447 research outputs found
Mass-loss rates from early-type stars
The mass loss rates are derived for a number of unevolved O-type stars and a few WN stars from high dispersion IUE spectra of their P Cygni profiles. When combined with other published mass loss rates, it is found that the relationship between log m and M sub BOL is a broad band rather than a linear relation, suggesting that the line radiation driven wind theory may not be sufficient to explain mass loss. The mass loss rates for the WN stars, while more uncertain, confirm that these stars lose mass about 100 times faster than O-stars
Spectroscopic observations of selected stellar systems
Spectra of very luminous, high temperature stars, the o-type stars with the largest masses among stars, and the Wolf-Rayet (W-R) stars are studied. These stars are characterized by strong stellar winds which produce signiicant mass loss. The nature and evolution of these winds are studied to learn the densities, velocity structue, ionization balance, and composition. The IUE satellite provides the best way to study these phenomena because many of the most important ground state and excited state lines of common highly ionized species are found in the spectral range
B supergiants in open clusters and associations
The final report on project NAG5-78, 'IUE Observations of B Supergiants in the Large Magellanic Cloud', a collaborative effort between Garmany (U. of Colorado), Sonneborn (Goddard Space Flight Center) and Fitzpatrick (Princeton Univ.) is presented. Over 90 B supergiants in the Large Magellanic Cloud with the IUE satellite, using the low dispersion mode were observed. These stars were chosen because they resemble the precursor star to SN 1987a, and a data base in the continuing effort to understand why the precursor star was a blue, not a red supergiant was needed. The observations were all reduced and made into an atlas, and efforts to understand the evolutionary history of stars of the H-R diagram are underway
Hygienisation, gentrification and urban displacement in Brazil
This article engages recent debates over gentrification and urban displacement in the global South. While researchers increasingly suggest that gentrification is becoming widespread in âSouthernâ cities, others argue that such analyses overlook important differences in empirical context and privilege EuroAmerican theoretical frameworks. To respond to this debate, in this article, we outline the concept of higieniza\ue7\ue3o (hygienisation), arguing that it captures important contextual factors missed by gentrification. Hygienisation is a Brazilian term that describes a particular form of urban displacement, and is directly informed by legacies of colonialism, racial and class stigma, informality, and state violence. Our objective is to show how âSouthernâ concepts like hygienisation help urban researchers gain better insight into processes of urban displacement, while also responding to recent calls to decentre and provincialise urban theory
âPost-third-world city' or neoliberal âcity of exception'? Rio de Janeiro in the Olympic era
This article considers processes of urban development within the context of mega-event preparations in Rio de Janeiro. We begin with a brief overview of these development processes, highlighting their connections to political and economic change in recent years. Proponents of these mega-event-led initiatives argue that Rio is undergoing a period of inclusive growth and integration: a perspective we call here a âpost-Third-World city' narrative of urban renewal. Critics, however, contend that urban officials are harnessing mega-events (e.g. the 2014 World Cup and the 2016 Olympic Games) to push forward a neoliberal agenda of socially unjust policies benefiting the interests of capital and marginalizing the city's poor and especially its favelas (i.e. the âcity-of-exception' thesis). In this article we explore the insights of these two perspectives and consider why they have grown popular in recent years. Though we side generally with the city-of-exception thesis, we argue that important geographic and historical particularities must also be accounted for. Without carefully situating analytical perspectives empiricallyâin particular, cases in which theoretical models are drawn from European and North American contextsâurban researchers risk concealing more than they reveal in analyses of rapidly developing countries like Brazil
A "Post-Third World City" or a neoliberal "City of Exception"? Rio de Janeiro in the Olympic era
This article considers processes of urban development within the context of mega-event preparations in Rio de Janeiro. We begin with a brief overview of these development processes, highlighting their connections to political and economic change in recent years. Proponents of these mega-event-led initiatives argue that Rio is undergoing a period of inclusive growth and integration: a perspective we call here a âpost-Third-World cityâ narrative of urban renewal. Critics, however, contend that urban officials are harnessing mega-events (e.g. the 2014 World Cup and the 2016 Olympic Games) to push forward a neoliberal agenda of socially unjust policies benefiting the interests of capital and marginalizing the cityâs poor and especially its favelas (i.e. the âcity-of-exceptionâ thesis). In this article we explore the insights of these two perspectives and consider why they have grown popular in recent years. Though we side generally with the city-of-exception thesis, we argue that important geographic and historical particularities must also be accounted for. Without carefully situating analytical perspectives empiricallyâin particular, cases in which theoretical models are drawn from European and North American contextsâurban researchers risk concealing more than they reveal in analyses of rapidly developing countries like Brazil
The politics of crime and militarised policing in Brazil
This article queries the effects of international police assistance in the Global South, focusing specifically on Brazil. Utilising recently declassified documents accessed in Washington, DC, this article shows how United States officials sought to intervene in Latin American politics through international police assistance to Brazil during the 1960sâ1980s. The article considers the geopolitical motivations behind these programs and highlights the connections between international police assistance, weak democratic institutions in Latin America and legacies of authoritarian policing in the region. The academic objectives are twofold: to foreground debates that emphasise the need for Southern Criminological research perspectives and to explore the broader effects of international police assistance programs in the Global South. By drawing attention to these issues, the article contributes to studies of policing, politics and public security in contexts like Brazil, where extreme levels of everyday violence are a threat to democracy and human rights
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