniformity and high color rendering index, using diffusing color mixing of red, cyan, and white-light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Thorseth, Anders; Corell, Dennis D.; Poulsen, Peter B.; Hansen, Søren S.; Dam-Hansen, Carsten

    2012-03-01

    Museum lighting present challenges due to the demand for a high color rendering index (CRI), color uniformity and the damaging effects of both visible and invisible radiation. Golden objects are furthermore normally displayed with illumination which has a correlated color temperature (CCT) of 2200 K, a CCT that is not commercially available from single LEDs. An LED system that conforms with these requirements has been developed and implemented at The Royal Danish Collection at Rosenborg Castle. Color mixing of commercial LEDs (red, cyan, and white) was employed to achieve the spectral power distribution needed for the CCT and a CRI above 90, for all CRI test color samples. Replacing the traditional low voltage incandescent lighting has shown energy saving above 70 %. Harmful IR radiation was reduced by 99 %. Temperature fluctuations in the display cases were reduced from several degrees Celsius to below one, despite the fact that the lighting units were placed within the display case. Spatial color uniformity of the illumination and uniformly colored shadows was achieved by use of a highly diffusing reflector dish which avoids direct illumination from the LEDs.

  20. Romidepsin in Treating Patients With Lymphoma, Chronic Lymphocytic Leukemia, or Solid Tumors With Liver Dysfunction

    ClinicalTrials.gov

    2016-09-09

    Adult Mixed Glioma; Adult Pineal Gland Astrocytoma; Adult Solid Neoplasm; AIDS Related Immunoblastic Lymphoma; AIDS-Related Burkitt Lymphoma; AIDS-Related Diffuse Large Cell Lymphoma; AIDS-Related Diffuse Mixed Cell Lymphoma; AIDS-Related Diffuse Small Cleaved Cell Lymphoma; AIDS-Related Hodgkin Lymphoma; AIDS-Related Lymphoblastic Lymphoma; AIDS-Related Lymphoma; AIDS-Related Primary Central Nervous System Lymphoma; Glioma; Lymphoma; Recurrent Adult Brain Neoplasm; Recurrent Adult Soft Tissue Sarcoma; Recurrent Bladder Carcinoma; Recurrent Breast Carcinoma; Recurrent Chronic Lymphocytic Leukemia; Recurrent Colorectal Carcinoma; Recurrent Cutaneous T-Cell Non-Hodgkin Lymphoma; Recurrent Head and Neck Carcinoma; Recurrent Lung Carcinoma; Recurrent Mature T- and NK-Cell Non-Hodgkin Lymphoma; Recurrent Melanoma; Recurrent Pancreatic Carcinoma; Recurrent Prostate Carcinoma; Recurrent Renal Cell Carcinoma; Recurrent Thyroid Gland Carcinoma; Refractory Chronic Lymphocytic Leukemia; Refractory Cutaneous T-Cell Non-Hodgkin Lymphoma; Refractory Mature T-Cell and NK-Cell Non-Hodgkin Lymphoma

  1. Holographic diffusers

    NASA Astrophysics Data System (ADS)

    Wadle, Stephen; Wuest, Daniel; Cantalupo, John; Lakes, Roderic S.

    1994-01-01

    Holographic diffusers are prepared using silver halide (Agfa 8E75 and Kodak 649F) and photopolymer (Polaroid DMP 128 and DuPont 600, 705, and 150 series) media. It is possible to control the diffusion angle in three ways: by selection of the properties of the source diffuser, by control of its subtended angle, and by selection of the holographic medium. Several conventional diffusers based on refraction or scattering of light are examined for comparison.

  2. 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.

  3. Outcome of Patients with Relapsed/Refractory AIDS-Related Lymphoma Diagnosed 1999–2008 and Treated with Curative Intent in the AIDS Malignancy Consortium

    PubMed Central

    Bayraktar, U. D.; Ramos, J. C.; Petrich, A.; Gupta, N.; Lensing, S.; Moore, Page; Reid, E. G.; Aboulafia, D. M.; Ratner, L.; Mitsuyasu, R.; Cooley, Timothy; Henry, D. H.; Barr, P.; Noy, A.

    2012-01-01

    No comparative studies exist for relapsed/refractory (rel/rfr) AIDS-related lymphomas (ARLs). To determine practices over the last decade and to assess the outcomes of salvage chemotherapy with curative intent and autologous stem cell transplantation (ASCT), we retrospectively evaluated treatment outcomes in patients with rel/rfr ARL who were treated in 13 national AIDS Malignancy Consortium (AMC) sites between 1999 and 2008 (N=88). The most commonly used second line therapies were ICE (n=34), dose adjusted EPOCH (n=17), and ESHAP (n=11). The odds of achieving a response were lower for those with non-Hodgkin lymphoma (NHL) than those with HL and for those with primary refractory disease than those with relapse. Overall survival (OS) was significantly longer for those with relapsed disease compared to those with refractory disease and for those with non-Burkitt NHL compared to those with Burkitt. OS was longer in patients who underwent ASCT compared to those who did not (1-year OS: 63.2% vs. 37.2%). However, among 32 patients (36%) who achieved CR/PR after second-line therapy 1-year OS was not different between the 2 groups (87.5% for ASCT vs. 81.8% for non-ASCT). Long-term survival in some patients with rel/rfr ARL may be possible without transplant, although transplant remains the standard of care for chemotherapy sensitive disease. PMID:22642936

  4. Understanding the relationships among HIV/AIDS-related stigma, health service utilization, and HIV prevalence and incidence in Sub-Saharan Africa: a multi-level theoretical perspective.

    PubMed

    Williams, Leslie D

    2014-03-01

    HIV-positive individuals often face community-wide discrimination or public shame and humiliation as a result of their HIV-status. In Sub-Saharan Africa, high HIV incidence coupled with unique cultural contexts make HIV-positive individuals particularly likely to experience this kind of HIV/AIDS-related (HAR) stigma. To date, there is a relatively small amount of high-quality empirical literature specific to HAR stigma in this context, supporting the notion that a better understanding of this phenomenon is needed to inform potential interventions. This paper provides a thorough review of the literature specific to HAR stigma in Sub-Saharan Africa, finding (a) qualitative support for the existence of important relationships between HAR stigma and health service utilization and barriers; (b) a need for more quantitative study of stigma and its relationships both to health service utilization and to HIV outcomes directly; and (c) a disconnect between methodological techniques used in this context-specific literature and well-known theories about stigma as a general phenomenon. This paper then draws from its empirical literature review, as well as from well-known theoretical frameworks from multiple disciplines, to propose a theoretical framework for the ecological and multilevel relationships among HAR stigma, health service utilization, and HIV outcomes in this context. PMID:24477769

  5. 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.

  6. 40 CFR 227.29 - Initial mixing.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...) Initial mixing is defined to be that dispersion or diffusion of liquid, suspended particulate, and solid... adequate to predict initial dispersion and diffusion of the waste, these shall be used, if necessary, in.... (2) When field data on the dispersion and diffusion of a waste of characteristics similar to...

  7. 40 CFR 227.29 - Initial mixing.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...) Initial mixing is defined to be that dispersion or diffusion of liquid, suspended particulate, and solid... adequate to predict initial dispersion and diffusion of the waste, these shall be used, if necessary, in.... (2) When field data on the dispersion and diffusion of a waste of characteristics similar to...

  8. 40 CFR 227.29 - Initial mixing.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...) Initial mixing is defined to be that dispersion or diffusion of liquid, suspended particulate, and solid... adequate to predict initial dispersion and diffusion of the waste, these shall be used, if necessary, in.... (2) When field data on the dispersion and diffusion of a waste of characteristics similar to...

  9. 40 CFR 227.29 - Initial mixing.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...) Initial mixing is defined to be that dispersion or diffusion of liquid, suspended particulate, and solid... adequate to predict initial dispersion and diffusion of the waste, these shall be used, if necessary, in.... (2) When field data on the dispersion and diffusion of a waste of characteristics similar to...

  10. A mix of S and ΔS variants of STAT3 enable survival of activated B-cell-like diffuse large B-cell lymphoma cells in culture.

    PubMed

    Zheng, M; Turton, K B; Zhu, F; Li, Y; Grindle, K M; Annis, D S; Lu, L; Drennan, A C; Tweardy, D J; Bharadwaj, U; Mosher, D F; Rui, L

    2016-01-01

    Activated B-cell-like diffuse large B-cell lymphoma (ABC DLBCL) is characterized by increased expression and activator of signal transducer and activator of transcription 3 (STAT3). ABC DLBCL cells require STAT3 for growth in culture. In ABC DLBCL cells, eosinophils and perhaps all cells, four variant STAT3 mRNAs (Sα, ΔSα, Sβ and ΔSβ) are present as a result of two alternative splicing events, one that results in the inclusion of a 55-residue C-terminal transactivation domain (α) or a truncated C-terminal domain with 7 unique residues (β) and a second that includes (S) or excludes (ΔS) the codon for Ser-701 in the linker between the SH2 and C-terminal domains. A substantial literature indicates that both α and β variants are required for optimal STAT3 function, but nothing is known about functions of ΔS variants. We used a knockdown/re-expression strategy to explore whether survival of ABC DLBCL cells requires that the four variants be in an appropriate ratio. No single variant rescued survival as well as STAT3Sα-C, Sα with activating mutations (A661C and N663C) in the SH2 domain. Better rescue was achieved when all four variants were re-expressed or Sα and ΔSα or Sβ and ΔSβ were re-expressed in pairs. Rescue correlated with expression of STAT3-sensitive genes NFKBIA and NFKBIZ. We consider a variety of explanations why a mix of S and ΔS variants of STAT3 should enable survival of ABC DLBCL cells. PMID:26727576

  11. IgM, IgG and IgA rheumatoid factors and circulating immune complexes in patients with AIDS and AIDS-related complex with serological abnormalities.

    PubMed Central

    Procaccia, S; Lazzarin, A; Colucci, A; Gasparini, A; Forcellini, P; Lanzanova, D; Foppa, C U; Novati, R; Zanussi, C

    1987-01-01

    To investigate some humoral aspects which may reflect the involvement of B lymphocytes in the acquired immunodeficiency syndrome (AIDS), we used an enzyme-linked immunoassay (ELISA) to determine the levels of IgM, IgG and IgA rheumatoid factors (RF) in 16 patients suffering from full-blown AIDS and 32 patients with AIDS-related complex (ARC), in the clinical form of lymphoadenopathy syndrome (LAS), compared with 40 healthy, young heterosexual subjects. Both AIDS and ARC patients showed a greater incidence of high IgM RF levels, with mean values significantly higher than controls, but with no differences between the two pathological groups. IgG RF behaviour was similar in the two patient populations and the healthy subjects. IgA RF were significantly raised in AIDS and ARC. Further information on RF was obtained by determination of the immunoglobulin levels of the respective isotypes in the same patients. Mean IgG levels were above normal in AIDS and ARC patients, but the latter group showed a higher incidence of increased values and higher mean levels. The IgA isotype was significantly increased mainly in AIDS patients. The behaviour of IgM was virtually the same in the three groups studied. A difference between AIDS and ARC patients was established by the detection of circulating immune-complexes (IC) by the C1q-binding and CIC-conglutinin assays. IC were significantly high, by both methods, only in the ARC group, but normal or very low in AIDS. These overall findings suggest once again the impairment of B cell function in AIDS, with prevalent hyperactivation in ARC and exhaustion in full-blown AIDS, and apparent preservation, in the latter group, of the antibody responses which are more closely related to the activity of subsets of T helper cells. PMID:3608224

  12. High-dose cytosine-arabinoside and cisplatin regimens as salvage therapy for refractory or relapsed AIDS-related non-Hodgkin's lymphoma.

    PubMed

    Bi, J; Espina, B M; Tulpule, A; Boswell, W; Levine, A M

    2001-12-15

    No effective salvage regimen has been defined for patients with AIDS-related non-Hodgkin's lymphoma (AIDS-NHL) who do not respond to first-line chemotherapy that contains anthracycline. Combined dexamethasone, cytosine arabinoside, and cisplatin (DHAP) and etoposide, methylprednisolone, cytosine arabinoside, and cisplatin (ESHAP) have shown good response rates in HIV-negative patients with relapsed lymphomas. We retrospectively analyzed patients with refractory or relapsed AIDS-NHL who had been treated with either DHAP or ESHAP to evaluate the feasibility and efficacy of these regimens. Twenty-six patients with refractory or relapsed AIDS-NHL were treated between 1990 and 1999 either with DHAP ( n = 13) or with ESHAP ( n = 13). Only 1 patient from each group (8%) had achieved complete remission with any previous therapy, and most had progressive disease after the regimen immediately preceding DHAP or ESHAP. In the ESHAP group, 4 patients (31%) achieved complete remission (CR) and 3 patients (23%) attained partial remission (PR) for an overall response rate of 54%. The median survival was 7.1 months (range, 1-58.9+ months) from the time ESHAP was begun. Among the 3 patients with primary refractory lymphoma, there was 1 CR, 1 PR, and one patient with stable disease. In contrast, only 1 PR (7%) was observed with DHAP; the median survival was 3 months. Myelosuppression was the most significant toxicity with grade 4 neutropenia occurring in all who received ESHAP and in 54% of patients treated with DHAP. Neutropenic fever occurred in 8 (62%) ESHAP-treated and 6 (46%) DHAP-treated patients. Although hematologic toxicity is profound, ESHAP appears to be an active salvage regimen for patients with relapsed or refractory AIDS-NHL. PMID:11744828

  13. 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

  14. Vaneless diffusers

    NASA Astrophysics Data System (ADS)

    Senoo, Y.

    The influence of vaneless diffusers on flow in centrifugal compressors, particularly on surge, is discussed. A vaneless diffuser can demonstrate stable operation in a wide flow range only if it is installed with a backward leaning blade impeller. The circumferential distortion of flow in the impeller disappears quickly in the vaneless diffuser. The axial distortion of flow at the diffuser inlet does not decay easily. In large specific speed compressors, flow out of the impeller is distorted axially. Pressure recovery of diffusers at distorted inlet flow is considerably improved by half guide vanes. The best height of the vanes is a little 1/2 diffuser width. In small specific speed compressors, flow out of the impeller is not much distorted and pressure recovery can be predicted with one-dimensional flow analysis. Wall friction loss is significant in narrow diffusers. The large pressure drop at a small flow rate can cause the positive gradient of the pressure-flow rate characteristic curve, which may cause surging.

  15. 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.

  16. 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.

  17. Ti Diffusion in Pyroxene

    NASA Astrophysics Data System (ADS)

    Cherniak, D.; Liang, Y.

    2008-12-01

    Diffusion of titanium has been characterized in natural enstatite and diopside under buffered conditions and in air. The sources of diffusant for the enstatite experiments were mixtures of Mg, Si and Ti oxide powders, which were combined and heated at 1300°C overnight, and then thoroughly mixed with synthesized enstatite powder and heated for an additional day at 1300°C. Sources for diopside experiments were prepared similarly, using Ca, Mg, Si, and Ti oxide powders combined with synthesized diopside powder, with heating of source materials at 1200°C. Buffered experiments were prepared by enclosing source material and pyroxene (polished and pre-annealed under conditions comparable to those to be experienced in the experiment) in AgPd or platinum capsules, placing the metal capsule in a silica glass capsule with a solid buffer (to buffer at NNO or IW) and sealing the assembly under vacuum. Some experiments on enstatite were run in air; sample and source were placed in Pt capsules and crimped shut. Prepared capsules were then annealed in 1 atm furnaces for times ranging from 8 hours to a few months, at temperatures from 950 to 1200°C. The Ti distributions in the pyroxene were profiled with Rutherford Backscattering Spectrometry (RBS). The following Arrhenius relation is obtained for Ti diffusion in a natural enstatite, for diffusion normal to the (210) cleavage face (950 - 1150°C, experiments run in air): DTi = 1.9×10-10 exp(-300 ± 44 kJ mol-1/RT) m2 sec-1. Diffusion under NNO and IW-buffered conditions is similar to that for experiments run in air, suggesting little dependence of Ti diffusion on oxygen fugacity. There is also little evidence of anisotropy, as diffusion normal to (001) does not differ significantly from diffusion for the other orientation. Preliminary findings for Ti diffusion in diopside suggest diffusivities similar to those for enstatite. Ti diffusivities in enstatite are similar to those of the trivalent REEs (Cherniak and Liang, 2007

  18. Mixed Dementia

    MedlinePlus

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

  19. 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…

  20. Relativistic diffusion

    NASA Astrophysics Data System (ADS)

    Haba, Z.

    2009-02-01

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

  1. 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)

  2. Relativistic diffusion.

    PubMed

    Haba, Z

    2009-02-01

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

  3. Correlation between viral load, plasma levels of CD4 - CD8 T lymphocytes and AIDS-related oral diseases: a multicentre study on 30 HIV+ children in the HAART era.

    PubMed

    Nesti, M; Carli, E; Giaquinto, C; Rampon, O; Nastasio, S; Giuca, M R

    2012-01-01

    This experimental retrospective multicenter study carried out on 30 seropositive children treated with Highly Active Antiretroviral Therapy (HAART), between the ages of 18 months and 14 years, in the clinical categories Centers for Disease Control (CDC) classification 1993 A (mildly symptomatic), B (moderately symptomatic) and C (severely symptomatic) aims to: 1) clinically and immunologically demonstrate the therapeutic benefits of HAART; 2) monitor the frequency of AIDS-related oral diseases in seropositive children with HAART therapy; 3) monitor the plasma levels of total CD4, CD4 percent, CD8 percent, CD4-CD8 lymphocytes and viral load from 1997 to 30 April, 2011. The statistic methods used are the analysis of covariance and the Bonferroni Test. More than 100 AIDS-related oral diseases were found in the study samples, the most frequent being: oral candidiasis, oropharyngeal candidiasis, HSV-1 herpetic esophagyitis, herpetic gingivolstomatitis (RHOG), recurrent aphthous stomatitis (RAS), parotid swelling, oral hairy leukoplakia (OHL), Herpes simplex 1 (HSV-1), linear gingival erythema (LGE), necrotizing gingivitis (NUG), facial lipodistrophy, facial-cervical lymphadenopathy (FCL), xerostomia, dysgeusia, hyposmia, oral mucosa hyperpigmentation (OMP). The Bonferroni test showed a significant difference between the mean plasma values (mpVTL) of total CD4, CD4 percentage, CD4-CD8 T lymphocytes and Viral Load (VL) of the various oral diseases found in the study samples. The therapeutic benefits of HAART are: immune reconstitution; reduction of the HIV/AIDS-related stomatology diseases; prevention and cure of the AIDS correlated neoplasias; reduction in maternal-fetal transmission of the HIV virus. The negative effects of HAART in relation to odontostomatolgy are: increase in oral lesions from HPV; xerostomia; dysgeusia/ageusia, hyposmia, perioral paresthesia; hyperpigmentation of oral mucosa; facial lipodystrophy, recurrent aphthous stomatitis (RAS). No case of

  4. 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.

  5. Optimal Control of Evolution Mixed Variational Inclusions

    SciTech Connect

    Alduncin, Gonzalo

    2013-12-15

    Optimal control problems of primal and dual evolution mixed variational inclusions, in reflexive Banach spaces, are studied. The solvability analysis of the mixed state systems is established via duality principles. The optimality analysis is performed in terms of perturbation conjugate duality methods, and proximation penalty-duality algorithms to mixed optimality conditions are further presented. Applications to nonlinear diffusion constrained problems as well as quasistatic elastoviscoplastic bilateral contact problems exemplify the theory.

