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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

Influence of ionic strength on the surface charge and interaction of layered silicate particles.  

PubMed

The surface charge densities and surface potentials of selected phyllosilicate surfaces were calculated from AFM surface force measurements and reported as a function of ionic strength at pH 5.6. The results show that the silica faces of clay minerals follow the constant surface charge model because of isomorphous substitution in the silica tetrahedral layer. A decreasing surface charge density sequence was observed as follows: muscovite silica face>kaolinite silica face>talc silica face, which is expected to be due to the extent of isomorphous substitution. In contrast, at pH 5.6, the alumina face and the edge surface of kaolinite follow the constant surface potential model with increasing ionic strength, and the surface charge density increased with increasing ionic strength. The cluster size of suspended kaolinite particles at pH 5.6 was found to increase with increasing ionic strength due to an increase in the surface charge density for the alumina face and the edge surface. However, the cluster size decreased at 100mM KCl as a result of an unexpected decrease in the surface charge of the alumina face. When the ionic strength continued to increase above 100mM KCl, the van der Waals attraction dominated and larger clusters of micron size were stabilized. PMID:25086721

Liu, Jing; Miller, Jan D; Yin, Xihui; Gupta, Vishal; Wang, Xuming

2014-10-15

3

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

4

Controlling mixed-protein adsorption layers on colloidal alumina particles by tailoring carboxyl and hydroxyl surface group densities.  

PubMed

We show that different ratios of bovine serum albumin (BSA) and lysozyme (LSZ) can be achieved in a mixed protein adsorption layer by tailoring the amounts of carboxyl (-COOH) and aluminum hydroxyl (AlOH) groups on colloidal alumina particles (d50 ? 180 nm). The particles are surface-functionalized with -COOH groups, and the resultant surface chemistry, including the remaining AlOH groups, is characterized and quantified using elemental analysis, ? potential measurements, acid-base titration, IR spectroscopy, electron microscopy, nitrogen adsorption, and dynamic light scattering. BSA and LSZ are subsequently added to the particle suspensions, and protein adsorption is monitored by in situ ? potential measurements while being quantified by UV spectroscopy and gel electrophoresis. A comparison of single-component and sequential protein adsorption reveals that BSA and LSZ have specific adsorption sites: BSA adsorbs primarily via AlOH groups, whereas LSZ adsorbs only via -COOH groups (1-2 -COOH groups on the particle surface is enough to bind one LSZ molecule). Tailoring such groups on the particle surface allows control of the composition of a mixed BSA and LSZ adsorption layer. The results provide further insight into how particle surface chemistry affects the composition of protein adsorption layers on colloidal particles and is valuable for the design of such particles for biotechnological and biomedical applications. PMID:23875793

Meder, Fabian; Kaur, Supreet; Treccani, Laura; Rezwan, Kurosch

2013-10-01

5

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

6

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

7

Electrokinetics of Concentrated Suspensions of Spherical Colloidal Particles with Surface Conductance, Arbitrary Zeta Potential, and Double-Layer Thickness in Static Electric Fields  

Microsoft Academic Search

In this paper the electrophoretic mobility and the electrical conductivity of concentrated suspensions of spherical colloidal particles have been numerically studied under arbitrary conditions including zeta potential, particle volume fraction, double-layer thickness (overlapping of double layers is allowed), surface conductance by a dynamic Stern layer model (DSL), and ionic properties of the solution. We present an extensive set of numerical

F. Carrique; F. J. Arroyo; A. V. Delgado

2002-01-01

8

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

E-print Network

Surface chemistry and infrared absorbance changes during ZnO atomic layer deposition on ZrO2 and Ba deposition (ALD) was achieved using sequential exposures of Zn CH2CH3 2 and H2O on ZrO2 and BaTiO3 particles spectroscopy. The BaTiO3 and ZrO2 particles initially displayed vibrational features consistent with surface

George, Steven M.

9

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

10

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

11

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

12

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

NASA Astrophysics Data System (ADS)

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

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

2015-03-01

13

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

14

Parameterization of the Atmospheric Surface Layer  

Microsoft Academic Search

A parameterization of the constant flux surface layer is developed in order to provide boundary conditions for numerical models of the atmospheric boundary layer and moist convective layer. Algebraic expressions are found for the turbulence covariances in the surface layer under all stability conditions.

M. J. Manton; W. R. Cotton

1977-01-01

15

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

16

Light emission during impact stressing of a particle layer  

NASA Astrophysics Data System (ADS)

The mechanical stress detection technique was developed based on light emission properties of ZnS:Mn particles. The light emission properties of ZnS:Mn particles were characterized by the use of the impact tester that includes a stressing tool, photomultiplier and a contact time measurement system. The mechanical stressing of particles was caused by the impact of a metallic ball, dropped from different heights. At impact, the metallic ball achieves direct contact with the upper surface of the metallic anvil. This allows the measurement of the contact time by means of the electrical current that flows between the anvil and the metallic ball during contact time. The stress, caused at the collision, is transmitted through a metallic anvil to the layer of particles and produces the deformation of particles. The applied stress was detected using a piezoelectric sensor. It was shown that the ZnS:Mn particles generate the light during the action of the loading force. After removal of the loading force the light emission from the particle layer disappears in a few microseconds. The measurement was carried out using different ranges of applied forces. In this way, it was shown that the particle layer exhibits a high damping factor and failure resistance. One of the possible applications of these sensor systems based on light emission properties of ZnS:Mn particles is structural health monitoring.

Pisarevskiy, A.; Aman, S.; Tatmyshevskiy, K.; Hirsch, S.; Tomas, J.

2015-04-01

17

Detector for Particle Surface Contamination  

NASA Technical Reports Server (NTRS)

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

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

1999-01-01

18

Double layers acting as particles accelerators  

SciTech Connect

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

Sanduloviciu, M.; Lozneanu, E. [Al. I. Cuza Univ. (Romania)

1995-12-31

19

Porosity and tortuosity of layer-by-layer assemblies of spherical particles  

NASA Astrophysics Data System (ADS)

We have used the extended random sequential adsorption model of hard spheres to mimic the layer by layer self-assembling process of monodisperse colloidal particles at a solid-liquid interface. We have studied five multilayers of similar thickness, each created at a different single-layer surface coverage. Our results suggest that the single-layer coverage has a significant effect on the film transport properties. The local values of multilayer porosity and tortuosity exhibit decaying oscillatory variations in the distance range dependent on the surface coverage. The mean multilayer porosity and tortuosity describe equations linear with respect to the surface coverage. The mean tortuosity and porosity of multilayers created with our model are also connected by a linear equation valid for any single-layer coverage and any number of layers. We have also determined the normalized equivalent thickness of stagnant solution layer as a function of the multilayer coverage and number of layers. This parameter grows asymptotically with the number of layers and can be approximated with good accuracy by the ratio of the squared mean tortuosity to the mean porosity of a multilayer.

Batys, Piotr; Wero?ski, Pawe?

2014-09-01

20

WOCE Ocean Surface Layer Group  

NASA Astrophysics Data System (ADS)

The initial meeting of a U.S. working group to consider the surface layers of the ocean and their role in the World Ocean Circulation Experiment (WOCE) was held January 25, 1985, at the Scripps Institution of Oceanography (SIO) in La Jolla, Calif., under the auspices of the U.S. WOCE Science Steering Committee. Present were A. Bennett (Institute of Ocean Sciences, Sydney, Canada), F. Bretherton (National Center for Atmospheric Research (NCAR), Boulder, Colo.), C. Collins (National Science Foundation (NSF), Washington, D.C.), R. Davis (SIO), R. deSzoeke (Oregon State University (OSU), Corvallis), D. Halpern (University of Washington, Seattle), W. Large (NCAR), J . Luyten (Woods Hole Oceanographic Institution (WHOI), Woods Hole, Mass.), J. McWilliams, (NCAR), W. Nowlin (Texas A&M University, College Station, Tex.), C. Paulson (OSU), C. Rooth (Rosenstiel School of Marine and Atmospheric Sciences, Miami, Fla.), R. Weiss (SIO), R. Weller (WHOI), W. White (SIO), and C. Wunsch (Massachusetts Institute of Technology, Cambridge, Mass.).

deSzoeke, Roland

21

Elastic Properties of Liquid Surfaces Coated with Colloidal Particles  

E-print Network

The physical mechanism of elasticity of liquid surfaces coated with colloidal particles is proposed. It is suggested that particles are separated by water clearings and the capillary interaction between them is negligible. The case is treated when the colloidal layer is deformed normally to its surface. The elasticity arises as an interfacial effect. The effective Young modulus of a surface depends on the interfacial tension, equilibrium contact angle, radius of colloidal particles and their surface density. For the nanometrically scaled particles the line tension becomes essential and has an influence on the effective Young modulus.

Edward Bormashenko; Gene Whyman; Oleg Gendelman

2015-03-10

22

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

23

Vacuum probe sampler removes micron-sized particles from surfaces  

NASA Technical Reports Server (NTRS)

Vacuum probe sampler removes micron-sized particles from sensitive surfaces, without damage to the surface. The probe has a critical orifice to ensure an optimum airflow rate that disturbs the boundary layer of air and raises bacteria from the surface into the probe with the moving air stream.

Whitfield, W. J.

1968-01-01

24

Shielding by an electron surface layer  

Microsoft Academic Search

We seek to determine whether the shielding observed in the electron free-fall experiment could be performed by electrons in a surface layer. An idealized model is used to estimate the shielding of the uniform electric field produced by the gravitational compression of the ionic lattice. We allow for the possibility that the charges in the surface layer can obey either

Richard Squier Hanni; John M. Madey

1978-01-01

25

Mercury: Remote Estimation of Surface Layer Structure  

NASA Astrophysics Data System (ADS)

Results of the optical observations of Mercury and the Moon confirm the close simi- larity of photometric properties of the bodies. Experience of lunar studies shows that space weathering processes on the Mercury (such as micrometeorite bombardment, solar wind ion bombardment etc.) can form properties of the upper layer of regolith. The amount of fused glassy particles and others agglutinates in the lunar upper layer is the direct index of the soil reworking caused be the micrometeorite bombardment. Besides, this micrometeorite bombardment is also responsible for the mechanical pro- cess through which the large particles are broken down into smaller ones. For lunar re- golith was showed that increasingly mature soils become progressively finer-grained, better-sorted, and composed of a greater proportion of agglutinates. The increasing rate of the fused glassy fragments, of agglutinates, and of fine size fraction in the regolith during its space weathering affects the polarization of the light reflected by an exposed lunar or Mercurian soil. Therefore, polarimetric properties of the regolith may be modified by the soil reworking process in the course of time. Comparison of the lunar and Mercurian optic observations confirms the remarkable similarity of the polarimetric properties of Mercury and the Moon. From of summary of polarization measurements of whole disk of Mercury it is possible to conclude that maturity of the soil on the Mercurian surface in scale of whole disk is similar to one in large old craters on the lunar highland. Comparison of the lunar and Mercurian disk-integrated photometric functions indicates the likeness of the surface layer structures of the bod- ies. Analysis of the phase curve inclination and magnitude of the opposition effect shows that Mercurian relief in scale of meter details is smoother than lunar one. It was measured brightness of number of small plots (10x10 cm) on the lunar surface (Luna-13 data). The range of phase angles was from 68 to 75 deg. These values close correlate with corresponding part of the Mercurian disk-integrated phase function. ItSs possible if Mercurian phase function received from Earth-based telescopes and lunar one received in cm-scale is coincided the structures of regolith may be similar in both cases. These conclusions may be used for planning BepiColombo mission. This work was supported by INTAS-ESA grant No. 99-00403.

Shevchenko, V. V.

26

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

27

Electromagnetic precipitation and ducting of particles in turbulent boundary layers  

Microsoft Academic Search

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

K. R. Davey; J. R. Melcher

1980-01-01

28

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

29

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

30

The coherent structure of atmospheric surface layers  

Microsoft Academic Search

The structure of two-point correlation statistics in the atmospheric surface layer are studied from measurements on the western Utah salt flats at the SLTEST facility. Large-scale features in the stable, neutral and unstable surface layers that adhere to Monin-Obukhov similarity (-10

Kapil Chauhan; Nick Hutchins; Ivan Marusic; Jason Monty

2010-01-01

31

Mixing layer under a free surface  

NASA Astrophysics Data System (ADS)

In the long-wave approximation, the flow of a homogeneous fluid with a free surface in the gravity field is considered. Mathematical models of the surface turbulent layer in shear flows are derived. Steady solutions of the problem of evolution of the mixing layer under the free surface and formation of a surface turbulent jet are constructed. In particular, the problem of the structure of a turbulent bore in a supercritical flow is solved, and the conditions for the formation of a local subcritical zone ahead of the obstacle are studied.

Liapidevskii, V. Yu.; Chesnokov, A. A.

2014-03-01

32

Laser treatment of alumina surface with chemically distinct carbide particles  

NASA Astrophysics Data System (ADS)

Laser treatment of pre-prepared alumina tile surface with a carbon film containing a mixture of 3 wt% TiC and 3 wt% B4C hard particles was conducted. Morphological and metallurgical changes at the laser treated surface were examined using optical and electron scanning microscopes, energy dispersive spectroscopy, and X-ray diffraction. Microhardness and fracture toughness of the treated surface were measured together with indentation tests. Residual stress generated at the surface region was determined from the X-ray diffraction data. It was found that TiC and B4C hard particles cause micro-crack formation in the vicinity of hard particles on the surface. This behavior is attributed to the differences between the thermal expansion coefficients of these particles. The laser treated surface is composed of a dense layer with fine sized grains and columnar structures formed below the dense layer. The presence of hard particles enhances the microhardness and lowers the fracture toughness of the surface. The formation of nitride compounds (AlN and AlON) contributes to volume shrinkage in the dense layer. Residual stress formed in the surface region is compressive.

Yilbas, Bekir S.; Ali, Haider

2014-12-01

33

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

NASA Technical Reports Server (NTRS)

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

Hughes, David W. (Inventor)

2012-01-01

34

Correlation studies on surface particle detection methods  

NASA Technical Reports Server (NTRS)

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

Peterson, Ronald V.; White, James C.

1988-01-01

35

Surface layering properties of Intralipid phantoms  

NASA Astrophysics Data System (ADS)

Intralipid has become an extensively studied and widely used reference and calibration phantom for diffuse optical imaging technologies. In this study we call attention to the layering properties of Intralipid emulsions, which are commonly assumed to have homogeneous optical properties. By measurement of spatial frequency domain reflectance in combination with an analytical solution of the radiative transfer equation for two-layered media, we make quantitative investigations on the formation of a surface layer on different dilutions of Intralipid. Our findings are verified by an independent spatially resolved reflectance setup giving evidence of a time dependent, thin and highly scattering surface layer on top of Intralipid-water emulsions. This layer should be considered when using Intralipid as an optical calibration or reference phantom.

Bodenschatz, Nico; Krauter, Philipp; Foschum, Florian; Nothelfer, Steffen; Liemert, André; Simon, Emanuel; Kröner, Sabrina; Kienle, Alwin

2015-02-01

36

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

SciTech Connect

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

Longrie, Delphine, E-mail: delphine.longrie@asm.com; Deduytsche, Davy; Detavernier, Christophe, E-mail: christophe.detavernier@ugent.be [Department of Solid State Sciences, Ghent University, Krijgslaan 281/S1, B-9000 Gent (Belgium)

2014-01-15

37

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

38

Surface layer effects on waste glass corrosion  

SciTech Connect

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

Feng, X.

1993-12-31

39

Structurized surface layers of normal alkanes  

NASA Astrophysics Data System (ADS)

The elevated viscosity of micron interlayers of certain normal alkanes compared to their viscosity in the "volume" is determined experimentally in shear flow using a rotational viscometer. The observed difference is considered to be caused by the manifestation, in such interlayers, of structural inhomogeneity due to the presence of structurized polymolecular surface layers on the substrates bounding them. The structural parameters of such layers, i.e., their equilibrium initial thickness and "hydrodynamic strength," are calculated in the model of a constant-viscosity layer. The measured effective viscosity of the interlayers diminishes with growth in the shear-flow velocity, which is attributed to the "cutting" of the structurized layer. Surfactant doping of the liquids leads to an increase in the effective viscosity of the interlayers, which is produced by the strengthening of the layer structure.

Altoiz, B. A.; Kiriyan, S. V.

2010-07-01

40

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

EPA Science Inventory

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

41

Boundary layer flow on a vibrating surface  

NASA Astrophysics Data System (ADS)

Boundary layers subjected to vibrating surfaces occur in many engineering applications. The surfaces of vehicles may vibrate, for instance, a ship’s hull vibrates at varying eigenfrequencies and eigenmodes due to the power plant of these vessels. There is little information available on this subject, and it is therefore not generally understood how these vibrations affect the fluid flows on the vibrating surface. To investigate these phenomena in greater detail, a test rig is designed and evaluated. The rig consists of a vibrating surface attached to a larger flat plate mounted in a low-speed wind tunnel. Two-dimensional vibrations of the surface in the fundamental mode are considered, and therefore the vibrating surface is clamped only on two sides to the flat plate. The surface is excited in the centerline using a crankshaft with adjustable amplitude (0-5 mm), designed and manufactured for this purpose. A frequency range of zero up to the first fundamental frequency of the surface can be studied. Detailed information of the rig and its performance characteristics along with preliminary measurements in the boundary layer over the vibrating surface will be presented.

Carlsson, Fredrik; Bakchinov, Andrey; Löfdahl, Lennart

2000-11-01

42

Damage Free Particle Removal from EUVL Mask Layers by High Energy Laser Shock Cleaning (LSC)  

Microsoft Academic Search

The paper deals about the method of small particle removal based on laser induced plasma (LIP) shock wave has been recently applied to clean wafers and masks in semiconductor processes. The silica particles of 50 nm removed from EUVL mask layers by high energy LSC without surface damage by controlling the gap distance. High temperature of plasma plume by the

Tae-Gon Kim; Young-Sam Yoo; Il-Ryong Son; Tae-Geun Kim; Jinho Ahn; Jong-Myoung Lee; Jae-Sung Choi; A. A. Busnaina; Jin-Goo Park

2007-01-01

43

On the structure formation of hydrophobed particles in the boundary layer of water and octane phases  

Microsoft Academic Search

Two-dimensional aggregation of the surface modified glass beads was carried out in the boundary layer of water and octane phases. The effect of particles' hydrophobicity was investigated on the structure of forming aggregates and the growth process. The structure of the aggregates and their growth were characterized by a density function which demonstrates the change of mean particle density as

Z. Hórvölgyi; G. Medveczky; M. Zrinyi

1993-01-01

44

Effect of mechanical activation on the structure of adsorbed polymer layers on the surface of pigment particles in aqueous disperse systems  

Microsoft Academic Search

In the context of the wide use of disperse systems, it is important to develop new methods for improving their quality and controllably changing their properties, including the production of aqueous suspensions of highly stable finely dispersed pigments used as components of paints and varnishes, oil and fuel additives, etc. Among the problems involved are surface phenomena; polymer adsorption on

R. F. Ganiev; N. A. Bulychev; V. N. Fomin; I. A. Arutyunov; S. D. Eisenbach; V. P. Zubov; E. B. Malyukova

2008-01-01

45

Characteristics of the Martian atmosphere surface layer  

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

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

Surface shear stress fluctuations in the atmospheric surface layer  

Microsoft Academic Search

A lightweight, high frequency response (25Hz), floating element sensor was used to measure wall shear stress fluctuations in the atmospheric surface layer formed over a salt flat at the SLTEST site, Utah, USA. The sensor uses a laser position measurement system to track the motion of the floating element which consisted of a 50mm diameter foam disc, as described by

Jason Monty; Nick Hutchins; Min Chong

2005-01-01

48

The coherent structure of atmospheric surface layers  

NASA Astrophysics Data System (ADS)

The structure of two-point correlation statistics in the atmospheric surface layer are studied from measurements on the western Utah salt flats at the SLTEST facility. Large-scale features in the stable, neutral and unstable surface layers that adhere to Monin-Obukhov similarity (-10surface layers. The changes in structure of Ruu can be characterized by z/? making it feasible to incorporate the trends in near-wall models of LES of atmospheric flows under stable and unstable conditions.

Chauhan, Kapil; Hutchins, Nick; Marusic, Ivan; Monty, Jason

2010-11-01

49

Characteristics of the Martian atmosphere surface layer  

NASA Technical Reports Server (NTRS)

Researchers extend elements of various terrestrial boundary layer models to Mars in order to estimate sensible heat, latent heat, and momentum fluxes within the Martian atmospheric surface layer. To estimate the molecular viscosity and thermal conductivity of a CO2-H2O gas mixture under Martian conditions, parameterizations were developed. Parameterizations for specific heat and and binary diffusivity were also determined. The Prandtl and Schmidt numbers derived from these thermophysical properties were found to range from 0.78 - 1.0 and 0.47 - 0.70, respectively, for Mars. Brutsaert's model for sensible and latent heat transport within the interfacial sublayer for both aerodynamically smooth and rough airflow was experimentally tested under similar conditions, validating its application to Martian conditions. For the surface sublayer, the researchers modified the definition of the Monin-Obukhov length to properly account for the buoyancy forces arising from water vapor gradients in the Martian atmospheric boundary layer. This length scale was then utilized with similarity theory turbulent flux profiles with the same form as those used by Businger et al. and others. It was found that under most Martian conditions, the interfacial and surface sublayers offer roughly comparable resistance to sensible heat and water vapor transport and are thus both important in determining the associated fluxes.

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

1991-01-01

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

Surface sulfur measurements on stratospheric particles  

Microsoft Academic Search

The surface chemistries of three particulate samples collected from the lower stratosphere have been determined using a Scanning Auger Microprobe (SAM). These samples are typical of the most abundant natural and anthropogenic particles observed within the stratosphere in the greater-than-2-micron diameter size fraction. Succsessive sputtering and analysis below the first few adsorbed monolayers of all particles shows the presence of

I. D. R. MacKinnon; D. W. Mogk

1985-01-01

53

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

54

Analysis of surface layers on bioactive glasses.  

PubMed

FT-Raman spectroscopy proves to be a powerful technique to study surface reactions on bioactive glasses and it eliminates the fluorescence of the organic phase of whole bone, thereby making it possible to compare the reaction layers formed on bioactive glasses with the mineral phase of bone. The spectrum of hydroxycarbonate apatite (HCA) developed on the bioactive glasses is closer to that of bone than synthetic hydroxyapatite (HA) and closely matches that of bone mineral obtained by deproteination of whole human femoral cortical bone. PMID:7986953

Rehman, I; Hench, L L; Bonfield, W; Smith, R

1994-08-01

55

Surface Properties of PEMFC Gas Diffusion Layers  

SciTech Connect

The wetting properties of PEMFC Gas Diffusion Layers (GDLs) were quantified by surface characterization measurements and modeling of material properties. Single-fiber contact-angle and surface energy (both Zisman and Owens-Wendt) data of a wide spectrum of GDL types is presented to delineate the effects of hydrophobic post-processing treatments. Modeling of the basic sessile-drop contact angle demonstrates that this value only gives a fraction of the total picture of interfacial wetting physics. Polar forces are shown to contribute 10-20 less than dispersive forces to the composite wetting of GDLs. Internal water contact angles obtained from Owens-Wendt analysis were measured at 13-19 higher than their single-fiber counterparts. An inverse relationship was found between internal contact angle and both Owens-Wendt surface energy and % polarity of the GDL. The most sophisticated PEMFC mathematical models use either experimentally measured capillary pressures or the standard Young-Laplace capillary-pressure equation. Based on the results of the Owens-Wendt analysis, an advancement to the Young-Laplace equation is proposed for use in these mathematical models, which utilizes only solid surface energies and fractional surface coverage of fluoropolymer. Capillary constants for the spectrum of analyzed GDLs are presented for the same purpose.

WoodIII, David L [Los Alamos National Laboratory (LANL); Rulison, Christopher [Augustine Scientific; Borup, Rodney [Los Alamos National Laboratory (LANL)

2010-01-01

56

Beta particle monitor for surfaces  

DOEpatents

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

MacArthur, Duncan W. (Los Alamos, NM)

1997-01-01

57

Beta particle monitor for surfaces  

DOEpatents

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

MacArthur, D.W.

1997-10-21

58

The Surface Layer during Artificial Carious Lesion Formation  

Microsoft Academic Search

This paper gives a detailed description of the development of the surface layer during demineralization of human enamel. Optical inspection of microradiograms of lesions in different stages of development can give the impression that the surface layer increases in thickness with time. Using a more objective method of inspection together with an explicit description, the development of the surface layer

H. M. Theuns; J. W. E. van Dijk; F. C. M. Driessens; A. Groeneveld

1984-01-01

59

Body surface adaptations to boundary-layer dynamics.  

PubMed

Evolutionary processes have adapted nektonic animals to interact efficiently with the water that surrounds them. Not all these adaptations serve the same purpose. This paper concentrates on reduction of drag due to friction in the boundary layer close to the body surface. Mucus, compliant skins, scales, riblets and roughness may influence the flow velocity gradient, the type of flow and the thickness of the boundary layer around animals, and may seriously affect their drag in a positive or negative way. The long-chain polymers found in mucus decrease the pressure gradient and considerably reduced drag due to friction. The effect is probably due to channelling of the flow particles in the direction of the main flow, resulting in a reduction of turbulence. Compliant surfaces could probably reduce drag by equalising and distributing pressure pulses. However, the existing evidence that drag reduction actually occurs is not convincing. There is no indication that instantaneous heating, reducing the viscosity in the boundary layer, is used by animals as a drag-reducing technique. Small longitudinal ridges on rows of scales on fish can reduce shear stress in the boundary by a maximum of 10% compared with the shear stress of a smooth surface. The mechanism is based on the impedance of cross flow under well-defined conditions. The effect has been visualized with the use of particle image velocimetry techniques. The function of the swords and spears of several fast, pelagic, predatory fish species is still enigmatic. The surface structure of the sword of a swordfish is shown to be both rough and porous. The height of the roughness elements on the tip of the sword is close to the critical value for the induction of a laminar-to-turbulent flow transition at moderate cruising speeds. A flow tank is described that is designed to visualize the effects of surface imperfections on flow in the boundary layer in direct comparison with a smooth flat wall. The flow in a 1 m long, 10 cm high and 1 cm wide channel is visualized by illuminating the particles in a thin laser light sheet. The first results show that a rough surface increases the shear stress in the boundary layer and makes it thinner. The function of the roughness on the sword of a swordfish is probably to reduce the total drag by generating premature turbulence and by boundary layer thinning, despite an increased friction over the surface of the sword. The function of the porous surface structures on the sword, and of the porous skins of sharks and of the castor oil fish, will probably be discovered soon using new particle image velocimetry techniques applied under strong magnification to visualize the local behaviour of the flow. PMID:8571218

Videler, J J

1995-01-01

60

Electrorotation of colloidal particles and cells depends on surface charge.  

PubMed Central

The importance of surface conductivity to the frequency-dependent polarizability and the rotation of particles in circular electric fields (electrorotation) is emphasized by various theoretical and experimental investigations. Although surface conductivity seems to be naturally related to the ionic double layer, there is rare experimental evidence of a direct relationship. To highlight the role of surface charges in electrorotation, an apparatus was developed with a symmetrical three-electrode arrangement for field frequencies between 25 Hz and 80 MHz. The three-dimensional electrostatic field distribution between the electrodes was evaluated numerically. With this device, rotating, gradient, and homogeneous electric fields of defined precision and homogeneity could be applied to slightly conducting suspensions. Surface properties of monodisperse latex particles (O 9.67 microm), carrying weak acid groups, were characterized by suspension conductometric titration. This procedure determined the amount of carboxyl groups and showed that strong acid groups were missing on the surface of these particles. To obtain the electrophoretic mobility, the spheres were separated by free-flow electrophoresis, and the zeta-potential was calculated from these data. Single-particle rotation experiments on fractions of specified electrophoretic mobility were carried out at frequencies between 25 Hz and 20 MHz. By analyzing the pH dependence of the rotation velocity, it could be shown that the rotation rate is determined by surface charges, both at the peak in rotation rate near the Maxwell-Wagner frequency (MWF) and at low frequencies. The inversion of the rotation direction at the MWF peak for vanishing surface charges was demonstrated. An analytical model for the double layer and dissociation on a charged surface was developed that is valid for low and high zeta-potentials. This model could provide convincing evidence of the linear dependence of the MWF rotation velocity on surface charge. Images FIGURE 1 PMID:9284328

Maier, H

1997-01-01

61

Electrorotation of colloidal particles and cells depends on surface charge.  

PubMed

The importance of surface conductivity to the frequency-dependent polarizability and the rotation of particles in circular electric fields (electrorotation) is emphasized by various theoretical and experimental investigations. Although surface conductivity seems to be naturally related to the ionic double layer, there is rare experimental evidence of a direct relationship. To highlight the role of surface charges in electrorotation, an apparatus was developed with a symmetrical three-electrode arrangement for field frequencies between 25 Hz and 80 MHz. The three-dimensional electrostatic field distribution between the electrodes was evaluated numerically. With this device, rotating, gradient, and homogeneous electric fields of defined precision and homogeneity could be applied to slightly conducting suspensions. Surface properties of monodisperse latex particles (O 9.67 microm), carrying weak acid groups, were characterized by suspension conductometric titration. This procedure determined the amount of carboxyl groups and showed that strong acid groups were missing on the surface of these particles. To obtain the electrophoretic mobility, the spheres were separated by free-flow electrophoresis, and the zeta-potential was calculated from these data. Single-particle rotation experiments on fractions of specified electrophoretic mobility were carried out at frequencies between 25 Hz and 20 MHz. By analyzing the pH dependence of the rotation velocity, it could be shown that the rotation rate is determined by surface charges, both at the peak in rotation rate near the Maxwell-Wagner frequency (MWF) and at low frequencies. The inversion of the rotation direction at the MWF peak for vanishing surface charges was demonstrated. An analytical model for the double layer and dissociation on a charged surface was developed that is valid for low and high zeta-potentials. This model could provide convincing evidence of the linear dependence of the MWF rotation velocity on surface charge. PMID:9284328

Maier, H

1997-09-01

62

Surface shear stress fluctuations in the atmospheric surface layer  

NASA Astrophysics Data System (ADS)

A lightweight, high frequency response (25Hz), floating element sensor was used to measure wall shear stress fluctuations in the atmospheric surface layer formed over a salt flat at the SLTEST site, Utah, USA. The sensor uses a laser position measurement system to track the motion of the floating element which consisted of a 50mm diameter foam disc, as described by Heuer & Marusic (Meas. Sci. Tech., Vol. 16, 1644- -1649, 2005). The measurements were taken as part of an internationally coordinated experimental program designed to make extensive spatial and temporal measurements of velocity, temperature and wall shear stress of the surface layer. Velocity measurements were made with both a 30m high vertical array and a 100m wide horizontal array of sonic anemometers; 18 anemometers in total were employed. Cross-correlations of shear stress and streamwise velocity fluctuations were analysed in an attempt to identify structure angles in the flow. The results were also compared with experimental data from controlled, laboratory turbulent boundary layers having three orders of magnitude lower Reynolds number.

Monty, Jason; Hutchins, Nick; Chong, Min

2005-11-01

63

Surface plasmon resonance on the surface: metal - liquid crystal layer  

NASA Astrophysics Data System (ADS)

Surface plasmon resonance (SPR) is widely used in different types of optical detection schemes and for light manipulation at sub-wavelength scale. Usually Kretschmann configuration is used for effective SPR excitation. There are a lot of experimental and theoretical investigations about the influence of the dielectric, adjacent to the metal, on SPR. However, till now the influence on liquid crystal layer, adjacent to the metal, is not considered to our best knowledge. The purpose of the present paper is to cover this gap. We simulate the influence of thin layer of liquid crystal, adjacent to the metal, on the SPR characteristics. For this purpose Maxwell equations are numerically solved for layer structure: prism/gold/liquid crystal/air. The light reflection spectra are calculated for chiral structure of ferroelectric smectic C (SmC*) liquid crystal layer. The angular and wavelength response are considered. Special attention is paid to SPR excitation for variation of tilt angle and different angle of incident light. The influence of SPR of the pitch length and cell thickness is also considered.

Zhelyazkova, K.; Petrov, M.; Katranchev, B.; Dyankov, G.

2014-12-01

64

Texturing of layered surfaces for optimal viewing.  

PubMed

This paper is a contribution to the literature on perceptually optimal visualizations of layered three-dimensional surfaces. Specifically, we develop guidelines for generating texture patterns, which, when tiled on two overlapped surfaces, minimize confusion in depth-discrimination and maximize the ability to localize distinct features. We design a parameterized texture space and explore this texture space using a "human in the loop" experimental approach. Subjects are asked to rate their ability to identify Gaussian bumps on both upper and lower surfaces of noisy terrain fields. Their ratings direct a genetic algorithm, which selectively searches the texture parameter space to find fruitful areas. Data collected from these experiments are analyzed to determine what combinations of parameters work well and to develop texture generation guidelines. Data analysis methods include ANOVA, linear discriminant analysis, decision trees, and parallel coordinates. To confirm the guidelines, we conduct a post-analysis experiment, where subjects rate textures following our guidelines against textures violating the guidelines. Across all subjects, textures following the guidelines consistently produce high rated textures on an absolute scale, and are rated higher than those that did not follow the guidelines. PMID:17080843

Bair, Alethea S; House, Donald H; Ware, Colin

2006-01-01

65

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

66

Surface preparation of substances for continuous convective assembly of fine particles  

SciTech Connect

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

67

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

SciTech Connect

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

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

1982-09-27

68

Preparation and Surface Layer Modification of Silicon Nanoparticles Dispersed in 2-Propanol  

NASA Astrophysics Data System (ADS)

Silicon nanoparticles dispersed in 2-propanol were prepared by using an arc plasma with gas flow method in a new designed home-made apparatus. The particles are composed of silicon crystal core covered by oxidized amorphous silicon shell. The composition of the particle surface layer can be modified by preparing the sample in different atmosphere. The particles can be also obtained with different core composition and different size which we need.

Zhu, Yong; S, Iwasaki; K, Kimura; Zhang, Li-de

1998-12-01

69

Electrophoresis of a charged soft particle in a charged cavity with arbitrary double-layer thickness.  

