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Sample records for mixed lipid layers

  1. MHD turbulent mixing layers

    SciTech Connect

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

    2005-09-28

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

  2. Mixing in straight shear layers

    NASA Technical Reports Server (NTRS)

    Karasso, P. S.; Mungal, M. G.

    1992-01-01

    Planar laser-induced fluorescence measurements were performed in a liquid plane mixing layer to extract the probability density function (pdf) of the mixture fraction of a passive scalar across the layer. Three Reynolds number (Re) cases were studied, 10,000, 33,000 and 90,000, with Re based on velocity difference and visual thickness. The results show that a non-marching pdf (central hump invariant from edge to edge of the layer) exists for Re = 10,000 but that a marching type pdf characterizes the Re = 33,000 and Re = 90,000 cases. For all cases, a broad range of mixture fraction values is found at each location across the layer. Streamwise and spanwise ramps across the layer, and structure-to-structure variation were observed and are believed to be responsible for the above behavior of the composition field. Tripping the boundary layer on the high-speed side of the splitter plate for each of the above three cases resulted in increased three-dimensionality and a change in the composition field. Average and average mixed fluid compositions are reported for all cases.

  3. Composite S-layer lipid structures

    PubMed Central

    Schuster, Bernhard; Sleytr, Uwe B.

    2010-01-01

    Designing and utilization of biomimetic membrane systems generated by bottom-up processes is a rapidly growing scientific and engineering field. Elucidation of the supramolecular construction principle of archaeal cell envelopes composed of S-layer stabilized lipid membranes led to new strategies for generating highly stable functional lipid membranes at meso- and macroscopic scale. In this review, we provide a state of the art survey how S-layer proteins, lipids, and polysaccharides may be used as basic building blocks for the assembly of S-layer supported lipid membranes. These biomimetic membrane systems are distinguished by a nanopatterned fluidity, enhanced stability and longevity and thus, provide a dedicated reconstitution matrix for membrane-active peptides and transmembrane proteins. Exciting areas for application of composite S-layer membrane systems concern sensor systems involving specific membrane functions. PMID:19303933

  4. Helicity in supercritical temporal mixing layers

    NASA Technical Reports Server (NTRS)

    Bellan, J.; Okong'o, N.

    2003-01-01

    Databases of transitional states obtained from Direct Numerical Simulations (DNS) of temporal, supercritical mixing layers for two species systems, 02/H2 and C7Hle/N2, are analyzed to elucidate species-specific turbulence aspects.

  5. 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.

  6. Cylindrical Mixing Layer Model in Stellar Jet

    NASA Astrophysics Data System (ADS)

    Choe, Seung-Urn; Yu, Kyoung Hee

    1994-12-01

    We have developed a cylindrical mixing layer model of a stellar jet including cooling effect in order to understand an optical emission mechanism along collimated high velocity stellar jets associated with young stellar objects. The cylindrical results have been calculated to be the same as the 2D ones presented by Canto & Raga(1991) because the entrainment efficiency in our cylindrical model has been obtained to be the same value as the 2D model has given. We have discussed the morphological and physical characteristics of the mixing layers by the cooling effect. As the jet Mach number increases, the initial temperature of the mixing layer goes high because the kinetic energy of the jet partly converts to the thermal energy of the mixing layer. The initial cooling of the mixing layer is very severe, changing its outer boundary radius. A subsequent change becomes adiabatic. The number of the Mach disks in the stellar jet and the total radiative luminosity of the mixing layer, based on our cylindrical calculation, have quite agreed with the observation.

  7. Lipid Layer-based Corrosion Monitoring on Metal Substrates

    DTIC Science & Technology

    2013-04-01

    explore lipid layers as a potential biosensor for corrosion. It is hypothesized that applying a lipid layer to metals will allow for corrosion monitoring...Corrosion monitoring, lipid layers, biosensor 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT UU 18. NUMBER OF PAGES 14 19a...occurs as the material’s surface is oxidized in an electrochemical reaction, commonly in the presence of oxygen and water, which initially causes

  8. Vortex simulation of forced mixing layers

    NASA Technical Reports Server (NTRS)

    Inoue, O.; Leonard, A.

    1986-01-01

    Two-dimensional, spatially growing, turbulent mixing layers are simulated numerically by a vortex method and the results are compared with those determined experimentally. The effects of artificial forcing on flow development are also studied. Many of the flow features which have been observed experimentally are reproduced, and good quantitative agreements between experiments and computations are obtained.

  9. A random distribution reacting mixing layer model

    NASA Technical Reports Server (NTRS)

    Jones, Richard A.

    1994-01-01

    A methodology for simulation of molecular mixing and the resulting velocity and temperature fields has been developed. The ideas are applied to the flow conditions present in the NASA Lewis Planar Reacting Shear Layer (PRSL) facility, and results compared to experimental data. A gaussian transverse turbulent velocity distribution is used in conjunction with a linearly increasing time scale to describe the mixing of different regions of the flow. Equilibrium reaction calculations are then performed on the mix to arrive at a new species composition and temperature. Velocities are determined through summation of momentum contributions. The analysis indicates a combustion efficiency of the order of 80 percent for the reacting mixing layer, and a turbulent Schmidt number of 2/3. The success of the model is attributed to the simulation of large-scale transport of fluid. The favorable comparison shows that a relatively quick and simple PC calculation is capable of simulating the basic flow structure in the reacting and non-reacting shear layer present in the facility given basic assumptions about turbulence properties.

  10. A random distribution reacting mixing layer model

    NASA Technical Reports Server (NTRS)

    Jones, Richard A.; Marek, C. John; Myrabo, Leik N.; Nagamatsu, Henry T.

    1994-01-01

    A methodology for simulation of molecular mixing, and the resulting velocity and temperature fields has been developed. The ideas are applied to the flow conditions present in the NASA Lewis Research Center Planar Reacting Shear Layer (PRSL) facility, and results compared to experimental data. A gaussian transverse turbulent velocity distribution is used in conjunction with a linearly increasing time scale to describe the mixing of different regions of the flow. Equilibrium reaction calculations are then performed on the mix to arrive at a new species composition and temperature. Velocities are determined through summation of momentum contributions. The analysis indicates a combustion efficiency of the order of 80 percent for the reacting mixing layer, and a turbulent Schmidt number of 2/3. The success of the model is attributed to the simulation of large-scale transport of fluid. The favorable comparison shows that a relatively quick and simple PC calculation is capable of simulating the basic flow structure in the reacting and nonreacting shear layer present in the facility given basic assumptions about turbulence properties.

  11. 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.

  12. Locating the mixing layer: algorithms to identify the mixing layer height using lidar signals

    NASA Astrophysics Data System (ADS)

    Mehnert, Jan; Pesch, Markus

    2007-10-01

    The mixing layer (ML) provides a vertical atmospheric barrier and its height has become an important parameter in meteorology and air quality control. In locating the mixing layer using Lidar it has always to be considered that the signals may be biased by noise and the mixing layer itself can contain more than a single layer. In previous studies use was made of the fact that the main part of aerosols are located within the mixing layer and outside this layer, in the so called free atmosphere, the concentration of aerosols decreased significantly. This leads to a sharp change of the backscattering signal at the boundary layers. In this paper an algorithm is presented that determines the height of the mixing layer (MLH) by an intensive analysis of the global and local maxima of the Lidar signal and its first derivative. The algorithm searches for a maximum of the backscatter signal followed by a minimum in the first derivative. The results are compared with the MLH calculated by a model.

  13. Numerical simulation of excited jet mixing layers

    NASA Astrophysics Data System (ADS)

    Scott, J. N.; Hankey, W. L.

    1987-01-01

    A numerical simulation of unsteady flow in jet mixing layers, both with and without external excitation, has been performed by solving the time-dependent compressible Navier-Stokes equations. Computations were performed on a CRAY X-MP computer using MacCormick's explicit finite difference algorithm. Different excitation methods were investigated and were shown to be very effective in controlling the well organized periodic production, shedding and pairing of large scale vortex structures. It is found that pressure excitation was generally more effective than temperature excitation, and that grid refinement results in substantial improvement in the resolution of unsteady features. The location and orientation, in addition to the frequency, of the excitation source are shown to have a significant influence on the production and interaction of large scale vortex structures in the jet mixing layer.

  14. Cumulus cloud venting of mixed layer ozone

    NASA Technical Reports Server (NTRS)

    Ching, J. K. S.; Shipley, S. T.; Browell, E. V.; Brewer, D. A.

    1985-01-01

    Observations are presented which substantiate the hypothesis that significant vertical exchange of ozone and aerosols occurs between the mixed layer and the free troposphere during cumulus cloud convective activity. The experiments utilized the airborne Ultra-Violet Differential Absorption Lidar (UV-DIAL) system. This system provides simultaneous range resolved ozone concentration and aerosol backscatter profiles with high spatial resolution. Evening transects were obtained in the downwind area where the air mass had been advected. Space-height analyses for the evening flight show the cloud debris as patterns of ozone typically in excess of the ambient free tropospheric background. This ozone excess was approximately the value of the concentration difference between the mixed layer and free troposphere determined from independent vertical soundings made by another aircraft in the afternoon.

  15. 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.

  16. Anelastic Rayleigh-Taylor mixing layers

    NASA Astrophysics Data System (ADS)

    Schneider, N.; Gauthier, S.

    2016-07-01

    Anelastic Rayleigh-Taylor mixing layers for miscible fluids are investigated with a recently built model (Schneider and Gauthier 2015 J. Eng. Math. 92 55-71). Four Chebyshev-Fourier-Fourier direct numerical simulations are analyzed. They use different values for the compressibility parameters: Atwood number (the dimensionless difference of the heavy and light fluid densities) and stratification (accounts for the vertical variation of density due to gravity). For intermediate Atwood numbers and finite stratification, compressibility effects quickly occurs. As a result only nonlinear behaviours are reached. The influence of the compressibility parameters on the growth speed of the RTI is discussed. The 0.1—Atwood number/0.4—stratification configuration reaches a turbulent regime. This turbulent mixing layer is analyzed with statistical tools such as moments, PDFs, anisotropy indicators and spectra.

  17. Kinetics of lipid mixing between bicelles and nanolipoprotein particles

    PubMed Central

    Lai, Ginny; Forti, Kevin Muñoz; Renthal, Robert

    2015-01-01

    Nanolipoprotein particles (NLPs), also known as nanodiscs, are lipid bilayers bounded by apolipoprotein. Lipids and membrane proteins cannot exchange between NLPs. However, addition of bicelles opens NLPs and transfers their contents to bicelles, which freely exchange lipids and proteins. NLP-bicelle interactions may provide a new method for studying membrane protein oligomerization. The interaction mechanism was investigated by stopped flow fluorometry. NLP lipids included fluorescence resonance energy transfer donors and acceptors. NLPs were mixed with a 200-fold molar excess of dihexanoyl phosphatidylcholine (DHPC)/dimyristoyl phosphatidylcholine bicelles, and the rate of lipid transfer was monitored by the appearance of dequenched lipid donor fluorescence. The observed pseudo-first-order rate constant was surprisingly small. NLPs did not react with DHPC alone below its critical micelle concentration (cmc). Above the cmc, the reaction was complete within the instrument dead time. Thus, the rate-limiting step is not the reaction of NLPs with DHPC monomers or micelles. Added MSP1E3D1 had no effect on the rate, ruling out free apolipoprotein involvement. The NLP-bicelle mixing rate showed a strong temperature dependence (activation energy = 28 kcal/mol). Near or below the DMPC phase transition temperature, the kinetics were sigmoidal. Models are proposed for the NLP-bicelle mixing, including one involving fusion pores. PMID:25660392

  18. Stabilization of concentration fluctuations in mixed membranes by hybrid lipids

    NASA Astrophysics Data System (ADS)

    Palmieri, Benoit; Safran, Samuel

    2012-02-01

    Finite-size domains have been observed at the surface of cells. These lipids ``rafts'' are stable nanodomains enriched in saturated lipids and cholesterol. While line tension favors macrodomains, one explanation for raft stabilization suggests that the membrane composition is tuned close to a spinodal temperature. From this point of view, rafts are long-lived concentration fluctuations in the mixed phase. We propose a ternary mixture model for the cell membrane that includes hybrid lipids which have one saturated and one unsaturated hydrocarbon chain. Finite amount of hybrid lipids reduces the packing incompatibility at the saturated/unsaturated lipid interface and stabilizes the concentration fluctuations. Hybrid-Hybrid interactions are included in the model and further increase the life-time of the rafts and decrease their length-scales. Moreover, the hybrid has extra orientational degrees of freedom that may lead to modulated phases.

  19. Phase decorrelation, streamwise vortices and acoustic radiation in mixing layers

    NASA Technical Reports Server (NTRS)

    Ho, C. M.; Zohar, Y.; Moser, R. D.; Rogers, M. M.; Lele, S. K.; Buell, J. C.

    1988-01-01

    Several direct numerical simulations were performed and analyzed to study various aspects of the early development of mixing layers. Included are the phase jitter of the large-scale eddies, which was studied using a 2-D spatially-evolving mixing layer simulation; the response of a time developing mixing layer to various spanwise disturbances; and the sound radiation from a 2-D compressible time developing mixing layer.

  20. Mixed Layer Heat Budget During Pomme Experiment

    NASA Astrophysics Data System (ADS)

    Giordani, H.; Caniaux, G.; Prieur, L.; Gavart, M.; Reverdin, G.

    A simplified 3D oceanic model derived from 1D turbulent mixing model was built in order to evaluate separately the impacts of the different processes of the mixed layer. This model is run from the hydrological networks collected during the POMME ex- periment (NE Atlantic, February to April 2001). Five simulations were performed be- tween Pomme1 (13/02) and Pomme2 (04/04), each one deduced from the previous one by adding one new physical process. The performance of the model to retrieve the final analysed fields increases with the number of the processes. A significant improvement is reached when the ageostrophic circulation (associated with the geostrophic adjust- ment of the large scale structures) is activated. In this case, the vertical heat transport has a clear signature in fronts and in some eddies present in the domain. Therefore, these local strong intensities seems well to be associated to the synoptic structures in permanent geostrophic adjustment. Thus subduction seems to be linked to the evolu- tion of the fronts and eddies.

  1. Wavy structures in compressible mixing layers

    NASA Astrophysics Data System (ADS)

    Chen, Jun; Shi, Xiao-Tian; Wang, Tie-Jin; She, Zhen-Su

    2013-10-01

    Semi-periodic structures namely inclined wavy structures (IWS) are experimentally observed in compressible mixing layers at two convective Mach numbers ( M c = 0.11 and 0.47). Flow structures are visualized by the laserinduced planar laser Mie scattering (PLMS) technique. Two methods are developed to investigate the spatial distribution and geometry of IWS: (1) the dominant mode extraction (DME) method, to extract the dominant modes of IWS from the streamwise gray-level fluctuation, and (2) the phase tracking (PT) method, to identify the shape of IWS. The results suggest that pressure perturbations account for the formation of IWS in the initialmixing region and the joint effect of dilatation and coherent vortices enhances IWS in the welldeveloped region. The large transverse (cross-flow) scale of the IWS and their relation to coherent vortices (CV) indicate that the disturbance originated from CV in the mixing center propagates far into the free streams. The DME and the PT method are shown to be the effective tools to study the geometrical features of wavy structures in compressible shear flows.

  2. Stabilization of composition fluctuations in mixed membranes by hybrid lipids

    NASA Astrophysics Data System (ADS)

    Safran, Samuel; Palmieri, Benoit

    2013-03-01

    A ternary mixture model is proposed to describe composition fluctuations in mixed membranes composed of saturated, unsaturated and hybrid lipids. The asymmetric hybrid lipid has one saturated and one unsaturated hydrocarbon chain and it can reduce the packing incompatibility between saturated and unsaturated lipids. A methodology to recast the free-energy of the lattice in terms of a continuous isotropic field theory is proposed and used to analyze composition fluctuations above the critical temperature. The effect of hybrid lipids on fluctuations domains rich in saturated/unsaturated lipids is predicted. The correlation length of such fluctuations decreases significantly with increasing amounts of hybrids even if the temperature is maintained close to the critical temperature. This provides an upper bound for the domain sizes expected in rafts stabilized by hybrids, above the critical temperature. When the hybrid composition of the membrane is increased further, a crossover value is found above which ``stripe-like'' fluctuations are observed. The wavelength of these fluctuations decreases with increasing hybrid fraction and tends toward a molecular size in a membrane that contains only hybrids.

  3. Lipid Layers on Polyelectrolyte Multilayers: Understanding Lipid-Polyelectrolyte Interactions and Applications on the Surface Engineering of Nanomaterials.

    PubMed

    Diamanti, Eleftheria; Gregurec, Danijela; Gabriela, Romero; Cuellar, J L; Donath, E; Moya, S E

    2016-06-01

    In this manuscript we review work of our group on the assembly of lipid layers on top of polyelectrolyte multilayers (PEMs). The assembly of lipid layers with zwitterionic and charged lipids on PEMs is studied as a function of lipid and polyelectrolyte composition by the Quartz Crystal Microbalance. Polyelectrolyte lipid interactions are studied by means of Atomic Force Spectroscopy. We also show the coating of lipid layers for engineering different nanomaterials, i.e., carbon nanotubes and poly(lactic-co-glycolic) nanoparticles and how these can be used to decrease in vitro toxicity and to direct the intracellular localization of nanomaterials.

  4. Transverse ageostrophic circulations associated with elevated mixed layers

    NASA Technical Reports Server (NTRS)

    Keyser, D.; Carlson, T. N.

    1984-01-01

    The nature of the frontogenetically forced transverse ageostrophic circulations connected with elevated mixed layer structure is investigated as a first step toward diagnosing the complex vertical circulation patterns occurring in the vicinity of elevated mixed layers within a severe storm environment. The Sawyer-Eliassen ageostrophic circulation equation is reviewed and applied to the elevated mixed layer detected in the SESAME IV data set at 2100 GMT of May 9, 1979. The results of the ageostrophic circulation diagnosis are confirmed and refined by considering an analytic specification for the elevated mixed layer structure.

  5. Investigation on flow and mixing characteristics of supersonic mixing layer induced by forced vibration of cantilever

    NASA Astrophysics Data System (ADS)

    Zhang, Dongdong; Tan, Jianguo; Lv, Liang

    2015-12-01

    The mixing process has been an important issue for the design of supersonic combustion ramjet engine, and the mixing efficiency plays a crucial role in the improvement of the combustion efficiency. In the present study, nanoparticle-based planar laser scattering (NPLS), particle image velocimetry (PIV) and large eddy simulation (LES) are employed to investigate the flow and mixing characteristics of supersonic mixing layer under different forced vibration conditions. The indexes of fractal dimension, mixing layer thickness, momentum thickness and scalar mixing level are applied to describe the mixing process. Results show that different from the development and evolution of supersonic mixing layer without vibration, the flow under forced vibration is more likely to present the characteristics of three-dimensionality. The laminar flow region of mixing layer under forced vibration is greatly shortened and the scales of rolled up Kelvin-Helmholtz vortices become larger, which promote the mixing process remarkably. The fractal dimension distribution reveals that comparing with the flow without vibration, the turbulent fluctuation of supersonic mixing layer under forced vibration is more intense. Besides, the distribution of mixing layer thickness, momentum thickness and scalar mixing level are strongly influenced by forced vibration. Especially, when the forcing frequency is 4000 Hz, the mixing layer thickness and momentum thickness are 0.0391 m and 0.0222 m at the far field of 0.16 m, 83% and 131% higher than that without vibration at the same position, respectively.

  6. Temperature Versus Salinity Gradients Below the Ocean Mixed Layer

    DTIC Science & Technology

    2012-05-03

    13] The effects of density compensated gradients below the mixed layer are not limited to ocean circulation and cli- mate. Since sound speed and...The Impact of Spice on Ocean circulation . The second is the 6.2 program element 62435N Full Column Mixing for Numerical Ocean Models. The authors would...and F. Paparella (2003), Compensation and alignment of thermohaline gradients in the ocean mixed layer, J. Phys. Oceanogr., 33, 2214–2223, doi

  7. Tear film lipid layer: A molecular level view.

    PubMed

    Cwiklik, Lukasz

    2016-10-01

    Human cornea is covered by an aqueous tear film, and the outermost layer of the tear film is coated by lipids. This so-called tear film lipid layer (TFLL) reduces surface tension of the tear film and helps with the film re-spreading after blinks. Alterations of tear lipids composition and properties are related to dry eye syndrome. Therefore, unveiling structural and functional properties of TFLL is necessary for understanding tear film function under both normal and pathological conditions. Key properties of TFLL, such as resistance against high lateral pressures and ability to spread at the tear film surface, are directly related to the chemical identity of TFLL lipids. Hence, a molecular-level description is required to get better insight into TFLL properties. Molecular dynamics simulations are particularly well suited for this task and they were recently used for investigating TFLL. The present review discusses molecular level organization and properties of TFLL as seen by these simulation studies. This article is part of a Special Issue entitled: Biosimulations edited by Ilpo Vattulainen and Tomasz Róg.

  8. The salinity effect in a mixed layer ocean model

    NASA Technical Reports Server (NTRS)

    Miller, J. R.

    1976-01-01

    A model of the thermally mixed layer in the upper ocean as developed by Kraus and Turner and extended by Denman is further extended to investigate the effects of salinity. In the tropical and subtropical Atlantic Ocean rapid increases in salinity occur at the bottom of a uniformly mixed surface layer. The most significant effects produced by the inclusion of salinity are the reduction of the deepening rate and the corresponding change in the heating characteristics of the mixed layer. If the net surface heating is positive, but small, salinity effects must be included to determine whether the mixed layer temperature will increase or decrease. Precipitation over tropical oceans leads to the development of a shallow stable layer accompanied by a decrease in the temperature and salinity at the sea surface.

  9. Evaluation of the lipid-rich layer of reamer aspirate.

    PubMed

    Kay Sinclair, Sarina S; Jeray, Kyle J; Tanner, Stephanie L; Burg, Karen J L

    2010-08-01

    The fatty layer of aspirate obtained by reaming the femoral shaft using a reamer/irrigator/aspirator (RIA) device was characterized for fatty acid content and the presence of adult stem cells. Gas chromatography analysis was performed on samples taken from multiple patients to determine and compare the fatty acid contents of aspirate lipid samples. All four patients had the same four fatty acids present in the highest percentages: oleic, palmitic, linoleic and stearic. After successful isolation from bulk material, cells isolated from this lipid-rich layer were studied to determine their osteogenic and growth potential on a clinically available ceramic bone graft substitute. The results of metabolic activity and intracellular protein assays indicated that the ceramics supported growth of the cells isolated from the aspirate fat layer, although levels of alkaline phosphatase (ALP) expression were low for cells grown on the ceramics. Cells will not transition along the osteogenic pathway when they are actively dividing, and active growth may have contributed to the lack of ALP expression in this study. Isolated cells grown on tissue culture plastic expressed significant levels of the bone marker ALP. The results of this study suggest that cells isolated from the fat layer of RIA aspirate proliferate on ceramic bone void filler and have the potential to differentiate along an osteogenic pathway. Previously considered waste, the lipid-rich fat layer of aspirate may be a source of mesenchymal stem cells that, either alone or in conjunction with currently available synthetic bone graft material, could be used to stimulate new bone growth.

  10. Crowding-induced mixing behavior of lipid bilayers: Examination of mixing energy, phase, packing geometry, and reversibility

    DOE PAGES

    Zeno, Wade F.; Rystov, Alice; Sasaki, Darryl Y.; ...

    2016-04-20

    In an effort to develop a general thermodynamic model from first-principles to describe the mixing behavior of lipid membranes, we examined lipid mixing induced by targeted binding of small (Green Fluorescent Protein (GFP)) and large (nanolipoprotein particles (NLPs)) structures to specific phases of phase-separated lipid bilayers. Phases were targeted by incorporation of phase-partitioning iminodiacetic acid (IDA)-functionalized lipids into ternary lipid mixtures consisting of DPPC, DOPC, and cholesterol. GFP and NLPs, containing histidine tags, bound the IDA portion of these lipids via a metal, Cu2+, chelating mechanism. In giant unilamellar vesicles (GUVs), GFP and NLPs bound to the Lo domains ofmore » bilayers containing DPIDA, and bound to the Ld region of bilayers containing DOIDA. At sufficiently large concentrations of DPIDA or DOIDA, lipid mixing was induced by bound GFP and NLPs. The validity of the thermodynamic model was confirmed when it was found that the statistical mixing distribution as a function of crowding energy for smaller GFP and larger NLPs collapsed to the same trend line for each GUV composition. Moreover, results of this analysis show that the free energy of mixing for a ternary lipid bilayer consisting of DOPC, DPPC, and cholesterol varied from 7.9 × 10–22 to 1.5 × 10–20 J/lipid at the compositions observed, decreasing as the relative cholesterol concentration was increased. It was discovered that there appears to be a maximum packing density, and associated maximum crowding pressure, of the NLPs, suggestive of circular packing. A similarity in mixing induced by NLP1 and NLP3 despite large difference in projected areas was analytically consistent with monovalent (one histidine tag) versus divalent (two histidine tags) surface interactions, respectively. In addition to GUVs, binding and induced mixing behavior of NLPs was also observed on planar, supported lipid multibilayers. Furthermore, the mixing process was reversible, with

  11. EXCESS FIBRINOGEN ADSORPTION TO MONOLAYERS OF MIXED LIPIDS

    PubMed Central

    Deshmukh, V.; Britt, D.W.; Hlady, V.

    2010-01-01

    Adsorption of fibrinogen to the monolayers of mixed lipids, dipalmitoyl phosphatidyl choline (DPPC) and eicosylamine (EA) was measured at a surface pressure of 20 mN/m by an in situ surface plasmon resonance technique. Pressure-area isotherms of DPPC+EA mixtures on water and buffer subphases indicated good lipid miscibility and some contraction of the monolayers at intermediate and higher surface pressures. Surface electric potential of the DPPC+EA monolayers showed excess values for intermediate DPPC:EA ratios. Fibrinogen adsorption and its adsorption rates from a dilute solution (0.03 mg/ml) were proportional to the fraction of EA in the monolayer indicating that protein binding was primarily driven by electrostatic interactions between positive EA charges in the monolayer and a net negative protein charge. At a higher protein concentration (0.06 mg/ml) both the fibrinogen adsorbed amount and its maximum adsorption rate showed excess values relative to the pure EA for 1:1, 2:1 and 3:1 DPPC+EA monolayers. This excess adsorption could be explained, in part, by the contraction of the monolayers with intermediate DPPC:EA ratios which resulted in an excess surface electric potential. PMID:20829000

  12. Baroclinic mixed layer instability in the presence of convection

    NASA Astrophysics Data System (ADS)

    Callies, Joern; Ferrari, Raffaele

    2015-11-01

    It has recently been discovered that geostrophic turbulence in the upper ocean undergoes a seasonal cycle at submesoscales, the scales smaller than the most energetic mesoscale eddies. Observations and theory suggest that baroclinic mixed layer instabilities release potential energy stored in deep mixed layers, energizing the submesoscales in winter. In shallow summer mixed layers, there is no such energization. The oceanic mixed layer, besides being prone to baroclinic instabilities, is subject to atmospheric forcing, which drives convective overturns. We here study how this forced convection interacts with baroclinic instabilities in a set of idealized numerical simulations resolving both processes. A major question is whether baroclinic instabilities can be damped out by convection. Implications for the seasonal cycle in submesoscale turbulence will be discussed.

  13. Modeling a Rain-Induced Mixed Layer

    DTIC Science & Technology

    1990-06-01

    te -)-A-- e e -2)- . (7) ’&Z AZ Az D Using the exponential relations with trigonometry , equation (7) becomes, Ok n) 3 (I- cos2ikAz)+ D (1- cos ikAz...completely unknown because there are no prior studies which predict what portion of total energy may go into subsurface mixing. The biggest obstacle

  14. Lipid and protein maps defining arterial layers in atherosclerotic aorta

    PubMed Central

    Martin-Lorenzo, Marta; Balluff, Benjamin; Maroto, Aroa S.; Carreira, Ricardo J.; van Zeijl, Rene J.M.; Gonzalez-Calero, Laura; de la Cuesta, Fernando; Barderas, Maria G; Lopez-Almodovar, Luis F; Padial, Luis R; McDonnell, Liam A.; Vivanco, Fernando; Alvarez-Llamas, Gloria

    2015-01-01

    Subclinical atherosclerosis cannot be predicted and novel therapeutic targets are needed. The molecular anatomy of healthy and atherosclerotic tissue is pursued to identify ongoing molecular changes in atherosclerosis development. Mass Spectrometry Imaging (MSI) accounts with the unique advantage of analyzing proteins and metabolites (lipids) while preserving their original localization; thus two dimensional maps can be obtained. Main molecular alterations were investigated in a rabbit model in response to early development of atherosclerosis. Aortic arterial layers (intima and media) and calcified regions were investigated in detail by MALDI-MSI and proteins and lipids specifically defining those areas of interest were identified. These data further complement main findings previously published in J Proteomics (M. Martin-Lorenzo et al., J. Proteomics. (In press); M. Martin-Lorenzo et al., J. Proteomics 108 (2014) 465–468.) [1,2]. PMID:26217810

  15. Effects of Fatty Acids on the Interfacial and Solution Behavior of Mixed Lipidic Aggregates Called Solid Lipid Nanoparticles.

    PubMed

    Karmakar, Gourab; Nahak, Prasant; Guha, Pritam; Roy, Biplab; Chettri, Priyam; Sapkota, Manish; Koirala, Suraj; Misono, Takeshi; Torigoe, Kanjiro; Ghosh, Shilpi; Panda, Amiya Kumar

    2016-01-01

    Mutual miscibility of soylecithin, tristearin, fatty acids (FAs), and curcumin was assessed by means of surface pressure-area isotherms at the air-solution interface in order to formulate modified solid lipid nanoparticles (SLN). Appearance of minima in the excess area (Aex) and changes in free energy of mixing (∆G(0)ex) were recorded for systems with 20 mole% FAs. Modified SLNs, promising as topical drug delivery systems, were formulated using the lipids in combination with curcumin, stabilized by an aqueous Tween 60 solution. Optimal formulations were assessed by judiciously varying the FA chain length and composition. Physicochemical properties of SLNs were studied such as the size, zeta potential (by dynamic light scattering), morphology (by freeze fracture transmission electron microscopy), and thermal behavior (by differential scanning calorimetry). The size and zeta potential of the formulations were in the range 300-500 nm and -10 to -20 mV, respectively. Absorption and emission spectroscopic analyses supported the dynamic light scattering and differential scanning calorimetry data and confirmed localization of curcumin to the palisade layer of SLNs. These nanoparticles showed a sustained release of incorporated curcumin. Curcumin-loaded SLNs were effective against a gram-positive bacterial species, Bacillus amyloliquefaciens. Our results on the physicochemical properties of curcumin-loaded SLNs, the sustained release, and on antibacterial activity suggest that SLNs are promising delivery agents for topical drugs.

  16. Single-step assembly of homogenous lipid-polymeric and lipid-quantum dot nanoparticles enabled by microfluidic rapid mixing.

    PubMed

    Valencia, Pedro M; Basto, Pamela A; Zhang, Liangfang; Rhee, Minsoung; Langer, Robert; Farokhzad, Omid C; Karnik, Rohit

    2010-03-23

    A key challenge in the synthesis of multicomponent nanoparticles (NPs) for therapy or diagnosis is obtaining reproducible monodisperse NPs with a minimum number of preparation steps. Here we report the use of microfluidic rapid mixing using hydrodynamic flow focusing in combination with passive mixing structures to realize the self-assembly of monodisperse lipid-polymer and lipid-quantum dot (QD) NPs in a single mixing step. These NPs are composed of a polymeric core for drug encapsulation or a QD core for imaging purposes, a hydrophilic polymeric shell, and a lipid monolayer at the interface of the core and the shell. In contrast to slow mixing of lipid and polymeric solutions, rapid mixing directly results in formation of homogeneous NPs with relatively narrow size distribution that obviates the need for subsequent thermal or mechanical agitation for homogenization. We identify rapid mixing conditions that result in formation of homogeneous NPs and show that self-assembly of polymeric core occurs independent of the lipid component, which only provides stability against aggregation over time and in the presence of high salt concentrations. Physicochemical properties of the NPs including size (35-180 nm) and zeta potential (-10 to +20 mV in PBS) are controlled by simply varying the composition and concentration of precursors. This method for preparation of hybrid NPs in a single mixing step may be useful for combinatorial synthesis of NPs with different properties for imaging and drug delivery applications.

  17. A perspective view of the plane mixing layer

    NASA Technical Reports Server (NTRS)

    Jimenez, J.; Cogollos, M.; Bernal, L. P.

    1984-01-01

    A three-dimensional model of the plane mixing layer is constructed by applying digital image processing and computer graphic techniques to laser fluorescent motion pictures of its transversal sections. A system of streamwise vortex pairs is shown to exist on top of the classical spanwise eddies. Its influence on mixing is examined.

  18. Evolution of a forced stratified mixing layer

    NASA Astrophysics Data System (ADS)

    Rotter, J.; Fernando, H. J. S.; Kit, E.

    2007-06-01

    Laboratory measurements were carried out in a spatially developing stably stratified shear layer generated downstream of a splitter plate. The instabilities were controlled using a flapper spanning the entire shear layer, with the flapper forced at the fastest growing frequency of the primary [Kelvin-Helmholtz (KH)] instability. The measurements were taken as the KH instabilities roll up, break down, and degenerate into stratified turbulence. Both stratified and homogeneous shear layers were considered, the latter acting as the "baseline" case. The measurements included the streamwise and vertical velocities (made using X-wire hot film probes), which allowed calculation of the mean and rms velocities, turbulent kinetic energy (TKE) dissipation, and TKE production. The density and its gradients were measured using miniature conductivity probes. The measurements and flow visualization elicited interesting features of KH evolution, namely that KH billows may be turbulent from the onset, the TKE dissipation is largest at early stages of evolution, the production of TKE is a maximum at the breakdown of billows, the decay of turbulence to fossilized motions and concomitant formation of fine (layered) structure occur rapidly after the breakdown of billows, and episodic rebirth of (zombie) turbulence develops before a final permanently fossilized state is achieved.

  19. Laboratory simulations of the atmospheric mixed-layer in flow ...

    EPA Pesticide Factsheets

    A laboratory study of the influence of complex terrain on the interface between a well-mixed boundary layer and an elevated stratified layer was conducted in the towing-tank facility of the U.S. Environmental Protection Agency. The height of the mixed layer in the daytime boundary layer can have a strong influence on the concentration of pollutants within this layer. Deflections of streamlines at the height of the interface are primarily a function of hill Froude number (Fr), the ratio of mixed-layer height (zi) to terrain height (h), and the crosswind dimension of the terrain. The magnitude of the deflections increases as Fr increases and zi / h decreases. For mixing-height streamlines that are initially below the terrain top, the response is linear with Fr; for those initially above the terrain feature the response to Fr is more complex. Once Fr exceeds about 2, the terrain related response of the mixed layer interface decreases somewhat with increasing Fr (toward more neutral flow). Deflections are also shown to increase as the crosswind dimensions of the terrain increases. Comparisons with numerical modeling, limited field data and other laboratory measurements reported in the literature are favorable. Additionally, visual observations of dye streamers suggests that the flow structure exhibited for our elevated inversions passing over three dimensional hills is similar to that reported in the literature for continuously stratified flow over two-dimensional h

  20. Gradient layer entrainment in a thermohaline system with mixed layer circulation

    SciTech Connect

    Incropera, F.P.; Lents, C.E.; Viskanta, R.

    1986-11-01

    Entrainment of salt-stratified fluid into a bottom mixed layer is investigated under conditions for which mixing is driven by bottom heating and/or an imposed horizontal flow. Entrainment rate measurements and mixed layer flow visualization suggest that entrainment is strongly influenced by a shear mechanism involving both horizontal and vertical fluid velocity components. Under certain conditions, imposition of the horizontal flow inhibits the buoyancy flow and entrainment rates for combined mixing are less than those for pure buoyant mixing. Attempts to correlate entrainment rates in terms of conventional dimensionless parameters were unsuccessful.

  1. Criteria for lipid layer pattern evaluation: Pli-marker database

    NASA Astrophysics Data System (ADS)

    García-Resúa, Carlos; Pena-Verdeal, Hugo; Remeseiro, Beatriz; Penedo, Manuel G.; Giráldez, María. Jesús; Yebra-Pimentel, Eva

    2013-11-01

    The purpose of this study is to establish the procedure of acquisition and evaluate the Lipid layer pattern (LLP) by Tearscope in order to enhance this useful technique. To aid this purpose, we present a new broad LLP images database (included in a web application called Pli-marker) The tear film lipid layer was examined using a Tearscope-plus (Keeler, Windsor, UK). To capture LLPs videos a Topcon DV-3 digital camera was used and attached to the slit lamp. All videos were stored in a computer via Topcon IMAGEnet i-base software and LLP images were obtained and uploaded at Pli-marker web application, which offers the manual selection of regions associated to a specific LLP. 50 images were analysed by 4 experienced optometrists. Each of them marked (using Pli-marker) those areas in the 50 images that corresponded with some of the 5 LLP: open meshwork (OM), closed meshwork, (CM), wave (W), amorphous (AM) and color fringe (CO). From the 50 images we obtained 25 areas of OM, 22 areas of CM, 20 areas of W, 46 areas of AM and 17 areas of CO that 4 observers were in accordance. We present an example of 4 pictures for each area of concordance together with the description of the features used for categorizing the LLP in our study. This work describes the methodology used in our research project, including settings for capture image, and the criteria for subjective categorization of the LLP accomplished by a set of images.

  2. Transmission of thin light beams through turbulent mixing layers

    NASA Astrophysics Data System (ADS)

    Wissler, John B.

    1991-09-01

    Light transmission through incompressible gaseous turbulent mixing layers is investigated with the objective of understanding the effects of large-scale coherent structures and mixing transition on the optical quality of the mixing layer. Experiments are done in a vertically flowing mixing layer which is enclosed inside a pressure tank and fed by two banks of high-pressure gas bottles. The study considers both the unequal density (high-speed Helium and low-speed Nitrogen) and equal density (high-speed N2 and low-speed He-Ar) cases; the mixing of dissimilar gases is the source of the optical aberrations. Large-scale Reynolds numbers range between 3500 and 80000 over pressures from 2 to 6 bar. Light transmission characteristics are first studied qualitatively using a network of thin sheets of short-exposure (about 1 microsec) white light which are aberrated by the mixing layer and then image directly onto photographic film. Light transmission characteristics are then studied quantitatively using a lateral effect detector to dynamically track a thin Helium-Neon laser beam as it wanders under the influence of the passing coherent structures. The study finds that the spanwise coherent structures generate systematic deflections of the light beam in the streamwise direction; the greatest deflections occur near the trailing edges of the structures at a formation called the cusp, where the high-speed fluid and low-speed fluid are entrained into the vortex core.

  3. Numerical simulation of the non-Newtonian mixing layer

    NASA Technical Reports Server (NTRS)

    Azaiez, Jalel; Homsy, G. M.

    1993-01-01

    This work is a continuing effort to advance our understanding of the effects of polymer additives on the structures of the mixing layer. In anticipation of full nonlinear simulations of the non-Newtonian mixing layer, we examined in a first stage the linear stability of the non-Newtonian mixing layer. The results of this study show that, for a fluid described by the Oldroyd-B model, viscoelasticity reduces the instability of the inviscid mixing layer in a special limit where the ratio (We/Re) is of order 1 where We is the Weissenberg number, a measure of the elasticity of the flow, and Re is the Reynolds number. In the present study, we pursue this project with numerical simulations of the non-Newtonian mixing layer. Our primary objective is to determine the effects of viscoelasticity on the roll-up structure. We also examine the origin of the numerical instabilities usually encountered in the simulations of non-Newtonian fluids.

  4. Direct simulations of chemically reacting turbulent mixing layers, part 2

    NASA Technical Reports Server (NTRS)

    Metcalfe, Ralph W.; Mcmurtry, Patrick A.; Jou, Wen-Huei; Riley, James J.; Givi, Peyman

    1988-01-01

    The results of direct numerical simulations of chemically reacting turbulent mixing layers are presented. This is an extension of earlier work to a more detailed study of previous three dimensional simulations of cold reacting flows plus the development, validation, and use of codes to simulate chemically reacting shear layers with heat release. Additional analysis of earlier simulations showed good agreement with self similarity theory and laboratory data. Simulations with a two dimensional code including the effects of heat release showed that the rate of chemical product formation, the thickness of the mixing layer, and the amount of mass entrained into the layer all decrease with increasing rates of heat release. Subsequent three dimensional simulations showed similar behavior, in agreement with laboratory observations. Baroclinic torques and thermal expansion in the mixing layer were found to produce changes in the flame vortex structure that act to diffuse the pairing vortices, resulting in a net reduction in vorticity. Previously unexplained anomalies observed in the mean velocity profiles of reacting jets and mixing layers were shown to result from vorticity generation by baroclinic torques.

  5. Mixing layer resonance under high-speed stream forcing

    NASA Astrophysics Data System (ADS)

    Thomassin, Jean; Mureithi, Njuki; Vo, Huu Duc

    2014-12-01

    In the majority of fluid-structure interaction problems, the biggest challenge lies in the fundamental understanding of the flow physics. Forced mixing layers is an important phenomenon found in many cases of flow-induced vibrations and acoustics. The response of a mixing layer to high-speed stream acoustic forcing is investigated with a theoretical and experimental approach. Two different experiments demonstrating the fluid mechanic phenomenon are presented. The first experiment consists of a circular jet impinging on a vibrating plate. The second experiment demonstrates the mixing layer resonance in the context of a fluidelastic instability causing high-amplitude vibrations in gas turbine high-pressure compressor rotor blades. Both the plate and the adjacent blade vibration induce an acoustic feedback that propagates within the jet and blade tip clearance flow, respectively. The resonance was found to occur when the feedback wavelength matched either the jet-to-plate or the inter-blade distance. In both experimental cases, the resonance condition has been simply modeled by the coincidence of a 1D feedback wave, which propagates upstream at reduced velocity by the high-speed flow. The coupling between the jet induced mixing layer and the feedback wave is assumed to naturally occur when one of the wave crests reaches the separation edge. The objective of this study is to improve the understanding of the coupling mechanism between an emanating shear layer and the acoustic forcing originating within a fast flow stream. The study is based on a simplified analytical model in order to enlarge the current understanding of the mixing layer receptivity to the more specific case of its response to high-speed stream forcing. To identify the mixing layer resonant modes, an analytical resonance condition is proposed. It is found that the mixing layer response becomes spatially resonant for specific source locations downstream in the high-speed flow. The study also provides an

  6. Prediction of dynamic and mixing characteristics of drop-laden mixing layers using DNS and LES

    NASA Technical Reports Server (NTRS)

    Okong'o, N.; Leboissetier, A.; Bellan, J.

    2004-01-01

    Direct Numerical Simulation (DNS) and Large Eddy Simulation (LES) have been conducted of a temporal mixing layer laden with evaporating drops, in order to assess the ability of LES to reproduce dynamic and mixing aspects of the DNS which affect combustion, independently of combustion models.

  7. Transmission of light through a turbulent mixing layer

    NASA Astrophysics Data System (ADS)

    Roshko, Anatol; Wissler, John

    1992-08-01

    Light transmission through incompressible gaseous turbulent mixing layers was investigated with the objective of understanding the effects of large-scale coherent structures and mixing transition on the optical quality of the mixing layer. Experiments were done in a vertically flowing mixing layer which is enclosed inside a pressure tank and fed by two banks of high-pressure gas bottles. The study considered both the unequal density (high-speed He and low-speed N2) and equal density (high-speed N2 and low-speed He-Ar) cases; the mixing of dissimilar gases is the source of the optical aberrations. Large-scale Reynolds numbers ranged between 3500 and 80000 over pressures from 2 to 6 bar. Light transmission characteristics were first studied qualitatively using a network of thin sheets of short-exposure (approximately 1 microsec) white light which were aberrated by the mixing layer and then imaged directly onto photographic film. Light transmission characteristics were then studied quantitatively using a lateral effect detector to dynamically track a thin He-Ne laser beam as it wandered under the influence of the passing coherent structures. The study found that the spanwise coherent structures generate systematic deflections of the light beam in the streamwise direction; the greatest deflections occur near the trailing edges of the structures at a formation called the cusp, where the high-speed fluid and low-speed fluid are entrained into the vortex core. The streamwise coherent structures, which form later in the mixing layer's development than the spanwise structures, generate substantial beam deflections in the spanwise direction which are closely associated with the streamwise streaks in plan-view shadowgraphs.

  8. LIF measurements of scalar mixing in turbulent shear layers

    NASA Technical Reports Server (NTRS)

    Karasso, Paris S.; Mungal, M. G.

    1993-01-01

    The structure of shear layer flows at high Reynolds numbers remains a very interesting problem. Straight mixing layers have been studied and yielded information on the probability density function (pdf) of a passive scalar across the layer. Konrad and Koochesfahani & Dimotakis measured the pdf of the mixture fraction for mixing layers of moderate Reynolds numbers, each about 25,000 (Re based on velocity difference and visual thickness). Their measurements showed a 'non-marching' pdf (central hump which is invariant from edge to edge across the layer), a result which is linked to the visualizations of the spanwise Kelvin-Helmholtz (K-H) instability mode, which is the primary instability for plane shear layer flows. A secondary instability mode, the Taylor-Gortler (T-G) instability, which is associated with streamwise vortical structures, has also been observed in shear layers. Image reconstruction by Jimenez et al. and volume renderings by Karasso & Mungal at low Re numbers have demonstrated that the K-H and the T-G instability modes occur simultaneously in a non-mutually destructive way, evidence that supports the quasi two-dimensional aspect of these flows and the non-marching character of the pdf at low Reynolds numbers. At higher Re numbers though, the interaction of these two instability modes is still unclear and may affect the mixing process. In this study, we perform measurements of the concentration pdf of plane mixing layers for different operating conditions. At a speed ratio of r = U(sub 1)/U(sub 2) = 4:1, we examine three Reynolds number cases: Re = 14,000, Re = 31,000, and Re = 62,000. Some other Re number cases' results, not presented in detail, are invoked to explain the behavior of the pdf of the concentration field. A case of r = 2.6:1 at Re = 20,000 is also considered. The planar laser-induced fluorescence technique is used to yield quantitative measurements. The different Re are obtained by changing the velocity magnitudes of the two streams. The

  9. A procedure for the automatic estimation of mixed layer height.

    SciTech Connect

    Coulter, R. L.

    1998-04-15

    The daytime mixed layer results from mechanical and thermal turbulence processes driven by differences in air-surface temperature and moisture. As such, the height of the mixed layer (z{sub i}) is a measure of the effectiveness of energy transfer from the sun to the earth's surface and, in turn, to the lower atmosphere (Stun, 1989). Maximum daytime values for z{sub i} in the region of the Southern Great Plains (SGP) Cloud and Radiation Testbed (CART) vary from less than 100 m in cloudy, moist, calm, stable conditions to nearly 3 km in clear, dry, unstable conditions. The principal characteristic of the mixed layer is that scalar quantities such as moisture and temperature are mixed throughout. Thus, z{sub i} becomes one of the principal scaling parameters used to describe the structure of the lower planetary boundary layer. Normally, a stable layer (a potential temperature inversion) at the top of the mixed layer interfaces between processes in the lower atmosphere and in the free atmosphere above. The strength of this inversion limits the rate of growth of z{sub i} with time and the vertical transfer of energy and moisture. When and if z{sub i} reaches the condensation level, clouds can form; hence, cloud base height (particularly for fair-weather cumulus clouds) often coincides with z{sub i} later in the day. Although the concept of the mixed layer height is straightforward, its measurement can be relatively difficult, or at least awkward. The most reliable method is an analysis of potential temperature and mixing ratio profiles retrieved from balloon ascents. (The potential temperature changes from constant to increasing with height; the mixing ratio changes from constant to decreasing with height.) Often however, the profiles of temperature and moisture are ambiguous, with multiple inversions or none at all. In addition these profiles supply only a snapshot of the atmospheric structure that may well be unrepresentative of the average, either in time or space

  10. Internal wave energy radiated from a turbulent mixed layer

    SciTech Connect

    Munroe, James R.; Sutherland, Bruce R.

    2014-09-15

    We examine mixed-layer deepening and the generation of internal waves in stratified fluid resulting from turbulence that develops in response to an applied surface stress. In laboratory experiments the stress is applied over the breadth of a finite-length tank by a moving roughened conveyor belt. The turbulence in the shear layer is characterized using particle image velocimetry to measure the kinetic energy density. The internal waves are measured using synthetic schlieren to determine their amplitudes, frequencies, and energy density. We also perform fully nonlinear numerical simulations restricted to two dimensions but in a horizontally periodic domain. These clearly demonstrate that internal waves are generated by transient eddies at the integral length scale of turbulence and which translate with the background shear along the base of the mixed layer. In both experiments and simulations we find that the energy density of the generated waves is 1%–3% of the turbulent kinetic energy density of the turbulent layer.

  11. Crowding-induced mixing behavior of lipid bilayers: Examination of mixing energy, phase, packing geometry, and reversibility

    SciTech Connect

    Zeno, Wade F.; Rystov, Alice; Sasaki, Darryl Y.; Risbud, Subhash H.; Longo, Marjorie L.

    2016-04-20

    In an effort to develop a general thermodynamic model from first-principles to describe the mixing behavior of lipid membranes, we examined lipid mixing induced by targeted binding of small (Green Fluorescent Protein (GFP)) and large (nanolipoprotein particles (NLPs)) structures to specific phases of phase-separated lipid bilayers. Phases were targeted by incorporation of phase-partitioning iminodiacetic acid (IDA)-functionalized lipids into ternary lipid mixtures consisting of DPPC, DOPC, and cholesterol. GFP and NLPs, containing histidine tags, bound the IDA portion of these lipids via a metal, Cu2+, chelating mechanism. In giant unilamellar vesicles (GUVs), GFP and NLPs bound to the Lo domains of bilayers containing DPIDA, and bound to the Ld region of bilayers containing DOIDA. At sufficiently large concentrations of DPIDA or DOIDA, lipid mixing was induced by bound GFP and NLPs. The validity of the thermodynamic model was confirmed when it was found that the statistical mixing distribution as a function of crowding energy for smaller GFP and larger NLPs collapsed to the same trend line for each GUV composition. Moreover, results of this analysis show that the free energy of mixing for a ternary lipid bilayer consisting of DOPC, DPPC, and cholesterol varied from 7.9 × 10–22 to 1.5 × 10–20 J/lipid at the compositions observed, decreasing as the relative cholesterol concentration was increased. It was discovered that there appears to be a maximum packing density, and associated maximum crowding pressure, of the NLPs, suggestive of circular packing. A similarity in mixing induced by NLP1 and NLP3 despite large difference in projected areas was analytically consistent with monovalent (one histidine tag) versus divalent (two histidine tags) surface interactions, respectively. In addition to GUVs, binding and induced mixing behavior of NLPs was also observed on planar, supported lipid multibilayers. Furthermore, the mixing

  12. Transmission of thin light beams through turbulent mixing layers

    NASA Astrophysics Data System (ADS)

    Wissler, John B.

    Light transmission through incompressible gaseous turbulent mixing layers is investigated with the objective of understanding the effects of large-scale coherent structures and mixing transition on the optical quality of the mixing layer. Experiments are done in a vertically flowing mixing layer which is enclosed inside a pressure tank and fed by two banks of high-pressure gas bottles. The study considers both the unequal density (high-speed [...] and low-speed [...]) and equal density (high-speed [...] and low-speed [...]) cases; the mixing of dissimilar gases is the source of the optical aberrations. Large-scale Reynolds numbers range between 3500 and 80000 over pressures from 2 to 6 bar. Light transmission characteristics are first studied qualitatively using a network of thin sheets of short-exposure ([...]) white light which are aberrated by the mixing layer and then image directly onto photographic film. Light transmission characteristics are then studied quantitatively using a lateral effect detector to dynamically track a thin He-Ne laser beam as it wanders under the influence of the passing coherent structures.The study finds that the spanwise coherent structures generate systematic deflections of the light beam in the streamwise direction; the greatest deflections occur near the trailing edges of the structures at a formation called the cusp, where the high-speed fluid and low-speed fluid are entrained into the vortex core. The streamwise coherent structures, which form later in the mixing layer's development than the spanwise structures, generate substantial beam deflections in the span-wise direction which are closely associated with the streamwise streaks in plan-view shadowgraphs. The rms fluctuations of the streamwise and spanwise deflection angles increase rapidly during mixing transition, peaking at 380 high-speed-side momentum thicknesses downstream from the splitter plate, then decrease far down-stream to asymptotic values of 0.6 to 0.8 as scaled

  13. Transmission of Thin Light Beams Through Turbulent Mixing Layers.

    NASA Astrophysics Data System (ADS)

    Wissler, John B.

    1992-01-01

    Light transmission through incompressible gaseous turbulent mixing layers is investigated with the objective of understanding the effects of large-scale coherent structures and mixing transition on the optical quality of the mixing layer. Experiments are done in a vertically flowing mixing layer which is enclosed inside a pressure tank and fed by two banks of high-pressure gas bottles. The study considers both the unequal density (high-speed He and low-speed N_2) and equal density (high-speed N_2 and low-speed He-Ar) cases; the mixing of dissimilar gases is the source of the optical aberrations. Large-scale Reynolds numbers range between 3500 and 80000 over pressures from 2 to 6 bar. Light transmission characteristics are first studied qualitatively using a network of thin sheets of short-exposure (~ 1musec) white light which are aberrated by the mixing layer and then image directly onto photographic film. Light transmission characteristics are then studied quantitatively using a lateral effect detector to dynamically track a thin He-Ne laser beam as it wanders under the influence of the passing coherent structures. The study finds that the spanwise coherent structures generate systematic deflections of the light beam in the streamwise direction; the greatest deflections occur near the trailing edges of the structures at a formation called the cusp, where the high-speed fluid and low-speed fluid are entrained into the vortex core. The streamwise coherent structures, which form later in the mixing layer's development than the spanwise structures, generate substantial beam deflections in the spanwise direction which are closely associated with the streamwise streaks in plan-view shadowgraphs. The rms fluctuations of the streamwise and spanwise deflection angles increase rapidly during mixing transition, peaking at 380 high-speed-side momentum thicknesses downstream from the splitter plate, then decrease far downstream to asymptotic values of 0.6 to 0.8 as scaled by

  14. Three-Dimensional Structure of Plane Mixing Layers.

    NASA Astrophysics Data System (ADS)

    Bell, James Horatio

    Recent studies have shown the existence of an organized and persistent streamwise vortex structure in plane mixing layers, which is believed to take the form of a row of alternating-sign streamwise vortices. So far, this streamwise vortex structure has been studied mostly through flow-visualization at relatively low Reynolds numbers. The main objective of the present work was to obtain quantitative measurements of the streamwise vorticity at Reynolds numbers more comparable to those commonly found in practical applications. In the first experiment, the artificially induced streamwise vortex was observed to decay as approximately 1/X^2 within the mixing layer. The effect of the vortex was to locally distort the mean strain distribution in the mixing layer, thus altering the production of the Reynolds stresses. Peak values of the normal stresses were increased by about 20% over the undisturbed case in the region of the streamwise vortex. In particular a strong, pronounced peak was generated in the secondary shear stress, (overline{u^' w^ '}).. In the second experiment, "naturally-occurring" streamwise vorticity was clearly observed in a two-stream mixing layer. Concentrated streamwise vortices appeared just downstream of the first roll-up of the spanwise vorticity, with an initial circulation which was roughly half that of the spanwise vortex circulation. The streamwise vortices first appeared in "clusters", the positions of which seemed to be related to small disturbances in one of the upstream boundary layers. The clusters quickly reorganized into a single row of alternating-sign vortices under the influence of vortex dynamics and changes in the normal stress anisotropy. The streamwise vortex spacing increased in a stepwise fashion, at least partially through the amalgamation of like-sign vortices. The wavelength of the streamwise vortices increased approximately as the mixing layer vorticity thickness, while their strength decayed as roughly 1/X^ {1.5}. In the

  15. Isotopic evidence for nitrification in the Antarctic winter mixed layer

    NASA Astrophysics Data System (ADS)

    Smart, Sandi M.; Fawcett, Sarah E.; Thomalla, Sandy J.; Weigand, Mira A.; Reason, Chris J. C.; Sigman, Daniel M.

    2015-04-01

    We report wintertime nitrogen and oxygen isotope ratios (δ15N and δ18O) of seawater nitrate in the Southern Ocean south of Africa. Depth profile and underway surface samples collected in July 2012 extend from the subtropics to just beyond the Antarctic winter sea ice edge. We focus here on the Antarctic region (south of 50.3°S), where application of the Rayleigh model to depth profile δ15N data yields estimates for the isotope effect (the degree of isotope discrimination) of nitrate assimilation (1.6-3.3‰) that are significantly lower than commonly observed in the summertime Antarctic (5-8‰). The δ18O data from the same depth profiles and lateral δ15N variations within the mixed layer, however, imply O and N isotope effects that are more similar to those suggested by summertime data. These findings point to active nitrification (i.e., regeneration of organic matter to nitrate) within the Antarctic winter mixed layer. Nitrite removal from samples reveals a low δ15N for nitrite in the winter mixed layer (-40‰ to -20‰), consistent with nitrification, but does not remove the observation of an anomalously low δ15N for nitrate. The winter data, and the nitrification they reveal, explain the previous observation of an anomalously low δ15N for nitrate in the temperature minimum layer (remnant winter mixed layer) of summertime depth profiles. At the same time, the wintertime data require a low δ15N for the combined organic N and ammonium in the autumn mixed layer that is available for wintertime nitrification, pointing to intense N recycling as a pervasive condition of the Antarctic in late summer.

  16. Hybrid lipids increase nanoscale fluctuation lifetimes in mixed membranes

    NASA Astrophysics Data System (ADS)

    Palmieri, Benoit; Safran, Samuel A.

    2013-09-01

    A recently proposed ternary mixture model is used to predict fluctuation domain lifetimes in the one phase region. The membrane is made of saturated, unsaturated, and hybrid lipids that have one saturated and one unsaturated hydrocarbon chain. The hybrid lipid is a natural linactant which can reduce the packing incompatibility between saturated and unsaturated lipids. The fluctuation lifetimes are predicted as a function of the hybrid lipid fraction and the fluctuation domain size. These lifetimes can be increased by up to three orders of magnitude compared to the case of no hybrids. With hybrid, small length scale fluctuations have sizable amplitudes even close to the critical temperature and, hence, benefit from enhanced critical slowing down. The increase in lifetime is particularly important for nanometer scale fluctuation domains where the hybrid orientation and the other lipids composition are highly coupled.

  17. Hybrid lipids increase nanoscale fluctuation lifetimes in mixed membranes.

    PubMed

    Palmieri, Benoit; Safran, Samuel A

    2013-09-01

    A recently proposed ternary mixture model is used to predict fluctuation domain lifetimes in the one phase region. The membrane is made of saturated, unsaturated, and hybrid lipids that have one saturated and one unsaturated hydrocarbon chain. The hybrid lipid is a natural linactant which can reduce the packing incompatibility between saturated and unsaturated lipids. The fluctuation lifetimes are predicted as a function of the hybrid lipid fraction and the fluctuation domain size. These lifetimes can be increased by up to three orders of magnitude compared to the case of no hybrids. With hybrid, small length scale fluctuations have sizable amplitudes even close to the critical temperature and, hence, benefit from enhanced critical slowing down. The increase in lifetime is particularly important for nanometer scale fluctuation domains where the hybrid orientation and the other lipids composition are highly coupled.

  18. Vortex simulation of forced/unforced mixing layers

    NASA Technical Reports Server (NTRS)

    Inoue, Osamu; Leonard, Anthony

    1987-01-01

    Two-dimensional, spatially growing, turbulent mixing layers are simulated numerically by a vortex method and the results are compared with those determined experimentally. The effects of artificial forcing on flow development are also studied. Many of the flow features which have been observed experimentally are reproduced, and good quantitative agreements between experiments and computations are obtained.

  19. Disintegration of fluids under supercritical conditions from mixing layer studies

    NASA Technical Reports Server (NTRS)

    Okong'o, N.; Bellan, J.

    2003-01-01

    Databases of transitional states obtained from Direct Numerical simulations (DNS) of temporal, supercritical mixing layers for two species systems, O2/H2 and C7H16/N2, are analyzed to elucidate species-specific turbulence aspects and features of fluid disintegration.

  20. Simultaneous measurements and flow visualization in a plane mixing layer

    NASA Astrophysics Data System (ADS)

    Sherikar, S. V.; Chevray, R.

    Wind tunnel experiments performed to determine the flow characteristics of a plane mixing layer are described. Two parallel streams of air moving at different velocities were separated by a splitter plate prior to their mixing in the test section. Gaseous NH3 and gaseous HCI were introduced near the splitter plate to produce an ammonium chloride aerosol which made flow visualization possible. Flow visualization records (movies) and velocity measurements, using laser-doppler-velocimeters tracking silicone oil particles in the flow, were made simultaneously and synchronized using a chopped beam of a He-Ne laser which left a signature on the move film and provided a signal for flow rate data acquisition. Analysis of these synchronized data verified the existence of large, essentially two-dimensional coherent structures in the plane mixing layer.

  1. Modeling the iron cycling in the mixed layer

    NASA Astrophysics Data System (ADS)

    Weber, L.; Voelker, C.; Schartau, M.; Wolf-Gladrow, D.

    2003-04-01

    We present a comprehensive model of the iron cycling within the mixed layer of the ocean, which predicts the time course of iron concentration and speciation. The speciation of iron within the mixed layer is heavily influenced by photochemistry, organic complexation, colloid formation and aggregation, as well as uptake and release by marine biota. The model is driven by mixed layer dynamics, dust deposition and insolation, as well as coupled to a simple ecosystem model (based on Schartau at al.2001: Deep-Sea Res.II.48,1769-1800) and applied to the site of the Bermuda Atlantic Time-series Study (BATS). Parameters in the model were chosen to reproduce the small number of available speciation measurements resolving a daily cycle. The model clearly reproduces the available Fe concentration at the BATS station but the annual balance of Fe fluxes at BATS is less constrained, due to uncertainties in the model parameters. Hence we discuss the model's sensitivity to parameter uncertainties and which observations might help to better constrain the relevant model parameters. Futher we discuss how the most important model parameters are constrained by the data. The mixed layer cycle in the model strongly influences seasonality of primary production as well as light dependency of photoreductive processes and therefore controlls iron speciation. Futhermore short events within a day (e.g. heavy rain, change of irradiance, intense dust deposition and temporary deepening of the mixed layer) may push processes like colloidal aggregation. For this reason we compare two versions of the model: The first one is forced by monthly averaged climatological variables, the second one by daily climatological variabilities.

  2. Mixed-layer carbon cycling at the Kuroshio Extension Observatory

    NASA Astrophysics Data System (ADS)

    Fassbender, Andrea J.; Sabine, Christopher L.; Cronin, Meghan F.; Sutton, Adrienne J.

    2017-02-01

    Seven years of data from the NOAA Kuroshio Extension Observatory (KEO) surface mooring, located in the North Pacific Ocean carbon sink region, were used to evaluate drivers of mixed-layer carbon cycling. A time-dependent mass balance approach relying on two carbon tracers was used to diagnostically evaluate how surface ocean processes influence mixed-layer carbon concentrations over the annual cycle. Results indicate that the annual physical carbon input is predominantly balanced by biological carbon uptake during the intense spring bloom. Net annual gas exchange that adds carbon to the mixed layer and the opposing influence of net precipitation that dilutes carbon concentrations make up smaller contributions to the annual mixed-layer carbon budget. Decomposing the biological term into annual net community production (aNCP) and calcium carbonate production (aCaCO3) yields 7 ± 3 mol C m-2 yr-1 aNCP and 0.5 ± 0.3 mol C m-2 yr-1 aCaCO3, giving an annually integrated particulate inorganic carbon to particulate organic carbon production ratio of 0.07 ± 0.05, as a lower limit. Although we find that vertical physical processes dominate carbon input to the mixed layer at KEO, it remains unclear how horizontal features, such as eddies, influence carbon production and export by altering nutrient supply as well as the depth of winter ventilation. Further research evaluating linkages between Kuroshio Extension jet instabilities, eddy activity, and nutrient supply mechanisms is needed to adequately characterize the drivers and sensitivities of carbon cycling near KEO.

  3. Initial development of a hypersonic free mixing layer

    NASA Technical Reports Server (NTRS)

    Harvey, W. D.; Bolton, R. L.

    1972-01-01

    A preliminary experimental investigation to establish some of the characteristics and further the understanding of the initial development of a turbulent free mixing layer for hypersonic speeds has been conducted. Mean profile data at about 6 inches downstream of the exit of a hypersonic nozzle have been obtained in nitrogen for a nominal Mach number of 19.5, total temperature of about 1670 K and Reynolds number range from about 50,000 to 110,000 per foot and have been compared with profiles upstream of the nozzle exit. Static pressure varied across the shear layer for the present tests. The outer 80 percent of the high-velocity portion of the free shear layer can be calculated by a rotational method of characteristics. However, turbulent mixing is evidently important in the low-velocity region, and effects of eddy viscosity and eddy conductivity should be included in a theoretical analysis.

  4. Mixed mosaic membranes prepared by layer-by-layer assembly for ionic separations.

    PubMed

    Rajesh, Sahadevan; Yan, Yu; Chang, Hsueh-Chia; Gao, Haifeng; Phillip, William A

    2014-12-23

    Charge mosaic membranes, which possess distinct cationic and anionic domains that traverse the membrane thickness, are capable of selectively separating dissolved salts from similarly sized neutral solutes. Here, the generation of charge mosaic membranes using facile layer-by-layer assembly methodologies is reported. Polymeric nanotubes with pore walls lined by positively charged polyethylenimine moieties or negatively charged poly(styrenesulfonate) moieties were prepared via layer-by-layer assembly using track-etched membranes as sacrificial templates. Subsequently, both types of nanotubes were deposited on a porous support in order to produce mixed mosaic membranes. Scanning electron microscopy demonstrates that the facile deposition techniques implemented result in nanotubes that are vertically aligned without overlap between adjacent elements. Furthermore, the nanotubes span the thickness of the mixed mosaic membranes. The effects of this unique nanostructure are reflected in the transport characteristics of the mixed mosaic membranes. The hydraulic permeability of the mixed mosaic membranes in piezodialysis operations was 8 L m(-2) h(-1) bar(-1). Importantly, solute rejection experiments demonstrate that the mixed mosaic membranes are more permeable to ionic solutes than similarly sized neutral molecules. In particular, negative rejection of sodium chloride is observed (i.e., the concentration of NaCl in the solution that permeates through a mixed mosaic membrane is higher than in the initial feed solution). These properties illustrate the ability of mixed mosaic membranes to permeate dissolved ions selectively without violating electroneutrality and suggest their utility in ionic separations.

  5. Determination of mixing layer heights from ceilometer data

    NASA Astrophysics Data System (ADS)

    Schafer, Klaus; Emeis, Stefan M.; Rauch, Andreas; Munkel, Christoph; Vogt, Siegfried

    2004-11-01

    The Vaisala ceilometer LD40 is an eye-safe commercial lidar. It is designed originally to detect cloud base heights and vertical visibility for aviation safety purposes. The instrument was operated continuously at different measurement campaigns to detect mixing layer height from aerosol backscatter profiles. First results with the CT25K ceilometer were presented last year in the paper SPIE 5235-64 from the environmental measuring campaign in the frame of the BMBF-funded project VALIUM in Hanover, Germany, investigating the air pollution in a street canyon and the surrounding with various sensors. A software for routine retrieval of mixing layer height (MLH) from ceilometer data was developed. A comparison with mixing layer height retrievals from a SODAR and a wind-temperature-radar (WTR) operated in the urban region of Munich will be shown. The three instruments give information that partly agree and partly complement each other. The ceilometer gives information on the aerosol content of the air and the WTR provides a direct measurement of the vertical temperature distribution in the boundary layer. The WTR and the ceilometer add information on the moisture structure of the boundary layer that is not detected by the SODAR which gives information on the thermal structure. On the other hand this comparison validates known techniques by which the MLH is derived from SODAR data. In the absence of low clouds and precipitation ceilometers can estimate the mixing-layer-height fairly well. The potential of the ceilometer, being the smallest instrument among the used ones as LIDAR, SODAR and WTR, will be discussed to be used in future MLH studies.

  6. 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

  7. Mixed Layer Depth in the Aegean, Marmara, Black and Azov Seas: Part II: Relation to the Sonic Layer Depth

    DTIC Science & Technology

    2009-03-03

    r.com/ locate / jmarsysMixed layer depth in the Aegean, Marmara, Black and Azov Seas : Part II: Relation to the sonic layer depth Robert W. Helber a...index terms: The Aegean Sea The Black Sea The Azov Sea Keywords: Sound transmission Mixed layer depth Climatologyt analysis of the seasonal evolution of...the sonic layer depth (SLD) relative to the mixed layer depth (MLD) for the Aegean, Marmara, Black, and Azov Seas . SLD identifies the acoustic ducting

  8. 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.

  9. Dynamics of coherent structures in a plane mixing layer

    NASA Technical Reports Server (NTRS)

    Hussain, Fazle; Moser, R. D.; Colonius, T.; Moin, P.; Rogers, M. M.

    1988-01-01

    An incompressible, time developing 3-D mixing layer with idealized initial conditions was simulated numerically. Consistent with the suggestions from experimental measurements, the braid region between the dominant spanwise vortices or rolls develops longitudinal vortices or ribs, which are aligned upstream and downstream of a roll and produce spanwise distortion of the rolls. The process by which this distortion occurs is explained by studying a variety of quantities of dynamic importance (e.g., production of enstrophy, vortex stretching). Other quantities of interest (dissipation, helicity density) are also computed and discussed. The currently available simulation only allows the study of the early evolution (before pairing) of the mixing layer. New simulations in progress will relieve this restriction.

  10. Streamwise vortex meander in a plane mixing layer

    NASA Technical Reports Server (NTRS)

    Leboeuf, Richard L.; Mehta, Rabindra D.

    1993-01-01

    The present experimental study was conducted in order to determine the existence of streamwise vortex meander in a mixing layer, and if present, its significance on the measured properties. The dependence of the velocity cross-correlation on the fixed probe location was shown to be a good indicator of the stationarity of the streamwise vortex location. The cross-correlation measurements obtained here indicate that spanwise meander is negligible, although transverse apparent meander (normal to the plane of the mixing layer) was indicated. The transverse meander, exemplified by the elliptical shape of the mean streamwise vorticity contours, was expected, since the streamwise vorticity in the braid region is essentially inclined, with respect to the streamwise direction. These conclusions were supported by results of estimated spanwise profiles of the transverse velocity component. The balance of evidence suggests that the measured mean streamwise vorticity decay is representative of the decay of the vorticity rather than an artifact of meander.

  11. A Parameterization of Cholesterol for Mixed Lipid Bilayer Simulation within the Amber Lipid14 Force Field.

    PubMed

    Madej, Benjamin D; Gould, Ian R; Walker, Ross C

    2015-09-24

    The Amber Lipid14 force field is expanded to include cholesterol parameters for all-atom cholesterol and lipid bilayer molecular dynamics simulations. The General Amber and Lipid14 force fields are used as a basis for assigning atom types and basic parameters. A new RESP charge derivation for cholesterol is presented, and tail parameters are adapted from Lipid14 alkane tails. 1,2-Dimyristoyl-sn-glycero-3-phosphocholine (DMPC), 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) bilayers are simulated at a range of cholesterol contents. Experimental bilayer structural properties are compared with bilayer simulations and are found to be in good agreement. With this parameterization, another component of complex membranes is available for molecular dynamics with the Amber Lipid14 force field.

  12. Application of large eddy interaction model to a mixing layer

    NASA Technical Reports Server (NTRS)

    Murthy, S. N. B.

    1989-01-01

    The large eddy interaction model (LEIM) is a statistical model of turbulence based on the interaction of selected eddies with the mean flow and all of the eddies in a turbulent shear flow. It can be utilized as the starting point for obtaining physical structures in the flow. The possible application of the LEIM to a mixing layer formed between two parallel, incompressible flows with a small temperature difference is developed by invoking a detailed similarity between the spectra of velocity and temperature.

