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Sample records for particle surface layer

  1. Layer-by-layer deposition of oppositely charged polyelectrolytes on the surface of condensed DNA particles.

    PubMed Central

    Trubetskoy, V S; Loomis, A; Hagstrom, J E; Budker, V G; Wolff, J A

    1999-01-01

    DNA can be condensed with an excess of poly-cations in aqueous solutions forming stable particles of submicron size with positive surface charge. This charge surplus can be used to deposit alternating layers of polyanions and polycations on the surface surrounding the core of condensed DNA. Using poly-L-lysine (PLL) and succinylated PLL (SPLL) as polycation and polyanion, respectively, we demonstrated layer-by-layer architecture of the particles. Polyanions with a shorter carboxyl/backbone distance tend to disassemble binary DNA/PLL complexes by displacing DNA while polyanions with a longer carboxyl/backbone distance effectively formed a tertiary complex. The zeta potential of such complexes became negative, indicating effective surface recharging. The charge stoichiometry of the DNA/PLL/SPLL complex was found to be close to 1:1:1, resembling poly-electrolyte complexes layered on macrosurfaces. Recharged particles containing condensed plasmid DNA may find applications as non-viral gene delivery vectors. PMID:10454604

  2. Layer-by-layer deposition of oppositely charged polyelectrolytes on the surface of condensed DNA particles.

    PubMed

    Trubetskoy, V S; Loomis, A; Hagstrom, J E; Budker, V G; Wolff, J A

    1999-08-01

    DNA can be condensed with an excess of poly-cations in aqueous solutions forming stable particles of submicron size with positive surface charge. This charge surplus can be used to deposit alternating layers of polyanions and polycations on the surface surrounding the core of condensed DNA. Using poly-L-lysine (PLL) and succinylated PLL (SPLL) as polycation and polyanion, respectively, we demonstrated layer-by-layer architecture of the particles. Polyanions with a shorter carboxyl/backbone distance tend to disassemble binary DNA/PLL complexes by displacing DNA while polyanions with a longer carboxyl/backbone distance effectively formed a tertiary complex. The zeta potential of such complexes became negative, indicating effective surface recharging. The charge stoichiometry of the DNA/PLL/SPLL complex was found to be close to 1:1:1, resembling poly-electrolyte complexes layered on macrosurfaces. Recharged particles containing condensed plasmid DNA may find applications as non-viral gene delivery vectors.

  3. Layer-by-layer assembly of polymersomes and polyelectrolytes on planar surfaces and microsized colloidal particles.

    PubMed

    Coustet, Marcos; Irigoyen, Joseba; Garcia, Teodoro Alonso; Murray, Richard A; Romero, Gabriela; Susana Cortizo, M; Knoll, Wolfgang; Azzaroni, Omar; Moya, Sergio E

    2014-05-01

    Hybrid polyelectrolyte multilayer systems were fabricated on top of planar surfaces and colloidal particles via layer by layer (LbL) assembly of polystyrene sulphonate (PSS) and polybenzyl methacrylate-block-poly(dimethylamino)ethyl methacrylate (PBzMA-b-PDMAEMA) polymersomes. Polymersomes were prepared by self assembly of PBzMA-b-PDMAEMA copolymer, synthesised by group transfer polymerisation. Polymersomes display a diameter of 270 nm and a shell thickness of 11nm. Assembly on planar surfaces was followed by means of the Quartz Crystal Microbalance with Dissipation (QCM-D) and Atomic Force Microscopy (AFM). Detailed information on the assembly mechanism and surface topology of the polymersome/polyelectrolyte films was thereby obtained. The assembly of polymersomes and PSS on top of silica particles of 500 nm in diameter was confirmed by ζ-potential measurements. Confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that polymersome/PSS coated silica particles increase in total diameter up to 3-5μm. This hints toward the formation of densely packed polymersome layers. In addition, CLSM showed that polymersome/PSS films exhibit a high loading capacity that could potentially be used for encapsulation and delivery of diverse chemical species. These results provide an insight into the formation of multilayered films with compartmentalised hydrophilic/hydrophobic domains and may lead to the successful application of polymersomes in surface-engineered colloidal systems.

  4. Surface molecular imprinting in layer-by-layer films on silica particles.

    PubMed

    Gauczinski, Jan; Liu, Zhihua; Zhang, Xi; Schönhoff, Monika

    2012-03-01

    An improvement to molecular imprinting in polymers, where bulk systems often suffer from slow dynamics of release and uptake, is the formation of thin films with imprinting sites that are more rapid to access by guest molecules. Based on our previous development of surface molecular imprinting layer-by-layer (LbL) films (SMILbL), the present paper presents selective imprinted sites in a surface film on dispersed silica particles, thus designing a SMILbL system with maximized active area and in addition allowing studies with bulk techniques. The multilayer is designed to include the template during the LbL buildup and to form a cross-linked network upon UV-irradiation for enhanced stability. A theophylline moiety is grafted to poly(acrylic acid) as the template, while a UV-sensitive diazo polycation cross-links the polymers after irradiation. Electrophoretic measurements prove the successful buildup of the multilayers by an alternating sign of the zeta potential. Template release is achieved by cleavage of the grafted template. The released amount of template is quantified in solution by (1)H NMR spectra and is in good agreement with the prediction from surface coverage calculations. Rebinding studies of template to the now empty imprinted binding sites show a high affinity for a theophylline derivative with a rebound amount on the order of the original template content. In contrast to theophylline, caffeine with a very similar chemical structure-only differing in one functional group-shows very different binding properties due to a thiol moiety in the binding site. Thus, a particle system with very selective molecular imprinting sites is demonstrated. PMID:22324368

  5. Layer by Layer, Nano-particle "Only" Surface Modification of Filtration Membranes

    NASA Astrophysics Data System (ADS)

    Escobar-Ferrand, Luis

    Layer by Layer (LbL) deposition using primarily inorganic silica nanoparticles is employed for the modification of polymeric micro and ultrafiltration (MF/UF) membranes to produce thin film composites (TFC) with potential nanofiltration (NF) and reverse osmosis (RO) capabilities.. A variety of porous substrate membranes with different membrane surface characteristics are employed, but exhibiting in common that wicking of water does not readily occur into the pore structure, including polycarbonate track etched (PCTE), polyethersulfone (PES) and sulfonated PES (SPEES) MF/UF membranes. Both spherical (cationic/anionic) and eccentric elongated (anionic) silica nanoparticles are deposited using conditions similar to those reported by Lee et al. Appropriate selection of the pH's for anionic and cationic particle deposition enables the construction of nanoparticle only layers 100--1200 nm in thickness atop the original membrane substrates. The surface layer thickness varies monotonically with the number of bilayers (anionic/cationic deposition cycles) as expected. The deposition process is optimized to eliminate drying induced cracking and to improve mechanical durability via thickness control and post-deposition hydro-thermal treatment. The hydrodynamic permeability of these TFC membranes is measured to evaluate their performance under typical NF operating conditions using dead-end permeation experiments and their performance compared quantitatively with realistic hydrodynamic models, with favorable results. For track etched polycarbonate MF substrates, surface modification causes a permeability reduction of approximately two orders of magnitude with respect to the bare substrates, to values comparable to those for typical commercial NF membranes. Good quantitative agreement with hydrodynamic models with no adjustable parameters was also established for this case, providing indirect confirmation that the LbL deposited surface layers are largely defect (crack) free

  6. Effect of Plasma-Polymerized Layer Formed on a Surface of Titanium Dioxide Particle on Its Photocatalytic Activity

    NASA Astrophysics Data System (ADS)

    Yamada, Kenji; Iwasawa, Naoko; Sonoda, Tatsuhiko; Yamane, Hirokazu; Matsushima, Shigenori; Nakamura, Hiroyuki

    If TiO2 particles are used as components of paint without any surface modification, binding resin of the paint will be easily decomposed by the photocatalytic activity of the particles. In this work, plasma polymerization of octamethylcyclotetrasiloxane as a siloxane monomer is tried to form thin layer stable to the photocatalytic activity on the surface of TiO2 particles. The plasma-polymerized layer containing Si-O and Si-C bonds is formed on the surface of the particles and shows stability to the photocatalytic activity of TiO2. The particles surface-modified with the plasma polymerization exhibit visible-light activity. The visible-light activity is originated from carbon doping which brings about in the particles during the plasma polymerization, and is thermally stable to be maintained after annealing at 673 K.

  7. Compliant layer chucking surface

    DOEpatents

    Blaedel, Kenneth L.; Spence, Paul A.; Thompson, Samuel L.

    2004-12-28

    A method and apparatus are described wherein a thin layer of complaint material is deposited on the surface of a chuck to mitigate the deformation that an entrapped particle might cause in the part, such as a mask or a wafer, that is clamped to the chuck. The harder particle will embed into the softer layer as the clamping pressure is applied. The material composing the thin layer could be a metal or a polymer for vacuum or electrostatic chucks. It may be deposited in various patterns to affect an interrupted surface, such as that of a "pin" chuck, thereby reducing the probability of entrapping a particle.

  8. Structure and function of airway surface layer of the human lungs & mobility of probe particles in complex fluids

    NASA Astrophysics Data System (ADS)

    Cai, Liheng

    Numerous infectious particles such as bacteria and pathogens are deposited on the airway surface of the human lungs during our daily breathing. To avoid infection the lung has evolved to develop a smart and powerful defense system called mucociliary clearance. The airway surface layer is a critical component of this mucus clearance system, which consists of two parts: (1) a mucus layer, that traps inhaled particles and transports them out of the lung by cilia-generated flow; and (2) a periciliary layer, that provides a favorable environment for ciliary beating and cell surface lubrication. For 75 years, it has been dogma that a single gel-like mucus layer, which is composed of secreted mucin glycoproteins, is transported over a "watery" periciliary layer. This one-gel model, however, does not explain fundamental features of the normal system, e.g. formation of a distinct mucus layer, nor accurately predict how the mucus clearance system fails in disease. In the first part of this thesis we propose a novel "Gel-on-Brush" model with a mucus layer (the "gel") and a "brush-like" periciliary layer, composed of mucins tethered to the luminal of airway surface, and supporting data accurately describes both the biophysical and cell biological bases for normal mucus clearance and its failure in disease. Our "Gel-on-Brush" model describes for the first time how and why mucus is efficiently cleared in health and unifies the pathogenesis of major human diseases, including cystic fibrosis and chronic obstructive pulmonary disease. It is expected that this "Gel-on-Brush" model of airway surface layer opens new directions for treatments of airway diseases. A dilemma regarding the function of mucus is that, although mucus traps any inhaled harmful particulates, it also poses a long-time problem for drug delivery: mobility of cargos carrying pharmaceutical agents is slowed down in mucus. The second part of this thesis aims to answer the question: can we theoretically understand the

  9. Surface modification of Cu metal particles by the chemical reaction between the surface oxide layer and a halogen surfactant

    NASA Astrophysics Data System (ADS)

    Yokoyama, Shun; Takahashi, Hideyuki; Itoh, Takashi; Motomiya, Kenichi; Tohji, Kazuyuki

    2014-01-01

    Surface oxides on small (2-5 μm) copper metal particles can be removed by chemical reaction with tris(2,3-dibromopropyl) isocyanurate (TIC) in diethylene glycol mono-n-hexyl ether (DGHE) solution under mild conditions where metal particles are not damaged. Surface oxides convert to copper bromide species and subsequently dissolve into the solvent. It was found that resultant surface species are resistant to re-oxidation due to remaining surface bromides. This finding opens up a possibility to create microclines based on cheap copper nanoparticles.

  10. Atomic force microscopy surface analysis of layered perovskite La2Ti2O7 particles grown by molten flux method

    NASA Astrophysics Data System (ADS)

    Orum, Aslihan; Takatori, Kazumasa; Hori, Shigeo; Ikeda, Tomiko; Yoshimura, Masamichi; Tani, Toshihiko

    2016-08-01

    Rectangular platelike particles of La2Ti2O7, a layered perovskite, were synthesized in KCl, NaCl, and LiCl by the molten flux method. The formation mechanism of the equilibrium shape in these alkali chloride fluxes was discussed in terms of the surface and interfacial energies of crystallographic planes. The atomic force microscopy (AFM) observations revealed that the developed plane of the platelike particles is along the interlayers in the {110}-type layered crystal structure, and is considered to represent the lowest surface energy plane in which strong, periodic Ti–O bond chains terminate. Herein, for the first time, a growth mechanism for La2Ti2O7 particles is proposed and discussed. Triangular prism structures along the c-axis were observed on the developed planes of KCl-grown particles whereas no such structures were found on those of LiCl-grown ones. AFM measurements suggest that the prism facets are {210}-La2Ti2O7, which results in lower interfacial energy within KCl.

  11. Atomic force microscopy surface analysis of layered perovskite La2Ti2O7 particles grown by molten flux method

    NASA Astrophysics Data System (ADS)

    Orum, Aslihan; Takatori, Kazumasa; Hori, Shigeo; Ikeda, Tomiko; Yoshimura, Masamichi; Tani, Toshihiko

    2016-08-01

    Rectangular platelike particles of La2Ti2O7, a layered perovskite, were synthesized in KCl, NaCl, and LiCl by the molten flux method. The formation mechanism of the equilibrium shape in these alkali chloride fluxes was discussed in terms of the surface and interfacial energies of crystallographic planes. The atomic force microscopy (AFM) observations revealed that the developed plane of the platelike particles is along the interlayers in the {110}-type layered crystal structure, and is considered to represent the lowest surface energy plane in which strong, periodic Ti-O bond chains terminate. Herein, for the first time, a growth mechanism for La2Ti2O7 particles is proposed and discussed. Triangular prism structures along the c-axis were observed on the developed planes of KCl-grown particles whereas no such structures were found on those of LiCl-grown ones. AFM measurements suggest that the prism facets are {210}-La2Ti2O7, which results in lower interfacial energy within KCl.

  12. Virosome engineering of colloidal particles and surfaces: bioinspired fusion to supported lipid layers.

    PubMed

    Fleddermann, J; Diamanti, E; Azinas, S; Košutić, M; Dähne, L; Estrela-Lopis, I; Amacker, M; Donath, E; Moya, S E

    2016-04-21

    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. PMID:27006101

  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. Prediction and rational correlation of thermophoretically reduced particle mass transfer to hot surfaces across laminar or turbulent forced-convection gas boundary layers

    NASA Technical Reports Server (NTRS)

    Gokoglu, Suleyman A.; Rosner, Daniel E.

    1986-01-01

    A formulation previously developed to predict and correlate the thermophoretically-augmented submicron particle mass transfer rate to cold surfaces is found to account for the thermophoretically reduced particle mass transfer rate to overheated surfaces such that thermophoresis brings about a 10-decade reduction below the convective mass transfer rate expected by pure Brownian diffusion and convection alone. Thermophoretic blowing is shown to produce effects on particle concentration boundary-layer (BL) structure and wall mass transfer rates similar to those produced by real blowing through a porous wall. The applicability of the correlations to developing BL-situations is demonstrated by a numerical example relevant to wet-steam technology.

  15. Particle transport and adjustments of the boundary layer over rough surfaces with an unrestricted, upwind supply of sediment

    NASA Astrophysics Data System (ADS)

    McKenna Neuman, Cheryl

    1998-10-01

    Most natural surfaces containing non-erodible roughness elements are considerably more complex than those studied in modelling exercises and wind tunnel simulations. Unlike idealized roughness elements, which are uniform in size, shape (i.e., spheres or cylinders) and spacing, natural elements are challenging to measure in 3-dimensional space. Similarly, most deflation lag surfaces, such those as found on sandar and beaches, are spatially heterogeneous open systems in which sediment transport from an external supply is very likely. The development of irregular deflation lag surfaces, and the transport of sediment over these surfaces from an upwind source of sediment, was studied in a series of wind tunnel simulations. Surfaces prepared with crushed gravel and natural beach shingle respond conservatively in terms of the adjustment to the deflation and deposition of sediment. Deflation lag surfaces, prepared with no spacing between the roughness elements (i.e., close packed), demonstrate little to no change in coverage with the introduction of particles from an upwind source. Neither the element type nor the friction velocity affect this outcome. As the center-to-center element spacing increases to 60 mm, infilling of the lag surface eventually is observed, with the element coverage reduced by a factor between 2 and 4. For a given threshold ratio ( Rt), the roughness density ( λ) is smaller than observed in previous simulation studies based on idealized roughness elements.

  16. Simulation of the interaction of electromagnetic waves with dispersed particles in the propagation of breather in the surface layer of a liquid medium

    SciTech Connect

    Zabolotin, V.V.; Uvarova, L.A.

    2015-03-10

    A numerical simulation of the interaction of laser radiation with dispersed particles in the course of propagation of breather in the surface layer of the liquid breather was performed. The shape and amplitude of the acoustic signal formed in this interaction were obtained. Two acoustic signals, before and after the impact of a breather on the process of optical sound generation, were compared. Results of the comparison showed that the breather spreading over the surface of the liquid medium affecst the acoustic signal and its effect must be considered in the measurements.

  17. Effect of temperature, atmospheric condition, and particle size on extinction in a plume of volatile aerosol dispersed in the atmospheric surface layer.

    PubMed

    Tsang, T T; Pai, P; Korgaonkar, N V

    1988-02-01

    The objective of this work is to study the effects of ambient temperature, atmospheric condition, and particle size on the extinction coefficient of diesel fuel and fog oil smoke. A first-order closure model is used to describe the turbulent diffusion of the smoke in the atmospheric surface layer. Mean values of wind speed and diffusivity in the vertical direction are obtained by the use of the Monin-Obukhov similarity theory. The 2-D crosswind line source model also includes the aerosol kinetic processes of evaporation, sedimentation, and deposition. Numerical results are obtained from simulations on a supercomputer.

  18. The Martian surface layer

    NASA Technical Reports Server (NTRS)

    Christensen, Philip R.; Moore, Henry J.

    1992-01-01

    The global characteristics of the Martian surface layer are discussed on the basis of thermal, albedo, color, and radar data for the region between approximately 60 deg S and 60 deg N. Thermal data reveal the presence of large low- and high-inertia regions of the northern hemisphere, with much of the south covered by material of moderate inertia. There is a strong anticorrelation between inertia and albedo, a correlation between inertia and rock abundance, and, over much of the planet, a correlation of radar-derived density with inertia. Viking Orbiter color data indicate the presence of three major surface materials: low-inertia, bright-red material that is presumably dust; high-inertia, dark-grey material interpreted to be lithic material mixed with palagonitelike dust; and moderate-inertia, dark-red material that is rough at subpixel scales and interpreted to be indurated. Observations from the Viking landing sites show rocks, fines of varying cohesion and crusts. These sites have indications of aeolian erosion and deposition in the recent past.

  19. Observed particle sizes and fluxes of Aeolian sediment in the near surface layer during sand-dust storms in the Taklamakan Desert

    NASA Astrophysics Data System (ADS)

    Huo, Wen; He, Qing; Yang, Fan; Yang, Xinghua; Yang, Qing; Zhang, Fuyin; Mamtimin, Ali; Liu, Xinchun; Wang, Mingzhong; Zhao, Yong; Zhi, Xiefei

    2016-08-01

    Monitoring, modeling and predicting the formation and movement of dust storms across the global deserts has drawn great attention in recent decades. Nevertheless, the scarcity of real-time observations of the wind-driven emission, transport and deposition of dusts has severely impeded progress in this area. In this study, we report an observational analysis of sand-dust storm samples collected at seven vertical levels from an 80-m-high flux tower located in the hinterland of the great Taklamakan Desert for ten sand-dust storm events that occurred during 2008-2010. We analyzed the vertical distribution of sandstorm particle grain sizes and horizontal sand-dust sediment fluxes from the near surface up to 80 m high in this extremely harsh but highly representative environment. The results showed that the average sandstorm grain size was in the range of 70 to 85 μm. With the natural presence of sand dunes and valleys, the horizontal dust flux appeared to increase with height within the lower surface layer, but was almost invariant above 32 m. The average flux values varied within the range of 8 to 14 kg m-2 and the vertical distribution was dominated by the wind speed in the boundary layer. The dominant dust particle size was PM100 and below, which on average accounted for 60-80 % of the samples collected, with 0.9-2.5 % for PM0-2.5, 3.5-7.0 % for PM0-10, 5.0-14.0 % for PM0-20 and 20.0-40.0 % for PM0-50. The observations suggested that on average the sand-dust vertical flux potential is about 0.29 kg m-2 from the top of the 80 m tower to the upper planetary boundary layer and free atmosphere through the transport of particles smaller than PM20. Some of our results differed from previous measurements from other desert surfaces and laboratory wind-dust experiments, and therefore provide valuable observations to support further improvement of modeling of sandstorms across different natural environmental conditions.

  20. Formulation of stability-dependent empirical relations for turbulent intensities from surface layer turbulence measurements for dispersion parameterization in a lagrangian particle dispersion model

    NASA Astrophysics Data System (ADS)

    Hari Prasad, K. B. R. R.; Srinivas, C. V.; Satyanarayana, A. N. V.; Naidu, C. V.; Baskaran, R.; Venkatraman, B.

    2015-08-01

    Season- and stability-dependent turbulence intensity ( σ u / u *, σ v / u *, σ w / u *) relationships are derived from experimental turbulence measurements following surface layer scaling and local stability at the tropical coastal site Kalpakkam, India for atmospheric dispersion parameterization. Turbulence wind components ( u', v', w') measured with fast response UltraSonic Anemometers during an intense observation campaign for wind field modeling called Round Robin Exercise are used to formulate the flux-profile relationships using surface layer similarity theory and Fast Fourier Transform technique. The new relationships (modified Hanna scheme) are incorporated in a Lagrangian Particle Dispersion model FLEXPART-WRF and tested by conducting simulations for a field tracer dispersion experiment at Kalpakkam. Plume dispersion analysis of a ground level hypothetical release indicated that the new turbulent intensity formulations provide slightly higher diffusivity across the plume relative to the original Hanna scheme. The new formulations for σ u , σ v , σ w are found to give better agreement with observed turbulent intensities during both stable and unstable conditions under various seasonal meteorological conditions. The simulated concentrations using the two methods are compared with those obtained from a classical Gaussian model and the observed SF6 concentration. It has been found that the new relationships provide comparatively higher diffusion across the plume relative to the model default Hanna scheme and provide downwind concentration results in better agreement with observations.

  1. The neutral surface layer above rough surfaces

    NASA Astrophysics Data System (ADS)

    Smedman, Ann-Sofi; Sahlee, Erik

    2014-05-01

    It is generally accepted that turbulent fluxes (momentum and scalar fluxes) are approx. constant with height above horizontal surfaces with low roughness. But what will happen when the roughness sub-layer is large as found over cities, forests and rough seas? In a study of the kinematic structure of the near neutral atmospheric surface layer, Högström, Hunt and Smedman, 2002, it was demonstrated that a model with detached eddies from above the surface layer impinging on to the surface (Hunt and Morison, 2000) could explain some of the observed features in the neutral atmospheric boundary layer. Thus the detached eddy model proved successful in explaining the dynamic structure of the near neutral atmospheric surface layer, especially the shape of the spectra of the wind components and scalars and corresponding fluxes. Here we make the hypothesis that the detached-eddy model can also be used to explain the experimental results related to the 3-dimensional turbulence structure above rough surfaces. Measurements are taken both over land (grass and forest) and over sea (Baltic Sea and hurricane Fabian in the Atlantic) above the roughness sub-layer. Analysis of the turbulence structure shows a striking similarity between the different sites. Hunt, J.C.R and Morrison, J.F., 2000: Eddy structure in turbulent boundary layers, Euro. J. Mech. B-Fluids, 19, 673-694. Högström, U., Hunt, J.C.R., and Smedman, A., 2002: Theory and measurements for turbulence spectra and variances in the atmospheric neutral surface layer, Bound.-Layer Meteorol., 103,101-124.

  2. Layer-by-layer self-assembly of ceramic particles for complex shape coating synthesis

    NASA Astrophysics Data System (ADS)

    Qiu, Hongwei

    Layer-by-layer (LbL) self-assembly was explored as a non-line-of-sight method for uniform infiltration and deposition of a multilayer of ceramic particles into complex structures. Key parameters for controlling the LbL self-assembly process were studied using a model system which consisted of a silicon substrate, 100 nm and 500 nm silica particles, and a polycation/polyanion combination. We correlated the surface coverage of the silica particles to the NaCl concentration used in deposition of the polyelectrolyte layers and to the number of the polyelectrolyte layers deposited. The effect of particle size on the surface coverage was rationally explained based on the screening length. We found that the effects of particle size, polydispersity, and electrolyte concentration in the particle suspension on the surface coverage and morphology of the first silica particle layer deposited on the polyelectrolyte layer surface were highly coupled, and resolving these effects was important for infiltrating a uniform coating of multilayer silica particle assemblies into a cellular structure as an ultimate complex substrate. Based on this understanding, the Lbl, self-assembly method was applied as a method of assembling, infiltrating, and immobilizing a 4-layer coating of negatively charged ˜3 mum Pd/NaAI(Si)O catalyst particles in the confined space of the cellular structure with ˜400 mum interconnected cells. The 4-layer coating deposited on the inner wall of a stainless steel capillary tube was mechanically stable under water flow rate up to 10 ml/min over the pH range of 3 to 11. Scotch tape peeling evaluation suggested that failure locations were mostly within the catalyst particle assembly, but near the assembly-PEM interface region.

  3. Boundary layer effects on particle impaction and capture

    NASA Technical Reports Server (NTRS)

    Rosner, D. E.; Fernandez De La Mora, J.

    1984-01-01

    The inertial impaction and deposition of small particles on larger bodies with viscous boundary layers are considered theoretically, in a detailed comment on a paper by Menguturk et al. (1983). Topics addressed include cushion effects, the dimensionless groups corresponding to the diameter range (3-6 microns) examined by Menguturk et al. in a numerical example, analogous effects of particle-gas energy and mass exchange in boundary layers, and the combined effects of particle inertia and diffusion. It is argued that the inertial effects can be characterized in terms of a body, boundary-layer, or sublayer Stokes number. In a reply by Menguturk et al., the focus is on the application of the theoretical model to the erosion of blade surfaces in large gas turbines; the Stokes number is found to be of limited practical value in these cases, because the particle motion is not primarily normal to the blade surfaces.

  4. Particle motion in atmospheric boundary layers of Mars and Earth

    NASA Technical Reports Server (NTRS)

    White, B. R.; Iversen, J. D.; Greeley, R.; Pollack, J. B.

    1975-01-01

    To study the eolian mechanics of saltating particles, both an experimental investigation of the flow field around a model crater in an atmospheric boundary layer wind tunnel and numerical solutions of the two- and three-dimensional equations of motion of a single particle under the influence of a turbulent boundary layer were conducted. Two-dimensional particle motion was calculated for flow near the surfaces of both Earth and Mars. For the case of Earth both a turbulent boundary layer with a viscous sublayer and one without were calculated. For the case of Mars it was only necessary to calculate turbulent boundary layer flow with a laminar sublayer because of the low values of friction Reynolds number; however, it was necessary to include the effects of slip flow on a particle caused by the rarefied Martian atmosphere. In the equations of motion the lift force functions were developed to act on a single particle only in the laminar sublayer or a corresponding small region of high shear near the surface for a fully turbulent boundary layer. The lift force functions were developed from the analytical work by Saffman concerning the lift force acting on a particle in simple shear flow.

  5. Synergistic Effect of Surface Plasmonic particles and Surface Passivation layer on ZnO Nanorods Array for Improved Photoelectrochemical Water Splitting

    NASA Astrophysics Data System (ADS)

    Liu, Yichong; Yan, Xiaoqin; Kang, Zhuo; Li, Yong; Shen, Yanwei; Sun, Yihui; Wang, Li; Zhang, Yue

    2016-07-01

    One-dimensional zinc oxide nanorods array exhibit excellent electron mobility and thus hold great potential as photoanode for photoelelctrochemical water splitting. However, the poor absorption of visible light and the prominent surface recombination hider the performance improvement. In this work, Au nanoparticles and aluminium oxide were deposited onto the surface of ZnO nanorods to improve the PEC performance. The localized surface plasmon resonance of Au NPs could expand the absorption spectrum to visible region. Simultaneously, the surface of passivation with Au NPs and Al2O3 largely suppressed the photogenerated electron-hole recombination. As a result, the optimal solar-to-hydrogen efficiency of ZnO/Au/Al2O3 with 5 cycles was 6.7 times that of pristine ZnO, ascribed to the synergistic effect of SPR and surface passivation. This research reveals that the synergistic effect could be used as an important method to design efficient photoanodes for photoelectrochemical devices.

  6. Synergistic Effect of Surface Plasmonic particles and Surface Passivation layer on ZnO Nanorods Array for Improved Photoelectrochemical Water Splitting.

    PubMed

    Liu, Yichong; Yan, Xiaoqin; Kang, Zhuo; Li, Yong; Shen, Yanwei; Sun, Yihui; Wang, Li; Zhang, Yue

    2016-01-01

    One-dimensional zinc oxide nanorods array exhibit excellent electron mobility and thus hold great potential as photoanode for photoelelctrochemical water splitting. However, the poor absorption of visible light and the prominent surface recombination hider the performance improvement. In this work, Au nanoparticles and aluminium oxide were deposited onto the surface of ZnO nanorods to improve the PEC performance. The localized surface plasmon resonance of Au NPs could expand the absorption spectrum to visible region. Simultaneously, the surface of passivation with Au NPs and Al2O3 largely suppressed the photogenerated electron-hole recombination. As a result, the optimal solar-to-hydrogen efficiency of ZnO/Au/Al2O3 with 5 cycles was 6.7 times that of pristine ZnO, ascribed to the synergistic effect of SPR and surface passivation. This research reveals that the synergistic effect could be used as an important method to design efficient photoanodes for photoelectrochemical devices. PMID:27443692

  7. Synergistic Effect of Surface Plasmonic particles and Surface Passivation layer on ZnO Nanorods Array for Improved Photoelectrochemical Water Splitting

    PubMed Central

    Liu, Yichong; Yan, Xiaoqin; Kang, Zhuo; Li, Yong; Shen, Yanwei; Sun, Yihui; Wang, Li; Zhang, Yue

    2016-01-01

    One-dimensional zinc oxide nanorods array exhibit excellent electron mobility and thus hold great potential as photoanode for photoelelctrochemical water splitting. However, the poor absorption of visible light and the prominent surface recombination hider the performance improvement. In this work, Au nanoparticles and aluminium oxide were deposited onto the surface of ZnO nanorods to improve the PEC performance. The localized surface plasmon resonance of Au NPs could expand the absorption spectrum to visible region. Simultaneously, the surface of passivation with Au NPs and Al2O3 largely suppressed the photogenerated electron-hole recombination. As a result, the optimal solar-to-hydrogen efficiency of ZnO/Au/Al2O3 with 5 cycles was 6.7 times that of pristine ZnO, ascribed to the synergistic effect of SPR and surface passivation. This research reveals that the synergistic effect could be used as an important method to design efficient photoanodes for photoelectrochemical devices. PMID:27443692

  8. Simple ray-tracing model for a rough surface of an ink layer including internal scattering particles printed on a light guide plate.

    PubMed

    Sekiguchi, Yoshifumi; Kaneko, Hiroki

    2016-02-01

    For simulating light guide lighting systems, we have developed a ray-tracing model for an ink layer extracting light from a light guide. The model consists of the volume and the rough surface scattering calculated on the basis of Mie theory and the facet model, respectively. The model of an ink layer was required to conserve energy for analyzing how much light loss occurs in each component in the lighting system. Though a single-scattering rough surface model with a shadowing/masking function successfully describes the scattering distribution, shadowing light violates the energy conservation law because of a lack of multiple scattering. We developed the rough surface ray-tracing model (RSRT model), which includes the multiple scattering instead of the shadowing/masking effect. We investigated the applicability of the RSRT model for an ink layer by comparing the RSRT model with recent physical and facet models. Finally, we compared the calculated and measured scattering distributions of an ink layer, applied the developed ink layer model to the lighting system, and confirmed the developed model to be valid.

  9. Particle detection on flat surfaces

    NASA Astrophysics Data System (ADS)

    van der Donck, Jacques; Snel, Rob; Stortelder, Jetske; Abutan, Alfred; Oostrom, Sjoerd; van Reek, Sander; van der Zwan, Bert; van der Walle, Peter

    2011-04-01

    Since 2006 EUV Lithographic tools have been available for testing purposes giving a boost to the development of fab infrastructure for EUV masks. The absence of a pellicle makes the EUV reticles extremely vulnerable to particles. Therefore, the fab infrastructure for masks must meet very strict particle requirements. It is expected that all new equipment must be qualified on particles before it can be put into operation. This qualification requirement increases the need for a low cost method for particle detection on mask substrates. TNO developed its fourth generation particle scanner, the Rapid Nano. This scanner is capable of detecting nanometer sized particles on flat surfaces. The particle detection is based on dark field imaging techniques and fast image processing. The tool was designed for detection of a single added particle in a handling experiment over a reticle sized substrate. Therefore, the Rapid Nano is very suitable for the validation of particle cleanliness of equipment. During the measurement, the substrate is protected against particle contamination by placing it in a protective environment. This environment shields the substrate from all possible contamination source in the Nano Rapid (stages, elevator, cabling). The imaging takes place through a window in the protective cover. The geometry of the protective environment enables large flexibility in substrate shape and size. Particles can be detected on substrates varying from 152 x 152 mm mask substrates to wafers up to 200 mm. PSL particles of 50 nm were detected with signal noise ratio of 26. Larger particles had higher signal noise ratios. By individually linking particles in two measurements the addition of particles can be detected. These results show that the Rapid Nano is capable of detecting particles of 50 nm and larger of a full reticle substrate.

  10. Detector for Particle Surface Contamination

    NASA Technical Reports Server (NTRS)

    Mogan, Paul A. (Inventor); Schwindt, Christian J. (Inventor); Mattson, Carl B. (Inventor)

    1999-01-01

    A system and method for detecting and quantizing particle fallout contamination particles which are collected on a transparent disk or other surface employs an optical detector, such as a CCD camera, to obtain images of the disk and a computer for analyzing the images. From the images, the computer detects, counts and sizes particles collected on the disk The computer also determines, through comparison to previously analyzed images, the particle fallout rate, and generates an alarm or other indication if the rate exceeds a maximum allowable value. The detector and disk are disposed in a housing having an aperture formed therein for defining the area on the surface of the disk which is exposed to the particle fallout. A light source is provided for evenly illuminating the disk. A first drive motor slowly rotates the disk to increase the amount of its surface area which is exposed through the aperture to the particle fallout. A second motor is also provided for incrementally scanning the disk in a radial direction back and forth over the camera so that the camera eventually obtains images of the entire surface of the disk which is exposed to the particle fallout.

  11. Particle simulation of auroral double layers

    NASA Technical Reports Server (NTRS)

    Smith, Bruce L.; Okuda, Hideo

    1987-01-01

    Work on the simulation of auroral double layers (DLs) with realistic particle-in-cell models is presented. An early model simulated weak DLs formed in a self-consistent circuit but under conditions subject to the ion-acoustic instability. Recent work has focused on strong DLs formed when currentless jets are injected into a dipole magnetic field.

  12. Application of Analytical Model of the Electric Potential Distribution for Calculation of Charged Particle Dynamics in a Near-Wall Layer and Sputtering of the Plasma Facing Surfaces

    NASA Astrophysics Data System (ADS)

    Borodkina, I. E.; Komm, M.; Tsvetkov, I. V.

    2015-08-01

    Simple analytical formulas are derived for calculation of the electric field potential distribution in the magnetic pre-layer and the Debye layer near the plasma facing surfaces. It is shown that the calculated potential profiles are in good agreement with the dependences of the potential distribution on the magnetic field inclination obtained by solving the magnetic hydrodynamic (MHD) equations and modeling using the PIC code SPICE2. Dependences of the angular distribution of ions incident on the surface of plasma facing elements on the magnetic field inclination are obtained. Results of calculations demonstrate that the surface areas, on which the magnetic field is incident at sliding angles, are critical from the viewpoint of the increase of sputtering.

  13. Production Rates of Noble Gases in the Near-Surface Layers of Europa by Energetic Charged Particles and the Potential for Determining Exposure Ages

    NASA Technical Reports Server (NTRS)

    Swindle, T. D.; Reedy, R. C.; Masarik, J.

    2003-01-01

    The surface of Europa is expected to be extremely active, undergoing tectonic and/or tidal geological activity and sputtering/ deposition, as well as impact cratering. Determination of the actual age of the surface at one or more places would greatly simplify trying to sort out what processes are occurring, and at what rate. If there is K present, as the spectral and compositional modeling discussed predict, it should be possible, in principle, to determine K-Ar crystallization ages. Whether or not there is K present, a consideration of the environment suggests we can determine an energetic particle exposure age if we can make in situ measurements of the abundances of major elements and of noble gas isotopes. This requires instrumentation that is within reach of current technology. In this paper, we calculate production rates for noble-gas isotopes in a simplified Europan surface, to quantify the amount of light noble gases produced by exposure to energetic particles.

  14. Double layers acting as particles accelerators

    SciTech Connect

    Sanduloviciu, M.; Lozneanu, E.

    1995-12-31

    It is shown that self-consistent stable and unstable double layers generated in plasma after a self-organisation process are able to accelerate charged particles. The implication of cosmic double layers (Dls) in the acceleration of electrical charged particles long been advocated by Alfven and his Stockholm school is today disputed by argument that static electric fields associated with Dls are conservative and consequently the line integral of the electric field outside the DL balances the line integral inside it. Related with this dispute we will evidence some, so far not considered, facts which are in our opinion arguments that aurora Dls are able to energize particles. For justifying this assertion we start from recent experimental results concerning the phenomenology of self-consistent Dls whose generation involve beside ionisations the neutrals excitations which are at tile origin of the light phenomena as those observed in auroras.

  15. Subnanometer Palladium Particles Synthesized by Atomic Layer Deposition

    SciTech Connect

    Feng, Hao P.; Libera, Joseph A.; Stair, Peter C.; Miller, Jeffrey T.; Elam, Jeffrey W.

    2011-06-03

    Monodispersed palladium nanoparticle catalysts were synthesized by atomic layer deposition (ALD) using alternating exposures of Pd hexafluoroacetylacetonate (Pd(hfac)₂) and formalin on an alumina support. The size of the ALD Pd particles could be tuned by adjusting the preparation conditions. Conventional ALD conditions produced Pd particles with an average size of 1.4 nm. Removal of surface hydroxyls from the alumina support by a chemical treatment using trimethyl aluminum (TMA) before performing Pd ALD led to nanoparticles larger than 2 nm. Ultrasmall (subnanometer) Pd particles were synthesized using low-temperature metal precursor exposures, followed by applying protective ALD alumina overcoats. The ALD Pd particles were characterized by transmission electron microscopy, extended X-ray absorption fine structure, and diffuse reflectance infrared Fourier transform spectroscopy techniques. The Pd loadings were measured by X-ray fluorescence. The catalytic performance of ALD Pd particles of different sizes was compared in the methanol decomposition reaction. The specific activity (normalized by Pd loading) of the ultrasmall Pd particles was higher than those of the larger particles. Considering the metal dispersion factor, the turnover frequency (TOF) of the ultrasmall Pd particles is comparable to that of the medium-sized (1.4 nm, on average) Pd particles synthesized under standard ALD conditions. The large Pd particles (>2 nm) are a factor of 2 less active than the smaller Pd particles.

  16. Charged layer with undulated surface: configuration of electrical double layer.

    PubMed

    Lin, Sung-Hwa

    2010-06-15

    A charged layer with undulated surface exists commonly in natural entities (for example the biological membrane layer and the surface of charged colloid) and in artificial fabrications (for example the peripheral surface of ion-exchange membrane pores). When the micro- or nano-scale charged layer systems are concerned, the effect of undulation of charged layer surface on the electrical phenomenon may become great significant. In this work, using the perturbation method, the significance of undulated surface on a charged layer in the electrical phenomenon is investigated. Under assumptions that the undulation amplitude is small and that the Debye-Huckel approximation is applicable, the electrical potential field in three regions is solved simultaneously. Based on the analytical results it is found that, if compared with that in condition of flat surface, the undulation of charged layer surface decreases/increases the magnitude of electrical potential field near the wave crest/trough, due to the curvature of undulated surface. In addition, the surface potential on the undulated surface shows a wavelike distribution. The analytical results also show that, the significance of undulated surface is determined by the physical parameters, including the geometry of undulated surface, the amplitude and the period of undulation, and the fixed charge density in charged layer.

  17. Structure analysis of layer-by-layer multilayer films of colloidal particles

    NASA Astrophysics Data System (ADS)

    Batys, Piotr; Nosek, Magdalena; Weroński, Paweł

    2015-03-01

    We have mimicked the layer-by-layer self-assembling process of monodisperse colloidal particles at a solid-liquid interface using the extended random sequential adsorption model of hard spheres. We have studied five multilayer structures of similar thickness, each created at a different single-layer surface coverage. For each multilayer, we have determined its particle volume fraction as a function of distance from the interface. Additionally, we have characterized the film structure in terms of 2D and 3D pair-correlation functions. We have found that the coverage of about 0.3 is optimal for producing a uniform, constant-porosity multilayer in a minimum number of adsorption cycles. The single-layer coverage has also a significant effect on the primary maximum of 2D radial distribution function. In the case of multilayer with the coverage lower than 0.30 the 2D pair-correlation functions of even layers exhibit maxima decreasing with the increase in the layer number. We have verified our theoretical predictions experimentally. We have used fluorescence microscopy to determine the 2D pair-correlation functions for the second, third, and fourth layers of multilayer formed of micron-sized spherical latex particles. We have found a good agreement between our theoretical and experimental results, which confirms the validity of the extended RSA model.

  18. Heavy-Particle Deposition in the Atmospheric Boundary Layer.

    NASA Astrophysics Data System (ADS)

    Liao, Yingcheng

    A set of experiments of heavy-particle deposition on the ground in a wind-tunnel simulated atmospheric boundary layer has been conducted. Different particle fall velocities and different wind speeds were used. In order to analyze inertial, continuity, and crossing-trajectories effects of heavy particles, a new random-walk model has been developed in which vertical velocity variance is a function of height. For calibration of the numerical model, a set of tracer-gas concentration measurements was also carried out. The analysis of experimental results reveals that, in the atmospheric surface layer, for most of the practical situations, the crossing-trajectories and the inertia of heavy particles have a very limited effect on heavy-particle dispersion and deposition. However, the continuity effect greatly affects the lateral dispersion and deposition of heavy particles. The continuity effect is strongly height dependent. Influences of different factors on heavy-particle deposition are discussed. This includes the fall-velocity distribution of heavy particles, the integral-time scales of turbulent flow, longitudinal turbulent velocity components, release height, etc. Comparisons between the theoretical prediction and the calculated results from both the model used in this study and the model of Legg and Raupach (1982) support the author's approach in which vertical velocity variance is taken to be height dependent. For practical purposes, the new random-walk model has greatly improved the accuracy of predicting longitudinal deposition of heavy particles compared to that of the traditional Gaussian model. Experiments with more release heights and larger differences of particle fall velocity are suggested in order to further confirm the findings of this dissertation.

  19. Heavy-particle deposition in the atmospheric boundary layer

    NASA Astrophysics Data System (ADS)

    Liao, Yingcheng

    A set of experiments of heavy-particle deposition on the ground in a wind-tunnel simulated atmospheric boundary layer was conducted. Different particle fall velocities and different wind speeds were used. In order to analyze inertial, continuity, and crossing-trajectories effects of heavy particles, a new random-walk model was developed in which vertical velocity variance is a function of height. For calibration of the numerical model, a set of tracer-gas concentration measurements was also carried out. The analysis of experimental results reveals that, in the atmospheric surface layer, for most of the practical situations, the crossing-trajectories and the inertia of heavy particles have a very limited effect on heavy-particle dispersion and deposition. However, the continuity effect greatly affects the lateral dispersion and deposition of heavy particles. The continuity effect is strongly height dependent. Influences of different factors on heavy-particle deposition are discussed. This includes the fall-velocity distribution of heavy particles, the integral-time scales of turbulent flow, longitudinal turbulent velocity components, release height, etc. Comparisons between the theoretical prediction and the calculated results from both the model used in this study and the model of Legg and Raupach (1982) support the author's approach in which vertical velocity variance is taken to be height dependent. For practical purposes, the new random-walk model has greatly improved the accuracy of predicting longitudinal deposition of heavy particles compared to that of the traditional Gaussian model. Experiments with more release heights and larger differences of particle fall velocity are suggested in order to further confirm the findings.

  20. Respirable Particle Transport from Surfaces by Shock Waves

    NASA Astrophysics Data System (ADS)

    Truman, C. R.; Vorobieff, P.; Conroy, J.; Wayne, P.; White, R.; Anderson, M.; Kumar, S.

    2011-11-01

    Resuspension of particles from planar surfaces was studied in a shock tube. Respirable particles (aerodyn. diam. <=5 μm) and slightly larger non-respirable particles were tested on smooth and rough surfaces at Mach 1.2 to 2.0. Particles of specified size were deposited on substrates of prescribed roughness. Surface roughness and particle-surface adhesion forces were quantified by atomic force microscopy. Alkylthiol self assembled monolayers (SAMs) were applied to precisely control surface roughness and surface chemistry. The advection of particles initially at rest on the surface by the rapidly accelerated flow were measured by Mie scattering. An ultra-high-speed digital camera with pulsed laser sheet illumination enables time-resolved particle transport diagnostics. Although particles are initially swept off a smooth surface with greater ease, cloud propagation speed is higher for a rough surface. At late times the cloud height is greater for a rough surface so that particles end up in a faster region of the boundary layer. Because our respirable and non-respirable particle size distributions overlap, further study is required. Shear-driven Kelvin-Helmholtz vortices clearly visible in some images likely play a prominent role in particle transport. Supported by DTRA Threat Agent Science, Agent Characterization.

  1. Influence of particle surface roughness on creeping granular motion.

    PubMed

    Sheng, Li-Tsung; Chang, Wei-Ching; Hsiau, Shu-San

    2016-07-01

    A core is formed at the center of a quasi-two-dimensional rotating drum filled more than half with granular material. The core rotates slightly faster than the drum (precession) and decreases in radius over time (erosion) due to the granular creeping motion that occurs below the freely flowing layer. This paper focuses on the effect of the surface roughness of particles on core dynamics, core precession, and core erosion. Two different surface roughness of glass particles having the same diameter were used in the experiments. The surface structures of the particles were quantitatively compared by measuring the coefficients of friction and using a simple image contrast method. The experiments were performed with five different filling levels in a 50-cm-diameter rotating drum. According to the results, core precession and core erosion are both dependent on the particle surface roughness. Core precession becomes weaker and erosion becomes stronger when using particles having a rough surface in the experiments. To explain the physics of core dynamics, the particles' surface roughness effect on the freely flowing layer and the creeping motion region were also investigated. The granular bed velocity field, maximum flowing layer depth δ, shear rate in the flowing layer γ[over ̇], and the creeping region decay constant y_{0} were also calculated in this paper. The effect of the particles' surface roughness on these physical variables well illustrates the physics of core dynamics and creeping granular motion.

  2. Influence of particle surface roughness on creeping granular motion

    NASA Astrophysics Data System (ADS)

    Sheng, Li-Tsung; Chang, Wei-Ching; Hsiau, Shu-San

    2016-07-01

    A core is formed at the center of a quasi-two-dimensional rotating drum filled more than half with granular material. The core rotates slightly faster than the drum (precession) and decreases in radius over time (erosion) due to the granular creeping motion that occurs below the freely flowing layer. This paper focuses on the effect of the surface roughness of particles on core dynamics, core precession, and core erosion. Two different surface roughness of glass particles having the same diameter were used in the experiments. The surface structures of the particles were quantitatively compared by measuring the coefficients of friction and using a simple image contrast method. The experiments were performed with five different filling levels in a 50-cm-diameter rotating drum. According to the results, core precession and core erosion are both dependent on the particle surface roughness. Core precession becomes weaker and erosion becomes stronger when using particles having a rough surface in the experiments. To explain the physics of core dynamics, the particles' surface roughness effect on the freely flowing layer and the creeping motion region were also investigated. The granular bed velocity field, maximum flowing layer depth δ , shear rate in the flowing layer γ ˙, and the creeping region decay constant y0 were also calculated in this paper. The effect of the particles' surface roughness on these physical variables well illustrates the physics of core dynamics and creeping granular motion.

  3. Influence of particle surface roughness on creeping granular motion.

    PubMed

    Sheng, Li-Tsung; Chang, Wei-Ching; Hsiau, Shu-San

    2016-07-01

    A core is formed at the center of a quasi-two-dimensional rotating drum filled more than half with granular material. The core rotates slightly faster than the drum (precession) and decreases in radius over time (erosion) due to the granular creeping motion that occurs below the freely flowing layer. This paper focuses on the effect of the surface roughness of particles on core dynamics, core precession, and core erosion. Two different surface roughness of glass particles having the same diameter were used in the experiments. The surface structures of the particles were quantitatively compared by measuring the coefficients of friction and using a simple image contrast method. The experiments were performed with five different filling levels in a 50-cm-diameter rotating drum. According to the results, core precession and core erosion are both dependent on the particle surface roughness. Core precession becomes weaker and erosion becomes stronger when using particles having a rough surface in the experiments. To explain the physics of core dynamics, the particles' surface roughness effect on the freely flowing layer and the creeping motion region were also investigated. The granular bed velocity field, maximum flowing layer depth δ, shear rate in the flowing layer γ[over ̇], and the creeping region decay constant y_{0} were also calculated in this paper. The effect of the particles' surface roughness on these physical variables well illustrates the physics of core dynamics and creeping granular motion. PMID:27575202

  4. Determination of physical and dynamic properties of suspended particles in water column with ultrasonic scanning in between the water surface and stable sediment layer.

    NASA Astrophysics Data System (ADS)

    Acar, Dursun; Alpar, Bedri; Ozeren, Sinan; Cagatay, Namık; Sari, Erol; Vardar, Denizhan; Eris, Kadir

    2015-04-01

    The behavior of seafloor sediment with its water column should be known against any occurrences of anoxic or oxic conditions. The most important ones of these conditions are possible leakage of natural gas or escape of liquids from sediment. On the basis of combined solid/liquid flow dynamics in sedimentation, such kind of events can change, even in an effective manner, the dynamic movements of molecules and their cumulative mass of particules, i.e. the suspended materials. The deployment of suitable sediment traps or ultrasonic transducers somewhere in the water column are not easy attempts in order to obtain useful information about the state of suspended materials during sedimentation. These are usually bulky instruments; therefore they may behave like an anti-move suppresser on the particles moving in the float direction, in oxic and anoxic manner. These instruments, on the other hand, may cover the effects of diffusive flow or bubble formed gas and fluid escape from the sediment surface into the water column. Ultrasonic scanners, however, are able to make observations in a remote manner, without affecting such artificial events. Our field trials were successfully completed at the historical estuary called Halic of Marmara sea . The physical properties; such as the velocity of particles, their travel directions, their dimensions and the ability to observe anti-compositor crushes of shock waves of the bubbles are only a few of these observations in natural ambience. The most important problem solved about water pressure during 3 atmosphere . The sensor has been tested successfully few times. We used the ''High voltage electric isolator oil filling'' to the inside of the scanner for pressure equalization between outer side and inner body of probe at a depth of (20 meters) beneath the sea surface . The transmitted signals by the planar crystal of the transducer become weaker under the pressure of overlying water column in depths. Our efforts are now focused on the

  5. Friction microprobe investigation of particle layer effects on sliding friction

    SciTech Connect

    Blau, P.J.

    1993-01-01

    Interfacial particles (third-bodies), resulting from wear or external contamination, can alter and even dominate the frictional behavior of solid-solid sliding in the absence of effective particle removal processes (e.g., lubricant flow). A unique friction microprobe, developed at Oak Ridge National Laboratory, was used to conduct fine- scale friction studies using 1.0 mm diameter stainless steel spheres sliding on several sizes of loose layers of fine aluminum oxide powders on both aluminum and alumina surfaces. Conventional, pin-on-disk experiments were conducted to compare behavior with the friction microprobe results. The behavior of the relatively thick particle layers was found to be independent of the nature of underlying substrate, substantiating previous work by other investigators. The time-dependent behavior of friction, for a spherical macrocontact starting from rest, could generally be represented by a series of five rather distinct phases involving static compression, slider breakaway, transition to steady state, and dynamic layer instability. A friction model for the steady state condition, which incorporates lamellar powder layer behavior, is described.

  6. Carbides composite surface layers produced by (PTA)

    NASA Astrophysics Data System (ADS)

    Tajoure, Meloud; Tajouri, Ali; Abuzriba, Mokhtar; Akreem, Mosbah

    2013-12-01

    The plasma transferred arc technique was applied to deposit a composite layer of nickel base with tungsten carbide in powder form on to surface of low alloy steel 18G2A type according to polish standard. Results showed that, plasma transferred arc hard facing process was successfully conducted by using Deloro alloy 22 plus tungsten carbide powders. Maximum hardness of 1489 HV and minimum dilution of 8.4 % were achieved by using an arc current of 60 A. However, when the current was further increased to 120 A & the dilution increases with current increase while the hardness decreases. Microstructure of the nickel base deposit with tungsten carbide features uniform distribution of reinforcement particles with regular grain shape half - dissolved in the matrix.

  7. Carbides composite surface layers produced by (PTA)

    SciTech Connect

    Tajoure, Meloud; Tajouri, Ali E-mail: dr.mokhtarphd@yahoo.com; Abuzriba, Mokhtar E-mail: dr.mokhtarphd@yahoo.com; Akreem, Mosbah

    2013-12-16

    The plasma transferred arc technique was applied to deposit a composite layer of nickel base with tungsten carbide in powder form on to surface of low alloy steel 18G2A type according to polish standard. Results showed that, plasma transferred arc hard facing process was successfully conducted by using Deloro alloy 22 plus tungsten carbide powders. Maximum hardness of 1489 HV and minimum dilution of 8.4 % were achieved by using an arc current of 60 A. However, when the current was further increased to 120 A and the dilution increases with current increase while the hardness decreases. Microstructure of the nickel base deposit with tungsten carbide features uniform distribution of reinforcement particles with regular grain shape half - dissolved in the matrix.

  8. Permeability changes in layered sediments: impact of particle release.

    PubMed

    Blume, Theresa; Weisbrod, Noam; Selker, John S

    2002-01-01

    One of the mechanisms of sudden particle release from grain surfaces in natural porous media is a decrease in salt concentration of the permeating fluid to below the critical salt concentration. Particle release can cause a change in hydraulic conductivity of the matrix, either by washing out the fines and thus increasing the pore sizes or by the plugging of pore constrictions. The phenomenon of permeability changes as a result of particle detachment was investigated in a series of column experiments. Coarse and fine sediments from the Hanford Formation in southeast Washington were tested. Columns were subject to a pulse of highly saline solution (NaNO3) followed by a fresh water shock causing particle release. Outflow rates and changes in hydraulic head as well as electric conductivity and pH were monitored over time. No permeability decrease occurred within the coarse matrix alone. However, when a thin layer of fine sediment was embedded within the coarse material (mimicking field conditions at the Hanford site), permeability irreversibly decreased to 10% to 20% of the initial value. Evidence suggests that most of this permeability decrease was a result of particles detached within the fine layer and its subsequent clogging. An additional observation was a sudden increase in pH in the outflow solution, generated in situ during the fresh water shock. Because layered systems are common in natural settings, our results suggest that alteration between sodium solution and fresh water can lead to particle release and subsequently reduce the overall permeability of the matrix. PMID:12236259

  9. Correlation studies on surface particle detection methods

    NASA Technical Reports Server (NTRS)

    Peterson, Ronald V.; White, James C.

    1988-01-01

    The accurate determination of dust levels on optical surfaces is necessary to assess sensor system performance. A comparison study was made on several particle measurement methods including those based on direct imaging and light scattering. The effectiveness of removing the particles from the surface prior to determining particle size distributions was also assessed. These studies revealed that some methods, especially those requiring particle removal before analysis, are subject to large systematic errors affecting particle size distributions. Thus, an understanding of the particle measurement methods employed is necessary before any surface cleanliness or obstruction value assignments are accepted as true representations of an optical surface contamination condition.

  10. Specific zeta-potential response of layer-by-layer coated colloidal particles triggered by polyelectrolyte ion interactions.

    PubMed

    Irigoyen, J; Moya, S E; Iturri, J J; Llarena, I; Azzaroni, O; Donath, E

    2009-04-01

    The zeta-potential of PSS/PAH and PSS/PDADMAC coated silica particles was studied in the presence of ClO4(-) and H2PO4(-) salts. In the presence of ClO4(-), layer-by-layer (LbL) coated silica particles with PDADMAC as the top layer show a reversal in the surface charge with increasing salt concentration but remain positive in phosphate solutions. LbL particles with PAH as the top layer become, however, negative in the presence of H2PO4(-) but retain their positive charge in the presence of ClO4(-). Charge reversal was explained by specific interaction of ClO4(-) ions with the quaternary amine groups and of H2PO4(-) with the primary amines through hydrogen bonding. Atomic force microscopy (AFM) and quartz crystal microbalance with dissipation (QCM-D) were employed to study the corresponding layer stability on planar surfaces.

  11. Particle-Surface Interaction Model and Method of Determining Particle-Surface Interactions

    NASA Technical Reports Server (NTRS)

    Hughes, David W. (Inventor)

    2012-01-01

    A method and model of predicting particle-surface interactions with a surface, such as the surface of a spacecraft. The method includes the steps of: determining a trajectory path of a plurality of moving particles; predicting whether any of the moving particles will intersect a surface; predicting whether any of the particles will be captured by the surface and/or; predicting a reflected trajectory and velocity of particles reflected from the surface.

  12. Uncertainties in Surface Layer Modeling

    NASA Astrophysics Data System (ADS)

    Pendergrass, W.

    2015-12-01

    A central problem for micrometeorologists has been the relationship of air-surface exchange rates of momentum and heat to quantities that can be predicted with confidence. The flux-gradient profile developed through Monin-Obukhov Similarity Theory (MOST) provides an integration of the dimensionless wind shear expression where is an empirically derived expression for stable and unstable atmospheric conditions. Empirically derived expressions are far from universally accepted (Garratt, 1992, Table A5). Regardless of what form of these relationships might be used, their significance over any short period of time is questionable since all of these relationships between fluxes and gradients apply to averages that might rarely occur. It is well accepted that the assumption of stationarity and homogeneity do not reflect the true chaotic nature of the processes that control the variables considered in these relationships, with the net consequence that the levels of predictability theoretically attainable might never be realized in practice. This matter is of direct relevance to modern prognostic models which construct forecasts by assuming the universal applicability of relationships among averages for the lower atmosphere, which rarely maintains an average state. Under a Cooperative research and Development Agreement between NOAA and Duke Energy Generation, NOAA/ATDD conducted atmospheric boundary layer (ABL) research using Duke renewable energy sites as research testbeds. One aspect of this research has been the evaluation of legacy flux-gradient formulations (the ϕ functions, see Monin and Obukhov, 1954) for the exchange of heat and momentum. At the Duke Energy Ocotillo site, NOAA/ATDD installed sonic anemometers reporting wind and temperature fluctuations at 10Hz at eight elevations. From these observations, ϕM and ϕH were derived from a two-year database of mean and turbulent wind and temperature observations. From this extensive measurement database, using a

  13. Nanoshells made easy: improving Au layer growth on nanoparticle surfaces.

    PubMed

    Brinson, Bruce E; Lassiter, J Britt; Levin, Carly S; Bardhan, Rizia; Mirin, Nikolay; Halas, Naomi J

    2008-12-16

    The growth of a continuous, uniform Au layer on a dielectric nanoparticle is the critical step in the synthesis of nanoparticles such as nanoshells or nanorice, giving rise to their unique geometry-dependent plasmon resonant properties. Here, we report a novel, streamlined method for Au layer metallization on prepared nanoparticle surfaces using carbon monoxide as the reducing agent. This approach consistently yields plasmonic nanoparticles with highly regular shell layers and is immune to variations in precursor or reagent preparation. Single particle spectroscopy combined with scanning electron microscopy reveal that thinner, more uniform shell layers with correspondingly red-shifted optical resonances are achievable with this approach. PMID:19360963

  14. Water molecules orientation in surface layer

    NASA Astrophysics Data System (ADS)

    Klingo, V. V.

    2000-08-01

    The water molecules orientation has been investigated theoretically in the water surface layer. The surface molecule orientation is determined by the direction of a molecule dipole moment in relation to outward normal to the water surface. Entropy expressions of the superficial molecules in statistical meaning and from thermodynamical approach to a liquid surface tension have been found. The molecules share directed opposite to the outward normal that is hydrogen protons inside is equal 51.6%. 48.4% water molecules are directed along to surface outward normal that is by oxygen inside. A potential jump at the water surface layer amounts about 0.2 volts.

  15. Laser-Based Transient Surface Acceleration of Thermoelastic Layers

    NASA Astrophysics Data System (ADS)

    CETINKAYA, CETIN; WU, CUNLI; LI, CHEN

    2000-03-01

    The removal of particles from elastic substrates has been an important practical problem in the electronics industry especially as the sizes of electronic units shrink. In recent years, there has been an interest in removingsubmicron level particles from surfaces. The use of traditional surface cleaning methods, such as ultrasonically induced fluid flow, vibrational methods, centrifugal techniques, is limited to particles that require surface acceleration lower than 107m/s2. For the effective removal of submicron particles, a higher level surface acceleration is needed since the adhesion forces (mainly van der Waals force for dry surfaces) are related to the particle size and increase approximately linearly as the characteristic radius of small particles that are to be removed decreases. In current work, based on the generalized dynamic theory of thermoelasticity reported, a transfer matrix formulation including the second sound effect is developed for a thermoelastic layer. The transfer matrix for axisymmetric wave propagation in a thermoelastic layer is obtained by adopting a double integral transform approach. The second sound effect is included to eliminate the thermal wave travelling with infinite velocity as predicted by the diffusion heat transfer model, and, consequently, the immediate arrival of waves. Using the current formulation and the periodic systems framework, a transfer function formulation for calculating the accelerations is developed for transient analysis. A double integral transform inversion method is used for transient response calculations. Acceleration levels, sufficient for submicron particle removal, are reported. Various processes such as thermoelastic stresses, surface evaporation, and optical breakdown may be responsible for surface acceleration components and particle removal. In current work, only the surface acceleration due to transient thermoelastic wave propagation is under investigation.

  16. Reactor concepts for atomic layer deposition on agitated particles: A review

    SciTech Connect

    Longrie, Delphine Deduytsche, Davy; Detavernier, Christophe

    2014-01-15

    The number of possible applications for nanoparticles has strongly increased in the last decade. For many applications, nanoparticles with different surface and bulk properties are necessary. A popular surface modification technique is coating the particle surface with a nanometer thick layer. Atomic layer deposition (ALD) is known as a reliable method for depositing ultrathin and conformal coatings. In this article, agitation or fluidization of the particles is necessary for performing ALD on (nano)particles. The principles of gas fluidization of particles will be outlined, and a classification of the gas fluidization behavior of particles based on their size and density will be given. Following different reactor concepts that have been designed to conformally coat (nano)particles with ALD will be described, and a concise overview will be presented of the work that has been performed with each of them ending with a concept reactor for performing spatial ALD on fluidized particles.

  17. Enrichment and association of lead and bacteria at particulate surfaces in a salt-marsh surface layer

    USGS Publications Warehouse

    Harvey, R.W.; Lion, Leonard W.; Young, L.Y.; Leckie, J.O.

    1982-01-01

    The particle-laden surface layer (approx 150-370 mu m) and subsurface waters of a South San Francisco Bay salt marsh were sampled over 2 tidal cycles and analyzed for particle numbers and particulate-associated and total concentrations of Pb and bacteria. Laboratory studies examined the ability of a bacterial isolate from the surface layer and a bacterial 'film-former' to sorb Pb at environmentally significant concentrations in seawater. Degrees by which Pb concentrated in the surface layer relative to the subsurface strongly correlated with enrichments of surface layer bacteria (bacterioneuston). A significant fraction of the bacterioneuston and surface layer Pb were associated with particles. Particle-bound bacterioneuston may interact with Pb at particulate surfaces in this microenvironment.

  18. Particle generation by ultraviolet-laser ablation during surface decontamination.

    PubMed

    Lee, Doh-Won; Cheng, Meng-Dawn

    2006-11-01

    A novel photonic decontamination method was developed for removal of pollutants from material surfaces. Such a method relies on the ability of a high-energy laser beam to ablate materials from a contaminated surface layer, thus producing airborne particles. In this paper, the authors presented the results obtained using a scanning mobility particle sizer (SMPS) system and an aerosol particle sizer (APS). Particles generated by laser ablation from the surfaces of cement, chromium-embedded cement, and alumina were experimentally investigated. Broad particle distributions from nanometer to micrometer in size were measured. For stainless steel, virtually no particle > 500 nm in aerodynamic size was detected. The generated particle number concentrations of all three of the materials were increased as the 266-nm laser fluence (millijoules per square centimeter) increased. Among the three materials tested, cement was found to be the most favorable for particle removal, alumina next, and stainless steel the least. Chromium (dropped in cement) showed almost no effects on particle production. For all of the materials tested except for stainless steel, bimodal size distributions were observed; a smaller mode peaked at approximately 50-70 nm was detected by SMPS and a larger mode (peaked at approximately 0.70-0.85 microm) by APS. Based on transmission electron microscopy observations, the authors concluded that particles in the range of 50-70 nm were aggregates of primary particles, and those of size larger than a few hundred nanometers were produced by different mechanisms, for example, massive object ejection from the material surfaces.

  19. Stable water layers on solid surfaces.

    PubMed

    Hong, Ying-Jhan; Tai, Lin-Ai; Chen, Hung-Jen; Chang, Pin; Yang, Chung-Shi; Yew, Tri-Rung

    2016-02-17

    Liquid layers adhered to solid surfaces and that are in equilibrium with the vapor phase are common in printing, coating, and washing processes as well as in alveoli in lungs and in stomata in leaves. For such a liquid layer in equilibrium with the vapor it faces, it has been generally believed that, aside from liquid lumps, only a very thin layer of the liquid, i.e., with a thickness of only a few nanometers, is held onto the surface of the solid, and that this adhesion is due to van der Waals forces. A similar layer of water can remain on the surface of a wall of a microchannel after evaporation of bulk water creates a void in the channel, but the thickness of such a water layer has not yet been well characterized. Herein we showed such a water layer adhered to a microchannel wall to be 100 to 170 nm thick and stable against surface tension. The water layer thickness was measured using electron energy loss spectroscopy (EELS), and the water layer structure was characterized by using a quantitative nanoparticle counting technique. This thickness was found for channel gap heights ranging from 1 to 5 μm. Once formed, the water layers in the microchannel, when sealed, were stable for at least one week without any special care. Our results indicate that the water layer forms naturally and is closely associated only with the surface to which it adheres. Our study of naturally formed, stable water layers may shed light on topics from gas exchange in alveoli in biology to the post-wet-process control in the semiconductor industry. We anticipate our report to be a starting point for more detailed research and understanding of the microfluidics, mechanisms and applications of gas-liquid-solid systems. PMID:26856872

  20. Layer Control of WSe2 via Selective Surface Layer Oxidation.

    PubMed

    Li, Zhen; Yang, Sisi; Dhall, Rohan; Kosmowska, Ewa; Shi, Haotian; Chatzakis, Ioannis; Cronin, Stephen B

    2016-07-26

    We report Raman and photoluminescence spectra of mono- and few-layer WSe2 and MoSe2 taken before and after exposure to a remote oxygen plasma. For bilayer and trilayer WSe2, we observe an increase in the photoluminescence intensity and a blue shift of the photoluminescence peak positions after oxygen plasma treatment. The photoluminescence spectra of trilayer WSe2 exhibit features of a bilayer after oxygen plasma treatment. Bilayer WSe2 exhibits features of a monolayer, and the photoluminescence of monolayer WSe2 is completely absent after the oxygen plasma treatment. These changes are observed consistently in more than 20 flakes. The mechanism of the changes observed in the photoluminescence spectra of WSe2 is due to the selective oxidation of the topmost layer. As a result, N-layer WSe2 is reduced to N-1 layers. Raman spectra and AFM images taken from the WSe2 flakes before and after the oxygen treatment corroborate these findings. Because of the low kinetic energy of the oxygen radicals in the remote oxygen plasma, the oxidation is self-limiting. By varying the process duration from 1 to 10 min, we confirmed that the oxidation will only affect the topmost layer of the WSe2 flakes. X-ray photoelectron spectroscopy shows that the surface layer WOx of the sample can be removed by a quick dip in KOH solution. Therefore, this technique provides a promising way of controlling the thickness of WSe2 layer by layer. PMID:27391161

  1. Limiting diffusion current at rotating disk electrode with dense particle layer.

    PubMed

    Weroński, P; Nosek, M; Batys, P

    2013-09-28

    Exploiting the concept of diffusion permeability of multilayer gel membrane and porous multilayer we have derived a simple analytical equation for the limiting diffusion current at rotating disk electrode (RDE) covered by a thin layer with variable tortuosity and porosity, under the assumption of negligible convection in the porous film. The variation of limiting diffusion current with the porosity and tortuosity of the film can be described in terms of the equivalent thickness of stagnant solution layer, i.e., the average ratio of squared tortuosity to porosity. In case of monolayer of monodisperse spherical particles, the equivalent layer thickness is an algebraic function of the surface coverage. Thus, by means of cyclic voltammetry of RDE with a deposited particle monolayer we can determine the monolayer surface coverage. The effect of particle layer adsorbed on the surface of RDE increases non-linearly with surface coverage. We have tested our theoretical results experimentally by means of cyclic voltammetry measurements of limiting diffusion current at the glassy carbon RDE covered with a monolayer of 3 μm silica particles. The theoretical and experimental results are in a good agreement at the surface coverage higher than 0.7. This result suggests that convection in a monolayer of 3 μm monodisperse spherical particles is negligibly small, in the context of the coverage determination, in the range of very dense particle layers. PMID:24089793

  2. Mean motion and trajectories of heavy particles falling through a boundary layer

    SciTech Connect

    Stout, J.E.; Arya, S.P.

    1994-12-31

    As particles fall through a turbulent boundary layer they experience a rather complex and unique time series of aerodynamic forces and, thus, each individual particle follows a rather complex and unique trajectory to the surface. For sufficiently large and heavy particles, the turbulence induced particle motion can be thought of as a small perturbation superimposed on the mean trajectory. By ignoring the turbulent contribution to particle motion it is possible to calculate the trajectory of a particle due to the mean flow alone. The mean trajectory provides an estimate of the ensemble-averaged path of a set of particles released from a given point in the atmosphere. The effect of turbulence on individual particle trajectories, the distribution of particle displacements from the mean trajectory, and their deposition patterns on the surface will be investigated in a separate study, using a random walk model.

  3. Surface layer characterization at Paranal Observatory

    NASA Astrophysics Data System (ADS)

    Lombardi, G.; Melnick, J.; Hinojosa Goñi, R. H.; Navarrete, J.; Sarazin, M.; Berdja, A.; Tokovinin, A.; Wilson, R.; Osborn, J.; Butterley, T.; Shepherd, H.

