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1

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

PubMed

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 ?-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 3-5?m. 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. PMID:24594041

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

2

Electrical Double-Layer Interaction between Charged Particles near Surfaces and in Confined Geometries  

E-print Network

Electrical Double-Layer Interaction between Charged Particles near Surfaces and in Confined The proximity effect of one or two flat surfaces on the double- layer interaction between two identically. INTRODUCTION The electrical double-layer interaction between two charged spheres immersed in an unbounded

Chan, Derek Y C

3

Nanocrystalline Surface Layer on AISI 52100 Steel Induced by Supersonic Fine Particles Bombarding  

NASA Astrophysics Data System (ADS)

Surface treatment of AISI 52100 steel by supersonic fine particles bombarding (SFPB) was studied in this article. The surface topography, morphology of the surface layer, and microhardness distribution of the surface layer have been investigated using a surface profiler system, a scanning electron microscopy (SEM), and a microvickers hardness tester. The microstructure, phase composition, and residual stress distribution of the surface layer in AISI 52100 steel after the SFBP treatment have been characterized by means of x-ray diffraction, SEM, and transmission electron microscopy. The results showed that a nanocrystalline surface (NS) layer was formed on the top surface of the SFBP-treated AISI 52100 steel samples. The NS layer is about 2 ?m in thickness with a surface roughness of R a = 1.2 ?m, R y = 6.7 ?m, R z = 6.0 ?m. Phase transitions occurred in the surface of the SFBP-treated samples. Residual compressive stress is obtained at the surface of the SFBP-treated samples. The maximum value of compressive stress appears at the outermost of the surface, and the affection region of the whole surface is about 60 ?m in thickness. A hardened surface layer has been fabricated in the AISI 52100 steel. The thickness of the hardened surface layer is about 70 ?m. The maximum value of hardness occurs at the depth of 20 ?m from the outermost surface.

Kong, Lingyan; Lao, Yuanxia; Xiong, Tianying; Li, Tiefan

2013-08-01

4

Influence of surface chemistry and topography of particles on their immersion into the lung's surface-lining layer.  

PubMed

Inhaled and deposited spherical particles, 1-6 micrometer in diameter and of differing surface chemistry and topography, were studied in hamster intrapulmonary conducting airways and alveoli by electron microscopy. Polystyrene and Teflon particles, as well as puffball spores, were found submersed in the aqueous lining layer and adjacent to epithelial cells. The extent of particle immersion promoted by a surfactant film was assessed in a "floating-drop-surface balance" by light microscopy. Teflon and polystyrene spheres were immersed into the subphase by 50-60% at film surface tensions of 25 and 30 mJ/m(2), respectively, and totally submersed at 15 and 25 mJ/m(2), respectively. Puffball spores were immersed by approximately 50% at 22 mJ/m(2) and totally submersed at film surface tensions of surface tension in the intrapulmonary conducting airways of hamsters may reach particles (<10 micrometer in diameter) are wetted and displaced into the surface lining layer, which may facilitate interactions with many lung cells. PMID:12547838

Geiser, Marianne; Schurch, Samuel; Gehr, Peter

2003-05-01

5

Compliant layer chucking surface  

DOEpatents

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.

Blaedel, Kenneth L. (Dublin, CA); Spence, Paul A. (Pleasanton, CA); Thompson, Samuel L. (Pleasanton, CA)

2004-12-28

6

Atomic Layer Deposition of SiO2 Films on BN Particles Using Sequential Surface Reactions  

E-print Network

matrix of composite materials.7 The SiO2 film should be thin to minimize the effect of the oxide coating on the thermal conductivity of the BN particles. Wet chemical processing and chemical vapor deposi- tion or fluidized.10 In contrast, atomic layer deposition (ALD) is an ideal technique for depositing ultrathin films

George, Steven M.

7

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

NASA Astrophysics Data System (ADS)

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 relation between the motion of a probe particle and the local structure and dynamics of complex fluids such as mucus, or even one step back, simple polymer solutions and gels? It is well known that the thermal motion of a particle in simple solutions like water can be described by Stokes-Einstein relation, in which the mean-square displacement of the particle is (1) linearly proportional to time and (2) inversely proportional to the bulk viscosity of the solution. We found that these two statements become questionable if the particle size is relatively small and the solutions become complex fluids such as polymer solutions and gels. The motion of small particles with size smaller than the entanglement length (network mesh size) of a polymer solution (gel) is sub-diffusive with mean-square displacement proportional to the square root of time at relatively short time scales. Even at long time scales at which the mean-square displacement of the particles is diffusive, the mean-square displacement of the particles is not necessarily determined by the bulk viscosity, and is inversely proportional to an effective viscosity that is much smaller than the bulk value. An interesting question related to the particle motion in polymer gels is whether particles with size larger than the network mesh size can move through the gel? An intuitive answer would be that such large particles are trapped by the local network cages. We argue that the large particles can still diffuse via hopping mechanism, i.e., particles can wait for fluctuations of surrounding network cages that could be large enough to allow them to slip though. This hopping diffusion can be applied to understand the motion of large particles subjected to topological constraints such as permanent or reversible crosslinked networks as well as entanglements in high molecular weight polymer solutions, melts, and networks.

Cai, Liheng

8

Aerosol Measurements in the Atmospheric Surface Layer at L'Aquila, Italy: Focus on Biogenic Primary Particles  

NASA Astrophysics Data System (ADS)

Two year measurements of aerosol concentration and size distribution (0.25 ?m < d < 30 ?m) in the atmospheric surface layer, collected in L'Aquila (Italy) with an optical particle counter, are reported and analysed for the different modes of the particle size distribution. A different seasonal behaviour is shown for fine mode aerosols (largely produced by anthropogenic combustion), coarse mode and large-sized aerosols, whose abundance is regulated not only by anthropogenic local production, but also by remote natural sources (via large scale atmospheric transport) and by local sources of primary biogenic aerosols. The observed total abundance of large particles with diameter larger than 10 ?m is compared with a statistical counting of primary biogenic particles, made with an independent technique. Results of these two observational approaches are analysed and compared to each other, with the help of a box model driven by observed meteorological parameters and validated with measurements of fine and coarse mode aerosols and of an atmospheric primary pollutant of anthropogenic origin (NOx). Except in winter months, primary biogenic particles in the L'Aquila measurement site are shown to dominate the atmospheric boundary layer population of large aerosol particles with diameter larger than 10 ?m (about 80 % of the total during summer months), with a pronounced seasonal cycle, contrary to fine mode aerosols of anthropogenic origin. In order to explain these findings, the main mechanisms controlling the abundance and variability of particulate matter tracers in the atmospheric surface layer are analysed with the numerical box-model.

Pitari, Giovanni; Coppari, Eleonora; De Luca, Natalia; Di Carlo, Piero; Pace, Loretta

2014-09-01

9

Aerosol Measurements in the Atmospheric Surface Layer at L'Aquila, Italy: Focus on Biogenic Primary Particles  

NASA Astrophysics Data System (ADS)

Two year measurements of aerosol concentration and size distribution (0.25 ?m < d < 30 ?m) in the atmospheric surface layer, collected in L'Aquila (Italy) with an optical particle counter, are reported and analysed for the different modes of the particle size distribution. A different seasonal behaviour is shown for fine mode aerosols (largely produced by anthropogenic combustion), coarse mode and large-sized aerosols, whose abundance is regulated not only by anthropogenic local production, but also by remote natural sources (via large scale atmospheric transport) and by local sources of primary biogenic aerosols. The observed total abundance of large particles with diameter larger than 10 ?m is compared with a statistical counting of primary biogenic particles, made with an independent technique. Results of these two observational approaches are analysed and compared to each other, with the help of a box model driven by observed meteorological parameters and validated with measurements of fine and coarse mode aerosols and of an atmospheric primary pollutant of anthropogenic origin (NOx). Except in winter months, primary biogenic particles in the L'Aquila measurement site are shown to dominate the atmospheric boundary layer population of large aerosol particles with diameter larger than 10 ?m (about 80 % of the total during summer months), with a pronounced seasonal cycle, contrary to fine mode aerosols of anthropogenic origin. In order to explain these findings, the main mechanisms controlling the abundance and variability of particulate matter tracers in the atmospheric surface layer are analysed with the numerical box-model.

Pitari, Giovanni; Coppari, Eleonora; De Luca, Natalia; Di Carlo, Piero; Pace, Loretta

2014-03-01

10

Molecularly imprinted polydopamine nano-layer on the pore surface of porous particles for protein capture in HPLC column.  

PubMed

Bio-inspired Human Serum Albumin (HSA) imprinted polydopamine nano-layer was produced through oxidative polymerization of dopamine on the pore surface of HSA modified porous silica particles. The coating thickness was controlled by the reaction time and thereby varied within 0-12 nm. The samples were characterized by elemental analysis, FT-IR, DSC, SEM, TEM, TGA, physisorption and thermoporometry. The characterization confirmed the success of evolution and deposition of polydopamine layer on the silica pore surface. Batch rebinding experiment showed that the molecularly imprinted polymer (MIP) with 8.7 nm coating thickness, in comparison with the thinner and thicker coatings, displays the highest uptake of the target protein. The chromatographic evaluation of the materials packed in HPLC columns showed that the HSA imprinted polydopamine offers good mechanical stability and retains practically all the target protein from an HSA solution or human plasma. Affinity of the imprinting column was examined by using Bovine Serum Albumin (BSA) and Immunoglobulin G (IgG) as competitive proteins. The results showed that the template, HSA, was the most adsorbed protein by the imprinted polydopamine layer. PMID:23692917

Nematollahzadeh, Ali; Shojaei, Akbar; Abdekhodaie, Mohammad J; Sellergren, Börje

2013-08-15

11

A Method of Measuring Hydrogen Isotopes in Surface Layers of Planetary Soils by Spectroscopy of Recoil Protons in Alpha Particle Elastic Scattering  

Microsoft Academic Search

A theoretical and experimental feasibility study of possible determination of the hydrogen and deuterium concentrations in the surface layers of planetary bodies is presented. The method under study is the recoil proton and deuteron spectrometry of forward scattering in the course of elastic interaction of alpha particles with the nuclei of hydrogen isotopes. The spectra of recoil protons and deuterons

B. N. Korchuganov; G. G. Dol'nikov; M. V. Gerasimov; O. F. Prilutskii; R. Rider; G. Waenke; T. Economou

2004-01-01

12

Formation of a wear-resistant nanocrystalline layer strengthened by TiO2 (Rutile) particles on the surface of titanium  

NASA Astrophysics Data System (ADS)

The effect of a thermomechanical treatment including severe plastic deformation under dry sliding friction conditions and subsequent heating in air to 350-650°C with further holding for 1 h on the structure and wear resistance of commercial titanium of grade VT1-0 has been studied. It has been shown that the deformation by friction leads to the formation of a nanocrystalline structure with ? crystals 20-100 nm in size in a surface layer of titanium of about 10 ?m thick. The heating of titanium deformed by friction at temperatures of 450-650°C for 1 h in air leads to the formation in the surface layer of this material ˜10 ?m thick of nanocrystalline particles of the titanium oxide TiO2 (rutile), the volume fraction of which reaches tens of percents, while the dimensions are ˜10 nm. The presence in the surface layer of titanium of a nanocrystalline two-phase (?-Ti + rutile) structure leads to a significant increase in the wear resistance of the VT1-0 titanium in pair with steel 40Kh13. This is explained by the enhanced strength of the arising nanocrystalline layer and its positive influence (as of a transition layer) on the reduction of the level of internal stresses that exist at the interface between the titanium oxide TiO2 and the host metal.

Korshunov, L. G.; Chernenko, N. L.

2013-09-01

13

Comparative study of the surface layer density of liquid surfaces  

NASA Astrophysics Data System (ADS)

Capillary wave fluctuations blur the inherent structure of liquid surfaces in computer simulations. The intrinsic sampling method subtracts capillary wave fluctuations and yields the intrinsic surface structure, leading to a generic picture of the liquid surface. The most relevant magnitude of the method is the surface layer density ns that may be consistently determined from different properties: the layering structure of the intrinsic density profiles, the turnover rate for surface layer particles, and the hydrodynamic damping rate of capillary waves. The good agreement among these procedures provides evidence for the physical consistency of the surface layering hypothesis, as an inherent physical property of the liquid surfaces. The dependence of the surface compactness, roughness, and exchange rate with temperature is analyzed for several molecular interaction models.

Chacón, E.; Fernández, E. M.; Duque, D.; Delgado-Buscalioni, R.; Tarazona, P.

2009-11-01

14

Surface chemistry and infrared absorbance changes during ZnO atomic layer deposition on ZrO2 and BaTiO3 particles  

NASA Astrophysics Data System (ADS)

ZnO atomic layer deposition (ALD) was achieved using sequential exposures of Zn(CH2CH3)2 and H2O on ZrO2 and BaTiO3 particles at 450 K. The surface chemistry of ZnO ALD was monitored in vacuum using Fourier transform infrared spectroscopy. The BaTiO3 and ZrO2 particles initially displayed vibrational features consistent with surface hydroxyl (-OH) groups. Zn(CH2CH3)2 exposure removed the surface hydroxyl groups and created Zn(CH2CH3)* surface species. The subsequent H2O exposure removed the Zn(CH2CH3)* surface species and produced ZnOH* surface species. Repeating the Zn(CH2CH3)2 and H2O exposures in an ABAB... reaction sequence at 450 K progressively deposited ZnO. Because ZnO is a semiconductor, the background infrared absorbance increased with the number of AB cycles during the deposition of the ZnO film. The increasing background infrared absorbance during long Zn(CH2CH3)2 exposures also revealed that the Zn(CH2CH3)2 reaction is not self-limiting. The background absorbance was modulated dramatically by the presence of ethyl (-CH2CH3) or hydroxyl (-OH) groups on the surface of the growing ZnO film. The infrared absorbance was higher with hydroxyl (-OH) groups and lower with ethyl (-CH2CH3) groups on the ZnO surface. The background absorbance changes were not linear with surface coverage. The large changes in absorbance after low reactant exposure suggested that the most reactive surface sites may be most influential in affecting the film conductance. Transmission electron microscopy (TEM) was used to examine the ZnO films deposited on the ZrO2 and BaTiO3 particles. The TEM images revealed ZrO2 and BaTiO3 particles encapsulated by conformal ZnO films. The ZnO films had a thickness of ~43 A? after 20 AB reaction cycles and ~65 A? after 30 AB reaction cycles, respectively. These TEM images are consistent with a ZnO ALD growth rate at 450 K of ~2.2 A?/AB cycle.

Ferguson, J. D.; Weimer, A. W.; George, S. M.

2005-01-01

15

Characterization of Surface and Grain Boundary Layer of Barium Titanate.  

National Technical Information Service (NTIS)

The object of this investigation was to characterize the surface layer of ceramic particles and the grain boundary layer of ceramic materials by a few selected electrical and optical experiments, observe their unusual changes, if any, and infer from them ...

A. K. Goswami

1970-01-01

16

Surface layers of bacteria.  

PubMed Central

Since bacteria are so small, microscopy has traditionally been used to study them as individual cells. To this end, electron microscopy has been a most powerful tool for studying bacterial surfaces; the viewing of macromolecular arrangements of some surfaces is now possible. This review compares older conventional electron-microscopic methods with new cryotechniques currently available and the results each has produced. Emphasis is not placed on the methodology but, rather, on the importance of the results in terms of our perception of the makeup and function of bacterial surfaces and their interaction with the surrounding environment. Images PMID:1723487

Beveridge, T J; Graham, L L

1991-01-01

17

The neutral surface layer above rough surfaces  

NASA Astrophysics Data System (ADS)

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.

Smedman, Ann-Sofi; Sahlee, Erik

2014-05-01

18

Surface engineering using layer-by-layer assembly of pH-sensitive polymers and nanoparticles  

E-print Network

Surface engineering of a variety of materials including colloidal particles and porous membranes has been achieved by using layer-by-layer assembly of pH-sensitive polymers and nanoparticles. In the first part of this ...

Lee, Daeyeon

2007-01-01

19

Transient deposition of colloidal particles onto oppositely charged porous media surfaces: Experimental investigation on the role of lateral double layer repulsion  

SciTech Connect

Previous theoretical and experimental particle deposition studies have focused on the effect of colloidal interactions on particle deposition kinetics in the initial stage of the deposition process. In most colloidal transport processes, however, the {open_quotes}clean-collector{close_quotes} assumption is not valid. After a short period of time, particles interact with previously retained particles rather than bare collectors. In this study, we present experimental results regarding the role of retained particles in particle deposition dynamics. We investigated the effects of solution chemistry, particle concentration, and particle size on the coverage of collector surfaces during particle deposition dynamics. Results show that as collectors are covered with retained particles, deposition rates can significantly decrease or increase, depending on the chemistry of the solution. When particle-particle interactions are not favorable, the {open_quotes}blocking{close_quotes} effect predominates, while under favorable particle-particle interactions {open_quotes}ripening{close_quotes} is important. The area blocked by one retained particle at various ionic strengths was calculated from the experimental particle breakthrough curves.

Johnson, P.R.; Liu, D.; Elimelech, M. [Univ. of California, Los Angeles, CA (United States)

1995-12-01

20

Surface Plasmonic Core-Shell Particles for Solar Energy Harvesting.  

E-print Network

??Plasmonic core-shell particles, consisting of a spherical dielectric core coated with a concentric layer of metallic nanoshell, are versatile subwavelength optical components. Their surface plasmon… (more)

Bo, Ding

2014-01-01

21

Optical sensing quantum dot-labeled polyacrolein particles prepared by layer-by-layer deposition technique  

Microsoft Academic Search

Optical sensing polymer particles with tailored semiconductor nanocrystal (QD) loading are prepared by layer-by-layer deposition technique (LbL). Polyacrolein particles of 1.2?m diameter are used as solid support for deposition of hydrophilic CdSe\\/ZnS nanocrystal\\/polyelectrolyte multilayers formed by electrostatic interactions. The pH-dependent fluorescence of QDs and pH-dependent conformations of polyelectrolytes, which likely passivate the surface state of nanocrystals, allow a creation of

Alla N. Generalova; Vladimir A. Oleinikov; Margarita M. Zarifullina; Ekaterina V. Lankina; Svetlana V. Sizova; Michail V. Artemyev; Vitali P. Zubov

2011-01-01

22

Particle motion in atmospheric boundary layers of Mars and Earth  

NASA Technical Reports Server (NTRS)

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.

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

1975-01-01

23

Particle tracking around surface nanobubbles.  

PubMed

The exceptionally long lifetime of surface nanobubbles remains one of the biggest questions in the field. One of the proposed mechanisms for producing the stability is the dynamic equilibrium model, which describes a constant flux of gas in and out of the bubble. Here, we describe results from particle tracking experiments carried out to measure this flow. The results are analysed by measuring the Voronoï cell size distribution, the diffusion, and the speed of the tracer particles. We show that there is no detectable difference in the movement of particles above nanobubble-laden surfaces as compared to ones above nanobubble-free surfaces. PMID:23598947

Dietrich, Erik; Zandvliet, Harold J W; Lohse, Detlef; Seddon, James R T

2013-05-01

24

Kinetic double-layer model of aerosol surface chemistry and gas-particle interactions (K2-SURF): Degradation of polycyclic aromatic hydrocarbons exposed to O3, NO2, H2O, OH and NO3  

NASA Astrophysics Data System (ADS)

We present a kinetic double-layer surface model (K2-SURF) that describes the degradation of polycyclic aromatic hydrocarbons (PAHs) on aerosol particles exposed to ozone, nitrogen dioxide, water vapor, hydroxyl and nitrate radicals. The model is based on multiple experimental studies of PAH degradation and on the PRA framework (Pöschl-Rudich-Ammann, 2007) for aerosol and cloud surface chemistry and gas-particle interactions. For a wide range of substrates, including solid and liquid organic and inorganic substances (soot, silica, sodium chloride, octanol/decanol, organic acids, etc.), the concentration- and time-dependence of the heterogeneous reaction between PAHs and O3 can be efficiently described with a Langmuir-Hinshelwood-type mechanism. Depending on the substrate material, the Langmuir adsorption constants for O3 vary over three orders of magnitude (Kads,O3 ? 10-15-10-13 cm3), and the second-order rate coefficients for the surface layer reaction of O3 with different PAH vary over two orders of magnitude (kSLR,PAH,O3 ? 10-18-10-17 cm2 s-1). The available data indicate that the Langmuir adsorption constants for NO2 are similar to those of O3, while those of H2O are several orders of magnitude smaller (Kads,H2O ? 10-18-10-17 cm3). The desorption lifetimes and adsorption enthalpies inferred from the Langmuir adsorption constants suggest chemisorption of NO2 and O3 and physisorption of H2O. Note, however, that the exact reaction mechanisms, rate limiting steps and possible intermediates still remain to be resolved (e.g., surface diffusion and formation of O atoms or O3- ions at the surface). The K2-SURF model enables the calculation of ozone uptake coefficients, ?O3, and of PAH concentrations in the quasi-static particle surface layer. Competitive adsorption and chemical transformation of the surface (aging) lead to a strong non-linear dependence of ?O3 on time and gas phase composition, with different characteristics under dilute atmospheric and concentrated laboratory conditions. Under typical ambient conditions, ?O3 of PAH-coated aerosol particles are expected to be in the range of 10-6-10-5. At ambient temperatures, NO2 alone does not efficiently degrade PAHs, but it was found to accelerate the degradation of PAHs exposed to O3. The accelerating effect can be attributed to highly reactive NO3 radicals formed in the gas phase or on the surface. Estimated second-order rate coefficients for O3-NO2 and PAH-NO3 surface layer reactions are in the range of 10-17-10-16 cm2 s-1 and 10-15-10-12 cm2 s-1, respectively. The chemical half-life of PAHs is expected to range from a few minutes on the surface of soot to multiple hours on organic and inorganic solid particles and days on liquid particles. On soot, the degradation of particle-bound PAHs in the atmosphere appears to be dominated by a surface layer reaction with adsorbed ozone. On other substrates, it is likely dominated by gas-surface reactions with OH or NO3 radicals (Eley-Rideal-type mechanism). To our knowledge, K2-SURF is the first atmospheric process model describing multiple types of parallel and sequential surface reactions between multiple gaseous and particle-bound chemical species. It illustrates how the general equations of the PRA framework can be simplified and adapted for specific reaction systems, and we suggest that it may serve as a basis for the development of a general master mechanism of aerosol and cloud surface chemistry.

Shiraiwa, M.; Garland, R. M.; Pöschl, U.

2009-12-01

25

Formation of the Surface Space Charge Layer in Fair Weather  

NASA Astrophysics Data System (ADS)

It is widely known that the positive space charge, caused by electrode effect action, is obtained near surface in fair weather. Space charge density depends on the different local features: meteorological conditions, aerosol particles concentration, convective transfer of the surface layer. Namely space charge determines the local variations of electric field. Space charge could be negative in condition of strong ionization rate in thin air layer near surface. The electrodynamic model, consisting of transfer equations of light ions and nucleuses, generated by interactions between lights ions and aerosol particles, and Poisson equation. The turbulent transfer members, electric field near the surface, the mobility of positive and negative ions, recombination coefficient, ionization rate, the number of elementary charges on the nuclei were took into account in the model equations. The time-space variations of positive and negative small and heavy ions, electric field, electrical conductivity, current density and space charge, depending on aerosol particles concentrations, turbulence and convective transfer ionization rate, aerosol particles size and number of charged on the particles are calculated. The mechanisms of turbulent and convection-turbulent surface layer electrodynamic structure forming in dependence of single and multi-charged aerosol particles for different physical and meteorological conditions are investigated. Increasing of turbulent mixing intensity leads to increasing of character electrode layer thickness, decreasing of space charge density value, decreasing of electric current conductivity value. The electrode effect of the whole layer remains constant. Increasing of aerosol particles concentration leads to decreasing of electrode effect within the whole electrode layer and increasing of electric field values, decreasing of space charge density values and current conductivity density. It was received that increasing of the aerosol particles concentration under weak turbulent mixing leads to increasing of the negative space charge density and its displacement to the surface level. Under severe contamination condition the electrodynamic structure of surface layer is primarily determined by negative space charge, generated by nucleuses. It was received that in case of small aerosol particles the surface layer electrodynamic structure is basically established by single- and double-charged particles. Single-charged and double-charged as triply-charged, fourfold-charged and fivefold-charged aerosol particles primarily affect on electrodynamic structure of the surface layer in case of increasing of aerosol particles size. The local variations of the electric field in different conditions were studied. Theoretical results are in a good agreement with experimental facts.

Redin, Alexander; Kupovykh, Gennady; Boldyreff, Anton

2014-05-01

26

Kinetic double-layer model of aerosol surface chemistry and gas-particle interactions (K2-SURF): degradation of polycyclic aromatic hydrocarbons exposed to O3, NO2, H2O, OH and NO3  

NASA Astrophysics Data System (ADS)

We present a kinetic double-layer surface model (K2-SURF) that describes the degradation of polycyclic aromatic hydrocarbons (PAHs) on aerosol particles exposed to ozone, nitrogen dioxide, water vapor, hydroxyl and nitrate radicals. The model is based on multiple experimental studies of PAH degradation and on the PRA framework (Pöschl et al., 2007) for aerosol and cloud surface chemistry and gas-particle interactions. For a wide range of substrates, including solid and liquid organic and inorganic substances (soot, silica, sodium chloride, octanol/decanol, organic acids, etc.), the concentration- and time-dependence of the heterogeneous reaction between PAHs and O3 can be efficiently described with a Langmuir-Hinshelwood-type mechanism. Depending on the substrate material, the Langmuir adsorption constants for O3 vary over three orders of magnitude (Kads,O3?10-15-10-13 cm3), and the second-order rate coefficients for the surface layer reaction of O3 with different PAH vary over two orders of magnitude (kSLR,PAH,O3?10-18-10-17 cm2 s-1). The available data indicate that the Langmuir adsorption constants for NO2 are similar to those of O3, while those of H2O are several orders of magnitude smaller (Kads,H2O?10-18-10-17 cm3). The desorption lifetimes and adsorption enthalpies inferred from the Langmuir adsorption constants suggest chemisorption of NO2 and O3 - possibly in the form of O atoms - and physisorption of H2O. The K2-SURF model enables the calculation of ozone uptake coefficients, ?O3, and of PAH concentrations in the quasi-static particle surface layer. Competitive adsorption and chemical transformation of the surface (aging) lead to a strong non-linear dependence of ?O3 on time and gas phase composition, with different characteristics under dilute atmospheric and concentrated laboratory conditions. Under typical ambient conditions, ?O3 of PAH-coated aerosol particles are expected to be in the range of 10-6-10-5. At ambient temperatures, NO2 alone does not efficiently degrade PAHs, but it was found to accelerate the degradation of PAHs exposed to O3. The accelerating effect can be attributed to highly reactive NO3 radicals formed in the gas phase or on the surface. Estimated second-order rate coefficients for O3-NO2 and PAH-NO3 surface layer reactions are in the range of 10-17-10-16 cm2 s-1 and 10-15-10-12 cm2 s-1, respectively. The chemical half-life of PAH is expected to range from a few minutes on the surface of soot to multiple hours on organic and inorganic solid particles and days on liquid particles. On soot, the degradation of particle-bound PAHs in the atmosphere appears to be dominated by a surface layer reaction with adsorbed ozone. On other substrates, it is likely dominated by gas-surface reactions with OH or NO3 radicals (Eley-Rideal-type mechanism). To our knowledge, K2-SURF is the first atmospheric process model describing multiple types of parallel and sequential surface reactions between multiple gaseous and particle-bound chemical species. It illustrates how the general equations of the PRA framework can be simplified and adapted for specific reaction systems, and we suggest that it may serve as a basis for the development of a general master mechanism of aerosol and cloud surface chemistry.

Shiraiwa, M.; Garland, R. M.; Pöschl, U.

2009-09-01

27

Generation of Reaction Layers on Machined Surfaces  

Microsoft Academic Search

Machined surfaces are influenced by the generation of reaction layers resulting from the formulation of the metalworking fluid. Coolants reduce friction at the tool\\/surface interface and significantly influence the heat dissipation in machining operations and the generation of the surface layer. Nowadays, machining processes are evaluated with respect to the forces, grinding wheel wear, surface roughness, surface integrity, residual stresses,

E. Brinksmeier; A. Walter

2000-01-01

28

Optical sensing quantum dot-labeled polyacrolein particles prepared by layer-by-layer deposition technique.  

PubMed

Optical sensing polymer particles with tailored semiconductor nanocrystal (QD) loading are prepared by layer-by-layer deposition technique (LbL). Polyacrolein particles of 1.2 ?m diameter are used as solid support for deposition of hydrophilic CdSe/ZnS nanocrystal/polyelectrolyte multilayers formed by electrostatic interactions. The pH-dependent fluorescence of QDs and pH-dependent conformations of polyelectrolytes, which likely passivate the surface state of nanocrystals, allow a creation of both mono- and multiplex coded polymer particles with pH-dependent fluorescence intensity. Bovine serum albumin (BSA) as outermost layer makes it possible to design the optical sensing polymer particles with reversibly responded fluorescence at pH variations. The fluorescence of such polymer particles with BSA outer layer is sensitive to copper(II) ion while the fluorescence of these particles is practically insensitive to the other divalent cations (Zn(2+), Ca(2+), Ba(2+), Co(2+), Mg(2+)). The detection limit of Cu(2+) is about 15 nM. Adaptation of LbL method to prepare QD-labeled polymer particles with enhanced complexity (e.g. several types of QDs, multiple biofunctionality) is expected to open new opportunities in biotechnological applications. PMID:21377163

Generalova, Alla N; Oleinikov, Vladimir A; Zarifullina, Margarita M; Lankina, Ekaterina V; Sizova, Svetlana V; Artemyev, Michail V; Zubov, Vitali P

2011-05-15

29

Adaptive slicing with sloping layer surfaces  

Microsoft Academic Search

Presents an adaptive slicing procedure for improving the geometric accuracy of layered manufacturing techniques which, unlike previous procedures, uses layers with sloping boundary surfaces that closely match the shape of the required surface. This greatly reduces the stair case effect which is characteristic of layered components with square edges. Considers two measures of error, and outlines a method of predicting

R. L. Hope; R. N. Roth; P. A. Jacobs

1997-01-01

30

Improvement of Surface Layer Characteristics by Shot Lining  

Microsoft Academic Search

In the present study, lining of the metal with foils using shot peening was investigated to improve the surface layer characteristics. In the shot peening experiment, the foils set on the metal are pelted with hard particles traveling at a high velocity. The foils are bonded to the metal surface due to plastic deformation induced by the collision of the

Yasunori Harada

2005-01-01

31

Comparative study of the surface layer density of liquid surfaces  

Microsoft Academic Search

Capillary wave fluctuations blur the inherent structure of liquid surfaces in computer simulations. The intrinsic sampling method subtracts capillary wave fluctuations and yields the intrinsic surface structure, leading to a generic picture of the liquid surface. The most relevant magnitude of the method is the surface layer density ns that may be consistently determined from different properties: the layering structure

E. Chacón; E. M. Fernández; D. Duque; R. Delgado-Buscalioni; P. Tarazona

2009-01-01

32

Electromagnetic precipitation and ducting of particles in turbulent boundary layers  

NASA Technical Reports Server (NTRS)

A method for analyzing magnetic migration of particles in turbulent flows is applied to the prediction of particle trajectories and densities in turbulent aerodynamic boundary layers. Results for conditions typical of aircraft with 30-40 micron particles indicate a large upstream collection and a 5% loss of particles during one pass through the boundary layer. The capacity of the magnetic field to achieve a balance with turbulent diffusion in confining the particles to the boundary layer is discussed.

Davey, K. R.; Melcher, J. R.

1980-01-01

33

Carbides composite surface layers produced by (PTA)  

SciTech Connect

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.

Tajoure, Meloud, E-mail: Tajoore2000@yahoo.com [MechanicalEng.,HIHM,Gharian (Libya); Tajouri, Ali, E-mail: Tajouri-am@yahoo.com, E-mail: dr.mokhtarphd@yahoo.com; Abuzriba, Mokhtar, E-mail: Tajouri-am@yahoo.com, E-mail: dr.mokhtarphd@yahoo.com [Materials and Metallurgical Eng., UOT, Tripoli (Libya); Akreem, Mosbah, E-mail: makreem@yahoo.com [Industrial Research Centre,Tripoli (Libya)

2013-12-16

34

Onset of new particle formation in boundary layer  

NASA Astrophysics Data System (ADS)

At this moment, the mechanisms of atmospheric new particle formation (NPF), and the vapors participating in this process are not truly understood. Especially, in which part of the atmosphere the NPF takes place, is still an open question. To detect directly the very first steps of NPF in the atmosphere, we measured these chemical and physical processes within the Planetary Boundary Layer (PBL). We used airborne Zeppelin and Cessna measurements, and ground based in-situ measurements. Using Zeppelin, we focused on the time of the development of the PBL (altitudes up to 1 km) from sunrise until noon to measure vertical profiles of aerosol particles and chemical compounds. This is also the time when NPF typically occurs at ground level. On summer 2012, Zeppelin was measuring nucleation occurring in the polluted Po Valley area, Northern Italy, especially over the San Pietro Capofiume field site. A year later, Zeppelin had a spring campaign in boreal forest area, close to Hyytiälä field site in Southern Finland. During both campaigns, we aimed on measuring the vertical and the horizontal extension for NPF events using an instrumented Zeppelin. The vertical profile measurements represent the particle and gas concentrations in the lower parts of the atmosphere: the residual layer, the nocturnal boundary layer, and the PBL. At the same time, the ground based measurements records present conditions in the surface layer. The key instruments to measure the onset of NPF were an Atmospheric Pressure interface Time-Of-Flight mass spectrometer (APi-TOF), a Particle Size Magnifier (PSM), and a Neutral cluster and Air Ion Spectrometer (NAIS). These instruments are able to measure particles at the size range ~1-2 nm where atmospheric nucleation and cluster activation takes place. The onset of NPF was usually observed onboard Zeppelin when it was measuring inside the rising mixed layer which is connected to the surface layer by effective vertical mixing. The newly formed, subsequently growing, particles were observed to be homogeneously distributed inside the mixed layer. These measurements are part of the PEGASOS project which aims to quantify the magnitude of regional to global feedbacks between the atmospheric chemistry and physics, and thus quantify the changing climate.

Manninen, Hanna E.; Lampilahti, Janne; Mirme, Sander; Nieminen, Tuomo; Ehn, Mikael; Pullinen, Iida

2014-05-01

35

Regulation of Surface Potentialat Amphoteric Surfaces during Particle-Particle Interaction  

E-print Network

Regulation of Surface Potentialat Amphoteric Surfaces during Particle-Particle Interaction BY D and constant potential assumptions and is applicable to oxide colloids and amphoteric biosurfaces in particular

Chan, Derek Y C

36

The surface roughness and planetary boundary layer  

Microsoft Academic Search

Applications of the entrainment process to layers at the boundary, which meet the self similarity requirements of the logarithmic profile, have been studied. By accepting that turbulence has dominating scales related in scale length to the height above the surface, a layer structure is postulated wherein exchange is rapid enough to keep the layers internally uniform. The diffusion rate is

James W. Telford

1980-01-01

37

Friction microprobe investigation of particle layer effects on sliding friction  

SciTech Connect

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.

Blau, P.J.

1993-01-01

38

Improved field emission characteristic of carbon nanotubes by an Ag micro-particle intermediation layer  

Microsoft Academic Search

An efficient way to improve field emission characteristic of carbon nanotubes (CNTs) through an Ag micro-particle intermediation layer is presented. In this way, the intermediation layer is deposited on an indium tin oxide glass substrate by electrochemical method and then the CNTs are covered onto surface of the intermediation layer by electrophoretic method as CNT field emitters. The field emission

Wenhui Lu; Hang Song; Yixin Jin; Haifeng Zhao; Zhiming Li; Hong Jiang; Guoqing Miao

2008-01-01

39

Light scattering from particles located under a rough dielectric layer.  

PubMed

A discussion is presented of the effect of roughness on the detectability of subsurface particles by means of the light-scattering method. We have studied the scattering of light by calibrated spheres located under a slightly rough dielectric surface both experimentally and theoretically. In our experiments, the scattering from slightly rough layers with nonresonant particles was dominated by the roughness, and the scattering diagram did not bear any discernible indications of the spheres. However, at resonance, the subsurface particles manifested themselves by an increase in the total scattered intensity and by well-pronounced maxima in the angular dependence of both the scattering diagram and the backscattered intensity. Theoretical calculations show that the angular positions of the maxima in the scattering diagram are essentially determined by the interference of fields scattered by the particles and by the surface, whereas the contribution of the multiple interparticle scattering is negligible. By contrast, the oscillations in the angular dependence of the backscattered intensity are due primarily to the scattering between neighboring spheres. PMID:17728820

Freilikher, Valentin; S Kaganovskii, Yuri; Kotlyar, Alexey

2007-07-01

40

Formation of nanosized particles of silicon carbide and diamonds in surface layer of silicon target during short-pulsed implantation of carbon ions  

Microsoft Academic Search

In the paper the study results of silicon carbide and diamond nanosized particle synthesis during short-pulsed implantation of carbon ions and protons into the silicon target are presented. The experiments have been performed at the source of high-power pulsed ion beams “TEMP” based on the magnetically isolated diode with Br field. The beam parameters are the following: ion energy is

G. E. Remnev; Yu. F. Ivanov; E. P. Naiden; M. S. Saltymakov; A. V. Stepanov; V. F. Shtanko

2008-01-01

41

Microstructure and mechanical properties of GTA surface modified composite layer on magnesium alloy AZ31 with SiC P  

Microsoft Academic Search

A novel fabrication process of surface modified composite layer by gas tungsten arc (GTA) surface modification process was used to deposit SiC particles on the surface of magnesium alloy AZ31. This method is an effective technique in producing a high performance surface modified composite layer. The microstructure and mechanical properties of the GTA surface modified composite layer were evaluated. The

Ding Wenbin; Jiang Haiyan; Zeng Xiaoqin; Li Dehui; Yao Shoushan

2007-01-01

42

Where surface physics and fluid dynamics meet: rupture of an amphiphile layer by fluid flow  

E-print Network

We investigate the fluctuating pattern created by a jet of fluid impingent upon an amphiphile-covered surface. This microscopically thin layer is initially covered with 50 $\\mu$m floating particles so that the layer can be visualized. A vertical jet of water located below the surface and directed upward drives a hole in this layer. The hole is particle-free and is surrounded by the particle-laden amphiphile region. The jet ruptures the amphiphile layer creating a particle-free region that is surrounded by the particle-covered surface. The aim of the experiment is to understand the (fluctuating) shape of the ramified interface between the particle-laden and particle-free regions.

