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  • Rat  (826)
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  • growth  (687)
  • stability
  • Springer  (2.965)
  • Frontiers Media SA  (4)
  • Taylor & Francis  (4)
  • Institut de recherche sur l’Asie du Sud-Est contemporaine  (2)
  • Annapolis, MD
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  • MDPI Publishing
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  • 1
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    A review of the biology, ecology and management of Scirpus Olneyi. Volume 1: An annotated bibliography of selected references (2021)
    Maryland Department of Natural Resources, Water Resources Administration, Wetlands Permit Section | Annapolis, MD
    In:  http://aquaticcommons.org/id/eprint/3736 | 130 | 2015-04-28 20:49:02 | 3736
    Details
    Publikationsdatum: 2021-06-29
    Beschreibung: This annotated bibliography of selected literature on Olney's three7square (Scirpus olneyi Gray )compiled basically for two reasons: 1) to assist a task force in its pursuit of an explanation for the substantial reduction in marsh acreage at the Blackwater National Wildlife Refuge in Dorchester County, Maryland, and 2) to serve as the author's foundation for the initiation of ecological research on this species as partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Botany Department of the University of Maryland. Both purposes are directly related in that the Author's research will be of use to the task force, along I with its other technical information and research results, in under-standing and possibly correcting the marshland loss problem at the Refuge. (PDF contains 100 pages)
    Schlagwort(e): Ecology ; Management ; Blackwater National Wildlife Refuge ; Dorchester County ; Maryland ; anatomy ; distribution ; ecology ; genetics ; growth ; development ; management ; morphology ; ontogeny ; reproduction ; soil
    Repository-Name: AquaDocs
    Materialart: monograph
    Format: application/pdf
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    Standort Signatur Erwartet Verfügbarkeit
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    ARTIKEL (OA)
  • 2
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    Physiological Adaptations to Swimming in Fish (2021)
    Frontiers Media SA
    Details
    Publikationsdatum: 2024-03-31
    Beschreibung: Swimming is an integral part of the life history of many fish species as is intimately linked with their ability to express feeding and predator avoidance behaviors, habitat selection and environmental preferences, social and reproductive behaviors as well as migratory behaviors. Therefore, swimming is an important determinant factor of fitness in a true Darwinian sense and, not surprisingly, swimming performance has been often used as a measure of physiological fitness in fish. The main aim of this Research Topic is to showcase some of the current studies designed to improve our understanding of the physiological energetic and metabolic requirements of swimming and of the adaptive responses to swimming in fish.
    Schlagwort(e): QP1-981 ; GC1-1581 ; Q1-390 ; swimming economy ; performance ; fish ; swimming exercise ; growth ; thema EDItEUR::M Medicine and Nursing::MF Pre-clinical medicine: basic sciences::MFG Physiology
    Sprache: Englisch
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    E-BOOK
  • 3
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    Tropical Forest Ecosystem Responses to Increasing Nutrient Availability (2021)
    Frontiers Media SA
    Details
    Publikationsdatum: 2022-01-31
    Beschreibung: Deforestation and land use change have led to a strong reduction of tropical forest cover during the last decades. Climate change will amplify the pressure to the remaining refuges in the next years. In addition, tropical regions are facing increasing atmospheric inputs of nutrients, which will have unknown consequences for the structure and functioning of these systems, no matter if they are within protected areas or not. Even remote areas are expected to receive rising amounts of nutrients. The effects of higher rates of atmospheric nutrient deposition on the biological diversity and ecosystem functioning of tropical ecosystems are poorly understood and our knowledge of nutrient fluxes and nutrient limitation in tropical forest ecosystems is still limited. Yet, it will be of paramount importance to know the effects of increased nutrient availability to conserve these ecosystems with their biological and functional diversity. During the last years, research efforts have more and more focused on the understanding of the role of nutrients in tropical ecosystems and several coordinated projects have been established that study the effects of experimental nutrient addition. This Research Topic combines results from experiments and from observational studies with the aim to review and conclude on our current knowledge on the role of additional nutrients in ecosystems.
    Schlagwort(e): GB3-5030 ; Q1-390 ; experimental nutrient manipulation ; global change ; nitrogen ; CO2 ; nutrient limitation ; foliar nutrients ; biogeochemical cycles ; wood anatomy ; phosphorus
    Sprache: Englisch
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    E-BOOK
  • 4
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    Implications of the Euro (2021)
    Taylor & Francis
    Details
    Publikationsdatum: 2024-03-29
    Beschreibung: To date, critical analysis of the EMU project has largely been advanced from the centre-right spectrum of British politics. Comparable questions from the centre-left have failed to find a coherent voice. Although, the European fault-line cannot be characterized as a neat Left-Right issue there are noticeable divisions in opinion across British business, the trade union movement and within the Labour Party. Offering a unique insight into this key debate from the ‘centre-left’, eurosceptic view point, this book provides a rigorous analysis of all the salient economic and political issues of concern, such as: * the economics of a single currency * employment and social implications * sovereignty * political determination. The arguments presented in this volume highlight the emergence of a coherent alternative to deepening economic integration as a platform to build a just and equitable society. Contributions are drawn from leading academics, trade union leaders and prominent politicians, both from the Labour Party and the wider progressive Left in British politics. This informative and thought provoking book will be indispensable reading for students and practitioners in economics, politics and international relations, as well as those interested in this highly contentious topic.
    Schlagwort(e): single ; currency ; european ; union ; central ; bank ; exchange ; rate ; growth ; stability ; thema EDItEUR::J Society and Social Sciences::JP Politics and government::JPQ Central / national / federal government::JPQB Central / national / federal government policies ; thema EDItEUR::K Economics, Finance, Business and Management::KC Economics ; thema EDItEUR::K Economics, Finance, Business and Management::KC Economics::KCB Macroeconomics::KCBM Monetary economics ; thema EDItEUR::K Economics, Finance, Business and Management::KC Economics::KCL International economics ; thema EDItEUR::K Economics, Finance, Business and Management::KJ Business and Management ; thema EDItEUR::J Society and Social Sciences::JP Politics and government::JPQ Central / national / federal government::JPQB Central / national / federal government policies ; thema EDItEUR::K Economics, Finance, Business and Management::KC Economics ; thema EDItEUR::K Economics, Finance, Business and Management::KC Economics::KCB Macroeconomics::KCBM Monetary economics ; thema EDItEUR::K Economics, Finance, Business and Management::KC Economics::KCL International economics ; thema EDItEUR::K Economics, Finance, Business and Management::KJ Business and Management
    Sprache: Englisch
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    E-BOOK
  • 5
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    Energy, Wealth and Governance in the Caucasus and Central Asia (2021)
    Taylor & Francis
    Details
    Publikationsdatum: 2024-03-28
    Beschreibung: Drawing upon recent progress in development economics and political science, the book provides fresh analysis of the Caucasus and Central Asia (CCA) countries transition to a market economy by tracing the impact of natural resource endowment. The book examines the synergies between energy-rich and energy-poor states and highlights the practical consequences of both well-managed and poorly-managed deployment of energy. Featuring contributions from prominent specialists on resource-driven economies, the book argues that unless CCA elites change the way in which they deploy natural resource, revenues regional development will fall short of its potential with possible disastrous consequences. The contributors apply the experience of the developing market economies to demonstrate that the region still holds considerable potential to become an important, stable supplier of raw materials and a source of industrial demand to the global economy. However, the CCA is equally likely to become a threat to the global economy as a consequence of the misuse of energy revenues to promote the interests of predatory political elites.
    Schlagwort(e): cca ; region ; resource ; poor ; countries ; growth ; collapse ; rent ; caspian ; sea ; thema EDItEUR::G Reference, Information and Interdisciplinary subjects::GT Interdisciplinary studies::GTM Regional / International studies ; thema EDItEUR::J Society and Social Sciences::JB Society and culture: general::JBS Social groups, communities and identities::JBSL Ethnic studies ; thema EDItEUR::J Society and Social Sciences::JP Politics and government ; thema EDItEUR::G Reference, Information and Interdisciplinary subjects::GT Interdisciplinary studies::GTM Regional / International studies ; thema EDItEUR::J Society and Social Sciences::JB Society and culture: general::JBS Social groups, communities and identities::JBSL Ethnic studies ; thema EDItEUR::J Society and Social Sciences::JP Politics and government
    Sprache: Englisch
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    E-BOOK
  • 6
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    Novel Aspects of Nucleolar Functions in Plant Growth and Development (2021)
    Frontiers Media SA
    Details
    Publikationsdatum: 2024-04-05
    Beschreibung: The nucleolus is a prominent nuclear domain that is common to eukaryotes. Since the nucleolus was first described in the 1830s, its identity had remained a mystery for longer than 100 years. Major advances in understanding of the nucleolus were achieved through electron microscopic and biochemical studies in the 1960s to 1970s followed by molecular biological studies. These studies finally established the view of the nucleolus that it is a large aggregate of RNA-protein complexes associated with the rRNA gene region of chromosome DNA, serving mainly as a site of ribosome biogenesis, where pre-rRNA transcription, pre-rRNA processing, and ribosome assembly occur. This function of the nucleolus appears to indicate that the nucleolus plays a constitutive and essential role in fundamental cellular activities by producing ribosomes. Recent research has shown, however, that the nucleolus is more dynamic and can have more specific and wider functions. In plants, nucleolar functions have been implicated in developmental regulations and environmental responses by accumulating pieces of evidence obtained mostly from genetic studies of nucleolar factor-related mutants. Comprehensive analysis of nucleolar proteins and molecular cytological characterization of sub-nucleolar and peri-nucelolar bodies have also provided new insights into behaviors and functions of the plant nucleolus.〈/p〉In this Research Topic, we would like to collect physiological and molecular links between the nucleolus to plant growth and development, shed light on novel aspects of nucleolar functions beyond its classical view, and stimulate research activities focusing on the nucleolus across various fields of plant science, including molecular biology, cell biology, genetics, developmental biology, physiology, and evolutionary biology.
    Schlagwort(e): QK1-989 ; Q1-390 ; environmental response ; development ; plant ; nucleolus ; growth ; ribosome biogenesis ; thema EDItEUR::P Mathematics and Science::PS Biology, life sciences::PST Botany and plant sciences
    Sprache: Englisch
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    Standort Signatur Erwartet Verfügbarkeit
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    E-BOOK
  • 7
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    Norms and Practices in Contemporary Rural Vietnam : Social Interactions between Authorities and People (2021)
    Institut de recherche sur l’Asie du Sud-Est contemporaine
    Details
    Publikationsdatum: 2022-01-31
    Beschreibung: Since the 1980s, while trying to maintain political stability and territorial integrity, the Vietnamese state has strongly moved towards the transformation of a centrally-planned economy to a more market-oriented model, in which private, foreign and joint-venture businesses are increasingly becoming the key pillars of the national economy. Another key aspect of the Đổi Mới's agenda was a fundamental shift in the party-state's foreign relations policy toward a normalization of Vietnam's diplomatic and trading relations with China, the United States, and other countries since the early 1990s. Over twenty years after the Đổi Mới renewal renovation, Vietnam has been praised by various domestic and international institutions for its “impressive” achievements in socio-economic development and poverty reduction and for its gradual liberalization and market diversification, coupled with its commitment to equality. Consequently, this has changed the relationship between the party-state and society in a number of fields, including the control of agricultural land and other forms of natural resources. Such transition marks a great change in our scholarly understanding of Vietnam. It has opened the door for intellectual exchange between academics and has resulted in a great amount of research and new knowledge/publications in different languages about various domains regarding Vietnamese society, including the relationships between the state and society at different levels and in various sectors or geographic areas. Among them, studies like those of Kerkvliet, Fforde and others, have developed the “everyday politics approach”, which examines social interactions on an everyday action basis. This approach “from below” has given a fresh impetus to the study of social relations in Vietnam. However, our observations regarding academic research show that besides a number of rich ethnographic studies, there are many analyses from different social science disciplines that give a generalized view of trends of development and change in Vietnamese society over the past decades with limited field data. This means that research projects based on first-hand data from longer periods of fieldwork and qualitative investigations are still inadequate. As a result, we are suggesting that more field-based research be carried out in order to enhance and promote our understanding of Vietnam, especially its processes of socio-political changes.
    Schlagwort(e): JA1-92 ; economics ; development ; tourism ; growth ; land conflicts ; industrialization
    Sprache: Englisch
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    E-BOOK
  • 8
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    Economic and Social Transformation in China (2021)
    Taylor & Francis
    Details
    Publikationsdatum: 2023-09-12
    Beschreibung: The Center for China Studies is among China’s most influential think-tanks, and its China Studies Reports are read at the highest levels of government. Now for the first time, the most important of these reports is collected in book form in Eng, providing a fascinating insight into the challenges and opportunities for Chinese development and the government’s thinking on economic and social issues. Including comparative studies with developed and developing nations, analysis of past economic performance and future trends, and effects of demographic shifts such as population ageing and urbanization, this book is an essential collection of research and includes notes made by central party leaders. Compiled by the founder of the Center for China Studies, one of the country’s leading economists, this book is key to understanding Chinese development and the likely future path of government policy.
    Schlagwort(e): guojia ; tongjiju ; zhongguo ; tongji ; chubanshe ; chinas ; growth ; statistics ; press ; deng ; bic Book Industry Communication::G Reference, information & interdisciplinary subjects::GT Interdisciplinary studies::GTB Regional studies ; bic Book Industry Communication::J Society & social sciences::JF Society & culture: general::JFS Social groups::JFSL Ethnic studies ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics ; bic Book Industry Communication::K Economics, finance, business & management::KC Economics::KCP Political economy
    Sprache: Englisch
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    E-BOOK
  • 9
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    Le Viêt Nam dans l’Organisation mondiale du commerce : Impact sur la croissance et l’emploi (2021)
    Institut de recherche sur l’Asie du Sud-Est contemporaine
    Details
    Publikationsdatum: 2023-12-20
    Beschreibung: Le Viêt Nam est devenu en janvier 2007 le 150e membre de l’OMC (Organisation mondiale du commerce). Depuis le lancement du « Doi Moi » (Renouveau) intervenu fin 1986, ce pays connaît une croissance économique très rapide, parmi les plus élevées du monde. Le processus d’intégration accélérée du Viêt Nam à l’économie mondiale après plusieurs décennies de guerre et d’isolement, dont l’adhésion à l’OMC représente une étape supplémentaire, joue un rôle majeur dans le développement du pays. Grâce à la croissance, la pauvreté a reculé très rapidement. Même si le Viêt Nam fait partie des pays en développement les moins inégalitaires selon les comparaisons internationales, les inégalités sociales sont en augmentation depuis le début du processus d’ouverture. En quoi l’adhésion du Viêt Nam à l’OMC, qui intervient peu après celle de la Chine (2001), est-elle susceptible d’influer sur le sentier de croissance de l’économie vietnamienne et sur son intégration à l’économie mondiale ? Quel peut être son impact sur l’emploi et sur le processus de restructuration de la population active ? Au-delà, quel impact sur les inégalités et la pauvreté ? Toutes ces questions sont au cœur des débats de politique économique au Viêt Nam. La Table ronde consacrée à « L’adhésion du Viêt Nam à l’OMC ; l’impact sur la croissance et l’emploi », co-organisée en janvier 2008 par l’Ambassade de France au Viêt Nam et l’Académie des Sciences Sociales du Viêt Nam dans le cadre du Fonds de Solidarité Prioritaire (FSP) en Sciences sociales, cherchait à apporter des premiers éléments de réponse à ces questions un an après l’adhésion du pays à l’OMC. Cette synthèse comprend les quatre articles présentés par des chercheurs vietnamiens et français lors de cette Table ronde. Pour enrichir l’analyse, les éléments de réflexion apportés par les deux discutants des communications lors de la Table ronde sont également publiés.
    Schlagwort(e): JA1-92 ; Industry ; Economy ; WTO ; norms ; openness ; socialism ; growth ; services ; economic transition ; industrialization ; international organizations ; bic Book Industry Communication::G Reference, information & interdisciplinary subjects::GT Interdisciplinary studies::GTJ Peace studies & conflict resolution
    Sprache: Französisch
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    E-BOOK
  • 10
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    Optimizing Miscanthus for the Sustainable Bioeconomy: From Genes to Products (2021)
    Frontiers Media SA
    Details
    Publikationsdatum: 2024-04-05
    Beschreibung: In this Research Topic we report advances in fundamental and applied aspects of the perennial C4 bioenergy crop Miscanthus (Miscanthus spp.) and its role in mitigating climate change as part of the bioeconomy. Miscanthus is extremely well suited for bioenergy, biofuel and bioproduct production over a wide geographic area including Europe and North America as well as its native Asia. 〈/p〉〈p〉Miscanthus offers a unique perspective within plant science: the challenge is to domesticate this novel crop for diverse environments and uses while simultaneously developing sustainable value chains to displace fossil fuels and contribute to climate change mitigation. Contributions to this Research Topic were offered from leading Miscanthus researchers from different parts of the world. We accepted 16 articles from 95 authors, which have generated 21,161 views at March 26 2018. Nine of the articles are the output of the European FP7 OPTIMISC project and describe multiple experiments investigating a common set of Miscanthus genotypes in Europe and Asia. These papers are complemented by seven additional articles from global authors, providing a comprehensive analysis of the state of the art of Miscanthus research and application.
