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排序方式: 共有104条查询结果,搜索用时 31 毫秒
81.
82.
Jonzén N Lindén A Ergon T Knudsen E Vik JO Rubolini D Piacentini D Brinch C Spina F Karlsson L Stervander M Andersson A Waldenström J Lehikoinen A Edvardsen E Solvang R Stenseth NC 《Science (New York, N.Y.)》2006,312(5782):1959-1961
Several bird species have advanced the timing of their spring migration in response to recent climate change. European short-distance migrants, wintering in temperate areas, have been assumed to be more affected by change in the European climate than long-distance migrants wintering in the tropics. However, we show that long-distance migrants have advanced their spring arrival in Scandinavia more than short-distance migrants. By analyzing a long-term data set from southern Italy, we show that long-distance migrants also pass through the Mediterranean region earlier. We argue that this may reflect a climate-driven evolutionary change in the timing of spring migration. 相似文献
83.
Development of sediment quality criteria in Norway 总被引:1,自引:0,他引:1
Torgeir Bakke Torsten Källqvist Anders Ruus Gijs D. Breedveld Ketil Hylland 《Journal of Soils and Sediments》2010,10(2):172-178
Introduction
A Norwegian system for classification of environmental quality of contaminated marine sediments has been in force since 1997 and was revised in 2007. 相似文献84.
Annabelle Heier Christian Sonne Andrea Gr?ne Pall S Leifsson Rune Dietz Erik W Born Luca N Bacciarini 《Journal of zoo and wildlife medicine》2005,36(3):440-446
From 1999 to 2002 samples from 114 free-ranging polar bears (Ursus maritimus) were collected in the municipality of Scoresby Sound, East Greenland, to detect levels of organochlorines and potential histopathologic changes. Livers of 16 female polar bears from this group were evaluated histologically and analyzed for hepatic retinol-binding protein by immunohistochemistry. Retinol-binding protein is the main transport protein for retinol, an important vitamin A metabolite in the polar bear. Only mild pathologic changes were noted on histologic evaluation of the livers. Small lymphocytic or lymphohistiocytic infiltrates were present in all the livers. Small lipid granulomas, mild periportal fibrosis, and bile duct proliferation were found in several cases. Immunohistochemistry for retinol-binding protein of hepatic tissue from free-ranging polar bears showed no distinct difference in staining intensity by a number of criteria: age, season (fasting and nonfasting), or lactation status. The staining was diffuse to finely stippled in the cytoplasm and showed very little variation among the animals. Because of the lack of macroscopic changes and the absence of severe histologic liver lesions, these polar bears were assumed to be healthy. The diffuse cytoplasmic retinol-binding protein staining in hepatocytes of free-ranging polar bears varies markedly from the prominent granular, less intense staining of captive polar bears investigated previously. 相似文献
85.
In the Norwegian fjord Masfjorden, different developmental stages of the mesopelagic planktivore Maurolicus muelleri form vertically separate sound scattering layers (SSLs) and in late autumn display different diel vertical migration (DVM) behaviour. Post‐larvae and juvenile fish perform normal crepuscular DVM, whereas the large majority of adults remain at depth throughout the diel period. In this study we examined the stomach contents of juvenile and adult fish caught at different times and depths during a 24‐h period in autumn. The different DVM behaviour of these two SSLs in addition to a shallow layer believed to be composed of post‐larvae is explained with a model for visual foraging in aquatic environments that uses gradients in vertical light intensity and copepod density and size as input variables. Field data revealed that vertically migrating juveniles distributed at a higher ambient light intensity and on average consumed 25 times more copepods than non‐migrating adult fish. The model showed that juveniles experienced a 15 times higher prey encounter rate and a higher level of predation risk than non‐migrating adults, and that the energetic benefits for post larvae and juveniles from prolonged feeding in a nearly constant and brighter environment outweigh the associated predation risk. The model also suggests that the visual detection range of piscivore predators is relatively more limited by the turbid surface water than that of their prey, which provide the post‐larva and juvenile life‐stages of M. muelleri a window of reduced visual predation near the surface. 相似文献
86.
Effects of diet supplementation of soya‐saponins,isoflavones and phytosterols on Atlantic salmon (Salmo salar,L) fry fed from start‐feeding 下载免费PDF全文
A 14‐week trial was conducted to investigate the effects of antinutritional factors (ANFs) commonly present in soybean ingredients, singly and in combination, on Atlantic salmon (Salmo salar L.) fed from start‐feeding. The experimental diets consisted of a negative control fish meal diet (FM), and a positive control diet with 167 g kg?1 soybean meal inclusion (SBM) and four diets based on the FM diet supplemented with 2 g kg?1 soya‐saponins (SAP), 1.5 g kg?1 isoflavones (IFL), 0.3 g kg?1 phytosterols (PHS) or a mixture of these (MIX). Fish fed the SAP diet showed significantly higher growth performance than those fed FM, while the IFL treatment significantly decreased growth performance of salmon fry. Fish fed the IFL diet had significantly lower maltase activity and higher trypsin activity in proximal intestine than fish fed the FM diet. Histological differences were observed in the liver of fish fed the IFL diet, characterized by reduced size of the hepatocytes. Fish fed the PHS and IFL diets showed the highest frequencies of skeletal deformities among the six treatments. In conclusion, the results indicate that purified isoflavones may negatively affect growth performance, intestinal function, liver metabolism and bone formation of salmon fry. 相似文献
87.
A M Bakke‐McKellep C McL Press G Baeverfjord
Krogdahl T Landsverk 《Journal of fish diseases》2000,23(2):115-127
Extracted soybean meal (SBM) in the diet for Atlantic salmon, Salmo salar L., causes an inflammatory response in the distal intestine. The morphological changes of the epithelial cells and a characterization of the inflammatory cell infiltrate of the distal intestinal mucosa were studied using a panel of enzyme and immunohistochemical markers. The salmon (average body weight 927 g) used in the study were fed either a fishmeal‐based diet (control diet) or a diet in which 30% of the fishmeal protein was replaced with SBM protein (SBM diet). In salmon fed SBM, there were markedly reduced enzyme reactivities in the distal intestinal epithelial cells, both in the brush border [5′‐nucleotidase (5′N), Mg2+‐ATPase, alkaline phosphatase (ALP) and leucine aminopeptidase (LAP)] and in the intracellular structures [alkaline and acid phosphatase, non‐specific esterase (NSE) and alanine aminopeptidase (AAP)]. There appeared to be an increased presence of cells of monocytic lineage, including macrophages, as well as neutrophilic granulocytes and immunoglobulin (Ig) M in the lamina propria of the SBM‐fed fish. The mid intestine showed little response to the diet. The results suggest that toxic/antigenic component(s) of SBM affect the differentiation of the distal intestinal epithelial cells and may help explain the reduced nutrient digestibilities previously reported in salmonids fed extracted SBM. 相似文献
88.
This paper explores the extent to which firms perceive to benefit from university-industry collaborations in their innovation processes, building on survey data from 232 Norwegian firms. We find that firms experience not only direct innovation benefits from collaborations, but also indirect benefits in the form of closer proximity to universities, which can in turn improve future collaboration. We compare the reported outputs from various types of collaboration, finding that firms engaging mainly in research-oriented interactions more often report that collaborations result in innovation than those engaging in education-oriented or more informal collaborations. However, education-oriented and informal collaborations are equally important for building cognitive, organizational, institutional and social proximities between firms and universities. 相似文献
89.
90.