Mahesh Bandi; Walter Goldburg; John Cressman Jr.; Hamid Kellay

2006-07-19

43

Paracrystalline surface layers of dairy propionibacteria.  

PubMed Central

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

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

1993-01-01

44

Clustering of Floating Particles by Surface Waves  

Microsoft Academic Search

We study experimentally and theoretically how waves affect the distribution of particles floating on a liquid surface. According\\u000a to the Archimedes’ law the weight of floating particle is equal to the weight of displaced liquid. This law is not quite precise\\u000a for small floating objects. An additional force generating by surface tension pulls a hydrophilic particle deeper into the\\u000a water

Sergei Lukaschuk; Petr Denissenko; Gregory Falkovich

2006-01-01

45

The surface roughness and planetary boundary layer  

NASA Astrophysics Data System (ADS)

Applications of the entrainment process to layers at the boundary, which meet the self similarity requirements of the logarithmic profile, have been studied. By accepting that turbulence has dominating scales related in scale length to the height above the surface, a layer structure is postulated wherein exchange is rapid enough to keep the layers internally uniform. The diffusion rate is then controlled by entrainment between layers. It has been shown that theoretical relationships derived on the basis of using a single layer of this type give quantitatively correct factors relating the turbulence, wind and shear stress for very rough surface conditions. For less rough surfaces, the surface boundary layer can be divided into several layers interacting by entrainment across each interface. This analysis leads to the following quantitatively correct formula compared to published measurements. 1 24_2004_Article_BF00877766_TeX2GIFE1.gif {? _w }/{u^* } = ( {2/{9Aa}} )^{{1/4}} ( {1 - 3^{{1/2}{ a/k{d_n }/z{? _w }/{u^* }z/L} )^{{1/4}} = 1.28(1 - 0.945({{? _w }/{u^* }}}) {{z/L}})^{{1/4 where u^* = ( {{tau/?}}^{{1/2}}, ? w is the standard deviation of the vertical velocity, z is the height and L is the Obukhov scale lenght. The constants a, A, k and d n are the entrainment constant, the turbulence decay constant, Von Karman's constant, and the layer depth derived from the theory. Of these, a and A, are universal constants and not empirically determined for the boundary layer. Thus the turbulence needed for the plume model of convection, which resides above these layers and reaches to the inversion, is determined by the shear stress and the heat flux in the surface layers. This model applies to convection in cool air over a warm sea. The whole field is now determined except for the temperature of the air relative to the water, and the wind, which need a further parameter describing sea surface roughness. As a first stop to describing a surface where roughness elements of widely varying sizes are combined this paper shows how the surface roughness parameter, z 0, can be calculated for an ideal case of a random distribution of vertical cylinders of the same height. To treat a water surface, with various sized waves, such an approach modified to treat the surface by the superposition of various sized roughness elements, is likely to be helpful. Such a theory is particularly desirable when such a surface is changing, as the ocean does when the wind varies. The formula, 2 24_2004_Article_BF00877766_TeX2GIFE2.gif {0.118}/{a_s C_D }< z_0< {0.463}/{a_s C_D (u^* )} is the result derived here. It applies to cylinders of radius, r, and number, m, per unit boundary area, where a s = 2rm, is the area of the roughness elements, per unit area perpendicular to the wind, per unit distance downwind. The drag coefficient of the cylinders is C D . The smaller value of z o is for large Reynolds numbers where the larger scale turbulence at the surface dominates, and the drag coefficient is about constant. Here the flow between the cylinders is intermittent. When the Reynolds number is small enough then the intermittent nature of the turbulence is reduced and this results in the average velocity at each level determining the drag. In this second case the larger limit for z 0 is more appropriate.

Telford, James W.

1980-03-01

46

Algorithm for Computing Particle/Surface Interactions  

NASA Technical Reports Server (NTRS)

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.

Hughes, David W.

2009-01-01

47

Interaction forces between particles containing grafted or adsorbed polymer layers.  

PubMed

The interaction forces between particles containing grafted or adsorbed polymer layers have been investigated using rheological and surface force measurements. Polystyrene latex dispersions with grafted poly(ethylene oxide) (PEO) chains (M=2000) were used for the rheological measurements. Results were also obtained for latex dispersions stabilised with adsorbed graft copolymers of poly(methyl methacrylate-methacrylic acid) with methoxy capped PEO chains (M=750). The relative viscosity eta(r)-volume fraction phi curves for the latex dispersions with grafted PEO chains were established for three particle radii of 77.5, 306 and 502 nm. For comparison the eta(r)-phi curve was calculated using the Dougherty-Krieger equation. This allows one to obtain the adsorbed layer thickness delta as a function of phi. The results showed a decrease of delta with increase of phi, which was attributed to the interpenetration and/or compression of the PEO chains on increasing phi. Viscoelastic measurements as a function of phi showed a change from predominantly viscous to predominantly elastic response at a critical volume fraction, which indicated the onset of the strong steric repulsion when the polymer layers begin to overlap. A similar trend was obtained with the latex particles containing adsorbed graft copolymer layers. A scaling law was used to fit the elastic part of the logG'-log phi curve (where G' is the elastic modulus). This fit could be used to estimate the compressibility of the PEO chains. The correlation of the rheology of concentrated sterically stabilised dispersions with interparticle interactions was investigated by measuring the energy-distance curves for the graft copolymer that was adsorbed on smooth mica sheets. Using de Gennes scaling theory, it was possible to calculate the energy of interaction between the polymer layers. The high frequency modulus of the latex dispersions was obtained as a function of the volume fraction and the results were compared with those calculated from the potential of the mean force. The trends in the variation of the modulus with volume fraction were similar for the experimental rheological results and those calculated using the directly measured interaction forces. The above results demonstrated the powerful use of rheological measurements for studying the interaction between sterically stabilised dispersions in concentrated systems. PMID:12818496

Tadros, Tharwat

2003-07-01

48

Surface Temperature and Surface-Layer Turbulence in a Convective Boundary Layer  

NASA Astrophysics Data System (ADS)

Previous laboratory and atmospheric experiments have shown that turbulence influences the surface temperature in a convective boundary layer. The main objective of this study is to examine land-atmosphere coupled heat transport mechanism for different stability conditions. High frequency infrared imagery and sonic anemometer measurements were obtained during the boundary layer late afternoon and sunset turbulence (BLLAST) experimental campaign. Temporal turbulence data in the surface-layer are then analyzed jointly with spatial surface-temperature imagery. The surface-temperature structures (identified using surface-temperature fluctuations) are strongly linked to atmospheric turbulence as manifested in several findings. The surface-temperature coherent structures move at an advection speed similar to the upper surface-layer or mixed-layer wind speed, with a decreasing trend with increase in stability. Also, with increasing instability the streamwise surface-temperature structure size decreases and the structures become more circular. The sequencing of surface- and air-temperature patterns is further examined through conditional averaging. Surface heating causes the initiation of warm ejection events followed by cold sweep events that result in surface cooling. The ejection events occur about 25 % of the time, but account for 60-70 % of the total sensible heat flux and cause fluctuations of up to 30 % in the ground heat flux. Cross-correlation analysis between air and surface temperature confirms the validity of a scalar footprint model.

Garai, Anirban; Pardyjak, Eric; Steeneveld, Gert-Jan; Kleissl, Jan

2013-07-01

49

Surface state and normal layer effects  

SciTech Connect

In addition to the conducting CuO{sub 2} (S) layers, most high-T{sub c} superconductors also contain other conducting (N) layers, which are only superconducting due to the proximity effect. The combination of S and N layers can give rise to complicated electronic densities of states, leading to quasilinear penetration depth and NMR relaxation rate behavior at low temperatures. Surface states can also complicate the analysis of tunneling and, photoemission measurements. Moreover, geometrical considerations and in homogeneously trapped flux axe possible explanations of the paramagnetic Meissner effect and of corner and ring SQUID experiments. Hence, all of the above experiments could be consistent with isotropic s-wave superconductivity within the S layers.

Klemm, R.A.; Ledvij, M. [Argonne National Lab., IL (United States); Liu, S.H. [Univ. of California, San Diego, CA (United States). Dept. of Physics

1995-08-01

50

Polymer surface treatment with particle beams  

DOEpatents

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.

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

1999-05-04

51

Polymer surface treatment with particle beams  

DOEpatents

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.

Stinnett, Regan W. (1033 Tramway La. NE., Albuquerque, NM 87122); VanDevender, J. Pace (7604 Lamplighter NE., Albuquerque, NM 87109)

1999-01-01

52

Spontaneous dispersion of particles on liquid surfaces  

PubMed Central

When small particles (e.g., flour, pollen, etc.) come in contact with a liquid surface, they immediately disperse. The dispersion can occur so quickly that it appears explosive, especially for small particles on the surface of mobile liquids like water. This explosive dispersion is the consequence of capillary force pulling particles into the interface causing them to accelerate to a relatively large velocity. The maximum velocity increases with decreasing particle size; for nanometer-sized particles (e.g., viruses and proteins), the velocity on an air-water interface can be as large as ?47 m/s. We also show that particles oscillate at a relatively high frequency about their floating equilibrium before coming to stop under viscous drag. The observed dispersion is a result of strong repulsive hydrodynamic forces that arise because of these oscillations. PMID:19906995

Singh, Pushpendra; Joseph, Daniel D.; Gurupatham, Sathish K.; Dalal, Bhavin; Nudurupati, Sai

2009-01-01

53

Regular surface layer of Azotobacter vinelandii.  

PubMed Central

Washing Azotobacter vinelandii UW1 with Burk buffer or heating cells at 42 degrees C exposed a regular surface layer which was effectively visualized by freeze-etch electron microscopy. This layer was composed of tetragonally arranged subunits separated by a center-to-center spacing of approximately 10 nm. Cells washed with distilled water to remove an acidic major outer membrane protein with a molecular weight of 65,000 did not possess the regular surface layer. This protein, designated the S protein, specifically reattached to the surface of distilled-water-washed cells in the presence of the divalent calcium, magnesium, strontium, or beryllium cations. All of these cations except beryllium supported reassembly of the S protein into a regular tetragonal array. Although the surface localization of the S protein has been demonstrated, radioiodination of exposed envelope proteins in whole cells did not confirm this. The labeling behavior of the S protein could be explained on the basis of varying accessibilities of different tyrosine residues to iodination. Images PMID:6735982

Bingle, W H; Doran, J L; Page, W J

1984-01-01

54

Irreversible adsorption of particles on heterogeneous surfaces.  

PubMed

Methods of theoretical and experimental evaluation of irreversible adsorption of particles, e.g., colloids and globular proteins at heterogeneous surfaces were reviewed. The theoretical models were based on the generalized random sequential adsorption (RSA) approach. Within the scope of these models, localized adsorption of particles occurring as a result of short-ranged attractive interactions with discrete adsorption sites was analyzed. Monte-Carlo type simulations performed according to this model enabled one to determine the initial flux, adsorption kinetics, jamming coverage and the structure of the particle monolayer as a function of the site coverage and the particle/site size ratio, denoted by lambda. It was revealed that the initial flux increased significantly with the site coverage theta(s) and the lambda parameter. This behavior was quantitatively interpreted in terms of the scaled particle theory. It also was demonstrated that particle adsorption kinetics and the jamming coverage increased significantly, at fixed site coverage, when the lambda parameter increased. Practically, for alpha = lambda2theta(s) > 1 the jamming coverage at the heterogeneous surfaces attained the value pertinent to continuous surfaces. The results obtained prove unequivocally that spherically shaped sites were more efficient in binding particles in comparison with disk-shaped sites. It also was predicted that for particle size ratio lambda < 4 the site multiplicity effect plays a dominant role, affecting significantly the structure of particle monolayers and the jamming coverage. Experimental results validating main aspects of these theoretical predictions also have been reviewed. These results were derived by using monodisperse latex particles adsorbing on substrates produced by covering uniform surface by adsorption sites of a desired size, coverage and surface charge. Particle deposition occurred under diffusion-controlled transport conditions and their coverage was evaluated by direct particle counting using the optical and electron microscopy. Adsorption kinetics was quantitatively interpreted in terms of numerical solutions of the governing diffusion equation with the non-linear boundary condition derived from Monte-Carlo simulations. It was proven that for site coverage as low as a few percent the initial flux at heterogeneous surfaces attained the maximum value pertinent to homogeneous surfaces. It also was demonstrated that the structure of larger particle monolayers, characterized in terms of the pair correlation function, showed much more short-range ordering than predicted for homogeneous surface monolayers at the same coverage. The last part of this review was devoted to detection of polyelectrolyte multilayers on various substrates via particle deposition experiments. PMID:15961056

Adamczyk, Zbigniew; Jaszczó?t, Katarzyna; Michna, Aneta; Siwek, Barbara; Szyk-Warszy?ska, Lilianna; Zembala, Maria

2005-12-30

55

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

NASA Astrophysics Data System (ADS)

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.

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

1993-08-01

56

Dynamic air layer on textured superhydrophobic surfaces.  

PubMed

We provide an experimental demonstration that a novel macroscopic, dynamic continuous air layer or plastron can be sustained indefinitely on textured superhydrophobic surfaces in air-supersaturated water by a natural gas influx mechanism. This type of plastron is an intermediate state between Leidenfrost vapor layers on superheated surfaces and the equilibrium Cassie-Baxter wetting state on textured superhydrophobic surfaces. We show that such a plastron can be sustained on the surface of a centimeter-sized superhydrophobic sphere immersed in heated water and variations of its dynamic behavior with air saturation of the water can be regulated by rapid changes of the water temperature. The simple experimental setup allows for quantification of the air flux into the plastron and identification of the air transport model of the plastron growth. Both the observed growth dynamics of such plastrons and millimeter-sized air bubbles seeded on the hydrophilic surface under identical air-supersaturated solution conditions are consistent with the predictions of a well-mixed gas transport model. PMID:23919719

Vakarelski, Ivan U; Chan, Derek Y C; Marston, Jeremy O; Thoroddsen, Sigurdur T

2013-09-01

57

Surface layer modification of ion bombarded HDPE  

Microsoft Academic Search

Press-moulded, high density polyethylene (HDPE) samples were subjected to ion bombardment and effects of the modification studied. He+ ions of energy 100 keV or Ar+ ions of energy 130 keV were applied in the range of dose 1–30×1015\\/cm2 or 1–100×1014\\/cm2, respectively. This paper has been focused on structural changes of the surface layer. The consequences of the modification were studied

D. Bielinski; P. Lipinski; L. Slusarski; J. Grams; T. Paryjczak; J. Jagielski; A. Turos; N. K. Madi

2004-01-01

58

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

NASA Astrophysics Data System (ADS)

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.

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

2013-09-01

59

Effect of particle size on the kinetics of particle deposition under attractive double layer interactions  

SciTech Connect

Particle deposition plays an important role in such diverse phenomena as granular filtration, chromatographic separation, colloidal contamination of semiconductor wafers, colloidal fouling of pressure driven membranes, and colloid-facilitated transport of pollutants in soils and groundwater aquifers. The effect of particle size on the kinetics of particle deposition in the presence of attractive double layer interactions has been studied theoretically and experimentally. Particle deposition experiments were carried out with several model suspensions of positively charged latex particles and negatively charged glass beads using the packed bed column technique. The model particles used in the deposition experiments covered a wide size range, from 0.08 to 2.51 [mu]m. Experimental deposition rates were compared to theoretical predictions based on a numerical solution of the convective diffusion equation with colloidal, hydrodynamic, and gravitational forces fully incorporated. Theoretical and experimental results reveal that the enhancement in particle deposition rate (i.e., the deposition rate in the presence of double layer interaction divided by the rate in the absence of double layer interaction) is dependent on particle size. At low ionic strengths, the enhancement in deposition rate passes through a maximum as the particle size increases. This maximum corresponds to particles with a size around 1 [mu]m. It is also concluded that this maximum is determined by the interplay between the size of the particles and the range of the attractive double layer interactions.

Elimelech, M. (Univ. of California, Los Angeles, CA (United States). School of Engineering and Applied Science)

1994-04-01

60

Diurnal ocean surface layer model validation  

NASA Technical Reports Server (NTRS)

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.

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

1990-01-01

61

Colloidal dynamics near a particle-covered surface.  

PubMed

How the diffusive dynamics of colloidal spheres changes in the vicinity of a particle-coated surface is of importance for industrial challenges such as fouling and sedimentation as well as for fundamental studies into confinement effects. We addressed this question by studying colloidal dynamics in a partially coated surface layer, using video microscopy. Particle mean squared displacement (MSD) functions were measured as a function of a (local) effective volume fraction (EVF), which was varied by making use of gravity settling. Comparison of MSDs at the bare and coated surfaces for EVF of 0.2-0.4 revealed that at the latter surface the motion amplitudes are strongly reduced, accompanied by a sharp transition from diffusive to nearly caged motion. This clearly indicates that the surface-attached particles cannot be taken into account via volume fraction and that their immobility has a distinct effect. For EVF > 0.45, the caging becomes dominated by the suspended particles, making the dynamics at the bare and coated surfaces similar. PMID:21827156

Eral, H B; Mugele, F; Duits, M H G

2011-10-18

62

Estimating Optical Properties of Layered Surfaces Using the Spider Model  

E-print Network

properties than diffuse surfaces. Although the characteristics of layered surfaces, like layer opacity to extracting the approximated optical properties of the two layers: the top layer's opacity, and the top) Simulation by reducing the opacity of the original 10%, (c) by reducing 50%, (d) by increasing the opacity 3

Tokyo, University of

63

Particle Levitation in a Plasma Sheath Above a Surface  

NASA Astrophysics Data System (ADS)

Dust grains suspended above the lunar surface have been observed on multiple occasions. Virtually all small, airless bodies in the solar system are coated with a dusty regolith; therefore, charged dust particle levitation and transport may also occur in planetary ring systems, on Mars, Mercury, planetary satellites, asteroids, and comets. The interaction between charged dust particles and a photoelectron layer or plasma sheath above the surface is the most likely explanation for these dust dynamics. We report the results of experiments on the levitation, dynamics, and charging of dust particles in an Ar plasma sheath above a flat plate. Types of particles tested include hollow and solid glass microballoons (<45 microns in diameter), polystyrene DVB beads (5 microns and 10 microns in diameter), and JSC-1, a lunar regolith simulant (<25 microns in diameter). Plasma and sheath characteristics are determined through Langmuir probe and floating potential probe sweeps. An agitator under the surface provides a disturbance to inject dust into the sheath. Dust particles levitating above the surface of the plate are illuminated by an Ar laser and observed by a video camera.

Sickafoose, Amanda; Colwell, Josh; Horanyi, Mihaly; Robertson, Scott

2001-10-01

64

Rebound characteristics for ash particles impacting a planar surface  

NASA Astrophysics Data System (ADS)

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.

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

2013-06-01

65

Numerical simulation of particle transport in planar shear layers  

Microsoft Academic Search

Numerical simulations of particle dispersion in a planar shear dominated by large scale vortical structures are reported. The shear layer is formed by two co-flowing streams past a splitter plate. The emphasis of this work is on examining how the particle dynamics are affected by the large-scale coherent structures in the initial development of the instabilities in a spatially-developing mixing

S. K. Aggarwal; J. B. Yapo; F. F. Grinstein; K. Kailasanath

1996-01-01

66

On the interaction of a vertical shear layer with a free surface  

Microsoft Academic Search

New experiments have been conducted using a combined free-surface gradient detector (FSGD) and digital particle image velocimetry (DPIV) technique to study the interaction between a vertical shear layer, created by a surface-piercing splitter plate, and a free surface. The emphasis of this study is on understanding aspects of the interaction between the free-surface deformation (FSD) and the near-surface turbulence through

Dana Dabiri

2003-01-01

67

Particle transport and flow modulation in particle-laden mixing layers  

Microsoft Academic Search

Shear flows provide a means to rapidly mix and disperse discrete solid particles and droplets in natural and industrial processes. Moderate mass loadings of particles in a gas mixing layer may also alter the gas shear flow. While the modeling of single-phase shear flows has undergone several decades of development and validation, the consideration of the corresponding problem in two-

Xiao-Ling Tong

1998-01-01

68

Surface preparation of substances for continuous convective assembly of fine particles  

DOEpatents

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.

Rossi, Robert (Rochester, MN)

2003-01-01

69

Turbulent boundary layer heat transfer on curved surfaces  

Microsoft Academic Search

Heat transfer measurements for a turbulent boundary layer on a convex and concave, constant-temperature surface are presented. The heat transferred on the convex surface was found to be less than that for a flat surface, while the heat transferred to the boundary layer on the concave surface was greater. It was also found that the heat transferred on the convex

R. E. Mayle; M. F. Blair; F. C. Kopper

1979-01-01

70

Effect of coating temperature on properties of the SiC layer in TRISO-coated particles  

Microsoft Academic Search

The effect of coating temperature on properties of the SiC layer in TRISO-coated particles was investigated. An increase in coating temperature resulted in a significant coarsening of surface microstructures and an increase of the pore size and porosity of SiC layers. The SiC layers formed at 1400–1550°C had nearly stoichiometric compositions whereas the SiC layer formed at 1600°C contained a

Weon-Ju Kim; Jeong Nam Park; Moon Sung Cho; Ji Yeon Park

2009-01-01

71

Lunar surface outgassing and alpha particle measurements  

SciTech Connect

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.

Lawson, S. L. (Stefanie L.); Feldman, W. C. (William C.); Lawrence, David J. (David Jeffery),; Moore, K. R. (Kurt R.); Elphic, R. C. (Richard C.); Maurice, S. (Sylvestre); Belian, Richard D.; Binder, Alan B.

2002-01-01

72

Surface Layer Turbulence During a Frontal Passage  

SciTech Connect

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 calculations using these techniques are employed using data from both the sonic and hotwire anemometers, when possible. Unfortunately, direct calculations of {var_epsilon} were not possible during a part of the frontal passage because the high wind speeds concurrent with the frontal passage demand very high frequency resolution, beyond that possible with the hotwire anemometer, for direct {var_epsilon} calculations. The calculations resulting from these three techniques are presented for the cold front as a time series. Quantitative comparisons of the direct and indirect calculation techniques are also given. More detail, as well as a discussion of energy spectra, can be found in Piper & Lundquist(2004).

Piper, M; Lundquist, J K

2004-06-15

73

Small particle transport across turbulent nonisothermal boundary layers  

NASA Technical Reports Server (NTRS)

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.

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

1982-01-01

74

Step like surface potential on few layered graphene oxide  

NASA Astrophysics Data System (ADS)

We report surface potential maps of few layered graphene oxide films on different substrates. Kelvin probe force microscopy images reveal that the surface potential decreases in steps with increasing number of layers on the substrate until five layers are reached, where it saturates to a constant value. This intrinsic behavior is smeared out in the presence of ambient humidity where the surface potential is shielded by the presence of a thin water layer on the surface. This effect can be exploited to quickly determine the number of layers of graphene oxide on a substrate.

Jaafar, M.; López-Polín, G.; Gómez-Navarro, C.; Gómez-Herrero, J.

2012-12-01

75

Magnetic screening by a thin superconducting surface layer  

Microsoft Academic Search

A solid may have a superconducting surface layer because of changes from the bulk in structure, atomic spacing, and composition. If fluxoids do not come into thermal equilibrium by penetration of the surface barrier, magnetic screening by the layer may simulate in part the diamagnetic susceptibility of a bulk superconductor if the layer thickness exceeds 2lambda2\\/R, where lambda is the

Charles Kittel; S. Fahy; Steven G. Louie

1988-01-01

76

Fluorescent particle tracers for surface hydrology  

NASA Astrophysics Data System (ADS)

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 flow rates. Experimental results demonstrate that the fluorescent particles can be used to reliably trace high velocity streams in adverse illumination conditions and in the presence of foam and reflections on the water surface. Furthermore, flow velocities and travel times calculated through an array of commonly used tracers are consistent with results obtained through the proposed methodology and demonstrate a higher reliability of the fluorescent particles versus traditional tracers that are affected by dispersions and turbulence. Additional proof-of-concept experiments are conducted on a semi-natural hillslope plot under high turbidity loads and soil and rain drops interaction. Ad-hoc experiments with particles of varying diameters ranging from 75 to 1180 ?m are performed to assess the visibility and detectability of the particle tracers in these severe environmental conditions and their feasibility in estimating overland flow velocities. Videos of beads' transit are processed through both supervised and unsupervised techniques to obtain average surface velocities of water flowing on the hill. Experimental results have demonstrated the feasibility of using the particles for environmental applications and have led to the identification of optimal diameters, namely, 1000-1180 ?m, for flow measurements in the described hillslope plot.

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

2012-12-01

77

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

DOEpatents

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.

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

2013-02-19

78

Free and guided convection in evaporating layers of aqueous solutions of sucrose. Transport and sedimentation of solid particles  

Microsoft Academic Search

In a thin layer of an aqueous solution of sucrose, convection due to evaporation takes place, after a chaotic regime, as a unique toroidal roll occupying the whole container. When a mask drilled with holes is placed just above the upper surface of the fluid layer, there is cellular convection imposed by the distribution of holes. Immersed solid particles preferentially

Blaise Simon; Yves Pomeau

1991-01-01

79

MULTI-LAYER COATING OF ULTRATHIN POLYMER FILMS ON NANO-PARTICLES OF ALUMINA BY A PLASMA TREATMENT  

E-print Network

MULTI-LAYER COATING OF ULTRATHIN POLYMER FILMS ON NANO- PARTICLES OF ALUMINA BY A PLASMA TREATMENT during the plasma treatment. After single layer coating, hexamethyldisiloxane (HMDSO) was coated again. The deposition mechanisms and the effects of plasma treatment parameters are discussed. INTRODUCTION Surface

Dalal, Vikram

80

Fluid-driven motion of passive cilia enables the layer to expel sticky particles.  

PubMed

Inspired by marine organisms that utilize active cilia to prevent the biofouling of their surfaces, we use computational and theoretical modeling to determine if passive cilia, which are driven to undulate by an oscillatory shear flow, can be harnessed for antifouling applications. By modeling the oscillating shear flow near a ciliated wall within a channel, we show that the fluid-driven motion of cilia enables the layer to repel adhesive particles away from the surface. Compared to the behavior of the system in a non-oscillating shear, the oscillations also help transport the particles more rapidly along the flow direction. Moreover, the oscillations allow "stickier" particles to be conveyed by the flow relative to the case involving non-oscillatory flow. A simple theoretical model that considers the motion of an adhesive particle interacting with an oscillating, elastic layer captures the behavior observed in the simulations and indicates that the adhesive particle can be repelled away for a wide range of oscillation frequencies. The findings suggest that passive cilia can be used to create self-cleaning surfaces, utilizing oscillations in the flow to prevent the attachment of microparticles and biological cells. PMID:24652071

Tripathi, Anurag; Shum, Henry; Balazs, Anna C

2014-03-01

81

Phospho-silicate and silicate layers modified by hydroxyapatite particles  

NASA Astrophysics Data System (ADS)

Common used metal materials do not ensure good connection between an implant and biological neighbourhood. Covering implants by thin silicate or phosphate layers enable to improve biological properties of implants and create conditions for producing the non-concrete bonding between the implant and tissue. The project includes preparing silicate sols of different concentrations and proper (powder) fraction of synthetic as well as natural ox hydroxyapatite, depositing the sol mixed with hydroxyapatite onto the base material (metal, ceramic carbon) and heat treatment. Our work includes also preparation of phospho-silicate layers deposited onto different base materials using sol-gel method. Deposited sols were prepared regarding composition, concentration and layer heat treatment conditions. The prepared layers are examined to determine their phase composition (XRD, IR spectroscopy methods), density and continuity (scanning microscopy with EDX methods). Biological activity of layers was evaluated by means of estimation of their corrosive resistance in synthetic body fluids ('in vitro' method) and of bone cells growth on the layers surface. Introducing hydroxyapatite to the layer sol should improve connection between tissue and implant as well as limit the disadvantageous, corrosive influence of implant material (metal) on the tissue.

Rokita, M.; Bro?ek, A.; Handke, M.

2005-06-01

82

Effects of Surface Oxide on the Nitridation Behavior of Aluminum Particles  

NASA Astrophysics Data System (ADS)

A detailed transmission electron microscopy study coupled with electron energy loss spectroscopy was conducted on AlN formed by the direct nitridation of Al particles under nitrogen atmosphere. The nitridation mechanism comprised two steps: the formation of AlN shell on Al particles and the growth of AlN with a lath type in Al droplets. Here, we found that the surface oxide layer of the Al particles acted as a channel layer, which supplied nitrogen in the atomic state to liquid Al, after being transformed into a thin AlON layer during the initial nitridation. In the Al particles, the inward growth of AlN with a shell structure occurred at the sub layer of the AlON layer. On the other hand, the extracted liquid Al droplets formed after the cracking of the AlN shell rested on the Al particles surrounded by the AlON layer. The nitridation of the droplets began at the interface between the Al particle and droplet and not at the free surface and grew outward from the droplet. Herein, based on the observation of the AlON layer formation, we propose a new mechanism for the nitridation of Al particles.

Kim, Sung-Hoon; Noh, Jae-Hong; Ahn, Jae-Pyoung; Lee, Jae-Chul; Kwon, Hoon; Lee, Jaegab; Yang, Heang Ryeal; Lee, Kon-Bae

2014-11-01

83

Optimization of Single and Layered Surface Texturing  

E-print Network

In visualization problems, surface shape is often a piece of data that must be shown effectively. One factor that strongly affects shape perception is texture. For example, patterns of texture on a surface can show the surface orientation from...

Bair, Alethea S.

2010-07-14

84

Layer silicates in a chondritic porous interplanetary dust particle  

NASA Technical Reports Server (NTRS)

Analytical electron microscopy on individual grains from a portion of a chondritic porous interplanetary dust particle (aggregate W7029C1 from the NASA Johnson Space Center Cosmic Dust Collection) shows that layer silicates compose 50 percent of the silicate fraction examined. These layer silicates can be classified into two distinct crystallochemical groups: (1) fine-grained, polycrystalline smectite minerals; and (2) well-ordered, single crystals of kaolinite and Mg-poor talc. The layer silicates in this portion of sample W7029(asterisk)A are dissimilar to those described in other chondritic porous aggregates. The predominant layer silicate assemblage in W7029(asterisk)A indicates that heating of the aggregate during atmospheric entry was brief and probably to a temperature less than 300 C. Comparison with terrestrial phyllosilicate occurrences suggests that some layer silicates in aggregate W7029(asterisk)A may have been formed by alteratiton from preexisting silicate minerals at low temperatures (less than 25 C) after aggregate formation.

Rietmeijer, F. J. M.; Mackinnon, I. D. R.

1985-01-01

85

Dry deposition of large, airborne particles onto a surrogate surface  

NASA Astrophysics Data System (ADS)

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 ?m - 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 ( ?dI) 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 ?m).

Kim, Eugene; Kalman, David; Larson, Timothy

86

Energetic Particle Synthesis of Metastable Layers for Superior Mechanical Properties  

SciTech Connect

Energetic particle methods have been used to synthesize two metastable layers with superior mechanical properties: amorphous Ni implanted with overlapping Ti and C, and amorphous diamond-like carbon (DLC) formed by vacuum-arc deposition or pulsed laser deposition. Elastic modulus, yield stress and hardness were reliably determined for both materials by fitting finite-element simulations to the observed layer/substrate responses during nanoindentation. Both materials show exceptional properties, i.e., the yield stress of amorphous Ni(Ti,C) exceeds that of hardened steels and other metallic glasses, and the hardness of DLC (up to 88 GPa) approaches that of crystalline diamond (approx. 100 GPa). Tribological performance of the layers during unlubricated sliding contact appears favorable for treating Ni-based micro-electromechanical systems: stick-slip adhesion to Ni is eliminated, giving a low coefficient of friction (approx. 0.3-0.2) and greatly reduced wear. We discuss how energetic particle synthesis is critical to forming these phases and manipulating their properties for optimum performance.

Follstaedt, D.M.; Knapp, J.A.; Myers, S.M.; Dugger, M.T.; Friedmann, T.A.; Sullivan, J.P. [Sandia National Labs., Albuquerque, NM (United States); Monteiro, O.R.; Ager, J.W. III; Brown, I.G.; Christenson, T. [Lawrence Berkeley National Lab., CA (United States)

1998-01-01

87

Particle transport and flow modulation in particle-laden mixing layers  

NASA Astrophysics Data System (ADS)

Shear flows provide a means to rapidly mix and disperse discrete solid particles and droplets in natural and industrial processes. Moderate mass loadings of particles in a gas mixing layer may also alter the gas shear flow. While the modeling of single-phase shear flows has undergone several decades of development and validation, the consideration of the corresponding problem in two- phase shear flows has just began. This dissertation represents a systematic effort to use a tool known as direct numerical simulations (DNS) to advance our understanding of particle transport and flow modulation in a gas mixing layer laden with solid particles. In DNS, almost all dynamically important flow scales are directly resolved. Previously, DNS of three-dimensional (3D) particle-laden shear flows have not been possible due to their high computational cost. Therefore, we first set out to develop and validate a computationally efficient and numerically accurate DNS methodology for particle-laden mixing layer. The method relies on a Fourier vorticity-based formulation together with a divergence-free decomposition. While almost all previous numerical studies adopted the trajectory approach for the dispersed phase in the context of DNS, a continuum approach has been developed and shown to reduce the computational time by a factor of 15 for the simulations of 3D particle-laden mixing layers. The validity and interpretation of the continuum approach were illustrated analytically with a stagnation point flow model. Detailed comparisons showed that the continuum approach and the trajectory approach yielded very similar results. Since the particulate field is compressible, numerical diffusion must be applied to remove local singularities. A dynamic-diffusion model has been developed as an optimum numerical diffusion model to ensure spectral resolution of particulate continuum fields. The numerical method was then used to study the interactions of finite-inertia particles with 3D flow structures. During the early stage of 3D mixing layer evolution, we found that 3D intense rib vortices can eject particles and add smaller scale features to the particulate concentration field. They could also cause a larger transverse dispersion of particles. The particles can selectively respond to new flow structures when the structures are at their peak intensity. The gradient transport closure model has been tested and shown to fail to predict the particulate mass flux correctly. Finally, flow modulation in 2D particle-laden mixing layers was studied both numerically and theoretically. At the linear instability stage, we found that the particles of large Stokes number can stabilize the gas flow while the particles with small inertia have destabilizing effect on the gas phase at finite flow Reynolds number. These qualitatively different effects have been shown to be directly related to the direction of interphase energy transfer. Particles of intermediate Stokes number have the strongest stabilizing effect on the gas flow. Nonlinear flow evolution showed vortex rollup and pairing with physical length scale of the order of the instability wavelength and time scale of the inverse of the linear growth rate. This coupling term acts as a forcing to the fluid vorticity equation, which, at intermediate Stokes number, leads to rupture of the vortices. In short, this dissertation study has laid down the groundwork for future studies on the modeling of turbulent two-phase flows.

Tong, Xiao-Ling

88

Melting of surface layers of nanoparticles: Landau model  

Microsoft Academic Search

The melting of metal nanoparticles is considered in the framework of the Landau mean-field model. For the definition of the order parameter, the Lindemann criterion is employed. The phenomenological principle, implying that surface layer of nanoparticles can be in metastable states indefinitely, put forward to explain the formation of pseudo-crystalline surface layer. Therefore, the metastable states of bulk crystal correspond

A. P. Chernyshev

2008-01-01

89

Surface plasma source with anode layer plasma acceleratora)  

NASA Astrophysics Data System (ADS)

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.

Dudnikov, Vadim

2012-02-01

90

Surface plasma source with anode layer plasma accelerator.  

PubMed

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. PMID:22380222

Dudnikov, Vadim

2012-02-01

91

Carbon Surface Layers on a High-Rate LiFePO4  

SciTech Connect

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.

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

2005-09-06

92

Hypervelocity particle penetration in multi-layered thermal blankets  

NASA Technical Reports Server (NTRS)

Micrometeoroid and related hypervelocity particle impacts into 0.04-sq m samples cut from Scheldahl G411500 thermal blankets (STB) covering trays D05 and D07 in the NASA-LDEF satellite are characterized in detail. These impacts usually produced unique penetration features that generally consist of a delamination zone extending tens of penetration-hole diameters, separating the Teflon layer from the silver/Inconel film and the paint backing layers. When viewed from the space-facing side, the penetration holes are usually surrounded by rings or concentric halos within the delamination zone and radial cracks extending from the ejecta-rim surrounding the hole to the edge of the delamination zone. The phenomena responsible for the formation of these features are examined.

Liu, Jean; Niou, C.-S.; Murr, L. E.; Wang, P. W.

1993-01-01

93

Electric double layer for spherical particles in salt-free concentrated suspensions including ion size effects  

E-print Network

The equilibrium electric double layer (EDL) that surrounds the colloidal particles is determinant for the response of a suspension under a variety of static or alternating external fields. An ideal salt-free suspension is composed by the charged colloidal particles and the ionic countercharge released by the charging mechanism. The existing macroscopic theoretical models can be improved by incorporating different ionic effects usually neglected in previous mean-field approaches, which are based on the Poisson-Boltzmann equation (PB). The influence of the finite size of the ions seems to be quite promising because it has been shown to predict phenomena like charge reversal, which has been out of the scope of classical PB approximations. In this work we numerically obtain the surface electric potential and the counterions concentration profiles around a charged particle in a concentrated salt-free suspension corrected by the finite size of the counterions. The results show the large importance of such corrections for moderate to high particle charges at every particle volume fraction, specially, when a region of closest approach of the counterions to the particle surface is considered. We conclude that finite ion size considerations are obeyed for the development of new theoretical models to study nonequilibrium properties in concentrated colloidal suspensions, particularly the salt-free ones with small and highly charged particles.

R. Roa; F. Carrique; E. Ruiz-Reina

2011-02-01

94

Layer-by-layer assembly of colloidal particles deposited onto the polymer-grafted elastic substrate  

E-print Network

We demonstrate a novel route of spatially organizing the colloid arrangements on the polymer-grafted substrate by use of self-consistent field and density functional theories. We find that grafting of polymers onto a substrate can effectively control spatial dispersions of deposited colloids as a result of the balance between colloidal settling force and entropically elastic force of brushes, and colloids can form unexpected ordered structures on a grafting substrate. The depositing process of colloidal particles onto the elastic "soft" substrate includes two steps: brush-mediated one-dimensional arrangement of colloidal crystals and controlled layer-by-layer growth driven entropically by non-adsorbing polymer solvent with increasing the particles. The result indicates a possibility for the production of highly ordered and defect-free structures by simply using the grafted substrate instead of periodically patterned templates, under appropriate selection of colloidal size, effective depositing potential, and brush coverage density.

Kang Chen; Yu-qiang Ma

2006-11-04

95

Contact mechanics for layered materials with randomly rough surfaces.  