PubMed

An analysis for the quasi-steady electrophoretic motion of a soft particle composed of a charged spherical rigid core and an adsorbed porous layer positioned at the center of a charged spherical cavity filled with an arbitrary electrolyte solution is presented. Within the porous layer, frictional segments with fixed charges are assumed to distribute uniformly. Through the use of the linearized Poisson-Boltzmann equation and the Laplace equation, the equilibrium double-layer potential distribution and its perturbation caused by the applied electric field are separately determined. The modified Stokes and Brinkman equations governing the fluid flow fields outside and inside the porous layer, respectively, are solved subsequently. An explicit formula for the electrokinetic migration velocity of the soft particle in terms of the fixed charge densities on the rigid core surface, in the porous layer, and on the cavity wall is obtained from a balance between its electrostatic and hydrodynamic forces. This formula is valid for arbitrary values of ?a, ?a, r0/a, and a/b, where ? is the Debye screening parameter, ? is the reciprocal of the length characterizing the extent of flow penetration inside the porous layer, a is the radius of the soft particle, r0 is the radius of the rigid core of the particle, and b is the radius of the cavity. In the limiting cases of r0 = a and r0 = 0, the migration velocity for the charged soft sphere reduces to that for a charged impermeable sphere and that for a charged porous sphere, respectively, in the charged cavity. The effect of the surface charge at the cavity wall on the particle migration can be significant, and the particle may reverse the direction of its migration. PMID:23898800

Chen, Wei J; Keh, Huan J

2013-08-22

70

Superhydrophobic surfaces fabricated by surface modification of alumina particles  

NASA Astrophysics Data System (ADS)

The fabrication of superhydrophobic surfaces has attracted intense interest because of their widespread potential applications in various industrial fields. Recently, some attempts have been carried out to prepare superhydrophobic surfaces using metal oxide nanoparticles. In the present work, superhydrophobic surfaces were fabricated with low surface energy material on alumina particles with different sizes. It was found that particle size of alumina is an important factor in achieving stable superhydrophobic surface. It was possible to obtain alumina surface with water contact angle (WCA) of 156° and a sliding angle of <2°. Superhydrophobicity of the modified alumina is attributed to the combined effect of the micro-nanostructure and low surface energy of fatty acid on the surface. The surface morphology of the alumina powder and coatings was determined by FESEM. The stability of the coatings was assessed by conducting water immersion test. Effect of heat treatment on WCA of the coating was also studied. The transition of alumina from hydrophilic to superhydrophobic state was explained using Wenzel and Cassie models. The method is shown to have potential application for creating superhydrophobic surface on cotton fabrics.

Richard, Edna; Aruna, S. T.; Basu, Bharathibai J.

2012-10-01

71

Purification and Characterization ofCampylobacter rectus Surface Layer Proteins  

Microsoft Academic Search

Campylobacter rectus is a putative periodontopathogen which expresses a proteinaceous surface layer (S- layer) external to the outer membrane. S-layers are considered to play a protective role for the microorganism in hostile environments. The S-layer proteins from six different C. rectus strains (five human isolates and a nonhuman primate (NHP) isolate) were isolated, purified, and characterized. The S-layer proteins of

Hiroshi Nitta; Stanley C. Holt; Andjeffrey L. Ebersole

72

The Structure of the Near-Neutral Atmospheric Surface Layer  

Microsoft Academic Search

Recent observational data (turbulence variables by sonic anemometers and three-dimensional flow pattern by Doppler lidar), obtained during the Cooperative Atmosphere Surface Exchange Study field campaign in October 1999 (CASES-99), show evidence of a layered structure of the near-neutral surface layer: (i) the eddy surface layer (ESL), which is the lower sublayer where blocking of impinging eddies is the dominating mechanism;

Philippe Drobinski; Pierre Carlotti; Rob K. Newsom; Robert M. Banta; Ralph C. Foster; Jean-Luc Redelsperger

2004-01-01

73

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

PubMed Central

Surface activation of nanoparticles in suspension using amino organosilane has been carried out via strict control of a particle surface ad-layer of water using a simple but efficient protocol ‘Tri-phasic Reverse Emulsion’ (TPRE). This approach produced thin and ordered layers of particle surface functional groups which allowed the efficient conjugation of biomolecules. When used in bio-sensing applications, the resultant conjugates were highly efficient in the hybrid capture of complementary oligonucleotides and the detection of food borne microorganism. TPRE overcomes a number of fundamental problems associated with the surface modification of particles in aqueous suspension viz. particle aggregation, density and organization of resultant surface functional groups by controlling surface condensation of the aminosilane. The approach has potential for application in areas as diverse as nanomedicine, to food technology and industrial catalysis. PMID:22872809

Sen, Tapas; Bruce, Ian J.

2012-01-01

74

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

75

Surface heterogeneity effects on regional-scale fluxes in stable boundary layers: surface temperature transitions  

E-print Network

understanding of homogeneous stable boundary layers (SBLs). However, in general, the atmospheric boundary layerSurface heterogeneity effects on regional-scale fluxes in stable boundary layers: surface temperature distributions on regional-scale turbulent fluxes in the stable boundary layer (SBL). Simulations

Stoll, Rob

76

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

77

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

78

Near surface turbulence in a smooth wall atmospheric boundary layer  

E-print Network

1 Near surface turbulence in a smooth wall atmospheric boundary layer Scott C. Morris (s is to acquire measurements in the atmospheric boundary layer. For example, Van Atta and Chen (1970) used hot-wires in the atmospheric boundary layer over an ocean sur- face to learn more about structure functions in wall bounded

Morris, Scott C.

79

Radiative transfer theory for active remote sensing of a layer of nonspherical particles  

NASA Technical Reports Server (NTRS)

The radiative transfer theory is applied to calculate the scattering by a layer of randomly positioned and oriented nonspherical particles. The scattering amplitude functions of each individual particle are calculated with Waterman's T matrix method, which utilizes vector spherical wave functions for expansion of incident, scattered, and surface fields. The orientation of the particles is described by a probability density function of the Eulerian angles of rotation. A rotation matrix is used to relate the T matrix of the principal frame to that of the natural frame of the particle. The extinction matrix and phase matrix of the radiative transfer equations are expressed in terms of the T matrix elements. The extinction matrix for nonspherical particles is generally nondiagonal. There are only two attenuation rates in a specified direction of propagation. The radiative transfer equations are solved by an iterative method to first order in albedo. Numerical results are illustrated as functions of incidence angle and frequency with applications to active remote sensing.

Tsang, L.; Kong, J. A.; Shin, R. T.

1984-01-01

80

Remote estimation of the Mercury surface layer structure  

NASA Astrophysics Data System (ADS)

Results of the optical observations of Mercury and the Moon confirm the close similarity of photometric properties of the bodies. Experience of lunar studies shows that space weathering processes on the Mercury (such as micrometeorite bombardment, solar wind ion bombardment etc.) can form properties of the upper layer of regolith. The amount of fused glassy particles and others agglutinates in the lunar upper layer is the direct index of the soil reworking caused be the micrometeorite bombardment. Besides, this micrometeorite bombardment is also responsible for the mechanical process through which the large particles are broken down into smaller ones. For lunar regolith was showed that increasingly mature soils become progressively finer-grained, better-sorted, and composed of a greater proportion of agglutinates. The increasing rate of the fused glassy fragments, of agglutinates, and of fine size fraction in the regolith during its space weathering affects the polarization of the light reflected by an exposed lunar or Mercurian soil. Therefore, polarimetric properties of the regolith may be modified by the soil reworking process in the course of time. Comparison of the lunar and Mercurian optic observations confirms the remarkable similarity of the polarimetric properties of Mercury and the Moon. From of summary of polarization measurements of whole disk of Mercury it is possible to conclude that maturity of the soil on the Mercurian surface in scale of whole disk is similar to one in large old craters on the lunar highland. Comparison of the lunar and Mercurian disk-integrated photometric functions indicates the likeness of the surface layer structures of the bodies. Analysis of the phase curve inclination and magnitude of the opposition effect shows that Mercurian relief in scale of meter details is smoother than lunar one. It was measured brightness of number of small plots (10x10 cm) on the lunar surface (Luna-13 data). The range of phase angles was from 68 to 75 deg. These values close correlate with corresponding part of the Mercurian disk-integrated phase function. ItSs possible if Mercurian phase function received from Earth-based telescopes and lunar one received in cm-scale is coincided the structures of regolith may be similar in both cases. These conclusions may be used for planning BepiColombo mission. This work was supported by INTAS-ESA grant No. 99-00403.

Shevchenko, V.

81

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

82

Effects of Surface Modification of Rubber Particles on Pavement Concrete Performance  

Microsoft Academic Search

In this article, the effects of surface modification of rubber particles on slump, strength, fatigue property and shrinkage for 28d have been investigated. The results show that the interface finishing agent can improve the fluidity of rubberized concrete as well as the weak layer between cement matrix and rubber particles, and enhance the strength. The strength doesn't decrease significantly when

Liu Juan-hong; Sun Yong-mei; Song Shao-min

2010-01-01

83

Euler-Lagrange Modeling of Vortex Interaction with a Particle-Laden Turbulent Boundary Layer  

NASA Astrophysics Data System (ADS)

Rotorcraft operation in austere environments can result in difficult operating conditions, particularly in the vicinity of sandy areas. The uplift of sediment by rotorcraft downwash, a phenomenon known as brownout, hinders pilot visual cues and may result in a potentially dangerous situation. Brownout is a complex multiphase flow problem that is not unique and depends on both the characteristics of the rotorcraft and the sediment. The lack of fundamental understanding constrains models and limits development of technologies that could mitigate the adverse effects of brownout. This provides the over-arching motivation of the current work focusing on models of particle-laden sediment beds. The particular focus of the current investigations is numerical modeling of near-surface fluid-particle interactions in turbulent boundary layers with and without coherent vortices superimposed on the background flow, that model rotorcraft downwash. The simulations are performed with two groups of particles having different densities both of which display strong vortex-particle interaction close to the source location. The simulations include cases with inter-particle collisions and gravitational settling. Particle effects on the fluid are ignored. The numerical simulations are performed using an Euler- Lagrange method in which a fractional-step approach is used for the fluid and with the particulate phase advanced using Discrete Particle Simulation. The objectives are to gain insight into the fluid-particle dynamics that influence transport near the bed by analyzing the competing effects of the vortices, inter-particle collisions, and gravity. Following the introduction of coherent vortices into the domain, the structures convect downstream, dissipate, and then recover to an equilibrium state with the boundary layer. The particle phase displays an analogous return to an equilibrium state as the vortices dissipate and the boundary layer recovers, though this recovery is slower than for the fluid and is sensitive to the particle response time. The effects of inter-particle collisions are relatively strong and apparent throughout the flow, being most effective in the boundary layer. Gravitational settling increases the particle concentration near the wall and consequently increase inter-particle collisions.

Morales, Fernando

84

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

85

Surface plasma source with anode layer plasma accelerator  

SciTech Connect

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 [Muons, Inc., Batavia, Illinois 60510 (United States)

2012-02-15

86

Modes of ejecta emplacement at Martian craters from laboratory experiments of an expanding vortex ring interacting with a particle layer  

Microsoft Academic Search

Ejecta morphologies of many Martian craters indicate fluidized emplacement which differs from ballistic emplacement in dry, airless environments. Double Layered Ejecta craters possess particularly interesting ejecta morphologies: two lobes and radial lineations on their surface, which probably result from gas-dominated radial flow during the emplacement. To examine how a radial flow interacts with surface particles to generate some of the

A. Suzuki; I. Kumagai; Y. Nagata; K. Kurita; O. S. Barnouin-Jha

2007-01-01

87

Surface effects of thin luminescence LC layers  

NASA Astrophysics Data System (ADS)

The experimental investigation of the influence of electric field on luminescence of thin liquid crystal layers are presented. It is shown that the observed luminescence quenching is nearsurface phenomena dye to the exiton nature of liquid crystal luminescence.

Danilov, V. V.; Khrebtov, Igor A.

1996-01-01

88

Generation and characterization of surface layers on acoustically levitated drops  

Microsoft Academic Search

Surface layers of natural and technical amphiphiles, e.g., octadecanol, stearic acid and related compounds as well as perfluorinated fatty alcohols (PFA), have been investigated on the surface of acoustically levitated drops. In contrast to Langmuir troughs, traditionally used in the research of surface layers at the air–water interface, acoustic levitation offers the advantages of a minimized and contact-less technique. Although

Rudolf Tuckermann; Sigurd Bauerecker; Heiko K. Cammenga

2007-01-01

89

Characterization and use of crystalline bacterial cell surface layers  

NASA Astrophysics Data System (ADS)

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

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

2001-10-01

90

Inertial particles in a shearless mixing layer: direct numerical simulations  

NASA Astrophysics Data System (ADS)

Entrainment, the drawing in of external fluid by a turbulent flow, is present in nearly all turbulent processes, from exhaust plumes to oceanic thermoclines to cumulus clouds. While the entrainment of fluid and of passive scalars in turbulent flows has been studied extensively, comparatively little research has been undertaken on inertial particle entrainment. We explore entrainment of inertial particles in a shearless mixing layer across a turbulent-non-turbulent interface (TNI) and a turbulent-turbulent interface (TTI) through direct numerical simulation (DNS). Particles are initially placed on one side of the interface and are advanced in time in decaying turbulence. Our results show that the TTI is more efficient in mixing droplets than the TNI. We also find that without the influence of gravity, over the range of Stokes numbers present in cumulus clouds, particle concentration statistics are essentially independent of the dissipation scale Stokes number. The DNS data agrees with results from experiments performed in a wind tunnel with close parametric overlap. We anticipate that a better understanding of the role of gravity and turbulence in inertial particle entrainment will lead to improved cloud evolution predictions and more accurate climate models. Sponsored by the U.S. NSF.

Ireland, Peter; Collins, Lance

2010-11-01

91

Interactions of hyaluronan layers with similarly charged surfaces: the effect of divalent cations.  

PubMed

We used colloidal probe atomic force microscopy to measure the normal forces between the surface of a silica colloidal particle and a sparse layer of hyaluronan (hyaluronic acid, HA, MW ? 10(6) Da) covalently attached to a planar silica surface, both across pure water and following the addition of 1 mM MgCl2. It was found that in the absence of salt the HA layer repelled the colloidal silica surface during both approach and retraction. The addition of the MgCl2, however, changes the net force between the negatively charged HA layer and the opposing negatively charged silica surface from repulsion to adhesion. This interaction reversal is attributed to the bridging effect of the added Mg(2+) ions. Our results provide first direct force data to support earlier simulation and predictions that such divalent cations could bridge between negative charges on opposing surfaces, leading to an overall reversal of force from repulsion to attraction. PMID:24011082

Jiang, Lei; Titmuss, Simon; Klein, Jacob

2013-10-01

92

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

93

Surface layers on a borosilicate nuclear waste glass corroded in MgCl 2 solution  

NASA Astrophysics Data System (ADS)

Surface layers on the French borosilicate nuclear waste glass, R7T7, corroded in MgCl 2 solution were studied to determine the composition, structure and stability of crystalline phases. The characteristics of the phases constituting the surface layer varied with the parameter {S}/{V} × t , the glass surface area ( S) to solution volume ( V) ratio, times time ( t). At low {S}/{V} × t values (< 360 days/m; ? 36 d) th surface layer was thin and contained mainly iron hydroxide particles and hydrotalcite crystals. At an intermediate {S}/{V} × t value (2800 d/m; 5.5 y) the surface layer contained hydrotalcite-, chlorite- and saponite-type phases. At the highest {S}/{V} × t value (10 7 d/m; 463 d) the major phases were saponite, powellite, barite and cerianite solid solutions. About 95% of the uranium and > 98% of the neodymium released from the glass were precipitated in the surface layer. In the 463 day experiment, 86% of the neodymium in the surface layer was in solid solution with powellite, the rest with saponite. Uranium was contained exclusively in saponite. High {S}/{V} ratios, typical of disposal conditions for vitrified high-level radioactive waste, favor retention of actinides in fairly insoluble corrosion products. Observation of similar corrosion products on natural glasses as on nuclear waste glasses lend support to the hypothesis that the host phases for actinides observed in the laboratory are stable over geological periods of time.

Abdelouas, Abdesselam; Crovisier, Jean-Louis; Lutze, Werner; Grambow, Bernd; Dran, Jean-Claude; Müller, Regina

1997-01-01

94

Surface properties of red mud particles from potentiometric titration  

Microsoft Academic Search

Acid\\/basic potentiometric titration has been used to obtain data on the surface charge and the amount of surface hydroxyl groups on red mud particles generated from different bauxite sources. It has been demonstrated that this can be used to quantify the surface properties of red mud particles. Red mud particles carry a significant negative charge under the basic conditions that

D Chvedov; S Ostap; T Le

2001-01-01

95

Generation and characterization of surface layers on acoustically levitated drops.  

PubMed

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

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

2007-06-15

96

Chemical composition of pen surface layers of beef cattle feedyards  

Technology Transfer Automated Retrieval System (TEKTRAN)

The biological, physical, and chemical characteristics of beef cattle feedyard pen surfaces may affect nutrient transformations and losses to the atmosphere, ground water, or surface water. Feedyard pen surfaces can typically segregate into three or four layers. The purpose of this study was to dete...

97

Tailoring molecular layers at metal surfaces  

Microsoft Academic Search

The design of networks of organic molecules at metal surfaces, highly attractive for a variety of applications ranging from molecular electronics to gas sensors to protective coatings, has matured to a degree that patterns with multinanometre unit cells and almost any arbitrary geometry can be fabricated. This Review provides an overview of vacuum-deposited organic networks at metal surfaces, using intermolecular

Ludwig Bartels

2010-01-01

98

Particle assembly on patterned surfaces bearing circular (dots) and rectangular (stripes) surface features.  

PubMed

Irreversible and localized adsorption of spherical particles on surface features of various shapes (collectors) was studied using the random sequential adsorption (RSA) model. Collectors in the form of dots and rectangles were considered, including the two limiting cases of squares and stripes. Numerical simulation of the Monte Carlo type enabled one to determine particle configurations, average coverage of particles, and the distribution for various collector length to particle size ratios L = L/d and collector width to particle size ratios B = b/d. It was predicted that particle coverage under the jamming state was highly nonuniform, exhibiting a maximum at the center and at the periphery of the collectors. The averaged number of particles Np adsorbed at the jamming state was also determined as a function of the L and B parameters, as well as the averaged number of particles per unit length in the case of stripes. It was revealed that Np was the highest for the circular and square collectors (for a fixed value of L). On the other hand, for L > 5, our numerical results could be well approximated by the analytical expressions Np = thetainfinityL2 for circles, Np = 4thetainfinityL2/pi for squares, Np = 4thetainfinityBL/pi for rectangles, and Np = 4thetainfinityB/pi for stripes (per unit length). It was demonstrated that the theoretical results are in agreement with experimental data obtained for latex particles adsorbing on patterned surfaces obtained by a polymer-on-polymer stamping technique of gold covered silicon and on photolitographically patterned silane layers on silica. PMID:18198909

Adamczyk, Zbigniew; Barbasz, Jakub; Nattich, Ma?gorzata

2008-03-01

99

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.

100

Porosity determinations in buried and surface layers of porous silicon  

SciTech Connect

Gravimetric techniques offer a convenient and accurate method of determining surface layer porosity in both n- and p-type porous silicon (PS). Porosity of the PS affects its volume expansion on oxidation and the insulating properties of the resulting oxide. Optimal porosity (ca. 55%) yields fully dense, insulating oxides with minimal expansion-induced stresses. Two factors affect the porosity: chemical dissolution of PS by the anodization electrolyte, and oxidation of the PS to produce a native oxide on the surface. Buried layer porosities cannot normally be measured by gravimetric techniques unless the volume of the buried layer is large enough to yield a measurable weight change on anodization. We therefore used a form of Faraday's Law to determine buried layer porosities and determined that they can be correlated with porosities of surface layers formed under identical conditions. 9 refs., 4 figs.

Guilinger, T.R.; Kelly, M.J.; Tsao, S.S.

1987-01-01

101

Boride-enhanced diffusion in silicon: Bulk and surface layers  

Microsoft Academic Search

Epitaxial silicon boride layers, located at the surface or within the bulk of single-crystal silicon, give rise to enhanced diffusion of B during annealing. A submonolayer buried boride layer releases ~0.4 interstitials per B atom in the layer, generating a transient diffusion enhancement in the range of 10-100 for several minutes at 900 °C. The resulting profile broadening is comparable

N. E. B. Cowern; M. J. J. Theunissen; F. Roozeboom; J. G. M. van Berkum

1999-01-01

102

Boride-enhanced diffusion in silicon: Bulk and surface layers  

Microsoft Academic Search

Epitaxial silicon boride layers, located at the surface or within the bulk of single-crystal silicon, give rise to enhanced diffusion of B during annealing. A submonolayer buried boride layer releases ≈0.4 interstitials per B atom in the layer, generating a transient diffusion enhancement in the range of 10–100 for several minutes at 900 °C. The resulting profile broadening is comparable

N. E. B. Cowern; M. J. J. Theunissen; F. Roozeboom; J. G. M. van Berkum

1999-01-01

103

Oxygen reduction reaction over silver particles with various morphologies and surface chemical states  

NASA Astrophysics Data System (ADS)

The oxygen reduction reaction (ORR) in an alkaline solution was carried out using Ag powders having various particle morphologies and surface chemical states (Size: ca. 40-110 nm in crystalline size. Shape: spherical, worm like, and angular. Surface: smooth with easily reduced AgOx, defective with AgOx, and Ag2CO3 surface layer). The various Ag powders were well characterized by X-ray diffraction, X-ray photoelectron spectroscopy, N2 adsorption, scanning electron microscopy, Raman spectroscopy, cyclic voltammetry, and stripping voltammetry of underpotential-deposited lead. Defective and oxidized surfaces enhanced the Ag active surface area during the ORR. The ORR activity was affected by the morphology and surface chemical state: Ag particles with defective and angular surfaces showed smaller electron exchange number between three and four but showed higher specific activity compared to Ag particles with smooth surfaces.

Ohyama, Junya; Okata, Yui; Watabe, Noriyuki; Katagiri, Makoto; Nakamura, Ayaka; Arikawa, Hidekazu; Shimizu, Ken-ichi; Takeguchi, Tatsuya; Ueda, Wataru; Satsuma, Atsushi

2014-01-01

104

Structure of the regular surface layer of Sporosarcina ureae.  

PubMed Central

Optical diffraction and computer image processing of electron micrographs were employed to analyze the structure of the regular surface layer of Sporosarcina ureae at high resolution. Negatively stained preparations of regular surface layer fragments showed two types of tetragonal pattern, each having p4 symmetry in projection with a = 12.8 nm. Although the two patterns differed greatly in overall appearance, both had a common pattern of areas of high stain density which we interpret as arising from gaps or holes in the structure. We speculate that these holes may be related to a protective role of the regular surface layer, whereby hostile environmental agents (such as muramidases) larger than about 2 nm would be screened from the underlying layers of the bacterial surface, while the free passage of nutrients and waste products into and out of the cell would still be allowed. Images PMID:7372574

Stewart, M; Beveridge, T J

1980-01-01

105

Theory of the Work Function. II. The Surface Double Layer  

Microsoft Academic Search

An expression for the work function of a monovalent metal, previously obtained by E. Wigner and the author, included a term which represents the energy required to move an electron through an electrostatic double layer at the surface of the metal. In order to determine the moment of this double layer, it is necessary to make an explicit calculation of

John Bardeen

1936-01-01

106

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

107

Surface Science Letters Surface electron accumulation in indium nitride layers grown  

E-print Network

Surface Science Letters Surface electron accumulation in indium nitride layers grown by high­H ter- mination with no indium overlayer or droplets and indicate that the layer is N-polar. Broad accumulation. These results indi- cate that surface electron accumulation on InN does not require excess indium

Dietz, Nikolaus

108

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

109

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

110

Tribological Properties of Surface Layer with Boron in Friction Pairs  

NASA Astrophysics Data System (ADS)

The aim of the present work is to determine the influence of technologically produced boron surface layers on the friction parameters in the sliding pairs under the conditions of mixed friction. The tribological evaluation included ion nitrided, pack borided, laser borided, quenched and tempered surface layers and TiB2 coating deposited on 38CrAlMo5-10, 46Cr2 and 30MnB4 steels. Modified surface layers of annular samples were matched under test conditions with counter-sample made from AlSn20 bearing alloy. Tested sliding pairs were lubricated with 15 W/40 Lotos mineral engine oil. The tribological tests were conducted on a T-05 block on ring tester. The applied steel surface layer modification with boron allows surface layers to be created with pre-determined tribological characteristics required for the elements of kinematic pairs operating in the conditions of sliding friction. Pack boronizing reduces the friction coefficient during the start-up of the frictional pair and the maximum start-up resistance level is similar to the levels of pairs with nitrided surface layers.

Lubas, Janusz

111

Turbulence Structure of the Unstable Atmospheric Surface Layer and Transition to the Outer Layer  

NASA Astrophysics Data System (ADS)

We present a new model of the structure of turbulence in the unstable atmospheric surface layer, and of the structural transition between this and the outer layer. The archetypal element of wall-bounded shear turbulence is the Theodorsen ejection amplifier (TEA) structure, in which an initial ejection of air from near the ground into an ideal laminar and logarithmic flow induces vortical motion about a hairpin-shaped core, which then creates a second ejection that is similar to, but larger than, the first. A series of TEA structures form a TEA cascade. In real turbulent flows TEA structures occur in distorted forms as TEA-like (TEAL) structures. Distortion terminates many TEAL cascades and only the best-formed TEAL structures initiate new cycles. In an extended log layer the resulting shear turbulence is a complex, self-organizing, dissipative system exhibiting self-similar behaviour under inner scaling. Spectral results show that this structure is insensitive to instability. This is contrary to the fundamental hypothesis of Monin--Obukhov similarity theory. All TEAL cascades terminate at the top of the surface layer where they encounter, and are severely distorted by, powerful eddies of similar size from the outer layer. These eddies are products of the breakdown of the large eddies produced by buoyancy in the outer layer. When the outer layer is much deeper than the surface layer the interacting eddies are from the inertial subrange of the outer Richardson cascade. The scale height of the surface layer, zs, is then found by matching the powers delivered to the creation of emerging TEAL structures to the power passing down the Richardson cascade in the outer layer. It is zs = u* 3ks, where u*s friction velocity, k is the von Káán constant and s is the rate of dissipation of turbulence kinetic energy in the outer layer immediately above the surface layer. This height is comparable to the Obukhov length in the fully convective boundary layer. Aircraft and tower observations confirm a strong qualitative change in the structure of the turbulence at about that height. The tallest eddies within the surface layer have height zs, so zs is a new basis parameter for similarity models of the surface layer.

McNaughton, K. G.

112

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

113

Many-body microhydrodynamics of colloidal particles with active boundary layers  

E-print Network

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

Rajesh Singh; Somdeb Ghose; R. Adhikari

2015-01-30

114

Surface-layer lattices as patterning element for multimeric extremozymes.  

PubMed

A promising new approach for the production of biocatalysts comprises the use of surface-layer (S-layer) lattices that present functional multimeric enzymes on their surface, thereby guaranteeing most accurate spatial distribution and orientation, as well as maximal effectiveness and stability of these enzymes. For proof of concept, a tetrameric and a trimeric extremozyme are chosen for the construction of S-layer/extremozyme fusion proteins. By using a flexible peptide linker, either one monomer of the tetrameric xylose isomerase XylA from the thermophilic Thermoanaerobacterium strain JW/SL-YS 489 or, in another approach, one monomer of the trimeric carbonic anhydrase from the methanogenic archaeon Methanosarcina thermophila are genetically linked to one monomer of the S-layer protein SbpA of Lysinibacillus sphaericus CCM 2177. After isolation and purification, the self-assembly properties of both S-layer fusion proteins as well as the specific activity of the fused enzymes are confirmed, thus indicating that the S-layer protein moiety does not influence the nature of the multimeric enzymes and vice versa. By recrystallization of the S-layer/extremozyme fusion proteins on solid supports, the active enzyme multimers are exposed on the surface of the square S-layer lattice with 13.1 nm spacing. PMID:23757161

Ferner-Ortner-Bleckmann, Judith; Gelbmann, Nicola; Tesarz, Manfred; Egelseer, Eva M; Sleytr, Uwe B

2013-11-25

115

Particles in Surface Waters: Coagulation and Transport  

E-print Network

-averaged, unsteady particle transport were developed to approximate the size-dependent particle transport processes, which included advection, dispersion, and settling. Coupled exchange of discrete particles between the water column and sediment bed was modeled using...

Culkin, Gerald W.; Lawler, Desmond F.

116

Cake Filtration With Particle Penetration at the Cake Surface  

Microsoft Academic Search

Particles in drilling muds build a filter cake on borehole walls and can migrate into the adjacent porous formation and cause formation damage. This study analyzes cake formation, including particle penetration at the cake surface. Mass-balance equations for captured and suspended particles and the fluid phase are averaged along the cake thickness, taking into account conditions of the surface and

M. Y. Corapcioglu; Nelly Abboud

1990-01-01

117

Modeling impact cratering in layered surfaces Laurel E. Senft1  

E-print Network

Modeling impact cratering in layered surfaces Laurel E. Senft1 and Sarah T. Stewart1 Received 12 craters are potentially powerful tools for probing large-scale structure beneath planetary surfaces. However, the details of how target structure affects the impact cratering process and final crater forms

Stewart, Sarah T.

118

Shape-selective sieving layers on an oxide catalyst surface  

E-print Network

- allel, mesostructured oxides are available with high surfaces area and 2­50 nm pores that are ableShape-selective sieving layers on an oxide catalyst surface Christian P. Canlas1 , Junling Lu2 such as zeolites, metal­organic frameworks and mesostructured oxides are of immense practical utility for gas

Mohseni, Hooman

119

Effects of surface wave breaking on the oceanic boundary layer  

Microsoft Academic Search

Existing laboratory studies suggest that surface wave breaking may exert a significant impact on the formation and evolution of oceanic surface boundary layer, which plays an important role in the ocean-atmosphere coupled system. However, present climate models either neglect the effects of wave breaking or treat them implicitly through some crude parameterization. Here we use a one-dimensional ocean model (General

Hailun He; Dake Chen

2011-01-01

120

Insulating surface layer on single crystal K3C60  

NASA Astrophysics Data System (ADS)

Using angle-dependent photoemission spectra of core and valence levels we show that metallic, single crystal K3C60 is terminated by an insulating or weakly-conducting surface layer. We attribute this to the effects of strong intermolecular correlations combined with the average surface charge state. Several controversies on the electronic structure are thereby resolved.

Schiessling, J.; Kjeldgaard, L.; Käämbre, T.; Marenne, I.; Qian, L.; O'Shea, J. N.; Schnadt, J.; Garnier, M. G.; Nordlund, D.; Nagasono, M.; Glover, C. J.; Rubensson, J.-E.; Mårtensson, N.; Rudolf, P.; Nordgren, J.; Brühwiler, P. A.

2004-10-01

121

Characterization of Cathode Keeper Wear by Surface Layer Activation  

Microsoft Academic Search

In this study, the erosion rates of the discharge cathode keeper in a 30 cm NSTAR configuration ion thruster were measured using a technique known as Surface Layer Activation (SLA). This diagnostic technique involves producing a radioactive tracer in a given surface by bombardment with high energy ions. The decrease in activity of the tracer material may be monitored as

Robert D. Kolasinski; James E. Polk

2004-01-01

122

Role of surface active layers on localized breakdown of aluminum alloy 7075  

NASA Astrophysics Data System (ADS)

Potentiodynamic polarization curves for AA7075-T6 in NaCl solution exhibit two breakdowns. The current increases at the first breakdown, reaches a peak and then decreases. At the second, higher breakdown potential, the current increases again. The second breakdown is dominated by sustained localized corrosion and the first one is believed to be associated with transient dissolution that precedes the onset of stable localized corrosion. This study is aimed at understanding the details of the transient dissolution phenomenon. The first breakdown mechanism of AA7xxx was studied by an in-situ observation system in which a combination of a magnified image of the surface with the instantaneous polarization curve allowed determination of the corrosion process as a function of potential. As-polished (to 1 mum) AA7075-T6 clearly exhibited dissolution of a thin surface layer corresponding to a sharp increase of current just above the first breakdown. No surface layer dissolution was observed for samples that were either ion milled or chemically etched to remove the effects of polishing. This susceptible surface layer was apparently the result of the mechanical polishing process. The surface microstructure of an as-polished sample was analyzed by TEM and several distinct features were found: (1) a unique thin layer with thickness of 100 nm on average; (2) many fewer fine hardening particles in the thin layer compared to bulk matrix, which means that the fine particles were destroyed and eliminated by polishing; (3) high aspect ratio nano-grains elongate along the final polishing direction; EDS analysis in STEM mode revealed a higher concentration of Zn at the nano-grain boundaries. The attack of the surface layer might initiate at the active nanograin boundary followed by nano-grain dissolution. Samples in other tempers were also examined. No surface layer dissolution and no first breakdown peak were observed for the solutionized + quenched alloy because no comparable Zn enriched bands were present and the composition of the surface layer was not substantially different than the bulk matrix. The solutionized samples did not contain hardening particles so there was no effect of the shearing on the surface composition. The overaged samples also exhibited no layer attack and only one breakdown potential. The particles in the overaged samples were larger and farther apart so that the shear associated with polishing was unable to destroy them fully. Zn-rich bands were observed at the nano-brain boundaries for the overaged temper, but the localized attack propagated into the bulk matrix rather than laterally as layer attack. Underaged samples showed thin layer dissolution and current peaks associated with a first breakdown phenomenon. However, the magnitude of the current peaks changed with the extent of aging as a result of differences in the hardness, and thus layer thickness and dissolution rate of the thin layer. A study of filiform corrosion (FFC) was performed on T6 and T7 temper samples either as-polished or chemically etched. FFC kinetics were higher on as-polished samples than on chemically etched samples, which confirmed higher activity of the altered surface layer induced by polishing. FFC on T6 sample of all the conditions was worse than T7 tempered samples.

