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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 438 (1984), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Pure and applied geophysics 156 (1999), S. 503-524 
    ISSN: 1420-9136
    Keywords: Key Words: Optical turbulence, thermosonde, isoplanometer, isoplanatic angle.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract —A comparison of isoplanatic angles θ 0 derived from (1) balloon-borne in situ measurements of the index of refraction structure constant (C n 2) profiles and (2) ground-based optical measurements of stellar intensity fluctuations using an isoplanometer is presented. Concurrent data taken over a six-day period in the spring of 1986 show reasonably good agreement between the mean values determined by the two methods. Comparisons in light of meteorological conditions suggest an isoplanatic angle behavior consistent with the Kelvin-Helmholtz instability where the best correlation was found between the optically-measured isoplanatic angle and the layer-averaged wind shear. Differences between the two measurement methods are largest for isoplanometer azimuth angles perpendicular to the balloon trajectory and for lower values of mean shear.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To investigate the role of sea ice cover on penguin populations we used principal component analysis to compare population variables of Adélie (Pygoscelis adeliae) and chinstrap (Pygoscelis antarctica) penguins breeding on Signy Island, South Orkney Islands with local (from direct observations) and regional (from remote sensing data) sea ice variables. Throughout the study period, the Adélie penguin population size remained stable, whereas that of chinstrap penguins decreased slightly. For neither species were there significant relationships between population size and breeding success, except for an apparent inverse density-dependent relationship between the number of Adélie breeding pairs and the number of eggs hatching. For both species, no general relationship was found between either population size or breeding success and the local sea ice conditions. However, the regional sea ice extent at a particular time prior to the start of the breeding season was related to the number of birds that arrived to breed. For both species, this period occurred before the sea ice reached its maximum extent and was slightly earlier for Adélie than for chinstrap penguins. These results suggest that sea ice conditions outside the breeding season may play an important role in penguin population processes.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 373 (1995), S. 201-202 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] SIR - Acoustic target strength (TS)1 is an important parameter when using acoustic survey data to estimate the abundance of Antarctic krill (Euphausia superba Dana). Recently, when the TS of krill was reassessed2,3, it emerged that the previous values had been too high, leading to unrealistically ...
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 381 (1996), S. 413-415 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] We collected data over a three-month summer period as part of a study of the foraging biology of albatrosses in the South Atlantic5. Electronic recording devices were attached to the legs of five different adult albatrosses on Bird Island, South Georgia (54° 00' S, 38 ° 06' W), on 19 ...
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 53 (1984), S. 304-314 
    ISSN: 1432-1106
    Keywords: Rabbit ; Visual cortex ; Development ; Golgi
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Lamina IV stellate cells and lamina V pyramidal cells were studied in Golgi material of visual cortex of rabbits ranging in age from 10 days to adult. Spine density counts revealed that primary branches have lower spine density than secondary or tertiary branches in both stellate and basilar pyramidal dendrites. Most areas sampled showed an increase in spine density from age 10 days to a peak at 25–30 days. In some areas this was followed by a plateau, but in most dendritic areas sampled there was a significant decrease from peak levels to adult levels. Measurements of dendritic length revealed that basilar dendrites undergo changes in length which parallel the changes in spine density counts: a peak in the length of basilar dendrites was followed by a decline to adult levels. However, the dendritic length of stellate cells showed much less change with age after 10 days. We propose that the time period during which spine density and pyramidal cell dendritic organization peaks above adult levels may coincide with, and provide a morphological correlate of, the critical period.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 50 (1983), S. 367-372 
    ISSN: 1432-1106