PubMed

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. PMID:22301779

Persson, B N J

2012-03-01

96

Modification of arc emitted W particles in a model scrape-off layer plasma  

NASA Astrophysics Data System (ADS)

In fusion machines (like e.g. ASDEX Upgrade and JET) equipped with W-coated plasma facing components (PFCs) arc tracks are observed post-mortem and W particles are identified as a component of the dust. Results from laboratory arcing of W-coated PFC-material concerning the size, velocity and direction of macro-particles are combined with model calculations of the heating, cooling and evaporation of W particles flying through a simplified scrape-off layer (SOL) plasma to assess the role of arc-produced particles as a source of W impurities. W atoms or ions eroded from a macro-particle flying across the SOL plasma are not subject to prompt re-deposition onto a PFC. Therefore, macro-particles constitute an essential source of W in the SOL and may even result in an impurity input into the region of confined plasma if the particle succeeds in pathing the SOL and crosses the last closed flux surface. The main result of the modelling is that a W particle from the large-size end of the distribution obtained in laboratory arcing and having a typical velocity (also known from laboratory experiment) is able to pass a SOL of 10 cm thickness filled with a realistic plasma and, finally, inject a certain amount of W-material into the confined plasma region.

Laux, M.; Balden, M.; Siemroth, P.

2014-04-01

97

Droplet morphologies on particles with macroscopic surface roughness.  

PubMed

The equilibrium configuration of liquid droplets on the surface of macroscopically rough solid particles was determined by numerical simulations using the volume-of-fluid (VOF) method. The fractional surface coverage of the particle as a function of the droplet size, equilibrium contact angle, and the particle surface roughness amplitude and correlation length has been systematically investigated. Droplet size and contact angle were found to generally have a stronger effect on surface coverage than particle surface roughness. Because of droplet coalescence, a relatively large variation in surface coverage was observed for any given total liquid volume, particularly for larger values of the equilibrium contact angle. PMID:16430249

Stepánek, Frantisek; Rajniak, Pavol

2006-01-31

98

Effects of solar particle events on the hydroxyl airglow layer  

NASA Astrophysics Data System (ADS)

The so-called Meinel emissions of vibrationally-rotationally excited hydroxyl molecules OH* near the mesopause are useful indicators for dynamical and chemical processes in this region. It is well established that the main source of OH* in the Earth's mesosphere is the reaction H + O3 ? OH* + O2. During solar particle events (SPEs) energetic protons and electrons enter the polar atmosphere. The precipitating particles give rise to chemical perturbations. Of particular interest for the OH chemistry is the ion-chemical conversion of water molecules into H + OH. Additionally, there is SPE induced ozone loss. As the formation of OH* is dependent on O3 and H, large SPEs are expected to affect the hydroxyl airglow layer. Additionally, the changed abundance of atomic oxygen will impact the quenching of OH*. In addition to the direct initial chemical composition changes, SPEs are known to affect temperatures, and in turn reaction rates coefficients. We present satellite (SABER) observations of OH* emissions during the large SPE in October/November 2003. Preliminary results indicate significant disturbances of the OH* airglow layer, and a decrease in the OH* emission altitude. The measurement data are compared to results of model simulations. SPE effects on OH* are modelled by means of the UBIC (University of Bremen Ion Chemistry) model using SPE ionisation rates from AIMOS (Atmospheric Ionization Module Osnabrück). Temperature effects are accounted for by synthetic temperature disturbances as well as Aura-MLS measurements.

Winkler, Holger; von Savigny, Christian; Maik Wissing, Jan

2014-05-01

99

Capillary Interception of Floating Particles by Surface-Piercing Vegetation  

E-print Network

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 ...

Peruzzo, Paolo

100

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

NASA Astrophysics Data System (ADS)

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.

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

101

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

NASA Astrophysics Data System (ADS)

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 ?m 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.

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

2013-06-01

102

Reflection from layered surfaces due to subsurface scattering  

Microsoft Academic Search

The reflection of light from most materials consists of two ma- jor terms: the specular and the diffuse. Specular reflection may be modeled from first principles by considering a rough surface consisting of perfect reflectors, or micro-facets. Diffuse reflection is generally considered to result from multiple scattering either from a rough surface or from within a layer near the surface.

Pat Hanrahan; Wolfgang Krueger

1993-01-01

103

Resuspension of particles from surfaces: Technological, environmental and pharmaceutical aspects  

Microsoft Academic Search

Particles that were previously deposited on the surface of any substrate are resuspended to the surrounding environment due to complex effects. The effectiveness of resuspension depends on the geometry of deposits in the form of mono- or multilayer geometries, material properties of the particle and the substrate and the interaction of particles with external excitations. The particle leaves the substrate

Leon Grado?

2009-01-01

104

Stability of boundary layers along curved surfaces  

NASA Astrophysics Data System (ADS)

The stability of a boundary layer along a curved wall was first studied by Gortler (27) in 1940. Further investigations have been conducted since 1980. An important contribution was made by Hall (29), when he first proposed a more rigorous approach to this problem. Gortler had used a simple approximation which allowed him to reduce the problem to a set of ordinary differential equations. However such an assumption ignored the growth of the boundary layer, which Hall showed could not be neglected. Hall then rederived the formulation to obtain a set of partial differential equations. We solved the system of equations, including the nonlinear terms, with a method proposed by Herbert (3), called the Parabolic Stability Equations (PSE). The flow is divided into a basic profile, which satisfies the Prandtl boundary layer equations, and a perturbation. We compared our results for the Blasius profile with those of Bottaro, Klinnmann, and Zebib (8) and found excellent agreement between our calculations and their finite- volume simulations. We then applied our code to the wall jet profile. We were able to capture the growth of steady vortices, located in the inner region of the jet for a concave wall, and the outer region for a convex wall, as predicted by Florian's (20) linear inviscid argument. Our calculations were in good agreement with Matsson's (49) experimental results. We also studied the influence of crossflow on a boundary layer. Crossflow might lead to streamwise vortices along a flat plate, and contrary to Gortler vortices, crossflow vortices are co-rotating instead of counter-rotating. We investigated the interactions between these two types of vortices and compared the results with experimental measurements obtained by Bippes (4). The final part of the thesis is the simulation of the secondary time-dependent instability originating from the shear profiles created by the primary streamwise vortices. The onset of the instability is studied by marching both in space and time. If no forcing is prescribed the time-dependent code predicts a steady solution. Time-dependent boundary conditions are then applied by solving the linear stability problem at some streamwise location to obtain the most dangerous streamwise perturbation velocity and the corresponding frequency. We found that the varicose mode is more amplified in the streamwise direction than the sinuous mode. Similarly, if both modes are included in the initial conditions, the varicose mode is still dominant. Furthermore, as the flow evolves downstream, the unsteady behavior exhibits a more complex time-dependence, which was also observed in the experiments of Swearingen and Blackwealder (66). In our computations, higher harmonics are observed near the wall and propagate into the boundary layer.

Le Cunff, Cedric

105

Layer removal from triso-coated particles with a cold plasma  

Microsoft Academic Search

Summary form only given. Generation IV nuclear reactors generally use small spherical UO2 particles that are coated with a multitude of layers including graphite and SiC. These particles are called TRISO-particles. During the manufacturing process some of the particles are scrapped because of defective layer formation or layer densities and are therefore outside the prescribed specifications. In order to recover

I. J. van der Walt; J. T. Nel; P. L. Crouse

2010-01-01

106

The effects of particle size and surface coating on the cytotoxicity of nickel ferrite.  

PubMed

The safety and toxicity of nanoparticles are of growing concern despite their significant scientific interests and promising potentials in many applications. The properties of nanoparticles depend not only on the size but also the structure, microstructure and surface coating. These in turn are controlled by the synthesis and processing conditions. The dependence of cytotoxicity on particle size and on the presence of oleic acid as surfactant on nickel ferrite particles were investigated in vitro using the Neuro-2A cell line as a model. For nickel ferrite particles without oleic acid prepared by ball milling, cytotoxicity was independent of particle size within the given mass concentrations and surface areas accessible to the cells. For nickel ferrite particles coated with oleic acid prepared by the polyol method, the cytotoxicity significantly increased when one or two layers of oleic acid were deposited. Large particles (150+/-50 nm diameter) showed a higher cytotoxicity than smaller particles (10+/-3 nm diameter). PMID:15949547

Yin, H; Too, H P; Chow, G M

2005-10-01

107

ELLIPSOMETRY OF SURFACE LAYERS ON LEAD AND LITHIUM  

E-print Network

surface layers. Corrosion films on this metal are studied inlithium metal representing of the deposit, The corrosionmetal and solution. The lithium electrode exhibits two reactions, anodic dissolution and corrosion

Peters, Richard Dudley

2011-01-01

108

The Apparent Thermal Inertia of Layered Surfaces on Mars  

NASA Astrophysics Data System (ADS)

We examine the effects of shallow layering in the martian subsurface on the diurnal and seasonal surface temperatures, and on the apparent thermal inertia as has been derived from temperature measurements and assuming soil homogeneity.

Mellon, M. T.; Putzig, N. E.

2007-03-01

109

Buffer Layer Assisted Laser Patterning of Metals on Surfaces  

E-print Network

Buffer Layer Assisted Laser Patterning of Metals on Surfaces Gabriel Kerner and Micha Asscher, variable width metallic wires. By employing laser desorption of a physisorbed buffer gas, a grating of gold controlled metallic clusters via buffer layer assisted growth (BLAG).9-11 To create clusters, the metal

Asscher, Micha

110

Subgrid-scale Modeling in the Atmospheric Surface Layer^1  

NASA Astrophysics Data System (ADS)

Subgrid-scale (SGS) modeling is crucial in the surface layer of wall-bounded flows where the vertical velocity fluctuations cannot be well resolved. We focus on the distinct characteristics of the surface layer of the atmospheric boundary layer (ABL), and analyze, from a highly resolved surface-layer field of a moderately convective ABL, the extent to which Smagorinsky-based SGS models predict these characteristics. The fields were generated using a nested-mesh large-eddy simulation (LES) with the finest mesh having an effective grid resolution of 512^3 covering 1/16^th of the boundary-layer depth. At a height where the fine mesh resolves 90 % of the total fluxes and variances, the resolved fields were treated as surrogate fully resolved fields that were filtered onto a coarser mesh to get ``resolvable'' and ``subgrid'' fields. Preliminary results show that Smagorinsky-based models fail to capture many of the distinctive characteristics of the ABL surface layer. For example, they do not capture the anisotropic distribution of subgrid-scale energy among the horizontal and the vertical components, and they grossly underestimate the SGS horizontal temperature flux. Currently we are focusing on more suitable closures for the atmospheric surface layer. A DNS-based study is also underway and will be used to supplement this analysis. ^1 supported by ARO (# DAAL03-92-G-0117) and ONR (# N00014-92-J-1688)

Khanna, S.; Wyngaard, J. C.; Brasseur, J. G.

1996-11-01

111

Electrodynamic Model of the Atmospheric Convective-Turbulent Surface Layer  

NASA Astrophysics Data System (ADS)

We developed a nonstationary electrodynamic model of the atmospheric convective-turbulent surface layer. As a result of numerical calculations, spatio-temporal distributions of the aero-ion concentration, electric field, conduction current density, and space charge density were obtained under various physical conditions. Depending on the flow direction, convective transfer can strengthen or weaken the effect of turbulent mixing on the electrical state of the atmospheric surface layer.

Redin, A. A.; Kupovykh, G. V.; Boldyrev, A. S.

2014-04-01

112

Nanostructured surface layer on metallic materials induced by surface mechanical attrition treatment  

Microsoft Academic Search

In terms of the grain refinement mechanism induced by plastic straining, a novel surface mechanical attrition treatment (SMAT) was developed for synthesizing a nanostructured surface layer on metallic materials in order to upgrade the overall properties and performance. In this paper, the SMAT technique and the microstructure of the SMAT surface layer will be described. The grain refinement mechanism of

K. Lu; J. Lu

2004-01-01

113

Particle impact tests. [simulation of micrometeoroid damage to orbiter surface  

NASA Technical Reports Server (NTRS)

Particle impact tests were performed on three types of orbiter surface with a micrometeoroid facility. The test equipment electrostatically accelerated micron sized particles to high velocities simulating micrometeoroid impacts. Test particles were titanium diboride with typical velocities in the range 1 to 2.3 km x sec/1 and equivalent particle diameters in the range 4 to 16 microns. Impact angles to the material surface were 90, 60 and 30 degrees. The particle impact sites were located on the sample surfaces and craters were photographed with a magnification of 400X.

Komatsu, G. K.

1978-01-01

114

Fabrication of Nano-Composite Surface Layers on Aluminium Employing Friction Stir Processing Technique  

SciTech Connect

Al/Al{sub 2}O{sub 3} nano-composite surface layer was fabricated via friction stir processing technique. Commercial AA6082 aluminium alloy extruded bar and nanometric Al{sub 2}O{sub 3} powder were subjected to friction stir processing at a substrate travel speed of 80 mm/min and a tool rotation speed of 1000 rpm using a hardened H-13 tool steel. The grain structure and reinforcement particles were investigated by using optical and scanning electron microscopy. Results show that Al{sub 2}O{sub 3} particles can be more uniformly dispread in aluminium substrate by increasing the number of processing passes. Also, hardness enhancement of the nano-composite surface layer was found. This is attributed to uniform dispersion of Al{sub 2}O{sub 3} particles.

Bozorg, S. F. K.; Zarghani, A. S.; Zarei-Hanzaki, A. [School of Metallurgy and Materials Engineering, Faculty of Engineering, University of Tehran, Tehran, P.O. Box: 14395-553 (Iran, Islamic Republic of)

2010-03-11

115

Particles in Surface Waters: Coagulation and Transport  

E-print Network

Conventional water quality assessment and simulation of particles in natural waters focus on bulk concentrations of the suspended solid phase. These analyses rely directly or indirectly on a linear, 'average particle' approach to describe processes...

Culkin, Gerald W.; Lawler, Desmond F.

116

Interior dynamics of subharmonious surface wave in an idealized bidimensional granular layer.  

PubMed

In this paper, high-speed photography was used to investigate the intrinsic dynamics of subharmonious surface wave in a vertical vibrated and idealized bidimensional granular layer. Using the high-speed photography, velocity fields of the granular layer at different stages through two cycles were obtained, which show the continuous particle motions during a cycle. From the velocity fields, a crystal structure in the wave-hollow was observed, which is reported for the first time. Furthermore, quantitative results of kinetic energy distribution in the layer were calculated, which shows temporal correspondence with the evolution of the wave pattern. PMID:16806350

Zhang, Peng; Huang, Kai; Miao, Guoqing; Wei, Rongjue

2006-12-22

117

Turbulent boundary layer on a convex, curved surface  

NASA Technical Reports Server (NTRS)

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.

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

1980-01-01

118

Surface plasmon resonance spectroscopy study of electrostatically adsorbed layers.  

PubMed

The use of 4-(dimethylamino)pyridine to form an adhesion layer for the adsorption of anionic polyelectrolytes on gold surfaces is investigated. In situ surface plasmon resonance spectroscopy is used to monitor the changes in thickness of the adsorbed layers as a function of pH changes. Weak (poly(acrylate)) and strong (poly(styrenesulfonate)) polyelectrolytes have been studied. Although 4-(dimethylamino)pyridine is weakly bound to gold, it is not displaced by these polyelectrolytes and acts as an adhesion layer. The relationship of the interaction of anionic polyelectrolytes with 4-(dimethylamino)pyridine-modified planar gold and gold nanoparticles is discussed. PMID:16649768

Gandubert, Valérie J; Lennox, R Bruce

2006-05-01

119

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

NASA Astrophysics Data System (ADS)

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.

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

2013-09-01

120

Polyvalent surface modification of hydrocarbon polymers via covalent layer-by-layer self-assembly  

E-print Network

Layer-by-layer (LbL) assembly based on ionic interactions has proven to be a versatile route for surface modification and construction of ultrathin nanocomposites. Covalent LbL assembly based on facile ‘click’ covalent bond formation is an effective...

Liao, Kang-Shyang

2009-05-15

121

Influence of starting material particle size on pellet surface roughness.  

PubMed

The purpose of this study was to investigate the effect of pelletization aids, i.e., microcrystalline cellulose (MCC) and cross-linked polyvinyl pyrrolidone (XPVP), and filler, i.e., lactose, particle size on the surface roughness of pellets. Pellets were prepared from powder blends containing pelletization aid/lactose in 1:3 ratio by extrusion-spheronization. Surface roughness of pellets was assessed quantitatively and qualitatively using optical interferometry and scanning electron microscopy, respectively. Both quantitative and qualitative surface studies showed that surface roughness of pellets depended on the particle size of XPVP and lactose used in the formulation. Increase in XPVP or lactose particle size resulted in rougher pellets. Formulations containing MCC produced pellets with smoother surfaces than those containing XPVP. Furthermore, surface roughness of the resultant pellets did not appear to depend on MCC particle size. Starting material particle size was found to be a critical factor for determining the surface roughness of pellets produced by extrusion-spheronization. Smaller particles can pack well with lower peaks and valleys, resulting in pellets with smoother surfaces. Similar surface roughness of pellets containing different MCC grades could be due to the deaggregation of MCC particles into smaller subunits with more or less similar sizes during wet processing. Hence, for starting materials that deaggregate during the wet processing, pellet surface roughness is influenced by the particle size of the material upon deaggregation. PMID:24198222

Sarkar, Srimanta; Ang, Bee Hwee; Liew, Celine Valeria

2014-02-01

122

Thermocapillary convection in two immiscible liquid layers with free surface  

NASA Technical Reports Server (NTRS)

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.

Doi, Takao; Koster, Jean N.

1993-01-01

123

Surface plasmon polariton modulator with optimized active layer  

NASA Astrophysics Data System (ADS)

A multilayered waveguide, which supports surface plasmon polaritons, is considered as an absorption modulator. The waveguide core consists of a silicon nitride layer and ultrathin layer with the varied carrier density embedded between two silver plates, which also serve as electrodes. Under applying voltage to electrodes the carrier density in the transparent conducting oxide layer (we study indium tin oxide - ITO) changes according to the Thomas-Fermi screening theory. We employ analytical solutions for a multilayered system as well as numerical simulations with the commercial software package CST Microwave Studio in the frequency domain. We explore different permittivities of the ITO layer, which can be achieved by utilizing different anneal conditions. To increase transmittance and enhance modulation depth or efficiency, we propose to pattern the continuous active layer. Dependence from the pattern size and filling factor of the active material are analyzed for tuned permittivity of the ITO layer. Direct simulation of the device functionality validates optimization design.

Babicheva, Viktoriia E.; Lavrinenko, Andrei V.

2012-04-01

124

Entrainment of fine particles from surfaces by impinging shock waves  

Microsoft Academic Search

When a shock wave impinges on a surface, it reflects and propagates across the surface at supersonic velocity. The gas is\\u000a impulsively accelerated by the passing shock wave. The resulting high-speed flow imparts sufficiently strong forces to particles\\u000a on the surface to overcome strong adhesive forces and entrain the surface-bound particles into the gas. This paper describes\\u000a an experimental study

G. T. Smedley; D. J. Phares; R. C. Flagan

1999-01-01

125

Medical applications of diamond particles and surfaces.  

SciTech Connect

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).

Narayan, R. J.; Boehm, R. D.; Sumant, A. V. (Center for Nanoscale Materials); (Univ. of California)

2011-04-01

126

Reconstructing Surfaces of Particle-Based Fluids Using Anisotropic Kernels  

E-print Network

Hydrodynamics (SPH) is the most popular approach for simulating fluid since it is computationally si reconstruction method for particle- based fluid simulators such as smoothed particle hydrodynamics. In particle- based simulations, fluid surfaces are usually defined as a level set of an implicit function. We

Turk, Greg

127

Generalized optical theorem for surface waves and layered media  

SciTech Connect

We present a generalized optical theorem for surface waves. The theorem also applies to body waves since under many circumstances body waves can be written in terms of surface-wave modal summations. This theorem therefore extends the domain of applicability of the optical theorem from homogeneous background media to a general class of body and surface-wave propagation regimes within layered elastic media.

Halliday, David; Curtis, Andrew [School of GeoSciences, Grant Institute, University of Edinburgh, Kings Buildings, West Mains Road, Edinburgh EH93JW (United Kingdom)

2009-05-15

128

Scaled temperature spectrum in the unstable oceanic surface layer  

Microsoft Academic Search

A nondimensional form of the temperature spectrum in a convective near-surface layer was derived empirically as a function of stability parameter ? = z\\/L and surface wave parameter ? = u*\\/(gz)1\\/2, under the assumption of horizontal isotropy, where z is the depth of the measurement, L is the Monin-Obukhov length scale, u* is the surface friction velocity, and g is

Hemantha W. Wijesekera; Clayton A. Paulson; Eric D. Skyllingstad

2004-01-01

129

Method for producing functionally graded nanocrystalline layer on metal surface  

DOEpatents

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.

Ajayi, Oyelayo O. (Oswego, IL); Hershberger, Jeffrey G. (Berwyn, IL)

2010-03-23

130

Alpha particle backscattering measurements used for chemical analysis of surfaces  

NASA Technical Reports Server (NTRS)

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.

Patterson, J. H.

1967-01-01

131

Particle-surface interactions in chemical mechanical polishing  

SciTech Connect

Material removal in chemical mechanical polishing (CMP) occurs by a pressure accentuated chemical attack of the surface. The polishing slurry typically consists of abrasive particles and reactive chemicals that may or may not include an oxidant. Post-CMP cleaning processes must remove both the ionic contaminants and any remaining polishing slurry particles. Central to the effectiveness of a clean is the use of conditions that will minimize the binding force between the residual particles and the wafer surface. The morphology and composition of the particle, the surface from which it must be removed, and the environment surrounding the wafer will determine the magnitude of forces that hold a particle to the wafer surface. At the Sandia/SEMATECH Center for Contamination Free Manufacturing, two techniques--atomic force microscopy (AFM) and electrokinetic deposition--are being used to explore these interactions for CMP of both oxide and tungsten surfaces. A basic understanding of particle-surface interaction forces and how they are affected by the chemical/physical environment of the particle and surface is the objective of this task. Modification of the binding forces between particles and wafer surfaces may be used to maximize post-CMP cleaning effectiveness.

Dugger, M.T.; Adkins, C.L.J.; Resnick, P.J. [Sandia National Labs., Albuquerque, NM (United States); Jeon, J.S.; Raghavan, S. [Univ. of Arizona, Tucson, AZ (United States). Dept. of Materials Science and Engineering

1996-10-01

132

Synthesis and characterization of macromolecular layers grafted to polymer surfaces  

NASA Astrophysics Data System (ADS)

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 membranes modified with a reactive anchoring layer can be successfully used to build membrane assemblies by incorporating silica, aluminum, or titanium oxide microparticles as spacers. It is expected that the proposed approaches for the surface modification of the membranes and for the generation of multilayered membrane assemblies can be employed straightforwardly to provide an efficient platform for fabrication of breathable protective materials. Characterization of modified membranes with a cantilever-based method, which can be used for prediction of properties and behavior of thin grafted films, is reported. This technique can be used as a method for fast screening of modified membranes. The method is very robust and capable of detecting very small quantities of substance adsorbed; kinetics of the process can be tracked, as well. This approach can be further developed as a handheld sensor for early warning of the presence of chemical vapors and nerve agents.

Burtovyy, Oleksandr

133

Single-layer graphene oxide films on a silicon surface  

NASA Astrophysics Data System (ADS)

A method is proposed to produce large-area single-layer graphene oxide films on the surface of semiconductor silicon wafers by precipitation from aqueous suspensions. Graphene oxide is synthesized from natural crystalline graphite during chemical oxidation and represents a wide-gap insulator. Single-layer graphene with a homogeneous-fragment size up to 50 ?m can be formed by the reduction of graphene oxide films, and this size is significantly larger than those achieved to date.

Aleksenskii, A. E.; Brunkov, P. N.; Dideikin, A. T.; Kirilenko, D. A.; Kudashova, Yu. V.; Sakseev, D. A.; Sevryuk, V. A.; Shestakov, M. S.

2013-11-01

134

Structural rearrangements in self-assembled surfactant layers at surfaces  

SciTech Connect

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.

Sushko, Maria L.; Liu, Jun

2010-03-25

135

Alternative barrier layers for surface covers in dry climates  

SciTech Connect

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.

Stormont, J.C.

1994-09-01

136

An experimental investigation of turbulent boundary layers along curved surfaces  

NASA Technical Reports Server (NTRS)

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.

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

1972-01-01

137

Assessment of surface turbulent fluxes using geostationary satellite surface skin temperatures and a mixed layer planetary boundary layer scheme  

NASA Technical Reports Server (NTRS)

A method is presented for evaluating the fluxes of sensible and latent heating at the land surface, using satellite-measured surface temperature changes in a composite surface layer-mixed layer representation of the planetary boundary layer. The basic prognostic model is tested by comparison with synoptic station information at sites where surface evaporation climatology is well known. The remote sensing version of the model, using satellite-measured surface temperature changes, is then used to quantify the sharp spatial gradient in surface heating/evaporation across the central United States. An error analysis indicates that perhaps five levels of evaporation are recognizable by these methods and that the chief cause of error is the interaction of errors in the measurement of surface temperature change with errors in the assigment of surface roughness character. Finally, two new potential methods for remote sensing of the land-surface energy balance are suggested which will relay on space-borne instrumentation planned for the 1990s.

Diak, George R.; Stewart, Tod R.

1989-01-01

138

Structure and catalytic property of coherent spinel surface layers on hexaaluminate microcrystals  

SciTech Connect

Formation of coherent surface layers of Mn{sub 3}O{sub 4} on hexaaluminate microcrystals has been studied as a structural modification to enhance the catalytic activity for methane combustion. The spinel oxide surface layer was successfully produced on planar microcrystals of hexaaluminate by employing the air oxidation of an aqueous Mn(II) solution. As evident from TEM, XPS, and CO{sub 2} chemisorption measurements, as-prepared surface layers completely covered the basal plane of planar microcrystals. This characteristic structure appears to be a result of liquid phase epitaxy at the structurally coherent interface between hexaaluminate and spinel. A completely different structure was observed for the samples from the conventional impregnation method, which contain insular Mn{sub 3}O{sub 4} particles dispersed on hexaaluminate. The catalytic activity for methane combustion was evaluated as a function of the Mn{sub 3}O{sub 4} loading and the metal composition of the spinel surface layer. It was revealed that the higher specific activity was observed over air-oxidation-derived samples than over the impregnated samples. Partial substitution of Fe for Mn on the surface layer was effective in enhancing the combustion activity as a result of promoting the reduction/oxidation property. 20 refs., 9 figs.

Machida, Masato; Sato, Akihiro; Murakami, Manabu [Miyazaki Univ. (Japan)] [and others] [Miyazaki Univ. (Japan); and others

1995-12-01

139

Surface Processes of Dust Particles in Low Pressure Plasmas  

NASA Astrophysics Data System (ADS)

This paper presents several aspects of applied dusty plasma research. New applications of dust particles are emerging; there is growing demand for particles with special properties, and for particle-seeded composite materials. Low-pressure plasmas offer a unique possibility of confinement, control and fine tailoring of particle properties. The role of low-pressure technology in surface modification (coating) of dust grains is discussed and illustrated with examples. Fundamental research related to industrial particle treatment aims at the understanding the surface chemistry of processing. More specifically, the nature of plasma-particle interactions must be resolved. Heat exchange and particle temperature, discussed in this paper, are of major interest in the applied dusty plasma studies.

Stoffels, E.; Stoffels, W. W.; Kersten, H.; Swinkels, G. H. P. M.; Kroesen, G. M. W.

140

Complex dielectric response of ellipsoidal particles with surface conduction.  

PubMed

Both particle shape and surface phenomena significantly affect the effective complex dielectric properties of colloidal systems. The treatment of particle shape has generally relied on the extrapolation from the solution of the spherical case proposed by O'Konski [J. Chem. Phys. 64, 605 (1960)] that treats ellipsoidal particles possessing surface conductivity as equivalent homogeneous anisotropic ellipsoids with bulk conduction. To test this approach, we have performed a rigorous analysis of the complex dielectric response of an ellipsoidal particle with surface conductivity using the generalization of the O'Konski boundary conditions to an ellipsoidal shape. The resulting closed-form solution obtained shows that surface conduction effects are represented by an equivalent inhomogeneous anisotropic ellipsoid. For the case of a spheroidal particle, the principle axes of the effective dielectric permittivity tensor of the equivalent particle are aligned with its geometrical principal axes; the effective permittivity varies in the direction of the unique spheroidal axis. In addition, numerical results indicate that the product of the surface area to volume ratio and the specific surface conductivity completely characterizes the effect of the surface phenomena on the response of spheroidal particles with a given shape. Numerical simulations show that spherical and prolate spheroidal particles exhibit a progressive dielectric enhancement while more disklike oblate spheroidal particles undergo an initial dielectric suppression followed by a subsequent enhancement with increasing surface conduction. A comparison of our model predictions with those obtained using the O'Konski approximation revealed significant differences in the magnitude of the low-frequency dielectric enhancement and relaxation frequency for ellipsoidal particle suspensions. PMID:19530782

Bertrand, Edward A; Endres, Anthony L

2009-06-14

141

Alumina atomic layer deposition nanocoatings on primary diamond particles using a fluidized bed reactor  

E-print Network

Alumina atomic layer deposition nanocoatings on primary diamond particles using a fluidized bed particles in a scalable fluidized bed reactor. The studies of fluidization at reduced pressure show; Atomic layer deposition (ALD); Fluidized bed reactor 1. Introduction Due to its extreme hardness, diamond

George, Steven M.

142

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

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

143

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

PubMed

The long-time self-diffusion coefficient, D(L), 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 D(L) 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 D(L) 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 D(L). 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. PMID:24985627

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

2014-06-28

144

Defect Ordering on the Surface of Layered Strontium Ruthenates  

Microsoft Academic Search

Surfaces of layered strontium ruthenates, Sr_2RuO4 and Sr_3Ru_2O_7, exhibit an array of defects after cleaving in vacuum which have been observed using atomic resolution scanning tunneling microscopy (STM). ^1 At room temperature, surface defects are randomly distributed, but are surprisingly ordered at below 200 K and form extended lines, which on Sr_3Ru_2O7 produce a new super-lattice structure with a periodicity

S. V. Kalinin; V. Meunier; E. W. Plummer; J. Guo; Rob G. Moore; A. P. Baddorf

2004-01-01

145

A scheme for computing surface layer turbulent fluxes from mean flow surface observations  

NASA Technical Reports Server (NTRS)

A physical model and computational scheme are developed for generating turbulent surface stress, sensible heat flux and humidity flux from mean velocity, temperature and humidity at some fixed height in the atmospheric surface layer, where conditions at this reference level are presumed known from observations or the evolving state of a numerical atmospheric circulation model. The method is based on coupling the Monin-Obukov surface layer similarity profiles which include buoyant stability effects on mean velocity, temperature and humidity to a force-restore formulation for the evolution of surface soil temperature to yield the local values of shear stress, heat flux and surface temperature. A self-contained formulation is presented including parameterizations for solar and infrared radiant fluxes at the surface. Additional parameters needed to implement the scheme are the thermal heat capacity of the soil per unit surface area, surface aerodynamic roughness, latitude, solar declination, surface albedo, surface emissivity and atmospheric transmissivity to solar radiation.

Hoffert, M. I.; Storch, J.

1978-01-01

146

The particle track record of the lunar surface.  

NASA Technical Reports Server (NTRS)

Information about lunar surface history revealed by fossil particle tracks is summarized. Such tracks are the result of damage left in dielectric materials by highly ionizing charged particles including heavy solar and galactic cosmic ray nuclei, heavy nuclei recoiling from cosmic ray induced spallation reactions, and induced- and spontaneous-fission fragments. From the distribution of cosmic ray and spallation tracks in the lunar rock, surface residence times of 1 to 30 million years and rock erosion rates of 1 to 10 A/yr have been determined. Particle tracks also record surface orientation and depth history of the rocks and contain information about ancient solar activity.

Comstock, G. M.

1972-01-01

147

Effects of WC particle size on the wear resistance of laser surface alloyed medium carbon steel  

NASA Astrophysics Data System (ADS)

The CO 2 laser surface alloying technique was used to form wear resistance layers on medium carbon steel with a kind of spherical WC powder. The effects of WC particle size on the abrasive wear resistance were thoroughly investigated. The results indicate that the laser alloyed layer is characterized by dendritic primary phase and ledeburite microstructure, consisting of austenite, martensite and carbides of Fe 3W 3C, W 2C and WC. The laser surface alloying with WC powder could improve the abrasive wear resistance of the medium carbon steel by over 63%. The factors such as the hardness, the amount and the distribution of WC particle determined the laser alloyed samples' wear resistance, and the laser alloyed sample with WC powder of 88-100 ?m diameter presented the best wear resistance in this study. Furthermore, the wear resistance mechanisms of the laser alloyed layers were also explored.

Tong, Xin; Li, Fu-hai; Kuang, Min; Ma, Wen-you; Chen, Xing-chi; Liu, Min

2012-01-01

148

Surface Energy Balance and The Mixed Layer at Lake Tanganyika  

NASA Astrophysics Data System (ADS)

Lake Tanganyika is a very large (670 by 50 km) and deep rift lake (max depth 1.5 km) in East Africa between 3.5 and 9 degree south of the equator. Mixing of the upper layers in this meromictic lake is most intense in the trade wind season (May - September). Apart from increased wind speeds, lower air temperatures and evaporative cooling of the surface layer combine to enhance mixing. Previous work indicated that correlation of evaporation and heat loss from the lake leaves room for a significant portion in the variability of heat content to be explained by other factors. The components of the energy balance which contribute to mixing were compared among seasons and between the north and south ends of the lake, over diel and annual cycles. Sensible heat and latent heat fluxes were estimated with bulk aerodynamic formulas and the heat storage change in the surface water layer was determined. Solar radiation was measured and longwave and all-wave net radiation calculated. Evaporation provided a major contribution to mixing but varied per site and over seasons. Mixing intensity was related to oxygen and nutrient cycles. Apart from evaporative cooling, sensible heat transfer and the emission of long wave radiation were important mechanisms in cooling the surface layer at night. Sensible heat transfer and outgoing longwave radiation were relatively more important at the north end of the lake, compared with the south end, in explaining nocturnal heat loss from the surface.

Verburg, P.; Hecky, R.

2002-12-01

149

Surface Science Letters Structures of adsorbed water layers  

E-print Network

methods) the consecutive ad- sorption of water molecules and found that, as the coverage increasedSurface Science Letters Structures of adsorbed water layers on MgO: an ab initio study R.M. Lynden density-functional method has been carried out for energy minima for a monolayer of water on MgO. Minima

Alavi, Ali

150

Terahertz surface plasmon propagation in nanoporous silicon layers  

Microsoft Academic Search

We describe the fabrication and measurement of a terahertz surface plasmon waveguide in which the optical mode is localized within a nanoporous silicon slab. We compare the propagation characteristics among waveguides with different porous layer thickness, and present an analytical model that accurately describes the dispersion and loss in the waveguides.

Shu-Zee A. Lo; Thomas E. Murphy

2010-01-01

151

Particle image velocimetry measurements of a shock wave\\/turbulent boundary layer interaction  

Microsoft Academic Search

Particle image velocimetry is used to investigate the interaction between an incident shock wave and a turbulent boundary\\u000a layer at Mach 2.1. A particle response assessment establishes the fidelity of the tracer particles. The undisturbed boundary\\u000a layer is characterized in detail. The mean velocity field of the interaction shows the incident and reflected shock wave pattern,\\u000a as well as the

R. A. Humble; F. Scarano; B. W. van Oudheusden

2007-01-01

152

Stabilization of Leidenfrost vapour layer by textured superhydrophobic surfaces.  

PubMed

In 1756, Leidenfrost observed that water drops skittered on a sufficiently hot skillet, owing to levitation by an evaporative vapour film. Such films are stable only when the hot surface is above a critical temperature, and are a central phenomenon in boiling. In this so-called Leidenfrost regime, the low thermal conductivity of the vapour layer inhibits heat transfer between the hot surface and the liquid. When the temperature of the cooling surface drops below the critical temperature, the vapour film collapses and the system enters a nucleate-boiling regime, which can result in vapour explosions that are particularly detrimental in certain contexts, such as in nuclear power plants. The presence of these vapour films can also reduce liquid-solid drag. Here we show how vapour film collapse can be completely suppressed at textured superhydrophobic surfaces. At a smooth hydrophobic surface, the vapour film still collapses on cooling, albeit at a reduced critical temperature, and the system switches explosively to nucleate boiling. In contrast, at textured, superhydrophobic surfaces, the vapour layer gradually relaxes until the surface is completely cooled, without exhibiting a nucleate-boiling phase. This result demonstrates that topological texture on superhydrophobic materials is critical in stabilizing the vapour layer and thus in controlling--by heat transfer--the liquid-gas phase transition at hot surfaces. This concept can potentially be applied to control other phase transitions, such as ice or frost formation, and to the design of low-drag surfaces at which the vapour phase is stabilized in the grooves of textures without heating. PMID:22972299

Vakarelski, Ivan U; Patankar, Neelesh A; Marston, Jeremy O; Chan, Derek Y C; Thoroddsen, Sigurdur T

2012-09-13

153

Parameterization of heat fluxes at heterogeneous surfaces by integrating satellite measurements with surface layer and atmospheric boundary layer observations  

Microsoft Academic Search

The regional heat flux exchange between heterogeneous landscapes and the nearby surface layer (SL) is a key issue in the study\\u000a of land-atmosphere interactions over arid areas such as the Heihe River basin in northwestern China and in high elevation\\u000a areas such as the Tibetan Plateau. Based on analysis of the land surface heterogeneity and its effects on the overlying

Yaoming Ma; Massimo Menenti; Reinder Feddes

2010-01-01

154

CORRELATIVE SURFACE ANALYSIS STUDIES OF ENVIRONMENTAL PARTICLES  

EPA Science Inventory

Various surface analysis techniques (scanning electron microscopy/energy dispersive X-ray microanalysis (SEM/EDX), electron spectroscopy for chemical analysis (ESCA), and secondary ion mass spectrometry (SIMS) were evaluated in a correlative regimen for the chemical characterizat...

155

Assessment of Fluorescent Particles for Surface Flow Analysis  

PubMed Central

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

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

2012-01-01

156

Spectrometers for particle measurements in space based on surface reflection  

NASA Astrophysics Data System (ADS)

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.