  6. 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

  7. AIDS-related primary cardiac lymphoma with right-sided heart failure and high-grade AV block: insights from magnetic resonance imaging.

    PubMed

    Llitjos, J-F; Redheuil, A; Puymirat, E; Vedrenne, G; Danchin, N

    2014-04-01

    A 44-year-old patient, with personal history of AIDS, was referred to our emergency unit with tachycardia and moderate signs of right-sided heart failure. The cardiac MRI study showed an impairment of the right ventricular free and inferior wall and the interventricular septum. The mass was characterized by notable heterogeneity with mixed areas of hypo- and hypersignal intensity in SSFP and T2-weighted images with fat saturation. There was global hyperenhancement of the mass after gadolinium contrast injection on T1-weighted images with and without fat saturation. The entire right coronary artery was included into the infiltrative mass. One day after the admission, the patient suddenly presented a paroxysmal third degree atrioventricular block, permanently corrected by an implanted cardiac pacemaker. Endomyocardial biopsy conformed the diagnosis of B-cell lymphoma. The patient died 4months after the diagnosis of acute heart failure with multi-organ dysfunction, after a short period of improvement under chemotherapy. We present this case to highlight the importance to consider that a large, solitary, right atrial mass in conjunction with pericardial effusion in a patient with HIV infection should lead to consider, as soon as possible, the diagnosis of lymphoma. MRI has explained the conduction disorders by showing the septal extension of the mass, and by demonstrating right coronary artery involvement. PMID:23830566

  8. Quantum diffusion

    SciTech Connect

    Habib, S.

    1994-10-01

    We consider a simple quantum system subjected to a classical random force. Under certain conditions it is shown that the noise-averaged Wigner function of the system follows an integro-differential stochastic Liouville equation. In the simple case of polynomial noise-couplings this equation reduces to a generalized Fokker-Planck form. With nonlinear noise injection new ``quantum diffusion`` terms rise that have no counterpart in the classical case. Two special examples that are not of a Fokker-Planck form are discussed: the first with a localized noise source and the other with a spatially modulated noise source.

  9. 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)

  10. Diffusion from a line source

    NASA Technical Reports Server (NTRS)

    Burns, R. E.

    1973-01-01

    The problem with predicting pollutant diffusion from a line source of arbitrary geometry is treated. The concentration at the line source may be arbitrarily varied with time. Special attention is given to the meteorological inputs which act as boundary conditions for the problem, and a mixing layer of arbitrary depth is assumed. Numerical application of the derived theory indicates the combinations of meteorological parameters that may be expected to result in high pollution concentrations.

  11. [Mixed marriages].

    PubMed

    Harmsen, C N

    1998-08-01

    The author examines the extent and characteristics of mixed marriages in the Netherlands. "Nine out of ten married persons born in Turkey or Morocco have a partner who was born in the same country. The majority of married Surinamese also have a partner originating from the same country. Those who spend (a part of) their youth in Indonesia (the former Dutch East Indies), on the other hand, are mostly married to someone born in the Netherlands." (EXCERPT) PMID:12294179

  12. Transversal and longitudinal mixing in compound channels

    NASA Astrophysics Data System (ADS)

    Besio, G.; Stocchino, A.; Angiolani, S.; Brocchini, M.

    2012-12-01

    An experimental campaign, based on particle image velocimetry (PIV) measurements of free-surface velocities, forms the basis for an analysis of the mixing processes which occur in a compound-channel flow. The flow mixing is characterized in terms of Lagrangian statistics (absolute dispersion and diffusivity) and of the related mean flow characteristics. Mixing properties strongly depend on the ratiorh between the main channel flow depth (h*mc) and the floodplain depth (h*fp), and three flow classes can be identified, namely shallow, intermediate, and deep flows. In the present study the large time asymptotic behavior of the mixing characteristics is analyzed in terms of the absolute diffusivity in order to characterize typical values of longitudinal and transversal diffusivity coefficients. Various sets of experiments, which cover a wide range of the governing physical parameters, have been performed and the asymptotic values of the absolute diffusivity have been evaluated. The results are then compared with several studies of flow dispersion for both the longitudinal diffusivity coefficient and the transversal turbulent mixing coefficient. The present results highlight a stronger dependence of such coefficients with the flow-depth ratio than with the flow regime (Froude number).

  13. CO Diffusion into Amorphous H2O Ices

    NASA Astrophysics Data System (ADS)

    Lauck, Trish; Karssemeijer, Leendertjan; Shulenberger, Katherine; Rajappan, Mahesh; Öberg, Karin I.; Cuppen, Herma M.

    2015-03-01

    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 H2O, and diffusion on external and internal (pore) surfaces of H2O-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 H2O-dominated ices at low temperatures (15-23 K), by measuring the mixing rate of initially layered H2O(:CO2)/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 H2O 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 H2O ice. The extracted energy barrier for CO diffusion into amorphous H2O 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.

  14. Detailed flow measurements in a centrifugal compressor vaneless diffuser

    SciTech Connect

    Pinarbasi, A. . Dept. of Mechanical Engineering); Johnson, M.W. . Dept. of Mechanical Engineering)

    1994-07-01

    Hot-wire anemometer measurements have been made in the vaneless diffuser of a 1-m-dia low-speed backswept centrifugal compressor using a phase lock loop technique. Radial, tangential, and axial velocity measurements have been made on eight measurement planes through the diffuser. The flow field at the diffuser entry clearly shows the impeller jet-wake flow pattern and the blade wakes. The passage wake is located on the shroud side of the diffuser and mixes out slowly as the flow moves through the diffuser. The blade wakes, on the other hand, distort and mix out rapidly in the diffuser. Contours of turbulent kinetic energy are also presented on each of the measurement stations, from which the regions of turbulent mixing can be deduced.

  15. Mixed results with mixed disulfides.

    PubMed

    Brigelius-Flohé, Regina

    2016-04-01

    A period of research with Helmut Sies in the 1980s is recalled. Our experiments aimed at an in-depth understanding of metabolic changes due to oxidative challenges under near-physiological conditions, i.e. perfused organs. A major focus were alterations of the glutathione and the NADPH/NADP(+) system by different kinds of oxidants, in particular formation of glutathione mixed disulfides with proteins. To analyze mixed disulfides, a test was adapted which is widely used until today. The observations in perfused rat livers let us believe that glutathione-6-phosphate dehydrogenase (G6PDH), i.a. might be activated by glutathionylation. Although we did not succeed to verify this hypothesis for the special case of G6PDH, the regulation of enzyme/protein activities by glutathionylation today is an accepted posttranslational mechanism in redox biology in general. Our early experimental approaches are discussed in the context of present knowledge. PMID:27095221

  16. Chemical mixing in smoothed particle hydrodynamics simulations

    NASA Astrophysics Data System (ADS)

    Greif, Thomas H.; Glover, Simon C. O.; Bromm, Volker; Klessen, Ralf S.

    2009-02-01

    We introduce a simple and efficient algorithm for diffusion in smoothed particle hydrodynamics (SPH) simulations and apply it to the problem of chemical mixing. Based on the concept of turbulent diffusion, we link the diffusivity of a pollutant to the local physical conditions and can thus resolve mixing in space and time. We apply our prescription to the evolution of an idealized supernova remnant and find that we can model the distribution of heavy elements without having to explicitly resolve hydrodynamic instabilities in the post-shock gas. Instead, the dispersal of the pollutant is implicitly modelled through its dependence on the local velocity dispersion. Our method can thus be used in any SPH simulation that investigates chemical mixing but lacks the necessary resolution on small scales. Potential applications include the enrichment of the interstellar medium in present-day galaxies, as well as the intergalactic medium at high redshifts.

  17. Dynamic mixing in magma bodies - Theory, simulations, and implications

    NASA Technical Reports Server (NTRS)

    Oldenburg, Curtis M.; Spera, Frank J.; Yuen, David A.; Sewell, Granville

    1989-01-01

    The magma-mixing process is different from the mantle mixing process in that the mixing components of magma are dynamically active, with the melt density depending strongly on composition. This paper describes simulations of time-dependent variable-viscosity double-diffusive convection which were carried out to investigate quantitatively the mixing dynamics of magma in melt-dominated magma bodies. Results show that the dynamics of double-diffusive convection can impart complex patterns of composition, through time and space. The mixing time depends nonlinearly on many factors, including heat flux driving convection, the rate of diffusion of chemical species, the relative importance of thermal and chemical buoyancy, the viscosities of the mixing components, and the shape of the magma body.

  18. 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.

  19. 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.

  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. 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.

  2. 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. PMID:17218741

  3. 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

  4. Treatment Options for AIDS-Related Lymphoma

    MedlinePlus

    ... the picture. This procedure is also called nuclear magnetic resonance imaging (NMRI). Lumbar puncture : A procedure used to collect cerebrospinal fluid (CSF) from the spinal column . This is done ...

  5. Treatment Option Overview (AIDS Related-Lymphoma)

    MedlinePlus

    ... the picture. This procedure is also called nuclear magnetic resonance imaging (NMRI). Lumbar puncture : A procedure used to collect cerebrospinal fluid (CSF) from the spinal column . This is done ...

  6. Stages of AIDS-Related Lymphoma

    MedlinePlus

    ... the picture. This procedure is also called nuclear magnetic resonance imaging (NMRI). Lumbar puncture : A procedure used to collect cerebrospinal fluid (CSF) from the spinal column . This is done ...

  7. 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

  8. Women and AIDS-Related Concerns

    PubMed Central

    Cochran, Susan D.; Mays, Vickie M.

    2014-01-01

    Acquired Immunodeficiency Syndrome (AIDS) has important implications for the practice of psychology. As the epidemic continues, the role of behavior change and psychosocial factors in the spread and transmission of Human Immunodeficiency Virus (HIV) infections assumes increasing significance. Psychologists, as behavior change experts, have a special and challenging role to play in educating the public, particularly women, about AIDS. This article examines AIDS- and HIV-related concerns in women with a focus on the personal dilemmas for the practicing psychologist, problems in health behavior advocacy, and methods and pitfalls in modifying sexual behaviors. PMID:2930055

  9. Computational simulations of vorticity enhanced diffusion

    NASA Astrophysics Data System (ADS)

    Vold, Erik L.

    1999-11-01

    Computer simulations are used to investigate a phenomenon of vorticity enhanced diffusion (VED), a net transport and mixing of a passive scalar across a prescribed vortex flow field driven by a background gradient in the scalar quantity. The central issue under study here is the increase in scalar flux down the gradient and across the vortex field. The numerical scheme uses cylindrical coordinates centered with the vortex flow which allows an exact advective solution and 1D or 2D diffusion using simple numerical methods. In the results, the ratio of transport across a localized vortex region in the presence of the vortex flow over that expected for diffusion alone is evaluated as a measure of VED. This ratio is seen to increase dramatically while the absolute flux across the vortex decreases slowly as the diffusion coefficient is decreased. Similar results are found and compared for varying diffusion coefficient, D, or vortex rotation time, τv, for a constant background gradient in the transported scalar vs an interface in the transported quantity, and for vortex flow fields constant in time vs flow which evolves in time from an initial state and with a Schmidt number of order unity. A simple analysis shows that for a small diffusion coefficient, the flux ratio measure of VED scales as the vortex radius over the thickness for mass diffusion in a viscous shear layer within the vortex characterized by (Dτv)1/2. The phenomenon is linear as investigated here and suggests that a significant enhancement of mixing in fluids may be a relatively simple linear process. Discussion touches on how this vorticity enhanced diffusion may be related to mixing in nonlinear turbulent flows.

  10. Vapor diffusion electrode improves fuel cell operation

    NASA Technical Reports Server (NTRS)

    Smith, J. O.

    1966-01-01

    Vapor diffusion type fuel cell electrode presents a nonwetting barrier to the liquid feedstocks so they may contact the electrolyte only in the vapor state. Thus, it effects feedstock mixing with the electrolyte at the electrolyte/catalyst interface but prevents feedstock decomposition and catalyst poisoning from liquid mingling.

  11. 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.

  12. Mixing in thermally stratified energy stores

    SciTech Connect

    Berkle, J. van

    1996-10-01

    Two important aspects of short-term thermally stratified energy storage, thermocline mixing and thermocline thickness, are studied analytically, experimentally and numerically. The storage detrimental aspects are investigated for a simplified configuration, i.e., an adiabatic box containing a quasi-stationary thermocline. Numerical finite difference/volume simulations agree well with experiments. The dissipation-free 1D analytical model shows a large discrepancy. It appears that mixing inside thermally stratified stores is a two-state process. First fluid is withdrawn from the thermocline by viscous drag. Subsequent mixing takes place by stretching and folding of fluid particles, thereby enabling diffusion to become active. 17 refs., 10 figs., 2 tabs.

  13. Enhanced Fluid Mixing in Nanochannels: A Molecular Dynamics Study

    NASA Astrophysics Data System (ADS)

    Oliver, Eric C. J.; Slater, Gary W.

    2006-03-01

    The efficient mixing of fluids is of paramount importance in several applications such as lab-on-a-chip and microfluidic devices. The main limitation to efficiency is that on small scales where the Reynolds number of the flow is low, mixing is dominated by diffusion. Purely diffusive motion is very slow and is an inefficient mixing mechanism unless the channel width is extremely small. Starting with the basic result for diffusive mixing of a binary fluid in a Poiseuille flow we explore methods to enhance the level of mixing between the two fluid species. We simulate the system using Molecular Dynamics and model the fluids as assemblies of Lennard-Jones beads. In order to increase the rate of mixing we have forced lateral motion in the fluid using configurations of mid-stream posts. Specifically, posts set in a prism-like structure have proven to be extremely well suited to reducing the channel length required to achieve complete mixing. In order to measure efficiency we have proposed a mathematical function that quantifies the level mixing associated with a fluid element. Furthermore, we have developed a basic theory for the position of the mixing front in a flow with spatially dependent velocity and diffusion coefficient.

  14. Microfluidic mixing technology for biological applications

    NASA Astrophysics Data System (ADS)

    Jang, Ling-Sheng

    Mixing plays a significant role in most biological analysis systems. An example that motivates this thesis is the purification or "clean-up" of sequencing reaction products prior to sequencing. Magnetic beads, DNA, and reagents must be quickly and thoroughly mixed to process samples in an automated, high-throughput system. Efficient mixing is achieved by layering and folding the fluids being mixed to decrease the characteristic length over which diffusion must act to create a locally equilibrated homogenous mixture. At the microscale this challenge is amplified by the characteristics of low Reynolds number flows present in microfluidic environments where flows are laminar and no turbulent mixing is present. Many mixing techniques have been developed to achieve thorough mixing of different fluids in Microsystems. However, mixing based on circulatory flow patterns has not been reported. We have developed a new mixing technique using circulatory flow patterns generated by PZT (lead-zirconate-titanate) vibration. A micromixer based on PZT was fabricated to demonstrate the principle of mixing using circulatory flow patterns. The circulatory flow patterns were observed at different driving frequencies using fluorescent beads. A protocol was developed to quantify the mixing performance using fluorescein. Efficient mixing was achieved by alternating between two different driving frequencies to produce two circulatory flow patterns that mix all regions in the mixing chamber. In addition, a simulation model was created to predict the mode shapes of the structure with fluid included in the model using CFD-ACE+. Empirical characterization of two-circulatory flow was performed using the confocal laser-scanning microscope to understand the underlying mechanism and generation of circulatory flow. The preliminary analysis suggests that circulatory flow is driven by fluid streaming which is believed to result from the propagation of acoustic waves induced by PZT vibration or to be

  15. CONVECTIVE DIFFUSION FIELD MEASUREMENTS COMPARED WITH LABORATORY AND NUMERICAL EXPERIMENTS

    EPA Science Inventory

    Some of the more fundamental diffusion parameters measured in the CONDORS convective diffusion field experiment are compared with laboratory experiment and numerical modeling results by means of nondimensionalizations using convective scaling (i.e., mixing depth, z sub i, for len...

  16. Diffusely Reflecting Paints Containing TFE

    NASA Technical Reports Server (NTRS)

    Shai, M. C.; Schutt, J. B.

    1985-01-01

    Highly reflective, diffused coatings developed by incorporating polytetrafluoroethylene (TFE) pigment with alcohol-soluble binders. Alcohol and binder mixed together in blender before adding TFE. TFE preferably outgassed in mechanical-pump vacuum for typical interval of 4 hours before adding to liquid. Like wetting agent, vacuum treatment helps to prevent clumping of TFE and eases dispersion throughout mixture. Mixture blended for 3 to 5 minutes before used. Coatings useful on reflectance-standard surfaces for calibrating radiometric instruments in both laboratory and field. Paints washable and usable as optical reference surfaces.

  17. Housing Mix, School Mix: Barriers to Success

    ERIC Educational Resources Information Center

    Camina, M. M.; Iannone, P.

    2014-01-01

    Recent UK policy has emphasised both the development of socially mixed communities and the creation of balanced school intakes. In this paper, we use a case study of an area of mixed tenure in eastern England to explore policy in practice and the extent to which mechanisms of segregation impact on both the creation of socially mixed neighbourhoods…

  18. Mixing and Transport.

    PubMed

    Chang, Chein-Chi; Chapman, Tom; Siverts-Wong, Elena; Wei, Li; Mei, Ying

    2016-10-01

    This section covers research published during the calendar year 2015 on mixing and transport processes. The review covers mixing of anaerobic digesters, mixing of heat transfer, and environmental fate and transport. PMID:27620101

  19. 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.

  20. 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.

  1. 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.

  2. Fluid dynamics of double diffusive systems

    SciTech Connect

    Koseff, J.R.

    1988-05-01

    A study of mixing processes in doubly diffusive systems is being conducted. Continuous gradients of two diffusing components (heat and salinity) are being used as initial conditions, and forcing is introduced by lateral heating, surface shear and sloping boundaries. The goals of the proposed work include: quantification of the effects of finite amplitude disturbances on stable, double diffusive systems, particularly with respect to lateral heating, development of an improved understanding of the physical phenomena present in wind-driven shear flows in double diffusive stratified environments, increasing our knowledge-base on turbulent flow in stratified environments and how to represent it, and formulation of numerical code for such flows. The work is being carried out in a new experimental facility at Stanford and on laboratory minicomputers and CRAY computers. In particular we are focusing on the following key issues. The formation and propagation of double diffusive intrusions away from a heated wall and the effects of lateral heating on the double diffusive system; The interaction between the double diffusively influenced fluxes and the turbulence induced fluxes; The formation of gravitational intrusions; and The influence of double diffusive gradients on mixed layer deepening. The goals of the project were as follows. Physical experiments: Construct experimental facility; Modify and fabricate instrument rakes; Develop sampling and calibration software; Develop stratification techniques; Conduct flow visualization studies; Qualify wind tunnel over a range of wind speeds. Numerical experiments: Adapt REMIXCS to handle turbulent flows; Investigate approaches for specifying wind field; Perform calculations for low wind speeds. With the exception of the wind tunnel qualification, all the tasks have already been completed and we are now conducting quantitative experiments. 2 figs.

  3. Diffusion on spatial network

    NASA Astrophysics Data System (ADS)

    Hui, Zi; Tang, Xiaoyue; Li, Wei; Greneche, Jean-Marc; Wang, Qiuping A.

