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Rough Surface (rough + surface)
Selected AbstractsCost-Efficient Metal,Ceramic Composites,Novel Foam-Preforms, Casting Processes and Characterisation,ADVANCED ENGINEERING MATERIALS, Issue 3 2010Gisela Standke Because of their dissatisfactory cost-performance ratio metal matrix composites (MMCs) are still not established in industry, although they show improved properties compared to pure metals in some application fields. The present paper describes the development of enhanced MMCs based on silicon carbide (SiC) foams made by the Schwartzwalder process. Therefore, foams with cell sizes of 30, 45 and 60,ppi based on pressure less sintered SiC (SSiC) were developed. They were coated with layers of coarse SiC particles, which form a rough strut surface. The ceramic content of the foams could be increased to values of 20,30,mass%. Additionally, foam preforms based on clay-bonded SiC (as they are known from molten metal infiltration) were tested. The preforms were infiltrated with aluminium alloys AlSi9Cu3 and AlSi7Mg0.6 and cast iron EN-GJSA-XNiCr35-5-2 and EN-GJL-250. For aluminium alloys high pressure die casting (HPC) as well as gravity casting was applied, whereas iron was only infiltrated by gravity casting. For HPC an excellent interlocking of metal and preform was observed because of the microporosity of the rough surface of the SSiC foam struts. By the use of gravity casting preform cells up to 45,ppi could be well infiltrated. Microporosity in the ceramic coating and the typical hollow struts of the foams did not show metal infiltration. Even by use of moderate ceramic volume fractions pressure-infiltrated aluminium matrix composites showed a high specific stiffness of up to E/,,=,42,GPa,cm3,g,1 compared to conventional Al or Mg alloys (E/,,=,25,27,GPa,cm3,g,1). Ceramic foam based MMCs produced by pressure less casting showed no advantages in mechanical properties compared to pure metals. Nevertheless it can be expected that they can provide improved wear resistance and lower thermal expansion coefficients. [source] Diffraction imaging in depthGEOPHYSICAL PROSPECTING, Issue 5 2008T.J. Moser ABSTRACT High resolution imaging is of great value to an interpreter, for instance to enable identification of small scale faults, and to locate formation pinch-out positions. Standard approaches to obtain high-resolution information, such as coherency analysis and structure-oriented filters, derive attributes from stacked, migrated images. Since they are image-driven, these techniques are sensitive to artifacts due to an inadequate migration velocity; in fact the attribute derivation is not based on the physics of wave propagation. Diffracted waves on the other hand have been recognized as physically reliable carriers of high- or even super-resolution structural information. However, high-resolution information, encoded in diffractions, is generally lost during the conventional processing sequence, indeed migration kernels in current migration algorithms are biased against diffractions. We propose here methods for a diffraction-based, data-oriented approach to image resolution. We also demonstrate the different behaviour of diffractions compared to specular reflections and how this can be leveraged to assess characteristics of subsurface features. In this way a rough surface such as a fault plane or unconformity may be distinguishable on a diffraction image and not on a traditional reflection image. We outline some characteristic properties of diffractions and diffraction imaging, and present two novel approaches to diffraction imaging in the depth domain. The first technique is based on reflection focusing in the depth domain and subsequent filtering of reflections from prestack data. The second technique modifies the migration kernel and consists of a reverse application of stationary-phase migration to suppress contributions from specular reflections to the diffraction image. Both techniques are proposed as a complement to conventional full-wave pre-stack depth migration, and both assume the existence of an accurate migration velocity. [source] Potential of low cost close-range photogrammetry system in soil microtopography quantificationHYDROLOGICAL PROCESSES, Issue 10 2009Mohamed A. M. Abd Elbasit Abstract Soil microtopography is a dynamic soil property which affects most soil-surface and water interaction processes. The importance of soil microtopography has been recognized for a long time, but only limited reports are available in the literature. In this study, the potential of using consumer-grade cameras and close-range photogrammetry procedures to quantify soil microtopography at plot-scale level (,1 m2) were assessed. Five fabricated gypsum surfaces with different degrees of roughness were used to simulate the soil surface conditions with different soil aggregates. The surfaces' digital elevation model (DEM) was generated using the photogrammetry system (PHM) involving a consumer-grade camera, and pin-microrelief meter (PM). The DEM generated using the PHM was assessed for accuracy, roughness indices (RI), depression area percentage (DA%), depression storage capacity (DSC), and micro-rills delineation in comparison with the PM. The