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  • Humans  (26,754)
  • 550 - Earth sciences  (19,122)
  • Chemical Engineering  (17,982)
  • Fisheries  (14,769)
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  • 1
    Keywords: Biomass conversion ; Biotechnology ; Chemical Engineering ; Chemistry industry ; Industrial Chemistry ; Kent ; Riegel ; biochemical engineering
    Description / Table of Contents: Substantially revising and updating the classic reference in the field, this handbook offers a valuable overview and myriad details on current chemical processes, products, and practices. No other source offers as much data on the chemistry, engineering, economics, and infrastructure of the industry. The Handbook serves a spectrum of individuals, from those who are directly involved in the chemical industry to others in related industries and activities. It provides not only the underlying science and technology for important industry sectors, but also broad coverage of critical supporting topics. Industrial processes and products can be much enhanced through observing the tenets and applying the methodologies found in chapters on Green Engineering and Chemistry (specifically, biomass conversion), Practical Catalysis, and Environmental Measurements; as well as expanded treatment of Safety, chemistry plant security, and Emergency Preparedness. Understanding these factors allows them to be part of the total process and helps achieve optimum results in, for example, process development, review, and modification. Important topics in the energy field, namely nuclear, coal, natural gas, and petroleum, are covered in individual chapters. Other new chapters include energy conversion, energy storage, emerging nanoscience and technology. Updated sections include more material on biomass conversion, as well as three chapters covering biotechnology topics, namely, Industrial Biotechnology, Industrial Enzymes, and Industrial Production of Therapeutic Proteins.
    Pages: Online-Ressource (XIV, 1562 pages)
    ISBN: 9780387278438
    Language: English
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  • 2
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    Frontiers Media SA
    Publication Date: 2024-03-31
    Description: Echolocation has evolved in different groups of animals, from bats and cetaceans to birds and humans, and enables localization and tracking of objects in a dynamic environment, where light levels may be very low or absent. Nature has shaped echolocation, an active sense that engages audiomotor feedback systems, which operates in diverse environments and situations. Echolocation production and perception vary across species, and signals are often adapted to the environment and task. In the last several decades, researchers have been studying the echolocation behavior of animals, both in the air and underwater, using different methodologies and perspectives. The result of these studies has led to rich knowledge on sound production mechanisms, directionality of the sound beam, signal design, echo reception and perception. Active control over echolocation signal production and the mechanisms for echo processing ultimately provide animals with an echoic scene or image of their surroundings. Sonar signal features directly influence the information available for the echolocating animal to perceive images of its environment. In many echolocating animals, the information processed through echoes elicits a reaction in motor systems, including adjustments in subsequent echolocation signals. We are interested in understanding how echolocating animals deal with different environments (e.g. clutter, light levels), tasks, distance to targets or objects, different prey types or other food sources, presence of conspecifics or certain predators, ambient and anthropogenic noise. In recent years, some researchers have presented new data on the origins of echolocation, which can provide a hint of its evolution. Theoreticians have addressed several issues that bear on echolocation systems, such as frequency or time resolution, target localization and beam-forming mechanisms. In this Research Topic we compiled recent work that elucidates how echolocation – from sound production, through echolocation signals to perception- has been shaped by nature functioning in different environments and situations. We strongly encouraged comparative approaches that would deepen our understanding of the processes comprising this active sense.
    Keywords: QP1-981 ; Q1-390 ; bats ; Biosonar ; Humans ; marine mammals ; sensory biology ; Birds ; Behavior ; Communication ; thema EDItEUR::M Medicine and Nursing::MF Pre-clinical medicine: basic sciences::MFG Physiology
    Language: English
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  • 3
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    Frontiers Media SA
    Publication Date: 2024-03-30
    Description: In the ancient past, cocoa has been appreciated as a high-calorie food to boost energy in soldiers and for its undefined medicinal and mystical properties. During other times, chocolate has been considered as the forbidden “food of God”: a treasure of pleasure for the mind and the soul. The overall perception of the consumer for chocolate was of a “charming” and appealing food with lots of negative aspects related to high sugar content leading to consider chocolate as “junk food” for its “obesigen” calories. Recently, in association with the renewed interest of nutrition science in alternative source of health-promoting foods and ingredients, a large body of research has been conducted to unravel the pro and cons of cocoa in relation to human health. Epidemiological evidences indicate that cocoa consumption helps preventing cardiovascular disease for its high content in bioactive flavonoids. Clinical trials show that chocolate consumption might improve vascular function, decreasing platelet aggregation and display an antioxidant and anti-inflammatory effect. The putative protective action of cocoa seems to be multi-factorial and involving different aspects of vascular, antioxidant and endothelial function. However, the mechanism(s) that account for the benefits of cocoa it is still unclear. The aim of this Research Topic is therefore to provide the reader with an objective picture of the state of art on the association between cocoa and health, mainly through the evidences of human trials; overwhelmingly considered the golden standard for nutritional science. The Research Topic will cover the analysis of the manufacturing processes of the chocolate and the antioxidant effects in humans as well as the majority of the putative health effects of chocolate and cocoa, such as anti-inflammatory properties, effect on immunity, platelet aggregation, blood pressure, endothelial function and cognitive behavior. Unraveling the functional properties of cocoa will help to understand if the 'food of God' is a primordial gift for the health of mankind.
    Keywords: R5-920 ; RC581-607 ; TX341-641 ; Antioxidants ; Obesity ; Flavonoids ; Humans ; Chocolate ; Blood pressure ; Inflammation ; Cognitive function ; Cocoa ; Immunity
    Language: English
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  • 4
    Publication Date: 2024-04-04
    Description: This eBook is a collection of articles from a Frontiers Research Topic. Frontiers Research Topics are very popular trademarks of the Frontiers Journals Series: they are collections of at least ten articles, all centered on a particular subject. With their unique mix of varied contributions from Original Research to Review Articles, Frontiers Research Topics unify the most influential researchers, the latest key findings and historical advances in a hot research area! Find out more on how to host your own Frontiers Research Topic or contribute to one as an author by contacting the Frontiers Editorial Office: frontiersin.org/about/contact
    Keywords: living marine resources ; Forecasting ; prediction ; fish ; Fisheries ; Seasonal to Decadal Prediction ; Climate services ; thema EDItEUR::P Mathematics and Science::PD Science: general issues ; thema EDItEUR::R Earth Sciences, Geography, Environment, Planning::RB Earth sciences::RBK Hydrology and the hydrosphere::RBKC Oceanography (seas and oceans)
    Language: English
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  • 5
    Publication Date: 2024-04-05
    Description: This eBook comprises s series of original research and review articles dealing with the anatomical, genetic, and physiological organization of the auditory system from humans to monkeys and mice.
    Keywords: RC321-571 ; Q1-390 ; audition ; monkeys ; gens ; translational ; Humans ; Rodents ; Memory ; Perception ; Physiology ; functional imaging ; Anatomy ; thema EDItEUR::P Mathematics and Science::PS Biology, life sciences::PSA Life sciences: general issues::PSAN Neurosciences
    Language: English
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  • 6
    Publication Date: 2024-04-05
    Description: The global population aged over 60 is set to rise dramatically in the coming decades. In many countries, the older population now faces the prospect of spending a quarter of their lives aged over 65, and a significant proportion will have to cope with cognitive decline associated with normal ageing or with dementia disorders. Given that these fundamental demographic changes will pose a significant challenge to health care systems, a detailed understanding of age-related cognitive and neurobiological changes is essential in helping elderly populations maintain cognitive performance. In addition, developing sensitive biomarkers to identify those at risk of developing dementia is crucial for early and effective interventions. To make inferences about the ageing process from the animal model back to the human, rigorous behavioral paradigms must be used to ensure that the same function is being examined across species. Given that similar navigational paradigms can easily be applied to humans and animals, recent years have seen an expansion of studies attempting to bridge the gap between age-related changes in animal and human spatial cognition. These studies begin to suggest that disruptions in spatial computations are among the earliest indicators of impending cognitive decline. In addition, although many animal studies have identified pathological mechanisms with paradigms involving spatial navigation, these mechanisms support many nonspatial cognitive functions as well. As a consequence, a successful characterization of how spatial processing changes in the ageing brain could reveal fundamental effects of cognitive ageing that could inform about general mechanisms underlying decline in perception, mnemonic processing and multisensory integration.
    Keywords: RC321-571 ; Q1-390 ; Neuroscience ; spatial navigation ; Humans ; Aging ; Animal Models ; Dementia ; thema EDItEUR::P Mathematics and Science::PS Biology, life sciences::PSA Life sciences: general issues::PSAN Neurosciences
    Language: English
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  • 7
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    MDPI - Multidisciplinary Digital Publishing Institute
    Publication Date: 2023-06-23
    Description: The aim of this second Eng Special Issue is to collect experimental and theoretical re-search relating to engineering science and technology. The general topics of Eng are as follows: electrical, electronic and information engineering; chemical and materials engineering; energy engineering; mechanical and automotive engineering; industrial and manufacturing engineering; civil and structural engineering; aerospace engineering; biomedical engineering; geotechnical engineering and engineering geology; and ocean and environmental engineering. Therefore, the following editorial is a selection of representative works of these topics.
    Keywords: &nbsp ; Environment Management ; Environmental Engineering ; Chemical Engineering ; Materials Engineering&nbsp ; bic Book Industry Communication::T Technology, engineering, agriculture::TB Technology: general issues ; bic Book Industry Communication::T Technology, engineering, agriculture::TB Technology: general issues::TBX History of engineering & technology
    Language: English
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  • 8
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    De Gruyter | De Gruyter
    Publication Date: 2024-04-05
    Description: The essential principles of green chemistry are the use of renewable raw materials, highly efficient catalysts and green solvents linked with energy efficiency and process optimization in real-time. Experts from different fields show, how to examine all levels from the molecular elementary steps up to the design and operation of an entire plant for developing novel and efficient production processes.
