Local non-negative initial data scalar characterization of the Kerr solution

For any vacuum initial data set, we define a local, non-negative scalar quantity which vanishes at every point of the data hypersurface if and only if the data are Kerr initial data. Our scalar quantity only depends on the quantities used to construct the vacuum initial data set which are the Riemannian metric defined on the initial data hypersurface and a symmetric tensor which plays the role of the second fundamental form of the embedded initial data hypersurface. The dependency is algorithmic in the sense that given the initial data one can compute the scalar quantity by algebraic and differential manipulations, being thus suitable for an implementation in a numerical code. The scalar could also be useful in studies of the non-linear stability of the Kerr solution because it serves to measure the deviation of a vacuum initial data set from the Kerr initial data in a local and algorithmic way.

Wear of PEEK-Ti6Al4V systems under micro-abrasion and linear sliding conditions

Dissertação de mestrado integrado em Engenharia Biomédica

Sensores de fibra ótica baseados em novos materiais flexíveis

Dissertação de mestrado integrado em Engenharia Eletrónica Industrial e de Computadores

Comparing different methods to measure biofilm thickness: the techniques are: optical coherence tomography, confocal laser scanning microscopy and low load compression test

Dissertação de mestrado integrado em Engenharia Biomédica (área de especialização em Engenharia Clínica)

Characterization of physical, mechanical and chemical properties of quiscal fibres: the influence of atmospheric dbd plasma treatment

This paper reports the first attempt of characterizing several physical, mechanical and chemical properties of Quiscal fibres, usually used by the native communities in Chile and on investigations concerning the influence of atmospheric dielectric barrier discharge (DBD) plasma treatment on various properties such as diameter and linear density, percent of impurity, moisture regain, chemical elements and groups, thermal degradation, surface morphology, among others.

Low f-number microlenses for integration on optical microsystems

This paper presents microlenses (MLs) with low f-number made of AZ4562 photoresist for integration on optical microsystems. The fabrication process was based on the thermal reflow and rehydration. Large series of MLs were fabricated with a width of 35 μm, a thickness of 5 μm, and spaced apart by 3 μm. The MLs were fabricated directly on the surface of a die with type n+/p-substrate junction photodiode fabricated in a standard CMOS process. The measured focal length was 49 μm with a tolerance of ±2 μm (maximum error of ±4%), resulting in a numerical aperture of 33.6 × 10-2 (±1.3 × 10-2). The measurements also revealed an f-number of 1.4.

Development and characterization of lipid-based nanosystems for controlled release of bioactive compounds

Tese de Doutoramento em Engenharia Química e Biológica.

A Characterization of single-peaked preferences

We identify in this paper two conditions that characterize the domain of single-peaked preferences on the line in the following sense: a preference profile satisfies these two properties if and only if there exists a linear order $L$ over the set of alternatives such that these preferences are single-peaked with respect L. The first property states that for any subset of alternatives the set of alternatives considered as the worst by all agents cannot contains more than 2 elements. The second property states that two agents cannot disagree on the relative ranking of two alternatives with respect to a third alternative but agree on the (relative) ranking of a fourth one. Classification-JEL: D71, C78

A dual characterization of incentive efficiency

We show that incentive efficient allocations in economies with adverse selection and moral hazard can be determined as optimal solutions to a linear programming problem and we use duality theory to obtain a complete characterization of the optima. Our dual analysis identifies welfare effects associated with the incentives of the agents to truthfully reveal their private information. Because these welfare effects may generate non-convexities, incentive efficient allocations may involve randomization. Other properties of incentive efficient allocations are also derived.

Comparability of clinical wear measurements by optical 3D laser scanning in two different centers.