accuracy was evaluated using the root mean square error (RMSE) in the x-, y-, and z-directions. Visual comparison between the 3D-visions of the DEM showed strong agreement between the DEM generated by the PHM and the PM, and between the PHM and the 2D images for the different gypsum surfaces. The average RMSE in the x-. y-, and z-direction were 2·08, 1·52, and 0·82 mm for the rough surface, and 4·42, 1·65, and 3·22 mm for the smooth surface. The RIs calculated from the two methods were highly correlated. The small discrepancy between the two methods was discussed. The micro-rills delineation was also similar for the two methods regarding the network density. The grid size did not effect the RI calculation, and has a strong influence on the DA%, DSC, and the delineated micro-rills orders. Results suggest that a consumer-grade camera and close-range photogrammetry have the potential to quantify the soil microtopography. Copyright © 2009 John Wiley & Sons, Ltd. [source] Bioinspired Degradable Substrates with Extreme Wettability PropertiesADVANCED MATERIALS, Issue 18 2009Wenlong Song Robust superhydrophobic poly(L -lactic acid) (PLLA) substrates are prepared using a new phase-separation-based method. The wettability of the surfaces can be controlled in the range from superhydrophobic to superhydrophilic using argon-plasma treatment. The figure shows water droplets with different contact angles on differently modified PLLA surfaces superimposed on a SEM image of a rough surface. [source] Numerical studies of shear banding in interface shear tests using a new strain calculation method,INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 12 2007Jianfeng Wang Abstract Strain localization is closely associated with the stress,strain behaviour of an interphase system subject to quasi-static direct interface shear, especially after peak stress state is reached. This behaviour is important because it is closely related to deformations experienced by geotechnical composite structures. This paper presents a study using two-dimensional discrete element method (DEM) simulations on the strain localization of an idealized interphase system composed of densely packed spherical particles in contact with rough manufactured surfaces. The manufactured surface is made up of regular or irregular triangular asperities with varying slopes. A new simple method of strain calculation is used in this study to generate strain field inside a simulated direct interface shear box. This method accounts for particle rotation and captures strain localization features at high resolution. Results show that strain localization begins with the onset of non-linear stress,strain behaviour. A distinct but discontinuous shear band emerges above the rough surface just before the peak stress state, which becomes more expansive and coherent with post-peak strain softening. It is found that the shear bands developed by surfaces with smaller roughness are much thinner than those developed by surfaces with greater roughness. The maximum thickness of the intense shear zone is observed to be about 8,10 median particle diameters. The shear band orientations, which are mainly dominated by the rough boundary surface, are parallel with the zero extension direction, which are horizontally oriented. Published in 2007 by John Wiley & Sons, Ltd. [source] Numerical analysis of a 3D hydrodynamic contactINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 12 2006Costin Alin Caciu Abstract We study here the numerical analysis of a hydrodynamic contact in a particular configuration: the 3D incompressible viscous flow of a fluid dragged by a smooth plate over a rough surface. The mathematical model takes into account and discretizes the local topography of the rough profile. The simulation outcome will be the 3D velocity and pressure fields of the fluid film within the contact borders. This work is limited to the study of numerical resolution methods working solely in finite differences. The algorithms will be tested by analysing and comparing their results with analytically known flows. Copyright © 2006 John Wiley & Sons, Ltd. [source] Dynamic scaling for Eley-Rideal reactions over rough surfaceINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 5 2004Ajay Chaudhari Eley-Rideal reaction mechanism is studied over rough surface of random deposition model. Two types of rough surface are considered: (1) different rough surface with same surface density and (2) different rough surface with different surface density. Dynamic scaling theory, which is generally applied to the growing surface, is applied for this reaction mechanism to obtain the temporal and spatial scaling parameters , and ,. The scaling parameters are found to be negative in contrast to the positive scaling parameters in surface growth model. The values of , are the same for both types of surface whereas the values of , are different. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 286,292, 2004 [source] A quasi-planar incident wave excitation for time-domain scattering analysis of periodic structuresINTERNATIONAL JOURNAL OF NUMERICAL MODELLING: ELECTRONIC NETWORKS, DEVICES AND FIELDS, Issue 5 2006David Degerfeldt Abstract We present a quasi-planar incident wave excitation for time-domain scattering analysis of periodic structures. It uses a particular superposition of plane waves that yields an incident wave with the same periodicity as the periodic structure itself. The duration of the incident wave is controlled by means of its frequency spectrum or, equivalently, the angular spread in its constituting plane waves. Accuracy and convergence properties of the method are demonstrated by scattering computations for a planar dielectric half-space. Equipped with the proposed source, a time-domain solver based on linear elements yields an error of roughly 1% for a resolution of 20 points per wavelength and second-order convergence is achieved for smooth scatterers. Computations of the scattering characteristics for a sinusoidal surface and a random rough surface show similar performance. Copyright © 2006 John Wiley & Sons, Ltd. [source] Mesenchymal stem cell interaction with a non-woven hyaluronan-based scaffold suitable for tissue repairJOURNAL OF ANATOMY, Issue 5 2008G. Pasquinelli Summary The fabrication of biodegradable 3-D scaffolds enriched with multipotent stem cells seems to be a promising strategy for the repair of irreversibly injured tissues. The fine mechanisms of the interaction of rat mesenchymal stem cells (rMSCs) with a hyaluronan-based scaffold, i.e. HYAFF®11, were investigated to evaluate the potential clinical application of this kind of engineered construct. rMSCs were seeded (2 × 106 cells cm,2) on the scaffold, cultured up to 21 days and analysed using appropriate techniques. Light (LM), scanning (SEM) and transmission (TEM) electron microscopy of untreated scaffold samples showed that scaffolds have a highly porous structure and are composed of 15-µm-thick microfibres having a rough surface. As detected by trypan blue stain, cell adhesion was high at day 1. rMSCs were viable up to 14 days as shown by CFDA assay and proliferated steadily on the scaffold as revealed by MTT assay. LM showed rMSCs in the innermost portions of the scaffold at day 3. SEM revealed a subconfluent cell monolayer covering 40 ± 10% of the scaffold surface at day 21. TEM of early culture showed rMSCs wrapping individual fibres with regularly spaced focal contacts, whereas confocal microscopy showed polarized expression of CD44 hyaluronan receptor; TEM of 14-day cultures evidenced fibronexus formation. Immunohistochemistry of 21-day cultures showed that fibronectin was the main matrix protein secreted in the extracellular space; decorin and versican were seen in the cell cytoplasm only and type IV collagen was minimally expressed. The expression of CD90, a marker of mesenchymal stemness, was found unaffected at the end of cell culture. Our results show that HYAFF®11 scaffolds support the adhesion, migration and proliferation of rMSCs, as well as the synthesis and delivery of extracellular matrix components under static culture conditions without any chemical induction. The high retention rate and viability of the seeded cells as well as their fine modality of interaction with the substrate suggest that such scaffolds could be potentially useful when wide tissue defects are to be repaired as in the case of cartilage repair, wound healing and large vessel replacement. [source] Some soft tissue characteristics at implant abutments with different surface topographyJOURNAL OF CLINICAL PERIODONTOLOGY, Issue 1 2003A study in humans Abstract Background: If an implant with a rough surface is exposed to the oral cavity, it may accumulate greater amounts of plaque than a smooth surface, which may lead to severe problems with mucositis and peri-implantitis. The purpose of the present paper was to investigate the early inflammatory response to mucosa-penetrating abutments prepared with varying surface roughness. Methods: Nine patients had all five of their original abutments exchanged to test abutments for a 4-week period. The test abutments were prepared with five different roughnesses. The surface roughness was measured with an optical profilometer. At the end of the test period, clinical evaluation was performed; the health of the surrounding mucosa, the amount of accumulated plaque and marginal bleeding were registered. One biopsy was taken from each test abutment. Qualitative and quantitative histological evaluations were performed. Results: There was a statistically significant difference between patients regarding the amount of accumulated plaque on the abutment surfaces and inflammatory cells, but no difference between the surface modifications in relation to plaque accumulation or number of inflammatory cells. Conclusion: No relation was found between inflammatory response and abutment surface roughness after an evaluation time of 4 weeks in a human test model. Zusammenfassung Hintergrund: Wenn ein Implantat mit einer rauhen Oberfläche der Mundhöhle ausgesetzt wird, kann es zu stärkerer Plaqueakkumulation kommen als bei glatten Oberflächen, was zu ernsthaften Problemen mit Mukositis und Periimplantitis führen kann. Zielsetzung: Untersuchung der frühen Entzündungsreaktion auf durch die Schleimhaut tretende Implantatpfeiler mit unterschiedlicher Oberflächenrauhigkeit. Methoden: Bei jedem von 9 Patienten wurden alle 5 ursprünglichen Implantatpfeiler für einen Zeitraum von 4 