    Keywords: Process Engineering ; Chemical Engineering ; Technical Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry ; thema EDItEUR::R Earth Sciences, Geography, Environment, Planning::RN The environment ; thema EDItEUR::R Earth Sciences, Geography, Environment, Planning::RN The environment::RNU Sustainability ; thema EDItEUR::T Technology, Engineering, Agriculture, Industrial processes::TD Industrial chemistry and manufacturing technologies::TDC Industrial chemistry and chemical engineering ; thema EDItEUR::T Technology, Engineering, Agriculture, Industrial processes::TG Mechanical engineering and materials::TGM Materials science ; thema EDItEUR::T Technology, Engineering, Agriculture, Industrial processes::TQ Environmental science, engineering and technology
    Language: English
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  • 9
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    White Rose University Press | White Rose University Press
    Publication Date: 2022-12-06
    Description: In Hidden Depths, Professor Penny Spikins explores how our emotional connections have shaped human ancestry. Focusing on three key transitions in human origins, Professor Spikins explains how the emotional capacities of our early ancestors evolved in response to ecological changes, much like similar changes in other social mammals. For each transition, dedicated chapters examine evolutionary pressures, responses in changes in human emotional capacities and the archaeological evidence for human social behaviours. Starting from our earliest origins, in Part One, Professor Spikins explores how after two million years ago, movement of human ancestors into a new ecological niche drove new types of collaboration, including care for vulnerable members of the group. Emotional adaptations lead to cognitive changes, as new connections based on compassion, generosity, trust and inclusion also changed our relationship to material things. Part Two explores a later key transition in human emotional capacities occurring after 300,000 years ago. At this time changes in social tolerance allowed ancestors of our own species to further reach out beyond their local group and care about distant allies, making human communities resilient to environmental changes. An increasingly close relationship to animals, and even to cherished possessions, appeared at this time, and can be explained through new human vulnerabilities and ways of seeking comfort and belonging. Lastly, Part Three focuses on the contrasts in emotional dispositions arising between ourselves and our close cousins, the Neanderthals. Neanderthals are revealed as equally caring yet emotionally different humans, who might, if things had been different, have been in our place today. This new narrative breaks away from traditional views of human evolution as exceptional or as a linear progression towards a more perfect form. Instead, our evolutionary history is situated within similar processes occurring in other mammals, and explained as one in which emotions, rather than ‘intellect’, were key to our evolutionary journey. Moreover, changes in emotional capacities and dispositions are seen as part of differing pathways each bringing strengths, weaknesses and compromises. These hidden depths provide an explanation for many of the emotional sensitivities and vulnerabilities which continue to influence our world today.
    Keywords: Human demography ; Group size ; Lithic transfers ; Raw material movements ; Bonobos ; Dog burial ; Comfort ; Symbolic objects ; Symbolism ; Mobiliary art ; Attachment fluidity ; Hypersociability ; Human-animal relationships ; Dog domestication ; Attachment object ; Approachability ; Approach behaviour ; Avoidance behaviour ; Androgens ; Physiological responses ; Cognitive Archaeology ; Autism Spectrum Condition ; Handaxe ; Biface ; Neurodiversity ; Palaeolithic stone tools ; Evolution of neurodiversity ; Rock art ; Ice age art ; Material Culture ; Cultural transmission ; Emotional commitment ; Biopsychosocial approach ; Social tolerance ; Attachment ; Genus Homo ; Acheulian ; Cultural evolution ; Skeletal abnormality ; Injury ; Illness ; Interdependence ; Emotional sensitivity ; Moral emotions ; Evolution of Altruism ; Hominins ; Upper Palaeolithic ; Lower Palaeolithic ; Ecological niche ; Selective pressure ; Behavioural ecology ; Wolves ; Affective empathy ; Cognitive empathy ; Theory of mind ; Human Cognition ; Vulnerability ; Evolutionary Psychology ; Developmental psychology ; Helping behaviours ; Social cognition ; Social mammals ; Human Emotion ; Human social collaboration ; Generosity ; Emotional brain ; Social emotions ; Comparative behaviour ; Evolution ; Social carnivores ; Primate behavioural ecology ; Primate social systems ; Human Evolution ; Human ancestors ; Collaboration ; Evolutionary Biology ; Emotional vulnerability ; Social connection ; Decolonisation ; Social networks ; Middle Palaeolithic ; Community resilience ; Convergent evolution ; Chimpanzee ; Origin of modern humans ; Social safeness ; Wolf domestication ; Cherished possessions ; Compensatory attachment ; Loneliness ; Palaeolithic art ; Stress reactivity ; Bonding hormones ; Humans ; Hunter-gatherers ; Intergroup collaboration ; Tolerance ; Emotional connection ; Autism ; Trust ; Early Prehistory ; Palaeopathology ; Origins of healthcare ; Human self-domestication ; Palaeolithic Archaeology ; Social brain ; Care-giving ; Empathy ; Neanderthals ; Compassion ; Social Connection ; Evolution of Emotions ; Human Origins ; Adaptation ; Prehistory ; bic Book Industry Communication::J Society & social sciences::JH Sociology & anthropology::JHM Anthropology ; bic Book Industry Communication::H Humanities::HD Archaeology ; bic Book Industry Communication::P Mathematics & science::PS Biology, life sciences ; bic Book Industry Communication::P Mathematics & science::PS Biology, life sciences::PSA Life sciences: general issues::PSAF Ecological science, the Biosphere ; bic Book Industry Communication::P Mathematics & science::PS Biology, life sciences::PSA Life sciences: general issues::PSAJ Evolution ; bic Book Industry Communication::J Society & social sciences::JP Politics & government::JPW Political activism::JPWQ Revolutionary groups & movements ; bic Book Industry Communication::J Society & social sciences::JM Psychology
    Language: English
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  • 10
    Publication Date: 2024-04-04
    Description: This eBook is a collection of articles from a Frontiers Research Topic. Frontiers Research Topics are very popular trademarks of the Frontiers Journals Series: they are collections of at least ten articles, all centered on a particular subject. With their unique mix of varied contributions from Original Research to Review Articles, Frontiers Research Topics unify the most influential researchers, the latest key findings and historical advances in a hot research area! Find out more on how to host your own Frontiers Research Topic or contribute to one as an author by contacting the Frontiers Editorial Office: frontiersin.org/about/contact
    Keywords: drugs ; Behavior ; Memory tasks ; pre-clinical ; clinical ; Humans ; Animals ; thema EDItEUR::P Mathematics and Science::PD Science: general issues ; thema EDItEUR::M Medicine and Nursing::MK Medical specialties, branches of medicine::MKG Pharmacology
    Language: English
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  • 11
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    Springer Nature | Palgrave Macmillan
    Publication Date: 2024-03-29
    Description: This open access book explores fishing livelihoods in the context of the wider contexts in which they are embedded. Drawing on case studies from across the Asia-Pacific region, the book highlights how fishing livelihoods are shaped by globalisation, social relationships and governance. The book concludes by showing how better understanding these relationships can contribute to governance for healthier ecosystems and social wellbeing. This is an open access book. This is an open access book.
    Keywords: Fisheries ; marine social science ; fishing livelihoods in the Asia-Pacific ; sustainable fishing ; environmental sustainability ; food security ; coastal conservation ; fish stocks ; fisheries governance ; Fishing livelihoods and social diversity ; Fishing livelihoods and wellbeing ; Open Access ; thema EDItEUR::J Society and Social Sciences::JP Politics and government::JPQ Central / national / federal government::JPQB Central / national / federal government policies ; thema EDItEUR::J Society and Social Sciences::JH Sociology and anthropology::JHB Sociology ; thema EDItEUR::R Earth Sciences, Geography, Environment, Planning::RN The environment ; thema EDItEUR::R Earth Sciences, Geography, Environment, Planning::RG Geography::RGB Physical geography and topography ; thema EDItEUR::R Earth Sciences, Geography, Environment, Planning::RN The environment::RNF Environmental management ; thema EDItEUR::R Earth Sciences, Geography, Environment, Planning::RG Geography::RGC Human geography
    Language: English
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  • 12
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    De Gruyter | De Gruyter Open Poland
    Publication Date: 2022-11-22
    Description: This edited volume examines the opportunities to think, do, and/or create jointly afforded by digital storytelling. The contributors discuss digital storytelling in the context of educational programs, teaching anthropology, and ethnographic research involving a variety of populations and subjects that will appeal to researchers and practitioners engaged with qualitative methods and pedagogies that rely on media technology.
