Carleton University

About: Carleton University is a education organization based out in Ottawa, Ontario, Canada. It is known for research contribution in the topics: Population & Context (language use). The organization has 15852 authors who have published 39650 publications receiving 1106610 citations.

Biochemical adaption for freezing tolerance in the wood frog, Rana sylvatica

Abstract: 1. The wood frog,Rana sylvatica, can survice extracellular freezing during overwintering. Under laboratory conditions freezing occurred at about −2°C and animals survived several days at −6°C. 2. Frogs accumulated glucose as a cryoprotectant; glycerol, sorbitol and other sugars were not produced. Average levels of glucose in frozen antimals were 185±40 μmol/ml in blood and 387.8±44.8, 198.3±27.3, 120.8±14.1 and 26.5±2.7 μmol/g wet weight in liver, heart, kidney and leg muscle, respectively. 3. Two methods of cold acclimation, 11 weeks at 3°C or a 1°C per day decrease in temperature from 23°C to 0°C, failed to stimulate an anticipatory rise in glucose levels. Only direct exposure to subzero temperature between 0°C and −2°C stimulated synthesis. 4. Glucose synthesis appeared to be confined to liver with glucose distributed through the blood to other tissues. Freezing exposure resulted in a decrease in liver glycogen content of over 700 μmol/g wet weight while glycogen content of other tissues was not affected. 5. Activities of 17 enzymes in liver and leg muscle were monitored in control and freezing exposed frogs. Freezing exposure increased liver phosphorylase activity by 520% from 3 to 18.6 units/g wet weight and increased phosphorylasea content from 37 to 80%. Freezing also elevated glucose-6-phosphatase activity by 140%. Activities of most other enzymes in liver increased by 30–90% with freezing exposure. Activities of phosphorylase and glucose-6-phosphatase increased in leg muscle with freezing exposure although phosphorylasea content remained at 35%. 6. Freezing exposure resulted in the accumulation of lactate in all tissues. Both total adenylates and adenylate energy charge decreased in liver during freezing. In leg muscle adenylates were unaffected but creatine phosphate reserves were depleted.

What determines the spatial extent of landscape effects on species

Abstract: Landscape ecologists are often interested in measuring the effects of an environmental variable on a biological response; however, the strength and direction of effect depend on the size of the area within which the environmental variable is measured. Thus a central objective is to identify the optimal spatial extent within which to measure the environmental variable, i.e. the “scale of effect”. Our objectives are (1) to provide a comprehensive summary of the hypotheses concerning what determines the scale of effect, (2) to provide predictions that can be tested in empirical studies, and (3) to show, with a review of the literature, that most of these predictions have so far been inadequately tested. We propose 14 predictions derived from five hypotheses explaining what determines the scale of effect, and review the literature (if any) supporting each prediction. These predictions involve five types of factors: (A) species traits, (B) landscape variables, (C) biological responses (e.g. abundance vs. occurrence), (D) indirect influences, and (E) regional context of the study. We identify methodological issues that hinder estimation of the scale of effect. Of the 14 predictions, only nine have been tested empirically and only five have received some empirical support. Most support is from simulation studies. Empirical evidence usually does not support predictions. The study of the spatial scale at which landscape variables influence biological outcomes is in its infancy. We provide directions for future research by clarifying predictions concerning the determinants of the scale of effect.

The International Organization for Migration and the International Government of Borders

Abstract: Early debates often read globalisation as a powerful tendency destined to make state borders less pertinent. Recent research has challenged this view by suggesting that globalisation and (re)bordering frequently advance hand-in-hand, culminating in a condition that might be described as ‘gated globalism’. But somewhat neglected in this recent wave of research is the role that particular international agencies are playing in shaping the norms and forms that pertain to emergent regimes of border control—what we call the international government of borders. Focusing on the International Organization for Migration (IOM) and its involvement in the promotion of what it calls better ‘border management’, this paper aims to partially redress this oversight. The IOM is interesting because it illustrates how the control of borders has become constituted as an object of technical expertise and intervention within programmes and schemes of international authority. Two themes are pursued. First, recent work on neoliber...