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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Morphogenesis of the early post-implantation mouse embryo

Kyprianou, Christos January 2019 (has links)
The morphogenetic events that give rise to the early post-implantation mouse embryo (egg cylinder) have not been thoroughly studied and our knowledge is restricted to "snap-shot" descriptions of embryos recovered at different stages of implantation from the mother. A central feature of the egg cylinder is the pro-amniotic cavity, which spans the embryo and participates in formation of the extraembryonic membranes. The major aims of my PhD studies have been to reveal how this cavity is formed (Aim 1) and then how the egg cylinder grows (Aim 2). In order to address how the pro-amniotic cavity forms (Aim 1), I first characterised in detail development of the architecture of the extra-embryonic ectoderm (ExE), which has to be remodelled to permit cavity formation. My findings indicate that the ExE comprises cells in direct contact with a basement membrane and cells that lie deeper in the tissue. The ExE originates in the polar trophectoderm, a monolayer covering the epiblast of the blastocyst, which expands and undergoes invagination to form a slit-like cavity. By carrying out analyses of fixed specimens and live imaging of cultured embryos, I have found that the epiblast and ExE cavity extend towards each other through the formation and resolution of multiple rosette structures. This leads to the fusion of the ExE and epiblast cavities to form the unified pro-amniotic cavity. I show that this process is dependent on signalling cues stemming from the underlying basement membrane that activate the b1-integrin signalling pathway to regulate cell polarity, ExE tissue architecture and rosette formation. In addition to the basement membrane's role in b1-integrin signalling, it also has physical functions that I characterise in the second part of my study (Aim 2). High resolution imaging revealed that the basement membrane underlying the epiblast is highly perforated during the implantation stages. These perforations are initially evenly distributed and then accumulate asymmetrically at the future posterior part of the embryo, just prior to gastrulation. Finally, I demonstrate that remodelling of the basement membrane requires the expression of matrix metalloproteinases (MMPs) in the epiblast under the control of Nodal. The anterior visceral endoderm inhibits Nodal signalling and hence MMP inhibition in the anterior. I demonstrate that activity of the MMPs and perforations in the basement membrane are essential for embryo growth. The domain of posterior basement membrane perforations persists beyond gastrulation suggesting a potential role for these perforations in primitive streak formation and extension. Together, my studies bring new important insights into the understanding of early mouse embryo morphogenesis.
2

Localização de impactos em materiais compósitos /

Razzini, Adrielly Hokama. January 2017 (has links)
Orientador: Vicente Lopes Junior / Resumo: Materiais compósitos têm sido cada vez mais utilizados na indústria aeronáutica, devido a inúmeras vantagens que serão apresentadas nesse trabalho. Entretanto, impactos podem comprometer significativamente a estrutura. Tais impactos podem ocorrer a “baixa velocidade”, através de ferramentas derrubadas e contato com veículos/equipe de manutenção, e também a “alta velocidade”, como colisões com aves, raios elétricos, detritos de pneus ou pequenas pedras na pista. Conhecer a ocorrência e localização dos mesmos, assim como o progresso de danos subsequentes, permite realizar inspeções mais focadas e otimizar o custo e eficiência de manutenção. Este trabalho propõe a utilização de transdutores piezelétricos em formato de rosetas piezelétricas para localização de impacto em estruturas de materiais compósitos. As rosetas são compostas de transdutores retangulares de Macro-Fiber Composite (MFC), que apresentam uma resposta altamente diretiva para ondas ultrassonoras, o que foi explorado para determinar a localização da onda emitida, independente da velocidade de propagação da onda na estrutura. A acuracidade do mé- todo foi demonstrada experimentalmente em uma placa de fibra de carbono/ resina epóxi de dimensões 1060 ×1100×2mm, formada de 13 camadas plain-weave com duas rosetas piezelétricas coladas à superfície via adesivo cianoacrilato. Os impactos foram conduzidos utilizando um pequeno martelo com ponta metálica, simulando impactos realísticos sofridos por uma estrutu... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The usage of composite materials has been experiencing a continuous growth in aeronautic industry, due to countless advantages. However, impacts can significantly compromise the structure. These impacts can occur at "low velocity", by tools dropped, contact with maintenance vehicles or personnel and also at "high velocity", by bird/hail strikes, runaway debris from tires os lightnings. Knowing the occurrence and location of the impacts, as well as the progression of any subsequent damage, allows performing focused follow-up inspections, which can optimize maintenance cost and effectiveness. This work proposes using piezoelectric transducers arranged as rosettes to locate impacts on composite materials structures. The rosettes are comprised of rectangular transducers of Macro-Fiber Composite (MFC), which exhibit an highly directive response to ultrasonic waves that will were explored to determine the source of the incoming wave, regardless of the wave velocity. The accuracy of this method is experimentally demonstrated on a 1060x1100x2mm carbon/epoxy plate, formed by 13 plain-weave layers with two piezoelectric rosettes bounded to the surface via cyanoacrylate. The impacts were carried out using a small hammer with hardened steel tip, simulating realistic impacts suffered by an in-service structure. The impact point is determined by the proposed method and compared with the actual location of impact. / Mestre
3

