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B. Gail Ivanoff 《Environmental and Ecological Statistics》2009,16(2):153-171
The concept of the renewal property is extended to processes indexed by a multidimensional time parameter. The definition
given includes not only partial sum processes, but also Poisson processes and many other point processes whose jump points
are not totally ordered. Various properties of renewal processes are discussed. Renewal processes are proposed as a basis
for modelling the spread of a forest fire under a prevailing wind.
相似文献
B. Gail IvanoffEmail: |
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Ciannelli L Knutsen H Olsen EM Espeland SH Asplin L Jelmert A Knutsen JA Stenseth NC 《Ecology》2010,91(10):2918-2930
Until the last decade it was assumed that most marine species have pronounced gene flow over vast areas, largely because of their potential for dispersal during early life stages. However, recent genetic, modeling, and field studies have shown that marine populations may be structured at scales that are inconsistent with extensive dispersal of eggs and larvae. Such findings have stimulated the birth of new studies explaining the mechanisms that promote population structure and isolation in the oceans, in the face of high potential for dispersal. Here we study the vertical and horizontal distribution of cod (Gadus morhua) eggs in relation to small-scale circulation and water column hydrography in a coastal location of southern Norway. Previous studies conducted in this region have shown that cod populations inhabiting fjord locations, which are on average 30 km apart, are genetically differentiated, a remarkable outcome considering that Atlantic cod have pelagic egg stages and long pelagic larval duration. We document that cod eggs are found in greater abundance in shallow water layers, which on average are flowing up the fjord (away from the open ocean), and in the inner portion of the fjord, which is subject to lower current speeds compared to the outer or mouth of the fjord. Eggs were found to be neutrally buoyant at shallow depths, a trait that also favors local retention, given the local circulation. The same patterns held during two environmentally contrasting years. These results strongly suggest that population structure of Atlantic cod is favored and maintained by a balance between water circulation and egg characteristics. 相似文献
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Possible links between plasma testosterone levels, heavy metal loads and dominance in juvenile male willow tits (Parus montanus) are studied during winter conditions in Norway. Dominant individuals have better access to food resources, significantly higher cadmium content in the liver and higher plasma testosterone level compared to subordinates. A positive correlation was also found between plasma testosterone level and content of cadmium in the liver. Although the results in our study shows only a limited difference in testosterone level of dominant and subordinate juvenile male willow tits, possible small changes in behaviour might have crucial effects on winter survival of these birds. 相似文献
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The pre-Quaternary fossil record of Canis in the Old World is scarce, and the first appearance of this genus in Europe remains an enigma. Amongst the oldest fossils assigned to this genus, there is a natural cast of the brain (endocast) collected in W??e 1, Poland, from Pliocene deposits dated between 3.3 and 4.0 Ma. We reexamined this specimen and found that it differs from the brain of Canis in having its region medial to the coronal sulcus heart-shaped in dorsal view, its region rostral to the presylvian sulcus shorter and less constricted laterally, and its cerebellum less overlapped by the cerebrum and lacking a lateral twist of the posterior vermis. We identified this fossil, as well as another fossil canid endocast from W??e 1, as representing the raccoon dog genus Nyctereutes. The previously reported presence of Canis in W??e 1 is therefore not confirmed. Specifically, both endocasts can be referred to N. donnezani because this is the only species of Nyctereutes that has been recognised in this locality on the basis of craniomandibular and dental fossils. Our study represents a taxonomic application of comparative neuroanatomical and palaeoneurological data, an approach that may become increasingly useful with the growing knowledge of the endocranial morphology of fossil mammals. 相似文献
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L. I. Van Der Ham T. E. Cohen-Overbeek H. D. Y Paz Geuze Chr. Vermeij-Keers MD PhD 《黑龙江环境通报》1995,15(12):1189-1192
The prenatal detection of scaphocephaly, an isolated form of craniosynostosis, is presented. The diagnosis was made at 34 weeks of gestation in a woman with polyhydramnios. The ultrasound appearance and postnatal follow-up are presented. 相似文献
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H. Chr. Weber 《Die Naturwissenschaften》1977,64(12):640-641