title: Vacuum-assisted infiltration of chitosan or polycaprolactone as a structural reinforcement for sintered cancellous bovine bone graft

authors: Laird, Dougal Frazer

subjects: Sintered cancellous bovine bone

abstract: Sintered cancellous bovine bone (SCBB) offers numerous advantages as a bone graft substitute material; however, its mechanical properties require improvement. In this study, SCBB was infiltrated with ε-polycaprolactone (PCL) or chitosan/monetite to improve mechanical properties while retaining valuable SCBB structure. Organic infiltrating solutions consisted of (i) chitosan and monetite (CaHPO₄) dissolved in hydrochloric acid; (ii) chitosan, monetite (CaHPO₄), and genipin dissolved in hydrochloric acid; or (iii) PCL polymer dissolved in tetrahydrofuran (THF). Porous SCBB materials were infiltrated with one of the three solutions using vacuum-assisted infiltration. Chitosan and CaHPO₄ were immobilized in the SCBB structure by reprecipitation following a pH increase in an ammonia atmosphere. Genipin was used in one sample group to immobilize chitosan via crosslinking. PCL was immobilized by evaporating the THF carrier solvent. Mechanical compression testing showed an improvement in ultimate stress for the SCBB with chitosan/CaHPO₄ infiltrates, whereas PCL samples showed an increase in modulus. All SCBB samples were found to demonstrate favorable in vitro biocompatibility when subjected to L929 mouse fibroblast cells but required a vigorous washing regime to eradicate toxic ammonia residue. In conclusion, infiltration of SCBB with a polymeric or organic/mineral composite matrix positively modifies SCBB mechanical properties in favor of bone grafting applications.

text: Vacuum-assisted infiltration of chitosan or polycaprolactone as a structural reinforcement for sintered cancellous bovine bone graft Sintered cancellous bovine bone (SCBB) offers numerous advantages as a bone graft substitute material; however, its mechanical properties require improvement. In this study, SCBB was infiltrated with ε-polycaprolactone (PCL) or chitosan/monetite to improve mechanical properties while retaining valuable SCBB structure. Organic infiltrating solutions consisted of (i) chitosan and monetite (CaHPO₄) dissolved in hydrochloric acid; (ii) chitosan, monetite (CaHPO₄), and genipin dissolved in hydrochloric acid; or (iii) PCL polymer dissolved in tetrahydrofuran (THF). Porous SCBB materials were infiltrated with one of the three solutions using vacuum-assisted infiltration. Chitosan and CaHPO₄ were immobilized in the SCBB structure by reprecipitation following a pH increase in an ammonia atmosphere. Genipin was used in one sample group to immobilize chitosan via crosslinking. PCL was immobilized by evaporating the THF carrier solvent. Mechanical compression testing showed an improvement in ultimate stress for the SCBB with chitosan/CaHPO₄ infiltrates, whereas PCL samples showed an increase in modulus. All SCBB samples were found to demonstrate favorable in vitro biocompatibility when subjected to L929 mouse fibroblast cells but required a vigorous washing regime to eradicate toxic ammonia residue. In conclusion, infiltration of SCBB with a polymeric or organic/mineral composite matrix positively modifies SCBB mechanical properties in favor of bone grafting applications.

year: 2012

title: A spectrally-accurate FVTD technique for complicated amplification and reconfigurable filtering EMC devices

authors: Kantartzis, Nikolaos V.

subjects: electromagnetic compatibility

abstract: The consistent and computationally economical analysis of demanding amplification and filtering structures is introduced in this paper via a new spectrally-precise finite-volume time-domain algorithm. Combining a family of spatial derivative approximators with controllable accuracy in general curvilinear coordinates, the proposed method employs a fully conservative field flux formulation to derive electromagnetic quantities in areas with fine structural details. Moreover, the resulting 3-D operators assign the appropriate weight to each spatial stencil at arbitrary media interfaces, while for periodic components the domain is systematically divided to a number of nonoverlapping subdomains. Numerical results from various real-world configurations verify our technique and reveal its universality.

