• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 72
  • 16
  • 7
  • 6
  • 3
  • 3
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 132
  • 50
  • 45
  • 24
  • 24
  • 22
  • 14
  • 14
  • 12
  • 11
  • 11
  • 11
  • 10
  • 9
  • 9
  • 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.
71

Sedenions Cayley-dickson e dilatação de funções k-quaseconformes /

Roque, Michele Regina Dornelas. January 2009 (has links)
Orientador: Manoel Ferreira Borges Neto / Banca: Masoyoshi Tsuchida / Banca: José Arnaldo Frutuoso Roveda / Resumo: Nesta dissertação, estuda-se estruturas matemáticas relacionadas à álgebra dos sedenions de Cayley-Dickson. O conceito de funções sedeniônicas do tipo f(z) = zn, z 2 S e n 2 N, é desenvolvido a partir da distância jf(y)¡f(x)j, com o objetivo de obter-se uma generalização. A este tipo de mapeamentos trata-se por funções quaseconformes, ou seja, mapeamentos que não preservam a magnitude dos ângulos. Em particular, através de métodos de resolução, apresenta-se e discute-se polinômios de 2n graus com coeficientes sedeniônicos com o intuito de enfatizar o valor da k-dilatação causada quando trabalha-se com o número sedeniônico em coordenadas esféricas. Por fim, ilustra-se geometricamente os cortes produzidos em hiperesferas B(x; r) quando submetidas às transformações do tipo z2 e z3. / Abstract: In this work, we propose to study the mathematical construction related with algebra of Cayley-Dickson sedenions. We will present the concept of sedenions functions of f(z) = zn type, z 2 S and n 2 N, developing jf(y) ¡ f(x)j distance, with the objective of creating a generalization. This type of mappings is known as quasiconformal functions, that is, mapping that don't preserve the magnitude of angles. Specially, by means of resolution methods, we will discuss polynomials of 2n degrees with sedenions coefficients focused on highlighting the value of the k-dilation caused when we work with the sedenion number in spherical coordinates. Finally, it is illustrated geometrically the cuts produced in hiperspheres B(x; r) when submitted to the transformations of the type z2 and z3. / Mestre
72

Mechanisms underlying the endothelium-dependent modulation of vascular tone

Iarova, Polina January 2011 (has links)
No description available.
73

Gastrosquise fetal isolada: relação entre dilatação intestinal e resultados perinatais adversos / Isolated fetal gastroschisis: relation between bowel dilation and adverse perinatal outcome