    2015-04-01

    In this work, we study the problem of diffusing a product (idea, opinion, disease etc.) among agents on spatial network. The network is constructed by random addition of nodes on the planar. The probability for a previous node to be connected to the new one is inversely proportional to their spatial distance to the power of α. The diffusion rate between two connected nodes is inversely proportional to their spatial distance to the power of β as well. Inspired from the Fick's first law, we introduce the diffusion coefficient to measure the diffusion ability of the spatial network. Using both theoretical analysis and Monte Carlo simulation, we get the fact that the diffusion coefficient always decreases with the increasing of parameter α and β, and the diffusion sub-coefficient follows the power-law of the spatial distance with exponent equals to -α-β+2. Since both short-range diffusion and long-range diffusion exist, we use anomalous diffusion method in diffusion process. We get the fact that the slope index δ in anomalous diffusion is always smaller that 1. The diffusion process in our model is sub-diffusion.

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

    PubMed

    Murphy, Anthony B

    2014-01-01

    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. PMID:24603457

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

    PubMed Central

    Murphy, Anthony B.

    2014-01-01

    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. PMID:24603457

  6. Mixing of III-V compound semiconductor superlattices

    SciTech Connect

    Mei, Ping.

    1989-01-01

    In this work, the methods as well as mechanisms of III-V compound superlattice mixing are discussed, with particular attention on the AlGaAs based superlattice system. Comparative studies of ion-induced mixing showed two distinct effects resulting from ion implantation followed by a thermal anneal; i.e. collisional mixing and impurity induced mixing. It was found that Ga and As ion induced mixing are mainly due to the collisional effect, where the extent of the mixing can be estimated theoretically, with the parameters of ion mass, incident energy and the implant dose. The impurity effect was dominant for Si, Ge, Be, Zn and Te. Quantitative studies of impurity induced mixing have been conducted on samples doped with Si or Te during the growth process. It was discovered that Si induced AlGaAs superlattice mixing yielded an activation energy of approximately 4 eV for the Al diffusion coefficient with a high power law dependence of the prefactor on the Si concentration. In the Te doped AlGaAs superlattice the Al diffusion coefficient exhibited an activation energy of {approximately}3.0 eV, with a prefactor approximately proportional to the Te concentration. These results are of importance in examining the current diffusion models. Zn and Si induced InP/InGaAs superlattice mixing are examined. It was found that Zn predominantly induces cation interdiffusion, while Si induces comparable cation and anion interdiffusion. In addition, widely dispersed Zn rich islands form with Zn residing in the InP layers in the form of Zn{sub 3}P{sub 2}. With unstrained starting material, the layer bandgap disparity increases due to mixing induced strain, while in the Si diffused sample the mixed region would be expected to exhibit bandgaps intermediate between those of the original layers. Semiconductor superlattice mixing shows technological potential for optoelectronic device fabrication.

  7. Effects of core mixing on solar oscillation frequencies

    SciTech Connect

    Cox, A.N.; Kidman, R.B.

    1984-07-27

    This paper discusses predicted p- and g-mode periods for two solar models provided by Schatzman and Maeder (1981). One model has no mixing while the other has turbulent diffusion mixing (allowed for by a Reynolds number of 100). The resulting g-mode period spacings allow a very close look at the central solar structure which, like the p-mode period splittings, indicate little or no mixing over the lifetime of the sun.

  8. UPDATING APPLIED DIFFUSION MODELS

    EPA Science Inventory

    Most diffusion models currently used in air quality applications are substantially out of date with understanding of turbulence and diffusion in the planetary boundary layer. Under a Cooperative Agreement with the Environmental Protection Agency, the American Meteorological Socie...

  9. 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.

  10. 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)

  11. 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…

  12. Diffusion of uranium 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 uranium hexafluoride

  13. 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…

  14. 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.

  15. Metal Diffusion in Smoothed Particle Hydrodynamics Simulations of Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Williamson, David; Martel, Hugo; Kawata, Daisuke

    2016-05-01

    We perform a series of smoothed particle hydrodynamics simulations of isolated dwarf galaxies to compare different metal mixing models. In particular, we examine the role of diffusion in the production of enriched outflows and in determining the metallicity distributions of gas and stars. We investigate different diffusion strengths by changing the pre-factor of the diffusion coefficient, by varying how the diffusion coefficient is calculated from the local velocity distribution, and by varying whether the speed of sound is included as a velocity term. Stronger diffusion produces a tighter [O/Fe]–[Fe/H] distribution in the gas and cuts off the gas metallicity distribution function at lower metallicities. Diffusion suppresses the formation of low-metallicity stars, even with weak diffusion, and also strips metals from enriched outflows. This produces a remarkably tight correlation between “metal mass-loading” (mean metal outflow rate divided by mean metal production rate) and the strength of diffusion, even when the diffusion coefficient is calculated in different ways. The effectiveness of outflows at removing metals from dwarf galaxies and the metal distribution of the gas is thus dependent on the strength of diffusion. By contrast, we show that the metallicities of stars are not strongly dependent on the strength of diffusion, provided that some diffusion is present.

  16. Metal Diffusion in Smoothed Particle Hydrodynamics Simulations of Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Williamson, David; Martel, Hugo; Kawata, Daisuke

    2016-05-01

    We perform a series of smoothed particle hydrodynamics simulations of isolated dwarf galaxies to compare different metal mixing models. In particular, we examine the role of diffusion in the production of enriched outflows and in determining the metallicity distributions of gas and stars. We investigate different diffusion strengths by changing the pre-factor of the diffusion coefficient, by varying how the diffusion coefficient is calculated from the local velocity distribution, and by varying whether the speed of sound is included as a velocity term. Stronger diffusion produces a tighter [O/Fe]-[Fe/H] distribution in the gas and cuts off the gas metallicity distribution function at lower metallicities. Diffusion suppresses the formation of low-metallicity stars, even with weak diffusion, and also strips metals from enriched outflows. This produces a remarkably tight correlation between “metal mass-loading” (mean metal outflow rate divided by mean metal production rate) and the strength of diffusion, even when the diffusion coefficient is calculated in different ways. The effectiveness of outflows at removing metals from dwarf galaxies and the metal distribution of the gas is thus dependent on the strength of diffusion. By contrast, we show that the metallicities of stars are not strongly dependent on the strength of diffusion, provided that some diffusion is present.

  17. 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.

  18. TURBULENT DIFFUSION BEHIND VEHICLES: EXPERIMENTALLY DETERMINED TURBULENCE MIXING PARAMETERS

    EPA Science Inventory

    The wake of a moving vehicle was simulated using a specially constructed wind tunnel with a moving floor. A 'blocked-shaped' model vehicle was fixed in position over the test-section floor while the floor moved at the freestream air speed to produce a uniform, shear-free, approac...

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

    NASA Astrophysics Data System (ADS)

    Pinsky, M.; Khain, A.; Korolev, A.

    2015-11-01

    An idealized model of time-dependent mixing between cloud and non-cloud volumes is analyzed. Initial droplet size distribution (DSD) in cloud volume is assumed to be monodisperse. Both analytical investigation and parcel model investigation are used to study mixing processes and solve diffusion-evaporation equations. It is shown that the evolution of microphysical variables and the final equilibrium stage are unambiguously determined by two non-dimensional parameters. The first parameter, R, which is proportional to the ratio of the saturation deficit to the liquid water content in a cloud volume, determines whether the equilibrium stage is reached at 100 % relative humidity, or, rather, leads to a full evaporation of cloud droplets. The second parameter, Da, is the Damkölher number, which is equal to the ratio of the characteristic mixing time and phase relaxation time. This parameter (together with parameter R) determines whether mixing takes place according to a homogeneous or an inhomogeneous scenario. An analysis of the results obtained within a wide range of parameters R and Da is presented. It is shown that there is no pure homogeneous mixing, since the first stage of mixing is always inhomogeneous. Turbulent mixing between different volumes always starts as inhomogeneous and the mixing type can change during the mixing process. At any values of governing parameters, mixing leads to the formation of a tail of small droplets in the DSD and therefore to DSD broadening. The broadening depends onDa and the final DSD dispersion can be as large as 0.2 at large Da. The total duration of the mixing process varies from several to one hundred phase relaxation times, depending on R and Da. Delimitation between the types of mixing on the Da-R plane is carried out. The definitions of homogeneous and inhomogeneous mixings are reconsidered and clarified. The paper also compares the results of the current study with those obtained with classical mixing concepts.

  20. Mesoscale studies of mixing in reactive materials during shock loading

    NASA Astrophysics Data System (ADS)

    Lomov, Ilya; Herbold, Eric B.; Austin, Ryan A.

    2012-03-01

    One of the requisite processes for chemical reactions between solid powder particles resulting from shock loading is that the particles undergo large deformations, exposing new surfaces while mixing with surrounding material. Reactions under shock loading occur in a reaction zone, the extent of which is defined by the interfacial surface area and the depth of the diffusion layer. The former depends on the level of hydrodynamic mixing of heterogeneous material under shock, while the latter depends on temperaturedependent species diffusion. To investigate diffusion-limited reactions at the grain scale level, mass diffusion and simple reaction kinetics depending on the interfacial surface area have been implemented in an Eulerian hydrocode GEODYN. Diffusion-reaction processes that are initiated by rapid heating of a Ni/Al nanolaminate and by shock loading of a micron-scale Ni/Al powder mixture are considered.

  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. 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.

  3. 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.

  4. Anomalous Diffusion in a Trading Model

    NASA Astrophysics Data System (ADS)

    Khidzir, Sidiq Mohamad; Wan Abdullah, Wan Ahmad Tajuddin

    2009-07-01

    The result of the trading model by Chakrabarti et al. [1] is the wealth distribution with a mixed exponential and power law distribution. Based on the motivation of studying the dynamics behind the flow of money similar to work done by Brockmann [2, 3] we track the flow of money in this trading model to observe anomalous diffusion in the form of long waiting times and Levy Flights.

  5. Molecular simulations of diffusion in electrolytes

    NASA Astrophysics Data System (ADS)

    Wheeler, Dean Richard

    This work demonstrates new methodologies for simulating multicomponent diffusion in concentrated solutions using molecular dynamics (MD). Experimental diffusion data for concentrated multicomponent solutions are often lacking, as are accurate methods of predicting diffusion for nonideal solutions. MD can be a viable means of understanding and predicting multicomponent diffusion. While there have been several prior reports of MD simulations of mutual diffusion, no satisfactory expressions for simulating Stefan-Maxwell diffusivities for an arbitrary number of species exist. The approaches developed here allow for the computation of a full diffusion matrix for any number of species in both nonequilibrium and equilibrium MD ensembles. Our nonequilibrium approach is based on the application of constant external fields to drive species diffusion. Our equilibrium approach uses a newly developed Green-Kubo formula for Stefan-Maxwell diffusivities. In addition, as part of this work, we demonstrate a widely applicable means of increasing the computational efficiency of the Ewald sum, a technique for handling long-range Coulombic interactions in simulations. The theoretical development is applicable to any solution which can be simulated using MD; nevertheless, our primary interest is in electrochemical applications. To this end, the methods are tested by simulations of aqueous salt solutions and lithium-battery electrolytes. KCl and NaCl aqueous solutions were simulated over the concentration range 1 to 4 molal. Intermolecular-potential models were parameterized for these transport-based simulations. This work is the first to simulate all three independent diffusion coefficients for aqueous NaCl and KCl solutions. The results show that the nonequilibrium and equilibrium methods are consistent with each other, and in moderate agreement with experiment. We simulate lithium-battery electrolytes containing LiPF6 in propylene carbonate and mixed ethylene carbonate

  6. Diffusivity of Mixtures in Warm Dense Matter Regime

    NASA Astrophysics Data System (ADS)

    Haxhimali, Tomorr; Rudd, Robert; Jackson, Julie; Langdon, A. Bruce; Glosli, James; Graziani, Frank

    2013-10-01

    Modeling of ionic diffusion in warm dense plasma mixtures has been of longstanding interest in astrophysics and in Inertial Confinement Fusion. In this work we employ classical Molecular Dynamics (MD) to calculate diffusion coefficients in mixed plasmas. In the MD study we make use of the Yukawa potential as an effective ion-ion interaction potential that accounts for the screening effects of the electrons. We focus in binary asymmetric mixtures between Deuterium and Argon at Temperatures from 10-100eV and ion densities from 1023-1025 ion/cc. In uniform mixed systems we use Green-Kubo techniques to calculate self-diffusivities and Maxwell-Stefan diffusivities over a range of conditions. The new results from this study show that a simple linear relations between Maxwell-Stefan diffusivity and self-diffusivities is not always valid. The interdiffusivity that enters in Fickian equation can be related to the Maxwell-Stefan diffusivities through the thermodynamic factor. The latter requires knowledge of the equation of state of the mixture. We compare these results with classical kinetic theories that assume binary collisions. To test these Green-Kubo approaches and to estimate the activity contribution we have also employed large-scale non-equilibrium, non-uniform mixed, MD. This work was performed under the auspices of the US Dept. of Energy by Lawrence Livermore National Security, LLC under Contract DE-AC52-07NA27344.

  7. 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

  8. 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. PMID:24460103

  9. Organic aerosol mixing observed by single-particle mass spectrometry.

    PubMed

    Robinson, Ellis Shipley; Saleh, Rawad; Donahue, Neil M

    2013-12-27

    We present direct measurements of mixing between separately prepared organic aerosol populations in a smog chamber using single-particle mass spectra from the high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS). Docosane and docosane-d46 (22 carbon linear solid alkane) did not show any signs of mixing, but squalane and squalane-d62 (30 carbon branched liquid alkane) mixed on the time scale expected from a condensational-mixing model. Docosane and docosane-d46 were driven to mix when the chamber temperature was elevated above the melting point for docosane. Docosane vapors were shown to mix into squalane-d62, but not the other way around. These results are consistent with low diffusivity in the solid phase of docosane particles. We performed mixing experiments on secondary organic aerosol (SOA) surrogate systems finding that SOA derived from toluene-d8 (a surrogate for anthropogenic SOA (aSOA)) does not mix into squalane (a surrogate for hydrophobic primary organic aerosol (POA)) but does mix into SOA derived from α-pinene (biogenic SOA (bSOA) surrogate). For the aSOA/POA, the volatility of either aerosol does not limit gas-phase diffusion, indicating that the two particle populations do not mix simply because they are immiscible. In the aSOA/bSOA system, the presence of toluene-d8-derived SOA molecules in the α-pinene-derived SOA provides evidence that the diffusion coefficient in α-pinene-derived SOA is high enough for mixing on the time scale of 1 min. The observations from all of these mixing experiments are generally invisible to bulk aerosol composition measurements but are made possible with single-particle composition data. PMID:24131283

  10. Diffusion in disordered media

    NASA Astrophysics Data System (ADS)

    Havlin, Shlomo; Ben-Avraham, Daniel

    2002-01-01

    Diffusion in disordered systems does not follow the classical laws which describe transport in ordered crystalline media, and this leads to many anomalous physical properties. Since the application of percolation theory, the main advances in the understanding of these processes have come from fractal theory. Scaling theories and numerical simulations are important tools to describe diffusion processes (random walks: the 'ant in the labyrinth') on percolation systems and fractals. Different types of disordered systems exhibiting anomalous diffusion are presented (the incipient infinite percolation cluster, diffusion-limited aggregation clusters, lattice animals, and random combs), and scaling theories as well as numerical simulations of greater sophistication are described. Also, diffusion in the presence of singular distributions of transition rates is discussed and related to anomalous diffusion on disordered structures.

  11. Hereditary Diffuse Infiltrating Retinoblastoma.

    PubMed

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

    2016-03-01

    Retinoblastoma is one of the most common childhood cancers. The diffuse infiltrating retinoblastoma is a rare subtype of this neoplasm. The majority of cases of diffuse infiltrating retinoblastoma are unilateral and occur sporadically. Herein we report on a family with three children affected by retinoblastoma, among them one girl with diffuse infiltrating retinoblastoma. This girl was diagnosed at the age of 8 years with a unilateral diffuse infiltrating retinoblastoma. By contrast, the two brothers became clinically apparent in the first 2 years of life with bilateral retinoblastoma. The parents were clinically unremarkable. Genetic analysis of RB1 gene was performed. The girl with diffuse infiltrating RB was found to be heterozygous for an oncogenic mutation in the RB1 gene that was also carried by both brothers and the father of the family. These results show that diffuse infiltrating retinoblastoma can develop on the background of a hereditary predisposition to retinoblastoma. PMID:24892564

  12. Multinomial diffusion equation

    NASA Astrophysics Data System (ADS)

    Balter, Ariel; Tartakovsky, Alexandre M.

    2011-06-01

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

  13. Multinomial diffusion equation

    SciTech Connect

    Balter, Ariel I.; Tartakovsky, Alexandre M.

    2011-06-24

    We describe a new, microscopic model for diffusion that captures diffusion induced uctuations at scales where the concept of concentration gives way to discrete par- ticles. We show that in the limit as the number of particles N ! 1, our model is equivalent to the classical stochastic diffusion equation (SDE). We test our new model and the SDE against Langevin dynamics in numerical simulations, and show that our model successfully reproduces the correct ensemble statistics, while the classical model fails.

  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. /sup 13/C spin diffusion of adamantane

    SciTech Connect

    Bronniman, C.E.; Szeverenyi, N.M.; Maciel, G.E.

    1983-10-15

    Two-dimensional exchange spectroscopy of natural abundance /sup 13/C--/sup 13/C spin diffusion in solid adamantane illustrates the influence that /sup 13/C--/sup 1/H dipole--dipole coupling exerts on /sup 13/C spin diffusion by determining spectral overlap in the /sup 13/C system. 2D /sup 13/C spectra were obtained for several values of mixing time tau/sub m/ and compared with spectra calculated in the limit of nearest-neighbor coupling. Good agreement is obtained for short tau/sub m/, during which the equilibration of neighboring spins dominates. For longer tau/sub m/, slower spin diffusion that is not acounted for by the simple model is seen; after nearest-neighbor spins equilibrate, communication over larger distances produces further mixing. It is possible to modify spin diffusion rates by altering experimental conditions, e.g., magic-angle spinning, low-power /sup 1/H decoupling, or spin locking /sup 13/C in the rotating frame during tau/sub m/.

  16. Fluid dynamics of double diffusive systems

    NASA Astrophysics Data System (ADS)

    Koseff, J. R.

    1991-04-01

    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 heatings 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, our overall goals are as follows: (1) develop more general stability and scaling criteria for the destabilization of doubly-stratified systems, (2) further study the variation of flow structure and scales with Rayleigh ratio and lateral heating ratio, (3) further delineate the mechanisms governing convective layer formation and merging, (4) study the mixing processes within the convective layers and across interfaces, and estimate the heat and mass fluxes in such a system, (5) quantify the effects of turbulence and coherent structures (due to a wind-driven surface shear) on a doubly stratified system, and (6) study the interaction between surface shear and side-wall heating destabilization mechanisms.

  17. 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.

  18. 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.

  19. Microgravity Turbulent Gas-Jet Diffusion Flames

    NASA Technical Reports Server (NTRS)

    1996-01-01

    A gas-jet diffusion flame is similar to the flame on a Bunsen burner, where a gaseous fuel (e.g., propane) flows from a nozzle into an oxygen-containing atmosphere (e.g., air). The difference is that a Bunsen burner allows for (partial) premixing of the fuel and the air, whereas a diffusion flame is not premixed and gets its oxygen (principally) by diffusion from the atmosphere around the flame. Simple gas-jet diffusion flames are often used for combustion studies because they embody the mechanisms operating in accidental fires and in practical combustion systems. However, most practical combustion is turbulent (i.e., with random flow vortices), which enhances the fuel/air mixing. These turbulent flames are not well understood because their random and transient nature complicates analysis. Normal gravity studies of turbulence in gas-jet diffusion flames can be impeded by buoyancy-induced instabilities. These gravitycaused instabilities, which are evident in the flickering of a candle flame in normal gravity, interfere with the study of turbulent gas-jet diffusion flames. By conducting experiments in microgravity, where buoyant instabilities are avoided, we at the NASA Lewis Research Center hope to improve our understanding of turbulent combustion. Ultimately, this could lead to improvements in combustor design, yielding higher efficiency and lower pollutant emissions. Gas-jet diffusion flames are often researched as model flames, because they embody mechanisms operating in both accidental fires and practical combustion systems (see the first figure). In normal gravity laboratory research, buoyant air flows, which are often negligible in practical situations, dominate the heat and mass transfer processes. Microgravity research studies, however, are not constrained by buoyant air flows, and new, unique information on the behavior of gas-jet diffusion flames has been obtained.

