Showing papers on "Surface roughness published in 1998"

Titanium surface roughness alters responsiveness of MG63 osteoblast‐like cells to 1α,25‐(OH)2D3

Abstract: Surface roughness has been shown to affect differentiation and local factor production of MG63 osteoblast-like cells. This study examined whether surface roughness alters cellular response to circulating hormones such as 1 alpha,25-(OH)2D3. Unalloyed titanium (Ti) disks were pretreated with HF/HNO3 (PT) and then were machined and acid-etched (MA). Ti disks also were sandblasted (SB), sandblasted and acid etched (CA), or plasma sprayed with Ti particles (PS). The surfaces, from smoothest to roughest, were: PT, MA, CA, SB, and PS. MG63 cells were cultured to confluence on standard tissue culture polystyrene (plastic) or the Ti surfaces and then treated for 24 h with either 10(-8) M or 10(-7) M 1 alpha,25-(OH)2D3 or vehicle (control). Cellular response was measured by assaying cell number, cell layer alkaline phosphatase specific-activity, and the production of osteocalcin, latent (L) TGF beta, and PGE2. Alkaline phosphatase activity was affected by surface roughness; as the surface became rougher, the cells showed a significant increase in alkaline phosphatase activity. Addition of 1 alpha,25-(OH)2D3 to the cultures caused a dose-dependent stimulation of alkaline phosphatase activity that was synergistic with the effect caused by surface roughness alone. 1 alpha,25-(OH)2D3 also caused a synergistic increase in osteocalcin production as well as local factor (LTGF beta and PGE2) production on the rougher CA, SB, and PS surfaces, but it had no effect on the production on smooth surfaces. The inhibitory effect of surface roughness on cell number was not affected by 1 alpha,25-(OH)2D3 except on the SB surface. 1 alpha,25-(OH)2D3 decreased cell number, increased alkaline phosphatase activity and osteocalcin production, and had no effect on LTGF beta or PGE2 production by MG63 cells grown on tissue culture polystyrene. These data suggest that bone cell response to systemic hormones is modified by surface roughness and that surface roughness increases the responsiveness of MG63 cells to 1 alpha,25-(OH)2D3. They also suggest that the endocrine system is actively involved in normal bone healing around implants.

DLVO interaction between rough surfaces

Abstract: The interaction energy between microscopic bodies is almost exclusively determined assuming perfectly smooth and geometrically regular surfaces. Quite often, such interactions fail to explain several colloidal phenomena. These inexplicable behaviors of colloidal systems are generally ascribed to surface chemical and morphological heterogeneities. Here, we employ the surface element integration technique to determine the interaction energy between surfaces containing morphological heterogeneity. Random asperities are generated to represent surface morphological heterogeneity (roughness), and their influence on the DLVO interaction potential is investigated. Incorporation of surface roughness causes a significant reduction in the repulsive interaction energy, the extent of which depends on the size of the asperities and their densities on the surface. Predictions of interaction energy indicate that the DLVO interaction energy profiles for rough surfaces deviate significantly from those derived assuming perf...

A histomorphometric evaluation of screw‐shaped implants each prepared with two surface roughnesses

Abstract: Four different surface modifications were designed. Forty screw-shaped implants were divided into 4 groups, 10 screws in each. Every screw was prepared with 2 different surface topographies. The surface topography was measured with a confocal laser scanning profilometer and the surface roughness was characterized using 1 height, 1 spatial and 1 hybrid descriptive parameter. After 12 weeks in rabbit bone all screws were histomorphometrically evaluated. Blasted surfaces demonstrated more bone in contact to implant surface compared with turned surfaces. Most bone in close contact to implant surface was found for a surface blasted with 75 microns sized particles, numerically characterized with an average height deviation (Sa) of 1.4 microns, an average wavelength (Scx) of 11.6 microns and a developed surface area ratio (Sdr) of 1.5.

