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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.
31

O modelo logístico com erros assimétricos e heterocedásticos aplicado a dados de altura do milho / Logistic model with skewed and heteroskedastic errors applied to maize height data

Rick Anderson Freire Mangueira 22 January 2015 (has links)
A produção de milho tem uma grande importância para o país. Ter o conhecimento sobre o crescimento da planta é de fundamental importância para seu manejo. Pode-se obter esse conhecimento fazendo um estudo por meio de modelos de crescimento, para se obter informações por meio de parâmetros com interpretações biológicas que trazem consigo um resumo sobre a curva característica do crescimento da planta, que podem ajudar no planejamento da cultura e principalmente conhecer qual período a planta mais cresce, a época mais adequada para adubação e realização do controle de pragas. Considerar características não comuns de suposições do modelo pode dar maior confiabilidade nos resultados do ajuste, como por exemplo a consideração da heterocedasticidade e não normalidade residual. Sendo assim, esse trabalho teve o objetivo de ajustar o modelo logístico considerando a heterocedasticidade e diferentes distribuições para o erro como normalidade, assimetria normal e assimetria t-student, a dados da altura da planta do milho do híbrido transgênico 30F35 Y (Yieldgard), observados ao longo do tempo. O experimento foi realizado no município de Votuporanga-SP, em área experimental do Pólo Regional Noroeste Paulista da APTA (Agência Paulista de Tecnologia dos Agro-negócios), no ano agrícola 2011/2012. A primeira medição da altura da planta de milho foi realizada 15 dias após a semeadura. As medições seguintes ocorreram com 30, 40, 50 e 122 dias, respectivamente, após a semeadura. Em cada dia de avaliação foi medido a altura das plantas em centímetros, com auxílio de uma régua, sendo esta medida da base da planta (solo) até o ápice da última folha expandida do cartucho. Toda a análise foi realizada utilizando o software R. Todos os modelos considerados se ajustaram bem a curva de crescimento do híbrido transgênico 30F35 Y (Yieldgard), porém o modelo logístico considerando erros normais assimétricos foi escolhido como mais adequado para modelar a curva, com base nos avaliadores utilizados. / Maize production is of great importance for the country. Knowing the plant development is of major importance to its management. Such knowledge may be attained through growth curves studies, to obtain information through parameters with biological interpretation which are able to synthesize the plantt\'s growth curve. This synthesis may help in management issues, such as information on the period of most rapid growth, best time to apply fertilizers and control pests. Considering uncommon features of the model assumptions may provide greater reliability on the results of the fitted model, such as residual heteroscedasticity and non-normality. In that sense, this work aimed to fit the logistic model considering variance heterogeneity and different error distributions such as normal, skew-normal and skew-t, to the transgenic hybrid 30F35Y maize height data through time. The experiment was conducted in the municipality of Votuporanga-SP, in an experimental station of the Pólo Regional Noroeste Paulista da Agência Paulista de Tecnologia dos Agro-Negócios (APTA) during the agronomic year of 2011/2012. The first height data measurement was taken 15 days after sewing. The following measurements were taken at 30, 40, 50 and 122 days after sewing. Each day the plant height was measured in centimeters using a ruler, measuring from the plant base (soil) until the edge of the last expanded leaf. All analyses were carried out using software R. All considered models fitted the data reasonably well, however the logistic model considering skew-normal errors was chosen as most adequate to model the data, basing on the goodness-of-fit tests.
32

Mécanismes de ségrégation asymétrique des agrégats protéiques liés à Hsp104 chez Saccharomyces cerevisiae / Mechanisms of asymmetrical segregation of Hsp104-bounded protein aggregates in budding yeast