Zhao, Zhijun

123

Multi-layer enhancement to polysilicon surface-micromachining technology  

SciTech Connect

A multi-level polysilicon surface-micromachining technology consisting of 5 layers of polysilicon is presented. Surface topography and film mechanical stress are the major impediments encountered in the development of a multilayer surface-micromachining process. However, excellent mechanical film characteristics have been obtained through the use of chemical-mechanical polishing for planarization of topography and by proper sequencing of film deposition with thermal anneals. Examples of operating microactuators, geared power-transfer mechanisms, and optical elements demonstrate the mechanical advantages of construction with 5 polysilicon layers.

Sniegowski, J.J.; Rodgers, M.S. [Sandia National Labs., Albuquerque, NM (United States). Intelligent Micromachine Dept.

1997-10-01

124

Synthesis and characterization of silica-silver core-shell composite particles with uniform thin silver layers  

SciTech Connect

Silica-silver core-shell composite particles with uniform thin silver layers were successfully synthesized by a facile and one-step ultrasonic electrodeposition method. By electrolysis of the slurry consisting of preformed silica spheres and silver perchlorate without any additives, the homogenous composite particles can be prepared. The average size of single silver crystals in the composite is about 12 nm and the thickness of silver layer is 14{+-}2 nm. Moreover, the continuity of Ag distribution, the surface roughness and the thickness of silver layer are controllable by adjusting the current density (I), the concentration of electrolyte (C) and the reaction time (t). Optical properties of the composite particles with different silver content were also investigated. - Graphical abstract: Silica-silver core-shell composite particles with uniform thin silver layers are prepared by a facile and one-step ultrasonic electrodeposition method. Moreover, the continuity of Ag distribution, the surface roughness and the thickness of silver layer are controllable. Optical properties of the composite particles with different silver content were also investigated.

Tang Shaochun; Tang Yuefeng; Zhu Shaopeng; Lu Haiming [Department of Materials Science and Engineering, National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China); Meng Xiangkang [Department of Materials Science and Engineering, National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093 (China)], E-mail: mengxk@nju.edu.cn

2007-10-15

125

Surface Collisions Involving Particles and Moisture (SCIP'M)  

NASA Technical Reports Server (NTRS)

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

Davis, Robert H.

2005-01-01

126

TiO2 atomic layer deposition on ZrO2 particles using alternating exposures of TiCl4 and H2O  

E-print Network

TiO2 atomic layer deposition on ZrO2 particles using alternating exposures of TiCl4 and H2O J was deposited with atomic layer control on ZrO2 particles using alternating exposures of TiCl4 and H2O chemistry in vacuum. The ZrO2 particles initially displayed vibrational modes consistent with ZrOH* surface

George, Steven M.

127

Particle morphological and roughness controls on mineral surface charge development  

NASA Astrophysics Data System (ADS)

Effects of mineral particle morphology and roughness on potential determining ion (p.d.i.; H+, OH-) loadings achieved at synthetic lepidocrocite (?-FeOOH) surfaces were predominantly investigated by potentiometry and thermodynamic modeling. Nanosized rod- (RL) and lath-shaped (LL) particles exhibiting different proportions of the same predominant crystallographic faces acquired largely comparable pH, ionic strength and counterion (NaCl, NaClO4) dependencies on p.d.i. loadings. These results supported previous claims that faces ideally containing proton silent sites only, are likely populated by additional proton active sites. This concept was supported further by results of roughened LL-like particles (LLR) also showing highly congruent pH-, ionic strength- and composition-dependent p.d.i. loadings with those of LL and RL. These loadings thereby correspond to maximal levels allowed by net attractive and repulsive forces at each solution composition, irrespective of particle morphology. Contrasting equilibration times required to achieve these loadings revealed considerably slower exchange of p.d.i. and electrolyte ions near the point of zero charge in the rough LLR than in the more idealized LL and RL particles. Thermodynamic modeling was used to test various concepts accounting for these results. The model made use of a novel framework capable of isolating electrostatic contributions from different faces, and of accounting for ion-specific double-layer properties within a single crystallographic face. These efforts made use of capacitance values for each electrolyte ions within the framework of a recently developed Variable Capacitance Model. Attempts at modeling all three particle types were used to suggest that the (0 1 0) face contains ?0.9 site nm-2 of proton active sites, a value notably constrained by recently published Na+, Cl-, and ClO4- loadings derived by cryogenic X-ray photoelectron spectroscopy. The model presented in this work thus provides a means to predict p.d.i. loadings on multifaceted mineral particle surfaces, and can therefore be used to constrain further our understanding of mineral/water interface reactivity.

Boily, Jean-François; Kozin, Philipp A.

2014-09-01

128

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

PubMed

Bio-inspired surfaces that exhibit high contact angle and low contact angle hysteresis for various liquids and demonstrate mechanical durability and anti-smudge properties are of interest for various applications. The fabrication of such surfaces has often involved complex or expensive processes, required techniques that may not be suitable for various substrates and particles, may require surface post-treatment, or may lack durability. Dual layered coatings of roughness-induced superomniphobic surfaces that demonstrate good mechanical durability were fabricated on glass substrates using hydrophobic SiO2 nanoparticles and low surface energy fluorobinders using dip coating and spray coating techniques. The particle-to-binder ratio was optimized for contact angles of interest. The mechanical durability of these coatings was examined under mechanical rubbing action. The anti-smudge properties were examined by wiping an artificially contaminated coating using oil-impregnated microfiber cloth. PMID:23993782

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

2013-11-01

129

Interactions of Hyperthermal Gas Particles with Contaminated Surfaces  

Microsoft Academic Search

Interactions of hyperthermal molecules with contaminated surfaces are studied analytically for a simple classical model in which the surface is covered by a monolayer of physisorbed contaminant and the gas particle energy is much greater than that corresponding to the temperature of the solid. Calculations indicate that if the adsorption potential varies periodically along the surface, then the adsorbed particles

K. C. Chiang; E. L. Knuth

1970-01-01

130

Lactobacillus surface layer proteins: structure, function and applications.  

PubMed

Bacterial surface (S) layers are the outermost proteinaceous cell envelope structures found on members of nearly all taxonomic groups of bacteria and Archaea. They are composed of numerous identical subunits forming a symmetric, porous, lattice-like layer that completely covers the cell surface. The subunits are held together and attached to cell wall carbohydrates by non-covalent interactions, and they spontaneously reassemble in vitro by an entropy-driven process. Due to the low amino acid sequence similarity among S-layer proteins in general, verification of the presence of an S-layer on the bacterial cell surface usually requires electron microscopy. In lactobacilli, S-layer proteins have been detected on many but not all species. Lactobacillus S-layer proteins differ from those of other bacteria in their smaller size and high predicted pI. The positive charge in Lactobacillus S-layer proteins is concentrated in the more conserved cell wall binding domain, which can be either N- or C-terminal depending on the species. The more variable domain is responsible for the self-assembly of the monomers to a periodic structure. The biological functions of Lactobacillus S-layer proteins are poorly understood, but in some species S-layer proteins mediate bacterial adherence to host cells or extracellular matrix proteins or have protective or enzymatic functions. Lactobacillus S-layer proteins show potential for use as antigen carriers in live oral vaccine design because of their adhesive and immunomodulatory properties and the general non-pathogenicity of the species. PMID:23677442

Hynönen, Ulla; Palva, Airi

2013-06-01

131

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 have been deposited on the surfaces of nanoparticles of alumina using a plasma polymerization treatment efforts have been focused on nanoparticle synthesis, assembly, interfaces, dis- persions, and functional

Dalal, Vikram

132

Re-suspension Process In Turbulent Particle-fluid Mixture Boundary Layers  

NASA Astrophysics Data System (ADS)

Many theoretical applications of geophysical flows, such as sediment transport (e.g. Jenkins &Hanes, 1998) and aeolian transport of particles (e.g. Hopwood et al., 1995) utilize concepts for describing the near wall velocity profiles of particle suspensions originally arising from classical single phase theories. This approach is supported by experiments indicating the existence of a logarithmic fluid velocity profile similar to single phase flows also in case of high Reynolds number wall bounded particle sus- pension flows with low particle volume fractions (Nishimura &Hunt, 2000). Since the concept of a logarithmic near wall profile follows from classic asymptotic the- ory of high Reynolds number wall bounded flows the question arises to what extent this theory can be modified to account for particles being suspended in the ambient fluid. To this end, the asymptotic theory developed by Mellor (1972) is applied to the Favré-averaged equations for the carrier fluid as well as the dispersed phase derived on the basis of a volume averaged dispersed two-phase theory (Gray &Lee, 1977). Numerical solutions for profiles of main stream velocities and particle volume frac- tion in the fully turbulent region of the boundary layer for different turbulent Schmidt numbers are computed applying a Finite Difference box scheme. In particular, atten- tion is focused on the turbulent re-suspension process of particles from dense granular flow adjacent to the bounding surface into the suspension. From these results boundary conditions in form of wall functions for velocities as well as the volume fraction of the particles can be derived and the validity of analogy laws between turbulent mass and momentum transfer at the bounding surface can be proved from an asymptotic point of view. The application of these concepts in the field of snow avalanche simulation (Zwinger, 2000) is discussed.

Zwinger, T.; Kluwick, A.

133

Kinetics of dust particles around the scrape off layer in fusion devices  

NASA Astrophysics Data System (ADS)

A kinetic model based on the balance of charge and energy over the dust particle surface around the scrape off layer (SOL) region in fusion devices has been developed; for describing the dust mass diminution, its temperature evolution and phase change process have been taken into account. The formulation has been utilized to determine the lifetime of cylindrical and spherical dust particles. A realistic situation in fusion devices, when the plasma exhibits meso-thermal flow, has been taken into account; for this purpose a rigorous approach, pioneered by Mott-Smith and Langmuir (1926 Phys. Rev. 28 727), has been adopted to derive the general expressions for the electron (ion) current on cylindrical dust surfaces and the corresponding mean energy of accreting electrons/ions in a flowing plasma. On the basis of analytical modelling the numerical results for the dust electric potential energy and the lifetime of the dust particles corresponding to a typical plasma environment near the SOL region of Mega Ampere Spherical tokamak (MAST)/Joint European Torus (JET) fusion devices have been evaluated for graphite and tungsten dust particles. The results are graphically illustrated as functions of particle size, electron/ion temperature and plasma ionization. It is seen that a large dust particle immersed in low temperature plasma can survive for long time; as an important outcome it is also noticed that the cylindrical particles of tungsten last longer than spherical particles. The findings are of relevance in characterizing and simulating the effects of a variety of dusts for experimental campaigns in large scale (ITER/Demo-like) fusion devices.

Mishra, S. K.; Misra, Shikha; Sodha, M. S.

2014-05-01

134

Erosion of Galilean satellite surfaces by Jovian magnetosphere particles  

NASA Astrophysics Data System (ADS)

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

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

1981-05-01

135

Polymer hollow particles with controllable holes in their surfaces  

NASA Astrophysics Data System (ADS)

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

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

2005-09-01

136

Multi-layer surface profiling using gated wavefront sensing  

NASA Astrophysics Data System (ADS)

Recently, multi-layer surface profiling and inspection has been considered an emerging topic that can be used to solve various manufacturing inspection problems, such as graded index lenses, TSV (Thru-Silicon Via), and optical coating. In our study, we proposed a gated wavefront sensing approach to estimate the multi-layer surface profile. In this paper, we set up an experimental platform to validate our theoretical models and methods. Our test bed consists of pulse laser, collimator, prism, well-defined focusing lens, testing specimen, and gated wavefront sensing assembly (e.g., lenslet and gated camera). Typical wavefront measurement steps are carried out for the gated system, except the reflectance is timed against its time of flight as well as its intensity profile. By synchronizing the laser pulses to the camera gate time, it is possible to discriminate a multi-layer wavefront from its neighbouring discrete layer reflections.

Wang, Xin; Nordin, Nur Dalilla; Tik, Eddy Chow Mun; Tan, ChingSeong; Chew, Kuew Wai; Menoni, Carmen

2015-01-01

137

Optical refraction in the atmospheric surface layer  

NASA Astrophysics Data System (ADS)

The nature was studied of atmospheric refraction and criteria was developed when refraction may cause errors in tank gunnery in deserts. Refraction can be remotely sensed as a function of time through point to point measurements of the elevation of a distant object relative to the atmospheric neutral events that occur approximately 1/2 hr before sunset and 1/2 hr after sunrise. The vertical position change of a distant object can be measured using either another object close enough to the observer that effects will be minimal (thus providing a fixed reference point) or a theodolite that has its own internal reference through the leveling bubble. Extensive measurements were made of diurnal variations in elevation of distant objects at White Sands Missile Range (WSMR), NM. Lessons learned from these experiments include accounting for numerous potential error sources when taking readings using theodolites and the photographic techniques necessary to cope with changing light levels and atmospheric turbulence effects. Measurements were made at other locations that exhibit similar vertical shifting characteristics. A surface energy budget model was developed to predict refraction situations based on meteorological measurements.

Gillespie, James B.; Tofsted, David H.

1992-02-01

138

Intermittency in the atmospheric surface layer: Unresolved or slowly varying?  

Microsoft Academic Search

We present streamwise velocity structure functions ??vL(?)?=?|v(t+?)?v(t)|p? (with p=1:5) obtained in the near neutral atmospheric surface layer at the Utah SLTEST site at the highest terrestrial Reynolds number Re?=O(106). We show that the occurrence of very large scale coherent oscillations in the streamwise velocity throughout the wall region, interpreted as genuine structural features of the canonical turbulent boundary layer, affects

M. Guala; M. Metzger; B. J. McKeon

2010-01-01

139

Electron tunneling in tantalum surface layers on niobium  

Microsoft Academic Search

We have performed electron tunneling measurements on tantalum surface layers on niobium. The tunnel junctions comprise 2000-A-circle Nb base electrodes with 10--100-A-circle i-italicn-italic s-italici-italict-italicu-italic--deposited Ta overlayers, an oxide barrier, and Ag, Pb, or Pb-Bi alloy counterelectrodes. The base electrodes were prepared by ion-beam sputter deposition. The characteristics of these junctions have been studied as a function of Ta-layer thickness. These

S. T. Ruggiero; D. E. Prober; G. B. Arnold; M. J. DeWeert

1986-01-01

140

Electron tunneling in tantalum surface layers on niobium  

Microsoft Academic Search

We have performed electron tunneling measurements on tantalum surface layers on niobium. The tunnel junctions comprise 2000-Å Nb base electrodes with 10-100-Å in situ-deposited Ta overlayers, an oxide barrier, and Ag, Pb, or Pb-Bi alloy counterelectrodes. The base electrodes were prepared by ion-beam sputter deposition. The characteristics of these junctions have been studied as a function of Ta-layer thickness. These

S. T. Ruggiero; E. K. Track; D. E. Prober; G. B. Arnold; M. J. Deweert

1986-01-01

141

Effects of dust particles and layer properties on organic electronic devices fabricated by stamping  

NASA Astrophysics Data System (ADS)

The mechanical properties of organic semiconductor thin films are determined using nanoindentation. The measured mechanical properties are incorporated into finite element simulations of deformation that arise during cathode patterning of organic electronic devices by pressure stamping methods. Simulations show that dust particles interposed between the stamp and film surface affect the evolution of contact areas when silicon or compliant polydimethyl-siloxane stamp dies are employed. We also examine the effects of the transferred metal layer thickness and stamp bulk modulus. Experimental and modeling results are found to be in good agreement. The implications of the results are discussed for the fabrication of a range of organic electronic devices.

Cao, Yifang; Kim, Changsoon; Forrest, Stephen R.; Soboyejo, Wole

2005-08-01

142

Particle growth and sedimentation equations Particle sizes in the nucleation layer are calculated based on condensational growth of the seeded  

E-print Network

, as they sediment from the nucleation layer, is dependent on vortex shear. The vortex-wide displacement of particles can be illustrated by considering a simple case of two particles orginating at different altitudes(km) Figure 5: Altitudinal and azimuthal displacement is shown for particles orginating from two different

Wennberg, Paul

143

The Turbulent Boundary Layer on a Rough Curvilinear Surface  

NASA Technical Reports Server (NTRS)

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

Droblenkov, V. F.

1958-01-01

144

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

145

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

146

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

147

Surface reactions on thin layers of silane coupling agents  

SciTech Connect

The reactivity of immobilized functional groups in thin layers of (3-aminopropyl)triethoxysilane (APS), (3-mercaptopropyl)trimethoxysilane, (3-bromopropyl)trimethoxysilane, and (8-bromooctyl)trimethoxysilane on oxidized aluminum substrates was studied with reflection-adsorption infrared spectroscopy (RAIR), optical ellipsometry and contact-angle measurements. Mass changes on the surface associated with the surface-confined reactions were measured with the quartz crystal microbalance (QCM). Single layers of (3-aminopropyl)triethoxysilane on oxidized aluminum react with chlorodimethylsilane to give [(-O)[sub 3]Si(CH[sub 2])[sub 3]NH[sub 2][sup +]SiMe[sub 2]H]Cl[sup [minus

Kurth, D.G.; Bein, T. (Purdue Univ., West Lafayette, IN (United States))

1993-11-01

148

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

149

A surface-layer model of ferroelectric nanowire  

NASA Astrophysics Data System (ADS)

In this paper, a surface-layer model is established to study the axial polarization distributions and critical diameters of nanowires with different surface compositions. Analytical solutions are obtained based on this model, which are validated by the ab initio results for small-size nanowires and can also predict the behaviors of large-size specimen. Compared to the traditional Landau-Ginzburg-Devonshire theory using an extrapolation length, the present model describes more microstructure information of the surface-layer, and is thus capable of characterizing the influences of different surface compositions. Furthermore, this model may shed insight into the mechanisms of the size effect and polarization distribution patterns in nanoscale ferroelectrics.

Zhang, Yihui; Hong, Jiawang; Liu, Bin; Fang, Daining

2010-12-01

150

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

151

Formation of silver particles and periodic precipitate layers in silicate glass induced by thermally assisted hydrogen permeation  

NASA Astrophysics Data System (ADS)

Nanoscale silver particles embedded in sodium silicate glass were produced by Na/Ag ion exchange and subsequent thermal treatment in a hydrogen atmosphere. Their structure and spatial distribution were studied by conventional and high-resolution electron microscopy (HREM). Two different mechanisms of particle formation could be identified: (i) reduction of ionic silver by hydrogen and formation of mostly defective particles (twinned) within a near-surface region; and (ii) formation of single-crystalline particles in the interior of the glass resulting from reduction by means of polyvalent iron ions. Electron microscopy investigation revealed the completion of periodic layers of silver particles in near-surface regions with high silver concentration induced by thermally assisted hydrogen permeation. The self-organized periodic layer formation may be explained in terms of Ostwald's supersaturation theory, assuming interdiffusion of two mobile species. Analysis of lattice plane spacings from HREM images of silver particles revealed the typical size-dependent lattice contraction. The extent of this, however, was found to be different for particles formed by hydrogen permeation and those formed by interaction with polyvalent iron ions. These differences reflect different influences of the surrounding glass matrix, probably originating from the conditions of particle formation (thermal history).

Mohr, C.; Dubiel, M.; Hofmeister, H.

2001-01-01

152

Particle resuspension and associated coherent structures in a turbulent boundary layer  

NASA Astrophysics Data System (ADS)

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

Braaten, David Alan

153

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

E-print Network

turbulence-induced surface-temperature variations should also be accounted for in numerical models,turbulence above a grass surface. Water Resour Res Kormann R, Meixner FX (2001) An analytical footprint model

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

2013-01-01

154

Characterization of triboelectrically charged particles deposited on dielectric surfaces  

NASA Astrophysics Data System (ADS)

A device for the measurement of q/m-values and charge degradation of triboelectrically charged particles deposited on a surface was developed. The setup is based on the integration of currents, which are induced in a Faraday cage by insertion of a solid support covered with charged particles. The conductivity of different particle supports was taken into account. The 'blow-off' method, in which the particles are first deposited, and then blown off using an air stream, can be used for characterization of triboelectric properties of particles relative to different surfaces.

Nesterov, A.; Löffler, F.; Cheng, Yun-Chien; Torralba, G.; König, K.; Hausmann, M.; Lindenstruth, V.; Stadler, V.; Bischoff, F. R.; Breitling, F.

2010-04-01

155

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

156

Modeling Dry Deposition of Aerosol Particles onto Rough Surfaces  

Microsoft Academic Search

Dry deposition is a primary mechanism by which suspended particles are transported from gas onto surfaces. Prediction of this transport rate is needed in a vast range of applications including environmental, industrial, engineering, and impacts of aerosols. Besides air flow characteristics and properties of aerosol particles, the dry deposition velocity depends greatly on surface properties. However, existing models describe rough

Tareq Hussein; Ji?í Smolik; Veli-Matti Kerminen; Markku Kulmala

2011-01-01

157

The structure of turbulent boundary layers along mildly curved surfaces  

Microsoft Academic Search

The structure of turbulence in boundary layers along mildly curved convex and concave surfaces is studied. Measurements of turbulent energy balance, autocorrelations, auto- and cross-power spectra, amplitude probability distributions, and conditional correlations are reported. It is observed that even mild curvature has very strong effects on the various aspects of the turbulent structure. For example, convex curvature suppresses the diffusion

B. R. Ramaprian; B. G. Shivaprasad

1978-01-01

158

Turbulence measurements in boundary layers along mildly curved surfaces  

Microsoft Academic Search

This paper presents results of turbulence measurements in boundary layers over surfaces of mild longitudinal curvature. The study indicates that convex wall curvature decreases both the length and velocity scales of turbulent motions, whereas concave curvature has the opposite effect. While being qualitatively similar to those brought about by stronger wall curvature, mild curvature effects are found to be much

B. G. Shivaprasad; B. R. Ramaprian

1978-01-01

159

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

160

Physics of neutron star surface layers and their thermal radiation  

E-print Network

, Thermodynamic processes, conduction, convection, equations of state PACS: 97.60.Jd, 95.30.Tg INTRODUCTIONPhysics of neutron star surface layers and their thermal radiation Alexander Y. Potekhin Ioffe radiation, taking into consideration the effects of strong magnetic fields. Keywords: Neutron stars

161

Fluctuating wall shear stress measurements in the atmospheric surface layer  

Microsoft Academic Search

A new sensor is described for measuring the fluctuating component of the wall shear stress in the atmospheric surface layer over relatively smooth uniform terrain. The sensor was tested at the SLTEST site on the western salt-flats of Utah, giving the first ever direct measurements of this quantity in an atmospheric scale flow. The device consists of a lightweight floating

Weston Daniel Clarence Heuer

2005-01-01

162

Seasonal cycles of surface layer salinity in the Pacific Ocean  

Microsoft Academic Search

The seasonal variability of surface layer salinity (SLS) is examined in the Pacific Ocean between 40° S and 60° N using a variety of data sources. Significant seasonal cycles were found in 5 regions: 1) The western North Pacific, 2) The northeastern North Pacific and Alaska gyre, 3) the intertropical convergence zone (ITCZ), 4) an area of the central North

F. M. Bingham; G. R. Foltz; M. J. McPhaden

2010-01-01

163

Porosity determinations in buried and surface layers of porous silicon  

Microsoft Academic Search

Gravimetric techniques offer a convenient and accurate method of determining surface layer porosity in both n- and p-type porous silicon (PS). Porosity of the PS affects its volume expansion on oxidation and the insulating properties of the resulting oxide. Optimal porosity (ca. 55%) yields fully dense, insulating oxides with minimal expansion-induced stresses. Two factors affect the porosity: chemical dissolution of

T. R. Guilinger; M. J. Kelly; S. S. Tsao

1987-01-01

164

Laminarization of Turbulent Boundary Layer on Flexible and Rigid Surfaces  

NASA Technical Reports Server (NTRS)

An investigation of the control of turbulent boundary layer flow over flexible and rigid surfaces downstream of a concave-convex geometry has been made. The concave-convex curvature induces centrifugal forces and a pressure gradient on the growth of the turbulent boundary layer. The favorable gradient is not sufficient to overcome the unfavorable; thus, the net effect is a destabilizing, of the flow into Gortler instabilities. This study shows that control of the turbulent boundary layer and structural loading can be successfully achieved by using localized surface heating because the subsequent cooling and geometrical shaping downstream over a favorable pressure gradient is effective in laminarization of the turbulence. Wires embedded in a thermally insulated substrate provide surface heating. The laminarized velocity profile adjusts to a lower Reynolds number, and the structure responds to a lower loading. In the laminarization, the turbulent energy is dissipated by molecular transport by both viscous and conductivity mechanisms. Laminarization reduces spanwise vorticity because of the longitudinal cooling gradient of the sublayer profile. The results demonstrate that the curvature-induced mean pressure gradient enhances the receptivity of the flow to localized surface heating, a potentially viable mechanism to laminarize turbulent boundary layer flow; thus, the flow reduces the response of the flexible structure and the resultant sound radiation.

Maestrello, Lucio

2001-01-01

165

Estimating Active Layer Thickness from Remotely Sensed Surface Deformation  

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

166

Ris-R-1429(EN) Surface layer characteristics and SVAT  

E-print Network

taken in and above a temperate beech forest canopy. The SVAT modelling framework used here has beenRisø-R-1429(EN) Surface layer characteristics and SVAT modelling of a fetch-limited forest Ebba to the ecosystem level. The beech forest site is fetch limited and influence on forest mast measurements from

167

NMR of thin layers using a meanderline surface coil  

DOEpatents

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

Cowgill, Donald F. (San Ramon, CA)

2001-01-01

168

Mercurian megaregolith layer and surface heat flows constraints  

NASA Astrophysics Data System (ADS)

Mercury is covered by a thermally insulating megaregolith layer. Despite the fact that it is known that this poor conducting layer has important influences on surface heat flows, most thermal modeling studies have overlooked it. Mercurian megaregolith is not very well known, but data provided by MESSENGER suggest that mercurian megaregolith is less insulating than its lunar counterpart. This information together with brittle-ductile transition (BDT) depths, estimated from the analysis of fault geometries associated with lobate scarps, allow us to constrain the surface heat flow on Mercury at the time of scarps formation. In this work, we have solved the heat conduction equation in order to constrain surface heat flows. Firstly, we obtain an upper limit in surface heat flows by using published values of the BDT depth and by neglecting the megaregolith layer. Then, we calculate a lower limit by including in the heat equation a top layer with thermal properties representative of the lunar megaregolith. In our calculations we have taken into account volumetric heat production rates obtained from the surface abundances of radioactive elements provided by MESSENGER. Heat equation solutions constrain surface heat flows to a range of 6 - 29 mWm-2. These results suggest the possibility that surface heat flows could be lower than those calculated in previous works, which is in agreement with the small amount of radial contraction detected on Mercury. Furthermore, the procedure followed in this article can be easily applied to other planets and satellites, which will improve our knowledge about the thermal evolution of these bodies.

Egea-Gonzalez, Isabel; Ruiz, Javier

2013-04-01

169

Photoelectrochemical water splitting promoted with a disordered surface layer created by electrochemical reduction.  

PubMed

The recent discovery of colored TiO2 indicated that the disordered surface layer over the TiO2 particles/photoelectrodes is beneficial for higher photocatalytic performance; however, the role of the disordered surface TiO2 layer is not well understood. Here, we report an electrochemical strategy for tuning the surface structure of TiO2 nanorod arrays (NRAs) and try to understand the role of the disordered surface TiO2 layer. Photoelectrodes of TiO2 NRAs with a disordered shell were prepared by an electrochemical reduction method. The photocurrent of the NRAs with a disordered shell can reach as high as ?1.18 mA/cm(2) at 1.23 V, which is 2.2 times of that of the pristine TiO2 NRAs. Our results show that the surface disordered layer not only improves the bulk charge separation but also suppresses the charge recombination at the electrode/electrolyte interface, acting as an efficient water oxidation cocatalyst of photoelectrochemical cell for solar water splitting. PMID:25621529

Yan, Pengli; Liu, Guiji; Ding, Chunmei; Han, Hongxian; Shi, Jingying; Gan, Yang; Li, Can

2015-02-18

170

Ethylene glycol-based microgels at solid surfaces: swelling behavior and control of particle number density.  

PubMed

The adsorption of ethylene glycol (EG)-based microgel particles at silicon surfaces was investigated. Monodisperse p-MeO2MA-co-OEGMA microgel particles were synthesized by precipitation polymerization. Particle size and the volume phase transition temperature (VPTT) can be tailored by changing the amount of comonomer. The effect of geometrical confinement on the microgel particles was studied at the solid/liquid interface. Therefore, layer formation, particle number density, and swelling/deswelling at the surface were studied in dependence on the spin-coating preparation parameters and characterized by means of AFM against ambient conditions. The deswelling/swelling behavior was investigated by AFM in the water-swollen state. PMID:25654206

Wellert, Stefan; Kesal, Dikran; Schön, Sebastian; von Klitzing, Regine; Gawlitza, Kornelia

2015-02-24

171

Resuspension onset and crater erosion by a vortex ring interacting with a particle layer  

E-print Network

Resuspension onset and crater erosion by a vortex ring interacting with a particle layer N. Bethke and crater erosion by a vortex ring interacting with a particle layer N. Bethkea) and S. B. Dalziel velocimetry, while a light attenuation method provides accurate measurements of the final eroded crater shape

Dalziel, Stuart

172

Effects of mesoscale surface inhomogeneities on atmospheric boundary layer transfer  

SciTech Connect

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

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

1992-09-01

173

Characterization of double layer alterations induced by charged particles and protein-membrane interactions using contactless impedance spectroscopy.  

PubMed

Double layer interactions between charged particles and surfaces play a vital role in a variety of technical and biological systems because they determine the stability of, e.g., protein-membrane biointerfaces. The underlying theoretical principle is based on the overlap of two different double layers that induce surface charges to be shifted to a new equilibrium distribution, which can be approximated by the Poisson-Boltzmann equation. In the present work we show theoretical and experimental results involving double layer capacitance of surfaces that exhibit charge regulation behavior. Charge regulation is an important parameter to consider when investigating protein-membrane interactions because it defines surface properties between ideal constant charge and constant potential behavior. In this work we introduce a novel theoretical model that also includes charge regulation behavior and can assess changes of double layer disruptions at TiO(2) and supported lipid-bilayers (SLB). The selected surfaces represent important biointerfaces that can be found on implants or cell membranes. We also demonstrate that contactless impedance spectroscopy is well suited to measure double layer capacitance interactions using differently charged silica beads. The combination of a theoretical model with experimental data allowed us further to identify charge regulation effects during protein adsorption (BSA and Annexin V) events at supported lipid-bilayers (SLB) used as a simple cell membrane model. Finally, the first indications of changed charge regulation behavior during protein surface crystallization events were also documented. PMID:22594659

Steinkuehler, Jan; Charwat, Verena; Richter, Lukas; Ertl, Peter

2012-09-01

174

Molecular Dynamics Simulations of Layer-by-Layer Assembly of Polyelectrolytes at Charged Surfaces: Effects  

E-print Network

allows the fabrication of multilayer films from synthetic polyelectrolytes, DNA,10 proteins,11 simulations of the electrostatic assembly of multilayers of flexible polyelectrolytes at a charged surface-by-layer fashion from dilute polyelectrolyte solutions. The steady- state multilayer growth proceeds through

Mather, Patrick T.

175

Surface forces of colloidal particles from micrometer to nanometer  

NASA Astrophysics Data System (ADS)

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

Cho, Jeong-Min

2003-10-01

176

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

SciTech Connect

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

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

2014-04-21

177

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

Microsoft Academic Search

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

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

2006-01-01

178

New particle formation in the continental boundary layer: Meteorological and gas phase parameter influence  

Microsoft Academic Search

New particle formation in the polluted continental boundary layer was studied, based on 1.5-year observations of the particle size distribution, meteorological and gas phase parameters. Events of new particle formation involving significant ultrafine particle number concentrations (>104cm-3 in the size range 3-11 nm) were observed on 20% of all days, pointing out that a frequent particle production from gaseous precursors

Wolfram Birmili; Alfred Wiedensohler

2000-01-01

179

Cake filtration with particle penetration at the cake surface  

SciTech Connect

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

Corapcioglu, M.Y. (Washington State Univ., Olympia, WA (USA)); Abboud, N.M. (Univ. of Connecticut, CT (US))

1990-08-01

180

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

181

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

182

Nanostructured coatings by adhesion of phosphonated polystyrene particles onto titanium surface for implant material applications.  

PubMed

Titanium that is covered with a native oxide layer is widely used as an implant material; however, it is only passively incorporated in the human bone. To increase the implant-bone interaction, one can graft multifunctional phosphonic compounds onto the implant material. Phosphonate groups show excellent adhesion properties onto metal oxide surfaces such as titanium dioxide, and therefore, they can be used as anchor groups. Here, we present an alternative coating material composed of phosphonate surface-functionalized polystyrene nanoparticles synthesized via free radical copolymerization in a direct (oil-in-water) miniemulsion process. Two types of functional monomers, namely, vinylphosphonic acid (VPA) and vinylbenzyl phosphonic acid (VBPA), were employed in the copolymerization reaction. Using VBPA as a comonomer leads to particles with a higher density of surface phosphonate groups in comparison to those obtained with VPA. VBPA-functionalized particles were used for the coating formation on the titanium surface. The particles monolayer was investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM) employing titanium and silicium tip with the native OH groups. Force versus distance curves proves the strong adhesion between the phosphonated particles and the titanium (or silicium) surfaces in contrast to the nonfunctionalized polystyrene particles. Finally, as a proof of concept, the particles adhered to the surface were further used to nucleate hydroxyapatite, which has high potential for bioimplants. PMID:20690639

Zeller, Anke; Musyanovych, Anna; Kappl, Michael; Ethirajan, Anitha; Dass, Martin; Markova, Dilyana; Klapper, Markus; Landfester, Katharina

2010-08-01

183

Modeling skin-layer salinity with an extended surface-salinity layer  

NASA Astrophysics Data System (ADS)

Due to near-surface salinity stratification, it is problematic to compare satellite-measured surface salinity within the first few centimeters (skin-layer) of the ocean with Argo-measured top-level salinity at about 5 m or with ocean models that do not resolve the skin layer. Although an instrument can be designed to measure the surface salinity, a global scale measurement is currently not available. A regional model can be configured to have a vertical grid in centimeters but it would be computationally prohibited on a global scale due to time step constraints. Here we propose an extended surface-salinity layer (ESSL) within a global ocean circulation model to diagnose skin SSS without increasing the computational cost, while allowing comparable solutions with both satellite and Argo salinity at the respective depths. Using a quarter-degree global ocean model, we show that the ESSL improves near-surface salinity significantly in comparisons with the Aquarius SSS and Argo salinity at 5 and 10 m, respectively. Comparing with data-assimilated HYCOM results reveal that the ESSL provides much stronger seasonal variability of SSS, similar to the Aquarius observations. We also demonstrate that the ESSL solution can be used to constrain the global mean SSS in Aquarius SSS retrieval.

