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  • Chemistry  (50,887)
  • Humans  (2,455)
  • 2020-2024  (52)
  • 1990-1994  (53,289)
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  • 1
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    IntechOpen | IntechOpen
    Publication Date: 2024-04-05
    Description: Mineralogy includes thirteen chapters that discuss the methodology of specific mineralogical methods, the composition of minerals from different igneous rocks, and the composition of minerals from different sedimentary rocks.It contains detailed mineralogical studies from Africa, Asia, and Europe. Chapters present different scientific mineralogical methods and detailed descriptions of minerals from different magmatic and sedimentary rocks.
    Keywords: Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNV Chemistry of minerals, crystals and gems
    Language: English
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  • 2
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    IntechOpen | IntechOpen
    Publication Date: 2024-04-05
    Description: Benzimidazole is a comprehensive survey of the known and new methods of benzimidazole synthesis, the spectral and theoretical aspects of existing benzimidazole derivatives, and the anticancer properties of a new class of benzimidazole derivatives. This book examines aspects and newer mechanisms of benzimidazoles containing heterocyclic moiety. Chapters report on anticancer properties of benzimidazole derivatives, novel methods of synthesis of benzimidazoles, versatile nature of the benzimidazoles, spectral and theoretical studies of benzimidazole derivatives, and medicinal importance and pharmacological aspects of benzimidazole derivatives.
    Keywords: Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNN Organic chemistry
    Language: English
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  • 3
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    IntechOpen | IntechOpen
    Publication Date: 2024-04-05
    Description: Green Chemistry - New Perspectives is at the frontiers of this continuously evolving interdisciplinary science, and publishes research that attempts to reduce the environmental impact of the chemical enterprise by developing a technology base that is inherently non-toxic to living things and the environment. The book covers all aspects of green chemistry, including chemical synthesis, nano synthesis, eco-friendly processes, biomass, extraction techniques, environmental remediation, and energy, making it a unique reference resource. This will continue to encourage scientists around the world to develop novel synthetic methods or improve the existing ones to circumvent some of the problems and favours all aspects of green chemistry. This book is intended for academia, professionals, scientists, as well as graduate and undergraduate students without any geographical limitations.
    Keywords: Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNN Organic chemistry
    Language: English
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  • 4
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    EDP SCIENCES
    Publication Date: 2024-04-05
    Description: Chemistry
    Keywords: Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNN Organic chemistry::PNNP Polymer chemistry
    Language: French
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  • 5
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    EDP SCIENCES
    Publication Date: 2024-04-05
    Description: Chemistry
    Keywords: Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNN Organic chemistry::PNNP Polymer chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNN Organic chemistry::PNNP Polymer chemistry
    Language: French
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  • 6
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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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  • 7
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    IntechOpen | IntechOpen
    Publication Date: 2024-04-05
    Description: This book consists of several selected chapters on important subjects in modern high-performance liquid chromatography (HPLC) and ultra-performance liquid chromatography (UPLC). The content addresses aspects related to both improvements in the mainstream HPLC/UPLC technology and utilization, as well as developments of exploratory new materials and equipment. The book presents useful details about the presented subjects as well as describes new applications and/or relevant case studies for each subject. It is addressed to a large audience of analytical chemists involved in separation science. Each chapter is authored by scientists with considerable field and academic experience.
    Keywords: Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNF Analytical chemistry
    Language: English
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  • 8
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    EDP SCIENCES
    Publication Date: 2024-04-07
    Description: Chemistry
    Keywords: Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNN Organic chemistry::PNNP Polymer chemistry
    Language: French
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  • 9
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    IntechOpen | IntechOpen
    Publication Date: 2024-04-05
    Description: Recent Advances in Chemical Kinetics provides a comprehensive overview of several types of chemical reactions. It includes six chapters that discuss solvent catalysis, customized flow reactors, p-conjugation in kinetics, kinetics of autoxidation, molecular chameleon for cations and anions, and internal clocks of atoms.
    Keywords: Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNR Physical chemistry
    Language: English
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  • 10
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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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  • 11
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    Taylor & Francis | CRC Press
    Publication Date: 2024-03-31
    Description: Hydroxyapatite coatings are of great importance in the biological and biomedical coatings fields, especially in the current era of nanotechnology and bioapplications. With a bonelike structure that promotes osseointegration, hydroxyapatite coating can be applied to otherwise bioinactive implants to make their surface bioactive, thus achieving faster healing and recovery. In addition to applications in orthopedic and dental implants, this coating can also be used in drug delivery. Hydroxyapatite Coatings for Biomedical Applications explores developments in the processing and property characterization and applications of hydroxyapatite to provide timely information for active researchers and newcomers alike. In eight carefully reviewed chapters, hydroxyapatite experts from the United States, Japan, Singapore, and China present the latest on topics ranging from deposition processes to biomedical applications in implants and drug delivery. This book discusses: Magnetron sputtering and electrochemical deposition The modification of hydroxyapatite properties by sol–gel deposition to incorporate other elements found in natural bones, such as zinc, magnesium, and fluorine The use of pure hydroxyapatite in drug delivery applications The growth or self-assembly of hydroxyapatite on shape memory alloy Hydroxyapatite composite coatings—with carbon nanotubes, titanium dioxide (TiO2), and others—on the titanium alloy Offering valuable insights and a wealth of data, including numerous tables and figures, this is a rich source of information for research on hydroxyapatite coatings. Each chapter also covers material that provides an accessible stepping stone for those who are new to the field.
    Keywords: Pre-clinical medicine: basic sciences ; Chemistry ; Materials science ; thema EDItEUR::M Medicine and Nursing::MF Pre-clinical medicine: basic sciences ; thema EDItEUR::P Mathematics and Science::PN Chemistry ; thema EDItEUR::T Technology, Engineering, Agriculture, Industrial processes::TG Mechanical engineering and materials::TGM Materials science
    Language: English
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  • 12
    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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  • 13
    Publication Date: 2024-04-05
    Description: Chemiebezogene Kompetenzen werden bereits im Sachunterricht der Grundschule entwickelt und sollen im Chemieunterricht der Sekundarstufe I aufgegriffen und weiterentwickelt werden. Ziel dieser Studie war es, die chemiebezogenen Kompetenzen der Schülerinnen und Schüler in der Übergangsphase zwischen Sachunterricht und Chemieunterricht zu analysieren. In einer Ergänzungsstudie wurden zusätzlich sowohl die Auswirkungen der Schulschließungen aufgrund der SARS-CoV-II Pandemie auf die Kompetenzen der Schülerinnen und Schüler als auch der Einfluss einer veränderten Testadministration untersucht. Insgesamt wurden die Kompetenzen von 2262 Lernenden der Jahrgangsstufen 5 bis 9 zu drei Messzeitpunkten analysiert. Die Ergebnisse zeigen, dass die chemiebezogenen Kompetenzen sowohl zum Ende der Grundschulzeit als auch zu Beginn des Chemieunterrichts über alle Kompetenzbereiche hinweg sehr heterogen ausfallen. Dennoch sind sie zu Beginn des Chemieunterrichts in einigen Kompetenzbereichen höher ausgeprägt als zum Ende der Grundschulzeit. Nach den pandemiebedingten Schulschließungen waren die Kompetenzen ähnlich ausgeprägt wie in den gleichen Jahrgangsstufen vor den Schulschließungen. Eine während der Schulschließungen notwendige Bearbeitung der Testhefte von zu Hause aus führte vor allem bei den jüngeren Schülerinnen und Schülern zu besseren Testergebnissen als die Bearbeitung in der Schule. Um die Entwicklung chemiebezogener Kompetenzen in der Übergangsphase zu optimieren, sollte der Erwerb dieser Kompetenzen bereits im Sachunterricht einheitlicher gestaltet werden.
    Keywords: Science ; Chemistry ; Education ; thema EDItEUR::P Mathematics and Science::PN Chemistry ; thema EDItEUR::J Society and Social Sciences::JN Education
    Language: German
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  • 14
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    IntechOpen | IntechOpen
    Publication Date: 2024-04-05
    Description: Redox reactions are involved in biochemistry, energy, corrosion, and much more. In both biology and electrochemistry, the redox reaction is complex and varied. For example, redox shuttles in supercapacitors show aspects of molecular electrochemistry applied to electrode porosity. In pseudocapacitors, the formalism associated with their electrochemical response requires investigation and formalism. Similarly, the simple definition of redox potential opens fundamental questions about its measurement in solutions without supporting salts. This book illustrates the variety of redox reactions in its examination of the importance of redox molecules in the development of new electrical energy storage devices.
    Keywords: Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNR Physical chemistry::PNRH Electrochemistry and magnetochemistry
    Language: English
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  • 15
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    Logos Verlag Berlin | Logos Verlag Berlin
    Publication Date: 2024-04-05
    Description: In 2005, the hybrid model was published by Prof. H.-D. Alber and Prof. P. Zhu as an alternative to the Allen-Cahn model for the description of phase field transformations. With low interfacial energy, it is more efficient, since the resolution of the diffuse interface is numerically broader for the same solution accuracy and allows coarser meshing. The solutions of both models are associated with energy minimisation and in this work the error terms introduced in the earlier publications are discussed and documented using one and two dimensional numerical simulations. In the last part of this book, phase field problems, initially not coupled with material equations, are combined with linear elasticity and, after simple introductory examples, a growing martensitic inclusion is simulated and compared with literature data. In addition to the confirmed numerical advantage, another phenomenon not previously described in the literature is found: with the hybrid model, in contrast to the examples calculated with the Allen-Cahn model, an inclusion driven mainly by curvature energy does not disappear completely. The opposite problem prevents inclusions from growing from very small initial configurations, but this fact can be remedied by a very finely chosen diffuse interface width and by analysing and adjusting the terms that generate the modelling errors. The last example shows that the hybrid model can be used with numerical advantages despite the above mentioned peculiarities.
    Keywords: Science ; Chemistry ; Mathematics ; Science ; Physics ; thema EDItEUR::P Mathematics and Science::PN Chemistry ; thema EDItEUR::P Mathematics and Science::PB Mathematics ; thema EDItEUR::P Mathematics and Science::PH Physics
    Language: English
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  • 16
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    IntechOpen | IntechOpen
    Publication Date: 2024-04-05
    Description: We are living in a critical time, both for humanity and the planet, which has led us to look for more sustainable formulas to interact with the environment. One of the important changes in the design and operation of chemical processes is the search for environmentally friendly technologies. Supercritical carbon dioxide has been revealed as a promising environmentally friendly solvent that is energy efficient, selective and capable of reducing waste, making it a promising alternative to conventional organic solvents. However, reliable and versatile mathematical models of phase equilibrium thermodynamics are needed for the use of supercritical carbon dioxide in process design and viability studies. This book reviews experimental procedures for obtaining high-pressure phase equilibria data and describes the phase diagrams of binary mixtures and some thermodynamic models capable of determining the conditions of phase equilibria at high pressures. These concepts are applied to the components of the transesterification reaction of rac-2-pentanol with a vinyl ester, which is important in the pharmaceutical industry because (S)-2-pentanol can be obtained as a reaction product. This product is a key intermediate in the synthesis of drugs against Alzheimer’s disease.