Paoletti, Camille 12 December 2014 (has links)
La levure du boulanger a une durée de vie réplicative limitée : chaque cellule mère produit un nombre fini de filles avant de mourir. Cette entrée en sénescence est supposée notamment résulter de l’accumulation d’agrégats de protéines endommagées au sein de la cellule mère. La rétention des agrégats au sein des mères permettrait de produire des filles rajeunies. Cependant, ce mécanisme de ségrégation asymétrique reste controversé, en partie car il est complexe de suivre la dynamique des agrégats protéiques in vivo. Nous avons développé une méthodologie pour suivre la formation des agrégats protéiques au cours d’un choc thermique au sein de cellules uniques. Associées à un modèle simple d’agrégation, nos données montrent que l’asymétrie peut être expliquée quantitativement par la croissance polarisée du bourgeon. De plus, des expériences de vieillissement réplicatif réalisées au sein d’une puce microfluidique suggérèrent que l’accumulation d’agrégats dans les mères pourrait induire la mort, mais seulement lorsque les cellules subissent un stress protéotoxique. Cette étude apporte donc un éclairage nouveau sur les mécanismes d’héritabilité des agrégats protéiques et leur contribution au vieillissement réplicatif chez la levure du boulanger. / Budding yeast cells have a limited replicative life span: a mother cell can produce a limited number of daughter cells before it dies. It has been proposed that the progressive accumulation of aggregates of damaged proteins within mother cells drives entry into senescence. The retention of such damages by mothers is thought to permit the daughter lineage rejuvenation. Yet the mechanism of their asymmetrical segregation is still controversial, in part because of difficulties inherent to the tracking of the dynamics of protein aggregates in vivo. In this context, we have developed a single cell methodology to track the formation of protein aggregates upon heat shock in single cells. In combination with a simple computational model of aggregation, our data reveal that the asymmetry can be explained quantitatively by the polarized growth of the bud. In addition, replicative aging experiments performed in a microfluidic device suggest that the accumulation and retention of protein aggregates in mothers may be responsible for cell death, but only under particular proteotoxic stress. Therefore, this study sheds new light on the mechanism of inheritance of protein aggregates and its contribution to replicative aging in budding yeast.
33

The impact of corporatisation on access and equity at the University of Dar es Salaam

Sarakikya, A.M. January 2014 (has links)
The purpose of this study was to examine and analyse how the transformation taking place at the University of Dar es Salaam in the context of corporatisation addressed the challenges of access and equity as central features of national development. The study was based on the premise that widening access to and equity in higher education contributes to the development and prosperity of the nation in Tanzania. The study used a qualitative case study design. Epistemologically, the study was located within the constructivist paradigm which is premised on a social construction of reality. I used both purposive and snowball sampling techniques to select both the research site and the participants. Face-to-face, semi-structured interviews and an in-depth document analysis were used to collect the requisite data. The data were analysed qualitatively by developing themes using the Atlas.ti program. The findings revealed firstly that both internal and external factors had provided the impetus for the transformation of the university. The findings also indicated a strong move towards the privatisation of the university. This was evident in the outsourcing of the non-core activities of the university as well as the introduction of market-driven programmes. Secondly, the implementation of corporate strategies had both–positive and negative, planned and unplanned consequences. While the university had significantly increased its student intake, improved the efficient utilisation of its resources and diversified its sources of income, it had, nevertheless, been unable to match the increased student intake with improved teaching and learning resources as well as enhanced student support services. In addition, the influence of both donors and the organisational culture shaped and influenced the adoption and implementation of a corporate culture with regard to the management of the university. With respect to the role played by the university in national development, the adoption and implementation of the market approach was characterised by a paradigm shift from viewing the university as a social institution that serves the community to that of an institution that meets the demands of the market. Overall, the findings indicate that effective leadership, supported by a favourable policy environment, was a critical component in the realisation of the institutional transformation goals. The study suggests that a combination of both the state-controlled model and the market model in public higher education institutions should be encouraged and promoted for the purposes of equity, efficiency and effectiveness. Accordingly, this study suggests that the idea of „asymmetrical balance‟ is a strategic approach that will enable the university to mediate the contesting demands of both the national and the market imperatives. The notion of asymmetrical balance argues that the goals of national development and efficiency are not mutually exclusive and that they could potentially be mutually beneficial. / Thesis (PhD)--University of Pretoria, 2014. / lk2014 / Education Management and Policy Studies / PhD / Unrestricted
34

