Documents disponibles écrits par cet auteur

Insight into role of clay-fluid molecular interactions on permeability and consolidation behavior of na-montmorillonite swelling clay / Priyanthi M. Amarasinghe in Journal of geotechnical and geoenvironmental engineering, Vol. 138 N° 2 (Fevrier 2012) 

Public ISBD [article]  in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 2 (Fevrier 2012) . - pp. 138-146 Titre : Insight into role of clay-fluid molecular interactions on permeability and consolidation behavior of na-montmorillonite swelling clay Type de document : texte imprimé Auteurs : Priyanthi M. Amarasinghe, Auteur ; Kalpana S. Katti, Auteur ; Dinesh R. Katti, Auteur Année de publication : 2012 Article en page(s) : pp. 138-146 Note générale : Géotechnique Langues : Anglais (eng) Mots-clés : Expansive  soils  Permeability  Solvents  Clay  Interactions  Clay  liners  Cohesive  soils  Microscopy  Microstructures  Consolidation Résumé : Swelling clays, also known as expansive clays, are encountered extensively all over the world. These clays are problematic for geotechnical engineering applications because of distress caused to structures and infrastructure as a result of swelling and swelling pressure. These clays are also often used in geoenvironmental engineering applications because of their effective barrier properties as liner materials, e.g., in landfills, ponds, and cutoff trenches. In this study, we report the effect of dielectric constant of fluid on the permeability and consolidation characteristics of Na-montmorillonite swelling clay to investigate the role of clay-fluid molecular interactions on the macroscale properties of the clay. A new “porous rigid wall, flexible wall” permeability device specifically designed for swelling clays that allows for accurate measurement of permeability, swelling pressure and consolidation characteristics, and evaluation of microstructure of swelling clays with fluids with different polarities is used in this study. Results show that clay-fluid molecular interactions have a tremendous effect on the permeability and consolidation characteristics of swelling clay and its microstructure. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v138/i2/p138_s1?isAuthorized=no [article] Insight into role of clay-fluid molecular interactions on permeability and consolidation behavior of na-montmorillonite swelling clay [texte imprimé] / Priyanthi M. Amarasinghe, Auteur ; Kalpana S. Katti, Auteur ; Dinesh R. Katti, Auteur . - 2012 . - pp. 138-146. Géotechnique Langues : Anglais (eng) in Journal of geotechnical and geoenvironmental engineering > Vol. 138 N° 2 (Fevrier 2012) . - pp. 138-146 Mots-clés : Expansive  soils  Permeability  Solvents  Clay  Interactions  Clay  liners  Cohesive  soils  Microscopy  Microstructures  Consolidation Résumé : Swelling clays, also known as expansive clays, are encountered extensively all over the world. These clays are problematic for geotechnical engineering applications because of distress caused to structures and infrastructure as a result of swelling and swelling pressure. These clays are also often used in geoenvironmental engineering applications because of their effective barrier properties as liner materials, e.g., in landfills, ponds, and cutoff trenches. In this study, we report the effect of dielectric constant of fluid on the permeability and consolidation characteristics of Na-montmorillonite swelling clay to investigate the role of clay-fluid molecular interactions on the macroscale properties of the clay. A new “porous rigid wall, flexible wall” permeability device specifically designed for swelling clays that allows for accurate measurement of permeability, swelling pressure and consolidation characteristics, and evaluation of microstructure of swelling clays with fluids with different polarities is used in this study. Results show that clay-fluid molecular interactions have a tremendous effect on the permeability and consolidation characteristics of swelling clay and its microstructure. DEWEY : 624.1 ISSN : 1090-0241 En ligne : http://ascelibrary.org/gto/resource/1/jggefk/v138/i2/p138_s1?isAuthorized=no