    Schlagwort(e): QK1-989 ; Q1-390 ; salt-tolerance ; bioeconomy ; phyto-remediation ; nitrogen ; perennial C4 grass ; biomass quality ; miscanthus ; LCA ; thema EDItEUR::P Mathematics and Science::PS Biology, life sciences::PST Botany and plant sciences
    Sprache: Englisch
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    Standort Signatur Erwartet Verfügbarkeit
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    E-BOOK
  • 11
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    Urban Design Futures (2021)
    Taylor & Francis
    Details
    Publikationsdatum: 2024-04-11
    Beschreibung: The last decade has seen the rise of urban design which has taken a central position in the new agendas for urban regeneration and renaissance. Urban design has moved from marginality to mainstream. The principles espoused by urban designers over the past thirty years are now accepted as key to a better urban environment and as we move towards greater sustainability, different ideas are emerging that are challenging some of the accepted urban design norms; urban design is at a watershed. Urban Design Futures presents essays from an international cast of authors to review progress and explore emerging ideas: should urban design reflect the future rather than recreate the past? What are the new driving forces that will shape urban living and hence urban design in the future? This book explores new concepts and points the way towards a series of urban design paradigms for the twenty-first century.
    Schlagwort(e): public ; realm ; space ; lan ; kwai ; fong ; corbusier ; smart ; growth ; renaissance ; thema EDItEUR::A The Arts::AM Architecture ; thema EDItEUR::A The Arts::AM Architecture::AMV Landscape architecture and design ; thema EDItEUR::J Society and Social Sciences::JB Society and culture: general::JBS Social groups, communities and identities::JBSD Urban communities
    Sprache: Englisch
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    E-BOOK
  • 12
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    Editorial: Flank dynamics, sector collapses, lahars, and rockfalls: analysis, monitoring, and modelling of small to large scale volcanic slope instability (2020)
    Springer
    Details
    Publikationsdatum: 2020-11-12
    Beschreibung: Slope dynamics in volcanic environments comprise a wide spectrum of phenomena, from large lateral collapse to shallow debris remobilization, which may represent a major threat for human communities and infrastructures. Many volcanos built up from the ocean floor and large portions of the volcano edifice are submerged. In these settings, only the edifice’s summit can be investigated by terrestrial remote sensing and in-situ approaches. Growth and destruction, including tectonics and gravitational phenomena, affect entire volcano flanks and are not limited to the physical boundary of the sea level but could comprise their subaqueous parts.
    Beschreibung: Published
    Beschreibung: 2615–2618
    Beschreibung: 6V. Pericolosità vulcanica e contributi alla stima del rischio
    Beschreibung: JCR Journal
    Schlagwort(e): volcanoes ; flanks ; volcano-tectonics ; structure ; collapse ; stability ; 04.08. Volcanology ; 05.08. Risk
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Materialart: article
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    ARTIKEL (OA)
  • 13
    Digitale Medien
    Digitale Medien
    Stabilization of smoothness priors time-varying autoregressive models (2000)
    Springer
    Circuits, systems and signal processing 19 (2000), S. 423-435 
    Details
    ISSN: 1531-5878
    Schlagwort(e): Time-varying autoregressive models ; stability ; smoothness priors ; Tihkonov regularization ; constrained optimization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Abstract The stability of time-varying autoregressive (AR) models is an important issue in such applications as time-varying spectrum estimation and electroencephalography simulation and estimation. In some cases, such as time-varying spectrum estimation, the models that exhibit roots near unit moduli are difficult to use. Thus a tighter stability condition such as stability with a positive margin is needed. A time-varying AR model is stable with a positive margin if the moduli of the roots of the time-varying characteristic polynomial are somewhat less than unity for every time instant. Recently, a new method for the estimation of the time-varying AR models was introduced. This method is based on the interpretation of the underdetermined time-varying prediction equations as an ill-posed inverse problem that is solved by Tikhonov regularization. The method is referred to as the deterministic regression smoothness priors (DRSP) scheme. In this paper, a stabilization method in which the DRSP scheme is augmented with nonlinear stability constrainst is proposed. The problem is formulated so that stability with a positive margin can also be achieved. The problem is solved iteratively with an exterior point algorithm. The performance of the algorithm is studied with a simulation. It is shown that the proposed approach is well suited to stable modeling of signals containing narrowband transitions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01196156
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  • 14
    Digitale Medien
    Digitale Medien
    Stability of constant coefficient linear singular systems with delay (2000)
    Springer
    Circuits, systems and signal processing 19 (2000), S. 13-25 
    Details
    ISSN: 1531-5878
    Schlagwort(e): Singular systems ; delay ; consistency condition ; stability ; instability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Abstract In this paper, the general class of singular systems with delay and linear constant coefficient singular systems with delay are discussed. First, several definitions of stability are presented for singular systems with delay, and general sufficient stability conditions and instability conditions are obtained. Second, stability and instability are analyzed for linear constant coefficient singular systems with delay.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF01229989
    Standort Signatur Erwartet Verfügbarkeit
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  • 15
    Digitale Medien
    Digitale Medien
    Do Maculinea rebeli caterpillars provide vestigial mutualistic benefits to ants when living as social parasites inside Myrmica ant nests? (2000)
    Springer
    Entomologia experimentalis et applicata 95 (2000), S. 97-103 
    Details
    ISSN: 1570-7458
    Schlagwort(e): butterfly ; Formicidae ; food ; growth ; mutualism ; myrmecophily ; parasitism
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Caterpillars of the lycaenid butterfly Maculinea rebeli Hirschke (Lepidoptera: Lycaenidae) live for 11–23 months as social parasites in Myrmica (Hymenoptera: Formicidae) red ant nests, a trait that is believed to have evolved from mutualistic myrmecophilous ancestry. Although Maculinea rebeli caterpillars harm Myrmica larvae, they simultaneously produce copious secretions which the adult worker ants imbibe, perhaps representing a vestige of the ancestral mutualism. We report the results of laboratory experiments designed to test alternative hypotheses: (i) Maculinea rebeli caterpillars provide a beneficial source of sugar in return for being tended by Myrmicaworkers; (ii) Maculinea rebeli harms its host by stressing the workers by competing for available sugar. Comparisons were made of Myrmica worker fitness after 90–450 days under all possible combinations of three experimental treatments: ± M. rebeli caterpillars, ± sucrose and ± ant brood. Caterpillars always reduced the survival of both ant workers and their larvae, even when sugar was not provided, suggesting that M. rebeli is wholly parasitic on all stages in its host colony. The results also confirmed the importance of sucrose in the diet of Myrmica, and showed that M. rebeli caterpillars which eat ant brood to supplement their normal trophallactic feeding by workers develop more quickly - but have the same survival and pupal weights – as caterpillars that are fed solely by worker ants.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1003950318095
    Standort Signatur Erwartet Verfügbarkeit
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  • 16
    Digitale Medien
    Digitale Medien
    Difficulties in location and acceptance of phloem sap combined with reduced concentration of phloem amino acids explain lowered performance of the aphid Rhopalosiphum padi on nitrogen deficient barley (Hordeum vulgare) seedlings (2000)
    Springer
    Entomologia experimentalis et applicata 97 (2000), S. 203-210 
    Details
    ISSN: 1570-7458
    Schlagwort(e): EPG ; stylectomy ; phloem amino acids ; nitrogen ; aphid-plant interaction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Effects of nitrogen deficiency in hydroponically grown barley seedlings (Hordeum vulgare L.) on the development and reproduction of the aphid Rhopalosiphum padi (L.) (Hemiptera: Aphididae) were investigated. Plant growth was significantly reduced in seedlings grown without nitrogen. Aphid intrinsic rate of increase (r m) was also significantly lower on these plants compared with that on plants grown with 8 mol m−3 nitrogen. Phloem sap was collected from seedling stems by aphid stylectomy and amino acids quantified by HPLC. There was a significant reduction in the concentration of non-essential amino acids as a group, but not of essential amino acids. Electrical penetration graphs (EPG) indicated that aphids reached the phloem more quickly and fed for longer on plants grown with nitrogen. This is the first reported study in which this combination of techniques has been used to understand the interactions of an aphid and plant under different environmental conditions.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004022608401
    Standort Signatur Erwartet Verfügbarkeit
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  • 17
    Digitale Medien
    Digitale Medien
    The Dynamics of a Fish Stock Exploited in Two Fishing Zones (2000)
    Springer
    Acta biotheoretica 48 (2000), S. 207-218 
    Details
    ISSN: 1572-8358
    Schlagwort(e): Dynamical population ; fishing efforts ; metapopulation ; time scales ; aggregation method ; equilibrium ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract This work presents a specific stock-effort dynamical model. The stocks correspond to two populations of fish moving and growing between two fishery zones. They are harvested by two different fleets. The effort represents the number of fishing boats of the two fleets that operate in the two fishing zones. The bioeconomical model is a set of four ODE's governing the fishing efforts and the stocks in the two fishing areas. Furthermore, the migration of the fish between the two patches is assumed to be faster than the growth of the harvested stock. The displacement of the fleets is also faster than the variation in the number of fishing boats resulting from the investment of the fishing income. So, there are two time scales: a fast one corresponding to the migration between the two patches, and a slow time scale corresponding to growth. We use aggregation methods that allow us to reduce the dimension of the model and to obtain an aggregated model for the total fishing effort and fish stock of the two fishing zones. The mathematical analysis of the model is shown. Under some conditions, we obtain a stable equilibrium, which is a desired situation, as it leads to a sustainable harvesting equilibrium, keeping the stock at exploitable densities.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010208910738
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  • 18
    Digitale Medien
    Digitale Medien
    An Ab Initio Study of the Complexes Formed by the Positive Acetylene Ion with the Hydrogen and Nitrogen Molecules and the Argon Atom (2000)
    Springer
    Journal of cluster science 11 (2000), S. 381-389 
    Details
    ISSN: 1572-8862
    Schlagwort(e): acetylene ion ; complex ; hydrogen ; nitrogen ; argon
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract The complexes formed by the positive acetylene ion with the hydrogen molecule, the nitrogen molecule, and the argon atom are investigated with ab initio calculations using the 6-311G** and the 6-31+G(2df,2pd) basis sets. MP2/6-311G** energies and optimum geometries are obtained, as well as single-point MP3, MP4, and QCISD(T) energies with the MP2/6-311G** optimized geometries. Single-point calculations are performed with the 6-31+G(2df,2pd) basis set at MP2/6-311G** optimized geometries.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009053924254
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  • 19
    Digitale Medien
    Digitale Medien
    Performance analysis of a slotted-ALOHA protocol on a capture channel with fading (2000)
    Springer
    Queueing systems 34 (2000), S. 1-35 
    Details
    ISSN: 1572-9443
    Schlagwort(e): multiple access ; CDMA ; rates of convergence ; stability ; functional limit theorems ; transient analysis ; Markov-modulated capture channel
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Notizen: Abstract We consider the slotted ALOHA protocol on a channel with a capture effect. There are M 〈 ∞ users each with an infinite buffer. If in a slot, i packets are transmitted, then the probability of a successful reception of a packet is q i. This model contains the CDMA protocols as special cases. We obtain sufficient rate conditions, which are close to necessary for stability of the system, when the arrival streams are stationary ergodic. Under the same rate conditions, for general regenerative arrival streams, we obtain the rates of convergence to stationarity, finiteness of stationary moments and various functional limit theorems. Our arrival streams contain all the traffic models suggested in the recent literature, including the ones which display long range dependence. We also obtain bounds on the stationary moments of waiting times which can be tight under realistic conditions. Finally, we obtain several results on the transient performance of the system, e.g., first time to overflow and the limits of the overflow process. We also extend the above results to the case of a capture channel exhibiting Markov modulated fading. Most of our results and proofs will be shown to hold also for the slotted ALOHA protocol without capture.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1019192600091
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  • 20
    Digitale Medien
    Digitale Medien
    Normal Form Invariants Around Spin-orbit Periodic Orbits (2000)
    Springer
    Celestial mechanics and dynamical astronomy 78 (2000), S. 227-241 
    Details
    ISSN: 1572-9478
    Schlagwort(e): stability ; normal form ; spin-orbit resonance
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We consider a model of spin-orbit interaction, describing the motion of an oblate satellite rotating about an internal spin-axis and orbiting about a central planet. The resulting second order differential equation depends upon the parameters provided by the equatorial oblateness of the satellite and its orbital eccentricity. Normal form transformations around the main spin-orbit resonances are carried out explicitly. As an outcome, one can compute some invariants; the fact that these quantities are not identically zero is a necessary condition to prove the existence of nearby periodic orbits (Birkhoff fixed point theorem). Moreover, the nonvanishing of the invariants provides also the stability of the spin-orbit resonances, since it guarantees the existence of invariant curves surrounding the periodic orbit.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1011161605935
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  • 21
    Digitale Medien
    Digitale Medien
    A New ADI Scheme for Solving Three-Dimensional Parabolic Equations with First-Order Derivatives and Variable Coefficients (2000)
    Springer
    Journal of computational analysis and applications 2 (2000), S. 293-308 
    Details
    ISSN: 1572-9206
    Schlagwort(e): parabolic equations ; ADI scheme ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract An ADI scheme for solving three-dimensional parabolic equations withfirst-order derivatives and variable coefficients has been developed basedon our previous papers and the idea of the modified upwind differencescheme. This ADI scheme is second-order accurate and unconditionallystable. Further, a small parameter can be chosen which makes it suitablefor simulating fast-transient phenomena or for computations on fine spatialmeshes. The method is illustrated with numerical examples.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1010108620966
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  • 22
    Digitale Medien
    Digitale Medien
    A Multiclass Feedback Queueing Network with a Regular Skorokhod Problem (2000)
    Springer
    Queueing systems 36 (2000), S. 327-349 
    Details
    ISSN: 1572-9443
    Schlagwort(e): multiclass networks ; networks with feedback ; Skorokhod Problem ; Skorokhod Mapping ; Lipschitz continuity ; stability ; load conditions
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Notizen: Abstract We consider a four-class two-station network with feedback, with fluid inputs and a head-of-the-line generalized processor sharing discipline at each station. We derive the Skorokhod Problem associated with the network and obtain algebraic sufficient conditions for Lipschitz continuity of the associated Skorokhod Map. This provides the first example of a multiclass network with feedback for which the associated Skorokhod Problem has been proved to be regular. As an elementary application, we show that under the conditions which guarantee Lipschitz continuity the network is stable if and only if the usual load conditions apply.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1011037419624
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  • 23
    Digitale Medien
    Digitale Medien
    Bifurcation Phenomena from Standing Pulse Solutions in Some Reaction-Diffusion Systems (2000)
    Springer
    Journal of dynamics and differential equations 12 (2000), S. 117-167 
    Details
    ISSN: 1572-9222
    Schlagwort(e): singular perturbation ; standing pulses ; stability ; Hopf bifurcation ; reaction-diffusion system
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract Bifurcation phenomena from standing pulse solutions of the problem $$\varepsilon \tau u_t = \varepsilon ^2 u_{xx} + f(u,v),{\text{ }}v_t = v_{xx} + g(u,v)$$ is considered. ε(〉0) is a sufficiently small parameter and τ is a positive one. It is shown that there exist two types of destabilization of standing pulse solutions when τ decreases. One is the appearance of travelling pulse solutions via the static bifurcation and the other is that of in-phase breathers via the Hopf bifurcation. Furthermore which type of destabilization occurs first with decreasing τ is discussed for the piecewise linear nonlinearities f and g.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009098719440
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  • 24
    Digitale Medien
    Digitale Medien
    The influence of OH groups on the growth of rhodium on alumina: a model study (2000)
    Springer
    Catalysis letters 68 (2000), S. 19-24 
    Details
    ISSN: 1572-879X
    Schlagwort(e): aluminum oxide ; hydroxyl groups ; rhodium ; growth ; scanning tunneling microscopy ; infrared spectroscopy
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract In order to investigate how the presence of surface hydroxyl groups on oxide surfaces affects the interaction with the supported metal, we have modified a well-ordered alumina film on NiAl(110) by Al deposition and subsequent exposure to water. This procedure yields a hydroxylated alumina surface as revealed by infrared and high-resolution electron energy loss spectroscopy. By means of scanning tunneling microscopy, we have studied the growth of rhodium on the modified film at 300 K. Clear differences in the particle distribution and density are observed in comparison to the clean substrate. While, in the latter case, decoration of domain boundaries as typical defects of the oxide film governs the growth mode, a more isotropic island distribution and a drastically increased particle density is found on the hydroxylated surface. From infrared data, it can be deduced that the growth is connected with the consumption of the hydroxyl groups due to the interaction between the metal deposit and the hydroxylated areas. This finding is in line with photoemission results published earlier.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1019058714724
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  • 25
    Digitale Medien
    Digitale Medien
    Activity and stability of Cu/ZnO/Al2O3 catalyst promoted with B2O3 for methanol synthesis (2000)
    Springer
    Catalysis letters 68 (2000), S. 55-58 
    Details
    ISSN: 1572-879X
    Schlagwort(e): promoting effect ; B2O3 ; Cu/ZnO/Al2O3 catalyst ; methanol synthesis ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The addition of B2O3 to a Cu/ZnO/Al2O3 catalyst increased the activity of the catalyst for methanol synthesis after an induction period during the reaction. The stability of the B2O3-containing Cu/ZnO/Al2O3 catalyst was greatly improved by the addition of a small amount of colloidal silica to the catalyst.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1019010831562
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  • 26
    Digitale Medien
    Digitale Medien
    Stability and excitation of potassium promoter in iron catalysts – the role of KFeO2 and KAlO2 phases (2000)
    Springer
    Catalysis letters 67 (2000), S. 129-134 
    Details
    ISSN: 1572-879X
    Schlagwort(e): potassium desorption ; stability ; excitation ; iron catalyst ; Rydberg atoms
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Well‐characterized catalyst model compounds of KAlO2 and KFeO2 are investigated by thermal desorption of potassium from the material. The desorbing fluxes of ions, atoms and highly excited states (field ionizable Rydberg states) were studied with surface and field ionization detectors in a vacuum apparatus. From the Arrhenius plots the activation energies for desorption of K and K+ were determined. The chemical state of potassium at the surfaces is concluded to be: ionic on KAlO2 (with the K desorption barrier of 1.76 eV) and covalent on KFeO2 (barrier of 2.73 eV). These results agree with the data obtained earlier for industrial catalysts for ammonia and styrene production. They are interpreted in terms of the Schottky cycle, which is completed for KAlO2 and fails for KFeO2. This failure indicates a non‐equilibrium desorption process. K Rydberg states are only found to desorb from KFeO2, in agreement with the suggestion that such states in some way are responsible for the catalytic activity.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1019013504729
