We analyze the resolved stellar populations of the faint stellar system, Crater, based on deep optical imaging taken with the Advanced Camera for Surveys on the Hubble Space Telescope. Crater's color-magnitude diagram (CMD) extends similar to 4 mag below the oldest main-sequence (MS) turnoff. Structurally, we find that Crater has a half-light radius of similar to 20 pc and no evidence for tidal distortions. We model. Crater's CMD as a simple stellar population (SSP) and alternatively by solving for its full star formation history. In both cases, Crater is well. described by an SSP with an age of similar to 7.5 Gyr, a metallicity of [ M / H] similar to 1.65, a total stellar mass of M-star similar to 1e4 M-circle dot, and. a luminosity of M-V similar to - 5.3, located at a distance of d similar to 145 kpc, with modest uncertainties due to differences in the underlying stellar evolution models. We argue that the sparse sampling of stars above the turnoff and subgiant branch are likely to be 1.0-1.4 M-circle dot blue stragglers and their evolved descendants, as opposed to intermediate- age MS stars. We find that. Crater is an unusually young cluster given its location in the Galaxy's outer halo. We discuss scenarios for Crater's origin, including the possibility of being stripped from the SMC or the accretion from lower- mass dwarfs such as Leo I or Carina. Despite uncertainty over its progenitor system, Crater appears to have been incorporated into the Galaxy more recently than z similar to 1 (8 Gyr ago), providing an important new constraint on the accretion history of the Galaxy.

Demands for using electrical resistivity techniques (surface and bulk resistivity) as an alternative to the rapid chloride penetrability test (RCPT) have been growing, for example by a number of transportation agencies in North America, to give an indication of the relative penetrability of concrete. While resistivity measurements may reflect the quality of pore structure in the cementitious matrix, their accuracy might be affected by a multitude of parameters including the concentration of ionic species in the pore solution, particularly when supplementary cementitious materials (SCMs) are incorporated in the binder. Hence, a systematic investigation on the resistivity of concrete and its corresponding physical penetrability is warranted. Zinc sacrificial anodes are considered an effective and economical method to prevent the electrochemical corrosion of steel bars by providing cathodic current to bars, which can provide corrosion protection at low galvanic current densities in the range of 0.2 to 2 mA/m2. Sacrificial anodes are commonly used in RC structures particularly in bridge decks to mitigate a critical phenomenon that occurs in the original concrete beside the repaired patches, which is known as the ‘halo effect’. One of the key factors affecting the efficacy of zinc anodes is the resistivity of concrete or cementitious repair material in which these anodes are embedded. There is a general notion that the higher the electrical resistivity of concrete or repair material, the less likely that zinc anodes produce the target galvanic current for optimum protection of steel bars. However, no systematic data are available on the maximum allowable electrical resistivity of repair materials/concretes beyond which zinc anodes cannot properly function to prevent corrosion. In the first part of this thesis, a tripartite relationship (nomogram) to correlate surface resistivity with penetrability (migration coefficient) and porosity of concrete using a wide range ii of concrete mixtures, taking into account the effect of key mixture design parameters (water-to-binder ratio, air-entrainment, SCMs and type of cement) was established. Relationships between surface and bulk resistivity as well as migration coefficient and porosity of concrete were also introduced. In addition, a penetrability classification of concrete based on the corresponding ranges of surface resistivity, migration coefficient and porosity has been proposed. The nomogram and penetrability classification provided reasonable assessment for the condition of field cores extracted from newly constructed and aging concrete pavement. In the second part of this thesis, the functionality of zinc anodes at mitigating patch accelerated corrosion (halo effect) in repaired concrete was explored. Concrete slabs were cast to simulate the patch repair configuration in the field, and the main parameters in this study were changing the resistivity of the repair section in the slabs (5,000, 15,000, 25,000, 50,000 and 100,000 Ω-cm), and anode spacing (25, 100, and 250 mm) inside the repair patch. Analysis of current and potential data shows a high level of effectiveness of the anodes at controlling corrosion in this slab configuration up to 52 weeks under a wetting-drying exposure. / February 2017

