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Relative asymptotics for orthogonal matrix polynomials

Branquinho, A.; Marcellán, F.; Mendes, A.
Fonte: Centro de Matemática da Universidade de Coimbra Publicador: Centro de Matemática da Universidade de Coimbra
Tipo: Pré-impressão
ENG
Relevância na Pesquisa
36.19%
In this paper we study sequences of matrix polynomials that satisfy a non-symmetric recurrence relation. To study this kind of sequences we use a vector interpretation of the matrix orthogonality. In the context of these sequences of matrix polynomials we introduce the concept of the generalized matrix Nevai class and we give the ratio asymptotics between two consecutive polynomials belonging to this class. We study the generalized matrix Chebyshev polynomials and we deduce its explicit expression as well as we show some illustrative examples. The concept of a Dirac delta functional is introduced. We show how the vector model that includes a Dirac delta functional is a representation of a discrete Sobolev inner product. It also allows to reinterpret such perturbations in the usual matrix Nevai class. Finally, the relative asymptotics between a polynomial in the generalized matrix Nevai class and a polynomial that is orthogonal to a modification of the corresponding matrix measure by the addition of a Dirac delta functional is deduced.

The matrix-tolerance hypothesis: an empirical test with frogs in the Atlantic Forest

DIXO, Marianna; METZGER, Jean Paul
Fonte: SPRINGER Publicador: SPRINGER
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.2%
The matrix-tolerance hypothesis suggests that the most abundant species in the inter-habitat matrix would be less vulnerable to their habitat fragmentation. This model was tested with leaf-litter frogs in the Atlantic Forest where the fragmentation process is older and more severe than in the Amazon, where the model was first developed. Frog abundance data from the agricultural matrix, forest fragments and continuous forest localities were used. We found an expected negative correlation between the abundance of frogs in the matrix and their vulnerability to fragmentation, however, results varied with fragment size and species traits. Smaller fragments exhibited stronger matrix-vulnerability correlation than intermediate fragments, while no significant relation was observed for large fragments. Moreover, some species that avoid the matrix were not sensitive to a decrease in the patch size, and the opposite was also true, indicating significant differences with that expected from the model. Most of the species that use the matrix were forest species with aquatic larvae development, but those species do not necessarily respond to fragmentation or fragment size, and thus affect more intensively the strengthen of the expected relationship. Therefore...

Matrix effects observed during pesticides residue analysis in fruits by GC

FREITAS, Silvia de Sousa; LANCAS, Fernando M.
Fonte: WILEY-V C H VERLAG GMBH Publicador: WILEY-V C H VERLAG GMBH
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
36.21%
The influence of the sample matrix in the CC-electron-capture detection analysis of the pesticides dimethoate, diazinon, chlorothalonil.. parathion methyl and fenitrothion in fruits samples has been studied. Experiments have been carried out where the pesticide responses in standard solutions prepared in selected solvent were compared with their response when present in apple, mango, papaya, banana, pineapple and melon extracts. The presence of matrix effects (MEs) and their extent were shown to be simultaneously influenced by several factors (matrix concentration, matrix type, pesticide concentration, analytical range). Pronounced MEs were observed particularly for dimethoate and diazinon in all matrices tested; in lower concentrations, all pesticides presented significant ME. The other pesticides presented variable ME. Higher ME enhancement was detected at lower pesticide concentration levels of and/or at higher matrix concentration solutions. The ME detected for fenitrothion, in the analytical range evaluated, were dependent on matrix type. For each pesticide, solvent and matrix-matched calibrations were compared for all fruit samples, and it could be concluded that quantitation based on standard solutions prepared in blank matrix extract (matrix-matched calibration) should be used to compensate the MEs and to obtain more accurate results for the pesticides studied.; CAPES; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES); Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP); FAPESP; CNPq; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Fibras de sisal: estudo de propriedades e modificações químicas visando a aplicação em compósitos de matriz fenólica; Sisal fibers: studies on the properties and chemical modifications for use in phenolic matrix composites