Mechanisms of load-deformation behavior of molecular collagen in hydroxyapatite-tropocollagen molecular system / Rahul Bhowmik in Journal of engineering mechanics, Vol. 135 N° 5 (Mai 2009) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 135 N° 5 (Mai 2009) . - pp. 413-421 Titre : Mechanisms of load-deformation behavior of molecular collagen in hydroxyapatite-tropocollagen molecular system : steered molecular dynamics study Type de document : texte imprimé Auteurs : Rahul Bhowmik, Auteur ; Kalpana S. Katti, Auteur ; Dinesh R. Katti, Auteur Année de publication : 2009 Article en page(s) : pp. 413-421 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Deformation  Human  factors  Biological  properties  Mechanical  properties. Résumé : Bone is a widely studied structure due to its important function in the human body and also for its unique mechanical properties, which depend upon several factors, such as, its hierarchal structure, its constituents, degree of interactions between different constituents, etc. The major constituents of bone are collagen and hydroxyapatite (HAP). In this work, the load-carrying behavior of collagen is evaluated using steered molecular dynamics simulations. It is observed that the mineral HAP influences the load-deformation behavior of collagen. The collagen molecule (tropocollagen) requires more energy to deform when it is in close proximity of HAP. The reasons for a typical load-deformation behavior are also analyzed. It is observed that with stretching of the tropocollagen, first hydrogen bonds between the tropocollagen chains break, as a result of which more water molecules start interacting with chains. HAP significantly alters the interaction between tropocollagen and water. The load-carrying behavior of tropocollagen at different loading rates is also analyzed by pulling collagen at different velocities. These simulations give important information about the molecular mechanics of collagen and are also useful for the development of novel biomimetic artificial implant materials. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...] [article] Mechanisms of load-deformation behavior of molecular collagen in hydroxyapatite-tropocollagen molecular system : steered molecular dynamics study [texte imprimé] / Rahul Bhowmik, Auteur ; Kalpana S. Katti, Auteur ; Dinesh R. Katti, Auteur . - 2009 . - pp. 413-421. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 135 N° 5 (Mai 2009) . - pp. 413-421 Mots-clés : Deformation  Human  factors  Biological  properties  Mechanical  properties. Résumé : Bone is a widely studied structure due to its important function in the human body and also for its unique mechanical properties, which depend upon several factors, such as, its hierarchal structure, its constituents, degree of interactions between different constituents, etc. The major constituents of bone are collagen and hydroxyapatite (HAP). In this work, the load-carrying behavior of collagen is evaluated using steered molecular dynamics simulations. It is observed that the mineral HAP influences the load-deformation behavior of collagen. The collagen molecule (tropocollagen) requires more energy to deform when it is in close proximity of HAP. The reasons for a typical load-deformation behavior are also analyzed. It is observed that with stretching of the tropocollagen, first hydrogen bonds between the tropocollagen chains break, as a result of which more water molecules start interacting with chains. HAP significantly alters the interaction between tropocollagen and water. The load-carrying behavior of tropocollagen at different loading rates is also analyzed by pulling collagen at different velocities. These simulations give important information about the molecular mechanics of collagen and are also useful for the development of novel biomimetic artificial implant materials. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...]

Nanomechanics of surface modified nanohydroxyapatite particulates used in biomaterials / Rohit Khanna in Journal of engineering mechanics, Vol. 135 N° 5 (Mai 2009) 