  20. 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.

  1. 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.

  2. 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.

  3. Experimental study of vortex diffusers

    SciTech Connect

    Shakerin, S.; Miller, P.L.

    1995-11-01

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

  4. 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

  5. Determination of eddy diffusivity in the lowermost stratosphere

    NASA Astrophysics Data System (ADS)

    Hegglin, M. I.; Brunner, D.; Peter, T.; Staehelin, J.; Wirth, V.; Hoor, P.; Fischer, H.

    2005-07-01

    We present a 2D-advection-diffusion model that simulates the main transport pathways influencing tracer distributions in the lowermost stratosphere (LMS). The model describes slow diabatic descent of aged stratospheric air, vertical (cross-isentropic) and horizontal (along isentropes) diffusion within the LMS and across the tropopause using equivalent latitude and potential temperature coordinates. Eddy diffusion coefficients parameterize the integral effect of dynamical processes leading to small scale turbulence and mixing. They were specified by matching model simulations to observed CO distributions. Interestingly, the model suggests mixing across isentropes to be more important than horizontal mixing across surfaces of constant equivalent latitude, shining new light on the interplay between various transport mechanisms in the LMS. The model achieves a good description of the small scale tracer features at the tropopause with squared correlation coefficients R2 = 0.72...0.94.

  6. Electro-diffusion in a plasma with two ion species

    SciTech Connect

    Kagan, Grigory; Tang Xianzhu

    2012-08-15

    Electric field is a thermodynamic force that can drive collisional inter-ion-species transport in a multicomponent plasma. In an inertial confinement fusion capsule, such transport causes fuel ion separation even with a target initially prepared to have equal number densities for the two fuel ion species. Unlike the baro-diffusion driven by ion pressure gradient and the thermo-diffusion driven by ion and electron temperature gradients, electro-diffusion has a critical dependence on the charge-to-mass ratio of the ion species. Specifically, it is shown here that electro-diffusion vanishes if the ion species have the same charge-to-mass ratio. An explicit expression for the electro-diffusion ratio is obtained and used to investigate the relative importance of electro- and baro-diffusion mechanisms. In particular, it is found that electro-diffusion reinforces baro-diffusion in the deuterium and tritium mix, but tends to cancel it in the deuterium and helium-3 mix.

  7. 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.

  8. Galactic Diffuse Emissions

    SciTech Connect

    Digel, Seth W.; /SLAC

    2007-10-25

    Interactions of cosmic rays with interstellar nucleons and photons make the Milky Way a bright, diffuse source of high-energy {gamma}-rays. Observationally, the results from EGRET, COMPTEL, and OSSE have now been extended to higher energies by ground-based experiments, with detections of diffuse emission in the Galactic center reported by H.E.S.S. in the range above 100 GeV and of diffuse emission in Cygnus by MILAGRO in the TeV range. In the range above 100 keV, INTEGRAL SPI has found that diffuse emission remains after point sources are accounted for. I will summarize current knowledge of diffuse {gamma}-ray emission from the Milky Way and review some open issues related to the diffuse emission -- some old, like the distribution of cosmic-ray sources and the origin of the 'excess' of GeV emission observed by EGRET, and some recently recognized, like the amount and distribution of molecular hydrogen not traced by CO emission -- and anticipate some of the advances that will be possible with the Large Area Telescope on GLAST. We plan to develop an accurate physical model for the diffuse emission, which will be useful for detecting and accurately characterizing emission from Galactic point sources as well as any Galactic diffuse emission from exotic processes, and for studying the unresolved extragalactic emission.

  9. 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.

  10. 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…

  11. 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…

  12. 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.

  13. Evolution of density compensated fronts in simulated ocean mixed layers

    NASA Astrophysics Data System (ADS)

    Helber, R. W.; Hebert, D. A.; Koch, A.

    2015-12-01

    Observations within the ocean surface mixed layer indicate a tendency for temperature gradients to form that are compensated for their effect on density by salinity gradients. These density compensated fronts tend to occur in the absence of strong surface forcing and thus weak vertical mixing. Observations show that density compensated fronts are quickly erased by surface cooling events. The presence of density compensated gradients in the surface mixed layer, however, are not well represented in regional and global ocean circulation model predictions. In these models, subgrid-scale processes are parameterized with minimal ability to represent double diffusion. Recent advances in parameterizations have been developed to model the re-stratification of the mixed layer by sub-mesoscale eddies. These ageostrophic dynamics can lead to long filaments that are governed by process on length scales from 100 m to 10 km and time scales near a day. The impact of these processes in model physics on density compensated fronts is unclear. To improve our understanding of compensated front evolution in the ocean, three different mixing schemes are tested to evaluate the creation of horizontally density compensated gradients in model simulations. One scheme extracts potential energy of ocean fronts for mixing dependent on horizontal and vertical buoyancy gradients, mixed layer depth, and inertial period. The other two schemes mix temperature and salinity horizontally dependent on the buoyancy gradient. All schemes provide a three dimensional approach to mixing that differentiates the horizontal eddy diffusion of temperature and salinity.

  14. Model for compound formation during ion-beam mixing

    SciTech Connect

    Desimoni, J.; Traverse, A. )

    1993-11-01

    We propose an ion-beam-mixing model that accounts for compound formation at a boundary between two materials during ion irradiation. It is based on Fick's law together with a chemical driving force in order to simulate the chemical reaction at the boundary. The behavior of the squared thickness of the mixed layer, [ital X][sup 2], with the irradiation fluence, [Phi], has been found in several mixing experiments to be either quadratic ([ital X][sup 2][alpha][Phi][sup 2]) or linear ([ital X][sup 2][alpha][Phi]), a result which is qualitatively reproduced. Depending on the fluence range, compound formation or diffusion is the limiting process of mixing kinetics. A criterion is established in terms of the ratio of the diffusion coefficient [ital D] due to irradiation to the chemical reaction rate squared which allows us to predict quadratic or linear behavior. When diffusion is the limiting process, [ital D] is enhanced by a factor which accounts for the formation of a compound in the mixed layer. Good agreement is found between the calculated mixing rates and the data taken from mixing experiments in metal/Si bilayers.

  15. 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.

  16. 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.

  17. Foundations of chaotic mixing.

    PubMed

    Wiggins, Stephen; Ottino, Julio M

    2004-05-15

    The simplest mixing problem corresponds to the mixing of a fluid with itself; this case provides a foundation on which the subject rests. The objective here is to study mixing independently of the mechanisms used to create the motion and review elements of theory focusing mostly on mathematical foundations and minimal models. The flows under consideration will be of two types: two-dimensional (2D) 'blinking flows', or three-dimensional (3D) duct flows. Given that mixing in continuous 3D duct flows depends critically on cross-sectional mixing, and that many microfluidic applications involve continuous flows, we focus on the essential aspects of mixing in 2D flows, as they provide a foundation from which to base our understanding of more complex cases. The baker's transformation is taken as the centrepiece for describing the dynamical systems framework. In particular, a hierarchy of characterizations of mixing exist, Bernoulli --> mixing --> ergodic, ordered according to the quality of mixing (the strongest first). Most importantly for the design process, we show how the so-called linked twist maps function as a minimal picture of mixing, provide a mathematical structure for understanding the type of 2D flows that arise in many micromixers already built, and give conditions guaranteeing the best quality mixing. Extensions of these concepts lead to first-principle-based designs without resorting to lengthy computations. PMID:15306478

  18. Diffusion in Coulomb crystals.

    PubMed

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

    2011-07-01

    Diffusion in Coulomb crystals can be important for the structure of neutron star crusts. We determine diffusion constants D from molecular dynamics simulations. We find that D for Coulomb crystals with relatively soft-core 1/r interactions may be larger than D for Lennard-Jones or other solids with harder-core interactions. Diffusion, for simulations of nearly perfect body-centered-cubic lattices, involves the exchange of ions in ringlike configurations. Here ions "hop" in unison without the formation of long lived vacancies. Diffusion, for imperfect crystals, involves the motion of defects. Finally, we find that diffusion, for an amorphous system rapidly quenched from Coulomb parameter Γ=175 to Coulomb parameters up to Γ=1750, is fast enough that the system starts to crystalize during long simulation runs. These results strongly suggest that Coulomb solids in cold white dwarf stars, and the crust of neutron stars, will be crystalline and not amorphous. PMID:21867316

  19. 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.

  20. Diffusion on strained surfaces

    NASA Astrophysics Data System (ADS)

    Schroeder, M.; Wolf, D. E.

    1997-03-01

    The change of diffusion kinetics when elastic fields are present is discussed for diffusion on (001) surfaces of simple cubic, fcc and bcc lattices. All particles interact pairwise with a Lennard-Jones potential. The simple cubic lattice was stabilized by an anisotropic prefactor. It is found that generically compressive strain enhances diffusion whereas tensile strain increases the activation barrier. An approximately linear dependence of the barrier in a wide range of misfits is found. In heteroepitaxy, diffusion on top of large clusters is inhomogeneous and anisotropic. The kinetics close to edges and centers of islands are remarkably different. In many cases changes of binding energies are small compared to those of saddle point energies. Thermodynamic arguments (minimization of free energy) are not appropriate to describe diffusion on strained surfaces in these cases.

  1. Mixing and compaction temperatures for Superpave mixes

    NASA Astrophysics Data System (ADS)

    Yildirim, Yetkin

    According to Superpave mixture design, gyratory specimens are mixed and compacted at equiviscous binder temperatures corresponding to viscosities of 0.17 and 0.28 Pa.s. respectively. These were the values previously used in the Marshal mix design method to determine optimal mixing and compaction temperatures. In order to estimate the appropriate mixing and compaction temperatures for Superpave mixture design, a temperature-viscosity relationship for the binder needs to be developed (ASTM D 2493, Calculation of Mixing and Compaction Temperatures). The current approach is simple and provides reasonable temperatures for unmodified binders. However, some modified binders have exhibited unreasonably high temperatures for mixing and compaction using this technique. These high temperatures can result in construction problems, damage of asphalt, and production of fumes. Heating asphalt binder to very high temperatures during construction oxidizes the binder and separates the polymer from asphalt binder. It is known that polymer modified asphalt binders have many benefits to the roads, such as; increasing rutting resistance, enhancing low temperature cracking resistance, improving traction, better adhesion and cohesion, elevating tensile strength which are directly related to the service life of the pavement. Therefore, oxidation and separation of the polymer from the asphalt binder results in reduction of the service life. ASTM D 2493 was established for unmodified asphalt binders which are Newtonian fluids at high temperatures. For these materials, viscosity does not depend on shear rate. However, most of the modified asphalt binders exhibit a phenomenon known as pseudoplasticity, where viscosity does depend on shear rate. Thus, at the high shear rates occurring during mixing and compaction, it is not necessary to go to very high temperatures. This research was undertaken to determine the shear rate during compaction such that the effect of this parameter could be

  2. Double-diffusive instabilities in ancient seawater

    NASA Astrophysics Data System (ADS)

    Pawlowicz, Rich; Scheifele, Ben; Zaloga, Artem; Wuest, Alfred; Sommer, Tobias

    2015-04-01

    Powell Lake, British Columbia, Canada is a geothermally heated lake about 350m deep with a saline lower layer that was isolated from the ocean by coastal uplift about 11000 years ago, after the last ice age. Careful temperature and conductivity profiling measurements show consistent, stable, and spatially/temporally coherent steps resulting from double-diffusive processes in certain ranges of depth, vertically interspersed with other depth ranges where these signatures are not present. These features are quasi-stable for at least several years. Although molecular diffusion has removed about half the salt from the deepest waters and biogeochemical processes have slightly modified the water composition, the lack of tidal processes and shear-driven mixing, as well as an accurate estimate of heat flux from both sediment heat flux measurements and gradient measurements in a region not susceptible to diffusive instabilities, makes this a unique geophysical laboratory to study double diffusion. Here we present a detailed picture of the structure of Powell Lake and its double-diffusive stair cases, and suggest shortcomings with existing parameterizations for fluxes through such staircases.

  3. 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.

  4. Note: X-ray radiography for measuring chemical diffusion in metallic melts

    NASA Astrophysics Data System (ADS)

    Griesche, A.; Zhang, B.; Solórzano, E.; Garcia-Moreno, F.

    2010-05-01

    A x-ray radioscopy technique for measuring in situ chemical diffusion coefficients in metallic melts is presented. The long-capillary diffusion measurement method is combined with imaging techniques using microfocus tubes and flat panel detectors in order to visualize and quantitatively analyze diffusive mixing of two melts of different chemical composition. The interdiffusion coefficient as function of temperature and time is obtained by applying Fick's diffusion laws. Tracking the time dependence of the mean square penetration depth of the mixing process allows to detect changes in the mass transport caused by convective flow. The possibility to sort out convective mass transport contributions from analysis enhances significantly the accuracy compared to the conventional long-capillary diffusion measurement method with postmortem analysis. The performance of this novel diffusion measurement method with x-ray radiography technique is demonstrated by a diffusion experiment in an Al-Ni melt.

  5. Note: X-ray radiography for measuring chemical diffusion in metallic melts

    SciTech Connect

    Griesche, A.; Zhang, B.; Solorzano, E.; Garcia-Moreno, F.

    2010-05-15

    A x-ray radioscopy technique for measuring in situ chemical diffusion coefficients in metallic melts is presented. The long-capillary diffusion measurement method is combined with imaging techniques using microfocus tubes and flat panel detectors in order to visualize and quantitatively analyze diffusive mixing of two melts of different chemical composition. The interdiffusion coefficient as function of temperature and time is obtained by applying Fick's diffusion laws. Tracking the time dependence of the mean square penetration depth of the mixing process allows to detect changes in the mass transport caused by convective flow. The possibility to sort out convective mass transport contributions from analysis enhances significantly the accuracy compared to the conventional long-capillary diffusion measurement method with postmortem analysis. The performance of this novel diffusion measurement method with x-ray radiography technique is demonstrated by a diffusion experiment in an Al-Ni melt.

  6. On Atomic Diffusion and the Cosmological Lithium Abundance

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

    When it comes to lithium in late-type stars, atomic diffusion (AD) refers to the slow gravitational settling below the convective zone. Richard, Michaud & Richter, J. (2005) computed the influence of diffusion on the lithium abundance with different additional mixing (AddMix) parameters, after 13.5 Gyr with an initial Li abundance compatible with BBN. Without AddMix the abundance of lithium would decrease when the temperature of the star increases. This is depicted by the dashed green line in the left panel of Fig. 1 and is in contradiction with the existence of a lithium plateau. But with a model including ad-hoc AddMix, where the AddMix diffusion coefficient is given by D T and is connected to D He(AD) at a reference temperature of log T 0=6.25, it is possible to reproduce the plateau as seen in the figure (solid green line). AD with AddMix has so far been shown to be at work in two globular clusters (GC) with different metallicities. Korn et al. (2007) showed the effects in NGC 6397 at [Fe/H] = -2.1. More recently Gruyters et al. (2013) have shown smaller effects, but similar in nature, in NGC 6752 at [Fe/H] = -1.6. The Li abundance for both clusters can be brought in to agreement with predictions from the cosmic microwave background radiation and Big Bang nucleosynthesis (CMB+BBN) by using stellar structure models including AD and AddMix, although with different efficiencies of AddMix. It seems there is an evolution of AddMix with metallicity which renders AD less efficient. As AddMix acts only in the outer regions, helium settling in the core is not affected, and so the overall evolution (e.g. T eff-age relation) will be similar regardless of this parameter.

  7. 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.

  8. 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. >

  9. 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.

  10. Turbidity Current Head Mixing

    NASA Astrophysics Data System (ADS)

    Hernandez, David; Sanchez, Miguel Angel; Medina, Pablo

    2010-05-01

    coastal diffusion using image analysis. Applied Scientific Research 59,.191-204. 1998. [5] J.M. Redondo. Turbulent mixing in the Atmosphere and Ocean. Fluid Physics. 584-597. World Scientific. New York. 1994

  11. 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.

  12. Tungsten diffusion in olivine

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

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

  13. 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.

  14. 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.

  15. Diffusion of dye solution in the intermolecular nanostructure of polydimethylsiloxane

    NASA Astrophysics Data System (ADS)

    Saito, Mitsunori; Nishimura, Tatsuya; Sakiyama, Kohei; Nakagawa, Michinori

    2012-09-01

    Polydimethylsiloxane (PDMS) contains a large, flexible free space between weakly-bonded molecules, which allows notable molecular diffusion. A toluene solution of diarylethene (photochromic dye) was mixed with a PDMS oil, and then the mixture was cured in a glass vessel by adding a curing agent. Violet laser (405 nm wavelength) irradiation induced an absorption band at around 530 nm, and consequently, the irradiated portion exhibited a red color. The colored portion gradually expanded to the entire sample because of diffusion of the dye molecules. This diffusion characteristic was used for improving an organic dye durability against a photo-induced degradation.

  16. 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.

  17. Fractionation of soil gases by diffusion of water vapor, gravitational settling, and thermal diffusion

    SciTech Connect

    Severinghaus, J.P.; Bender, M.L.; Keeling, R.F.; Broecker, W.S.

    1996-03-01

    Air sampled from the moist unsaturated zone in a sand dune exhibits depletion in the heavy isotopes of N{sub 2} and O{sub 2}. We propose that the depletion is caused by a diffusive flux of water vapor out of the dune, which sweeps out the other gases, forcing them to diffuse back into the dune. The heavy isotopes of N{sub 2} and O{sub 2} diffuse back more slowly, resulting in a steady-state depletion of the heavy isotopesin the dune interior. We predict the effect`s magnitude with molecular diffusion theory and reproduce it in a laboratory simulation, finding good agreement between field, theory, and lab. The magnitude of the effect is governed by the ratio of the binary diffusivities against water vapor of a pair of gases, and increases {approximately} linearly with the difference between the water vapor mole fraction of the site and the advectively mixed reservoir with which it is in diffusive contact (in most cases the atmosphere). 32 refs., 1 fig., 3 tabs.

  18. Incomplete mixing and reactions in laminar shear flow

    NASA Astrophysics Data System (ADS)

    Paster, A.; Aquino, T.; Bolster, D.

    2015-07-01

    Incomplete mixing of reactive solutes is well known to slow down reaction rates relative to what would be expected from assuming perfect mixing. In purely diffusive systems, for example, it is known that small initial fluctuations in reactant concentrations can lead to reactant segregation, which in the long run can reduce global reaction rates due to poor mixing. In contrast, nonuniform flows can enhance mixing between interacting solutes. Thus, a natural question arises: Can nonuniform flows sufficiently enhance mixing to restrain incomplete mixing effects and, if so, under what conditions? We address this question by considering a specific and simple case, namely, a laminar pure shear reactive flow. Two solution approaches are developed: a Lagrangian random walk method and a semianalytical solution. The results consistently highlight that if shear effects in the system are not sufficiently strong, incomplete mixing effects initially similar to purely diffusive systems will occur, slowing down the overall reaction rate. Then, at some later time, dependent on the strength of the shear, the system will return to behaving as if it were well mixed, but represented by a reduced effective reaction rate.

