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Performance Improvement of an Optical Coherence Tomography System by use of an Optical Pupil SlicerMeade, Jeffrey January 2011 (has links)
Spectral domain optical coherence tomography (SD-OCT) is a dispersed interferometric technology used to obtain tomographic images, typically of tissue for medical applications. OCT is a competing technology with confocal microscopy (CM) and confocal fluorescent microscopy (CFM), which are both used for biopsy imaging for pathology as the gold standard. OCT offers several advantages over CM/CFM: it is able to acquire a full 3D image in a single pass, it requires little or no sample preparation time, and the axial (depth) and lateral (transverse) resolution are not dependent on one another. SD-OCT is limited in imaging depth to a few millimetres due to the quality performance of the spectrograph section of the instrument--that which determines the sensitivity of the SD-OCT system.
In this thesis a design for an SD-OCT system is presented that is suitable for biopsy imaging for pathological studies, i.e. an OCT microscope. The purpose of this system is to provide a fast diagnosis to be made in a surgical environment to reduce the amount of tissue removed from a patient and lower the chance of a returned visit at a later date due to insufficient tissue removal. The secondary purpose of the SD-OCT microscope is to serve as a research testbed system for implementing novel hardware advancements. One such technology, called an optical pupil slicer (OPS), will be implemented in the instrument to improve the depth imaging performance of the SD-OCT system over conventional SD-OCT systems. The OPS is a device that generally improves the performance of a dispersive-type spectrograph by increasing the spectral resolution without a loss in throughput, thereby increasing the sensitivity of the SD-OCT system.
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Automatic Interferometric Alignment of a Free-Space Optical Coherence Tomography SystemCenko, Andrew January 2011 (has links)
Optical Coherence Tomography (OCT) is a relatively new interferometric technology that allows for high-resolution and non-destructive tomographic imaging. One of its primary current uses is for in vivo and ex vivo examination of medical samples. It is used for non-destructive examination of ocular disease, dermatological examination, blood vessel imaging, and many other applications. Some primary advantages of OCT imaging include rapid imaging of biological tissue with minimal sample preparation, 3D high-resolution imaging with depth penetrations of several millimeters, and the capability to obtain results in real time, allowing for fast and minimally invasive identification of many diseases.
Current commercial OCT systems rely heavily on optical fiber-based designs. They depend on the robustness of the fiber to maintain system performance in variable environmental
conditions but sacrifice the performance and flexibility of free-space optical designs. We discuss the design and implementation of a free-space OCT interferometer that can automatically maintain its alignment, allowing for the use of a free-space optical design outside of tightly controlled laboratory environments.
In addition, we describe how similar enhancements can be made to other optical interferometric systems. By extending these techniques, we can provide similar improvements to many related fields, such as interferometric metrology and Fourier Transform Spectroscopy. Improvements in these technologies can help bring powerful interferometric tools to a wider audience.
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Jämförelse mellan Scheimpflug imaging och anterior segment OCT i mätning av Corneal tjocklek.Fournstedt, Daniel January 2015 (has links)
Purpose: The purpose of this study was to compare corneal thickness measured both centrally and midperipherally, between two instruments using different measuring principles. The study also looked at correlation between corneal thickness and intraocular pressure (IOP). Methods: Central and midperipheral corneal thickness was measured on the right eyes of 31 subjects with two different instruments. Instruments were Scheimpflug-camera from Bon Sirius and an AS/OCT from Optos. Measurements were taken on central cornea (CCT) and midperipheral (nasal (NCT), temporal (TCT), superior (SCT) and inferior (ICT)) at a distance of 1.75 mm from the apex. Mean age of the subjects was 23.6 ± 4.5 years. (19-44 years). A CT-80A non-contact tonometer (NonCT) from Topcon was used to measure the intraocular pressure (IOP). Results: A mean-value for central corneal thickness was calculated to 542.4 µm and 540.4 µm for Bon Sirius and AS/OCT repectively. Remaining measured points had mean-values for corneal thickness of, NCT: 577.7 µm & 558.5 µm. TCT: 555.0 µm & 545.2 µm. SCT: 585.7 µm & 554.5 µm. ICT: 563.0 µm & 548.9 µm, respectively. Mean-difference for CCT was 2.4 µm and it showed a significant difference between the two instruments with a p-value of 0.007. Remaining measured points all showed a significant difference of p<0.05. NCT: 19.2 µm. TCT: 9.8 µm. SCT: 31 µm. ICT: 14 µm. A correlation between IOP and CCT measured in both Sirius and AS/OCT was positive with r = 0.7 and p<0.05. Conclusion: The results showed that Sirius gives higher values for corneal thickness then ASOCT in all five measurement points. The results show that these instruments can be used interchangeably when measuring central corneal thickness. However, caution should be used when measuring midperipheral corneal thickness as the there is a significant differences between these two instruments.