Uno de los pilares fundamentales en el tratamiento de las patologías respiratorias es la oxígenoterapia, por lo cual, es de suma importancia determinar el dispositivo de administración de oxígeno (O2) que se utilizará. También es fundamental determinar qué dispositivo es mejor, en función del estado de la patología, y cuando es conveniente realizar una transición de un sistema de administración a otro. Este estudio, prospectivo, transversal y experimental, tiene como objetivo determinar los efectos de la transición desde el halo a la cánula nasal en pacientes lactantes menores con patología respiratoria, y medir estos efectos a través de cambios en parámetros funcionales. La hipótesis planteada fue que la transición de halo a cánula nasal no genera un deterioro en la condición del paciente con patología respiratoria al administrar una Fracción inspirada de O2 (FiO2) similar a la que se entrega por el sistema de alto flujo. Luego de realizar la transición, se redujo la cantidad de oxígeno administrado sin cambios significativos en la condición clínica de los pacientes, posiblemente debido al efecto CPAP que se produce al administrar oxígeno a través de una cánula nasal.

We present a multi-epoch Hubble Space Telescope (HST) study of stellar proper motions (PMs) for four fields along the Orphan Stream. We determine absolute PMs of several individual stars per target field using established techniques that utilize distant background galaxies to define a stationary reference frame. Five Orphan Stream stars are identified in one of the four fields based on combined color-magnitude and PM information. The average PM is consistent with the existing model of the Orphan Stream by Newberg et al. In addition to the Orphan Stream stars, we detect stars that likely belong to other stellar streams. To identify which stellar streams these stars belong to, we examine the 2d bulk motion of each group of stars on the sky by subtracting the PM contribution of the solar motion (which is a function of position on the sky and distance) from the observed PMs, and comparing the vector of net motion with the spatial extent of known stellar streams. By doing this, we identify candidate stars in the Sagittarius and Lethe streams, and a newly found stellar stream at a distance of similar to 17 kpc, which we tentatively name the "Parallel Stream." Together with our Sagittarius stream study, this work demonstrates that even in the Gaia era, HST will continue to be advantageous in measuring PMs of old stellar populations on a star-by-star basis, especially for distances beyond similar to 10 kpc.

In this Thesis, I explore the formation and evolution of stellar spiral structures embedded in realistic dark matter haloes with very high resolution simulations. I first study the impact of the shape of the dark matter haloes. I find that non-adiabatic changes to the dark matter halo shape, commonly found in cosmological simulations due to the assembly history of haloes, can trigger strong two-armed grand-design spiral structures extending from the inner disc to the outer region. The nature of the spiral structures is found to be consistent with kinematic density waves based on the study of their power spectra. Such grand-design spiral structures may help the formation of transient multi-armed spiral structures if the self-gravity in disc is strong enough. Evolution of spiral structures is similar when the disc and the halo are misaligned, although warps develop additionally. I further find a strong correlation between the torque strength from the halo and the strength of the corresponding spiral structures. In the second part of my Thesis I then study the influence of subhaloes by including them from realistic cosmological simulations. I identify five different massive subhaloes that hit the central region of the disc, two out of which hit the disc twice. Aside from disc heating, three distinct generations of spiral structures are found in the stellar disc, which can be related to different subhaloes. For each generation, counter-rotating single-armed spiral structures develop first. They wind up very quickly before two-armed spiral structures become prominent. These spiral structures are again identified as kinematic density waves. We find that rather than interacting with the disc through resonances, subhaloes preferentially trigger spiral structures impulsively, due to their relatively short impact time with the disc. The strength of spiral structures can be related to the integrated strength of the torque generated by subhaloes. The correlation between the torque strength exerted by a triaxial dark matter halo and by subhaloes and the spiral strength may provide constraints on the distribution of dark matter.