    2010-07-01

    In this paper the Paranal Surface Layer characterization is presented. Causes, physics and behavior of the SL above Paranal surface are discussed. The analysis is developed using data from different turbulence profilers operated during several campaigns between 2007 and 2009. Instruments used are SL-SLODAR, DIMM, Elevated DIMM, MASS, Lunar Scintillometer and Ultrasonic Anemometers with temperature sensors positioned at different strategic heights.

  4. Algorithm for Computing Particle/Surface Interactions

    NASA Technical Reports Server (NTRS)

    Hughes, David W.

    2009-01-01

    An algorithm has been devised for predicting the behaviors of sparsely spatially distributed particles impinging on a solid surface in a rarefied atmosphere. Under the stated conditions, prior particle-transport models in which (1) dense distributions of particles are treated as continuum fluids; or (2) sparse distributions of particles are considered to be suspended in and to diffuse through fluid streams are not valid.

  5. Particle motion inside Ekman and Bödewadt boundary layers

    NASA Astrophysics Data System (ADS)

    Duran Matute, Matias; van der Linden, Steven; van Heijst, Gertjan

    2014-11-01

    We present results from both laboratory experiments and numerical simulations of the motion of heavy particles inside Ekman and Bödewadt boundary layers. The particles are initially at rest on the bottom of a rotating cylinder filled with water and with its axis parallel to the axis of rotation. The particles are set into motion by suddenly diminishing the rotation rate and the subsequent creation of a swirl flow with the boundary layer above the bottom plate. We consider both spherical and non-spherical particles with their size of the same order as the boundary layer thickness. It was found that the particle trajectories define a clear logarithmic spiral with its shape depending on the different parameters of the problem. Numerical simulations show good agreement with experiments and help explain the motion of the particles. This research is funded by NWO (the Netherlands) through the VENI Grant 863.13.022.

  6. Surface layer effects on waste glass corrosion

    SciTech Connect

    Feng, X.

    1993-12-31

    Water contact subjects waste glass to chemical attack that results in the formation of surface alteration layers. Two principal hypotheses have been advanced concerning the effect of surface alteration layers on continued glass corrosion: (1) they act as a mass transport barrier and (2) they influence the chemical affinity of the glass reaction. In general, transport barrier effects have been found to be less important than affinity effects in the corrosion of most high-level nuclear waste glasses. However, they can be important under some circumstances, for example, in a very alkaline solution, in leachants containing Mg ions, or under conditions where the matrix dissolution rate is very low. The latter suggests that physical barrier effect may affect the long-term glass dissolution rate. Surface layers influence glass reaction affinity through the effects of the altered glass and secondary phases on the solution chemistry. The reaction affinity may be controlled by various precipitates and crystalline phases, amorphous silica phases, gel layer, or all the components of the glass. The surface alteration layers influence radionuclide release mainly through colloid formation, crystalline phase incorporation, and gel layer retention. This paper reviews current understanding and uncertainties.

  7. Paracrystalline surface layers of dairy propionibacteria.

    PubMed Central

    Lortal, S; Rouault, A; Cesselin, B; Sleytr, U B

    1993-01-01

    We examined 70 dairy propionibacteria and detected a crystalline surface layer (S-layer) in only 2 organisms (Propionibacterium freudenreichii CNRZ 722 and Propionibacterium jensenii CNRZ 87) by freeze-etching and sodium dodecyl sulfate-polyacrylamide electrophoresis (SDS-PAGE). Both S-layers exhibited oblique (p2) symmetry (a = 9.9 nm; b = 5.4 nm; gamma = 80 degrees) and completely covered the cell surface. Treatment for 15 min at the ambient temperature with 5 M guanidine hydrochloride or acidic conditions (250 mM ammonium acetate, pH 2.7) efficiently extracted the S-layer protein from intact cells of strain CNRZ 722, whereas treatment with 5 M guanidine hydrochloride at 100 degrees C for 15 min was necessary to isolate the S-layer protein of strain CNRZ 87. The precipitates obtained after dialysis of the extracting agents produced no regular patterns. The molecular masses of the two S-layer proteins, as estimated by SDS-PAGE, were 58.5 kDa for the strain CNRZ 722 and 67.3 kDa for the strain CNRZ 87. Mass spectrometry of the isolated S-layer protein of strain CNRZ 722 gave a molecular mass value close to the expected value (56,533 Da). The N-terminal sequences of the two purified S-layer proteins differed, as did their amino acid compositions, except that the same high hydrophobic amino acid content (52%) was observed. Images PMID:8304753

  8. Charged particles constrained to a curved surface

    NASA Astrophysics Data System (ADS)

    Müller, Thomas; Frauendiener, Jörg

    2013-01-01

    We study the motion of charged particles constrained to arbitrary two-dimensional curved surfaces but interacting in three-dimensional space via the Coulomb potential. To speed up the interaction calculations, we use the parallel compute capability of the Compute Unified Device Architecture of today's graphics boards. The particles and the curved surfaces are shown using the Open Graphics Library. This paper is intended to give graduate students, who have basic experiences with electrostatics and the Lagrangian formalism, a deeper understanding of charged particle interactions and a short introduction of how to handle a many particle system using parallel computing on a single home computer.

  9. Characterization of carbides composite surface layers produced by PTA

    NASA Astrophysics Data System (ADS)

    Tajoure, M.; Tajouri, A.

    2015-03-01

    Composite surface layer of nickel base with titanium carbide in powder form was deposited on to surface of low alloy steel 18G2A type according to polish standard by using plasma transferred arc technique. Results showed that, plasma transferred arc hardfacin process was successfully conducted by using PMNICr50P alloy plus titanium carbide powders. Maximum hardness of 754 HV and minimum dilution of 4.6 % were achieved by using an arc current of 80 A. However, when the current was further increased to 120 A& the dilution increases with current increase while the hardness decreases. Microstructure of the nickel base with titanium carbide feature uniform distribution of reinforcement particles with irregular grain shape and relatively small particles size, and regular boundary line between the substrate and over layer with presence of black area along the boundary line. A few micro - porosities are located in the matrix.

  10. Surface free energy of polyimide aligning layers

    NASA Astrophysics Data System (ADS)

    Borycki, Jerzy; Okulska-Bozek, Malgorzata

    2000-05-01

    Polyimides from four selected dianhydrides and seven diamines were synthesized by two-step polycondensation method. During the first step 10% solutions of poly(amic acid)s in N,N-dimethylformamide and 1-methyl-2-pyrrolidinone were obtained. The thin polyimide layers on soda glass were prepared by thermal cyclodehydration. Contact angles of series of standard liquids for tested polyimide films were measured. The values of surface free energy and its components were calculated accordingly to Zisman, Owens et al. and van Oss equations. Some correlation between the surface properties and the chemical structure of polyimide aligning layers were presented.

  11. Polymer surface treatment with particle beams

    DOEpatents

    Stinnett, Regan W.; VanDevender, J. Pace

    1999-01-01

    A polymer surface and near surface treatment process produced by irradiation with high energy particle beams. The process is preferably implemented with pulsed ion beams. The process alters the chemical and mechanical properties of the polymer surface in a manner useful for a wide range of commercial applications.

  12. Polymer surface treatment with particle beams

    DOEpatents

    Stinnett, R.W.; VanDevender, J.P.

    1999-05-04

    A polymer surface and near surface treatment process produced by irradiation with high energy particle beams is disclosed. The process is preferably implemented with pulsed ion beams. The process alters the chemical and mechanical properties of the polymer surface in a manner useful for a wide range of commercial applications. 16 figs.

  13. Extending the Diffuse Layer Model of Surface Acidity Constant Behavior: IV. Diffuse Layer Charge/Potential Relationships

    EPA Science Inventory

    Most current electrostatic surface complexation models describing ionic binding at the particle/water interface rely on the use of Poisson - Boltzmann (PB) theory for relating diffuse layer charge densities to diffuse layer electrostatic potentials. PB theory is known to contain ...

  14. Transition induced by fixed and freely convecting spherical particles in laminar boundary layers

    NASA Astrophysics Data System (ADS)

    Petrie, H. L.; Morris, P. J.; Bajwa, A. R.; Vincent, D. C.

    1993-08-01

    An experimental and analytical study of aspects of transition induced by disturbances from spherical particles in laminar boundary layers is discussed. The generation of turbulent wedges by fixed spherical particles in a laminar boundary layer on or near the surface of a flat plate is considered experimentally using flow visualization with fluorescent dye and laser Doppler velocimetry. Turbulent spots generated by freely convecting spherical particles that are released in the freestream to fall into a flat plate laminar boundary layer and impact the plate are also discussed. A combination of dye flow visualization and a video based particle tracking technique was used to study the convecting particle problem. Although the Reynolds number at the critical condition for turbulent wedge generation by fixed particles and turbulent spot generation by convecting particles are similar, transition in these two situations appears to be fundamentally different. The development of a turbulent wedge near the critical condition is a relatively gradual process. In contrast, turbulent spots form relatively quickly after the convecting particles enter the boundary layer and impact the plate. Turbulent wedge formation downstream of a fixed particle results from the destabilization of the near wall flow by the vortical structures shed into particle wake. This shedding process is dominated by periodically shed loop shaped hairpin vortices. Observation of subharmonic oscillations at 1/2 and 1/4 of this shedding frequency suggest that a chaotic route to turbulence by a series of period doubling bifurcations is possible.

  15. Surface structuring of particle laden drops using electric fields

    NASA Astrophysics Data System (ADS)

    Dommersnes, P.; Fossum, J. O.

    2016-07-01

    Emulsion drops readily adsorb particles at their surfaces, which may lead to a fluid or solid layer encapsulating the drop, known as an armored drop. In this review, we discuss how electric fields can be used to manipulate colloidal surface structures, by dielectrophoretic or electro-hydrodynamic mechanisms and we also compare this to related phenomena in lipid bilayer vesicles. The phenomena discussed are important for a wide range of uses of particle laden drops, including emulsion stabilization, Janus or patchy mesocapsule-, scaffold- or other materials-production.

  16. Chaotic particle motion under linear surface waves.

    PubMed

    Bohr, Tomas; Hansen, Jonas Lundbek

    1996-12-01

    We investigate the motion of infinitesimal particles in the flow field inside the fluid under a traveling surface wave. It is shown that, even for two-dimensional waves, a superposition of two or more traveling harmonic waves is enough to generate chaotic particle motion, i.e., Lagrangian chaos. (c) 1996 American Institute of Physics.

  17. Beta particle monitor for surfaces

    DOEpatents

    MacArthur, Duncan W.

    1997-01-01

    A beta radiation detector which is capable of reliably detecting beta radiation emitted from a surface. An electrically conductive signal collector is adjustably mounted inside an electrically conductive enclosure which may define a single large opening for placing against a surface. The adjustable mounting of the electrically conductive signal collector can be based on the distance from the surface or on the expected beta energy range. A voltage source is connected to the signal collector through an electrometer or other display means for creating an electric field between the signal collector and the enclosure. Air ions created by the beta radiation are collected and the current produced is indicated on the electrometer or other display means.

  18. Beta particle monitor for surfaces

    DOEpatents

    MacArthur, D.W.

    1997-10-21

    A beta radiation detector which is capable of reliably detecting beta radiation emitted from a surface. An electrically conductive signal collector is adjustably mounted inside an electrically conductive enclosure which may define a single large opening for placing against a surface. The adjustable mounting of the electrically conductive signal collector can be based on the distance from the surface or on the expected beta energy range. A voltage source is connected to the signal collector through an electrometer or other display means for creating an electric field between the signal collector and the enclosure. Air ions created by the beta radiation are collected and the current produced is indicated on the electrometer or other display means. 2 figs.

  19. The refraction in the atmospheric surface layer

    NASA Astrophysics Data System (ADS)

    Golitsyn, G. S.

    1982-12-01

    An analytical theory of refraction for the atmospheric layer is developed in which the vertical profiles of the refraction are calculated based on the theory of Monin and Obukhov (1954). A similarity parameter is found for the refraction in such conditions. These results are used to clarify the idea of Moroz (1976) that the nearness of the horizon as recorded by the automatic stations on the surface of Venus can be explained by the decrease in the temperature at the very surface of the planet. In addition, several other optical phenomena which occur near the surface of the earth are examined.

  20. Characteristics of the Martian atmosphere surface layer

    NASA Astrophysics Data System (ADS)

    Clow, G. D.; Haberle, R. M.

    Elements of various terrestrial boundary layer models are extended to Mars in order to estimate sensible heat, latent heat, and momentum fluxes within the Martian atmospheric surface ('constant flux') layer. The atmospheric surface layer consists of an interfacial sublayer immediately adjacent to the ground and an overlying fully turbulent surface sublayer where wind-shear production of turbulence dominates buoyancy production. Within the interfacial sublayer, sensible and latent heat are transported by non-steady molecular diffusion into small-scale eddies which intermittently burst through this zone. Both the thickness of the interfacial sublayer and the characteristics of the turbulent eddies penetrating through it depend on whether airflow is aerodynamically smooth or aerodynamically rough, as determined by the Roughness Reynold's number. Within the overlying surface sublayer, similarity theory can be used to express the mean vertical windspeed, temperature, and water vapor profiles in terms of a single parameter, the Monin-Obukhov stability parameter. To estimate the molecular viscosity and thermal conductivity of a CO2-H2O gas mixture under Martian conditions, parameterizations were developed using data from the TPRC Data Series and the first-order Chapman-Cowling expressions; the required collision integrals were approximated using the Lenard-Jones potential. Parameterizations for specific heat and binary diffusivity were also determined. The Brutsart model for sensible and latent heat transport within the interfacial sublayer for both aerodynamically smooth and rough airflow was experimentally tested under similar conditions, validating its application to Martian conditions. For the surface sublayer, the definition of the Monin-Obukhov length was modified to properly account for the buoyancy forces arising from water vapor gradients in the Martian atmospheric boundary layer. It was found that under most Martian conditions, the interfacial and surface

  1. Lunar particle shadows and boundary layer experiment: Plasma and energetic particles on the Apollo 15 and 16 subsatellites

    NASA Technical Reports Server (NTRS)

    Anderson, K. A.; Chase, L. M.; Lin, R. P.; Mccoy, J. E.; Mcguire, R. E.

    1974-01-01

    The lunar particle shadows and boundary layer experiments aboard the Apollo 15 and 16 subsatellites and scientific reduction and analysis of the data to date are discussed with emphasis on four major topics: solar particles; interplanetry particle phenomena; lunar interactions; and topology and dynamics of the magnetosphere at lunar orbit. The studies of solar and interplanetary particles concentrated on the low energy region which was essentially unexplored, and the studies of lunar interaction pointed up the transition from single particle to plasma characteristics. The analysis concentrated on the electron angular distributions as highly sensitive indicators of localized magnetization of the lunar surface. Magnetosphere experiments provided the first electric field measurements in the distant magnetotail, as well as comprehensive low energy particle measurements at lunar distance.

  2. Electronic structure of bacterial surface protein layers

    SciTech Connect

    Maslyuk, Volodymyr V.; Mertig, Ingrid; Bredow, Thomas; Mertig, Michael; Vyalikh, Denis V.; Molodtsov, Serguei L.

    2008-01-15

    We report an approach for the calculation of the electronic density of states of the dried two-dimensional crystalline surface protein layer (S layer) of the bacterium Bacillus sphaericus NCTC 9602. The proposed model is based on the consideration of individual amino acids in the corresponding conformation of the peptide chain which additively contribute to the electronic structure of the entire protein complex. The derived results agree well with the experimental data obtained by means of photoemission (PE), resonant PE, and near-edge x-ray absorption spectroscopy.

  3. Solid-Particle Erosion Behaviour of WC/Ni Composite Clad layers with Different Contents of WC Particles

    NASA Astrophysics Data System (ADS)

    Paul, C. P.; Mishra, S. K.; Tiwari, P.; Kukreja, L. M.

    2013-09-01

    We investigated the solid particle erosion behaviour of WC-reinforced Ni-matrix based laser clad layers to improve the performance of engineering components for potential power plant applications. WC-reinforced Ni-matrix based laser clad layers having various compositions of WC (5, 10 and 15wt%) were deposited on austenitic stainless steel substrates. The laser clad layers were characterised using optical and scanning electron microscopy, microhardness testing and air-jet erosion testing. In solid particle erosion studies using the air-jet erosion tester, the set of testing parameters, including air-erodent compositions, erodent particle velocities and impact angles, was selected by using the Taguchi technique. The morphologies of the worn surfaces were used to predict the wear mechanisms. The results of a microstructural examination of the cross-sections of laser clad revealed a good metallurgical bond between the WC-reinforced Ni matrix and the austenitic stainless steel substrate. Dissociation/partial melting/full melting of WC particles was not observed in the laser clad layers. The microhardness value in the laser cladding zone was between 900-2400 VHN, while it was 230-270 VHN on the substrate. The results of erosion wear studies of the WC-Ni laser clad surface revealed that the erosion behaviour of the WC-Ni laser clad is primarily governed by erodent jet velocity followed by impact angle. The erosion does not much depend on the Ni-concentration in the MMC or the erodent feed rate. The wear signature at the erosion wear surface indicated that the erosion was primarily governed by a ductile erosion mechanism followed by the removal of WC particles from the matrix. The erosion resistance of the Ni-clad layer with WC was found to be at least four times higher than that without WC particles. The quantified contribution of various erosion parameters is useful for function-based design of components with extended service life.

  4. Creation of giant two-dimensional crystal of zinc oxide nanodisk by method of single-particle layer of organo-modified inorganic fine particles.

    PubMed

    Meng, Qi; Honda, Nanami; Uchida, Saki; Hashimoto, Kazuaki; Shibata, Hirobumi; Fujimori, Atsuhiro

    2015-09-01

    In this study, the formation and structure of a single-particle layer of organo-zinc oxide are investigated using surface-pressure-area (π-A) isotherms, out-of-plane X-ray diffraction (XRD) analysis, and atomic force microscopy (AFM). Further, techniques for achieving the solubilization of inorganic fine particles in general solvents have been proposed, and a single-particle layer has been formed using such an inorganic solution as a "spreading solution" for an interfacial film. Surface modification of ZnO is performed using a long-chain carboxylic acid. Accordingly, a regular arrangement of ZnO can be easily achieved in order to overcome the relatively weak van der Walls interactions between inorganic materials. A condensed Langmuir monolayer of these particles is also formed. A multiparticle layered structure is constructed by the Langmuir-Blodgett (LB) technique. Out-of-plane XRD measurement results for a single-particle layer of organo-ZnO clearly show a sharp peak at 42 Å. This peak is attributed to the distance between ZnO layers. The AFM image of this single-particle layer of organo-ZnO shows a particle assembly with a uniform height of 60 nm. These aggregated particles form large two-dimensional crystals. In other words, a regular periodic structure along the c-axis and a condensed single-particle layer had been fabricated using Langmuir and LB techniques.

  5. Equivalent medium theory of layered sphere particle with anisotropic shells

    NASA Astrophysics Data System (ADS)

    Li, Xingcai; Wang, Minzhong; Zhang, Beidou

    2016-08-01

    Researches on the optical properties of small particle have been widely concerned in the atmospheric science, astronomy, astrophysics, biology and medical science. This paper provides an equivalent dielectric theory for the functional graded particle with anisotropic shells, in which inhomogeneous and anisotropic particle was equivalently transformed into a new kind of homogeneous, continuous and isotropic sphere with same size but different permittivity, and then greatly simplify the calculation process of particle's optical property. Meanwhile, the paper also discusses whether the charge on the particle can change the expression of its equivalent permittivity or not. These results proposed in this paper can be used to simulate the electrical, optical properties of layered sphere, it also meet the research requirement in the design of functional graded particles in different subjects.

  6. Distribution of icy particles across Enceladus' surface

    NASA Astrophysics Data System (ADS)

    Jaumann, R.; Stephan, K.; Wagner, R.; Hansen, G. B.; Brown, R. H.; Cassini Vims Science Team

    Compositionally, the surface of Enceladus is build up almost completely by water ice [1]. However, distinct variations in the size of water ice particles are apparent. The Visual and Infrared Mapping Spectrometer [2] observed Enceladus with high spatial resolution during two Cassini flybys in 2005 (orbit 4 and 11). A detailed analysis of the VIMS spectra in comparison to theoretically calculated water ice spectra supports the assumption that almost pure water ice characterizes the surface of Enceladus and that the particle size varies between 0.002 and 0.1mm. Three dis-tinct spectral units can be separated exhibiting different particle sizes which are strongly correlated to surface features. A comparison between the classifications of particle sizes and geological maps of the regions observed during the flybys 4 and 11 demonstrate this result. Our measurements show that the particle size of water ice increases toward younger regions with the largest ones in "fresh" surface material. The smallest particles were generally found in old more or less densely cratered plains and the larger ones in younger tectonically resurfaced areas [4]. The largest particles are concentrated in the so called "tiger stripes" of the south polar area [1,5]. Our findings support the results of [1,7] with amorphous water ice being concen-trated in older terrain due to the longterm exposure to incoming radiation, and crys-talline water ice in the vicinity of the younger resurfaced regions, esp. the South Pole. Amorphization usually goes along with the destruction of water ice particles, resulting in the decrease of mean particle size. Unlike the Galilean satellites, which undergo a daily thermal cycle resulting in the crystallization of ice particles, the surface stays cooler (70K) [6] on Enceladus and the water ice remains in an amor-phous state. In contrast the sulci esp. the "tiger stripes" close to the South Pole are characterized by higher temperature [1,5,6], which leads to the

  7. Particle aggregation with simultaneous surface growth

    SciTech Connect

    pablo.mitchell@cal.Berkeley.EDU

    2003-04-29

    Particle aggregation with simultaneous surface growth was modeled using a dynamic Monte Carlo method. The Monte Carlo algorithm begins in the particle inception zone and constructs aggregates via ensemble-averaged collisions between spheres and deposition of gaseous species on the sphere surfaces. Simulations were conducted using four scenarios. The first, referred to as scenario 0, is used as a benchmark and simulates aggregation in the absence of surface growth. Scenario 1 forces all balls to grow at a uniform rate while scenario 2 only permits them to grow once they have collided and stuck to each other. The last one is a test scenario constructed to confirm conclusions drawn from scenarios 0-2. The transition between the coalescent and the fully-developed fractal aggregation regimes is investigated using shape descriptors to quantify particle geometry. They are used to define the transition between the coalescent and fractal growth regimes. The simulations demonstrate that the morphology of aggregating particles is intimately related to both the surface deposition and particle nucleation rates.

  8. Rebound characteristics for ash particles impacting a planar surface

    NASA Astrophysics Data System (ADS)

    Dong, Ming; Li, Sufen; Han, Jian; Xie, Jun

    2013-06-01

    The formation of ash deposition on the heat transfer tubes in a boiler reduces the heat transfer coefficient by about 25%. Because of these fouling layers, the efficiency with which energy can be absorbed from flue gases is reduced. The growth of ash deposition is strongly dependent on the interaction of the incident particle with the surface of heat transfer tubes. In this study the interaction is modeled as the outcome of collision between an incident fly ash particle and planar surface that represents a heat transfer surface. The present paper focuses on the applicability of the experimental results to indicate the rebound characteristics of fly ash particles impacting a planar surface. This is studied by impaction experiments of fly ash particles from the power plant dust, under various particle diameters and with different velocities (ranging from 0.1 to 20 m/s). The experiments are carried out in an atmospheric column, and using a digital camera system, individual impacts are recorded. Furthermore, the measured coefficient of restitution values can be predicted by a dynamic simulation model.

  9. Actuated cilial layers regulate deposition of microscopic solid particles

    NASA Astrophysics Data System (ADS)

    Ghosh, Rajat; Buxton, Gavin A.; Berk Usta, O.; Balazs, Anna C.; Alexeev, Alexander

    2009-11-01

    We use computational modeling to examine the three-dimensional interactions between oscillating, synthetic cilia and microscopic solid particles in a fluid-filled microchannel. The synthetic cilia are elastic filaments that are tethered to a substrate and are actuated by a sinusoidal force, which is applied to their free ends. The cilia are arranged in a square pattern and a neutrally buoyant particle is initially located between these filaments. Our computational studies reveal that depending on frequency of the beating cilia, the particle can be either driven downwards toward the substrate or driven upwards and expelled into the fluid above the cilial layer. This behavior mimics the performance of biological cilia used by certain marine animals to extract suspended food particles. The findings uncover a new route for controlling the deposition of microscopic particles in microfluidic devices.

  10. Diurnal ocean surface layer model validation

    NASA Technical Reports Server (NTRS)

    Hawkins, Jeffrey D.; May, Douglas A.; Abell, Fred, Jr.

    1990-01-01

    The diurnal ocean surface layer (DOSL) model at the Fleet Numerical Oceanography Center forecasts the 24-hour change in a global sea surface temperatures (SST). Validating the DOSL model is a difficult task due to the huge areas involved and the lack of in situ measurements. Therefore, this report details the use of satellite infrared multichannel SST imagery to provide day and night SSTs that can be directly compared to DOSL products. This water-vapor-corrected imagery has the advantages of high thermal sensitivity (0.12 C), large synoptic coverage (nearly 3000 km across), and high spatial resolution that enables diurnal heating events to be readily located and mapped. Several case studies in the subtropical North Atlantic readily show that DOSL results during extreme heating periods agree very well with satellite-imagery-derived values in terms of the pattern of diurnal warming. The low wind and cloud-free conditions necessary for these events to occur lend themselves well to observation via infrared imagery. Thus, the normally cloud-limited aspects of satellite imagery do not come into play for these particular environmental conditions. The fact that the DOSL model does well in extreme events is beneficial from the standpoint that these cases can be associated with the destruction of the surface acoustic duct. This so-called afternoon effect happens as the afternoon warming of the mixed layer disrupts the sound channel and the propagation of acoustic energy.

  11. Surface roughness scattering in multisubband accumulation layers

    NASA Astrophysics Data System (ADS)

    Fu, Han; Reich, K. V.; Shklovskii, B. I.

    2016-06-01

    Accumulation layers with very large concentrations of electrons where many subbands are filled became recently available due to ionic liquid and other new methods of gating. The low-temperature mobility in such layers is limited by the surface roughness scattering. However, theories of roughness scattering so far dealt only with the small-density single subband two-dimensional electron gas (2DEG). Here we develop a theory of roughness-scattering limited mobility for the multisubband large concentration case. We show that with growing 2D electron concentration n the surface dimensionless conductivity σ /(2 e2/h ) first decreases as ∝n-6 /5 and then saturates as ˜(d aB/Δ2)≫1 , where d and Δ are the characteristic length and height of the surface roughness and aB is the effective Bohr radius. This means that in spite of the shrinkage of the 2DEG thickness and the related increase of the scattering rate the 2DEG remains a good metal.

  12. Are atmospheric surface layer flows ergodic?

    NASA Astrophysics Data System (ADS)

    Higgins, Chad W.; Katul, Gabriel G.; Froidevaux, Martin; Simeonov, Valentin; Parlange, Marc B.

    2013-06-01

    The transposition of atmospheric turbulence statistics from the time domain, as conventionally sampled in field experiments, is explained by the so-called ergodic hypothesis. In micrometeorology, this hypothesis assumes that the time average of a measured flow variable represents an ensemble of independent realizations from similar meteorological states and boundary conditions. That is, the averaging duration must be sufficiently long to include a large number of independent realizations of the sampled flow variable so as to represent the ensemble. While the validity of the ergodic hypothesis for turbulence has been confirmed in laboratory experiments, and numerical simulations for idealized conditions, evidence for its validity in the atmospheric surface layer (ASL), especially for nonideal conditions, continues to defy experimental efforts. There is some urgency to make progress on this problem given the proliferation of tall tower scalar concentration networks aimed at constraining climate models yet are impacted by nonideal conditions at the land surface. Recent advancements in water vapor concentration lidar measurements that simultaneously sample spatial and temporal series in the ASL are used to investigate the validity of the ergodic hypothesis for the first time. It is shown that ergodicity is valid in a strict sense above uniform surfaces away from abrupt surface transitions. Surprisingly, ergodicity may be used to infer the ensemble concentration statistics of a composite grass-lake system using only water vapor concentration measurements collected above the sharp transition delineating the lake from the grass surface.

  13. Double-layer interaction between two plates with hairy surfaces.

    PubMed

    Huang, Haohao; Ruckenstein, Eli

    2004-05-01

    In most theoretical treatments of colloidal particles with hairy surfaces, only the steric effect is taken into account. The steric force is a short-range interaction and acts only when the chains on different particles begin to interpenetrate each other. However, since the hairy chains are extended into the continuous phase, they constrain the orientation of the water molecules near the surface and, as a result, the dielectric constant in that region can become very different from that in the bulk. The low dielectric constant affects the distributions of ion concentrations and the gradient of the electric field. Therefore, the double-layer interactions between two plates with hairy surfaces cannot be calculated on the basis of the classical Gouy-Chapman theory, which involves a uniform dielectric constant in the Poisson-Boltzmann equation. A model which accounts for the difference in dielectric constants in the hairy region and outside that region is therefore proposed. The ion specificity is also taken into account by using Born's expression for the free energy of hydration of ions. The repulsive forces calculated via the Gouy-Chapman theory and via the new model are compared. The hairy region can have a long range effect on the repulsive double-layer interactions.

  14. Modeled heating and surface erosion comparing motile (gas borne) and stationary (surface coating) inert particle additives

    SciTech Connect

    Buckingham, A.C.; Siekhaus, W.J.

    1982-09-27

    The unsteady, non-similar, chemically reactive, turbulent boundary layer equations are modified for gas plus dispersed solid particle mixtures, for gas phase turbulent combustion reactions and for heterogeneous gas-solid surface erosive reactions. The exterior (ballistic core) edge boundary conditions for the solutions are modified to include dispersed particle influences on core propellant combustion-generated turbulence levels, combustion reactants and products, and reaction-induced, non-isentropic mixture states. The wall surface (in this study it is always steel) is considered either bare or coated with a fixed particle coating which is conceptually non-reactive, insulative, and non-ablative. Two families of solutions are compared. These correspond to: (1) consideration of gas-borne, free-slip, almost spontaneously mobile (motile) solid particle additives which influence the turbulent heat transfer at the uncoated steel surface and, in contrast, (2) consideration of particle-free, gas phase turbulent heat transfer to the insulated surface coated by stationary particles. Significant differences in erosive heat transfer are found in comparing the two families of solutions over a substantial range of interior ballistic flow conditions. The most effective influences on reducing erosive heat transfer appear to favor mobile, gas-borne particle additives.

  15. Small particle transport across turbulent nonisothermal boundary layers

    NASA Technical Reports Server (NTRS)

    Rosner, D. E.; Fernandez De La Mora, J.

    1982-01-01

    The interaction between turbulent diffusion, Brownian diffusion, and particle thermophoresis in the limit of vanishing particle inertial effects is quantitatively modeled for applications in gas turbines. The model is initiated with consideration of the particle phase mass conservation equation for a two-dimensional boundary layer, including the thermophoretic flux term directed toward the cold wall. A formalism of a turbulent flow near a flat plate in a heat transfer problem is adopted, and variable property effects are neglected. Attention is given to the limit of very large Schmidt numbers and the particle concentration depletion outside of the Brownian sublayer. It is concluded that, in the parameter range of interest, thermophoresis augments the high Schmidt number mass-transfer coefficient by a factor equal to the product of the outer sink and the thermophoretic suction.

  16. Lunar surface outgassing and alpha particle measurements

    SciTech Connect

    Lawson, S. L.; Feldman, W. C.; Lawrence, David J. ,; Moore, K. R.; Elphic, R. C.; Maurice, S.; Belian, Richard D.; Binder, Alan B.

    2002-01-01

    The Lunar Prospector Alpha Particle Spectrometer (LP APS) searched for lunar surface gas release events and mapped their distribution by detecting alpha particle?; produced by the decay of gaseous radon-222 (5.5 MeV, 3.8 day half-life), solid polonium-2 18 (6.0 MeV, 3 minute half-life), and solid polonium-210 (5.3 MeV, 138 day half-life, but held up in production by the 21 year half-life of lead-210). These three nuclides are radioactive daughters from the decay of uranium-238.

  17. Adsorption of sterically stabilized latex particles at liquid surfaces: effects of steric stabilizer surface coverage, particle size, and chain length on particle wettability.

    PubMed

    Reed, K M; Borovicka, J; Horozov, T S; Paunov, V N; Thompson, K L; Walsh, A; Armes, S P

    2012-05-01

    A series of five near-monodisperse sterically stabilized polystyrene (PS) latexes were synthesized using three well-defined poly(glycerol monomethacrylate) (PGMA) macromonomers with mean degrees of polymerization (DP) of 30, 50, or 70. The surface coverage and grafting density of the PGMA chains on the particle surface were determined using XPS and (1)H NMR spectroscopy, respectively. The wettability of individual latex particles adsorbed at the air-water and n-dodecane-water interfaces was studied using both the gel trapping technique and the film calliper method. The particle equilibrium contact angle at both interfaces is relatively insensitive to the mean DP of the PGMA stabilizer chains. For a fixed stabilizer DP of 30, particle contact angles were only weakly dependent on the particle size. The results are consistent with a model of compact hydrated layers of PGMA stabilizer chains at the particle surface over a wide range of grafting densities. Our approach could be utilized for studying the adsorption behavior of a broader range of sterically stabilized inorganic and polymeric particles of practical importance. PMID:22502638

  18. Surface preparation of substances for continuous convective assembly of fine particles

    DOEpatents

    Rossi, Robert

    2003-01-01

    A method for producing periodic nanometer-scale arrays of metal or semiconductor junctions on a clean semiconductor substrate surface is provided comprising the steps of: etching the substrate surface to make it hydrophilic, forming, under an inert atmosphere, a crystalline colloid layer on the substrate surface, depositing a metal or semiconductor material through the colloid layer onto the surface of the substrate, and removing the colloid from the substrate surface. The colloid layer is grown on the clean semiconductor surface by withdrawing the semiconductor substrate from a sol of colloid particles.

  19. Lunar Surface Outgassing and Alpha Particle Measurements

    NASA Astrophysics Data System (ADS)

    Lawson, S. L.; Feldman, W. C.; Lawrence, D. J.; Moore, K. R.; Elphic, R. C.; Maurice, S.; Belian, R. D.; Binder, A. B.

    2002-01-01

    The Lunar Prospector Alpha Particle Spectrometer (LP APS) searched for lunar surface gas release events and mapped their distribution by detecting alpha particles produced by the decay of gaseous radon-222 (5.5 MeV, 3.8 day half-life), solid polonium-218 (6.0 MeV, 3 minute half-life), and solid polonium-210 (5.3 MeV, 138 day half-life, but held up in production by the 21 year half-life of lead-210). These three nuclides are radioactive daughters from the decay of uranium-238. Radon reaches the lunar surface either at areas of high soil porosity or where fissures release the trapped gases in which radon is entrained. Once released, the radon spreads out by "bouncing" across the surface on ballistic trajectories in a randomwalk process. The half-life of radon-222 allows the gas to spread out by several 100 km before it decays (depositing approximately half of the polonium-218 recoil nuclides on the lunar surface) and allows the APS to detect gas release events up to several days after they occur. The long residence time of the lead-210 precursor to polonium-210 allows the mapping of gas vents which have been active over the last approximately 60 years. Because radon and polonium are daughter products of the decay of uranium, the background level of alpha particle activity is a function of the lunar crustal uranium distribution.

  20. Double layer -- a particle accelerator in the magnetosphere

    SciTech Connect

    Fu, Xiangrong

    2015-07-16

    Slides present the material under the following topics: Introduction (What is a double layer (DL)? Why is it important? Key unsolved problems); Theory -- time-independent solutions of 1D Vlasov--Poisson system; Particle-in-cell simulations (Current-driven DLs); and Electron acceleration by DL (Betatron acceleration). Key problems include the generation mechanism, stability, and electron acceleration. In summary, recent observations by Van Allen Probes show large number of DLs in the outer radiation belt, associated with enhanced flux of relativistic electrons. Simulations show that ion acoustic double layers can be generated by field-aligned currents. Thermal electrons can gain energy via betatron acceleration in a dipole magnetic field.

  1. Particle transport across the transpired turbulent boundary layer

    NASA Astrophysics Data System (ADS)

    Kozlu, Hamdi; Louis, Jean F.

    1987-05-01

    Wind tunnel data and theoretical results are used to study the effects of surface inclination and density of particulates on deposition control by transpiration, with application to the control of deposition of small particles contributing most of the mass of the solid carryover entering turbines burning coal-derived fuel. The effects of size and injection rates on deposition are considered, and the interaction between transpiration and the inertial impaction of particles is investigated using glass particles. Turbulent Schmidt numbers obtained from tests conducted on an inclined plate with coal particles in order to determine the density effects on the particle concentration profiles were in agreement with the predictions of Tchen (1974) for the flat plate.

  2. Computer simulations of particle-surface dynamics

    SciTech Connect

    Karo, A.M.; Hiskes, J.R.; DeBoni, T.M.

    1986-10-01

    Our simulations of particle-surface dynamics use the molecular dynamics codes that we have developed over the past several years. The initial state of a molecule and the parameters defining the incoming trajectory can be specifically described or randomly selected. Statistical analyses of the states of the particles and their trajectories following wall collisions are carried out by the code. We have carried out calculations at high center-of-mass energies and low incidence angles and have examined the survival fraction of molecules and the dependence upon the incoming trajectory. We report also on preliminary efforts that are being made to simulate sputtering and recombinant desorption processes, since the recombinant desorption of hydrogen from typical wall materials may be an important source for vibrationally-excited hydrogen in volume sources; for surface sources the presence of occluded hydrogen may affect the concentration of atomic species.

  3. Fluorescent particle tracers for surface hydrology

    NASA Astrophysics Data System (ADS)

    Tauro, F.; Grimaldi, S.; Rapiti, E.; Porfiri, M.

    2012-12-01

    Accurate estimates of flow velocity in natural environments are essential for the understanding of runoff and overland flow formation, rill development, erosion, and infiltration and evaporation mechanisms. Tracing technologies are generally considered valuable tools to estimate flow velocity in small watershed streams and shallow water flows. In this framework, a novel tracing methodology based on the deployment and observation of enhanced fluorescence particles for surface flow measurements is proposed. This approach aims at mitigating practical limitations of traditional techniques for monitoring stream and overland flows. Specifically, the insolubility of the particles minimizes tracer adhesion to natural substrates and, therefore, is expected to reduce the requisite quantity of tracing material as compared to liquid dyes. Further, the enhanced visibility of the fluorescent particles allows for non-intrusively detecting the tracer through imaging techniques without deploying bulky probes and samplers in the water. These features along with the use of basic and resilient equipment provide grounding for applying the proposed methodology in ephemeral micro-channels, high-sediment load flows, and heavy floods. The feasibility of the methodology is studied by conducting characterization analysis in laboratory settings and proof-of-concept experiments in natural environments. In addition, image analysis techniques are developed to automatically and noninvasively detect and trace the trajectory of the particles on surface flows. Experiments are performed in a natural mountainous river to assess the performance of the particles in stream flow settings, where high velocity regimes, presence of foam, and light reflections pose serious challenges to bead detection. Particles are used to conduct flow measurements at a stream cross-section and travel time experiments in stream reaches of up to 30 m. Bead diameters of a few millimeters are selected to compensate for high

  4. Observations of specular reflective particles and layers in crystal clouds.

    PubMed

    Balin, Yurii S; Kaul, Bruno V; Kokhanenko, Grigorii P; Penner, Ioganes E

    2011-03-28

    In the present article, results of observations of high crystal clouds with high spatial and temporal resolution using the ground-based polarization LOSA-S lidar are described. Cases of occurrence of specularly reflective layers formed by particles oriented predominantly in the horizontal plane are demonstrated. Results of measuring echo-signal depolarization are compared for linear and circular polarization states of the initial laser beam.

  5. Surface chemistry of LiNi0.5Mn1.5O4 particles coated by Al2O3 using atomic layer deposition for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Kim, Jin Wook; Kim, Dong Hyeon; Oh, Dae Yang; Lee, Hyeyoun; Kim, Ji Hyun; Lee, Jae Hyun; Jung, Yoon Seok

    2015-01-01

    The effects of depositing ultrathin (<1 nm) Al2O3 coatings on LiNi0.5Mn1.5O4 (LNMO) particles using atomic layer deposition (ALD) are presented. Promising electrochemical performance of the Al2O3 ALD coated LNMO at 30 °C is demonstrated in not only significantly improved coulombic efficiency, cycle retention, and rate capability, but also in dramatically suppressed self-discharge and dissolution of transition metals. Combined analyses by electrochemical impedance spectroscopy, ex-situ X-ray photoelectron spectroscopy, and ex-situ time-of-flight secondary ion mass spectrometry reveal that the solid electrolyte interphase layer on the Al2O3 ALD coated LNMO is much thinner and contains fewer organic species than the one on the bare LNMO. This difference originates from the suppression of the side reaction at high voltage by the Al2O3 ALD protective coating. Also, fluorination of Al2O3 ALD layer upon repeated charge-discharge cycling is confirmed, and this can account for the capacity increases during the initial charge-discharge cycles. Finally, it is also demonstrated that a full LNMO/Li4Ti5O12 battery incorporating the Al2O3 ALD coated LNMO outperforms the one incorporating only bare LNMO.

  6. Surface Layer Turbulence During a Frontal Passage

    SciTech Connect

    Piper, M; Lundquist, J K

    2004-06-15

    Some recent investigations have begun to quantify turbulence and dissipation in frontal zones to address the question of what physical mechanism counteracts the intensification of temperature and velocity gradients across a developing front. Frank (1994) examines the turbulence structure of two fronts that passed a 200m instrumented tower near Karlsruhe, Germany. In addition to showing the mean vertical structure of the fronts as they pass the tower, Frank demonstrates that there is an order of magnitude or more increase in turbulent kinetic energy across the frontal zone. Blumen and Piper (1999) reported turbulence statistics, including dissipation rate measurements, from the MICROFRONTS field experiment, where high-frequency turbulence data were collected from tower-mounted hotwire and sonic anemometers in a cold front and in a density current. Chapman and Browning (2001) measured dissipation rate in a precipitating frontal zone with high-resolution Doppler radar. Their measurements were conducted above the surface layer, to heights of 5km. The dissipation rate values they found are comparable to those measured in Kennedy and Shapiro (1975) in an upper-level front. Here, we expand on these recent studies by depicting the behavior of the fine scales of turbulence near the surface in a frontal zone. The primary objective of this study is to quantify the levels of turbulence and dissipation occurring in a frontal zone through the calculation of kinetic energy spectra and dissipation rates. The high-resolution turbulence data used in this study are taken during the cold front that passed the MICROFRONTS site in the early evening hours of 20 March 1995. These new measurements can be used as a basis for parameterizing the effects of surface-layer turbulence in numerical models of frontogenesis. We present three techniques for calculating the dissipation rate: direct dissipation technique, inertial dissipation technique and Kolmogorov's four-fifths law. Dissipation rate

  7. Charged particle detectors with active detector surface for partial energy deposition of the charged particles and related methods

    DOEpatents

    Gerts, David W; Bean, Robert S; Metcalf, Richard R

    2013-02-19

    A radiation detector is disclosed. The radiation detector comprises an active detector surface configured to generate charge carriers in response to charged particles associated with incident radiation. The active detector surface is further configured with a sufficient thickness for a partial energy deposition of the charged particles to occur and permit the charged particles to pass through the active detector surface. The radiation detector further comprises a plurality of voltage leads coupled to the active detector surface. The plurality of voltage leads is configured to couple to a voltage source to generate a voltage drop across the active detector surface and to separate the charge carriers into a plurality of electrons and holes for detection. The active detector surface may comprise one or more graphene layers. Timing data between active detector surfaces may be used to determine energy of the incident radiation. Other apparatuses and methods are disclosed herein.

  8. Particle Swarm Transport through Immiscible Fluid Layers in a Fracture

    NASA Astrophysics Data System (ADS)

    Teasdale, N. D.; Boomsma, E.; Pyrak-Nolte, L. J.

    2011-12-01

    Immiscible fluids occur either naturally (e.g. oil & water) or from anthropogenic processes (e.g. liquid CO2 & water) in the subsurface and complicate the transport of natural or engineered micro- or nano-scale particles. In this study, we examined the effect of immiscible fluids on the formation and evolution of particle swarms in a fracture. A particle swarm is a collection of colloidal-size particles in a dilute suspension that exhibits cohesive behavior. Swarms fall under gravity with a velocity that is greater than the settling velocity of a single particle. Thus a particle swarm of colloidal contaminants can potentially travel farther and faster in a fracture than expected for a dispersion or emulsion of colloidal particles. We investigated the formation, evolution, and break-up of colloidal swarms under gravity in a uniform aperture fracture as hydrophobic/hydrophyllic particle swarms move across an oil-water interface. A uniform aperture fracture was fabricated from two transparent acrylic rectangular prisms (100 mm x 50 mm x 100 mm) that are separated by 1, 2.5, 5, 10 or 50 mm. The fracture was placed, vertically, inside a glass tank containing a layer of pure silicone oil (polydimethylsiloxane) on distilled water. Along the length of the fracture, 30 mm was filled with oil and 70 mm with water. Experiments were conducted using silicone oils with viscosities of 5, 10, 100, or 1000 cSt. Particle swarms (5 μl) were comprised of a 1% concentration (by mass) of 25 micron glass beads (hydrophilic) suspended in a water drop, or a 1% concentration (by mass) of 3 micron polystyrene fluorescent beads (hydrophobic) suspended in a water drop. The swarm behavior was imaged using an optical fluorescent imaging system composed of a CCD camera and by green (525 nm) LED arrays for illumination. Swarms were spherical and remained coherent as they fell through the oil because of the immiscibility of oil and water. However, as a swarm approached the oil-water interface, it

  9. Surface engineering of nanoparticles in suspension for particle based bio-sensing

    NASA Astrophysics Data System (ADS)

    Sen, Tapas; Bruce, Ian J.

    2012-08-01

    Surface activation of nanoparticles in suspension using amino organosilane has been carried out via strict control of a particle surface ad-layer of water using a simple but efficient protocol `Tri-phasic Reverse Emulsion' (TPRE). This approach produced thin and ordered layers of particle surface functional groups which allowed the efficient conjugation of biomolecules. When used in bio-sensing applications, the resultant conjugates were highly efficient in the hybrid capture of complementary oligonucleotides and the detection of food borne microorganism. TPRE overcomes a number of fundamental problems associated with the surface modification of particles in aqueous suspension viz. particle aggregation, density and organization of resultant surface functional groups by controlling surface condensation of the aminosilane. The approach has potential for application in areas as diverse as nanomedicine, to food technology and industrial catalysis.

  10. Turbulent transport process in atmospheric surface layer

    NASA Astrophysics Data System (ADS)

    Hayashi, T.; Awasaki, T.

    2012-04-01

    The organized motion or the coherent motion can be detected in wind tunnel and water channel experiments and those motions play an important role for the production of turbulent energy and transport of turbulent fluxes. Similar phenomena can be found in the atmospheric surface layer (Gao et al., 1989). The purpose of this study is to clarify the transport structure and process of turbulent fluxes, especially heat, water vapor and carbon dioxide. The organized motions are detected by using the wavelet transform analysis as well as the conventional statistical method such as Fourier spectral analysis. We consider the dependency of transport process by the organized motion to the atmospheric stability in the surface layer. The observation was carried out at the test field of Shionomisaki Wind Effect Laboratory, where two sets of the combination of sonic anemometer thermometer and open path H2O/CO2 analyzer were mounted at 2m and 20m height. The evident ramp and inverse ramp structures can be found in the time series of temperature, water vapor and CO2 in the unstable stability, using the Mexican hut wavelet transform analysis. The co-spectral density in wavelet analysis is considered as the flux at each time scale. The large amount of fluxes is transported at the sudden decrease in scalar ramp structure and the sudden increase in inverse ramp structure in several tens of seconds. The scalar and vertical wind velocity are completely either in phase or out of phase, which means that the turbulent transport by the organized motion occurs at time scales of several tens of seconds. The quadrant analysis of turbulent flux shows that the rate of the transport amount of scalar by ejection and sweep to the total transport flux increases according to the increase of the atmospheric stability. At 2m height, the transport by ejection is dominant in unstable condition, and that by sweep is larger in the stable condition. At 20m height, transport by ejection is larger than that by

  11. Correlation and prediction of thermophoretic and inertial effects on particle deposition from non-isothermal turbulent boundary layers

    NASA Technical Reports Server (NTRS)

    Rosner, D. E.; Fernandez De La Mora, J.

    1982-01-01

    The problem of small particle deposition which can cause hot stage corrosion and/or fouling in combustion turbines operating on fuels containing ash or inorganic salts is investigated. Two boundary layer transport phenomena are shown to assume importance in these cases: particle thermophoresis (migration down a temperature gradient) and particle inertia. Thermophoretic and eddy transport across turbulent boundary layers without and with particle inertia effects are quantitatively analyzed. The effects of streamwise blade curvature on particle transport across turbulent boundary layers are determined. It is shown that these phenomena destroy the analogy between mass and heat transfer or mass and momentum transfer. Also studied are the effects on particle deposition of distributed or localized wall blowing, surface roughness, and mainstream turbulence.

  12. Layer-by-layer modification of high surface curvature nanoparticles with weak polyelectrolytes using a multiphase solvent precipitation process.

    PubMed

    Nagaraja, Ashvin T; You, Yil-Hwan; Choi, Jeong-Wan; Hwang, Jin-Ha; Meissner, Kenith E; McShane, Michael J

    2016-03-15

    The layer-by-layer modification of ≈5 nm mercaptocarboxylic acid stabilized gold nanoparticles was studied in an effort to illustrate effective means to overcome practical issues in handling and performing surface modification of such extremely small materials. To accomplish this, each layer deposition cycle was separated into a multi-step process wherein solution pH was controlled in two distinct phases of polyelectrolyte adsorption and centrifugation. Additionally, a solvent precipitation step was introduced to make processing more amenable by concentrating the sample and exchanging solution pH before ultracentrifugation. The pH-dependent assembly on gold nanoparticles was assessed after each layer deposition cycle by monitoring the plasmon peak absorbance location, surface charge, and the percentage of nanoparticles recovered. The selection of solution pH during the adsorption phase was found to be a critical parameter to enhance particle recovery and maximize surface charge when coating with weak polyelectrolytes. One bilayer was deposited with a high yield and the modified particles exhibited enhanced colloidal stability across a broad pH range and increased ionic strength. These findings support the adoption of this multi-step processing approach as an effective and generalizable approach to improve stability of high surface curvature particles. PMID:26771506

  13. Dry deposition of large, airborne particles onto a surrogate surface

    NASA Astrophysics Data System (ADS)

    Kim, Eugene; Kalman, David; Larson, Timothy

    Simultaneous measurements of particle dry deposition flux and airborne number concentration in the open atmosphere were made using three different types of artificially generated particles in the size range 10-100 μm - perlite, diatomaceous earth and glass beads. A combination of gravimetric analysis, automated microscopy and sonic anemometry provided size-resolved estimates of both the inertial and gravitational components of the quasi-laminar layer particle deposition velocity, ( Vd) b, as a function of size. Eddy inertial deposition efficiency ( ηdI) was determined as a function of dimensionless eddy Stokes number (Stk e). In the range 3particles and gases to environmental surfaces. DOE Report PNL-SA-6721, Pacific Northwest Laboratories, Richland, WA), used in several regulatory models, significantly under-predicted (up to seven times) ( Vd) b for large particles ( da>10 μm).

  14. Electrical double-layer effects on the deposition of zeolite A on surfaces.

    PubMed

    Oonkhanond, Bovornlak; Mullins, Michael E

    2005-04-01

    Zeolite particles formed from an aluminosilicate solution possess a negative surface charge due to the substitution of aluminum atoms into a SiO4 tetrahedral structure making it difficult to form a continuous layer in solution. The particle interactions with surfaces and each other can be studied using the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. The interaction energy between zeolite-zeolite and zeolite-substrate on various materials can be estimated in this fashion. The zeolite LTA particles show a stronger repulsion interaction on all substrates and on the each other as compared to the ZSM-5 particles. This repulsive energy also increases as the particles size increases. This results in the formation of conglomerate in the solution rather than forming an adhered layer on the substrate.

  15. Particle nucleation in the tropical boundary layer and its coupling to marine sulfur sources

    PubMed

    Clarke; Davis; Kapustin; Eisele; Chen; Paluch; Lenschow; Bandy; Thornton; Moore; Mauldin; Tanner; Litchy; Carroll; Collins; Albercook

    1998-10-01

    New particle formation in a tropical marine boundary layer setting was characterized during NASA's Pacific Exploratory Mission-Tropics A program. It represents the clearest demonstration to date of aerosol nucleation and growth being linked to the natural marine sulfur cycle. This conclusion was based on real-time observations of dimethylsulfide, sulfur dioxide, sulfuric acid (gas), hydroxide, ozone, temperature, relative humidity, aerosol size and number distribution, and total aerosol surface area. Classic binary nucleation theory predicts no nucleation under the observed marine boundary layer conditions.

  16. Saltation and incipient suspension above a flat particle bed below a turbulent boundary layer

    NASA Astrophysics Data System (ADS)

    Nishimura, K.; Hunt, J. C. R.

    2000-08-01

    Experiments were conducted in a wind tunnel in which a turbulent boundary layer was naturally grown over flat beds of three types of nearly mono-disperse spherical particles with different diameters, densities and coefficient of restitution (r) (snow, 0.48 mm, 910 kg m[minus sign]3; mustard seeds, 1.82 mm, 1670 kg m[minus sign]3, r = 0.7; ice particles, 2.80 mm, 910 kg m[minus sign]3, r = 0.8 0.9). The surface wind speeds (defined by the friction velocity u[low asterisk]) were varied between 1.0 and 1.9 times the threshold surface wind speed (defined by u[low asterisk]t). The trajectories, and ejection and impact velocities of the particles were recorded and analysed, even those that were raised only about one diameter into the flow.

  17. Particle Resolved DNS of Turbulent Oscillatory Flow Over a Layer of Fixed Particles

    NASA Astrophysics Data System (ADS)

    Ghodke, Chaitanya; Urzay, Javier; Apte, Sourabh

    2014-11-01

    Particle resolved direct numerical simulations are performed using fictitious domain approach (Apte et al., JCP 2009) to investigate oscillatory turbulent flow over a layer of fixed particles representative of a sediment layer in coastal environments. Five particle Reynolds numbers in the range, ReD = 660 - 4240 are studied and results are compared against available experimental data (Keiller & Sleath, JFM 1976). Flow is characterized in terms of coherent vortex structures, Reynolds stress variation, turbulent cross-correlations and PDF distributions. The nature of the unsteady hydrodynamic forces on particles and their correlation to sweep and burst events is reported. The net lift coefficient remains positive over the cycle and is well correlated with phase averaged near-bed velocity. Maximum in the lift coefficient occurs when the strength of the horseshoe vortices is maximum. At this phase the lift fluctuations are correlated negatively with pressure and positively with velocity fluctuations in the region above the particle bed. Preliminary analysis shows non-Gaussian distribution for velocity fluctuation and follows 4th order Gram-Charlier. These detailed findings could eventually be useful in improving the existing criterion for predicting sediment incipient motion. Supported by NSF Project # 1133363 as well as Center for Turbulence Research Stanford University Summer Program 2014.

  18. Model of Heat and Mass Transfer in Random Packing Layer of Powder Particles in Selective Laser Melting

    NASA Astrophysics Data System (ADS)

    Kovaleva, I.; Kovalev, O.; Smurov, I.

    Discretegrid model of heat transfer in granular porous mediumto describe the processes of selective laser melting of powdersis developed. The thermal conductivity in this mediumis performed through thecontact surfaces between the particles. The calculation method of morphology of random packing layer of powder considering the adhesive interaction between the particles is proposed. The internal structure of the obtained loose powder layer is a granular medium where spherical particles of different sizes are arranged in contact with each other randomly. Analytical models of powder balling process and formation of the remelted track are proposed.

  19. Carbon Surface Layers on a High-Rate LiFePO4

    SciTech Connect

    Gabrisch, Heike; Wilcox, James D.; Doeff, Marca M.

    2005-09-06

    Transmission electron microscopy (TEM) was used to image particles of a high-rate LiFePO4 sample containing a small amount of in situ carbon. The particle morphology is highly irregular, with a wide size distribution. Nevertheless, coatings, varying from about 5-10 nm in thickness, could readily be detected on surfaces of particles as well as on edges of agglomerates. Elemental mapping using Energy Filtered TEM (EFTEM) indicates that these very thin surface layers are composed of carbon. These observations have important implications for the design of high-rate LiFePO4 materials in which, ideally, a minimal amount of carbon coating is used.

  20. Surface plasma source with anode layer plasma accelerator

    SciTech Connect

    Dudnikov, Vadim

    2012-02-15

    Proposed plasma generation system can be used for high current negative ion beam production and for directed deposition by flux of sputtered neutrals and negative ions. The main mechanism of negative ion formation in surface plasma sources is the secondary emission from low work function surface bombarded by a flux of positive ion or neutrals. The emission of negative ions is enhanced significantly by introducing a small amount of cesium or other substance with low ionization potential. In the proposed source are used positive ions generated by Hall drift plasma accelerator (anode layer plasma accelerator or plasma accelerator with insulated channel, with cylindrical or race track configuration of emission slit). The target-emitter is bombarded by the ion beam accelerated in crossed ExB fields. Negative ions are extracted from the target surface with geometrical focusing and are accelerated by negative voltage applied between emitter and plasma, contacting with the plasma accelerator. Hall drift ion source has a special design with a space for passing of the emitted negative ions and sputtered particles through the positive ion source.

  1. From surface to subsurface and back again: the contribution of subsurface particle motion to surface armoring

    NASA Astrophysics Data System (ADS)

    Ferdowsi, B.; Jerolmack, D. J.; Ortiz, C. P.; Houssais, M.

    2015-12-01

    Armoring is the development of a coarse surface layer of sediments on a river bed, which overlies a smaller and typically more heterogeneous substrate. All existing models for this phenomenon are predicated on the idea that armoring develops due to size-selective transport and kinetic sieving at the surface of the granular bed. Here examine the development of armoring in the absence of size-selective surface transport, and demonstrate that subsurface particle movement can create an armored surface layer. We first conduct experiments in a laminar and annular flume, over a range of Shields stresses, with bimodal and refractive index-matched spherical sediments; this allows us to image the internal motion of the granular bed that is sheared from above by a viscous oil. Fluid-driven particle motion of the surface layer results in granular shear, that drives motion deep into the bed. This subsurface motion causes an upward migration of coarser particles, at a rate that is proportional to the granular shear rate. Comparison of experimental results to an existing continuum-granular flow model suggest that armoring in our bed-load exeriments is entirely consistent with shear-induced segregation in dry avalanches - but is slower. There is no size-selective transport at the surface in the experiments, as the annular flume is mass conserving and all particles move as bed load; this was confirmed by observation. To probe the granular physics of armor development further, we perform numerical simulations using a discrete element model (DEM) of granular flow, with and without damping. Simulations reproduce salient features of the experiments, and indicate that armoring is robust but that the rate of segregation is related to the degree of viscous damping. We posit that subsurface granular flow is an important and perhaps dominant contributor to surface armoring in rivers. More generally, this work shows how information is transferred from the surface to the subsurface and back

  2. Layers of Porous Superhydrophobic Surfaces for Robust Water Repellency

    NASA Astrophysics Data System (ADS)

    Ahmadi, Farzad; Boreyko, Jonathan; Nature-Inspired Fluids; Interfaces Team

    2015-11-01

    In nature, birds exhibit multiple layers of superhydrophobic feathers that repel water. Inspired by bird feathers, we utilize porous superhydrophobic surfaces and compare the wetting and dewetting characteristics of a single surface to stacks of multiple surfaces. The superhydrophobic surfaces were submerged in water in a closed chamber. Pressurized gas was regulated to measure the critical pressure for the water to fully penetrate through the surfaces. In addition to using duck feathers, two-tier porous superhydrophobic surfaces were fabricated to serve as synthetic mimics with a controlled surface structure. The energy barrier for the wetting transition was modeled as a function of the number of layers and their orientations with respect to each other. Moreover, after partial impalement into a subset of the superhydrophobic layers, it was observed that a full dewetting transition was possible, which suggests that natural organisms can exploit their multiple layers to prevent irreversible wetting.

  3. Contact mechanics for layered materials with randomly rough surfaces.

    PubMed

    Persson, B N J

    2012-03-01

    The contact mechanics model of Persson is applied to layered materials. We calculate the M function, which relates the surface stress to the surface displacement, for a layered material, where the top layer (thickness d) has different elastic properties than the semi-infinite solid below. Numerical results for the contact area as a function of the magnification are presented for several cases. As an application, we calculate the fluid leak rate for laminated rubber seals.

  4. Monte Carlo simulation of light reflection from cosmetic powder particles near the human skin surface

    NASA Astrophysics Data System (ADS)

    Okamoto, Takashi; Kumagawa, Tatsuya; Motoda, Masafumi; Igarashi, Takanori; Nakao, Keisuke

    2013-06-01

    The reflection and scattering properties of light incident on human skin covered with powder particles have been investigated. A three-layer skin structure with a pigmented area is modeled, and the propagation of light in the skin's layers and in a layer of particles near the skin's surface is simulated using the Monte Carlo method. Assuming that only single scattering of light occurs in the powder layer, the simulation results show that the reflection spectra of light from the skin change with the size of powder particles. The color difference between normal and discolored skin is found to decrease considerably when powder particles with a diameter of approximately 0.25 μm are present near the skin's surface. The effects of the medium surrounding the particles, and the influence of the distribution of particle size (polydispersity), are also examined. It is shown that a surrounding medium with a refractive index close to that of the skin substantially suppresses the extreme spectral changes caused by the powder particles covering the skin surface.

  5. Monte Carlo simulation of light reflection from cosmetic powder particles near the human skin surface.

    PubMed

    Okamoto, Takashi; Kumagawa, Tatsuya; Motoda, Masafumi; Igarashi, Takanori; Nakao, Keisuke

    2013-06-01

    The reflection and scattering properties of light incident on human skin covered with powder particles have been investigated. A three-layer skin structure with a pigmented area is modeled, and the propagation of light in the skin's layers and in a layer of particles near the skin's surface is simulated using the Monte Carlo method. Assuming that only single scattering of light occurs in the powder layer, the simulation results show that the reflection spectra of light from the skin change with the size of powder particles. The color difference between normal and discolored skin is found to decrease considerably when powder particles with a diameter of approximately 0.25 μm are present near the skin's surface. The effects of the medium surrounding the particles, and the influence of the distribution of particle size (polydispersity), are also examined. It is shown that a surrounding medium with a refractive index close to that of the skin substantially suppresses the extreme spectral changes caused by the powder particles covering the skin surface.

  6. Ice nucleating particles in the Saharan Air Layer

    NASA Astrophysics Data System (ADS)

    Boose, Yvonne; Sierau, Berko; García, M. Isabel; Rodríguez, Sergio; Alastuey, Andrés; Linke, Claudia; Schnaiter, Martin; Kupiszewski, Piotr; Kanji, Zamin A.; Lohmann, Ulrike

    2016-07-01

    This study aims at quantifying the ice nucleation properties of desert dust in the Saharan Air Layer (SAL), the warm, dry and dust-laden layer that expands from North Africa to the Americas. By measuring close to the dust's emission source, before aging processes during the transatlantic advection potentially modify the dust properties, the study fills a gap between in situ measurements of dust ice nucleating particles (INPs) far away from the Sahara and laboratory studies of ground-collected soil. Two months of online INP concentration measurements are presented, which were part of the two CALIMA campaigns at the Izaña observatory in Tenerife, Spain (2373 m a.s.l.), in the summers of 2013 and 2014. INP concentrations were measured in the deposition and condensation mode at temperatures between 233 and 253 K with the Portable Ice Nucleation Chamber (PINC). Additional aerosol information such as bulk chemical composition, concentration of fluorescent biological particles as well as the particle size distribution was used to investigate observed variations in the INP concentration. The concentration of INPs was found to range between 0.2 std L-1 in the deposition mode and up to 2500 std L-1 in the condensation mode at 240 K. It correlates well with the abundance of aluminum, iron, magnesium and manganese (R: 0.43-0.67) and less with that of calcium, sodium or carbonate. These observations are consistent with earlier results from laboratory studies which showed a higher ice nucleation efficiency of certain feldspar and clay minerals compared to other types of mineral dust. We find that an increase of ammonium sulfate, linked to anthropogenic emissions in upwind distant anthropogenic sources, mixed with the desert dust has a small positive effect on the condensation mode INP per dust mass ratio but no effect on the deposition mode INP. Furthermore, the relative abundance of biological particles was found to be significantly higher in INPs compared to the ambient

  7. Kinetics of Initial Layer-by-Layer Oxidation of Si(001) Surfaces

    NASA Astrophysics Data System (ADS)

    Watanabe, Heiji; Kato, Koichi; Uda, Tsuyoshi; Fujita, Ken; Ichikawa, Masakazu; Kawamura, Takaaki; Terakura, Kiyoyuki

    1998-01-01

    Layer-by-layer oxidation of Si(001) surfaces has been studied by scanning reflection electron microscopy (SREM). The oxidation kinetics of the top and second layers were independently investigated from the change in oxygen Auger peak intensity calibrated from the SREM observation. A barrierless oxidation of the first subsurface layer, as well as oxygen chemisorption onto the top layer, occurs at room temperature. The energy barrier of the second-layer oxidation was found to be 0.3 eV. The initial oxidation kinetics are discussed based on first-principles calculations.

  8. Equilibrium of wetting layers on rough surfaces

    NASA Astrophysics Data System (ADS)

    Liu, Kuang-Yu

    The objective of this dissertation is to study physical adsorption on solids with complex surface geometry--especially on self-similar and self-affine fractal surfaces--in the context of three phase equilibria. Such studies will facilitate the prediction of the adsorbed film from known surface properties, e.g., topography or interactions (direct problem), and the inference of unknown surface properties from experimental data (inverse problem). These results will then be compared against wetting phenomena on planar surfaces and with other methods of probing complex surface geometries of solids. Chapter One offers the basic context, including wetting phenomena on planar surfaces, the cornerstone prediction of wetting transition on planar surfaces by Cahn, the concepts of fractal geometry, and the formation of fractal objects, for later comparison. The rest of this dissertation will be devoted to the study of multilayer adsorption on fractal surfaces. When a liquid film completely wets the surface, the number of adsorbed molecules as a function of the vapor pressure will depend strongly on the underlying surface geometry. The fractal structure leads to the Frenkel-Halsey-Hill type isotherms with the exponents in the corresponding power laws depending on the fractal dimension and on whether the dominant influence is from the substrate potential (van der Waals wetting) or from the film-vapor surface tension (capillary wetting). The transition between the two is the analog of Cahn's transition: The thermal disorder is replaced by the quenched disorder. This analogy is studied in Chapter Two for self-similar surfaces, and in Chapter Four for self-affine surfaces. In Chapter Two the derivation framework also automatically identifies well-defined coexistence lines in the pressure-dimension diagram. The effect of the repulsive part is examined there too. A simple analysis of adsorption/desorption hysteresis on self-similar surfaces in Chapter Three concludes that the

  9. Characterization and use of crystalline bacterial cell surface layers

    NASA Astrophysics Data System (ADS)

    Sleytr, Uwe B.; Sára, Margit; Pum, Dietmar; Schuster, Bernhard

    2001-10-01

    Crystalline bacterial cell surface layers (S-layers) are one of the most common outermost cell envelope components of prokaryotic organisms (archaea and bacteria). S-layers are monomolecular arrays composed of a single protein or glycoprotein species and represent the simplest biological membranes developed during evolution. S-layers as the most abundant of prokaryotic cellular proteins are appealing model systems for studying the structure, synthesis, genetics, assembly and function of proteinaceous supramolecular structures. The wealth of information existing on the general principle of S-layers have revealed a broad application potential. The most relevant features exploited in applied S-layer research are: (i) pores passing through S-layers show identical size and morphology and are in the range of ultrafiltration membranes; (ii) functional groups on the surface and in the pores are aligned in well-defined positions and orientations and accessible for chemical modifications and binding functional molecules in very precise fashion; (iii) isolated S-layer subunits from a variety of organisms are capable of recrystallizing as closed monolayers onto solid supports (e.g., metals, polymers, silicon wafers) at the air-water interface, on lipid films or onto the surface of liposomes; (iv) functional domains can be incorporated in S-layer proteins by genetic engineering. Thus, S-layer technologies particularly provide new approaches for biotechnology, biomimetics, molecular nanotechnology, nanopatterning of surfaces and formation of ordered arrays of metal clusters or nanoparticles as required for nanoelectronics.

  10. Continuous production of nanostructured particles using spatial atomic layer deposition

    SciTech Connect

    Ommen, J. Ruud van Kooijman, Dirkjan; Niet, Mark de; Talebi, Mojgan; Goulas, Aristeidis

    2015-03-15

    In this paper, the authors demonstrate a novel spatial atomic layer deposition (ALD) process based on pneumatic transport of nanoparticle agglomerates. Nanoclusters of platinum (Pt) of ∼1 nm diameter are deposited onto titania (TiO{sub 2}) P25 nanoparticles resulting to a continuous production of an active photocatalyst (0.12–0.31 wt. % of Pt) at a rate of about 1 g min{sup −1}. Tuning the precursor injection velocity (10–40 m s{sup −1}) enhances the contact between the precursor and the pneumatically transported support flows. Decreasing the chemisorption temperature (from 250 to 100 °C) results in more uniform distribution of the Pt nanoclusters as it decreases the reaction rate as compared to the rate of diffusion into the nanoparticle agglomerates. Utilizing this photocatalyst in the oxidation reaction of Acid Blue 9 showed a factor of five increase of the photocatalytic activity compared to the native P25 nanoparticles. The use of spatial particle ALD can be further expanded to deposition of nanoclusters on porous, micron-sized particles and to the production of core–shell nanoparticles enabling the robust and scalable manufacturing of nanostructured powders for catalysis and other applications.

  11. Laboratory study of opposition surge of rock chips and particle layers

    NASA Astrophysics Data System (ADS)

    Honda, T.; Nakamura, A. M..; Mukai, T.