Luciana de Freitas Garcia 30 November 2011 (has links)
Objetivos: Este estudo foi desenvolvido para avaliar o diâmetro transverso da alça intestinal exteriorizada como fator preditor de resultado adverso, nas gestações com gastrosquise fetal isolada. Métodos: Estudo retrospectivo envolvendo 94 gestações únicas. Foi realizada a medida do diâmetro transverso da alça intestinal (DTA) herniada, por meio da ultrassonografia antenatal, até 3 semanas antes do parto. Foi considerado resultado perinatal adverso: óbito intra-útero, óbito neonatal e complicações intestinais. Resultados: a última medida ultrassonográfica do DTA foi realizada com 35,6 ± 1,6 semanas e o tempo médio do intervalo entre a última medida e o parto foi de 6,2 ± 5,0 dias. Ocorreram 10 (10,6%) casos de óbitos intraútero e neonatal; foram observadas complicações intestinais em 8 (8,5%) casos. DTA 15, 20, 25 e 30 mm foram identificadas em 87, 46, 13 e 4% das gestações com prognóstico favorável, respectivamente. O DTA 25 mm apresentou valores de sensibilidade de 38%, e, valores preditivo positivo e preditivo negativo de 38% e 87%, na predição de resultados adversos. Para o DTA 30 mm, os valores foram: 19, 50 e 85%. A área sob a curva ROC do valor observado/esperado do DTA para cada idade gestacional foi de 0,67, sendo o melhor ponto-de-corte em 1,39; e, seus valores preditivos foram semelhantes aos do DTA 25 mm. Dilatação intestinal esteve significantemente associada com baixa taxa de fechamento primário da parede abdominal, longo período para iniciar a dieta via oral e internação hospitalar prolongada. Conclusões: Dilatação intestinal demonstrada até 3 semanas antes do parto é preditora de complicações intestinais e está associado a baixa taxa de fechamento primário da parede abdominal, longo período para iniciar a dieta via oral e de internação hospitalar / Objectives: Evaluate bowel diameter as a predictor of adverse outcome in isolated fetal gastroschisis. Methods: Retrospective study involving 94 singleton pregnancies. Ultrasound measurements of herniated bowel transverse diameter (BTD) were performed up to 3 weeks before delivery. Adverse outcome was intrauterine/ neonatal death and/or bowel complications. Results: Last BTD was recorded at 35,6 ± 1,6 weeks and mean interval to delivery was 6,2 ± 5,0 days. Intrauterine/ neonatal death occurred in 10 (10,6%) cases; bowel complications were observed in 8 (8,5%). BTD 15, 20, 25 and 30mm were found in 87, 46, 13 and 4% of pregnancies with a favorable outcome, respectively. BTD 25 mm sensitivity was 38%, positive and negative predictive values, 38% and 87%. For BTD 30 mm, the values were: 19, 50 and 85%. Observed/expected BTD ROC curve showed an area of 0,67, with best cut-off at 1,39; prediction values were similar to those for BTD 25 mm. Bowel dilatation was also significantly associated with lower rate of primary surgical closure, longer period to full oral feeding and prolonged hospital stay. Conclusions: Bowel dilatation demonstrated up to 3 weeks before delivery is a predictor of intestinal complications and is associated with lower rate of primary surgical closure, longer period to achieve full oral feeding and hospital stay
74

Gastrosquise fetal isolada: relação entre dilatação intestinal e resultados perinatais adversos / Isolated fetal gastroschisis: relation between bowel dilation and adverse perinatal outcome

Garcia, Luciana de Freitas 30 November 2011 (has links)
Objetivos: Este estudo foi desenvolvido para avaliar o diâmetro transverso da alça intestinal exteriorizada como fator preditor de resultado adverso, nas gestações com gastrosquise fetal isolada. Métodos: Estudo retrospectivo envolvendo 94 gestações únicas. Foi realizada a medida do diâmetro transverso da alça intestinal (DTA) herniada, por meio da ultrassonografia antenatal, até 3 semanas antes do parto. Foi considerado resultado perinatal adverso: óbito intra-útero, óbito neonatal e complicações intestinais. Resultados: a última medida ultrassonográfica do DTA foi realizada com 35,6 ± 1,6 semanas e o tempo médio do intervalo entre a última medida e o parto foi de 6,2 ± 5,0 dias. Ocorreram 10 (10,6%) casos de óbitos intraútero e neonatal; foram observadas complicações intestinais em 8 (8,5%) casos. DTA 15, 20, 25 e 30 mm foram identificadas em 87, 46, 13 e 4% das gestações com prognóstico favorável, respectivamente. O DTA 25 mm apresentou valores de sensibilidade de 38%, e, valores preditivo positivo e preditivo negativo de 38% e 87%, na predição de resultados adversos. Para o DTA 30 mm, os valores foram: 19, 50 e 85%. A área sob a curva ROC do valor observado/esperado do DTA para cada idade gestacional foi de 0,67, sendo o melhor ponto-de-corte em 1,39; e, seus valores preditivos foram semelhantes aos do DTA 25 mm. Dilatação intestinal esteve significantemente associada com baixa taxa de fechamento primário da parede abdominal, longo período para iniciar a dieta via oral e internação hospitalar prolongada. Conclusões: Dilatação intestinal demonstrada até 3 semanas antes do parto é preditora de complicações intestinais e está associado a baixa taxa de fechamento primário da parede abdominal, longo período para iniciar a dieta via oral e de internação hospitalar / Objectives: Evaluate bowel diameter as a predictor of adverse outcome in isolated fetal gastroschisis. Methods: Retrospective study involving 94 singleton pregnancies. Ultrasound measurements of herniated bowel transverse diameter (BTD) were performed up to 3 weeks before delivery. Adverse outcome was intrauterine/ neonatal death and/or bowel complications. Results: Last BTD was recorded at 35,6 ± 1,6 weeks and mean interval to delivery was 6,2 ± 5,0 days. Intrauterine/ neonatal death occurred in 10 (10,6%) cases; bowel complications were observed in 8 (8,5%). BTD 15, 20, 25 and 30mm were found in 87, 46, 13 and 4% of pregnancies with a favorable outcome, respectively. BTD 25 mm sensitivity was 38%, positive and negative predictive values, 38% and 87%. For BTD 30 mm, the values were: 19, 50 and 85%. Observed/expected BTD ROC curve showed an area of 0,67, with best cut-off at 1,39; prediction values were similar to those for BTD 25 mm. Bowel dilatation was also significantly associated with lower rate of primary surgical closure, longer period to full oral feeding and prolonged hospital stay. Conclusions: Bowel dilatation demonstrated up to 3 weeks before delivery is a predictor of intestinal complications and is associated with lower rate of primary surgical closure, longer period to achieve full oral feeding and hospital stay
75

