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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.
1

The hologram and its antecedents, 1891-1965 : the illusory history of a three-dimensional illusion

Gamble, Susan Ann January 2005 (has links)
Since 1962, a photographic invention by Gabriel Lippmann (1845-1921), his Nobel Prize winning interference colour photograph of 1891, has been cited by physicists as the antecedent of the three-dimensional hologram. However, Dennis Gabor (1900-1979) in his original publications on the hologram of 1948 and 1949 did not cite Lippmann’s work. This thesis explores how the hologram that featured in Gabor’s original theory, as an imaging technique to improve the electron-microscope, was significantly different from the hologram for which Gabor was awarded the Nobel Prize for Physics in 1971. The citation of Lippmann’s work as the antecedent to the hologram confirmed that the hologram was to be seen as a three-dimensional photograph, and attempted to give the invention a progressive historical lineage that would conform to photography’s existing history. This popular narrative, as demonstrated in this text, could overlook the pursuit of the hologram for Cold War surveillance by researchers at the University of Michigan on behalf of the United States military. This technology was, from 1955, engaged with aerial radar image processing, a significant application that was classified and hidden from the public, and initially from Gabor himself. Two researchers at the University of Michigan, Emmett Leith (1927–) and Juris Upatnieks (1936–) attracted the attention of the popular press for their development of a three-dimensional laser hologram. This thesis reveals the fragmented nature of the new discipline at the peak of holography’s popularity. This analysis explores some of the historical traits between the two Nobel Prize winning inventions, the Lippmann photograph and the hologram, that were exploited to promote a new imaging medium to the public. In presenting these technologies as images the text also reviews devices and papers––some cited within the popular Lippmann-to Gabor historical narrative––by father and son Frederic (1856-1937) and Herbert Ives (1882-1953), that have competed to produce a three-dimensional full-colour image.
2

Morphology Dependence of Stellar Age in Quenched Galaxies at Redshift ∼1.2:Massive Compact Galaxies Are Older than More Extended Ones

Williams, Christina C., Giavalisco, Mauro, Bezanson, Rachel, Cappelluti, Nico, Cassata, Paolo, Liu, Teng, Lee, Bomee, Tundo, Elena, Vanzella, Eros 30 March 2017 (has links)
We report the detection of morphology-dependent stellar age in massive quenched galaxies (QGs) at z similar to 1.2. The sense of the dependence is that compact QGs are 0.5-2 Gyr older than normal-sized ones. The evidence comes from three different age indicators-D(n)4000, H-delta, and fits to spectral synthesis models-applied to their stacked optical spectra. All age indicators consistently show that the stellar populations of compact QGs are older than those of their normal-sized counterparts. We detect weak [O II] emission in a fraction of QGs, and the strength of the line, when present, is similar between the two samples; however, compact galaxies exhibit a. significantly lower frequency of [O II] emission than normal ones. Fractions of both samples are individually detected in 7Ms Chandra X-ray images (luminosities similar to 10(40) - 10(41) erg s(-1)). The 7Ms stacks of nondetected galaxies show similarly low luminosities in the soft band only, consistent with a hot gas origin for the X-ray emission. While both [O II] emitters and nonemitters are also X-ray sources among normal galaxies, no compact galaxy with [O II] emission is an X-ray source, arguing against an active galactic nucleus (AGN) powering the line in compact galaxies. We interpret the [O II] properties as further evidence that compact galaxies are older and further along in. the process of quenching star formation and suppressing gas accretion. Finally, we argue that the older age of compact QGs is evidence of progenitor bias: compact QGs simply reflect the smaller sizes of galaxies at their earlier quenching epoch, with stellar density most likely having nothing directly to do with cessation of star formation.
3

Geo-Visualization Tools for Participatory Urban Planning - The Case of Tripoli, Lebanon

