7,215 research outputs found
Will Geographical Indications Supply Excessive Quality?
Consumer/Household Economics, Marketing,
AJAE Appendix: Optimal Investment in Transportation Infrastructure When Middlemen Have Market Power: A Developing-Country Analysis
The material contained herein is supplementary to the article named in the title and published in the American Journal of Agricultural Economics.Public Economics,
Examination of Beluga-habitat Relationships through the Use of Telemetry and a Geographic Information System
The spatial and temporal relationships between belugas (Delphinapterus leucas) and two characteristics of their habitat - bathymetry and ice concentration - were examined. Observed location-habitat correspondence histograms were compared to random location-habitat histograms, using a Kolmogorov-Smirnoff (K-S) statistical test. Results show that beluga distribution is bimodal with respect to bathymetry, with a larger mode in shallow water and a smaller mode in water approximately 500 m deep. They occur more often than expected by chance in the 0/10 ice class and less often than expected in the 10/10 ice class. Males and females associate differently with both depth and ice concentration. Females associate with bathymetry very differently in the fall than in the summer. There is a general tendency for males in the eastern North American Arctic to be associated with shallow water during the summer and deeper water (modes at 100 and 500 m) in the fall. Female locations are associated more often with the 0/10 ice class and less often with the 10/10 class than expected by chance. These trends were stronger in the western than in the eastern portions of the Canadian Arctic.On a étudié les rapports spatiaux et temporels entre les bélougas (Delphinapterus leucas) et deux caractéristiques de leur habitat (bathymétrie et concentration de glace). À l'aide d'un test statistique de Kolmogorov-Smirnov (K-S), on a comparé les histogrammes de la correspondance observée emplacement-habitat à des histogrammes emplacement-habitat pris au hasard. Les résultats montrent que la distribution du bélouga est bimodale en ce qui a trait à la bathymétrie, un mode plus grand étant associé à l'eau peu profonde et un mode plus petit à l'eau profonde d'environ 500 m. On les trouve plus fréquemment qu'on ne peut le prédire au hasard dans de la glace de cote 0/10 et moins souvent dans de la glace de cote 10/10. Les mâles et les femelles s'associent différemment selon la profondeur comme la concentration de glace. Les femelles s'associent très différemment avec la bathymétrie en automne et en été. Dans les mers arctiques de l'Amérique du Nord orientale, il y a une tendance générale pour les mâles à s'associer aux eaux peu profondes durant l'été et aux eaux plus profondes (modes à 100 et 500 m) en automne. Les emplacements des femelles sont associés plus souvent à la glace de cote 0/10 et moins souvent à la cote 10/10 qu'on ne peut le prédire au hasard. Ces tendances étaient plus marquées dans les parties occidentales que dans les zones orientales de l'Arctique canadien
Calibration of Aerial Thermal Infrared Imagery for Walrus Population Assessment
Concurrent aerial photography and emitted thermal infrared (10.6 micro meters) imagery were acquired over walrus hauled out on sea ice in Foxe Basin, Northwest Territories, Canada. Digital thermal infrared data from a Forward Looking Infrared (FLIR) imager provides a method for estimating walrus numbers, since the objects (walrus groups) are considerably warmer than the background (ocean and sea ice). Coincident photographic counts and thermal infrared pixel counts are regressed by means of a least squares linear regression and an estimate of group size predicted from the number of pixels represented by each group. The results indicate that analog thermal imagery provides an effective means for obtaining a stratification variable that can subsequently be used in survey design. The FLIR walrus estimation approach is evaluated in the context of replicability, both through the physical mechanics and within a limited range of environmental conditions. Precision of FLIR estimated walrus counts is evaluated relative to the precision of photo counts. Walrus numbers extracted from the digital thermal imagery at a sample swath of 1778 m are as precise as those obtained from three independent photo counts at a sample swath of 686 m. In this configuration the FLIR provides a 160% increase in the sampling (area) fraction. Based on these results, we recommend a stratified approach to estimating walrus abundance using a thermal infrared sensor coupled with visual and photographic censusing techniques. We conclude with recommendations for continued analysis of this infrared censusing technique.Key words: walrus, thermal infrared remote sensing, eastern Canadian Arctic, aerial surveysMots clés: morse, télédétection thermique infrarouge, Arctique canadien oriental, relevés aérien
Foraminiferal Evidence of Younger Dryas Age Cooling on the British Columbia Shelf