    Keywords: Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNR Physical chemistry
    Language: English
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  • 17
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    MDPI - Multidisciplinary Digital Publishing Institute
    Publication Date: 2024-04-05
    Description: Nanofibers, particularly those of a carbonaceous content, have received increased interest in the past two decades due to their outstanding physico-chemical characteristics and their possibility to form and contribute towards a plethora of potentially advantageous materials for consumer, industrial and medical applications. Despite this, and together with the numerous research studies and published articles that have sought to investigate these aspects, the potential impact of CNTs is still not understood. Whether or not nanofibers may be able to provide a sophisticated alternative to conventional materials is still debatable, whilst their effects upon both environmental and human health are highly equivocal. How nanofibers are conceived can determine how they may interact with different environments, such as the human body. Understanding each key step of the synthesis and production of nanofibers to their use within potential applications is therefore essential in gaining an insight into how they may be perceived by any biological system and environment. Thus, obtaining such information will enable all scientific communities to begin to realize the potential advantages posed by nanofibers. The aim of this Special Issue therefore, was to provide a collective overview of nanofibers; ‘from synthesis to application’. The Issue particularly focuses upon carbon-based nanofibers, but also highlights alternative nanofiber types. Emphasis is given holistically, with articles discussing the production routes of nanofibers, their plight during their life-cycle (origin to applied form and effects over time), as well as how nanofibers could either incite conflict, or provide aid to human and environmental health.
    Keywords: QD1-999 ; Toxicology ; Chemistry ; Biology ; Material Science ; Nanofibers ; Nanotechnology ; thema EDItEUR::P Mathematics and Science::PN Chemistry
    Language: English
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  • 18
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    IntechOpen | IntechOpen
    Publication Date: 2024-04-05
    Description: In recent decades, artificial porous structures have attracted increasing enthusiasm from researchers inspired by the fascinating molecular pores in nature and their unique biological functions. Although substantial achievements in porous materials have been realized, the construction of topologically designed pores is still challenging. Recently, the emergence of covalent organic frameworks (COFs), which are constructed based on organic and polymer chemistry, has made it possible to design artificial pores with controlled pore size, topology and interface properties. COFs are crystalline porous materials constructed by the precise reticulation of organic building blocks via dynamic covalent bonds. Distinct from non-covalent interactions which tend to produce isostructures, covalent bonds enable accurate pore design owing to their predetermined reaction pathways. In addition, the appropriate polycondensation of organic building units enables the formation of extended two-dimensional (2D) and three-dimensional (3D) polymer architectures with periodically ordered skeletons and well-defined pores. With their large surface area, tailorable structures, and tunable chemistry, COFs are regarded as potentially superior candidates for various applications including catalysis, energy storage and conversion, mass transport and biotechnology. This book examines the historic achievement of COFs, providing clear and comprehensive guidance for researchers on their structural design, synthetic protocols and functional exploration.
    Keywords: Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNN Organic chemistry
    Language: English
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  • 19
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    IntechOpen | IntechOpen
    Publication Date: 2024-04-05
    Description: Fluoride covers a continuum of topics that are frequently studied in the broad area of fluoride (F) research. It provides an overview of the primary sources of environmental fluoride in typical high-fluoride environments and demonstrates the transitions and transformations that emerge and culminate in hydro-geochemical interactions that result in fluoride-fouling of large portions of the world’s water and agricultural resources. This way, the book pinpoints the connection between F enrichment of water sources and the prevalence of endemic fluorosis in certain areas of the world. In order to contribute to a better understanding of the global fluoride problem, new fluoride detection and quantification technologies are proposed with an in-depth analysis of emerging trends in the use of portable user-friendly devices in point-of-use measurements of water fluoride. This has been presented against the backdrop of a robust overview of traditional fluoride quantification methodologies that are still in wide application among the scientific communities. In addressing fluoride toxicities, which are not limited to dental and skeletal dilapidations, the authors have explored the role of natural antioxidants in ameliorating physiological fluoride-induced noxious effects in mammalian systems. Nonetheless, since community dependence on high-fluoride water due to a lack of alternative clean water sources remains to be the principal pathway of human fluoride over-exposure, a review chapter on F mitigation techniques applied all over the world is incorporated aiming at providing a succinct overview of water defluoridation techniques and strategies being used to combat the impacts of human F overexposure around the globe. Since every cloud has a silvery lining, the possibility of using ammonium fluorides as a novel reagent in mineral processing has been considered convenient industrial fluorinating agents, which present the possibility of complete regeneration that is not afforded by the reagents presently used in decomposing silicon component of the ores.
    Keywords: Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNK Inorganic chemistry
    Language: English
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  • 20
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    IntechOpen | IntechOpen
    Publication Date: 2024-04-05
    Description: This book discusses the chemistry and applications of pyridine derivatives. The library of pyridine derivatives is growing steadily with numerous synthetic analogues already described and the identification of new, naturally occurring pyridine-based compounds. The book includes ten chapters organized into two parts. The first part focuses on the numerous types of reactions that arise from pyridine derivatives. The second part examines the pharmaceutical applications of pyridine derivatives as well as their usefulness as sensors for metal cations and extracting agents for platinum group metals.
    Keywords: Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNN Organic chemistry
    Language: English
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  • 21
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    IntechOpen | IntechOpen
    Publication Date: 2024-04-05
    Description: The book discusses multiple issues associated with modern dosimetry in physics and treatment planning and how investigators from diverse world centers and institutions approach problem-solving in these important areas. It examines topics including pretreatment validation and factors affecting reference dosimetry. It also addresses unique issues affecting pediatric populations as well as the modern role of thermoluminescence validation. Several chapters discuss intensity modulation, including defining modern problems associated with both treatment planning and the definition of tumor and normal tissue contours. Furthermore, the book examines the role of imaging as both a vehicle to define tumor targets and normal tissue as well as a tool for dose validation.
    Keywords: Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNR Physical chemistry::PNRL Nuclear chemistry, photochemistry and radiation
    Language: English
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  • 22
    Publication Date: 2024-04-05
    Description: Das selbstgesteuerte Experimentieren ist laut den nationalen Bildungsstandards sowie den Lehrplänen im Fach Chemie ein wichtiger Bestandteil der naturwissenschaftlichen Schulbildung. Offene Experimentierformen sind jedoch wenig etabliert. Um das selbstgesteuerte Experimentieren in die Unterrichtspraxis zu implementieren, wurde im Rahmen dieses Forschungsprojekts eine eintägige Lehrkräftefortbildung zur Konzeption von selbstgesteuerten Experimenten im Chemieunterricht durchgeführt. Dazu wurde ein literaturbasiertes Strukturierungskonzept entwickelt, mit dem die Lehrkräfte kochbuchartige Schulversuche zu selbstgesteuerten und kompetenzorientierten Experimenten mit beliebigen Öffnungsgraden modifizieren können. Begleitend zur Fortbildung wurde im Prä-Post-Follow-Up-Design das fachdidaktische Wissen der Teilnehmenden hinsichtlich der Planung von selbstgesteuerten Experimenten empirisch überprüft. Zur Erfassung dieses Konstrukts wurde ein neues Messinstrument literaturbasiert entwickelt und die Güte des Messinstruments evaluiert. Die Auswertungen zeigen, dass die Fortbildung hinsichtlich des fachdidaktischen Wissens der Lehrkräfte kurz- sowie langfristig lernförderlich ist und die Fortbildung von den Teilnehmenden positiv bewertet wird. Die Reliabilitätsanalyse sowie die Validierungsstudie zeigen, dass der Test sowohl reliabel als auch valide ist. In Folgestudien könnte die langfristige Verhaltensänderung der Lehrkräfte bezüglich der Implementierung des selbstgesteuerten Experimentierens in den Unterricht untersucht werden.
    Keywords: Science ; Chemistry ; Science ; Education ; thema EDItEUR::P Mathematics and Science::PN Chemistry ; thema EDItEUR::P Mathematics and Science::PD Science: general issues ; thema EDItEUR::J Society and Social Sciences::JN Education
    Language: German
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  • 23
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    IntechOpen | IntechOpen
    Publication Date: 2024-04-05
    Description: The book comprises 14 chapters covering all the issues related to water desalination. These chapters emphasize the relationship between problems encountered with the use of feed water, the processes developed to address them, the operation of the required plants and solutions actually implemented. This compendium will assist designers, engineers and investigators to select the process and plant configuration that are most appropriate for the particular feed water to be used, for the geographic region considered, as well as for the characteristics required of the treated water produced. This survey offers a comprehensive, hierarchical and logical assessment of the entire desalination industry. It starts with the worldwide scarcity of water and energy, continues with the thermal - and membrane-based processes and, finally, presents the design and operation of large and small desalination plants. As such, it covers all the scientific, technological and economical aspects of this critical industry, not disregarding its environmental and social points of view. One of InTech's books has received widespread praise across a number of key publications. Desalination, Trends and Technologies (Ed. Schorr, M. 2011) has been reviewed in Corrosion Engineering, Science & Technology – the official magazine for the Institute of Materials, Minerals & Mining, and Taylor & Francis's Desalination Publications. Praised for its “multi-faceted content [which] contributes to enrich it,” and described as “an essential companion...[that] enables the reader to gain a deeper understanding of the desalination industry,” this book is testament to the quality improvements we have been striving towards over the last twelve months.
    Keywords: Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNF Analytical chemistry
    Language: English
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  • 24
    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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  • 25
    Publication Date: 2024-04-05
    Description: The Global Methane Initiative (GMI) is a voluntary international partnership that promotes methane recovery and reuse activities in developing and transition economies. The U.S. Department of State requested an evaluation of the activities and outcomes supported in whole or in part by its contributions to GMI to gauge its value added to the program.