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  • 27
    Digitale Medien
    Digitale Medien
    Stability of Linear Inequality Systems Measured by the Hausdorff Metric (2000)
    Springer
    Set-valued analysis 8 (2000), S. 253-266 
    Details
    ISSN: 1572-932X
    Schlagwort(e): Hausdorff metric ; linear inequality systems ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract In this paper, we propose a Hausdorff metric to measure the “distance” between two linear inequality systems on a real normed space X. For this topology, which comes through a pseudo-metric in the set Σ of linear inequality systems, the closedness of the feasible set mapping is studied, and at the same time a characterization of the stability of the subset Σ c of consistent sytems is given.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008701026782
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  • 28
    Digitale Medien
    Digitale Medien
    Stability Properties of a Bond Portfolio Management Problem (2000)
    Springer
    Annals of operations research 99 (2000), S. 251-265 
    Details
    ISSN: 1572-9338
    Schlagwort(e): stochastic programming ; bond portfolio management ; interest ratescenarios ; stability ; sensitivity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik , Wirtschaftswissenschaften
    Notizen: Abstract The bond portfolio management problem is formulated as a multiperiod two-stage or multistage stochastic program based on interest rate scenarios. These scenarios depend on the available market data, on the applied estimation and sampling techniques, etc., and are used to evaluate coefficients of the resulting large scale mathematical program. The aim of the contribution is to analyze stability and sensitivity of this program on small changes of the coefficients – the (scenario dependent) values of future interest rates and prices. We shall prove that under sensible assumptions, the scenario subproblems are stable linear programs and that also the optimal first-stage decisions and the optimal value of the considered stochastic program possess acceptable continuity properties.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1019275817688
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  • 29
    Digitale Medien
    Digitale Medien
    Destabilization for quasivariational inequalities of reaction-diffusion type (2000)
    Springer
    Applications of mathematics 45 (2000), S. 161-176 
    Details
    ISSN: 1572-9109
    Schlagwort(e): reaction-diffusion system ; unilateral conditions ; quasivariational inequality ; Leray-Schauder degree ; eigenvalue ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract We consider a reaction-diffusion system of the activator-inhibitor type with unilateral boundary conditions leading to a quasivariational inequality. We show that there exists a positive eigenvalue of the problem and we obtain an instability of the trivial solution also in some area of parameters where the trivial solution of the same system with Dirichlet and Neumann boundary conditions is stable. Theorems are proved using the method of a jump in the Leray-Schauder degree.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1023033910657
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  • 30
    Digitale Medien
    Digitale Medien
    Diagonally implicit Runge–Kutta methods for 3D shallow water applications (2000)
    Springer
    Advances in computational mathematics 12 (2000), S. 229-250 
    Details
    ISSN: 1572-9044
    Schlagwort(e): numerical analysis ; shallow water problems ; DIRK methods ; stability ; 65L06 ; 65L20 ; 65M12 ; 65M20
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract We construct A‐stable and L‐stable diagonally implicit Runge–Kutta methods of which the diagonal vector in the Butcher matrix has a minimal maximum norm. If the implicit Runge–Kutta relations are iteratively solved by means of the approximately factorized Newton process, then such iterated Runge–Kutta methods are suitable methods for integrating shallow water problems in the sense that the stability boundary is relatively large and that the usually quite fine vertical resolution of the discretized spatial domain is not involved in the stability condition.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1018969203026
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  • 31
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    Digitale Medien
    On the Robustness of Gaussian Elimination with Partial Pivoting (2000)
    Springer
    BIT 40 (2000), S. 62-73 
    Details
    ISSN: 1572-9125
    Schlagwort(e): Gaussian elimination ; stability ; pivoting
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract It has been recently shown that large growth factors might occur in Gaussian Elimination with Partial Pivoting (GEPP) also when solving some plausibly natural systems. In this note we argue that this potential problem could be easily solved, with much smaller risk of failure, by very small (and low cost) modifications of the basic algorithm, thus confirming its inherent robustness. To this end, we first propose an informal model with the goal of providing further support to the comprehension of the stability properties of GEPP. We then report the results of numerical experiments that confirm the viewpoint embedded in the model. Basing on the previous observations, we finally propose a simple scheme that could be turned into (even more) accurate software for the solution of linear systems.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022314201484
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  • 32
    Digitale Medien
    Digitale Medien
    Runge-Kutta Methods for the Numerical Solution of Stiff Semilinear Systems (2000)
    Springer
    BIT 40 (2000), S. 611-639 
    Details
    ISSN: 1572-9125
    Schlagwort(e): Runge-Kutta methods ; stability ; convergence ; stiff problems
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract This paper studies the stability and convergence properties of general Runge-Kutta methods when they are applied to stiff semilinear systems y′(t) = J(t)y(t) + g(t, y(t)) with the stiffness contained in the variable coefficient linear part. We consider two assumptions on the relative variation of the matrix J(t) and show that for each of them there is a family of implicit Runge-Kutta methods that is suitable for the numerical integration of the corresponding stiff semilinear systems, i.e. the methods of the family are stable, convergent and the stage equations possess a unique solution. The conditions on the coefficients of a method to belong to these families turn out to be essentially weaker than the usual algebraic stability condition which appears in connection with the B-stability and convergence for stiff nonlinear systems. Thus there are important RK methods which are not algebraically stable but, according to our theory, they are suitable for the numerical integration of semilinear problems. This paper also extends previous results of Burrage, Hundsdorfer and Verwer on the optimal convergence of implicit Runge-Kutta methods for stiff semilinear systems with a constant coefficients linear part.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022332200092
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  • 33
    Digitale Medien
    Digitale Medien
    Stochastic Methods for Ill-Posed Problems (2000)
    Springer
    BIT 40 (2000), S. 226-240 
    Details
    ISSN: 1572-9125
    Schlagwort(e): Stochastic differential equations ; regularisation ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract This paper is devoted to the numerical analysis of ill-posed problems of evolution equations in Banach spaces using certain classes of stochastic one-step methods. The linear stability properties of these methods are studied. Regularisation is given by the choice of the regularisation parameter as α = $$\sqrt {\tau _n }$$ , where τ n is the stepsize and provides the convergence on smooth initial data. The case of the approximation of well-posed problems is also considered.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1022386822865
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  • 34
    Digitale Medien
    Digitale Medien
    Hydraulic analysis of free-surface flows with solidification (2000)
    Springer
    Archive of applied mechanics 70 (2000), S. 17-29 
    Details
    ISSN: 1432-0681
    Schlagwort(e): Key words free-surface flow ; solidification ; strip casting ; steady state ; nonuniqueness ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Summary The paper is concerned with a one-dimensional analysis of plane open-channel flow with continuous solidification. The process is of relevance for recent developments in the casting of steel and other metals. The bottom of the channel consists of a rotating casting roll and a horizontal cooling table, where the solidified material is withdrawn with given velocity. The study is restricted to the region downstream of the top of the casting roll. Surface tension is neglected. In the main part of the analysis inviscid fluid flow is considered since the Reynolds number is very large in the applications. It is found that the steady-state solutions are nonunique in a certain parameter range. In addition to a continuous solution, there are two solutions including hydraulic jumps, with one hydraulic jump being located on the casting roll, the other one on the cooling table. Regarding the stability of the non unique solutions, the evolution of disturbances is investigated numerically as an initial-value problem. It is concluded that the hydraulic jump on the cooling table is unstable, while the other discontinuous solution as well as the continuous solution are stable for sufficiently small disturbances. Which stable solution is attained in the steady state, depends on the history of the process. Friction at the liquid/solid interface is taken into account in the last part of the analysis. A constant friction coefficient is assumed. It is found that the history of the process determines the steady-state solution if, and only if, the friction coefficient is sufficiently small. For larger values of the friction coefficient, the steady-state solution is unique and independent of the history of the transient process. Furthermore, for sufficiently large friction coefficients, stable hydraulic jumps are found, in contrast to the inviscid case, also on the cooling table.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s004199900031
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  • 35
    Digitale Medien
    Digitale Medien
    Concerning a Technique for Increasing Stability of Climbing Robots (2000)
    Springer
    Journal of intelligent and robotic systems 27 (2000), S. 195-209 
    Details
    ISSN: 1573-0409
    Schlagwort(e): wall-climbing robot ; electromagnetic grippers ; stability ; additional support element ; sliding and turning over conditions
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Maschinenbau
    Notizen: Abstract Legged-climbing robot is considered. Each foot of the robot has an electromagnet system for robot"s holding on a metal surface. This surface can be both vertical and inclined, including negative slope. Analytical calculation of robot stability under turn over or sliding conditions has been made. Critical slopes have been determined. One of these slopes corresponds to minimal reserve of robot stability towards sliding and another to minimal reserve of robot stability towards turning-over. As total reserve of stability of a robot is always equal to the minimal one of these reserves. Additional support elements of elastic material with high coefficient of friction, along with electromagnet, allows to increase minimal reserve of robot stability towards sliding. The use of such support elements leads to redistributing force of normal support reaction between electromagnet (which surface has low coefficient of friction) and additional support element (which surface has high coefficient of friction). It is just what leads to increasing the total friction force and as a consequence to increasing of minimal reserve of robot stability towards sliding.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008158332368
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  • 36
    Digitale Medien
    Digitale Medien
    Perron–Frobenius Theory and Symmetry of Solutions to Nonlinear PDE's (2000)
    Springer
    Letters in mathematical physics 53 (2000), S. 313-320 
    Details
    ISSN: 1573-0530
    Schlagwort(e): partial differential equations ; nonlinearities ; symmetries ; stability ; minimization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik , Physik
    Notizen: Abstract We suggest a simple but general method of establishing symmetry properties of stable solutions of nonlinear elliptic equations. The method relies on characterization of symmetry breaking with a help of zero modes and on a generalization of the Perron–Frobenius theory.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007622208894
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  • 37
    Digitale Medien
    Digitale Medien
    Nitrogen leaching and crop availability in manured catch crop systems in Sweden (2000)
    Springer
    Nutrient cycling in agroecosystems 56 (2000), S. 139-152 
    Details
    ISSN: 1573-0867
    Schlagwort(e): nitrogen ; N leaching ; liquid manure ; catch crops ; N mineralization
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Results are presented from five years (1990–1995) of a field leaching experiment on a sandy soil in south-west Sweden. The aim was to study N leaching, change in soil organic N and N mineralization in cropping systems with continuous use of liquid manure (two application rates) and catch crops. N leaching from drains, N uptake in crops and mineral N in the soil were measured. Simulation models were used to calculate the N budget and N mineralization in the soil and to make predictions of improved fertilization strategies in relation to manure applications and changing the time for incorporation of catch crops. In treatments without catch crops, a normal and a double application of manure increased average N leaching by 15 and 34%, respectively, compared to treatment with commercial fertilizer. Catch crops reduced N leaching by, on average, 60% in treatments with a normal application of manure and commercial fertilizer, but only by 35% in the treatment with double the normal application rate of manure. Incorporation of catch crops in spring increased simulated net N mineralization during the crop vegetation period, and also during early autumn. In conclusion, manured systems resulted in larger N leaching than those receiving commercial fertilizer, mainly due to larger applications of mineral N in spring. More careful adaptation of commercial N fertilization with respect to the amounts of NH4-N applied with manure could, according to the simulations, reduce N leaching. Under-sown ryegrass catch crops effectively reduced N leaching in manured systems. Incorporating catch crop residues in late autumn instead of spring might be preferable with respect to N availability in the soil for the next crop, and would not increase N leaching.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009821519042
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  • 38
    Digitale Medien
    Digitale Medien
    Do Small Innovating Firms Outperform Non-Innovators? (2000)
    Springer
    Small business economics 14 (2000), S. 195-210 
    Details
    ISSN: 1573-0913
    Schlagwort(e): growth ; manufacturing ; performance ; product innovation ; small firms
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Wirtschaftswissenschaften
    Notizen: Abstract The paper considers the relative performance [along a number of parameters] of a sample of 228 small manufacturing firms categorised by level of innovation. Whilst innovators appear no more likely to have experienced some form of sales or employment growth, they are significantly more likely to have grown more. In other words, the innovators' growth rate distributions are highly negatively skewed. With regards to export intensities, profitability and productivity levels, the findings are less clear. On the whole, the results reported here are similar to those of other small firm studies, yet vary markedly from large firm equivalents; suggesting that the nature of the returns to innovation may be contingent, at least in part, upon firm size. Moreover, the high levels of variation in firm performance should caution us against proffering innovative imperatives. If we are to counsel firms to "innovate at all costs", we must be clear about, and clearly demonstrate, the nature of the returns they may reasonably expect and the processes through which these may be optimised.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008100206266
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  • 39
    Digitale Medien
    Digitale Medien
    Stability of Attractive Bose–Einstein Condensates (2000)
    Springer
    Journal of statistical physics 101 (2000), S. 731-746 
    Details
    ISSN: 1572-9613
    Schlagwort(e): attractive Bose–Einstein condensates ; nonlinear Schrödinger equation ; stability ; ground state ; variational arguments
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We propose the critical nonlinear Schrödinger equation with a harmonic potential as a model of attractive Bose–Einstein condensates. By an elaborate mathematical analysis we show that a sharp stability threshold exists with respect to the number of condensate particles. The value of the threshold agrees with the existing experimental data. Moreover with this threshold we prove that a ground state of the condensate exists and is orbital stable. We also evaluate the minimum of the condensate energy.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026437923987
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  • 40
    Digitale Medien
    Digitale Medien
    Nutrient flows and land use change in a rural catchment: a modelling approach (2000)
    Springer
    Landscape ecology 15 (2000), S. 187-199 
    Details
    ISSN: 1572-9761
    Schlagwort(e): BOD5 ; catchment ; empirical model ; land use change ; land use scenarios ; nitrogen ; phosphorus ; runoff ; SO4
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Due largely to unprecedented land-use changes in the Porijõgi River catchment (southern Estonia) losses of nutrients and organic matter have decreased significantly. During the period 1987–1997 abandoned lands increased from 1.7 to 10.5% and arable lands decreased from 41.8 to 23.9%. At the same time, the runoff of total-N, total-P, SO4 and organic matter (after BOD5) decreased from 25.9 to 5.1, 0.32 to 0.13, 78 to 48, and 7.4 to 3.5 kg ha−1 yr−1, respectively. The most significant decreases occurred in agricultural subcatchments while the changes were insignificant in the forested upper course catchment. A simple empirical model which incorporates land-use pattern, fertilization intensity, soil parameters and water discharge accurately described the variations of total-N and total-P runoff in both the whole catchment and its agricultural subcatchments (R 2 varies from 0.95–0.99 for N to 0.49–0.93 for P). In small agricultural subcatchments the rate of fertilization is found the most important factor for nitrogen runoff, whereas in larger mosaic watersheds land use pattern plays the main role. Seven alternative scenarios compiled on the base of the empirical model allow to forecast potential nitrogen and phosphorus losses from the catchment. This information can be used in further landscape and regional planning of the whole region.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008181811552
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  • 41
    Digitale Medien
    Digitale Medien
    A polymorphism of the rat T-cell receptor β-chain variable gene 13 (BV13S1) correlates with the frequency of BV13S1-positive CD4 cells (2000)
    Springer
    Immunogenetics 51 (2000), S. 296-305 
    Details
    ISSN: 1432-1211
    Schlagwort(e): Key words Vβ13 ; CD4/CD8 ratio ; Rat ; Tcrb ; Polymorphism
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract. Three rat BV13S1 alleles (T-cell receptor β-chain variable gene 13) were characterized by new BV13S1-allele specific monoclonal antibodies (18B1 and 17D5) and sequence analysis of expressed and genomic BV13S1. Two alleles were functional and designated BV13S1A1 present in strains LEW, BUF, PVG, and BV13S1A2 present in BN and WF. Their products differed by six amino acids, two of them in complementarity-determing region (CDR)1 and one in CDR2. A third nonfunctional allele, BV13S1A3P, was found in strains F344 and DA. Apart from a single nucleotide insertion, it was identical to BV13S1A2. All 12 rat strains tested showed association of TCRBC1 with BV8S2/4 alleles but not with the BV13S1 alleles, which may reflect a different gene order of the rat BV compared to mouse. BV13S1A1-encoded T-cell receptors (TCRs) which bind both monoclonal antibody (mAb) 18B1 and mAb 17D5 are over-represented in the CD4 lymphocyte subset. BV13S1A2-encoded TCRs which are stained by mAb 18B1 but not by mAb 17D5 show a slight CD8-biased expression. Preferential usage of BV13S1A1-positive TCRs by CD4 but not by CD8 cells in (LEW×WF)F1 hybrids and cosegregation of BV13SA1 and increased frequency of BV13S1 TCR-positive CD4 cells in a (LEW×BN)×BN backcross suggest structural differences of the two allelic products as the reason for their contrasting CD4/CD8 subset bias.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s002510050623
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  • 42
    Digitale Medien
    Digitale Medien
    Localization of endothelin receptors in bleomycin-induced pulmonary fibrosis in the rat (2000)
    Springer
    Histochemistry and cell biology 122 (2000), S. 507-517 
    Details
    ISSN: 1432-119X
    Schlagwort(e): Endothelin-A receptor ; Endothelin-B receptor ; Rat ; Pulmonary fibrosis ; Immunohistochemistry ; Quantitative PCR