Cluster analysis of foraminifera from a ~12,000-9000 radiocarbon year old piston core from Goose Island Trough, Queen Charlotte Sound, indicates that a cold interval correlative with the Younger Dryas stadial occurred during a shallow water phase. The reduction in depth was caused by the passage across the area, between 11,500 and 10,000 years BP, of a glacial forebulge associated with the retreat of the Late Wisconsinian ice sheets. Published sedimentological evidence indicate that water depths decreased to ~75-90 m, placing the site above the permanent North Pacific pycnocline (100 m). Low salinity-near glacial conditions, at these depths, between -11,100 and 10,000 years BP were recognized by abundant populations of Cassidulina reniforme and lslandiella helenae. This cold interval has also been recognized in cores from elsewhere in Queen Charlotte Sound. The depressed salinity and temperature may have resulted from a modification of regional weather patterns. Decreased mean continental summer temperatures could have reduced the seasonal influence of the North Pacific High and lengthened that of the Aleutian Low. This would have resulted in a near continuous onshore surface Ekman transport and enhanced coastal runoff, effectively blocking the movement onto the shelf of deep, saline, warm water of the California Undercurrent. The resultant isolated inshore basin comprised of present-day Hecate Strait and Queen Charlotte Sound is tentatively named the "Hecate Sea". By ~10,000 years BP, weather and ocean circulation had returned to near modern patterns as indicated by the disappearance of lslandiella helenae and by the development of an Epistominella vitrea - dominated biofacies.L'analyse des groupements effectuée sur des populations de foraminifères d'une carotte à piston couvrant la période de 12 000 à 9000 ans BP, provenant du Goose Island Trough, dans le bassin de la Reine-Charlotte, démontre l'existence d'un intervalle froid contemporain du Dryas récent. Il coïncide avec une phase à bathymétrie réduite qui résulte du déplacement vers l'est, entre 11 500 et 10 000 ans BP, du bombement isostatique associé à l'Inlandsis de la Cordillière à la suite de son retrait. Des données sédimentologiques publiées montrent que la profondeur a diminué jusqu'à ~75-90 m, amenant le site étudié au-dessus de la pycnocline permanente du Pacifique Nord (100 m). L'existence de conditions hyposalines de type glaciaire, à ces profondeurs, entre 11 100 et 10 000 ans BP ont été reconnues grâce à la présence d'assemblages à Cassidulina reniforme et lslandiella helenae. Cet intervalle froid a également été reconnu ailleurs dans le bassin de la Reine-Charlotte. Les salinités et les températures réduites sont peut-être le résultat d'un changement dans les configurations météorologiques régionales. Des températures estivales plus basses sur le continent auraient réduit l'influence saisonnière de l'anticyclone du Pacifique Nord et rallongé celle de la dépression des Aloutiennes. Ceci aurait engendré un transport d'Ekman de surface quasi permanent vers la côte et provoqué une augmentation des précipitations, ayant eu pour effet de bloquer la remontée des eaux salées et tièdes du sous-courant de Californie. Nous proposons d'appeler « Mer d'Hécate » le bassin côtier ainsi créé comprenant l'actuel détroit d'Hécate et le bassin de la Reine-Charlotte. Dès avant ~10 000 ans BP, les circulations atmosphérique et océanique étaient revenues à une configuration presque moderne.Die Analyse der Foraminiferen-Anhàufungen von einem -12,000-9000 Radiokarbonjahre alten Bohrkern von Goose Island Trough im Queen Charlotte Sund zeigt, daB ein kaltes Intervall gleichzeitig mit dem jùngeren Dryas-Stadium wàhrend einer Phase seichten Wassers eintrat. Die Verringerung der Tiefe wurde durch die Passage einer glazialen Emporwôlbung zwischen 11,500 und 10,000 Jahren v.u.Z. quer durch das Gebiet bewirkt, zusammen mit dem Rùckzug der Eisdecken vom spàten Wisconsinium. Die verôfent-lichten sedimentologischen Belege zeigen, daf3 die Wassertiefen auf -75-90 m abnahmen, und so den Platz ùber die stàndige Dichte-Gradient des Nordpazifik (100 m) stellten. Fast glaziale Bedingungen mit niedrigem Salzgehalt wurden in diesen Tiefen zwischen -11,100 und 10,000 Jahren v.u.Z. auf Grund von reichlichen Populationen von Cassidulina reniforme und lslandiella helenae erkannt. Der verringerte Salzgehalt und die niedrigere Temperatur kônnten auch durch eine Ànderung der regionalen Wetterkonstellationen bewirkt worden sein. Gesunkene durchschnittliche kontinentale Sommertemperaturen kônnten den jahreszeitlichen EinfluB des nordpazifischen Hochs verringert und den des atlantischen Tiefs verlàngert haben. Das kônnte einen fast kontinuierlichen Ekman-Transport an der Oberflâche zur Kùste hin bewirkt und die Kùsten-Niederschlàge verstàrkt haben, und so ware die Bewegung von tiefem, salzhaltigem warmem Wasser der kalifornischen Unterstromung zur Terrasse hin blockiert worden. Das daraus resultierende isolierte Binnen-Becken, bestehend aus der heutigen Hecate-Meerenge und dem Queen Charlotte Sund, wird probeweise "Hecate Sea" genannt. Um -10,000 Jahre v.u.Z. sind Wetter und Ozeanstromung zu nahezu modernen Mustern zuruckgekehrt
An X-ray Atlas of Groups of Galaxies
A search was conducted for a hot intragroup medium in 109 low-redshift galaxy
groups observed with the ROSAT PSPC. Evidence for diffuse, extended X-ray
emission is found in at least 61 groups. Approximately one-third of these
detections have not been previously reported in the literature.
