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(2007) Wright, Christopher; Burton, Michael; Van Dishoeck, Ewine; van Langevelde, Huib-Jan; Wilner, David; Hughes, Annie; Lommen, Dave; Maddison, Sarah; Jorgensen, Jes; Bourke, TylerJournal ArticleContext. Low-mass stars form with disks in which the coagulation of grains may eventually lead to the formation of planets. It is not known when and where grain growth occurs, as models that explain the observations are often degenerate. A way to break this degeneracy is to resolve the sources under study. Aims. Our aim is to find evidence for the existence of grains of millimetre sizes in disks around T Tauri stars, implying grain growth. Methods. The Australia Telescope Compact Array (ATCA) was used to observe 15 southern T Tauri stars, five in the constellation Lupus and ten in Chamaeleon, at 3.3 mm. The five Lupus sources were also observed with the SubMillimeter Array (SMA) at 1.4 mm. Our new data are complemented with data from the literature to determine the slopes of the spectral energy distributions in the millimetre regime. Results. Ten sources were detected at better than 3 sigma with the ATCA, with sigma approximate to 1-2 mJy, and all sources that were observed with the SMA were detected at better than 15 sigma, with sigma approximate to 4 mJy. Six of the sources in our sample are resolved to physical radii of similar to 100 AU. Assuming that the emission from such large disks is predominantly optically thin, the millimetre slope can be related directly to the opacity index. For the other sources, the opacity indices are lower limits. Four out of six resolved sources have opacity indices <= 1, indicating grain growth to millimetre sizes and larger. The masses of the disks range from < 0.01 to 0.08 M-circle dot, which is comparable to the minimum mass solar nebula. A tentative correlation is found between the millimetre slope and the strength and shape of the 10-mu m silicate feature, indicating that grain growth occurs on similar (short) timescales in both the inner and outer disk.
(2006) Maercker, M; Burton, Michael; Wright, ChristopherJournal ArticleContext. We present a JHK(s)L survey of the massive star forming region RCW 57 (NGC 3576) based on L-band data at 3.5 mu m taken with SPIREX ( South Pole Infrared Explorer), and 2MASS JHK(s) data at 1.25-2.2 mu m. This is the second of two papers, the first one concerning a similar JHK(s)L survey of 30 Doradus. Aims. Colour-colour and colour-magnitude diagrams are used to detect sources with infrared excess. This excess emission is interpreted as coming from circumstellar disks, and hence gives the cluster disk fraction (CDF). Based on the CDF and the age of RCW 57, it is possible to draw conclusions on the formation and early evolution of massive stars. Methods. The infrared excess is detected by comparing the locations of sources in JHKsL colour-colour and L vs. (K-s - L) colour - magnitude diagrams to the reddening band due to interstellar extinction. Results. A total of 251 sources were detected. More than 50% of the 209 sources included in the diagrams have an infrared excess. Conclusions. Comparison with other JHKsL surveys, including the results on 30 Doradus from the first paper, support a very high initial disk fraction (> 80%) even for massive stars, although there is an indication of a possible faster evolution of circumstellar disks around high mass stars. 33 sources only found in the L-band indicate the presence of heavily embedded, massive Class I protostars. We also report the detection of diffuse PAHs emission throughout the RCW 57 region.
(2022) Ayshan, HanThesisVideo game trailers are an effective promotional form of intermediation that enables audiences to navigate and engage with old and new media. Although video game trailers function as advertisements designed to sell a game, they are also stories that provoke social media commentary and debate. Trailers aim to draw the viewer in, convey sound and imagery, and evoke an involuntary reaction of excitement and awe. In this thesis, I will be using the games Fallout 4, Watch Dogs 2, and Assassin’s Creed: Syndicate. In the case studies, I investigate how viewers make sense of the promotional and storytelling aspects of video game trailers. I examine how video game trailers have the potential to arouse emotions and interest before viewers even play the game. Trailers provide an insight into the basic gameplay, not only into the gameplay but also into the story and the characters (protagonists and antagonists). They show audiences the video game theme genre and provide the viewer with a visual and auditory tool to entice possession. This project explores these themes, showing how video game trailers have an inherited cinematic quality but also how trailers actually spend little time presenting actual gameplay. There is a clear connection with movie trailers, teasing the events that will take place in the game and asking the player what will happen next. In this study, I used the methods of narrative analysis and textual analysis to analyse comments from YouTube, Facebook, and a survey of video gamers. The textual analysis of the trailers raises questions of representation and authenticity. In this research, I identified an incongruity between the representation of the core features of a game and the promotion of those features in the trailer. The narrative analysis of the trailers focused on storytelling and emplotment in the trailers. A key theme that has emerged from the analysis is that superheroes engage in vigilantism, a justifiable form of self-administered violence. Gamers may feel at ease with the violence used to correct perceived injustices. There is potential for gamers to consider the moral grey area of vigilante violence and romanticised vigilantism. With their enhanced ability to simulate complex interactive narratives for actual and simulated authenticity, video games offer a sophisticated engagement with players that contributes significantly to their widespread and universal support. The role of culturally created characters in the experience of playing a video game helps stimulate philosophical research. I explore whether normative audience expectations can speed up the development of cultural expectations about the relationship between the player and the narrative of the game and its audience. In this context, I examine case study video game trailers and ask what it means to revise our understanding of the relationship between power, law, and morality while playing the game. I examine and critique how the narrative, and thus the mechanics of a specific game, shapes our understanding of connection, power, law, or morality; I contend that prestige reflects normative privilege and law.