    Surfaces of small bodies such as asteroids are covered with regolith particles The intensity of the scattered light from such surface nonlinearly increases at small solar phase angles the angle between the light source and the detector as seen from the target The degree and the sharpness of the phenomena opposition surge are considered to depend on the physical state of the surface It was shown the opposition surge appears on scattered light from surface of rocks Shepard and Arvidson 1999 However it remains to be incompletely understood how the opposition surge varies with the structure and optical characteristics of the scattering target First we performed measurements of scattered light from rock chips and particle layers at low phase angles Measurements were performed using a multi phase angle near infrared spectrometer at Kobe University with the incident angle fixed at 2 degree and the phase angle varied within 0-25 degrees A clear differences were found between the phase curves of dunite chip and particles whereas there were no apparent difference between the chips and the powders for a meteorite and mortar We then performed new measurements to focus on clarifying whether or not 1 bulk chips consisting of uniform composition also show opposition surge 2 difference in size of the constituent grains of bulk chips affects the opposition surge and 3 difference in surface roughness of bulk chips has dominant effect We will show the results of several types of bulk chips and sintered powders and will discuss on the possible

  12. Preservation of Archaeal Surface Layer Structure During Mineralization

    PubMed Central

    Kish, Adrienne; Miot, Jennyfer; Lombard, Carine; Guigner, Jean-Michel; Bernard, Sylvain; Zirah, Séverine; Guyot, François

    2016-01-01

    Proteinaceous surface layers (S-layers) are highly ordered, crystalline structures commonly found in prokaryotic cell envelopes that augment their structural stability and modify interactions with metals in the environment. While mineral formation associated with S-layers has previously been noted, the mechanisms were unconstrained. Using Sulfolobus acidocaldarius a hyperthermophilic archaeon native to metal-enriched environments and possessing a cell envelope composed only of a S-layer and a lipid cell membrane, we describe a passive process of iron phosphate nucleation and growth within the S-layer of cells and cell-free S-layer “ghosts” during incubation in a Fe-rich medium, independently of metabolic activity. This process followed five steps: (1) initial formation of mineral patches associated with S-layer; (2) patch expansion; (3) patch connection; (4) formation of a continuous mineral encrusted layer at the cell surface; (5) early stages of S-layer fossilization via growth of the extracellular mineralized layer and the mineralization of cytosolic face of the cell membrane. At more advanced stages of encrustation, encrusted outer membrane vesicles are formed, likely in an attempt to remove damaged S-layer proteins. The S-layer structure remains strikingly well preserved even upon the final step of encrustation, offering potential biosignatures to be looked for in the fossil record. PMID:27221593

  13. Ameriflux data used for verification of surface layer parameterizations

    NASA Astrophysics Data System (ADS)

    Tassone, Caterina; Ek, Mike

    2015-04-01

    The atmospheric surface-layer parameterization is an important component in a coupled model, as its output, the surface exchange coefficients for momentum, heat and humidity, are used to determine the fluxes of these quantities between the land-surface and the atmosphere. An accurate prediction of these fluxes is therefore required in order to provide a correct forecast of the surface temperature, humidity and ultimately also the precipitation in a model. At the NOAA/NCEP Environmental Modeling Center, a one-dimensional Surface Layer Simulator (SLS) has been developed for simulating the surface layer and its interface. Two different configurations of the SLS exist, replicating in essence the way in which the surface layer is simulated in the GFS and the NAM, respectively. Input data for the SLS are the basic atmospheric quantities of winds, temperature, humidity and pressure evaluated at a specific height above the ground, surface values of temperature and humidity, and the momentum roughness length z0. The output values of the SLS are the surface exchange coefficients for heat and momentum. The exchange coefficients computed by the SLS are then compared with independent estimates derived from measured surface heat fluxes. The SLS is driven by a set of Ameriflux data acquired at 22 stations over a period of several years. This provides a large number of different vegetation characteristics and helps ensure statistical significance. Even though there are differences in the respective surface layer formulations between the GFS and the NAM, they are both based on similarity theory, and therefore lower boundary conditions, i.e. roughness lengths for momentum and heat, and profile functions are among the main components of the surface layer that need to be evaluated. The SLS is a very powerful tool for this type of evaluation. We present the results of the Ameriflux comparison and discuss the implications of our results for the surface layer parameterizations of the NAM

  14. Surface Collisions Involving Particles and Moisture (SCIP'M)

    NASA Technical Reports Server (NTRS)

    Davis, Robert H.

    2005-01-01

    Experiments were performed on the collision of a solid sphere with a nearly horizontal flat surface covered with a thin layer of viscous liquid. High-speed collisions were obtained by dropping the ball onto the surface from various heights, using gravitational acceleration. Low-speed collisions were obtained using pendulums with long strings or by launching the balls at low velocities in the reduced-gravity environment of parabolic flight. The sphere bounces only when the impact velocity exceeds a critical value. The coefficient of restitution (ratio of rebound velocity to impact velocity) increases with increasing impact velocity above the critical value, indicating the increasing relative importance of elastic deformation to viscous dissipation. The critical impact velocity increases, and the coefficient of restitution decreases, with increasing viscosity or thickness of the liquid layer and with decreasing density or size of the sphere. The ratio of the wet and dry coefficients is expressed as a function of the Stokes number (ratio of particle inertia and viscous forces), showing good agreement between theory and experiment. Similar experiments were performed with the flat surface inclined at various angles to the approaching sphere. A modified Stokes number, which is a measure of the ratio of inertia of the sphere in the normal direction to the viscous forces exerted by the fluid layer, was used for the analysis of oblique collisions. Even for these oblique collisions, it was found that no rebound of the ball was observed below a certain critical Stokes number. The coefficient of normal restitution, defined as a ratio of normal rebound velocity to normal approach velocity, was found to increase beyond the critical Stokes number and even out as it approaches the value for dry restitution at high Stokes numbers. It was also found that, for smooth spheres like steel, the normal restitution at the same modified Stokes number is independent of the angle of impact

  15. Temperature Dependence of Surface Layering in a Dielectric Liquid

    SciTech Connect

    Mo,H.; Kewalramani, S.; Evmenenko, G.; Kim, K.; Ehrlich, S.; Dutta, P.

    2007-01-01

    The temperature dependence of the density oscillations (layers) at the free surface of tetrakis(2-ethylhexoxy)silane, a nonmetallic molecular liquid, was investigated using x-ray reflectivity. Below {approx}215K , the layer parameters weakly vary with temperature, if at all. Above this temperature, the layer spacings and intrinsic layer widths increase continuously, until there is no identifiable layering above 230K . This transition occurs at T/{Tc}{approx}0.23 , a temperature region that is usually accessible in metallic liquids but is preempted by freezing in many dielectric liquids.

  16. Polymer hollow particles with controllable holes in their surfaces

    NASA Astrophysics Data System (ADS)

    Hyuk Im, Sang; Jeong, Unyong; Xia, Younan

    2005-09-01

    Colloidal particles with hollow interiors play important roles in microencapsulation-a process that has found widespread use in applications such as controlled release of drugs, cosmetics, inks, pigments or chemical reagents; protection of biologically active species; and removal of pollutants. The hollow particles are most commonly prepared by coating the surfaces of colloidal templates with thin layers of the desired material (or its precursor), followed by selective removal of the templates by means of calcination or chemical etching. This simple and straightforward approach works for a variety of materials that include polymers, ceramics, composites and metals. For polymers, methods such as emulsion polymerization, phase separation, crosslinking of micelles and self-assembly have also been demonstrated for generating hollow structures. However, diffusion through these closed shells with pores <10 nm is often a slow process. To solve this problem, macroporous capsules have been fabricated by organizing colloids around liquid droplets to form colloidosomes or by controlling the mixing of liquid droplets. Here we report the preparation of another class of macroporous capsules-polymer shells with controllable holes in their surfaces. After loading of functional materials, the holes can be closed by means of thermal annealing or solvent treatment.

  17. Erosion of Galilean satellite surfaces by Jovian magnetosphere particles

    NASA Technical Reports Server (NTRS)

    Johnson, R. E.; Lanzerotti, L. J.; Brown, W. L.; Armstrong, T. P.

    1981-01-01

    The effects on the surfaces of the Galilean satellites Europa, Ganymede and Callisto of impacts by particles of the Jupiter magnetosphere in which they are immersed are estimated. Differential ion fluxes measured by the Voyager low-energy magnetosphere particle analyzer as a function of ion energy were used to calculate ice erosion fluxes for the satellites under the assumption that each is 50% ice covered. Calculations were performed on the basis of laboratory data concerning the ice sputtering coefficients of protons and oxygen ions of various energies. A water erosion rate of greater than 10 to the 10th/sq cm per sec is obtained for Europa, which implies a total erosion over 1 billion years of an ice layer 100 m deep. Atmospheric column densities of the H2O molecules sputtered from the surface but not escaping the satellites are also calculated for the three satellites assuming a sputtered ion temperature of 2000 K, and are found to dominate those produced by sublimation. Finally, estimates are presented of the source and loss processes for an oxygen atmosphere around Ganymede created by sputtering or sublimation.

  18. Generation and characterization of surface layers on acoustically levitated drops.

    PubMed

    Tuckermann, Rudolf; Bauerecker, Sigurd; Cammenga, Heiko K

    2007-06-15

    Surface layers of natural and technical amphiphiles, e.g., octadecanol, stearic acid and related compounds as well as perfluorinated fatty alcohols (PFA), have been investigated on the surface of acoustically levitated drops. In contrast to Langmuir troughs, traditionally used in the research of surface layers at the air-water interface, acoustic levitation offers the advantages of a minimized and contact-less technique. Although the film pressure cannot be directly adjusted on acoustically levitated drops, it runs through a wide pressure range due to the shrinking surface of an evaporating drop. During this process, different states of the generated surface layer have been identified, in particular the phase transition from the gaseous or liquid-expanded to the liquid-condensed state of surface layers of octadecanol and other related amphiphiles. Characteristic parameters, such as the relative permeation resistance and the area per molecule in a condensed surface layer, have been quantified and were found comparable to results obtained from surface layers generated on Langmuir troughs. PMID:17376468

  19. Observation of Surface Layering in a Nonmetallic Liquid

    SciTech Connect

    Mo,H.; Evmenenko, G.; Kewalramani, S.; Kim, K.; Ehrlich, S.; Dutta, P.

    2006-01-01

    Oscillatory density profiles (layers) have previously been observed at the free surfaces of liquid metals but not in other isotropic liquids. We have used x-ray reflectivity to study a molecular liquid, tetrakis(2-ethylhexoxy)silane. When cooled to T/T{sub c}{approx}0.25 (well above the freezing point for this liquid), density oscillations appear at the surface. Lateral order within the layers is liquidlike. Our results confirm theoretical predictions that a surface-layered state will appear even in dielectric liquids at sufficiently low temperatures, if not preempted by freezing.

  20. Observation of surface layering in a nonmetallic liquid.

    PubMed

    Mo, Haiding; Evmenenko, Guennadi; Kewalramani, Sumit; Kim, Kyungil; Ehrlich, Steven N; Dutta, Pulak

    2006-03-10

    Oscillatory density profiles (layers) have previously been observed at the free surfaces of liquid metals but not in other isotropic liquids. We have used x-ray reflectivity to study a molecular liquid, tetrakis(2-ethylhexoxy)silane. When cooled to T/Tc approximately 0.25 (well above the freezing point for this liquid), density oscillations appear at the surface. Lateral order within the layers is liquidlike. Our results confirm theoretical predictions that a surface-layered state will appear even in dielectric liquids at sufficiently low temperatures, if not preempted by freezing.

  1. Improve oxidation resistance at high temperature by nanocrystalline surface layer

    PubMed Central

    Xia, Z. X.; Zhang, C.; Huang, X. F.; Liu, W. B.; Yang, Z. G.

    2015-01-01

    An interesting change of scale sequence occurred during oxidation of nanocrystalline surface layer by means of a surface mechanical attrition treatment. The three-layer oxide structure from the surface towards the matrix is Fe3O4, spinel FeCr2O4 and corundum (Fe,Cr)2O3, which is different from the typical two-layer scale consisted of an Fe3O4 outer layer and an FeCr2O4 inner layer in conventional P91 steel. The diffusivity of Cr, Fe and O is enhanced concurrently in the nanocrystalline surface layer, which causes the fast oxidation in the initial oxidation stage. The formation of (Fe,Cr)2O3 inner layer would inhabit fast diffusion of alloy elements in the nanocrystalline surface layer of P91 steel in the later oxidation stage, and it causes a decrease in the parabolic oxidation rate compared with conventional specimens. This study provides a novel approach to improve the oxidation resistance of heat resistant steel without changing its Cr content. PMID:26269034

  2. Determination of colloidal particle surface charge from dielectrophoresis

    NASA Astrophysics Data System (ADS)

    Chavez, Marko; Nuansri, Rittirong; Mazza, Jacob; Ou-Yang, H. Daniel

    2015-03-01

    Electrophoresis (EP) is used to determine colloidal particle surface charge. However, when the Debye length is comparable to or larger than the particle size, electrophoresis cannot be reliably used to determine the surface charge due to counter ion retardation flow. Alexander et al. developed a theory relating colloidal osmotic pressure and particle surface charge. We use dielectrophoresis (DEP) to obtain a potential landscape based on the number density distribution of the particles in a non-uniform AC electric field. We determine the osmotic pressure from the DEP force and density profiles using Einstein's osmotic equilibrium equation. Surface charge obtained by DEP (thermodynamics) will be compared to that obtained by EP (electrokinetics).

  3. The Cold Surface Layer of Kahiltna Glacier, Central Alaska Range

    NASA Astrophysics Data System (ADS)

    Harrison, W. D.; Gusmeroli, A.; Arendt, A. A.; Atwood, D. K.; Kampes, B.; Sanford, M.; Young, J. C.; Aschwanden, A.; Truffer, M.; Herreid, S. J.; Hock, R. M.

    2011-12-01

    In Arctic, sub-Arctic and high-Alpine settings the ablation area of many mountain glaciers is rarely entirely temperate, and a cold near-surface layer of variable thickness, whose temperature remains below freezing throughout the year, can be found. This occurs when summer ablation rates do not melt the near-surface ice enough to remove the cold layer from the previous winter. A cold near-surface layer is a useful climatological parameter because, for example, its thinning over time can be related to climatic warming. In April 2011 we conducted several 100 MHz ground penetrating radar (GPR) surveys in the upper ablation area (˜1200 m a.s.l.) of the Kahiltna glacier, in the central Alaska Range. Surface ice temperatures, measured continuously during the preceding winter remained at ˜-4°C for 6 months. The GPR data showed the presence of a spatially variable, ˜20 m thick, transparent layer which we interpret to be the cold surface layer. A layer of similar thickness was retrieved by airborne IFSAR P-band radar surveys on several Alaskan glaciers. We use these observations to discuss the occurrence of a cold-surface layer in the Alaska Range and its usefulness for glacier monitoring studies.

  4. Surface structures of cerium oxide nanocrystalline particles from the size dependence of the lattice parameters

    NASA Astrophysics Data System (ADS)

    Tsunekawa, S.; Ito, S.; Kawazoe, Y.

    2004-10-01

    Cerium oxide nanocrystalline particles are synthesized and monodispersed in the size range from 2 to 8nm in diameter. The dependence of the lattice parameters on particle size is obtained by x-ray and electron diffraction analyses. The size dependence well coincides with the estimation based on the assumption that the surface is composed of one layer of Ce2O3 and the inside consists of CeO2. The effect of particle size on lattice parameters is discussed from the differences in the fabrication method and the surface structure.

  5. Process Conditions of Forming the Surface Layer of Aluminum Powder Product by Layer-by-layer Laser Sintering

    NASA Astrophysics Data System (ADS)

    Saprykina, N. A.; Saprykin, A. A.; Ibragimov, E. A.; Arkhipova, D. A.

    2016-07-01

    The paper presents data on state of the art in selective laser sintering of products. Layer-by-layer sintering is shown to be a future-oriented technology, making it possible to synthesize products of metal powder materials. Factors, influencing the quality of a sintered product, are revealed in the paper. It presents outcomes of experiments, focused on the dependence of surface layer thickness of sintered aluminum powder PA-4 on laser processing conditions. Basic factors, influencing the quality of a sintered surface layer include laser power, speeds of scanning and moving the laser beam on the layer of powder. Thickness of the sintered layer varies from 0.74 to 1.55 mm, as the result of changing the laser processing conditions.

  6. Surface properties of polyimide layers used in microelectronics

    NASA Astrophysics Data System (ADS)

    Borycki, Jerzy; Okulska-Bozek, Malgorzata

    1998-01-01

    Dozens of poly(amic acids) from selected aromatic diamines and dianhydrides were prepared in the first step of the classical two-step polycondensation. Polyimide layers on different surfaces were obtained by the poly(amic acids) imidization. Some of mechanical properties of these layers were tested. Some correlations between these properties and chemical structure of them wee noticed and discussed.

  7. Thin gold layer in Ni electroforming process: optical surface characterization

    NASA Astrophysics Data System (ADS)

    Sironi, G.; Spiga, D.; Pareschi, G.; Missaglia, N.; Paganini, L.

    2009-08-01

    Mandrel replication by Nickel electroforming is a well-suited process to manufacture X-ray mirrors, making use of Gold layer playing the twofold role of release agent and reflective coating. To increase the optical performances of mirrors it is crucial to minimize the impact of X-ray scattering effects related to surface microroughness, especially when the mirror is intended to operate in hard X-rays. In this case, the Gold layer simply acts as release agent because the reflection is demanded to interferential over-coatings. Even though the replicated optical surface is usually believed to reproduce the smooth topography of the master, a surface degradation is commonly observed. Such a worsening can also suffer from a contribution from the spontaneous roughness growth of the Gold layer itself: if this is the case, the mirror's optical quality could potentially benefit from the utilization of a thin Gold layer (< 100 nm) instead of the traditional thick gold layer (> 100 nm). To prove the effectiveness of the Gold thickness reduction, a microroughness characterization of replicated thin gold layers has been achieved. We report here a preliminary roughness study of 3 electroformed Ni samples replicated from a super-polished Zerodur flat master with various Gold layer thicknesses, in the spectral range 0.02-1000 μm. The study is organized as follows: (a) characterization of the 3 replicated samples; (b) comparison of the Gold roughness for thin vs. thick layers; (c) comparison of the two sides of Gold layers.

  8. Medical applications of diamond particles and surfaces.

    SciTech Connect

    Narayan, R. J.; Boehm, R. D.; Sumant, A. V.

    2011-04-01

    Diamond has been considered for use in several medical applications due to its unique mechanical, chemical, optical, and biological properties. In this paper, methods for preparing synthetic diamond surfaces and particles are described. In addition, recent developments involving the use of diamond in prostheses, sensing, imaging, and drug delivery applications are reviewed. These developments suggest that diamond-containing structures will provide significant improvements in the diagnosis and treatment of medical conditions over the coming years. Diamond is an allotrope of carbon that is being considered for use in several medical applications. Ramachandran determined that the crystal structure of diamond consists of two close packed interpenetrating face centered cubic lattices; one lattice is shifted with respect to the other along the elemental cube space diagonal by one-quarter of its length. If one approximates carbon atoms as equal diameter rigid spheres, the filling of this construction is 34%. Due to the carbon-carbon distance (1.54 {angstrom}), diamond crystal exhibits the highest atomic density (1.76 x 10{sup 23} cm{sup -3}) of any solid. The very high bond energy between two carbon atoms (83 kcal/mol) and the directionality of tetrahedral bonds are the main reasons for the high strength of diamond. Diamond demonstrates the highest Vickers hardness value of any material (10,000 kg/mm{sup 2}). The tribological properties of diamond are also impressive; the coefficient of friction of polished diamond is 0.07 in argon and 0.05 in humid air. Diamond is resistant to corrosion except in an oxygen atmosphere at temperatures over 800 C. In addition, type IIa diamond exhibits the highest thermal conductivity of all materials (20 W cm{sup -1} K{sup -1} at room temperature).

  9. Enhanced surface plasmon resonance by Au nanoparticles immobilized on a dielectric SiO2 layer on a gold surface.

    PubMed

    Jung, Jaeyeon; Na, Kyunga; Lee, Jonghwan; Kim, Ki-Woo; Hyun, Jinho

    2009-09-28

    This paper introduces strategies for enhancement of a surface plasmon resonance (SPR) signal by adopting colloidal gold nanoparticles (AuNPs) and a SiO(2) layer on a gold surface. AuNPs on SiO(2) on a gold surface were compared with an unmodified gold surface and a SiO(2) layer on a gold surface with no AuNPs attached. The modified surfaces showed significant changes in SPR signal when biomolecules were attached to the surface as compared with an unmodified gold surface. The detection limit of AuNPs immobilized on a SPR chip was 0.1 ng mL(-1) for the prostate-specific antigen (PSA), a cancer marker, as measured with a spectrophotometer. Considering that the conventional ELISA method can detect approximately 10 ng mL(-1) of PSA, the strategy described here is much more sensitive (approximately 100 fold). The enhanced shift of the absorption curve resulted from the coupling of the surface and particle plasmons by the SiO(2) layer and the AuNPs on the gold surface.

  10. Acid drainage response to surface limestone layers

    SciTech Connect

    Geidel, G.; Caruccio, F.T.

    1982-12-01

    A 150 acre drainage basin in an unreclaimed coal strip mine in east-central Ohio was studied and extensively monitored to determine the effect of a surface application of limestone on the ground water quality. Prior to the limestone treatment the ground and surface water of the basin was acidic due to pyrite oxidation in the spoil. In order to assess the effect of the limestone application the basin was divided into seven sub-basins, five of which were treated and two which served as controls. The seeps from the treated sub-basins with low acid concentrations became alkaline due to neutralization but after a long dry period, they returned to their acid condition. The moderately and highly acidic seeps showed a decline in the acid concentrations which could be attributed to a combination of neutralization and a decrease in the rate of pyrite oxidation. The results of this field study and simultaneous laboratory experiments showed that under natural conditions, with no limestone application, the acidity generated by pyrite oxidation in a backfill decreased. A surface application of limestone slightly enhanced the decrease in acidity by both neutralization and decreasing the rate of pyrite oxidation. However, the limestone application did not provide sufficient alkalinity to produce either neutral or alkaline discharges from the abandoned coal strip mine site.

  11. Anisotropy measurement of pyrolytic carbon layers of coated particles

    SciTech Connect

    Vesyolkin, Ju. A. Ivanov, A. S.; Trushkina, T. V.

    2015-12-15

    Equipment at the National Research Center Kurchatov Institute intended for the anisotropy determination of pyrolytic carbon layers in coated particles (CPs) of the GT-MGR reactor is tested and calibrated. The dependence of the anisotropy coefficient on the size of the measurement region is investigated. The results of measuring the optical anisotropy factor (OPTAF) for an aluminum mirror, rutile crystal, and available CP samples with the known characteristics measured previously using ORNL equipment (United States) are presented. In addition, measurements of CP samples prepared at VNIINM are performed. A strong dependence of the data on the preparation quality of metallographic sections is found. Our investigations allow us to make the conclusion on the working capacity of the existing equipment for measuring the anisotropy of pyrolytic carbon CP coatings using the equipment at the Kurchatov Institute with the relative error of about 1%. It is shown that the elimination of the errors caused by the stochastic fluctuations in a measuring path by mathematical processing of the signal allows us to decrease the relative error of OPTAF measurements to ∼0.3%.

  12. Metastable states of plasma particles close to a charged surface

    SciTech Connect

    Shavlov, A. V.; Dzhumandzhi, V. A.

    2015-09-15

    The free energy of the plasma particles and the charged surface that form an electroneutral system is calculated on the basis of the Poisson-Boltzmann equation. It is shown that, owing to correlation of light plasma particles near the charged surface and close to heavy particles of high charge, there can be metastable states in plasma. The corresponding phase charts of metastable states of the separate components of plasma, and plasma as a whole, are constructed. These charts depend on temperature, the charge magnitude, the size of the particles, and the share of the charge of the light carriers out of the total charge of the plasma particles.

  13. Turbulent boundary layer on a convex, curved surface

    NASA Technical Reports Server (NTRS)

    Gillis, J. C.; Johnston, J. P.; Kays, W. M.; Moffat, R. J.

    1980-01-01

    The effects of strong convex curvature on boundary layer turbulence were investigated. The data gathered on the behavior of Reynolds stress suggested the formulation of a simple turbulence model. Three sets of data were taken on two separate facilities. Both rigs had flow from a flat surface, over a convex surface with 90 deg of turning, and then onto a flat recovery surface. The geometry was adjusted so that, for both rigs, the pressure gradient along the test surface was zero - thus avoiding any effects of streamwise acceleration on the wall layers. Results show that after a sudden introduction of curvature, the shear stress in the outer part of the boundary layer is sharply diminished and is even slightly negative near the edge. The wall shear also drops off quickly downstream. In contrast, when the surface suddenly becomes flat again, the wall shear and shear stress profiles recover very slowly towards flat wall conditions.

  14. Alpha particle backscattering measurements used for chemical analysis of surfaces

    NASA Technical Reports Server (NTRS)

    Patterson, J. H.

    1967-01-01

    Alpha particle backscattering performs a chemical analysis of surfaces. The apparatus uses a curium source and a semiconductor detector to determine the energy spectrum of the particles. This in turn determines the chemical composition of the surface after calibration to known samples.

  15. Boundary layer flow visualisation patterns on a riblet surface

    NASA Astrophysics Data System (ADS)

    Clark, D. G.

    Boundary layer flow visualization methods, developed at Queen Mary and Westfield College, have been applied to a riblet surface. The results reveal cellular crossflows developing in the grooves between the riblets. These local flor regimes appear to have little direct effect on the flow in the wall layers immediately adjacent to them. Qualitatively, the behavior of the wall layers appears to be that which would be expected if a virtual surface existed at a level slightly above the riblet tops, but a tendency for the origin of longitudinal eddy pairs to become anchored to the top of a riblet is noted.

  16. Particle resuspension and associated coherent structures in a turbulent boundary layer

    NASA Astrophysics Data System (ADS)

    Braaten, David Alan

    Fundamental properties of particle resuspension from a surface solely by turbulent fluid forces was examined experimentally by observing intermittent particle resuspension and associated turbulent flow properties. Experiments were conducted in an environmental wind tunnel, where sparse beds of monodisperse Lycopodium spores (Club Moss) were placed flush with the floor of the wind tunnel, and exposed to a steady, well developed turbulent boundary layer flow. Particle bed concentration was monitored in situ throughout each experimental trial using an optical system designed to detect forward scattering from a HeNe laser beam. Simultaneous measurements of streamwise and vertical velocity were made immediately downstream of the illuminated particles using hot film anemometry. Experimental trials were conducted at three free-stream velocities (6.0, 7.5, and 9.0 m s(-1)) for a duration of 35 minutes. A Monte-Carlo particle resuspension model was developed to simulate the resuspension process associated with coherent structures of varying magnitude. Simulations were compared with experimental results to identify a probability distribution of coherent structure magnitude.

  17. Thermocapillary convection in two immiscible liquid layers with free surface

    NASA Technical Reports Server (NTRS)

    Doi, Takao; Koster, Jean N.

    1993-01-01

    Thermocapillary convection is studied in two immiscible liquid layers with one free surface, one liquid/liquid interface, and differential heating applied parallel to the interfaces. An analytical solution is introduced for infinite horizontal layers. The defining parameter for the flow pattern is lambda, the ratio of the temperature coefficient of the interfacial tension to that of the surface tension. Four different flow patterns exist under zero gravity conditions. 'Halt' conditions which halt the fluid motion in the lower encapsulated liquid layer have been found. A numerical experiment is carried out to study effects of vertical end walls on the double layer convection in a 2D cavity. The halt condition obtained from the analytical study is found to be valid in the limit of small Reynolds numbers. The flow in the encapsulated liquid layer can be suppressed substantially.

  18. Dusty boundary layer in a surface-burst explosion

    SciTech Connect

    Kuhl, A.L.; Ferguson, R.E.; Chien, K.Y.; Collins, J.P.

    1993-08-01

    Dusty boundary layers are an inherent feature of explosions over ground surfaces. Detailed knowledge of dusty boundary layer characteristics is needed in explosion safety analysis (e.g., to calculate the drag loads on structures). Also, to predicct the amount of dust in the rising fireball of an explsion, one must know the dusty boundary layer swept up during the positive and negative phases of the blast wave and how much of this boundary layer dust is entrained into the stem of the dust cloud. This paper describes the results of numerical simulations of the dusty boundary layer created by a surface burst explosion. The evolution of the flow was calculated by a high-order Godunov code that solves the nonsteady conservation laws.

  19. Kinematics of fluid particles on the sea surface: Hamiltonian theory

    NASA Astrophysics Data System (ADS)

    Fedele, F.; Chandre, C.; Farazmand, M.

    2016-08-01

    We derive the John-Sclavounos equations describing the motion of a fluid particle on the sea surface from first principles using Lagrangian and Hamiltonian formalisms applied to the motion of a frictionless particle constrained on an unsteady surface. The main result is that vorticity generated on a stress-free surface vanishes at a wave crest when the horizontal particle velocity equals the crest propagation speed, which is the kinematic criterion for wave breaking. If this holds for the largest crest, then the symplectic two-form associated with the Hamiltonian dynamics reduces instantaneously to that associated with the motion of a particle in free flight, as if the surface did not exist. Further, exploiting the conservation of the Hamiltonian function for steady surfaces and traveling waves we show that particle velocities remain bounded at all times, ruling out the possibility of the finite-time blowup of solutions.

  20. Deposition of polymer powder particles on the product surface at jet spraying

    NASA Astrophysics Data System (ADS)

    Fedyaev, V. L.; Galimov, E. R.; Gimranov, I. R.; Takhaviev, M. S.; Morenko, I. V.; Siraev, A. R.

    2016-01-01

    Gas-thermodynamic processes taking place during spraying of polymer powder materials are considered. Numerical and analytical models describing these processes are proposed. For the case of circular cylinder rotating with a constant angular velocity results of calculations and engineering formulas for estimating the thickness of powder particles layer deposited on the processed surface are present.

  1. Particle-induced indentation of the alveolar epithelium caused by surface tension forces

    PubMed Central

    Kojic, M.; Tsuda, A.

    2010-01-01

    Physical contact between an inhaled particle and alveolar epithelium at the moment of particle deposition must have substantial effects on subsequent cellular functions of neighboring cells, such as alveolar type-I, type-II pneumocytes, alveolar macrophage, as well as afferent sensory nerve cells, extending their dendrites toward the alveolar septal surface. The forces driving this physical insult are born at the surface of the alveolar air-liquid layer. The role of alveolar surfactant submerging a hydrophilic particle has been suggested by Gehr and Schürch's group (e.g., Respir Physiol 80: 17–32, 1990). In this paper, we extended their studies by developing a further comprehensive and mechanistic analysis. The analysis reveals that the mechanics operating in the particle-tissue interaction phenomena can be explained on the basis of a balance between surface tension force and tissue resistance force; the former tend to move a particle toward alveolar epithelial cell surface, the latter to resist the cell deformation. As a result, the submerged particle deforms the tissue and makes a noticeable indentation, which creates unphysiological stress and strain fields in tissue around the particle. This particle-induced microdeformation could likely trigger adverse mechanotransduction and mechanosensing pathways, as well as potentially enhancing particle uptake by the cells. PMID:20634359

  2. Roughness Characterization of and Turbulent Boundary Layer Flow over flat Snow Surfaces

    NASA Astrophysics Data System (ADS)

    Gromke, C.; Guala, M.; Manes, C.; Walter, B.; Lehning, M.

    2009-12-01

    The surface roughness is essential for all turbulent exchange processes within the lower part of the atmospheric boundary layer. Consequently, a proper representation of the surfaces roughness is needed in every mathematical description of near surface mass-, energy- and momentum exchange processes. Considering the vertical mean velocity profile of turbulent boundary layer flow, this is done by assigning an aerodynamic roughness length z0 to the surface. We followed two procedures to describe the roughness of freshly fallen snow surfaces. First, photographs of snow surfaces have been taken and evaluated using digital image analysis giving snow surface contour line coordinates. Applying structure functions to the snow surface coordinates and statistical fitting procedures, resulted in classes of surface characteristic length scales and scaling exponents. These results allow to identify the deposition process of snow fall as scaling exponents corresponded to that of Ballistic Deposition. Moreover, the resulting characteristic length scales can be assigned to typical particle size and aggregation size length scales consistent with results found by Lowe et al. (2007) and Manes et al. (2008). Second, aerodynamic roughness lengths z0 have been estimated from log-law fitting of velocity profiles over the snow surfaces measured in the SLF cold atmospheric boundary layer wind tunnel. The aerodynamic roughness lengths found are in general agreement with available literature data and suggest the presence of aerodynamically rough regimes with flow independent z0. In the synthesis of both approaches, we found evidence for a linear relationship between one class of surface characteristic length scales, which is associated with typical snow particle sizes, and aerodynamic roughness lengths z0. The correlation with the aggregation length scale is weaker for the few (4) samples analyzed thus far. The relatively weak pronounced scale separation between particle and aggregation size

  3. Boundary Layer Flow Over a Moving Wavy Surface

    NASA Astrophysics Data System (ADS)

    Hendin, Gali; Toledo, Yaron

    2016-04-01

    Boundary Layer Flow Over a Moving Wavy Surface Gali Hendin(1), Yaron Toledo(1) January 13, 2016 (1)School of Mechanical Engineering, Tel-Aviv University, Israel Understanding the boundary layer flow over surface gravity waves is of great importance as various atmosphere-ocean processes are essentially coupled through these waves. Nevertheless, there are still significant gaps in our understanding of this complex flow behaviour. The present work investigates the fundamentals of the boundary layer air flow over progressive, small-amplitude waves. It aims to extend the well-known Blasius solution for a boundary layer over a flat plate to one over a moving wavy surface. The current analysis pro- claims the importance of the small curvature and the time-dependency as second order effects, with a meaningful impact on the similarity pattern in the first order. The air flow over the ocean surface is modelled using an outer, inviscid half-infinite flow, overlaying the viscous boundary layer above the wavy surface. The assumption of a uniform flow in the outer layer, used in former studies, is now replaced with a precise analytical solution of the potential flow over a moving wavy surface with a known celerity, wavelength and amplitude. This results in a conceptual change from former models as it shows that the pressure variations within the boundary layer cannot be neglected. In the boundary layer, time-dependent Navier-Stokes equations are formulated in a curvilinear, orthogonal coordinate system. The formulation is done in an elaborate way that presents additional, formerly neglected first-order effects, resulting from the time-varying coordinate system. The suggested time-dependent curvilinear orthogonal coordinate system introduces a platform that can also support the formulation of turbulent problems for any surface shape. In order to produce a self-similar Blasius-type solution, a small wave-steepness is assumed and a perturbation method is applied. Consequently, a

  4. Surface forces of colloidal particles from micrometer to nanometer

    NASA Astrophysics Data System (ADS)

    Cho, Jeong-Min

    2003-10-01

    Surface forces of colloidal particles play critical roles in the macroscopic behavior of particulate systems such as dispersion and coagulation, adhesion and coating, and the rheological behavior of ceramic slurries. As particle size is decreased from micrometer to nanometer range, surface forces are increasingly important. Polyelectrolytes are the chemical additives commonly used to efficiently control the stabilization of the colloidal system. Their conformations on the solid surfaces as well as the interactions between the adsorbed polyelectrolytes are important issues in colloidal processing. Most experimental and theoretical approaches to the surface forces are based on particle sizes in the micrometer range. However, nanoparticles at close proximity or high solids loading are expected to show different behavior than what can be estimated from conventional theories such as continuum or mean field theories. My study examined the effect of pH, ionic strength, and molecular weight of the polyelectrolytes on the surface forces of colloidal particles by the interplay with the adsorption, turbidity, and direct surface force measurement in terms of the conformation on the solid surfaces. The colloid probe technique based on atomic force microscopy (AFM) is well established for micron size particles; and could be extended for nanosize particles by using carbon nanotubes as proximal probes. Nanotubes with their high aspect ratio avoid the contribution from cone shapes that happens with AFM tips. The difference in particle size significantly influences surface forces for sterically dispersed colloidal systems.

  5. Flux-Profile Relationship for Dust Concentration in the Stratified Atmospheric Surface Layer

    NASA Astrophysics Data System (ADS)

    Freire, L. S.; Chamecki, M.; Gillies, J. A.

    2016-08-01

    Flux-profile relationships are usually obtained under the assumption that the mean field of interest is in equilibrium with the associated surface fluxes. In this study, the existence of an equilibrium state for dust concentration in the atmospheric surface layer above sources and sinks is evaluated using large-eddy simulation. Results show that for steady-state turbulence and negligible horizontal advection, an equilibrium mean vertical profile of dust concentration is reached after one boundary-layer eddy turnover time. This is true for cases over a source or sink, under different atmospheric stabilities, and for particles with negligible or significant settling velocity. A new model relating the net surface flux to the vertical concentration profile that accounts for both atmospheric stability and particle settling velocity is proposed. The model compares well with the simulation results for all particle sizes and atmospheric stability conditions evaluated, and it can be used to estimate the concentration profile based on the surface flux, and also to estimate the surface flux by fitting the vertical concentration profile. The resulting equation can be considered as an extension of Monin-Obukhov similarity theory to the concentration of settling particles, such as mineral dust, sea-salt, pollen and other suspended aerosols.

  6. Cake filtration with particle penetration at the cake surface

    SciTech Connect

    Corapcioglu, M.Y. ); Abboud, N.M. )

    1990-08-01

    Particles in drilling muds build a filter cake on borehole walls and can migrate into the adjacent porous formation and cause formation damage. This study analyzes cake formation, including particle penetration at the cake surface. Mass-balance equations for captured and suspended particles and the fluid phase are averaged along the cake thickness, taking into account conditions of the surface and the septum. Capture mechanisms, such as surface straining, and internal cake erosion and particle capture are included in the analysis. The results are ordinary differential equations in terms of thickness, average particle concentration, average porosity, and such operational parameters as slurry concentration, injection rate, and volumetric solid fraction. Results show that during early stages of cake formation, penetrated-particle concentration peaks and then declines rapidly shortly thereafter.

  7. Long-time self-diffusion of charged spherical colloidal particles in parallel planar layers

    NASA Astrophysics Data System (ADS)

    Contreras-Aburto, Claudio; Báez, César A.; Méndez-Alcaraz, José M.; Castañeda-Priego, Ramón

    2014-06-01

    The long-time self-diffusion coefficient, DL, of charged spherical colloidal particles in parallel planar layers is studied by means of Brownian dynamics computer simulations and mode-coupling theory. All particles (regardless which layer they are located on) interact with each other via the screened Coulomb potential and there is no particle transfer between layers. As a result of the geometrical constraint on particle positions, the simulation results show that DL is strongly controlled by the separation between layers. On the basis of the so-called contraction of the description formalism [C. Contreras-Aburto, J. M. Méndez-Alcaraz, and R. Castañeda-Priego, J. Chem. Phys. 132, 174111 (2010)], the effective potential between particles in a layer (the so-called observed layer) is obtained from integrating out the degrees of freedom of particles in the remaining layers. We have shown in a previous work that the effective potential performs well in describing the static structure of the observed layer (loc. cit.). In this work, we find that the DL values determined from the simulations of the observed layer, where the particles interact via the effective potential, do not agree with the exact values of DL. Our findings confirm that even when an effective potential can perform well in describing the static properties, there is no guarantee that it will correctly describe the dynamic properties of colloidal systems.

  8. Dual-layered-coated mechanically-durable superomniphobic surfaces with anti-smudge properties.

    PubMed

    Muthiah, Palanikkumaran; Bhushan, Bharat; Yun, Kyungsung; Kondo, Hirofumi

    2013-11-01

    Bio-inspired surfaces that exhibit high contact angle and low contact angle hysteresis for various liquids and demonstrate mechanical durability and anti-smudge properties are of interest for various applications. The fabrication of such surfaces has often involved complex or expensive processes, required techniques that may not be suitable for various substrates and particles, may require surface post-treatment, or may lack durability. Dual layered coatings of roughness-induced superomniphobic surfaces that demonstrate good mechanical durability were fabricated on glass substrates using hydrophobic SiO2 nanoparticles and low surface energy fluorobinders using dip coating and spray coating techniques. The particle-to-binder ratio was optimized for contact angles of interest. The mechanical durability of these coatings was examined under mechanical rubbing action. The anti-smudge properties were examined by wiping an artificially contaminated coating using oil-impregnated microfiber cloth.

  9. Vapor layer evolution during drop impact on a heated surface

    NASA Astrophysics Data System (ADS)

    Lee, Sanghyeon; Lee, Sangjun; Lee, Jisan; Fezzaa, Kamel; Je, Jung Ho

    2015-11-01

    When a liquid drop impacts on a sufficiently hot surface above the boiling point, a vapor layer is formed between the drop and the surface, preventing direct contact between them and as a result levitating the drop, known as the Leidenfrost effect. Understanding the evolution of the vapor layer is largely unexplored despite its importance in estimating heat transfer in cooling systems of thermal or nuclear power plants. The side-profile visualization of the vapor layer, as absolutely required for investigating its evolution, has been however unavailable by conventional optical microscopy. In this study, by employing ultrafast X-ray phase contrast imaging, we directly visualize the profiles of the vapor layers during liquid drop impact on a hot surface and elucidate the evolution of the vapor layers during spreading and retraction of the drop as functions of impact height and surface temperature. We reveal that the evolution is governed by the propagation of capillary waves generated in retraction and the wavelength of capillary waves λ is inversely proportional to the impact height h with a relation ~σ/ρh ~We-1 where We is weber number. Capillary waves that converge at the center of the vapor layers are linked to the bouncing behavior of the drop.

  10. Particle zips: vertical emulsion films with particle monolayers at their surfaces.

    PubMed

    Horozov, Tommy S; Aveyard, Robert; Clint, John H; Neumann, Bernd

    2005-03-15

    Vertical emulsion films with particle monolayers at their surfaces have been studied by direct microscope observations. The effects of particle wettability and surface coverage on the structure and stability of water films in octane and octane films in water have been investigated. Monodisperse silica particles (3 microm in diameter) hydrophobized to different extents have been used. It is found that the structure and stability of emulsion films strongly depend on the film type (water-in-oil or oil-in-water), the particle contact angle, the interactions between particles from the same and the opposite monolayer, and the monolayer density. Stable films are observed only when the particle wettability fulfills the condition for stable particle bridges--in agreement with the concept that hydrophilic particles can give stable oil-in-water emulsions, whereas hydrophobic ones give water-in-oil emulsions. In the case of water films with dilute disordered monolayers at their surfaces, the hydrophilic particles are expelled from the film center toward its periphery, giving a dimple surrounded by a ring of particles bridging the film surfaces. In contrast, the thinning of octane films with dilute ordered monolayers at their surfaces finally leads to the spontaneous formation of a dense crystalline monolayer of hydrophobic particles bridging both surfaces at the center of the film. The behaviors of water and octane films with dense close-packed particle monolayers at their surfaces are very similar. In both cases, a transition from bilayer to bridging monolayer is observed at rather low capillary pressures. The implications of the above finding for particle stabilized emulsions are discussed.

  11. Particle current on flexible surfaces excited by harmonic waves.

    PubMed

    Verma, Neeta; DasGupta, Anirvan

    2013-11-01

    In this paper, a study on the directed particle current on flexible surfaces excited by a harmonic wave is reported. The proposed theory considers three different models for the kinematics of the surface, namely the Euler-Bernoulli, Timoshenko, and Rayleigh surface wave models. The particle-surface interaction terms in the theory incorporate Coulomb friction and inelastic collision between the particle and the surface. Three possible phases of motion, namely sticking, sliding, and jumping, are considered, and the phase transition boundaries are estimated analytically for a general surface model. The effect of various parameters on the particle current and certain statistical features of the particle motion are then studied numerically. Remarkably, the particle current spectra exhibit, in addition to resonance modes, antiresonance and secondary resonance modes and transversal zero crossings. These features have interesting implications for the particle dynamics in terms of dynamic jamming states and particle eddies, which are pointed out. Under certain restricted conditions, averaging calculations are also performed and compared with the corresponding numerical simulations. PMID:24329339

  12. Method for producing functionally graded nanocrystalline layer on metal surface

    DOEpatents

    Ajayi, Oyelayo O.; Hershberger, Jeffrey G.

    2010-03-23

    An improved process for the creation or formation of nanocrystalline layers on substrates' surfaces is provided. The process involves "prescuffing" the surface of a substrate such as a metal by allowing friction to occur on the surface by a load-bearing entity making rubbing contact and moving along and on the substrate's surface. The "prescuffing" action is terminated when the coefficient of friction between the surface and the noise is rising significantly. Often, the significant rise in the coefficient of friction is signaled by a change in pitch of the scuffing action sound emanating from the buffeted surface. The "prescuffing" gives rise to a harder and smoother surface which withstands better any inadequate lubrication that may take place when the "prescuffed" surface is contacted by other surfaces.

  13. Atomic and molecular layer deposition for surface modification

    SciTech Connect

    Vähä-Nissi, Mika; Sievänen, Jenni; Salo, Erkki; Heikkilä, Pirjo; Kenttä, Eija; Johansson, Leena-Sisko; Koskinen, Jorma T.; Harlin, Ali

    2014-06-01

    Atomic and molecular layer deposition (ALD and MLD, respectively) techniques are based on repeated cycles of gas–solid surface reactions. A partial monolayer of atoms or molecules is deposited to the surface during a single deposition cycle, enabling tailored film composition in principle down to molecular resolution on ideal surfaces. Typically ALD/MLD has been used for applications where uniform and pinhole free thin film is a necessity even on 3D surfaces. However, thin – even non-uniform – atomic and molecular deposited layers can also be used to tailor the surface characteristics of different non-ideal substrates. For example, print quality of inkjet printing on polymer films and penetration of water into porous nonwovens can be adjusted with low-temperature deposited metal oxide. In addition, adhesion of extrusion coated biopolymer to inorganic oxides can be improved with a hybrid layer based on lactic acid. - Graphical abstract: Print quality of a polylactide film surface modified with atomic layer deposition prior to inkjet printing (360 dpi) with an aqueous ink. Number of printed dots illustrated as a function of 0, 5, 15 and 25 deposition cycles of trimethylaluminum and water. - Highlights: • ALD/MLD can be used to adjust surface characteristics of films and fiber materials. • Hydrophobicity after few deposition cycles of Al{sub 2}O{sub 3} due to e.g. complex formation. • Same effect on cellulosic fabrics observed with low temperature deposited TiO{sub 2}. • Different film growth and oxidation potential with different precursors. • Hybrid layer on inorganic layer can be used to improve adhesion of polymer melt.

  14. Switch-like surface binding of competing multivalent particles

    NASA Astrophysics Data System (ADS)

    Tito, N. B.; Frenkel, D.

    2016-07-01

    Multivalent particles competing for binding on the same surface can exhibit switch-like behaviour, depending on the concentration of receptors on the surface. When the receptor concentration is low, energy dominates the free energy of binding, and particles having a small number of strongly-binding ligands preferentially bind to the surface. At higher receptor concentrations, multivalent effects become significant, and entropy dominates the binding free energy; particles having many weakly-binding ligands preferentially bind to the surface. Between these two regimes there is a "switch-point", at which the surface binds the two species of particles equally strongly. We demonstrate that a simple theory can account for this switch-like behaviour and present numerical calculations that support the theoretical predictions. We argue that binding selectivity based on receptor density, rather than identity, may have practical applications.

  15. Dead layer on silicon p-i-n diode charged-particle detectors

    NASA Astrophysics Data System (ADS)

    Wall, B. L.; Amsbaugh, J. F.; Beglarian, A.; Bergmann, T.; Bichsel, H. C.; Bodine, L. I.; Boyd, N. M.; Burritt, T. H.; Chaoui, Z.; Corona, T. J.; Doe, P. J.; Enomoto, S.; Harms, F.; Harper, G. C.; Howe, M. A.; Martin, E. L.; Parno, D. S.; Peterson, D. A.; Petzold, L.; Renschler, P.; Robertson, R. G. H.; Schwarz, J.; Steidl, M.; Van Wechel, T. D.; VanDevender, B. A.; Wüstling, S.; Wierman, K. J.; Wilkerson, J. F.

    2014-04-01

    Semiconductor detectors in general have a dead layer at their surfaces that is either a result of natural or induced passivation, or is formed during the process of making a contact. Charged particles passing through this region produce ionization that is incompletely collected and recorded, which leads to departures from the ideal in both energy deposition and resolution. The silicon p-i-n diode used in the KATRIN neutrino-mass experiment has such a dead layer. We have constructed a detailed Monte Carlo model for the passage of electrons from vacuum into a silicon detector, and compared the measured energy spectra to the predicted ones for a range of energies from 12 to 20 keV. The comparison provides experimental evidence that a substantial fraction of the ionization produced in the "dead" layer evidently escapes by diffusion, with 46% being collected in the depletion zone and the balance being neutralized at the contact or by bulk recombination. The most elementary model of a thinner dead layer from which no charge is collected is strongly disfavored.

  16. Dead layer on silicon p-i-n diode charged-particle detectors

    SciTech Connect

    Wall, B. L.; Amsbaugh, John F.; Beglarian, A.; Bergmann, T.; Bichsel, H. C.; Bodine, L. I.; Boyd, N. M.; Burritt, Tom H.; Chaoui, Z.; Corona, T. J.; Doe, Peter J.; Enomoto, S.; Harms, F.; Harper, Gregory; Howe, M. A.; Martin, E. L.; Parno, D. S.; Peterson, David; Petzold, Linda; Renschler, R.; Robertson, R. G. H.; Schwarz, J.; Steidl, M.; Van Wechel, T. D.; VanDevender, Brent A.; Wustling, S.; Wierman, K. J.; Wilkerson, J. F.

    2014-04-21

    Abstract Semiconductor detectors in general have a dead layer at their surfaces that is either a result of natural or induced passivation, or is formed during the process of making a contact. Charged particles passing through this region produce ionization that is incompletely collected and recorded, which leads to departures from the ideal in both energy deposition and resolution. The silicon p-i-n diode used in the KATRIN neutrinomass experiment has such a dead layer. We have constructed a detailed Monte Carlo model for the passage of electrons from vacuum into a silicon detector, and compared the measured energy spectra to the predicted ones for a range of energies from 12 to 20 keV. The comparison provides experimental evidence that a substantial fraction of the ionization produced in the "dead" layer evidently escapes by discussion, with 46% being collected in the depletion zone and the balance being neutralized at the contact or by bulk recombination. The most elementary model of a thinner dead layer from which no charge is collected is strongly disfavored.

  17. Anomalous surface fatigue in a nano-layered material.

    PubMed

    Yang, Liu; Czajkowsky, Daniel M; Sun, Jielin; Hu, Jun; Shao, Zhifeng

    2014-10-01

    Nanoscale materials fatigue within a single 7 Å layer of a 2D nano-layered material, muscovite mica, resembles fatigue in macroscopic systems except for two remarkable properties: first, there is an Å-scale precision in the depth of the damage and second, there are sharply defined "magical" stresses, beyond yield, at which the surface remains intact regardless of the number of applications of stress.

  18. Synthesis and characterization of macromolecular layers grafted to polymer surfaces

    NASA Astrophysics Data System (ADS)

    Burtovyy, Oleksandr

    The composition and behavior of surfaces and interfaces play a pivotal role in dictating the overall efficiency of the majority of polymeric materials and devices. Surface properties of the materials can be altered using surface modification techniques. It is necessary to highlight that successful methods of surface modification should affect only the upper layer of the polymer material without changing bulk properties. The processes must introduce new functionalities to the surface, optimize surface roughness, lubrication, hydrophobicity, hydrophilicity, adhesion, conductivity, and/or biocompatibility. Research presented in this dissertation is dedicated to the synthesis, characterization, and application of thin macromolecular layers anchored to polymer substrates. Specifically, attachment of functional polymers via a "grafting to" approach has been extensively studied using PET and nylon model substrates. First, poly(glycidyl methacrylate) was used to introduce permanent functionalities to the model substrates by anchoring it to model films. Then, three different functional polymers were grafted on top of the previous layer. As one part of this study, the temperature and time dependence of grafting functional layers were studied. The surface coverage by hydrophobic polymer was determined from experimental data and predicted by a model. In general, the model has a high degree of predictive capability. Next, surface modification of polymeric fibers and membranes is presented as an important application of the polymer thin layers targeted in the study. Specifically, the procedures developed for surface modification of model substrates was employed for modification of PET, nylon, and cotton fabrics as well as PET track-etched membranes. Since epoxy groups are highly reactive in various chemical reactions, the approach becomes virtually universal, allowing both various surfaces and end-functionalized macromolecules to be used in the grafted layer synthesis. PET

  19. Alternative barrier layers for surface covers in dry climates

    SciTech Connect

    Stormont, J.C.

    1994-09-01

    Surface covers are one of the most widespread remediation and waste management options in all climates. Barrier layers to limit percolation through cover systems are principal features of engineered, multi-component cover designs. Conventional barrier layer components developed for humid climates have limitations in dry climates. One alternative barrier layer is a capillary barrier, which consists of a fine-over-coarse soil arrangement. The capacity of capillary barrier to laterally divert downward moving water is the key to their success. Another alternative is a dry barrier, in which atmospheric air is circulated through a coarse layer within the cover to remove water vapor. Incorporating a coarse layer which stores water for subsequent removal by air flow reduces the requirements for the air flow velocity and increases the applicability of the dry barrier.

  20. Surface stress of graphene layers supported on soft substrate

    PubMed Central

    Du, Feng; Huang, Jianyong; Duan, Huiling; Xiong, Chunyang; Wang, Jianxiang

    2016-01-01

    We obtain the surface stress of a single layer and multilayers of graphene supported on silicone substrates by measuring the deformation of the graphene-covered substrates induced by the surface tension of liquid droplets together with the Neumann’s triangle concept. We find that the surface stress of the graphene-covered substrate is significant larger than that of the bare substrate, and it increases with increasing graphene layers, and finally reaches a constant value of about 120 mN/m on three and more layers of graphene. This work demonstrates that the apparent surface stress of graphene-substrate systems can be tuned by the substrate and the graphene layers. The surface stress and the tuning effect of the substrate on it may have applications in design and characterization of graphene-based ultra-sensitive sensors and other devices. Moreover, the method may also be used to measure the surface stress of other ultrathin films supported on soft substrates. PMID:27166087

  1. Biphasic surface amorphous layer lubrication of articular cartilage.

    PubMed

    Graindorge, Simon; Ferrandez, Wendy; Jin, Zhongmin; Ingham, Eileen; Grant, Colin; Twigg, Peter; Fisher, John

    2005-12-01

    The biphasic nature of articular cartilage has been acknowledged for some time and is known to play an important role in many of the biomechanical functions performed by this unique tissue. From the lubrication point of view however, a simple biphasic model is unable to account for the extremely low friction coefficients that have been recorded experimentally, particularly during start-up. In addition, research over the last decade has indicated the presence of a surface amorphous layer on top of articular cartilage. Here, we present results from a finite element model of articular cartilage that includes a thin, soft, biphasic surface amorphous layer (BSAL). The results of this study show that a thin BSAL, with lower elastic modulus, dramatically altered the load sharing between the solid and liquid phases of articular cartilage, particularly in the near-surface regions of the underlying bulk cartilage and within the surface amorphous layer itself where the fluid load support exceeded 85%. By transferring the load from the solid phase to the fluid phase, the biphasic surface layer improves lubrication and reduces friction, whilst also protecting the underlying cartilage surface by 'shielding' the solid phase from elevated stresses. The increase in lubrication effectiveness is shown to be greatest during short duration loading scenarios, such as shock loads.

  2. Structural rearrangements in self-assembled surfactant layers at surfaces

    SciTech Connect

    Sushko, Maria L.; Liu, Jun

    2010-03-25

    The transition from compact to extended configuration in ionic surfactant layers under the influence of salt, surfactant surface density and temperature is studied using the classical density functional theory (cDFT). The increase in ionic strength of aqueous salt solution or in surfactant surface density leads to the transition from the hemicylindrical to the perpendicular monolayer configuration of the molecules. Although producing the same structural rearrangement in the surfactant layer the origin of the effect of salt and surface density is different. While the addition of salt increases the out-of-plane attractive interactions with the solvent, the increase in density results in the increase in the in-plane repulsion in surfactant layer. The temperature effects are subtler and are mainly manifested in the reduction of the solution structuring at elevated temperatures.

  3. The Turbulent Boundary Layer on a Rough Curvilinear Surface

    NASA Technical Reports Server (NTRS)

    Droblenkov, V. F.

    1958-01-01

    A number of semiempirical approximate methods exist for determining the characteristics of the turbulent boundary layer on a curvilinear surface. At present, among these methods, the one proposed by L. G. Loitsianskii is given frequent practical application. This method is sufficiently effective and permits, in the case of wing profiles with technically smooth surfaces, calculating the basic characteristics of the boundary layer and the values of the overall drag with an accuracy which suffices for practical purposes. The idea of making use of the basic integral momentum equation ((d delta(sup xx))/dx) + ((V' delta(sup xx))/V) (2 + H) = (tau(sub 0))/(rho V(exp 2)) proves to be fruitful also for the solution of the problems in the determination of the characteristics of the turbulent boundary layer on a rough surface.

  4. An experimental investigation of turbulent boundary layers along curved surfaces

    NASA Technical Reports Server (NTRS)

    So, R. M. C.; Mellor, G. L.

    1972-01-01

    A curved wall tunnel was designed, and an equilibrium turbulent boundary layer was set up on the straight section preceding the curved test section. Turbulent boundary layer flows with uniform and adverse pressure distributions along convex and concave walls were investigated. Hot-wire measurements along the convex surface indicated that turbulent mixing between fluid layers was very much reduced. However, the law of the wall held and the skin friction, thus determined, correlated well with other measurements. Hot-wire measurements along the concave test wall revealed a system of longitudinal vortices inside the boundary layer and confirmed that concave curvature enhances mixing. A self-consistent set of turbulent boundary layer equations for flows along curved surfaces was derived together with a modified eddy viscosity. Solution of these equations together with the modified eddy viscosity gave results that correlated well with the present data on flows along the convex surface with arbitrary pressure distribution. However, it could only be used to predict the mean characteristics of the flow along concave walls because of the existence of the system of longitudinal vortices inside the boundary layer.

  5. Determination of contact angles on microporous particles using the thin-layer wicking technique.

    PubMed

    Cui, Zheng-Gang; Binks, Bernard P; Clint, John H

    2005-08-30

    The properties of particle-stabilized emulsions, especially with regard to phase inversion, are very dependent on the contact angle that the particles experience at the oil-water interface. For the very small particles used for such emulsions (often a few tens of nm), it is impossible to measure this contact angle directly. Its value could be calculated if it were possible to determine the components of the solid surface free energy. To establish a method suitable for such particles, we have investigated the imbibition of five probe liquids into a porous bed of silica (commercial TLC plates) using the thin-layer wicking technique. For all liquids, the difference between wicking rate for bare plates and for those pre-contacted with the vapors is large but it is not due to an advancing angle effect on bare plates. Our analysis shows that it is due to the diversion of flowing liquid into blind pores which are already filled in the pre-contacted case. Thus a new model is proposed describing wicking in a porous medium with very small blind pores by introducing a parameter into the Washburn equation that corrects for this capillary condensation effect. The parameter needed is determined independently using gravimetric adsorption measurements. When this modified Washburn equation is used, the difference between advancing and receding contact angle is actually quite small. When the averages are used as the Young's contact angles, values for the surface energy components of silica are obtained that are completely consistent between the five liquids and have magnitudes expected for this type of silica surface.

  6. Impact of small changes in particle surface chemistry for unentangled polymer nanocomposites.

    PubMed

    Ranka, Moulik; Varkey, Nihal; Ramakrishnan, Subramanian; Zukoski, Charles F

    2015-02-28

    We report microstructural and rheological consequences of altering silica particle surface chemistry when the particles are suspended in unentangled polyethylene glycol with a molecular weight of 400. The particle surfaces are altered by reacting them with isobutyltrimethyoxysilane. Levels of silanization are chosen so that the particles remain dispersed in the polymer at all volume fractions studied. Our studies indicate that at the levels studied, silanization does not alter the hydrodynamic thickness of the absorbed polymer layer thickness. Rheological properties are not sensitive to levels of silanization up to particle volume fractions where the average particle separation h ∼ 6Rg (4.8 nm). At these volume fractions, composite microstructure undergoes changes associated with jamming of soft particles (decorrelations in the first peak of the particle structure factor and the onset of a non-diffusive mechanism that dominates particle density fluctuations at short times.) In the region of volume fractions where h/Rg < 6, the zero-shear rate viscosity of the composites is extremely sensitive to level of silanization with a decrease in the zero-shear rate viscosity by four orders of magnitude observed for the highest levels of silanization studied in comparison to the bare particles.

  7. Surface modification of polypropylene based particle foams

    NASA Astrophysics Data System (ADS)

    Schreier, P.; Trassl, C.; Altstädt, V.

    2014-05-01

    This paper deals with the modification of the surface properties of expanded polypropylene (EPP). EPP is a semi-hard to soft elastic thermoplastic foam. The characteristic surface of EPP shows process-related steam nozzle imprints and gussets. Therefore EPP does not satisfy the quality requirements for visible automotive applications. In order to meet these demands, plastic surfaces are usually enhanced with functional or decorative coatings, e.g. textiles, plastic films or paint. The coating of plastics with low surface energies such as PP often leads to adhesion problems by reason of the missing polar and functional groups. This paper gives an evaluation of activation and pre-treatment methods of EPP, with the aim to identify the most suitable pre-treatment method. For this purpose five typical surface treatment methods - flame treatment, corona, fluorination, atmospheric and low-pressure plasma - were performed on EPP samples. As a comparison criterion the maximum increase in the adhesion force between a polyurethane-based coating and the modified EPP substrate was selected. Moreover the influence of the selected pre-treatment method on the increase in the total surface energy and its polar component was investigated by the drop shape analysis method. The results showed that the contact angle measurement is a suitable method to determine the polar and disperse fractions of the surface tension of EPP. Furthermore, all performed methods increased the adhesion of EPP.

  8. Saturn's rings - Particle size distributions for thin layer model

    NASA Technical Reports Server (NTRS)

    Zebker, H. A.; Marouf, E. A.; Tyler, G. L.

    1985-01-01

    A model incorporating limited interaction between the incident energy and particles in the ring is considered which appears to be consistent with the multiple scattering process in Saturn's rings. The model allows for the small physical thickness of the rings and can be used to relate Voyager 1 observations of 3.6- and 13-cm wavelength microwave scatter from the rings to the ring particle size distribution function for particles with radii ranging from 0.001 to 20 m. This limited-scatter model yields solutions for particle size distribution functions for eight regions in the rings, which exhibit approximately inverse-cubic power-law behavior.

  9. Many-body microhydrodynamics of colloidal particles with active boundary layers

    NASA Astrophysics Data System (ADS)

    Singh, Rajesh; Ghose, Somdeb; Adhikari, R.

    2015-06-01

    Colloidal particles with active boundary layers—regions surrounding the particles where non-equilibrium processes produce large velocity gradients—are common in many physical, chemical and biological contexts. The velocity or stress at the edge of the boundary layer determines the exterior fluid flow and, hence, the many-body interparticle hydrodynamic interaction. Here, we present a method to compute the many-body hydrodynamic interaction between N spherical active particles induced by their exterior microhydrodynamic flow. First, we use a boundary integral representation of the Stokes equation to eliminate bulk fluid degrees of freedom. Then, we expand the boundary velocities and tractions of the integral representation in an infinite-dimensional basis of tensorial spherical harmonics and, on enforcing boundary conditions in a weak sense on the surface of each particle, obtain a system of linear algebraic equations for the unknown expansion coefficients. The truncation of the infinite series, fixed by the degree of accuracy required, yields a finite linear system that can be solved accurately and efficiently by iterative methods. The solution linearly relates the unknown rigid body motion to the known values of the expansion coefficients, motivating the introduction of propulsion matrices. These matrices completely characterize hydrodynamic interactions in active suspensions just as mobility matrices completely characterize hydrodynamic interactions in passive suspensions. The reduction in the dimensionality of the problem, from a three-dimensional partial differential equation to a two-dimensional integral equation, allows for dynamic simulations of hundreds of thousands of active particles on multi-core computational architectures. In our simulation of 104 active colloidal particle in a harmonic trap, we find that the necessary and sufficient ingredients to obtain steady-state convective currents, the so-called ‘self-assembled pump’, are (a) one

  10. Sputtered silver oxide layers for surface-enhanced Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Büchel, D.; Mihalcea, C.; Fukaya, T.; Atoda, N.; Tominaga, J.; Kikukawa, T.; Fuji, H.

    2001-07-01

    We present results of reactively sputtered silver oxide thin films as a substrate material for surface-enhanced Raman spectroscopy (SERS). Herein, we show that deposited layers develop an increasingly strong SERS activity upon photoactivation at 488 nm. A benzoic acid/2-propanol solution was used to demonstrate that the bonding of molecules to SERS active sites at the surface can be followed by investigating temporal changes of the corresponding Raman intensities. Furthermore, the laser-induced structural changes in the silver oxide layers lead to a fluctuating SERS activity at high laser intensities which also affects the spectral features of amorphous carbon impurities.

  11. Tape method of forming a thin layer of doped lanthanum chromite particles and of bonding such on an electrode

    DOEpatents

    Richards, Von L.; Singhal, Subhash C.; Pal, Uday B.

    1992-01-01

    A combustible polymer film, useful for application of an interconnection on an electrode is made by: (1) providing doped LaCro.sub.3 particles; (2) dispersing doped LaCrO.sub.3 particles in a solvent, to provide a dispersion; (3) screening the dispersion to provide particles in the range of from 30 micrometers to 80 micrometers; (4) admixing a fugitive polymer with the particles; (5) casting the dispersion to provide a film; (6) drying the film; and (7) stripping the film. The film can then be applied to a porous, preheated electrode top surface, and then electrochemical vapor depositing a dense skeletal LaCrO.sub.3 structure, between and around the doped LaCrO.sub.3 particles. Additional solid oxide electrolyte and fuel electrode layers can then be added to provide a fuel cell.

  12. Tape method of forming a thin layer of doped lanthanum chromite particles and of bonding such on an electrode

    DOEpatents

    Richards, V.L.; Singhal, S.C.; Pal, U.B.

    1992-07-21

    A combustible polymer film, useful for application of an interconnection on an electrode is made by: (1) providing doped LaCro[sub 3] particles; (2) dispersing doped LaCrO[sub 3] particles in a solvent, to provide a dispersion; (3) screening the dispersion to provide particles in the range of from 30 micrometers to 80 micrometers; (4) admixing a fugitive polymer with the particles; (5) casting the dispersion to provide a film; (6) drying the film; and (7) stripping the film. The film can then be applied to a porous, preheated electrode top surface, and then a dense skeletal LaCrO[sub 3] structure is electrochemically vapor deposited between and around the doped LaCrO[sub 3] particles. Additional solid oxide electrolyte and fuel electrode layers can then be added to provide a fuel cell. 4 figs.

  13. Effect of nanoconfinement on polymer dynamics: surface layers and interphases.

    PubMed

    Krutyeva, M; Wischnewski, A; Monkenbusch, M; Willner, L; Maiz, J; Mijangos, C; Arbe, A; Colmenero, J; Radulescu, A; Holderer, O; Ohl, M; Richter, D

    2013-03-01

    We present neutron spin echo experiments that address the much debated topic of dynamic phenomena in polymer melts that are induced by interacting with a confining surface. We find an anchored surface layer that internally is highly mobile and not glassy as heavily promoted in the literature. The polymer dynamics in confinement is, rather, determined by two phases, one fully equal to the bulk polymer and another that is partly anchored at the surface. By strong topological interaction, this phase confines further chains with no direct contact to the surface. These form the often invoked interphase, where the full chain relaxation is impeded through the interaction with the anchored chains. PMID:23521308

  14. Spectrometers for particle measurements in space based on surface reflection

    NASA Astrophysics Data System (ADS)

    Barabash, S.; Wieser, M.; Wurz, P.

    2012-04-01

    This is a review talk on space particle spectrometers based on the surface reflection technique. We sum up the experience in development and operation of such instruments accumulated for the last 15 years at the Swedish Institute of space Physics, Kiruna, Sweden in close cooperation with University of Bern, Bern, Switzerland. The technique is relatively new and used in space for measurements of few eV - few keV particles. It was first introduced for neutral atom detection in the GAS instrument onboard the ESA/NASA Ulysses mission (Witte et al., 1992) and later for ion measurements (Barabash et al., 2007) onboard Indian Chandrayaan-1. When a particle hit a surface, secondary electrons release and the particle is either absorbed by the surface or get scattered or reflected. The charge state of the reflected particles normally does not depend on the initial charge state and is neutral but also includes a fraction of negative and positive ions. These charged particles can be analyzed by conventional ion optics. The secondary electrons can be used for triggering a time-of-flight system. The surface reflection technique is close to the usage of foils/ulta-thin foils for particle detections but has a number of advantages. First, it does not require high pre-acceleration potentials and thus allows making more compact and light weight instruments. Secondly, it permits detection of neutral atoms down to 10 eV. Despite the interaction with the surface modifies the original particle velocity, the proper design of the following analyzer section and ion optics can mitigate this effect. We shortly introduce main characteristics of the particle - surface interactions important for this application, describe designs of the instruments flown in space, and show performances of the surface reflection based ENA and ion spectrometers developed for Mars / Venus Express, Chandrayaan-1, BepiColombo, Phobos-Grunt, and Swedish PRISMA.

  15. Assessment of Fluorescent Particles for Surface Flow Analysis

    PubMed Central

    Tauro, Flavia; Mocio, Gabriele; Rapiti, Emiliano; Grimaldi, Salvatore; Porfiri, Maurizio

    2012-01-01

    In this paper, a systematic performance assessment of the measurement system for surface flow analysis developed by our group in (Tauro et al., Sensors, 2010) is presented. The system is based on the detection of buoyant fluorescent microspheres through a low-cost apparatus, which incorporates light sources to elicit fluorescence response and a digital camera to identify the particles' transit. Experiments are conducted using green fluorescent particles and further tests are executed to evaluate the system performance for red and orange particles varying in emission wavelength, degree of biocompatibility, and cost. The influence of the following parameters on surface flow sensing using fluorescent beads is investigated: (i) distance of the light sources from the water surface, (ii) presence of an ad-hoc filter tuned at the particle emission wavelength, (iii) camera resolution and frame rate, (iv) flow regime, and (v) ambient light. Experimental results are used to inform implementation guidelines for surface flow analysis in natural environments. PMID:23202234

  16. Financial Brownian Particle in the Layered Order-Book Fluid and Fluctuation-Dissipation Relations

    NASA Astrophysics Data System (ADS)

    Yura, Yoshihiro; Takayasu, Hideki; Sornette, Didier; Takayasu, Misako

    2014-03-01

    We introduce a novel description of the dynamics of the order book of financial markets as that of an effective colloidal Brownian particle embedded in fluid particles. The analysis of comprehensive market data enables us to identify all motions of the fluid particles. Correlations between the motions of the Brownian particle and its surrounding fluid particles reflect specific layering interactions; in the inner layer the correlation is strong and with short memory, while in the outer layer it is weaker and with long memory. By interpreting and estimating the contribution from the outer layer as a drag resistance, we demonstrate the validity of the fluctuation-dissipation relation in this nonmaterial Brownian motion process.

  17. Particle accumulation on periodic orbits by repeated free surface collisions

    NASA Astrophysics Data System (ADS)

    Hofmann, Ernst; Kuhlmann, Hendrik C.

    2011-07-01

    The motion of small particles suspended in cylindrical thermocapillary liquid bridges is investigated numerically in order to explain the experimentally observed particle accumulation structures (PAS) in steady two- and time-dependent three-dimensional flows. Particles moving in this flow are modeled as perfect tracers in the bulk, which can undergo collisions with the free surface. By way of free-surface collisions the particles are transferred among different streamlines which represents the particle trajectories in the bulk. The inter-streamline transfer-process near the free surface together with the passive transport through the bulk is used to construct an iterative map that can describe the accumulation process as an attraction to a stable fixed point which represents PAS. The flow topology of the underlying azimuthally traveling hydrothermal wave turns out to be of key importance for the existence of PAS. In a frame of reference exactly rotating with the hydrothermal wave the three-dimensional flow is steady and exhibits co-existing regular and chaotic streamlines. We find that particles are attracted to accumulation structures if a closed regular streamline exists in the rotating frame of reference which closely approaches the free surface locally. Depending on the closed streamline and the particle radius PAS can arise as a specific trajectory which winds about the closed regular streamline or as the surface of a particular stream tube containing the closed streamline.

