1,225 research outputs found
The Bruce Collection of Eskimo Material Culture from Kotzebue Sound, Alaska, by James W. VanStone
Early Dorset in the High Arctic: A Report from Karluk Island, N.W.T.
During the months of July and August 1978, a programme of archaeological excavations was conducted on Karluk Island in the Crozier Strait region of the Canadian High Arctic. The purpose of this project was to continue the examination, begun in 1977, of a number of early Dorset sites .... The objectives were to recover a sufficient sample of artifacts to legitimately conduct inter-regional comparisons, and to obtain ancillary data pertaining to structure types, subsistence patterns, seasonality and date of occupation. In the ... paper, the data obtained during the 1978 season are summarized and the significance of this material to High Arctic prehistory is briefly assessed
The Palaeo-Eskimo Prehistory of the North Devon Lowlands
In this paper the distinguishing characteristics of six chronologically discrete Palaeo-Eskimo occupations discovered in the North Devon Lowlands region of Devon Island, Northwest Territories, are summarized and their cultural/chronological positions briefly assessed. Observed variations in the intensity of occupation in the study area and major shifts in the extra-regional cultural affiliations of these six occupational episodes are discussed in reference to a high-mobility subsistence/settlement strategy model of High Arctic Palaeo-Eskimo socioecological adaptations.Key words: Arctic, Devon Island, prehistory, Palaeo-Eskimo, Pre-Dorset, DorsetMots clés: Arctique, île Devon, préhistoire, paléo-esquimau, pré-Dorset, Dorse
On the zero set of G-equivariant maps
Let be a finite group acting on vector spaces and and consider a
smooth -equivariant mapping . This paper addresses the question of
the zero set near a zero of with isotropy subgroup . It is known
from results of Bierstone and Field on -transversality theory that the zero
set in a neighborhood of is a stratified set. The purpose of this paper is
to partially determine the structure of the stratified set near using only
information from the representations and . We define an index
for isotropy subgroups of which is the difference of
the dimension of the fixed point subspace of in and . Our main
result states that if contains a subspace -isomorphic to , then for
every maximal isotropy subgroup satisfying , the zero
set of near contains a smooth manifold of zeros with isotropy subgroup
of dimension . We also present a systematic method to study
the zero sets for group representations and which do not satisfy the
conditions of our main theorem. The paper contains many examples and raises
several questions concerning the computation of zero sets of equivariant maps.
These results have application to the bifurcation theory of -reversible
equivariant vector fields
The Holocene Paleoecology of Jenny Lake Area, Southwest Yukon, and Its Implications for Prehistory
The pollen stratigraphy of a core extracted from Jenny Lake, southwest Yukon, in 1984 has marked archaeological significance. Five palynological zones are identified as follows: Zone JL1, the oldest (ca. 12,500-9,500 B.P.), is a Betula shrub tundra assemblage; Zone JL2 (ca. 9,500-8,500 B.P.) an Alnus shrub tundra; Zone JL3 (ca. 8,500-4,500 B.P.) a Picea forest; Zone JL4 (ca. 4,500-2,000 B.P.) a Picea-Alnus woodland; and JL5 (ca. 2,000 B.P.-present) a Picea forest. The widely held belief that the Kluane-Aishihik area of the SW Yukon was covered by extensive grasslands well into the Holocene period is not supported by the palynology of the Jenny Lake Core. Instead, palynological evidence suggests that the area, which initially was a Betula shrub tundra, then Alnus shrub tundra, became a Picea-dominated forest by approximately 8,500 B.P. and remained forested to the present. The hypothesis stating early prehistoric hunters and gatherers in the SW Yukon were adapted to extensive Holocene grasslands until ca. 3,300-2,600 B.P. will have to be modified in view of these findings.Key words: Yukon, paleoecology, palynology, archaeologyMots clés: Yukon, paléoécologie, palynologie, archéologi
Gecontroleerd overstromingsgebied Kruibeke-Bazel-Rupelmonde: naar een vrij toegankelijk natuurgebied en vergroting van de veiligheid
Quantized spin wave modes in magnetic tunnel junction nanopillars
We present an experimental and theoretical study of the magnetic field
dependence of the mode frequency of thermally excited spin waves in rectangular
shaped nanopillars of lateral sizes 60x100, 75x150, and 105x190 nm2, patterned
from MgO-based magnetic tunnel junctions. The spin wave frequencies were
measured using spectrally resolved electrical noise measurements. In all
spectra, several independent quantized spin wave modes have been observed and
could be identified as eigenexcitations of the free layer and of the synthetic
antiferromagnet of the junction. Using a theoretical approach based on the
diagonalization of the dynamical matrix of a system of three coupled, spatially
confined magnetic layers, we have modeled the spectra for the smallest pillar
and have extracted its material parameters. The magnetization and exchange
stiffness constant of the CoFeB free layer are thereby found to be
substantially reduced compared to the corresponding thin film values. Moreover,
we could infer that the pinning of the magnetization at the lateral boundaries
must be weak. Finally, the interlayer dipolar coupling between the free layer
and the synthetic antiferromagnet causes mode anticrossings with gap openings
up to 2 GHz. At low fields and in the larger pillars, there is clear evidence
for strong non-uniformities of the layer magnetizations. In particular, at zero
field the lowest mode is not the fundamental mode, but a mode most likely
localized near the layer edges.Comment: 16 pages, 4 figures, (re)submitted to PR
Single-artificial-atom lasing using a voltage-biased superconducting charge qubit
We consider a system composed of a single artificial atom coupled to a cavity
mode. The artificial atom is biased such that the most dominant relaxation
process in the system takes the atom from its ground state to its excited
state, thus ensuring population inversion. A recent experimental manifestation
of this situation was achieved using a voltage-biased superconducting charge
qubit. Even under the condition of `inverted relaxation', lasing action can be
suppressed if the `relaxation' rate is larger than a certain threshold value.
Using simple transition-rate arguments and a semiclassical calculation, we
derive analytic expressions for the lasing suppression condition and the state
of the cavity in both the lasing and suppressed-lasing regimes. The results of
numerical calculations agree very well with the analytically derived results.
We start by analyzing a simplified two-level-atom model, and we then analyze a
three-level-atom model that should describe accurately the recently realized
superconducting artificial-atom laser.Comment: 21 pages in preprint format, 6 figure
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