  19. 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.

  20. Hereditary Diffuse Gastric Cancer

    MedlinePlus

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

  1. Multinomial Diffusion Equation

    SciTech Connect

    Balter, Ariel I.; Tartakovsky, Alexandre M.

    2011-06-01

    We have developed a novel stochastic, space/time discrete representation of particle diffusion (e.g. Brownian motion) based on discrete probability distributions. We show that in the limit of both very small time step and large concentration, our description is equivalent to the space/time continuous stochastic diffusion equation. Being discrete in both time and space, our model can be used as an extremely accurate, efficient, and stable stochastic finite-difference diffusion algorithm when concentrations are so small that computationally expensive particle-based methods are usually needed. Through numerical simulations, we show that our method can generate realizations that capture the statistical properties of particle simulations. While our method converges converges to both the correct ensemble mean and ensemble variance very quickly with decreasing time step, but for small concentration, the stochastic diffusion PDE does not, even for very small time steps.

  2. Investigating diffusion with technology

    NASA Astrophysics Data System (ADS)

    Miller, Jon S.; Windelborn, Augden F.

    2013-07-01

    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 (darkness) of the digital pictures are recorded and then plotted on a graph. The resulting graph of darkness versus time allows students to see the results of diffusion of the dye over time. Through modification of the basic lesson plan, students are able to investigate the influence of a variety of variables on diffusion. Furthermore, students are able to expand the boundaries of their thinking by formulating hypotheses and testing their hypotheses through experimentation. As a result, students acquire a relevant science experience through taking measurements, organizing data into tables, analysing data and drawing conclusions.

  3. 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 ( ...

  4. Lung diffusion testing

    MedlinePlus

    Lung diffusion testing measures how well the lungs exchange gases. This is an important part of lung testing , because ... Gender Height Hemoglobin (the protein in red blood cells that carries oxygen) level

  5. 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.

  6. Hydrogen Diffusion in Forsterite

    NASA Astrophysics Data System (ADS)

    Demouchy, S.; Mackwell, S.

    2002-12-01

    Physical and chemical properties of Earth's mantle are readily modified by interaction with volatiles, such as water. Thus, characterization of solubility and kinetics of incorporation for water in nominally anhydrous minerals is important in order to understand the behavior of Earth's interior under hydrous conditions. Experimental studies on the olivine-water system indicate that significant amounts of OH can dissolve within olivine as point defects (Bell and Rossman, 1992; Kohlstedt et al. 1996). Extending Kohlstedt and Mackwell's (1998) work, our study concerns the kinetics of hydrogen transport in the iron-free olivine-water system. This study is based on hydrogenation of forsterite samples during piston-cylinder and TZM cold-seal vessel experiments. We use infrared analyses in order to constrain the speciation of the mobile water-derived defects in forsterite single-crystal sample, and the rates of diffusion of such species under uppermost mantle conditions (0.2 to 1.5 GPa, 900 to 1100° C). Hydrogen defect transport in single crystals of forsterite is investigated for diffusion parallel to each crystallographic axis. Defect diffusivities are obtained by fitting a diffusion law to the OH content as a function of position in the sample. Our current results indicate that incorporation of hydroxyl species into iron-free olivine is a one-stage process with hydrogen diffusion linked to magnesium vacancy self-diffusion DV, such that DV = D~/3 = 10-12 m2/s at 1000° C parallel to [001], where D~ represents the chemical diffusivity. Those diffusion rates are slightly lower than in iron-bearing olivine for the same incorporation mechanism. The different concentration profiles show a clear anisotropy of diffusion, with fastest diffusion parallel to [001] as in iron-bearing olivine. Thus, while hydrogen solubilities are dependent on iron content, the rate of incorporation of water-derived species in olivine is not strongly coupled to the concentration of iron. This

  7. Nodal Diffusion & Transport Theory

    1992-02-19

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

  8. 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.

  9. 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.

  10. Mixing in suspensions of active particles

    NASA Astrophysics Data System (ADS)

    Pushkin, Dmitri O.; Yeomans, Julia M.

    2014-03-01

    Microscopic active particles self-propelling in the surrounding fluid create flows that eventually lead to emergence of non-equilibrium states with long-ranged fluctuations. One of the technologically important consequences of these fluctuations is enhanced mixing of the surrounding fluid. It is also critical for understanding the ecology of a particular type of biological active systems, bacterial suspension, as the enhanced mixing strongly alters the fluxes of nutrients. We consider the theoretical foundations of fluid mixing enhancement in dilute suspensions of active force-free swimmers. We describe the impediments to fluid mixing imposed by the physical nature of fluid flows created by swimmers, and different ways of overcoming them. We show that fluid mixing in 3D suspensions of force-free (dipolar) swimmers is dominated by the effect of curvature of their trajectories, and obtain an exact analytical expression for the corresponding effective diffusion coefficient. Our results highlight limitations of alternative ``effective temperature'' approaches and may serve as a quantitative tool for designing technological applications.

  11. 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. PMID:25968481

  12. 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.

  13. Cation Diffusion in Xenotime

    NASA Astrophysics Data System (ADS)

    Cherniak, D. J.

    2004-05-01

    Xenotime is an important mineral in metamorphic paragenesis, and useful in isotopic dating, garnet-xenotime thermometry, and monazite-xenotime thermometry, so diffusion data for xenotime of cations of geochronological and geochemical importance are of some interest. We report here on diffusion of the rare earth elements Sm, Dy and Yb in synthetic xenotime under dry conditions. The synthetic xenotime was grown via a Na2}CO{3}-MoO_{3 flux method. The source of diffusant for the experiments were REE phosphate powders, with experiments run with sources containing a single REE. Experiments were performed by placing source and xenotime in Pt capsules, and annealing capsules in 1 atm furnaces for times ranging from thirty minutes to a month, at temperatures from 1000 to 1400C. The REE distributions in the xenotime were profiled by Rutherford Backscattering Spectrometry (RBS). The following Arrhenius relations are obtained for diffusion in xenotime, normal to (101): DSm = 1.7x10-4 exp(-442 kJ mol-1/RT) m2}sec{-1 DDy = 3.5x10-7 exp(-365 kJ mol-1/RT) m2}sec{-1 DYb = 7.4x10-7 exp(-371 kJ mol-1/RT) m2}sec{-1. Diffusivities of these REE do not differ greatly in xenotime, in contrast to the findings noted for the REE in zircon (Cherniak et al., 1997), where the LREE diffuse more slowly, and with higher activation energies for diffusion, than the heavier rare earths. In zircon, these differences among diffusion of the rare earths are attributed to the relatively large size of the REE with respect to Zr, for which they substitute in the zircon lattice. With the systematic increase in ionic radius from the heavy to lighter REE, this size mismatch becomes more pronounced and diffusivities of the LREE are as consequence slower. Although xenotime is isostructural with zircon, the REE are more closely matched in size to Y, so in xenotime this effect appears much smaller and the REE diffuse at similar rates. In addition, the process of diffusion in xenotime likely involves simple REE+3

  14. Theory for Neutrino Mixing

    NASA Astrophysics Data System (ADS)

    He, Xiao-Gang

    2016-07-01

    Since the discovery of neutrino oscillations, for which Takaaki Kajita and Arthur B. McDonald were awarded the 2015 Nobel prize in physics, tremendous progresses have been made in measuring the mixing angles which determine the oscillation pattern. A lot of theoretical efforts have been made to understand how neutrinos mix with each other. Present data show that in the standard parameterization of the mixing matrix, θ23 is close to π/4 and the CP violating phase is close to ‑ π/2. In this talk I report results obtained in arXiv:1505.01932 (Phys. Lett. B750(2015)620) and arXive:1404.01560 (Chin. J. Phys.53(2015)100101) and discuss some implications for theoretical model buildings for such mixing pattern. Specific examples for neutrino mixing based on A4 family symmetry are given.

  15. High-mix insulins

    PubMed Central

    Kalra, Sanjay; Farooqi, Mohammad Hamed; El-Houni, Ali E.

    2015-01-01

    Premix insulins are commonly used insulin preparations, which are available in varying ratios of different molecules. These drugs contain one short- or rapid-acting, and one intermediate- or long-acting insulin. High-mix insulins are mixtures of insulins that contain 50% or more than 50% of short-acting insulin. This review describes the clinical pharmacology of high-mix insulins, including data from randomized controlled trials. It suggests various ways, in which high-mix insulin can be used, including once daily, twice daily, thrice daily, hetero-mix, and reverse regimes. The authors provide a rational framework to help diabetes care professionals, identify indications for pragmatic high-mix use. PMID:26425485

  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. 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.

  18. 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.

  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. Diffusion induced recrystallization of NiO

    SciTech Connect

    Parthasarathy, T.A.; Shewmon, P.G.

    1984-01-01

    It is shown that changing the composition of a sample from that in equilibrium with air at 1200/sup 0/C to that in equilibrium with oxygen saturated Ni at 800-900/sup 0/C recrystallize the surface to a finer grain size. Annealing back at 1200/sup 0/C in air will again recrystallize the surface layer. This type of diffusion-induced recrystallization has been observed in metals, but never reported in ceramics. Its occurrence in NiO is interpreted as a demonstration that diffusion-induced grain boundary motion is driven directly by the free energy of mixing defects into the matrix instead of indirectly as suggested by others.

  1. 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.

  2. Effect of grain boundary trapping kinetics on diffusion in polycrystalline materials: hydrogen transport in Ni

    NASA Astrophysics Data System (ADS)

    Ilin, Dmitrii N.; Kutsenko, Anton A.; Tanguy, Dome; Olive, Jean-Marc

    2016-03-01

    Due to experimental limitations, the solute distribution in polycrystalline materials is difficult to obtain directly, especially in the vicinity of grain boundaries. Using a newly developed computational method which mixes continuum diffusion equations and atomic scale jump rates, we study the interstitial diffusion in solids containing interfaces taking into account trapping kinetics. The model is applied to hydrogen diffusion in Ni in elementary configurations: fast intergranular diffusion with no segregation (in agreement with Fisher’s model), slow intergranular diffusion with trapping, diffusion through a triple junction and solute redistribution due to stress gradients across the interface. It is shown that the classical diffusion modes can be captured and a new diffusion regime with the effect of grain boundary trapping is revealed.

  3. Counterion Diffusion in Ionomers

    NASA Astrophysics Data System (ADS)

    Walter, Russell; Winey, Karen; Kim, Joon-Seop; Composto, Russell

    2004-03-01

    Diffusion of Cs counterions to the air/ionomer film interface is followed using Rutherford backscattering spectrometry and results compared with the "sticky reptation" model[1]. The ionomer system is poly(styrene-ran-methacrylic acid) (Cs-SMAA) neutralized at 100% by Cs. The concentration profiles exhibit a surface excess, z*, of Cs followed by a depletion of Cs. The z* and depletion layer thickness grow as t1/2, consistent with diffusion limited growth. Annealing studies at 130 °C, 145 °C and 208 °C were used to extract the diffusion coefficient, D. In all cases, D is greater than that of the matrix chains. These results suggest that the diffusion rate is controlled by the fraction of counterions that disassociate from the acid groups and migrate through the matrix. Moreover, the "sticky reptation" model doesn't appear to predict the diffusion behavior in the Cs-SMAA system. [1] Leibler, L, Ludwick, L., Rubinstein, M., Colby, R.H., Macromolecules 24 (1991) 4701.

  4. 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.

  5. 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.

  6. 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.

  7. 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

  8. 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

  9. Turbulent Mixing in the Ocean and Shelf Seas Surrounding Antarctica

    NASA Astrophysics Data System (ADS)

    Padman, L.

    2006-12-01

    Ocean turbulence and mixing data have been collected from the Southern Ocean and coastal seas surrounding Antarctica since the early 1990's. I summarize these observations, discuss their implications for parameterization of diapycnal mixing in southern seas, and identify regions and processes deserving of further study. Mixing data have been acquired from: the western Weddell Sea; Maud Rise in the eastern Weddell Sea; the Bellingshausen Sea continental shelf; the northwest Ross Sea; the shelf break and inner shelf near the Mertz Glacier Tongue; Drake Passage; the region surrounding the South Scotia Ridge; and locations near the Kerguelen Plateau and the adjacent Antarctic coastal zone. Vertical diffusivities estimated for these diverse regions span at least three orders of magnitude. The different regions exhibit a variety of primary mechanisms for mixing including shear-driven instabilities, nonlinear equation-of-state effects (cabbeling and thermobaricity), double diffusion, and boundary-layer stresses and buoyancy exchange. Energy sources include density flows, extreme surface forcing by cold coastal katabatic winds, tide-driven mixing in the benthic layer, and in the pycnocline due to locally strong baroclinic tides; downward propagation of wind-forced near-inertial waves, and flow interactions with large-scale topographic features. From this review I identify regions and processes for which we presently have little information on which to base mixing parameterizations, and suggest field and analysis activities to overcome these limitations in the representation of mixing in Southern Ocean and global models.

  10. A diffusion model for tungsten powder carburization

    NASA Astrophysics Data System (ADS)

    McCarty, Lewis V.; Donelson, Richard; Hehemann, Robert f.

    1991-01-01

    A mathematical model describes the carburization kinetics of tungsten powders mixed with carbon and heated in hydrogen. It is based on diffusion of carbon through a shell of WC growing into particles which are modeled as spheres. The activation energy is 58 kcal/mole in the temperature range 1056 to 1833 °C. Hydrogen gas is important to transport carbon as methane or acetylene, but increased hydrogen pressure increases the rate of carburization so little that an adsorbed species such as CH probably controls the carbon concentration at the particle surface.

  11. 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.

  12. 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.

  13. 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.

  14. Remotely controllable mixing system

    NASA Technical Reports Server (NTRS)

    Belew, R. R. (Inventor)

    1986-01-01

    This invention relates to a remotely controllable mixing system in which a plurality of mixing assemblies are arranged in an annular configuration, and wherein each assembly employs a central chamber and two outer, upper and lower chambers. Valves are positioned between chambers, and these valves for a given mixing assembly are operated by upper and lower control rotors, which in turn are driven by upper and lower drive rotors. Additionally, a hoop is compressed around upper control rotors and a hoop is compressed around lower control rotors to thus insure constant frictional engagement between all control rotors and drive rotors. The drive rollers are driven by a motor.

  15. Diffusion imaging concepts for clinicians.

    PubMed

    Neil, Jeffrey J

    2008-01-01

    This review covers the fundamentals of diffusion tensor imaging. It is written with the clinician in mind and assumes the reader has a passing familiarity with magnetic resonance imaging (MRI). Topics covered include comparison of diffusion MRI with conventional MRI, water apparent diffusion coefficient (ADC), diffusion anisotropy, tract tracing, and changes of water apparent diffusion in response to injury. The discussion centers primarily on applications to the central nervous system, but examples from other tissues are included. PMID:18050325

  16. Injection and Extraction Schemes to Enhance Mixing in Groundwater

    NASA Astrophysics Data System (ADS)

    Neupauer, R. M.; Mays, D. C.

    2009-12-01

    Remediation of contaminated groundwater may involve the injection of one or more reactants into the aquifer to stimulate reactions to degrade the contaminant, coupled with removal of water from an extraction well to increase circulation. Ideally, the reactants should be mixed throughout the contaminated area. Unfortunately, achieving such mixing is a nontrivial task, because mixing in the low Reynolds number flows characteristic of groundwater is an inherently slow process, limited by molecular diffusion. Past theoretical research has shown that pulsed injection and extraction wells can lead to chaotic advection that enhances mixing. Previous research along these lines has assumed that reactant particles removed at the extraction well are reinjected through the injection well in the same order and orientation at which they were extracted, which is physically unrealistic. We use numerical and analytical models to investigate injection and extraction schemes that may lead to enhanced mixing of reactants in an aquifer, without relying on prescribed reinjection patterns.

  17. 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

  18. Radon diffusion modelling.

    PubMed

    Wilkinson, P; Dimbylow, P J

    1985-10-01

    A mathematical model has been developed that examines the ingress of radon into houses, through a vertical crack in an otherwise impervious concrete floor. Initially, the model considered the diffusive flow of radon from its soil source and this simulation has highlighted the dependency of the flux of radon into the house on the magnitude of various parameters, such as the diffusion coefficient of radon in soil. A preliminary investigation of the modelling of pressure-driven flow into a building is presented, and the potential of this type of analysis is discussed. PMID:4081719

  19. Evolution of error diffusion

    NASA Astrophysics Data System (ADS)

    Knox, Keith T.

    1999-10-01

    As we approach the new millennium, error diffusion is approaching the 25th anniversary of its invention. Because of its exceptionally high image quality, it continues to be a popular choice among digital halftoning algorithms. Over the last 24 years, many attempts have been made to modify and improve the algorithm--to eliminate unwanted textures and to extend it to printing media and color. Some of these modifications have been very successful and are in use today. This paper will review the history of the algorithm and its modifications. Three watershed events in the development of error diffusion will be described, together with the lessons learned along the way.

  20. Evolution of error diffusion

    NASA Astrophysics Data System (ADS)

    Knox, Keith T.

    1998-12-01

    As we approach the new millennium, error diffusion is approaching the 25th anniversary of its invention. Because of its exceptionally high image quality, it continues to be a popular choice among digital halftoning algorithms. Over the last 24 years, many attempts have been made to modify and improve the algorithm - to eliminate unwanted textures and to extend it to printing media and color. Some of these modifications have been very successful and are in use today. This paper will review the history of the algorithm and its modifications. Three watershed events in the development of error diffusion will be described, together with the lesions learned along the way.

  1. Mass diffusion in liquids

    NASA Astrophysics Data System (ADS)

    Walter, H. U.

    Dimensionless number analysis indicates that diffusion-controlled conditions with liquid samples having characteristic dimensions larger than one millimetre can only be established under microgravity conditions.Consequently, heat and mass transport properties of fluids can only be quantitatively investigated in space.Results obtained from experiments on selfdiffusion, interdiffusion and thermodiffusion carried out during the SL-1 and D-1 Spacelab missions clearly demonstrate the potential of space platforms to determine such properties with a precision unattainable on earth. These results imply also that crystal growth from solutions, vapours and melts in the diffusive regime can be realised in space only.

  2. 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

  3. Irradiance calibration with solar diffuser

    NASA Technical Reports Server (NTRS)

    Haring, Robert E. (Inventor); Roeder, Herbert A. (Inventor); Hartmann, Ulli G. (Inventor)

    1993-01-01

    The sun's energy is used in combination of movable and fixed diffuser plates, windows and apertures which are positioned in a series of test sequences (modes) for reflectance monitoring and calibration without the use of man-made sources. There are three embodiments, or implementations, of the invention--one embodiment uses two diffusers--a working diffuser and a secondary diffuser--the second embodiment uses three diffusers, a working diffuser, a secondary diffuser and a reference diffuser--and the third embodiment uses two diffusers--a working diffuser and a secondary diffuser, the latter also functioning as a cover for the working diffuser. The movable diffusers are mounted on rotatable cones and, in all embodiments, the sun is blocked from reaching the diffusers when not in use. Thus, the sun is used as a stable source for calibration and monitoring and the sun/diffuser combination is used in such a way that the response of all elements of the optical subsystem of the TOMS can be unambiguously and efficiently characterized with high accuracy and precision.

  4. 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.

  5. 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.

  6. 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.

  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. 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.