  13. PDF calculation of scalar mixing layer with simple chemical reactions

    NASA Astrophysics Data System (ADS)

    Kanzaki, Takao; Pope, Stephen B.

    1999-11-01

    A joint velocity-composition-turbulent frequency PDF(JPDF) model is used to simulate reactive mixing layer in a grid-generated turbulence with the influence of second-order irreversible chemical reactions. To investigate the effects of molecular mixing, a gas flow and a liquid flow are simulated. For a gas flow, the oxidation reaction (NO+ O3 arrow NO2 +O2 ) between nitricoxide (NO) and ozone (O3 ) is used. For a liquid flow, the saponification reaction(NaOH+HCOOCH3 arrow HCOONa+CH_3OH) between sodiumhydroxide(NaOH) and methylformate(HCOOCH_3) is used. The both cases are moderately fast reactions. Therefore, reactive scalar statistics are affected by turbulent mixing. The results of caliculation are compared with experimental data of Komori et al.(1994) and Bilger et al.(1991)

  14. Optical transfer function of the supersonic mixing layer.

    PubMed

    Gao, Qiong; Yi, Shihe; Jiang, Zongfu; He, Lin; Wang, Xiaohu

    2012-12-01

    The optical path difference (OPD) of the supersonic mixing layer with convective Mach number 0.5 is measured using the nanoparticle-based planar laser scattering technique, and its short-exposure optical transfer function (OTF) is computed with the proper orthogonal decomposition (POD). The OPD is analyzed from the viewpoint of structure function, and remarkable power law behavior is found. The power exponent is computed and analyzed. Taking the advantage of POD in capturing the energy of a signal, we present a model for the temporal evolution of OPD, which combines the deterministic and random factors together. With this model, the short-exposure OTF of the mixing layer is computed and analyzed. The amplitude modulation is evident at low frequencies, and it is almost negligible at high frequencies. The imaginary part of OTF for the mixing layer with developed vortex structures is of considerable amplitude, and the phase modulation becomes important for image degradation. We compare this phenomenon with the early result in aero-optics and explain it with the non-Gaussian statistics of OPD.

  15. Irreversible Entropy Production in Two-Phase Mixing Layers

    NASA Technical Reports Server (NTRS)

    Okongo, Nora

    2003-01-01

    This report presents a study of dissipation (irreversible production of entropy) in three-dimensional, temporal mixing layers laden with evaporating liquid drops. The purpose of the study is to examine the effects of evaporating drops on the development of turbulent features in flows. Direct numerical simulations were performed to analyze transitional states of three mixing layers: one without drops, and two that included drops at different initial mass loadings. Without drops, the dissipation is essentially due to viscous effects. It was found that in the presence of drops, the largest contribution to dissipation was made by heating and evaporation of the drops, and that at large length scales, this contribution is positive (signifying that the drops reduce turbulence), while at small scales, this contribution is negative (the drops increase turbulence). The second largest contribution to dissipation was found to be associated with the chemical potential, which leads to an increase in turbulence at large scales and a decrease in turbulence at small scales. The next smaller contribution was found to be that of viscosity. The fact that viscosity effects are only third in order of magnitude in the dissipation is in sharp contrast to the situation for the mixing layer without the drops. The next smaller contribution - that of the drag and momentum of the vapor from the drops - was found to be negative at lower mass loading but to become positive at higher mass loading.

  16. Modeling and diagnosing interface mix in layered ICF implosions

    NASA Astrophysics Data System (ADS)

    Weber, C. R.; Berzak Hopkins, L. F.; Clark, D. S.; Haan, S. W.; Ho, D. D.; Meezan, N. B.; Milovich, J. L.; Robey, H. F.; Smalyuk, V. A.; Thomas, C. A.

    2015-11-01

    Mixing at the fuel-ablator interface of an inertial confinement fusion (ICF) implosion can arise from an unfavorable in-flight Atwood number between the cryogenic DT fuel and the ablator. High-Z dopant is typically added to the ablator to control the Atwood number, but recent high-density carbon (HDC) capsules have been shot at the National Ignition Facility (NIF) without this added dopant. Highly resolved post-shot modeling of these implosions shows that there was significant mixing of ablator material into the dense DT fuel. This mix lowers the fuel density and results in less overall compression, helping to explain the measured ratio of down scattered-to-primary neutrons. Future experimental designs will seek to improve this issue through adding dopant and changing the x-ray spectra with a different hohlraum wall material. To test these changes, we are designing an experimental platform to look at the growth of this mixing layer. This technique uses side-on radiography to measure the spatial extent of an embedded high-Z tracer layer near the interface. Work performed under the auspices of the U.S. D.O.E. by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344.

  17. Direct simulation of high-speed mixing layers

    NASA Technical Reports Server (NTRS)

    Mukunda, H. S.; Sekar, B.; Carpenter, M. H.; Drummond, J. Philip; Kumar, Ajay

    1992-01-01

    A computational study of a nonreacting high-speed mixing layer is performed. A higher order algorithm with sufficient grid points is used to resolve all relevant scales. In all cases, a temporal free-stream disturbance is introduced. The resulting flow is time-sampled to generate a statistical cross section of the flow properties. The studies are conducted at two convective Mach numbers, three free-stream turbulence intensities, three Reynolds numbers, and two types of initial profiles-hyperbolic tangent (tanh) and boundary layer. The boundary-layer profile leads to more realistic predictions of the transition processes. The predicted transition Reynolds number of 0.18 x 10(exp 6) compares well with experimental data. Normalized vortex spacings for the boundary-layer case are about 3.5 and compare favorably with the 1.5 to 2.5 found in experimental measurements. The tanh profile produces spacings of about 10. The growth rate of the layer is shown to be moderately affected by the initial disturbance field, but comparison with experimental data shows moderate agreement. For the boundary-layer case, it is shown that noise at the Strouhal number of 0.007 is selectively amplified and shows little Reynolds number dependence.

  18. DNS and LES of a Shear-Free Mixing Layer

    NASA Technical Reports Server (NTRS)

    Knaepen, B.; Debliquy, O.; Carati, D.

    2003-01-01

    The purpose of this work is twofold. First, given the computational resources available today, it is possible to reach, using DNS, higher Reynolds numbers than in Briggs et al.. In the present study, the microscale Reynolds numbers reached in the low- and high-energy homogeneous regions are, respectively, 32 and 69. The results reported earlier can thus be complemented and their robustness in the presence of increased turbulence studied. The second aim of this work is to perform a detailed and documented LES of the shear-free mixing layer. In that respect, the creation of a DNS database at higher Reynolds number is necessary in order to make meaningful LES assessments. From the point of view of LES, the shear-free mixing-layer is interesting since it allows one to test how traditional LES models perform in the presence of an inhomogeneity without having to deal with difficult numerical issues. Indeed, as argued in Briggs et al., it is possible to use a spectral code to study the shear-free mixing layer and one can thus focus on the accuracy of the modelling while avoiding contamination of the results by commutation errors etc. This paper is organized as follows. First we detail the initialization procedure used in the simulation. Since the flow is not statistically stationary, this initialization procedure has a fairly strong influence on the evolution. Although we will focus here on the shear-free mixing layer, the method proposed in the present work can easily be used for other flows with one inhomogeneous direction. The next section of the article is devoted to the description of the DNS. All the relevant parameters are listed and comparison with the Veeravalli & Warhaft experiment is performed. The section on the LES of the shear-free mixing layer follows. A detailed comparison between the filtered DNS data and the LES predictions is presented. It is shown that simple eddy viscosity models perform very well for the present test case, most probably because the

  19. Compressibility effects in a turbulent annular mixing layer

    NASA Astrophysics Data System (ADS)

    Freund, Jonathan Ben

    1998-12-01

    Mixing between supersonic streams is critical to many technological applications, especially scramjets. This work uses direct numerical simulations of time evolving annular mixing layers, which correspond to the early development of round jets, to study compressibility effects on turbulence dynamics and mixing in free shear flow. Nine cases were considered with convective Mach numbers ranging from Mc = 0.1 to 1.8 and turbulent Mach numbers reaching as high as Mt = 0.8. Growth rates of the simulated mixing layers are suppressed with increasing Mach number as observed experimentally. The Reynolds stresses, with exception of the axial normal stress, /overline[ux/sp/prime x/sp'], are also suppressed. Flow visualizations show a distinct change in turbulence structure with increasing Mach number. At low Mach numbers, the flow is dominated by large azimuthally correlated rollers whereas at high Mach numbers the flow is dominated by small streamwise oriented structures. Dilatational terms are found to have negligible net effect upon the turbulence energetics despite the fact that shocklets are found at high Mach numbers. The growth rate suppression is analyzed with the Reynolds stress transport equations and a simple relation between mixing layer growth rate and the pressure-strain-rate correlation is found. This correlation is suppressed at higher Mach numbers due to suppressed pressure fluctuations. A change in structure caused by a 'communication' breakdown across supersonically deforming eddies is found to be responsible for the suppression of pressure fluctuations and this effect is parameterized with a gradient Mach number, Mg=[/ell/over a][/partial/bar u/over/partial y]. Mixing is studied with a passive scalar transport equation. Increasing the Mach number changes the mixture fraction probability density function from non-marching to marching and the mixing efficiency from 0.5 at Mc = 0.1 to 0.67 at Mc = 1.5. The scalar concentration and the axial velocity

  20. Aspects of turbulent-shear-layer dynamics and mixing

    NASA Astrophysics Data System (ADS)

    Slessor, Michael David

    Experiments have been conducted in the GALCIT Supersonic Shear Layer Facility to investigate some aspects of high-Reynolds-number, turbulent, shearlayer flows in both incompressible- and compressible-flow regimes. Experiments designed to address several issues were performed; effects of inflow boundary conditions, freestream conditions (supersonic/subsonic flow), and compressibility, on both large-scale dynamics and small-scale mixing, are described. Chemically-reacting and non-reacting flows were investigated, the former relying on the (H2 + NO/F2) chemical system, in the fast-kinetic regime, to infer the structure and amount of molecular-scale mixing through use of "flip" experiments. A variety of experimental techniques, including a color-schlieren visualization system developed as part of this work, were used to study the flows. Both inflow conditions and compressibility are found to have significant effects on the flow. In particular, inflow conditions are "remembered" for long distances downstream, a sensitivity similar to that observed in low-dimensionality, non-linear (chaotic) systems. The global flowfields (freestreams coupled by the shear layer) of transonic flows exhibit a sensitivity to imposed boundary conditions, i. e., local area ratios. A previously-proposed mode-selection rule for turbulent-structure convection speeds, based on the presence of a lab-frame subsonic freestream, was experimentally demonstrated to be incorrect. Compressibility, when decoupled from all other parameters, e.g., Reynolds number, velocity and density ratios, etc., reduces laxge-scale entrainment and turbulent growth, but slightly enhances smallscale mixing, with an associated change in the structure of the molecularly-mixed fluid. This reduction in shear-layer growth rate is examined and a new parameter that interprets compressibility as an energy-exchange mechanism is proposed. The parameter reconciles and collapses experimentally-observed growth rates.

  1. Lipids from the nacreous and prismatic layers of two Pteriomorpha mollusc shells.

    PubMed

    Farre, B; Dauphin, Y

    2009-02-01

    Mollusc shells are acellular biominerals, in which macromolecular structures are intimately associated with mineral phases. Most studies are devoted to proteins, despite sugars have been described. Lipids were extracted from the calcite prismatic and aragonite nacreous layer of two mollusc shells. Fourier Transform Infrared Spectrometry shows that lipids are present in both samples, but they are not similar. Thin layer chromatography confirms that lipids are different in the two studied layers, so that it may be suggested they are species-dependant. Although not yet deciphered, their role in biomineralization and fossilisation processes is probably important.

  2. Design and calibration of the mixing layer and wind tunnel

    NASA Technical Reports Server (NTRS)

    Bell, James H.; Mehta, Rabindra D.

    1989-01-01

    A detailed account of the design, assembly and calibration of a wind tunnel specifically designed for free-shear layer research is contained. The construction of this new facility was motivated by a strong interest in the study of plane mixing layers with varying initial and operating conditions. The Mixing Layer Wind tunnel is located in the Fluid Mechanics Laboratory at NASA Ames Research Center. The tunnel consists of two separate legs which are driven independently by centrifugal blowers connected to variable speed motors. The blower/motor combinations are sized such that one is smaller than the other, giving maximum flow speeds of about 20 and 40 m/s, respectively. The blower speeds can either be set manually or via the Microvax II computer. The two streams are allowed to merge in the test section at the sharp trailing edge of a slowly tapering splitter plate. The test section is 36 cm in the cross-stream direction, 91 cm in the spanwise direction and 366 cm in length. One test section side-wall is slotted for probe access and adjustable so that the streamwise pressure gradient may be controlled. The wind tunnel is also equipped with a computer controlled, three-dimensional traversing system which is used to investigate the flow fields with pressure and hot-wire instrumentation. The wind tunnel calibration results show that the mean flow in the test section is uniform to within plus or minus 0.25 pct and the flow angularity is less than 0.25 deg. The total streamwise free-stream turbulence intensity level is approximately 0.15 pct. Currently the wind tunnel is being used in experiments designed to study the three-dimensional structure of plane mixing layers and wakes.

  3. Arctic Cloud-driven Mixed Layers and Surface Coupling State

    NASA Astrophysics Data System (ADS)

    Shupe, M.; Persson, O. P.; Solomon, A.; de Boer, G.

    2013-12-01

    Arctic low-level clouds interact with the atmosphere and underlying surface via many inter-related processes. The balance of cloud radiative warming and cooling effects imparts a strong control on the net surface energy budget. Cloud-driven atmospheric circulations can impact surface turbulent heat fluxes and influence the vertical mixing of atmospheric state parameters and aerosols. Large-scale advection of heat and moisture provides the background context within which these local interactions unfold. Importantly, these radiative, dynamical, and advective processes also contribute to a complex web of self-sustaining cloud processes that can promote cloud maintenance over long periods of time. We examine many of these processes, with a specific focus on the dynamical linkages between Arctic clouds and the surface that influence low-level atmospheric structure and mixing. Comprehensive, ground-based observations from meteorological towers, remote-sensors, and radiosondes are used to simultaneously characterize surface fluxes, atmospheric structure, cloud properties, in-cloud motions, and the depth of the cloud-driven mixed layer in multiple Arctic environments. Relationships among these parameters are explored to elucidate the properties of the system that determine the degree of vertical atmospheric mixing and the coupling state between cloud and surface. The influence of temperature and moisture inversions on this system is also explored. Transitions in the coupling state are utilized to illustrate the relative roles of different processes. Cases from a coastal Arctic site at Barrow, Alaska and a station embedded in the Arctic sea-ice pack are used to contrast conditional influences related to season and surface type. It is found that over sea-ice, where surface turbulent fluxes are weak, the coupling of cloud-level processes to the surface layer is largely due to proximity of the cloud-driven mixed layer to the surface, which appears to be primarily influenced by

  4. Direct numerical simulation of reacting scalar mixing layers

    NASA Astrophysics Data System (ADS)

    de Bruyn Kops, S. M.; Riley, J. J.; Kosály, G.

    2001-05-01

    Understanding the passive reaction of two chemical species in shear-free turbulence with order unity Schmidt number is important in atmospheric and turbulent combustion research. The canonical configuration considered here is the reacting scalar mixing layer; in this problem two initially separated species mix and react downstream of a turbulence generating grid in a wind tunnel. A conserved scalar in this flow is, with some restrictions, analogous to temperature in a thermal mixing layer, and considerable laboratory data are available on the latter. In this paper, results are reported from high resolution, direct numerical simulations in which the evolution of the conserved scalar field accurately matches that of the temperature field in existing laboratory experiments. Superimposed on the flow are passive, single-step reactions with a wide range of activation energies and stoichiometric ratios (r). The resulting data include species concentrations as a function of three spatial dimensions plus time, and statistical moments and spectra of all species. Several aspects of the flow are investigated here with the conclusions that (1) reactions in which r≠1 are more accurately modeled by frozen and equilibrium chemistry limits than are reactions in which r=1, (2) an existing definition of a reduced Damköhler number that includes temperature and stoichiometry effects is a useful measure of reaction rate, and (3) existing theoretical models for predicting the coherence and phase of fuel-oxidizer cross-spectra and the spectrum of the equilibrium fuel mass fraction when r=1 yield accurate predictions.

  5. Transient evolution and high stratification scaling in horizontal mixing layers

    NASA Astrophysics Data System (ADS)

    Arratia, C.; Ortiz, S.; Chomaz, J. M.

    Mixing layers (sheared flows in homogeneous or stratified fluid) are present in many geophysical contexts and may lead to turbulence and mixing. In several cases, mixing layers are known to exhibit the Kelvin-Helmholtz instability leading to the roll-up of spanwise vortices, the Kelvin-Helmholtz (KH) billows. This is an essentially two-dimensional (2D) process. In fact, in the homogeneous cases the Squire's theorem implies that the most unstable mode is 2D. However, Squire's theorem applies only for the exponentially growing perturbations that control the large time dynamics and is not valid for the transient dynamics at short time. Indeed, Iams et al.[1] have shown that, in the non-stratified case, the most amplified optimal perturbations for short times are three-dimensional (3D) and result from a cooperation between the lift-up and Orr mechanisms[2]. This provides a finite time mechanism for spanwise scale selection, scale that may persist at later times if nonlinearities are strong enough.

  6. Mixing layer height and air pollution levels in urban area

    NASA Astrophysics Data System (ADS)

    Schäfer, Klaus; Wagner, Patrick; Emeis, Stefan; Jahn, Carsten; Muenkel, Christoph; Suppan, Peter

    2012-10-01

    Ceilometers are applied by KIT/IMK-IFU to detect layering of the lower atmosphere continuously. This is necessary because not only wind speed and direction but also atmospheric layering and especially the mixing layer height (MLH) influence exchange processes of ground level emissions. It will be discussed how the ceilometer monitoring information is used to interpret the air pollution near the ground. The information about atmospheric layering is continuously monitored by uninterrupted remote sensing measurements with the Vaisala ceilometer CL51 which is an eye-safe commercial mini-lidar system. Special software for this ceilometer provides routine retrievals of lower atmosphere layering from vertical profiles of laser backscatter data. An intensive measurement period during the winter 2011/2012 is studied. The meteorological influences upon air pollutant concentrations are investgated and the correlations of air pollutant concentrations with ceilometer MLH are determined. Benzene was detected by department of Applied Climatology and Landscape Ecology, University of Duisburg-Essen (UDE) with a gas chromatograph during the measurement period. The meteorological data are collected by UDE and the monitoring station Essen of the German national meteorological service DWD. The concentrations of the air pollutants NO, NO2 and PM10 are provided by the national air pollution network LANUV.

  7. A comparison of hydrographically and optically derived mixed layer depths

    USGS Publications Warehouse

    Zawada, D.G.; Zaneveld, J.R.V.; Boss, E.; Gardner, W.D.; Richardson, M.J.; Mishonov, A.V.

    2005-01-01

    Efforts to understand and model the dynamics of the upper ocean would be significantly advanced given the ability to rapidly determine mixed layer depths (MLDs) over large regions. Remote sensing technologies are an ideal choice for achieving this goal. This study addresses the feasibility of estimating MLDs from optical properties. These properties are strongly influenced by suspended particle concentrations, which generally reach a maximum at pycnoclines. The premise therefore is to use a gradient in beam attenuation at 660 nm (c660) as a proxy for the depth of a particle-scattering layer. Using a global data set collected during World Ocean Circulation Experiment cruises from 1988-1997, six algorithms were employed to compute MLDs from either density or temperature profiles. Given the absence of published optically based MLD algorithms, two new methods were developed that use c660 profiles to estimate the MLD. Intercomparison of the six hydrographically based algorithms revealed some significant disparities among the resulting MLD values. Comparisons between the hydrographical and optical approaches indicated a first-order agreement between the MLDs based on the depths of gradient maxima for density and c660. When comparing various hydrographically based algorithms, other investigators reported that inherent fluctuations of the mixed layer depth limit the accuracy of its determination to 20 m. Using this benchmark, we found a ???70% agreement between the best hydrographical-optical algorithm pairings. Copyright 2005 by the American Geophysical Union.

  8. Linear models for sound from supersonic reacting mixing layers

    NASA Astrophysics Data System (ADS)

    Chary, P. Shivakanth; Samanta, Arnab

    2016-12-01

    We perform a linearized reduced-order modeling of the aeroacoustic sound sources in supersonic reacting mixing layers to explore their sensitivities to some of the flow parameters in radiating sound. Specifically, we investigate the role of outer modes as the effective flow compressibility is raised, when some of these are expected to dominate over the traditional Kelvin-Helmholtz (K-H) -type central mode. Although the outer modes are known to be of lesser importance in the near-field mixing, how these radiate to the far-field is uncertain, on which we focus. On keeping the flow compressibility fixed, the outer modes are realized via biasing the respective mean densities of the fast (oxidizer) or slow (fuel) side. Here the mean flows are laminar solutions of two-dimensional compressible boundary layers with an imposed composite (turbulent) spreading rate, which we show to significantly alter the growth of instability waves by saturating them earlier, similar to in nonlinear calculations, achieved here via solving the linear parabolized stability equations. As the flow parameters are varied, instability of the slow modes is shown to be more sensitive to heat release, potentially exceeding equivalent central modes, as these modes yield relatively compact sound sources with lesser spreading of the mixing layer, when compared to the corresponding fast modes. In contrast, the radiated sound seems to be relatively unaffected when the mixture equivalence ratio is varied, except for a lean mixture which is shown to yield a pronounced effect on the slow mode radiation by reducing its modal growth.

  9. Water Vapor Turbulence Profiles in Stationary Continental Convective Mixed Layers

    SciTech Connect

    Turner, D. D.; Wulfmeyer, Volker; Berg, Larry K.; Schween, Jan

    2014-10-08

    The U.S. Department of Energy Atmospheric Radiation Measurement (ARM) program’s Raman lidar at the ARM Southern Great Plains (SGP) site in north-central Oklahoma has collected water vapor mixing ratio (q) profile data more than 90% of the time since October 2004. Three hundred (300) cases were identified where the convective boundary layer was quasi-stationary and well-mixed for a 2-hour period, and q mean, variance, third order moment, and skewness profiles were derived from the 10-s, 75-m resolution data. These cases span the entire calendar year, and demonstrate that the q variance profiles at the mixed layer (ML) top changes seasonally, but is more related to the gradient of q across the interfacial layer. The q variance at the top of the ML shows only weak correlations (r < 0.3) with sensible heat flux, Deardorff convective velocity scale, and turbulence kinetic energy measured at the surface. The median q skewness profile is most negative at 0.85 zi, zero at approximately zi, and positive above zi, where zi is the depth of the convective ML. The spread in the q skewness profiles is smallest between 0.95 zi and zi. The q skewness at altitudes between 0.6 zi and 1.2 zi is correlated with the magnitude of the q variance at zi, with increasingly negative values of skewness observed lower down in the ML as the variance at zi increases, suggesting that in cases with larger variance at zi there is deeper penetration of the warm, dry free tropospheric air into the ML.

  10. Study of atmospheric aerosols and mixing layer by LIDAR.

    PubMed

    Angelini, Federico; Barnaba, Francesca; Landi, Tony Christian; Caporaso, Luca; Gobbi, Gian Paolo

    2009-12-01

    The LIDAR (laser radar) is an active remote sensing technique, which allows for the altitude-resolved observation of several atmospheric constituents. A typical application is the measurement of the vertically resolved aerosol optical properties. By using aerosol particles as a marker, continuous determination of the mixing layer height (MLH) can also be obtained by LIDAR. Some examples of aerosol extinction coefficient profiles and MLH extracted from a 1-year LIDAR data set collected in Milan (Italy) are discussed and validated against in situ data (from a balloon-borne optical particle counter). Finally a comparison of the observation-based MLH with relevant numerical simulations (mesoscale model MM5) is provided.

  11. Large-eddy simulation of a turbulent mixing layer

    NASA Technical Reports Server (NTRS)

    Mansour, N. N.; Ferziger, J. H.; Reynolds, W. C.

    1978-01-01

    The three dimensional, time dependent (incompressible) vorticity equations were used to simulate numerically the decay of isotropic box turbulence and time developing mixing layers. The vorticity equations were spatially filtered to define the large scale turbulence field, and the subgrid scale turbulence was modeled. A general method was developed to show numerical conservation of momentum, vorticity, and energy. The terms that arise from filtering the equations were treated (for both periodic boundary conditions and no stress boundary conditions) in a fast and accurate way by using fast Fourier transforms. Use of vorticity as the principal variable is shown to produce results equivalent to those obtained by use of the primitive variable equations.

  12. Weakly nonlinear models for turbulent mixing in a plane mixing layer

    NASA Technical Reports Server (NTRS)

    Liou, William W.; Morris, Philip J.

    1992-01-01

    New closure models for turbulent free shear flows are presented in this paper. They are based on a weakly nonlinear theory with a description of the dominant large-scale structures as instability waves. Two models are presented that describe the evolution of the free shear flows in terms of the time-averaged mean flow and the dominant large-scale turbulent structure. The local characteristics of the large-scale motions are described using linear theory. Their amplitude is determined from an energy integral analysis. The models have been applied to the study of an incompressible mixing layer. For both models, predictions of the mean flow developed are made. In the second model, predictions of the time-dependent motion of the large-scale structures in the mixing layer are made. The predictions show good agreement with experimental observations.

  13. Normal and lateral forces between lipid covered solids in solution: correlation with layer packing and structure.

    PubMed Central

    Grant, L M; Tiberg, F

    2002-01-01

    We report on the normal and lateral forces between controlled-density mono- and bilayers of phospholipid co-adsorbed onto hydrophobic and hydrophilic solid supports, respectively. Interactions between 1,2-dioleoyl-sn-glycero-3-phosphocholine layers were measured using an atomic force microscope. Notable features of the normal force curves (barrier heights and widths) were found to correlate with the thickness and density of the supported lipid layers. The friction and normal force curves were also found interrelated. Thus, very low friction values were measured as long as the supported layer(s) resisted the normal pressure of the tip. However, as the applied load exceeded the critical value needed for puncturing the layers, the friction jumped to values close to those recorded between bare surfaces. The lipid layers were self-healing between measurements, but a significant hysteresis was observed in the force curves measured on approach and retraction, respectively. The study shows the potential of using atomic force microscopy for lipid layer characterization both with respect to structure and interactions. It further shows the strong lubricating effect of adsorbed lipid layers and how this varies with surface density of lipids. The findings may have important implications for the issue of joint lubrication. PMID:11867453

  14. STUDIES OF MIXED LIPOSOMES WITH NOVEL SORBYL FUNCTIONALIZED HEAD GROUP LIPIDS

    PubMed Central

    Ratnayaka, Saliya N.; Elandaloussi, El Hadj; Korth, Bryan D.; Bates, Robert B.; Pyun, Jeffrey; Hall, Henry. K.; Saavedra, S. Scott

    2012-01-01

    Three novel polymerizable amphiphiles with a sorbyl-substituted head group were synthesized and systematically characterized. These amphiphiles are neutral in charge. None of these molecules forms vesicles by itself, presumably due to lack of amphiphilicity and/or extensive head group interaction. Therefore, mixed vesicles were formed with other fluid lipids such as DPenPC, eggPC, or DOPC. We investigated the properties of these mixtures in both vesicles and Langmuir films. The Langmuir isotherms show formation of monolayers by all three molecules. However, the isotherms for mixed monolayers suggest that two components are largely immiscible to the mixing lipid. Under polymerization conditions, mixed vesicles of these amphiphiles form oligomers, suggesting that in spite of a larger head group, they form mesophases. PMID:23127336

  15. Studies of mixed liposomes with novel sorbyl functionalized head group lipids.

    PubMed

    Ratnayaka, Saliya N; Elandaloussi, El Hadj; Korth, Bryan D; Bates, Robert B; Pyun, Jeffrey; Hall, Henry K; Saavedra, S Scott

    2012-12-01

    Three novel polymerizable amphiphiles with a sorbyl-substituted head group were synthesized and systematically characterized. These amphiphiles are neutral in charge. None of these molecules forms vesicles by itself, presumably due to lack of amphiphilicity and/or extensive head group interaction. Therefore, mixed vesicles were formed with other fluid lipids such as DPenPC, eggPC, or DOPC. We investigated the properties of these mixtures in both vesicles and Langmuir films. The Langmuir isotherms show formation of monolayers by all three molecules. However, the isotherms for mixed monolayers suggest that two components are largely immiscible to the mixing lipid. Under polymerization conditions, mixed vesicles of these amphiphiles form oligomers, suggesting that in spite of a larger head group, they form mesophases.

  16. Lipid production by a mixed culture of oleaginous yeast and microalga from distillery and domestic mixed wastewater.

    PubMed

    Ling, Jiayin; Nip, Saiwa; Cheok, Wai Leong; de Toledo, Renata Alves; Shim, Hojae

    2014-12-01

    Lipid productivity by mixed culture of Rhodosporidium toruloides and Chlorella pyrenoidosa was studied using 1:1 mixed real wastewater from distillery and local municipal wastewater treatment plant with initial soluble chemical oxygen demand (SCOD) around 25,000 mg/L, initial cell density of 2×10(7) cells/mL (yeast) and 5×10(6) cells/mL (microalga), at 30 °C and 2.93 W/m2 (2000 lux, 12:12 h light and dark cycles). Lipid content and lipid yield achieved were 63.45±2.58% and 4.60±0.36 g/L with the associated removal efficiencies for SCOD, total nitrogen (TN), and total phosphorus (TP) at 95.34±0.07%, 51.18±2.17%, and 89.29±4.91%, respectively, after 5 days of cultivation without the pH adjustment. Inoculation of microalgae at 40 h of the initial yeast cultivation and harvesting part of inactive biomass at 72 h by sedimentation could improve both lipid production and wastewater treatment efficiency under non-sterile conditions.

  17. Gold nanoparticle encapsulation into a mixed lipid nanodisk: molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Sharma, Hari; Wang, Zilu; Dormidontova, Elena

    There is a growing interest in applications of nanoparticles in biomedicine. For practical applications of gold nanoparticles it is often desirable to encapsulate them into lipid nanocarriers. To this end it is important to understand gold-lipid interactions at the molecular level. We have performed coarse grained molecular dynamics simulations using a MARTINI force field of a lipid nanodisk composed of long and short tail lipids, DPPC and DHPC mixed in the ratio of 3:1 and studied its interaction with small gold nanoparticles (AuNP) functionalized with hydrophobic alkane tethers. We found that the inhomogeneous distribution of lipids in the nanodisk affects the outcome the AuNP-nanodisk interaction. The ordered arrangement of long chain lipids forming the interior region of the nanodisk are found to be less accessible for AuNP penetration compared to the rim of the nanodisk, where more mobile short lipids are located. Once encapsulated into a nanodisk, AuNP's have tendency to aggregate, especially if temperature is not too low. The results of computer modeling will be compared to experiment and the implications of our findings for experimental design of lipid nanocarriers for AuNP delivery will be discussed.

  18. Phase behavior of stratum corneum lipids in mixed Langmuir-Blodgett monolayers.

    PubMed Central

    ten Grotenhuis, E; Demel, R A; Ponec, M; Boer, D R; van Miltenburg, J C; Bouwstra, J A

    1996-01-01

    The lipids found in the bilayers of the stratum corneum fulfill the vital barrier role of mammalian bodies. The main classes of lipids found in stratum corneum are ceramides, cholesterol, and free fatty acids. For an investigation of their phase behavior, mixed Langmuir-Blodgett monolayers of these lipids were prepared. Atomic force microscopy was used to investigate the structure of the monolayers as a function of the monolayer composition. Three different types of ceramide were used: ceramide extracted from pigskin, a commercially available ceramide with several fatty acid chain lengths, and two synthetic ceramides that have only one fatty acid chain length. In pigskin ceramide-cholesterol mixed monolayers phase separation was observed. This phase separation was also found for the commercially available type III Sigma ceramide-cholesterol mixed monolayers with molar ratios ranging from 1:0.1 to 1:1. These monolayers separated into two phases, one composed of the long fatty acid chain fraction of Sigma ceramide III and the other of the short fatty acid chain fraction of Sigma ceramide III mixed with cholesterol. Mixtures with a higher cholesterol content consisted of only one phase. These observations were confirmed by the results obtained with synthetic ceramides, which have only one fatty acid chain length. The synthetic ceramide with a palmitic acid (16:0) chain mixed with cholesterol, and the synthetic ceramide with a lignoceric acid (24:0) chain did not. Free fatty acids showed a preference to mix with one of these phases, depending on their fatty acid chain lengths. The results of this investigation suggest that the model system used in this study is in good agreement with those of other studies concerning the phase behavior of the stratum corneum lipids. By varying the composition of the monolayers one can study the role of each lipid class in detail. Images FIGURE 2 FIGURE 3 FIGURE 4 FIGURE 5 FIGURE 6 PMID:8874014

  19. Direct simulations of chemically reacting turbulent mixing layers

    NASA Technical Reports Server (NTRS)

    Riley, J. J.; Metcalfe, R. W.

    1984-01-01

    The report presents the results of direct numerical simulations of chemically reacting turbulent mixing layers. The work consists of two parts: (1) the development and testing of a spectral numerical computer code that treats the diffusion reaction equations; and (2) the simulation of a series of cases of chemical reactions occurring on mixing layers. The reaction considered is a binary, irreversible reaction with no heat release. The reacting species are nonpremixed. The results of the numerical tests indicate that the high accuracy of the spectral methods observed for rigid body rotation are also obtained when diffusion, reaction, and more complex flows are considered. In the simulations, the effects of vortex rollup and smaller scale turbulence on the overall reaction rates are investigated. The simulation results are found to be in approximate agreement with similarity theory. Comparisons of simulation results with certain modeling hypotheses indicate limitations in these hypotheses. The nondimensional product thickness computed from the simulations is compared with laboratory values and is found to be in reasonable agreement, especially since there are no adjustable constants in the method.

  20. Statistics of High Atwood Number Turbulent Mixing Layers

    NASA Astrophysics Data System (ADS)

    Baltzer, Jon; Livescu, Daniel

    2015-11-01

    The statistical properties of incompressible shear-driven planar mixing layers between two miscible streams of fluids with different densities are investigated by means of Direct Numerical Simulations. The simulations begin from a thin interface perturbed by a thin broadband random disturbance, and the mixing layers are allowed to develop to self-similar states. The temporal simulations are performed in unprecedented domain sizes, with grid sizes up to 6144 x 2048 x 1536, which allows turbulent structures to grow and merge naturally. This allows the flow to reach states far-removed from the initial disturbances, thereby enabling high-quality statistics to be obtained for higher moments, pdfs, and other quantities critical to developing closure models. A wide range of Atwood numbers are explored, ranging from nearly constant density to At=0.87. The consequences of increasing the density contrast are investigated for global quantities, such as growth rates, and asymmetries that form in statistical profiles. Additional simulations in smaller domains are performed to study the effects of domain size.

  1. Turbulence and mixing in the stable atmospheric boundary layer

    NASA Astrophysics Data System (ADS)

    Yagüe, C.; Morales, G.; Terradellas, E.; Cuxart, J.

    2003-04-01

    Transport and mixing in the Stable Atmospheric Boundary Layer is not well understood yet. However this is an important feature in atmospheric pollution as well as in other environmental studies. A Stable Atmospheric Boundary Layer Experiment in Spain (SABLES98) took place from the 10th to the 28th of September 1998. Two masts (100 m and 10 m) were instrumented with five sonic anemometers, 14 thermocouples, 8 cup anemometers, vanes,radiometers, etc. In addition, a sodar, a tethered balloon and a triangular array of cup anemometers were operating during the campaign. The experiment showed three different regimes, being specially interesting the one between 14th and 21st of September where stable and very stable conditions were present. In this work we present the behaviour of turbulent and stability parameters at several heights. The different evolutions of the Nocturnal Boundary Layer and the main parameters that controle its behaviour are discussed.The influence of internal gravity waves and their interaction with turbulence is also studied using wavelets.

  2. Lipid demixing and protein-protein interactions in the adsorption of charged proteins on mixed membranes.

    PubMed Central

    May, S; Harries, D; Ben-Shaul, A

    2000-01-01

    The adsorption free energy of charged proteins on mixed membranes, containing varying amounts of (oppositely) charged lipids, is calculated based on a mean-field free energy expression that accounts explicitly for the ability of the lipids to demix locally, and for lateral interactions between the adsorbed proteins. Minimization of this free energy functional yields the familiar nonlinear Poisson-Boltzmann equation and the boundary condition at the membrane surface that allows for lipid charge rearrangement. These two self-consistent equations are solved simultaneously. The proteins are modeled as uniformly charged spheres and the (bare) membrane as an ideal two-dimensional binary mixture of charged and neutral lipids. Substantial variations in the lipid charge density profiles are found when highly charged proteins adsorb on weakly charged membranes; the lipids, at a certain demixing entropy penalty, adjust their concentration in the vicinity of the adsorbed protein to achieve optimal charge matching. Lateral repulsive interactions between the adsorbed proteins affect the lipid modulation profile and, at high densities, result in substantial lowering of the binding energy. Adsorption isotherms demonstrating the importance of lipid mobility and protein-protein interactions are calculated using an adsorption equation with a coverage-dependent binding constant. Typically, at bulk-surface equilibrium (i.e., when the membrane surface is "saturated" by adsorbed proteins), the membrane charges are "overcompensated" by the protein charges, because only about half of the protein charges (those on the hemispheres facing the membrane) are involved in charge neutralization. Finally, it is argued that the formation of lipid-protein domains may be enhanced by electrostatic adsorption of proteins, but its origin (e.g., elastic deformations associated with lipid demixing) is not purely electrostatic. PMID:11023883

  3. Optimal Linear Fitting for Objective Determination of Ocean Mixed Layer Depth from Glider Profiles

    DTIC Science & Technology

    2010-09-06

    profile is around 1 m . All the profiles are deeper than 700 m and clearly show the existence of layered structure: mixed layer, thermocline, and deep...controlled profiles observed by the two Seagliders. With high vertical resolution (1 m ), we chose n 5 4. The value of Hmix was calculated for each...compared to the fluctuations in the mixed layer depth observed after this date. The mixed layer depth oscillates between 50 and 90 m before 25 November 2007

  4. A theoretical study of ignition in the laminar mixing layer

    SciTech Connect

    Law, C.K.; Law, H.K.

    1981-01-01

    The structure of the weakly-reactive states leading to ignition in the laminar mixing layer flow is studied both analytically and numerically. It is shown that the flow consists of a reactive region and a self-similar frozen region separated by a transitional, non-similar frozen region that the reactive region is intrinsically non-similar because of its excessively slow diffusion rate and that the ignition characteristics are primarily governed by the velocity of the hot stream and therefore minimally dependent on the velocity distribution. Fundamental functional groups are identified and an explicit prescription is presented, for large activation energy reactions, for the evaluation of the minimum streamwise distance to achieve ignition.

  5. Local structures around the substituted elements in mixed layered oxides

    PubMed Central

    Akama, Shota; Kobayashi, Wataru; Amaha, Kaoru; Niwa, Hideharu; Nitani, Hiroaki; Moritomo, Yutaka

    2017-01-01

    The chemical substitution of a transition metal (M) is an effective method to improve the functionality of a material, such as its electrochemical, magnetic, and dielectric properties. The substitution, however, causes local lattice distortion because the difference in the ionic radius (r) modifies the local interatomic distances. Here, we systematically investigated the local structures in the pure (x = 0.0) and mixed (x = 0.05 or 0.1) layered oxides, Na(M1−xM′x)O2 (M and M′ are the majority and minority transition metals, respectively), by means of extended X-ray absorption fine structure (EXAFS) analysis. We found that the local interatomic distance (dM-O) around the minority element approaches that around the majority element to reduces the local lattice distortion. We further found that the valence of the minority Mn changes so that its ionic radius approaches that of the majority M. PMID:28252008

  6. Local structures around the substituted elements in mixed layered oxides

    NASA Astrophysics Data System (ADS)

    Akama, Shota; Kobayashi, Wataru; Amaha, Kaoru; Niwa, Hideharu; Nitani, Hiroaki; Moritomo, Yutaka

    2017-03-01

    The chemical substitution of a transition metal (M) is an effective method to improve the functionality of a material, such as its electrochemical, magnetic, and dielectric properties. The substitution, however, causes local lattice distortion because the difference in the ionic radius (r) modifies the local interatomic distances. Here, we systematically investigated the local structures in the pure (x = 0.0) and mixed (x = 0.05 or 0.1) layered oxides, Na(M1‑xM‧x)O2 (M and M‧ are the majority and minority transition metals, respectively), by means of extended X-ray absorption fine structure (EXAFS) analysis. We found that the local interatomic distance (dM-O) around the minority element approaches that around the majority element to reduces the local lattice distortion. We further found that the valence of the minority Mn changes so that its ionic radius approaches that of the majority M.

  7. Vortex simulation of three-dimensional mixing layers

    NASA Technical Reports Server (NTRS)

    Inoue, Osamu

    1987-01-01

    Spanwise structures of 'nominally' two-dimensional (2D), spatially growing, turbulent mixing layers are simulated numerically by a three-dimensional (3D) vortex method. Small-amplitude 3D disturbances are introduced into an otherwise 2D flow field. Results show that a large-scale spanwise variation of the flow field is produced because of amplification of initial disturbances. Pairs of counterrotating streamwise vortices are formed as a result of stretching of primary spanwise vortices. The streamwise vortices are formed at a fixed spanwise location which depends on initial disturbances. The calculated magnitude of streamwise vorticity is close to that of the spanwise vorticity. The results also suggest that the presence of background disturbances may be essential for the formation of streamwise vortices. The results are in good qualitative agreement with experiments.

  8. Direct numerical simulations of a reacting turbulent mixing layer by a pseudospectral-spectral element method

    NASA Technical Reports Server (NTRS)

    Mcmurtry, Patrick A.; Givi, Peyman

    1992-01-01

    An account is given of the implementation of the spectral-element technique for simulating a chemically reacting, spatially developing turbulent mixing layer. Attention is given to experimental and numerical studies that have investigated the development, evolution, and mixing characteristics of shear flows. A mathematical formulation is presented of the physical configuration of the spatially developing reacting mixing layer, in conjunction with a detailed representation of the spectral-element method's application to the numerical simulation of mixing layers. Results from 2D and 3D calculations of chemically reacting mixing layers are given.

  9. A preliminary investigation into the relationship between ocular surface temperature and lipid layer thickness.

    PubMed

    Giraldez, Maria Jesus; Naroo, Shehzad A; Resua, Carlos Garcia

    2009-08-01

    The aim of this study was to establish the relationship between OST, tear film stability as assessed by NIBUT and subjective evaluation of the lipid layer thickness in a young, asymptomatic, sample group (N=29). Non-invasive tear break-up time (NIBUT) and tear lipid layer structure were evaluated through a slit-lamp mounted Tearscope Plus. A self-calibrating infrared thermography camera was used to record two OST values (one immediately post-blink and one immediately pre the subsequent blink). The most common lipid layer pattern observed was the amorphous pattern (48.3%). Differences between post- and pre-blink OST values were observed (paired t-test; p<0.001). Significant differences of pre-blink OST values were observed between the closed marmoreal group with that from the amorphous and flow groups (Tukey post hoc test, p<0.05). There were no differences of NIBUT values between each lipid layer thickness (Kruskal-Wallis test; p=0.152). A no significant tendency for higher OST in eyes with increased NIBUT was observed. This study suggests that higher OST values could be associated with thicker tear lipid layer in normal subjects. The lack of significant results in relation with tear film stability may be due to only normal subjects were included.

  10. Lidar determination of mixing layer height with high resolution

    NASA Astrophysics Data System (ADS)

    Martucci, Giovanni; Matthey, Renaud; Mitev, Valentin; Richner, Hans

    2005-10-01

    Ecological monitoring and analysis of the planetary boundary layer (PBL) dynamics require determination of the mixing layer height (MLH) on a continuous basis. In a number of cases it is necessary to determine the MLH with sufficiently high resolution - both altitude and temporal. The backscatter lidar provides a convenient tool for such determination, using the aerosol as tracer and determining its vertical profile and its time-evolution, with the capability for continuous measurements. Although methods already exist, based on the altitude derivative of the backscatter lidar signal (altitude Gradient method) and its time-variance (Variance method), the application of these methods with high resolution is limited by the background noise presence. We report here a further development of backscatter lidar gradient and variance methods for MLH determination, allowing higher resolutions. In it, the MLH determination from the gradient and the variance of the lidar signal is supported by a convenient filter technique. Time scale of increased temporal resolution allows the investigation of the fine atmospheric dynamic structures like convective motion. A number of examples in MLH retrieval are presented. The examples are based on backscatter lidar measurements performed in the PBL above Neuchatel, Switzerland (47.00°N, 6.95°S, 485m asl). The examples show the applicability and the usefulness of the reported technique in measurements of the daily cycle of the MLH dynamics.

  11. Turbulent Mixing Layer Control using Ns-DBD Plasma Actuators

    NASA Astrophysics Data System (ADS)

    Singh, Ashish; Little, Jesse

    2016-11-01

    A low speed turbulent mixing layer (Reθo =1282, U1 /U2 = 0 . 28 and U2 = 11 . 8 m / s) is subject to nanosecond pulse driven dielectric barrier discharge (ns-DBD) plasma actuation. The forcing frequency corresponds to a Strouhal number (St) of 0.032 which is the most amplified frequency based on stability theory. Flow response is studied as a function of the pulse energy, the energy input time scale (carrier frequency) and the duration of actuation (duty cycle). It is found that successful actuation requires a combination of forcing parameters. An evaluation of the forcing efficacy is achieved by examining different flow quantities such as momentum thickness, vorticity and velocity fluctuations. In accordance with past work, a dependence is found between the initial shear layer thickness and the energy coupled to the flow. More complex relationships are also revealed such as a limitation on the maximum pulse energy which yields control. Also, the pulse energy and the carrier frequency (inverse of period between successive pulses) are interdependent whereby an optimum exists between them and extreme values of either parameter is inconsonant with the control desired. These observations establish a rich and complex process behind ns-DBD plasma actuation. Air Force Office of Scientific Research (FA9550-12-1-0044).

  12. Computation of three-dimensional mixed convective boundary layer flow

    NASA Technical Reports Server (NTRS)

    Gadepalli, Prashandt; Rahman, Muhammad M.

    1995-01-01

    The paper presents the numerical solution of heat and mass transfer during cross-flow (orthogonal) mixed convection. In this class of flow, a buoyancy-driven transport in the vertical direction and a forced convective flow in the horizontal direction results in a three-dimensional boundary layer structure adjacent to the plate. The rates of heat and mass transfer are determined by a combined influence of the two transport processes. The equations for the conservation of mass, momentum, energy, and species concentration were solved along with appropriate boundary conditions to determine the distributions of velocity components, temperature, and concentration across the thickness of the boundary layer at different locations on the plate. Results were expressed in dimensionless form using Reynolds number, Richardson number for heat transfer, Richardson number for mass transfer, Prandtl number, and Schmidt number as parameters. It was found that the transport is dominated by buoyancy at smaller vertical locations and at larger distances away from the forced convection leading edge. Effects of forced convection appeared to be very strong at smaller horizontal distances from the leading edge. The cross stream forced convection enhanced the rate of heat and mass transfer by a very significant amount.

  13. Online Detection of Mixed Layer Depth for Autonomous Underwater Vehicles

    NASA Astrophysics Data System (ADS)

    Chu, S.; Estlin, T.; Castano, R.; Woodward, G.; Gierach, M. M.; Thompson, A. F.; Schaffer, S.

    2015-12-01

    The accurate determination of the mixed layer depth (MLD) plays a crucial role in studying ocean dynamics and climate change. Various methods to estimate MLD have been proposed [1, 2]. However there is no current consensus on the best model, which leads to large uncertainty in the estimation. The variability, coupled with the complexity of physical, chemical and biological processes involved and the uncertainty and instabilities of the upper ocean surface, makes estimating MLD a challenging task. MLD varies significantly, even across a small spatial area (< 10km), and this depth is fluctuating, even over a short period of time (< 24 hrs), depending on the season. This abstract describes our proposed online algorithm for detecting mixed layer depth that would operate onboard an autonomous underwater vehicle (AUV). Using an online method permits a more adaptive approach to estimating MLD. Our proposed algorithm is based on an ensemble approach, which includes data mining techniques for real-time peak and change detection, learned seasonal variability profile, combined with MLD estimation criteria in [1]. In this study, we analyze measurements using glider data collected from the OSMOSIS (Ocean Surface Mixing, Ocean Submesoscale Interaction Study) project, concatenated into a year-long time series [3]. The glider data consists of nine full-depth moorings, which were deployed in a 15 km by 15 km box at the Porcupine Abyssal Plain in the northeast Atlantic, centered at 16.2°W, 48.7°N. Our algorithm utilizes direct measurements of salinity, temperature, depth and time and the design is based on the spatial and temporal variability of MLD learned. We will present our initial work on tracking the MLD based on real-time simulations using the OSMOSIS glider data and discussed for the case of deploying on a single AUV. Using an online algorithm for estimating MLD in-situ enables the system to rapidly adapt to the variability in a real-world environment and also allows for

  14. Four Characteristics and a Model of an Effective Tear Film Lipid Layer (TFLL)

    PubMed Central

    King-Smith, P. Ewen; Bailey, Melissa D.; Braun, Richard J.

    2015-01-01

    It is proposed that a normal, effective tear film lipid layer (TFLL) should have the following four characteristics: 1) high evaporation resistance to prevent water loss and consequent hyperosmolarity; 2) respreadability, so it will return to its original state after the compression-expansion cycle of the blink; 3) fluidity sufficient to avoid blocking secretion from meibomian glands; 4) gel-like and incompressible structure that can resist forces that may tend to disrupt it. These characteristics tend to be incompatible; for example, lipids that form good evaporation barriers tend to be disrupted by compression-expansion cycles. It is noted that clues about the function and organization of the TFLL can be obtained by comparison with other biological lipid layers, such as lung surfactant and the lipid evaporation barrier of the skin. In an attempt to satisfy the conflicting characteristics, a “multilamellar sandwich model” of the TFLL is proposed, having features in common with the skin evaporation barrier. PMID:24112227

  15. Estimation of Atmospheric Mixing Layer Height from radiosonde data

    NASA Astrophysics Data System (ADS)

    Wang, X.; Wang, K.

    2013-12-01

    Mixing layer is the lowest layer of the troposphere where surface turbulence can reach during the daytime. Mixing layer height (MLH) is an important parameter for understanding the transport process, air pollution, weather and climate change. MLH can be determined from the radiosonde profiles of relative humidity (RH), specific humidity (q), potential temperature (θ) and atmospheric refractivity (N) by searching for the strongest gradients of these parameters within a specific height above the surface. However, substantially different MLHs have been found from different parameters. The occurrence of cloud impacts on MLHs derived in two ways: (1) clouds impact the measurements of θ and RH, resulting in spurious MLHs derived by θ and RH, (2) clouds may amplify or depress turbulence, that is MLH can be at cloud top or cloud base when it occurs. However, MLHs determined by existing methods can generally be at cloud top. To solve these problems, we propose a method to estimate MLH by integrating the information of θ, RH, q, N and discriminating different cloud impacts on MLH. We apply this method to high vertical resolution (~30 m) radiosonde data collected at the 79 stations over North America during the period of 1998 to 2008 released by the Stratospheric Processes and their Role in Climate Data Center. The results show good agreement with those from N as the information of temperature and humidity contained in N, however the impact of clouds including in the new method has increased the reliability of MLH. The new results show good agreement with independent MLH determined from Lidar observations. MLH over the North America is 1647×323 meter with a strong east-west gradient, higher MLH (generally greater than 1800 m) over the Midwest America and lower MLH (less than 1300 m) over Alaska and west coast of America. The scatter plot of climatological MLHnew with MLHθ, MLHRH, MLHq, MLHN and MLHint for the period of 1998 to 2008. Pattern of climatological MLH of our

  16. Laboratory simulations of the atmospheric mixed-layer in flow over complex topography

    EPA Science Inventory

    A laboratory study of the influence of complex terrain on the interface between a well-mixed boundary layer and an elevated stratified layer was conducted in the towing-tank facility of the U.S. Environmental Protection Agency. The height of the mixed layer in the daytime boundar...

  17. Analysis and quantification of plant membrane lipids by thin-layer chromatography and gas chromatography.

    PubMed

    Wewer, Vera; Dörmann, Peter; Hölzl, Georg

    2013-01-01

    Galactolipids represent the predominant membrane lipid class in plants. In general, galactolipids are restricted to plastids, but during phosphate deficiency, they also accumulate in extraplastidial membranes. Two groups of plants can be distinguished based on the presence of a specific fatty acid, hexadecatrienoic acid (16:3), in chloroplast lipids. Plants that contain galactolipids with 16:3 acids are designated "16:3-plants"; the other group of plants which lack 16:3 contain mostly 18:3 in their galactolipids ("18:3-plants"). The methods in this chapter describe the extraction of membrane lipids from whole leaves, or from subcellular fractions, and their analysis via thin-layer chromatography (TLC) with different staining methods. Furthermore, a protocol for membrane lipid quantification is presented starting with the separation via TLC, transmethylation of the isolated lipids to fatty acid methyl esters, and their quantitative analysis via gas chromatography (GC).

  18. Releasable layer-by-layer assembly of stabilized lipid nanocapsules on microneedles for enhanced transcutaneous vaccine delivery.

    PubMed

    DeMuth, Peter C; Moon, James J; Suh, Heikyung; Hammond, Paula T; Irvine, Darrell J

    2012-09-25

    Here we introduce a new approach for transcutaneous drug delivery, using microneedles coated with stabilized lipid nanocapsules, for delivery of a model vaccine formulation. Poly(lactide-co-glycolide) microneedle arrays were coated with multilayer films via layer-by-layer assembly of a biodegradable cationic poly(β-amino ester) (PBAE) and negatively charged interbilayer-cross-linked multilamellar lipid vesicles (ICMVs). To test the potential of these nanocapsule-coated microneedles for vaccine delivery, we loaded ICMVs with a protein antigen and the molecular adjuvant monophosphoryl lipid A. Following application of microneedle arrays to the skin of mice for 5 min, (PBAE/ICMV) films were rapidly transferred from microneedle surfaces into the cutaneous tissue and remained in the skin following removal of the microneedle arrays. Multilayer films implanted in the skin dispersed ICMV cargos in the treated tissue over the course of 24 h in vivo, allowing for uptake of the lipid nanocapsules by antigen presenting cells in the local tissue and triggering their activation in situ. Microneedle-mediated transcutaneous vaccination with ICMV-carrying multilayers promoted robust antigen-specific humoral immune responses with a balanced generation of multiple IgG isotypes, whereas bolus delivery of soluble or vesicle-loaded antigen via intradermal injection or transcutaneous vaccination with microneedles encapsulating soluble protein elicited weak, IgG(1)-biased humoral immune responses. These results highlight the potential of lipid nanocapsules delivered by microneedles as a promising platform for noninvasive vaccine delivery applications.

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  20. Ignition of hydrogen/air mixing layer in turbulent flows

    SciTech Connect

    Im, H.G.; Chen, J.H.; Law, C.K.

    1998-03-01

    Autoignition of a scalar hydrogen/air mixing layer in homogeneous turbulence is studied using direct numerical simulation. An initial counterflow of unmixed nitrogen-diluted hydrogen and heated air is perturbed by two-dimensional homogeneous turbulence. The temperature of the heated air stream is chosen to be 1,100 K which is substantially higher than the crossover temperature at which the rates of the chain branching and termination reactions become equal. Three different turbulence intensities are tested in order to assess the effect of the characteristic flow time on the ignition delay. For each condition, a simulation without heat release is also performed. The ignition delay determined with and without heat release is shown to be almost identical up to the point of ignition for all of the turbulence intensities tested, and the predicted ignition delays agree well within a consistent error band. It is also observed that the ignition kernel always occurs where hydrogen is focused, and the peak concentration of HO{sub 2} is aligned well with the scalar dissipation rate. The dependence of the ignition delay on turbulence intensity is found to be nonmonotonic. For weak to moderate turbulence the ignition is facilitated by turbulence via enhanced mixing, while for stronger turbulence, whose timescale is substantially smaller than the ignition delay, the ignition is retarded due to excessive scalar dissipation, and hence diffusive loss, at the ignition location. However, for the wide range of initial turbulence fields studied, the variation in ignition delay due to the corresponding variation in turbulence intensity appears to be quite small.

  1. Heat budget of the surface mixed layer south of Africa

    NASA Astrophysics Data System (ADS)

    Faure, Vincent; Arhan, Michel; Speich, Sabrina; Gladyshev, Sergey

    2011-10-01

    ARGO hydrographic profiles, two hydrographic transects and satellite measurements of air-sea exchange parameters were used to characterize the properties and seasonal heat budget variations of the Surface Mixed Layer (SML) south of Africa. The analysis distinguishes the Subtropical domain (STZ) and the Subantarctic Zone (SAZ), Polar Frontal Zone (PFZ) and Antarctic Zone (AZ) of the Antarctic Circumpolar Current. While no Subantarctic Mode Water forms in that region, occurrences of deep SML (up to ˜450 m) are observed in the SAZ in anticyclones detached from the Agulhas Current retroflection or Agulhas Return Current. These are present latitudinally throughout the SAZ, but preferentially at longitudes 10-20° E where, according to previous results, the Subtropical Front is interrupted. Likely owing to this exchange window and to transfers at the Subantarctic Front also enhanced by the anticyclones, the SAZ shows a wide range of properties largely encroaching upon those of the neighbouring domains. Heat budget computations in each zone reveal significant meridional changes of regime. While air-sea heat fluxes dictate the heat budget seasonal variability everywhere, heat is mostly brought through lateral geostrophic advection by the Agulhas Current in the STZ, through lateral diffusion in the SAZ and through air-sea fluxes in the PFZ and AZ. The cooling contributions are by Ekman advection everywhere, lateral diffusion in the STZ (also favoured by the ˜10° breach in the Subtropical Front) and geostrophic advection in the SAZ. The latter likely reflects an eastward draining of water warmed through mixing of the subtropical eddies.

  2. Mixing layers in stellar outflows-II. Interfaces between two moving fluids

    NASA Astrophysics Data System (ADS)

    Raga, A. C.; Cabrit, S.; Canto, J.

    1995-03-01

    We present a formalism for describing turbulent mixing layers between two moving inhomogeneous media. This represents an extension of the model of Canto & Raga, who considered the case of a mixing layer between a uniform stream and a motionless environment. We apply this formalism to two problems: (i) the mixing layer between a fast, uniform beam of gas in contact with a slower (also uniform) flow; and (ii) the mixing layer formed by the interaction of a stellar wind with an impinging supersonic stream. These problems have direct applicability in the field of stellar outflows, and provide an illustration of the capabilities of the formalism that we have developed.

  3. Dynamics of crowding-induced mixing in phase separated lipid bilayers

    DOE PAGES

    Zeno, Wade F.; Johnson, Kaitlin E.; Sasaki, Darryl Y.; ...

    2016-10-10

    We use fluorescence microscopy to examine the dynamics of the crowding-induced mixing transition of liquid ordered (Lo)–liquid disordered (Ld) phase separated lipid bilayers when the following particles of increasing size bind to either the Lo or Ld phase: Ubiquitin, green fluorescent protein (GFP), and nanolipoprotein particles (NLPs) of two diameters. These proteinaceous particles contained histidine-tags, which were phase targeted by binding to iminodiacetic acid (IDA) head groups, via a Cu2+ chelating mechanism, of lipids that specifically partition into either the Lo phase or Ld phase. The degree of steric pressure was controlled by varying the size of the bound particlemore » (10–240 kDa) and the amount of binding sites present (i.e., DPIDA concentrations of 9 and 12 mol%) in the supported lipid multibilayer platform used here. We develop a mass transfer-based diffusional model to analyze the observed Lo phase domain dissolution that, along with visual observations and activation energy calculations, provides insight into the sequence of events in crowding-induced mixing. Furthermore, our results suggest that the degree of steric pressure and target phase influence not only the efficacy of steric-pressure induced mixing, but the rate and controlling mechanism for which it occurs.« less

  4. Dynamics of crowding-induced mixing in phase separated lipid bilayers

    SciTech Connect

    Zeno, Wade F.; Johnson, Kaitlin E.; Sasaki, Darryl Y.; Risbud, Subhash H.; Longo, Marjorie L.

    2016-10-10

    We use fluorescence microscopy to examine the dynamics of the crowding-induced mixing transition of liquid ordered (Lo)–liquid disordered (Ld) phase separated lipid bilayers when the following particles of increasing size bind to either the Lo or Ld phase: Ubiquitin, green fluorescent protein (GFP), and nanolipoprotein particles (NLPs) of two diameters. These proteinaceous particles contained histidine-tags, which were phase targeted by binding to iminodiacetic acid (IDA) head groups, via a Cu2+ chelating mechanism, of lipids that specifically partition into either the Lo phase or Ld phase. The degree of steric pressure was controlled by varying the size of the bound particle (10–240 kDa) and the amount of binding sites present (i.e., DPIDA concentrations of 9 and 12 mol%) in the supported lipid multibilayer platform used here. We develop a mass transfer-based diffusional model to analyze the observed Lo phase domain dissolution that, along with visual observations and activation energy calculations, provides insight into the sequence of events in crowding-induced mixing. Furthermore, our results suggest that the degree of steric pressure and target phase influence not only the efficacy of steric-pressure induced mixing, but the rate and controlling mechanism for which it occurs.

  5. Biomimetic interfaces based on S-layer proteins, lipid membranes and functional biomolecules

    PubMed Central

    Schuster, Bernhard; Sleytr, Uwe B.

    2014-01-01

    Designing and utilization of biomimetic membrane systems generated by bottom-up processes is a rapidly growing scientific and engineering field. Elucidation of the supramolecular construction principle of archaeal cell envelopes composed of S-layer stabilized lipid membranes led to new strategies for generating highly stable functional lipid membranes at meso- and macroscopic scale. In this review, we provide a state-of-the-art survey of how S-layer proteins, lipids and polymers may be used as basic building blocks for the assembly of S-layer-supported lipid membranes. These biomimetic membrane systems are distinguished by a nanopatterned fluidity, enhanced stability and longevity and, thus, provide a dedicated reconstitution matrix for membrane-active peptides and transmembrane proteins. Exciting areas in the (lab-on-a-) biochip technology are combining composite S-layer membrane systems involving specific membrane functions with the silicon world. Thus, it might become possible to create artificial noses or tongues, where many receptor proteins have to be exposed and read out simultaneously. Moreover, S-layer-coated liposomes and emulsomes copying virus envelopes constitute promising nanoformulations for the production of novel targeting, delivery, encapsulation and imaging systems. PMID:24812051

  6. Biomimetic interfaces based on S-layer proteins, lipid membranes and functional biomolecules.

    PubMed

    Schuster, Bernhard; Sleytr, Uwe B

    2014-07-06

    Designing and utilization of biomimetic membrane systems generated by bottom-up processes is a rapidly growing scientific and engineering field. Elucidation of the supramolecular construction principle of archaeal cell envelopes composed of S-layer stabilized lipid membranes led to new strategies for generating highly stable functional lipid membranes at meso- and macroscopic scale. In this review, we provide a state-of-the-art survey of how S-layer proteins, lipids and polymers may be used as basic building blocks for the assembly of S-layer-supported lipid membranes. These biomimetic membrane systems are distinguished by a nanopatterned fluidity, enhanced stability and longevity and, thus, provide a dedicated reconstitution matrix for membrane-active peptides and transmembrane proteins. Exciting areas in the (lab-on-a-) biochip technology are combining composite S-layer membrane systems involving specific membrane functions with the silicon world. Thus, it might become possible to create artificial noses or tongues, where many receptor proteins have to be exposed and read out simultaneously. Moreover, S-layer-coated liposomes and emulsomes copying virus envelopes constitute promising nanoformulations for the production of novel targeting, delivery, encapsulation and imaging systems.

  7. Binding of DNA to zwitterionic lipid layers mediated by divalent cations.

    PubMed

    Mengistu, Demmelash H; Bohinc, Klemen; May, Sylvio

    2009-09-10

    Divalent cations, i.e., calcium, magnesium, and others, are able to enhance the ability of DNA to interact with membranes that are composed of zwitterionic lipids such as phosphatidylcholine. The resulting condensed complexes offer potential applications as nontoxic gene delivery vehicles. The present study suggests a generic theoretical model to describe the energetics and structural features of a zwitterionic lipid-DNA complex in the presence of divalent cations. Specifically, we consider the adsorption of a single molecule of double-stranded DNA onto a planar zwitterionic lipid layer. Our theoretical model is based on the continuum Poisson-Boltzmann formalisms, which we modified so as to account for the two opposite charges and orientational freedom of the zwitterionic lipid headgroups. We find a substantially more favorable adsorption free energy of the DNA if divalent cations are present. In addition, our model predicts the divalent cations to preferentially interact with the phosphate groups of the zwitterionic lipids, given these lipids are located in close vicinity to the DNA. This is accompanied by a small but notable reorientation of the zwitterionic headgroups toward the DNA. We demonstrate that the binding of DNA onto a zwitterionic lipid layer is not driven by the release of counterions. Instead, the binding leads to a partial redistribution of the divalent cations, from the phosphate groups of the DNA (prior to the binding) to the phosphate groups of the zwitterionic lipids (after the binding). Our results thus suggest a general physical mechanism underlying complex formation between DNA and zwitterionic lipids in terms of mean-field electrostatics, i.e., neither involving correlations nor specific interactions of the divalent cations.

  8. Actual fusion efficiency in the lipid mixing assay - Comparison between nanodiscs and liposomes

    PubMed Central

    François-Martin, Claire; Pincet, Frédéric

    2017-01-01

    Lipid exchange occurs between membranes during fusion or active lipid transfer. These processes are necessary in vivo for the homeostasis of the cell at the level of the membranes, the organelles and the cell itself. They are also used by the cell to interact with the surrounding medium. Several assays have been developed to characterize in vitro these processes on model systems. The most common one, relying on fluorescence dequenching, measures lipid mixing between small membranes such as liposomes or nanodiscs in bulk. Usually, relative comparisons of the rate of lipid exchange are made between measurements performed in parallel. Here, we establish a quantitative standardization of this assay to avoid any bias resulting from the temperatures, the chosen fluorescent lipid fractions and from the various detergents used to normalize the measurements. We used this standardization to quantitatively compare the efficiency of SNARE-induced fusion in liposome-liposome and liposome-nanodisc configurations having similar collision frequency. We found that the initial yield of fusion is comparable in both cases, 1 per 2–3 million collisions in spite of a much larger dequenching signal with nanodiscs. Also, the long-term actual fusion rate is slightly lower with nanodiscs than in the liposome-liposome assay. PMID:28266607

  9. Actual fusion efficiency in the lipid mixing assay - Comparison between nanodiscs and liposomes

    NASA Astrophysics Data System (ADS)

    François-Martin, Claire; Pincet, Frédéric

    2017-03-01

    Lipid exchange occurs between membranes during fusion or active lipid transfer. These processes are necessary in vivo for the homeostasis of the cell at the level of the membranes, the organelles and the cell itself. They are also used by the cell to interact with the surrounding medium. Several assays have been developed to characterize in vitro these processes on model systems. The most common one, relying on fluorescence dequenching, measures lipid mixing between small membranes such as liposomes or nanodiscs in bulk. Usually, relative comparisons of the rate of lipid exchange are made between measurements performed in parallel. Here, we establish a quantitative standardization of this assay to avoid any bias resulting from the temperatures, the chosen fluorescent lipid fractions and from the various detergents used to normalize the measurements. We used this standardization to quantitatively compare the efficiency of SNARE-induced fusion in liposome-liposome and liposome-nanodisc configurations having similar collision frequency. We found that the initial yield of fusion is comparable in both cases, 1 per 2–3 million collisions in spite of a much larger dequenching signal with nanodiscs. Also, the long-term actual fusion rate is slightly lower with nanodiscs than in the liposome-liposome assay.

  10. Optical path difference of the supersonic mixing layer.

    PubMed

    Gao, Qiong; Jiang, Zongfu; Yi, Shihe; Zhao, Yuxin

    2010-07-01

    The distorted wavefront due to the density fluctuation of the supersonic mixing layer is measured by the nano-based planar laser scattering technique, with the spatiotemporal resolutions as 10(-1) mm and 1 micros (time interval between two exposures), respectively. The optical path difference (OPD) is analyzed from the viewpoints of correlation and structure functions. Depending on the structure of the flow field, the type of the correlation function is Gaussian or exponential. The power index of the structure function is about 1.1, and the consistency over many cases is quite good. The far-field propagation of the Gaussian beam is simulated by Fourier transform, and the Strehl ratio is calculated with the rms of the OPD. The beam center and beam spread about the center in the far field are calculated, and are dominated by the statistics of the tilt of the distorted wavefront. The results indicate that aero-optical aberrations can severely limit the performance of airborne laser systems.

  11. On the viscosity stratification in temporal mixing layer

    NASA Astrophysics Data System (ADS)

    Danaila, Luminita; Taguelmimt, Noureddine; Hadjadj, Abdellah; Turbulence Team

    2015-11-01

    We assess the effects of viscosity variations in low-speed temporally-evolving turbulent mixing layer. The two streams are density-matched, but the slow fluid is Rv times more viscous than the rapid stream. Direct Numerical Simulations (DNS) are performed for several viscosity ratios, Rv varying between 1 and 9. The space-time evolution of Variable-Viscosity Flow (VVF) is compared with that of the Constant-Viscosity Flow (CVF). The velocity fluctuations occur earlier and are more enhanced for VVF. In particular, the kinetic energy peaks earlier and is up to three times larger for VVF than for CVF at the earliest stages of the flow. Over the first stages of the flow, the temporal growth rate of the fluctuations kinetic energy is exponential, in full agreement with linear stability theory. The transport equation for the fluctuations kinetic energy is favourably compared with simulations data. The enhanced kinetic energy for VVF is mainly due to an increased production at the interface between the two fluids, in tight correlation with enlarged values of mean velocity gradient at the inflection point of the mean velocity profile. The transport equations of the one-and two-point kinetic energy show that self-preservation cannot be complete in variable-viscosity flows. ANR is acknowledged for financial support.

  12. Chaos in a spatially-developing plane mixing layer

    NASA Technical Reports Server (NTRS)

    Broze, J. G.; Hussain, Fazle; Buell, J. C.

    1988-01-01

    A spatially-developing plane mixing layer was analyzed for chaotic behavior. A direct numerical simulation of the Navier-Stokes equations in a 2-D domain infinite in y and having inflow-outflow boundary conditions in x was used for data. Spectra, correlation dimension and the largest Lyapunov exponent were computed as functions of downstream distance x. When forced at a single (fundamental) frequency with maximum amplitude, the flow is periodic at the inflow but becomes aperiodic with increasing x. The aperiodic behavior is caused by the presence of a noisy subharmonic caused by the feedback between the necessarily nonphysical inflow and outflow boundary conditions. In order to overshadow this noise the flow was also studied with the same fundamental forcing and added random forcing of amplitude upsilon prime sub R/delta U = 0.01 at the inlet. Results were qualitatively the same in both cases: for small x, spectral peaks were sharp and dimension was nearly 1, but as x increased a narrowband spectral peak grew, spectra decayed exponentially at high frequencies and dimension increased to greater than 3. Based on these results, the flow appears to exhibit deterministic chaos. However, at no location was the largest Lyapunov exponent found to be significantly greater than zero.

  13. Biophysical investigations of the structure and function of the tear fluid lipid layers and the effect of ectoine. Part B: artificial lipid films.