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: AbstractPulmonary fibrosis is characterized by excessive extracellular matrix deposition with concomitant loss of gas exchange units, and endothelin-1 (ET-1) has been implicated in its pathogenesis. Increased levels of ET-1 from tissues and bronchoalveolar lavage have been reported in patients with pulmonary fibrosis and in animal models after intratracheal bleomycin. We characterized the cellular distribution of alveolar ET receptors by immunohistochemistry in bleomycin-induced pulmonary fibrosis in the rat and determined the regulation by bleomycin of ET receptor mRNA expression in isolated alveolar macrophages and rat lung fibroblasts. We found significant increases in the numbers of fibroblasts and macrophages at day 7 compared to day 28 and control animals. ETB receptor immunoreactivity was observed on fibroblasts and invading monocytes. Isolated fibroblasts expressed both ETA and ETB receptor mRNA, and ETA receptor mRNA was upregulated by bleomycin. Isolated resident alveolar macrophages expressed neither ETA nor ETB receptor mRNA which were also not induced by bleomycin. We conclude that, while ETB receptor stimulation of fibroblasts and monocytes recruited during bleomycin-induced lung injury exerts antagonistic effects on fibroblast collagen synthesis, the observed increase in the number of fibroblasts in vivo and upregulation of fibroblast ETA receptor mRNA by bleomycin in vitro point to a predominance of the profibrotic effects of ET receptor engagement.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s00418-004-0708-7
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  • 43
    Digitale Medien
    Digitale Medien
    Education funding and regional convergence (2000)
    Springer
    Journal of population economics 13 (2000), S. 403-424 
    Details
    ISSN: 1432-1475
    Schlagwort(e): JEL classification: O41 ; F22 ; Key words: Altruism ; education ; growth ; convergence ; capital mobility
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Sociologie , Wirtschaftswissenschaften
    Notizen: Abstract. The aim of this paper is to discuss the process of regional convergence within the framework of an overlapping generations model in which the engine of growth is the accumulation of human capital. In particular, we consider different education funding systems and compare their performance in terms of growth rates and pace of convergence between two heterogeneous regions. The analysis suggests that the choice of a particular education system incorporates a possible trade-off between long run growth rate and short run convergence. In such choice, the initial capital stock and the extent of regional human capital discrepancy appear as central variables.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s001480050144
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  • 44
    Digitale Medien
    Digitale Medien
    Patterns and propensities in reproduction and growth of marine fishes (2000)
    Springer
    Ecological research 15 (2000), S. 101-106 
    Details
    ISSN: 1440-1703
    Schlagwort(e): comparative ecology ; growth ; marine fish ; patterns ; reproduction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: A number of strong regularities characterize certain very basic biological parameters in marine fishes. For example, the ovulated eggs of fish usually measure approximately 1 mm in diameter. The small, relatively uniform size of the eggs means that almost all fish larvae experience environmental variability at very similar scales, which itself establishes strong constraints for, and links between reproduction and recruitment. Additional constraints emerge from seawater being a poor medium for respiration, which establishes further linkages between growth and mortality. These constraints have produced strongly convergent features, and thence the patterns in reproduction and growth of marine fishes that are presented.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1440-1703.2000.00321.x
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  • 45
    Digitale Medien
    Digitale Medien
    Kinetics of the Electrons in Striations of Spherical Glow Discharges (2000)
    Springer
    Plasma chemistry and plasma processing 20 (2000), S. 87-110 
    Details
    ISSN: 1572-8986
    Schlagwort(e): striations ; nitrogen ; spherical discharge ; spatially inhomogeneous Boltzmann equation ; electron velocity distribution function ; dc glow discharge
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Maschinenbau , Technik allgemein
    Notizen: Abstract Recent observations of spherical striations in large-volume nitrogen dcdischarges with a central anode have stimulated investigations of thenonlocal electron kinetics in these striations by solving the spatiallyinhomogeneous Boltzmann equation adapted to spherical geometry. Becausethe radial course of the electric potential is largely unknown in thisdischarge, different models concerning its radial course have been developedand used. These models are based on the measured radii of the striationsand the assumption that the potential drop between successive striationsdoes not change. As a consequence, with decreasing distance between thestriations the electric field strongly increases toward the centralanode. It has been found that spherical striations are only obtained ifthe electric field is strongly modulated. In this case, a highly nonlocalbehavior of the velocity distribution function and strongly modulatedradial courses of the macroscopic quantities have been obtained.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1006973911319
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  • 46
    Digitale Medien
    Digitale Medien
    Effects of feeding rate on growth, feed utilizationand body composition of a tropical bagrid catfish (2000)
    Springer
    Aquaculture international 8 (2000), S. 19-29 
    Details
    ISSN: 1573-143X
    Schlagwort(e): body composition ; catfish (Mystus nemurus) ; feeding rate ; growth
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract A 10 week experiment was conducted to determine theeffects of feeding rate on growth, feed utilizationand body composition of the tropical bagrid catfish,Mystus nemurus. Catfish fingerlings with anaverage initial body weight of 12 g were fed apractical diet (36.2% protein, 16.5 kJ/g diet) atrates of 1, 2, 2.5, 3, 3.5, 4 or 5% of their bodyweight (BW) per day in two equal meals. Watertemperature was approximately 29 °C throughoutthe experiment. Percent weight gain increased almostlinearly with increasing feeding rates up to 2.5%BW/day beyond which no significant (P 〉 0.05)improvement in weight gain was observed. The specificgrowth rate of catfish fed rations of 1% BW/day was0.72%/day and this increased significantly to anaverage of 1.39%/day for catfish fed 2.5% BW/day andbeyond. Feed utilization did not differ significantly(P 〉 0.05) between fish fed 1.0 to 2.5%BW/day but decreased when rations were increased to3.0% BW/day and above. Feed efficiency ratio was0.79 for catfish fed 1.0% BW/day compared to a ratioof 0.27 for fish fed at 5% BW/day. Catfish fed 1.0%BW/day had the lowest condition factor, hepato- andviscerosomatic indices, but the highest carcass tobody weight ratio. These fish also had lowerproportions of whole body dry matter, lipid andprotein, carcass dry matter and lipid, and visceraldry matter and lipid than fish in other groups. Therewere no significant differences in either conditionindices or relative body composition of fish fedrations of 2.0 to 5.0% BW/day. Based on the growth,feed efficiency and body composition data obtained, afeeding rate of 2.5% BW per day is recommended forM. nemurus fingerlings raised at 29 °C.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009216831360
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  • 47
    Digitale Medien
    Digitale Medien
    Growth and feed utilisation of rainbow trout subjected to changes in feed lipid concentrations (2000)
    Springer
    Aquaculture international 8 (2000), S. 531-542 
    Details
    ISSN: 1573-143X
    Schlagwort(e): feed intake ; growth ; protein utilisation ; proximate ; composition ; rainbow trout (Oncorhynchus mykiss)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Rainbow trout Oncorhynchus mykiss grew from 44 to 326 g in 96days when held at ∼12 °C. Fish were fed to satiation twice dailywith either high (L1: 30.8%, L2:31.4%) or lower-lipid feeds (C1: 18.8%,C2: 21.8%). Four feeding treatments were studied.Group C1C2 received feed C1 for 43 days(days 0–43) and C2 thereafter (days 44–96).Groups L1L2, L1C2 andC1L2 were subjected to dietary changes asindicated by the feed designations. After a short period of feedadaptation, fish ingested similar amounts of feed energy i.e., they ateless by weight of the lipid-rich (L) feeds. Feed lipid content did notaffect growth but fish fed L-feed had reduced feed conversion ratio(FCR) compared to fish fed C-feed (0.731 vs. 0.773) during days0–43 (P 〈 0.01). After 96 days,L1L2-fish were lower in body protein(15.8%) than the C1C2-fish (16.8%)(P 〈 0.01). L-feeds also tended to increase percentage lipidand reduce percentage whole body moisture and ash. A higher net proteinutilisation (NPU) was recorded in fish fed L-feeds (43.6%)compared to fish fed C-feeds (38.8%) in days 0–43(P 〈 0.05). This seemed to be the result of a lower proteinintake rather than a protein-sparing effect of feed lipid. Above athreshold value of approximately 6.5 mg protein eaten·g bodywtminus 1·day−1, NPU decreased.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009291227550
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  • 48
    Digitale Medien
    Digitale Medien
    Size heterogeneity can reduce aggression and promote growth in Atlantic salmon parr (2000)
    Springer
    Aquaculture international 8 (2000), S. 543-549 
    Details
    ISSN: 1573-143X
    Schlagwort(e): aggression ; Atlantic salmon (Salmo salar) ; dominance ; growth
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Aggression in groups of 0+ Atlantic salmon (Salmo salar) was monitoredat weekly intervals in two tanks containing 100 fish each. Three 1 + salmonparr were added to one of these. After 5 weeks, fish weights were measuredin both tanks and the conditions reversed. At ten weeks, weights of fish inboth tanks were measured again. In both populations, levels of aggressionamong the smaller fish were significantly lower and growth ratessignificantly higher when the large fish were present. Although the largefish attacked the small ones, the rate at which they did so was an order ofmagnitude lower that the rate at which small fish attacked each other in theabsence of larger conspecifics. This raises the possibility that levels ofaggression among farmed salmon might be reduced by the addition of a fewlarge conspecifics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009255612529
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  • 49
    Digitale Medien
    Digitale Medien
    On the Stability of Functional Equations and a Problem of Ulam (2000)
    Springer
    Acta applicandae mathematicae 62 (2000), S. 23-130 
    Details
    ISSN: 1572-9036
    Schlagwort(e): stability ; functional equations ; Cauchy difference ; semigroup ; inequalities ; approximate
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract In this paper, we study the stability of functional equations that has its origins with S. M. Ulam, who posed the fundamental problem 60 years ago and with D. H. Hyers, who gave the first significant partial solution in 1941. In particular, during the last two decades, the notion of stability of functional equations has evolved into an area of continuing research from both pure and applied viewpoints. Both classical results and current research are presented in a unified and self-contained fashion. In addition, related problems are investigated. Some of the applications deal with nonlinear equations in Banach spaces and complementarity theory.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1006499223572
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  • 50
    Digitale Medien
    Digitale Medien
    Conversion of Nitrogen to Protein and Amino Acids in Wild Fruits (2000)
    Springer
    Journal of chemical ecology 26 (2000), S. 1749-1763 
    Details
    ISSN: 1573-1561
    Schlagwort(e): Conversion factor ; free amino acids ; fruits ; Kjeldahl ; nitrogen ; nutrition ; protein ; pulp ; secondary metabolites
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract Protein content of plant tissues is usually estimated by multiplying total nitrogen by a conversion factor of 6.25. This technique assumes that all nitrogen originates from protein. When applied to fruit pulp, it overestimates protein content because pulp typically contains free amino acids and many nitrogenous secondary metabolites. At issue is the extent of error and, consequently, what the conversion factor between nitrogen and protein should be. We calculated a conversion factor based on pulp samples from 18 species collected in the southeastern United States. We also report a new and simple method of estimating protein and free amino acids in fruit pulp. Because previous studies have found high variation in protein and secondary metabolite content among fruit species, use of a single conversion factor for all species will generate error. In an attempt to reduce such error, we calculated protein contents and conversion factors separately for two common fruit types: lipid-rich/carbohydrate-poor and lipid-poor/carbohydrate-rich. We found no difference between these types of fruit and hence combined results in calculating an average conversion factor of 5.64. Use of an accurate conversion factor is important in estimating protein consumption by wild animals and in formulating diets of captive animals. It can also reveal whether loss of body mass in captive animals on fruit diets is due to insufficient protein consumption, secondary metabolite toxicity, or an imbalance of amino acids.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1005503316406
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  • 51
    Digitale Medien
    Digitale Medien
    Allelopathic Effects of Humus Phenolics on Growth and Respiration of Mycorrhizal Fungi (2000)
    Springer
    Journal of chemical ecology 26 (2000), S. 2015-2023 
    Details
    ISSN: 1573-1561
    Schlagwort(e): Allelopathy ; growth ; phenolics ; Hebeloma ; Hymenoscyphus ; Picea abies ; Vaccinium myrtillus
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Chemie und Pharmazie
    Notizen: Abstract Allelopathy due to humus phenolics is a cause of natural regeneration deficiency in subalpine Norway spruce (Picea abies) forests. If inhibition of spruce germination and seedling growth due to allelochemicals is generally accepted, in contrast there is a lack of knowledge about phenolic effects on mycorrhizal fungi. Thus, this work tested effects of a humic solution and its naturally occurring phenolics on the growth and respiration of two mycorrhizal fungi: Hymenoscyphus ericae (symbiont of Vaccinium myrtillus, the main allelochemical-producing plant) and Hebeloma crustuliniforme (symbiont of P. abies, the target plant). Growth and respiration of H. crustuliniforme were inhibited by growth medium with the original humic solution (−6% and −30%), respectively, whereas the same humic solution did not affect growth but decreased respiration of H. ericae (−55%). When naturally occurring phenolics (same chemicals and concentrations in the original humic solution) were added to the growth medium, growth of H. crustuliniforme was not affected, whereas that of H. ericae significantly increased (+10%). We conclude that H. ericae is better adapted to the allelopathic constraints of this forest soil than H. crustuliniforme and that the dominance of V. myrtillus among understory species could be explained in this way.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1005551912405
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  • 52
    Digitale Medien
    Digitale Medien
    Debonding of the interface as 'crack arrestor' (2000)
    Springer
    International journal of fracture 105 (2000), S. 57-79 
    Details
    ISSN: 1573-2673
    Schlagwort(e): Interface toughness ; interface debonding ; stability ; adhesive interface ; bimaterial.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract In this paper, we studied the interface debonding when a crack perpendicularly approaches an interface between two dissimilar elastic materials. An interface toughness law was first defined according to an adhesive model governing the interface fracture. By analysing the interaction between the normally approaching crack and the interface crack and by tacking account of the adhesive forces at ends of the interfacial crack, a model for studying the interface debonding and the debonding stability was established. It is observed that the interface debonding toughness depends strongly on the mixed mode locally produced over the plastic adhesive zone of the interface. Moreover, the interface debonding may be unstable, i.e. the interface debonding length may jump from an initial value to a certain final value under critical remote loading. This jump may be surprisedly important in certain cases. These results agree with the experimental works gathered so far and can be used to explain the mechanism of 'crack arrestor' formed by an interface.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1007603809972
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  • 53
    Digitale Medien
    Digitale Medien
    Effects of Ca2+ on the Activity and Stability of Methanol Dehydrogenase (2000)
    Springer
    The protein journal 19 (2000), S. 469-473 
    Details
    ISSN: 1573-4943
    Schlagwort(e): Methanol dehydrogenase ; Ca2+ ; binding ; activity ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The effects of exogenously added Ca2+ on the enzymatic activity and structural stability of methanol dehydrogenase were studied for various Ca2+ concentrations. Methanol dehydrogenase activity increased significantly with increasing concentration of Ca2+, approaching saturation at 200 mM Ca2+. The effect of Ca2+ on the activation of MDH was time dependent and Ca2+ specific and was due to binding of the metal ions to the enzyme. Addition of increasing concentration of Ca2+ caused a decrease of the intrinsic tryptophan fluorescence intensity in a concentration-dependent manner to a minimum at 200 mM, but with no change in the fluorescence emission maximum wavelength or the CD spectra. The results revealed that the activation of methanol dehydrogenase by Ca2+ occurred concurrently with the conformational change. In addition, exogenously bound Ca2+ destabilized MDH. The potential biological significance of these results is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026597314542
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  • 54
    Digitale Medien
    Digitale Medien
    Bifurcations of a cantilevered pipe conveying steady fluid with a terminal nozzle (2000)
    Springer
    Acta mechanica Sinica 16 (2000), S. 264-272 
    Details
    ISSN: 1614-3116
    Schlagwort(e): nonlinear dynamics ; bifurcation ; stability ; fluid-solid interaction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Notizen: Abstract This paper studies interactions of pipe and fluid and deals with bifurcations of a cantilevered pipe conveying a steady fluid, clamped at one end and having a nozzle subjected to nonlinear constraints at the free end. Either the nozzle parameter or the flow velocity is taken as a variable parameter. The discrete equations of the system are obtained by the Ritz-Galerkin method. The static stability is studied by the Routh criteria. The method of averaging is employed to examine the analytical results and the chaotic motions. Three critical values are given. The first one makes the system lose the static stability by pitchfork bifurcation. The second one makes the system lose the dynamical stability by Hopf bifurcation. The third one makes the periodic motions of the system lose the stability by doubling-period bifurcation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02487667
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  • 55
    Digitale Medien
    Digitale Medien
    Metabolism of Poly-β-Hydroxybutyric Acid in Yersinia pseudotuberculosis and Listeria monocytogenes Cultivated at Different Temperatures (2000)
    Springer
    Microbiology 69 (2000), S. 652-654 
    Details
    ISSN: 1608-3237
    Schlagwort(e): poly-β-hydroxybutyric acid ; Yersinia pseudotuberculosis ; Listeria monocytogenes ; temperature ; growth
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A comparative investigation of the intracellular content of poly-β-hydroxybutyric acid showed that Yersinia pseudotuberculosis strains accumulated, on the average, lower amounts of this reserve substance than Listeria monocytogenes strains. The intracellular pool of poly-β-hydroxybutyric acid was responsible for the growth of the bacteria at low temperatures (4–6°C) in the absence of any exogenous carbon and energy source.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026645922491
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  • 56
    Digitale Medien
    Digitale Medien
    On the Nature of the Three-Phase Response of Scenedesmus quadricauda Populations to the Action of Imazalil Sulfate (2000)
    Springer
    Russian journal of plant physiology 47 (2000), S. 772-778 
    Details
    ISSN: 1608-3407
    Schlagwort(e): Scenedesmus quadricauda ; growth ; cell size ; photosynthetic activity ; imazalil sulfate ; three-phase dose response
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Three-phase dose responses of biological systems of different levels of organization are often called “paradoxical” because the biological effects are clearly manifested under low- and high-intensity treatments, but are absent during moderate-strength treatments. In this work, we found anomalous changes in the cell number of a green alga Scenedesmus quadricauda (Turp.) Breb. grown in the presence of the fungicide imazalil sulfate. At low imazalil concentrations (2.5 × 10–9–2.5 × 10–6 M), the slow increase in the cell number as compared to an untreated culture was not related to cell death. As seen by the dynamics of the population structure and cell functional characteristics (photosynthesis, thermal stability of photosynthetic membranes, etc.), the decrease in the growth rate at low concentrations of imazalil (2–10 × 10–9 M) was due to a long-term arrest of cell division in a fraction of the cell population rather than to a decrease in the rate of division. The absence of a toxic effect or even a slight stimulation of culture growth at moderate concentrations (0.05–1.25 × 10–6 M) was due to the resumption of cell division after a temporal cessation. At these concentrations, imazalil induced cell stress and adaptive elevation of cell tolerance to the fungicide (acclimation). Cell death was observed only at a high fungicide content in the medium (6.25 × 10–6 and higher). Thus, the three-phase (bimodal) dose response corresponds to two regimes (steady-states) of cell functioning which differ in cell sensitivity to external stimuli. The low-sensitivity state, which is characteristic of cells that have experienced stress, is likely to be the state known as “hormesis.”