  9. Incomplete Mixing and Reactions - A Lagrangian Approach in a Pure Shear Flow

    NASA Astrophysics Data System (ADS)

    Paster, Amir; Bolster, Diogo; Aquino, Tomas

    2015-04-01

    Incomplete mixing of reactive solutes is well known to slow down reaction rates relative to what would be expected from assuming perfect mixing. As reactions progress in a system and deplete reactant concentrations, initial fluctuations in the concentrations of reactions can be amplified relative to mean background concentrations and lead to spatial segregation of reactants. As the system evolves, in the absence of sufficient mixing, this segregation will increase, leading to a persistence of incomplete mixing that fundamentally changes the effective rate at which overall reactions will progress. On the other hand, nonuniform fluid flows are known to affect mixing between interacting solutes. Thus a natural question arises: Can non-uniform flows sufficiently enhance mixing to suppress incomplete mixing effects, and if so, under what conditions? In this work we address this question by considering one of the simplest possible flows, a laminar pure shear flow, which is known to significantly enhance mixing relative to diffusion alone. To study this system we adapt a novel Lagrangian particle-based random walk method, originally designed to simulate reactions in purely diffusive systems, to the case of advection and diffusion in a shear flow. To interpret the results we develop a semi-analytical solution, by proposing a closure approximation that aims to capture the effect of incomplete mixing. The results obtained via the Lagrangian model and the semi-analytical solutions consistently highlight that if shear effects in the system are not sufficiently strong, incomplete mixing effects initially similar to purely diffusive systems will occur, slowing down the overall reaction rate. Then, at some later time, dependent on the strength of the shear, the system will return to behaving as if it were well-mixed, but represented by a reduced effective reaction rate. If shear effects are sufficiently strong, the incomplete mixing regime never emerges and the system can behave

  10. 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.

  11. Diffusion in random networks

    NASA Astrophysics Data System (ADS)

    Padrino, Juan C.; Zhang, Duan Z.

    2015-11-01

    The ensemble phase averaging technique is applied to model mass transport in a porous medium. The porous material is idealized as an ensemble of random networks, where each network consists of a set of junction points representing the pores and tortuous channels connecting them. 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 pores mass density. Instead of attempting to solve this equation, and equivalent set of partial differential equations is derived whose solution is sought numerically. As a test problem, we consider the one-dimensional diffusion of a substance from one end to the other in a bounded domain. For a statistically homogeneous and isotropic material, results show that for relatively large times the pore mass density evolution from the new theory is significantly delayed in comparison with the solution from the classical diffusion equation. In the short-time case, when the solution evolves with time as if the domain were semi-infinite, numerical results indicate that the pore mass density becomes a function of the similarity variable xt- 1 / 4 rather than xt- 1 / 2 characteristic of classical diffusion. This result was verified analytically. Possible applications of this framework include flow in gas shales. Work supported by LDRD project of LANL.

  12. 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.

  13. Thermodynamics of diffusion

    NASA Astrophysics Data System (ADS)

    Matuszak, Daniel

    Diffusion is the migration of molecules in the reference frame of a system's center of mass and it is a physical process that occurs in all chemical and biological systems. Diffusion generally involves intermolecular interactions that lead to clustering, adsorption, and phase transitions; as such, it is difficult to describe theoretically on a molecular level in systems containing both intermolecular repulsions and attractions. This work describes a simple thermodynamic approach that accounts for intermolecular attractions and repulsions (much like how the van der Waals equation does) to model and help provide an understanding of diffusion. The approach is an extension of the equilibrium Lattice Density Functional Theory of Aranovich and Donohue; it was developed with Mason and Lonsdale's guidelines on how to construct and test a transport theory. In the framework of lattice fluids, this new approach gives (a) correct equilibrium limits, (b) Fickian behavior for non-interacting systems, (c) correct departures from Fickian behavior in non-ideal systems, (d) the correct Maxwell-Stefan formulation, (e) symmetry behavior upon re-labeling species, (f) reasonable non-equilibrium phase behavior, (g) agreement with Molecular Dynamics simulations, (h) agreement with the theory of non-equilibrium thermodynamics, (i) a vanishing diffusive flux at the critical point, and (j) other qualitatively-correct behaviors when applied to problems in porous membranes and in packed beds.

  14. Diffuse sorption modeling.

    PubMed

    Pivovarov, Sergey

    2009-04-01

    This work presents a simple solution for the diffuse double layer model, applicable to calculation of surface speciation as well as to simulation of ionic adsorption within the diffuse layer of solution in arbitrary salt media. Based on Poisson-Boltzmann equation, the Gaines-Thomas selectivity coefficient for uni-bivalent exchange on clay, K(GT)(Me(2+)/M(+))=(Q(Me)(0.5)/Q(M)){M(+)}/{Me(2+)}(0.5), (Q is the equivalent fraction of cation in the exchange capacity, and {M(+)} and {Me(2+)} are the ionic activities in solution) may be calculated as [surface charge, mueq/m(2)]/0.61. The obtained solution of the Poisson-Boltzmann equation was applied to calculation of ionic exchange on clays and to simulation of the surface charge of ferrihydrite in 0.01-6 M NaCl solutions. In addition, a new model of acid-base properties was developed. This model is based on assumption that the net proton charge is not located on the mathematical surface plane but diffusely distributed within the subsurface layer of the lattice. It is shown that the obtained solution of the Poisson-Boltzmann equation makes such calculations possible, and that this approach is more efficient than the original diffuse double layer model. PMID:19159896

  15. Diffusion welding tool

    NASA Technical Reports Server (NTRS)

    Milam, T. B.

    1973-01-01

    Tool allows flat plate diffusion welding to be done in standard brazing furnace. Weld is achieved using high water pressure applied by hand-operated positive-displacement pump. Good welds have been obtained between nickel and nickel-base alloy plates at temperature of 1200 K and water pressure of 13.8 million N/sq m.

  16. 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.

  17. Using multiscale norms to quantify mixing and transport

    NASA Astrophysics Data System (ADS)

    Thiffeault, Jean-Luc

    2012-02-01

    Mixing is relevant to many areas of science and engineering, including the pharmaceutical and food industries, oceanography, atmospheric sciences and civil engineering. In all these situations one goal is to quantify and often then to improve the degree of homogenization of a substance being stirred, referred to as a passive scalar or tracer. A classical measure of mixing is the variance of the concentration of the scalar, which is the L2 norm of a mean-zero concentration field. Recently, other norms have been used to quantify mixing, in particular the mix-norm as well as negative Sobolev norms. These norms have the advantage that unlike variance they decay even in the absence of diffusion, and their decay corresponds to the flow being mixing in the sense of ergodic theory. General Sobolev norms weigh scalar gradients differently, and are known as multiscale norms for mixing. We review the applications of such norms to mixing and transport, and show how they can be used to optimize the stirring and mixing of a decaying passive scalar. We then review recent work on the less-studied case of a continuously replenished scalar field—the source-sink problem. In that case the flows that optimally reduce the norms are associated with transport rather than mixing: they push sources onto sinks, and vice versa.

  18. Ti Diffusion in Zircon

    NASA Astrophysics Data System (ADS)

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

    2006-12-01

    Diffusion of Ti under anhydrous conditions at 1 atmosphere and under fluid-present conditions at 1.1-1.2 GPa has been measured in natural zircon. The source of diffusant for 1-atm experiments was a ZrO2- TiO2-ZrSiO4 mixture, with experiments run in Pt capsules. Diffusion experiments conducted in the presence of H2O-CO2 fluid were run in a piston-cylinder apparatus, using a source of ground TiO2, ZrSiO4 and SiO2, with oxalic acid added to produce H2O-CO2 vapor and partially melt the solid source material, yielding an assemblage of rutile + zircon + melt + vapor. Resonant nuclear reaction analysis (NRA) with the nuclear reaction ^{48}Ti(p,Γ)^{49}V was used to measure diffusion profiles for both sets of experiments. The following Arrhenius relation was obtained for Ti diffusion normal to c over the temperature range 1350-1550C at one atmosphere: DTi = 3.3x102 exp(-754 ± 56 kJ mol-1 /RT) m2sec-1 Ti diffusivities were found to be similar for experiments run under fluid-present conditions. A fit to all of the data yields the Arrhenius relation D = 1.3x103 exp(-741 ± 46 kJ mol-1 /RT) m2sec-1. These data suggest that zircon should be extremely retentive of Ti chemical signatures, indicating that the recently developed Ti-in-zircon crystallization geothermometer (Watson and Harrison, 2005; Watson et al., 2006) will be quite robust in preserving temperatures of zircon crystallization. Titanium diffuses somewhat faster in zircon than larger tetravalent cations U, Th, and Hf, but considerably more slowly than Pb, the REE, and oxygen; hence Ti crystallization temperatures may be retained under circumstances when radiometric ages or other types of geochemical information are lost. Watson EB, Harrison TM (2005) Science 308, 841-844. Watson EB, Wark DA, Thomas JB (2006) CMP(in press).

  19. 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.

  20. (DCAM) Diffusion Controlled Crystallization Apparatus for Microgravity Tray Assembly

    NASA Technical Reports Server (NTRS)

    1995-01-01

    DCAM, developed by MSFC, grows crystals by the dialysis and liquid-liquid diffusion methods. In both methods, protein crystal growth is induced by changing conditions in the protein. In dialysis, a semipermeable membrane retains the protein solution in one compartment, while allowing molecules of precipitant to pass freely through the membrane from an adjacent compartment. As the precipitant concentration increases within the protein compartment, crystallization begins. In liquid-liquid diffusion, a protein solution and a precipitant solution are layered in a container and allowed to diffuse into each other. This leads to conditions which may induce crystallization of the protein. Liquid-liquid diffusion is difficult on Earth because density and temperature differences cause the solutions to mix rapidly.

  1. 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.

  2. 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

  3. 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

  4. Ion-beam mixing in crystalline and amorphous germanium isotope multilayers

    SciTech Connect

    Bracht, H.; Radek, M.; Kube, R.; Knebel, S.; Posselt, M.; Schmidt, B.; Haller, E. E.; Bougeard, D.

    2011-11-01

    Gallium (Ga) implantation induced self-atom mixing in crystalline and amorphous germanium (Ge) is investigated utilizing isotopically controlled Ge multilayer structures grown by molecular beam epitaxy. The distribution of the Ga ions and the ion-beam induced depth-dependent mixing of the isotope structure was determined by means of secondary ion mass spectrometry. Whereas the distribution of Ga in the crystalline and amorphous Ge is very similar and accurately reproduced by computer simulations based on binary collision approximation (BCA), the ion-beam induced self-atom mixing is found to depend strongly on the state of the Ge structure. The experiments reveal stronger self-atom mixing in crystalline than in amorphous Ge. Atomistic simulations based on BCA reproduce the experimental results only when unphysically low Ge displacement energies are assumed. Analysis of the self-atom mixing induced by silicon implantation confirms the low displacement energy deduced within the BCA approach. This demonstrates that thermal spike mixing contributes significantly to the overall mixing of the Ge isotope structures. The disparity observed in the ion-beam mixing efficiency of crystalline and amorphous Ge indicates different dominant mixing mechanisms. We propose that self-atom mixing in crystalline Ge is mainly controlled by radiation enhanced diffusion during the early stage of mixing before the crystalline structure turns amorphous, whereas in an already amorphous state self-atom mixing is mediated by cooperative diffusion events.

  5. Instrumentation in Diffuse Optical Imaging

    PubMed Central

    Zhang, Xiaofeng

    2014-01-01

    Diffuse optical imaging is highly versatile and has a very broad range of applications in biology and medicine. It covers diffuse optical tomography, fluorescence diffuse optical tomography, bioluminescence, and a number of other new imaging methods. These methods of diffuse optical imaging have diversified instrument configurations but share the same core physical principle – light propagation in highly diffusive media, i.e., the biological tissue. In this review, the author summarizes the latest development in instrumentation and methodology available to diffuse optical imaging in terms of system architecture, light source, photo-detection, spectral separation, signal modulation, and lastly imaging contrast. PMID:24860804

  6. 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.

  7. 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.

  8. 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.

  9. 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

  10. 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.

  11. Layered convection in double diffusive fluids

    NASA Astrophysics Data System (ADS)

    Zaussinger, F.; Kupka, F.; Muthsam, H. J.; Happenhofer, N.; Grimm-Strele, H.

    2012-04-01

    Double diffusive convection plays an important role in astrophysics and oceanography where under certain conditions a thermally unstable temperature gradient is counteracted by a stable solute gradient. This configuration is well known from salt lakes, where the salt concentration stabilizes convective motions and a layered structure emerges. Similar conditions are found in stellar interiors, where helium as the stabilizing component inhibits the development of convection and the occurrence of double-diffusive staircases is assumed. We investigate mixing timescales and stability conditions using theoretical estimates and numerical simulations covering a broad range of parameter sets by varying Prandtl-, Lewis- and Rayleigh numbers. To shed light on the numerically inaccessible astrophysical case we extrapolate to the relevant parameter range. We investigate the initial layer formation process as well as the stability of evolved layers by performing direct numerical simulations in 2D and 3D using the Boussinesq approximation. A fitting formula for the Nusselt numbers and the effective mixing rates is given. Finally, we present a semi-implicit method to solve the compressible counterpart of the governing equations which has the advantage to cover the entire relevant Mach number range.

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

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

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

  13. 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.

  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. [Mixed states and schizophrenia].

    PubMed

    Fakra, E; Belzeaux, R; Pringuey, D; Cermolacce, M; Corréard, N; Micoulaud-Franchi, J-A; Azorin, J-M

    2013-12-01

    Because of their compilation of contrasted symptoms and their variable clinical presentation, mixed episodes have been withdrawn from the DSM. However, mixed states question not only the bonds between depression and mania, but also the distinction between bipolar disorders and schizophrenia. Indeed, doubts about the dichotomy introduced by Kraepelin between bipolar disorders and schizophrenia is as old as the nosolgy itself, as attest the later works of this author revealing his hesitations on his own classification. But findings here reviewed issued from recent technical advances, particularly in the imaging and genetic fields, offer a better understanding of the boundaries between these two disorders. Yet, when confronted to an acute episode, clinicians may find it challenging to distinguish a mixed state from a schizophrenic relapse. Indeed, there is no pathognomonic manifestation allowing to retain a diagnosis with confidence. The physician will therefore have to identify a pattern of signs, which will orient his assessment with no certainty. Thus, negative rather than affective or psychotic symptomatology appears to be useful in discriminating schizophrenia (or schizoaffective) disorders from mixed mania. However, a conclusion during this acute stage appears in definitive a formal exercise, first because the final diagnosis will only be ascertained once the symptoms are amended, and second because, according to our classifications, a mood episode, including mania and mixed mania, can be observed without ruling out the diagnosis of schizophrenia. PMID:24359851

  16. Enhanced mixing in laminar flows using ultrahydrophobic surfaces.

    PubMed

    Ou, Jia; Moss, Geoffrey R; Rothstein, Jonathan P

    2007-07-01

    Under laminar, microscale flow conditions, rapid mixing can be difficult to achieve. In these low Reynolds number flows, mixing rates are governed by molecular diffusion, and in the absence of enhanced mixing techniques, mixing lengths and residence times can be much longer than most applications will allow. A number of active mixing techniques have been developed to improve mixing; however, they can be complex to implement and expensive to fabricate. In this paper, we describe a passive mixing method that utilizes a series of ultrahydrophobic surfaces. Our previous experiments have demonstrated that a shear-free air-water interface supported between hydrophobic microridges results in large slip velocities along these ultrahydrophobic surfaces, and significant drag reduction. By aligning the microridges and therefore the air-water interface at an oblique angle to the flow direction, a secondary flow is generated, which is shown to efficiently stretch and fold the fluid elements and reduce the mixing length by more than an order of magnitude compared to that of a smooth microchannel. The designs of the ultrahydrophobic surfaces were optimized through experiments and numerical simulations. A Y-shaped channel was used to bring two streams of water together, one tagged with a fluorescent dye. A confocal microscope was used to measure fluorescence intensity and dye concentration. Quantitative agreement between the experiments and the numerical simulations was achieved for both the flow patterns and degree of mixing. Increasing the angle of the microridges was found to reduce the mixing length up to a critical angle of about 60 degrees , beyond which the mixing length was found to increase with further increases to the angle of the microridge. The mixing enhancement was found to be much less sensitive to changes in microridge width or separation. PMID:17677560

  17. [Diffuse Pulmonary Ossification].

    PubMed

    Avsar, K; Behr, J; Morresi-Hauf, A

    2016-04-01

    Diffuse pulmonary ossification (DPO) represents an uncommon condition usually associated with different underlying pulmonary and extrapulmonary diseases. In this work, we discuss eleven patients of our clinic with the diagnosis of a diffuse pulmonary ossification. We focus on histological changes in the surrounding lung tissue. Clinical and radiological findings were analysed. The aim of the study is to collect data for a better understanding of this condition, especially in association with interstitial lung disease.Three patients with interstitial lung disease had histological findings of UIP. The follow-up data of these patients showed a benign course of the disease.The analysis of the clinical data yielded a very heterogenous group. Regarding these fact we assume, that DPO is not an own entity, but a pathological epiphenomenon in the context of different conditions, possibly with pathogenetic overlap. PMID:26829606

  18. Diffusion dans les liquides

    NASA Astrophysics Data System (ADS)

    Dianoux, A. J.

    2003-09-01

    Après une brève introduction qui rappelle les concepts détaillés dans le cours de M. Bée, nous présentons un aperçu de trois de nos travaux sur l'étude de la diffusion. Tout d'abord la dynamique de l'eau, dans son état normal ou surfondu, révèle la complexité apportée par le réseau de liaisons hydrogène. Ensuite l'effet du confinement sur la dynamique de l'eau sera étudié dans le cas de la membrane Nafion. Enfin la diffusion dans les phases nématique et smectique A d'un cristal liquide permet d'obtenir la valeur du potentiel qui maintient les couches dans la phase smectique.

  19. Galactic Diffuse Polarized Emission

    NASA Astrophysics Data System (ADS)

    Carretti, Ettore

    2011-12-01

    Diffuse polarized emission by synchrotron is a key tool to investigate magnetic fields in the Milky Way, particularly the ordered component of the large scale structure. Key observables are the synchrotron emission itself and the RM is by Faraday rotation. In this paper the main properties of the radio polarized diffuse emission and its use to investigate magnetic fields will be reviewed along with our current understanding of the galactic magnetic field and the data sets available. We will then focus on the future perspective discussing RM-synthesis - the new powerful instrument devised to unlock the information encoded in such an emission - and the surveys currently in progress like S-PASS and GMIMS.

  20. Thermal diffusivity imaging

    NASA Astrophysics Data System (ADS)

    Gfroerer, Tim; Phillips, Ryan; Rossi, Peter

    2015-11-01

    The tip of a rod is heated with a torch and brought into contact with the center of a metal sheet. A thermal camera is then used to image the temperature profile of the surface as a function of time. The infrared camera is capable of recording radiometric data with 1 mK resolution in nearly 105 pixels, so thermal diffusion can be monitored with unprecedented precision. With a frame rate of approximately 10 Hz, the pace of the data acquisition minimizes the loss of accuracy due to inevitable cooling mechanisms. We report diffusivity constants equal to 1.23 ± 0.06 cm2/s in copper and 0.70 ± 0.05 cm2/s in aluminum. The behavior is modeled with a straightforward but oddly under-utilized one-dimensional finite difference method.

  1. 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.

  2. 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.

  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. 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.

  5. 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.

