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1

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

PubMed Central

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

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

1999-01-01

2

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

3

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

E-print Network

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

Chan, Derek Y C

4

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

5

Antifouling surface layers for improved signal-to-noise of particle-based immunoassays.  

PubMed

A 10-fold improvement in the signal-to-noise (S/N) ratio of an optically encoded silica particle-based immunoassay was achieved through incorporating a protein resistant poly(ethylene glycol) (PEG) surface layer and optimizing antibody immobilization conditions. PEG was activated using 2,2,2-trifluoroethanesulfonyl chloride (tresyl) and required a minimum reaction time of 1.5 h. The activated PEG had a reactive half-life of approximately 5 h when stored in acidified dimethyl sulfoxide (DMSO). By increasing the protein incubation time and concentration, a maximum antibody loading on the particle surface of 1.6 x 10(-2) molecules per nm(2) was achieved. The assay S/N ratio was assessed using a multiplexed multicomponent optically encoded species-specific immunoassay. Encoded particles were covalently grafted or nonspecifically coated with either bovine or mouse IgG for the simultaneous detection of complementary anti-IgG "target" or uncomplementary anti-IgG "noise". The versatility and potential as a serum-based assay platform was demonstrated by immobilizing either a polyclonal antibody or an engineered single-chain variable fragment (scFv) capture probe on particles for the detection of the ovarian cancer biomarker, mesothelin (MSLN). The MLSN antigen was spiked into PBS buffer or 50% human serum. Both capture probe orientations, and media conditions showed similar low level detection limits of 5 ng/mL; however, a 40% decrease in maximum signal intensity was observed for assays run in 50% serum. PMID:19928944

Chen, Annie; Kozak, Darby; Battersby, Bronwyn J; Forrest, Robin M; Scholler, Nathalie; Urban, Nicole; Trau, Matt

2009-12-01

6

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

7

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

NASA Technical Reports Server (NTRS)

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

Gokoglu, Suleyman A.; Rosner, Daniel E.

1986-01-01

8

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

9

Smart surface for elution of protein-protein bound particles: nanonewton dielectrophoretic forces using atomic layer deposited oxides.  

PubMed

By increasing the strength of the negative dielectrophoresis force, we demonstrated a significantly improved electrokinetic actuation and switching microsystem that can be used to elute specifically bound beads from the surface. In this work using atomic layer deposition we deposited a pinhole free nanometer-scale thin film oxide as a protective layer to prevent electrodes from corrosion, when applying high voltages (>20 V(pp)) at the electrodes. Then, by exciting the electrodes at high frequency, we capacitively coupled the electrodes to the buffer in order to avoid electric field degradation and, hence, reduction in dielectrophoresis force due to the presence of the insulating oxide layer. To illustrate the functionality of our system, we demonstrated 100% detachment of anti-IgG and IgG bound beads (which is on the same order of magnitude in strength as typical antibody-antigen interactions) from the surface, upon applying the improved negative dielectrophoresis force. The significantly enhanced switching performance presented in this work shows orders of magnitude of improvement in on-to-off ratio and switching response time, without any need for chemical eluting agents, as compared to the previous work. The promising results from this work vindicates that the functionality of this singleplexed platform can be extended to perform a multiplexed bead-based assay where in a single channel an array of proteins are patterned each targeting a different antigen or protein. PMID:23176521

Emaminejad, Sam; Javanmard, Mehdi; Dutton, Robert W; Davis, Ronald W

2012-12-18

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

[Surface layers of methanotrophic bacteria].  

PubMed

Structural and functional characteristics of the regular glycoprotein layers in prokaryotes are analyzed with a special emphasis on aerobic methanotrophic bacteria. S-layers are present at the surfaces of Methylococcus, Methylothermus, and Methylomicrobium cells. Different Methylomicrobium species either synthesize S-layers with planar (p2, p4) symmetry or form cup-shaped or conicalstructures with hexagonal (p6) symmetry. A unique, copper-binding polypeptide 'CorA'/MopE (27/45 kDa), which is coexpressed with the diheme periplasmic cytochrome c peroxidase 'CorB'/Mca (80 kDa) was found in Methylomicrobium album BG8, Methylomicrobium alcaliphilum 20Z, and Methylococcus capsulatus Bath. This tandem of the surface proteins is functionally analogous to a new siderophore, methanobactin. Importantly, no 'CorA'/MopE homologue was found in methanotrophs not forming S-layers. The role of surface proteins in copper metabolism and initial methane oxidation is discussed. PMID:25509389

Khmelenina, V N; Suzina, N E; Trotsenko, Iu A

2013-01-01

12

Materials for surface layer treatments  

Microsoft Academic Search

Surface engineering employs a number of processes to coat or treat the surface (Chapt. A.3, p. 71), and optimised materials\\u000a are available for some of them. We will now discuss one thermal and two thermochemical heat treatments that affect the surface\\u000a layer and also present the appropriate materials. All three processes have a common objective: above a ductile core, the

Hans Berns

13

The Martian Surface Boundary Layer  

NASA Technical Reports Server (NTRS)

The acquisition of meteorological data from the surface of Mars by the two Viking Landers and Mars Pathfinder make it possible to estimate atmospheric boundary layer parameters and surface properties at three different locations on the planet. Because the Martian atmosphere is so thin the majority of the solar radiance is converted to heat at the surface. The difference between surface and atmospheric temperature can also constraint surface albedo, thermal inertia, and infrared emissivity. The Mars Pathfinder Atmospheric Structure Instrument/Meteorological package (ASI/MET) was the most capable weather monitoring system ever sent to the surface of another planet to date. One of the prime objectives of the ASI/MET package is to characterize the surface boundary layer parameters, particularly the heat and momentum fluxes, scaling temperature and friction velocity, and estimate surface roughness. Other important boundary layer parameters, such as Richardson Number, Monin-Obukhov length, analysis of turbulence characteristics of wind and temperature, and atmospheric stability class can also be determined from these measurements.

Wilson, G. R.; Joshi, M.

1999-01-01

14

Boundary layer effects on particle impaction and capture  

NASA Technical Reports Server (NTRS)

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

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

1984-01-01

15

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

16

Polyelectrolyte adsorption layers studied by streaming potential and particle deposition  

Microsoft Academic Search

Adsorption of a cationic polyelectrolyte, polyallylamine hydrochloride (PAH), having a molecular weight of 70,000 on mica was characterized by the streaming potential method and by deposition of negative polystyrene latex particles. Formation of PAH layers was followed by determining the apparent zeta potential of surface ? as function of bulk PAH concentration. The zeta potential was calculated from the streaming

Z. Adamczyk; M. Zembala; A. Michna

2006-01-01

17

How coatings with hydrophobic particles may change the drying of water droplets: incompressible surface  

E-print Network

configurations. We first focus on the drying of flat water surfaces coated with a single or several layers of hydrophobic micronic particles. Quite surprisingly, surfaces coated with a single layer of densely packed particles dry at the same speed as the bare surfaces. However, when coated with several layers of particles

Paris-Sud XI, Université de

18

Energetic particle acceleration in shear layers  

E-print Network

A plasma velocity shear layer and/or a tangential flow discontinuity provide conditions allowing for energetic particle acceleration. We review such acceleration processes acting both in non-relativistic and in relativistic flows. In heliospheric conditions shear layers can provide particles with energies compatible with the observed values (from several keV up to MeV), while in relativistic extragalactic jets proton energies even in excess of 10^{19} eV can be obtained. Application of the discussed theory to particular astrophysical objects is severely limited by inadequate knowledge of local physical conditions.

M. Ostrowski

1999-11-05

19

Particle simulation of auroral double layers  

NASA Technical Reports Server (NTRS)

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

Smith, Bruce L.; Okuda, Hideo

1987-01-01

20

Atmospheric boundary layer over steep surface waves  

NASA Astrophysics Data System (ADS)

Turbulent air-sea interactions coupled with the surface wave dynamics remain a challenging problem. The needs to include this kind of interaction into the coupled environmental, weather and climate models motivate the development of a simplified approximation of the complex and strongly nonlinear interaction processes. This study proposes a quasi-linear model of wind-wave coupling. It formulates the approach and derives the model equations. The model is verified through a set of laboratory (direct measurements of an airflow by the particle image velocimetry (PIV) technique) and numerical (a direct numerical simulation (DNS) technique) experiments. The experiments support the central model assumption that the flow velocity field averaged over an ensemble of turbulent fluctuations is smooth and does not demonstrate flow separation from the crests of the waves. The proposed quasi-linear model correctly recovers the measured characteristics of the turbulent boundary layer over the waved water surface.

Troitskaya, Yuliya; Sergeev, Daniil A.; Druzhinin, Oleg; Kandaurov, Alexander A.; Ermakova, Olga S.; Ezhova, Ekaterina V.; Esau, Igor; Zilitinkevich, Sergej

2014-08-01

21

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

22

Surface rheology of saponin adsorption layers.  

PubMed

Extracts of the Quillaja saponaria tree contain natural surfactant molecules called saponins that very efficiently stabilize foams and emulsions. Therefore, such extracts are widely used in several technologies. In addition, saponins have demonstrated nontrivial bioactivity and are currently used as essential ingredients in vaccines, food supplements, and other health products. Previous preliminary studies showed that saponins have some peculiar surface properties, such as a very high surface modulus, that may have an important impact on the mechanisms of foam and emulsion stabilization. Here we present a detailed characterization of the main surface properties of highly purified aqueous extracts of Quillaja saponins. Surface tension isotherms showed that the purified Quillaja saponins behave as nonionic surfactants with a relatively high cmc (0.025 wt %). The saponin adsorption isotherm is described well by the Volmer equation, with an area per molecule of close to 1 nm(2). By comparing this area to the molecular dimensions, we deduce that the hydrophobic triterpenoid rings of the saponin molecules lie parallel to the air-water interface, with the hydrophilic glucoside tails protruding into the aqueous phase. Upon small deformation, the saponin adsorption layers exhibit a very high surface dilatational elasticity (280 ± 30 mN/m), a much lower shear elasticity (26 ± 15 mN/m), and a negligible true dilatational surface viscosity. The measured dilatational elasticity is in very good agreement with the theoretical predictions of the Volmer adsorption model (260 mN/m). The measured characteristic adsorption time of the saponin molecules is 4 to 5 orders of magnitude longer than that predicted theoretically for diffusion-controlled adsorption, which means that the saponin adsorption is barrier-controlled around and above the cmc. The perturbed saponin layers relax toward equilibrium in a complex manner, with several relaxation times, the longest of them being around 3 min. Molecular interpretations of the observed trends are proposed when possible. Surprisingly, in the course of our study we found experimentally that the drop shape analysis method (DSA method) shows a systematically lower surface elasticity, in comparison with the other two methods used: Langmuir trough and capillary pressure tensiometry with spherical drops. The possible reasons for the observed discrepancy are discussed, and the final conclusion is that the DSA method has specific problems and may give incorrect results when applied to study the dynamic properties of systems with high surface elasticity, such as adsorption layers of saponins, lipids, fatty acids, solid particles, and some proteins. The last conclusion is particularly important because the DSA method recently became the preferred method for the characterization of fluid interfaces because of its convenience. PMID:21894983

Stanimirova, R; Marinova, K; Tcholakova, S; Denkov, N D; Stoyanov, S; Pelan, E

2011-10-18

23

Carbides composite surface layers produced by (PTA)  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

24

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

25

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

PubMed

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

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

2008-12-16

26

Onset of new particle formation in boundary layer  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

27

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

28

Laser-Based Transient Surface Acceleration of Thermoelastic Layers  

NASA Astrophysics Data System (ADS)

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

CETINKAYA, CETIN; WU, CUNLI; LI, CHEN

2000-03-01

29

Optimization of Single and Layered Surface Texturing  

E-print Network

investigated specific texture parameters for optimal textures. Textures with significant directionality and structure were found to be useful on both surface layers. A range of viable top surface opacities was found, and relationships between texture sizes... ............................................................................... 29 23 Exploded View Example ............................................................................ 30 24 Human in the Loop Diagram ...................................................................... 33 25 Bottom and Top Surfaces...

Bair, Alethea S.

2010-07-14

30

New particle formation in the marine boundary layer  

SciTech Connect

Aerosol measurements were made in the marine boundary layer along the coast of Washington State during the Pacific Stratus Sulfur Investigation. On April 22 the particle concentration increased to levels much higher than usual for the clean marine boundary layer. The total particulate number concentration greater than 3 nm diameter increased rapidly from about 250 cm[sup [minus]3] to 3,200 cm[sup [minus]3], remained near that level for 7 hours, and then decreased over the next 2 hours to less than 400 cm[sup [minus]3]. The change could not be attributed to either local or distant contamination. Immediately before the increase particulate surface area concentration dropped from 25 [mu]m[sup 2] cm[sup [minus]3] to less than 5 [mu]m[sup 2] cm[sup [minus]3]. The SO[sub 2] concentration increased from about 20 pptv to 40-60 pptv just before the increase in particle concentration. While these measurements cannot distinguish between changes in number concentration caused by particle nucleation versus advection or vertical mixing, clearly there was recent or continuing particle production on a mesoscale in the air mass. Related aircraft measurements and model results support the hypothesis of new particle formation. These data provide evidence that at times high concentrations of new, ultrafine particles are formed at low SO[sub 2] concentrations under mareine conditions. This homogeneous nucleation, as opposed to heterogeneous condensation on existing particles, is strongly and inversely dependent on the concentration of existing particles. 19 refs., 4 figs.

Covert, D.S. (Univ. of Washington, Seattle (United States)); Kapustin, V.N. (Inst. of Atmospheric Physics, Moscow (Russian Federation)); Quinn, P.K.; Bates, T.S. (NOAA Pacific Marine Environmental Lab., Seattle, WA (United States))

1992-12-20

31

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

32

Layer-by-Layer Rose Petal Mimic Surface with Oleophilicity and Underwater Oleophobicity.  

PubMed

Surfaces designed with specific wetting properties are still a key challenge in materials science. We present here a facile preparation of a surface assembled by the layer-by-layer technique, using a colloidal dispersion of ionomer particles and linear polyethylene imine. The colloidal ethylene-co-methacrylic acid (EMAA) particles are on the order of half a micron in size with surface features from 40 to 100 nm in width. The resultant surface has roughness on two length scales, one on the micron scale due to the packing of particles and one on the nanoscale due to these surface features on the EMAA particles. This hierarchical structure results in a hydrophobic surface with good water pinning properties (?550 ?N). We show that there is a balance between maximizing contact angle and water pinning force. Furthermore, this surface is oleophilic with regard to many organic solvents, also demonstrating underwater oleophobicity, and given the difference in wetting between aqueous and organic phases, this material may be a candidate material for oil/water separations. PMID:25517482

Huang, Hsiu-Chin; Zacharia, Nicole S

2015-01-20

33

Surface layering properties of Intralipid phantoms.  

PubMed

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. PMID:25590919

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

2015-02-01

34

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

35

Modeling impact cratering in layered surfaces  

Microsoft Academic Search

Impact 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 remain poorly understood. Here, we present a study of cratering in layered surfaces using numerical simulations. We implement the rheologic model for geologic materials described by Collins et al. (2004) into

Laurel E. Senft; Sarah T. Stewart

2007-01-01

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

The Role of Surface Layer Processes in Solid Propellant Combustion.  

NASA Astrophysics Data System (ADS)

The qualitative multidimensional theory of composite solid propellant combustion based on the sandwich burning methodology was applied to certain specific problems: (a) burning rate enhancement by ferric oxide, (b) plateau burning behavior caused by binder melt flow effects, and (c) characterization of the combustion of new energetic oxidizers--ADN and HNIW. Exothermic reactions at the interfacial contact lines between AP particles and the binder in the surface layer of the burning propellant assume significance in the presence of ferric oxide, and control the burning rate. Binder melt flow covers adjacent AP particle surfaces increasingly at higher pressures, and disperses the O/F leading edge flames attached to coarse particles. It also causes fine AP/binder matrix areas on the surface not to support a steady premixed flame at intermediate pressures, resulting in an overall decrease in the burning rate with increasing pressure, which implies plateau or mesa effects. ADN self -deflagration rate is significantly higher than that of AP, and controls the sandwich burning rate to a great extent. The O/F flame of ADN and binder still behaves as rate limiting, although strongly supported by ADN self-deflagration. ADN melts and vaporizes substantially before the binder, allowing for the possibility of complex physical processes in the surface layer. The strong exothermic decomposition of HNIW at moderate temperatures causes the oxidizer particles in the surface layer to be the sites of burning rate control. The problems addressed in this study combinedly point to the significance of crucial surface layer processes under the situations of interest, and signal a need to characterize such processes directly and in greater detail.

Chakravarthy, Satyanarayanan R.

38

DNS of Rough Surface Turbulent Boundary Layer  

NASA Astrophysics Data System (ADS)

A dynamic method for prescribing realistic inflow boundary conditions is presented for simulations of spatially developing turbulent boundary layers subject to surface roughness. Direct Numerical Simulation (DNS) of a moderate Reynolds number, zero pressure gradient (ZPG) turbulent boundary layer was performed. The boundary layer was subjected to transitional, 24-grit sand grain surface roughness, modeled with a roughness parameter of k^+ ˜12 and a Reynolds number of R?= 2400. The computational method involves a synergy of the multi-scale dynamic approach and a new methodology for mapping high-resolution topographical surface data into a computational fluid dynamics environment. It is shown here that the multi-scale dynamic approach can be successfully extended to simulations, which incorporate surface roughness. In terms of the mean velocity and Reynolds stresses, the DNS results are encouraging as they demonstrate good agreement with the LDA measurements performed under similar conditions.

Cardillo, James; Araya, Guillermo; Chen, Yi; Jansen, Kenneth; Sahni, Onkar; Castillo, Luciano

2011-11-01

39

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

40

Characterization of the Martian Surface Layer  

Microsoft Academic Search

The authors have estimated the diurnal evolution of Monin-Obukhov length, friction velocity, tempera- ture scale, surface heat flux, eddy-transfer coefficients for momentum and heat, and turbulent viscous dissipation rate on the Martian surface layer for a complete sol belonging to the Pathfinder mission. All these magnitudes have been derived from in situ wind and temperature measurements at around 1.3-m height

F RANCISCOVALERO GERMÁNMARTÍNEZ

41

Oscillatory forces of nanoparticle suspensions confined between rough surfaces modified with polyelectrolytes via the layer-by-layer technique.  

PubMed

This paper addresses the systematic study of surface roughness effects on the internal structuring of silica nanoparticle suspensions under confinement. The confining surfaces are modified by physisorption of layers of oppositely charged polyelectrolytes with the so-called layer-by-layer technique. The layer-by-layer technique modifies the surface roughness without changing the surface potential of a multilayer with the same outermost layer, by increasing the number of constituent layers and ionic strength of the polyelectrolyte solutions and by selecting an appropriate pair of polyelectrolytes. The oscillatory forces of nanoparticle suspensions with a particle diameter of 26 nm are measured by a colloidal-probe atomic force microscope (CP-AFM). The characteristic lengths of the oscillatory force, i.e., wavelength, which indicates interparticle distance, and decay length, or particle correlation length, are not affected by the surface roughness. The corresponding reduction in the oscillatory amplitude and the shift in the phase correlate with an increase in surface roughness. Increasing surface roughness further induces a disappearance of the oscillations, and both confining surfaces contribute to the effect of surface roughness on the force reduction. In order to show an oscillatory force, the particles have to show positional correlation over a reasonably long range perpendicular to the surface, and the correlation function should be the same over a larger lateral area. This requires that both the particles and the surfaces have a high degree of order or symmetry; otherwise, the oscillation does not occur. A roughness of a few nanometers on a single surface, which corresponds to about 10% of the nanoparticle diameter, is sufficient to eliminate the oscillatory force. PMID:22420681

Zeng, Yan; von Klitzing, Regine

2012-04-17

42

Particle Deposition onto a Permeable Surface in Laminar Flow  

Microsoft Academic Search

A theoretical investigation of particle deposition onto a permeable surface in a parallel-plate channel is presented in this paper. The convective diffusion equation is rigorously formulated with the inclusion of lateral transport due to permeation drag and inertial lift, and transport due to gravitational, double layer, and van der Waals forces. A numerical procedure for solving the governing equation is

Lianfa Song; Menachem Elimelech

1995-01-01

43

Water vapor interactions with FeOOH particle surfaces  

NASA Astrophysics Data System (ADS)

Interactions between iron (oxyhydr)oxide particle surfaces and water are of fundamental importance to natural and technological processes. In this Letter, we probe the interactions between submicron-sized lepidocrocite (?-FeOOH) surfaces and gaseous water using Fourier transform infrared spectroscopy. Formation of hydrogen bonds between different lepidocrocite surface OH functional groups and water was specifically monitored in the O-H stretching region. Molecular dynamics simulations of the dominant crystallographic terminations of these particles provided insights into interfacial water structures and hydrogen bonding networks. Theoretical power spectra were moreover used to validate interpretations of experimental spectra. This Letter constrains our understanding of incipient water adsorption reactions leading to thermodynamically stable and reversible thin water films at FeOOH particle surfaces. It also suggests that these water layers are structurally analogous precursors to those occurring at a FeOOH surfaces contacted with liquid water.

Song, Xiaowei; Boily, Jean-François

2013-02-01

44

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

45

Does Surface Disorder Influence Light Scattering by Small Particles?  

NASA Astrophysics Data System (ADS)

Crystalline particles have a surface layer roughly 3 atoms/molecules thick whose structure is not periodic. This is due to the asymmetric distribution of ionic and covalent bonds that occur at any free surface. The effect is called surface reconstruction (Somorjai, G.A "Surface Reconstruction and Catalysis", Annual Review of Physical Chemistry , 45, 721-751, 1994). and is analogous to surface tension in liquids. In amorphous material like glass the it is called the gel layer. As the particle size decreases, the volume fraction of the outer layers increases. The optical properties of this layer are slightly different than those of the interior. Thus the particle acts like a coated sphere and can be treated using Mie theory (Johnson, B.R. "Light scattering from a multilayered sphere," Applied Optics, 35, 3286-3296, 1996). To study the effect we have computed the extinction cross sections, differential scattering cross sections and single scattering albedos for both highly absorbing (m = 1.6 + i 0.5) and purely scattering (m=1.6) particles in the 0.01 - 1 micron radius range. Optical constants of the outer layers were derived using the continuous distribution of oscillators approximation (Lynch, D.K. ``A New Model for the Infrared Dielectric Function of Amorphous Materials'', Astrophys. J., 467, 894-898, 1996). We found that changes in the single scattering albedoes can be as large as 40% for 0.01 micron particles with a 0.001 micron coating compared to uncoated sphere. More complete results and their significance to astrophysical situations will be presented at the meeting.

Lynch, D. K.; Mazuk, S.

1997-12-01

46

Regular surface layer of Azotobacter vinelandii.  

PubMed Central

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

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

1984-01-01

47

Subwavelength particle layers for improved light outcoupling of OLEDs  

NASA Astrophysics Data System (ADS)

Subwavelength silica particle layers have been applied between glass and thin film luminescent layers of Alq3 and a polymer MEH-PPV layer, respectively. The layers acted as a randomised two-dimensional diffraction lattice, which increased the fraction of emitted power from thin film organic layers into air. In contrast to perfectly ordered structures strong interference emission patterns did not occur. Still, an optical feedback of the particle layer on the emission spectrum could be observed, which can be used to improve colour saturation for blue and green emission and to increase the lumen efficiency for red emission, without changing the colour point of the red emitter. In photoluminescence experiments a gain factor of 3 and 2.5 in light outcoupling was realized for Alq3 and MEH-PPV layers, respectively. With a MEH-PPV polymer OLED device an efficiency gain of 30 to 40 % has been realized in electroluminescence.

Bechtel, Helmut; Busselt, Wolfgang; Opitz, Joachim

2004-11-01

48

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

49

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

50

Hygroscopic behavior and liquid-layer composition of aerosol particles generated from natural and artificial seawater  

NASA Astrophysics Data System (ADS)

Sea-salt aerosol (SSA) particles affect the Earth's radiative balance and moderate heterogeneous chemistry in the marine boundary layer. Using conventional and environmental transmission electron microscopes (ETEM), we investigated the hygroscopic growth and liquid-layer compositions of particles generated from three types of aqueous salt solutions: sodium chloride, laboratory-synthesized seawater (S-SSA particles), and natural seawater (N-SSA particles). Three levels of morphological change were observed with the ETEM as the laboratory-generated particles were exposed to increasing relative humidity (RH). The first level, onset of observable morphological changes, occurred on average at 70, 48, and 35% RH for the NaCl, S-SSA, and N-SSA particles, respectively. The second level, rounding, occurred at 74, 66, and 57% RH for NaCl, S-SSA, and N-SSA particles, respectively. The third level, complete deliquescence, occurred at 75% RH for all particles. Collected ambient SSA particles were also examined. With the exception of deliquescence, they did not exhibit the same hygroscopic characteristics as the NaCl particles. The ambient particles, however, behaved most similarly to the synthesized and natural SSA particles, although the onset of morphological change was slightly higher for the S-SSA particles. We used energy-dispersive X-ray spectrometry to study the composition of the liquid layer formed on the S-SSA and N-SSA particles. The layer was enriched in Mg, S, and O relative to the solid particle core. An important implication of these results is that MgSO4-enriched solutions on the surface of SSA particles may be the solvents of many heterogeneous reactions.

Wise, Matthew E.; Freney, Evelyn J.; Tyree, Corey A.; Allen, Jonathan O.; Martin, Scot T.; Russell, Lynn M.; Buseck, Peter R.

2009-02-01

51

Structure of the Azotobacter vinelandii surface layer.  