El Nabbout, Khaled 08 June 2007 (has links) (PDF)
Geo-data visualization has always been an important tool in the urban planning process. Recent trends in geo-information technology are, however, offering additional opportunities for the development of new visualization tools. In parallel, developments have also taken place in the field of urban planning, which has evolved from the rational planning model towards a more strategic planning process with a greater emphasis on collaboration and inclusiveness. This study investigates how an innovative geo-data visualisation tool can be used to develop more inclusive and participatory planning processes, and it tests this approach by means of a case study in Tripoli, Lebanon. The study compared two geo-data visualization techniques regarding their potential for an increased involvement of different types of stakeholders in the urban planning processes: The first technique employed coloured printed transparency maps of the present land-use and the 2000-2020 Master Plan, both geo-referenced to a mosaic of QuickBird satellite imagery used to assist the participant’s orientation. The second technique was the Lenticular Foil Display (LFD) using the so-called flip effect, also based on the geo-coding of the same three “layers”. By tilting this product the observer was easily able to interpret the changes between present and planned state. The LFD technology is particularly useful for true-3D (auto-stereoscopic) viewing. Statistical evaluations of questionnaires concerning sociological and perception-scientific aspects revealed interesting details regarding the role of the new visualization method in the participatory city planning process. The result of the interviews revealed that all stakeholders were readily able to participate in the planning process and to contribute their ideas by sketch-map drawing and writing, using the LFD technology. Regarding the possibilities to stimulate the participation of different stakeholders in the planning process, the LFD was found to be more effective than the conventional approach using transparencies overlaid over orthophotos. Non-experts, in particular, preferred the LFD technology to the transparent overlays which were, however, the preferred approach for the professionals and experts familiar with Master Plan map-reading. One conclusion of the present study is that an efficient participatory urban-planning process should explicitly consider the level of map-reading skills of the stakeholders. Geo-data visualization products like the Multi-Flip-LFDs and other innovative approaches offer possibilities to improve stakeholder participation. The monograph closes by making concrete suggestions for further research into the development and optimization of LFDs.
4

Kinematics and stellar populations of galaxies in the local universe / Cinemática e populações estelares de galáxias no universo local

Barbosa, Carlos Eduardo 26 September 2016 (has links)
Galaxies are the major building blocks of the universe, but we are still learning about fundamental aspects of their formation. In particular, we would like to understand how galaxies acquire their stars, and where and when these stars were born. In this thesis, we investigate these questions by the study of the dynamical and chemical abundances of galaxies in the local universe. Extending previous works in the field, we have developed a Bayesian framework to obtain luminosity-weighted ages, metallicities and alpha-element abundances. In our initial study, we have surveyed six galaxy groups to understand how this particular environment may be related to morphological transformations. We have obtained a sample of 59 group members with a wide range of dynamical masses, which have been used to demonstrate that the mass-metallicity relation extends to low-mass galaxies. We then proceeded to the study of NGC 3311, a cD galaxy at the center of the Hydra I cluster. We have confirmed previous observations of the velocity dispersion profile of the system, which indicates the presence of a large photometric substructure which illustrates the ongoing accretion of the diffuse stellar halo. We performed a study of the stellar populations of the system, which indicated that stars in the diffuse stellar halo have been accreted from past merger events of large elliptical galaxies, whereas the central region of the galaxy is most probably the remnant of a rapid dissipative collapse. Moreover, the metallicity of the stars in the photometric substructure suggest an ongoing disruption of dwarf galaxies possibly related to the presence of an infalling group. These results are consistent with the two-phase model for the mass assembly of galaxies, in which massive ellipticals are formed by dissipative processes at high-redshifts, but continue to build-up their halos by the continuous accretion of satellite systems. / Galáxias são os principais blocos de construção do universo, mas ainda estamos aprendendo sobre aspectos fundamentais da sua formação. Em particular, gostaríamos de entender como as galáxias adquirem suas estrelas, e onde e quando essas estrelas nasceram. Nesta tese, investigamos estas questões pelo estudo da dinâmica e das abundâncias químicas de galáxias no universo local. Estendendo trabalhos anteriores na área, desenvolvemos um método Bayesiano para a obtenção de idades, metalicidades e abundância de elementos alfa ponderados pela luminosidade. Em nosso estudo inicial, pesquisamos seis grupos de galáxias para compreender como esse ambiente em particular pode estar relacionado às transformações morfológicas. Obtivemos uma amostra de 59 membros de grupos com uma vasta gama de massas dinâmicas, que foram utilizados para demonstrar que a relação massa-metalicidade se estende para galáxias de baixa massa. Então, procedemos ao estudo de NGC 3311, uma galáxia cD no centro do aglomerado Hydra I. Confirmamos as observações anteriores do perfil de dispersão da velocidades do sistema, que indicam a presença de uma grande subestrutura fotométrica que ilustra a acreção atual de estrelas no halo estelar difuso. Foi realizado um estudo das populações estelares do sistema, que indica que as estrelas no halo estelar difuso foram obtidas em eventos passados de fusão de grandes galáxias elípticas, enquanto que a região central da galáxia é provavelmente o remanescente de uma rápido colapso dissipativo. Além disso, a metalicidade das estrelas na subestrutura fotométrica sugere a ruptura atual de galáxias anãs relacionadas com a presença de um grupo se movimentando em direção ao centro do aglomerado. Estes resultados são consistentes com o modelo de duas fases para a acumulação da massa de galáxias, no qual galáxias elípticas gigantes são formadas por processos dissipativos em altos redshifts, mas continuam a acrescentar estrelas em seus halos pelo deposição de sistemas satélite.
5

