The Experts below are selected from a list of 17502 Experts worldwide ranked by ideXlab platform
De Chen - One of the best experts on this subject based on the ideXlab platform.
-
the influence of Pore Geometry of pt containing zsm 5 beta and sba 15 catalysts on dehydrogenation of propane
Microporous and Mesoporous Materials, 2009Co-Authors: Santhosh M Kumar, Anders Holmen, De ChenAbstract:The influence of the Pore Geometry of the catalyst supports on dehydrogenation of propane (DHP) activity, selectivity to propylene and the degree of coke formation was evaluated over micro-(Pt-ZSM-5 and Pt-Beta) and meso-(Pt-SBA-15) porous materials in a tapered element oscillating microbalance (TEOM) reactor by analyzing reaction products and mass changes simultaneously. The catalysts were prepared by incipient wetness impregnation and were characterized by N2-physisorption, X-ray diffraction (XRD) and H2-chemisorption. The characterization results indicate that catalysts contain Pt within the Pores and Pt nanoparticles of more or less similar sizes however stabilized on markedly different Pore geometries (structure and size). This allowed to (i) largely marginalize the effect of the sizes of Pt particles on DHP and (ii) evaluate exclusively the vital role of Pore Geometry of the supports, where a fraction of Pt is located within the Pores, on the catalytic performance. Pt-ZSM-5 presents the highest propane conversion followed by Pt-Beta and Pt-SBA-15 indicating that the activity decreases with increasing Pore size (ZSM-5 < Beta < SBA-15) of the support. TEOM results evidence that the amount of coke formed during DHP is the highest on Pt-ZSM-5 and is the lowest on Pt-Beta thus, the latter exhibits better catalytic stability than the former and Pt-SBA-15. Among Pt-ZSM-5 and Pt-SBA-15, the former shows better selectivity and stability than the latter despite higher coke content. These observations demonstrate that the three dimensional microporous materials are better catalytic supports for DHP than the mesoporous SBA-15 because of their intrinsic nature that may induce optimum catalytic properties of Pt sites.
-
The influence of Pore Geometry of Pt containing ZSM-5, Beta and SBA-15 catalysts on dehydrogenation of propane
Microporous and Mesoporous Materials, 2009Co-Authors: M. Santhosh Kumar, Anders Holmen, De ChenAbstract:The influence of the Pore Geometry of the catalyst supports on dehydrogenation of propane (DHP) activity, selectivity to propylene and the degree of coke formation was evaluated over micro-(Pt-ZSM-5 and Pt-Beta) and meso-(Pt-SBA-15) porous materials in a tapered element oscillating microbalance (TEOM) reactor by analyzing reaction products and mass changes simultaneously. The catalysts were prepared by incipient wetness impregnation and were characterized by N2-physisorption, X-ray diffraction (XRD) and H2-chemisorption. The characterization results indicate that catalysts contain Pt within the Pores and Pt nanoparticles of more or less similar sizes however stabilized on markedly different Pore geometries (structure and size). This allowed to (i) largely marginalize the effect of the sizes of Pt particles on DHP and (ii) evaluate exclusively the vital role of Pore Geometry of the supports, where a fraction of Pt is located within the Pores, on the catalytic performance. Pt-ZSM-5 presents the highest propane conversion followed by Pt-Beta and Pt-SBA-15 indicating that the activity decreases with increasing Pore size (ZSM-5
Andrew L. Zydney - One of the best experts on this subject based on the ideXlab platform.
-
Permeability - Selectivity Analysis for Ultrafiltration: Effect of Pore Geometry.
Journal of membrane science, 2010Co-Authors: Dharmesh M Kanani, William H Fissell, Shuvo Roy, Anna Dubnisheva, Aaron Fleischman, Andrew L. ZydneyAbstract:The effects of Pore size on the performance of ultrafiltration membranes are fairly well understood, but there is currently no information on the impact of Pore Geometry on the trade-off between the selectivity and permeability for membranes with Pore size below 100 nm. Experimental data are presented for both commercial ultrafiltration membranes and for novel silicon membranes having slit-shaped nanoPores of uniform size fabricated by photolithography using a sacrificial oxide technique. Data are compared with theoretical calculations based on available hydrodynamic models for solute and solvent transport through membranes composed of a parallel array of either cylindrical or slit-shaped Pores. The results clearly demonstrate that membranes with slit-shaped Pores have higher performance, i.e., greater selectivity at a given value of the permeability, than membranes with cylindrical Pores. Theoretical calculations indicate that this improved performance becomes much less pronounced as the breadth of the Pore size distribution increases. These results provide new insights into the effects of Pore Geometry on the performance of ultrafiltration membranes.