Influence of Surface Roughness on Liquid Drop Impact

Abstract: The impact of a drop on a rough solid surface is studied experimentally using a shadowgraph method with a rapid CCD camera system. Depending upon the physical parameters of impact a drop either spreads or splashes. For water drops colliding with aluminum surfaces, our experimental results for the onset of splashing on rough surfaces agree with those of Stow and Hadfield (1). The experimental results obtained here for various liquids and surfaces are correlated by an empirical formula relating the minimum “critical” Weber number for splashing to the ratio of the drop radius to the surface roughness coefficient. This formula was proposed by Wu (2) under the assumption that viscous forces can be neglected. By using various mixtures of water and glycerin, the critical Weber number for splashing is found to be indeed independent of viscosity. The formula is however not universal since two coefficients have to be adjusted for each liquid/surface combination. The real shape of the surface also introduces some discrepancy. Perturbations have been observed on the rim of the spreading film. These perturbations appear for a minimum impact velocity and their number depends on surface roughness.

Single-scattering properties of complex ice crystals in terrestrial atmosphere

Abstract: Various ice crystal shapes including fernlike geometry, plates with dendritic extensions and with sector-like and broad branches, fractal geometry, and aggregates, have been numerically defined on the basis of available observations. The surface roughness of ice crystals is also accounted for by specifying the facet-tilt distribution in terms of Gram Charlier series for the small facets of which the rough surface consists. These ice crystal geometries along with those defined in our previous studies may approximately represent the ice crystal shapes frequently observed in cirrus clouds. An improved Monte Carlo/ray-tracing method has been developed to compute the single-scattering parameters for these complex ice crystals. The polarization configurations of the localized waves associated with Fresnelian rays are comprehensively accounted for by the improved method in ray-tracing procedure. Complex ice crystals, in particular, those with fernlike structures, scatter more energy in the angular region 2°-20° and in the lateral and backward directions than hexagonal ice crystals. The former ice crystal geometries normally produce smaller polarization values. In particular, a substantial reduction for the negative polarization associated with the backscattering is found as a result of the complex crystal geometries. The surface roughness of ice crystals incorporated into the single-scattering calculation tends to smooth out the scattering peaks corresponding to halos. The roughness also significantly reduces the backscattering. When a substantial roughness condition is imposed, the computed phase function and the polarization configuration of scattered light are essentially featureless. A database of the single-scattering parameters of ice crystals at solar wavelengths covering 0.2-5 μm has been established for various ice crystal shapes and sizes. This database can be useful in the parameterization of the bulk radiative properties of cirrus clouds to account for the effects of ice crystal size distribution and the percentage of various crystal habits. By applying this database to cold and warm cirrus clouds, it is demonstrated that the scattering and absorption characteristics of these clouds depend on both the size distribution and the shapes of ice crystals.

Fluid jet polishing of optical surfaces.

Abstract: We present a new finishing process that is capable of locally shaping and polishing optical surfaces of complex shapes. A fluid jet system is used to guide a premixed slurry at pressures less than 6 bars to the optical surface. We used a slurry comprising water and 10% #800 SiC abrasives (21.8 μm to reduce the surface roughness of a BK7 sample from 350 to 25 nm rms and to vary the shape of a polished sample BK7, maintaining its surface roughness of 1.6 m rms, thereby proving both the shaping and polishing possibilities of the presented method. © 1998 Optical Society of America.

Condition for precise measurement of soil surface roughness

Abstract: Whereas it is well known that electromagnetic scattering by a randomly rough surface is strongly influenced by the surface-height correlation function, it is not clear as to how long a surface-height profile is needed and at what interval it should be sampled to experimentally quantify the correlation function of a real surface. This paper presents the results of a Monte Carlo simulation conducted to answer these questions. It was determined that, in order to measure the rms height and the correlation length with a precision of /spl plusmn/10%, the surface segment should be at least 40l long and 200l long, respectively, where l is the mean (or true) value of the surface correlation length. Shorter segment lengths can be used if multiple segments are measured and then the estimated values are averaged. The second part of the study focused on the relationship between sampling interval and measurement precision. It was found that, in order to estimate the surface roughness parameters with a precision of /spl plusmn/5%, it is necessary that the surface be sampled at a spacing no longer than 0.2 of the correlation length.