    PubMed

    Dwivedi, Mridula; Brinkkötter, Marc; Harishchandra, Rakesh Kumar; Galla, Hans-Joachim

    2014-10-01

    The tear fluid lipid layer is present at the outermost part of the tear film which lines the ocular surface and functions to maintain the corneal surface moist by retarding evaporation. Instability in the structure of the tear fluid lipid layer can cause an increased rate of evaporation and thus dry eye syndrome. Ectoine has been previously shown to fluidize lipid monolayers and alter the phase behavior. In the current study we have investigated the effect of ectoine on the artificial tear fluid lipid layer composed of binary and ternary lipid mixtures of dipalmitoyl phosphatidylcholine (DPPC), cholesteryl esters and tri-acyl-glycerols. The focus of our study was mainly the structural and the biophysical aspects of the artificial tear fluid lipid layer using surface activity studies and topology analysis. The presence of ectoine consistently causes an expansion of the pressure-area isotherm indicating increased intermolecular spacing. The topology studies showed the formation of droplet-like structures due to the addition of ectoine only when tri-acyl-glycerol is present in the mixture of DPPC and chol-palmitate, similar to the natural meibomian lipids. Consequently, the hypothesis of an exclusion of tri/di-acyl-glycerol from the meibomian lipid film in the presence of ectoine in the subphase is confirmed. A model describing the effect of ectoine on meibomian lipid films is further presented which may have an application for the use of ectoines in eye drops as a treatment for the dry eye syndrome.

  14. In situ laser sensing of mixed layer turbulence

    NASA Astrophysics Data System (ADS)

    Dalgleish, Fraser; Hou, Weilin; Vuorenkoski, Anni; Nootz, Gero; Ouyang, Bing

    2013-06-01

    This paper will discuss and compare some recent oceanic test results from the Bahamas Optical Turbulence Exercise (BOTEX) cruise, where vertical profiling was conducted with both time-resolved laser backscatter measurements being acquired via a subsurface light detection and ranging (lidar) profiling instrument, and laser beam forward deflection measurements were acquired from a matrix of continuous wave (cw) laser beams (i.e. structured lighting) being imaged in the forward direction with a high speed camera over a one-way path, with both transmitter and camera firmly fixed on a rigid frame. From the latter, it was observed that when within a natural turbulent layer, the laser beams were being deflected from their still water location at the image plane, which was 8.8 meters distance from the laser dot matrix transmitter. As well as suggesting that the turbulent structures being encountered were predominately larger than the beam diameter, the magnitude of the deflection has been confirmed to correlate with the temperature dissipation rate. The profiling lidar measurements which were conducted in similar conditions, also used a narrow collimated laser beam in order to resolve small-scale spatial structure, but with the added attribute that sub-nanosecond short pulse temporal profile could potentially resolve small-scale vertical structure. In the clear waters of the Tongue of the Ocean in the Bahamas, it was hypothesized that the backscatter anomalies due to the effect of refractive index discontinuities (i.e. mixed layer turbulence) would be observable. The processed lidar data presented herein indicates that higher backscatter levels were observed in the regions of the water column which corresponded to higher turbulent mixing which occurs at the first and second themoclines. At the same test stations that the laser beam matrix and lidar measurements were conducted, turbulence measurements were made with two non-optical instruments, the Vertical Microstructure

  15. Mixed layer formation and restratification in presence of mesoscale and submesoscale turbulence

    NASA Astrophysics Data System (ADS)

    Couvelard, X.; Dumas, F.; Garnier, V.; Ponte, A. L.; Talandier, C.; Treguier, A. M.

    2015-12-01

    Recent realistic high resolution modeling studies show a net increase of submesoscale activity in fall and winter when the mixed layer depth is at its maximum. This submesoscale activity increase is associated with a reduced deepening of the mixed layer. Both phenomena can be related to the development of mixed layer instabilities, which convert available potential energy into submesoscale eddy kinetic energy and contribute to a fast restratification by slumping the horizontal density gradient in the mixed layer. In the present work, the mixed layer formation and restratification were studied by uniformly cooling a fully turbulent zonal jet in a periodic channel at different resolutions, from eddy resolving (10 km) to submesoscale permitting (2 km). The effect of the submesoscale activity, highlighted by these different horizontal resolutions, was quantified in terms of mixed layer depth, restratification rate and buoyancy fluxes. Contrary to many idealized studies focusing on the restratification phase only, this study addresses a continuous event of mixed layer formation followed by its complete restratification. The robustness of the present results was established by ensemble simulations. The results show that, at higher resolution, when submesoscale starts to be resolved, the mixed layer formed during the surface cooling is significantly shallower and the total restratification is almost three times faster. Such differences between coarse and fine resolution models are consistent with the submesoscale upward buoyancy flux, which balances the convection during the formation phase and accelerates the restratification once the surface cooling is stopped. This submesoscale buoyancy flux is active even below the mixed layer. Our simulations show that mesoscale dynamics also cause restratification, but on longer time scales. Finally, the spatial distribution of the mixed layer depth is highly heterogeneous in the presence of submesoscale activity, prompting the

  16. Mixing layer height retrievals by multichannel microwave radiometer observations

    NASA Astrophysics Data System (ADS)

    Cimini, D.; De Angelis, F.; Dupont, J.-C.; Pal, S.; Haeffelin, M.

    2013-06-01

    The mixing layer height (MLH) is a key parameter for boundary layer studies, including meteorology, air quality, and climate. MLH estimates are inferred from in situ radiosonde measurements or remote sensing observations from instruments like lidar, wind profiling radar, or sodar. Methods used to estimate MLH from radiosonde profiles are also used with atmospheric temperature and humidity profiles retrieved by microwave radiometers (MWR). This paper proposes an alternative approach to estimate MLH from MWR data, based on direct observations (brightness temperatures, Tb) instead of retrieved profiles. To our knowledge, MLH estimates directly from Tb observations has never been attempted before. The method consists of a multivariate linear regression trained with an a priori set of collocated MWR Tb observations (multi-frequency and multi-angle) and MLH estimates from a state-of-the-art lidar system. Results show that the method is able to follow both the diurnal cycle and the day-to-day variability as suggested by the lidar measurements, and also it can detect low MLH values that are below the full overlap limit (~ 200 m) of the lidar system used. Statistics of the comparison between MWR- and reference lidar-based MLH retrievals show mean difference within 10 m, RMS within 340 m, and correlation coefficient higher than 0.77. Monthly mean analysis for day-time MLH from MWR, lidar, and radiosonde shows consistent seasonal variability, peaking at ~ 1200-1400 m in June and decreasing down to ~ 600 m in October. Conversely, night-time monthly mean MLH from all methods are within 300-500 m without any significant seasonal variability. The proposed method provides results that are more consistent with radiosonde estimates than MLH estimates from MWR retrieved profiles. MLH monthly mean values agree well within 1 std with bulk Richardson number method applied at radiosonde profiles at 11:00 and 23:00 UTC. The method described herewith operates continuously and it is

  17. Mixing layer height retrievals by multichannel microwave radiometer observations

    NASA Astrophysics Data System (ADS)

    Cimini, D.; De Angelis, F.; Dupont, J.-C.; Pal, S.; Haeffelin, M.

    2013-11-01

    The mixing layer height (MLH) is a key parameter for boundary layer studies, including meteorology, air quality, and climate. MLH estimates are inferred from in situ radiosonde measurements or remote sensing observations from instruments like lidar, wind profiling radar, or sodar. Methods used to estimate MLH from radiosonde profiles are also used with atmospheric temperature and humidity profiles retrieved by microwave radiometers (MWR). This paper proposes an alternative approach to estimate MLH from MWR data, based on direct observations (brightness temperatures, Tb) instead of retrieved profiles. To our knowledge, MLH estimates directly from Tb observations have never been attempted before. The method consists of a multivariate linear regression trained with an a priori set of collocated MWR Tb observations (multifrequency and multi-angle) and MLH estimates from a state-of-the-art lidar system. The proposed method was applied to a 7-month data set collected at a typical midlatitude site. Results show that the method is able to follow both the diurnal cycle and the day-to-day variability as suggested by the lidar measurements, and also it can detect low MLH values that are below the full overlap limit (~200 m) of the lidar system used. Statistics of the comparison between MWR- and reference lidar-based MLH retrievals show mean difference within 10 m, root mean square within 340 m, and correlation coefficient higher than 0.77. Monthly mean analysis for daytime MLH from MWR, lidar, and radiosonde shows consistent seasonal variability, peaking at ~1200-1400 m in June and decreasing down to ~600 m in October. Conversely, nighttime monthly mean MLH from all methods are within 300-500 m without any significant seasonal variability. The proposed method provides results that are more consistent with radiosonde estimates than MLH estimates from MWR-retrieved profiles. MLH monthly mean values agree well within 1 standard deviation with the bulk Richardson number method

  18. Releasable Layer-by-Layer Assembly of Stabilized Lipid Nanocapsules on Microneedles for Enhanced Transcutaneous Vaccine Delivery

    PubMed Central

    DeMuth, Peter C.; Moon, James J.; Suh, Heikyung; Hammond, Paula T.; Irvine, Darrell J.

    2012-01-01

    Here we introduce a new approach for transcutaneous drug delivery, using microneedles coated with stabilized lipid nanocapsules for delivery of a model vaccine formulation. Poly(lactide-co-glycolide) (PLGA) microneedle arrays were coated with multilayer films via layer-by-layer (LbL) assembly of a biodegradable cationic poly(β-amino ester) (PBAE) and negatively-charged interbilayer-crosslinked multilamellar lipid vesicles (ICMVs). To test the potential of these nanocapsule-coated microneedles for vaccine delivery, we loaded ICMVs with a protein antigen and the molecular adjuvant monophosphoryl lipid A (MPLA). Following application of microneedle arrays to the skin of mice for 5 minutes, (PBAE/ICMV) films were rapidly transferred from microneedle surfaces into the cutaneous tissue, and remained in the skin following removal of the microneedle arrays. Multilayer films implanted in the skin dispersed ICMV cargos in the treated tissue over the course of 24 hours in vivo, allowing for uptake of the lipid nanocapsules by antigen presenting cells (APCs) in the local tissue and triggering their activation in situ. Microneedle-mediated transcutaneous vaccination with ICMV-carrying multilayers promoted robust antigen-specific humoral immune responses with a balanced generation of multiple IgG isotypes, whereas bolus delivery of soluble or vesicle-loaded antigen via intradermal injection or transcutaneous vaccination with microneedles encapsulating soluble protein elicited weak, IgG1-biased humoral immune responses. These results highlight the potential of lipid nanocapsules delivered by microneedles as a promising platform for non-invasive vaccine delivery applications. PMID:22920601

  19. Mixing layer produced by a screen and its dependence on initial conditions

    NASA Astrophysics Data System (ADS)

    Oguchi, H.; Inoue, O.

    1984-05-01

    Attention is given to dependence on initial disturbances in an attempt to elucidate the structure of turbulent mixing layers produced by setting a woven wire screen perpendicular to the freestream in a wind tunnel test section in order to obstruct part of the flow. Three kinds of model geometry screens yielded mixing layers that can be regarded as the equivalents of the plane mixing layer, and of two-dimensional and axisymmetric wakes, issuing into ambient streams of higher velocity. Flow features are visualized by the smoke-wire method, and statistical quantities are measured by a laser-Doppler velocimeter. Large scale transverse vortices persist in all cases. The mixing layers are in self-preserving state up to at least the third-order moments, but the self-preserving state is different in each case. Mixing layer growth rates strongly depend on the disturbance initially imposed.

  20. A Simplified Direct Lipid Mixing Lipoplex Preparation: Comparison of Liposomal-, Dimethylsulfoxide-, and Ethanol-Based Methods

    PubMed Central

    Meisel, Joseph W.; Gokel, George W.

    2016-01-01

    Established transfection methodology often uses commercial reagents, which must be formed into liposomes in a sequence of about half a dozen steps. The simplified method reported here is a direct lipid mixing approach that requires fewer steps, less manipulation, and is less time-consuming. Results are comparable to those obtained with more commonly used methods, as judged by a variety of analytical techniques and by comparisons of transfection results. The method reported here may be applied to non-liposome-forming compounds, thereby greatly expanding the range of structures that can be tested for transfection ability. PMID:27323668

  1. Wind, mixed-layer depth and Chl-a variability in the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Gille, S. T.; Carranza, M. M.; Franks, P. J. S.; Girton, J. B.; Johnson, K. S.

    2014-12-01

    The Southern Ocean, contains some of the ocean's deepest mixed layers and is under the constant influence of strong winds and buoyancy forcing. Phytoplankton growth is hypothesized to be co-limited by iron and light. Because deep mixed layers can transport phytoplankton below the depth of the euphotic zone, light levels depend on mixed-layer depth. We use satellite winds from multiple wind sensors, combined with Argo data, to show that deep mixed layers are generally correlated with strong winds over the Southern Ocean. These deep mixed layers correspond to cold sea surface temperatures. This might also be expected to lead to nutrient upwelling and high chlorophyll-a (Chl-a), as measured by satellite ocean color sensors. However, Chl-a is less strongly correlated with wind speed than SST is, particularly at the mesoscale, and in summer Chl-a is not well correlated with mixed-layer depth. Using new in situ observations of subsurface Chl-a from sensors on southern elephant seals, EM-APEX floats, and bio-optical Argo floats, we find that Chl-a typically has a subsurface maximum in spring, summer, and fall. As a result satellite-sensed Chl-a is an inadequate measure of total biomass within the mixed layer. Satellite Chl-a and integrated Chl-a over the euphotic zone are negatively correlated with MLD from fall through spring, and uncorrelated during the summer. However, integrated Chl-a within the mixed layer shows significant positive correlations with MLD in all seasons. The fact that the deep Chl-a maximum sits at the base of the MLD, closer to the nutrient (or iron) maximum than the light maximum, suggests nutrient limitation plays a greater role than light limitation in governing productivity, and that wind and buoyancy forcing likely govern the mixing processes at the base of the mixed layer that control phytoplankton growth.

  2. Numerical simulation of topographically forced mesoscale variability in a well-mixed marine layer

    NASA Technical Reports Server (NTRS)

    Eddington, Lee W.; O'Brien, J. J.; Stuart, D. W.

    1992-01-01

    A simple nonlinear numerical model of a well-mixed marine layer is employed to examine topographically forced mesoscale variability off coastal California. This model is utilized to simulate a persistent wind maximum observed near Point Conception during northwesterly winds. The model solves for the two horizontal components of the marine-layer height and the marine-layer wind.

  3. Lipids from the nacreous and prismatic layers of two Pteriomorpha Mollusc shells

    NASA Astrophysics Data System (ADS)

    Farre, B.; Dauphin, Y.

    2009-04-01

    Mollusc shells are the best-known Ca-carbonate biominerals. They are commonly described as a mineralized two layered structure: an outer layer composed of calcite prismatic units, and an internal layer composed of tablets of aragonite: the nacreous layer. An external organic layer (periostracum) is present in most taxa. However, the most common structure in the Mollusc shell is the aragonite crossed lamellar layer, but aragonite prisms, calcite foliated layers and homogeneous layers have been also described by Boggild (1930) in all the Mollusc orders. Since, more detailed descriptions of Bivalve shells have been done (Taylor et al., 1969, 1973). Despite the nacroprismatic arrangement is rare, calcite prismatic and aragonite nacreous layers are the best studied because of their simple 3D structure and large units. Among these Molluscs, some Bivalve species composed of these two layers are of commercial interest, such as the pearl oyster, Pinctada margaritifera, cultivated in French Polynesia to produce black pearls. It is well established that Mollusc shells are composite structures of organic and inorganic components (Hatchett, 1799; Grégoire et al., 1955; Beedham, 1958; Simkiss, 1965; Mutvei, 1969; Cuif et al., 1980; Berman et al., 1993; Kobayashi and Samata, 2006). Numerous studies are concerned with the organic matrix of the shell. Organic components are commonly obtained after a strong or mild decalcification process. They are said to consist of both a soluble and insoluble fraction. The main part of studies is dedicated to the soluble components, and among them, proteins (Grégoire et al., 1955; Grégoire, 1961; Krampitz et al., 1976; Samata et al., 1980, 2004; Weiner, 1983; Miyamoto et al., 2006). Despite the pioneering work of Wada (1980) sugars are usually neglected despite their role in biomineralization. The third component of the organic matrix of calcareous biominerals is lipids. To date, there is a paucity of information concerning the presence

  4. Lipid modification gives rise to two distinct Haloferax volcanii S-layer glycoprotein populations.

    PubMed

    Kandiba, Lina; Guan, Ziqiang; Eichler, Jerry

    2013-03-01

    The S-layer glycoprotein is the sole component of the protein shell surrounding Haloferax volcanii cells. The deduced amino acid sequence of the S-layer glycoprotein predicts the presence of a C-terminal membrane-spanning domain. However, several earlier observations, including the ability of EDTA to selectively solubilize the protein, are inconsistent with the presence of a trans-membrane sequence. In the present report, sequential solubilization of the S-layer glycoprotein by EDTA and then with detergent revealed the existence of two distinct populations of the S-layer glycoprotein. Whereas both S-layer glycoprotein populations underwent signal peptide cleavage and N-glycosylation, base hydrolysis followed by mass spectrometry revealed that a lipid, likely archaetidic acid, modified only the EDTA-solubilized version of the protein. These observations are consistent with the S-layer glycoprotein being initially synthesized as an integral membrane protein and subsequently undergoing a processing event in which the extracellular portion of the protein is separated from the membrane-spanning domain and transferred to a waiting lipid moiety.

  5. Probing Peptide and Protein Insertion in a Biomimetic S-Layer Supported Lipid Membrane Platform

    PubMed Central

    Damiati, Samar; Schrems, Angelika; Sinner, Eva-Kathrin; Sleytr, Uwe B.; Schuster, Bernhard

    2015-01-01

    The most important aspect of synthetic lipid membrane architectures is their ability to study functional membrane-active peptides and membrane proteins in an environment close to nature. Here, we report on the generation and performance of a biomimetic platform, the S-layer supported lipid membrane (SsLM), to investigate the structural and electrical characteristics of the membrane-active peptide gramicidin and the transmembrane protein α-hemolysin in real-time using a quartz crystal microbalance with dissipation monitoring in combination with electrochemical impedance spectroscopy. A shift in membrane resistance is caused by the interaction of α-hemolysin and gramicidin with SsLMs, even if only an attachment onto, or functional channels through the lipid membrane, respectively, are formed. Moreover, the obtained results did not indicate the formation of functional α-hemolysin pores, but evidence for functional incorporation of gramicidin into this biomimetic architecture is provided. PMID:25633104

  6. [Particle dispersion by ordered motion in mixing layers]. [Annual report

    SciTech Connect

    Troutt, T.R.

    1989-12-31

    Multiphase mixing in turbulent flows is a key element in many practical energy conversion, chemical mixing and pollutant dispersal problems. Numerous important technological and environmental processes could be better addressed with improvements in understanding in this area. Progress in developing understanding of this field, however, has traditionally been difficult because of the complexities involved with the turbulent flows employed to provide the mixing mechanisms. To address this problem from a new perspective several years ago this research group initiated an ongoing investigation concerning the potential connections between organized turbulent vortex structures and the particle dispersion process. This report details activities during this reporting period.

  7. The Closure of the Ocean Mixed Layer Temperature Budget using Level-Coordinate Model Fields

    NASA Technical Reports Server (NTRS)

    Kim, Seung-Bum; Fukumori, Ichiro; Lee, Tong

    2005-01-01

    Entrainment is an important element of the mixed layer mass, heat, and temperature budgets. Conventional procedures to estimate entrainment heat advection often do not permit the closure of heat and temperature budgets because of inaccuracies in its formulation. In this study a rigorous approach to evaluate the effect of entrainment using the output of a general circulation model (GCM) that does not have an explicit prognostic mixed layer model is described. The integral elements of the evaluation are 1) the rigorous estimates of the temperature difference between mixed layer water and entrained water at each horizontal grid point, 2) the formulation of the temperature difference such that the budget closes over a volume greater than one horizontal grid point, and 3) the apparent warming of the mixed layer during the mixed layer shoaling to account for the weak vertical temperature gradient within the mixed layer. This evaluation of entrainment heat advection is compared with the estimates by other commonly used ad hoc formulations by applying them in three regions: the north-central Pacific, the Kuroshio Extension, and the Nino-3 areas in the tropical Pacific. In all three areas the imbalance in the mixed layer temperature budget by the ad hoc estimates is significant, reaching a maximum of about 4 K yr(exp -1).

  8. Ordered mixed-layer structures in the Mighei carbonaceous chondrite matrix

    NASA Technical Reports Server (NTRS)

    Mackinnon, I. D. R.

    1982-01-01

    High resolution transmission electron microscopy of the Mighei carbonaceous chondrite matrix has revealed the presence of a new mixed layer structure material. This mixed-layer material consists of an ordered arrangement of serpentine-type (S) and brucite-type (B) layers in the sequence SBBSBB. Electron diffraction and imaging techniques show that the basal periodicity is approximately 17 A. Discrete crystals of SBB-type material are typically curved, of small size (less than 1 micron) and show structural variations similar to the serpentine group minerals. Mixed-layer material also occurs in association with planar serpentine. Characteristics of SBB-type material are not consistent with known terrestrial mixed-layer clay minerals. Evidence for formation by a condensation event or by subsequent alteration of pre-existing material is not yet apparent.

  9. Enhancement of Exciton Emission in Lead Halide-Based Layered Perovskites by Cation Mixing.

    PubMed

    Era, Masanao; Komatsu, Yumeko; Sakamoto, Naotaka

    2016-04-01

    Spin-coated films of a lead halide, PbX: X = I and Br, layered perovskites having cyclohexenylethyl ammonium molecule as an organic layer, which were mixed with other metal halide-based layered perovskites consisting of various divalent metal halides (for example, Ca2, Cdl2, FeI2, SnBr2 and so on), were prepared. The results of X-ray diffraction measurements exhibited that solid solution formation between PbX-based layered perovskite and other divalent metal halide-based layered perovskites was observed up to very high molar concentration of 50 molar% in the mixed film samples when divalent cations having ionic radius close to that of Pb2+ were employed. In the solid solution films, the exciton emission was much enhanced at room temperature. Exciton emission intensity of Pbl-based layered perovskite mixed with Cal-based layered perovskite (20 molar%) is about 5 times large that of the pristine Pbl-based layered perovskite, and that of PbBr-based layered perovskite mixed with SnBr-based layered perovskite (20 molar%) was also about 5 times large that of the pristine PbBr-based layered perovskite at room temperature.

  10. Problem of the thermodynamic status of the mixed-layer minerals

    USGS Publications Warehouse

    Zen, E.-A.

    1962-01-01

    Minerals that show mixed layering, particularly with the component layers in random sequence, pose problems because they may behave thermodynamically as single phases or as polyphase aggregates. Two operational criteria are proposed for their distinction. The first scheme requires two samples of mixed-layer material which differ only in the proportions of the layers. If each of these two samples are allowed to equilibrate with the same suitably chosen monitoring solution, then the intensive parameters of the solution will be invariant if the mixed-layer sample is a polyphase aggregate, but not otherwise. The second scheme makes use of the fact that portions of many titration curves of clay minerals show constancy of the chemical activities of the components in the equilibrating solutions, suggesting phase separation. If such phase separation occurs for a mixed-layer material, then, knowing the number of independent components in the system, it should be possible to decide on the number of phases the mixed-layer material represents. Knowledge of the phase status of mixed-layer material is essential to the study of the equilibrium relations of mineral assemblages involving such material, because a given mixed-layer mineral will be plotted and treated differently on a phase diagram, depending on whether it is a single phase or a polyphase aggregate. Extension of the titration technique to minerals other than the mixed-layer type is possible. In particular, this method may be used to determine if cryptoperthites and peristerites are polyphase aggregates. In general, for any high-order phase separation, the method may be used to decide just at what point in this continuous process the system must be regarded operationally as a polyphase aggregate. ?? 1962.

  11. Determination of the Mixing Layer Height Over two Sites, Using Pilot Balloons During the MILAGRO Campaign

    NASA Astrophysics Data System (ADS)

    Wohrnschimmel, H.; Alonso, A. L.; Ángeles, F.; Sosa, G.; Varela, J.; Cárdenas, B.

    2007-12-01

    Among the mechanisms that affect air quality there is a variety of meteorological processes. An important process in this context are the changes in the mixing layer height during a day and over the year. The mixing layer height is the portion of the atmosphere close to the surface layer where air pollutants get diluted, without leaving this layer. Therefore, it is important to describe the variations in the height of the mixing layer, i.e. the vertical dilution of air pollution, since this is a process mitigating naturally the impact of emissions. There exist different methods to obtain information on the mixing layer height, among them radio soundings, the application of vertical wind profilers, and launching pilot balloons. In this study, pilot balloons have been used simultaneously over two sites of the Mexico City Metropolitan Area during the MILAGRO campaign in March 2006. The objective was to determine the vertical wind profiles and derive information on the mixing layer height. Daily, four pilot balloons were launched, at 9:00, 12:00, 15:00, and 18:00 hours, over Tenango del Aire (a rural area in the Southeast of Mexico City), and over Ciudad Universitaria, in the Southern metropolitan area. At some occasions, night time measurements have been carried out at 21:00 and 24:00. A variability of the diurnal evolution of the mixing layer was observed along March, which could be related to surface temperature. The diurnal evolution showed a sudden growth of the mixing layer between 9:00 and 12:00 hours. Data intercomparisons were carried out for pilot balloons versus radio soundings during a few days at a third site, Tula, in the North of Mexico City. Both intercomparisons showed that pilot balloons are an effective method to obtain information about the development of the mixing layer.

  12. Development of "all natural" layer-by-layer redispersible solid lipid nanoparticles by nano spray drying technology.

    PubMed

    Wang, Taoran; Hu, Qiaobin; Zhou, Mingyong; Xia, Yan; Nieh, Mu-Ping; Luo, Yangchao

    2016-10-01

    Solid lipid nanoparticles (SLNs) have gained tremendous attraction as carriers for controlled drug delivery. Despite numerous advances in the field, one long-standing historical challenge for their practical applications remains unmet: redispersibility after drying. In this work, a novel design of SLNs using a layer-by-layer (LbL) technique was developed and the formulations were optimized by surface response methodology (Box-Behnken design). To the best of our knowledge, this is the first study reporting the fabrication of SLNs from all natural ingredients in the absence of any synthetic surfactants or coatings. The SLNs were prepared by a combined solvent-diffusion and hot homogenization method, with soy lecithin as natural emulsifier (first layer), followed by the subsequent coating with sodium caseinate (second layer) and pectin (third layer), both of which are natural food biopolymers. The adsorption of pectin coating onto caseinate was reinforced by hydrophobic and electrostatic interactions induced by a pH-driven process along with thermal treatment. The innovative nano spray drying technology was further explored to obtain ultra-fine powders of SLNs. Compared to uncoated or single-layer coated SLNs powders, which showed severe aggregation after spray drying, the well-separated particles with spherical shape and smooth surface were obtained for layer-by-layer (LbL) SLNs, which were redispersible into water without variation of dimension, shape and morphology. The SLNs were characterized by Fourier transform infrared and high-performance differential scanning calorimetry for their physical properties. The LbL-coated SLNs based on all natural ingredients have promising features for future applications as drug delivery systems, overcoming the major obstacles in conventional spray drying and redispersing SLNs-based formulations.

  13. Effect of mixed micellar lipid on the absorption of cholesterol and vitamin D3 into lymph

    PubMed Central

    Thompson, Gilbert R.; Ockner, Robert K.; Isselbacher, Kurt J.

    1969-01-01

    The absorption of endogenous cholesterol, labeled with tracer doses of cholesterol 14C or cholesterol-3H and of near physiological doses of vitamin D3-3H was studied in rats with cannulated intestinal lymphatics. The effects of administering mixed micellar solutions of fatty acid, monoglyceride, and bile salt on the absorption of these labeled sterols was determined. It was observed that the specific activity of free cholesterol and the amounts of vitamin D3 appearing in lymph were significantly increased during the intraduodenal administration of mixed micellar solutions of either linoleic or palmitic acid, in contrast to control rats receiving a micellar solution of taurocholate. These increases were related linearly to the lymph triglyceride level. In addition it was observed that when the linoleic acid solution was administered there was a more marked increase in the ratio of the specific activities of free and esterified cholesterol in lymph than with either the palmitic acid or taurocholate solutions. Additional studies in rats with intact lymphatics showed that the uptake of labeled cholesterol and vitamin D3 from the intestinal lumen into the wall was similar whether the sterols were administered in taurocholate or in mixed micellar solution. These findings suggest that mixed micellar lipid increased the rate of appearance of labeled free cholesterol and vitamin D3 in lymph by enhancing their transport out of the intestinal mucosa, rather than by an effect on uptake. PMID:4303790

  14. Low Velocity Difference Thermal Shear Layer Mixing Rate Measurements

    NASA Technical Reports Server (NTRS)

    Bush, Robert H.; Culver, Harry C. M.; Weissbein, Dave; Georgiadis, Nicholas J.

    2013-01-01

    Current CFD modeling techniques are known to do a poor job of predicting the mixing rate and persistence of slot film flow in co-annular flowing ducts with relatively small velocity differences but large thermal gradients. A co-annular test was devised to empirically determine the mixing rate of slot film flow in a constant area circular duct (D approx. 1ft, L approx. 10ft). The axial rate of wall heat-up is a sensitive measure of the mixing rate of the two flows. The inflow conditions were varied to simulate a variety of conditions characteristic of moderate by-pass ratio engines. A series of air temperature measurements near the duct wall provided a straightforward means to measure the axial temperature distribution and thus infer the mixing rate. This data provides a characterization of the slot film mixing rates encountered in typical jet engine environments. The experimental geometry and entrance conditions, along with the sensitivity of the results as the entrance conditions vary, make this a good test for turbulence models in a regime important to modern air-breathing propulsion research and development.

  15. [Particle dispersion by order motion in mixing layers

    SciTech Connect

    Troutt, T.R.

    1993-09-01

    Multiphase mixing in turbulent flows is a key element in many energy conversion and chemical processes. There is considerable need for improving the design and control of these processes. Free turbulent shear flows are the primary agents for particle mixing in these systems. Previous studies by this research group have shown that, if particle coupling effects are neglected, the organized vortex structures generated by these shear flows control the character of the particle mixing process. A coordinated experimental and numerical study is proposed to investigate the coupled effects of droplet mass and energy transfer on the turbulent multiphase mixing process in free shear flows. This study has important implications concerning the design of reacting flow systems. Experimental visualizations of the multiphase flow will be carried out using laser-sheet lighting and high speed photography. Local measurements of droplet size, velocity and concentration diagnostics, will be made with laser anemometry and phase Doppler diagnostics. Complementary analytical and numerical analyses will be carried out to assess the effect of coupling on vortex structure, stability and growth. The results of the proposed research will provide basic understanding concerning the coupled effects of particle concentration on the rate of multiphase mixing in turbulent flows. Information of this nature is essential to the improved designs of engineering systems with particulate or droplet flows.

  16. Filtered Rayleigh scattering based measurements in compressible mixing layers

    NASA Technical Reports Server (NTRS)

    Elliott, G. S.; Samimy, M.; Arnette, S. A.

    1992-01-01

    Results are presented of experiments in which a Rayleigh-scattering-based technique was used to make quantitative planar measurements in the compressible free shear layers. To this end, the absorption characteristics of the iodine molecular filter were investigated, and initial planar density measurements in M(c) = 0.51 shear layer were performed. The preliminary results presented here demonstrate the validity of the measurement technique.

  17. Lipid modification of proteins in Archaea: attachment of a mevalonic acid-based lipid moiety to the surface-layer glycoprotein of Haloferax volcanii follows protein translocation.

    PubMed Central

    Konrad, Zvia; Eichler, Jerry

    2002-01-01

    Once the newly synthesized surface (S)-layer glycoprotein of the halophilic archaeaon Haloferax volcanii has traversed the plasma membrane, the protein undergoes a membrane-related, Mg(2+)-dependent maturation event, revealed as an increase in the apparent molecular mass and hydrophobicity of the protein. To test whether lipid modification of the S-layer glycoprotein could explain these observations, H. volcanii cells were incubated with a radiolabelled precursor of isoprene, [(3)H]mevalonic acid. In Archaea, isoprenoids serve as the major hydrophobic component of archaeal membrane lipids and have been shown to modify other haloarchaeal S-layer glycoproteins, although little is known of the mechanism, site or purpose of such modification. In the present study we report that the H. volcanii S-layer glycoprotein is modified by a derivative of mevalonic acid and that maturation of the protein was prevented upon treatment with mevinolin (lovastatin), an inhibitor of mevalonic acid biosynthesis. These findings suggest that lipid modification of S-layer glycoproteins is a general property of halophilic archaea and, like S-layer glycoprotein glycosylation, lipid-modification of the S-layer glycoproteins takes place on the external cell surface, i.e. following protein translocation across the membrane. PMID:12069685

  18. Detailed characteristics of drop-laden mixing layers: LES predictions compared to DNS

    NASA Technical Reports Server (NTRS)

    Okong'o, N.; Leboissetier, A.; Bellan, J.

    2004-01-01

    Results have been compared from Direct Numerical Simulation (DNS) and Large Eddy Simulation (LES) of a temporal mixing layer laden with evaporating drops, to assess the ability of LES to reproduce detailed characteristics of DNS.

  19. Development of a Hybrid RANS/LES Method for Compressible Mixing Layer Simulations

    NASA Technical Reports Server (NTRS)

    Georgiadis, Nicholas J.; Alexander, J. Iwan D.; Reshotko, Eli

    2001-01-01

    A hybrid method has been developed for simulations of compressible turbulent mixing layers. Such mixing layers dominate the flows in exhaust systems of modem day aircraft and also those of hypersonic vehicles currently under development. The hybrid method uses a Reynolds-averaged Navier-Stokes (RANS) procedure to calculate wall bounded regions entering a mixing section, and a Large Eddy Simulation (LES) procedure to calculate the mixing dominated regions. A numerical technique was developed to enable the use of the hybrid RANS/LES method on stretched, non-Cartesian grids. The hybrid RANS/LES method is applied to a benchmark compressible mixing layer experiment. Preliminary two-dimensional calculations are used to investigate the effects of axial grid density and boundary conditions. Actual LES calculations, performed in three spatial directions, indicated an initial vortex shedding followed by rapid transition to turbulence, which is in agreement with experimental observations.

  20. 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

  1. Submesoscale Flows and Mixing in the Ocean Surface Layer Using the Regional Oceanic Modeling System (ROMS)

    DTIC Science & Technology

    2013-09-30

    DISTRIBUTION A: Approved for public release; distribution unlimited. Submesoscale Flows and Mixing in the Ocean Surface Layer Using the Regional...long-term goals of this project are to further the insight into the dynamics of submesoscale flow in the oceanic surface layer. Using the regional...oceanic modeling system (ROMS) we aim to understand the impact of submesoscale processes on the mixing at small scales of tracers and the transfer of

  2. Submesoscale Flows and Mixing in the Oceanic Surface Layer Using the Regional Oceanic Modeling System (ROMS)

    DTIC Science & Technology

    2014-09-30

    Submesoscale Flows and Mixing in the Oceanic Surface Layer Using the Regional Oceanic Modeling System (ROMS) M. Jeroen Molemaker (PI) James C...long-term goals of this project are to further the insight into the dynamics of submesoscale flow in the oceanic surface layer. Using the Regional...Oceanic Modeling System (ROMS), we aim to understand the impact of submesoscale processes on tracer mixing at small scales and the transfer of energy

  3. Lidar Characterization of Boundary Layer Transport and Mixing for Estimating Urban-Scale Greenhouse Gas Emissions

    NASA Astrophysics Data System (ADS)

    Hardesty, R. Michael; Brewer, W. Alan; Sandberg, Scott P.; Weickmann, Ann M.; Shepson, Paul B.; Cambaliza, Maria; Heimburger, Alexie; Davis, Kenneth J.; Lauvaux, Thomas; Miles, Natasha L.; Sarmiento, Daniel P.; Deng, A. J.; Gaudet, Brian; Karion, Anna; Sweeney, Colm; Whetstone, James

    2016-06-01

    A compact commercial Doppler lidar has been deployed in Indianapolis for two years to measure wind profiles and mixing layer properties as part of project to improve greenhouse measurements from large area sources. The lidar uses vertical velocity variance and aerosol structure to measure mixing layer depth. Comparisons with aircraft and the NOAA HRDL lidar generally indicate good performance, although sensitivity might be an issue under low aerosol conditions.

  4. Oceanic upper mixed layer depth determination by the use of satellite data

    NASA Technical Reports Server (NTRS)

    Yan, Xiao-Hai; Schubel, J. R.; Pritchard, D. W.

    1990-01-01

    A method has been developed to determine the oceanic daily mean mixed layer depth from satellite observations and a mixed layer thermal inertia (MLTI) model. The algorithms were developed to use remotely-sensed values of sea surface temperature, albedo, and surface wind speeds to calculate the thermal inertia and to predict changes in subsurface diurnal mixed layer depth. The MLTI model, based on a mixed layer model of the upper ocean, has been used to simulate the diurnal mixing process and thermal inertia distribution in the Sargasso Sea around 34 deg N, 70 deg W. Sea surface temperature and albedo have been obtained from the NOAA7-AVHRR images. Surface wind speeds have been derived from the Scanning Multichannel Microwave Radiometer (SMMR) aboard Nimbus 7. Image processing was performed for images gathered between June and July 1982. The daily mean mixed layer depths predicted by the MLTI model agree well with data gathered at the LOTUS mooring located in the Sargasso Sea. This suggests that vertical mixing is the dominant physical process that controls the thermal inertia distribution in the midocean, far from major current systems, and that remote sensing is a promising tool to study such upper ocean processes.

  5. Laboratory simulations of the atmospheric mixed-layer in flow over complex topography

    NASA Astrophysics Data System (ADS)

    Perry, Steven G.; Snyder, William H.

    2017-02-01

    A laboratory study of the influence of complex terrain on the interface between a well-mixed boundary layer and an elevated stratified layer was conducted in the towing-tank facility of the U.S. Environmental Protection Agency. The height of the mixed layer in the daytime boundary layer can have a strong influence on the concentration of pollutants within this layer. Deflections of streamlines at the height of the interface are primarily a function of hill Froude number (Fr), the ratio of mixed-layer height (zi) to terrain height (h), and the crosswind dimension of the terrain. The magnitude of the deflections increases as Fr increases and zi/h decreases. For mixing-height streamlines that are initially below the terrain top, the response is linear with Fr; for those initially above the terrain feature the response to Fr is more complex. Once Fr exceeds about 2, the terrain-related response of the mixed layer interface decreases somewhat with increasing Fr (toward more neutral flow). Deflections are also shown to increase as the crosswind dimensions of the terrain increase. Comparisons with numerical modeling, limited field data, and other laboratory measurements reported in the literature are favorable. Additionally, visual observations of dye streamers suggest that the flow structure exhibited for our elevated inversions passing over three dimensional hills is similar to that reported in the literature for continuously stratified flow over two-dimensional hills.

  6. Hydrogen Bonding and Binding of Polybasic Residues with Negatively Charged Mixed Lipid Monolayers

    SciTech Connect

    Lorenz, C.; Feraudo, J.; Travesset, A.

    2008-01-23

    Phosphoinositides, phosphorylated products of phosphatidylinositol, are a family of phospholipids present in tiny amounts (1% or less) in the cytosolic surface of cell membranes, yet they play an astonishingly rich regulatory role, particularly in signaling processes. In this letter, we use molecular dynamics simulations on a model system of mixed lipid monolayers to investigate the interaction of phosphatidylinositol 4,5-bisphosphate (PIP{sub 2}), the most common of the phosphoinositides, with a polybasic peptide consisting of 13 lysines. Our results show that the polybasic peptide sequesters three PIP{sub 2} molecules, forming a complex stabilized by the formation of multiple hydrogen bonds between PIP{sub 2} and the Lys residues. We also show that the polybasic peptide does not sequester other charged phospholipids such as phosphatidylserine because of the inability to form long-lived stable hydrogen bonds.

  7. Discrete element simulation of charging and mixed layer formation in the ironmaking blast furnace

    NASA Astrophysics Data System (ADS)

    Mitra, Tamoghna; Saxén, Henrik

    2016-11-01

    The burden distribution in the ironmaking blast furnace plays an important role for the operation as it affects the gas flow distribution, heat and mass transfer, and chemical reactions in the shaft. This work studies certain aspects of burden distribution by small-scale experiments and numerical simulation by the discrete element method (DEM). Particular attention is focused on the complex layer-formation process and the problems associated with estimating the burden layer distribution by burden profile measurements. The formation of mixed layers is studied, and a computational method for estimating the extent of the mixed layer, as well as its voidage, is proposed and applied on the results of the DEM simulations. In studying a charging program and its resulting burden distribution, the mixed layers of coke and pellets were found to show lower voidage than the individual burden layers. The dynamic evolution of the mixed layer during the charging process is also analyzed. The results of the study can be used to gain deeper insight into the complex charging process of the blast furnace, which is useful in the design of new charging programs and for mathematical models that do not consider the full behavior of the particles in the burden layers.

  8. Acceleration of Lateral Equilibration in Mixed Lipid Bilayers Using Replica Exchange with Solute Tempering.

    PubMed

    Huang, Kun; García, Angel E

    2014-10-14

    The lateral heterogeneity of cellular membranes plays an important role in many biological functions such as signaling and regulating membrane proteins. This heterogeneity can result from preferential interactions between membrane components or interactions with membrane proteins. One major difficulty in molecular dynamics simulations aimed at studying the membrane heterogeneity is that lipids diffuse slowly and collectively in bilayers, and therefore, it is difficult to reach equilibrium in lateral organization in bilayer mixtures. Here, we propose the use of the replica exchange with solute tempering (REST) approach to accelerate lateral relaxation in heterogeneous bilayers. REST is based on the replica exchange method but tempers only the solute, leaving the temperature of the solvent fixed. Since the number of replicas in REST scales approximately only with the degrees of freedom in the solute, REST enables us to enhance the configuration sampling of lipid bilayers with fewer replicas, in comparison with the temperature replica exchange molecular dynamics simulation (T-REMD) where the number of replicas scales with the degrees of freedom of the entire system. We apply the REST method to a cholesterol and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) bilayer mixture and find that the lateral distribution functions of all molecular pair types converge much faster than in the standard MD simulation. The relative diffusion rate between molecules in REST is, on average, an order of magnitude faster than in the standard MD simulation. Although REST was initially proposed to study protein folding and its efficiency in protein folding is still under debate, we find a unique application of REST to accelerate lateral equilibration in mixed lipid membranes and suggest a promising way to probe membrane lateral heterogeneity through molecular dynamics simulation.

  9. A study of compressible mixing layers using filtered Rayleigh scattering

    NASA Technical Reports Server (NTRS)

    Elliott, Gregory S.; Samimy, MO; Arnette, Stephen A.

    1992-01-01

    High Reynolds number compressible planar free shear layers were studied using a planar laser visualization technique. Two convective Mach numbers, M(c) = 0.51 and 0.86, were studied in the developing and fully developed regions. The structures in the M(c) = 0.51 case were characterized by 2D core and roller regions, similar to subsonic shear layers. Also for the M(c) = 0.51 case, plan views in the developing region showed the existence of streamwise streaks, possibly indicating the presence of organized streamwise vorticity. The M(c) = 0.86 flow was much less organized than the lower convective Mach number case and highly three dimensional.

  10. Mixing and non-equilibrium chemical reaction in a compressible mixing layer. M.S. Thesis Final Report

    NASA Technical Reports Server (NTRS)

    Steinberger, Craig J.

    1991-01-01

    The effects of compressibility, chemical reaction exothermicity, and non-equilibrium chemical modeling in a reacting plane mixing layer were investigated by means of two dimensional direct numerical simulations. The chemical reaction was irreversible and second order of the type A + B yields Products + Heat. The general governing fluid equations of a compressible reacting flow field were solved by means of high order finite difference methods. Physical effects were then determined by examining the response of the mixing layer to variation of the relevant non-dimensionalized parameters. The simulations show that increased compressibility generally results in a suppressed mixing, and consequently a reduced chemical reaction conversion rate. Reaction heat release was found to enhance mixing at the initial stages of the layer growth, but had a stabilizing effect at later times. The increased stability manifested itself in the suppression or delay of the formation of large coherent structures within the flow. Calculations were performed for a constant rate chemical kinetics model and an Arrhenius type kinetic prototype. The choice of the model was shown to have an effect on the development of the flow. The Arrhenius model caused a greater temperature increase due to reaction than the constant kinetic model. This had the same effect as increasing the exothermicity of the reaction. Localized flame quenching was also observed when the Zeldovich number was relatively large.

  11. The Effects of Curvature on Turbulent Mixing Layers,

    DTIC Science & Technology

    1984-01-01

    bances when the Taylor number is smaller than a critical value of 1708 (the numerical value cited was obtained by Peliew and Southwell [ 1940 ] by a...streamwise vortices are caused by Taylor- Gortler instability and are similar to Taylor vortices. Aryshev. Golovin , and Ershin (1981) indicated that an...layer. According to Aryshev, Golovin and Ershin (1981), the local streamline cur- vature associated with such colliding streams can lead to Taylor

  12. Spectroscopic study of 3-Hydroxyflavone - protein interaction in lipidic bi-layers immobilized on silver nanoparticles

    NASA Astrophysics Data System (ADS)

    Voicescu, Mariana; Ionescu, Sorana; Nistor, Cristina L.

    2017-01-01

    The interaction of 3-Hydroxyflavone with serum proteins (BSA and HSA) in lecithin lipidic bi-layers (PC) immobilized on silver nanoparticles (SNPs), was studied by fluorescence and Raman spectroscopy. BSA secondary structure was quantified with a deconvolution algorithm, showing a decrease in α-helix structure when lipids were added to the solution. The effect of temperature on the rate of the excited-state intra-molecular proton transfer and on the dual fluorescence emission of 3-HF in the HSA/PC/SNPs systems was discussed. Evaluation of the antioxidant activity of 3-HF in HSA/PC/SNPs systems was also studied. The antioxidant activity of 3-HF decreased in the presence of SNPs. The results are discussed with relevance to the secondary structure of proteins and of the 3-HF based nano-systems to a topical formulation useful in the oxidative stress process.

  13. Protected Sulfur Cathode with Mixed Conductive Coating Layer for Lithium Sulfur Battery

    NASA Astrophysics Data System (ADS)

    Jin, Jun; Wen, Zhaoyin; Wang, Qingsong; Gu, Sui; Huang, Xiao; Chen, Chunhua

    2016-10-01

    A mixed conductive coating layer composed of lithium ion conductive ceramic powder, carbon and binder was introduced on the surface of a sulfur electrode. This coating layer is designed to suppress the migration of lithium polysulfides from the sulfur electrode, and improve the cycling capacity of a lithium sulfur battery. The protected sulfur cathode with a mixed conductive coating layer delivered an initial specific capacity of 1236 mAh g-1 at 0.5C and maintained a capacity of 842 mAh g-1 after 100 cycles. In particular, a soft package battery with protected cathode exhibits improved cycling capacity and excellent rate performance.

  14. Mixed-layer deepening during Heinrich events: a multi-planktonic foraminiferal delta18O approach.

    PubMed

    Rashid, Harunur; Boyle, Edward A

    2007-10-19

    Proxies from Greenland ice cores and North Atlantic marine sediment cores document repeated extreme climate swings of a few decades to millennia during the last glacial cycle, including periods of intense ice rafting called Heinrich events (HEs). We have found similar oxygen isotope variations recorded in mixed-layer-and thermocline-dwelling planktonic foraminifera during HEs 0, 1, and 4, suggesting that three foraminiferal taxa calcified their shells at similar temperatures in a homogenized upperwater column. This implies that the surface mixed layer was deeper during HEs. Similar deepening occurred on the northern margin of the ice-rafted-debris belt, implying that these deep mixed layers during HEs were widespread in the region. We suggest that an increase in storminess during HEs intensified the vertical mixing of meltwater from ice rafting in the upper ocean.

  15. Substantial energy input to the mesopelagic ecosystem from the seasonal mixed-layer pump

    NASA Astrophysics Data System (ADS)

    Dall'Olmo, Giorgio; Dingle, James; Polimene, Luca; Brewin, Robert J. W.; Claustre, Hervé

    2016-11-01

    The ocean region known as the mesopelagic zone, which is at depths of about 100-1,000 m, harbours one of the largest ecosystems and fish stocks on the planet. Life in this region is believed to rely on particulate organic carbon supplied by the biological carbon pump. Yet this supply appears insufficient to meet mesopelagic metabolic demands. An additional organic carbon source to the mesopelagic zone could be provided by the seasonal entrainment of surface waters in deeper layers, a process known as the mixed-layer pump. Little is known about the magnitude and spatial distribution of this process globally or its potential to transport carbon to the mesopelagic zone. Here we combine mixed-layer depth data from Argo floats with satellite estimates of particulate organic carbon concentrations to show that the mixed-layer pump supplies an important seasonal flux of organic carbon to the mesopelagic zone. We estimate that this process is responsible for a global flux of 0.1-0.5 Pg C yr-1. In high-latitude regions where the mixed layer is usually deep, this flux amounts on average to 23% of the carbon supplied by fast sinking particles, but it can be greater than 100%. We conclude that the seasonal mixed-layer pump is an important source of organic carbon for the mesopelagic zone.

  16. 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.

  17. MAPLE preparation and characterization of mixed arylenevinylene based oligomers:C60 layers

    NASA Astrophysics Data System (ADS)

    Stanculescu, A.; Socol, G.; Vacareanu, L.; Socol, M.; Rasoga, O.; Breazu, C.; Girtan, M.; Stanculescu, F.

    2016-06-01

    This paper presents some studies about the preparation by matrix-assisted pulsed laser evaporation (MAPLE) of mixed layers based on two arylenevinylene oligomers, 1,4-bis [4-(N,N‧-diphenylamino)phenylvinyl] benzene (L78) and 3,3‧-bis(N-hexylcarbazole)vinylbenzene (L13) as donor and buckminsterfullerene (C60) as acceptor, blended in three different weight ratios: 1:1, 1:2 and 1:3. The optical, morphological, structural and electrical properties of these mixed layers have been investigated emphasizing the effect of the layer composition and of the significant degree of disorder. I-V characteristics have revealed typically solar cell behaviour for the heterostructures prepared with mixed layers containing L78 (L13) and fullerene blended in a weight ratio of 1:2. The solar cell structure glass/ITO/L13:C60/Al has shown the best parameters.

  18. Measurements of the streamwise vortical structures in a plane mixing layer

    NASA Technical Reports Server (NTRS)

    Bell, James H.; Mehta, Rabindra D.

    1992-01-01

    The 3D structure of a plane two-stream mixing layer of velocity ratio 0.6 and originating from laminar initial boundary layers was investigated through direct measurements made in a specially constructed mixing-layer wind tunnel. The main objective of the study was to establish quantitatively the presence and the role of the secondary streamwise vortex structure (of the kind that has been shown in past flow visualization investigations to ride among the primary spanwise vortices) in the development of a plane turbulent mixing layer at relatively high Reynolds numbers. Results indicate that the instability leading to the formation of streamwise vortices is initially amplified just downstream of the first spanwise roll-up. The streamwise vortices, which first appear in clusters containing vorticity of both signs, realign further downstream to form counterrotating pairs. Due to the amalgamation of like-sign vortices, the streamwise vortex spacing increases in a stepwise fashion.

  19. Sea ice and the ocean mixed layer over the Antarctic shelf seas

    NASA Astrophysics Data System (ADS)

    Petty, A.; Holland, P.; Feltham, D. L.

    2013-12-01

    An ocean mixed layer model has been incorporated into the Los Alamos sea ice model CICE, to investigate regional variations in the surface-driven formation of Antarctic shelf sea waters. The model captures well the expected sea ice thickness distribution and produces deep (>500 m) mixed layers in the Weddell and Ross shelf seas each winter. By deconstructing the surface power input to the mixed layer, we have shown that the salt/fresh water flux from sea ice growth/melt dominates the evolution of the mixed layer in all shelf sea regions, with a smaller contribution from the mixed layer-surface heat flux. The Weddell and Ross shelf seas have the highest annual ice growth, with a large fraction exported northwards each year, whereas the Bellingshausen shelf sea experiences the highest annual ice melt, driven by the advection of ice from the northeast. Forcing the model with ERA-Interim (1980-2011) and hadGEM2-ES (1980-2099) atmospheric data allows us to look at the impact of atmospheric trends on the sea ice and ocean mixed layer. Both simulations show a shallowing of the wintertime mixed layer in the Amundsen & Bellingshausen seas, potentially increasing the access of warm CDW to ice shelves in both regions. The ERA-I hindcast simulation shows a significant freshening in the Ross and salinification in the Weddell due to surface driven trends (primarily through changes in the sea ice). The Ross freshening is smaller than observed however, highlighting the important role of ice shelf melt in the Amundsen Sea.

  20. The Daytime Mixed Layer Observed by Radiosonde, Profiler, and Lidar during MILAGRO

    NASA Astrophysics Data System (ADS)

    Shaw, W. J.; Pekour, M. S.; Coulter, R. L.; Martin, T. J.; Walters, J.

    2007-12-01

    During the 2006 MILAGRO field campaign centered in the Mexico City area, scientists from Pacific Northwest National Laboratory (PNNL), Argonne National Laboratory (ANL), and the University of Alabama in Huntsville (UAH) operated a variety of atmospheric profiling systems. The systems were located at the Mexican Petroleum Institute (IMP) in central Mexico City, at Tecámac University on the northeastern edge of the Mexico City urban area, and at Rancho la Bisnaga, a privately owned ranch. These sites are referred to as T0, T1, and T2 to reflect the idea of sequential arrival times of air parcels at each site under common transport conditions. T2 was approximately 50 km north of T1. Similar 915 MHz wind profiling radars were operated at all three sites. ANL additionally operated a sodar, a 523-nm micropulse lidar, and a radiosonde system at T1. At T2, PNNL additionally operated a radiosonde system. On aircraft sampling days, five radiosondes were launched at T1 during the daytime, and three were launched at T2. The collocation of profiling systems afforded an opportunity to compare the three primary methods of measuring the depth of deep mixing layers in the Mexico City environment. In this paper we will describe the methods of extracting mixing layer depth from each system as well as the results of the comparison. The results highlight the general agreement among the various methods, but also the ambiguity that results from multiple inversions for radiosondes and from elevated layers with significant particulate matter for lidars. We conclude that the wind profiler is the system of choice for identifying mixing layer depth from the MILAGRO campaign. In addition to the instrument comparison, we also have completed a description of the temporal variability of the mixing layer during the campaign as well as spatial variations among the three sites. We have interpreted our results in the contexts of the widely reported Norte events, of the days with and without

  1. Efficiency enhancement of blue phosphorescent organic light-emitting diodes using mixed electron transport layer

    NASA Astrophysics Data System (ADS)

    Yoo, Seung Il; Yoon, Ju-An; Kim, Nam Ho; Kim, Jin Wook; Lee, Ho Won; Kim, Young Kwan; He, Gufeng; Kim, Woo Young

    2015-01-01

    Blue phosphorescent organic light-emitting diodes (OLED) using mixed electron transport layer (ETL) were fabricated with the device structure of ITO/NPB/mCP:Firpic-8%/TPBi:BCP or TPBi:3TPYMB/Liq/Al to observe mixed ETL's influence on their electrical and optical characteristics. OLED device with mixed ETL of TPBi with BCP or 3TPYMB significantly improved its current efficiency to 30.4 and 34.2 cd/A comparing to 19.8 cd/A of single ETL with BCP only. We examined mixed ETL's capability of electron transport and triplet exciton confinement enhancing phosphorescent OLED's luminance and luminous efficiency.

  2. Studying calcium triggered vesicle fusion in a single vesicle-vesicle content/lipid mixing system

    PubMed Central

    Kyoung, Minjoung; Zhang, Yunxiang; Diao, Jiajie; Chu, Steven; Brunger, Axel T.

    2013-01-01

    This Protocol describes a single vesicle-vesicle microscopy system to study Ca2+-triggered vesicle fusion. Donor vesicles contain reconstituted synaptobrevin and synaptotagmin-1. Acceptor vesicles contain reconstituted syntaxin and SNAP-25, and are tethered to a PEG-coated glass surface. Donor vesicles are mixed with the tethered acceptor vesicles and incubated for several minutes at zero Ca2+-concentration, resulting in a collection of single interacting vesicle pairs. The donor vesicles also contain two spectrally distinct fluorophores that allow simultaneous monitoring of temporal changes of the content and membrane. Upon Ca2+-injection into the sample chamber, our system therefore differentiates between hemifusion and complete fusion of interacting vesicle pairs and determines the temporal sequence of these events on a sub-hundred millisecond timescale. Other factors, such as complexin, can be easily added. Our system is unique by monitoring both content and lipid mixing, and by starting from a metastable state of interacting vesicle pairs prior to Ca2+-injection. PMID:23222454

  3. Lipid-Based Immuno-Magnetic Separation of Archaea from a Mixed Community

    NASA Astrophysics Data System (ADS)

    Frickle, C. M.; Bailey, J.; Lloyd, K. G.; Shumaker, A.; Flood, B.

    2014-12-01

    Despite advancing techniques in microbiology, an estimated 98% of all microbial species on Earth have yet to be isolated in pure culture. Natural samples, once transferred to the lab, are commonly overgrown by "weed" species whose metabolic advantages enable them to monopolize available resources. Developing new methods for the isolation of thus-far uncultivable microorganisms would allow us to better understand their ecology, physiology and genetic potential. Physically separating target organisms from a mixed community is one approach that may allow enrichment and growth of the desired strain. Here we report on a novel method that uses known physiological variations between taxa, in this case membrane lipids, to segregate the desired organisms while keeping them alive and viable for reproduction. Magnetic antibodies bound to the molecule squalene, which is found in the cell membranes of certain archaea, but not bacteria, enable separation of archaea from bacteria in mixed samples. Viability of cells was tested by growing the separated fractions in batch culture. Efficacy and optimization of the antibody separation technique are being evaluated using qPCR and cell counts. Future work will apply this new separation technique to natural samples.

  4. Saturn's Polar Cyclones: Idealized 2-layer Experiments of Vorticity Mixing

    NASA Astrophysics Data System (ADS)

    O'Neill, M. E.; Emanuel, K.; Flierl, G.

    2013-12-01

    The Cassini mission has provided unprecedented high-resolution observations of Saturn's atmosphere. Among many discoveries, a massive warm-core cyclonic vortex has been observed on each pole. The South Polar Vortex (SPV), specifically, has the highest measured temperatures on Saturn, a double eyewall, deep eye and a rapid cyclonic jet with the second highest windspeeds observed on the planet. However, in part because Saturn lacks the thermal disequilibrium mechanism understood to be the energy source for tropical cyclones, scientists have yet to explain the storms' dynamics and energy source. Interestingly, numerous small, vortical (in the case of at least the SPV), and potentially convective systems are embedded within the large-scale flow of both polar vortices. We explore one potential mechanism of vortex maintenance: up-scale, poleward vorticity flux due to vortical hot towers (VHTs). Large GCMs cannot yet resolve local deep convection in the weather layer. Using a two-layer shallow water model on a polar β-plane, we represent deep convection with heton-like vortex pairs and allow them to move freely. We present results from a forced-dissipative system where the forcing is only at the convective scale, and show the effect of this 'convection' on a polar cyclone.

  5. Analysis of mixed-layer clay mineral structures

    USGS Publications Warehouse

    Bradley, W.F.

    1953-01-01

    Among the enormously abundant natural occurrences of clay minerals, many examples are encountered in which no single specific crystallization scheme extends through a single ultimate grain. The characterization of such assemblages becomes an analysis of the distribution of matter within such grains, rather than the simple identification of mineral species. It having become established that the particular coordination complex typified by mica is a common component of many natural subcrystalline assemblages, the opportunity is afforded to analyze scattering from random associations of these complexes with other structural units. Successful analyses have been made of mixed hydration states of montmorillonite, of montmorillonite with mica, of vermiculite with mica, and of montmorillonite with chlorite, all of which are variants of the mica complex, and of halloysite with hydrated halloysite.

  6. Automatic classification of the interferential tear film lipid layer using colour texture analysis.

    PubMed

    Remeseiro, B; Penas, M; Barreira, N; Mosquera, A; Novo, J; García-Resúa, C

    2013-07-01

    The tear film lipid layer is heterogeneous among the population. Its classification depends on its thickness and can be done using the interference pattern categories proposed by Guillon. This papers presents an exhaustive study about the characterisation of the interference phenomena as a texture pattern, using different feature extraction methods in different colour spaces. These methods are first analysed individually and then combined to achieve the best results possible. The principal component analysis (PCA) technique has also been tested to reduce the dimensionality of the feature vectors. The proposed methodologies have been tested on a dataset composed of 105 images from healthy subjects, with a classification rate of over 95% in some cases.

  7. A hydrated phospholipid polymer-grafted layer prevents lipid-related oxidative degradation of cross-linked polyethylene.

    PubMed

    Kyomoto, Masayuki; Moro, Toru; Yamane, Shihori; Takatori, Yoshio; Tanaka, Sakae; Ishihara, Kazuhiko

    2017-01-01

    The surface and substrate of a cross-linked polyethylene (CLPE) liner are designed to achieve resistance against oxidative degradation in the construction of hip joint replacements. In this study, we aimed to evaluate the oxidative degradation caused by lipid absorption of a highly hydrophilic nanometer-scaled thickness layer prepared by grafting a poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) layer and a high-dose gamma-ray irradiated CLPE with vitamin E blending (HD-CLPE[VE]). The HD-CLPE(VE) and PMPC-grafted HD-CLPE(VE) exhibited extremely high oxidation resistance regardless of lipid absorption, even though residual-free radical levels were detectable. The water wettability of the PMPC-grafted CLPE and PMPC-grafted HD-CLPE(VE) surfaces was considerably greater than that of untreated surfaces. The hydrated PMPC-grafted layer also exhibited extremely low solubility for squalene. Lipids such as squalene and cholesterol esters diminished the oxidation resistance of CLPE despite the vitamin E improvement. Notably, the PMPC-grafted surface was resistant to lipid absorption and diffusion as well as subsequent lipid-related oxidative degradation, likely because of the presence of the hydrated PMPC-grafted layer. Together, these results provide preliminary evidence that the resistance against lipid absorption and diffusion of a hydrated PMPC-grafted layer might positively affect the extent of resistance to the in vivo oxidation of orthopedic implants.

  8. Microstructures of mixed group III-nitride epitaxial layers

    NASA Astrophysics Data System (ADS)

    Westmeyer, Andrew Nathan

    InGaN and AlGaN epitaxial layers were deposited by metalorganic chemical vapor deposition on sapphire substrates with GaN buffer layers. For the growth of InGaN at a given temperature, the trimethylgallium flow rate has the greatest influence on the In incorporation, whereas the trimethylindium flow rate has little influence. These effects are attributed to the suppression of In desorption by increasing the growth rate and the saturation of the surface with In adatoms, respectively. If the growth temperature is increased by 2.4°C, then the In content is lowered by 1% for the investigated temperature range of 785--845°C. For the growth of AlGaN, the solid fraction of Al has a sub-linear dependence on the gas composition. This was attributed to the composition pulling effect, in which incoming species are rejected in order to reduce the strain with the underlying buffer layer. A strain analysis was performed on all samples by X-ray diffraction in order to determine the composition and degree of relaxation. These values were compared to those obtained by Rutherford backscattering spectroscopy. By this method the varied reported values for elastic constants were evaluated to ascertain which set provided the best correlation. Transmission electron microscopy was performed. Plan-view images of InGaN contain domains differing in the direction of the modulations. Zone-axis diffraction patterns reveal sidebands adjacent to several Bragg reflections. These observations can be explained by diffraction effects resulting from periodic composition modulations, which are an intermediate stage in the process of phase separation. Since Young's modulus for the nitrides is isotropic in the (0001) plane, no particular direction is favored for the modulations based on strain energy considerations. In the case of AlGaN, periodic composition modulations are observed not in the growth plane (0001) but in the growth direction [0001]. Satellites in diffraction patterns are aligned in this

  9. Effect of velocity ratio on plane mixing layer development - Influence of the splitter plate wake

    NASA Technical Reports Server (NTRS)

    Mehta, R. D.

    1991-01-01

    The effect of the velocity ratio on the approach of a plane mixing layer to self-similarity was investigated experimentally. In the experiment, plane mixing layers with velocity ratios 0.5, 0.6, 0.7, 0.8, and 0.9 were generated in a mixing-layer wind tunnel consisting of two individually driven legs, in which the two streams were allowed to merge at the sharp edge of a tappered splitter plate. The leg driven by the bigger blower was operated at a free-stream velocity in the test section of 21 m/s, while the flow speed in the other leg was varied to change the velocity ratio. For each velocity ratio, the mean flow- and turbulence measurements were carried out at eight streamwise locations. Results showed that, for velocity ratios between 0.5 and 0.7, self-similarity of the mixing layer was achieved, with the asymptotic states comparable; mixing layers with higher velocity ratios failed to achieve a self-similar state within the measurement domain.

  10. Evaluation of the parameterization for cloud top-down mixing in the boundary layer

    NASA Astrophysics Data System (ADS)

    Lee, Eun-Hee; Hong, Song-You; Dudhia, Jimy

    2015-04-01

    An enhanced turbulent mixing due to radiative cooling at cloud or fog top located in the planetary boundary layer (PBL) is parameterized by adopting the top-down diffusivity profile and the cloud top entrainment. The algorithm is first implemented to YSU PBL scheme to be evaluated for idealized cases and then applied for the regional and global real case simulations. Since the modified algorithm consider the mixing height as near surface cloud top, its enhanced mixing effect appears more distinctly especially for the stabilized nocturnal boundary layer. As a result, in the idealized radiation fog case study, it is found that near-surface air temperature decreases due to both radiative cooling at fog top and boundary layer mixing of the new algorithm. Also, the moisture is diffused more effectively to the above the boundary layer, which leads to the rapid dispersion of the fog in the modified algorithm. As a result, the new algorithm simulates the warm and dried near-surface and the cool and moistened boundary layer top in the following daytime. It is also found that the modified algorithm affects the cloud structure frequently occurring at the ocean boundary layer top in the regional and global simulation results.

  11. A diagnostic relation to estimate the mixing layer height under convective conditions

    NASA Astrophysics Data System (ADS)

    Casasanta, Giampietro; Pietroni, Ilaria; Petenko, Igor; Argentini, Stefania

    2014-05-01

    In the framework of the "Atmospheric Boundary Layer Climate" (ABLCLIMAT) project, measurements of mixing-layer height were carried out with a high resolution surface-layer sodar at the French-Italian station of Concordia (Dome C, Antarctica). The behaviour of the mixing-layer height was monitored and estimated during several days in the austral summer 2011-2012. Despite the low temperatures, the mixing layer evolution at Dome C is similar to that observed at mid-latitudes, i.e. a nocturnal shallow stable layer followed by a typical diurnal growth. The mixing-layer heights were found to vary between 10 and 300 m. These observations were complemented by radiosounding profiles, and continuous near-surface turbulent fluxes measurements. Focusing on convective conditions only, a new diagnostic equation is proposed and evaluated. The diagnostic equation is based on a dimensional analysis that takes into account the time-averaged integral of the near-surface turbulent heat flux, the background static stability, and the buoyancy parameter. Despite its simplicity, the proposed model is in good agreement with the observations, and it is able to reproduce the entire diurnal evolution with satisfactory accuracy. To test the diagnostic relation on a larger and completely different data set, it was also applied to measurement from the suburb of Rome (Italy). Although diagnostic models are applicable under quasi-stationary conditions only, the obtained results support the use of a limited number of variables to characterize the general convective mixing layer behaviour. This equation can be a useful tool when direct measurements are not available, or more sophisticated model cannot be used.

  12. Spontaneous adsorption of coiled-coil model peptides K and E to a mixed lipid bilayer.

    PubMed

    Pluhackova, Kristyna; Wassenaar, Tsjerk A; Kirsch, Sonja; Böckmann, Rainer A

    2015-03-26

    A molecular description of the lipid-protein interactions underlying the adsorption of proteins to membranes is crucial for understanding, for example, the specificity of adsorption or the binding strength of a protein to a bilayer, or for characterizing protein-induced changes of membrane properties. In this paper, we extend an automated in silico assay (DAFT) for binding studies and apply it to characterize the adsorption of the model fusion peptides E and K to a mixed phospholipid/cholesterol membrane using coarse-grained molecular dynamics simulations. In addition, we couple the coarse-grained protocol to reverse transformation to atomistic resolution, thereby allowing to study molecular interactions with high detail. The experimentally observed differential binding of the peptides E and K to membranes, as well as the increased binding affinity of helical over unstructered peptides, could be well reproduced using the polarizable Martini coarse-grained (CG) force field. Binding to neutral membranes is shown to be dominated by initial binding of the positively charged N-terminus to the phospholipid headgroup region, followed by membrane surface-aligned insertion of the peptide at the interface between the hydrophobic core of the membrane and its polar headgroup region. Both coarse-grained and atomistic simulations confirm a before hypothesized snorkeling of lysine side chains for the membrane-bound state of the peptide K. Cholesterol was found to be enriched in peptide vicinity, which is probably of importance for the mechanism of membrane fusion. The applied sequential multiscale method, using coarse-grained simulations for the slow adsorption process of peptides to membranes followed by backward transformation to atomistic detail and subsequent atomistic simulations of the preformed peptide-lipid complexes, is shown to be a versatile approach to study the interactions of peptides or proteins with biomembranes.

  13. Determination of mixing layer heights by ceilometer and influences upon air quality at Mexico City airport

    NASA Astrophysics Data System (ADS)

    Schäfer, Klaus; Flores-Jardines, Edgar; Emeis, Stefan; Grutter, Michel; Kurtenbach, Ralf; Wiesen, Peter; Münkel, Christoph

    2009-09-01

    Monitoring of mixing layer height (MLH) was performed during different measurement campaigns in urban and suburban area (Hannover, Munich, Budapest, Zürich, Augsburg) by the Vaisala ceilometer LD40. It is an eye-safe commercial lidar and designed originally to detect cloud base heights and vertical visibility for aviation safety purposes. Software for routine retrieval of mixing layer height from ceilometer data was developed and improved continuously. MLH was determined during a one-week-campaign at the airport Mexico City. Air pollutants like NO, NOx, CO and O3 as well as meteorological parameters like wind, temperature and irradiance are measured at the airport in addition to the air quality monitoring network RAMA in Mexico City. The influence of MLH together with wind, temperature and cloudiness upon air pollution is investigated. These continuous MLH and meteorological data are correlated with simultaneous measured air pollutants. The influence of mixing layer height upon air quality is shown.

  14. Three-dimensional numerical simulation of a compressible, spatially evolving mixing layer

    NASA Astrophysics Data System (ADS)

    Grinstein, Fernando F.; Oran, Elaine S.; Hussain, Fazle

    1988-01-01

    The results from three-dimensional finite-difference simulations of a subsonic, spatially evolving mixing layer are presented. The numerical model solves the compressible time-dependent conservation equations for mass, momentum and energy density using the Flux-Corrected Transport algorithm and direction and timestep splitting. The mixing layer was found to be very sensitive to spanwise perturbations of the cross-stream velocity. Streamwise vortices, appearing in counter-rotating pairs, occurred in the region of the braids in response to sinusoidal coherent spanwise perturbations. These vortices are observed as identifiable coherent structures superimposed on the primary spanwise rolls and affecting considerably the vorticity distribution within their cores. Mass-density drops associated with the maxima of spanwise vorticity, were due to the formation and interaction of coherent structures. The growth rate of the mixing layer was observed to be much faster when streamwise vortical structures are present.

  15. Does the vertical profile of ethane contain more insight into mixing layer height than carbon monoxide?

    NASA Astrophysics Data System (ADS)

    Herndon, Scott; Yacovitch, Tara; Pusede, Sally; Diskin, Glenn; DiGangi, Joshua; Sachse, Glenn; Crawford, James

    2015-04-01

    To improve the interpretation of satellite data measurements near the surface, the DISCOVER-AQ project embarked on a four year campaign to produce an integrated dataset of airborne and surface based measurements at various locations in North America. One of the key metrics when pursuing the the goal of measuring the surface air quality from space is the mixing layer height. The measurement phase in 2014 included the novel 1-Hz Aerodyne Research, Inc. fast Ethane Spectrometer to distinguish the methane emissions from thermogenic (oil&gas) and biogenic sources in the Denver-Julesberg basin. A second potential use of ethane as a determinant of mixing layer height is revealed in the analysis of 213 vertical profiles collected at 7 points during 21 flights. The findings are evaluated relative to other in-situ metrics, such as carbon monoxide and remote sensing attributions of mixing layer height.