    Keywords: Discourse ; Climate Change ; Humans ; Nature ; Oceania ; Resilience ; Environmental Ethics ; Environmental Change ; Worldview ; bic Book Industry Communication::J Society & social sciences::JF Society & culture: general::JFF Social issues & processes::JFFC Social impact of disasters ; bic Book Industry Communication::J Society & social sciences::JF Society & culture: general::JFH Popular beliefs & controversial knowledge::JFHF Folklore, myths & legends ; bic Book Industry Communication::J Society & social sciences::JF Society & culture: general::JFS Social groups::JFSL Ethnic studies::JFSL9 Indigenous peoples ; bic Book Industry Communication::J Society & social sciences::JH Sociology & anthropology::JHB Sociology::JHBD Population & demography ; bic Book Industry Communication::J Society & social sciences::JH Sociology & anthropology::JHM Anthropology ; bic Book Industry Communication::P Mathematics & science::PS Biology, life sciences::PSX Human biology::PSXM Medical anthropology
    Language: English
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  • 13
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Free Radical Biology and Medicine 10 (1991), S. 177-184 
    ISSN: 0891-5849
    Keywords: Free radicals ; Humans ; Noninvasive analytical techniques ; Oxidative stress status
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Type of Medium: Electronic Resource
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  • 14
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Mutation Research DNAging 256 (1991), S. 45-48 
    ISSN: 0921-8734
    Keywords: Ageing ; Humans ; Skin cells ; Telomeres
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
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  • 15
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis 304 (1994), S. 285-294 
    ISSN: 0027-5107
    Keywords: Cotinine ; Genetic monitoring ; Hprt mutation ; Humans ; Lymphocytes ; Pregnancy ; Smoking ; Tobacco
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Medicine
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  • 16
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Mutation Research DNAging 237 (1990), S. 123-130 
    ISSN: 0921-8734
    Keywords: Aging ; Humans ; Ionizing radiation ; Single cell electrophoresis
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
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  • 17
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Peptides 10 (1989), S. 489-492 
    ISSN: 0196-9781
    Keywords: Angiotensin II ; Blood ; Humans ; Radioimmunoassay ; Rats ; [des-Leu^1^0]-angiotensin I
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 18
    ISSN: 0196-9781
    Keywords: Autocrine feedback mechanism ; Cholecystokinin ; Feeding ; Humans ; Radioimmunoassay
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 19
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Applied Animal Behaviour Science 39 (1994), S. 141-150 
    ISSN: 0168-1591
    Keywords: Cats ; Foraging ; Humans ; Livestock ; Predators ; Vampire bats
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
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  • 20
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Applied Animal Behaviour Science 41 (1994), S. 101-114 
    ISSN: 0168-1591
    Keywords: Fear ; Handling ; Humans ; Poultry ; Productivity
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
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  • 21
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Journal of Thermal Biology 5 (1980), S. 249-251 
    ISSN: 0306-4565
    Keywords: Humans ; exercise ; hyperthermia ; oesophageal temperature
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology
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  • 22
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Marine Policy 9 (1985), S. 39-52 
    ISSN: 0308-597X
    Keywords: Ecology ; Fisheries ; Marine resources
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Political Science , Law
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  • 23
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Marine Policy 6 (1982), S. 43-57 
    ISSN: 0308-597X
    Keywords: Atlantic ; Fisheries ; Management
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Political Science , Law
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  • 24
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Marine Policy 9 (1985), S. 126-133 
    ISSN: 0308-597X
    Keywords: Fisheries ; Government ; USA
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Political Science , Law
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  • 25
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Marine Policy 6 (1982), S. 61-62 
    ISSN: 0308-597X
    Keywords: Fisheries ; Marketing ; UK
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Political Science , Law
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  • 26
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Marine Policy 8 (1984), S. 137-150 
    ISSN: 0308-597X
    Keywords: Fisheries ; International organizations ; Management
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Political Science , Law
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  • 27
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Marine Policy 7 (1983), S. 197-211 
    ISSN: 0308-597X
    Keywords: Fisheries ; Management ; Property rights
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Political Science , Law
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  • 28
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Marine Policy 6 (1982), S. 219-235 
    ISSN: 0308-597X
    Keywords: Canada ; Fisheries ; Foreign relations
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Political Science , Law
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  • 29
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Marine Policy 6 (1982), S. 66-68 
    ISSN: 0308-597X
    Keywords: Fisheries ; Regional government organizations ; West Africa
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Political Science , Law
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  • 30
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Marine Policy 9 (1985), S. 120-125 
    ISSN: 0308-597X
    Keywords: Exclusive Economic Zones ; Fisheries ; Law of the Sea
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Political Science , Law
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  • 31
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Marine Policy 6 (1982), S. 27-42 
    ISSN: 0308-597X
    Keywords: Fisheries ; International law ; United Nations Organization
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Political Science , Law
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  • 32
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Marine Policy 6 (1982), S. 131-139 
    ISSN: 0308-597X
    Keywords: Economic measurements ; Fisheries ; Pacific
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Political Science , Law
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  • 33
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Marine Policy 7 (1983), S. 267-278 
    ISSN: 0308-597X
    Keywords: Environment ; Fisheries ; Resource management
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Political Science , Law
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  • 34
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Marine Policy 6 (1982), S. 121-130 
    ISSN: 0308-597X
    Keywords: Atlantic ; Fisheries ; Management
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Political Science , Law
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  • 35
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Marine Policy 8 (1984), S. 239-258 
    ISSN: 0308-597X
    Keywords: Antarctica ; Fisheries ; Krill
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Political Science , Law
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    Marine Policy 9 (1985), S. 220-236 
    ISSN: 0308-597X
    Keywords: Fisheries ; Resource economics, UK
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Political Science , Law
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  • 37
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    Agriculture and human values 17 (2000), S. 125-139 
    ISSN: 1572-8366
    Keywords: Environment ; Fisheries ; Fordism ; Nation-State ; Regulation ; Supranational State ; Transnational corporations ; Transnational State
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract This analysis uses an analytical frameworkgrounded in political economy perspectives of theglobalization of the agro-food sector combined with acase study approach focusing on the Marine StewardshipCouncil (MSC) to inform discussions regarding thecharacteristics of societal regulation in thepost-Fordist era. More specifically, this analysisuses the case of the emergence of the MSC toinvestigate propositions regarding the existence of,and location of, nascent forms of a transnationalState. The MSC proposes to regulate the certificationof sustainable fisheries at the global level throughan eco-labeling program. The MSC was created in 1996by the transnational environmental organization theWorld Wildlife Fund and the transnational corporationUnilever. The emergence of the MSC has generatedheated discussion in fisheries management circles thatis in general divided along North/South lines. Thisanalysis indicates that the case of the MSC providesvaluable insights into the possible characteristics ofsupranational regulatory mechanisms that might emulatethe role of the nation-State in the post-Fordist era.
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  • 38
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    Journal of molecular evolution 27 (1988), S. 311-320 
    ISSN: 1432-1432
    Keywords: Genome composition ; Coding sequences ; Isochores ; Humans ; Murids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The compositional distributions of coding sequences and DNA molecules (in the 50-100-kb range) are remarkably narrower in murids (rat and mouse) compared to humans (as well as to all other mammals explored so far). In murids, both distributions begin at higher and end at lower GC values. A comparison of homologous coding sequences from murids and humans revealed that their different compositional distributions are due to differences in GC levels in all three codon positions, particularly of genes located at both ends of the distribution. In turn, these differences are responsible for differences in both codon usage and amino acids. When GC levels at first+second codon positions and third codon positions, respectively, of murid genes are plotted against corresponding GC levels of homologous human genes, linear relationships (with very high correlation coefficients and slopes of about 0.78 and 0.60, respectively) are found. This indicates a conservation of the order of GC levels in homologous genes from humans and murids. (The same comparison for mouse and rat genes indicates a conservation of GC levels of homologous genes.) A similar linear relationship was observed when plotting GC levels of corresponding DNA fractions (as obtained by density gradient centrifugation in the presence of a sequence-specific ligand) from mouse and human. These findings indicate that orderly compositional changes affecting not only coding sequences but also noncoding sequences took place since the divergence of murids. Such directional fixations of mutations point to the existence of selective pressures affecting the genome as a whole.
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  • 39
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    Journal of molecular evolution 35 (1992), S. 7-16 
    ISSN: 1432-1432
    Keywords: Alu source genes ; Humans ; Gorillas ; Retrotransposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A member of the young PV Alu sub-family is detected in chimpanzee DNA showing that the PV subfamily is not specific to human DNA. This particular Alu is absent from the orthologous loci in both human and gorilla DNAs, indicating that PV subfamily members transposed within the chimpanzee lineage following the divergence of chimpanzee from both gorilla and human. These findings and previous reports describing the transpositional activity of other Alu sequences within the human, gorilla, and chimpanzee lineages provide phylogenetic evidence for the existence of multiple Alu source genes. Sequences surrounding this particular Alu resemble known transcriptional control elements associated with RNA polymerase III, suggesting a mechanism by which cis-acting elements might be acquired upon retrotransposition.
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    Journal of molecular evolution 33 (1991), S. 442-449 
    ISSN: 1432-1432
    Keywords: Humans ; Mouse ; Rat ; Codon usage ; Mutation bias ; Selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A new statistical test has been developed to detect selection on silent sites. This test compares the codon usage within a gene and thus does not require knowledge of which genes are under the greatest selection, that there exist common trends in codon usage across genes, or that genes have the same mutation pattern. It also controls for mutational biases that might be introduced by the adjacent bases. The test was applied to 62 mammalian sequences, the significant codon usage biases were detected in all three species examined (humans, rats, and mice). However, these biases appear not to be the consequence of selection, but of the first base pair in the codon influencing the mutation pattern at the third position.
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  • 41
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    Journal of molecular evolution 34 (1992), S. 336-344 
    ISSN: 1432-1432
    Keywords: Humans ; Mitochondrial DNA ; Nuclear polymorphisms ; Heteroplasmy ; Genetic differentiation ; Sickle cell ; Rain forest refuges
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The identification of genetically coherent populations is essential for understanding human evolution. Among the culturally uniform ethnic groups of west Africa, there are two geographically distinct populations with high frequencies of sickle-cell hemoglobin (HbS). Although the HbS mutation in each group is found on distinguishable chromosomes 11, these populations have been assumed to be parts of a single population. Analysis of mitochondrial DNA (mtDNA) in these populations demonstrated that the two populations identified by alternative chromosomes 11 bearing HbS have distinct distributions of mitochondrial genotypes, i.e., they are maternally separate. These studies also showed that, contrary to expectation, the mtDNA of some individuals is heteroplasmic. For nuclear loci, a comparison of the frequency of alternative alleles established that these populations are genetically distinct. Both the mitochondrial and nuclear data indicate that these populations have been separate for approximately 50,000 years. Although HbS in the two populations is usually attributed to recent, independent mutations, the duration of the separation and the observed geographic distribution of the population allow for the possibility of an ancient origin of HbS. Assuming an ancient mutation and considering the known biogeography, we suggest that HbS protected selected populations from malaria in rain forest refuges during the most recent ice age.
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  • 42
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    Peptides 4 (1983), S. 451-455 
    ISSN: 0196-9781
    Keywords: Biliary system ; Cat ; Guinea-pig ; Humans ; Mucosa ; Rabbit ; Radioimmunoassay ; Respiratory system ; Skin ; Substance P ; Sympathetic nervous system ; Urinary system
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
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    Peptides 1 (1980), S. 55-57 
    ISSN: 0196-9781
    Keywords: ACTH ; Aging ; Attention ; Cognition ; Humans ; MSH ; Peptide ; Visual retention
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
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    Peptides 5 (1984), S. 319-323 
    ISSN: 0196-9781
    Keywords: Blood flow ; Circulation ; Electromagnetic flowmetry ; Humans ; VIP
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    Topics: Chemistry and Pharmacology
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  • 45
    ISSN: 0165-7992
    Keywords: Cytochrome P-450 ; Dogs ; Humans ; Monkeys ; P-448-H ; Rats
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    Topics: Biology , Medicine
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    Ethology and Sociobiology 6 (1985), S. 183-187 
    ISSN: 0162-3095
    Keywords: Assortative mating ; Genetic similarity ; Heritability ; Humans ; Kin recognition
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    Ethology and Sociobiology 8 (1987), S. 215-220 
    ISSN: 0162-3095
    Keywords: Humans ; Paternity confidence ; Relatedness
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    Mycopathologia 124 (1993), S. 73-77 
    ISSN: 1573-0832
    Keywords: Assessment ; Cancer ; Humans ; Hydrazines ; Mushroom
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    Topics: Biology , Medicine
    Notes: Abstract This assessment focuses on the concentrations of some chemicals present in theAgaricus bisporus mushroom, the cancer-inducing doses of these chemicals or mushroom used in the animal experiments, the total amounts of these chemicals or mushroom needed to induce cancer in these mice, and the estimated total amounts of these chemicals or mushroom needed to induce cancer in humans. By adding the estimated amounts of chemicals needed to induce cancer and by comparing it with the amount of raw mushroom needed to induce the same effect, it becomes obvious that we have accounted for less than 2% of the carcinogenic components of theAgaricus bisporus mushroom. Since some unavailable data handicapped this assessment, it should be regarded as tentative and subject to further adjustment.