PubMed Central

Electron microscopy of the Azotobacter vinelandii tetragonal surface array, negatively stained with ammonium molybdate in the presence of 1 mM calcium chloride, showed an apparent repeat frequency of 12 to 13 nm. Image processing showed dominant tetrad units alternating with low-contrast cruciform structures formed at the junction of slender linkers extending from corner macromolecules of four adjoining dominant units. The actual unit cell showed p4 symmetry, and a = b = 18.4 nm. Distilled water extraction of the surface array released a multimeric form of the single 60,000 molecular-weight protein (S protein) which constitutes the surface layer. The molecular weight of the multimer was estimated at 255,000 by gel filtration, indicating a tetrameric structure of four identical subunits and suggesting that this multimer was the morphological subunit of the S layer. Tetrameric S protein exhibited low intrinsic stability once released from the outer membrane, dissociating into monomers when incubated in a variety of buffers including those which served as the base for defined media used to cultivate A. vinelandii. The tetramer could not be stabilized in these buffers at any temperature between 4 and 30 degrees C, but the addition of 2 to 5 mM Ca2+ or Mg2+ completely prevented its dissociation into monomers. Circular dichroism measurements indicated that the secondary structure of the tetramer was dominated by aperiodic and beta-sheet conformations, and the addition of Ca2+ did not produce any gross changes in this structure. Only the tetrameric form of S protein was able to reassemble in vitro in the presence of divalent cations onto the surface of cells stripped of their native S layer. Images PMID:3804978

Bingle, W H; Whippey, P W; Doran, J L; Murray, R G; Page, W J

1987-01-01

52

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

53

Transonic laminar boundary layers with surface curvature.  

NASA Technical Reports Server (NTRS)

The effect of surface curvature (both longitudinal and transverse) and the associated pressure gradient across the flow is investigated analytically for a laminar boundary layer subjected to pressure gradients along the flow. Property variation which results from heat transfer and compressibility is taken into account. Numerical solutions of the boundary layer equations are obtained for locally similar sonic flow through the throat of a nozzle for a range of flow conditions and for various shaped nozzle surfaces with different amounts of wall cooling. A few solutions were also obtained for the analogous flow around the shoulder of a flat-faced body in a supersonic flow. The effect of various parameters that arise in the equations upon application of the Levy-Mangler transformation are investigated and discussed with respect to their influence on the velocity and total enthalpy profiles and the corresponding profile slopes at the surface to which the shear stress and heat transfer are related. An important finding is that at throat Reynolds numbers less than 100,000 the heat transfer parameter at a nozzle throat decreases as the throat radius of curvature decreases.

Back, L. H.

1973-01-01

54

Humidity variations in the atmospheric surface layer  

E-print Network

Subject: Meteorology HUMIDITY VARIATIONS IN THE ATMOSPHERIC SURFACE LAYER A Thesis by SCOTT RICHARD HUMPHREY Approved as to style and content by: Dr. James R. Sc 'ns (Chairman of Committee) Dr. T. Stev Yuen (Member r. J. M. Macha (Member) Dr..., and for making readily available to me all of the resources of the Department of Meteorology. In addi- tion I would like to thank Dr. T. S. Yuen and Dr. J. M. Macha who also served on my graduate committee, the Aerospace Engineering Department for the use...

Humphrey, Scott Richard

2012-06-07

55

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

Microsoft Academic Search

Particle deposition plays an important role in such diverse phenomena as granular filtration, chromatographic separation, colloidal contamination of semiconductor wafers, colloidal fouling of pressure driven membranes, and colloid-facilitated transport of pollutants in soils and groundwater aquifers. The effect of particle size on the kinetics of particle deposition in the presence of attractive double layer interactions has been studied theoretically and

M Elimelech

1994-01-01

56

Nano boundary layers over stretching surfaces  

NASA Astrophysics Data System (ADS)

In this paper, we present similarity solutions for the nano boundary layer flows with Navier boundary condition. We consider viscous flows over a two-dimensional stretching surface and an axisymmetric stretching surface. The resulting nonlinear ordinary differential equations are solved analytically by the Homotopy Analysis Method. Numerical solutions are obtained by using a boundary value problem solver, and are shown to agree well with the analytical solutions. The effects of the slip parameter K and the suction parameter s on the fluid velocity and on the tangential stress are investigated and discussed. As expected, we find that for such fluid flows at nano scales, the shear stress at the wall decreases (in an absolute sense) with an increase in the slip parameter K.

Van Gorder, Robert A.; Sweet, Erik; Vajravelu, K.

2010-06-01

57

Surface layer modification of ion bombarded HDPE  

NASA Astrophysics Data System (ADS)

Press-moulded, high density polyethylene (HDPE) samples were subjected to ion bombardment and effects of the modification studied. He + ions of energy 100 keV or Ar + ions of energy 130 keV were applied in the range of dose 1-30 × 10 15/cm 2 or 1-100 × 10 14/cm 2, respectively. This paper has been focused on structural changes of the surface layer. The consequences of the modification were studied with TOF-SIMS and FTIR-IRS techniques. The results point on two mechanisms taking place simultaneously: ionization of polymer macromolecules and chain scission--resulting in creation of macroradicals. Both of them produce oxidation and lead to significant release of hydrogen. The former diminishes for the highest ion doses, however, creation of molecular oxygen cannot be excluded. The latter in the case of Ar + ion bombardment is reflected by prevailing degradation of the surface layer of HDPE. Contrary to the effect of heavy ions, He + ion bombardment was found to produce significant increase of the material hardness, which was explained by crosslinking of polyethylene. A mechanism of polyacetylene formation, proceeding finally to cross-polymerization of the polymer was proposed. Apart from structural changes, the modification revealed additionally a possibility to improve the wettability of the polymer.

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

2004-08-01

58

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

59

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

60

Scaling laws of passive tracer dispersion in the turbulent surface layer  

E-print Network

Experimental results for passive tracer dispersion in the turbulent surface layer under stable conditions are presented. In this case, the dispersion of tracer particles is determined by the interplay of three mechanisms: relative dispersion (celebrated Richardson's mechanism), shear dispersion (particle separation due to variation of the mean velocity field) and specific surface-layer dispersion (induced by the gradient of the energy dissipation rate in the turbulent surface layer). The latter mechanism results in the rather slow (ballistic) law for the mean squared particle separation. Based on a simplified Langevin equation for particle separation we found that the ballistic regime always dominates at large times. This conclusion is supported by our extensive atmospheric observations. Exit-time statistics are derived from the experimental dataset and show a reasonable match with the simple dimensional asymptotes for different mechanisms of tracer dispersion, as well as predictions of the multifractal model and experimental data from other sources.

Alex Skvortsov; Milan Jamriska; Timothy C. DuBois

2011-07-28

61

Surface preparation of substances for continuous convective assembly of fine particles  

DOEpatents

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

Rossi, Robert (Rochester, MN)

2003-01-01

62

Turbulent boundary layer over porous surfaces with different surface geometries  

NASA Technical Reports Server (NTRS)

The turbulent boundary layer over three porous walls with different surface geometries was studied in order to investigate the individual influences of porosity and small roughness, as well as their combined effects, on turbulent boundary layer behavior. The tests were conducted in a 2 m x 2 m tunnel on a large axisymmetric model at speeds corresponding to Re(L) = 5,000,000-6,000,000. The development of the turbulent boundary layer was compared for that of sintered metal, bonded screening, and perforated sheet and then to that for the flow over a solid smooth wall and a solid, sand-roughened wall. The comparisons reveal that the effect of porosity is to shift the logarithmic region of the wall law down by a certain amount from the solid wall results and to increase the skin friction values by about 30-40%. The downward shift of the logarithmic region of the wall law and the increase of the skin friction value by the combined effects of small roughness and porosity are found to be roughly the sum of their individual effects.

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

1982-01-01

63

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

64

Turbulence Modulation by MicroParticles in Boundary Layers  

Microsoft Academic Search

Turbulent dispersed flows over boundary layers are crucial in a number of industrial and environmental applications. In most applications, the key information is the spatial distribution of inertial particles, which is known to be highly non-homogeneous and may exhibit a complex pattern driven by the structures of the turbulent flow field. Theoretical and experimental evidence shows that fluid motions in

Maurizio Picciotto; Andrea Giusti; Cristian Marchioli; Alfredo Soldati

65

Actuated cilial layers regulate deposition of microscopic solid particles  

NASA Astrophysics Data System (ADS)

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

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

2009-11-01

66

Electrical properties of polyelectrolyte layers adsorbed on colloidal particles at different ionic strength.  

PubMed

The investigation presents results on the low-frequency electrical polarization of ?-FeOOH particles with adsorbed layers from sodium salts of poly(4-styrene sulfonate), poly(acrylic acid), and carboxymethyl cellulose, obtained by electric light scattering. The adsorption is realized in aqueous NaCl solutions of different concentration, and the suspensions of the coated particles are then rinsed to low conductivity. Several electro-optical parameters are sensitive to the conformation of the adsorbed polyelectrolyte layer. The particle electrical polarizability increases drastically with the concentration of NaCl (correlating with significant increase of the adsorbed amount of polyelectrolyte), while their electrophoretic mobility remains practically unchanged. Two time scales are involved in the stepwise relaxation of the electrical polarizability. The faster process is attributed to movement of ions in the polymer layer, restricted by the coiled conformation to smaller distances. The contribution of the Debye atmosphere outside the polymer layer remains almost unchanged, which correlates with the low sensitivity of the electrophoretic mobility to the increasing amount of adsorbed polyelectrolyte. Abrupt increase in a narrow interval of salt concentrations is observed both for the low-frequency component of the particle polarization and for the hydrodynamic layer thickness, indicating changes in the surface electric state, most probably due to swelling of the adsorbed polymer layer. PMID:20735019

Milkova, Viktoria; Kamburova, Kamelia; Radeva, Tsetska; Stoimenova, Maria

2010-09-21

67

Compact Layer of Alkali Ions at the Surface of Colloidal Silica  

E-print Network

The forces of electrical imaging strongly polarize the surface of colloidal silica. I used X-ray scattering to study the adsorbed 2-nm-thick compact layer of alkali ions at the surface of concentrated solutions of 5-nm, 7-nm, and 22-nm particles, stabilized either by NaOH or a mixture of NaOH and CsOH, with the total bulk concentration of alkali ions ranging from 0.1- to 0.7-mol/L. The observed structure of the compact layer is almost independent of the size of the particles and concentration of alkali base in the sol; it can be described by a two-layer model, i.e., an ~ 8 Angstrom thick layer of directly adsorbed hydrated alkali ions with a surface concentration 3x10(18) m(-2), and a ~ 13 Angstrom thick layer with a surface concentration of sodium ions 8x10(18) m(-2). In cesium-enriched sols, Cs+ ions preferentially adsorb in the first layer replacing Na+; their density in the second layer does not depend on the presence of cesium in the sol. The difference in the adsorption of Cs+ and Na+ ions can be explained by the ion-size-dependent term in the electrostatic Gibbs energy equation derived earlier by others. I also discuss the surface charge density and the value of surface tension at the sol's surface.

Aleksey M. Tikhonov

2006-09-18

68

Small particle transport across turbulent nonisothermal boundary layers  

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

69

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

NASA Astrophysics Data System (ADS)

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.

Sen, Tapas; Bruce, Ian J.

2012-08-01

70

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

PubMed

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

71

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

72

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

73

Effects of Surface Oxide on the Nitridation Behavior of Aluminum Particles  

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

74

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

75

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.

76

Buffer Layer Assisted Laser Patterning of Metals on Surfaces  

E-print Network

Buffer Layer Assisted Laser Patterning of Metals on Surfaces Gabriel Kerner and Micha Asscher has been patterned on a Ru(100) substrate under UHV conditions. Upon annealing, the physisorbed layer controlled metallic clusters via buffer layer assisted growth (BLAG).9-11 To create clusters, the metal

Asscher, Micha

77

Aspects Of The Atmospheric Surface Layers On Mars And Earth  

Microsoft Academic Search

The structures of mean flow and turbulence in the atmospheric surface boundary layer have been extensively studied on Earth, and to a far less extent on Mars, where only the Viking missions and the Pathfinder mission have delivered in-situ data. Largely the behaviour of surface-layer turbulence and mean flow on Mars is found to obey the same scaling laws as

S. E. Larsen; H. E. Jørgensen; L. Landberg; J. E. Tillman

2002-01-01

78

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. However, the details of how target structure affects the impact cratering process and final crater forms (2007), Modeling impact cratering in layered surfaces, J. Geophys. Res., 112, E11002, doi:10.1029/2007JE

Stewart, Sarah T.

79

Surface modification of nanocolloidal silica for use as polishing abrasive particles  

Microsoft Academic Search

A new type of abrasive particle for polishing the dielectric layer on silicon wafers has been synthesized by modifying colloidal silica with cerium ions. Cerium ions in active silicic acid were titrated into a basic solution at 100°C to modify the surface of the colloidal silica. The new abrasive particles are easily suspended in an aqueous medium. The removal rate

Ming-Shyong Tsai

2003-01-01

80

Heating and ignition of combustible dust layers on a hot surface: Influence of layer shrinkage  

Microsoft Academic Search

A combustible dust layer on a hot surface may ignite if the temperature is sufficiently high. Based on experimental observations, a model is developed to include the layer shrinkage as the combustible material is consumed in the process of heating that may lead to ignition. During the pyrolysis, the packed dust layer shrinks as a result of a variation of

Hyung Min Kim; C. C. Hwang

1996-01-01

81

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

82

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

83

Particle Swarm Transport through Immiscible Fluid Layers in a Fracture  

NASA Astrophysics Data System (ADS)

Immiscible fluids occur either naturally (e.g. oil & water) or from anthropogenic processes (e.g. liquid CO2 & water) in the subsurface and complicate the transport of natural or engineered micro- or nano-scale particles. In this study, we examined the effect of immiscible fluids on the formation and evolution of particle swarms in a fracture. A particle swarm is a collection of colloidal-size particles in a dilute suspension that exhibits cohesive behavior. Swarms fall under gravity with a velocity that is greater than the settling velocity of a single particle. Thus a particle swarm of colloidal contaminants can potentially travel farther and faster in a fracture than expected for a dispersion or emulsion of colloidal particles. We investigated the formation, evolution, and break-up of colloidal swarms under gravity in a uniform aperture fracture as hydrophobic/hydrophyllic particle swarms move across an oil-water interface. A uniform aperture fracture was fabricated from two transparent acrylic rectangular prisms (100 mm x 50 mm x 100 mm) that are separated by 1, 2.5, 5, 10 or 50 mm. The fracture was placed, vertically, inside a glass tank containing a layer of pure silicone oil (polydimethylsiloxane) on distilled water. Along the length of the fracture, 30 mm was filled with oil and 70 mm with water. Experiments were conducted using silicone oils with viscosities of 5, 10, 100, or 1000 cSt. Particle swarms (5 ?l) were comprised of a 1% concentration (by mass) of 25 micron glass beads (hydrophilic) suspended in a water drop, or a 1% concentration (by mass) of 3 micron polystyrene fluorescent beads (hydrophobic) suspended in a water drop. The swarm behavior was imaged using an optical fluorescent imaging system composed of a CCD camera and by green (525 nm) LED arrays for illumination. Swarms were spherical and remained coherent as they fell through the oil because of the immiscibility of oil and water. However, as a swarm approached the oil-water interface, it decreased in speed and came to rest on the interface while maintaining its spherical shape. After the interface between a swarm and the oil thinned sufficiently, the swarm was rapidly released into the water layer. The time that this took depended on the viscosity of the oil layer, which determines the rate of thinning, and on the size and properties of the particles. The swarm geometry and velocity in the water layer depended on the aperture of the fracture, the viscosity of the oil and the hydrophobicity or hydrophyllicity of the particles in the swarm. Hydrophobic beads result in multiple mini swarms after breaking through the interface rather than a single large swarm like that observed for hydrophilic swarms. After many experiments a pile formed at the bottom of the tank near the center of the fracture, indicating that swarms can lead to locally high concentration of colloidal contaminants. Acknowledgment: The authors wish to acknowledge support of this work by the Geosciences Research Program, Office of Basic Energy Sciences US Department of Energy (DE-FG02-09ER16022) and the Summer Undergraduate Research Fellowship program at Purdue University.

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

2011-12-01

84

Layer silicates in a chondritic porous interplanetary dust particle  

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

85

Computation of Capillary Interactions among Many Particles at Free Surface  

NASA Astrophysics Data System (ADS)

We have developed a new computational method to efficiently estimate capillary interactions among many moving particles at a free surface. A novelty of the method is the immersed free surface (IFS) model that transforms the surface tension exerted on a three-phase contact line on a particle surface into the surface tension exerted on an artificially created virtual free surface in the particle. Using the IFS model along with a level set method and an immersed boundary method, we have reasonably simulated a capillary-force-induced self-assembly of particles that is common in coating-drying of particle suspension.

Fujita, Masahiro; Koike, Osamu; Yamaguchi, Yukio

2013-03-01

86

On the effect of induced electro-osmosis on a cylindrical particle next to a surface.  

PubMed

The effect of induced electro-osmosis on a cylindrical particle positioned next to a planar surface (wall) is studied theoretically both under the thin double layer approximation utilizing the Smoluchowski slip velocity approximation and under thick electric double layer conditions by solving the Poisson-Nernst-Planck (PNP) equations. The imposed, undisturbed electric field is parallel to the planar surface. The induced hydrodynamic and electrostatic forces are calculated as functions of the particle's and the medium's dielectric constants and the distance between the particle and the surface. The resultant force acting on the particle is directed normal to and away from the wall. The presence of such a repulsive force may adversely affect the interactions between macromolecules suspended in solution and wall-immobilized molecules and may be significant to near-wall particle imaging velocimetry (PIV) in electrokinetic flows. PMID:17311434

Zhao, Hui; Bau, Haim H

2007-03-27

87

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

E-print Network

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

Kang Chen; Yu-qiang Ma

2006-11-04

88

Tunable hybrid surface waves supported by a graphene layer  

E-print Network

We study surface waves localized near a surface of a semi-infinite dielectric medium covered by a layer of graphene in the presence of a strong external magnetic field. We demonstrate that both TE-TM hybrid surface plasmons can propagate along the graphene surface. We analyze the effect of the Hall conductivity on the disper- sion of hybrid surface waves and suggest a possibility to tune the plasmon dispersion by the magnetic field.

Iorsh, Ivan; Belov, Pavel; Kivshar, Yuri

2012-01-01

89

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

90

Passive hypervelocity boundary layer control using an ultrasonically absorptive surface  

Microsoft Academic Search

A series of exploratory boundary layer transition experiments was performed on a sharp 5.06 degree half-angle round cone at zero angle-of-attack in the T5 Hypervelocity Shock Tunnel in order to test a novel hypersonic boundary layer control scheme. Recently performed linear stability analyses suggested that transition could be delayed in hypersonic boundary layers by using an ultrasonically absorptive surface that

Adam Rasheed

2001-01-01

91

Capillary Interception of Floating Particles by Surface-Piercing Vegetation  

E-print Network

Surface-piercing vegetation often captures particles that flow on the water surface, where surface tension forces contribute to capture. Yet the physics of capillary capture in flow has not been addressed. Here we model ...

Peruzzo, Paolo

92

Turbulent boundary layer at moving surface of cylindrical body  

Microsoft Academic Search

An analysis is made of the two dimensional turbulent boundary on the moving surface of a cylindrical body (a Rankine oval with an aspect ratio of 4) moving at constant velocity in an incompressible fluid. A numerical simulation is used in which the boundary layer is divided in accordance with a two layer model into inner and outer regions, for

V. M. Zubarev

1986-01-01

93

Thin gold layer in Ni electroforming process: optical surface characterization  

NASA Astrophysics Data System (ADS)

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

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

2009-08-01

94

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

95

Turbulent boundary layer on a convex, curved surface  

NASA Technical Reports Server (NTRS)

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

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

1980-01-01

96

Many-body microhydrodynamics of colloidal particles with active boundary layers  

E-print Network

Colloidal particles with active boundary layers - regions surrounding the particles where non-equilibrium processes produce large velocity gradients - are common in many physical, chemical and biological contexts. The velocity or stress at the edge of the boundary layer determines the exterior fluid flow and, hence, the many-body interparticle hydrodynamic interaction. Here, we present a method to compute the many-body hydrodynamic interaction between $N$ spherical active particles induced by their exterior microhydrodynamic flow. First, we use a boundary integral representation of the Stokes equation to eliminate bulk fluid degrees of freedom. Then, we expand the boundary velocities and tractions of the integral representation in an infinite-dimensional basis of tensorial spherical harmonics and, on enforcing boundary conditions in a weak sense on the surface of each particle, obtain a system of linear algebraic equations for the unknown expansion coefficients. The truncation of the infinite series, fixed by the degree of accuracy required, yields a finite linear system that can be solved accurately and efficiently by iterative methods. The 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

2014-11-02

97

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

98

Dusty boundary layer in a surface-burst explosion  

SciTech Connect

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

Kuhl, A.L. [Lawrence Livermore National Lab., El Segundo, CA (United States); Ferguson, R.E.; Chien, K.Y.; Collins, J.P. [Naval Surface Warfare Center, Silver Spring, MD (United States)

1993-08-01

99

Response of the Tropical Boundary Layer to Weak Surface Forcing  

NASA Technical Reports Server (NTRS)

During the Tropical Ocean Global Atmosphere Coupled Ocean Atmosphere Response Experiment (TOGA COARE), a series of airborne thermal infrared observations and in situ atmospheric measurements were made near the sea surface through heights exceeding 4 km. Air movements associated with the sea surface temperature and the marine atmospheric boundary layer were studied.

Hagan, D.; Rogers, D.

1995-01-01

100

Surface plasmon polariton modulator with optimized active layer  

NASA Astrophysics Data System (ADS)

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

Babicheva, Viktoriia E.; Lavrinenko, Andrei V.

2012-04-01

101

Solid\\/free-surface juncture boundary layer and wake  

Microsoft Academic Search

The Reynolds-averaged flow for a solid\\/free-surface juncture boundary layer and wake is documented. The three mean-velocity\\u000a components and five of the Reynolds stresses are measured for a surface-piercing flat plate in a towing tank using a laser-Doppler\\u000a velocimeter system for both boundary-layer and wake planes in regions close to the free surface. The experimental method is\\u000a described, including the foil-plate

J. Longo; H. P. Huang; F. Stern

1998-01-01

102

Nano-porous layer on steel surface as lubricant carrier.  

PubMed

In cold forging of steels, metal soap on zinc-phosphate coating is excellent lubrication system. However, the system is not only less productive, but produces hazardous wastes. In this study, an alternative lubrication system using surface porous layer is proposed. Surface oxide on low carbon steel turns into porous layer by chemical reduction using hydrogen. It is found that liquid lubricant decreases the friction coefficient in compression greatly. The porous surface enhances the decrease, especially in the cases of heavy deformation. PMID:21456283

Utsunomiya, Hiroshi; Kawajiri, Shogo; Takahira, Nobuyuki; Sakai, Tetsuo; Tanaka, Toshihiro

2011-02-01

103

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

104

Formation of Al/B4C Surface Nano-composite Layers on 7075 Al Alloy Employing Friction Stir Processing  

NASA Astrophysics Data System (ADS)

Al/B4C surface nano-composite layers was achieved on commercial 7075 Al substrate employing friction stir processing technique. Agglomeration of B4C particles was occurred after a single pass. The dispersion of B4C particles was found to be affected by the number of FSP passes. A distribution of nano-size B4C particle was achieved after four passes. Moreover, the increasing in number of FSP passes causes a decreasing in matrix grain size of the surface nano-composite layer. The micro hardness of the surface nano-composite layer improves by almost two times as compared to that of the as-received substrate; this is attributed to the finer matrix grains and dispersion of nano-sized B4C particles.

Kashani-Bozorg, S. F.; Jazayeri, K.

2009-06-01

105

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

106

Generalized optical theorem for surface waves and layered media  

SciTech Connect

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

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

2009-05-15

107

Polymer hollow particles with controllable holes in their surfaces.  

PubMed

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. PMID:16086022

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

2005-09-01

108

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

109

Surface acoustic wave-induced precise particle manipulation in a trapezoidal glass microfluidic channel  

NASA Astrophysics Data System (ADS)

Surface acoustic wave (SAW) excitation of an acoustic field in a trapezoidal glass microfluidic channel for particle manipulation in continuous flow has been demonstrated. A unidirectional interdigital transducer (IDT) on a Y-cut Z-propagation lithium niobate (LiNbO3) substrate was used to excite a surface acoustic wave at approximately 35 MHz. An SU8 layer was used for adhesive bonding of the superstrate glass layer and the substrate piezoelectric layer. This work extends the use of SAWs for acoustic manipulation to also include glass channels in addition to prior work with mainly poly-di-methyl-siloxane channels. Efficient alignment of 1.9 µm polystyrene particles to narrow nodal regions was successfully demonstrated. In addition, particle alignment with only one IDT active was realized. A finite element method simulation was used to visualize the acoustic field generated in the channel and the possibility of 2D alignment into small nodal regions was demonstrated.

Johansson, L.; Enlund, J.; Johansson, S.; Katardjiev, I.; Wiklund, M.; Yantchev, V.

2012-02-01

110

Preparation of ultrathin coating layers using surface modified silica nanoparticles  

Microsoft Academic Search

Silica nanoparticles are used in various applications including catalysts, paints and coatings. To reach an optimal performance via stability and functionality, in most cases, the surface properties of the particles are altered using complex procedures. Here we describe a simple method for surface modification of silica nanoparticles (SNP) using sequential adsorption of oppositely charged components. First, the SNPs were made

Tiina Nypelö; Monika Österberg; Xuejie Zu; Janne Laine

111

Effect of surface chemistry and metallic layer thickness on the clustering of metallodielectric janus spheres.  