  16. Mixing layer development in compound channel flows with submerged and emergent rigid vegetation over the floodplains

    NASA Astrophysics Data System (ADS)

    Dupuis, Victor; Proust, Sébastien; Berni, Céline; Paquier, André

    2017-04-01

    This laboratory study aims at investigating the longitudinal development of a mixing layer in a compound open-channel (two-stage geometry with a main channel and adjacent floodplains). The floodplains are covered with two roughness types: either a bed roughness representing a submerged dense meadow or emergent roughness elements (cylinders) representing an alluvial forest. The theoretical background used for plane mixing layers is adapted to the highly three-dimensional mixing layer that develops at the main channel/floodplain interface. The mixing layer width is divided into two parts on either side of the interface. For the wooded floodplain, the mixing layer width on the floodplain side levels off downstream much more rapidly than for the grassed floodplain. The lateral profiles of normalised velocity and turbulence quantities are found to be self-similar in the longitudinal direction for a fixed elevation. However, shallowness effects prevented the normalised lateral profiles of velocity and turbulence quantities from coinciding at different elevations. The respective contributions of lateral Reynolds stresses and secondary currents to the lateral exchange of momentum are estimated. At the main channel/floodplain interface, the momentum exchange is driven by Reynolds stresses. In the main channel, both Reynolds stresses and secondary currents contribute to the lateral flux of momentum. Secondary currents are stronger with emergent macro-roughness elements than with bed-roughness only on the floodplains. Large-scale turbulent coherent structures are investigated based on two-point space-time correlations of velocity. These structures are found to span the entire floodplain flow depth, and their convection velocity is close to the depth-averaged longitudinal velocity at the interface. The coherent fluctuations of the longitudinal and lateral velocities have different Strouhal number values, similar to those found in plane mixing layers.

  17. Mixing layer growth and background air-quality measurements over the Colorado oil-shale area

    SciTech Connect

    Laulainen, N.S.; Whiteman, C.D.; Davis, W.E.; Thorp, J.M.

    1981-06-01

    The daily growth of convective boundary layers over the complex terrain of the oil shale areas of Colorado is a prominent feature of the meteorology of the region. The development of these layers was investigated using airsondes, rawinsondes, and aircraft. The deep growth of the layers in August, to heights in excess of 5500-m MSL on clear or partly cloudy days, is expected to have important implications for the dispersal of pollutants released in the region as the oil shale resource undergoes future development. Aircraft observations show that the present background air quality is good over the region and that pollutants, when present, become well mixed throughout the depth of the convective boundary layer. The layer therefore represents an important natural means of dilution for pollutants introduced into the atmosphere. Work is proceeding to incorporate the time-dependent convective boundary layer growth into air pollution models for the region.

  18. An Optical Spectroscopic Study of HH 110: a Turbulent Mixing Layer?

    NASA Astrophysics Data System (ADS)

    Ayala, S.; Raga, A. C.; Curiel, S.

    2003-01-01

    The HH 110 jet extends 3 arcmin in length and consists of numerous knots forming the flow. Noriega-Crespo et al. (1996) found that the turbulent optical and near-infrared morphology of the HH 110 jet is consistent with that of a boundary layer. In this work, we have analyzed some line ratios along and across the jet in order to make a quantitative comparison with the line ratios predicted by the current mixing layer models.

  19. Biophysical investigations of the structure and function of the tear fluid lipid layer and the effect of ectoine. Part A: natural meibomian lipid films.

    PubMed

    Dwivedi, Mridula; Backers, Hannes; Harishchandra, Rakesh Kumar; Galla, Hans-Joachim

    2014-10-01

    The tear fluid lipid layer is the outermost part of the tear film on the ocular surface which protects the eye from inflammations and injuries. We investigated the influence of ectoine on the structural organization of natural meibomian lipid films using surface activity analysis and topographical studies. These films exhibit a continuous pressure-area isotherm without any phase transition. With the addition of ectoine, the isotherm is expanded towards higher area per molecule values suggesting an increased area occupied by the interfacial lipid molecules. The AFM topology scans of natural meibomian lipid films reveal a presence of fiber-like structures. The addition of ectoine causes an appearance of droplet-like structures which are hypothesized to be tri-acyl-glycerols and other hydrophobic components excluded from the lipid film. Further the material properties of the droplet-like structure with respect to the surrounding were determined by using the quantitative imaging mode of the AFM technique. The droplet-like structures were found to be comparatively softer than the surrounding. Based on the observations a preliminary hypothesis is proposed explaining the mechanism of action of ectoine leading to the fluidization of meibomian lipid films. This suggests the possibility of ectoine as a treatment for the dry eye syndrome.

  20. Profiling the Triacylglyceride Contents in Bat Integumentary Lipids by Preparative Thin Layer Chromatography and MALDI-TOF Mass Spectrometry

    PubMed Central

    Pannkuk, Evan L.; Risch, Thomas S.; Savary, Brett J.

    2013-01-01

    The mammalian integument includes sebaceous glands that secrete an oily material onto the skin surface. Sebum production is part of the innate immune system that is protective against pathogenic microbes. Abnormal sebum production and chemical composition are also a clinical symptom of specific skin diseases. Sebum contains a complex mixture of lipids, including triacylglycerides, which is species-specific. The broad chemical properties exhibited by diverse lipid classes hinder the specific determination of sebum composition. Analytical techniques for lipids typically require chemical derivatizations that are labor-intensive and increase sample preparation costs. This paper describes how to extract lipids from mammalian integument, separate broad lipid classes by thin-layer chromatography, and profile the triacylglyceride contents using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. This robust method enables a direct determination of the triacylglyceride profiles among species and individuals, and it can be readily applied to any taxonomic group of mammals. PMID:24056580

  1. Comparison of different remote sensing methods for mixing layer height monitoring

    NASA Astrophysics Data System (ADS)

    Emeis, Stefan; Schäfer, Klaus; Münkel, Christoph; Friedl, Roman; Suppan, Peter

    2010-10-01

    Since 2006 different remote monitoring methods for mixing layer height have been operated in Augsburg. One method is based on eye-safe commercial mini-lidar systems (ceilometers). The optical backscatter intensities recorded with these ceilometers provide information about the range-dependent aerosol concentration; gradient minima within this profile mark the tops of mixed layers. A special software for these ceilometers provides routine retrievals of lower atmosphere layering. A second method, based on SODAR (Sound Detection and Ranging) observations, detects the height of a turbulent layer characterized by high acoustic backscatter intensities due to thermal fluctuations and a high variance of the vertical velocity component. This information is extended by measurements with a RASS (Radio-Acoustic Sounding System) which provide the vertical temperature profile from the detection of acoustic signal propagation and thus temperature inversions which mark atmospheric layers. These SODAR and RASS data are the input to a software-based determination of mixing layer heights developed with MATLAB. A comparison of results of the three remote sensing methods during simultaneous measurements was performed. The information content of the ceilometer data is assessed by comparing it to the results from the other two instruments and near-by radiosonde data.

  2. HST STIS Observations of the Mixing Layer in the Cat’s Eye Nebula

    NASA Astrophysics Data System (ADS)

    Fang, Xuan; Guerrero, Martín A.; Toalá, Jesús A.; Chu, You-Hua; Gruendl, Robert A.

    2016-05-01

    Planetary nebulae (PNe) are expected to have a ˜105 K interface layer between the ≥slant 106 K inner hot bubble and the ˜104 K optical nebular shell. The PN structure and evolution, and the X-ray emission, depend critically on the efficiency of the mixing of material at this interface layer. However, neither its location nor its spatial extent have ever been determined. Using high-spatial resolution HST STIS spectroscopic observations of the N v λ λ 1239,1243 lines in the Cat’s Eye Nebula (NGC 6543), we have detected this interface layer and determined its location, extent, and physical properties for the first time in a PN. We confirm that this interface layer, as revealed by the spatial distribution of the N v λ1239 line emission, is located between the hot bubble and the optical nebular shell. We estimate a thickness of 1.5× {10}16 cm and an electron density of ˜200 cm-3 for the mixing layer. With a thermal pressure of ˜2 × 10-8 dyn cm-2, the mixing layer is in pressure equilibrium with the hot bubble and ionized nebular rim of NGC 6543. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. The observations are associated with program #12509.

  3. The daytime mixing layer observed by radiosonde, profiler, and lidar during MILAGRO

    NASA Astrophysics Data System (ADS)

    Shaw, W. J.; Pekour, M. S.; Coulter, R. L.; Martin, T. J.; Walters, J. T.

    2007-10-01

    During the MILAGRO campaign centered in the Mexico City area, Pacific Northwest National Laboratory (PNNL) and Argonne National Laboratory (ANL) operated atmospheric profiling systems at Veracruz and at two locations on the Central Mexican Plateau in the region around Mexico City. These systems included radiosondes, wind profilers, a sodar, and an aerosol backscatter lidar. An additional wind profiler was operated by the University of Alabama in Huntsville (UAH) at the Mexican Petroleum Institue (IMP) near the center of Mexico City. Because of the opportunity afforded by collocation of profilers, radiosondes, and a lidar, and because of the importance of boundary layer depth for aerosol properties, we have carried out a comparison of mixing layer depth as determined independently from these three types of measurement systems during the campaign. We have then used results of this comparison and additional measurements to develop a detailed description of the daily structure and evolution of the boundary layer on the Central Mexican Plateau during MILAGRO. Our analysis indicates that the profilers were more consistently successful in establishing the mixing layer depth during the daytime. The boundary layer growth was similar at the three locations, although the mixing layer tended to be slightly deeper in the afternoon in central Mexico City. The sodar showed that convection began about an hour after sunrise. Maximum daily mixing layer depths always reached 2000 m a.g.l. and frequently extended to 4000 m. The rate and variability of mixing layer growth was essentially the same as that observed during the IMADA-AVER campaign in the same season in 1997. This growth did not seem to be related to whether deep convection was reported on a given day. Wind speeds within the boundary layer exhibited a daily low-altitude maximum in the late afternoon with lighter winds aloft, consistent with previous reports of diurnal regional circulations. Norte events, which produced high

  4. A Hybrid Numerical Method for Turbulent Mixing Layers. Degree awarded by Case Western Reserve Univ.

    NASA Technical Reports Server (NTRS)

    Georgiadis, Nicholas J.

    2001-01-01

    A hybrid method has been developed for simulations of compressible turbulent mixing layers. Such mixing layers dominate the flows in exhaust systems of modern day aircraft and also those of hypersonic vehicles currently under development. The method configurations in which a dominant structural feature provides an unsteady mechanism to drive the turbulent development in the mixing layer. The hybrid method uses a Reynolds-averaged Navier-Stokes (RANS) procedure to calculate wall bounded regions entering a mixing section, and a Large Eddy Simulation (LES) procedure to calculate the mixing dominated regions. A numerical technique was developed to enable the use of the hybrid RANS-LES method on stretched, non-Cartesian grids. Closure for the RANS equations was obtained using the Cebeci-Smith algebraic turbulence model in conjunction with the wall-function approach of Ota and Goldberg. The wall-function approach enabled a continuous computational grid from the RANS regions to the LES region. The LES equations were closed using the Smagorinsky subgrid scale model. The hybrid RANS-LES method is applied to a benchmark compressible mixing layer experiment. Preliminary two dimensional calculations are used to investigate the effects of axial grid density and boundary conditions. Vortex shedding from the base region of a splitter plate separating the upstream flows was observed to eventually transition to turbulence. The location of the transition, however, was much further downstream than indicated by experiments. Actual LES calculations, performed in three spatial directions, also indicated vortex shedding, but the transition to turbulence was found to occur much closer to the beginning of the mixing section. which is in agreement with experimental observations. These calculations demonstrated that LES simulations must be performed in three dimensions. Comparisons of time-averaged axial velocities and turbulence intensities indicated reasonable agreement with experimental

  5. Mixed layer warming-deepening in the Mediterranean Sea and its effect on the marine environment

    NASA Astrophysics Data System (ADS)

    Rivetti, Irene; Boero, Ferdinando; Fraschetti, Simonetta; Zambianchi, Enrico; Lionello, Piero

    2015-04-01

    This work aims at investigating the evolution of the ocean mixed layer in the Mediterranean Sea and linking it to the occurrence of mass mortalities of benthic invertebrates. The temporal evolution of selected parameters describing the mixed layer and the seasonal thermocline is provided for the whole Mediterranean Sea for spring, summer and autumn and for the period 1945-2011. For this analysis all temperature profiles collected in the basin with bottles, Mechanical Bathy-Thermographs (MBT), eXpendable Bathy-Thermographs (XBT), and Conductivity-Temperature-Depth (CTD) have been used (166,990). These data have been extracted from three public sources: the MEDAR-MEDATLAS, the World Ocean Database 2013 and the MFS-VOS program. Five different methods for estimating the mixed layer depth are compared using temperature profiles collected at the DYFAMED station in the Ligurian Sea and one method, the so-called three-segment method, has been selected for a systematic analysis of the evolution of the uppermost part of the whole Mediterranean Sea. This method approximates the upper water column with three segments representing mixed layer, thermocline and deep layer and has shown to be the most suitable method for capturing the mixed layer depth for most shapes of temperature profiles. Mass mortalities events of benthic invertebrates have been identified by an extensive search of all data bases in ISI Web of Knowledge considering studies published from 1945 to 2011. Studies reporting the geographical coordinates, the timing of the events, the species involved and the depth at which signs of stress occurred have been considered. Results show a general increase of thickness and temperature of the mixed layer, deepening and cooling of the thermocline base in summer and autumn. Possible impacts of these changes are mass mortalities events of benthic invertebrates that have been documented since 1983 mainly in summer and autumn. It is also shown that most mass mortalities

  6. Evaluations of Threshold and Curvature Mixed Layer Depths by Various Mixing Schemes in the Mediterranean Sea

    DTIC Science & Technology

    2010-01-01

    Research 800 N . Quincy St. Arlington, VA 22217-5660 10. SPONSOR/MONITOR S ACRONYM(S) ONR 11. SPONSOR/MONITORS REPORT NUMBER(S) 12. DISTRIBUTION...longi- tude). Thus, the model has a resolution of 3.8 km at the southern regions (at approximately 32° N ) and 3.3 km at the northern lati- tudes (at...approximately 42° N ). Zonal and meridional array sizes are 1235 and 549. respectively. The model has 20 hybrid layers. The target density values (in

  7. Estimation of the mixing layer height over a high altitude site in Central Himalayan region by using Doppler lidar

    SciTech Connect

    Shukla, K. K.; Phanikumar, D. V.; Newsom, Rob K.; Kumar, Niranjan; Ratnam, Venkat; Naja, M.; Singh, Narendra

    2014-03-01

    A Doppler lidar was installed at Manora Peak, Nainital (29.4 N; 79.2 E, 1958 amsl) to estimate mixing layer height for the first time by using vertical velocity variance as basic measurement parameter for the period September-November 2011. Mixing layer height is found to be located ~0.57 +/- 0.1and 0.45 +/- 0.05km AGL during day and nighttime, respectively. The estimation of mixing layer height shows good correlation (R>0.8) between different instruments and with different methods. Our results show that wavelet co-variance transform is a robust method for mixing layer height estimation.

  8. [Mineralogy and genesis of mixed-layer clay minerals in the Jiujiang net-like red soil].

    PubMed

    Yin, Ke; Hong, Han-Lie; Li, Rong-Biao; Han, Wen; Wu, Yu; Gao, Wen-Peng; Jia, Jin-Sheng

    2012-10-01

    Mineralogy and genesis were investigated using X-ray diffraction (XRD), Fourier infrared absorption spectroscopy (FTIR) and high resolution transmission electron microscopy (HRTEM) to understand the mineralogy and its genesis significance of mixed-layer clay minerals in Jiujiang red soil section. XRD and FTIR results show that the net-like red soil sediments are composed of illite, kaolinite, minor smectite and mixed-layer illite-smectite and minor mixed-layer kaolinite-smectite. HRTEM observation indicates that some smectite layers have transformed into kaolinite layers in net-like red soil. Mixed-layer illite-smectite is a transition phase of illite transforming into smectite, and mixed-layer kaolinite-smectite is a transitional product relative to kaolinite and smectite. The occurrence of two mixed-layer clay species suggests that the weathering sequence of clay minerals in net-like red soil traversed from illite to mixed-layer illite-smectite to smectite to mixed-layer kaolinite-smectite to kaolinite, which indicates that net-like red soil formed under a warm and humid climate with strengthening of weathering.

  9. The Daytime Mixed Layer Observed by Radiosonde, Profiler, and LIDAR during MILAGRO

    SciTech Connect

    Shaw, William J.; Pekour, Mikhail S.; Coulter, Richard L.; Martin, Tim J.; Walters, Justin

    2007-10-19

    During the MILAGRO campaign centered in the Mexico City area, Pacific Northwest National Laboratory (PNNL) and Argonne National Laboratory (ANL) operated several atmospheric profiling systems at Veracruz and at two locations on the Central Mexican Plateau in the region around Mexico City. These systems included radiosondes, wind profilers, a sodar, and an aerosol backscatter lidar. An additional wind profiler was operated by the University of Alabama in Huntsville (UAH) at the Mexican Petroleum Institue (IMP) near the center of Mexico City. Because of the opportunity afforded by collocation of profilers, radiosondes, and a lidar, and because of the importance of boundary layer depth on aerosol properties, we have carried out a comparison of mixed layer depth as determined independently from these three types of measurement systems during the campaign. We have then used results of this comparison and additional measurements to develop a detailed description of the daily structure and evolution of the boundary layer on the Central Mexican Plateau during MILAGRO. Our analysis indicates that the profilers were more consistently successful in establishing the mixing layer depth during the daytime. The boundary layer growth was similar at the three locations, although the mixing layer tended to be slightly deeper in the afternoon in central Mexico City. The sodar showed that convection began about an hour after sunrise. Maximum daily mixed layer depths always reached 2000 m AGL and frequently extended to 4000 m. The rate and variability of mixing layer growth was essentially the same as that observed during the IMADA-AVER campaign in the same season in 1997. This growth did not seem to be related to whether deep convection was reported on a given day. Wind speeds within the boundary layer exhibited a daily low-altitude maximum in the late afternoon with lighter winds aloft, consistent with previous reports of diurnal regional circulations. Norte events, which produced

  10. Substantial energy input to the mesopelagic ecosystem from the seasonal mixed-layer pump

    PubMed Central

    Dall’Olmo, Giorgio; Dingle, James; Polimene, Luca; Brewin, Robert J.W.; Claustre, Hervé

    2016-01-01

    The “mesopelagic” is the region of the ocean between about 100 and 1000 m that harbours one of the largest ecosystems and fish stocks on the planet1,2. This vastly unexplored ecosystem is believed to be mostly sustained by chemical energy, in the form of fast-sinking particulate organic carbon, supplied by the biological carbon pump3. Yet, this supply appears insufficient to match mesopelagic metabolic demands4–6. The mixed-layer pump is a physically-driven biogeochemical process7–11 that could further contribute to meet these energetic requirements. However, little is known about the magnitude and spatial distribution of this process at the global scale. Here we show that the mixed-layer pump supplies an important seasonal flux of organic carbon to the mesopelagic. By combining mixed-layer depths from Argo floats with satellite retrievals of particulate organic carbon, we estimate that this pump exports a global flux of about 0.3 Pg C yr−1 (range 0.1 – 0.5 Pg C yr−1). In high-latitude regions where mixed-layers are deep, this flux is on average 23%, but can be greater than 100% of the carbon supplied by fast sinking particles. Our results imply that a relatively large flux of organic carbon is missing from current energy budgets of the mesopelagic. PMID:27857779

  11. Study of compressible mixing layers using filtered Rayleigh scattering based visualizations

    NASA Technical Reports Server (NTRS)

    Elliott, Gregory S.; Samimy, MO; Arnette, Stephen A.

    1992-01-01

    Filtered Rayleigh scattering-based flow visualizations of compressible mixing layers are reported. The lower compressibility case (Mc = 0.51) displays well-defined roller-type spanwise structures and streamwise streaks. The structures of the high compressibility case (Mc = 0.86) are more 3D and oblique.

  12. Mixed layer depth variations in the Kuroshio Extension in relation to Japanese sardine

    NASA Astrophysics Data System (ADS)

    Yasuda, I.; Nishikawa, H.; Itoh, S.

    2008-12-01

    Mixed layer depths in and south of the Kuroshio Extension changed from deep to shallow states in the late- 1980s and early-1990s. This change corresponded to the collapse of Japanese sardine (Sardinops melanostictus). This mixed layer shoaling was accompanied by lower temperature in 200-400m depths and higher temperature near the surface. Wintertime field survey in 2006 (Hakuho-maru KH06-1 cruise) demonstrated that late winter maximum mixed layer depth reach deeper with the greater isothermal depth of 14-15degC and higher temperature in 300-400m depth. High-resolution ocean model hindcast data suggests that the accelerated near-surface Kuroshio/Kuroshio Extension associated with the elevated sea-surface height anomaly enhanced the heat transport near the surface. This greater heat advection near the surface overrides the cooler subtropical mode water that was created in the previous years possibly causes the shallower winter mixed layer and collapse of the Japanese sardine.

  13. Significant mixed layer nitrification in a natural iron-fertilized bloom of the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Fripiat, F.; Elskens, M.; Trull, T. W.; Blain, S.; Cavagna, A.-J.; Fernandez, C.; Fonseca-Batista, D.; Planchon, F.; Raimbault, P.; Roukaerts, A.; Dehairs, F.

    2015-11-01

    Nitrification, the microbially mediated oxidation of ammonium into nitrate, is generally expected to be low in the Southern Ocean mixed layer. This paradigm assumes that nitrate is mainly provided through vertical mixing and assimilated during the vegetative season, supporting the concept that nitrate uptake is equivalent to the new primary production (i.e., primary production which is potentially available for export). Here we show that nitrification is significant (~40-80% of the seasonal nitrate uptake) in the naturally iron-fertilized bloom over the southeast Kerguelen Plateau. Hence, a large fraction of the nitrate-based primary production is regenerated, instead of being exported. It appears that nitrate assimilation (light dependent) and nitrification (partly light inhibited) are spatially separated between the upper and lower parts, respectively, of the deep surface mixed layers. These deep mixed layers, extending well below the euphotic layer, allow nitrifiers to compete with phytoplankton for the assimilation of ammonium. The high contributions of nitrification to nitrate uptake are in agreement with both low export efficiency (i.e., the percentage of primary production that is exported) and low seasonal nitrate drawdown despite high nitrate assimilation.

  14. Transient effects in unstable ablation fronts and mixing layers in HEDP

    NASA Astrophysics Data System (ADS)

    Clarisse, J.-M.; Gauthier, S.; Dastugue, L.; Vallet, A.; Schneider, N.

    2016-07-01

    We report results obtained for two elementary unstable flow configurations relevant to high energy density physics: the ablation front instability and the Rayleigh-Taylor -instability induced mixing layer. These two flows are characterized by a transience of their perturbation dynamics. In the ablative flow case, this perturbation dynamics transience takes the form of finite-durations of successive linear-perturbation evolution phases until reaching regimes of decaying oscillations. This behaviour is observed in various regimes: weakly or strongly accelerated ablation fronts, irradiation asymmetries or initial external-surface defects, and is a result of the mean-flow unsteadiness and stretching. In the case of the Rayleigh-Taylor-instability induced mixing layer, perturbation dynamics transience manifests itself through the extinction of turbulence and mixing as the flow reaches a stable state made of two stably stratified layers of pure fluids separated by an unstratified mixing layer. A second feature, also due to compressibility, takes the form of an intense acoustic wave production, mainly localized in the heavy fluid. Finally, we point out that a systematic short-term linear-perturbation dynamics analysis should be undertaken within the framework of non-normal stability theory.

  15. Revealing the Location of the Mixing Layer in a Hot Bubble

    NASA Astrophysics Data System (ADS)

    Guerrero, M. A.; Fang, X.; Chu, Y. H.; Toalá, J. A.; Gruendl, R. A.

    2017-03-01

    The fast stellar winds can blow bubbles in the circumstellar material ejected from previous phases of stellar evolution. These are found at different scales, from planetary nebulae (PNe) around stars evolving to the white dwarf stage, to Wolf-Rayet (WR) bubbles and up to large-scale bubbles around massive star clusters. In all cases, the fast stellar wind is shock-heated and a hot bubble is produced. At the mixing layer between the hot bubble and optical nebula, processes of mass evaporation and mixing of nebular material and heat conduction are key to determine the thermal structure of these bubbles and their evolution. In this contribution we review our current understanding of the X-ray observations of hot bubbles in PNe and present the first spatially-resolved study of a mixing layer in a PN.

  16. The three-dimensional evolution of a plane mixing layer - The Kelvin-Helmholtz rollup

    NASA Technical Reports Server (NTRS)

    Rogers, Michael M.; Moser, Robert D.

    1992-01-01

    The hydrodynamic evolution of an incompressible plane mixing layer is addressed to elucidate scalar mixing in free shear flows. A detailed description of the onset of three-dimensionality in a mixing layer before or in the absence of pairing is presented. Various simulations were performed to investigate the sensitivity of these results to variations in initial conditions. These variations included changes in amplitude, wavelength, functional form, and relative phasing of the initial low-wavenumber disturbances. Pierrehumber and Widnall's (1982) translative instability eigenfunctions are found to include rib vortices in the braid region and oppositely signed streamwise vorticity in the roller core. The translative instability is an instability of the late-time oversaturated flow. Three-dimensional perturbation growth similar to that of the translative instability can occur whenever spanwise vorticity is present in the braid region. The nonlinear effects that occur when the initial rib circulation is sufficiently high are discussed.

  17. Interobserver and intraobserver repeatability of lipid layer pattern evaluation by two experienced observers

    NASA Astrophysics Data System (ADS)

    García-Resúa, Carlos; Pena-Verdeal, Hugo; Lira, Madalena; Penedo, Manuel G.; Giráldez, Maria Jesús; Yebra-Pimentel, Eva

    2013-11-01

    The lipid layer plays a major role in limiting evaporation of the tear film. Based on interference phenomena, there is a test directed to lipid layer pattern (LLP) evaluation, but is affected by subjective interpretation of the patterns. The aim of this study is to compare the LLP evaluation between two experienced observers on a group of healthy patients. Furthermore, the observers re-evaluated the same images in order to check their individual repeatability. LLP was examined using a Tearscope-plus (Keeler, Windsor, UK) attached to a slit lamp. Tear film was recorded by a Topcon DV-3 digital camera video and LLP images were captured. This yielded 124 LLP images that were categorized (based on Guillon's schema) by two expert observers in two sessions separated by one month. Interobserver repeatability and intraobserver repeatability between both sessions were studied by using Cohen's kappa coefficient. Comparing LLP categorization between both observers, Cohen's kappa coefficient was 0.615 and 0.633 for first and second session, respectively. When comparing LLP categorization by the same observer between both sessions, Cohen's kappa coefficient was 0.770 and 0.812 for Observer 1 and Observer 2. These results indicate substantial correlation in all cases [range of 0.61-0.80]. The most frequent misinterpretations were between open and closed meshwork and Wave and closed meshwork patterns. Although substantial correlation was found between categorizations of experienced observers, misinterpretation of the patters may appear even in the same observer. Some misinterpretations between adjacent patterns could be palliated by including intermediate patterns between those categories.

  18. The potential flow bounded by a mixing layer and a solid surface

    NASA Astrophysics Data System (ADS)

    Wood, D. H.; Ferziger, J. H.

    1984-10-01

    The present investigation is a companion study to that of Wood and Bradshaw (1982), who measured the change in turbulence structure as the single-stream mixing layer approached that wind tunnnel floor. On the basis of spatial correlation measurements taken where the influence of the wall is small, Wood and Bradshaw concluded that the large turbulent eddies were essentially three-dimensional. In the present investigation it is shown that the extensions of Phillips's (1955) theory to include one-dimensional spectra and spatial correlations in the near-field potential flow provide an explanation for the large correlation scales, relative to the shear layer thickness, which have been measured outside turbulent mixing layers.

  19. Buoyant production and consumption of turbulence kinetic energy in cloud-topped mixed layers

    NASA Technical Reports Server (NTRS)

    Randall, D. A.

    1984-01-01

    It is pointed out that studies of the entraining planetary boundary layer (PBL) have generally emphasized the role of buoyancy fluxes in driving entrainment. The buoyancy flux is proportional to the rate of conversion of the potential energy of the mean flow into the kinetic energy of the turbulence. It is not unusual for conversion to proceed in both directions simultaneously. This occurs, for instance, in both clear and cloudy convective mixed layers which are capped by inversions. A partitioning of the net conversion into positive parts, generating turbulence kinetic energy (TKE), and negative parts (TKE-consuming), would make it possible to include the positive part in the gross production rate, and closure would be achieved. Three different approaches to partitioning have been proposed. The present investigation is concerned with a comparison of the three partitioning theories. Particular attention is given to the cloud-topped mixed layer because in this case the differences between two partitioning approaches are most apparent.

  20. Direct numerical simulations of a reacting mixing layer with chemical heat release

    NASA Technical Reports Server (NTRS)

    Mcmurtry, P. A.; Jou, W.-H.; Metcalfe, R. W.; Riley, J. J.

    1985-01-01

    In order to study the coupling between chemical heat release and fluid dynamics, direct numerical simulations of a chemically reacting mixing layer with heat release are performed. The fully compressible equations as well as an approximate set of equations that is asymptotically valid for low-Mach-number flows are treated. These latter equations have the computational advantage that high-frequency acoustic waves have been filtered out, allowing much larger time steps to be taken in the numerical solution procedure. A detailed derivation of these equations along with an outline of the numerical solution technique is given. Simulation results indicate that the rate of chemical product formed, the thickness of the mixing layer, and the amount of mass entrained into the layer all decrease with increasing rates of heat release.

  1. An Observational Study of Wind Profiles in the Baroclinic Convective Mixed Layer

    NASA Astrophysics Data System (ADS)

    Lemone, Margaret A.; Zhou, Mingyu; Moeng, Chin-Hoh; Lenschow, Donald H.; Miller, L. Jay; Grossman, Robert L.

    A comprehensive planetary boundary-layer (PBL) and synoptic data set is used to isolate the mechanisms that determine the vertical shear of the horizontal wind in the convective mixed layer. To do this, we compare a fair-weather convective PBL with no vertical shear through the mixed layer (10 March 1992), with a day with substantial vertical shear in the north-south wind component (27 February). The approach involves evaluating the terms of the budget equations for the two components of the vertical shear of the horizontal wind; namely: the time-rate-of-change or time-tendency term, differential advection, the Coriolis terms (a thermal wind term and a shear term), and the second derivative of the vertical transport of horizontal momentum with respect to height (turbulent-transport term). The data, gathered during the 1992 STorm-scale Operational and Research Meteorology (STORM) Fronts Experiments Systems Test (FEST) field experiment, are from gust-probe aircraft horizontal legs and soundings, 915-MHz wind profilers, a 5-cm Doppler radar, radiosondes, and surface Portable Automated Mesonet (PAM) stations in a roughly 50 × 50 km boundary-layer array in north-eastern Kansas, nested in a mesoscale-to-synoptic array of radiosondes and surface data.We present evidence that the shear on 27 February is related to the rapid growth of the convective boundary layer. Computing the shear budget over a fixed depth (the final depth of the mixed layer), we find that the time-tendency term dominates, reflecting entrainment of high-shear air from above the boundary layer. We suggest that shear within the mixed layer occurs when the time-tendency term is sufficiently large that the shear-reduction terms - namely the turbulent-transport term and differential advection terms - cannot compensate. In contrast, the tendency term is small for the slowly-growing PBL of 10 March, resulting in a balance between the Coriolis terms and the turbulent-transport term. Thus, the thermal wind

  2. Tear lipid layer thickness with eye drops in meibomian gland dysfunction

    PubMed Central

    Fogt, Jennifer S; Kowalski, Matthew J; King-Smith, P Ewen; Epitropolous, Alice T; Hendershot, Andrew J; Lembach, Carrie; Maszczak, John Paul; Jones-Jordan, Lisa A; Barr, Joseph T

    2016-01-01

    Purpose The aim of this study was to evaluate the efficacy of a lipid containing emollient eye drop, Soothe XP, which was reformulated in 2014 with a more stable preservative and buffer system, compared to a control, non-emollient, eye drop (Systane Ultra) in improving lipid layer thickness (LLT) in subjects with dry eye due to meibomian gland dysfunction (MGD). Patients and methods This prospective single-center, open-label, cross-over, examiner masked-study enrolled subjects aged 30–75 years with lipid-deficient dry eye and a clinical diagnosis of MGD as determined by a slit lamp examination, an evaluation of meibomian gland drop out with meibography, and a standard patient evaluation of eye dryness questionnaire of >5. Eligibility was then determined by a LLT of <75 nm at baseline and the inability to increase LLT ≥15 nm with three blinks, as determined by interferometric methods. Subjects were randomized to receive a single emollient or non-emollient eye drop at Visit 1 and were crossed over for the alternate treatment at Visit 2. At each visit, LLT was measured prior to and 15 minutes following the instillation of the assigned eye drop. The primary endpoint was the change in LLT from baseline. Results Subjects (n=40) were enrolled and 35 completed the two study arms. Mean (±SD) patient age was 55.7 years (10.9) and 69% were female. Mean (±SD) LLT at baseline was 49.5 nm (9.2). Instillation of Soothe XP resulted in an increase in LLT to 77.5 nm (29.3) 15 minutes following drop instillation, which is an increase of 28.0 nm (27.4) (P<0.001). In contrast, LLT 15 minutes after the instillation of Systane Ultra was 50.8 nm (14.1), which was not statistically significant when compared to the baseline LLT. Conclusion In this study of subjects with MGD, the emollient, or lipid containing eye drop, increased the LLT of tears when measured 15 minutes after instilling a single eye drop. PMID:27853352

  3. Biodiesel from mixed culture algae via a wet lipid extraction procedure.

    PubMed

    Sathish, Ashik; Sims, Ronald C

    2012-08-01

    Microalgae are a source of renewable oil for liquid fuels. However, costs for dewatering/drying, extraction, and processing have limited commercial scale production of biodiesel from algal biomass. A wet lipid extraction procedure was developed that was capable of extracting 79% of transesterifiable lipids from wet algal biomass (84% moisture) via acid and base hydrolysis (90 °C and ambient pressures), and 76% of those extracted lipids were isolated, by further processing, and converted to FAMEs. Furthermore, the procedure was capable of removing chlorophyll contamination of the algal lipid extract through precipitation. In addition, the procedure generated side streams that serve as feedstocks for microbial conversion to additional bioproducts. The capability of the procedure to extract lipids from wet algal biomass, to reduce/remove chlorophyll contamination, to potentially reduce organic solvent demand, and to generate feedstocks for high-value bioproducts presents opportunities to reduce costs of scaling up algal lipid extraction for biodiesel production.

  4. Growth rate of a shocked mixing layer with known initial perturbations [Mixing at shocked interfaces with known perturbations

    SciTech Connect

    Weber, Christopher R.; Cook, Andrew W.; Bonazza, Riccardo

    2013-05-14

    Here we derive a growth-rate model for the Richtmyer–Meshkov mixing layer, given arbitrary but known initial conditions. The initial growth rate is determined by the net mass flux through the centre plane of the perturbed interface immediately after shock passage. The net mass flux is determined by the correlation between the post-shock density and streamwise velocity. The post-shock density field is computed from the known initial perturbations and the shock jump conditions. The streamwise velocity is computed via Biot–Savart integration of the vorticity field. The vorticity deposited by the shock is obtained from the baroclinic torque with an impulsive acceleration. Using the initial growth rate and characteristic perturbation wavelength as scaling factors, the model collapses the growth-rate curves and, in most cases, predicts the peak growth rate over a range of Mach numbers (1.1 ≤Mi≤1.9), Atwood numbers (₋0.73 ≤ A ≤ ₋0.35 and 0.22 ≤ A ≤ 0.73), adiabatic indices (1.40/1.67≤γ12≤1.67/1.09) and narrow-band perturbation spectra. Lastly, the mixing layer at late times exhibits a power-law growth with an average exponent of θ=0.24.

  5. Shear, Stability and Mixing within the Ice-Shelf-Ocean Boundary Layer

    NASA Astrophysics Data System (ADS)

    Jenkins, Adrian

    2016-04-01

    Ocean-forced basal melting has been implicated in the widespread thinning of Antarctic ice shelves that has been causally linked with acceleration in the outflow of grounded ice. What determines the distribution and rates of basal melting and freezing beneath an ice shelf and how these respond to changes in the ocean temperature or circulation are therefore key questions. Recent years have seen major progress in our ability to observe basal melting and the ocean conditions that drive it, but data on the latter remain sparse, limiting our understanding of the key processes of ice-ocean heat transfer. In particular, we have no observations of current profiles through the buoyancy- and frictionally-controlled flows along the ice shelf base that drive mixing through the ice-ocean boundary layer. This presentation represents an attempt to address this gap in our knowledge through application of a very simple model of such boundary flows that considers only the spatial dimension perpendicular to the boundary. Initial results obtained with an unrealistic assumuption of constant eddy viscosity/diffusivity are nevertheless informative. For the buoyancy-driven flow two possible regimes exist: a weakly-stratified, geostrophic cross-slope current with an embedded Ekman layer, somewhat analogous to a conventional density current on a slope; or a strongly-stratified upslope jet with weak cross-slope flow, more analogous to an inverted katabatic wind. The latter is most appropriate when the ice-ocean interface is very steep, while for the gentle slopes typical of ice shelves the buoyant Ekman regime prevails. Introduction of a variable eddy viscosity/diffusivity derived from a local turbulence closure scheme modifies the current structure and stratification. There is a sharp step in properties across the surface layer, where the viscosity/diffusivity is low, weak gradients across the outer part of the boundary layer, where shear-driven mixing is strong, and a relatively strong

  6. Stratus: An interactive steady state mixed layer model for personal computers

    NASA Technical Reports Server (NTRS)

    Guinn, Thomas A.; Schubert, Wayne H.

    1990-01-01

    A steady-state, horizontally homogeneous, cloud-topped marine boundary layer model based primarily on the work of Lilly (1968) and Schubert et al., (1979) is presented. The conservative thermodynamic variables are equivalent potential temperature, theta(sub e), and total water mixing ratio, q + l. Some of the differences between this and Lilly's (1968) model are: radiation is allowed to penetrate into the boundary layer; cloud top values of longwave radiation, equivalent potential temperature, and water vapor mixing ratio are linear functions of height derived from climatological data at California coastal stations; and the closure assumption assumes a weighted average of Lilly's (1968) maximum and minimum entrainment theories. This model was programmed in FORTRAN and will run interactively on an IBM-compatible personal computer. The program allows the user to specify the geographical location, the wind speed, the sea-surface temperature, the large scale horizontal divergence, and the initial guess for cloud top height. Output includes the steady state values of cloud top and cloud base height, mixed layer equivalent potential temperature and total water mixing ratio, and the associated convective and radiative fluxes.

  7. Observed mesoscale eddy signatures in Southern Ocean surface mixed-layer depth

    NASA Astrophysics Data System (ADS)

    Hausmann, U.; McGillicuddy, Dennis J.; Marshall, John

    2017-01-01

    Combining satellite altimetry with Argo profile data a systematic observational estimate of mesoscale eddy signatures in surface mixed-layer depth (MLD) is provided across the Southern Ocean (SO). Eddy composite MLD anomalies are shallow in cyclones, deep in anticyclones, and increase in magnitude with eddy amplitude. Their magnitudes show a pronounced seasonal modulation roughly following the depth of the climatological mixed layer. Weak eddies of the relatively quiescent SO subtropics feature peak late-winter perturbations of ±10 m. Much larger MLD perturbations occur over the vigorous eddies originating along the Antarctic Circumpolar Current (ACC) and SO western boundary current systems, with late-winter peaks of -30 m and +60 m in the average over cyclonic and anticyclonic eddy cores (a difference of ≈ 100 m). The asymmetry between modest shallow cyclonic and pronounced deep anticyclonic anomalies is systematic and not accompanied by corresponding asymmetries in eddy amplitude. Nonetheless, the net deepening of the climatological SO mixed layer by this asymmetry in eddy MLD perturbations is estimated to be small (few meters). Eddies are shown to enhance SO MLD variability with peaks in late winter and eddy-intense regions. Anomalously deep late-winter mixed layers occur disproportionately within the cores of anticyclonic eddies, suggesting the mesoscale heightens the frequency of deep winter surface-mixing events along the eddy-intense regions of the SO. The eddy modulation in MLD reported here provides a pathway via which the oceanic mesoscale can impact air-sea fluxes of heat and carbon, the ventilation of water masses, and biological productivity across the SO.

  8. The structure of variable property, compressible mixing layers in binary gas mixtures

    NASA Technical Reports Server (NTRS)

    Kozusko, F.; Grosch, C. E.; Jackson, T. L.; Kennedy, Christipher A.; Gatski, Thomas B.

    1996-01-01

    We present the results of a study of the structure of a parallel compressible mixing layer in a binary mixture of gases. The gases included in this study are hydrogen (H2), helium (He), nitrogen (N2), oxygen (02), neon (Ne) and argon (Ar). Profiles of the variation of the Lewis and Prandtl numbers across the mixing layer for all thirty combinations of gases are given. It is shown that the Lewis number can vary by as much as a factor of eight and the Prandtl number by a factor of two across the mixing layer. Thus assuming constant values for the Lewis and Prandtl numbers of a binary gas mixture in the shear layer, as is done in many theoretical studies, is a poor approximation. We also present profiles of the velocity, mass fraction, temperature and density for representative binary gas mixtures at zero and supersonic Mach numbers. We show that the shape of these profiles is strongly dependent on which gases are in the mixture as well as on whether the denser gas is in the fast stream or the slow stream.

  9. Vorticity-production mechanisms in shock/mixing-layer interaction problems

    NASA Astrophysics Data System (ADS)

    Tritarelli, R. C.; Kleiser, L.

    2017-03-01

    In this study, we investigate analytically the importance of different vorticity-production mechanisms contributing to the shock-induced vorticity caused by the interaction of a steady oblique shock wave with a steady, planar, supersonic, laminar mixing layer. The inviscid analysis is performed under the condition of a supersonic post-shock flow, which guarantees that the shock refraction remains regular. Special attention is paid to the vorticity production induced by a change in shock strength along the shock. Our analysis subdivides the total vorticity production into its contributions due to bulk or volumetric compression, pre-shock density gradients and variable shock strength. The latter is the only contribution dependent on the shock-wave curvature. The magnitudes of these contributions are analysed for two limiting cases, i.e., the interaction of an oblique shock wave with a constant-density shear layer and the interaction with a constant-velocity mixing layer with density gradients only. Possible implications for shock/mixing-layer interactions occurring in scramjet combustors are briefly discussed.

  10. The convection of large and intermediate scale fluctuations in a turbulent mixing layer

    NASA Astrophysics Data System (ADS)

    Buxton, O. R. H.; de Kat, R.; Ganapathisubramani, B.

    2013-12-01

    The convection velocity of large and intermediate scale velocity fluctuations in a nominally two-dimensional planar mixing layer, and its dependence upon the length scale, is explored by carrying out particle image velocimetry (PIV) experiments. A "global" convection velocity, containing the convection of all the length scales present in the flow, is produced by examining the autocorrelation functions between velocity fluctuations in successive PIV records across the mixing layer. This "global" convection velocity is found to be similar to the mean flow, although fluctuations on the low speed side of the mixing layer on average convect at speeds greater than the mean and fluctuations on the high speed side of the mixing layer are observed to convect at speeds less than the mean. Scale specific convection velocity profiles are then produced by examining the phase difference between the spectral content specific to one wavenumber in streamwise velocity fluctuation traces in successive PIV records, offset by time τ. Probability density functions (pdfs) are produced of this phase difference, which is subsequently converted into a convection displacement, and these show that the convection of single length scale fluctuations exhibits a significant variance, particularly so for larger scale fluctuations and in the high speed side of the mixing layer. Convection velocity profiles are produced from these pdfs using both the mean convection distance and the modal convection distance. It is observed that the convection velocity is relatively insensitive to the length scale of the fluctuations considered, particularly when the mean convection distance is used. A slight sensitivity to length scale is, however, observed for convection velocities based on the modal convection distance. This dependence is primarily observed in the high speed side of the mixing layer, in which smaller length-scale fluctuations convect more quickly than larger length-scale fluctuations. It is also

  11. Control of shock wave-boundary layer interactions by bleed in supersonic mixed compression inlets

    NASA Technical Reports Server (NTRS)

    Fukuda, M. K.; Hingst, W. G.; Reshotko, E.

    1975-01-01

    An experimental investigation was conducted to determine the effect of bleed on a shock wave-boundary layer interaction in an axisymmetric mixed-compression supersonic inlet. The inlet was designed for a free-stream Mach number of 2.50 with 60-percent supersonic internal area contraction. The experiment was conducted in the NASA Lewis Research Center 10-Foot Supersonic Wind Tunnel. The effects of bleed amount and bleed geometry on the boundary layer after a shock wave-boundary layer interaction were studied. The effect of bleed on the transformed form factor is such that the full realizable reduction is obtained by bleeding of a mass flow equal to about one-half of the incident boundary layer mass flow. More bleeding does not yield further reduction. Bleeding upstream or downstream of the shock-induced pressure rise is preferable to bleeding across the shock-induced pressure rise.

  12. a Novel pt and Npt Mixed Igbt Having a New n-BUFFER Layer

    NASA Astrophysics Data System (ADS)

    Zhang, Fei; Luo, Shuhua; Zhang, Liang; Wang, Wei; Yu, Wen; Li, Chengfang; Sun, Xiaowei

    For the first time, a novel mixed insulated gate bipolar transistor (MIGBT) is proposed and verified by two-dimensional (2D) mixed device-circuit simulations. The structure of the proposed device is almost identical with that of the conventional IGBT, except for the buffer layer which is formed by employing the n+/n- structure, so that the trade-off relation between the conduction and switching losses is greatly improved and efficiently decoupled. Furthermore, the proposed device exhibits larger forward blocking voltage and positive temperature coefficient of the forward voltage drop, facilitating parallel integration.

  13. Aerosol black carbon characteristics over Central India: Temporal variation and its dependence on mixed layer height

    NASA Astrophysics Data System (ADS)

    Kompalli, Sobhan Kumar; Babu, S. Suresh; Moorthy, K. Krishna; Manoj, M. R.; Kumar, N. V. P. Kiran; Shaeb, K. Hareef Baba; Joshi, Ashok Kumar

    2014-10-01

    In a first of its kind study over the Indian region, concurrent and extensive measurements of black carbon (BC) concentration and atmospheric boundary layer parameters are used to quantify the role of atmospheric boundary layer in producing temporal changes in BC. During this study, 18 months (2011-12) data of continuous measurements of BC aerosols, made over a semi-urban location, Nagpur, in Central India are used along with concurrent measurements of vertical profiles of atmospheric thermodynamics, made using weekly ascents of GPS aided Radiosonde for a period of 1 year. From the balloon data, mixed layer heights and ventilation coefficients are estimated, and the monthly and seasonal changes in BC mass concentration are examined in the light of the boundary layer changes. Seasonally, the BC mass concentration was highest (~ 4573 ± 1293 ng m- 3) in winter (December-February), and lowest (~ 1588 ± 897 ng m- 3) in monsoon (June-September), while remained moderate (~ 3137 ± 1446 ng m- 3) in pre-monsoon (March-May), and post-monsoon (~ 3634 ± 813 ng m- 3) (October-November) seasons. During the dry seasons, when the rainfall is scanty or insignificantly small, the seasonal variations in BC concentrations have a strong inverse relationship with mixed layer height and ventilation coefficient. However, the lowest BC concentrations do not occur during the season when the mixed layer height (MLH) is highest or the ventilation coefficient is the highest; rather it occurs when the rainfall is strong (during summer monsoon season) and airmass changes to primarily of marine origin.

  14. Mixed-layer kaolinite-montmorillonite from the Yucatan Peninsula, Mexico

    USGS Publications Warehouse

    Schultz, L.G.; Shepard, A.O.; Blackmon, P.D.; Starkey, H.C.

    1971-01-01

    Clay beds 1-2 m thick and interbedded with marine limestones probably of early Eocene age are composed of nearly pure mixed-layer kaolinite-montmorillonite. Particle size studies, electron micrographs, X-ray diffraction studies, chemical analyses, cation exchange experiments, DTA, and TGA indicate that clays from three different localities contain roughly equal proportions of randomly interlayered kaolinite and montmorillonite layers. The montmorillonite structural formulas average K0??2Na0??2Ca0??2Mg0??2(Al2??5Fe1??03+Mg0??5)(Al0??75Si7??25)O20+(OH)4-, with a deficiency of structural (OH) in either the montmorillonite or kaolinite layers. Nonexchangeable K+ indicates that a few layers are mica-like. Crystals are mostly round plates 1 10 to 1 20 ?? across. The feature most diagnostic of the mixed-layer character is an X-ray reflection near 8 A?? after heating at 300 ??C. The clays are inferred to have developed by weathering of volcanic ash and subsequent erosion and deposition in protected nearshore basins. ?? 1971.

  15. Mixed-layer kerolite/stevensite from the Amargosa Desert, Nevada.

    USGS Publications Warehouse

    Eberl, D.D.; Jones, B.F.; Khoury, H.N.

    1982-01-01

    Mixed-layer clays of randomly interstratified kerolite/stevensite occur as an abundant mineral in lake and/or spring deposits of probable Pliocene and Pleistocene age in the Amargosa Desert of S Nevada, USA. Kerolite is a trioctahedral mineral similar to talc, but with a basal spacing of approx 9.65 A (cf. talc at 9.38 A). The data suggest that talc, kerolite and stevensite may form a continuous structural series based on layer charge. (Following abstract) -D.F.B.

  16. Numerical implementation of the mixed potential integral equation for planar structures with ferrite layers arbitrarily magnetized

    NASA Astrophysics Data System (ADS)

    Mesa, F.; Medina, F.

    2006-12-01

    This work presents a new implementation of the mixed potential integral equation (MPIE) for planar structures that can include ferrite layers arbitrarily magnetized. The implementation of the MPIE here reported is carried out in the space domain. Thus it will combine the well-known numerical advantages of working with potentials as well as the flexibility for analyzing nonrectangular shape conductors with the additional ability of including anisotropic layers of arbitrarily magnetized ferrites. In this way, our approach widens the scope of the space domain MPIE and sets this method as a very efficient and versatile numerical tool to deal with a wide class of planar microwave circuits and antennas.

  17. Control of shock-wave boundary-layer interactions by bleed in supersonic mixed compression inlets

    NASA Technical Reports Server (NTRS)

    Fukuda, M. K.; Reshotko, E.; Hingst, W. R.

    1975-01-01

    An experimental investigation has been conducted to determine the effect of bleed region geometry and bleed rate on shock wave-boundary layer interactions in an axisymmetric, mixed-compression inlet at a Mach number of 2.5. The full realizable reduction in transformed form factor is obtained by bleeding off about half the incident boundary layer mass flow. Bleeding upstream or downstream of the shock-induced pressure rise is preferable to bleeding across the shock-induced pressure rise. Slanted holes are more effective than normal holes. Two different bleed hole sizes were tested without detectable difference in performance.

  18. The design of naproxen solid lipid nanoparticles to target skin layers.

    PubMed

    Akbari, Jafar; Saeedi, Majid; Morteza-Semnani, Katayoun; Rostamkalaei, Seyyed Sohrab; Asadi, Masoumeh; Asare-Addo, Kofi; Nokhodchi, Ali

    2016-09-01

    The aim of the current investigation was to produce naproxen solid lipid nanoparticles (Nap-SLNs) by the ultrasonication method to improve its skin permeation and also to investigate the influence of Hydrophilic-lipophilic balance (HLB) changes on nanoparticles properties. The properties of obtained SLNs loaded with naproxen were characterized by photon correlation spectroscopy (PCS), transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). FT-IR was also used to investigate any interaction between naproxen and the excipients used at the molecular level during the preparation of the SLNs. The performance of the formulations was investigated in terms of skin permeation and also the retention of the drug by the skin. It was found that generally, with increasing the lipid concentration, the average particle size and polydispersity index (PDI) of SLNs increased from 94.257±4.852nm to 143.90±2.685nm and from 0.293±0.037 to 0.525±0.038 respectively. The results also showed that a reduction in the HLB resulted in an increase in the PDI, particle size, zeta potential and entrapment efficiency (EE%). DSC showed that the naproxen encapsulated in the SLNs was in its amorphous form. The peaks of prominent functional groups of naproxen were found in the FT-IR spectra of naproxen-SLN, which confirmed the entrapment of naproxen in the lipid matrix. FT-IR results also ruled out any chemical interaction between drug and the chemicals used in the preparation of SLNs. The amount of naproxen detected in the receptor chamber at all the sampling times for the reference formulation (naproxen solution containing all surfactants at pH 7.4) was higher than that of the Nap-SLN8 formulation. Nap-SLN8 showed an increase in the concentration of naproxen in the skin layer with less systemic absorption. This indicates that most of the drug in Nap-SLN8 remains in the skin which can reduce the side effect of systemic absorption of the drug and increases the

  19. A theoretical study of mixing downstream of transverse injection into a supersonic boundary layer

    NASA Technical Reports Server (NTRS)

    Baker, A. J.; Zelazny, S. W.

    1972-01-01

    A theoretical and analytical study was made of mixing downstream of transverse hydrogen injection, from single and multiple orifices, into a Mach 4 air boundary layer over a flat plate. Numerical solutions to the governing three-dimensional, elliptic boundary layer equations were obtained using a general purpose computer program. Founded upon a finite element solution algorithm. A prototype three-dimensional turbulent transport model was developed using mixing length theory in the wall region and the mass defect concept in the outer region. Excellent agreement between the computed flow field and experimental data for a jet/freestream dynamic pressure ratio of unity was obtained in the centerplane region of the single-jet configuration. Poorer agreement off centerplane suggests an inadequacy of the extrapolated two-dimensional turbulence model. Considerable improvement in off-centerplane computational agreement occured for a multi-jet configuration, using the same turbulent transport model.

  20. Asymptotic solution of the turbulent mixing layer for velocity ratio close to unity

    NASA Technical Reports Server (NTRS)

    Higuera, F. J.; Jimenez, J.; Linan, A.

    1996-01-01

    The equations describing the first two terms of an asymptotic expansion of the solution of the planar turbulent mixing layer for values of the velocity ratio close to one are obtained. The first term of this expansion is the solution of the well-known time-evolving problem and the second, which includes the effects of the increase of the turbulence scales in the stream-wise direction, obeys a linear system of equations. Numerical solutions of these equations for a two-dimensional reacting mixing layer show that the correction to the time-evolving solution may explain the asymmetry of the entrainment and the differences in product generation observed in flip experiments.

  1. Inviscid spatial stability of a compressible mixing layer. Part 2: The flame sheet model

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

    The results of an inviscid spatial calculation for a compressible reacting mixing layer are reported. The limit of infinitive activation energy is taken and the diffusion flame is approximated by a flame sheet. Results are reported for the phase speeds of the neutral waves and maximum growth rates of the unstable waves as a function of the parameters of the problem: the ratio of the temperature of the stationary stream to that of the moving stream, the Mach number of the moving streams, the heat release per unit mass fraction of the reactant, the equivalence ratio of the reaction, and the frequency of the disturbance. These results are compared to the phase speeds and growth rates of the corresponding nonreacting mixing layer. We show that the addition of combustion has important, and complex effects on the flow stability.

  2. Crossover between two- and three-dimensional turbulence in spatial mixing layers

    NASA Astrophysics Data System (ADS)

    Biancofiore, Luca

    2016-11-01

    We investigate how the domain depth affects the turbulent behaviour in spatially developing mixing layers by means of large-eddy simulations (LES) based on a spectral vanishing viscosity technique. Analyses of spectra of the vertical velocity, of Lumley's diagrams, of the turbulent kinetic energy and of the vortex stretching show that a two-dimensional behaviour of the turbulence is promoted in spatial mixing layers by constricting the fluid motion in one direction. This finding is in agreement with previous works on turbulent systems constrained by a geometric anisotropy, pioneered by Smith, Chasnov & Waleffe. We observe that the growth of the momentum thickness along the streamwise direction is damped in a confined domain. A full two-dimensional turbulent behaviour is observed when the momentum thickness is of the same order of magnitude as the confining scale.

  3. On the Interaction of Buoyant Plumes With Ocean Mixed-Layer Fronts (Invited)

    NASA Astrophysics Data System (ADS)

    Ozgokmen, T. M.; Fischer, P. F.

    2010-12-01

    The ocean's surface mixed layer is notoriously complex due to high spatial and temporal gradients of density and velocity fields. The understanding and modeling of such flows have a wide range of applications. For instance, anomalous currents and density perturbations in the acoustic and optical environment can affect a variety of naval operations. These flows can also influence strongly the dispersion of surface and sub-surface pollutants. Large eddy simulations of an idealized mixed-layer problem are conducted using a non-hydrostatic spectral element model. Sampling strategies of these fields are investigated using passive tracers and Lagrangian particles. These idealized fields are then used in order to explore the behavior of a buoyant plume through the water column, namely its surface and sub-surface dispersion, which is motivated by the Deepwater Horizon oil spill.

  4. On the Interaction of Buoyant Plumes With Ocean Mixed-Layer Fronts

    NASA Astrophysics Data System (ADS)

    Özgökmen, Tamay

    2010-11-01

    The ocean's surface mixed layer is notoriously complex due to high spatial and temporal gradients of density and velocity fields. The understanding and modeling of such flows have a wide range of applications. For instance, anomalous currents and density perturbations in the acoustic and optical environment can affect a variety of naval operations. These flows can also influence strongly the dispersion of surface and sub-surface pollutants. Large eddy simulations of an idealized mixed-layer problem are conducted using the spectral element model Nek5000. Sampling strategies of these fields are investigated using passive tracers and Lagrangian particles. These idealized fields are then used in order to explore the behavior of a buoyant plume through the water column, namely its surface and sub-surface dispersion, which is motivated by the Deepwater Horizon oil spill.

  5. Simulation of mixed-host emitting layer based organic light emitting diodes

    NASA Astrophysics Data System (ADS)

    Riku, C.; Kee, Y. Y.; Ong, T. S.; Yap, S. S.; Tou, T. Y.

    2015-04-01

    `SimOLED' simulator is used in this work to investigate the efficiency of the mixed-host organic light emitting devices (MH-OLEDs). Tris-(8-hydroxyquinoline) aluminum(3) (Alq3) and N,N-diphenyl-N,N-Bis(3-methylphenyl)-1,1-diphenyl-4,4-diamine (TPD) are used as the electron transport layer (ETL) material and hole transport layer (HTL) material respectively, and the indium-doped tin oxide (ITO) and aluminum (Al) as anode and cathode. Three MH-OLEDs, A, B and C with the same structure of ITO / HTM (15 nm) / Mixed host (70 nm) / ETM (10 nm) /Al, are stimulated with ratios TPD:Alq3 of 3:5, 5:5, and 5:3 respectively. The Poole-Frenkel model for electron and hole mobilities is employed to compute the current density-applied voltage-luminance characteristics, distribution of the electric field, carrier concentrations and recombination rate.

  6. Mixed-layered bismuth-oxygen-iodine materials for capture and waste disposal of radioactive iodine

    SciTech Connect

    Krumhansl, James L; Nenoff, Tina M

    2013-02-26

    Materials and methods of synthesizing mixed-layered bismuth oxy-iodine materials, which can be synthesized in the presence of aqueous radioactive iodine species found in caustic solutions (e.g. NaOH or KOH). This technology provides a one-step process for both iodine sequestration and storage from nuclear fuel cycles. It results in materials that will be durable for repository conditions much like those found in Waste Isolation Pilot Plant (WIPP) and estimated for Yucca Mountain (YMP). By controlled reactant concentrations, optimized compositions of these mixed-layered bismuth oxy-iodine inorganic materials are produced that have both a high iodine weight percentage and a low solubility in groundwater environments.

  7. Mixed-layered bismuth--oxygen--iodine materials for capture and waste disposal of radioactive iodine

    SciTech Connect

    Krumhansl, James L; Nenoff, Tina M

    2015-01-06

    Materials and methods of synthesizing mixed-layered bismuth oxy-iodine materials, which can be synthesized in the presence of aqueous radioactive iodine species found in caustic solutions (e.g. NaOH or KOH). This technology provides a one-step process for both iodine sequestration and storage from nuclear fuel cycles. It results in materials that will be durable for repository conditions much like those found in Waste Isolation Pilot Plant (WIPP) and estimated for Yucca Mountain (YMP). By controlled reactant concentrations, optimized compositions of these mixed-layered bismuth oxy-iodine inorganic materials are produced that have both a high iodine weight percentage and a low solubility in groundwater environments.

  8. Fabrication of fracture-free nanoglassified substrates by layer-by-layer deposition with a paint gun technique for real-time monitoring of protein-lipid interactions.

    PubMed

    Linman, Matthew J; Culver, Sean P; Cheng, Quan

    2009-03-03

    New sensing materials that are robust, biocompatible, and amenable to array fabrication are vital to the development of novel bioassays. Herein we report the fabrication of ultrathin (ca. 5-8 nm) glass (silicate) layers on top of a gold surface for surface plasmon resonance (SPR) biosensing applications. The nanoglass layers are fabricated by layer-by-layer (LbL) deposition of poly(allylamine) hydrochloride (PAH) and sodium silicate (SiO(x)), followed by calcination at high temperature. To deposit these layers in a uniform and reproducible manner, we employed a high-volume, low-pressure (HVLP) paint gun technique that offers high precision and better control through pressurized nitrogen gas. The new substrates are stable in solution for a long period of time, and scanning electron microscopy (SEM) images confirm that these films are nearly fracture-free. In addition, atomic force microscopy (AFM) indicates that the surface roughness of the silicate layers is low (rms = 2 to 3 nm), similar to that of bare glass slides. By tuning the experimental parameters such as HVLP gun pressure and layers deposited, different surface morphology could be obtained as revealed by fluorescence microscopy and SEM images. To demonstrate the utility of these ultrathin, fracture-free substrates, lipid bilayer membranes composed of phosphorylated derivatives of phosphoinositides (PIs) were deposited on the new substrates for biosensing applications. Fluorescence recovery after photobleaching (FRAP) data indicated that these lipid components in the membranes were highly mobile. Furthermore, interactions of PtdIns(4,5)P2 and PtdIns(4)P lipids with their respective binding proteins were detected with high sensitivity by using SPR spectroscopy. This method of glass deposition can be combined with already well-developed surface chemistry for a range of planar glass assay applications, and the process is amenable to automation for mass production of nanometer thick silicate chips in a highly

  9. Divalent cation-induced lipid mixing between phosphatidylserine liposomes studied by stopped-flow fluorescence measurements: effects of temperature, comparison of barium and calcium, and perturbation by DPX.

    PubMed

    Walter, A; Siegel, D P

    1993-04-06

    To understand the mechanism of membrane fusion, it is important to study the processes that mix the lipids of two apposed membranes. We measured the rates of divalent cation-induced aggregation and lipid mixing of bovine brain phosphatidylserine (BBPS) LUV, using light scattering and a resonance energy transfer assay. The lipid and divalent cation solutions were combined by stopped-flow mixing, which permitted measuring the half-times of aggregation and lipid mixing between pairs of liposomes. The collisional quencher DPX [p-xylene-bis(pyridinium bromide)], used in a liposome contents-mixing assay, lowered the main transition temperature (Tm) of BBPS by about 10 degrees C and decreased the temperature threshold for lipid mixing. Since DPX was inside the liposomes for the latter measurements, this implies that perturbations to the inner monolayer affect the reactivity of the liposome. When palmitoyl-oleoyl-PS (POPS) was substituted for BBPS, little or no lipid mixing occurred. Ca(2+)- and Ba(2+)-induced BBPS aggregation and lipid mixing were compared as a function of temperature and divalent cation concentration. Aggregation rates were nearly insensitive to temperature and correlated with the percent of PS bound to either Ba2+ or Ca2+. Above Tm, lipid-mixing rates increased with the Ba2+ and Ca2+ concentrations and temperature, even above the Tm of the Ba2+/PS complex. Arrhenius plots were linear for both ions. The temperature dependence was greater for Ca(2+)- than Ba(2+)-induced reactions, and the slopes were independent of divalent cation concentration. When equivalent fractions of PS were bound with divalent cation at, and above, 20 degrees C, the lipid-mixing rate was greater with Ca2+ than with Ba2+. The faster rate may reflect greater activation entropies and/or greater attempt frequencies at one or more steps in the Ca(2+)-induced process. We conclude that stopped-flow mixing permits better characterization of initial interaction between liposomes, that

  10. The sensitivity of subannual and intraseasonal tropical variability to model ocean mixed layer depth

    NASA Astrophysics Data System (ADS)

    Watterson, I. G.

    2002-01-01

    The influence of air-sea interaction on subannual and intraseasonal tropical variability is explored through analysis of three long simulations of the Commonwealth Scientific and Industrial Research Organisation atmospheric general circulation model (GCM) with differing ocean specifications: a coupled ocean GCM, a simple 50-m mixed layer model, or climatological sea surface temperatures (SST); together with 50-year simulations with mixed layer depths of 10 m and 20 m. The analysis focuses initially on a signal similar to a Madden-Julian Oscillation (MJO) contained in the first two empirical orthogonal functions (EOF) of monthly anomalies of tropical 807-hPa winds in January in the coupled model. Time-lag regression is used to demonstrate that these patterns propagate eastward, although at only half the speed of the MJO, and induce perturbations to the Australian monsoon. The specified SST model shows no such propagation. Similar results are then obtained using daily data filtered to retain subannual periods. The eastward propagation speed is faster in the shallower mixed layer cases, with the 10-m case producing speeds close to observations. In the interactive models, surface energy fluxes force SST anomalies propagating ahead of the EOF convergence. These fluxes are largely consistent with evaporation perturbed by wind anomalies to the monsoon westerlies, augmented by solar radiation. The SST anomalies then further perturb the winds, as is confirmed by a separate SST perturbation experiment. From the examination of other seasons, it is seen that air-sea interaction generally enhances the amplitude of the MJO-like patterns. It also enhances their eastward propagation along westerly wind bands. Analysis of zonal wave number one winds confirms the strong sensitivity to mixed layer depth in the amplitude and period of the eastward propagating component, particularly during September through February. The results suggest that air-sea interaction may be important to the

  11. The Impact of Iron-induced Phytoplankton Blooms on the Heat Budget of the Mixed Layer

    NASA Astrophysics Data System (ADS)

    Strutton, P. G.; Chavez, F. P.; Barber, R. T.

    2002-12-01

    Heating of the oceanic mixed layer is influenced by (1) its biogenic content, (2) the magnitude of the incoming solar radiation and (3) the mixed layer depth. The Southern Ocean Iron Experiment (SOFeX), conducted in early 2002, generated two mesoscale phytoplankton blooms with chlorophyll concentrations at least 10-fold higher than background. The heating effect due to increased attenuation of solar radiation by these blooms was quantified using (1) direct, in situ measurements of the diffuse attenuation coefficient of photosynthestically available radiation (KPAR), and (2) an empirical relationship between chlorophyll concentration and KPAR. Preliminary results indicate that the blooms contributed an additional 2 to 3 W m-2 to the heat budget of the mixed layer - an increase of approximately 2% which would have penetrated into the deeper ocean in the absence of the SOFeX blooms. Given the significance of the Southern Ocean to global climate, and the suggestion that large scale iron fertilization could be employed as a greenhouse mitigation tool, it is important that the heating effects of iron-induced blooms are accurately quantified. This presentation will describe the biologically-mediated heating rates resulting from both the SOFeX blooms and hypothetical large-scale fertilization events, and contrast them with (1) the observed temperature changes during SOFeX and (2) the non-biological terms in the mixed layer heat budget such as wind-induced cooling at the surface. Ultimately, these calculations could be compared with the percieved cooling effect of removing carbon dioxide from the atmosphere.

  12. An experimental study of curved mixing layers: Flow visualization using volume rendering

    NASA Technical Reports Server (NTRS)

    Karasso, Paris S.; Mungal, M. G.

    1991-01-01

    The existence and importance of large-scale spanwise vortical structures for 2-D straight mixing layers has been well documented in the last decade. Computer models and simulations have sought to reproduce these vortical structures associated with the Kelvin-Helmholtz (K-H) instability mode which is due to the shear per se. Secondary streamwise vortical structures for the same flows were also seen experimentally and have recently been given importance in computational efforts. Curved mixing layers can be characterized as stable (the high-speed stream is placed on the outside of the longitudinal bend), leading to a suppression of the Taylor-Gortler (T-G) instability, and unstable (high-speed stream on the inside of the bend), leading to an enhancement of the T-G instability. The T-G instability is associated with the centripetal acceleration that the curvature imparts. Thus, curvature superimposed on 2-D shear layer flows provides a way for studying the importance of streamwise vorticity, its competition with spanwise vorticity, and changes to entrainment and mixing. Furthermore, the outcome of the competition of a relatively enhanced or suppressed T-G instability with the K-H instability offers the possibility of achieving passive mixing enhancement. As a first step in understanding the competition between the K-H and the T-G instabilities and the resulting changes to the structure of the flow, highly resolved visualizations of the flow structure for the stable and the unstable configurations are provided. The straight layer is also visualized for comparison with earlier works.

  13. Using dissolved oxygen concentrations to determine mixed layer depths in the Bellingshausen Sea

    NASA Astrophysics Data System (ADS)

    Castro-Morales, K.; Kaiser, J.

    2012-01-01

    Concentrations of oxygen (O2) and other dissolved gases in the oceanic mixed layer are often used to calculate air-sea gas exchange fluxes. The mixed layer depth (zmix) may be defined using criteria based on temperature or density differences to a reference depth near the ocean surface. However, temperature criteria fail in regions with strong haloclines such as the Southern Ocean where heat, freshwater and momentum fluxes interact to establish mixed layers. Moreover, the time scales of air-sea exchange differ for gases and heat, so that zmix defined using oxygen may be different than zmix defined using temperature or density. Here, we propose to define an O2-based mixed layer depth, zmix(O2), as the depth where the relative difference between the O2 concentration and a reference value at a depth equivalent to 10 dbar equals 0.5 %. This definition was established by analysis of O2 profiles from the Bellingshausen Sea (west of the Antarctic Peninsula) and corroborated by visual inspection. Comparisons of zmix(O2) with zmix based on potential temperature differences, i.e., zmix(0.2 °C) and zmix(0.5 °C), and potential density differences, i.e., zmix(0.03 kg m-3) and zmix(0.125 kg m-3), showed that zmix(O2) closely follows zmix(0.03 kg m-3). Further comparisons with published zmix climatologies and zmix derived from World Ocean Atlas 2005 data were also performed. To establish zmix for use with biological production estimates in the absence of O2 profiles, we suggest using zmix(0.03 kg m-3), which is also the basis for the climatology by de Boyer Montégut et al. (2004).

  14. Helicity in Supercritical O2/H2 and C7H16/N2 Mixing Layers

    NASA Technical Reports Server (NTRS)

    Okongo, Nora; Bellan, Josette

    2004-01-01

    This report describes a study of databases produced by direct numerical simulation of mixing layers developing between opposing flows of two fluids under supercritical conditions, the purpose of the study being to elucidate chemical-species-specific aspects of turbulence, with emphasis on helicity. The simulations were performed for two different fluid pairs -- O2/H2 and C7H16/N2 -- at similar values of reduced pressure.