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026659228774
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  • 57
    Digitale Medien
    Digitale Medien
    Long-term monitoring of benthic macroinvertebrate community structure: a perspective from a Colorado river* (2000)
    Springer
    Aquatic ecology 34 (2000), S. 261-278 
    Details
    ISSN: 1573-5125
    Schlagwort(e): discharge effects on lotic invertebrates ; disturbance ; persistence ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Temporal and spatial trends were examined in benthic macroinvertebrate and physical-chemical data collected for at least ten years at ten sites along the plains reach of the Cache la Poudre River, Colorado, USA. A distinct longitudinal environment gradient was found as many of the water chemistry parameter levels changed downstream from the reference site. Seasonal Kendall analyses on individual sites indicated that several chemical parameters, including conductivity, un-ionized NH3-N and NO2-N have increased since the beginning of the study within most sites. Levels of some parameters (e.g., dissolved oxygen, un-ionized NH3-N) violated aquatic life standards a few times during the study. Over 175 taxa of macroinvertebrates (primarily insects) were collected in the study reach from 1981–1996. Results from detrended correspondence analyses (DCA) on macroinvertebrate data indicated that this stretch of the river exhibited little longitudinal change beyond the two farthest upstream sites. There was a decline in macroinvertebrate density and total number of taxa within most individual sites during 1983–1984, corresponding with the highest recorded discharge in 75 years (1983) and a prolonged, heavy spring runoff in 1984. Taxa richness and density recovered to pre-1983 levels within a few months to a year following the high flows at most sites. These findings suggested that the macroinvertebrate assemblages had low resistance to disturbance, but high resilience. However, the results from DCAs and Kendall's Coefficient of Concordance (W) on individual sites for the entire study period suggested a similar macroinvertebrate community structure through time. It would appear that the composition and abundance of the lotic macroinvertebrate assemblages in the Poudre River has remained relatively constant over the long-term. This has occurred even with some potentially negative changes in water chemistry and increased urban development.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009989510721
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  • 58
    Digitale Medien
    Digitale Medien
    Influence of CO2, light and watering on growth of Nostoc flagelliforme mats (2000)
    Springer
    Journal of applied phycology 12 (2000), S. 185-189 
    Details
    ISSN: 1573-5176
    Schlagwort(e): blue-green alga ; cyanobacterium ; carbon dioxide ; culture ; growth ; Nostocflagelliforme ; rehydration, watering
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The terrestrial blue-green alga (cyanobacterium), Nostoc flagelliforme, was cultured in air at variouslevels of CO2, light and watering to see theireffects on its growth. The alga showed the highestrelative growth rate at the conditions of highCO2 (1500 ppm), high light regime (219–414μmol m-2s-1) and twice daily watering,but the lowest rate at the conditions of low light(58–114 μmol m-2s-1) and daily twicewatering. Increased watering had little effect ongrowth rate at 350 ppm CO2, but increased byabout 70% at 1500ppm CO2 under high lightconditions. It was concluded that enriched CO2could enhance the growth of N. flagelliformewhen sufficient light and water was supplied.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008123203409
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  • 59
    Digitale Medien
    Digitale Medien
    High rate algal pond operating strategies for urban wastewater nitrogen removal (2000)
    Springer
    Journal of applied phycology 12 (2000), S. 331-339 
    Details
    ISSN: 1573-5176
    Schlagwort(e): algal biomass ; algal uptake ; ammonia stripping ; biological nutrient removal ; high rate algal ponds ; nitrogen ; nutrients ; nitrification ; urban wastewater treatment ; waste stabilisation ponds
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Two experimental high rate algal ponds (HRAPs) (1.5m2, 570 L per unit), each with a secondaryclarifier for algal biomass separation (0.025 m2,without recirculation), were fed with urban wastewaterfor a one-year period (June 1993 to July 1994). TheHRAPs were installed on the roof of the Department ofHydraulic, Coastal and Environmental Engineering ofthe Technical University of Catalonia, Barcelona,Spain (lat. 41° 24′ 42″ N; long. 2° 7′42″ E). Nitrogen removal efficiency and changes intotal nitrogen, total organic nitrogen,NH4 +-N, and oxidized nitrogen underdifferent hydraulic retention times (HRTs) werecompared. HRAP A was always operated at a higherHRT than HRAP B. Both HRAPs were subjected to thesame environmental conditions of solar radiation, airtemperature and influent water quality. Grab samplesof influent, effluent of the HRAP (mixed liquor) andfinal effluent from the clarifiers were taken once aweek. The annual average nitrogen removal was 73% forHRAP A, and 57% for HRAP B. Higher removal in HRAP Awas due to a lower inorganic nitrogen concentration inits effluent. Significant differences (p〉 0.05) inthe relative proportions of nitrogen forms between thetwo HRAPs were observed only in autumn and winter.This was mainly because HRAP B did not achieve a highlevel of NH4 +-N removal by stripping andalgal uptake, as observed in HRAP A. NH4 +-Nstripping was the most important mechanism fornitrogen removal (mean efficiency of 47% and 32% inHRAP A and B, respectively) followed by algal uptake,and subsequent algal separation in the clarifiers(mean efficiency of 26% and 25% in HRAP A and Brespectively). The conclusion of this study is thatHRT determines both the nitrogen removal efficiencyand the distribution of nitrogen forms in the effluentof a HRAP. The nitrogen removal level can becontrolled through suitable HRT operating strategies.By operating at a HRT of 4 days in spring and summer,and 10 days in autumn and winter, nitrogenconcentration in the effluent of a HRAP system can bereduced to less than 15 mg L-1 N.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008146421368
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  • 60
    Digitale Medien
    Digitale Medien
    Numerical solutions for a coupled non-linear oscillator (2000)
    Springer
    Journal of mathematical chemistry 28 (2000), S. 325-340 
    Details
    ISSN: 1572-8897
    Schlagwort(e): numerical method ; stability ; Hopf bifurcation ; coupled oscillator
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Mathematik
    Notizen: Abstract A second-order accurate numerical method has been proposed for the solution of a coupled non-linear oscillator featuring in chemical kinetics. Although implicit by construction, the method enables the solution of the model initial-value problem (IVP) to be computed explicitly. The second-order method is constructed by taking a linear combination of first-order methods. The stability analysis of the system suggests the existence of a Hopf bifurcation, which is confirmed by the numerical method. Both the critical point of the continuous system and the fixed point of the numerical method will be seen to have the same stability properties. The second-order method is more competitive in terms of numerical stability than some well-known standard methods (such as the Runge–Kutta methods of order two and four).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1011025104111
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  • 61
    Digitale Medien
    Digitale Medien
    Life history comparisons of Daphnia obtusa from temporary ponds, cultured with a low-quality food (2000)
    Springer
    Aquatic ecology 34 (2000), S. 19-27 
    Details
    ISSN: 1573-5125
    Schlagwort(e): adaptation ; fitness ; food quality ; growth ; reproduction ; temporary ponds
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Temporary pond Daphnia flourish on relatively poor-quality food, suggesting adaptation to stringent temporary pond conditions. We conducted laboratory life history experiments on populations of Daphnia obtusa from a shaded woodland temporary pond (short hydroperiod, dystrophic) and an open farmland temporary pond (long hydroperiod, eutrophic), and compared a suite of physical/chemical conditions in the ponds to evaluate habitat conditions. We hypothesized that the shaded woodland pond population would be more fit in terms of life history variables for individuals (age and size at first reproduction, mean brood size, mean number of neonates) and populations (generation time, net reproductive rate R 0, and intrinsic reproductive rate r) given a standard, low-quality food (trout chow and yeast). Life history traits of woodland pond animals were mixed, relative to farm pond animals, and consistent with bet-hedging for an unpredictable habitat. Values of life history traits rivaled or exceeded those of other studies using phytoplankton as food, and were influenced by the pond water used for our study. Life histories clearly differ among local and regional temporary pond Daphnia obtusa populations, and should be valuable for examining the relative influences of local selection and metapopulation dynamics on population structure.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009985529660
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  • 62
    Digitale Medien
    Digitale Medien
    Responses of Porphyra linearis (Rhodophyta) to environmental factors under controlled culture conditions (2000)
    Springer
    Journal of applied phycology 12 (2000), S. 535-542 
    Details
    ISSN: 1573-5176
    Schlagwort(e): desiccation ; growth ; growth model ; inorganic carbon ; nutrients ; photoperiod ; photosynthesis ; pigments ; Porphyra linearis ; PPF ; respiration ; temperature ; water velocity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The effect of environmental parameters on the growthof Porphyra linearis gametophytes was examinedunder controlled conditions, and related to themultilinear regression growth model recently developedfor this seaweed under coastal conditions in theeastern Mediterranean. Growth chambers, a gradienttable, special culture devices and analytical methodswere combined for this culture study.The major factors significantly controlling thegrowth rate of the P. linearis gametophytein glass dishes were: photoperiod, temperature, agein culture, photosynthetic photon flux (PPF), salinityand water dynamics. Maximal growth occurred underdaylength of 12 h, medium temperature (15–20 °C), low PPF (70–140 μmol photon m-2s-1), ambient salinity (30–40 ppt), 1–3 h ofdaily air exposure, and water velocity of 4 cm s-1.Photosynthesis and respiration rates weredominantly affected by daylength and temperature,while the concentration of pigments was dominantlyaffected by PPF and temperature.These conditions correspond well to the optimalnatural growth environment of this local species andare in agreement with the optimum estimated throughthe recently developed outdoor mathematical growthmodel.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008138227520
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  • 63
    Digitale Medien
    Digitale Medien
    Differential growth of crayfish Procambarus alleni in relation to hydrological conditions in marl prairie wetlands of Everglades National Park, USA (2000)
    Springer
    Aquatic ecology 34 (2000), S. 389-395 
    Details
    ISSN: 1573-5125
    Schlagwort(e): crayfish ; Procambarus alleni ; growth ; Florida Everglades ; hydroperiod
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Environmental conditions influence crustacean growth by affecting molt intervals and incremental increases in length and weight. In the seasonally-flooded marl prairie wetlands of eastern Everglades National Park, U.S.A., hydropattern exerts considerable influence on aquatic primary productivity, and so may influence the availability of food resources for higher trophic levels. The seasonal hydroperiod has been drastically altered by anthropogenic factors, but the impacts on the aquatic community are not well known. We studied whether differences in growth of crayfish Procambarus alleni could be detected in habitats with different hydroperiods. We first described growth patterns based on incremental increases in length and weight of crayfish on a high protein diet in the laboratory. Regression analyses indicated that growth patterns in males and females were similar. Although the intermolt period increased with age, the proportional increases in length and weight were similar through successive molts. The relationship between length and weight of crayfish was best described by a power equation for allometric growth. We then compared growth curves for crayfish subpopulations from different areas of the marl prairie. In habitats with the longest hydroperiods, crayfish weight-at-size was not significantly different from that in laboratory crayfish on the high protein diet. However, weight gain per unit increase in length in short hydroperiod sites was significantly less than in long hydroperiod sites or in the laboratory. These results indicate that crayfish productivity may be associated with hydroperiod in these stressed wetlands, and this may contribute to observed source-sink population regulation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1011472828639
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  • 64
    Digitale Medien
    Digitale Medien
    1,3-Dihydrobenzo[c]thienylium (thiophthalylium) salts. (Review) (2000)
    Springer
    Chemistry of heterocyclic compounds 36 (2000), S. 115-133 
    Details
    ISSN: 1573-8353
    Schlagwort(e): thiophthalylium salts ; methods of preparation ; structure ; stability ; reactivity ; electrophilic properties
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Methods of preparation, chemical reactions, the structures and reactivity of thiophthalylium ions are reviewed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02283539
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  • 65
    Digitale Medien
    Digitale Medien
    Solving A $$\underline x $$ = $$\underline b $$ Using a Modified Conjugate Gradient Method Based on Roots of A (2000)
    Springer
    Journal of scientific computing 15 (2000), S. 441-456 
    Details
    ISSN: 1573-7691
    Schlagwort(e): modified conjugate gradient method ; conjugate gradient method ; Krylov space ; convergence rate ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Notizen: Abstract We consider the modified conjugate gradient procedure for solving A $$\underline x $$ = $$\underline b $$ in which the approximation space is based upon the Krylov space associated with A 1/p and $$\underline b $$ , for any integer p. For the square-root MCG (p=2) we establish a sharpened bound for the error at each iteration via Chebyshev polynomials in $$\sqrt A$$ . We discuss the implications of the quickly accumulating effect of an error in $$\sqrt A$$ $$\underline b $$ in the initial stage, and find an error bound even in the presence of such accumulating errors. Although this accumulation of errors may limit the usefulness of this method when $$\sqrt A$$ $$\underline b $$ is unknown, it may still be successfully applied to a variety of small, “almost-SPD” problems, and can be used to jump-start the conjugate gradient method. Finally, we verify these theoretical results with numerical tests.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1011132730828
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  • 66
    Digitale Medien
    Digitale Medien
    Associative Memories in Infinite Dimensional Spaces (2000)
    Springer
    Neural processing letters 12 (2000), S. 129-144 
    Details
    ISSN: 1573-773X
    Schlagwort(e): associative memory ; dynamical systems ; Glauber dynamics ; Hopfield model ; infinite dimensional state space ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Notizen: Abstract A generalization of the Little–Hopfield neural network model for associative memories is presented that considers the case of a continuum of processing units. The state space corresponds to an infinite dimensional euclidean space. A dynamics is proposed that minimizes an energy functional that is a natural extension of the discrete case. The case in which the synaptic weight operator is defined through the autocorrelation rule (Hebb rule) with orthogonal memories is analyzed. We also consider the case of memories that are not orthogonal. Finally, we discuss the generalization of the non deterministic, finite temperature dynamics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009689025427
