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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.
61

New Directions In The Direction Of Time

Bagci, Gokhan Baris 01 June 2006 (has links) (PDF)
This thesis analyzes the direction of time problem in the framework of philosophy of science. The radiation arrow, Newtonian arrow, thermodynamical arrow and quantum mechanical arrow have been studied in detail. The importance of the structure of space-time concerning direction of time is emphasized.
62

Fabrication of Hollow Optical Waveguides on Planar Substrates

Barber, John P. 16 October 2006 (has links) (PDF)
This dissertation presents the fabrication of hollow optical waveguides integrated on planar substrates. Similar in principle to Bragg waveguides and other photonic crystal waveguides, the antiresonant reflecting optical waveguide (ARROW) is used to guide light in hollow cores filled with liquids or gases. Waveguides with liquid or gas cores are an important new building block for integrated optical sensors. The fabrication method developed for hollow ARROW waveguides makes use of standard microfabrication processes and materials. Dielectric layers are deposited on a silicon wafer using plasma-enhanced chemical vapor deposition (PECVD) to form the bottom layers of the ARROW waveguide. A sacrificial core material is then deposited and patterned. Core materials used include aluminum, SU-8 and reflowed photoresist, each resulting in a different core geometry. Additional dielectric layers are then deposited, forming the top and sides of the waveguide. The sacrificial core is then removed in an acid solution, resulting in a hollow ARROW waveguide. Experiments investigating the mechanical strength of the hollow waveguides and the etching characteristics of the sacrificial core suggest design rules for the different core types. Integration of solid-core waveguides is accomplished by etching a ridge into the top dielectric layer of the ARROW structure. Improved optical performance can be obtained by forming the waveguides on top of a raised pedestal on the silicon substrate. Loss measurements on hollow ARROW waveguides fabricated in this manner gave loss coefficients of 0.26 cm-1 for liquid-core waveguides and 2.6 cm-1 for air-core waveguides. Fluorescence measurements in liquid-core ARROW waveguides have achieved single-molecule detection sensitivity. Integrated optical filters based on ARROW waveguides were fabricated, and preliminary results of a capillary electrophoresis separation device using a hollow ARROW indicate the feasibility of such devices for future investigation.
63

An Integrated Model of Optofluidic Biosensor Function and Performance

Wright, Jr., Joel Greig 31 August 2021 (has links)
Optofluidic flow-through biosensor devices have been in development for fast bio-target detection. Utilizing the fabrication processes developed by the microelectronics industry, these biosensors can be fabricated into lab-on-a-chip devices with a degree of platform portability. This biosensor technology can be used to detect a variety of targets, and is particularly useful for the detection single molecules and nucleic acid strands. Microfabrication also offers the possibility of production at scale, and this will offer a fast detection method for a range of applications with promising economic viability. The development of this technology has advanced to now warrant a descriptive model that will aid in the design of future iterations. The biosensor consists of multiple integrated waveguides and a microfluidic channel. This platform therefore incorporates multiple fields of study: fluorescence, optical waveguiding, microfluidics, and signal counting. This dissertation presents a model theory that integrates all these factors and predicts a biosensor design's sensitivity. The model is validated by comparing simulated tests with physical tests done with fabricated devices. Additionally, the model is used to investigate and comment on designs that have not yet been allocated time and resources to fabricate. Tangentially, an improvement to the fabrication process is investigated and implemented.
64

The Time-Symmetric Gold Universe Reconsidered

Weinert, Friedel January 2016 (has links)
yes / The present article proposes to re-examine the parity-of-reasoning or double-standard fallacy argument, which favours a time-symmetric Gold universe model over a cosmological arrow of time. There are two reasons for this re-examination. One is empirical: 1) the recent discovery of an expanding and accelerating universe questions the symmetry assumption of the Gold universe on empirical grounds; 2) the other is theoretical: the argument from t-symmetry fails to take into account some important aspects of the topology of phase space and recently developed typicality arguments. If the parity-of-reasoning argument, which depends on the t-symmetry of probability, is reconsidered in terms of the topology of phase space and typicality arguments, the double-standard fallacy argument loses much of its appeal. The Gold universe model itself suffers from unexplained dynamic asymmetries. The upshot of this paper is that the Gold universe model is implausible or far less plausible than asymmetric models.
65

Maya Use And Prevalence Of The Atlatl: Projectile Point Classification Function Analysis From Chichen Itza, Tikal, And Caracol