  15. Shear rheology of mixed protein adsorption layers vs their structure studied by surface force measurements.

    PubMed

    Danov, Krassimir D; Kralchevsky, Peter A; Radulova, Gergana M; Basheva, Elka S; Stoyanov, Simeon D; Pelan, Eddie G

    2015-08-01

    The hydrophobins are proteins that form the most rigid adsorption layers at liquid interfaces in comparison with all other investigated proteins. The mixing of hydrophobin HFBII with other conventional proteins is expected to reduce the surface shear elasticity and viscosity, E(sh) and η(sh), proportional to the fraction of the conventional protein. However, the experiments show that the effect of mixing can be rather different depending on the nature of the additive. If the additive is a globular protein, like β-lactoglobulin and ovalbumin, the surface rigidity is preserved, and even enhanced. The experiments with separate foam films indicate that this is due to the formation of a bilayer structure at the air/water interface. The more hydrophobic HFBII forms the upper layer adjacent to the air phase, whereas the conventional globular protein forms the lower layer that faces the water phase. Thus, the elastic network formed by the adsorbed hydrophobin remains intact, and even reinforced by the adjacent layer of globular protein. In contrast, the addition of the disordered protein β-casein leads to softening of the HFBII adsorption layer. Similar (an even stronger) effect is produced by the nonionic surfactant Tween 20. This can be explained with the penetration of the hydrophobic tails of β-casein and Tween 20 between the HFBII molecules at the interface, which breaks the integrity of the hydrophobin interfacial elastic network. The analyzed experimental data for the surface shear rheology of various protein adsorption layers comply with a viscoelastic thixotropic model, which allows one to determine E(sh) and η(sh) from the measured storage and loss moduli, G' and G″. The results could contribute for quantitative characterization and deeper understanding of the factors that control the surface rigidity of protein adsorption layers with potential application for the creation of stable foams and emulsions with fine bubbles or droplets.

  16. The effects of temporal variability of mixed layer depth on primary productivity around Bermuda

    NASA Technical Reports Server (NTRS)

    Bissett, W. Paul; Meyers, Mark B.; Walsh, John J.; Mueller-Karger, Frank E.

    1994-01-01

    Temporal variations in primary production and surface chlorophyll concentrations, as measured by ship and satellite around Bermuda, were simulated with a numerical model. In the upper 450 m of the water column, population dynamics of a size-fractionated phytoplankton community were forced by daily changes of wind, light, grazing stress, and nutrient availability. The temporal variations of production and chlorophyll were driven by changes in nutrient introduction to the euphotic zone due to both high- and low-frequency changes of the mixed layer depth within 32 deg-34 deg N, 62 deg-64 deg W between 1979 and 1984. Results from the model derived from high-frequency (case 1) changes in the mixed layer depth showed variations in primary production and peak chlorophyll concentrations when compared with results from the model derived from low-frequency (case 2) mixed layer depth changes. Incorporation of size-fractionated plankton state variables in the model led to greater seasonal resolution of measured primary production and vertical chlorophyll profiles. The findings of this study highlight the possible inadequacy of estimating primary production in the sea from data of low-frequency temporal resolution and oversimplified biological simulations.

  17. Variations of surface mixed layer heat and salinity budget during DYNAMO

    NASA Astrophysics Data System (ADS)

    Chi, N.; Lien, R.; D'Asaro, E. A.

    2012-12-01

    The response of the oceanic surface mixed layer heat and salinity budget to different phases of the Madden-Julian oscillation (MJO) in the central Indian Ocean is evaluated. Data from shipboard and mooring observations (September 2011 - January 2012) from the DYNAMO field campaign is analyzed. During the DYNAMO campaign, 2 to 3 MJO events (depending on definition) were recorded. Of particular interest is the 2011 Thanksgiving arrival of a strong cyclone-assisted MJO event. Variations in surface heat flux, time rate of change of heat content, turbulent flux, and the definition of the mixed layer depth seem to dominate the overall results for the mixed layer throughout the observation period. During the Thanksgiving event, preliminary results suggest a complicated combination of factors modulating the near surface salinity. Interestingly, each of the following factors: wind, precipitation and horizontal advection, appears to dominate over the others for a period of time. We anticipate that these results can provide accurate tests of air-sea coupled models and help interpret the role of air-sea coupling and ocean heat storage on the evolution of the MJO.

  18. Estimation of Mixed Layer Depth in the Gulf of Aden: A New Approach

    PubMed Central

    Alsaafani, M. A.; Alraddadi, T. M.; Albarakati, A. M.

    2016-01-01

    The mixed layer depth (MLD) in Gulf of Aden is analyzed using vertical high resolution (1m) profiles of both temperature and density. Firstly, we examined threshold and gradient methods for estimating the MLD. Close evaluation with individual profiles reveals the failure of both methods for most of the profiles. Furthermore, the curvature method, a relatively recent approach to define ocean MLDs, is established for open water profiles but for marginal seas, like the Gulf of Aden, it detects shallower depths than the actual MLD. These considerable differences motivated us to introduce a new approach of MLD identification, which is developed based on curvature method and is called segment method. Our segment method produces adequate MLD estimates for more than 95% of the profiles and overcomes major limitations of conventional methods. It is less biased and least scattered compared to other methods with a correlation coefficient > 0.95. The mixed layer in Gulf of Aden displays significant seasonal variability and is deeper in winter. Throughout the year, the western part of gulf experiences deeper mixed layer than the eastern part. Regional eddies dominate Gulf of Aden’s MLD pattern during all seasons. PMID:27788181

  19. Boundary Layer CO2 mixing ratio measurements by an airborne pulsed IPDA lidar

    NASA Astrophysics Data System (ADS)

    Ramanathan, A. K.; Mao, J.; Abshire, J. B.; Allan, G. R.

    2014-12-01

    Since the primary signature of CO2 fluxes at the surface occurs in the planetary boundary layer (PBL), remote sensing measurements of CO2 that can resolve the CO2 absorption in the PBL separate from the total column are more sensitive to fluxes than those that can only measure a total column. The NASA Goddard CO2 sounder is a pulsed, range-resolved lidar that samples multiple (presently 30) wavelengths across the 1572.335 nm CO2 absorption line. The range resolution and line shape measurement enable CO2 mixing ratio measurements to be made in two or more altitude layers including the PBL via lidar cloud-slicing and multi-layer retrievals techniques. The pulsed lidar approach allows range-resolved backscatter of scattering from ground and cloud tops. Post flight data analysis can be used split the vertical CO2 column into layers (lidar cloud-slicing) and solve for the CO2 mixing ratio in each layer. We have demonstrated lidar cloud slicing with lidar measurements from a flight over Iowa, USA in August 2011 during the corn-growing season, remotely measuring a ≈15 ppm drawdown in the PBL CO2. We will present results using an improved lidar cloud slicing retrieval algorithm as well as preliminary measurements from the upcoming ASCENDS 2014 flight campaign. The CO2 absorption line is also more pressure broadened at lower altitudes. Analyzing the line shape also allows solving for some vertical resolution in the CO2 distribution. By allowing the retrieval process to independently vary the column concentrations in two or more altitude layers, one can perform a best-fit retrieval to obtain the CO2 mixing ratios in each of the layers. Analysis of airborne lidar measurements (in 2011) over Iowa, USA and Four Corners, New Mexico, USA show that for altitudes above 8 km, the CO2 sounder can detect and measure enhanced or diminished CO2 mixing ratios in the PBL even in the absence of clouds. We will present these results as well as preliminary measurements from the upcoming

  20. Self-assembly of mixed lipids into bicelles and vesicles: molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Sharma, Hari; Wang, Zilu; Dormidontova, Elena

    Formation of complex supramolecular nanostructures, such as micelles, bicelles, vesicles (liposomes) etc. via self-assembly of simple molecules has provided a new pathway for the design and development of effective drug carriers. Solid nanoparticles or functional biopolymers, such as RNA, DNA, peptides can be encapsulated into these carriers for controlled delivery or selective targeting. We performed coarse grained molecular dynamics simulation using the MARTINI force field to study the self-assembly of a binary surfactant mixture composed of long and short phospholipids, DPPC and DHPC, in the ratio 3:1. We found that at low temperature lipids self-assemble into a bicelle (nanodisc) with the longer lipid mainly forming the interior and short lipid the rim of the bicelle. At higher temperature the nanodisc transforms into a vesicle with homogeneously distributed lipids. The structural changes of these nanodiscs and vesicles imposed by gold nanoparticle encapsulation and pegylation will be addressed.

  1. Turbulence in Supercritical O2/H2 and C7H16/N2 Mixing Layers

    NASA Technical Reports Server (NTRS)

    Bellan, Josette; Harstad, Kenneth; Okong'o, Nora

    2003-01-01

    This report presents a study of numerical simulations of mixing layers developing between opposing flows of paired fluids under supercritical conditions, the purpose of the study being to elucidate chemical-species-specific aspects of turbulence. The simulations were performed for two different fluid pairs O2/H2 and C7H16/N2 at similar reduced initial pressures (reduced pressure is defined as pressure divided by critical pressure). Thermodynamically, O2/H2 behaves more nearly like an ideal mixture and has greater solubility, relative to C7H16/N2, which departs strongly from ideality. Because of a specified smaller initial density stratification, the C7H16/N2 layers exhibited greater levels of growth, global molecular mixing, and turbulence. However, smaller density gradients at the transitional state for the O2/H2 system were interpreted as indicating that locally, this system exhibits enhanced mixing as a consequence of its greater solubility and closer approach to ideality. These thermodynamic features were shown to affect entropy dissipation, which was found to be larger for O2/H2 and concentrated in high-density-gradient-magnitude regions that are distortions of the initial density-stratification boundary. In C7H16/N2, the regions of largest dissipation were found to lie in high-density-gradient-magnitude regions that result from mixing of the two fluids.

  2. Vertical velocity variance in the mixed layer from radar wind profilers

    USGS Publications Warehouse

    Eng, K.; Coulter, R.L.; Brutsaert, W.

    2003-01-01

    Vertical velocity variance data were derived from remotely sensed mixed layer turbulence measurements at the Atmospheric Boundary Layer Experiments (ABLE) facility in Butler County, Kansas. These measurements and associated data were provided by a collection of instruments that included two 915 MHz wind profilers, two radio acoustic sounding systems, and two eddy correlation devices. The data from these devices were available through the Atmospheric Boundary Layer Experiment (ABLE) database operated by Argonne National Laboratory. A signal processing procedure outlined by Angevine et al. was adapted and further built upon to derive vertical velocity variance, w_pm???2, from 915 MHz wind profiler measurements in the mixed layer. The proposed procedure consisted of the application of a height-dependent signal-to-noise ratio (SNR) filter, removal of outliers plus and minus two standard deviations about the mean on the spectral width squared, and removal of the effects of beam broadening and vertical shearing of horizontal winds. The scatter associated with w_pm???2 was mainly affected by the choice of SNR filter cutoff values. Several different sets of cutoff values were considered, and the optimal one was selected which reduced the overall scatter on w_pm???2 and yet retained a sufficient number of data points to average. A similarity relationship of w_pm???2 versus height was established for the mixed layer on the basis of the available data. A strong link between the SNR and growth/decay phases of turbulence was identified. Thus, the mid to late afternoon hours, when strong surface heating occurred, were observed to produce the highest quality signals.

  3. Vertical distribution and composition of phytoplankton under the influence of an upper mixed layer.

    PubMed

    Ryabov, Alexei B; Rudolf, Lars; Blasius, Bernd

    2010-03-07

    The vertical distribution of phytoplankton is of fundamental importance for the dynamics and structure of aquatic communities. Here, using an advection-reaction-diffusion model, we investigate the distribution and competition of phytoplankton species in a water column, in which inverse resource gradients of light and a nutrient can limit growth of the biomass. This problem poses a challenge for ecologists, as the location of a production layer is not fixed, but rather depends on many internal parameters and environmental factors. In particular, we study the influence of an upper mixed layer (UML) in this system and show that it leads to a variety of dynamic effects: (i) Our model predicts alternative density profiles with a maximum of biomass either within or below the UML, thereby the system may be bistable or the relaxation from an unstable state may require a long-lasting transition. (ii) Reduced mixing in the deep layer can induce oscillations of the biomass; we show that a UML can sustain these oscillations even if the diffusivity is less than the critical mixing for a sinking phytoplankton population. (iii) A UML can strongly modify the outcome of competition between different phytoplankton species, yielding bistability both in the spatial distribution and in the species composition. (iv) A light limited species can obtain a competitive advantage if the diffusivity in the deep layers is reduced below a critical value. This yields a subtle competitive exclusion effect, where the oscillatory states in the deep layers are displaced by steady solutions in the UML. Finally, we present a novel graphical approach for deducing the competition outcome and for the analysis of the role of a UML in aquatic systems.

  4. Unified Cloud and Mixing Parameterizations of the Marine Boundary Layer: EDMF and PDF-based Cloud Approaches

    DTIC Science & Technology

    2012-09-30

    600 m, topped by a non-precipitating shallow cumulus cloud layer. The boundary layer turbulence is forced mainly by buoyancy flux, the wind shear...STATEMENT A. Approved for public release; distribution is unlimited. Unified Cloud and...Mixing Parameterizations of the Marine Boundary Layer: EDMF and PDF-based cloud approaches Joao Teixeira Jet Propulsion Laboratory, California

  5. Development of a Hybrid RANS/LES Method for Turbulent Mixing Layers

    NASA Technical Reports Server (NTRS)

    Georgiadis, Nicholas J.; Alexander, J. Iwan D.; Reshotko, Eli

    2001-01-01

    Significant research has been underway for several years in NASA Glenn Research Center's nozzle branch to develop advanced computational methods for simulating turbulent flows in exhaust nozzles. The primary efforts of this research have concentrated on improving our ability to calculate the turbulent mixing layers that dominate flows both in the exhaust systems of modern-day aircraft and in those of hypersonic vehicles under development. As part of these efforts, a hybrid numerical method was recently developed to simulate such turbulent mixing layers. The method developed here is intended for configurations in which a dominant structural feature provides an unsteady mechanism to drive the turbulent development in the mixing layer. Interest in Large Eddy Simulation (LES) methods have increased in recent years, but applying an LES method to calculate the wide range of turbulent scales from small eddies in the wall-bounded regions to large eddies in the mixing region is not yet possible with current computers. As a result, the hybrid method developed here uses a Reynolds-averaged Navier-Stokes (RANS) procedure to calculate wall-bounded regions entering a mixing section and uses a LES procedure to calculate the mixing-dominated regions. A numerical technique was developed to enable the use of the hybrid RANS-LES method on stretched, non-Cartesian grids. With this technique, closure for the RANS equations is obtained by using the Cebeci-Smith algebraic turbulence model in conjunction with the wall-function approach of Ota and Goldberg. The LES equations are closed using the Smagorinsky subgrid scale model. Although the function of the Cebeci-Smith model to replace all of the turbulent stresses is quite different from that of the Smagorinsky subgrid model, which only replaces the small subgrid turbulent stresses, both are eddy viscosity models and both are derived at least in part from mixing-length theory. The similar formulation of these two models enables the RANS

  6. Observing entrainment mixing, photochemical ozone production, and regional methane emissions by aircraft using a simple mixed-layer framework

    NASA Astrophysics Data System (ADS)

    Trousdell, Justin F.; Conley, Stephen A.; Post, Andy; Faloona, Ian C.

    2016-12-01

    In situ flight data from two distinct campaigns during winter and summer seasons in the San Joaquin Valley (SJV) of California are used to calculate boundary-layer entrainment rates, ozone photochemical production rates, and regional methane emissions. Flights near Fresno, California, in January and February 2013 were conducted in concert with the NASA DISCOVER-AQ project. The second campaign (ArvinO3), consisting of 11 days of flights spanning June through September 2013 and 2014, focused on the southern end of the SJV between Bakersfield and the small town of Arvin, California - a region notorious for frequent violations of ozone air quality standards. Entrainment velocities, the parameterized rates at which free tropospheric air is incorporated into the atmospheric boundary layer (ABL), are estimated from a detailed budget of the inversion base height. During the winter campaign near Fresno, we find an average midday entrainment velocity of 1.5 cm s-1, and a maximum of 2.4 cm s-1. The entrainment velocities derived during the summer months near Bakersfield averaged 3 cm s-1 (ranging from 0.9 to 6.5 cm s-1), consistent with stronger surface heating in the summer months. Using published data on boundary-layer heights we find that entrainment rates across the Central Valley of California have a bimodal annual distribution peaking in spring and fall when the lower tropospheric stability (LTS) is changing most rapidly.Applying the entrainment velocities to a simple mixed-layer model of three other scalars (O3, CH4, and H2O), we solve for ozone photochemical production rates and find wintertime ozone production (2.8 ± 0.7 ppb h-1) to be about one-third as large as in the summer months (8.2 ± 3.1 ppb h-1). Moreover, the summertime ozone production rates observed above Bakersfield-Arvin exhibit an inverse relationship to a proxy for the volatile organic compound (VOC) : NOx ratio (aircraft [CH4] divided by surface [NO2]), consistent with a NOx-limited photochemical

  7. Biomimetic biosensor based on lipidic layers containing tyrosinase and lutetium bisphthalocyanine for the detection of antioxidants.

    PubMed

    Apetrei, C; Alessio, P; Constantino, C J L; de Saja, J A; Rodriguez-Mendez, M L; Pavinatto, F J; Ramos Fernandes, E Giuliani; Zucolotto, V; Oliveira, O N

    2011-01-15

    This paper describes the preparation of a biomimetic Langmuir-Blodgett film of tyrosinase incorporated in a lipidic layer and the use of lutetium bisphthalocyanine as an electron mediator for the voltammetric detection of phenol derivatives, which include one monophenol (vanillic acid), two diphenols (catechol and caffeic acid) and two triphenols (gallic acid and pyrogallol). The first redox process of the voltammetric responses is associated with the reduction of the enzymatically formed o-quinone and is favoured by the lutetium bisphthalocyanine because significant signal amplification is observed, while the second is associated with the electrochemical oxidation of the antioxidant and occurs at lower potentials in the presence of an electron mediator. The biosensor shows low detection limit (1.98×10(-6)-27.49×10(-6) M), good reproducibility, and high affinity to antioxidants (K(M) in the range of 62.31-144.87 μM). The excellent functionality of the enzyme obtained using a biomimetic immobilisation method, the selectivity afforded by enzyme catalysis, the signal enhancement caused by the lutetium bisphthalocyanine mediator and the increased selectivity of the curves due to the occurrence of two redox processes make these sensors exceptionally suitable for the detection of phenolic compounds.

  8. Biodiesel production by simultaneous extraction and conversion of total lipids from microalgae, cyanobacteria, and wild mixed-cultures.

    PubMed

    Wahlen, Bradley D; Willis, Robert M; Seefeldt, Lance C

    2011-02-01

    Microalgae have been identified as a potential biodiesel feedstock due to their high lipid productivity and potential for cultivation on marginal land. One of the challenges in utilizing microalgae to make biodiesel is the complexities of extracting the lipids using organic solvents followed by transesterification of the extracts to biodiesel. In the present work, reaction conditions were optimized that allow a single step extraction and conversion to biodiesel in high yield from microalgae. From the optimized conditions, it is demonstrated that quantitative conversion of triglycerides from several different microalgae and cyanobacteria could be achieved, including from mixed microbial biomass collected from a municipal wastewater lagoon. Evidence is presented that for some samples, significantly more biodiesel can be produced than would be expected from available triglycerides, indicating conversion of fatty acids contained in other molecules (e.g., phospholipids) using this approach. The effectiveness of the approach on wet algae is also reported.

  9. Determination of mixing-layer height by ground-based remote sensing

    NASA Astrophysics Data System (ADS)

    Emeis, S.; Schäfer, K.; Münkel, C.

    2009-09-01

    Different ground-based remote sensing methods are today available to profile the boundary-layer and to derive such information as vertical layering and mixing-layer height (MLH). A SODAR detects the vertical profile of temperature fluctuations and gradients. By an algorithm which uses the acoustic backscatter intensity and the variance of the vertical velocity component estimates of the MLH can be made. A ceilometer detects the vertical distribution of aerosol particles and water droplets. By an algorithm which uses the vertical gradient of the optical backscatter intensity estimates of the MLH can be made. A RASS directly detects the vertical temperature profile and therefore allows for a direct measurement of MLH by analysing the vertical temperature gradient. In this presentation MLH determination from all three instruments will be compared and a few applications in the fields of air quality and wind energy will be presented. Limitations and restrictions of the different methods will be discussed.

  10. Interactions between a tropical mixed boundary layer and cumulus convection in a radiative-convective model

    SciTech Connect

    Dean, Caryn L.

    1993-05-01

    This report details a radiative-convective model, combining previously developed cumulus, stable cloud and radiation parameterizations with a boundary layer scheme, which was developed in the current study. The cloud model was modified to incorporate the effects of both small and large clouds. The boundary layer model was adapted from a mixed layer model was only slightly modified to couple it with the more sophisticated cloud model. The model was tested for a variety of imposed divergence profiles, which simulate the regions of the tropical ocean from approximately the intertropical Convergence Zone (ITCZ) to the subtropical high region. The sounding used to initialize the model for most of the runs is from the trade wind region of ATEX. For each experiment, the model was run with a timestep of 300 seconds for a period of 7 days.

  11. Iron supply to the Southern Ocean mixed layer from below; the ocean model effect

    NASA Astrophysics Data System (ADS)

    Schourup-Kristensen, Vibe; Hauck, Judith; Losch, Martin; Wolf-Gladrow, Dieter A.; Völker, Christoph

    2015-04-01

    In the iron limited Southern Ocean, the biogeochemical results of commonly used ocean general circulation biogeochemical models differ greatly dependent on the ocean model used. This is largely due to the difficulties in reproducing a realistic mixed layer depth (MLD), which leads to different degrees of light limitation and nutrient supply from below. Regarding the iron sources to the Southern Ocean, research has traditionally focused on the input from dust and the sediment, but recent studies have highlighted the importance of the vertical supply to the mixed layer from the nutrient rich deeper water. This latter supply mechanism may also be affected by the large inter-model differences in the MLD and thereby influence the total net primary production and export production in the models. We have performed a model study in which the biogeochemical model REcoM2 was coupled to two different ocean models, the Finite Element Sea-ice Ocean Model (FESOM) and the MIT general circulation model (MITgcm). The effect of the ocean mixed layer on the magnitude of the iron sources from below in the two models was analyzed, as was the effect on the export and net primary production. Our results revealed a remarkable difference in terms of mode and magnitude of transport dependent on the mixed layer depth in the two models; the mean iron supply from below in the Southern Ocean was on average four times higher in MITgcm than in FESOM. The dominant pathway was entrainment in MITgcm, whereas diffusion dominated in FESOM. We discuss how the difference in the depth and seasonal amplitude of the mixed layer between the models has a major effect on the vertical iron profile and thereby also on the iron fluxes. A further effect of the difference in supply is that the fraction of exported net primary production is higher in MITgcm than in FESOM, showing that the choice of ocean model has a significant impact on the modeled carbon cycle in the Southern Ocean, with possible implications for

  12. Counterintuitive effect of fall mixed layer deepening on eukaryotic new production in the Sargasso Sea

    NASA Astrophysics Data System (ADS)

    Fawcett, S. E.; Lomas, M. W.; Ward, B. B.; Sigman, D. M.

    2012-12-01

    The Sargasso Sea is characterized by a short period of deep vertical mixing in the late winter and early spring, followed by strong thermal stratification during the summer. Stratification persists into the fall, impeding the upward flux of nitrate from depth so that recycled forms of nitrogen (N) such as ammonium are thought to support most primary production. We collected particles from surface waters during March, July, October, and December, used flow cytometry to separate the prokaryotic and eukaryotic phytoplankton, and analyzed their respective 15N/14N. In all months, the 15N/14N of the prokaryotic genera, Prochlorococcus and Synechococcus, was low, indicative of reliance on recycled N throughout the year. In July, the 15N/14N of eukaryotic phytoplankton was variable but consistently higher than that of the prokaryotes, reflecting eukaryotic consumption of subsurface nitrate. Two eukaryotic profiles from October and December were similar to those from July. In three other fall profiles, the eukaryotes had a 15N/14N similar to that of the prokaryotes, suggesting a switch toward greater reliance on recycled N. This change in the dominant N source supporting eukaryotic production appears to be driven by the density structure of the upper water column. The very shallow low-density surface "mixed layer" (≤20 m) that develops in early-to-mid summer does not contribute to stratification at the base of the euphotic zone, and subsurface nitrate can mix up into the lower euphotic zone, facilitating continued production. The deepening of the mixed layer into the fall, typically taken as an indication of weaker overall stratification, actually strengthens the isolation of the euphotic zone as a whole, reducing the upward supply of nitrate to the photosynthetically active layer. The same counterintuitive dynamic explains the latitudinal patterns in a set of three October depth profiles. Two northern stations (32°N and 27°N) were characterized by a thick, low

  13. Observation and modeling of mixing-layer development in HED blast-wave-driven shear flow

    NASA Astrophysics Data System (ADS)

    di Stefano, Carlos

    2013-10-01

    This talk describes work exploring the sensitivity to initial conditions of hydrodynamic mixing-layer growth due to shear flow in the high-energy-density regime. This work features an approach in two parts, experimental and theoretical. First, an experiment, conducted at the OMEGA-60 laser facility, seeks to measure the development of such a mixing layer. This is accomplished by placing a layer of low-density (initially of either 0.05 or 0.1 g/cm3, to vary the system's Atwood number) carbon foam against a layer of higher-density (initially 1.4 g/cm3) polyamide-imide that has been machined to a nominally-flat surface at its interface with the foam. Inherent roughness of this surface's finish is precisely measured and varied from piece to piece. Ten simultaneous OMEGA beams, comprising a 4.5 kJ, 1-ns pulse focused to a roughly 1-mm-diameter spot, irradiate a thin polycarbonate ablator, driving a blast wave into the foam, parallel to its interface with the polyamide-imide. The ablator is framed by a gold washer, such that the blast wave is driven only into the foam, and not into the polyamide-imide. The subsequent forward motion of the shocked foam creates the desired shear effect, and the system is imaged by X-ray radiography 35 ns after the beginning of the driving laser pulse. Second, a simulation is performed, intending to replicate the flow observed in the experiment as closely as possible. Using the resulting simulated flow parameters, an analytical model can be used to predict the evolution of the mixing layer, as well as track the motion of the fluid in the experiment prior to the snapshot seen in the radiograph. The ability of the model to predict growth of the mixing layer under the various conditions observed in the experiment is then examined. This work is funded by the Predictive Sciences Academic Alliances Program in NNSA-ASC via grant DEFC52- 08NA28616, by the NNSA-DS and SC-OFES Joint Program in High-Energy-Density Laboratory Plasmas, grant number DE

  14. Direct numerical simulations of supercritical fluid mixing layers applied to heptane nitrogen

    NASA Astrophysics Data System (ADS)

    Miller, Richard S.; Harstad, Kenneth G.; Bellan, Josette

    2001-06-01

    Direct numerical simulations (DNS) are conducted of a model hydrocarbon nitrogen mixing layer under supercritical conditions. The temporally developing mixing layer configuration is studied using heptane and nitrogen supercritical fluid streams at a pressure of 60 atm as a model system related to practical hydrocarbon-fuel/air systems. An entirely self-consistent cubic Peng Robinson equation of state is used to describe all thermodynamic mixture variables, including the pressure, internal energy, enthalpy, heat capacity, and speed of sound along with additional terms associated with the generalized heat and mass transport vectors. The Peng Robinson formulation is based on pure-species reference states accurate to better than 1% relative error through comparisons with highly accurate state equations over the range of variables used in this study (600 [less-than-or-eq, slant] T [less-than-or-eq, slant] 1100 K, 40 [less-than-or-eq, slant] p [less-than-or-eq, slant] 80 atm) and is augmented by an accurate curve fit to the internal energy so as not to require iterative solutions. The DNS results of two-dimensional and three-dimensional layers elucidate the unique thermodynamic and mixing features associated with supercritical conditions. Departures from the perfect gas and ideal mixture conditions are quantified by the compression factor and by the mass diffusion factor, both of which show reductions from the unity value. It is found that the qualitative aspects of the mixing layer may be different according to the specification of the thermal diffusion factors whose value is generally unknown, and the reason for this difference is identified by examining the second-order statistics: the constant Bearman Kirkwood (BK) thermal diffusion factor excites fluctuations that the constant Irwing Kirkwood (IK) one does not, and thus enhances overall mixing. Combined with the effect of the mass diffusion factor, constant positive large BK thermal diffusion factors retard

  15. Characteristics and Evolution of Passive Tracers in the Oceanic Mixed Layer

    NASA Astrophysics Data System (ADS)

    Smith, Katherine; Hamlington, Peter; Fox-Kemper, Baylor

    2015-11-01

    Ocean tracers such as CO2 and plankton reside primarily in the mixed layer where air-sea gas exchange occurs and light is plentiful for photosynthesis. There can be substantial heterogeneity in the distributions of these tracers due to turbulent mixing, particularly in the submesoscale range where partly geostrophic eddies and small-scale 3D turbulence are both active. In this talk, LES spanning scales from 20km down to 5m are used to examine the role of turbulent mixing on nonreactive passive ocean tracers. The simulations include the effects of both wave-driven Langmuir turbulence and submesoscale eddies, and tracers with different initial and boundary conditions are examined. Tracer properties are characterized using spatial fields, statistics, multiscale fluxes, and spectra, and results show that passive tracer mixing depends on air-sea flux rate, release depth, and flow regime. The results indicate that while submesoscale eddies transport buoyancy upward to extract potential energy, the same is not true of passive tracers, whose entrainment is instead suppressed. Early in the evolution of some tracers, counter-gradient transport occurs co-located with regions of negative potential vorticity, suggesting that symmetric instabilities may act to oppose turbulent mixing.

  16. Mixing and reaction in the subsonic 2-D turbulent free shear layer

    NASA Astrophysics Data System (ADS)

    Frieler, Clifford Eugene

    Several aspects of mixing and reaction in a turbulent two-dimensional shear layer have been studied. Experiments have been performed with reacting H2, F2, and NO in inert diluent gases. Sensing the heat release by these reactions, several aspects of the mixing process can be examined without the usual resolution limitations. For example, in contrast with direct measurements of composition, the amount of mixed fluid can be conservatively estimated with the results of the "flip" experiments. These have been performed over a range of density ratios, Reynolds numbers and heat release.The effects of initial conditions are of primary importance when comparisons to other studies are undertaken. Aspects as fundamental as growth rate of the turbulent region, or as obscure as the mixed fluid flux ratio depend strongly on the boundary conditions of this flow. These effects are examined in conjunction with those of Reynolds number and density ratio. For most cases studied here, tripping of the high speed boundary layer led to growth rate decreases. An exception was found for the case of high density ratio where the opposite effect was observed. This anomalous result occurred at conditions under which a new mode of instability has been shown to exist. Parallels exist between this unusual result and those of Batt in the uniform density case.An extensive study of the effects of density ratio on the mixing and reaction in the 2-D shear layer has been performed. Results indicate that several aspects of the mixing process are remarkably similar. Profiles of mixed fluid change little as the density ratio varies by a factor of 30. The integral amount of mixed fluid varies less than 6% for all density ratios examined. This insensitivity contrasts with that of the profiles of mixed fluid composition. While having very similar shapes the profiles are offset by an amount which depends very strongly upon the density ratio. The entrainment into the mixing layer has also been examined. Power

  17. Comparison of Four Mixed Layer Mesoscale Parameterizations and the Equation for an Arbitrary Tracer

    NASA Technical Reports Server (NTRS)

    Canuto, V. M.; Dubovikov, M. S.

    2011-01-01

    In this paper we discuss two issues, the inter-comparison of four mixed layer mesoscale parameterizations and the search for the eddy induced velocity for an arbitrary tracer. It must be stressed that our analysis is limited to mixed layer mesoscales since we do not treat sub-mesoscales and small turbulent mixing. As for the first item, since three of the four parameterizations are expressed in terms of a stream function and a residual flux of the RMT formalism (residual mean theory), while the fourth is expressed in terms of vertical and horizontal fluxes, we needed a formalism to connect the two formulations. The standard RMT representation developed for the deep ocean cannot be extended to the mixed layer since its stream function does not vanish at the ocean's surface. We develop a new RMT representation that satisfies the surface boundary condition. As for the general form of the eddy induced velocity for an arbitrary tracer, thus far, it has been assumed that there is only the one that originates from the curl of the stream function. This is because it was assumed that the tracer residual flux is purely diffusive. On the other hand, we show that in the case of an arbitrary tracer, the residual flux has also a skew component that gives rise to an additional bolus velocity. Therefore, instead of only one bolus velocity, there are now two, one coming from the curl of the stream function and other from the skew part of the residual flux. In the buoyancy case, only one bolus velocity contributes to the mean buoyancy equation since the residual flux is indeed only diffusive.

  18. A conceptual framework to quantify the influence of convective boundary layer development on carbon dioxide mixing ratios

    NASA Astrophysics Data System (ADS)

    Pino, D.; Vilà-Guerau de Arellano, J.; Peters, W.; Schroter, J.; van Heerwaarden, C. C.; Krol, M.

    2011-12-01

    Interpretation of observed diurnal carbon dioxide (CO2) mixing ratios near the surface requires knowledge of the local dynamics of the planetary boundary layer. In this paper, we quantify the relationship between the boundary layer dynamics and the CO2 budget in convective conditions through a newly derived set of analytical equations. From these equations, we are able to quantify how uncertainties in boundary layer dynamical variables or in the morning CO2 distribution in the mixed-layer or in the free atmosphere influence the bulk CO2 mixing ratio. We find that the largest uncertainty incurred on the mid-day CO2 mixing ratio comes from the prescribed early morning CO2 mixing ratios in the stable boundary layer, and in the free atmosphere. Errors in these values influence CO2 mixing ratios inversely proportional to the boundary layer depth (h), just like uncertainties in the assumed initial boundary layer depth and surface CO2 flux. The influence of uncertainties in the boundary layer depth itself are one order of magnitude smaller. If we "invert" the problem and calculate CO2 surface exchange from observed or simulated CO2 mixing ratios, the sensitivities to errors in boundary layer dynamics also invert: they become linearly proportional to the boundary layer depth. We demonstrate these relations for a typical well characterized situation at the Cabauw tower in the Netherlands, and conclude that knowledge of the temperature and carbon dioxide vertical profiles in the early morning are of vital importance to correctly interpret observed CO2 mixing ratios during midday.

  19. A conceptual framework to quantify the influence of convective boundary layer development on carbon dioxide mixing ratios

    NASA Astrophysics Data System (ADS)

    Pino, D.; Vilà-Guerau de Arellano, J.; Peters, W.; Schröter, J.; van Heerwaarden, C. C.; Krol, M. C.

    2012-03-01

    Interpretation of observed diurnal carbon dioxide (CO2) mixing ratios near the surface requires knowledge of the local dynamics of the planetary boundary layer. In this paper, we study the relationship between the boundary layer dynamics and the CO2 budget in convective conditions through a newly derived set of analytical equations. From these equations, we are able to quantify how uncertainties in boundary layer dynamical variables or in the morning CO2 distribution in the mixed-layer or in the free atmosphere (FA) influence the bulk CO2 mixing ratio. We find that the largest uncertainty incurred on the mid-day CO2 mixing ratio comes from the prescribed early morning CO2 mixing ratios in the stable boundary layer, and in the free atmosphere. Errors in these values influence CO2 mixing ratios inversely proportional to the boundary layer depth (h), just like uncertainties in the assumed initial boundary layer depth and surface CO2 flux. The influence of uncertainties in the boundary layer depth itself is one order of magnitude smaller. If we "invert" the problem and calculate CO2 surface exchange from observed or simulated CO2 mixing ratios, the sensitivities to errors in boundary layer dynamics also invert: they become linearly proportional to the boundary layer depth. We demonstrate these relations for a typical well characterized situation at the Cabauw site in The Netherlands, and conclude that knowledge of the temperature and carbon dioxide profiles of the atmosphere in the early morning are of vital importance to correctly interpret observed CO2 mixing ratios during midday.

  20. Deriving boundary layer mixing height from LIDAR measurements using a Bayesian statistical inference method.

    NASA Astrophysics Data System (ADS)

    Riccio, A.; Caporaso, L.; di Giuseppe, F.; Bonafè, G.; Gobbi, G. P.; Angelini, A.

    2010-09-01

    The nowadays availability of low-cost commercial LIDAR/ceilometer, provides the opportunity to widely employ these active instruments to furnish continuous observation of the planetary boundary layer (PBL) evolution which could serve the scope of both air-quality model initialization and numerical weather prediction system evaluation. Their range-corrected signal is in fact proportional to the aerosol backscatter cross section, and therefore, in clear conditions, it allows to track the PBL evolution using aerosols as markers. The LIDAR signal is then processed to retrieve an estimate of the PBL mixing height. A standard approach uses the so called wavelet covariance transform (WCT) method which consists in the convolution of the vertical signal with a step function, which is able to detect local discontinuities in the backscatter profile. There are, nevertheless, several drawbacks which have to be considered when the WCT method is employed. Since water droplets may have a very large extinction and backscattering cross section, the presence of rain, clouds or fog decreases the returning signal causing interference and uncertainties in the mixing height retrievals. Moreover, if vertical mixing is scarce, aerosols remain suspended in a persistent residual layer which is detected even if it is not significantly connected to the actual mixing height. Finally, multiple layers are also cause of uncertainties. In this work we present a novel methodology to infer the height of planetary boundary layers (PBLs) from LIDAR data which corrects the unrealistic fluctuations introduced by the WCT method. It implements the assimilation of WCT-PBL heights estimations into a Bayesian statistical inference procedure which includes a physical model for the boundary layer (bulk model) as the first guess hypothesis. A hierarchical Bayesian Markov chain Monte Carlo (MCMC) approach is then used to explore the posterior state space and calculate the data likelihood of previously assigned

  1. Estimating uncertainties on a Gulf Stream mixed-layer heat budget from stochastic modeling

    NASA Astrophysics Data System (ADS)

    Ayoub, Nadia K.; Lucas, Marc; De Mey, Pierre

    2015-10-01

    This study aims to explore the robustness of the mixed-layer heat budget as estimated from an eddy-permitting model with respect to uncertainties in atmospheric forcing. We illustrate how statistics from an ensemble can be used in a first step towards the calculation of error bars of any simulated quantity, such as the mixed-layer heat budget. The statistics from an ensemble of 33 simulations are derived in order to infer information on the model errors space and time variability of the main terms of the heat budget. The ensemble is generated by perturbing the wind forcing and the incoming solar radiation as uncertainties on these fields are expected to be a main source of errors for the surface layer representation in the model at monthly to seasonal scales. We focus on the mixed-layer in the Gulf Stream system during the deepening period (Sept.-March). The results indicate that large errors are expected at the Gulf Stream front location and just north of it. The largest errors are found on the zonal and meridional advection and vertical diffusion terms: they can locally reach values that are larger than the terms themselves. We observe a rapid increase with time of the errors for both these terms. The error growth is mainly due to the mesoscale decorrelation. The impact of wind errors on southward Ekman transport and surface turbulence generates uncertainties on the vertical diffusion term just north of the Gulf Stream front. We work with an eddy-permitting configuration similar to those used in ocean reanalysis projects (e.g. SODA, and GLORYS). Our results suggest that for such configurations, at monthly to seasonal time scales, the impact of uncertainties in the atmospheric forcing is weak on the mixed-layer cooling but very large on the zonal and meridional advection and vertical diffusion heat budget terms. In consequence, the estimate of these quantities from ocean reanalyses is not robust with respect to the atmospheric forcing and should be provided with

  2. Effects of High-frequency Wind Sampling on Simulated Mixed Layer Depth and Upper Ocean Temperature

    NASA Technical Reports Server (NTRS)

    Lee, Tong; Liu, W. Timothy

    2005-01-01

    Effects of high-frequency wind sampling on a near-global ocean model are studied by forcing the model with a 12 hourly averaged wind product and its 24 hourly subsamples in separate experiments. The differences in mixed layer depth and sea surface temperature resulting from these experiments are examined, and the underlying physical processes are investigated. The 24 hourly subsampling not only reduces the high-frequency variability of the wind but also affects the annual mean wind because of aliasing. While the former effect largely impacts mid- to high-latitude oceans, the latter primarily affects tropical and coastal oceans. At mid- to high-latitude regions the subsampled wind results in a shallower mixed layer and higher sea surface temperature because of reduced vertical mixing associated with weaker high-frequency wind. In tropical and coastal regions, however, the change in upper ocean structure due to the wind subsampling is primarily caused by the difference in advection resulting from aliased annual mean wind, which varies with the subsampling time. The results of the study indicate a need for more frequent sampling of satellite wind measurement and have implications for data assimilation in terms of identifying the nature of model errors.

  3. Data/model integration for vertical mixing in the stable Arctic boundary layer

    SciTech Connect

    Barr, S.; ReVelle, D.O.; Kao, C.Y.J.; Bigg, E.K.

    1998-12-31

    This is the final report of a short Laboratory Directed Research and Development (LDRD) project at Los Alamos National Laboratory (LANL). Data on atmospheric trace constituents and the vertical structure of stratus clouds from a 1996 expedition to the central Arctic reveal mechanisms of vertical mixing that have not been observed in mid-latitudes. Time series of the altitude and thickness of summer arctic stratus have been observed using an elastic backscatter lidar aboard an icebreaker. With the ship moored to the pack ice during 14 data collection stations and the lidar staring vertically, the time series represent advected cloud fields. The lidar data reveal a significant amount of vertical undulation in the clouds, strongly suggestive of traveling waves in the buoyantly damped atmosphere that predominates in the high Arctic. Concurrent observations of trace gases associated with the natural sulfur cycle (dimethyl sulfide, SO{sub 2}, NH{sub 3}, H{sub 2}O{sub 2}) and aerosols show evidence of vertical mixing events that coincide with a characteristic signature in the cloud field that may be called dropout or lift out. A segment of a cloud deck appears to be relocated from the otherwise quasicontinuous layer to another altitude a few hundred meters lower or higher. Atmospheric models have been applied to identify the mechanism that cause the dropout phenomenon and connect it dynamically to the surface layer mixing.

  4. 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.

  5. Numerical simulation of small-scale mixing processes in the upper ocean and atmospheric boundary layer

    NASA Astrophysics Data System (ADS)

    Druzhinin, O.; Troitskaya, Yu; Zilitinkevich, S.

    2016-02-01

    The processes of turbulent mixing and momentum and heat exchange occur in the upper ocean at depths up to several dozens of meters and in the atmospheric boundary layer within interval of millimeters to dozens of meters and can not be resolved by known large- scale climate models. Thus small-scale processes need to be parameterized with respect to large scale fields. This parameterization involves the so-called bulk coefficients which relate turbulent fluxes with large-scale fields gradients. The bulk coefficients are dependent on the properties of the small-scale mixing processes which are affected by the upper-ocean stratification and characteristics of surface and internal waves. These dependencies are not well understood at present and need to be clarified. We employ Direct Numerical Simulation (DNS) as a research tool which resolves all relevant flow scales and does not require closure assumptions typical of Large-Eddy and Reynolds Averaged Navier-Stokes simulations (LES and RANS). Thus DNS provides a solid ground for correct parameterization of small-scale mixing processes and also can be used for improving LES and RANS closure models. In particular, we discuss the problems of the interaction between small-scale turbulence and internal gravity waves propagating in the pycnocline in the upper ocean as well as the impact of surface waves on the properties of atmospheric boundary layer over wavy water surface.

  6. On a relation between particle size distribution and mixing layer height

    NASA Astrophysics Data System (ADS)

    Schäfer, Klaus; Emeis, Stefan; Höß, Markus; Cyrys, Josef; Pitz, Mike; Münkel, Christoph; Suppan, Peter

    2011-11-01

    Ceilometers are applied to detect layering of the lower atmosphere continuously. This is necessary because not only wind speeds and directions but also atmospheric layering and especially the mixing layer height (MLH) influence exchange processes of ground level emissions. It will be discussed how the ceilometer monitoring information can be used to determine the MLH influence upon the particle size distribution (PSD) which is detected near the ground. The information about atmospheric layering is continuously monitored by uninterrupted remote sensing measurements with the Vaisala ceilometers LD40 and CL31 which are eye-safe commercial lidar systems. Special software for these ceilometers provides routine retrievals of lower atmosphere layering from vertical profiles of laser backscatter data. The meteorological data are collected by the air pollution monitoring station of the Bavarian State Agency of Environment (LfU) at the southern edge of Augsburg and at the airport at the northern edge of Augsburg by the German National Meteorological Service (DWD). PSD are measured at the aerosol measurement station in the centre of Augsburg by the Cooperative Health Research in the Region of Augsburg (KORA). The two intensive measurement periods during the winter 2006/2007 and 2007/2008 are studied. The weather situations are characterized, the meteorological influences upon air pollutant concentrations like wind speed and wind direction are studied and the correlations of ceilometer backscatter densities and MLH with PSD are determined.

  7. Boundary-layer turbulence modeling and vorticity dynamics: I. A kangaroo-process mixing model of boundary-layer turbulence

    NASA Astrophysics Data System (ADS)

    Dekker, H.; de Leeuw, G.; van den Brink, A. Maassen

    A nonlocal turbulence transport theory is presented by means of a novel analysis of the Reynolds stress, inter alia involving the construct of a sample path space and a stochastic hypothesis. An analytical sampling rate model (satisfying exchange) and a nonlinear scaling relation (mapping the path space onto the boundary layer) lead to an integro-differential equation for the mixing of scalar densities, which represents fully-developed boundary-layer turbulence as a nondiffusive (Kubo-Anderson or kangaroo) type stochastic process. The underlying near-wall behavior (i.e. for y +→0) of fluctuating velocities fully agrees with recent direct numerical simulations. The model involves a scaling exponent ɛ, with ɛ→∞ in the diffusion limit. For the (partly analytical) solution for the mean velocity profile, excellent agreement with the experimental data yields ɛ≈0.58. The significance of ɛ as a turbulence Cantor set dimension (in the logarithmic profile region, i.e. for y +→∞) is discussed.

  8. Molecular organization of bacterial membrane lipids in mixed systems--A comprehensive monolayer study combined with Grazing Incidence X-ray Diffraction and Brewster Angle Microscopy experiments.

    PubMed

    Wydro, Paweł; Flasiński, Michał; Broniatowski, Marcin

    2012-07-01

    To properly design and investigate new antibacterial drugs a detailed description of the organization of bacterial membrane is highly important. Therefore in this work we performed a comprehensive characteristic of the Langmuir monolayers composed of phosphatidylethanolamine (PE) and phosphatidylglycerol (PG) mixed in a wide range of composition and treated as an artificial cytoplasmic layer of bacterial membrane. To obtain detailed information on the properties of these films we combined the analysis of the surface pressure-area curves with the surface potential measurements, Brewster Angle Microscopy studies and Grazing Incidence X-ray Diffraction experiments. It was found that the investigated phospholipids mix nonideally in the monolayers and that the most favorable packing of molecules occurs at their equimolar proportion. This is directly connected with the formation of hydrogen bonds between both types of molecules in the system. All the collected experimental data evidenced that dipalmitoylphosphatidylethanolamine (DPPE) and dipalmitoylphosphatidylglycerol (DPPG) form highly ordered associates of fixed (DPPE:DPPG 1:1) stoichiometry. The obtained results allow one to conclude a nonuniform distribution of lipids in bacterial membranes and the existence of domains composed of the investigated phospholipids. The latter seems to be of great importance in the perspective of further studies on the mechanism of action of antibacterial agents.

  9. Intraseasonal mixed-layer heat budget in the equatorial Atlantic during the cold tongue development in 2006

    NASA Astrophysics Data System (ADS)

    Giordani, Hervé; Caniaux, Guy; Voldoire, Aurore

    2013-02-01

    Estimating the mixed-layer heat budget is a key issue for understanding the cold tongue development in the eastern equatorial Atlantic. A high-resolution ocean regional model is used to diagnose the mixed-layer heat budget online during the EGEE-3 experiment from May to August 2006. The heat budget shows the major role of the horizontal advection and turbulent mixing in the mixed-layer temperature balance in the cold tongue. The surface net heat flux and entrainment processes play a minor role. The equatorial cooling is mainly induced by low-frequency advection, which is balanced by high-frequency zonal and meridional advections. The high-frequency advections are organized in patterns along the northern edge of the cold tongue, where they are associated with strong sea surface temperature gradients and well-developed tropical instability waves in the western Atlantic. Special attention is paid to the wind energy flux, which controls horizontal advection and turbulent mixing. We suggest that the wind energy flux drives the vertical velocity, which in turn adjusts the mixed-layer depth, its stratification, and the vertical shear of the horizontal current. Although vertical advection is not essential in providing cold water in the Atlantic cold tongue, it is shown that the vertical velocity plays a central role in preconditioning the mixed layer and maximizes the turbulent mixing.

  10. Evaluation of layered and mixed passive treatment systems for acid mine drainage.

    PubMed

    Jeen, Sung-Wook; Mattson, Bruce

    2016-11-01

    Laboratory column tests for passive treatment systems for mine drainage from a waste rock storage area were conducted to evaluate suitable reactive mixture, system configuration, effects of influent water chemistry, and required residence time. Five columns containing straw, chicken manure, mushroom compost, and limestone (LS), in either layered or mixed configurations, were set up to simulate the treatment system. The results showed that all of the five columns removed metals of concern (i.e. Al, Cd, Co, Cu, Fe, Ni, and Zn) with a residence time of 15 h and greater. Reaction mechanisms responsible for the removal of metals may include sulfate reduction and subsequent sulfide precipitation, precipitation of secondary carbonates and hydroxides, co-precipitation, and sorption on organic substrates and secondary precipitates. The results suggest that the mixed systems containing organic materials and LS perform better than the layered systems, sequentially treated by organic and LS layers, due to the enhanced pH adjustment, which is beneficial to bacterial activity and precipitation of secondary minerals. The column tests provide a basis for the design of a field-scale passive treatment system, such as a reducing and alkalinity producing system or a permeable reactive barrier.

  11. Modeling of the Electric Field near the Surface Layer under Strong Turbulent Mixing

    NASA Astrophysics Data System (ADS)

    Boldyreva, Ksenya; Boldyreff, Anton

    2015-04-01

    The problem of the electrode effect under strong turbulent mixing with taking into account the molecular diffusion layer was discovered by J.C. Willet (1978) for the first time. The equations were solved in this layer and then were coupled with the solution in the area where the turbulent diffusion takes place. Comparison of the results shows that such detail specification of the problem does not lead to any significant differences of the solution. Thus, it can be considered the quite sufficient solution of the problem within the turbulent diffusion action area with the introduction of the parameter z0. Solution of the problem (J.C. Willet, 1978) is required when the roughness parameter becomes significant (about 0.1 - 1 m). The problem was considered by J.C.Willet (1983). The problem of surface layer electrical state under strong turbulent mixing and analytical solution were observed by Kupovykh, Morozov, Schwartz (1998). Theoretical assessment indicated that if the dimensionless parameter ξ1,2

  12. Evaluation of the heat balance constituents of the upper mixed layer in the North Atlantic

    NASA Astrophysics Data System (ADS)

    Polonsky, A. B.; Sukhonos, P. A.

    2016-11-01

    Different physical mechanisms which cause interannual and interdecadal temperature anomalies in the upper mixed layer (UML) of the North Atlantic are investigated using the data of ORA-S3 reanalysis for the period of 1959-2011. It is shown that the annual mean heat budget in UML is mainly caused by the balance between advective heat transfer and horizontal turbulent mixing (estimated as a residual term in the equation of thermal balance). The local UML temperature change and contribution from the heat fluxes on the lower boundary of the UML to the heat budget of the upper layer are insignificant for the time scale under consideration. The contribution of the heat fluxes on the upper UML boundary to the low-frequency variability of the upper layer temperature in the whole North Atlantic area is substantially less than 30%. Areas like the northwestern part of the Northern Subtropical Anticyclonic Gyre (NSAG), where their contribution exceeds 30-60%, are exceptions. The typical time scales of advective heat transfer variability are revealed. In the NSAG area, an interannual variability associated with the North Atlantic Oscillation dominates, while in the North Atlantic subpolar gyre, an interdecadal variability of advective transfers with periods of more than 30 years prevails.

  13. Organic matter in sediment layers of an acidic mining lake as assessed by lipid analysis. Part II: Neutral lipids.

    PubMed

    Poerschmann, Juergen; Koschorreck, Matthias; Górecki, Tadeusz

    2017-02-01

    Natural neutralization of acidic mining lakes is often limited by organic matter. The knowledge of the sources and degradability of organic matter is crucial for understanding alkalinity generation in these lakes. Sediments collected at different depths (surface sediment layer from 0 to 1 cm and deep sediment layer from 4 to 5cm) from an acidic mining lake were studied in order to characterize sedimentary organic matter based on neutral signature markers. Samples were exhaustively extracted, subjected to pre-chromatographic derivatizations and analyzed by GC/MS. Herein, molecular distributions of diagnostic alkanes/alkenes, terpenes/terpenoids, polycyclic aromatic hydrocarbons, aliphatic alcohols and ketones, sterols, and hopanes/hopanoids were addressed. Characterization of the contribution of natural vs. anthropogenic sources to the sedimentary organic matter in these extreme environments was then possible based on these distributions. With the exception of polycyclic aromatic hydrocarbons, combined concentrations across all marker classes proved higher in the surface sediment layer as compared to those in the deep sediment layer. Alkane and aliphatic alcohol distributions pointed to predominantly allochthonous over autochthonous contribution to sedimentary organic matter. Sterol patterns were dominated by phytosterols of terrestrial plants including stigmasterol and β-sitosterol. Hopanoid markers with the ββ-biohopanoid "biological" configuration were more abundant in the surface sediment layer, which pointed to higher bacterial activity. The pattern of polycyclic aromatic hydrocarbons pointed to prevailing anthropogenic input. Pyrolytic makers were likely to due to atmospheric deposition from a nearby former coal combustion facility. The combined analysis of the array of biomarkers provided new insights into the sources and transformations of organic matter in lake sediments.

  14. What percentage of the oceanic mixed layer is accessible to marine Lidar? Global and the Gulf of Mexico prospective.

    PubMed

    Bogucki, D J; Spiers, G

    2013-10-07

    The oceanic mixed layer is a nearly homogenous region of the upper ocean which, in principle, has a little or no variation in turbulence strength, temperature or density with depth. This layer mediates oceanic fluxes of gas, momentum and heat. Here, based on the chosen marine Lidar system, we have carried out estimates of the depth penetration of the Lidar when compared to the local mixed layer depth. On average, we have found that at least 50% of the global oceanic mixed layer depth is accessible to the Lidar observations. When operating in a single scattering mode, which is more attenuating but more amenable to analysis, the modeled Lidar was found to access 0.4 of global mixed layer depth in half of the cases. The single scattering Lidar was found to access a large fraction of the equatorial mixed layer - a region very important when addressing global climatic issues. In a coastal environment such as the Gulf of Mexico the single scattering Lidar was found to penetrate upper half of the mixed layer, underscoring the potential for Lidar to address environmental issues there.

  15. Mechanism of lipid bilayer penetration by mixed monolayer-protected gold nanoparticles

    NASA Astrophysics Data System (ADS)

    van Lehn, Reid; Atukorale, Prabhani; Carney, Randy; Stellacci, Francesco; Irvine, Darrell; Alexander-Katz, Alfredo

    2013-03-01

    Recently, gold nanoparticles (AuNPs) protected by a binary mixture of hydrophobic and hydrophilic alkanethiol ligands were observed to spontaneously penetrate cellular membranes via a non-specific mechanism. Penetration was observed even at low temperatures and in the presence of endocytotic inhibitors, implying that AuNPs crossed the membrane by a non-endocytotic process. Furthermore, penetration was shown to depend on the amphiphilicity and nanoscale morphology of the protecting monolayer. In this work, we use a variety of simulation techniques to elucidate the mechanism of lipid bilayer penetration and compare our results to experiments with lipid vesicles. We show that these AuNPs can stably embed within lipid bilayers by ``snorkeling'' charges out of the bilayer core; the stability of such a state is a function of particle size, the composition of the protecting monolayer, and other environmental conditions. We use detailed simulations to analyze structural changes in the surrounding lipids and show that the energy barrier for embedding is considerably reduced in the presence of bilayer defects. We expect that these results will enable the design of novel drug delivery carriers and biosensors.

  16. Promoting the selection and maintenance of fetal liver stem/progenitor cell colonies by layer-by-layer polypeptide tethered supported lipid bilayer.

    PubMed

    Lee, I-Chi; Liu, Yung-Chiang; Tsai, Hsuan-Ang; Shen, Chia-Ning; Chang, Ying-Chih

    2014-12-10

    In this study, we designed and constructed a series of layer-by-layer polypeptide adsorbed supported lipid bilayer (SLB) films as a novel and label-free platform for the isolation and maintenance of rare populated stem cells. In particular, four alternative layers of anionic poly-l-glutamic acid and cationic poly-l-lysine were sequentially deposited on an anionic SLB. We found that the fetal liver stem/progenitor cells from the primary culture were selected and formed colonies on all layer-by-layer polypeptide adsorbed SLB surfaces, regardless of the number of alternative layers and the net charges on those layers. Interestingly, these isolated stem/progenitor cells formed colonies which were maintained for an 8 day observation period. Quartz crystal microbalance with dissipation measurements showed that all SLB-polypeptide films were protein resistant with serum levels significantly lower than those on the polypeptide multilayer films without an underlying SLB. We suggest the fluidic SLB promotes selective binding while minimizing the cell-surface interaction due to its nonfouling nature, thus limiting stem cell colonies from spreading.

  17. Solid lipid nanoparticles coated with cross-linked polymeric double layer for oral delivery of curcumin.

    PubMed

    Wang, Taoran; Ma, Xiaoyu; Lei, Yu; Luo, Yangchao

    2016-12-01

    Solid lipid nanoparticles (SLNs) are regarded as promising carriers to improve the safety and effectiveness of delivery for drugs and nutrients, however, the clinic applications for oral administration are limited by their poor stability in gastrointestinal conditions. In this study, surface modification was explored to confer new physicochemical properties to SLNs and thus achieve enhanced functionalities. Novel SLNs with biopolymeric double layer (DL) coating using two natural biopolymers, i.e. caseinate (NaCas) and pectin, were prepared to encapsulate and deliver curcumin, a lipophilic bioactive compound studied as a model drug/nutrient. The DL coating was chemically cross-linked by creating covalent bonds between NaCas and pectin, using two different cross-linkers, i.e. glutaraldehyde (GA) and 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide/N-Hydroxysuccinimide (EDC/NHS). Prior to cross-linking, the mean particle size, polydispersity index and zeta potential of DL-SLNs were 300-330nm, 0.25-0.30, -45-40mV, respectively. It was found that cross-linking with GA had a more prominent effect on particle size and polydispersity index than EDC/NHS. The cross-linking process significantly improved physicochemical properties of DL-SLNs, resulting in higher encapsulation efficiency and loading capacity, better stability and slower release profile in simulated gastrointestinal conditions. Particularly, an optimal zero-order release kinetic was observed for EDC/NHS crosslinked DL-SLNs. The electron microscopy revealed that both cross-linked DL-SLNs exhibited spherical shape with homogeneous size and smooth surface. Encapsulation of curcumin in SLNs dramatically enhanced its antioxidant activity in aqueous condition. The cross-linking process further helped spray drying of SLNs by forming homogenous powder particles. These results indicated that coating with cross-linked polymers could significantly improve the physicochemical properties of SLNs and expand their potentials as

  18. Direct numerical simulation of a transitional supercritical binary mixing layer: heptane and nitrogen

    NASA Astrophysics Data System (ADS)

    Okong'o, Nora A.; Bellan, Josette

    2002-08-01

    Direct numerical simulations (DNS) of a supercritical temporal mixing layer are conducted for the purpose of exploring the characteristics of high-pressure transitional mixing behaviour. The conservation equations are formulated according to fluctuation-dissipation (FD) theory, which is consistent with non-equilibrium thermodynamics and converges to kinetic theory in the low-pressure limit. According to FD theory, complementing the low-pressure typical transport properties (viscosity, diffusivity and thermal conductivity), the thermal diffusion factor is an additional transport property which may play an increasingly important role with increasing pressure. The Peng Robinson equation of state with appropriate mixing rules is coupled to the dynamic conservation equations to obtain a closed system. The boundary conditions are periodic in the streamwise and spanwise directions, and of non-reflecting outflow type in the cross-stream direction. Due to the strong density stratification, the layer is considerably more difficult to entrain than equivalent gaseous or droplet-laden layers, and exhibits regions of high density gradient magnitude that become very convoluted at the transitional state. Conditional averages demonstrate that these regions contain predominantly the higher-density, entrained fluid, with small amounts of the lighter, entraining fluid, and that in these regions the mixing is hindered by the thermodynamic properties of the fluids. During the entire evolution of the layer, the dissipation is overwhelmingly due to species mass flux followed by heat flux effects with minimal viscous contribution, and there is a considerable amount of backscatter in the flow. Most of the species mass flux dissipation is due to the molecular diffusion term with significant contributions from the cross-term proportional to molecular and thermal diffusion. These results indicate that turbulence models for supercritical fluids should primarily focus on duplicating the species

  19. Band gap and refractive index tunability in thallium based layered mixed crystals

    SciTech Connect

    Gasanly, N. M.

    2015-07-21

    Compositional variation of the band gap energy and refractive index of TlMeX{sub 2}-type (Me = Ga or In and X = S or Se) layered mixed crystals have been studied by the transmission and reflection measurements in the wavelength range of 400–1100 nm. The analysis of absorption data of TlGa{sub 1-x}In{sub x}Se{sub 2}, TlGa(S{sub 1−x}Se{sub x}){sub 2}, TlGa{sub 1−x}In{sub x}S{sub 2}, and TlIn(Se{sub 1−x}S{sub x}){sub 2} mixed crystals revealed the presence of both optical indirect and direct transitions. It was found that the energy band gaps of mixed crystals decrease at the replacing of gallium atoms by indium and of sulfur atoms by selenium ones. Through the similar replacing of atoms (smaller atoms by larger ones) in the studied mixed crystals, the refractive index shows the quite opposite behavior.

  20. Growth rate of Rayleigh-Taylor turbulent mixing layers with the foliation approach.

    PubMed

    Poujade, Olivier; Peybernes, Mathieu

    2010-01-01

    For years, astrophysicists, plasma fusion, and fluid physicists have puzzled over Rayleigh-Taylor turbulent mixing layers. In particular, strong discrepancies in the growth rates have been observed between experiments and numerical simulations. Although two phenomenological mechanisms (mode-coupling and mode-competition) have brought some insight on these differences, convincing theoretical arguments are missing to explain the observed values. In this paper, we provide an analytical expression of the growth rate compatible with both mechanisms and is valid for a self-similar, low Atwood Rayleigh-Taylor turbulent mixing subjected to a constant or time-varying acceleration. The key step in this work is the presentation of foliated averages and foliated turbulent spectra highlighted in our three-dimensional numerical simulations. We show that the exact value of the Rayleigh-Taylor growth rate not only depends upon the acceleration history but is also bound to the power-law exponent of the foliated spectra at large scales.

  1. Growth rate of Rayleigh-Taylor turbulent mixing layers with the foliation approach

    SciTech Connect

    Poujade, Olivier; Peybernes, Mathieu

    2010-01-15

    For years, astrophysicists, plasma fusion, and fluid physicists have puzzled over Rayleigh-Taylor turbulent mixing layers. In particular, strong discrepancies in the growth rates have been observed between experiments and numerical simulations. Although two phenomenological mechanisms (mode-coupling and mode-competition) have brought some insight on these differences, convincing theoretical arguments are missing to explain the observed values. In this paper, we provide an analytical expression of the growth rate compatible with both mechanisms and is valid for a self-similar, low Atwood Rayleigh-Taylor turbulent mixing subjected to a constant or time-varying acceleration. The key step in this work is the presentation of foliated averages and foliated turbulent spectra highlighted in our three-dimensional numerical simulations. We show that the exact value of the Rayleigh-Taylor growth rate not only depends upon the acceleration history but is also bound to the power-law exponent of the foliated spectra at large scales.

  2. Long-term observations of the urban mixing-layer height with ceilometers

    NASA Astrophysics Data System (ADS)

    Emeis, S.; Schäfer, K.; Münkel, C.

    2008-05-01

    Urban air quality assessment requires the knowledge of the temporal and spatial structure of the mixing-layer height (MLH), because this variable controls the vertical space for rapid mixing of near-surface pollutants. Because MLH is a consequence of vertical temperature and moisture profiles in the lower atmosphere, remote sensing is a suitable tool to monitor MLH. Two ceilometers, a Vaisala LD40 and a Vaisala CL31, have been run for many months in the German city of Augsburg to observe the vertical aerosol distribution. Wind and temperature profile information have been obtained for the same period from sodar observations. This paper compares the MLH determined from the optical backscatter intensity received by the two ceilometers among each other and with the MLH derived from the acoustic backscatter intensity and the variance of the vertical wind component from sodar measurements.

  3. Defining the ecologically relevant mixed-layer depth for Antarctica's coastal seas

    NASA Astrophysics Data System (ADS)

    Carvalho, Filipa; Kohut, Josh; Oliver, Matthew J.; Schofield, Oscar

    2017-01-01

    Mixed-layer depth (MLD) has been widely linked to phytoplankton dynamics in Antarctica's coastal regions; however, inconsistent definitions have made intercomparisons among region-specific studies difficult. Using a data set with over 20,000 water column profiles corresponding to 32 Slocum glider deployments in three coastal Antarctic regions (Ross Sea, Amundsen Sea, and West Antarctic Peninsula), we evaluated the relationship between MLD and phytoplankton vertical distribution. Comparisons of these MLD estimates to an applied definition of phytoplankton bloom depth, as defined by the deepest inflection point in the chlorophyll profile, show that the maximum of buoyancy frequency is a good proxy for an ecologically relevant MLD. A quality index is used to filter profiles where MLD is not determined. Despite the different regional physical settings, we found that the MLD definition based on the maximum of buoyancy frequency best describes the depth to which phytoplankton can be mixed in Antarctica's coastal seas.

  4. Mixing layer height and its implications for air pollution over Beijing, China

    NASA Astrophysics Data System (ADS)

    Tang, Guiqian; Zhang, Jinqiang; Zhu, Xiaowan; Song, Tao; Münkel, Christoph; Hu, Bo; Schäfer, Klaus; Liu, Zirui; Zhang, Junke; Wang, Lili; Xin, Jinyuan; Suppan, Peter; Wang, Yuesi

    2016-03-01

    The mixing layer is an important meteorological factor that affects air pollution. In this study, the atmospheric mixing layer height (MLH) was observed in Beijing from July 2009 to December 2012 using a ceilometer. By comparison with radiosonde data, we found that the ceilometer underestimates the MLH under conditions of neutral stratification caused by strong winds, whereas it overestimates the MLH when sand-dust is crossing. Using meteorological, PM2.5, and PM10 observational data, we screened the observed MLH automatically; the ceilometer observations were fairly consistent with the radiosondes, with a correlation coefficient greater than 0.9. Further analysis indicated that the MLH is low in autumn and winter and high in spring and summer in Beijing. There is a significant correlation between the sensible heat flux and MLH, and the diurnal cycle of the MLH in summer is also affected by the circulation of mountainous plain winds. Using visibility as an index to classify the degree of air pollution, we found that the variation in the sensible heat and buoyancy term in turbulent kinetic energy (TKE) is insignificant when visibility decreases from 10 to 5 km, but the reduction of shear term in TKE is near 70 %. When visibility decreases from 5 to 1 km, the variation of the shear term in TKE is insignificant, but the decrease in the sensible heat and buoyancy term in TKE is approximately 60 %. Although the correlation between the daily variation of the MLH and visibility is very poor, the correlation between them is significantly enhanced when the relative humidity increases beyond 80 %. This indicates that humidity-related physicochemical processes is the primary source of atmospheric particles under heavy pollution and that the dissipation of atmospheric particles mainly depends on the MLH. The presented results of the atmospheric mixing layer provide useful empirical information for improving meteorological and atmospheric chemistry models and the forecasting

  5. Mixed Layer Depth in the Aegean, Marmara, Black and Azov Seas: Part I: General Features

    DTIC Science & Technology

    2009-02-28

    r.com/ locate / jmarsysMixed layer depth in the Aegean, Marmara, Black and Azov Seas : Part I: General features A. Birol Kara a,⁎, Robert W. Helber a...suffer from lack of input T and S profiles in the Marmara and Azov Seas , thus they may not be representative.MonthlyMLDfields presented in this paper are...Boyer), .V.there has been no study which describes seasonal characteristics of MLD in the Aegean, Marmara, Black and Azov Seas , whose bottom

  6. Mixing layer height and the implications for air pollution over Beijing, China

    NASA Astrophysics Data System (ADS)

    Tang, G.; Zhang, J.; Münkel, C.; Song, T.; Hu, B.; Schäfer, K.; Liu, Z.; Xin, J.; Suppan, P.; Wang, Y.

    2015-10-01

    The mixing layer is an important meteorological factor that affects atmospheric pollution. A study of atmospheric pollution in the Beijing area was performed from July 2009 to December 2012, using a ceilometer, to observe and study the atmospheric mixing layer height (MLH). Based on a comparison and validation of multiple types of data, we evaluated the quality of the MLH data as observed by the ceilometer and found that the ceilometer underestimates MLH during neutral stratification caused by strong winds, whereas it overestimates MLH during dust crossing. By combining conventional meteorological data and PM2.5 and PM10 observational data, we screened the observational results for the MLH, and the ceilometer observations were fairly consistent with the meteorological radiosonde profile results. The correlation coefficient is more than 0.9, and the effective rate of acquired data is near 80 %. Further analysis of the variation in the MLH indicates that the MLH in the Beijing area exhibits the feature of being low in autumn and winter and being high in spring and summer. There is a significant correlation between the variation in the MLH and the sensible heat flux, whereas the diurnal variation in the mixing layer during summer is affected by the circulation of mountainous plain winds. By applying visibility as the index for the classification of atmospheric pollution degree, it is found that in comparison with a clear day, the variation of sensible heat and buoyancy term in turbulent kinetic energy (TKE) of a slight haze day is insignificant, but the reduction of shear term in TKE is near 70 % when visibility decreased from 10 to 5 km; in comparison with the slight haze day, the variation of shear term in TKE of medium and heavy haze days is insignificant, but the declination of sensible heat and buoyancy term in TKE are about 60 % when visibility decreased from 5 to 1 km. Although the correlation between the daily variation of MLH and visibility is very poor, the

  7. Degenerate four-wave mixing from layered semiconductor clusters in the quantum size regime

    NASA Astrophysics Data System (ADS)

    Sarid, Dror; Rhee, Bum Ku; McGinnis, Brian P.; Sandroff, Claude J.

    1986-11-01

    We report the first measurement of the third-order nonlinear susceptibility χ(3) in layered semiconductor clusters exhibiting pronounced quantum size effects at room temperature. BiI3 clusters prepared in colloidal form in acetonitrile had a thickness of ≂7 Å and lateral dimensions between 60 and 90 Å. Using degenerate four-wave mixing, we observed that the conjugate pulses from the small and the large gratings had comparable intensities, verifying the electronic origin of the nonlinearity. The nonlinear susceptibility was found to be 2.3×10-11 esu for a colloid with a cluster volume fraction of 10-5.

  8. The interaction of a surface cold front with a prefrontal thermodynamically well-mixed boundary layer

    NASA Technical Reports Server (NTRS)

    Reeder, Michael J.

    1986-01-01

    The dynamics of a surface cold front as it proceeds from sea to shore and interacts with a thermodynamically well-mixed boundary layer are investigated by means of numerical simulations using a modified version of the two-dimensional model of Reeder and Smith (1987). The theoretical basis of the model is explained, and the results are presented graphically and characterized in detail. Good agreement is found with observational data on Australian summer cold fronts, and the transverse frontal circulation is shown to be significantly affected by diabatic heating.

  9. Using dissolved oxygen concentrations to determine mixed layer depths in the Bellingshausen Sea

    NASA Astrophysics Data System (ADS)

    Castro-Morales, K.; Kaiser, J.