Wochen gegen Testpfeiler ausgetauscht. Die Testpfeiler waren jeweils mit unterschiedlichen Oberflächenrauhigkeiten präpariert. Die Rauhigkeiten waren mit einem Profilometer gemessen worden. Am Ende des Untersuchungszeitraumes wurden klinische Parameter bestimmt: der Zustand der periimplantären Mukosa, die Menge der akkumulierten Plaque und marginales Bluten. An jedem Pfeiler wurde eine Biopsie entnommen, die jeweils qualitativ und quantitativ histologisch ausgewertet wurde. Ergebnisse: Es bestanden statistisch signifikante interindividuelle Unterschiede zwischen den Patienten hinsichtlich abgelagerter Plaque und Zahl der Entzündungszellen an den Implantatpfeilern, aber keine diesbezüglichen intraindividuellen Unterschiede zwischen den verschiedenen Oberflächenrauhigkeiten. Schlussfolgerung: In einem menschlichen Versuchsmodell wurden über einen Zeitraum von 4 Wochen keine Beziehungen zwischen Entzündungsreaktion und Implantatpfeileroberflächenrauhigkeit beobachtet. Résumé Origine: Lorsqu'un implant à surface rugueuse est exposé dans la cavité buccale, il peut accumuler davantage de plaque qu'une surface lisse, ce qui peut conduire à des problèmes graves associés à une mucite ou une péri-implantite. Le but de cette étude était d'examiner la réponse inflammatoire précoce aux implants pénétrant la muqueuse et ayant une rugosité de surface variable. Méthodes: Les cinq implants d'origine de chacun des neuf patients ont été remplacés par des implants expérimentaux pour une période de quatre semaines. Ces implants expérimentaux ont été conçus avec cinq rugosités différentes. La rugosité de surface a été mesurée à l'aide d'un profilomètre optique. A l'issue de la période expérimentale, une évaluation clinique a été réalisée: l'état de la muqueuse environnante, la quantité de plaque accumulée et le saignement marginal ont été relevés. Une biopsie a été prélevée sur chaque implant expérimental et des évaluations histologiques qualitatives et quantitatives ont été faites. Résultats: Il y avait une différence statistiquement significative entre les patients en ce qui concerne la quantité de plaque accumulée à la surface des implants et les cellules inflammatoires, mais aucune différence entre les modifications de surface en rapport avec l'accumulation de plaque ou le nombre de cellules inflammatoires. Conclusion: Aucune relation n'a étéétablie entre la réponse inflammatoire et la rugosité de surface des implants au bout de quatre semaines d'évaluation dans un modèle expérimental humain. Mots clés: Pilier d'implant; réponse des tissus mous; étude clinique; histologie. [source] Effect of surface roughness on the spatial coherence of X-ray beams from third-generation synchrotron radiation sourcesJOURNAL OF SYNCHROTRON RADIATION, Issue 4 2000Yun Wang The effect of the surface roughness of optical elements, such as Be windows and reflection mirrors, in synchrotron radiation beamlines on the spatial coherence of the X-ray beam is investigated systematically by means of digital simulation, in which a new model for X-ray reflection from a rough surface is proposed. A universal factor is employed to evaluate the spatial coherence quantitatively, based on which critical values for surface roughness are reached. The results from simulation are consistent with those from experiments. [source] Fibrous and Helical Calcite Crystals Induced by Synthetic Polypeptides Containing O -Phospho- L -Serine and O -Phospho- L -ThreonineMACROMOLECULAR BIOSCIENCE, Issue 1 2008Shinya Hayashi Abstract The modification of CaCO3 crystal growth by synthetic L -Ser(PO3H2) and L -Thr(PO3H2) containing polypeptides is described. The amino acids Gly, L -Glu, L -Asp, L -Ser, L -Ala, and L -Lys induced rhombohedral calcite with a rough surface. Dipeptides, Xaa- L -Ser(PO3H2) (Xaa,=,Gly, L -Glu, L -Asp, L -Ser, L -Ala and L -Lys) induced vaterite crystals in the lower [Ca2+]. On the other hand, L -Ser(PO3H2)-containing polypeptides formed spherical vaterite and fibrous calcite. The characteristic helical calcite was found in the presence of copoly[L -Ser(PO3H2)75L -Asp25] or poly[L -Ser(PO3H2)3,L -Asp]. Fibrous calcite, spherical vaterite, and helical calcite crystals were subjected to XRD and EDX analysis. XRD revealed the specific faces of these crystals. EDX spectra and surface analysis visualized the localization of the polypeptides and CaCO3 components. Together with TEM and SAED data, we propose hypothetical growth mechanisms for the fibrous and helical calcite crystals. [source] Fabrication of Biomimetic Superhydrophobic Coating with a Micro-Nano-Binary StructureMACROMOLECULAR RAPID COMMUNICATIONS, Issue 13 2005Ning Zhao Abstract Summary: A superhydrophobic coating was facilely fabricated in one step by casting bisphenol A polycarbonate (PC) solution under moisture. Vapor-induced phase separation occurred during the solidifying process and a rough surface with a micro-nano-binary structure (MNBS) similar to the microstructure shown on lotus leaf was formed. SEM image of a single micro-flower. [source] Integral equation methods for scattering by infinite rough surfacesMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 6 2003Bo Zhang Abstract In this paper, we consider the Dirichlet and impedance boundary value problems for the