    Keywords: Physics ; Environmental Science ; Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry ; thema EDItEUR::T Technology, Engineering, Agriculture, Industrial processes::TQ Environmental science, engineering and technology ; thema EDItEUR::R Earth Sciences, Geography, Environment, Planning::RB Earth sciences::RBP Meteorology and climatology
    Language: English
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    Publication Date: 2024-04-04
    Description: This volume, occasioned by the centenary of the Fritz Haber Institute, formerly the Institute for Physical Chemistry and Electrochemistry, covers the institute's scientific and institutional history from its founding until the present. The institute was among the earliest established by the Kaiser Wilhelm Society, and its inauguration was one of the first steps in the development of Berlin-Dahlem into a center for scientific research. Its establishment was made possible by an endowment from Leopold Koppel, granted on the condition that Fritz Haber, well-known for his discovery of a method to synthesize ammonia from its elements, be made its director. The history of the institute has largely paralleled that of 20th-century Germany. It undertook controversial weapons research during World War I, followed by a "Golden Era" during the 1920s, in spite of financial hardships.
    Keywords: Chemistry ; Chemistry ; Fritz Haber Institute ; thema EDItEUR::P Mathematics and Science::PD Science: general issues::PDX History of science
    Language: English
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    IntechOpen | IntechOpen
    Publication Date: 2024-04-05
    Description: Progress in agricultural, biomedical and industrial applications' is a compilation of recent advances and developments in gas chromatography and its applications. The chapters cover various aspects of applications ranging from basic biological, biomedical applications to industrial applications. Book chapters analyze new developments in chromatographic columns, microextraction techniques, derivatisation techniques and pyrolysis techniques. The book also includes several aspects of basic chromatography techniques and is suitable for both young and advanced chromatographers. It includes some new developments in chromatography such as multidimensional chromatography, inverse chromatography and some discussions on two-dimensional chromatography. The topics covered include analysis of volatiles, toxicants, indoor air, petroleum hydrocarbons, organometallic compounds and natural products. The chapters were written by experts from various fields and clearly assisted by simple diagrams and tables. This book is highly recommended for chemists as well as non-chemists working in gas chromatography.
    Keywords: Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNF Analytical chemistry
    Language: English
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    IntechOpen | IntechOpen
    Publication Date: 2024-04-05
    Description: This book discusses electrocatalysis and electrocatalysts for energy, water electrolysis, water treatment, CO2 conversion, and green chemistry. It reviews various electrocatalysts and their properties and electrochemical performances. The first section of the book covers topics in direct alcohol fuel cells including Pt-based electrocatalysts as non-carbon electrode support materials and the development of electrocatalysts for direct methanol fuel cells. The second section of the book covers various topics in electrocatalysis and electrocatalysts for a cleaner environment, including electrocatalysts for the conversion of CO2 to valuable products and SYNGAS, electrocatalysts for water electrolysis, and much more.
    Keywords: Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNR Physical chemistry::PNRH Electrochemistry and magnetochemistry
    Language: English
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    transcript Verlag | transcript Verlag
    Publication Date: 2024-04-04
    Description: Die Chemie büßt zugunsten physikalischer und lebenswissenschaftlicher Konzeptionen zunehmend an Deutungsmacht über die molekulare Welt ein. Sandra Lang untersucht, inwiefern die Ausdifferenzierung der chemischen Wissenschaften mit sich ebenfalls ausdifferenzierenden Zugriffen auf das Molekulare zusammenhängt. Anhand der vier exemplarischen Grenzfelder Materialwissenschaften, Biomedizin, Pharmazie und Quantenchemie und deren Narrative zur molekularen Eigenschaft der Chiralität veranschaulicht sie die transformative Phase der Chemie angesichts sich wandelnder Innovationsdispositive.
    Keywords: Chemie ; Chiralität ; Molekülkonzept ; Naturwissenschaften ; Grenzarbeit ; Interdisziplinarität ; Hybridität ; Wissenschaft ; Technik ; Wissenschaftssoziologie ; Techniksoziologie ; Wissenssoziologie ; Wissenschaftsgeschichte ; Soziologie ; Chemistry ; Chirality ; Molecule Concept ; Natural Sciences ; Border Work ; Interdisciplinarity ; Hybridity ; Science ; Technology ; Sociology of Science ; Sociology of Technology ; Sociology of Knowledge ; History of Science ; Sociology ; thema EDItEUR::P Mathematics and Science::PD Science: general issues::PDR Impact of science and technology on society ; thema EDItEUR::J Society and Social Sciences::JH Sociology and anthropology::JHB Sociology
    Language: German
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    IntechOpen | IntechOpen
    Publication Date: 2024-04-05
    Description: Surfactants are ubiquitous and have applications in diverse areas, including food, cosmetics, detergents, lubricants, enhanced oil recovery (EOR), and targeted drug delivery systems. Their wide diversity of applications owes to their unique structure, namely, a hydrophilic and a hydrophobic group present in the same molecule. Although most surfactants used industrially are synthetic, there is a growing need for natural surfactants, as the latter is obtainable from renewable sources and are less toxic and highly biodegradable in contrast to their synthetic counterparts. This book is a compilation of interesting articles by various experts that cover various applications of both synthetic and natural surfactants.
    Keywords: Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNR Physical chemistry::PNRC Colloid chemistry
    Language: English
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    IntechOpen | IntechOpen
    Publication Date: 2024-04-05
    Description: The chemical sensor plays an essential role in the fields of environmental conservation and monitoring, disaster and disease prevention, and industrial analysis. A typical chemical sensor is a device that transforms chemical information in a selective and reversible way, ranging from the concentration of a specific sample component to total composition analysis, into an analytically useful signal. Much research work has been performed to achieve a chemical sensor with such excellent qualities as quick response, low cost, small size, superior sensitivity, good reversibility and selectivity, and excellent detection limit. This book introduces the latest advances on chemical sensors. It consists of 15 chapters composed by the researchers active in the field of chemical sensors, and is divided into 5 sections according to the classification following the principles of signal transducer. This collection of up-to-date information and the latest research progress on chemical sensor will provide valuable references and learning materials for all those working in the field of chemical sensors.
    Keywords: Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNF Analytical chemistry
    Language: English
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    EDP SCIENCES
    Publication Date: 2024-04-05
    Description: Chemistry
    Keywords: Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNN Organic chemistry::PNNP Polymer chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNN Organic chemistry::PNNP Polymer chemistry
    Language: French
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    Publication Date: 2024-04-05
    Description: Chemistry
    Keywords: Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNN Organic chemistry::PNNP Polymer chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNN Organic chemistry::PNNP Polymer chemistry
    Language: French
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    De Gruyter | De Gruyter
    Publication Date: 2024-04-11
    Description: Presents technologies and key concepts to produce suitable smart materials and intelligent structures for sensing, information and communication technology, biomedical applications (drug delivery, hyperthermia therapy), self-healing, flexible memories and construction technologies. Novel developments of environmental friendly, cost-effective and scalable production processes are discussed by experts in the field.
    Keywords: Science ; Chemistry ; Industrial & Technical ; Technology & Engineering ; Textiles & Polymers ; 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
    Language: English
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    IntechOpen | IntechOpen
    Publication Date: 2024-04-05
    Description: Distillation is an important separation technique that has been used for many centuries to exploit the volatility differences between components in a mixture. The distillation process has many variations and applications. This book includes two sections on desalination and reactive distillation. It discusses desalination in the processes of solar and membrane distillation, with a focus on the reduction of energy costs to obtain potable water. It also discusses reactive distillation, which can be used in some cases to reduce the power duty in the separation process by using the reaction heat directly in the separation. The book includes cases of mathematical modeling, simulation, and optimization of the distillation process.
    Keywords: Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNF Analytical chemistry
    Language: English
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    Logos Verlag Berlin | Logos Verlag Berlin
    Publication Date: 2024-04-05
    Description: Konsumgüter werden beispielsweise mit Slogans wie "Gut in Bio. Schlecht in Chemie." beworben. Dabei wird intendiert, sich gezielt von "Chemie" abzugrenzen und sich das positive Bild von "Natur" zu Nutze zu machen. Dies prägt die öffentliche Meinung und trägt zu einer antagonistisch-wertenden Sicht von "Chemie" und "Natur" bei. Dass Chemie als Naturwissenschaft der Beschreibung der Natur dient, um deren Stoffe und Stoffumwandlungen zu erklären, ist dem Laien selten bewusst. Chemie findet überall statt, insbesondere in der Natur! Genau an diesem Punkt setzt das Unterrichtskonzept "Chemie Pur - Unterrichten in der Naturglqq an. Ziel ist es, im Freiland, mit direkt vor Ort gewonnenen Naturstoffen, Umweltprozesse experimentell zu erarbeiten. Die projektbegleitende Evaluationsstudie stellte sich der Forschungsfrage, wie sich das Unterrichtskonzept auf das Fach- und Sachinteresse, auf die Naturverbundenheit sowie auf die Einstellung zu Chemie und Natur von Schülerinnen und Schülern der Sekundarstufe II auswirkt. Die Auswertung der Fragebogenergebnisse mit latenten Veränderungsmodellen haben gezeigt, dass die Intervention im Freiland das inhaltsbezogene Sachinteresse steigert und die Einstellung zu Chemie und Natur positiv beeinflusst sowie ein erhöhten Fachwissenszuwachs ermöglicht. Die gewonnenen Erkenntnisse können die Grundlage für die Entwicklung und Evaluation von good-practice-Ansätzen naturwissenschaftlicher Lernsituationen bilden. Das Unterrichtskonzept Chemie Pur leistet zudem einen Beitrag im Bereich Outdoor Education, um den Antagonismus von Chemie und Natur zu verringern.
    Keywords: Science ; Chemistry ; Science ; Education ; thema EDItEUR::P Mathematics and Science::PN Chemistry ; thema EDItEUR::P Mathematics and Science::PD Science: general issues ; thema EDItEUR::J Society and Social Sciences::JN Education
    Language: German
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    De Gruyter | De Gruyter
    Publication Date: 2024-04-05
    Description: Comprise definition of 1500 terms. Innovation from A to Z presents a glossary, including: Terms, older terms whose meanings have changed, acronyms, synonyms, famous names, selected abbreviations, and cross-references. A highly interdisciplinary approach incorporating strategy and entrepreneurship with technology and engineering sciences, economics, marketing, organizational behavior and theory. Ideal for engineers, managers, sales people and economists. Innovation Technology from A to Z Glossary of terms, including acronyms, synonyms, abbreviations, cross-references 1500 terms supplemented by figures and tables that clearly demonstrate the state-of-the-art in Innovation Technology
    Keywords: Science ; Chemistry ; Technology & Engineering ; Agriculture ; thema EDItEUR::P Mathematics and Science::PN Chemistry ; thema EDItEUR::T Technology, Engineering, Agriculture, Industrial processes::TV Agriculture and farming
    Language: English
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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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    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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    EDP SCIENCES
    Publication Date: 2024-04-08
    Description: Chemistry
    Keywords: Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNN Organic chemistry::PNNP Polymer chemistry
    Language: French
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    IntechOpen | IntechOpen
    Publication Date: 2024-04-05
    Description: Cyclodextrins (CDs) have attracted great interest from the research community as well as industries in an array of sectors because of their unique structural features. This book provides a comprehensive overview of CDs, beginning with their historical background. Chapters address such topics as the structure and physiochemical properties of CDs, advancements in the field, and potential applications of these materials in fields such as drug delivery and sensing. This book reveals new frontiers in the CD world and is a useful resource for organic, analytical, and supramolecular chemists as well as scientists engaged in biological and material sciences.