  18. Tailoring surface properties of paper using nanosized precipitated calcium carbonate particles.

    PubMed

    Nypelö, Tiina; Österberg, Monika; Laine, Janne

    2011-09-01

    Pigment particles used in paper coatings are typically of micrometer size and consequently the thickness of the coatings is, even at its lowest, in micrometer scale. Progress in nanotechnology has given way to the development of nanosized materials to be used in coatings, yet their exploitation has not been studied to a great extent. This study examines utilization of nanosized precipitated calcium carbonate (nanoPCC) particles in nanoscale thin coating layers. In contrast to commonly used coatings, a thin nanoparticle-based coating was targeted to change the substrate surface characteristics via controlled surface structure rather than via high coat weight. A novel approach for stabilizing and modifying the nanoPCC particles with pectin and alkenyl succinic anhydride (ASA) was utilized and a nanoparticle coating with uniform particle distribution was created. The coating applied on paper substrate was hydrophobic, having a water contact angle of 125°. Particle surface modification provided dispersion stability, enabling control of the coating layer structure. The introduced concept provides a new approach to paper coatings utilizing controlled deposition of nanoparticles with extremely low coat weight, yet having high impact on substrate surface properties. Additionally, as paper is an environmentally sound product, the approach to form a controllable nanostructure on a green substrate has potential in applications outside the traditional paper products.

  19. Interactions between protein coated particles and polymer surfaces studied with the rotating particles probe.

    PubMed

    Kemper, M; Spridon, D; van IJzendoorn, L J; Prins, M W J

    2012-05-29

    Nonspecific interactions between proteins and polymer surfaces have to be minimized in order to control the performance of biosensors based on immunoassays with particle labels. In this paper we investigate these nonspecific interactions by analyzing the response of protein coated magnetic particles to a rotating magnetic field while the particles are in nanometer vicinity to a polymer surface. We use the fraction of nonrotating (bound) particles as a probe for the interaction between the particles and the surface. As a model system, we study the interaction of myoglobin coated particles with oxidized polystyrene surfaces. We measure the interaction as a function of the ionic strength of the solution, varying the oxidation time of the polystyrene and the pH of the solution. To describe the data we propose a model in which particles bind to the polymer by crossing an energy barrier. The height of this barrier depends on the ionic strength of the solution and two interaction parameters. The fraction of nonrotating particles as a function of ionic strength shows a characteristic shape that can be explained with a normal distribution of energy barrier heights. This method to determine interaction parameters paves the way for further studies to quantify the roles of protein coated particles and polymers in their mutual nonspecific interactions in different matrixes.

  20. Surface morphological evolution during annealing of epitaxial Cu(001) layers

    SciTech Connect

    Purswani, J. M.; Gall, D.

    2008-08-15

    Single crystal Cu(001) layers were grown on MgO(001) by ultrahigh vacuum magnetron sputtering at T{sub s}=100 deg. C. Quantitative surface morphological analyses by in situ scanning tunneling microscopy show that the surfaces exhibit self-affine mound structures with a scaling exponent of 0.82{+-}0.03 and a mound radius r{sub c} that increases from 31{+-}8 to 39{+-}6 nm for increasing layer thickness t=24-120 nm. In situ annealing at 200 and 300 deg. C leads to a thermodynamically driven mass transport that minimizes the surface step density, resulting in broader mounds and a smaller root mean square surface roughness {sigma}. This effect is most pronounced for t=24 nm, for which r{sub c} increases from 31{+-}8 to 70{+-}20 nm and {sigma} decreases from 1.3{+-}0.1 to 0.74{+-}0.08 nm, resulting in a decrease in the average surface slope from {chi}=7 deg. to 2 deg. and an increase in the average terrace width w{sub T} by more than a factor of 4. In contrast, w{sub T} increases by only 20% for t=120 nm. This remarkable difference between 'thin' and 'thick' layers is attributed to diverging surface morphological pathways during annealing: The strong smoothening for t=24 nm is due to a competitive coalescence process where some mounds grow laterally at the expense of their smaller neighbors, which die out. In contrast, the initially wider mounds of thicker layers (t=120 nm) combine to form a quasistable surface morphology that exhibits anisotropic mound structures, which limit mass transport and stabilize the surface step density.

  1. Thermal radiation and Hall effects on boundary layer flow past a non-isothermal stretching surface embedded in porous medium with non-uniform heat source/sink and fluid-particle suspension

    NASA Astrophysics Data System (ADS)

    Gireesha, B. J.; Mahanthesh, B.; Gorla, Rama Subba Reddy; Manjunatha, P. T.

    2016-04-01

    Theoretical study on hydromagnetic heat transfer in dusty viscous fluid on continuously stretching non-isothermal surface, with linear variation of surface temperature or heat flux has been carried out. Effects of Hall current, Darcy porous medium, thermal radiation and non-uniform heat source/sink are taken into the account. The sheet is considered to be permeable to allow fluid suction or blowing, and stretching with a surface velocity varied according to a linear. Two cases of the temperature boundary conditions were considered at the surface namely, PST and PHF cases. The governing partial differential equations are transferred to a system of non-linear ordinary differential equations by employing suitable similarity transformations and then they are solved numerically. Effects of various pertinent parameters on flow and heat transfer for both phases is analyzed and discussed through graphs in detail. The values of skin friction and Nusselt number for different governing parameters are also tabulated. Comparison of the present results with known numerical results is presented and an excellent agreement is found.

  2. Turbulent dusty boundary layer in an ANFO surface-burst explosion

    NASA Astrophysics Data System (ADS)

    Kuhl, A. L.; Ferguson, R. E.; Chien, K. Y.; Collins, J. P.

    1992-01-01

    This paper describes the results of numerical simulations of the dusty, turbulent boundary layer created by a surface burst explosion. The blast wave was generated by the detonation of a 600-T hemisphere of ANFO, similar to those used in large-scale field tests. The surface was assumed to be ideally noncratering but contained an initial loose layer of dust. The dust-air mixture in this fluidized bed was modeled as a dense gas (i.e., an equilibrium model, valid for very small-diameter dust particles). The evolution of the flow was calculated by a high-order Godunov code that solves the nonsteady conservation laws. Shock interactions with dense layer generated vorticity near the wall, a result that is similar to viscous, no-slip effects found in clean flows. The resulting wall shear layer was unstable, and rolled up into large-scale rotational structures. These structures entrained dense material from the wall layer and created a chaotically striated flow. The boundary layer grew due to merging of the large-scale structures and due to local entrainment of the dense material from the fluidized bed. The chaotic flow was averaged along similarity lines (i.e., lines of constant values of x = r/Rs and y = z/Rs where R(sub s) = ct(exp alpha)) to establish the mean-flow profiles and the r.m.s. fluctuating-flow profiles of the boundary layer.

  3. Turbulent dusty boundary layer in an ANFO surface-burst explosion

    SciTech Connect

    Kuhl, A.L.; Ferguson, R.E.; Chien, K.Y.; Collins, J.P.

    1992-01-01

    This paper describes the results of numerical simulations of the dusty, turbulent boundary layer created by a surface burst explosion. The blast wave was generated by the detonation of a 600-T hemisphere of ANFO, similar to those used in large-scale field tests. The surface was assumed to be ideally noncratering but contained in initial loose layer of dust. The dust-air mixture in this fluidized bed was modeled as a dense gas (i.e., an equilibrium model, valid for very small-diameter dust particles). The evolution of the flow was calculated by a high-order Godunov code that solves the nonsteady conservation laws. Shock interactions with dense layer generated vorticity near the wall -- similar to viscous, no-slip effects found in clean flows. The resulting will shear layer was unstable, and rolled up into large-scale rotational structures. These structures entrained dense material from the wall layer and created a chaotically striated flow. The boundary layer grew due to merging of the large-scale structures and due to local entrainment of the dense material from the fluidized bed. The chaotic flow was averaged along similarity lines (i.e., lines of constant values of x = r/Rs and y = z/Rs where R{sub s} = ct{sup {alpha}}) to establish the mean-flow profiles and the r.m.s. fluctuating-flow profiles of the boundary layer.

  4. Fabrication of nanocrystalline surface composite layer on Cu plate under ball collisions.

    PubMed

    Romankov, S; Park, Y C; Yoon, J M

    2014-10-01

    It was demonstrated that the severe plastic deformation of a surface induced by repeated ball collisions can be effectively used for fabrication of the nanocrystalline surface composite layers. The Cu disk was fixed at the top of a vibration chamber and ball treated. Al, Zr, Ni, Co and Fe were introduced into a Cu plate as contaminants from the grinding media one after the other by 15-min ball treatment. The composite structure was formed as a result of mechanical intermixing of the components. The particle size in as-fabricated layer ranged from 2 nm to 20 nm, with average values of about 7 nm. As-fabricated layer contained non-equilibrium multicomponent solid solution based on FCC Cu crystal structure, Zr-based phase, nanosized steel debris and amorphous phase. The hardness of the as-fabricated composite was almost ten times that of the initial Cu plate. PMID:25942932

  5. Homogenous Surface Nucleation of Solid Polar Stratospheric Cloud Particles

    NASA Technical Reports Server (NTRS)

    Tabazadeh, A.; Hamill, P.; Salcedo, D.; Gore, Warren J. (Technical Monitor)

    2002-01-01

    A general surface nucleation rate theory is presented for the homogeneous freezing of crystalline germs on the surfaces of aqueous particles. While nucleation rates in a standard classical homogeneous freezing rate theory scale with volume, the rates in a surface-based theory scale with surface area. The theory is used to convert volume-based information on laboratory freezing rates (in units of cu cm, seconds) of nitric acid trihydrate (NAT) and nitric acid dihydrate (NAD) aerosols into surface-based values (in units of sq cm, seconds). We show that a surface-based model is capable of reproducing measured nucleation rates of NAT and NAD aerosols from concentrated aqueous HNO3 solutions in the temperature range of 165 to 205 K. Laboratory measured nucleation rates are used to derive free energies for NAT and NAD germ formation in the stratosphere. NAD germ free energies range from about 23 to 26 kcal mole, allowing for fast and efficient homogeneous NAD particle production in the stratosphere. However, NAT germ formation energies are large (greater than 26 kcal mole) enough to prevent efficient NAT particle production in the stratosphere. We show that the atmospheric NAD particle production rates based on the surface rate theory are roughly 2 orders of magnitude larger than those obtained from a standard volume-based rate theory. Atmospheric volume and surface production of NAD particles will nearly cease in the stratosphere when denitrification in the air exceeds 40 and 78%, respectively. We show that a surface-based (volume-based) homogeneous freezing rate theory gives particle production rates, which are (not) consistent with both laboratory and atmospheric data on the nucleation of solid polar stratospheric cloud particles.

  6. Super-hydrophobic surfaces of layer-by-layer structured film-coated electrospun nanofibrous membranes

    NASA Astrophysics Data System (ADS)

    Ogawa, Tasuku; Ding, Bin; Sone, Yuji; Shiratori, Seimei

    2007-04-01

    We have recently fabricated super-hydrophobic membrane surfaces based on the inspiration of self-cleaning silver ragwort leaves. This biomimetic super-hydrophobic surface was composed of fluoroalkylsilane (FAS)-modified layer-by-layer (LBL) structured film-coated electrospun nanofibrous membranes. The rough fibre surface caused by the electrostatic LBL coating of TiO2 nanoparticles and poly(acrylic acid) (PAA) was used to imitate the rough surface of nanosized grooves along the silver ragwort leaf fibre axis. The results showed that the FAS modification was the key process for increasing the surface hydrophobicity of the fibrous membranes. Additionally, the dependence of the hydrophobicity of the membrane surfaces upon the number of LBL coating bilayers was affected by the membrane surface roughness. Moreover, x-ray photoelectron spectroscopy (XPS) results further indicated that the surface of LBL film-coated fibres absorbed more fluoro groups than the fibre surface without the LBL coating. A (TiO2/PAA)10 film-coated cellulose acetate nanofibrous membrane with FAS surface modification showed the highest water contact angle of 162° and lowest water-roll angle of 2°.

  7. Estimating Active Layer Thickness from Remotely Sensed Surface Deformation

    NASA Astrophysics Data System (ADS)

    Liu, L.; Schaefer, K. M.; Zhang, T.; Wahr, J. M.

    2010-12-01

    We estimate active layer thickness (ALT) from remotely sensed surface subsidence during thawing seasons derived from interferometric synthetic aperture radar (InSAR) measurements. Ground ice takes up more volume than ground water, so as the soil thaws in summer and the active layer deepens, the ground subsides. The volume of melted ground water during the summer thaw determines seasonal subsidence. ALT is defined as the maximum thaw depth at the end of a thawing season. By using InSAR to measure surface subsidence between the start and end of summer season, one can estimate the depth of thaw over a large area (typically 100 km by 100 km). We developed an ALT retrieval algorithm integrating InSAR-derived surface subsidence, observed soil texture, organic matter content, and moisture content. We validated this algorithm in the continuous permafrost area on the North Slope of Alaska. Based on InSAR measurements using ERS-1/2 SAR data, our estimated values match in situ measurements of ALT within 1--10 cm at Circumpolar Active Layer Monitoring (CALM) sites within the study area. The active layer plays a key role in land surface processes in cold regions. Current measurements of ALT using mechanical probing, frost/thaw tubes, or inferred from temperature measurements are of high quality, but limited in spatial coverage. Using InSAR to estimate ALT greatly expands the spatial coverage of ALT observations.

  8. Luna 9 photographs: Evidence for a fragmental surface layer

    USGS Publications Warehouse

    Gault, D.E.; Quaide, W.L.; Oberbeck, V.R.; Moore, H.J.

    1966-01-01

    The morphological features of the lunar surface photographed by Luna 9 indicate a surficial layer of weakly cohesive to noncohesive fragmental material. Most of this material is finer than a centimeter and probably finer than a few millimeters, although objects of centimeter size and larger are plentiful.

  9. Effect of particle momentum transfer on an oblique-shock-wave/laminar-boundary-layer interaction

    NASA Astrophysics Data System (ADS)

    Teh, E.-J.; Johansen, C. T.

    2016-11-01

    Numerical simulations of solid particles seeded into a supersonic flow containing an oblique shock wave reflection were performed. The momentum transfer mechanism between solid and gas phases in the shock-wave/boundary-layer interaction was studied by varying the particle size and mass loading. It was discovered that solid particles were capable of significant modulation of the flow field, including suppression of flow separation. The particle size controlled the rate of momentum transfer while the particle mass loading controlled the magnitude of momentum transfer. The seeding of micro- and nano-sized particles upstream of a supersonic/hypersonic air-breathing propulsion system is proposed as a flow control concept.

  10. NMR of thin layers using a meanderline surface coil

    DOEpatents

    Cowgill, Donald F.

    2001-01-01

    A miniature meanderline sensor coil which extends the capabilities of nuclear magnetic resonance (NMR) to provide analysis of thin planar samples and surface layer geometries. The sensor coil allows standard NMR techniques to be used to examine thin planar (or curved) layers, extending NMRs utility to many problems of modern interest. This technique can be used to examine contact layers, non-destructively depth profile into films, or image multiple layers in a 3-dimensional sense. It lends itself to high resolution NMR techniques of magic angle spinning and thus can be used to examine the bonding and electronic structure in layered materials or to observe the chemistry associated with aging coatings. Coupling this sensor coil technology with an arrangement of small magnets will produce a penetrator probe for remote in-situ chemical analysis of groundwater or contaminant sediments. Alternatively, the sensor coil can be further miniaturized to provide sub-micron depth resolution within thin films or to orthoscopically examine living tissue. This thin-layer NMR technique using a stationary meanderline coil in a series-resonant circuit has been demonstrated and it has been determined that the flat meanderline geometry has about he same detection sensitivity as a solenoidal coil, but is specifically tailored to examine planar material layers, while avoiding signals from the bulk.

  11. Eliminated Phototoxicity of TiO2 Particles by an Atomic-Layer-Deposited Al2 O3 Coating Layer for UV-Protection Applications.

    PubMed

    Jang, Eunyong; Sridharan, Kishore; Park, Young Min; Park, Tae Joo

    2016-08-16

    We demonstrate the conformal coating of an ultrathin Al2 O3 layer on TiO2 nanoparticles through atomic layer deposition by using a specifically designed rotary reactor to eliminate the phototoxicity of the particles for cosmetic use. The ALD reactor is modified to improve the coating efficiency as well as the agitation of the particles for conformal coating. Elemental and microstructural analyses show that ultrathin Al2 O3 layers are conformally deposited on the TiO2 nanoparticles with a controlled thickness. Rhodamine B dye molecules on Al2 O3 -coated TiO2 exhibited a long life time under UV irradiation, that is, more than 2 h, compared to that on bare TiO2 , that is, 8 min, indicating mitigation of photocatalytic activity by the coated layer. The effect of carbon impurities in the film resulting from various deposition temperatures and thicknesses of the Al2 O3 layer on the photocatalytic activity are also thoroughly investigated with controlled experimental condition by using dye molecules on the surface. Our results reveal that an increased carbon impurity resulting from a low processing temperature provides a charge conduction path and generates reactive oxygen species causing the degradation of dye molecule. A thin coated layer, that is, less than 3 nm, also induced the tunneling of electrons and holes to the surface, hence oxidizing dye molecules. Furthermore, the introduction of an Al2 O3 layer on TiO2 improves the light trapping thus, enhances the UV absorption. PMID:27405514

  12. Eliminated Phototoxicity of TiO2 Particles by an Atomic-Layer-Deposited Al2 O3 Coating Layer for UV-Protection Applications.

    PubMed

    Jang, Eunyong; Sridharan, Kishore; Park, Young Min; Park, Tae Joo

    2016-08-16

    We demonstrate the conformal coating of an ultrathin Al2 O3 layer on TiO2 nanoparticles through atomic layer deposition by using a specifically designed rotary reactor to eliminate the phototoxicity of the particles for cosmetic use. The ALD reactor is modified to improve the coating efficiency as well as the agitation of the particles for conformal coating. Elemental and microstructural analyses show that ultrathin Al2 O3 layers are conformally deposited on the TiO2 nanoparticles with a controlled thickness. Rhodamine B dye molecules on Al2 O3 -coated TiO2 exhibited a long life time under UV irradiation, that is, more than 2 h, compared to that on bare TiO2 , that is, 8 min, indicating mitigation of photocatalytic activity by the coated layer. The effect of carbon impurities in the film resulting from various deposition temperatures and thicknesses of the Al2 O3 layer on the photocatalytic activity are also thoroughly investigated with controlled experimental condition by using dye molecules on the surface. Our results reveal that an increased carbon impurity resulting from a low processing temperature provides a charge conduction path and generates reactive oxygen species causing the degradation of dye molecule. A thin coated layer, that is, less than 3 nm, also induced the tunneling of electrons and holes to the surface, hence oxidizing dye molecules. Furthermore, the introduction of an Al2 O3 layer on TiO2 improves the light trapping thus, enhances the UV absorption.

  13. Hydrodynamics of interaction of particles (including cells) with surfaces

    NASA Astrophysics Data System (ADS)

    Duszyk, Marek; Doroszewski, Jan

    The study of the phenomena related to the motion of particles flowing in the proximity of the wall is pursued for purely cognitive reason as well as for some important practical purposes in various fields of technology, biology and medicine. When small spherical rigid particles move in the direction parallel to the surface their velocity is smaller than that of the fluid and depends on the ratio of the distance from the wall to the particle radius. The velocity of a particle falling down in a vertical cylinder is maximal in an eccentric position. A sphere in contact with the wall remains stationary. Translational velocity of spherical rigid particles the dimension of which are comparable to that of the tube is only slightly dependent of their lateral position. The differences in the flow parameters of deformable particles in comparison with rigid ones depend on the particle and fluid viscosity coefficient. When the particles move perpendicularly toward the wall, their velocity decreases as the particle approaches the surface. The change of particle velocity is inversely proportional to the gap. There are several theories explaining the influence of the channel diameter on the suspension viscosity (sigma phenomenon); a modern approach is based on the analysis of rheological properties of suspensions. The explanations of the Fahraeus effect (i.e. the fact that the concentration of particles flowing in a tube linking two containers are smaller than that in the containers) are based on non-uniform particle distribution in a transverse cross section and on the differences of velocities of particles and medium. The deviation of the velocity profile of a suspension of rigid particles flowing through a tube from the parabolic shape (blunting) does not depend on the flow velocity; as concerns deformable particles, however, this effect is the smaller the greater is the flow velocity. When the Reynolds number for particles is greater than 10 -3, there appears a component of

  14. Adhering grains and surface features on two Itokawa particles

    NASA Astrophysics Data System (ADS)

    Dobrică, E.; Ogliore, R. C.

    2016-02-01

    We investigated the surface texture and chemical compositions of two ~40-μm particles returned from the surface regolith of asteroid Itokawa (RB-DQ04-0062 and RB-DQ04-0091) by the Japan Aerospace Exploration Agency's Hayabusa mission. We identified splash melts, surface blistering, and many small adhering particles. Seven focused ion beam sections were extracted from both Itokawa particles, targeting one splash melt and ten adhering particles to investigate their composition and provenance and the role of micrometeoroid impacts on Itokawa's surface. Based on the particle's structure, mineralogy, and interface between the adhering particle and host grain, we identified lithic fragments and particles deposited by impact. These have morphologies and compositions consistent with impact-generated deposits: two have morphologies and compositions that are consistent with impact-generated silica glass, and one was a Ni-free, metallic Fe, and S-rich assemblage that was likely generated by vapor recondensation during a micrometeoroid impact. This study shows that, even though its regolith is young, micrometeoroid impacts have altered the regolith of asteroid Itokawa.

  15. Particle concentrations and number size distributions in the planetary boundary layer derived from airship based measurements

    NASA Astrophysics Data System (ADS)

    Tillmann, Ralf; Zhao, Defeng; Ehn, Mikael; Hofzumahaus, Andreas; Holland, Frank; Rohrer, Franz; Kiendler-Scharr, Astrid; Wahner, Andreas

    2014-05-01

    Atmospheric particles play a key role for regional and global climate due to their direct and indirect radiative forcing effects. The concentration and size of the particles are important variables to these effects. Within the continental planetary boundary layer (PBL) the particle number size distribution is influenced by meteorological parameters, local sinks and sources resulting in variable spatial distributions. However, measurements of particle number size distributions over a broad vertical range of the PBL are rare. The airship ZEPPELIN NT is an ideal platform to measure atmospheric aerosols on a regional scale within an altitude range up to 1000 m. For campaigns in the Netherlands, Northern Italy and South Finland in 2012 and 2013 the airship was deployed with a wide range of instruments, including measurements of different trace gases, short lived radicals, solar radiation, aerosols and meteorological parameters. Flights were carried out at different times of the day to investigate the influence of the diurnal evolution of the PBL on atmospheric trace gases and aerosols. During night and early morning hours the concentration and size distribution of atmospheric particles were found to be strongly influenced by the layered structure of the PBL, i.e. the nocturnal boundary layer and the residual layer. Within the residual layer particle concentrations stay relatively constant as this layer is decoupled from ground sources. The particles persist in the accumulation mode as expected for an aged aerosol. In the nocturnal boundary layer particle concentrations and size are more dynamic with higher concentrations than in the residual layer. A few hours after sunrise, the layered structure of the PBL intermixes. During daytime the PBL is well mixed and a negative concentration gradient with increasing height is observed. Several height profiles at different times of the day and at different locations in Europe were measured. The aerosol measurements will be

  16. The impact of surface properties on particle-interface interactions

    NASA Astrophysics Data System (ADS)

    Wang, Anna; Kaz, David; McGorty, Ryan; Manoharan, Vinothan N.

    2013-03-01

    The propensity for particles to bind to oil-water interfaces was first noted by Ramsden and Pickering over a century ago, and has been attributed to the huge reduction in surface energy when a particle breaches an oil-water interface and straddles it at its equilibrium height. Since then materials on a variety of length scales have been fabricated using particles at interfaces, from Pickering emulsions to Janus particles. In these applications, it is simply assumed that the particle sits at its hugely energetically favourable equilibrium position. However, it was recently shown that the relaxation of particles towards their equilibrium position is logarithmic in time and could take months, much longer than typical experiments. Here we investigate how surface charge and particle 'hairiness' impact the interaction between micron-sized particles and oil-water interfaces, and explore a molecular kinetic theory model to help understand these results. We use digital holographic microscopy to track micron-sized particles as they approach an oil-water interface with a resolution of 2 nm in all three dimensions at up to thousands of frames per second.

  17. Utilization of surface-treated rubber particles from waste tires

    SciTech Connect

    Smith, F.G. |

    1994-12-01

    During a 12-month program, the author successfully demonstrated commercial applications for surface-treated rubber particles in two major markets: footwear (shoe soles and components) and urethane-foam carpet underlay (padding). In these markets, he has clearly demonstrated the ease of using R-4080 and R-4030 surface-treated rubber particles in existing manufacturing plants and processes and have shown that the material meets or exceeds existing standards for performance, quality, and cost-effectiveness. To produce R-4080 and R-4030, vulcanized rubber, whole-tire material is finely ground to particles of nominal 80 and mesh size respectively. Surface treatment is achieved by reacting these rubber particles with chlorine gas. In this report, the author describes the actual test and evaluations of the participant companies, and identifies other potential end uses.

  18. Effects of mesoscale surface inhomogeneities on atmospheric boundary layer transfer

    SciTech Connect

    Shaw, W.J.; Doran, J.C.; Hubbe, J.M.

    1992-09-01

    Defining the nature of turbulent transfer over horizontally inhomogeneous surfaces remains one of the challenges in meteorology. Because the transfer of energy and momentum through the atmospheric boundary layer forms part of the lower boundary condition for global climate models (GCMs), the problem is important. Over the last two decades, advances in sensor and computer technology wave made good point measurements of turbulent fluxes fairly routine. A fundamental question with respect to climate models, however, is how such point measurements are related to average fluxes over the area of a GCM grid box. In this paper we will use data from the field program to depict the evolution of the boundary layer over adjacent, sharply contrasting surface types on two separate occasions. We will then use simple scaling based on the observations to argue that sub-gridscale motions would often be likely to significantly alter the estimates and resulting parameterizations of GCM-scale surface fluxes in the region.

  19. Lateral optical force on chiral particles near a surface

    PubMed Central

    Wang, S. B.; Chan, C. T.

    2014-01-01

    Light can exert radiation pressure on any object it encounters and that resulting optical force can be used to manipulate particles. It is commonly assumed that light should move a particle forward and indeed an incident plane wave with a photon momentum ħk can only push any particle, independent of its properties, in the direction of k. Here we demonstrate, using full-wave simulations, that an anomalous lateral force can be induced in a direction perpendicular to that of the incident photon momentum if a chiral particle is placed above a substrate that does not break any left–right symmetry. Analytical theory shows that the lateral force emerges from the coupling between structural chirality (the handedness of the chiral particle) and the light reflected from the substrate surface. Such coupling induces a sideway force that pushes chiral particles with opposite handedness in opposite directions. PMID:24598792

  20. Nucleation and Early Stages of Layer-by-Layer Growth of Metal Organic Frameworks on Surfaces

    PubMed Central

    2015-01-01

    High resolution atomic force microscopy (AFM) is used to resolve the evolution of crystallites of a metal organic framework (HKUST-1) grown on Au(111) using a liquid-phase layer-by-layer methodology. The nucleation and faceting of individual crystallites is followed by repeatedly imaging the same submicron region after each cycle of growth and we find that the growing surface is terminated by {111} facets leading to the formation of pyramidal nanostructures for [100] oriented crystallites, and triangular [111] islands with typical lateral dimensions of tens of nanometres. AFM images reveal that crystallites can grow by 5–10 layers in each cycle. The growth rate depends on crystallographic orientation and the morphology of the gold substrate, and we demonstrate that under these conditions the growth is nanocrystalline with a morphology determined by the minimum energy surface. PMID:26709359

  1. Microhydrodynamics of flotation processes in the sea surface layer

    NASA Astrophysics Data System (ADS)

    Grammatika, Marianne; Zimmerman, William B.

    2001-10-01

    The uppermost surface of the ocean forms a peculiarly important ecosystem, the sea surface microlayer (SML). Comprising the top 1-1000 μm of the ocean surface, the SML concentrates many chemical substances, particularly those that are surface active. Important economically as a nursery for fish eggs and larvae, the SML unfortunately is also especially vulnerable to pollution. Contaminants that settle out from the air, have low solubility, or attach to floatable matter tend to accumulate in the SML. Bubbles contribute prominently to the dynamics of air-sea exchanges, playing an important role in geochemical cycling of material in the upper ocean and SML. In addition to the movement of bubbles, the development of a bubble cloud interrelates with the single particle dynamics of all other bubbles and particles. In the early sixties, several in situ oceanographic techniques revealed an "unbelievably immense" number of coastal bubbles of radius 15-300 μm. The spatial and temporal variation of bubble numbers were studied; acoustical oceanographers now use bubbles as tracers to determine ocean processes near the ocean surface. Sea state and rain noises have both been definitively ascribed to the radiation from huge numbers of infant micro bubbles [The Acoustic Bubble. Academic Press, San Diego]. Our research programme aims at constructing a hydrodynamic model for particle transport processes occurring at the microscale, in multi-phase flotation suspensions. Current research addresses bubble and floc microhydrodynamics as building blocks for a microscale transport model. This paper reviews sea surface transport processes in the microlayer and the lower atmosphere, and identifies those amenable to microhydrodynamic modelling and simulation. It presents preliminary simulation results including the multi-body hydrodynamic mobility functions for the modelling of "dynamic bubble filters" and floc suspensions. Hydrodynamic interactions versus spatial anisotropy and size of

  2. Oxygen inhibition layer of composite resins: effects of layer thickness and surface layer treatment on the interlayer bond strength.

    PubMed

    Bijelic-Donova, Jasmina; Garoushi, Sufyan; Lassila, Lippo V J; Vallittu, Pekka K

    2015-02-01

    An oxygen inhibition layer develops on surfaces exposed to air during polymerization of particulate filling composite. This study assessed the thickness of the oxygen inhibition layer of short-fiber-reinforced composite in comparison with conventional particulate filling composites. The effect of an oxygen inhibition layer on the shear bond strength of incrementally placed particulate filling composite layers was also evaluated. Four different restorative composites were selected: everX Posterior (a short-fiber-reinforced composite), Z250, SupremeXT, and Silorane. All composites were evaluated regarding the thickness of the oxygen inhibition layer and for shear bond strength. An equal amount of each composite was polymerized in air between two glass plates and the thickness of the oxygen inhibition layer was measured using a stereomicroscope. Cylindrical-shaped specimens were prepared for measurement of shear bond strength by placing incrementally two layers of the same composite material. Before applying the second composite layer, the first increment's bonding site was treated as follows: grinding with 1,000-grit silicon-carbide (SiC) abrasive paper, or treatment with ethanol or with water-spray. The inhibition depth was lowest (11.6 μm) for water-sprayed Silorane and greatest (22.9 μm) for the water-sprayed short-fiber-reinforced composite. The shear bond strength ranged from 5.8 MPa (ground Silorane) to 36.4 MPa (water-sprayed SupremeXT). The presence of an oxygen inhibition layer enhanced the interlayer shear bond strength of all investigated materials, but its absence resulted in cohesive and mixed failures only with the short-fiber-reinforced composite. Thus, more durable adhesion with short-fiber-reinforced composite is expected.

  3. Boundary layer flow past a stretching sheet with fluid-particle suspension and convective boundary condition

    NASA Astrophysics Data System (ADS)

    Ramesh, G. K.; Gireesha, B. J.; Gorla, Rama Subba Reddy

    2015-08-01

    The steady two-dimensional boundary layer flow of a viscous dusty fluid over a stretching sheet with the bottom surface of the sheet heated by convection from a hot fluid is considered. The governing partial differential equations are transformed into ordinary differential equations using a similarity transformation, before being solved numerically by a Runge-Kutta-Fehlberg fourth-fifth order method (RKF45 Method) with the help of MAPLE. The effects of convective Biot number, fluid particle interaction parameter, and Prandtl number on the heat transfer characteristics are discussed. It is found that the temperature of both fluid and dust phase increases with increasing Biot number. A comparative study between the previous published and present results in a limiting sense is found in an excellent agreement.

  4. Transport of spherical colloids in layered phases of binary mixtures with rod-like particles.

    PubMed

    Piedrahita, Mauricio; Cuetos, Alejandro; Martínez-Haya, Bruno

    2015-05-01

    The transport properties of colloids in anisotropic media constitute a general problem of fundamental interest in experimental sciences, with a broad range of technological applications. This work investigates the transport of soft spherical colloids in binary mixtures with rod-like particles by means of Monte Carlo and Brownian Dynamics simulations. Layered phases are considered, that range from smectic phases to lamellar phases, depending on the molar fraction of the spherical particles. The investigation serves to characterize the distinct features of transport within layers versus those of transport across neighboring layers, both of which are neatly differentiated. The insertion of particles into layers and the diffusion across them occur at a smaller rate than the intralayer diffusion modulated by the formation of transitory cages in its initial stages. Collective events, in which two or more colloids diffuse across layers in a concerted way, are described as a non-negligible process in these fluids.

  5. Modification of Surface Layers by Surfacing Intermetallic Coatings with Variable Properties

    NASA Astrophysics Data System (ADS)

    Makeev, D. N.; Zakharov, O. V.; Vinogradov, A. N.; Kochetkov, A. V.

    2016-02-01

    The paper considers the possibility of forming coating layers for parts within wide limits of microhardness. The technology uses surfacing of intermetallic coatings provided by a unique experimental setup. Theoretical and experimental dependence of the coating layer microhardness on the filler concentration using the changes in the speed of the filler wire feed and current intensity were determined.

  6. Erosion of galilean satellite surfaces by jovian magnetosphere particles.

    PubMed

    Johnson, R E; Lanzerotti, L J; Brown, W L; Armstrong, T P

    1981-05-29

    The Galilean satellites of Jupiter-Io (J1), Europa (J2), Ganymede (J3), and Callisto (J4)-are embedded in the intense ion and electron fluxes of the Jovian magnetosphere. The effect of these particles on the icy surfaces of the outer three satellites depends on the fluxes and the efficiency of the sputtering of water ice by such particles. Recent laboratory measurements provided data on the erosion of water ice by energetic particles and showed that it occurs much faster than would be expected from normal sputtering theory. The Voyager spacecraft encounters with Jupiter provided the first measurements of ion fluxes (energies greater, similar 30 kiloelectron volts) in the vicinity of the Galilean satellites. Using the laboratory sputtering data together with particle measurements from the Voyager 1 low-energy charged particle experiment, the effects of erosion on the surfaces of J2 to J4 are estimated. It is shown that the surface of Europa could be eroded by as much as 100 meters over an eon (10(9) years). Column densities of water vapor that could be produced around the three satellites from particle bombardment of their surfaces are also calculated, and the sources and losses of oxygen in the gravitationally bound gas produced by sputtering or sublimation are estimated.

  7. Particle transport and flow modification in planar temporally evolving laminar mixing layers. I. Particle transport under one-way coupling

    NASA Astrophysics Data System (ADS)

    Narayanan, Chidambaram; Lakehal, Djamel

    2006-09-01

    Simulations of two-dimensional, particle-laden mixing layers were performed for particles with Stokes numbers of 0.3, 0.6, 1, and 2 under the assumption of one-way coupling using the Eulerian-Lagrangian method; two-way coupling is addressed in Part II. Analysis of interphase momentum transfer was performed in the Eulerian frame of reference by looking at the balance of fluid-phase mean momentum, mean kinetic energy, modal kinetic energy, and particle-phase mean momentum. The differences in the dominant mechanisms of vertical transport of streamwise momentum between the fluid and particle phases is clearly brought out. In the fluid phase, growth of the mixing layer is due to energy transfer from the mean flow to the unstable Kelvin-Helmholtz modes, and transport of mean momentum by these modes. In contrast, in the particle phase, the primary mechanism of vertical transport of streamwise momentum is convection due to the mean vertical velocity induced by the centrifuging of particles by the spanwise Kelvin-Helmholtz vortices. Although the drag force and the particle-phase modal stress play an important role in the early stages of the evolution of the mixing layer, their role is shown to decrease during the pairing process. After pairing, the particle-phase mean streamwise momentum balance is accounted for by the convection and drag force term. The particle-phase modal stress term is shown to be strongly connected to the fluid phase modal stress with a Stokes-number-dependent time lag in its evolution.

  8. [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.

  9. Surface reconstruction and chemical evolution of stoichiometric layered cathode materials for lithium-ion batteries.

    PubMed

    Lin, Feng; Markus, Isaac M; Nordlund, Dennis; Weng, Tsu-Chien; Asta, Mark D; Xin, Huolin L; Doeff, Marca M

    2014-03-27

    The present study sheds light on the long-standing challenges associated with high-voltage operation of LiNi(x)Mn(x)Co(1-2x)O2 cathode materials for lithium-ion batteries. Using correlated ensemble-averaged high-throughput X-ray absorption spectroscopy and spatially resolved electron microscopy and spectroscopy, here we report structural reconstruction (formation of a surface reduced layer, to transition) and chemical evolution (formation of a surface reaction layer) at the surface of LiNi(x)Mn(x)Co(1-2x)O2 particles. These are primarily responsible for the prevailing capacity fading and impedance buildup under high-voltage cycling conditions, as well as the first-cycle coulombic inefficiency. It was found that the surface reconstruction exhibits a strong anisotropic characteristic, which predominantly occurs along lithium diffusion channels. Furthermore, the surface reaction layer is composed of lithium fluoride embedded in a complex organic matrix. This work sets a refined example for the study of surface reconstruction and chemical evolution in battery materials using combined diagnostic tools at complementary length scales.

  10. Surface reconstruction and chemical evolution of stoichiometric layered cathode materials for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Lin, Feng; Markus, Isaac M.; Nordlund, Dennis; Weng, Tsu-Chien; Asta, Mark D.; Xin, Huolin L.; Doeff, Marca M.

    2014-03-01

    The present study sheds light on the long-standing challenges associated with high-voltage operation of LiNixMnxCo1-2xO2 cathode materials for lithium-ion batteries. Using correlated ensemble-averaged high-throughput X-ray absorption spectroscopy and spatially resolved electron microscopy and spectroscopy, here we report structural reconstruction (formation of a surface reduced layer, to transition) and chemical evolution (formation of a surface reaction layer) at the surface of LiNixMnxCo1-2xO2 particles. These are primarily responsible for the prevailing capacity fading and impedance buildup under high-voltage cycling conditions, as well as the first-cycle coulombic inefficiency. It was found that the surface reconstruction exhibits a strong anisotropic characteristic, which predominantly occurs along lithium diffusion channels. Furthermore, the surface reaction layer is composed of lithium fluoride embedded in a complex organic matrix. This work sets a refined example for the study of surface reconstruction and chemical evolution in battery materials using combined diagnostic tools at complementary length scales.

  11. Enceladus: Correlation of Surface Particle Distribution and Geology

    NASA Astrophysics Data System (ADS)

    Jaumann, R.; Stephan, K.; Brown, R. H.; Clark, R. N.; Filacchione, G.; Buratti, B. J.; Nelson, R. M.; Nicholson, P. D.; Le Mouélic, S.; Rodriguez, S.; Hansen, G. B.; Roatsch, T.; Capaccionii, F.; Sotin, C.

    2012-04-01

    The surface of Enceladus consists almost completely of water ice [1,2]. The band depths of water ice absorptions are sensitive to the size of particles [2,3,4] covering the surface. The Visual and Infrared Mapping Spectrometer [5] observed Enceladus with high spatial resolution during multiple Cassini fly-bys. Based on these data we measured the band depths of water ice absorptions over Enceladus' surface and mapped their distribution. The spatial resolution of VIMS is sufficient to distinguish three major geologic units: heavily cratered terrain, fractured and ridged terrain and complex tectonically deformed regions of troughs and ridges [6], which include the south pole region. Surface ages, as derived from the impact flux models of [7,8] indicate the cratered terrain being oldest while the Sulci the youngest unit [2,9]. From the distribution of particle sizes we can conclude that the largest particle diameters are those inside the tectonically deformed regions, with a decrease in size departing from the fractures. These occur not only at the south pole but also in older tectonic regions [2]. The basic correlation between particle diameter, geologic unit and age suggests the following relative stratigraphic sequence [2,10]: (1) Formation of a primary crust (heavily cratered terrain); (2) Mechanical weathering of the surface particles by microimpacts and sputtering during the last 4 billion years; (3) Tectonic disruption of the surface and deposition of new material with large particles. Although this newly deposited material has undergone mechanical weathering of the particles by microimpacts and sputtering, these particles are larger due to a shorter exposure time; (4) Recent deposition of larger particles in the south polar region. If the larger particles in the tectonically deformed regions have of the same cryovolcanic origin as at the south pole, the volcanic activity must have a temporal evolution. However, there are still different possibilities to explain

  12. Surface morphological evolution of epitaxial CrN(001) layers

    SciTech Connect

    Frederick, J.R.; Gall, D.

    2005-09-01

    CrN layers, 57 and 230 nm thick, were grown on MgO(001) at T{sub s}=600-800 deg. C by ultrahigh-vacuum magnetron sputter deposition in pure N{sub 2} discharges from an oblique deposition angle {alpha}=80 deg. . Layers grown at 600 deg. C nucleate as single crystals with a cube-on-cube epitaxial relationship with the substrate. However, rough surfaces with cauliflower-type morphologies cause the nucleation of misoriented CrN grains that develop into cone-shaped grains that protrude out of the epitaxial matrix to form triangular faceted surface mounds. The surface morphology of epitaxial CrN(001) grown at 700 deg. C is characterized by dendritic ridge patterns extending along the orthogonal <110> directions superposed by square-shaped super mounds with <100> edges. The ridge patterns are attributed to a Bales-Zangwill instability while the supermounds form due to atomic shadowing which leads to the formation of epitaxial inverted pyramids that are separated from the surrounding layer by tilted nanovoids. Growth at 800 deg. C yields complete single crystals with smooth surfaces. The root-mean-square surface roughness for 230-nm-thick layers decreases from 18.8 to 9.3 to 1.1 nm as T{sub s} is raised from 600 to 700 to 800 deg. C. This steep decrease is due to a transition in the roughening mechanism from atomic shadowing to kinetic roughening. Atomic shadowing is dominant at 600 and 700 deg. C, where misoriented grains and supermounds, respectively, capture a larger fraction of the oblique deposition flux in comparison to the surrounding epitaxial matrix, resulting in a high roughening rate that is described by a power law with an exponent {beta}>0.5. In contrast, kinetic roughening controls the surface morphology for T{sub s}=800 deg. C, as well as the epitaxial fraction of the layers grown at 600 and 700 deg. C, yielding relatively smooth surfaces and {beta}{<=}0.27.

  13. In situ ceramic layer growth on coated fuel particles dispersed in a zirconium metal matrix

    SciTech Connect

    Terrani, Kurt A; Silva, G W Chinthaka M; Kiggans, Jim; Cai, Zhonghou; Shin, Dongwon; Snead, Lance Lewis

    2013-01-01

    The extent and nature of the chemical interaction between the outermost coating layer of coated fuel particles embedded in zirconium metal during fabrication of metal matrix microencapsulated fuels was examined. Various particles with outermost coating layers of pyrocarbon, SiC, and ZrC have been investigated in this study. ZrC-Zr interaction was least substantial while PyC-Zr reaction can be exploited to produce a ZrC layer at the interface in an in situ manner. The thickness of the ZrC layer in the latter case can be controlled by adjusting the time and temperature during processing. The kinetics of ZrC layer growth is significantly faster from what is predicted using literature carbon diffusivity data in ZrC. SiC-Zr interaction is more complex and results in formation of various chemical phases in a layered aggregate morphology at the interface.

  14. In situ ceramic layer growth on coated fuel particles dispersed in a zirconium metal matrix

    NASA Astrophysics Data System (ADS)

    Terrani, K. A.; Silva, C. M.; Kiggans, J. O.; Cai, Z.; Shin, D.; Snead, L. L.

    2013-06-01

    The extent and nature of the chemical interaction between the outermost coating layer of coated fuel particles embedded in zirconium metal during fabrication of metal matrix microencapsulated fuels were examined. Various particles with outermost coating layers of pyrocarbon, SiC, and ZrC have been investigated in this study. ZrC-Zr interaction was the least substantial, while the PyC-Zr reaction can be exploited to produce a ZrC layer at the interface in an in situ manner. The thickness of the ZrC layer in the latter case can be controlled by adjusting the time and temperature during processing. The kinetics of ZrC layer growth is significantly faster from what is predicted using literature carbon diffusivity data in ZrC. SiC-Zr interaction is more complex and results in formation of various chemical phases in a layered aggregate morphology at the interface.

  15. Exoelectronic emission of particles of lunar surface material

    NASA Technical Reports Server (NTRS)

    Mints, R. I.; Alimov, V. I.; Melekhin, V. P.; Milman, I. I.; Kryuk, V. I.; Kunin, L. L.; Tarasov, L. S.

    1974-01-01

    A secondary electron multiplier was used to study the thermostimulated exoelectronic emission of particles of lunar surface material returned by the Soviet Luna 16 automatic station. The natural exoemission from fragments of slag, glass, anorthosite, and a metallic particle was recorded in the isochronic and isothermal thermostimulation regimes. The temperature of emission onset depended on the type of regolith fragment. For the first three particles the isothermal drop in emission is described by first-order kinetic equations. For the anorthosite fragment, exoemission at constant temperature is characterized by a symmetric curve with a maximum. These data indicate the presence of active surface defects, whose nature can be due to the prehistory of the particles.

  16. Recrystallization of bacterial S-layers on flat polyelectrolyte surfaces and hollow polyelectrolyte capsules.

    PubMed

    Toca-Herrera, José Luis; Krastev, Rumen; Bosio, Vera; Küpcü, Seta; Pum, Dietmar; Fery, Andreas; Sára, Margit; Sleytr, Uwe B

    2005-03-01

    Polyelectrolyte multilayer (PE) deposition and S-layer technology have been combined to make novel robust biomimetic surfaces and membranes. Isolated subunits of the bacterial cell surface layer from Bacillus sphaericus CCM2177 SbpA was self-assembled on PE multilayer supports, with the composition of the multilayer playing a crucial role in determining the structure of the resulting supported protein layers. Flat substrates were studied using atomic force microscopy and neutron reflectometry; protein on suitable PE combinations showed a crystalline structure with lattice constants equal to those found in vivo on bacterial surfaces. The mechanical stability of the S-layer is higher when recrystallized on PEs than directly on silicon supports. The recrystallization process was subsequently used to coat colloidal particles, permitting the determination of zeta potentials before and after coating. Hollow capsules could also be coated in the same way, as proven by various techniques. Our results suggest that electrostatic interactions via divalent cations are important for the assembly process. The results also demonstrate that the versatility of the PE multilayer membranes can be successfully combined with the well-defined surface chemistry and structure of 2D protein crystals.

  17. Development of gold induced surface plasmon enhanced CIGS absorption layer on polyimide substrate

    NASA Astrophysics Data System (ADS)

    Park, Seong-Un; Sharma, Rahul; Sim, Jae-Kwan; Baek, Byung Joon; Ahn, Haeng-Kwun; Kim, Jin Soo; Lee, Cheul-Ro

    2013-09-01

    Localized surface plasmon resonance (LSPR) with metal nanoparticles is the promising phenomenon to increase light absorption by trapping light in thin film solar cells. In this study we demonstrate a successful LSPR effect with gold (Au) nanoparticles onto the Cu(In,Ga)Se2 (CIGS) absorption layer. First, the CIGS absorber layers is fabricated onto the Mo coated polyimide (PI) substrate by using two stage process as DC sputtering of CIG thin film followed by the selenization at 400 °C. Finally, the Au nanoparticles are deposited onto the CIGS layer with increasing particles size from 4-15 nm by using sputter coater for 10-120 s. The X-ray diffraction (XRD) patterns confirm the formation of CIGS/Au nanocomposite structure with prominent peak shift of CIGS reflections and increasing intensity for Au phase. The CIGS/Au nanocomposite morphologies with Au particle size distribution uniformity and surface coverage is examined under ultra-high resolution field effect scanning electron microscope (UHR-FESEM). A peak at 176 cm-1 in Raman spectra, associated with the “A1” mode of lattice vibration for the attributed to the pure chalcopyrite structure. The secondary ion mass spectroscopy (SIMS) showed ∼200 nm depth converge of Au nanoparticles into the CIGS absorption layer. The optical properties as transmittance, reflectance and absorbance of CIGS/Au layers were found to expand in the infrared region and the LSPR effect is the most prominent for Au particles (5-7 nm) deposited for 60 s. The absorption coefficient and band gap measurement also confirms that the LSPR effect for 5-7 nm Au particles with band gap improvement from 1.31 to 1.52 eV for CIGS/Au layer as the defect density decreases due to the deposition of Au nanoparticles onto the CIGS layer. Such LSPR effect in CIGS/Au nanocomposite absorption layer will be a key parameter to further improve performance of the solar cell.

  18. Smooth- and rough-wall boundary layer structure from high spatial range particle image velocimetry

    NASA Astrophysics Data System (ADS)

    Squire, D. T.; Morrill-Winter, C.; Hutchins, N.; Marusic, I.; Schultz, M. P.; Klewicki, J. C.

    2016-10-01

    Two particle image velocimetry arrangements are used to make true spatial comparisons between smooth- and rough-wall boundary layers at high Reynolds numbers across a very wide range of streamwise scales. Together, the arrangements resolve scales ranging from motions on the order of the Kolmogorov microscale to those longer than twice the boundary layer thickness. The rough-wall experiments were obtained above a continuous sandpaper sheet, identical to that used by Squire et al. [J. Fluid Mech. 795, 210 (2016), 10.1017/jfm.2016.196], and cover a range of friction and equivalent sand-grain roughness Reynolds numbers (12 000 ≲δ+≲ 18000, 62 ≲ks+≲104 ). The smooth-wall experiments comprise new and previously published data spanning 6500 ≲δ+≲17 000 . Flow statistics from all experiments show similar Reynolds number trends and behaviors to recent, well-resolved hot-wire anemometry measurements above the same rough surface. Comparisons, at matched δ+, between smooth- and rough-wall two-point correlation maps and two-point magnitude-squared coherence maps demonstrate that spatially the outer region of the boundary layer is the same between the two flows. This is apparently true even at wall-normal locations where the total (inner-normalized) energy differs between the smooth and rough wall. Generally, the present results provide strong support for Townsend's [The Structure of Turbulent Shear Flow (Cambridge University Press, Cambridge, 1956), Vol. 1] wall-similarity hypothesis in high Reynolds number fully rough boundary layer flows.

  19. Air-sea fluxes and surface layer turbulence around a sea surface temperature front

    NASA Technical Reports Server (NTRS)

    Friehe, C. A.; Shaw, W. J.; Davidson, K. L.; Rogers, D. P.; Large, W. G.; Stage, S. A.; Crescenti, G. H.; Khalsa, S. J. S.; Greenhut, G. K.; Li, F.

    1991-01-01

    The observed effects of sharp changes in sea surface temperature (SST) on the air-sea fluxes, surface roughness, and the turbulence structure in the surface layer and the marine atmospheric boundary layer are discussed. In situ flux and turbulence observations were carried out from three aircraft and two ships within the FASINEX framework. Three other aircraft used remote sensors to measure waves, microwave backscatter, and lidar signatures of cloud tops. Descriptions of the techniques, intercomparison of aircraft and ship flux data, and use of different methods for analyzing the fluxes from the aircraft data are described. Changing synoptic weather on three successive days yielded cases of wind direction both approximately parallel and perpendicular to a surface temperature front. For the wind perpendicular to the front, wind over both cold-to-warm and warm-to-cold surface temperatures occurred. Model results consistent with the observations suggest that an internal boundary layer forms at the SST.

  20. Modes of surface premelting in colloidal crystals composed of attractive particles.

    PubMed

    Li, Bo; Wang, Feng; Zhou, Di; Peng, Yi; Ni, Ran; Han, Yilong

    2016-03-24

    Crystal surfaces typically melt into a thin liquid layer at temperatures slightly below the melting point of the crystal. Such surface premelting is prevalent in all classes of solids and is important in a variety of metallurgical, geological and meteorological phenomena. Premelting has been studied using X-ray diffraction and differential scanning calorimetry, but the lack of single-particle resolution makes it hard to elucidate the underlying mechanisms. Colloids are good model systems for studying phase transitions because the thermal motions of individual micrometre-sized particles can be tracked directly using optical microscopy. Here we use colloidal spheres with tunable attractions to form equilibrium crystal-vapour interfaces, and study their surface premelting behaviour at the single-particle level. We find that monolayer colloidal crystals exhibit incomplete premelting at their perimeter, with a constant liquid-layer thickness. In contrast, two- and three-layer crystals exhibit conventional complete melting, with the thickness of the surface liquid diverging as the melting point is approached. The microstructures of the surface liquids differ in certain aspects from what would be predicted by conventional premelting theories. Incomplete premelting in the monolayer crystals is triggered by a bulk isostructural solid-solid transition and truncated by a mechanical instability that separately induces homogeneous melting within the bulk. This finding is in contrast to the conventional assumption that two-dimensional crystals melt heterogeneously from their free surfaces (that is, at the solid-vapour interface). The unexpected bulk melting that we observe for the monolayer crystals is accompanied by the formation of grain boundaries, which supports a previously proposed grain-boundary-mediated two-dimensional melting theory. The observed interplay between surface premelting, bulk melting and solid-solid transitions challenges existing theories of surface

  1. Modes of surface premelting in colloidal crystals composed of attractive particles

    NASA Astrophysics Data System (ADS)

    Li, Bo; Wang, Feng; Zhou, Di; Peng, Yi; Ni, Ran; Han, Yilong

    2016-03-01

    Crystal surfaces typically melt into a thin liquid layer at temperatures slightly below the melting point of the crystal. Such surface premelting is prevalent in all classes of solids and is important in a variety of metallurgical, geological and meteorological phenomena. Premelting has been studied using X-ray diffraction and differential scanning calorimetry, but the lack of single-particle resolution makes it hard to elucidate the underlying mechanisms. Colloids are good model systems for studying phase transitions because the thermal motions of individual micrometre-sized particles can be tracked directly using optical microscopy. Here we use colloidal spheres with tunable attractions to form equilibrium crystal–vapour interfaces, and study their surface premelting behaviour at the single-particle level. We find that monolayer colloidal crystals exhibit incomplete premelting at their perimeter, with a constant liquid-layer thickness. In contrast, two- and three-layer crystals exhibit conventional complete melting, with the thickness of the surface liquid diverging as the melting point is approached. The microstructures of the surface liquids differ in certain aspects from what would be predicted by conventional premelting theories. Incomplete premelting in the monolayer crystals is triggered by a bulk isostructural solid–solid transition and truncated by a mechanical instability that separately induces homogeneous melting within the bulk. This finding is in contrast to the conventional assumption that two-dimensional crystals melt heterogeneously from their free surfaces (that is, at the solid–vapour interface). The unexpected bulk melting that we observe for the monolayer crystals is accompanied by the formation of grain boundaries, which supports a previously proposed grain-boundary-mediated two-dimensional melting theory. The observed interplay between surface premelting, bulk melting and solid–solid transitions challenges existing theories of

  2. Electrostatic double layers as auroral particle accelerators - a problem

    NASA Astrophysics Data System (ADS)

    Bryant, D. A.; Courtier, G. M.

    2015-04-01

    A search of the Annales Geophysicae database shows that double layers and other quasi-static electric potential structures have been invoked hundreds of times since the year 2000 as being the agents of auroral electron acceleration. This is despite the fact that energy transfer by conservative fields has been known for some 200 years to be impossible. Attention is drawn to a long-standing interpretation of the acceleration process in terms of the dynamic fields of electrostatic waves.

  3. Charged particle detectors made from thin layers of amorphous silicon

    SciTech Connect

    Morel, J.R.

    1986-05-01

    A series of experiments was conducted to determine the feasibility of using hydrogenated amorphous silicon (..cap alpha..-Si:H) as solid state thin film charged particle detectors. /sup 241/Am alphas were successfully detected with ..cap alpha..-Si:H devices. The measurements and results of these experiments are presented. The problems encountered and changes in the fabrication of the detectors that may improve the performance are discussed.

  4. Particle simulation of auroral double layers. Doctoral thesis

    SciTech Connect

    Smith, B.L.

    1992-06-01

    Externally driven magnetic reconnection has been proposed as a possible mechanism for production of auroral electrons during magnetic substorms. Fluid simulations of magnetic reconnection lead to strong plasma flows towards the increasing magnetic field of the earth. These plasma flows must generate large scale potential drops to preserve global charge neutrality. We have examined currentless injection of plasma along a dipole magnetic field into a bounded region using both analytic techniques and particle simulation.

  5. Detection of charged particles in amorphous silicon layers

    SciTech Connect

    Kaplan, S.N.; Morel, J.R.; Mulera, T.A.; Perez-Mendez, V.; Schnurmacher, G.; Street, R.A.

    1985-10-01

    The successful development of radiation detectors made from amorphous silicon could offer the possibility for relatively easy construction of large area position-sensitive detectors. We have conducted a series of measurements with prototype detectors, on signals derived from alpha particles. The measurement results are compared with simple model calculations, and projections are made of potential applications in high-energy and nuclear physics. 4 refs., 7 figs.

  6. Surface charge features of kaolinite particles and their interactions

    NASA Astrophysics Data System (ADS)

    Gupta, Vishal

    Kaolinite is both a blessing and a curse. As an important industrial mineral commodity, kaolinite clays are extensively used in the paper, ceramic, paint, plastic and rubber industries. In all these applications the wettability, aggregation, dispersion, flotation and thickening of kaolinite particles are affected by its crystal structure and surface properties. It is therefore the objective of this research to investigate selected physical and surface chemical properties of kaolinite, specifically the surface charge of kaolinite particles. A pool of advanced analytical techniques such as XRD, XRF, SEM, AFM, FTIR and ISS were utilized to investigate the morphological and surface chemistry features of kaolinite. Surface force measurements revealed that the silica tetrahedral face of kaolinite is negatively charged at pH>4, whereas the alumina octahedral face of kaolinite is positively charged at pH<6, and negatively charged at pH>8. Based on electrophoresis measurements, the apparent iso-electric point for kaolinite particles was determined to be less than pH 3. In contrast, the point of zero charge was determined to be pH 4.5 by titration techniques, which corresponds to the iso-electric point of between pH 4 and 5 as determined by surface force measurements. Results from kaolinite particle interactions indicate that the silica face--alumina face interaction is dominant for kaolinite particle aggregation at low and intermediate pH values, which explains the maximum shear yield stress at pH 5-5.5. Lattice resolution images reveal the hexagonal lattice structure of these two face surfaces of kaolinite. Analysis of the silica face of kaolinite showed that the center of the hexagonal ring of oxygen atoms is vacant, whereas the alumina face showed that the hexagonal surface lattice ring of hydroxyls surround another hydroxyl in the center of the ring. High resolution transmission electron microscopy investigation of kaolinite has indicated that kaolinite is indeed

  7. Global chaotization of fluid particle trajectories in a sheared two-layer two-vortex flow.

    PubMed

    Ryzhov, Evgeny A; Koshel, Konstantin V

    2015-10-01

    In a two-layer quasi-geostrophic approximation, we study the irregular dynamics of fluid particles arising due to two interacting point vortices embedded in a deformation flow consisting of shear and rotational components. The two vortices are arranged within the bottom layer, but an emphasis is on the upper-layer fluid particle motion. Vortices moving in one layer induce stirring of passive scalars in the other layer. This is of interest since point vortices induce singular velocity fields in the layer they belong to; however, in the other layer, they induce regular velocity fields that generally result in a change in passive particle stirring. If the vortices are located at stagnation points, there are three different types of the fluid flow. We examine how properties of each flow configuration are modified if the vortices are displaced from the stagnation points and thus circulate in the immediate vicinity of these points. To that end, an analysis of the steady-state configurations is presented with an emphasis on the frequencies of fluid particle oscillations about the elliptic stagnation points. Asymptotic relations for the vortex and fluid particle zero-oscillation frequencies are derived in the vicinity of the corresponding elliptic points. By comparing the frequencies of fluid particles with the ones of the vortices, relations between the parameters that lead to enhanced stirring of fluid particles are established. It is also demonstrated that, if the central critical point is elliptic, then the fluid particle trajectories in its immediate vicinity are mostly stable making it harder for the vortex perturbation to induce stirring. Change in the type of the central point to a hyperbolic one enhances drastically the size of the chaotic dynamics region. Conditions on the type of the central critical point also ensue from the derived asymptotic relations. PMID:26520074

  8. Global chaotization of fluid particle trajectories in a sheared two-layer two-vortex flow.

    PubMed

    Ryzhov, Evgeny A; Koshel, Konstantin V

    2015-10-01

    In a two-layer quasi-geostrophic approximation, we study the irregular dynamics of fluid particles arising due to two interacting point vortices embedded in a deformation flow consisting of shear and rotational components. The two vortices are arranged within the bottom layer, but an emphasis is on the upper-layer fluid particle motion. Vortices moving in one layer induce stirring of passive scalars in the other layer. This is of interest since point vortices induce singular velocity fields in the layer they belong to; however, in the other layer, they induce regular velocity fields that generally result in a change in passive particle stirring. If the vortices are located at stagnation points, there are three different types of the fluid flow. We examine how properties of each flow configuration are modified if the vortices are displaced from the stagnation points and thus circulate in the immediate vicinity of these points. To that end, an analysis of the steady-state configurations is presented with an emphasis on the frequencies of fluid particle oscillations about the elliptic stagnation points. Asymptotic relations for the vortex and fluid particle zero-oscillation frequencies are derived in the vicinity of the corresponding elliptic points. By comparing the frequencies of fluid particles with the ones of the vortices, relations between the parameters that lead to enhanced stirring of fluid particles are established. It is also demonstrated that, if the central critical point is elliptic, then the fluid particle trajectories in its immediate vicinity are mostly stable making it harder for the vortex perturbation to induce stirring. Change in the type of the central point to a hyperbolic one enhances drastically the size of the chaotic dynamics region. Conditions on the type of the central critical point also ensue from the derived asymptotic relations.

  9. Global chaotization of fluid particle trajectories in a sheared two-layer two-vortex flow

    SciTech Connect

    Ryzhov, Evgeny A.; Koshel, Konstantin V.

    2015-10-15

    In a two-layer quasi-geostrophic approximation, we study the irregular dynamics of fluid particles arising due to two interacting point vortices embedded in a deformation flow consisting of shear and rotational components. The two vortices are arranged within the bottom layer, but an emphasis is on the upper-layer fluid particle motion. Vortices moving in one layer induce stirring of passive scalars in the other layer. This is of interest since point vortices induce singular velocity fields in the layer they belong to; however, in the other layer, they induce regular velocity fields that generally result in a change in passive particle stirring. If the vortices are located at stagnation points, there are three different types of the fluid flow. We examine how properties of each flow configuration are modified if the vortices are displaced from the stagnation points and thus circulate in the immediate vicinity of these points. To that end, an analysis of the steady-state configurations is presented with an emphasis on the frequencies of fluid particle oscillations about the elliptic stagnation points. Asymptotic relations for the vortex and fluid particle zero–oscillation frequencies are derived in the vicinity of the corresponding elliptic points. By comparing the frequencies of fluid particles with the ones of the vortices, relations between the parameters that lead to enhanced stirring of fluid particles are established. It is also demonstrated that, if the central critical point is elliptic, then the fluid particle trajectories in its immediate vicinity are mostly stable making it harder for the vortex perturbation to induce stirring. Change in the type of the central point to a hyperbolic one enhances drastically the size of the chaotic dynamics region. Conditions on the type of the central critical point also ensue from the derived asymptotic relations.

  10. Dust Devils on Mars: Effects of Surface Roughness on Particle Threshold

    NASA Technical Reports Server (NTRS)

    Neakrase, Lynn D.; Greeley, Ronald; Iversen, James D.; Balme, Matthew L.; Foley, Daniel J.; Eddlemon, Eric E.

    2005-01-01

    Dust devils have been proposed as effective mechanisms for lofting large quantities of dust into the martian atmosphere. Previous work showed that vortices lift dust more easily than simple boundary layer winds. The aim of this study is to determine experimentally the effects of non-erodable roughness elements on vortex particle threshold through laboratory simulations of natural surfaces. Additional information is included in the original extended abstract.

  11. Guiding Catalytically Active Particles with Chemically Patterned Surfaces

    NASA Astrophysics Data System (ADS)

    Uspal, W. E.; Popescu, M. N.; Dietrich, S.; Tasinkevych, M.

    2016-07-01

    Catalytically active Janus particles suspended in solution create gradients in the chemical composition of the solution along their surfaces, as well as along any nearby container walls. The former leads to self-phoresis, while the latter gives rise to chemiosmosis, providing an additional contribution to self-motility. Chemiosmosis strongly depends on the molecular interactions between the diffusing chemical species and the wall. We show analytically, using an approximate "point-particle" approach, that by chemically patterning a planar substrate one can direct the motion of Janus particles: the induced chemiosmotic flows can cause particles to either "dock" at the chemical step between the two materials or follow a chemical stripe. These theoretical predictions are confirmed by full numerical calculations. Generically, docking occurs for particles which tend to move away from their catalytic caps, while stripe following occurs in the opposite case. Our analysis reveals the physical mechanisms governing this behavior.

  12. "Sticky Business": the Influence of Surface Biofilm on Particle Deposition and Infiltration in Streams

    NASA Astrophysics Data System (ADS)

    Salant, N. L.; Hassan, M. A.

    2007-12-01

    filamentous assemblages are collected from nearby channels and used to replace the surface layer of flume substrate. Low-profile forms are cultivated on a cobble-gravel substrate in an artificial stream system and tested at each of three growth stages. Immediately following a dose of fine particles (< 125 µm ground silica), short-term rates of particle deposition are determined by continuous measurements of near-bed particle concentrations. Hourly vertical concentration, grain size profiles, and 3-D velocity profiles are measured for the duration of the experiment (8h). Infiltration rate is determined from bed samplers sealed from the flow at 1, 2, 4, and 8 hours. At the end of each experiment, three surface samples are collected and analyzed for ash-weight, ash-free dry weight, and chlorophyll a. Four stratified bed samples and samplers are removed, dried, sieved and weighed to determine the amount and depth of fine particle infiltration into the bed with time and surface condition. Preliminary results indicate that particle deposition is significantly enhanced by biofilm presence relative to surfaces without biofilm; this effect is greater for mucilaginous forms. However, near-bed shear stresses and velocity profiles are not significantly altered by either mucilaginous or filamentous forms; bed topography has a dominant effect. Results also indicate that particle deposition is more strongly influenced by surface condition (e.g. particle size, biofilm presence) than by flow level or duration. Particle infiltration below the surface, however, is more a function of pore space and flow level than biofilm coverage on the streambed surface.

  13. Magnetic Or Optical Surface Layer Would Indicate Strain

    NASA Technical Reports Server (NTRS)

    Heyman, Joseph S.

    1995-01-01

    In proposed method of obtaining information on strain at surface of material specimen, magnetic coat (like that on magnetic tape) or optical coat (like that on compact disk) applied to all or part of surface monitored. Coating layer and associated measuring equipment, taken together, constitute system called "material strain monitor" (MSM). MSM important in research in materials and mechanics; in particular, expected to compete strongly with systems based on image-analysis and laser techniques now being developed to obtain information on strain fields.

  14. Elemental analyses of hypervelocity micro-particle impact sites on interplanetary dust experiment sensor surfaces

    NASA Technical Reports Server (NTRS)

    Simon, Charles G.; Hunter, J. L.; Griffis, D. P.; Misra, V.; Ricks, D. R.; Wortman, Jim J.

    1992-01-01

    The Interplanetary Dust Experiment (IDE) had over 450 electrically active ultra-high purity metal-oxide-silicon impact detectors located on the six primary sides of the Long Duration Exposure Facility (LDEF). Hypervelocity micro-particles that struck the active sensors with enough energy to breakdown the 0.4 to 1.0 micron thick SiO2 insulator layer separating the silicon base (the negative electrode), and the 1000 A thick surface layer of aluminum (the positive electrode) caused electrical discharges that were recorded for the first year of orbit. These discharge features, which include 50 micron diameter areas where the aluminum top layer has been vaporized, facilitate the location of the impacts. The high purity Al-SiO2-Si substrates allow detection of trace (ppm) amounts of hypervelocity impactor residues. After sputtering through a layer of surface contamination, secondary ion mass spectrometry (SIMS) is used to create two-dimensional elemental ion intensity maps of micro-particle impact sites on the IDE sensors. The element intensities in the central craters of the impacts are corrected for relative ion yields and instrumental conditions and then normalized to silicon. The results are used to classify the particles' origins as 'manmade', 'natural' or 'indeterminate'. The last classification results from the presence of too little impactor residue (a frequent occurrence on leading edge impacts), analytical interference from high background contamination, the lack of information on silicon residue, the limited usefulness of data on aluminum in the central craters, or a combination of these circumstances. Several analytical 'blank' discharges were induced on flight sensors by pressing down on the sensor surface with a pure silicon shard. Analyses of these blank discharges showed that the discharge energy blasts away the layer of surface contamination. Only Si and Al were detected inside the discharge zones, including the central craters, of these features. A

  15. Engineering of an MBR supernatant fouling layer by fine particles addition: a possible way to control cake compressibility.

    PubMed

    Teychene, Benoît; Guigui, Christelle; Cabassud, Corinne

    2011-02-01

    For membrane bioreactors (MBR) applied to wastewater treatment membrane fouling is still the prevalent issue. The main limiting phenomena related to fouling is a sudden jump of the transmembrane pressure (TMP) often attributed to the collapse of the fouling layer. Among existing techniques to avoid or to delay this collapse, the addition of active particles membrane fouling reducers (polymer, resins, powdered activated carbon (PAC), zeolithe...) showed promising results. Thus the main objective of this work is to determine if fouling can be reduced by inclusion of inert particles (500 nm and inert compared to other fouling reducers) and which is the impact on filtration performances of the structuring of the fouling. Those particles were chosen for their different surface properties and their capability to form well structured layer. Results, obtained at constant pressure in dead end mode, show that the presence of particles changes foulant deposition and induces non-compressible fouling (in the range of 0.5-1 bar) and higher rejection values compared to filtration done on supernatant alone. Indeed dead end filtration tests show that whatever interactions between biofluid and particles, the addition of particles leads to better filtration performances (in terms of rejection, and fouling layer compressibility). Moreover results confirm the important role played by macromolecular compounds, during supernatant filtration, creating highly compressible and reversible fouling. In conclusion, this study done at lab-scale suggests the potential benefit to engineer fouling structure to control or to delay the collapse of the fouling layer. Finally this study offers the opportunities to enlarge the choice of membrane fouling reducers by taking into consideration their ability to form more consistent fouling (i.e. rigid, structured fouling). PMID:21232780

  16. Surface alloys as interfacial layers between quasicrystalline and periodic materials

    NASA Astrophysics Data System (ADS)

    Duguet, T.; Ledieu, J.; Dubois, J. M.; Fournée, V.

