416 research outputs found

    The Role of Scientific Evidence in Canada\u27s West Coast Energy Conflicts

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    With salience, credibility, and legitimacy as organizing themes, we investigated how opposing communities engaged with scientific information for two contentious proposed energy projects in western Canada, and how their perceptions of science influenced its use in decision-making. The Trans Mountain pipeline expansion, to carry diluted bitumen from northern Alberta’s oil sands to tankers on British Columbia’s (BC) south coast, was expected to adversely impact biodiversity and contribute to climate change. The Bute Inlet hydroelectric project, a large renewable energy project planned for BC’s Central Coast, was anticipated to impact biodiversity but was largely seen as climate-friendly. Based on surveys and interviews with 68 participants who had made one or more personal or professional decisions pertaining to the projects, we discovered that values, cultural cognition, and media effects permeated all aspects of using scientific evidence—from commissioning scientific research to selecting, assessing, and weighing it with other forms of information. As a result, science was developed and used to support positions rather than to inform decisions. We discuss ways to improve the use of science in environmental assessments and other planning and development processes where engaged communities are divided by oppositional positions. We hope this research will lead to community-university partnerships that identify broadly salient, credible, and legitimate sources of information about energy and climate issues, and foster knowledge mobilization across conflict divides

    Composite Fermion Description of Correlated Electrons in Quantum Dots: Low Zeeman Energy Limit

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    We study the applicability of composite fermion theory to electrons in two-dimensional parabolically-confined quantum dots in a strong perpendicular magnetic field in the limit of low Zeeman energy. The non-interacting composite fermion spectrum correctly specifies the primary features of this system. Additional features are relatively small, indicating that the residual interaction between the composite fermions is weak. \footnote{Published in Phys. Rev. B {\bf 52}, 2798 (1995).}Comment: 15 pages, 7 postscript figure

    A Monolayer of Primary Colonic Epithelium Generated on a Scaffold with a Gradient of Stiffness for Drug Transport Studies

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    Animal models are frequently used for in vitro physiologic and drug transport studies of the colon, but there exists significant pressure to improve assay throughput as well as to achieve tighter control of experimental variables than can be achieved with animals. Thus, development of a primary in vitro colonic epithelium cultured as high resistance with transport protein expression and functional behavior similar to that of a native colonic would be of enormous value for pharmaceutical research. A collagen scaffold, in which the degree of collagen cross-linking was present as a gradient, was developed to support the proliferation of primary colonic cells. The gradient of cross-linking created a gradient in stiffness across the scaffold, enabling the scaffold to resist deformation by cells. mRNA expression and quantitative proteomic mass spectrometry of cells growing on these surfaces as a monolayer suggested that the transporters present were similar to those in vivo. Confluent monolayers acted as a barrier to small molecules so that drug transport studies were readily performed. Transport function was evaluated using atenolol (a substrate for passive paracellular transport), propranolol (a substrate for passive transcellular transport), rhodamine 123 (Rh123, a substrate for P-glycoprotein), and riboflavin (a substrate for solute carrier transporters). Atenolol was poorly transported with an apparent permeability (Papp) of < 5 Ă— 10-7 cm s-1, while propranolol demonstrated a Papp of 9.69 Ă— 10-6 cm s-1. Rh123 was transported in a luminal direction (Papp,efflux/Papp,influx = 7) and was blocked by verapamil, a known inhibitor of P-glycoprotein. Riboflavin was transported in a basal direction, and saturation of the transporter was observed at high riboflavin concentrations as occurs in vivo. It is anticipated that this platform of primary colonic epithelium will find utility in drug development and physiological studies, since the tissue possesses high integrity and active transporters and metabolism similar to that in vivo

    Holographic Description of AdS Cosmologies

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    To gain insight in the quantum nature of the big bang, we study the dual field theory description of asymptotically anti-de Sitter solutions of supergravity that have cosmological singularities. The dual theories do not appear to have a stable ground state. One regularization of the theory causes the cosmological singularities in the bulk to turn into giant black holes with scalar hair. We interpret these hairy black holes in the dual field theory and use them to compute a finite temperature effective potential. In our study of the field theory evolution, we find no evidence for a "bounce" from a big crunch to a big bang. Instead, it appears that the big bang is a rare fluctuation from a generic equilibrium quantum gravity state.Comment: 34 pages, 8 figures, v2: minor changes, references adde

    Fluid Models of Many-server Queues with Abandonment

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    We study many-server queues with abandonment in which customers have general service and patience time distributions. The dynamics of the system are modeled using measure- valued processes, to keep track of the residual service and patience times of each customer. Deterministic fluid models are established to provide first-order approximation for this model. The fluid model solution, which is proved to uniquely exists, serves as the fluid limit of the many-server queue, as the number of servers becomes large. Based on the fluid model solution, first-order approximations for various performance quantities are proposed

    On-site Coulomb interaction and the magnetism of (GaMn)N and (GaMn)As

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    We use the local density approximation (LDA) and LDA+U schemes to study the magnetism of (GaMn)As and (GaMn)N for a number of Mn concentrations and varying number of holes. We show that for both systems and both calculational schemes the presence of holes is crucial for establishing ferromagnetism. For both systems, the introduction of UU increases delocalization of the holes and, simultaneously, decreases the p-d interaction. Since these two trends exert opposite influences on the Mn-Mn exchange interaction the character of the variation of the Curie temperature (TC_C) cannot be predicted without direct calculation. We show that the variation of TC_C is different for two systems. For low Mn concentrations we obtain the tendency to increasing TC_C in the case of (GaMn)N whereas an opposite tendency to decreasing TC_C is obtained for (GaMn)As. We reveal the origin of this difference by inspecting the properties of the densities of states and holes for both systems. The main body of calculations is performed within a supercell approach. The Curie temperatures calculated within the coherent potential approximation to atomic disorder are reported for comparison. Both approaches give similar qualitative behavior. The results of calculations are related to the experimental data.Comment: to appear in Physical Review

    A Growth Model for North Queensland Rainforests

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    A model to predict the growth of commercial timber in north Queensland's rainforests is described. More than 100 commercial species and several hundred other tree species are aggregated into about 20 species groups based on growth habit, volume relationships and commercial criteria. Trees are grouped according to species group and tree size into cohorts, which form the basis for simulation. Equations for predicting increment, mortality and recruitment are presented. The implications of the model on rainforest management for timber production are examined. The model has been used in setting the timber harvest from these rainforests, and should provide an objective basis for investigating the impact of rainforest management strategies. The approach should be applicable to other indigenous forests

    Entanglement of positive definite functions on compact groups

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    We define and study entanglement of continuous positive definite functions on products of compact groups. We formulate and prove an infinite-dimensional analog of Horodecki Theorem, giving a necessary and sufficient criterion for separability of such functions. The resulting characterisation is given in terms of mappings of the space of continuous functions, preserving positive definiteness. The relation between the developed group-theoretical formalism and the conventional one, given in terms of density matrices, is established through the non-commutative Fourier analysis.Comment: published versio
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