Megiatto Júnior, Jackson Dirceu
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 23/06/2006 PT
Relevância na Pesquisa
36.21%
Este trabalho relata a utilização das fibras de sisal (Agavea sisalana) como agente de reforço na preparação de compósitos de matriz termorrígida fenólica. Considerando que não se encontra na literatura informações detalhadas sobre a estrutura química de dois dos principais constituintes da fibra de sisal, lignina e hemiceluloses (polioses) foram extraídas e caracterizadas. Além da questão ambiental, em que materiais oriundos de fontes não renováveis, como a matriz fenólica, são substituídos por materiais provenientes de fontes renováveis, como as fibras de sisal, este trabalho também teve como motivação desenvolver materiais compósitos com melhores propriedades. Para alcançar tal objetivo, optou-se por dividir o trabalho em três partes. A primeira etapa correspondeu a otimização dos principais parâmetros envolvidos no processo de preparação dos compósitos, tais como: pressão final de moldagem aplicada, ciclo de cura da matriz fenólica e fração e comprimento das fibras de sisal a serem empregadas como agente de reforço. Os resultados obtidos indicaram que um maior valor de força final de moldagem (20 ton) pode levar a compósitos com melhores propriedades desde que esta maior pressão seja paliçada no ponto de gelificação da matriz fenólica durante o ciclo de cura. Com relação a formulação dos compósitos...

Aspectos celulares, teciduais e moleculares da osteogênese ectópica e ortotópica induzida pela matriz alogênica óssea e dentinária; Cellular, tissue and molecular aspects of the ectopic and orthotopic osteogenese induced by bone and dentine allogenic matrix

Cestari, Tania Mary
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 08/04/2009 PT
Relevância na Pesquisa
36.19%
O objetivo do atual trabalho, foi correlacionar os eventos celulares e teciduais com a expressão das proteínas VEGF, BMP-7, RANKL e OPG durante a osteogênese ectópica e ortotópica, induzida pela matriz óssea (MO) e dentinária (MD) alogênica. Matrizes alogênicas desmineralizada em HCl a 0,6N, obtidas de fêmur e incisivo de ratos, fori implantada entre as fáscias musculares da coxa e em defeito trans-ósseo de 8mm de diâmetro nos ossos parietais. As análises radiográfica e histomorfométrica da neoformação óssea e, a imunohistoquímica e o western blotting para as proteínas VEGF, BMP, RANKL e OPG, mostraram que: a) o volume da região do enxerto nos sítios ortotópicos reduziu 19% em 42 dias; b) em ambos tipos de enxerto e locais de implantação, ocorreu formação de tecido cartilaginoso e ósseo; c) nos sítios intramusculares, a reabsorção da matriz alogênica e a remodelação do tecido cartilaginoso, ósseo e medular foi mais acelerado, em relação a implantação ortotópico; d) o aumento na densidade de volume dos vasos sanguíneos e no número de osteoblastos/osteócitos e osteoclastos ocorreu simultaneamente e estava associado à maior reabsorção da matriz alogênica e à formação do tecido medular (hematopoiético); e) as proteínas VEGF...

Uma proposta de estimação da matriz OD a partir dos fluxos de tráfego observados nas interseções da rede de transportes; A proposal for OD matrix estimation from traffic flow observed at transportation network intersections