Song, Y. Tony; Lee, Tong; Moon, Jae-Hong; Qu, Tangdong; Yueh, Simon

2015-02-01

184

Magnetorheology and sedimentation behavior of an aqueous suspension of surface modified carbonyl iron particles  

NASA Astrophysics Data System (ADS)

Surface modified carbonyl iron particles (SMCIPs) were synthesized by coating carbonyl iron particles with an organic reagent (N-polyether, N, N, N,-acetyloxy) 2, 6-aminion-1, 3, 4-thiadiazole dimer. The properties of these SMCIPs, including morphology, structure, and magnetic behavior, were characterized using scanning electron microscopy and a vibrating sample magnetometer. Aqueous magnetorheological (MR) fluids were prepared using SMCIPs. MR properties were measured via a strain-controlled parallel disk rheometer equipped with a magnetic field source. Addition of the organic surface coating layer was found to greatly improve sedimentation stability of the aqueous MR fluids at a small cost of a reduction in field dependent yield stress.

Cheng, H. B.; Zuo, L.; Song, J. H.; Zhang, Q. J.; Wereley, N. M.

2010-05-01

185

Deterioration of ZrC-coated fuel particle caused by failure of pyrolytic carbon layer  

Microsoft Academic Search

The ZrC coating layer is a candidate to replace the SiC coating layer of the Triso-coated fuel particles for high-temperature gas-cooled reactors. To understand the behavior of the ZrC-Triso-coated fuel particles at 1800 to 2000°C, a ceramographic examination and an electron probe microanalysis were performed on the ZrC-Triso-coated fuel particles after the post-irradiation heating tests and a thermodynamic analysis of

Kazuo Minato; Kousaku Fukuda; Hajime Sekino; Akiyoshi Ishikawa; Etsuro Oeda

1998-01-01

186

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

187

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

PubMed

We report microstructural and rheological consequences of altering silica particle surface chemistry when the particles are suspended in unentangled polyethylene glycol with a molecular weight of 400. The particle surfaces are altered by reacting them with isobutyltrimethyoxysilane. Levels of silanization are chosen so that the particles remain dispersed in the polymer at all volume fractions studied. Our studies indicate that at the levels studied, silanization does not alter the hydrodynamic thickness of the absorbed polymer layer thickness. Rheological properties are not sensitive to levels of silanization up to particle volume fractions where the average particle separation h ? 6Rg (4.8 nm). At these volume fractions, composite microstructure undergoes changes associated with jamming of soft particles (decorrelations in the first peak of the particle structure factor and the onset of a non-diffusive mechanism that dominates particle density fluctuations at short times.) In the region of volume fractions where h/Rg < 6, the zero-shear rate viscosity of the composites is extremely sensitive to level of silanization with a decrease in the zero-shear rate viscosity by four orders of magnitude observed for the highest levels of silanization studied in comparison to the bare particles. PMID:25600762

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

2015-02-28

188

The effect of concave surface curvature on turbulent boundary layers  

NASA Astrophysics Data System (ADS)

The response of a turbulent boundary layer to suddenly applied concave surface curvature is investigated. The main conclusion of this and the companion paper by Muck, Hoffmann and Bradshaw (1985) is that the effects of concave (destabilizing) and convex (stabilizing) curvature on boundary layers - and presumably on other shear layers - are totally different, even qualitatively. As shown in Muck, Hoffmann and Bradshaw (1985), convex curvature tends to attenuate the pre-existing turbulence and, at least in the case of mild curvature, there are no large changes in statistical average shape. Concave curvature, on the other hand, can lead to the quasi-inviscid generation of longitudinal ('Taylor-Goertler') vortices, and it is shown that significant changes in the turbulence structure are induced both directly by the curvature and indirectly by the vortices.

Hoffmann, P. H.; Muck, K. C.; Bradshaw, P.

1985-12-01

189

Intermittency in the atmospheric surface layer: Unresolved or slowly varying?  

NASA Astrophysics Data System (ADS)

We present streamwise velocity structure functions =<|> (with p=1:5) obtained in the near neutral atmospheric surface layer at the Utah SLTEST site at the highest terrestrial Reynolds number Re?=O(106). We show that the occurrence of very large scale coherent oscillations in the streamwise velocity throughout the wall region, interpreted as genuine structural features of the canonical turbulent boundary layer, affects the scaling exponents of the p>3 order structure functions. This results in a slight alteration of the intermittent behavior of the velocity field. It was found that for positive (fast) large scale oscillation of the low-pass filtered velocity signal, deviations from the Kolmogorov K41 prediction (absence of multiscaling) are more marked, as compared to negative (slow) excursion. The results are discussed in terms of convergence of statistics from atmospheric boundary layer measurements.

Guala, M.; Metzger, M.; McKeon, B. J.

2010-07-01

190

Balloon observations of a particle layer injected by a stratospheric aircraft at 23 KM  

Microsoft Academic Search

An extensive layer of small particles (r>0.01 mum) was observed in association with the passage of a jet aircraft at 23 km altitude. The data are used to estimate the small particle emission index and the source strength of such aircraft at stratospheric altitudes. The impact of such flights on the stratospheic particle population is probably negligible; however, when the

D. J. Hofmann; J. M. Rosen

1978-01-01

191

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 electrochemical vapor depositing a dense skeletal LaCrO.sub.3 structure, between and around the doped LaCrO.sub.3 particles. Additional solid oxide electrolyte and fuel electrode layers can then be added to provide a fuel cell.

Richards, Von L. (Murrysville, PA); Singhal, Subhash C. (Murrysville, PA); Pal, Uday B. (Cambridge, MA)

1992-01-01

192

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

193

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

194

Interaction between surface and atmosphere in a convective boundary layer  

NASA Astrophysics Data System (ADS)

Solar heating of the surface causes the near surface air to warm up and with sufficient buoyancy it ascends through the atmosphere as surface-layer plumes and thermals. The cold fluid from the upper part of the boundary layer descends as downdrafts. The downdrafts and thermals form streamwise roll vortices. All these turbulent coherent structures are important because they contribute most of the momentum and heat transport. While these structures have been studied in depth, their imprint on the surface through energy budget in a convective atmospheric boundary layer has received little attention. The main objective of the present study is to examine the turbulence-induced surface temperature fluctuations for different surface properties and stratification. Experiments were performed to measure atmospheric turbulence using sonic anemometers, fine wire thermocouples and LIDAR; and surface temperature using an infra-red camera over grass and artificial turf fields. The surface temperature fluctuations were found to be highly correlated to the turbulent coherent structures and follow the processes postulated in the surface renewal theory. The spatio-temporal scales and advection speed of the surface temperature fluctuation were found to match with those of turbulent coherent structures. A parametric direct numerical simulation (DNS) study was then performed by solving the solid-fluid heat transport mechanism numerically for varying solid thermal properties, solid thickness and strength of stratification. Even though there were large differences in the friction Reynolds and Richardson numbers between the experiments and numerical simulations, similar turbulent characteristics were observed. The ejection (sweep) events tend to be aligned with the streamwise direction to form roll vortices with unstable stratification. The solid-fluid interfacial temperature fluctuations increase with the decreases in solid thermal inertia; and with the increase in solid thickness to attain a constant value for a sufficiently thick solid. The temperature fluctuation changes from a Gaussian distribution near the wall to a positively skewed distribution away from the wall. The turbulent temperature fluctuations influence the solid interfacial temperature by thermal conduction only. These studies provided unique insights into the solid-fluid coupled heat transport in low and high Reynolds number flows. This turbulence induced surface temperature fluctuation can influence the performances of several satellite remote sensing models.

Garai, Anirban

195

Marangoni instability in a liquid layer with two free surfaces  

NASA Technical Reports Server (NTRS)

The onset of the Marangoni instability in a liquid layer with two free nearly insulating surfaces heated from below is studied. Linear stability analysis yields a condition for the emergence of a longwave or a finite wavelength instability from the quiescent equilibrium state. Using the method of asymptotic expansions, a weakly nonlinear evolution equation describing the spatiotemporal behavior of the velocity and temperature fields at the onset of the longwave instability is derived. The latter is given by delta(M) = 24, delta(M) being the difference between the upper and the lower Marangoni numbers. It is shown that in some parametric range one convective cell forms across the layer, while in other parametric domains two convective cells emerge between the two free surfaces.

Deissler, Robert J.; Oron, Alxander; Duh, J. C.

1993-01-01

196

Effects of surface wave breaking on the oceanic boundary layer  

NASA Astrophysics Data System (ADS)

Existing laboratory studies suggest that surface wave breaking may exert a significant impact on the formation and evolution of oceanic surface boundary layer, which plays an important role in the ocean-atmosphere coupled system. However, present climate models either neglect the effects of wave breaking or treat them implicitly through some crude parameterization. Here we use a one-dimensional ocean model (General Ocean Turbulence Model, GOTM) to investigate the effects of wave breaking on the oceanic boundary layer on diurnal to seasonal time scales. First a set of idealized experiments are carried out to demonstrate the basic physics and the necessity to include wave breaking. Then the model is applied to simulating observations at the northern North Sea and the Ocean Weather Station Papa, which shows that properly accounting for wave breaking effects can improve model performance and help it to successfully capture the observed upper ocean variability.

He, Hailun; Chen, Dake

2011-04-01

197

Measurement of surface layer optical turbulence above AMOS  

NASA Astrophysics Data System (ADS)

Temperature fluctuations in the atmosphere severely limit the angular resolution of earth bound observation facilities to around 1 arcsecond. This corresponds to an effective, coherent, aperture size of 10 cm even though the telescope may have a 2 to 4 m primary mirror. Understanding the spatial and temporal distribution of atmospheric optical turbulence is essential to maximize the performance of large astronomical telescopes. This thesis made use of a 5 kHz high frequency, short range Doppler acoustic sounder to investigate the first 100 meters of the mountain boundary layer turbulence above the Air Force Maui Observation Site, AMOS, Haleakala, HI. These measurements were part of a coordinated site evaluation for a proposed 4 m telescope to be built at AMOS in the near future. Tentative results revealed significant layering, 15 to 20 m and occasionally thicker, in the turbulent surface layers above AMOS. Additionally, a comparison of two proposed construction sites near the top of Haleakala showed that the turbulent surface layer tends to follow the contours of the mountain.

1991-12-01

198

On the Effects of Surface Roughness on Boundary Layer Transition  

NASA Technical Reports Server (NTRS)

Surface roughness can influence laminar-turbulent transition in many different ways. This paper outlines selected analyses performed at the NASA Langley Research Center, ranging in speed from subsonic to hypersonic Mach numbers and highlighting the beneficial as well as adverse roles of the surface roughness in technological applications. The first theme pertains to boundary-layer tripping on the forebody of a hypersonic airbreathing configuration via a spanwise periodic array of trip elements, with the goal of understanding the physical mechanisms underlying roughness-induced transition in a high-speed boundary layer. The effect of an isolated, finite amplitude roughness element on a supersonic boundary layer is considered next. The other set of flow configurations examined herein corresponds to roughness based laminar flow control in subsonic and supersonic swept wing boundary layers. A common theme to all of the above configurations is the need to apply higher fidelity, physics based techniques to develop reliable predictions of roughness effects on laminar-turbulent transition.

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

2009-01-01

199

Time Scales in the Unstable Atmospheric Surface Layer  

Microsoft Academic Search

Calculation of eddy covariances in the atmospheric surface layer (ASL) requires separating the instantaneous signal into mean\\u000a and fluctuating components. Since the ASL is not statistically stationary, an inherent ambiguity exists in defining the mean\\u000a quantities. The present study compares four methods of calculating physically relevant time scales in the unstable ASL that\\u000a may be used to remove the unsteady

Meredith Metzger; Heather Holmes

2008-01-01

200

Surface-plasmons lasing in double-graphene-layer structures  

SciTech Connect

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. [Research Institute for Electrical Communication, Tohoku University, Sendai 980-8577 (Japan); Institute for Physics of Microstructures of Russian Academy of Sciences, and Lobachevsky State University of Nizhny Novgorod, Nizhny Novgorod 603950 (Russian Federation); Aleshkin, V. Ya. [Institute for Physics of Microstructures of Russian Academy of Sciences, and Lobachevsky State University of Nizhny Novgorod, Nizhny Novgorod 603950 (Russian Federation); Ryzhii, V. [Research Institute for Electrical Communication, Tohoku University, Sendai 980-8577 (Japan); Center for Photonics and Infrared Engineering, Bauman Moscow State Technical University, Moscow 105005 (Russian Federation); Shur, M. S. [Department of Electrical, Electronics, and System Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Otsuji, T. [Research Institute for Electrical Communication, Tohoku University, Sendai 980-8577 (Japan)

2014-01-28

201

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

202

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

NASA Astrophysics Data System (ADS)

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.

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

2014-03-01

203

Microstructural evolution of surface layers during Electrolytic Plasma Processing  

NASA Astrophysics Data System (ADS)

Electrolytic Plasma Processing is an emerging technology for surface modification. The EPP process is based on electrolysis of an aqueous electrolyte by application of an electrical potential between the workpiece and counter-electrode, and the production of plasma (micro-arc discharges on the workpiece surface). The plasma micro-arcs provide a heat source for surface modification via localized surface melting and rapid cooling (cleaning process) and, if desirable, enhance ion deposition on a given substrate (coating). Three substrates (low carbon steel, pure Al and pure Ti) were "cleaned" by EPP and their near surface layer microstructure was studied. It was found that the uppermost layer for all three substrate materials was developing a "hill and valley" surface morphology, with individual characteristics influence by material's properties such as melting point, undercooling and surface energy. The affected layer extends up to 2mum for all three substrates and the top layer was found to exhibit ultrafine grains. The EPP modified surface layer developed compressive residual stresses. The magnitude of the stress is correlated to the melting point which controls the annealing and grain growth kinetics, for each material. Three coating materials, Zn, Ni and Mo, with a wide range of melting temperature were deposited by EPP on steel substrates. The topography exhibited by each coating was found to be influenced by its surface energy. Low surface energy coating material will present large nodules, high deposition rate and increased porosity. Medium surface energy coating materials were found to develop large nodules, lower deposition rates and low porosity. High surface energy coatings tend to present nodule coalescence and may exhibit crack formation, depending on the difference in TM between the substrate and the coating material. The microstructure at the coating/substrate interface was studied. Two controlling parameters were found regarding substrate/coating interface evolution. These are difference in melting point between substrate and coating material and the phase diagram characteristics. The extent of the interface was related to the difference in TM between the coating and the substrate material. A low TM coating material (Zn) interface will form intermetallics as predicted by the phase diagram. A coating with comparable TM with the substrate (Ni) results in a liquid phase with both elements soluble and depending on the phase diagram characteristics, significant mixing can occur at the interface. The formation of the high melting temperature coating (Mo) was found to be dominated by its large TM compared to the substrate. The continuous presence of a liquid phase of the substrate material was resulting in the extension of the interface far into the coating. Depending on the phase diagram, intermetallics may form at the interface. The present findings show that a judicious selection of coating materials can be made by considering the coupling substrate -- coating TM and their binary phase diagram.

Cionea, Cristian

204

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

205

Magnetoconductance Oscillations of n-Type Inversion Layers in InSb Surfaces  

Microsoft Academic Search

The galvanomagnetic properties of conduction electrons in n-type inversion layers of InSb have been investigated. The motion of electrons in an inversion layer is quantized in the direction normal to the surface by the surface electric field associated with the inversion layer. In a strong magnetic field normal to the surface, the motion parallel to the surface is also quantized

Nobuo Kotera; Yoshifumi Katayama; Kiichi F. Komatsubara

1972-01-01

206

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

207

Synthesis and surface chemistry of nano silver particles  

Microsoft Academic Search

In this report, we present a simple wet chemical route to synthesize nano-sized silver particles, and their surface properties are discussed in detail. Silver nano particles of the size 40–80nm are formed in the process of oxidation of glucose to gluconic acid by amine in the presence of silver nitrate, and the gluconic acid caps the nano silver particle. The

Revathi Janardhanan; Murugan Karuppaiah; Neha Hebalkar; Tata Narsinga Rao

2009-01-01

208

Characterization of triboelectrically charged particles deposited on dielectric surfaces  

Microsoft Academic Search

A device for the measurement of q\\/m-values and charge degradation of triboelectrically charged particles deposited on a surface was developed. The setup is based on the integration of currents, which are induced in a Faraday cage by insertion of a solid support covered with charged particles. The conductivity of different particle supports was taken into account. The 'blow-off' method, in

A. Nesterov; F. Löffler; Yun-Chien Cheng; G. Torralba; K. König; M. Hausmann; V. Lindenstruth; V. Stadler; F. R. Bischoff; F. Breitling

2010-01-01

209

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...

210

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...

211

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

212

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

213

Time Scales in the Unstable Atmospheric Surface Layer  

NASA Astrophysics Data System (ADS)

Calculation of eddy covariances in the atmospheric surface layer (ASL) requires separating the instantaneous signal into mean and fluctuating components. Since the ASL is not statistically stationary, an inherent ambiguity exists in defining the mean quantities. The present study compares four methods of calculating physically relevant time scales in the unstable ASL that may be used to remove the unsteady mean components of instantaneous time signals, in order to yield local turbulent fluxes that appear to be statistically stationary. The four mean-removal time scales are: ( t c ) based on the location of the maximum in the ogive of the heat flux cospectra, (tilde t_{MR}) the location of the zero crossing in the multiresolution decomposition of the heat flux, ( t *) the ratio of the mixed-layer depth over the convective velocity, and (tilde t ) the convergence time of the vertical velocity and temperature variances. The four time scales are evaluated using high quality, three-dimensional sonic anemometry data acquired at the Surface Layer Turbulence and Environmental Science Test (SLTEST) facility located on the salt flats of Utah’s western desert. Results indicate that t_c? t_{MR} and t^*? tilde t , with t c achieving values about 2-3 times greater than t *. The sensitivity of the eddy covariances to the mean-removal time scale (given a fixed 4-h averaging period during midday) is also demonstrated.

Metzger, Meredith; Holmes, Heather

2008-01-01

214

Consideration of the Effect on Fuel Particle Behavior from Shrinkage Cracks in the Inner Pyrocarbon Layer  

SciTech Connect

The fundamental design for a gas-cooled pebble bed reactor relies on an understanding of the behavior of coated particle fuel. The coating layers surrounding the fuel kernels in these spherical particles consist of pyrolytic carbon layers and a silicon carbide (SiC) layer. These coating layers act as a pressure vessel that retains fission product gases. A small percentage of fuel particles may fail during irradiation in the mode of a traditional pressure vessel failure. Fuel performance models used to predict particle behavior have traditionally been one-dimensional models that focus on this failure mechanism. Results of irradiation experiments, however, show that many more fuel particles fail than would be predicted by this mechanism alone. Post-irradiation examinations indicate that multi-dimensional effects, such as the presence of shrinkage cracks in the inner pyrolytic carbon layer (IPyC), contribute to these unexplained failures. Results of a study performed to evaluate the significance of cracking in the IPyC layer on behavior of a fuel particle are presented herein, which indicate that shrinkage cracks could contribute significantly to fuel particle failures.

Miller, Gregory Kent; Petti, David Andrew; Varacalle, Dominic Joseph; Maki, John Thomas

2001-06-01

215

Fluorescent eco-particles for surface flow physics analysis  

NASA Astrophysics Data System (ADS)

In this letter, we describe a novel methodology for fabricating inexpensive environmentally-friendly fluorescent microparticles for quantitative surface flow visualization. Particles are synthesized from natural white beeswax and a highly diluted solution of a nontoxic fluorescent red dye. Bead fluorescence exhibits a long lifetime in adverse conditions, such as exposure to weathering agents, and is enhanced by Ultra Violet radiation. The fluorescent eco-particles are integrated in a particle image velocimetry study of circular hydraulic jump to demonstrate their feasibility in tracing complex surface flows.

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

2013-03-01

216

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

217

Theory And Measurements For Turbulence Spectra And Variances In The Atmospheric Neutral Surface Layer  

Microsoft Academic Search

Predictions from a new theory for high Reynolds number turbulent boundary layers during near-neutral conditions are shown to agree well with measurements of atmospheric surface-layer variances and spectra. The theory suggests surface-layer turbulence is determined by detached eddies that largely originate in the shearing motion immediately above the surface layer; as they descend into this layer, they are strongly distorted

Ulf Högström; J. C. R. Hunt; Ann-Sofi Smedman

2002-01-01

218

Tribology and Superhydrophobicity of Laser-Controlled-Melted Alumina Surfaces with Hard Particles  

NASA Astrophysics Data System (ADS)

Laser-controlled melting of alumina surface with a carbon film of about 40- ?m thickness formed prior to the laser treatment process is carried out to improve its hardness, durability, and superhydrophocity. The carbon film consisted of a uniformly distributed mixture of hard particles of WC, SiC, and B4C. The presence of carbon film improves the absorption of the laser beam during the treatment process. The morphology and hydrophobicity of the laser-treated surface were evaluated using optical microscopy, atomic force microscopy, and the contact angle measurement, respectively. The chemical changes of the treated layer were examined using scanning electron microscopy and energy-dispersive spectroscopy. The structure of the nitride compound formed at the surface was characterized using x-ray diffraction, which was also used to determine the residual stress at the surface. Both microhardness and fracture toughness of the laser-treated surface were determined using indentation tests. Scratch tests were conducted to measure the friction coefficient and scratch resistance of the laser-treated surface. Laser treatment produces micropoles, nanopoles, and small size cavities at the surface, which enhance hydrophobicity of the surface. The microhardness of the laser-treated surface increases almost 50% because of the dense layer formed at the surface and the residual stress is in the order of -2 GPa, which is compressive. The scratch resistance and friction coefficient of the laser-treated surface is superior.

Yilbas, Bekir Sami; Bhushan, Bharat; Abdul Aleem, B. J.; Gaseem, Zuhair

2014-06-01

219

Laser surface treatment of aluminum based composite mixed with B4C particles  

NASA Astrophysics Data System (ADS)

Laser treatment of hot pressed mixture of aluminum (85 wt%) and B4C (15 wt%) is carried out. Metallurgical and morphological changes at the laser treated surface are examined using the analytical tools. Microhardness and fracture toughness of the workpiece surfaces are determined prior to and after the laser treatment process. Texture and hydrophobicity of the laser treated surface is assessed incorporating the atomic force microscopy and contact angle measurements. It is found that a dense layer consisting of fine grains of sub-micron sizes (0.8-0.4 ?m) and B4C particles is formed at the laser treated surface. Microhardness increases at the laser treated surface because of the presence of the dense layer and the formation of AlN compounds at the surface. Fracture toughness of the laser treated surface reduces slightly because of the microhardness enhancement at the surface. The textures of the laser treated surface compose of micro/nano poles, which result in higher contact angles than that of the untreated surface, and formation of AlN compound adds to the surface hydrophobicity enhancements.

Yilbas, B. S.; Karatas, C.; Karakoc, Halil; Abdul Aleem, B. J.; Khan, S.; Al-Aqeeli, N.

2015-03-01

220

Utilization of surface-treated rubber particles from waste tires  

SciTech Connect

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

Smith, F.G. [Argonne National Lab., IL (United States). Energy Systems Div.]|[Environmental Technologies Alternatives, Inc., Lima, OH (United States)

1994-12-01

221

Simultaneous detection of separation and transition in surface shear layers  

NASA Technical Reports Server (NTRS)

Flush-mounted hot-film gages have proved effective in detecting boundary-layer transition and in measuring skin friction but with limited success in detecting laminar separation and reattachment. The development of multielement micro hot-film sensors, and the recent discovery of the phase reversal phenomena associated with low-frequency dynamic shear stress signals across regions of laminar separation and turbulent reattachment, have made it possible to simultaneously and unambiguously detect these surface shear layer characteristics. Experiments were conducted on different airfoils at speeds ranging from low subsonic to transonic speeds to establish the technique for incompressible and compressible flow applications. The multielement dynamic shear stress sensor technique was successfully used to detect laminar separation, turbulent reattachment, as well as, shock induced laminar and turbulent separation.

Mangalam, Siva M.; Stack, J. P.; Sewall, W. G.

1989-01-01

222

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

223

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

224

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...

225

Reducing the adhesion between surfaces using surface structuring with PS latex particle  

E-print Network

Force Microscope (AFM),9­11 capacitive force sensors12 or nanoindentation testers.13,14 The modeling by polystyrene latex particles (PS particles) with radii from 100 to 1500 nm. The adhesion force measurements methods to measure micro/nanoforces between surfaces are the Surface Force Apparatus (SFA),7,8 the Atomic

Paris-Sud XI, Université de

226

Characteristics of shear layer with pyrolysing coal particles in one of the streams  

SciTech Connect

This article presents an experimental study of the growth and structure of a two-dimensional shear layer formed by two gas streams, one of which contained coal particles undergoing pyrolysis. Apparatus consisted of a low speed shear layer wind-tunnel designed to generate two gas streams, initially with uniform velocity profiles and isotropic turbulence, which mix at the end of a splitter plate. A fluidized bed injector system was used to introduce bituminous coal particles into one of the streams which was heated to cause their pyrolysis. The test section was optically accessible. The instrumentation included thermocouple, Pitot tube, laser velocimeter, and gas analyzers. Velocity profiles, temperature profiles, shear layer growth rate parameter, and turbulent intensity measurements were obtained. Results indicate that the presence of coal particles affect the velocity and decreases the shear layer growth rate (visible and vorticity thickness) significantly; however, the mass addition due to pyrolysis alone does not change the shear layer characteristics significantly.

Gollahalli, S.R.; Butuk, N.

1998-07-01

227

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

228

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

NASA Technical Reports Server (NTRS)

The Interplanetary Dust Experiment (IDE) had over 450 electrically active ultra-high purity metal-oxide-silicon impact detectors located on the six primary sides of the Long Duration Exposure Facility (LDEF). Hypervelocity micro-particles that struck the active sensors with enough energy to breakdown the 0.4 to 1.0 micron thick SiO2 insulator layer separating the silicon base (the negative electrode), and the 1000 A thick surface layer of aluminum (the positive electrode) caused electrical discharges that were recorded for the first year of orbit. These discharge features, which include 50 micron diameter areas where the aluminum top layer has been vaporized, facilitate the location of the impacts. The high purity Al-SiO2-Si substrates allow detection of trace (ppm) amounts of hypervelocity impactor residues. After sputtering through a layer of surface contamination, secondary ion mass spectrometry (SIMS) is used to create two-dimensional elemental ion intensity maps of micro-particle impact sites on the IDE sensors. The element intensities in the central craters of the impacts are corrected for relative ion yields and instrumental conditions and then normalized to silicon. The results are used to classify the particles' origins as 'manmade', 'natural' or 'indeterminate'. The last classification results from the presence of too little impactor residue (a frequent occurrence on leading edge impacts), analytical interference from high background contamination, the lack of information on silicon residue, the limited usefulness of data on aluminum in the central craters, or a combination of these circumstances. Several analytical 'blank' discharges were induced on flight sensors by pressing down on the sensor surface with a pure silicon shard. Analyses of these blank discharges showed that the discharge energy blasts away the layer of surface contamination. Only Si and Al were detected inside the discharge zones, including the central craters, of these features. A total of 35 impacts on leading edge sensors and 22 impacts on trailing edge sensors were analyzed.

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

1992-01-01

229

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

230

The structure of the near neutral atmospheric surface layer as observed during the CASES'99 experiment  

Microsoft Academic Search

Recent observational data obtained during the Cooperative Surface-Atmosphere Exchange Study field campaign in October 1999 (CASES'99), show evidence of layered structure of the near-neutral surface layer (SL): (i) the upper surface layer (USL) which corresponds to the upper part of the surface layer, where the mean velocity profile is logarithmic and the spectrum decays as k_1-5\\/3 (where k_1 is the

P. Drobinski; P. Carlotti; R. K. Newsom; R. M. Banta; R. C. Foster; J. L. Redelsperger

2003-01-01

231

Surface-sensitive macrobolometers for the identification of external charged particles  

E-print Network

We report the performance of two prototype TeO2 macrobolometers, operated at ~25 mK, able to identify events due to energy deposited at the detector surface. This capability is obtained by thermally coupling thin Ge active layers to the main energy absorber of the bolometer, and is demonstrated by irradiating the detectors with alpha particles. The temperature variations of the main absorber and of the active layer are measured independently with doped Ge thermistors. These results show clearly that an intrinsic limitation of monolithic low temperature calorimeters, e.g., the impossibility to give information about event position, can be efficiently overcome using composite structures.

Luca Foggetta; Andrea Giuliani; Claudia Nones; Marisa Pedretti; Samuele Sangiorgio

2009-09-04

232

Lateral optical force on chiral particles near a surface  

PubMed Central

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

233

Thermodynamic model of hydrogen-induced silicon surface layer cleavage  

NASA Astrophysics Data System (ADS)

A thermodynamic model of hydrogen-induced silicon surface layer splitting with the help of a bonded silicon wafer is proposed in this article. Wafer splitting is the result of lateral growth of hydrogen blisters in the entire hydrogen-implanted region during annealing. The blister growth rate depends on the effective activation energies of both hydrogen complex dissociation and hydrogen diffusion. The hydrogen blister radius was studied as a function of annealing time, annealing temperature, and implantation dose. The critical radius was obtained according to the Griffith energy condition. The time required for wafer splitting at the cut temperature was calculated in accordance with the growth of hydrogen blisters.

Han, Weihua; Yu, Jinzhong

2001-06-01

234

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

PubMed Central

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

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

2013-01-01

235

Near-wall micro-PIV reveals a hydrodynamically relevant endothelial surface layer in venules in vivo.  

PubMed

High-resolution near-wall fluorescent microparticle image velocimetry (micro-PIV) was used in mouse cremaster muscle venules in vivo to measure velocity profiles in the red cell-depleted plasma layer near the endothelial lining. micro-PIV data of the instantaneous translational speeds and radial positions of fluorescently labeled microspheres (0.47 microm) in an optical section through the midsagittal plane of each vessel were used to determine fluid particle translational speeds. Regression of a linear velocity distribution based on near-wall fluid-particle speeds consistently revealed a negative intercept when extrapolated to the vessel wall. Based on a detailed three-dimensional analysis of the local fluid dynamics, we estimate a mean effective thickness of approximately 0.33 micro m for an impermeable endothelial surface layer or approximately 0.44 micro m assuming the lowest hydraulic resistivity of the layer that is consistent with the observed particle motions. The extent of plasma flow retardation through the layer required to be consistent with our micro-PIV data results in near complete attenuation of fluid shear stress on the endothelial-cell surface. These findings confirm the presence of a hydrodynamically effective endothelial surface layer, and emphasize the need to revise previous concepts of leukocyte adhesion, stress transmission to vascular endothelium, permeability, and mechanotransduction mechanisms. PMID:12829517

Smith, Michael L; Long, David S; Damiano, Edward R; Ley, Klaus

2003-07-01

236

Mini-Review Facing extremes: archaeal surface-layer (glyco)proteins  

E-print Network

in some of the most drastic environments on Earth. The protein-based surface layer that envelopes manyMini-Review Facing extremes: archaeal surface-layer (glyco)proteins Jerry Eichler Correspondence or in acidic surroundings. Study of archaeal surface-layer (glyco)proteins has thus offered insight

Eichler, Jerry

237

Semiclassical Aspect of Collective Motion in a Layer-Structured Many Particle System  

Microsoft Academic Search

Semiclassical argument is presented for the layer vibration in the many particle system with a layer structure, which is expected to be realized in a dense nuclear matter. Within a toy model, the presence of this collective mode is shown to result in a small reduction of system's energy.

Koichi Takahashi; Tatsuo Tsukamoto

1992-01-01

238

Interaction energy and surface reconstruction between sheets of layered silicates  

NASA Astrophysics Data System (ADS)

Interactions between two layered silicate sheets, as found in various nanoscale materials, are investigated as a function of sheet separation using molecular dynamics simulation. The model systems are periodic in the xy plane, open in the z direction, and subjected to stepwise separation of the two silicate sheets starting at equilibrium. Computed cleavage energies are 383mJ /m2 for K-mica, 133mJ/m2 for K-montmorillonite (cation exchange capacity=91), 45mJ/m2 for octadecylammonium (C18)-mica, and 40mJ/m2 for C18-montmorillonite. These values are in quantitative agreement with experimental data and aid in the molecular-level interpretation. When alkali ions are present at the interface between the silicate sheets, partitioning of the cations between the surfaces is observed at 0.25nm separation (mica) and 0.30nm separation (montmorillonite). Originally strong electrostatic attraction between the two silicate sheets is then reduced to 5% (mica) and 15% (montmorillonite). Weaker van der Waals interactions decay within 1.0nm separation. The total interaction energy between sheets of alkali clay is less than 1mJ/m2 after 1.5nm separation. When C18 surfactants are present on the surfaces, the organic layer (>0.8nm) acts as a spacer between the silicate sheets so that positively charged ammonium head groups remain essentially in the same position on the surfaces of the two sheets at any separation. As a result, electrostatic interactions are efficiently shielded and dispersive interactions account for the interfacial energy. The flexibility of the hydrocarbon chains leads to stretching, disorder, and occasional rearrangements of ammonium head groups to neighbor cavities on the silicate surface at medium separation (1.0-2.0nm). The total interaction energy amounts to less than 1mJ/m2 after 3nm separation.

Heinz, Hendrik; Vaia, R. A.; Farmer, B. L.