    2011-06-01

    Concentrations of oxygen (O2) and other dissolved gases in the oceanic mixed layer are often used to calculate air-sea gas exchange fluxes; for example, in the context of net and gross biological production estimates. The mixed layer depth (zmix) may be defined using criteria based on temperature or density differences to a reference depth near the ocean surface. However, temperature criteria fail in regions with strong haloclines such as the Southern Ocean where heat, freshwater and momentum fluxes interact to establish mixed layers. Moreover, the time scales of air-sea exchange differ for gases and heat, so that zmix defined using O2 may be different to zmix defined using temperature or density. Here, we propose to define an O2-based mixed layer depth, zmix(O2), as the depth where the relative difference between the O2 concentration and a reference value at a depth equivalent to 10 dbar equals 0.5 %. This definition was established by numerical analysis of O2 profiles in coastal areas of the Southern Ocean and corroborated by visual inspection. Comparisons of zmix(O2) with zmix based on potential temperature differences, i.e. zmix(Δθ = 0.2 °C) and zmix(Δθ = 0.5 °C), and potential density differences, i.e. zmix(Δσθ = 0.03 kg m-3) and zmix(Δσθ = 0.125 kg m-3), showed that zmix(O2) closely follows zmix(Δσθ = 0.03 kg m-3). Further comparisons with published zmix climatologies and zmix derived from World Ocean Atlas 2005 data were also performed. To establish zmix for use with biological production estimates in the absence of O2 profiles, we suggest using zmix(Δσθ = 0.03 kg m-3), which is also the basis for the climatology by de Boyer Montégut et al. (2004).

  10. Transmission of acoustic waves through mixing layers and 2D isotropic turbulence

    NASA Astrophysics Data System (ADS)

    Juve, D.; Blanc-Benon, P.; Comte-Bellot, G.

    Ray tracing and parabolic equation methods have been used to study the properties of acoustic waves transmitted through turbulent velocity fields. A numerical simulation permits individual realizations of the turbulent field, which then allow, if desired, an ensemble averaging of the fields. Two flows have been considered, 2D isotropic turbulence and a 2D mixing layer. The following complementary aspects are developed: the occurrence of caustics, the reinforced or weakened zones of the acoustic field, the eigenrays between a source and a receiver, and the associated travel times, variances, and scintillation index.

  11. Characterization of coherent structures in a turbulent mixing layer by digital image analysis

    NASA Technical Reports Server (NTRS)

    Bernal, L. P.; Hernan, M. A.; Sarohia, V.

    1985-01-01

    Digital image analysis has been applied to a shadowgraph motion picture of a helium nitrogen mixing layer in order to characterize the coherent vortex structures in the flow. Both the primary spanwise coherent vortices and secondary streamwise vortices are considered. Pattern recognition algorithms were designed to take advantage of the more pronounced features of the vortices and of their temporal coherence to isolate them and to measure their characteristics. The resulting data base permits a deterministic description of the evolution of primary and seconary vortices.

  12. Influence of Gas Turbulence on the Instability of an Air-Water Mixing Layer.

    PubMed

    Matas, Jean-Philippe; Marty, Sylvain; Dem, Mohamed Seydou; Cartellier, Alain

    2015-08-14

    We present the first evidence of the direct influence of gas turbulence on the shear instability of a planar air-water mixing layer. We show with two different experiments that increasing the level of velocity fluctuations in the gas phase continuously increases the frequency of the instability, up to a doubling of frequency for the largest turbulence intensity investigated. A modified spatiotemporal stability analysis taking turbulence into account via a simple Reynolds stress closure provides the right trend and magnitude for this effect.

  13. Seasonal cycle of the mixed-layer heat and freshwater budget in the eastern tropical Atlantic

    NASA Astrophysics Data System (ADS)

    Rath, Willi; Dengler, Marcus; Lüdke, Jan; Schmidtko, Sunke; Schlundt, Michael; Brandt, Peter; Partners, Preface

    2016-04-01

    A new seasonal mixed-layer heat flux climatology is used to explore the mechanisms driving seasonal variability of sea surface temperature and salinity in the eastern tropical Atlantic (ETA) with a focus on the eastern boundary upwelling regions. Until recently, large areas at the continental margins of the ETA were not well covered by publically available hydrographic data hampering a detailed understanding of the involved processes. In a collaborative effort between African and European partners within the EU-funded PREFACE program, a new seasonal climatology for different components of the heat and freshwater budget was compiled for the ETA using all publically available hydrographic data sets and a large trove of previously not-publically available hydrographic measurements from the territorial waters of western African countries, either from national programs or from the FAO supported EAF-Nansen program. The publically available data includes hydrographic data from global data repositories including most recent ARGO floats and glider measurements. This data set was complemented by velocity data from surface drifter and ARGO floats to allow determining horizontal heat and freshwater advection. Monthly means of air-sea heat fluxes were derived from the TropFlux climatology while precipitation rates were derived from monthly mean fields of the Global Precipitation Climatology Project. Finally, microstructure data from individual measurement campaigns allow estimating diapycnal heat and salt fluxes for certain regions during specific months. A detailed analysis of the seasonal cycle of mixed-layer heat and freshwater balance in previously poorly covered regions in the eastern tropical Atlantic upwelling is presented. In both eastern boundary upwelling region, off Senegal/Mauritania and off Angola/Namibia, average net surface heat fluxes warm the mixed layer at a rate between 50 and 80 W/m2 with maxima in the respective summer seasons. Horizontal advection

  14. Parametric representation of heat and moisture fluxes in cloud-topped mixed layers

    NASA Technical Reports Server (NTRS)

    Penc, Richard S.; Albrecht, Bruce A.

    1987-01-01

    The Betts (1973, 1978) parametrization of heat and moisture fluxes is tested using measurements made in thin, broken, and solid stratocumulus clouds by the NCAR Electra off the California coast in June 1976. The turbulence data are used to determine updraft-downdraft properties, heat and moisture fluxes, spectra, and cospectra. From the convective properties, vertical mass flux profiles are obtained and examined for consistency. A convective scaling which is appropriate for cloud-topped mixed layers is discussed. The results demonstrate the usefulness of a mass flux formulation in modeling applications for cloud conditions varying between solid and broken.

  15. Average Cosine Meter and High Spectral Resolution Measurements at the Marine Light Mixed Layer Site.

    DTIC Science & Technology

    1994-09-30

    1991 10 6 Monterey Bay Apr. Sep. Oct. 9 2 1989 TT010 July 1992 5 5 TBX: Tampa Bay eXperiment (subtropical Gulf of Mexico ) MLML: Marine Light Mixed Layer...accuracy for describing the different shape of a, curves is necessary. By analyzing surface a. curves collected for waters from the Gulf of Mexico with a...for 1.85 x DOCuv in rich regions. the respective absorption coefficients, ad/ap, in As much as 33% of the DOCpt may instead be the Gulf of Mexico

  16. Analysis of horizontal and vertical processes contributing to natural iron supply in the mixed layer in southern Drake Passage

    NASA Astrophysics Data System (ADS)

    Frants, Marina; Gille, Sarah T.; Hatta, Mariko; Hiscock, William T.; Kahru, Mati; Measures, Christopher I.; Greg Mitchell, B.; Zhou, Meng

    2013-06-01

    Horizontal advection, vertical mixing, and mixed-layer entrainment all affect iron concentrations and biological productivity in the Ona Basin, near the Shackleton Transverse Ridge (STR) in southern Drake Passage. Trace metal sampling in the region indicates that dissolved iron concentrations are significantly higher on the continental shelf near the Antarctic Peninsula and the South Shetland Islands than they are in the deep waters away from the shelf. Comparisons between satellite-derived sea surface height (SSH) and Chlorophyll-a (Chl-a) levels in the Ona Basin show >95% correlation between Chl-a concentrations and horizontal advection of these iron-rich shelf waters during the months of November and December for the years 1997-2010. However, no significant correlations are found for January-April, while high Chl-a concentrations in the Ona Basin persist through March. Enhanced vertical (diapycnal) mixing and mixed-layer entrainment are considered as alternative mechanisms for delivering iron into the Ona Basin mixed layer and sustaining the high Chl-a concentrations. Estimates of iron flux based on in situ measurements of dissolved iron concentrations suggest that diapycnal mixing alone can supply iron to the base of the mixed layer at a rate of 64±2 nmol m-2 day-1 during the summer. In addition, the summer mixed layer in the Ona Basin deepens from January to April, allowing for iron-rich water to be steadily entrained from below. Estimates based on monthly mixed-layer climatologies produce average daily entrainment rates ranging from 5 to 25 nmol m-2 day-1. While neither diapycnal mixing nor entrainment alone is always sufficient to meet the estimated iron demand for the Ona Basin bloom, numerical simulation suggests that the combined effect of the two processes can consistently supply sufficient iron to sustain the bloom.

  17. The development of a mixing layer under the action of weak streamwise vortices

    NASA Technical Reports Server (NTRS)

    Goldstein, M. E.; Mathew, Joseph

    1993-01-01

    The action of weak, streamwise vortices on a plane, incompressible, steady mixing layer is examined in the large Reynolds number limit. The outer, inviscid region is bounded by a vortex sheet to which the viscous region is confined. It is shown that the local linear analysis becomes invalid at streamwise distances O(epsilon sup -1), where (epsilon much less than 1) is the crossflow amplitude, and a new nonlinear analysis is constructed for this region. Numerical solutions of the nonlinear problem show that the vortex sheet undergoes an O(1) change in position and that the solution is ultimately terminated by a breakdown in the numerical procedure. The corresponding viscous layer shows downstream thickening, but appears to remain well behaved up to the terminal location.

  18. The development of a mixing layer under the action of weak streamwise vortices

    NASA Technical Reports Server (NTRS)

    Goldstein, Marvin E.; Mathew, Joseph

    1993-01-01

    The action of weak, streamwise vortices on a plane, incompressible, steady mixing layer is examined in the large Reynolds-number limit. The outer, inviscid region is bounded by a vortex sheet to which the viscous region is confined. It is shown that the local linear analysis becomes invalid at streamwise distances O(epsilon(sup -1)), where epsilon is much less than 1 is the cross flow amplitude, and a new nonlinear analysis is constructed for this region. Numerical solutions of the nonlinear problem show that the vortex sheet undergoes an O(1) change in position and that the solution is ultimately terminated by the appearance of a singularity. The corresponding viscous layer shows downstream thickening, but appears to remain well behaved up to the singular location.

  19. Uncertainties in model derived mixed-layer heights over North America

    NASA Astrophysics Data System (ADS)

    Kim, M. G.; Lin, J. C.

    2010-12-01

    Regional scale weather forecasting models and reanalysis datasets may be useful in estimation of transportation of trace gas and airborne pollutants, by providing high resolution representative flow fields. However, uncertainties in model simulated vertical mixing in the atmospheric boundary layer are widely cited as the primary cause of errors in a various regional scale atmospheric modeling. The mixing layer heights (zi) are retrieved from multiple meteorological datasets commonly used by the atmospheric community: Global Data Assimilation System (GDAS), Eta Data Assimilation System (EDAS), North American Regional Reanalysis (NARR), and Weather Research and Forecasting (WRF) model. Errors in model-derived zi are then evaluated by comparison to zi calculated with the ground measurements from radiosonde (RAOB) and the profiler network (CAP) across North America. The zi is determined using the bulk Richardson number method. The critical number used for this study is 0.25, and uncertainties in mixing height are quantified with the normalized gross error (NGE) indicating the biases and the root mean squared errors (RMSE). Comparisons focus on four months spanning the different seasons of the year 2004: January, April, July, and October. The spatio-temporal variations of the mixing height uncertainties are clearly seen in the results. First of all, both the biases and the overall magnitude of errors in mixing heights differ site to site and seem to vary over time, but not necessarily covarying in space. Certain areas, however, show very large positive biases and RMSE persisting throughout the period. For these areas, vertical profiles of temperature and horizontal winds are examined to investigate possible causes of the symptom. Secondly, regional scale products with higher resolutions (i.e., EDAS, WRF, and NARR) show better representation of the vertical mixing as expected. Lastly, effects of data assimilations seem to become evident when the WRF at 40 km horizontal

  20. Mixed Layer Depth Seasonality within the Coral Sea Based on Argo Data

    PubMed Central

    Jaffrés, Jasmine B. D.

    2013-01-01

    The worldwide deployment of Argo floats has enabled much more detailed studies of global and regional seas over the last decade. Here, the seasonal variability of the mixed layer depth (MLD) within the Coral Sea was examined with CTD profiles from Argo floats. Multiple threshold values for both temperature and density have been employed to determine the most suitable threshold values for the Coral Sea. A threshold value of 0.04 kg/m3 for density and 0.2°C for temperature appear the most fitting for this region. Although MLD and isothermal layer depth (ILD) coincide quite well in most cases, the relatively common presence of temporary, non-seasonal barrier layers induces an ILD that is significantly deeper than the MLD. Consequently, an MLD estimation based on density is more appropriate. A distinct seasonality in the MLD is evident throughout the Coral Sea, but is generally more pronounced in higher southern latitudes (20–30°S). Salinity inversions are rare and mainly occur in the south-eastern Coral Sea, while barrier layers are more commonly associated with the north-eastern Coral Sea, a region characterised by high rainfall. The significance of regional currents is evident in the north-western Coral Sea, where temperature and ocean heat content is relatively low due to a northward moving boundary current. Shallow bathymetry, in turn, is linked to the absence of Argo data on the continental shelf and in the central Coral Sea. PMID:23593368

  1. Comparison of continuous detection of mixing layer heights by ceilometer with radiosonde observations

    NASA Astrophysics Data System (ADS)

    Schäfer, Klaus; Emeis, Stefan; Höß, Markus; Friedl, Roman; Münkel, Christoph; Suppan, Peter

    2011-11-01

    The mixing layer height (MLH) is an important factor which influences exchange processes of ground level emissions. The continuous knowledge of MLH is supporting the understanding of processes directing air quality. If the MLH is located near to the ground, which occurs mainly during winter and night-time, air pollution can be high due to a strongly limited air mass dilution. Ceilometers CL31 (backscatter profiles at 910 nm) were applied to detect the MLH in Augsburg since 2006. Radiosonde data cannot be used alternatively because they do not provide sufficient information. The Vaisala ceilometers LD40 and CL31 are operated which are eye-safe commercial lidar systems. Special software for these ceilometers provides routine retrievals of lower atmosphere layering from vertical profiles (vertical gradient) of laser backscatter density data. The performance of the ceilometers is sufficient to detect convective layer depths exceeding 2000 m and nocturnal stable layers down to 50 m. The radiosonde data from the station Oberschleissheim near Munich (about 50 km away from Augsburg city) are also used for MLH determination. A summer and a winter episode of MLH measurement results are investigated. The profile behaviour of relative humidity (strong decrease) and virtual potential temperature (inversion) of the radiosonde agree mostly well with the MLH indication from ceilometer laser backscatter density gradients. The remote sensing by ceilometers can fill the temporal gap of information between the two radiosonde profiles per day so that the daily course of the MLH is available.

  2. Histological analysis of esophageal muscular layers from 27 autopsy cases with mixed connective tissue disease (MCTD).

    PubMed

    Uzuki, Miwa; Kamataki, Akihisa; Watanabe, Mika; Sasaki, Nobuhito; Miura, Yasuhiro; Sawai, Takashi

    2011-06-15

    Esophageal symptoms in mixed connective tissue disease (MCTD) have been investigated radiologically. We investigated the esophageal lesions in MCTD histopathologically, and analyzed relationships between these lesions and autoantibodies extracted from the serum of MCTD patients. Esophageal tissues from 27 MCTD patients submitted to autopsy were examined. We compared histopathological features of the esophagus in different wall layers from the mucosa, submucosa, and muscular layer to the adventitia, and in the upper, middle, and lower portions of esophagus. The most striking change observed was severe atrophy and occasional loss of smooth muscle cells in the muscular layer, followed by fibrosis. These muscular changes were particularly prominent in the inner layer of the lower esophagus. Immunohistochemically, degenerated muscular tissues of the esophagus were positive for anti-IgG and anti-C3 antibodies, but not for anti-IgM antibodies. IgG fractions extracted from three MCTD patients were immunohistochemically used to examine whether some antibodies in MCTD patients showed reactivity for esophageal components. The IgG fractions isolated from MCTD patients reacted with smooth muscle from non-connective tissue disease cases, suggesting that some serum antibodies may trigger esophageal changes. These findings suggest that esophageal lesions associated with clinical dysphagia in MCTD may be related to autoantibodies.

  3. One-year observation of urban mixed layer characteristics at Tsukuba, Japan using a micro pulse lidar

    NASA Astrophysics Data System (ADS)

    Chen, Weibiao; Kuze, Hiroaki; Uchiyama, Akihiro; Suzuki, Yoshihide; Takeuchi, Nobuo

    One-year characteristics of the urban mixed layer is observed by an eye-safe, compact micro pulse lidar (MPL). Retrieval method of the mixed layer height (MLH) and the encroachment model of the mixed layer growing are presented. Two case studies are carried out using summer and late winter data. Comparisons are made between the aerosol optical thickness, the rawinsonde data and the model calculation. The development of the mixed layer exhibits temporal behavior similar to that of the aerosol optical thickness, but with a time difference of about 1- 2 h. The growth rate of the MLH agrees well with the encroachment model only in the morning, with considerate deviation during the daytime because of the wind effect. One-year growth rate and the maximum MLH are estimated from the MPL measurement between May 1999 and May 2000. The results show that the properties of mixed layer are strongly correlated with the seasonal meteorological conditions. This work also demonstrates that an automated, compact lidar system such as a MPL is quite useful for long-term monitoring of the mixed layer.

  4. Chlorophyll-a Variability in the Southern Ocean Mixed Layer and Euphotic Zone From Elephant Seals and Profiling Floats

    NASA Astrophysics Data System (ADS)

    Carranza, M. M.; Gille, S. T.; Franks, P. J. S.; Johnson, K. S.; Girton, J. B.

    2015-12-01

    The Southern Ocean contains some of the ocean's deepest mixed layers. Because deep mixed layers can transport phytoplankton below the euphotic zone, light levels depend on mixed-layer depth (MLD), and phytoplankton growth is hypothesized to be co-limited by iron and light. Estimates of Chl-a fluorescence, particle backscattering and hydrographic profiles collected by southern elephant seals, EM-APEX, and biogeochemical Argo floats are used to evaluate the extent to which MLD influences phytoplankton bloom development and the vertical structure of chlorophyll-a (Chl-a) in the Southern Ocean. We find that surface Chl-a (i.e., mean Chl-a for the upper light penetration depth) is a relatively good proxy of phytoplankton biomass (i.e., depth-integrated Chl-a) within the euphotic zone but gives an inadequate representation of biomass within the mixed layer, particularly in the summer. Although nearly vertically homogeneous Chl-a within the mixed layer prevails in seasonal mean profiles, subsurface Chl-a maxima are not uncommon from spring through fall. Deep Chl-a maxima that correlate with particle backscattering in summer and fall are found near the base of the mixed layer, closer to the nutrient maximum than the light maximum, suggesting that nutrient limitation (i.e., essentially iron) can play a greater role than light limitation in governing productivity.

  5. Atmospheric forcing during active convection in the Labrador Sea and its impact on mixed-layer depth

    NASA Astrophysics Data System (ADS)

    Schulze, Lena M.; Pickart, Robert S.; Moore, G. W. K.

    2016-09-01

    Hydrographic data from the Labrador Sea collected in February-March 1997, together with atmospheric reanalysis fields, are used to explore relationships between the air-sea fluxes and the observed mixed-layer depths. The strongest winds and highest heat fluxes occurred in February, due to the nature and tracks of the storms. While greater numbers of storms occurred earlier and later in the winter, the storms in February followed a more organized track extending from the Gulf Stream region to the Irminger Sea where they slowed and deepened. The canonical low-pressure system that drives convection is located east of the southern tip of Greenland, with strong westerly winds advecting cold air off the ice edge over the warm ocean. The deepest mixed layers were observed in the western interior basin, although the variability in mixed-layer depth was greater in the eastern interior basin. The overall trend in mixed-layer depth through the winter in both regions of the basin was consistent with that predicted by a 1-D mixed-layer model. We argue that the deeper mixed layers in the west were due to the enhanced heat fluxes on that side of the basin as opposed to oceanic preconditioning.

  6. Nonlocal stochastic mixing-length theory and the velocity profile in the turbulent boundary layer

    NASA Astrophysics Data System (ADS)

    Dekker, H.; de Leeuw, G.; Maassen van den Brink, A.

    1995-02-01

    Turbulence mixing by finite size eddies will be treated by means of a novel formulation of nonlocal K-theory, involving sample paths and a stochastic closure hypothesis, which implies a well defined recipe for the calculation of sampling and transition rates. The connection with the general theory of stochastic processes will be established. The relation with other nonlocal turbulence models (e.g. transilience and spectral diffusivity theory) is also discussed. Using an analytical sampling rate model (satisfying exchange) the theory is applied to the boundary layer (using a scaling hypothesis), which maps boundary layer turbulence mixing of scalar densities onto a nondiffusive (Kubo-Anderson or kangaroo) type stochastic process. The resulting transpport equation for longitudinal momentum P x ≡ ϱ U is solved for a unified description of both the inertial and the viscous sublayer including the crossover. With a scaling exponent ε ≈ 0.58 (while local turbulence would amount to ε → ∞) the velocity profile U+ = ƒ(y +) is found to be in excellent agreement with the experimental data. Inter alia (i) the significance of ε as a turbulence Cantor set dimension, (ii) the value of the integration constant in the logarithmic region (i.e. if y+ → ∞), (iii) linear timescaling, and (iv) finite Reynolds number effects will be investigated. The (analytical) predictions of the theory for near-wall behaviour (i.e. if y+ → 0) of fluctuating quantities also perfectly agree with recent direct numerical simulations.

  7. Intercomparison and validation of the mixed layer depth fields of global ocean syntheses

    NASA Astrophysics Data System (ADS)

    Toyoda, Takahiro; Fujii, Yosuke; Kuragano, Tsurane; Kamachi, Masafumi; Ishikawa, Yoichi; Masuda, Shuhei; Sato, Kanako; Awaji, Toshiyuki; Hernandez, Fabrice; Ferry, Nicolas; Guinehut, Stéphanie; Martin, Matthew J.; Peterson, K. Andrew; Good, Simon A.; Valdivieso, Maria; Haines, Keith; Storto, Andrea; Masina, Simona; Köhl, Armin; Zuo, Hao; Balmaseda, Magdalena; Yin, Yonghong; Shi, Li; Alves, Oscar; Smith, Gregory; Chang, You-Soon; Vernieres, Guillaume; Wang, Xiaochun; Forget, Gael; Heimbach, Patrick; Wang, Ou; Fukumori, Ichiro; Lee, Tong

    2015-05-01

    Intercomparison and evaluation of the global ocean surface mixed layer depth (MLD) fields estimated from a suite of major ocean syntheses are conducted. Compared with the reference MLDs calculated from individual profiles, MLDs calculated from monthly mean and gridded profiles show negative biases of 10-20 m in early spring related to the re-stratification process of relatively deep mixed layers. Vertical resolution of profiles also influences the MLD estimation. MLDs are underestimated by approximately 5-7 (14-16) m with the vertical resolution of 25 (50) m when the criterion of potential density exceeding the 10-m value by 0.03 kg m-3 is used for the MLD estimation. Using the larger criterion (0.125 kg m-3) generally reduces the underestimations. In addition, positive biases greater than 100 m are found in wintertime subpolar regions when MLD criteria based on temperature are used. Biases of the reanalyses are due to both model errors and errors related to differences between the assimilation methods. The result shows that these errors are partially cancelled out through the ensemble averaging. Moreover, the bias in the ensemble mean field of the reanalyses is smaller than in the observation-only analyses. This is largely attributed to comparably higher resolutions of the reanalyses. The robust reproduction of both the seasonal cycle and interannual variability by the ensemble mean of the reanalyses indicates a great potential of the ensemble mean MLD field for investigating and monitoring upper ocean processes.

  8. Inviscid spatial stability of a compressible mixing layer. Part 3: Effect of thermodynamics

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

    The results of a comprehensive comparative study of the inviscid spatial stability of a parallel compressible mixing layer using various models for the mean flow are reported. The models are: (1) the hyperbolic tangent profile for the mean speed and the Crocco relation for the mean temperature, with the Chapman viscosity-temperature relation and a Prandtl number of one; (2) the Lock profile for the mean speed and the Crocco relation for the mean temperature, with the Chapman viscosity-temperature relation and a Prandtl number of one; and (3) the similarity solution for the coupled velocity and temperature equations using the Sutherland viscosity temperature relation and arbitrary but constant Prandtl number. The purpose was to determine the sensitivity of the stability characteristics of the compressible mixing layer to the assumed thermodynamic properties of the fluid. It is shown that the quantative features of the stability characteristics are quite similiar for all models but that there are quantitative differences resulting from the difference in the thermodynamic models. In particular, it is shown that the stability characteristics are sensitive to the value of the Prandtl number.

  9. Variable but persistent coexistence of Prochlorococcus ecotypes along temperature gradients in the ocean's surface mixed layer.

    PubMed

    Chandler, Jeremy W; Lin, Yajuan; Gainer, P Jackson; Post, Anton F; Johnson, Zackary I; Zinser, Erik R

    2016-04-01

    The vast majority of the phytoplankton communities in surface mixed layer of the oligotrophic ocean are numerically dominated by one of two ecotypes of Prochlorococcus, eMIT9312 or eMED4. In this study, we surveyed large latitudinal transects in the Atlantic and Pacific Ocean to determine if these ecotypes discretely partition the surface mixed layer niche, or if populations exist as a continuum along key environmental gradients, particularly temperature. Transitions of dominance occurred at approximately 19-21°C, with the eMED4 ecotype dominating the colder, and eMIT9312 ecotype dominating the warmer regions. Within these zones of regional dominance, however, the minority ecotype was not competed to extinction. Rather, a robust log-linear relationship between ecotype ratio and temperature characterized this stabilized coexistence: for every 2.5°C increase in temperature, the eMIT9312:eMED4 ratio increased by an order of magnitude. This relationship was observed in both quantitative polymerase chain reaction and in pyrosequencing assays. Water column stratification also contributed to the ecotype ratio along the basin-scale transects, but to a lesser extent. Finally, instances where the ratio of the eMED4 and eMIT9312 abundances did not correlate well with temperature were identified. Such occurrences are likely due to changes in water temperatures outpacing changes in community structure.

  10. Investigation of the frozen-turbulence hypothesis for temperature spectra in a convectively mixed layer

    NASA Astrophysics Data System (ADS)

    Deardorff, J. W.; Willis, G. E.

    1982-01-01

    Taylor's frozen turbulence hypothesis is investigated in a laboratory free-convection mixed layer which can simulate buoyancy-driven turbulence in an atmospheric mixed layer (of height h) for mean wind speeds of up to several meters per second. For large turbulence intensities the temperature spectra at the height 0.1h are found to be spuriously enhanced at higher wavenumbers based on the frozen turbulence hypothesis, as deduced theoretically by previous investigators. The excess is borrowed from spectral intensities within the energy-containing range. A theory based on the concept of longitudinal-temporal isotropy, after proper scaling of the coordinates, is shown to predict a simple shift of the entire spectrum toward higher wavenumbers with increasing turbulence intensity. The failure of the observed spectra to behave this simply is associated with a complicated structure of the correlation coefficient as a function of longitudinal-temporal lag coordinates when the former is measured relative to a frame moving with the mean flow speed. The temperature spectrum based on the frozen-turbulence hypothesis appears to be a satisfactory representation of the true spectrum in wavenumber space, in tubulence dominated by thermal convection, if the mean wind speed exceeds 2.7-3.6 times the root-mean-square horizontal velocity fluctuation.

  11. Parametric analysis of a complex flow: a mixing layer- wake interaction

    NASA Astrophysics Data System (ADS)

    Braud, Caroline; Heitz, Dominique

    2004-11-01

    The flow studied is a cross interaction from two canonical flows, a wake and a mixing layer, realized for the first time by Heitz(1999) for a particular configuration (Reynolds number 7, 500, aspect ratio 18, shear parameter 0.42). He found that the difference of velocity between two sides of the mixing layer gives rise to a pressure gradient along the cylinder responsible for a secondary flow from the low to high velocity side in the near wake. As a consequence the suction coefficient (C_p), the frequency distribution (f) and the vortex length formation (L_f) are locally greatly modified if we compare them to uniform flow. Nevertheless, the aspect ratio, according to Norberg (1994), and the shear parameter (in uniform shear wake: 0.02) are control parameters of great importance for the shedding organization in the near wake. In order to investigate the influence of those control parameters (Reynolds numbers, two aspects ratio and five shear parameters) hot wire and pressure measurement have been carried out. We mainly found that even if the magnitude of the mean characteristic parameters is locally strongly perturbated along the cylinder, the resulting wake keeps its general behavior.

  12. Quantifying subtropical North Pacific gyre mixed layer primary productivity from Seaglider observations of diel oxygen cycles

    NASA Astrophysics Data System (ADS)

    Nicholson, David P.; Wilson, Samuel T.; Doney, Scott C.; Karl, David M.

    2015-05-01

    Using autonomous underwater gliders, we quantified diurnal periodicity in dissolved oxygen, chlorophyll, and temperature in the subtropical North Pacific near the Hawaii Ocean Time-series (HOT) Station ALOHA during summer 2012. Oxygen optodes provided sufficient stability and precision to quantify diel cycles of average amplitude of 0.6 µmol kg-1. A theoretical diel curve was fit to daily observations to infer an average mixed layer gross primary productivity (GPP) of 1.8 mmol O2 m-3 d-1. Cumulative net community production (NCP) over 110 days was 500 mmol O2 m-2 for the mixed layer, which averaged 57 m in depth. Both GPP and NCP estimates indicated a significant period of below-average productivity at Station ALOHA in 2012, an observation confirmed by 14C productivity incubations and O2/Ar ratios. Given our success in an oligotrophic gyre where biological signals are small, our diel GPP approach holds promise for remote characterization of productivity across the spectrum of marine environments.

  13. 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.

  14. Simulation of mixed-host emitting layer based organic light emitting diodes

    SciTech Connect

    Riku, C.; Kee, Y. Y.; Ong, T. S.; Tou, T. Y.; Yap, S. S.

    2015-04-24

    ‘SimOLED’ simulator is used in this work to investigate the efficiency of the mixed-host organic light emitting devices (MH-OLEDs). Tris-(8-hydroxyquinoline) aluminum(3) (Alq{sub 3}) and N,N-diphenyl-N,N-Bis(3-methylphenyl)-1,1-diphenyl-4,4-diamine (TPD) are used as the electron transport layer (ETL) material and hole transport layer (HTL) material respectively, and the indium-doped tin oxide (ITO) and aluminum (Al) as anode and cathode. Three MH-OLEDs, A, B and C with the same structure of ITO / HTM (15 nm) / Mixed host (70 nm) / ETM (10 nm) /Al, are stimulated with ratios TPD:Alq{sub 3} of 3:5, 5:5, and 5:3 respectively. The Poole-Frenkel model for electron and hole mobilities is employed to compute the current density-applied voltage-luminance characteristics, distribution of the electric field, carrier concentrations and recombination rate.

  15. Mixed mode transition in zero and adverse pressure gradient boundary layers

    NASA Astrophysics Data System (ADS)

    Bose, Rikhi; Durbin, Paul

    2015-11-01

    Flow regimes exist where interaction of Klebanoff streaks and the Tollmien-Sclichting waves trigger transition but either mode is individually insufficient. Such interaction between orderly and bypass routes of transition is called Mixed mode transition. In zero pressure gradient boundary layers, mixed mode transition follows three routes depending upon strength of these perturbation modes. At high free-stream turbulence intensity (Tu), bypass transition is dominant and the flow is very weakly sensitive to the TS mode strength. In the presence of a strong TS mode, low Tu triggers secondary instability of the TS wave forming Λ vortices. The Λ vortices are forced response due to the weak streaks rather than resonance mechanism seen in monochromatic excitations. When both of these modes are weak, secondary instability of streaks trigger consequent breakdown to turbulent spots. Three-dimensional visualization of the perturbation fields shows toroidal n = 0 and helical n = 1 modes observed in instability of axisymmetric jets and wakes. In adverese pressure gradient boundary layers, the presence of an inflection point significantly increases the growth rate of TS mode thereby strengthening the secondary instability route and the interaction is more interesting. This work was supported by NSF grant CBET-1228195. Computer time was provided by the Extreme Science and Engineering Discovery Environment (XSEDE).

  16. Profiling float-based observations of net respiration beneath the mixed layer

    NASA Astrophysics Data System (ADS)

    Hennon, Tyler D.; Riser, Stephen C.; Mecking, Sabine

    2016-06-01

    We employ profiling floats with dissolved oxygen sensors to observe in situ temporal oxygen evolution below the mixed layer, allowing us to characterize net respiration of organic carbon in eight distinct regions over the globe. Export and export efficiency are generally high in locations with strong seasonal variability and low in locations of weak seasonality. Vertically integrated respiration is weakly, yet significantly, correlated with remote observations of chlorophyll, net primary production, and planktonic community size structure. These correlations suggest that regimes of high net primary production and large phytoplankton fuel elevated respiration at depth. Several regions of float-based observations intersect with sites of other detailed observations (e.g., Hawaii and Sargasso Sea), which allows us to compare our results to independent studies. We find that there is good agreement among export production estimates at highly seasonal locations, and that float-based observations may be biased low at weakly seasonal locations. We posit that the reason for the low-latitude discrepancy is the relative steady state of oxygen concentration caused by weak seasonality and shallow wintertime mixed layer depths.

  17. Mach waves produced in the supersonic jet mixing layer by shock/vortex interaction

    NASA Astrophysics Data System (ADS)

    Oertel Sen, H.; Seiler, F.; Srulijes, J.; Hruschka, R.

    2016-05-01

    The noise emission of free jets has been extensively investigated for many decades. At subsonic jet velocities, coherent structures of the mixing layer move at subsonic speed and emit sound waves. Free jets blowing at supersonic speeds, however, can emit weak shock waves, called Mach waves. At supersonic speeds, two cases must be distinguished: the structures move either subsonically or supersonically relative to the inside and/or outside speed of sound. In the case of supersonic movement, the Mach waves exist inside as well as outside the jet. At subsonic speeds, no Mach waves appear. Although numerous theories have been established to find the origin of the Mach waves, to the authors' best knowledge, the mechanism of the Mach wave formation has not yet been clearly explained. Recently another theory of Mach waves in supersonic jets was developed, as described herein, which outlines the causes for the Mach wave production and stability as well as their dynamics. The theory's principle is that the Mach waves are initiated by vortices which move downstream at three speeds w, {w}' and {w}'' inside of the mixing layer. These three types of vortices and Mach waves are described in a comprehensive manner by the theory and are called the " w-, {w}'- and {w}''-vortices" and " w-, {w}'- and {w}''-Mach waves," respectively.

  18. Observed and modeled mixed-layer variability on the continental shelf of Sardinia (Western Mediterranean)

    NASA Astrophysics Data System (ADS)

    Onken, Reiner

    2016-04-01

    An important task of Military Oceanography is the prediction of mixed-layer properties and their spatial and temporal variability. In the mainframe of the REP14-MED sea trial which was conducted under the lead of CMRE in June 2014 in the waters west of Sardinia, an oceanographic mooring was deployed on the continental shelf which recorded the seawater temperature between the surface and 40-m depth with high resolution for about twelve days; meteorological parameters were collected at the same time on top of the mooring by a meteorological buoy. A series of ROMS model runs was conducted and validated against the observations. Those runs applied different setups for the forcing at the lateral open boundaries and at the surface, different arrangements of the vertical coordinates, and different strategies for the assimilation of data from CTD casts and gliders. The goal was to test the sensitivity of the forecast skill to the different setups and to find a "cheap" setup which predicts the observed temperature and the mixed-layer depth and their temporal variabilities to a satisfactory degree. That setup is supposed to provide also reliable forecasts for the other areas of the model domain.

  19. Perturbation Effects on a Supercritical C7H16/N2 Mixing Layer

    NASA Technical Reports Server (NTRS)

    Okongo'o, Nora; Bellan, Josette

    2008-01-01

    A computational-simulation study has been presented of effects of perturbation wavelengths and initial Reynolds numbers on the transition to turbulence of a heptane/nitrogen mixing layer at supercritical pressure. The governing equations for the simulations were the same as those of related prior studies reported in NASA Tech Briefs. Two-dimensional (2D) simulations were performed with initially im posed span wise perturbations whereas three-dimensional (3D) simulations had both streamwise and spanwise initial perturbations. The 2D simulations were undertaken to ascertain whether perturbations having the shortest unstable wavelength obtained from a linear stability analysis for inviscid flow are unstable in viscous nonlinear flows. The goal of the 3D simulations was to ascertain whether perturbing the mixing layer at different wavelengths affects the transition to turbulence. It was found that transitions to turbulence can be obtained at different perturbation wavelengths, provided that they are longer than the shortest unstable wavelength as determined by 2D linear stability analysis for the inviscid case and that the initial Reynolds number is proportionally increased as the wavelength is decreased. The transitional states thus obtained display different dynamic and mixture characteristics, departing strongly from the behaviors of perfect gases and ideal mixtures.

  20. The 2008 North Atlantic Spring Bloom Experiment II: Autonomous Platforms and Mixed Layer Evolution

    NASA Astrophysics Data System (ADS)

    Lee, C. M.; D'Asaro, E. A.; Perry, M.; Fennel, K.; Gray, A.; Rehm, E.; Briggs, N.; Sackmann, B. S.; Gudmundsson, K.

    2008-12-01

    The 2008 North Atlantic Spring Bloom Experiment (NAB08) employed a system of drifting floats, mobile gliders and ship-based measurements to resolve patch-scale physical and biological variability over the 3- month course of an entire bloom. Although both autonomous and ship-based elements were essential to achieving NAB08 goals, the autonomous system provided a novel perspective by employing long-range gliders to repeatedly survey the volume surrounding a drifting Lagrangian float, thus characterizing patch- scale bloom evolution. Integration of physical and biogeochemical sensors (temperature, conductivity, dissolved oxygen, chlorophyll and CDOM fluorescence, light transmission, optical backscatter, spectral light, and nitrate) and development of in situ calibration techniques were required to support this new autonomous approach. Energetic, small-scale eddy activity at the experiment site (southeast of Iceland, near the Joint Global Ocean Flux Study and Marine Light Mixed Layer sites) produced a swift, heterogeneous velocity field that challenged the gliders" operational abilities and drove refinements to the piloting techniques used to maintain float-following surveys. Although intentionally deployed outside of energetic eddies, floats and gliders were rapidly entrained into these features. Floats circulated within eddies near the start and end of the experiment, drifting generally northwest, across the basin, in-between. An eddy sampled late in the deployment provided particularly interesting signatures, with elevated biological signals manifest consistently in one quadrant. As measurements were collected in a parcel-following Lagrangian frame, this suggests energetic small-scale exchange process (such as vertical or lateral mixing) paired with fast-acting biological processes capable of modifying the newly entrained water as it navigates its path around the eddy. Despite this energetic kilometer-scale heterogeneity, broadly distributed platforms appeared to

  1. Tear-film lipid layer morphology and corneal sensation in the development of blinking in neonates and infants

    PubMed Central

    Lawrenson, John G; Birhah, Rosalind; Murphy, Paul J

    2005-01-01

    The aim of the study was to evaluate the role of lipid layer thickness and corneal sensation in the development of blinking in neonates. The study group comprised sixty-four neonates and infants (mean age 27.5 ± 15 (sd) weeks, range 3.4–52) whose mothers were attending a general practice healthy baby clinic. Spontaneous eye-blink activity was determined from digital videographic recordings; tear film lipid layer morphology wasexamined using interference patterns produced by the Keeler Tearscope™ Plus over a five-point grading scale (higher grades are associated with thick and stable lipid films); corneal sensation threshold was assessed with the Non-Contact Corneal Aesthesiometer (NCCA), using the eye-blink response as an objective indication that the cooling stimulus had been felt; palpebral aperture dimensions were measured using calibrated digital still images of the eye in the primary position. The overall mean spontaneous blink-rate was found to be 3.6 (± 0.3) blinks min−1, and the mean interblink time was 21.6 (± 2.8) s. The lowest blink-rates were observed in the 0–17-week age group (average 2 blinks min−1). The blink-rate showed a highly significant correlation with age (r = 0.46, P < 0.01). The overall mean lipid layer grading was 3.6 (± 0.2 SE) arbitrary units. Higher grades were found in the newborn and the mean grading score reduced with age (P < 0.01). The mean sensation threshold to blink (TTB) was 0.69 (0.04 SE) mbar, which did not differ from a control group of older subjects (P > 0.05). There was a rapid increase in palpebral aperture length and width from birth to 1 year old, with surface area increasing by 50% over the same period. We concluded that the low rate of spontaneous eye blink activity in neonates is associated with a thick stable lipid layer that may be a function of a small palpebral aperture. Furthermore, neonates appear to have the capacity to detect ocular surface cooling, which is a major trigger for spontaneous

  2. Surface enhanced Raman spectroscopy of self-assembled layers of lipid molecules on nanostructured Au and Ag substrates.

    PubMed

    Slekiene, Nora; Ramanauskaite, Lina; Snitka, Valentinas

    2017-03-01

    In this work surface enhanced Raman spectroscopy (SERS) has been used for the investigation of the self-assembled layers of lipid molecules (SALLMs) deposited on the nanostructured Au and Ag surfaces. The SALLMs were prepared from one part of 1,2-dioleoyl-sn-glycero-3-phospho-l-serine (DOPS) and four parts of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) lipids. The synthesis of Au and Ag SERS substrates was based on the direct gold and silver ions reduction onto HF etched silicon wafers. Au SERS substrates were not suitable for the formation of SALLMs because of the inappropriate contact angle of surface. It was found that the formation of the SALLM does not take place on Au SERS substrate. However, it has been shown that the modification of Au SERS substrate with 1-dodecanothiol layer allows building the SALLM on its surface. In the case of Ag SERS substrate, the SALLM was deposited directly on its surface. The SERS spectra of the SALLMs were recorded in the CH stretching (2800-3000cm(-1)) and the fingerprint (<1.800cm(-1)) regions. It has been demonstrated that the SERS spectra of the SALLM recorded on Au substrate differs from that one recorded on Ag SERS substrate. These spectral differences were found to be determined by the different interaction mechanisms of the lipid molecules with nanostructured surfaces.

  3. Unified Cloud and Mixing Parameterizations of the Marine Boundary Layer: EDMF and PDF-Based Cloud Approaches

    DTIC Science & Technology

    2013-09-30

    against observations and LES results for GCSS cloud transition cases – i.e. from stratocumulus to cumulus . Implementation and evaluation of new EDMF...flow, and in the cumulus -dominated boundary layer they represent convective clouds . Therefore, the solutions have to account for a realistic...LES results. In the SCM, the well mixed boundary layer is more moist than in the LES results and consequently the cumulus dominated cloud layer is

  4. Mixed culture of oleaginous yeast Rhodotorula glutinis and microalga Chlorella vulgaris for lipid production from industrial wastes and its use as biodiesel feedstock.

    PubMed

    Cheirsilp, Benjamas; Suwannarat, Warangkana; Niyomdecha, Rujira

    2011-07-01

    A mixed culture of oleaginous yeast Rhodotorula glutinis and microalga Chlorella vulgaris was performed to enhance lipid production from industrial wastes. These included effluent from seafood processing plant and molasses from sugar cane plant. In the mixed culture, the yeast grew faster and the lipid production was higher than that in the pure cultures. This could be because microalga acted as an oxygen generator for yeast, while yeast provided CO(2) to microalga and both carried out the production of lipids. The optimal conditions for lipid production by the mixed culture were as follows: ratio of yeast to microalga at 1:1; initial pH at 5.0; molasses concentration at 1%; shaking speed at 200 rpm; and light intensity at 5.0 klux under 16:8 hours light and dark cycles. Under these conditions, the highest biomass of 4.63±0.15 g/L and lipid production of 2.88±0.16 g/L were obtained after five days of cultivation. In addition, the plant oil-like fatty acid composition of yeast and microalgal lipids suggested their high potential for use as biodiesel feedstock.

  5. Cooling and deepening of the mixed layer in the central Arabian Sea during MONSOON-77: observations and simulations

    NASA Astrophysics Data System (ADS)

    Rao, R. R.

    1986-10-01

    A one-dimensional numerical model developed by Kraus and Turner (1967, Tellus, 19, 98-106) and modified by DENMAN (1973, Journal of Physical Oceanography, 3, 173-184) and MILLER (1976, Journal of Physical Oceanography, 6, 29-35) was utilized to simulate the observed cooling and deepening of the mixed layer in the central Arabian Sea during the onset of the summer monsoon. Wind stress, surface salt and heat budgets as destabilizing factors with below layer thermohaline gradients as stabilizing factors are considered in the simulation of mixed layer depth (MLD). Surface heat budget processes and entrainment at the base of the mixed layer are considered for the simulation of mixed layer temperature (MLT). Simulated values achieve minimum r.m.s. errors of 4.5 m and 0.1°C in MLD and MLT, respectively. Inclusion of vertical entrainment at the base of the mixed layer significantly increases the error in MLT simulation, relative to that achieved with the surface heat budget alone.

  6. Dried flour-oil composites for lipid delivery in low-fat cake mix

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Excess steam jet-cooked wheat flour and canola oil composites containing 30 to 55% oil were drum dried. The composites were used to replace the flour and oil in the low-fat cake mix formulations. The cake batter specific gravity and viscosity were measured. The cakes were analyzed for crumb grain...

  7. Effect of chemical heat release in a temporally evolving mixing layer

    NASA Technical Reports Server (NTRS)

    Higuera, F. J.; Moser, R. D.

    1994-01-01

    Two-dimensional numerical simulations of a temporally evolving mixing layer with an exothermic infinitely fast diffusion flame between two unmixed reactants have been carried out in the limit of zero Mach number to study the effect of the heat release on the early stages of the evolution of the flow. Attention has been directed to relatively large values of the oxidizer-to-fuel mass stoichiometric ratio typical of hydrocarbon flames, and initial vorticity distributions thicker than the temperature and species distributions have been chosen to mimic the situation at the outlet of a jet. The results show that, during the stages of the evolution covered by the present simulations, enhancement of combustion occurs by local stretching of the flame without much augmentation of its area. The rate of product generation depends strongly on the initial conditions, which suggests the possibility of controlling the combustion by acting on the flow. Rollup and vortex amalgamation still occur in these reacting flows but are very much affected by the production of new vorticity by baroclinic torques. These torques lead to counter rotating vortex pairs around the flame and, more importantly, in thin layers of light fluid that leave the vicinity of the flame when the Kelvin-Helmholtz instability begins to develop. Propelled by the vortex pairs, these layers wind around, split on reaching high pressure regions, and originate new vortex pairs in a process that ends up building large-scale vortices with a vorticity distribution more complex than for a constant density fluid.

  8. Recent changes of Mixed Layer Depth in the East/Japan Sea: 1994-2007

    NASA Astrophysics Data System (ADS)

    Chang, Pil-Hun; Cho, Chun-Ho; Ryoo, Sang-Boom

    2011-11-01

    Recent changes of Mixed Layer Depth (MLD) in the East/Japan Sea (EJS) is investigated by using ocean reanalysis data. There is a significant shoaling of MLD in the southern EJS for 1994-2007, showing the change rate of - 1.24 m yr-1. The present study demonstrates that the wind stress curl mostly attributes to the MLD changes. The long-term variation of wind stress curl with a positive trend in the southern EJS is generally well consistent with the MLD variation. In addition, upward displacement estimated from the wind stress curl reaches 14.6 m during 14 years, which is comparable to the shoaling of MLD (i.e., 17.4 m). Thus, the wind stress curl with positive trend would induce the increase of upward Ekman pumping which in turn lead to the shoaling of MLD. The change of temperature structure in the subsurface layer, that is shrinking and upward displacement of thermal layer from the reanalysis and observational data, also supports this conclusion.

  9. High-brightness and long-lifetime OLED with mixing layer technology

    NASA Astrophysics Data System (ADS)

    Lee, Jiun H.; Liu, S. W.; Huang, Ching-An; Yang, K. H.; Chang, Yih

    2004-09-01

    In this paper, we demonstrate organic light emitting devices (OLED) that exhibit high brightness, low driving voltage and long lifetime. Devices with the brightness of 10,000 cd/m2 can be achieved at 4 V by the use of the high mobility electron-transport layer (ETL) material, bis(10-hydroxybenzo[h]qinolinato)beryllium (Bebq2), and the mixing host (MH) technology. Electron mobility of Bebq2 is two orders of magnitude higher than that of the typical ETL material, tris-(8-hydroxyquinoline) aluminum (Alq3), from the time-of-flight (TOF) measurement and hence the driving voltage can be decreased. By co-evaporating the hole-transport layer (HTL) material and the ETL material as the host of the emitting layer, it reduces two volts in driving voltage because of its bipolar transport characteristics. MH technology can not only decrease the driving voltage, but also increase the device lifetime since it eliminates the sharp boundary of HTL/ETL interface and decreases the carriers piling up near this interface which causes the organic material degradation. Compared to the conventional heterojunction (HJ) OLED, operation lifetime of MH devices was enhanced by a factor of 4.

  10. Evaluation of continuous ceilometer-based mixing layer heights and correlations with PM2.5 concentrations in Beijing

    NASA Astrophysics Data System (ADS)

    Schäfer, Klaus; Wang, Yuesi; Münkel, Christoph; Emeis, Stefan; Xin, Jinyuan; Tang, Guiqian; Norra, Stefan; Schleicher, Nina; Vogt, Joachim; Suppan, Peter

    2009-09-01

    Beijing air quality suffers from frequently occurring inversion layers. These inversion layers can last for several days and below these layers, pollution is accumulated. In the absence of inversions an urban boundary layer still exists delimiting the urban atmosphere from the free atmosphere. The height of this layer can potentially influence the urban atmospheric pollution. In both cases, particle concentration might change with height. A measurement campaign was performed to study those meteorological conditions, which are one of the causes for intensive air pollution in the region of Beijing during spring 2009. The mixing layer height (MLH) was studied by a ceilometer continuously. It was used to analyse the actual development of the height of inversion and boundary layers and the distribution of particles. Additionally, meteorological data from a radiosonde station are available. The measurements to study the vertical distribution of atmospheric layers in combination with particulate concentrations for specific times will be presented. The results of that campaign will be discussed.

  11. Transitional Boundary-Layer Solutions Using a Mixing-Length and a Two-Equation Turbulence Model

    NASA Technical Reports Server (NTRS)

    Anderson, E. C.; Wilcox, D. C.

    1978-01-01

    Boundary-layer solutions were obtained using the conventional two-layer mixing-length turbulence model and the Wilcox-Traci two-equation model of turbulence. Both flatplate and blunt-body geometries were considered. The most significant result of the study is development of approximations for the two-equation model which permit streamwise stepsize comparable to that used in mixing-length computations. Additionally, a set of model-equation boundary conditions derived which apply equally well to both flat-plate and blunt-body geometries. Solutions obtained with the two-equations turbulence model are compared with experimental data and/or corresponding solutions obtained using the mixing-length model. Agreement is satisfactory for flat-plate boundary layers but not for blunt body boundary layers.

  12. Selectivity of layered double hydroxides and their derivative mixed metal oxides as sorbents of hydrogen sulfide.

    PubMed

    Othman, Mohamed A; Zahid, Waleed M; Abasaeed, Ahmed E

    2013-06-15

    In the context of finding high efficient sorbent materials for removing hydrogen sulfide (H2S) from air stream, a screening study was performed to find the best combination of metals for the synthesis of layered double hydroxides (LDHs) and their derivative mixed metal oxides. Based on selectivity of 998 natural mineral species of sulfur-containing compounds, Cu(2+), Ni(2+) and Zn(2+) were selected as divalent metals, and Fe(3+), Al(3+) and Cr(3+) as trivalent metals to synthesis the LDHs sorbents. 10 LDHs materials and their calcined mixed metal oxides, Ni(0.66)Al(0.34), Cu(0.35)Ni(0.32)Al(0.33), Zn(0.66)Al(0.34), Cu(0.36)Zn(0.32)Al(0.32), Ni(0.64)Fe(0.36), Cu(0.35)Ni(0.31)Fe(0.34), Ni(0.66)Cr(0.34), Cu(0.35)Ni(0.31)Cr(0.34), Zn(0.66)Cr(0.34), Cu(0.33)Zn(0.32)Cr(0.35) were synthesized, characterized chemically and physically, and then tested using breakthrough test to determine their sulfur uptake. Ni(0.64)Fe(0.36) mixed metal oxides was found to have the best uptake of hydrogen sulfide (136 mg H₂S/g). Regeneration of spent Ni(0.64)Fe(0.36) mixed metal oxides was studied using two different mixture solutions, NaCl/NaOH and acetate-buffer/NaCl/NaOH. The latter mixture successfully desorbed the sulfur from the Ni0.64Fe0.36 sorbent for 2 cycles of regeneration/sorption.

  13. [Characteristics of Winter Atmospheric Mixing Layer Height in Beijing-Tianjin-Hebei Region and Their Relationship with the Atmospheric Pollution].

    PubMed

    Li, Meng; Tang, Gui-qian; Huang, Jun; Liu, Zi-rui; An, Jun-lin; Wang, Yue-si

    2015-06-01

    Atmospheric mixing layer height (MLH) is one of the main factors affecting the atmospheric diffusion and plays an important role in air quality assessment and distribution of the pollutants. Based on the ceilometers data, this paper has made synchronous observation on MLH in Beijing-Tianjin-Hebei region (Beijing, Tianjin, Shijiazhuang and Qinhuangdao) in heavy polluted February 2014 and analyzed the respective overall change and its regional features. Results show that in February 2014,the average of mixing layer height in Qinhuangdao is the highest, up to 865 +/- 268 m, and in Shijiazhuang is the lowest (568 +/- 207 m), Beijing's and Tianjin's are in between, 818 +/- 319 m and 834 +/- 334 m respectively; Combined with the meteorological data, we find that radiation and wind speed are main factors of the mixing layer height; The relationship between the particle concentration and mixing layer height in four sites suggests that mixing layer is less than 800 m, concentration of fine particulate matter in four sites will exceed the national standard (GB 3095-2012, 75 microg x m(-3)). During the period of observation, the proportion of days that mixing layer is less than 800 m in Beijing, Tianjin, Shijiazhuang and Qinhuangdao are 50%, 43%, 80% and 50% respectively. Shijiazhuang though nearly formation contaminant concentration is high, within the atmospheric mixed layer pollutant load is not high. Unfavorable atmospheric diffusion conditions are the main causes of heavy pollution in Shijiazhuang for a long time. The results of the study are of great significance for cognitive Beijing-Tianjin-Hebei area pollution distribution, and can provide a scientific reference for reasonable distribution of regional pollution sources.

  14. Improved pharmacokinetics and enhanced tumor growth inhibition using a nanostructured lipid carrier loaded with doxorubicin and modified with a layer-by-layer polyelectrolyte coating

    PubMed Central

    Mussi, Samuel V.; Parekh, Gaurav; Pattekari, Pravin; Levchenko, Tatyana; Lvov, Yuri; Ferreira, Lucas A.M.; Torchilin, Vladimir P.

    2015-01-01

    A nanostructured lipid carrier (NLC) loaded with doxorubicin (DOX) has been shown to be cytotoxic against the human cancer cell lines A549 and MCF-7/Adr. In attempts to improve formulation characteristics, enhance pharmacokinetics and antitumor effects, we modified the surface of these NLC with an alternating layer-by-layer (LbL) assembly of polycation and polyanion polyelectrolytes and an additional coating with PEG using a simple method of core shell attachment. The formulation had a narrow size distribution, longer residence in the blood, lower accumulation in the liver, higher accumulation in tumors and a significant tumor growth inhibition effect. Thus, NLC-DOX nanopreparations complexes modified by LbL coating have the potential to enhance the anticancer effects of DOX against tumors. PMID:26325314

  15. Connection between Magnetic Topology, Mixing and the Reconnection Rate in Asymmetric Layers

    NASA Astrophysics Data System (ADS)

    Daughton, W. S.; Nakamura, T.; Roytershteyn, V.; Karimabadi, H.; Hesse, M.; Loring, B.

    2013-12-01

    The entry of solar wind plasma into the magnetosphere occurs in thin boundary layers, which are typically asymmetric and have large magnetic and/or velocity shear across them. Magnetic reconnection is the dominant entry mechanism, but in regions with strong nearly perpendicular velocity shear, the Kelvin-Helmholtz instability dominates and can lead to vortex induced reconnection [1]. In both of these limits, recent fully kinetic simulations feature the development of 3D turbulence, characterized by electron-scale current sheets and interacting magnetic flux ropes. The 3D magnetic field, characterized by the Lyapunov exponent, reveals a chaotic structure within the reconnection layer in which neighboring field lines undergo rapid separation. In the presence of this complex 3D dynamics, defining and accurately computing the time evolving reconnection rate is a major challenge. One of the leading theoretical ideas [2] for computing the rate is based on integrating the parallel electric field. However, applying this approach is complicated by the chaotic magnetic field, which can lead to different answers on closely neighboring field lines. Furthermore, it is difficult to cleanly identify a transition back into an ideal region where the integration can be terminated. Here we explore a new approach that exploits the connection between the magnetic topology and the mixing of electrons that originate from separate sides of the asymmetric current layer. This idea is motivated by a clear correlation between the Lyapunov exponent for the magnetic field and the boundaries between mixed and unmixed regions. This correlation implies that mixing is a good proxy for quickly identifying 3D surfaces separating different topologies, and thus accurately measuring the time changing flux between topologies. The 3D reconnection rate obtained from this approach is contrasted with corresponding 2D simulations in the limits of both weak and strong velocity shear. [1] T.K.M Nakamura et al

  16. Configurational entropies of lipids in pure and mixed bilayers from atomic-level and coarse-grained molecular dynamics simulations.

    PubMed

    Baron, Riccardo; de Vries, Alex H; Hünenberger, Philippe H; van Gunsteren, Wilfred F

    2006-08-10

    Single-chain and single-fragment configurational entropies of lipid tails in hydrated lipid bilayers are evaluated from molecular dynamics simulations using the quasi-harmonic approximation. The entropy distribution along individual acyl tails is obtained and compared to that of corresponding hydrocarbon chains in the liquid phase. We consider pure dipalmitoylphosphatidylcholine and mixed dioleoylphosphatidylcholine/dioleoylphosphatidylethanolamine bilayers. The systems are modeled at different levels of spatial resolution: In an atomic-level (AL) model all (heavy) atoms are explicitly simulated; in a coarse-grained (CG) model particles (beads) representing groups of covalently bound atoms are used, which map approximately four non-hydrogen atoms to one interaction site. Single-chain and single-fragment entropies and correlations between the motions of (single) acyl chains are compared. A good correspondence is found between the flexibility of the AL and CG models. The loss in configurational entropy due to the reduction in the number of degrees of freedom upon coarse-graining of the model is estimated. The CG model shows about 4 times faster convergence of the chain entropies than the more detailed AL model. Corrections to the quasi-harmonic entropy estimates were found to be small for the CG model. For the AL model, the correction due to mode anharmonicities is small, but the correction due to pairwise (supralinear) mode correlations is sizable.

  17. Mechanisms Controlling the Interannual Variation of Mixed Layer Temperature Averaged over the Nino-3 Region

    NASA Technical Reports Server (NTRS)

    Kim, Seung-Bum; Lee, Tong; Fukumori, Ichiro

    2007-01-01

    The present study examines processes governing the interannual variation of MLT in the eastern equatorial Pacific.Processes controlling the interannual variation of mixed layer temperature (MLT) averaged over the Nino-3 domain (5 deg N-5 deg S, 150 deg-90 deg W) are studied using an ocean data assimilation product that covers the period of 1993-2003. The overall balance is such that surface heat flux opposes the MLT change but horizontal advection and subsurface processes assist the change. Advective tendencies are estimated here as the temperature fluxes through the domain's boundaries, with the boundary temperature referenced to the domain-averaged temperature to remove the dependence on temperature scale. This allows the authors to characterize external advective processes that warm or cool the water within the domain as a whole. The zonal advective tendency is caused primarily by large-scale advection of warm-pool water through the western boundary of the domain. The meridional advective tendency is contributed to mostly by Ekman current advecting large-scale temperature anomalies through the southern boundary of the domain. Unlike many previous studies, the subsurface processes that consist of vertical mixing and entrainment are explicitly evaluated. In particular, a rigorous method to estimate entrainment allows an exact budget closure. The vertical mixing across the mixed layer (ML) base has a contribution in phase with the MLT change. The entrainment tendency due to the temporal change in ML depth is negligible compared to other subsurface processes. The entrainment tendency by vertical advection across the ML base is dominated by large-scale changes in upwelling and the temperature of upwelling water. Tropical instability waves (TIWs) result in smaller-scale vertical advection that warms the domain during La Nina cooling events. However, such a warming tendency is overwhelmed by the cooling tendency associated with the large-scale upwelling by a factor of

  18. Simultaneous measurement of lipid and aqueous layers of tear film using optical coherence tomography and statistical decision theory

    NASA Astrophysics Data System (ADS)

    Huang, Jinxin; Clarkson, Eric; Kupinski, Matthew; Rolland, Jannick P.

    2014-03-01

    The prevalence of Dry Eye Disease (DED) in the USA is approximately 40 million in aging adults with about $3.8 billion economic burden. However, a comprehensive understanding of tear film dynamics, which is the prerequisite to advance the management of DED, is yet to be realized. To extend our understanding of tear film dynamics, we investigate the simultaneous estimation of the lipid and aqueous layers thicknesses with the combination of optical coherence tomography (OCT) and statistical decision theory. In specific, we develop a mathematical model for Fourier-domain OCT where we take into account the different statistical processes associated with the imaging chain. We formulate the first-order and second-order statistical quantities of the output of the OCT system, which can generate some simulated OCT spectra. A tear film model, which includes a lipid and aqueous layer on top of a rough corneal surface, is the object being imaged. Then we further implement a Maximum-likelihood (ML) estimator to interpret the simulated OCT data to estimate the thicknesses of both layers of the tear film. Results show that an axial resolution of 1 μm allows estimates down to nanometers scale. We use the root mean square error of the estimates as a metric to evaluate the system parameters, such as the tradeoff between the imaging speed and the precision of estimation. This framework further provides the theoretical basics to optimize the imaging setup for a specific thickness estimation task.

  19. Structural studies of mixed lipid bilayers on solid substrates using x-ray reflectivity

    NASA Astrophysics Data System (ADS)

    Chen, Gang; Mukhopadhyay, Mrinmay; Ma, Yicong; Sinha, Sunil; Jiang, Zhang; Decaro, Curt; Berry, Justin; Lurio, Laurence; Brozell, Adrian; Parikh, Atul

    2009-03-01

    The lipid bilayers of natural membranes generally exist in a fluid state which occurs above the gel to liquid crystalline phase transition temperature. Knowledge of the structure of such bilayers is important for understanding fundamental biological processes mediated by or occurring within membranes. We have performed systematic measurements on bilayers of 1,2-Dipalmitoyl-sn-Glycero-3-Phosphoethanolamine (DPPE) and its mixture with 1,2-Dioleoyl-sn-Glycero-3-Phosphocholine (DOPC) and cholesterol (CH) on silicon substrates with x-ray reflectivity both below and above their phase transition temperatures. Structural variations as a function of temperature are demonstrated by fitting the reflectivity data with both a model dependent and a model independent routine. Studies of Au nanoparticle labeled DOPC and DOPC + DPPE + CH mixture are also performed and the location of Au nanoparticles in these bilayers is established by analyzing the x-ray reflectivity data.

  20. Intercomparison of model simulations of mixed-phase clouds observed during the ARM Mixed-Phase Arctic Cloud Experiment. II: Multi layered cloud

    SciTech Connect

    Morrison, H.; McCoy, Renata; Klein, Stephen A.; Xie, Shaocheng; Luo, Yali; Avramov, Alexander; Chen, Mingxuan; Cole, Jason N.; Falk, Michael; Foster, Mike; Del Genio, Anthony D.; Harrington, Jerry Y.; Hoose, Corinna; Khrairoutdinov, Marat; Larson, Vince; Liu, Xiaohong; McFarquhar, Greg; Poellot, M. R.; Von Salzen, Knut; Shipway, Ben; Shupe, Matthew D.; Sud, Yogesh C.; Turner, David D.; Veron, Dana; Walker, Gregory K.; Wang, Zhien; Wolf, Audrey; Xu, Kuan-Man; Yang, Fanglin; Zhang, G.

    2009-05-21

    Results are presented from an intercomparison of single-column and cloud resolving model simulations of a deep, multi-layered, mixed-phase cloud system observed during the ARM Mixed-Phase Arctic Cloud Experiment. This cloud system was associated with strong surface turbulent sensible and latent heat fluxes as cold air flowed over the open Arctic Ocean, combined with a low pressure system that supplied moisture at mid-level. The simulations, performed by 13 single-column and 4 cloud-resolving models, generally overestimate the liquid water path and strongly underestimate the ice water path, although there is a large spread among the models. This finding is in contrast with results for the single-layer, low-level mixed-phase stratocumulus case in Part I of this study, as well as previous studies of shallow mixed-phase Arctic clouds, that showed an underprediction of liquid water path. The overestimate of liquid water path and underestimate of ice water path occur primarily when deeper mixed-phase clouds extending into the mid-troposphere were observed. These results suggest important differences in the ability of models to simulate Arctic mixed-phase clouds that are deep and multi-layered versus shallow and single-layered. In general, the cloud-resolving models and models with a more sophisticated, two-moment treatment of the cloud microphysics produce a somewhat smaller liquid water path that is closer to observations. The cloud-resolving models also tend to produce a larger cloud fraction than the single column models. The liquid water path and especially the cloud fraction have a large impact on the cloud radiative forcing at the surface, which is dominated by the longwave flux for this case.

  1. Intercomparison of model simulations of mixed-phase clouds observed during the ARM Mixed-Phase Arctic Cloud Experiment. Part II: Multi-layered cloud

    SciTech Connect

    Morrison, H; McCoy, R B; Klein, S A; Xie, S; Luo, Y; Avramov, A; Chen, M; Cole, J; Falk, M; Foster, M; Genio, A D; Harrington, J; Hoose, C; Khairoutdinov, M; Larson, V; Liu, X; McFarquhar, G; Poellot, M; Shipway, B; Shupe, M; Sud, Y; Turner, D; Veron, D; Walker, G; Wang, Z; Wolf, A; Xu, K; Yang, F; Zhang, G

    2008-02-27

    Results are presented from an intercomparison of single-column and cloud-resolving model simulations of a deep, multi-layered, mixed-phase cloud system observed during the ARM Mixed-Phase Arctic Cloud Experiment. This cloud system was associated with strong surface turbulent sensible and latent heat fluxes as cold air flowed over the open Arctic Ocean, combined with a low pressure system that supplied moisture at mid-level. The simulations, performed by 13 single-column and 4 cloud-resolving models, generally overestimate the liquid water path and strongly underestimate the ice water path, although there is a large spread among the models. This finding is in contrast with results for the single-layer, low-level mixed-phase stratocumulus case in Part I of this study, as well as previous studies of shallow mixed-phase Arctic clouds, that showed an underprediction of liquid water path. The overestimate of liquid water path and underestimate of ice water path occur primarily when deeper mixed-phase clouds extending into the mid-troposphere were observed. These results suggest important differences in the ability of models to simulate Arctic mixed-phase clouds that are deep and multi-layered versus shallow and single-layered. In general, models with a more sophisticated, two-moment treatment of the cloud microphysics produce a somewhat smaller liquid water path that is closer to observations. The cloud-resolving models tend to produce a larger cloud fraction than the single-column models. The liquid water path and especially the cloud fraction have a large impact on the cloud radiative forcing at the surface, which is dominated by the longwave flux for this case.

  2. Control of Evaporation Behavior of an Inkjet-Printed Dielectric Layer Using a Mixed-Solvent System

    NASA Astrophysics Data System (ADS)

    Yang, Hak Soon; Kang, Byung Ju; Oh, Je Hoon

    2016-01-01

    In this study, the evaporation behavior and the resulting morphology of inkjet-printed dielectric layers were controlled using a mixed-solvent system to fabricate uniform poly-4-vinylphenol (PVP) dielectric layers without any pinholes. The mixed-solvent system consisted of two different organic solvents: 1-hexanol and ethanol. The effects of inkjet-printing variables such as overlap condition, substrate temperature, and different printing sequences (continuous and interlacing printing methods) on the inkjet-printed dielectric layer were also investigated. Increasing volume fraction of ethanol (VFE) is likely to reduce the evaporation rate gradient and the drying time of the inkjet-printed dielectric layer; this diminishes the coffee stain effect and thereby improves the uniformity of the inkjet-printed dielectric layer. However, the coffee stain effect becomes more severe with an increase in the substrate temperature due to the enhanced outward convective flow. The overlap condition has little effect on the evaporation behavior of the printed dielectric layer. In addition, the interlacing printing method results in either a stronger coffee stain effect or wavy structures of the dielectric layers depending on the VFE of the PVP solution. All-inkjet-printed capacitors without electrical short circuiting can be successfully fabricated using the optimized PVP solution (VFE = 0.6); this indicates that the mixed-solvent system is expected to play an important role in the fabrication of high-quality inkjet-printed dielectric layers in various printed electronics applications.

  3. Change in Tear Film Lipid Layer Thickness, Corneal Thickness, Volume and Topography after Superficial Cauterization for Conjunctivochalasis.

    PubMed

    Chan, Tommy C Y; Ye, Cong; Ng, Paul K F; Li, Emmy Y M; Yuen, Hunter K L; Jhanji, Vishal

    2015-07-17

    We evaluated the change in tear film lipid layer thickness, corneal thickness, volume and topography after superficial cauterization of symptomatic conjunctivochalasis. Bilateral superficial conjunctival cauterization was performed in 36 eyes of 18 patients with symptomatic conjunctivochalasis. The mean age of patients (12 males, 6 females) was 68.6 ± 10.9 years (range: 44-83 years). Preoperatively, 28 eyes (77.8%) had grade 1 conjunctivochalasis, and 8 eyes (22.2%) had grade 2 conjunctivochalasis. At 1 month postoperatively, the severity of conjunctivochalasis decreased significantly (p < 0.001) and 29 eyes (80.6%) had grade 0 conjunctivochalasis whereas 7 eyes (19.4%) had grade 1 conjunctivochalasis. The mean Ocular Surface Disease Index score decreased from 31.5 ± 15.2 preoperatively to 21.5 ± 14.2 at the end of 1 month postoperatively (p = 0.001). There was a statistically significant increase in mean tear film lipid layer thickness 1 month after the surgery (49.6 ± 16.1 nm vs 62.6 ± 21.6 nm; p < 0.001). The central corneal thickness, thinnest corneal thickness and corneal volume decreased significantly postoperatively (p < 0.001). Our study showed that superficial conjunctival cauterization is an effective technique for management of conjunctivochalasis in the short term. An increase in tear film lipid layer thickness along with a decrease in corneal thickness and volume were observed after surgical correction of conjunctivochalasis.

  4. Behavior of streamwise rib vortices in a three-dimensional mixing layer

    NASA Technical Reports Server (NTRS)

    Lopez, J. M.; Bulbeck, C. J.

    1992-01-01

    The structure and behavior of a streamwise rib vortex in a direct numerical simulation of a time-developing three-dimensional incompressible plane mixing layer is examined. Where the rib vortex is being stretched, the vorticity vector is primarily directed in the vortex axial direction and the radial and azimuthal velocity distribution is similar to that of a Burger's vortex. In the region where the vortex stretching is negative, there is a change in the local topology of the vortex. The axial flow is decelerated and a negative azimuthal component of vorticity is induced. These features are characteristic of vortex breakdown. The temporal evolution of the rib vortex is similar to the evolution of an axisymmetric vortex in the early stages of vortex breakdown. The effect of vortex breakdown on other parts of the flow is, however, not as significant as the interaction between the rib vortex and other vortices.

  5. Use of passive scalar tagging for the study of coherent structures in the plane mixing layer

    NASA Technical Reports Server (NTRS)

    Ramaprian, B. R.; Sandham, N. D.; Mungal, M. G.; Reynolds, W. C.

