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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Decisions in economics and finance 13 (1990), S. 111-131 
    ISSN: 1129-6569
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Description / Table of Contents: Riassunto Si considera una versione modificata del modello di crescita non-lineare di Goodwin, in cui il reddito,Y, è una funzione quadratica dello stock di capitale,k, così da permettere la possibilità di rendimenti crescenti o decrescenti. La dinamica del modello viene allora rappresentata da un sistema non autonomo di due equazioni differenziali. Con l'ipotesi che l'offerta di lavoro,N, e la produttività,a, siano costanti nel tempo, il modello diventa autonomo e può essere immerso in una famiglia stabile di sistemi dinamici piani, di cui vengono descritti i flussi globali e le biforcazioni.
    Notes: Abstract We consider a modified version of Goodwin's celebrated non-linear model of fluctuating growth, where the incomeY is a quadratic function of the capital stockk, in order to take into account the possibility of increasing or decreasing returns. The dynamics of the model is then defined by a non-autonomous system of two differential equations. Assuming the labour supply,N, and the productivity,a, to be constant in the time, the model becomes autonomous and can be embedded in a stable family of planar dynamical systems whose flows and bifurcations are globally described
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Decisions in economics and finance 13 (1990), S. 133-145 
    ISSN: 1129-6569
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Description / Table of Contents: Riassunto Un modello non-lineare di crescita alla Goodwin, in cui i rendimenti possono essere non costanti, è rappresentato da un sistema dinamico piano non autonomo, che può essere trasformato in un sistema autonomo tridimensionale. Viene descritto il comportamento globale di quest'ultimo nei due casi di rendimenti crescenti o decrescenti. Si dimostra, in particolare, l'assenza di attrattori economicamente significativi ed il diverso carattere delle orbite: mentre, se i rendimenti sono crescenti, le traiettorie convergono asintoticamente ad un punto singolare dove “l'economia muore”, nel caso opposto le traiettorie sono illimitate e spiraleggiano intomo ad una retta che ha la direzione dell'assek (la variabile di stato che rappresenta lo stock di capitale).
    Notes: Abstract The dynamics of a model of fluctuating growth, where non-constant returns are allowed, is represented, under Goodwin's classical assumptions, by a non-autonomous two-dimensional system, which can be transformed into an autonomous three-dimensional one. We describe the global phase portrait of the latter, in the two cases of increasing and decreasing returns, proving, in particular, the absence of economically meaningful “attractors”. However the orbits exhibit different features in the two cases: namely they asymptotically converge to a singular point, where “the economy dies”, if the returns are decreasing, and diverge, spiralling around a certain line, if the returns are increasing.
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  • 3
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Banking and Finance 14 (1990), S. 199-214 
    ISSN: 0378-4266
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Economics
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of applied ichthyology 14 (1998), S. 0 
    ISSN: 1439-0426
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Many occasions arise in fish culture in which it is desirable to enhance the immune response. These include strengthening the normal immune response in order to enhance protection and reduce immunosuppressive conditions. Several categories of immunostimulators can be classified by their origin and mode of action: (I) bacteria and bacterial products; (2) complex carbohydrates; (3) vaccines (‘paramunity inducer’); (4) immu-noenhancing drugs; (5) nutritional factors; (6) animal extracts; (7) cytokines; (8) lectins, plant extracts. In this paper, the importance of many immunostimulatory substances and their effects on fish immune systems are discussed. Two main procedures for evaluating the efficiency of an immunostimulant are: (a) ‘in vivo’, e.g. protection tests against fish pathogens; (b) ‘in vitro’, e.g. measurement of the efficiency of cellular and humoral immune mechanisms; the efficiency of these different evaluation methods is discussed. Attention is focused on the lymphocyte proliferation test as an adequate method for providing a correct evaluation of cellular immune conditions which can be adapted together with the more commonly used parameters, such as phagocytosis and respiratory burst. The use of immunostimulants in the diets of marine fish and the evaluation of their effect on the immune system of fish are also discussed.