Kinematics and stellar populations of galaxies in the local universe / Cinemática e populações estelares de galáxias no universo local

Carlos Eduardo Barbosa 26 September 2016 (has links)
Galaxies are the major building blocks of the universe, but we are still learning about fundamental aspects of their formation. In particular, we would like to understand how galaxies acquire their stars, and where and when these stars were born. In this thesis, we investigate these questions by the study of the dynamical and chemical abundances of galaxies in the local universe. Extending previous works in the field, we have developed a Bayesian framework to obtain luminosity-weighted ages, metallicities and alpha-element abundances. In our initial study, we have surveyed six galaxy groups to understand how this particular environment may be related to morphological transformations. We have obtained a sample of 59 group members with a wide range of dynamical masses, which have been used to demonstrate that the mass-metallicity relation extends to low-mass galaxies. We then proceeded to the study of NGC 3311, a cD galaxy at the center of the Hydra I cluster. We have confirmed previous observations of the velocity dispersion profile of the system, which indicates the presence of a large photometric substructure which illustrates the ongoing accretion of the diffuse stellar halo. We performed a study of the stellar populations of the system, which indicated that stars in the diffuse stellar halo have been accreted from past merger events of large elliptical galaxies, whereas the central region of the galaxy is most probably the remnant of a rapid dissipative collapse. Moreover, the metallicity of the stars in the photometric substructure suggest an ongoing disruption of dwarf galaxies possibly related to the presence of an infalling group. These results are consistent with the two-phase model for the mass assembly of galaxies, in which massive ellipticals are formed by dissipative processes at high-redshifts, but continue to build-up their halos by the continuous accretion of satellite systems. / Galáxias são os principais blocos de construção do universo, mas ainda estamos aprendendo sobre aspectos fundamentais da sua formação. Em particular, gostaríamos de entender como as galáxias adquirem suas estrelas, e onde e quando essas estrelas nasceram. Nesta tese, investigamos estas questões pelo estudo da dinâmica e das abundâncias químicas de galáxias no universo local. Estendendo trabalhos anteriores na área, desenvolvemos um método Bayesiano para a obtenção de idades, metalicidades e abundância de elementos alfa ponderados pela luminosidade. Em nosso estudo inicial, pesquisamos seis grupos de galáxias para compreender como esse ambiente em particular pode estar relacionado às transformações morfológicas. Obtivemos uma amostra de 59 membros de grupos com uma vasta gama de massas dinâmicas, que foram utilizados para demonstrar que a relação massa-metalicidade se estende para galáxias de baixa massa. Então, procedemos ao estudo de NGC 3311, uma galáxia cD no centro do aglomerado Hydra I. Confirmamos as observações anteriores do perfil de dispersão da velocidades do sistema, que indicam a presença de uma grande subestrutura fotométrica que ilustra a acreção atual de estrelas no halo estelar difuso. Foi realizado um estudo das populações estelares do sistema, que indica que as estrelas no halo estelar difuso foram obtidas em eventos passados de fusão de grandes galáxias elípticas, enquanto que a região central da galáxia é provavelmente o remanescente de uma rápido colapso dissipativo. Além disso, a metalicidade das estrelas na subestrutura fotométrica sugere a ruptura atual de galáxias anãs relacionadas com a presença de um grupo se movimentando em direção ao centro do aglomerado. Estes resultados são consistentes com o modelo de duas fases para a acumulação da massa de galáxias, no qual galáxias elípticas gigantes são formadas por processos dissipativos em altos redshifts, mas continuam a acrescentar estrelas em seus halos pelo deposição de sistemas satélite.
6

Geo-Visualization Tools for Participatory Urban Planning - The Case of Tripoli, Lebanon