2006-06-01

239

Detection of charged particles in thick hydrogenated amorphous silicon layers  

SciTech Connect

We show our results in detecting particles of various linear energy transfer, including minimum ionizing electrons from a Sr-90 source with 5 to 12 micron thick n-i-p and p-i-n diodes. We measured W ( average energy to produce one electron-hole pair) using 17keV filtered xray pulses with a result W = 6.0 /+-/ 0.2eV. This is consistent with the expected value for a semiconductor with band gap of 1.7 to 1.9eV. With heavily ionizing particles such as 6 MeV alphas and 1 to 2 MeV protons, there was some loss of signal due to recombination in the particle track. The minimum ionizing electrons showed no sign of recombination. Applications to pixel and strip detectors for physics experiments and medical imaging will be discussed. 7 refs., 8 figs.

Fujieda, I.; Cho, G.; Kaplan, S.N.; Perez-Mendez, V.; Qureshi, S.; Ward, W.; Street, R.A.

1988-03-01

240

Confinement of dust particles in a double layer A. Barkan and R. L. Merlin0  

E-print Network

contains charged dust particles. These multicomponent plasmas are relatively common throughout the universe into a typical laboratory plasma, they become charged by the collection of ions and electrons. ElectronsConfinement of dust particles in a double layer A. Barkan and R. L. Merlin0 Department of Physics

Merlino, Robert L.

241

On the Impact of Collisions on Particle Dispersion in a Shear Layer  

Microsoft Academic Search

In this numerical study the impact of collisions on the evolution of a dispersed phase in a gaseous shear layer flow is investigated. The disperse phase consists of spherical particles which may experience two modes of collision: In the first, the collision has no effect on the particles themselves and is simply registered for accounting purposes. In the second, the

Marios Soteriou; John Mosley

1999-01-01

242

Microstructures of tribologically modified surface layers in two-phase alloys  

NASA Astrophysics Data System (ADS)

When ductile alloys are subject to sliding wear, small increments of plastic strain accumulate into severe plastic deformation and mechanical alloying of the surface layer. The authors constructed a simple coaxial tribometer, which was used to study this phenomenon in wrought Al-Sn and cast Cu-Mg-Sn alloys. The first class of materials is ductile and consists of two immiscible phases. Tribological modification is observed in the form of a transition zone from virgin material to severely deformed grains. At the surface, mechanical mixing of both phases competes with diffusional unmixing. Vortex flow patterns are typically observed. The experimental Cu-Mg-Sn alloys are ductile for Mg-contents up to 2 wt% and consist of a- dendrites with a eutectic consisting of a brittle Cu2Mg-matrix with ?-particles. In these, the observations are similar to the Al-Sn Alloys. Alloys with 5 wt% Mg are brittle due to the contiguity of the eutectic compound. Nonetheless, under sliding contact, this compound behaves in a ductile manner, showing mechanical mixing of a and Cu2Mg in the top layers and a remarkable transition from a eutectic to cellular microstructure just below, due to severe shear deformation. AFM-observations allow identifying the mechanically homogenized surface layers as a nanocrystalline material with a cell structure associated to the sliding direction.

Figueroa, C. G.; Ortega, I.; Jacobo, V. H.; Ortiz, A.; Bravo, A. E.; Schouwenaars, R.

2014-08-01

243

The Zeta Potential of Surface-Functionalized Metallic Nanorod Particles in Aqueous Solution  

SciTech Connect

Metallic nanoparticles suspended in aqueous solutions, and functionalized with chemical and biological surface coatings, are important elements in basic and applied nanoscience research. Many applications require an understanding of the electrokinetic or colloidal properties of such particles. In this paper we describe the results of experiments to measure the zeta potential of metallic nanorod particles in aqueous saline solutions, including the effects of pH, ionic strength, metallic composition, and surface functionalization state. Particle substrates tested include gold, silver, and palladium monometallic particles as well as gold/silver bimetallic particles. Surface functionalization conditions included 11-mercaptoundecanoic acid (MUA), mercaptoethanol (ME), and mercaptoethanesulfonic acid (MESA) self-assembled monolayers (SAMs), as well as MUA layers subsequently derivatized with proteins. Zeta potential data for typical charge-stabilized polystyrene particles are also presented for comparison. Experimental data are compared with theory. The results of these studies are useful in predicting and controlling the aggregation, adhesion, and transport of functionalized metallic nanoparticles within microfluidic devices and other systems.

Dougherty, G M; Rose, K A; Tok, J B; Pannu, S S; Chuang, F S; Sha, M Y; Chakarova, G; Penn, S G

2007-05-07

244

Particle selection through topographic surface patterns in nematic colloids  

E-print Network

We propose the use of topographic modulation of surfaces to select and localize particles in nematic colloids. By considering convex and concave deformations of one of the confining surfaces we show that the colloid-flat surface repulsion may be enhanced or switched into an attraction. In particular, we find that when the colloidal particles have the same anchoring conditions as the patterned surfaces, they are strongly attracted to concave dimples, while if they exhibit different anchoring conditions they are pinned at the top of convex protrusions. Although dominated by elastic interactions the first mechanism is reminiscent of the depletion induced attraction or of the key-lock mechanism, while the second is specific to liquid crystal colloids. These long-ranged, highly tunable, surface-colloid interactions contribute for the development of template-assisted assembly of large colloidal crystals, with well defined symmetries, required for applications.

Z. Eskandari; N. M. Silvestre; M. M. Telo da Gama; M. R. Ejtehadi

2014-06-03

245

Surface charge features of kaolinite particles and their interactions  

NASA Astrophysics Data System (ADS)

Kaolinite is both a blessing and a curse. As an important industrial mineral commodity, kaolinite clays are extensively used in the paper, ceramic, paint, plastic and rubber industries. In all these applications the wettability, aggregation, dispersion, flotation and thickening of kaolinite particles are affected by its crystal structure and surface properties. It is therefore the objective of this research to investigate selected physical and surface chemical properties of kaolinite, specifically the surface charge of kaolinite particles. A pool of advanced analytical techniques such as XRD, XRF, SEM, AFM, FTIR and ISS were utilized to investigate the morphological and surface chemistry features of kaolinite. Surface force measurements revealed that the silica tetrahedral face of kaolinite is negatively charged at pH>4, whereas the alumina octahedral face of kaolinite is positively charged at pH<6, and negatively charged at pH>8. Based on electrophoresis measurements, the apparent iso-electric point for kaolinite particles was determined to be less than pH 3. In contrast, the point of zero charge was determined to be pH 4.5 by titration techniques, which corresponds to the iso-electric point of between pH 4 and 5 as determined by surface force measurements. Results from kaolinite particle interactions indicate that the silica face--alumina face interaction is dominant for kaolinite particle aggregation at low and intermediate pH values, which explains the maximum shear yield stress at pH 5-5.5. Lattice resolution images reveal the hexagonal lattice structure of these two face surfaces of kaolinite. Analysis of the silica face of kaolinite showed that the center of the hexagonal ring of oxygen atoms is vacant, whereas the alumina face showed that the hexagonal surface lattice ring of hydroxyls surround another hydroxyl in the center of the ring. High resolution transmission electron microscopy investigation of kaolinite has indicated that kaolinite is indeed composed of silica/alumina bilayers with a c-spacing of 7.2 A. The surface charge densities of the silica face, the alumina face and the edge surface of kaolinite all influence particle interactions, and thereby affect the mechanical properties of kaolinite suspensions. The improved knowledge of kaolinite surface chemistry from this dissertation research provides a foundation for the development of improved process strategies for both the use and disposal of clay particles such as kaolinite.

Gupta, Vishal

246

Quartz crystal microbalance-based evaluation of the electrochemical formation of an aggregated polypyrrole particle-based layer.  

PubMed

Electrochemical quartz crystal microbalance (EQCM) was used for the evaluation of conducting polymer polypyrrole (Ppy), which was formed by a sequence of potential pulses on a Au-plated EQCM disc. The Ppy layer was obtained from freshly prepared polymerization solution consisting of pyrrole that was dissolved in phosphate buffer. The main aim of the study was to determine some aspects of the Ppy layer formation process. The polymerization process was estimated by EQCM and chronoamperometry. The Cottrell equation was used for the integration of total charge that was passing through the electrochemical cell during the formation of the Ppy-based layer. It was found that the charge of the electrical double layer, which was estimated while applying an Anson plot, is negative. From this observation, it could be assumed that the pyrrole oxidation process could be well described by principles of heterogeneous kinetics. The negative value of the electrical double layer was the result of a charge-transfer restriction. This restriction of charge transfer could occur due to partial blocking of the electrode surface by an aggregated Ppy particle-based layer. Quartz crystal motional resistance (R) was taken into account during this research. Ppy layer formation is represented schematically on the basis of the obtained experimental results and analytical data. PMID:25706444

Plausinaitis, Deivis; Ratautaite, Vilma; Mikoliunaite, Lina; Sinkevicius, Linas; Ramanaviciene, Almira; Ramanavicius, Arunas

2015-03-17

247

Real-time assessment of surface interactions with titanium passivation layer by surface plasmon resonance  

PubMed Central

The high corrosion resistance and strength-to-density ratio makes titanium widely used in major industry, but also in a gamut of medical applications. Here we report for the first time on our development of a titanium passivation layer sensor that makes use of surface plasmon resonance (SPR). The deposited titanium metal layer on the sensor was passivated in air, like titanium medical devices. Our ‘Ti-SPR sensor’ enables analysis of biomolecules interactions with the passivated surface of titanium in real time. As a proof of concept, corrosion of titanium passivation layer exposed to acid was monitored in real time. Also, the Ti-SPR sensor can accurately measure the time-dependence of protein adsorption onto titanium passivation layer with a sub-nanogram per square millimeter accuracy. Besides such SPR analyses, an SPR-imaging (SPRI) enables real-time assessment of chemical surface processes that occur simultaneously at ‘multiple independent spots’ on the Ti-SPR sensor, such as acid-corrosion or adhesion of cells. Our Ti-SPR sensor will therefore be very useful to study titanium-corrosion phenomena and biomolecular titanium-surface interactions with application in a broad range of industrial and biomedical fields. PMID:22154862

Hirata, Isao; Yoshida, Yasuhiro; Nagaoka, Noriyuki; Hiasa, Kyou; Abe, Yasuhiko; Maekawa, Kenji; Kuboki, Takuo; Akagawa, Yasumasa; Suzuki, Kazuomi; Van Meerbeek, Bart; Messersmith, Phillip B.; Okazaki, Masayuki

2011-01-01

248

Surface wave effects on long range IR imaging in the marine surface layer  

Microsoft Academic Search

The quality of long range infrared (IR) imaging depends on the effects of atmospheric refraction and other pathintegrated effects (e.g., transmission losses, scintillation and blurring), which are strongly related to the prevailing meteorological conditions. EOSTAR is a PC based computer program to quantify these strong nonlinear effects in the marine atmospheric surface layer and to present a spectrally resolved target

M. J. Francius; G. J. Kunz; A. M. J. van Eijk

2005-01-01

249

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

250

Enhanced TiO2 surface electrochemistry with carbonised layer-by-layer cellulose-PDDA composite films.  

PubMed

In this report we demonstrate a versatile (and potentially low-cost) cellulose nano-whisker-based surface carbonisation method that allows well-defined films of TiO(2) nanoparticles surface-modified with carbon to be obtained. In a layer-by-layer electrostatic deposition process based on TiO(2) nanoparticles, cellulose nano-whiskers, and poly(diallyl-dimethylammonium) or PDDA are employed to control the ratio of surface carbon to TiO(2). Characterisation based on optical, AFM, XRD, and XPS methods is reported. Electrochemical measurements suggest improved access to surface states, dopamine binding at the anatase surface, and surface redox cycling aided by the thin amorphous carbon film in mesoporous TiO(2). In future, the amorphous carbon layer method could be applied for surface processes for a wider range of semiconductor or insulator surfaces. PMID:21499622

Vuorema, Anne; Shariki, Sara; Sillanpää, Mika; Thielemans, Wim; Nelson, Geoffrey W; Foord, John S; Dale, Sara E C; Bending, Simon; Marken, Frank

2011-05-28

251

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

252

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

253

Surface Preparation Effects for Molecular Beam Epitaxial Growth of ZnSe Layers on InGaP Layers  

Microsoft Academic Search

The effect of InGaP surface preparation has been investigated for the molecular beam epitaxial (MBE) growth of ZnSe. The net acceptor concentration profile near the interface of nitrogen-doped p-type ZnSe layers was strongly affected by the surface preparation of InGaP layers. The low net acceptor concentration region for the samples grown on a thermally treated (580°C) or P2S5-treated InGaP surface

Shinji Saito; Yukie Nishikawa; Masaaki Onomura; Peter J. Parbrook; Masayuki Ishikawa; Genichi Hatakoshi

1994-01-01

254

Deposition of latex particles encapsulated in polyelectrolyte shells at heterogeneous metal surfaces modified by multilayer films  

NASA Astrophysics Data System (ADS)

We used an oblique impinging jet (OIJ) cell to determine the initial deposition rate for the microcapsules deposited on the heterogeneous metal surfaces bare or modified by polyelectrolyte (PE) films. The dependence of reduced particle flux on the Reynolds number of the flow in the OIJ cell was determined by direct counting of particles deposited on the studied surfaces. We used fluorescently labelled latex particles and microcapsules built on these fluorescent cores and the use of fluorescent microscope allowed us to observe "in situ" the deposition processes of particles on rough, highly reflective surfaces. We demonstrated that modification of metallic surfaces of various materials and heterogeneity by the multilayer PE films result in the formation of uniformly charged film of nanometers thickness. The formation of such a film leads to the increase of deposition efficiency and its initial rate is governed by the charge of the film covered surface and the outermost layer of the capsule shell being in agreement with the prediction of the convective-diffusion theory.

Szyk-Warszynska, Lilianna; Trybala, Anna; Warszynski, Piotr

2010-06-01

255

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

256

Particle production from marginally trapped surfaces of general spacetimes  

NASA Astrophysics Data System (ADS)

We provide a general formalism that allows us to analyze the phenomenon of tunneling in arbitrary spacetimes. We show that a flux of particles produced by tunneling through general marginally trapped surfaces (MTSs) may be perceived by some privileged observers. We discuss how this particle perception can be related to Hawking/Unruh radiation in specific cases. Our approach naturally leads to an expression for the effective surface gravity of MTSs. The procedure is applicable to general astrophysical and cosmological dynamical situations. Some practical examples for known and new cases are provided.

Senovilla, José M. M.; Torres, Ramón

2015-04-01

257

Electron microscopic evaluation of the endothelial surface layer of glomerular capillaries.  

PubMed

Recent data from various vascular beds suggest that a layer of mucopolysaccharides covering the endothelial cells play an important role in transport processes, among others. In this study, electron microscopy (EM) was used to explore the presence of an endothelial surface layer (ESL) in rat glomerular capillaries. We adopted various fixation and labeling techniques, as follows: (1) negatively charged lipid particles were used as a tracer that was expected to be excluded from the ESL. The density of intravascular lipid particles in flow-arrested capillaries was 89% lower in a 200-nm periendothelial area than in the rest of the luminal space (n = 6 rats, P < 0.001); (2) podocytes of cryofixed fresh tissue had a 20-nm extramembranous coat, interpreted as the true glycocalyx; the coat was less expressed on the endothelium; (3) on unfixed endothelial cells, colloidal lanthanum labeled a 60-nm-thick layer, occasionally forming lumps; (4) perfusion with a fluorocarbon-based oxygen-carrying fixative, followed by tannic acid contrast enhancement, revealed an extensive (> 200 nm) ESL not previously described; however, this finding was restricted to superficial glomerular capillaries; (5) Cupromeronic Blue cytochemistry displayed a loose proteoglycan network in fenestral openings and, occasionally, a semiordered ESL; (6) ferricyanide-reduced osmication resulted in increased numbers of fenestral diaphragms. In conclusion, this study provides novel morphological evidence to support the presence of a significant glomerular ESL. PMID:14709398

Hjalmarsson, Clara; Johansson, Bengt R; Haraldsson, Börje

2004-01-01

258

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

259

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

PubMed Central

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

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

2010-01-01

260

Land-Surface Heterogeneity Effects in the Planetary Boundary Layer  

NASA Astrophysics Data System (ADS)

We investigate the cumulative added value of assimilating temperature, moisture, and wind observations in the three-dimensional non-hydrostatic Fifth-Generation Pennsylvania State University/National Center for Atmospheric Research Mesoscale Model MM5 and use these forecasts to analyze the relationship between surface forcing and planetary boundary-layer (PBL) depth. A data assimilation methodology focused on the surface and the PBL, previously tested in a one-dimensional version of MM5, is applied to 29 May, 6 June, and 7 June 2002 during the International Project over the Southern Great Plains. Model-predicted PBL depth is evaluated against PBL depth diagnosed from data across 4,800 km of airborne lidar data (flight tracks 100-300 km long). The forecast with data assimilation verifies better against observations and is thus used to investigate the environmental conditions that govern PBL depth. The spatial structure in PBL depth is found to be most affected by spatial variations in surface buoyancy flux and capping inversion strength. The spatial scales of surface flux forcing reflected in the PBL depth are found through Fourier analysis and multiresolution decomposition. Correlations are at scales of 64 km or less and increase at larger scales for 29 May and 6 June, but on 7 June low correlations are found at all scales, possibly due to greater within-PBL wind speeds, a stronger capping inversion on this day, and clouds. The results suggest a minimum scale, a function of wind speed, below which heterogeneity in surface buoyancy fluxes is not reflected directly in PBL depth.

Reen, Brian P.; Stauffer, David R.; Davis, Kenneth J.

2014-01-01

261

Analysis of Nb3Sn surface layers for superconducting radio frequency cavity applications  

NASA Astrophysics Data System (ADS)

We present an analysis of Nb3Sn surface layers grown on a bulk Niobium (Nb) coupon prepared at the same time and by the same vapor diffusion process used to make Nb3Sn coatings on 1.3 GHz Nb cavities. Tunneling spectroscopy reveals a well-developed, homogeneous superconducting density of states at the surface with a gap value distribution centered around 2.7 ± 0.4 meV and superconducting critical temperatures (Tc) up to 16.3 K. Scanning transmission electron microscopy performed on cross sections of the sample's surface region shows an ˜2 ?m thick Nb3Sn surface layer. The elemental composition map exhibits a Nb:Sn ratio of 3:1 and reveals the presence of buried sub-stoichiometric regions that have a ratio of 5:1. Synchrotron x-ray diffraction experiments indicate a polycrystalline Nb3Sn film and confirm the presence of Nb rich regions that occupy about a third of the coating volume. These low Tc regions could play an important role in the dissipation mechanisms occurring during RF tests of Nb3Sn-coated Nb cavities and open the way for further improving a very promising alternative to pure Nb cavities for particle accelerators.

Becker, Chaoyue; Posen, Sam; Groll, Nickolas; Cook, Russell; Schlepütz, Christian M.; Hall, Daniel Leslie; Liepe, Matthias; Pellin, Michael; Zasadzinski, John; Proslier, Thomas

2015-02-01

262

Dehydration of the surfaces of the particles in a silicon dioxide hydrosol in the presence of electrolytes  

SciTech Connect

The spin-lattice relaxation time of the protons in a silicon dioxide hydrosol in the presence of ammonium molybdates have been measured by the spin echo method. The correlation times and thermodynamic activation parameters of the nuclear magnetic relaxation, as well as the thickness of the hydration layers of the sol particles within which the surface of the dispersed phase influences the relaxation processes of water protons, have been calculated. It has been shown that the chemical interaction of the molybdates with the surfaces of the sol particles results in dehydration of the particles and a change in the aggregative stability of the sol.

Valyukhov, A.A.; Ermakov, V.I.; Frolov, Y.G.; Nazarov, V.V.

1986-05-01

263

Defect Ordering on the Surface of Layered Strontium Ruthenates  

NASA Astrophysics Data System (ADS)

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 of 1.3 nm. We identify these defects for the first time as a pair of missing atoms: SrO. This idea is supported by the observation of SrO desorption from SrRuO3 during heating. First principles calculations compare removal of this neutral pair to removal of a single atom and simulate the observed STM images. The missing SrO pair leaves a surface defect with an effective dipole moment which provides the interaction producing alignment at low temperatures. ^1 E. W. Plummer, Ismail. R. Matzdorf, A. V. Melechko. and Jiandi Zhang, Prog. Surf. Sci., 67, 17 (2001)

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

2004-03-01

264

In vitro behavior of layer-by-layer deposited molecular oligoelectrolyte films on Ti–6Al–4V surfaces  

Microsoft Academic Search

Layer-by-layer self-assembled films of molecular oligoelectrolytes were used to modify Ti–6Al–4V surfaces in order to test\\u000a their ability as potential drug delivery system. With regard to medical application the in vitro behavior of the modified\\u000a material was investigated. The Ti–6Al–4V (6% aluminium, 4% vanadium) material was treated in a layer-by-layer (LbL) process\\u000a with 2, 4, 6 and 8 layers of

Sabine Ponader; Karin Rosenlehner; Eleftherios Vairaktaris; Cornelius von Wilmowsky; Karl A. Schlegel; Friedrich W. Neukam; Cordula D. Schmidt; Torsten Schunk; Andreas Hirsch; Emeka Nkenke

2009-01-01

265

Cellular interactions of surface modified nanoporous silicon particles  

NASA Astrophysics Data System (ADS)

In this study, the self-assembly of hydrophobin class II (HFBII) on the surface of thermally hydrocarbonized porous silicon (THCPSi) nanoparticles was investigated. The HFBII-coating converted the hydrophobic particles into more hydrophilic ones, improved the particles' cell viability in both HT-29 and Caco-2 cell lines compared to uncoated particles, and enhanced the particles' cellular association. The amount of HFBII adsorbed onto the particles was also successfully quantified by both the BCA assay and a HPLC method. Importantly, the permeation of a poorly water-soluble drug, indomethacin, loaded into THCPSi particles across Caco-2 monolayers was not affected by the protein coating. In addition, 125I-radiolabelled HFBII did not extensively permeate the Caco-2 monolayer and was found to be stably adsorbed onto the THCPSi nanoparticles incubated in pH 7.4, which renders the particles the possibility for further track-imaging applications. The results highlight the potential of HFBII coating for improving wettability, increasing biocompatibility and possible intestinal association of PSi nanoparticulates for drug delivery applications.In this study, the self-assembly of hydrophobin class II (HFBII) on the surface of thermally hydrocarbonized porous silicon (THCPSi) nanoparticles was investigated. The HFBII-coating converted the hydrophobic particles into more hydrophilic ones, improved the particles' cell viability in both HT-29 and Caco-2 cell lines compared to uncoated particles, and enhanced the particles' cellular association. The amount of HFBII adsorbed onto the particles was also successfully quantified by both the BCA assay and a HPLC method. Importantly, the permeation of a poorly water-soluble drug, indomethacin, loaded into THCPSi particles across Caco-2 monolayers was not affected by the protein coating. In addition, 125I-radiolabelled HFBII did not extensively permeate the Caco-2 monolayer and was found to be stably adsorbed onto the THCPSi nanoparticles incubated in pH 7.4, which renders the particles the possibility for further track-imaging applications. The results highlight the potential of HFBII coating for improving wettability, increasing biocompatibility and possible intestinal association of PSi nanoparticulates for drug delivery applications. Electronic supplementary information (ESI) available. See DOI: 10.1039/c2nr30397c

Bimbo, Luis M.; Sarparanta, Mirkka; Mäkilä, Ermei; Laaksonen, Timo; Laaksonen, Päivi; Salonen, Jarno; Linder, Markus B.; Hirvonen, Jouni; Airaksinen, Anu J.; Santos, Hélder A.

2012-05-01

266

Tuning the surface plasmon resonance of core-shell particles  

NASA Astrophysics Data System (ADS)

Gold coated silica core-shell microspheres were synthesized using chemical reduction growth method. Coreshell microspheres were characterized using Scanning electron microscopy (SEM) and Ultraviolet-Visible (UV-Visible) spectroscopy. SEM images show that the surface of microspheres becomes rough which reflects the presence of gold nanoparticles (AuNPs) after coating. UV-Visible spectroscopy shows that the surface plasmon resonance peak undergoes red shift with the shell growth. Core-shell particles were also investigated for different gold concentrations.

Sharma, Ankita; Singh, Bhanu P.; Gathania, Arvind K.

2013-06-01

267

Synthesis and surface properties of submicron barium sulfate particles  

NASA Astrophysics Data System (ADS)

Barium sulfate particles were synthesized in the presence of EDTA at room temperature. X-ray diffractometry (XRD), Fourier transform infrared resonance (FTIR) and scanning electron microscopy (SEM) were used to characterize the structure and morphology of BaSO 4 particles. The effect of the preparation parameters on the particle size distribution and morphology was investigated. The conditional formation constants of Ba-EDTA at different pH values were calculated. The results show that the size and morphology of BaSO 4 particles can be effectively controlled by adding EDTA in the precipitation process. Among all the operation conditions, the pH value has significant effect on the particle size. The obtained barium sulfate particles are spherical and well dispersed at pH = 9-10. Zeta potentials of BaSO 4 were measured at different pH. The isoelectric point (IEP) of barium sulfate colloid appears at pH 6.92. The model of the solid-solution interface at a particle of BaSO 4 was presented. The FTIR result indicates that the surface of the prepared BaSO 4 absorbs the functional groups of EDTA, which lower the IEP of the barium sulfate particles.

Zhang, Ming; Zhang, Bao; Li, Xinhai; Yin, Zhoulan; Guo, Xueyi

2011-10-01

268

Method and apparatus for measuring surface density of explosive and inert dust in stratified layers  

DOEpatents

A method for determining the surface density of coal dust on top of rock dust or rock dust on top of coal dust is disclosed which comprises directing a light source at either a coal or rock dust layer overlaying a substratum of the other, detecting the amount of light reflected from the deposit, generating a signal from the reflected light which is converted into a normalized output (V), and calculating the surface density from the normalized output. The surface density S.sub.c of coal dust on top of rock dust is calculated according to the equation: S.sub.c =1/-a.sub.c ln(V) wherein a.sub.c is a constant for the coal dust particles, and the surface density S.sub.r of rock dust on top of coal dust is determined by the equation: ##EQU1## wherein a.sub.r is a constant based on the properties of the rock dust particles. An apparatus is also disclosed for carrying out the method of the present invention.

Sapko, Michael J. (Finleyville, PA); Perlee, Henry E. (Bethel Park, PA)

1988-01-01

269

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

270

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

271

Microstructure of Fe-Cr Surface Infiltrated Composite Layer on Gray Iron Substrate  

NASA Astrophysics Data System (ADS)

The Fe-Cr surface infiltrated layers on gray iron substrate were fabricated through a vacuum infiltration casting technique (VICT) using Fe-Cr alloy powder as raw materials. The microstructures of surface infiltrated layer, the macro-hardness and the micro-hardness distribution are investigated. The infiltrated layer includes a surface composite layer and a transition layer. The surface infiltrated layer was mainly composed of Cr2B, Cr2C3, FeSi, FeNi and Ni-Cr-Fe and solid solution. The main composition of transition layer was graphite, eutectic ledeburite, carbide and Fe-based solid solution. The macro-hardness of surface infiltrated layer is HRC52.8, and the macro-hardness of substrate is HRC16.22. The distribution of micro-hardness presents gradient change.

Yang, Gui-Rong; Ma, Ying; Hao, Yuan; Li, Yuan-Dong; Song, Wen-Ming; Sun, Xian-Ming

2011-06-01

272

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

273

A macromolecular model for the endothelial surface layer  

NASA Astrophysics Data System (ADS)

The endothelial surface layer (ESL) is a micron-scale macromolecular lining of the luminal side of blood vessels composed of proteoglycans, glycoproteins, polysaccharides and associated plasma proteins all in dynamic equilibrium. It has numerous physiological roles including the regulation of blood flow and microvascular permeability, and active participation in mechanotransduction and stress regulation, coagulation, cell adhesion, and inflammatory response. The dynamic structure and the mechanical properties of the ESL are crucial for many of its physiological properties. We present a topological model for the ESL composed of three basic macromolecular elements: branched proteoglycans, linear polysaccharide chains, and small plasma proteins. The model was studied using non-equilibrium molecular dynamics simulations and compared with scaling theories for associating tethered polymers. We discuss the observed dynamical and mechanical properties of the ESL captured by this model, and the possible physical insight it provides into the physiological behavior of the ESL.

Harden, James; Danova-Okpetu, Darina; Grest, Gary

2006-03-01

274

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

275

Oil emulsification using surface-tunable carbon black particles.  

PubMed

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

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

2013-04-24

276

Influence of surface charge distributions and particle size distributions on particle attachment in granular media filtration.  

PubMed

Filtration experiments were performed with a laboratory-scale filter using spherical glass beads with 0.55 mm diameter as collectors. Suspensions were made with Min-U-Sil 5 particles, and two different methods (pH control and polymer dosing) were used for destabilization. In the pH control experiments, all particles had negative surface charge, and those with lower (absolute value) charge were selectively attached to the collectors, especially during the early stage of filtration. This selective attachment of the lower charged particles caused the zeta potential distribution (ZPD) of the effluent to move to a more negative range. However, the ZPD of the effluent did not continue moving to more negative values during the later stages of filtration, and this result was attributed to two reasons: ripening effects and detachment of flocs. In the polymer experiments, substantial differences were found between experiments performed with negatively charged particles (underdosing) and those with positively charged particles (overdosing). With under-dosing, the results were similar to the pH control experiments (which also had negatively charged particles), but with overdosing, the effluent's ZPDs in the early stages did not overlap with those of the influent and more highly charged particles were removed more efficiently than lesser-charged particles. It is hypothesized that, despite a substantial period of pre-equilibration of media and coagulant, this equilibrium shifted when particles were also added. It was assumed that coagulant molecules previously adsorbed to the particles desorbed and subsequently attached to the filter media because of surface area differences in the particle and filter media. PMID:18504996

Kim, Jinkeun; Nason, Jeffrey A; Lawler, Desmond F

2008-04-01

277

CALCINATION KINETICS AND SURFACE AREA OF DISPERSED LIMESTONE PARTICLES  

EPA Science Inventory

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 Ca...

278

ONLINE TOOL FOR VISUALIZING SURFACE HOAR LAYERS Simon Horton*, Michael Schirmer, Erik Kulyk, and Bruce Jamieson  

E-print Network

aspects at three elevation bands. Google Earth map layers are created to display the size of surface hoarONLINE TOOL FOR VISUALIZING SURFACE HOAR LAYERS Simon Horton*, Michael Schirmer, Erik Kulyk in preparing an avalanche forecast is estimating the location and sensitivity of critical snowpack layers

Jamieson, Bruce

279

ELECTROSTATIC SURFACE STRUCTURES OF COAL AND MINERAL PARTICLES  

SciTech Connect

We have developed a video image analyzer for measuring the size and charge of airborne particles. Particles are illuminated by laser light and subjected to a sinusoidal electric field while images of the trajectories of the particles are captured using a video camera and a frame grabber. Analysis of the particle tracks allows the size and charge of the particles to be determined. The instrument can be used to measure size and charge spectra of charged coal and mineral particles in real time. Appendix I shows size and charge distributions of coal and flyash particles measured with the image analyzer. A second instrument, an Ultraviolet Photoelectron Spectrometer (UPS) for measuring effective work functions of insulator and semiconductor surfaces in air is under development. Work function data for individual macerals and minerals in a coal matrix will be related to triboelectric charging properties. In this instrumental method, originally developed by Kirhata, the surface of a test sample is bombarded by monochromatic ultraviolet light of known wavelength. At atmospheric pressure, the photo-ejected electrons attach to air molecules forming negative ions. The ions are attracted by an applied electric field into a detector where they are accelerated to sufficient energy that they cause momentary dielectric breakdown or discharge in the air inside the detector. The rate at which these discharges occur is proportional to the rate at which photoelectrons are generated at the sample surface. From a plot of the discharge rate as a function of photon energy the minimum energy needed to remove an electron can be determined. The mechanical components of our instrument have been completed. A number of electronic circuit difficulties remain to be solved. The counting circuits are able to produce a count rate proportional to the ion concentration generated using a corona gun. However, when the high voltage accelerating potential is applied the circuit oscillates preventing proper operation. Our current focus on this instrument is to attain stability of operation.

M.K. Mazumder; D.A. Lindquist; K.B. Tennal

1999-04-01

280

Optical Anisotropy of Oxidized Si(001) Surfaces and Its Oscillation in the Layer-By-Layer Oxidation Process  

SciTech Connect

Reflectance-difference (RD) measurements for the oxidation of single-domain (2 x 1) -reconstructed Si(001) surfaces show that the polarity of the interface-induced optical anisotropy is reversed repeatedly with increasing oxide thickness. The oscillation of the RD amplitude, which we show is due to layer-by-layer progression of the oxidation, has allowed us to count the number of oxidized Si layers in situ during oxidation. The origins of the observed spectral line shape are discussed.

Yasuda, T.; Yamasaki, S.; Nishizawa, M.; Miyata, N.; Shklyaev, A.; Ichikawa, M.; Matsudo, T.; Ohta, T.

2001-07-16

281

Surface scattering of core-shell particles with anisotropic shell.  

PubMed

The Bobbert-Vlieger solution to light scattering of a spherical particle suspended above a surface is extended to model the scattering of core-shell structures with anisotropic shell. Numerical modeling demonstrates that ellipsometry has potential to resolve particle shell anisotropy down to 1.8×10(-4) for SiO(2)@Au core-shell particles in air with 50 nm core diameter and 10 nm shell thickness deposited on a silicon Si [100] substrate with a density of 1???m(-2). Application of the Ibrahim and Bashara criterion for ellipsometer parameter cross correlation identifies variable-angle ellipsometry as a viable experimental approach to separate particle core radius and shell thickness from the shell anisotropy. Ellipsometry is also identified as an alternative technique for determination of liposome anisotropy and for the study of liposome fusion with a substrate in the formation process of supported lipid bilayers. PMID:24561952

De Beule, Pieter A A

2014-01-01

282

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

283

Cellular interactions of surface modified nanoporous silicon particles.  

