2,422 research outputs found
Rossâs Gull (Rhodostethia rosea) Breeding in Penny Strait, Nunavut, Canada
We found a small, previously undiscovered breeding colony of Rossâs gulls (Rhodostethia rosea) in Nunavut, Canada, approximately 80 km from a previous colony location occupied during the 1970s. The birds nested in association with arctic terns (Sterna paradisaea). The collective observations from this region of the High Arctic suggest that Rossâs gulls may move colonies each year, or that colony occupation is intermittent.Nous avons repĂ©rĂ© une petite colonie de reproduction de mouettes rosĂ©es (Rhodostethia rosea) non dĂ©couverte jusquâĂ ce moment-lĂ au Nunavut, au Canada, Ă environ 80 kilomĂštres de lâemplacement dâune autre colonie occupĂ©e dans les annĂ©es 1970. Les oiseaux nichaient avec des sternes arctiques (Sterna paradisaea). Les observations collectives de cette rĂ©gion de lâExtrĂȘme-Arctique laissent supposer que les mouettes rosĂ©es peuvent changer de colonie chaque annĂ©e ou que lâoccupation des colonies est intermittente
Passive remote sensing of artificial relativistic electron beams in the middle atmosphere
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76955/1/AIAA-1999-4532-160.pd
Sources of Breeding Season Mortality in Canadian Arctic Seabirds
In more than 30 years of studies on marine birds in Arctic Canada, we have observed numerous instances of mortality of adults, eggs, and chicks that seem unusual when compared to known sources of mortality for seabirds breeding in temperate or tropical regions. The extreme cold weather and ice conditions of the Arctic might intuitively be expected to be a significant factor in mortality for these Arctic birds. While weather conditions led directly to seabird mortality, other factors, perhaps facilitated by typical Arctic climate features, caused more deaths. In this paper, we summarize mortality incidents that we have witnessed for nine species of Arctic marine birds, as a baseline against which future observations can be made. We also speculate on mechanisms by which climate change could increase mortality of breeding Arctic seabirds in the future.Dans le cadre dâĂ©tudes sur les oiseaux aquatiques qui se sont Ă©chelonnĂ©es sur plus de 30 ans dans lâArctique canadien, nous avons observĂ© de nombreuses incidences de mortalitĂ© chez les adultes, dans les oeufs et chez les oisillons, incidences qui semblent inhabituelles lorsquâelles sont comparĂ©es aux sources connues de mortalitĂ© des oiseaux de mer qui se reproduisent dans les rĂ©gions tempĂ©rĂ©es ou tropicales. Intuitivement, nous croyons que le temps froid extrĂȘme et le rĂ©gime des glaces de lâArctique peuvent reprĂ©senter un facteur de mortalitĂ© important chez ces oiseaux de lâArctique. Bien que les conditions climatiques aient directement entraĂźnĂ© la mort des oiseaux de mer, dâautres facteurs, qui sont peut-ĂȘtre dĂ©clenchĂ©s par les caractĂ©ristiques climatiques typiques de lâArctique, ont occasionnĂ© dâautres dĂ©cĂšs. Dans ce document, nous rĂ©sumons les incidents de mortalitĂ© dont nous avons Ă©tĂ© tĂ©moins pour neuf espĂšces dâoiseaux aquatiques de lâArctique comme point de rĂ©fĂ©rence en vue dâobservations futures. Nous Ă©mettons Ă©galement des hypothĂšses Ă propos des mĂ©canismes dans le cadre desquels le changement climatique pourrait accroĂźtre la mortalitĂ© des oiseaux de mer de lâArctique en reproduction Ă lâavenir
Non-Volatile Memory Characteristics of Submicrometre Hall Structures Fabricated in Epitaxial Ferromagnetic MnAl Films on GaAs
Hall-effect structures with submicrometre linewidths (<0.3pm) have been fabricated in ferromagnetic thin films of Mn[sub 0.60]Al[sub 0.40] which are epitaxially grown on a GaAs substrate. The MnAl thin films exhibit a perpendicular remanent magnetisation and an extraordinary Hall effect with square hysteretic behaviour. The presence of two distinct stable readout states demonstrates the potential of using ultrasmall ferromagnetic volumes for electrically addressable, nonvolatile storage of digital information
The extraordinary Hall effect in coherent epitaxial tau (Mn,Ni)Al thin films on GaAs