-
Permeability–selectivity analysis for ultrafiltration: Effect of Pore Geometry
Journal of Membrane Science, 2009Co-Authors: Dharmesh M Kanani, William H Fissell, Shuvo Roy, Anna Dubnisheva, Aaron J. Fleischman, Andrew L. ZydneyAbstract:The effects of Pore size on the performance of ultrafiltration membranes are fairly well understood, but there is currently no information on the impact of Pore Geometry on the trade-off between the selectivity and permeability for membranes with Pore size below 100 nm. Experimental data are presented for both commercial ultrafiltration membranes and for novel silicon membranes having slit-shaped nanoPores of uniform size fabricated by photolithography using a sacrificial oxide technique. Data are compared with theoretical calculations based on available hydrodynamic models for solute and solvent transport through membranes composed of a parallel array of either cylindrical or slit-shaped Pores. The results clearly demonstrate that membranes with slit-shaped Pores have higher performance, i.e., greater selectivity at a given value of the permeability, than membranes with cylindrical Pores. Theoretical calculations indicate that this improved performance becomes much less pronounced as the breadth of the Pore size distribution increases. These results provide new insights into the effects of Pore Geometry on the performance of ultrafiltration membranes.
-
effects of membrane Pore Geometry on fouling behavior during yeast cell microfiltration
Journal of Membrane Science, 2006Co-Authors: Martin Chandler, Andrew L. ZydneyAbstract:The effects of the Pore Geometry on yeast cell fouling during microfiltration were studied using novel micro-patterned membranes having well-defined slot-shaped or circular Pores. Normal flow filtration experiments were performed with Baker's yeast suspensions. The flux decline data were consistent with initial fouling by Pore blockage followed by cake filtration. The specific resistance of the cake layer was a function of both the Pore Geometry and the overall membrane porosity. The initial rate of flux decline was slower for the membrane with slotted Pores compared to the membrane with circular Pores since the initial cell deposition only covered a small fraction of the slotted Pore due to its high aspect ratio. The data then show a transition to cake filtration, with the nature of the transition also a function of the underlying Pore Geometry. A simple geometric model was developed to describe the cake growth phenomenon on slotted Pore membranes. These results provide important insights into the effects of Pore Geometry on membrane fouling.
Sandra Hofmann - One of the best experts on this subject based on the ideXlab platform.
-
Scaffold Pore Geometry guides gene regulation and bone-like tissue formation in dynamic cultures.
Tissue engineering. Part A, 2020Co-Authors: Marina Rubert, Jolanda Rita Vetsch, Iina Lehtoviita, Marianne Sommer, Feihu Zhao, AndrÉ R Studart, Ralph Müller, Sandra HofmannAbstract:Cells sense and respond to scaffold Pore Geometry and mechanical stimuli. Many fabrication methods used in bone tissue engineering render structures with poorly controlled Pore geometries. Given that cell-scaffold interactions are complex, drawing a conclusion on how cells sense and respond to uncontrolled scaffold features under mechanical loading is difficult. Here, monodisperse templated scaffolds (MTSC) were fabricated and used as a well-defined porous scaffolds to study the effect of dynamic culture conditions on bone-like tissue formation. Human bone marrow derived stromal cells were cultured on MTSC or conventional salt-leached scaffolds (SLSC) for up to 7 weeks, either under static or dynamic conditions (wall shear stress (WSS) using spinner flask bioreactors). The influence of controlled spherical Pore Geometry of MTSC subjected to static or dynamic conditions on osteoblast cells differentiation, bone-like tissue formation, structure and distribution was investigated. WSS generated within the two idealized geometrical scaffold features was assessed. Distinct response to fluid flow in osteoblast cell differentiation were shown to be dependent on scaffold Pore Geometry. As revealed by collagen staining and micro-computed tomography images, dynamic conditions promoted a more regular extracellular matrix (ECM) formation and mineral distribution in both scaffold types compared to static conditions. The results showed that regulation of bone-related genes and the amount and the structure of mineralized ECM were dependent on scaffold Pore Geometry and the mechanical cues provided by the two different culture conditions. Under dynamic conditions, SLSC favored osteoblast cell differentiation and ECM formation, while MTSC enhanced ECM mineralization. The spherical Pore shape in MTSC supported a more trabecular bone-like structure under dynamic conditions compared to MTSC statically cultured or to SLSC under either static or dynamic conditions. These results suggest that cell activity and bone-like tissue formation is driven not only by the Pore Geometry but also by the mechanical environment. This should be taken into account in the future design of complex scaffolds, which should favor cell differentiation while guiding the formation, structure and distribution of the engineered bone tissue. This could help to mimic the anatomical complexity of the bone tissue structure and to adapt to each bone defect needs.