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

2012-04-01

157

A BOLTZMANN MODEL FOR TRAPPED PARTICLES IN A SURFACE POTENTIAL  

E-print Network

the charged particle model with some numerical simulations of a gas discharge on a satellite solar array. We variables are the time, the position on the surface and the total energy of the particles. These kinds, see for example [3], [6], [4] or [21] in different contexts: radiative transfer, semi

Vignal, Marie-Hélène

158

The Canopy and Aerosol Particles Interactions in TOulouse Urban Layer (CAPITOUL) experiment  

NASA Astrophysics Data System (ADS)

The CAPITOUL experiment is a joint experimental effort in urban climate, including the energetic exchanges between the surface and the atmosphere, the dynamics of the boundary layer over the city and its interactions with aerosol chemistry. The campaign took place in the city of Toulouse in southwest France, for one year, from February 2004 to February 2005. This allowed the study of both the day-to-day and seasonal variability of urban climate processes. The observational network included surface stations (meteorology, energy balance, chemistry), profilers and, during intensive observing periods, aircraft and balloons. The urban Surface Energy Balance differs between summer and winter: in summer, the solar heat stored during the previous daytime period is enough to maintain the heat release at night, but in winter, almost all the energy comes from the anthropogenic heat released by space heating. Both processes produce the well known Urban Heat Island (UHI). The city is shown to impact the entire boundary layer on specific days, when an urban breeze is observed. In wintertime, fog is found to be modified due to the vertical structure of the nocturnal boundary layer above the city (which is slightly unstable and not stable). The measurements of aerosol properties in and downwind the city permitted documentation of the urban aerosol as well as the chemical transformation of these aerosols, in particular the ageing of carbonaceous aerosols during transport. The Toulouse aerosol is mainly composed of carbonaceous particles. There is important seasonal variation in the ratio of black carbon to organic carbon, in the concentration of sulfates and nitrates and in the related radiative aerosol impacts. SF6 was released as a tracer in a suburban area of Toulouse during anticyclonic conditions with weak winds. The tracer measurements show dispersion was mainly driven by the surface sensible heat flux, and was highly sensitive to the urban heat island and also to the transport of boundary layer clouds. Modeling was fully integrated into the campaign. Surface energy balance and urban boundary layer processes have already been used to complement the analyses of the physical processes observed during the campaign. Companion papers detail most of these observation or modeling studies.

Masson, V.; Gomes, L.; Pigeon, G.; Liousse, C.; Pont, V.; Lagouarde, J.-P.; Voogt, J.; Salmond, J.; Oke, T. R.; Hidalgo, J.; Legain, D.; Garrouste, O.; Lac, C.; Connan, O.; Briottet, X.; Lachérade, S.; Tulet, P.

2008-12-01

159

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

DOEpatents

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.

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

1992-07-21

160

Effects of SiC Particle Size and Process Parameters on the Microstructure and Hardness of AZ91\\/SiC Composite Layer Fabricated by FSP  

Microsoft Academic Search

In this study, friction stir processing (FSP) was employed to develop a composite layer on the surface of as-cast AZ91 magnesium\\u000a alloy using SiC particles (5 ?m and 30 nm). The effects of the rotational and traverse speeds and the FSP pass number on the\\u000a microstructure and microhardness of the friction stir processed (FSPed) layer with and without SiC particles were investigated.

P. Asadi; M. K. Besharati Givi; K. Abrinia; M. Taherishargh; R. Salekrostam

161

Surface Layers in General Relativity and Their Relation to Surface Tensions  

E-print Network

For a thin shell, the intrinsic 3-pressure will be shown to be analogous to -A, where A is the classical surface tension: First, interior and exterior Schwarzschild solutions will be matched together such that the surface layer generated at the common boundary has no gravitational mass; then its intrinsic 3-pressure represents a surface tension fulfilling Kelvin's relation between mean curvature and pressure difference in the Newtonian limit. Second, after a suitable definition of mean curvature, the general relativistic analogue to Kelvin's relation will be proven to be contained in the equation of motion of the surface layer.

H. -J. Schmidt

2001-05-28

162

MICROANALYSIS OF INDIVIDUAL LAYERED PARTICLES BY SECONDARY ION MASS SPECTROMETRY  

EPA Science Inventory

Secondary ion mass spectrometry is evaluated for application to the determination of the composition and structure of individual particles. Analyses of many elemental constituents at the ppm level can be obtained in individual particles as small as micrometers in diameter. Molecu...

163

Financial Brownian particle in the layered order-book fluid and fluctuation-dissipation relations.  

PubMed

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. PMID:24655287

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

2014-03-01

164

Financial Brownian particle in the layered order book fluid and Fluctuation-Dissipation relations  

E-print Network

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 a 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 (FDR) in this non-material Brownian motion process.

Yura, Yoshihiro; Sornette, Didier; Takayasu, Misako

2014-01-01

165

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

PubMed

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. PMID:24670975

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

2014-01-01

166

Motion of particles with inertia in a compressible free shear layer  

Microsoft Academic Search

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'

M. Samimy; S. K. Lele

1991-01-01

167

Electron Scattering at Surfaces of Epitaxial Metal Layers  

NASA Astrophysics Data System (ADS)

In the field of electron transport in metal films and wires, the 'size effect' refers to the increase in the resistivity of the films and wires as their critical dimensions (thickness of film, width and height of wires) approach or become less than the electron mean free path lambda, which is, for example, 39 nm for bulk copper at room temperature. This size-effect is currently of great concern to the semiconductor industry because the continued downscaling of feature sizes has already lead to Cu interconnect wires in this size effect regime, with a reported 2.5 times higher resistivity for 40 nm wide Cu wires than for bulk Cu. Silver is a possible alternate material for interconnect wires and titanium nitride is proposed as a gate metal in novel field-effect-transistors. Therefore, it is important to develop an understanding of how the growth, the surface morphology, and the microstructure of ultrathin (few nanometers) Cu, Ag and TiN layers affect their electrical properties. This dissertation aims to advance the scientific knowledge of electron scattering at surfaces (external surfaces and grain boundaries), that are, the primary reasons for the size-effect in metal conductors. The effect of surface and grain boundary scattering on the resistivity of Cu thin films and nanowires is separately quantified using (i) in situ transport measurements on single-crystal, atomically smooth Cu(001) layers, (ii) textured polycrystalline Cu(111) layers and patterned wires with independently varying grain size, thickness and line width, and (iii) in situ grown interfaces including Cu-Ta, Cu-MgO, Cu-vacuum and Cu-oxygen. In addition, the electron surface scattering is also measured in situ for single-crystal Ag(001), (111) twinned epitaxial Ag(001), and single-crystal TiN(001) layers. Cu(001), Ag(001), and TiN(001) layers with a minimum continuous thickness of 4, 3.5 and 1.8 nm, respectively, are grown by ultra-high vacuum magnetron sputter deposition on MgO(001) substrates with and without thin epitaxial TiN(001) wetting layers and are studied for structure, crystalline quality, surface morphology, density and composition by a combination of x-ray diffraction theta-2theta scans, o-rocking curves, pole figures, reciprocal space mapping, Rutherford backscattering, x-ray reflectometry and transmission electron microscopy. The TiN(001) surface suppresses Cu and Ag dewetting, yielding lower defect density, no twinning, and smaller surface roughness than if grown on MgO(001). Textured polycrystalline Cu(111) layers 25-50-nm-thick are deposited on a stack of 7.5-nm-Ta on SiO2/Si(001), and subsequent in situ annealing at 350°C followed by sputter etching in Ar plasma yields Cu layers with independently variable thickness and grain size. Cu nanowires, 75 to 350 nm wide, are fabricated from Cu layers with different average grain size using a subtractive patterning process. In situ electron transport measurements at room temperature in vacuum and at 77 K in liquid nitrogen for single-crystal Cu and Ag layers is consistent with the Fuchs-Sondheimer (FS) model and indicates specular scattering at the metal-vacuum boundary with an average specularity parameter p = 0.8 and 0.6, respectively. In contrast, layers measured ex situ show diffuse surface scattering due to sub-monolayer oxidation. Also, addition of Ta atoms on Cu(001) surface perturbs the smooth interface potential and results in completely diffuse scattering at the Cu-Ta interface, and in turn, a higher resistivity of single-crystal Cu layers. In situ exposure of Cu(001) layers to O2 between 10 -3 and 105 Pa-s results in a sequential increase, decrease and increase of the electrical resistance which is attributed to specular surface scattering for clean Cu(001) and for surfaces with a complete adsorbed monolayer, but diffuse scattering at partial coverage and after chemical oxidation. Electron transport measurements for polycrystalline Cu layers and wires show a 10-15% and 7-9% decrease in resistivity, respectively, when increasing the average lateral grain size by a factor of 1.8. The

Chawla, Jasmeet Singh

168

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

NASA Technical Reports Server (NTRS)

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.

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

169

Precipitation and Corrosion Behaviour of Nano-Structured Near-Surface Layers on an AA6111 Aluminium Alloy  

NASA Astrophysics Data System (ADS)

A nano-structured, near-surface layer has been generated by mechanically grinding an AA6111 alloy. After heat treatment at 180°C for 30 minutes, Q phase particles, ~20 nm diameter, were precipitated preferentially at grain boundaries within the nano-structured nearsurface layer. No such precipitates were observed in the bulk alloy after this heat treatment. This preferential precipitation results in the near-surface layers having increased corrosion susceptibility than the bulk microstructure, due to the micro-galvanic coupling between the precipitates at grain boundary and the grain matrix. The localized attack is predominately intergranular.

Liu, Y.; Zhou, X.; Thompson, G. E.; Hashimoto, T.; Scamans, G. M.; Afseth, A.

2006-02-01

170

Arctic Cloud-driven Mixed Layers and Surface Coupling State  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

171

Neutral particle release from Europa's surface  

E-print Network

In this paper, we look at space weathering processes on the icy surface of Jupiter's moon Europa. The heavy energetic ions of the Jovian plasma (H+, O+, S+, C+) can erode the surface of Europa via ion sputtering (IS), ejecting up to 1000 H2O molecules per ion and also break the chemical bonds of the ejected species which can result in the formation of new molecules (e.g. O2), a process called radiolysis. UV Photons impinging the Europa's surface can also result in neutral atom release via photon stimulated desorption (PSD) and chemical change (photolysis). In this work, we study the efficiency of these two processes (IS and PSD) for ejecting water molecules. We simulated the resulting neutral H2O density, finding that they alone cannot sustain the tenuous atmosphere deduced from the Galileo Orbiter data. We also estimate the contribution to the total neutral atom release by the Ion Backscattering and Neutralization (IBSN) process. Moreover, we estimate the possibility of etecting the sputtered high energy ato...

Plainaki, C; Mura, A; Orsini, S; Cassidy, T

2009-01-01

172

THEORETICAL MODEL OF SOILING OF SURFACES BY AIRBORNE PARTICLES  

EPA Science Inventory

A model is developed which can be used to predict the change in reflectance from a surface as a function of time. Reflectance change is a measure of soiling caused by the deposition of particles on a surface. The major inputs to the model are the parameters to a bimodal distribut...

173

Programming nanostructured soft biological surfaces by atomic layer deposition.  

PubMed

Here, we present the first successful attempt to programme the surface properties of nanostructured soft biological tissues by atomic layer deposition (ALD). The nanopatterned surface of lotus leaf was tuned by 3-125 nm TiO2 thin films. The lotus/TiO2 composites were studied by SEM-EDX, XPS, Raman, TG-DTA, XRR, water contact angle and photocatalysis measurements. While we could preserve the superhydrophobic feature of lotus, we managed to add a new property, i.e. photocatalytic activity. We also explored how surface passivation treatments and various ALD precursors affect the stability of the sensitive soft biological tissues. As we were able to gradually change the number of nanopatterns of lotus, we gained new insight into how the hollow organic nanotubes on the surface of lotus influence its superhydrophobic feature. PMID:23680967

Szilágyi, Imre Miklós; Teucher, Georg; Härkönen, Emma; Färm, Elina; Hatanpää, Timo; Nikitin, Timur; Khriachtchev, Leonid; Räsänen, Markku; Ritala, Mikko; Leskelä, Markku

2013-06-21

174

Surface-plasmons lasing in double-graphene-layer structures  

NASA Astrophysics Data System (ADS)

We consider the concept of injection terahertz lasers based on double-graphene-layer (double-GL) structures with metal surface-plasmon waveguide and study the conditions of their operation. The laser under consideration exploits the resonant radiative transitions between GLs. This enables the double-GL laser room temperature operation and the possibility of voltage tuning of the emission spectrum. We compare the characteristics of the double-GL lasers with the metal surface-plasmon waveguides with those of such laser with the metal-metal waveguides.

Dubinov, A. A.; Aleshkin, V. Ya.; Ryzhii, V.; Shur, M. S.; Otsuji, T.

2014-01-01

175

Lateral optical force on chiral particles near a surface.  

PubMed

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 ?k 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

Wang, S B; Chan, C T

2014-01-01

176

Lateral optical force on chiral particles near a surface  

NASA Astrophysics Data System (ADS)

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 ?k 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.

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

2014-03-01

177

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

NASA Astrophysics Data System (ADS)

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 discussed together with meteorological parameters and trace gas measurements. Acknowledgement: PEGASOS project funded by the European Commission and the Framework Program 7 (FP7-ENV-2010-265148).

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

2014-05-01

178

Surface-cooling effects on compressible boundary-layer instability  

NASA Technical Reports Server (NTRS)

The influence of surface cooling on compressible boundary layer instability is discussed theoretically for both viscous and inviscid modes, at high Reynolds numbers. The cooling enhances the surface heat transfer and shear stress, creating a high heat transfer sublayer. This has the effect of distorting and accentuating the viscous Tollmien-Schlichting modes to such an extent that their spatial growth rates become comparable with, and can even exceed, the growth rates of inviscid modes, including those found previously. This is for moderate cooling, and it applies at any Mach number. In addition, the moderate cooling destabilizes otherwise stable viscous or inviscid modes, in particular triggering outward-traveling waves at the edge of the boundary layer in the supersonic regime. Severe cooling is also discussed as it brings compressible dynamics directly into play within the viscous sublayer. All the new cooled modes found involve the heat transfer sublayer quite actively, and they are often multi-structured in form and may be distinct from those observed in previous computational and experimental investigations. The corresponding nonlinear processes are also pointed out with regard to transition in the cooled compressible boundary layer. Finally, comparisons with Lysenko and Maslov's (1984) experiments on surface cooling are presented.

Seddougui, Sharon O.; Bowles, R. I.; Smith, F. T.

1990-01-01

179

The Colloid Stability of Gold Particles Dispersed on Solid Surfaces.  

NASA Astrophysics Data System (ADS)

Available from UMI in association with The British Library. An electron microscope technique has been applied to the study of two-dimensional dispersions of small particles of gold (ca. 4 nm in diameter) supported on solid surfaces. It was found that when these dispersions were immersed in aqueous solutions of neutral inorganic electrolytes changes in both the number concentration and spatial distribution of the particles could be induced. It has been concluded that subjection of the dispersions to aqueous solutions induces the particles to undergo a motion analogous to the Brownian motion exhibited by conventional three-dimensional colloidal dispersions. Under certain solution conditions the particles aggregated to form agglomerates. Two modes of particle aggregation have been found to occur: formation of high density aggregate species in which the individual constituent particles had coalesced losing their individual identities; and formation of low density aggregate species in which all the component particles remained separated by a constant surface-surface separation distance. The aggregation behaviour of the two-dimensional particle dispersions has been studied as a function of the concentration of electrolyte solution, the nature of the electrolyte, the solution pH and temperature. The influence of sodium halide on the colloid stability of these systems was found to differ significantly from those of sodium nitrate and sodium perchlorate. Results obtained from electrokinetic studies indicated that this was due to the formation of halide complexes at the surfaces of the gold particles. It has been shown that the aggregation behaviour of the gold particles is not well described by the DLVO theory of colloid stability. In order to account for the finite distance of separation that was found to be obtained between particles in aggregates formed on the surfaces of the crystalline substrate materials it is proposed that the particles accumulate in a potential energy minimum. In accord with this picture of the interparticle potential energy it has been shown by modelling of the kinetics of particle aggregation, that doublet species have finite lifetimes in the experimental systems and consequently undergo dissociation. (Abstract shortened by UMI.).

Collins, Ian R.

180

A multi-layer soil moisture data assimilation using support vector machines and ensemble particle filter  

NASA Astrophysics Data System (ADS)

SummaryHybrid data assimilation (DA) is greatly used in recent hydrology and water resources research. In this study, one newly introduced technique, the ensemble particle filter (EnPF), formed by coupling ensemble Kalman filter (EnKF) with particle filter (PF), is applied for a multi-layer soil moisture prediction in the Meilin watershed based on the support vector machines (SVMs). The data used in this paper includes six-layer soil moisture: 0-5 cm, 30 cm, 50 cm, 100 cm, 200 cm and 300 cm and five meteorological parameters: soil temperature at 5 cm and 20 cm, air temperature, relative humidity and solar radiation in the study area. In order to investigate this EnPF approach, another two filters, EnKF and PF are applied as another two data assimilation methods to conduct a comparison. In addition, the SVM model simulated data without updating with data assimilation technique is discussed as well to evaluate the data assimilation technique. Two experimental cases are explored here, one with 200 initial training ensemble members in the SVM training phase while the other with 1000 initial training ensemble members. Three main findings are obtained in this study: (1) the SVMs machine is a statistically sound and robust model for soil moisture prediction in both the surface and root zone layers, and the larger the initial training data ensemble, the more effective the operator derived; (2) data assimilation technique does improve the performance of SVM modeling; (3) EnPF outweighs the performance of other two filters as well as the SVM model; Moreover, the ability of EnPF and PF is not positively related to the resampling ensemble size, when the resampling size exceeds a certain amount, the performance of EnPF and PF would be degraded. Because the EnPF still performs well than EnKF, it can be used as a powerful data assimilation tool in the soil moisture prediction.

Yu, Zhongbo; Liu, Di; Lü, Haishen; Fu, Xiaolei; Xiang, Long; Zhu, Yonghua

2012-12-01

181

Surface Reactions of Ferritic Steel Particles Atomized with Water or Mixtures of Water-Additive  

NASA Astrophysics Data System (ADS)

The production of metallic powders has been a very important industrial activity for many years. In this work, the water or a mixture water-additive atomization process has been used. During the production of steel particles by water atomization these particles are coated with a surface oxide layer. With particles under these conditions it is very difficult to obtain final products with high mechanical properties, so that it is desirable to diminish the surface oxide as much as possible. Experimental tests to know if the use of additives as corrosion inhibitors, used to avoid steel oxidation at room temperature, could modify the properties of particles during the manufacture of an AISI C1115 steel by water atomization were carried out. In order to improve the knowledge of the chemical surface reactions, characterization of the powder surfaces and interfaces of metal matrix/oxide layer by means of Energy Dispersive Spectroscopy (EDS), Scanning Electron Microscopy (SEM), X-ray Diffraction and Auger Electron Spectroscopy (AES) was carried out.

Estrada, J. L.; Godinez, J.; Herrera, H.

182

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

USGS Publications Warehouse

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 ? = 0.6 at low slip speeds to a coefficient near ? = 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 ? = 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 ? = 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 ?m. 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.

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

2011-01-01

183

Scaled temperature spectrum in the unstable oceanic surface layer  

NASA Astrophysics Data System (ADS)

A nondimensional form of the temperature spectrum in a convective near-surface layer was derived empirically as a function of stability parameter ? = z/L and surface wave parameter ? = u*/(gz)1/2, under the assumption of horizontal isotropy, where z is the depth of the measurement, L is the Monin-Obukhov length scale, u* is the surface friction velocity, and g is the acceleration due to gravity. The wave number-weighted, one-dimensional spectrum had +1 slope at low wave numbers and -2/3 slope at high wave numbers (characteristic of an inertial subrange). Spectral levels in the -2/3 range varied with ?, and the spectrum width was a function of ?. The wavelength of the spectral peak decreased as -? (>0) increased. The variation of spectral level in the inertial subrange suggested that dissipation due to wave breaking was enhanced by a factor of 1.7 at 2-m depth for a wind speed of 10 m s-1. Root-mean-square temperature fluctuations at 2-m depth versus -? were in excellent agreement with atmospheric surface layer observations and agreed moderately well (within 30%) with the results of large-eddy simulation experiments. Root-mean-square fluctuations were proportional to (-?)-1/3 for -? > 0.4, consistent with the predictions of similarity theory. The skewness of temperature fluctuations varied with -?, qualitatively similar to variation in the atmospheric surface layer. The skewness of the horizontal gradient of temperature at 2-m depth varied relative to the wind direction and was well described by a cosine function with amplitude 0.6.

Wijesekera, Hemantha W.; Paulson, Clayton A.; Skyllingstad, Eric D.

2004-03-01

184

Effect of coating temperature on properties of the SiC layer in TRISO-coated particles  

NASA Astrophysics Data System (ADS)

The effect of coating temperature on properties of the SiC layer in TRISO-coated particles was investigated. An increase in coating temperature resulted in a significant coarsening of surface microstructures and an increase of the pore size and porosity of SiC layers. The SiC layers formed at 1400-1550 °C had nearly stoichiometric compositions whereas the SiC layer formed at 1600 °C contained a small amount of free carbon. The degradation of hardness and elastic modulus of the SiC layers coated at 1550 and 1600 °C was attributed to the increased porosity of the specimens and partly to the existence of free carbon. The fracture stress of the SiC layer measured by the crush test of hemispherical shell specimen did not correlate with the hardness and elastic modulus, and there was no clear dependence of the fracture stress on the coating temperature; this lack of correlation can be explained by the large roughness of the inner surface of the SiC layer.

Kim, Weon-Ju; Park, Jeong Nam; Cho, Moon Sung; Park, Ji Yeon

2009-07-01

185

Particle dispersion within zonal jets in two-layer beta-plane turbulence  

E-print Network

Passive tracer dispersion is studied in a two-layer, quasigeostrophic, betaplane model in which persistent, steady, zonal jets are observed. Particle trajectories and statistics are examined for barriers to or mechanisms for mixing. Simulations...

Roman, Jennifer Claire

2012-06-07

186

Microstructure and wear properties of the electroslag remelting layer reinforced by TiC particles  

Microsoft Academic Search

The electroslag remelting (ESR) layer reinforced by TiC particles was obtained by electroslag remelting. The microstructure and wear properties of the ESR layer were studied by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), and wear test. The results indicate that TiC particles are synthesized by self-propagating high-temperature synthesis (SHS) reaction during the electroslag remelting process. The size of

Qianlin Wu; Yangshan Sun; Guoqing Li

2008-01-01

187

Local properties of the surface layer(s) of BiFeO3 single crystals  

NASA Astrophysics Data System (ADS)

The surface of BiFeO3 single crystals has been characterized at the local level using several AFM-based techniques. We have observed the presence of two different epilayers showing electrical and mechanical properties different from those of the bulk: a ferroelectrically "dead" outer skin of 5 nm sitting upon a subsurface layer that displays an extremely fine pattern of hierarchical self-ordered nanodomains. Based on the size of the nanodomains and applying a Kittel-like analysis, we argue that the nanotwinned region should be confined in a layer less than a micron deep. The superficial phase transition at T* = 275 °C is restricted to the outer skin layer (the "dead" layer), while the nanotwinned layer is insensitive to this transition. In view of the photovoltaic properties and spin-dependent transport of domain walls in BiFeO3, the existence of nanodomains (and thus a high density of domain walls) in bulk single crystals is likely to be relevant for understanding their functional properties.

Domingo, Neus; Narvaez, Jackeline; Alexe, Marin; Catalan, Gustau

2013-05-01

188

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

NASA Technical Reports Server (NTRS)

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.

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

2005-01-01

189

Exoelectronic emission of particles of lunar surface material  

NASA Technical Reports Server (NTRS)

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.

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

1974-01-01

190

Phase analysis of surface layers by Mössbauer spectroscopy  

NASA Astrophysics Data System (ADS)

Mössbauer spectroscopy—now 25 years old—is described as a very useful tool to perform phase analyses. The experimental technique and the use of the spectral parameters to derive qualitative and quantitative informations are briefly discussed. Special scattering techniques (gamma scattering and conversion electron detection) are now applied to investigate surface layers. Some examples, where the product composition as well as the kinetics were investigated, demonstrate the successful application in corrosion research: Corrosion of the inner surface of hot water pipes, the effect of corrosion inhibitors, the influence of aggressive components, and the nondestructive analysis of sublayer rusting beneath a coating. The general advantages of Mössbauer spectroscopy in surface studies are summarized.

Meisel, W.

191

Controlling protein-particle adsorption by surface tailoring colloidal alumina particles with sulfonate groups.  

PubMed

In this study, we demonstrate the control of protein adsorption by tailoring the sulfonate group density on the surface of colloidal alumina particles. The colloidal alumina (d(50)=179±8nm) is first accurately functionalized with sulfonate groups (SO(3)H) in densities ranging from 0 to 4.7SO(3)H nm(-2). The zeta potential, hydrophilic/hydrophobic properties, particle size, morphology, surface area and elemental composition of the functionalized particles are assessed. The adsorption of three model proteins, bovine serum albumin (BSA), lysozyme (LSZ) and trypsin (TRY), is then investigated at pH 6.9±0.3 and an ionic strength of 3mM. Solution depletion and zeta potential experiments show that BSA, LSZ and TRY adsorption is strongly affected by the SO(3)H surface density rather than by the net zeta potential of the particles. A direct correlation between the SO(3)H surface density, the intrinsic protein amino acid composition and protein adsorption is observed. Thus a continuous adjustment of the protein adsorption amount can be achieved between almost no coverage and a theoretical monolayer by varying the density of SO(3)H groups on the particle surface. These findings enable a deeper understanding of protein-particle interactions and, moreover, support the design and engineering of materials for specific biotechnology, environmental technology or nanomedicine applications. PMID:23164944

Meder, Fabian; Brandes, Christoph; Treccani, Laura; Rezwan, Kurosch

2013-03-01

192

Effects of evaporation layer on free-space optical communication links near sea surface at 1.55 mum  

Microsoft Academic Search

Free-space optics (FSO) holds the potential for high bandwidth communication in situations where landline communication is not practical, with relatively low cost and maintenance. For FSO communication in maritime environments, laser beams propagating through the evaporation layer near the sea surface are affected by turbulence, the scattering coefficients of the water particles, and the salt water itself. To better gauge

John Zeller; Tariq Manzur

2011-01-01

193

Tunable surface free energies of functionalized molecular layers on Si surfaces for microfluidic immunosensor applications  

NASA Astrophysics Data System (ADS)

Enhanced antigen-antibody interactions in microfluidic immunosensors can be effected by tailoring the surface free energies of the antibody immobilized surfaces to obtain the appropriate fluid-wall interactions. We report a systematic study to evaluate the surface free energies from contact angle measurements, using the LWAB method, of different antibody (anti-BSA, anti-PSA, and anti-CRP) surfaces, each immobilized separately on to non- and nanotextured Si surfaces via a stack of functionalized layers including aminosilanes of which three different types were used. The apolar surface free energy components were independent of the physical modification in the non-functionalized and the intermediate hydrolyzed surfaces where as they depended on the nature of the surface and the chemical modifications in the subsequent functionalized stages. Surface free energies of the different antibodies immobilized with the shorter chain length aminosilane (APTES) on non- and nanotextured surfaces were in the order of anti-BSA < anti-PSA < anti-CRP. A tunability of the surface free energy up to 9.6 mJ/m2 was achieved which is reasonably significant when compared to the surface free energy window (??s = 40 mJ/m2) of biofunctionalized surfaces. This fundamental understanding of the surface energetics of the biofunctionalized surfaces can be utilized in modulating the surface properties to design efficient immunosensors.

Chepyala, Ramchander; Panda, Siddhartha

2013-04-01

194

Heat flux and mixing efficiency in the surface mixing layer  

NASA Astrophysics Data System (ADS)

Fluctuations of vertical velocity and temperature, w' and T', were measured with a horizontal profiler that was towed at night in the oceanic boundary layer between 15 and 25 m depth. Stratified and convective turbulent regimes were encountered along the tow path. A direct estimate of the turbulent heat flux F was computed from the correlation of w' and T'. The concurrent measurement of the dissipation rate of turbulent kinetic energy ? allowed us to estimate the mixing efficiency ?0 = F/F?, where F? was the heat flux estimate based on the average dissipation rate. In regions where the turbulence in the stratified boundary layer was sustained by shear instabilities 0.08 ? ?0 ? 1.38. The average was ?¯0=0.46, a value close to the maximum mixing efficiency predicted by classical scaling arguments and laboratory results. The measurements of w' were significantly influenced by instrument motions and the orbital velocities induced by surface waves. A motion correction algorithm made it possible to resolve overturning length scales up to 33 m and thus to capture all scales that contributed to the heat flux F. For the surface mixing layer reported here the largest flux-supporting scales were ˜14 m. For the stably stratified regimes in particular the peak of the heat flux cospectrum was at one half of the Ozmidov wave number, 0.5ko.

Wolk, Fabian; Lueck, Rolf G.

2001-09-01

195

Linear stability of a layered fluid with mobile surface plates  

NASA Technical Reports Server (NTRS)

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.

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

1994-01-01

196

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

NASA Technical Reports Server (NTRS)

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.

Yushin, Gleb; Evanoff, Kara; Magasinski, Alexander

2012-01-01

197

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

NASA Technical Reports Server (NTRS)

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.

Blumberg, Dan G.; Greeley, Ronald

1992-01-01

198

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

PubMed

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 a salt in moisture content almost identical to that of the brine very quickly (17.3% at 4 d), whereas the salt in moisture content at the surface of the cheese block in saturated brine was only 11.9% at 4 d. There appears to be some critical concentration of salt in brine above which there is a large negative impact on salt uptake due to the creation of a barrier layer at the surface of the block of cheese. PMID:15956296

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

2005-07-01

199

The Gas Temperature in the Surface Layers of Protoplanetary Disks  

NASA Astrophysics Data System (ADS)

Models for the structure of protoplanetary disks have thus far been based on the assumption that the gas and dust temperatures are equal. The gas temperature, an essential ingredient in the equations of hydrostatic equilibrium of the disk, is then determined from a continuum radiative transfer calculation, in which the continuum opacity is provided by the dust. It has long been debated whether this assumption still holds in the surface layers of the disk, in which the dust infrared emission features are produced. In this paper we compute the temperature of the gas in the surface layers of the disk in a self-consistent manner. The gas temperature is determined from a heating-cooling balance equation in which processes such as photoelectric heating, dissociative heating, dust-gas thermal heat exchange, and line cooling are included. The abundances of the dominant cooling species such as CO, C, C+, and O are determined from a chemical network based on the atomic species H, He, C, O, S, Mg, Si, and Fe. The underlying disk models to our calculations are the models of Dullemond, van Zadelhoff, & Natta. We find that in general the dust and gas temperatures are equal to within 10% for AV>~0.1, which is above the location of the ``superheated surface layer'' in which the dust emission features are produced. High above the disk surface the gas temperature exceeds the dust temperature and can become-in the presence of polycyclic aromatic hydrocarbons-as high as 600 K at a radius of 100 AU. This is a region in which CO has fully dissociated, but a significant fraction of hydrogen is still in molecular form. The densities are still high enough for nonnegligible H2 emission to be produced. At radii inward of 50 AU, the temperature of the gas above the photosphere can reach up to ~104 K. In the disk surface layers, the gas temperature exceeds the virial temperature of hydrogen. Some of this material could possibly evaporate, but firm conclusions have to await fully self-consistent disk models, in which the disk structure and gas temperature determination will be solved iteratively.

Kamp, I.; Dullemond, C. P.

2004-11-01

200

Atmospheric surface and boundary layers of the Amazon Basin  

NASA Technical Reports Server (NTRS)

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.

Garstang, Michael

1987-01-01

201

Fabrication of nonaging superhydrophobic surfaces by packing flowerlike hematite particles  

NASA Astrophysics Data System (ADS)

The authors demonstrate the fabrication of nonaging superhydrophobic surfaces by packing flowerlike micrometer-sized hematite (?-Fe2O3) particles. Although hematite is intrinsically hydrophilic, the nanometer-sized protrusions on the particles form textures with overhanging structures that prevent water from entering into the textures and induce a macroscopic superhydrophobic phenomenon. These superhydrophobic surfaces do not age even in extremely oxidative environments—they retain the superhydrophobicity after being stored in ambient laboratory air for 4months, heated to 800°C in air for 10h, and exposed to ultraviolet ozone for 10h.

Cao, Anmin; Cao, Liangliang; Gao, Di

2007-07-01

202

Particle Resuspension in Turbulent Boundary Layers and the Influence of Non-Gaussian Removal Forces  

E-print Network

The work presented is concerned with the way very small micron-size particles attached to a surface are resuspended when exposed to a turbulent flow. Of particular concern is the remobilization of radioactive particles as a consequence of potential nuclear accidents. In this particular case the focus is on small particles, force holding such particles onto a surface arises from van der Waals inter-molecular adhesive forces. Here an improved version of the "Rock n Roll" model (Reeks & Hall, 2001) is developed where this model employs a stochastic approach to resuspension involving the rocking and rolling of a particle about surface asperities arising from the moments of the fluctuating drag forces acting on the particle close to the surface. In this work the model is significantly improved by using values of both the stream-wise fluid velocity and acceleration close to the wall obtained from Direct Numerical Simulation (DNS) of turbulent channelflow. Using an...

Zhang, F; Kissane, M

2012-01-01

203

Particle simulation of auroral double layers. Doctoral thesis  

SciTech Connect

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.

Smith, B.L.

1992-06-01

204

Copolyimide Surface Modifying Agents for Particle Adhesion Mitigation  

NASA Technical Reports Server (NTRS)

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.

Wohl, Christopher J.; Connell, John W.

2011-01-01

205

Suppression of nanosilica particle-induced inflammation by surface modification of the particles.  

PubMed

It has gradually become evident that nanomaterials, which are widely used in cosmetics, foods, and medicinal products, could induce substantial inflammation. However, the roles played by the physical characteristics of nanomaterials in inflammatory responses have not been elucidated. Here, we examined how particle size and surface modification influenced the inflammatory effects of nanosilica particles, and we investigated the mechanisms by which the particles induced inflammation. We compared the inflammatory effects of silica particles with diameters of 30-1,000 nm in vitro and in vivo. In macrophages in vitro, 30- and 70-nm nanosilica particles (nSP30 and nSP70) induced higher production of tumor necrosis factor-? (TNF?) than did larger particles. In addition, intraperitoneal injection of nSP30 and nSP70 induced stronger inflammatory responses involving cytokine production than did larger particles in mice. nSP70-induced TNF? production in macrophage depended on the production of reactive oxygen species and the activation of mitogen-activated protein kinases (MAPKs). Furthermore, nSP70-induced inflammatory responses were dramatically suppressed by surface modification of the particles with carboxyl groups in vitro and in vivo; the mechanism of the suppression involved reduction in MAPK activation. These results provide basic information that will be useful for the development of safe nanomaterials. PMID:22418595

Morishige, Tomohiro; Yoshioka, Yasuo; Inakura, Hiroshi; Tanabe, Aya; Narimatsu, Shogo; Yao, Xinglei; Monobe, Youko; Imazawa, Takayoshi; Tsunoda, Shin-ichi; Tsutsumi, Yasuo; Mukai, Yohei; Okada, Naoki; Nakagawa, Shinsaku

2012-08-01

206

Controlling rejections of spoof surface plasmon polaritons using metamaterial particles.  

PubMed

Based on the dispersion relation, surface plasmon polaritons (SPPs) or spoof SPPs are always propagating surface waves when the operating frequency is below the asymptotic limit - the surface plasma frequency. Here we propose a method to control the rejections of spoof SPPs using metamaterial particles. By introducing electrically resonant metamaterials near an ultrathin corrugated metallic strip - the spoof SPP waveguide - to produce tight coupling and mismatch of surface impedance, we show that the SPP modes are rejected near the resonant frequencies within the propagating band. Through the modulation of scaling factor of metamaterial particles, we can manipulate the rejections of SPP modes from narrowband to broadband. Both simulation and experiment results verify the tunability of SPP rejections, which have important applications in filtering SPP waves in plasmonic circuits and systems. PMID:24921585

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

2014-06-01

207

Effects of surface layer composition in stabilizing thin film ferroelectrics  

Microsoft Academic Search

Using first-principles density functional theory calculations, we explore the ramifications of chemically altering the properties of the metal\\/ferroelectric interfaces in thin film ferroelectric capacitors. We show that a 3 unit-cell-thick BaTiO3 film with SrRuO3 electrodes has a stable, bulk-like polarization when the surface BaO layers are replaced with PbO, in contrast to the unmodified SrRuO3\\/BaTiO3 film which only begins to

Alexie Kolpak; Andrew Rappe

2006-01-01

208

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

SciTech Connect

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

Troutt, T.R.

1989-12-31

209

Surface structure of nascent particles of ultrahigh molecular weight poly(ethylene) reactor powders  

NASA Astrophysics Data System (ADS)

A comparative investigation of the surface structure of three ultrahigh molecular weight poly(eth-ylene) (UHMWPE) reactor powders that differ by their ability to be processed to high-performance fibers is carried out with a JEOL 6300 scanning electron microscope and a nanoluminograph, which makes it possible to study thermoluminescence of ultrathin near-surface layers of solids. The activation energies of relaxation processes in near-surface layers of nascent particles and the sizes of kinetic units of motion, for which the mobility is defrozen in the temperature range of the corresponding transitions, are calculated from the glow curves. The possible location of kinetic units in supermolecular formations resolved in micrographs and their influence on the dissolution of the reactor powder are discussed.

Lebedev, D. V.; Ivan'kova, E. M.; Marikhin, V. A.; Myasnikova, L. P.; Seydewitz, V.

2009-08-01

210

Thin hydroxyapatite surface layers on titanium produced by ion implantation  

NASA Astrophysics Data System (ADS)

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 (?,?) backscattering and the resonant nuclear reaction 1H( 15N,??) 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.

Baumann, H.; Bethge, K.; Bilger, G.; Jones, D.; Symietz, I.

2002-11-01

211

Gyroscopic Pumping in the Solar Near-Surface Shear Layer  

E-print Network

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 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 maintains 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 non-diffusive and directed radially inward. Inferred mean flows are consistent with the idea that turbul...

Miesch, Mark S

2011-01-01

212

Study on theoretical bases of receiving composite alloy layers on surface of cast steel castings  

Microsoft Academic Search

The use of composite alloy layers on chosen surfaces of cast makes possible to obtain a special usable properties. Composite alloy layers on cast steel shapes with liquid phase. The processes which set in form during formation of composite layer, progress beside the transient heat flow that the transient thermal field. Decrease of temperature in surface layer of cast causes

J. Gawro?ski; J. Szajnar; P. Wróbel

2004-01-01

213

Colloidal Gold Particles Adsorption onto Silanized Glass Surfaces  

Microsoft Academic Search

The adsorption of colloidal gold onto glass surfaces previously treated with bifunctional silanes was studied aiming to enhance the recovery of colloidal gold particles from process water in the mining industry. Colloidal gold samples were prepared via the reduction of gold in HAuCl4 solution by sodium citrate. Glass plates used as model substrates were silanized with an ethanolic solution of

Sandra Magalhães Saraiva; José Farias Oliveira

2004-01-01

214

Prediction of transport behaviors of particulate composites considering microstructures of soft interfacial layers around ellipsoidal aggregate particles.  