    1988-01-01

    Data obtained from the numerical simulation of a 2-D mixing layer were used to study the feasibility of using the instantaneous concentration of a passive scalar for detecting the typical coherent structures in the flow. The study showed that this technique works quite satisfactorily and yields results similar to those that can be obtained by using the instantaneous vorticity for structure detection. Using the coherent events educed by the scalar conditioning technique, the contribution of the coherent events to the total turbulent momentum and scalar transport was estimated. It is found that the contribution from the typical coherent events is of the same order as that of the time-mean value. However, the individual contributions become very large during the pairing of these structures. The increase is particularly spectacular in the case of the Reynolds shear stress.

  6. White organic light-emitting devices with mixed interfaces between light emitting layers

    NASA Astrophysics Data System (ADS)

    Lee, Young Gu; Kee, In Seo; Shim, Hong Shik; Ko, Ick Hwan; Lee, Soonil; Koh, Ken Ha

    2007-06-01

    White organic light-emitting devices with mixed interfaces between emitting layers (MI-EML WOLEDs) showed luminance and efficiency as large as 26213cd/m2 and 9.85cd/A. Efficiencies of MI-EML WOLEDs were about 1.5 times better than those of conventional three-EML WOLEDs for luminance of 1000-5000cd/m2, and their half-decay lifetime showed 3.1 times improvement. Note that if the authors operate typical active-matrix mobile-phone displays based on combination of WOLED and color filters to produce standard white emission for high definition televisions and illumination sources, MI-EML WOLEDs will have advantages of 25% less power consumption and 2.8 times longer lifetime over conventional three-EML WOLEDs.

  7. Estimates of wintertime mixed layer nutrient concentrations in the North Atlantic

    NASA Astrophysics Data System (ADS)

    Glover, David M.; Brewer, Peter G.

    1988-09-01

    Nonlinear, time-dependent model sensitivity to initial conditions poses a challenging problem when attempting to initialize such a model. In order to intialize a chemical-physical model of the upper several hundred meters of the North Atlantic, we have calculated the initial concentrations of several chemical species from three estimation methods by a combination of the Climatological Atlas of the World Ocean ( LEVITUS, 1982) and the TTO north, and tropical, Atlantic study data bases. A 1° × 1° grid of the average initial concentrations over the mixed layer depth was generated for the method of preference and added to the inialization data base of the model. Contour maps of this calculated initial concentration set are presented and comparisons with the other methods and actual data are made.

  8. Core instabilities and ``bridging'' in the first pairing of plane mixing layers

    NASA Astrophysics Data System (ADS)

    Estevadeordal, Jordi; Kleis, Stanley J.

    1999-06-01

    Core instabilities and "bridging" in the first pairing of transitional plane mixing layers are identified experimentally through phase-locked measurements. Spanwise-uniform acoustic excitation is employed to stabilize the two-dimensional (2D) instability modes. The three-dimensional (3D) instability modes undergo amplification during pairing of the spanwise rollers. The most amplified 3D instability modes are associated with upstream perturbations generated by small imperfections in the splitter-plate surface that produce a kink [e.g., as in the graph of tanh(z)] and a bend [e.g., as in the graph of sech(z)] in the rollers. These perturbations produce core dynamics, bridging phenomena, and "lambda" structures.

  9. Tidally driven mixing and dissipation in the stratified boundary layer above steep submarine topography

    NASA Astrophysics Data System (ADS)

    Winters, K. B.

    2015-09-01

    A tidally driven, stratified boundary layer over supercritical topography is simulated numerically. The near-boundary flow is characterized by quasiperiodic, bore-like motions and episodic expulsion events where fluid is ejected into the stratified interior. The character of the bores is compared to the high-resolution ocean mooring data of van Haren (2006). The diffusivity of the flow near the boundary is estimated by means of a synthetic dye tracer experiment. The average dissipation rate within the dye cloud is computed and combined with the diffusivity estimate to yield an overall mixing efficiency of 0.15. Both the estimated diffusivity and dissipation rates are in reasonable agreement with the microstructure observations of Kunze et al. (2012) when scaled to the environmental conditions at the Monterey and Soquel Canyons and to the values estimated by van Haren and Gostiaux (2012) above the sloping bottom of the Great Meteor Seamount in the Canary Basin.

  10. Part 2 of a Computational Study of a Drop-Laden Mixing Layer

    NASA Technical Reports Server (NTRS)

    Okongo, Nora; Bellan, Josette

    2004-01-01

    This second of three reports on a computational study of a mixing layer laden with evaporating liquid drops presents the evaluation of Large Eddy Simulation (LES) models. The LES models were evaluated on an existing database that had been generated using Direct Numerical Simulation (DNS). The DNS method and the database are described in the first report of this series, Part 1 of a Computational Study of a Drop-Laden Mixing Layer (NPO-30719), NASA Tech Briefs, Vol. 28, No.7 (July 2004), page 59. The LES equations, which are derived by applying a spatial filter to the DNS set, govern the evolution of the larger scales of the flow and can therefore be solved on a coarser grid. Consistent with the reduction in grid points, the DNS drops would be represented by fewer drops, called computational drops in the LES context. The LES equations contain terms that cannot be directly computed on the coarser grid and that must instead be modeled. Two types of models are necessary: (1) those for the filtered source terms representing the effects of drops on the filtered flow field and (2) those for the sub-grid scale (SGS) fluxes arising from filtering the convective terms in the DNS equations. All of the filtered-sourceterm models that were developed were found to overestimate the filtered source terms. For modeling the SGS fluxes, constant-coefficient Smagorinsky, gradient, and scale-similarity models were assessed and calibrated on the DNS database. The Smagorinsky model correlated poorly with the SGS fluxes, whereas the gradient and scale-similarity models were well correlated with the SGS quantities that they represented.

  11. Transport of desert dust mixed with North African industrial pollutants in the subtropical Saharan Air Layer

    NASA Astrophysics Data System (ADS)

    Rodríguez, S.; Alastuey, A.; Alonso-Pérez, S.; Querol, X.; Cuevas, E.; Abreu-Afonso, J.; Viana, M.; Pérez, N.; Pandolfi, M.; de La Rosa, J.

    2011-07-01

    An analysis of chemical composition data of particulate matter samples (TSP, PM10 and PM2.5) collected from 2002 to 2008 in the North Atlantic free troposphere at the Izaña Global Atmospheric Watch (GAW) observatory (Tenerife, Canary Islands) shows that desert dust is very frequently mixed with particulate pollutants in the Saharan Air Layer (SAL). The study of this data set with Median Concentrations At Receptor (MCAR) plots allowed the identification of the potential source regions of the dust and particulate pollutants. Areas located at the south of the southern slope of the Atlas mountains emerge as the most frequent source of the soil desert dust advected to the northern edge of the SAL in summer. Industrial emissions occurring in Northern Algeria, Eastern Algeria, Tunisia and the Atlantic coast of Morocco appear as the most important source of the nitrate, ammonium and a fraction of sulphate (at least 60 % of the sulphate <10 μm transported from some regions) observed in the SAL. These emissions are mostly linked to crude oil refineries, phosphate-based fertilizer industry and power plants. Although desert dust emissions appear as the most frequent source of the phosphorous observed in the SAL, high P concentrations are observed when the SAL is affected by emissions from open mines of phosphate and phosphate based fertilizer industry. The results also show that a significant fraction of the sulphate (up to 90 % of sulphate <10 μm transported from some regions) observed in the SAL may be influenced by soil emissions of evaporite minerals in well defined regions where dry saline lakes (chotts) are present. These interpretations of the MCAR plots are consistent with the results obtained with the Positive Matrix Factorization (PMF2) receptor modelling. The results of this study show that North African industrial pollutants may be mixed with desert dust and exported to the North Atlantic in the Saharan Air Layer.

  12. Transport of desert dust mixed with North African industrial pollutants in the subtropical Saharan Air Layer

    NASA Astrophysics Data System (ADS)

    Rodríguez, S.; Alastuey, A.; Alonso-Pérez, S.; Querol, X.; Cuevas, E.; Abreu-Afonso, J.; Viana, M.; Pandolfi, M.; de La Rosa, J.

    2011-03-01

    The chemical composition of particulate matter samples (TSP, PM10 and PM2.5) collected from 2002 to 2008 in the North Atlantic free troposphere at Izaña Global Atmospheric Watch (GAW) observatory (Tenerife, The Canary Islands) was studied. The analysis of the samples collected in the Saharan Air Layer (SAL) shows that soil desert dust is very frequently mixed with particulate pollutants. An analysis of this data set with Median Concentrations At Receptor (MCAR) plots allowed to identify the potential source regions of the dust and particulate pollutants. Areas located at the south of the Southern slope of Atlas emerge as the most frequent source of the soil desert dust advected to the northern edge of the SAL in summer. Industrial emissions occurring along the Atlantic coast of Morocco, Northern Algeria, Eastern Algeria and Tunisia appear as the most important source of the nitrate, ammonium and a fraction of sulphate (at least a 60% of the sulphate <10 μm transported from some regions) observed in the SAL. These emissions are mostly linked to crude oil refineries, phosphate-based fertilizer industry and power plants. Although desert dust emissions appear as the most frequent source of the phosphorous observed in the SAL, high P concentrations are observed when the SAL is affected by emissions from open mines of phosphate and phosphate based fertilizer industry. The results also show that a significant fraction of the sulphate (up to 90% of sulphate <10 μm transported from some regions) observed in the SAL is linked to soil emissions of evaporite minerals in well defined regions where dry saline lakes (chotts) are present. These interpretations of the MCAR plots are consistent with the results obtained with the Positive Matrix Factorization receptor modelling. The results of this study show that North African industrial pollutants may be mixed with desert dust and exported to the North Atlantic in the Saharan Air Layer.

  13. Quantification of Mixing of a Sonic Jet in Supersonic Crossflow due to Thick Turbulent Boundary Layer Interaction

    NASA Astrophysics Data System (ADS)

    Rossmann, Tobias; Pizzaia, Adam

    2013-11-01

    The upstream injection surface boundary layer is shown to have a significant effect on the mixing characteristics of a sonic jet in supersonic cross flow. A circular, high-pressure, sonic jet is injected into a M =3.5 supersonic crossflow through different boundary layer thickness (δ/D = 7.5 and 1), with variable injection angles (-20 to +20 degrees), and variable momentum ratios (J = 2, 5, and 10). Planar Laser Mie Scattering of condensed ethanol droplets is used to quantitatively image the injected fluid concentration in both the side and end views. Jet fluid concentrations PDFs are constructed to better understand the mixing dynamics. These PDFs are integrated to create mixed fluid fraction profiles that are then reduced to mixing efficiency. Mixing efficiency values are computed from different two-dimensional planes to determine if centerline mixing efficiencies are characteristic of the entire three-dimensional flow. Through these analyses, it is seen that thick boundary layers tend to marginally alter jet penetration and spread, but significantly worsen jet mixing capabilities, regardless of momentum ratio or injection angle.

  14. Formation of mixed-layer structures in smectites intercalated with tryptone

    NASA Astrophysics Data System (ADS)

    Block, K. A.; Trusiak, A.; Steiner, J. C.; Katz, A.; Gottlieb, P.; Alimova, A.

    2012-12-01

    Stable clay-protein complexes are fundamental to studies of the critical zone, terrestrial ecosystems, pharmacology, and industrial applications such as bioremediation. Two sets of montmorillonite clays were purified and made homoionic for Na and Mg. Mg-montmorillonite and Na-montmorillonite were mixed with tryptone (casein digest) in a 9:1 and 18:1 clay:tryptone ratio, resulting in the formation of reversible intercalated structures. X-ray diffraction analysis of the protein-clay complexes produced profiles consisting of two peaks associated with the smectite 001 reflection and a related tryptone-packet peak similar to that produced by a mixed layer clay structure. Shifts in the 002, 003, and 004 diffraction maxima are attributed to disorder caused by the interaction with the protein. Line broadening in the smectite-tryptone XRD spectra is interpreted to be the result of interlayer absorption. Adsorption produces coherent crystalline packets of regularly interbedded tryptone and smectite platelets. SEM images reveal clay platelets with upwardly rolled edges that tend toward cylindrical structures with the production of occasional tubes in the smaller platelet size range as noted for organic compound-kaolinite intercalation reported by Fenoll Hach-Ali and Weiss (1969). Reference: Fenoll Hach-Ali, P.F., Weiss, A., 1969. Estudio de la reaccion de caolinita y N-metilform- amida. Quimica LXV, 769-790. Scanning electron micrograph of tryptone-intercalated clay platelets exhibiting rolled edge structure.

  15. Bio-nanocomposites by assembling of gelatin and layered perovskite mixed oxides.

    PubMed

    Ruiz, Ana I; Darder, Margarita; Aranda, Pilar; Jiménez, Ricardo; Van Damme, Henri; Ruiz-Hitzky, Eduardo

    2006-06-01

    A new class of bio-nanocomposites based on hybrid gelatin-perovskite hydrogels was prepared by mixing exfoliated perovskite-tetraalkylammonium species in aqueous suspensions with gelatin solutions. Colloidal nanosheets derived from the CsCa2Nb3O10 layered perovskite re-stacked in the gelatin solutions give bio-nanocomposite materials with different content in the inorganic moiety. These films can be easily processed as homogeneous self-supported films. The partial exfoliation of the pristine mixed oxide is produced from alkylammonium exchanged phases, being the tetraalkylammonium ions (tetraethylammonium, TEA+) an efficient intermediate to give the colloid phase constituted by well exfoliated materials useful to generate homogeneous films. The nanosheets are highly oriented in the bio-nanocomposite films in agreement with the XRD patterns and the FTIR dichroism. This orientation could be considered as a characteristic of this type of hybrid materials leading to new potential applications. In this way, we have observed that the assembling of perovskite to gelatin produces a greater increase of the dielectric permittivity than the dielectric loss in the studied samples.

  16. Behavior and mixing of a cold intermediate layer near a sloping boundary

    NASA Astrophysics Data System (ADS)

    Cyr, Frédéric; Bourgault, Daniel; Galbraith, Peter S.

    2015-03-01

    As in many other subarctic basins, a cold intermediate layer (CIL) is found during ice-free months in the Lower St. Lawrence Estuary (LSLE), Canada. This study examines the behavior of the CIL above the sloping bottom using a high-resolution mooring deployed on the northern side of the estuary. Observations show successive swashes/backwashes of the CIL on the slope at a semi-diurnal frequency. It is shown that these upslope and downslope motions are likely caused by internal tides generated at the nearby channel head sill. Quantification of mixing from 322 turbulence casts reveals that in the bottom 10 m of the water column, the time-average dissipation rate of turbulent kinetic energy is 𝜖 10 m = 1.6×10-7Wkg-1, an order of magnitude greater than found in the interior of the basin, far from boundaries. Near-bottom dissipation during the flood phase of the M2 tide cycle (upslope flow) is about four times greater than during the ebb phase (downslope flow). Bottom shear stress, shear instabilities, and internal wave scattering are considered as potential boundary mixing mechanisms near the seabed. In the interior of the water column, far from the bottom, increasing dissipation rates are observed with both increasing stratification and shear, which suggests some control of the dissipation by the internal wave field. However, poor fits with a parametrization for large-scale wave-wave interactions suggests that the mixing is partly driven by more complex non-linear and/or smaller scale waves.

  17. SPREADING LAYERS IN ACCRETING OBJECTS: ROLE OF ACOUSTIC WAVES FOR ANGULAR MOMENTUM TRANSPORT, MIXING, AND THERMODYNAMICS

    SciTech Connect

    Philippov, Alexander A.; Rafikov, Roman R.; Stone, James M.

    2016-01-20

    Disk accretion at a high rate onto a white dwarf (WD) or a neutron star has been suggested to result in the formation of a spreading layer (SL)—a belt-like structure on the object's surface, in which the accreted matter steadily spreads in the poleward (meridional) direction while spinning down. To assess its basic characteristics, we perform two-dimensional hydrodynamic simulations of supersonic SLs in the relevant morphology with a simple prescription for cooling. We demonstrate that supersonic shear naturally present at the base of the SL inevitably drives sonic instability that gives rise to large-scale acoustic modes governing the evolution of the SL. These modes dominate the transport of momentum and energy, which is intrinsically global and cannot be characterized via some form of local effective viscosity (e.g., α-viscosity). The global nature of the wave-driven transport should have important implications for triggering Type I X-ray bursts in low-mass X-ray binaries. The nonlinear evolution of waves into a system of shocks drives effective rearrangement (sensitively depending on thermodynamical properties of the flow) and deceleration of the SL, which ultimately becomes transonic and susceptible to regular Kelvin–Helmholtz instability. We interpret this evolution in terms of the global structure of the SL and suggest that mixing of the SL material with the underlying stellar fluid should become effective only at intermediate latitudes on the accreting object's surface, where the flow has decelerated appreciably. In the near-equatorial regions the transport is dominated by acoustic waves and mixing is less efficient. We speculate that this latitudinal nonuniformity of mixing in accreting WDs may be linked to the observed bipolar morphology of classical nova ejecta.

  18. Mixed Layer Heights Derived from the NASA Langley Research Center Airborne High Spectral Resolution Lidar

    NASA Technical Reports Server (NTRS)

    Scarino, Amy J.; Burton, Sharon P.; Ferrare, Rich A.; Hostetler, Chris A.; Hair, Johnathan W.; Obland, Michael D.; Rogers, Raymond R.; Cook, Anthony L.; Harper, David B.; Fast, Jerome; Dasilva, Arlindo; Benedetti, Angela

    2012-01-01

    The NASA airborne High Spectral Resolution Lidar (HSRL) has been deployed on board the NASA Langley Research Center's B200 aircraft to several locations in North America from 2006 to 2012 to aid in characterizing aerosol properties for over fourteen field missions. Measurements of aerosol extinction (532 nm), backscatter (532 and 1064 nm), and depolarization (532 and 1064 nm) during 349 science flights, many in coordination with other participating research aircraft, satellites, and ground sites, constitute a diverse data set for use in characterizing the spatial and temporal distribution of aerosols, as well as properties and variability of the Mixing Layer (ML) height. We describe the use of the HSRL data collected during these missions for computing ML heights and show how the HSRL data can be used to determine the fraction of aerosol optical thickness within and above the ML, which is important for air quality assessments. We describe the spatial and temporal variations in ML heights found in the diverse locations associated with these experiments. We also describe how the ML heights derived from HSRL have been used to help assess simulations of Planetary Boundary Layer (PBL) derived using various models, including the Weather Research and Forecasting Chemistry (WRF-Chem), NASA GEOS-5 model, and the ECMWF/MACC models.

  19. Long-term measurement of daytime atmospheric mixing layer height over Hong Kong

    NASA Astrophysics Data System (ADS)

    Yang, Dongwei; Li, Chengcai; Lau, Alexis Kai-Hon; Li, Ying

    2013-03-01

    Lidar has unique advantages in temporal and spatial resolution to measure the atmospheric mixing layer height (MLH), which is important for analyzing atmospheric phenomena. However, long-term MLH information over several years, which has important significance in air quality and climate studies, is seldom obtained from lidar data due to the scarcity of long-running lidar observations. In this paper, we retrieve and analyze daytime MLH from a data set of a lidar that operated continuously over 6.5 years at Yuen Long, Hong Kong. A new algorithm has been developed for consistently retrieving MLH from this large data set, handling all possible weather conditions and aerosol layer structures. We analyze the diurnal, seasonal and inter-annual variation of MLH over Hong Kong and find a unique phenomenon that the afternoon MLH is higher in autumn than in summer, which is verified by radiosonde results and explained by thermal stability and humidity effect. Moreover, we find a slightly decreasing trend of the daily maximum of MLH, which implies a continually compressed air volume into which pollutants and their precursors are emitted, which is one of the possible factors leading to deteriorated air quality over Hong Kong region.

  20. Reduced kinetic mechanism of ignition for nonpremixed hydrogen/air in a supersonic mixing layer

    SciTech Connect

    Ju, Y.; Niioka, T. . Inst. of Fluid Science)

    1994-11-01

    Transient ignition processes in a two-dimensional spatially evolving supersonic mixing layer consisting of a parallel nonpremixed airstream and a hydrogen stream both with temperatures higher than 1,000 K were investigated numerically by using the full chemistry and its reduced chemistry. A phenomenon different from that examined in previous studies, in which ignition of hydrogen/oxygen mixtures was considered, was found in the nonpremixed case examined here. It was shown that the concentration of O was greater than that of OH before ignition, but became smaller with the development of ignition process. Fourteen important reactions for ignition were obtained and verified using sensitivity analyses of ignition delay time and radical concentrations. Several different four-step and three-step reduced kinetic mechanisms were then deduced by introducing the steady-state approximation to different species. Comparison of these reduced kinetic mechanisms with the full chemistry showed that the steady-state approximation of O used in previous studies caused serious errors in the prediction of ignition delay time in supersonic flow, in which nonpremixed character is predominant and the transport phenomenon is important. Ignition locations predicted with the proper four-step and three-step reduced kinetic mechanisms were within 5% and 20% of those predicted with the full chemistry. Finally, these two reduced mechanisms were used to evaluate the effect of viscous dissipation on ignition in the supersonic shear layer. Good agreements between the results of the present reduced kinetic mechanisms and those of the full chemistry were obtained.

  1. On the instabilities of supersonic mixing layers - A high-Mach-number asymptotic theory

    NASA Technical Reports Server (NTRS)

    Balsa, Thomas F.; Goldstein, M. E.

    1990-01-01

    The stability of a family of tanh mixing layers is studied at large Mach numbers using perturbation methods. It is found that the eigenfunction develops a multilayered structure, and the eigenvalue is obtained by solving a simplified version of the Rayleigh equation (with homogeneous boundary conditions) in one of these layers which lies in either of the external streams. This analysis leads to a simple hypersonic similarity law which explains how spatial and temporal phase speeds and growth rates scale with Mach number and temperature ratio. Comparisons are made with numerical results, and it is found that this similarity law provides a good qualitative guide for the behavior of the instability at high Mach numbers. In addition to this asymptotic theory, some fully numerical results are also presented (with no limitation on the Mach number) in order to explain the origin of the hypersonic modes (through mode splitting) and to discuss the role of oblique modes over a very wide range of Mach number and temperature ratio.

  2. Ozone Transport and Mixing Processes in the Boundary Layer Observed with Lidar during Discover-AQ

    NASA Astrophysics Data System (ADS)

    Senff, C. J.; Langford, A. O.; Alvarez, R. J. _II, II; Choukulkar, A.; Brewer, A.; Weickmann, A. M.; Kirgis, G.; Sandberg, S.; Hardesty, M.; Delgado, R.; Long, R.; Brown, S. S.

    2014-12-01

    The final two Discover-AQ air quality studies were conducted in Houston, TX in September 2013 and the Colorado Front Range in July/August 2014. These two regions are characterized by different ozone precursor sources and exhibit unique regional wind flow patterns. During these studies, NOAA deployed its truck-based, scanning TOPAZ ozone lidar to document the vertical structure and temporal evolution of ozone concentrations from near the surface up to about 2.5 km above ground level. In Houston, TOPAZ was located next to a radar wind profiler while during the Colorado campaign, Doppler wind lidars collocated with TOPAZ measured wind profiles and vertical velocity statistics throughout the boundary layer (BL). For both studies, nearby in situ sensors provided continuous observations of surface ozone and NOx. These combinations of remote and in situ sensors lend themselves to study the influence of BL transport and mixing processes on surface-level ozone. In this presentation, we focus on characterizing and quantifying changes in surface ozone due to several BL processes, including the Houston land-sea breeze circulation, the terrain-driven BL flow in the Colorado Front Range area, thunderstorm outflows, BL growth rate and depth, and entrainment of air from the residual layer or lower free troposphere into the BL.

  3. Observed Variability of Global Atmospheric Mixing Layer Height from 1971 to 2014

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoyan; Wang, Kaicun

    2015-04-01

    It is important to determine the mixing layer height (MLH) for understanding the transport process in the troposphere, weather prediction, and climate monitoring. MLH is a key parameter in air pollution models which determines the volume available for pollutants to dispersion. The long-term variation of MLH can drive the change of surface air quality. Many methods have been proposed to estimate MLH from the temperature or atmospheric composition profiles provided by radiosonde and remote sounding systems. Radiosonde data are usually considered as a reference by other methods owing to its long-term history and direct observation. However, disagreements exist between MLHs derived from different variable profiles of radiosonde data. In this study, a method integrating the information of potential temperature, relative humidity, specific humidity, atmospheric refractivity and the effect of cloud on the boundary layer turbulence was applied to the global radiosonde data to generate long-term variation of the global MLH from 1971 to 2014. The radiosonde observations were released by the Integrated Global Radiosonde Archive (IGRA) of National Climatic Data Center (NCDC). The MLHs in the North America are fairly deep, with an average value between 1800 and 2200 m, however, the Europe and the Eastern Asia have shallow MLHs between 1200 and 1500 m. The majority of the North America and Australia stations showed a negative trend during the period of 1971 to 2014, while, for the Europe and Japan, the MLHs increased over time. The MLH had a negative correlation with surface relative humidity and a positive association with surface air temperature. Besides the effect of thermodynamic factors, the dynamical factors including the surface wind speed and its shear in the boundary layer influence the development of the boundary layer. However, there is no significant correlation between the surface wind speeds and MLH in this study. Weak negative association was found between

  4. Heterogeneous distribution of plankton within the mixed layer and its implications for bloom formation in tropical seas

    PubMed Central

    Calbet, Albert; Agersted, Mette Dalgaard; Kaartvedt, Stein; Møhl, Malene; Møller, Eva Friis; Enghoff-Poulsen, Søren; Paulsen, Maria Lund; Solberg, Ingrid; Tang, Kam W.; Tönnesson, Kajsa; Raitsos, Dionysios E.; Nielsen, Torkel Gissel

    2015-01-01

    Intensive sampling at the coastal waters of the central Red Sea during a period of thermal stratification, prior to the main seasonal bloom during winter, showed that vertical patches of prokaryotes and microplankton developed and persisted for several days within the apparently density uniform upper layer. These vertical structures were most likely the result of in situ growth and mortality (e.g., grazing) rather than physical or behavioural aggregation. Simulating a mixing event by adding nutrient-rich deep water abruptly triggered dense phytoplankton blooms in the nutrient-poor environment of the upper layer. These findings suggest that vertical structures within the mixed layer provide critical seeding stocks that can rapidly exploit nutrient influx during mixing, leading to winter bloom formation. PMID:26062783

  5. Heterogeneous distribution of plankton within the mixed layer and its implications for bloom formation in tropical seas

    NASA Astrophysics Data System (ADS)

    Calbet, Albert; Agersted, Mette Dalgaard; Kaartvedt, Stein; Møhl, Malene; Møller, Eva Friis; Enghoff-Poulsen, Søren; Paulsen, Maria Lund; Solberg, Ingrid; Tang, Kam W.; Tönnesson, Kajsa; Raitsos, Dionysios E.; Nielsen, Torkel Gissel

    2015-06-01

    Intensive sampling at the coastal waters of the central Red Sea during a period of thermal stratification, prior to the main seasonal bloom during winter, showed that vertical patches of prokaryotes and microplankton developed and persisted for several days within the apparently density uniform upper layer. These vertical structures were most likely the result of in situ growth and mortality (e.g., grazing) rather than physical or behavioural aggregation. Simulating a mixing event by adding nutrient-rich deep water abruptly triggered dense phytoplankton blooms in the nutrient-poor environment of the upper layer. These findings suggest that vertical structures within the mixed layer provide critical seeding stocks that can rapidly exploit nutrient influx during mixing, leading to winter bloom formation.

  6. Pattern formation in fatty acid-nanoparticle and lipid-nanoparticle mixed monolayers at water surface

    NASA Astrophysics Data System (ADS)

    Choudhuri, M.; Datta, A.; Iyengar, A. N. Sekar; Janaki, M. S.

    2015-06-01

    Dodecanethiol-capped gold nanoparticles (AuNPs) are self-organized in two different amphiphilic monolayers one of which is a single-tailed fatty acid Stearic acid (StA) and the other a double-tailed lipid 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC). In the StA-AuNP film the AuNPs self-organize to form an interconnected network of nanoclusters on compression while in the DMPC-AuNP film the AuNPs aggregate to form random, isolated clusters in the film. The long time evolution of the films at constant surface pressure reveals ring structures in the former and diffusion limited aggregates in the latter that with time evolve into an irregular porous maze of AuNPs in the DMPC film. The difference in structure of the AuNP patterns in the two films can be attributed to a difference in the lipophilic interactions between the NPs and the amphiphilic molecules. The mean square intensity fluctuations f(ln) calculated along a typical line for the 2D structures in both the films at initial and final stages of long time evolution reflect the structural changes in the films over time.

  7. Investigations of boundary layer structure, cloud characteristics and vertical mixing of aerosols at Barbados with large eddy simulations

    NASA Astrophysics Data System (ADS)

    Jähn, Michael; Muñoz-Esparza, Domingo; Chouza, Fernando; Reitebuch, Oliver; Knoth, Oswald; Haarig, Moritz; Ansmann, Albert; Tegen, Ina

    2016-04-01

    Large eddy simulations (LESs) with ASAM (All Scale Atmospheric Model) are performed for the area of the Caribbean island Barbados to investigate island effects on boundary layer modification, cloud generation and vertical mixing of aerosols. In order to generate inflow turbulence consistent with the upstream marine boundary layer forcing, we use the cell perturbation method based on finite amplitude potential temperature perturbations. This method is now also validated for moist boundary layer simulations with open lateral boundary conditions. Observational data obtained from the SALTRACE (Saharan Aerosol Long-range Transport and Aerosol-Cloud-Interaction Experiment) field campaign is used for both model initialization and comparisons. Several sensitivity tests are carried out to demonstrate the problems related to "gray zone modeling" or when the turbulent marine boundary layer flow is replaced by laminar winds. Additional simulation cases deal with modified surface characteristics and their impacts on the simulation results. Saharan dust layers that reach Barbados via long-range transport over the North Atlantic are included as passive tracers in the model. Effects of layer thinning, subsidence and turbulent downward transport near the layer bottom at z ≈ 1800 m become apparent. The exact position of these layers and strength of downward mixing is found to be mainly controlled atmospheric stability (especially inversion strength) and wind shear. Comparisons of LES model output with lidar data show similarities in the downwind vertical wind structure and accurately reproduces the development of the daytime convective boundary layer measured by the Raman lidar.

  8. On the Behavior of Three-dimensional Wave Packets in Viscously Spreading Mixing Layers

    NASA Technical Reports Server (NTRS)

    Balsa, Thomas F.

    1994-01-01

    We consider analytically the evolution of a three-dimensional wave packet generated by an impulsive source in a mixing layer. The base flow is assumed to be spreading due to viscous diffusion. The analysis is restricted to small disturbances (linearized theory). A suitable high-frequency ansatz is used to describe the packet; the key elements of this description are a complex phase and a wave action density. It is found that the product of this density and an infinitesimal material volume convecting at the local group velocity is not conserved: there is a continuous interaction between the base flow and the wave action. This interaction is determined by suitable mode-weighted averages of the second and fourth derivatives of the base-flow velocity profile. Although there is some tendency for the dominant wave number in the packet to shift from the most unstable value toward the neutral value, this shift is quite moderate. In practice, wave packets do not become locally neutral in a diverging base flow (as do instability modes), therefore, they are expected to grow more suddenly than pure instability modes and do not develop critical layers. The group velocity is complex; the full significance of this is realized by analytically continuing the equations for the phase and wave action into a complex domain. The implications of this analytic continuation are discussed vis-a-vis the secondary instabilities of the packet: very small scale perturbations on the phase can grow very rapidly initially, but saturate later because most of the energy in these perturbations is convected away by the group velocity. This remark, as well as the one regarding critical layers, has consequences for the nonlinear theories.

  9. Mixed layer depth and chlorophyll a: Profiling float observations in the Kuroshio-Oyashio Extension region

    NASA Astrophysics Data System (ADS)

    Itoh, Sachihiko; Yasuda, Ichiro; Saito, Hiroaki; Tsuda, Atsushi; Komatsu, Kosei

    2015-11-01

    Variability in the chlorophyll a concentration (Chl) in relation to fluctuations in the mixed layer (ML) was investigated together with turbidity (Tur) in the Kuroshio-Oyashio Extension region, using profiling floats. A particular focus was the validity of two hypotheses concerning the spring bloom: the critical depth hypothesis (CDH) and the recently proposed alternative, the disturbance-recovery hypothesis (DRH). During the period from winter to early spring, Chl and Tur integrated over the photosynthetically active layer (PL; defined as the greatest depth of the ML and the euphotic layer) increased with increasing PL depth (PLD), indicating an increase in the phytoplankton biomass. This result is partly consistent with the DRH in that the observed increase in biomass was not explained by an increase in production. Instead, it was more likely attributable to a reduction in the loss rate. However, theoretical analyses revealed that grazer dilution alone could not cause this increase in biomass because such an increase in the ML in the real ocean (as opposed to a dilution experiment within a bottle) would cause a reduction in the mean light intensity. Despite the loss-controlled fluctuation in biomass during the period of low light, a production-driven fluctuation in biomass was also revealed. This occurred when the light intensity was elevated, particularly after late spring, and was consistent with the CDH. Thus, the present study suggests that both the production-driven and loss-driven hypotheses are responsible for the dynamics of the phytoplankton dynamics from winter to spring in the Kuroshio-Oyashio Extension region.

  10. Mixing layer height measurements determines influence of meteorology on air pollutant concentrations in urban area

    NASA Astrophysics Data System (ADS)

    Schäfer, Klaus; Blumenstock, Thomas; Bonn, Boris; Gerwig, Holger; Hase, Frank; Münkel, Christoph; Nothard, Rainer; von Schneidemesser, Erika

    2015-10-01

    Mixing layer height (MLH) is a key parameter to determine the influence of meteorological parameters upon air pollutants such as trace gas species and particulate concentrations near the surface. Meteorology, and MLH as a key parameter, affect the budget of emission source strengths, deposition, and accumulation. However, greater possibilities for the application of MLH data have been identified in recent years. Here, the results of measurements in Berlin in 2014 are shown and discussed. The concentrations of NO, NO2, O3, CO, PM1, PM2.5, PM10 and about 70 volatile organic compounds (anthropogenic and biogenic of origin) as well as particle size distributions and contributions of SOA and soot species to PM were measured at the urban background station of the Berlin air quality network (BLUME) in Nansenstr./Framstr., Berlin-Neukölln. A Vaisala ceilometer CL51, which is a commercial mini-lidar system, was applied at that site to detect the layers of the lower atmosphere in real time. Special software for these ceilometers with MATLAB provided routine retrievals of MLH from vertical profiles of laser backscatter data. Five portable Bruker EM27/SUN FTIR spectrometers were set up around Berlin to detect column averaged abundances of CO2 and CH4 by solar absorption spectrometry. Correlation analyses were used to show the coupling of temporal variations of trace gas compounds and PM with MLH. Significant influences of MLH upon NO, NO2, PM10, PM2.5, PM1 and toluene (marker for traffic emissions) concentrations as well as particle number concentrations in the size modes 70 - 100 nm, 100 - 200 nm and 200 - 500 nm on the basis of averaged diurnal courses were found. Further, MLH was taken as important auxiliary information about the development of the boundary layer during each day of observations, which was required for the proper estimation of CO2 and CH4 source strengths from Berlin on the basis of atmospheric column density measurements.

  11. Long-term study of air urban quality together with mixing layer height

    NASA Astrophysics Data System (ADS)

    Schäfer, Klaus; Ling, Hong; Münkel, Christoph; Emeis, Stefan

    2013-10-01

    Air pollution episodes in urban areas often occur during low wind speeds and low mixing layer height (MLH) and can not only be ascribed to increased local anthropogenic emissions. The continuous knowledge of MLH is supporting the understanding of processes directing air quality. If the MLH is located near to the ground, which occurs mainly during winter and night-time, air pollution can be high due to a strongly limited air mass dilution. The Vaisala ceilometer CL31, which is an eye-safe commercial mini-lidar system, is used for long-term continuous remote sensing of MLH. The ceilometer measurements provide information about the range-dependent aerosol concentration; gradient minima within this profile mark the borders of mixed layers. Special software for this ceilometer developed with MATLAB provides routine retrievals of lower atmosphere layering from vertical profiles of laser backscatter data. To study the gaseous pollutants and those compounds important for secondary aerosol formation like NO and NO2 as well as O3 The data retrieval software is extended to improve remote sensing of MLH. The original 10-minute-interval values are used to calculate continuous 1-hour-mean values. Gaps and strong variations of the original data are considered. The results of investigations of the meteorological influences and the role of emissions within the context of the air quality in Augsburg are discussed. a DOAS is operated since March 2012 in Augsburg. Information about different road traffic emissions is provided by this one instrument i.e. by path-integrated air pollution information in different directions. The DOAS contains an analyser and an emitter/receiver unit pointing to three retroreflectors. The retroreflectors were installed at lamp masts so that the paths were about 10 m above street level and perpendicular across the streets. The emitter/receiver unit was in a distance of about 20 m to an in situ air pollution measurement station at the ground. Ground

  12. Three-dimensional structure of the curved mixing layer using image reconstruction and volume rendering

    NASA Astrophysics Data System (ADS)

    Karasso, P. S.; Mungal, M. G.

    1991-05-01

    This study investigates the structure and mixing of the two-dimensional turbulent mixing layer when subjected to longitudinal streamwise curvature. The straight layer is now well known to be dominated by the primary Kelvin-Helmholtz (KH) instability as well as the secondary Taylor-Goertler (TG) instability. For equal density fluids, placing the high-speed fluid on the inside of a streamwise bend causes the TG instability to be enhanced (unstable case), while placing the low-speed fluid on the inside of the same bend leads to the suppression of the TG instability (stable case). The location of the mixing transition is correspondingly altered. Our goal is to study the changes to the mixing field and growth rate resulting from the competition between instabilities. Our studies are performed in a newly constructed blow-down water facility capable of high Reynolds numbers and excellent optical access. Maximum flow speeds are 2 and 0.25 m/sec for the high- and low-speed sides, respectively, leading to maximum Reynolds numbers of 80 000 based on velocity difference and the width of the layer. We are able to dye one stream with a fluorescent dye, thus providing several planar views of the flow under laser sheet illumination. These views are superior to conventional approaches as they are free of wall effects and are not spatially integrating. However, our most useful diagnostic of the structure of the flow is the ability to record high-speed images of the end view of the flow that are then reconstructed by computer using the volume rendering technique of Jiménez et al.1 This approach is especially useful as it allows us to compare the structural changes to the flow resulting from the competition between the KH and TG instabilities. Another advantage is the fact that several hundred frames, covering many characteristic times, are incorporated into the rendered image and thus capture considerably more flow physics than do still images. We currently have our rendering

  13. Radon-222, a proxy for vertical mixing of emissions in the urban nocturnal boundary layer

    NASA Astrophysics Data System (ADS)

    Chambers, S.; Williams, A. G.; Griffiths, A.; Crawford, J.; Zahorowski, W.

    2012-04-01

    There has been growing concern in recent decades regarding the health implications of fine particles (≤ 2.5μm), which are readily deposited deep within the lungs. In the interests of public health, and improving the predictive ability of Chemical Transport Models, it is imperative to improve our understanding of the diurnal variability of primary pollutant and precursor concentrations by, among others, improving our understanding of the underlying physics of transport and mixing processes. From the time of their release until they are removed from the atmosphere, the level of public exposure to emissions is closely related to rates of near-surface horizontal and vertical dispersion, the depth of the atmospheric boundary layer, and the venting from the boundary layer. These parameters, in turn, are dependent upon the amount and nature of mixing, which is closely related to atmospheric stability. With the exception of bushfires and dust storms, the greatest risk of public exposure to emissions occurs under "inversion" conditions, when the atmosphere is stably stratified. These very conditions are notoriously the most problematic for contemporary weather and chemical transport models. At such times the structure of the lowest 10-100m of the atmosphere can be quite complex, potentially containing multiple disconnected layers, and even stability measures based on surface similarity theory can fail (or yield inconclusive results) without sufficient vertical and temporal measurement resolution. Near-surface radon measurements provide a direct measure of the degree of dilution of surface-emitted scalar quantities by vertical mixing at night that is completely independent of local meteorological measurements and does not fail under conditions of near calm, which occur on the most stable nights. As such, they are a valuable proxy for potential pollution accumulation. In this study we analyse and discuss 22 months of continuous hourly observations within an urban airshed

  14. Simulation of the tropical oceans with an ocean GCM coupled to an atmospheric mixed-layer model

    SciTech Connect

    Murtugudde, R.; Seager, R.; Busalacchi, A.

    1996-08-01

    A reduced gravity, primitive equation, ocean general circulation model (GCM) is coupled to an advective atmospheric mixed-layer (AML) model to demonstrate the importance of a nonlocal atmospheric mixed-layer parameterization for a proper simulation of surface heat fluxes and sea surface temperatures (SST). Seasonal variability of the model SSTs and the circulation are generally in good agreement with the observations in each of the tropical oceans. These results are compared to other simulations that use a local equilibrium mixed-layer model. Inclusion of the advective AML model is demonstrated to lead to a significant improvement in the SST simulation in all three oceans. Advection and diffusion of the air humidity play significant roles in determining SSTs even in the tropical Pacific where the local equilibrium assumption was previously deemed quite accurate. The main, and serious, model flaw is an inadequate representation of the seasonal cycle in the upwelling regions of the eastern Atlantic and Pacific Oceans. The results indicate that the feedback between mixed-layer depths and SSTs can amplify SST errors, implying that increased realism in the modeling of the ocean mixed layer increases the demand for realism in the representation of the surface heat fluxes. The performance of the GCM with a local-equilibrium mixed-layer model in the Atlantic is as poor as previous simple ocean model simulations of the Atlantic. The conclusion of earlier studies that the simple ocean model was at fault may, in fact, not be correct. Instead the local-equilibrium heat flux parameterization appears to have been the major source of error. Accurate SST predictions may, hence, be feasible by coupling the AML model to computationally efficient simple ocean models. 69 refs., 18 figs., 1 tab.

  15. Weakly Penetrative Mixing in the Surface Layer of the Bay of Bengal

    NASA Astrophysics Data System (ADS)

    Lozovatsky, I.; Jinadasa, S. U. P.; Lucas, A.; MacKinnon, J. A.; Fernando, H. J.; Wijesekera, H. W.

    2014-12-01

    The first microstructure measurements under the ASIRI program were conducted in Bay of Bengal (BoB) during November 2014 in a region bounded by 16.95-16.25 N and 86.7- 87.0 E. Measurements were taken during the research cruise of r/v Roger Revelle using the VMP profiler down to ~ 140 m to infer the kinetic energy dissipation rate eps, temperature T, salinity S, and potential density anomaly sigT. Very strong stratification was observed just below a thin (less than 15-20 m deep) vertically homogeneous turbulent surface layer (SL), which effectively decoupled the former from the underlying thermohalocline. The upper boundary of the near-surface pycnocline was at z ~ 10 - 11 m and its lower boundary at z ~ 15 m. Under moderate (11 - 12 m/s) winds, the dissipation in the SL gradually decreased from the sea surface down to 10^-6 - 10^-8 W/kg at depths z ~ 10 - 15 m. Below z ~ 15 m, the dissipation rate sharply dropped to ~10^-9 W/kg, remaining approximately constant downward. The horizontal/temporal differences of T, S and sigT in the middle of SL were as high as dT ~ 0.25 C, dS ~ 0.4 psu, and dsigT ~ 0.22, respectively, over a distance of ~ 2 km. On the next day, under higher winds (~ 16 - 18 m/s), the SL deepened only slightly, being nominally decoupled from the pycnocline. The intensification of wind stress from ~ 0.16 to ~ 0.51 N/m2, led to an increase of eps to 10^-6 - 10^-7 W/kg across the entire mixing layer. The enhanced turbulence not only produced vertical mixing, but also initiated horizontal stirring, thus dramatically reducing thermohaline differences in the mixed SL down to dT ~ 0.017C, dS ~ 0.02 psu, and dsigT ~ 0.008, respectively. However, very strong stratification in the pycnocline suppressed the wind-induced vertical mixing, which did not penetrate below z ~ 22 - 25 m. No internal sources of turbulence were evident in the water interior, suggesting that under mild or even relatively strong but short-sustained winds small-scale dynamics of the SL and

  16. The seasonal cycle of the mixing layer height and its impact on black carbon concentrations in the Kathmandu Valley (Nepal)

    NASA Astrophysics Data System (ADS)

    Mues, Andrea; Rupakheti, Maheswar; Hoor, Peter; Bozem, Heiko; Münkel, Christoph; Lauer, Axel; Butler, Tim

    2016-04-01

    The properties and the vertical structure of the mixing layer as part of the planetary boundary layer are of key importance for local air quality. They have a substantial impact on the vertical dispersion of pollutants in the lower atmosphere and thus on their concentrations near the surface. In this study, ceilometer measurements taken within the framework of the SusKat project (Sustainable Atmosphere for the Kathmandu Valley) are used to investigate the mixing layer height in the Kathmandu Valley, Nepal. The applied method is based on the assumption that the aerosol concentration is nearly constant in the vertical and distinctly higher within the mixing layer than in the air above. Thus, the height with the steepest gradient within the ceilometer backscatter profile marks the top of the mixing layer. Ceilometer and black carbon (BC) measurements conducted from March 2013 through February 2014 provide a unique and important dataset for the analysis of the meteorological and air quality conditions in the Kathmandu Valley. In this study the mean diurnal cycle of the mixing layer height in the Kathmandu Valley for each season (pre-monsoon, monsoon, post-monsoon and winter season) and its dependency on the meteorological situation is investigated. In addition, the impact of the mixing layer height on the BC concentration is analyzed and compared to the relevance of other important processes such as emissions, horizontal advection and deposition. In all seasons the diurnal cycle is typically characterized by low mixing heights during the night, gradually increasing after sun rise reaching to maximum values in the afternoon before decreasing again. Seasonal differences can be seen particularly in the height of the mixing layer, e.g. from on average 153/1200 m (pre-monsoon) to 241/755 m (monsoon season) during the night/day, and the duration of enhanced mixing layer heights during daytime (around 12 hours (pre-monsoon season) to 8 hours (winter)). During the monsoon

  17. A Lipid-Accumulating Alga Maintains Growth in Outdoor, Alkaliphilic Raceway Pond with Mixed Microbial Communities.

    PubMed

    Bell, Tisza A S; Prithiviraj, Bharath; Wahlen, Brad D; Fields, Matthew W; Peyton, Brent M

    2015-01-01

    Algal biofuels and valuable co-products are being produced in both open and closed cultivation systems. Growing algae in open pond systems may be a more economical alternative, but this approach allows environmental microorganisms to colonize the pond and potentially infect or outcompete the algal "crop." In this study, we monitored the microbial community of an outdoor, open raceway pond inoculated with a high lipid-producing alkaliphilic alga, Chlorella vulgaris BA050. The strain C. vulgaris BA050 was previously isolated from Soap Lake, Washington, a system characterized by a high pH (∼9.8). An outdoor raceway pond (200 L) was inoculated with C. vulgaris and monitored for 10 days and then the culture was transferred to a 2,000 L raceway pond and cultivated for an additional 6 days. Community DNA samples were collected over the 16-day period in conjunction with water chemistry analyses and cell counts. Universal primers for the SSU rRNA gene sequences for Eukarya, Bacteria, and Archaea were used for barcoded pyrosequence determination. The environmental parameters that most closely correlated with C. vulgaris abundance were pH and phosphate. Community analyses indicated that the pond system remained dominated by the Chlorella population (93% of eukaryotic sequences), but was also colonized by other microorganisms. Bacterial sequence diversity increased over time while archaeal sequence diversity declined over the same time period. Using SparCC co-occurrence network analysis, a positive correlation was observed between C. vulgaris and Pseudomonas sp. throughout the experiment, which may suggest a symbiotic relationship between the two organisms. The putative relationship coupled with high pH may have contributed to the success of C. vulgaris. The characterization of the microbial community dynamics of an alkaliphilic open pond system provides significant insight into open pond systems that could be used to control photoautotrophic biomass productivity in an open

  18. A lipid-accumulating alga maintains growth in outdoor, alkaliphilic raceway pond with mixed microbial communities

    DOE PAGES

    Bell, Tisza A.S.; Prithiviraj, Bharath; Wahlen, Brad D.; ...

    2016-01-07

    Algal biofuels and valuable co-products are being produced in both open and closed cultivation systems. Growing algae in open pond systems may be a more economical alternative, but this approach allows environmental microorganisms to colonize the pond and potentially infect or outcompete the algal “crop.” In this study, we monitored the microbial community of an outdoor, open raceway pond inoculated with a high lipid-producing alkaliphilic alga, Chlorella vulgaris BA050. The strain C. vulgaris BA050 was previously isolated from Soap Lake, Washington, a system characterized by a high pH (~9.8). An outdoor raceway pond (200 L) was inoculated with C. vulgarismore » and monitored for 10 days and then the culture was transferred to a 2,000 L raceway pond and cultivated for an additional 6 days. Community DNA samples were collected over the 16-day period in conjunction with water chemistry analyses and cell counts. Universal primers for the SSU rRNA gene sequences for Eukarya, Bacteria, and Archaea were used for barcoded pyrosequence determination. The environmental parameters that most closely correlated with C. vulgaris abundance were pH and phosphate. Community analyses indicated that the pond system remained dominated by the Chlorella population (93% of eukaryotic sequences), but was also colonized by other microorganisms. Bacterial sequence diversity increased over time while archaeal sequence diversity declined over the same time period. Using SparCC co-occurrence network analysis, a positive correlation was observed between C. vulgaris and Pseudomonas sp. throughout the experiment, which may suggest a symbiotic relationship between the two organisms. The putative relationship coupled with high pH may have contributed to the success of C. vulgaris. As a result, the characterization of the microbial community dynamics of an alkaliphilic open pond system provides significant insight into open pond systems that could be used to control photoautotrophic biomass

  19. A Lipid-Accumulating Alga Maintains Growth in Outdoor, Alkaliphilic Raceway Pond with Mixed Microbial Communities

    PubMed Central

    Bell, Tisza A. S.; Prithiviraj, Bharath; Wahlen, Brad D.; Fields, Matthew W.; Peyton, Brent M.

    2016-01-01

    Algal biofuels and valuable co-products are being produced in both open and closed cultivation systems. Growing algae in open pond systems may be a more economical alternative, but this approach allows environmental microorganisms to colonize the pond and potentially infect or outcompete the algal “crop.” In this study, we monitored the microbial community of an outdoor, open raceway pond inoculated with a high lipid-producing alkaliphilic alga, Chlorella vulgaris BA050. The strain C. vulgaris BA050 was previously isolated from Soap Lake, Washington, a system characterized by a high pH (∼9.8). An outdoor raceway pond (200 L) was inoculated with C. vulgaris and monitored for 10 days and then the culture was transferred to a 2,000 L raceway pond and cultivated for an additional 6 days. Community DNA samples were collected over the 16-day period in conjunction with water chemistry analyses and cell counts. Universal primers for the SSU rRNA gene sequences for Eukarya, Bacteria, and Archaea were used for barcoded pyrosequence determination. The environmental parameters that most closely correlated with C. vulgaris abundance were pH and phosphate. Community analyses indicated that the pond system remained dominated by the Chlorella population (93% of eukaryotic sequences), but was also colonized by other microorganisms. Bacterial sequence diversity increased over time while archaeal sequence diversity declined over the same time period. Using SparCC co-occurrence network analysis, a positive correlation was observed between C. vulgaris and Pseudomonas sp. throughout the experiment, which may suggest a symbiotic relationship between the two organisms. The putative relationship coupled with high pH may have contributed to the success of C. vulgaris. The characterization of the microbial community dynamics of an alkaliphilic open pond system provides significant insight into open pond systems that could be used to control photoautotrophic biomass productivity in an

  20. The effect of supplementing layer diets with shark cartilage or chitosan on egg components and yolk lipids.

    PubMed

    Nogueira, C M; Zapata, J F F; Fuentes, M F F; Freitas, E R; Craveiro, A A; Aguiar, C M

    2003-05-01

    1. An experiment was designed to evaluate the effects of the addition of shark cartilage (SC) or chitosan (CH) to layer diets on egg component weights, yolk lipids and hen plasma lipids. 2. Hy-Line laying hens (80) were used during a 56 d feeding trial. Treatments were: basal diet (BD), BD + 20 g/kg SC, BD + 30 g/kg SC, BD + 20 g/kg CH and BD + 30 g/kg CH. Eggs were analysed on d 14, 28, 42 and 56. 3. Egg weight and egg component weights were not affected by these treatments throughout the experimental period. 4. After 14d of experimental feeding, cholesterol levels were higher in eggs from birds given BD + 20 g/kg CH and BD + 30 g/kg CH than in those from birds given BD. 5. Furthermore, eggs from hens given BD + 20 g/kg SC or BD + 20 g/kg CH were higher in palmitic and stearic acids and lower in oleic acid than those from birds fed on BD. After 56 d feeding, however, palmitic and stearic acid contents in eggs from hens given any of the supplemented diets were lower than in those from hens given BD, and oleic acid in eggs from hens given BD + 20 g/kg SC, BD + 30 g/kg SC and BD + 30 g/kg CH was higher than in those from birds fed on BD. 6. Plasma cholesterol and triacylglycerol levels were not significantly affected by dietary treatment. 7. Shark cartilage or chitosan at up to 30 g/kg in layer diets did not affect egg component weights (yolk, white and shell) and total lipid contents. During the period from 42 to 56d of experimental feeding, diets containing up to 30 g/kg chitosan reduced egg yolk contents of cholesterol, palmitic and stearic acids and increased the content of oleic acid.

  1. Enhanced electrochemical sensing of leukemia cells using drug/lipid co-immobilized on the conducting polymer layer.

    PubMed

    Gurudatt, N G; Naveen, M Halappa; Ban, Changill; Shim, Yoon-Bo

    2016-12-15

    Electrochemical biosensors using five anticancer drug and lipid molecules attached on the conducting polymer layer to obtain the orientation of drug molecules toward cancer cells, were evaluated as sensing materials and their performances were compared. Conjugation of the drug molecules with a lipid, phosphatidylcholine (PC) has enhanced the sensitivity towards leukemia cells and differentiates cancer cells from normal cells. The composition of each layer of sensor probe was confirmed by electrochemical and surface characterization experiments. Both impedance spectroscopy and voltammetry show the enhanced interaction of leukemia cells using the drug/lipid modified sensor probe. As the number of leukemia cells increased, the charge transfer resistance (Rct) in impedance spectra increased and the amine oxidation peak current of drug molecules in voltammograms decreased at around 0.7-1.0V. Of test drug molecules, raltitrexed (Rtx) showed the best performance for the cancer cells detection. Cancer and normal cell lines from different origins were examined to evaluate the degree of expression of folate receptors (FR) on cells surface, where cervical HeLa cell line was found to be shown the highest expression of the receptor. Impedance and chronoamperometric experiments for leukemia cell line (Jurkat E6-1) showed linear dynamic ranges of 1.0×10(3)-2.5×10(5) cells/mL and 1.0×10(3)-8.0×10(3) cells/mL with detection limits of 68±5 cells/mL and 21±3 cells/mL, respectively.

  2. Measurements of mixing layer height variability during the Ligurian air-sea interaction experiment (LASIE '07)

    NASA Astrophysics Data System (ADS)

    Förster, J.

    2009-09-01

    about 70 km. The second case (TAirMixing Layer Height (MLH) by the lidar ceilometer and the radio soundings.

  3. High fat mixed lipid diet modifies protective effects of exercise on 1,2 dimethylhydrazine induced colon cancer in rats.

    PubMed

    Perše, M; Injac, R; Štrukelj, B; Cerar, A

    2012-06-01

    The aim of the present study was to evaluate the effect of long-term swimming exercise in conjunction with a high fat mixed lipid (HFML) diet on colon cancer (CC) development and lipid peroxidation in the large bowel. We used forty male Wistar rats, which were randomly divided into one control group and four cancer groups: sedentary and swimming groups fed a standard diet (LFCO) and sedentary and swimming groups fed an HFML diet. Corticosterone was determined during the experiment. After 6 months of swimming, the rats were sacrificed and blood, heart, liver, muscle and large bowel were taken for determining the activity of serum enzymes, antioxidant capacity and CC development. The results demonstrate that exercise has a protective role in CC development. Attenuated development of CC and increased levels of malondialdehyde (MDA) in the large bowel of exercised rats show that one of the protective effects of exercise on developing CC is induction of oxidative stress. However, in terms of the combined effects of dietary fat and exercise, our results indicate that the protective role of exercise on CC development is significantly depressed by an HFML diet. An HFML diet significantly reduced the protective influence of exercise on colon carcinogenesis in rats and affected the degree of peroxidation in the large bowel during exercise, as well as concentrations of serum enzymes (LDH, α-HBDH, CK, ALT and AST). Our results indicate that an HFML diet, which reflects the composition of a Western style diet, is a significant modifier of the protective effects of exercise on CC development in rats.

  4. A lipid-accumulating alga maintains growth in outdoor, alkaliphilic raceway pond with mixed microbial communities

    SciTech Connect

    Bell, Tisza A.S.; Prithiviraj, Bharath; Wahlen, Brad D.; Fields, Matthew W.; Peyton, Brent M.

    2016-01-07

    Algal biofuels and valuable co-products are being produced in both open and closed cultivation systems. Growing algae in open pond systems may be a more economical alternative, but this approach allows environmental microorganisms to colonize the pond and potentially infect or outcompete the algal “crop.” In this study, we monitored the microbial community of an outdoor, open raceway pond inoculated with a high lipid-producing alkaliphilic alga, Chlorella vulgaris BA050. The strain C. vulgaris BA050 was previously isolated from Soap Lake, Washington, a system characterized by a high pH (~9.8). An outdoor raceway pond (200 L) was inoculated with C. vulgaris and monitored for 10 days and then the culture was transferred to a 2,000 L raceway pond and cultivated for an additional 6 days. Community DNA samples were collected over the 16-day period in conjunction with water chemistry analyses and cell counts. Universal primers for the SSU rRNA gene sequences for Eukarya, Bacteria, and Archaea were used for barcoded pyrosequence determination. The environmental parameters that most closely correlated with C. vulgaris abundance were pH and phosphate. Community analyses indicated that the pond system remained dominated by the Chlorella population (93% of eukaryotic sequences), but was also colonized by other microorganisms. Bacterial sequence diversity increased over time while archaeal sequence diversity declined over the same time period. Using SparCC co-occurrence network analysis, a positive correlation was observed between C. vulgaris and Pseudomonas sp. throughout the experiment, which may suggest a symbiotic relationship between the two organisms. The putative relationship coupled with high pH may have contributed to the success of C. vulgaris. As a result, the characterization of the microbial community dynamics of an alkaliphilic open pond system provides significant insight into open pond systems that could be used to

  5. Study of the Impact of Polyanions on the Formation of Lipid Bilayers on Top of Polyelectrolyte Multilayers with Poly(allylamine hydrochloride) as the Top Layer.

    PubMed

    Diamanti, Eleftheria; Andreozzi, Patrizia; Kirby, Christopher; Anguiano, Ramiro; Yate, Luis; Heinz, Hendrik; Ziolo, Ronald F; Donath, Edwin; Moya, Sergio Enrique

    2017-02-09

    The impact of polyanions on the formation of lipid bilayers on top of polyelectrolyte multilayers (PEMs) with poly(allylamine hydrochloride) (PAH) as the top layer is studied for the deposition of vesicles of mixed lipid composition, 50:50 molar ratio of zwitterionic 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and negatively charged 1,2-dioleoyl-sn-glycero-3-phospho-l-serine (DOPS). PEMs are assembled with polystyrene sulfonate (PSS), poly(acrylic acid) (PAA), and alginic acid sodium salt (Alg) as polyanions. The assembly of the vesicles on the PEMs is followed by means of the quartz crystal microbalance with dissipation. Fluorescence recovery after photobleaching measurements are applied to evaluate bilayer formation. Whereas a bilayer is formed on top of PAH/PSS multilayers, the vesicles are adsorbed on top of PAH/Alg and PAH/PAA multilayers, remaining unruptured or only partially fused. The influence of the surface composition of the PEM and of the bulk properties of the film are analyzed. The phosphate ions present in phosphate-buffered saline (PBS) play a fundamental role in bilayer formation on top of PAH/PSS as they complex with PAH and render the surface potential close to zero. For PAH/PAA and PAH/Alg, PBS renders the surface negative. X-ray photoelectron spectroscopy shows that the dibasic phosphate ions from PBS complex preferentially with PAH in PAH/PAA and PAH/Alg multilayers, whereas monobasic phosphates complex with PAH in PAH/PSS. An explanation for the absence of bilayer formation on PAH/PAA and PAH/Alg is given on the basis of the different affinities of phosphate ions for PAH in combination with the different polyanions.

  6. Effects of Precipitation on Ocean Mixed-Layer Temperature and Salinity as Simulated in a 2-D Coupled Ocean-Cloud Resolving Atmosphere Model

    NASA Technical Reports Server (NTRS)

    Li, Xiaofan; Sui, C.-H.; Lau, K-M.; Adamec, D.

    1999-01-01

    A two-dimensional coupled ocean-cloud resolving atmosphere model is used to investigate possible roles of convective scale ocean disturbances induced by atmospheric precipitation on ocean mixed-layer heat and salt budgets. The model couples a cloud resolving model with an embedded mixed layer-ocean circulation model. Five experiment are performed under imposed large-scale atmospheric forcing in terms of vertical velocity derived from the TOGA COARE observations during a selected seven-day period. The dominant variability of mixed-layer temperature and salinity are simulated by the coupled model with imposed large-scale forcing. The mixed-layer temperatures in the coupled experiments with 1-D and 2-D ocean models show similar variations when salinity effects are not included. When salinity effects are included, however, differences in the domain-mean mixed-layer salinity and temperature between coupled experiments with 1-D and 2-D ocean models could be as large as 0.3 PSU and 0.4 C respectively. Without fresh water effects, the nocturnal heat loss over ocean surface causes deep mixed layers and weak cooling rates so that the nocturnal mixed-layer temperatures tend to be horizontally-uniform. The fresh water flux, however, causes shallow mixed layers over convective areas while the nocturnal heat loss causes deep mixed layer over convection-free areas so that the mixed-layer temperatures have large horizontal fluctuations. Furthermore, fresh water flux exhibits larger spatial fluctuations than surface heat flux because heavy rainfall occurs over convective areas embedded in broad non-convective or clear areas, whereas diurnal signals over whole model areas yield high spatial correlation of surface heat flux. As a result, mixed-layer salinities contribute more to the density differences than do mixed-layer temperatures.

  7. Upper ocean mixing processes and their impact on the mixed layer heat balance during the onset of the Atlantic Cold Tongue.

    NASA Astrophysics Data System (ADS)

    Dengler, M.; Brandt, P.; McPhaden, M. J.; Thomsen, S.; Krahmann, G.; Fischer, T.; Freitag, P.; Hummels, R.

    2012-04-01

    An extensive measurement program within the Atlantic Cold Tongue (ACT) region was carried out during the ACT onset in boreal summer 2011. During two consecutive cruises shipboard microstructure profiles, conductivity-temperature-depth-O2 (CTD-O2) profiles and shipboard velocity profiles were collected between mid-May and mid-July. The shipboard measurements were complemented by a Glider swarm experiment during which 5400 CTD-O2 profiles were collected along specified transects within the ACT region. One of those Gliders was equipped with a MicroRider turbulence package and collected a 5-week microstructure time series of about hourly-resolution in the center of the cold tongue on the equator at 10°W. The MicroRider/Glider package was circling a PIRATA mooring from which additionally high-resolution acoustic Doppler current profiles are available for this time period to allow analysis of the background conditions. In this contribution we use a subset from the above data to detail mixing processes in the upper stratified ocean and describe the background conditions favoring enhanced mixing. From end of May to mid-July, sea surface temperature decreased from 26°C to below 22°C at 10°W. During the whole period of autonomous microstructure observations, strong bursts of turbulence were observed extending from the mixed layer into the upper thermocline. These bursts lasted for 3-5 hours and were found to penetrate to about 30m below the base of the mixed layer. They were observed to occur predominately during night-time while during day-time they were less frequent. Dissipation rates of turbulent kinetic energy (ɛ) during these bursts were above 3x10-6Wkg-1 in the upper stratified water column and turbulent eddy diffusivities (Kρ) often reached 1x10-3m2s-1. The data set suggests that strength and frequency of occurrence of the turbulent bursts is modulated by the presents of Tropical Instability Waves which additionally enhance background shear at the equator. The

  8. Nonlinear interactions in mixing layers and compressible heated round jets. Ph.D. Thesis Final Report

    NASA Technical Reports Server (NTRS)

    Jarrah, Yousef Mohd

    1989-01-01

    The nonlinear interactions between a fundamental instability mode and both its harmonics and the changing mean flow are studied using the weakly nonlinear stability theory of Stuart and Watson, and numerical solutions of coupled nonlinear partial differential equations. The first part focuses on incompressible cold (or isothermal; constant temperature throughout) mixing layers, and for these, the first and second Landau constants are calculated as functions of wavenumber and Reynolds number. It is found that the dominant contribution to the Landau constants arises from the mean flow changes and not from the higher harmonics. In order to establish the range of validity of the weakly nonlinear theory, the weakly nonlinear and numerical solutions are compared and the limitation of each is discussed. At small amplitudes and at low-to-moderate Reynolds numbers, the two results compare well in describing the saturation of the fundamental, the distortion of the mean flow, and the initial stages of vorticity roll-up. At larger amplitudes, the interaction between the fundamental, second harmonic, and the mean flow is strongly nonlinear and the numerical solution predicts flow oscillations, whereas the weakly nonlinear theory yields saturation. In the second part, the weakly nonlinear theory is extended to heated (or nonisothermal; mean temperature distribution) subsonic round jets where quadratic and cubic nonlinear interactions are present, and the Landau constants also depend on jet temperature ratio, Mach number and azimuthal mode number. Under exponential growth and nonlinear saturation, it is found that heating and compressibility suppress the growth of instability waves, that the first azimuthal mode is the dominant instability mode, and that the weakly nonlinear solution describes the early stages of the roll-up of an axisymmetric shear layer. The receptivity of a typical jet flow to pulse type input disturbance is also studied by solving the initial value problem

  9. Seasonal variability in mixed layer height and its impact on trace gas distribution over a tropical urban site: Ahmedabad

    NASA Astrophysics Data System (ADS)

    Srivastava, Shuchita; Lal, S.; Subrahamanyam, D. Bala; Gupta, S.; Venkataramani, S.; Rajesh, T. A.

    2010-04-01

    Altitude profiles of virtual potential temperature ( θv) and specific humidity ( q) derived from meteorological data obtained from balloon-borne radiosonde ascents are used to investigate the seasonal variations in mixed layer height over Ahmedabad (23.03°N, 72.54°E), an urban site located on the western part of India. A total of 82 balloon ascents were conducted fortnightly in the morning hours during a period of about four years spanning from April 2003 to July 2007. Analysis of the vertical profiles of θv and q reveals a systematic seasonal variability in the mixed layer height (MLH), showing the decreasing trend from summer-monsoon to winter season. The MLH is observed to be maximum (˜ 1170 m) in summer-monsoon while a minimum (˜ 160 m) is observed during the winter months. In general, the mixed layer height was found to be highly variant during pre-monsoon and summer-monsoon seasons. This variability is observed to be comparatively lower in the post-monsoon and winter months. Effects of MLH have been investigated on the variations in surface ozone and MOPITT derived surface and vertical distributions of CO. The reverse trend is observed in surface ozone and CO with mixed layer seasonal variability. The impact of MLH over CO vertical distributions is observed up to an altitude of 3-4 km.

  10. A MULTI-STREAM MODEL FOR VERTICAL MIXING OF A PASSIVE TRACER IN THE CONVECTIVE BOUNDARY LAYER

    EPA Science Inventory

    We study a multi-stream model (MSM) for vertical mixing of a passive tracer in the convective boundary layer, in which the tracer is advected by many vertical streams with different probabilities and diffused by small scale turbulence. We test the MSM algorithm for investigatin...

  11. Quality control on the mixing layer height retrieved from LIDAR-ceilometer measurements

    NASA Astrophysics Data System (ADS)

    Laffineur, Quentin; De Backer, Hugo; Delcloo, Andy; Hamdi, Rafiq; Nemeghaire, Jean; Debal, Fabian

    2013-04-01

    LIDAR ceilometers were primarily designed for cloud base height detection (for air traffic safety and weather forecasting). They greatly improved over the last years and now offer the opportunity to monitor the vertical profile of aerosols and the mixing layer height (MLH) on a continuous temporal scale. The knowledge of MLH can improve the forecasting of the dispersion of trace gases and aerosols in the lowest layers of the atmosphere and can also improve the accuracy of the greenhouse gas concentration budgets highly depending on MLH. Therefore, during the next years, operational MLH monitoring networks of LIDAR ceilometers are established around the world, and in particular in Europe. To perform this task, different algorithms have been developed to retrieve the MLH from the ceilometer measurements. However, under specific atmospheric conditions, these algorithms fail to retrieve a similar MLH than other remote sensing retrieval techniques. On the other hand, the ceilometers are sometimes located in places where no other remote sensing measurements are available to assess the accuracy of the MLH retrieved by the algorithm. In this context, the development of several MLH quality control flags based on the ceilometer measurements only is desirable to detect automatically the failure of the MLH retrieval algorithms without the support of additional measurements. In Belgium, in 2013, three new ceilometers (Vaisala CL51) will be installed by the Royal Meteorological Institute of Belgium (RMI) in addition to the one in Uccle (Belgium) that has already been installed since May 2011. RMI developed its own MLH retrieval algorithm based on the gradient and variance methods. The computation of several quality flags will be presented. In this work, an assessment of these quality flags is made by comparing the MLH retrieved by ceilometer measurements with the MLH retrieved by radio-sounding and the boundary layer height (BLH) directly computed by the ECMWF and the ALARO7

  12. Altered lipid metabolism in the aging kidney identified by three layered omic analysis.

    PubMed

    Braun, Fabian; Rinschen, Markus M; Bartels, Valerie; Frommolt, Peter; Habermann, Bianca; Hoeijmakers, Jan H J; Schumacher, Björn; Dollé, Martijn E T; Müller, Roman-Ulrich; Benzing, Thomas; Schermer, Bernhard; Kurschat, Christine E

    2016-03-01

    Aging-associated diseases and their comorbidities affect the life of a constantly growing proportion of the population in developed countries. At the center of these comorbidities are changes of kidney structure and function as age-related chronic kidney disease predisposes to the development of cardiovascular diseases such as stroke, myocardial infarction or heart failure. To detect molecular mechanisms involved in kidney aging, we analyzed gene expression profiles of kidneys from adult and aged wild-type mice by transcriptomic, proteomic and targeted lipidomic methodologies. Interestingly, transcriptome and proteome analyses revealed differential expression of genes primarily involved in lipid metabolism and immune response. Additional lipidomic analyses uncovered significant age-related differences in the total amount of phosphatidylethanolamines, phosphatidylcholines and sphingomyelins as well as in subspecies of phosphatidylserines and ceramides with age. By integration of these datasets we identified Aldh1a1, a key enzyme in vitamin A metabolism specifically expressed in the medullary ascending limb, as one of the most prominent upregulated proteins in old kidneys. Moreover, ceramidase Asah1 was highly expressed in aged kidneys, consistent with a decrease in ceramide C16. In summary, our data suggest that changes in lipid metabolism are involved in the process of kidney aging and in the development of chronic kidney disease.

  13. Statistics of Vortical Structures in Variable-Density Turbulent Mixing Layers

    NASA Astrophysics Data System (ADS)

    Baltzer, Jon; Livescu, Daniel

    2016-11-01

    Direct Numerical Simulations are performed of temporal incompressible shear-driven planar mixing layers between two miscible streams of fluids with different densities. The simulations begin from thin disturbed interfaces and develop into self-similar states. We use very large domain sizes, corresponding to grids of up to 6144 x 2048 x 1536 points, to produce high-quality statistics and allow natural growth of turbulent structures. A wide range of Atwood numbers are explored, ranging from nearly constant density to A=0.87 (or a density ratio of 14). At high Atwood numbers, a variety of statistics show that variable-density effects produce significant asymmetries. Here we focus on the differences in vortical structure of the light and heavy fluid streams and the importance of non-Boussinesq effects as Atwood number increases. Detailed budgets of vorticity moments are examined in conjunction with the alignments of vorticity relative to other flow quantities. The results display the variable density effects due to compositional variations, a distinctly different mechanism from the density variations associated with compressibility in high-speed flows.

