The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform
John A. Jansen - One of the best experts on this subject based on the ideXlab platform.
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the effect of poly l lactic acid with Parallel Surface micro groove on osteoblast like cells in vitro
Biomaterials, 1999Co-Authors: Kenichi Matsuzaka, J.e. De Ruijter, X F Walboomers, John A. JansenAbstract:In this study we evaluated the behavior of rat bone marrow (RBM) cells on microgrooved poly-L-lactic acid (PLA) and polystyrene (PS) Surfaces. The applied groove depth was 0.5, 1.0 or 1.5 microns, with a groove and ridge width of 1, 2, 5 or 10 microns. Scanning electron microscopical examination showed that a collagen-rich mineralized layer of extracellular matrix (ECM) was deposited. Alignment of the cells and matrix to the Surface grooves was observed as described before. Quantitative evaluation, using a tetracycline labeling assay, revealed that more mineralized ECM was formed on the PLA than on the PS. Further, PLA Surfaces with a groove depth of 1.0 micron and groove widths of 1 and 2 microns induced most mineralized ECM. Finally, alkaline phosphatase activity was also higher on most microgrooved PLA Surfaces, compared with the other materials. On the basis of these observations, we concluded that microtextured Surfaces are able to influence the differentiation of osteoblast-like cells and the deposition of mineralized matrix. Probably, this phenomenon can be used to increase the bone regeneration around oral implants.
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orientation of ecm protein deposition fibroblast cytoskeleton and attachment complex components on silicone microgrooved Surfaces
Journal of Biomedical Materials Research, 1998Co-Authors: E Den T Braber, J.e. De Ruijter, L. A. Ginsel, A. F. Von Recum, John A. JansenAbstract:The microfilaments and vinculin-containing attachment complexes of rat dermal fibroblasts (RDF) incubated on microtextured Surfaces were investigated with confocal laser scanning microscopy (CLSM) and digital image analysis (DIA). In addition, depositions of bovine and endogenous fibronectin and vitronectin were studied. Smooth and microtextured silicone substrata were produced that possessed Parallel Surface grooves with a groove and ridge width of 2.0, 5.0, and 10.0 μm. The groove depth was approximately 0.5 μm. CLSM and DIA make it possible to visualize and analyze intracellular and extracellular proteins and the underlying Surface simultaneously. It was observed that the microfilaments and vinculin aggregates of the RDFs on the 2.0 μm grooved substrata were oriented along the Surface grooves after 1, 3, 5, and 7 days of incubation while these proteins were significantly less oriented on the 5.0 and 10.0 μm grooved Surfaces. Vinculin was located mainly on the Surface ridges on all textured Surfaces. In contrast, bovine and endogenous fibronectin and vitronectin were oriented along the Surface grooves on all textured Surfaces. These proteins did not seem to be hindered by the Surface grooves since many groove-spanning filaments were found on all the microgrooved Surfaces. In conclusion, it can be said that microtextured Surfaces influence the orientation of intracellular and extracellular proteins. Although results corroborate three earlier published hypotheses, they do not justify a specific choice of any one of these hypotheses. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 291–300, 1998.
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Quantitative analysis of cell proliferation and orientation on substrata with uniform Parallel Surface micro grooves
Biomaterials, 1996Co-Authors: E.t. Den Braber, J.e. De Ruijter, H. T. J. Smits, L. A. Ginsel, A. F. Von Recum, John A. JansenAbstract:In order to quantify the effect of the substrata Surface topography on cellular behaviour, planar and micro-textured silicon substrata were produced and made suitable for cell culture by radio frequency glow discharge treatment. These substrata possessed Parallel Surface grooves with a groove and ridge width of 2.0 (SilD02), 5.0 (SilD05) and 10 μm (SilD10). Groove depth was approximately 0.5 μm. Rat dermal fibroblasts (RDFs) were cultured on these substrata and a tissue culture polystyrene control Surface for 1, 2, 3, 5 and 7 days. After incubation the cell proliferation was quantified with a Coulter Counter, and RDF size, shape and orientation with digital image analysis. Cell counts proved that neither the presence of the Surface grooves nor the dimension of these grooves had an effect on the cell proliferation. However, RDFs on SilD02, and to a lesser extent on SilD05 substrata, were elongated and aligned Parallel to the Surface grooves. Orientation of the RDFs on SilD10 substrata proved to be almost comparable to the SilD00 substrata. Finally, it was observed that the cells on the micro-textured substrata were capable of spanning the Surface grooves.
