Narwhal hunting by Pond Inlet Inuit: An analysis of foraging mode in the floe-edge environment

The harvesting of narwhals by Baffin Island Inuit represents an important relationship in terms of the continuous utilization of an indigenous marine resource. However, research on Inuit hunting with respect to narwhals has been mainly confined to harvest counts despite the major role narwhals play in the local northern Baffin subsistence system. The present research examines Pond Inlet Inuit foraging behaviour for narwhals in the spring floe-edge environment. While sea ice is one of the most dominant features of the arctic marine environment for much of any year, it is in the spring that the dynamism of its physical and biological characteristics is most notable. This was especially evident at the fast ice-open water interface, or floe-edge, where rapid physical change in the condition of the ice is frequent and summer migratory marine mammals and birds are present in large numbers. In this paper, analysis of 14 observed hunts indicates that Inuit utilization of the spring floe edge for narwhal hunting, in contrast to most other hunt types, follows a sit-and-wait mode of foraging. The study also explicates aspects of Pond Inlet hunters traditional ecological knowledge necessary to travel and conduct harvesting operations successfully in this complex environment.La chasse au narval par les Inuit de la Terre de Baffin représente une relation importante en terme d’une utilisation continue d’une ressource marine indigène. Cependant, la recherche portant sur la chasse au narval par les Inuit a surtout été limitée aux dénombrements des récoltes, malgré le rôle majeur que les narvals jouent dans le système local de subsistance. La présente recherche explore le comportement alimentaire des Inuit face aux narvals dans l’environnement printanier de la lisière des banquises (floe-edge). Tandis que la glace marine est l’aspect dominant de l’environnement arctique marin pendant la majeure partie de l’année, c’est au printemps que le dynamisme de ses caractéristiques physiques et biologiques est le plus notable. Ceci est particulièrement évident à l’interface rapide de la glace et des eaux dégagées, nommément la lisière des banquises, où le changement physique rapide dans la condition de la glace est fréquent et où les mammifères marins et les oiseaux migrateurs estivaux sont présents en grand nombre. Dans cet article, une analyse de 14 voyages observés indique que l’utilisation par les Inuit de la lisière des banquises au printemps pour chasser le narval, comparativement aux autres types de chasse, suit un mode de chasse à l’affût (sit-and-wait). Cette étude expose les aspects du savoir écologique traditionnel appartenant aux Inuit de Pond Inlet, nécessaire pour voyager et conduire les opérations de chasse avec succès dans cet environnement complexe

Pre-selectable integer quantum conductance of electrochemically fabricated silver point contacts

The controlled fabrication of well-ordered atomic-scale metallic contacts is of great interest: it is expected that the experimentally observed high percentage of point contacts with a conductance at non-integer multiples of the conductance quantum G_0 = 2e^2/h in simple metals is correlated to defects resulting from the fabrication process. Here we demonstrate a combined electrochemical deposition and annealing method which allows the controlled fabrication of point contacts with pre-selectable integer quantum conductance. The resulting conductance measurements on silver point contacts are compared with tight-binding-like conductance calculations of modeled idealized junction geometries between two silver crystals with a predefined number of contact atoms

Metropolitan water intelligence systems completion report, phase III

Submitted to: U.S. Department of the Interior, Office of Water Resources Research.Series numbering taken from cover.June 1974.Grant no. 14-31-0001-9028

Numerical study of the one-dimensional quantum compass model

The ground state magnetic phase diagram of the one-dimensional quantum compass model (QCM) is studied using the numerical Lanczos method. A detailed numerical analysis of the low energy excitation spectrum is presented. The energy gap and the spin-spin correlation functions are calculated for finite chains. Two kind of the magnetic long-range orders, the Neel and a type of the stripe-antiferromagnet, in the ground state phase diagram are identified. Based on the numerical analysis, the first and second order quantum phase transitions in the ground state phase diagram are identified.Comment: 6 pages, 8 figures. arXiv admin note: text overlap with arXiv:1105.211

Breakdown of the Luttinger sum-rule at the Mott-Hubbard transition in the one-dimensional t1-t2 Hubbard model

We investigate the momentum distribution function near the Mott-Hubbard transition in the one-dimensional t1-t2 Hubbard model (the zig-zag Hubbard chain), with the density-matrix renormalization-group technique. We show that for strong interactions the Mott-Hubbard transition occurs between the metallic-phase and an insulating dimerized phase with incommensurate spin excitations, suggesting a decoupling of magnetic and charge excitations not present in weak coupling. We illustrate the signatures for the Mott-Hubbard transition and the commensurate-incommensurate transition in the insulating spin-gapped state in their respective ground-state momentum distribution functions

Numerical investigation of the stability of stationary solutions in the theory of cathode spots in arcs in vacuum and ambient gas

The stability of stationary spots on cathodes of arcs in vacuum and ambient gas is investigated by means of the simulation of the temporal evolution of perturbations imposed over steady-state solutions. Two cases of loading conditions are considered, namely, spots operating at a fixed current (the case typical of small-scale experiments) and spots operating at a fixed voltage (the case typical of high-power circuit breakers). Results are reported on spots on large copper cathodes of vacuum arcs and on spots on tungsten cathodes of high-pressure argon arcs. It is shown, in particular, that if the ballast resistance in small-scale laboratory experiments with a high-current arc is insufficient, the potential consequence may be a thermal explosion of a spot, if the arc burns in vacuum, and massive melting of the cathode surface, if the arc burns in ambient gas. This conclusion conforms to trends observed in the experiment.info:eu-repo/semantics/publishedVersio

Simulation of thermal instability in non-uniformities on the surface of cathodes of vacuum arcs

Instability stemming from the strong dependence of electron emission current on the local surface temperature plays an important role in current transfer to hot cathodes of arc discharges. In the case of vacuum arcs, this instability may lead to micro explosions on cathode surface even if the surface is planar. This work is concerned with numerical simulation of effect produced by surface non-uniformities. It is found that the effect is non-trivial: the presence of surface non-uniformities can not only accelerate the development of the instability, which is what one would expect intuitively, but also slow it down and even suppress.info:eu-repo/semantics/publishedVersio