    2008-08-01

    Low adhesion with normal metals is an intrinsic property of many quasicrystalline surfaces. Although this property could be useful to develop low friction or non-stick coatings, it is also responsible for the poor adhesion of quasicrystalline coatings on metal substrates. Here we investigate the possibility of using complex metallic surface alloys as interface layers to enhance the adhesion between quasicrystals and simple metal substrates. We first review some examples where such complex phases are formed as an overlayer. Then we study the formation of such surface alloys in a controlled way by annealing a thin film deposited on a quasicrystalline substrate. We demonstrate that a coherent buffer layer consisting of the γ-Al4Cu9 approximant can be grown between pure Al and the i-Al-Cu-Fe quasicrystal. The interfacial relationships between the different layers are defined by [111]_{\\mathrm {Al}}\\parallel [110]_{\\mathrm {Al_4Cu_9}}\\parallel [5\\mathrm {f}]_{i\\mbox {-}\\mathrm {Al\\mbox {--}Cu \\mbox {--}Fe}} .

  17. Dense medium radiative transfer theory for two scattering layers with a Rayleigh distribution of particle sizes

    SciTech Connect

    West, R.; Tsang, Leung; Winebrenner, D.P. )

    1993-03-01

    Dense medium radiative transfer theory is applied to a three-layer model consisting of two scattering layers overlying a homogeneous half space with a size distribution of particles in each layer. A model with a distribution of sizes gives quite different results than those obtained from a model with a single size. The size distribution is especially important in the low frequency limit when scattering is strongly dependent on particle size. The size distribution and absorption characteristics also affect the extinction behavior as a function of fractional volume. Theoretical results are also compared with experimental data. The sizes, permittivities, and densities used in the numerical illustrations are typical values for snow.

  18. Three-Dimensional Porous Particles Composed of Curved, Two-Dimensional, Nano-Sized Layers for Li-Ion Batteries

    NASA Technical Reports Server (NTRS)

    Yushin, Gleb; Evanoff, Kara; Magasinski, Alexander

    2012-01-01

    Thin Si films coated on porous 3D particles composed of curved 2D graphene sheets have been synthesized utilizing techniques that allow for tunable properties. Since graphene exhibits specific surface area up to 100 times higher than carbon black or graphite, the deposition of the same mass of Si on graphene is much faster in comparison -- a factor which is important for practical applications. In addition, the distance between graphene layers is tunable and variation in the thickness of the deposited Si film is feasible. Both of these characteristics allow for optimization of the energy and power characteristics. Thicker films will allow higher capacity, but slower rate capabilities. Thinner films will allow more rapid charging, or higher power performance. In this innovation, uniform deposition of Si and C layers on high-surface area graphene produced granules with specific surface area (SSA) of 5 sq. m/g.

  19. Monolayers of charged particles in a Langmuir trough: Could particle aggregation increase the surface pressure?

    PubMed

    Petkov, Plamen V; Danov, Krassimir D; Kralchevsky, Peter A

    2016-01-15

    The effect of aggregation on the surface pressure, Π, of monolayers from charged micrometer-sized colloidal particles on the air/water interface is investigated. Π is completely due to the long-range electrostatic repulsion between the particles mediated by their electrostatic field in the air. The most probable origin of particle aggregation is the attraction between capillary quadrupoles due to undulated contact lines on particle surfaces. Aggregates have higher charge and repel each other stronger than single particles. The data analysis by means of a theoretical model implies that Π linearly increases with n(1/2); n is the mean aggregation number, which can be determined from the experimental Π vs. area curves. The presence of electrolyte promotes aggregation, which tends to increase Π, but simultaneously reduces the surface charge that leads to lower Π. For our system, the first effect prevails and apparently paradoxical behavior is observed: the addition of salt in water enhances the electrostatic surface pressure. The data indicate limited aggregation: the rise of the electrostatic barrier prevents the further coalescence of aggregates if they have become sufficiently large. The results contribute for a better understanding of the factors that control the interactions in monolayers of charged particles at liquid interfaces.

  20. Spatially selective surface platforms for binding fibrinogen prepared by particle lithography with organosilanes

    PubMed Central

    Englade-Franklin, Lauren E.; Saner, ChaMarra K.; Garno, Jayne C.

    2013-01-01

    We introduce an approach based on particle lithography to prepare spatially selective surface platforms of organosilanes that are suitable for nanoscale studies of protein binding. Particle lithography was applied for patterning fibrinogen, a plasma protein that has a major role in the clotting cascade for blood coagulation and wound healing. Surface nanopatterns of mercaptosilanes were designed as sites for the attachment of fibrinogen within a protein-resistant matrix of 2-[methoxy(polyethyleneoxy)propyl] trichlorosilane (PEG-silane). Preparing site-selective surfaces was problematic in our studies, because of the self-reactive properties of PEG-organosilanes. Certain organosilanes presenting hydroxyl head groups will cross react to form mixed surface multi-layers. We developed a clever strategy with particle lithography using masks of silica mesospheres to protect small, discrete regions of the surface from cross reactions. Images acquired with atomic force microscopy (AFM) disclose that fibrinogen attached primarily to the surface areas presenting thiol head groups, which were surrounded by PEG-silane. The activity for binding anti-fibrinogen was further evaluated using ex situ AFM studies, confirming that after immobilization the fibrinogen nanopatterns retained capacity for binding immunoglobulin G. Studies with AFM provide advantages of achieving nanoscale resolution for detecting surface changes during steps of biochemical surface reactions, without requiring chemical modification of proteins or fluorescent labels. PMID:24427541

  1. Particle engineering in pharmaceutical solids processing: surface energy considerations.

    PubMed

    Williams, Daryl R

    2015-01-01

    During the past 10 years particle engineering in the pharmaceutical industry has become a topic of increasing importance. Engineers and pharmacists need to understand and control a range of key unit manufacturing operations such as milling, granulation, crystallisation, powder mixing and dry powder inhaled drugs which can be very challenging. It has now become very clear that in many of these particle processing operations, the surface energy of the starting, intermediate or final products is a key factor in understanding the processing operation and or the final product performance. This review will consider the surface energy and surface energy heterogeneity of crystalline solids, methods for the measurement of surface energy, effects of milling on powder surface energy, adhesion and cohesion on powder mixtures, crystal habits and surface energy, surface energy and powder granulation processes, performance of DPI systems and finally crystallisation conditions and surface energy. This review will conclude that the importance of surface energy as a significant factor in understanding the performance of many particulate pharmaceutical products and processes has now been clearly established. It is still nevertheless, work in progress both in terms of development of methods and establishing the limits for when surface energy is the key variable of relevance.

  2. Particle engineering in pharmaceutical solids processing: surface energy considerations.

    PubMed

    Williams, Daryl R

    2015-01-01

    During the past 10 years particle engineering in the pharmaceutical industry has become a topic of increasing importance. Engineers and pharmacists need to understand and control a range of key unit manufacturing operations such as milling, granulation, crystallisation, powder mixing and dry powder inhaled drugs which can be very challenging. It has now become very clear that in many of these particle processing operations, the surface energy of the starting, intermediate or final products is a key factor in understanding the processing operation and or the final product performance. This review will consider the surface energy and surface energy heterogeneity of crystalline solids, methods for the measurement of surface energy, effects of milling on powder surface energy, adhesion and cohesion on powder mixtures, crystal habits and surface energy, surface energy and powder granulation processes, performance of DPI systems and finally crystallisation conditions and surface energy. This review will conclude that the importance of surface energy as a significant factor in understanding the performance of many particulate pharmaceutical products and processes has now been clearly established. It is still nevertheless, work in progress both in terms of development of methods and establishing the limits for when surface energy is the key variable of relevance. PMID:25876912

  3. Copolyimide Surface Modifying Agents for Particle Adhesion Mitigation

    NASA Technical Reports Server (NTRS)

    Wohl, Christopher J.; Connell, John W.

    2011-01-01

    Marine biofouling, insect adhesion on aircraft surfaces, microbial contamination of sterile environments, and particle contamination all present unique challenges for which researchers have adopted an array of mitigation strategies. Particulate contamination is of interest to NASA regarding exploration of the Moon, Mars, asteroids, etc.1 Lunar dust compromised seals, clogged filters, abraded visors and space suit surfaces, and was a significant health concern during the Apollo missions.2 Consequently, NASA has instituted a multi-faceted approach to address dust including use of sacrificial surfaces, active mitigation requiring the use of an external energy source, and passive mitigation utilizing materials with an intrinsic resistance to surface contamination. One passive mitigation strategy is modification of a material s surface energy either chemically or topographically. The focus of this paper is the synthesis and evaluation of novel copolyimide materials with surface modifying agents (SMA, oxetanes) enabling controlled variation of surface chemical composition.

  4. Particles induce apical plasma membrane enlargement in epithelial lung cell line depending on particle surface area dose

    PubMed Central

    Brandenberger, Christina; Rothen-Rutishauser, Barbara; Blank, Fabian; Gehr, Peter; Mühlfeld, Christian

    2009-01-01

    Background Airborne particles entering the respiratory tract may interact with the apical plasma membrane (APM) of epithelial cells and enter them. Differences in the entering mechanisms of fine (between 0.1 μm and 2.5 μm) and ultrafine ( ≤ 0.1 μm) particles may be associated with different effects on the APM. Therefore, we studied particle-induced changes in APM surface area in relation to applied and intracellular particle size, surface and number. Methods Human pulmonary epithelial cells (A549 cell line) were incubated with various concentrations of different sized fluorescent polystyrene spheres without surface charge (∅ fine – 1.062 μm, ultrafine – 0.041 μm) by submersed exposure for 24 h. APM surface area of A549 cells was estimated by design-based stereology and transmission electron microscopy. Intracellular particles were visualized and quantified by confocal laser scanning microscopy. Results Particle exposure induced an increase in APM surface area compared to negative control (p < 0.01) at the same surface area concentration of fine and ultrafine particles a finding not observed at low particle concentrations. Ultrafine particle entering was less pronounced than fine particle entering into epithelial cells, however, at the same particle surface area dose, the number of intracellular ultrafine particles was higher than that of fine particles. The number of intracellular particles showed a stronger increase for fine than for ultrafine particles at rising particle concentrations. Conclusion This study demonstrates a particle-induced enlargement of the APM surface area of a pulmonary epithelial cell line, depending on particle surface area dose. Particle uptake by epithelial cells does not seem to be responsible for this effect. We propose that direct interactions between particle surface area and cell membrane cause the enlargement of the APM. PMID:19284624

  5. Capillary interception of floating particles by surface-piercing vegetation.

    PubMed

    Peruzzo, Paolo; Defina, Andrea; Nepf, Heidi M; Stocker, Roman

    2013-10-18

    Surface-piercing vegetation often captures particles that flow on the water surface, where surface tension forces contribute to capture. Yet the physics of capillary capture in flow has not been addressed. Here we model the capture of floating particles by surface-piercing collectors at moderately low Reynolds numbers (Re<10). We find a trade-off between the capillary force, which increases with the collector diameter, and the relative size of the meniscus, which decreases with the collector diameter, resulting in an optimal collector diameter of ~1-10 mm that corresponds to the regime in which many aquatic plant species operate. For this diameter range the angular distribution of capture events is nearly uniform and capture can be orders of magnitude more efficient than direct interception, showing that capillary forces can be major contributors to the capture of seeds and particulate matter by organisms.

  6. Capillary Interception of Floating Particles by Surface-Piercing Vegetation

    NASA Astrophysics Data System (ADS)

    Peruzzo, Paolo; Defina, Andrea; Nepf, Heidi M.; Stocker, Roman

    2013-10-01

    Surface-piercing vegetation often captures particles that flow on the water surface, where surface tension forces contribute to capture. Yet the physics of capillary capture in flow has not been addressed. Here we model the capture of floating particles by surface-piercing collectors at moderately low Reynolds numbers (Re<10). We find a trade-off between the capillary force, which increases with the collector diameter, and the relative size of the meniscus, which decreases with the collector diameter, resulting in an optimal collector diameter of ˜1-10mm that corresponds to the regime in which many aquatic plant species operate. For this diameter range the angular distribution of capture events is nearly uniform and capture can be orders of magnitude more efficient than direct interception, showing that capillary forces can be major contributors to the capture of seeds and particulate matter by organisms.

  7. Metal-like conductivity exhibited by triboelectrically deposited polyaniline (emeraldine base) particles on microtextured SiC surfaces

    NASA Astrophysics Data System (ADS)

    Bayer, I. S.; Caramia, V.; Biswas, A.; Cingolani, R.; Athanassiou, A.

    2012-05-01

    We demonstrate a simple and rapid way to deposit layers of polyaniline (emeraldine base) particles on flexible microtextured silicon carbide surfaces by contact charging them using a smooth dielectric rubber. Wetting of the layers by trifluoroacetic acid creates conductive, continuous polymeric films after drying. Pre-functionalization of the textured surfaces with anionic surfactants prevents particle coagulation during contact charging and decreases sheet resistance to metal-like levels (˜60 Ω/□). Conductivity of the films can be tuned by controlling the rate of acid evaporation. Conductive films are highly stable under ambient conditions and show no hysteresis when biased with zero delay-time.

  8. Shape-selective sieving layers on an oxide catalyst surface.

    PubMed

    Canlas, Christian P; Lu, Junling; Ray, Natalie A; Grosso-Giordano, Nicolas A; Lee, Sungsik; Elam, Jeffrey W; Winans, Randall E; Van Duyne, Richard P; Stair, Peter C; Notestein, Justin M

    2012-12-01

    New porous materials such as zeolites, metal-organic frameworks and mesostructured oxides are of immense practical utility for gas storage, separations and heterogeneous catalysis. Their extended pore structures enable selective uptake of molecules or can modify the product selectivity (regioselectivity or enantioselectivity) of catalyst sites contained within. However, diffusion within pores can be problematic for biomass and fine chemicals, and not all catalyst classes can be readily synthesized with pores of the correct dimensions. Here, we present a novel approach that adds reactant selectivity to existing, non-porous oxide catalysts by first grafting the catalyst particles with single-molecule sacrificial templates, then partially overcoating the catalyst with a second oxide through atomic layer deposition. This technique is used to create sieving layers of Al(2)O(3) (thickness, 0.4-0.7 nm) with 'nanocavities' (<2 nm in diameter) on a TiO(2) photocatalyst. The additional layers result in selectivity (up to 9:1) towards less hindered reactants in otherwise unselective, competitive photocatalytic oxidations and transfer hydrogenations. PMID:23174984

  9. Shape-selective sieving layers on an oxide catalyst surface

    NASA Astrophysics Data System (ADS)

    Canlas, Christian P.; Lu, Junling; Ray, Natalie A.; Grosso-Giordano, Nicolas A.; Lee, Sungsik; Elam, Jeffrey W.; Winans, Randall E.; van Duyne, Richard P.; Stair, Peter C.; Notestein, Justin M.

    2012-12-01

    New porous materials such as zeolites, metal-organic frameworks and mesostructured oxides are of immense practical utility for gas storage, separations and heterogeneous catalysis. Their extended pore structures enable selective uptake of molecules or can modify the product selectivity (regioselectivity or enantioselectivity) of catalyst sites contained within. However, diffusion within pores can be problematic for biomass and fine chemicals, and not all catalyst classes can be readily synthesized with pores of the correct dimensions. Here, we present a novel approach that adds reactant selectivity to existing, non-porous oxide catalysts by first grafting the catalyst particles with single-molecule sacrificial templates, then partially overcoating the catalyst with a second oxide through atomic layer deposition. This technique is used to create sieving layers of Al2O3 (thickness, 0.4-0.7 nm) with ‘nanocavities’ (<2 nm in diameter) on a TiO2 photocatalyst. The additional layers result in selectivity (up to 9:1) towards less hindered reactants in otherwise unselective, competitive photocatalytic oxidations and transfer hydrogenations.

  10. Oil emulsification using surface-tunable carbon black particles.

    PubMed

    Saha, Amitesh; Nikova, Ani; Venkataraman, Pradeep; John, Vijay T; Bose, Arijit

    2013-04-24

    Emulsification of oil from a subsurface spill and keeping it stable in the water is an important component of the natural remediation process. Motivated by the need to find alternate dispersants for emulsifying oil following a spill, we examine particle-stabilized oil-in-water emulsions. Emulsions that remain stable for months are prepared either by adding acid or salt to carboxyl-terminated carbon black (CB) suspension in water to make the particles partially hydrophobic, adding the oil to this suspension and mixing. When naphthalene, a model potentially toxic polycyclic aromatic hydrocarbon, is added to octane and an emulsion formed, it gets adsorbed significantly by the CB particles, and its transport into the continuous water is markedly reduced. In contrast to an undesirable seawater-in-crude oil emulsion produced using a commercially used dispersant, Corexit 9500A, we demonstrate the formation of a stable crude oil-in-seawater emulsion using the CB particles (with no added acid or salt), important for natural degradation. The large specific surface area of these surface functionalized CB particles, their adsorption capability and their ability to form stable emulsions are an important combination of attributes that potentially make these particles a viable alternative or supplement to conventional dispersants for emulsifying crude oil following a spill. PMID:23527962

  11. Nature of the Martian surface as inferred from the particle-size distribution of lunar-surface material.

    NASA Technical Reports Server (NTRS)

    Mason, C. C.

    1971-01-01

    Analysis of lunar particle size distribution data indicates that the surface material is composed of two populations. One population is caused by comminution from the impact of the larger-sized meteorites, while the other population is caused by the melting of fine material by the impact of smaller-sized meteorites. The results are referred to Mars, and it is shown that the Martian atmosphere would vaporize the smaller incoming meteorites and retard the incoming meteorites of intermediate and large size, causing comminution and stirring of the particulate layer. The combination of comminution and stirring would result in fine material being sorted out by the prevailing circulation of the Martian atmosphere and the material being transported to regions where it could be deposited. As a result, the Martian surface in regions of prevailing upward circulation is probably covered by either a rubble layer or by desert pavement; regions of prevailing downward circulation are probably covered by sand dunes.

  12. Nanoscale Structuring of Surfaces by Using Atomic Layer Deposition.

    PubMed

    Sobel, Nicolas; Hess, Christian

    2015-12-01

    Controlled structuring of surfaces is interesting for a wide variety of areas, including microelectronic device fabrication, optical devices, bio(sensing), (electro-, photo)catalysis, batteries, solar cells, fuel cells, and sorption. A unique feature of atomic layer deposition (ALD) is the possibility to form conformal uniform coatings on arbitrarily shaped materials with controlled atomic-scale thickness. In this Minireview, we discuss the potential of ALD for the nanoscale structuring of surfaces, highlighting its versatile application to structuring both planar substrates and powder materials. Recent progress in the application of ALD to porous substrates has even made the nanoscale structuring of high-surface-area materials now feasible, thereby enabling novel applications, such as those in the fields of catalysis and alternative energy.

  13. Surface Dynamics of Segregation Layer in Blockcopolymer Films

    NASA Astrophysics Data System (ADS)

    Song, Sanghoon; Cha, Wonsuk; Jiang, Zhang; Narayanan, Suresh; Ruehm, Adrian; Sinha, Sunil K.; Kim, Hyunjung

    2009-03-01

    We have investigated the surface dynamics of supported block copolymer films of poly(styrene)-b-poly(dimethylsiloxane) (PS-b- PDMS) in the spherical phase, i.e., PDMS cores surrounded by PS shells by x-ray photon correlation spectroscopy (XPCS) in grazing angle geometry. The experiment was performed at the beamline 8ID-I in Advanced Photon Source. We found that the PDMS-rich layer near the surface appears at the temperature higher than the glass transition temperature. We applied the modified theory for bilayer model with surface capillary waves on simple viscoelastic liquid films. The viscosity obtained in this study is compared with that from the rheology measurement for bulk.

  14. Linear stability of a layered fluid with mobile surface plates

    NASA Technical Reports Server (NTRS)

    Buffett, B. A.; Gable, C. W.; O'Connell, R. J.

    1994-01-01

    We develop a general method of calculating the linear stability of a fluid with homogeneous layers that is heated from below. The method employs a propagator technique to obtain expressions for the fluid velocity, stress, and temperature. The principal advantage of the method is the ease with which solutions are adapted to a wide variety of boundary conditions and fluid properties. We demonstrate the utility of the method using three examples which quantify the effects of (1) rheological layering, (2) mobile plates at the surface, and (3) multiple phase transitions. Each example is presented in the context of Earth's mantle. In the first example, we predict that convection becomes confined to the upper mantle once the viscosity increase between the upper and lower mantle exceeds a factor of 2000, consistent with the nonlinear calculations of Davies (1977). In the second example we find that the heat flux variations in a convecting fluid with variably sized, surface plates can be attributed, in part, to changes in the critical Rayleigh number. The linear stability of a fluid with multiple phase transitions is significantly affects by the locations of the transitions. We find that phase transitions have their largest effect when they are located at the center of the fluid layer and become much less important when they are located near the exterior boundaries.

  15. Multi-layer topological transmissions of spoof surface plasmon polaritons

    NASA Astrophysics Data System (ADS)

    Pan, Bai Cao; Zhao, Jie; Liao, Zhen; Zhang, Hao Chi; Cui, Tie Jun

    2016-03-01

    Spoof surface plasmon polaritons (SPPs) in microwave frequency provide a high field confinement in subwavelength scale and low-loss and flexible transmissions, which have been widely used in novel transmission waveguides and functional devices. To play more important roles in modern integrated circuits and systems, it is necessary and helpful for the SPP modes to propagate among different layers of devices and chips. Owing to the highly confined property and organized near-field distribution, we show that the spoof SPPs could be easily transmitted from one layer into another layer via metallic holes and arc-shaped transitions. Such designs are suitable for both the ultrathin and flexible single-strip SPP waveguide and double-strip SPP waveguide for active SPP devices. Numerical simulations and experimental results demonstrate the broadband and high-efficiency multi-layer topological transmissions with controllable absorption that is related to the superposition area of corrugated metallic strips. The transmission coefficient of single-strip SPP waveguide is no worse than -0.8 dB within frequency band from 2.67 GHz to 10.2 GHz while the transmission of double-strip SPP waveguide keeps above -1 dB within frequency band from 2.26 GHz to 11.8 GHz. The proposed method will enhance the realizations of highly complicated plasmonic integrated circuits.

  16. ELECTROSTATIC SURFACE STRUCTURES OF COAL AND MINERAL PARTICLES

    SciTech Connect

    1998-04-01

    This is the third semi-annual, technical progress report for this project. The following items are covered in the report: (1) Progress on the development of an instrument to perform ultraviolet photoelectron spectroscopy, UPS, on surfaces in air. (2) Further development plans for the video particle image analyzer. (3) Calculations on the effect of space charge on the electric field inside a separator. (4) Outreach education involving two Arkansas high school students in the project. (5) Additional data on the effects of processing atmosphere on beneficiation. Included in the last section is a description of planned experiments using charged, fluorescent, polystyrene micro-particles to map the charge distribution on the larger coal particles and on polished coal surfaces.

  17. Layer-like Structure of Radio-Frequency Discharge with Dust Particles

    SciTech Connect

    Kravchenko, O. Y.; Vakulenko, A. V.; Lisitchenko, T. Y.; Levada, G. I.

    2008-09-07

    In this paper we are carried out the computer simulation of the dust particles dynamics in the radio frequency discharges at the microgravity conditions using PIC/MCC method for electrons and ions and hydrodynamics model for dust particles. The moving of dust particles is governed by the electrostatic force, ion and neutral drag forces, which are averaged over period of RF discharge. The obtained results show that dust particles form layers with sharp boundaries in the discharge chamber that is response on the instability of the radio-frequency discharge.

  18. Composition, microstructure, and surface barrier layer development during brine salting.

    PubMed

    Melilli, C; Carcò, D; Barbano, D M; Tumino, G; Carpino, S; Licitra, G

    2005-07-01

    The goal of this study was to characterize the changes in chemical composition, porosity, and structure that occur at the surface of a block of brine-salted cheese and their relationship to the rate at which salt is taken up from the brine. To create a difference in composition, salt uptake, and barrier layer properties, identical blocks of Ragusano cheese were placed in saturated and 18% salt brine at 18 degrees C for 12 d. The overall moisture content and porosity decreased, whereas salt and salt in moisture content increased near the surface of blocks of brine-salted Ragusano cheese for all treatments. The general appearance of the microstructure of the surface of the blocks of brine-salted cheese was much more compact than the microstructure 1 mm inside the block at both brine concentrations. Large differences in porosity of the barrier layer were produced by brine-salting cheese in 18% vs. saturated brine, with cheese in saturated brine having much lower porosity at the surface and taking up much less salt during brining. The macro network of water channels within the microstructure of the cheese was less open near the surface of the block for cheese in both saturated and 18% brine after 4 d. However, no large differences in the size of the macro channels in the cheese structure due to the difference in brine concentration were observed by scanning electron microscopy. It is possible that the shrinkage of the much smaller pore structure within the casein matrix of the cheese is more important and will become more limiting to the rate of salt diffusion. Further microstructure work at higher resolution is needed to answer this question. The calculated decrease in porosity at the exterior 1-mm portion of the block was 50.8 and 29.2% for cheeses that had been in saturated vs. 18% brine for 12 d, respectively. The difference in brine concentration had a very large impact on the salt in moisture content of the cheese. The exterior of the cheese in 18% brine reached

  19. Soil moisture sensor calibration for organic soil surface layers

    NASA Astrophysics Data System (ADS)

    Bircher, Simone; Andreasen, Mie; Vuollet, Johanna; Vehviläinen, Juho; Rautiainen, Kimmo; Jonard, François; Weihermüller, Lutz; Zakharova, Elena; Wigneron, Jean-Pierre; Kerr, Yann H.

    2016-04-01

    This paper's objective is to present generic calibration functions for organic surface layers derived for the soil moisture sensors Decagon ECH2O 5TE and Delta-T ThetaProbe ML2x, using material from northern regions, mainly from the Finnish Meteorological Institute's Arctic Research Center in Sodankylä and the study area of the Danish Center for Hydrology (HOBE). For the Decagon 5TE sensor such a function is currently not reported in the literature. Data were compared with measurements from underlying mineral soils including laboratory and field measurements. Shrinkage and charring during drying were considered. For both sensors all field and lab data showed consistent trends. For mineral layers with low soil organic matter (SOM) content the validity of the manufacturer's calibrations was demonstrated. Deviating sensor outputs in organic and mineral horizons were identified. For the Decagon 5TE, apparent relative permittivities at a given moisture content decreased for increased SOM content, which was attributed to an increase of bound water in organic materials with large specific surface areas compared to the studied mineral soils. ThetaProbe measurements from organic horizons showed stronger nonlinearity in the sensor response and signal saturation in the high-level data. The derived calibration fit functions between sensor response and volumetric water content hold for samples spanning a wide range of humus types with differing SOM characteristics. This strengthens confidence in their validity under various conditions, rendering them highly suitable for large-scale applications in remote sensing and land surface modeling studies. Agreement between independent Decagon 5TE and ThetaProbe time series from an organic surface layer at the Sodankylä site was significantly improved when the here-proposed fit functions were used. Decagon 5TE data also well-reflected precipitation events. Thus, Decagon 5TE network data from organic surface layers at the Sodankylä and

  20. Soil moisture sensor calibration for organic soil surface layers

    NASA Astrophysics Data System (ADS)

    Bircher, S.; Andreasen, M.; Vuollet, J.; Vehviläinen, J.; Rautiainen, K.; Jonard, F.; Weihermüller, L.; Zakharova, E.; Wigneron, J.-P.; Kerr, Y. H.

    2015-12-01

    This paper's objective is to present generic calibration functions for organic surface layers derived for the soil moisture sensors Decagon ECH2O 5TE and Delta-T ThetaProbe ML2x, using material from northern regions, mainly from the Finish Meteorological Institute's Arctic Research Center in Sodankylä and the study area of the Danish Center for Hydrology HOBE. For the Decagon 5TE sensor such a function is currently not reported in literature. Data were compared with measurements from underlying mineral soils including laboratory and field measurements. Shrinkage and charring during drying were considered. For both sensors all field and lab data showed consistent trends. For mineral layers with low soil organic matter (SOM) content the validity of the manufacturer's calibrations was demonstrated. Deviating sensor outputs in organic and mineral horizons were identified: for the Decagon 5TE apparent relative permittivities at a given moisture content decreased for increased SOM content, which was attributed to an increase of bound water in organic materials with large surface areas compared to the studied mineral soils. ThetaProbe measurements from organic horizons showed stronger non-linearity in the sensor response and signal saturation in the high level data. The derived calibration fit functions between sensor response and volumetric water content hold for samples spanning a wide range of humus types with differing SOM characteristics. This strengthens confidence in their validity under various conditions, rendering them highly suitable for large-scale applications in remote sensing and land surface modeling studies. Agreement between independent Decagon 5TE and ThetaProbe time series from an organic surface layer at the Sodankylä site was significantly improved when the here proposed fit functions were used. Decagon 5TE data also well-reflected precipitation events. Thus, Decagon 5TE network data from organic surface layers at the Sodankylä and HOBE sites are

  1. Atmospheric surface and boundary layers of the Amazon Basin

    NASA Technical Reports Server (NTRS)

    Garstang, Michael

    1987-01-01

    Three phases of work were performed: design of and preparation for the Amazon Boundary Layer Experiment (ABLE 2-A); execution of the ABLE 2-A field program; and analysis of the ABLE 2-A data. Three areas of experiment design were dealt with: surface based meteorological measurements; aircraft missions; and project meteorological support. The primary goal was to obtain a good description of the structure of the atmosphere immediately above the rain forest canopy (top of canopy to a few thousand meters), to describe this region during the growing daytime phase of the boundary layer; and to examine the nighttime stratified state. A secondary objective was to examine the role that deep convective storms play in the vertical transport of heat, water vapor, and other trace gases. While significant progress was made, much of the analysis remains to be done.

  2. Detecting surface roughness effects on the atmospheric boundary layer via AIRSAR data: A field experiment in Death Valley, California

    NASA Technical Reports Server (NTRS)

    Blumberg, Dan G.; Greeley, Ronald

    1992-01-01

    The part of the troposphere influenced by the surface of the earth is termed the atmospheric boundary layer. Flow within this layer is influenced by the roughness of the surface; rougher surfaces induce more turbulence than smoother surfaces and, hence, higher atmospheric transfer rates across the surface. Roughness elements also shield erodible particles, thus decreasing the transport of windblown particles. Therefore, the aerodynamic roughness length (z(sub 0)) is an important parameter in aeolian and atmospheric boundary layer processes as it describes the aerodynamic properties of the underlying surface. z(sub 0) is assumed to be independent of wind velocity or height, and dependent only on the surface topography. It is determined using in situ measurements of the wind speed distribution as a function of height. For dry, unvegetated soils the intensity of the radar backscatter (sigma(sup 0)) is affected primarily by surface roughness at a scale comparable with the radar wavelength. Thus, both wind and radar respond to surface roughness variations on a scale of a few meters or less. Greeley showed the existence of a correlation between z(sub 0) and sigma(sup 0). This correlation was based on measurements over lava flows, alluvial fans, and playas in the southwest deserts of the United States. It is shown that the two parameters behave similarly also when there are small changes over a relatively homogeneous surface.

  3. Low energy charged particles interacting with amorphous solid water layers.

    PubMed

    Horowitz, Yonatan; Asscher, Micha

    2012-04-01

    The interaction of charged particles with condensed water films has been studied extensively in recent years due to its importance in biological systems, ecology as well as interstellar processes. We have studied low energy electrons (3-25 eV) and positive argon ions (55 eV) charging effects on amorphous solid water (ASW) and ice films, 120-1080 ML thick, deposited on ruthenium single crystal under ultrahigh vacuum conditions. Charging the ASW films by both electrons and positive argon ions has been measured using a Kelvin probe for contact potential difference (CPD) detection and found to obey plate capacitor physics. The incoming electrons kinetic energy has defined the maximum measurable CPD values by retarding further impinging electrons. L-defects (shallow traps) are suggested to be populated by the penetrating electrons and stabilize them. Low energy electron transmission measurements (currents of 0.4-1.5 μA) have shown that the maximal and stable CPD values were obtained only after a relatively slow change has been completed within the ASW structure. Once the film has been stabilized, the spontaneous discharge was measured over a period of several hours at 103 ± 2 K. Finally, UV laser photo-emission study of the charged films has suggested that the negative charges tend to reside primarily at the ASW-vacuum interface, in good agreement with the known behavior of charged water clusters.

  4. Low energy charged particles interacting with amorphous solid water layers

    NASA Astrophysics Data System (ADS)

    Horowitz, Yonatan; Asscher, Micha

    2012-04-01

    The interaction of charged particles with condensed water films has been studied extensively in recent years due to its importance in biological systems, ecology as well as interstellar processes. We have studied low energy electrons (3-25 eV) and positive argon ions (55 eV) charging effects on amorphous solid water (ASW) and ice films, 120-1080 ML thick, deposited on ruthenium single crystal under ultrahigh vacuum conditions. Charging the ASW films by both electrons and positive argon ions has been measured using a Kelvin probe for contact potential difference (CPD) detection and found to obey plate capacitor physics. The incoming electrons kinetic energy has defined the maximum measurable CPD values by retarding further impinging electrons. L-defects (shallow traps) are suggested to be populated by the penetrating electrons and stabilize them. Low energy electron transmission measurements (currents of 0.4-1.5 μA) have shown that the maximal and stable CPD values were obtained only after a relatively slow change has been completed within the ASW structure. Once the film has been stabilized, the spontaneous discharge was measured over a period of several hours at 103 ± 2 K. Finally, UV laser photo-emission study of the charged films has suggested that the negative charges tend to reside primarily at the ASW-vacuum interface, in good agreement with the known behavior of charged water clusters.

  5. Low energy charged particles interacting with amorphous solid water layers

    SciTech Connect

    Horowitz, Yonatan; Asscher, Micha

    2012-04-07

    The interaction of charged particles with condensed water films has been studied extensively in recent years due to its importance in biological systems, ecology as well as interstellar processes. We have studied low energy electrons (3-25 eV) and positive argon ions (55 eV) charging effects on amorphous solid water (ASW) and ice films, 120-1080 ML thick, deposited on ruthenium single crystal under ultrahigh vacuum conditions. Charging the ASW films by both electrons and positive argon ions has been measured using a Kelvin probe for contact potential difference (CPD) detection and found to obey plate capacitor physics. The incoming electrons kinetic energy has defined the maximum measurable CPD values by retarding further impinging electrons. L-defects (shallow traps) are suggested to be populated by the penetrating electrons and stabilize them. Low energy electron transmission measurements (currents of 0.4-1.5 {mu}A) have shown that the maximal and stable CPD values were obtained only after a relatively slow change has been completed within the ASW structure. Once the film has been stabilized, the spontaneous discharge was measured over a period of several hours at 103 {+-} 2 K. Finally, UV laser photo-emission study of the charged films has suggested that the negative charges tend to reside primarily at the ASW-vacuum interface, in good agreement with the known behavior of charged water clusters.

  6. Statistical properties of surfaces covered by deposited particles

    NASA Astrophysics Data System (ADS)

    Wojtaszczyk, P.; Mann, E. K.; Senger, B.; Voegel, J. C.; Schaaf, P.

    1995-11-01

    The statistical properties of surfaces covered by irreversibly adsorbed colloidal particles are studied as a function of the Péclet number (or equivalently as a function of their rescaled radius R*). More precisely, the radial distribution function g(r) is determined as a function of the coverage θ for five systems corresponding to different values of R*. Also measured is the reduced variance σ2/ of the number n of adsorbed particles on surfaces of given area out of the adsorption plane. Finally, the evolution of with the concentration of particles in solution during the deposition process is determined for the different systems. This allows us to obtain information on the available surface function Φ. All these parameters are compared to their expected behavior according to the random sequential adsorption (RSA) model and to the ballistic model (BM). It is found that the radial distribution function of the system of particles characterized by R*<1 is well predicted by the RSA model whereas for R*≳3 the BM can serve as a good first approximation. On the other hand, one finds surprisingly that the available surface function Φ and the reduced variance σ2/ vary with the coverage θ in a similar way for all the systems over the range of value of R* investigated. Their behavior corresponds, in first approximation, to the expectations from the BM. In particular, the reduced variance σ2/ exhibits a horizontal tangent at low coverage whereas the RSA model predicts an initial slope of -4. This result is the more intriguing that σ2/ is directly related to the radial distribution function g(r), which does vary with R*. Finally, higher order moments of the distribution of the number of particles n adsorbed on our surfaces are also determined as a function of the coverage. They behave, within experimental errors, like those of a Gaussian distribution as predicted by the central limit theorem.

  7. Thermophoretic motion behavior of submicron particles in boundary-layer-separation flow around a droplet.

    PubMed

    Wang, Ao; Song, Qiang; Ji, Bingqiang; Yao, Qiang

    2015-12-01

    As a key mechanism of submicron particle capture in wet deposition and wet scrubbing processes, thermophoresis is influenced by the flow and temperature fields. Three-dimensional direct numerical simulations were conducted to quantify the characteristics of the flow and temperature fields around a droplet at three droplet Reynolds numbers (Re) that correspond to three typical boundary-layer-separation flows (steady axisymmetric, steady plane-symmetric, and unsteady plane-symmetric flows). The thermophoretic motion of submicron particles was simulated in these cases. Numerical results show that the motion of submicron particles around the droplet and the deposition distribution exhibit different characteristics under three typical flow forms. The motion patterns of particles are dependent on their initial positions in the upstream and flow forms. The patterns of particle motion and deposition are diversified as Re increases. The particle motion pattern, initial position of captured particles, and capture efficiency change periodically, especially during periodic vortex shedding. The key effects of flow forms on particle motion are the shape and stability of the wake behind the droplet. The drag force of fluid and the thermophoretic force in the wake contribute jointly to the deposition of submicron particles after the boundary-layer separation around a droplet. PMID:26764827

  8. Thermophoretic motion behavior of submicron particles in boundary-layer-separation flow around a droplet.

    PubMed

    Wang, Ao; Song, Qiang; Ji, Bingqiang; Yao, Qiang

    2015-12-01

    As a key mechanism of submicron particle capture in wet deposition and wet scrubbing processes, thermophoresis is influenced by the flow and temperature fields. Three-dimensional direct numerical simulations were conducted to quantify the characteristics of the flow and temperature fields around a droplet at three droplet Reynolds numbers (Re) that correspond to three typical boundary-layer-separation flows (steady axisymmetric, steady plane-symmetric, and unsteady plane-symmetric flows). The thermophoretic motion of submicron particles was simulated in these cases. Numerical results show that the motion of submicron particles around the droplet and the deposition distribution exhibit different characteristics under three typical flow forms. The motion patterns of particles are dependent on their initial positions in the upstream and flow forms. The patterns of particle motion and deposition are diversified as Re increases. The particle motion pattern, initial position of captured particles, and capture efficiency change periodically, especially during periodic vortex shedding. The key effects of flow forms on particle motion are the shape and stability of the wake behind the droplet. The drag force of fluid and the thermophoretic force in the wake contribute jointly to the deposition of submicron particles after the boundary-layer separation around a droplet.

  9. Atomic-layer electroless deposition: a scalable approach to surface-modified metal powders.

    PubMed

    Cappillino, Patrick J; Sugar, Joshua D; El Gabaly, Farid; Cai, Trevor Y; Liu, Zhi; Stickney, John L; Robinson, David B

    2014-04-29

    Palladium has a number of important applications in energy and catalysis in which there is evidence that surface modification leads to enhanced properties. A strategy for preparing such materials is needed that combines the properties of (i) scalability (especially on high-surface-area substrates, e.g. powders); (ii) uniform deposition, even on substrates with complex, three-dimensional features; and (iii) low-temperature processing conditions that preserve nanopores and other nanostructures. Presented herein is a method that exhibits these properties and makes use of benign reagents without the use of specialized equipment. By exposing Pd powder to dilute hydrogen in nitrogen gas, sacrificial surface PdH is formed along with a controlled amount of dilute interstitial hydride. The lattice expansion that occurs in Pd under higher H2 partial pressures is avoided. Once the flow of reagent gas is terminated, addition of metal salts facilitates controlled, electroless deposition of an overlayer of subnanometer thickness. This process can be cycled to create thicker layers. The approach is carried out under ambient processing conditions, which is an advantage over some forms of atomic layer deposition. The hydride-mediated reaction is electroless in that it has no need for connection to an external source of electrical current and is thus amenable to deposition on high-surface-area substrates having rich, nanoscale topography as well as on insulator-supported catalyst particles. STEM-EDS measurements show that conformal Rh and Pt surface layers can be formed on Pd powder with this method. A growth model based on energy-resolved XPS depth profiling of Rh-modified Pd powder is in general agreement. After two cycles, deposits are consistent with 70-80% coverage and a surface layer with a thickness from 4 to 8 Å.

  10. Optical glass surfaces polishing by cerium oxide particles

    NASA Astrophysics Data System (ADS)

    Bouzid, D.; Belkhie, N.; Aliouane, T.

    2012-02-01

    The use of powders in metallic oxides as means of grinding and polishing of the optical glass components have seen recently a large application in optical industry. In fact, cerium oxide abrasive is more used in the optical glass polishing. It is used as grains abrasive in suspension or fixed abrasive (pellets); these pellets are manufactured from a mixture made of cerium oxide abrasive and a organic binder. The cerium oxide used in the experiments is made by (Logitech USA) of 99 % purity, the average grain size of the particle is 300 nm, the density being 6,74 g /cm3 and the specific surface is 3,3042 m2/g. In this study, we are interested in the surfaces quality of the optical glass borosilicate crown (BK7) polished by particles in cerium oxide bounded by epoxy. The surfaces of the optical glass treated are characterized by the roughness, the flatness by using the microscope Zygo and the SEM.

  11. Surface activation of CNT Webs towards layer by layer assembly of biosensors.

    PubMed

    Musameh, Mustafa; Huynh, Chi P; Hickey, Mark; Kyratzis, Ilias Louis

    2016-04-25

    Several surface activation methods such as chemical, electrochemical and plasma have been used for enhancing the electrochemical performance of carbon based electrodes for various applications. However, some of these surface activation methods may not be useful depending on the chemical and physical properties of the activated surface. Herein we investigate the surface activation of carbon nanotube (CNT) webs by electrochemical and plasma techniques to enhance their electrochemical performance and enable the fabrication of a biosensor using the layer-by-layer (LBL) approach. The pretreated CNT webs were characterized by SEM, TEM, Raman, XPS and electrochemical methods. TEM images and Raman analysis showed an increase in the level of surface defects upon pretreatment with higher number of defects after electrochemical pretreatment. XPS analysis showed an increase in the level of oxygen functional groups after pretreatment (4 to 5 times increase) which resulted in enhanced water wettability especially for plasma pretreated CNT webs. The pretreated CNT web electrodes also showed an enhanced electrochemical activity towards the oxidation and reduction of different redox probes with higher sensitivity for the electrochemically pretreated CNT web electrode that was accompanied by a higher level of noise in amperometric measurements. A highly linear response was obtained for the untreated and the electrochemically pretreated CNT web electrodes towards the amperometric detection of NADH (R(2) of 0.9996 and 0.9986 respectively) while a non-linear response was observed for the plasma pretreated CNT web electrode (R(2) of 0.8538). The pretreated CNT web electrodes enabled the fabrication of a LBL biosensor for alcohol detection with highest operational stability obtained for the plasma pretreated CNT web surface.

  12. Combined Photothermal and Surface-Enhanced Raman Spectroscopy Effect from Spiky Noble Metal Nanoparticles Wrapped within Graphene-Polymer Layers: Using Layer-by-layer Modified Reduced Graphene Oxide as Reactive Precursors.

    PubMed

    Li, Xiangming; Zhang, Yihe; Wu, Yaling; Duan, Yang; Luan, Xinglong; Zhang, Qian; An, Qi

    2015-09-01

    To fabricate functionally integrated hybrid nanoparticles holds high importance in biomedical applications and is still a challenging task. In this study, we report the first reduced graphene oxide (rGO)-nobel metal hybrid particles that present simultaneously the photothermal and surface-enhanced Raman spectroscopy (SERS) effect from the inorganic part and drug loading, dispersibility, and controllability features from LbL polyelectrolyte multilayers. The hybrid particles where spiky noble metal particles were wrapped within rGO-polyelectrolyte layers were prepared by a facile and controllable method. rGO template modified using polyethylenimine (PEI) and poly(acrylic acid) (PAA) via layer-by-layer technology served as the reactive precursors, and the morphologies of the particles could be facilely controlled via controlling the number of bilayers around the rGO template. The hybrid particle presented low cytotoxicity. After loading doxorubicin hydrochloride, the particles effectively induced cell death, and photothermal treatment further decreased cell viability. rGO-Ag hybrid particles could be prepared similarly. We expect the reported method provides an effective strategy to prepare rGO-noble metal hybrid nanoparticles that find potential biomedical applications. PMID:26269466

  13. Combined Photothermal and Surface-Enhanced Raman Spectroscopy Effect from Spiky Noble Metal Nanoparticles Wrapped within Graphene-Polymer Layers: Using Layer-by-layer Modified Reduced Graphene Oxide as Reactive Precursors.

    PubMed

    Li, Xiangming; Zhang, Yihe; Wu, Yaling; Duan, Yang; Luan, Xinglong; Zhang, Qian; An, Qi

    2015-09-01

    To fabricate functionally integrated hybrid nanoparticles holds high importance in biomedical applications and is still a challenging task. In this study, we report the first reduced graphene oxide (rGO)-nobel metal hybrid particles that present simultaneously the photothermal and surface-enhanced Raman spectroscopy (SERS) effect from the inorganic part and drug loading, dispersibility, and controllability features from LbL polyelectrolyte multilayers. The hybrid particles where spiky noble metal particles were wrapped within rGO-polyelectrolyte layers were prepared by a facile and controllable method. rGO template modified using polyethylenimine (PEI) and poly(acrylic acid) (PAA) via layer-by-layer technology served as the reactive precursors, and the morphologies of the particles could be facilely controlled via controlling the number of bilayers around the rGO template. The hybrid particle presented low cytotoxicity. After loading doxorubicin hydrochloride, the particles effectively induced cell death, and photothermal treatment further decreased cell viability. rGO-Ag hybrid particles could be prepared similarly. We expect the reported method provides an effective strategy to prepare rGO-noble metal hybrid nanoparticles that find potential biomedical applications.

  14. Turbulence-particle interactions under surface gravity waves

    NASA Astrophysics Data System (ADS)

    Paskyabi, Mostafa Bakhoday

    2016-11-01

    The dispersion and transport of single inertial particles through an oscillatory turbulent aquatic environment are examined numerically by a Lagrangian particle tracking model using a series of idealised test cases. The turbulent mixing is incorporated into the Lagrangian model by the means of a stochastic scheme in which the inhomogeneous turbulent quantities are governed by a one-dimensional k- ɛ turbulence closure scheme. This vertical mixing model is further modified to include the effects of surface gravity waves including Coriolis-Stokes forcing, wave breaking, and Langmuir circulations. To simplify the complex interactions between the deterministic and the stochastic phases of flow, we assume a time-invariant turbulent flow field and exclude the hydrodynamic biases due to the effects of ambient mean current. The numerical results show that the inertial particles acquire perturbed oscillations traced out as time-varying sinking/rising orbits in the vicinity of the sea surface under linear and cnoidal waves and acquire a non-looping single arc superimposed with the high-frequency fluctuations beneath the nonlinear solitary waves. Furthermore, we briefly summarise some recipes through the course of this paper on the implementation of the stochastic particle tracking models to realistically describe the drift and suspension of inertial particles throughout the water column.

  15. Electron density modification in ionospheric E layer by inserting fine dust particles

    SciTech Connect

    Misra, Shikha; Mishra, S. K.

    2015-02-15

    In this paper, we have developed the kinetics of E-region ionospheric plasma comprising of fine dust grains and shown that the electron density in E-layer can purposely be reduced/enhanced up to desired level by inserting fine dust particles of appropriate physical/material properties; this may certainly be promising for preferred rf-signal processing through these layers. The analytical formulation is based on average charge theory and includes the number and energy balance of the plasma constituents along with charge balance over dust particles. The effect of varying number density, work function, and photo-efficiency of dust particles on ionospheric plasma density at different altitude in E-layer has been critically examined and presented graphically.

  16. Electron density modification in ionospheric E layer by inserting fine dust particles

    NASA Astrophysics Data System (ADS)

    Misra, Shikha; Mishra, S. K.

    2015-02-01

    In this paper, we have developed the kinetics of E-region ionospheric plasma comprising of fine dust grains and shown that the electron density in E-layer can purposely be reduced/enhanced up to desired level by inserting fine dust particles of appropriate physical/material properties; this may certainly be promising for preferred rf-signal processing through these layers. The analytical formulation is based on average charge theory and includes the number and energy balance of the plasma constituents along with charge balance over dust particles. The effect of varying number density, work function, and photo-efficiency of dust particles on ionospheric plasma density at different altitude in E-layer has been critically examined and presented graphically.

  17. Epitaxially guided assembly of collagen layers on mica surfaces.

    PubMed

    Leow, Wee Wen; Hwang, Wonmuk

    2011-09-01

    Ordered assembly of collagen molecules on flat substrates has potential for various applications and serves as a model system for studying the assembly process. While previous studies demonstrated self-assembly of collagen on muscovite mica into highly ordered layers, the mechanism by which different conditions affect the resulting morphology remains to be elucidated. Using atomic force microscopy, we follow the assembly of collagen on muscovite mica at a concentration lower than the critical fibrillogenesis concentration in bulk. Initially, individual collagen molecules adsorb to mica and subsequently nucleate into fibrils possessing the 67 nm D-periodic bands. Emergence of fibrils aligned in parallel despite large interfibril distances agrees with an alignment mechanism guided by the underlying mica. The epitaxial growth was further confirmed by the formation of novel triangular networks of collagen fibrils on phlogopite mica, whose surface lattice is known to have a hexagonal symmetry, whereas the more widely used muscovite does not. Comparing collagen assembly on the two types of mica at different potassium concentrations revealed that potassium binds to the negatively charged mica surface and neutralizes it, thereby reducing the binding affinity of collagen and enhancing surface diffusion. These results suggest that collagen assembly on mica follows the surface adsorption, diffusion, nucleation, and growth pathway, where the growth direction is determined at the nucleation step. Comparison with other molecules that assemble similarly on mica supports generality of the proposed assembly mechanism, the knowledge of which will be useful for controlling the resulting surface morphologies.

  18. The role of adsorbed water on the friction of a layer of submicron particles

    USGS Publications Warehouse

    Sammis, Charles G.; Lockner, David A.; Reches, Ze’ev

    2011-01-01

    Anomalously low values of friction observed in layers of submicron particles deformed in simple shear at high slip velocities are explained as the consequence of a one nanometer thick layer of water adsorbed on the particles. The observed transition from normal friction with an apparent coefficient near μ = 0.6 at low slip speeds to a coefficient near μ = 0.3 at higher slip speeds is attributed to competition between the time required to extrude the water layer from between neighboring particles in a force chain and the average lifetime of the chain. At low slip speeds the time required for extrusion is less than the average lifetime of a chain so the particles make contact and lock. As slip speed increases, the average lifetime of a chain decreases until it is less than the extrusion time and the particles in a force chain never come into direct contact. If the adsorbed water layer enables the otherwise rough particles to rotate, the coefficient of friction will drop to μ = 0.3, appropriate for rotating spheres. At the highest slip speeds particle temperatures rise above 100°C, the water layer vaporizes, the particles contact and lock, and the coefficient of friction rises to μ = 0.6. The observed onset of weakening at slip speeds near 0.001 m/s is consistent with the measured viscosity of a 1 nm thick layer of adsorbed water, with a minimum particle radius of approximately 20 nm, and with reasonable assumptions about the distribution of force chains guided by experimental observation. The reduction of friction and the range of velocities over which it occurs decrease with increasing normal stress, as predicted by the model. Moreover, the analysis predicts that this high-speed weakening mechanism should operate only for particles with radii smaller than approximately 1 μm. For larger particles the slip speed required for weakening is so large that frictional heating will evaporate the adsorbed water and weakening will not occur.

  19. Crystalline particle packings on constant mean curvature (Delaunay) surfaces

    NASA Astrophysics Data System (ADS)

    Bendito, Enrique; Bowick, Mark J.; Medina, Agustin; Yao, Zhenwei

    2013-07-01

    We investigate the structure of crystalline particle arrays on constant mean curvature (CMC) surfaces of revolution. Such curved crystals have been realized physically by creating charge-stabilized colloidal arrays on liquid capillary bridges. CMC surfaces of revolution, classified by Delaunay in 1841, include the 2-sphere, the cylinder, the vanishing mean curvature catenoid (a minimal surface), and the richer and less investigated unduloid and nodoid. We determine numerically candidate ground-state configurations for 1000 pointlike particles interacting with a pairwise-repulsive 1/r3 potential, with distance r measured in three-dimensional Euclidean space R3. We mimic stretching of capillary bridges by determining the equilibrium configurations of particles arrayed on a sequence of Delaunay surfaces obtained by increasing or decreasing the height at constant volume starting from a given initial surface, either a fat cylinder or a square cylinder. In this case, the stretching process takes one through a complicated sequence of Delaunay surfaces, each with different geometrical parameters, including the aspect ratio, mean curvature, and maximal Gaussian curvature. Unduloids, catenoids, and nodoids all appear in this process. Defect motifs in the ground state evolve from dislocations at the boundary to dislocations in the interior to pleats and scars in the interior and then isolated sevenfold disclinations in the interior as the capillary bridge narrows at the waist (equator) and the maximal (negative) Gaussian curvature grows. We also check theoretical predictions that the isolated disclinations are present in the ground state when the surface contains a geodesic disk with integrated Gaussian curvature exceeding -π/3. Finally, we explore minimal energy configurations on sets of slices of a given Delaunay surface, and we obtain configurations and defect motifs consistent with those seen in stretching.

  20. Paint removal and surface cleaning using ice particles

    NASA Astrophysics Data System (ADS)

    Foster, Terry; Visaisouk, S.

    1993-03-01

    Research into the possibility of using ice particles as a blast medium was first initiated at Defence Research Establishment Pacific (DREP) in an effort to develop a more environmentally acceptable paint removal method. A paint removal process was also required that could be used in areas where normal grit blasting could not be used due to the possibility of the residual blasting grit contaminating machinery and other equipment. As a result of this research a commercial ice blasting system was developed by RETECH. This system is now being used to remove paint from substrates that cannot be easily blasted by conventional techniques and also to clean soiled or contaminated surfaces. The problems involved in the development of an ice blast system, and its components and their functions are described. Due to the complexity of paint removal using ice blasting, parameters such as air pressure, ice particle size and ice particle flow rate were studied and adjusted to suit the nature of the particular coating and substrate of interest. The mechanism of paint removal by ice particles has also been investigated. A theoretical model has been developed to explain the different paint removal mechanisms such as erosion by abrasion and erosion by fracture as they relate to ice blasting. Finally, the use of ice blasting to removal paint from a variety of substrates is presented as well as examples of surface cleaning and surface decontamination.

  1. Paint removal and surface cleaning using ice particles

    NASA Astrophysics Data System (ADS)

    Foster, Terry; Visaisouk, S.

    1995-04-01

    Research into the possibility of using ice particles as a blast medium was first initiated at Defence Research Establishment Pacific (DREP) in an effort to develop a more environmentally acceptable paint removal method. A paint removal process was also required that could be used in areas where normal grit blasting could not be used due to the possibility of the residual blasting grit contaminating machinery and other equipment. As a result of this research a commercial ice blasting system was developed by RETECH. This system is now being used to remove paint from substrates that cannot be easily blasted by conventional techniques and also to clean soiled or contaminated surfaces. The problems involved in the development of an ice blast system and its components and their functions are described. Due to the complexity of paint removal using ice blasting, parameters such as air pressure, ice particle size and ice particle flow rate were studied and adjusted to suit the nature of the particular coating and substrate of interest. The mechanism of paint removal by ice particles has also been investigated. A theoretical model has been developed to explain the different paint removal mechanisms such as erosion by abrasion and erosion by fracture as they relate to ice blasting. Finally, the use of ice blasting to removal paint from a variety of substrates is presented as well as examples of surface cleaning and surface decontamination.

  2. Atmospheric new particle formation as a source of CCN in the eastern Mediterranean marine boundary layer

    NASA Astrophysics Data System (ADS)

    Kalivitis, N.; Kerminen, V.-M.; Kouvarakis, G.; Stavroulas, I.; Bougiatioti, A.; Nenes, A.; Manninen, H. E.; Petäjä, T.; Kulmala, M.; Mihalopoulos, N.

    2015-08-01

    While cloud condensation nuclei (CCN) production associated with atmospheric new particle formation (NPF) is thought to be frequent throughout the continental boundary layers, few studies on this phenomenon in marine air exist. Here, based on simultaneous measurement of particle number size distributions, CCN properties and aerosol chemical composition, we present the first direct evidence on CCN production resulting from NPF in the eastern Mediterranean atmosphere. We show that condensation of both gaseous sulfuric acid and organic compounds from multiple sources leads to the rapid growth of nucleated particles to CCN sizes in this environment during the summertime. Sub-100 nm particles were found to be substantially less hygroscopic than larger particles during the period with active NPF and growth (the value of κ was lower by 0.2-0.4 for 60 nm particles compared with 120 nm particles), probably due to enrichment of organic material in the sub-100 nm size range. The aerosol hygroscopicity tended to be at minimum just before the noon and at maximum in the afternoon, which was very likely due to the higher sulfate-to-organic ratios and higher degree of oxidation of the organic material during the afternoon. Simultaneous with the formation of new particles during daytime, particles formed during the previous day or even earlier were growing into the size range relevant to cloud droplet activation, and the particles formed in the atmosphere were possibly mixed with long-range-transported particles.

  3. Tuning the particle-surface interactions in aqueous solutions by soft microgel particles.

    PubMed

    Gong, Xiangjun; Hua, Li; Wei, Jingjing; Ngai, To

    2014-11-11

    Due to the softness and deformability, interaction between colloidal surfaces induced by soft particles varies in a more complex way than for solid particles and thus has attracted much attention in recent years. In the present study, we use total internal reflection microscopy (TIRM) to directly measure the interaction between polystyrene (PS) microparticles and a flat glass surface in a poly(N-isopropylacrylamide) (PNIPAM) microgel dispersion with concentration varying from dilute (0.1 wt %) to highly concentrated regime (7.5 wt %). Our result shows that the PS particle-surface interactions mediated by the soft microgels are greatly affected by the particle concentration, the configuration of those microgels adsorbed on the surfaces, and the structure and packing of microgels in bulk solution. With increasing the microgel concentration (Cmicrogel), the interaction between the PS particle and surface turned from bridging attraction to steric repulsion, and then depletion attraction, which were mainly governed by the adsorption amount and configuration of microgels on the two surfaces. By further increasing Cmicrogel to condensed situation, structural force with oscillated energy wells was detected. The variation of interactions induced by the soft microgels was further confirmed by optical imaging. Crystallization of the PS microparticles appeared at moderate Cmicrogel; however, crystallization was hindered at higher Cmicrogel where the microgels are highly packed in the bulk solution. Furthermore, using TIRM, microgel packing with local energy well (0.1-1.0 kBT) at the highly condensed state (7.5 wt %) was resolved from the interaction profiles. Therefore, the shear force and modulus generated by such microgel packing can be determined as ∼0.2 pN and tens of mPa, respectively, which are much weaker than data given by conventional active methods.

  4. Nanofilms of hyaluronan/chitosan assembled layer-by-layer: An antibacterial surface for Xylella fastidiosa.

    PubMed

    Hernández-Montelongo, Jacobo; Nascimento, Vicente F; Murillo, Duber; Taketa, Thiago B; Sahoo, Prasana; de Souza, Alessandra A; Beppu, Marisa M; Cotta, Monica A

    2016-01-20

    In this work, nanofilms of hyaluronan/chitosan (HA/CHI) assembled layer by layer were synthesized; their application as a potential antimicrobial material was demonstrated for the phytopathogen Xylella fastidiosa, a gram-negative bacterium, here used as a model. For the synthesis, the influence of pH and ionic strength of these natural polymer stem-solutions on final characteristics of the HA/CHI nanofilms was studied in detail. The antibacterial effect was evaluated using widefield fluorescence microscopy. These results were correlated with the chemical properties of the nanofilms, studied by FTIR and Raman spectroscopy, as well as with their morphology and surface properties characterized using SEM and AFM. The present findings can be extended to design and optimize HA/CHI nanofilms with enhanced antimicrobial behavior for other type of phytopathogenic gram-negative bacteria species, such as Xanthomonas citri, Xanthomas campestri and Ralstonia solanacearum. PMID:26572322

  5. Buckling instabilities of nanoscale polymer films and colloidal particle layers

    NASA Astrophysics Data System (ADS)

    Gurmessa, Bekele Jemama

    remarkable. Finally, through an integrated experimental methods and theoretical modeling, the response of discrete colloidal layers to mechanical deformations have been exploited. The buckling profiles measured experimentally demonstrate a great insight that the continuum model may not be able to predict the response of discrete systems. Theoretically, a granular model was constructed and structural stability analysis was investigated to predict the experimental observations. The overall agreement of the experiment and the modeling was good.

  6. Effects of nanoparticle layering on nanofluid and base fluid pool boiling heat transfer from a horizontal surface under atmospheric pressure

    NASA Astrophysics Data System (ADS)

    White, Steven B.; Shih, Albert J.; Pipe, Kevin P.

    2010-06-01

    Previous heat transfer studies of nanofluids have shown that suspended nanoparticles can affect thermal properties within a fluid and furthermore can affect surface roughness by depositing on a heater surface. Pool boiling studies of nanofluids have demonstrated either enhanced or diminished heat transfer, yet have been unable to distinguish the contributions of increased surface roughness and suppression of bubble transport by suspended particles because they have used base fluids on a clean boiling surface as a comparison. We resolve this uncertainty by studying the boiling performance of a surface exposed to a series of boiling tests that alternate between water and a water-based nanofluid with suspended 40 nm ZnO nanoparticles. We find that the performance for the water tests increases significantly, showing a 62% enhancement after four cycles. This increase correlates well with a surface roughness model for boiling that uses atomic force microscopy-measured surface data to quantify the layering of nanoparticles in intervening nanofluid boiling tests. We find that the performance of the ZnO nanofluid initially shows a 24% enhancement versus water on a clean (unroughened) surface, but then steadily declines in later tests as nanoparticle layering occurs, showing a measured trend that is opposite that of water. We ascribe this decrease to the suppression of bubble formation and motion by the suspended particles. The results demonstrate that the effect of increased surface roughness due to nanoparticle layering can be twofold, greatly enhancing boiling for the base fluid and slightly decreasing performance for the nanofluid.

  7. Explosive particle soil surface dispersion model for detonated military munitions.

    PubMed

    Hathaway, John E; Rishel, Jeremy P; Walsh, Marianne E; Walsh, Michael R; Taylor, Susan

    2015-07-01

    The accumulation of high explosive mass residue from the detonation of military munitions on training ranges is of environmental concern because of its potential to contaminate the soil, surface water, and groundwater. The US Department of Defense wants to quantify, understand, and remediate high explosive mass residue loadings that might be observed on active firing ranges. Previously, efforts using various sampling methods and techniques have resulted in limited success, due in part to the complicated dispersion pattern of the explosive particle residues upon detonation. In our efforts to simulate particle dispersal for high- and low-order explosions on hypothetical firing ranges, we use experimental particle data from detonations of munitions from a 155-mm howitzer, which are common military munitions. The mass loadings resulting from these simulations provide a previously unattained level of detail to quantify the explosive residue source-term for use in soil and water transport models. In addition, the resulting particle placements can be used to test, validate, and optimize particle sampling methods and statistical models as applied to firing ranges. Although the presented results are for a hypothetical 155-mm howitzer firing range, the method can be used for other munition types once the explosive particle characteristics are known.

  8. Erosive particle kinematics in the turbulent combustion boundary layer contacting a solid wall

    SciTech Connect

    Buckingham, A.C.; Siekhaus, W.J.

    1983-04-15

    Measurements and numerical modeling are applied to observe and predict the interactive influence of sub-micron gas borne particles in an erosive turbulent combustion wall boundary layer. Some of the experiments and computations discussed are directed to study of turbulent free shear layers. Others ephasize wall boundary layers. The common purpose of all of these studies is to generate information on the particle interaction mechanisms active in alteration and reduction of the turbulent transport and the consequent reduction of the erosive heat and mass transfer. Primary emphasis here is given to analysis of erosive two phase wall boundary layers encountered in solid propellant combustion situations. Examples are gun barrel, rocket nozzle, and coal-fired gas turbine combustion flow fields.

  9. NMR Spectroscopy of the Hydrated Layer of Composite Particles Based on Nanosized Al2O3 and Vitreous Humor

    NASA Astrophysics Data System (ADS)

    Turov, V. V.; Gerashchenko, I. I.; Markina, A. I.

    2013-11-01

    The hydrated layer of composite particles prepared using Al2O3 and cattle vitreous humor was investigated using NMR spectroscopy. It was found that water bound to Al2O3 nanoparticles was present in the form of clusters with different degrees of association and energies of interaction with the surface. Water bound to the surface of the Al2O3/vitreous humor composite became more uniform upon immobilization of vitreous humor components on the surface of the Al2O3. With this, the clusters of adsorbed water had characteristics that were close to those found in air and weakly polar CHCl3 media. Addition of polar CH3CN led to the formation of very small water clusters. PMR spectra of the surface of the Al2O3/vitreous humor composite in the presence of trifluoroacetic acid differentiated four types of hydrated structures that differed in the degree of water association.

  10. Functionalization of Ag nanoparticles using local hydrophilic pool segment designed on their particle surface

    NASA Astrophysics Data System (ADS)

    Iijima, Motoyuki; Kurumiya, Aki; Esashi, Junki; Miyazaki, Hayato; Kamiya, Hidehiro

    2014-10-01

    The preparation of SiO2-coated Ag nanoparticles dispersible in various organic solvents has been achieved using a solgel reaction of tetraethylorthosilicate (TEOS), in the localized hydrophilic pool segments designed on Ag nanoparticle surfaces. First, oleylamine-capped core Ag nanoparticles were synthesized, followed by ligand exchange with polyethyleneimine (PEI) and further adsorption of an anionic surfactant comprising hydrophilic polyethylene glycol (PEG) chains and hydrophobic alkyl chains, which has previously been reported to improve the stability of nanoparticles in various solvents. Then, a reaction of TEOS with the localized hydrophilic PEI layer on the Ag nanoparticles' surface was conducted by stirring a toluene/TEOS solution of surface-modified Ag nanoparticles at various temperatures. It was found that a SiO2 layer was successfully formed on Ag nanoparticles when the reaction temperature was increased to 60 °C. It was also found, however, that at this elevated temperature, the primary particle size of Ag nanoparticles increased to several tens of nm, attributable to the dissolution and re-reduction of Ag+. Because the surface modifier, PEI and anionic surfactant all remained on the nanoparticle surface during the SiO2 coating process, the prepared SiO2-coated Ag nanoparticles were found to be dispersible in various organic solvents near to their primary particle size.

  11. Layered reactive particles with controlled geometries, energies, and reactivities, and methods for making the same

    DOEpatents

    Fritz, Gregory M; Knepper, Robert Allen; Weihs, Timothy P; Gash, Alexander E; Sze, John S

    2013-04-30

    An energetic composite having a plurality of reactive particles each having a reactive multilayer construction formed by successively depositing reactive layers on a rod-shaped substrate having a longitudinal axis, dividing the reactive-layer-deposited rod-shaped substrate into a plurality of substantially uniform longitudinal segments, and removing the rod-shaped substrate from the longitudinal segments, so that the reactive particles have a controlled, substantially uniform, cylindrically curved or otherwise rod-contoured geometry which facilitates handling and improves its packing fraction, while the reactant multilayer construction controls the stability, reactivity and energy density of the energetic composite.

  12. Layered reactive particles with controlled geometries, energies, and reactivities, and methods for making the same

    DOEpatents

    Fritz, Gregory M.; Weihs, Timothy P.; Grzyb, Justin A.

    2016-07-05

    An energetic composite having a plurality of reactive particles each having a reactive multilayer construction formed by successively depositing reactive layers on a rod-shaped substrate having a longitudinal axis, dividing the reactive-layer-deposited rod-shaped substrate into a plurality of substantially uniform longitudinal segments, and removing the rod-shaped substrate from the longitudinal segments, so that the reactive particles have a controlled, substantially uniform, cylindrically curved or otherwise rod-contoured geometry which facilitates handling and improves its packing fraction, while the reactant multilayer construction controls the stability, reactivity and energy density of the energetic composite.

  13. Layer-by-layer assembled antisense DNA microsponge particles for efficient delivery of cancer therapeutics.

    PubMed

    Roh, Young Hoon; Lee, Jong Bum; Shopsowitz, Kevin E; Dreaden, Erik C; Morton, Stephen W; Poon, Zhiyong; Hong, Jinkee; Yamin, Inbar; Bonner, Daniel K; Hammond, Paula T

    2014-10-28

    Antisense oligonucleotides can be employed as a potential approach to effectively treat cancer. However, the inherent instability and inefficient systemic delivery methods for antisense therapeutics remain major challenges to their clinical application. Here, we present a polymerized oligonucleotides (ODNs) that self-assemble during their formation through an enzymatic elongation method (rolling circle replication) to generate a composite nucleic acid/magnesium pyrophosphate sponge-like microstructure, or DNA microsponge, yielding high molecular weight nucleic acid product. In addition, this densely packed ODN microsponge structure can be further condensed to generate polyelectrolyte complexes with a favorable size for cellular uptake by displacing magnesium pyrophosphate crystals from the microsponge structure. Additional layers are applied to generate a blood-stable and multifunctional nanoparticle via the layer-by-layer (LbL) assembly technique. By taking advantage of DNA nanotechnology and LbL assembly, functionalized DNA nanostructures were utilized to provide extremely high numbers of repeated ODN copies for efficient antisense therapy. Moreover, we show that this formulation significantly improves nucleic acid drug/carrier stability during in vivo biodistribution. These polymeric ODN systems can be designed to serve as a potent means of delivering stable and large quantities of ODN therapeutics systemically for cancer treatment to tumor cells at significantly lower toxicity than traditional synthetic vectors, thus enabling a therapeutic window suitable for clinical translation.