Cardiovascular end-organ damage in response to increased blood pressure variability : impact of oxidative stress

Rarick, Kevin Richard 01 July 2012 (has links)
Baroreflex sensitivity (BRS) is often reduced in elderly populations and patients with chronic cardiovascular diseases leading to a concomitant rise in blood pressure variability (BPV) that is associated with increased cardiovascular related morbidity and mortality. Thus, there is a need to better understand the mechanisms by which BPV causes cardiovascular end-organ damage. Animal studies using sinoaortic denervation (SAD) to increase BPV have demonstrated pathologic changes in the structure of the heart and blood vessels; however, there is a paucity of data investigating changes in functional measures of the heart and smaller, resistance type arteries. Furthermore, the pathogenic mechanisms involved in BPV-induced cardiovascular end-organ damage remain unknown. Baroreceptor denervation results in multiple cardiac stressors, many of which are associated with production of reactive oxygen species. Oxidative stress is known to promote cardiovascular end-organ damage but it is unclear if it plays a role in models of increased BPV. Thus, this study was designed to investigate the functional responses of smaller resistance type arteries and the heart to chronic exposure to enhanced BPV. In addition, the role of oxidative stress on these functional responses in a normotensive rat model of increased BPV was also investigated. Rats were subjected to either SAD surgery or a sham procedure and were observed for six weeks. To determine the role of oxidative stress, SAD rats were either treated with the superoxide dismutase mimetic tempol or left untreated. During the observation period, mean blood pressure remained normotensive, whereas baroreflex sensitivity was reduced and BPV increased two to three fold. Weekly in vivo assessment of vascular function of the long posterior ciliary artery (LPCA) demonstrated a significant reduction in endothelial-dependent dilation starting three weeks after SAD surgery compared to the sham group. Endothelial-independent dilation was not affected by SAD. Structural changes were not evident in the LPCA following SAD. However, structural (wall thickness, wall area, and wall area/lumen area ratio) and functional (strain and distensibility) changes were observed in the aorta. Cardiac structural (hypertrophy) and functional (diastolic dysfunction) effects were also evident following six weeks of increased BPV. Antioxidant treatment with tempol did not have any effect on the SAD-induced increase in BPV or decrease in BRS. Nevertheless, chronic tempol treatment prevented or reduced the cardiovascular end-organ damage (endothelial-dependent vascular dysfunction, decreased aortic distensibility, cardiac and vascular hypertrophy, and cardiac dysfunction) observed in the untreated SAD group. These findings suggest that the pathology observed following SAD is at least partly mediated by oxidative stress. Antioxidant treatment in patients with increased BPV (e.g., hypertension, diabetes, heart failure) may prevent or ameliorate cardiovascular end-organ damage and reduce the overall risk for cardiovascular disease events.
76

