101 resultados para Buchanan Alumni House
em Deakin Research Online - Australia
Resumo:
The immunocompetence handicap hypothesis (ICHH) suggests that dominance signals are costly because their development is controlled by testosterone, which is immunosuppressive. Signal control therefore links an increased disease risk with a high quality signal. The chest bib of the house sparrow, Passer domesticus, is a signal known to be related to dominance and under control of testosterone levels. We experimentally manipulated testosterone in male sparrows during the breeding season and again independently during the post-breeding period to test whether variation in levels of testosterone could cause variation in levels of immunocompetence. There was no effect of testosterone manipulation on the cell-mediated response of birds to phytohaemagglutinin injection, nor did testosterone levels appear to affect either white blood cell ratios or red blood cell counts. In contrast, both breeding season and post-breeding season testosterone levels had significant effects upon the humoral response of the birds to sheep red blood cell injections. However, whilst testosterone during the breeding season appeared to act immunosuppressively, the role of post-breeding levels is less clear. In concordance with a previous study, there was an indication that corticosterone is involved in mediating the immunosuppressive effects of testosterone. The strength of the secondary humoral response and the cell-mediated response were negatively related suggesting the possibility of a trade-off between the different arms of the immune system. These results provide some support for the ICHH as a mechanism promoting the evolution of costly badges of status, although the results question whether the immunosuppressive cost can be mediated by testosterone at the time of badge development.
Resumo:
Badges of status function in many birds within a social context to establish dominance hierarchies and reduce antagonistic encounters. In order to maintain the honesty of the signalling system, such badges must be costly to produce or to maintain. The chest bib of the house sparrow functions as a badge of status and changes in size are known to be controlled by testosterone levels. We sought to test the relative importance of testosterone as opposed to bib size in determining dominance within a group of male house sparrows. We did this by manipulating testosterone levels independently during both breeding and post-breeding seasons in experimental birds and examining the effect of testosterone titre, as well as corticosterone titre relative to bib size on dominance levels. Dominance hierarchies within the groups were tested during both the breeding and post-breeding phases. We compared the results of these tests with dominance among intact (unmanipulated) birds. Results suggested that the breeding season dominance levels were largely determined by testosterone levels as well as bib size, whereas the post-breeding dominance levels were determined by postbreeding testosterone titre and previous breeding season dominance level. Within unmanipulated birds, basal corticosterone levels were significantly, negatively correlated with dominance level, but only during the breeding season. The influence of breeding season dominance on post-breeding dominance suggests social history is important in determining dominance interactions as well as current testosterone levels and bib size.
Resumo:
Secondary sexual signals are thought to indicate individual quality. In order to understand the evolutionary pressures that give rise to such traits it is important to understand the physiological mechanisms underlying their production. The black bib of the house sparrow Passer domesticus is known to function as a badge of social status in males. Past studies have found that the size of the bib in older males is determined, at least partly, by the androgen testosterone. The immunocompetence handicap hypothesis suggests that testosterone has a key role in maintaining honest signalling – it is both involved in the development or expression of sexual signals and is immunosuppressive. In this paper we test experimentally two hypo theses relating to bib size development, whether 1) testosterone is only immunosuppressive in conditions where the natural feedback loop from the testes has been removed, and 2) testosterone is, in addition to influencing the bib size of older males, responsible for the size of the bib in juvenile sparrows. In the first experiment we found that exogenous testosterone administered to intact males during the winter (when LH and FSH levels are very low and were not artificially increased by castration) caused significant immunosuppression, albeit in interaction with the stress hormone corticosterone. Second, we found that exogenous testosterone administration in castrated fledgling male house sparrows had no effect on subsequent post-juvenile moult bib size relative to controls. Our results suggest that in some circumstances testosterone can be immunosuppressive, but that its role in bib size determination is age-dependent.