Bertoncini, Bruno Vieira
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 19/11/2010 PT
Relevância na Pesquisa
36.19%
A meta do trabalho é propor e testar a hipótese que a contagem de tráfego nas interseções da rede de transportes, ao invés de contagem de tráfego nos arcos, reduz o grau de indeterminação e torna mais precisa a matriz OD estimada pelo modelo sintético. Ademais, é proposto e detalhado um método de estimação da matriz OD através de médias sucessivas (MEMS). É apresentada a descrição matemática das propostas e o detalhamento dos experimentos elaborados para testá-las. Três métodos de estimação, QUEENSOD, TransCAD e MEMS, foram utilizados na verificação da hipótese. A inserção de "arcos virtuais" na rede de transportes constituiu um artifício que permitiu aos programas QUEENSOD e TransCAD realizarem a estimação utilizando fluxos observados nas interseções. A utilização de contagens de fluxo nas interseções propiciou à matriz OD estimada, melhorias que acarretaram sua aproximação com a matriz OD "real". O experimento mostrou que a matriz OD estimada ao considerar contagens de tráfego nas interseções apresenta melhor desempenho em comparação a matriz estimada ao considerar contagens nos arcos da rede de transportes. A matriz estimada gradativamente aproximou-se da "real" à medida que foi aumentada a quantidade de informação de fluxo e sua distribuição na rede. Assim...

Avaliação in vitro de matriz colágena suína como arcabouço tridimensional para cultivo de fibroblastos gengivais; In vitro evaluation of porcine collagen matrix as a threedimensional scaffold for gingival fibroblasts seeding

Mandetta, Carolina de Moraes Rego
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 03/07/2012 PT
Relevância na Pesquisa
36.19%
Introdução: Fibroblastos gengivais desempenham um importante papel na regeneração de tecidos moles de proteção. Mucograft® (MCS-3D) é um substituto xenógeno novo que vem sendo utilizado na periodontia em técnicas de recobrimento radicular e aumento de tecido queratinizado. O objetivo do presente estudo foi avaliar morfológica e imunohistoquimicamente, se a MCS-3D é uma matriz tridimensional adequada, por meio de sua resposta à cultura de fibroblastos gengivais. Material e Métodos: Fibroblastos gengivais humanos (FGH) foram obtidos pela técnica do explante a partir de tecido conjuntivo gengival de três indivíduos. Os FGH foram cultivados sobre colágeno bovino bidimensional (ColB-2D), colágeno bovino tridimensional (ColB-3D) e matriz colágena suína tridimensional (MCS-3D) por até 10 dias. Em 3, 7 e 10 dias, os seguintes parâmetros foram avaliados: número, morfologia e distribuição de FGH por fluorescência direta; viabilidade celular por MTT; proliferação celular e expressão de proteínas citoesqueléticas: actina e tubulina e proteínas da matriz extracelular não colágena: fibronectina imunofluorescência indireta. Os dados quantitativos foram submetidos aos testes estatísticos de Friedman para comparação intra e intergrupos para as variáveis da análise de expressão das proteínas: fibronectina...

O ansatz do produto matricial: uma nova abordagem para modelos exatamente solúveis; The matrix product ansatz: a new formulation far the exact soluble

Lazo, Matheus Jatkoske
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 14/03/2006 PT
Relevância na Pesquisa
36.19%
Neste trabalho mostramos que uma grande variedade de modelos exatamente solúveis através do ansatz de Bethe coordenadas podem também ser resolvidos através de um ansatz do produto matricial. Estes modelos são descritos no caso unidimensional por cadeias quânticas, e por matrizes de transferência no caso de sistemas clássicos bi-dimensionais. Diferentemente do ansatz de Bethe, em que as auto-funções do modelo são escritas como uma combinação de ondas planas, no nosso ansatz do produto matricial elas são dadas por produtos de matrizes, onde as matrizes obedecem a uma álgebra associativa apropriada. Estas relações algébricas são obtidas impondo-se que as auto-funções escritas em termos do ansatz satisfaçam à equação de auto-valor do operador Hamiltoniano ou da matriz de transferência. A consistência das relações de comutatividade entre os elementos da álgebra implicam na exata integrabilidade do modelo. Além disso, o ansatz que propomos permite uma formulação simples e unificada para vários Hamiltonianos quânticos exatamente solúveis. Apresentamos nesta tese a formulação do nosso ansatz do produto matricial para uma grande família de redes quânticas, como os modelos anisotrópico de Heisenberg, Fateev-Zamolodchikov...