(2021) Mijangos Araujo, LuisThesisGenetic differentiation is a vital aspect of population genetics and is a direct consequence of evolutionary forces acting on genetic diversity. By interpreting patterns of genetic differentiation, we can detect, infer and estimate the extent to which natural selection, genetic drift and gene flow affect genetic diversity. In this thesis, estimation of genetic differentiation is used as a tool to answer the following questions, three mainly theoretical, and the other an applied study on platypus conservation. 1. Can a form of linked selection termed associative overdominance (AOD) explain lower levels of genetic differentiation between populations (FST), and higher heterozygosity, than expected under neutrality in experimental populations (Drosophila melanogaster) and in a feral population (Bos taurus)? 2. Under which circumstances does AOD affect FST and heterozygosity? 3. Can AOD be detected in natural populations? 4. Do dams restrict gene flow among platypus groups? AOD is triggered by the occurrence of recessive deleterious mutations that are physically linked and form haplotypes when recombination events are scarce, as in small populations. When haplotypes within an individual contain recessive deleterious mutations at different positions, a heterozygote for two different haplotypes is fitter than either one of the homozygotes. As a result, heterozygosity is higher, and FST lower than expected under neutrality. Here, using feral, experimental and computer- simulated populations, it is demonstrated how AOD might be prevalent in small populations, and a framework for predicting and detecting AOD is provided. The extent to which dams disrupt gene flow among platypus populations is investigated by using four rivers regulated by dams and three unregulated rivers. It was found that: genetic differentiation is significantly correlated with the number of generations since the dams were built; populations and individuals separated by dams are genetically more different than otherwise; and areas of high genetic differentiation coincide with the location of dams. It is suggested that dams jeopardise the long-term viability of platypus populations.
The effect of broadband noise on dynamic decision-making and the moderators that influence this effect(2023) Zhou, HangThesisNoise and workload are both stressors. Stressors are known to affect cognitive performance. While the effect of workload on cognition is widely known, the effect of noise is less understood. Broadband noise at moderate levels (<85 dBA) is typical in many workplaces. Dynamic decision-making (DDM), a complex cognitive task, is required in many workplace settings where moderate broadband noise is present. Understanding how stressors such as noise affect DDM is essential, especially in safety critical professions such as aviation and emergency response. Therefore, the aim of the present research was to understand the effect of moderate broadband noise on DDM and the moderators that can influence the extent of that effect. Study 1, the first of the three studies, was a systematic review for the effect of moderate broadband noise on cognition such as reaction time, attention, short-term memory, long-term memory and high(er)-order cognitive tasks such as DDM. The findings showed that no previous studies investigated the effect of moderate broadband noise on DDM. Study 2, the first of two empirical studies examined the link between noise at 75 dBA, sex, workload, and session on DDM (performance and learning). Study 3 introduced the moderator of financial incentive and additional instructions. The results indicated females’ performance in DDM was affected by noise at low workload, but not high workload. Males were overall unaffected by noise regardless of the workload level. In terms of learning, noise initially impaired females’ performance, however this was overcome in Day 2. The added instruction had the same positive effect on learning performance, as it neutralised the noise effect. Monetary incentives did not moderate the noise stressor. These results highlight the detrimental effect of the stressor noise on DDM, and how its effect on sex can be offset by clear training instructions. The effect of noise can be beneficial to performance in the presence of another stressor, such as high workload, which is supported by theories such as Arousal Theory and Maximal Adaptability Theory. From applied perspective, this finding implies that noise can be a tool to facilitate performance in high workload.