Softwarová podpora výuky kryptosystémů založených na eliptických křivkách / Software support of education in cryptography area based on elliptic curves

Szturc, Jakub January 2009 (has links)
The master‘s thesis is focusing on cryptography based on elliptical curves consists of four main parts. The first part provides an overview of the basic cryptographic and mathematical concepts. A key element of this work is the second part which are described in detail the mechanisms of counting two points on elliptic curve and counting point to themselves over the various fields. On this mechanism is based almost the entire issue. In the third section provides the best-known algorithms and protocols for key exchange, encryption and digital signature. The goal of this paper is to devise software to support teaching. This material is created as a web presentation, which described the theoretical foundations and the main characteristics of cryptosystems based on elliptical curves. The whole issue is supported by practical examples of calculations examples, there are also examples for independent work. Additionally, java applets are prepared that allow an interactive opportunity to try the basic parameters of curves, or verify the calculations.
35

Precarity and Asymmetries in Media Production: How Freelancers Experience their Working Conditions as Users of Coworking Spaces

Heise, Laurie January 2018 (has links)
This master’s thesis investigates how freelancers experience job precarity and asymmetrical power relations which have been established within the media production industry as well as the relevance and value of coworking spaces providing a workspace with the possibilities of knowledge sharing, networking and community building, as a framework in order to challenge their precarious working conditions. Furthermore, the research aims at examining the participants’ experiences in a qualitative manner to explore those rather new concepts of freelancing and coworking spaces as previous research has failed to address the individual experiences of how freelancers deal with the nature of work in the media production industry.Situated in the context of the structural changes within media production towards a project-based nature of work and the decrease of permanent employment, freelancers are increasingly facing precarious working conditions such as uncertainty and instability.Applying the theory of structure and agency as theoretical framework, it is discussed to what extent freelancers are influenced by the established structures, rules and norms within the media production industry and how their agency is enabled within these structures.Using a qualitative research approach, this study is based on an investigation of the experiences and knowledge of eleven freelancers working in the media production industry and who are users of coworking spaces by the means of semi-structured interviews. In summary, this thesis reveals that the majority of the participants experience asymmetrical power relations and precarity to a high degree. Furthermore, freelancers who seek for communities in order to challenge their precarious working conditions, experience coworking spaces as highly valuable concept in order to increase the possibilities for their individual agency. Having investigated those rather novel concepts, this thesis serves as a starting point for examining further research on freelancers’ individual experiences of their working conditions.
36

A deep polarimetric analysis of the debris disk HD 106906

Crotts, Katie 28 August 2020 (has links)
HD 106906 is a young, binary stellar system, located at ~103.3 parsecs away in the Lower Centaurus Crux (LCC) group. This system is completely unique among known systems in that it contains an asymmetrical debris disk, as well as an 11 M(Jup) planet companion, at a separation of ~735 AU. Only 4 other systems are known to contain both a disk and detected planet, where HD 106906 is the only one in which the planet has apparently been ejected. Furthermore, the debris disk is nearly edge on, and extends roughly from 70 AU to >500 AU, where previous polarimetric studies with HST have shown the outer regions to have high asymmetry. The presence of a planet companion sparks questions about the origin of this asymmetry. To better understand the structure and composition of the disk, deeper data have been taken with the Gemini Planet Imager (GPI), which we have used to perform a deep polarimetric study of HD 106906’s asymmetrical debris disk. The data were taken in the H-band, and were supplemented with both J- and K1-band polarimetric data which have been obtained through one of GPI’s Large and Long Programs (LLP). Polarimetry is important in the study of debris disks in scattered light, as it helps us constrain their dust grain characteristics, as well as allowing us to obtain high-contrast images. Modelling the disk, along with an empirical analysis of our data, supports a disk that is asymmetrical in surface brightness and structure, as well as a disk that is highly eccentric. These results will be discussed in terms of possible sources of asymmetry, such as dynamical interaction with the planet companion HD 106906b. / Graduate / 2021-07-26
37