OBJECTIVE: The purpose of this study was to compare the use of different variables to measure the clinical wear of two denture tooth materials in two analysis centers. METHODS: Twelve edentulous patients were provided with full dentures. Two different denture tooth materials (experimental material and control) were placed randomly in accordance with the split-mouth design. For wear measurements, impressions were made after an adjustment phase of 1-2 weeks and after 6, 12, 18, and 24 months. The occlusal wear of the posterior denture teeth of 11 subjects was assessed in two study centers by use of plaster replicas and 3D laser-scanning methods. In both centers sequential scans of the occlusal surfaces were digitized and superimposed. Wear was described by use of four different variables. Statistical analysis was performed after log-transformation of the wear data by use of the Pearson and Lin correlation and by use of a mixed linear model. RESULTS: Mean occlusal vertical wear of the denture teeth after 24 months was between 120μm and 212μm, depending on wear variable and material. For three of the four variables, wear of the experimental material was statistically significantly less than that of the control. Comparison of the two study centers, however, revealed correlation of the wear variables was only moderate whereas strong correlation was observed among the different wear variables evaluated by each center. SIGNIFICANCE: Moderate correlation was observed for clinical wear measurements by optical 3D laser scanning in two different study centers. For the two denture tooth materials, wear measurements limited to the attrition zones led to the same qualitative assessment.

Biochemical characterization of recombinant human telomerase

Résumé Les télomères sont les structures ADN-protéines des extrémités des chromosomes des eucaryotes. L'ADN télomérique est constitué de courtes séquences répétitives. L'intégrité des télomères est essentielle pour protéger les extrémités des chromosomes contre les systèmes de dégradations et pour les distinguer des cassures de l'ADN double brin. Parce que la machinerie de la réplication de l'ADN n'est pas capable de répliquer l'extrémité des chromosomes, les télomères raccourcissent au fur et à mesure des cycles de réplication. Dès que les télomères atteignent une longueur critique, leur structure protectrice est perdue. Cela induit un signal de dommage de l'ADN et l'arrêt du cycle cellulaire. Pour contrebalancer le raccourcissement des télomères, les cellules qui s'auto régénèrent, dont les cellules de la moelle osseuse, les lymphocytes activés et 80-90% des cellules cancéreuses, expriment la télomérase. C'est une ribonucléoprotéine qui a la capacité de synthétiser des séquences télomériques par transcription inverse d'une courte séquence contenue dans sa propre sous-unité ARN avec laquelle elle est associée. La télomérase humaine est une enzyme processive au niveau de l'addition des nucléotides et aussi des répétitions télomériques. La télomérase de levure et la télomérase humaine sont toutes deux dimériques et il a été montré que la télomérase humaine recombinante contient deux ARN qui coopèrent pour fonctionner ainsi que deux sous-unités catalytiques. Cependant, il n'a pas encore été montré quel est le rôle de la dimérisation dans l'activité de la télomérase. Afin d'élucider ce rôle, nous avons exprimé, reconstitué et purifié la télomérase humaine dimérique recombinante. Et pour étudier l'effet d'ARN mutants sur l'activité de la télomérase, nous avons développé une méthode pour reconstituer et enrichir en hétérodimères de télomérase. Les hétérodimères contiennent une sous-unité ARN sauvage et une sous-unité ARN mutée au niveau de la séquence de la matrice. Sur l'ARN muté nous avons introduit une étiquette aptamer ARN-S1 puis nous avons purifié la télomérase via l'etiquette Si. Nous avons montré que la dimérisation est essentielle pour l'activité de la télomérase. Nos données indiquent que chaque télomérase du dimère allonge leur substrat, l'ADN télomérique, indépendamment l'une de l'autre à chaque cycle d'élongation mais que l'addition itérative de répétitions télomériques nécessite une coopération entre les deux télomérases du dimère. Nous proposons donc un modèle dans lequel les deux télomérases du dimères se lient et allongent deux substrats télomères et que pendant l'élongation processive les deux enzymes subissent un changement de conformation de manière coordonnée, ce changement va permettre le repositionnement des substrats pour d'autres cycles d'additions de répétitions télomériques. Dyskeratosis congenita est une maladie mortelle due majoritairement au disfonctionnement de la moelle osseuse. Dans la forme autosomale de la maladie, l'ARN de la télomérase contient des mutations. En utilisant notre système de reconstitution, nous avons montré que ces ARN mutés, qui ont perdu leur activité enzymatique dans le cas d'un homodimère de mutants, sont dominant négatifs quand ils sont présents dans les hétérodimères sauvage/mutant. Cet effet trans-dominant négatif pourrait contribuer à la progression de la maladie. Abstract Telomeres are protein-DNA structures at the ends of linear eukaryotic chromosomes. The telomeric DNA consists of tandemly repeated sequences. Telomeric integrity is essential to protect chromosomal ends from nucleolytic degradation and to prevent their recognition as DNA double strand breaks. Due to the inability of the conventional DNA replication machinery to replicate terminal DNA stretches, telomeres shorten with continuous rounds of DNA replication. As soon as telomeres reach a critical length, their protective structure is lost and the deprotected telomeres will induce a DNA damage response leading to cell cycle arrest. To counteract telomere shortening, self-renewing cells, including bone marrow cells, activated lymphocytes and 80-90% of cancer cells express the cellular reverse transcriptase telomerase, which has the capacity to synthesize telomeric repeats by reverse transcription of a short template sequence encoded by its stably associated RNA subunit. Human telomerase is a processive enzyme for nucleotide as well as repeat addition. Both yeast and human telomerase are dimeric enzymes and recombinant human telomerase has been shown to contain two functionally cooperating RNAs and most probably also two protein subunits. However, it has remained unclear how dimerization may contribute to telomerase activity. To study the role of dimerization, we expressed, reconstituted and purified recombinant human telomerase. We also developed a new method to reconstitute and enrich for telomerase heterodimers containing wild-type (wt) and mutant telomerase RNA subunits. To this end we introduced an S1-RNA-aptamer tag into telomerase RNA and purified telomerase reconstituted with a mixture of untagged and tagged RNA via the S1-tag. Using this experimental system, we introduced template mutations in the tagged RNA subunit and examined the effect of mutant RNAs on wt telomerase activity in wt/mutant heterodimers. We obtained evidence that dimerization is essential for telomerase activity. Our data indicate that the two subunits elongate telomere substrates independently of each other during single rounds of elongation, but that iterative addition of telomeric repeats requires cooperation between the two subunits. We suggest a model, in which dimeric telomerases bind and elongate two telomere substrates and that the two subunits undergo coordinated conformational changes during processive elongation that enable repositioning the substrates for subsequent rounds of repeat addition. Dyskeratosis congenita is a multisystemic disease with bone marrow failure as the major cause of death. The autosomal form of this disease was found to harbor mutations in the telomerase RNA. Using our reconstitution system, we tested whether mutant dyskeratosis telomerase RNAs behaved in a dominant negative manner. We observed that dyskeratosis telomerase RNA mutants, which lacked enzymatic activity were dominant negative, when present in wt/ mutant heterodimers. The transdominant negative effect of these mutants may contribute to disease progression.