The doubly negative matrix completion problem

Araújo, C. Mendes; Torregrosa, Juan R.; Urbano, Ana M.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em 15/05/2005 ENG
Relevância na Pesquisa
36.2%
An $n imes n$ matrix over the field of real numbers is a doubly negative matrix if it is symmetric, negative definite and entry-wise negative. In this paper, we are interested in the doubly negative matrix completion problem, that is when does a partial matrix have a doubly negative matrix completion. In general, we cannot guarantee the existence of such a completion. In this paper, we prove that every partial doubly negative matrix whose associated graph is a $p$-chordal graph $G$ has a doubly negative matrix completion if and only if $p=1$. Furthermore, the question of completability of partial doubly negative matrices whose associated graphs are cycles is addressed.; Fundação para a Ciência e a Tecnologia (FCT) – Programa Operacional “Ciência, Tecnologia, Inovação” (POCTI).; Spanish DGI - BFM2001-0081-C03-02.

N-matrix completion problem

Araújo, C. Mendes; Torregrosa, Juan R.; Urbano, Ana M.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em 01/10/2003 ENG
Relevância na Pesquisa
36.23%
An n x n matrix is called an N-matrix if all principal minors are negative. In this paper, we are interested in N-matrix completion problems, that is, when a partial N-matrix hás an N-matrix completion. In general, a combinatorially or non-combinatorially symmetric partial N-matrix does not have an N-matrix completion. Here we prove that a combinatorially symmetric partial N-matrix has an N-matrix completion if the graph of its specified entries is a 1-chordal graph. We also prove that there exists an N-matrix completion for a partial N-matrix whose associated graph is an undirected cycle.; Fundação para a Ciência e a Tecnologia (FCT) – Programa Operacional “Ciência, Tecnologia, Inovação” (POCTI).

The N-matrix completion problem under digraphs assumptions

Araújo, C. Mendes; Torregrosa, Juan R.; Urbano, Ana M.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em 15/03/2004 ENG
Relevância na Pesquisa
36.2%
An $n imes n$ matrix is called an $N$--matrix if all principal minors are negative. In this paper, we are interested in the partial $N$--matrix completion problem, when the partial $N$--matrix is non-combinatorially symmetric. In general, this type of partial matrices does not have an $N$--matrix completion. We prove that a non-combinatorially symmetric partial $N$--matrix has an $N$--matrix completion if the graph of its specified entries is an acyclic graph or a cycle. We also prove that there exists the desired completion for partial $N$--matrices such that in its associated graphs the cycles play an important role.; Fundação para a Ciência e a Tecnologia (FCT) - Programa Operacional "Ciência, Tecnologia, Inovação" (POCTI). Spanish DGI - grant number BFM2001-0081-C03-02.

The symmetric N-matrix completion problem

Araújo, C. Mendes; Torregrosa, Juan R.; Urbano, Ana M.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Publicado em 01/09/2005 ENG
Relevância na Pesquisa
36.22%
An $n imes n$ matrix is called an $N$-matrix if all its principal minors are negative. In this paper, we are interested in the symmetric $N$-matrix completion problem, that is, when a partial symmetric $N$-matrix has a symmetric $N$-matrix completion. Here, we prove that a partial symmetric $N$-matrix has a symmetric $N$-matrix completion if the graph of its specified entries is chordal. Furthermore, if this graph is not chordal, then examples exist without symmetric $N$-matrix completions. Necessary and sufficient conditions for the existence of a symmetric $N$-matrix completion of a partial symmetric $N$-matrix whose associated graph is a cycle are given.; Fundação para a Ciência e a Tecnologia (FCT) - Programa Operacional "Ciência, Tecnologia, Inovação" (POCTI). Spanish DGI - grant number BFM2001-0081-C03-02. Generalitat Valenciana - GRUPOS03/062.