Submitted by PPG Medicina e Ci?ncias da Sa?de (medicina-pg@pucrs.br) on 2018-09-03T12:29:41Z No. of bitstreams: 1 GIORDANO_RAFAEL_TRONCO_ALVES.pdf: 4296387 bytes, checksum: 0ebd26ada0ccec344a04ffbbd329dfae (MD5) / Approved for entry into archive by Sheila Dias (sheila.dias@pucrs.br) on 2018-09-03T14:24:25Z (GMT) No. of bitstreams: 1 GIORDANO_RAFAEL_TRONCO_ALVES.pdf: 4296387 bytes, checksum: 0ebd26ada0ccec344a04ffbbd329dfae (MD5) / Made available in DSpace on 2018-09-03T14:30:50Z (GMT). No. of bitstreams: 1 GIORDANO_RAFAEL_TRONCO_ALVES.pdf: 4296387 bytes, checksum: 0ebd26ada0ccec344a04ffbbd329dfae (MD5) Previous issue date: 2018-08-13 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES / Introduction: The halo sign consists of an area of ground-glass opacity surrounding pulmonary lesions on chest computed tomography (CT) scans. Different diseases have already been described as causing this finding, though a larger and more objective analysis of this sign has not been conducted yet. Materials and methods: The authors compared CT images of immunocompetent and immunosuppressed patients in terms of halo sign features and seek to identify those of greatest diagnostic value. An observational study of exams performed between January of 2011 and May of 2015 was carried out. After initial database search with keywords, two thoracic radiologists reviewed the scans in order to determine the number of lesions, as well as their distribution, size, and contour, together with halo thickness and any other associated findings. The study obtained approval by the institutional ethics committee. The chi-squared test, Student t test and Mann-Whitney U test were adopted according to sample characteristics, with a bilateral level of significance of 0.05. Results: A total of 85 patients (46 male, 54%) were evaluated, with 53 (62%) immunocompetent and 32 (38%) immunosuppressed. The main diagnosis among immunocompetents was lung cancer (n=32, 64%), whereas aspergillosis was the main condition in immunosuppressed patients (n=25, 78%). Multiple and randomly distributed lesions were more frequent in the immunosuppressed group (p<0.001), with halo thickness also greater in this group (p<0.05). Conclusions: We concluded that the causes of the halo sign differ significantly according to immune status, and that halo thickness, the number and the distribution of lesions are the data with greatest diagnostic value. / Introdu??o: O sinal do halo consiste em uma ?rea de opacidade em vidro-fosco ao redor de les?es pulmonares em imagens de tomografia computadorizada (TC) de t?rax. Diferentes doen?as j? foram descritas como causadoras deste achado, por?m uma an?lise maior e mais objetiva deste sinal ainda n?o foi conduzida. Materiais e m?todos: Os autores compararam imagens tomogr?ficas de pacientes imunocompetentes e imunocomprometidos quanto a caracter?sticas do sinal do halo, a fim de identificar as de maior valor diagn?stico. Realizou-se um estudo observacional de exames realizados entre janeiro de 2011 e maio de 2015. Ap?s busca inicial em banco de dados com palavras-chave, dois radiologistas tor?cicos analisaram os exames para determinar o n?mero de les?es e sua distribui??o, tamanho e contorno, bem como a espessura do halo e outros achados associados. O estudo obteve aprova??o do comit? de ?tica institucional. Os testes de Qui-quadrado, t de Student e U de Mann-Whitney foram adotados de acordo com caracter?sticas amostrais, com um n?vel de signific?ncia de 0,05 bilateral. Resultados: Um total de 85 pacientes (46 homens, 54%), foram avaliados, sendo 53 (62%) imunocompetentes e 32 (38%) imunocomprometidos. O principal diagn?stico entre os imunocompetentes foi o de neoplasia pulmonar (n=32, 64%), enquanto a aspergilose foi a principal condi??o entre imunocomprometidos (n=25, 78%). Les?es m?ltiplas e de distribui??o rand?mica foram mais frequentes no grupo imunocomprometido (p<0,001), sendo a espessura do halo tamb?m maior neste grupo (p<0,05). Conclus?es: Conclui-se que as causas de sinal do halo diferem significativamente de acordo com o estado imunol?gico, sendo a espessura do halo, o n?mero e a distribui??o das les?es os dados de maior valor diagn?stico.