On the throughput-WIP trade-off in queueing systems, diminishing returns and the threshold property: A linear programming approach

We present a new unifying framework for investigating throughput-WIP(Work-in-Process) optimal control problems in queueing systems,based on reformulating them as linear programming (LP) problems withspecial structure: We show that if a throughput-WIP performance pairin a stochastic system satisfies the Threshold Property we introducein this paper, then we can reformulate the problem of optimizing alinear objective of throughput-WIP performance as a (semi-infinite)LP problem over a polygon with special structure (a thresholdpolygon). The strong structural properties of such polygones explainthe optimality of threshold policies for optimizing linearperformance objectives: their vertices correspond to the performancepairs of threshold policies. We analyze in this framework theversatile input-output queueing intensity control model introduced byChen and Yao (1990), obtaining a variety of new results, including (a)an exact reformulation of the control problem as an LP problem over athreshold polygon; (b) an analytical characterization of the Min WIPfunction (giving the minimum WIP level required to attain a targetthroughput level); (c) an LP Value Decomposition Theorem that relatesthe objective value under an arbitrary policy with that of a giventhreshold policy (thus revealing the LP interpretation of Chen andYao's optimality conditions); (d) diminishing returns and invarianceproperties of throughput-WIP performance, which underlie thresholdoptimality; (e) a unified treatment of the time-discounted andtime-average cases.