    Keywords: Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNN Organic chemistry::PNNP Polymer chemistry
    Language: English
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    IntechOpen | IntechOpen
    Publication Date: 2024-04-05
    Description: The book presents a comprehensive overview of sorption, which is a multi-parametric separation process. It is extensively used in the removal of various pollutants from the tertiary stage of wastewater treatment, from leachates, etc. It discusses fundamental points of the technique as well as kinetic theories and isotherms. It also examines the synthesis and characterizations of all studied adsorbent materials to find their paths of sorption. Finally, it highlights the importance of having a cost-estimation plan for the synthesis of sorbent materials as well as predictions for their reusability.
    Keywords: Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNR Physical chemistry::PNRX Surface chemistry and adsorption
    Language: English
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    EDP SCIENCES
    Publication Date: 2024-04-05
    Description: Chemistry;Materials science
    Keywords: Chemistry ; Materials science ; thema EDItEUR::P Mathematics and Science::PN Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNN Organic chemistry::PNNP Polymer chemistry
    Language: French
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    The MIT Press | The MIT Press
    Publication Date: 2024-03-27
    Description: The original 1818 text of Mary Shelley's classic novel, with annotations and essays highlighting its scientific, ethical, and cautionary aspects. Mary Shelley's Frankenstein has endured in the popular imagination for two hundred years. Begun as a ghost story by an intellectually and socially precocious eighteen-year-old author during a cold and rainy summer on the shores of Lake Geneva, the dramatic tale of Victor Frankenstein and his stitched-together creature can be read as the ultimate parable of scientific hubris. Victor, “the modern Prometheus,” tried to do what he perhaps should have left to Nature: create life. Although the novel is most often discussed in literary-historical terms—as a seminal example of romanticism or as a groundbreaking early work of science fiction—Mary Shelley was keenly aware of contemporary scientific developments and incorporated them into her story. In our era of synthetic biology, artificial intelligence, robotics, and climate engineering, this edition of Frankenstein will resonate forcefully for readers with a background or interest in science and engineering, and anyone intrigued by the fundamental questions of creativity and responsibility. This edition of Frankenstein pairs the original 1818 version of the manuscript—meticulously line-edited and amended by Charles E. Robinson, one of the world's preeminent authorities on the text—with annotations and essays by leading scholars exploring the social and ethical aspects of scientific creativity raised by this remarkable story. The result is a unique and accessible edition of one of the most thought-provoking and influential novels ever written. Essays by Elizabeth Bear, Cory Doctorow, Heather E. Douglas, Josephine Johnston, Kate MacCord, Jane Maienschein, Anne K. Mellor, Alfred Nordmann
    Keywords: science fiction ; gothic ; horror ; European ; British ; literature ; fiction ; cautionary tale ; STEM ; science ; bioethics ; classic ; bicentennial ; Josephine Johnston ; Cory Doctorow ; Jane Maienschein ; Kate MacCord ; Alfred Nordmann ; Elizabeth Bear ; Anne K. Mellor ; Heather E. Douglas ; Frankenstein ; Creature ; Monster ; Mary Shelley ; Makers ; women in science ; science and anti-science ; values in science ; responsible innovation ; Industrial Revolution ; Mary Wollstonecraft ; William Godwin ; Percy Bysshe Shelley ; Galvanism ; Mount Tambora ; Myths ; Two Cultures ; epistolary novel ; Victor Frankenstein ; Geneva ; Prometheus ; Arctic ; Lord Byron ; John Polidori ; ghost stories ; Revisions ; Electricity ; Lightning ; Vitalism ; Chemistry ; Extinction ; Magnetism ; Moral responsibility ; Legal responsibility ; Social responsibility ; Consequences ; Obligations ; Ethics ; Maker Culture ; DIY ; Technology Adjacent Possible ; Facebook ; Surveillance ; Aristotle ; Fetal development ; Epigenesis ; Embryo ; Person ; Technoscience ; Alchemy ; uncanny valley ; animation ; complexity ; Morality ; Monstrosity ; Christianity ; Otherness ; Gender ; Nature ; Domestic Affections ; Women ; Sexuality ; Technical Sweetness ; Los Alamos ; Trinity Test ; Scientific Responsibility ; Nuclear Weapons ; adjacent possible ; synthetic biology ; robotics ; thema EDItEUR::F Fiction and Related items::FB Fiction: general and literary::FBC Classic fiction: general and literary ; thema EDItEUR::F Fiction and Related items::FL Science fiction::FLC Classic science fiction
    Language: English
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    Coimbra University Press
    Publication Date: 2022-01-31
    Description: This work brings together various contributions from experts in very diverse areas of knowledge, to discuss the theme ‘Light’ from various points of view. The subjects gathered in this work come from the areas of Physics, Philosophy, Transcendence, Chemistry, Optics, Literature, History of Sciences, History, Geography, International Relations, Biology, Psychology, Art, Cinema and Photography, Medicine and Museology. The texts partially reflect the contents presented at the interdisciplinary colloquium ‘Visões da Luz’ held in October 2015, on the occasion of the International Year of Light 2015, under the aegis of III-UC and open to academia and society, to teachers of the Basic and Secondary Education.
    Keywords: Geography ; Chemistry ; Literature ; Geology ; Light ; Optics ; Biology ; History ; Physics
    Language: Portuguese
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    IntechOpen | IntechOpen
    Publication Date: 2024-04-05
    Description: Carotenoids are natural and versatile secondary metabolites, most of them showing colours that vary from yellow to red. They are widespread among living beings where they are involved in many biological roles reporting beneficial actions. To date, more than 750 carotenoids have been described in nature. Humans cannot synthesize carotenoids de novo, thus they are mainly obtained through diet. In fact, carotenoids are consistently found in tissues or biological fluids where they play a beneficial decreasing the risk of developing some diseases.During the last half-century, significant advances in carotenoids research have been made. This book highlights new perspectives and applications of carotenoids including characterization and isolation of new compounds (including rare carotenoids), their production at a mid-large scale (involving new innovative approaches), and uses of carotenoids in different biotechnological fields like food science, biomedicine, and cosmetics.
    Keywords: Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNN Organic chemistry
    Language: English
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    EDP SCIENCES
    Publication Date: 2024-04-05
    Description: Chemistry
    Keywords: Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNN Organic chemistry::PNNP Polymer chemistry
    Language: French
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    IntechOpen | IntechOpen
    Publication Date: 2024-04-05
    Description: Infrared Spectroscopy - Perspectives and Applications is a compendium of contributions from experts in the field of infrared (IR) spectroscopy. This assembly of investigations and reviews provides a comprehensive overview of the fundamentals as well as the groundbreaking applications in the field. Chapters discuss IR spectroscopy applications in the food and biomedicine sectors and for measuring transport through polymer membranes, characterizing lignocellulosic biomasses, detecting adulterants, and characterizing enamel surface advancements. This book is an invaluable resource and reference for students, researchers, and other interested readers.
    Keywords: Chemistry ; thema EDItEUR::P Mathematics and Science::PN Chemistry::PNF Analytical chemistry::PNFS Spectrum analysis, spectrochemistry, mass spectrometry
    Language: English
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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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    Logos Verlag Berlin | Logos Verlag Berlin
    Publication Date: 2024-04-05
    Description: When auralizing moving sound sources in Virtual Reality (VR) environments, the two main input parameters are the location and radiated signal of the source. An array measurement-based model is developed to characterize moving sound sources regarding the two parameters in this thesis. This model utilizes beamforming, i.e. delay and sum beamforming (DSB) and compressive beamforming (CB) to obtain the locations and signals of moving sound sources. A spiral and a pseudorandom microphone array are designed for DSB and CB, respectively, to yield good localization ability and meet the requirement of CB. The de-Dopplerization technique is incorporated in the time-domain DSB to address moving source problems. Time-domain transfer functions (TDTFs) are calculated in terms of the spatial locations within the steering window of the moving source. TDTFs then form the sensing matrix of CB, thus allowing CB to solve moving source problem. DSB and CB are further extended to localize moving sound sources, and the reconstructed signals from the beamforming outputs are investigated to obtain the source signals. Moreover, localization and signal reconstruction are evaluated through varying parameters in the beamforming procedures, i.e. steering position, steering window length and source speed for a moving periodic signal using DSB, and regularization parameter, signal to noise ratio (SNR), steering window length, source speed, array to source motion trajectory and mismatch for a moving engine signal using CB. The parameter studies show guidelines of parameter selection based on the given situations in this thesis for modeling moving source using beamforming. Both algorithms are able to reconstruct the moving signals in the given scenarios. Although CB outperforms DSB in terms of signal reconstruction under particular conditions, the localization abilities of the two algorithms are quite similar. The practicability of the model has been applied on pass-by measurements of a moving loudspeaker using the designed arrays, and the results can match the conclusions drawn above from simulations. Finally, a framework on how to apply the model for moving source auralization is proposed.
