No / The hair follicle has an established role in wound re-epithelialisation, a phenomenon that has been appreciated since at least the first half of the last century. The bulge niche, one location of hair follicle epithelial stem cells has been of particular interest to researchers over recent years, with numerous studies showing its ability to directly contribute to epidermal repair. However, recent work has highlighted other progenitor regions of the hair follicle that appear to act as stem cells during epidermal repair. In addition, several studies within the last 12 months have questioned the importance of the bulge during re-epithelialisation, producing conflicting literature. Here we provide a new model to demonstrate how several important differences in experimental design between studies could account for these seemingly opposing findings, which may have implications for how future studies are conducted.

Formation of globular clusters (GCs), the Galactic bulge, or galaxy bulges in general is an important unsolved problem in Galactic astronomy. Homogeneous infrared observations of large samples of stars belonging to GCs and the Galactic bulge field are one of the best ways to study these problems. We report the discovery by APOGEE (Apache Point Observatory Galactic Evolution Experiment) of a population of field stars in the inner Galaxy with abundances of N, C, and Al that are typically found in GC stars. The newly discovered stars have high [N/Fe], which is correlated with [Al/Fe] and anticorrelated with [C/Fe]. They are homogeneously distributed across, and kinematically indistinguishable from, other field stars within the same volume. Their metallicity distribution is seemingly unimodal, peaking at [Fe/H] similar to -1, thus being in disagreement with that of the Galactic GC system. Our results can be understood in terms of different scenarios. N-rich stars could be former members of dissolved GCs, in which case the mass in destroyed GCs exceeds that of the surviving GC system by a factor of similar to 8. In that scenario, the total mass contained in so-called 'first-generation' stars cannot be larger than that in 'second-generation' stars by more than a factor of similar to 9 and was certainly smaller. Conversely, our results may imply the absence of a mandatory genetic link between 'second-generation' stars and GCs. Last, but not least, N-rich stars could be the oldest stars in the Galaxy, the by-products of chemical enrichment by the first stellar generations formed in the heart of the Galaxy.

The VISTA Variables in the Vía Láctea survey is a multi-epoch, near-infrared (NIR) search for RR Lyrae stars, which trace the structure and evolutionary history of the Galactic Bulge. To measure accurate light-curves for these and other variable sources in the crowded fields of the Bulge, we have built a pipeline to perform difference imaging analysis (DIA) on VVV data. This is the first time DIA has been carried out with a large-scale NIR survey, which presents certain specific challenges such as the large pixel scales and high variable background. This thesis begins with an investigation into the wider problem of reference image selection for DIA. Through this study, we found that an alternative formulation of traditional DIA - Target Image Convolution - yields better results for VVV. This technique is employed in the core image subtraction engine for the VVV DIA pipeline. This work also details the pipelines for carrying out calibration, period-finding and Fourier modelling on the light-curves of DIA sources, as well as for obtaining their dereddened NIR magnitudes and colours. To validate the pipelines, the magnitude calibration is checked against another NIR survey (in the most challenging Galactic centre field) and analysis results are crosschecked against the OGLE-IV catalogue of RR Lyrae (in a low-extinction region of the Galactic bulge). Both studies are used to determine the efficacy of the existing pipeline and identify areas for improvement. DIA generally shows a significant improvement over existing aperture photometry. Using the NIR properties of VVV DIA counterparts to the OGLE-IV RR Lyrae, we demonstrate that it is possible to identify new variables with this pipeline, including RR Lyrae.