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    International journal of biometeorology 34 (1990), S. 42-48 
    ISSN: 1432-1254
    Keywords: Briths ; Humans ; Solar wind ; Geomagnetism ; Melatonin
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    Topics: Geography , Physics
    Notes: Abstract Data obtained from the literature on the annual pattern of human conceptions and plasma melatonin at high latitudes indicated that simple annual rhythms do not exist. Instead, prominent semiannual rhythms are found, with equinoctial troughs and solsticial peaks. A prominent semiannual environmental event is the magnetic disturbance induced by the solar wind. The semiannual magnetic disturbances are worldwide, but most pronounced in the auroral zones where the corpuscular radiation enters the atmosphere. Magnetic indices that predominantly reflect these events were obtained from the literature and correlated with the melatonin and conception data. Significant and inverse correlations were found for Inuit conceptions and the melatonin data. The correlations obtained for 48 contiguous states of the United States indicated that only the extreme northern states exhibited this relationship. These data were compared with a previous correlational study in the United States which established that sunshine was correlated with conceptions in the middle latitude and southern states. An hypothesis of dual control by electromagnetic and magnetic energies is proposed: melatonin is a progonadal hormone in humans controlled by both factors, depending on their relative strength. Other studies are reviewed regarding the possible factors involved in determining the annual pattern of human conceptions. Demographic studies of geographic variation in temporal patterns of conceptions, with particular regard to variations of the magnetic fields on the earth's surface, may provide some insight into the efficacy of these different factors.
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  • 50
    ISSN: 1432-1009
    Keywords: Reservoir ; Fisheries ; Breeding and wintering waterbirds ; Raising water levels ; Habitat change
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract A new, higher dam was installed at Kerkini Reservoir in 1982, causing habitat and landscape disruption. A decrease in the area of grassland and shallow water areas, the rapid disappearance of reedbeds, the appearance of beds ofNymphaea, and the disappearance of half the forest area were all observed between 1982 and 1991. With the new hydrological regime, a lacustrine system was created, with an extensive, rather deep (4–8 m), pelagic zone favorable for the development of coarse fish species throughout the year. After 1982, an increase in fishing effort and a change in the relative abundance of fish species in the catch, including the disappearance of eels and wels, were observed. The impact of the rise in the water level of breeding aquatic birds led to a general decline in species typical of marshy habitats in favor of species preferring deeper open water habitats. A decrease was recorded in bird species that feed largely on invertebrates and to a lesser extent fish (e.g., glossy ibis) and that require extensive shallow feeding areas. There was a decline in geese, whose nests were regularly flooded, and a major increase in piscivorous birds, particularly diving birds (e.g., cormorants), which prefer deeper open water and benefitted directly from the large increase in coarse fish biomass. The disappearance of birds breeding in flooded meadows (e.g., black-winged stilts) and of those restricted to reedbeds (e.g., marsh harrier) occurred from 1983. Over the same period, the changes in populations of wintering birds at Kerkini were different from those occurring in other wetlands in northern Greece. The changes recorded in the populations of wintering birds at Kerkini did not therefore result from overall regional trends but from the major habitat modifications that occurred to this wetland. As for breeding birds, strictly piscivorous species increased greatly as a result of the increased availability of fish, but also due to the appearance of many suitable night roosting sites (flooded trees) and to the great increase in the area of open water greater than 2 m deep. Today, Kerkini has become the most important breeding site in Greece for a majority of colonial waterbirds. In contrast, wintering shorebirds practically disappeared. The many changes recorded in the status of breeding and wintering birds at Kerkini can mostly be explained by the changes that occurred in the functioning of the ecosystem and in the habitat structure following the inauguration of the new hydrological regime. These changes did not all occur at the same time: some were immediate and others required a delay before they could be detected.
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  • 51
    ISSN: 1432-1009
    Keywords: Fisheries ; Phosphorus ; Contaminants ; Ecosystem ; Management ; Simulation model ; Great Lakes
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    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract A simulation model was developed to describe linkages among fish food web, nutrient cycling, and contaminant processes in the southern basin of Lake Michigan. The model was used to examine possible effects of management actions and an exotic zooplankter (Bythotrephes) on Lake Michigan food web and contaminant dynamics. The model predicts that contaminant concentrations in salmonines will decrease by nearly 20% ifBythotrephes successfully establishes itself in the lake. The model suggests that this decrease will result from lowered transfer efficiencies within the food web and increased flux of contaminants to the hypolimnion. The model also indicates that phosphorus management will have little effect on contaminant concentrations in salmonines. The modeling exercise helped identify weaknesses in the data base (e.g., incomplete information on contaminant loadings and on the biomass, production, and ecological efficiencies of dominant organisms) that should be corrected in order to make reliable management decisions.
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    Environmental management 7 (1983), S. 151-160 
    ISSN: 1432-1009
    Keywords: Grass carp ; Biological control ; Nuisance aquatic weeds ; Fisheries ; Aquaculture ; Reproductive requirements ; Arkansas management plan ; Sterile hybrids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Grass carp (Ctenopharyngodon idella Val.) were introduced into the United States in 1963 as potential biological control agents for nuisance aquatic weeds. Since that time an oftentimes bitter controversy has raged over its effects on sportfishing, and its possible natural reproduction and naturalization in North America. This review considers the history, ecology, and present status of grass carp in the United States in light of the voluminous scientific research conducted since its importation. Particular attention is given to the role of grass carp in the fisheries management plans of Arkansas. Recent development of a sterile, triploid grass carp hybrid may lead to widespread use of grass carp to control nuisance aquatic weeds in culturally eutrophicated waters of the United States.
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  • 53
    ISSN: 1432-1009
    Keywords: Flushing ; Scouring ; Channel Maintenance ; Fisheries ; Trinity River
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract The operation of Trinity and Lewiston Dams on the Trinity River in northern California in the United States, combined with severe watershed erosion, has jeopardized the existence of prime salmonid fisheries. Extreme streamflow depletion and stream sedimentation below Lewiston have resulted in heavy accumulation of coarse sediment on riffle gravel and filling of streambed pools, causing the destruction of spawning, nursery, and overwintering habitat for prized chinook salmon (Salmo gairdnerii) and steelhead trout (Oncorhynchus tschawytscha). Proposals to restore and maintain the degraded habitat include controlled one-time remedial peak flows or annual maintenance peak flows designed to flush the spawning gravel and scour the banks, deltas, and pools. The criteria for effective channel restoration or maintenance by streambed flushing and scouring are examined here, as well as the mechanics involved. The liabilities of releasing mammoth scouring-flushing flows approximating the magnitude that preceded reservoir construction make this option unviable. The resulting damage to fish habitat established under the postproject streamflow regime, as well as damage to human settlements in the floodplain, would be unacceptable, as would the opportunity costs to hydroelectric and irrigation water users. The technical feasibility of annual maintenance flushing flows depends upon associated mechanical and structural measures, particularly instream maintenance dredging of deep pools and construction of a sediment control dam on a tributary where watershed erosion is extreme. The cost effectiveness of a sediment dam with a limited useful economic life, combined with perpetual maintenance dredging, is questionable.
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    Environmental management 20 (1996), S. 523-539 
    ISSN: 1432-1009
    Keywords: Water control ; Floodplain ; Fisheries ; Bangladesh ; Chandpur
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Bangladesh is a very flat delta built up by the Ganges—Brahmaputra—Meghna/Barak river systems. Because of its geographical location, floods cause huge destruction of lives and properties almost every year. Water control programs have been undertaken to enhance development through mitigating the threat of disasters. This structural approach to flood hazard has severely affected floodplain fisheries that supply the major share of protein to rural Bangladesh, as exemplified by the Chandpur Irrigation Project. Although the regulated environment of the Chandpur project has become favorable for closed-water cultured fish farming, the natural open-water fishery loss has been substantial. Results from research show that fish yields were better under preproject conditions. Under project conditions per capita fish consumption has dropped significantly, and the price of fish has risen beyond the means of the poor people, so that fish protein in the diet of poor people is gradually declining. Bangladesh is planning to expand water control facilities to the remaining flood-prone areas in the next 15–20 years. This will cause further loss of floodplain fisheries. If prices for closed-water fish remain beyond the buying power of the poor, alternative sources of cheap protein will be required.
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    Environmental management 3 (1979), S. 133-144 
    ISSN: 1432-1009
    Keywords: Coastal zone Management ; Fisheries ; Marshes ; Wetlands ; Louisiana
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract This paper examines causes and consequences of wetland losses in coastal Louisiana. Land loss is a cumulative impact, the result of many impacts both natural and artificial. Natural losses are caused by subsidence, decay of abandoned river deltas, waves, and storms. Artificial losses result from flood-control practices, impoundments, and dredging and subsequent erosion of artificial channels. Wetland loss also results from spoil disposal upon wetlands and land reclamation projects. Total land loss in Louisiana's coastal zone is at least 4,300 ha/year. Some wetlands are converted to spoil banks and other eco-systems so that wetland losses are probably two to three times higher. Annual wetland losses in the Barataria Bay basin are 2.6% of the wetland area. Human activities are the principal determinants of land loss. The present total wetland area directly lost because of canals may be close to 10% if spoil area is included. The interrelationship between hydrology, land, vegetation, substrate, subsidence, and sediment supply are complicated; however, hydrologic units with high canal density are generally associated with higher rates of land loss and the rate may be accelerating. Some cumulative impacts of land loss are increased saltwater intrusion, loss of capacity to buffer the impact of storms, and large additions of nutrients. One measure of the impact is that roughly $8–17 × 106 (U.S.A.) of fisheries products and services are lost annually in Louisiana. Viewed at the level of the hydrologic unit, land loss transcends differences in local vegetation, substrate, geology, and hydrology. Land management should therefore focus at that level of organization. Proper guideline recommendations require an appreciation of the long-term interrelations of the wetland estuarine system.