    Keywords: Science ; Chemistry ; Technology & Engineering ; Construction ; Technology & Engineering ; thema EDItEUR::P Mathematics and Science::PN Chemistry ; thema EDItEUR::T Technology, Engineering, Agriculture, Industrial processes::TN Civil engineering, surveying and building::TNK Building construction and materials ; thema EDItEUR::T Technology, Engineering, Agriculture, Industrial processes::TB Technology: general issues
    Language: English
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    Publication Date: 2024-04-05
    Description: Neuere Erkenntnisse zum Umsatzverhalten an Dieseloxidationskatalysatoren (DOCs) zeigen, dass das Umsatzverhalten von Schadstoffen vom Oxidationsgrad der verwendeten Edelmetallkatalysatoren abhängen kann. Dabei wird deutlich, dass sich der Oxidationsgrad bei typischen Abgaszusammensetzungen langsam und reversibel mit der Katalysatortemperatur ändert. Das kann bei periodischen Katalysatortemperaturänderungen zu einem ausgeprägten Hystereseverhalten führen. Bisherige Ergebnisse liegen insbesondere zum Verhalten der NO-Oxidation an Platin-Katalysatoren vor. Ziel der vorliegenden Arbeit ist es daher, die Untersuchungen auf seriennahe Pd- und PtPd-Mischkatalysatoren sowie auf andere abgastypische Schadstoffe, wie CO und Kohlenwasserstoffe, zu erweitern und dabei auch den Einfluss der Katalysatoralterung zu erfassen. Es wurde ein globalkinetisches Modell entwickelt und an die experimentellen Befunde angepasst. Dabei zeigte sich, dass es in der Regel möglich ist, das Umsatzverhalten bei reinen Pt- und Pd-Katalysatoren mit diesem örtlich eindimensionalen, makrokinetischen Zweiphasenmodell zutreffend zu beschreiben, wohingegen das Verhalten auf Pt/Pd-Mischkatalysatoren weniger gut simuliert werden kann. Dies ist vermutlich auf die heterogene Struktur der Pt/Pd-legierten Partikel zurückzuführen.
    Keywords: Science ; Chemistry ; Technology & Engineering ; Chemical & Biochemical ; thema EDItEUR::P Mathematics and Science::PN Chemistry ; thema EDItEUR::T Technology, Engineering, Agriculture, Industrial processes::TD Industrial chemistry and manufacturing technologies::TDC Industrial chemistry and chemical engineering
    Language: German
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  • 52
    Publication Date: 2023-03-08
    Description: © The Author(s), 2022. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in LeClerc, H., Tompsett, G., Paulsen, A., McKenna, A., Niles, S., Reddy, C., Nelson, R., Cheng, F., Teixeira, A., & Timko, M. Hydroxyapatite catalyzed hydrothermal liquefaction transforms food waste from an environmental liability to renewable fuel. IScience, 25(9), (2022): 104916, https://doi.org/10.1016/j.isci.2022.104916.
    Description: Food waste is an abundant and inexpensive resource for the production of renewable fuels. Biocrude yields obtained from hydrothermal liquefaction (HTL) of food waste can be boosted using hydroxyapatite (HAP) as an inexpensive and abundant catalyst. Combining HAP with an inexpensive homogeneous base increased biocrude yield from 14 ± 1 to 37 ± 3%, resulting in the recovery of 49 ± 2% of the energy contained in the food waste feed. Detailed product analysis revealed the importance of fatty-acid oligomerization during biocrude formation, highlighting the role of acid-base catalysts in promoting condensation reactions. Economic and environmental analysis found that the new technology has the potential to reduce US greenhouse gas emissions by 2.6% while producing renewable diesel with a minimum fuel selling price of $1.06/GGE. HAP can play a role in transforming food waste from a liability to a renewable fuel.
    Description: This work was funded by the DOE Bioenergy Technology Office (DE-EE0008513), a DOE DBIR (DE-SC0015784) and the MassCEC. The authors thank WenWen Yao, Department of Environmental Science at WPI, for TOC analysis, Mainstream Engineering for heating value characterization of the oil and solid samples, Wei Fan for assistance in obtaining SEM images and, Julia Martin and Ronald Grimm for their assistance in collecting XPS data, and Jeffrey R. Page for his assistance with oil upgrading and analysis. HOL was partially funded for this work by NSF Graduate Research Fellowship award number 2038257. A portion of this work was performed at the National High Magnetic Field Laboratory Ion Cyclotron Resonance user facility, which is supported by the NSF Division of Materials Research and Division of Chemistry through DMR 16-44779 and the State of Florida.
    Keywords: Chemistry ; Chemical engineering ; Catalysis
    Repository Name: Woods Hole Open Access Server
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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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    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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    Mycopathologia 124 (1993), S. 73-77 
    ISSN: 1573-0832
    Keywords: Assessment ; Cancer ; Humans ; Hydrazines ; Mushroom
    Source: Springer Online Journal Archives 1860-2000
    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
    Source: Springer Online Journal Archives 1860-2000
    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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    Astrophysics and space science 216 (1994), S. 153-154 
    ISSN: 1572-946X
    Keywords: Chemistry ; Molecular Hydrogen ; Cloud Models
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Observations of the CO J=1-0 line are commonly used as a tracer for molecular material in clouds. The ratio of the H2 column density to the integrated intensity of this line,X, is often taken to be constant, despite theoretical and observational uncertainty. We have tried to identify how this ratio depends on cloud parameters, testing a simple theoretical argument suggesting its invariance with respect to density. The apparent constancy can be understood if clouds are clumpy on scales of Av ≈ 1-2 mag.
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  • 59
    ISSN: 1573-739X
    Keywords: Antimalarials ; Artemisia annua L ; Artemisinin ; Biosynthesis ; Chemistry ; Clinical trials ; Pharmacology ; Phytochemistry ; Sesquiterpenes ; Toxicology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Artemisinin, a sesquiterpene lactone endoperoxide isolated fromArtemisia annua L., and a number of its semisynthetic derivatives have shown to possess antimalarial properties. They are all eflective againstPlasmodium parasites that are resistant to the newest and commonly used antimalarial drugs. This article gives a survey of the literature dealing with artemisinin-relaled antimalarial issues that have appeared from the end of 1989 up to the beginning of 1994. A broad range of medical and pharmaceutical disciplines is covered, including phytochemical aspects like the selection of high-producing plants, analytical procedures, and plant biotechnology. Furthermore, the organic synthesis of artemisinin derivatives is discussed, as well as their mechanism of action and antimalarial activity, metabolism and pharmacokinetics, clinical studies, sideeffects and toxicology, and biological activities other than antimalarial activity.
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    Pharmacy world & science 13 (1991), S. 109-118 
    ISSN: 1573-739X
    Keywords: Chemistry ; Consumer product safety ; Drug packaging ; Environmental pollution ; Plasticizers ; Polyvinyls
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In this report the state of the art with respect to PVC as pharmaceutical packaging material is described. A general introduction into the applications of PVC is followed by a description of its production process. The metabolic effects of the monomer of PVC, vinyl chloride and of the most commonly used plasticizer diethylhexylphthalate are mentioned. Special attention is given to the pharmaceutical properties of plasticized PVC bags in comparison to other plastics and the environmental aspects of waste PVC disposal. Although there are emotional and political queries regarding the future use of PVC as a (pharmaceutical) packaging material, we conclude that there is no scientific justification for a total or partial ban of PVC. PVC will remain a fact of life as a cheap, versatile, high-performance and well-investigated plastic material for medical and pharmaceutical applications, to be replaced by newer plastics only for certain well-defined indications where the requirements of the plastic to be used are so specific that it will economically and technically be justified to use another polymer. Community and hospital pharmacists have to be prepared for a role in intake of waste plastic disposables, probably against deposit money, in order to fulfil the logistics needed for recycling.
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    Plant systematics and evolution 171 (1990), S. 1-14 
    ISSN: 1615-6110
    Keywords: Angiosperms ; Compositae ; Chemistry ; systematics ; evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The broad knowledge of the chemistry of theCompositae allows the discussion of its relevance for the systematics and evolution within the family. Furthermore a separation into subfamilies can be supported by the observed differences in the distribution of the main constituents in the tribes.
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    Angewandte Makromolekulare Chemie 175 (1990), S. 107-116 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Zur Beschreibung der Polymerisationsgeschwindigkeit der radikalischen Fallungspolymerisation von Acrylsäure in Toluol wurde ein Modell entewickelt. Die experimentelle Überprüfung des Modells erfolgte durch Messungen in einem isotherm betriebenen Reaktionskalorimeter. Das Modell beschreibt die Polymerisationsgeschwindigkeit bis zum vollständigen Umsatz in einem Temperaturbereich von 40 bis 60°C.
    Notes: A kinetic model for the free-radical precipitation polymerization of acrylic acid in toluene was developed and verified experimentally by using an isothermal reaction calorimeter. The model predicts the rate of polymerization accurately up to complete conversion in the temperature range of 40 to 60°C.
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    Angewandte Makromolekulare Chemie 175 (1990), S. 157-168 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Es wird über Untersuchungen an Legierungen aus isotaktischem Polypropylen und EPDM-Elastomer berichtet, die mit hochenergetischen Elektronen bestrahlt worden waren. Die Mischungsverhältnisse in den Proben überstrichen sowohl den für elastomermodifizierte Thermoplaste typischen Bereich als auch den der thermoplasticschen Elastomeren. Eine Vernetzung der Komponenten über die Grenzfläche hinweg wurde nachgewiesen. Diese grenzflächenübergreifende Vernetzung bewirkte eine merkliche Verbesserung der mechanischen Eigenschaften insbesondere des thermoplastischen Elastomeren.
    Notes: Blends of isotactic polypropylene and EPDM rubber have been treated by electron irradiation in the composition range of rubber modification and in the thermoplastic rubber composition range as well. Mutual crosslinking of the components through the interface could be detected. This intercrosslinking caused a remarkable improvement of the mechanical properties particularly of the thermoplastic rubber.
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    Angewandte Makromolekulare Chemie 175 (1990), S. 205-205 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
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  • 65
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The mechanisms of photooxidation usually envisaged, are perfected by taking into account photoreactions of peroxy radicals. They involve interaction of a peroxy radical with the polymer to yield a hydroperoxy radical and a pair of macroradicals. After peroxidation, this pair will usually undergo bimolecular termination. The influence of such a reaction on photooxidation kinetics is particularly important for polyethylene. Then, chain termination occurs mainly by interaction of two hydroperoxy radicals or of a hydroperoxy radical with a macroperoxy radical. The reaction does not only affect kinetics of photooxidation but also the nature of the photooxidation products. The latter is more important for polypropylene than for polyethylene.
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  • 66
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Isothermal Differential Thermal Analysis was used to test the thermooxidative stability of pipes of polybutene during internal pressure tests at 110°C. At low hoop stresses and long testing times pipe failure was exclusively caused by thermooxidative degradation of the polymer.The stabilizer distribution in the initial state and its alteration during the pressure tests could easily be measured by isothermal DTA. Leaching of antioxidants from pipe walls could be detected. The decrease of residual thermooxidative stability was degressive.Degradation of pipe material started from the exterior pipe wall. Molecular weight of polybutene decreased rapidly after stabilizer exhaustion which could be observed by isothermal DTA.