PubMed

The noncovalent binding of the gold hemispheres of polystyrene/gold colloidal Janus spheres in aqueous solution was found to depend more significantly on the deposition thickness of the particle's gold layer than the chemistry of a covalently affixed self-assembled monolayer on the gold. By means of two-channel confocal laser scanning microscopy, salt-induced clustering was observed and quantified for Janus particles with gold hemispheres functionalized with a thiol self-assembled monolayer that varied in hydrophobicity and chain length. The thickness of the gold layer on the Janus particles was also varied from 10 to 40 nm. The measured cluster distributions were strongly salt dependent, with clustering absent at 1 mM salt but present at salt concentrations in the range of 2-3 mM. For Janus spheres with a 40 nm thick gold hemisphere, the effects of both thiol monolayer hydrophobicity and chain length were modest. Varying the gold layer thickness from 10 to 40 nm, however, had a significant effect on the cluster distribution; the most abundant cluster size shifted from one to seven particles as the gold layer thickness increased from 10 to 40 nm. Thus, the gold layer thickness had an effect stronger than that of either self-assembled monolayer hydrophobicity or chain length on the self-assembly of metallodielectric Janus particles into clusters. The dominant effect of the metallic layer thickness suggests that van der Waals forces between metallic surfaces are more important than hydrophobic interactions in determining the pair potential interactions of metallodielectric Janus particles. PMID:25469598

Shemi, Onajite; Solomon, Michael J

2014-12-30

112

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

113

Particles in Surface Waters: Coagulation and Transport  

E-print Network

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

Culkin, Gerald W.; Lawler, Desmond F.

114

Surface modes in sheared boundary layers over impedance linings  

NASA Astrophysics Data System (ADS)

Surface modes, being duct modes localized close to the duct wall, are analysed within a lined cylindrical duct with uniform flow apart from a thin boundary layer. As well as full numerical solutions of the Pridmore-Brown equation, simplified mathematical models are given where the duct lining and boundary layer are lumped together and modelled using a single boundary condition (a modification of the Myers boundary condition previously proposed by the author), from which a surface mode dispersion relation is derived. For a given frequency, up to six surface modes are shown to exist, rather than the maximum of four for uniform slipping flow. Not only is the different number and behaviour of surface modes important for frequency-domain mode-matching techniques, which depend on having found all relevant modes during matching, but the thin boundary layer is also shown to lead to different convective and absolute stability than for uniform slipping flow. Numerical examples are given comparing the predictions of the surface mode dispersion relation to full solutions of the Pridmore-Brown equation, and the accuracy with which surface modes are predicted is shown to be significantly increased compared with the uniform slipping flow assumption. The importance of not only the boundary layer thickness but also its profile (tanh or linear) is demonstrated. A Briggs-Bers stability analysis is also performed under the assumption of a mass-spring-damper or Helmholtz resonator impedance model.

Brambley, E. J.

2013-08-01

115

Anomalous surface fatigue in a nano-layered material.  

PubMed

Nanoscale materials fatigue within a single 7 Å layer of a 2D nano-layered material, muscovite mica, resembles fatigue in macroscopic systems except for two remarkable properties: first, there is an Å-scale precision in the depth of the damage and second, there are sharply defined "magical" stresses, beyond yield, at which the surface remains intact regardless of the number of applications of stress. PMID:25163860

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

2014-10-01

116

Auroral particle acceleration by strong double layers: The upward current region  

E-print Network

Auroral particle acceleration by strong double layers: The upward current region R. E. Ergun,1 L in part, by strong double layers. The purpose of this article is to examine the role of double layers that a stationary, oblique double layer carries a substantial, albeit a minority fraction ($10% to $50

California at Berkeley, University of

117

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

118

Spontaneous surface flattening via layer-by-layer assembly of interdiffusing polyelectrolyte multilayers.  

PubMed

We report a facile means to achieve planarization of nonflat or patterned surfaces by utilizing the layer-by-layer (LbL) assembly of highly diffusive polyelectrolytes. The polyelectrolyte pair of linear polyethylenimine (LPEI) and poly(acrylic acid) (PAA) is known to maintain intrinsic diffusive mobility atop or even inside ionically complexed films prepared by LbL deposition. Under highly hydrated and swollen conditions during the sequential film buildup process, the LbL-assembled film of LPEI/PAA undergoes a topological self-deformation for minimizing surface area to satisfy the minimum-energy state of the surface, which eventually induces surface planarization along with spontaneous filling of surface textures or nonflat structures. This result is clearly different from other cases of applying nondiffusive polyelectrolytes onto patterned surfaces or confined structures, wherein surface roughening or incomplete filling is developed with the LbL assembly. Therefore, the approach proposed in this study can readily allow for surface planarization with the deposition of a relatively thin layer of polyelectrolyte multilayers. In addition, this strategy of planarization was extended to the surface modification of an indium tin oxide (ITO) substrate, where surface smoothing and enhanced optical transmittance were obtained without sacrificing the electronic conductivity. Furthermore, we investigated the potential applicability of surface-treated ITO substrates as photoelectrodes of dye-sensitized solar cells prepared at room temperature. As a result, an enhanced photoconversion efficiency and improved device characteristics were obtained because of the synergistic role of polyelectrolyte deposition in improving the optical properties and acting as a blocking layer to prevent electron recombination with the electrolytes. PMID:20883048

Kim, Young Hun; Lee, Yong Man; Park, Juhyun; Ko, Min Jae; Park, Jong Hyeok; Jung, Woncheol; Yoo, Pil J

2010-11-16

119

Surface morphological evolution of epitaxial CrN(001) layers  

NASA Astrophysics Data System (ADS)

CrN layers, 57 and 230 nm thick, were grown on MgO(001) at Ts=600-800 °C by ultrahigh-vacuum magnetron sputter deposition in pure N2 discharges from an oblique deposition angle ?=80°. Layers grown at 600 °C nucleate as single crystals with a cube-on-cube epitaxial relationship with the substrate. However, rough surfaces with cauliflower-type morphologies cause the nucleation of misoriented CrN grains that develop into cone-shaped grains that protrude out of the epitaxial matrix to form triangular faceted surface mounds. The surface morphology of epitaxial CrN(001) grown at 700 °C is characterized by dendritic ridge patterns extending along the orthogonal <110> directions superposed by square-shaped super mounds with <100> edges. The ridge patterns are attributed to a Bales-Zangwill instability while the supermounds form due to atomic shadowing which leads to the formation of epitaxial inverted pyramids that are separated from the surrounding layer by tilted nanovoids. Growth at 800 °C yields complete single crystals with smooth surfaces. The root-mean-square surface roughness for 230-nm-thick layers decreases from 18.8 to 9.3 to 1.1 nm as Ts is raised from 600 to 700 to 800 °C. This steep decrease is due to a transition in the roughening mechanism from atomic shadowing to kinetic roughening. Atomic shadowing is dominant at 600 and 700 °C, where misoriented grains and supermounds, respectively, capture a larger fraction of the oblique deposition flux in comparison to the surrounding epitaxial matrix, resulting in a high roughening rate that is described by a power law with an exponent ?>0.5. In contrast, kinetic roughening controls the surface morphology for Ts=800 °C, as well as the epitaxial fraction of the layers grown at 600 and 700 °C, yielding relatively smooth surfaces and ?<=0.27.

Frederick, J. R.; Gall, D.

2005-09-01

120

The numerical calculation of particle-size distributions in 2D jets and boundary layers  

Microsoft Academic Search

The Parmix program for calculating particle size distributions in 2D jets and boundary layers is presented. Parmix is a development of Genmix 4, which allows the fuel to be supplied as a suspension of condensed phase particles in a gaseous stream. The particles are allowed to vary in size, by membership of one of five differently sized groups of particles.

D. B. Spalding

1985-01-01

121

Particle Dry Deposition to Water Surfaces: Processes and Consequences  

E-print Network

- rameters in determining the transfer rate (the deposition velocity) a simple model of particle dry deposition is presented. The model describes the calculation of the rate at which a particle of a given sizeParticle Dry Deposition to Water Surfaces: Processes and Consequences SARA C. PRYOR * and REBECCA J

Pryor, Sara C.

122

Application of Atmospheric Plasma-Sprayed Ferrite Layers for Particle Accelerators  

E-print Network

A common problem in all kinds of cavity-like structures in particle accelerators is the occurrence of RF-resonances. Typically, ferrite plates attached to the walls of such structures as diagnostic devices, kickers or collimators, are used to dampen those undesired modes. However, the heat transfer rate from these plates to the walls is rather limited. Brazing ferrite plates to the walls is not possible in most cases due to the different thermal expansion coefficients. To overcome those limitations, atmospheric plasma spraying techniques have been investigated. Ferrite layers with a thickness from 50 ?m to about 300 ?m can be deposited on metallic surfaces like stainless steel exhibiting good thermal contact and still reasonable absorption properties. In this paper the technological aspects of plasma deposition are discussed and results of specifically developed RF loss measurement procedures for such thin magnetically lossy layers on metal are presented.

Caspers, F; Federmann, S; Taborelli, M; Schulz, C; Bobzin, K; Wu, J

2013-01-01

123

An Aerosol Model of the Marine and Coastal Atmospheric Surface Layer  

Microsoft Academic Search

We present a microphysical model for the surface layer marine and coastal atmospheric aerosols that is based on long-term observations of size distributions for 0.01–100 µm particles. The fundamental feature of the model is a parameterization of amplitudes and widths for aerosol modes of the aerosol size distribution function (ASDF) as functions of fetch and wind speed. The shape of

G. A. Kaloshin; I. A. Grishin

2011-01-01

124

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

PubMed Central

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

Kojic, M.; Tsuda, A.

2010-01-01

125

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

126

Alpha particle backscattering measurements used for chemical analysis of surfaces  

NASA Technical Reports Server (NTRS)

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

Patterson, J. H.

1967-01-01

127

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

128

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

129

Evolving surface cusps during strained-layer epitaxy  

SciTech Connect

We have combined Z-contrast imaging and Ge marker layer experiments to study the evolving surface morphology of Si{sub x}Ge{sub 1-x} alloys grown by molecular beam epitaxy (MBE). Surface cusps are seen to arise as the intersection lines between coherent islands. The potential implications of stress concentrations associated with cusps are considered with a view to strain relaxation in the film via dislocation nucleation.

Jesson, D.E.; Pennycook, S.J. [Oak Ridge National Lab., TN (United States); Baribeau, J.M.; Houghton, D.C. [National Research Council of Canada, Ottawa, ON (Canada). Inst. for Microstructural Sciences

1993-04-01

130

r-Process Nucleosynthesis in Shocked Surface Layers of O-Ne-Mg Cores  

E-print Network

We demonstrate that rapid expansion of the shocked surface layers of an O-Ne-Mg core following its collapse can result in r-process nucleosynthesis. As the supernova shock accelerates through these layers, it makes them expand so rapidly that free nucleons remain in disequilibrium with alpha-particles throughout most of the expansion. This allows heavy r-process isotopes including the actinides to form in spite of the very low initial neutron excess of the matter. We estimate that yields of heavy r-process nuclei from this site may be sufficient to explain the Galactic inventory of these isotopes.

H. Ning; Y. -Z. Qian; B. S. Meyer

2007-08-13

131

Resuspension of Small Particles from Multilayer Deposits in Turbulent Boundary Layers  

E-print Network

We present a hybrid stochastic model for the resuspension of micron-size particles from multilayer deposits in a fully-developed turbulent boundary layer. The rate of removal of particles from any given layer depends upon the rate of removal of particles from the layer above which acts as a source of uncovering and exposure of particles to the resuspending flow. The primary resuspension rate constant for an individual particle within a layer is based on the Rock'n'Roll (R'n'R) model using non-Gaussian statistics for the aerodynamic forces acting on the particles (Zhang et al., 2012). The coupled layer equations that describe multilayer resuspension of all the particles in each layer are based on the generic lattice model of Friess & Yadigaroglu (2001) which is extended here to include the influence of layer coverage and particle size distribution. We consider the influence of layer thickness on the resuspension along with the spread of adhesion within layers, and the statistics of non-Gaussian versus Gaussian removal forces including their timescale. Unlike its weak influence on long-term resuspension rates for monolayers, this timescale plays a crucial and influential role in multilayer resuspension. Finally we compare model predictions with those of a large-scale and a mesoscale resuspension test, STORM (Castelo et al., 1999) and BISE (Alloul-Marmor, 2002).

F. Zhang; M. Reeks; M. Kissane; R. J. Perkins

2012-06-09

132

Far infrared spectra of surface layers in ferroelectric triglycine sulfate  

Microsoft Academic Search

The study of TGS single crystal plates at 4 K shows that the part of the far infrared absorption spectra located at v < 80 cm-1 is hardly sensitive to thickness d for 4 mum < d < 1400 mum. This surprising result is interpreted in the frame of a new surface-layer model recently described to explain the drastic modifications

A. Hadni; X. Gerbaux

1984-01-01

133

Reflection from Layered Surfaces due to Subsurface Scattering Pat Hanrahan  

E-print Network

Reflection from Layered Surfaces due to Subsurface Scattering Pat Hanrahan Department of Computer Research Center for Computer Science Abstract The reflection of light from most materials consists of two ma- jor terms: the specular and the diffuse. Specular reflection may be modeled from first principles

Ramamoorthi, Ravi

134

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

135

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

Microsoft Academic Search

The response of the lower marine atmospheric boundary layer to sharp changes in sea surface temperature was studied in the Frontal Air-Sea Interaction Experiment (FASINEX) with aircraft and ships measuring mean and turbulence quantities, sea surface temperature, and wave state. Changing synoptic weather on 3 successive days provided cases of wind direction both approximately parallel and perpendicular to a surface

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

1991-01-01

136

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

137

Purification and characterization of Campylobacter rectus surface layer proteins.  

PubMed Central

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 these strains varied in molecular mass (ca. 150 to 166 kDa) as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. They all reacted with monospecific rabbit antiserum to the purified S-layer of C. rectus 314, but a quantitative enzyme-linked immunosorbent assay demonstrated a strong antigenic relationship among the five human strains, while the NHP strain, 6250, showed weaker reactivity. Amino acid composition analysis showed that the S-layers of four C. rectus strains contained large proportions of acidic amino acids (13 to 27%) and that >34% of the amino acid residues were hydrophobic. Amino acid sequence analysis of six S-layer proteins revealed that the first 15 amino-terminal amino acids were identical and showed seven residues of identity with the amino-terminal sequence of the Campylobacter fetus S-layer protein SapA1. CNBr peptide profiles of the S-layer proteins from C. rectus 314, ATCC 33238, and 6250 confirmed that the S-layer proteins from the human strains were similar to each other and somewhat different from that of the NHP isolate (strain 6250). However, the S-layer proteins from the two human isolates do show some structural heterogeneity. For example, there was a 17-kDa fragment unique to the C. rectus 314 S-layer. The amino-terminal sequence of this peptide had homology with the C. rectus 51-kDa porin and was composed of nearly 50% hydrophobic residues. Thus, the S-layer protein from C. rectus has structural heterogeneity among different human strains and immunoheterogeneity with the NHP strain. PMID:9009300

Nitta, H; Holt, S C; Ebersole, J L

1997-01-01

138

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

139

Estimation of the particle flux from the convective mixed layer by large eddy simulation  

E-print Network

the mixed layer; ws is the terminal velocity of a particle settling in still fluid; and wd is the deepening velocity corresponding to the terminal velocity of a particle settling in still fluid ws [Lande and Wood velocity of the mixed layer depth (MLD). It is in contrast with the previous hypothesis that W = ws for wd

Noh, Yign

140

Turbulent boundary layer at moving surface of cylindrical body  

NASA Astrophysics Data System (ADS)

An analysis is made of the two dimensional turbulent boundary on the moving surface of a cylindrical body (a Rankine oval with an aspect ratio of 4) moving at constant velocity in an incompressible fluid. A numerical simulation is used in which the boundary layer is divided in accordance with a two layer model into inner and outer regions, for which different expressions for the turbulent transport coefficients are employed. The following integral characteristics are determined for the body: the work of the friction force as the body moves; the work expended on the motion of its surface; and (for separated flow) the work of the pressure force. These characteristics are compared with corresponding integral characteristics obtained for laminar flow, on the moving surface of a flat plate, and on a wing of infinite span whose contour is a Rankine oval.

Zubarev, V. M.

1986-02-01

141

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

142

Particles movement and surface quality in PLD/PR systems  

NASA Astrophysics Data System (ADS)

A three-dimensional model based on Monte-Carlo and Finite Elements techniques has been used for simulating plume behavior, 'micron-sized particles' movement and interaction with obstacles in a Pulsed Laser Deposition with Plasma Reflection (PLD/PR) system. Have been investigated the influences of mass, surface size and emission time on trajectory and film surface quality as well. Droplet and 'big-size particles' deposition statistics are presented and a comparison between theoretical and experimental results upon thin film surface quality as well. One can observe that particles mass and surface size have a strong influence on the particles trajectory by affecting the collisions parameters during the entire propagation process. The emission time should influence the particles trajectory by affecting the probability of interaction with other particles. By making a 10,000 particles statistic for a normal distribution of these investigated parameters, we obtain reasonable good results in modeling 'big-size particles' tendency to be deposited at lower reflection angles. These results sustain assumption of 'big particles' deflection by plume fine particles during the propagation process.

Marcu, A.; Grigoriu, C.; Yatsui, K.

2006-04-01

143

Surface Layers in General Relativity and Their Relation to Surface Tensions  

E-print Network

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

H. -J. Schmidt

2001-05-28

144

Surface-lining layer of airways in cystic fibrosis mice.  

PubMed

Lung disease is the major cause of death in individuals suffering from cystic fibrosis (CF), with abnormal lung-lining fluids occurring as early as early infancy. However, the precise etiology of CF lung disease is still poorly understood. We investigated the structural components of the airway surface-lining layer in targeted Cftrtm1HGU/Cftrtm1HGU mutant mice and non-CF controls. Five lungs per animal group were fixed by intravascular triple perfusion. The ultrastructure of the surface-lining layer of large and small intrapulmonary conducting airways was systematically investigated according to a standard protocol in transmission and scanning electron micrographs. In both animal groups, the surface-lining layer consisted of an aqueous phase and an osmiophilic film of variable thickness at the air-fluid interface. The aqueous phase usually did extend <1 microm beyond the uppermost tips of the epithelial cells in both animal groups. The aqueous phase of the small airways was slightly more electron dense in Cftrtm1HGU/Cftrtm1HGU than in non-CF mice. Neither the ultrastructure of the surfactant film at the air-fluid interface nor the forms assumed by the osmiophilic structures associated with surfactant turnover in the aqueous layer differed significantly in Cftrtm1HGU/Cftrtm1HGU and non-CF mice. Hence, there were no signs of any ultrastructural abnormalities in the surface-lining layer of young adult Cftrtm1HGU/Cftrtm1HGU mice before infection with CF-related pathogens. PMID:12936909

Geiser, Marianne; Bastian, Sara

2003-12-01

145

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

PubMed

An oxygen inhibition layer develops on surfaces exposed to air during polymerization of particulate filling composite. This study assessed the thickness of the oxygen inhibition layer of short-fiber-reinforced composite in comparison with conventional particulate filling composites. The effect of an oxygen inhibition layer on the shear bond strength of incrementally placed particulate filling composite layers was also evaluated. Four different restorative composites were selected: everX Posterior (a short-fiber-reinforced composite), Z250, SupremeXT, and Silorane. All composites were evaluated regarding the thickness of the oxygen inhibition layer and for shear bond strength. An equal amount of each composite was polymerized in air between two glass plates and the thickness of the oxygen inhibition layer was measured using a stereomicroscope. Cylindrical-shaped specimens were prepared for measurement of shear bond strength by placing incrementally two layers of the same composite material. Before applying the second composite layer, the first increment's bonding site was treated as follows: grinding with 1,000-grit silicon-carbide (SiC) abrasive paper, or treatment with ethanol or with water-spray. The inhibition depth was lowest (11.6 ?m) for water-sprayed Silorane and greatest (22.9 ?m) for the water-sprayed short-fiber-reinforced composite. The shear bond strength ranged from 5.8 MPa (ground Silorane) to 36.4 MPa (water-sprayed SupremeXT). The presence of an oxygen inhibition layer enhanced the interlayer shear bond strength of all investigated materials, but its absence resulted in cohesive and mixed failures only with the short-fiber-reinforced composite. Thus, more durable adhesion with short-fiber-reinforced composite is expected. PMID:25556290

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

2015-02-01

146

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

2015-02-11

147

Microhydrodynamics of flotation processes in the sea surface layer  

NASA Astrophysics Data System (ADS)

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

Grammatika, Marianne; Zimmerman, William B.

2001-10-01

148

The particle track record of the lunar surface.  

NASA Technical Reports Server (NTRS)

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

Comstock, G. M.

1972-01-01

149

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

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

150

Using fluffy layer material to study the fate of particle-bound organic pollutants in the southern Baltic Sea.  

PubMed

This paper examines the utility of fluffy layer material for studying and monitoring the environmental levels, transport, and fate of particle-bound contaminants in coastal ecosystems. Fluffy layer material is the very young and mobile layer of particulate matter that accumulates on the sediment surface under quiescent conditions. We used this material to study the behavior of polycyclic aromatic hydrocarbons (PAHs) that are discharged by the Oder River into the Baltic Sea. With the fluffy layer material, it was possible to (i) do fingerprint analysis to trace the sources of PAHs in the river discharge, (ii) follow the modification of the PAHs from the mouth of the river to the depositional basin and identify the responsible processes, (iii) monitor the seasonal variation in the PAH input, (iv) study the influence of a major flood event on the PAH loading to the coastal ecosystem, and (v) conduct a PAH mass balance to estimate the contribution of the Oder River source to PAH accumulation in the depositional basin. The fluffy layer material integrated the particle-bound contaminant signal over a period ranging from several days to several months, depending on the sampling location. As such, fluffy layer material is a valuable addition to the matrixes commonly used for studying particle-associated chemicals: SPM and sediment, which reflect time scales of hours and years, respectively. PMID:11329703

Witt, G; Leipe, T; Emeis, K C

2001-04-15

151

Electrografted diazonium salt layers for antifouling on the surface of surface plasmon resonance biosensors.  

PubMed

Electrografted diazonium salt layers on the surface of surface plasmon resonance (SPR) sensors present potential for a significant improvement in antifouling coatings. A pulsed potential deposition profile was used in order to circumvent mass-transport limitations for layer deposition rate. The influence of number of pulses with respect to antifouling efficacy was evaluated by nonspecific adsorption surface coverage of crude bovine serum proteins. Instead of using empirical and rough estimated values, the penetration depth and sensitivity of the SPR instrument were experimentally determined for the calculation of nonspecific adsorption surface coverage. This provides a method to better examine antifouling surface coatings and compare crossing different coatings and experimental systems. Direct comparison of antifouling performance of different diazonium salts was facilitated by a tripad SPR sensor design. The electrografted 4-phenylalanine diazonium chloride (4-APhe) layers with zwitterionic characteristic demonstrate ultralow fouling. PMID:25526646

Zou, Qiongjing; Kegel, Laurel L; Booksh, Karl S

2015-02-17

152

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

PubMed

Pigment particles used in paper coatings are typically of micrometer size and consequently the thickness of the coatings is, even at its lowest, in micrometer scale. Progress in nanotechnology has given way to the development of nanosized materials to be used in coatings, yet their exploitation has not been studied to a great extent. This study examines utilization of nanosized precipitated calcium carbonate (nanoPCC) particles in nanoscale thin coating layers. In contrast to commonly used coatings, a thin nanoparticle-based coating was targeted to change the substrate surface characteristics via controlled surface structure rather than via high coat weight. A novel approach for stabilizing and modifying the nanoPCC particles with pectin and alkenyl succinic anhydride (ASA) was utilized and a nanoparticle coating with uniform particle distribution was created. The coating applied on paper substrate was hydrophobic, having a water contact angle of 125°. Particle surface modification provided dispersion stability, enabling control of the coating layer structure. The introduced concept provides a new approach to paper coatings utilizing controlled deposition of nanoparticles with extremely low coat weight, yet having high impact on substrate surface properties. Additionally, as paper is an environmentally sound product, the approach to form a controllable nanostructure on a green substrate has potential in applications outside the traditional paper products. PMID:21888413

Nypelö, Tiina; Österberg, Monika; Laine, Janne

2011-09-01

153

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

154

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

155

Assembled monolayers of hydrophilic particles on water surfaces.  

PubMed

A facile and quick approach to prepare self-assembled monolayers of water-dispersible particles on the water surface is presented. Particle suspensions in alcohols were dropped on a water reservoir to form long-range ordered monolayers of various particles, including spherical solid particles, soft hydrogel particles, metal nanoparticles, quantum dots, nanowires, single-wall carbon nanotubes (SWCNTs), nanoplates, and nanosheets. A systematic study was conducted on the variables affecting the monolayer assembly: the solubility parameter of spreading solvents, particle concentration, zeta potential of the particles in the suspension, surface tension of the water phase, hardness of the particles, and addition of a salt in the suspension. This method requires no hydrophobic surface treatment of the particles, which is useful to exploit these monolayer films without changing the native properties of the particles. The study highlights a quick 2D colloidal assembly without cracks in the wafer scale as well as transparent conductive thin films made of SWCNTs and graphenes. PMID:21962177

Moon, Geon Dae; Lee, Tae Il; Kim, Bongsoo; Chae, GeeSung; Kim, Jinook; Kim, SungHee; Myoung, Jae-Min; Jeong, Unyong

2011-11-22

156

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

157

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

158

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

159

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

160

Impact of beryllium surface layers on deuterium retention in tungsten  

NASA Astrophysics Data System (ADS)

In ITER mixed Be/W layers are likely to form and their retention behavior is unknown. A series of ITER-grade tungsten samples have been exposed in PISCES-B to deuterium plasma at 573 K, with and without beryllium impurity seeding of the plasma. If the beryllium concentration is small, the majority of the incident beryllium is re-eroded from the sample surface and only a few nm thick layer of mixed Be/W remains. The W samples exposed without beryllium seeding showed blister formation. The inclusion of 0.2% beryllium impurity ion fraction within the plasma eliminated the surface blisters, however did not change the amount of retained deuterium in the samples. When the beryllium impurity concentration in the plasma is large (2.5%), a beryllium layer grows as the fluence increases. The deuterium retention also increases and exceeds the amount retained in either the pure tungsten, or the thin mixed Be-W layer on tungsten, case.