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  • 56
    ISSN: 1432-0878
    Keywords: Skeletal muscles ; Ultrastructure ; Exercise ; Glycogen ; Humans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Distribution of glycogen particles in semithin and ultrathin sections of biopsy samples from human muscles subjected to either short- or long-term running were investigated using PAS and Periodic Acid-ThioSemiCarbazide-Silver Proteinate (PA-TSC-SP) staining methods. Glycogen particles were predominantly found immediately under the sarcolemma or aligned along the myofibrillar Iband. After long-term exhaustive exercise type-1 fibers with a few or no glycogen particles in the core of the fibers were frequently observed. The subsarcolemmal glycogen stores of these “depleted” type-1 fibers were about three times as large as after exhaustive short-time exercise. Another indication of utilization of subsarcolemmal glycogen stores during anaerobic exercise was that many particles displayed a pale, rudimentary shape. This observation suggests fragmental metabolization of glycogen. Thus, depending on type of exercise and type of fiber differential and sequential glycogen utilization patterns can be observed.
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  • 57
    ISSN: 1573-5133
    Keywords: Chondrichthyes ; Elasmobranchs ; Fisheries ; Ageing methods ; Growth rates ; Gestation periods ; Maturity ; Vertebral bands ; Weight-length relationships ; Life histories
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Synopsis The silky shark, Carcharhinus falciformis, and scalloped hammerhead, Sphyrna lewini, represent 〉80% of the shark by-catch of the winter swordfish/tuna longline fishery of the northwestern Gulf of Mexico. This catch represents a potential supplemental fishery, yet little is known of the life histories of the two species. This report relates reproductive biology data to age and growth estimates for 135 C. falciformis and 78 S. lewini. Unlike other regional populations, C. falciformis in the Gulf of Mexico may have a seasonal 12 month gestation period. Males mature at 210–220 cm TL (6–7 yr); females at 〉225 cm TL (7–9 yr). Application of age at length data for combined sexes produced von Bertalanffy growth model parameter estimates of L∞ = 291 cm TL, K = 0.153, t0 = −2.2 yr. Adult male S. lewini outnumbered adult females in catches because of differences in the distributions of the sexually segregated population. Males mature at 180 cm TL (10 yr); females at 250 cm TL (15 yr). von Bertalanffy parameter estimates for combined sexes of this species were L∞ = 329 cm TL, K = 0.073, to = −2.2 yr.
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    Environmental biology of fishes 2 (1977), S. 241-259 
    ISSN: 1573-5133
    Keywords: Production ; Fisheries ; Population dynamics ; Energetics ; Fishes ; Competition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Synopsis Production rates of seven species of fishes were determined for one year in a 0.95 ha pond. Total annual production of all fishes in the pond was 209 g m−2y−1 (after the subtraction of 16.2 g m−2y−1 of negative production). Over 90% of the production occurred in the months of June through September, with young-of-the-year fishes contributing 84% of the total. When Y of Y fishes shifted to benthic diets in the spring, the small biomass of benthos available could not sustain the large biomas of fish. Severe competition for the available food then resulted in decreased production rates for the entire fish taxocene.
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    Environmental biology of fishes 7 (1982), S. 177-180 
    ISSN: 1573-5133
    Keywords: Temperature ; Behavior ; Ecology ; Fisheries ; Fish ; Marine juveniles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Synopsis Sixteen yearling winter flounder, tested individually for 3-day periods in electronic shuttleboxes, voluntarily occupied an 8–27°C range of temperature, with a modal final thermal preferendum of 18.5°C (mean 18.7°C, median 19°C, midpoint 17.5°C, s.d. 1.9°C, S k + 0.33). The locomotor activity pattern of the yearling fish in the laboratory was markedly nocturnal, with mean hourly nocturnal activity exceeding mean hourly diurnal activity by a factor of 3.4. Maximum activity occurred at 0300 EST, minimum activity at 1400 EST. While activity generally increased with temperature, a local activity minimum occurred at 18.7°C, coinciding with the 24-hour mean final thermal preferendum. Comparison of these laboratory data with previously published field data suggest that behavioral responses to temperature and light play significant roles in determining age- and size-specific differences in seasonal depth stratification and onshore-offshore distributions in this species.
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    Environmental biology of fishes 30 (1991), S. 253-271 
    ISSN: 1573-5133
    Keywords: Rockfish ; Longevity ; Reproductive value ; Fisheries ; Scorpaenidae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Synopsis The characteristics of lightly and heavily exploited Pacific ocean perch,Sebastes alutus, stocks are evaluated relative to the predictions of life history theory. These long-lived species (50–100 year lifespan) show limited phenotypic plasticity and have little buffering against the effects of reduced lifespan. Reduced stock abundance has generated some compensatory increase in growth rate. Length at first maturity varies only slightly with increased growth rate, although age at maturity may decrease by 1–4 years. Grooth increases yield larger (15–20%) size at age and increased reproductive effort at younger ages, but lower size-specific fecundity for these faster-growing fish. This suggests an energy allocation protocol favouring growth over reproduction in these long-lived animals. Rockfishes have late recruitment to fisheries (ages 10–15), and the detection time for results of management actions is equally long. Their vulnerability to overfishing means that indices of population changes, more representative of fishing effects than the catch rate index presently used, are required. Reproductive value indices are shown to be extremely sensitive and continuous with population abundance changes. Their incorporation into monitoring programs would permit more timely evaluation of management actions. Management policies developed for shorter-lived species are shown to be inappropriate for rockfishes. The need for an improved match in the time frame of the species' life history, and that of management strategies, is stressed.
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    Environmental biology of fishes 35 (1992), S. 187-203 
    ISSN: 1573-5133
    Keywords: California ; Elasmobranchs ; Exploitation ; Fisheries ; Life history ; Tagging ; Triakidae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Synopsis The age, growth, and sexual maturation of the leopard shark, Triakis semifasciata, from central California were studied. Growth band counts in vertebral centra of 162 leopard sharks produced von Bertalanffy growth curves with L∞, K. and to parameters of 1536 mm. 0.082, and -2.31, respectively, for both sexes combined. The L8 value for females (1602 mm TL) was slightly but insignificantly higher than for males (1499 mm TL), but the K and to values were almost identical. Seasonal changes in size modes of young-of-the-year leopard sharks, centrum edge characteristics, and growth and tetracycline mark-recapture from the field were used to validate annual deposition of vertebral centrum band pairs. Sexual maturity was evaluated by the gonads and presence of sperm and eggs; males mature at 7 yr and at about 63% of asymptotic length, and females mature at 10 yr, and at about 72% of asymptotic length. This slow growth, late maturity, and relatively low fecundity may increase their susceptibility to over-exploitation.
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    Environmental biology of fishes 45 (1996), S. 219-235 
    ISSN: 1573-5133
    Keywords: Ecology ; Behaviour ; Evolution ; Cichlids ; Fisheries ; Conservation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Synopsis Ecological conditions in tropical lacustrine systems are considered by focusing on the evolution, maintenance, exploitation and vulnerability of fish communities in the African Great Lakes. The exceptionally high biodiversities in the littoral/sublittoral zones of the very ancient, deep, clear, permanently stratified rift lakes Tanganyika and Malawi, are contrasted with the simpler systems in their pelagic zones, also with biodiversity in the much younger, shallower Victoria, the world's largest tropical lake.
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    Animal cognition 1 (1998), S. 25-35 
    ISSN: 1435-9456
    Keywords: Key words Shape from shading ; Visual search ; Texture segregation ; Chimpanzees ; Humans
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The perception of shape from shading was tested in two chimpanzees (Pan troglodytes) and five humans (Homo sapiens), using visual search tasks. Subjects were required to select and touch an odd item (target) from among uniform distractors. Humans found the target faster when shading was vertical than when it was horizontal, consistent with results of previous research. Both chimpanzees showed the opposite pattern: they found the target faster when shading was horizontal. The same difference in response was found in texture segregation tasks. This difference between the species could not be explained by head rotation or head shift parallel to the surface of the monitor. Furthermore, when the shaded shape was changed from a circle to a square, or the shading type was changed from gradual to stepwise, the difference in performance between vertical and horizontal shading disappeared in chimpanzees, but persisted in humans. These results suggest that chimpanzees process shading information in a different way from humans.
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    Environmental biology of fishes 23 (1988), S. 141-154 
    ISSN: 1573-5133
    Keywords: Cyanide ; Diversity ; Development ; Ecology ; Environment ; Fisheries ; Pollution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Synopsis The biological diversity and productivity of Philippine coral reefs are threatened by siltation, destructive fishing methods, coral and shell collecting and overfishing. Destructive fishing includes: the widespread, illegal use of explosives; poisons such as sodium cyanide; muro-ami and kayakas fishing; and trawling. The recent decline in catch rates threatens the livelihood of 700 000 near-shore subsistence fishermen who catch 55% of the total landings. The new government under Corazon Aquino wishes to protect the marine environment through the creation of a viable marine conservation management plan, enforcement of existing laws and through cooperation between government, non-government and international agencies to provide education and research. The Department of Agriculture, which has the authority for fisheries, has designated the International Marinelife Alliance as the lead non-government agency involved with fund raising, net-training and finding alternatives to destructive fishing methods.
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    ISSN: 1573-5133
    Keywords: Cyprinids ; Ethiopia ; Morphotypes ; Food-niche ; Biodiversity ; Feeding ; Evolution ; Fisheries ; Resource partitioning ; Piscivory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Synopsis In October–December 1990, the large barbs (Barbus) that contribute more than 35% of the catch in lake Tana (northern Ethiopia) were studied. Previous authors (Rüppell 1837, Boulenger 1902,1911, Bini 1940) described from 6 to 23 (sub)species for the lake. Banister (1973) lumped all of these into one subspecies: Barbus intermedius intermedius Rüppell,1837. We found that the Lake Tana Barbus could be readily categorized in at least 13 discrete morphotypes, some of which were already distinguished by local fishermen. None of the known descriptions are adequate to distinguish the barbs unambiguously, which is important for monitoring and management of developing fisheries. Intermediates between morphotypes were rare (〈 10%). By applying canonical discriminant analysis on a set of 17 morphometric characters (including some directly associated with feeding) our initial morphotype-distinction was confirmed. Also, differences between the morphotypes in distribution, related to depth and substratum were found, as well as differences in intestinal contents, a key to the food-niche. The high number of piscivorous morphotypes (8 out of 13) was striking as piscivory is relatively rare among cyprinids. Piscivory was found to be highly correlated with morphological (feeding related) characters. The presence of discrete morphotypes, that also differ in food-niche and distribution, strongly suggests that several distinct populations exist, that may be (partly or completely) reproductively segregated. Knowledge about these populations, that may represent separate units of fish stock, is of crucial importance for the management of sustainable fisheries and protection of the biodiversity in Lake Tana. It is possible that several species or even a unique cyprinid species flock are present, that urgently need protection.
