2,168 research outputs found

    Design and fabrication of a mid infra-red photonic crystal defect laser in indium antimonide

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    This paper presents 2D FDTD modelling and prototype fabrication of a mid-infrared photonic crystal defect laser. The device is fabricated using a two stage Focused Ion Beam process which results in improved hole profiles

    World status of wild Rangifer tarandus populations

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    We recognized 184 herds of wild Rangifer tarandus, 102 in North America, 55 in Europe, 24 in Asia and 3 on South Georgia. Seventy-five percent of the world population of 3.3 to 3.9 million animals occurred in nine herds. All seven herds larger than 120 000 animals were censused by some means of aerial photography and all were increasing. Herds between 20 000 and 120 000 were most often censused using aerial strip transect methods, while total counts were usually employed to census smaller herds. The most pronounced changes in Rangifer herd status between 1979 and 1985 occurred in North America where population "estimates for five herds increased by a total of about one million animals. Part of this increase is attributable to a change from visual to photographic surveys. Eighty-three percent of North American, 88% of European, and 68% of Asian herds were stable or increasing

    Ice and mineral licks used by caribou in winter

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    In winter, barren-ground caribou obtain minerals from ice and soil licks. Between December and April we have seen caribou cratering on the surface of frozen lakes and licking the ice. Ice samples from eight licks on four lakes contained concentrations of calcium, magnesium, sodium, potassium, phosphorus, chloride and sulphate many times higher than in the surrounding unlicked ice or than would be expected in lake water. Soil licks being used in March and June had high concentrations of calcium, magnesium, sodium phosphorus and potassium. In winter caribou may be seeking supplements of all of the major mineral elements (calcium, magnesium, sodium and potassium) at ice and soil licks because lichens, their staple winter diet, are low in minerals and may also reduce the absorption of some minerals

    On conjectures of Hovey-Strickland and Chai

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    We prove the height two case of a conjecture of Hovey and Strickland that provides a K(n)K(n)-local analogue of the Hopkins--Smith thick subcategory theorem. Our approach first reduces the general conjecture to a problem in arithmetic geometry posed by Chai. We then use the Gross--Hopkins period map to verify Chai's Hope at height two and all primes. Along the way, we show that the graded commutative ring of completed cooperations for Morava EE-theory is coherent, and that every finitely generated Morava module can be realized by a K(n)K(n)-local spectrum as long as 2p−2>n2+n2p-2>n^2+n. Finally, we deduce consequences of our results for descent of Balmer spectra

    Observations on the Kalliapseudid Tanaidacea (Crustacea: Malacostraca: Peracarida) from the Northwestern Atlantic, with an Illustrated Key to the Species

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    New information for the kalliapseudid Tanaidacea occurring in the northwestern Atlantic is presented and discussed, including data on range extensions and new depth ranges for 4 species. The taxa studied came from the shelf and coastal waters of the southeastern United States, Puerto Rico and Trinidad. The occurrence of Mesokalliapseudes bahamensis Sieg is extended from the Bahamas and Belize to the coastal waters of East and Gulf coasts (South Carolina to West Florida). The range of Psammokalliapseudes granulosus Brum is expanded northward into the eastern Gulf of Mexico and new locality records for this species are established for Tobago and Puerto Rico. Mesokalliapseudes brasiliensis (Băcescu), previously known from the southwestern Atlantic off Brazil, is reported from the coastal waters off Trinidad. The range of Tanapseudes gutui Hansknecht, Heard, and Bamber is expanded northward into the eastern Gulf of Mexico. New depth ranges are established for Alokalliapseudes macsweenyi (Drumm) (82 m), M. bahamensis (52 m), P. granulosus (53 m), and T. gutui (82 m). An offshore form of A. macsweenyi occurs at depths ranging from 10-82 m on the inner and mid continental shelf off the west coast of Florida (Gulf of Mexico); it differs from the coastal form by the shape and dentition of the male and female chelipeds. Synonymies, diagnoses, life history remarks, and an illustrated key to the seven kalliapseudid species known from the NW Atlantic are presented

    On stratification for spaces with Noetherian mod pp cohomology

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    Let XX be a topological space with Noetherian mod pp cohomology and let C∗(X;Fp)C^*(X;\mathbb{F}_p) be the commutative ring spectrum of Fp\mathbb{F}_p-valued cochains on XX. The goal of this paper is to exhibit conditions under which the category of module spectra on C∗(X;Fp)C^*(X;\mathbb{F}_p) is stratified in the sense of Benson, Iyengar, Krause, providing a classification of all its localizing subcategories. We establish stratification in this sense for classifying spaces of a large class of topological groups including Kac--Moody groups as well as whenever XX admits an HH-space structure. More generally, using Lannes' theory we prove that stratification for XX is equivalent to a condition that generalizes Chouinard's theorem for finite groups. In particular, this relates the generalized telescope conjecture in this setting to a question in unstable homotopy theory

    Tanaidacea (Crustacea: Peracardia) of the Gulf of Mexico. II. The Occurrence of Halmyrapseudes bahamensis Băcescu and Gutu, 1974 (Apseudidae) in the Eastern Gulf with Redescription and Ecological Notes

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    Halmyrapseudes bahamensis Băcescu and Gutu, 1974 is reported from two localities in the northeastern Gulf of Mexico. A redescription is presented based on examination of type material and a large collection of Gulf specimens. Ecological notes are presented on the occurrence, seasonality and distribution of H. bahamensis in two tidal marsh systems near St. Marks, Florida. The taxonomic status of H. bahamensis in relation to the two other described species of Halmyrapseudes is discussed

    Tanaidacea (Crustacea: Peracardia) of the Gulf of Mexico. I. Introduction and an Annotated Bibliography of Tanaidacea Previously Reported from the Gulf of Mexico

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    A brief summary of the biology and a historical review are presented for the Tanaidacea. An annotated bibliography is provided for published reports and records of Tanaidacea from the Gulf of Mexico

    Space tug propulsion system failure mode, effects and criticality analysis

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    For purposes of the study, the propulsion system was considered as consisting of the following: (1) main engine system, (2) auxiliary propulsion system, (3) pneumatic system, (4) hydrogen feed, fill, drain and vent system, (5) oxygen feed, fill, drain and vent system, and (6) helium reentry purge system. Each component was critically examined to identify possible failure modes and the subsequent effect on mission success. Each space tug mission consists of three phases: launch to separation from shuttle, separation to redocking, and redocking to landing. The analysis considered the results of failure of a component during each phase of the mission. After the failure modes of each component were tabulated, those components whose failure would result in possible or certain loss of mission or inability to return the Tug to ground were identified as critical components and a criticality number determined for each. The criticality number of a component denotes the number of mission failures in one million missions due to the loss of that component. A total of 68 components were identified as critical with criticality numbers ranging from 1 to 2990
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