Doerner, R. P.; Baldwin, M. J.; Nishijima, D.; Roth, J.; Schmid, K.

2011-08-01

161

Programming nanostructured soft biological surfaces by atomic layer deposition  

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

162

Laser removal of thin layers for surface cleaning  

NASA Astrophysics Data System (ADS)

In micro- and nano- device fabrication technology, localized material removal is one of the basic operations for structure formation. Classical methods for structure formation on the surface of a silicon wafer are based mainly on chemical processing, starting with photo etching, chemical etching, and chemical-mechanical linearization. In order to propose new methods of higher quality from the point of view of both environment protection and processing quality, we have studied the possibility of thin films controlled removal under the action of laser radiation. We are presenting some qualitative results of laser induced surface removal of polymer thin films, of interest for microelectronic industry (e.g. photoresist), under the action of different laser sources. As laser sources we have used the most spread and commercially available laser systems with different wavelengths and pulse lengths in order to compare their action on the surfaces and to establish the characteristic parameters for removal of thin layers for surface cleaning.

Apostol, Ileana; Apostol, D.; Damian, V.; Iordache, Iuliana; Garoi, F.; Capello, E.

2008-03-01

163

Programming nanostructured soft biological surfaces by atomic layer deposition.  

PubMed

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

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

2013-06-21

164

Surface modification of polypropylene based particle foams  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

165

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

166

Quantitative layer analysis of single crystal surfaces by LEIS  

Microsoft Academic Search

The quantitative interpretation of energy and angle resolved low-energy ion scattering intensity distributions is achieved by comparing the experimental results with those from numerical simulations using the MARLOWE code with extensions for layer selective analysis. The example used is the CuAu(100) alloy crystal surface. For adequate analysis the potential parameter (i.e. the screening length) has to be calibrated. This is

Robert Beikler; Edmund Taglauer

2002-01-01

167

Impact of Sea-Spray on the Atmospheric Surface Layer  

NASA Astrophysics Data System (ADS)

The feedback effects of sea-spray on the heat and momentum fluxes under equilibrium conditions associated with winds of tropical cyclones are investigated using a one-dimensional coupled sea-spray and atmospheric surface-layer (ASL) model. This model is capable of simulating the microphysical aspects of the evaporation of saline water droplets of various sizes and their dynamic and thermal interaction with the turbulence mixing that is simulated by the Mellor-Yamada 1.5-order closure scheme. Sea-spray droplet generation is described by a state-of-the-art parametrization that predicts the size spectrum of sea-spray droplets for a given surface forcing. The results from a series of simulations indicate the way in which evaporating droplets of various sizes modify the turbulence mixing near the surface, which in turn affects further droplet evaporation. All these results are direct consequences of the effects of sea-spray on the balance of turbulent kinetic energy in the spray-filled surface layer. In particular, the overall impact of sea-spray droplets on the mean wind depends on the wind speed at the level of sea-spray generation. When the wind speed is below 40 m s-1, the droplets are small in size and tend to evaporate substantially and thus cool the spray-filled layer, while for wind speeds above 50 m s-1, the size of the droplets is so large that they do not have enough time to evaporate much before falling back into the sea. The sensible heat carried by the droplets is released to the ambient air, increasing the buoyancy of the surface layer and enhancing the turbulent mixing. The suspension of sea-spray droplets reduces the buoyancy and makes the surface layer more stable, decreasing the friction velocity and the downward turbulent mixing of momentum. The results from the numerical experiments also suggest that, in order not to violate the constant flux assumption critical to the Monin-Obukhov similarity theory, a displacement equal to the mean wave height should be included in the logarithmic profiles of the wind and thermal fields.

Bianco, L.; Bao, J.-W.; Fairall, C. W.; Michelson, S. A.

2011-09-01

168

Rapid Particle Size Measurement Using 3D Surface Imaging  

Microsoft Academic Search

The present study introduces a new three-dimensional (3D) surface image analysis technique in which white light illumination\\u000a from different incident angles is used to create 3D surfaces with a photometric approach. The three-dimensional features of\\u000a the surface images created are then used in the characterization of particle size distributions of granules. This surface\\u000a image analysis method is compared to sieve

Ira Soppela; Sari Airaksinen; Juha Hatara; Heikki Räikkönen; Osmo Antikainen; Jouko Yliruusi; Niklas Sandler

2011-01-01

169

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

170

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

171

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...

172

EFFECT OF SURFACE HETEROGENEITIES ON CONDENSATION ON AN AEROSOL PARTICLE  

Microsoft Academic Search

Aerosol particles undergo a multitude of interactions with background gases and vapors as a result of their comparatively large surface areas and long residence times in suspension. These interactions, in turn, modify the physical and chemical properties of the particles, including those properties that affect their toxicity. While the importance of these interactions has always been recognized, the subject has

L. J. Willett; S. A. F. Hashim; R. V. Tompson; S. K. Loyalka

1999-01-01

173

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

174

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

PubMed

We introduce a novel description of the dynamics of the order book of financial markets as that of an effective colloidal Brownian particle embedded in fluid particles. The analysis of comprehensive market data enables us to identify all motions of the fluid particles. Correlations between the motions of the Brownian particle and its surrounding fluid particles reflect specific layering interactions; in the inner layer the correlation is strong and with short memory, while in the outer layer it is weaker and with long memory. By interpreting and estimating the contribution from the outer layer as a drag resistance, we demonstrate the validity of the fluctuation-dissipation relation in this nonmaterial Brownian motion process. PMID:24655287

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

2014-03-01

175

Homogenous Surface Nucleation of Solid Polar Stratospheric Cloud Particles  

NASA Technical Reports Server (NTRS)

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

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

2002-01-01

176

On the behaviour of solid particles in a horizontal boundary layer with turbulence and saltation effects  

Microsoft Academic Search

A horizontal turbulent boundary layer of air carrying heavy solid particles is investigated experimentally. Mean and r.m.s.\\u000a velocities of air and particles are measured by LDA, and particle mass flux distributions are obtained by means of a sampling\\u000a method. The influence of the saltation mechanism is revealed by the large particle r.m.s. velocity in the near-wall region,\\u000a and by the

A. Tanière; B. Oesterlé; J. C. Monnier

1997-01-01

177

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...

178

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

NASA Technical Reports Server (NTRS)

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

Blumberg, Dan G.; Greeley, Ronald

1992-01-01

179

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

180

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

181

The zeta potential of surface-functionalized metallic nanorod particles in aqueous solution.  

PubMed

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. 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. For comparison, we present zeta potential data for typical charge-stabilized polystyrene particles. We compare experimental zeta potential data with theoretically predicted values for SAM-coated and bimetallic particles. 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. PMID:18246574

Dougherty, George M; Rose, Klint A; Tok, Jeffrey B-H; Pannu, Satinderpall S; Chuang, Frank Y S; Sha, Michael Y; Chakarova, Gabriela; Penn, Sharron G

2008-03-01

182

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

183

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

184

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...

185

SURFACE ANALYSIS OF PARTICLES EMITTED TO THE ATMOSPHERE (JOURNAL VERSION)  

EPA Science Inventory

A number of potentially toxic trace metal and organic species have been shown to be preferentially enriched on the surfaces of most types of anthropogenic particles which are emitted to the atmosphere. The use of several surface analytical techniques including ion microprobe mass...

186

Electrical Double Layer Interactions under Regulation by Surface Ionization Equilibria--Dissimilar  

E-print Network

Electrical Double Layer Interactions under Regulation by Surface Ionization Equilibria-Chapman theory of electrical double layers, it has been usual to assume, as boundary conditions important colloidal systems. The problem of interacting dissimilar double layers has been considered

Chan, Derek Y C

187

Shape-selective sieving layers on an oxide catalyst surface.  

PubMed

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

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

2012-12-01

188

The Role of Adsorbed Water on the Friction of a Layer of Submicron Particles  

NASA Astrophysics Data System (ADS)

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 a 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 allows the otherwise rough particles to rotate, then 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 1nm thick layer of adsorbed water, with a minimum particle radius of about 20 nm, and with reasonable assumptions about the distribution of force chains guided by experimental observation. The reduction of friction and range of velocities over which it occurs decreases 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 about 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, C. G.; Lockner, D. A.; Reches, Z.

2011-12-01

189

The Role of Adsorbed Water on the Friction of a Layer of Submicron Particles  

NASA Astrophysics Data System (ADS)

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

2011-12-01

190

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

191

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

E-print Network

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

Roman, Jennifer Claire

2012-06-07

192

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

193

Simultaneous detection of separation and transition in surface shear layers  

NASA Astrophysics Data System (ADS)

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.

1989-04-01

194

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

195

Direct numerical simulation of particle dispersion in a spatially developing turbulent boundary layer  

NASA Astrophysics Data System (ADS)

We performed DNS of particle-laden spatially developing turbulent boundary layer at Re?=1000-3200. We computed the Lagrangian trajectories of millions of fluid points and solid particles with Stokes number St=0.1, 1, and 5, where St=?p/?k, and ?k was computed at z+ at the streamwise location where particles were released. The particles were gradually released from a line source in the viscous sublayer, buffer layer, and log-layer. We computed the time development of particle mean displacement, dispersion, and turbulent diffusivity. Our DNS results of fluid point mean-displacements are in excellent agreement with those of Batchelor's (1964) theory. Also, our DNS results show that in general particle statistics are strongly influenced by particle's Stokes number. Such dependence is mostly caused by the particles tendency to preferentially accumulate in the viscous sublayer as their Stokes number increases. Furthermore, for t/T L < 1 where TL is the Lagrangian integral time scale, the streamwise and wall-normal dispersions are ? t2 for fluid points and ? t3 for solid particles. For 20 < t/TL < 80, the streamwise dispersion of fluid points and particles with St = 0.1 is approximately ? t5/3, while that of particles with St = 1 and 5 is approximately ? t5/2. For all cases studied and for 20 < t/T L < 80, the wall-normal dispersion is approximately ? t.

Ferrante, A.; Dodd, M.

2012-12-01

196

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

NASA Technical Reports Server (NTRS)

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

Yushin, Gleb; Evanoff, Kara; Magasinski, Alexander

2012-01-01

197

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

198

45S5 Bioactive glass surface charge variations and the formation of a surface calcium phosphate layer in a  

E-print Network

45S5 Bioactive glass surface charge variations and the formation of a surface calcium phosphate- phate (Ca-P) layer formation kinetics on the surface of 45S5 bioactive glass (BG). We hypothesize a surface calcium phosphate layer in vivo, bioactive materials, such as 45S5 bioactive glass (BG), are able

Lu, Helen H.

199

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

200

Characteristics of turbulent structures in the unstable atmospheric surface layer  

NASA Astrophysics Data System (ADS)

An atmospheric surface-layer (ASL) experiment conducted at a meteorological site in the Oostelijk-Flevoland polder of the Netherlands is described. Turbulent fluctuations of wind velocity, air temperature and static pressure were measured, using three 10 m towers. Simultaneous turbulent signals at several heights on the towers were used to investigate the properties of the turbulent structures which contribute most significantly to the turbulent vertical transports in the unstable ASL. These turbulent structures produce between 30 and 50% of the mean turbulent vertical transport of horizontal alongwind momentum and they contribute to between 40 and 50% of the mean turbulent vertical heat transport; in both cases this occurs during 15 to 20% of the total observation time. The translation speed of the turbulent structures equals the wind speed averaged over the depth of the ASL, which scales on the surface friction velocity. The inclination angle of the temperature interface at the upstream edge of the turbulent structures to the surface is significantly smaller than that of the internal shear layer, which is associated with the temperature interface. The turbulent structures in the unstable ASL are determined by a large-scale temperature field: Convective motions, which encompass the whole depth of the planetary boundary layer (PBL), penetrate into the ASL. The curvature of the vertical profile of mean horizontal alongwind velocity forces the alignment of the convective cells in the flow direction (Kuettner, 1971), which have an average length of several hundreds of metres and an average width of a few tens of metres. This mechanism leads to the formation of turbulent structures, which extend throughout the depth of the ASL.

Schols, J. L. J.; Jansen, A. E.; Krom, J. G.

1985-10-01

201

Effect of the surface layer parameters on the fretting fatigue of contacting surfaces  

NASA Astrophysics Data System (ADS)

Specimens of VT3-1 titanium alloy were tested in fretting fatigue at 50 GHz, 15 MPA, 20 C in order to determine the effect of various surface layer parameters on the intensity of fretting wear. It is found that the intensity of fretting wear is largely determined by the height of surface microirregularities. Residual stresses do not affect fretting wear. Surface hardening to an optimal degree may slightly reduce fretting wear. However, surface hardening in excess of the optimal level significantly increases seizing and adhesive wear, thus contributing to fretting wear.

Semenov, A. N.

202

Particle transport and reattachment on a mask surface  

NASA Astrophysics Data System (ADS)

The cleaning processes used today for photomasks were developed over decades and optimized to fulfill customer specifications. Some mask procedures were adapted from wafer cleaning technology. A principal technique, megasonic (MS) cleaning, yields high particle removal efficiencies (PRE). However, MS can frequently cause feature damage, and so damage becomes the principle limitation to MS power levels applied to small feature sizes. The use of lower MS power levels can benefit from a better understanding of removal mechanisms. In several publications the effects influencing the mechanisms of particle cleaning were discussed [1]. Particle transfer was investigated experimentally on wafer surfaces using bath tools and was tracked using fluorescent optical microscopy [2]. The goal of our investigation is to test the validity of the aforementioned models for mask cleaning using a spinning mask and a megasonic head mounted on a arm swinging over the mask surface, which is the most common hardware setup used for mask cleaning tools. While this equipment setup provides a useful variability, it also introduces disadvantages e.g. non-equal distribution of the megasonic power across the cleaned surface as will be shown. We will focus on some of the main parameters e.g. chuck speed, arm swing speed and media flow, which are strongly coupled by the fluid dynamics and cannot be treated separately. All three parameters influence particle-mask decoupling and reattachment during particle transport by the media stream across the mask surface. The approach to estimate the particle removal and reattachment rate is illustrated. The experiments performed allow the conclusion that the reattachment rate on a flat spinning mask surface is lower than previously assumed and the most critical part of the cleaning process is the detachment of the particle from the surface.

Nesladek, Pavel; Osborne, Steve; Kohl, Christian

2009-01-01

203

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

PubMed

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

Teychene, Benoît; Guigui, Christelle; Cabassud, Corinne

2011-02-01

204

Gyroscopic Pumping in the Solar Near-Surface Shear Layer  

E-print Network

We use global and local helioseismic inversions to explore the prevailing dynamical balances in the solar Near-Surface Shear Layer (NSSL). The differential rotation and meridional circulation are intimately linked, with a common origin in the turbulent stresses of the upper solar convection zone. The existence and structure of the NSSL cannot be attributed to the conservation of angular momentum by solar surface convection, as is often supposed. Rather, the turbulent angular momentum transport accounts for the poleward meridional flow while the often overlooked meridional force balance maintains the mid-latitude rotational shear. We suggest that the base of the NSSL is marked by a transition from baroclinic to turbulent stresses in the meridional plane which suppress Coriolis-induced circulations that would otherwise establish a cylindrical rotation profile. The turbulent angular momentum transport must be non-diffusive and directed radially inward. Inferred mean flows are consistent with the idea that turbul...

Miesch, Mark S

2011-01-01

205

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

206

Distributions of surface-layer buoyance versus lifting condensation level over a heterogeneous land surface  

Microsoft Academic Search

Onset and coverage of small cumulus clouds depend on the relative abundance of surface-layer air parcels possessing favorable buoyancy and moisture - two variables that are coupled through the surface energy budget. This abundance is described using a joint frequency distribution (JFD) as a function of virtual potential temperature θ{sub v} and height of the lifting condensation level z{sub LCL}.

K. Schrieber; Qing Zhang; R. Stull

1996-01-01

207

Distributions of Surface-Layer Buoyancy Versus Lifting Condensation Level over a Heterogeneous Land Surface  

Microsoft Academic Search

Onset and coverage of small cumulus clouds depend on the relative abundance of surface-layer air parcels possessing favourable buoyancy and moisture-two variables that are coupled through the surface energy budget. This abundance is described using a joint frequency distribution (JFD) as a function of virtual potential temperature v. and height of lifting condensation level zLCL. It is shown analytically that

Kelly Schrieber; Roland Stull; Qing Zhang

1996-01-01

208

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

209

Diffusion of particles on the patchwise bivariate surfaces  

NASA Astrophysics Data System (ADS)

The diffusion of particles adsorbed on patchwise surfaces is investigated in the framework of a lattice-gas model. We propose the analytical expressions for the center-of-mass and Fickian diffusion coefficients. The theoretical dependencies are compared with the numerical data obtained by the kinetic Monte Carlo simulations for three different patchwise lattices. The good coincidence of the theoretical dependencies and the numerical data corroborates the validity of the approach developed to describe the particle migration on such lattices.

Tarasenko, Alexander; Jastrabik, Lubomir

2015-02-01

210

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

211

Parameterization of turbulence characteristics of Atmospheric surface layer in Qatar  

NASA Astrophysics Data System (ADS)

Turbulent characteristics of atmospheric boundary layer are of utmost importance in modeling the large-scale meteorological processes, diffusion of atmospheric contaminants, heat transfer and evaporation from the earth surface. Available data are for some areas on the globe and are really sparse in tropical regions, except a few recent studies in Asia. There had been some recent studies in tropical weather in southwestern Asia but no study is carried out in Persian Gulf region. An atmospheric measurement station has been designed and installed in a site in the coastal region of Doha, Qatar, to characterize the nature of atmosphere surface layer (ASL) and ocean wave characteristics in this field. The aim of the present study is to report the micrometeorological data collected from this site. The normalized variation of the turbulent velocity components and temperature were studied using Monin-Obukhov similarity theory (MOST). This study also attempts to verify the validity of MOST in the context of the data collected for a marine ASL in Qatar, and compares the modeling parameters with other investigations around the world. This is the first ever study of ASL in this area, and is expected to be a foundation of further atmospheric research endeavors in Qatar.

Singha, Arindam; Sadr, Reza

2011-11-01

212

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

SciTech Connect

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

West, R.; Tsang, Leung; Winebrenner, D.P. (Univ. of Washington, Seattle (United States))

1993-03-01

213

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

214

Nano sized clay detected on chalk particle surfaces  

NASA Astrophysics Data System (ADS)

Chalk is a sedimentary rock consisting mostly of micrometer sized particles of biogenic calcite (CaCO3). It forms the reservoirs for oil in the Danish part of the North Sea and important drinking water aquifers in northern Europe. The interaction between organic molecules and the particle surfaces has a strong influence on the migration of oil in the reservoirs. Adhesion of oil components to chalk particle surfaces is thought to significantly reduce production and efforts are being made to determine the mechanisms behind enhanced/improved oil recovery (EOR/IOR) during water flooding. Aquifers beneath industrial areas can be heavily polluted with organic compounds and similar adsorption mechanisms could influence the geographical extent of the contaminant plume. Chalk, as a sedimentary rock, has been studied extensively for many years but the properties of the particle surfaces, where adsorption takes place, are largely unknown. In this study, we have used atomic force microscopy (AFM) to show that the grain surfaces in offshore and onshore chalk are more heterogeneous than previously assumed. The particles are not simply calcite surfaces but are partially covered by clay that is only 1-4 nm thick. With chemical force mapping (CFM), we have probed the surface using a tip coated with organic molecules to represent a tiny, mono-functionalized oil droplet. The functional groups of the self assembled monolayer on the tip were either -CH3 or -COO-. From maps of adhesion, it is evident that in calcite saturated water, both the polar and the nonpolar functional groups adhere to the nano sized clay particles but not to calcite. This is fundamentally important information for the development of conceptual and chemical models to explain wettability alterations in chalk reservoirs.

Skovbjerg, L. L.; Hassenkam, T.; Makovicky, E.; Hem, C. P.; Yang, M.; Bovet, N.; Stipp, S. L. S.

2012-12-01

215

Copolyimide Surface Modifying Agents for Particle Adhesion Mitigation  

NASA Technical Reports Server (NTRS)

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

Wohl, Christopher J.; Connell, John W.

2011-01-01

216

Capillary Interception of Floating Particles by Surface-Piercing Vegetation  

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

217

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

218

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

PubMed Central

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

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

2009-01-01

219

Characterization of cathode keeper wear by surface layer activation  

NASA Technical Reports Server (NTRS)

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

Polk, James E.

2003-01-01

220

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

NASA Astrophysics Data System (ADS)

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

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

2013-11-01

221

Surface impacts and collisions of particle-laden nanodrops  

E-print Network

The surface impact and collisions of particle-laden nanodrops are studied using molecular dynamics computer simulations. The drops are composed of Lennard- Jones dimers and the particles are rigid spherical sections of a cubic lattice, with radii about 11 nm and 0.6 nm, respectively. Uniform suspensions of 21% and 42% particle concentrations and particle-coated drops are studied, and their behavior is compared to that of pure fluid drops of the same size. The relative velocities studied span the transition to splashing, and both wetting/miscible and non-wetting/immiscible cases are considered. Impacts normal to the surface and head-on collisions are studied and compared. In surface impact, the behavior of low-density suspensions and liquid marble drops is qualitatively similar to that of pure liquid, while the concentrated drops are solid-like on impact. Collisions produce a splash only at velocities signif- icantly higher than in impact, but the resulting drop morphology shows a similar dependence on solid concentration as in impact. In all cases the collision or impact produces a strong local enhancement in the kinetic energy density and temperature but not in the particle or potential energy densities. Mixing of the two colliding species is not enhanced by collisions, unless the velocity is so high as to cause drop disintegration.

Joel Koplik

2014-12-17

222

Particle behavior in the turbulent boundary layer. II. Velocity and distribution profiles  

NASA Astrophysics Data System (ADS)

The velocity, flux, and concentration distribution of solid particles in a turbulent boundary layer of a horizontal water flume were investigated experimentally by means of LDA and visualization techniques. The particles were of polystyrene (specific density ˜1.05). Results show that coherent wall structures are responsible for most of the characteristics of particle behavior throughout the boundary layer. Particles are often concentrated in regions of low velocity, associated with wall structures, and as a result the average particle velocity is lower than the fluid's. This was also noted previously by Rashidi et al., but not explained. The actual relative velocity between the particles and the surrounding fluid is often small. In addition, the data suggest that as the shear rate increases, the particle flux profiles asymptotically approach a shape where a strong gradient of particle flux exists in the lower part of the boundary layer (y+?250), while it is relatively constant at higher elevations. This phenomenon may also be attributable to interactions with the wall structures.

Kaftori, D.; Hetsroni, G.; Banerjee, S.

1995-05-01

223

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

224

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

225

Physico-chemical characterisation of surface modified particles for inhalation.  

PubMed

Surface modification of drugs for inhalation is a possibility to influence interparticulate forces. This can be necessary to achieve a sufficient aerosolisation during powder inhalation as the cohesiveness of the micronised drug can be reduced. In addition, the interaction with propellants in pressurised metered dose inhaler can be changed. This can be used to improve the physical stability of the suspension based formulations. A dry particle coating process was used for the alteration of particle surfaces. The blending of micronised salbutamol sulphate (SBS) with different concentrations of magnesium stearate (Mgst) or glycerol monostearate (GMS) was followed by co-milling with an air jet mill. The powder properties were characterised by SEM, EDX, laser diffraction, BET and inverse gas chromatography. Physical mixtures generated by Turbula blending were compared to co-milled samples. A slight particle size reduction was determined. The Mgst deposition on SBS particles was detected by EDX measurements. The dispersive surface energy of SBS is lowered and the energy distribution is more homogenous for the co-milled samples. This study proves the application of co-milling for surface modification in the inhalation area. PMID:23518364

Stank, Katharina; Steckel, Hartwig

2013-05-01

226

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...

227

ELECTROSTATIC SURFACE STRUCTURES OF COAL AND MINERAL PARTICLES  

SciTech Connect

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

NONE

1998-04-01

228

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

SciTech Connect

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

Kravchenko, O. Y.; Vakulenko, A. V.; Lisitchenko, T. Y.; Levada, G. I. [National Taras Shevchenko University of Kyiv, Volodymirs'ka str. 64, 01033 Kyiv (Ukraine)

2008-09-07

229

Lofting of Triboelectrostatically Charged Particles From the Lunar Surface  

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

230

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

231

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

232

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: March 25, 1994" In this paper we study the double layer interaction between two heterogeneous surfacesof, the surface forces are dominated by long-range electrostatics, the familiar double layer force.' For many

Chan, Derek Y C

233

Producing Nanocomposite Layer on the Surface of As-Cast AZ91 Magnesium Alloy by Friction Stir Processing  

NASA Astrophysics Data System (ADS)

Friction stir processing (FSP) is an effective tool to produce a surface composite layer with enhanced mechanical properties and modified microstructure of as-cast and sheet metals. In the present work, the mechanical and microstructural properties of as-cast AZ91 magnesium alloy were enhanced by FSP and an AZ91/SiC surface nanocomposite layer has been produced using 30 nm SiC particles. Effect of the FSP pass number on the microstructure, grain size, microhardness, and powder distributing pattern of the surface developed has been investigated. The developed surface nanocomposite layer presents a higher hardness, an ultra fine grain size and a better homogeneity. Results show that, increasing the number of FSP passes enhances distribution of nano-sized SiC particles in the AZ91 matrix, decreases the grain size, and increases the hardness significantly. Also, changing of the tool rotating direction results much uniform distribution of the SiC particles, finer grains, and a little higher hardness.

Asadi, P.; Besharati Givi, M. K.; Faraji, G.