3D seismic facies characterization and geological patterns recognition (Australian North West Shelf)

EXECUTIVE SUMMARY This PhD research, funded by the Swiss Sciences Foundation, is principally devoted to enhance the recognition, the visualisation and the characterization of geobodies through innovative 3D seismic approaches. A series of case studies from the Australian North West Shelf ensures the development of reproducible integrated 3D workflows and gives new insight into local and regional stratigraphic as well as structural issues. This project was initiated in year 2000 at the Geology and Palaeontology Institute of the University of Lausanne (Switzerland). Several collaborations ensured the improvement of technical approaches as well as the assessment of geological models. - Investigations into the Timor Sea structural style were carried out at the Tectonics Special Research Centre of the University of Western Australia and in collaboration with Woodside Energy in Perth. - Seismic analysis and attributes classification approach were initiated with Schlumberger Oilfield Australia in Perth; assessments and enhancements of the integrated seismic approaches benefited from collaborations with scientists from Schlumberger Stavanger Research (Norway). Adapting and refining from "linear" exploration techniques, a conceptual "helical" 3D seismic approach has been developed. In order to investigate specific geological issues this approach, integrating seismic attributes and visualisation tools, has been refined and adjusted leading to the development of two specific workflows: - A stratigraphic workflow focused on the recognition of geobodies and the characterization of depositional systems. Additionally, it can support the modelling of the subsidence and incidentally the constraint of the hydrocarbon maturity of a given area. - A structural workflow used to quickly and accurately define major and secondary fault systems. The integration of the 3D structural interpretation results ensures the analysis of the fault networks kinematics which can affect hydrocarbon trapping mechanisms. The application of these integrated workflows brings new insight into two complex settings on the Australian North West Shelf and ensures the definition of astonishing stratigraphic and structural outcomes. The stratigraphic workflow ensures the 3D characterization of the Late Palaeozoic glacial depositional system on the Mermaid Nose (Dampier Subbasin, Northern Carnarvon Basin) that presents similarities with the glacial facies along the Neotethys margin up to Oman (chapter 3.1). A subsidence model reveals the Phanerozoic geodynamic evolution of this area (chapter 3.2) and emphasizes two distinct mode of regional extension for the Palaeozoic (Neotethys opening) and Mesozoic (abyssal plains opening). The structural workflow is used for the definition of the structural evolution of the Laminaria High area (Bonaparte Basin). Following a regional structural characterization of the Timor Sea (chapter 4.1), a thorough analysis of the Mesozoic fault architecture reveals a local rotation of the stress field and the development of reverse structures (flower structures) in extensional setting, that form potential hydrocarbon traps (chapter 4.2). The definition of the complex Neogene structural architecture associated with the fault kinematic analysis and a plate flexure model (chapter 4.3) suggest that the Miocene to Pleistocene reactivation phases recorded at the Laminaria High most probably result from the oblique normal reactivation of the underlying Mesozoic fault planes. This episode is associated with the deformation of the subducting Australian plate. Based on these results three papers were published in international journals and two additional publications will be submitted. Additionally this research led to several communications in international conferences. Although the different workflows presented in this research have been primarily developed and used for the analysis of specific stratigraphic and structural geobodies on the Australian North West Shelf, similar integrated 3D seismic approaches will have applications to hydrocarbon exploration and production phases; for instance increasing the recognition of potential source rocks, secondary migration pathways, additional traps or reservoir breaching mechanisms. The new elements brought by this research further highlight that 3D seismic data contains a tremendous amount of hidden geological information waiting to be revealed and that will undoubtedly bring new insight into depositional systems, structural evolution and geohistory of the areas reputed being explored and constrained and other yet to be constrained. The further development of 3D texture attributes highlighting specific features of the seismic signal, the integration of quantitative analysis for stratigraphic and structural processes, the automation of the interpretation workflow as well as the formal definition of "seismo-morphologic" characteristics of a wide range of geobodies from various environments would represent challenging examples of continuation of this present research. The 21st century will most probably represent a transition period between fossil and other alternative energies. The next generation of seismic interpreters prospecting for hydrocarbon will undoubtedly face new challenges mostly due to the shortage of obvious and easy targets. They will probably have to keep on integrating techniques and geological processes in order to further capitalise the seismic data for new potentials definition. Imagination and creativity will most certainly be among the most important quality required from such geoscientists.