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  • 67
    Digitale Medien
    Digitale Medien
    Partial Compensation for Mismatched Uncertain Discrete Systems (2000)
    Springer
    Dynamics and control 10 (2000), S. 47-61 
    Details
    ISSN: 1573-8450
    Schlagwort(e): stability ; robust control ; Lyapunov approach ; discrete system
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Abstract Control design of nonlinear discrete-time uncertain systems with (possibly fast) uncertain parameters is considered. We study the effect of only partially compensating the uncertainty. The optimal choice of a design parameter, which indicates the amount of compensation, is recommended.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008395928788
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  • 68
    Digitale Medien
    Digitale Medien
    Optimal Model Reduction with a Frequency Weighted Extension (2000)
    Springer
    Dynamics and control 10 (2000), S. 255-276 
    Details
    ISSN: 1573-8450
    Schlagwort(e): continuous-time systems ; frequency weighted model reduction ; gradient flow ; optimization ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Abstract Inthis paper, a model reduction technique based on optimizationis presented. The objective function minimized is the impulseenergy of the overall system. An extension of the technique tothe frequency weighted case is also presented, where single-sidedor double-sided weightings can be incorporated in the reductionprocedure. The paper proposes an alternative to find an optimizationsolution by solving ordinary differential equations which aregradient flow associated with the objective function to be minimized.Two examples are presented to illustrate the effectiveness ofthe method.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008366812002
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  • 69
    Digitale Medien
    Digitale Medien
    Effects of air emersion on survival and growth of hatchery rearedgreat scallop spat (2000)
    Springer
    Aquaculture international 8 (2000), S. 159-168 
    Details
    ISSN: 1573-143X
    Schlagwort(e): emersion ; growth ; Pecten maximus ; scallop spat ; survival ; transport
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Scallop spat production normally requires transfer between growthsystems. Simulated transport experiments were carried out in April, June,December and February to evaluate effects of transport time on greatscallop (Pecten maximus) spat growth and survival. The spat (1.7–1.8 mm in shell-height and 21–25 µg ash free dry weight [AFDW]) wereheld in moist coffee filters at a temperature of 10 °C for up to 24 h,before being replaced into sieves in rearing tanks at 15 °C. The studyshowed that by increasing air emersion time, survival and growthdecreased. No significant difference in the results between 0 and 4 h of airemersion was found, while the effects after 12 and 24 h differed betweenspat groups. Survival and growth rates showed seasonal differences. Meansurvival was 35–71% in April and 77–99% from June to February. In Junemean growth rates attained were 115–128 µm shell-height and 15–18µg AFDW per day compared with 49–69 µm and 3.8–7.0 µgper day for the other spat groups. Great scallop spat may survive atransfer time of 24 h, but transportation for longer than 12 h is notrecommended if subsequent high survival and growth rates are to beensured.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009294413599
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  • 70
    Digitale Medien
    Digitale Medien
    Growth and mortality of the king scallop grown in suspended culture in Malaga, Southern Spain (2000)
    Springer
    Aquaculture international 8 (2000), S. 207-225 
    Details
    ISSN: 1573-143X
    Schlagwort(e): growth ; mortality ; Pecten maximus ; suspended culture
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Growth and mortality of the king scallop, Pecten maximus, werecompared when grown in cages and by ear hanging in suspended culturein Fuengirola, Malaga, in southern Spain. Seed (juveniles) used in theexperiment was collected in September 1997 that had settled on collectorsin April-June, of that year. Culture in suspended cages began in January1998 when the seed measured 42.7 (3.3) mm shell height and ended inFebruary 1999. Significantly faster growth was found at a minimum culturedensity (16 scallops/cage) than at two other densities (24 and 36scallops/cage). Depth (1, 5 and 10 m from the bottom) influenced growth,poorest growth occurred closest to the bottom. Under optimum growingconditions, 16 scallops/cage suspended 10 m from the bottom, scallops grewto 10 cm shell length (legal size) by February 1999.In ear hanging culture, ropes were moored in April (51.3 (4.5) mm),June (58.2 (4.5) mm) and November 1998 (64.3 (4.9) mm).Initially, rapid shell growth was observed in all three cultures.Subsequently, the shells became covered with barnacles, Balanus sp.,that possibly caused total mortality of the April culture and led to highmortalities in the two other cultures.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009202801304
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  • 71
    Digitale Medien
    Digitale Medien
    Effects of larger fish and size grading on growth and size variation in fingerling silver perch (2000)
    Springer
    Aquaculture international 8 (2000), S. 391-401 
    Details
    ISSN: 1573-143X
    Schlagwort(e): growth ; silver perch (Bidyanus bidyanus) ; size grading ; size variation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract This study presents two experiments addressing growth and size variation in fingerling silver perch (Bidyanus bidyanus. In the first experiment, fish close to mean population size were raised either in the presence or absence of five larger fish for 60 days. Mean specific growth rate (SGR) and increases in the coefficient of variation and skewness were lower in the presence of larger fish, indicating a negative effect of large fish on the growth of smaller ones. In the second experiment, fingerlings were graded into groups smaller and larger than the median size of the population and raised in size-sorted groups of 60 large or small fish and mixed groups of 30 fish of each size category, for 60 days. There was no difference in mean SGR among groups, nor between the mixed group ad the weighted mean of the small and large groups. Biomass gain was higher in the mixed groups than in the weighted small-and-large groups, probably due to a slightly lower survival in the groups comprised of large fish. The fact that the effect of large fingerlings on the growth of smaller ones was evident in the first, but not the second, experiment may be attributed to higher size disparity between large and small fingerlings in the first experiment.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009274726380
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  • 72
    Digitale Medien
    Digitale Medien
    Partial or total replacement of fish meal byplant protein affects gonadal development and plasma17 β-estradiol levels in female Nile tilapia (2000)
    Springer
    Aquaculture international 8 (2000), S. 299-313 
    Details
    ISSN: 1573-143X
    Schlagwort(e): 17 β-estradiol ; fish meal ; gonadal development ; growth ; Nile tilapia (Oreochromis niloticus) ; plant proteins
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract This study was conducted to evaluate theeffect of plant protein‐based diets on gonadaldevelopment and plasma 17 β-estradiol (E2) levelin female Nile tilapia Oreochromis niloticus.Fish with a mean body weight of 6.7 (0.1) g were fedfour different diets with the same digestible protein(DP) and digestible energy (DE) containing gradedlevels of a mixture of plant ingredients as partial ortotal replacement of fish meal protein for 20 weeks.The control diet (D0) was based on fish meal, twodiets containing 33% (D33) and 66% (D66) of plantprotein, and one diet containing only plant protein(D100). Fish were sampled at 12 and 20 weeks. Nosignificant differences were found in different stagesof oocyte development and plasma E2 levels betweentilapia fed diets D0 and D100 at 12 weeks. Eight weekslater tilapia fed diet D0 showed a higher (P 〈 0.05)level of E2 than the D100 group. This difference andthe reduced proportion of vitellogenic and matureoocytes demonstrated that diets containing only plantprotein are less efficient in terms of tilapia growthand consequently ovarian development.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009217310464
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  • 73
    Digitale Medien
    Digitale Medien
    Growth performance of pink dentex as compared to four other sparids reared in marine cages in Croatia (2000)
    Springer
    Aquaculture international 8 (2000), S. 455-461 
    Details
    ISSN: 1573-143X
    Schlagwort(e): floating cages ; growth ; pink dentex (Dentex gibbosus) ; sparids (Dentex dentex, Sparus aurata, Spondyliosoma cantharus, Diplodus puntazzo)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009276204516
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  • 74
    Digitale Medien
    Digitale Medien
    The Equation of State of Lakes (2000)
    Springer
    Aquatic geochemistry 6 (2000), S. 1-17 
    Details
    ISSN: 1573-1421
    Schlagwort(e): lakes ; density ; compressibility ; expansibility ; conductivity ; stability ; pvt properties
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Geologie und Paläontologie
    Notizen: Abstract In recent years, a number of workers have studied the stability of deep lakes such as Lake Tanganyika, Lake Baikal and Lake Malawi. In this paper, the methods that can be used to determine the effect that the components of lakes have on the equation of state are examined. The PVT properties of Lakes have been determined by using apparent molal volume data for the major ionic components of the lake. The estimated PVT properties (densities, expansibility and compressibilities) of the lakes are found to be in good agreement with the PVT properties (P) of seawater diluted to the same salinity. This is similar to earlier work that showed that the PVT properties of rivers and estuarine waters could also be estimated from the properties of seawater. The measured densities of Lake Tanganyika were found to be in good agreement (± 2 × 10-6 g cm-3) with the values estimated from partial molal properties and the values of seawater at the same total salinity (ST = 0.568‰). The increase in the densities of Lake Tanganyika waters increased due to changes in the composition of the waters. The measured increase in the measured density (45 × 10-6 g cm-3) is in good agreement (46 × 10-6 g cm-3) with the values calculated for the increase in Na+, HCO3 -, Mg2+, Ca2+ and Si(OH)4. Methods are described that can be used to determine the conductivity salinity of lakes using the equations developed for seawater. By combining these relationships with apparent molal volume data, one can relate the PVT properties of the lake to those of seawater.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009626325650
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  • 75
    Digitale Medien
    Digitale Medien
    The effect of photoperiod, tank colour and light intensity on growth of larval haddock (2000)
    Springer
    Aquaculture international 7 (2000), S. 369-382 
    Details
    ISSN: 1573-143X
    Schlagwort(e): growth ; haddock (Melanogrammus aeglefinus) ; larvae ; light intensity ; photperiod ; tank colour
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract In two separate experiments, haddock (Melanogrammus aeglefinus) larvae were raised under different photoperiods (24L : 0D or 15L : 9D), or different combinations of tank colour (black or white) and light intensity (1.1 μmol s−1 m−2 or 18 μmol s−1 m−2). Growth (0.8% day−1 in standard length; 2.9% day−1 in body area) and survival (2%) were not significantly different between photoperiod treatments after 35 days. Larval survival was greater in white versus black tanks after 41 days (2% versus l%, respectively). Growth of larvae was impaired in black tanks at low (1.1 μmol s−1 m−2) light intensity (0.8% day−1 in standard length and 2.2% day−1 in body area versus 1.1% day 21 in standard length and 3.1% day−1 in body area, for all other treatments). Transmission and reflection of light was low in black tanks at low incident light, and there was very little upwelling light. The resultant poor prey to background contrast probably resulted in larvae being unable to consume sufficient food to sustain a level of growth comparable to that in other treatments.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009204909992
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  • 76
    Digitale Medien
    Digitale Medien
    Influence of season, initial size, depth, gear type and stocking density on the growth rates and recovery of sea scallop, Placopecten magellancius, on a farm-based nursery (2000)
    Springer
    Aquaculture international 8 (2000), S. 183-206 
    Details
    ISSN: 1573-143X
    Schlagwort(e): bivalve ; fouling ; growth ; Newfoundland ; nursery ; sea scallop (Placopecten magellanicus) ; spat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Hatchery-reared sea scallop (Placopecten magellanicus) spat weremonitored for growth and recovery in three experiments to determine themost suitable system for nursery culture. In Experiment I, four size classesof nursery-sized spat held at two depths from October to July exhibiteddeclining growth rates over the winter period and increased growth ratesin the spring. Overall, season, depth and initial size had a significantinfluence on the absolute and specific growth rates of scallops. Recovery,defined as number of scallops remaining after mortality and loss of spatthrough gear mesh, was influenced by season and initial size, but notdepth. Scallops in the 3.0 mm+ size class had higher growth rates andrecovery than those in the 1.4–1.6 mm, 1.7–1.9 mm and 2.0–2.9 mm sizeclasses. In Experiment II, two gear types containing similar size spat werecompared. Growth rates were significantly higher in 3.0 mm pearl nets thanin 3.0 mm collector bags, although recovery was similar between the twoequipment types. Experiment III, two stocking densities of nursery-sizedspat were compared in collector bags. Neither growth rate nor recoverywere significantly different for the two densities (2600 and 5200spat/collector bag) tested. Overall, these studies indicated that importantparameters for optimizing the growth and recovery of scallops in a farm-based nursery system include season, initial spat size, deployment depthand gear type.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009298631346
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  • 77
    Digitale Medien
    Digitale Medien
    Incidence of bacteria involved in nitrogen and sulphur cycles in tropical shrimp culture ponds (2000)
    Springer
    Aquaculture international 8 (2000), S. 463-472 
    Details
    ISSN: 1573-143X
    Schlagwort(e): nitrogen ; organic matter ; shrimp culture ; sulphur cycle bacteria ; water quality
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009250004999
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  • 78
    Digitale Medien
    Digitale Medien
    Growth effects in Arctic charr reared in cold water: Feed frequency, access to bottom feeding and stocking density (2000)
    Springer
    Aquaculture international 8 (2000), S. 381-389 
    Details
    ISSN: 1573-143X
    Schlagwort(e): Arctic charr (Salvelinus alpinus) ; growth ; low temperature ; stocking density ; time restricted feeding,/kwd〉
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The effects of time restricted feeding, possibility of bottomfeeding and stocking density on the growth of Arctic charr(Salvelinus alpinus L.) were examined in fish held at lowtemperature (〈2 °C). Fish fed for a restricted time (1 h) hadsignificantly (p 〈 0.05) lower specific growth rate (0.15 vs0.32% per day) than those fed the same ration over an extendedtime period (12 h). Increasing stocking densities had a positive andsignificant effect (p 〈 0.05) on growth with SGR increasing from 0.27to 0.52% per day at 2–30 kg m-3. Fish withaccess to feed on the tank floor had a significantly higher (p 〈0.05) growth rate (0.3 vs 0.13% per day) than those without thepossibility to feed from the bottom. When fish were held underconditions without access to the bottom a doubling of the feed rationdid not result in a significant (p 〉 0.05) increase in growth rate(0.13 vs 0.12%percnt; per day).
