Macquarie University

About: Macquarie University is a education organization based out in Sydney, New South Wales, Australia. It is known for research contribution in the topics: Population & Context (language use). The organization has 14075 authors who have published 47673 publications receiving 1416184 citations. The organization is also known as: Macquarie uni.

Late Paleozoic glacial episodes in Gondwanaland reflected in transgressive-regressive depositional sequences in Euramerica

Abstract: The Late Paleozoic glaciation of Gondwanaland comprised two short episodes, in the Famennian (I) and Visean (II) confined to Brazil and adjacent northwest Africa, and a long episode that started in the Namurian (IIIA) of eastern Australia and Bolivia/Argentina, expanded to cover much of Gondwanaland in the Stephanian/Asselian (IIIB), and collapsed in the early Sakmarian (IIIC). Dropstones in eastern Australia indicate that small ice centers lingered to the Kazanian. Across the belt of low latitudes north of Gondwanaland, short-ranging fossils in widespread shallow-marine and paralic deposits indicate synchronous deposition of transgressive-regressive sequences in different parts of Euramerica. These sequences correlate with glacial events in Gondwanaland at three levels: (a) four major regressions in Euramerica, in the Famennian (1), Visean (2), Namurian (3), Stephanian (4), and the Tastubian transgression that preceded the Sterlitamakian regression (5), also recorded in Gondwanaland, correlate with glacial episodes I, II, and IIIA, IIIB, and IIIC; (b) the time-interval of cyclothemic deposition in Euramerica (Brigantian or latest Visean to Sterlitamakian) correlates with that of glacial episode III; and (c) the dominant period of the Euramerican cyclothems, as estimated from the Middle and Late Pennsylvanian deposits of the mid-continent of North America, and of the thickest known Gondwanaland glacigenic sediment (the earliest Permian Lyons Group of Western Australia) is 0.4 Ma, equivalent in turn to the long orbital-eccentricity period of the Quaternary ice age, and the dominant period of fluctuation of the late Miocene Antarctic ice cap. The three levels of correlations confirm Wanless and Shepard9s (1936) hypothesis that the Late Paleozoic cyclothems are controlled largely by sea-level fluctuations related to the Gondwanaland glaciation.

Global patterns in plant height

Abstract: Summary 1. Plant height is a central part of plant ecological strategy. It is strongly correlated with life span, seed mass and time to maturity, and is a major determinant of a species’ ability to compete for light. Plant height is also related to critical ecosystem variables such as animal diversity and carbon storage capacity. However, remarkably little is known about global patterns in plant height. Here, we use maximum height data for 7084 plant Species · Site combinations to provide the first global, cross-species quantification of the latitudinal gradient in plant height. 2. The mean maximum height of species growing within 15� of the equator (7.8 m) was 29 times greater than the height of species between 60� and 75� N (27 cm), and 31 times greater than the height of species between 45� and 60� S (25 cm). There was no evidence that the latitudinal gradient in plant height was different in the northern hemisphere than in the southern hemisphere (P = 0.29). A 2.4-fold drop in plant height at the edge of the tropics (P = 0.006) supports the idea that there might be a switch in plant strategy between temperate and tropical zones. 3. We investigated 22 environmental variables to determine which factors underlie the latitudinal gradient in plant height. We found that species with a wide range of height strategies were present in cold, dry, low productivity systems, but there was a noticeable lack of very short species in wetter, warmer, more productive sites. Variables that capture information about growing conditions during the harsh times of the year were relatively poor predictors of height. The best model for global patterns in plant height included only one term: precipitation in the wettest month (R 2 =0 .256). 4. Synthesis. We found a remarkably steep relationship between latitude and height, indicating a major difference in plant strategy between high and low latitude systems. We also provide new, surprising information about the correlations between plant height and environmental variables.

Knowing what to think by knowing who you are: self-categorization and the nature of norm formation, conformity and group polarization.

Abstract: We contrast two theoretical approaches to social influence, one stressing interpersonal dependence, conceptualized as normative and informational influence (Deutsch & Gerard, 1955), and the other stressing group membership, conceptualized as self-categorization and referent informational influence (Turner, Hogg, Oakes, Reicher & Wetherell, 1987). We argue that both social comparisons to reduce uncertainty and the existence of normative pressure to comply depend on perceiving the source of influence as belonging to one's own category. This study tested these two approaches using three influence paradigms. First we demonstrate that, in Sherif's (1936) autokinetic effect paradigm, the impact of confederates on the formation of a norm decreases as their membership of a different category is made more salient to subjects. Second, in the Asch (1956) conformity paradigm, surveillance effectively exerts normative pressure if done by an in-group but not by an out-group. In-group influence decreases and out-group influence increases when subjects respond privately. Self-report data indicate that in-group confederates create more subjective uncertainty than out-group confederates and public responding seems to increase cohesiveness with in-group — but decrease it with out-group — sources of influence. In our third experiment we use the group polarization paradigm (e.g. Burnstein & Vinokur, 1973) to demonstrate that, when categorical differences between two subgroups within a discussion group are made salient, convergence of opinion between the subgroups is inhibited. Taken together the experiments show that self-categorization can be a crucial determining factor in social influence.