PubMed

The effect of microstructures of interfacial layers on transport behaviors of particulate composites has been found to be significant, thus microstructural characteristics of interfacial layers should be considered in the analysis for better prediction of transport properties of particulate composites. However, it is very difficult to determine the volume fraction of soft interfacial layers around polydisperse three-dimensional (3D) ellipsoidal aggregate particles and to practically estimate the influence of such a microstructural characteristic on transport properties of particulate composites by traditional experimental methods and simple models proposed so far. In this article, an approximate analytical model for the volume fraction of soft interfacial layers is proposed on the basis of a theory of the nearest-surface distribution functions and geometric characteristics of polydisperse ellipsoidal particle systems. A theoretical model that adopts a three-phase composite ellipsoid structure by a generalized self-consistent scheme is further presented to predict the effective transport properties of particulate composites containing such soft interfacial layers. To test the developed models, numerical results of the soft interfacial volume fraction from the previous work, experimental data in the literature, the Hashin-Shtrikman bounds model and the Maxwell-Garnett model for the effective electrical conductivity are compared respectively. Finally, by virtue of the present models, the effects of key factors on the effective electrical conductivity of particulate composites are investigated in a quantitative manner. PMID:24651952

Xu, Wenxiang; Chen, Huisu; Chen, Wen; Jiang, Linhua

2014-01-28

215

Lofting of Triboelectrostatically Charged Particles From the Lunar Surface  

NASA Astrophysics Data System (ADS)

Tribocharging of lunar regolith can occur by micrometeorite gardening and by anthropogenic interaction with the lunar surface. The tribocharged material may then be lofted into the exosphere by near-surface electrical fields created by solar wind and radiation effects. On the basis of a simple charge-to-mass ratio, the finest dust should be the most readily lofted. However, this model assumes that all particles in the affected material become charged, and that charging is a homogeneous process. Laboratory experiments have demonstrated that it is not simply the smallest particles that are subject to lofting. In an analog Debye-sheath electrical field between capacitor plates, tribocharged (vibrated) lunar simulant materials released both dust and silt/sand size materials into the electrical field. This observation was made with scanning electron microscopy of particle traps within the electrical field. The lab experiments also demonstrated an extreme inhomogeneity of tribocharging in the test samples. Ostensibly, the tribocharging vibrational energy was uniform throughout the sample, but observations of surface 'bursting', ' ballistic fountaining', and other phenomena indicated localized (millimeter-scale) electrical inhomogeneity. Theoretical modeling of tribocharging also suggests that there may be an optimum size fraction for charging. The coarsest particles undergo the greatest number of contact electrification events, but are too massive to be lifted. The finest particles are hidden or shielded from tribocharging by adhering to larger host grains in mechanical recesses. Medium-size particles receive moderate charging and are light enough to be lifted in the electrical fields; particles of several tens of microns may be optimally sized for lofting.

Davis, S.; Marshall, J.; Richard, D.; Laub, J.

2008-12-01

216

Photometric imaging in particle size measurement and surface visualization.  

PubMed

The aim of this paper is to give an insight into photometric particle sizing approaches, which differ from the typical particle size measurement of dispersed particles. These approaches can often be advantageous especially for samples that are moist or cohesive, when dispersion of particles is difficult or sometimes impossible. The main focus of this paper is in the use of photometric stereo imaging. The technique allows the reconstruction of three-dimensional images of objects using multiple light sources in illumination. The use of photometric techniques is demonstrated in at-line measurement of granules and on-line measurement during granulation and dry milling. Also, surface visualization and roughness measurements are briefly discussed. PMID:21075186

Sandler, Niklas

2011-09-30

217

Cr Ni Mo Co surface alloying layer formed by plasma surface alloying in pure iron  

NASA Astrophysics Data System (ADS)

Using double glow plasma alloying technique, a multi-elements alloyed layer containing elements of Cr, Ni, Mo and Co was formed on the surface of pure iron. After undergoing suitable aging treatment followed solid solution treatment, the formed alloying layer keeps a good combination of corrosion resistance and wear resistance. The relationship between the process parameters of heat treatments and the properties of the formed Cr-Ni-Mo-Co alloying layer, such as the chemical composition, hardness, corrosion resistance and wear resistance, was investigated in this study. It was revealed that the formed alloying layer exhibits a better behavior than that of 304 stainless steel and pure iron by employing a suitable heat treatment system. The temperature employed in solid solution treatment is 1453 K (1180 °C) followed by water quenching and the aging temperature is 813 K (540 °C) followed by water cooling.

Liu, Xiaoping; Gao, Yuan; Li, Zhonghou; Xu, Zhong; Tian, Wenhuai; Tang, Bin

2006-03-01

218

Numerical Computations of Hypersonic Boundary-Layer over Surface Irregularities  

NASA Technical Reports Server (NTRS)

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.

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

2010-01-01

219

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

PubMed

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/r(3) potential, with distance r measured in three-dimensional Euclidean space R(3). 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 -?/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. PMID:23944467

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

2013-07-01

220

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

NASA Astrophysics Data System (ADS)

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.

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

2013-11-01

221

Paint removal and surface cleaning using ice particles  

NASA Astrophysics Data System (ADS)

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.

Foster, Terry; Visaisouk, S.

1993-03-01

222

Paint removal and surface cleaning using ice particles  

NASA Astrophysics Data System (ADS)

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.

Foster, Terry; Visaisouk, S.

1995-04-01

223

Layer-by-layer composite films of polyaniline and vanadium pentoxide sol gels studied by electrochemical surface plasmon spectroscopy  

Microsoft Academic Search

Electroactive multilayer films of polyaniline (PAni) and vanadium pentoxide (V2O5) sol-gels were prepared on gold surfaces by means of the layer-by-layer (LBL) method. The stepwise buildup and the optoelectrochemical\\u000a behaviour of the composite films were investigated in-situ by electrochemical surface plasmon spectroscopy (ESPS). A thickness\\u000a increment of 2.3 nm per deposited bilayer was obtained by modelling the surface plasmon spectra. The

R. Schweiss; N. Zhang; W. Knoll

2007-01-01

224

Determination of overlapping degree of interfacial layers around polydisperse ellipsoidal particles in particulate composites  

NASA Astrophysics Data System (ADS)

The determination of overlapping degree of interfacial layers is crucial to evaluate physical properties of particulate composites. The purpose of the present work is to develop a theoretical scheme for the overlapping degree of interfacial layers around polydisperse ellipsoidal particles in particulate composites. Comparing with numerical results of the actual interfacial volume fraction and theoretical results of the interfacial overlapping degree around spherical particles in the literature, the accuracy of the developed theoretical scheme is tested. Based on the present scheme, the dependence of the interfacial overlapping degree on geometrical configurations of particles is investigated quantitatively through sensitivity analysis. It is found that the effects of those factors on the interfacial overlapping degree have similar behaviours to that on the actual interfacial volume fraction. For instance, the interfacial overlapping degree increases with the increase of the interfacial layer thickness and the volume fraction particles, but it decreases with the increase of the maximum equivalent diameter of ellipsoidal particles. Interestingly, we find that the interfacial overlapping degree strongly depends on the shape of particles; that is, the interfacial overlapping degree increases as particles deviate from perfect spheres. These results can further be used as theoretical criteria for guiding practical works.

Xu, Wenxiang; Chen, Wen; Chen, Huisu; Tian, Xia; Zhao, Haitao

2014-04-01

225

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

PubMed

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. PMID:25312378

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

2014-11-11

226

An evaluation of the effects of SiC layer thinning on failure of TRISO-coated fuel particles  

Microsoft Academic Search

The fundamental design for a gas-cooled reactor relies on the behavior of the coated particle fuel. The coating layers surrounding the fuel kernels in these spherical particles, consisting of pyrolytic carbon and silicon carbide layers, act as a pressure vessel that retains fission products. Many more fuel particles have failed in US irradiations than would be expected when only one-dimensional

Gregory K. Miller; David A. Petti; John T. Maki; Darrell L. Knudson

2006-01-01

227

Turbulent Mixing in the Surface Layers of Accreting Neutron Stars  

NASA Astrophysics Data System (ADS)

During accretion, a neutron star (NS) is spun up as angular momentum is transported through its surface layers. We study the resulting differentially rotating profile, focusing on the impact this has for type I X-ray bursts. The predominant viscosity is likely provided by the Tayler-Spruit dynamo, where toroidal magnetic field growth and Tayler instabilities balance to support a steady state magnetic field. The radial and azimuthal components have strengths of ~105 and ~1010 G, respectively. This leads to nearly uniform rotation at the depths of X-ray bursts. A remaining small shear transmits the accreted angular momentum inward to the NS interior. Although this shear gives little viscous heating, it can trigger turbulent mixing. Detailed simulations will be required to fully understand the consequences of mixing, but our models illustrate some general features. Mixing has the greatest impact when the buoyancy at the compositional discontinuity between accreted matter and ashes is overcome. This occurs preferentially at high accretion rates or low spin frequencies and may depend on the ash composition from the previous burst. We then find two new regimes of burning. The first is ignition in a layer containing a mixture of heavier elements from the ashes. If ignition occurs at the base of the mixed layer, recurrence times as short as ~5-30 minutes are possible. This may explain the short recurrence time of some bursts, but incomplete burning is still needed to explain these bursts' energetics. When mixing is sufficiently strong, a second regime is found where accreted helium mixes deep enough to burn stably, quenching X-ray bursts. The carbon-rich material produced by stable helium burning would be important for triggering and fueling superbursts.

Piro, Anthony L.; Bildsten, Lars

2007-07-01

228

Large Eddy Simulation of the Upper Atmospheric Surface Layer.  

NASA Astrophysics Data System (ADS)

The von Karman constant (kappa) and the Monin-Obukhov similarity formulation occupy very important positions in the theoretical framework of the atmospheric surface layer (ASL). Measurements, however, provide a great scatter in their estimates mainly because the requirements of neutrality (only for estimate of kappa), stationarity and horizontal homogeneity in the real atmospheric boundary layer (ABL) are hardly achieved. Therefore, a long-time dispute over the value of the value of the von Karman constant applicable in the neutral-static-stability ABL has not been settled yet; another controversy concerns the form of the universal Monin-Obukhov similarity functions in very unstable conditions. A numerical tool, three-dimensional large eddy simulation (LES), is adopted to simulate turbulence in the ABL, with a fine resolution in the ASL, so that an "a priori value" of the von Karman constant and the Monin -Obukhov similarity formulas can be derived from the resolved -scale turbulence in the upper surface layer (USL). Only an ideal geometry, flat but rough surface, is treated. Horizontal homogeneity of all dependent mean variables is assumed except the mean pressure, which is the driving mechanism of the whole turbulent boundary layer due to the geostrophic flow aloft. Smagorinsky's sub grid scale (SGS) model is adopted. In the present study, the Smagorinsky-model Reynolds number (Re_{SM}) is proposed for a LES adopting the Smagorinsky SGS model. This number is shown to be an independent model parameter, which determines the statistics of resolved scale (RS) turbulence in the USL. If Re_{SM} is smaller than a critical value, RS fields are damped out. This fact establishes a criterion for a LES adopting the Smagorinsky SGS model. For a neutral-static-stability ABL, the present study uses grid spacings that fall within the inertial subrange of the USL turbulence in order to follow the assumption of the Smagorinsky SGS model. Other specifications of grid spacing are also used to show the influence of grid spacing and validity of Re_{SM} . The largest computation involves 64 x 64 x 50 grids. The average of the velocity fields over the whole horizontal plane and time domain yields a logarithmic velocity profile in the USL, from which the von Karman constant can be derived. The value of kappa found in the study ranges from 0.17 to 0.35, depending on the value of Re_{SM} when the domain size and the Rossby number are fixed. Other quantities in the USL, such as profiles of < ~{u}^2>/{u} _sp{*}{2}, < ~{v}^2>/{u} _sp{*}{2}, < ~{w}^2>/{u} _sp{*}{2}, -< ~{u}~{w}>/ {u}_sp{*}{2} and -<~{v} ~{w}>/{u}_sp {*}{2}, also exhibit a very strong dependence on Re_{SM} . For an unstable ABL, in which an additional turbulent sensible heat flux is imposed on the surface, profiles of the mean velocity in the USL yield a Monin-Obukhov similarity formula for the dimensionless momentum flux. For -5 < z/L < -1, where L is the Monin -Obukhov length, the formula gives smaller values of phi_{m}(z/L) than existing empirical formulas, but close to Carl et al.'s -1/3 power law (1973). LES results of sigma_{~theta}/T _{*,s} fit the empirical similarity formulas fairly well, and derive a power law exponent of about -0.4, which is smaller than -1/3. Similarity results for sigma_{~{w}}/ {u}_* in the USL has also been examined.

Cai, Xiaoming

229

Influence of pyrogenic particles on the micromechanical behavior of thin sol-gel layers.  

PubMed

Coatings based on sol-gel technology with different types of nanoparticles embedded into the sol-gel matrix were fabricated, and the resulting properties were investigated. Pyrogenic silica nanoparticles were added to the sol before coating. The silica particles varied in primary particle size and agglomerate size, and in their surface modification. The particles were wetted in ethanol and dispersed to certain finenesses. The difference in agglomerate size was partly caused by varying particle types, but also by the dispersing processes that were applied to the particles. The resulting coatings were examined by visual appearance and SEM microscopy. Furthermore, their micromechanical properties were determined by nanoindentation. The results show an important influence from the added nanoparticles and their properties on the visual appearance as well as the micromechanical behavior of the sol-gel coatings. It is shown that, in fact, the particle size distribution can have a major impact on the coating properties as well as the surface modification. PMID:21630652

Schönstedt, B; Garnweitner, G; Barth, N; Mühlmeister, A; Kwade, A

2011-07-01

230

Layer-by-Layer Assembled Antisense DNA Microsponge Particles for Efficient Delivery of Cancer Therapeutics.  

PubMed

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. PMID:25198246

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

231

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

NASA Technical Reports Server (NTRS)

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.

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

1991-01-01

232

GYROSCOPIC PUMPING IN THE SOLAR NEAR-SURFACE SHEAR LAYER  

SciTech Connect

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.

Miesch, Mark S. [High Altitude Observatory, National Center for Atmospheric Research, Boulder, CO 80307-3000 (United States); Hindman, Bradley W., E-mail: miesch@ucar.edu [JILA and Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO 80309-0440 (United States)

2011-12-10

233

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

DOEpatents

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.

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

2013-04-30

234

Modeling fragmentation of the self-gravitating molecular layer by smoothed particle hydrodynamics  

E-print Network

We revisit the modeling of ion-neutral (or ambipolar) diffusion with two fluid smoothed particle hydrodynamics, as discussed by Hosking & Whitworth. Some parts of the technique are optimized to testify the pioneer works on behavior of the ambipolar diffusion in an isothermal self-gravitating layer. The frictional heating by ambipolar diffusion is examined, and its effect on fragmentation of the layer is studied. The results are compared to the thermal phases of instability as obtained by Nejad-Asghar.

M. Nejad-Asghar; D. Molteni

2008-02-18

235

Controlling surface enrichment in polymeric hole extraction layers to achieve high-efficiency organic photovoltaic cells.  

PubMed

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. PMID:22945400

Kim, Dong-Hun; Lim, Kyung-Geun; Park, Jong Hyeok; Lee, Tae-Woo

2012-10-01

236

Erosion processes due to energetic particle-surface interaction  

SciTech Connect

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.

Schmid, K.; Roth, J. [Max-Planck-Institut fuer Plasmaphysik, EURATOM Association, Boltzmannstrasse 2, 85748 Garching (Germany)

2010-05-20

237

ELECTROSTATIC SURFACE STRUCTURES OF COAL AND MINERAL PARTICLES  

SciTech Connect

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. There was also evidence that the carbon is present at a higher ratio in larger particles than in small particles. An ultraviolet photoelectron counter for use in ambient atmosphere is nearing completion. The counter will be used to measure work functions of different maceral and mineral types in the coal matrix. A Particle Image Analyzer for measuring size and charge of airborne particles is also under contruction and its current status is presented. A charged, monodisperse, droplet generator is also being constructed for calibration of the Particle Image Analyzer and other airborne particle analyzers in our labs.

NONE

1998-12-01

238

Effective surface viscosities of a particle-laden fluid interface.  

PubMed

The Einstein formula for the effective shear viscosity of low Reynolds number suspension flows is generalized to the case of flat, low-concentration, particle-laden interfaces separating two immiscible fluids. The effective surface shear and dilational viscosities of this system is found to be eta{s}=5/3(eta{1}+eta{2})R phi and zeta{s}=5(eta_{1}+eta_{2})R phi , correspondingly, where eta{1} and eta{2} are the shear viscosities of two bulk fluids and phi is the surface concentration of spherical particles of radius R . The formula is found to be in excellent agreement with data obtained using multicomponent lattice Boltzmann equation simulation. PMID:19658805

Lishchuk, S V; Halliday, I

2009-07-01

239

Geometrical model for a particle on a rough inclined surface.  

PubMed

A simple geometrical model is presented for the gravity-driven motion of a single particle on a rough inclined surface. Adopting a simple restitution law for the collisions between the particle and the surface, we arrive at a model in which the dynamics is described by a one-dimensional map. This map is studied in detail and it is shown to exhibit several dynamical regimes (steady state, chaotic behavior, and accelerated motion) as the model parameters vary. A phase diagram showing the corresponding domain of existence for these regimes is presented. The model is also found to be in good qualitative agreement with recent experiments on a ball moving on a rough inclined line. PMID:11969547

Vasconcelos, G L; Veerman, J J

1999-05-01

240

Tokamak dust particle size and surface area measurement  

SciTech Connect

The INEEL has analyzed a variety of dust samples from experimental tokamaks: General Atomics` DII-D, Massachusetts Institute of Technology`s Alcator CMOD, and Princeton`s TFTR. These dust samples were collected and analyzed because of the importance of dust to safety. The dust may contain tritium, be activated, be chemically toxic, and chemically reactive. The INEEL has carried out numerous characterization procedures on the samples yielding information useful both to tokamak designers and to safety researchers. Two different methods were used for particle characterization: optical microscopy (count based) and laser based volumetric diffraction (mass based). Surface area of the dust samples was measured using Brunauer, Emmett, and Teller, BET, a gas adsorption technique. The purpose of this paper is to present the correlation between the particle size measurements and the surface area measurements for tokamak dust.

Carmack, W.J.; Smolik, G.R.; Anderl, R.A.; Pawelko, R.J.; Hembree, P.B.

1998-07-01

241

The North Atlantic surface layer and the shallow overturning circulation  

NASA Astrophysics Data System (ADS)

The sea surface salinity maximum (SSS-max) is an integral part of the shallow overturning (SOC) circulation in the North Atlantic. The temperature and salinity of the SSS-max set the density of the subducted water thus are important for the transport properties of the SOC, which has been shown to be important for the large-scale climate. The region requires a net influx of freshwater at near surface level to balance net evaporation. The processes that achieve this task likely influence the variability of SSS-max properties on various time scales in addition to the surface forcing. We are testing the hypothesis that changes in the large-scale wind field in the North Atlantic drive variability of freshwater import by ocean processes into the SSS-max, resulting in seasonal and interannual variability as previously documented. To evaluate the role of said processes for the variability of the upper limb of the SOC, AQUARIUS sea surface salinity (SSS), eddy kinetic energy (EKE) derived from altimetry data (AVISO), sea surface temperature (SST, NOAA OI SST V2) and wind fields (NCEP reanalysis) are used. Previous studies point out the importance of mesoscale dynamics for the freshwater flux into the region which seems to be enhanced by an increased density gradient at the southern edge of the SSS-max as seen from 2012 to 2013. The interannual comparison of meridional density gradient and EKE underline the importance of baroclinic instability for the formation of mesoscale turbulence in the SSS-max in accordance with previous studies. Further analysis, using the SST gradient (extending further back in time than the SSS satellite record) reveals significant seasonal cycles of zonal wind, SST gradient and EKE within the SSS-max region. Spatial correlations between aforementioned variables within the SSS-max region are found, with the EKE peaking about 2-4 months after the large-scale temperature gradient and the zonal wind. Ekman induced set up of the meridional density gradient might be a mechanism for seasonally enhanced mesoscale turbulence, which could be important for the seasonal mixed layer budget as well as interannual variability in surface properties within the SSS-max.

Busecke, Julius; Gordon, Arnold L.

2014-05-01

242

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

NASA Astrophysics Data System (ADS)

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.

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

2011-11-01

243

Calcination kinetics and surface area of dispersed limestone particles  

Microsoft Academic Search

The paper gives results of measurements of the rates of calcination of two types of limestones, ranging in particle size from 1 to 90 micrometers, and over the temperature range of 516 to 1000 C. A kinetic model, based on the B.E.T. (Brunauer-Emmett-Teller) surface area of the CaCOâ, correlates the results over five orders of magnitude in reaction rate. The

R. H. Borgwardt

1985-01-01

244

Effective surface viscosities of a particle-laden fluid interface  

Microsoft Academic Search

The Einstein formula for the effective shear viscosity of low Reynolds number suspension flows is generalized to the case of flat, low-concentration, particle-laden interfaces separating two immiscible fluids. The effective surface shear and dilational viscosities of this system is found to be etas=(5)\\/(3)(eta1+eta2)Rvarphi and zetas=5(eta1+eta2)Rvarphi , correspondingly, where eta1 and eta2 are the shear viscosities of two bulk fluids and

S. V. Lishchuk; I. Halliday

2009-01-01

245

The Point of Departure of a Particle Sliding on a Curved Surface  

ERIC Educational Resources Information Center

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 =…

Aghamohammadi, Amir

2012-01-01

246

Six antigenic determinants in the surface layer of the archaebacterium Methanococcus vannielii revealed by mononclonal antibodies  

Microsoft Academic Search

The immunogenicity and antigenic characteristics of the unique surface layer (S layer) of Methanococcus vanielii was studied with a panel of six monoclonal antibodies. Six surface determinants were identified for the first time, each recognized by one antibody exclusively. The determinants are proteins, located in the S layer, and accessible to antibody in whole unfixed, as well as formalinized bacteria.

E. Conway de Macario; H. Koenig; A. J. L. Marcario; O. Kandler

1984-01-01

247

Six antigenic determinants in the surface layer of the archaebacterium Methanococcus vannielii revealed by monoclonal antibodies  

Microsoft Academic Search

The immunogenicity and antigenic characteristics of the unique surface layer (S layer) of Methanococcus vannielii was studied with a panel of six monoclonal antibodies. Six surface determinants were identified for the first time, each recognized by one antibody exclusively. The determinants are proteins, located in the S layer, and accessible to antibody in whole, unfixed, as well as formalinized bacteria.

E. C. de Macario; H. Koenig; A. J. L. Macario; O. Kandler

1984-01-01

248

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

DOEpatents

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.

Caputo, Anthony J. (Knoxville, TN); Costanzo, Dante A. (Oak Ridge, TN); Lackey, Jr., Walter J. (Oak Ridge, TN); Layton, Frank L. (Clinton, TN); Stinton, David P. (Knoxville, TN)

1980-01-01

249

Surface wave propagation in fiber-reinforced anisotropic elastic layer between liquid saturated porous half space and uniform liquid layer  

NASA Astrophysics Data System (ADS)

Surface wave propagation in fiber-reinforced anisotropic elastic layer between a liquid saturated porous half space and a uniform liquid layer is considered. Equation of motion and suitable boundary conditions give rise to a dispersion equation in the form of a ninth order determinant. Phase velocity and group velocity of a particular model have been studied.

Samal, Sapan K.; Chattaraj, Ranjan

2011-06-01

250

Exothermic surface chemistry on aluminum particles promoting reactivity  

NASA Astrophysics Data System (ADS)

The exothermic surface chemistry associated with the alumina passivation shell surrounding aluminum (Al) particles and fluorine from fluoropolymer materials is investigated. In particular, polytetrafluoroethylene (PTFE) has been synthesized with varying chain lengths and combined with nanometric Al fuel particles. The Al-PTFE kinetics were analyzed using equilibrium diagnostics including differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) for calorific and phase change behavior coupled with additional flame speed measurements. The objective was to understand the effects of varying PTFE molecular structure on the kinetic and energy propagation behaviors of these composites. Results showed a pre-ignition reaction (PIR) with longer chained PTFE samples and not with the shorter chained PTFE samples. The PIR is attributed to fluorine dislodging hydroxyls from the alumina (Al2O3) passivation surface and forming Al-F structures. Composites exhibiting the PIR correspondingly result in significantly higher flame speeds. The PIR surface chemistry may contribute to promoting the melt dispersion mechanism (MDM) responsible for propagating energy in nano Al reactions. Composites with a PIR also have higher heats of combustion in both the PIR and main reaction exotherms. These results help elucidate the influence of molecular scale surface chemistry on macroscopic energy propagation.

Mulamba, Oliver; Pantoya, Michelle L.

2014-10-01

251

Characterization and Transferring of Human Rotavirus Double-Layered Particles in MA104 Cells  

PubMed Central

Background: Rotavirus (RV) is a major cause of gastroenteritis in infants and children and is one of the most severe public health problems. Rotaviruses outer layer contains two proteins including VP4 and VP7. These proteins are necessary for host-cell binding and penetration. TLP (triple layer virus particle) of RV is a complete infectious virion that binds to the target cells and internalized at the cytoplasm. The DLP (double layer virus particle) is a non-infectious particle that is formed through exclusion of the outer layer proteins including VP4 and VP7. These DLPs are the transcriptionally active forms of rotavirus. Objectives: The aim of this study was to transfer DLP of RV into cytoplasm of MA104 cells by Lipofectamine and to analyze their replication. Materials and Methods: Initially, rotavirus was purified by CsCl discontinuous gradient and DLP was separated from TLP based on density differences. For confirmation, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) of the proteins were conducted Then the purified DLP of RV was transferred into MA104 cells using Lipofectamine. Results: We attempt to avoid the attachment and entry of the rotavirus by using Lipofectamine to mediate the delivery of viral particles directly into the cytoplasm. DLP was endocytosed into the cytoplasm following treatment by Lipofectamine and then replicated in cytoplasm. Conclusions: Therefore the non-infectious DLPs were became infectious if introduced into the cytoplasm of permissive and cancerous cells, without passing attachment and entry process. PMID:25371799

Teimoori, Ali; Soleimanjahi, Hoorieh; Makvandi, Manoochehr

2014-01-01

252

Surface acoustic wave concentration of particle and bioparticle suspensions.  

PubMed

A rapid particle concentration method in a sessile droplet has been developed using asymmetric surface acoustic wave (SAW) propagation on a substrate upon which the droplet is placed. Due to the asymmetry in the SAW propagation, azimuthal bulk liquid recirculation (acoustic streaming) is generated. Once the local particle concentration is sufficiently high within a particular streamline of the acoustic streaming convective flow, shear-induced migration gives rise to an inward radial force that concentrates the particles at the centre of the droplet. In this paper, a SAW device consists of a 0.75-mm thick, 127.68 degrees Y-X-axis-rotated cut, X-propagating LiNbO3 for a substrate and an interdigital transducer electrode (IDT) with 25 straight finger pairs in a simple repeating pattern, 12 mm aperture, and a wavelength of lambda=440 microm was patterned on the substrate. The IDT was then driven with a sinusoidal signal at the resonance frequency f0 of 8.611 MHz. To investigate the effect of particle type and size on the concentration process, three types of particles were used in this study, including fluorescent particles (1 microm), polystyrene microspheres (3, 6, 20, 45 microm), and living yeast cells (10-20 microm). Different RF powers were applied ranging from 120 to 510 mW. The concentration processes occurs within 2 to 20 s, depending on the particle size, type and input radio frequency (RF) power, much faster than currently available particle concentration mechanisms due to the large convective velocities achieved using the SAW device. Moreover, this concentration method is efficient, concentrating the particles into an aggregate one-tenth the size of the original droplet. Most importantly, bioparticles can also be concentrated by this method; we have verified that yeast cells are not lysed by the SAW radiation during concentration. By using the rapid concentration process described in this work, the breadth of applications and measurement sensitivity of SAW biosensor systems should be greatly enhanced. PMID:17530412

Li, Haiyan; Friend, James R; Yeo, Leslie Y

2007-10-01

253

Superhydrophobic surfaces: A model approach to predict contact angle and surface energy of soil particles  

NASA Astrophysics Data System (ADS)

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 -coated smooth glass plates, except for the clay soil. Contact angles measured on plane surfaces were related to contact angles measured on rough grain surfaces using the new model based on the combined Cassie-Baxter Wenzel equation which takes into account the particle packing density on the sample surface.

Shirtcliffe, Neil; Hamlett, Christopher; McHale, Glen; Newton, Michael; Bachmann, Joerg; Woche, S.

2010-05-01

254

Fabrication of bifunctional core-shell Fe3O4 particles coated with ultrathin phosphor layer  

NASA Astrophysics Data System (ADS)

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.

Atabaev, Timur Sh; Kim, Hyung-Kook; Hwang, Yoon-Hwae

2013-08-01

255

Fabrication of bifunctional core-shell Fe3O4 particles coated with ultrathin phosphor layer  

PubMed Central

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

2013-01-01

256

Polyethylene wear particles induce TLR 2 upregulation in the synovial layer of mice.  

PubMed

A cellular and receptor mediated response to ultra-high-molecular-weight-polyethylene (UHMWPE) wear particles results in a release of proinflammatory cytokines and induces an inflammatory reaction causing osteolysis in total joint replacement. This investigation offers insight into the toll-like receptor (TLR) mediated activation by polyethylene wear particles in the synovial layer of mice. We hypothesized that, similar to recent in vitro results, UHMWPE particles lead to an upregulation of TLR 1 and 2 and TLR 4 in vivo in the synovial tissue of mice as well. Therefore, UHMWPE particles were generated in a common knee simulator according to the ISO standard, separated by acid digestion and determined by scanning electron microscopy. Endotoxin was removed using a method based on ultracentrifugation. A particle suspension (50 ?l; 0.1 vol./vol.%) was injected into the left knee joint of female Balb/c mice (n = 8). In a control group, phosphate-buffered saline was injected into the left knee of Balb/c mice (n = 8). The mice were sacrificed after 7 days. Immunohistochemical staining was performed with TLR 1, 2 and 4 polyclonal antibodies for Balb/c mice and evaluated by light microscopy. The particle-stimulated group showed a thickened synovial layer, an increased cellular infiltration and a TLR 2-upregulation in the synovial layer compared to the control group. An increased expression of TLR 1 and TLR 4 could not be demonstrated. These results indicate a mainly TLR 2-induced inflammation to polyethylene wear debris in the synovial layer of mice. PMID:24249629

Paulus, A C; Frenzel, J; Ficklscherer, A; Roßbach, B P; Melcher, C; Jansson, V; Utzschneider, S

2014-02-01

257

The surface and through crack problems in layered orthotropic plates  

NASA Technical Reports Server (NTRS)

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.

Erdogan, Fazil; Wu, Binghua

1991-01-01

258

SH surface acoustic wave propagation in a cylindrically layered piezomagnetic/piezoelectric structure  

E-print Network

SH surface acoustic wave propagation in a cylindrically layered piezomagnetic Accepted 30 July 2008 Available online 22 August 2008 Keywords: SH surface acoustic waves Cylindrically layered structure Piezoelectric Piezomagnetic Dispersive relation a b s t r a c t SH surface acoustic wave

Wang, Ji

259

Solid-Liquid Transition and Hydrodynamic Surface Waves in Vibrated Granular Layers  

Microsoft Academic Search

Experiments on thin layers of granular material subjected to vertical vibration have revealed a series of subharmonic bifurcations from flat surface to standing wave patterns. From pressure and surface dilation measurements we show that a solid-liquid-type transition precedes surface wave bifurcation, indicating that these waves are associated with the fluidlike behavior of the layer. Also, we show that depending on

Nicolás Mujica; Francisco Melo

1998-01-01

260

Characterizing atmospheric surface layer turbulence using chaotic return map analysis  

NASA Astrophysics Data System (ADS)

Nonlinear time series analysis methods are used to investigate the dynamics of mechanical and convective turbulences in the atmospheric surface layer flow. Using dynamical invariant analysis (e.g. correlation dimension, Lyapunov exponent and mutual information) along with recurrence quantification analysis (e.g. recurrent rate, determinism, average diagonal length of recurrence plot, etc.) of the vertical wind component data, it is confirmed that a convective turbulence is a lower order manifold in its phase space exhibiting higher degree of organization than a mechanical turbulence. Applying a quasi-one-dimensional chaotic return map technique, the topological differences between the mechanical and convective turbulences are explored. These quasi-one-dimensional return maps are produced using the local maxima of the first principal component of the reconstructed turbulence data. A comparison of the probability distribution of the local maxima of a forced Lorenz model with the turbulence data indicates the possible existence of a stable fixed point for both type of turbulences. Furthermore, dynamically the mechanical turbulence is found to resemble an unforced Lorenz model whereas the convective turbulence resembles a forced Lorenz model.

Mukherjee, Sandipan; Zawar-Reza, Peyman; Sturman, Andrew; Mittal, Ashok Kumar

2013-11-01

261

Surface Passivation by Quantum Exclusion Using Multiple Layers  

NASA Technical Reports Server (NTRS)

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.

Hoenk, Michael E. (Inventor)

2013-01-01

262

Determination of particle dry deposition velocities to a surrogate surface  

SciTech Connect

Dry deposition of atmospheric aerosol particles is thought to be an important pathway for the introduction of toxic trace elements and heavy metals into Lake Michigan, which lies in close proximity to the large urban and heavily industrialized Chicago, Illinois/Gary, Indiana area. However, dry deposition fluxes are difficult to measure and, instead, are often estimated as the product of the dry deposition velocity (V{sub d}) and the corresponding ambient pollutant concentration. Herein, we apply a new chemical mass balance deposition (CMBD) model to derive size-dependent deposition velocities for atmospheric particles to a surrogate surface. The CMBD model results are compared with those calculated with the Williams model under the prevailing meteorological conditions.

Caffrey, P.F.; Ondov, J.M. [Univ. of Maryland, College Park, MD (United States); Zufall, M.J.; Davidson, C.I. [Carnegie-Mellon Univ., Pittsburgh, PA (United States)

1997-12-01

263

Two-layered electromagnetic wave-absorbing E-glass\\/epoxy plain weave composites containing carbon nanofibers and NiFe particles  

Microsoft Academic Search

Two-layered radar-absorbing structures (RASs) were investigated for the broadband absorbing characteristics for the X-band (8.2–12.4 GHz) and Ku-band (12.0–18.0 GHz). E-glass\\/epoxy plain weave composites containing carbon nanofibers (CNFs) and submicron NiFe particles were fabricated and their complex permittivities and permeabilities measured in the range 2–18 GHz. The surface and absorbing layers of two-layered RASs consisted of the low and high

Ki-Yeon Park; Jae-Hung Han; Jin-Bong Kim; Sang-Kwan Lee

2011-01-01

264

Motion of particles with inertia in a compressible free shear layer  

NASA Technical Reports Server (NTRS)

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.

Samimy, M.; Lele, S. K.

1991-01-01

265

Gold Nanoparticle Clusters in Quasinematic Layers of Liquid-Crystalline Dispersion Particles of Double-Stranded Nucleic Acids  

PubMed Central

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

Yevdokimov, Yu.M.; Salyanov, V.I.; Katz, E.I.; Skuridin, S.G.

2012-01-01

266

Particle-in-cell simulations of a current-free double layer  

SciTech Connect

Current-free double layers of the type reported in plasmas in the presence of an expanding magnetic field [C. Charles and R. W. Boswell, Appl. Phys. Lett. 82, 1356 (2003)] are modeled theoretically and with particle-in-cell/Monte Carlo simulations. Emphasis is placed on determining what mechanisms affect the electron velocity distribution function (EVDF) and how the EVDF influences the double layer. A theoretical model is developed based on depletion of electrons in certain velocity intervals due to wall losses and repletion of these intervals due to ionization and elastic electron scattering. This model is used to predict the range of neutral pressures over which a double layer can form and the electrostatic potential drop of the double layer. These predictions are shown to compare well with simulation results.

Baalrud, S. D.; Lafleur, T.; Boswell, R. W.; Charles, C. [Space Plasma, Power and Propulsion Group, Research School of Physics and Engineering, Australian National University, Canberra ACT 0200 (Australia)

2011-06-15

267

First-order control of surface roughness at three scales: boundary layer dynamics, tracer dispersion and pebble abrasion  

NASA Astrophysics Data System (ADS)

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 preferentially removed, abrasion rates slow down accordingly.

Jerolmack, D. J.; Litwin, K. L.; Phillips, C. B.; Martin, R. L.

2012-12-01

268

Mass transport of deposited particles by surface-to-surface contact.  

PubMed

The spread of particle-borne contamination by surface-to-surface contact and its implications for exposures within the indoor environment have been observed - largely qualitatively. The present study was conducted with the aim of quantifying the mass transfer efficiency (TE) of deposited aerosol particles when selected soft and hard surfaces come in contact. The surfaces used were 100% cotton, synthetic fleece, plastic laminate and brass. Contact transfer efficiencies ranging from 2 to 45% were observed; these are very significant numbers in terms of hazardous aerosol transport in the environment. Other observations include an increase in the mass transferred with increased surface roughness. An increase in the applied pressure between the two surfaces in contact leads to a step change in transfer efficiency, so that two pressure regimes can be identified, with a transition pressure between them that depends on surface type. Time of contact appears to have little to no effect on the mass transfer efficiency for the surfaces studied, while contaminant loading has some effect that is not systematic. PMID:22683108

McDonagh, A; Sextro, R G; Byrne, M A

2012-08-15

269

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

Microsoft Academic Search

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

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

1980-01-01

270

How Waves Affect the Distribution of Particles that Float on a Liquid Surface P. Denissenko,1  

E-print Network

How Waves Affect the Distribution of Particles that Float on a Liquid Surface P. Denissenko,1 G of particles that float on a liquid surface. We show that clustering of small particles in a standing wave,9,10]. Here we study the effect of clustering by waves on a liquid surface. In a single-mode standing wave

Falkovich, Gregory

271

Hydrate layers on ice particles and superheated ice: a {sup 1}H NMR microimaging study  

SciTech Connect

Recent observations on the interaction of methane gas with ice surfaces have led to the suggestion that the resulting hydrate layer prevents the encapsulated ice from melting at its usual temperature. This would require ice to exist in a superheated state. The authors have examined the product of the gas-solid reaction with {sup 1}H NMR imaging. The imaging experiments show that the hydrate-encapsulated ice is able to melt at its usual melting point. As a possible alternative model, the authors suggest that a considerable amount of ice inside the hydrate layer can be converted to hydrate and liquid water under isothermal and constant volume conditions, the hydrate layer acting as an insulating, semipermeable layer that insulates processes inside the hydrate layer from external bulk temperature and pressure measurements.