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The notion of fair and equitable treatment of foreign direct investment /Fouret, Julien January 2003 (has links)
To be fair and equitable are aims inherent in most legal systems, whether domestic or international, but are usually tacitly stated. With respect to foreign direct investment (FDI) they constitute a standard of treatment which lacks a clear definition. Nevertheless, the recurrence of this standard in conventional instruments makes it one of the focal points of this branch of international law. / The main goal of this thesis is to explore and understand the standard of fair and equitable treatment. To understand its definition, it is first necessary to undertake a theoretical analysis of the notion. Secondly, having assessed the general meaning to fair and equitable treatment, an attempt is made to assess the difficulties which have arisen from its incorporation in Chapter 11 of the North American Free Trade Agreement (NAFTA). Finally, the thesis tries to assess where the concept stands in international law and whether or not it has passed into the corpus of customary international law.
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Design, Fabrication, and Characterization of a 2-D SOI MEMS Micromirror with Sidewall Electrodes for Confocal MACROscope ImagingBai, Yanhui January 2010 (has links)
Micro-Electro-Mechanical Systems (MEMS) micromirrors have been developed for more than two decades along with the development of MEMS technology. They have been used into many application fields: optical switches, digital light projector (DLP), adoptive optics (AO), high definition (HD) display, barcode reader, endoscopic optical coherence tomography (OCT) and confocal microscope, and so on. Especially, MEMS mirrors applied into endoscopic OCT and confocal microscope are the intensive research field. Various actuation mechanisms, such as electrostatic, electromagnetic, electro bimorph thermal, electrowetting, piezoelectric (PZT) and hybrid actuators, are adopted by different types of micromirrors. Among these actuators, the electrostatic is easily understood and simple to realize, therefore, it is broadly adopted by a large number of micromirrors.
This thesis reports the design, fabrication, and characterization of a 2-D Silicon-on-insulation (SOI) MEMS micromirror with sidewall (SW) electrodes for endoscopic OCT or confocal microscope imaging. The biaxial MEMS mirror with SW electrodes is actuated by electrostatic actuators. The dimension of mirror plate is 1000micron×1000micron, with a thickness of a 35micron. The analytical modeling of SW electrodes, fabrication process, and performance characteristics are described. In comparison to traditional electrostatic actuators, parallel-plate and comb-drive, SW electrodes combined with bottom electrodes achieve a large tilt angle under a low drive voltage that the comb-drive does and possess fairly simple fabrication process same as that of the parallel-plate. A new fabrication process based on SOI wafer, hybrid bulk/surface micromachined technology, and a high-aspect-ratio shadow mask is presented. Moreover, the fabrication process is successfully extended to fabricate 2×2 and 4×4 micromirror arrays. Finally, a biaxial MEMS mirror with SW electrodes was used into Confocal MACROscope for imaging. Studied optical requirements in terms of two optical configurations and frequency optimization of the micromirror, the biaxial MEMS mirror replaces the galvo-scanner and improves the MACROscope. Meanwhile, a new Micromirror-based Laser Scanning Microscope system is presented and allows 2D images to be acquired and displayed.
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Financial integration of NAFTA : measurement and analysis of the North American financial markets convergence / Yueming (Roy) SunSun, Yueming (Roy), University of Lethbridge. Faculty of Management January 2010 (has links)
Applying market arbitrage theory on daily data, we measure the empirical financial market convergence of NAFTA’s financial markets since 1994. Radar diagram and wavelet multi-resolution analysis (MRA) scalogram movies of the statistical moments of the term interest rate differentials visualize the multidimensional convergence. From the radar movies, we find: 1) a uniform disappearance of the average forward premia; 2) a non-uniform decline of bilateral financial market risk; 3) variation of bilateral financial market pressure measured by skewness; and 4) emergence of uniform market microstructures as measured by vanishing excess-kurtosis. From the MRA movies, we find that the national term structures of interest rates converge, since the stochastic resonance coefficients of the interest rate differentials lose significance: market energy at all frequencies dissipates into “white noise.” Testing Obrimah, Prakash and Rangan’s (2009) Lemma, we find that, after 2002, higher financial flow pressure is a necessary condition for lower financial market risk. / vii, 67 leaves ; 29 cm
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Choice of forum for NAFTA governments between NAFTA Chapter 20 and the WTO dispute settlement mechanismsLuna, Julieta Uribe January 2002 (has links)
NAFTA's Article 2005 prescribes that the NAFTA governments, being Canada, Mexico and the US, may choose either a multilateral or a regional forum within which to solve their trade disputes. Thus, they may choose between either the new WTO dispute settlement mechanism or the NAFTA Chapter 20 dispute settlement mechanism. Nevertheless, in order to have an effective choice of forum, there is one essential condition: the subject matter of the dispute must be similar or identical, and there must be some degree of subject matter overlap in both the NAFTA and WTO provisions. The relationship between NAFTA, the WTO and GATT is complex. The core problem is whether there is a legal distinction between the GATT 1947 and the GATT 1994, incorporated into the WTO Agreement, in order to establish either NAFTA or WTO primacy. The latter-in-time treaty general rule will decide the issue. Nevertheless, a decisive conclusion cannot be drawn, as this should be studied on a case-by-case basis.
