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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 2 (1972), S. 0 
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The properties of waves on a lake surface and the influence of water depth on these properties are discussed.The method, derived by the Beach Erosion Board, of predicting wave characteristics if the wind speed and fetch are known is outlined and the validity of the method in Loch Leven, Scotland, is confirmed.This prediction technique is then combined with the equations of classical hydrodynamics to form a method of assessing the nature and extent of wave action in lakes without direct measurement. The value of the ratio of the wave-mixed volume to the total lake volume as a meausre of hydraulic conditions in lakes is suggested.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 12 (1982), S. 0 
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY. A model describing the deposition of algae in a turbulent environment is outlined, it being assumed that all algae falling on the bed are trapped there forever. Its main features are that, above a certain threshold of turbulence the rate of deposition is independent of the turbulent intensity, and the rate of algal loss by sedimentation, in such conditions, is described by a first order kinetic equation. The hydraulic conditions under which algae settle at their intrinsic, still-water rate and those for which the model is applicable, are examined. Some ecological implications of the model are discussed.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 9 (1979), S. 0 
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: SUMMARY. The paper considers the forms of water movement that occur in unstratified lakes. Although not dealing directly with ecological implications, it is hoped that it will encourage the inclusion of observations of underwater weather as part of normal limnological routine. It is particularly concerned to show what observations are most effective in revealing hydraulic conditions.Relations between wind, lake geometry and wave characteristics are examined. Factors determining the steady, wind-driven circulation are reviewed and examined in sequence: the action of wind on a water surface and the current directly generated by the wind drag; the effect of the earth's rotation; the need to balance the flow in and out of any part of the lake; the influence of lake morphometry. A simple model of lake circulation is developed that may help in the interpretation of on-lake observations. Some other features of isothermal motion are discussed including the horizontal currents associated with unsteady wind conditions (seiches).The possible interaction between waves and currents are discussed. A tentative classification of hydraulic conditions in terms of wind speed, lake depth and fetch is suggested as a basis for forming hypotheses about the motion prior to on-lake observations and as a possible starting point for a comparative approach.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: In a 2-year grow-out trial, triploid Sydney rock oysters, Saccostrea commercialis (Iredale & Roughley), from two initial size grades grew faster (in terms of both mean whole weight and shell height) than the equivalent initial size grades of sibling diploids (P 〈 0.05). Small size grade triploids caught up with and had significantly heavier (P 〈 0.05) final whole weights than large size grade diploids after a 2-years grow-out period. The initial size grade had a significant effect on final mean whole weight and shell height for both ploidy types. After the 2-years grow-out trial, the final mean whole weights (but not shell heights) of small and large diploids (35.8 ± 0.6 g and 39.4 ± 0.5 g, respectively) were significantly different (P 〈 0.05). Small and large triploids grew at a similar rate for the first 18 months despite the significantly (P 〈 0.05) heavier final mean weight of large grade triploids (48.4 ± 0.8 g and 61.2 ± 0.7 g, respectively). The effect of the initial size grade on subsequent growth of both diploid and triploid oysters which was demonstrated in the present study is of significant commercial value to hatchery and nursery operators as well as growers of single seed oysters. In addition, small-grade triploids appeared to be more valuable in terms of potential growth rate than all diploid grades. There was no significant difference in the final percentage triploidy between small and large grade triploids. A large proportion of diploid/triploid mosaicism was detected in adult oysters.
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Aquaculture research 18 (1987), S. 0 
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract. These analyses of the tilapia fingerling industry in the Philippines focus on the economics of production in different hatchery systems and on fingerling marketing channels. The analyses are based on cross-sectional data from government and private hatcheries in late 1982 and from December 1983 to March 1984.The relative profitabilities of different hatchery systems (land-based and lake-based) are estimated and economies of scale are analysed. Conceptual and methodological issues inherent in analyses based on cross-sectional data are discussed in the context of the extreme difficult standardizing inputs and output from private tilapia hatcheries which are characterized by wide variation in management practices.