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    Environmental biology of fishes 27 (1990), S. 303-308 
    ISSN: 1573-5133
    Keywords: Fish introductions ; Africa ; Cichlids ; Barbus ; Haplochromis ; Lake management ; Fisheries
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Synopsis Cyprinid fishes apparently constituted the major part of the original fish fauna in Lake Luhondo, Rwanda, at least until 1934. At that time only three species, all cyprinids, were known from the lake:Barbus neumayeri, a small barbel, very common in the lake (described from the lake asBarbus luhondo) and two larger cyprinid species:Barbus microbarbis andVaricorhinus ruandae. These two large species were probably not very common in the lake. Between 1935 and 1938 some youngTilapia were introduced into Lake Luhondo. Since then and certainly since 1952 the large cyprinids seem to have disappeared completely from the lake. The smallBarbus neumayeri has become extremely rare; at present it survives only in some small tributaries of the lake. In the lake itselfTilapia andHaplochromis species are now the dominant fauna. A survey of the available information is given.
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    Environmental biology of fishes 43 (1995), S. 381-391 
    ISSN: 1573-5133
    Keywords: Fisheries ; Irrigation ; Reproductive seasonality ; Sarotherodon galilaeus ; Species richness ; Water quality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Synopsis A preliminary study of the ecology and commercial fish catches was carried out in the Toho-Todougba, Ahouangan and Dati lakes (1500 ha) in southern Benin (West Africa) over a period of 18 consecutive months. Water quality, species richness, and the reproductive biology of the dominant species, Sarotherodon galilaeus, were examined. Unlike Lagoon Toho-Todougba, lakes Ahouangan and Dati are less favourable for fish production because of their high total iron content and their relative low pH. The study revealed the existence of 19 species belonging to eleven (11) families: 16 species in Lagoon Toho-Todougba,12 in Lake Ahouangan, and 7 in Lake Dati. Lakes Ahouangan and Dati had a relatively high faunal similarity whereas Lagoon Toho-Todougba exhibited a relatively low faunal similarity with the former systems. In Lagoon Toho-Todougba, six cichlid species were the most important component of the fishery: Sarotherodon galilaeus, Tilapia guineensis, T. zillii, T. mariae, Chromidotilapia guntheri, Hemichromis fasciatus. Three catfish species Chrysichthys auratus, Clarias agboyiensis, and Clarias lazera were harvested in low abundances. Some other fish, such as Polypterus senegalus senegalus, Protopterus annectens and Heterotis niloticus were captured sporadically, with H. niloticus appearing more consistently in catches than the others. Although not abundant, Gymnarchus niloticus and the African pike, Hepsetus odoe, were almost always present in the catches. Ctenopoma kingsleyae appeared only in Ahouangan. Some predatory species, such as Notopterus afer and Xenomystus nigri, are encountered only in lakes Ahouangan and Dati. In Lagoon Toho-Todougba, Sarotherodon galilaeus had a sex ratio (♂: ♀) of 0.49:1, and size at maturation was estimated as 12.3 cm TL. The spawning period extended from May to September with the peak occurring in July. Fecundity was correlated to log-body length (r = 0.74) and log-body weight (r = 0.76). Fish catches were estimated at 389 kg ha−1 year−1; about 73% of which was Sarotherodon galilaeus. The overexploitation of juvenile fish and the use of this lagoon for the irrigation of palm tree plantations have reduced fish recruitment and mean size.
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    Environment, development and sustainability 2 (2000), S. 277-304 
    ISSN: 1573-2975
    Keywords: Systems of Knowledge ; Local Knowledge ; Fisheries ; Resource Management
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Sociology
    Notes: Abstract During the last 20 years, the existence of rich systems of local knowledge, and their vital support to resource use and management regimes, has been demonstrated in a wide range of biological, physical and geographical domains, such as agriculture, animal husbandry, forestry and agroforestry, medicine, and marine science and fisheries. Local knowledge includes empirical and practical components that are fundamental to sustainable resource management. Among coastal-marine fishers, for example, regular catches and, often, long-term resource sustainment are ensured through the application of knowledge that encompasses empirical information on fish behaviour, marine physical environments, fish habitats and the interactions among ecosystem components, as well as complex fish taxonomies. Local knowledge is therefore an important cultural resource that guides and sustains the operation of customary management systems. The sets of rules that compose a fisheries management system derive directly from local concepts and knowledge of the resources on which the fishery is based. Beyond the practical and the empirical, it is essential to recognise the fundamental socio-cultural importance of local knowledge to any society. It is through knowledge transmission and socialisation that worldviews are constructed, social institutions perpetuated, customary practices established, and social roles defined. In this manner, local knowledge and its transmission, shape society and culture, and culture and society shape knowledge. Local knowledge is of great potential practical value. It can provide an important information base for local resources management, especially in the tropics, where conventionally-used data are usually scarce to non-existent, as well as providing a shortcut to pinpoint essential scientific research needs. To be useful for resources management, however, it must be systematically collected and scientifically verified, before being blended with complementary information derived from Western-based sciences. But local knowledge should not be looked on with only a short-term utilitarian eye. Arguments widely accepted for conserving biodiversity, for example, are also applicable to the intellectual cultural diversity encompassed in local knowledge systems: they should be conserved because their utility may only be revealed at some later date or owing to their intrinsic value as part of the world's global heritage. At least in cultures with a Western liberal tradition, more than lip-service is now being paid to alternative systems of knowledge. The denigration of alternative knowledge systems as backward, inefficient, inferior, and founded on myth and ignorance has recently begun to change. Many such practices are a logical, sophisticated and often still-evolving adaptation to risk, based on generations of empirical experience and arranged according to principles, philosophies and institutions that are radically different from those prevailing in Western scientific circles, and hence all-but incomprehensible to them. But steadfastly held prejudices remain powerful. In this presentation I describe the 'design principles' of local knowledge systems, with particular reference to coastal-marine fishing communities, and their social and practical usefulness. I then examine the economic, ideological and institutional factors that combine to perpetuate the marginalisation and neglect of local knowledge, and discuss some of the requirements for applying local knowledge in modern management.
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    Polymer Engineering and Science 28 (1988) 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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    Polymer Engineering and Science 28 (1988), S. 413-420 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: This paper presents the development of the boundary element equations for the compression molding process of isothermal Newtonian fluids. It shows the numerical implementation of the boundary element equations and presents a simple method of carrying out the domain integral present in the governing equations. The results and accuracy of a boundary element simulation are discussed, and the numerical results compared to experimental values.
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    Polymer Engineering and Science 28 (1988), S. 605-609 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The static delamination behavior of graphite/epoxy composite specimens subjected to mode I tensile opening (using UDCBUniform double cantilever beam. specimens), and pure mode II shear loading (using ENFEnd-notched flexural. specimens) were studied. The graphite epoxy composites for the study were made from commercially treated fibers, with and without an electropolymerized interlayer. The mode I fracture energy (GIC) was found to be significantly higher (more than 50 percent) for the coated fibers. However, this improvement was accompanied by a high reduction (more than 3 times) in the mode II fracture energy (GIIC). This effect is apparently related to poor adhesion between the interlayer and the epoxy resin, which may be corrected by use of a “top layer” of appropriate composition to form chemical bonds between the phases. The fracture toughness (KIC) of composites made with commercially treated fibers was also evaluated, using double side-notched specimens.
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    Polymer Engineering and Science 28 (1988), S. 583-591 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: An analytical methodology was developed capable of describing interrelations between thermal processing and polymer structure for thermoplastic based composite laminates. Specifically, this modeling methodology was used to describe experimental results generated with a specially designed match die quench mold by processing both neat PEEK polymer and carbon fiber reinforced laminate samples at different cooling rates. The developed model accurately predicted temperature profiles for PEEK laminates of different thicknesses, under normal as well as extreme quenching conditions of 114°C/s. surface cooling rates that are possible to generate with the quench mold. In general, the modeling methodology is capable of predicting a part's thermal profile during processing in terms of the composite's microscopic intrinsic properties (fiber and matrix), composition, and lamina orientation. Furthermore, by coupling to the thermal profile description, a previously developed crystallization kinetics model for PEEK polymer and its carbon reinforced composite, a quantitative description of structural development during processing was obtained. Thus, with this analytical methodology, a skin-core crystallinity profile, where the crystallinity varies with part-thickness as a result of uneven cooling experienced during processing, was predicted both for the neat PEEK polymer and its carbon reinforced laminate forms. Finally, the developed methodology clearly established the interplay of both microscopic heat transfer and kinetics of crystallization/solidification of the matrix that must be accounted for in predicting the final structure of a carbon fiber reinforced laminate that will, in turn, govern microscopic and macroscopic performance.
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    Polymer Engineering and Science 28 (1988), S. 634-639 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Neat poly(ether-ether-ketone) (PEEK) and carbon fiber reinforced PEEK (APC-2) specimens were prepared using a variety of cooling rates to achieve a range of crystallinities. Amorphous specimens were exposed to a variety of fluids to determine the penetrant types which are able to strongly influence the material. This allowed the estimation of the solubility parameter and hydrogen bonding index for PEEK to be 9.5 and 3.1, respectively. Methylene chloride was used to investigate the kinetics of penetrant sorption. The data demonstrated Case II behavior, with the initial crystallinity having a pronounced effect on both the kinetic and equilibrium data. Accordingly, a model was proposed capable of describing the sorption level and penetration depth as a function of time given the sample crystallinity and sorption temperature. With Case II behavior there was no difference in the sorption kinetics of neat and fiber reinforced PEEK. Finally, the dynamic mechanical properties measured during sorption were found to be dependent on the sorption process.