PubMed

In this study, the self-assembly of hydrophobin class II (HFBII) on the surface of thermally hydrocarbonized porous silicon (THCPSi) nanoparticles was investigated. The HFBII-coating converted the hydrophobic particles into more hydrophilic ones, improved the particles' cell viability in both HT-29 and Caco-2 cell lines compared to uncoated particles, and enhanced the particles' cellular association. The amount of HFBII adsorbed onto the particles was also successfully quantified by both the BCA assay and a HPLC method. Importantly, the permeation of a poorly water-soluble drug, indomethacin, loaded into THCPSi particles across Caco-2 monolayers was not affected by the protein coating. In addition, (125)I-radiolabelled HFBII did not extensively permeate the Caco-2 monolayer and was found to be stably adsorbed onto the THCPSi nanoparticles incubated in pH 7.4, which renders the particles the possibility for further track-imaging applications. The results highlight the potential of HFBII coating for improving wettability, increasing biocompatibility and possible intestinal association of PSi nanoparticulates for drug delivery applications. PMID:22508528

Bimbo, Luis M; Sarparanta, Mirkka; Mäkilä, Ermei; Laaksonen, Timo; Laaksonen, Päivi; Salonen, Jarno; Linder, Markus B; Hirvonen, Jouni; Airaksinen, Anu J; Santos, Hélder A

2012-05-21

284

Surface Enhanced Raman Correlation Spectroscopy of Particles in Solution  

PubMed Central

Surface enhanced Raman correlation spectroscopy (SERCS) is shown as a label-free, chemically specific method for monitoring individual polymer beads and lipid vesicles interacting with a 2-D planar surface enhanced Raman (SERS) substrate in solution. The enhancement afforded by the SERS substrate allows for spectral data to be acquired in series at rates between 31 and 83 Hz. Auto- and cross-correlation of spectral data facilitates the measurement of diffusion constants for particles ranging in radius from 50 to 500 nm while discriminating signal associated with the target analyte from extraneous fluctuations. The measured diffusion coefficients are on the order of 10–10–10–11 cm2/s, a factor of 40 times slower than predicted from the Stokes–Einstein equation, suggesting that particles are experiencing hindered diffusion at the surface. The enhanced signals appear to originate from particles less than 5 nm of the SERS substrate, consistent with adsorption to the surface. This work provides a means to measure and monitor surface interactions and demonstrates the utility and limits of SERS detection in solution over planar SERS substrates. PMID:24502388

2015-01-01

285

Large-eddy simulation of particle-laden atmospheric boundary layer  

NASA Astrophysics Data System (ADS)

Pollen dispersion in the atmospheric boundary layer (ABL) is numerically investigated using a hybrid large-eddy simulation (LES) Lagrangian approach. Interest in prediction of pollen dispersion stems from two reasons, the allergens in the pollen grains and increasing genetic manipulation of plants leading to the problem of cross pollination. An efficient Eulerian-Lagrangian particle dispersion algorithm for the prediction of pollen dispersion in the atmospheric boundary layer is outlined. The volume fraction of the dispersed phase is assumed to be small enough such that particle-particle collisions are negligible and properties of the carrier flow are not modified. Only the effect of turbulence on particle motion has to be taken into account (one-way coupling). Hence the continuous phase can be treated separate from the particulate phase. The continuous phase is determined by LES in the Eulerian frame of reference whereas the dispersed phase is simulated in a Lagrangian frame of reference. Numerical investigations are conducted for the convective, neutral and stable boundary layer as well different topographies. The results of the present study indicate that particles with small diameter size follow the flow streamlines, behaving as tracers, while particles with large diameter size tend to follow trajectories which are independent of the flow streamlines. Particles of ellipsoidal shape travel faster than the ones of spherical shape.

Ilie, Marcel; Smith, Stefan Llewellyn

2008-11-01

286

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

NASA Astrophysics Data System (ADS)

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

Misra, Shikha; Mishra, S. K.

2015-02-01

287

ELECTRONIC SURFACE STRUCTURES OF COAL AND MINERAL PARTICLES  

SciTech Connect

Surface science studies related to tribocharging and charge separation studies were performed on electrostatic beneficiation of coal. In contrast to other cleaning methods, electrostatic beneficiation is a dry cleaning process requiring no water or subsequent drying. Despite these advantages, there is still uncertainty in implementing large-scale commercial electrostatic beneficiation of coal. The electronic surface states of coal macerals and minerals are difficult to describe due to their chemical complexity and variability. The efficiency in separation of mineral particles from organic macerals depends upon these surface states. Therefore, to further understand and determine a reason for the bipolar charging observed in coal separation, surface analysis studies using Ultra-violet Photoelectron Spectroscopy (UPS) and X-ray Photoelectron Spectroscopy (XPS) were performed on coal samples and several materials that are used or considered for use in tribocharging. Electrostatic charging is a surface phenomenon, so the electronic surface states of the particles, which are influenced by the environmental conditions, determine both polarity and magnitude of tribocharging. UPS was used to measure the work function of the materials as typically used in ambient air. XPS was used to determine the surface chemistry in the form of contamination and degree of oxidation under the same environmental conditions.

M.K.Mazumder; D.A. Linduist; K.B. Tennal

2001-04-01

288

Single molecule desorption studies on immobilized nanoclay particle surfaces.  

PubMed

AFM-based single molecule force spectroscopy was performed on sheetlike inorganic particles of Na-montmorillonite to study the pH-dependent adsorption and desorption behavior of polyelectrolytes in aqueous solutions. Polyallylamine macromolecules were covalently attached on gold-coated AFM cantilevers. Heterogeneous surfaces were formed by immobilizing the nanoclay sheets on mica-stripped ultraflat Au(111) surfaces using aminothiol chemistry. Because of the constant surface charge of the particles over a wide pH range, polymer line charge density was the only parameter that affected the adsorption and desorption behavior when the ionic concentration was kept constant. Polarization modulation infrared-reflection absorption spectroscopy (PM-IRRAS) was performed on cast polyallylamine films to study the pH-dependent charge density of polyallylamine molecules. A good correlation was found between the line charge density and the adsorption characteristics of polyallylamine. PMID:20230055

Ozkaya, Berkem; Ozcan, Ozlem; Thissen, Peter; Grundmeier, Guido

2010-06-01

289

Mixed and mixing layer depths in the ocean surface boundary layer under conditions of diurnal stratification  

NASA Astrophysics Data System (ADS)

A comparison between mixed (MLD) and mixing (XLD) layer depths is presented from the SubTRopical Atlantic Surface Salinity Experiment (STRASSE) cruise in the subtropical Atlantic. This study consists of 400 microstructure profiles during fairly calm and moderate conditions (2 < U10 < 10 m s-1) and strong solar heating O(1000 W m-2). The XLD is determined from a decrease in the turbulent dissipation rate to an assumed background level. Two different thresholds for the background dissipation level are tested, 10-8 and 10-9 m2 s-3, and these are compared with the MLD as calculated using a density threshold. The larger background threshold agrees with the MLD during restratification but only extends to half the MLD during nighttime convection, while the lesser threshold agrees well during convection but is deeper by a factor of 2 during restratification. Observations suggest the use of a larger density threshold to determine the MLD in a buoyancy driven regime.

Sutherland, G.; Reverdin, G.; Marié, L.; Ward, B.

2014-12-01

290

Characterization of Floating Surface Layers of Lipids and Lipopolymers by Surface-Sensitive Scattering  

NASA Astrophysics Data System (ADS)

Nanotechnology and molecular (bio-)engineering are making ever deepening inroads into everybodys daily life. Physicochemical and biotechnological achievements in the design of physiologically active supramolecular assemblies have brought about the quest for their submolecular-level characterization. We employ surface-sensitive scattering techniques for the investigation of planar lipid membranes - floating monolayers on aqueous surfaces - to correlate structural, functional and dynamic aspects of biomembrane models. This chapter surveys recent work on the submolecular structure of floating phospholipid monolayers - where the advent of third-generation synchrotron X-ray sources has driven the development of realistic, submolecular-scale quasi-chemical models - as well as of more complex systems: cation binding to anionic lipid surfaces; conformational changes of lipopolymers undergoing phase transitions; the conformational organization of phosphatidylinositol and phosphatidylinositides, as examples of physiologically important lipids; and the adsorption of peptides (neuropeptide Y, NPY) or solvents (dimethylsulfoxide, DMSO) onto phospholipid surface layers.

Krüger, Peter; Lösche, Mathias

291

Influencing an Aerodynamic Boundary Layer using a Surface Layer of One Atmosphere Uniform Glow Discharge Plasma.*  

NASA Astrophysics Data System (ADS)

The results of low-speed wind tunnel testing at the NASA Langley Research Center of a flat panel substantially covered by a thin layer of one atmosphere uniform glow discharge plasma (OAUGDP)^1 will be reported. The orientation of the electrode strips and the resulting lineation of the OAUGDP with respect to the airflow was found to have a significant effect on the amount of measured drag. When the plasma panel is oriented so that the electrode strips are parallel to the airflow, the measured drag increases. Utilizing standard circuit board technology, a multi-strip OAUGDP layer was created on a rectangular surface (30 × 34 cm). One side of the panel was a series of connected strip electrodes and the other side a single sheet electrode. The panel was operated at a RMS voltage of 1.0-4.0 kV, RF frequency of 1.0-4.0 kHz, in a parallel and perpendicular airflow. ^1 Roth, J.R. (1995): Industrial Plasma Engineering: Vol. I - Principles. Institute of Physics Press, Bristol, UK ISBN 0-7503-0318-2. Supported in part by the NASA Langley Research Center, NCC1-223.

Sherman, D. M.; Roth, J. R.; Wilkinson, S. P.

1996-11-01

292

Crystalline particle packings on constant mean curvature (Delaunay) surfaces  

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

293

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

294

Kinetics and mechanism of the thermal decomposition of sodium percarbonate: role of the surface product layer.  

PubMed

The reaction mechanism and overall kinetics of the thermal decomposition of sodium percarbonate crystals were investigated by thermoanalytical measurements and morphological observations. The reaction proceeds via a surface reaction and subsequent advancement of the as-produced reaction interface toward the center of the crystals, where the seemingly smooth mass-loss behavior can be described by the apparent activation energy Ea of ca. 100 kJ mol(-1). However, considering the rate behavior, as the reaction advances, it is expected that the secondary reaction step characterized by an autocatalytic rate behavior takes part in the overall reaction. The hindrance of the diffusional removal of the evolved gases by the surface product layer, Na2CO3, is the most probable reason for the change in the reaction mechanism. In the deceleration part of the first reaction step, the second reaction step is accelerated due to an increase in the water vapor pressure at the reaction interface inside the reacting particles. We also expect the self-generated reaction condition of the high water vapor pressure and the existence of liquid phase due to the formation of Na2CO3 whiskers as the solid product and the insensitive rate behavior of the second reaction step to a higher atmospheric water vapor pressure. A relevant reaction model for the thermal decomposition of SPC crystals are discussed by focusing on the role of the surface product layer. PMID:23402671

Wada, Takeshi; Koga, Nobuyoshi

2013-03-01

295

On the Interaction between Marine Boundary Layer Cellular Cloudiness and Surface Heat Fluxes  

SciTech Connect

The interaction between marine boundary layer cellular cloudiness and surface uxes of sensible and latent heat is investigated. The investigation focuses on the non-precipitating closed-cell state and the precipitating open-cell state at low geostrophic wind speed. The Advanced Research WRF model is used to conduct cloud-system-resolving simulations with interactive surface fluxes of sensible heat, latent heat, and of sea salt aerosol, and with a detailed representation of the interaction between aerosol particles and clouds. The mechanisms responsible for the temporal evolution and spatial distribution of the surface heat fluxes in the closed- and open-cell state are investigated and explained. It is found that the horizontal spatial structure of the closed-cell state determines, by entrainment of dry free tropospheric air, the spatial distribution of surface air temperature and water vapor, and, to a lesser degree, of the surface sensible and latent heat flux. The synchronized dynamics of the the open-cell state drives oscillations in surface air temperature, water vapor, and in the surface fluxes of sensible and latent heat, and of sea salt aerosol. Open-cell cloud formation, cloud optical depth and liquid water path, and cloud and rain water path are identified as good predictors of the spatial distribution of surface air temperature and sensible heat flux, but not of surface water vapor and latent heat flux. It is shown that by enhancing the surface sensible heat flux, the open-cell state creates conditions by which it is maintained. While the open-cell state under consideration is not depleted in aerosol, and is insensitive to variations in sea-salt fluxes, it also enhances the sea-salt flux relative to the closed-cell state. In aerosol-depleted conditions, this enhancement may replenish the aerosol needed for cloud formation, and hence contribute to the perpetuation of the open-cell state as well. Spatial homogenization of the surface fluxes is found to have only a small effect on cloud properties in the investigated cases. This indicates that sub-grid scale spatial variability in the surface flux of sensible and latent heat and of sea salt aerosol may not be required in large scale and global models to describe marine boundary layer cellular cloudiness.

Kazil, J.; Feingold, G.; Wang, Hailong; Yamaguchi, T.

2014-01-02

296

Fiber-Optic Near-Field Chemical Sensors Based on Wavelength Scale Tin Dioxide Particle Layers  

Microsoft Academic Search

In this paper, the surprising sensing performance of fiber-optic near-field chemical sensors, based on wavelength scale tin dioxide particle layers, against chemical pollutants in air environment at room temperature are reported. The layers were deposited upon the distal end of standard single-mode optical fibers by means of the very simple, versatile, and low-cost electrostatic spray pyrolysis technique. The morphologic and

Antonietta Buosciolo; Marco Consales; Marco Pisco; Andrea Cusano; Michele Giordano

2008-01-01

297

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

2008-04-13

298

Granular layers on vibrating plates: effective bending stiffness and particle-size effects.  

PubMed

Acoustic methods of land mine detection rely on the vibrations of the top plate of the mine in response to sound. For granular soil (e.g., sand), the particle size is expected to influence the mine response. This hypothesis is studied experimentally using a plate loaded with dry sand of various sizes from hundreds of microns to a few millimeters. For low values of sand mass, the plate resonance decreases with added mass and eventually reaches a minimum without particle size dependence. After the minimum, a frequency increase is observed with additional mass that includes a particle-size effect. Analytical nondissipative continuum models for granular media capture the observed particle-size dependence qualitatively but not quantitatively. In addition, a continuum-based finite element model (FEM) of a two-layer plate is used, with the sand layer replaced by an equivalent elastic layer for evaluation of the effective properties of the layer. Given a thickness of sand layer and corresponding experimental resonance, an inverse FEM problem is solved iteratively to give the effective Young's modulus and bending stiffness that matches the experimental frequency. It is shown that a continuum elastic model must employ a thickness-dependent elastic modulus in order to match experimental values. PMID:17348513

Kang, Wonmo; Turner, Joseph A; Bobaru, Florin; Yang, Liyong; Rattanadit, Kitti

2007-02-01

299

Low energy charged particles interacting with amorphous solid water layers  

SciTech Connect

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

Horowitz, Yonatan; Asscher, Micha [Institute of Chemistry, Hebrew University of Jerusalem, Edmund J. Safra Campus, Givat-Ram, Jerusalem 91904 (Israel)

2012-04-07

300

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

301

New Material Development for Surface Layer and Surface Technology in Tribology Science to Improve Energy Efficiency  

NASA Astrophysics Data System (ADS)

This paper reviews the development of new material and surface technology in tribology and its contribution to energy efficiency. Two examples of the economic benefits, resulted from the optimum tribology in the transportation sector and the manufacturing industry are discussed. The new materials are proposed to modify the surface property by laminating the bulk material with thin layer/coating. Under a suitable condition, the thin layer on a surface can provide a combination of good wear, a low friction and corrosion resistance for the mechanical components. The innovation in layer technology results molybdenum disulfide (MoS2), diamond like carbon (DLC), cubic boron nitride (CBN) and diamond which perform satisfactory outcome. The application of the metallic coatings to carbon fibre reinforced polymer matrix composites (CFRP) has the capacity to provide considerable weight and power savings for many engineering components. The green material for lubricant and additives such as the use of sunflower oil which possesses good oxidation resistance and the use of mallee leaves as bio-degradable solvent are used to answer the demand of the environmentally friendly material with good performance. The tribology research implementation for energy efficiency also touches the simple things around us such as: erasing the laser-print in a paper with different abrasion techniques. For the technology in the engineering surface, the consideration for generating the suitable surface of the components in running-in period has been discussed in order to prolong the components life and reduce the machine downtime. The conclusion, tribology can result in reducing manufacturing time, reducing the maintenance requirements, prolonging the service interval, improving durability, reliability and mechanical components life, and reducing harmful exhaust emission and waste. All of these advantages will increase the energy efficiency and the economic benefits.

Ismail, R.; Tauviqirrahman, M.; Jamari, Jamari; Schipper, D. J.

2009-09-01

302

The asymptotic shape of a boundary layer of symmetric Willmore surfaces of revolution*  

E-print Network

The asymptotic shape of a boundary layer of symmetric Willmore surfaces of revolution* Hans insights into analysis. Abstract We consider the Willmore boundary value problem for surfaces of revolution surfaces of revolution, asymptotic shape, boundary layer. AMS classification. 49Q10; 53C42, 35J65, 34L30. 1

Grunau, Hans-Christoph

303

The asymptotic shape of a boundary layer of symmetric Willmore surfaces of revolution*  

E-print Network

The asymptotic shape of a boundary layer of symmetric Willmore surfaces of revolution* Hans insights into analysis. Abstract We consider the Willmore boundary value problem for surfaces of revolution boundary conditions, Willmore surfaces of revolution, asymptotic shape, boundary layer. AMS classification

Grunau, Hans-Christoph

304

Surface layers on a borosilicate nuclear waste glass corroded in MgCl 2 solution  

Microsoft Academic Search

Surface layers on the French borosilicate nuclear waste glass, R7T7, corroded in MgCl2 solution were studied to determine the composition, structure and stability of crystalline phases. The characteristics of the phases constituting the surface layer varied with the parameter SV × t, the glass surface area (S) to solution volume (V) ratio, times time (t). At low SV × t

Abdesselam Abdelouas; Jean-Louis Crovisier; Werner Lutze; Bernd Grambow; Jean-Claude Dran; Regina Müller

1997-01-01

305

Fluctuating wall shear stress measurements in the atmospheric surface layer  

NASA Astrophysics Data System (ADS)

A new sensor is described for measuring the fluctuating component of the wall shear stress in the atmospheric surface layer over relatively smooth uniform terrain. The sensor was tested at the SLTEST site on the western salt-flats of Utah, giving the first ever direct measurements of this quantity in an atmospheric scale flow. The device consists of a lightweight floating element whose position is detected using a spherical mirror that deflects a laser beam onto a duo-lateral position sensing photodiode. The sensor has a frequency response of 25 Hz, and a circular sensing area, of 50 mm diameter, making it suitable for atmospheric scale measurements. Measurements were made under near-neutral buoyant conditions at SLTEST using the new sensor and a rake of five sonic anemometers, positioned at wall-normal positions from z = 0.62 m to 2.5 m. Cross-correlations of the wall-shear stress and velocity measurements indicate a structure-inclination angle of 14°, which is consistent with analogous laboratory-scale turbulent boundary layer measurements at three orders of magnitude lower Reynolds number. Other quantities were also found to agree well with canonical laboratory scale results. This includes the RMS of the fluctuating wall-shear stress and the power spectra. The structure of the near-wall turbulence is further studied by looking at the cross-correlations of the two components of fluctuating wall-shear stress with the three components of velocity at the various wall-normal positions, and using VITA analysis.

Heuer, Weston Daniel Clarence

306

Patterning of gold nanoparticles on fluoropolymer films by using patterned surface grafting and layer-by-layer deposition techniques.  

PubMed

The patterning of gold nanoparticles (GNPs) on the surface of a fluoropolymer substrate by using patterned surface grafting and layer-by-layer deposition techniques is described. The surface of a poly(tetrafluoroethylene-co-perfluorovinyl ether) (PFA) substrate was selectively implanted with 150 keV proton ions. Peroxide groups were successfully formed on the implanted PFA surface, and their concentration depended on the fluence. Acrylic acid was graft polymerized onto the implanted regions of the PFA substrate, resulting in well-defined patterns of poly(acrylic acid) (PAA) on the PFA substrate. The surface properties of the PAA-patterned PFA surface, such as chemical compositions, wettability, and morphology, were investigated. The surface analysis results revealed that PAA was definitely present on the implanted regions of the PFA surface, and the degree of grafting was dependent on three factors: fluence, grafting time, and monomer concentration. Furthermore, GNP patterns were generated on the prepared PAA-patterned PFA surface by layer-by-layer deposition of GNPs and poly(diallyldimethyl ammonium chloride). The multilayers of GNPs were deposited only onto the PAA-grafted regions separated by bare PFA regions, and the resulting GNP patterns exhibited good electrical conductivity. PMID:23927646

Jung, Chang-Hee; Hwang, In-Tae; Jung, Chan-Hee; Choi, Jae-Hak; Kwon, Oh-Sun; Shin, Kwanwoo

2013-09-11

307

In situ observation of oxidation of liquid droplets of tin and melting behavior of a tin particle covered with a tin oxide layer.  

PubMed

Oxidation of a liquid droplet of tin (Sn) was observed using an in situ specimen heating holder in an oxygen environment. The surface of the Sn liquid droplet was covered with a tin oxide layer, Sn(3)O(4), the thickness of which depended on the oxygen pressure and temperature. Subsequent cooling of the droplet resulted in the formation of a solid Sn particle covered with a Sn(3)O(4) layer. The solid Sn particle was then heated above the melting temperature of Sn, and the melting behavior of Sn was observed. PMID:19156703

Mima, Takayuki; Takeuchi, Hironori; Arai, Shigeo; Kishita, Keisuke; Kuroda, Kotaro; Saka, Hiroyasu

2009-03-01

308

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

309

Experimental Investigation of Turbulent Momentum Transfer in a Neutral Boundary Layer over a Rough Surface  

NASA Astrophysics Data System (ADS)

The turbulent characteristics of the neutral boundary layer developing over rough surfaces are not well predicted with operational weather-forecasting models. The problem is attributed to inadequate mixing-length models, to the anisotropy of the flow and to a lack of controlled experimental data against which to validate numerical studies. Therefore, in order to address directly the modelling difficulties for the development of a neutral boundary layer over rough surfaces, and to investigate the turbulent momentum transfer of such a layer, a set of hydraulic flume experiments were carried out. In the experiments, the mean and turbulent quantities were measured by a particle image velocimetry (PIV) technique. The measured velocity variances and fluxes {(overline{{ui^'{uj^')} in longitudinal vertical planes allowed the vertical and longitudinal gradients (?/? z and ?/? x) of the mean and turbulent quantities (fluxes, variances and third-order moments) to be evaluated and the terms of the evolution equations for ? e/? t, {partial overline{u^' 2}}/partial t}, {partial overline{w^' 2}}/partial t} and {partial overline{{u^'{w^'/partial t} to be quantified, where e is the turbulent kinetic energy. The results show that the pressure-correlation terms allow the turbulent energy to be transferred equitably from {overline{{u^'2}} to {overline{{w^'2}}. It appears that the repartition between the constitutive terms of the budget of e, {overline{{u^'2}}, {overline{{w^'2}} and {overline{{u^'{w^' is not significantly affected by the development of the rough neutral boundary layer. For the whole evolution, the transfers of energy are governed by the same terms that are also very similar to the smooth-wall case. The PIV measurements also allowed the spatial integral scales to be computed directly and to be compared with the dissipative and mixing length scales, which were also computed from the data.

Tomas, Severine; Eiff, Olivier; Masson, Valery

2011-03-01

310

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

311

Erosion processes due to energetic particle-surface interaction  

NASA Astrophysics Data System (ADS)

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.

2010-05-01

312

Particle resuspension and associated coherent structures in a turbulent boundary layer  

Microsoft Academic Search

Fundamental properties of particle resuspension from a surface solely by turbulent fluid forces was examined experimentally by observing intermittent particle resuspension and associated turbulent flow properties. Experiments were conducted in an environmental wind tunnel, where sparse beds of monodisperse Lycopodium spores (Club Moss) were placed flush with the floor of the wind tunnel, and exposed to a steady, well developed

David Alan Braaten

1988-01-01

313

Surface plasmon sensors on ZnO:Ga layer surfaces: Electric field distributions and absorption-sensitivity enhancements  

NASA Astrophysics Data System (ADS)

Surface plasmon resonances (SPRs) on ZnO:Ga layer surfaces (ZnO-SPR) enhanced absorption bands related to molecular-vibrations (OH and CH3 modes) in the near-infrared range by controlling layer thickness. These behaviors were due to the interaction between SPR excitations and molecular vibrations. Further investigation revealed that the high detection sensitivity of SPRs on ZnO:Ga layer surfaces was 6837 nm/RIU using water and methanol mixtures. The detection region of ZnO-SPR was limited within several hundred nanometers from the layer surfaces, which is discussed relative to theoretical analysis of field distributions and spatial coherence of SPRs on ZnO:Ga layer surfaces.

Matsui, Hiroaki; Ikehata, Akifumi; Tabata, Hitoshi

2015-01-01

314

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

315

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

316

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

317

High-Speed Transport of Fluid Drops and Solid Particles via Surface Acoustic Waves  

NASA Technical Reports Server (NTRS)

A compact sampling tool mechanism that can operate at various temperatures, and transport and sieve particle sizes of powdered cuttings and soil grains with no moving parts, has been created using traveling surface acoustic waves (SAWs) that are emitted by an inter-digital transducer (IDT). The generated waves are driven at about 10 MHz, and it causes powder to move towards the IDT at high speed with different speeds for different sizes of particles, which enables these particles to be sieved. This design is based on the use of SAWs and their propelling effect on powder particles and fluids along the path of the waves. Generally, SAWs are elastic waves propagating in a shallow layer of about one wavelength beneath the surface of a solid substrate. To generate SAWs, a piezoelectric plate is used that is made of LiNbO3 crystal cut along the x-axis with rotation of 127.8 along the y-axis. On this plate are printed pairs of fingerlike electrodes in the form of a grating that are activated by subjecting the gap between the electrodes to electric field. This configuration of a surface wave transmitter is called IDT. The IDT that was used consists of 20 pairs of fingers with 0.4-mm spacing, a total length of 12.5 mm. The surface wave is produced by the nature of piezoelectric material to contract or expand when subjected to an electric field. Driving the IDT to generate wave at high amplitudes provides an actuation mechanism where the surface particles move elliptically, pulling powder particles on the surface toward the wavesource and pushing liquids in the opposite direction. This behavior allows the innovation to separate large particles and fluids that are mixed. Fluids are removed at speed (7.5 to 15 cm/s), enabling this innovation of acting as a bladeless wiper for raindrops. For the windshield design, the electrodes could be made transparent so that they do not disturb the driver or pilot. Multiple IDTs can be synchronized to transport water or powder over larger distances. To demonstrate the transporting action, a video camera was used to record the movement. The speed of particles was measured from the video images.

Bar-Cohen, Yoseph; Bao, Xiaoqi; Sherrit, Stewart; Badescu, Mircea; Lih, Shyh-shiuh

2012-01-01

318

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

319

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

320

Incipient motion of a small particle in the viscous boundary layer at a pipe wall  

Microsoft Academic Search

A force balance is derived for a hemispherical particle in the viscous boundary layer at the wall of a horizontal pipe conveying Newtonian fluid; the hemisphere, of radius much less than that of the pipe, rests on the bottom with its flat face against the wall. The drag on the hemisphere is calculated from the creeping flow field of Price

P Stevenson; R. B Thorpe; J. F Davidson

2002-01-01

321

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

322

The surface modification of TiN nano-particles using macromolecular coupling agents, and their resulting dispersibility  

NASA Astrophysics Data System (ADS)

Titanium nitride (TiN) nano-particles were modified by the grafting of a random copolymerization functionalized macromolecular coupling agent (F-MCA) via a direct blending method. The hydroxyl groups on the surface of the nano-TiN particles interact with the silanol groups [SiOCH3] of the F-MCA to form an organic coating layer. The formation of covalent bonds [TiOSi] was verified using Fourier transform infrared spectroscopy. An X-ray diffraction analysis suggests that the presence of the F-MCA inhibited the growth of the crystal plane but did not change the crystal structure of the TiN. Thermogravimetric analysis and contact angle measurement indicated that the F-MCA molecules were adsorbed or anchored to the surface of the nano-TiN particles, which hindered their aggregation. Pristine nano-TiN particles are poorly dispersed in ethyl acetate. Compared with the pristine TiN particles, the modified TiN particles show good dispersibility and form a stable colloidal dispersion in ethyl acetate. The surface hydrophobicity of the modified TiN increases, and the F-MCA molecules are anchored on the surface of the TiN particles. TiN particles modified by a F-MCA can be used in polymer blends, thermoplastic elastomers and polymer nanocomposites that have a better performance and longer life cycle.

Cheng, Guojun; Qian, Jiasheng; Miao, Jibin; Yang, Bin; Xia, Ru; Chen, Peng

2014-05-01

323

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

NASA Astrophysics Data System (ADS)

Atmospheric new particle formation (NPF) is a frequent and ubiquitous process in the atmosphere and a major source of newly formed aerosol particles [1]. However, it is still unclear how the aerosol particle distribution evolves in space and time during an NPF. We investigated where in the planetary boundary layer does NPF begin and how does the aerosol number size distribution develop in space and time during it. We measured in Hyytiälä, southern Finland using ground based and airborne measurements. The measurements were part of the PEGASOS project. NPF was studied on six scientific flights during spring 2013 using a Zeppelin NT class airship. Ground based measurements were simultaneously conducted at SMEAR II station located in Hyytiälä. The flight profiles over Hyytiälä were flown between sunrise and noon during the growth of the boundary layer. The profiles over Hyytiälä covered vertically a distance of 100-1000 meters reaching the mixed layer, stable (nocturnal) boundary layer and the residual layer. Horizontally the profiles covered approximately a circular area of four kilometers in diameter. The measurements include particle number size distribution by Neutral cluster and Air Ion Spectrometer (NAIS), Differential Mobility Particle Sizer (DMPS) and Particle Size Magnifier (PSM) [2], meteorological parameters and position (latitude, longitude and altitude) of the Zeppelin. Beginning of NPF was determined from an increase in 1.7-3 nm ion concentration. Height of the mixed layer was estimated from relative humidity measured on-board the Zeppelin. Particle growth rate during NPF was calculated. Spatial inhomogeneities in particle number size distribution during NPF were located and the birthplace of the particles was estimated using the growth rate and trajectories. We observed a regional NPF event that began simultaneously and evolved uniformly inside the mixed layer. In the horizontal direction we observed a long and narrow high concentration plume of growing particles that moved over the measurement site. The particles of the regional event as well as the particles of the plume were uniformly distributed in the vertical direction and showed a similar growth rate of approximately 2 nm/h. The plume caused sharp discontinuities in the number size distribution of the growing particle mode. These kinds of discontinuities are seen quite often on SMEAR II data during NPF events and it is likely that they are caused by inhomogeneous NPF in the horizontal direction (possibly narrow long plumes). This work is supported by European Commission under the Framework Programme 7 (FP7-ENV-2010-265148) and by the Academy of Finland Centre of Excellence program (project no. 1118615). The Zeppelin is accompanied by an international team of scientists and technicians. They are all warmly acknowledged. References [1] Kulmala, M., et al., (2013), Direct Observations of Atmospheric Aerosol Nucleation, Science, 339, 943-946 [2] Kulmala, M., et al., (2012), Measurement of the nucleation of atmospheric aerosol particles, Nature Protocols, 7, 1651-1667

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

2014-05-01

324

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

325

Layer-by-layer construction of the heparin/fibronectin coatings on titanium surface:stability and functionality  

NASA Astrophysics Data System (ADS)

Layer-by-layer assembly as a versatile bottom-up nanofabrication technique has been widely used in the development of biomimetic materials with superior mechanical and biological properties. In this study, layer-by-layer assembled heparin/fibronectin biofunctional films were fabricated on titanium (Ti) surface to enhance the blood anticoagulation and accelerate the endothelialization simultaneously. The wettability and chemical changes of the assembled films were investigated by static water contact angle measurement and fourier transform infrared spectroscopy (FTIR). The morphology of modified Ti surfaces were observed using scanning electron microscopy (SEM). The real time assembly process was in-situ monitored by quartz crystal microbalance with dissipation (QCM-D). The stability of the films was evaluated by measuring the changes in wettability and the quantity of heparin and fibronectin on the surfaces. The anticoagulation properties of the films were quantitatively rated using Activated partial thromboplastin time (APTT) analysis. New peaks of hydroxyl and amino group were observed on the assembled Ti srufaces by FTIR. The contact angles varied among the films with different bilayer numbers, indicating the successful graft of the heparin and fibronectin layer-by-layer. QCM-D results showed that the frequency shift increased with the bilayer numbers, and the heparin and fibronectin could form multilayers. The assembly films were stable after incubation in PBS for 24 h based on the results of the contact angle measurement and the quantity of heparin and fibronectin analysis. APTT results suggested that the assembled films kept excellent antithrombotic properties. All these results revealed that the assembled heparin/fibronectin films with stabiltiy and anticoagulation property could be firmly formed on titanium surfaces. Our study further demonstrates that layer-by-layer assembly of heparin and fibronectin will provide a potential and effective tool for biomaterials surface modification.

Li, Guicai; Yang, Ping; Huang, Nan

326

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

327

Uptake of gas phase nitrous acid onto boundary layer soil surfaces.  