Helmholtz equation in a non-locally perturbed half-plane. These boundary value problems arise in a study of time-harmonic acoustic scattering of an incident field by a sound-soft, infinite rough surface where the total field vanishes (the Dirichlet problem) or by an infinite, impedance rough surface where the total field satisfies a homogeneous impedance condition (the impedance problem). We propose a new boundary integral equation formulation for the Dirichlet problem, utilizing a combined double- and single-layer potential and a Dirichlet half-plane Green's function. For the impedance problem we propose two boundary integral equation formulations, both using a half-plane impedance Green's function, the first derived from Green's representation theorem, and the second arising from seeking the solution as a single-layer potential. We show that all the integral equations proposed are uniquely solvable in the space of bounded and continuous functions for all wavenumbers. As an important corollary we prove that, for a variety of incident fields including an incident plane wave, the impedance boundary value problem for the scattered field has a unique solution under certain constraints on the boundary impedance. Copyright © 2003 John Wiley & Sons, Ltd. [source] Existence of solution in elastic wave scattering by unbounded rough surfacesMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 6 2002T. Arens We consider the two-dimensional problem of the scattering of a time-harmonic wave, propagating in an homogeneous, isotropic elastic medium, by a rough surface on which the displacement is assumed to vanish. This surface is assumed to be given as the graph of a function ,,C1,1(,). Following up on earlier work establishing uniqueness of solution to this problem, existence of solution is studied via the boundary integral equation method. This requires a novel approach to the study of solvability of integral equations on the real line. The paper establishes the existence of a unique solution to the boundary integral equation formulation in the space of bounded and continuous functions as well as in all Lp spaces, p,[1, ,] and hence existence of solution to the elastic wave scattering problem. Copyright © 2002 John Wiley & Sons, Ltd. [source] On the stability and convergence of the finite section method for integral equation formulations of rough surface scatteringMATHEMATICAL METHODS IN THE APPLIED SCIENCES, Issue 4 2001A. Meier We consider the Dirichlet and Robin boundary value problems for the Helmholtz equation in a non-locally perturbed half-plane, modelling time harmonic acoustic scattering of an incident field by, respectively, sound-soft and impedance infinite rough surfaces. Recently proposed novel boundary integral equation formulations of these problems are discussed. It is usual in practical computations to truncate the infinite rough surface, solving a boundary integral equation on a finite section of the boundary, of length 2A, say. In the case of surfaces of small amplitude and slope we prove the stability and convergence as A,, of this approximation procedure. For surfaces of arbitrarily large amplitude and/or surface slope we prove stability and convergence of a modified finite section procedure in which the truncated boundary is ,flattened' in finite neighbourhoods of its two endpoints. Copyright © 2001 John Wiley & Sons, Ltd. [source] Third and fourth Stokes parameters in polarimetric passive microwave remote sensing of rough surfaces over layered mediaMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 12 2008Leung Tsang Abstract We consider the four Stokes parameters in microwave emission from a layered medium with the top interface being a rough surface. The rough surface varies in one horizontal direction so that azimuthal asymmetry exists in the 3-D problem. Dyadic Green's functions of multilayered media are used to formulate the surface integral equations. Periodic boundary conditions are used. The numerical results show that the presence of the layered media below the rough surface reduces the vertical and horizontal brightness temperatures. The interaction between the rough surface and the layered media also enhance the third and fourth Stokes parameters. In particular, the fourth Stokes parameter can be large for such geometrical configurations. Results show that the nonzero third and fourth Stokes parameters exist for all frequencies and are particularly large when the rough surface has large slope. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 3063,3069, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23892 [source] Modeling absorption of rough interface between dielectric and conductive mediumMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 1 2007Xiaoxiong Gu Abstract The effects of a random rough surface between dielectric and lossy conductive medium on power absorption are analyzed by considering incident plane waves impinging on the interface. We use two methods to formulate and solve the 2-D problem: the two-media small perturbation method to second order (SPM2) and the numerical system transfer operator matrix method, referred to as T-matrix method. The two methods are in agreement within the regimes of validity. The results show significant difference between absorption of a rough surface and that of a smooth surface. Surface fields are further examined numerically. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 7,13, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22023 [source] Multiple sweep method of moments analysis of electromagnetic scattering from 3D targets on ocean-like rough surfacesMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 1 2007D. Çolak Abstract This paper presents the multiple sweep method of moments (MSMM) analysis of electromagnetic (EM) scattering from three dimensional (3D) targets on ocean-like rough surfaces. The MSMM is a recursive method for solving the large matrix equations which arise in the method of moments (MoM) analysis of electrically large bodies. In the MSMM, the body is split into P sections and the currents on these sections are found in a sequential downrange-uprange fashion. The first sweep includes the dominant scattering mechanisms and each subsequent sweep includes higher order mechanisms. The results obtained from this study demonstrate that the MSMM is a very reliable and efficient tool for the analysis of this class of problems. The numerical results yield insight into electromagnetic scattering mechanisms associated with a 3D target on a rough surface, and provide accurate and robust reference solutions for more approximate techniques which can handle larger geometries more efficiently. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 241,247, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22074 [source] Ag buffer layer effect on magnetization reversal of epitaxial Co filmsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 15 2004D. H. Wei Abstract Nano-sized Ag(111) islands were first prepared by using molecular beam epitaxy technique on diluted-hydrofluoric acid etched Si(111) substrate. Epitaxial Co films were then grown onto the Ag films at 100 °C to decrease interdiffusion. The Ag buffer layer designed to form isolated islands with {111} sidewalls on the Si(111) substrate, and provided Co films (111) texture growth to study the correlation between magnetic properties of Co films and Ag buffer layer effect. It reveals that the Ag rough surface acts as a pinning source and Ag {111} sidewalls also plays an important role on the magnetoresistance transition of Co films. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Properties of Ga2O3 -based (Inx Ga1,x)2O3 alloy thin films grown by molecular beam epitaxyPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 9 2008Takayoshi Oshima Abstract A series of Ga2O3 -based (Inx Ga1,x)2O3 alloy thin films have been grown on c-plane sapphire substrates with a thin Ga2O3 buffer layer by plasma-assisted molecular beam epitaxy. At growth temperatures of 700 °C and higher, even with a slight inclusion of In2O3 to Ga2O3, for example, the film of (In0.08Ga0.92)2O3, exhibited a rough surface and degraded transmission spectrum resulting from phase separation of In2O3. Due to low temperature growth at 600 °C, however, the phase separation was suppressed for the In composition up to 35%, which was confirmed by X-ray diffraction measurement, and the films exhibited high transmittance over 85% with sharp absorption edges. The bandgap could be tuned form 5.0 to 4.0 eV. The results encourage the application of (Inx Ga1,x)2O3 thin films in short-wavelength optical devices. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Deposition of Barrier Layers for Thin Film Solar Cells Assisted by Bipolar Substrate BiasingPLASMA PROCESSES AND POLYMERS, Issue S1 2009Evelyn Häberle Abstract For the development of diffusion and insulation barriers for thin film solar cells on unpolished steel with a rough surface as substrate, investigations of the shape of deposited SiOx layers in dependence on an applied substrate biasing are carried out. Si-wafers with a well-defined surface structure in the range of micrometre are used as ,model' substrate. As a result, the deposition in the indentations of this surface is much higher in the case of a biased substrate. To determine the influence of the bias on the molecular structure, first investigations of the deposited layer without an applied bias are performed with in situ Fourier Transform InfraRed (FTIR) spectroscopy. Hence the molecular composition of the films is monitored during the deposition. In these spectra the Berreman effect occurs and is analysed. [source] Preparation, morphology, and adhesive and mechanical properties of ultrahigh-molecular-weight polyethylene/SiO2 nanocomposite fibersPOLYMER COMPOSITES, Issue 4 2010Yi Zhang A simple treatment approach has been performed to achieve enhanced surface properties of ultrahigh-molecular-weight polyethylene (UHMWPE) fibers by incorporation of nano-silicon dioxide (SiO2) in the presence of silane coupling agent during gel-spinning process. The SiO2 -treated UHMWPE (UHMWPE/SiO2) nanocomposite fibers with different nano-SiO2 compositions were characterized with Fourier transform infrared spectra, scanning electron microscopy, and wide-angle X-ray diffraction, and their interfacial adhesion and mechanical properties were also investigated. The nano-SiO2 can be trapped on the surface of the fibers to form rough surface for UHMWPE/SiO2 fibers, and diffused into the inner of fibers to induce the lower crystal sizes and higher crystallinity of polyethylene in UHMWPE/SiO2 fibers. The resulting UHMWPE/SiO2 fibers therefore exhibit a dramatic enhancement in the adhesive properties because of the combination of rougher surface compared with those of UHMWPE fiber and polar groups absorbed on the surface of fibers. The mechanical properties of UHMWPE/SiO2 nanocomposite fibers are enhanced simultaneously because of the influence of nano-SiO2 on the structure of UHMWPE crystalline regions and fibrils. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers [source] A Thermo-Mechanical Formulation Describing the Frictional Behavior of RubberPROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2003K. Hofstetter Dipl.-Ing. In this paper mechanical and thermal phenomena during the sliding motion of a rubber block on a rough surface are investigated. The presented formulation describes the frictional behavior of rubber on a macroscopic scale. Thus, it is not necessary to consider the roughness of the surface explicitly. Only macroscopic characteristics of the involved solids are required for the contact formulation. For the purpose of parameter identification and model verification, experiments have been carried out. The results from numerical simulations by means of the Finite Element Method (FEM) agree well with the experimental results. [source] Fabrication and Characteristics of Carbon Nanofiber-Reinforced Carbon/Carbon Composites by Fast Catalytic Infiltration Processes,CHEMICAL VAPOR DEPOSITION, Issue 1-3 2009Jin-Cao Zhang Abstract The simultaneous in-situ growth of carbon nanofibers (CNFs) and densification of a CNFs/CF hybrid multiscale felt are accomplished in a single step by thermal gradient chemical vapor infiltration using Fe as the catalyst and vaporized kerosene under atmospheric pressure. A three-dimensional CNF network which could bridge dissimilar components of composites is formed on carbon fibers (CFs). The length of CNFs can reach several micrometers and the diameters are about 80,nm. Smooth and rough surface densified CNFs can be produced after further higher temperature infiltration. CNFs, anchoring to CFs by the adherence of the catalyst nanoparticles, enhance the bonding between CFs and pyrocarbon as well as promoting the formation of a rough laminar pyrocarbon matrix. The deposition mechanisms and physical model are also discussed. This fast catalytic infiltration process can be applied to other ceramic materials and has significant enlargement potential. [source] Clinical Experience of TiUniteÔ Implants: A 5-year Cross-Sectional, Retrospective Follow-Up StudyCLINICAL IMPLANT DENTISTRY AND RELATED RESEARCH, Issue 2010Bertil Friberg DDS ABSTRACT Background: Little is known of the long-term clinical and radiographic performance of moderately rough surface implants. Purpose: The aim of the present retrospective investigation was to study two pioneer cohorts of patients, that is, the first patients to receive Brånemark System® implants with a moderately rough surface (TiUniteÔ, Nobel Biocare AB, Göteborg, Sweden) at the present clinic. TiUnite implants were inserted either in compromised bone sites in a mixed-mouth concept together with turned implants or used solely. Patients were followed up over a period of 5 years with regard to implant survival and the marginal bone response. Materials and Methods: Patients who received both implant types (mixed group) comprised 41 subjects, and the second group (TiUnite group) comprised 70 subjects. A total of 110 turned and 68 TiUnite implants were placed in the mixed group, and 212 TiUnite implants in the TiUnite group. Follow-up radiographs were obtained at prosthesis placement and at the 1- and 5-year check-ups, and examined by independent observers. Results: One turned (0.9%) and two TiUnite (2.9%) implants failed in the mixed group, and three implants (1.6%) failed in the TiUnite group, indicating no significant differences between surfaces or groups (p < .05). The mean marginal bone loss at 5 years was 0.6 mm to 0.8 mm, also indicating no significant differences for the two implant types tested in the mixed group. Conclusions: Cumulative survival rates for the two implant surfaces were favorable at 5 years, and the marginal bone loss was low and similar for both implant surfaces. [source] Biomechanical and histological behavior of zirconia implants: an experiment in the ratCLINICAL ORAL IMPLANTS RESEARCH, Issue 4 2009Ralf J. Kohal Abstract Objective: This study aimed at evaluating the integration of zirconia implants in a rat femur model. Material and methods: Zirconia implants with two distinct surface topographies were compared with titanium implants with similar topographies. Titanium and zirconia implants were placed into the femurs of 42 male Sprague,Dawley rats. Four groups of implants were utilized: machined zirconia implants, zirconia implants with a rough surface, machined titanium implants, and titanium implants with an electrochemically roughened surface. After a healing period of 28 days, the load-bearing capacity between the bone and the implant surface was evaluated by a push-in test. Additionally, after a healing period of 14 and 28 