Moudrakovski, I.L.; Ratcliffe, C.I.; McLaurin, G.E.; Simard, B.; Ripmeester, J.A. [National Research Council of Canada, Ottawa, Ontario (Canada). Steacie Inst. for Molecular Sciences] [National Research Council of Canada, Ottawa, Ontario (Canada). Steacie Inst. for Molecular Sciences

1999-07-01

272

Control of the morphology of lipid layers by substrate surface chemistry.  

PubMed

In this study, surface coatings were used to control the morphology of the deposited lipid layers during vesicle spreading, i.e., to control if liposomes self-assemble on a surface into a supported lipid bilayer or a supported vesicular layer. The influence of the properties of the surface coating on formation of the deposited lipid layer was studied with quartz crystal microbalance and two-wavelength multiparametric surface plasmon resonance techniques. Control of lipid self-assembly on the surface was achieved by two different types of soft substrate materials, i.e., dextran and thiolated polyethylene glycol, functionalized with hydrophobic linkers for capturing the lipid layer. The low-molecular-weight dextran-based surface promoted formation of supported lipid bilayers, while the thiolated polyethylene glycol-based surface promoted supported vesicular layer formation. A silicon dioxide surface was used as a reference surface in both measurement techniques. In addition to promoting supported lipid bilayer formation of known lipid mixtures, the dextran surface also promoted supported lipid bilayer formation of vesicles containing the cell membrane extract of human hepatoblastoma cells. The new dextran-based surface was also capable of protecting the supported lipid bilayer against dehydration when exposed to a constant flow of air. The well-established quartz crystal microbalance technique was effective in determining the morphology of the formed lipid layer, while the two-wavelength surface plasmon resonance analysis enabled further complementary characterization of the adsorbed supported lipid bilayers and supported vesicular layers. PMID:24564782

Granqvist, Niko; Yliperttula, Marjo; Välimäki, Salla; Pulkkinen, Petri; Tenhu, Heikki; Viitala, Tapani

2014-03-18

273

Impact of turbulence, land surface, and radiation parameterizations on simulated boundary layer properties in a coastal environment  

E-print Network

with an advanced urban parameterization, produced lower than expected heat and momentum fluxes and mixed layerImpact of turbulence, land surface, and radiation parameterizations on simulated boundary layer layer (PBL) turbulence, land surface, and radiation parameterizations on mesoscale simulations

Clements, Craig

274

Simple solution route to uniform MoS{sub 2} particles with randomly stacked layers  

SciTech Connect

MoS{sub 2} particles of uniform size (ca. 70 nm) consisting of random and loosely stacked layers have been synthesized from hydrazine solution with (NH{sub 4}){sub 2}Mo{sub 3}S{sub 13} as the precursor at 180 deg. C for 16 h under hydrothermal conditions. The particles were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HREM). The influences of reaction conditions are discussed while a mechanism is proposed to explain the formation of this peculiar morphology.

Li Qing; Li Ming; Chen Zhiqian; Li Chunmei

2004-06-08

275

Formation of nanostructured surface layer on AISI 304 stainless steel by means of surface mechanical attrition treatment  

Microsoft Academic Search

A nanostructured surface layer was formed on an AISI 304 stainless steel with low stacking-fault energy by means of the surface mechanical attrition treatment (SMAT). The microstructure of the surface layer of the SMATed sample was characterized by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and cross-sectional TEM observation was performed to reveal the

H. W Zhang; Z. K Hei; G Liu; J Lu; K Lu

2003-01-01

276

Creating deformations and tunnels in a surface using layered geometry with adaptive filtering  

E-print Network

With this thesis, I present a method for creating footprints and tunnels in a surface through the use of layered geometry. Rather than using a single geometric surface, deformations are created through the interaction of a polygonal object...

Brooks, Jacob Kirk

2005-11-01

277

Smooth particle approach for surface tension calculation in moving particle semi-implicit method  

NASA Astrophysics Data System (ADS)

We present here an algorithm to solve three-dimensional multi-phase flow problems based on the moving particle semi-implicit (MPS) method. The method is fully Lagrangian and can treat flows with large deformations of the interface such as encountered in the break-up and coalescence of drops. The mean curvature and normal vector of the interface, needed for surface tension calculation, are estimated by a blending of smooth particle hydrodynamics (SPH) and MPS differential schemes. The method is applied to two problems: the free oscillation of a droplet and the transition of a falling drop into a vortex ring. The results are consistent with theory and experiment. This method can be successfully applied to the calculation of a process in planetary core formation, where centimetre scale liquid metal droplets form an emulsion in liquid silicate.

Ichikawa, Hiroki; Labrosse, Stéphane

2010-06-01

278

Observations of the sensitivity of beam attenuation to particle size in a coastal bottom boundary layer  

NASA Astrophysics Data System (ADS)

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 ?m 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 ?m. 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.

Hill, P. S.; Boss, E.; Newgard, J. P.; Law, B. A.; Milligan, T. G.

2011-02-01

279

Effect of mechanical vibration on platinum particle agglomeration and growth in proton exchange membrane fuel cell catalyst layer  

NASA Astrophysics Data System (ADS)

The objective of the current research is to study the effect of mechanical vibration on catalyst layer degradation via Platinum (Pt) particle agglomeration and growth in the membrane electrode assembly (MEA) of a proton exchange membrane fuel cell (PEM Fuel Cell). This study is of great importance, since many PEM fuel cells operate under a vibrating environment, such as the case of vehicular applications, and this may influence the catalyst layer degradation and fuel cell performance. Through extensive literature review, there are only few researches that have been studied the effect of mechanical vibration on PEM fuel cells. These studies focused only on PEM fuel cell performance under vibration for less than 50 hours and none of them considered the degradation of the fuel cell components, such as MEA and its catalyst layer. To study the effect of the mechanical vibration on the catalyst layer an accelerated test with potential cycling was specially designed to simulate a typical vehicle driving condition. The length of the accelerated test was designed to be 300 hour with potential cycling comprised of idle running, constant load, triangle (variable) load and overload running at various mechanical vibration conditions. These mechanical vibration conditions were as follows: 1g 20 Hz, 1g 40 Hz, 4g 20 Hz and 4g 40 Hz. No vibration tests were also conducted to study the influence of operating time and were used as a baseline for comparison study. The series of accelerated tests were followed by microscopy and spectroscopy analyses using environmental scanning electron microscopy (ESEM), transmission electron microscopy (TEM) and X-Ray diffraction (XRD). An ESEM was used to qualitatively analyze pristine and degraded catalyst. TEM and XRD were used to quantitatively analyze catalyst layer degradation via Pt agglomeration and growth in pristine and degraded states. For each test condition, PEM fuel cell performance by means of Voltage - Current (VI) curves was 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).

Diloyan, Georgiy

280

Piezoacoustic wave spectra using improved surface impedance matrix: Application to high impedance-contrast layered plates  

Microsoft Academic Search

Starting from the general modal solutions for a homogeneous layer of arbitrary material and crystalline symmetry, a matrix formalism is developed to establish the semi analytical expressions of the surface impedance matrices (SIM) for a single piezo-electric layer. By applying the electrical boundary conditions, the layer impedance matrix is reduced to a unified elastic form whether the material is piezoelectric

Victor Y. Zhang; Bertrand Dubus; Bernard Collet; Michel Destrade

2008-01-01

281

Surface Science Prospectives Weakly bound buffer layers: A versatile template for metallic nano-clusters  

E-print Network

Surface Science Prospectives Weakly bound buffer layers: A versatile template for metallic nano layers Metallic nano-crystals Film patterning Laser ablation a b s t r a c t Buffer layers composed controlled growth of nano-clusters and for patterning of thin metallic films. Metallic nano-crystals can

Asscher, Micha

282

A simple model of the atmospheric boundary layer; sensitivity to surface evaporation  

Microsoft Academic Search

A simple formulation of the boundary layer is developed for use in large-scale models and other situations where simplicity is required. The formulation is suited for use in models where some resolution is possible within the boundary layer, but where the resolution is insufficient for resolving the detailed boundary-layer structure and overlying capping inversion. Surface fluxes are represented in terms

I B Troen; L. Mahrt

1986-01-01

283

Transverse surface waves in a layered structure with a functionally graded piezoelectric substrate and a hard dielectric layer.  

PubMed

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. PMID:19036395

Qian, Zheng-Hua; Jin, Feng; Lu, Tianjian; Kishimoto, Kikuo

2009-03-01

284

Dielectric relaxation of suspensions of nanoscale particles surrounded by a thick electric double layer  

NASA Astrophysics Data System (ADS)

Dielectric relaxations of suspensions of nanoscale silica particles surrounded by a thick electric double layer are investigated to examine the effect of the concentration of particles. It is found that at low concentrations, the low-frequency dispersion gradually merges with the high-frequency one to become a broad dispersion. The relaxation mechanisms are discussed by using the observed relaxation time. The low-frequency dispersion is caused by the electric double layer polarization while the high-frequency dispersion results from the interfacial polarization. The inner characteristics of the dispersed particles and the dispersing media are obtained from a two-step analytical method developed by the authors [K. He and K. Zhao, Langmuir 21, 11878 (2005)]. With the results of the analysis, Hill’s standard electrokinetic model is employed to interpret the merging of the low- and high-frequency dispersions. The discrepancy between the experimentally observed ?a and that derived from the model estimation is preliminarily explained by the overlap of an electric double layer.

Zhao, Kongshuang; He, Kejuan

2006-11-01

285

Electromotive force measurements in the combustion wave front during layer-by-layer surface laser sintering of exothermic powder compositions.  

PubMed

Electric potentials arise between the combustion wave front and final products during layer-by-layer surface laser sintering of exothermic powder compositions (Ni-Ti, Ni-Al, Ti-Al). By using an analog-digital-analog converter to control the laser movement and hence the exothermic reaction itself, we show that near optimal conditions can be obtained for the formation of layered 3D articles. Comparative results of the structural-phase transformations that occur during laser-controlled SHS in related reaction-capable compositions are also presented. PMID:19421554

Shishkovskiy, Igor V; Morozov, Yury G; Kuznetsov, Maxim V; Parkin, Ivan P

2009-05-14

286

Settling of heavy particles in a turbulent Stokes layer: Numerical simulations  

NASA Astrophysics Data System (ADS)

The influence of the turbulence structure on the motion of a small heavy sphere settling in a turbulent Stokes layer is numerically investigated for moderately high values of the flow Reynolds number. A one-way coupling numerical scheme is implemented in order to evaluate the forces instantaneously acting on the particle and calculate particle trajectories. The flow field is obtained through a 3D direct numerical simulation of an oscillatory flow over a flat smooth unbounded wall. We compare results based on an averaged formulation for the hydrodynamic force acting on the particle with results based on an instantaneous formulation. The main results of our analysis, performed on a limited number of sample computations, may be summarized as follows. Firstly, for sufficiently small particles, the settling speed based on the averaged flow field turns out to be not markedly different from the settling speed based on the instantaneous flow field. Secondly, particle trajectories may be qualitatively different in the two cases, especially where turbulent events are fairly intense and the hydrodynamic force on the particle may take values up to twice as large as gravity: as a result, under the latter conditions, re-suspension may occur. Thirdly, lift is invariably found to be negligible in the present simulations.

Mazzuoli, Marco; Seminara, Giovanni; Vittori, Giovanna

2014-10-01

287

In situ study of particle growth in convective eddies of the planetary boundary layer  

NASA Astrophysics Data System (ADS)

A measurement flight was performed by a motorglider equipped with an aerosol size spectrometer and nano-particle counter over a large area in the rural vicinity of Budapest, Hungary. The flight was carried out in the early afternoon under unstable air dynamical conditions in August 2010. These conditions allowed flying in glider mode, with the engine switched off, using thermal lifts for altitude gain. A significant part of the flight was spent in thermals that allow studying how the atmospheric dynamics acts on the particle formation. It was found that hygroscopic growth affects the particle size distribution in the 30-500 nm interval. In the 30-280 nm interval, the growth rate was found to be similar to that of ammonium sulphate particles. Indirect signs of cloud droplet formation were found during cloud cross, as a concentration drop in size bins fallen in the 280-400 nm size range. In three thermal lifts significantly higher ultrafine particle concentration (30 < d < 280 nm) was measured, with decreased average diameter. The results support the supposition that convective eddies in the boundary layer affect the aerosol composition via hygroscopic growth and secondary particle formation.

Alföldy, B.; Groma, V.; Börcsök, E.; Nagy, A.; Czitrovszky, A.; Török, S.

2011-11-01

288

Method and system for treating an interior surface of a workpiece using a charged particle beam  

DOEpatents

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.

Swenson, David Richard (Georgetown, MA)

2007-05-23

289

Dusty gas compressible turbulent boundary layers: Dusty surface reaction influences on heat transfer  

Microsoft Academic Search

Results of theoretical studies on the erosive influences of dilute concentrations of solid aerosol dispersants are discussed. The boundary layer flows studied are turbulent and compressible. Numerical procedures for boundary layer simulations have been applied. The procedures include consideration of concomitant influences of dispersed non-colliding particles in the large interphase velocity slip limit. These flow situations are encountered in supersonic

Buckingham

1987-01-01

290

Effect of free surface heat transfer on thermocapillary flow in double-layer fluid structures  

NASA Astrophysics Data System (ADS)

In this paper, we examine the effect of heat transfer at the free encapsulant-air surface on thermocapillary flow in a rectangular melt-encapsulant double-layer fluid structure. We show that increased heat transfer to the double-layer system through the free surface weakens thermocapillary convection in the encapsulant phase and enhances the convection in the melt phase.

Gupta, N. R.; Haj-Hariri, H.; Borhan, A.

2014-03-01

291

Dynamic scale theory for characterizing surface morphology of layer-by-layer films of poly(o-methoxyaniline).  

PubMed

The dynamic scale theory and fractal concepts are employed in the characterization of surface morphological properties of layer-by-layer (LBL) films from poly(o-methoxyaniline) (POMA) alternated with poly(vinyl sulfonic acid) (PVS). The fractal dimensions are found to depend on the procedures to fabricate the POMA/PVS multilayers, particularly with regard to the drying procedures. LBL films obtained via drying in ambient air show a more homogeneous surface, compared to films dried under vacuum or a flow of nitrogen, due to a uniform rearrangement of polymer molecules during solvent evaporation. PMID:15503441

de Souza, Nara C; Silva, Josmary R; Pereira-da-Silva, Marcelo A; Raposo, Maria; Faria, Roberto M; Giacometti, José A; Oliveira, Osvaldo N

2004-05-01

292

Improving the tribological characteristics of aluminum 6061 alloy by surface compositing with sub-micro-size ceramic particles via friction stir processing  

Microsoft Academic Search

This study presents a solid state surface engineering technique for forming a composite surface layer on aluminum to improve surface hardness and wear resistance without sacrificing the ductility and conductivity of the bulk. Friction stir processing (FSP) was used to stir and mix sub-micro-size Al2O3 and SiC particles into the surface of an aluminum 6061-T651 alloy plate to form an

Jun Qu; Hanbing Xu; Zhili Feng; D. Alan Frederick; Linan An; Helge Heinrich

2011-01-01

293

Surface-charge layers on ferroelectric KNbO3 crystals  

Microsoft Academic Search

The nature of surface-charge layers is studied, with the help of AF electro-luminescence (EL), in single crystals of ferroelectric KNbO3. The variation of EL output with the applied potential and its frequency suggests that the crystal surface has a domain reversal charge layer. The origin and growth of EL pulses reveal a non-uniform charge density on these layers. The observation

A G Katpatal; K G Deshmukh

1972-01-01

294

Layered devices having surface curvature and method of constructing same  

DOEpatents

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.

Woodbury, Richard C. (Provo, UT); Perkins, Raymond T. (Provo, UT); Thorne, James M. (Provo, UT)

1989-01-01

295

Surface Layer Investigation of a Shot-Peened Duplex Stainless Steel Utilizing X-ray Diffraction  

NASA Astrophysics Data System (ADS)

Distributions of residual stresses and microstructure in the surface layers of shot-peened duplex stainless steel (DSS) S32205 were investigated. The results reveal that both compressive residual stresses (CRS) and microhardness increase with the enhancement of shot-peening (SP) intensity in the surface deformation layers. The maximum value of CRS of ferrite lies in the surface layer but that of austenite locates below the surface layer after SP. SP influence on the microstructure of DSS was studied using x-ray diffraction profiles, and the domain size and microstrain were calculated via Voigt method. After SP, the domain sizes are refined, and microstrain becomes severe at surface layers in both phases. On comparing the calculated results, it is found that the more evident domain size subdivision and the more serious microstrain increase in austenite than those in ferrite are due to the higher work hardening of austenite.

Feng, Qiang; Wu, Xueyan; Jiang, Chuanhai; Xu, Zhou; Wu, Lihong

2013-07-01

296

Influence of ultrathin water layer on the van der Waals/Casimir force between gold surfaces  

SciTech Connect

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.

Palasantzas, G.; Zwol, P. J. van [Materials Innovation Institute M2i and Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen (Netherlands); Svetovoy, V. B. [MESA Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede (Netherlands)

2009-06-15

297

Microstructure and wear resistance of composite layers on a ductile iron with multicarbide by laser surface alloying  

NASA Astrophysics Data System (ADS)

Multicarbide reinforced metal matrix composite (MMC) layers on a ductile iron (QT600-3) were fabricated by laser surface alloying (LSA) using two types of laser: a 5 kW continuous wave (CW) CO 2 laser and a 400 W pulsed Nd:YAG laser, respectively. The research indicated that LSA of the ductile iron with multicarbide reinforced MMC layers demonstrates sound alloying layers free of cracks and porosities. The microstructure, phase structure and wear properties of MMC layers were investigated by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD), as well as dry sliding wear testing. The microstructure of the alloyed layer is composed of pre-eutectic austenite, ledeburite, spherical TiC, Cr 7C 3 and Cr 23C 6 with various morphologies. TiC particles are dispersed uniformly in the upper region of MMC layers. The average hardness of LSA layers by CO 2 laser and pulsed Nd:YAG laser is 859 HV 0.2 and 727 HV 0.2, respectively. The dry sliding wear testing shows the wear resistance of ductile iron is significantly improved after LSA with multicarbide.

Yan, Hua; Wang, Aihua; Xiong, Zhaoting; Xu, Kaidong; Huang, Zaowen

2010-09-01

298

The surface deposition of meteoric smoke particles - possible climate impact  

NASA Astrophysics Data System (ADS)

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 (?mol Fe m-2 y-1)

Plane, J. M.; Dhomse, S.; Saunders, R. W.; Tian, W.; Chipperfield, M.

2013-12-01

299

High-speed Particle Image Velocimetry Near Surfaces  

PubMed Central

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. PMID:23851899

Lu, Louise; Sick, Volker

2013-01-01

300

When do pyroclastic particles move? Wind tunnel experiments on saltation threshold and surface roughness.  

NASA Astrophysics Data System (ADS)

Our understanding of the dynamics of pyroclastic density currents (PDCs) is largely based on the study of their deposits. Pyroclasts have strongly deviating properties in density and angularity compared to the wind blown and fluvial sand usually studied in clastic sedimentology. In order to test whether these specificities have an impact on the sedimentation processes and dynamic behavior of dilute PDCs, wind tunnel experiments were carried out in order to characterize the onset of saltation and surface roughness induced by pyroclastic material. Saltation is the major transport process occurring at the boundary between a flow and the sediment, and corresponds to alternate, sub-planar jumps and landing of particles on the ground. The surface roughness is a measure of how rough a bed is seen by a wind, and is a property of the bed depending on grains' size and shape. The static saltation threshold corresponds to the minimum shearing necessary for particles to be lifted off the ground and begin to bounce. The dynamic saltation threshold corresponds to the minimum shearing necessary to maintain an already saltating bed in that state. Experiments were done in a 6 m long, inclinable, wind tunnel in Aarhus (Denmark). Two sample types (pumices and scoriaceous particles) were investigated individually at 1 Phi grain-size intervals between 0.125 and 16 mm. The surface roughness was measured over a quiescent bed of particles. The static saltation threshold was derived from wind profiles reaching the onset of particle transport and was measured for bed slopes between -20° and 25° (every 5°). The surface roughness measured are of the order expected for rounded particles of similar grain sizes (c.a. 1/30th of the grain diameter). However, a slight deviation to smaller surface roughness is observed for particles < 1 mm, possibly due to the occurrence of a laminar sub-layer near the bed, and a deviation to higher surface roughness values for particles > 1 mm, possibly showing the increasing influence of shape for larger grains. The static saltation thresholds (given as a shear velocity value) for horizontal surfaces show that the shearing necessary to initiate transport is smaller for fines than for coarse grains, thus only macro-scale forces are acting over the whole range of grain sizes. The shear velocity necessary to erode scoria is 2 to 3 times higher than for low-density pumices. The results agree remarkably well with standard curves for rounded particles of similar densities for both pumice and scoria, suggesting that shape is not a relevant factor in these experiments. Additionally, a downslope wind lowers the threshold shear velocity by a factor 0.6 to 0.9, whereas it increases the value when blowing upslope by a factor up to 1.2. Dynamic saltation threshold is predicted (15-20% lower than static) derived from the static saltation threshold and the ratio of dynamic over static repose angles for grain piles. Our experimental results contribute to a better understanding of the genesis of dune bedforms produced by dilute pyroclastic density currents, provide inputs for models, and serve as analogue for other sedimentary environments (other planets, nuclear base surges). They also permit to give a lower estimate of near bed velocities for field-observed erosion-planes truncating stratification.

Douillet, G. A.; Rasmussen, K. R.; Kueppers, U.; Merrison, J.; Dingwell, D. B.

2012-04-01

301

Surface modification of tin oxide by VUV rays and charge particle treatment: An effective method to improve the efficiency of surface catalytic behavior  

NASA Astrophysics Data System (ADS)

Plasma processing is a promising method to modify the chemical and physical properties of the semiconductor oxide surfaces. However, the tuning of surface characteristics is also influenced by plasma-emitted VUV and UV radiations. Different combinations of argon and oxygen partial pressures were applied in the capacitively coupled plasma. The highest surface conductivity was achieved with increasing plasma power, which was attributed to the interstitial defects with increased Tamm states created by the following two processes. First, the charge particle bombardment on the oxide surface, which etches the surface atoms and second, the absorption of VUV and UV radiation in the exposed layers of tin oxide nanoflakes scission the covalent bonds connecting the Sn-O atoms. The catalytic behavior of the tin oxide nanoflakes towards reducing gases have been studied as the function of Ar-O partial pressures, plasma power and voltage, and the ambient sensing temperature. Modified surface characteristics were also supported by SEM, TEM and XPS analysis.

Ganesan, Rajesh; Tolner, Harm

2011-11-01

302

Improved magnetic tunnel junction with amorphous seed layer, surface treatment,and high-polarization magnetic materials  

Microsoft Academic Search

Dependence of magnetic tunnel junction (MTJ) properties on seed layer, surface treatment and magnetic materials was investigated to improve TMR ratio. Roughness of tunnel oxide layer generated from seed layer roughness reduces TMR ratio as well as RA product owing to locally reduced oxide layer thickness. Crystallinity of seed layer is found to be important to enhance TMR ratio. Surface

J. E. Lee; Y. Rho; S. C. Oh; H.-J. Kim; Y. K. Ha; J. S. Bae; I. G. Baek; S. O. Park; U.-I. Chung; J. T. Moon

2004-01-01

303

Evaluation of filter media for particle number, surface area and mass penetrations.  

PubMed

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-law correlations between the penetrations measured by different instruments show that the NIOSH TSI 8130 test may be used to predict penetrations at the MPPS as well as the CPC and NSAM results with polydisperse aerosols. It is recommended to use dry air (<20% RH) as makeup air in the test system to prevent sodium chloride particle deliquescing and minimizing the challenge particle dielectric constant and to use an adequate neutralizer to fully neutralize the polydisperse challenge aerosol. For a simple nanoparticle penetration test, it is recommended to use a polydisperse aerosol challenge with a geometric mean of ~50 nm with the CPC or the NSAM as detectors. PMID:22752097

Li, Lin; Zuo, Zhili; Japuntich, Daniel A; Pui, David Y H

2012-07-01

304

A literature review of surface alteration layer effects on waste glass behavior  

SciTech Connect

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.

Feng, X.; Cunnane, J.C.; Bates, J.K.

1993-01-01

305

A literature review of surface alteration layer effects on waste glass behavior  

SciTech Connect

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.

Feng, X.; Cunnane, J.C.; Bates, J.K.

1993-05-01

306

Assessment of PEG on polymeric particles surface, a key step in drug carrier translation.  

PubMed

Injectable drug nanocarriers have greatly benefited in their clinical development from the addition of a superficial hydrophilic corona to improve their cargo pharmacokinetics. The most studied and used polymer for this purpose is poly(ethylene glycol), PEG. However, in spite of its wide use for over two decades now, there is no general consensus on the optimum PEG chain coverage-density and size required to escape from the mononuclear phagocyte system and to extend the circulation time. Moreover, cellular uptake and active targeting may have conflicting requirements in terms of surface properties of the nanocarriers which complicate even more the optimization process. These persistent issues can be largely attributed to the lack of straightforward characterization techniques to assess the coverage-density, the conformation or the thickness of a PEG layer grafted or adsorbed on a particulate drug carrier and is certainly one of the main reasons why so few clinical applications involving PEG coated particle-based drug delivery systems are under clinical trial so far. The objective of this review is to provide the reader with a brief description of the most relevant techniques used to assess qualitatively or quantitatively PEG chain coverage-density, conformation and layer thickness on polymeric nanoparticles. Emphasis has been made on polymeric particle (solid core) either made of copolymers containing PEG chains or modified after particle formation. Advantages and limitations of each technique are presented as well as methods to calculate PEG coverage-density and to investigate PEG chains conformation on the NP surface. PMID:24768790

Rabanel, Jean-Michel; Hildgen, Patrice; Banquy, Xavier

2014-07-10

307

Effect of suspended particles upon drying process of volatile droplet sitting on solid surface  

NASA Astrophysics Data System (ADS)

Particle motion in volatile droplet on the solid surface especially the behavior of particles depositing in the vicinity of solid-liquid-gas boundary line contact line is focused This phenomenon is called as coffee stain problem Particle motion in the droplet is analyzed by reconstruction of spatio-temporal particle motion by applying three-dimensional particle tracking velocimetry 3-D PTV We discuss the effect of the suspended particles upon the drying process of the droplet Morphological discussion on the particles stuck on the solid surface after the dryout the droplet is also conducted

Ueno, I.; Kochiya, K.

308

Structure of surface reaction layer of poly-Si etched by fluorocarbon plasma  

SciTech Connect

A structure of surface reaction layer of poly-Si substrate during fluorocarbon plasma etching was studied by using a plasma beam irradiation apparatus and a quasi-in situ x-ray photoelectron spectroscopy. A fluorinated silicon (SiF) layer was formed under a fluorocarbon (CF) layer. It was found that the thickness of the SiF layer linearly increased with the etch yield of poly-Si regardless of the change of the CF layer thickness. The average ratio of the number of Si to that of F in the SiF layer did not strongly depend on the etch yield. The carbon-rich region of the CF layer was formed just above the SiF layer due to the consumption of fluorine for the formation of SiF layer.

Kurihara, Kazuaki; Egami, Akihiko; Nakamura, Moritaka [Corporate Research and Development Center, Toshiba Corporation, 8 Shinsugita-cho, Isogo-ku, Yokohama 235-8522 (Japan); Environmentally Benign Etching Technology Laboratory, Association of Super-Advanced Electronics Technologies (ASET), 3-1 Morinosato Wakamiya, Atsugi-shi, Kanagawa 243-0198 (Japan)

2006-03-15

309

Polymethylhydrosiloxane surface deactivation of silica particles for packed capillary column supercritical fluid chromatography  

Microsoft Academic Search

Spherical porous silica particles (10 ?m diameter, 300 Å and 80 Å pores), spherical nonporous silica particles (10 ?m diameter), and irregular porous silica particles (?10 ?m diameter, 80 Å pores) were deactivated with polymethylhydrosiloxane (PS). The surface activities of the deactivated silica particles were investigated using various polar compounds under supercritical fluid chromatography (SFC) conditions (neat CO2), and compared

Y. Shen; M. L. Lee

1995-01-01

310

Surface Extraction from Multi-field Particle Volume Data Using Multi-dimensional Cluster Visualization  

E-print Network

in astrophysics, particle simulations. 1 INTRODUCTION The Smoothed Particle Hydrodynamics (SPH) method extract a surface from the volume data. Our driving applications are Smoothed Particle Hydrodynamics (SPH are less well sampled by SPH particles.Consequently, SPH simulations often pro- duce highly clustered

Linsen, Lars

311

Nanoindentation characterization of surface layers of electrical discharge machined WC–Co  

Microsoft Academic Search

This study applies nanoindentation and other analysis techniques to investigate the influence of wire electrical discharge machining (EDM) process on the structure and properties of machined surface layers of WC–Co composites. Multiple indents were conducted on the cross-section of the surface recast layer, sub-surface heat-affected zone, and bulk material. The energy disperse X-ray spectrometry and X-ray diffraction were used to

Jun Qu; Laura Riester; Albert J. Shih; Ronald O. Scattergood; Edgar Lara-Curzio; Thomas R. Watkins

2003-01-01

312

Physical Layer Effects on MAC Layer Performance of IEEE 802.11 a and b WLAN on the Martian Surface  

E-print Network

are chosen as example sites based on the mission science and mission success criteria. The radio frequency. Instead of develop- ing and testing such networks from scratch, a cost effective approach would car- ried out for different data rates on several sites on the Mar- tian surface. Physical layer

De Leon, Phillip

313

Ion size effects on the electric double layer of a spherical particle in a realistic salt-free concentrated suspension  

E-print Network

A new modified Poisson-Boltzmann equation accounting for the finite size of the ions valid for realistic salt-free concentrated suspensions has been derived, extending the formalism developed for pure salt-free suspensions [Roa et al., Phys. Chem. Chem. Phys., 2011, 13, 3960-3968] to real experimental conditions. These realistic suspensions include water dissociation ions and those generated by atmospheric carbon dioxide contamination, in addition to the added counterions released by the particles to the solution. The electric potential at the particle surface will be calculated for different ion sizes and compared with classical Poisson-Boltzmann predictions for point-like ions, as a function of particle charge and volume fraction. The realistic predictions turn out to be essential to achieve a closer picture of real salt-free suspensions, and even more important when ionic size effects are incorporated to the electric double layer description. We think that both corrections have to be taken into account when developing new realistic electrokinetic models, and surely will help in the comparison with experiments for low-salt or realistic salt-free systems.

Rafael Roa; Félix Carrique; Emilio Ruiz-Reina

2011-05-05

314

Effect of the interplay between protein and surface on the properties of adsorbed protein layers  

PubMed Central

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 ?-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 ?-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

Ouberai, Myriam M.; Xu, Kairuo; Welland, Mark E.

2014-01-01

315

Method for removing surface-damaged layers from nickel alloys  

NASA Technical Reports Server (NTRS)

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.

Fawley, R. W.

1968-01-01

316

Capillary-wave roughening of surface-induced layering in liquid gallium  

SciTech Connect

The temperature dependence of surface-induced atomic layering in liquid gallium has been investigated with x-ray reflectivity. The prominent layering peak at {ital q}{sub {ital z}}=2.4 A{sup {minus}1} decreases dramatically upon heating from 22 to 170{degree}C, but its width stays, unexpectedly, unchanged. The decrease is traced to the temperature dependence of capillary-wave induced surface roughness. The constant width indicates a temperature-independent layering decay length. The measured layering amplitudes are found to be significantly underestimated by existing theory and molecular simulations. {copyright} {ital 1996 The American Physical Society.}

Regan, M.J.; Pershan, P.S. [Division of Applied Sciences and Department of Physics, Harvard University, Cambridge, Massachusetts 02138 (United States)] [Division of Applied Sciences and Department of Physics, Harvard University, Cambridge, Massachusetts 02138 (United States); Magnussen, O.M.; Ocko, B.M. [Department of Physics, Brookhaven National Laboratory, Upton, New York 11973 (United States)] [Department of Physics, Brookhaven National Laboratory, Upton, New York 11973 (United States); Deutsch, M. [Department of Physics, Bar-Ilan University, Ramat-Gan 52100 (Israel)] [Department of Physics, Bar-Ilan University, Ramat-Gan 52100 (Israel); Berman, L.E. [National Synchrotron Light Source, Brookhaven National Laboratory, Upton, New York 11973 (United States)] [National Synchrotron Light Source, Brookhaven National Laboratory, Upton, New York 11973 (United States)

1996-10-01

317

X-ray reflectivity measurements of surface layering in liquid mercury  

SciTech Connect

The surface normal structure of the mercury liquid-vapor interface has been investigated by measuring the x-ray reflectivity out to a momentum transfer of {ital q}{sub {ital z}}=2.5 A{sup --1}. The results provide direct experimental proof of surface layering in liquid metals. The layer spacing is given by the atomic dimensions of the Hg atoms. The minimum layer width agrees well with the predictions of capillary wave theory; the layering amplitude decays into the bulk with a characteristic length of 3--3.5 A, which is close to the decay length of the bulk pair correlation function.

Magnussen, O.M.; Ocko, B.M. [Department of Physics, Brookhaven National Laboratory, Upton, New York 11973 (United States)] [Department of Physics, Brookhaven National Laboratory, Upton, New York 11973 (United States); Regan, M.J.; Penanen, K.; Pershan, P.S. [Division of Applied Science and Department of Physics, Harvard University, Cambridge, Massachusetts 02138 (United States)] [Division of Applied Science and Department of Physics, Harvard University, Cambridge, Massachusetts 02138 (United States); Deutsch, M. [Department of Physics, Bar-Ilan University, Ramat-Gan 52100 (Israel)] [Department of Physics, Bar-Ilan University, Ramat-Gan 52100 (Israel)

1995-05-29

318

Microporous structure with layered interstitial surface treatment, and method and apparatus for preparation thereof  

NASA Technical Reports Server (NTRS)

A microporous structure with layered interstitial surface treatments, and method and apparatus for preparation thereof is presented. The structure is prepared by sequentially subjecting a uniformly surface-treated structure to atomic oxygen treatment to remove an outer layer of surface treatment to a generally uniform depth, and then surface treating the so exposed layer with another surface treating agent. The atomic oxygen/surface treatment steps may optionally be repeated, each successive time to a lesser depth, to produce a microporous structure having multilayered surface treatments. The apparatus employs at least one side arm from a main atomic oxygen-containing chamber. The side arm has characteristic relaxation times such that a uniform atomic oxygen dose rate is delivered to a specimen positioned transversely in the side arm spaced from the main gas chamber.

Koontz, Steven L. (inventor)

1994-01-01

319

Microporous structure with layered interstitial surface treatment, and method and apparatus for preparation thereof  

NASA Technical Reports Server (NTRS)

A microporous structure with layered interstitial surface treatments, and the method and apparatus for its preparation are disclosed. The structure is prepared by sequentially subjecting a uniformly surface treated structure to atomic oxygen treatment to remove an outer layer of surface treatment to a generally uniform depth, and then surface treating the so exposed layer with another surface treating agent. The atomic oxygen/surface treatment steps may optionally be repeated, each successive time to a lesser depth, to produce a microporous structure having multilayered surface treatments. The apparatus employs at least one side arm from a main oxygen-containing chamber. The side arm has characteristic relaxation times such that a uniform atomic oxygen dose rate is delivered to a specimen positioned transversely in the side arm spaced from the main gas chamber.

Koontz, Steven L. (inventor)

1992-01-01

320

Transient Heat Transfer in a Semitransparent Radiating Layer with Boundary Convection and Surface Reflections  

NASA Technical Reports Server (NTRS)

Surface convection and refractive index are examined during transient radiative heating or cooling of a grey semitransparent layer with internal absorption, emission and conduction. Each side of the layer is exposed to hot or cold radiative surroundings, while each boundary is heated or cooled by convection. Emission within the layer and internal reflections depend on the layer refractive index. The reflected energy and heat conduction distribute energy across the layer and partially equalize the transient temperature distributions. Solutions are given to demonstrate the effect of radiative heating for layers with various optical thicknesses, the behavior of the layer heated by radiation on one side and convectively cooled on the other, and a layer heated by convection while being cooled by radiation. The numerical method is an implicit finite difference procedure with non-uniform space and time increments. The basic method developed in earlier work is expanded to include external convection and incident radiation.

Siegel, Robert

1996-01-01

321

Terahertz surface plasmon propagation in nanoporous silicon layers Shu-Zee A. Loa  

E-print Network

Terahertz surface plasmon propagation in nanoporous silicon layers Shu-Zee A. Loa and Thomas E American Institute of Physics. doi:10.1063/1.3432071 Terahertz THz surface plasmon waveguides have at surface plasmon waveguide in which the optical mode is localized within a nanoporous silicon slab. We

Murphy, Thomas E.

322

Metallic transport in a monatomic layer of in on a silicon surface.  

PubMed

We have succeeded in detecting metallic transport in a monatomic layer of In on an Si(111) surface, Si(111)-sqrt[7]×sqrt[3]-In surface reconstruction, using the micro-four-point probe method. The In layer exhibited conductivity higher than the minimum metallic conductivity (the Ioffe-Regel criterion) and kept the metallic temperature dependence of resistivity down to 10 K. This is the first example of a monatomic layer, with the exception of graphene, showing metallic transport without carrier localization at cryogenic temperatures. By introducing defects on this surface, a metal-insulator transition occurred due to Anderson localization, showing hopping conduction. PMID:21469886

Yamazaki, Shiro; Hosomura, Yoshikazu; Matsuda, Iwao; Hobara, Rei; Eguchi, Toyoaki; Hasegawa, Yukio; Hasegawa, Shuji

2011-03-18

323

Effect of Surface Thermal Perturbations on Compressible Boundary Layer Stability  

NASA Astrophysics Data System (ADS)

High-speed laminar-turbulent boundary layer transition is a critical issue for re-entry and sustained hypersonic cruise vehicles. Turbulent wall heating rates can increase several orders of magnitude compared to laminar rates and skin friction drag can become a major component of the overall drag. We analyze approaches to modulate transition by altering the stability features of the boundary layer through the use of thermal perturbations. To this end, high-fidelity numerical simulations to generate basic states for Mach 1.5 and Mach 5.6 flat plate boundary layers with and without thermal bumps. Linear Parabolized Stability Equations (PSE) are solved using the STABL software suite to establish the flow stability characteristics under baseline (no excitation), constant and pulsed bump cases for each freestream Mach number. The effects are described in terms of neutral curves showing amplification for various frequencies versus Reynolds number. The three-dimensional flow structure is also examined near the breakdown to turbulence flow region to gain insight into the final stages of transition.