Most of the groups are detected out to less than half of the virial radius
with ROSAT. Although some spiral-rich groups do contain an intragroup medium,
diffuse emission is restricted to groups that contain at least one early-type
galaxy.Comment: 39 pages, 12 figures, to appear in The Astrophysical Journal Sup
Occurrence, Distribution and Behaviour of Beluga (Delphinapterus leucas) and Bowhead (Balaena mysticetus) Whales at the Franklin Bay Ice Edge in June 2008
Ice edges and polynyas have long been noted for their high biological productivity within the Arctic environment. In June 2008, an aggregation of belugas and bowheads was identified at the Franklin Bay ice edge in the eastern Beaufort Sea, adjacent to the Cape Bathurst polynya. We conducted five ice-edge surveys by helicopter to study the distribution and behaviour of the whales. Bowheads were sighted in significantly shallower water than belugas. In addition, we used the helicopter platform to observe behaviour. Belugas and bowheads were engaged in directed travel and diving near and under the ice. Five beluga dives were timed and found to have an average duration of 106 ± 61 s (± SD) and a range of 30 – 197 s. One bowhead under-ice dive was timed and had a duration of 417 s. The under-ice dives are consistent with feeding behaviour observed for belugas and bowheads in other ice-edge locations. We hypothesize that higher prey densities along the Franklin Bay ice edge than in the adjacent open water may attract belugas and bowheads to the ice edge in June. Further research is needed to identify the abundance and type of prey species consumed and to assess the relative energetic importance of spring ice-edge feeding to the eastern Beaufort Sea beluga and bowhead populations.Depuis longtemps, les lisières de glace et les polynies sont connues pour leur grande productivité biologique au sein de l’environnement arctique. En juin 2008, un groupement de bélugas et de baleines boréales a été repéré à la lisière de glace de la baie Franklin, dans l’est de la mer de Beaufort, lisière adjacente à la polynie du cap Bathurst. Au moyen d’hélicoptères, nous avons effectué cinq études de lisières de glace afin d’examiner la répartition des baleines de même que leur comportement. Les baleines boréales évoluaient dans des eaux beaucoup moins profondes que les bélugas. De plus, nous avons étudié le comportement des baleines à partir de la plateforme destinée aux hélicoptères. Les bélugas et les baleines boréales se déplaçaient de manière dirigée et plongeaient près de la glace et sous celle-ci. Les plongeons de bélugas ont été chronométrés, et leur durée moyenne s’établissait à 106 ± 61 s (± SD), avec une étendue de 30 – 197 s. Le plongeon sous glace d’une baleine boréale a duré 417 s. Les plongeons sous glace vont de pair avec le comportement alimentaire observé chez les bélugas et les baleines boréales d’autres emplacements en lisières de glace. Nous avançons l’hypothèse que la plus grande densité de proies le long de la lisière de glace de la baie Franklin comparativement aux eaux libres adjacentes peut attirer les bélugas et les baleines boréales à la lisière de glace en juin. Il faut pousser les recherches plus loin pour déterminer l’abondance et le type d’espècesproies consommées et pour évaluer l’importance énergétique relative de l’alimentation à la lisière de glace au printemps pour les populations de bélugas et de baleines boréales de l’est de la mer de Beaufort
Extracting gene expression patterns and identifying co-expressed genes from microarray data reveals biologically responsive processes
Abstract Background A common observation in the analysis of gene expression data is that many genes display similarity in their expression patterns and therefore appear to be co-regulated. However, the variation associated with microarray data and the complexity of the experimental designs make the acquisition of co-expressed genes a challenge. We developed a novel method for Extracting microarray gene expression Patterns and Identifying co-expressed Genes, designated as EPIG. The approach utilizes the underlying structure of gene expression data to extract patterns and identify co-expressed genes that are responsive to experimental conditions. Results Through evaluation of the correlations among profiles, the magnitude of variation in gene expression profiles, and profile signal-to-noise