Ultrathin coherent epitaxial films of ferromagnetic tau(Mn,Ni)0.60Al0.40 have been grown by molecular beam epitaxy on GaAs substrates. X-ray scattering and cross-sectional transmission electron microscopy measurements confirm that the c axis of the tetragonal tau unit cell is aligned normal to the (001) GaAs substrate. Measurements of the extraordinary Hall effect (EHE) show that the films are perpendicularly magnetized, exhibiting EHE resistivities saturating in the range of 3.3-7.1 muOMEGA-cm at room temperature. These values of EHE resistivity correspond to signals as large as +7 and -7 mV for the two magnetic states of the film with a measurement current of 1 mA. Switching between the two magnetic states is found to occur at distinct field values that depend on the previously applied maximum field. These observations suggest that the films are magnetically uniform. As such, tau(Mn,Ni)Al films may be an excellent medium for high-density storage of binary information
Incidental Observations of Birds in the Vicinity of Hell Gate Polynya, Nunavut: Species, Timing, and Diversity
Our knowledge of the distribution of Arctic birds and how their ranges may be responding to environmental changes in the Canadian Arctic is limited. We gathered five years of species observation data from three sites in the Hell Gate â Cardigan Strait Polynya (Cape Vera, St. Helena Island, and Devil Island) to create an inventory of avian species observed in the polynya, and we compared it to previous observations made at our sites and other sites throughout the Arctic. We examined species diversity measurements over time to suggest possible effects of the polynya on the timing of spring arrival of breeding and migrant species. Of the 39 species observed during our study, 12 were local breeders. Our records provide the northernmost observations for eight species. Species diversity index values at St. Helena Island peaked quickly in mid-June and stabilized by late June, reflecting the arrival and dispersal of migrating species relatively early in the season. These data highlight the importance of the open-water feeding habitat of the polynya not only for breeding birds, but also for migrants.Nos connaissances de la distribution des oiseaux de lâArctique et de la façon dont leurs parcours sont adaptĂ©s en fonction des changements environnementaux de lâArctique canadien sont restreintes. Nous avons rassemblĂ© les donnĂ©es dâobservation dâespĂšces diverses Ă©chelonnĂ©es sur cinq ans Ă partir de trois emplacements de la polynie de Hell Gate â Cardigan Strait (cap Vera, Ăźle St. Helena et Ăźle Devil) dans le but de dresser lâinventaire des espĂšces aviaires observĂ©es dans la polynie, puis nous les avons comparĂ©es aux observations faites antĂ©rieurement Ă nos emplacements de mĂȘme quâĂ dâautres emplacements de lâArctique. Nous avons examinĂ© les mesures de la diversitĂ© des espĂšces au fil du temps afin de pouvoir suggĂ©rer les effets possibles de la polynie sur le moment de lâarrivĂ©e du printemps des espĂšces nicheuses et des espĂšces migrantes. Au nombre des 39 espĂšces ayant fait lâobjet de notre Ă©tude, 12 Ă©taient des oiseaux nicheurs de la rĂ©gion. Nos donnĂ©es constituent les observations prĂ©levĂ©es les plus au nord pour huit des espĂšces. Les valeurs de lâindice de la diversitĂ© des espĂšces Ă lâĂźle St. Helena ont atteint leur sommet Ă la mi-juin, puis se sont stabilisĂ©es vers la fin juin, ce qui Ă©tait le reflet de lâarrivĂ©e et de la dispersion dâespĂšces migrantes relativement tĂŽt dans la saison. Ces donnĂ©es font ressortir lâimportance de lâhabitat alimentaire en eaux libres de la polynie, non seulement pour les oiseaux nicheurs mais Ă©galement pour les oiseaux migrants
Status, Trends and Attendance Patterns of the Northern Fulmar Fulmarus glacialis in Nunavut, Canada
Nunavut supports ten breeding colonies of northern fulmars (Fulmarus glacialis), most of which have rarely been visited on the ground by biologists. During 2000â04, we surveyed six colonies previously thought to support more than 80% of the Canadian Arctic population, which was believed to number about 300 000 breeding pairs. Our counts suggested that the breeding populations of some colonies, especially those at the largest colonies, Cape Searle and Prince Leopold Island, were substantially smaller than previously estimated. Our estimate for the total population of Nunavut was approximately 200 000 occupied sites. However, counts made at fixed monitoring plots at Prince Leopold Island and total colony estimates at Cape Vera, Devon Island, suggested no change in numbers at those colonies since the 1970s. Numbers present at the colony peaked in late Juneâearly July and fell sharply after the end of July. Cyclical attendance, identified in an earlier study, was irregular in period length and was not seen in all years. We concluded that counts of Apparently