  14. Surface ozone-aerosol behaviour and atmospheric boundary layer structure in Saharan dusty scenario

    NASA Astrophysics Data System (ADS)

    Adame, Jose; Córdoba-Jabonero, Carmen; Sorrribas, Mar; Gil-Ojeda, Manuel; Toledo, Daniel; Yela, Margarita

    2016-04-01

    A research campaign was performed for the AMISOC (Atmospheric Minor Species relevant to the Ozone Chemistry) project at El Arenosillo observatory (southwest Spain) in May-June 2012. The campaign focused on the impact of Saharan dust intrusions at the Atmospheric Boundary Layer (ABL) and ozone-aerosol interactions. In-situ and remote-sensing techniques for gases and aerosols were used moreover to modelling analyses. Meteorology features, ABL structures and evolution, aerosol profiling distributions and aerosol-ozone interactions on the surface were analysed. Two four-day periods were selected according to non-dusty (clean conditions) and dusty (Saharan dust) situations. In both scenarios, sea-land breezes developed in the lower atmosphere, but differences were found in the upper levels. Results show that surface temperatures were greater than 3°C and humidity values were lower during dusty conditions than non-dusty conditions. Thermal structures on the surface layer (estimated using an instrument on a 100 m tower) show differences, mainly during nocturnal periods with less intense inversions under dusty conditions. The mixing layer during dusty days was 400-800 m thick, less than observed on non-dusty days. Dust also disturbed the typical daily ABL evolution. Stable conditions were observed during the early evening during intrusions. Aerosol extinction on dusty days was 2-3 times higher, and the dust was confined between 1500 and 5500 m. Back trajectory analyses confirmed that the dust had an African origin. On the surface, the particle concentration was approximately 3.5 times higher during dusty events, but the local ozone did not exhibit any change. The arrival of Saharan dust in the upper levels impacted the meteorological surface, inhibited the daily evolution of the ABL and caused an increase in aerosol loading on the surface and at higher altitudes; however, no dust influence was observed on surface ozone.

  15. Possible Albedo Proton Signature of Hydrated Lunar Surface Layer

    NASA Astrophysics Data System (ADS)

    Schwadron, N.; Wilson, J. K.; Looper, M. D.; Jordan, A.; Spence, H. E.; Blake, J. B.; Case, A. W.; Iwata, Y.; Kasper, J. C.; Farrell, W. M.; Lawrence, D. J.; Livadiotis, G.; Mazur, J. E.; Petro, N. E.; Pieters, C. M.; Robinson, M. S.; Smith, S. S.; Townsend, L. W.; Zeitlin, C. J.

    2015-12-01

    We find evidence for a surface layer of hydrated material in the lunar regolith using "albedo protons" measured by the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) on the Lunar Reconnaissance Orbiter (LRO). Fluxes of these albedo protons, which are emitted from the regolith due to steady bombardment by high-energy radiation (Galactic Cosmic Rays), are observed to peak near the poles, and cannot be accounted for by either heavy element enrichment (e.g., enhanced Fe abundance), or by deeply buried (> 50 cm) hydrogenous material. The latitudinal distribution of albedo protons does not correlate with that of epithermal or high-energy neutrons. The high latitude enhancement may be due to the conversion of upward directed secondary neutrons from the lunar regolith into tertiary protons due to neutron-proton collisions in a thin (~ 1-10 cm) layer of hydrated regolith near the surface that is more prevalent near the poles. The CRaTER instrument thus provides critical measurements of volatile distributions within lunar regolith and potentially, with similar sensors and observations, at other bodies within the Solar System.

  16. Plasma-enhanced deposition of antifouling layers on silicone rubber surfaces

    NASA Astrophysics Data System (ADS)

    Jiang, Hongquan

    In food processing and medical environments, biofilms serve as potential sources of contamination, and lead to food spoilage, transmission of diseases or infections. Because of its ubiquitous and recalcitrant nature, Listeria monocytogenes biofilm is especially hard to control. Generating antimicrobial surfaces provide a method to control the bacterial attachment. The difficulty of silver deposition on polymeric surfaces has been overcome by using a unique two-step plasma-mediated method. First silicone rubber surfaces were plasma-functionalized to generate aldehyde groups. Then thin silver layers were deposited onto the functionalized surfaces according to Tollen's reaction. X-ray photoelectron spectroscopy (XPS), atomic force spectroscopy (AFM) and scanning electron microscopy (SEM) showed that silver particles were deposited. By exposing the silver coated surfaces to L. monocytogenes, it was demonstrated that they were bactericidal to L. monocytogenes. No viable bacteria were detected after 12 to 18 h on silver-coated silicone rubber surfaces. Another antifouling approach is to generate polyethylene glycol (PEG) thin layer instead of silver on polymer surfaces. Covalent bond of PEG structures of various molecular weights to cold-plasma-functionalized polymer surfaces, such as silicone rubber, opens up a novel way for the generation of PEG brush-like or PEG branch-like anti-fouling layers. In this study, plasma-generated surface free radicals can react efficiently with dichlorosilane right after plasma treatment. With the generation of halo-silane groups, this enables PEG molecules to be grafted onto the modified surfaces. XPS data clearly demonstrated the presence of PEG molecules on plasma-functionalized silicone rubber surfaces. AFM images showed the changed surface morphologies as a result of covalent attachment to the surface of PEG molecules. Biofilm experiment results suggest that the PEG brush-like films have the potential ability to be the next

  17. Erosion processes due to energetic particle-surface interaction

    SciTech Connect

    Schmid, K.; Roth, J.

    2010-05-20

    The interaction of the fast particles from the hot plasma of a magnetic confinement fusion experiment with the first wall is one of the most challenging problems toward the realization of a fusion power plant. The erosion of the first wall by the fast particles leads to life time limitations and the radiative cooling of the plasma by the eroded impurity species lowers the energy confinement. Apart from these obvious consequences also the trapping of large quantities of the fuelling species (deuterium and tritium) in re-deposited layers of the eroded species poses a problem due to accumulation of large radiative inventories and plasma fuelling inefficiency. The source of all these challenges is the erosion of first wall components due to physical sputtering, chemical erosion and radiation enhanced sublimation. This paper will give an overview about the physical principles behind these erosion channels.

  18. Surface layer composition of titania produced by various methods. The change of layer state under illumination

    NASA Astrophysics Data System (ADS)

    Zakharenko, V.; Daibova, E.; Kosova, N.; Zmeeva, O.

    2016-01-01

    The comparative analysis of experimental data over titanium dioxide powders prepared by various ways under ambient air is carried out. The results over TiO2 prepared by high-temperature heating of anatase, produced by burning of titanium micro particles and grinding of rutile crystal are used for that comparison. Water and carbon dioxide were the main products released from the surface of the titania powders. It was found that under UV irradiation absorbed by titania, in absent oxygen, water effectively reacts with lattice oxygen of titanium dioxide.

  19. Atomic layer deposition of ultrathin platinum films on tungsten atomic layer deposition adhesion layers: Application to high surface area substrates

    SciTech Connect

    Clancey, Joel W.; Cavanagh, Andrew S.; Kukreja, Ratandeep S.; Kongkanand, Anusorn; George, Steven M.

    2015-01-15

    Platinum (Pt) atomic layer deposition (ALD) usually yields Pt nanoparticles during initial film growth. In contrast, deposition of continuous and ultrathin Pt films is needed for many important applications, such as the oxygen reduction reaction in polymer electrolyte membrane (PEM) fuel cells. A continuous and high radius of curvature Pt film is more stable and has a higher area-specific activity than the Pt nanoparticles commonly used in PEM fuel cells. However, the Pt film must be ultrathin and have a large surface area to be cost effective. In this paper, a review of earlier Pt ALD studies on flat substrates is presented that demonstrates that tungsten, with a higher surface energy than platinum, can serve as an adhesion layer to achieve Pt ALD films that are continuous at ultrathin thicknesses of ∼1.5 nm. This work utilized MeCpPtMe{sub 3} and H{sub 2} plasma as the Pt ALD reactants. The deposition of continuous and ultrathin Pt ALD films using MeCpPtMe{sub 3} and H{sub 2} plasma as the reactants is then studied on two high surface area substrate materials: TiO{sub 2} nanoparticles and 3M nanostructured thin film (NSTF). Transmission electron microscopy (TEM) showed uniform and continuous Pt films with thicknesses of ∼4 nm on the TiO{sub 2} nanoparticles. TEM with electron energy loss spectroscopy analysis revealed W ALD and Pt ALD films with thicknesses of ∼3 nm that were continuous and conformal on the high aspect ratio NSTF substrates. These results demonstrate that cost effective use of Pt ALD on high surface area substrates is possible for PEM fuel cells.

  20. Computational and experimental analysis of particle clustering in a shearless turbulent mixing layer

    NASA Astrophysics Data System (ADS)

    Ireland, Peter; Good, Garrett; Warhaft, Zellman; Collins, Lance

    2011-11-01

    Entrainment, the drawing in of external fluid by a turbulent flow, is ubiquitous to both industrial and natural turbulent processes. This mechanism is particularly important in atmospheric clouds, where the entrainment of dry air by turbulence can affect precipitation mechanisms. We use parametrically matched wind-tunnel experiments and direct numerical simulations with inhomogeneous particle seeding to explore particle clustering in a shearless turbulent mixing layer. We find high degrees of clustering, both visually and statistically, even for particles with negligible inertia. These particle clusters have characteristic sizes on the order of the integral lengthscale of the turbulence and are thus much larger than those resulting from particle inertia. The degree of clustering at a particular location generally decreases as the mixing layer evolves and depends on both the turbulent kinetic energy ratio in the mixing layer and the magnitude and orientation of gravity. We observe the same qualitative trends in both the experiments and the simulations. We anticipate that a better understanding of particle clustering in entraining flows will lead to, among other things, improved cloud evolution predictions and more accurate climate models.

  1. Controllable surface-plasmon resonance in engineered nanometer epitaxial silicide particles embedded in silicon

    NASA Technical Reports Server (NTRS)

    Fathauer, R. W.; Ksendzov, A.; Iannelli, J. M.; George, T.

    1991-01-01

    Epitaxial CoSi2 particles in a single-crystal silicon matrix are grown by molecular-beam epitaxy using a technique that allows nanometer control over particle size in three dimensions. These composite layers exhibit resonant absorption predicted by effective-medium theory. Selection of the height and diameter of disklike particles through a choice of growth conditions allows tailoring of the depolarization factor and hence of the surface-plasmon resonance energy. Resonant absorption from 0.49 to 1.04 eV (2.5 to 1.2 micron) is demonstrated and shown to agree well with values predicted by the Garnett (1904, 1906) theory using the bulk dielectric constants for CoSi2 and Si.

  2. Atmospheric new particle formation as source of CCN in the Eastern Mediterranean marine boundary layer

    NASA Astrophysics Data System (ADS)

    Kalivitis, N.; Kerminen, V.-M.; Kouvarakis, G.; Stavroulas, I.; Bougiatioti, A.; Nenes, A.; Manninen, H. E.; Petäjä, T.; Kulmala, M.; Mihalopoulos, N.

    2015-04-01

    While Cloud Condensation Nuclei (CCN) production associated with atmospheric new particle formation (NPF) is thought to be frequent throughout the continental boundary layers, few studies on this phenomenon in marine air exist. Here, based on simultaneous measurement of particle number size distributions, CCN properties and aerosol chemical composition, we present the first direct evidence on CCN production resulting from NPF in the Eastern Mediterranean atmosphere. We show that condensation of both gaseous sulfuric acid and organic compounds from multiple sources leads to the rapid growth of nucleated particles to CCN sizes in this environment during the summertime. Sub-100 nm particles were found to be substantially less hygroscopic than larger particles during the period with active NPF and growth (0.2-0.4 lower κ between the 60 and 120 nm particles), probably due to enrichment of organic material in the sub-100 nm size range. The aerosol hygroscopicity tended to be at minimum just before the noon and at maximum in afternoon, which was very likely due to the higher sulfate to organic ratios and higher degree of oxidation of the organic material during the afternoon. Simultaneously to the formation of new particles during daytime, particles formed in the previous day or even earlier were growing into the size range relevant to cloud droplet activation, and the particles formed in the atmosphere were possibly mixed with long-range transported particles.

  3. Discovering sub-micron ice particles across Dione' surface

    NASA Astrophysics Data System (ADS)

    Scipioni, Francesca; Schenk, Pual; Tosi, Federico; Clark, Roger; Dalle Ore, Cristina; Combe, Jean-Philippe

    2015-11-01

    Water ice is the most abundant component of Saturn’s mid-sized moons. However, these moons show an albedo asymmetry - their leading sides are bright while their trailing side exhibits dark terrains. Such differences arise from two surface alteration processes: (i) the bombardment of charged particles from the interplanetary medium and driven by Saturn’s magnetosphere on the trailing side, and (ii) the impact of E-ring water ice particles on the satellites’ leading side. As a result, the trailing hemisphere appears to be darker than the leading side. This effect is particularly evident on Dione's surface. A consequence of these surface alteration processes is the formation or the implantation of sub-micron sized ice particles.The presence of such particles influences and modifies the surfaces' spectrum because of Rayleigh scattering by the particles. In the near infrared range of the spectrum, the main sub-micron ice grains spectral indicators are: (i) asymmetry and (ii) long ward minimum shift of the absorption band at 2.02 μm (iii) a decrease in the ratio between the band depths at 1.50 and 2.02 μm (iv) a decrease in the height of the spectral peak at 2.6 μm (v) the suppression of the Fresnel reflection peak at 3.1 μm and (vi) the decrease of the reflection peak at 5 μm relative to those at 3.6 μm.We present results from our ongoing work mapping the variation of sub-micron ice grains spectral indicators across Dione' surface using Cassini-VIMS cubes acquired in the IR range (0.8-5.1 μm). To characterize the global variations of spectral indicators across Dione' surface, we divided it into a 1°x1° grid and then averaged the band depths and peak values inside each square cell.We will investigate if there exist a correspondence with water ice abundance variations by producing water ice' absorption band depths at 1.25, 1.52 and 2.02 μm, and with surface morphology by comparing the results with ISS color maps in the ultraviolet, visible and infrared

  4. ELECTROSTATIC SURFACE STRUCTURES OF COAL AND MINERAL PARTICLES

    SciTech Connect

    1998-12-01

    It is the purpose of this research to study electrostatic charging mechanisms related to electrostatic beneficiation of coal with the goal of improving models of separation and the design of electrostatic separators. Areas addressed in this technical progress report are (a) electrostatic beneficiation of Pittsburgh #8 coal powders as a function of grind size and processing atmosphere; (b) the use of fluorescent micro-spheres to probe the charge distribution on the surfaces of coal particles; (c) the use of electrostatic beneficiation to recover unburned carbon from flyash; (d) the development of research instruments for investigation of charging properties of coal. Pittsburgh #8 powders were beneficiated as a function of grind size and under three atmosphere conditions: fresh ground in air , after 24 hours of air exposure, or under N2 atmosphere. The feed and processed powders were analyzed by a variety of methods including moisture, ash, total sulfur, and pyritic sulfur content. Mass distribution and cumulative charge of the processed powders were also measured. Fresh ground coal performed the best in electrostatic beneficiation. Results are compared with those of similar studies conducted on Pittsburgh #8 powders last year (April 1, 1997 to September 30, 1997). Polystyrene latex spheres were charged and deposited onto coal particles that had been passed through the electrostatic separator and collected onto insulating filters. The observations suggest bipolar charging of individual particles and patches of charge on the particles which may be associated with particular maceral types or with mineral inclusions. A preliminary investigation was performed on eletrostatic separation of unburned carbon particles from flyash. Approximately 25% of the flyash acquired positive charge in the copper tribocharger. This compares with 75% of fresh ground coal. The negatively charged material had a slightly reduced ash content suggesting some enrichment of carbonaceous material

  5. Crystalline Bacterial Surface Layer (S-Layer) Opens Golden Opportunities for Nanobiotechnology in Textiles.

    PubMed

    Asadi, Narges; Chand, Nima; Rassa, Mehdi

    2015-12-01

    This study focuses on the successful recrystallization of bacterial S-layer arrays of the Lactobacillus acidophilus ATCC 4356 at textile surfaces to create a novel method and material. Optimum bacterial growth was obtained at approximately 45 °C, pH 5.0, and 14 h pi. The cells were resuspended in guanidine hydrochloride and the 43 kDa S-protein was dialyzed and purified. The optimum reassembly on the polypropylene fabric surface in terms of scanning electron microscopy (SEM), reflectance, and uniformity (spectrophotometry) was obtained at 30 °C, pH 5.0 for 30 minutes in the presence of 2 gr/l (liquor ratio; 1:40) of the S-protein. Overall, our data showed that the functional aspects and specialty applications of the fabric would be very attractive for the textile and related sciences, and result in advanced technical textiles. PMID:26552090

  6. Surface-imprinted nanostructured layer-by-layer film for molecular recognition of theophylline derivatives.

    PubMed

    Niu, Jia; Liu, Zhihua; Fu, Long; Shi, Feng; Ma, Hongwei; Ozaki, Yukihiro; Zhang, Xi

    2008-10-21

    In this article we report the introduction of the cooperativity of various specific interactions combined with photo-cross-linking of the interlayers to yield binding sites that can realize better selectivity and imprinting efficiency of a surface molecularly imprinted LbL film (SMILbL), thus providing a new approach toward fabrication of nanostructured molecularly imprinted thin films. It involves preassembly of poly(acrylic acid) (PAA) conjugated of the theophylline residue template via a disulfide bridge, denoted as PAAtheo 15, in solution, and layer-by-layer (LbL) assembly of PAAtheo 15 and a positively charged photoreactive diazo resin (DAR) to form multilayer thin film with designed architecture. After photo-cross-linking of the film and template removal, binding sites specific to 7-(beta-hydroxyethyl)theophylline (Theo-ol) molecules are introduced within the film. Binding assay demonstrates that the SMILbL has a high selectivity of SMILbL to Theo-ol over caffeine. A control experiment demonstrates that the selectivity of SMILbL derives from nanostructured recognition sites among the layers. The imprinting amount per unit mass of the film can be 1 order of magnitude larger than that of the conventional bulk molecular imprinting systems. As this concept of construction SMILbL can be easily extended to the other molecules by the following similar protocol: its applications in building many other different molecular recognition systems are greatly anticipated. PMID:18788771

  7. Numerical Computations of Hypersonic Boundary-Layer over Surface Irregularities

    NASA Technical Reports Server (NTRS)

    Chang, Chau-Lyan; Choudhari, Meelan M.; Li, Fei

    2010-01-01

    Surface irregularities such as protuberances inside a hypersonic boundary layer may lead to premature transition on the vehicle surface. Early transition in turn causes large localized surface heating that could damage the thermal protection system. Experimental measurements as well as numerical computations aimed at building a knowledge base for transition Reynolds numbers with respect to different protuberance sizes and locations have been actively pursued in recent years. This paper computationally investigates the unsteady wake development behind large isolated cylindrical roughness elements and the scaled wind-tunnel model of the trip used in a recent flight measurement during the reentry of space shuttle Discovery. An unstructured mesh, compressible flow solver based on the space-time conservation element, solution element (CESE) method is used to perform time-accurate Navier-Stokes calculations for the flow past a roughness element under several wind-tunnel conditions. For a cylindrical roughness element with a height to the boundary-layer thickness ratio from 0.8 to 2.5, the wake flow is characterized by a mushroom-shaped centerline streak and horse-shoe vortices. While time-accurate solutions converged to a steady-state for a ratio of 0.8, strong flow unsteadiness is present for a ratio of 1.3 and 2.5. Instability waves marked by distinct disturbance frequencies were found in the latter two cases. Both the centerline streak and the horse-shoe vortices become unstable downstream. The oscillatory vortices eventually reach an early breakdown stage for the largest roughness element. Spectral analyses in conjunction with the computed root mean square variations suggest that the source of the unsteadiness and instability waves in the wake region may be traced back to possible absolute instability in the front-side separation region.

  8. Microstructures and properties of ceramic particle-reinforced metal matrix composite layers produced by laser cladding

    NASA Astrophysics Data System (ADS)

    Zhang, Qingmao; He, Jingjiang; Liu, Wenjin; Zhong, Minlin

    2005-01-01

    Different weight ratio of titanium, zirconium, WC and Fe-based alloy powders were mixed, and cladded onto a medium carbon steel substrate using a 3kW continuous wave CO2 laser, aiming at producing Ceramic particles- reinforced metal matrix composites (MMCs) layers. The microstructures of the layers are typical hypoeutectic, and the major phases are Ni3Si2, TiSi2, Fe3C, FeNi, MC, Fe7Mo3, Fe3B, γ(residual austenite) and M(martensite). The microstructure morphologies of MMCs layers are dendrites/cells. The MC-type reinforcements are in situ synthesis Carbides which main compositions consist of transition elements Zr, Ti, W. The MC-type particles distributed within dendrite and interdendritic regions with different volume fractions for single and overlapping clad layers. The MMCs layers are dense and free of cracks with a good metallurgical bonding between the layer and substrate. The addition ratio of WC in the mixtures has the remarkable effect on the microhardness of clad layers.

  9. Laser modification of ceramic surfaces with micro- and nano- particles

    NASA Astrophysics Data System (ADS)

    Rohde, Magnus

    2007-02-01

    Laser supported processes can be used to modify the electrical and thermal properties of ceramic substrates locally. These processes are characterised by a strong thermal interaction between the laser beam and the ceramic surface which leads to localised melting. During the dynamic melting process metal particles are introduced into the melt pool in order to modify the physical properties. Different alumina samples were treated with metal powders of tungsten, copper, and oxides of these metals. The interface between the metal and the ceramic can be designed by using selected combinations of metal- and metal-oxide-powders and also by a thermal post-processing. The application of nano-particles during the laser-dispersing process resulted in completely different characteristics of the micro-structure and the electrical properties compared to the conventional metal powders with an average grain size of 5 - 15 microns. The micron sized metal particles are embedded within the ceramic matrix as particle agglomerates or as distinct metal phase the nano-particle phase covers the grain boundaries of the ceramics leading to network of nano-scaled electrically conducting "wires". The resulting resistance of the laser tracks can be adjusted from semi-conducting to metallic behavior with a resistivity down to 2x10 -6W/m. The modified ceramic can be used for heating elements working at operation temperatures of up to 1000 °C, high current resistances which can be loaded with currents of up to 100 A.

  10. Guiding catalytically active particles with chemically patterned surfaces

    NASA Astrophysics Data System (ADS)

    Uspal, William; Popescu, Mihail; Dietrich, Siegfried; Tasinkevych, Mykola

    Catalytically active Janus particles in solution create gradients in the chemical composition of the solution along their surfaces, as well as along any nearby container walls. The former leads to self-phoresis, while the latter gives rise to chemi-osmosis, providing an additional contribution to self-motility. Chemi-osmosis strongly depends on the molecular interactions between the diffusing chemical species and the wall. We show analytically, using an approximate ``point-particle'' approach, that by chemically patterning a planar substrate (e.g., by adsorbing two different materials) one can direct the motion of Janus particles: the induced chemi-osmotic flows can cause particles to either ``dock'' at a chemical step between the two materials, or to follow a chemical stripe. These theoretical predictions are confirmed by full numerical calculations. Generically, docking occurs for particles which tend to move away from their catalytic caps, while stripe-following occurs in the opposite case. Our analysis reveals the physical mechanisms governing this behavior.

  11. Synthesis, characterization, and evaluation of a superficially porous particle with unique, elongated pore channels normal to the surface.

    PubMed

    Wei, Ta-Chen; Mack, Anne; Chen, Wu; Liu, Jia; Dittmann, Monika; Wang, Xiaoli; Barber, William E

    2016-04-01

    In recent years, superficially porous particles (SPPs) have drawn great interest because of their special particle characteristics and improvement in separation efficiency. Superficially porous particles are currently manufactured by adding silica nanoparticles onto solid cores using either a multistep multilayer process or one-step coacervation process. The pore size is mainly controlled by the size of the silica nanoparticles and the tortuous pore channel geometry is determined by how those nanoparticles randomly aggregate. Such tortuous pore structure is also similar to that of all totally porous particles used in HPLC today. In this article, we report on the development of a next generation superficially porous particle with a unique pore structure that includes a thinner shell thickness and ordered pore channels oriented normal to the particle surface. The method of making the new superficially porous particles is a process called pseudomorphic transformation (PMT), which is a form of micelle templating. Porosity is no longer controlled by randomly aggregated nanoparticles but rather by micelles that have an ordered liquid crystal structure. The new particle possesses many advantages such as a narrower particle size distribution, thinner porous layer with high surface area and, most importantly, highly ordered, non-tortuous pore channels oriented normal to the particle surface. This PMT process has been applied to make 1.8-5.1μm SPPs with pore size controlled around 75Å and surface area around 100m(2)/g. All particles with different sizes show the same unique pore structure with tunable pore size and shell thickness. The impact of the novel pore structure on the performance of these particles is characterized by measuring van Deemter curves and constructing kinetic plots. Reduced plate heights as low as 1.0 have been achieved on conventional LC instruments. This indicates higher efficiency of such particles compared to conventional totally porous and

  12. Layer-by-Layer Surface Molecular Imprinting on Polyacrylonitrile Nanofiber Mats.

    PubMed

    Liu, Yuxuan; Cao, Bing; Jia, Peng; An, Junhu; Luo, Chao; Ma, Lijing; Chang, Jiao; Pan, Kai

    2015-06-25

    Surface molecular imprinting in layer-by-layer (SMI-LbL) film is known as a facile and effective strategy to build imprinting sites that are more accessible to template molecules compared with molecular imprinting in polymers. Herein, we accomplished the formation of SMI-LbL film on electrospun nanofibers for the first time. The SMI-LbL nanofibers were prepared by a template-induced LbL process on the polyacrylonitrile (PAN) nanofiber substrates, followed by postinfiltrating and photo-cross-linking of photosensitive agent 4,4'-diazostilbene-2,2'-disulfonic acid disodium salt (DAS). The obtained nanofiber mat maintained the nanofibrous structure and showed rapid absorption and extraction of template molecules of meso-tetra(4-carboxyphenyl)-porphine (Por). The binding capacity of Por reached 2.1 mg/g when 3.5 bilayers were deposited on the nanofibers. After six cycles of extraction and reabsorption, the binding capacity of Por remained at 83%. Moreover, the absorption results of the targeted templated molecule of Por and the control molecule of Fast Green, which had a very similar chemical structure and charge status to Por, indicated the specific absorption for template molecule of Por. Thus, a surface molecular imprinted nanofiber mat with high selectivity of the templated molecule has been demonstrated. PMID:26038802

  13. Generic Nitric Oxide (NO) Generating Surface by Immobilizing Organoselenium Species via Layer-by-Layer Assembly

    PubMed Central

    Yang, Jun; Welby, Jenna L.; Meyerhoff, Mark E.

    2010-01-01

    A universal nitric oxide (NO) generating surface is assembled via Layer-by-Layer (LbL) deposition of sodium alginate (Alg) and organoselenium modified polyethyleneimine (SePEI) on quartz and polymeric substrates. The immobilized SePEI species is capable of catalytically decomposing S-nitrosothiol species (RSNO) to NO in the presence of thiol reducing agents (e.g., glutathione, cysteine, etc.). The stepwise buildup of the multilayer films is monitored by UV-Vis spectroscopy, SEM and surface contact angle measurements. X-ray photoelectron spectroscopy is used to study the stoichiometry between the polyanion and polycation, and also the presence of Se in the catalytic LbL film. A reductive annealing process is necessary to improve the stability of freshly coated multilayer films via chain rearrangement. Chemiluminescence measurements illustrate the ability of the LbL films to generate NO from S-nitrosoglutathione (GSNO) in the presence of S-glutathione (GSH). Enhanced NO fluxes can be achieved by increasing the number of catalytic (SePEI/Alg) bilayers coated on the substrates. Nitric oxide generation is observed even after prolonged contact with sheep whole blood. Preliminary applications of this LbL on silicone rubber tubings and polyurethane catheters reveal similar NO generation behavior from these biomedical grade polymeric substrates. PMID:18710268

  14. Impact of particle shape on the laser-contaminant interaction induced damage on the protective capping layer of 1ω high reflector mirror coatings

    NASA Astrophysics Data System (ADS)

    Qiu, S. R.; Norton, M. A.; Honig, J.; Rubenchik, A. M.; Boley, C. D.; Rigatti, A.; Stolz, C. J.; Matthews, M. J.

    2015-12-01

    We report an investigation on the response to laser exposure of a protective capping layer of 1ω (1053 nm) high-reflector mirror coatings, in the presence of differently shaped Ti particles. We consider two candidate capping layer materials, namely SiO2 and Al2O3. They are coated over multiple silica-hafnia multilayer coatings. Each sample is exposed to a single oblique (45°) shot of a 1053 nm laser beam (p polarization, fluence ~ 10 J/cm2, pulse length 14 ns), in the presence of spherically or irregularly shaped Ti particles on the surface. We observe that the two capping layers show markedly different responses. For spherically shaped particles, the Al2O3 cap layer exhibits severe damage, with the capping layer becoming completely delaminated at the particle locations. In contrast, the SiO2 capping layer is only mildly modified by a shallow depression, likely due to plasma erosion. For irregularly shaped Ti filings, the Al2O3 capping layer displays minimal to no damage while the SiO2 capping layer is significantly damaged. In the case of the spherical particles, we attribute the different response of the capping layer to the large difference in thermal expansion coefficient of the materials, with that of the Al2O3 about 15 times greater than that of the SiO2 layer. For the irregularly shaped filings, we attribute the difference in damage response to the large difference in mechanical toughness between the two materials, with that of the Al2O3 being about 10 times stronger than that of the SiO2.

  15. Method of evaluating the integrity of the outer carbon layer of triso-coated reactor fuel particles

    DOEpatents

    Caputo, Anthony J.; Costanzo, Dante A.; Lackey, Jr., Walter J.; Layton, Frank L.; Stinton, David P.

    1980-01-01

    This invention relates to a method for determining defective final layers of carbon on triso-coated fuel particles and the like. Samples of the particles are subjected to a high temperature treatment with gaseous chlorine and thereafter radiographed. The chlorine penetrates through any defective carbon layer and reacts with the underlying silicon carbide resulting in the volatilization of the silicon as SiCl.sub.4 leaving carbon as a porous layer. This porous carbon layer is easily detected by the radiography.

  16. Modulation on coherent vortex structures by dispersed solid particles in a three-dimensional mixing layer.

    PubMed

    Fan, Jianren; Luo, Kun; Zheng, Youqu; Jin, Hanhui; Cen, Kefa

    2003-09-01

    Large-scale vortex structures and their effects on the dispersion of particles in turbulent free shear flows are very important in many industrial applications, such as combustion, pollution control, and materials processing. In order to understand large-scale vortex structures and particle dispersion in depth, as well as their interaction effects, a two-way-coupled three-dimensional mixing layer laden with particles at a Stokes number of 5 initially located in the upper half region is studied numerically. A pseudospectral method was used to directly simulate the flow fluid, and the Lagrangian approach was used to trace particles. The concept of computational particles is introduced to vary the mass loading of particles. The momentum coupling effect introduced by a particle approximates to a point force. The simulation results show that coherent structures are still dominant in the mixing layer, but the flow dynamics and particle dispersion are modulated. The length of large-scale vortex structures is shortened and the pairing is delayed. Higher mass loading results in lower energy of the fluid in the phase of Kelvin-Helmholtz rolling up, while in the pairing process of large-scale vortex structures, the energy of the fluid increases as the mass loading increases. Higher mass loading also leads to larger mixed fluid thickness and Reynolds stresses of the flow. In addition, the particle dispersion along the transverse direction differs from that along the spanwise direction, which indicates that the effects of the addition of a particle on the spanwise large-scale vortex structures are different from those on the streamwise large-scale vortex structures.

  17. Characterization of cathode keeper wear by surface layer activation

    NASA Technical Reports Server (NTRS)

    Polk, James E.

    2003-01-01

    In this study, the erosion rates of the discharge cathode keeper in a 30 cm NSTAR configuration ion thruster were measured using a technique known as Surface Layer Activation (SLA). This diagnostic technique involves producing a radioactive tracer in a given surface by bombardment with high energy ions. The decrease in activity of the tracer material may be monitored as the surface is subjected to wear processes and correlated to a depth calibration curve, yielding the eroded depth. Analysis of the activities was achieved through a gamma spectroscopy system. The primary objectives of this investigation were to reproduce erosion data observed in previous wear studies in order to validate the technique, and to determine the effect of different engine operating parameters on erosion rate. The erosion profile at the TH 15 (23 kw) setting observed during the 8200 hour Life Demonstration Test (LDT) was reproduced. The maximum keeper erosion rate at this setting was determined to be 0.085 pm/hr. Testing at the TH 8 (1.4 kw) setting demonstrated lower erosion rates than TH 15, along with a different wear profile. Varying the keeper voltage was shown to have a significant effect on the erosion, with a positive bias with respect to cathode potential decreasing the erosion rate significantly. Accurate measurements were achieved after operating times of only 40 to 70 hours, a significant improvement over other erosion diagnostic methods.

  18. Modelling boundary layer flow over barnacle-fouled surfaces

    NASA Astrophysics Data System (ADS)

    Sadique, Jasim; Yang, Xiang; Meneveau, Charles; Mittal, Rajat

    2014-11-01

    Macro-biofouling is a critical concern for the marine industry. However, there is little data on flow and drag over such surfaces. Accurate modelling of such multi-scale flows remains a big challenge. Such simulations are vital in providing insights into the fundamental flow physics, and they can be used to estimate the timing, need and effectiveness of measures used to counteract bio-fouling. This talk focuses on the use of a sharp-interface immersed boundary method coupled with a wall model and large-eddy simulations to carry out accurate simulations of a turbulent boundary layer flow over macro-fouled surfaces. For the current study, high resolution scans of barnacles were used to create simple geometrical representations. Simulations were then carried out to test how well these simpler geometric models mimic the flow over actual barnacles. Simulations of array of modeled barnacles, with different barnacle densities have also been carried out and we present results on the effect distribution density on the flow physics and drag on the surfaces. This work is funded by ONR Grant N00014-12-1-0582.

  19. Exploring the bronzing effect at the surface of ink layers

    NASA Astrophysics Data System (ADS)

    Hébert, Mathieu; Mallet, Maxime; Deboos, Alexis; Chavel, Pierre; Kuang, Deng-Feng; Hugonin, Jean-Paul; Besbes, Mondher; Cazier, Anthony

    2015-03-01

    We investigate the optical phenomenon responsible for the colored shine that sometimes appears at the surface of ink layers in the specular direction, often called bronzing or gloss differential. It seems to come from the wavelength-dependent refractive index of the ink, which induces a wavelength-dependent reflectance of the ink-air interface. Our experiments on cyan and magenta inkjet inks confirm this theory. Complex refractive indices can be obtained from measurements of the spectral reflectance and transmittance of a transparency film coated with the ink. We propose a correction of the classical Clapper-Yule model in order to include the colored gloss in the prediction of the spectral reflectance of an inked paper. We also explored effects of scattering by the micrometric or nanometric roughness of the ink surface. The micrometric roughness, easy to model with a geometrical optics model, can predict the spreading of the colored gloss over a large cone. Electromagnetic models accounting for the effect of the nanometric roughness of the surface also predict the attenuation of short wavelengths observed under collimated illumination.

  20. Airborne observations of new particle formation events in the boundary layer using a Zeppelin

    NASA Astrophysics Data System (ADS)

    Lampilahti, Janne; Manninen, Hanna E.; Nieminen, Tuomo; Mirme, Sander; Pullinen, Iida; Yli-Juuti, Taina; Schobesberger, Siegfried; Kangasluoma, Juha; Kontkanen, Jenni; Lehtipalo, Katrianne; Ehn, Mikael; Mentel, Thomas F.; Petäjä, Tuukka; Kulmala, Markku

    2014-05-01

    Atmospheric new particle formation (NPF) is a frequent and ubiquitous process in the atmosphere and a major source of newly formed aerosol particles [1]. However, it is still unclear how the aerosol particle distribution evolves in space and time during an NPF. We investigated where in the planetary boundary layer does NPF begin and how does the aerosol number size distribution develop in space and time during it. We measured in Hyytiälä, southern Finland using ground based and airborne measurements. The measurements were part of the PEGASOS project. NPF was studied on six scientific flights during spring 2013 using a Zeppelin NT class airship. Ground based measurements were simultaneously conducted at SMEAR II station located in Hyytiälä. The flight profiles over Hyytiälä were flown between sunrise and noon during the growth of the boundary layer. The profiles over Hyytiälä covered vertically a distance of 100-1000 meters reaching the mixed layer, stable (nocturnal) boundary layer and the residual layer. Horizontally the profiles covered approximately a circular area of four kilometers in diameter. The measurements include particle number size distribution by Neutral cluster and Air Ion Spectrometer (NAIS), Differential Mobility Particle Sizer (DMPS) and Particle Size Magnifier (PSM) [2], meteorological parameters and position (latitude, longitude and altitude) of the Zeppelin. Beginning of NPF was determined from an increase in 1.7-3 nm ion concentration. Height of the mixed layer was estimated from relative humidity measured on-board the Zeppelin. Particle growth rate during NPF was calculated. Spatial inhomogeneities in particle number size distribution during NPF were located and the birthplace of the particles was estimated using the growth rate and trajectories. We observed a regional NPF event that began simultaneously and evolved uniformly inside the mixed layer. In the horizontal direction we observed a long and narrow high concentration plume of

  1. Secondary electron emission from the surface covered by a dust layer

    NASA Astrophysics Data System (ADS)

    Richterova, Ivana; Vaverka, Jakub; Pavlu, Jiri; Nemecek, Zdenek; Safrankova, Jana

    2015-04-01

    Bodies immersed in the plasma are charged to the floating potential that is determined by a balance of the currents onto/from the surface. The collection of charged particles and the photoemission current dominate but if the temperature of the electron component of the ambient plasma is high enough (10 eV or more) the secondary electron emission current should be considered. For an explanation of observed surface potentials of the bodies covered with a dust layer like the Moon, a depression of the secondary electron emission yield by a factor of 2 or 3 with respect to the smooth planar surface is expected. However, our previous calculations of an influence of the surface roughness on the secondary electron emission from dust grains have shown that these effects do not lead to required yield reduction. The present paper is devoted to a search for dust grain configurations on a planar surface that can provide the yield reduction consistent with observed surface potentials. The results are compared with the calculations of the yield from porous (lava type) surfaces. This approach can be also applied to other processes as the photoemission or ion induced electron emission.

  2. Surface waves on a soft viscoelastic layer produced by an oscillating microbubble

    PubMed Central

    Tinguely, Marc; Hennessy, Matthew G.; Pommella, Angelo; Matar, Omar K.

    2016-01-01

    Ultrasound-driven bubbles can cause significant deformation of soft viscoelastic layers, for instance in surface cleaning and biomedical applications. The effect of the viscoelastic properties of a boundary on the bubble–boundary interaction has been explored only qualitatively, and remains poorly understood. We investigate the dynamic deformation of a viscoelastic layer induced by the volumetric oscillations of an ultrasound-driven microbubble. High-speed video microscopy is used to observe the deformation produced by a bubble oscillating at 17–20 kHz in contact with the surface of a hydrogel. The localised oscillating pressure applied by the bubble generates surface elastic (Rayleigh) waves on the gel, characterised by elliptical particle trajectories. The tilt angle of the elliptical trajectories varies with increasing distance from the bubble. Unexpectedly, the direction of rotation of the surface elements on the elliptical trajectories shifts from prograde to retrograde at a distance from the bubble that depends on the viscoelastic properties of the gel. To explain these behaviours, we develop a simple three-dimensional model for the deformation of a viscoelastic solid by a localised oscillating force. By using as input for the model the values of the shear modulus obtained from the propagation velocity of the Rayleigh waves, we find good qualitative agreement with the experimental observations. PMID:27071851

  3. Surface waves on a soft viscoelastic layer produced by an oscillating microbubble.

    PubMed

    Tinguely, Marc; Hennessy, Matthew G; Pommella, Angelo; Matar, Omar K; Garbin, Valeria

    2016-05-14

    Ultrasound-driven bubbles can cause significant deformation of soft viscoelastic layers, for instance in surface cleaning and biomedical applications. The effect of the viscoelastic properties of a boundary on the bubble-boundary interaction has been explored only qualitatively, and remains poorly understood. We investigate the dynamic deformation of a viscoelastic layer induced by the volumetric oscillations of an ultrasound-driven microbubble. High-speed video microscopy is used to observe the deformation produced by a bubble oscillating at 17-20 kHz in contact with the surface of a hydrogel. The localised oscillating pressure applied by the bubble generates surface elastic (Rayleigh) waves on the gel, characterised by elliptical particle trajectories. The tilt angle of the elliptical trajectories varies with increasing distance from the bubble. Unexpectedly, the direction of rotation of the surface elements on the elliptical trajectories shifts from prograde to retrograde at a distance from the bubble that depends on the viscoelastic properties of the gel. To explain these behaviours, we develop a simple three-dimensional model for the deformation of a viscoelastic solid by a localised oscillating force. By using as input for the model the values of the shear modulus obtained from the propagation velocity of the Rayleigh waves, we find good qualitative agreement with the experimental observations. PMID:27071851

  4. Layer-dependent surface potential of phosphorene and anisotropic/layer-dependent charge transfer in phosphorene-gold hybrid systems.

    PubMed

    Xu, Renjing; Yang, Jiong; Zhu, Yi; Yan, Han; Pei, Jiajie; Myint, Ye Win; Zhang, Shuang; Lu, Yuerui

    2016-01-01

    The surface potential and the efficiency of interfacial charge transfer are extremely important for designing future semiconductor devices based on the emerging two-dimensional (2D) phosphorene. Here, we directly measured the strong layer-dependent surface potential of mono- and few-layered phosphorene on gold, which is consistent with the reported theoretical prediction. At the same time, we used an optical way photoluminescence (PL) spectroscopy to probe charge transfer in the phosphorene-gold hybrid system. We firstly observed highly anisotropic and layer-dependent PL quenching in the phosphorene-gold hybrid system, which is attributed to the highly anisotropic/layer-dependent interfacial charge transfer.

  5. Method and apparatus for measuring surface density of explosive and inert dust in stratified layers

    DOEpatents

    Sapko, Michael J.; Perlee, Henry E.

    1988-01-01

    A method for determining the surface density of coal dust on top of rock dust or rock dust on top of coal dust is disclosed which comprises directing a light source at either a coal or rock dust layer overlaying a substratum of the other, detecting the amount of light reflected from the deposit, generating a signal from the reflected light which is converted into a normalized output (V), and calculating the surface density from the normalized output. The surface density S.sub.c of coal dust on top of rock dust is calculated according to the equation: S.sub.c =1/-a.sub.c ln(V) wherein a.sub.c is a constant for the coal dust particles, and the surface density S.sub.r of rock dust on top of coal dust is determined by the equation: ##EQU1## wherein a.sub.r is a constant based on the properties of the rock dust particles. An apparatus is also disclosed for carrying out the method of the present invention.

  6. Fabrication of bifunctional core-shell Fe3O4 particles coated with ultrathin phosphor layer

    PubMed Central

    2013-01-01

    Bifunctional monodispersed Fe3O4 particles coated with an ultrathin Y2O3:Tb3+ shell layer were fabricated using a facile urea-based homogeneous precipitation method. The obtained composite particles were characterized by powder X-ray diffraction, transmission electron microscopy (TEM), quantum design vibrating sample magnetometry, and photoluminescence (PL) spectroscopy. TEM revealed uniform spherical core-shell-structured composites ranging in size from 306 to 330 nm with a shell thickness of approximately 25 nm. PL spectroscopy confirmed that the synthesized composites displayed a strong eye-visible green light emission. Magnetic measurements indicated that the composite particles obtained also exhibited strong superparamagnetic behavior at room temperature. Therefore, the inner Fe3O4 core and outer Y2O3:Tb3+ shell layer endow the composites with both robust magnetic properties and strong eye-visible luminescent properties. These composite materials have potential use in magnetic targeting and bioseparation, simultaneously coupled with luminescent imaging. PMID:23962025

  7. Amorphous chalcogenide layers and nanocomposites for direct surface patterning

    NASA Astrophysics Data System (ADS)

    Molnar, Sandor; Bohdan, Roland; Csarnovics, Istvan; Burunkova, Iulia; Kokenyesi, Sandor

    2015-03-01

    Homogeneous, 200 - 3000 nm thick layers of chalcogenide glasses, 1 - 2 mm thick plane-parallel plates as well as nanocomposite structures, containing gold nanoparticles have been produced and used for in situ surface optical and geometrical relief fabrication by optical- or electron-, ion-beam recording. Investigations were focused on the formation of giant (height modulation from nanometers up to micrometers) geometrical reliefs and elements (dots, lines and diffractive elements) applicable in the 0.5 - 10 micrometer spectral range. Recording parameters were compared with available data on acrylic polymer nanocomposites. The mechanism of the recording processes, which include thermal, electron and mass-transport components were explained and the selection of the materials from As(Ge)-S(Se) binary systems with best recording parameters was done.

  8. Spin-glass-like freezing of inner and outer surface layers in hollow γ-Fe2O3 nanoparticles

    DOE PAGESBeta

    Khurshid, Hafsa; Lampen-Kelley, Paula; Iglesias, Òscar; Alonso, Javier; Phan, Manh-Huong; Sun, Cheng-Jun; Saboungi, Marie-Louise; Srikanth, Hariharan

    2015-10-27

    Disorder among surface spins largely dominates the magnetic response of ultrafine magnetic particle systems. In this work, we examine time-dependent magnetization in high-quality, monodisperse hollow maghemite nanoparticles (NPs) with a 14.8±0.5 nm outer diameter and enhanced surface-to-volume ratio. The nanoparticle ensemble exhibits spin-glass-like signatures in dc magnetic aging and memory protocols and ac magnetic susceptibility. The dynamics of the system slow near 50 K, and becomes frozen on experimental time scales below 20 K. Remanence curves indicate the development of magnetic irreversibility concurrent with the freezing of the spin dynamics. A strong exchange-bias effect and its training behavior point tomore » highly frustrated surface spins that rearrange much more slowly than interior spins with bulk coordination. Monte Carlo simulations of a hollow particle reproducing the experimental morphology corroborate strongly disordered surface layers with complex energy landscapes that underlie both glass-like dynamics and magnetic irreversibility. Calculated hysteresis loops reveal that magnetic behavior is not identical at the inner and outer surfaces, with spins at the outer surface layer of the 15 nm hollow particles exhibiting a higher degree of frustration. Lastly, our combined experimental and simulated results shed light on the origin of spin-glass-like phenomena and the important role played by the surface spins in magnetic hollow nanostructures.« less

  9. High-Speed Transport of Fluid Drops and Solid Particles via Surface Acoustic Waves

    NASA Technical Reports Server (NTRS)

    Bar-Cohen, Yoseph; Bao, Xiaoqi; Sherrit, Stewart; Badescu, Mircea; Lih, Shyh-shiuh

    2012-01-01

    A compact sampling tool mechanism that can operate at various temperatures, and transport and sieve particle sizes of powdered cuttings and soil grains with no moving parts, has been created using traveling surface acoustic waves (SAWs) that are emitted by an inter-digital transducer (IDT). The generated waves are driven at about 10 MHz, and it causes powder to move towards the IDT at high speed with different speeds for different sizes of particles, which enables these particles to be sieved. This design is based on the use of SAWs and their propelling effect on powder particles and fluids along the path of the waves. Generally, SAWs are elastic waves propagating in a shallow layer of about one wavelength beneath the surface of a solid substrate. To generate SAWs, a piezoelectric plate is used that is made of LiNbO3 crystal cut along the x-axis with rotation of 127.8 along the y-axis. On this plate are printed pairs of fingerlike electrodes in the form of a grating that are activated by subjecting the gap between the electrodes to electric field. This configuration of a surface wave transmitter is called IDT. The IDT that was used consists of 20 pairs of fingers with 0.4-mm spacing, a total length of 12.5 mm. The surface wave is produced by the nature of piezoelectric material to contract or expand when subjected to an electric field. Driving the IDT to generate wave at high amplitudes provides an actuation mechanism where the surface particles move elliptically, pulling powder particles on the surface toward the wavesource and pushing liquids in the opposite direction. This behavior allows the innovation to separate large particles and fluids that are mixed. Fluids are removed at speed (7.5 to 15 cm/s), enabling this innovation of acting as a bladeless wiper for raindrops. For the windshield design, the electrodes could be made transparent so that they do not disturb the driver or pilot. Multiple IDTs can be synchronized to transport water or powder over larger

  10. GYROSCOPIC PUMPING IN THE SOLAR NEAR-SURFACE SHEAR LAYER

    SciTech Connect

    Miesch, Mark S.; Hindman, Bradley W.

    2011-12-10

    We use global and local helioseismic inversions to explore the prevailing dynamical balances in the solar near-surface shear layer (NSSL). The differential rotation and meridional circulation are intimately linked, with a common origin in the turbulent stresses of the upper solar convection zone. The existence and structure of the NSSL cannot be attributed solely to the conservation of angular momentum by solar surface convection, as is often supposed. Rather, the turbulent angular momentum transport accounts for the poleward meridional flow while the often overlooked meridional force balance is required to maintain the mid-latitude rotational shear. We suggest that the base of the NSSL is marked by a transition from baroclinic to turbulent stresses in the meridional plane which suppress Coriolis-induced circulations that would otherwise establish a cylindrical rotation profile. The turbulent angular momentum transport must be nondiffusive and directed radially inward. Inferred mean flows are consistent with the idea that turbulent convection tends to mix angular momentum but only if the mixing efficiency is inhomogeneous and/or anisotropic. The latitudinal and longitudinal components of the estimated turbulent transport are comparable in amplitude and about an order of magnitude larger than the vertical component. We estimate that it requires 2%-4% of the solar luminosity to maintain the solar NSSL against the inertia of the mean flow. Most of this energy is associated with the turbulent transport of angular momentum out of the layer, with a spin-down timescale of {approx}600 days. We also address implications of these results for numerical modeling of the NSSL.

  11. Gyroscopic Pumping in the Solar Near-surface Shear Layer

    NASA Astrophysics Data System (ADS)

    Miesch, Mark S.; Hindman, Bradley W.

    2011-12-01

    We use global and local helioseismic inversions to explore the prevailing dynamical balances in the solar near-surface shear layer (NSSL). The differential rotation and meridional circulation are intimately linked, with a common origin in the turbulent stresses of the upper solar convection zone. The existence and structure of the NSSL cannot be attributed solely to the conservation of angular momentum by solar surface convection, as is often supposed. Rather, the turbulent angular momentum transport accounts for the poleward meridional flow while the often overlooked meridional force balance is required to maintain the mid-latitude rotational shear. We suggest that the base of the NSSL is marked by a transition from baroclinic to turbulent stresses in the meridional plane which suppress Coriolis-induced circulations that would otherwise establish a cylindrical rotation profile. The turbulent angular momentum transport must be nondiffusive and directed radially inward. Inferred mean flows are consistent with the idea that turbulent convection tends to mix angular momentum but only if the mixing efficiency is inhomogeneous and/or anisotropic. The latitudinal and longitudinal components of the estimated turbulent transport are comparable in amplitude and about an order of magnitude larger than the vertical component. We estimate that it requires 2%-4% of the solar luminosity to maintain the solar NSSL against the inertia of the mean flow. Most of this energy is associated with the turbulent transport of angular momentum out of the layer, with a spin-down timescale of ~600 days. We also address implications of these results for numerical modeling of the NSSL.

  12. Particle deposition on superhydrophobic surfaces by sessile droplet evaporation

    NASA Astrophysics Data System (ADS)

    Dicuangco, Mercy Grace

    Prediction and active control of the spatial distribution of particulate deposits obtained from sessile droplet evaporation is essential in ink-jet printing, nanostructure assembly, biotechnology, and other applications that require localized deposits. In recent years, sessile droplet evaporation on bio-inspired superhydrophobic surfaces has become an attractive method for depositing materials on a site-specific, localized region, but is less explored compared to evaporative deposition on hydrophilic surfaces. It is therefore of interest to understand particle deposition during droplet evaporation on superhydrophobic surfaces to enable accurate prediction and tunable control of localized deposits on such surfaces. The purpose of the present work is to explore the morphology of particles deposited on superhydrophobic surfaces by the evaporation of sessile water droplets containing suspended latex spheres. Droplet evaporation experiments are performed on non-wetting, textured surfaces with varying geometric parameters. The temporal evolution of the droplet contact radius and contact angle throughout the evaporation process are tracked by visualizing the transient droplet shape and wetting behavior. The droplets are observed to exhibit a combination of the following modes of evaporation: the constant contact radius mode, the constant contact angle mode, and the mixed mode in which the contact angle and the contact radius change simultaneously. After complete dry-out, the remaining particulate deposits are qualitatively and quantitatively characterized to describe their spatial distribution. In the first part of the study, the test surfaces are maintained at different temperatures. Experiments are conducted at ambient conditions and at elevated substrate temperatures of approximately 40°C, 50°C, and 60°C. The results show that droplet evaporation on superhydrophobic surfaces, driven by either mass diffusion at ambient conditions or by substrate heating, suppresses

  13. Surface composition of solid-rocket exhausted aluminum oxide particles

    NASA Technical Reports Server (NTRS)

    Cofer, Wesley R., III; Winstead, Edward L.; Key, Lawrence E.

    1989-01-01

    Particulate samples of aluminum oxide were collected on Teflon filters from the exhaust plume of the Space Shuttle (STS-61A, October 30, 1985) over the altitude interval 4.6-7.6 km immediately after launch. These particles were analyzed using SEM, energy-dispersive X-ray analysis, electron spectroscopy for chemical analysis, X-ray fluorescent spectroscopy, and conventional wet-chemical techniques. The samples were 0.6-1.0 percent surface-chlorided (chlorided meaning predominantly aluminum chlorides and oxychlorides, possibly including other adsorbed forms of chloride) by weight. This level of chloriding is about one-third of the amount determined previously from laboratory-prepared alumina and surface site samples of solid-rocket-produced alumina (SRPA) after both had been exposed to moist HCl vapor at temperatures down to ambient. This level is equivalent to previous laboratory results with samples exposed to moist HCl at temperatures above the boiling point of water. It is suggested that the present lower chloriding levels, determined for samples from a 'dry' Shuttle exhaust cloud, underscore the importance of a liquid water/hydrochloric acid phase in governing the extent of surface chloriding of SRPA. The reduced chloriding is not trivial with respect to potential physical/chemical modification of the SRPA particle surfaces and their corresponding interaction with the atmosphere.

  14. Interplay between Depletion and Double-Layer Forces Acting between Charged Particles in Solutions of Like-Charged Polyelectrolytes

    NASA Astrophysics Data System (ADS)

    Moazzami-Gudarzi, Mohsen; Kremer, Tomislav; Valmacco, Valentina; Maroni, Plinio; Borkovec, Michal; Trefalt, Gregor

    2016-08-01

    Direct force measurements between negatively charged silica particles in the presence of a like-charged strong polyelectrolyte were carried out with an atomic force microscope. The force profiles can be quantitatively interpreted as a superposition of depletion and double-layer forces. The depletion forces are modeled with a damped oscillatory profile, while the double-layer forces with the mean-field Poisson-Boltzmann theory for a strongly asymmetric electrolyte, whereby an effective valence must be assigned to the polyelectrolyte. This effective valence is substantially smaller than the bare valence due to ion condensation effects. The unusual aspect of the electrical double layer in these systems is the exclusion of the like-charged polyelectrolyte from the vicinity of the surface, leading to a strongly nonexponential diffuse ionic layer that is dominated by counterions and has a well-defined thickness. As the oscillatory depletion force sets in right after this layer, this condition can be used to predict the phase of the oscillatory depletion force.

  15. Interplay between Depletion and Double-Layer Forces Acting between Charged Particles in Solutions of Like-Charged Polyelectrolytes.

    PubMed

    Moazzami-Gudarzi, Mohsen; Kremer, Tomislav; Valmacco, Valentina; Maroni, Plinio; Borkovec, Michal; Trefalt, Gregor

    2016-08-19

    Direct force measurements between negatively charged silica particles in the presence of a like-charged strong polyelectrolyte were carried out with an atomic force microscope. The force profiles can be quantitatively interpreted as a superposition of depletion and double-layer forces. The depletion forces are modeled with a damped oscillatory profile, while the double-layer forces with the mean-field Poisson-Boltzmann theory for a strongly asymmetric electrolyte, whereby an effective valence must be assigned to the polyelectrolyte. This effective valence is substantially smaller than the bare valence due to ion condensation effects. The unusual aspect of the electrical double layer in these systems is the exclusion of the like-charged polyelectrolyte from the vicinity of the surface, leading to a strongly nonexponential diffuse ionic layer that is dominated by counterions and has a well-defined thickness. As the oscillatory depletion force sets in right after this layer, this condition can be used to predict the phase of the oscillatory depletion force. PMID:27588884

  16. Controlling surface enrichment in polymeric hole extraction layers to achieve high-efficiency organic photovoltaic cells.

    PubMed

    Kim, Dong-Hun; Lim, Kyung-Geun; Park, Jong Hyeok; Lee, Tae-Woo

    2012-10-01

    Hole extraction in organic photovoltaic cells (OPVs) can be modulated by a surface-enriched layer formed on top of the conducting polymer-based hole extraction layer (HEL). This tunes the surface work function of the HEL to better align with the ionization potential of the polymeric photoactive layer. Results show noticeable improvement in device power conversion efficiencies (PCEs) in OPVs. We achieved a 6.1 % PCE from the OPV by optimizing the surface-enriched layer.

  17. The Point of Departure of a Particle Sliding on a Curved Surface

    ERIC Educational Resources Information Center

    Aghamohammadi, Amir

    2012-01-01

    A particle is thrown tangentially on a surface. It is shown that for some surfaces and for special initial velocities the thrown particle immediately leaves the surface, and for special conditions it never leaves the surface. The conditions for leaving the surface are investigated. The problem is studied for a surface with the cross-section y =…

  18. Morphological features of the copper surface layer under sliding with high density electric current

    NASA Astrophysics Data System (ADS)

    Fadin, V. V.; Aleutdinova, M. I.; Rubtsov, V. Ye.; Aleutdinova, V. A.

    2015-10-01

    Conductivity and wear intensity of copper under the influence of dry friction and electric current with contact density higher 100 A/cm2 are presented. It is shown that an increase in hardness and heat outflow from a friction zone leads to the reduction of wear intensity and current contact density increase corresponding to the beginning of catastrophic wear. Structural changes, such as the formation of FeO oxide and α-Fe particles in the copper surface layer, have also been found. It is observed that a worn surface is deformed according to a viscous liquid mechanism. Such singularity is explained in terms of appearance of high-excited atomic states in deforming micro-volumes near contact spots that lead to easy stress relaxation by local plastic shears in the vicinity of stress concentrators. In common this effect allows to achieve high wear resistance.

  19. Morphological features of the copper surface layer under sliding with high density electric current

    SciTech Connect

    Fadin, V. V.; Aleutdinova, M. I.; Rubtsov, V. Ye.; Aleutdinova, V. A.

    2015-10-27

    Conductivity and wear intensity of copper under the influence of dry friction and electric current with contact density higher 100 A/cm{sup 2} are presented. It is shown that an increase in hardness and heat outflow from a friction zone leads to the reduction of wear intensity and current contact density increase corresponding to the beginning of catastrophic wear. Structural changes, such as the formation of FeO oxide and α-Fe particles in the copper surface layer, have also been found. It is observed that a worn surface is deformed according to a viscous liquid mechanism. Such singularity is explained in terms of appearance of high-excited atomic states in deforming micro-volumes near contact spots that lead to easy stress relaxation by local plastic shears in the vicinity of stress concentrators. In common this effect allows to achieve high wear resistance.

  20. Water Surface Ripples Generated by the Turbulent Boundary Layer of a Surface-Piercing Moving Wall

    NASA Astrophysics Data System (ADS)

    Washuta, N.; Masnadi, N.; Duncan, J. H.

    2014-11-01

    Free surface ripples created by subsurface turbulence along a surface-piercing moving wall are studied experimentally. In this experiment, a meter-wide stainless steel belt travels horizontally in a loop around two rollers with vertically oriented axes, which are separated by 7.5 meters. One of the two 7.5-m-long belt sections between the rollers is in contact with the water in a large open-surface water tank and the water level is adjusted so that the top of the belt pierces the water free surface. The belt is launched from rest with a 3 g acceleration in order to quickly reach a steady state velocity. This belt motion creates a temporally evolving boundary layer analogous to the spatially evolving boundary layer created along the side of a ship hull moving at the belt velocity, with a length equivalent to the length of belt that has passed the measurement region. The water surface ripples generated by the subsurface turbulence are measured in a plane normal to the belt using a cinematic LIF technique. It is found that the overall RMS surface fluctuations increase linearly with belt speed and that the spatial distributions of the fluctuations show a sharp increase near the wall. The support of the Office of Naval Research is gratefully acknowledged.

  1. Motion of particles with inertia in a compressible free shear layer

    NASA Technical Reports Server (NTRS)

    Samimy, M.; Lele, S. K.

    1991-01-01

    The effects of the inertia of a particle on its flow-tracking accuracy and particle dispersion are studied using direct numerical simulations of 2D compressible free shear layers in convective Mach number (Mc) range of 0.2 to 0.6. The results show that particle response is well characterized by tau, the ratio of particle response time to the flow time scales (Stokes' number). The slip between particle and fluid imposes a fundamental limit on the accuracy of optical measurements such as LDV and PIV. The error is found to grow like tau up to tau = 1 and taper off at higher tau. For tau = 0.2 the error is about 2 percent. In the flow visualizations based on Mie scattering, particles with tau more than 0.05 are found to grossly misrepresent the flow features. These errors are quantified by calculating the dispersion of particles relative to the fluid. Overall, the effect of compressibility does not seem to be significant on the motion of particles in the range of Mc considered here.

  2. Surface Roughness and Dislocation Distribution in Compositionally Graded Relaxed SiGe Buffer Layer with Inserted Strained Si Layers

    NASA Astrophysics Data System (ADS)

    Yoon, Tae-Sik

    2005-03-01

    We report the experimental investigation of surface roughness and dislocation distribution of 1 μm-thick, compositionally graded, relaxed SiGe buffer layer with a final Ge surface content of 30%. Tensile-strained Si layers are inserted at various locations in the graded buffer during SiGe epitaxial growths. Slight reduction in surface roughness from about 10.3 nm to about 7.8 nm by inserting two 20 nm thick tensile-strained Si layers followed by SiGe growths. It turns out that majority of the residual surface roughness is developed during the SiGe growths on top of the topmost strain Si layer. The surface immediately after the growth of tensile strained Si is very flat with about 1.1 nm RMS roughness and without crosshatch morphology. Cross-sectional TEM shows clear signs of increased interaction between dislocation half-loops at the top surface of the strained Si layers. Our observation shows that although thin Si layers under tensile-strain are effective in reducing cross-hatch, they could in the meantime impede dislocation propagation leading to higher threading dislocation density. Considerations for an optimized scheme exploiting the flattening function of tensile-strained layers will be discussed.

  3. Global ocean wind power sensitivity to surface layer stability

    NASA Astrophysics Data System (ADS)

    Capps, Scott B.; Zender, Charles S.

    2009-05-01

    Global ocean wind power has recently been assessed (W. T. Liu et al., 2008) using scatterometry-based 10 m winds. We characterize, for the first time, wind power at 80 m (typical wind turbine hub height) above the global ocean surface, and account for the effects of surface layer stability. Accounting for realistic turbine height and atmospheric stability increases mean global ocean wind power by +58% and -4%, respectively. Our best estimate of mean global ocean wind power is 731 W m-2, about 50% greater than the 487 W m-2 based on previous methods. 80 m wind power is 1.2-1.5 times 10 m power equatorward of 30° latitude, between 1.4 and 1.7 times 10 m power in wintertime storm track regions and >6 times 10 m power in stable regimes east of continents. These results are relatively insensitive to methodology as wind power calculated using a fitted Weibull probability density function is within 10% of power calculated from discrete wind speed measurements over most of the global oceans.

  4. Thin hydroxyapatite surface layers on titanium produced by ion implantation

    NASA Astrophysics Data System (ADS)

    Baumann, H.; Bethge, K.; Bilger, G.; Jones, D.; Symietz, I.

    2002-11-01

    In medicine metallic implants are widely used as hip replacement protheses or artificial teeth. The biocompatibility is in all cases the most important requirement. Hydroxyapatite (HAp) is frequently used as coating on metallic implants because of its high acceptance by the human body. In this paper a process is described by which a HAp surface layer is produced by ion implantation with a continuous transition to the bulk material. Calcium and phosphorus ions are successively implanted into titanium under different vacuum conditions by backfilling oxygen into the implantation chamber. Afterwards the implanted samples are thermally treated. The elemental composition inside the implanted region was determined by nuclear analysis methods as (α,α) backscattering and the resonant nuclear reaction 1H( 15N,αγ) 12C. The results of X-ray photoelectron spectroscopy indicate the formation of HAp. In addition a first biocompatibility test was performed to compare the growing of marrow bone cells on the implanted sample surface with that of titanium.

  5. Superhydrophobic surfaces: A model approach to predict contact angle and surface energy of soil particles

    NASA Astrophysics Data System (ADS)

    Shirtcliffe, Neil; Hamlett, Christopher; McHale, Glen; Newton, Michael; Bachmann, Joerg; Woche, S.

    2010-05-01

    C. Hamlett(a), G. McHALE(a), N. Shirtcliffe(a), M. Newton(a), S.K. Woche(b), and J. BACHMANN(b) aSchool of Science & Technology, Nottingham Trent University, Clifton Lane, Nottingham, NG11 8NS, UK and bInstitute of Soil Science, Leibniz University Hannover, Herrenhaeuser Str.2, 30419, Hannover, Germany. Summary Wettability of soil affects a wide variety of processes including infiltration, preferential flow and surface runoff. The problem of determining contact angles and surface energy of powders, such as soil particles, remains unsolved. So far, several theories and approaches have been proposed, but formulation of surface and interfacial free energy, as regards its components, is still a very debatable issue. In the present study, the general problem of the interpretation of contact angles and surface free energy on chemically heterogeneous and rough soil particle surfaces are evaluated by a reformulation of the Cassie-Baxter equation assuming that the particles are attached on to a plane and rigid surface. Compared with common approaches, our model considers a roughness factor which depends on the Young's Law contact angle determined by the surface chemistry. Results of the model are discussed and compared with independent contact angle measurements using the Sessile Drop and the Wilhelmy Plate methods. Based on contact angle data, the critical surface tension of the grains were determined by the method proposed by Zisman. Experiments were made with glass beads and three soil materials ranging from sand to clay. Soil particles were coated with different loadings of dichlorodimethylsilane (DCDMS) to vary the wettability. Varying the solid surface tension using DCDMS treatments provided pure water wetting behaviours ranging from wettable to extremely hydrophobic with contact angles >150°. Results showed that the critical surface energy measured on grains with the highest DCDMS loadings was similar to the surface energy measured independently on ideal DCDMS

  6. Evolutions of hairpin vortexes over a superhydrophobic surface in turbulent boundary layer flow

    NASA Astrophysics Data System (ADS)

    Zhang, Jingxian; Tian, Haiping; Yao, Zhaohui; Hao, Pengfei; Jiang, Nan

    2016-09-01

    Turbulent flows over a superhydrophobic surface and a smooth surface have been measured and studied by particle image velocimetry technology at Reθ = 990. The Reynolds shear stress distributions over the two surfaces are significantly different. Specifically, for the superhydrophobic surface, the Reynolds shear stress is suppressed in the near-wall region (y/δ < 0.3, δ is the boundary layer thickness) and increases in the outer region (0.3 < y/δ < 0.5), which forms a second peak of the Reynolds shear stress curve. Evolutions of hairpin vortexes are analyzed to interpret differences in the Reynolds shear stress, based on some comparisons in the low-speed streaks and Q2/Q4 (ejection/sweep) events. The results show that, in the near wall region, the turbulent coherent structures (low-speed streaks and hairpin vortex) over the superhydrophobic surface are more stable and flat, due to the suppression in the strength and the lifting effect of the hairpin vortex. In the outer region, the superhydrophobic surface lifts the hairpin vortex away from the wall with a value of 0.14δ in our experiment, which makes the Q4 events occur further from the wall and contribute less to skin friction.

  7. Statistics of particle concentration in free-surface turbulence

    SciTech Connect

    Bandi, Mahesh M; Larkin, J; Goldburg, W

    2009-01-01

    Particles on the surface of an incompressible fluid maintained in a turbulent steady-state cluster into spatio-temporally complex flow structures. We experimentally study the statistics of particle concentration n(r, t) over various coarse-grained scales r' in the inertial range. Another control parameter is the Taylor Microscale Reynolds number Re{sub {lambda}}. The focus is on the steady state probability density function {Pi}(n{sub r}). Attention is also given to the variance {sigma}{sup 2}(r, t) of this PDF, since it yields information about the topology of the coagulated structures. Where possible, the results are compared and contrasted with those obtained in a recent analytical and numerical study of two-dimensional synthetic turbulence by Ducasse and Pumir. There, but not here, the dimensionless compressibility C is an important control parameter.

  8. Gold Nanoparticle Clusters in Quasinematic Layers of Liquid-Crystalline Dispersion Particles of Double-Stranded Nucleic Acids

    PubMed Central

    Yevdokimov, Yu.M.; Salyanov, V.I.; Katz, E.I.; Skuridin, S.G.

    2012-01-01

    The interaction between gold nanoparticles and particles of cholesteric liquid-crystalline dispersions formed by double-stranded DNA and poly(I)×poly(C) molecules is considered. It is shown that small-sized (~ 2 nm) gold nanoparticles induce two different structural processes. First, they facilitate the reorganization of the spatial cholesteric structure of the particles into a nematic one. This process is accompanied by a fast decrease in the amplitude of an abnormal band in the CD spectrum. Second, they induce cluster formation in a “free space” between neighboring nucleic acid molecules fixed in the structure of the quasinematic layers of liquid-crystalline particles. This process is accompanied by slow development of the surface plasmon resonance band in the visible region of the absorption spectrum. Various factors influencing these processes are outlined. Some assumptions concerning the possible mechanism(s) of fixation of gold nanoparticles between the neighboring double-stranded nucleic acid molecules in quasinematic layers are formulated. PMID:23346383

  9. Cell and tissue kinetics of the subependymal layer in mouse brain following heavy charged particle irradiation

    SciTech Connect

    Manley, N.B.; Fabrikant, J.I.; Alpen, E.L.

    1988-12-01

    The following studies investigate the cellular response and cell population kinetics of the subependymal layer in the mouse brain exposed to heavy charged particle irradiation. Partial brain irradiation with helium and neon ions was confined to one cortex of the brain. Both the irradiated and the unirradiated contralateral cortex showed similar disturbances of the cell and tissue kinetics in the subependymal layers. The irradiated hemisphere exhibited histological damage, whereas the unirradiated side appeared normal histologically. This study concerns the cell population and cell cycle kinetics of the subependymal layer in the mouse brain, and the effects of charged particle irradiations on this cell population. Quantitative high resolution autoradiography was used to study the kinetic parameters in this cell layer. This study should help in understanding the effects of these high-energy heavy ions on normal mammalian brain tissue. The response of the mammalian brain exposure to charged particle ionizing radiation may be extremely variable. It varies from minimal physiological changes to overt tissue necrosis depending on a number of factors such as: the administered dose, dose-rate, the volume of the irradiated tissue, and the biological end-point being examined.