The growing cost of energy combined with the increasing energy demand has driven the need for more efficient energy use. Air-to-air energy recovery in buildings has been shown to provide substantial energy savings in many cases. A new type of air-to-air energy recovery system, known as a run-around energy exchanger (RAEE), and which has excellent potential for the retrofit market, has been proposed and numerically modelled for heat and moisture exchange by Fan et al. (2006). This thesis focuses on the material properties of semi-permeable membranes required for each RAEE exchanger core.<p>Two commercially available membranes are considered in this thesis: a spunbonded polyolefin manufactured by DuPont with the trade name Tyvek®, and a two layer polypropylene laminate material manufactured by the 3M Company with the trade name Propore.<p>The moisture transfer effectiveness of the RAEE system depends mostly on the ability of its membrane to transfer water vapour. This effectiveness is investigated by measuring the vapour diffusion resistance of Tyvek® and Propore using a dynamic moisture permeation cell (DMPC). For Tyvek®, the average vapour diffusion resistance is 440 s/m, which corresponds to an expected typical RAEE energy recovery effectiveness of 52%. For Propore, the average vapour diffusion resistance is 140 s/m, which corresponds to an RAEE effectiveness of 62% in the same exchanger system.<p>The air permeability is also measured using the DMPC with Tyvek® having a Darcy air flow resistance of 27 nm-1 and Propore having a Darcy air flow resistance of 111 nm-1. The lower air flow resistance of Tyvek® is undesirable since air transfer is undesirable in the RAEE system. <p>The liquid penetration pressure is determined using a modified standard method that resembles the geometry of a membrane in the RAEE exchanger. It is found that the Propore has a liquid penetration pressure beyond the measurement capabilities of the apparatus (276 kPa); while the Tyvek® membrane has a liquid penetration pressure of 18 kPa which agrees well with published values. <p>The elastic moduli of the membranes are required to predict the membrane deflection under typical operating pressures and to properly size a support screen. The elastic modulus is determined using two tensile standards and a bulge test. The bulge test results are used in the design since the geometry of the bulge test better represents the situation of a pressurized membrane in the RAEE. The elastic modulus of Propore is found to be 20 ± 3 MPa and the elastic modulus of Tyvek® is found to be 300 ± 45 MPa. The values are used in subsequent calculations for sizing the square screen, where it is found that a screen with square openings of 12.7 mm (0.5 in.) is required to support the membrane. <p>The degradation of Tyvek® and Propore with UVC exposure is also investigated. It is found that both materials deteriorate when exposed to UVC radiation, and that the degradation is primarily a function of the exposure time and not the exposure intensity. <p>Considering all material properties tested, it is concluded that the Propore membrane is a better membrane choice for the RAEE than the Tyvek® membrane.

The growing cost of energy combined with the increasing energy demand has driven the need for more efficient energy use. Air-to-air energy recovery in buildings has been shown to provide substantial energy savings in many cases. A new type of air-to-air energy recovery system, known as a run-around energy exchanger (RAEE), and which has excellent potential for the retrofit market, has been proposed and numerically modelled for heat and moisture exchange by Fan et al. (2006). This thesis focuses on the material properties of semi-permeable membranes required for each RAEE exchanger core.<p>Two commercially available membranes are considered in this thesis: a spunbonded polyolefin manufactured by DuPont with the trade name Tyvek®, and a two layer polypropylene laminate material manufactured by the 3M Company with the trade name Propore.<p>The moisture transfer effectiveness of the RAEE system depends mostly on the ability of its membrane to transfer water vapour. This effectiveness is investigated by measuring the vapour diffusion resistance of Tyvek® and Propore using a dynamic moisture permeation cell (DMPC). For Tyvek®, the average vapour diffusion resistance is 440 s/m, which corresponds to an expected typical RAEE energy recovery effectiveness of 52%. For Propore, the average vapour diffusion resistance is 140 s/m, which corresponds to an RAEE effectiveness of 62% in the same exchanger system.<p>The air permeability is also measured using the DMPC with Tyvek® having a Darcy air flow resistance of 27 nm-1 and Propore having a Darcy air flow resistance of 111 nm-1. The lower air flow resistance of Tyvek® is undesirable since air transfer is undesirable in the RAEE system. <p>The liquid penetration pressure is determined using a modified standard method that resembles the geometry of a membrane in the RAEE exchanger. It is found that the Propore has a liquid penetration pressure beyond the measurement capabilities of the apparatus (276 kPa); while the Tyvek® membrane has a liquid penetration pressure of 18 kPa which agrees well with published values. <p>The elastic moduli of the membranes are required to predict the membrane deflection under typical operating pressures and to properly size a support screen. The elastic modulus is determined using two tensile standards and a bulge test. The bulge test results are used in the design since the geometry of the bulge test better represents the situation of a pressurized membrane in the RAEE. The elastic modulus of Propore is found to be 20 ± 3 MPa and the elastic modulus of Tyvek® is found to be 300 ± 45 MPa. The values are used in subsequent calculations for sizing the square screen, where it is found that a screen with square openings of 12.7 mm (0.5 in.) is required to support the membrane. <p>The degradation of Tyvek® and Propore with UVC exposure is also investigated. It is found that both materials deteriorate when exposed to UVC radiation, and that the degradation is primarily a function of the exposure time and not the exposure intensity. <p>Considering all material properties tested, it is concluded that the Propore membrane is a better membrane choice for the RAEE than the Tyvek® membrane.