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Effect of Parallel Surface microgrooves and Surface energy on cell growth.
Journal of biomedical materials research, 1995Co-Authors: E.t. Den Braber, J.e. De Ruijter, H. T. J. Smits, L. A. Ginsel, A. F. Von Recum, John A. JansenAbstract:To evaluate the effect of Surface treatment and Surface microtexture on cellular behavior, smooth and microtextured silicone substrata were produced. The microtextured substrata possessed Parallel Surface grooves with a width and spacing of 2.0 (SilD02), 5.0 (SilD05), and 10 microns (SilD10). The groove depth was approximately 0.5 microns. Subsequently, these substrata were either left untreated (NT) or treated by ultraviolet irradiation (UV), radiofrequency glow discharge treatment (RFGD), or both (UVRFGD). After characterization of the substrata, rat dermal fibroblasts (RDF) were cultured on the UV, RFGD, and UVRFGD treated Surfaces for 1, 3, 5, and 7 days. Comparison between the NT and UV substrata revealed that UV treatment did not influence the contact angles and Surface energies of Surfaces with a similar Surface topography. However, the contact angles of the RFGD and UVRFGD substrata were significantly smaller than those of the UV and NT substrata. The dimension of the Surface microevents did not influence the wettability characteristics. Cell culture experiments revealed that RDF cell growth on UV-treated Surfaces was lower than on the RFGD and UVRFGD substrata. SEM examination demonstrated that the Parallel Surface grooves on the SilD02 and SilD05 substrata were able to induce stronger cell orientation and alignment than the events on SilD10 Surfaces. By combining all of our findings, the most important conclusion was that physicochemical parameters such as wettability and Surface free energy influence cell growth but play no measurable role in the shape and orientation of cells on microtextured Surfaces.
Yongjae Lee - One of the best experts on this subject based on the ideXlab platform.
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control method for mono inverter dual Parallel Surface mounted permanent magnet synchronous machine drive system
IEEE Transactions on Industrial Electronics, 2015Co-Authors: Yongjae Lee, Jungik HaAbstract:This paper presents the control method for mono inverter dual Parallel (MIDP) Surface-mounted permanent-magnet synchronous motor (SPMSM) drive system. Unlike the MIDP induction machine drive system, MIDP SPMSM drive system suffers from the inherent instability due to the lack of slip. The proposed active damping control method refrains the system oscillation coming from the mechanical and electrical unbalances and enables the stable operation. This paper also presents the simple maximum torque per ampere control method for MIDP SPMSM drive system. Mathematically calculated optimal currents reduce the amplitude of the currents and improve the drive efficiency. To maximize the merits of the MIDP motor drive system, a sensorless algorithm is also applied. Experiments with the 600-W SPMSMs are executed to verify the feasibility of the proposed control method.
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control method for mono inverter dual Parallel Surface mounted permanent magnet synchronous machine drive system
IEEE Transactions on Industrial Electronics, 2015Co-Authors: Yongjae LeeAbstract:This paper presents the control method for mono inverter dual Parallel (MIDP) Surface-mounted permanent-magnet synchronous motor (SPMSM) drive system. Unlike the MIDP induction machine drive system, MIDP SPMSM drive system suffers from the inherent instability due to the lack of slip. The proposed active damping control method refrains the system oscillation coming from the mechanical and electrical unbalances and enables the stable operation. This paper also presents the simple maximum torque per ampere control method for MIDP SPMSM drive system. Mathematically calculated optimal currents reduce the amplitude of the currents and improve the drive efficiency. To maximize the merits of the MIDP motor drive system, a sensorless algorithm is also applied. Experiments with the 600-W SPMSMs are executed to verify the feasibility of the proposed control method.