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Exploring access to NAFTA's environment commission complaint processHernandez, Roberto January 2003 (has links)
This paper raises questions about the accessibility of the Articles 14 & 15 submissions mechanism, a public complaint process that attempts to use the eyes of ordinary persons in Canada, Mexico and the US to monitor an important environmental treaty obligation: NAFTA signatories' commitment to effectively enforce their environmental laws. In order to consider whether the Articles 14 & 15 review tool is accessible, we assemble a set of indicators that nourish four hypotheses, which may reveal if the review tool is sufficiently well installed to attain its long term objectives in a significant measure. The hypotheses are: 1) that the CEC receives an insufficient amount of submissions; 2) that it takes considerable or random times to process them; 3) that it consistently takes longer, or has more troubles, to process Mexican and disadvantaged-group cases; 4) that few complainants harvest any benefits from complaining, being more likely that they do if they are rich environmental NGOs than if they are ordinary individuals. The information we present is based on primary research and statistical information on the processing of NAAEC Articles 14 and 15 submissions. Our chief objective is not to conclusively prove or disprove these hypotheses, but to provide a framework to respond these questions. By consistently focusing their efforts on evaluating the attainment of the ultimate objectives of this review tool, all authors who have critiqued the Articles 14 & 15 submissions process have failed to consider whether the complaint mechanism is effectively positioned to capture environmental law enforcement information from all of its target population. Instead, this paper explores the implementation of Articles 14 & 15 by generating information on the attainment of its midcourse objectives. This paper may be of interest to persons working on issues concerning the implementation and further elaboration of NAAEC Articles 14 and 15 and to those pondering whether and how the proposed FTAA and the Canada-Chile Free Trade Accord should be structured to deal with the environmental consequences of further economic integration.
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Access to genetic resources and sharing of benefits arising out of their utilization : a critical analysis of the contribution of the Nagoya Protocol to the existing international regime on access and benefit-sharing.Kizungu, Dieu-Donne Mushamalirwa. 05 November 2013 (has links)
Prior to the commencement of the Convention on Biological Diversity (CBD), genetic
resources were considered to be the common heritage of mankind; this principle gave
the right to developed countries to obtain and freely use the genetic material of developing countries.
Growing concern over the controversial ‘free access’ system and the monopolization of
benefits led to the negotiation of an international treaty, the CBD, to regulate access to
genetic resources and the sharing of benefits resulting from the utilisation of such resources.
The CBD makes some important innovations. It recognizes that the authority to
determine access to genetic resources depends on national governments and is subject to
national legislation. Thus, the CBD recognizes state sovereignty over genetic resources
and institutes the principles of Prior informed Consent (PIC), Mutually Agreed Terms and Benefit-Sharing.
However, the CBD and other international instruments relating to genetic resources
have not had the desired effect of preventing the misappropriation of genetic resources
and associated traditional knowledge (TK). Developing countries suffered and continue
to suffer from the piracy of their resources. This state of affairs has led to the recent
adoption of the ‘Nagoya Protocol on Access to Genetic Resources and the Fair and Equitable Sharing of Benefits Arising from their Utilization to The Convention on Biological Diversity,’ (2010 Nagoya Protocol).
This dissertation will consider the contribution of the Nagoya Protocol to the existing
global and regional instruments concerning the access and benefit sharing of genetic
resources. After explaining the gaps in the existing instruments, it will explore whether the Protocol is a miracle solution to the recurrent concern over misappropriation of genetic resources from biologically rich countries, or whether there is still much work to do to sort out this problem. / Thesis (LL.M.)-University of KwaZulu-Natal, Pietermaritzburg, 2012.
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Développement et application de la tomographie par cohérence optique plein champ pour l'étude du matériau papierBlavier, Marie 10 January 2008 (has links) (PDF)
La structure interne du papier détermine la majorité des propriétés de ce matériau. Sa connaissance est donc très utile pour les papetiers. Cependant, il n'existe pas de méthode simple et rapide pour obtenir cette structure. Lors de la thèse, un montage de tomographie par cohérence optique (OCT) plein champ avec une source thermique a été développé afin d'appliquer à l'étude du papier cette technique non destructive issue de la biologie. La résolution spatiale est de l'ordre du micron dans les trois dimensions. Des images de la structure de feuilles de papier ont été obtenues. Les résultats et la profondeur d'imagerie dépendent fortement du type de papier et de ses propriétés optiques. La limite fondamentale de cette méthode est la forte diffusion multiple dans ce matériau. L'OCT présente cependant de nombreuses applications potentielles en papeterie et les essais expérimentaux montrent que des améliorations pourront être apportées afin d'augmenter la profondeur d'imagerie.
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