  10. Material transport in a convective surface mixed layer under weak wind forcing

    NASA Astrophysics Data System (ADS)

    Mensa, Jean A.; Özgökmen, Tamay M.; Poje, Andrew C.; Imberger, Jörg

    2015-12-01

    Flows in the upper ocean mixed layer are responsible for the transport and dispersion of biogeochemical tracers, phytoplankton and buoyant pollutants, such as hydrocarbons from an oil spill. Material dispersion in mixed layer flows subject to diurnal buoyancy forcing and weak winds (| u10 | = 5m s-1) are investigated using a non-hydrostatic model. Both purely buoyancy-forced and combined wind- and buoyancy-forced flows are sampled using passive tracers, as well as 2D and 3D particles to explore characteristics of horizontal and vertical dispersion. It is found that the surface tracer patterns are determined by the convergence zones created by convection cells within a time scale of just a few hours. For pure convection, the results displayed the classic signature of Rayleigh-Benard cells. When combined with a wind stress, the convective cells become anisotropic in that the along-wind length scale gets much larger than the cross-wind scale. Horizontal relative dispersion computed by sampling the flow fields using both 2D and 3D passive particles is found to be consistent with the Richardson regime. Relative dispersion is an order of magnitude higher and 2D surface releases transition to Richardson regime faster in the wind-forced case. We also show that the buoyancy-forced case results in significantly lower amplitudes of scale-dependent horizontal relative diffusivity, kD(ℓ), than those reported by Okubo (1970), while the wind- and buoyancy-forced case shows a good agreement with Okubo's diffusivity amplitude, and the scaling is consistent with Richardson's 4/3rd law, kD ∼ ℓ4/3. These modeling results provide a framework for measuring material dispersion by mixed layer flows in future observational programs.

  11. Characterization of Floating Surface Layers of Lipids and Lipopolymers by Surface-Sensitive Scattering

    NASA Astrophysics Data System (ADS)

    Krüger, Peter; Lösche, Mathias

    Nanotechnology and molecular (bio-)engineering are making ever deepening inroads into everybodys daily life. Physicochemical and biotechnological achievements in the design of physiologically active supramolecular assemblies have brought about the quest for their submolecular-level characterization. We employ surface-sensitive scattering techniques for the investigation of planar lipid membranes - floating monolayers on aqueous surfaces - to correlate structural, functional and dynamic aspects of biomembrane models. This chapter surveys recent work on the submolecular structure of floating phospholipid monolayers - where the advent of third-generation synchrotron X-ray sources has driven the development of realistic, submolecular-scale quasi-chemical models - as well as of more complex systems: cation binding to anionic lipid surfaces; conformational changes of lipopolymers undergoing phase transitions; the conformational organization of phosphatidylinositol and phosphatidylinositides, as examples of physiologically important lipids; and the adsorption of peptides (neuropeptide Y, NPY) or solvents (dimethylsulfoxide, DMSO) onto phospholipid surface layers.

  12. Fabrication of large-sized two-dimensional ordered surface array with well-controlled structure via colloidal particle lithography.

    PubMed

    Meng, Xiaohui; Zhang, Xinping; Ye, Lei; Qiu, Dong

    2014-06-17

    Epoxy resin coated glass slides were used for colloidal particle lithography, in order to prepare well-defined 2D surface arrays. Upon the assistance of a large-sized 2D colloidal single crystal as template, centimeter-sized ordered surface arrays of bowl-like units were obtained. Systematic studies revealed that the parameters of obtained surface arrays could be readily controlled by some operational factors, such as temperature, epoxy resin layer thickness, and template particle size. With epoxy resin substituting for normal linear polymer, the height/diameter ratio of bowls in the formed surface arrays can be largely increased. With further reactive plasma etching, the parameters of ordered surface arrays could be finely tuned through controlling etching time. This study provides a facile way to prepare large-sized 2D surface arrays with tunable parameters.

  13. Separation and quantification of double- and triple-layered rotavirus-like particles by CZE.

    PubMed

    Castro-Acosta, Ricardo M; Revilla, Alma L; Ramírez, Octavio T; Palomares, Laura A

    2010-04-01

    Virus-like particles have been successfully used as safe vaccines, as their structure is identical to their native counterparts but devoid of the viral genetic material. However, production of these complex structures is not easy, as recombinant proteins must assemble into virus-like particles. Techniques to differentiate assembled and soluble proteins, as well as assembly intermediaries often present in a sample, are required. An example of complex virus-like particles mixture occurs when rotavirus proteins are recombinantly expressed. Rotavirus-like particles (RLP) can be single (sl), double (dl), or triple layered (tl). The use of RLP preparations as vaccines requires their complete characterization, including separation and quantification of each RLP in a sample. In this work, CZE was evaluated for the separation and quantification of dl and triple-layered rotavirus-like particles (tlRLP). A fused-silica capillary with a deoxycholate running buffer efficiently separated dl and tlRLP in RLP preparations, as they migrated in two discrete peaks with electrophoretic mobilities of 1.24+/-0.04 and 2.95+/-0.03 Ti, respectively. Standard curves for dl and tlRLP were generated, and the response was linearly proportional to analyte concentration. The methodology developed was quantitative, specific, accurate, precise, and reproducible. CZE allowed the quantitative characterization of RLP preparations, which is required for evaluation of immunogens, for process development, and for quality control protocols.

  14. Charged Particle Alterations of Surfaces in the Solar System

    NASA Technical Reports Server (NTRS)

    Johnson, R. E.

    1995-01-01

    The surfaces of 'airless' bodies in the solar system are exposed to the ambient plasma, micrometeorites, and the solar UV. The effects of these space weathering agents on surfaces in the solar system has been studied in this project. In the last three years work was carried out on volatile depletion at Mars, on sputtering of the lunar surface, on absorption by implanted S in vapor-deposited H2O and its relevance to observations of Europa's surface in the UV, and on the spectral changes produced on irradiating SO2 and its possible relevance to Io. In addition, the role of plasma-induced charging of E-ring grains was evaluated because of its relevance to E-ring particle source and the lifetime of the E-ring. Finally, the detection of sputtered material from Dione by the CAPS instrument on CASSINI was evaluated as a tool for analysis of satellite surface composition, and the role of sputtering on the ambient OH in the vicinity of the ice satellites and the E-ring was evaluated.

  15. On the Interaction between Marine Boundary Layer Cellular Cloudiness and Surface Heat Fluxes

    SciTech Connect

    Kazil, J.; Feingold, G.; Wang, Hailong; Yamaguchi, T.

    2014-01-02

    The interaction between marine boundary layer cellular cloudiness and surface uxes of sensible and latent heat is investigated. The investigation focuses on the non-precipitating closed-cell state and the precipitating open-cell state at low geostrophic wind speed. The Advanced Research WRF model is used to conduct cloud-system-resolving simulations with interactive surface fluxes of sensible heat, latent heat, and of sea salt aerosol, and with a detailed representation of the interaction between aerosol particles and clouds. The mechanisms responsible for the temporal evolution and spatial distribution of the surface heat fluxes in the closed- and open-cell state are investigated and explained. It is found that the horizontal spatial structure of the closed-cell state determines, by entrainment of dry free tropospheric air, the spatial distribution of surface air temperature and water vapor, and, to a lesser degree, of the surface sensible and latent heat flux. The synchronized dynamics of the the open-cell state drives oscillations in surface air temperature, water vapor, and in the surface fluxes of sensible and latent heat, and of sea salt aerosol. Open-cell cloud formation, cloud optical depth and liquid water path, and cloud and rain water path are identified as good predictors of the spatial distribution of surface air temperature and sensible heat flux, but not of surface water vapor and latent heat flux. It is shown that by enhancing the surface sensible heat flux, the open-cell state creates conditions by which it is maintained. While the open-cell state under consideration is not depleted in aerosol, and is insensitive to variations in sea-salt fluxes, it also enhances the sea-salt flux relative to the closed-cell state. In aerosol-depleted conditions, this enhancement may replenish the aerosol needed for cloud formation, and hence contribute to the perpetuation of the open-cell state as well. Spatial homogenization of the surface fluxes is found to have

  16. Multi-disclinational description of pentagonal particles with subsurface layer free of twin boundaries

    NASA Astrophysics Data System (ADS)

    Yasnikov, I. S.; Kolesnikova, A. L.; Romanov, A. E.

    2015-09-01

    We present the results on the modelling of structural changes in pentagonal small particles (PSPs) during their growth. We prove that after a certain critical size it becomes energetically favourable for a PSP to form a subsurface layer free of twin boundaries (TBs), which are only typical structural elements for smaller size PSPs. In this layer, the low-angle dislocation boundaries (DBs) are formed. Our calculations of the energy stored in the transformed PSP are based on the disclination model of a PSP, in which the TB junctions, as well as TB-DB junctions are treated as wedge disclinations.

  17. The application of thick hydrogenated amorphous silicon layers to charged particle and x-ray detection

    SciTech Connect

    Perez-Mendez, V.; Cho, G.; Fujieda, I.; Kaplan, S.N.; Qureshi, S.; Street, R.A.

    1989-04-01

    We outline the characteristics of thick hydrogenated amorphous silicon layers which are optimized for the detection of charged particles, x-rays and ..gamma..-rays. Signal amplitude as a function of the linear energy transfer of various particles are given. Noise sources generated by the detector material and by the thin film electronics - a-Si:H or polysilicon proposed for pixel position sensitive detectors readout are described, and their relative amplitudes are calculated. Temperature and neutron radiation effects on leakage currents and the corresponding noise changes are presented. 17 refs., 12 figs., 2 tabs.

  18. New Material Development for Surface Layer and Surface Technology in Tribology Science to Improve Energy Efficiency

    NASA Astrophysics Data System (ADS)

    Ismail, R.; Tauviqirrahman, M.; Jamari, Jamari; Schipper, D. J.

    2009-09-01

    This paper reviews the development of new material and surface technology in tribology and its contribution to energy efficiency. Two examples of the economic benefits, resulted from the optimum tribology in the transportation sector and the manufacturing industry are discussed. The new materials are proposed to modify the surface property by laminating the bulk material with thin layer/coating. Under a suitable condition, the thin layer on a surface can provide a combination of good wear, a low friction and corrosion resistance for the mechanical components. The innovation in layer technology results molybdenum disulfide (MoS2), diamond like carbon (DLC), cubic boron nitride (CBN) and diamond which perform satisfactory outcome. The application of the metallic coatings to carbon fibre reinforced polymer matrix composites (CFRP) has the capacity to provide considerable weight and power savings for many engineering components. The green material for lubricant and additives such as the use of sunflower oil which possesses good oxidation resistance and the use of mallee leaves as bio-degradable solvent are used to answer the demand of the environmentally friendly material with good performance. The tribology research implementation for energy efficiency also touches the simple things around us such as: erasing the laser-print in a paper with different abrasion techniques. For the technology in the engineering surface, the consideration for generating the suitable surface of the components in running-in period has been discussed in order to prolong the components life and reduce the machine downtime. The conclusion, tribology can result in reducing manufacturing time, reducing the maintenance requirements, prolonging the service interval, improving durability, reliability and mechanical components life, and reducing harmful exhaust emission and waste. All of these advantages will increase the energy efficiency and the economic benefits.

  19. Ordering layers of [bmim][PF6] ionic liquid on graphite surfaces: molecular dynamics simulation.

    PubMed

    Maolin, Sha; Fuchun, Zhang; Guozhong, Wu; Haiping, Fang; Chunlei, Wang; Shimou, Chen; Yi, Zhang; Jun, Hu

    2008-04-01

    Microscopic structures of room temperature ionic liquid (IL) [bmim][PF6] on hydrophobic graphite surfaces have been studied in detail by molecular dynamics simulation. It is clearly shown that both the mass and electron densities of the surface adsorbed ionic liquid are oscillatory, and the first peak adjacent to the graphite surface is considerably higher than others, corresponding to a solidlike IL bottom layer of 6 angstroms thick. Three IL layers are indicated between the graphite surface and the inner bulk IL liquid. The individually simulated properties of single-, double-, and triple-IL layers on the graphite surface are very similar to those of the layers between the graphite surface and the bulk liquid, indicating an insignificant effect of vapor-IL interface on the ordered IL layers. The simulation also indicates that the imidazolium ring and butyl tail of the cation (bmim+) of the IL bottom layer lie flat on the graphite surface.

  20. Particle image velocimetry for the Surface Tension Driven Convection Experiment using a particle displacement tracking technique

    NASA Technical Reports Server (NTRS)

    Wernet, Mark P.; Pline, Alexander D.

    1991-01-01

    The Surface Tension Driven Convection Experiment (STDCE) is a Space Transportation System flight experiment to study both transient and steady thermocapillary fluid flows aboard the USML-1 Spacelab mission planned for 1992. One of the components of data collected during the experiment is a video record of the flow field. This qualitative data is then quantified using an all electronic, two-dimensional particle image velocimetry technique called particle displacement tracking (PDT) which uses a simple space domain particle tracking algorithm. The PDT system is successful in producing velocity vector fields from the raw video data. Application of the PDT technique to a sample data set yielded 1606 vectors in 30 seconds of processing time. A bottom viewing optical arrangement is used to image the illuminated plane, which causes keystone distortion in the final recorded image. A coordinate transformation was incorporated into the system software to correct this viewing angle distortion. PDT processing produced 1.8 percent false identifications, due to random particle locations. A highly successful routine for removing the false identifications was also incorporated, reducing the number of false identifications to 0.2 percent.

  1. Particle image velocimetry for the surface tension driven convection experiment using a particle displacement tracking technique

    NASA Technical Reports Server (NTRS)

    Wernet, Mark P.; Pline, Alexander D.

    1991-01-01

    The Surface Tension Driven Convection Experiment (STDCE) is a Space Transportation System flight experiment to study both transient and steady thermocapillary fluid flows aboard the USML-1 Spacelab mission planned for 1992. One of the components of data collected during the experiment is a video record of the flow field. This qualitative data is then quantified using an all electronic, two-dimensional particle image velocimetry technique called particle displacement tracking (PDT) which uses a simple space domain particle tracking algorithm. The PDT system is successful in producing velocity vector fields from the raw video data. Application of the PDT technique to a sample data set yielded 1606 vectors in 30 seconds of processing time. A bottom viewing optical arrangement is used to image the illuminated plane, which causes keystone distortion in the final recorded image. A coordinate transformation was incorporated into the system software to correct this viewing angle distortion. PDT processing produced 1.8 percent false identifications, due to random particle locations. A highly successful routine for removing the false identifications was also incorporated, reducing the number of false identifications to 0.2 percent.

  2. Analytic expressions for atomic layer deposition: Coverage, throughput, and materials utilization in cross-flow, particle coating, and spatial atomic layer deposition

    SciTech Connect

    Yanguas-Gil, Angel; Elam, Jeffrey W.

    2014-05-15

    In this work, the authors present analytic models for atomic layer deposition (ALD) in three common experimental configurations: cross-flow, particle coating, and spatial ALD. These models, based on the plug-flow and well-mixed approximations, allow us to determine the minimum dose times and materials utilization for all three configurations. A comparison between the three models shows that throughput and precursor utilization can each be expressed by universal equations, in which the particularity of the experimental system is contained in a single parameter related to the residence time of the precursor in the reactor. For the case of cross-flow reactors, the authors show how simple analytic expressions for the reactor saturation profiles agree well with experimental results. Consequently, the analytic model can be used to extract information about the ALD surface chemistry (e.g., the reaction probability) by comparing the analytic and experimental saturation profiles, providing a useful tool for characterizing new and existing ALD processes.

  3. Optical detector having a plurality of matrix layers with cobalt disilicide particles embedded therein

    NASA Technical Reports Server (NTRS)

    Fathauer, Robert W. (Inventor); Schowalter, Leo (Inventor)

    1994-01-01

    Silicon and metal are coevaporated onto a silicon substrate in a molecular beam epitaxy system with a larger than stoichiometric amount of silicon so as to epitaxially grow particles of metal silicide embedded in a matrix of single crystal epitaxially grown silicon. The particles interact with incident photons by resonant optical absorption at the surface plasmon resonance frequency. Controlling the substrate temperature and deposition rate and time allows the aspect ratio of the particles to be tailored to desired wavelength photons and polarizations. The plasmon energy may decay as excited charge carriers of phonons, either of which can be monitored to indicate the amount of incident radiation at the selected frequency and polarization.

  4. Surface-layer protein from Caulobacter crescentus: expression, purification and X-ray crystallographic analysis.

    PubMed

    Jones, Michael D; Chan, Anson C K; Nomellini, John F; Murphy, Michael E P; Smit, John

    2016-09-01

    Protein surface layers are self-assembling, paracrystalline lattices on the surface of many prokaryotes. Surface-layer proteins have not benefited from widespread structural analysis owing to their resistance to crystallization. Here, the successful expression of a truncated version of RsaA, the surface-layer protein from Caulobacter crescentus, from a Caulobacter protein-expression system is reported. The purification, crystallization and initial X-ray diffraction analysis of the truncated RsaA, the largest surface-layer protein studied to date and the first from a Gram-negative bacterium, are also reported. PMID:27599857

  5. Mass loading of soil particles on plant surfaces

    SciTech Connect

    Pinder, J.E. III; McLeod, K.W. )

    1989-12-01

    Radionuclide-bearing soil particles on plant surfaces can be ingested and contribute to human dose, but evaluating the potential dose is limited by the relatively few data available on the masses of soil particles present on plant surfaces. This report summarizes mass loading data (i.e., mass of soil per unit of vegetation) for crops in the southeastern United States and compares these data to (1) those from other regions and (2) the mass loadings used in radionuclide transfer models to predict soil contamination of plant surfaces. Mass loadings were estimated using the 238Pu content of crops as an indicator of soil on plant surfaces. Crops were grown in two soils: a sandy clay loam soil and a loamy sand soil. Concentrations of soil on southeastern crops (i.e., mg soil g-1 plant) differed by more than a factor of 100 due to differences in crop growth form and biomass. Mean concentrations ranged from 1.7 mg g-1 for corn to 260 mg g-1 for lettuce. Differences in mass loadings between soils were less than those among crops. Concentrations differed by less than a factor of two between the two soil types. Because of (1) the differences among crops and (2) the limited data available from other systems, it is difficult to draw conclusions regarding regional or climatic variation in mass loadings. There is, however, little evidence to suggest large differences among regions. The mass loadings used to predict soil contamination in current radionuclide transfer models appear to be less than those observed for most crops.

  6. Laser Absorption and Particle Acceleration at the Critical Surface

    NASA Astrophysics Data System (ADS)

    May, J.; Tonge, J.; Mori, W. B.; Fiuza, F.; Fonseca, R.; Silva, L. O.

    2014-10-01

    Using high intensity lasers (I >= 5 ×1019 W /cm2) to accelerate particles at the critical surface offers the potential to deliver high fluence particle beams into dense matter. Potential applications include Fast Ignition Inertial Confinement Fusion, Radiation Pressure Acceleration, and probing high-density matter for basic plasma research. In order to tailor the beam characteristics of laser conversion efficiency, energy spectrum, beam divergence, and accelerated species (ions or electrons) to the given application - and of course to interpret the results of experiments - it is key to have an understanding of the underlying absorption and acceleration mechanisms. Much theoretical and simulation work has been done on this regime in recent years, and although it has become clear that mechanisms often invoked at lower intensities (i.e. JxB and Bruenel heating) are less or unimportant in these systems, debate still exists as to exactly what mechanisms will play the dominant role in laboratory relevant scenarios. We present recent results of simulations with the Particle-in-Cell code OSIRIS which sheds light on these issues. The authors acknowledge the support of the DOE Fusion Science Center for Extreme States of Matter and Fast Ignition Physics under DOE Contract No. FC02-04ER54789 and DOE contracts DE-NA0001833 and DE-SC-0008316, and NSF grant ACI-13398893.

  7. Structural properties of particle deposits at heterogeneous surfaces

    NASA Astrophysics Data System (ADS)

    Stojiljković, D.; Šćepanović, J. R.; Vrhovac, S. B.; Švrakić, N. M.

    2015-06-01

    The random sequential adsorption (RSA) approach is used to analyze adsorption of spherical particles of a fixed radius on nonuniform flat surfaces covered by rectangular cells. The configuration of the cells (heterogeneities) was produced by performing RSA simulations to a prescribed coverage fraction θ_0{(cell)} . Adsorption was assumed to occur if the particle (projected) center lies within a rectangular cell area, i.e. if sphere touches the cells. The jammed-state properties of the model were studied for different values of cell size α (comparable with the adsorbing particle size) and density θ_0{(cell)} . Numerical simulations were carried out to investigate adsorption kinetics, jamming coverage, and structure of coverings. Structural properties of the jammed-state coverings were analyzed in terms of the radial distribution function g(r) and distribution of the Delaunay ‘free’ volumes P(v). It was demonstrated that adsorption kinetics and the jamming coverage decreased significantly, at a fixed density θ_0{(cell)} , when the cell size α increased. The predictions following from our calculation suggest that the porosity (pore volumes) of deposited monolayer can be controlled by the size and shape of landing cells, and by anisotropy of the cell deposition procedure.

  8. Wind induced mixing processes in the coastal surface layer

    NASA Astrophysics Data System (ADS)

    Fraunie, Philippe; Schaeffer, Amandine; Molcard, Anne; Forget, Philippe; Garreau, Pierre; Poitevin, Joel

    2010-05-01

    Mesoscale and submescale patterns participate in mixing processes in the coastal surface layer. A process oriented numerical investigation using MARS 3D code and high resolution atmospheric forcing using AROME is presented by comparison with HF radar measurements in the Gulf of Lions, Western Mediterranean Sea. As a result, wind reversal conditions have been observed to be responsible for inertial motion and anticyclonic eddy formation when vertical mixing due to internal waves is expected to erode the halocline. Acknowledgements : MeteoFrance and Ifremer support Amandine Schaeffer's PhD. This work is part of the GIRAC project in the framework of the Pole Mer http://polemerpaca.tvt.fr/ References : André G., Garreau P., Garnier V., Fraunie P., 2005. Modelled variability of the sea surface circulation in the North-western Mediterranean Sea and in the Gulf of Lions. Ocean Dynamics, 55: 294-308 André G., Garreau P., Fraunié P., (2009) Mesoscale slope current variability in the Gulf of Lions. Interpretation of in-situ measurements using a three-dimensional model, Cont. Shelf Res.29, 407-423 Bouttier F., 2007, "AROME, avenir de la prévision régionale", La Météorologie, 58, 12-20 Langlais C., Barnier B., Fraunié P. and Schiller A. 2009b: Resolving the diurnal variability of atmospheric forcing in a coastal ocean circulation model of the Gulf of Lions (NW Mediterranean): impact on the thermodynamical state of the upper ocean. Submitted. Schaeffer A. Molcard A. Forget P. Fraunié P. Gareau P. Generation mechanism of sub-mesoscale eddy in the Gulf of Lions : radar observation and modelling. Submitted Xing J., A.M. Davies, P. Fraunié, Model studies of near-inertial motion on the continental shelf off northeast Spain : a 3D/2D model comparison study, 24p, J. Geophys. Res., 109, C01017, doi:10.1029/2003JC001822, 2004.

  9. The surface and through crack problems in layered orthotropic plates

    NASA Technical Reports Server (NTRS)

    Erdogan, Fazil; Wu, Binghua

    1991-01-01

    An analytical method is developed for a relatively accurate calculation of Stress Intensity Factors in a laminated orthotropic plate containing a through or part-through crack. The laminated plate is assumed to be under bending or membrane loading and the mode 1 problem is considered. First three transverse shear deformation plate theories (Mindlin's displacement based first-order theory, Reissner's stress-based first-order theory, and a simple-higher order theory due to Reddy) are reviewed and examined for homogeneous, laminated and heterogeneous orthotropic plates. Based on a general linear laminated plate theory, a method by which the stress intensity factors can be obtained in orthotropic laminated and heterogeneous plates with a through crack is developed. Examples are given for both symmetrically and unsymmetrically laminated plates and the effects of various material properties on the stress intensity factors are studied. In order to implement the line-spring model which is used later to study the surface crack problem, the corresponding plane elasticity problem of a two-bonded orthotropic plated containing a crack perpendicular to the interface is also considered. Three different crack profiles: an internal crack, an edge crack, and a crack terminating at the interface are considered. The effect of the different material combinations, geometries, and material orthotropy on the stress intensity factors and on the power of stress singularity for a crack terminating at the interface is fully examined. The Line Spring model of Rice and Levy is used for the part-through crack problem. The surface crack is assumed to lie in one of the two-layered laminated orthotropic plates due to the limitation of the available plane strain results. All problems considered are of the mixed boundary value type and are reduced to Cauchy type of singular integral equations which are then solved numerically.

  10. Dual Nature of Heat Flux in Stable Atmospheric Surface Layer

    NASA Astrophysics Data System (ADS)

    Srivastava, P.; Sharan, M.

    2015-12-01

    The behavior of heat flux (H) with respect to the stability parameter (ζ) in stable surface layer (SSL) is analyzed with in the framework of Monin-Obukhov similarity (MOS) theory. The analytical expressions of H are obtained as functions of wind speed (U) and wind shear (dU/dz) using the linear similarity functions and accordingly two cases, (i) U = δ (constant) and (ii) dU/dz = δ are considered. The mathematical analysis shows that the magnitude of H increases with ζ till it attains a maximum value at ζ =ζc and then starts decreasing with increasing stability suggesting the dual characteristic of heat flux with stability parameter. The point of maximum heat flux is found to be dependent on the roughness length (z0) as well as the height above the surface. An attempt has been made to analyze the sensitivity of this dual characteristic of H with ζ using the non-linear similarity functions. The analysis shows that the dual nature of H persists in the case of linear as well as non-linear similarity functions. However, the point of extremum appears to be dependent on the nature of the similarity functions. Turbulent data over a tropical site Ranchi (India) is analyzed to validate the observed nature of H with the theoretical nature as predicted by MOS. The analysis of observational data reveals the non-existence of any preferred stability state in SSL as speculated by Wang and Bras (2010, 2011) and supports the conclusions of Malhi 1995, Derbyshire 1999, van de Wiel et al. 2007, Basu et al. 2008, and van de Wiel et al. 2011. Thus, the non-uniqueness of MOS equations does not appear to be a mathematical artifact and it is consistent with the observations as far as the nature of heat flux with respect to stability parameter in SSL is concerned.

  11. Surface Passivation by Quantum Exclusion Using Multiple Layers

    NASA Technical Reports Server (NTRS)

    Hoenk, Michael E. (Inventor)

    2013-01-01

    A semiconductor device has a multilayer doping to provide improved passivation by quantum exclusion. The multilayer doping includes a plurality M of doped layers, where M is an integer greater than 1. The dopant sheet densities in the M doped layers need not be the same, but in principle can be selected to be the same sheet densities or to be different sheet densities. M-1 interleaved layers provided between the M doped layers are not deliberately doped (also referred to as "undoped layers"). Structures with M=2, M=3 and M=4 have been demonstrated and exhibit improved passivation.

  12. Surface pressure fluctuations in hypersonic turbulent boundary layers

    NASA Technical Reports Server (NTRS)

    Raman, K. R.

    1974-01-01

    The surface pressure fluctuations on a flat plate model at hypersonic Mach numbers of 5.2, 7.4 and 10.4 with an attached turbulent boundary layer were measured using flush mounted small piezoelectric sensors. A high frequency resolution of the pressure field was achieved using specially designed small piezoelectric sensors that had a good frequency response well above 300 KHz. The RMS pressures and non-dimensional energy spectra for all above Mach numbers are presented. The convective velocities, obtained from space time correlation considerations are equal to 0.7 U sub infinity. The results indicate the RMS pressures vary from 5 to 25 percent of the mean static pressures. The ratios of RMS pressure to dynamic pressure are less than the universally accepted subsonic value of 6 x 10/3. The ratio decreases in value as the Mach number or the dynamic pressure is increased. The ratio of RMS pressure to wall shear for Mach number 7.4 satisfies one smaller than or equal to p/tau sub w smaller than or equal to three.

  13. Planetary boundary layer response to surface temperature anomalies forcing

    NASA Astrophysics Data System (ADS)

    Perrot, Xavier; Lapeyre, Guillaume; Plougonven, Riwal

    2015-04-01

    Recent studies showed that strong sea surface temperature (SST) fronts, on the scale of the western boundary currents, strongly affect the planetary boundary layer (PBL) but also all the troposphere. This renewed the interest of air-sea interactions at oceanic meso-scales. Mainly two mechanisms are proposed in the literature, the first one (due to Wallace et al 1989) is based on the destabilization of the PBL above SST anomalies, the second one (Lindzen and Nigam 1987) is based on the pressure anomalies linked to the atmosphere temperature adjustment to the SST. These two mechanisms predict different responses of the PBL to the SST. We did numerical simulations with a meso-scale atmospheric model (WRF) with the same configuration as the one described in Lambert et al 2013. The model is forced by a SST anomaly which is first a zonally or meridionally constant field and secondly a field of meso-scale structures. Firstly we studied the influence of the initial wind strength on the PBL response for the two different types of SST anomalies. We showed that the dominant mechanism can change according to weak or strong wind and to the orientation of the SST anomaly. Secondly after considering a dry atmosphere we switched on the humidity in our configuration. We studied how it influences the PBL response and whether the mechanism driving the PBL response is still the same as in the dry case.

  14. Experimental Investigation of Turbulent Momentum Transfer in a Neutral Boundary Layer over a Rough Surface

    NASA Astrophysics Data System (ADS)

    Tomas, Severine; Eiff, Olivier; Masson, Valery

    2011-03-01

    The turbulent characteristics of the neutral boundary layer developing over rough surfaces are not well predicted with operational weather-forecasting models. The problem is attributed to inadequate mixing-length models, to the anisotropy of the flow and to a lack of controlled experimental data against which to validate numerical studies. Therefore, in order to address directly the modelling difficulties for the development of a neutral boundary layer over rough surfaces, and to investigate the turbulent momentum transfer of such a layer, a set of hydraulic flume experiments were carried out. In the experiments, the mean and turbulent quantities were measured by a particle image velocimetry (PIV) technique. The measured velocity variances and fluxes {(overline{{ui^'{uj^')} in longitudinal vertical planes allowed the vertical and longitudinal gradients (∂/∂ z and ∂/∂ x) of the mean and turbulent quantities (fluxes, variances and third-order moments) to be evaluated and the terms of the evolution equations for ∂ e/∂ t, {partial overline{u^' 2}}/partial t}, {partial overline{w^' 2}}/partial t} and {partial overline{{u^'{w^'/partial t} to be quantified, where e is the turbulent kinetic energy. The results show that the pressure-correlation terms allow the turbulent energy to be transferred equitably from {overline{{u^'2}} to {overline{{w^'2}}. It appears that the repartition between the constitutive terms of the budget of e, {overline{{u^'2}}, {overline{{w^'2}} and {overline{{u^'{w^' is not significantly affected by the development of the rough neutral boundary layer. For the whole evolution, the transfers of energy are governed by the same terms that are also very similar to the smooth-wall case. The PIV measurements also allowed the spatial integral scales to be computed directly and to be compared with the dissipative and mixing length scales, which were also computed from the data.

  15. Observations of the sensitivity of beam attenuation to particle size in a coastal bottom boundary layer

    NASA Astrophysics Data System (ADS)

    Hill, P. S.; Boss, E.; Newgard, J. P.; Law, B. A.; Milligan, T. G.

    2011-02-01

    The goal of this study was to test the hypothesis that the aggregated state of natural marine particles constrains the sensitivity of optical beam attenuation to particle size. An instrumented bottom tripod was deployed at the 12-m node of the Martha's Vineyard Coastal Observatory to monitor particle size distributions, particle size-versus-settling-velocity relationships, and the beam attenuation coefficient (cp) in the bottom boundary layer in September 2007. An automated in situ filtration system on the tripod collected 24 direct estimates of suspended particulate mass (SPM) during each of five deployments. On a sampling interval of 5 min, data from a Sequoia Scientific LISST 100x Type B were merged with data from a digital floc camera to generate suspended particle volume size distributions spanning diameters from approximately 2 μm to 4 cm. Diameter-dependent densities were calculated from size-versus-settling-velocity data, allowing conversion of the volume size distributions to mass distributions, which were used to estimate SPM every 5 min. Estimated SPM and measured cp from the LISST 100x were linearly correlated throughout the experiment, despite wide variations in particle size. The slope of the line, which is the ratio of cp to SPM, was 0.22 g m-2. Individual estimates of cp:SPM were between 0.2 and 0.4 g m-2 for volumetric median particle diameters ranging from 10 to 150 μm. The wide range of values in cp:SPM in the literature likely results from three factors capable of producing factor-of-two variability in the ratio: particle size, particle composition, and the finite acceptance angle of commercial beam-transmissometers.

  16. Rate of evolution of the specific surface area of surface snow layers.

    PubMed

    Cabanes, Axel; Legagneux, Loïc; Dominé, Florent

    2003-02-15

    The snowpack can impact atmospheric chemistry by exchanging adsorbed or dissolved gases with the atmosphere. Modeling this impact requires the knowledge of the specific surface area (SSA) of snow and its variations with time. We have therefore measured the evolution of the SSA of eight recent surface snow layers in the Arctic and the French Alps, using CH4 adsorption at liquid nitrogen temperature (77 K). The SSA of fresh snow layers was found to decrease with time, from initial values in the range 613-1540 cm2/g to values as low as 257 cm2/g after 6 days. This is explained by snow metamorphism, which causes modifications in crystal shapes, here essentially crystal rounding and the disappearance of microstructures. A parametrization of the rate of SSA decrease is proposed. We fit the SSA decrease to an exponential law and find that the time constant alpha(exp) (day(-1)) depends on temperature according to alpha(exp) = 76.6 exp (-1708/7), with Tin kelvin. Our parametrization predicts that the SSA of a snow layer evolving at -40 degrees C will decrease by a factor of 2 after 14 days, while a similar decrease at -1 degrees C will only require 5 days. Wind was found to increase the rate of SSA decrease, but insufficient data did not allow a parametrization of this effect. PMID:12636262

  17. Spin-glass-like freezing of inner and outer surface layers in hollow γ-Fe2O3 nanoparticles

    NASA Astrophysics Data System (ADS)

    Khurshid, Hafsa; Lampen-Kelley, Paula; Iglesias, Òscar; Alonso, Javier; Phan, Manh-Huong; Sun, Cheng-Jun; Saboungi, Marie-Louise; Srikanth, Hariharan

    2015-10-01

    Disorder among surface spins is a dominant factor in the magnetic response of magnetic nanoparticle systems. In this work, we examine time-dependent magnetization in high-quality, monodisperse hollow maghemite nanoparticles (NPs) with a 14.8 ± 0.5 nm outer diameter and enhanced surface-to-volume ratio. The nanoparticle ensemble exhibits spin-glass-like signatures in dc magnetic aging and memory protocols and ac magnetic susceptibility. The dynamics of the system slow near 50 K, and become frozen on experimental time scales below 20 K. Remanence curves indicate the development of magnetic irreversibility concurrent with the freezing of the spin dynamics. A strong exchange-bias effect and its training behavior point to highly frustrated surface spins that rearrange much more slowly than interior spins. Monte Carlo simulations of a hollow particle corroborate strongly disordered surface layers with complex energy landscapes that underlie both glass-like dynamics and magnetic irreversibility. Calculated hysteresis loops reveal that magnetic behavior is not identical at the inner and outer surfaces, with spins at the outer surface layer of the 15 nm hollow particles exhibiting a higher degree of frustration. Our combined experimental and simulated results shed light on the origin of spin-glass-like phenomena and the important role played by the surface spins in magnetic hollow nanostructures.

  18. Spin-glass-like freezing of inner and outer surface layers in hollow γ-Fe2O3 nanoparticles.

    PubMed

    Khurshid, Hafsa; Lampen-Kelley, Paula; Iglesias, Òscar; Alonso, Javier; Phan, Manh-Huong; Sun, Cheng-Jun; Saboungi, Marie-Louise; Srikanth, Hariharan

    2015-01-01

    Disorder among surface spins is a dominant factor in the magnetic response of magnetic nanoparticle systems. In this work, we examine time-dependent magnetization in high-quality, monodisperse hollow maghemite nanoparticles (NPs) with a 14.8 ± 0.5 nm outer diameter and enhanced surface-to-volume ratio. The nanoparticle ensemble exhibits spin-glass-like signatures in dc magnetic aging and memory protocols and ac magnetic susceptibility. The dynamics of the system slow near 50 K, and become frozen on experimental time scales below 20 K. Remanence curves indicate the development of magnetic irreversibility concurrent with the freezing of the spin dynamics. A strong exchange-bias effect and its training behavior point to highly frustrated surface spins that rearrange much more slowly than interior spins. Monte Carlo simulations of a hollow particle corroborate strongly disordered surface layers with complex energy landscapes that underlie both glass-like dynamics and magnetic irreversibility. Calculated hysteresis loops reveal that magnetic behavior is not identical at the inner and outer surfaces, with spins at the outer surface layer of the 15 nm hollow particles exhibiting a higher degree of frustration. Our combined experimental and simulated results shed light on the origin of spin-glass-like phenomena and the important role played by the surface spins in magnetic hollow nanostructures. PMID:26503506

  19. Spin-glass-like freezing of inner and outer surface layers in hollow γ-Fe2O3 nanoparticles

    PubMed Central

    Khurshid, Hafsa; Lampen-Kelley, Paula; Iglesias, Òscar; Alonso, Javier; Phan, Manh-Huong; Sun, Cheng-Jun; Saboungi, Marie-Louise; Srikanth, Hariharan

    2015-01-01

    Disorder among surface spins is a dominant factor in the magnetic response of magnetic nanoparticle systems. In this work, we examine time-dependent magnetization in high-quality, monodisperse hollow maghemite nanoparticles (NPs) with a 14.8 ± 0.5 nm outer diameter and enhanced surface-to-volume ratio. The nanoparticle ensemble exhibits spin-glass-like signatures in dc magnetic aging and memory protocols and ac magnetic susceptibility. The dynamics of the system slow near 50 K, and become frozen on experimental time scales below 20 K. Remanence curves indicate the development of magnetic irreversibility concurrent with the freezing of the spin dynamics. A strong exchange-bias effect and its training behavior point to highly frustrated surface spins that rearrange much more slowly than interior spins. Monte Carlo simulations of a hollow particle corroborate strongly disordered surface layers with complex energy landscapes that underlie both glass-like dynamics and magnetic irreversibility. Calculated hysteresis loops reveal that magnetic behavior is not identical at the inner and outer surfaces, with spins at the outer surface layer of the 15 nm hollow particles exhibiting a higher degree of frustration. Our combined experimental and simulated results shed light on the origin of spin-glass-like phenomena and the important role played by the surface spins in magnetic hollow nanostructures. PMID:26503506

  20. Ammonia Surface-Atmosphere Exchange in the Arctic Marine Boundary Layer

    NASA Astrophysics Data System (ADS)

    Murphy, J. G.; Wentworth, G.; Tremblay, J. E.; Gagnon, J.; Côté, J. S.; Courchesne, I.

    2014-12-01

    The net flux of ammonia between the ocean and the atmosphere is poorly known on global and regional scales. Data from high-latitude research cruises suggest that deposition from the atmosphere to the surface dominates, but the magnitude and drivers of this flux are not well understood. In the polar marine boundary layer, the surface may be composed of not only open ocean, but also first-year or multi-year sea ice which may be covered with meltponds. To characterize the air-sea exchange of ammonia in the polar marine boundary layer, data were collected aboard the Canadian Coast Guard Ship Amundsen between July 10 and Aug 14, 2014 in the Eastern Canadian Arctic. The Ambient Ion Monitor Ion Chromatograph was used to make hourly measurements of the mixing ratio of gas phase ammonia, and the water-soluble constituents of fine particle matter (PM2.5). Fluorometry was used to measure dissolved ammonium concentrations in the ocean between 0 and 20 m, and in low-salinity melt ponds encountered in regions of extensive sea ice. Observations indicate that the atmosphere contains higher levels of ammonia than are calculated to be in equilibrium with surface reservoirs, implying net deposition of ammonia from the atmosphere. While ammonium levels tended to be higher in melt ponds, the lower water temperatures still mean that these are unlikely to be sources of NH3 to the atmosphere. The disequilibrium between atmospheric and surface reservoirs of ammonia imply relatively large sources to the atmosphere (possibly nearby bird colonies) or high consumption rates in surface waters.

  1. Effect of mechanical vibration on platinum particle agglomeration and growth in proton exchange membrane fuel cell catalyst layer

    NASA Astrophysics Data System (ADS)

    Diloyan, Georgiy

    monitored and recorded. It was observed that the mean diameter of Pt particles tested under mechanical vibration is 10% smaller than the ones that were tested under no vibration conditions. The Pt particles in the order of 2 to 2.5 nm in the pristine state have grown to 6.14 nm (after 300 hour accelerated test at no vibration condition), to 5.64 nm (after 300 hours accelerated test under 4g 20 Hz vibration condition) and to 5.55 nm (after 300 hours accelerated test under 1g 20 Hz vibration condition). The mean Pt particle diameters, after 300 hour accelerated test under 1g 40 Hz and 4g 40 Hz vibration conditions, were 5.89 nm. With an increase of the mean Pt particle diameter, the active surface area of the catalyst layer of the MEA decreases and as a result, performance of MEA and PEM fuel also decreases. It was observed that performance of the MEA tested under no vibration condition is about 10% lower than the one tested under 1g 20 Hz. The VI curve showed that the lowest performance of the MEA after 300 hour accelerated test corresponded to no vibration conditions and equaled to 7.85 Watts at 0.5 V (Pt particle size ˜ 6.14 nm) and highest performance, corresponded to the MEA tested under 1g 20 Hz, and equaled to 8.66 Watts at 0.5 V (Pt particle size ˜ 5.55 nm).

  2. An ellipsometry study of silica nanoparticle layers at the water surface.

    PubMed

    Zang, Duyang; Stocco, Antonio; Langevin, Dominique; Wei, Bingbo; Binks, Bernard P

    2009-11-01

    We have studied silica nanoparticle layers spread at the air/water interface. The surface pressure of the layers has been determined in a Langmuir trough via two orthogonal Wilhelmy plates. We observed significant differences in surface pressure according to the preparation protocol: layers spread then compressed or layers obtained after successive spreading steps. We also studied the two types of layers by multiple angle of incidence ellipsometry. We introduce a two-layer model which enables us to evaluate the radius of interfacial aggregates and their contact angle with the air/water interface. PMID:19830337

  3. Study of particle transport in the boundary layer of an electrostatic precipitator

    SciTech Connect

    Mozumdar, S.

    1986-01-01

    The design and construction of a new, nonintrusive optical instrument for the measurement of particle velocity in the boundary layer of a laboratory model electrostatic precipitator with transparent collector plates is presented. The instrument is a two-color-component laser Doppler velocimeter (LDV). It uses the blue (488.0 nm) and green (514.5 nm) beams from an argon ion laser source. It simultaneously measures two components of particle velocity, one parallel to the axis of the precipitator and the other perpendicular to the collector plate of the precipitator. These measurements are performed by detecting the Doppler frequency shift in the light scattered by the particle. The design is modular and the LDV system can be easily switched between a user selected 30/sup 0/ to 60/sup 0/ off-axis micro-LDV system and a regular LDV system. The micro-LDV instrument was used to study particle velocity in the boundary layer of a laboratory model, wireplate type electrostatic precipitator.

  4. Large-eddy simulation of a solid-particles suspension in a turbulent boundary layer

    NASA Astrophysics Data System (ADS)

    Rahman, Mustafa; Samtaney, Ravi

    2014-11-01

    We decribe a framework for the large-eddy simulation of solid particles suspended and transported within an incompressible turbulent boundary layer. The underlying approach to simulate the solid-particle laden flow is Eulerian-Eulerian in which the particles are characterized by statistical descriptors. For the fluid phase, the large-eddy simulation (LES) of incompressible turbulent boundary layer employs stretched spiral vortex subgrid-scale model and a virtual wall model similar to the work of Inoue & Pullin (J. Fluid Mech. 2011). Furthermore, a recycling method to generate turbulent inflow is implemented. For the particle phase, the direct quadrature method of moments (DQMOM) is chosen in which the weights and abscissas of the quadrature approximation are tracked directly rather than the moments themselves. The numerical method in this framework is based on a fractional-step method with an energy-conservative fourth-order finite difference scheme on a staggered mesh. It is proposed to utilize this framework to examine transport of sand in desert sandstorms. Supported by KAUST OCRF funded CRG project on simulation of sandstorms.

  5. A simple stochastic quadrant model for the transport and deposition of particles in turbulent boundary layers

    SciTech Connect

    Jin, C.; Potts, I.; Reeks, M. W.

    2015-05-15

    We present a simple stochastic quadrant model for calculating the transport and deposition of heavy particles in a fully developed turbulent boundary layer based on the statistics of wall-normal fluid velocity fluctuations obtained from a fully developed channel flow. Individual particles are tracked through the boundary layer via their interactions with a succession of random eddies found in each of the quadrants of the fluid Reynolds shear stress domain in a homogeneous Markov chain process. In this way, we are able to account directly for the influence of ejection and sweeping events as others have done but without resorting to the use of adjustable parameters. Deposition rate predictions for a wide range of heavy particles predicted by the model compare well with benchmark experimental measurements. In addition, deposition rates are compared with those obtained from continuous random walk models and Langevin equation based ejection and sweep models which noticeably give significantly lower deposition rates. Various statistics related to the particle near wall behavior are also presented. Finally, we consider the model limitations in using the model to calculate deposition in more complex flows where the near wall turbulence may be significantly different.

  6. First-order control of surface roughness at three scales: boundary layer dynamics, tracer dispersion and pebble abrasion

    NASA Astrophysics Data System (ADS)

    Jerolmack, D. J.; Litwin, K. L.; Phillips, C. B.; Martin, R. L.

    2012-12-01

    In many situations it may be appropriate to treat surfaces as smooth and particles as spherical, however here we focus on scenarios in which the roughness of the surface exerts a first-order control on flow and transport dynamics. We describe three vignettes at three different scales: (1) roughness transitions and resulting sediment transport dynamics over ~10-km distance in a desert dune field; (2) reach-scale river bed roughness and its influence on dispersion of tracer particles in bed load; and (3) the control of particle surface roughness on the nature and rate of pebble abrasion. For (1), we show how the abrupt transition from a flat surface to a dune field may be treated as a step increase in the aerodynamic roughness parameter - so long as the spatial scale considered is significantly larger than that of an individual dune. This increase causes a spatial decline in the boundary stress downwind that may be understood using simple boundary layer theory, resulting in a factor of three decrease in the sand flux over a distance of kilometers. For (2), laboratory and field studies of tracer particles in bed load indicate that they undergo short flights separated by long rest periods having a power-law tail - even in steady flows. We hypothesize that for near-threshold transport - which predominates is coarse-grained rivers - particles become trapped in 'wells' produced by surface roughness, and their rest time is controlled by the time for the surface to scour down and release them. Laboratory observations support this hypothesis, while comparison to non-geophysical 'flows' indicates that these dynamics are generic to transport in disordered systems. Finally, for (3) we report laboratory experiments by our group and others showing how abrasion rate decreases with decreasing particle roughness. Geometric models quantitatively support the intuition that locations of high positive curvature on pebble surfaces are more susceptible to abrasion; as they are

  7. Modification of surface oxide layers of titanium targets for increasing lifetime of neutron tubes

    SciTech Connect

    Zakharov, A. M. Dvoichenkova, O. A.; Evsin, A. E.

    2015-12-15

    The peculiarities of interaction of hydrogen ions with a titanium target and its surface oxide layer were studied. Two ways of modification of the surface oxide layers of titanium targets for increasing the lifetime of neutron tubes were proposed: (1) deposition of an yttrium oxide barrier layer on the target surface; (2) implementation of neutron tube work regime in which the target is irradiated with ions with energies lower than 1000 eV between high-energy ion irradiation pulses.

  8. Drag reduction by means of dimpled surfaces in turbulent boundary layers

    NASA Astrophysics Data System (ADS)

    van Nesselrooij, M.; Veldhuis, L. L. M.; van Oudheusden, B. W.; Schrijer, F. F. J.

    2016-09-01

    Direct force measurements and particle image velocimetry (PIV) were used to investigate the drag and flow structure caused by surfaces with patterns of shallow spherical dimples with rounded edges subject to turbulent boundary layers. Drag reduction of up to 4 % is found compared to a flat surface. The largest drag reduction was found at the highest tested Reynolds number of 40,000 (based on dimple diameter). A favorable trend promises further improvements at higher Reynolds numbers. PIV revealed the absence of significant separation inside the dimples but did show the existence of a converging/diverging flow in the upstream and downstream dimple half, respectively. This leads to the rejection of theories proposed by other authors concerning the mechanism responsible for drag reduction. Instead, a fundamental dependence on pattern orientation is observed. Furthermore, preliminary Reynolds-averaged Navier-Stokes (RANS) simulations have been compared with the PIV data. Although the large-scale mean flows show good agreement, the numerical simulation predicts no drag reduction. As the RANS approach is inherently incapable of resolving effects on the behavior of small-scale turbulence structure, the origin of drag reduction is attributed to effects on the small-scale turbulence, which is not resolved in the simulations. It is argued that dimples, when placed in well-designed patterns to create the necessary large-scale flow structure, lead to drag reduction by affecting the turbulent structures in the boundary layer, possibly in a way similar to spanwise oscillations of the wall.

  9. Layer-by-layer construction of the heparin/fibronectin coatings on titanium surface:stability and functionality

    NASA Astrophysics Data System (ADS)

    Li, Guicai; Yang, Ping; Huang, Nan

    Layer-by-layer assembly as a versatile bottom-up nanofabrication technique has been widely used in the development of biomimetic materials with superior mechanical and biological properties. In this study, layer-by-layer assembled heparin/fibronectin biofunctional films were fabricated on titanium (Ti) surface to enhance the blood anticoagulation and accelerate the endothelialization simultaneously. The wettability and chemical changes of the assembled films were investigated by static water contact angle measurement and fourier transform infrared spectroscopy (FTIR). The morphology of modified Ti surfaces were observed using scanning electron microscopy (SEM). The real time assembly process was in-situ monitored by quartz crystal microbalance with dissipation (QCM-D). The stability of the films was evaluated by measuring the changes in wettability and the quantity of heparin and fibronectin on the surfaces. The anticoagulation properties of the films were quantitatively rated using Activated partial thromboplastin time (APTT) analysis. New peaks of hydroxyl and amino group were observed on the assembled Ti srufaces by FTIR. The contact angles varied among the films with different bilayer numbers, indicating the successful graft of the heparin and fibronectin layer-by-layer. QCM-D results showed that the frequency shift increased with the bilayer numbers, and the heparin and fibronectin could form multilayers. The assembly films were stable after incubation in PBS for 24 h based on the results of the contact angle measurement and the quantity of heparin and fibronectin analysis. APTT results suggested that the assembled films kept excellent antithrombotic properties. All these results revealed that the assembled heparin/fibronectin films with stabiltiy and anticoagulation property could be firmly formed on titanium surfaces. Our study further demonstrates that layer-by-layer assembly of heparin and fibronectin will provide a potential and effective tool for

  10. Accurate Sound Velocity Measurement in Ocean Near-Surface Layer

    NASA Astrophysics Data System (ADS)

    Lizarralde, D.; Xu, B. L.

    2015-12-01

    Accurate sound velocity measurement is essential in oceanography because sound is the only wave that can propagate in sea water. Due to its measuring difficulties, sound velocity is often not measured directly but instead calculated from water temperature, salinity, and depth, which are much easier to obtain. This research develops a new method to directly measure the sound velocity in the ocean's near-surface layer using multi-channel seismic (MCS) hydrophones. This system consists of a device to make a sound pulse and a long cable with hundreds of hydrophones to record the sound. The distance between the source and each receiver is the offset. The time it takes the pulse to arrive to each receiver is the travel time.The errors of measuring offset and travel time will affect the accuracy of sound velocity if we calculated with just one offset and one travel time. However, by analyzing the direct arrival signal from hundreds of receivers, the velocity can be determined as the slope of a straight line in the travel time-offset graph. The errors in distance and time measurement result in only an up or down shift of the line and do not affect the slope. This research uses MCS data of survey MGL1408 obtained from the Marine Geoscience Data System and processed with Seismic Unix. The sound velocity can be directly measured to an accuracy of less than 1m/s. The included graph shows the directly measured velocity verses the calculated velocity along 100km across the Mid-Atlantic continental margin. The directly measured velocity shows a good coherence to the velocity computed from temperature and salinity. In addition, the fine variations in the sound velocity can be observed, which is hardly seen from the calculated velocity. Using this methodology, both large area acquisition and fine resolution can be achieved. This directly measured sound velocity will be a new and powerful tool in oceanography.

  11. Effect of impression material on surface reactive layer when casting pure titanium in phosphate investment.

    PubMed

    Komasa, Y; Moriguchi, A; Asai, M; Nezumi, M; Kakimoto, K; Gonda, Y

    1998-10-01

    We evaluated the effect of impression materials used in preparation of pure titanium castings on the surface reactive layer. Surface roughness of the refractory models before and after firing was smaller when silicone rather than agar impression material was used. The surface roughness of castings prepared with T-invest varied little with the impression material. However, the surface roughness of the castings prepared with CD Titaninvest was less when silicone impression material was used. Surface hardness of the castings was slightly greater when agar impression material was used, and metallic texture analysis of the surface of the castings showed a chill layer and a columnar crystal layer extending from the surface toward the interior. A relatively non-corroded white layer and a markedly corroded black layer were observed in the chill layer, and their thickness was smaller when silicone impression material was used. Use of the Electron Probe Micro Analyzer (EPMA) to determine distribution of various elements in the superficial layer of the casting plates showed that the reactive layer contained less P and Si when silicone impression material was used rather than agar. NH4H2 PO4, which is a component of the bonding material in the investment, was present at a high concentration in the superficial layer of the agar impression material. This shows the importance of preparing refractory models with a non-water-absorbing impression material to obtain pure titanium casting plates with a smaller reactive layer.

  12. Method and system for treating an interior surface of a workpiece using a charged particle beam

    DOEpatents

    Swenson, David Richard

    2007-05-23

    A method and system of treating an interior surface on an internal cavity of a workpiece using a charged particle beam. A beam deflector surface of a beam deflector is placed within the internal cavity of the workpiece and is used to redirect the charged particle beam toward the interior surface to treat the interior surface.

  13. Thiol Adsorption on and Reduction of Copper Oxide Particles and Surfaces.

    PubMed

    Wang, Yiwen; Im, Jisun; Soares, Jason W; Steeves, Diane M; Whitten, James E

    2016-04-26

    The adsorption of 1-dodecanethiol at room temperature and at 75 °C on submicron cuprous and cupric oxide particles suspended in ethanol has been investigated by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and transmission electron microscopy. Thiol adsorption occurs in all cases via Cu-S bond formation, with partial dissolution of CuO at 75 °C and formation of a copper-thiolate complex replacement layer. Regardless of temperature, the surface of the CuO particles is essentially completely reduced to either Cu2O or metallic copper, as evidenced by loss of the characteristic Cu(2+) XPS features of dried powder samples. Companion ultrahigh-vacuum studies have been performed by dosing clean, oxygen-dosed, and ozone-treated single crystal Cu(111) with methanethiol (MT) gas at room temperature. In the latter case, the surface corresponds to CuO/Cu(111). XPS confirms MT adsorption in all cases, with an S 2p peak binding energy of 162.9 ± 0.1 eV, consistent with methanethiolate adsorption. Heating of MT-covered Cu(111) and oxygen-dosed Cu(111) leads to decomposition/desorption of the MT by 100 °C and formation of copper sulfide with an S 2p binding energy of 161.8 eV. Dosing CuO/Cu(111) with 50-200 L of MT leads to only partial reduction/removal of the CuO surface layers prior to methanethiolate adsorption. This is confirmed by ultraviolet photoelectron spectroscopy (UPS), which measures the occupied states near the Fermi level. For both the colloidal CuO and single crystal CuO/Cu(111) studies, the reduction of the Cu(2+) surface is believed to occur by formation and desorption of the corresponding dithiol prior to thiolate adsorption. PMID:27036074

  14. Thiol Adsorption on and Reduction of Copper Oxide Particles and Surfaces.

    PubMed

    Wang, Yiwen; Im, Jisun; Soares, Jason W; Steeves, Diane M; Whitten, James E

    2016-04-26

    The adsorption of 1-dodecanethiol at room temperature and at 75 °C on submicron cuprous and cupric oxide particles suspended in ethanol has been investigated by X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and transmission electron microscopy. Thiol adsorption occurs in all cases via Cu-S bond formation, with partial dissolution of CuO at 75 °C and formation of a copper-thiolate complex replacement layer. Regardless of temperature, the surface of the CuO particles is essentially completely reduced to either Cu2O or metallic copper, as evidenced by loss of the characteristic Cu(2+) XPS features of dried powder samples. Companion ultrahigh-vacuum studies have been performed by dosing clean, oxygen-dosed, and ozone-treated single crystal Cu(111) with methanethiol (MT) gas at room temperature. In the latter case, the surface corresponds to CuO/Cu(111). XPS confirms MT adsorption in all cases, with an S 2p peak binding energy of 162.9 ± 0.1 eV, consistent with methanethiolate adsorption. Heating of MT-covered Cu(111) and oxygen-dosed Cu(111) leads to decomposition/desorption of the MT by 100 °C and formation of copper sulfide with an S 2p binding energy of 161.8 eV. Dosing CuO/Cu(111) with 50-200 L of MT leads to only partial reduction/removal of the CuO surface layers prior to methanethiolate adsorption. This is confirmed by ultraviolet photoelectron spectroscopy (UPS), which measures the occupied states near the Fermi level. For both the colloidal CuO and single crystal CuO/Cu(111) studies, the reduction of the Cu(2+) surface is believed to occur by formation and desorption of the corresponding dithiol prior to thiolate adsorption.

  15. Degree of ice particle surface roughness inferred from polarimetric observations

    NASA Astrophysics Data System (ADS)

    Hioki, Souichiro; Yang, Ping; Baum, Bryan A.; Platnick, Steven; Meyer, Kerry G.; King, Michael D.; Riedi, Jerome

    2016-06-01

    The degree of surface roughness of ice particles within thick, cold ice clouds is inferred from multi-directional, multi-spectral satellite polarimetric observations over oceans, assuming a column-aggregate particle habit. An improved roughness inference scheme is employed that provides a more noise-resilient roughness estimate than the conventional best-fit approach. The improvements include the introduction of a quantitative roughness parameter based on empirical orthogonal function analysis and proper treatment of polarization due to atmospheric scattering above clouds. A global 1-month data sample supports the use of a severely roughened ice habit to simulate the polarized reflectivity associated with ice clouds over ocean. The density distribution of the roughness parameter inferred from the global 1-month data sample and further analyses of a few case studies demonstrate the significant variability of ice cloud single-scattering properties. However, the present theoretical results do not agree with observations in the tropics. In the extratropics, the roughness parameter is inferred but 74 % of the sample is out of the expected parameter range. Potential improvements are discussed to enhance the depiction of the natural variability on a global scale.

  16. Leonid's Particle Analyses from Stratospheric Balloon Collection on Xerogel Surfaces

    NASA Technical Reports Server (NTRS)

    Noever, David; Phillips, Tony; Horack, John; Porter, Linda; Myszka, Ed

    1999-01-01

    Recovered from a stratospheric balloon above 20 km on 17-18 November 1998, at least eight candidate microparticles were collected and analyzed from low-density silica xerogel collection plates. Capture time at Leonids' storm peak was validated locally along the balloon trajectory by direct video imaging of meteor fluence up to 24/hr above 98% of the Earth's atmosphere. At least one 30 micron particle agrees morphologically to a smooth, unmelted spherule and compares most closely in non-volatile elemental ratios (Mg/Si, Al/Si, and Fe/Si) to compositional data in surface/ocean meteorite collections. A Euclidean tree diagram based on composition makes a most probable identification as a non-porous stratospherically collected particle and a least probable identification as terrestrial matter or an ordinary chondrite. If of extraterrestrial origin, the mineralogical class would be consistent with a stony (S) type of silicate, olivine [(Mg,Fe)2SiO4] and pyroxene [(Mg, Fe)Si!O3)--or oxides, herecynite [(Fe,Mg) Al2O4].

  17. High-speed particle image velocimetry near surfaces.

    PubMed

    Lu, Louise; Sick, Volker

    2013-06-24

    Multi-dimensional and transient flows play a key role in many areas of science, engineering, and health sciences but are often not well understood. The complex nature of these flows may be studied using particle image velocimetry (PIV), a laser-based imaging technique for optically accessible flows. Though many forms of PIV exist that extend the technique beyond the original planar two-component velocity measurement capabilities, the basic PIV system consists of a light source (laser), a camera, tracer particles, and analysis algorithms. The imaging and recording parameters, the light source, and the algorithms are adjusted to optimize the recording for the flow of interest and obtain valid velocity data. Common PIV investigations measure two-component velocities in a plane at a few frames per second. However, recent developments in instrumentation have facilitated high-frame rate (>1 kHz) measurements capable of resolving transient flows with high temporal resolution. Therefore, high-frame rate measurements have enabled investigations on the evolution of the structure and dynamics of highly transient flows. These investigations play a critical role in understanding the fundamental physics of complex flows. A detailed description for performing high-resolution, high-speed planar PIV to study a transient flow near the surface of a flat plate is presented here. Details for adjusting the parameter constraints such as image and recording properties, the laser sheet properties, and processing algorithms to adapt PIV for any flow of interest are included.

  18. Controllable surface haptics via particle jamming and pneumatics.

    PubMed

    Stanley, Andrew A; Okamura, Allison M

    2015-01-01

    The combination of particle jamming and pneumatics allows the simultaneous control of shape and mechanical properties in a tactile display. A hollow silicone membrane is molded into an array of thin cells, each filled with coffee grounds such that adjusting the vacuum level in any individual cell rapidly switches it between flexible and rigid states. The array clamps over a pressure-regulated air chamber with internal mechanisms designed to pin the nodes between cells at any given height. Various sequences of cell vacuuming, node pinning, and chamber pressurization allow the surface to balloon into a variety of shapes. Experiments were performed to expand existing physical models of jamming at the inter-particle level to define the rheological characteristics of jammed systems from a macroscopic perspective, relevant to force-displacement interactions that would be experienced by human users. Force-displacement data show that a jammed cell in compression fits a Maxwell model and a cell deflected in the center while supported only at the edges fits a Zener model, each with stiffness and damping parameters that increase at higher levels of applied vacuum. This provides framework to tune and control the mechanical properties of a jamming haptic interface.

  19. The surface deposition of meteoric smoke particles - possible climate impact

    NASA Astrophysics Data System (ADS)

    Plane, J. M.; Dhomse, S.; Saunders, R. W.; Tian, W.; Chipperfield, M.

    2013-12-01

    There are large uncertainties in the transport and surface deposition of upper atmospheric particles, such as meteoric smoke particles (MSPs) formed in the upper mesosphere. Here we use a 3D chemistry-climate model (CCM) to simulate the transport and deposition of MSPs from the upper mesosphere. The CCM was first validated by predicting the deposition of plutonium-238 oxide nanoparticles formed after the ablation of a power unit in the upper stratosphere (~11o S) in 1964. The observed hemispheric asymmetry and timescale of Pu-238 deposition is well-captured. In the case of MSPs, the model predicts more deposition in Greenland than Antarctica by a factor of ~15, in agreement with ice core measurements. The strongest MSP deposition is predicted to occur at mid-latitudes, providing a significant source of Fe fertilization to the Southern Ocean where there is a shortage of bio-available Fe. The resulting increase in CO2 drawdown may have a significant climate impact. Map of annual mean Fe deposition rate (μmol Fe m-2 y-1)

  20. Evaluation of filter media for particle number, surface area and mass penetrations.

    PubMed

    Li, Lin; Zuo, Zhili; Japuntich, Daniel A; Pui, David Y H

    2012-07-01

    The National Institute for Occupational Safety and Health (NIOSH) developed a standard for respirator certification under 42 CFR Part 84, using a TSI 8130 automated filter tester with photometers. A recent study showed that photometric detection methods may not be sensitive for measuring engineered nanoparticles. Present NIOSH standards for penetration measurement are mass-based; however, the threshold limit value/permissible exposure limit for an engineered nanoparticle worker exposure is not yet clear. There is lack of standardized filter test development for engineered nanoparticles, and development of a simple nanoparticle filter test is indicated. To better understand the filter performance against engineered nanoparticles and correlations among different tests, initial penetration levels of one fiberglass and two electret filter media were measured using a series of polydisperse and monodisperse aerosol test methods at two different laboratories (University of Minnesota Particle Technology Laboratory and 3M Company). Monodisperse aerosol penetrations were measured by a TSI 8160 using NaCl particles from 20 to 300 nm. Particle penetration curves and overall penetrations were measured by scanning mobility particle sizer (SMPS), condensation particle counter (CPC), nanoparticle surface area monitor (NSAM), and TSI 8130 at two face velocities and three layer thicknesses. Results showed that reproducible, comparable filtration data were achieved between two laboratories, with proper control of test conditions and calibration procedures. For particle penetration curves, the experimental results of monodisperse testing agreed well with polydisperse SMPS measurements. The most penetrating particle sizes (MPPSs) of electret and fiberglass filter media were ~50 and 160 nm, respectively. For overall penetrations, the CPC and NSAM results of polydisperse aerosols were close to the penetration at the corresponding median particle sizes. For each filter type, power

  1. Non-extensive treatment of surface nucleation on glass particles

    NASA Astrophysics Data System (ADS)

    Nascimento, Marcio Luis Ferreira

    2012-12-01

    Experimental data of phase transformation kinetics was used to fit a new model based on a non-extensive formalism derived from Tsallis thermostatistics and another based on the Johnson-Mehl-Avrami-Yerofeyev-Kolmogorov (JMAYK) theory. For this we considered the same experimental parameters such as crystal geometric factor g, the density of nucleation sites, NS and crystal growth rates U on glass powders. The kinetics of nucleation and growth of diopside crystals (MgOṡCaOṡ2SiO2) on the glass surface at 825 °C (Tg˜727 °C) were studied. Treatments for sinter-crystallization were performed in compacts of diopside glass particles by varying the treatment time. The crystallized fraction of the samples subjected to such treatments, which develop from the particles’ surface toward their volume, was characterized by means of optical microscopy and X-ray diffraction. The two models were then fitted to the measured crystallized fraction data and compared to each other. It was found that surface nucleation occurs very rapidly from a random number of active sites. The JMAYK theory describes the case of fast heterogeneous nucleation from a constant number of sites on the glass surface. The Tsallis approach is better than the JMAYK model considering that the q factor equals 1.268±0.062 and does not require taking into account the change in crystallization mode from three dimensional to one dimensional as JMAYK predicts, and this is advantageous. Furthermore, Tsallis thermostatistics contains the Austin-Rickett model as a special and limiting case study for this system. A generalized Avrami plot is also presented.

  2. A two-dimensional particle simulation of the magnetopause current layer

    SciTech Connect

    Berchem, J.; Okuda, H.

    1988-11-01

    We have developed a 2/1/2/-D (x, y, v/sub x/, v/sub y/, v/sub z/) electromagnetic code to study the formation and the stability of the magnetopause current layer. This code computes the trajectories of ion and electron particles in their self-consistently generated electromagnetic field and an externally imposed 2-D vacuum dipolar magnetic field. The results presented here are obtained for the simulation of the solar wind-magnetosphere interaction in the subsolar region of the equatorial plane. We observe the self-consistent establishment of a current layer resulting from both diamagnetic drift and E /times/ B drift due to the charge separation. The simulation results show that during the establishment of the current layer, its thickness is of the order of the hybrid gyroradius /rho//sub H/ = ..sqrt../rho//sub i//rho//sub e/ predicted by the Ferraro-Rosenbluth model. However, diagnostics indicate that the current sheet is subject to an instability which broadens the width of the current layer. Ripples with amplitudes of the order of the ion gyroradius appear at the interface between the field and the particles. These pertubations are observed both on the electrostatic field and on the compressional component of the magnetic field. This instability has a frequency of the order of the local ion cyclotron frequency. However, the modulation propagates in the same direction as the electron diamagnetic drift which indicates that the instability is not a classical gradient-driven instability, such as the lower hybrid or ion drift cyclotron instabilities. The nonlinear phase of the instability is characterized by the filamentation of the current layer which causes anomalous diffusion inside the central current sheet. 79 refs., 7 figs.

  3. TASTRAK spectroscopy of polonium-210 alpha-particle activity at bone surfaces: Evidence for a concentrated surface deposit less than 3 {mu}m deep

    SciTech Connect

    Salmon, P.L.; Henshaw, D.L.; Keitch, P.A.; Allen, J.E.; Fews, A.P.

    1994-10-01

    The technique of {alpha}-particle spectroscopy by CR-39 type TASTRAK plastic has been used to study the depth distribution of natural {alpha}-particle emitters at the surface of human bone. The predominant component of this {alpha}-particle activity was {sup 210}Po supported by {sup 210}Pb, although a smaller activity of {sup 226}Ra was also detected. Autopsy samples of human femur and cranium were obtained from subjects age 63 to 86. Both cortical and trabecular surfaces were analyzed. The results indicate that {sup 210}Pb-supported {sup 210}Po is concentrated at the surfaces of human bone from elderly subjects, in a narrow band 3 {mu}m deep or less, by a factor of about four. As a result, the {alpha}-particle dose to the nuclei of cells lining bone surfaces is around 1.8 times greater than that calculated for a uniform volume distribution. Polonium-210 activity indicates the distribution of {sup 210}Pb, and of stable lead, received by continuous intake throughout life at a very low level. A persistent bone surface concentration of lead and other osteotropic metals may be associated with the hypermineralized layer about 1 {mu}m thick which occurs at the surface of resting bone mineral. 31 refs., 9 figs., 3 tabs.

  4. Parameterizing Urban Canopy Layer transport in an Lagrangian Particle Dispersion Model

    NASA Astrophysics Data System (ADS)

    Stöckl, Stefan; Rotach, Mathias W.

    2016-04-01

    The percentage of people living in urban areas is rising worldwide, crossed 50% in 2007 and is even higher in developed countries. High population density and numerous sources of air pollution in close proximity can lead to health issues. Therefore it is important to understand the nature of urban pollutant dispersion. In the last decades this field has experienced considerable progress, however the influence of large roughness elements is complex and has as of yet not been completely described. Hence, this work studied urban particle dispersion close to source and ground. It used an existing, steady state, three-dimensional Lagrangian particle dispersion model, which includes Roughness Sublayer parameterizations of turbulence and flow. The model is valid for convective and neutral to stable conditions and uses the kernel method for concentration calculation. As most Lagrangian models, its lower boundary is the zero-plane displacement, which means that roughly the lower two-thirds of the mean building height are not included in the model. This missing layer roughly coincides with the Urban Canopy Layer. An earlier work "traps" particles hitting the lower model boundary for a recirculation period, which is calculated under the assumption of a vortex in skimming flow, before "releasing" them again. The authors hypothesize that improving the lower boundary condition by including Urban Canopy Layer transport could improve model predictions. This was tested herein by not only trapping the particles, but also advecting them with a mean, parameterized flow in the Urban Canopy Layer. Now the model calculates the trapping period based on either recirculation due to vortex motion in skimming flow regimes or vertical velocity if no vortex forms, depending on incidence angle of the wind on a randomly chosen street canyon. The influence of this modification, as well as the model's sensitivity to parameterization constants, was investigated. To reach this goal, the model was

  5. Turbulent dusty boundary layer in an ANFO surface-burst explosion. Technical report 1 Oct 88-31 Dec 89

    SciTech Connect

    Kuhl, A.L.; Ferguson, R.E.; Chen, K.; Collins, J.P.