El Nabbout, Khaled 18 January 2007 (has links)
Geo-data visualization has always been an important tool in the urban planning process. Recent trends in geo-information technology are, however, offering additional opportunities for the development of new visualization tools. In parallel, developments have also taken place in the field of urban planning, which has evolved from the rational planning model towards a more strategic planning process with a greater emphasis on collaboration and inclusiveness. This study investigates how an innovative geo-data visualisation tool can be used to develop more inclusive and participatory planning processes, and it tests this approach by means of a case study in Tripoli, Lebanon. The study compared two geo-data visualization techniques regarding their potential for an increased involvement of different types of stakeholders in the urban planning processes: The first technique employed coloured printed transparency maps of the present land-use and the 2000-2020 Master Plan, both geo-referenced to a mosaic of QuickBird satellite imagery used to assist the participant’s orientation. The second technique was the Lenticular Foil Display (LFD) using the so-called flip effect, also based on the geo-coding of the same three “layers”. By tilting this product the observer was easily able to interpret the changes between present and planned state. The LFD technology is particularly useful for true-3D (auto-stereoscopic) viewing. Statistical evaluations of questionnaires concerning sociological and perception-scientific aspects revealed interesting details regarding the role of the new visualization method in the participatory city planning process. The result of the interviews revealed that all stakeholders were readily able to participate in the planning process and to contribute their ideas by sketch-map drawing and writing, using the LFD technology. Regarding the possibilities to stimulate the participation of different stakeholders in the planning process, the LFD was found to be more effective than the conventional approach using transparencies overlaid over orthophotos. Non-experts, in particular, preferred the LFD technology to the transparent overlays which were, however, the preferred approach for the professionals and experts familiar with Master Plan map-reading. One conclusion of the present study is that an efficient participatory urban-planning process should explicitly consider the level of map-reading skills of the stakeholders. Geo-data visualization products like the Multi-Flip-LFDs and other innovative approaches offer possibilities to improve stakeholder participation. The monograph closes by making concrete suggestions for further research into the development and optimization of LFDs.
7

Probing the cool interstellar and circumgalactic gas of three massive lensing galaxies at z = 0.4–0.7

Zahedy, Fakhri S., Chen, Hsiao-Wen, Rauch, Michael, Wilson, Michelle L., Zabludoff, Ann 21 May 2016 (has links)
We present multisightline absorption spectroscopy of cool gas around three lensing galaxies at z = 0.4-0.7. These lenses have half-light radii r(e) = 2.6-8 kpc and stellar masses of log M-*/M-circle dot = 10.9-11.4, and therefore resemble nearby passive elliptical galaxies. The lensed QSO sightlines presented here occur at projected distances of d = 3-15 kpc (or d approximate to 1-2 r(e)) from the lensing galaxies, providing for the first time an opportunity to probe both interstellar gas at r similar to r(e) and circumgalactic gas at larger radii r >> r(e) of these distant quiescent galaxies. We observe distinct gas absorption properties among different lenses and among sightlines of individual lenses. Specifically, while the quadruple lens for HE 0435-1223 shows no absorption features to very sensitive limits along all four sightlines, strong MgII, Fe II, Mg I, and Ca II absorption transitions are detected along both sightlines near the double lens for HE 0047-1756, and in one of the two sightlines near the double lens for HE 1104-1805. The absorbers are resolved into 8-15 individual components with a line-of-sight velocity spread of Delta v approximate to 300-600 km s(-1). The large ionic column densities, log N greater than or similar to 14, observed in two components suggest that these may be Lyman limit or damped Ly a absorbers with a significant neutral hydrogen fraction. The majority of the absorbing components exhibit a uniform supersolar Fe/Mg ratio with a scatter of < 0.1 dex across the full Delta v range. Given a predominantly old stellar population in these lensing galaxies, we argue that the observed large velocity width and Fe-rich abundance pattern can be explained by SNe Ia enriched gas at radius r similar to r(e). We show that additional spatial constraints in line-of-sight velocity and relative abundance ratios afforded by a multisightline approach provide a powerful tool to resolve the origin of chemically enriched cool gas in massive haloes.
8

The fundamental plane of EDisCS galaxies (Corrigendum)