  6. Peridynamic thermal diffusion

    NASA Astrophysics Data System (ADS)

    Oterkus, Selda; Madenci, Erdogan; Agwai, Abigail

    2014-05-01

    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.

  7. 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.

  8. Mass transport by diffusion

    NASA Technical Reports Server (NTRS)

    Baird, James K.

    1987-01-01

    For the purpose of determining diffusion coefficients as required for electrodeposition studies and other applications, a diaphragm cell and an isothermal water bath were constructed. the calibration of the system is discussed. On the basis of three calibration runs on the diaphram cell, researchers concluded that the cell constant beta equals 0.12 cm -2 . Other calibration runs in progress should permit the cell constant to be determined with an accuracy of one percent.

  9. Simulation of coupled sputter-diffusion effects

    NASA Astrophysics Data System (ADS)

    von Toussaint, U.; Mutzke, A.; Sugiyama, K.; Schwarz-Selinger, T.

    2016-02-01

    The simultaneous effects of sputtering, implantation and solid-state diffusion determine the surface profiles of mixed-material systems under ion-bombardment at elevated temperatures due to the enhanced atomic mobility. To simulate the joint processes the Monte Carlo code SDTrimSP for the simulation of the ion-solid interaction has been augmented by a diffusion model for solid-state diffusion. The combined model has been applied to a tungsten-iron system under deuterium bombardment as model system for EUROFER. The simulation results reveal a strong dependence of the surface profile on initial tungsten concentration, ion energy, temperature and fluence but also on the impinging flux, a parameter which is often not appropriately taken into account. For reactor relevant parameters of low-energy (200 eV) deuterium fluxes of {10}21{at} {{{m}}}-2 {{{s}}}-1 at 873 K a tungsten-iron system exhibits an increase of the tungsten surface concentration from initially 1% by a factor of more than 20, which drops at lower fluxes.

  10. Resilience in reaction-diffusion systems

    NASA Astrophysics Data System (ADS)

    van Vuuren, J. H.

    1999-10-01

    Reaction-diffusion systems with zero-flux Neumann boundaries are widely used to model various kinds of interaction in, for example, the scientific fields of ecology, biology, chemistry, medicine and industry. The physical systems within these fields are often known to be (conditionally or unconditionally) resilient with respect to shocks, disturbances or catastrophies in the immediate environment. In order to be good mathematical models of such situations the reaction-diffusion systems must have the same resilient or asymptotic behaviour as that of the physical situation. Three fundamentally different kinds of reaction terms are usually distinguished according to the entry signs of the reaction Jacobian: mutualism, mixed (predator-prey) interaction and competition. The asymptotic stability (in the Poincare sense) of mutualistic systems has already been studied extensively, but the results cannot be generalized (globally) to the other two fundamental types, which are not order-preserving. A partial (local) generalization is, however given here for these two types, involving simple Jacobian inequalities and knowledge (often prompted by the underlying physical situation) of invariant sets in solution space. The return time of resilient systems and the approach rate of asymptotically stable solutions are also estimated. Key words: reaction-diffusion system; competition; resilience; asymptotic stability.

  11. [Diffuse Lewy body disease].

    PubMed

    Kosaka, K

    1995-12-01

    Diffuse Lewy body disease (DLBD), which we have proposed since 1976, has received great attention among both researchers and clinicians. Recently, it was reported by some English and American research groups that DLBD is the second most frequent dementing illness in the elderly, following Alzheimer-type dementia (ATD). Our recent research of 79 autopsied dementia cases in a hospital disclosed that DLBD (15.4%) was the second most common degenerative dementia, following ATD (43.6%). In 1980 we proposed Lewy body disease, and classified it into three types: brain stem type, transitional type, and diffuse type. Diffuse type of LBD is now called DLBD. In 1990 we divided DLBD into two forms: common form and pure form. The common form of DLBD has more or less Alzheimer pathology, and pure form has none. Very recently, we proposed the cerebral type of LBD, in which numerous Lewy bodies are found in the cerebral cortex and amygdala, but no PD pathology is present in the brain stem. Therefore, LBD is now classified as follows: [table: see text] PMID:8752428

  12. Rapid mixing kinetic techniques.

    PubMed

    Martin, Stephen R; Schilstra, Maria J

    2013-01-01

    Almost all of the elementary steps in a biochemical reaction scheme are either unimolecular or bimolecular processes that frequently occur on sub-second, often sub-millisecond, time scales. The traditional approach in kinetic studies is to mix two or more reagents and monitor the changes in concentrations with time. Conventional spectrophotometers cannot generally be used to study reactions that are complete within less than about 20 s, as it takes that amount of time to manually mix the reagents and activate the instrument. Rapid mixing techniques, which generally achieve mixing in less than 2 ms, overcome this limitation. This chapter is concerned with the use of these techniques in the study of reactions which reach equilibrium; the application of these methods to the study of enzyme kinetics is described in several excellent texts (Cornish-Bowden, Fundamentals of enzyme kinetics. Portland Press, 1995; Gutfreund, Kinetics for the life sciences. Receptors, transmitters and catalysis. Cambridge University Press, 1995).There are various ways to monitor changes in concentration of reactants, intermediates and products after mixing, but the most common way is to use changes in optical signals (absorbance or fluorescence) which often accompany reactions. Although absorbance can sometimes be used, fluorescence is often preferred because of its greater sensitivity, particularly in monitoring conformational changes. Such methods are continuous with good time resolution but they seldom permit the direct determination of the concentrations of individual species. Alternatively, samples may be taken from the reaction volume, mixed with a chemical quenching agent to stop the reaction, and their contents assessed by techniques such as HPLC. These methods can directly determine the concentrations of different species, but are discontinuous and have a limited time resolution. PMID:23729251

  13. 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.

  14. A new gauge-invariant method for diagnosing eddy diffusivities

    NASA Astrophysics Data System (ADS)

    Mak, J.; Maddison, J. R.; Marshall, D. P.

    2016-08-01

    Coarse resolution numerical ocean models must typically include a parameterisation for mesoscale turbulence. A common recipe for such parameterisations is to invoke mixing of some tracer quantity, such as potential vorticity or buoyancy. However, it is well known that eddy fluxes include large rotational components which necessarily do not lead to any mixing; eddy diffusivities diagnosed from unfiltered fluxes are thus contaminated by the presence of these rotational components. Here a new methodology is applied whereby eddy diffusivities are diagnosed directly from the eddy force function. The eddy force function depends only upon flux divergences, is independent of any rotational flux components, and is inherently non-local and smooth. A one-shot inversion procedure is applied, minimising the mis-match between parameterised force functions and force functions derived from eddy resolving calculations. This enables diffusivities associated with the eddy potential vorticity and Gent-McWilliams coefficients associated with eddy buoyancy fluxes to be diagnosed. This methodology is applied to multi-layer quasi-geostrophic ocean gyre simulations. It is found that: (i) a strictly down-gradient scheme for mixing potential vorticity and quasi-geostrophic buoyancy has limited success in reducing the mis-match compared to one with no sign constraint on the eddy diffusivity or Gent--McWilliams coefficient, with prevalent negative signals around the time-mean jet; (ii) the diagnostic is successful away from the jet region and wind-forced top layer; (iii) the locations of closed mean stream lines correlate with signals of positive eddy potential vorticity diffusivity; (iv) there is indication that the magnitude of the eddy potential vorticity diffusivity correlates well with the eddy energy. Implications for parameterisation are discussed in light of these diagnostic results.

  15. A traceable physical calibration of the vertical advection-diffusion equation for modeling ocean heat uptake

    NASA Astrophysics Data System (ADS)

    Huber, Markus; Tailleux, Remi; Ferreira, David; Kuhlbrodt, Till; Gregory, Jonathan

    2015-04-01

    The classic vertical advection-diffusion (VAD) balance is a central concept in studying the ocean heat budget, in particular in simple climate models (SCMs). Here we present a new framework to calibrate the parameters of the VAD equation to the vertical ocean heat balance of two fully-coupled climate models that is traceable to the models' circulation as well as to vertical mixing and diffusion processes. Based on temperature diagnostics, we derive an effective vertical velocity w∗ and turbulent diffusivity kν∗ for each individual physical process. In steady state, we find that the residual vertical velocity and diffusivity change sign in middepth, highlighting the different regional contributions of isopycnal and diapycnal diffusion in balancing the models' residual advection and vertical mixing. We quantify the impacts of the time evolution of the effective quantities under a transient 1% CO2 simulation and make the link to the parameters of currently employed SCMs.

  16. 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.

  17. 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.

  18. 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.

  19. Mixed waste characterization strategy

    SciTech Connect

    Baldwin, C.E.; Stakebake, J.; Peters, M.

    1992-01-01

    Radioactive mixed wastes containing a radioactive component subject to the Atomic Energy Act (AEA) and hazardous waste subject to resource Conservation and Recovery Act (RCRA) are generated, treated, and stored at the Rocky Flats Plant (RFP) and are subject to federal and state statutory and regulatory requirements. The US Environmental Protection Agency (EPA) and the Colorado Department of Health (CDH) are the two primary regulatory agencies which enforce these requirements. This paper describes the mechanism by which RFP will characterize mixed wastes within the LDR provisions of RCRA and the LDR FFCA as well as for meeting the waste acceptance criteria for disposal.

  20. Mixed waste characterization strategy

    SciTech Connect

    Baldwin, C.E.; Stakebake, J.; Peters, M.

    1992-08-01

    Radioactive mixed wastes containing a radioactive component subject to the Atomic Energy Act (AEA) and hazardous waste subject to resource Conservation and Recovery Act (RCRA) are generated, treated, and stored at the Rocky Flats Plant (RFP) and are subject to federal and state statutory and regulatory requirements. The US Environmental Protection Agency (EPA) and the Colorado Department of Health (CDH) are the two primary regulatory agencies which enforce these requirements. This paper describes the mechanism by which RFP will characterize mixed wastes within the LDR provisions of RCRA and the LDR FFCA as well as for meeting the waste acceptance criteria for disposal.

  1. MixDown

    2010-01-01

    MixDown is a meta-build tool that orchestrates and manages the building of multiple 3rd party libraries. It can manage the downloading, uncompressing, unpacking, patching, configuration, build, and installation of 3rd party libraries using a variety of configuration and build tools. As a meta-build tool, it relies on 3rd party tools such as GNU Autotools, make, Cmake, scons, etc. to actually confugure and build libraries. MixDown includes an extensive database of settings to be used formore » general machines and specific leadership class computing resources.« less

  2. Turbulence and Interfacial Mixing

    SciTech Connect

    Glimm, James; Li, Xiaolin

    2005-03-15

    The authors study mix from analytical and numerical points of view. These investigations are linked. The analytical studies (in addition to laboratory experiments) provide bench marks for the direct simulation of mix. However, direct simulation is too detailed to be useful and to expensive to be practical. They also consider averaged equations. Here the major issue is the validation of the closure assumptions. They appeal to the direct simulation methods for this step. They have collaborated with several NNSA teams; moreover, Stony Brook alumni (former students, faculty and research collaborators) presently hold staff positions in NNSA laboratories.

  3. Percolation of interaction diffusing particles

    NASA Technical Reports Server (NTRS)

    Selinger, Robin Blumberg; Stanley, H. Eugene

    1990-01-01

    The connectivity properties of systems of diffusing interacting particles with the blind and myopic diffusion rules are studied. It is found that the blind rule case is equivalent to the lattice gas with J = 0 in all dimensions. The connectivity properties of blind rule diffusion are described by random site percolation due to the fact that the density on neighboring sites is uncorrelated.

  4. Rapid magnetofluidic mixing in a uniform magnetic field.

    PubMed

    Zhu, Gui-Ping; Nguyen, Nam-Trung

    2012-11-21

    This paper reports the investigation of mixing phenomena caused by the interaction between a uniform magnetic field and a magnetic fluid in a microfluidic chamber. The flow system consists of a water-based ferrofluid and a mixture of DI water and glycerol. Under a uniform magnetic field, the mismatch in magnetization of the fluids leads to instability at the interface and subsequent rapid mixing. The mismatch of magnetization is determined by concentration of magnetic nanoparticles. Full mixing at a relatively low magnetic flux density up to 10 mT can be achieved. The paper discusses the impact of key parameters such as magnetic flux density, flow rate ratio and viscosity ratio on the mixing efficiency. Two main mixing regimes are observed. In the improved diffusive mixing regime under low field strength, magnetic particles of the ferrofluid migrate into the diamagnetic fluid. In the bulk transport regime under high field strength, the fluid system is mixed rapidly by magnetically induced secondary flow in the chamber. The mixing concept potentially provides a wireless solution for a lab-on-a-chip system that is low-cost, robust, free of induced heat and independent of pH level or ion concentration. PMID:22990170

  5. Diffusion of Zonal Variables Using Node-Centered Diffusion Solver

    SciTech Connect

    Yang, T B

    2007-08-06

    Tom Kaiser [1] has done some preliminary work to use the node-centered diffusion solver (originally developed by T. Palmer [2]) in Kull for diffusion of zonal variables such as electron temperature. To avoid numerical diffusion, Tom used a scheme developed by Shestakov et al. [3] and found their scheme could, in the vicinity of steep gradients, decouple nearest-neighbor zonal sub-meshes leading to 'alternating-zone' (red-black mode) errors. Tom extended their scheme to couple the sub-meshes with appropriate chosen artificial diffusion and thereby solved the 'alternating-zone' problem. Because the choice of the artificial diffusion coefficient could be very delicate, it is desirable to use a scheme that does not require the artificial diffusion but still able to avoid both numerical diffusion and the 'alternating-zone' problem. In this document we present such a scheme.

  6. Transport and diffusion of overdamped Brownian particles in random potentials

    NASA Astrophysics Data System (ADS)

    Simon, Marc Suñé; Sancho, J. M.; Lindenberg, Katja

    2013-12-01

    We present a numerical study of the anomalies in transport and diffusion of overdamped Brownian particles in totally disordered potential landscapes in one and in two dimensions. We characterize and analyze the effects of three different disordered potentials. The anomalous regimes are characterized by the time exponents that exhibit the statistical moments of the ensemble of particle trajectories. The anomaly in the transport is always of the subtransport type, but diffusion presents a greater variety of anomalies: Both subdiffusion and superdiffusion are possible. In two dimensions we present a mixed anomaly: subdiffusion in the direction perpendicular to the force and superdiffusion in the parallel direction.

  7. 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.

  8. 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.

  9. Turbulent thermal diffusion: a way to concentrate dust in protoplanetary discs

    NASA Astrophysics Data System (ADS)

    Hubbard, Alexander

    2016-03-01

    Turbulence acting on mixes of gas and particles generally diffuses the latter evenly through the former. However, in the presence of background gas temperature gradients, a phenomenon known as turbulent thermal diffusion appears as a particle drift velocity (rather than a diffusive term). This process moves particles from hot regions to cold ones. We re-derive turbulent thermal diffusion using astrophysical language and demonstrate that it could play a major role in protoplanetary discs by concentrating particles by factors of tens. Such a concentration would set the stage for collective behaviour such as the streaming instability and hence planetesimal formation.

  10. 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

  11. 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.

  12. 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.

  13. Josephson junction mixing.

    NASA Technical Reports Server (NTRS)

    Thompson, E. D.

    1973-01-01

    A theory is presented which, though too simple to explain quantitative details in the Josephson junction mixing response, is sufficient for explaining qualitatively the results observed. Crucial to the theory presented, and that which differentiates it from earlier ones, is the inclusion of harmonic voltages across the ideal Josephson element.

  14. Mixed valent metals.

    PubMed

    Riseborough, P S; Lawrence, J M

    2016-08-01

    We review the theory of mixed-valent metals and make comparison with experiments. A single-impurity description of the mixed-valent state is discussed alongside the description of the nearly-integer valent or Kondo limit. The degeneracy N of the f-shell plays an important role in the description of the low-temperature Fermi-liquid state. In particular, for large N, there is a rapid cross-over between the mixed-valent and the Kondo limit when the number of f electrons is changed. We discuss the limitations on the application of the single-impurity description to concentrated compounds such as those caused by the saturation of the Kondo effect and those due to the presence of magnetic interactions between the impurities. This discussion is followed by a description of a periodic lattice of mixed-valent ions, including the role of the degeneracy N. The article concludes with a comparison of theory and experiment. Topics covered include the single-impurity Anderson model, Luttinger's theorem, the Friedel sum rule, the Schrieffer-Wolff transformation, the single-impurity Kondo model, Kondo screening, the Wilson ratio, local Fermi-liquids, Fermi-liquid sum rules, the Noziéres exhaustion principle, Doniach's diagram, the Anderson lattice model, the Slave-Boson method, etc. PMID:27376888

  15. 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.

  16. Progress in mix modeling

    SciTech Connect

    Harrison, A.K.

    1997-03-14

    We have identified the Cranfill multifluid turbulence model (Cranfill, 1992) as a starting point for development of subgrid models of instability, turbulent and mixing processes. We have differenced the closed system of equations in conservation form, and coded them in the object-oriented hydrodynamics code FLAG, which is to be used as a testbed for such models.

  17. 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…

  18. Mixed valent metals

    NASA Astrophysics Data System (ADS)

    Riseborough, P. S.; Lawrence, J. M.

    2016-08-01

    We review the theory of mixed-valent metals and make comparison with experiments. A single-impurity description of the mixed-valent state is discussed alongside the description of the nearly-integer valent or Kondo limit. The degeneracy N of the f-shell plays an important role in the description of the low-temperature Fermi-liquid state. In particular, for large N, there is a rapid cross-over between the mixed-valent and the Kondo limit when the number of f electrons is changed. We discuss the limitations on the application of the single-impurity description to concentrated compounds such as those caused by the saturation of the Kondo effect and those due to the presence of magnetic interactions between the impurities. This discussion is followed by a description of a periodic lattice of mixed-valent ions, including the role of the degeneracy N. The article concludes with a comparison of theory and experiment. Topics covered include the single-impurity Anderson model, Luttinger’s theorem, the Friedel sum rule, the Schrieffer–Wolff transformation, the single-impurity Kondo model, Kondo screening, the Wilson ratio, local Fermi-liquids, Fermi-liquid sum rules, the Noziéres exhaustion principle, Doniach’s diagram, the Anderson lattice model, the Slave-Boson method, etc.

  19. Mixing of Supersonic Streams

    NASA Technical Reports Server (NTRS)

    Hawk, Clark W.; Landrum, D. Brian; Turner, Matthew; Wagner, David K.; Lambert, James

    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. 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. Initial cold flow testing of the model is underway to determine both, the behavior of the ingested air in the duct and to validate the mixing diagnostics. During the tests, each of the two rocket nozzles ejected up to two pounds mass per second into the 13.6 square inch duct. The tests showed that the mass flow of the rockets was great enough to cause the entrained air to go sonic at the strut, which is the location of the rocket nozzles. More tests are necessary to determine whether the entrained air chokes due to the reduction in the area of the duct at the strut (a physical choke), or because of the addition of mass inside the duct at the nozzle exit (a Fabri choke). The initial tests of the mixing diagnostics are showing promise.