PubMed

Nitrous acid (HONO) is an important OH radical source that is formed on both ground and aerosol surfaces in the well-mixed boundary layer. Large uncertainties remain in quantifying HONO sinks and determining the mechanism of HONO uptake onto surfaces. We report here the first laboratory determination of HONO uptake coefficients onto actual soil under atmospheric conditions using a coated-wall flow tube coupled to a highly sensitive chemical ionization mass spectrometer (CIMS). Uptake coefficients for HONO decrease with increasing RH from (2.5 ± 0.4) × 10(-4) at 0% RH to (1.1 ± 0.4) × 10(-5) at 80% RH. A kinetics model of competitive adsorption of HONO and water onto the particle surfaces fits the dependence of the HONO uptake coefficients on the initial HONO concentration and relative humidity. However, a multiphase resistor model based on the physical and chemical processes affecting HONO uptake is more flexible as it accounts for the pH dependence of HONO uptake and bulk diffusion in the soil matrix. Fourier transform infrared (FTIR) spectrometry and cavity-enhanced absorption spectroscopy (CEAS) studies indicate that NO and N2O (16% and 13% yield, respectively) rather than NO2 are the predominant gas phase products, while NO2(-) and NO3(-) were detected on the surface post-exposure. Results are compared to uptake coefficients inferred from models and field measurements, and the atmospheric implications are discussed. PMID:24328088

Donaldson, Melissa A; Berke, Andrew E; Raff, Jonathan D

2014-01-01

328

Particle scale modeling of material removal and surface roughness in chemical mechanical polishing  

NASA Astrophysics Data System (ADS)

Chemical mechanical polishing (CMP) is widely adopted in producing excellent local and global planarization of microelectronic devices. It has been demonstrated experimentally that the polishing performance is a result of the synergistic effect of both the chemicals and the particles involved in CMP. However, the fundamental mechanisms of material removal and the interactions of the chemical and mechanical effects are not well understood. A comprehensive model for CMP was developed taking into account both the chemical and mechanical effects for slurries with a given particle size distribution. The model developed (PERC II) is based on a previously developed model (PERC I). The chemical aspect is attributed to the chemical modification of the surface layer due to slurry chemistry, whereas the mechanical aspect is incorporated by indentation of particles into the modified layer and the substrate depending on the operating conditions. In this study, the effects of particle size and pad asperity distributions are included in the model. The contact area of pad with wafer was measured in dry and wet conditions in different pH solutions using optical microscopy and Fourier transform infrared spectroscopy respectively. Pad surface mechanical properties in dry and wet states were also investigated using atomic force microscopy. The contact area results obtained were utilized in modeling to estimate the pad modulus leading to pad-wafer contact stress distribution. The predictions of the model show a reasonable agreement with the experimental data. The model is validated for oxide and metal CMP systems. The PERC II model not only predicts the overall removal rate, but also the surface roughness of the polished wafer in selected systems. The developed model can be used to optimize the current CMP systems and provide insights into future CMP endeavors.

Yeruva, Suresh Babu

2005-11-01

329

Structure of shear layer with coal particles in one of the streams  

SciTech Connect

This paper describes an experimental study of the structure of a two-dimensional shear layer formed by two gas streams, one of which contained coal particles. Experimental facility consists of a low speed wind-0tunnel designed to be capable of providing two gas streams, initially with uniform velocity profiles and isotropic turbulence, which mix at the end of a splitter plate. A fluidized bed injector system was provided to introduce coal particles into one of the streams. An optically accessible test section and instrumentation including thermocouple, Pitot tube, and laser velocimeter were used for obtaining measurements. Velocity profiles, growth rate parameter, and turbulent intensity measurements were obtained. Results indicate that when coal particles were present in cold streams, the velocity profiles depart from their error function behavior, and the shear layer growth rate (visible and vorticity thickness) decreases significantly.

Gollahalli, S.R.; Butuk, N. [Univ. of Oklahoma, Norman, OK (United States). School of Aerospace and Mechanical Engineering

1998-12-31

330

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

331

Surface-confined single-layer covalent organic framework on single-layer graphene grown on copper foil.  

PubMed

The integration of 2D covalent organic frameworks (COFs) with atomic thickness with graphene will lead to intriguing two-dimensional materials. A surface-confined covalently bonded Schiff base network was prepared on single-layer graphene grown on copper foil and the dynamic reaction process was investigated with scanning tunneling microscopy. DFT simulations provide an understanding of the electronic structures and the interactions between the surface COF and graphene. Strong coupling between the surface COF and graphene was confirmed by the dispersive bands of the surface COF after interaction with graphene, and also by the experimental observation of tunneling condition dependent contrast of the surface COF. PMID:25145927

Xu, Lirong; Zhou, Xin; Tian, Wei Quan; Gao, Teng; Zhang, Yan Feng; Lei, Shengbin; Liu, Zhong Fan

2014-09-01

332

Injury to the Endothelial Surface Layer Induces Glomerular Hyperfiltration Rats with Early-Stage Diabetes  

PubMed Central

Glomerular endothelial surface layer (ESL) may play a role in the mechanisms of albuminuria in diabetic nephropathy, which lack evidence in vivo. The effects of high glucose on the passage of albumin across the glomerular ESL were analysed in streptozotocin-induced diabetic Sprague-Dawley rats for 4 weeks. Albuminuria and glomerular mesangial matrix were significantly increased in diabetic rats. The passage of albumin across the ESL, as measured by albumin-colloid gold particle density in the glomerular basement membrane (GBM), was increased significantly in diabetic rats. The thickness of the glomerular ESL, examined indirectly by infusing Intralipid into vessels using an electron microscope, was significantly decreased and the GBM exhibited little change in diabetic rats. In summary, the glomerular ESL may play a role in the pathogenesis of albuminuria in rats with early-stage diabetes. PMID:24812636

Zhang, Chunyang; Meng, Yao; Liu, Qi; Xuan, Miao; Zhang, Lanyu; Deng, Bo; Zhang, Keqin; Liu, Zhimin; Lei, Tao

2014-01-01

333

Boosting Fano resonances in single layered concentric core-shell particles  

NASA Astrophysics Data System (ADS)

Efficient excitation of Fano resonances in plasmonic systems usually requires complex nano-structure geometries and some degree of symmetry breaking. However, a single-layered concentric core-shell particle presents inherent Fano profiles in the scattering spectra when sphere and cavity modes spectrally overlap. Weak hybridization and suitable choice of core and shell materials gives rise to strong electric dipolar Fano resonances in these systems and retardation effects can result in resonances of higher multipolar order or of magnetic type. Furthermore, suitable tailoring of illumination conditions leads to an enhancement of the Fano resonance by quenching of unwanted electromagnetic modes. Overall, it is shown that single layered core-shell particles can act as robust Fano resonators.Efficient excitation of Fano resonances in plasmonic systems usually requires complex nano-structure geometries and some degree of symmetry breaking. However, a single-layered concentric core-shell particle presents inherent Fano profiles in the scattering spectra when sphere and cavity modes spectrally overlap. Weak hybridization and suitable choice of core and shell materials gives rise to strong electric dipolar Fano resonances in these systems and retardation effects can result in resonances of higher multipolar order or of magnetic type. Furthermore, suitable tailoring of illumination conditions leads to an enhancement of the Fano resonance by quenching of unwanted electromagnetic modes. Overall, it is shown that single layered core-shell particles can act as robust Fano resonators. Electronic supplementary information (ESI) available: Fits of the scattering spectra of core-shell particles to the electromagnetic model for Fano resonances proposed by Gallinet and Martin54 and efficiency spectra for particles having a gold shell are provided. See DOI: 10.1039/c4nr03879g

Sancho-Parramon, Jordi; Jelovina, Denis

2014-10-01

334

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

335

Surface modification of inorganic layer compound with organic compound and preparation of thin films  

Microsoft Academic Search

Water treated ZnAl layered double hydroxide (LDH) was prepared by the reaction of LDH oxide and water. By the reaction of the water treated ZnAl LDH or amorphous metal hydroxide and organic oxychloride, surface modified inorganic layer compounds were prepared. Their layer structures were similar to those of the orginal LDHs except the reaction product of amorphous metal hydroxide and

Hideyuki Tagaya; Hiroyuki Morioka; Sumikazu Ogata; Masa Karasu; Jun-ichi Kadokawa; Koji Chiba

1997-01-01

336

Novel approach to material evaluation of thin surface layers by resonant ultrasound spectroscopy  

Microsoft Academic Search

The laser-based modal resonant ultrasound spectroscopy is modified for measurements of thin surface layers on a substrate. This paper describes determination of all in-plane elastic properties of thin layers from small resonant frequency shifts of substrate induced by deposition of the layer.

Michal Landa; Michal Ruzek; Petr Sedlák; Hanus Seiner; Lucie Bodnárová; Jan Zídek

2010-01-01

337

Modeling the Atmospheric Boundary Layer Wind Response to Mesoscale Sea Surface Temperature  

E-print Network

Modeling the Atmospheric Boundary Layer Wind Response to Mesoscale Sea Surface Temperature, a number of recent modeling studies have addressed the response of the atmospheric boundary layer-Bretherton-McCaa (GBM) boundary layer mixing scheme (sU =0.40 m s-1 °C-1 ), and a COAMPS simulation with a form

338

Electric double-layer potentials and surface regulation properties measured by colloidal-probe atomic force microscopy.  

PubMed

We show how the colloidal-probe technique, which is based on force measurements made with the atomic force microscope, can be used to accurately determine the charging parameters of water-solid interfaces. Besides yielding accurate values of the double-layer or diffuse-layer potential, the method also allows reliable determination of the charge regulation properties of the surfaces. The latter can be quantified with a regulation parameter, which is essential to properly describe forces between interfaces, especially in asymmetric situations when one of the interfaces is charged and the other one is close to neutral. The technique relies on a highly charged probe particle, for which the charging properties are accurately determined by interpreting the double-layer contribution of the measured force profiles in the symmetric sphere-sphere geometry with Poisson-Boltzmann (PB) theory. Once the probe particle is calibrated, this particle is used to measure the force profile between an unknown substrate in the asymmetric sphere-sphere or sphere-plane geometry. From this profile, the diffuse-layer potential and regulation parameter of the substrate can be again determined with PB theory. The technique is highly versatile, as it can be used for a wide variety of substrates, including colloidal particles and planar substrates. The technique is also applicable in salt solutions containing multivalent ions. The current drawbacks of the technique are that it can only be applied up to moderately high salt levels, typically to 10 mM, and only for relatively large particles, typically down to about 1 ?m in diameter. How the technique could be extended to higher salt levels and smaller particle size is also briefly discussed. PMID:25122297

Montes Ruiz-Cabello, F Javier; Trefalt, Gregor; Maroni, Plinio; Borkovec, Michal

2014-07-01

339

Antimicrobial and antioxidant surface modification of cellulose fibers using layer-by-layer deposition of chitosan and lignosulfonates.  

PubMed

To confer cellulose fibers antimicrobial and antioxidant activities, chitosan (CS)/lignosulfonates (LS) multilayers were constructed on fibers surfaces through layer-by-layer deposition technique. The formation of CS/LS multilayers on cellulose fibers surfaces was verified by X-ray photoelectron spectroscopy (XPS) and zeta potential measurement. The surface morphologies of CS/LS multilayers on fibers surfaces were observed by atomic force microscopy (AFM). The results showed that characteristic element (i.e. N and S element) content increased with increasing bilayers number, the surface LS content increased linearly as a function of bilayers. Zeta potential of modified fibers was inversed after deposition of each layer. AFM phase images indicated that the cellulose microfibrils on fibers surfaces were gradually covered by granular LS aggregate. The antimicrobial testing results demonstrated that CS/LS multilayers modified fibers with CS in the outermost layer exhibited higher antimicrobial activity against Escherichia coli. The antioxidant testing results showed that antioxidant activity of CS/LS multilayers modified fibers was better than that of original fibers under the same oxidation conditions. PMID:25839791

Li, Hui; Peng, Lincai

2015-06-25

340

Analytic expressions for atomic layer deposition: Coverage, throughput, and materials utilization in cross-flow, particle coating, and spatial atomic layer deposition  

SciTech Connect

In this work, the authors present analytic models for atomic layer deposition (ALD) in three common experimental configurations: cross-flow, particle coating, and spatial ALD. These models, based on the plug-flow and well-mixed approximations, allow us to determine the minimum dose times and materials utilization for all three configurations. A comparison between the three models shows that throughput and precursor utilization can each be expressed by universal equations, in which the particularity of the experimental system is contained in a single parameter related to the residence time of the precursor in the reactor. For the case of cross-flow reactors, the authors show how simple analytic expressions for the reactor saturation profiles agree well with experimental results. Consequently, the analytic model can be used to extract information about the ALD surface chemistry (e.g., the reaction probability) by comparing the analytic and experimental saturation profiles, providing a useful tool for characterizing new and existing ALD processes.

Yanguas-Gil, Angel; Elam, Jeffrey W., E-mail: jelam@anl.gov [Argonne National Laboratory, Energy Systems Division, 9700 S Cass Ave, Lemont, Illinois 60439 (United States)

2014-05-15

341

A PARAMETRIC DESCRIPTION OF A SKEWED PUFF IN THE DIABATIC SURFACE LAYER  

E-print Network

Ris0-R~476 A PARAMETRIC DESCRIPTION OF A SKEWED PUFF IN THE DIABATIC SURFACE LAYER Torben Mikkelsen, and unstable surface layers is parameterized in a form appropriate for use with an operational puff diffusion report (Ris0-R-476) is part of the thesis: FORMULATION AND EXPERIMENTAL EVALUATION OF AN OPERATIONAL PUFF

342

Turbulence wall-shear stress sensor for the atmospheric surface layer  

Microsoft Academic Search

A new sensor is described for measuring the fluctuating component of the wall-shear stress in the atmospheric surface layer over relatively smooth uniform terrain. The sensor was tested at the Surface Layer Turbulence and Environmental Science Test (SLTEST) site on the western salt flats of Utah, giving the first ever direct measurements of this quantity in an atmospheric-scale flow. The

Weston D. C. Heuer; Ivan Marusic

2005-01-01

343

Electrical and mechanical properties of surface layers deposited on copper by the novel IBAD method  

Microsoft Academic Search

A new system for ion beam assisted deposition (IBAD) of metal layers on solid surfaces is described. A new original procedure for IBAD modification of metal surface covers a few physical processes such as in situ ion implantation, metal layer deposition and ion beam mixing. A truncated cone serves as a sputter target. A beam of ions enters the cone

Cz. Karwat; F. F. Komarov; Cz. Kozak; M. ?ozak; F. Romaniuk; P. ?ukowski

2003-01-01

344

A statistical model for variability of the Arctic Ocean surface layer salinity1 Ekaterina Chernyavskaya1  

E-print Network

A statistical model for variability of the Arctic Ocean surface layer salinity1 2 Ekaterina obtained prognostic fields of the Arctic Ocean surface layer salinity for the22 winter period 2013,26 clusters analysis.27 28 29 Introduction30 The Arctic Ocean is very sensitive to changing

345

A Semi-Automatic Approach for Estimating Near Surface Internal Layers From Snow Radar  

E-print Network

MHz 3 km 100 W TBD Dual-Freq Dipole Yak Small UAV UWB Radar Under development Ice Thickness Int snow radar echograms #12;Future Work · Improve near surface layer detection algorithms for more dataA Semi-Automatic Approach for Estimating Near Surface Internal Layers From Snow Radar Imagery

346

The Influence of the Composition of Demineralizing Buffers on the Surface Layers of Artificial Carious Lesions  

Microsoft Academic Search

This paper deals with the influence of (1) the pH, (2) the degree of saturation with respect to hydroxylapatite (OHA) and (3) the fluoride concentration of demineralizing buffer solutions on the development of surface layers of artificial carious lesions. The pH did not affect the surface layer during demineralization. With increasing saturation with respect to OHA, the mineral content of

H. M. Theuns; J. W. E. van Dijk; F. C. M. Driessens; A. Groeneveld

1984-01-01

347

Spatial pattern and stability of the cold surface layer of Storglaciären, Sweden  

Microsoft Academic Search

The mechanisms controlling the spatial distribution and temporal fluctuations of the thermal structure in polythermal glaciers have, to date, been poorly investigated and are not fully understood. We have investigated the sensitivity of the cold surface layer thickness to different forcing parameters and the causes for an observed thinning of the cold surface layer on Storglaciären, northern Sweden, between 1989

Rickard Pettersson; Peter Jansson; Hendrik Huwald; Heinz Blatter

2007-01-01

348

A new family of unsteady boundary layers over a stretching surface  

Microsoft Academic Search

In this paper, a new family of unsteady boundary layers over a stretching flat surface was proposed and studied. This new class of unsteady boundary layers involves the flows over a constant speed stretching surface from a slot, and the slot is moving at a certain speed. Depending on the slot moving parameter, the flow can be treated as a

Tiegang Fang; Ji Zhang; Shanshan Yao

2010-01-01

349

Assimilating Surface Data to Improve the Accuracy of Atmospheric Boundary Layer Simulations  

Microsoft Academic Search

Large errors in atmospheric boundary layer (ABL) simulations can be caused by inaccuracies in the speci- fication of surface characteristics in addition to assumptions and simplifications made in boundary layer for- mulations or other model deficiencies. For certain applications, such as air quality studies, these errors can have significant effects. To reduce such errors, a continuous surface data assimilation technique

Kiran Alapaty; Nelson L. Seaman; Devdutta S. Niyogi; Adel F. Hanna

2001-01-01

350

Resonant absorption and scattering suppression of localized surface plasmons in Ag particles on green LED.  

PubMed

The metallic-structure dependent localized surface plasmons (LSPs) coupling behaviors with InGaN QWs in a green LED epitaxial wafer are investigated by optical transmission, scanning electron microscopy (SEM) and photoluminescence (PL) measurements. Ag nanoparticles (NPs) are formed by thermal annealing Ag layer on the green LED wafer. SEM images show that for higher annealing temperature and/or thicker deposited Ag layer, larger Ag NPs can be produced, leading to the redshift of absorption peaks in the transmission spectra. Time resolved PL (TRPL) measurements indicate when LSP-MQW coupling occurs, PL decay rate is greatly enhanced especially at the resonant wavelength 560 nm. However, the PL intensity is suppressed by 3.5 folds compared to the bare LED. The resonant absorption and PL suppression are simulated by three dimension finite-difference-time-domain (FDTD), which suggests that Ag particle with smaller size and lower height lead to the larger dissipation of LSP. PMID:23736430

Jiang, Shuang; Hu, Zhe; Chen, Zhizhong; Fu, Xingxing; Jiang, Xianzhe; Jiao, Qianqian; Yu, Tongjun; Zhang, Guoyi

2013-05-20

351

Cell and tissue kinetics of the subependymal layer in mouse brain following heavy charged particle irradiation  

SciTech Connect

The following studies investigate the cellular response and cell population kinetics of the subependymal layer in the mouse brain exposed to heavy charged particle irradiation. Partial brain irradiation with helium and neon ions was confined to one cortex of the brain. Both the irradiated and the unirradiated contralateral cortex showed similar disturbances of the cell and tissue kinetics in the subependymal layers. The irradiated hemisphere exhibited histological damage, whereas the unirradiated side appeared normal histologically. This study concerns the cell population and cell cycle kinetics of the subependymal layer in the mouse brain, and the effects of charged particle irradiations on this cell population. Quantitative high resolution autoradiography was used to study the kinetic parameters in this cell layer. This study should help in understanding the effects of these high-energy heavy ions on normal mammalian brain tissue. The response of the mammalian brain exposure to charged particle ionizing radiation may be extremely variable. It varies from minimal physiological changes to overt tissue necrosis depending on a number of factors such as: the administered dose, dose-rate, the volume of the irradiated tissue, and the biological end-point being examined.

Manley, N.B.; Fabrikant, J.I.; Alpen, E.L.

1988-12-01

352

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

353

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

354

Depth profile analysis of native oxide layer on GaAs (100) surface  

NASA Astrophysics Data System (ADS)

Ar+ ion etching and X-ray photoelectron spectroscopy (XPS)depth profile analysis have been performed on the native oxide layerof GaAs(100) surface. The composition of the native oxide layer,that isthe oxide phases of gallium and arsenic, was characterized precisely. It is indicated that native oxide phases on extreme surface of GaAs(100) consist of a mixture of Ga2O3, As2O3 and As2O5. Furthermore, the respective distribution of oxide phases of gallium and arsenic along the depthwere compared and analyzed.A seemingly contradictory phenomenon was found, that is As enrichment exist in total oxide layer, but the content of Ga oxide was greater than that of As oxide in the oxide layer except for the outmost surface layer.Based on the comprehensive influence of oxidation process, etching, segregation and growth process, the intrinsic mechanism of the change of oxides along etching depth was discussed. According to the analyzed results, the oxide layer of GaAs (100) surface should be divided to two layers,that is the outmost layer containing oxides of Ga and As and the intermediate layer including only oxide of Ga.The concentration of As oxides in the outmost layer and the enrichment of As in total oxide layer are derived from surface structure inhomogeneity. The throughout total oxide layer of Ga oxide is attributed to its stronger oxidability.In the present work, the system study for native oxide layer of GaAs surface provides the powerful foundation for understanding surface state of GaAs and surface treatment.

Cheng, Xing; Shi, Feng; Cheng, Hongchang; Niu, Sen; Wang, Long; Miao, Zhuang; Chen, Chang

2014-12-01

355

X-ray reflectivity measurements of surface layering in liquid mercury  

Microsoft Academic Search

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⁻⁻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

O. M. Magnussen; B. M. Ocko; M. J. Regan; K. Penanen; P. S. Pershan; M. Deutsch

1995-01-01

356

X-Ray Reflectivity Measurements of Surface Layering in Liquid Mercury  

Microsoft Academic Search

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 qz = 2.5 Å-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

O. M. Magnussen; B. M. Ocko; M. J. Regan; K. Penanen; P. S. Pershan; M. Deutsch

1995-01-01

357

Double-layered nanoparticle stacks for surface enhanced infrared absorption spectroscopy  

E-print Network

Double-layered nanoparticle stacks for surface enhanced infrared absorption spectroscopy Johannes, surface enhanced infrared absorption spectroscopy (SEIRAS)7­9,18,19 was developed in analogy with surface enhanced Raman scattering (SERS)2,20­22 and surface enhanced uorescence (SEF).23­25 Herein, we demonstrate

Rotter, Stefan

358

9022 J. Phys. Chem. 1994, 98, 9022-9032 Double Layer Forces between Heterogeneous Charged Surfaces  

E-print Network

9022 J. Phys. Chem. 1994, 98, 9022-9032 Double Layer Forces between Heterogeneous Charged Surfaces either constant charge or constant potential. The surface heterogeneities are assumed to be distributed, but net neutral, surface interacts with a uniform surface (charged or uncharged), the interaction can

Chan, Derek Y C

359

Turbulent boundary layer over solid and porous surfaces with small roughness  

NASA Technical Reports Server (NTRS)

Skin friction and profiles of mean velocity, axial and normal turbulence intensity, and Reynolds stress in the untripped boundary layer were measured directly on a large diameter, axisymmetric body with: (1) a smooth, solid surface; (2) a sandpaper-roughened, solid surface; (3) a sintered metal, porous surface; (4) a smooth, perforated titanium surface; (5) a rough solid surface made of fine, diffusion bonded screening, and (6) a rough, porous surface of the same screening. Results obtained for each of these surfaces are discussed. It is shown that a rough, porous wall simply does not influence the boundary layer in the same way as a rough solid wall. Therefore, turbulent transport models for boundary layers over porous surfaces either with or without injection or suction, must include both surface roughness and porosity effects.

Kong, F. Y.; Schetz, J. A.; Collier, F.

1982-01-01

360

Application of silicon surface barrier detector for fast neutral particles  

SciTech Connect

A design study of a small-size neutral particle analyzer using a silicon surface barrier detector (SSD) is performed. The SSD is very sensitive to x rays or photons, so that a pair of 45/sup 0/ sector magnets to separate a reionized neutral from x rays and photons will be used for this analyzer. In order to examine the performance, the SSD was applied to measure the species ratio of the prototype neutral beam injector for JT-60. It was confirmed that the energy resolution was 12% at 40 keV and the linear relation between the incident energy of particles and the pulse height was held over the energy range from 16.7 to 100 keV. The species ratio measured by the SSD was in good agreement with that by the Doppler-shift spectrometer. The SSD has a sufficient capability for the energy analysis of fast neutrals.

Miura, Y.; Takeuchi, H.; Ohara, Y.; Konagai, C.; Kimura, H.

1985-05-01

361

Surface studies with (clean) supported metal particles and clusters  

NASA Technical Reports Server (NTRS)

Small particles are ideal for combined studies with surface analytical and electron microscopy/diffraction methods. In this way crystallography, microstructure, morphology, physical stability, and electronic structure can be correlated directly with chemical reactivity. Various integrated experimental approaches for conducting model studies with UHV-evaporated particles have been successfully developed; they entail the use of TPD, AES, XPS, and work function measurements on one hand and standard TEM/TED, in-situ TEM/TED, and in-situ STED/TEM techniques on the other hand. The essential features of four particular experimental approaches are discussed and a selection of representative results is presented to illustrate the potential usefulness of such studies in the field of catalysis.

Poppa, H. R.

1983-01-01

362

Statistics of particle concentration in free-surface turbulence  

SciTech Connect

Particles on the surface of an incompressible fluid maintained in a turbulent steady-state cluster into spatio-temporally complex flow structures. We experimentally study the statistics of particle concentration n(r, t) over various coarse-grained scales r' in the inertial range. Another control parameter is the Taylor Microscale Reynolds number Re{sub {lambda}}. The focus is on the steady state probability density function {Pi}(n{sub r}). Attention is also given to the variance {sigma}{sup 2}(r, t) of this PDF, since it yields information about the topology of the coagulated structures. Where possible, the results are compared and contrasted with those obtained in a recent analytical and numerical study of two-dimensional synthetic turbulence by Ducasse and Pumir. There, but not here, the dimensionless compressibility C is an important control parameter.

Bandi, Mahesh M [Los Alamos National Laboratory; Larkin, J [UNIV. OF PITTSBURGH; Goldburg, W [UNIV. OF PITTSBURGH

2009-01-01

363

An investigation in the variance in particle surface interactions and their effects in gas turbines  

Microsoft Academic Search

This paper presents the results of a study conducted to investigate particle surface interaction characteristics and their effects on the particle dynamics and blade erosion in axial flow gas turbines. The particle restitution velocities measured experimentally using Laser Doppler Velocimetry in a special tunnel are analyzed using statistical methods. The resulting distribution functions of the rebounding particle velocities after surface

A. Hamed

1992-01-01

364

Electronic Surface Structures of Coal and Mineral Particles  

SciTech Connect

Surface science studies related to tribocharging and charge separation studies were performed on electrostatic beneficiation of coal. In contrast to other cleaning methods, electrostatic beneficiation is a dry cleaning process requiring no water or subsequent drying. Despite these advantages, there is still uncertainty in implementing large scale commercial electrostatic beneficiation of coal. The electronic surface states of coal macerals and minerals are difficult to describe due to their chemical complexity and variability [1]. The efficiency in separation of mineral particles from organic macerals depends upon these surface states. Therefore, to further understand and determine a reason for the bipolar charging observed in coal separation, surface analysis studies using Ultra-violet Photoelectron Spectroscopy (UPS) and X-ray Photoelectron Spectroscopy (XPS) were performed on coal samples and several materials that are used or considered for use in tribocharging. Electrostatic charging is a surface phenomenon, so the electronic surface states of the particles, which are influenced by the environmental conditions, determine both polarity and magnitude of tribocharging. UPS was used to measure the work function of the materials as typically used in ambient air. XPS was used to determine the surface chemistry in the form of contamination and degree of oxidation under the same environmental conditions. Mineral bearing coals are those amenable to electrostatic beneficiation. Three types of coal, Illinois No. 6, Pittsburgh No. 8, and Kentucky No. 9 were investigated in this study. Pulverized coal powder was tribocharged against copper. Pyritic and other ashes forming minerals in coal powders should charge with a negative polarity from triboelectrification, and organic macerals should acquire positive charge, according to the relative differences in the surface work functions between the material being charged and the charging medium. Different types of minerals exhibit different magnitudes of negative charge and some may also charge positively against copper [2]. Only the mineral sulfur fraction of the total sulfur content is accessible by the electrostatic method since organic sulfur is covalently bound with carbon in macerals. The sizes of mineral constituents in coal range from about 0.1 to 100 {micro}m, but pyrites in many coals are on the lower end of this scale necessitating fine grinding for their liberation and separation. A ready explanation for coal powder macerals to charge positively by triboelectrification is found in the large numbers of surface carbon free radicals available to release electrons to form aromatic carbocations. There is evidence that these cationic charges are delocalized over several atoms [3]. Only perhaps one in one hundred thousand of the surface atoms is charged during triboelectrification [4], making it difficult to predict charging levels since the data depends upon the surface chemical species involved in charging. Based on the high electron affinity of oxygen atoms, oxidation is expected to decrease the extent of a coal particle to charge positively. Also, ion transfer may contribute to the increasingly negative charging character of oxidized coal carbons. A variety of oxidized surface functional groups may influence charge properties. For example, carboxylic acid functions can lose protons to form carboxylate anions. The samples of coal investigated in this study showed differing degrees of beneficiation, consistent with a more extensively oxidized Illinois No. 6 coal sample relative to that of Pittsburgh No. 8. Even though oxygen in air is deleterious to coal stored prior to beneficiation, other gases might favorably influence charge properties. To this end, coal exposed to vapors of acetone, ammonia, and sulfur dioxide also were beneficiated and analyzed in this study.

M.K. Mazumder; D.A. Lindquist; K.B. Tennal; Steve Trigwell; Steve Farmer; Albert Nutsukpul; Alex Biris

2001-04-01

365

Charged Particle Alterations of Surfaces in the Solar System  

NASA Technical Reports Server (NTRS)

The surfaces of 'airless' bodies in the solar system are exposed to the ambient plasma, micrometeorites, and the solar UV. The effects of these space weathering agents on surfaces in the solar system has been studied in this project. In the last three years work was carried out on volatile depletion at Mars, on sputtering of the lunar surface, on absorption by implanted S in vapor-deposited H2O and its relevance to observations of Europa's surface in the UV, and on the spectral changes produced on irradiating SO2 and its possible relevance to Io. In addition, the role of plasma-induced charging of E-ring grains was evaluated because of its relevance to E-ring particle source and the lifetime of the E-ring. Finally, the detection of sputtered material from Dione by the CAPS instrument on CASSINI was evaluated as a tool for analysis of satellite surface composition, and the role of sputtering on the ambient OH in the vicinity of the ice satellites and the E-ring was evaluated.

Johnson, R. E.

1995-01-01

366

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

367

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

368

Surface States and the Charge of a Dust Particle in a Plasma F. X. Bronold,1  

E-print Network

Surface States and the Charge of a Dust Particle in a Plasma F. X. Bronold,1 H. Fehske,1 H. Kersten electron and ion surface states of a negatively charged dust particle in a gas discharge and identify the charge of the particle with the electron surface density bound in the polarization-induced short

Fehske, Holger

369

Colloid Surface Chemistry Critically Affects Multiple Particle Tracking Measurements of Biomaterials  

E-print Network

Colloid Surface Chemistry Critically Affects Multiple Particle Tracking Measurements they probe. We here show that colloid surface chemistry can profoundly affect multiple particle tracking present a simple protocol to render the surface of colloidal probe particles protein-resistant by grafting

Gardel, Margaret

370

Pair and multi-particle dispersion in numerical simulations of convective boundary layer turbulence  

NASA Astrophysics Data System (ADS)

Tracer dispersion within a highly convective planetary boundary layer is studied by means of a large-eddy simulation (LES) model for the continuous phases describing the temperature and velocity fields, and with the Lagrangian tracking of particle trajectories. Particle velocities are decomposed into their resolved and unresolved (or sub-grid) components. The former are evaluated by interpolation from the LES velocity field, the latter are given by a Lagrangian kinematic model that correctly describes the turbulent dispersion of clouds of particles. It is shown that, thanks to the Lagrangian sub-grid model, a clear inertial range is detectable in the time domain. In this range, particle separation grows according to Richardson's law, and nicely compares with previous experimental and numerical measurements. The collective motion of four particles, initially located at the vertices of regular tetrahedra, is also studied. The evolution of tetrad shape and orientation is contrasted with those obtained in homogeneous and isotropic flows. Results show that an agreement is achieved at small time lags. At larger times, the boundary layer reveals its anisotropic structure and the tetrad shape statistics deviate from results obtained in ideal flows.

Mazzitelli, I. M.; Fornarelli, F.; Lanotte, A. S.; Oresta, P.

2014-05-01

371

Surface coating for flame retardant behavior of cotton fabric by layer-by-layer processing  

Technology Transfer Automated Retrieval System (TEKTRAN)

Flame retardant behavior has been prepared by the layer-by layer assemblies of branched polyethylenimine (BPEI), kaolin, urea, diammonium phosphate (dibasic) on cotton fabrics. Three different kinds of cotton fabrics (print cloth, mercerized print cloth, and mercerized twill fabric) were prepared wi...

372

Toughening of layered ceramic composites with residual surface compression  

SciTech Connect

Effects of macroscopic residual stresses on fracture toughness of multilayered ceramic laminates were studied analytically and experimentally. Stress intensities for edge cracks in three-layer, single-edge-notch-bend (SENB) specimens with stepwise varying residual stresses in the absence of the crack and superimposed bending were calculated as a function of the crack length by the method of weight function. The selected weight function and the method of calculation were validated by calculating stress intensities for edge cracks in SENB specimens without the residual stresses and obtaining agreement with the stress-intensity equation recommended in ASTM Standard E-399. The stress-intensity calculations for the three-layer laminates with the macroscopic residual stresses were used to define an apparent fracture toughness. The theoretical predictions of the apparent fracture toughness were verified by experiments on three-layer SENB specimens of polycrystalline alumina with 15 vol% of unstabilized zirconia dispersed in the outer layers and 15 vol% of fully stabilized zirconia dispersed in the inner layer. A residual compression of {approximately} 400 MPa developed in the outer layers by the constrained transformation of the unstabilized zirconia from the tetragonal to the monoclinic phase enhanced the apparent fracture toughness to values of 30 MPa {center_dot} m{sup 1/2} in a system where the intrinsic fracture toughness was only 5 to 7 MPa {center_dot} m{sup 1/2}.