Sebastian W. Hoch - One of the best experts on this subject based on the ideXlab platform.
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Topographic Effects on the Surface Radiation Balance in and around Arizona’s Meteor Crater
Journal of Applied Meteorology and Climatology, 2010Co-Authors: Sebastian W. Hoch, C. David WhitemanAbstract:The individual components of the slope-Parallel Surface radiation balance were measured in and around Arizona’s Meteor Crater to investigate the effects of topography on the radiation balance. The crater basin has a diameter of 1.2 km and a depth of 170 m. The observations cover the crater floor, the crater rim, four sites on the inner sidewalls on an east‐west transect, and two sites outside the crater. Interpretation of the role of topography on radiation differences among the sites on a representative clear day is facilitated by the unique symmetric crater topography. The shortwave radiation balance was affected by the topographic effects of terrain exposure, terrain shading, and terrain reflections, and by Surface albedo variations. Terrain exposure caused a site on the steeper upper eastern sidewall of the crater to receive 6% more daily integrated shortwave energy than a site on the lower part of the same slope. Terrain shading had a larger effect on the lower slopes than on the upper slopes. At the lower western slope site the daily total was reduced by 6%. Measurements indicate a diffuse radiation enhancement due to sidewall reflections. The longwave radiation balance was affected by counterradiation from the crater sidewalls and by reduced emissions due to the formation of a nighttime temperature inversion. The total nighttime longwave energy loss at the crater floor was 72% of the loss observed at the crater rim.
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topographic effects on the Surface radiation balance in and around arizona s meteor crater
Journal of Applied Meteorology and Climatology, 2010Co-Authors: Sebastian W. Hoch, David C. WhitemanAbstract:The individual components of the slope-Parallel Surface radiation balance were measured in and around Arizona’s Meteor Crater to investigate the effects of topography on the radiation balance. The crater basin has a diameter of 1.2 km and a depth of 170 m. The observations cover the crater floor, the crater rim, four sites on the inner sidewalls on an east‐west transect, and two sites outside the crater. Interpretation of the role of topography on radiation differences among the sites on a representative clear day is facilitated by the unique symmetric crater topography. The shortwave radiation balance was affected by the topographic effects of terrain exposure, terrain shading, and terrain reflections, and by Surface albedo variations. Terrain exposure caused a site on the steeper upper eastern sidewall of the crater to receive 6% more daily integrated shortwave energy than a site on the lower part of the same slope. Terrain shading had a larger effect on the lower slopes than on the upper slopes. At the lower western slope site the daily total was reduced by 6%. Measurements indicate a diffuse radiation enhancement due to sidewall reflections. The longwave radiation balance was affected by counterradiation from the crater sidewalls and by reduced emissions due to the formation of a nighttime temperature inversion. The total nighttime longwave energy loss at the crater floor was 72% of the loss observed at the crater rim.
J.e. De Ruijter - One of the best experts on this subject based on the ideXlab platform.
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the effect of poly l lactic acid with Parallel Surface micro groove on osteoblast like cells in vitro
Biomaterials, 1999Co-Authors: Kenichi Matsuzaka, J.e. De Ruijter, X F Walboomers, John A. JansenAbstract:In this study we evaluated the behavior of rat bone marrow (RBM) cells on microgrooved poly-L-lactic acid (PLA) and polystyrene (PS) Surfaces. The applied groove depth was 0.5, 1.0 or 1.5 microns, with a groove and ridge width of 1, 2, 5 or 10 microns. Scanning electron microscopical examination showed that a collagen-rich mineralized layer of extracellular matrix (ECM) was deposited. Alignment of the cells and matrix to the Surface grooves was observed as described before. Quantitative evaluation, using a tetracycline labeling assay, revealed that more mineralized ECM was formed on the PLA than on the PS. Further, PLA Surfaces with a groove depth of 1.0 micron and groove widths of 1 and 2 microns induced most mineralized ECM. Finally, alkaline phosphatase activity was also higher on most microgrooved PLA Surfaces, compared with the other materials. On the basis of these observations, we concluded that microtextured Surfaces are able to influence the differentiation of osteoblast-like cells and the deposition of mineralized matrix. Probably, this phenomenon can be used to increase the bone regeneration around oral implants.