Localização de impactos em materiais compósitos / Location of impacts on composite materials

Razzini, Adrielly Hokama [UNESP] 08 May 2017 (has links)
Submitted by Adrielly Hokama Razzini null (adrielly91100@aluno.feis.unesp.br) on 2017-06-08T18:25:27Z No. of bitstreams: 1 Razzini_AH_me_iha.pdf: 17122324 bytes, checksum: 018bdb7d8435fdfe61da7f226c07a068 (MD5) / Approved for entry into archive by Luiz Galeffi (luizgaleffi@gmail.com) on 2017-06-13T13:40:20Z (GMT) No. of bitstreams: 1 razzini_ah_me_ilha.pdf: 17122324 bytes, checksum: 018bdb7d8435fdfe61da7f226c07a068 (MD5) / Made available in DSpace on 2017-06-13T13:40:20Z (GMT). No. of bitstreams: 1 razzini_ah_me_ilha.pdf: 17122324 bytes, checksum: 018bdb7d8435fdfe61da7f226c07a068 (MD5) Previous issue date: 2017-05-08 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Materiais compósitos têm sido cada vez mais utilizados na indústria aeronáutica, devido a inúmeras vantagens que serão apresentadas nesse trabalho. Entretanto, impactos podem comprometer significativamente a estrutura. Tais impactos podem ocorrer a “baixa velocidade”, através de ferramentas derrubadas e contato com veículos/equipe de manutenção, e também a “alta velocidade”, como colisões com aves, raios elétricos, detritos de pneus ou pequenas pedras na pista. Conhecer a ocorrência e localização dos mesmos, assim como o progresso de danos subsequentes, permite realizar inspeções mais focadas e otimizar o custo e eficiência de manutenção. Este trabalho propõe a utilização de transdutores piezelétricos em formato de rosetas piezelétricas para localização de impacto em estruturas de materiais compósitos. As rosetas são compostas de transdutores retangulares de Macro-Fiber Composite (MFC), que apresentam uma resposta altamente diretiva para ondas ultrassonoras, o que foi explorado para determinar a localização da onda emitida, independente da velocidade de propagação da onda na estrutura. A acuracidade do mé- todo foi demonstrada experimentalmente em uma placa de fibra de carbono/ resina epóxi de dimensões 1060 ×1100×2mm, formada de 13 camadas plain-weave com duas rosetas piezelétricas coladas à superfície via adesivo cianoacrilato. Os impactos foram conduzidos utilizando um pequeno martelo com ponta metálica, simulando impactos realísticos sofridos por uma estrutura em serviço. O ponto de impacto foi determinado pelo método proposto e comparado com a localização real do impacto. / The usage of composite materials has been experiencing a continuous growth in aeronautic industry, due to countless advantages. However, impacts can significantly compromise the structure. These impacts can occur at "low velocity", by tools dropped, contact with maintenance vehicles or personnel and also at "high velocity", by bird/hail strikes, runaway debris from tires os lightnings. Knowing the occurrence and location of the impacts, as well as the progression of any subsequent damage, allows performing focused follow-up inspections, which can optimize maintenance cost and effectiveness. This work proposes using piezoelectric transducers arranged as rosettes to locate impacts on composite materials structures. The rosettes are comprised of rectangular transducers of Macro-Fiber Composite (MFC), which exhibit an highly directive response to ultrasonic waves that will were explored to determine the source of the incoming wave, regardless of the wave velocity. The accuracy of this method is experimentally demonstrated on a 1060x1100x2mm carbon/epoxy plate, formed by 13 plain-weave layers with two piezoelectric rosettes bounded to the surface via cyanoacrylate. The impacts were carried out using a small hammer with hardened steel tip, simulating realistic impacts suffered by an in-service structure. The impact point is determined by the proposed method and compared with the actual location of impact. / CNPq: 131152/2015-7
4