Lakshminarayanan, R.; Shetty, D.K. [Univ. of Utah, Salt Lake City, UT (United States). Dept. of Materials Science and Engineering; Cutler, R.A. [Ceramatec, Inc., Salt Lake City, UT (United States)

1996-01-01

373

Optical detector having a plurality of matrix layers with cobalt disilicide particles embedded therein  

NASA Technical Reports Server (NTRS)

Silicon and metal are coevaporated onto a silicon substrate in a molecular beam epitaxy system with a larger than stoichiometric amount of silicon so as to epitaxially grow particles of metal silicide embedded in a matrix of single crystal epitaxially grown silicon. The particles interact with incident photons by resonant optical absorption at the surface plasmon resonance frequency. Controlling the substrate temperature and deposition rate and time allows the aspect ratio of the particles to be tailored to desired wavelength photons and polarizations. The plasmon energy may decay as excited charge carriers of phonons, either of which can be monitored to indicate the amount of incident radiation at the selected frequency and polarization.

Fathauer, Robert W. (inventor); Schowalter, Leo (inventor)

1994-01-01

374

Chemical-thermal quantitative methodology for carbon speciation in damage layers on building surfaces.  

PubMed

The issue of environment protection, including the conservation of the monumental heritage worldwide, is related to atmospheric pollution, and its future therefore depends on air pollutant reduction. Carbonaceous particles emitted by combustion processes are the main factors responsible for the blackening of buildings. The identification and evaluation of the carbon species constituting the noncarbonate fraction of total carbon in damage layers, particularly in urban areas, are required in orderto investigate atmospheric deposition on building surfaces. Since noncarbonate carbon contains organic and elemental carbon originating from various human activities, its measurement and speciation are crucial to the protection and conservation of monuments and ancient masonry, playing an important role both in the proposal of mitigation strategies and in the definition of conservation treatments. The availability of a correct, accurate, and reproducible analytical method for a complete carbon balance is essential in studying the effects of atmospheric pollutants on the environment, including those affecting cultural heritage. A chemical-thermal methodology was set up, and its sensitivity, accuracy, repeatability, and reproducibility were tested on appropriate standard samples of composition similar to the black crusts on stones and mortars. The results indicate thatthe technique satisfactorily distinguishes among carbon species, particularly those of anthropogenic origin, allowing a reliable evaluation of their quantities in damage layers. In view of the difficulties encountered in applying the thermo-optical methods adopted for the measurement of carbon filters, the proposed methodology contributes to filling the current gap in suitable and reliable analytical procedures in the field of cultural heritage protection. PMID:16509340

Ghedini, Nadia; Sabbioni, Cristina; Bonazza, Alessandra; Gobbi, Giancarlo

2006-02-01

375

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

376

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

377

Effect of surface wave breaking on the surface boundary layer of temperature in the Yellow Sea in summer  

Microsoft Academic Search

Near-surface enhancement of turbulent mixing and vertical mixing coefficient for temperature owing to the effect of surface wave breaking is investigated using a two-dimensional (2-D) ocean circulation model with a tidal boundary condition in an idealized shelf sea. On the basis of the 2-D simulation, the effect of surface wave breaking on surface boundary layer deepening in the Yellow Sea

Zhang Xuefeng; Han Guijun; Wang Dongxiao; Li Wei; He Zhongjie

2011-01-01

378

Surface Improvement Technology “Wonder Process Craft (WPC)” by Rapid Impact of Fine Particle  

NASA Astrophysics Data System (ADS)

Based on our sandblast and shot peening technology, we have found that utilizing relatively smaller powder for sandblasting enables the modification or the organizational and mechanical features of the ingredient's surface, defying the conventional thought in this subject manner. The technology mentioned previously can be utilized on various ingredients and machinery parts, and its effect is widely recognized. By blasting titanium particles onto the surface of metals, ceramics, or combined substances utilizing the previously mentioned technology, it is possible to attain a thin film layer of titanium deposit that is effective in catalyzing light. This is PIP (Powder Impact Plating) natural catalyst. In today's world where environmental destruction has become a serious issue, we hope to contribute to the improvement of the environment with our highly efficient catalyst.

Miyasaka, Yoshio

379

Modifying of Cotton Fabric Surface with Nano-ZnO Multilayer Films by Layer-by-Layer Deposition Method  

PubMed Central

ZnO nanoparticle–based multilayer nanocomposite films were fabricated on cationized woven cotton fabrics via layer-by-layer molecular self-assembly technique. For cationic surface charge, cotton fabrics were pretreated with 2,3-epoxypropyltrimethylammonium chloride (EP3MAC) by pad-batch method. XPS and SEM were used to examine the deposited nano-ZnO multilayer films on the cotton fabrics. The nano-ZnO films deposited on cotton fabrics exhibited excellent antimicrobial activity against Staphylococcus aureus bacteria. The results also showed that the coated fabrics with nano-ZnO multilayer films enhanced the protection of cotton fabrics from UV radiation. Physical tests (tensile strength of weft and warp yarns, air permeability and whiteness values) were performed on the fabrics before and after the treatment with ZnO nanoparticles to evaluate the effect of layer-by-layer (LbL) process on cotton fabrics properties. PMID:20596450

2010-01-01

380

Effective surface modification by stimuli-responsive polymers onto the magnetite nanoparticles by layer-by-layer method  

NASA Astrophysics Data System (ADS)

Effective surface modification of poly( N-isopropylacrylamide)-based temperature-responsive polymers onto the magnetite nanoparticles was investigated. To achieve this purpose, layer-by-layer method was applied. This technique is based on sequential chemical reactions between the temperature-responsive polymers with carboxyl groups and other another polymers with amino groups. After the polyion complex formation, carbodiimide chemistry was used to cross-link both the functional polymers. As a result, we could confirm the successful preparation using X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and the dispersion measurement of the modified magnetite nanoparticles. The thickness was tunable be the number of the layer-by layer reaction. As expected, the magnetite nanoparticles show the very sensitive temperature-responsive behavior.

Yamamoto, Kazuya; Matsukuma, Daisuke; Nanasetani, Kazuyuki; Aoyagi, Takao

2008-11-01

381

Scaling of layer spacing of charged particles under slit-pore confinement: an effect of concentration or of effective particle diameter?  

NASA Astrophysics Data System (ADS)

This paper tests the generality of the scaling law for layer spacing of charged particles under confinement and resolves the established contradictions in the literature. The present determined layer spacings ?, also called the wavelength of oscillatory force, by colloidal probe atomic force microscopy are compared to previously obtained ones, ?h, also called step size, by using a thin film pressure balance. For charged particles, e.g. silica nanoparticles and micelles of anionic surfactant, the layer spacing under confinement is found to depend solely on the particle number density ? in the relation ? (or ?h) =?-1/3. The previous description for the layer spacing using the effective particle diameter 2(R + ?-1) is not general and only applicable at specific conditions of particle volume fraction and ionic strength. We claim that when particles are dominated by electrostatic repulsion and in a low pressure reservoir, ?-1/3 is a general scaling law for layer spacing of particles, which indicates that particles under confinement are still randomly distributed in a fluid-like manner as they are in bulk. As a side-effect an equation to obtain the ionic strength I of colloidal suspension from measured conductivity is established. Ionic strength I is needed to determine the values for Debye length ?-1, which are in very good agreement with the theoretical ones.

Zeng, Yan; von Klitzing, Regine

2012-11-01

382

Facile synthesis of methotrexate intercalated layered double hydroxides: particle control, structure and bioassay explore.  

PubMed

To study the influence of particle size on drug efficacy and other properties, a series of methotrexate intercalated layered double hydroxides (MTX/LDHs) were synthesized through the traditional coprecipitation method, using a mixture of water and polyethylene glycol (PEG-400) as the solvent. To adjust the particle size of MTX/LDHs, the dropping way, the volume ratio of water to PEG-400 and different hydrothermal treatment time changed accordingly, and the results indicate that the particle size can be controlled between 90 and 140 nm. Elemental C/H/N and inductive coupled plasma (ICP) analysis indicated that different synthesis conditions almost have no effect on the compositions of the nanohybrids. X-ray diffraction (XRD) patterns manifested the successful intercalation of MTX anions into the LDH interlayers, and it's also found out that different volume ratios of water to PEG-400 and variable dropping way can affect the crystallinity of the final samples, i.e., the volume ratio of 3:1 and pH decreasing are proved to be optimum conditions. Furthermore, both antiparallel monolayer and bilayers adopting different orientations are suggested for four samples from XRD results. Fourier transform infrared spectroscopy (FTIR) investigations proved the coexistence of CO3(2-) and MTX anions in the interlayer of the nanohybrids. MTX/LDH particles exhibited hexagonal platelet morphology with round corner and different dropping ways can affect the morphology greatly. Moreover, a DSC study indicated that longer time treatment can weaken the bond between the MTX anions and LDH layers. The kinetic release profiles told us that larger MTX/LDH particles have enhanced the ability of LDH layers to protect interlayer molecules. At last, the bioassay study indicated that the nanohybrids with larger diameters have higher tumor suppression efficiency. PMID:25491832

Tian, De-Ying; Liu, Zhen-Lei; Li, Shu-Ping; Li, Xiao-Dong

2014-12-01

383

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

384

Layered Model for Radiation-Induced Chemical Evolution of Icy Surface Composition on Kuiper Belt and Oort Cloud Bodies  

NASA Technical Reports Server (NTRS)

The diversity of albedos and surface colors on observed Kuiper Belt and Inner Oort Cloud objects remains to be explained in terms of competition between primordial intrinsic versus exogenic drivers of surface and near-surface evolution. Earlier models have attempted without success to attribute this diversity to the relations between surface radiolysis from cosmic ray irradiation and gardening by meteoritic impacts. A more flexible approach considers the different depth-dependent radiation profiles produced by low-energy plasma, suprathermal, and maximally penetrating charged particles of the heliospheric and local interstellar radiation environments. Generally red objects of the dynamically cold (low inclination, circular orbit) Classical Kuiper Belt might be accounted for from erosive effects of plasma ions and reddening effects of high energy cosmic ray ions, while suprathermal keV-MeV ions could alternatively produce more color neutral surfaces. The deepest layer of more pristine ice can be brought to the surface from meter to kilometer depths by larger impact events and potentially by cryovolcanic activity. The bright surfaces of some larger objects, e.g. Eris, suggest ongoing resurfacing activity. Interactions of surface irradiation, resultant chemical oxidation, and near-surface cryogenic fluid reservoirs have been proposed to account for Enceladus cryovolcanism and may have further applications to other icy irradiated bodies. The diversity of causative processes must be understood to account for observationally apparent diversities of the object surfaces.

Cooper, John F.; Hill, Matthew E.; Richardson, John D.; Sturner, Steven J.

2010-01-01

385

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

386

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

387

Scanning near-field optical images of ordered polystyrene particle layers in transmission and luminescence excitation modes.  

PubMed

Scanning near-field optical images of hexagonally close-packed layers of polystyrene spherical particles with a diameter of 1.0 microm have been investigated. The layers were composed of particles that were doped either totally or partially with an organic fluorescent dye. Observations were made in the transmission and luminescence excitation modes with a scanning near-field optical microscope (SNOM) with a spatial resolution shorter than the wavelength of light. The patterns observed in the SNOM images are significantly dependent on the microstructures of layers, that is, the layers are either single or double layered, and the particles are either totally or partially doped. These results are discussed in terms of specific modes of electromagnetic waves transmitting across and along the layers after the local excitation at the tip end of the scanning microprobe. PMID:18183243

Fujimura, T; Edamatsu, K; Itoh, T; Shimada, R; Imada, A; Koda, T; Chiba, N; Muramatsu, H; Ataka, T

1997-04-15

388

Layer-by-layer self-assembled mutilayer films of gold nanoparticles for surface-assisted laser desorption/ionization mass spectrometry.  

PubMed

Layer-by-layer (LBL) self-assembled multilayer films of gold nanoparticles (AuNPs) on a silicon wafer were demonstrated to be promising substrates for surface-assisted laser desorption/ionization (SALDI) mass spectrometry (MS) of peptides and environmental pollutants for the first time. LBL multilayer films, (AuNPs/PAHC)n, consisting of alternating layers of ammonium citrate capped AuNPs and poly(allylamine hydrochloride) (PAHC) were prepared on a silicon surface. Silicon plates with aggregated AuNPs were more suitable than those with dispersed AuNPs for the SALDI-MS of peptides. The number of particle layers had a significant effect on the laser desorption/ionization of angiotensin I; the peak intensity of the peptide (molecular ion amount) increased with an increase in the number of layers of AuNPs. As a result, the (AuNPs/PAHC)5 multilayer films increased the sensitivity of the angiotensin I to subfemtomoles and raised the useful analyte mass range, thus making it possible to detect small proteins (a 12 kDa cytochrome c). The signal enhancement when using (AuNPs/PAHC)5 may be due to (i) the high absorption of the UV laser light at 337 nm by the AuNP layers, (ii) the low thermal conductivity due to the AuNPs being covered with a thin monolayer of PAHC, and (iii) the increase in the surface roughness (approximately 100 nm) with the number of AuNP layers. Thus, laser-induced rapid high heating of AuNPs for effective desorption/ionization of peptides is possible. In addition, it was found that (AuNPs/PAHC)5 could be used to extract environmental pollutants (pyrene and dimethyldistearylammonium chloride) from very dilute aqueous solutions with concentrations less than 10(-10) mg/mL, and the analytes trapped in the LBL film could be identified by introducing the film directly into the SALDI mass spectrometer without needing to elute the analytes out of the film. PMID:18778032

Kawasaki, Hideya; Sugitani, Tsuyoshi; Watanabe, Takehiro; Yonezawa, Tetsu; Moriwaki, Hiroshi; Arakawa, Ryuichi

2008-10-01

389

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

390

Genetic particle filter application to land surface temperature downscaling  

NASA Astrophysics Data System (ADS)

Thermal infrared data are widely used for surface flux estimation giving the possibility to assess water and energy budgets through land surface temperature (LST). Many applications require both high spatial resolution (HSR) and high temporal resolution (HTR), which are not presently available from space. It is therefore necessary to develop methodologies to use the coarse spatial/high temporal resolutions LST remote-sensing products for a better monitoring of fluxes at appropriate scales. For that purpose, a data assimilation method was developed to downscale LST based on particle filtering. The basic tenet of our approach is to constrain LST dynamics simulated at both HSR and HTR, through the optimization of aggregated temperatures at the coarse observation scale. Thus, a genetic particle filter (GPF) data assimilation scheme was implemented and applied to a land surface model which simulates prior subpixel temperatures. First, the GPF downscaling scheme was tested on pseudoobservations generated in the framework of the study area landscape (Crau-Camargue, France) and climate for the year 2006. The GPF performances were evaluated against observation errors and temporal sampling. Results show that GPF outperforms prior model estimations. Finally, the GPF method was applied on Spinning Enhanced Visible and InfraRed Imager time series and evaluated against HSR data provided by an Advanced Spaceborne Thermal Emission and Reflection Radiometer image acquired on 26 July 2006. The temperatures of seven land cover classes present in the study area were estimated with root-mean-square errors less than 2.4 K which is a very promising result for downscaling LST satellite products.

Mechri, Rihab; Ottlé, Catherine; Pannekoucke, Olivier; Kallel, Abdelaziz

2014-03-01

391

Shear-induced surface alignment of polymer dispersed liquid crystal microdroplets on the boundary layer  

NASA Technical Reports Server (NTRS)

Polymer dispersed liquid crystal thin films have been deposited on a glass substrate, utilizing the processes of polymerization and solvent evaporation induced phase separation. Liquid crystal microdroplets trapped on the upper surface of the thin film respond to the shear stress due to air or gas flow on the surface layer. Response to an applied step shear stress input on the surface layer has been measured by measuring the time response of the transmitted light intensity. Initial results on the measurements of the light transmission as a function of the air flow differential pressure indicate that these systems offer features suitable for boundary layer and gas flow sensors.

Parmar, D. S.; Singh, J. J.

1993-01-01

392

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

393

UV modification of surface pretilt of alignment layers for multidomain liquid crystal displays  

Microsoft Academic Search

Two types of ultraviolet (UV) light induced modification of the surface pretilt of alignment layers are reported. The UV modification allows the liquid crystal (LC) surface pretilt angle of a polyimide film to be selectively altered in a small area. Two device structures for fabricating two-domain liquid crystal displays based on this selective alteration of the LC surface pretilt angle

A. Lien; R. A. John; M. Angelopoulos; K. W. Lee; H. Takano; K. Tajima; A. Takenaka

1995-01-01

394

Surface Modification of Layered Zirconium Phosphates: A Novel Pathway to Multifunctional Nanomaterials  

E-print Network

to deposit metal ions on the surface. The metal ion layer was then coordinated with phosphonic acid ligands to produce surface functionalized ZrP. In all cases the exclusive functionalization of the surface and covalent attachment of the reactive groups...

Mosby, Brian Matthew

2014-04-08

395

Reconstruction of the surface impedance of an inhomogeneous planar boundary beyond layered media  

Microsoft Academic Search

Determination of the boundary conditions of a surface from the remote field measurements is an important and interesting topic in the inverse scattering theory. As an example of such problems a method is developed for the reconstruction of the surface impedance of a planar boundary beyond a layered structure. The surface impedance is recovered from the boundary condition itself, which

Ali Yapar; Ibrahim Akduman

2001-01-01

396

Wall Shear stress measurements in the atmosperhic surface layer  

E-print Network

an unprecedented range of Reynolds numbers. The shear stress measurements were made at the unique SLTEST (Sur- face was to further understand similarities that may exist between the SLTEST sur- face layer and the wind tunnel Marusic, Jason Monty, Nicholas Hutchins, and Min Chong Fig. 1. Photograph of the SLTEST measurement site

Marusic, Ivan

397

Turbulent boundary layer on a mildly curved convex surface  

Microsoft Academic Search

Extensive single point turbulence measurements made in the boundary layer on a mildly curved heated convex wall show that the turbulence heat fluxes and Stanton number are more sensitive to a change in wall curvature than the Reynolds stresses and skinfriction coefficient, and that downstream, as the flow adjusts to new curved conditions, the St\\/cf ratio of Reynolds analogy is

M. M. Gibson; C. A. Verriopoulos

1984-01-01

398

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

399

Surface Tension Driven Instability in a Horizontal Liquid Layer with a Deformable Free Surface. I. Stationary Convection  

Microsoft Academic Search

The effect of a free surface deformation on the onset of surface tension driven instability in a horizontal thin liquid layer subjected to a vertical temperature gradient is examined using linear stability theory. Assuming that the neutral state is a stationary one, the conditions under which instability sets in are determined in detail. It is shown that when the upside

Masaki Takashima

1981-01-01

400

Boundary layer surface vorticity flux measurements at high Reynolds number  

Microsoft Academic Search

Under isothermal conditions vorticity enters a flow through a flux at the wall. If the walls are stationary, this flux is proportional to the pressure gradients in the plane of the surface. Wall vorticity flux measurements were acquired through the use of closely spaced microphones in arrays mounted flush with the surface. The measurements were acquired at Rtheta= O(10^6) under

Joe Klewicki; David Kenney

2005-01-01

401

Evolution of the surface area of a snow layer  

SciTech Connect

Atmospheric trace gases can partition between the atmosphere and the snow surface. Because snow has a large surface-to-volume ratio, an important interaction potential between ice and atmospheric trace gases exists. Quantifying this partitioning requires the knowledge of the surface area (SA) of snow. Eleven samples were taken from a 50 cm thick snow fall at Col de Porte, near Grenoble (French Alps) between January 20 and February 4, 1998. Fresh snow and 3, 8, and 15-day-old snow were sampled at three different depths. Surface hoar, formed after the fall, was also sampled. Air and surface snow temperature, snow density, and snow fall rate were measured. Snow temperature always remained below freezing. Snow SA was measured using methane adsorption at 77.15 K. Values ranged from 2.25 m{sup 2}/g for fresh snow to 0.25 m{sup 2}/g for surface hoar and surface snow after 15 days. These values are much too high to be explained by the macroscopic aspect of snow crystals, and microstructures such as small rime droplets must have been present. Large decrease in SA with time were observed. The first meter of snowpack had a total surface area of about 50,000 m{sup 2} per m{sup 2} of ground. Reduction in SA will lead to the emission of adsorbed species by the snowpack, with possible considerable increase in atmospheric concentrations.

Hanot, L.; Domine, F.

1999-12-01

402

Quantitative Study of Energization of Plasma Particles in the Magnetic Reconnection Layer of a Laboratory Plasma  

NASA Astrophysics Data System (ADS)

Quantitative study of the energization of plasma particles in the magnetic reconnection layer has been carried out by monitoring the behavior of electrons and ions in MRX (1, 2). The measured profiles of plasma parameters are quantitatively analyzed with symmetric as well as asymmetric upstream conditions in the context of the two-fluid reconnection physics (1) and compared with the recent numerical simulation results. The electron heating is observed to extend beyond the electron diffusion region and considered to be due to energization by magnetic instabilities of incoming electrons trapped in the magnetic mirror. This energization often occurs impulsively. Ions are accelerated by an electrostatic field across the separatrices to the plasma exhaust region of the reconnection layer and become thermalized through re-magnetization by the exiting magnetic fields. In this paper, the acceleration and heating of ions and electrons which extents much wider than the length scale of the ion skin depth, is addressed quantitatively for the first time in a laboratory reconnection layer. A total energy inventory is calculated based on analysis of the Poynting, enthalpy, flow energy, and heat flux in the measured diffusion layer (3). More than half of the incoming magnetic energy is converted to particle energy during collisionless reconnection. The results will bring a new insight into the conversion mechanism of magnetic energy to that of plasma particles during magnetic reconnection. (1) M. Yamada, R. Kulsrud, H. Ji, Rev. Mod. Phys. v.82, 602 (2010) (2) J. Yoo et al, Phys. Rev. Letts. 110, 215007 (2013) (3) J. Eastwood et al., PRL 110, 225001 (2013) Fig. 1. Measured in-plane ion flow vectors along with the measured 2-D profile of the in-plane plasma potential ?p in the half reconnection plane of MRX. The thin black lines are measured contours of poloidal flux ?p. While ions flow across the separatrices, they turn in-plane electric field Ein.

Yamada, M.; Yoo, J.; Swanson, C.; Jara Almonte, J.; Ji, H.; Myers, C. E.; Chen, L.

2013-12-01

403

Multiscale structure, interfacial cohesion, adsorbed layers, miscibility and properties in dense polymer-particle mixtures  

NASA Astrophysics Data System (ADS)

A major goal in polymer nanocomposite research is to understand and predict how the chemical and physical nature of individual polymers and nanoparticles, and thermodynamic state (temperature, composition, solvent dilution, filler loading), determine bulk assembly, miscibility and properties. Microscopic PRISM theory provides a route to this goal for equilibrium disordered mixtures. A major prediction is that by manipulating the net polymer-particle interfacial attraction, miscibility is realizable via the formation of thin thermodynamically stable adsorbed layers, which, however, are destroyed by entropic depletion and bridging attraction effects if interface cohesion is too weak or strong, respectively. This and related issues are quantitatively explored for miscible mixtures of hydrocarbon polymers, silica nanospheres, and solvent using x-ray scattering, neutron scattering and rheology. Under melt conditions, quantitative agreement between theory and silica scattering experiments is achieved under both steric stabilization and weak depletion conditions. Using contrast matching neutron scattering to characterize the collective structure factors of polymers, particles and their interface, the existence and size of adsorbed polymer layers, and their consequences on microstructure, is determined. Failure of the incompressible RPA, accuracy of PRISM theory, the nm thickness of adsorbed layers, and qualitative sensitivity of the bulk modulus to interfacial cohesion and particle size are demonstrated for concentrated PEO-silica-ethanol nanocomposites. Temperature-dependent complexity is discovered when water is the solvent, and nonequilibrium effects emerge for adsorbing entangled polymers that strongly impact structure. By varying polymer chemistry, the effect of polymer-particle attraction on the intrinsic viscosity is explored with striking non-classical effects observed. This work was performed in collaboration with S.Y.Kim, L.M.Hall, C.Zukoski and B.Anderson.

Schweizer, Ken

2012-02-01

404

ELECTROSTATIC SURFACE STRUCTURES OF COAL AND MINERAL PARTICLES  

Microsoft Academic Search

We have developed a video image analyzer for measuring the size and charge of airborne particles. Particles are illuminated by laser light and subjected to a sinusoidal electric field while images of the trajectories of the particles are captured using a video camera and a frame grabber. Analysis of the particle tracks allows the size and charge of the particles

M. K. Mazumder; D. A. Lindquist; K. B. Tennal

1999-01-01

405

Dusty Plasma Technology of DCM with Nanostructure Surface Layer Production  

SciTech Connect

The technique of disperse composite material (DCM) production was developed. The technique based on using special dusty plasma trap in RF plasma, in which fine particles levitate and are exposed by the atomic beam. The two types of covering were obtained: ''cauliflower'' or smooth, depending on process condition.

Gavrikov, A. V.; Ivanov, A. S.; Petrov, O. F.; Shulga, Yu. M.; Starostin, A. N.; Fortov, V. E. [Joint Institute for High Temperatures of RAS, 13/19 Izhorskaya Street, Moscow, 125412 (Russian Federation); Pal, A. F.; Ryabinkin, A. N.; Serov, A. O. [Lomonosov Moscow State University Skobeltsyn Institute of Nuclear Physics, 1 (2), Leninskie gory, GSP-1, Moscow, 119991 (Russian Federation)

2008-09-07

406

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

407

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

408

Roles of the Surface Layer Proteins of Campylobacter fetus subsp. fetus in Ovine Abortion  

Microsoft Academic Search

The role of the surface (S)-layer proteins of Campylobacter fetus subsp. fetus has been investigated using an ovine model of abortion. Wild-type strain 23D induced abortion in up to 90% of pregnant ewes challenged subcutaneously. Isolates recovered from both dams and fetuses expressed S-layer proteins with variable molecular masses. The spontaneous S-layer-negative variant, strain 23B, neither colonized nor caused abor-

R. Grogono-Thomas; J. Dworkin; M. J. Blaser; D. G. Newell

2000-01-01

409

Hydraulic jumps in two-layer flow with a free surface  

NASA Astrophysics Data System (ADS)

This paper presents a closure relation which describes hydraulic jumps in two-layer flows with a free surface over a flat bottom. This relation is derived from the momentum equations for each layer, which, subject to the condition of conservation of the total momentum and mass of each layer, become conservative in a sense. It is shown that use of this relation provides a reduction in the total energy at the jump.

Gavrilyuk, S. L.; Kazakova, M. Yu.

2014-03-01

410

Origin and consequences of silicate glass passivation by surface layers  

PubMed Central

Silicate glasses are durable materials, but are they sufficiently durable to confine highly radioactive wastes for hundreds of thousands years? Addressing this question requires a thorough understanding of the mechanisms underpinning aqueous corrosion of these materials. Here we show that in silica-saturated solution, a model glass of nuclear interest corrodes but at a rate that dramatically drops as a passivating layer forms. Water ingress into the glass, leading to the congruent release of mobile elements (B, Na and Ca), is followed by in situ repolymerization of the silicate network. This material is at equilibrium with pore and bulk solutions, and acts as a molecular sieve with a cutoff below 1?nm. The low corrosion rate resulting from the formation of this stable passivating layer enables the objective of durability to be met, while progress in the fundamental understanding of corrosion unlocks the potential for optimizing the design of nuclear glass-geological disposal. PMID:25695377

Gin, Stéphane; Jollivet, Patrick; Fournier, Maxime; Angeli, Frédéric; Frugier, Pierre; Charpentier, Thibault

2015-01-01

411

Origin and consequences of silicate glass passivation by surface layers.  

PubMed

Silicate glasses are durable materials, but are they sufficiently durable to confine highly radioactive wastes for hundreds of thousands years? Addressing this question requires a thorough understanding of the mechanisms underpinning aqueous corrosion of these materials. Here we show that in silica-saturated solution, a model glass of nuclear interest corrodes but at a rate that dramatically drops as a passivating layer forms. Water ingress into the glass, leading to the congruent release of mobile elements (B, Na and Ca), is followed by in situ repolymerization of the silicate network. This material is at equilibrium with pore and bulk solutions, and acts as a molecular sieve with a cutoff below 1?nm. The low corrosion rate resulting from the formation of this stable passivating layer enables the objective of durability to be met, while progress in the fundamental understanding of corrosion unlocks the potential for optimizing the design of nuclear glass-geological disposal. PMID:25695377

Gin, Stéphane; Jollivet, Patrick; Fournier, Maxime; Angeli, Frédéric; Frugier, Pierre; Charpentier, Thibault

2015-01-01

412

Origin and consequences of silicate glass passivation by surface layers  

NASA Astrophysics Data System (ADS)

Silicate glasses are durable materials, but are they sufficiently durable to confine highly radioactive wastes for hundreds of thousands years? Addressing this question requires a thorough understanding of the mechanisms underpinning aqueous corrosion of these materials. Here we show that in silica-saturated solution, a model glass of nuclear interest corrodes but at a rate that dramatically drops as a passivating layer forms. Water ingress into the glass, leading to the congruent release of mobile elements (B, Na and Ca), is followed by in situ repolymerization of the silicate network. This material is at equilibrium with pore and bulk solutions, and acts as a molecular sieve with a cutoff below 1?nm. The low corrosion rate resulting from the formation of this stable passivating layer enables the objective of durability to be met, while progress in the fundamental understanding of corrosion unlocks the potential for optimizing the design of nuclear glass-geological disposal.

Gin, Stéphane; Jollivet, Patrick; Fournier, Maxime; Angeli, Frédéric; Frugier, Pierre; Charpentier, Thibault

2015-02-01

413

Upper Surface of Icy Layers Covering Mars' South Polar Region  

NASA Technical Reports Server (NTRS)

[figure removed for brevity, see original site] Annotated Version

This map shows the topography of the south polar region of Mars. The data were collected by the Mars Orbiter Laser Altimeter aboard NASA's Mars Global Surveyor orbiter between 1997 and 2001. The elevation of the terrain is shown by colors, with purple and blue representing the lowest areas, and orange and red the highest. The total range of elevation shown is about 5 kilometers (3 miles). The black line shows the boundary of the south polar layered deposits, an ice-rich geologic unit that was probed by the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) aboard the European Space Agency's Mars Express orbiter.

The radar data indicate that the deposit is more than 3.7 kilometers (2.3 miles) thick in places, and that the material consists of nearly pure water ice, with only a small component of dust. The MARSIS team also determined that the total volume of ice in the layered deposits is equivalent to a water layer 11 meters (36 feet) deep, if spread evenly across the planet. The boundary of the layered deposits was mapped by scientists from the U.S. Geological Survey. The dark circle in the upper center is the area poleward of 87 degrees south latitude, where MARSIS data cannot be collected. The image covers an area 1,670 by 1,800 kilometers (1,035 by 1,115 miles).

MARSIS is an instrument on the European Space Agency's Mars Express orbiter. NASA and the Italian Space Agency jointly funded the instrument. The Mars Orbiter Laser Altimeter flew on NASA's Mars Global Surveyor orbiter.

2007-01-01

414

Microstructure and biocompatibility of titanium oxides produced on nitrided surface layer under glow discharge conditions.  

PubMed

The disadvantages of titanium implants are their low wear resistance and the release of titanium elements into surrounding tissue. These can be eliminated by modifying the surface by surface engineering methods, among them nitriding under glow discharge conditions which allow to produce diffusive surface layers. Their combining with an oxide layer might be valuable for biological events occurring at the bone implant interface. The aim of this study was to enhance the titanium biomaterial performance via combining nitriding and oxidizing treatments in one process under glow discharge conditions. The oxynitrided surface layers were produced at 680 degrees C. The obtained layer was TiO + TiN + Ti2N + alphaTi(N) type and about 4-microm thick and was of diffusive character. This layer significantly increased wear resistance and slightly corrosion resistance compared to that of the reference titanium alloy. The produced titanium oxide was about 400-nm thick and built from fine crystallites. This oxide exhibits bioactivity in SBF (simulated body fluid). Osteoblasts of Saos-2 line incubated on this surface exhibited good adhesion and proliferation and ALP release comparable with cells cultured on the reference titanium alloy and TiN + Ti2N + alphaTi(N) surface layers. A quantitative analysis of blood platelets adhering to this layer revealed their highest amount in comparison to that on both the nitrided surface layer and titanium alloy. The presented study provided a simple and reproducible method of combining oxidizing and nitriding under glow discharge in one process. Experimental data in vitro suggests that titanium alloy oxynitriding under low temperatures at glow discharge conditions improves titanium alloy properties and biocompatibility and tissue healing. Therefore, the layer of TiO + TiN +Ti2N + alphaTi(N) type could be valuable for long-term bone implants. PMID:22400281

Czarnowska, E; Morgiel, J; Ossowski, M; Major, R; Sowinska, A; Wierzchon, T

2011-10-01

415

Observations of Turbulence in the Ocean Surface Boundary Layer: Energetics and Transport  

E-print Network

Observations of turbulent kinetic energy (TKE) dynamics in the ocean surface boundary layer are presented here and compared with results from previous observational, numerical, and analytic studies. As in previous studies, ...

Gerbi, Gregory P.

416

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

417

Evaluation of infiltration in layered pavements using surface GPR reflection techniques  

E-print Network

Evaluation of infiltration in layered pavements using surface GPR reflection techniques K. Grotea-coupled ground penetrating radar (GPR) techniques were used to non-destructively monitor the volumetric water contained a sub-asphalt drainage layer. GPR travel time data were used to estimate the water content in each

Hubbard, Susan

418

Removal of surface layer of concrete by a pulse-periodical discharge  

Microsoft Academic Search

To clean concrete (e.g., floor) contaminated by hazardous chemicals or radionuclides, its surface layer has to be removed. In our experiments and large area trials, 0.5 cm to 3 cm thick concrete layers have been removed either by the shock waves and cavitation initiated in water by a discharge or by a direct breakdown through concrete. The discharge mode is

V. Goldfarb; R. Budny; A. Dunton; G. Shneerson; S. Krivosheev; Yu. Adamian

1997-01-01

419

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

420

A manufacturing method for multi-layer polysilicon surface-micromachining technology  

SciTech Connect

An advanced manufacturing technology which provides multi-layered polysilicon surface micromachining technology for advanced weapon systems is presented. Specifically, the addition of another design layer to a 4 levels process to create a 5 levels process allows consideration of fundamentally new architecture in designs for weapon advanced surety components.

Sniegowski, J.J.; Rodgers, M.S.

1998-01-01