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  • 5
    ISSN: 1365-2761
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Photobacterium damsela ssp. piscicida (Phdp) isolates were grown in various bacteriological media, in eukaryotic cell culture media and in the presence of fish cells (resembling some aspects of in vivo growth environments). Bacterial cells, extracellular products (ECPs) and crude capsular polysaccharide were isolated and analysed by electrophoresis and Western blot using sea bass sera. Growth in bacteriological media conserved the synthesis of cell and extracellular components when these were compared with those prepared under near-in vivo growth conditions. In fact, synthesis of a larger range of cell components was induced after growth in bacteriological media. Certain media based on yeast extract and peptones from various sources and a specific salt formulation induced the synthesis of novel cell components at approximately 21.3 and 14 kDa. These antigens were recognized by sea bass sera collected after natural pasteurellosis outbreaks and other sea bass sera raised against live or inactivated Phdp cells. The ECPs of the pathogen were not good immunogens in their soluble form despite various treatments prior to immunization. The results are discussed with respect to vaccine development.
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  • 6
    ISSN: 1365-2761
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Bacterial cells of the marine fish pathogen Photobacterium damsela subsp. piscicida were grown in novel culture media. A mixture of whole cells and extracellular components was inactivated and used in bath, intraperitoneal (i.p.) and oral vaccination of sea bass, Dicentrarchus labrax, employing two sizes of fish. A commercial vaccine was used for comparative purposes. Control and immunized fish were either bath or intraperitoneally challenged 6 and 12 weeks post-vaccination. Small fish had significantly higher relative percentage survival with the novel vaccine mixture both at 6 and 12 weeks post-vaccination by bath, in comparison with the commercial vaccine. No protection was afforded at 6 or 12 weeks post-immunization by either vaccine after challenge via i.p. injection. Sea bass (1.5–2 g) intraperitoneally vaccinated with various adjuvanted vaccine mixtures were not protected against pasteurellosis. In contrast, larger sea bass (20 g) benefited from vaccination with the novel vaccine mixtures. Intraperitoneal challenge with the pathogen resulted in protection in both fish groups vaccinated with novel vaccine mixtures, whereas control fish suffered high mortalities (〉80%). Orally vaccinated fish were immersion challenged with the pathogen. At 6 and 12 weeks post-vaccination the control fish had a high mortality and the fish vaccinated with the novel vaccine mixture achieved good protection.
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  • 7
    ISSN: 1365-2761
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Photobacterium damsela subsp. piscicida, the causative agent of fish pasteurellosis, was grown in vivo. Bacterial cells and extracellular products (ECPs) were analysed via electrophoresis and immunoblot analysis, using specific sea bass antisera. Growth in vivo induced the synthesis of unique bacterial cell proteins at 〉206, 206, 21.3, 18, 7.6 and 〈7.6 kDa. Sea bass serum raised against live bacterial cells of the pathogen and especially a sea bass serum raised against formalin-inactivated bacterial cells grown in a specific novel medium recognized the novel antigens at 〉206 (associated with iron sequestration), 21.3, 7.6 and 〈7.6 kDa, suggesting that the latter medium conserves the synthesis of natural bacterial cell proteins in vitro. In vivo growth of the pathogen induced the synthesis of more toxic ECPs in comparison with in vitro growth and an inverse correlation between total protein concentration in the ECPs and toxicity per unit of protein was observed. Substrate-polyacrylamide electrophoresis revealed the presence of in vivo synthesized ECPs of the pathogen (proteases) at 175, 132, 〈79 and 48.3 kDa. Histological examination of tissues isolated from fish injected with these ECPs revealed inflammatory and necrotic lesions in the spleen, liver, head kidney, intestine and heart as soon as 48 h post-introduction of the ECPs.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Metroeconomica 40 (1989), S. 0 
    ISSN: 1467-999X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Economics
    Notes: We study three different versions of the Kaldor's 1940 Business-Cycle Model (13, and we show that they can all be reduced, through suitable changes of variables, to a planar dynamical system of Lienard-type.By applying a classical result due to A. Filippov (8) and a quite recent theorem of the Chinese mathematician Zhang Zhi Fen (19, it is easily proved that our systems present a unique attracting limit-cycle encircling the only existing equilibrium.Our analysis does not require any extra hypothesis regarding the symmetry of the investment and saving functions, except the «classical» ones and those needed to reducing the system to Lienard form.It extends, so far, a few previous results obtained by H.W. Lorenz (16) on the very same model.
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  • 9
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Metroeconomica 38 (1986), S. 0 
    ISSN: 1467-999X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Economics
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Economic Dynamics and Control 10 (1986), S. 205-212 
    ISSN: 0165-1889
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Economics
    Type of Medium: Electronic Resource
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