text: A spectrally-accurate FVTD technique for complicated amplification and reconfigurable filtering EMC devices The consistent and computationally economical analysis of demanding amplification and filtering structures is introduced in this paper via a new spectrally-precise finite-volume time-domain algorithm. Combining a family of spatial derivative approximators with controllable accuracy in general curvilinear coordinates, the proposed method employs a fully conservative field flux formulation to derive electromagnetic quantities in areas with fine structural details. Moreover, the resulting 3-D operators assign the appropriate weight to each spatial stencil at arbitrary media interfaces, while for periodic components the domain is systematically divided to a number of nonoverlapping subdomains. Numerical results from various real-world configurations verify our technique and reveal its universality.

year: 2012

title: Honouring our ancestors: Reclaiming the power of Māori maternities

authors: Simmonds, Naomi Beth

abstract: Māori¹ maternal knowledges are intimately tied to ancestors, to ancestral knowledges, and to whenua (land).² Iwi (tribes), hapū (smaller tribal groupings), and whānau (families)³ have their own maternal knowledges, which are woven into their cosmologies, histories, songs, carvings, place names, chants, and incantations. These knowledges, though spatially and temporally specific, speak to the sanctity of the maternal body, the power and prestige of women’s reproductive capabilities, and the empowering collective approach to raising children. Māori knowledges pertaining to pregnancy, childbirth, and parenting were imparted generation to generation as they were lived, embodied and emplaced by our ancestors, sustaining the sacred and empowering approach to maternities within our communities.
This chapter considers the challenges and possibilities of reclaiming Māori maternal knowledges and their associated practices and ceremonies for Māori women and whānau in contemporary Aotearoa-New Zealand. Three key themes frame this chapter. First, I consider the ways in which colonialism has served to silence Māori maternal knowledges to such an extent that whānau are left trying to find meaning in the voices, knowledges, and advices of others. Indigenous women are largely birthing within Western ideologies and institutions that do not adequately provide for Indigenous ways of being and birthing. The chapter then considers the ways in which women and whānau are reclaiming ancient knowledges and practices in new and contemporary ways. I seek to illustrate the ways in which traditional practices and ritual customs have the potential to transform and empower individual and collective experiences of birth and afterbirth. The chapter ends with arguing that Indigenous maternities, Māori maternities, are an important site of decolonization. Reclaiming the messages and embodied practices left to us by our ancestors can provide an empowering collective approach to pregnancy, birth, and afterbirth, and can facilitate a “decolonized pathway” (Simpson 28) into and through the world for our children and for generations to come.

text: Honouring our ancestors: Reclaiming the power of Māori maternities Māori¹ maternal knowledges are intimately tied to ancestors, to ancestral knowledges, and to whenua (land).² Iwi (tribes), hapū (smaller tribal groupings), and whānau (families)³ have their own maternal knowledges, which are woven into their cosmologies, histories, songs, carvings, place names, chants, and incantations. These knowledges, though spatially and temporally specific, speak to the sanctity of the maternal body, the power and prestige of women’s reproductive capabilities, and the empowering collective approach to raising children. Māori knowledges pertaining to pregnancy, childbirth, and parenting were imparted generation to generation as they were lived, embodied and emplaced by our ancestors, sustaining the sacred and empowering approach to maternities within our communities.
This chapter considers the challenges and possibilities of reclaiming Māori maternal knowledges and their associated practices and ceremonies for Māori women and whānau in contemporary Aotearoa-New Zealand. Three key themes frame this chapter. First, I consider the ways in which colonialism has served to silence Māori maternal knowledges to such an extent that whānau are left trying to find meaning in the voices, knowledges, and advices of others. Indigenous women are largely birthing within Western ideologies and institutions that do not adequately provide for Indigenous ways of being and birthing. The chapter then considers the ways in which women and whānau are reclaiming ancient knowledges and practices in new and contemporary ways. I seek to illustrate the ways in which traditional practices and ritual customs have the potential to transform and empower individual and collective experiences of birth and afterbirth. The chapter ends with arguing that Indigenous maternities, Māori maternities, are an important site of decolonization. Reclaiming the messages and embodied practices left to us by our ancestors can provide an empowering collective approach to pregnancy, birth, and afterbirth, and can facilitate a “decolonized pathway” (Simpson 28) into and through the world for our children and for generations to come.

year: 2017