The bulge test is a commonly used experiment to establish the material stress-strain response at the highest possible strain levels. It consists of a metal sheet placed in a die with a circular opening. It is clamped in place and inflated with hydraulic pressure. In this thesis, a bulge testing apparatus was designed, fabricated, calibrated and used to measure the stress-strain response of an aluminum sheet metal and establish its onset of failure. The custom design incorporates a draw-bead for clamping the plate. A closed loop controlled servohydraulic pressurization system consisting of a pressure booster is used to pressurize the specimens. Deformations of the bulge are monitored with a 3D digital image correlation (DIC) system. Bulging experiments on 0.040 in thick Al-2024-T3 sheets were successfully performed. The 3D nature of the DIC enables simultaneous estimates of local strains as well as the local radius of curvature. The successful performance of the tests required careful design of the draw-bead clamping arrangement. Experiments on four plates are presented, three of which burst in the test section as expected. Finite deformation isotropic plasticity was used to extract the true equivalent stress-strain responses from each specimen. The bulge test results correlated well with the uniaxial results as they tended to fall between tensile test results in the rolling and transverse directions. The bulge tests results extended the stress-strain response to strain levels of the order of 40%, as opposed to failure strains of the order of 10% for the tensile tests. Three-dimensional shell and solid models were used to investigate the onset of localization that precedes failure. In both models, the calculated pressure-deformation responses were found to be in reasonable agreement with the measured ones. The solid element model was shown to better capture the localization and its evolution. The corresponding pressure maximum was shown to be imperfection sensitive. / text

Hydraulic bulge forming has been used as a method to determine the properties of sheet metal alloys in biaxial stretching at room temperature. Gas-pressure bulge forming alleviates the issues of using hydraulic fluids when the tests are conducted at high temperatures (above 200°C). Testing a sheet metal alloy by gas-pressure blow-forming (GPBF) under controlled temperature and pressure conditions requires an accurate and reliable mechanism that delivers repeatable results. It was the purpose of this work to design and implement such an instrument. This instrument should deliver real-time data for material displacement during forming, which can then be used to better understand material plastic response and formability. Four different subsystems within this mechanism must interact, but also have enough independence for analysis and for assembly purposes. The combined sub-systems produced a GPBF apparatus capable of forming a sheet aluminum alloy AA5182 with a thickness of 1.5 mm into a dome with a height nearly equal to its radius under a constant gas pressure as low as 40 psi at 450°C. This GPBF apparatus produced, for the first time, in-situ data for dome peak displacement during gas-pressure bulge forming of AA5182 sheet at 450°C. / text