Ciofalo, Andrew J 01 January 2012 (has links)
Multiple scholars have briefly discussed the Maya use of the atlatl. Yet, there has never been a decisive encompassing discussion of prevalence and use of the atlatl in the Maya region with multiple lines of support from iconographic and artifactual analyses. This thesis explores the atlatl at Chichén Itzá, Tikal, and Caracol Maya sites to prove that atlatl prevalence can be interpreted primarily based on projectile point “classification function” analysis with support from iconographic and artifactual remains. The classification functions are derived from creating mutually exclusive groups of dart points and arrow points by using discrete functional analysis. Discerning between dart and arrow points can be completed with a high degree of accuracy based on maximum shoulder width of lithic points in an assemblage. Because the atlatl and bow complexes have been primarily constructed of perishable materials, the best method to determine the prevalence of atlatl use is by identifying the launcher based on projectile point identification. Using a cross-site comparison of projectile point size, the Maya use and prevalence of the atlatl will be elucidated
66

Improved Single Molecule Detection Platform Using a Buried ARROW Design

Wall, Thomas Allen 01 September 2017 (has links)
As the microelectronics industry pushes microfabrication processes further, the lab-on-a-chip field has continued to piggy-back off the industry's fabrication capabilities with the goal of producing total chemical and biological systems on small chip-size platforms. One important function of such systems is the ability to perform single molecule detection. There are currently many methods being researched for performing single molecule detection, both macro and micro in scale. This dissertation focuses on an optofluidic, lab-on-a-chip platform called the ARROW biosensor, which possesses several advantages over macro-scale single molecule detection platforms. These advantages include an amplification-free detection scheme, cheap parallel fabrication techniques, rapid single molecule detection results, and extremely low volume sample probing, which leads to ultra-sensitive detection. The ARROW biosensor was conceived in the early 2000s; however, since then it has undergone many design changes to improve and add new functionality to the lab-on-a-chip; however, water absorption in the plasma enhanced chemical vapor deposited silicon dioxide has been a problem that has plagued the biosensor platform for some time. Moisture uptake in the oxide layer of the ARROWs leads to loss of waveguiding confinement and drastically decreases the overall sensitivity of the ARROW biosensors. New ARROW designs were investigated to alleviate the negative water absorption effects in the ARROWs. The new waveguide designs were tested for resiliency to water absorption and the buried ARROW (bARROW) design was determined to be the most successful at preventing negative water absorption effects from occurring in the PECVD oxide waveguides. The bARROWs were integrated into the full biosensor platforms and used to demonstrate high sensitivity single molecule detection without any signs of water absorption affecting the bARROWs' waveguiding capabilities. The bARROW biosensors are not only water resistant, they also proved to be the most sensitive biosensors yet fabricated with average signal-to-noise ratios around 80% higher than any previously fabricated ARROW biosensors.
67

Feeding ecology of the New Zealand sea lion (Phocarctos hookeri) : a thesis presented in partial fulfilment of the requirements for the degree of Doctor Philosophy in Zoology at Massey University, Palmerston North, New Zealand

Meynier, Laureline January 2009 (has links)
The New Zealand (NZ) sea lion Phocarctos hookeri is the only pinniped endemic to NZ with a population of approximately 12,000 individuals. Its breeding range is currently restricted to NZ sub-Antarctic islands, and it has failed to recolonise its pristine distribution around the NZ main islands despite its protection since 1881. The current hypothesis is that the population growth of this pinniped is limited by the distribution of suitable prey on the Auckland Islands (50°30'S, 166°E) shelf, and by the direct and indirect pressure exerted by the arrow squid Nototodarus sloani fishery. However, this hypothesis has not been fully tested to date as there has been limited information on the diet of the NZ sea lion and their potential prey. The objective of this thesis is to analyse the diet of NZ sea lions over several years with particular emphasis on the most reproductively important segment of the population: lactating females. This thesis provides the first quantification by percentage mass of the diet of NZ sea lion using a combination of stomach content analysis, qualitative fatty acid (FA) analysis, and quantitative FA signature analysis (QFASA). Stomach contents and blubber FAs were analysed from 121 individuals incidentally caught (by-caught) in the southern arrow squid fishery from the years 1997 to 2006. The blubber FAs of 78 freeranging lactating females captured at Enderby Island, Auckland Islands, were also examined during January and February of 2000 to 2005. Data obtained from both stomach analysis and QFASA indicate that arrow squid, rattails Macrouridae, hoki Macruronus novaezelandiae and red cod Pseudophycis bachus are key prey species for NZ sea lions in the Auckland Islands region. Because these prey species live mostly at depths greater than 200 m, lactating females must undertake long foraging trips and dive regularly to greater depths than other sea lion species. Data from QFASA indicates that this foraging pattern is conducted over an extended period through the summer and autumn. The daily food requirement of a lactating female was estimated by a simple energetic model to be greater than 20% of its body mass. During years of low arrow squid recruitment such as 1999 and 2001, the amounts of squid required by the NZ sea lion population may have been similar to the amount harvested by the fishery, suggesting that resource competition is likely to occur between the arrow squid fishery and NZ sea lions in years of low squid abundance. Half of the fishing activity of the southern squid fishery occurs in the north of the Auckland Islands shelf where NZ sea lions forage, leading to incidental captures every year. This research emphasises that management of the NZ sea lion must not only consider the direct interactions with the arrow squid fishery, but also the likelihood of food resource competition between the fishery and NZ sea lions.
68