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    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A base of experimental data on the ageing of commerial grade plastics is created. In includes assorted physical and chemical properties of plastics and their changes at natural ageing. An automated system for storing and processing of the experimental data is designed. Processing involves mathematical modeling of the changes in properties that aids in empirical prediction. The possibilities of the system are verified with experimental results from a 5-year ageing period of PE-LD and PE-HD. The results show a good agreement between the predicted and real data for selected models.
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    Angewandte Makromolekulare Chemie 179 (1990), S. 35-56 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Morphologie von Polypropylen-Spritzgußteilen mit Bindenaht wurde mit Röntgenweit-und Kleinwinkelstreuung, Lichtstreuung und Polarisationsmikroskopie untersucht. Die erhaltenen morphologischen Daten wurden mit mechanischen Werten aus Zugversuchen korreliert. Es wird gefunden, daß die mechanischen Eigenschaften der untersuchten Proben im wesentlichen von der sphärolithstruktur beeinflußt werden. Anhäufungen von Sphärolithen mit Kristallen der hexagonalen β-Modifikation und eine starke Inhomogenität der Sphärolithstruktur senkrecht zur Bindenaht sind der wesentliche Grund für die verschlechterten mechanischen Eigenschaften. Diese Sphärolithstruktur wird durch die Temperatur des Spritzgußwerkzeugs stark beeinflußt. Die Lamellen-Überstruktur hat dagegen einen vernachlässigbar kleinen Einfluß auf das mechanische Verhalten.
    Notes: The morphology of polypropylene plaques containing a weld line, has been investigated by x-ray wide and small angle scattering, light scattering and polarization microscopy. The results are correlated to mechanical values obtained from tensile tests. While the lamellar morphology is of neglectable influence, it is found, that the mechanical properties of the samples are strongly influenced by the spherulitic structure. Clustering of β-type spherulites and strong morphological inhomogeneities in the vicinity of the weld line are the primary reason for the mechanical weakening of the plaques. The temperature of the mould has a strong effect on the spherulitic structure and thus on the tensile properties of the samples.
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    Angewandte Makromolekulare Chemie 179 (1990), S. 77-85 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Füllstoffe für PVC- und PP-Formmassen wurden mit Mikrowellenplasma behandelt. Photoakustische FT-IR-Spektren zeigen, daß die Plasma-Polymerhülle auf der Füllstoffoberfläche —C=C—, —CH2—, CH3— und andere Gruppen enthält. Aus Röntgenelektronenspektren geht hervor, daß zwischen Siliciumdioxid und der organischen Beschichtung chemische Bindungen existieren. Durch Compoundieren von plasmabehandelten Füllstoffen mit PVC und PP werden Materialien mit guten mechanischen Eigenschaften bei niedrigen Kosten erhalten.
    Notes: Fillers for PVC and PP compounds have been treated by microwave plasma. FT-IR photoacoustic spectroscopy studies show that the plasma polymer sheath on filler's surface contains —C=C—, —CH2—, —CH3 groups, etc. X-ray photoelectron spectroscopy studies reveal that interfacial chemical bondings exist between silica and the organic coating. Application of plasma-treated fillers in PVC and PP compounds gives rise to materials of good mechanical properties and low cost.
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    Angewandte Makromolekulare Chemie 179 (1990), S. 135-148 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Poly-(alkylenadipat)-diole mit Molmassen von 1500, 2000 und 3000 wurden bei Temperaturen von 25 und 60°C in Gegenwart verschiedener Alkohole und unterschiedlicher PUR-Katalysatoren (1,4-Diazabicyclo[2.2.2]octan (DABCO), Dibutylzinndilaurat (DBTL),Dibutylzinndiethoxid (DBTEO) und Dibutylzinnoxid (DBTO)) in Ethylacetat bzw. Toluol gelagert und die Alkoholyse verfolgt. Die erhaltenen Ergebnisse werden mit dem Alkoholyseverhalten verschiedener Dialkyladipate sowie des Lösungsmittels Ethylacetat unter den selben Bedingungen verglichen. Die Alkoholyse verlauft in Gegenwart der zinnorganischen Verbindungen etwa mit gleicher Geschwindigkeit, ohne daß diese selbst signifikant zersetzt werden, wahrend DABCO praktisch inaktiv ist. Die Aktivitat der Alkohole ist starker von ihrer sterischen Struktur als von ihrer Basizitat abhangig. Die Stabilität der Polyalkylenadipate gegenüber einer Umesterung nimmt mit der Lange der Diolalkyleneinheiten des Polyols zu. Die Umesterung von Adipinsäuredialkylestern findet auch partiell in Anwesenheit eines großen Uberschusses an Ethylacetat statt.
    Notes: Poly(alkylene adipate)diols having molar masses of 1500, 2000 and 3000 were stored at temperatures of 25 and 60°C in the presence of low amounts of different alcohols and some polyurethane (PUR) catalysts, such as dibutyltindilaurate (DBTL), dibutyltindiethoxide (DBTEO), dibutyltinoxide (DBTO), and 1,4-diazabicyclo[2.2.2]octane (DABCO). Alcoholysis was studied using either ethyl acetate (EA) or toluene as solvent. The results were compared with those obtained by examining the behaviour of several dialkyl adipates and ethyl acetate under identical conditions. The alcoholysis in the presence of the tin catalysts proceeds at the same reaction rate without significant decomposition of the catalyst, whereas DABCO is practically inactive. The nucleophilic activity of the alcohols depends on their bulk size rather than their basicity. The resistance of polyalkylene adipates to transesterification increases with the increasing alkyl chain length of diol units in polyester. A partial transesterification of dialkyl adipates takes place too, in spite of ethyl acetate being present in excess.
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    Angewandte Makromolekulare Chemie 179 (1990), S. 157-171 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Es wurde das Permeations- und Trennverhalten von Alkohol/Wasser-Systemen durch poröse PVA-Membranen untersucht. PVA-Membranen mit unterschiedlicher Anzahl und Große von Poren wurden über Mischungen in Lösung mit verschiedenen synthetisierten Polymeren und Copolymeren, wie Polyacrylsäure, Polyacrylnitril, Polyacrylamid, Poly(Methylmethacrylat-co-Maleinsäureanhydrid) etc., anschließendes Gießen von Filmen und Extraktion der Polymeren oder Copolymeren durch Lösungsmittel hergestellt. Die Abhängigkeit der Durchlässigkeit und Trennwirkung von der Größe und Form der permeierenden Moleköle wurde qualitativ diskutiert. Des weiteren wurde die Selektivität der Trennwirkung in Abhangigkeit von der Zusammensetzung von Alkohol/Wasser-Gemischen und von der Größe und Anzahl der Poren untersucht. Es wurde gefunden, daß die Selektivität von der Menge und dem Molekulargewicht der in die Membranen eingebrachten Polymeren abhängt. Wenn der Gewichtsanteil des verwendeten Polymeren größer als 0,1 war, permeierte bevorzugt der Alkoholanteil bei methanolischen Msungen, wobei der Trennfaktor mit steigender Methanolkonzentration anstieg. In Gemischen mit anderen Alkoholen zeigten die Membranen andererseits eine selektive Durchlässigkeit für Wasser. Der Einfluß der Versuchsbedingungen wurde ebenfalls untersucht.
    Notes: The permeation and separation characteristics of alcohol/water systems through porous PVA membranes were investigated. Porous PVA membranes with different pore size and number were prepared by solution blending of PVA with several synthesized polymers or copolymers, such as polyacrylic acid, polyacrylamide, polyacrylonitrile, and methylmethacrylate-co-maleic anhydride, etc. Then casting, and finally extracting the blended polymers or copolymers by solvent from the membranes. The dependency of both permeation and separation on the molecular size and shape of the permeating species was dicussed qualitatively. Moreover, the permselectivity was investigated with attention to the feed composition of alcohol/water mixture and the effect of pore size and number. The selectivity was found to depend on the weight ratio and the molecular weight of polymer introduced to the membrane. When the weight ratio of polymer introduced into the membrane was larger than 0.1, methanol was permeated through membrane preferentially in methanol/water system, and the separation factor increased with increasing the methanol feed concentration. On the other hand, membrane had a selective permeability for water in the other alcohol/water systems. The influence of operating conditions was also studied.
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  • 72
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    Angewandte Makromolekulare Chemie 175 (1990), S. 29-38 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Temperatur des T1-Minimums für die Segmentbewegung in Polypropylen, das einen hohen ataktischen Anteil besitzt, ist niedriger als die in isotaktischem Polypropylen. Ein kurzes T1, T1s, tritt bei beiden Materialien auf. Bei Temperaturerhöhung nimmt T2a (T2 der beweglichen amorphen Bezirke) stark und T2m (T2 der dazwischen liegenden Bezirke) leicht zu, während sich T2c (T2 der steifen kristallinen Bezirke) kaum ändert. T2a in Polypropylen mit hohem ataktischem Anteil ist länger als in isotaktischem Polypropylen.Der Massenbruch der kristallinen Bezirke, Fc, nimmt bei Temperaturerhöhung ab und der der amorphen Bezirke, Fa, zu. Die Relaxationsgeschwindigkeit, 1/ (T1min), steigt linear mit Zunahme des amorphen Anteils an, außer bei der mit siedendem n-Heptan extrahierten Probe. Mit Zunahme der Peaktemperatur von tan δ fällt T2a nahezu linear ab, während die Temperatur des T1-Minimums zunimmt.
    Notes: The temperature of the T1 minimum for the segmental motion in polypropylene containing a lot of atactic fraction is lower than that in isotactic polypropylene. A short T1, T1s, appears for both materials. As the temperature is raised, there is a large increase in T2a (T2 of the mobile amorphous regions), and a mild increase in T2m (T2 of the intermediate regions), while there is no substantial change in T2c (T2 of the rigid crystalline regions). T2a in polypropylene containing a lot of atactic fraction is longer than that in isotactic polypropylene.The mass fraction of crystalline regions, Fc, decreases and that of the amorphous regions, Fa, increases as the temperature is raised. There is a linear increase in the relaxation rate, 1/(T1min), as the amorphous fraction is increased, except for the sample extracted with boiling n-heptane. With increase of the peak temperature of tanδ, T2a decreases nearly linearly, while the temperature of the T1 minimum increases.