  20. Mixed Markov models

    PubMed Central

    Fridman, Arthur

    2003-01-01

    Markov random fields can encode complex probabilistic relationships involving multiple variables and admit efficient procedures for probabilistic inference. However, from a knowledge engineering point of view, these models suffer from a serious limitation. The graph of a Markov field must connect all pairs of variables that are conditionally dependent even for a single choice of values of the other variables. This makes it hard to encode interactions that occur only in a certain context and are absent in all others. Furthermore, the requirement that two variables be connected unless always conditionally independent may lead to excessively dense graphs, obscuring the independencies present among the variables and leading to computationally prohibitive inference algorithms. Mumford [Mumford, D. (1996) in ICIAM 95, eds. Kirchgassner, K., Marenholtz, O. & Mennicken, R. (Akademie Verlag, Berlin), pp. 233–256] proposed an alternative modeling framework where the graph need not be rigid and completely determined a priori. Mixed Markov models contain node-valued random variables that, when instantiated, augment the graph by a set of transient edges. A single joint probability distribution relates the values of regular and node-valued variables. In this article, we study the analytical and computational properties of mixed Markov models. In particular, we show that positive mixed models have a local Markov property that is equivalent to their global factorization. We also describe a computationally efficient procedure for answering probabilistic queries in mixed Markov models. PMID:12829802

  1. Color mixing models

    NASA Astrophysics Data System (ADS)

    Harrington, Steven J.

    1992-05-01

    In black-and-white printing the page image can be represented within a computer as an array of binary values indicating whether or not pixels should be inked. The Boolean operators of AND, OR, and EXCLUSIVE-OR are often used when adding new objects to the image array. For color printing the page may be represented as an array of continuous tone color values, and the generalization of these logic functions to gray-scale or full-color images is, in general, not defined or understood. When incrementally composing a page image new colors can replace old in an image buffer, or new colors and old can be combined according to some mixing function to form a composite color which is stored. This paper examines the properties of the Boolean operations and suggests full-color mixing functions which preserve the desired properties. These functions can be used to combine colored images, giving various transparency effects. The relationships between the mixing functions and physical models of color mixing are also discussed.

  2. 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)

  3. Mesoscale Studies of Mixing in Reactive Materials During Shock Loading

    NASA Astrophysics Data System (ADS)

    Lomov, Ilya; Herbold, Eric

    2011-06-01

    One of the requisite processes for reactions between solid powder particles resulting from shock loading is that they undergo large deformations, exposing new surfaces while mixing with surrounding material. The deformability of Al particles on the scale of hundreds of nanometers to several microns with an oxide layer or Ni coating during shock loading is investigated. Mesoscale simulations with an Eulerian hydrocode GEODYN show enhanced fracture of the outside layer of the Al particles when even small volume fractions of a larger or dense material is added to the mixture. Rate of reactions in solid-solid mixtures is not a unique function of pressure, temperature and the plastic strain. Reactions under shock loading happen in reaction zone, which extent is defined by the surface of interfacial area and the depth of the diffusion layer. The former depends on the level of hydrodynamic mixing of heterogeneous material under shock, while the latter depends on the temperature-dependent species diffusion. These processes introduce time and length scales onto the problem. To study diffusion-limited reactions on the grain scale level, material diffusion and a simple reaction kinetic which depends on the interfacial surface area is implemented in GEODYN. Several scenarios of diffusion-reaction processes initiated by shock loading in loose or consolidated powders with initially well- defined material interfaces are considered.

  4. Anisotropic fractional diffusion tensor imaging

    PubMed Central

    Meerschaert, Mark M; Magin, Richard L; Ye, Allen Q

    2015-01-01

    Traditional diffusion tensor imaging (DTI) maps brain structure by fitting a diffusion model to the magnitude of the electrical signal acquired in magnetic resonance imaging (MRI). Fractional DTI employs anomalous diffusion models to obtain a better fit to real MRI data, which can exhibit anomalous diffusion in both time and space. In this paper, we describe the challenge of developing and employing anisotropic fractional diffusion models for DTI. Since anisotropy is clearly present in the three-dimensional MRI signal response, such models hold great promise for improving brain imaging. We then propose some candidate models, based on stochastic theory.

  5. Insights of Mixing on the Assembly of DNA Nanoparticles

    NASA Astrophysics Data System (ADS)

    Williams, Manda S.

    Size is a crucial parameter in the delivery of nanoparticle therapeutics, affecting mechanisms such as tissue delivery, clearance, and cellular uptake. The morphology of nanoparticles is dependent both upon chemistry and the physical process of assembly. Polyplexes, a major class of non-viral gene delivery vectors, are conventionally prepared by vortex mixing, resulting in non-uniform nanoparticles and poor reproducibility. Better understanding and control of the physical process of assembly, and mixing in particular, will produce polyplexes of a more uniform and reliable size, optimizing their efficiency for laboratory and clinical use. "Mixing" is the reduction of length scale of a system to accelerate diffusion until a uniform concentration is achieved. Vortex mixing is poorly characterized and sensitive to protocols. Microfluidic systems are notable for predictable fluid behavior, and are ideal for analyzing and controlling the physical interaction of reagents on the microscale, realm where mixing occurs. Several microdevices for the preparation of DNA polyplexes are explored here. Firstly, the staggered herringbone mixer, a chaotic advection micromixer, is used to observe the effects of mixing time on nanoparticle size. Next, a novel device to surround the reagent flows with a sheath of buffer, preventing interaction with the walls and confining the complexation to a zone of lower, less variable shear and residence time, is used to demonstrate the role of shear in nanoparticle assembly. Lastly, uneven diffusion between ion pairs produces a small separation of charge at fluid interfaces; this short-lived electric field has a significant impact on the transport of DNA over the time scales of mixing and complexation. The effects of common buffers on the transport of DNA are examined for possible applications to mixing and complexation. These three investigations demonstrate the importance of the physical process in polyplex assembly, and indicate several

  6. 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.

  7. Diffusion in silicon isotope heterostructures

    SciTech Connect

    Silvestri, Hughes Howland

    2004-05-14

    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 {sup 28}Si enriched layers, enables the observation of {sup 30}Si self-diffusion from the natural layers into the {sup 28}Si 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 positively charged P

  8. Magma mixing enhanced by bubble ascent

    NASA Astrophysics Data System (ADS)

    Wiesmaier, S.; Morgavi, D.; Perugini, D.; De Campos, C. P.; Hess, K.; Lavallee, Y.; Dingwell, D. B.

    2012-12-01

    Understanding the processes that affect the rate of liquid state homogenization provides fundamental clues on the otherwise inaccessible subsurface dynamics of magmatic plumbing systems. Compositional heterogeneities detected in the matrix of magmatic rocks represent the arrested state of a chemical equilibration. Magmatic homogenization has been divided into a) the mechanical interaction of magma batches (mingling) and b) the diffusive equilibration of compositional gradients, where diffusive equilibration is exponentially enhanced by progressive mechanical interaction [1]. The mechanical interaction between two distinct batches of magma has commonly been attributed to shear and folding movements between two liquids of distinct viscosities. A mode of mechanical interaction scarcely invoked is the advection of mafic material into a felsic one through bubble motion. Yet, experiments with analogue materials demonstrated that bubble ascent has the potential to enhance the fluid mechanical component of magma mixing [2]. Here, we present preliminary results from bubble-advection experiments. For the first time, experiments of this kind were performed using natural materials at magmatic temperatures. Cylinders of Snake River Plain (SRP) basalt were drilled with a cavity of defined volume and placed underneath cylinders of SRP rhyolite. Upon melting, the gas pocket, or bubble trapped within the cavity, rose into the rhyolite, so entraining a layer of basalt. Successive iterations of the same experiment at progressive intervals ensured a time series of magmatic interaction caused by bubble segregation. Variations in initial bubble size allowed the tracking of bubble volume to advected material ratio at defined viscosity contrast. The resulting plume-like structures that the advected basalt formed within the rhyolite were characterized by microCT and subsequent high-resolution EMP analyses. The mass of advected material per bubble correlated positively with bubble size. The

  9. Unitarity constraints on trimaximal mixing

    SciTech Connect

    Kumar, Sanjeev

    2010-07-01

    When the neutrino mass eigenstate {nu}{sub 2} is trimaximally mixed, the mixing matrix is called trimaximal. The middle column of the trimaximal mixing matrix is identical to tribimaximal mixing and the other two columns are subject to unitarity constraints. This corresponds to a mixing matrix with four independent parameters in the most general case. Apart from the two Majorana phases, the mixing matrix has only one free parameter in the CP conserving limit. Trimaximality results in interesting interplay between mixing angles and CP violation. A notion of maximal CP violation naturally emerges here: CP violation is maximal for maximal 2-3 mixing. Similarly, there is a natural constraint on the deviation from maximal 2-3 mixing which takes its maximal value in the CP conserving limit.

  10. 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.

  11. 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.

  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. Sampling diffusive transition paths

    SciTech Connect

    F. Miller III, Thomas; Predescu, Cristian

    2006-10-12

    We address the problem of sampling double-ended diffusive paths. The ensemble of paths is expressed using a symmetric version of the Onsager-Machlup formula, which only requires evaluation of the force field and which, upon direct time discretization, gives rise to a symmetric integrator that is accurate to second order. Efficiently sampling this ensemble requires avoiding the well-known stiffness problem associated with sampling infinitesimal Brownian increments of the path, as well as a different type of stiffness associated with sampling the coarse features of long paths. The fine-features sampling stiffness is eliminated with the use of the fast sampling algorithm (FSA), and the coarse-feature sampling stiffness is avoided by introducing the sliding and sampling (S&S) algorithm. A key feature of the S&S algorithm is that it enables massively parallel computers to sample diffusive trajectories that are long in time. We use the algorithm to sample the transition path ensemble for the structural interconversion of the 38-atom Lennard-Jones cluster at low temperature.

  15. Sampling diffusive transition paths.

    PubMed

    Miller, Thomas F; Predescu, Cristian

    2007-04-14

    The authors address the problem of sampling double-ended diffusive paths. The ensemble of paths is expressed using a symmetric version of the Onsager-Machlup formula, which only requires evaluation of the force field and which, upon direct time discretization, gives rise to a symmetric integrator that is accurate to second order. Efficiently sampling this ensemble requires avoiding the well-known stiffness problem associated with the sampling of infinitesimal Brownian increments of the path, as well as a different type of stiffness associated with the sampling of the coarse features of long paths. The fine-feature sampling stiffness is eliminated with the use of the fast sampling algorithm, and the coarse-feature sampling stiffness is avoided by introducing the sliding and sampling (S&S) algorithm. A key feature of the S&S algorithm is that it enables massively parallel computers to sample diffusive trajectories that are long in time. The authors use the algorithm to sample the transition path ensemble for the structural interconversion of the 38-atom Lennard-Jones cluster at low temperature. PMID:17444696

  16. Anisotropic Thermal Diffusion

    NASA Astrophysics Data System (ADS)

    Gardiner, Thomas

    2013-10-01

    Anisotropic thermal diffusion in magnetized plasmas is an important physical phenomena for a diverse set of physical conditions ranging from astrophysical plasmas to MFE and ICF. Yet numerically simulating this phenomenon accurately poses significant challenges when the computational mesh is misaligned with respect to the magnetic field. Particularly when the temperature gradients are unresolved, one frequently finds entropy violating solutions with heat flowing from cold to hot zones for χ∥ /χ⊥ >=102 which is substantially smaller than the range of interest which can reach 1010 or higher. In this talk we present a new implicit algorithm for solving the anisotropic thermal diffusion equations and demonstrate its characteristics on what has become a fairly standard set of test problems in the literature. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. SAND2013-5687A.

  17. 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. PMID:23888042

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. Sucrose diffusion in aqueous solution.

    PubMed

    Price, Hannah C; Mattsson, Johan; Murray, Benjamin J

    2016-07-28

    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

  3. [Mixed leg ulcers].

    PubMed

    Willenberg, Torsten

    2011-03-01

    Coexisting peripheral arterial disease is not uncommon (15 - 21 %) in patients with ulcera cruris primarily based on a venous etiology. Patient's history, clinical examination and detection of ABI as well as duplex scan will establish diagnosis of mixed arterial-venous ulcera. Clinical significance of coexisting arterial disease is often difficult to define and should be evaluated by a vascular specialist. The concept of treatment of mixed ulcers should always include the arterial component. Frequently peripheral arterial perfusion and healing can be improved by minimal invasive, endovascular revascularization. Compression therapy is the corner stone in treatment of venous disease and should be complemented by contemporary two piece graduated compression systems if ulcera are present. According to circumstances ablation of varicose veins must be considered. PMID:21360460

  4. Nozzle mixing apparatus

    SciTech Connect

    Mensink, D.L.

    1992-12-31

    This invention is comprised of a nozzle device for causing two fluids to mix together. In particular, a spray nozzle comprise two hollow, concentric housings, an inner housing and an outer housing. The inner housing has a channel formed therethrough for a first fluid. Its outer surface cooperates with the interior surface of the outer housing to define the second channel for a second fluid. The outer surface of the inner housing and the inner surface of the outer housing each carry a plurality of vanes that interleave but do not touch, each vane of one housing being between two vanes of the other housing. The vanes are curved and the inner surface of the outer housing and the outer surface of the inner housing converge to narrow the second channel. The shape of second channel results in a swirling, accelerating second fluid that will impact the first fluid just past the end of the nozzle where mixing will take place.

  5. 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.

  6. 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.

  7. Turbulent mixing and beyond.

    PubMed

    Abarzhi, S I; Sreenivasan, K R

    2010-04-13

    Turbulence is a supermixer. Turbulent mixing has immense consequences for physical phenomena spanning astrophysical to atomistic scales under both high- and low-energy-density conditions. It influences thermonuclear fusion in inertial and magnetic confinement systems; governs dynamics of supernovae, accretion disks and explosions; dominates stellar convection, planetary interiors and mantle-lithosphere tectonics; affects premixed and non-premixed combustion; controls standard turbulent flows (wall-bounded and free-subsonic, supersonic as well as hypersonic); as well as atmospheric and oceanic phenomena (which themselves have important effects on climate). In most of these circumstances, the mixing phenomena are driven by non-equilibrium dynamics. While each article in this collection dwells on a specific problem, the purpose here is to seek a few unified themes amongst diverse phenomena. PMID:20211872

  8. Diffusion limited aggregation. The role of surface diffusion

    NASA Astrophysics Data System (ADS)

    García-Ruiz, Juan M.; Otálora, Fermín

    1991-11-01

    We present a growth model in which the hitting particles are able to diffuse to more stable growth sites in the perimeter of a cluster growing by diffusion limited aggregation. By tuning the diffusion path Ls, the morphological output - from disordered fractal to perfect single crystals - can be controlled. Instabilities appear when the mean length of the crystal faces Lf are greater than 2 Ls.

  9. 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.

  10. The effect of particle shape on mixing in a high shear mixer

    NASA Astrophysics Data System (ADS)

    Sinnott, Matthew D.; Cleary, Paul W.

    2015-09-01

    Discrete element method modelling is used to study the effect of particle shape on the flow dynamics and mixing in a high shear mixer. The blade generates strong flow over its top surface while compacting and pushing forward particles that are directly in front of the blade. A complex three dimensional flow is established with vertical and radial flow components that are shape dependent and which control the nature of the mixing. Mixing was found to be fast in the azimuthal direction, of intermediate speed in the vertical direction and comparatively slow in the radial mixing. Diffusive mixing is characterised using the granular temperature which shows that the regions of higher granular temperature are larger for round particles than non-round ones leading to stronger diffusive mixing. The spatial distribution of the convective component of mixing is identified using novel calculation of shear strain rate. This size and shape of the high shear region is found to be only slightly sensitive to the particle shape indicating that the convective mixing is relatively independent of shape, except in the middle of the mixer. The blockiness of the particles has the strongest impact on flow and mixing while the mixing has only a weak dependence on the particle aspect ratio.

  11. The Harrison Diffusion Kinetics Regimes in Solute Grain Boundary Diffusion

    SciTech Connect

    Belova, Irina; Fiedler, T; Kulkarni, Nagraj S; Murch, Prof. Graeme

    2012-01-01

    Knowledge of the limits of the principal Harrison kinetics regimes (Type-A, B and C) for grain boundary diffusion is very important for the correct analysis of the depth profiles in a tracer diffusion experiment. These regimes for self-diffusion have been extensively studied in the past by making use of the phenomenological Lattice Monte Carlo (LMC) method with the result that the limits are now well established. The relationship of those self-diffusion limits to the corresponding ones for solute diffusion in the presence of solute segregation to the grain boundaries remains unclear. In the present study, the influence of solute segregation on the limits is investigated with the LMC method for the well-known parallel grain boundary slab model by showing the equivalence of two diffusion models. It is shown which diffusion parameters are useful for identifying the limits of the Harrison kinetics regimes for solute grain boundary diffusion. It is also shown how the measured segregation factor from the diffusion experiment in the Harrison Type-B kinetics regime may differ from the global segregation factor.

  12. Mixing of siliciclastic and carbonate sediments in shallow shelf environments

    NASA Astrophysics Data System (ADS)

    Mount, Jeffrey F.

    1984-07-01

    The inhibiting effect that siliciclastic material has on carbonate-secreting organisms has lead to the generalization that sediments composed of mixtures of carbonate and siliciclastic material should rarely form. However, many modern and ancient shelf deposits contain a spectrum of sediments that are of “mixed” composition. The processes responsible for this mixing can be grouped into four categories: (1) punctuated mixing, where sporadic storms and other extreme periodic events transfer sediments from one depositional environment to another; (2) facies mixing, where sediments are mixed along the diffuse boundaries between contrasting facies; (3) in situ mixing, where the carbonate fraction consists of the autochthonous or parautochthonous death assemblages of calcareous organisms that accumulated on or within siliciclastic substrates; and (4) source mixing, where admixtures are formed by the uplift and erosion of nearby carbonate source terranes. The allochemical constituents of mixed sediments are both coralgal and foram-mollusc in composition. The foram-mollusc assemblage is the most common because of the effects of increased turbidity, unstable substrates, and the clogging of filter-feeding mechanisms associated with a siliciclastic influx.

  13. Rapid mixing using two-phase hydraulic focusing in microchannels.

    PubMed

    Wu, Zhigang; Nguyen, Nam-Trung

    2005-03-01

    Rapid mixing is important in biomedical analysis. In this study, rapid mixing is obtained through two-phase hydraulic focusing in microchannels. Two mixing streams are focused by two sheath streams. Assuming a laminar flow in the channel, the spreading behavior of the two immiscible fluids is modeled and solved analytically. The results show that both viscosity ratio and flow rate ratio between the sheath flow and the sample flow can affect the focusing ratio. Thus, the mixing path of the sample flows can be adjusted by either viscosity ratio or flow rate ratio. Furthermore, an analytical model was proposed and solved for convective/diffusive mixing between the sample streams. According to this model, the focusing ratio is a key parameter for rapid mixing. A fully polymeric micro mixer was fabricated and tested for verification of the presented analytical models. The micromixer was fabricated by laser micromachining and adhesive bonding. The characterization results show the promising potential of mixing in microscale using two-phase hydraulic focusing. PMID:15834516

  14. 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.

  15. 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…

  16. 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.

  17. Modeling and Simulation of Fluid Mixing Laser Experiments and Supernova

    SciTech Connect

    Glimm, James

    2008-06-24

    The three year plan for this project is to develop novel theories and advanced simulation methods leading to a systematic understanding of turbulent mixing. A primary focus is the comparison of simulation models (both Direct Numerical Simulation and subgrid averaged models) to experiments. The comprehension and reduction of experimental and simulation data are central goals of this proposal. We will model 2D and 3D perturbations of planar interfaces. We will compare these tests with models derived from averaged equations (our own and those of others). As a second focus, we will develop physics based subgrid simulation models of diffusion across an interface, with physical but no numerical mass diffusion. We will conduct analytic studies of mix, in support of these objectives. Advanced issues, including multiple layers and reshock, will be considered.

  18. 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

  19. 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

  20. 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.