This thesis explores topics related to the formation and development of the large-scale structure in the Universe, with the focus being to compute properties of the evolved non-linear density field in an approximate way. The first three chapters form an introduction: Chapter 1 contains the theoretical basis of modern cosmology, Chapter 2 discusses the role of N-body simulations in the study of structure formation and Chapter 3 considers the phenomenological halo model. In Chapter 4 a novel method of computing the matter power spectrum is developed. This method uses the halo model directly to make accurate predictions for the matter spectrum. This is achieved by fitting parameters of the model to spectra from accurate simulations. The final predictions are good to 5% up to k = 10 hMpc-1 across a range of cosmological models at z = 0, however accuracy degrades at higher redshift and at quasi-linear scales. Chapter 5 is dedicated to a new method of rescaling a halo catalogue that has previously been generated from a simulation of a specific cosmological model to a different model; a gross rescaling of the simulation box size and redshift label takes place, then individual halo positions are modified in accord with the large scale displacement field and their internal structure is altered. The final power spectrum of haloes can be matched at the 5% level up to k = 1 hMpc-1, as can the spectrum of particles within haloes reconstituted directly from the rescaled catalogues. Chapter 6 applies the methods of the previous two chapters to modified gravity models. This is done in as general a way possible but tests are restricted to f(R) type models, which have a scale-dependent linear growth rate as well as having 'chameleon screening' - by which modifications to gravity are screened within some haloes. Taking these effects into account leads to predictions of the matter spectrum at the 5% level and rescaled halo distributions that are accurate to 5% in both real and redshift space. For the spectrum of halo particles it is demonstrated that accurate results may be obtained by taking the enhanced gravity in some haloes into account.

Post asymptotic giant branch (post-AGB) stars, central stars of planetary nebulae (CSPNe) and planetary nebulae (PNe) are important phases of stellar evolution as the material they feedback is the seed of subsequent star formation in a galaxy. The majority of low and intermediate mass stars are expected to evolve through these channels, however, it is uncertain how many actually do, and at what rate. The Galactic halo, with its older population, provides a direct test of evolutionary models for low mass stars. Birthrate estimates of PNe are uncertain and worse still, are in contradiction with accepted white dwarf (WD) birthrate estimates. Much of the uncertainty stems from the lack of complete samples and poorly determined distance estimates. New surveys such as the Sloan Digital Sky Survey (SDSS), Galaxy Evolutionary Ex- plorer (GALEX) and the INT Photometric H® Survey (IPHAS) have discovered many new PNe and have observed the far edges of the Galaxy. Improved methods of determining distances to CSPNe are presented here, using model atmospheres, evolutionary tracks and high resolution reddening maps utilising these revolution- ary surveys. Locating the CSPN is non-trivial particularly for evolved PNe, as they are ex- tended with their central star often displaced from the centre of the nebula. There- fore, photometric criteria are required to locate the CSPN in the nebula’s field. Synthetic photometry of the CSPNe is derived from spectral energy distributions (SEDs) computed from a grid of model atmospheres covering the parameter range of CSPNe. The SEDs are convolved with filter transmission curves to compute synthetic magnitudes for a given photometric system which are then calibrated with standard stars and WDs. A further project borne out of a search for luminous central stars of faint PNe, resulted in a systematic search for post-AGB stars in the Galactic halo. In this work, new candidate halo post-AGB stars are discovered from a search through the SDSS spectroscopic database. Combined with previously identified halo post- AGB stars, including the results of a sub-sample from the Palomar-Green (PG) survey, the number of observed and predicted populations are compared. The number of observed post-AGB candidates shows a remarkable deficit to expecta- tions. A survey within a subset of the photometric database of SDSS supports the findings of the PG and SDSS spectroscopic surveys. These findings provide strong evidence for a lack of post-AGB stars in the Galac- tic halo and thick disc. A plausible explanation is that a large fraction of stars in these old, metal-poor populations are evolving via alternative channels. The implications of such a result are far reaching with knock on effects for stellar evolutionary theory, galactic evolution and extragalactic redshift estimates.