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009235130015
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  • 79
    Digitale Medien
    Digitale Medien
    Sources, sinks, and fluxes of nutrients (N + P) in a small highly modified urban estuary in southern California (2000)
    Springer
    Urban ecosystems 4 (2000), S. 125-144 
    Details
    ISSN: 1573-1642
    Schlagwort(e): nitrogen ; phosphorus ; macroalgae ; estuary ; anthropogenic
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Architektur, Bauingenieurwesen, Vermessung , Energietechnik
    Notizen: Abstract Our objective was to begin to investigate sources, sinks, and flux rates of nitrogen (N) and phosphorus (P) in Famosa Slough, a small (12 ha) highly modified urban estuary in San Diego, California, U.S.A. The hydrology of Famosa Slough has been modified by culverts that dampen tidal influence and seasonal runoff from two urban watersheds, each of which has been implicated as a nutrient source that generates nuisance algal blooms. In 1995 and 1996, the ranges of nutrients measured in the water column were extremely wide; upper values exceeded those in other estuaries identified as eutrophic. Average dissolved inorganic nitrogen ranged from 2 to 250 μM, while dissolved inorganic phosphorus ranged from 〈1 to 15 μM. Nutrient content of the water changed rapidly both spatially and temporally depending on the tides and rainfall. While tidal water dominated this system, especially in the dry season, our results indicate that Famosa Slough's small watershed, not the larger watershed of the San Diego River, was the major source of nutrients during rainfall. Sediment nutrients were also high (∼3 mg N g dry wt−1 and 0.600 mg P g dry wt−1). Short-term flux studies suggest that the large accumulations of opportunistic green macroalgae commonly found in this estuary, and possibly the sediments, may act as a large and rapid sink for nutrients during times of high nutrient supply. We suggest that small, shallow estuaries in urban settings may have more complex and rapid nutrient dynamics than those found in larger systems.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1011359311384
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  • 80
    Digitale Medien
    Digitale Medien
    Surface Instability of Laminated Coatings upon Inelastic Deformation (2000)
    Springer
    Mechanics of composite materials 36 (2000), S. 475-480 
    Details
    ISSN: 1573-8922
    Schlagwort(e): stability ; three-dimensional theory ; tribotechnics ; elastoplastic deformations ; viscoelasticity ; surface ; tracking and dead loads ; laminated coating ; piecewise-homogeneous model ; active loading
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: Abstract The problem of surface instability of laminated coatings with inelastic properties is considered within the framework of a model of piecewise-homogeneous media on the basis of the three-dimensional linearized theory of stability. A general statement of the problem is formulated and the basic characteristic equations are derived. The solutions of particular problems are obtained for elastoplastic and viscoelastic models of solids.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1006758600457
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  • 81
    Digitale Medien
    Digitale Medien
    Short-term Cover Crop Decomposition in Organic and Conventional Soils: Characterization of Soil C, N, Microbial and Plant Pathogen Dynamics (2000)
    Springer
    European journal of plant pathology 106 (2000), S. 37-50 
    Details
    ISSN: 1573-8469
    Schlagwort(e): carbon ; cellulose ; cover crop ; damping-off ; discriminant analysis ; lignin ; nitrogen
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Stages of oat–vetch cover crop decomposition were characterized over time in terms of carbon and nitrogen cycling, microbial activity and damping-off pathogen dynamics in organically and conventionally managed soils in a field and a controlled incubation experiment. A measurement of relative growth consisting of radial growth of a fungal colony over non-sterilized soil divided by that over sterilized soil was used as an assay of suppressiveness. No differences in relative growth of Pythium aphanidermatum and Rhizoctonia solani were detected between organic and conventionally managed soils amended with cover crop residue. Significant effects of cover crop decomposition stage on the relative growth of both pathogens were obtained. Relative growth of P. aphanidermatum was highest just after incorporation and decreased 3 weeks after incorporation. Relative growth of R. solani was highest about 20 days after incorporation, and decreased 2 weeks later in the organic system, but continued to increase in the conventional system. In both experiments, the N or C content, C:N ratio or dry weight of retrieved debris were significantly correlated with relative growth of P. aphanidermatum. Relative growth of R. solani was significantly correlated with the C:N ratio of soil or the C or N content of debris. Microbial activity was not consistently associated with relative growth of either pathogen.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008720731062
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  • 82
    Digitale Medien
    Digitale Medien
    On the Stability of Nonconservative Systems with Estimation of the Attraction Domain (2000)
    Springer
    Journal of dynamical and control systems 6 (2000), S. 503-510 
    Details
    ISSN: 1573-8698
    Schlagwort(e): nonconservative mechanical systems ; stability ; Lyapunov functions ; attraction domain
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Abstract Mechanical systems subjected to dissipative, gyroscopic, conservative, and also nonconservative positional forces are considered. The question of the effect of dissipative, gyroscopic, and conservative forces on the motion stability of a mechanical systems is determined by classical Kelvin–Chetaev theorems [1]. The presence of nonconservative positional forces considerably complicates the situation and excludes direct application of these theorems. Applying Lyapunov's functions method the condition of asymptotic stability of a mechanical system under the action of all listed above forces is obtained. Moreover, the estimation of the attraction domain in phase space is found. The precession system which is used in the solution of some problems in the applied theory of the gyroscopic systems is also examined. The connection between the stability of origin and precession systems is detected. Theoretical results are applied to the stabilization problem of stationary motion of the balanced gimbal suspension gyro by means of external moments.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1009500527061
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  • 83
    Digitale Medien
    Digitale Medien
    Co-development of wetland soils and benthic invertebrate communities following salt marsh creation (2000)
    Springer
    Wetlands ecology and management 8 (2000), S. 197-207 
    Details
    ISSN: 1572-9834
    Schlagwort(e): benthic invertebrates ; mitigation ; nitrogen ; organic matter ; pedogenesis ; phosphorus ; plant productivity ; restoration and rehabilitation ; salt marsh ; wetland creation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The development of wetland soil characteristics andbenthic invertebrate communities were evaluated increated Spartina alterniflorasalt marshes inNorth Carolina ranging in age from 1 to 25 years-old.A combination of measurements from different-agecreated marshes as well as periodic measurements overtime on two marshes were used to (1) document rates ofwetland pedogenesis, especially soil organic matter,and, (2) explore relationships between soil andbenthic invertebrate community development. Soilmacro-organic matter (MOM, the living and dead rootand rhizome mat), organic C and N increased and bulkdensity decreased during the 25 years following marshestablishment. The most dramatic changes in bulkdensity, MOM, C and N occurred within the upper 10 cmof the soil with lesser changes below this depth.Created marshes were sinks for organic C (90–140g·m-2·yr-1) and N (7–11g·m-2·yr-1) but not for P (0–1g·m-2·yr-1). The density of benthicinvertebrates (〉250 μm) and subsurface-depositfeeding oligochaetes also increased over time oncreated salt marshes. Invertebrate and oligochaetedensity were strongly related to MOM content(r2= 0.83–0.87) and soil organic C(r2= 0.52–0.82) and N (r2= 0.62–0.84). Thesefindings suggest that, in created salt marshes,development of the benthic invertebrate community istied to marsh soil formation, especially accumulationof organic matter as MOM and soil. Field studies thatmanipulate the quantity and quality of soil organicmatter are needed to elucidate the relationshipbetween salt marsh pedogenesis and benthicinvertebrate community development.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1008448620605
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  • 84
    Digitale Medien
    Digitale Medien
    Modulation of Paired-Pulse Responses in the Dentate Gyrus: Effects of Normal Maturation and Vigilance State (2000)
    Springer
    Annals of biomedical engineering 28 (2000), S. 128-134 
    Details
    ISSN: 1573-9686
    Schlagwort(e): Hippocampus ; Vigilance states ; Paired-pulse ; Dentate gyrus ; Dentate granule cells ; Evoked response ; Rat ; In vivo studies ; Perforant path ; Maturation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin , Technik allgemein
    Notizen: Abstract This study examined the effect of normal development and vigilance state on the modulation of dentate granule cell activity in the freely moving rat at 15, 30, and 90 days of age across three vigilance states: quiet waking, slow-wave sleep, and rapid eye movement sleep. Using paired-pulse stimulation, the paired-pulse index (PPI) was obtained for the dentate evoked field potentials elicited by the stimulation of the medial perforant path. Although significant differences in PPI values were observed during development, no significant vigilance state related changes were obtained. Preweaning infant rats, i.e., 15-day old, exhibited significantly less early (interpulse intervals, IPI= 20–50 ms) and late (IPI = 300–1000 ms) inhibition, and less facilitation (IPI = 50–150 ms) when compared to the 90-day old adult rats during all three vigilance states. PPI values obtained from the 30-day old group fell intermediate between the 15- and 90-day old animals. These changes in PPI values provide a quantitative measure of changes in the modulation of dentate granule cell excitability during normal maturation. They can now can be used to evaluate the impact of various insults, such as prenatal protein malnutrition or neonatal stress, on hippocampal development. © 2000 Biomedical Engineering Society. PAC00: 8717Nn, 8719La, 8719Nn
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1114/1.261
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  • 85
    Digitale Medien
    Digitale Medien
    Left Ventricular Contractility is Impaired Following Myocardial Infarction in the Pig and Rat: Assessment by the End Systolic Pressure–Volume Relation Using a Single-Beat Estimation Technique and Cine Magnetic Resonance Imaging (2000)
    Springer
    Annals of biomedical engineering 28 (2000), S. 484-494 
    Details
    ISSN: 1573-9686
    Schlagwort(e): Heart ; Left ventricle ; LV contractility ; ESPVR ; Pig ; Rat ; Magnetic resonance imaging
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin , Technik allgemein
    Notizen: Abstract The end systolic pressure–volume relation (ESPVR) has been shown to be a relatively load independent measure of left ventricular (LV) contractility. Recently, several single-beat ESPVR computation methods have been developed, enabling the quantification of LV contractility without the need to alter vascular loading conditions on the heart. Using a single-beat ESPVR method, which has been validated previously in humans and assumes that normalized elastance is constant between individuals of a species, we studied the effects of myocardial infarction on LV contractility in two species, the rat and the pig. In our studies, LV pressure was acquired invasively and LV volume determined noninvasively with magnetic resonance imaging, at one week postinfarction in pigs and at 12 weeks postinfarction in rats. Normalized systolic elastance curves in both animal species were not statistically different from that of humans. Also, the slope of the ESPVR $$\left( {E_{es} } \right)$$ decreased significantly following infarction in both species, while the volume-axis intercept $$\left( {V_0 } \right)$$ was unaffected. These results indicate that a single-beat ESPVR method can be used to measure the inotropic response of the heart to myocardial infarction, and that the basis for this method (i.e., constant normalized elastance) is applicable to a variety of mammalian species. © 2000 Biomedical Engineering Society. PAC00: 8719Uv, 8761Lh, 8719Hh, 8719Rr, 8719Ff
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1114/1.289
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  • 86
    Digitale Medien
    Digitale Medien
    Quantifying Coevolution of Nonstationary Biomedical Signals Using Time-Varying Phase Spectra (2000)
    Springer
    Annals of biomedical engineering 28 (2000), S. 1101-1115 
    Details
    ISSN: 1573-9686
    Schlagwort(e): Time–frequency analysis ; Coherence ; Cross correlation ; Nonstationary persistent signals ; Central pattern generator ; Rat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin , Technik allgemein
    Notizen: Abstract We present a novel time-varying phase spectrum (TVPS) method to quantify the dynamics of coevolution of two persistent nonstationary coupled signals. Based on the TVPS, an instantaneous intersignal phase shift is defined within the primary frequency range in which the two signals are highly correlated. The TVPS is estimated using a fixed-window method or an adaptive-window method. In the latter method, the window length changes dynamically and automatically as a function of change in frequency of the signals. The effects of altering window types and lengths on the accuracy of the estimation of the primary phase shift is assessed by analyzing synthesized linear chirp signals with decaying amplitude and constant relative phase shift or decaying amplitude and changing relative phase shifts. The methods developed are also used for determining the evolution of the primary phase shift among ventral root activities during fictive locomotion in an in vitro rat spinal cord preparation. The analyses indicate that the TVPS method in conjunction with the determination of the primary frequency range, allows determination of both the evolution of the coupling strength and the evolution of the phase shift between two persistent nonstationary rhythmic signals in the joint time–frequency domain. An adaptive window reduces the estimation bias and the estimation variability. © 2000 Biomedical Engineering Society. PAC00: 0230-f, 8780Tq
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1114/1.1313775
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  • 87
    Digitale Medien
    Digitale Medien
    Physiological regulation of plant-atmosphere ammonia exchange (2000)
    Springer
    Plant and soil 221 (2000), S. 95-102 
    Details
    ISSN: 1573-5036
    Schlagwort(e): ammonia exchange ; apoplast ; atmosphere ; glutamine synthetase ; nitrogen ; photorespiration
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Plants have a compensation point for NH3 which ranges from 0.1 to 20 nmol mol-1, and may be several-fold higher or lower than naturally occurring atmospheric NH3 concentrations. This implies that NH3 fluxes over vegetated surfaces are bi-directional and that ammonia exchange with the atmosphere in many cases contributes significantly to the nitrogen economy of vegetation. Physiological regulation of plant–atmosphere NH3 fluxes is mediated via processes involved in nitrogen uptake, transport and metabolism. A rapid turnover of NH3 + in plant leaves leads to the establishment of a finite NH3 + concentration in the leaf apoplastic solution. This concentration determines, together with that of H+, the size of the NH3 compensation point. Barley and oilseed rape plants with access to NH3 + in the root medium have higher apoplastic NH3 + concentrations than plants absorbing NO3 -. Furthermore, the apoplastic NH3 + concentration increases with the external NH3 + concentration. Inhibition of GS leads to a rapid and substantial increase in apoplastic NH3 + and barley mutants with reduced GS activity have higher apoplastic NH3 + than wild-type plants. Increasing rates of photorespiration do not affect the steady-state NH3 + or H+ concentration in tissue or apoplast of oilseed rape, indicating that the NH3 + produced is assimilated efficiently. Nevertheless, NH3 emission increases due to a temperature-mediated displacement of the chemical equilibrium between gaseous and aqueous NH3 in the apoplast. Sugarbeet plants grown with NO3 - seem to be temporarily C-limited in the light due to a repression of respiration. As a consequence, the activity of chloroplastic GS declines during the day causing a major part of NH3 + liberated in photorespiration to be assimilated during darkness when 2-oxoglutarate is supplied in high rates by respiration.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004761931558
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  • 88
    Digitale Medien
    Digitale Medien
    The effects of external potassium and magnesium concentrations on the magnesium and potassium inflow rates and growth of micropropagated cherry rootstocks, “F.12/1” (Prunus avium L.) and “Colt” (Prunus avium L.) × Prunus pseudocerasus L.) (2000)
    Springer
    Plant and soil 225 (2000), S. 73-82 
    Details
    ISSN: 1573-5036
    Schlagwort(e): growth ; inflow ; magnesium ; potassium ; (Prunus)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The effects (and interaction) of two solution concentrations of Mg (50, 500, μM) and two of K (250, 4250 μM) on the growth of micropropagated plants of “F. 12/1” and “Colt” were investigated using a flowing solution culture system. Magnesium inflow and growth of “Colt” and “F. 12/1” were inhibited to a similar extent by an increased concentration of K in the nutrient solution. However, the consequences of this inhibition were different. Reduced inflow of Mg in “F. 12/1” caused Mg deficiency symptoms at high and low concentrations of K, whereas this only occurred with a combination of high K concentration and low Mg concentration in “Colt”. The distribution of dry matter within the plant was significant in determining susceptibility to Mg deficiency. Since “F. 12/1” has a smaller root:shoot ratio than Colt it is unable to sustain the same concentration of Mg in leaves as “Colt” irrespective of external K concentration. The molar ratio of K:Mg in soil solutions should remain 〈8.5:1 in order to ensure maximum growth of “F. 12/1” and “Colt”.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026596612035
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  • 89
    Digitale Medien
    Digitale Medien
    The effect of three or five years of set-aside on the husbandry and grain yield of subsequent cereal crops in the UK (2000)
    Springer
    Plant and soil 225 (2000), S. 279-297 
    Details
    ISSN: 1573-5036
    Schlagwort(e): cereal ; cereal quality ; cereal yields ; natural regeneration ; nitrogen ; nitrogen uptake ; rye-grass ; set-aside ; white clover
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract During the period 1993–1997, at six contrasting sites located throughout England, two successive cereal test crops were grown both with and without nitrogen fertiliser after three or five years of set-aside or after continuous arable cropping. Vegetation during set-aside included natural regeneration and perennial rye-grass (Lolium perenne) with or without white clover (Trifolium repens), managed by mowing on one or more occasions per year. Establishment of the successive cereal test crops after destruction of the set-aside was generally not a problem. Fertile tiller numbers were increased by inclusion of clover in the set-aside cover or application of inorganic nitrogen. The presence of couch grass (Elytrigia repens) or volunteer cereals in the set-aside covers provided alternative hosts for take-all (Gaeumanomyces graminis) and eyespot (Pseudocercosporella herpotrichoides) and take-all caused some yield reductions in following cereal crops. Management during the set-aside period significantly affected grain yields of the subsequent cereal crops in the majority of the site-year combinations. However, these effects were not as large as would be expected after traditional break crops and were frequently masked by the application of nitrogen fertiliser. Mean yields increased by 80% due to the application nitrogen at the optimum rate compared to nil nitrogen. Most of the effects of set-aside treatment on grain yield were shown to be attributable to soil mineral nitrogen content, but at some sites, infections by take-all or eyespot also accounted for some of the variation. There were no effects of pests that could be related to treatment. The presence of sown clover during the set-aside period had the most consistent effect across sites, affecting tiller populations, grain yield and grain quality of cereal crops. At some sites, establishing a sown cover during the set-aside period, or cutting the cover more than once a year, improved grain yield and quality, and reduced the incidence of some specific weeds and disease.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026531528082
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  • 90
    Digitale Medien
    Digitale Medien
    Root-shoot interactions in mineral nutrition (2000)
    Springer
    Plant and soil 226 (2000), S. 57-69 
    Details
    ISSN: 1573-5036
    Schlagwort(e): ABA ; K/Na selectivity ; nitrate reduction ; nitrogen ; phloem ; phosphate ; root-shoot interactions ; salinity ; xylem
