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.

Optical fiber refractometer using narrowband cladding-mode resonance shifts.

Abstract: Short-period fiber Bragg gratings with weakly tilted grating planes generate multiple strong resonances in transmission. Our experimental results show that the wavelength separation between selected resonances allows the measurement of the refractive index of the medium surrounding the fiber for values between 1.25 and 1.44 with an accuracy approaching 1x10(-4). The sensor element is 10 mm long and made from standard single-mode telecommunication grade optical fiber by ultraviolet light irradiation through a phase mask.

Response of generalist and specialist insect herbivores to landscape spatial structure

Abstract: The purpose of this study was to investigate the effect of changes in landscape pattern on generalist and specialist insects. We did this by comparing the species richness and abundance of generalist and specialist herbivorous insects in alfalfa (Medicago sativa, L.) fields on 26 agricultural landscapes that differed in spatial structure. The insects were from the families Curculionidae (Coleoptera), weevils, and Cicadellidae (Auchennorhyncha), leafhoppers. We hypothesized that: (1) generalist richness and abundance would be highest in landscapes with high diversity (Shannon-Wiener); (2) specialist richness and abundance would be highest in landscapes with (i) high percent cover alfalfa and (ii) low mean inter-patch distance. We tested for these effects after con- trolling for the patch-level effects of field size, field age, frequency of disturbance and vegetation texture. The important findings of the study are: (1) generalist richness and abundance increased with increas- ing landscape diversity and (2) isolation (percent cover alfalfa in the landscape and/or mean inter-patch distance) does not affect specialist insects. These results are significant because they indicate that both generalist and specialist insects may move over much larger distances than previously thought. This is one of the first studies to demonstrate a large scale effect of spatial structure on insects across a broad range of landscapes.

Using anthropogenic contaminants and stable isotopes to assess the feeding ecology of greenland sharks

Abstract: Organochlorine contaminants (OCs) are a large group of ubiquitous pollutants that have potential as tracers of ecological processes. To examine this utility, we measured OCs, stable isotopes of nitrogen (δ15N) and carbon (δ15C), and stomach contents in a large Arctic marine fish, the Greenland shark (Somniosus microcephalus), collected in the Davis Strait region to examine the feeding ecology of this little studied elasmobranch. Stable isotopes and OCs were also measured in the turbot (Reinhardtius hippoglossoides) and stable isotopes in the ringed seal (Phoca hispida) and harp seal (Pagophilus groenlandicus) to put the shark results in context. Values of δ15N suggest that the Greenland shark feeds at a similar trophic level as the turbot and ringed seal (about the fourth trophic level) and at a higher trophic level than harp seals, despite the presence of many turbot and a single ringed seal in the stomach contents of 14 sharks. Values of δ13C indicate that source of carbon in turbot and Greenland shark ...

Ghrelin Promotes and Protects Nigrostriatal Dopamine Function via a UCP2-Dependent Mitochondrial Mechanism

Abstract: Ghrelin targets the hypothalamus to regulate food intake and adiposity. Endogenous ghrelin receptors [growth hormone secretagogue receptor (GHSR)] are also present in extrahypothalamic sites where they promote circuit activity associated with learning and memory, and reward seeking behavior. Here, we show that the substantia nigra pars compacta (SNpc), a brain region where dopamine (DA) cell degeneration leads to Parkinson's disease (PD), expresses GHSR. Ghrelin binds to SNpc cells, electrically activates SNpc DA neurons, increases tyrosine hydroxylase mRNA and increases DA concentration in the dorsal striatum. Exogenous ghrelin administration decreased SNpc DA cell loss and restricted striatal dopamine loss after 1-methyl-4-phenyl-1,2,5,6 tetrahydropyridine (MPTP) treatment. Genetic ablation of ghrelin or the ghrelin receptor (GHSR) increased SNpc DA cell loss and lowered striatal dopamine levels after MPTP treatment, an effect that was reversed by selective reactivation of GHSR in catecholaminergic neurons. Ghrelin-induced neuroprotection was dependent on the mitochondrial redox state via uncoupling protein 2 (UCP2)-dependent alterations in mitochondrial respiration, reactive oxygen species production, and biogenesis. Together, our data reveal that peripheral ghrelin plays an important role in the maintenance and protection of normal nigrostriatal dopamine function by activating UCP2-dependent mitochondrial mechanisms. These studies support ghrelin as a novel therapeutic strategy to combat neurodegeneration, loss of appetite and body weight associated with PD. Finally, we discuss the potential implications of these studies on the link between obesity and neurodegeneration.

When the Smart Grid Meets Energy-Efficient Communications: Green Wireless Cellular Networks Powered by the Smart Grid

Abstract: Recently, there is great interest in considering the energy efficiency aspect of cellular networks. On the other hand, the power grid infrastructure, which provides electricity to cellular networks, is experiencing a significant shift from the traditional electricity grid to the smart grid. When a cellular network is powered by the smart grid, only considering energy efficiency in the cellular network may not be enough. In this paper, we consider not only energy-efficient communications but also the dynamics of the smart grid in designing green wireless cellular networks. Specifically, the dynamic operation of cellular base stations depends on the traffic, real-time electricity price, and the pollutant level associated with electricity generation. Coordinated multipoint (CoMP) is used to ensure acceptable service quality in the cells whose base stations have been shut down. The active base stations decide on which retailers to procure electricity from and how much electricity to procure. We formulate the system as a Stackelberg game, which has two levels: a cellular network level and a smart grid level. Simulation results show that the smart grid has significant impacts on green wireless cellular networks, and our proposed scheme can significantly reduce operational expenditure and CO_2 emissions in green wireless cellular networks.