Ecological comparison of three closely related species from \kur{Myosotis palustris} group / Ecological comparison of three closely related species from \kur{Myosotis palustris} group

KOUTECKÁ, Eva January 2011 (has links)
The study is focused on comparative ecology of three closely related species from Myosotis palustris group. Importance of various functional traits of individual species was evaluated experimentally in the greenhouse (germination experiments), in the pot experiment and in the reciprocal transplant field experiment. Germination, production of clonal structures and response to various environmental conditions (competition, moisture conditions, etc.) were studied. The experimental data are supplemented with an analysis of phytosociological relationships of the studied species.
5

Decoding ancient Egyptian diadems: symbolism and iconography as a means of interpreting feminine identity

Harris, Stephanie Joan 02 1900 (has links)
Text in English / Ancient Egyptian distinctive headdresses made from precious or semi-precious materials date to prehistoric times, indicating a growing sense of individuality and hierarchy. Women’s headdresses were indicators of rulership, divinity, social status, cultic affiliation and wealth. Visual evidence indicates that female identity was emphasised by external and outward appearance and headdresses in the form of diadems followed recognised stylistic dictates throughout the Dynastic Period. The floral and faunal motifs used in the embellishment were believed to have protective amuletic and magical powers. Although a considerable amount of investigation has been undertaken into the use of materials and techniques used in the manufacture of diadems, the incorporation of symbolism and iconography of these gendered artefacts as a means of interpreting visual messages and self-expression has largely been unexplored. The study has been limited to well-provenanced, extant Old, Middle and New Kingdom diadems housed in various museums worldwide. / Old Testament and Ancient Near Eastern Studies / M.A. (Ancient Near Eastern Studies)
6

Vliv biotických a abiotických faktorů na populační dynamiku kriticky ohroženého druhu Spiranthes spiralis / Influence of biotic and abiotic factors on population dynamics of a critically endangered species Spiranthes spiralis

IPSER, Zdeněk January 2012 (has links)
A population of a critically endangered species Spiranthes spiralis was discovered in 1980 in the National Natural Monument Pastviště u Fínů near village Albrechtice, close to Sušice city. Since 1985 the number of flowering individuals in this population has been annually monitored. Since autumn 1998 all the specimen found there have been marked and biometrically measured. During these periods (12 or 26 years, respectively), large year-on-year fluctuations in the number of flowering plants and in the survival of the individual rosettes have been recorded. The main aim of my work was to assess the effect of weather conditions (temperature, precipitation, the number of days of snow) on the population dynamics and on the fitness of plants (leaf area, probability of flowering and probability of death). The year-round lower temperature and the wet end of autumn during the previous year (t-1) together with the wet spring of the following year (t) had a positive effect on the leaf area during the period of maximal rosette growth (end May in the year t). The probability of flowering was positively affected by the lower temperatures in May and June in the previous year (t-1) and in August just before flowering (year t). The probability of death (in the year t) was increased when the March precipitation (in t) and October temperatures (in t-1) were low. The average number of seeds in the capsule was 1528 ? 885 (s.d.). The number of flowers was positively correlated with the number of mature capsules. However, it did not affect the ratio of mature capsules. Capsules developed on average from 44% ? 24.6 % (s.d.) of the flowers. The average life time of individual plant cohorts was 4.7 years. The number of rosettes per each position was variable from 1 to 7 rosettes (73.2% positions had only 1 rosette). The annual life cycle of the underground organs is described at the end of the thesis.

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