Sputter depth profile analysis of interfaces

Abstract: Beginning with some introductory remarks about aims and scope, historical background and present state of the art, a brief survey of the technique of sputter depth profiling is given. The fundamental principles of ion/solid interactions during sputtering and the resulting changes in surface composition and surface topography as well as their influence on the conversion of sputtering time to sputtered depth are illustrated by some examples. Together with the specific analysis method employed, such as secondary ion mass spectrometry or Auger electron spectroscopy, these effects determine the shape of the depth profile of interfaces and of thin layers. Recent developments in evaluation and quantification of depth profiles are reviewed with emphasis on the role of the depth resolution function in profile reconstruction, including experimental determination and theoretical modelling of the depth resolution function by the three fundamental parameters: atomic mixing, surface roughness and information depth (MRI model). A summary of optimized experimental conditions for high-resolution depth profiles highlights the use of sample rotation and of low-energy primary ions. Practical application of depth profiling at interfaces is further elucidated by typical examples in the fields of surface and grain boundary segregation, corrosion, oxidation and interdiffusion controlled reactions at thin-film interfaces in electronic materials. An outlook on future trends focuses on theoretical profile simulation methods and on instrumental developments.

Surface Roughness Related Processes of Runoff and Soil Loss: A Flume Study

Abstract: Soil surface roughness greatly affects surface sealing and runoff generation, yet little information is available about the effect of roughness on the spatial distribution of runoff and on flow concentration. This study tested the hypothesis that runoff distribution and flow concentration differ with roughness and affect the amount of soil loss. Sequences of four rainstorms of constant rainfall amount but decreasing intensity (60, 45, 30, and 15 mm h -1 ) were applied to the Ap horizon material of a loess soil (Glossic Fragiudalf) packed into a 0.6 by 3.7 m flume. Rough, medium, and smooth soil surfaces were studied at 17, 8, and 2% slope steepness. Surface roughness and flow pathways were visualized with digital elevation maps obtained from laser microrelief measurements. On the smooth surfaces, runoff was uniformly distributed during the first two rainstorms and soil losses were 0.23, 0.07, and 0.12 kg m -2 for the first and 2.26, 0.35, and 0.2 kg m -2 for the second storm at 17, 8, and 2% slope steepness, respectively. On the rough and medium surfaces, flow concentrated in pathways between clods and soil losses were up to eight and three times that on the smooth surfaces during the first and second storms, respectively. During the last two storms, flow concentrated also on the smooth surfaces and soil losses were similar for the three initially different surface configurations. Surface roughness effects on runoff amount were minor, but roughness affected the spatial distribution of runoff, thereby affecting the amount of soil loss.

Diffuse and Specular Reflectance from Rough Surfaces

Abstract: We present a reflection model for isotropic rough surfaces that have both specular and diffuse components. The surface is assumed to have a normal distribution of heights. Parameters of the model are the surface roughness given by the rms slope, the albedo, and the balance between diffuse and specular reflection. The effect of roughness on diffuse reflection is taken into account, instead of our modeling this component as a constant Lambertian term. The model includes geometrical effects such as masking and shadowing. The model is compared with experimental data obtained from goniophotometric measurements on samples of tiles and bricks. The model fits well to samples with very different reflection properties. Measurements of the sample profiles performed with a laser profilometer to determine the rms slope show that the assumed surface model is realistic. The model could therefore be used in machine vision and computer graphics to approximate reflection characteristics of surfaces. It could also be used to predict the texture of surfaces as a function of illumination and viewing angles.