A 70-W Asymmetrical Doherty Power Amplifier for 5G Base Stations

Abdulkhaleq, Ahmed M., Al-Yasir, Yasir I.A., Ojaroudi Parchin, Naser, Brunning, J., McEwan, N., Rayit, A., Abd-Alhameed, Raed, Noras, James M., AbdulJabbar, N. 22 August 2018 (has links)
Yes / Much attention has been paid to making 5G developments more en-ergy efficient, especially in view of the need for using high data rates with more complex modulation schemes within a limited bandwidth. The concept of the Doherty power amplifier for improving amplifier efficiency is explained in addi-tion to a case study of a 70W asymmetrical Doherty power Amplifier using two GaN HEMTs transistors with peak power ratings of 45W and 25W. The rationale for this choice of power ratio is discussed. The designed circuit works in the 3.4GHz frequency band with 200 MHz bandwidth. Rogers RO4350B substrate with dielectric constant εr=4.66 and thickness 0.035 mm is used. The perfor-mance analysis of the Doherty power amplifier is simulated using AWR MWO software. The simulated results showed that 54-64% drain efficiency has been achieved at 8 dB back-off within the specified bandwidth with an average gain of 10.7 dB.
38

Synchronous Machine for Unidirectional Application

Yu, Yang January 2012 (has links)
This master thesis investigates the possibilities for performance improvements of synchronous machines with unidirectional application.The literature review part presents theories and applications of asymmetrical machine. Four categories regarding asymmetrical machine, namely mixed pole, saturation mitigation, pole shifting and asymmetrical pole shaping, are summarized. It is shown that asymmetrical concept offers characteristic improvement in one or both rotational directions. A field winding synchronous model was used in FEM simulation (FLUX 2D). Armature reaction effecton this machine is investigated. It is found that armature reaction has different effects with varying current angle.Two ideas regarding asymmetrical pole shaping are investigated. First of all, pole shoe cutting idea is investigated. It leads to increased airgap length and less output torque. Secondly, progressive airgap idea shows reduced armature reaction effect and improved power factor, but higher torque ripple.Furthermore, an improved idea is suggested to reduce the torque ripple. Performance improvement by assisted permanent magnet is also studied. Four ideas of this field are investigated. It is found that permanent magnet can be used to reduce saturation, improve power factor and output torque. The reasons for limited improvements are analyzed.
39

Lateralization Performance in Normal-hearing Adults Evaluated During Short-term Induced Asymmetrical Changes of Auditory Periphery

Smurzynski, Jacek 19 May 2005 (has links)
No description available.
40

Molecular Genetic Analysis of CRELD1 in Patients with Heterotaxy Disorder

Zhian, Samaneh 01 January 2011 (has links)
Heterotaxy refers to the abnormal arrangement of internal organs in relation to each other. Model organism studies have shown that functions of more than eighty genes are required for normal asymmetric left-right organ development. CRELD1 has been shown to be necessary for proper heart development and mutations in CRELD1 are known to increase risk of cardiac atrioventricular septal defects (AVSD). AVSD is the most common form of heart defect associated with heterotaxy, and we have previously shown that some individuals with heterotaxy-related AVSD have mutations in CRELD1. Therefore, we propose to examine the CRELD1 gene in a large sample of patients with heterotaxy syndrome. Our goal was to determine if mutations in CRELD1 are associated with other manifestations of heterotaxy or if they only coincide with AVSD. To achieve this aim, a sample size of 126 patients with heterotaxy collected by Dr. Belmont, Baylor college of Medicine, Texas, with approximately 66% of the heterotaxy population with different types of heart defects, were used for this study. Ten exons, promoter regions, and regulatory elements in the introns of CRELD1 gene were sequenced and analyzed. In this study three different heterozygous missense mutations in CRELD1 were identified in three unrelated individuals. These three individuals were diagnosed with different forms of heart defects in addition to AVSD. All three mutations were identified in highly conserved regions of CRELD1 possibly altering the CRELD1 properties. This demonstrates that mutations in CRELD1 may increase the susceptibility of AVSD in heterotaxy population. This information can help us to find factors effecting disease susceptibility in heterotaxy patients since the heart defects are a complex trait with incomplete penetrance.

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