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orientation of ecm protein deposition fibroblast cytoskeleton and attachment complex components on silicone microgrooved Surfaces
Journal of Biomedical Materials Research, 1998Co-Authors: E Den T Braber, J.e. De Ruijter, L. A. Ginsel, A. F. Von Recum, John A. JansenAbstract:The microfilaments and vinculin-containing attachment complexes of rat dermal fibroblasts (RDF) incubated on microtextured Surfaces were investigated with confocal laser scanning microscopy (CLSM) and digital image analysis (DIA). In addition, depositions of bovine and endogenous fibronectin and vitronectin were studied. Smooth and microtextured silicone substrata were produced that possessed Parallel Surface grooves with a groove and ridge width of 2.0, 5.0, and 10.0 μm. The groove depth was approximately 0.5 μm. CLSM and DIA make it possible to visualize and analyze intracellular and extracellular proteins and the underlying Surface simultaneously. It was observed that the microfilaments and vinculin aggregates of the RDFs on the 2.0 μm grooved substrata were oriented along the Surface grooves after 1, 3, 5, and 7 days of incubation while these proteins were significantly less oriented on the 5.0 and 10.0 μm grooved Surfaces. Vinculin was located mainly on the Surface ridges on all textured Surfaces. In contrast, bovine and endogenous fibronectin and vitronectin were oriented along the Surface grooves on all textured Surfaces. These proteins did not seem to be hindered by the Surface grooves since many groove-spanning filaments were found on all the microgrooved Surfaces. In conclusion, it can be said that microtextured Surfaces influence the orientation of intracellular and extracellular proteins. Although results corroborate three earlier published hypotheses, they do not justify a specific choice of any one of these hypotheses. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 291–300, 1998.
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Quantitative analysis of cell proliferation and orientation on substrata with uniform Parallel Surface micro grooves
Biomaterials, 1996Co-Authors: E.t. Den Braber, J.e. De Ruijter, H. T. J. Smits, L. A. Ginsel, A. F. Von Recum, John A. JansenAbstract:In order to quantify the effect of the substrata Surface topography on cellular behaviour, planar and micro-textured silicon substrata were produced and made suitable for cell culture by radio frequency glow discharge treatment. These substrata possessed Parallel Surface grooves with a groove and ridge width of 2.0 (SilD02), 5.0 (SilD05) and 10 μm (SilD10). Groove depth was approximately 0.5 μm. Rat dermal fibroblasts (RDFs) were cultured on these substrata and a tissue culture polystyrene control Surface for 1, 2, 3, 5 and 7 days. After incubation the cell proliferation was quantified with a Coulter Counter, and RDF size, shape and orientation with digital image analysis. Cell counts proved that neither the presence of the Surface grooves nor the dimension of these grooves had an effect on the cell proliferation. However, RDFs on SilD02, and to a lesser extent on SilD05 substrata, were elongated and aligned Parallel to the Surface grooves. Orientation of the RDFs on SilD10 substrata proved to be almost comparable to the SilD00 substrata. Finally, it was observed that the cells on the micro-textured substrata were capable of spanning the Surface grooves.
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Effect of Parallel Surface microgrooves and Surface energy on cell growth.