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Aquaculture research 31 (2000), S. 0 
    ISSN: 1365-2109
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: In 1990, NSW Fisheries initiated a mass selection programme in Port Stephens, NSW, with the aim of breeding faster growing Sydney rock oysters Saccostrea glomerata (Gould 1850). After two generations of selection, an average weight for age advantage of 18% (range 14–23% per breeding line) was achieved. This equates to a reduction of 3 months in the time taken to reach market size. Experiments are planned to determine how much of this 3 months advantage is additive to the 6 months advantage this laboratory has already obtained using triploid S. glomerata. A parallel set of S. glomerata breeding lines was established on the Georges River, NSW, to include selection for resistance to the protistan parasite Mikrocytos roughleyi, the causal agent of winter mortality. The programme was disrupted by the outbreak of QX disease Marteilia sydneyi, another protistan parasite, in 1994. In 1997, the breeding programme was reorganized and expanded. New lines were bred from oysters that had survived both QX and winter mortality. After one generation, a small improvement in resistance to QX has been recorded; however, the exposure of further generations to M. sydneyi will be required to confirm an increase in resistance.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of fish diseases 10 (1987), S. 0 
    ISSN: 1365-2761
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Abstract. Epidermal papillomas affect white suckers, Catostomus commersoni (Lacepede), from various areas of the Great Lakes of North America, particularly regions receiving industrial pollution. Three morphologically distinct but histologically similar papillomas were found on a group of fish from a polluted site. The diameter of focal soft-skin plaques, focal hard-skin papillomas and focal lip tumours was monitored on individual fish before and after a 12–week observation period in our laboratory. Many papillomas disappeared completely, while others persisted. Individually lip tumours had a lesser frequency of regression (22%), compared to skin plaques (79%) or papillomas (64%). Papillomas which persisted had only slightly smaller diameters after 12 weeks. New tumours developed on 23 and 60% of the survivors in two separate groups. The development of tumours in the laboratory suggests a cause unrelated to the environmental pollution which is correlated with papilloma incidences in wild white suckers. The behaviour of white sucker papillomas under laboratory conditions contrasts with the persistence and often enlargement of similar papillomas reported for other poikilothermic species.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1365-2761
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Abstract. White sucker, Catostomus commersoni (Lacépède), and brown bullhead, Ictalurus nebulosus (Lesueur), populations throughout the Great Lakes examined for evidence of pollution associated neoplasia exhibited a variety of morphologically distinct skin lesions. Three types of skin lesions affected white suckers: (a) focal on the lips, (b) discrete on the body, or (c) raised mucoid focal lesions on the skin and fins. Histologically, all three types featured a continuum between mild epidermal hyperplasia and benign papillomata. Brown bullheads exhibited a single variably shaped raised lesion on all body surfaces and within the oral cavity in addition to focal lip lesions. All bullhead lesions exhibited a continuum between mild epithelial hyperplasia and papillomata. Some skin lesions in both species were invasive but most abnormalities represented some stage in the development of epidermal papillomas. These papillomas superficially resemble papillomas common in many fish species and which are associated with viruses, but sucker and bullhead papillomas exhibit a unique range of histopathological and gross morphological appearances. The high prevalence of these papillomas, affecting up to 60% of some populations in polluted areas, supports the possibility that carcinogenic chemicals in the sediments are influencing papilloma development.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 287 (1980), S. 580-582 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] A recent conference* showed that new types of scanning microscope which promise unique imaging capabilities are rapidly being developed. As well as improved optical microscopes, X rays and acoustic waves are being used for high resolution scanned imaging and energy conversion techniques are ...
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of nondestructive evaluation 2 (1981), S. 203-207 
    ISSN: 1573-4862
    Keywords: ultrasonics ; synthetic aperture ; spatial frequency ; interior imaging ; acoustic microscopy ; defect detection ; NDE
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mathematics
    Notes: Abstract A new acoustic synthetic aperture geometry is demonstrated in which the image field is sampled in the spatial frequency domain. This means the sampled field is recorded in a particularly convenient form for presentation to the back propagation algorithms used to reconstruct the field at the object plane. The method has applications in interior visualization. It is difficult to image the interior of solid objects using lens based imaging systems because a different lens geometry must be used for each distinct object material. The system presented here overcomes such problems since both the angular variation of the transmission coefficient at the object-water interface and the aberrations introduced by the velocity mismatch at the object surface may be readily compensated for in the back propagation routine. Experimental results are presented illustrating the detection of four half wavelength diameter defects, spaced by three wavelengths, at a depth of eight wavelengths below the surface of an aluminum block.
    Type of Medium: Electronic Resource
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