234

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

235

Winter-to-Winter Recurrence of Sea Surface Temperature, Salinity and Mixed Layer Depth Anomalies  

Microsoft Academic Search

The mean seasonal cycle of mixed layer depth (MLD) in the extratropical oceans has the potential to influence temperature, salinity and mixed layer depth anomalies from one winter to the next. Temperature and salinity anoma- lies that form at the surface and spread throughout the deep winter mixed layer are sequestered beneath the mixed layer when it shoals in spring

Michael A. Alexander; Mike S. Timlin; James D. Scott

2000-01-01

236

Winter-to-winter recurrence of sea surface temperature, salinity and mixed layer depth anomalies  

Microsoft Academic Search

The mean seasonal cycle of mixed layer depth (MLD) in the extratropical oceans has the potential to influence temperature, salinity and mixed layer depth anomalies from one winter to the next. Temperature and salinity anomalies that form at the surface and spread throughout the deep winter mixed layer are sequestered beneath the mixed layer when it shoals in spring, and

Michael A Alexander; Michael S Timlin; James D Scott

2001-01-01

237

Global ocean wind power sensitivity to surface layer stability  

NASA Astrophysics Data System (ADS)

Global ocean wind power has recently been assessed (W. T. Liu et al., 2008) using scatterometry-based 10 m winds. We characterize, for the first time, wind power at 80 m (typical wind turbine hub height) above the global ocean surface, and account for the effects of surface layer stability. Accounting for realistic turbine height and atmospheric stability increases mean global ocean wind power by +58% and -4%, respectively. Our best estimate of mean global ocean wind power is 731 W m-2, about 50% greater than the 487 W m-2 based on previous methods. 80 m wind power is 1.2-1.5 times 10 m power equatorward of 30° latitude, between 1.4 and 1.7 times 10 m power in wintertime storm track regions and >6 times 10 m power in stable regimes east of continents. These results are relatively insensitive to methodology as wind power calculated using a fitted Weibull probability density function is within 10% of power calculated from discrete wind speed measurements over most of the global oceans.

Capps, Scott B.; Zender, Charles S.

2009-05-01

238

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

239

Surface Chemistry at Size-Selected Nano-Aerosol Particles  

NASA Astrophysics Data System (ADS)

A method has been developed to conduct surface chemistry and extract surface kinetic rates from size-selected aerosol nanoparticles. The measurements encompass broad ranges of particle size, phase, and composition. Results will be presented on the uptake of water by aerosolized soot nanoparticles of radius between 10 and 40 nm. Water uptake was monitored by tandem differential mobility analysis (T-DMA), which is capable of measuring changes in particle diameter as little as 0.2 nm. Soot particles were produced in an ethene diffusion flame and extracted into an atmospheric pressure aerosol flow tube reactor. The particles were subjected to various thermal and oxidative treatments, and the effects of these treatments on the ability of soot to adsorb monolayer quantities of water was determined. The results are important because soot nucleates atmospheric cloud particles. More generally, the results represent one of the first kinetic and mechanistic studies of gas-phase nanoparticle reactivity. Co-author: Henry Ajo, University of Minnesota

Roberts, Jeffrey

2005-03-01

240

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

241

A pressure-driven three-dimensional turbulent boundary layer documented with stereo particle image velocimetry  

Microsoft Academic Search

A three-dimensional turbulent boundary layer (3DTBL) over a flat plate is carefully documented with Stereo Particle Image Velocimetry (SPIV). At the first measurement station, the boundary layer is nearly two-dimensional with the following parameters: Red211 = 3972, delta = 78.45 mm, Cf = 0.0032 and Uinlet = 9.0 m\\/s. The secondary flow is generated via the removal of mass through

Steve Peter Gravante

2003-01-01

242

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

243

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

PubMed

Antisense oligonucleotides can be employed as a potential approach to effectively treat cancer. However, the inherent instability and inefficient systemic delivery methods for antisense therapeutics remain major challenges to their clinical application. Here, we present a polymerized oligonucleotides (ODNs) that self-assemble during their formation through an enzymatic elongation method (rolling circle replication) to generate a composite nucleic acid/magnesium pyrophosphate sponge-like microstructure, or DNA microsponge, yielding high molecular weight nucleic acid product. In addition, this densely packed ODN microsponge structure can be further condensed to generate polyelectrolyte complexes with a favorable size for cellular uptake by displacing magnesium pyrophosphate crystals from the microsponge structure. Additional layers are applied to generate a blood-stable and multifunctional nanoparticle via the layer-by-layer (LbL) assembly technique. By taking advantage of DNA nanotechnology and LbL assembly, functionalized DNA nanostructures were utilized to provide extremely high numbers of repeated ODN copies for efficient antisense therapy. Moreover, we show that this formulation significantly improves nucleic acid drug/carrier stability during in vivo biodistribution. These polymeric ODN systems can be designed to serve as a potent means of delivering stable and large quantities of ODN therapeutics systemically for cancer treatment to tumor cells at significantly lower toxicity than traditional synthetic vectors, thus enabling a therapeutic window suitable for clinical translation. PMID:25198246

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

2014-10-28

244

Split-screen single-camera stereoscopic PIV application to a turbulent confined swirling layer with free surface  

NASA Astrophysics Data System (ADS)

An annular liquid wall jet, or vortex tube, generated by helical injection inside a tube is studied experimentally as a possible means of fusion reactor shielding. The hollow confined vortex/swirling layer exhibits simultaneously all the complexities of swirling turbulence, free surface, droplet formation, bubble entrapment; all posing challenging diagnostic issues. The construction of flow apparatus and the choice of working liquid and seeding particles facilitate unimpeded optical access to the flow field. A split-screen, single-camera stereoscopic particle image velocimetry (SPIV) scheme is employed for flow field characterization. Image calibration and free surface identification issues are discussed. The interference in measurements of laser beam reflection at the interface are identified and discussed. Selected velocity measurements and turbulence statistics are presented at Re_{\\uplambda}=70 (Re = 3500 based on mean layer thickness).

Bardet, Philippe M.; Peterson, Per F.; Sava?, Ömer

2010-08-01

245

Simulation of Multi-Layer-Liquid Sloshing Effects on Vessel Motions by Using Moving Particle Simulation  

E-print Network

newly adopted models which are buoyancy-correction, surface tension, and boundary conditions at interfaces. Each new model is validated either mathematically or theoretically for comparison. Moreover, a new tracing method of interface particles...

Kim, Kyung Sung

2014-05-07

246

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

247

Effect of coarse particles on the heat transfer in a particle-laden turbulent boundary layer  

Microsoft Academic Search

The temperature distribution in particle-laden turbulent flow, in a flume, was investigated both by DNS and experimentally. Simulations were performed at Re=171 and Pr=5.4 in order to study the interaction between the particle motion and flow turbulence. Two-way coupling was used to obtain various turbulence statistics, the grid resolution was sufficiently fine to resolve all essential turbulent scales. The effect

G. Hetsroni; A. Mosyak; E. Pogrebnyak

2002-01-01

248

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

249

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

250

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

251

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

252

Comparison of the structures of the hot-work tool steels laser modified surface layers  

Microsoft Academic Search

Investigations include comparison between structure and properties of remelting and alloying the X40CrMoV5-1 hot-work tool steel surface layer using the high power diode laser (HPDL). The tungsten carbide powder was used as an alloying material. The X40CrMoV5-1 conventionally heat treated steel was used as reference material. The structural mechanism was determined of surface layers development. Development of the surface layer

L. A. Dobrza?ski; M. Bonek; E. Hajduczek; A. Klimpel; A. Lisiecki

2005-01-01

253

Charged particle sputtering of ice surfaces in Saturn's magnetosphere  

NASA Astrophysics Data System (ADS)

Following recent investigations of the Saturn system in situ by Pioneer 11 and Voyager 1 and 2 and remotely by the International Ultraviolet Explorer, the sputtering of water ice surfaces by magnetospheric ions has been reconsidered as a possible source of hydrogen atoms and heavy ions. Results from laboratory measurements of water ice sputtering and dissociation rates as a function of ice temperature are used, as well as Voyager charged particle data from the low energy charged particle experiment to obtain more accurate assessments of energetic ion fluxes and loss rates. Ion phase space densities show that, if charged particle sputtering is an important physical process, it will occur predominantly in the vicinity of Saturn's E ring and the moons Dione and Tethys, not at the outer edge of the A ring as previously suggested prior to the availability of in situ data. Charged particle sputtering of ice surfaces between 4.5 and 8 Saturnian radii followed by the ionization of H2O and dissociation fragments, may be an important local source of the heavy ion plasma reported in the magnetosphere by Pioneer 11. Several existing theories for the ring atmosphere are reviewed and it is concluded that difficulties remain with all of them.

Cheng, A. F.; Lanzerotti, L. J.; Pirronello, V.

1982-06-01

254

Calcination kinetics and surface area of dispersed limestone particles  

Microsoft Academic Search

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

R. H. Borgwardt

1985-01-01

255

The surface and through crack problems in layered orthotropic plates  

NASA Technical Reports Server (NTRS)

An analytical method is developed for a relatively accurate calculation of Stress Intensity Factors in a laminated orthotropic plate containing a through or part-through crack. The laminated plate is assumed to be under bending or membrane loading and the mode 1 problem is considered. First three transverse shear deformation plate theories (Mindlin's displacement based first-order theory, Reissner's stress-based first-order theory, and a simple-higher order theory due to Reddy) are reviewed and examined for homogeneous, laminated and heterogeneous orthotropic plates. Based on a general linear laminated plate theory, a method by which the stress intensity factors can be obtained in orthotropic laminated and heterogeneous plates with a through crack is developed. Examples are given for both symmetrically and unsymmetrically laminated plates and the effects of various material properties on the stress intensity factors are studied. In order to implement the line-spring model which is used later to study the surface crack problem, the corresponding plane elasticity problem of a two-bonded orthotropic plated containing a crack perpendicular to the interface is also considered. Three different crack profiles: an internal crack, an edge crack, and a crack terminating at the interface are considered. The effect of the different material combinations, geometries, and material orthotropy on the stress intensity factors and on the power of stress singularity for a crack terminating at the interface is fully examined. The Line Spring model of Rice and Levy is used for the part-through crack problem. The surface crack is assumed to lie in one of the two-layered laminated orthotropic plates due to the limitation of the available plane strain results. All problems considered are of the mixed boundary value type and are reduced to Cauchy type of singular integral equations which are then solved numerically.

Erdogan, Fazil; Wu, Binghua

1991-01-01

256

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

257

Interaction between surface and atmosphere in a convective boundary layer /  

E-print Network

or heat transfer) from rough and smooth surfaces at groundand heat transfer between surface and air. The cooler surface results in a smaller groundheat transfer between the surface and the air. The ground

Garai, Anirban

2013-01-01

258

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

259

Rate of evolution of the specific surface area of surface snow layers.  

PubMed

The snowpack can impact atmospheric chemistry by exchanging adsorbed or dissolved gases with the atmosphere. Modeling this impact requires the knowledge of the specific surface area (SSA) of snow and its variations with time. We have therefore measured the evolution of the SSA of eight recent surface snow layers in the Arctic and the French Alps, using CH4 adsorption at liquid nitrogen temperature (77 K). The SSA of fresh snow layers was found to decrease with time, from initial values in the range 613-1540 cm2/g to values as low as 257 cm2/g after 6 days. This is explained by snow metamorphism, which causes modifications in crystal shapes, here essentially crystal rounding and the disappearance of microstructures. A parametrization of the rate of SSA decrease is proposed. We fit the SSA decrease to an exponential law and find that the time constant alpha(exp) (day(-1)) depends on temperature according to alpha(exp) = 76.6 exp (-1708/7), with Tin kelvin. Our parametrization predicts that the SSA of a snow layer evolving at -40 degrees C will decrease by a factor of 2 after 14 days, while a similar decrease at -1 degrees C will only require 5 days. Wind was found to increase the rate of SSA decrease, but insufficient data did not allow a parametrization of this effect. PMID:12636262

Cabanes, Axel; Legagneux, Loïc; Dominé, Florent

2003-02-15

260

Surface pressure fluctuations in hypersonic turbulent boundary layers  

NASA Technical Reports Server (NTRS)

The surface pressure fluctuations on a flat plate model at hypersonic Mach numbers of 5.2, 7.4 and 10.4 with an attached turbulent boundary layer were measured using flush mounted small piezoelectric sensors. A high frequency resolution of the pressure field was achieved using specially designed small piezoelectric sensors that had a good frequency response well above 300 KHz. The RMS pressures and non-dimensional energy spectra for all above Mach numbers are presented. The convective velocities, obtained from space time correlation considerations are equal to 0.7 U sub infinity. The results indicate the RMS pressures vary from 5 to 25 percent of the mean static pressures. The ratios of RMS pressure to dynamic pressure are less than the universally accepted subsonic value of 6 x 10/3. The ratio decreases in value as the Mach number or the dynamic pressure is increased. The ratio of RMS pressure to wall shear for Mach number 7.4 satisfies one smaller than or equal to p/tau sub w smaller than or equal to three.

Raman, K. R.

1974-01-01

261

Surface Passivation by Quantum Exclusion Using Multiple Layers  

NASA Technical Reports Server (NTRS)

A semiconductor device has a multilayer doping to provide improved passivation by quantum exclusion. The multilayer doping includes a plurality M of doped layers, where M is an integer greater than 1. The dopant sheet densities in the M doped layers need not be the same, but in principle can be selected to be the same sheet densities or to be different sheet densities. M-1 interleaved layers provided between the M doped layers are not deliberately doped (also referred to as "undoped layers"). Structures with M=2, M=3 and M=4 have been demonstrated and exhibit improved passivation.

Hoenk, Michael E. (Inventor)

2013-01-01

262

X-ray bremsstrahlung by relativistic particles crossing a thin layer of a medium  

NASA Astrophysics Data System (ADS)

Anomalous phenomena in the relativistic electron bremsstrahlung are investigated theoretically for the case when an emitting particle crosses a thin layer of amorphous medium. Peculiarities in the manifestation of Ter-Mikaelian effect as well as unexpected oscillations in the spectral-angular distribution of emitted photons are shown in this work.

Nasonov, N.

2001-01-01

263

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

264

Surface Softening in Polymers and Their Nanocomposites Determined by Surface Mechanical Properties through Spontaneous Particle Embedment  

NASA Astrophysics Data System (ADS)

In the present work, we have used the particle embedment technique with sub-micron particles to estimate the surface modulus of epoxy/POSS composites at a temperature far below the glass transition temperature. The embedment of the particle is determined from atomic force microscope measurements and the modulus was determined using the elastic analysis of Johnson, Kendall and Roberts (JKR) with surface energy estimates of the work of adhesion as the driving force for embedment. The surface modulus values were found much smaller than the macroscopic modulus values. The maximum embedment depth obtained for all surfaces was low enough so that it did not cause plastic deformation on the surface. The maximum stress values on all surfaces induced by the particle embedment were estimated to verify the expected response in close to the linear regime. [4pt] [1] K. L. Johnson, K. Kendall and A. D. Roberts, P. Royal Society of Lonodon A, 324, 301-313 (1971). [0pt] [2] J. H. Teichroeb and J. A. Forrest, Physical Review Letter, 91, 016104 (2003).

Karim, Taskin; McKenna, Gregory

2011-03-01

265

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

266

Particle deposition on superhydrophobic surfaces by sessile droplet evaporation  

NASA Astrophysics Data System (ADS)

Prediction and active control of the spatial distribution of particulate deposits obtained from sessile droplet evaporation is essential in ink-jet printing, nanostructure assembly, biotechnology, and other applications that require localized deposits. In recent years, sessile droplet evaporation on bio-inspired superhydrophobic surfaces has become an attractive method for depositing materials on a site-specific, localized region, but is less explored compared to evaporative deposition on hydrophilic surfaces. It is therefore of interest to understand particle deposition during droplet evaporation on superhydrophobic surfaces to enable accurate prediction and tunable control of localized deposits on such surfaces. The purpose of the present work is to explore the morphology of particles deposited on superhydrophobic surfaces by the evaporation of sessile water droplets containing suspended latex spheres. Droplet evaporation experiments are performed on non-wetting, textured surfaces with varying geometric parameters. The temporal evolution of the droplet contact radius and contact angle throughout the evaporation process are tracked by visualizing the transient droplet shape and wetting behavior. The droplets are observed to exhibit a combination of the following modes of evaporation: the constant contact radius mode, the constant contact angle mode, and the mixed mode in which the contact angle and the contact radius change simultaneously. After complete dry-out, the remaining particulate deposits are qualitatively and quantitatively characterized to describe their spatial distribution. In the first part of the study, the test surfaces are maintained at different temperatures. Experiments are conducted at ambient conditions and at elevated substrate temperatures of approximately 40°C, 50°C, and 60°C. The results show that droplet evaporation on superhydrophobic surfaces, driven by either mass diffusion at ambient conditions or by substrate heating, suppresses deposition of particles at the contact-line during droplet evaporation. This behavior provides an effective means of localizing the deposition of suspended particles. In the second part of the study, the droplets are allowed to evaporate at ambient conditions on test substrates with significant relative differences in surface morphology. These differing surfaces yield a wide range of surface wettability as a means to control the particulate deposition process. Analysis of the droplet wetting behavior throughout the evaporation process show that the droplet could either remain in the Cassie state (resting on top of the roughness elements) or transition into the Wenzel state (roughness elements flooded). Top- and side-view images of the droplet profile are visualized to confirm the droplet wetting state near the end of evaporation. Experimental observations are compared with a theoretical trend of the Cassie-to-Wenzel transition based on the capillary-Laplace pressure balance at transition between wetting states. The results reveal a relationship between localized deposit size and surface morphology based on this ultimate wetting state. An optimum surface morphology for minimizing the deposit coverage area is identified.

Dicuangco, Mercy Grace

267

Wettability of terminally anchored polymer brush layers on a polyamide surface.  

PubMed

Surface wettability of terminally anchored hydrophilic polymer brush layers on polyamide-silicon (PA-Si) surfaces was evaluated with respect to surface topography at the nanoscale. Hydrophilic polyvinylpyrrolidone (PVP) and polyacrylamide (PAAm) brush layers were synthesized via graft polymerization onto a PA-Si surface previously activated by surface treatment with atmospheric pressure plasma. Hydrophilicity (or wettability) of the PA substrate, as quantified by the free energy of hydration, was increased upon surface coverage with the PVP and PAAm brush layers by 13-24% (-101.4 to -111.3 mJ/m(2)) and 19-37% (-106.1 to -122.4 mJ/m(2)), respectively. Surface hydrophilicity increased with both increasing surface roughness (0.55-2.89 nm and 1.54-5.84 nm for PVP and PAAm, respectively) and polymer volume (1.3×10(6)-7.3×10(6) nm(3)/?m(2) and 3.3×10(6)-2.8×10(7) nm(3)/?m(2) for PVP and PAAm surfaces, respectively). The present study suggests that a specific level of surface wettability can be attained by tailor-designing the polymer brush layer's physicochemical characteristics (e.g., surface roughness, wettability, and polymer water affinity) by adjusting surface topography and surface chemistry, which are controlled by surface activation and polymerization conditions. The above indicates that there is merit in structuring various surfaces with hydrophilic brush layers to increase surface wettability in membrane filtration, biomedical devices, and lubrication applications. PMID:25305445

Varin, Kari J Moses; Cohen, Yoram

2014-12-15

268

Exothermic surface chemistry on aluminum particles promoting reactivity  

NASA Astrophysics Data System (ADS)

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

Mulamba, Oliver; Pantoya, Michelle L.

2014-10-01

269

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

270

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

NASA Astrophysics Data System (ADS)

Bifunctional monodispersed Fe3O4 particles coated with an ultrathin Y2O3:Tb3+ shell layer were fabricated using a facile urea-based homogeneous precipitation method. The obtained composite particles were characterized by powder X-ray diffraction, transmission electron microscopy (TEM), quantum design vibrating sample magnetometry, and photoluminescence (PL) spectroscopy. TEM revealed uniform spherical core-shell-structured composites ranging in size from 306 to 330 nm with a shell thickness of approximately 25 nm. PL spectroscopy confirmed that the synthesized composites displayed a strong eye-visible green light emission. Magnetic measurements indicated that the composite particles obtained also exhibited strong superparamagnetic behavior at room temperature. Therefore, the inner Fe3O4 core and outer Y2O3:Tb3+ shell layer endow the composites with both robust magnetic properties and strong eye-visible luminescent properties. These composite materials have potential use in magnetic targeting and bioseparation, simultaneously coupled with luminescent imaging.

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

2013-08-01

271

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

272

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

273

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

274

5A.8 IDENTIFYING NONSTATIONARITY IN THE ATMOSPHERIC SURFACE LAYER Edgar L Andreas*1  

E-print Network

--especially the atmospheric surface layer--relies on two assumptions that seem at odds with this depiction of the atmospheric cooler than in full sunlight. Hence, a meteorological tower fixed on the surface would experience

Geiger, Cathleen

275

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

PubMed

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

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

2014-02-01

276

Exploring the Depletion Layer: An Investigation into How Water Reacts when Confined to a Hydrophobic Surface  

NASA Astrophysics Data System (ADS)

We observe water interacting with surfaces everyday. It forms spherical drops on hydrophobic surfaces, such as a freshly waxed car, and it spreads out on hydrophilic surfaces. However, water acts much differently when it is confined to a hydrophobic area. In our experiment, Surface Plasmon Resonance (SPR) is utilized to find differences in surface conditions. Tests are done for the interface of a hydrophobic surface surrounded by water and also for a hydrophobic surface surrounded by methanol, which we know will not form a depletion layer. With this data we are able to analyze the optical properties of the depletion layer in much greater detail.

Marx, Isaac; Poynor, Adele

2011-03-01

277

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

SciTech Connect

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

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

2011-06-15

278

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

279

Direct measurements of ensemble particle and surface interactions on homogeneous and patterned substrates  

E-print Network

in colloidal ensembles levitated above macroscopic surfaces. TIRM and VM are well established optical microscopy techniques for measuring normal and lateral colloidal excursions near macroscopic planar surfaces. The interactions between particle-particle...

Wu, Hung-Jen

2006-08-16

280

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

281

Atmospheric sounding over the winter Kuroshio Extension: Effect of surface stability on atmospheric boundary layer structure  

E-print Network

: Effect of surface stability on atmospheric boundary layer structure, Geophys. Res. Lett., 33, L04703, doi the Pacific equatorial front [Hashizume et al., 2002] show marked changes in atmospheric boundary layer (ABL boundary layer structure Hiroki Tokinaga,1,2 Youichi Tanimoto,3,4 Masami Nonaka,5 Bunmei Taguchi,6 Tomohiro

Xie, Shang-Ping

282

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

283

THEORY AND MEASUREMENTS FOR TURBULENCE SPECTRA AND VARIANCES IN THE ATMOSPHERIC NEUTRAL SURFACE LAYER  

E-print Network

LAYER ULF HÃ?GSTRÃ?M1, J. C. R. HUNT2 and ANN-SOFI SMEDMAN1 1Uppsala University, Department of Earth 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

Hunt, Julian

284

On the suspension mechanism of small heavy particles in a horizontal turbulent boundary layer flow, pipe flow or channel flow  

Microsoft Academic Search

Developments of Lumley's mixing length model for the heavy particle suspension mechanism are summarized. Lumley's model is only valid in the constant stress layer, not in the viscous sublayer and generation layer. Experimental results show that in the latter regions deposition occurs in downsweeps, whereas particle detachment and reentrainment are caused by ejections. Predictions of a model for the heavy

G. Ooms; F. G. J. Absil

1983-01-01

285

The Role of Adsorbed Water on the Friction of a Layer of Submicron Particles CHARLES G. SAMMIS,1  

E-print Network

friction with an apparent coefficient near l = 0.6 at low slip speeds to a coefficient near l = 0 layer enables the otherwise rough particles to rotate, the coefficient of friction will drop to l = 0 layer vaporizes, the particles contact and lock, and the coefficient of friction rises to l = 0

Ze'ev, Reches

286

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

287

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

288

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

289

Determination of physical properties of planetary sub-surface layers by artificial impacts and penetrometry  

Microsoft Academic Search

In recent years the exploration of planetary bodies by surface probes has entered a new phase of interest. The mechanical properties of the near-surface layers of cometary and planetary bodies, including their strength, texture and layering, are important parameters needed both for a proper physical understanding of these bodies and for the design of lander missions.The strength properties of such

N. I. Kömle; G. Kargl; A. J. Ball

2001-01-01

290

Comparison of regional surface fluxes from boundary-layer budgets and aircraft measurements above boreal forest  

Microsoft Academic Search

Daytime surface sensible and latent heat fluxes (H s and ;Es) above boreal forest, derived independently from the boundary-layer budgets of heat and water vapor and by eddy correlation from the Twin Otter aircraft, are compared. The aircraft and boundary-layer budget values of Hs + ;Es underestimated surface available energy by 25% and 4%, respectively, when the sum of the

Alan G. Barr; Alan K. Betts; R. L. Desjardins; J. I. MacPherson

1997-01-01

291

Mass sensitivity of layered shear-horizontal surface acoustic wave devices for sensing applications  

Microsoft Academic Search

Layered Surface Acoustic Wave (SAW) devices that allow the propagation of Love mode acoustic waves will be studied in this paper. In these devices, the substrate allows the propagation of Surface Skimming Bulks Waves (SSBWs). By depositing layers, that the speed of Shear Horizontal (SH) acoustic wave propagation is less than that of the substrate, the propagation mode transforms to

Kourosh Kalantar-Zadeh; Adrian Trinchi; Wojtek Wlodarski; Anthony Holland; Kosmas Galatsis

2001-01-01

292

Contribution of surface and subsurface layers of soil on wheat nutrition under fertilized and unfertilized conditions  

Microsoft Academic Search

A pot experiment was conducted to study the contribution of surface and subsurface layers of soil on wheat nutrition under fertilized and unfertilized conditions. Artificial columns of soils were used for this purpose. A column consisted of three layers of different soils, varying in their native P, and concomitant chemical and physical properties.A rise in the surface fertility increased the

I. M. Chhibba; G. S. Sekhon

1983-01-01

293

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

294

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

295

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

PubMed

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

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

2009-05-14

296

Particle migration and free-surface topography in inclined plane flow of a suspension  

NASA Astrophysics Data System (ADS)

Gravity-driven free-surface flow of a suspension of neutrally buoyant particles down an inclined plane channel of constant width has been studied experimentally and by flow modelling. A uniform suspension of spheres, sieved to radii of a {=} 53-125 ?m or 125 150 ?m, was introduced to create films of initial depth h_o. The flow was always at small film-depth-based Reynolds numbers. The film depth and the mixture flow profile were measured at the initial and two locations at least 200 h_o and 400 h_o downstream. The bulk particle volume fraction, phi_B, was varied in the range 0.01 {le} phi_B {le} 0.5; h_o {approx} 1.8 3.2 mm and the inclination angle relative to horizontal, 0.1^{circ} {<} alpha {le} 90^{circ}, were also varied. Analysis of the particle velocity was performed by stereoscopic imaging to determine particle location followed by particle correlation velocimetry. A two-layer Newtonian viscosity model was applied to the velocimetry results in order to infer particle concentration information. Measured velocity profiles and film depth show that film thickness decreases from h_o, while the velocity gradient at the wall and the mean velocity increase, as the mixture flows down the plane. The free surface, examined using direct imaging, becomes progressively more deformed as alpha and phi_B increase, with the onset of observable deformation found at a particle-scale capillary number of hboxCa_{p} {sim} {rho g_x a^2}/{sigma} {=} O(10^{-4}); rho is the mixture density, g_x {=} g sin alpha is the axial component of gravitational acceleration and sigma is the surface tension of the suspending liquid. An existing model for suspension flow which describes phase migration as driven by normal stresses caused by the suspended particles is used to predict the flow, with satisfactory agreement for film depth and development distance for the non-uniform local solid volume fraction, phi. The agreement with the detailed phi profile is less good, as the model fails to predict the observed phi {approx} 0 near the solid boundary while phi$ is overpredicted adjacent to the free surface.