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  • 73
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    Angewandte Makromolekulare Chemie 180 (1990), S. 191-198 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Bestrahlung von PTFE mit Elektronen niedriger Energie führt zur Abspaltung von Fluor und zum Einbau von Sauerstoff in die Polymeroberfläche. Es wird gezeigt, daß das Ausmaß der Oberflächenveränderungen hauptsächlich von der Zahl und kaum von der Energie der Elektronen abhängt, die die Oberfläche erreichen. Änderungen in der Oberflächenenergie resultieren in unterschiedlichem Benetzungsverhalten. Kontaktwinkelmessungen und Kurvenanalysen der C-1s-Peaks aus Röntgenphotonenspektroskopiemessungen zeigen, daß der am wenigsten benetzbare Teil der bestrahlten Oberflächen in den meisten Fällen aus —CF2 —CF-Einheiten besteht. Werden bei der Bestrahlung nahezu alle Fluoratome abgespalten, bleiben nur isolierte —CF2-oder —CF-Gruppen zurück. Die „receding“-Winkel werden mit zunehmender Sauerstoffkonzentration in der Oberfläche kleiner, was auf die Bildung stark oxidierter Bereiche hinweist. Die Unabhängigkeit der Kontaktwinkel von der Alterungsdauer deutet auf eine sehr geringe Beweglichkeit der Makromoleküle hin, was mit einer starken Vernet-zung an der Oberfläche zusammenhängen könnte.
    Notes: Low energy electron irradiation of PTFE induced fluorine depletion and introduction of oxygen on the surface. The effect on surface chemistry was shown to be dependent mostly on the amount of electrons reaching the sample, rather than on their energy.Changes in surface energy resulted in different wetting behaviors. The measurement of advancing water contact angles and the analysis of XPS C-1s peak shapes showed that the least wettable portion of irradiated surfaces is made in most cases of —CF2—CF — units. When the treatment caused a nearly complete fluorine depletion, only isolated —CF2— or —CF— groups are present. Receding angle values decreased linearly depending on the amount of oxygen introduced on the sample during the treatment, suggesting the formation of strongly oxidized polymer islets. The invariance of contact angles with aging time indicated very low macromolecular mobility, probably related to extensive surface crosslinking.
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  • 74
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    Angewandte Makromolekulare Chemie 181 (1990), S. 41-52 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: In aqueous dispersions of anionic polyurethanes containing the triethylammonium salt of 2,2-dimethylol propionic acid as chain extender, triethylamine can be largely replaced by ammonia. For electrostatic reasons, NH4+ is namely more tightly bound in the ion pairs located in the Stern layer than NH(C2H5)3+. Thermal treatment of films leads to a loss of base, whereby ammonia is more rapidly released than triethylamine. Therefore, crosslinking with partially methylated hexamethylolmelamine proceeds the faster the more triethylamine is replaced by ammonia.
    Notes: In Dispersionen aus anionischen Polyurethanen, die das Triethylammoniumsalz der 2,2-Dimethylolpropionsäure als Kettenverlängerungsmittel enthalten, läßt sich durch Zugabe von Ammoniak eine weitgehende Verdrängung des Triethylamins erreichen. Aus elektrostatischen Gründen ist nämlich in den in der Sternschen Schicht lokalisierten Ionenpaaren NH4+ fester gebunden als NH(C2H5)3+. Bei der thermischen Behandlung der Filme tritt Basenabspaltung ein, dabei erfolgt die Abgabe von Ammoniak deutlich schneller als die von Triethylamin. Die Spannungswerte der mit teilmethyliertem Hexamethylolmelamin vernetzten Proben sind daher um so höher, je mehr Triethylamin durch Ammoniak ersetzt wurde.
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  • 75
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    Angewandte Makromolekulare Chemie 181 (1990), S. 53-66 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Viskoelastizitäts-Parameter von geschmolzenem Polystyrol (PS) wurden mit einem Instron-Kapillarrheometer gemessen.Die Drucknachgiebigkeit B(t) zeigt ein Plateau sowohl im Schmelze (B1)- als auch im Glaszustand (Bg); beide nehmen mit abnehmender Spannung ab. Durch Verschiebung der B(t)-Kurven werden Master-Kurven erhalten, mit denen das Gesamtdruckverhalten (überlagerte elastische und viskose Deformationen) analysiert werden kann. Die stationäre Nachgiebigkeit (Bs) erlaubt eine Beschreibung des elastischen Energieanteils und scheint mit der Extrusions-Strangaufweitung (Bcs/Bds) korreliert zu sein. Die Volumenviskosität (ηk) nimmt mit zunehmender Spannung (P), zunehmender Belastungsgeschwindigkeit (k) und abnehmender Temperatur ab.
    Notes: Viscoelastic parameters of polystyrene (PS) melt in compression creep have been measured in an lnstron capillary-rheometer.Bulk compression creep compliance B(t) shows plateau regions in the molten state (B1) and the glassy state (Bg), both decreasing with increasing stress. Shifting of B(t) curves provides master curves suitable to analysing the total (superposed elastic and viscous deformations) bulk compression behaviour. The steady-state creep compliance (Bs) allows to describe the recoverable elastic energy (Be) and seems to be related to the extrusion die swell (Bcs/Bds). Volume viscosity (ηk) decreases with decreasing stress (P), increasing compression rates (k) and decreasing temperature (T).
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  • 76
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    Angewandte Makromolekulare Chemie 181 (1990), S. 67-74 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Es wurden Untersuchungen über Molekulargewichtsänderungen an physikalisch bei Raumtemperatur gealterten isotaktischen Polypropylenfilamenten (iPP) mit Hilfe der Hochtemperaturgelpermeationschromatographie (HTGPC) durchgeführt. Das Ergebnis der Untersuchungen weist auf eine sehr unbedeutende Änderung des Molekulargewichts des Materials während der Alterung hin.Das Materialgranulat wurde als Bezugsstandard gewählt. Basierend auf der Uneinheitlichkeit D = Mw/Mn des Granulats wurden Filamente der Handelsprodukte GYE 47 und PXC 31399 charakterisiert, deren Alterungsdauer zwischen 2 Wochen und 8 Monaten lag. Bei den Filamenten der Qpe GYE 47 verringerte sich die Breite der Molekulargewichtsverteilung D um durchschnittlich 12%. Andererseits zeigen die Filamente des PXC 31399-vps einen weniger eindeutigen Trend zur Änderung, jedoch im Mittel hat sich die Breite der Verteilung um etwa 20% erniedrigt. Bei letzterem ist die Verteilung iiber die Alterungsdauer stark gestreut. Der GYE 47-Typ zeigt eine nahezu asymptotische Abnahme. Es wird angenommen, daß die Ungleichartigkeit in der Ändenz der Anderung von D zwischen beiden Proben in ihrer unterschiedlichen thermodynamischen Stabilitat liegen ktinnte; PXC 31399 ist weniger stabil.
    Notes: Experiments on the molecular weight variations of physically, room temperature aged isotactic polypropylene (iPP) filaments were done using the High Temperature Gel Permeation Chromatography (HTGPC). Evidence emanating from the studies indicates a very marginal change in molecular weight of the materials during aging.The granules of the materials were chosen as the reference standard. Based on the polydispersity D = Mw/Mn of the granules, filaments of commercial grades GYE 47 and PXC 31399 were characterized between an aging period ranging from 2 weeks to 8 months. The filaments of the GYE 47 grade have their distributions D lowered on the average by about 12%. On the other hand, those of the PXC 31399 grade have a less definite trend in change, but on the average, D is lowered by about 20%. The distributions of this latter grade are highly scattered over the period of aging. The GYE 47 grade shows a reduction in the distribution of a near asymptotic nature. It is believed that the disparity in the trend of change of D between the two samples could be attributed to their relative thermodynamic stability with the PXC 31399 grade being less stable.
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  • 77
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The properties (squared dimensions, anisotropy, numbers of intra- and intermolecular contacts) of a single five-way cubic lattice chain embedded into an environment (matrix) of chains of the same length n = 50 were evaluated as a function of matrix volume fraction (matrix density) v and intermolecular interaction between the matrix polymer and the minority chain segments, characterized by a parameter φ. No convincing evidence was found for the occurrence of a coil-globule transition in the range of matrix densities (v ≤ 0.7) and repulsive interactions between matrix and minority chain (φ ≤ 0.2) investigated. For moderate attractive interaction (φ ≈ -0.17) a compensation of the chaincompressing action of the matrix and the chain-expanding interaction with the matrix was observed resulting in a zero-dependence of the size and shape of the minority chain on matrix density. It further turned out that there are fixed relations among the various size and shape data irrespective of the specific combination of matrix density and thermodynamic interaction by which a particular polymer dimension is produced. These interrelations are fairly the same as those evaluated for isolated chains the size of which is varied by an intramolecular energy parameter φi.
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  • 78
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: New three phases composite materials made of glassbeads as filler, water as liquid dispersed phase and polystyrene as matrix were obtained by polymerization of a water in oil emulsion formed by water dispersed in styrene in which glass beads are added. For this purpose glass beads have to be modified by silanization by a coupling agent 3-(Trimethoxysilyl)propylmethacrylate (TPM) or a silane Octadecyltrichlorosilane (ODMS), in order to prevent the wetting of the glass by water. Only low coverage of the glass surface by the coupling agent (0,05% of TPM) are convenient for the preparation cellular materials having good mechanical properties. At higher coverage ratio, strong hydrophobic glass beads are obtained which destabilize the water / styrene emulsion and lead to macroporous products. Study of the rheology of the filled emulsion appears to be the more simple and more sensitive method to determine the level of wettability of the glass bead by the emulsion which is the most significant parameter for the preparation of such three phases composite materials. Composite materials made of glass beads, air and polystyrene are simply obtained by evaporation of water under vacuum.
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  • 79
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: To test the molecular parameters concerning gas sorption in polymers, the concentration of CO2, N2O, CO, N2, CH4 and the noble gases Ne, He in glassy poly(butylene terephthalate) films (PBTP) has been studied gravimetrically with a recording microbalance at 25°C. The sorption isotherms exhibit downward curvature to the pressure axis. As neither solubility nor adsorption can explain the experimental results, analysis was carried out based on the dual-sorption model: gas dissolution and microvoid filling are considered as independent sorption mechanisms. The parameters of the dual-sorption model for the mentioned penetrants are determined. The results indicate that for parameter correlation the Lennard-Jones potential parameters give a rough idea, but size exclusion of gases in small diameter microvoids is proposed and special chemical interactions must be considered.
