85 research outputs found

    Radar echo characteristics at Ny-Alesund, Svalbard and Arctic storms over the Norwegian Sea

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    This paper is a preliminary report on radar echo characteristics and Arctic storms near Svalbard. Using an X-band vertically pointing radar data at Ny-Alesund, Svalbard, Norway and synoptic weather charts, the radar echo characteristics are investigated for one year between April 1994 and March 1995. Radar echoes have distinct seasonal variations with respect to height. Taking account of synoptic conditions, each series of radar echoes is classified into four patterns and it is found that they have strong seasonal variations. The low pressure system echo patterns appear throughout the year; their appearance frequencies exceed 50 of all radar echo appearances and increase in early summer and early winter. The appearance frequencies of low pressure systems over the Norwegian Sea have also characteristic strong seasonal variations. These low pressure activities appear to be related to precipitation behavior at Ny-Alesund and vapor transportation to the high Arctic from lower latitudes

    Habitat segregation and genetic relationship of two heptageniid mayflies, Epeorus latifolium and Epeorus l-nigrus, in the Shinano-gawa River basin

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    The heptageniid mayflies Epeorus latifolium and Epeorus l-nigrus are often the dominant species in the upper and midstream areas of Japanese rivers; as such, they play a significant role in river ecosystems. However, although these two species have been identified using the morphological characteristics of the male in its adult stage, it is impossible to differentiate them in their nymphal stage. We conducted a study to elucidate their distribution pattern, i.e., the current distribution of these two species in the Shinano-gawa River basin, based on quantitative field sampling and genetic analysis of nymphs and also some male adults; for these, it was possible to differentiate between the two species reliably. The data collected from the 30 study sites of the 1-year-long study revealed that the E. latifolium and/or E. l-nigrus mayflies are clearly distributed over a very broad area, and they appeared to be the dominant species at about a third of the study sites. Based on our genetic analysis, including several male adult specimens of E. latifolium and E. l-nigrus, it was clearly revealed that E. latifolium and E. l-nigrus respectively form two separate monophyletic clades. That is, E. latifolium and E. l-nigrus are clearly genetically differentiated, and they are considered to each represent a discrete species. Then, we plotted the collection sites of reliably identified specimens of E. latifolium and E. l-nigrus on the Shinano-gawa River basin map. This resultant map clearly displays that E. latifolium is distributed in the upper stream area rather than E. l-nigrus. To conclude, a pronounced 'habitat segregation' or 'current distribution' is clearly observable.ArticleLIMNOLOGY. 12(2):117-125 (2011)journal articl

    AN EXPERIMENTAL STUDY OF TRANSPOSITION OF DISCRIMINATION LEARNING IN THE WHITE RAT

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