Timberlake, Brian D.; Morris, Jeffrey F.

2005-08-01

297

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

298

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

299

Monolithic surface micromachined fluidic devices for dielectrophoretic preconcentration and routing of particles  

NASA Astrophysics Data System (ADS)

We describe a batch fabrication process for producing encapsulated monolithic microfluidic structures. The process relies on sacrificial layers of silicon oxide to produce surface micromachined fluid channels. Bulk micromachined interconnects provide an interface between the microchannels and meso-scale fluidics. The full integration of the fabrication processing significantly increases device reproducibility and reduces long-term costs. The design and fabrication of dielectrophoresis (DEP) gating structures configured in both batch-flow and continuous-flow modes are detailed. Highly efficient microparticle preconcentration (up to ~100× in 100 s) and valving (97% particle routing efficiency) are demonstrated using ac DEP and an accompanying phase separation. The low aspect-ratio fluid channels with integrated microelectrodes are well suited for µm and sub-µm particle manipulation with electric fields.

James, Conrad D.; Okandan, Murat; Mani, Seethambal S.; Galambos, Paul C.; Shul, Randy

2006-10-01

300

Transient behavior of the hydrophobic surface/water interface: from nanobubbles to organic layer.  

PubMed

We report the formation and subsequent change of the water-depleted layer at a hydrophobic surface/water interface. With water as the solvent, surface plasmon resonance measurements indicate time dependent evolution of two separate states. The first state is the water-depleted layer, and it is characterized by a layer of nanobubbles on the surface and is short-lived in time (order of 10 min). The second state is a final equilibrium state, which occurs in approximately 30 h, where a layer is formed with organic characteristics. If, instead of water, an aqueous solution is exposed to the hydrophobic surface, the evolution from nanobubbles to an organic like layer shows dependency on the surface energy of the liquid media. PMID:18047320

Martinez, Julio; Stroeve, Pieter

2007-12-27

301

Effect of particle size on the surface properties and morphology of ground flax.  

PubMed

Flax fibers were ground with a ball-mill and four fractions with different size ranges were collected by sieving. These were tested for water sorption, degree of polymerization (DP), copper number, hydroxyl number and analyzed by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and inverse gas chromatography (IGC). Significant differences were found between the properties of the flax fiber and those of the ground versions, including fragmentation of fibers, increase of water sorption, copper number, hydroxyl number and surface O/C ratio, and decrease of DP, crystallite size and dispersive component of surface energy (?s(d)). Some parameters depended on the particle size: O/C ratio and hydroxyl number had local maxima at 315-630 ?m, while ?s(d) increased steadily with the decrease of particle size. These relationships were explained by fiber disintegration, destruction of waxy surface layer, exposure of cellulosic components, increase of surface area and crystalline imperfections. PMID:23544651

Csiszár, E; Fekete, E; Tóth, A; Bandi, E; Koczka, B; Sajó, I

2013-05-15

302

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...

303

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

304

Analysis of convection in immiscible liquid layers with novel particle tracking velocimetry  

NASA Technical Reports Server (NTRS)

The problem under study is convective flow in immiscible liquid layers with one or two horizontal interfaces. In one-g the flow results primarily from the buoyancy force acting perpendicular to the interfaces. This creates a fluid mechanical system in which the coupling of the fluid layers across an interface plays a fundamental role. The contribution of two horizontal interface tension forces is marginal. Interface tension driven flow requires testing in microgravity. A flight experiment on the Bubble, Drop, and Particle Unit (BDPU) is planned for the second International Microgravity Laboratory (IML-2) mission onboard the Shuttle in 1994. The flow velocity fields will be analyzed by a whole-field Particle Displacement Tracking (PDT) velocimetry technique. The capabilities of this technique to address fundamental issues, such as those regarding the flow stucture, will be discussed with a few sample experiments. Experimental and numerical flow patterns are compared.

Koster, J. N.; Prakash, A.; Campbell, T. A.; Pline, A.

1992-01-01

305

Turbulence Spectra in the Surface Layer with a Steady Surface Thermal Inversion  

NASA Astrophysics Data System (ADS)

the EBEX-2000 (International Energy Balance Experiment, 2000, EBEX-2000) was carried out over a flood- irrigated cotton field with very strong evaporation and transpiration. And thus the latent heat flux took most part of the solar radiation and the sensible heat flux, which would directly heat the atmosphere, was very small and even became negative in mid-afternoon. Therefore, the thermal turbulence was suppressed and there always existed a surface thermal inversion during the observation. The temperatures measured at 8.7 m were always higher than that at 2.7 m, which further restrained the development of the turbulence in the lower part of the surface layer, and the turbulence exchanges for the momentum, energy and other were restrained too. Owing to strong action of the underlying surface, there is distinct wind shear, and the nearer the distance to the ground, the stronger the wind shear. Moreover, the surface thermal inversion makes the wind shear sustainable and stable. On the other hand, due to the strong blocking and friction action of the underlying surface, eddies would be strongly impacted when they came close to the ground, in particular for small eddies. That is to say, the nearer the distance to the ground, the stronger the influence of the ground on small eddies and the larger the range of eddy-size that can be directly influenced by the ground. Both the above factors contribute to the differences between the spectra at intermediate frequencies at the two heights: the horizontal power spectrum at 8.7 m does not obey -1 power law at intermediate frequencies, but it does at 2.7 m. The vertical power spectra at 8.7 m are somewhat flatter and broader at the spectral peak, while they are sharper and narrower at 2.7 m.

Peng, Z.; Hu, F.; Ma, X.; Liu, S.

2007-12-01

306

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

307

Study of microstructure of surface layers of low-carbon steel after turning and ultrasonic finishing  

NASA Astrophysics Data System (ADS)

Profilometry and optical and transmission electron microscopy are used to examine the microstructure of surface layers of a low-carbon ferrite-pearlite steel subjected to turning and ultrasonic finishing. It is shown that turning peaks and valleys have different microstructures, which stipulates manifestation of technological hereditary when processing surfaces of machined parts. Ultrasonic finishing causes the severe plastic deformation of the surface layer, which favors the elimination of a technological heredity that is acquired during turning.

Kovalevskaya, Zh. G.; Ivanov, Yu. F.; Perevalova, O. B.; Klimenov, V. A.; Uvarkin, P. V.

2013-01-01

308

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

SciTech Connect

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 order to 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 that the 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. 24 refs., 1 fig., 4 tabs.

Nadia Ghedini; Cristina Sabbioni; Alessandra Bonazza; Giancarlo Gobbi [National Research Council (CNR), Bologna (Italy). Institute of Atmospheric Sciences and Climate

2006-02-01

309

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

310

Particle image velocimetry for the Surface Tension Driven Convection Experiment using a particle displacement tracking technique  

NASA Technical Reports Server (NTRS)

The Surface Tension Driven Convection Experiment (STDCE) is a Space Transportation System flight experiment to study both transient and steady thermocapillary fluid flows aboard the USML-1 Spacelab mission planned for 1992. One of the components of data collected during the experiment is a video record of the flow field. This qualitative data is then quantified using an all electronic, two-dimensional particle image velocimetry technique called particle displacement tracking (PDT) which uses a simple space domain particle tracking algorithm. The PDT system is successful in producing velocity vector fields from the raw video data. Application of the PDT technique to a sample data set yielded 1606 vectors in 30 seconds of processing time. A bottom viewing optical arrangement is used to image the illuminated plane, which causes keystone distortion in the final recorded image. A coordinate transformation was incorporated into the system software to correct this viewing angle distortion. PDT processing produced 1.8 percent false identifications, due to random particle locations. A highly successful routine for removing the false identifications was also incorporated, reducing the number of false identifications to 0.2 percent.

Wernet, Mark P.; Pline, Alexander D.

1991-01-01

311

Particle image velocimetry for the surface tension driven convection experiment using a particle displacement tracking technique  

NASA Technical Reports Server (NTRS)

The Surface Tension Driven Convection Experiment (STDCE) is a Space Transportation System flight experiment to study both transient and steady thermocapillary fluid flows aboard the USML-1 Spacelab mission planned for 1992. One of the components of data collected during the experiment is a video record of the flow field. This qualitative data is then quantified using an all electronic, two-dimensional particle image velocimetry technique called particle displacement tracking (PDT) which uses a simple space domain particle tracking algorithm. The PDT system is successful in producing velocity vector fields from the raw video data. Application of the PDT technique to a sample data set yielded 1606 vectors in 30 seconds of processing time. A bottom viewing optical arrangement is used to image the illuminated plane, which causes keystone distortion in the final recorded image. A coordinate transformation was incorporated into the system software to correct this viewing angle distortion. PDT processing produced 1.8 percent false identifications, due to random particle locations. A highly successful routine for removing the false identifications was also incorporated, reducing the number of false identifications to 0.2 percent.

Wernet, Mark P.; Pline, Alexander D.

1991-01-01

312

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

313

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 140nm. 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

314

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

PubMed

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. PMID:23114378

Zeng, Yan; von Klitzing, Regine

2012-11-21

315

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

316

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

317

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

NASA Astrophysics Data System (ADS)

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.

U?ur, ?ule S.; Sar????k, Merih; Akta?, A. Hakan; Uçar, M. Çi?dem; Erden, Emre

2010-07-01

318

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

319

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

320

Spatial simulation of boundary layer instability - Effects of surface roughness  

NASA Technical Reports Server (NTRS)

The effects of an isolated, two-dimensional roughness element on the spatial development of instability waves in boundary layers are investigated by numerically integrating the two-dimensional, time-dependent, incompressible Navier-Stokes equations, using a finite difference/Chebyshev discretization. It is shown that (high) inviscid frequencies have higher growth rates than Tollmien-Schlichting frequencies, indicating that disturbances growing in the separation zone are controlled by the inviscid instability of the shear layer at the edge of the separation zone.

Danabasoglu, G.; Bringen, S.; Streett, C. L.

1993-01-01

321

Layer-by-layer assembly of polysaccharide-based nanostructured surfaces containing polyelectrolyte complex nanoparticles.  

PubMed

Nanoscale chemical and topographical features have been demonstrated to influence a variety of significant responses of mammalian cells to biomaterials surfaces. Thus, an important goal for biomaterials scientists is the ability to engineer the nanoscale surface features of biologically active materials. The goal of the current work is to demonstrate that polyelectrolyte complex nanoparticles (PCNs) in polyelectrolyte multilayers (PEMs) can be combined to create surfaces with controlled nanoscale surface topography and nanoscale presentation of surface chemistry. The polysaccharides used in this work are the biomedically relevant chitosan, heparin, and hyaluronan. Nanostructured surface coatings were characterized on both modified gold substrates and tissue-culture polystyrene surfaces. PCNs were adsorbed to oppositely charged PEMs, and were also embedded within PEMs. The construction of the surface coatings was characterized by quartz crystal microbalance with dissipation (QCM-D). The surface morphology was characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The chemistry of the coatings was confirmed by both X-ray photoelectron spectroscopy (XPS) and polarization modulation infra-red reflection absorption spectroscopy (PM-IRRAS). Morphologically, we found that PCNs were colloidally stable and homogeneously distributed when adsorbed on or in the PEMs. Chemical analysis confirms that the PCNs adsorbed to PEMs significantly altered the surface chemistry, indicating significant surface coverage. Furthermore, the position of the PCNs normal to the surface can be adjusted by adding PEMs on top of adsorbed PCNs. Thus, PCNs can be used to introduce discrete nanoscale surface topographical features and varying surface chemistry into PEM surface coatings in a controlled way. PMID:20137902

Boddohi, Soheil; Almodóvar, Jorge; Zhang, Hao; Johnson, Patrick A; Kipper, Matt J

2010-05-01

322

Quality of the surface layer and operating properties of aircraft engine components  

NASA Astrophysics Data System (ADS)

The papers presented in this volume are concerned with analytical determination of the distribution of surface layer parameters in aircraft engine parts during machining, effect of surface layer parameters on the service-related characteristics of gas turbine engines, and automation of the design of technological processes which would ensure the required properties of the surface layer. Specific topics discussed include determination of the hardening modulus of machined materials, calculation of the process-induced residual stresses from friction test results, effect of ion treatment methods on the residual strength of blades, and automation of process design with incorporation of the hardening-finishing treatment of parts.

Bez'iazychnyi, V. F.

323

Surface layering and melting in an ionic liquid studied by resonant soft X-ray reflectivity  

PubMed Central

The molecular-scale structure of the ionic liquid [C18mim]+[FAP]? near its free surface was studied by complementary methods. X-ray absorption spectroscopy and resonant soft X-ray reflectivity revealed a depth-decaying near-surface layering. Element-specific interfacial profiles were extracted with submolecular resolution from energy-dependent soft X-ray reflectivity data. Temperature-dependent hard X-ray reflectivity, small- and wide-angle X-ray scattering, and infrared spectroscopy uncovered an intriguing melting mechanism for the layered region, where alkyl chain melting drove a negative thermal expansion of the surface layer spacing. PMID:23431181

Mezger, Markus; Ocko, Benjamin M.; Reichert, Harald; Deutsch, Moshe

2013-01-01

324

Atomic Layer Deposition to Fine-Tune the Surface Properties and Diameters of Fabricated Nanopores  

Microsoft Academic Search

Atomic layer deposition of alumina enhanced the molecule sensing characteristics of fabricated nanopores by fine-tuning their surface properties, reducing 1\\/f noise, neutralizing surface charge to favor capture of DNA and other negative polyelectrolytes, and controlling the diameter and aspect ratio of the pores with near single Ångstrom precision. The control over the chemical and physical nature of the pore surface

Peng Chen; Toshiyuki Mitsui; Damon B. Farmer; Jene Golovchenko; Roy G. Gordon; Daniel Branton

2004-01-01

325

MEASUREMENTS OF CONFORMATION CHANGES DURING ADHESION OF LIPID PROTEIN (POLYLYSINE AND S-LAYER) SURFACES  

EPA Science Inventory

The adhesion forces between various surfaces were measured using the "surface forces apparatus" technique which allows for the thickness of surface layers and the adhesion force between them to be directly measured in controlled vapor or liquid environments. hree types of biologi...

326

Using radar sea echo to estimate surface layer refractivity profiles  

Microsoft Academic Search

A method for inferring the atmospheric boundary layer evaporation duct height from sea clutter is described. The method is based on the observation that the radar signal from the evaporation duct manifests itself in the slope of the clutter power, while the horizontal variability of the sea clutter RCS (radar cross section) is a contaminant in the problem. The inversion

L. Ted ROgersl; Claude P. Hattan; Jeffery L. Krolik

1999-01-01

327

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

328

Cryoscanning electron microscopic study of the surface amorphous layer of articular cartilage.  

PubMed Central

In order to elucidate the structure near the articular surface, frozen unfixed hydrated articular cartilage with subchondral bone from the pig knee was examined using a cryoscanning electron microscope (cryo-SEM). This method is considered to reduce the introduction of artefacts due to fixation and drying. An amorphous layer, without a collagen-fibril network or chondrocytes, covered most of the surface of the cartilage. This layer was termed the surface amorphous layer. It showed various appearances, which were classified into 4 groups. The average thickness of the layer did not differ among the 8 anatomical regions from which the specimens were taken. The thickness of the layer was found to correlate with the type of appearance of the layer. The 4 appearances associated with thicknesses in descending order are: 'streaked', 'foliate', 'spotted', and 'vestigial'. The surface layer observed in the cryo-SEM was thicker than that observed by a conventional SEM. This difference may be attributable to dehydration of the specimen used in specimen preparation for the latter technique. The layer was also observed in articular cartilage taken from human and rabbit knees. The layer was found to be unstable and to have very variable features. Its thickness and appearance may be influenced by various factors such as dehydration, fluid absorption or mechanical stress. Images Fig. 1 Fig. 3 Fig. 5 Fig. 6 Fig. 7 Fig. 8 Fig. 9 Fig. 10 Fig. 11 Fig. 12 Fig. 13 Fig. 14 Fig. 15 Fig. 16 Fig. 17 Fig. 18 Fig. 19 PMID:7592006

Kobayashi, S; Yonekubo, S; Kurogouchi, Y

1995-01-01

329

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

PubMed

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

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

2014-07-10

330

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

331

On a relation between particle size distribution and mixing layer height  

NASA Astrophysics Data System (ADS)

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

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

2011-11-01

332

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

333

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

334

Preparation of a Langmuir-Blodgett layer of ultrafine platinum particles and its application to n-Si for efficient photoelectrochemical solar cells  

SciTech Connect

A Langmuir layer of ultrafine platinum particles (2--6 nm in diam) has been developed on a water surface by dropping a Pt colloid solution, prepared by refluxing an ethanol-water (1:1) solution of hexachloroplatinic(IV) acid in the presence of poly(N-vinyl-2-pyrrolidone) as a stabilizer. The layer is transferred onto a single-crystal n-type silicon (n-Si) wafer by the horizontal lifting method. The Pt particles are rather homogeneously scattered on n-Si, and the particle density can be controlled on a nanometer scale by changing the area of the Langmuir layer at the time of transfer. The open-circuit photovoltage (V[sub oc]) for photoelectrochemical (PEC) solar cells with such n-Si electrodes is inversely related to Pt-particle density, and reaches 0.635 V, much higher than that for n-Si coated with a continuous Pt layer (ca. 0.30 V) or that for the conventional p-n junction Si solid solar cell of a similar simple cell structure (ca. 0.59 V). This result is in harmony with the previously proposed theory, the above increase in V[sub oc] being explained by the decrease in the majority carrier dark saturation current density.

Yae, Shinji; Nakanishi, Isao; Nakato, Yoshihiro; Mori, Hirotaro (Osaka Univ. (Japan)); Toshima, Naoki (Univ. of Tokyo (Japan). Dept. of Industrial Chemistry)

1994-11-01

335

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

PubMed

The National Institute for Occupational Safety and Health (NIOSH) developed a standard for respirator certification under 42 CFR Part 84, using a TSI 8130 automated filter tester with photometers. A recent study showed that photometric detection methods may not be sensitive for measuring engineered nanoparticles. Present NIOSH standards for penetration measurement are mass-based; however, the threshold limit value/permissible exposure limit for an engineered nanoparticle worker exposure is not yet clear. There is lack of standardized filter test development for engineered nanoparticles, and development of a simple nanoparticle filter test is indicated. To better understand the filter performance against engineered nanoparticles and correlations among different tests, initial penetration levels of one fiberglass and two electret filter media were measured using a series of polydisperse and monodisperse aerosol test methods at two different laboratories (University of Minnesota Particle Technology Laboratory and 3M Company). Monodisperse aerosol penetrations were measured by a TSI 8160 using NaCl particles from 20 to 300 nm. Particle penetration curves and overall penetrations were measured by scanning mobility particle sizer (SMPS), condensation particle counter (CPC), nanoparticle surface area monitor (NSAM), and TSI 8130 at two face velocities and three layer thicknesses. Results showed that reproducible, comparable filtration data were achieved between two laboratories, with proper control of test conditions and calibration procedures. For particle penetration curves, the experimental results of monodisperse testing agreed well with polydisperse SMPS measurements. The most penetrating particle sizes (MPPSs) of electret and fiberglass filter media were ~50 and 160 nm, respectively. For overall penetrations, the CPC and NSAM results of polydisperse aerosols were close to the penetration at the corresponding median particle sizes. For each filter type, power-law correlations between the penetrations measured by different instruments show that the NIOSH TSI 8130 test may be used to predict penetrations at the MPPS as well as the CPC and NSAM results with polydisperse aerosols. It is recommended to use dry air (<20% RH) as makeup air in the test system to prevent sodium chloride particle deliquescing and minimizing the challenge particle dielectric constant and to use an adequate neutralizer to fully neutralize the polydisperse challenge aerosol. For a simple nanoparticle penetration test, it is recommended to use a polydisperse aerosol challenge with a geometric mean of ~50 nm with the CPC or the NSAM as detectors. PMID:22752097

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

2012-07-01

336

Infrared and Raman spectroscopic studies on iron oxide magnetic nano-particles and their surface modifications  

NASA Astrophysics Data System (ADS)

Iron oxide magnetic nano-particles (MNPs) have been prepared in aqueous solution by a modified co-precipitation method. Surface modifications have been carried out using tetraethoxysilane (TEOS), triethoxysilane (TES) and 3-aminopropyltrimethoxysilane (APTMS). The uncoated and coated particle products have been characterized with transmission electron microscope (TEM), energy dispersive X-ray (EDX) spectroscopy, infrared (IR) and Raman spectroscopy, and thermal gravimetric analysis (TGA). The particle sizes were determined from TEM images and found to have mean diameters of 13, 16 and 14 nm for Fe3O4, TES/Fe3O4 and APTMS/Fe3O4, respectively. IR and Raman spectroscopy has been applied to study the effect of thermal annealing on the uncoated and coated particles. The results have shown that magnetite nano-particles are converted to maghemite at 109 °C and then to hematite by 500 °C. In contrast, the study of the effect of thermal annealing of micro-crystalline magnetite by IR spectroscopy revealed that the conversion to hematite began by 300 °C and that no maghemite could be identified as an intermediate phase. IR spectra and TGA measurements revealed that the Si-H and 3-aminopropyl functional groups in TES and APTMS coated magnetite nano-particles decomposed below 500 °C while the silica layer around the iron oxide core remained unchanged. The molecular ratio of APTMS coating to iron oxide core was determined to be 1:7 from the TGA data. Raman scattering signals have indicated that MNPs could be converted to maghemite and then to hematite using increasing power of laser irradiation in a manner similar to that observed for thermal annealing.

Li, Ying-Sing; Church, Jeffrey S.; Woodhead, Andrea L.

2012-04-01

337

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

338

Dusty Plasma Technology of DCM with Nanostructure Surface Layer Production  

NASA Astrophysics Data System (ADS)

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.; Pal, A. F.; Petrov, O. F.; Ryabinkin, A. N.; Serov, A. O.; Shulga, Yu. M.; Starostin, A. N.; Fortov, V. E.

2008-09-01

339

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

340

Loading and release of fluorescent dye from layer-by-layer film-coated magnetic particles in response to hydrogen peroxide.  