-
Scaffold Pore Geometry influences bone-like tissue formation in dynamic cell culture conditions
2020Co-Authors: Marina Rubert, Jolanda Rita Vetsch, Iina Lehtoviita, Marianne Sommer, AndrÉ R Studart, R. Mueller, Sandra HofmannAbstract:Cells sense and respond to scaffold Pore Geometry and mechanical stimuli. Many fabrication methods used in bone tissue engineering render structures with poorly controlled Pore geometries. Given that cell-scaffold interactions are complex, drawing a conclusion on how cells sense and respond to uncontrolled scaffold features under mechanical loading is difficult. Here, monodisperse templated scaffolds (MTSC) were fabricated and used as a well-defined porous scaffolds to study the effect of dynamic culture conditions on bone-like tissue formation. Human bone marrow derived stromal cells were cultured on MTSC or conventional salt-leached scaffolds (SLSC) for up to 7 weeks, either under static or dynamic conditions. Spinner flask bioreactors were used to provide dynamic culture conditions to apply mechanical loading on the seeded cells through wall shear stress. The influence of controlled spherical Pore Geometry of MTSC subjected to static or dynamic conditions on the cell response, specifically on bone-like tissue formation, structure and distribution was investigated. As revealed by collagen staining, mRNA expression levels and micro-computed tomography (micro-CT) images, dynamic conditions supported osteoblast cell differentiation and promoted a more regular extracellular matrix (ECM) formation and mineral distribution in both scaffold types compared to static conditions. The results showed that regulation of bone-related genes and the amount and the structure of mineralized ECM were dependent on scaffold Pore Geometry and the mechanical cues provided by the two different culture conditions. Under dynamic conditions, SLSC favored osteoblast cell differentiation and ECM formation, while MTSC enhanced ECM mineralization. The spherical Pore shape in MTSC supported a more trabecular bone-like structure under dynamic conditions compared to MTSC statically cultured or to SLSC under either static or dynamic conditions. These results suggest that cell activity and bone-like tissue formation is driven not only by the Pore Geometry but also by the mechanical environment. This should be taken into account in the future design of complex scaffolds, which should favor cell differentiation while guiding the formation, structure and distribution of the engineered bone tissue. This could help to mimic the anatomical complexity of the bone tissue structure and to adapt to each bone defect needs.
Bg G Sengers - One of the best experts on this subject based on the ideXlab platform.
-
Pore Geometry regulates early stage human bone marrow cell tissue formation and organisation
Annals of Biomedical Engineering, 2013Co-Authors: J Knychala, Nikolaos Bouropoulos, Cj J Catt, Ol L Katsamenis, Cp P Please, Bg G SengersAbstract:Porous architecture has a dramatic effect on tissue formation in porous biomaterials used in regenerative medicine. However, the wide variety of 3D structures used indicates there is a clear need for the optimal design of Pore architecture to maximize tissue formation and ingrowth. Thus, the aim of this study was to characterize initial tissue growth solely as a function of Pore Geometry. We used an in vitro system with well-defined open Pore slots of varying width, providing a 3D environment for neo-tissue formation while minimizing nutrient limitations. Results demonstrated that initial tissue formation was strongly influenced by Pore Geometry. Both velocity of tissue invasion and area of tissue formed increased as Pores became narrower. This is associated with distinct patterns of actin organisation and alignment depending on Pore width, indicating the role of active cell generated forces. A mathematical model based on curvature driven growth successfully predicted both shape of invasion front and constant rate of growth, which increased for narrower Pores as seen in experiments. Our results provide further evidence for a front based, curvature driven growth mechanism depending on Pore Geometry and tissue organisation, which could provide important clues for 3D scaffold design.
Ol L Katsamenis - One of the best experts on this subject based on the ideXlab platform.
-
Pore Geometry regulates early stage human bone marrow cell tissue formation and organisation
Annals of Biomedical Engineering, 2013Co-Authors: J Knychala, Nikolaos Bouropoulos, Cj J Catt, Ol L Katsamenis, Cp P Please, Bg G SengersAbstract:Porous architecture has a dramatic effect on tissue formation in porous biomaterials used in regenerative medicine. However, the wide variety of 3D structures used indicates there is a clear need for the optimal design of Pore architecture to maximize tissue formation and ingrowth. Thus, the aim of this study was to characterize initial tissue growth solely as a function of Pore Geometry. We used an in vitro system with well-defined open Pore slots of varying width, providing a 3D environment for neo-tissue formation while minimizing nutrient limitations. Results demonstrated that initial tissue formation was strongly influenced by Pore Geometry. Both velocity of tissue invasion and area of tissue formed increased as Pores became narrower. This is associated with distinct patterns of actin organisation and alignment depending on Pore width, indicating the role of active cell generated forces. A mathematical model based on curvature driven growth successfully predicted both shape of invasion front and constant rate of growth, which increased for narrower Pores as seen in experiments. Our results provide further evidence for a front based, curvature driven growth mechanism depending on Pore Geometry and tissue organisation, which could provide important clues for 3D scaffold design.