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract In this paper four classes of co-operative root-shoot interations are addressed. (I) Nitrogen concentrations in the xylem sap originating from the root and in the phloem sap as exported from source leaves are much lower than those required for growth by apices and developing organs. Enrichment of xylem sap N is achieved by xylem to xylem (X-X) transfer, by which reduced N, but not nitrate, is abstracted from the xylem of leaf traces and loaded into xylem vessels serving the shoot apex. Nitrogen enrichment of phloem sap from source leaves is enacted by transfer of reduced N from xylem to phloem (X-P transfer). Quantitative data for the extent of the contribution of X-X and X-P transfer to the nutrition of young organs of Ricinus communis L. and for their change with time are presented. (II) Shoot and root cooperate in nitrate reduction and assimilation. The partitioning of this process between shoot and root is shifted towards the root under conditions of nitrate- and K-deficiency and under salt stress, while P deficiency shifts nitrate reduction almost totally to the shoot. All four changes in partitioning can be attributed to the need for cation-anion balance during xylem transport and the change in electrical charge occurring with nitrate reduction. (III) Even maintenance of the specificity of ion uptake by the root may – in addition to its need for energy – require a shoot-root interaction. This is shown to be needed in the case of the maintenance of K/Na selectivity under the highly adverse condition of salt stress and absence of K supply from the soil. (IV) Hormonal root to shoot interactions are required in the whole plant for sensing mineral imbalances in the soil. This is shown and addressed for conditions of salt stress and of P deficiency, both of which lead to a strong ABA signalling from root to shoot but result in different patterns of response in the shoot.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026431408238
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  • 91
    Digitale Medien
    Digitale Medien
    Dynamics of biomass and N accumulation of alfalfa under three N fertilization rates (2000)
    Springer
    Plant and soil 219 (2000), S. 177-185 
    Details
    ISSN: 1573-5036
    Schlagwort(e): alfalfa ; growth ; Medicago sativa L. ; nitrogen
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The dynamics of biomass and N accumulation following defoliation of alfalfa and the application of N fertilization has rarely been studied under field conditions, particularly in the seeding year. Our objectives were to determine the effect of N fertilization on the dynamics of biomass and N accumulation during the first regrowth of alfalfa in the seeding year, and to determine if a model describing critical N concentration developed for established stands could be used in the seeding year. In two separate experiments conducted in 1992 and 1993, the biomass and N accumulation of alfalfa grown with three N rates (0, 40 and 80 kg N ha-1) were determined weekly. Maximum shoot growth was reached with 40 kg N ha-1 in 1992, and maximum shoot growth was not reached with the highest N fertilization rate in 1993. Nitrogen fixation, root N reserves and soil inorganic N uptake when no N was applied were, therefore, not sufficient to ensure non-limiting N conditions, particularly when growth rates were the highest between 14 to 21 d after defoliation. Nitrogen fertilization increased shoot biomass accumulation in the first 21 d of regrowth, biomass partitioning to the shoots and shoot and taproot N concentrations. The model parameters of critical N concentration developed by Lemaire et al. (1985) for established stands of alfalfa were not adequate in the seeding year. The N requirements per unit of shoot biomass produced are greater in the seeding year than on established stands, and this was attributed to a greater proportion of leaves in the seeding year.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004749828745
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  • 92
    Digitale Medien
    Digitale Medien
    13C NMR study of pine needle decomposition (2000)
    Springer
    Plant and soil 219 (2000), S. 273-278 
    Details
    ISSN: 1573-5036
    Schlagwort(e): cellulose ; lignin ; litter ; nitrogen ; Pinus radiata ; tannins
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The quality of substrates in plantation forest litter, and their chemistry, can influence decomposition and N cycling. We studied the decomposition of Pinus radiata D. Don needles suspended on branches in windrows, for 3 yr after clear-cutting, using improved solid-state 13C NMR and chemical analysis. The NMR spectra suggested that the concentration of condensed tannins was 12–22%, and showed they were chemically altered during the period 4–12 months after clear-cutting. The spectra showed no evidence for further chemical modification of the tannins during the second or third years. Data for P. radiata needle decomposition in New Zealand indicated rapid loss of mass in the first 3 months, and condensed tannins did not appear to prevent mineralization of C or N. The tannin and lignin concentrations increased with decomposition of the needles, which was consistent with the early mineralization of readily available C compounds.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004783502067
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  • 93
    Digitale Medien
    Digitale Medien
    Interaction effects of phosphorus and zinc on photosynthesis, growth and yield of dwarf bean grown in two environments (2000)
    Springer
    Plant and soil 220 (2000), S. 219-228 
    Details
    ISSN: 1573-5036
    Schlagwort(e): growth ; light intensity ; Phaseolus vulgaris L. ; phosphorus–zinc interaction ; photosynthesis ; yield ; zinc deficiency
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Two experiments were conducted in a factorial combination of three Zn levels (0, 10 and 40 mg Zn kg-1 soil) and two P levels (0 and 200 mg P kg-1 soil). Experiment 1 was carried out during winter in a heated glasshouse, and experiment 2 during summer under a rain shelter. Plants of dwarf bean (Phaseolus vulgaris L., cv. Borlotto nano) were grown in pots filled with sandy soil. In both experiments, leaf Zn concentration was reduced by the addition of P to plants grown at low Zn supply. However, leaf Zn concentration lower than the critical level was observed only during experiment 2, and the main effects of low Zn were reductions of internode length, light use efficiency and maximum photosynthetic rate. In plants with leaf Zn concentration lower than the critical level, saturating irradiance levels fell from ∼1000 μmol m-2 s-1 PPFD to ∼300–400 μmol m-2 s-1 PPFD. Reduction of net photosynthesis was observed from the beginning of flowering and led to decreased seed production.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004705008101
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  • 94
    Digitale Medien
    Digitale Medien
    The effects of slash burning on ecosystem nutrients during the land preparation phase of shifting cultivation (2000)
    Springer
    Plant and soil 220 (2000), S. 247-260 
    Details
    ISSN: 1573-5036
    Schlagwort(e): cations ; fire ; nitrogen ; nutrients ; phosphorus ; slash-and-burn ; soil ; tropical forests
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The most commonly observed change in soil following slash-and-burn clearing of tropical forest is a short-term increase in nutrient availability. Studies of shifting cultivation commonly cite the incorporation of nutrient-rich ash from consumed aboveground biomass into soil as the reason for this change. The effects of soil heating on nutrient availability have been examined only rarely in field studies of slash-and-burn, and soil heating as a mechanism of nutrient release is most often assumed to be of minor importance in the field. Few budgets for above and belowground nutrient flux have been developed in the tropics, and a survey of results from field and laboratory studies indicates that soils are sufficiently heated during most slash-and-burn events, particularly in dry and monsoonal climates, to cause significant, even substantial release of nutrients from non-plant-available into plant-available forms in soil. Conversely, large aboveground losses of nutrients during and after burning often result in low quantities of nutrients that are released to soil. Assessing the biophysical sustainability of an agricultural practice requires detailed information about nutrient flux and loss incurred during management. To this end, current conceptual models of shifting cultivation should be revised to more accurately describe these fluxes and losses.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004741125636
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  • 95
    Digitale Medien
    Digitale Medien
    Soil patchiness in juniper-sagebrush-grass communities of central Oregon (2000)
    Springer
    Plant and soil 223 (2000), S. 47-61 
    Details
    ISSN: 1573-5036
    Schlagwort(e): correlograms ; nitrogen ; soil arthropods ; soil resource islands ; variograms ; vesicular-arbuscular mycorrhizae
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract This study compared the sizes, spacings and properties (soil moisture, pH, nitrogen, soil arthropods and VAM) of soil resource islands and bare patches in sagebrush-grass communities invaded by western juniper versus those without juniper. We analyzed 1000 surface soil samples taken from nine 50-m radius circular plots sampled in December of 1991 and May of 1992 on ‘The Island’, one of the few undisturbed areas of sagebrush-grass shrubland in Oregon. Spatial structure was interpreted from correlograms (Moran's I) and standardized semivariograms. The presence of juniper was associated with increased bare area and smaller, more widely spaced grass and sagebrush plants. Soil arthropod numbers and biomass in plots with juniper were only roughly one-fifth of those in sagebrush-grass plots in December. The dominant soil pattern in both sagebrush-grass and juniper-sagebrush-grass plots was regularly-distributed patches spanning a range of sizes and spacings. Plots with juniper had greater patchiness at shorter lags (〈3 m), and patchiness was more developed for soil moisture, net nitrification, and net N mineralization, whereas sagebrush-grass plots had greater patchiness at longer lags (3 – 9 m) and patchiness was more developed for NO3–N, arthropod numbers and biomass. These differences in soil patterns with and without juniper indicate that juniper responds to, or causes, changes in the size of resource islands under sage and grass when it invades sage-grass communities.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004745329332
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  • 96
    Digitale Medien
    Digitale Medien
    Estimating crop N uptake from organic residues using a new approach to the 15N isotope dilution technique (2000)
    Springer
    Plant and soil 223 (2000), S. 33-46 
    Details
    ISSN: 1573-5036
    Schlagwort(e): crop residues ; nitrogen ; organic residues
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Experiments were conducted to test a new approach to the 15N isotope dilution technique for estimating crop N uptake from organic inputs. Soils were pre-labelled with 15N fertiliser and a carbon source. These were then incubated until there was stabilisation of the 15N abundance of the inorganic N pool and resumption of inorganic N concentrations. Residues were then applied to the soils and planted with ryegrass (Lolium perenneL.) to determine the nitrogen derived from the residue (Ndfr) using the isotope dilution equations. This method was compared with the direct method, i.e. where 15N-labelled residues were added to the soil and Ndfr in the ryegrass calculated directly. Estimates of percentage nitrogen derived from the residue (%Ndfr) alfalfa (Medicago sativaL.) in the ryegrass, were similar, 22 and 23% for the direct and soil pre-labelling methods, respectively, in the Wechsel sandy loam. Also, estimates of the %Ndfr from soybean (Glycine max (L.) Merr) residues in the Krumbach sandy loam were similar 34% (direct) and 36% (soil pre-labelling approach). However, in the Seibersdorf clay loam, the %Ndfr from soybean was 49% using the direct method and 61% using the soil pre-labelling method; yet Ndfr from common bean residue was 46% using the direct approach and 40% using the pre-labelling, not significantly different (P 〉 0.05). The soil pre-labelling approach appears to give realistic values for Ndfr. It was not possible to obtain an estimate of Ndfr using the soil pre-labelling method from the maize residues (Zea mays L.) in two of the soils, as there was no increase in the total N of the ryegrass over the growing period. This was probably due to microbial immobilisation of inorganic N, as a result of the wide C:N ratio of the residue added. The results suggest that the new soil pre-labelling method is feasible and that it is a potentially useful technique for measuring N release from a wide range or organic residues, but it requires further field-testing.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004789103949
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  • 97
    Digitale Medien
    Digitale Medien
    Chemistry and toughness predict leaf litter decomposition rates over a wide spectrum of functional types and taxa in central Argentina (2000)
    Springer
    Plant and soil 218 (2000), S. 21-30 
    Details
    ISSN: 1573-5036
    Schlagwort(e): carbon ; functional types ; leaf tensile strength ; litter quality ; mass loss ; nitrogen
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Litter decomposition, a major determinant of ecosystem functioning, is strongly influenced by the litter quality of different species. We aimed at (1) relating interspecific variation in leaf litter decomposition rate to the functional types different species belong to; and (2) understanding the chemical and/or physical basis for such variation and its robustness to environmental factors. We selected 52 Angiosperms from a climatic gradient in central-western Argentina, representing the widest range of functional types and habitats published so far. Ten litter samples of each species were simultaneously buried for 9 weeks during the 1996 summer in an experimental decomposition bed. Decomposition rate was defined as the percentage of dry mass loss after incubation. Chemical litter quality was measured as carbon (C) content, nitrogen (N) content, and C-to-N ratio. Since tensile strength of litter and living leaves were strongly correlated, the latter was chosen as an indicator of physical litter quality. A subset of 15 species representing different functional types was also incubated in England for 15 weeks, following a similar experimental procedure. Litter C-to-N and leaf tensile strength of the leaves showed the strongest negative associations with decomposition rate, both at the species and at the functional-type level. Decomposition rates of the same species in Argentina and in England were strongly correlated. This reinforces previous evidence that species rankings in terms of litter decomposition rates are robust to methodological and environmental factors. This paper has shown new evidence of plant control over the turnover of organic matter through litter quality, and confirms, over a broad spectrum of functional types, general models of resource allocation. The strong correlations between leaf tensile strength – a trait that is easy and quick to measure in a large number of species – decomposition rate, and C-to-N ratio indicate that leaf tensile strength can be useful in linking plant quality to decomposition patterns at the ecosystem level.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1014981715532
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  • 98
    Digitale Medien
    Digitale Medien
    On variation in forest floor thickness across four red pine plantations in Pennsylvania, USA (2000)
    Springer
    Plant and soil 219 (2000), S. 57-69 
    Details
    ISSN: 1573-5036
    Schlagwort(e): decomposition ; litter quality ; mycorrhiza ; nitrogen ; phosphorus ; saprotrophic microorganisms ; tannins ; forest soils ; acidification
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract We studied variation in forest floor thickness in four plantations of red pine (Pinus resinosa Ait.) which were similar in age, soil type and associated vegetation. The plantations were located (west to east) in the Clear Creek, Moshannon, Sproul and Tiadaghton State Forests of Pennsylvania, USA. A gradient in forest floor thickness exists across these plantations; the forest floor is thickest in the west and it becomes progressively thinner toward the east. Decomposition of imported litter increased from west to east, suggesting that the variation in forest floor thickness is related to variation in the rate of decomposition. Decomposition rates were related to saprotroph abundance. Variation in forest floor N and phenolic concentrations, in overall mycorrhiza density and in the relative proportions of three common mycorrhiza morphotypes could not explain the variation in decomposition rate. The P concentrations and pH of the forest floor were significantly lower at Clear Creek and Moshannon, where decomposition rates were lowest, compared to Sproul and Tiadaghton, where decomposition rates were most rapid. This suggests that P concentration and pH may have exerted some control on decomposition.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004748220856
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  • 99
    Digitale Medien
    Digitale Medien
    Dynamics of mineral N availability in grassland ecosystems under increased [CO2]: hypotheses evaluated using the Hurley Pasture Model (2000)
    Springer
    Plant and soil 224 (2000), S. 153-170 
    Details
    ISSN: 1573-5036
    Schlagwort(e): climate change ; immobilisation ; mineralisation ; N-turnover ; nitrogen ; soil organic matter
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The following arguments are outlined and then illustrated by the response of the Hurley Pasture Model to [CO2] doubling in the climate of southern Britain. 1. The growth of N-limited vegetation is determined by the concentration of N in the soil mineral N pools and high turnover rates of these pools (i.e., large input and output fluxes) contribute positively to growth. 2. The size and turnover rates of the soil mineral N pools are determined overwhelmingly by N cycling into all forms of organic matter (plants, animals, soil biomass and soil organic matter — `immobilisation' in a broad sense) and back again by mineralisation. Annual system N gains (by N2 fixation and atmospheric deposition) and losses (by leaching, volatilisation, nitrification and denitrification) are small by comparison. 3. Elevated [CO2] enriches the organic matter in plants and soils with C, which leads directly to increased removal of N from the soil mineral N pools into plant biomass, soil biomass and soil organic matter (SOM). ‘Immobilisation’ in the broad sense then exceeds mineralisation. This is a transient state and as long as it exists the soil mineral N pools are depleted, N gaseous and leaching losses are reduced and the ecosystem gains N. Thus, net immobilisation gradually increases the N status of the ecosystem. 4. At the same time, elevated [CO2] increases symbiotic and non-symbiotic N2 fixation. Thus, more N is gained each year as well as less lost. Effectively, the extra C fixed in elevated [CO2] is used to capture and retain more N and so the N cycle tracks the C cycle. 5. However, the amount of extra N fixed and retained by the ecosystem each year will always be small (ca. 5–10 kg N ha-1 yr-1) compared with amount of N in the immobilisation-mineralisation cycle (ca. 1000 kg N ha-1 yr-1). Consequently, the ecosystem can take decades to centuries to gear up to a new equilibrium higher-N state. 6. The extent and timescale of the depletion of the mineral N pools in elevated [CO2] depends on the N status of the system and the magnitude of the overall system N gains and losses. Small changes in the large immobilisation—mineralisation cycle have large effects on the small mineral N pools. Consequently, it is possible to obtain a variety of growth responses within 1–10 year experiments. Ironically, ecosystem models — artificial constructs — may be the best or only way of determining what is happening in the real world.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1004640327512
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  • 100
    Digitale Medien
    Digitale Medien
    A comparison of nine species of arbuscular mycorrhizal fungi on the development and nutrition of micropropagated Rubus idaeus L. cv. Glen Prosen (Red Raspberry) (2000)
    Springer
    Plant and soil 225 (2000), S. 53-61 
    Details
    ISSN: 1573-5036
    Schlagwort(e): AM fungi ; colonisation ; growth ; mineral nutrition ; red raspberry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Growth, development and nutrient status of micropropagated Rubus idaeus cv. Glen Prosen in response to inoculation with nine species of arbuscular mycorrhizal (AM) fungi from three different genera was investigated. The nine species of AM fungi included, Glomus clarum, G. etunicatum, G. intraradices, Gigaspora rosea, Gi. gigantea, Gi. margarita, Scutellospora calospora, S. heterogama and S. persica. Plant responses to AM fungi varied from growth enhancement to growth depression. Depressive growth effects were specific to Gigaspora species. Furthermore, particular species of AM fungi had unique effects on the mineral status of the raspberry plants. Importance of isolate selection for inoculation of micropropagated raspberry plants is discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1026519431096
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