PubMed

Polymer-coated magnetic particles (MPs) were prepared to study the binding of fluorescence dye on the surface and its H2O2-induced release. For this goal, multilayer films were prepared by layer-by-layer deposition of shikimic acid-appended poly(allylamine hydrochloride) (SA-PAH) and poly(styrenesulfonate) (PSS) on the surface of MPs. 3-(Dansylamino)phenylboronic acid (DPBA) was loaded on the MPs through boronate ester bonding between SA-PAH and DPBA. DPBA was released from the MPs in response to H2O2 as a result of breakage of the boronate ester bond by an oxidative reaction with H2O2. DPBA release was dependent on the H2O2 concentration. For example, 65% and 93% of the DPBA was released from (SA-PAH/PSS)4SA-PAH film-coated MPs in 30min after the addition of 0.1 and 0.5mM H2O2, respectively. In addition, the multilayer film-coated MPs were further modified by using glucose oxidase (GOx) to develop glucose-induced release systems. GOx-modified MPs released DPBA in response to 0.1mM d-glucose as a result of H2O2 generation through a GOx-catalyzed oxidation reaction of d-glucose. The results suggest a potential use of the multilayer film-coated MPs in the development of H2O2- and/or glucose-sensitive drug delivery systems. PMID:25084230

Sato, Katsuhiko; Abe, Eiichi; Takahashi, Mao; Anzai, Jun-ichi

2014-10-15

341

Relationships Among Particle Number, Surface Area, and Respirable Mass Concentrations in Automotive Engine Manufacturing  

Microsoft Academic Search

This study investigated the relationships between particle number, surface area, and respirable mass concentration measured simultaneously in a foundry and an automotive engine machining and assembly center. Aerosol concentrations were measured throughout each plant with a condensation particle counter for number concentration, a diffusion charger for active surface area concentration, and an optical particle counter for respirable mass concentration. At

William A. Heitbrink; Douglas E. Evans; Bon Ki Ku; Andrew D. Maynard; Thomas J. Slavin; Thomas M. Peters

2008-01-01

342

Surface acoustic wave-induced precise particle manipulation in a trapezoidal glass microfluidic channel  

E-print Network

, particle alignment with only one IDT active was realized. A finite element method simulation was usedSurface acoustic wave-induced precise particle manipulation in a trapezoidal glass microfluidic.1088/0960-1317/22/2/025018 Surface acoustic wave-induced precise particle manipulation in a trapezoidal glass microfluidic channel L

343

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

PubMed

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

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

2013-05-01

344

High-speed Particle Image Velocimetry Near Surfaces  

PubMed Central

Multi-dimensional and transient flows play a key role in many areas of science, engineering, and health sciences but are often not well understood. The complex nature of these flows may be studied using particle image velocimetry (PIV), a laser-based imaging technique for optically accessible flows. Though many forms of PIV exist that extend the technique beyond the original planar two-component velocity measurement capabilities, the basic PIV system consists of a light source (laser), a camera, tracer particles, and analysis algorithms. The imaging and recording parameters, the light source, and the algorithms are adjusted to optimize the recording for the flow of interest and obtain valid velocity data. Common PIV investigations measure two-component velocities in a plane at a few frames per second. However, recent developments in instrumentation have facilitated high-frame rate (> 1 kHz) measurements capable of resolving transient flows with high temporal resolution. Therefore, high-frame rate measurements have enabled investigations on the evolution of the structure and dynamics of highly transient flows. These investigations play a critical role in understanding the fundamental physics of complex flows. A detailed description for performing high-resolution, high-speed planar PIV to study a transient flow near the surface of a flat plate is presented here. Details for adjusting the parameter constraints such as image and recording properties, the laser sheet properties, and processing algorithms to adapt PIV for any flow of interest are included. PMID:23851899

Lu, Louise; Sick, Volker

2013-01-01

345

Leonid's Particle Analyses from Stratospheric Balloon Collection on Xerogel Surfaces  

NASA Technical Reports Server (NTRS)

Recovered from a stratospheric balloon above 20 km on 17-18 November 1998, at least eight candidate microparticles were collected and analyzed from low-density silica xerogel collection plates. Capture time at Leonids' storm peak was validated locally along the balloon trajectory by direct video imaging of meteor fluence up to 24/hr above 98% of the Earth's atmosphere. At least one 30 micron particle agrees morphologically to a smooth, unmelted spherule and compares most closely in non-volatile elemental ratios (Mg/Si, Al/Si, and Fe/Si) to compositional data in surface/ocean meteorite collections. A Euclidean tree diagram based on composition makes a most probable identification as a non-porous stratospherically collected particle and a least probable identification as terrestrial matter or an ordinary chondrite. If of extraterrestrial origin, the mineralogical class would be consistent with a stony (S) type of silicate, olivine [(Mg,Fe)2SiO4] and pyroxene [(Mg, Fe)Si!O3)--or oxides, herecynite [(Fe,Mg) Al2O4].

Noever, David; Phillips, Tony; Horack, John; Porter, Linda; Myszka, Ed

1999-01-01

346

The surface deposition of meteoric smoke particles - possible climate impact  

NASA Astrophysics Data System (ADS)

There are large uncertainties in the transport and surface deposition of upper atmospheric particles, such as meteoric smoke particles (MSPs) formed in the upper mesosphere. Here we use a 3D chemistry-climate model (CCM) to simulate the transport and deposition of MSPs from the upper mesosphere. The CCM was first validated by predicting the deposition of plutonium-238 oxide nanoparticles formed after the ablation of a power unit in the upper stratosphere (~11o S) in 1964. The observed hemispheric asymmetry and timescale of Pu-238 deposition is well-captured. In the case of MSPs, the model predicts more deposition in Greenland than Antarctica by a factor of ~15, in agreement with ice core measurements. The strongest MSP deposition is predicted to occur at mid-latitudes, providing a significant source of Fe fertilization to the Southern Ocean where there is a shortage of bio-available Fe. The resulting increase in CO2 drawdown may have a significant climate impact. Map of annual mean Fe deposition rate (?mol Fe m-2 y-1)

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

2013-12-01

347

Effect of paracrystalline protein surface layers on predation by Bdellovibrio bacteriovorus.  

PubMed Central

We determined that paracrystalline protein surface arrays (S layers) protected gram-negative eubacteria from predation by Bdellovibrio bacteriovorus. Aquaspirillum serpens VHA and MW5 and Aquaspirillum sinuosum were resistant to predation by B. bacteriovorus 6-5-S when fully covered by their S layers. The S layer of Aeromonas salmonicida A449 protected the cells from predication by B. bacteriovorus 109J. A predacious, plaque-forming vibrio that lysed an S-layer- variant of Caulobacter crescentus but was not predacious on the parental strain which possessed an S layer was isolated from raw sewage. Since S layers are stable components of many bacterial surfaces in nature, they can provide this protective function in both aquatic and terrestrial habitats where Bdellovibrio spp. are found. Images PMID:2007549

Koval, S F; Hynes, S H

1991-01-01

348

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

349

Scalable preparation of alginate templated-layered double hydroxide mesoporous composites with enhanced surface areas and surface acidities.  

PubMed

Layered double hydroxides (LDHs), also known as hydrotalcite-like layered clays, have previously been investigated as a potential solid alkaline catalyst. A necessary calcinations/rehydration procedure, however, is utilized to enhance surface area and catalytic activity of LDHs involved. Here we report on a scalable preparation of sodium alginate-templated MgAI-LDH (LDH/SA) mesoporous composites with high surface area and surface acidity. The powdery LDH/SA mesoporous composites are prepared using alginate as template by a scalable method of separate nucleation and aging steps (SNAS). Comparison with the pristine MgAl-LDH shows that the obtained LDH/SA composites exhibit the greatly enhanced surface area and surface activity of surface acid sites at the elevated high temperatures which have scarcely been reported previously. Our results may allow designing a variety of mesoporous LDH-containing composites with potential applications in specific catalysis and purification processes. PMID:21776699

Zhao, Lina; Xu, Ting; Lei, Xiaodong; Xu, Sailong; Zhang, Fazhi

2011-04-01

350

Turbulence structure of the surface layer Boun 2247-03D TURBULENCE STRUCTURE OF THE UNSTABLE ATMOSPHERIC  

E-print Network

ATMOSPHERIC SURFACE LAYER AND TRANSITION TO THE OUTER LAYER K.G. McNAUGHTON School of GeoSciences, University of Edinburgh, Scotland EH9 3JU. (Accepted by Boundary-Layer Meteorology, 3 Nov. 2003) Abstract. This paper presents a new model of the structure of turbulence in the unstable atmospheric surface layer

Moncrieff, John B.

351

Surface roughness and dislocation density in InP\\/InGaAs layers  

Microsoft Academic Search

A subtle roughening of the surface of a buried 60 nm InGaAs epitaxial layer was detected using a combination of sample cleaving, selective chemical etching and Field Emission Scanning Electron Microscopy (FESEM). In our technology, InGaAs is the photo-absorbing layer of Metal Organic Chemical Vapor Deposition (MOCVD) grown layers used in the monolithic integration of active photo detectors and a

Denis P. Masson; Sylvain Laframboise

2004-01-01

352

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

353

One-dimensional particle simulations of Knudsen-layer effects on D-T fusion  

NASA Astrophysics Data System (ADS)

Particle simulations are used to solve the fully nonlinear, collisional kinetic equation describing the interaction of a high-temperature, high-density, deuterium-tritium plasma with absorbing boundaries, a plasma source, and the influence of kinetic effects on fusion reaction rates. Both hydrodynamic and kinetic effects influence the end losses, and the simulations show departures of the ion velocity distributions from Maxwellian due to the reduction of the population of the highest energy ions (Knudsen-layer effects). The particle simulations show that the interplay between sources, plasma dynamics, and end losses results in temperature anisotropy, plasma cooling, and concomitant reductions in the fusion reaction rates. However, for the model problems and parameters considered, particle simulations show that Knudsen-layer modifications do not significantly affect the velocity distribution function for velocities most important in determining the fusion reaction rates, i.e., the thermal fusion reaction rates using the local densities and bulk temperatures give good estimates of the kinetic fusion reaction rates.

Cohen, Bruce I.; Dimits, Andris M.; Zimmerman, George B.; Wilks, Scott C.

2014-12-01

354

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

E-print Network

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

Thompson, Andrew

355

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

356

Layered surface acoustic wave devices for film characterization and sensor applications  

Microsoft Academic Search

This work has introduced novel applications for Layered Surface Acoustic Wave (SAW) devices along with concepts for enhanced sensitivity via refined modeling techniques. The derivation of Love Wave and Rayleigh wave propagation pertinent to SAW substrates with thin film overlayers was explored. Novel aspects were presented for Finite Element analysis of Layered SAW sensors. This included coordinate transformations of model

Michael K. Pedrick

2007-01-01

357

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

358

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

359

Turbulent boundary layer on the moving surface of a cylindrical body  

Microsoft Academic Search

An analysis is made of the two-dimensional turbulent boundary on the moving surface of a cylindrical body (a Rankine oval with an aspect ratio of 4) moving at constant velocity in an incompressible fluid. A numerical simulation is used in which the boundary layer is divided in accordance with a two-layer model into inner and outer regions, for which different

V. M. Zubarev

1984-01-01

360

The turbulent boundary layer on the moving surface of a cylindrical body  

Microsoft Academic Search

A study is made of the problem of a two-dimensional turbulent boundary layer on the moving surface of a cylindrical body (a Rankine oval with a relative elongation of four) moving at constant velocity in an incompressible fluid. For the numerical simulation of the turbulent flow of the fluid, the boundary layer is divided into exterior and interior regions in

V. M. Zubarev

1984-01-01

361

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 IntA Semi-Automatic Approach for Estimating Near Surface Internal Layers From Snow Radar Imagery. Layering Bed Properties Adjustable 350 MHz Up to 450 MHz 4 km 800 W TBD Array Basler MCoRDS/I Radar Depth

362

Formation of nanoscale carbon structures in the surface layer of metals under the impact of high intensity ion beam  

NASA Astrophysics Data System (ADS)

This work represents the results of phase composition and the mechanical properties of tungsten and titanium after high-intensity pulsed ion beam (HPIB) treatment. It was shown that nanoscale carbide particles are formed under the HPIB influence in the surface layers of metals. Raising the pulse number results in increase of volume fraction of the carbide phases. The microhardness is 1.5-2 times more than the initial value and wear resistance of the metals improves in response to alloying of tungsten and titanium with carbon atoms accompanied by the formation of carbides.

Remnev, G. E.; Uglov, V. V.; Shymanski, V. I.; Pavlov, S. K.; Kuleshov, A. K.

2014-08-01

363

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

NASA Technical Reports Server (NTRS)

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

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

1999-01-01

364

Positive buoyancy in eel leptocephali: an adaptation for life in the ocean surface layer  

Microsoft Academic Search

Many planktonic organisms have adaptations such as floats or lighter substances to obtain buoyancy to help them remain in\\u000a the surface layer of the ocean where photosynthetic primary production occurs and food is most abundant. The almost totally\\u000a transparent eel larvae, called leptocephali, are a unique member of the planktonic community of the surface layer, but their\\u000a ecology and physiology

Katsumi Tsukamoto; Yoshiaki Yamada; Akihiro Okamura; Toyoji Kaneko; Hideki Tanaka; Michael J. Miller; Noriyuki Horie; Naomi Mikawa; Tomoko Utoh; Satoru Tanaka

2009-01-01

365

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

E-print Network

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

Landrum, David Brian

1986-01-01

366

Characteristics of thin surface layers of cobalt-based alloys deposited by laser cladding  

Microsoft Academic Search

Thin surface layers of cobalt-based alloys (Stellite 6 and Tribaloy T-900) and 410 stainless steel (SS) were deposited on mild steel substrates by a coaxial laser cladding process. This process could produce a thin surface layer of less than 0.5 mm with low energy input. Laser-clad Stellite 6 and Tribaloy T-900 specimens exhibited refined dendritic microstructure. The interdendritic eutectics consisted

W. C. Lin; C. Chen

2006-01-01

367

Sensitivity of climate simulations to land-surface and atmospheric boundary-layer treatments - a review  

Microsoft Academic Search

Aspects of the land-surface and boundary-layer treatments in 20 or so atmospheric general circulation models (GCMs) are summarized. only a few of these have had significant sensitivity studies published. The sensitivity studies focus upon the parameterization of land- surface processes and specification of land-surface properties including albedo, roughness length, soil moisture status, and vegetation density. The impacts of surface albedo

J. R. Garratt

1993-01-01

368

THERMALLY STABLE SURFACE PASSIVATION BY A-SI:H / SIN DOUBLE LAYERS FOR CRYSTALLINE SILICON SOLAR CELLS  

E-print Network

THERMALLY STABLE SURFACE PASSIVATION BY A-SI:H / SIN DOUBLE LAYERS FOR CRYSTALLINE SILICON SOLAR of the amorphous silicon / silicon nitride double layer surface passivation on p-type crystalline silicon surfaces, which is identical to the range for depositing a-Si:H films. Their a-Si:H / SiNx double layer

369

Role of Patterned Surface Charge Heterogeneity on Particle Deposition  

Microsoft Academic Search

A finite element analysis of the fluid flow and the colloidal particle transport equations near a micropatterned charged substrate under radial impinging jet flow conditions is presented to investigate the charge heterogeneity effects on particle deposition. The particle Sherwood number representing the dimensionless particle deposition flux is obtained as a function of the radial distance from the stagnation point. The

Neda Nazemifard; Jacob Masliyah; Subir Bhattacharjee

2005-01-01

370

Surface Navigation Using Optimized Waypoints and Particle Swarm Optimization  

NASA Technical Reports Server (NTRS)

The design priority for manned space exploration missions is almost always placed on human safety. Proposed manned surface exploration tasks (lunar, asteroid sample returns, Mars) have the possibility of astronauts traveling several kilometers away from a home base. Deviations from preplanned paths are expected while exploring. In a time-critical emergency situation, there is a need to develop an optimal home base return path. The return path may or may not be similar to the outbound path, and what defines optimal may change with, and even within, each mission. A novel path planning algorithm and prototype program was developed using biologically inspired particle swarm optimization (PSO) that generates an optimal path of traversal while avoiding obstacles. Applications include emergency path planning on lunar, Martian, and/or asteroid surfaces, generating multiple scenarios for outbound missions, Earth-based search and rescue, as well as human manual traversal and/or path integration into robotic control systems. The strategy allows for a changing environment, and can be re-tasked at will and run in real-time situations. Given a random extraterrestrial planetary or small body surface position, the goal was to find the fastest (or shortest) path to an arbitrary position such as a safe zone or geographic objective, subject to possibly varying constraints. The problem requires a workable solution 100% of the time, though it does not require the absolute theoretical optimum. Obstacles should be avoided, but if they cannot be, then the algorithm needs to be smart enough to recognize this and deal with it. With some modifications, it works with non-stationary error topologies as well.

Birge, Brian

2013-01-01

371

The CCN activity of internally mixed organic-inorganic particles: the effect of solubility and surface tension on particle activation  

NASA Astrophysics Data System (ADS)

The ability of internally mixed organic-inorganic aerosols to act as cloud condensation nuclei (CCN) will be discussed. Internally mixed particles were produced through a variety of methods, including particle coating and atomization of mixed solutions. These experiments were designed to address several key questions concerning particle activation. How does surface tension play a role and can a surface active organic species impact activation? Does a trace amount of a highly soluble species impact the activation of organic particles of moderate to low solubility? Can the activation properties of ammonium sulfate be "shut off" through coating with an inactive organic species? To systematically address these issues, the CCN activity of various mixed particles such as ammonium sulfate(AS)/oleic acid, AS/stearic acid, AS/adipic acid, AS/hexanoic acid and others have been studied. These results are among the first to specifically address the effect of surface tension on CCN activity in the laboratory.

Broekhuizen, K.; Kumar, P.; Abbatt, J.

2004-05-01

372

Scale properties of microscale convection in the marine surface layer  

SciTech Connect

We analyze the scale distribution of coherent water vapor structures in the marine atmospheric boundary layer as measured by a shipboard Raman lidar during the Combined Sensor Program (March 1996) using a two-dimensional continuous wavelet transform. Coherent structures in the lidar measured water vapor concentration field correspond to locations where covariance with the wavelet is a local extremum. Scales of the significant structures are identified using a filtered wavelet variance (detection density) derived from 24 {open_quotes}images{close_quotes} in a horizontal plane. A dominant radius of 14 m is identified using complimentary approaches to the analysis. {copyright} 1998 American Geophysical Union

Hagelberg, C.R.; Cooper, D.I.; Winter, C.L. [Los Alamos National Laboratory, Los Alamos, New Mexico (United States)] [Los Alamos National Laboratory, Los Alamos, New Mexico (United States); Eichinger, W.E. [Department of Civil and Environmental Engineering, University of Iowa, Iowa City (United States)] [Department of Civil and Environmental Engineering, University of Iowa, Iowa City (United States)

1998-07-01

373

Monte Carlo simulations of light scattering by composite particles in a planetary surface  

NASA Technical Reports Server (NTRS)

Composite particles containing internal scatterers have been proposed as an explanation for the fact that most photometric studies of planetary surfaces based on Hapke's bidirectional reflectance model have found the planetary particles to exhibit moderately backscattering phase functions.

Hillier, J.; Buratti, B.

2001-01-01

374

Film formation from monodisperse acrylic lattices 1. Influence of concentration and layer thickness on particle ordering.  

PubMed

The influence of concentration and layer thickness on particle ordering in polymer latex films, both open and closed, has been studied by means of rheology, microscopy and turbidimetry. Monodisperse acrylic lattices were synthesized by semicontinuous emulsion polymerization. The lattices exhibited a distinct thixotropy above a certain concentration, which is attributed to crystallization. Microscopy revealed a three-layer structure and a dependence of crystal size and crystal packing on layer thickness and layer concentration. Turbidimetry (i.e., analysis of light transmission and interference) was used to study the progress of ordering in open and closed systems. In closed films crystallization proceeds faster at higher concentrations and in thinner films. Above a sufficiently high concentration no crystallization was observed. Furthermore, an induction time was found below certain concentrations. The drying of open latex films at temperatures below the minimum film formation temperature (MFFT) was shown to proceed through five distinct stages. The drying of open films at temperatures below the MFFT was studied by analysis of the turbidity of rewetted films. A more compact structure was found in thinner films. The structure in lattices is discussed as a result of long-range and short-range ordering. PMID:15752793

Zohrehvand, Shiva; Cai, Rong; Reuvers, Bart; te Nijenhuis, Klaas; de Boer, Abe Posthuma

2005-04-01

375

Surface band-gap narrowing in quantized electron accumulation layers.  

PubMed

An energy gap between the valence and the conduction band is the defining property of a semiconductor, and the gap size plays a crucial role in the design of semiconductor devices. We show that the presence of a two-dimensional electron gas near to the surface of a semiconductor can significantly alter the size of its band gap through many-body effects caused by its high electron density, resulting in a surface band gap that is much smaller than that in the bulk. Apart from reconciling a number of disparate previous experimental findings, the results suggest an entirely new route to spatially inhomogeneous band-gap engineering. PMID:20867408

King, P D C; Veal, T D; McConville, C F; Zúñiga-Pérez, J; Muñoz-Sanjosé, V; Hopkinson, M; Rienks, E D L; Jensen, M Fuglsang; Hofmann, Ph

2010-06-25

376

Synthesis of superhydrophobic SiO{sub 2} layers via combination of surface roughness and fluorination  

SciTech Connect

We describe the preparation of superhydrophobic SiO{sub 2} layers through a combination of surface roughness and fluorination. Electrospraying SiO{sub 2} precursor solutions that were prepared by a sol-gel route and included trichloro(1H,1H,2H,2H-perfluorooctyl)silane as a fluorination source produced highly rough, fluorinated SiO{sub 2} layers. In sharp contrast to the fluorinated flat SiO{sub 2} layer, the fluorinated rough SiO{sub 2} layer showed much enhanced repellency toward liquid droplets of different surface tensions. The surface fraction and the work of adhesion of the superhydrophobic SiO{sub 2} layers were determined, respectively, based on Cassie-Baxter and Young-Dupre equations. The satisfactory long-term stability for 30 days, the ultraviolet resistance and the thermal stability up to 400 {sup o}C of the superhydrophobic SiO{sub 2} layers prepared in this work confirm a promising practical application. - Graphical abstract: A schematic illustration of the electrospray deposition used for preparing SiO{sub 2} layers. Shapes of liquid droplets of water, glycerol, coffee, juice and milk created on the fluorinated rough SiO{sub 2} layer deposited on a silicon wafer. Highlights: Black-Right-Pointing-Pointer Superhydrophobic SiO{sub 2} layers are realized by a combination of surface roughness and fluorination. Black-Right-Pointing-Pointer The fluorinated rough SiO{sub 2} layer shows enhanced repellency toward various liquid droplets. Black-Right-Pointing-Pointer The wetting behavior is explained based on Cassie-Baxter and Young-Dupre equations. Black-Right-Pointing-Pointer The superhydrophobic SiO{sub 2} layers confirm a promising practical application.

Kim, Eun-Kyeong; Yeong Kim, Ji [School of Materials Science and Engineering, Inha University, Incheon 402-751 (Korea, Republic of); Sub Kim, Sang, E-mail: sangsub@inha.ac.kr [School of Materials Science and Engineering, Inha University, Incheon 402-751 (Korea, Republic of)

2013-01-15

377

Assimilation of surface soil moisture in a multi-layer soil model: a case study  

NASA Astrophysics Data System (ADS)

In climate and numerical weather prediction (NWP), surface-atmosphere interaction processes are represented by land surface models (LSM). LSM have been improved considerably in the last two decades. In this study, the ISBA LSM new soil diffusion scheme is used (with 11 soil layers represented). A Simplified Extented Kalman Filter (SEKF) is implemented to assimilate surface soil moisture (SSM) in the multi-layer LSM in order to constrain the root-zone soil moisture. In parallel, the SEKF is applied to the simpler ISBA version LSM with 2 soil layers (a thin surface layer and a bulk reservoir). Simulations are performed over a 3-yr period (2003-2005) for a bare soil field in southwestern France, at the SMOSREX experimental site. It is shown that both open-loop simulations and those integrating SSM observations are better using the multilayer model. The assimilation statistics (Kalman gain, Jacobians, and increments) are analyzed for the two models. In the case of the multilayer model, the Kalman gain is greater close to the surface, especially in dry conditions. During winters and wet periods, lower Kalman gain values are observed close to the surface but the vertical gain profile is more evenly distributed. Prior data assimilation, the preconditioning of the observations is needed. A CDF-matching technique is used, either year by year or over the whole period. The way CDF matching is implemented has a significant impact on the result of the assimilation. In order to investigate the impact of the implementation of the B matrix, two other experiments were performed, adding covariance terms between soil layers: (1) the soil layer n is linked to layers n-1 and n+1, (2) the soil layer n is linked to layers n-2, n-1, n+1 and n+2. In these experiments, Kalman gain is greater than for experiments performed with a diagonal B matrix.

Calvet, Jean-Christophe; Parrens, Marie; Mahfouf, Jean-François; Barbu, Alina

2013-04-01

378

In situ mass analysis of particles by surface ionization mass spectrometry  

NASA Technical Reports Server (NTRS)

A qualitative study of the application of surface ionization and mass spectrometry to the in situ detection and constituent analysis of atmospheric particles was conducted. The technique consists of mass analysis of ions formed as a result of impingement of a stream of particles on a hot filament where, it is presumed, surface ionization takes place. Laboratory air particles containing K, Ca, and possibly hydrocarbons were detected. Other known particles such as Al2O3, Pb(NO3)2, and Cr2O3 were analyzed by detecting the respective metal atoms making up the particles. In some cases, mass numbers indicative of compounds making up the particles were detected showing surface ionization of particles sometimes leads to chemical analysis as well as to elemental analysis. Individual particles were detected, and it was shown that the technique is sensitive to Al2O3 particles with a mass of a few nanograms.

Lassiter, W. S.; Moen, A. L.

1974-01-01

379

Bidirectional Reflectance of Flat, Optically Thick Particulate Layers: An Efficient Radiative Transfer Solution and Applications to Snow and Soil Surfaces  

NASA Technical Reports Server (NTRS)

We describe a simple and highly efficient and accurate radiative transfer technique for computing bidirectional reflectance of a macroscopically flat scattering layer composed of nonabsorbing or weakly absorbing, arbitrarily shaped, randomly oriented and randomly distributed particles. The layer is assumed to be homogeneous and optically semi-infinite, and the bidirectional reflection function (BRF) is found by a simple iterative solution of the Ambartsumian's nonlinear integral equation. As an exact Solution of the radiative transfer equation, the reflection function thus obtained fully obeys the fundamental physical laws of energy conservation and reciprocity. Since this technique bypasses the computation of the internal radiation field, it is by far the fastest numerical approach available and can be used as an ideal input for Monte Carlo procedures calculating BRFs of scattering layers with macroscopically rough surfaces. Although the effects of packing density and coherent backscattering are currently neglected, they can also be incorporated. The FORTRAN implementation of the technique is available on the World Wide Web at http://ww,,v.giss.nasa.gov/-crmim/brf.html and can be applied to a wide range of remote sensing, engineering, and biophysical problems. We also examine the potential effect of ice crystal shape on the bidirectional reflectance of flat snow surfaces and the applicability of the Henyey-Greenstein phase function and the 6-Eddington approximation in calculations for soil surfaces.