Dynamics of dilative slope failure

You, Yao 18 February 2014 (has links)
Submarine slope failure releases sediments; it is an important mechanism that changes the Earth surface morphology and builds sedimentary records. I study the mechanics of submarine slope failure in sediment that dilates under shear (dilative slope failure). Dilation drops pore pressure and increases the strength of the deposit during slope failure. Dilation should be common in the clean sand and silty sand deposits on the continental shelf, making it an important mechanism in transferring sand and silt into deep sea. Flume experiments show there are two types of dilative slope failure: pure breaching and dual-mode slope failure. Pure breaching is a style of retrogressive subaqueous slope failure characterized by a relatively slow (mm/s) and steady retreat of a near vertical failure front. The retreating rate, or the erosion rate, of breaching is proportional to the coefficient of consolidation of the deposit due to an equilibrium between pore pressure drop from erosion and pore pressure dissipation. The equilibrium creates a steady state pore pressure that is less than hydrostatic and is able to keep the deposit stable during pure breaching. Dual-mode slope failure is a combination of breaching and episodic sliding; during sliding a triangular wedge of sediment falls and causes the failure front to step back at a speed much faster than that from the breaching period. The pore pressure fluctuates periodically in dual-mode slope failure. Pore pressure rises during breaching period, weakens the deposit and leads to sliding when the deposit is unstable. Sliding drops the pore pressure, stabilizes the deposit and resumes breaching. The frequency of sliding is proportional to the coefficient of consolidation of the deposit because dissipation of pore pressure causes sliding. Numerical model results show that more dilation or higher friction angle in the deposit leads to pure breaching while less dilation or lower friction angle leads to dual-mode slope failure. As a consequence, pure breaching is limited to thinner deposits and deposits have higher relative density. / text
77

The contribution of whole blood viscosity in assessment of vascular function

Parkhurst, Kristin Louise 07 July 2011 (has links)
Although blood viscosity is an important component in determining vascular function, it is often assumed constant. Emerging evidence linking individual differences in viscosity to cardiovascular disease casts doubt on this assumption. The purpose of this study was to determine the contribution of whole blood viscosity to key measures of vascular function. To address this aim as comprehensively as possible, first, whole blood viscosity was compared with traditional risk factors for cardiovascular disease. Then flow-mediated dilation (FMD), carotid-femoral pulse wave velocity (cfPWV), and carotid artery compliance were calculated either with or without blood viscosity taken into account. Lastly, we tested whether the removal of blood viscosity could influence well-established associations between age and vascular function. Blood viscosity and vascular function were measured in 97 adults ranging in age from 18-63 years. No significant differences were observed between whole blood viscosity and traditional risk factors for cardiovascular disease. Whole blood viscosity was not significantly correlated with FMD, cfPWV, and carotid compliance. As expected, age was positively correlated with cfPWV (r=0.65, p<0.001) and negatively correlated with FMD (r=-0.21, p<0.05) and carotid compliance (r=-0.45, p<0.01). Even after controlling for viscosity, these relationships remained statistically significant (cfPWV r=0.65, p<0.001; FMD r=-0.24, p<0.05; carotid compliance r=-0.44, p<0.05). These results indicate that whole blood viscosity does not appear to significantly impact measures of vascular function and that the rationale for including whole blood viscosity in the calculation of vascular function remains weak. / text
78

A Framework for Routing in Fully- and Partially-Covered Three Dimensional Wireless Sensor Networks