Alba, Christopher; Gaitonde, Datta

2009-11-01

324

Immunocytochemical approach for surface layer proteins of freeze-substituted Tannerella forsythensis by energy-filtering transmission electron microscopy.  

PubMed

Tannerella forsythensis (Bacteroides forsythus), an anaerobic gram-negative potential periodontal pathogens in the progression of periodontitis. IT forsythensis has unique bacterial protein profiles containing major proteins with apparent molecular weight of more than 200-kDa shown by sodium dodecylsulfate-polyacrylamide gel electrophoresis. It is also known to have a typical surface layer (S-layer) consisting of regularly arrayed subunits outside the outer membrane revealed by electron microscopy. On the other hand, electron microscopy showed that the best preservation of structure was obtained when cells were postfixed with OsO4, but this resulted in very low levels of gold particles labeling. Therefore, cells were applied to pieces of filter paper and freeze-substituted by plung-freezing in Liquid propane, substituted in methanol containing 0.5% uranyl acetate, and infiltrated with LR-White resin. We also examined the relation between high molecular weight proteins and S-layer in energy-filtering transmission electron microscopy (EF-TEM) to visualize 3,3'-diaminobenzidene, tetrahydrochloride (DAB) reaction. The three-window method in electron spectroscopic images (ESI) of nitrogen (N) element, reflecting the presence of DAB moieties by the DAB reaction solution, horseradish peroxidase (HRP)-conjugated secondary antibodies instead of immunogold particles obtained by the EF-TEM. The mapping patterns of net N element were restricted to the outermost cell surface. PMID:18975614

Moriguchi, Keiichi; Jogahara, Takamichi; Kurihara, Takayuki; Iwami, Jun; Higuchi, Naoya; Murakami, Yukitaka; Maeda, Hatsuhiko; Yoshimura, Fuminobu; Nakamura, Hiroshi; Ohno, Norikazu

2008-08-01

325

Vector solution for the mean electromagnetic fields in a layer of random particles  

NASA Technical Reports Server (NTRS)

The mean electromagnetic fields are found in a layer of randomly oriented particles lying over a half space. A matrix-dyadic formulation of Maxwell's equations is employed in conjunction with the Foldy-Lax approximation to obtain equations for the mean fields. A two variable perturbation procedure, valid in the limit of small fractional volume, is then used to derive uncoupled equations for the slowly varying amplitudes of the mean wave. These equations are solved to obtain explicit expressions for the mean electromagnetic fields in the slab region in the general case of arbitrarily oriented particles and arbitrary polarization of the incident radiation. Numerical examples are given for the application to remote sensing of vegetation.

Lang, R. H.; Seker, S. S.; Levine, D. M.

1986-01-01

326

Particle image velocimetry study of shock-induced turbulent boundary layer separation  

NASA Astrophysics Data System (ADS)

An experimental study was conducted to investigate the characteristics of a Mach 2 shock wave/boundary layer interaction, by using particle image velocimetry (PIV). The objective was to investigate how the global flow structure is related to the shock-foot dynamics. A major component of this work was the development of a new multi-camera, multi-laser PIV system, which enables the acquisition of wide-field and time-sequenced velocity fields. The wide-field images are obtained by placing four cameras side-by-side giving an effective resolution of 4k x 1k pixels. Four-image time sequences can be acquired where the time between frames is 30 to 200 mus. The PIV system was used to characterize the upstream Mach 2 boundary layer. The measured mean and RMS velocity profiles agreed well with previous measurements in compressible boundary layers and this provided important validation of the PIV system. The wide-field PIV system was used to image the entire interaction, spanning the upstream boundary layer, intermittent region, separated flow and the reattachment region on the ramp face. The separation shock wave location inferred from the PIV images agreed well with the shock-foot position inferred from the pressure data. The instantaneous vector fields reveal that boundary layer separation is not immediately induced by the shock foot, but sometimes develops substantially farther downstream. Significant reverse-flow velocities are seen in the instantaneous images, but: on average no reverse-flow was observed. The global structure of the interaction was found to depend strongly on the location of the separation shock foot. Ensemble averages, conditioned upon the shock-foot position, showed that when the shock is upstream, the scale of the separated flow, the velocity fluctuations, and the domain of perturbed flow, are all substantially larger than when the shock-foot is downstream. Perhaps most importantly, the conditional upstream boundary layer profiles, conditioned on the shock position, showed that the boundary layer is thicker when the shock is upstream and vice versa. Furthermore, the conditional measurements confirmed the results of a previous study that reported a correlation between velocity fluctuations in the upstream boundary layer and shock foot motion. A preliminary study was used to test the hypothesis that acceleration fluctuations in the upstream boundary layer correlate with shock foot motion. These results showed no meaningful relationship between upstream acceleration with the shock motion, but given certain limitations of the experiment this conclusion cannot be considered definitive.

Hou, Yongxi

327

Convection and correlation of coherent structure in turbulent boundary layer using tomographic particle image velocimetry  

NASA Astrophysics Data System (ADS)

The present experimental work focuses on a new model for space—time correlation and the scale-dependencies of convection velocity and sweep velocity in turbulent boundary layer over a flat wall. A turbulent boundary layer flow at Re? = 2460 is measured by tomographic particle image velocimetry (tomographic PIV). It is demonstrated that arch, cane, and hairpin vortices are dominant in the logarithmic layer. Hairpins and hairpin packets are responsible for the elongated low-momentum zones observed in the instantaneous flow field. The conditionally-averaged coherent structures systemically illustrate the key roles of hairpin vortice in the turbulence dynamic events, such as ejection and sweep events and energy transport. The space—time correlations of instantaneous streamwise fluctuation velocity are calculated and confirm the new elliptic model for the space—time correlation instead of Taylor hypothesis. The convection velocities derived from the space—time correlation and conditionally-averaged method both suggest the scaling with the local mean velocity in the logarithmic layer. Convection velocity result based on Fourier decomposition (FD) shows stronger scale- dependency in the spanwise direction than in streamwise direction. Compared with FD, the proper orthogonal decomposition (POD) has a distinct distribution of convection velocity for the large- and small-scales which are separated in light of their contributions of turbulent kinetic energy.

Wang, Wei; Guan, Xin-Lei; Jiang, Nan

2014-10-01

328

A simple method to synthesize nanowires titanium dioxide from layered titanate particles  

NASA Astrophysics Data System (ADS)

Nanowires TiO 2 were successfully synthesized from layered titanate Na 2Ti 3O 7 particles by a simple soft chemical process. Compared with other synthetic routes where some templates or reactants were introduced into reaction system, only raw material and dilute HCl were used in this simple method. The diameters of nanowires are ca. 20-100 nm and the length up to several hundred micrometers. Formation of brookite TiO 2 phase in the nanowires was confirmed by XRD and TEM measurement. Based on our experimental results, an exfoliating-splitting model was proposed for formation of nanowire structure.

Wei, Mingdeng; Konishi, Yoshinari; Zhou, Haoshen; Sugihara, Hideki; Arakawa, Hironori

2004-12-01

329

Electrophoretic mobility of a charged cylindrical colloidal particle covered with an ion-penetrable uncharged polymer layer.  

PubMed

Expressions are derived for the electrophoretic mobility of a cylindrical charged colloidal particle carrying a low zeta potential covered with an ion-penetrable uncharged polymer layer in an electrolyte solution. These expressions involve numerical integration of modified Bessel functions but are easily calculable with Mathematica. The obtained mobility expressions are a modification of Henry's mobility formula for a cylindrical particle taking into account the presence of the uncharged polymer layer. PMID:12618094

Ohshima, Hiroyuki

2003-02-15

330

Shock Surface Undulation and Particle Acceleration at Oblique Shocks  

NASA Astrophysics Data System (ADS)

Considering the average Parker spiral magnetic field configuration, CME-driven interplanetary (IP) shocks within 1 AU should have oblique portions over much of their domain. Indeed, CME-driven shocks observed close to Earth are often oblique. However, it is well known that the standard diffusive shock acceleration mechanism, which relies on self-consistent wave generation via upstream propagating ions and their scattering, becomes increasingly inefficient with greater shock normal angle. Not only is a higher threshold energy required for the ions to leave the shock upstream, but also, approximately-parallel propagating waves are more quickly convected back into the shock, and the growth rate for waves propagating normal to the shock (the ones with the largest convective growth) decreases. As a result, typical, small-scale hybrid simulations of oblique shocks only show a dilute upstream beam, similar to what is often observed at the oblique Earth's bow shock - and no scattered, highly-energized ions. On the other hand, there are many "energetic storm particle" (ESP) events associated with oblique shocks that have significant fluxes of energetic ions. Recently, we have found that when run for a long time, our hybrid simulations (kinetic ions, electron fluid) show that the initial, weak beam is sufficient to generate compressive, steepening upstream waves. These waves are capable of disturbing the shock surface, resulting in an undulation that is propagating along the surface and growing in amplitude over time. The process is akin to that of the well-known reformation occurring at sufficiently strong quasi-parallel shocks. However, here the perturbations require at least two dimensions, show a strong spatial correlation, and travel along the shock surface. This process not only leads to enhanced ion acceleration, but also means that the shock characteristics are difficult to pinpoint, observationally: both the local jumps and the shock normal angle are highly variable. Shock undulation is also of interest to electron acceleration, since the undulated surface gives locally much larger shock normal angles and provides multiple mirroring and escape opportunities to accelerated electrons. We compare our simulations with a set of oblique shocks that we compiled from ACE observations, and discuss the results in the context of developing quantitative models of the flux and spectrum of energetic ions at IP shocks.

Krauss-Varban, D.; Li, Y.; Luhmann, J. G.

2006-12-01

331

Dynamics of magnetic particles near a surface: model and experiments on field-induced disaggregation.  

PubMed

Magnetic particles are widely used in biological research and bioanalytical applications. As the corresponding tools are progressively being miniaturized and integrated, the understanding of particle dynamics and the control of particles down to the level of single particles become important. Here, we describe a numerical model to simulate the dynamic behavior of ensembles of magnetic particles, taking account of magnetic interparticle interactions, interactions with the liquid medium and solid surfaces, as well as thermal diffusive motion of the particles. The model is verified using experimental data of magnetic field-induced disaggregation of magnetic particle clusters near a physical surface, wherein the magnetic field properties, particle size, cluster size, and cluster geometry were varied. Furthermore, the model clarifies how the cluster configuration, cluster alignment, magnitude of the field gradient, and the field repetition rate play a role in the particle disaggregation process. The simulation model will be very useful for further in silico studies on magnetic particle dynamics in biotechnological tools. PMID:24827250

van Reenen, A; Gao, Y; de Jong, A M; Hulsen, M A; den Toonder, J M J; Prins, M W J

2014-04-01

332

The Canopy and Aerosol Particles Interactions in TOulouse Urban Layer (CAPITOUL) experiment  

Microsoft Academic Search

Summary  The CAPITOUL experiment is a joint experimental effort in urban climate, including the energetic exchanges between the surface\\u000a and the atmosphere, the dynamics of the boundary layer over the city and its interactions with aerosol chemistry. The campaign\\u000a took place in the city of Toulouse in southwest France, for one year, from February 2004 to February 2005. This allowed the

V. Masson; L. Gomes; G. Pigeon; C. Liousse; V. Pont; J.-P. Lagouarde; J. Voogt; J. Salmond; T. R. Oke; J. Hidalgo; D. Legain; O. Garrouste; C. Lac; O. Connan; X. Briottet; S. Lachérade; P. Tulet

2008-01-01

333

Pauli equation for a charged spin particle on a curved surface in an electric and magnetic field  

NASA Astrophysics Data System (ADS)

We derive the Pauli equation for a charged spin particle confined to move on a spatially curved surface S in an electromagnetic field. Using the thin-layer quantization scheme to constrain the particle on S , and in the transformed spinor representations, we obtain the well-known geometric potential Vg and the presence of e-i ?, which can generate additive spin connection geometric potentials by the curvilinear coordinates derivatives, and we find that the two fundamental evidences in the literature [Giulio Ferrari and Giampaolo Cuoghi, Phys. Rev. Lett. 100, 230403 (2008), 10.1103/PhysRevLett.100.230403] are still valid in the present system without source current perpendicular to S . Finally, we apply the surface Pauli equation to spherical, cylindrical, and toroidal surfaces, in which we obtain expectantly the geometric potentials and new spin connection geometric potentials, and find that only the normal Pauli matrix appears in these equations.

Wang, Yong-Long; Du, Long; Xu, Chang-Tan; Liu, Xiao-Jun; Zong, Hong-Shi

2014-10-01

334

Liquid drops and surface tension with smoothed particle applied mechanics  

Microsoft Academic Search

Smoothed particle applied mechanics (SPAM), also referred to as smoothed particle hydrodynamics, is a Lagrangian particle method for the simulation of continuous flows. Here we apply it to the formation of a liquid drop, surrounded by its vapor, for a van der Waals (vdW) fluid in two dimensions. The cohesive pressure of the vdW equation of state gives rise to

S. Nugent; H. A. Posch

2000-01-01

335

[Texture variation of CC 5052 aluminum alloy slab from surface to center layer by XRD].  

PubMed

For improvement of the processing and gaining uniformity texture structure and performance of direct chill cast CCAA 5052 aluminum alloy band after first hot rolling with different reduction, the material was annealed at 454 degrees C and then cold rolling with different reduction was conducted, the texture at surface, quarter and center layer of the sample was tested and examined by X-ray diffraction method, the data calculated using special software and the difference of texture at surface, quarter and center layer was analyzed. There existed an elevated gradient of intensity from surface layer to center layer after cold rolled with less than or equal to 40% reduction, The main texture of beta is stronger mainly due to transformation from remainder exposure, while the goss and remainder is infirm, the state of texture at each layer is close to each other after cold rolling with reduction high than 56.1%. PMID:23905353

Chen, Ming-Biao; Liu, Wen-Chang; Ma, Xiao-Yi; Li, Jian; Yang, Qing-Xiang; Wang, Shan; Ma, Min; Liu, Chang; Zhao, Y M

2013-05-01

336

Numerical analysis of the influence of surface-active substance in the melt on the distribution of modifying particles and crystallization at the treatment of metal surface by a laser pulse  

NASA Astrophysics Data System (ADS)

A mathematical model is proposed for the process of modifying the metal surface layer by refractory nano-size particles with the aid of the pulse laser radiation, which accounts for the surface tension dependence on the presence of surface-active substance in the melt. Numerical modeling has been carried out, from the results of which the influence of the surface -active admixture on the character of forming flows, distribution of particles of the modifying substance in the metal, and the melt crystallization process have been estimated.

Cherepanov, A. N.; Popov, V. N.

2014-06-01

337

Characterization of surface layers on M-50 steel exposed to perfluoropolyalkyethers at elevated temperatures  

NASA Astrophysics Data System (ADS)

Complex surface layers have been identified on M-50 steel samples exposed to a linear perfluoropolyalkyether (PFPAE) in the presence of air at 260°C. An understanding of the mechanisms that drive the formation of these layers is believed to be crucial for efforts to develop PFPAEs as effective lubricants for advanced high temperature turbine engines. Work presented here shows that the extreme surface region contains physisorbed PFPAE and Fe fluoride under which an Fe 3O 4 layer is observed followed by an FeF 2 layer which is adjacent to the substrate. Similar layered structures have been observed for Fe-containing materials exposed to HF but have not been reported for PFPAE systems. X-ray photoelectron spectroscopy (XPS) and conversion electron Mössbauer spectroscopy (CEMS) were used to unambiguously characterize these layers.

Sanders, J. H.; Cutler, J. N.; John, G.

1998-09-01

338

Insights Into Sill Formation Processes From Particle Image Velocimetry (PIV) Analysis of Layered Elastic Media Experiments  

NASA Astrophysics Data System (ADS)

A key issue in magma intrusion mechanics is constraining the conditions required to initiate sill formation from feeder dykes. To investigate these processes, we present a series of layered gelatine analogue experiments monitored with a Particle Image Velocimetry (PIV) system to document the fluid dynamics in the magma and small-scale deformation processes in the host material as a sill is formed along a weak contact beneath a more rigid layer. Gelatine is a good crustal analogue material to study the dynamics of dyke and sill propagation in the crust. Although gelatine is viscoelastic, tests carried out using a rheometer show that at experimental conditions the gelatine behaves as an almost ideal elastic material at 5-10 °C. Forty litres of hot liquid gelatine is poured into a clear-perspex tank and left to solidify in a fridge at ~5 °C. Experiments are prepared comprising multiple layers, with small strength contrasts (comparable to those between crustal strata) created by varying the gelatine concentration and allowing sufficient time for it to reach the plateau Young's modulus. Both strong and weak interface strengths are investigated by varying the extent of welding between the layers. Injection of dyed water (the magma analogue) into the solid gelatine from below causes a penny-shaped experimental dyke to form. With a constant driving pressure, the propagating experimental dyke becomes arrested beneath a more rigid layer if the Young's modulus contrast is greater than 12%. In the case of a weak interface, a sill is formed by intrusion along the contact between the layers; if the interface is strong a blade-like dyke forms. To monitor displacements within the gelatine using the PIV technique, neutrally buoyant polyamide reflective particles are added to the gelatine during experiment preparation. Two high-speed cameras are positioned outside the tank in a plane perpendicular to the strike of the experimental feeder dyke, and parallel to a high-power laser sheet that illuminates the reflective particles in the gelatine in short intense pulses. The cameras and laser sheet are triggered so that images are recorded at known time intervals. Incremental displacement vectors are calculated by cross-correlation between successive images. Spatial derivatives of the velocity field yield maps of the 2-D strain components within the laser sheet in the gelatine. The velocity component perpendicular to the laser sheet is also calculated from digital image stereo pairs. In separate experiments, reflective particles are added to the magma analogue to map fluid flow within the intrusion itself. PIV provides new insights into the dynamics of sill formation by allowing magma fluid dynamics and small-scale stress and strain perturbations within the host gelatine layers (and their interfaces) to be measured for the first time at the time of sill inception. These experiments represent an important step towards understanding sill formation mechanisms, with implications for crustal magma storage and the construction of larger igneous bodies such as laccoliths, magma chambers and plutons.

Kavanagh, J. L.; Boutelier, D. A.; Cruden, A. R.

2012-12-01

339

Surface Modified Particles By Multi-Step Addition And Process For The Preparation Thereof  

DOEpatents

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.

Cook, Ronald Lee (Lakewood, CO); Elliott, Brian John (Superior, CO); Luebben, Silvia DeVito (Golden, CO); Myers, Andrew William (Arvada, CO); Smith, Bryan Matthew (Boulder, CO)

2006-01-17

340

Two-Layer Variable Infiltration Capacity Land Surface Representation for General Circulation Models  

NASA Technical Reports Server (NTRS)

A simple two-layer variable infiltration capacity (VIC-2L) land surface model suitable for incorporation in general circulation models (GCMs) is described. The model consists of a two-layer characterization of the soil within a GCM grid cell, and uses an aerodynamic representation of latent and sensible heat fluxes at the land surface. The effects of GCM spatial subgrid variability of soil moisture and a hydrologically realistic runoff mechanism are represented in the soil layers. The model was tested using long-term hydrologic and climatalogical data for Kings Creek, Kansas to estimate and validate the hydrological parameters. Surface flux data from three First International Satellite Land Surface Climatology Project Field Experiments (FIFE) intensive field compaigns in the summer and fall of 1987 in central Kansas, and from the Anglo-Brazilian Amazonian Climate Observation Study (ABRACOS) in Brazil were used to validate the mode-simulated surface energy fluxes and surface temperature.

Xu, L.

1994-01-01

341

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).

342

Solution-processed amorphous silicon surface passivation layers  

NASA Astrophysics Data System (ADS)

Amorphous silicon thin films, fabricated by thermal conversion of neopentasilane, were used to passivate crystalline silicon surfaces. The conversion is investigated using X-ray and constant-final-state-yield photoelectron spectroscopy, and minority charge carrier lifetime spectroscopy. Liquid processed amorphous silicon exhibits high Urbach energies from 90 to 120 meV and 200 meV lower optical band gaps than material prepared by plasma enhanced chemical vapor deposition. Applying a hydrogen plasma treatment, a minority charge carrier lifetime of 1.37 ms at an injection level of 1015/cm3 enabling an implied open circuit voltage of 724 mV was achieved, demonstrating excellent silicon surface passivation.

Mews, Mathias; Mader, Christoph; Traut, Stephan; Sontheimer, Tobias; Wunnicke, Odo; Korte, Lars; Rech, Bernd

2014-09-01

343

On the Kinetic Energy Budget of the Unstable Atmospheric Surface Layer  

Microsoft Academic Search

We present a new account of the kinetic energy budget within an unstable atmospheric surface layer (ASL) beneath a convective outer layer. It is based on the structural model of turbulence introduced by McNaughton (Boundary-Layer Meteorology, 112: 199 221, 2004). In this model the turbulence is described as a self-organizing system with a highly organized structure that resists change by

K. G. McNaughton

2006-01-01

344

On the Kinetic Energy Budget of the Unstable Atmospheric Surface Layer  

Microsoft Academic Search

We present a new account of the kinetic energy budget within an unstable atmospheric surface layer (ASL) beneath a convective\\u000a outer layer. It is based on the structural model of turbulence introduced by McNaughton (Boundary-Layer Meteorology, 112:\\u000a 199–221, 2004). In this model the turbulence is described as a self-organizing system with a highly organized structure that\\u000a resists change by instability.

K. G. Mcnaughton

2006-01-01

345

Rapid Melt and Resolidification of Surface Layers Using Intense, Pulsed Ion Beams Final Report  

SciTech Connect

The emerging technology of pulsed intense ion beams has been shown to lead to improvements in surface characteristics such as hardness and wear resistance, as well as mechanical smoothing. We report hereon the use of this technology to systematically study improvements to three types of metal alloys - aluminum, iron, and titanium. Ion beam tieatment produces a rapid melt and resolidification (RMR) of the surface layer. In the case of a predeposited thin-fihn layer, the beam mixes this layer into the substrate, Ieading to improvements that can exceed those produced by treatment of the alloy alone, In either case, RMR results in both crystal refinement and metastable state formation in the treated surface layer not accessible by conventional alloy production. Although more characterization is needed, we have begun the process of relating these microstructural changes to the surface improvements we discuss in this report.

Renk, Timothy J.

1998-10-02

346

Tunable THz surface plasmon polariton based on a topological insulator/layered superconductor hybrid structure  

E-print Network

We theoretically investigate the surface plasmon polariton (SPP) at the interface between a three-dimensional strong topological insulator (TI) and a layered superconductor/magnetic insulator structure, within the random ...

Li, Mingda

347

Dynamic Air Layer on Textured Superhydrophobic Surfaces Ivan U. Vakarelski,*,  

E-print Network

to the nucleate boiling regime, depending upon the surface roughness and hydrophobicity.9,13-15 Our earlier, cooling occurs entirely in the Leidenfrost regime without transition to nucleate boiling.9 When the hot from the liquid9-12 in the film boiling regime but, as the sphere cools, may subsequently transition

Chan, Derek Y C

348

Surface wave induced high transparency of an overdense warm plasma layer.  

PubMed

We have found conditions in which a structure consisting of an overdense warm plasma layer spaced between two underdense warm plasma layers becomes transparent to a p-polarized obliquely incident electromagnetic wave. The energy of the incident wave is transferred across the overdense region by a pair of coupled surface waves. PMID:19741802

Dragila, R; Vukovic, S

1987-08-01

349

Ultrahigh Heat Transfer Enhancement by Nano and Microscale Porous Layer Formed on Surface  

Microsoft Academic Search

A new nano- and microscale porous layer formed on the wall surface is developed by combing the chemical etching method with nanoparticles, called the “nano porous layer” method, and the non-electrolyzed plating technique, called the “fine precipitate” method. The ultrahigh convective heat transfer performance compared to the conventional heat transfer correlations has been achieved: around 60–100% increase for the fundamental

Tomoaki Kunugi; Katsumi Muko; Masahiko Shibahara

2006-01-01

350

Aerosol model development for environmental monitoring in the coastal atmosphere surface layer  

Microsoft Academic Search

Extinction of radiation in the marine boundary layer is dominated by scattering and absorption due to atmospheric aerosol. It is known, that the extinction of optical radiation visible and near IR spectra in the marine surface layer is determined mainly by scattering and absorption atmospheric aerosol. It influences on a dependence of spectral transmission and extinction both natural, and artificial

Gennady A. Kaloshin; Gennady G. Matvienko

2007-01-01

351

Including Atmospheric Layers in Vegetation and Urban Offline Surface Schemes VALE RY MASSON AND YANN SEITY  

E-print Network

of the SBL into the urban Town Energy Balance scheme is presented in a paper by Hamdi and Masson in which balance and no canopy. The more detailed schemes have several layers in the soil, several energy budgetsIncluding Atmospheric Layers in Vegetation and Urban Offline Surface Schemes VALE´ RY MASSON

Ribes, Aurélien

352

Effects of surface wave breaking on the oceanic boundary layer Hailun He1,2  

E-print Network

Effects of surface wave breaking on the oceanic boundary layer Hailun He1,2 and Dake Chen1 (General Ocean Turbulence Model, GOTM) to investigate the effects of wave breaking on the oceanic boundary wave breaking on the oceanic boundary layer, Geophys. Res. Lett., 38, L07604, doi:10.1029/2011GL046665

Chen, .Dake

353

An Approach to Estimating Bedrock and Surfaces Layers in Polar Radar Imagery Jerome E. Mitchell1  

E-print Network

, David J. Crandall1 , Geoffrey C. Fox1 , and John D. Paden2 1 School of Informatics and Computing with detected bedrock (red) and surface layers (green). #12;References [1] S. Osher, J.A. Sethian, "Fronts. vol. 79 Issue 1, 1988, 12-49. [2] David J. Crandall, Geoffrey C. Fox, John D. Paden, "Layer

354

Friction, Frontogenesis, and the Stratification of the Surface Mixed Layer LEIF THOMAS*  

E-print Network

Friction, Frontogenesis, and the Stratification of the Surface Mixed Layer LEIF THOMAS* Department restratification resulting from frontogenesis in regions of confluent flow. Frictional forces acting of friction versus frontogenesis in the restratification of the mixed layer and are tested using numerical

Thompson, Andrew

355

Thin-layer chromatography–matrix-assisted laser desorption ionisation–time-of-flight mass spectrometry using particle suspension matrices  

Microsoft Academic Search

Particle suspension matrices have been successfully utilized for the analysis of tetracycline antibiotics by thin-layer chromatography–matrix-assisted laser desorption ionisation–time-of-flight mass spectrometry (TLC–MALDI–TOF–MS). Particles of different materials and sizes have been investigated (Co-UFP, TiN, TiO2, Graphite and Silicon) by applying particle suspensions to eluted TLC plates. Mass spectra and mass chromatograms have been recorded directly from the TLC plates. Strong cationization

Anna Crecelius; Malcolm R. Clench; Don S. Richards; Vic Parr

2002-01-01

356

Near Surface Vapor Bubble Layers in Buoyant Low Stretch Burning of Polymethylmethacrylate  

NASA Technical Reports Server (NTRS)

Large-scale buoyant low stretch stagnation point diffusion flames over solid fuel (polymethylmethacrylate) were studied for a range of aerodynamic stretch rates of 2-12/ sec which are of the same order as spacecraft ventilation-induced stretch in a microgravity environment. An extensive layer of polymer material above the glass transition temperature is observed. Unique phenomena associated with this extensive glass layer included substantial swelling of the burning surface, in-depth bubble formation, and migration and/or elongation of the bubbles normal to the hot surface. The bubble layer acted to insulate the polymer surface by reducing the effective conductivity of the solid. The reduced in-depth conduction stabilized the flame for longer than expected from theory neglecting the bubble layer. While buoyancy acts to move the bubbles deeper into the molten polymer, thermocapillary forces and surface regression both act to bring the bubbles to the burning surface. Bubble layers may thus be very important in low gravity (low stretch) burning of materials. As bubbles reached the burning surface, monomer fuel vapors jetted from the surface, enhancing burning by entraining ambient air flow. Popping of these bubbles at the surface can expel burning droplets of the molten material, which may increase the fire propagation hazards at low stretch rates.

Olson, Sandra L.; Tien, J. S.

1999-01-01

357

On the coupling between a supersonic boundary layer and a flexible surface  

NASA Technical Reports Server (NTRS)

The coupling between a two-dimensional, supersonic, laminar boundary layer and a flexible surface is studied using direct numerical computations of the Navier-Stokes equations coupled with the plate equation. The flexible surface is forced to vibrate by plane acoustic waves at normal incidence emanated by a sound source located on the side of the flexible surface opposite to the boundary layer. The effect of the source excitation frequency on the surface vibration and boundary layer stability is analyzed. We find that, for frequencies near the fifth natural frequency of the surface or lower, large disturbances are introduced in the boundary layer which may alter its stability characteristics. The interaction between a stable two-dimensional disturbance of Tollmien-Schlichting (TS) type with the vibrating surface is also studied. We find that the disturbance level is higher over the vrating flexible surface than that obtained when the surface is rig id, which indicates a strong coupling between flow and structure. However, in the absence of the sound source the disturbance level over the rigid and flexible surfaces are identical. This result is due to the high frequency of the TS disturbance which does not couple with the flexible surface.

Frendi, Abdelkader; Maestrello, Lucio; Bayliss, Alvin

1992-01-01

358

On the coupling between a supersonic boundary layer and a flexible surface  

NASA Technical Reports Server (NTRS)

The coupling between a two-dimensional, supersonic, laminar boundary layer and a flexible surface is studied using direct numerical computations of the Navier-Stokes equations coupled with the plate equation. The flexible surface is forced to vibrate by plane acoustic waves at normal incidence emanated by a sound source located on the side of the flexible surface opposite to the boundary layer. The effect of the source excitation frequency on the surface vibration and boundary layer stability is analyzed. We find that, for frequencies near the fifth natural frequency of the surface or lower, large disturbances are introduced in the boundary layer which may alter its stability characteristics. The interaction between a stable two-dimensional disturbance of Tollmien-Schlichting (TS) type with the vibrating surface is also studied. We find that the disturbance level is higher over the vibrating flexible surface than that obtained when the surface is rigid, which indicates a strong coupling between flow and structure. However, in the absence of the sound source the disturbance level over the rigid and flexible surfaces are identical. This result is due to the high frequency of the TS disturbance which does not couple with the flexible surface.

Frendi, Abdelkader; Maestrello, Lucio; Bayliss, Alvin

1992-01-01

359

Free vibration of functionally graded material beams with surface-bonded piezoelectric layers in thermal environment  

Microsoft Academic Search

Free vibration of statically thermal postbuckled functionally graded material (FGM) beams with surface-bonded piezoelectric\\u000a layers subject to both temperature rise and voltage is studied. By accurately considering the axial extension and based on\\u000a the Euler-Bernoulli beam theory, geometrically nonlinear dynamic governing equations for FGM beams with surface-bonded piezoelectric\\u000a layers subject to thermo-electromechanical loadings are formulated. It is assumed that the

Shi-rong Li; Hou-de Su; Chang-jun Cheng

2009-01-01

360

On the relationship between temperature and wind speed in the atmospheric surface layer  

E-print Network

of Dynamic Stability V ~ ~ ~ ~ ~ ~ ~ 10 The Profile Equations for Diabatic Conditions . o. . . ~ ~ . ~ - ~ 11 Steady-State Surface Layer Theory The Temperature-Rind Speed Relationship ~ e ~ ~ ~ ~ ~ ~ i, ~ ~ ~ ~ o ~ ~ 18 Simulation of Temperature and 7... height term appended, which are derived as approximations to theo- retically deduced forms, are utilired to account for departures of wind speed and temperature from logarithmic height dependence in the upper reaches of the surface layer...

Pierrard, John Martin

2012-06-07

361

Influence of surface heating on the boundary layer stability of flows with favorable pressure gradients  

E-print Network

INFLUENCE OF SURFACE HEATING ON THE BOUNDARY LAYER STABILITY OF FLOWS WITH FAVORABI E PRESSURE GRADIENTS A Thesis by DAVID BRIAN LANDRUM Submitted to the Graduate College of Texas AAM University in partial fulfillment of the requirements... for the degree of MASTER OF SCIENCE August 1986 Major Subject: Aerospace Engineering INFLUENCE OF SURFACE HEATING ON THE BOUNDARY LAYER STABILITY OF FLOWS WITH FAVORABLE PRESSURE GRADIENTS A Thesis by DAVID BRIAN LANDRUM Approved as to style and content...

Landrum, David Brian

2012-06-07

362

Surface-Layer Wind and Turbulence Profiling from LIDAR: Theory and Measurements  

E-print Network

Surface-Layer Wind and Turbulence Profiling from LIDAR: Theory and Measurements Régis DANIELIAN of a new and small wind Lidar system named `ZephIR1 'able to profile the surface layer up to ~200 metersQ's series produced ZephIR wind LIDAR system ZephIR consists of a CW (1.55 m) wind LIDAR operating in the so

363

Simulation of oxidation of carbon particles at the surface of mixed oxide catalysts  

Microsoft Academic Search

A model of catalytic oxidation of a cylindrical carbon particle was suggested. The model considers the rate of layer-by-layer\\u000a burning of the particle, variation of its geometry, and remote action of the catalyst. A software for calculations was developed;\\u000a the data obtained correlate well with the experimental data for catalysts based on lanthanum cesium vanadate. The kinetics\\u000a of carbon oxidation

A. A. Ostroushko; M. Yu. Sennikov; M. O. Tonkushina

2007-01-01

364

Can new particle formation occur in the clean marine boundary layer?  

NASA Astrophysics Data System (ADS)

An analysis of new particle formation probability in the marine boundary layer (MBL) is conducted using a detailed aerosol dynamics and gas-phase chemistry model, thermodynamically correct classical binary (H2O-H2SO4) nucleation theory, and recently developed ternary (H2O-H2SO4-NH3) nucleation theory. Additionally, the effect of boundary-layer meteorology (i.e., adiabatic cooling, small scale fluctuations, and entrainment) in enhancing nucleation is also examined. The results indicate that for typical marine conditions, binary nucleation does not occur for any realistic conditions regardless of adiabatic cooling, turbulent fluctuations, or entrainment. For polar marine conditions, binary nucleation does occur due to lower temperatures, and is enhanced due to turbulent fluctuations. An increase in detectable particle sizes (N3>3nm), is only seen after multiple boundary layer circulations for conditions of high dimethyl sulphide (DMS) concentrations (400 ppt). Under extreme conditions of entrainment of free-troposphere layers containing very low aerosol condensation sinks and extraordinary high sulphuric acid concentrations (>108moleculescm-3), increases in detectable particles up to 10,000 cm-3 are predicted only in polar marine air, but are viewed as unlikely to occur in reality. Comparison of model simulations with observed values of DMS and sulphuric acid in polar marine air masses suggest that binary nucleation may lead to an enhancement of ~1000 cm-3 in N3 particle concentration, but not to enhancements of ~10,000 cm-3. Ternary nucleation is predicted to occur under realistic sulphuric acid (1.2×107moleculescm-3) and ammonia (>5 ppt) concentrations; however, significant growth to detectable sizes (N3) only occurs for DMS concentrations of the order of 400 ppt and very low aerosol condensation sinks, but these conditions are thought to be very infrequent in the MBL and are unlikely to make a significant contribution to the general MBL aerosol concentration. It is plausible that the background MBL aerosol concentration could be maintained by a slow, almost undetectable production rate, and not by noticeable nucleation events where large enhancements in N3 concentrations are observed. The former requires sustained DMS concentrations of the order of 100 ppt which seems unlikely. In summary, the occurrence of new particles in the unperturbed MBL would be difficult to explain by DMS emissions alone. DMS emissions can explain the occurrence of thermodynamically stable sulphate clusters, but under most conditions, to grow these clusters to detectable sizes before they are scavenged by coagulation, an additional condensable species other than DMS-derived sulphuric acid would be required. In the event, however, of significant removal of the preexisting aerosol due to precipitation, the MBL aerosol can be replenished through growth of new particle formed through ternary nucleation under moderately high DMS concentrations.

Pirjola, Liisa; O'Dowd, Colin D.; Brooks, Ian M.; Kulmala, Markku

2000-11-01

365

Appearance of aldehydes in the surface layer of lake waters.  

PubMed

The paper presents results concerning the changes in the content of aldehydes in samples of lake water collected near the lake surface. The study of lake waters was undertaken to explain which physicochemical parameters of the environment have the greatest influence on the level of aldehydes, which of the aldehydes are most often met in surface water and in what concentrations. We observed that formaldehyde, acetaldehyde, propanal, glyoxal, methylglyoxal and acetone were commonly present in surface water samples, while semi-volatile and poorly soluble aldehydes such as nonanal and decanal were observed seasonally. The contents of total aldehydes varied in a wide range, from 55 to 670 ?g/l, and the concentration of total organic carbon varied significantly from 3 to 18 mg /l, but there was no evident correlation between them in all of samples. The total content of aldehydes did not depend on the meteorological parameters such as air temperature, UV radiation and ozone concentration; however, it was noted that the level of carbonyl concentration is related to the period of intense precipitation: in the period of very low precipitations, the highest contents of total aldehydes were determined in all of the water samples, and in the periods of intense precipitations, the content of total aldehydes was drastically smaller. PMID:24671617

D?browska, Agata; Nawrocki, Jacek; Szel?g-Wasielewska, El?bieta

2014-07-01

366

Estimation of Surface Heat Fluxes at Field Scale Using Surface Layer Versus Mixed-Layer Atmospheric Variables with Radiometric Temperature Observations.  