Analyse des données ordinales et modélisation explicative

Dridi, Mohamed-Tahar 06 June 1979 (has links) (PDF)
On expose les propriétés générales des graphes de surclassement et une condition suffisante pour qu'un graphe de surclassement sort sans circuit. On étudie la recherche de structures latentes. On établit le caractère erroné d'une conjecture Marschack pour tout ensemble de plus de 5 éléments. On caractérise les graphes values admettant certaines structures latentes. On propose un algorithme pour engendrer des "états de l'opinion
69

Microbiological and molecular biological analysis of oil contaminated marine sediments : 30 years after the spill

AlRoumi, Dina K. January 2003 (has links)
In 1970 the Arrow oil spill off Cape Breton contaminated 305 kilometres of shoreline. Aerial and land surveys have demonstrated that natural weathering has occurred throughout this period, but it was relatively slow, especially in sheltered areas like Black Duck Cove lagoon. This study analyzed the microbial hydrocarbon degradation potential in the lagoon sediments using direct and culture-based techniques. Mineralization of hydrocarbon substrates (hexadecane, octacosane and naphthalene) indicated the presence of an active degradative microbial community, however, genes from known bacterial hydrocarbon degradation pathways (alkB, ndoB, phnAc) were not detected by direct extraction of sediment DNA and PCR amplification. Sediment enrichment cultures had increased mineralization rates for naphthalene and hexadecane, and a hexadecane-degrading pure culture, Rhodococcus sp. BDC14, with a typical alkB gene was isolated. PCR analysis of total community DNA extracted directly from the enrichments indicated the presence of the Alcanivorax borkumensis alkB1 genotype. The results demonstrated that there were notable differences between culture-based and direct molecular analytical techniques in characterizing the contaminated sediments.
70

Sur la stabilisation de systèmes dynamiques continus non linéaires exploitant les matrices de formes en flèche : application à la synchronisation de systèmes chaotiques / On the stabilization of nonlinear continuous dynamical systems using the arrow forms matrices : application to the synchronization of chaotic systems

Hammami, Sonia 21 December 2009 (has links)
Les travaux effectués, dans le cadre de cette thèse, concernent l’analyse et la synthèse de systèmes dynamiques continus complexes de grande dimension. Pour la classe des systèmes étudiés, est mise en exergue en particulier l’importance du choix de la description des systèmes sur l’étendue des résultats pouvant être obtenus lorsque la méthode d’étude de la stabilité est fixée.L’utilisation des normes vectorielles comme fonction d’agrégation et du critère pratique de Borne et Gentina pour l’étude de la stabilité, associée à la description des systèmes par des matrices caractéristiques de forme en flèche, a permis l’élaboration de nouvelles conditions suffisantes de stabilisabilité de systèmes dynamiques continus non linéaires, monovariables et multivariables, formulées en théorèmes et corollaires.Ces résultats obtenus, pour une classe de processus, pouvant être caractérisés par des matrices instantanées de forme en flèche mince, ont été généralisés au cas des matrices quelconques, pouvant être mises sous forme en flèche mince généralisée ou en flèche épaisse.Les critères élaborés, soit pour l’analyse de la stabilité soit pour la synthèse d’une loi de commande stabilisante, sont ensuite exploités, avec succès, pour la formulation de nouvelles conditions suffisantes de vérification des propriétés de synchronisation, d’anti-synchronisation et de synchronisation hybride de systèmes chaotiques du type maître-esclave, d’un grand intérêt, en particulier, pour garantir une transmission sécurisée / This Thesis deals with the analysis and the synthesis of dynamic large scale continuous systems depending on the choice of the system description.Stability and stabilisability proposed studies are based on the use of vector norms as an aggregation function and of the practical Borne-Gentina criterion, associated to the description of the system by instantaneous characteristic matrix in arrow form.Practical stability conditions, easy to use, are obtained for both dynamic nonlinear continuous single input single output systems and multiple inputs multiple outputs ones, formulated by means of theorems and corollaries. These obtained results for thin arrow form, are generalized to the case of matrices, which can be putted under thin generalized arrow form or thick arrow form. The proposed stability and stabilisability criteria are afterwards, successfully, exploited to formulate new sufficient conditions, guaranteeing the synchronization, the anti-synchronization and the hybrid synchronization properties, for chaotic master-slave systems, having an increasing interest throughout their application in the secure communication field

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