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  • 1
    Electronic Resource
    Electronic Resource
    Zonal distribution and seasonal vertical migration of copepod assemblages in the Scotia Sea (2000)
    Springer
    Polar biology 23 (2000), S. 46-58 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Large, biomass-dominant Southern Ocean copepod species have been much studied, but small and mesopelagic species also play major rôles in these ecosystems. However, little is known of some basic aspects of their ecology. To address this, the abundances of 23 copepod species and genera were analysed from 72 stations sampled during the Discovery Expeditions in the 1920s to 1950s. Stratified net samples, usually to a depth of 1000 m, provided year-round coverage in the Scotia Sea from the Subantarctic Front to the Weddell-Scotia Confluence. Small copepods (Microcalanus pygmaeus, Ctenocalanus spp., Oncaea spp. and Oithona spp.) formed ∼75% of total copepod abundance in the top 1000 m across all major zones. Oithona spp. composed ∼40% of copepod numbers in the Polar Front area and to its south: further north their importance declined. All mesopelagic taxa except for the warmer-water species Metridia lucens and Pleuromamma robusta, extended throughout the entire study area, with smaller regional differences than for the shallower-living species. The species showed a continuum of temperature ranges, and there was no evidence that the Polar Front was a major biogeographic boundary to their distribution. Indeed, several important species, including Oithona spp. (mainly Oithona similis), Ctenocalanus spp., Metridia lucens and Rhincalanus gigas reached maximum numbers in this area. Total copepod abundance was thus higher in the vicinity of the Polar Front than in any other region. Only two copepod families made pronounced seasonal vertical migrations: Eucalaniidae (Eucalanus longiceps and R. gigas) and Calaniidae (Neocalanus tonsus, Calanoides acutus, Calanus simillimus and Calanus propinquus). Some evidence for a winter descent was found for Ctenocalanus spp. and some deeper-living groups: Euchaeta spp. and the Metridiidae, although their migrations were not so great as for the eucalanids and calanids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003000050007
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  • 2
    Electronic Resource
    Electronic Resource
    A summer-winter comparison of zooplankton in the oceanic area Around South Georgia (1988)
    Springer
    Polar biology 8 (1988), S. 463-473 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Zooplankton was sampled with RMT (1+8) gear on a synoptic grid of stations centred on South Georgia during the austral summer (November/December 1981) and winter (July/August 1983). This initial paper compares zooplankton biomass, vertical distribution and species composition from RMT 1 catches in the oceanic portion of the grid (water depth greater than 2000 m) during the two surveys. In the winter survey, mean zooplankton biomass within the top 1000 m of the water column was 68% of its summer level. This drop was largely due to a decrease in abundance of krill (Euphausia superba), although biomass of copepods and remaining zooplankton also decreased. Copepods averaged 48% of total biomass in summer and winter, but outnumbered all other taxa put together by a factor of 10. Antarctic epipelagic species predominated around the island in the summer survey but tended to be replaced by sub-Antarctic or cosmopolitan species during the winter survey. The majority of zooplankton also showed a downwards seasonal migration out of the top 250 m layer in winter. However, several epipelagic species, including E. superba, did not migrate, and these tended to have the largest summer-winter differences in overall abundance. These trends were attributed to variation in the position of the Polar Front, which lay north of the island during the summer survey but lay across the survey area in winter, resulting in a greater influence of sub-Antarctic water and the displacement of Antarctic species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00264723
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  • 3
    Electronic Resource
    Electronic Resource
    The distribution of income: Evidence, theories and policy (1996)
    Springer
    De economist 144 (1996), S. 1-21 
    Details
    ISSN: 1572-9982
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Summary This Tinbergen Lecture begins by reviewing empirical evidence about trends in income inequality in a number of Western countries. There is considerable diversity of experience across countries. The first quarter century after the Second World War was not generally characterised by a steady downward trend in inequality, but by episodes of inequality reduction at different dates. More recently, several OECD countries have seen a rise in inequality, but the rates of increase differed and in around half of the countries shown there was no significant upward trend over the 1980s. The differing experiences, and the episodic nature of changes, have implications for the explanations of inequality considered in Sections 2 and 3 of the Lecture. I begin with the mechanism which Tinbergen described in Chapter 6 of hisIncome Distribution: the race between technological development and education. It is argued that behind the supply and demand model there lie a variety of factors, and that the explanation we give may be important in determining whether what we are observing are wagedifferentials or wageinequality. Moreover, we need to consider non-labour income, and Section 3 examines the determination of state transfers and of capital income. Finally, in Section 4, I consider some of the policy implications, focusing on one particular set of policy proposals in which Jan Tinbergen was interested: the idea of a basic income.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01680258
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  • 4
    Electronic Resource
    Electronic Resource
    Diets and feeding selectivity among the epipelagic copepod community near South Georgia in summer (1994)