Regulation of pituitary hormones and cell proliferation by components of the extracellular matrix

Paez-Pereda,M.; Kuchenbauer,F.; Arzt,E.; Stalla,G.K.
Fonte: Associação Brasileira de Divulgação Científica Publicador: Associação Brasileira de Divulgação Científica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/10/2005 EN
Relevância na Pesquisa
36.22%
The extracellular matrix is a three-dimensional network of proteins, glycosaminoglycans and other macromolecules. It has a structural support function as well as a role in cell adhesion, migration, proliferation, differentiation, and survival. The extracellular matrix conveys signals through membrane receptors called integrins and plays an important role in pituitary physiology and tumorigenesis. There is a differential expression of extracellular matrix components and integrins during the pituitary development in the embryo and during tumorigenesis in the adult. Different extracellular matrix components regulate adrenocorticotropin at the level of the proopiomelanocortin gene transcription. The extracellular matrix also controls the proliferation of adrenocorticotropin-secreting tumor cells. On the other hand, laminin regulates the production of prolactin. Laminin has a dynamic pattern of expression during prolactinoma development with lower levels in the early pituitary hyperplasia and a strong reduction in fully grown prolactinomas. Therefore, the expression of extracellular matrix components plays a role in pituitary tumorigenesis. On the other hand, the remodeling of the extracellular matrix affects pituitary cell proliferation. Matrix metalloproteinase activity is very high in all types of human pituitary adenomas. Matrix metalloproteinase secreted by pituitary cells can release growth factors from the extracellular matrix that...

Two iterative algorithms for solving coupled matrix equations over reflexive and anti-reflexive matrices

Dehghan,Mehdi; Hajarian,Masoud
Fonte: Sociedade Brasileira de Matemática Aplicada e Computacional Publicador: Sociedade Brasileira de Matemática Aplicada e Computacional
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2012 EN
Relevância na Pesquisa
36.21%
An n × n real matrix P is said to be a generalized reflection matrix if P T = P and P² = I (where P T is the transpose of P). A matrix A ∈ Rn×n is said to be a reflexive (anti-reflexive) matrix with respect to the generalized reflection matrix P if A = P A P (A = - P A P). The reflexive and anti-reflexive matrices have wide applications in many fields. In this article, two iterative algorithms are proposed to solve the coupled matrix equations { A1 XB1 + C1X T D1 = M1. A2 XB2 + C2X T D2 = M2. over reflexive and anti-reflexive matrices, respectively. We prove that the first (second) algorithm converges to the reflexive (anti-reflexive) solution of the coupled matrix equations for any initial reflexive (anti-reflexive) matrix. Finally two numerical examples are used to illustrate the efficiency of the proposed algorithms. Mathematical subject classification: 15A06, 15A24, 65F15, 65F20.

A Role for Topographic Cues in the Organization of Collagenous Matrix by Corneal Fibroblasts and Stem Cells

Karamichos, Dimitrios; Funderburgh, Martha L.; Hutcheon, Audrey E. K.; Zieske, James D.; Du, Yiqin; Wu, Jian; Funderburgh, James L.
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
EN_US
Relevância na Pesquisa
36.21%
Human corneal fibroblasts (HCF) and corneal stromal stem cells (CSSC) each secrete and organize a thick stroma-like extracellular matrix in response to different substrata, but neither cell type organizes matrix on tissue-culture polystyrene. This study compared cell differentiation and extracellular matrix secreted by these two cell types when they were cultured on identical substrata, polycarbonate Transwell filters. After 4 weeks in culture, both cell types upregulated expression of genes marking differentiated keratocytes (KERA, CHST6, AQP1, B3GNT7). Absolute expression levels of these genes and secretion of keratan sulfate proteoglycans were significantly greater in CSSC than HCF. Both cultures produced extensive extracellular matrix of aligned collagen fibrils types I and V, exhibiting cornea-like lamellar structure. Unlike HCF, CSSC produced little matrix in the presence of serum. Construct thickness and collagen organization was enhanced by TGF-ß3. Scanning electron microscopic examination of the polycarbonate membrane revealed shallow parallel grooves with spacing of 200–300 nm, similar to the topography of aligned nanofiber substratum which we previously showed to induce matrix organization by CSSC. These results demonstrate that both corneal fibroblasts and stromal stem cells respond to a specific pattern of topographical cues by secreting highly organized extracellular matrix typical of corneal stroma. The data also suggest that the potential for matrix secretion and organization may not be directly related to the expression of molecular markers used to identify differentiated keratocytes.