Current models of cosmology and galaxy formation are possibly at odds with observations of small-scale galaxies. Such is the case for the dwarf spheroidal (dSph) galaxies of the Milky Way (MW), where tension exists in explaining their observed abundance, mass, and internal structure. Here we present an analysis of the substructure surrounding MW-sized haloes in a Lambda Cold Dark Matter (LCDM) simulation suite. Combined with a semi-analytic model of galaxy formation and evolution, we identify substructures that are expected to host dSph galaxies similar to the satellites of the MW. We subsequently use these simulations to investigate the orbital properties of dSph satellite galaxies to make contact with those orbiting the MW. After accretion into the main halo, the higher mass ``luminous'' substructure remains on highly radial orbits while the orbits of lower mass substructure, which are not expected to host stars, tend to scatter off of the luminous substructure, and thus circularize over time. The orbital ellipticity distribution of the luminous substructure shows little dependence on the mass or formation history of the main halo, making this distribution a robust prediction of LCDM. Through comparison with the ellipticity distribution computed from the positions and velocities of the nine MW dSph galaxies that currently have proper motion estimates as a function of the assumed MW mass, we present a novel means of estimating the virial mass of the Milky Way. The best match is obtained assuming a mass of 1.1 x 10^12 M_sun with 95 per cent confidence limits of (0.6 - 3.1) x 10^12 M_sun. The uncertainty in this estimate is dominated by the large uncertainties in the proper motions and small number of MW satellites used, and will improve significantly with better proper motion measurements from Gaia. We also measure the shape of the gravitational potential of subhaloes likely to host dSphs, down to radii comparable to the half-light radii of MW dSphs. Field haloes are triaxial in general, while satellite haloes become more spherical over time due to tidal interactions with the host. Thus through the determination of the shape of a MW dSph's gravitational potential via line of sight velocity measurements, one could in principle deduce the impact of past tidal interactions with the MW, and thus determine its dynamical history. Additionally, luminous subhaloes experience a radial alignment of their major axes with the direction to the host halo over time, caused by tidal torquing with the host's gravitational potential during close pericentric passages. This effect is seen at all radii, even down to the half-light radii of the satellites. Radial alignment must be taken into account when calibrating weak-lensing surveys which often assume isotropic orientations of satellite galaxies surrounding host galaxies and clusters. / Graduate / 0606

Current models of cosmology and galaxy formation are possibly at odds with observations of small-scale galaxies. Such is the case for the dwarf spheroidal (dSph) galaxies of the Milky Way (MW), where tension exists in explaining their observed abundance, mass, and internal structure. Here we present an analysis of the substructure surrounding MW-sized haloes in a Lambda Cold Dark Matter (LCDM) simulation suite. Combined with a semi-analytic model of galaxy formation and evolution, we identify substructures that are expected to host dSph galaxies similar to the satellites of the MW. We subsequently use these simulations to investigate the orbital properties of dSph satellite galaxies to make contact with those orbiting the MW. After accretion into the main halo, the higher mass ``luminous'' substructure remains on highly radial orbits while the orbits of lower mass substructure, which are not expected to host stars, tend to scatter off of the luminous substructure, and thus circularize over time. The orbital ellipticity distribution of the luminous substructure shows little dependence on the mass or formation history of the main halo, making this distribution a robust prediction of LCDM. Through comparison with the ellipticity distribution computed from the positions and velocities of the nine MW dSph galaxies that currently have proper motion estimates as a function of the assumed MW mass, we present a novel means of estimating the virial mass of the Milky Way. The best match is obtained assuming a mass of 1.1 x 10^12 M_sun with 95 per cent confidence limits of (0.6 - 3.1) x 10^12 M_sun. The uncertainty in this estimate is dominated by the large uncertainties in the proper motions and small number of MW satellites used, and will improve significantly with better proper motion measurements from Gaia. We also measure the shape of the gravitational potential of subhaloes likely to host dSphs, down to radii comparable to the half-light radii of MW dSphs. Field haloes are triaxial in general, while satellite haloes become more spherical over time due to tidal interactions with the host. Thus through the determination of the shape of a MW dSph's gravitational potential via line of sight velocity measurements, one could in principle deduce the impact of past tidal interactions with the MW, and thus determine its dynamical history. Additionally, luminous subhaloes experience a radial alignment of their major axes with the direction to the host halo over time, caused by tidal torquing with the host's gravitational potential during close pericentric passages. This effect is seen at all radii, even down to the half-light radii of the satellites. Radial alignment must be taken into account when calibrating weak-lensing surveys which often assume isotropic orientations of satellite galaxies surrounding host galaxies and clusters. / Graduate / 0606