plan A / Pacific Islands Studies

Les tubes métalliques de précision sont largement utilisés pour des applications biomédicales. De tels tubes sont fabriqués par étirage à froid car ce procédé garanti le meilleur aspect de surface, le plus grand contrôle des dimensions du tube et le contrôle des propriétés mécaniques. L'objet de cette étude est de modéliser le procédé d'étirage de tube sur mandrin afin d'en améliorer la compréhension et de construire un outil permettant l'optimisation du procédé et de prédire la rupture des tubes en étirage. La construction du modèle élément finis s'appuie sur la réalisation d'essais expérimentaux afin de caractériser les propriétés mécaniques des matériaux et le frottement entre le tube et les outils d'étirage (mandrin, filière). Le comportement mécanique des alliages est caractérisé par des essais de traction sur tube, des essais de traction sur des éprouvettes découpées dans différentes orientations dans un tube déplié et des essais de gonflement de tube. Pour ces derniers, une machine et un outillage de gonflement de tubes ont été développés spécifiquement. Par le biais de ces essais différents aspects ont été étudiés : la viscoplasticité, l'anisotropie plastique, l'hétérogénéité des propriétés dans l'épaisseur du tube, la thermomécanique. Les coefficients de frottements ont été identifiés par analyse inverse sur des essais d'étirage instrumentés par des cellules d'effort. Des essais d'étirage ont été spécifiquement conçus en modifiant la géométrie du mandrin afin de conduire à la rupture des tubes lors de l'étirage. L'objectif de tels essais étant d'identifier la limite de formabilité des tubes. L'approche choisie pour prédire de la rupture a été d'utiliser des critères de ruptures qui pouvaient être calibrés sur des essais de traction uniquement. Les critères ont été calculés au cours de la simulation numérique de l'étirage sur mandrin et ils ont été évalués par rapport à leur capacité à prédire les réductions de section et d'épaisseur maximales. Enfin, des méthodes analytiques de calcul d'effort d'étirage ont été développées et comparées à la modélisation éléments finis. / Precision metallic tubes are widely used for biomedical applications. The requirements of such tubes in term of surface quality, precise dimensions and mechanical properties can be achieved by cold tube drawing only. The purpose of this study is to model the mandrel tube drawing in order improve the process understanding and to build a tool both for process optimisation and for failure prediction during drawing. Building the finite element modelling requires to perform a series of experimental tests in order to characterise the material mechanical behaviour and the friction between the tube and the forming tools (mandrel, die). The materials mechanical behaviour is characterized by means of tube tensile tests, tensile tests of oriented samples cut in different directions from flattened tubes and tube bulge test. For the latter, a tube bulge test device was specifically designed. Different aspects were covered by these tests: viscoplasticity, plastic anisotropy, materials properties heterogeneity in the tube thickness, thermomechanics. Friction coefficients were identified by inverse analysis on instrumented tube drawing tests. A specific drawing test was designed in order to identify the tube fracture during drawing by modifying the mandrel geometry. The goal of such test was to identify the tube formability limit. Among the different techniques available to predict tube failure, the approach of failure criterion was chosen. Different failure criteria that could be calibrated on tensile test were selected. Failure criteria were computed during the simulation of the mandrel tube drawing and they were evaluated in term of predictability of the maximum section and thickness reductions before fracture. Finally, analytical methods that enable to compute the drawing force were developed and compared with the finite element modelling.