Journal of biomedical materials research, 1995Co-Authors: E.t. Den Braber, J.e. De Ruijter, H. T. J. Smits, L. A. Ginsel, A. F. Von Recum, John A. JansenAbstract:To evaluate the effect of Surface treatment and Surface microtexture on cellular behavior, smooth and microtextured silicone substrata were produced. The microtextured substrata possessed Parallel Surface grooves with a width and spacing of 2.0 (SilD02), 5.0 (SilD05), and 10 microns (SilD10). The groove depth was approximately 0.5 microns. Subsequently, these substrata were either left untreated (NT) or treated by ultraviolet irradiation (UV), radiofrequency glow discharge treatment (RFGD), or both (UVRFGD). After characterization of the substrata, rat dermal fibroblasts (RDF) were cultured on the UV, RFGD, and UVRFGD treated Surfaces for 1, 3, 5, and 7 days. Comparison between the NT and UV substrata revealed that UV treatment did not influence the contact angles and Surface energies of Surfaces with a similar Surface topography. However, the contact angles of the RFGD and UVRFGD substrata were significantly smaller than those of the UV and NT substrata. The dimension of the Surface microevents did not influence the wettability characteristics. Cell culture experiments revealed that RDF cell growth on UV-treated Surfaces was lower than on the RFGD and UVRFGD substrata. SEM examination demonstrated that the Parallel Surface grooves on the SilD02 and SilD05 substrata were able to induce stronger cell orientation and alignment than the events on SilD10 Surfaces. By combining all of our findings, the most important conclusion was that physicochemical parameters such as wettability and Surface free energy influence cell growth but play no measurable role in the shape and orientation of cells on microtextured Surfaces.
Slobodan Žumer - One of the best experts on this subject based on the ideXlab platform.
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Ring defects in a strongly confined chiral liquid crystal.
Physical review letters, 2011Co-Authors: Jun-ichi Fukuda, Slobodan ŽumerAbstract:We find numerically that a regular array of isolated ring defects can exist as a stable state in a highly chiral liquid crystal confined in a thin cell imposing fixed planar anchoring at the Parallel confining Surfaces. This peculiar defect structure can be stable when the cell thickness d is around 3/4 of the helical pitch p. A cell of thickness 3p/4 with Parallel Surface anchoring is incompatible with helical alignment that favors d=mp/2 (with m being an integer). Formation of ring defects can thus be regarded as a result of frustrations between the helical alignment with a specific pitch and the confining Surfaces that prevent it.
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Nematic director‐fields captured in polymer networks confined to spherical droplets
Journal of Applied Physics, 1994Co-Authors: Gregory P. Crawford, R. D. Polak, A. Scharkowski, Liang-chy Chien, Joseph W. Doane, Slobodan ŽumerAbstract:The director‐field of a nematic liquid crystal droplet is captured by a polymer network. The anisotropic polymer network is formed by photopolymerizing a small amount of monomer (2 wt %) in a nematic solvent suspended in a glycerin matrix. The glycerin matrix enforces Parallel Surface anchoring and a lecithin dopant is used to promote homeotropic Surface anchoring. Polymer networks formed under these Surface conditions as well as under applied electric fields are characterized with optical polarizing microscopy.
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Structures of the cholesteric liquid crystal droplets with Parallel Surface anchoring
Liquid Crystals, 1992Co-Authors: J. Bezić, Slobodan ŽumerAbstract:Abstract Model structures of cholesteric liquid crystal droplets embedded in a medium which enforces Parallel Surface anchoring are treated. Structures with disclination lines of integer and half-integer strength are obtained by minimising the Frank free energy. The constant order parameter approximation appropriate for droplets which are large compared to the cores of defects and the approximate ansatz with the molecular director everywhere tangential to the concentric spherical Surfaces are used. Within this approach the structure with a diametrical disclination line is the most stable. Its free energy is compared to that of the non-twisted bipolar structure and to that of the two twisted structures. The well-known structure with a radial disclination line and that with a double radial disclination line not found in the known literature are presented. It is shown that Surface free energy terms, usually omitted in the minimization, do not influence substantially the stability of the structures discussed....