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    Polymer Engineering and Science 28 (1988), S. 670-678 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The dynamic shear viscosity and the morphology of polypropylene homopolymer and copolymer blended with linear low density polyethylene are studied. A maximum in the dynamic shear viscosity vs. blend composition is reported for the polypropylene copolymer, linear low density polyethylene system. The increasing dynamic shear viscosity is in accordance with the occurrence of a morphology of polyethylene inclusions in rubber surrounded by a polypropylene matrix. Comparing calculations of the dynamic shear viscosities - based on a shell model with interlayer - and experimental results supports this view.
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    Polymer Engineering and Science 28 (1988), S. 684-687 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Hydroxy-terminated copoly(fstyrene-b-1,2-butadiene) (HPSB) containing rubber-affinitive vinyl side chains and having a molecular weight of 2000 to 4000 were prepared, and block copolyurethanes were synthesized by using a low molecular weight hydroxy-terminated poly (ethyl en e terephthalate) as a PET-affinitive component and 4,4′-diphenylmethane diisocyanate as a chain extender. The relationships between the molecular weight of HPSB, copolymerization ratio of styrene to butadiene and the adhesive strength of PKT/rubber in high temperature atmospheres were examined. A peak of adhesive strength was observed at styrene copolymerization ratio of 20 wt percent and a HPSB molecular weight of 3000. The adhesion mechanism was estimated from the behavior of the characteristic infrared absorption of block Copolyurethane in heating.
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    Polymer Engineering and Science 28 (1988), S. 718-727 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: In vibration welding of thermoplastics, frictional work done by vibrating two parts under pressure, along their common interface, is used to generate heat to effect a weld. The main process parameters in vibration welding are the weld frequency, the amplitude of the vibratory motion, the weld pressure, and the weld time. How these parameters affect weld quality, the conditions that result in the best welds, the weldability of dissimilar plastics, and the effect of fillers such as glass are of interest. To address these issues, a research vibration welding machine in which all the parameters can be independently and accurately controlled and monitored was designed and fabricated. The phenomenology of welding, as determined by experiments on the four thermoplastics polycarbonate, poly (butylene terephthalate), polyetherimide, and modified poly (phenylene oxide), is described.
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    Polymer Engineering and Science 28 (1988), S. 743-757 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: An engineering analysis of the reactive extrusion process of a thermoplastic polyurethane was made through numerical simulation and actual experiment. The reactants used in this system were 4,4′diphenylmethane diisocyanate, polycaprolactone diol (M.W., 824), and 1,4-bu-tanediol with equivalent weight ratio of 2:1:1. As a catalyst, dibutyltin dilaurate was used. The reaction kinetics and the viscosity function were obtained through experiments, and the mathematical model which includes the conservation equations of mass, momentum, energy, and chemical species was solved numerically to obtain the velocity, concentration, temperature, viscosity, and pressure profiles. The actual experiments were performed in the laboratory scale extruder to compare the experimental results with those of the numerical simulation.
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    Polymer Engineering and Science 28 (1988), S. 775-784 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A series of polyurethane-urea/polyvinyl simultaneous interpenetrating polymer networks (SINs) were prepared starting from a mixture of isocyanate prepolymer blocked with N-(1-1′-dimethyl-3-cxobutyl) acrylamide oxime, chain extender, vinyl monomers, and catalysts. Their physical properties and morphology were investigated using differential scanning calorimetry, dynamic mechanical measurements, and small-angle X-ray scattering. The polyurethane-urea networks examined were two-phase in nature. The vinyl network was formed with diacetone acrylamide oxime, trimethylolpropane trimethacrylate, and N-vinyl-pyrrolidone. Calorimetric analyses revealed that the polyether soft segment phase separated within the SINs. At higher temperature, dynamic mechanical measurements demonstrated the presence of only one glass transition temperature (Tg) intermediate in temperature to the Tg of the vinyl network and the Tg of the urethane hard phase. This is indicative of chain entanglement (interpenetration) between the vinyl network and the polyurethane hard segments resulting in a two-phase morphology. Small-angle X-ray scattering analyses provided measurements of diffuse phase boundary thickness, phase mixing, and domain size distribution. Appreciable interfacial thickness was not observed and thus phase mixing occurred within the phases. Domain size distribution indicated that high network constraints hindered the development of domains and limited the phase segregation.
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    Polymer Engineering and Science 28 (1988) 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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    Polymer Engineering and Science 27 (1987), S. 1021-1034 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Equations are derived that relate the orientation of “pseudo-affine” reoriented structural units after a biaxial deformation to the degrees and the directions of the effective drawings. The connection between these drawing parameters and those externally applied is analyzed in detail. It is shown how a comparison of these two sets of drawing parameters allows conclusions regarding the distribution throughout the material of the stresses that cause the deformation, the inhomogeneity of the deformation, and the role of non-orienting flow during deformation. In particular, the orientation of biaxially drawn poly(ethylene terephthalate) films is investigated, and it is shown what general information can be obtained on the deformation behavior of this material on the basis of these considerations.
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    Polymer Engineering and Science 27 (1987), S. 1059-1068 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Scale-up from small laboratory size extruders to large production size extruders is a procedure of great practical importance. Many scale-up rules and theories have been proposed in the past, however it is not always clear how the different scale-up methods will affect extruder performance. A basic analysis of scale-up in plasticating single screw extruders is developed from which the effect of a certain scale-up strategy on extrusion performance can be evaluated in terms of solids conveying, melting, melt conveying, mixing, residence time, heat transfer, power consumption, and specific energy consumption. Various existing scale-up theories are evaluated and compared using the basic analysis. A number of existing scale-up theories have some significant drawbacks, in particular with non-constant specific energy consumption and imbalance between melting rate and pumping rate. Conditions that are desirable to achieve in scale-up are enumerated and ranked in terms of importance. This leads to two new scale-up methods that result in constant mechanical specific energy consumption and high throughput rates. The first scale-up method keeps the specific surface area constant. This scale-up should work well for high values of the Brinkman number. However, at low values of the Brinkman number, the melting rate may be insufficient. The second scale-up method keeps the melting rate at low Brinkman number equal to the pumping rate and, thus, should be useful in cases where the first scale-up method cannot be used.
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    Polymer Engineering and Science 27 (1987) 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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    Polymer Engineering and Science 27 (1987), S. 1128-1136 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The plane strain fracture toughness and fracture mechanisms of several tough engineering plastics have been studied and compared with poly(methyl methacrylate) (PMMA), a relatively brittle polymer. The tough polymers all are observed to form a multiple craze zone at the crack tip, which is shown to be the primary source of plane strain fracture toughness in these materials. The multiple craze zone is retained during slow crack growth but is metastable, and at a critical stress intensity and associated crack velocity, the system passes through a transition to a greatly accelerated single craze mode of unstable propagation.
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    Polymer Engineering and Science 27 (1987), S. 1148-1155 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The optical properties of bisphenol-A polycarbonate resin as described by the complex index of refraction, N = n - ik, are derived by Kramers-Kronig analysis of experimental absorption and reflectance data obtained in the range 40μm ≥ λ ≥ 105 nm. Electronic absorption processes in polycarbonate are characterized by two broad absorption peaks centered at ∼200 and ∼100 nm.
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    Polymer Engineering and Science 27 (1987), S. 1182-1186 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Three-layer coextruded blown (either blend or composite) films, made of low-density polyethylene and linear lowdensity polyethylene (1:1 ratio) of identical density, were compared. The tensile properties of both systems are nearly as high as those of the linear polyethylene while high strain rate properties including impact strength and tear resistance of the composite film are superior. Some structural insight was obtained by thermal analysis and thermoelastic measurements. Structure property relationships are discussed in light of the unique behavior, structure, and morphology of linear low-density polyethylene. The two polyethylenes are only compatible to a rather limited extent mainly affecting their blend behavior. However, a strong mutual reinforcement effect was observed.
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  • 86
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 27 (1987), S. 1203-1208 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A Viton copolymer containing vinylidene fluoride (VF2) and hexafluoropropylene (HFP), and a terpolymer containing VF2, HFP, and tetrafluoroethylene (TFE) were cross linked using varying amounts of Bisphenol AF to yield two series of fluoroelastomer networks, Stress-strain isotherms in elongation were determined for these samples at several temperatures and at two degrees of swelling with phenyl acetate. Strain-induced crystallization was observed, as evidenced by upturns in the isotherms at high elongations. It appears to be more pronounced in the terpolymer samples, presumably because the TFE units not only can crystallize themselves, but can co-crystallize with the VF2 units. The crystallization was found to persist upon moderate increase in temperature, but was suppressed when the networks were swollen, Thermoelastic (force-temperature) measurements were used to obtain values of the fraction fe/f of the elastic force that is due to energetic effects. Negative values were obtained for both types of samples and, in the case of two samples studied in detail, their magnitudes increased with increase in elongation. The magnitudes were larger and the increases more pronounced in the case of the terpolymer networks, as would be expected from a greater tendency for straininduced crystallization.
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  • 87
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    Polymer Engineering and Science 27 (1987), S. 1221-1228 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The transesterification reaction of molten ethylene and vinyl alcohol copolymers (EVA), in presence of paraffinic alcohols and basic catalysts, leads to high conversion of the ester groups to secondary alcohol in both discontinuous and continuous processing equipment. Various kinds of alcohols and two different catalysts were used. Sodium methoxide is a powerful catalyst for the equilibrated transesterification reaction, but we also observed side reactions, such as cross-linking with low-molecular-weight alcohols and hydrolysis of the catalyst followed by partial saponification of the EVA. Kinetic studies were performed in the presence of dibutyltin dilaurate, an efficient catalyst without any side reactions. The solubility of the main alcohol reagents was verified by diffusion measurements. The general reaction scheme and the related kinetics, corresponding to a homogeneous system, lead to a fair evaluation of the rate constants.
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  • 88
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    Polymer Engineering and Science 27 (1987), S. 1252-1257 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The mechanical properties of polyurethane-unsaturated polyester interpenetrating polymer networks (IPNs) that were prepared by reaction injection molding (RIM) process were measured with variations In composition, cross-link density, and relative reaction rate. From dynamic mechanical analysis (DMA), it was found that the two component polymers had a good compatibility over the whole composition range. The tensile strengths of the blends were greater than those of the pure components and had a maximum value at 50/50 composition. The modulus of elasticity and surface hardness decreased and the impact strength increased as the polyurethane content was increased, but the changes were not high at low polyurethane content, below 50%. For higher cross-link density, the compatibility was enhanced and the mechanical properties were improved. When the reaction rates of the components were different, some extent of phase separation was found in DMA and the properties were affected adversely.