Effect of vitronectin on the deposition, conformation, and physiologic properties of extracellular matrix fibronectin

Gildner, Candace D. (1979 - ); Hocking, Denise C.
Fonte: University of Rochester Publicador: University of Rochester
Tipo: Tese de Doutorado Formato: Illustrations:ill.; Number of Pages:xiv, 261 leaves
ENG
Relevância na Pesquisa
36.24%
Thesis (Ph. D.)--University of Rochester. Dept. of Biomedical Engineering, 2011.; Extracellular matrix (ECM) fibronectin directs many cellular activities that are critical for tissue development and regeneration, including cell growth, migration, and contractility. The factors that regulate the deposition of fibronectin into the ECM and govern how cells respond to ECM fibronectin during tissue repair processes are unknown. The deposition of other ECM proteins, including vitronectin and fibrin, into a provisional ECM in response to tissue injury may be one mechanism by which cellular responses to ECM fibronectin are controlled. Vitronectin has been shown to modulate the deposition of ECM fibronectin, suggesting that the presence of vitronectin during tissue regenerative processes regulates cellular responses to ECM fibronectin. The goal of the studies performed in this thesis was to examine the effects of vitronectin on the functional properties of ECM fibronectin and the deposition of fibronectin into the ECM. The data presented in this thesis show that vitronectin-adherent fibronectin-null cells produce a fibrillar detergent-insoluble fibronectin matrix when cultured in a defined serum-free media. The fibronectin matrix produced by vitronectin-adherent cells was 10-fold less effective at stimulating cell growth than the fibronectin matrix produced by collagen-adherent cells (EC50 = 3.7 ± 1.2 nM and 41.1 ± 1.17 nM for collagen- and vitronectin-adherent cells...

Development and transplantation of a mineralized matrix formed by osteoblasts in vitro for bone regeneration

Xiao, Y.; Haase, H.; Young, W.; Bartold, P.
Fonte: Cognizant Communication Corp Publicador: Cognizant Communication Corp
Tipo: Artigo de Revista Científica
Publicado em //2004 EN
Relevância na Pesquisa
36.21%
The use of extracellular matrix materials as scaffolds for the repair and regeneration of tissues is receiving increased attention. The current study was undertaken to test whether extracellular matrix formed by osteoblasts in vitro could be used as a scaffold for osteoblast transplantation and induce new bone formation in critical size osseous defects in vivo. Human osteoblasts derived from alveolar bone were cultured in six-well plates until confluent and then in mineralization media for a further period of 3 weeks to form an osteoblast-mineralized matrix complex. Histologically, at this time point a tissue structure with a "connective tissue"-like morphology was formed. Type I collagen was the major extracellular component present and appeared to determine the matrix macrostructure. Other bone-related proteins such as alkaline phosphatase (ALP), bone morphogenetic protein (BMP)-2 and -4, bone sialoprotein (BSP), osteopontin (OPN), and osteocalcin (OCN) also accumulated in the matrix. The osteoblasts embedded in this matrix expressed mRNAs for these bone-related proteins very strongly. Nodules of calcification were detected in the matrix and there was a correlation between calcification and the distribution of BSP and OPN. When this matrix was transplanted into a critical size bone defect in skulls of immunodeficient mice (SCID)...

Functional characterisation of the cumulus oocyte matrix during maturation of oocytes.