Wetting of rough surfaces

Abstract: A theory is presented to describe the wetting phenomena and the contact line depinning as a function of the microstructure of rough surfaces. The noise and fluctuations of the quenched disorder on self-affine rough surfaces play a important role in the analysis of the spreading of liquids on non-planar substrates. By using the long-range noise correlation function, functional relationships that show the influence of surface roughness on the contact angle, the critical surface tension and the depinning of the contact line are derived. Roughness enhances wetting and broadens the three-phase contact line.

Effect of Surface Roughness on Room-Temperature Wafer Bonding by Ar Beam Surface Activation

Abstract: Using Ar beam etching in vacuum, strong bonding of Si wafers is attained at room temperature. With appropriate etching time, the bonding occurs spontaneously without any load to force two wafers together. However, surface roughness of the wafers increases during Ar beam etching. Because surface roughness has a strong influence on wafer bonding, long etching time degrades the bonding strength. Using atomic force microscope, we measured surface roughness enhancement caused by Ar beam etching, and investigated the relationship between surface roughness and bonding properties such as strength and interfacial voids. The results agree well with theoretical predictions using elastic theory and energy gain by bond formation. A guideline for successful room-temperature bonding is proposed from these results.

Surface roughness of orthodontic wires via atomic force microscopy, laser specular reflectance, and profilometry

Abstract: The surface roughness of orthodontic archwires is an essential factor that determines the effectiveness of arch-guided tooth movement. Using the non-destructive techniques of atomic force microscopy (AFM) and of laser specular reflectance, the surface roughness of 11 nickel-titanium orthodontic wires, a stainless steel and a beta-titanium wire was measured. The results were compared with those obtained using surface profilometry. The smoothest wire, stainless steel, had an optical roughness of 0.10 micron, compared with 0.09 micron from AFM and 0.06 from profilometry. The surface roughness for the beta-titanium wire measured by all three methods was approximately 0.21 micron, while that of the NiTi wires ranged from 0.10 to 1.30 microns. As the surface roughness not only affects the effectiveness of sliding mechanics, but also the corrosion behaviour and the aesthetics of orthodontic components, the manufacturers of orthodontic wires should make an effort to improve the surface quality of their products.

Control of Packing Order of Self-Assembled Monolayers of Magnetite Nanoparticles with and without SiO2 Coating by Microwave Irradiation

Abstract: A close packed layer of Fe3O4 and SiO2-coated Fe3O4 nanoparticles can be assembled on silicon and glass substrates modified with polyelectrolytes following the principle of the layer-by-layer self-assembly (Science 1997, 277, 1232). Microwave (MW) treatment of the poly(dimethyldiallylammonium chloride) layer prior to the nanoparticle adsorption results in substantial reduction of the surface roughness of the particulate films. This effect is attributed to reduction of the length of partially desorbed segments of macromolecules protruding into the aqueous phase at a distance of about 70 nm as estimated from force−distance curves. Aggregation of nanoparticles on these segments is responsible for a relatively high degree of disorder in layer-by-layer self-assembled films. A brief MW exposure results in cross-linking of polyelectrolyte chains. This substantially reduces the number of loose segments, and improves 2D packing of nanoparticles. For optimized conditions, the rms roughness, R, of magnetite self-ass...

Land Surface-Induced Regional Climate Change in Southern Israel

Abstract: Since the mid-1960s, the southern part of Israel has experienced major land use changes following the start of the irrigation scheme and the subsequent intensification of agricultural practice. Several studies, mainly based on the analysis of climatic time series, have shown that this has been followed by a significant change of the local climate, especially during the summer and early fall. They indicate a reduced diurnal amplitude of surface air temperature and wind speed, and a threefold increase of the October (early wet season) convective precipitation. In this paper, these phenomena are investigated by simulating the influence of the land surface on local meteorological variables with a two-dimensional version of a mesoscale atmospheric model containing a detailed land surface scheme. Particular attention is given to the correct estimation of land surface parameters from soil and vegetation maps and remote sensing data. The simulations confirm the observed reduction of the diurnal amplitude of temperature and wind speed when replacing a semiarid surface by a partly irrigated one. Furthermore, it is shown that the potential for moist convection increases with the surface moisture availability and is rather insensitive to the surface roughness.