  14. A Model Chain Application to Estimate Mixing Layer Height Related to PM10 Dispersion Processes.

    PubMed

    Guarnieri, F; Calastrini, F; Busillo, C; Messeri, G; Gozzini, B

    2015-01-01

    The mixing layer height (MLH) is a crucial parameter in order to investigate the near surface concentrations of air pollutants. The MLH can be estimated by measurements of some atmospheric variables, by indirect estimates based on trace gases concentration or aerosol, or by numerical models. Here, a modelling approach is proposed. The developed modelling system is based on the models WRF-ARW and CALMET. This system is applied on Firenze-Prato-Pistoia area (Central Italy), during 2010, and it is compared with in situ measurements. The aim of this work is to evaluate the use of MLH model estimates to characterize the critical episodes for PM10 in a limited area. In order to find out the meteorological conditions predisposing accumulation of PM10 in the atmosphere's lower level, some indicators are used: daily mean wind speed, cumulated rainfall, and mean MLH estimates from CALMET model. This indicator is linked to orography, which has important consequences on local weather dynamics. However, during critical events the local emission sources are crucial to the determination of threshold exceeding of PM10. Results show that the modelled MLH, together with cumulative rainfall and wind speed, can identify the meteorological conditions predisposing accumulation of air pollutant at ground level.

  15. Effects of radiative heat transfer on the turbulence structure in inert and reacting mixing layers

    SciTech Connect

    Ghosh, Somnath; Friedrich, Rainer

    2015-05-15

    We use large-eddy simulation to study the interaction between turbulence and radiative heat transfer in low-speed inert and reacting plane temporal mixing layers. An explicit filtering scheme based on approximate deconvolution is applied to treat the closure problem arising from quadratic nonlinearities of the filtered transport equations. In the reacting case, the working fluid is a mixture of ideal gases where the low-speed stream consists of hydrogen and nitrogen and the high-speed stream consists of oxygen and nitrogen. Both streams are premixed in a way that the free-stream densities are the same and the stoichiometric mixture fraction is 0.3. The filtered heat release term is modelled using equilibrium chemistry. In the inert case, the low-speed stream consists of nitrogen at a temperature of 1000 K and the highspeed stream is pure water vapour of 2000 K, when radiation is turned off. Simulations assuming the gas mixtures as gray gases with artificially increased Planck mean absorption coefficients are performed in which the large-eddy simulation code and the radiation code PRISSMA are fully coupled. In both cases, radiative heat transfer is found to clearly affect fluctuations of thermodynamic variables, Reynolds stresses, and Reynolds stress budget terms like pressure-strain correlations. Source terms in the transport equation for the variance of temperature are used to explain the decrease of this variance in the reacting case and its increase in the inert case.

  16. Comparative Study of Three High Order Schemes for LES of Temporally Evolving Mixing Layers

    NASA Technical Reports Server (NTRS)

    Yee, Helen M. C.; Sjogreen, Biorn Axel; Hadjadj, C.

    2012-01-01

    Three high order shock-capturing schemes are compared for large eddy simulations (LES) of temporally evolving mixing layers (TML) for different convective Mach numbers (Mc) ranging from the quasi-incompressible regime to highly compressible supersonic regime. The considered high order schemes are fifth-order WENO (WENO5), seventh-order WENO (WENO7) and the associated eighth-order central spatial base scheme with the dissipative portion of WENO7 as a nonlinear post-processing filter step (WENO7fi). This high order nonlinear filter method (H.C. Yee and B. Sjogreen, Proceedings of ICOSAHOM09, June 22-26, 2009, Trondheim, Norway) is designed for accurate and efficient simulations of shock-free compressible turbulence, turbulence with shocklets and turbulence with strong shocks with minimum tuning of scheme parameters. The LES results by WENO7fi using the same scheme parameter agree well with experimental results of Barone et al. (2006), and published direct numerical simulations (DNS) work of Rogers & Moser (1994) and Pantano & Sarkar (2002), whereas results by WENO5 and WENO7 compare poorly with experimental data and DNS computations.

  17. Defect physics vis-à-vis electrochemical performance in layered mixed-metal oxide cathode materials

    NASA Astrophysics Data System (ADS)

    Hoang, Khang; Johannes, Michelle

    Layered mixed-metal oxides with different compositions of (Ni,Co,Mn) [NCM] or (Ni,Co,Al) [NCA] have been used in commercial lithium-ion batteries. Yet their defect physics and chemistry is still not well understood, despite having important implications for the electrochemical performance. In this presentation, we report a hybrid density functional study of intrinsic point defects in the compositions LiNi1/3Co1/3Mn1/3O2 (NCM1/3) and LiNi1/3Co1/3Al1/3O2 (NCA1/3) which can also be regarded as model compounds for NCM and NCA. We will discuss defect landscapes in NCM1/3 and NCA1/3 under relevant synthesis conditions with a focus on the formation of metal antisite defects and its implications on the electrochemical properties and ultimately the design of NCM and NCA cathode materials.

  18. Effects of radiative heat transfer on the turbulence structure in inert and reacting mixing layers

    NASA Astrophysics Data System (ADS)

    Ghosh, Somnath; Friedrich, Rainer

    2015-05-01

    We use large-eddy simulation to study the interaction between turbulence and radiative heat transfer in low-speed inert and reacting plane temporal mixing layers. An explicit filtering scheme based on approximate deconvolution is applied to treat the closure problem arising from quadratic nonlinearities of the filtered transport equations. In the reacting case, the working fluid is a mixture of ideal gases where the low-speed stream consists of hydrogen and nitrogen and the high-speed stream consists of oxygen and nitrogen. Both streams are premixed in a way that the free-stream densities are the same and the stoichiometric mixture fraction is 0.3. The filtered heat release term is modelled using equilibrium chemistry. In the inert case, the low-speed stream consists of nitrogen at a temperature of 1000 K and the highspeed stream is pure water vapour of 2000 K, when radiation is turned off. Simulations assuming the gas mixtures as gray gases with artificially increased Planck mean absorption coefficients are performed in which the large-eddy simulation code and the radiation code PRISSMA are fully coupled. In both cases, radiative heat transfer is found to clearly affect fluctuations of thermodynamic variables, Reynolds stresses, and Reynolds stress budget terms like pressure-strain correlations. Source terms in the transport equation for the variance of temperature are used to explain the decrease of this variance in the reacting case and its increase in the inert case.

  19. Evolution of streamwise vortices and generation of small-scale motion in a plane mixing layer

    NASA Technical Reports Server (NTRS)

    Nygaard, K. J.; Glezer, A.

    1991-01-01

    The present study investigates the evolution of streamwise vortices in a plane mixing layer and their role in the generation of small-scale 3D motion in a closed-return water facility. Spanwise-periodic streamwise vortices are excited by a time-harmonic wavetrain with spanwise-periodic amplitude variations synthesized by a mosaic of 32 surface film heaters flush-mounted on the low partition. The onset of streamwise vortices is accompanied by significant distortion in the transverse distribution of the streamwise velocity component. The presence of inflexion points, absent in corresponding velocity distributions of the unforced flow, suggests the formation of locally unstable regions of large shear in which broadband perturbations already present in the base flow undergo rapid amplification, followed by breakdown to small-scale motion. The cores of the primary vortices are significantly altered as a result of spanwise nonuniform excitation. The 3D features of the streamwise vortices and their interaction with the base flow are inferred from surfaces or rms velocity fluctuations and an approximation to cross-stream vorticity using 3D single component velocity data.

  20. Mesoporous mixed metal oxides derived from P123-templated Mg-Al layered double hydroxides

    SciTech Connect

    Wang Jun; Zhou Jideng; Li Zhanshuang; He Yang; Lin Shuangshuang; Liu Qi; Zhang Milin; Jiang Zhaohua

    2010-11-15

    We report the preparation of mesoporous mixed metal oxides (MMOs) through a soft template method. Different amounts of P123 were used as structure directing agent to synthesize P123-templated Mg-Al layered double hydroxides (LDHs). After calcination of as-synthesized LDHs at 500 {sup o}C, the ordered mesopores were obtained by removal of P123. The mesoporous Mg-Al MMOs fabricated by using 2 wt% P123 exhibited a high specific surface area of 108.1 m{sup 2}/g, and wide distribution of pore size (2-18 nm). An investigation of the 'memory effect' of the mesoporous MMOs revealed that they were successfully reconstructed to ibuprofen intercalated LDHs having different gallery heights, which indicated different intercalation capacities. Due to their mesoporosity these unique MMOs have particular potential as drug or catalyst carriers. - Graphical abstract: Ordered mesoporous Mg-Al MMOs can be obtained through the calcination of P123-templated Mg-Al-CO{sub 3} LDHs. The pore diameter is 2.2 nm. At the presence of ibuprofen, the Mg-Al MMOs can recover to Mg-Al-IBU LDHs, based on its 'remember effect'. Display Omitted

  1. Baroclinic mixing of potential vorticity as the principal sharpening mechanism for the extratropical Tropopause Inversion Layer

    NASA Astrophysics Data System (ADS)

    Wang, Shu Meir; Geller, Marvin A.

    2016-09-01

    Previous works have shown that a dry, idealized general circulation model could produce many features of the extratropical Tropopause Inversion Layer (TIL). In particular, the following have been shown, but no explanations were given for these results. (1) A sharper extratropical TIL resulted more from increased horizontal resolution than from increased vertical resolution. (2) If the Equator-to-Pole temperature gradient was varied, the annual variation of the extratropical TIL found in observations could be reproduced. (3) The extratropical TIL altitude showed excellent correlation with the upper tropospheric relative vorticity, as had been previously proposed. (4) Increased horizontal model resolutions led to extratropical TILs that were at lower altitudes. We show that these conclusions follow from baroclinic mixing of high stratospheric potential vorticity into the troposphere being the principal sharpening mechanism for the extratropical TIL and the increased baroclinic activity occurring in higher horizontal resolution models. We furthermore suggest that the distance from the jet exerts a greater influence on the height and sharpness of the extratropical TIL than does the upper tropospheric relative vorticity, and this accounts for the annual behavior of the extratropical TIL found in observations and reproduced with a dry, mechanistic, global model.

  2. FerryBox-assisted monitoring of mixed layer pH in the Norwegian Coastal Current

    NASA Astrophysics Data System (ADS)

    Reggiani, Emanuele R.; King, Andrew L.; Norli, Marit; Jaccard, Pierre; Sørensen, Kai; Bellerby, Richard G. J.

    2016-10-01

    The evaluation of marine carbonate system variability and the impacts of ocean acidification (OA) on coastal marine ecosystems increasingly rely on monitoring platforms capable of delivering near real-time in situ carbonate system observations. These observations are also used for developing models and scenarios of OA, including potential impacts on marine ecosystem structure and function. An embedded flow-through spectrophotometric pH detection system has been developed alongside an underway seawater sampling system - termed a FerryBox - operating on ships of opportunity (SOOP), and can deliver a continuous data stream of mixed layer seawater pH with an in situ uncertainty of < 0.003. We report metrological approaches behind the pH detection procedure and the evaluation of dye addition perturbation with analytical precision as low as 0.0005. In addition, we present field-based observations from a deployment of the pH detection system along the Norwegian Coastal Current in winter, spring, and summer periods of 2015. Spring and summertime pH was generally 0.1 higher, and up to 0.255 higher, in comparison to winter pH observations. Here we show the necessity for a regular, high density monitoring approach, and the suitability of this pH detection technique for unmanned observational platforms.

  3. Numerical simulations of a chemically reacting Richtmyer-Meshkov turbulent mixing layer

    NASA Astrophysics Data System (ADS)

    Varshochi, Hilda; Attal, Nitesh; Ramaprabhu, Praveen

    2014-11-01

    We report on results from detailed numerical simulations that capture the evolution through the Richtmyer-Meshkov instability of a multi-mode interface that initially separates a fuel (H2) and a corresponding oxidizer (O2) . The three-dimensional simulations were carried out at a resolution of 512 × 512 × 3072 using a modified version of the FLASH code, capable of handling detailed H2-O2 combustion chemistry, temperature-dependent equation of state, and temperature-dependent molecular transport properties. The perturbation interface was initialized with ``alpha-group'' type perturbations, and impacted by a Mach 1.2 incident shock travelling from the light (H2) to heavy (O2) fluid. We track several quantities through the linear, non-linear and turbulent stages of evolution, and make comparisons with the corresponding non-reacting flowfield from a separate set of simulations. The turbulent mixing layer is also subjected to reshock, which dramatically increases the combustion efficiency at the interface.

  4. Vapor phase hydrogenation of furfural over nickel mixed metal oxide catalysts derived from layered double hydroxides

    SciTech Connect

    Sulmonetti, Taylor P.; Pang, Simon H.; Claure, Micaela Taborga; Lee, Sungsik; Cullen, David A.; Agrawal, Pradeep K.; Jones, Christopher W.

    2016-05-01

    The hydrogenation of furfural is investigated over various reduced nickel mixed metal oxides derived from layered double hydroxides (LDHs) containing Ni-Mg-Al and Ni-Co-Al. Upon reduction, relatively large Ni(0) domains develop in the Ni-Mg-Al catalysts, whereas in the Ni-Co-Al catalysts smaller metal particles of Ni(0) and Co(0), potentially as alloys, are formed, as evidenced by XAS, XPS, STEM and EELS. All the reduced Ni catalysts display similar selectivities towards major hydrogenation products (furfuryl alcohol and tetrahydrofurfuryl alcohol), though the side products varied with the catalyst composition. The 1.1Ni-0.8Co-Al catalyst showed the greatest activity per titrated site when compared to the other catalysts, with promising activity compared to related catalysts in the literature. The use of base metal catalysts for hydrogenation of furanic compounds may be a promising alternative to the well-studied precious metal catalysts for making biomass-derived chemicals if catalyst selectivity can be improved in future work by alloying or tuning metal-oxide support interactions.

  5. Vapor phase hydrogenation of furfural over nickel mixed metal oxide catalysts derived from layered double hydroxides

    DOE PAGES

    Sulmonetti, Taylor P.; Pang, Simon H.; Claure, Micaela Taborga; ...

    2016-03-09

    The hydrogenation of furfural is investigated over various reduced nickel mixed metal oxides derived from layered double hydroxides (LDHs) containing Ni-Mg-Al and Ni-Co-Al. Upon reduction, relatively large Ni(0) domains develop in the Ni-Mg-Al catalysts, whereas in the Ni-Co-Al catalysts smaller metal particles of Ni(0) and Co(0), potentially as alloys, are formed, as evidenced by XAS, XPS, STEM and EELS. All the reduced Ni catalysts display similar selectivities towards major hydrogenation products (furfuryl alcohol and tetrahydrofurfuryl alcohol), though the side products varied with the catalyst composition. The 1.1Ni-0.8Co-Al catalyst showed the greatest activity per titrated site when compared to the othermore » catalysts, with promising activity compared to related catalysts in the literature. In conclusion, the use of base metal catalysts for hydrogenation of furanic compounds may be a promising alternative to the well-studied precious metal catalysts for making biomass-derived chemicals if catalyst selectivity can be improved in future work by alloying or tuning metal-oxide support interactions.« less

  6. Vapor phase hydrogenation of furfural over nickel mixed metal oxide catalysts derived from layered double hydroxides

    SciTech Connect

    Sulmonetti, Taylor P.; Pang, Simon H.; Claure, Micaela Taborga; Lee, Sungsik; Cullen, David A.; Agrawal, Pradeep K.; Jones, Christopher W.

    2016-03-09

    The hydrogenation of furfural is investigated over various reduced nickel mixed metal oxides derived from layered double hydroxides (LDHs) containing Ni-Mg-Al and Ni-Co-Al. Upon reduction, relatively large Ni(0) domains develop in the Ni-Mg-Al catalysts, whereas in the Ni-Co-Al catalysts smaller metal particles of Ni(0) and Co(0), potentially as alloys, are formed, as evidenced by XAS, XPS, STEM and EELS. All the reduced Ni catalysts display similar selectivities towards major hydrogenation products (furfuryl alcohol and tetrahydrofurfuryl alcohol), though the side products varied with the catalyst composition. The 1.1Ni-0.8Co-Al catalyst showed the greatest activity per titrated site when compared to the other catalysts, with promising activity compared to related catalysts in the literature. In conclusion, the use of base metal catalysts for hydrogenation of furanic compounds may be a promising alternative to the well-studied precious metal catalysts for making biomass-derived chemicals if catalyst selectivity can be improved in future work by alloying or tuning metal-oxide support interactions.

  7. Improved layered mixed transition metal oxides for Li-ion batteries

    SciTech Connect

    Doeff, Marca M.; Conry, Thomas; Wilcox, James

    2010-03-05

    Recent work in our laboratory has been directed towards development of mixed layered transition metal oxides with general composition Li[Ni, Co, M, Mn]O2 (M=Al, Ti) for Li ion battery cathodes. Compounds such as Li[Ni1/3Co1/3Mn1/3]O2 (often called NMCs) are currently being commercialized for use in consumer electronic batteries, but the high cobalt content makes them too expensive for vehicular applications such as electric vehicles (EV), plug-in hybrid electric vehicles (PHEVs), or hybrid electric vehicles (HEVs). To reduce materials costs, we have explored partial or full substitution of Co with Al, Ti, and Fe. Fe substitution generally decreases capacity and results in poorer rate and cycling behavior. Interestingly, low levels of substitution with Al or Ti improve aspects of performance with minimal impact on energy densities, for some formulations. High levels of Al substitution compromise specific capacity, however, so further improvements require that the Ni and Mn content be increased and Co correspondingly decreased. Low levels of Al or Ti substitution can then be used offset negative effects induced by the higher Ni content. The structural and electrochemical characterization of substituted NMCs is presented in this paper.

  8. LES of Temporally Evolving Mixing Layers by an Eighth-Order Filter Scheme

    NASA Technical Reports Server (NTRS)

    Hadjadj, A; Yee, H. C.; Sjogreen, B.

    2011-01-01

    An eighth-order filter method for a wide range of compressible flow speeds (H.C. Yee and B. Sjogreen, Proceedings of ICOSAHOM09, June 22-26, 2009, Trondheim, Norway) are employed for large eddy simulations (LES) of temporally evolving mixing layers (TML) for different convective Mach numbers (Mc) and Reynolds numbers. The high order filter method is designed for accurate and efficient simulations of shock-free compressible turbulence, turbulence with shocklets and turbulence with strong shocks with minimum tuning of scheme parameters. The value of Mc considered is for the TML range from the quasi-incompressible regime to the highly compressible supersonic regime. The three main characteristics of compressible TML (the self similarity property, compressibility effects and the presence of large-scale structure with shocklets for high Mc) are considered for the LES study. The LES results using the same scheme parameters for all studied cases agree well with experimental results of Barone et al. (2006), and published direct numerical simulations (DNS) work of Rogers & Moser (1994) and Pantano & Sarkar (2002).

  9. Kinetic study of the aggregation and lipid mixing produced by alpha-sarcin on phosphatidylglycerol and phosphatidylserine vesicles: stopped-flow light scattering and fluorescence energy transfer measurements.

    PubMed Central

    Mancheño, J. M.; Gasset, M.; Lacadena, J.; Ramón, F.; Martínez del Pozo, A.; Oñaderra, M.; Gavilanes, J. G.

    1994-01-01

    alpha-Sarcin is a fungal cytotoxic protein that inactivates the eukaryotic ribosomes. A kinetic study of the aggregation and lipid mixing promoted by this protein on phosphatidylglycerol (PG) and phosphatidylserine (PS) vesicles has been performed. Egg yolk PG, bovine brain PS, dimyristoyl-PG (DMPG) and dimyristoyl-PS (DMPS) vesicles have been considered. The initial rates of the vesicle aggregation induced by the protein have been measured by stopped-flow 90 degrees light scattering. The formation of a vesicle dimer as the initial step of this process was deduced from the second-order dependence of the initial rates on phospholipid concentration. The highest alpha-sarcin concentration studied did not inhibit the vesicle aggregation, indicating that many protein molecules are involved in the vesicle cross-linking. These are common characteristics of the initial steps of the aggregation produced by alpha-sarcin in the four types of phospholipid vesicles considered. However, the kinetics of the scattering values revealed that more complex changes occurred in the later steps of the aggregation process of egg PG and brain PS vesicles than in those of their synthetic counterparts. alpha-Sarcin produced lipid mixing in vesicles composed of DMPG or DMPS, which was measured by fluorescence resonance energy transfer assays. A delay in the onset of the process, dependent on the protein concentration, was observed. Measurement of the rates of lipid mixing revealed that the process is first order on phospholipid concentration. Egg PG and brain PS vesicles did not show lipid mixing, although they avidly aggregated. However, alpha-sarcin was able to promote lipid mixing in heterogeneous systems composed of egg PG+DMPG or brain PS+DMPS vesicles. The dilution of the fluorescence probes was faster when these were incorporated into the bilayers made of synthetic phospholipids than were present in those made of natural phospholipids. The bilayer destabilization produced by the

  10. Intercomparison of model simulations of mixed-phase clouds observed during the ARM Mixed-Phase Arctic Cloud Experiment. I: Single layer cloud

    SciTech Connect

    Klein, Stephen A.; McCoy, Renata; Morrison, H.; Ackerman, Andrew; Avramov, Alexander; DeBoer, GIJS; Chen, Mingxuan; Cole, Jason N.; DelGenio, Anthony D.; Falk, Michael; Foster, Mike; Fridlind, Ann; Golaz, Jean-Christophe; Hashino, Tempei; Harrington, Jerry Y.; Hoose, Corinna; Khairoutdinov, Marat; Larson, Vince; Liu, Xiaohong; Luo, Yali; McFarquhar, Greg; Menon, Surabi; Neggers, Roel; Park, Sungsu; Poellot, M. R.; Schmidt, Jerome M.; Sednev, Igor; Shipway, Ben; Shupe, Matthew D.; Spangenberg, D.; Sud, Yogesh; Turner, David D.; Veron, Dana; Von Salzen, Knut; Walker, Gregory K.; Wang, Zhien; Wolf, Audrey; Xie, Shaocheng; Xu, Kuan-Man; Yang, Fanglin; Zhang, G.

    2009-05-21

    Results are presented from an intercomparison of single-column and cloud-resolving model simulations of a cold-air outbreak mixed-phase stratocumulus cloud observed during the ARM Mixed-Phase Arctic Cloud Experiment. The observed cloud occurred in a well-mixed boundary layer with a cloud top temperature of –15°C. While the cloud was water dominated, ice precipitation appears to have lowered the liquid water path to about 2/3 of the adiabatic value. The simulations, which were performed by seventeen single column and nine cloud-resolving models, generally underestimate the liquid water path with the median single-column and cloud-resolving model liquid water path a factor of 3 smaller than observed. While the simulated ice water path is in general agreement with the observed values, results from a sensitivity study in which models removed ice microphysics indicate that in many models the interaction between liquid and ice phase microphysics is responsible for the strong model underestimate of liquid water path. Although no single factor is found to lead to a good simulation, these results emphasize the need for care in the model treatment of mixed-phase microphysics. This case study, which has been well observed from both aircraft and ground-based remote sensors, could be benchmark for model simulations of mixed-phase clouds.

  11. Evolution of a Canada Basin ice-ocean boundary layer and mixed layer across a developing thermodynamically forced marginal ice zone

    NASA Astrophysics Data System (ADS)

    Gallaher, Shawn G.; Stanton, Timothy P.; Shaw, William J.; Cole, Sylvia T.; Toole, John M.; Wilkinson, Jeremy P.; Maksym, Ted; Hwang, Byongjun

    2016-08-01

    A comprehensive set of autonomous, ice-ocean measurements were collected across the Canada Basin to study the summer evolution of the ice-ocean boundary layer (IOBL) and ocean mixed layer (OML). Evaluation of local heat and freshwater balances and associated turbulent forcing reveals that melt ponds (MPs) strongly influence the summer IOBL-OML evolution. Areal expansion of MPs in mid-June start the upper ocean evolution resulting in significant increases to ocean absorbed radiative flux (19 W m-2 in this study). Buoyancy provided by MP drainage shoals and freshens the IOBL resulting in a 39 MJ m-2 increase in heat storage in just 19 days (52% of the summer total). Following MP drainage, a near-surface fresh layer deepens through shear-forced mixing to form the summer mixed layer (sML). In late summer, basal melt increases due to stronger turbulent mixing in the thin sML and the expansion of open water areas due in part to wind-forced divergence of the sea ice. Thermal heterogeneities in the marginal ice zone (MIZ) upper ocean led to large ocean-to-ice heat fluxes (100-200 W m-2) and enhanced basal ice melt (3-6 cm d-1), well away from the ice edge. Calculation of the upper ocean heat budget shows that local radiative heat input accounted for at least 89% of the observed latent heat losses and heat storage (partitioned 0.77/0.23). These results suggest that the extensive area of deteriorating sea ice observed away from the ice edge during the 2014 season, termed the "thermodynamically forced MIZ," was driven primarily by local shortwave radiative forcing.

  12. Super-resolved thickness maps of thin film phantoms and in vivo visualization of tear film lipid layer using OCT

    PubMed Central

    dos Santos, Valentin Aranha; Schmetterer, Leopold; Triggs, Graham J.; Leitgeb, Rainer A.; Gröschl, Martin; Messner, Alina; Schmidl, Doreen; Garhofer, Gerhard; Aschinger, Gerold; Werkmeister, René M.

    2016-01-01

    In optical coherence tomography (OCT), the axial resolution is directly linked to the coherence length of the employed light source. It is currently unclear if OCT allows measuring thicknesses below its axial resolution value. To investigate spectral-domain OCT imaging in the super-resolution regime, we derived a signal model and compared it with the experiment. Several island thin film samples of known refractive indices and thicknesses in the range 46 – 163 nm were fabricated and imaged. Reference thickness measurements were performed using a commercial atomic force microscope. In vivo measurements of the tear film were performed in 4 healthy subjects. Our results show that quantitative super-resolved thickness measurement can be performed using OCT. In addition, we report repeatable tear film lipid layer visualization. Our results provide a novel interpretation of the OCT axial resolution limit and open a perspective to deeper extraction of the information hidden in the coherence volume. PMID:27446696

  13. Virosome engineering of colloidal particles and surfaces: bioinspired fusion to supported lipid layers

    NASA Astrophysics Data System (ADS)

    Fleddermann, J.; Diamanti, E.; Azinas, S.; Košutić, M.; Dähne, L.; Estrela-Lopis, I.; Amacker, M.; Donath, E.; Moya, S. E.

    2016-04-01

    Immunostimulating reconstituted influenza virosomes (IRIVs) are liposomes with functional viral envelope glycoproteins: influenza virus hemagglutinin (HA) and neuraminidase intercalated in the phospholipid bilayer. Here we address the fusion of IRIVs to artificial supported lipid membranes assembled on polyelectrolyte multilayers on both colloidal particles and planar substrates. The R18 assay is used to prove the IRIV fusion in dependence of pH, temperature and HA concentration. IRIVs display a pH-dependent fusion mechanism, fusing at low pH in analogy to the influenza virus. The pH dependence is confirmed by the Quartz Crystal Microbalance technique. Atomic Force Microscopy imaging shows that at low pH virosomes are integrated in the supported membrane displaying flattened features and a reduced vertical thickness. Virosome fusion offers a new strategy for transferring biological functions on artificial supported membranes with potential applications in targeted delivery and sensing.Immunostimulating reconstituted influenza virosomes (IRIVs) are liposomes with functional viral envelope glycoproteins: influenza virus hemagglutinin (HA) and neuraminidase intercalated in the phospholipid bilayer. Here we address the fusion of IRIVs to artificial supported lipid membranes assembled on polyelectrolyte multilayers on both colloidal particles and planar substrates. The R18 assay is used to prove the IRIV fusion in dependence of pH, temperature and HA concentration. IRIVs display a pH-dependent fusion mechanism, fusing at low pH in analogy to the influenza virus. The pH dependence is confirmed by the Quartz Crystal Microbalance technique. Atomic Force Microscopy imaging shows that at low pH virosomes are integrated in the supported membrane displaying flattened features and a reduced vertical thickness. Virosome fusion offers a new strategy for transferring biological functions on artificial supported membranes with potential applications in targeted delivery and sensing

  14. Combined urea-thin layer chromatography and silver nitrate-thin layer chromatography for micro separation and determination of hard-to-detect branched chain fatty acids in natural lipids.

    PubMed

    Yan, Yuanyuan; Wang, Xingguo; Liu, Yijun; Xiang, Jingying; Wang, Xiaosan; Zhang, Huijun; Yao, Yunping; Liu, Ruijie; Zou, Xiaoqiang; Huang, Jianhua; Jin, Qingzhe

    2015-12-18

    A simple, fast and efficient procedure was developed for micro separation and enrichment of branched chain fatty acids (BCFA) from natural products using successive thin layer chromatography (TLC) technique coupling novel urea-TLC with AgNO3-TLC, which rely on the formation of urea adduction and AgNO3 bonding in methanol. These natural lipids contain a significant amount of straight chain fatty acids (FA). Fresh and fast urea-TLC and AgNO3-TLC plate making techniques were developed with more even coating and less coating material contamination before being utilized for separation. Goat milk fat was used as a model. Various experimental parameters that affect urea-TLC and AgNO3-TLC separation of BCFA were investigated and optimized, including coating of urea, concentration of original oil sample, mobile phase and sample application format. High efficiency of removal of straight chain FA was achieved with a low amount of sample in an easy and fast way. A total BCFA mix with much higher purity than previous studies was successfully achieved. The developed method has also been applied for the concentration and analysis of BCFA in cow milk fat and Anchovy oil.

  15. Investigations of boundary layer structure, cloud characteristics and vertical mixing of aerosols at Barbados with large eddy simulations

    NASA Astrophysics Data System (ADS)

    Jähn, M.; Muñoz-Esparza, D.; Chouza, F.; Reitebuch, O.

    2015-08-01

    Large eddy simulations (LES) are performed for the area of the Caribbean island Barbados to investigate island effects on boundary layer modification, cloud generation and vertical mixing of aerosols. Due to the presence of a topographically structured island surface in the domain center, the model setup has to be designed with open lateral boundaries. In order to generate inflow turbulence consistent with the upstream marine boundary layer forcing, we use the cell perturbation method based on finite amplitude perturbations. In this work, this method is for the first time tested and validated for moist boundary layer simulations with open lateral boundary conditions. Observational data obtained from the SALTRACE field campaign is used for both model initialization and a comparison with Doppler wind lidar data. Several numerical sensitivity tests are carried out to demonstrate the problems related to "gray zone modeling" when using coarser spatial grid spacings beyond the inertial subrange of three-dimensional turbulence or when the turbulent marine boundary layer flow is replaced by laminar winds. Especially cloud properties in the downwind area west of Barbados are markedly affected in these kinds of simulations. Results of an additional simulation with a strong trade-wind inversion reveal its effect on cloud layer depth and location. Saharan dust layers that reach Barbados via long-range transport over the North Atlantic are included as passive tracers in the model. Effects of layer thinning, subsidence and turbulent downward transport near the layer bottom at z ~ 1800 m become apparent. The exact position of these layers and strength of downward mixing is found to be mainly controlled atmospheric stability (especially inversion strength) and wind shear. Comparisons of LES model output with wind lidar data show similarities in the formation of the daytime convective plume and the mean vertical wind structure.

  16. Mixing-layer height retrieval with ceilometer and Doppler lidar: from case studies to long-term assessment

    NASA Astrophysics Data System (ADS)

    Schween, J. H.; Hirsikko, A.; Löhnert, U.; Crewell, S.

    2014-11-01

    Aerosol signatures observed by ceilometers are frequently used to derive mixing-layer height (MLH) which is an essential variable for air quality modelling. However, Doppler wind lidar measurements of vertical velocity can provide a more direct estimation of MLH via simple thresholding. A case study reveals difficulties in the aerosol-based MLH retrieval during transition times when the mixing layer builds up in the morning and when turbulence decays in the afternoon. The difficulties can be explained by the fact that the aerosol distribution is related to the history of the mixing process and aerosol characteristics are modified by humidification. The results of the case study are generalized by evaluating one year of joint measurements by a Vaisala CT25K and a HALO Photonics Streamline wind lidar. On average the aerosol-based retrieval gives higher MLH than the wind lidar with an overestimation of MLH by about 300 m (600 m) in the morning (late afternoon). Also, the daily aerosol-based maximum MLH is larger and occurs later during the day and the average morning growth rates are smaller than those derived from the vertical wind. In fair weather conditions classified by less than 4 octa cloud cover the mean diurnal cycle of cloud base height corresponds well to the mixing-layer height showing potential for a simplified MLH estimation.

  17. Mixing layer height retrieval with ceilometer and Doppler lidar: from case studies to long-term assessment

    NASA Astrophysics Data System (ADS)

    Schween, J. H.; Hirsikko, A.; Löhnert, U.; Crewell, S.

    2014-04-01

    Aerosol signatures observed by ceilometers are frequently used to derive mixing layer height (MLH) which is an essential variable for air quality modeling. Doppler wind lidar measurements of vertical velocity can provide a more direct estimation of MLH via simple thresholding. A case study reveals difficulties in the aerosol based MLH retrieval during transition times when the mixing layer is built up in the morning and when turbulence decays in the afternoon. The differences can be explained by the fact that the aerosol distribution is related to the history of the mixing process and aerosol characteristics are modified by humidification. The results of the case study are generalized by evaluating one year of joint measurements by a Vaisala CT25K and a HALO Photonics Streamline wind lidar. On average the aerosol based retrieval gives higher MLH than the wind lidar with an overestimation of MLH by about 300 m (600 m) in the morning (late afternoon). When turbulence is fully developed around noon best agreement is found between both methods. This diurnal behavior is even more pronounced in fair weather conditions classified by less than 4 octa. In these conditions the mean diurnal cycle of cloud base height corresponds well to the mixing layer height showing potential for a simplified MLH estimation.

  18. Whole wheat versus mixed layer diet as supplementary feed to layers foraging a sequence of different forage crops.

    PubMed

    Horsted, K; Hermansen, J E

    2007-05-01

    In many cases health and welfare problems are observed in organic egg production systems, as are high environmental risks related to nutrient leaching. These disadvantages might be reduced if the layers are allowed to utilise their ability to forage to a higher degree thereby reducing the import of nutrients into the system and stimulating the hens to perform a natural behaviour. However, very little is known about the ability of modern high-producing layers to take advantage of foraging to cover their nutritional needs, and the aim of the present work was to clarify this subject. Six flocks, each of 26 hens and one cock, were moved regularly in a rotation between different forage crops for a period of 130 days. Half of the flocks were fed typical layer feed for organic layers and half were fed whole wheat. The forage crops consisted of grass/clover, pea/vetch/oats, lupin and quinoa. At the beginning of the experiment, wheat-fed hens had a lower intake of supplementary feed (wheat) and a lower laying rate, egg weight and body weight. However, after a period of 6 to 7 weeks, the intake of wheat increased to approximately 100 g per hen per day and the laying rate increased to the same level as for the hens fed layer feed. For both groups of hens egg weight and body weight increased during the remaining part of the experiment. Crop analysis revealed different food preferences for hens fed layer feed and wheat-fed hens. Wheat-fed hens ate less of the cultivated seeds, whereas the amounts of plant material, oyster shells, insoluble grit stone and soil were larger in the crops from wheat-fed hens. Floor eggs were significantly more frequent in the hens fed layer feed, whereas wheat-fed hens only rarely laid floor eggs. Irrespective of treatment, hens were found to have excellent health and welfare. We conclude that nutrient-restricted, high-producing organic layers are capable of finding and utilising considerable amounts of different feed items from a cultivated

  19. Mixed Layer Sub-Mesoscale Parameterization - Part 1: Derivation and Assessment

    NASA Technical Reports Server (NTRS)

    Canuto, V. M.; Dubovikov, M. S.

    2010-01-01

    Several studies have shown that sub-mesoscales (SM 1km horizontal scale) play an important role in mixed layer dynamics. In particular, high resolution simulations have shown that in the case of strong down-front wind, the re-stratification induced by the SM is of the same order of the de-stratification induced by small scale turbulence, as well as of that induced by the Ekman velocity. These studies have further concluded that it has become necessary to include SM in ocean global circulation models (OGCMs), especially those used in climate studies. The goal of our work is to derive and assess an analytic parameterization of the vertical tracer flux under baroclinic instabilities and wind of arbitrary directions and strength. To achieve this goal, we have divided the problem into two parts: first, in this work we derive and assess a parameterization of the SM vertical flux of an arbitrary tracer for ocean codes that resolve mesoscales, M, but not sub-mesoscales, SM. In Part 2, presented elsewhere, we have used the results of this work to derive a parameterization of SM fluxes for ocean codes that do not resolve either M or SM. To carry out the first part of our work, we solve the SM dynamic equations including the non-linear terms for which we employ a closure developed and assessed in previous work. We present a detailed analysis for down-front and up-front winds with the following results: (a) down-front wind (blowing in the direction of the surface geostrophic velocity) is the most favorable condition for generating vigorous SM eddies; the de-stratifying effect of the mean flow and re-stratifying effect of SM almost cancel each other out,

  20. Investigating CloudSat Retrievals Sensitivity to Forward Iterative Algorithm Parameters in the Mixed Cloud Layers

    NASA Astrophysics Data System (ADS)

    Qiu, Yujun; Lu, Chunsong

    2016-09-01

    When millimeter-wave cloud radar data are used for the forward iterative retrieval of the liquid water content (LWC) and effective radius of cloud droplets ( R e) in a cloud layer, the prior values and tolerance ranges of the cloud droplet number density ( N t), scale parameter ( R g) and spectral width parameter ( W g) in the iterative algorithm are the main factors that affect the retrieval accuracy. In this study, we used data from stratus and convective clouds that were simultaneously observed by CloudSat and aircraft to conduct a sensitivity analysis of N t, R g, and W g for the retrieval accuracies of LWC and R e in both stratus and convective clouds. N t is the least sensitive parameter for accurately retrieving stratus LWC and R e in both stratus and convective clouds, except for retrieving the convective cloud LWC. Opposite to N t, R g is the most sensitive parameter for both LWC and R e retrievals. As to the effects of parameter tolerance ranges on the retrievals of LWC and R e, the least important parameter is the N t tolerance range; the most important one is the W g tolerance range for retrieving convective cloud LWC and R e, the R g is the important parameter for retrieving stratus LWC and R e. To obtain accurate retrieved values for clouds in a specific region, it is important to use typical values of the sensitive parameters, which could be calculated from in situ observations of cloud droplet size distributions. In addition, the sensitivities of the LWC and R e to the three parameters are stronger in convective clouds than in stratus clouds. This may be related to the melting and merging of solid cloud droplets during the convective mixing process in the convective clouds.

  1. Anthropogenic Aerosol Effects on Sea Surface Temperatures: Mixed-Layer Ocean Experiments with Explicit Aerosol Representation

    NASA Astrophysics Data System (ADS)

    Dallafior, Tanja; Folini, Doris; Wild, Martin; Knutti, Reto

    2014-05-01

    Anthropogenic aerosols affect the Earth's radiative balance both through direct and indirect effects. These effects can lead to a reduction of the incoming solar radiation at the surface, i.e. dimming, which may lead to a change in sea surface temperatures (SST) or SST pattern. This, in turn, may affect precipitation patterns. The goal of the present work is to achieve an estimate of the equilibrium SST changes under anthropogenic aerosol forcing since industrialisation. We show preliminary results from mixed-layer ocean (MLO) experiments with explicit aerosol representation performed with ECHAM6-HAM. The (fixed) MLO heat flux into the deep ocean was derived from atmosphere only runs with fixed climatological SSTs (1961-1990 average) and present day (year 2000) aerosols and GHG burdens. Some experiments we repeated with an alternative MLO deep ocean heat flux (based on pre-industrial conditions) to test the robustness of our results with regard to this boundary condition. The maximum surface temperature responses towards anthropogenic aerosol and GHG forcing (separately and combined) were derived on a global and regional scale. The same set of experiments was performed with aerosol and GHG forcings representative of different decades over the past one and a half centuries. This allows to assess how SST patterns at equilibrium changed with changing aerosol (and GHG) forcing. Correlating SST responses with the change in downward clear-sky and all-sky shortwave radiation provides a first estimate of the response to anthropogenic aerosols. Our results show a clear contrast in hemispheric surface temperature response, as expected from the inter-hemispheric asymmetry of aerosol forcing The presented work is part of a project aiming at quantifying the effect of anthropogenic aerosol forcing on SSTs and the consequences for global precipitation patterns. Results from this study will serve as a starting point for further experiments involving a dynamic ocean model, which

  2. Mixed-layer ocean responses to anthropogenic aerosol dimming from 1870 to 2000

    NASA Astrophysics Data System (ADS)

    Dallafior, Tanja; Folini, Doris; Knutti, Reto; Wild, Martin

    2016-04-01

    It is still debated, to what extent anthropogenic aerosol-induced changes in surface solar radiation (SSR) since industrialization affected surface temperatures (tsurf). We use mixed-layer ocean (MLO) experiments with the general circulation model ECHAM6.1 and explicit aerosols (HAM2.2) to identify regions where this effect is discernible. For each decade from 1870 to 2000 we derive three equilibria: anthropogenic aerosol emissions and greenhouse gas concentrations at the respective decade's levels (ALL), either aerosols or greenhouse gases fixed at year 1850 levels (GHG and AERO). We duplicated parts of the experiments with different prescribed divergence of ocean heat transport (Q_ALL, Q_AERO, Q_GHG). Comparing year 2000 with year 1870 equilibria, we find global average cooling of -1.4K for AERO, and warming of 1.4K for GHG. ALL and Q_ALL warm by 0.6K and 0.4K, respectively. The way divergence of ocean heat transport is prescribed thus matters. Pattern correlations of year 2000 tsurf responses in ALL with the sum of AERO and GHG are higher (0.88) than with Q_ALL (0.71) confirming additivity of global patterns, but not of global means. The imprint of anthropogenic aerosols on tsurf response patterns in ALL is distinct, thus potentially detectable. Over the decades, ocean fractions affected by either changing aerosol optical depth or all-sky SSR vary in concert, supporting linkage between anthropogenic aerosols and all-sky SSR. SSR changes and tsurf responses are marginally collocated. Oceanic regions with strongest tsurf response to aerosol-induced SSR changes are the northern mid-latitudes and North Pacific with tsurf sensitivities up to -0.7K per Wm-2 SSR change. Results presented have been published under the same title in the Journal of Geophysical Research, Volume 121, DOI 10.1002/2015JD024070.

  3. A numerical study of ignition in the supersonic hydrogen/air laminar mixing layer

    SciTech Connect

    Nishioka, M.; Law, C.K.

    1997-01-01

    The ignition evolution in the supersonic nonpremixed hydrogen/air laminar mixing layer, consisting of a relatively hot, fast air stream next to a cold, slower hydrogen stream, was computationally simulated using detailed transport and chemical reaction mechanisms and compared with results from asymptotic analysis with reduced mechanisms. The study emphasizes identifying the controlling chemical mechanisms in effecting ignition, on the relative importance of external versus viscous heating as the dominant ignition source, on the roles of thermal versus kinetic-induced ignition in which heat release and hence nonlinear thermal feedback are not needed in initiating system runaway, and on the consequences of imposing the conventional constant property assumptions in analytical studies. Results show that the state of the hydrogen/oxygen second explosion limit has the dominant influence in the system response in that, for all practical purposes, ignition is not possible when the air-stream temperature is lower than the crossover temperature, even allowing for viscous heating. On the other hand, when the air-stream temperature is higher than the crossover temperature, the predicted ignition distance indicates that ignition is feasible within practical supersonic combustion engines. Furthermore, for the latter situations, the ignition event is initiated by radical proliferation and hence runaway instead of thermal runaway. Finally, it is shown that, while the present computed results qualitatively agree well with those from the asymptotic analysis with reduced mechanisms, the analytically predicted ignition distances are much shorter than the computed values because the analysis has overemphasized the viscous effect through the constant Chapman-Rubesin parameter {rho}{mu} and unity Prandtl number assumptions.

  4. Dimming over the oceans: mixed layer ocean experiments from 1870 to 2000

    NASA Astrophysics Data System (ADS)

    Dallafior, Tanja; Folini, Doris; Knutti, Reto; Wild, Martin

    2015-04-01

    Sea surface temperature (SSTs) changes are known to affect precipitation patterns. However, it is still subject to debate, whether anthropogenic aerosols are capable of affecting SSTs, which could feed back on precipitation patterns. To influence SSTs, anthropogenic aerosols need to reduce incoming surface solar radiation (SSR) through direct or indirect effects for a sufficiently long time span over a sufficiently large area. To quantify the maximum potential SST response to anthropogenic aerosol dimming over the past decades, we performed equilibrium experiments with the general circulation model, ECHAM and explicit aerosol representation (ECHAM6-HAM2.2) and a mixed-layer ocean (MLO). Every ten years, we let the system equilibrate to the conditions (aerosol and greenhouse gas burdens, GHG) of that specific year. Each experiment is conducted over 50 years, of which the first 10 years are discarded. We generated three sets of decadal equilibria covering the entire 20th century and part of the 19th century (from 1870) : One, where both GHG and anthropogenic aerosols are set to the respective decade, one where GHG levels are held constant at 1850s levels, and one where anthropogenic aerosols are held constant at 1850s levels. Deep ocean heat fluxes are prescribed based on the surface energy flux climatology derived from an atmosphere-only integration with pre-industrial (year 1850) conditions for aerosols and GHG and climatological SSTs (average of Hadley Center SSTs, observation based, over the years 1871-1900). Results of these findings will be discussed, especially the SST and precipitation responses seen in the different equilibria. Moreover, results will be put in context with transient experiments with prescribed SSTs. The presented results are part of a project aiming at quantifying the effect of anthropogenic aerosols on SSTs. The results will serve as a basis for future experiments using a dynamic ocean model to quantify the transient response of the ocean

  5. Mixed-layer ocean responses to anthropogenic aerosol dimming from 1870 to 2000

    NASA Astrophysics Data System (ADS)

    Dallafior, T. N.; Folini, D.; Knutti, R.; Wild, M.

    2016-01-01

    It is debated to what extent surface solar radiation (SSR) changes through varying anthropogenic aerosol emissions since industrialization affected surface temperatures (tsurf). We use mixed-layer ocean experiments with the general circulation model ECHAM6.1 and explicit aerosols (HAM2.2) to identify regions where this effect is discernible. For each decade from 1870 to 2000 we derive three equilibria: anthropogenic aerosol emissions and greenhouse gas concentrations at the respective decade's levels (ALL), either aerosols or greenhouse gases fixed at year 1850 levels (GHG and AERO). We duplicated parts of the experiments with different prescribed divergence of ocean heat transport (Q_ALL, Q_AERO, and Q_GHG). Comparing year 2000 with year 1870 equilibria, we find global average cooling of -1.4 K for AERO and warming of 1.4 K for GHG. ALL and Q_ALL warm by 0.6 K and 0.4 K, respectively. The way divergence of ocean heat transport is prescribed thus matters. Pattern correlations of year 2000 tsurf responses in ALL with the sum of AERO and GHG are higher (0.88) than with Q_ALL (0.71) confirming additivity of global patterns, but not of global means. The imprint of anthropogenic aerosols on tsurf response patterns in ALL is distinct, thus potentially detectable. Over the decades, ocean fractions affected by either changing aerosol optical depth or all-sky SSR vary in concert, supporting linkage between anthropogenic aerosols and all-sky SSR. SSR changes and tsurf responses are marginally collocated. Oceanic regions with strongest tsurf response to aerosol-induced SSR changes are the northern midlatitudes and North Pacific with tsurf sensitivities up to -0.7 K W m-2 SSR change.

  6. Data Assimilation In A Marine Ecosystem Coupled To A Mixed Layer Model of The Upper Ocean.

    NASA Astrophysics Data System (ADS)

    Magri, S.; Brasseur, P.; Lacroix, G.

    Data assimilation have been conducted in a one-dimensional, coupled physical ecosys- tem model of the upper ocean to characterize the observability properties of in situ and satellite observing systems. The assimilation method is based on the Singular Evolu- tive Extended Kalman (SEEK) filter, in which the error sub-space is decomposed into multivariate orthogonal functions of the system's variability. The coupled model simulates the primary production in a coastal zone of the Ligurian Sea, where oligotrophic conditions prevail. The ecosystem dynamics is represented by 12 interacting compartments expressed in nitrogen units. The coupling with a hydrodynamic model determines the physical constraints asso- ciated to the development of a seasonal mixed layer. The stratification of the water column, according to the computation of the vertical turbulent diffusivities, is a key parameter of the evolution of the marine ecosystem. The coupled system has been developed and validated on the basis of field data col- lected during the FRONTAL campains, between 1984 and 1988. As a first approach, twin experiments are performed to check the algorithmic imple- mentation of the SEEK filter, and to verify the statistical consistence of the assimila- tion scheme in non-linear regimes. Vertical temperature and salinity profiles have been assimilated to evaluate the impact of a better representation of the water column strat- ification on the primary production. Then, nitrate and chlorophyll-a profiles have been assimilated to try to control the ecosystem in spite of an imperfect physical model. Finally, physical and biological profiles of in situ data collected during the FRONTAL campains, will be used to reconstruct the seasonal evolution of the ecosystem.

  7. A case study of mixed-layer ozone diurnal variation by ozone DIAL and Large-eddy simulation coupled a chemical module

    NASA Astrophysics Data System (ADS)

    Huang, G.; Newchurch, M.; Kuang, S.; Wang, L.; Ouwersloot, H.

    2014-12-01

    We investigate the diurnal variation of mixed-layer ozone in Huntsville AL, Southeast United States on September, 6, 2013 during the SEAC4RS field campaign. The dynamics and chemistry of the mixed layer are studied with a Large-Eddy Simulation model coupled with a chemical module and Ozone DIAL observations. In this study, we will present calculations of ozone entrainment fluxes using continuous observation by co-located ozone DIAL and Compact Wind Aerosol Lidar (CWAL) at the campus of University of Alabama in Huntsville (UAH). As a part of Tropospheric Ozone Lidar NETwork (TOLNET), UAH ozone DIAL can provide continuous ozone observation in the altitude range from 125 m AGL to 12 km, with 10-min temporal resolution and 150 - 550 m vertical resolution. We also perform an ozone budget study using the Dutch Atmospheric Large-Eddy Simulation (DALES), reasonable approximations of dry deposition, in conjunction with ozone entrainment observations. In this case study, the enhancement of ozone in the mixed layer results from the local emissions of NOx and VOCs. The NOx and VOCs emitted at surface entered into mixed layer by atmospheric turbulence and produced ozone within the whole mixed layer. Simultaneously, non-turbulent air in the residual layer, which is at top of the morning mixed layer, participates in convective mixing through entrainment processes. The clean air in the residual layer decreases the ozone enhancement rate in the mixed layer. After the mixed layer reaches its stable height at 1700m, the large-scale subsidence not only decreases PBL growth but also enhances the entrainment process. The PBL NOx and VOCs mix into the free troposphere through detrainment before producing ozone by photochemical reaction. We have following conclusions from this case study: 1) the relationship between boundary layer height and PBL ozone is complicated. Higher PBL height does not always mean lower PBL ozone. 2) The LES calculation results illuminate the interaction between

  8. Upper mixed layer temperature anomalies at the North Atlantic storm-track zone

    NASA Astrophysics Data System (ADS)

    Moshonkin, S. N.; Diansky, N. A.

    1995-10-01

    Synoptic sea surface temperature anomalies (SSTAs) were determined as a result of separation of time scales smaller than 183 days. The SSTAs were investigated using daily data of ocean weather station C (52.75°N; 35.5°W) from 1 January 1976 to 31 December 1980 (1827 days). There were 47 positive and 50 negative significant SSTAs (lifetime longer than 3 days, absolute value greater than 0.10 °C) with four main intervals of the lifetime repetitions: 1. 4-7 days (45% of all cases), 2. 9-13 days (20-25%), 3. 14-18 days (10-15%), and 4. 21-30 days (10-15%) and with a magnitude 1.5-2.0 °C. An upper layer balance model based on equations for temperature, salinity, mechanical energy (with advanced parametrization), state (density), and drift currents was used to simulate SSTA. The original method of modelling taking into account the mean observed temperature profiles proved to be very stable. The model SSTAs are in a good agreement with the observed amplitudes and phases of synoptic SSTAs during all 5 years. Surface heat flux anomalies are the main source of SSTAs. The influence of anomalous drift heat advection is about 30-50% of the SSTA, and the influence of salinity anomalies is about 10-25% and less. The influence of a large-scale ocean front was isolated only once in February-April 1978 during all 5 years. Synoptic SSTAs develop just in the upper half of the homogeneous layer at each winter. We suggest that there are two main causes of such active sublayer formation: 1. surface heat flux in the warm sectors of cyclones and 2. predominant heat transport by ocean currents from the south. All frequency functions of the ocean temperature synoptic response to heat and momentum surface fluxes are of integral character (red noise), though there is strong resonance with 20-days period of wind-driven horizontal heat advection with mixed layer temperature; there are some other peculiarities on the time scales from 5.5 to 13 days. Observed and modelled frequency functions

  9. The Effect of Particle Size on the Deposition of Solid Lipid Nanoparticles in Different Skin Layers: A Histological Study

    PubMed Central

    Mardhiah Adib, Zahra; Ghanbarzadeh, Saeed; Kouhsoltani, Maryam; Yari Khosroshahi, Ahmad; Hamishehkar, Hamed

    2016-01-01

    Purpose: In the present study the effect of particle size, as a substantial parameters in skin penetration, on the deposition depth and rate of SLNs in different layers of skin was explored. Methods: SLNs in different particle size ranges (80, 333 and 971 nm) made of Precirol as solid lipid were prepared using hot melt homogenization technique and pigmented by Rhodamine B to be able to be tracked in the skin under inspection of fluorescent microscopy. After 0.5 h, 3 h, 6 h and 24 h of SLNs administration on rat skin, animals were sacrificed and exercised skins were sliced by a freeze microtome. SLNs were monitored in the skin structure under fluorescence microscope. Results: The size of SLNs played a crucial role in the penetration to deep skin layers. The sub100 nm size range of SLNs showed the most promising skin penetration rate and depth mainly via hair follicles. Conclusion: The results of the present study indicated that the selection of an appropriate size of particles may be a valuable factor impacting the therapeutic outcomes of dermal drug administration. PMID:27123415

  10. Results from long-term detection of mixing layer height: ceilometer and comparison with Radio-Acoustic Sounding System

    NASA Astrophysics Data System (ADS)

    Schäfer, Klaus; Emeis, Stefan; Jahn, Carsten; Tuma, Michael; Münkel, Christoph; Suppan, Peter

    2012-11-01

    The mixing layer height (MLH) is an important factor which influences exchange processes of ground level emissions. The continuous knowledge of MLH is supporting the understanding of processes directing air quality. If the MLH is located near to the ground, which occurs mainly during winter and night-time, air pollution can be high due to a strongly limited air mass dilution. Since 2006 different methods for long-term continuous remote sensing of mixing layer height (MLH) are operated in Augsburg. The Vaisala ceilometers LD40 and CL31 are used which are eye-safe commercial mini-lidar systems. The ceilometer measurements provide information about the range-dependent aerosol concentration; gradient minima within this profile mark the borders of mixed layers. Special software for these ceilometers provides routine retrievals of lower atmosphere layering from vertical profiles of laser backscatter data. The radiosonde data from the station Oberschleissheim near Munich (about 50 km away from Augsburg city) are also used for MLH determination. The profile behavior of relative humidity (strong decrease) and virtual potential temperature (inversion) of the radiosonde agree mostly well with the MLH indication from ceilometer laser backscatter density gradients. A RASS (Radio-Acoustic Sounding System) from Metek is applied which detects the height of a turbulent layer characterized by high acoustic backscatter intensities due to thermal fluctuations and a high variance of the vertical velocity component as well as the vertical temperature profile from the detection of acoustic signal propagation and thus temperature inversions which mark atmospheric layers. These data of RASS measurements are the input for a software-based determination of MLH. A comparison of the results of the remote sensing methods during simultaneous measurements was performed. The information content of the different remote sensing instruments for MLH in dependence from different weather classes was

  11. Improved performances of organic light-emitting diodes with mixed layer and metal oxide as anode buffer

    NASA Astrophysics Data System (ADS)

    Xue, Qin; Liu, Shouyin; Zhang, Shiming; Chen, Ping; Zhao, Yi; Liu, Shiyong

    2013-01-01

    We fabricated organic light-emitting devices (OLEDs) employing 2-methyl-9,10-di(2-naphthyl)-anthracene (MADN) as hole-transport material (HTM) instead of commonly used N,N'-bis-(1-naphthyl)-N,N'-diphenyl,1,1'-biphenyl-4,4'-diamine (NPB). After inserting a 0.9 nm thick molybdenum oxide (MoOx) layer at the indium tin oxide (ITO)/MADN interface and a 5 nm thick mixed layer at the organic/organic heterojunction interface, the power conversion efficiency of the device can be increased by 4-fold.

  12. The prediction of sea-surface temperature variations by means of an advective mixed-layer ocean model

    NASA Technical Reports Server (NTRS)

    Atlas, R. M.

    1976-01-01

    An advective mixed layer ocean model was developed by eliminating the assumption of horizontal homogeneity in an already existing mixed layer model, and then superimposing a mean and anomalous wind driven current field. This model is based on the principle of conservation of heat and mechanical energy and utilizes a box grid for the advective part of the calculation. Three phases of experiments were conducted: evaluation of the model's ability to account for climatological sea surface temperature (SST) variations in the cooling and heating seasons, sensitivity tests in which the effect of hypothetical anomalous winds was evaluated, and a thirty-day synoptic calculation using the model. For the case studied, the accuracy of the predictions was improved by the inclusion of advection, although nonadvective effects appear to have dominated.

  13. A Priori Analysis of Subgrid-Scale Models for Large Eddy Simulations of Supercritical Binary-Species Mixing Layers

    NASA Technical Reports Server (NTRS)

    Okong'o, Nora; Bellan, Josette

    2005-01-01

    Models for large eddy simulation (LES) are assessed on a database obtained from direct numerical simulations (DNS) of supercritical binary-species temporal mixing layers. The analysis is performed at the DNS transitional states for heptane/nitrogen, oxygen/hydrogen and oxygen/helium mixing layers. The incorporation of simplifying assumptions that are validated on the DNS database leads to a set of LES equations that requires only models for the subgrid scale (SGS) fluxes, which arise from filtering the convective terms in the DNS equations. Constant-coefficient versions of three different models for the SGS fluxes are assessed and calibrated. The Smagorinsky SGS-flux model shows poor correlations with the SGS fluxes, while the Gradient and Similarity models have high correlations, as well as good quantitative agreement with the SGS fluxes when the calibrated coefficients are used.

  14. Lidar measurements of the atmospheric entrainment zone and the potential temperature jump across the top of the mixed layer

    NASA Technical Reports Server (NTRS)

    Boers, R.; Eloranta, E. W.

    1986-01-01

    Lidar data of the atmospheric entrainment zone from six days of clear air convection obtained in central Illinois during July 1979 are presented. A new method to measure the potential temperature jump across the entrainment zone based on only one temperature sounding and continuous lidar measurements of the mixed layer height is developed. An almost linear dependence is found between the normalized entrainment rate and the normalized thickness of the entrainment zone.

  15. Intercomparison of model simulations of mixed-phase clouds observed during the ARM Mixed-Phase Arctic Cloud Experiment. Part I: Single layer cloud

    SciTech Connect

    Klein, S A; McCoy, R B; Morrison, H; Ackerman, A; Avramov, A; deBoer, G; Chen, M; Cole, J; DelGenio, A; Golaz, J; Hashino, T; Harrington, J; Hoose, C; Khairoutdinov, M; Larson, V; Liu, X; Luo, Y; McFarquhar, G; Menon, S; Neggers, R; Park, S; Poellot, M; von Salzen, K; Schmidt, J; Sednev, I; Shipway, B; Shupe, M; Spangenberg, D; Sud, Y; Turner, D; Veron, D; Falk, M; Foster, M; Fridlind, A; Walker, G; Wang, Z; Wolf, A; Xie, S; Xu, K; Yang, F; Zhang, G

    2008-02-27

    Results are presented from an intercomparison of single-column and cloud-resolving model simulations of a cold-air outbreak mixed-phase stratocumulus cloud observed during the Atmospheric Radiation Measurement (ARM) program's Mixed-Phase Arctic Cloud Experiment. The observed cloud occurred in a well-mixed boundary layer with a cloud top temperature of -15 C. The observed liquid water path of around 160 g m{sup -2} was about two-thirds of the adiabatic value and much greater than the mass of ice crystal precipitation which when integrated from the surface to cloud top was around 15 g m{sup -2}. The simulations were performed by seventeen single-column models (SCMs) and nine cloud-resolving models (CRMs). While the simulated ice water path is generally consistent with the observed values, the median SCM and CRM liquid water path is a factor of three smaller than observed. Results from a sensitivity study in which models removed ice microphysics indicate that in many models the interaction between liquid and ice-phase microphysics is responsible for the large model underestimate of liquid water path. Despite this general underestimate, the simulated liquid and ice water paths of several models are consistent with the observed values. Furthermore, there is some evidence that models with more sophisticated microphysics simulate liquid and ice water paths that are in better agreement with the observed values, although considerable scatter is also present. Although no single factor guarantees a good simulation, these results emphasize the need for improvement in the model representation of mixed-phase microphysics. This case study, which has been well observed from both aircraft and ground-based remote sensors, could be a benchmark for model simulations of mixed-phase clouds.

  16. Imaging of oil layers, curvature and contact angle in a mixed-wet and a water-wet carbonate rock

    NASA Astrophysics Data System (ADS)

    Singh, Kamaljit; Bijeljic, Branko; Blunt, Martin J.

    2016-03-01

    We have investigated the effect of wettability of carbonate rocks on the morphologies of remaining oil after sequential oil and brine injection in a capillary-dominated flow regime at elevated pressure. The wettability of Ketton limestone was altered in situ using an oil phase doped with fatty acid which produced mixed-wet conditions (the contact angle where oil contacted the solid surface, measured directly from the images, θ=180°, while brine-filled regions remained water-wet), whereas the untreated rock (without doped oil) was weakly water-wet (θ=47 ± 9°). Using X-ray micro-tomography, we show that the brine displaces oil in larger pores during brine injection in the mixed-wet system, leaving oil layers in the pore corners or sandwiched between two brine interfaces. These oil layers, with an average thickness of 47 ± 17 µm, may provide a conductive flow path for slow oil drainage. In contrast, the oil fragments into isolated oil clusters/ganglia during brine injection under water-wet conditions. Although the remaining oil saturation in a water-wet system is about a factor of two larger than that obtained in the mixed-wet rock, the measured brine-oil interfacial area of the disconnected ganglia is a factor of three smaller than that of oil layers.

  17. Self-similarity of a Rayleigh-Taylor mixing layer at low Atwood number with a multimode initial perturbation

    NASA Astrophysics Data System (ADS)

    Morgan, Brandon; Olson, Britton; White, Justin; McFarland, Jacob

    2016-11-01

    High-fidelity large eddy simulation (LES) of a low-Atwood number (A = 0.05) Rayleigh-Taylor mixing layer is performed using the tenth-order compact difference code Miranda. An initial multimode perturbation spectrum is specified in Fourier space as a function of mesh resolution such that a database of results is obtained in which each successive level of increased grid resolution corresponds approximately to one additional doubling of the mixing layer width, or generation. The database is then analyzed to determine approximate requirements for self-similarity, and a new metric is proposed to quantify how far a given simulation is from the limit of self-similarity. It is determined that the present database reaches a high degree of self-similarity after approximately 4.5 generations. Finally, self-similar turbulence profiles from the LES database are compared with one-dimensional simulations using the k- L- a and BHR-2 Reynolds-averaged Navier-Stokes (RANS) models. The k- L- a model, which is calibrated to reproduce a quadratic turbulence kinetic energy profile for a self-similar mixing layer, is found to be in better agreement with the LES than BHR-2 results. This work was preformed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52-07NA27344.

  18. Observation and analysis of emergent coherent structures in a high-energy-density shock-driven planar mixing layer experiment

    NASA Astrophysics Data System (ADS)

    Doss, F. W.; Flippo, K. A.; Merritt, E. C.

    2016-08-01

    Coherent emergent structures have been observed in a high-energy-density supersonic mixing layer experiment. A millimeter-scale shock tube uses lasers to drive Mbar shocks into the tube volume. The shocks are driven into initially solid foam (60 mg /cm3 ) hemicylinders separated by an Al or Ti metal tracer strip; the components are vaporized by the drive. Before the experiment disassembles, the shocks cross at the tube center, creating a very fast (Δ U > 200 km/s) shear-unstable zone. After several nanoseconds, an expanding mixing layer is measured, and after 10+ ns we observe the appearance of streamwise-periodic, spanwise-aligned rollers associated with the primary Kelvin-Helmholtz instability of mixing layers. We additionally image roller pairing and spanwise-periodic streamwise-aligned filaments associated with secondary instabilities. New closures are derived to connect length scales of these structures to estimates of fluctuating velocity data otherwise unobtainable in the high-energy-density environment. This analysis indicates shear-induced specific turbulent energies 103-104 times higher than the nearest conventional experiments. Because of difficulties in continuously driving systems under these conditions and the harshness of the experimental environment limiting the usable diagnostics, clear evidence of these developing structures has never before been observed in this regime.

  19. Physical and chemical properties of the regional mixed layer of Mexico's Megapolis

    NASA Astrophysics Data System (ADS)

    Baumgardner, D.; Grutter, M.; Allan, J.; Ochoa, C.; Rappenglueck, B.; Russell, L. M.; Arnott, P.

    2009-08-01

    The concentration of gases and aerosol particles have been measured at the mountain site of Altzomoni, 4010 m in altitude, located 60 km southeast of Mexico City, 50 km east of Puebla and 70 km northeast of Cuernavaca. The objective of this study was to evaluate the properties of gases and particles in the Regional Mixed Layer (RML) of Mexico's Megapolis. Altzomoni is generally above the RML from late evening until late morning at which time the arrival of the RML is marked by increasing concentrations of CO and aerosol particles that reach their maxima in mid-afternoon. The average diurnal cycles for fourteen days in March, 2006 were evaluated during which time the synoptic scale circulation had three principal patterns: from the east (E), southwest (SW) and west northwest (WNW). The original hypothesis was that air arriving from the direction of Mexico City would have much higher concentrations of anthropogenic gases and particles than air from Puebla or Cuernavaca, due to the relatively large differences in populations. In fact, not only were the average, maximum concentrations of CO and O3 (0.3 and 0.1 ppmv) approximately the same for air originating from the WNW and E, but the average maximum concentrations of Peroxyacyl nitrates (PAN,PPN) and particle organic matter (POM) in air from the E exceeded those in air from the WNW. Comparisons of measurements from the mountain site with those made by aircraft during the same period, using the same type of aerosol mass spectrometer, show that the total masses of POM, NO3-, SO42- and NH4+ were approximately the same from aircraft measurements made over Mexico City and when winds were from the east at the mountain site. In contrast 75% of the total aerosol mass at the mountain site was POM whereas over Mexico City the fraction of POM was less than 60%. The measurements suggest the occasional influence of emissions from the nearby volcano, Popocatepetl, as well as possible incursions of biomass combustion; however, the

  20. Sensitivity of the Arctic Climate to Leads in a Coupled Atmosphere-Mixed Layer Ocean Model.

    NASA Astrophysics Data System (ADS)

    Vavrus, Stephen J.

    1995-02-01

    The thermodynamic sea ice code in a coupled atmosphere-mixed layer ocean GCM has been altered to allow the presence of open water within an ice pack (leads) and a prescribed turbulent oceanic heat flux at the ice bottom. Two experiments with the GCM are then performed: one with leads included and one without. A comparison between the two model runs is presented, in addition to a comparison between observations and the simulation with leads. Selected sea ice and atmospheric variables in the high-latitude Northern Hemisphere are analyzed to assess the sensitivity of these climatic components to the presence of leads and to identify feedback mechanisms that are introduced by leads.The inclusion of leads causes Northern Hemispheric sea ice concentration to decrease in every season, with year-round statistically significant reductions at the highest latitude band (81°N). Using the improved sea ice code, the model's simulation of sea ice concentration in the central Arctic is consistent with observations in every season. Simulated summertime sea ice concentration at 81°N averages 93.8%, which agrees well with observations. There is a pronounced longitudinal variation to the lead fraction in summer, with the smallest values (0.01) neat the Canadian Archipelago and the largest (0.25) north of the East Siberian Sea. Consistent with observations, the model produces wintertime turbulent sensible heat fluxes over leads that are one to two orders of magnitude larger than over adjacent sea ice and of the opposite sign. Annual solar radiation absorption by leads in the central Arctic is 1.8 times as large as over adjacent sea ice, resulting in a summertime shortwave energy gain of over 2.5 W m2 at 8 1°N compared to the model run without leads.The inclusion of leads causes thicker sea ice in every season, because the very rapid ice growth rate in the leads is translated into enhanced accretion at the bottom of adjacent sea ice once a prescribed minimum lead fraction is reached

  1. Influence of Computational Drop Representation in LES of a Droplet-Laden Mixing Layer

    NASA Technical Reports Server (NTRS)

    Bellan, Josette; Radhakrishnan, Senthilkumaran

    2013-01-01

    Multiphase turbulent flows are encountered in many practical applications including turbine engines or natural phenomena involving particle dispersion. Numerical computations of multiphase turbulent flows are important because they provide a cheaper alternative to performing experiments during an engine design process or because they can provide predictions of pollutant dispersion, etc. Two-phase flows contain millions and sometimes billions of particles. For flows with volumetrically dilute particle loading, the most accurate method of numerically simulating the flow is based on direct numerical simulation (DNS) of the governing equations in which all scales of the flow including the small scales that are responsible for the overwhelming amount of dissipation are resolved. DNS, however, requires high computational cost and cannot be used in engineering design applications where iterations among several design conditions are necessary. Because of high computational cost, numerical simulations of such flows cannot track all these drops. The objective of this work is to quantify the influence of the number of computational drops and grid spacing on the accuracy of predicted flow statistics, and to possibly identify the minimum number, or, if not possible, the optimal number of computational drops that provide minimal error in flow prediction. For this purpose, several Large Eddy Simulation (LES) of a mixing layer with evaporating drops have been performed by using coarse, medium, and fine grid spacings and computational drops, rather than physical drops. To define computational drops, an integer NR is introduced that represents the ratio of the number of existing physical drops to the desired number of computational drops; for example, if NR=8, this means that a computational drop represents 8 physical drops in the flow field. The desired number of computational drops is determined by the available computational resources; the larger NR is, the less computationally

  2. Inferring strength and deformation properties of hot mix asphalt layers from the GPR signal: recent advances

    NASA Astrophysics Data System (ADS)

    Tosti, Fabio; Benedetto, Andrea; Bianchini Ciampoli, Luca; Adabi, Saba; Pajewski, Lara

    2015-04-01

    , of both the different strength provision of each layer composing the hot mix asphalt pavement structure, and of the attenuation occurring to electromagnetic waves during their in-depth propagation. Promising results are achieved by matching modelled and measured elastic modulus data. This continuous statistically-based model enables to consider the whole set of information related to each single depth, in order to provide a more comprehensive prediction of the strength and deformation behavior of such a complex multi-layered medium. Amongst some further developments to be tackled in the near future, a model improvement could be reached through laboratory activities under controlled conditions and by adopting several frequency bandwidths suited for purposes. In addition, the perspective to compare electromagnetic data with mechanical measurements retrieved continuously, i.e., by means of specifically equipped lorries, could pave the way to considerable enhancements in this field of research. Acknowledgements - This work has benefited from networking activities carried out within the EU funded COST Action TU1208 "Civil Engineering Applications of Ground Penetrating Radar".

  3. Slow Phospholipid Exchange between a Detergent-Solubilized Membrane Protein and Lipid-Detergent Mixed Micelles: Brominated Phospholip