Public ISBD [article]  in Journal of engineering mechanics > Vol. 135 N° 5 (Mai 2009) . - pp. 468-478 Titre : Nanomechanics of surface modified nanohydroxyapatite particulates used in biomaterials Type de document : texte imprimé Auteurs : Rohit Khanna, Auteur ; Kalpana S. Katti, Auteur ; Dinesh R. Katti, Auteur Article en page(s) : pp. 468-478 Note générale : Mécanique appliquée Langues : Anglais (eng) Mots-clés : Bioengineering  Particle  size  Composite  materials  Microstructure  Material  properties  Interfaces  Biological  properties. Résumé : Hydroxyapatite is an important constituent of natural bone, and possesses excellent biocompatibility and bioactivity, but its brittle nature limits its use for bone tissue engineering. Nanohydroxyapatite (nanoHAP) has been used in synthesis of biomimetic composites for more than a decade, yet the mechanics of nanoHAP particles is not fully understood. The present work attempts to advance the current understanding of mechanics of hydroxyapatite at nanoscale, by carrying out systematic nanoindentation experiments on nanoHAP and surface modified nanoHAP [prepared by in situ mineralization in presence of polyacrylic acid (PAAc)]. Quantitative nanomodulus maps of both modified and unmodified HAP nanoparticles indicate that various surface features of HAP nanoparticles can be probed. Dips in values of elastic moduli across the nanoparticle surfaces in modified nanohydroxyapatite are indicative of composite responses from both polymer and mineral phases (PAAc-HAP) on the surface. Nanoindentation experiments were performed at 100, 1,000, 3,000, 5,000, and 8,000 µN loads, respectively, to obtain the indentation response from both shallow and deep penetration depths. Nanoindentation results at shallow penetration depths are influenced by nanoscale surface roughness of irregular-shaped HAP nanoparticles and nonuniform distribution of PAAc in the microstructure. Significant nonbonded interactions between HAP and PAAc, as well as the mechanical properties of individual constituents (HAP and PAAc) lead to superior nanomechanical properties of surface-modified nanoHAP as compared to unmodified HAP. The overall inelastic nanomechanical response (including damage leading to reduced overall elastic modulus) is strongly influenced by the nature of the interfaces between the nanoparticles, especially when indent size is much larger than the particle size. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...] [article] Nanomechanics of surface modified nanohydroxyapatite particulates used in biomaterials [texte imprimé] / Rohit Khanna, Auteur ; Kalpana S. Katti, Auteur ; Dinesh R. Katti, Auteur . - pp. 468-478. Mécanique appliquée Langues : Anglais (eng) in Journal of engineering mechanics > Vol. 135 N° 5 (Mai 2009) . - pp. 468-478 Mots-clés : Bioengineering  Particle  size  Composite  materials  Microstructure  Material  properties  Interfaces  Biological  properties. Résumé : Hydroxyapatite is an important constituent of natural bone, and possesses excellent biocompatibility and bioactivity, but its brittle nature limits its use for bone tissue engineering. Nanohydroxyapatite (nanoHAP) has been used in synthesis of biomimetic composites for more than a decade, yet the mechanics of nanoHAP particles is not fully understood. The present work attempts to advance the current understanding of mechanics of hydroxyapatite at nanoscale, by carrying out systematic nanoindentation experiments on nanoHAP and surface modified nanoHAP [prepared by in situ mineralization in presence of polyacrylic acid (PAAc)]. Quantitative nanomodulus maps of both modified and unmodified HAP nanoparticles indicate that various surface features of HAP nanoparticles can be probed. Dips in values of elastic moduli across the nanoparticle surfaces in modified nanohydroxyapatite are indicative of composite responses from both polymer and mineral phases (PAAc-HAP) on the surface. Nanoindentation experiments were performed at 100, 1,000, 3,000, 5,000, and 8,000 µN loads, respectively, to obtain the indentation response from both shallow and deep penetration depths. Nanoindentation results at shallow penetration depths are influenced by nanoscale surface roughness of irregular-shaped HAP nanoparticles and nonuniform distribution of PAAc in the microstructure. Significant nonbonded interactions between HAP and PAAc, as well as the mechanical properties of individual constituents (HAP and PAAc) lead to superior nanomechanical properties of surface-modified nanoHAP as compared to unmodified HAP. The overall inelastic nanomechanical response (including damage leading to reduced overall elastic modulus) is strongly influenced by the nature of the interfaces between the nanoparticles, especially when indent size is much larger than the particle size. DEWEY : 620.1 ISSN : 0733-9399 En ligne : http://ascelibrary.aip.org/getabs/servlet/GetabsServlet?prog=normal&id=JENMDT000 [...]