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  • 89
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    Polymer Engineering and Science 28 (1988), S. 1152-1155 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Effects of absorbed moisture on degradation behavior of high nitrile barrier polymers were monitored using thermogravimetric analysis techniques. Non-modified and 10 percent rubber modified samples were heated isothermally at nitrile processing temperatures (200°C to 240°C) in air and nitrogen environments. Degradation was evaluated in terms of weight loss as a function of heating time and sample coloration. It was determined that complete removal of moisture, as well as high moisture concentration, contribute to increased degradation at the temperatures evaluated. Moisture levels in the range of 0.15 to 0.5 percent were found to minimize degradation. Heating environment, time, temperature, and rubber modification were also found to influence thermal stability.
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  • 90
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    Polymer Engineering and Science 28 (1988), S. 1167-1172 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: High density polyethylene has been chlorinated by three different methods: in suspension and in solutions of two different solvents. Carbon-13 NMR and infrared analysis show that chlorination in chlorobenzene solution leads to statistically random distribution while chlorination in suspension gives highly blocky substitution. An intermediate distribution was obtained by chlorination in tetrachloroethane solution.
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  • 91
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    Polymer Engineering and Science 28 (1988), S. 1198-1202 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The energy stored in polystyrene after plastic deformation is measured by the differential scanning calorimetry (DSC) technique. Similar to metals, the stored energy increases with plastic straining, first rapidly, and then more slowly, and finally the stored energy seems to approach a saturation value (about 1 cal/gram). By comparing to the plastic work done, the fraction stored ranges from 30 percent after 10 percent compression to 10 percent after 60 percent compression. The fraction is about twice as large as that of copper. The release of stored energy has two distinct parts, one below Tg and the other above Tg. Most of the strain recovery seems to accompany the second part. By using the Kissinger plot, the second part has an activation energy, of 142 kcal/mole which is about 10 percent larger than that of compressive strain recovery.
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  • 92
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    Polymer Engineering and Science 28 (1988), S. 1219-1226 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A trial and error approach reflects the state of the art in reaction injection molding. Material and process parameters determine the “moldability” of a specific system in a particular application. The concept of “molding areas” on the critical parameters plane can be extended form thermoplastic injection molding (TIM) to reaction injection molding (RIM).In this work moldability diagrams for the filling and curing stages of a RIM process are obtained based on a simplified engineering approach. The key process parameters chosen for the filling stage are initial material temperature and filling time. In the curing stage, the critical parameters are considered to be mold wall temperature and demold time. Experimental results obtained on a laboratory-scale RIM machine on a Crosslinking polyurethane system are used to check the validity of the predicted molding areas. The agreement obtained is satisfactory considering the broad range of processing parameters used.
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  • 93
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The microstructure of injection molded bars (2.9 and 5.8 mm thick) of thermotropic liquid crystalline poly(p-hydroxy-benzoic acid-co-ethylene terephthalate) has been studied by SEM on samples etched with n-propylamine, SEM fractography, DSC, IR, ESCA, WAXS and polarized microscopy. The 2.9 mm bar consists of three different layers: a highly oriented surface skin, an oriented intermediate layer and a non-oriented core. The 5.8 mm bar has a more complex microstructure and is composed of five different layers: a highly oriented surface skin, an oriented layer just beneath, a non-oriented layer, another oriented layer and a non-oriented core. The thicknesses of the different layers vary, significantly, with distance from the mold gate. The thickness of the core increases, significantly, with increasing distance from the mold gate at the expense of the oriented layers. The structure within the different morphological layers is not perfectly uniform. Tensile testing demonstrated the mechanical anisotropy of the surface material (a ratio of almost 20 between the longitudinal and transverse moduli) and the isotropy of the central core material.
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  • 94
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    Polymer Engineering and Science 28 (1988), S. 1264-1269 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Rolling-drawing is a simple, effective, solid state processing technique for manufacturing high strength and high modulus oriented polymer sheet products. The process is capable of increasing the tensile modulus and strength of polypropylene by more, than an order of magnitude with inexpensive equipment and straight forward controllable techniques. This paper gives an overview of the rolling-drawing of polypropylene. It is intended to answer the following questions. What is rolling-drawing? What changes in tensile properties can be expected as a result of this process? What deformation processes occur during rolling-drawing? What are the processing variables and how do these variables relate to the deformation ratio achieved by rolling-drawing? A tensile flow stress relationship was formulated from experimental data for oriented polypropylene. This constitutive equation, estimates the flow stress (or yield stress) of the polymer as a function of deformation ratio, strain rate and temperature. Since stretching was found to provide a significant portion of the deformation during the rolling-drawing process a Hoffman-Sachs computer analysis was written to predict plastic deformation and drawing forces in the stretch zone. The results of experimentation and the analysis are briefly compared in this paper.
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  • 95
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: An extrusion-grade of high density polyethylene (HOPE) (3 ethyl groups per 1000 carbons) has been divided into 16 fractions by preparative GPC and selective p-xylene extraction. The fractions, with molecular weights ranging from 900 to 1,000,000, have been studied by IR spectros-copy, DSC, WAXS, polarized microscopy, and small-angle light scattering (SALS), The average degree of chain branching (percent C2H5) is 0.5 percent for the part of the sample having a molecular weight lower than 10,000 and it decreases monotonically with increasing molecular weight, finally approaching 0.1 percent C2H5. A crystallinity depression with respect to linear PE equivalent to 20 percent/(percent C2H5) is recorded for all samples except for the very low molecular weight samples for which the crystallinity depression is much larger (30 to 35 percent/ (percent C2H5)). The unit cell volume increases with increasing percent C2H5, presumably due to the inclusion of ethyl groups in the crystals as interstitlals at 2gl kinks. The concentration of ethyl groups in the crystals (∊c) unanimously follows the relationship: ∊c(percent) = 0.32 + 0.25 log(percent C2H5) except for the low molecular weight fractions which have significantly lower values for ∊c. Our admittedly speculative explanation for this major discrepancy between high and low molecular weight samples is based on the idea that segments with ethyl groups close to chain ends have a greater difficulty in crystallizing than segments containing ethyl groups located at positions far from the chain ends. The fractions obtained from the extrusion-grade HDPE show a solidification temperature depression with respect to linear PE which can only be explained by the presence of chain branches in these samples. The depression is particularly pronounced for the low molecular weight samples as is expected from the data on molecular structure. Well-developed non-banded spherulites are observed in rapidly cooled (crystallized at about 35 K supercooling), low molecular weight samples (6,000 〈 Mw 〈 8,000)from the extrusion-grade HDPE in contrast to the axialites observed in linear PE of the same molecular weight and thermal treatment. This discrepancy in morphology has been related to the presence of ethyl groups in the extrusion grade HDPE fractions. Higher molecular weight samples (20,000 〈 Mw 〈 1,000,000)from the extrusion-grade HDPE and linear PE both display well-developed banded spherulites of similar nature as is expected due to the similarity in molecular structure of the two sets of sample.
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  • 96
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    Polymer Engineering and Science 28 (1988), S. 1066-1070 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: In this work, a concept of distributed damage, including its inception and propagation, was applied to creep induced buckling of specimens prepared from high density polyethylene (HDPE). Using a kinetic relationship for damage accumulation, an integral equation for the front of the damage zone was derived. A time parameter associated with the inception of the damage front was obtained. The motion of the front was approximated for small times. Long time estimation was obtained using an assumption for a shape of the damage distribution. These results enabled us to review reported experimental results on creep induced buckling using a new insight into the relationship between applied load and time to buckle.
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  • 97
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    Polymer Engineering and Science 28 (1988), S. 1095-1106 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: We present a basic study of the thermal, dielectric, Theological, and mechanical properties of hydroxybenzoic acid-ethylene terephthalate copolymers (PHB-PET). It is argued that they have two-phase structures, one rich in ethylene terephthalate (PET) and one rich in hydroxybenzoic acid (PHB). Polystyrene (PS) is immiscible in 60% PHB-PET (60-PHB-PET) blends. Polycarbonate (PC) is partially miscible with the high PET phase of 60-PHB-PET. PET seems completely miscible with this high PET phase. Shear viscosity measurements on blends indicate that 60-PHB-PET gives rise to large reductions of viscosity. Extrudates and melt-spun fibers have been prepared. The phase morphologies of low PHB-PET blends as determined by scanning electron microscopy indicate ellipsoids or long fibrils of the, 60-PHB-PET in PS or PC matrices. High extrusion rates and melt spinning produce fibrillar structures. The mechanical properties of films, extrudates, and melt-spun fibers were studied. Blends with 10% 60-PHB-PET exhibited significant increases in Young's modulus and tensile strength.
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  • 98
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    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 28 (1988) 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
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  • 99
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    Polymer Engineering and Science 28 (1988), S. 1145-1151 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The kinetics of the activated anionic polymerization of caprolactam to nylon-6 and its copolymers has been studied. Nylon-6 block copolymer and nylon-6 were prepared at various initial reaction temperatures (140°C to 165°C) by anionic polymerization in an adiabatic dewar flask. Different concentrations of poly(ethylene oxide) (PEO) in 4,4′-diphenyl methane diisocyanate (MDI)-capped PEO and 1 mole percent MDI, in a caprolactam solution, were used as the activators with the catalyst, the sodium salt of caprolactam. The kinetics of the reaction were analyzed from an adiabatic temperature rise. A new method was applied to determine the rate parameters. The activation energy, Ea, of nylon-6 and nylon-6 block copolymers were found to be 22 kcal/mole. The collision frequency factor, Ao, steadily decreased and the autocatalytic constant, Bo, decreased to a constant value of 16 with the introduction of PEO. However, it was found that the order of reaction, n, was almost a constant value at the second order for all experiments.
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  • 100
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    Polymer Engineering and Science 28 (1988), S. 1173-1181 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Chlorination of high density; polyethylene results in polymers which consist of unmodified methylene units and chlorinated methylene co-units. The effect of the concentration and distribution of chlorinated units on the solid state structure has been examined by thermal, wide angle X-ray diffraction and dynamic mechanical analysis. As the substitution becomes more random, the crystallinity, crystallite size, and crystalline perfection decrease for a given chlorine content. The chlorinated units are shown to be capable of co-crystallizing, and the concentration of chlorine in the crystalline phase increases as the distribution is made more random. Concurrently, the chlorine concentration of the amorphous phase decreases. Segregation of chlorine into the amorphous regions is most efficient when the substitution is blocky.
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