El Salti, TAREK 02 January 2013 (has links)
Recently, many natural disasters have occurred (e.g., the 2011 tsunami in Japan). In response to those disasters, Wireless Sensor Networks have been proposed to improve their detection level. This new technology has two main challenges which are routing and topology control where their multi-dimensional dilations need to be improved/balanced. Related to those metrics, the packet delivery factor also needs to be improved/guaranteed. This thesis presents the design of new routing protocols, referred to as: 1) the 3-D Sensing Sphere close to the Line:Smallest Angle to the Line (SSL:SAL) protocol, 2) the 3-D Randomized Sensing Spheres (RSS) protocol, and 3) the SSL:SAL version 1 and version 2 (i.e., SSL:SALv1 and SSL:SALv2, respectively). Through simulations, these protocols are shown to balance/improve the multi-dimensional dilations metrics which also include new bandwidth metrics. The balance/improvement is achieved over some existing position-based protocols. In addition, packet delivery is guaranteed mathematically for new and existing protocols. Furthermore, some experimental evidences are gathered regarding the delivery rate impact on the multi-dimensional metrics. The thesis also proposes a new set of 2-D and 3-D graphs, so called: 1) the Derived Circle version 1 (DCv1) graphs and 2) the Derived Sphere (DSv1) graphs. The new approaches improve the multi-dimensional dilations over some existing graphs. In addition, connectivity, rotability, fault tolerance properties are achieved. Lastly, the thesis develops a framework that combines routing protocols and graphs in fully covered regions. Some experimental evidences demonstrate the improvement of the multi-dimensional metrics and the packet delivery rate for the routing protocols based on the DSv1. This is compared to the routing protocols based on an existing graph. Furthermore, based on either the proposed or existing graphs, some important findings are demonstrated for routing in terms of multi-dimensional metrics and packet delivery rate. Among those findings, the proposed protocol and an exiting protocol have higher delivery rates compared to another existing protocol. Furthermore, the proposed graph improves the multi-dimensional metrics for the proposed and existing protocols over another existing protocol for low communication ranges.
79

Comparison of High-Nitrate versus Low-Nitrate Diets on Cardiovascular Health in Post-Menopausal Women

January 2017 (has links)
abstract: Background. Despite research aimed at understanding the mechanisms of essential hypertension, instances of this condition continue to rise. Recent findings indicate that the administration of dietary nitrates, in the form of beetroot juice and other nitrate-rich vegetables, may offer anti-hypertensive effects in various study populations. Objective. This randomized, placebo-controlled, crossover trial sought to compare the effects of high-nitrate vegetable salads to the effects of low-nitrate canned vegetables on plasma nitrate/nitrite concentration, peripheral and central-aortic systolic and diastolic blood pressures, pulse wave velocity, and flow-mediated dilation. Methods. Healthy, post-menopausal women (n=5; 80% Caucasian; 52.6 ± 5.7 years) with mildly elevated blood pressure (mean blood pressure ≥ 115/70 mm Hg and < 140/80 mm Hg) were randomly assigned to ingest a fresh, high-nitrate vegetable salad or a low-nitrate vegetable medley, twice per day, for a total of 10 consecutive days. Given the crossover design of the trial, participants observed a two to three week washout period followed by reassignment to the opposite condition. Findings were considered significant at a p-value < 0.05, and Wilcoxon Signed-Rank tests compared mean differences between conditions. Results. Plasma nitrate/nitrite concentration was significantly higher following consumption of the high-nitrate versus the low-nitrate condition (p = 0.043). Conversely, the differences in peripheral systolic and diastolic blood pressures were not statistically significant (p = 0.345 and p = 0.684 for systolic and diastolic pressures, respectively) nor were the differences in central-aortic systolic and diastolic blood pressures statistically significant (p = 0.225 and p = 0.465 for systolic and diastolic pressures, respectively). Similarly, when comparing the effects of the high-nitrate condition to the low-nitrate condition, the difference in pulse wave velocity was not statistically significant (p = 0.465). Finally, flow-mediated dilation tended to improve following consumption of the high nitrate condition (p = 0.080). Conclusion. Twice daily consumption of a fresh, high-nitrate vegetable salad significantly increased plasma nitrate/nitrite concentration. Although the trial was underpowered, there was a trend for improved flow-mediated dilation. Finally, twice daily consumption of a fresh, high-nitrate vegetable salad did not significantly lower peripheral or central-aortic systolic or diastolic blood pressures or pulse wave velocity. / Dissertation/Thesis / Masters Thesis Nutrition 2017
80

Sequência didática para ensino de dilatação térmica através de experimentos demonstrativos