    Springer
    Polar biology 14 (1994), S. 551-560 
    Details
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract During the austral midsummers of 1989/1990 and 1990/1991, seven grazing experiments were undertaken near South Georgia. The copepods spanned 3 orders of magnitude in body mass, from young copepodids of small pseudocalanids to adult females of Rhincalanus gigas. Incubations were in natural sea-water and feeding rates were determined by microscope counts of food items (size range 7–1200 μm). Daily rations of the smallest copepods were up to 120% body carbon per day. These high rations contrast with values of less than 10% for large copepods (older copepodids of Calanoides acutus and R. gigas). All sizes of copepods could ingest the full size spectrum of measured particles. However, maximum filtration rates of small copepods were on cells 〈100 μm whereas the large grazers cleared the largest cells (usually long diatoms) at maximum rates. Motile, non-diatom taxa (mainly heterotrophic, aloricate dinoflagellates and ciliates) did not appear to have been eaten in preference to diatoms of similar size, but their abundance and high calorific value meant that they comprised a median of 43% of carbon intake across the experiments. These motile, mainly 〈50 μm cells were of a suitable size for ingestion by small copepods and consequently featured more prominently in their diets. The ability of small copepods to feed heavily on cells 〈50 μm, before, during or after blooms, may be important in their life cycles, leading to reduced competition with their larger relatives.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00238225
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  • 5
    Electronic Resource
    Electronic Resource
    Life cycles ofCalanoides acutus, Calanus simillimus andRhincalanus gigas (Copepoda: Calanoida) within the Scotia Sea (1991)
    Springer
    Marine biology 109 (1991), S. 79-91 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The life cycles and distribution of three dominant copepods,Calanoides acutus, Calanus simillimus andRhincalanus gigas were studied from the “Discovery” collections in the Scotia Sea earlier this century.C. simillimus is a sub-Antarctic species which mates in the top 250 m mainly in spring. The rapid development of the summer generation may allow a second mating period and a smaller second generation to appear in late summer.C. simillimus remains in the surface layers for a longer period thanCalanoides acutus orR. gigas, and its depth distribution is bimodal throughout the winter.R. gigas is most abundant in sub-Antarctic waters to the north of the Polar Front. It mates within the top 750 m later in spring, and development seems less synchronised than that of the other two species, with egg laying and the growth season being more protracted. Stages CIII and CIV are reached by the first autumn and further development resumes very early the following spring. It is not clear whether the majority then spawn or whether a further year may be needed to complete the life cycle. The predominantly Antarctic species,C. acutus mates below 750 m in middle to late winter and the summer generation develops rapidly to either CIV or CV. Its lifespan seems typically 1 yr, but some of the CVs which fail to moult and spawn in winter survive into their second summer, and their subsequent fate is uncertain. The cold-water speciesCalanus propinquus is comparatively rare in the Scotia Sea and aspects of its distribution and life cycle are briefly described for comparison. Regional variations in the timing of these events were apparent forC. simillimus and possiblyCalanoides acutus, but were not seen inR. gigas. Their geographic and vertical separation, together with their asynchronous life cycles support the concept of habitat-partitioning of these dominant herbivores.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01320234
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  • 6
    Electronic Resource
    Electronic Resource
    Feeding rates and diel vertical migration of copepods near South Georgia: comparison of shelf and oceanic sites (1992)
    Springer
    Marine biology 114 (1992), S. 49-56 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Seventeen Longhurst Hardy Plankton Recorder profiles were taken over a diel cycle in January 1990 to study the feeding of four major copepods over the South Georgia shelf. Ontogenetic changes in vertical migration were followed and feeding cycles determined by gut fluorometry for Calanoides acutus Stage CV, Calanus sinillimus CV and CVI♀, C. propinquus CV and Rhincalanus gigas CV and CVI♀. In common with a neighbouring oceanic site visited two weeks later and reported elsewhere, all four species had a diel cycle of feeding and migration. The vertical distributions of C. simillimus (all stages), R. gigas (nauplii) and Euphausia frigida (postlarvae) were similar at both sites, the night being spent within the chlorophyll maximum at 15 to 30 m. However, the biomass dominants, C. acutus and R. gigas, dwelt below the chlorophyll maximum, about 30 m deeper than their oceanic counterparts. Unlike the oceanic site, feeding at the shelf site was not restricted to darkness, but increased 6 to 10 h before nightfall and finished at dawn; the intervening period coincided with sinking and digestion. Daylight feeding may have been induced by the shorter night, lower light levels or greater food requirements at the shelf site, despite planktonic predators being over three times more abundant. Daily ration estimates for R. gigas at both sites were only ∼2% body carbon per day. These low values contrast with its smaller competirors, whose rations were in the range 5.6 to 27%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00350855
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  • 7
    Electronic Resource
    Electronic Resource
    Diel vertical migration and feeding of copepods at an oceanic site near South Georgia (1992)
    Springer
    Marine biology 113 (1992), S. 583-593 
    Details