Submitted by Raquel Vasconcelos Guimarães de Castro null (rvgcastro@hotmail.com) on 2016-06-10T17:22:52Z No. of bitstreams: 1 Definitivo v11 VERSÃO IMPRESSA.pdf: 3954271 bytes, checksum: fbf5e7559a791827787906302174080b (MD5) / Approved for entry into archive by Ana Paula Grisoto (grisotoana@reitoria.unesp.br) on 2016-06-15T17:22:54Z (GMT) No. of bitstreams: 1 castro_rvg_me_jabo.pdf: 3954271 bytes, checksum: fbf5e7559a791827787906302174080b (MD5) / Made available in DSpace on 2016-06-15T17:22:54Z (GMT). No. of bitstreams: 1 castro_rvg_me_jabo.pdf: 3954271 bytes, checksum: fbf5e7559a791827787906302174080b (MD5) Previous issue date: 2016-02-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A pele é um órgão extenso e de fácil acesso, e possui vários tipos celulares diferentes que estão em constante renovação. Dentre estas células, alguns tipos de células-tronco com potencial proliferativo, de autorrenovação e de diferenciação, são responsáveis pela manutenção da homeostase deste órgão e pela cura de feridas. Estudos anteriores sugerem a existência de um nicho de células-tronco presente no “bulge” dos folículos pilosos, que contém populações positivas para CD200 e CD34. Este trabalho foi realizado com o intuito de: 1- Obter tecidos derivados da pele de cães adultos e fetos, isolar e cultivar as células in vitro derivadas destes, empregando um método de isolamento celular através de digestão enzimática simples 2- Comprovar a presença de células do “bulge”, positivas para CD200 e CD34 após cultivo celular in vitro, comparando com a análise do tecido; Uma coloração por hematoxilina e eosina foi realizada da pele de cães adultos e fetos, e biopsias e células cultivadas in vitro foram caracterizadas pela presença das proteínas CD200 e CD34 através de imunofluorescência, imunocitoquímica e citometria de fluxo. Os resultados da imunofluorescência foram negativos para ambos CD200 e CD34 nas peles de feto e adulto. Na imunocitoquímica, as células foram positivas para CD34 e CD200, tanto em fetos quanto adultos. Adicionalmente, o marcador de pluripotência OCT4 foi testado, sendo expresso em células de feto. Por citometria de fluxo, a porcentagem média de células marcadas duplamente por CD200 e CD34 nos adultos foi de 3,1% e nos fetos de 0,33% (n=3). A marcação somente por CD200 foi encontrada somente nos adultos, sendo de 2,8% (n=3). Os resultados sugerem ser possível a obtenção de células-tronco do “bulge” do folículo piloso através do método de digestão enzimática simples, utilizado neste trabalho. Este estudo é o primeiro passo para novas pesquisas que envolvam esse nicho, na pele de cães. / Skin is an extensive and easily accessible organ, possessing various cell types which are in constant renovation. Some stem cell types found in the skin have the potential of self-renewal, proliferation and differentiation, processes which are responsible for the organ’s maintenance of homeostasis and the healing of wounds. Previous studies suggested the presence of a stem cell niche at the bulge region of the hair follicle, which contains cell populations positive for CD200 and CD34. Thus, this work sought to identify these cell populations in canine cultures using the following methods: 1. 1- Collecting samples of adult and fetus canine skin, isolating and culturing these cells in vitro using a method of simple enzymatic digestion; 2- Testing the cell cultures for CD200 and CD34 in vitro, comparing them with analyzed tissue material. Hematoxylin and eosin staining were conducted for the biopsies and analysis of fetal and adult canine skin, with the extracted cell cultures being characterized for the presence of the proteins CD200 and CD34 through immunofluorescence, immunocytochemistry and flow cytometry. In both adult and fetal tissue samples, CD200 and CD34 immunofluorescence results were negative. In immunocytochemistry, both fetal and adult cultures cells tested positive for CD34 and CD200. The pluripotency marker OCT4 was also tested, and was positive for fetal culture cells. Flow cytometer results showed that, for samples with a double staining of CD200 and CD34 the average percentage of marked cells was 3.1% in adults and 0.33% in fetal cells (n=3). For the CD200 marker alone, positive cells were found only in adult cultures, representing 2.8% of the total population (n=3). In conclusion, the results suggest that obtaining bulge stem cells from both fetuses and adults, with use of CD200 and CD34 markers, is validated through the simple enzymatic digestion and cell culture methods utilized in this study. The present work is the first step towards developing new research involving this niche in dogs.