ratio's, EPIG extracts a set of patterns representing co-expressed genes. The method is shown to work well with a simulated data set and microarray data obtained from time-series studies of dauer recovery and L1 starvation in C. elegans and after ultraviolet (UV) or ionizing radiation (IR)-induced DNA damage in diploid human fibroblasts. With the simulated data set, EPIG extracted the appropriate number of patterns which were more stable and homogeneous than the set of patterns that were determined using the CLICK or CAST clustering algorithms. However, CLICK performed better than EPIG and CAST with respect to the average correlation between clusters/patterns of the simulated data. With real biological data, EPIG extracted more dauer-specific patterns than CLICK. Furthermore, analysis of the IR/UV data revealed 18 unique patterns and 2661 genes out of approximately 17,000 that were identified as significantly expressed and categorized to the patterns by EPIG. The time-dependent patterns displayed similar and dissimilar responses between IR and UV treatments. Gene Ontology analysis applied to each pattern-related subset of co-expressed genes revealed underlying biological processes affected by IR- and/or UV- induced DNA damage. Conclusion EPIG competed with CLICK and performed better than CAST in extracting patterns from simulated data. EPIG extracted more biological informative patterns and co-expressed genes from both C. elegans and IR/UV-treated human fibroblasts. Using Gene Ontology analysis of the genes in the patterns extracted by EPIG, several key biological categories related to p53-dependent cell cycle control were revealed from the IR/UV data. Among them were mitotic cell cycle, DNA replication, DNA repair, cell cycle checkpoint, and G0-like status transition. EPIG can be applied to data sets from a variety of experimental designs
Genes related to apoptosis predict necrosis of the liver as a phenotype observed in rats exposed to a compendium of hepatotoxicants
<p>Abstract</p> <p>Background</p> <p>Some of the biochemical events that lead to necrosis of the liver are well-known. However, the pathogenesis of necrosis of the liver from exposure to hepatotoxicants is a complex biological response to the injury. We hypothesize that gene expression profiles can serve as a signature to predict the level of necrosis elicited by acute exposure of rats to a variety of hepatotoxicants and postulate that the expression profiles of the predictor genes in the signature can provide insight to some of the biological processes and molecular pathways that may be involved in the manifestation of necrosis of the rat liver.</p> <p>Results</p> <p>Rats were treated individually with one of seven known hepatotoxicants and were analyzed for gene expression by microarray. Liver samples were grouped by the level of necrosis exhibited in the tissue. Analysis of significantly differentially expressed genes between adjacent necrosis levels revealed that inflammation follows programmed cell death in response to the agents. Using a Random Forest classifier with feature selection, 21 informative genes were identified which achieved 90%, 80% and 60% prediction accuracies of necrosis against independent test data derived from the livers of rats exposed to acetaminophen, carbon tetrachloride, and allyl alcohol, respectively. Pathway and gene network analyses of the genes in the signature revealed several gene interactions suggestive of apoptosis as a process possibly involved in the manifestation of necrosis of the liver from exposure to the hepatotoxicants. Cytotoxic effects of TNF-α, as well as transcriptional regulation by JUN and TP53, and apoptosis-related genes possibly lead to necrosis.</p> <p>Conclusion</p> <p>The data analysis, gene selection and prediction approaches permitted grouping of the classes of rat liver samples exhibiting necrosis to improve the accuracy of predicting the level of necrosis as a phenotypic end-point observed from the exposure. The strategy, along with pathway analysis and gene network reconstruction, led to the identification of 1) expression profiles of genes as a signature of necrosis and 2) perturbed regulatory processes that exhibited biological relevance to the manifestation of necrosis from exposure of rat livers to the compendium of hepatotoxicants.</p
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