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Twelve Longhurst Hardy Plankton Recorder (LHPR) profiles were taken over a 16 h period in January 1990, in order to study feeding of four copepod species at an Antarctic oceanic site near South Georgia. Vertical distributions of their life stages, as well as those of dominant competitors and predators, are described in relation to the feeding cycles of Calanoides acutus CV, Calanus simillimus CV, Calanus propinquus CV and Rhincalanus gigas CIII, CV and CVI♀. Comparisons with vertical ring-net catches, which were used for concomitant gutevacuation experiments, demonstrated the suitability of the LHPR for these fine-scale studies. Planktonic predators, with the exception of the diel migrant Themisto gaudichaudii, resided deeper than the herbivores. During the day and around midnight, when feeding rates were low, species and stages reached their maximum vertical separation. At these times, new generation copepodites of the four species lived progressively deeper and the overwintered generation (i.e., R. gigas Stages CIV, CV, CVI) were progressively shallower. During the afternoon or evening (depending on species), all stages older than CII, as well as Euphausia frigida and T. gaudichaudii, migrated upwards, to amass in the surface mixed layer. Feeding was restricted to darkness, although R. gigas commenced several hours before dusk. In detail their migration and feeding differed widely, with combinations of unimodal and apparent bimodal cycles. As a whole, the results suggest that (1) feeding could occur during sinking as well as during upward migrations, (2) upward migrations were not always associated with feeding increases, and (3) individuals appeared to descend after filling their guts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00349702
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  • 8
    Electronic Resource
    Electronic Resource
    The diffusion of ions through water-saturated cement (1984)
    Springer
    Journal of materials science 19 (1984), S. 3068-3078 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The interdiffusion of l− and Cl− ions and the tracer diffusion of Cs+ ions in watersaturated Ordinary Portland Cement have been measured at 30° C as a function of water/ cement ratio at fabrication. The diffusion was strongly influenced by the water/cement ratio in an approximately exponential manner and the Cs+ ions were significantly less mobile than the other ions. Diffusion measurements and electrical conductivity measurements have also been made as a function of temperature and reveal that significant irreversible changes in pore structure were induced on heating. The implications of the observations for the diffusion mechanism and the probable pore structure of the cement paste are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01026986
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  • 9
    Electronic Resource
    Electronic Resource
    Some Recent Developments in Aqueous Sol-Gel Processing (1998)
    Springer
    Journal of sol gel science and technology 13 (1998), S. 133-139 
    Details
    ISSN: 1573-4846
    Keywords: membranes ; catalysts ; pillared clays ; phosphors ; pigments ; ink-jet printing
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In this overview we describe the recent use of aqueous sol-gel processing for the preparation of ceramics that have very different end-uses. Zirconia nanofiltration membranes with 50% rejection of solutes at a molecular weight of about 1000 have been produced using zirconia sols containing inorganic polymeric “particles” and evaluated on the pilot-plant scale. Microporous alumina- and zirconia-pillared clays having a large and hydrothermally stable interlayer spacing (2 nm) and specific surface area (approximately 400 m2 g−1) have been prepared using similar polymeric sols. These have been produced on the 20 kg scale and evaluated for catalytic applications. Cathodoluminescent phosphor powders, based on the doped-yttrium aluminium gallium oxide system, have been synthesized for high resolution displays using a combination of aqueous sol-gel precursors and aerosol techniques to produce particles of controlled size and shape. Finally, ceramic stains for decorating ceramic bodies have been synthesized using this method, not only in powder form but also for direct application to ceramic ware by ink-jet printing. These examples illustrate the versatility of aqueous sol-gel processing for the preparation of a wide range of ceramic compositions and forms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008675927144
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  • 10
    Electronic Resource
    Electronic Resource
    Variability of Stress in Alumina Corrosion Layers Formed in Thermal-Barrier Coatings (2000)
    Springer
    Oxidation of metals 54 (2000), S. 371-384 
    Details
    ISSN: 1573-4889
    Keywords: thermal barrier ; stress ; alumina ; mapping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Residual stress distributions have been measured and mapped usingphotoluminescence, piezo spectroscopy in thermally grown alumina oxides(TGO) formed on platinum-aluminide bond coats with thermal-barrier coatings(TBC) of thickness 0, 3, and 200 μm. When there is a 3-μm TBC or noTBC, the residual stress varies substantially with position and the meanstress is much lower than expected from simple thermoelastic, plane-stressanalysis. This is partly explained by the stress being relaxed by surfaceroughness, but stress mapping indicates that local fracture hasoccurred. The stress in the TGO formed under 200 μm TBCs appear muchmore uniform and the mean value is approximately equal to the estimatedthermoelastic plane stress. This could be due to the extra constraintimposed by the TBC. The luminescence line width is much greater forspecimens with 200-μm TBC and is too large to be explained by varyingmacroscopic stresses due to interface roughness. The effects of oxidationtime and reactive-element additions to the substrate at the level of30 ppm, on the residual stress, are relatively minor over the rangesexplored in these experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004613332338
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