    1992-08-01

    This paper describes the results of numerical simulations of the dusty, turbulent boundary layer created by a surface burst explosion. The blast wave was generated by the detonation of a 600-T hemisphere of ANFO, similar to those used in large-scale field tests. The surface was assumed to be ideally noncratering but contained an initial loose layer of dust. The dust-air mixture in this fluidized bed was modeled as a dense gas (i.e., an equilibrium model, valid for very-small-diameter dust particles). The evolution of the flow was calculated by a high-order Godunov code that solves the nonsteady conservation laws. Shock interactions with dense layer generated vorticity near the wall-similar to viscous, no-slip effects found in clean flows. The resulting wall shear layer was unstable, and rolled up into large-scale rotational structures. These structures entrained dense material from the wall layer and created a chaotically striated flow. The boundary layer grew due to merging of the large-scale structures and due to local entrainment of the dense material from the fluidized bed.

  6. Antimicrobial and antioxidant surface modification of cellulose fibers using layer-by-layer deposition of chitosan and lignosulfonates.

    PubMed

    Li, Hui; Peng, Lincai

    2015-06-25

    To confer cellulose fibers antimicrobial and antioxidant activities, chitosan (CS)/lignosulfonates (LS) multilayers were constructed on fibers surfaces through layer-by-layer deposition technique. The formation of CS/LS multilayers on cellulose fibers surfaces was verified by X-ray photoelectron spectroscopy (XPS) and zeta potential measurement. The surface morphologies of CS/LS multilayers on fibers surfaces were observed by atomic force microscopy (AFM). The results showed that characteristic element (i.e. N and S element) content increased with increasing bilayers number, the surface LS content increased linearly as a function of bilayers. Zeta potential of modified fibers was inversed after deposition of each layer. AFM phase images indicated that the cellulose microfibrils on fibers surfaces were gradually covered by granular LS aggregate. The antimicrobial testing results demonstrated that CS/LS multilayers modified fibers with CS in the outermost layer exhibited higher antimicrobial activity against Escherichia coli. The antioxidant testing results showed that antioxidant activity of CS/LS multilayers modified fibers was better than that of original fibers under the same oxidation conditions.

  7. Surface processes on the asteroid deduced from the external 3D shapes and surface features of Itokawa particles

    NASA Astrophysics Data System (ADS)

    Tsuchiyama, A.; Matsumoto, T.

    2015-10-01

    Particles on the surface of S-type Asteroid 25143 Itokawa were successfully recovered by the Hayabusa mission of JAXA (e.g., [1,2]). They are not only the first samples recovered from an asteroid, but also the second extraterrestrial regolith to have been sampled, the first being the Moon by Apollo and Luna missions. The analysis of tiny sample particles (20-200 μm) shows that the Itokawa surface material is consistent with LL chondrites suffered by space weathering as expected and brought an end to the origin of meteorites (e.g., [2-4]). In addition, the examination of Itokawa particles allow studies of surface processes on the asteroid because regolith particles can be regarded as an interface with the space environment, where the impacts of small objects and irradiation by the solar wind and galactic cosmic rays should have been recorded. External 3D shapes and surface features of Itokawa regolith particles were examined. Two kinds of surface modification, formation of space-weathering rims mainly by solar wind implantation and surface abrasion by grain migration, were recognized. Spectral change of the asteroid proceeded by formation of space-weathering rims and refreshment of the regolith surfaces. External 3D shapes and surface morphologies of the regolith particles can provide information about formation and evolution history of regolith particles in relation to asteroidal surface processes. 3D shapes of Itokawa regolith particles were obtained using microtomography [3]. The surface nanomiromorpholgy of Itokawa particles were also observed using FE-SEM [5]. However, the number of particles was limited and genial feature on the surface morphology has not been understood. In this study, the surface morphology of Itokawa regolith particles was systematically investigated together with their 3D structures.

  8. One-dimensional particle simulations of Knudsen-layer effects on D-T fusion

    SciTech Connect

    Cohen, Bruce I.; Dimits, Andris M.; Zimmerman, George B.; Wilks, Scott C.

    2014-12-15

    Particle simulations are used to solve the fully nonlinear, collisional kinetic equation describing the interaction of a high-temperature, high-density, deuterium-tritium plasma with absorbing boundaries, a plasma source, and the influence of kinetic effects on fusion reaction rates. Both hydrodynamic and kinetic effects influence the end losses, and the simulations show departures of the ion velocity distributions from Maxwellian due to the reduction of the population of the highest energy ions (Knudsen-layer effects). The particle simulations show that the interplay between sources, plasma dynamics, and end losses results in temperature anisotropy, plasma cooling, and concomitant reductions in the fusion reaction rates. However, for the model problems and parameters considered, particle simulations show that Knudsen-layer modifications do not significantly affect the velocity distribution function for velocities most important in determining the fusion reaction rates, i.e., the thermal fusion reaction rates using the local densities and bulk temperatures give good estimates of the kinetic fusion reaction rates.

  9. The accuracy of tomographic particle image velocimetry for measurements of a turbulent boundary layer

    NASA Astrophysics Data System (ADS)

    Atkinson, Callum; Coudert, Sebastien; Foucaut, Jean-Marc; Stanislas, Michel; Soria, Julio

    2011-04-01

    To investigate the accuracy of tomographic particle image velocimetry (Tomo-PIV) for turbulent boundary layer measurements, a series of synthetic image-based simulations and practical experiments are performed on a high Reynolds number turbulent boundary layer at Reθ = 7,800. Two different approaches to Tomo-PIV are examined using a full-volume slab measurement and a thin-volume "fat" light sheet approach. Tomographic reconstruction is performed using both the standard MART technique and the more efficient MLOS-SMART approach, showing a 10-time increase in processing speed. Random and bias errors are quantified under the influence of the near-wall velocity gradient, reconstruction method, ghost particles, seeding density and volume thickness, using synthetic images. Experimental Tomo-PIV results are compared with hot-wire measurements and errors are examined in terms of the measured mean and fluctuating profiles, probability density functions of the fluctuations, distributions of fluctuating divergence through the volume and velocity power spectra. Velocity gradients have a large effect on errors near the wall and also increase the errors associated with ghost particles, which convect at mean velocities through the volume thickness. Tomo-PIV provides accurate experimental measurements at low wave numbers; however, reconstruction introduces high noise levels that reduces the effective spatial resolution. A thinner volume is shown to provide a higher measurement accuracy at the expense of the measurement domain, albeit still at a lower effective spatial resolution than planar and Stereo-PIV.

  10. Silver-particle-based surface-enhanced resonance Raman scattering spectroscopy for biomolecular sensing and recognition.

    PubMed

    Kim, Kwan; Lee, Hyun Sook; Kim, Nam Hoon

    2007-05-01

    We demonstrate in this work that 2-microm-sized Ag (microAg) powders can be used as a core material for constructing biomolecular sensing/recognition units operating via surface-enhanced resonance Raman scattering (SERRS). This is possible because microAg powders are very efficient substrates for both the diffuse reflectance IR and the surface-enhanced Raman scattering-SERRS spectroscopic characterization of molecular adsorbates prepared in a similar manner on silver surfaces. Besides, the agglomeration of microAg particles in a buffer solution can be prevented by the layer-by-layer deposition of cationic and anionic polyelectrolytes such as poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA). In this particular study, we used rhodamine B isothiocyanate (RhBITC) as a SERRS marker molecule, and microAg powders adsorbed consecutively with RhBITC and PAH-PAA bilayers were finally derivatized with biotinylated poly(L-lysine). On the basis of the nature of the SERRS peaks of RhBITC, those microAg powders were confirmed to selectively recognize streptavidin molecules down to concentrations of 10(-10) g mL-1. Since a number of different molecules can be used as SERS-SERRS marker molecules, the present method proves to be an invaluable tool for multiplex biomolecular sensing/recognition via SERS and SERRS.

  11. Transverse surface waves in a layered structure with a functionally graded piezoelectric substrate and a hard dielectric layer.

    PubMed

    Qian, Zheng-Hua; Jin, Feng; Lu, Tianjian; Kishimoto, Kikuo

    2009-03-01

    As to an ideally layered structure with a functionally graded piezoelectric substrate (material parameters change continuously along the thickness direction) and a hard dielectric layer, the existence and propagation behavior of transverse surface waves is studied by analytical technique. The dispersion equations for the existence of the transverse surface waves with respect to phase velocity are obtained for electrically open and short circuit conditions, respectively. A detailed investigation of the effect of gradient coefficient on dispersion relation, electromechanical coupling factor and penetration depth is carried out. It is found by numerical examples that adjusting gradient coefficient makes the electromechanical coupling factor of the transverse surface waves achieve quite high values at some appropriate ratio values of the layer thickness to the wavelength, and at the same time, the penetration depth can be reduced to the same order as the wavelength.

  12. The surface layer of pharmaceutical compacts: the role of the punch surface and its impact on the mechanical properties of the compacts.

    PubMed

    Mazel, V; Busignies, V; Diarra, H; Reiche, I; Tchoreloff, P

    2013-02-14

    During pharmaceutical compaction, the interaction between the punch and the powder determines the formation and the aspect of the surface of the compact. In industry, the properties of the punch surface, which play a key role in this interaction, are sometimes changed by fixing an intermediate layer onto the punch to prevent sticking problems. In this article, the case of a polymer insert layer was studied. Firstly, sugar spheres were compacted with and without the polymer insert fixed onto the punches. After compaction with uncovered punches, the surface particles, which had been subjected to high deformation, were flattened on one side. However, it was observed, using confocal X-ray microfluorescence, that this kind of deformation was limited to the surface and that the bulk particles, which underwent a more isotropic deformation, still exhibited an approximately round shape. Secondly, the influence of the surface structure on the mechanical properties of the compacts was studied. The indentation hardness and the tensile strength of compacts of microcrystalline cellulose (MCC) and anhydrous calcium phosphate (aCP) were studied. No differences were found for the compacts of MCC produced with the two kinds of punches, but the compacts of aCP obtained with uncovered punches presented a higher hardness and a higher tensile strength than those obtained with covered punches.

  13. Enhanced and unusual angle-dependent optical forces exerted on Mie particles by Airy surface plasmon wave

    NASA Astrophysics Data System (ADS)

    Yang, Yang; Xue, Yanli; Li, Jiafang; Li, Zhi-Yuan

    2016-08-01

    In this paper, using an angular spectrum method, we develop an analytical theory for Airy surface plasmon wave excited in a classical Kretschmann setup. It is found that the center of an Airy surface plasmon polariton (SPP) wave has a giant positive lateral shift, and the sidelobes move forward along the surface. The intensity of the Airy SPP wave is greatly enhanced, the corresponding optical forces can be enhanced by more than one order of magnitude. Importantly, we show that the sidelobes of the Airy SPP beam can lead to the splitting of optical force spectra with the variation of incident angle, which is accompanied by strong oscillations emerging at the optimal metal layer thickness. Moreover, the effects of multiple scatterings of the Airy SPP wave between the particle and the metal layer are also discussed. The theoretical analysis could open up new perspectives for the applications of Airy beam in optical manipulation and surface-enhanced Raman scattering.

  14. Study of Local Profiles Relative to the Particle Surface in a Forced Particle-Laden Turbulent Flow

    NASA Astrophysics Data System (ADS)

    Castro, Oscar; Ayala, Orlando; Wang, Lian-Ping; Lian-Ping Wang Collaboration; Orlando Ayala Collaboration

    2013-11-01

    Turbulent flows laden with solid particles, liquid droplets, or air bubbles are relevant to many engineering applications and biological and environmental processes. When the particle size is much smaller than the Kolmogorov scale of the carrier flow, the motion of the particle can be described by a point-particle model. Currently, it is not clear how to treat the interaction of a solid particle with the carrier flow when its size is comparable or larger than the Kolmogorov scale. Here we address the interaction of finite-size particles with the carrier fluid turbulence using lattice-Boltzmann-based, particle-resolving simulations. Our recent results (Comput. & Math. with Applications, DOI: 10.1016/j.camwa.2013.04.001) on forced turbulence laden with non-sedimenting solid particles at a particle-to-fluid density ratio of 5, solid volume fraction of 0.102, and particle diameter to Kolmogorov length ratio of 8.05 reveal that the enhanced viscous dissipation is related to the local flow profiles near the particle surface. Here we repeat this simulation and present more accurate local profiles by averaging over time in addition to space. We will also analyze how such profiles change with the particle volume concentration and the particle size relative to the Kolmogorov scales. This work is partially supported by the National Science Foundation.

  15. The mechanics of active matter: Broken-symmetry hydrodynamics of motile particles and granular layers

    NASA Astrophysics Data System (ADS)

    Ramaswamy, Sriram; Simha, R. Aditi

    2006-09-01

    This articles reviews briefly our recent theoretical results on order, fluctuations and flow in collections of self-driven particles, in suspension or on a solid surface. The theoretical approach we have developed applies not only to collections of organisms such as schools of fish or collectively swimming bacteria, but also to motor-microtubule extracts with ATP and, most surprisingly, to agitated monolayers of orientable granular particles. We contrast the behaviour of these active systems with that of thermal equilibrium systems with the same symmetry. As an illustration of the role of activity we show that active smectics in three dimensions show true long-range order, unlike their thermal equilibrium counterparts.

  16. A novel technique for preparing a mono-particle layer on a substrate through the epoxy-amino cross-linking

    NASA Astrophysics Data System (ADS)

    Onishi, Shogo; Ogawa, Kazufumi

    2006-12-01

    We present a novel technique for immobilizing nanoparticles on a substrate. This method contains two techniques, which are a preparing technique of self-assembled monomolecular layers (SAMs) terminated in an epoxy group or an amino group on surface of nanoparticles or a substrate and a reaction technique between the epoxy and amino groups. The epoxy terminated SAMs or the amino terminated SAMs were prepared on nanoparticle surfaces or a substrate surface by a chemical adsorption technique using 3-glycidoxypropyltrimethoxysilane or (3-aminopropyl) trimethoxysilane. The particles dispersed in an organic solvent were coated on the substrate, and then the epoxy and amino groups were reacted each other. Unreacted nanoparticles were removed by washing. As a result, the nanoparticles were immobilized to the substrate surface through covalent bonds of the epoxy-amine cross-linking. By using this method, a mono nanoparticle layer could be formed on the substrate.

  17. Turbulent structure of scalars in the eddy surface layer over land and sea

    NASA Astrophysics Data System (ADS)

    Smedman, Ann-Sofi; Sahlee, Erik

    2015-04-01

    Turbulent structure of scalars in the 'eddy surface layer' over land and sea. In a study of the kinematic structure of the near neutral atmospheric surface layer, Högström, Hunt and Smedman, 2002, it was demonstrated that a model with detached eddies from above the surface layer impinging on to the surface (Hunt and Morison, 2000) could explain some of the observed features in the neutral atmospheric boundary layer. Thus the detached eddy model proved successful in explaining the dynamic structure of the near neutral atmospheric surface layer (eddy surface layer), especially the shape of the spectra of the wind components and corresponding fluxes. However, the structure of temperature and humidity fluctuations in the eddy surface layer shows quite different behaviour. In particular the efficiency of turbulent exchange of sensible and latent heat is observed to be more strongly enhanced than is consistent with standard similarity theory. Also the profiles of dissipation of turbulent kinetic energy and temperature fluctuation variance are found to depend on the height of the eddy surface layer and not the height above the surface. All these features are found to be similar in measurements at a marine site, a flat land site and during hurricane conditions (hurricane Fabian and Isabel). Hunt, J.C.R and Morrison, J.F., 2000: Eddy structure in turbulent boundary layers, Euro. J. Mech. B-Fluids, 19, 673-694.. Högström, U., Hunt, J.C.R., and Smedman, A., 2002: Theory and measurements for turbulence spectra and variances in the atmospheric neutral surface layer, Bound.-Layer Meteorol., 103,101-124.

  18. Exploratory investigation of the effect of porous surfaces on hypersonic turbulent boundary layers

    NASA Technical Reports Server (NTRS)

    Watson, R. D.

    1979-01-01

    Four different test surfaces were studied to determine the effect of porous walls on the characteristics of a hypersonic turbulent flat-plate boundary layer. The investigation was an attempt to decrease the surface shear of the boundary layer by transmitting fluctuating pressure energy through the wall and absorbing it in a cavity beneath the wall. Pitot surveys were made at two locations, schlieren photographs of the boundary layer were taken, and hot-wire measurements in the flow above the boundary layer were made to determine whether the surfaces affected the turbulent boundary layer. Neither an increase nor a decrease in surface shear or boundary-layer growth was detected. Tabulations of the pitot data are included.

  19. Mode instabilities and dynamic patterns in a colony of self-propelled surfactant particles covering a thin liquid layer.

    PubMed

    Pototsky, Andrey; Thiele, Uwe; Stark, Holger

    2016-05-01

    We consider a colony of point-like self-propelled surfactant particles (swimmers) without direct interactions that cover a thin liquid layer on a solid support. The particles predominantly swim normal to the free film surface with only a small component parallel to the film surface. The coupled dynamics of the swimmer density and film height profile is captured in a long-wave model allowing for diffusive and convective transport of the swimmers (including rotational diffusion). The dynamics of the film height profile is determined by i) the upward pushing force of the swimmers onto the liquid-gas interface, ii) the solutal Marangoni force due to gradients in the swimmer concentration, and iii) the rotational diffusion of the swimmers together with the in-plane active motion. After reviewing and extending the analysis of the linear stability of the uniform state, we analyse the fully nonlinear dynamic equations and show that point-like swimmers, which only interact via long-wave deformations of the liquid film, self-organise in highly regular (standing, travelling, and modulated waves) and various irregular patterns. PMID:27145959

  20. Surface Navigation Using Optimized Waypoints and Particle Swarm Optimization

    NASA Technical Reports Server (NTRS)

    Birge, Brian

    2013-01-01

    The design priority for manned space exploration missions is almost always placed on human safety. Proposed manned surface exploration tasks (lunar, asteroid sample returns, Mars) have the possibility of astronauts traveling several kilometers away from a home base. Deviations from preplanned paths are expected while exploring. In a time-critical emergency situation, there is a need to develop an optimal home base return path. The return path may or may not be similar to the outbound path, and what defines optimal may change with, and even within, each mission. A novel path planning algorithm and prototype program was developed using biologically inspired particle swarm optimization (PSO) that generates an optimal path of traversal while avoiding obstacles. Applications include emergency path planning on lunar, Martian, and/or asteroid surfaces, generating multiple scenarios for outbound missions, Earth-based search and rescue, as well as human manual traversal and/or path integration into robotic control systems. The strategy allows for a changing environment, and can be re-tasked at will and run in real-time situations. Given a random extraterrestrial planetary or small body surface position, the goal was to find the fastest (or shortest) path to an arbitrary position such as a safe zone or geographic objective, subject to possibly varying constraints. The problem requires a workable solution 100% of the time, though it does not require the absolute theoretical optimum. Obstacles should be avoided, but if they cannot be, then the algorithm needs to be smart enough to recognize this and deal with it. With some modifications, it works with non-stationary error topologies as well.

  1. Distributions of surface-layer buoyance versus lifting condensation level over a heterogeneous land surface

    SciTech Connect

    Schrieber, K.; Zhang, Qing; Stull, R.

    1996-04-15

    Onset and coverage of small cumulus clouds depend on the relative abundance of surface-layer air parcels possessing favorable buoyancy and moisture - two variables that are coupled through the surface energy budget. This abundance is described using a joint frequency distribution (JFD) as a function of virtual potential temperature {theta}{sub v} and height of the lifting condensation level z{sub LCL}. It is shown analytically that the shape and spread of this JFD depends on the ranges of Bowen ratios and solar forcings (albedoes, cloud shading, etc.) that exist within a domain of heterogeneous land use. To sample the character of such JFDs in the real atmosphere, a case study is presented using turbulence data gathered by aircraft flying in the surface layer of southwest France. This case study includes 4 days of clear skies during the Hydrologic Atmospheric Pilot Experiment (HAPEX) of 1986. The full flight track during HAPEX overflew a wide range of land use including evergreen forest, corn, vineyards, pastures, and irrigated fields over varied topography. The JFDs from these full tracks are found to be quite complex, being frequently multimodal with a convoluted perimeter. However, when a full track is broken into segments, each over a subdomain of quasi-homogeneous land use, the resulting segment JFDs are mono-modal with simpler topology. Such a characterization of JFDs provides guidance toward eventual subgrid cumulus parameterization in large-scale forecast models, with associated impacts in aviation forecasting, pollutant venting and chemical reactions, verticle dispersion and turbulence modulation, and radiation balance in climate-change models. 48 refs., 17 figs., 7 tabs.

  2. Multistep Kinetic Behavior of the Thermal Decomposition of Granular Sodium Percarbonate: Hindrance Effect of the Outer Surface Layer.

    PubMed

    Wada, Takeshi; Nakano, Masayoshi; Koga, Nobuyoshi

    2015-09-24

    The kinetics and mechanism of the thermal decomposition of granular sodium percarbonate (SPC), which is used as a household oxygen bleach, were studied by thermoanalytical measurements under systematically changing conditions and morphological observation of the reactant solids at different reaction stages. A physico-geometrical kinetic behavior of the reaction that occurs in a core-shell structure composed of an outer surface layer and internal aggregates of SPC crystalline particles was illustrated through detailed kinetic analyses using the kinetic deconvolution method. Simultaneously, the hazardous nature of SPC as a combustion improver was evaluated on the basis of the kinetic behavior of the thermal decomposition. It was found that the outer surface layers of the SPC granules hinder the diffusional removal of product gases generated by the thermal decomposition of the internal SPC crystalline particles. The reaction rate decelerates because of an increase in the internal gaseous pressure as the reaction advances. However, the reaction rate accelerates once crack formation occurs in the outer surface layer at the midpoint of the reaction. Therefore, the overall reaction was empirically demonstrated to consist of two overlapping reaction steps owing to the changes in the self-generated reaction conditions in the interior of the SPC granules. PMID:26372469

  3. Interfacial layer effects on surface capacitances and electro-osmosis in electrolytes.

    PubMed

    Bonthuis, Douwe Jan; Uematsu, Yuki; Netz, Roland R

    2016-02-13

    Many properties of the interfacial layer of water at surfaces differ significantly from those of bulk water. The consequences are most significant for the double-layer capacitance and the electrokinetic properties. We model the interfacial hydration layer by a modified dielectric constant and a modified local viscosity over a single interfacial width. Analytic expressions in the low-charge Debye-Hückel approximation are derived and shown to describe experimental surface capacitance and electro-osmotic data in a unified framework.

  4. Layered devices having surface curvature and method of constructing same

    DOEpatents

    Woodbury, Richard C.; Perkins, Raymond T.; Thorne, James M.

    1989-01-01

    A method of treating a substrate having first and second sides with corresponding oppositely facing first and second surfaces, to produce curvature in the first surface. The method includes the steps of removing material, according to a predetermined pattern, from the second side of the substrate, and applying a stress-producing film of material to at least one surface of the substrate to thereby cause the substrate to bend to produce the desired curvature in the first surface.

  5. Computed and experimental interactions between eddy structure and dispersed particles in developing free shear layers

    SciTech Connect

    Buckingham, A.C.; Siekhaus, W.J.; Keller, J.O.; Ellzey, J.; Hubbard, G.; Daily, J.W.

    1982-05-20

    We are investigating the interactive process between turbulent flow and dispersed phase particles. We are focusing on the mechanisms that appear to result in a reduction of local turbulent intensity and a corresponding reduction in wall heat transfer and subsequent wall erosion in turbulent solid propellant combustion flow. We apply computational simulations and physical experiments specialized to a developing free shear layer over a rearward facing step and over a parallel splitter plate. The flow configuration evolves in a two-dimensional, steady, combustion and non-combustion turbulent free shear mixing region, with and without particle additives. The computational simulations combine three basic components: gas phase Navier-Stokes solutions, Lagrange particle field solutions and a Monte Carlo technique for the random encounters, forces and accelerations between the two fields. We concentrate here on relatively large sized additive particles (of the order of tens of microns to 100 microns mean diameter). We examine their apparent influence in breaking up the larger, energy bearing eddy structures into smaller structures which are more readily dissipated.

  6. Large-eddy simulation of zero-pressure-gradient turbulent boundary layer with solid particle suspension

    NASA Astrophysics Data System (ADS)

    Rahman, Mustafa; Samtaney, Ravi

    2015-11-01

    We present results of solid particles suspension and transport in a fully-developed turbulent boundary layer flow using large-eddy simulation of the incompressible Navier-Stokes equations. We adopt the Eulerian-Eulerian approach to simulating particle laden flow with a large number of particles, in which the particles are characterized by statistical descriptors. For the particulate phase, the direct quadrature method of moments (DQMOM) is chosen in which the weights and abscissas of the quadrature approximation are tracked directly rather than the moments themselves. The underlying approach in modeling the turbulence of fluid phase utilizes the stretched spiral vortex subgrid-scale model and a virtual wall model similar to the work proposed by Inoue & Pullin (J. Fluid Mech. 2011). The solver is verified against simple analytical solutions and the computational results are found to be in a good agreement with these. The capability of the new numerical solver will be exercised to investigate turbulent transport of sand in sandstorms. Finally, the adequacy and limitations of the solver will be discussed. Supported by the KAUST Office of Competitive Research Funds under Award No. URF/1/1704-01.

  7. Influence of ultrathin water layer on the van der Waals/Casimir force between gold surfaces

    SciTech Connect

    Palasantzas, G.; Zwol, P. J. van; Svetovoy, V. B.

    2009-06-15

    In this paper we investigate the influence of ultrathin water layer ({approx}1-1.5 nm) on the van der Waals/Casimir force between gold surfaces. Adsorbed water is inevitably present on gold surfaces at ambient conditions as jump-up-to contact during adhesion experiments demonstrate. Calculations based on the Lifshitz theory give very good agreement with the experiment in the absence of any water layer for surface separations d > or approx. 10 nm. However, a layer of thickness h < or approx. 1.5 nm is allowed by the error margin in force measurements. At shorter separations, d < or approx. 10 nm, the water layer can have a strong influence as calculations show for flat surfaces. Nonetheless, in reality the influence of surface roughness must also be considered, and it can overshadow any water layer influence at separations comparable to the total sphere-plate rms roughness w{sub shp}+w.

  8. Turbulent boundary layer over solid and porous surfaces with small roughness

    NASA Technical Reports Server (NTRS)

    Kong, F. Y.; Schetz, J. A.; Collier, F.

    1982-01-01

    Skin friction and profiles of mean velocity, axial and normal turbulence intensity, and Reynolds stress in the untripped boundary layer were measured directly on a large diameter, axisymmetric body with: (1) a smooth, solid surface; (2) a sandpaper-roughened, solid surface; (3) a sintered metal, porous surface; (4) a smooth, perforated titanium surface; (5) a rough solid surface made of fine, diffusion bonded screening, and (6) a rough, porous surface of the same screening. Results obtained for each of these surfaces are discussed. It is shown that a rough, porous wall simply does not influence the boundary layer in the same way as a rough solid wall. Therefore, turbulent transport models for boundary layers over porous surfaces either with or without injection or suction, must include both surface roughness and porosity effects.

  9. Overlap region in turbulent boundary layer over a rough surface

    NASA Astrophysics Data System (ADS)

    Afzal, Noor

    2010-11-01

    The one term non-linear outer layer in George & Castillo (1997, AMR 50, 689), based on their AIP argument, was matched with inner wall layer leading to power law velocity, which denied very existence of traditional log law, while Clauser (1956) patched same outer layer with inner wall log law. Jones, Nickles & Marusic (2008, JFM 616, 195) proposal that free stream velocity (in GC97) and friction velocity (in Coles 1956) are potentially valid scalings according to their theoretical criterion in the outer layer, is misleading, being not correct. Further, in Nishioka (2010, FDR 42, 45502-5) and Prandtl (1935, AT) the additive constant in power law velocity is singular at large Reynolds numbers is also not correct, and this constant is shown to be zero. In the present work, two terms outer layer expansion is considered where leading term scales with free steam velocity and first order with friction velocity. The leading term turns out to be a non-linear wake type equation through application of Izakson-Millikan- Kolmogorov hypothesis. The first order terms lead to alternate functional equations, arising from ratios of two successive derivatives of the functional equations, each of which admits two functional solutions, the power law velocity profile in addition to log law velocity profile. The comparison with extensive data on rough & smooth walls also provide strong support to present work.

  10. In situ mass analysis of particles by surface ionization mass spectrometry

    NASA Technical Reports Server (NTRS)

    Lassiter, W. S.; Moen, A. L.

    1974-01-01

    A qualitative study of the application of surface ionization and mass spectrometry to the in situ detection and constituent analysis of atmospheric particles was conducted. The technique consists of mass analysis of ions formed as a result of impingement of a stream of particles on a hot filament where, it is presumed, surface ionization takes place. Laboratory air particles containing K, Ca, and possibly hydrocarbons were detected. Other known particles such as Al2O3, Pb(NO3)2, and Cr2O3 were analyzed by detecting the respective metal atoms making up the particles. In some cases, mass numbers indicative of compounds making up the particles were detected showing surface ionization of particles sometimes leads to chemical analysis as well as to elemental analysis. Individual particles were detected, and it was shown that the technique is sensitive to Al2O3 particles with a mass of a few nanograms.

  11. Chemical-thermal quantitative methodology for carbon speciation in damage layers on building surfaces.

    PubMed

    Ghedini, Nadia; Sabbioni, Cristina; Bonazza, Alessandra; Gobbi, Giancarlo

    2006-02-01

    The issue of environment protection, including the conservation of the monumental heritage worldwide, is related to atmospheric pollution, and its future therefore depends on air pollutant reduction. Carbonaceous particles emitted by combustion processes are the main factors responsible for the blackening of buildings. The identification and evaluation of the carbon species constituting the noncarbonate fraction of total carbon in damage layers, particularly in urban areas, are required in orderto investigate atmospheric deposition on building surfaces. Since noncarbonate carbon contains organic and elemental carbon originating from various human activities, its measurement and speciation are crucial to the protection and conservation of monuments and ancient masonry, playing an important role both in the proposal of mitigation strategies and in the definition of conservation treatments. The availability of a correct, accurate, and reproducible analytical method for a complete carbon balance is essential in studying the effects of atmospheric pollutants on the environment, including those affecting cultural heritage. A chemical-thermal methodology was set up, and its sensitivity, accuracy, repeatability, and reproducibility were tested on appropriate standard samples of composition similar to the black crusts on stones and mortars. The results indicate thatthe technique satisfactorily distinguishes among carbon species, particularly those of anthropogenic origin, allowing a reliable evaluation of their quantities in damage layers. In view of the difficulties encountered in applying the thermo-optical methods adopted for the measurement of carbon filters, the proposed methodology contributes to filling the current gap in suitable and reliable analytical procedures in the field of cultural heritage protection. PMID:16509340

  12. Chemical-thermal quantitative methodology for carbon speciation in damage layers on building surfaces.

    PubMed

    Ghedini, Nadia; Sabbioni, Cristina; Bonazza, Alessandra; Gobbi, Giancarlo

    2006-02-01

    The issue of environment protection, including the conservation of the monumental heritage worldwide, is related to atmospheric pollution, and its future therefore depends on air pollutant reduction. Carbonaceous particles emitted by combustion processes are the main factors responsible for the blackening of buildings. The identification and evaluation of the carbon species constituting the noncarbonate fraction of total carbon in damage layers, particularly in urban areas, are required in orderto investigate atmospheric deposition on building surfaces. Since noncarbonate carbon contains organic and elemental carbon originating from various human activities, its measurement and speciation are crucial to the protection and conservation of monuments and ancient masonry, playing an important role both in the proposal of mitigation strategies and in the definition of conservation treatments. The availability of a correct, accurate, and reproducible analytical method for a complete carbon balance is essential in studying the effects of atmospheric pollutants on the environment, including those affecting cultural heritage. A chemical-thermal methodology was set up, and its sensitivity, accuracy, repeatability, and reproducibility were tested on appropriate standard samples of composition similar to the black crusts on stones and mortars. The results indicate thatthe technique satisfactorily distinguishes among carbon species, particularly those of anthropogenic origin, allowing a reliable evaluation of their quantities in damage layers. In view of the difficulties encountered in applying the thermo-optical methods adopted for the measurement of carbon filters, the proposed methodology contributes to filling the current gap in suitable and reliable analytical procedures in the field of cultural heritage protection.

  13. Origin of non-spherical particles in the boundary layer over Beijing, China: based on balloon-borne observations.

    PubMed

    Chen, Bin; Yamada, Maromu; Iwasaka, Yasunobu; Zhang, Daizhou; Wang, Hong; Wang, Zhenzhu; Lei, Hengchi; Shi, Guangyu

    2015-10-01

    Vertical structures of aerosols from the ground to about 1,000 m altitude in Beijing were measured with a balloon-borne optical particle counter. The results showed that, in hazy days, there were inversions at approximately 500-600 m, below which the particulate matters were well mixed vertically, while the concentration of particles decreased sharply above the mixing layer. Electron microscopic observation of the particles collected with the balloon-borne impactor indicates that the composition of particles is different according to weather conditions in the boundary mixing layer of Beijing city and suggests that dust particles are always dominant in coarse-mode particles. Interestingly, sea-salt particles are frequently identified, suggesting the importance of marine air inflow to the Beijing area even in summer. The Ca-rich spherical particles are also frequently identified, suggesting chemical modification of dust particle by NOx or emission of CaO and others from local emission. Additionally, those types of particles showed higher concentration above the mixing layer under the relatively calm weather condition of summer, suggesting the importance of local-scale convection found in summer which rapidly transported anthropogenic particles above the mixing layer. Lidar extinction profiles qualitatively have good consistency with the balloon-borne measurements. Attenuation effects of laser pulse intensity are frequently observed due to high concentration of particulate matter in the Beijing atmosphere, and therefore quantitative agreement of lidar return and aerosol concentration can be hardly observed during dusty condition. Comparing the depolarization ratio obtained from the lidar measurements with the balloon-borne measurements, the contribution of the dry sea-salt particles, in addition to the dust particles, is suggested as an important factor causing depolarization ratio in the Beijing atmosphere.

  14. Origin of non-spherical particles in the boundary layer over Beijing, China: based on balloon-borne observations.

    PubMed

    Chen, Bin; Yamada, Maromu; Iwasaka, Yasunobu; Zhang, Daizhou; Wang, Hong; Wang, Zhenzhu; Lei, Hengchi; Shi, Guangyu

    2015-10-01

    Vertical structures of aerosols from the ground to about 1,000 m altitude in Beijing were measured with a balloon-borne optical particle counter. The results showed that, in hazy days, there were inversions at approximately 500-600 m, below which the particulate matters were well mixed vertically, while the concentration of particles decreased sharply above the mixing layer. Electron microscopic observation of the particles collected with the balloon-borne impactor indicates that the composition of particles is different according to weather conditions in the boundary mixing layer of Beijing city and suggests that dust particles are always dominant in coarse-mode particles. Interestingly, sea-salt particles are frequently identified, suggesting the importance of marine air inflow to the Beijing area even in summer. The Ca-rich spherical particles are also frequently identified, suggesting chemical modification of dust particle by NOx or emission of CaO and others from local emission. Additionally, those types of particles showed higher concentration above the mixing layer under the relatively calm weather condition of summer, suggesting the importance of local-scale convection found in summer which rapidly transported anthropogenic particles above the mixing layer. Lidar extinction profiles qualitatively have good consistency with the balloon-borne measurements. Attenuation effects of laser pulse intensity are frequently observed due to high concentration of particulate matter in the Beijing atmosphere, and therefore quantitative agreement of lidar return and aerosol concentration can be hardly observed during dusty condition. Comparing the depolarization ratio obtained from the lidar measurements with the balloon-borne measurements, the contribution of the dry sea-salt particles, in addition to the dust particles, is suggested as an important factor causing depolarization ratio in the Beijing atmosphere. PMID:25537163

  15. Surface Passivation by Quantum Exclusion Using Multiple Layers

    NASA Technical Reports Server (NTRS)

    Hoenk, Michael E. (Inventor)

    2015-01-01

    A semiconductor device has a multilayer doping to provide improved passivation by quantum exclusion. The multilayer doping includes at least two doped layers fabricated using MBE methods. The dopant sheet densities in the doped layers need not be the same, but in principle can be selected to be the same sheet densities or to be different sheet densities. The electrically active dopant sheet densities are quite high, reaching more than 1.times.10.sup.14 cm.sup.-2, and locally exceeding 10.sup.22 per cubic centimeter. It has been found that silicon detector devices that have two or more such dopant layers exhibit improved resistance to degradation by UV radiation, at least at wavelengths of 193 nm, as compared to conventional silicon p-on-n devices.

  16. Evaluation of Mercaptobenzothiazole Anticorrosive Layer on Cu Surface by Spectroscopic Ellipsometry

    NASA Astrophysics Data System (ADS)

    Nishizawa, Hideaki; Sugiura, Osamu; Matsumura, Yoshiyuki; Kinoshita, Masaharu

    2007-05-01

    Mercaptobenzothiazole (MBT) anticorrosive layer on copper surface prepared in MBT solutions was analyzed by spectroscopic ellipsometry (SE). The results showed that MBT anticorrosive layer was formed on Cu2O layer in the MBT solution at temperatures higher than 50 °C. Additionally, it was confirmed that MBT anticorrosive layer was formed in the MBT solution at room temperature by adding about 20 wt % acetone to the solution. From polishing experiments of MBT anticorrosive layer and benzotriazole (BTA) layer, it was revealed that MBT anticorrosive layer was physically stronger than BTA layer. It is considered that dishing amount in Cu chemical-mechanical polishing (CMP) can be reduced by using MBT. However, MBT anticorrosive layer was not formed in the MBT solution including Hydrogen peroxide (H2O2) suggesting that slurry should be composed without H2O2 in order to use MBT for Cu CMP.

  17. A literature review of surface alteration layer effects on waste glass behavior

    SciTech Connect

    Feng, X.; Cunnane, J.C.; Bates, J.K.

    1993-05-01

    When in contact with an aqueous solution, nuclear waste glass is subject to a chemical attack that results in progressive alteration. During tills alteration, constituent elements of the glass pass into the solution; elements initially in solution diffuse into, or are adsorbed onto, the solid; and new phases appear. This results in the formation of surface layers on the reacted glass. The glass corrosion and radionuclide release can be better understood by investigating these surface layer effects. In the past decade, there have been numerous studies regarding the effects of surface layers on glass reactions. This paper presents a systematic analysis and summary of the past knowledge regarding the effects of surface layers on glass-water interaction. This paper describes the major formation mechanisms of surface layers; reviews the role of surface layers in controlling mass transport and glass reaction affinity (through crystalline phases, an amorphous silica, a gel layer, or all the components in the glass); and discusses how the surface layers contribute to the retention of radionuclides during glass dissolution.

  18. A literature review of surface alteration layer effects on waste glass behavior

    SciTech Connect

    Feng, X.; Cunnane, J.C.; Bates, J.K.

    1993-01-01

    When in contact with an aqueous solution, nuclear waste glass is subject to a chemical attack that results in progressive alteration. During tills alteration, constituent elements of the glass pass into the solution; elements initially in solution diffuse into, or are adsorbed onto, the solid; and new phases appear. This results in the formation of surface layers on the reacted glass. The glass corrosion and radionuclide release can be better understood by investigating these surface layer effects. In the past decade, there have been numerous studies regarding the effects of surface layers on glass reactions. This paper presents a systematic analysis and summary of the past knowledge regarding the effects of surface layers on glass-water interaction. This paper describes the major formation mechanisms of surface layers; reviews the role of surface layers in controlling mass transport and glass reaction affinity (through crystalline phases, an amorphous silica, a gel layer, or all the components in the glass); and discusses how the surface layers contribute to the retention of radionuclides during glass dissolution.

  19. Layer-by-layer fabrication of supramolecular dyes on TiO2 surfaces for optoelectronic applications

    NASA Astrophysics Data System (ADS)

    Kong, Xiaoqing; Maguire, Shawn; Lye, Diane; Weck, Marcus; Lee, Stephanie

    We present a modular layer-by-layer approach based on metal coordination chemistry to assemble supramolecular dyes exhibiting increased absorption in the visible range on electrode surfaces. Specifically, palladiated bis-pincer complexes (Pd-BPCs) were employed as linkers between pyridyl-terminated organic molecules via dative bonding. By alternately immersing mesoporous TiO2-coated glass substrates in solutions containing dissolved zinc porphyin (ZnP) and Pd-BPCs, supramolecular dyes were assembled layer-by-layer on the TiO2 surfaces. UV-visible absorption spectra of these assembled structures revealed a linear increase in the Soret and Q bands of ZnP after each immersion of the substrate in the ZnP solution. Coordination of the ZnP layers with Pd-BPC resulted in a slight red shift (<10 nm) of the absorption bands. The modular nature of the assembly process afforded the incorporation of other pyridyl-terminated organic molecules in specific layers of the supramolecular assemblies. By assembling unique organic dyes that absorb different wavelengths of light, we expect to expand light absorption across the visible region of the solar spectrum for solar cell applications.

  20. Surface Layering at the Mercury-Electrolyte Interface

    SciTech Connect

    Ocko, B.M.; Elsen, A.; Murphy, B.M.; Tamam, L.; Deutsch, M.; Kuzmenko, I.; Magnussen, O.M.

    2010-03-12

    X-ray reflectometry reveals atomic layering at a liquid-liquid interface--mercury in a 0.01 M NaF solution. The interface width exceeds capillary wave theory predictions and displays an anomalous dependence on the voltage applied across it, displaying a minimum positive of the potential of zero charge. The latter is explained by electrocapillary effects and an additional intrinsic broadening of the interface profile, tentatively assigned to polarization of the conduction electrons due to the electric field of the electrochemical double layer at the interface.

  1. Surface electrical properties of coal particles on interaction with polyelectrolytes

    SciTech Connect

    Evmenova, G.L.

    2006-07-15

    The paper presents experimental data obtained in determining an electrokinetic potential of coal particles during their interaction with coagulation and flocculation agents. It is established that flocculation agents allow decreasing electrokinetic potential of mineral particles up to the values that promote aggregation of the particles thereby enabling the control over the stability of coal dispersions.

  2. Expansible apparatus for removing the surface layer from a concrete object

    DOEpatents

    Allen, Charles H.

    1979-01-01

    A method and apparatus for removing the surface layer from a concrete object. The method consists of providing a hole having a circular wall in the surface layer of the object, the hole being at least as deep as the thickness of the surface layer to be removed, and applying an outward wedging pressure on the wall of the hole sufficient to spall the surface layer around the hole. By the proper spacing of an appropriate number of holes, it is possible to remove the entire surface layer from an object. The apparatus consists of an elongated tubular-shaped body having a relatively short handle with a solid wall at one end, the wall of the remainder of the body containing a plurality of evenly spaced longitudinal cuts to form a relatively long expandable section, the outer end of the expandable section having an expandable, wedge-shaped spalling edge extending from the outer surface of the wall, perpendicular to the longitudinal axis of the body, and expanding means in the body for outwardly expanding the expandable section and forcing the spalling edge into the wall of a hole with sufficient outward pressure to spall away the surface layer of concrete. The method and apparatus are particularly suitable for removing surface layers of concrete which are radioactively contaminated.

  3. Modifying of Cotton Fabric Surface with Nano-ZnO Multilayer Films by Layer-by-Layer Deposition Method.

    PubMed

    Uğur, Sule S; Sarıışık, Merih; Aktaş, A Hakan; Uçar, M Ciğdem; Erden, Emre

    2010-01-01

    ZnO nanoparticle-based multilayer nanocomposite films were fabricated on cationized woven cotton fabrics via layer-by-layer molecular self-assembly technique. For cationic surface charge, cotton fabrics were pretreated with 2,3-epoxypropyltrimethylammonium chloride (EP3MAC) by pad-batch method. XPS and SEM were used to examine the deposited nano-ZnO multilayer films on the cotton fabrics. The nano-ZnO films deposited on cotton fabrics exhibited excellent antimicrobial activity against Staphylococcus aureus bacteria. The results also showed that the coated fabrics with nano-ZnO multilayer films enhanced the protection of cotton fabrics from UV radiation. Physical tests (tensile strength of weft and warp yarns, air permeability and whiteness values) were performed on the fabrics before and after the treatment with ZnO nanoparticles to evaluate the effect of layer-by-layer (LbL) process on cotton fabrics properties. PMID:20596450

  4. Modifying of Cotton Fabric Surface with Nano-ZnO Multilayer Films by Layer-by-Layer Deposition Method

    PubMed Central

    2010-01-01

    ZnO nanoparticle–based multilayer nanocomposite films were fabricated on cationized woven cotton fabrics via layer-by-layer molecular self-assembly technique. For cationic surface charge, cotton fabrics were pretreated with 2,3-epoxypropyltrimethylammonium chloride (EP3MAC) by pad-batch method. XPS and SEM were used to examine the deposited nano-ZnO multilayer films on the cotton fabrics. The nano-ZnO films deposited on cotton fabrics exhibited excellent antimicrobial activity against Staphylococcus aureus bacteria. The results also showed that the coated fabrics with nano-ZnO multilayer films enhanced the protection of cotton fabrics from UV radiation. Physical tests (tensile strength of weft and warp yarns, air permeability and whiteness values) were performed on the fabrics before and after the treatment with ZnO nanoparticles to evaluate the effect of layer-by-layer (LbL) process on cotton fabrics properties. PMID:20596450

  5. Modifying of Cotton Fabric Surface with Nano-ZnO Multilayer Films by Layer-by-Layer Deposition Method

    NASA Astrophysics Data System (ADS)

    Uğur, Şule S.; Sarıışık, Merih; Aktaş, A. Hakan; Uçar, M. Çiğdem; Erden, Emre

    2010-07-01

    ZnO nanoparticle-based multilayer nanocomposite films were fabricated on cationized woven cotton fabrics via layer-by-layer molecular self-assembly technique. For cationic surface charge, cotton fabrics were pretreated with 2,3-epoxypropyltrimethylammonium chloride (EP3MAC) by pad-batch method. XPS and SEM were used to examine the deposited nano-ZnO multilayer films on the cotton fabrics. The nano-ZnO films deposited on cotton fabrics exhibited excellent antimicrobial activity against Staphylococcus aureus bacteria. The results also showed that the coated fabrics with nano-ZnO multilayer films enhanced the protection of cotton fabrics from UV radiation. Physical tests (tensile strength of weft and warp yarns, air permeability and whiteness values) were performed on the fabrics before and after the treatment with ZnO nanoparticles to evaluate the effect of layer-by-layer (LbL) process on cotton fabrics properties.

  6. Optical pulling force on a particle near the surface of a dielectric slab waveguide

    NASA Astrophysics Data System (ADS)

    Paul, Nayan Kumar; Kemp, Brandon A.

    2016-01-01

    Optical forces on a Rayleigh particle near the surface of a dielectric slab waveguide are considered. A light wave of the lowest-order TE0 mode is used to excite the particle. The transverse and longitudinal forces acting on the particle are studied. The particle is always trapped near the surface of the slab, where the electric field intensity is high. The particle can be pushed away from or pulled toward the light source along the surface of the slab by tuning the frequency around a switching frequency. This phenomenon switches between scattering and gradient forces near the switching frequency of the dielectric slab waveguide.

  7. Method for removing surface-damaged layers from nickel alloys

    NASA Technical Reports Server (NTRS)

    Fawley, R. W.

    1968-01-01

    Electrical discharge machining /EDM/ damaged layer can be effectively removed from Rene 41, Inconel 625, Inconel 718, and Monel K-500 by abrasive-grit blasting or electropolishing /at room temperature/ at a current density of 5A/inches squared in a water solution of phosphoric and sulfuric acids.

  8. Dusty Plasma Technology of DCM with Nanostructure Surface Layer Production

    SciTech Connect

    Gavrikov, A. V.; Ivanov, A. S.; Petrov, O. F.; Shulga, Yu. M.; Starostin, A. N.; Fortov, V. E.

    2008-09-07

    The technique of disperse composite material (DCM) production was developed. The technique based on using special dusty plasma trap in RF plasma, in which fine particles levitate and are exposed by the atomic beam. The two types of covering were obtained: ''cauliflower'' or smooth, depending on process condition.

  9. Extreme Particle Acceleration in Reconnection Layers and Gamma-ray Flares in the Crab Nebula

    NASA Astrophysics Data System (ADS)

    Cerutti, Benoit; Uzdensky, D. A.; Begelman, M. C.

    2011-09-01

    The Fermi and Agile gamma-ray space telescopes recently discovered short and powerful gamma-ray flares in the Crab Nebula. These events presumably originate from a tiny region of the nebula where electrons are accelerated to PeV energies and radiate >100 MeV synchrotron radiation in a milli-Gauss magnetic field. In classical models of particle acceleration, where the accelerating electric field is smaller than the magnetic field, the synchrotron radiation cannot exceed 100 MeV because radiative losses balance the acceleration rate. We propose that particles are efficiently accelerated to PeV energies in a magnetic reconnection layer. We find that ultrarelativistic electron orbits are trapped and collapse rapidly deep into the current layer where the magnetic field becomes small. After a few days of acceleration by the reconnection electric field, electrons are accelerated to PeV energies and are focused into a tight, narrow beam. This mechanism provides a viable explanation to the gamma-ray flares in the Crab Nebula and could be at work in other astrophysical objects such as relativistic jets in AGN.

  10. Particle-Surface Interaction Databases in ALADDIN Format

    DOE Data Explorer

    These databases are listed as recommended resources by CFADC. They represent older data and are not necessarily DOE-originated or funded. However, they are cited in the DOE Data Explorer because of their availability through a DOE Data Center. The citations for these databases are: 1) Energy Dependence of Ion-Induced Sputtering Yields of Monatomic Solids in the Low Energy Region. N. Matsunami, Y. Yamamura, N. Itoh, H. Tawara, T. Kawamura. Report IPPJ-AM-52, Institute of Plasma Physics (National Institute for Fusion Science), Nagoya, Japan (1987); 2) Energy Dependence of the Yields of Ion-Induced Sputtering of Monatomic Solids. N. Maksunami, Y. Yamaura, Y. Itikawa, N. Itoh, Y. Kazumata, S. Miyagawer, K. Morita, R. Strimizu, H. Tawara. Report IPPJ-AM-32, Institute of Plasma Physics (National Institute for Fusion Science), Nagoya, Japan (1988); 3) Particle Reflection from Surfaces - A Recommended Data Base. E. W. Thomas, R. K. Janev and J. J. Smith. Report IAEA INDC(NDS)-249, July 1991; 4) Sputtering Data. W. Eckstein, C. Garcia-Rosales, J. Roth and W. Ottenberger. Max-Plank-Institute fur Plasmaphysik Report IPP9/82 (1993); 5) An Evaluated Database for Sputtering. E. W. Thomas, R. K. Janev, J. Botero, J. J. Smith and Y. Qiu. Report IAEA INDC(NDS)-287 (1993).

  11. Study of microstructure of surface layers of low-carbon steel after turning and ultrasonic finishing

    NASA Astrophysics Data System (ADS)

    Kovalevskaya, Zh. G.; Ivanov, Yu. F.; Perevalova, O. B.; Klimenov, V. A.; Uvarkin, P. V.

    2013-01-01

    Profilometry and optical and transmission electron microscopy are used to examine the microstructure of surface layers of a low-carbon ferrite-pearlite steel subjected to turning and ultrasonic finishing. It is shown that turning peaks and valleys have different microstructures, which stipulates manifestation of technological hereditary when processing surfaces of machined parts. Ultrasonic finishing causes the severe plastic deformation of the surface layer, which favors the elimination of a technological heredity that is acquired during turning.

  12. Atomic Layer Deposition to Fine-Tune the Surface Properties and Diameters of Fabricated Nanopores

    PubMed Central

    Chen, Peng; Mitsui, Toshiyuki; Farmer, Damon B.; Golovchenko, Jene; Gordon, Roy G.; Branton, Daniel

    2011-01-01

    Atomic layer deposition of alumina enhanced the molecule sensing characteristics of fabricated nanopores by fine-tuning their surface properties, reducing 1/f noise, neutralizing surface charge to favor capture of DNA and other negative polyelectrolytes, and controlling the diameter and aspect ratio of the pores with near single Ångstrom precision. The control over the chemical and physical nature of the pore surface provided by atomic layer deposition produced a higher yield of functional nanopore detectors. PMID:24991194

  13. Analysis of strain transfer of six-layer surface-bonded fiber Bragg gratings.

    PubMed

    Wang, Quan-bao; Qiu, Ye; Zhao, Hai-tao; Chen, Ji-an; Wang, Yue-ying; Fan, Zhen-min

    2012-06-20

    A theoretical analysis of strain transfer of six-layer surface-bonded fiber Bragg gratings (FBGs) subjected to uniform axial stress is presented. The proposed six-layer structure consists of optical fiber, protective coating, adhesive layer, substrate layer, outer adhesive layer, and host material, which is different from the four-layer case of common acknowledgement. A theoretical formula of strain transfer rate from host material to optical fiber is established to provide an accurate theoretical prediction. On the basis of the theoretical analysis, influence parameters of the middle layers that affect the average strain transfer rate of the six-layer surface-bonded FBG are discussed. After the parametric study, a selection scheme of sensor parameters for numerical validation, which makes the average strain transfer rate approach unity, is determined. Good agreement is observed between numerical results and theoretical predictions. In the end, the six-layer model is extended to the general situation of multiple substrate layers, which lays a theoretical groundwork for the research and design of surface-bonded FBGs with substrate layers in the future.

  14. Effect of the interplay between protein and surface on the properties of adsorbed protein layers.

    PubMed

    Ouberai, Myriam M; Xu, Kairuo; Welland, Mark E

    2014-08-01

    Although protein adsorption to surface is a common phenomenon, investigation of the process is challenging due to the complexity of the interplay between external factors, protein and surface properties. Therefore experimental approaches have to measure the properties of adsorbed protein layers with high accuracy in order to achieve a comprehensive description of the process. To this end, we used a combination of two biosensing techniques, dual polarization interferometry and quartz crystal microbalance with dissipation. From this, we are able to extract surface coverage values, layer structural parameters, water content and viscoelastic properties to examine the properties of protein layers formed at the liquid/solid interface. Layer parameters were examined upon adsorption of proteins of varying size and structural properties, on surfaces with opposite polarity. We show that "soft" proteins such as unfolded α-synuclein and high molecular weight albumin are highly influenced by the surface polarity, as they form a highly diffuse and hydrated layer on the hydrophilic silica surface as opposed to the denser, less hydrated layer formed on a hydrophobic methylated surface. These layer properties are a result of different orientations and packing of the proteins. By contrast, lysozyme is barely influenced by the surface polarity due to its intrinsic structural stability. Interestingly, we show that for a similar molecular weight, the unfolded α-synuclein forms a layer with the highest percentage of solvation not related to surface coverage but resulting from the highest water content trapped within the protein. Together, these data reveal a trend in layer properties highlighting the importance of the interplay between protein and surface for the design of biomaterials. PMID:24780165

  15. The effect of aerosol vertical profiles on satellite-estimated surface particle sulfate concentrations

    SciTech Connect

    Liu, Yang; Wang, Zifeng; Wang, Jun; Ferrare, Richard A.; Newsom, Rob K.; Welton, Ellsworth J.

    2011-02-15

    The aerosol vertical distribution is an important factor in determining the relationship between satellite retrieved aerosol optical depth (AOD) and ground-level fine particle pollution concentrations. We evaluate how aerosol profiles measured by ground-based lidar and simulated by models can help improve the association between AOD retrieved by the Multi-angle Imaging Spectroradiometer (MISR) and fine particle sulfate (SO4) concentrations using matched data at two lidar sites. At the Goddard Space Flight Center (GSFC) site, both lidar and model aerosol profiles marginally improve the association between SO4 concentrations and MISR fractional AODs, as the correlation coefficient between cross-validation (CV) and observed SO4 concentrations changes from 0.87 for the no-scaling model to 0.88 for models scaled with aerosol vertical profiles. At the GSFC site, a large amount of urban aerosols resides in the well-mixed boundary layer so the column fractional AODs are already excellent indicators of ground-level particle pollution. In contrast, at the Atmospheric Radiation Measurement Program (ARM) site with relatively low aerosol loadings, scaling substantially improves model performance. The correlation coefficient between CV and observed SO4 concentrations is increased from 0.58 for the no-scaling model to 0.76 in the GEOS-Chem scaling model, and the model bias is reduced from 17% to 9%. In summary, despite the inaccuracy due to the coarse horizontal resolution and the challenges of simulating turbulent mixing in the boundary layer, GEOS-Chem simulated aerosol profiles can still improve methods for estimating surface aerosol (SO4) mass from satellite-based AODs, particularly in rural areas where aerosols in the free troposphere and any long-range transport of aerosols can significantly contribute to the column AOD.

  16. Evolution of the surface area of a snow layer

    SciTech Connect

    Hanot, L.; Domine, F.

    1999-12-01

    Atmospheric trace gases can partition between the atmosphere and the snow surface. Because snow has a large surface-to-volume ratio, an important interaction potential between ice and atmospheric trace gases exists. Quantifying this partitioning requires the knowledge of the surface area (SA) of snow. Eleven samples were taken from a 50 cm thick snow fall at Col de Porte, near Grenoble (French Alps) between January 20 and February 4, 1998. Fresh snow and 3, 8, and 15-day-old snow were sampled at three different depths. Surface hoar, formed after the fall, was also sampled. Air and surface snow temperature, snow density, and snow fall rate were measured. Snow temperature always remained below freezing. Snow SA was measured using methane adsorption at 77.15 K. Values ranged from 2.25 m{sup 2}/g for fresh snow to 0.25 m{sup 2}/g for surface hoar and surface snow after 15 days. These values are much too high to be explained by the macroscopic aspect of snow crystals, and microstructures such as small rime droplets must have been present. Large decrease in SA with time were observed. The first meter of snowpack had a total surface area of about 50,000 m{sup 2} per m{sup 2} of ground. Reduction in SA will lead to the emission of adsorbed species by the snowpack, with possible considerable increase in atmospheric concentrations.

  17. Measurement of surface effects on the rotational diffusion of a colloidal particle.

    PubMed

    Lobo, Sebastian; Escauriaza, Cristian; Celedon, Alfredo

    2011-03-15

    A growing number of nanotechnologies involve rotating particles. Because the particles are normally close to a solid surface, hydrodynamic interaction may affect particle rotation. Here, we track probes composed of two particles tethered to a solid surface by a DNA molecule to measure for the first time the effect of a surface on the rotational viscous drag. We use a model that superimposes solutions of the Stokes equation in the presence of a wall to confirm and interpret our measurements. We show that the hydrodynamic interaction between the surface and the probe increases the rotational viscous drag and that the effect strongly depends on the geometry of the probe.

  18. Surface Modified Particles By Multi-Step Addition And Process For The Preparation Thereof

    DOEpatents

    Cook, Ronald Lee; Elliott, Brian John; Luebben, Silvia DeVito; Myers, Andrew William; Smith, Bryan Matthew

    2006-01-17

    The present invention relates to a new class of surface modified particles and to a multi-step surface modification process for the preparation of the same. The multi-step surface functionalization process involves two or more reactions to produce particles that are compatible with various host systems and/or to provide the particles with particular chemical reactivities. The initial step comprises the attachment of a small organic compound to the surface of the inorganic particle. The subsequent steps attach additional compounds to the previously attached organic compounds through organic linking groups.

  19. Layered Gold and Titanium Dioxide Substrates for Improved Surface Enhanced Raman Spectroscopic Sensing.

    PubMed

    Strobbia, Pietro; Henegar, Alex J; Gougousi, Theodosia; Cullum, Brian M

    2016-08-01

    This manuscript describes a simple process for fabricating gold-based, multi-layered, surface-enhanced Raman scattering (SERS) substrates that can be applied to a variety of different nanostructures, while still providing multi-layer enhancement factors comparable to those previously achieved only with optimized silver/silver oxide/silver substrates. In particular, gold multi-layered substrates generated by atomic layer deposition (ALD) have been fabricated and characterized in terms of their optimal performance, revealing multi-layer enhancements of 2.3-fold per spacer layer applied. These substrates were fabricated using TiO2 as the dielectric spacer material between adjacent gold layers, with ALD providing a conformal thin film with high surface coverage and low thickness. By varying the spacer layer thicknesses from sub-monolayer (non-contiguous) films through multiple TiO2 layer thick films, the non-monotonic spacer layer thickness response has been elucidated, revealing the importance of thin, contiguous dielectric spacer layers for optimal enhancement. Furthermore, the extended shelf life of these gold multi-layered substrates was characterized, demonstrating usable lifetimes (i.e. following storage in ambient conditions) of greater than five months, with the further potential for simple limited electrochemical regeneration even after this time. PMID:27329834

  20. Layer-by-layer self-assembled mutilayer films of gold nanoparticles for surface-assisted laser desorption/ionization mass spectrometry.

    PubMed

    Kawasaki, Hideya; Sugitani, Tsuyoshi; Watanabe, Takehiro; Yonezawa, Tetsu; Moriwaki, Hiroshi; Arakawa, Ryuichi

    2008-10-01

    Layer-by-layer (LBL) self-assembled multilayer films of gold nanoparticles (AuNPs) on a silicon wafer were demonstrated to be promising substrates for surface-assisted laser desorption/ionization (SALDI) mass spectrometry (MS) of peptides and environmental pollutants for the first time. LBL multilayer films, (AuNPs/PAHC)n, consisting of alternating layers of ammonium citrate capped AuNPs and poly(allylamine hydrochloride) (PAHC) were prepared on a silicon surface. Silicon plates with aggregated AuNPs were more suitable than those with dispersed AuNPs for the SALDI-MS of peptides. The number of particle layers had a significant effect on the laser desorption/ionization of angiotensin I; the peak intensity of the peptide (molecular ion amount) increased with an increase in the number of layers of AuNPs. As a result, the (AuNPs/PAHC)5 multilayer films increased the sensitivity of the angiotensin I to subfemtomoles and raised the useful analyte mass range, thus making it possible to detect small proteins (a 12 kDa cytochrome c). The signal enhancement when using (AuNPs/PAHC)5 may be due to (i) the high absorption of the UV laser light at 337 nm by the AuNP layers, (ii) the low thermal conductivity due to the AuNPs being covered with a thin monolayer of PAHC, and (iii) the increase in the surface roughness (approximately 100 nm) with the number of AuNP layers. Thus, laser-induced rapid high heating of AuNPs for effective desorption/ionization of peptides is possible. In addition, it was found that (AuNPs/PAHC)5 could be used to extract environmental pollutants (pyrene and dimethyldistearylammonium chloride) from very dilute aqueous solutions with concentrations less than 10(-10) mg/mL, and the analytes trapped in the LBL film could be identified by introducing the film directly into the SALDI mass spectrometer without needing to elute the analytes out of the film.

  1. Origin and consequences of silicate glass passivation by surface layers

    NASA Astrophysics Data System (ADS)

    Gin, Stéphane; Jollivet, Patrick; Fournier, Maxime; Angeli, Frédéric; Frugier, Pierre; Charpentier, Thibault

    2015-02-01

    Silicate glasses are durable materials, but are they sufficiently durable to confine highly radioactive wastes for hundreds of thousands years? Addressing this question requires a thorough understanding of the mechanisms underpinning aqueous corrosion of these materials. Here we show that in silica-saturated solution, a model glass of nuclear interest corrodes but at a rate that dramatically drops as a passivating layer forms. Water ingress into the glass, leading to the congruent release of mobile elements (B, Na and Ca), is followed by in situ repolymerization of the silicate network. This material is at equilibrium with pore and bulk solutions, and acts as a molecular sieve with a cutoff below 1 nm. The low corrosion rate resulting from the formation of this stable passivating layer enables the objective of durability to be met, while progress in the fundamental understanding of corrosion unlocks the potential for optimizing the design of nuclear glass-geological disposal.

  2. Origin and consequences of silicate glass passivation by surface layers.

    PubMed

    Gin, Stéphane; Jollivet, Patrick; Fournier, Maxime; Angeli, Frédéric; Frugier, Pierre; Charpentier, Thibault

    2015-02-19

    Silicate glasses are durable materials, but are they sufficiently durable to confine highly radioactive wastes for hundreds of thousands years? Addressing this question requires a thorough understanding of the mechanisms underpinning aqueous corrosion of these materials. Here we show that in silica-saturated solution, a model glass of nuclear interest corrodes but at a rate that dramatically drops as a passivating layer forms. Water ingress into the glass, leading to the congruent release of mobile elements (B, Na and Ca), is followed by in situ repolymerization of the silicate network. This material is at equilibrium with pore and bulk solutions, and acts as a molecular sieve with a cutoff below 1 nm. The low corrosion rate resulting from the formation of this stable passivating layer enables the objective of durability to be met, while progress in the fundamental understanding of corrosion unlocks the potential for optimizing the design of nuclear glass-geological disposal.

  3. Origin and consequences of silicate glass passivation by surface layers.

    PubMed

    Gin, Stéphane; Jollivet, Patrick; Fournier, Maxime; Angeli, Frédéric; Frugier, Pierre; Charpentier, Thibault

    2015-01-01

    Silicate glasses are durable materials, but are they sufficiently durable to confine highly radioactive wastes for hundreds of thousands years? Addressing this question requires a thorough understanding of the mechanisms underpinning aqueous corrosion of these materials. Here we show that in silica-saturated solution, a model glass of nuclear interest corrodes but at a rate that dramatically drops as a passivating layer forms. Water ingress into the glass, leading to the congruent release of mobile elements (B, Na and Ca), is followed by in situ repolymerization of the silicate network. This material is at equilibrium with pore and bulk solutions, and acts as a molecular sieve with a cutoff below 1 nm. The low corrosion rate resulting from the formation of this stable passivating layer enables the objective of durability to be met, while progress in the fundamental understanding of corrosion unlocks the potential for optimizing the design of nuclear glass-geological disposal. PMID:25695377

  4. Origin and consequences of silicate glass passivation by surface layers

    PubMed Central

    Gin, Stéphane; Jollivet, Patrick; Fournier, Maxime; Angeli, Frédéric; Frugier, Pierre; Charpentier, Thibault

    2015-01-01

    Silicate glasses are durable materials, but are they sufficiently durable to confine highly radioactive wastes for hundreds of thousands years? Addressing this question requires a thorough understanding of the mechanisms underpinning aqueous corrosion of these materials. Here we show that in silica-saturated solution, a model glass of nuclear interest corrodes but at a rate that dramatically drops as a passivating layer forms. Water ingress into the glass, leading to the congruent release of mobile elements (B, Na and Ca), is followed by in situ repolymerization of the silicate network. This material is at equilibrium with pore and bulk solutions, and acts as a molecular sieve with a cutoff below 1 nm. The low corrosion rate resulting from the formation of this stable passivating layer enables the objective of durability to be met, while progress in the fundamental understanding of corrosion unlocks the potential for optimizing the design of nuclear glass-geological disposal. PMID:25695377

  5. Single-Particle Black Carbon Aerosol Verticle Profiles From the Boundary Layer to the Lower Stratosphere

    NASA Astrophysics Data System (ADS)

    Schwarz, J. P.; Gao, R. S.; Fahey, D. W.; Laurel, W. A.; Thomson, D. S.; Kok, G. L.; Baumgardner, D.; Wilson, J. C.; Lopez, J.; Aikin, K.; Jost, H.; Thompson, T. L.; Reeves, J. M.; Lowenstein, M.

    2005-12-01

    A single-particle soot photometer (SP2) was flown on a NASA WB-57F high-altitude research aircraft in November 2004 from Houston, TX. The SP2 uses laser-induced incandescence to directly measure the mass of individual black-carbon (BC) particles in the mass range of ~0.3-300 fg. Scattered light is used to size non-absorbing aerosols in the range of ~150 - 700 nm diameter. Data from two mid-latitude flights has been used to generate size distributions and profiles of both aerosol types from the boundary layer to the lower stratosphere. Results for scattering aerosol concentrations are in good agreement with typical particle spectrometer measurements in the same region. Mass mixing ratios of BC between 5 and 18.7 km were roughly an order of magnitude lower than typical values as reported with wire impactor measurements and as predicted by two global BC models. The impact of this discrepancy on estimates of direct radiative forcing of BC aerosol will also be discussed.

  6. Layered Model for Radiation-Induced Chemical Evolution of Icy Surface Composition on Kuiper Belt and Oort Cloud Bodies

    NASA Technical Reports Server (NTRS)

    Cooper, John F.; Hill, Matthew E.; Richardson, John D.; Sturner, Steven J.

    2010-01-01

    The diversity of albedos and surface colors on observed Kuiper Belt and Inner Oort Cloud objects remains to be explained in terms of competition between primordial intrinsic versus exogenic drivers of surface and near-surface evolution. Earlier models have attempted without success to attribute this diversity to the relations between surface radiolysis from cosmic ray irradiation and gardening by meteoritic impacts. A more flexible approach considers the different depth-dependent radiation profiles produced by low-energy plasma, suprathermal, and maximally penetrating charged particles of the heliospheric and local interstellar radiation environments. Generally red objects of the dynamically cold (low inclination, circular orbit) Classical Kuiper Belt might be accounted for from erosive effects of plasma ions and reddening effects of high energy cosmic ray ions, while suprathermal keV-MeV ions could alternatively produce more color neutral surfaces. The deepest layer of more pristine ice can be brought to the surface from meter to kilometer depths by larger impact events and potentially by cryovolcanic activity. The bright surfaces of some larger objects, e.g. Eris, suggest ongoing resurfacing activity. Interactions of surface irradiation, resultant chemical oxidation, and near-surface cryogenic fluid reservoirs have been proposed to account for Enceladus cryovolcanism and may have further applications to other icy irradiated bodies. The diversity of causative processes must be understood to account for observationally apparent diversities of the object surfaces.

  7. Layered Model for Radiation-Induced Chemical Evolution of Icy Surface Composition on Kuiper Belt and Oort Cloud Bodies

    NASA Astrophysics Data System (ADS)

    Cooper, John F.; Hill, M. E.; Richardson, J. D.; Sturner, S. J.

    2010-10-01

    The diversity of albedos and surface colors on observed Kuiper Belt and Inner Oort Cloud objects remains to be explained in terms of competition between primordial intrinsic versus exogenic drivers of surface and near-surface evolution. Earlier models have attempted without success to attribute this diversity to the relations between surface radiolysis from cosmic ray irradiation and gardening by meteoritic impacts. A more flexible approach considers the different depth-dependent radiation profiles produced by low-energy plasma, suprathermal, and maximally penetrating charged particles of the heliospheric and local interstellar radiation environments. Generally red objects of the dynamically cold (low inclination, circular orbit) Classical Kuiper Belt might be accounted for from erosive effects of plasma ions and reddening effects of high energy cosmic ray ions, while suprathermal keV-MeV ions could alternatively produce more color neutral surfaces. The deepest layer of more pristine ice can be brought to the surface from meter to kilometer depths by larger impact events and potentially by cryovolcanic activity. The bright surfaces of some larger objects, e.g. Eris, suggest ongoing resurfacing activity. Interactions of surface irradiation, resultant chemical oxidation, and near-surface cryogenic fluid reservoirs have been proposed to account for Enceladus cryovolcanism (Cooper et al., Plan. Sp. Sci., 2009) and may have further applications to other icy irradiated bodies. The diversity of causative processes must be understood to account for observationally apparent diversities of the object surfaces