    Keywords: Rabbit ; Visual cortex ; Critical period ; Stroboscopic rearing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Previous studies have shown that rearing rabbits in a stroboscopically illuminated environment results in a decrease in orientation and direction selectivity and an increase in responsivity to stroboscopic stimuli among neurons in area 17. In the present study, the critical period for susceptibility to these effects was studied by varying the time of onset of the deprivation. Groups of Dutch belted rabbits were reared normally and then placed in a stroboscopically illuminated environment at ages 1, 2 or 3 months, and response characteristics of visual cortical neurons were compared with those obtained from normal rabbits and from rabbits reared in a stroboscopic environment from birth. Results show that the different effects of strobe rearing have different critical periods. Increased responsivity to stroboscopic stimuli was seen only in rabbits deprived from birth. The effects of strobe rearing on both direction and orientation selectivity decreased with increasing age at the time of onset of the deprivation. However, only direction selectivity was modified by deprivation beginning at 3 months of age.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-1106
    Keywords: Key words Cocaine ; Development ; MAP2 ; D1dopamine receptor ; Parvalbumin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Previous studies have reported that cocaine exposure in utero results in structural and functional alterations in the development of the anterior cingulate cortex (ACC). In the present study, the effects of maternal cocaine dosage and of cocaine-elicited maternal seizures on the progeny were studied. The incidence of maternal generalized tonic clonic seizures (GTCSs) elicited by cocaine was recorded. No GTCSs were elicited in pregnant rabbits by doses of 2 or 3 mg/kg of cocaine, but GTCSs were sometimes elicited by the highest dose (4 mg/kg per injection). We analyzed the offspring of cocaine-exposed and control animals using three assays of ACC development: (i) the structure of apical dendrites of pyramidal neurons, (ii) the distribution of a calcium binding protein (parvalbumin) in the dendrites of GABAergic neurons, and (iii) coupling of D1-like receptors and their G proteins. In all progeny of rabbits exposed to 3 or 4 mg/kg of cocaine during pregnancy, there was a significant change in the structure of apical dendrites, a significant increase in the number of dendrites of GABAergic neurons which were parvalbumin immunoreactive, and a significant reduction in D1/G protein coupling. In assays of apical dendrites, the effects on offspring of rabbits given 2 mg/kg cocaine were as pronounced as in offspring of rabbits given 3 or 4 mg/kg, but the effects on parvalbumin immunoreactivity and D1/G protein coupling were reduced at this low dose. Thus, previous findings of ACC developmental abnormalities in offspring of rabbits given a dose of 4 mg/kg were replicated, the effects were shown to be dose-related and to be independent of maternal seizures. A mechanism by which dysfunction of the D1receptor system could mediate cocaine-associated changes in all three parameters of ACC structure and function is discussed.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 43 (1981), S. 371-376 
    ISSN: 1432-1106
    Keywords: Eye alignment ; Corpus callosum ; Strabismus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Eye alignment was measured in cats using a technique involving projection of retinal landmarks, determination of receptive field separation in binocular units and measurement of ganglion cell density. This technique has an accuracy of 20′ of arc. Using this technique, we determined that alterations in eye alignment occur following surgical transection of the corpus callosum in cats. These changes are first observed two weeks after surgery and are still present ten months later.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  To investigate the role of sea ice cover on penguin populations we used principal component analysis to compare population variables of Adélie (Pygoscelis adeliae) and chinstrap (Pygoscelis antarctica) penguins breeding on Signy Island, South Orkney Islands with local (from direct observations) and regional (from remote sensing data) sea ice variables. Throughout the study period, the Adélie penguin population size remained stable, whereas that of chinstrap penguins decreased slightly. For neither species were there significant relationships between population size and breeding success, except for an apparent inverse density-dependent relationship between the number of Adélie breeding pairs and the number of eggs hatching. For both species, no general relationship was found between either population size or breeding success and the local sea ice conditions. However, the regional sea ice extent at a particular time prior to the start of the breeding season was related to the number of birds that arrived to breed. For both species, this period occurred before the sea ice reached its maximum extent and was slightly earlier for Adélie than for chinstrap penguins. These results suggest that sea ice conditions outside the breeding season may play an important role in penguin population processes.
    Type of Medium: Electronic Resource
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