Aerodynamic Roughness of Urban Areas Derived from Wind Observations

Abstract: This study contributes to the sparse literature on anemometrically determined roughness parameters in cities Data were collected using both slow and fast response anemometry in suburban areas of Chicago, Los Angeles, Miami and Vancouver In all cases the instruments were mounted on tall towers, data were sorted by stability condition, and zero-plane displacement (zd) was taken into account Results indicate the most reliable slow response estimates of surface roughness are based on the standard deviation of the wind speed obtained from observations at one level For residential areas, winter roughness values (leaf-off) are 80–90% of summer (leaf-on) values Direct comparison of fast and slow response methods at one site give very similar results However, when compared to estimates using morphometric methods at a wider range of sites, the fast response methods tend to give larger roughness length values A temperature variance method to determine zd from fast response sensors is found to be useful at only one of the four sites There is no clear best choice of anemometric method to determine roughness parameters There is a need for more high quality field observations, especially using fast response sensors in urban settings

Smooth n-type GaN surfaces by photoenhanced wet etching

Abstract: A room-temperature photoelectrochemical wet etching process is described that produces smoothly etched GaN surfaces using KOH solution and Hg arc lamp illumination. Atomic force microscope measurements indicate a root-mean-square etched surface roughness of 1.5 nm, which compares favorably to the unetched surface roughness of approximately 0.3 nm. Etch rates of 50 nm/min were obtained using a KOH solution concentration of 0.02 M and an illumination intensity of 40 mW/cm2. It is shown that the smooth etching occurs under conditions of low KOH solution concentration and high light intensities, which result in a diffusion-limited etch process.

The effect of scales of surface roughness on the settlement of barnacle (Semibalanus balanoides) cyprids

Abstract: Previous work on the effect of surface roughness on barnacle settlement has used natural surfaces differing in aspects other than surface roughness, or simplistic manufactured surfaces A new technique is presented which permits accurate, controlled and repeatable manufacturing of tiles with a range of complex naturalistic surfaces created from natural components Use of this technique permits an experimental approach to be used to investigate the effects of a range of complex surfaces on barnacle settlement Moulds with smooth (S), fine (F) ( M > C > S Settlement pattern, de

A study on the effects of vibrations on the surface finish using a surface topography simulation model for turning

Abstract: In this paper, a surface topography simulation model is established to simulate the surface finish profile generated after a turning operation. The surface topography simulation model incorporates the effects of the relative motion between the cutting tool and the workpiece with the effects of tool geometry to simulate the resultant surface geometry. It is experimentally shown that the surface topography simulation model can properly simulate the surface profile generated by turning operations. The surface topography simulation model is used to study the effects of vibrations on the surface finish profile. It is found that the vibration frequency ratio is a more important vibration parameter than the vibration frequency on the characterization of the surface finish profile. The vibration frequency ratio is the ratio between the vibration frequency and the spindle rotational speed.

Effect of femoral head surface roughness on the wear of ultrahigh molecular weight polyethylene acetabular cups

Abstract: We studied the effect of femoral head surface roughness on the wear of ultrahigh molecular weight polyethylene (UHMWPE) acetabular cups using a hip joint simulator and a reciprocating wear tester. Compared with the hip simulator, the reciprocating wear tester severely exaggerates the effect of counterface roughness on UHMWPE wear and drastically underestimates the wear rate of the UHMWPE against smooth undamaged counterfaces. According to the hip simulator test results, the wear rate of the UHMWPE cups is approximately proportional to the square root of the femoral head roughness Ra (center-line-average roughness) rather than to Ra raised to a power greater than one as predicted by pin-on-disk studies. Roughening of the femoral heads by an order of magnitude results in a 2- to 3-fold increase in the wear rate. Therefore, the much wider clinical variations of wear cannot be fully explained by variations in surface roughness of the femoral heads.