Mishchenko, Michael I.; Dlugach, Janna M.; Yanovitsku, Edgard G.; Zakharova, Nadia T.

1999-01-01

380

A boundary-layer analysis of atmospheric motion over a semi-elliptical surface obstruction  

NASA Technical Reports Server (NTRS)

Flow over surface obstructions can produce adverse flying conditions for helicopters, V/STOL vehicles, etc. The disturbed boundary-layer concept is applied in approximating the localized flow field induced around a surface obstruction (modeled by a two-dimensional cylinder with elliptical cross section) by an impinging wind. The analysis concludes that: (1) localized wind-speed maxima occur at the top of a surface obstruction, which are expected in physically real flows; (2) increased elliptical aspect ratio decreases with speed within the boundary layer at the top of the ellipse; (3) increased surface roughness decreases velocity in the boundary layer; (4) Reynolds number has a negligible effect on the overall flow for the Re range considered; (5) decreased elliptical aspect ratio and increased surface roughness cause larger separation regions.

Frost, W.; Maus, J. R.; Fichtl, G. H.

1974-01-01

381

Anisotropic layer-by-layer growth of graphene on vicinal SiC(0001) surfaces  

Microsoft Academic Search

Epitaxial graphene is formed on vicinal SiC(0001) surfaces via high temperature annealing in vacuum. Steps act as a significant ``kicker'' of graphene nucleation to feed C atoms. At elevated temperatures, graphene growth is controlled by the decomposition of Si-C bonds at step edges, Si desorption, and C diffusion on the surface. The limited Si desorption is due to the dependence

Satoru Tanaka; Kouhei Morita; Hiroki Hibino

2010-01-01

382

Correlation between space charge accumulation in polyethylene and its fluorinated surface layer characteristics  

NASA Astrophysics Data System (ADS)

Polyethylene (PE) samples were surface fluorinated by the F2/N2 mixture for 30, 60, 120 or 240 min to investigate the influence of the fluorinated layer characteristics on space charge accumulation. After polarization at 50 kV mm-1 dc electrical field and 40 °C for 240 min, the charge amounts of the samples fluorinated for the different times, normalized to the charge amount of the original sample, are 1.17, 0.51, 0.49 and 0.22, respectively, showing significant suppression of the charge accumulation by the longer treatments, especially for the 240 min treatment. Infrared analyses and SEM cross-section images of the fluorinated samples indicate the increases in degree of fluorination and thicknesses of the fluorinated layer with the treatment time, and the fluorinated layer thicknesses were determined to be 0.39, 0.45, 0.65 and 0.80 µm. Surface energy calculations show that the polar component increased from 2.9 to 14.7 mJ m-2 after the 30 min treatment, and subsequently decreased to 11.8, 11.5 and 9.5 mJ m-2 for the longer treatments of 60, 120 and 240 min. This suggests a similar change in surface layer permittivity with the treatment time. The fluorinations led to the shift of thermally stimulated discharge current peak from 156 °C of the original sample to 145, 142, 144 and 149 °C of the fluorinated samples, and thus reduced the trap depth of the surface layer. But, the longer treatments of 60, 120 and 240 min significantly improved the barrier properties of the surface layer to the diffusion of the chemical species from the semi-conductive electrode to the PE by the decrease in free volume of the surface layer. The chemical species diffused into the sample surface layer reduced the depth of surface traps. The decrease in free volume is more important in suppressing the charge accumulation than the increase in surface layer permittivity and the change in surface trap, because it would reduce the charge transport in the surface layer and the charge direct injection at both electrodes.

An, Zhenlian; Liu, Chenxia; Chen, Xuan; Zheng, Feihu; Zhang, Yewen

2012-01-01

383

Intermittency in the heat and particle transports in the SINP tokamak scrape-off layer  

SciTech Connect

The intermittent heat and particle transports have been studied in the scrape-off layer of the SINP tokamak. Properties of the plasma structures, responsible for the intermittency, have been measured by the conditional averaging technique. The probability distribution functions of the fluctuations, including temperature fluctuations, obey non-Gaussian statistics. Wavelet analysis has shown that the cross-correlation between two probes is also intermittent in time and is connected to the passage of plasma structures. The structures decay in density as they move radially outward but their temperature is found to decay more rapidly.

Saha, S. K.; Chowdhury, S. [Plasma Physics Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata-700064 (India)

2008-01-15

384

Structural characterization study of nickel ferrite particles dispersed in a corrosion product deposit layer  

NASA Astrophysics Data System (ADS)

Using X-ray absorption fine structure spectroscopy, both EXAFS and XANES, the cation distributions in NiFe 2O 4 particles dispersed in a corrosion product deposit layer have been studied. The specimen was obtained from a selected fuel rod used in a commercial boiling water reactor plant. EXAFS data allowed the quantitative determination of specific site distributions for all transition metal cations in Ni-ferrite deposits. The results show that the analyzed NiFe 2O 4 particles do not have a totally inverted spinel structure. The relative occupancy of iron and nickel cations in the tetrahedral and octahedral sites of the spinel lattice is determined from the measured data.

Kuri, G.; Degueldre, C.; Bertsch, J.; Borca, C. N.

2010-12-01

385

Anomalous diffusion and passage time distributions of microscopic particles through biological layers  

NASA Astrophysics Data System (ADS)

The field of passive microrheology was launched by Mason and Weitz in 1997, and has subsequently advanced in a variety of experimental and theoretical directions. The original aim is to infer viscoelastic properties from mean-squared displacement statistics of Brownian particles (beads) dispersed in the material. Extensions to bead-bead correlations have been advanced to screen local particle-material chemical potentials. The experimental measurements are equally, if not more so, ideal for characterizing the anomalous diffusive transport properties of soft matter, which are fundamental to pathogen or drug carrier diffusion through biological layers. Direct and inverse modeling and simulation tools will be presented, together with an evaluation of how well mean squared displacement serves as a proxy for passage time distributions.

Forest, M. Gregory; Hohenegger, Christel; McKinley, Scott; Yao, Lingxing

2008-03-01

386

Are atmospheric surface layer flows ergodic? Chad W. Higgins,1  

E-print Network

models yet are impacted by nonideal conditions at the land surface. Recent advancements in water vapor concentration lidar measurements that simultaneously sample spatial and temporal series in the ASL are used be used to infer the ensemble concentration statistics of a composite grass-lake system using only water

Katul, Gabriel

387

Laser removal of thin layers for surface cleaning  

Microsoft Academic Search

In micro- and nano- device fabrication technology, localized material removal is one of the basic operations for structure formation. Classical methods for structure formation on the surface of a silicon wafer are based mainly on chemical processing, starting with photo etching, chemical etching, and chemical-mechanical linearization. In order to propose new methods of higher quality from the point of view

Ileana Apostol; D. Apostol; V. Damian; Iuliana Iordache; F. Garoi; E. Capello

2008-01-01

388

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

Microsoft Academic Search

BACKGROUND: Airborne particles entering the respiratory tract may interact with the apical plasma membrane (APM) of epithelial cells and enter them. Differences in the entering mechanisms of fine (between 0.1 ?m and 2.5 ?m) and ultrafine ( ? 0.1 ?m) particles may be associated with different effects on the APM. Therefore, we studied particle-induced changes in APM surface area in

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

2009-01-01

389

Three-dimensional structure of the regularly constructed surface layer from Synechocystis sp. strain CLII.  

PubMed Central

The isolated, outermost cell wall layer from Synechocystis sp. strain CLII is described using electron microscopy and Fourier reconstruction to study the three-dimensional structure of the proteins within the layer to a resolution of ca. 3 nm. This surface layer forms regular hexagonal arrays (a = b = 15.2 nm). The two-dimensional space group is p6. The monomer proteins form hexamers arranged around a central hollow cylinder. The linkers between the hexamers are of the delta type and are located approximately in the central section between the top and bottom of the protein layer. Images PMID:6417112

Karlsson, B; Vaara, T; Lounatmaa, K; Gyllenberg, H

1983-01-01

390

Optimization of adsorption conditions of BSA on thermosensitive magnetic composite particles using response surface methodology.  

PubMed

Thermosensitive core-shell magnetic composite particles with a magnetic silica core and a rich poly (N-vinylcaprolactam) (PNVCL) shell layer were developed for studying the adsorption of bovine serum albumin (BSA) in a batch system. Various analytical and spectroscopic techniques including SEM, FT-IR, VSM and DSC were used to characterize the adsorbents prepared in this study. The combined effects of operating parameters such as initial temperature, pH and initial BSA concentration on the adsorption were analyzed using response surface methodology. The optimum conditions were 40°C, pH 4.68, and initial BSA concentration 2.0 mg/mL. Desorption experiments were conducted by altering the system temperature where a high recovery rate of protein was obtained. The separation process developed here indicates that the dual-responsive smart adsorbent could be an ideal candidate for the separation of protein. PMID:21353769

Song, Ming-Min; Branford-White, Christopher; Nie, Hua-Li; Zhu, Li-Min

2011-06-01

391

Surface passivation of InP solar cells with InAlAs layers  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

392

Structural analysis of nitride layer formed on uranium metal by glow plasma surface nitriding  

NASA Astrophysics Data System (ADS)

The nitride layer was formed on uranium metal by a glow plasma surface nitriding method. The structure and composition of the layer were investigated by X-ray diffraction and Auger electron spectroscopy. The nitride layer mainly consisted of ?-phase U2N3 nanocrystals with an average grain size about 10-20 nm. Four zones were identified in the layer, which were the oxide surface zone, the nitride mainstay zone, the oxide-existence interface zone, and the nitrogen-diffusion matrix zone. The gradual decrease of binding energies of uranium revealed the transition from oxide to nitride to metal states with the layer depth, while the chemical states of nitrogen and oxygen showed small variation.

Liu, Kezhao; Bin, Ren; Xiao, Hong; Long, Zhong; Hong, Zhanglian; Yang, Hui; Wu, Sheng

2013-01-01

393

The formation of a surface layer during microarc oxidation of aluminum alloys  

NASA Astrophysics Data System (ADS)

The formation of a surface layer during microarc oxidation has been investigated. The results of experimental studies aimed at determining the structure and composition of oxide coatings on aluminum alloys are presented. The studies found out that, in contrast to existing ideas about the initial stages of micro-arc oxidation, a "barrier layer" grows unevenly over the sample area and there is no clear boundary between a pre-spark and a spark mode of the process. Uneven growth of a " barrier layer " is connected with different distribution of electric field on the surface of a sample and different concentration of electrolyte components. Depending on the electrolytes used the inside coating layers consist mainly of aluminium oxide, and the outer layers contain components formed as a result of thermochemical transformation of the electrolyte.

Mikheev, A. Ye; Girn, A. V.; Vakhteev, E. V.; Alekseeva, E. G.; Ravodina, D. V.

2015-01-01

394

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

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

395

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

396

Artificially thickened turbulent boundary layers for studying heat transfer and skin friction on rough surfaces  

NASA Astrophysics Data System (ADS)

A technique has been developed to produce artificially thickened boundary layers on a uniformly rough surface which have two-dimensional, equilibrium properties representative of normal behavior at the level of spectra of the longitudinal velocity fluctuations. Skin surface friction coefficients and Stanton numbers are obtained for rough surface boundary layers much thicker than those previously studied. The results provide additional understanding of turbulent shear flow and a basis for testing engineering calculation schemes and design procedures for situations where thick, rough-wall boundary layers are present. The Stanton numbers and skin friction coefficients are shown to be representative of natural behavior because three higher levels of information, as well as the turbulent transport of momentum and heat, are the same as would have existed in naturally developed layers of the same thickness.

Ligrani, P. M.; Moffat, R. J.; Kays, W. M.

1983-06-01

397

Critical CuI buffer layer surface density for organic molecular crystal orientation change  

NASA Astrophysics Data System (ADS)

We have determined the critical surface density of the CuI buffer layer inserted to change the preferred orientation of copper phthalocyanine (CuPc) crystals grown on the buffer layer. X-ray reflectivity measurements were performed to obtain the density profiles of the buffer layers and out-of-plane and 2D grazing-incidence X-ray diffraction measurements were performed to determine the preferred orientations of the molecular crystals. Remarkably, it was found that the preferred orientation of the CuPc film is completely changed from edge-on (1 0 0) to face-on (1 1 -2) by a CuI buffer layer with a very low surface density, so low that a large proportion of the substrate surface is bare.

Ahn, Kwangseok; Kim, Jong Beom; Kim, Hyo Jung; Lee, Hyun Hwi; Lee, Dong Ryeol

2015-01-01

398

Measurement and correlation of aerodynamic heating to surface corrugation stiffened structures in thick turbulent boundary layers  

NASA Technical Reports Server (NTRS)

The flow conditions for which heating distributions were measured on corrugated surfaces and wavy walls in turbulent boundary layers are shown, along with the ratio of the displacement thickness to the roughness height versus the local edge Mach number for an equivalent smooth surface. The present data are seen to greatly extend the range of data available on corrugated surfaces in turbulent boundary layers. These data were obtained by testing fullscale corrugation roughened panels in the wall boundary layer of a supersonic and hypersonic wind tunnel. The experimental program used to obtain the data is described. The data are analyzed and correlated in terms of the pertinent flow and geometric parameters. The developed correlations are compared with the available thin boundary layer data, as well as with previously published correlation techniques.

Brandon, H. J.; Masek, R. V.

1974-01-01

399

The effect of aerosol vertical profiles on satellite-estimated surface particle sulfate concentrations  

SciTech Connect

The aerosol vertical distribution is an important factor in determining the relationship between satellite retrieved aerosol optical depth (AOD) and ground-level fine particle pollution concentrations. We evaluate how aerosol profiles measured by ground-based lidar and simulated by models can help improve the association between AOD retrieved by the Multi-angle Imaging Spectroradiometer (MISR) and fine particle sulfate (SO4) concentrations using matched data at two lidar sites. At the Goddard Space Flight Center (GSFC) site, both lidar and model aerosol profiles marginally improve the association between SO4 concentrations and MISR fractional AODs, as the correlation coefficient between cross-validation (CV) and observed SO4 concentrations changes from 0.87 for the no-scaling model to 0.88 for models scaled with aerosol vertical profiles. At the GSFC site, a large amount of urban aerosols resides in the well-mixed boundary layer so the column fractional AODs are already excellent indicators of ground-level particle pollution. In contrast, at the Atmospheric Radiation Measurement Program (ARM) site with relatively low aerosol loadings, scaling substantially improves model performance. The correlation coefficient between CV and observed SO4 concentrations is increased from 0.58 for the no-scaling model to 0.76 in the GEOS-Chem scaling model, and the model bias is reduced from 17% to 9%. In summary, despite the inaccuracy due to the coarse horizontal resolution and the challenges of simulating turbulent mixing in the boundary layer, GEOS-Chem simulated aerosol profiles can still improve methods for estimating surface aerosol (SO4) mass from satellite-based AODs, particularly in rural areas where aerosols in the free troposphere and any long-range transport of aerosols can significantly contribute to the column AOD.

Liu, Yang; Wang, Zifeng; Wang, Jun; Ferrare, Richard A.; Newsom, Rob K.; Welton, Ellsworth J.

2011-02-15

400

CHARACTERIZING SURFACE LAYERS IN NITINOL USING X-RAY PHOTOELECTRON SPECTROSCOPY  

SciTech Connect

Nitinol is a shape memory alloy whose properties allow for large reversible deformations and a return to its original geometry. This nickel-titanium (NiTi) alloy has become a material used widely in the biomedical fi eld as a stent to open up collapsed arteries. Both ambient and biological conditions cause surface oxidation in these devices which in turn change its biocompatibility. The thickness of oxidized layers can cause fractures in the material if too large and can allow for penetration if too thin. Depending on the type and abundance of the chemical species on or near the surface, highly toxic metal ions can leak into the body causing cell damage or even cell death. Thus, biocompatibility of such devices is crucial. By using highly surface sensitive x-ray photoelectron spectroscopy to probe the surface of these structures, it is possible to decipher both layer composition and layer thickness. Two samples, both of which were mechanically polished, were investigated. Of the two samples, one was then exposed to a phosphate buffered saline (PBS) solution to mimic the chemical properties of blood, while the other remained unexposed. Although both samples were found to have oxide layers of appropriate thickness (on the order of a few nm), it was found that the sample exposed to the saline solution had a slightly thicker oxide layer and more signifi cantly, a phosphate layer very near the surface suggesting toxic metal components are well contained within the sample. These are considerable indications of a biocompatible device.

Christopfel, R.; Mehta, A.

2008-01-01

401

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

SciTech Connect

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

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

2011-07-01

402

Surface and colloid chemical aspects of saliva particle interactions.  

PubMed

Sections of flash-frozen saliva particle mixture were examined by transmission electron microscopy. The saliva samples used consisted of 40% by volume parotid and 60% by volume submandibular sublingual fractions. One mL of the saliva was mixed with 0.1 mL of either hydrophilic or hydrophobic particles of 0.9 microns diameter. The micrographs of the saliva and hydrophilic particles mixes showed the multiple spherical particles in the salivary network structures. Micrographs of the saliva and hydrophilic particle mixes showed the presence of few such objects; when observed, the particles were located only in the electron dense part of the salivary structures. PMID:7472729

Glantz, P O; Friberg, S E; Christersson, C E; Baier, R E

1995-08-01

403

*** When a layer of particle-laden fresh water is placed above clear, saline water, both double-diffusive and  

E-print Network

*** When a layer of particle-laden fresh water is placed above clear, saline water, both double of particles with a Stokes settling velocity modifies the traditional double-diffusive fingering by creating into the rose region from above, the double-diffusive/ Rayleigh-Taylor flux out of the nose region below

Hu, Hui

404

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

DOEpatents

The present invention relates to a new class of surface modified particles and to a multi-step surface modification process for the preparation of the same. The multi-step surface functionalization process involves two or more reactions to produce particles that are compatible with various host systems and/or to provide the particles with particular chemical reactivities. The initial step comprises the attachment of a small organic compound to the surface of the inorganic particle. The subsequent steps attach additional compounds to the previously attached organic compounds through organic linking groups.

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

2006-01-17

405

Transient behavior of particle deposition in granular media under various surface interactions  

Microsoft Academic Search

Transient behavior of particle deposition in granular media arises from time-dependent changes of local particle deposition rates throughout the media. Many variables may affect the transient behavior. A system of equations describing the transient deposition phenomenon was derived by considering collector–particle and particle–particle interactions separately and by including other factors such as the excluded surface effect and the re-entrainment of

Renbi Bai; Chi Tien

2000-01-01

406

Measuring air layer volumes retained by submerged floating-ferns Salvinia and biomimetic superhydrophobic surfaces  

PubMed Central

Summary Some plants and animals feature superhydrophobic surfaces capable of retaining a layer of air when submerged under water. Long-term air retaining surfaces (Salvinia-effect) are of high interest for biomimetic applications like drag reduction in ship coatings of up to 30%. Here we present a novel method for measuring air volumes and air loss under water. We recorded the buoyancy force of the air layer on leaf surfaces of four different Salvinia species and on one biomimetic surface using a highly sensitive custom made strain gauge force transducer setup. The volume of air held by a surface was quantified by comparing the buoyancy force of the specimen with and then without an air layer. Air volumes retained by the Salvinia-surfaces ranged between 0.15 and 1 L/m2 depending on differences in surface architecture. We verified the precision of the method by comparing the measured air volumes with theoretical volume calculations and could find a good agreement between both values. In this context we present techniques to calculate air volumes on surfaces with complex microstructures. The introduced method also allows to measure decrease or increase of air layers with high accuracy in real-time to understand dynamic processes. PMID:24991518

Reker, Meike; Barthlott, Wilhelm

2014-01-01

407

The Budgets of Turbulent Kinetic Energy and Temperature Variance in the Atmospheric Surface Layer  

Microsoft Academic Search

Measurements of the shear production, buoyant production, turbulent transport (flux divergence) and dissipation terms in the budget of turbulent kinetic energy, and production and turbulent transport terms in the temperature variance budget are presented. Direct observations of the surface stress and heat flux over a horizontally uniform site enable presentation of the data in terms of surface layer similarity theory.The

J. C. Wyngaard; O. R. Coté

1971-01-01

408

Efficient Prediction of Ground Surface Temperature and Moisture, With Inclusion of a Layer of Vegetation  

Microsoft Academic Search

An efficient time-dependent equation for predicting ground surface temperature devised by Bhumralkar (1975) and Blackadar (1976) is tested against a 12-layer soil model and compared with five other approximate methods in current use. It is found to be generally superior if diurnal forcing is present and very much superior to the use of the insulated surface assumption. An analogous method

J. W. Deardorff

1978-01-01

409

Laboratory study of unsteady energy transfer in surface layers of stratified water  

Microsoft Academic Search

A Mach-Zehnder interferometer was used to study the energy transfer in the surface layers of stratified water cooled from above. Laboratory measurements of the unsteady temperature distributions indicate that the thermal structure between the interface and the stable region is controlled by a buoyancy induced flow which is established a small distance below the surface. The thermal structure is quite

R. Viskanta; J. R. Parkin

1976-01-01

410

Surface Passivation of Silicon Solar Cells using Amorphous Silicon Carbide Layers  

Microsoft Academic Search

Dielectric layers for the passivation of solar cell surfaces are a crucial component of future cell generations. Not only their electrical and optical properties are of importance but also the implementation into an industrial cell process. In this regard an easy preconditioning of the surface, low process temperature and high thermal stability are essential. Therefore, we have developed a new

S. W. Glunz; S. Janz; M. Hofmann; T. Roth; G. Willeke

2006-01-01

411

Laminar boundary layer on the moving surface of a Rankine oval  

Microsoft Academic Search

The paper presents a numerical analysis of a laminar boundary layer arising on the surface of a cylindrical body (a Rankine oval with a relative elongation of 4) moving with constant velocity in an incompressible fluid. Distributions of shear stress on the cylinder surface are determined for different velocities of the wall. Numerical integration is used to determine the magnitude

V. M. Zubarev

1984-01-01

412

Laminar boundary layer on the moving surface of a rankine oval  

Microsoft Academic Search

A numerical investigation has been made of the laminar boundary layer that arises on the moving surface of a cylindrical body (Rankine oval with relative elongation 4) that moves with constant velocity in an incompressible fluid. The distributions of the frictional stress on the surface of the cylinder for different velocities of the wall motion are found. Numerical integration was

V. M. Zubarev

1984-01-01

413

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

E-print Network

, reversible, reproducible wettability changes can be prepared by covalent LbL grafting using PNIPAM-c-PNASI and aminated silica nanoparticles. A 65º ?? value was observed with water vs. 1.4 M Na2SO4. The prepared film shows a high surface roughness of ~300 nm...

Liao, Kang-Shyang

2009-05-15

414

Growth of silicon microcrystals in thin surface layers of quartz glass with vacuum ultraviolet laser processing  

NASA Astrophysics Data System (ADS)

Silicon precipitates in surface layers as thin as 50 nm of quartz glass plates where 9.8 eV photons from an argon excimer laser are irradiated. The surfaces have many protrusions having a spherical shape with submicrometer diameter. Raman spectra indicates that they are made of crystalline silicon. Such a phenomenon has not been observed by 8.5 eV photons from a krypton excimer laser. VUV laser material processing offers a novel way to produce directly polycrystalline silicon circuits in thin surface layers of quartz glass plates.

Kurosawa, Kou; Sasaki, Wataru; Takigawa, Yasuo; Ohmukai, Masato; Katto, Masahito; Okuda, Masahiro

1993-06-01

415

Parameterization of surface heat fluxes above forest with satellite thermal sensing and boundary-layer soundings  

NASA Technical Reports Server (NTRS)

The paper is concerned with the feasibility of determining the surface flux of sensible heat from forest using surface temperatures measured by a satellite together with soundings of temperature aloft in the unstable atmospheric boundary layer. Consideration is also given to the effect of the spatial scale of the surface temperature measurement on the parameterization by means of the scalar roughness. The latent heat flux is derived from the sensible heat flux by means of the energy budget. The data used in the study have been obtained during the HAPEX-MOBILHY experiment of 1986. The approach is based on turbulence similarity for the unstable atmospheric boundary layer.

Brutsaert, Wilfried; Hsu, A. Y.; Schmugge, Thomas J.

1993-01-01

416

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

SciTech Connect

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

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

2012-07-15

417

Particle-Surface Interaction Databases in ALADDIN Format  

DOE Data Explorer

These databases are listed as recommended resources by CFADC. They represent older data and are not necessarily DOE-originated or funded. However, they are cited in the DOE Data Explorer because of their availability through a DOE Data Center. The citations for these databases are: 1) Energy Dependence of Ion-Induced Sputtering Yields of Monatomic Solids in the Low Energy Region. N. Matsunami, Y. Yamamura, N. Itoh, H. Tawara, T. Kawamura. Report IPPJ-AM-52, Institute of Plasma Physics (National Institute for Fusion Science), Nagoya, Japan (1987); 2) Energy Dependence of the Yields of Ion-Induced Sputtering of Monatomic Solids. N. Maksunami, Y. Yamaura, Y. Itikawa, N. Itoh, Y. Kazumata, S. Miyagawer, K. Morita, R. Strimizu, H. Tawara. Report IPPJ-AM-32, Institute of Plasma Physics (National Institute for Fusion Science), Nagoya, Japan (1988); 3) Particle Reflection from Surfaces - A Recommended Data Base. E. W. Thomas, R. K. Janev and J. J. Smith. Report IAEA INDC(NDS)-249, July 1991; 4) Sputtering Data. W. Eckstein, C. Garcia-Rosales, J. Roth and W. Ottenberger. Max-Plank-Institute fur Plasmaphysik Report IPP9/82 (1993); 5) An Evaluated Database for Sputtering. E. W. Thomas, R. K. Janev, J. Botero, J. J. Smith and Y. Qiu. Report IAEA INDC(NDS)-287 (1993).