Almeida, Celso Ponchio de 21 August 2017 (has links)
Submitted by Larissa Vitoria Cardoso Cusielo (larissavitoria@id.uff.br) on 2017-05-12T18:45:12Z No. of bitstreams: 4 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Celso Ponchio - Dissertacao final.pdf: 3773699 bytes, checksum: dbd199af5614502049fbece45a610e7c (MD5) APÊNDICE 1 - 18-10-2016.pdf: 228472 bytes, checksum: 7881892d315e4ab4368d0460c0380876 (MD5) APÊNDICE 2.pdf: 543831 bytes, checksum: 4ebe460790831243b33f988a0dadbaff (MD5) / Rejected by Biblioteca do Aterrado BAVR (bavr@ndc.uff.br), reason: oi on 2017-05-22T16:24:35Z (GMT) / Submitted by Larissa Vitoria Cardoso Cusielo (larissavitoria@id.uff.br) on 2017-05-22T17:11:14Z No. of bitstreams: 4 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Celso Ponchio - Dissertacao final.pdf: 3773699 bytes, checksum: dbd199af5614502049fbece45a610e7c (MD5) APÊNDICE 1 - 18-10-2016.pdf: 228472 bytes, checksum: 7881892d315e4ab4368d0460c0380876 (MD5) APÊNDICE 2.pdf: 543831 bytes, checksum: 4ebe460790831243b33f988a0dadbaff (MD5) / Approved for entry into archive by Biblioteca do Aterrado BAVR (bavr@ndc.uff.br) on 2017-08-21T15:57:44Z (GMT) No. of bitstreams: 4 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Celso Ponchio - Dissertacao final.pdf: 3773699 bytes, checksum: dbd199af5614502049fbece45a610e7c (MD5) APÊNDICE 1 - 18-10-2016.pdf: 228472 bytes, checksum: 7881892d315e4ab4368d0460c0380876 (MD5) APÊNDICE 2.pdf: 543831 bytes, checksum: 4ebe460790831243b33f988a0dadbaff (MD5) / Made available in DSpace on 2017-08-21T15:57:44Z (GMT). No. of bitstreams: 4 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Celso Ponchio - Dissertacao final.pdf: 3773699 bytes, checksum: dbd199af5614502049fbece45a610e7c (MD5) APÊNDICE 1 - 18-10-2016.pdf: 228472 bytes, checksum: 7881892d315e4ab4368d0460c0380876 (MD5) APÊNDICE 2.pdf: 543831 bytes, checksum: 4ebe460790831243b33f988a0dadbaff (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Universidade Federal Fluminense. Instituto de Ciências Exatas. Programa de Pós-Graduação em Ensino de Física. Volta Redonda,RJ. / Este trabalho descreve a elaboração, aplicação e avaliação de uma sequência didática para o ensino dos conceitos de dilatação térmica no ensino médio explorando experimentos demonstrativos. O produto apresentado é composto por um kit formado por quatro experimentos demonstrativos, a saber, acionamento de campainha por dilação de barra metálica, dilatação anel metálico com esfera, lâminas com dois materiais mostrando curvatura da lâmina e modelo de estrutura cristalina, além de um roteiro de atividades. O produto educacional está ancorado na Teoria de Aprendizagem Significativa, de Ausubel e busca interagir com os conhecimentos prévios dos alunos, através de atividades que relacionam os conceitos com consequências cotidianas. O material foi elaborado para ser aplicado em dois tempos de 50 minutos, em acordo com a reduzida carga horária da disciplina de Física nesta modalidade de ensino. O produto foi aplicado em colégio da rede estadual de ensino no Estado do Rio de Janeiro e o resultado da análise mostrou envolvimento dos alunos nas atividades e bom desempenho dos alunos nas mesmas. Acreditamos que o produto seja potencialmente significativo. / This work describes the elaboration, application and evaluation of a didactic sequence to teach linear dilation of materials in high school level. The educational product is composed by four demonstrative experiments namely bar dilation, ring dilation, bi-material strip, and a crystalline structure model. The experiments are followed by a sequence of activities which relies the physical concepts with quotidian situations. Our work is based on the Theory of Meaningful Learning, from David Ausubel. The activities requires interaction between previous knowledge and concrete situations in order to contribute to a meaningful learning. The resulting educational product was applied in a High School institution of the network of Rio de Janeiro State. The application time is two fifty minutes class, performing a hundred minutes, which is appropriate to the physical class in this level of teaching. The results of our analysis of the application show that our product is potential meaningful to teach thermal dilation

Page generated in 0.1106 seconds