Resumo:
Non-invasive techniques for measuring glucocorticoids (GCs) have become more prevalent, due to the advantage of eliminating the effects of animal disturbance on GC levels and their potential to provide an integrated, historic estimate of circulating GC levels. In the case of birds, corticosterone (CORT) is deposited in feathers, and may reflect a bird's GC status over the period of feather synthesis. This technique thus permits a retrospective view of the average circulating GC levels during the moult period. While it is generally assumed that differences in feather CORT content (CORTf) between individuals reflects their different stress histories during either natural or induced moult, it is not clear how much of this variation is due to extrinsic versus intrinsic factors. We examined this question by determining CORTf in free-living house sparrows (Passer domesticus) from two populations, one urban and the other rural, that were plucked before and after exposure to different plasma CORT levels while held captive. We experimentally manipulated plasma CORT by implanting birds with either a corticosterone-filled, metyrapone-filled, or empty ('sham') silastic capsule as replacement feathers first emerged. The pattern of post-treatment CORTf was consistent with our expectations, based on plasma CORT levels of an experimentally implanted reference group. However, there was no statistically significant difference in CORTf between these treatment groups unless sex, population origin, and CORTf of original feathers for each individual were included in a model. Thus, birds with higher CORTf in feathers removed for this experiment tended to have higher CORTf in post-treatment replacement feathers, irrespective of treatment. In addition, we found that feather fault bar scores were significantly higher in CORT-treated birds than in the other two treatment groups, but did not vary directly with CORTf level. Our study therefore broadly confirms the use of feathers as a non-invasive tool to estimate plasma CORT during moult in birds, but importantly demonstrates the potential for intrinsic differences in stress characteristics between populations and individuals to obscure the effects extrinsic stressors might have on CORTf .
Resumo:
The history of history's institutions can offer a gritty context in which to understand historical production. A wide spectrum of influences, from the personal to the intellectual to the political, can be seen at work in shaping the history made and communicated at Blundell's Cottage over the years. Even though it has always been a humble participant in the project of history, its products probably reach some of history's larger audiences. Hence it is worthwhile to review fifty years of historio-museography.
Resumo:
Based on an analysis of a corpus of forty of Sir Edwin Lutyens's country house designs (Rollo 1997) a procedure for developing Parallel Descriptions will be discussed. This procedure will attempt to facilitate an integrated approach to the analysis of complex architectural forms and will provide a framework for investigating the development of parallel grammars. This is an approach which acknowledges that design does not necessarily involve the importance of one aspect, but rather a number of coextensive issues with emphasis on the ordering and priority of these issues periodically shifting.
Resumo:
Ackerman begins his book "The Villa" (1995) with these words: 'A villa is a building in the country designed for its owner's enjoyment and relaxation .... [it] accommodates a fantasy which is impervious to reality.' He concludes: , ... the country, in exacting confrontations with the immanent brute forces and sensuous enchantments of nature, prompts inspired responses.' Blairgowrie House - the villa in the landscape - was built in the 1870s and the 'Portsea Palace' - a personal club med resort - in the late 1990s. The notion of an inspired response and the concept of dwelling poetically are manifestly absent in the Portsea Palace. Why?
This paper explores architecture and landscape - particularly 'domestic' architecture and coastal landscapes in Victoria's Nepean Peninsula. It looks closely at what architects mean when they say their design reflects place, relates to site, is climate specific, is close to nature, responds to the landscape, and/or is sensitive to the environment. Exemplars from different centuries are examined in their philosophical contexts and frames of reference. The complexities of the notion of place and identity, belonging, and dwelling (in the Heideggerian sense) are examined to identify the shift that has occurred over time as science and technology have ostensibly freed 'modern man' from 'a direct dependence on places' (Norberg Schultz). The alienation and loss that has eventuated - for humans and for the environment - will be critically analysed and assessed.
Resumo:
This study analyses the dynamic causality of four macroeconomic variables on house prices. The four macroeconomic variables have interrelationships with house prices in certain lagged terms, but these relationships are not always the same as the notions put forward in prior research. The relationships are detected to be unstable in the three observation periods. The instability of these relationships would cause difficulty in predicting house prices in the market, especially for policy makers and market participants.
Resumo:
In this article I will establish an underpinning theory to apply in measuring demand for a new arts center (theater, museum, gallery, multipurpose space, tourism destination, or cultural precinct). The new theory is called "Full House Theory"-so called because it aims to provide an equation among the factors that result in maximum occupancy and use of an arts center or cultural facility. Existing theories used in the retail sector offer a distance-and-time analysis of expected customer demand but do not include differentiated product-demand analysis. Cultural planning literature examines community need in relation to cultural development but fails to provide a formula to predict sustainable demand. In addition, I will analyze the theories and methodologies in current use as well as their weaknesses in assessing cultural facility demand.