Occupied Sites (AOS) conducted daily for 10â15 days are the best monitoring protocol for northern fulmars at these Arctic colonies. The great day-to-day variability in counts may have contributed to the large differences between past and recent population estimates.Le Nunavut permet la subsistance de dix colonies de nidification de fulmars borĂ©aux (Fulmarus glacialis), et rares sont les colonies qui ont Ă©tĂ© visitĂ©es par des biologistes au sol. De 2000 Ă 2004, nous avons recensĂ© six colonies qui, croyait-on, soutenaient plus de 80 % de la population arctique canadienne, estimĂ©e Ă environ 300 000 couples reproducteurs. Nos dĂ©nombrements laissent supposer que les populations dâoiseaux nicheurs de certaines colonies, surtout les colonies les plus grosses, soit celles de cap Searle et de lâĂźle Prince Leopold, sont nettement infĂ©rieures aux anciennes estimations. Notre estimation pour toute la population du Nunavut se chiffrait Ă environ 200 000 sites occupĂ©s. Toutefois, les dĂ©nombrements effectuĂ©s Ă des lieux de surveillance fixes Ă©tablis sur lâĂźle Prince Leopold et les estimations totales des colonies de cap Vera, sur lâĂźle Devon, laissent supposer quâil nây a pas eu de changement en ce qui a trait Ă ce nombre de colonies depuis les annĂ©es 1970. Les nombres prĂ©sents Ă la colonie ont atteint leur sommet vers la fin juin et le dĂ©but juillet, aprĂšs quoi ils ont chutĂ© considĂ©rablement aprĂšs la fin juillet. La frĂ©quentation cyclique, dont il a Ă©tĂ© question dans une Ă©tude antĂ©rieure, Ă©tait irrĂ©guliĂšre pour ce qui est de la longueur de la pĂ©riode et nâĂ©tait pas vue Ă toutes les annĂ©es. Nous en avons donc conclu que les dĂ©nombrements de sites apparemment occupĂ©s qui ont Ă©tĂ© effectuĂ©s quotidiennement pendant 10 Ă 15 jours reprĂ©sentent le meilleur protocole de surveillance des fulmars borĂ©aux de ces colonies arctiques. Lâimportante variabilitĂ© enregistrĂ©e dâun jour Ă lâautre sur le plan des dĂ©nombrements pourrait avoir contribuĂ© aux grandes diffĂ©rences entre les estimations de population passĂ©es et rĂ©centes
Relativistic electron beam propagation in the Earth's atmosphere: Modeling results
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95662/1/grl8999.pd
MicroRNA29a regulates IL-33-mediated tissue remodelling in tendon disease
MicroRNA (miRNA) has the potential for cross-regulation and functional integration of discrete biological processes during complex physiological events. Utilizing the common human condition tendinopathy as a model system to explore the cross-regulation of immediate inflammation and matrix synthesis by miRNA we observed that elevated IL-33 expression is a characteristic of early tendinopathy. Using in vitro tenocyte cultures and in vivo models of tendon damage, we demonstrate that such IL-33 expression plays a pivotal role in the transition from type 1 to type 3 collagen (Col3) synthesis and thus early tendon remodelling. Both IL-33 effector function, via its decoy receptor sST2, and Col3 synthesis are regulated by miRNA29a. Downregulation of miRNA29a in human tenocytes is sufficient to induce an increase in Col3 expression. These data provide a molecular mechanism of miRNA-mediated integration of the early pathophysiologic events that facilitate tissue remodelling in human tendon after injury
Optimal discrete stopping times for reliability growth tests
Often, the duration of a reliability growth development test is specified in advance and the decision to terminate or continue testing is conducted at discrete time intervals. These features are normally not captured by reliability growth models. This paper adapts a standard reliability growth model to determine the optimal time for which to plan to terminate testing. The underlying stochastic process is developed from an Order Statistic argument with Bayesian inference used to estimate the number of faults within the design and classical inference procedures used to assess the rate of fault detection. Inference procedures within this framework are explored where it is shown the Maximum Likelihood Estimators possess a small bias and converges to the Minimum Variance Unbiased Estimator after few tests for designs with moderate number of faults. It is shown that the Likelihood function can be bimodal when there is conflict between the observed rate of fault detection and the prior distribution describing the number of faults in the design. An illustrative example is provided
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