days, respectively, bone tissue specimens containing the implants were processed and histologically analyzed. Results: The mean mineralized bone-to-implant contact showed the highest values after 14 and 28 days for the rough surfaces (titanium: 36%/45%; zirconia: 45%/59%). Also, the push-in test showed higher values for the textured implant surfaces, with no statistical significance between titanium (34 N) and zirconia (45.8 N). Conclusions: Within the limits of the animal investigation presented, it was concluded that all tested zirconia and titanium implant surfaces were biocompatible and osseoconductive. The presented surface modification of zirconia implants showed no difference regarding the histological and biomechanical results compared with an established electrochemically modified titanium implant surface. [source] Direct loading of Nobel Direct® and Nobel Perfect® one-piece implants: a 1-year prospective clinical and radiographic studyCLINICAL ORAL IMPLANTS RESEARCH, Issue 4 2007Per-Olov Östman Abstract Objectives: The aim of this prospective study was to evaluate the Nobel Direct® and Nobel Perfect® one-piece implants (OPIs) when used for immediate function. Material and methods: Forty-eight patients were provided with 115 OPIs for loading with a provisional crown or a bridge within 24 h and followed for at least 12 months with clinical and radiographic examinations. A group of 97 patients previously treated under identical conditions by the same team with 380 two-piece implants (TPIs) for immediate loading in the mandible and maxilla served as the reference group. Results: Six (5.2%) OPIs failed during the follow-up due to extensive bone loss. Five (1.3%) implants failed in the reference group. After 1 year, the mean marginal bone loss was 2.1 mm (SD 1.3) for OPIs and 0.8 mm (SD 1) for TPIs. 20% of OPIs showed more than 3 mm of bone loss compared with 0.6% for TPIs. When compensating for vertical placement depth, OPIs still showed a lower marginal bone level and thus more exposed threads than TPIs. Depending on the criteria used, the success rate for OPIs was 46.1% or 72.2% compared with 85% or 91.6% for TPIs. Conclusions: The Nobel Direct® and Nobel Perfect® OPIs show lower success rates and more bone resorption than TPIs after 1 year in function. Factors such as implant design, insertion depth, rough surface towards the mucosa, in situ preparation and immediate loading may have an influence on the clinical outcome. [source] Aqueous films limit bacterial cell motility and colony expansion on partially saturated rough surfacesENVIRONMENTAL MICROBIOLOGY, Issue 5 2010Gang Wang Summary Bacterial motility is a key mechanism for survival in a patchy environment and is important for ecosystem biodiversity maintenance. Quantitative description of bacterial motility in soils is hindered by inherent heterogeneity, pore-space complexity and dynamics of microhydrological conditions. Unsaturated conditions result in fragmented aquatic habitats often too small to support full bacterial immersion thereby forcing strong interactions with mineral and air interfaces that significantly restrict motility. A new hybrid model was developed to study hydration effects on bacterial motility. Simulation results using literature parameter values illustrate sensitivity of colony expansion rates to hydration conditions and are in general agreement with measured values. Under matric potentials greater than ,0.5 kPa (wet), bacterial colonies grew fast at colony expansion rates exceeding 421 ± 94 µm h,1; rates dropped significantly to 31 ± 10 µm h,1 at ,2 kPa; as expected, no significant colony expansion was observed at ,5 kPa because of the dominance of capillary pinning forces in the submicrometric water film. Quantification of hydration-related constraints on bacterial motion provides insights into optimal conditions for bacterial dispersion and spatial ranges of resource accessibility important for bioremediation and biogeochemical cycles. Results define surprisingly narrow range of hydration conditions where motility confers ecological advantage on natural surfaces. [source] Hydroxyapatite/SiO2 Composites via Freeze Casting for Bone Tissue Engineering,ADVANCED ENGINEERING MATERIALS, Issue 11 2009Silke Blindow Freeze casting is a fabrication method that allows producing near-net-shaped ceramics with variable porosity. Hydroxyapatite (HA) was modified by the addition of different amounts of SiO2 nanoparticles during freeze cast preparation. The addition of SiO2 introduced a partial phase transformation of HA to , -tricalcium phosphate and improved the form stability due to less shrinkage after sintering. The impact of surface roughness of pure HA ceramics and the influence of SiO2 introduction during freeze casting on adhesion, proliferation, and differentiation of human osteoblast-like cells (MG-63) was investigated. While both cell attachment and proliferation of smooth pressed HA was significantly enhanced compared to rough freeze cast HA, the addition of SiO2 improved the cell numbers of the latter. The expression of cell differentiation markers osteocalcin and collagen I was found to be supported by rough surfaces (Ra,=,5,6,µm) in particular on ceramics containing SiO2 [source] | ||||||||||||||||||||||||||||