Saglia, R. P., Sánchez-Blázquez, P., Bender, R., Simard, L., Desai, V., Aragón-Salamanca, A., Milvang-Jensen, B., Halliday, C., Jablonka, P., Noll, S., Poggianti, B., Clowe, D. I., De Lucia, G., Pelló, R., Rudnick, G., Valentinuzzi, T., White, S. D. M., Zaritsky, D. 19 December 2016 (has links)
We discovered a mistake in Eqs. (7) and (10) of Saglia et al. (2010, A&A, 524, A6), which propagates to Tables 8 and 9 and Fig. 25. We revise the tables, the figure and the affected statements in the paper. As a result, the reduction in the luminosity evolution due to the effects of the size and velocity dispersion evolution is smaller than claimed in Saglia et al. (2010).
9

The Star Formation Histories of Red-Sequence Galaxies

Allanson, Steven January 2009 (has links)
This thesis addresses the challenge of understanding the typical star formation histories of red sequence galaxies, using linestrength indices, mass-to-light ratios and redshift evolution as complementary constraints on their stellar age distribution. We first construct simple parametric models of the star formation history that bracket a range of scenarios, and fit these models to the linestrength indices of low-redshift cluster red-sequence galaxies. For giant galaxies, we con firm the downsizing trend, i.e. the stellar populations are younger, on average, for lower σ galaxies. We find, however, that this trend flattens or reverses at σ < 70km/s. We then compare predicted stellar mass-to-light ratios with dynamical mass-to-light ratios derived from the Fundamental Plane, or by the SAURON group. For galaxies with σ ~ 70 km/s, models with a late 'frosting' of young stars and models with exponential star formation histories have stellar mass-to-light ratios that are larger than observed dynamical mass-to-light ratios by factors of 1.7 and 1.4, respectively, and so are rejected. The single stellar population (SSP) model is consistent with the Fundamental Plane, and requires a modest amount of dark matter (between 20% to 30%) to account for the difference between stellar and dynamical mass-to-light ratios. A model in which star formation was 'quenched' at intermediate ages is also consistent with the observations, although in this case less dark matter is required for low mass galaxies. We also find that the contribution of stellar populations to the 'tilt' of the Fundamental Plane is highly dependent on the assumed star-formation history: for the SSP model, the tilt of the FP is driven primarily by stellar-population effects. For a quenched model, two-thirds of the tilt is due to stellar populations and only one third is due to dark matter or non-homology. Comparing to high redshift cluster data, we find again the SSP and quenched models, as well as a model where strangulation begins at intermediate ages after a period of constant star formation, are preferred. They predict the recent faint-end build up of the red sequence, along with observed dwarf-to-giant ratios. Only the SSP model appears to predict the observed M/L evolution, but only if selection effects are carefully modeled.
10

The Star Formation Histories of Red-Sequence Galaxies

Allanson, Steven January 2009 (has links)
This thesis addresses the challenge of understanding the typical star formation histories of red sequence galaxies, using linestrength indices, mass-to-light ratios and redshift evolution as complementary constraints on their stellar age distribution. We first construct simple parametric models of the star formation history that bracket a range of scenarios, and fit these models to the linestrength indices of low-redshift cluster red-sequence galaxies. For giant galaxies, we con firm the downsizing trend, i.e. the stellar populations are younger, on average, for lower σ galaxies. We find, however, that this trend flattens or reverses at σ < 70km/s. We then compare predicted stellar mass-to-light ratios with dynamical mass-to-light ratios derived from the Fundamental Plane, or by the SAURON group. For galaxies with σ ~ 70 km/s, models with a late 'frosting' of young stars and models with exponential star formation histories have stellar mass-to-light ratios that are larger than observed dynamical mass-to-light ratios by factors of 1.7 and 1.4, respectively, and so are rejected. The single stellar population (SSP) model is consistent with the Fundamental Plane, and requires a modest amount of dark matter (between 20% to 30%) to account for the difference between stellar and dynamical mass-to-light ratios. A model in which star formation was 'quenched' at intermediate ages is also consistent with the observations, although in this case less dark matter is required for low mass galaxies. We also find that the contribution of stellar populations to the 'tilt' of the Fundamental Plane is highly dependent on the assumed star-formation history: for the SSP model, the tilt of the FP is driven primarily by stellar-population effects. For a quenched model, two-thirds of the tilt is due to stellar populations and only one third is due to dark matter or non-homology. Comparing to high redshift cluster data, we find again the SSP and quenched models, as well as a model where strangulation begins at intermediate ages after a period of constant star formation, are preferred. They predict the recent faint-end build up of the red sequence, along with observed dwarf-to-giant ratios. Only the SSP model appears to predict the observed M/L evolution, but only if selection effects are carefully modeled.

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