Dunning, Kylie Renee
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2008
Relevância na Pesquisa
36.23%
Female gametes, or oocytes grow and mature in a niche environment maintained by the somatic cells of the ovarian follicle. At ovulation ovarian follicle cells respond to the luteinising hormone (LH) surge coordinating the final maturation, meiotic resumption and release of oocytes. Simultaneously, production of a unique “mucified” extracellular matrix surrounding the oocyte through synthesis of Hyaluronan (HA) and HA cross-linking proteins produces an “expanded” and stabilised cumulus oocyte matrix with a specific composition, structure and function. In vitro maturation (IVM) of oocytes is a procedure by which cumulus oocyte complexes (COCs) are stimulated to produce cumulus matrix and undergo oocyte maturation ex vivo. In vitro maturation is a useful procedure for studying oocyte competence as well as offering health benefits for patients undergoing assisted reproduction. Oocytes derived from IVM have much lower developmental competence than in vivo matured oocytes, likely as a result of altered environmental conditions and gene expression leading to suboptimal maturation and/or inappropriate metabolic control in oocytes. Cumulus matrix expansion is widely used as an indicator of good oocyte developmental potential, however...

A mesh architecture for data management of matrix computations.

Burdeniuk, Adam
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2014
Relevância na Pesquisa
36.22%
Using super-resolution techniques to estimate the direction that a signal arrived at a radio receiver; Tracking moving targets using particle filters; Applying advanced coding techniques to radio transmissions. Real-world applications like these rely on high-speed matrix computations. Although the computational ability of general-purpose computer architectures is growing, some numerically intensive calculations (such as those above) may benefit from specialised matrix processing hardware. Work in this thesis builds on earlier dense matrix accelerators, which were previously implemented as coprocessors attached to general purpose processor cores. It is well known that matrix algorithms are highly parallelisable, so the coprocessor generally contains many cores to take advantage of this. However, encapsulating them within the coprocessor often prohibits their use in non-matrix computations. This limitation is addressed by the Matrix Data Management Layer (MDML), described in this thesis. The MDML doesnt share the coprocessor-based architecture of earlier systems. Growing transistor budgets have made it feasible to embed general purpose Commercial Off-The-Shelf (COTS) processors within the MDML. Programming is simplified as the system is homogeneous...

Monte Carlo Simulations in Positron Emission Tomography Reconstruction - Full matrix, dual matrix, and system matrix compression; Monte Carlo Simulationen in der PET-Bildrekonstruktion - Full Matrix, Dual Matrix und Matrixkompression

Rehfeld, Niklas Sebastian
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
EN
Relevância na Pesquisa
36.2%
In positron emission tomography (PET) emission density images are formed by photon coincidence measurements. This process is complicated, particularly with regard to the photons that can be scattered in the inhomogeneous patient. A method to incorporate Monte Carlo simulations into the image formation process to model the scattering is presented. This is achieved by simulating the system matrix that describes the map from emission density to detected coincidences. The problem of the very large size of the matrix is met by fitting and B-spline compression of Monte Carlo results. A dedicated Monte Carlo code for system matrix calculation using variance reduction techniques is presented to reduce simulation time. Other desirable properties like reduced sensitivity to Monte Carlo noise and the possibility for sequential compression are met by the presented compression method. In proof-of-principle simulations of single ring scanners it is shown that the matrices compressed by this scheme are good approximations to the uncompressed matrices and that scatter artifacts in the images are strongly suppressed. In the last part, noise in the images introduced by the noise of the Monte Carlo simulated system matrices is investigated and quantified.; In der Photonenemissionstomographie (PET) werden Bilder der Aktivitätsverteilung aus Photonen-Koinzidenzmessungen errechnet. Das ist insbesondere wegen der Streuung der Photonen im inhomogenen Patienten kompliziert. In der vorgestellten Methode werden Monte Carlo Simulationen in der Bildberechnung benutzt...