NASA Astrophysics Data System (ADS)

Radiometric surface temperature observations TR(), near-surface meteorological/surface energy flux (METFLUX), and atmospheric boundary layer (ABL) data were collected during the Washita '94 Experiment conducted in the Little Washita Experimental Watershed near Chickasha, Oklahoma. The TR() measurements were made from ground and aircraft platforms near the METFLUX stations located over vegetated surfaces of varying amounts of cover and over bare soil. Continuous, half-hourly averaged ground-based TR() measurements essentially at the point scale were calibrated with periodic ground transect and aircraft-based TR() observations at coarser resolutions so that the continuous TR() measurements would be representative of surface temperatures at the field scale (i.e., on the order of 104 m2). The METFLUX data were collected nominally at 2 m above the surface, while ABL measurements were made in the lower 8-10 km of the atmosphere. The `local' wind speed, u, and air temperature, TA, from the METFLUX stations, as well as the mixed-layer wind speed, UM, and potential temperature, M, were used in a two-source energy balance model for computing fluxes with continuous TR() measurements from the various surfaces. Standard Monin-Obukhov surface layer similarity was used with the `local' u and TA data from the METFLUX stations. Bulk similarity approaches were used with the UM and M data referenced either to ABL height or the top of the surface layer. This latter approach of using mixed-layer data to drive model computations for the different sites is similar to the so-called flux-aggregation schemes or methods proposed to account for subgrid variability in atmospheric models, such as the`tile' or `mosaic' approach. There was less agreement between modeled and measured fluxes when using mixed-layer versus local meteorological variables data for driving the model, and the type of bulk formulation used (i.e., whether local or regional surface roughness was used) also had a significant impact on the results. Differences between the flux observations and model predictions using surface layer similarity with local u and TA data were about 25% on average, while using the bulk formulations with UM and M differences averaged about 30%. This larger difference was caused by an increase in biases and scatter between modeled and measured fluxes for some sites. Therefore, computing spatially distributed local-scale fluxes with ABL observations of mixed-layer properties will probably yield less reliable flux predictions than using local meteorological data, if available. Given the uncertainty in flux observations is about 20%, these estimates are still considered reasonable and moreover permit the mapping of spatially distributed surface fluxes at regional scales using a single observation of UM and M with high resolution TR() data. Such TR() observations with a 90-m pixel resolution will be available from the Advanced Spaceborne Thermal Emission and Reflection Radiometer to be launched on NASA's Earth Observing System.

Kustas, William P.; Prueger, John H.; Humes, Karen S.; Starks, Patrick J.

1999-02-01

367

Mechanical characteristics of SiC coating layer in TRISO fuel particles  

SciTech Connect

Tristructural isotropic (TRISO) particles are considered as advanced fuel forms for a variety of fission platforms. While these fuel structures have been tested and deployed in reactors, the mechanical properties of these structures as a function of production parameters need to be investigated in order to ensure their reliability during service. Nanoindentation techniques, indentation crack testing, and half sphere crush testing were utilized in order to evaluate the integrity of the SiC coating layer that is meant to prevent fission product release in the coated particle fuel form. The results are complimented by scanning electron microscopy (SEM) of the grain structure that is subject to change as a function of processing parameters and can alter the mechanical properties such as hardness, elastic modulus, fracture toughness and fracture strength. Through utilization of these advanced techniques, subtle differences in mechanical properties that can be important for in-pile fuel performance can be distinguished and optimized in iteration with processing science of coated fuel particle production.

Hosemann, Peter [ORNL] [ORNL; Martos, J. N. [University of California, Berkeley] [University of California, Berkeley; Frazer, D. [University of California, Berkeley] [University of California, Berkeley; Vasudevamurthy, Gokul [ORNL] [ORNL; Byun, Thak Sang [ORNL] [ORNL; Hunn, John D [ORNL] [ORNL; Jolly, Brian C [ORNL] [ORNL; Terrani, Kurt A [ORNL] [ORNL; Okuniewski, Maria A. [Idaho National Laboratory (INL)] [Idaho National Laboratory (INL)

2013-01-01

368

Mechanical characteristics of SiC coating layer in TRISO fuel particles  

NASA Astrophysics Data System (ADS)

Tristructural isotropic (TRISO) particles are considered as advanced fuel forms for a variety of fission platforms. While these fuel structures have been tested and deployed in reactors, the mechanical properties of these structures as a function of production parameters need to be investigated in order to ensure their reliability during service. Nanoindentation techniques, indentation crack testing, and half sphere crush testing were utilized in order to evaluate the integrity of the SiC coating layer that is meant to prevent fission product release in the coated particle fuel form. The results are complimented by scanning electron microscopy (SEM) of the grain structure that is subject to change as a function of processing parameters and can alter the mechanical properties such as hardness, elastic modulus, fracture toughness and fracture strength. Through utilization of these advanced techniques, subtle differences in mechanical properties that can be important for in-pile fuel performance can be distinguished and optimized in iteration with processing science of coated fuel particle production.

Hosemann, P.; Martos, J. N.; Frazer, D.; Vasudevamurthy, G.; Byun, T. S.; Hunn, J. D.; Jolly, B. C.; Terrani, K.; Okuniewski, M.

2013-11-01

369

Mechanical Characteristics of SiC Coating Layer in TRISO Fuel Particles  

SciTech Connect

Tristructural isotropic (TRISO) particles are considered as advanced fuel forms for a variety of fission platforms. While these fuel structures have been tested and deployed in reactors, the mechanical properties of these structures as a function of production parameters need to be investigated in order to ensure their reliability during service. Nanoindentation techniques, indentation crack testing, and half sphere crush testing were utilized in order to evaluate the integrity of the SiC coating layer that is meant to prevent fission product release in the coated particle fuel form. The results are complimented by scanning electron microscopy (SEM) of the grain structure that is subject to change as a function of processing parameters and can alter the mechanical properties such as hardness, elastic modulus, fracture toughness and fracture strength. Through utilization of these advanced techniques, subtle differences in mechanical properties that can be important for in-pile fuel performance can be distinguished and optimized in iteration with processing science of coated fuel particle production.

P. Hosemann; J. N. Martos; D. Frazer; G. Vasudevamurthy; T. S. Byun; J. D. Hunn; B. C. Jolly; K. Terrani; M. Okuniewski

2013-11-01

370

Surface roughness measurements of beta-layered solid deuterium-tritium in toroidal geometries  

SciTech Connect

New experiments in a NIF-scale toroidal cylinder have resulted in true shadowgraphs of the DT ice surface. The spectral analysis of the images summed over l-modes 2 through 256 reveal that the surface roughness reaches values just below 1.0 {micro}m at temperatures of 19 K and above. Summing only modes l {ge} 10, the partial surface roughness is below 0.7 {micro}m at 19.5 K. These results indicate that native beta-layering will be sufficient to meet the NIF requirements for DT ice surface finish for both Be and CH ablating shells. The toroidal cylinder incorporates a linear heater along the cylindrical axis to test the concept of surface enhancement due to heat assisted beta-layering in DT. Additionally, with the use of this heater it is possible to symmetrize a pure D{sub 2} layer.

Hoffer, J.K.; Foreman, L.R. [Los Alamos National Lab., NM (United States); Sanchez, J.J.; Mapoles, E.R. [Lawrence Livermore National Lab., CA (United States); Sheliak, J.D. [General Atomics, Inc., Los Alamos, NM (United States)

1996-07-01

371

Electrostatic transport in L-mode scrape-off layer plasmas in the Tore Supra tokamak. I. Particle balance  

SciTech Connect

Particle balance is investigated using a Mach probe at the top of the scrape-off layer of circular ohmically heated L-mode plasmas in the Tore Supra tokamak [G. Giruzzi etal., Nucl. Fusion 49, 104010 (2009)]. Contributions from both poloidal EXB flows and ionization sources are found to be small. As a result the local parallel flow is a response of the radial flux distribution between the two strike points of open field lines, and the density profile is determined by the field-line-integrated radial flux. By scanning the poloidal position of the strike point on a secondary limiter situated at the outboard midplane, an indirect poloidal mapping of the radial flux distribution is obtained. The radial flux is centered at the outboard midplane and is relatively well described by a Gaussian distribution of half poloidal width of about 50 Degree-Sign at the last closed flux surface, decaying to about 30 Degree-Sign in the far scrape-off layer. The turbulent radial flux measured locally with a rake probe shows a reasonable agreement with the poloidal mapping obtained by the Mach probe. It is shown than the radial convective velocity decays along radius at the plasma top but should increase with radius at the outboard midplane.

Fedorczak, N. [Center for Momentum Transport and Flow Organisation, University of California at San Diego, San Diego, California 92093 (United States); Gunn, J. P.; Pascal, J.-Y.; Ghendrih, Ph.; Monier-Garbet, P. [Commissariat a l'Energie Atomique et aux Energies Alternatives, Institut de Recherche pour la Fusion Magnetique Controlee, F-13108 Saint-Paul-Lez-Durance (France); Marandet, Y. [Laboratoire de Physique des Interactions Ioniques et Moleculaires, UMR 6633 Universite de Provence/CNRS, Centre de St. Jerome, F-13397 Marseille, Cedex-20 (France)

2012-07-15

372

Cloud layer thicknesses from a combination of surface and upper-air observations  

NASA Technical Reports Server (NTRS)

Cloud layer thicknesses are derived from base and top altitudes by combining 14 years (1975-1988) of surface and upper-air observations at 63 sites in the Northern Hemisphere. Rawinsonde observations are employed to determine the locations of cloud-layer top and base by testing for dewpoint temperature depressions below some threshold value. Surface observations serve as quality checks on the rawinsonde-determined cloud properties and provide cloud amount and cloud-type information. The dataset provides layer-cloud amount, cloud type, high, middle, or low height classes, cloud-top heights, base heights and layer thicknesses, covering a range of latitudes from 0 deg to 80 deg N. All data comes from land sites: 34 are located in continental interiors, 14 are near coasts, and 15 are on islands. The uncertainties in the derived cloud properties are discussed. For clouds classified by low-, mid-, and high-top altitudes, there are strong latitudinal and seasonal variations in the layer thickness only for high clouds. High-cloud layer thickness increases with latitude and exhibits different seasonal variations in different latitude zones: in summer, high-cloud layer thickness is a maximum in the Tropics but a minimum at high latitudes. For clouds classified into three types by base altitude or into six standard morphological types, latitudinal and seasonal variations in layer thickness are very small. The thickness of the clear surface layer decreases with latitude and reaches a summer minimum in the Tropics and summer maximum at higher latitudes over land, but does not vary much over the ocean. Tropical clouds occur in three base-altitude groups and the layer thickness of each group increases linearly with top altitude. Extratropical clouds exhibit two groups, one with layer thickness proportional to their cloud-top altitude and one with small (less than or equal to 1000 m) layer thickness independent of cloud-top altitude.

Poore, Kirk D.; Wang, Junhong; Rossow, William B.

1995-01-01

373

Trapping and depth profile of tritium in surface layers of metallic materials  

NASA Astrophysics Data System (ADS)

Tritium amount retained in surface layers and release behavior from surface layers were examined using SS316L samples exposed to plasmas in the Large Helical Device and a commercial Cu-Be alloy plate. BIXS analyses and observation by SEM indicate that carbon and titanium deposited on the plasma-facing surface of the SS316L samples. Larger amount of tritium was trapped in the plasma-facing surface in comparison with the polished surface. Higher enrichment of tritium in surface layers was similarly found in the polished surface of both samples. The amount of surface tritium in both samples was almost same, while the bulk concentration of tritium in Cu-Be was much lower than that in SS316L. Tritium release from the SS316L and Cu-Be samples into water was examined by immersion experiments. Tritium elution was observed for both samples, but changes in the residual tritium amount in surface layers were different from each other.

Matsuyama, M.; Chen, Z.; Nisimura, K.; Akamaru, S.; Torikai, Y.; Hatano, Y.; Ashikawa, N.; Oya, Y.; Okuno, K.; Hino, T.

2011-10-01

374

Macrophage/particle interactions: effect of size, composition and surface area.  

PubMed

Particulate wear-debris are detected in histiocytes/macrophages of granulomatous tissues adjacent to loose joint prostheses. Such cell-particle interactions have been simulated in vitro by challenging macrophages with particles dosed according to weight percent, volume percent, and number of particles. Each of these dosage methods has inherent shortcomings due to varying size and density of challenging particles of different compositions. In this study we challenged P388D1 macrophages with titania and polystyrene particles (< 2 microns), with dosage based on the ratio of the surface area of the particles to the surface area of the cells. The effect of size and composition on (1) the bone resorbing activity, (2) fibroblast proliferation, and (3) secretion of IL-1 and PGE2 was determined. Macrophage response to particulate debris appears to be dependent on particle size, composition, and dose as given by surface area ratio. P388D1 macrophages challenged with titania particles released IL-1, but did not stimulate fibroblasts. Inhibition of macrophage DNA synthesis at higher surface area ratios suggests cell damage or death. Particle-stimulated cells increased bone resorption up to 125% of controls but released only basal levels of PGE2. Macrophages stimulated by wear particles are expected to synthesize numerous factors affecting events in the bone-implant interface. Using the concept of surface area ratio allows us to study and compare such cellular responses to wear particles in a standardized manner. PMID:8126033

Shanbhag, A S; Jacobs, J J; Black, J; Galante, J O; Glant, T T

1994-01-01

375

Thermal stresses in small meteoroids. II. Effects of an insulating surface layer  

NASA Astrophysics Data System (ADS)

Aims: We extend our previous analysis of thermal stresses in small, spherical and homogeneous meteoroids by taking into account the effects of a surface insulating layer. Methods: Using analytical computations, we determine the temperature distribution in a spherical inhomogeneous body smaller than ~10 cm with a high-conductivity core and a low-conductivity surface layer. Our main approximation consists in (i) linearization of the surface energy-conservation constraint and (ii) omission of the seasonal effects in the Fourier spectrum of the incident solar radiation flux. Using the temperature solution, we analytically compute the mechanical (thermal) stress field in the core, neglecting its effects in the particulate surface layer. Conditions for material failure in the whole volume of the body are analyzed. In particular, we pay attention to whether the surface layer depth evolves toward an equilibrium situation. Results: As the meteoroid approaches the Sun, the thermal stress first exceeds the material strength at the surface of meteoroid. If the fractured material is able to stay on meteoroid, a particulate shell begins to form. After one revolution about the Sun, this process is roughly completed. We determine the dependence of its thickness on perihelion distance, spin axis orientation with respect to the Sun, and the size of meteoroid. We estimate the distribution of the final depths of the surface layer for eight major meteoroid showers with perihelion distances smaller than 1 AU.

?apek, D.; Vokrouhlický, D.

2012-03-01

376

Six antigenic determinants in the surface layer of the archaebacterium Methanococcus vannielii revealed by monoclonal antibodies  

SciTech Connect

The immunogenicity and antigenic characteristics of the unique surface layer (S layer) of Methanococcus vannielii was studied with a panel of six monoclonal antibodies. Six surface determinants were identified for the first time, each recognized by one antibody exclusively. The determinants are proteins, located in the S layer, and accessible to antibody in whole, unfixed, as well as formalinized bacteria. Hence the six antigens and antibodies reported here should be useful for rapid identification of new isolates and for taxonomy of methanogens, notably Methanococcaceae. In this connection two novel applications of the slide immunoenzymatic assay were developed for analyses of monoclonal antibodies and their complementary sites in the bacterial envelope.

de Macario, E.C.; Koenig, H.; Macario, A.J.L.; Kandler, O.

1984-02-01

377

Six antigenic determinants in the surface layer of the archaebacterium Methanococcus vannielii revealed by monoclonal antibodies.  

PubMed

The immunogenicity and antigenic characteristics of the unique surface layer (S layer) of Methanococcus vanielii was studied with a panel of six monoclonal antibodies. Six surface determinants were identified for the first time, each recognized by one antibody exclusively. The determinants are proteins, located in the S layer, and accessible to antibody in whole, unfixed, as well as formalinized bacteria. Hence the six antigens and antibodies reported here should be useful for rapid identification of new isolates and for taxonomy of methanogens, notably Methanococcaceae. In this connection two novel applications of the slide immunoenzymatic assay were developed for analyses of monoclonal antibodies and their complementary sites in the bacterial envelope. PMID:6197477

Conway de Macario, E; König, H; Macario, A J; Kandler, O

1984-02-01

378

Numerical study on the adhesion and reentrainment of nondeformable particles on surfaces: the role of surface roughness and electrostatic forces.  

PubMed

In this paper, the reentrainment of nanosized and microsized particles from rough walls under various electrostatic conditions and various hydrodynamic conditions (either in air or aqueous media) is numerically investigated. This issue arises in the general context of particulate fouling in industrial applications, which involves (among other phenomena) particle deposition and particle reentrainment. The deposition phenomenon has been studied previously and, in the present work, we focus our attention on resuspension. Once particles are deposited on a surface, the balance between hydrodynamic forces (which tend to move particles away from the surface) and adhesion forces (which maintain particles on the surface) can lead to particle removal. Adhesion forces are generally described using van der Waals attractive forces, but the limit of these models is that any dependence of adhesion forces on electrostatic forces (due to variations in pH or ionic strength) cannot be reproduced numerically. For this purpose, we develop a model of adhesion forces that is based on the DLVO (Derjaguin and Landau, Verwey and Overbeek) theory and which includes also the effect of surface roughness through the use of hemispherical asperities on the surface. We first highlight the effect of the curvature radius on adhesion forces. Then some numerical predictions of adhesion forces or adhesion energies are compared to experimental data. Finally, the overall effects of surface roughness and electrostatic forces are demonstrated with some applications of the complete reentrainment model in some simple test cases. PMID:22107171

Henry, Christophe; Minier, Jean-Pierre; Lefèvre, Grégory

2012-01-10

379

Snell's law for particles moving on piecewise homogeneous two dimensional surface with linear boundaries  

Microsoft Academic Search

We study the properties of least time trajectories for particles moving on a two dimensional surface which consists of piecewise homogeneous regions. The particles are assumed to move with different constant speeds on different regions and on the boundary between regions. The speed of the particle is assumed to be highest when it moves along the edges formed by the

Pratik Mandrekar; Toby Joseph

2011-01-01

380

Electrostatic interactions between diffuse soft multi-layered (bio)particles: beyond Debye-Hückel approximation and Deryagin formulation.  

PubMed

We report a steady-state theory for the evaluation of electrostatic interactions between identical or dissimilar spherical soft multi-layered (bio)particles, e.g. microgels or microorganisms. These generally consist of a rigid core surrounded by concentric ion-permeable layers that may differ in thickness, soft material density, chemical composition and degree of dissociation for the ionogenic groups. The formalism allows the account of diffuse interphases where distributions of ionogenic groups from one layer to the other are position-dependent. The model is valid for any number of ion-permeable layers around the core of the interacting soft particles and covers all limiting situations in terms of nature of interacting particles, i.e. homo- and hetero-interactions between hard, soft or entirely porous colloids. The theory is based on a rigorous numerical solution of the non-linearized Poisson-Boltzmann equation including radial and angular distortions of the electric field distribution within and outside the interacting soft particles in approach. The Gibbs energy of electrostatic interaction is obtained from a general expression derived following the method by Verwey and Overbeek based on appropriate electric double layer charging mechanisms. Original analytical solutions are provided here for cases where interaction takes place between soft multi-layered particles whose size and charge density are in line with Deryagin treatment and Debye-Hückel approximation. These situations include interactions between hard and soft particles, hard plate and soft particle or soft plate and soft particle. The flexibility of the formalism is highlighted by the discussion of few situations which clearly illustrate that electrostatic interaction between multi-layered particles may be partly or predominantly governed by potential distribution within the most internal layers. A major consequence is that both amplitude and sign of Gibbs electrostatic interaction energy may dramatically change depending on the interplay between characteristic Debye length, thickness of ion-permeable layers and their respective protolytic features (e.g. location, magnitude and sign of charge density). This formalism extends a recent model by Ohshima which is strictly limited to interaction between soft mono-shell particles within Deryagin and Debye-Hückel approximations under conditions where ionizable sites are completely dissociated. PMID:21072398

Duval, Jérôme F L; Merlin, Jenny; Narayana, Puranam A L

2011-01-21

381

Modelling non-equilibrium secondary organic aerosol formation and evaporation with the aerosol dynamics, gas- and particle-phase chemistry kinetic multi-layer model ADCHAM  

NASA Astrophysics Data System (ADS)

We have developed the novel Aerosol Dynamics, gas- and particle-phase chemistry model for laboratory CHAMber studies (ADCHAM). The model combines the detailed gas phase Master Chemical Mechanism version 3.2, an aerosol dynamics and particle phase chemistry module (which considers acid catalysed oligomerization, heterogeneous oxidation reactions in the particle phase and non-ideal interactions between organic compounds, water and inorganic ions) and a kinetic multilayer module for diffusion limited transport of compounds between the gas phase, particle surface and particle bulk phase. In this article we describe and use ADCHAM to study: (1) the mass transfer limited uptake of ammonia (NH3) and formation of organic salts between ammonium (NH4+) and carboxylic acids (RCOOH), (2) the slow and almost particle size independent evaporation of ?-pinene secondary organic aerosol (SOA) particles, and (3) the influence of chamber wall effects on the observed SOA formation in smog chambers. ADCHAM is able to capture the observed ?-pinene SOA mass increase in the presence of NH3(g). Organic salts of ammonium and carboxylic acids predominantly form during the early stage of SOA formation. These salts contribute substantially to the initial growth of the homogeneously nucleated particles. The model simulations of evaporating ?-pinene SOA particles support the recent experimental findings that these particles have a semi-solid tar like amorphous phase state. ADCHAM is able to reproduce the main features of the observed slow evaporation rates if low-volatility and viscous oligomerized SOA material accumulates in the particle surface layer upon evaporation. The evaporation rate is mainly governed by the reversible decomposition of oligomers back to monomers. Finally, we demonstrate that the mass transfer limited uptake of condensable organic compounds onto wall deposited particles or directly onto the Teflon chamber walls of smog chambers can have profound influence on the observed SOA formation. During the early stage of the SOA formation the wall deposited particles and walls themselves serve as a SOA sink from the air to the walls. However, at the end of smog chamber experiments the semi-volatile SOA material may start to evaporate from the chamber walls. With these three model applications, we demonstrate that several poorly quantified processes, i.e. mass transport limitations within the particle phase, oligomerization, heterogeneous oxidation, organic salt formation, and chamber wall effects can have substantial influence on the SOA formation, lifetime, chemical and physical particle properties, and their evolution. In order to constrain the uncertainties related to these processes, future experiments are needed where as many of the influential variables as possible are varied. ADCHAM can be a valuable model tool in the design and analysis of such experiments.

Roldin, P.; Eriksson, A. C.; Nordin, E. Z.; Hermansson, E.; Mogensen, D.; Rusanen, A.; Boy, M.; Swietlicki, E.; Svenningsson, B.; Zelenyuk, A.; Pagels, J.

2014-01-01

382

Improving Efficiency of Layer-By Coating on Nanosized Particles with Non-Washing Assembly Technique  

NASA Astrophysics Data System (ADS)

Non-washing layer-by-layer assembly allows to obtain concentrated (3-5 mg/mL) colloids of 150-200 nm diameter capsules encasing poorly soluble drug nanocrystals or soft gellike nanoparticles. Aggregation of the nanoparticles is prevented by using low molecular weight block-copolymers of poly(amino acids) with polyethylene glycol (PEG) in a combination with heparin and bovine serum albumin at every bilayer building step. Minimal amounts of the polyelectrolytes are used to recharge the surface of nanoparticles in the non-washing LbL process. Such PEGylated shells result in drug nanocapsules with a high colloidal stability in PBS buffer and increased protein adhesion resistance.

Shutava, T.; Pattekari, P.; Parekh, G.; Lvov, Y.

2013-05-01

383

Gas phase water in the surface layer of protoplanetary disks  

E-print Network

Recent observations of the ground state transition of HDO at 464 GHz towards the protoplanetary disk of DM Tau have detected the presence of water vapor in the regions just above the outer disk midplane (Ceccarelli et al 2005). In the absence of non-thermal desorption processes, water should be almost entirely frozen onto the grain mantles and HDO undetectable. In this Letter we present a chemical model that explores the possibility that the icy mantles are photo-desorbed by FUV (6eV water vapor above the disk midplane over the entire disk. Assuming a photo-desorption yield of 10^{-3}, the water abundance in this layer is predicted to be ~ 3 x 10^{-7} and the average H2O column density is ~ 1.6x 10^{15} cm^{-2}. The predictions are very weakly dependent on the details of the model, like the incident FUV radiation field, and the gas density in the disk. Based on this model, we predict a gaseous HDO/H2O ratio in DM Tau of ~1%. In addition, we predict the ground state transition of water at 557 GHz to be undetectable with ODIN and/or HSO-HIFI.

C. Dominik; C. Ceccarelli; D. Hollenbach; M. Kaufman

2005-10-21

384

Surface passivation of InP solar cells with InAlAs layers  

NASA Technical Reports Server (NTRS)

The efficiency of indium phosphide solar cells is limited by high values of surface recombination. The effect of a lattice-matched In(0.52)Al(0.48)As window layer material for InP solar cells, using the numerical code PC-1D is investigated. It was found that the use of InAlAs layer significantly enhances the p(+)n cell efficiency, while no appreciable improvement is seen for n(+)p cells. The conduction band energy discontinuity at the heterojunction helps in improving the surface recombination. An optimally designed InP cell efficiency improves from 15.4 percent to 23 percent AMO for a 10 nm thick InAlAs layer. The efficiency improvement reduces with increase in InAlAs layer thickness, due to light absorption in the window layer.

Jain, Raj K.; Flood, Dennis J.; Landis, Geoffrey A.

1993-01-01

385

Liposomes coated with crystalline bacterial cells surface protein (S-layer) as immobilization structures for macromolecules.  

PubMed

Isolated subunits from the crystalline cell surface layer (S-layer) of Bacillus coagulans E38-66 were recrystallized on positively charged liposomes. The liposomes were composed of dipalmitoylphosphatidylcholine/cholesterol and stearylamine. The natural arrangement of the S-layer subunits on the bacterial surface is as an oblique (p2) lattice. The subunits attached to positively charged liposomes by their inner face (which bears a net negative charge) in an orientation identical to the lattice on intact cells. The S-layer protein, once recrystallized on liposomes, was crosslinked with glutaraldehyde and subsequently used as a matrix for the covalent attachment of macromolecules. The high stability of S-layer-coated liposomes and the possibility for immobilizing biologically active molecules on the crystalline array may offer potential in various different liposome applications. PMID:7756334

Küpcü, S; Sára, M; Sleytr, U B

1995-05-01

386

Control of Morphology and Surface Properties of Flaky Layered Titanate Nanosheets Using Surfactant in Hydrothermal Solution  

NASA Astrophysics Data System (ADS)

Layered titanate nanosheets were synthesized by hydrolyzing titanium tetraisopropoxide (TIPT) in hydrothermal solution using triethanolamine (TEOA), and dodecanediamine (DDA) as surfactant. The effects of synthesis conditions on the formation of layered titanate nanosheets were investigated. A layered structure of the titanate was produced under basic (pH12.8) conditions using NaOH or NH4OH aqueous solution. The flaky forms were observed only in reaction mixtures that included DDA, and the flaky forms had multilayer structure comprising several monolayer sheets. In addition, TEOA and DDA promote control of the crystalline structure of layered titanate. The surface acidity of layered titanate nanosheets was studied by coloration with color indicator reagents. The acidity of the sample corresponds to that of dilute hydrochloric acid. It is assumed that acid sites can be formed on the surface of titanate nanosheets by elimination of NH4+ caused by calcination in air.

Nakagawa, Keizo; Ogata, Toshimasa; Sotowa, Ken-Ichiro; Sugiyama, Shigeru; Adachi, Motonari

387

Optical measurements of surface oxide layer formation on metal films  

SciTech Connect

We have employed two optical techniques which give complementary indications of the formation of monolayers of oxide on freshly evaporated aluminum and silicon thin films. Visible ellipsometry is utilized to observe the growth of the initial monolayer of oxide on these films. From these data, we deduce the pressure and coverage dependence as well as the growth rate for the initial monolayer arising from these surface reactions. In addition, extreme ultraviolet (xuv) reflectance vs angle of incidence measurements at 58.4 nm wavelength clearly indicate the growth of oxide on the surface of our freshly deposited aluminum and silicon films as well. We have utilized this reflectance data to deduce the optical constants of aluminum and silicon at 58.4 nm. We find that previous xuv measurements of these optical constants were hampered by the presence of oxides. We also determined that the xuv reflectivity performance of aluminum films freshly deposited in our uhv system does not degrade appreciably when stored for four weeks in a helium atmosphere of 2 x 10/sup -9/ Torr. 11 refs., 7 figs., 1 tab.

Scott, M.L.

1987-01-01

388

The evolution of surface layers formed during chalcopyrite leaching  

NASA Astrophysics Data System (ADS)

Chalcopyrite (CuFeS 2) leaching in perchloric acid (HClO 4) at an initial pH of one and a temperature of 85 °C has been examined. The rate of leaching of Cu and Fe increased progressively over the duration of the experiment. The Cu leach rate was initially greater (up to 24 h) but thereafter the leach rates for Cu and Fe were approximately equal. After 313 h 81% Cu release was achieved at which time the leach experiment was terminated. Only 25% of the available S was released into solution during the leaching process. Surface speciation over the duration of the leach was examined using X-ray photoelectron spectroscopy (XPS), time of flight secondary ion mass spectrometry (ToF-SIMS) and scanning electron microscopy (SEM). As a result, a three-step reaction pathway is proposed. The first oxidation step involves the release of Cu and Fe into solution and the polymerisation of monosulfide (S 2-) to polysulfide Sn2-. The subsequent reduction step does not result in the release of cations to solution but does result in the reformation of surface S 2- and other short chain polysulfides, which then on further oxidation restructure to form crystalline elemental sulfur (S 0). This final oxidation step is accompanied by further cation release.

Harmer, Sarah L.; Thomas, Joan E.; Fornasiero, Daniel; Gerson, Andrea R.

2006-09-01

389

Surface Analysis of Silica Gel Particles after Mechanical Dry Coating with Magnesium Stearate  

E-print Network

1 Surface Analysis of Silica Gel Particles after Mechanical Dry Coating with Magnesium Stearate-218" #12;2 Abstract A dry coating technique has been used to change the surface properties of silica gel of the uncoated and coated silica gel particles was observed by environmental scanning electron microscopy (ESEM

Paris-Sud XI, Université de

390

Manipulating particle trajectories with phase-control in surface acoustic wave microfluidics  

E-print Network

Manipulating particle trajectories with phase-control in surface acoustic wave microfluidics Nathan microfluidic flow mixer Biomicrofluidics 6, 012803 (2012) Cell separation and transportation between two particle trajectories with phase-control in surface acoustic wave microfluidics Nathan D. Orloff,1 Jaclyn R

Rubloff, Gary W.

391

Surface Layer Accretion in Conventional and Transitional Disks Driven by Far-ultraviolet Ionization  

NASA Astrophysics Data System (ADS)

Whether protoplanetary disks accrete at observationally significant rates by the magnetorotational instability (MRI) depends on how well ionized they are. Disk surface layers ionized by stellar X-rays are susceptible to charge neutralization by small condensates, ranging from ~0.01 ?m sized grains to angstrom-sized polycyclic aromatic hydrocarbons (PAHs). Ion densities in X-ray-irradiated surfaces are so low that ambipolar diffusion weakens the MRI. Here we show that ionization by stellar far-ultraviolet (FUV) radiation enables full-blown MRI turbulence in disk surface layers. Far-UV ionization of atomic carbon and sulfur produces a plasma so dense that it is immune to ion recombination on grains and PAHs. The FUV-ionized layer, of thickness 0.01-0.1 g cm-2, behaves in the ideal magnetohydrodynamic limit and can accrete at observationally significant rates at radii >~ 1-10 AU. Surface layer accretion driven by FUV ionization can reproduce the trend of increasing accretion rate with increasing hole size seen in transitional disks. At radii lsim1-10 AU, FUV-ionized surface layers cannot sustain the accretion rates generated at larger distance, and unless turbulent mixing of plasma can thicken the MRI-active layer, an additional means of transport is needed. In the case of transitional disks, it could be provided by planets.

Perez-Becker, Daniel; Chiang, Eugene

2011-07-01

392

Histochemistry of the surface mucous gel layer of the human colon.  

PubMed Central

BACKGROUND AND AIMS: Histochemical analysis of the surface mucous gel layer of the human colon is difficult, as it dissolves in fixatives. This study was undertaken to explore the surface mucous gel layer on the normal mucosa and neoplastic tissues of the large intestine. In addition, the distribution of different mucins secreted from goblet cells was studied with a series of histochemical stains for mucins. METHODS: Twenty four surgically resected specimens were fixed in Carnoy's solution and embedded in paraffin. In four cases, the surface mucous gel layer was also studied in frozen sections. Serial sections were stained by a battery of histochemical techniques characterising mucins. RESULTS AND CONCLUSION: The surface mucous gel layer consisted of the inner and outer layers. The first covered the luminal surface of the mucosa, consisted of mucins, and showed a vertical striped pattern. The second overlaid the first, showed a lateral striped pattern, and was contaminated with bacteria and other substances. Their thickness in paraffin sections varied considerably among the sites in the large intestine, but was the thickest in the rectum and measured 12.7 (SEM 6.0) microns and 88.8 (SEM 80.1) microns respectively. Mucins forming the inner layer were obviously derived from goblet cells underlying it. Images PMID:9245933

Matsuo, K; Ota, H; Akamatsu, T; Sugiyama, A; Katsuyama, T

1997-01-01

393

SURFACE LAYER ACCRETION IN CONVENTIONAL AND TRANSITIONAL DISKS DRIVEN BY FAR-ULTRAVIOLET IONIZATION  

SciTech Connect

Whether protoplanetary disks accrete at observationally significant rates by the magnetorotational instability (MRI) depends on how well ionized they are. Disk surface layers ionized by stellar X-rays are susceptible to charge neutralization by small condensates, ranging from {approx}0.01 {mu}m sized grains to angstrom-sized polycyclic aromatic hydrocarbons (PAHs). Ion densities in X-ray-irradiated surfaces are so low that ambipolar diffusion weakens the MRI. Here we show that ionization by stellar far-ultraviolet (FUV) radiation enables full-blown MRI turbulence in disk surface layers. Far-UV ionization of atomic carbon and sulfur produces a plasma so dense that it is immune to ion recombination on grains and PAHs. The FUV-ionized layer, of thickness 0.01-0.1 g cm{sup -2}, behaves in the ideal magnetohydrodynamic limit and can accrete at observationally significant rates at radii {approx}> 1-10 AU. Surface layer accretion driven by FUV ionization can reproduce the trend of increasing accretion rate with increasing hole size seen in transitional disks. At radii {approx}<1-10 AU, FUV-ionized surface layers cannot sustain the accretion rates generated at larger distance, and unless turbulent mixing of plasma can thicken the MRI-active layer, an additional means of transport is needed. In the case of transitional disks, it could be provided by planets.

Perez-Becker, Daniel [Department of Physics, University of California, Berkeley, CA 94720 (United States); Chiang, Eugene [Departments of Astronomy and Earth and Planetary Science, University of California, Berkeley, CA 94720 (United States)

2011-07-01

394

Effect of surface tension on swell-induced surface instability of substrate-confined hydrogel layers  

E-print Network

with Biot's periodic surface wave analysis. Several theoretical models have also been proposed for swelling due to inhomogeneous transient state of swelling.16,17 Second, the effect of surface energy or surface

Huang, Rui

395

Graphene plasmon enhanced vibrational sensing of surface-adsorbed layers.  

PubMed

We characterize the influence of graphene nanoribbon plasmon excitation on the vibrational spectra of surface-absorbed polymers. As the detuning between the graphene plasmon frequency and a vibrational frequency of the polymer decreases, the vibrational peak intensity first increases and is then transformed into a region of narrow optical transparency as the frequencies overlap. Examples of this are provided by the carbonyl vibration in thin films of poly(methyl methacrylate) and polyvinylpyrrolidone. The signal depth of the plasmon-induced transparency is found to be 5 times larger than that of light attenuated by the carbonyl vibration alone. The plasmon-vibrational mode coupling and the resulting fields are analyzed using both a phenomenological model of electromagnetically coupled oscillators and finite-difference time-domain simulations. It is shown that this coupling and the resulting absorption enhancement can be understood in terms of near-field electromagnetic interactions. PMID:24528250

Li, Yilei; Yan, Hugen; Farmer, Damon B; Meng, Xiang; Zhu, Wenjuan; Osgood, Richard M; Heinz, Tony F; Avouris, Phaedon

2014-03-12

396

On the impact of surface heterogeneity on a realistic convective boundary layer  

Microsoft Academic Search

Turbulent interactions of momentum and scalars within the convective boundary layer (CBL) over a heterogeneous surface can have a strong influence on both local flow properties and regional weather and climate. Using realistic heterogeneous surface flux data as well as mean vertical soundings obtained from the Soil-Moisture Atmosphere Coupling Experiment 2002 (SMACEX) as boundary and initial conditions in a large-eddy

Hsin-Yuan Huang; Steven A. Margulis

2009-01-01

397

The Role of Longwave Radiation and Boundary Layer Thermodynamics in Forcing Tropical Surface Winds  

Microsoft Academic Search

This paper reveals major deficiencies of the existing intermediate climate models for tropical surface winds and elaborates the important roles of cloud-longwave radiational forcing and boundary layer thermodynamics in driving the tropical surface winds. The heat sink associated with the cloud-longwave radiation is demonstrated as an important driving force for boreal summer northeast trades and Indian Ocean southwest monsoons. Over

XIOUHUA F UA; NDBIN WANG

1999-01-01

398

Frication Property of Mo-Cr-Infiltrated Steel Layer by Plasma Surface Metallurgy  

Microsoft Academic Search

Introduced in this article is the technique to acquire a high performance strengthened layer on carbon steel samples, namely, plasma alloying on the surface of Q235 steel and heat treatment technology. With this technique the alloying elements of Mo, Cr, and C can be obtained on the surface of Q235 steel samples. The content of the constituent elements is approximately

Jinyong Xu; Zhicheng Kang; Yanping Liu; Jianzhong Wang; Yuan Gao; Zhong Xu

2006-01-01

399

An inverse method for determining the elastic properties of thin layers using Love surface waves  

Microsoft Academic Search

Estimation of the mechanical and geometrical parameters of thin coatings and surface layers in materials is of great practical importance in engineering and technology. Indeed, surface properties of many vital engineering components, such as turbine blades, pistons, or bearings, directly affect the longevity and safety of modern machinery. In this article, the authors present a novel inversion procedure for simultaneous

P. Kie?czy?ski; M. Szalewski

2011-01-01

400

Metallic surfaces as alignment layers for nondisplay applications of liquid crystals  

Microsoft Academic Search

Nearly all liquid crystal devices use a rubbed organic layer as a method of orienting the liquid crystals. This letter studies the alignment of nematic liquid crystals by rubbed and nonrubbed metallic surfaces. For rubbed metallic films, a homogeneous planar alignment of liquid crystals is found. Nonrubbed metallic surfaces align liquid crystals nonuniformly and randomly. The alignment produced by a

Yu. Garbovskiy; L. Reisman; Z. Celinski; R. E. Camley; A. Glushchenko

2011-01-01

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