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  • 80
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    Angewandte Makromolekulare Chemie 185 (1991), S. 283-292 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The ring opening metathesis polymerisation (ROMP) of 5-cyano-2-norbornene with tungsten hexachloride, tungesten oxytetrachloride, bis(dichloralkoxo)tungsten tetrachloride and bis(dichloralkoxo)tungsten oxydichloride as transition metal component was studied. Methylaluminoxan, diethylaluminium ethoxide, tetraisobutyldialuminoxan and tetrabutyltin served as cocatalyst. Toluene, Chlorobenzene and dichloromethane were used as solvents. The concentration of the tungsten components was in the range from 5 × 10-4 to 5 × 10-3 mol/l. Among the catalyst studied, tungsten hexachloride with diethylaluminium ethoxide proved to be the best. The polymerisation was highly selective with this system even at high monomer/tungsten ratios (e.q. 10200:1) and let to high conversions (≥82%).
    Notes: Die ringöffnende metathetische Polymerisation (ROMP) von 5-Cyano-2-norbornen wurde unter Einsatz von Wolframhexachlorid, Wolframoxidterachlorid, Bis(dichloralkoxo)wolframtetrachlorid und Bis(dichloralkoxo)wolframoxiddichlorid als Übergangsmetallkomponente untersucht. Als Cokatalysatoren dienten Methylaluminoxan, Diethylaluminiumethoxid, Tetraisobutyldialuminoxan und Tetrabutylzinn. Als Lösungsmittel wurden Toluol, Chlorbenzol und Dichlormethan verwendet. Die Konzentration der Wolframkomponente lag im Bereich 5 × 10-4 - 5 × 10-3 mol/l. Unter den geprüften Katalysatoren erwies sich Wolframhexachlorid in Verbindung mit Diethylalumiumethoxid als der geeignetste. Mit diesem System verlief die Polymerisation auch bei großen Monomer/Wolfram-Verhältnissen (10200 :1) hochselektiv und führte zu großen Umsätzen (≥82%).
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  • 81
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    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The dependence of dilution on the chain propagation and termination rate constants was investigated in the polymerization of ethyl acrylate in benzene solution at 50°C, with the rotating sector method. The errors of the above rate constants were determined and, by our method applied to decrease these errors, the errors of the propagation rate constant was reduced to its half value. By the application of our earlier results in polymerization kinetics, we found that in this system the chain propagation step is exclusively responsible for the solvent effects observed. Our experimental results can be quantitatively described in terms of the hot redical theory.
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  • 82
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    Angewandte Makromolekulare Chemie 185 (1991), S. 329-334 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
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  • 83
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    Angewandte Makromolekulare Chemie 174 (1990), S. 1-10 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Photopolymerisation von Ethylenglykoldimethacrylat (EGDMA) mit Methylmethacrylat (MMA) wurde mit Benzoinmethylether (BME) als Initiator in einem Glasrohr durchgeführt, um einen lichtfokussierenden Plastikstab (Radius Rp) mit parabolischer Brechungsindex-Verteilung (Verteilungskonstante A) in der Nähe der Stabachse (bis zum Radius Rc) herzustellen. Die Abhängigkeit von A und Rc/Rp vom Monomerenverhältnis MMA/EGDMA der Ausgangsmischung, der Einfluß der BME-Konzentration auf die Brechungsindex-Verteilung und die Reproduzierbarkeit der Photopolymerisationen wurden untersucht. Das Rc/Rp-Verhältnis stieg mit dem Monomerenverhältnis MMA/EGDMA bei BME = 1,0 Gew.-% und der Geschwindigkeit der UV-Lampe von V = 0,58 mm/min an. Andererseits stieg Rc/Rp bei BME = 0,6 Gew.-% und V = 0,735 mm/min bis zum Monomerenverhältnis von 0,2 an und fiel dann deutlich zwischen 0,20 und 0,25 ab. Die Plastikstäbe, die hier durch Photopolymerisation hergestellt wurden, haben Linseneigenschaften und sind gut reproduzierbar.
    Notes: The photocopolymerization of ethyleneglycol dimethacrylate (EGDMA) with methylmethacrylate (MMA) containing benzoin methyl ether (BME) as initiator was carried out in a glass tube to fabricate a light-focusing plastic rod (radius Rp) with a parabolic refractive index distribution (distribution constant A) in the region near the center axis (radius Rc). The dependence of A and Rc/Rp on MMA/EGDMA feed ratio, influence of BME concentration on the refractive index distribution, and the reproducibilities of the photopolymerizations were investigated. The Rc/Rp increased with the feed ratio used under BME = 1.0 wt.-% at velocity of UV lamp V = 0.58 mm/min. On the other hand, Rc/Rp increased with the feed ratio to 0.2 and then decreased remarkably with the feed ratio in the range of 0.2-0.25 with BME = 0.6 wt.-% at V = 0.735 mm/min. Plastic rods fabricated in the investigation using photopolymerization have lens characteristics and good reproducibilities.
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  • 84
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Polystyrol- und Polymethylmethacrylateinzelfäden mit verschiedenen Graden von Doppelbrechung wurden durch die kontinuierliche Änderung der Ziehgeschwindigkeit, der Temperatur der Polymerschmelze und des Molekulargewichts von Polystyrol (PS) und Polymethylmethacrylat (PMMA) gewonnen. Der “brittle to ductile” Übergangspunkt (Übergang des Polymeren vom spröden zum ziehbaren Zustand) wurde für das optisch reine Polystyrol im Bereich der Doppelbrechungszahlen -0,6 · 10-3 bis -2,6 · 10-3 gefunden. Höhe und Lage dieses Punktes werden durch das Molekulargewicht, die Molekulargewichtsverteilung und die Temperatur der Polymerschmelze beeinflußt. Die Werte des Doppelbrechungsindexes von PS sind um zwei Zehnerpotenzen höher als von PMMA. Bei PMMA wurde der “brittle to ductile” Übergangspunkt nicht beobachtet. Die mechanischen und optischen Eigenschaften hängen nicht nur vom mittleren Wert des durch die Doppelbrechung charakteri-sierten Orientierungsgrades ab, sondern auch davon, welcher Teil des Relaxations-spektrums des Polymeren vorzugsweise orientiert ist. Beim Ziehen der PS- und PMMA-Einzelfäden bilden sich in der Mitte des Fadens Risse (crazes), die jedoch nicht an die Oberflache des Fadens treten.
    Notes: Monofilaments possessing various degrees of birefringence were obtained by changing the drawing rate, the molten polymer temperature, and the molecular weight of polystyrene (PS) and poly(methyl methacrylate) (PMMA). The “brittle-toductile” transition point of optically pure PS was found in the range of birefringences of -0.6 · 10-3 to -2.6 · 10-3. Both the height and position of this point are influenced by M̄w, molecular weight distribution, and polymer melt temperature. The birefringence of PS is higher by two orders of magnitude than that of PMMA in which this transition point has not been observed. The mechanical and optical properties depend not only on the average amount of orientation characterized by the birefringence but on what portion of the relaxation spectrum of the polymer is preferentially oriented. During the drawing of PS and PMMA monofilaments crazes are formed in the centre of the fibers and do not reach the surface.
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  • 85
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    Angewandte Makromolekulare Chemie 174 (1990), S. 105-117 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The possibility of the application of atactic polypropylene is investigated as graft base for the preparation of graft copolymers of vinyl acetate and vinyl chloride respectively graft copolymers from vinyl acetate onto polypropylene as graft base for the preparation of graft copolymers of vinyl chloride in relation to the composition of the original mixture.After compounding of the graft products with polyvinyl chloride or ABS/polyvinyl-chloride mixtures selected mechanical properties are presented in relation to the quantity and composition of the incorporated graft copolymers.
    Notes: Die Möglichkeiten des Einsatzes von ataktischem Polypropylen als Pfropfgrundlage zur Herstellung von Pfropfcopolymerisaten des Vinylacetates und Vinylchlorids bzw. von Polypropylen-Vinylacetat-Pfropfprodukten als Pfropfgrundlage zur Herstellung von Pfropfcopolymerisaten des Vinylchlorids werden in Abhängigkeit von der Ausgangsgemischzusammensetzung untersucht.Nach Abmischung der Pfropfprodukte mit Polyvinylchlorid bzw. ABS/Polyvinylchlorid-Mischungen werden ausgewählte mechanische Eigenschaften sowohl in Abhängigkeit von der Menge des enthaltenen Pfropfproduktes als auch von der Zusammensetzung der Pfropfpolymerisate dargestellt.
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  • 86
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: A new spectroscopic method for determining the permeability of ammonia in transparent polymer layers is presented. It is based on the quantitative proof of the ammonia passing the test layer into a sensor layer, containing 4-nitrophenol as an NH3-sensitive probe, which is placed under the test film. The permeability (P) of the test layer is calculated from the slope of extinction with time in the sensor layer. The lag time (t1) gives the diffusion coefficient (D). The suitability of this method is confirmed by comparison with literature values. Diffusion coefficients obtained from t1 correspond well to those obtained by the sorption method.The temperature dependence of P and D in more than five different polymers (CDA, PVB, PVAc, PVC and different polyvinyl alcohols) demonstrates that peculiarities in the temperature dependence of the permeability result from the behaviour of the NH3-solubility (P/D) which is strongly dependent on the polymer structure.
    Notes: Es wird eine neuartige spektroskopische Methode zur Messung der Ammoniak-Permeabilität in transparenten Polymerfilmen vorgestellt. Sie beruht auf dem quantitativen Nachweis des den Testfilm durchdringenden Ammoniaks in einer darunter befindlichen Sensorschicht mit Hilfe der NH3-empfindlichen Sonde 4-Nitrophenol. Aus dem Anstieg der Extinktion mit der Zeit (ΔE/Δt) in der Sensorschicht wird die Permeabilität (P) und aus der Verzögerungszeit (lag time (t1)) der Diffusionskoeffizient (D) berechnet. Die Eignung der Methode wird durch Vergleich mit Literaturwerten belegt. Die aus t1 zugänglichen Diffusionskoeffizienten stimmen sehr gut mit denen überein, die mit der Sorptionsmethode gefunden werden.Die Temperaturabhängigkeiten von P und D in mehr als fünf verschiedenen Polymeren (CDA, PVB, PVAc, PVC und in verschiedenen Polyvinylalkoholen) zeigen, daß Besonderheiten im Temperaturgang der Permeabilität aus dem vom Aufbau des Polymeren stark abhängigen Verhalten der NH3-Löslichkeit (P/D) resultieren.
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  • 87
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    Angewandte Makromolekulare Chemie 179 (1990), S. 99-111 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Es wurde die strahleninduzierte Pfropfung von 4-Vinylpyridin (VP) auf Styrol-Butadien-Styrol-Copolymere (SBS) in Gegenwart von gelöstem Sauerstoff untersucht. Pfropfcopolymer-Membranen mit unterschiedlichen Pfropfgraden wurden durch Gießen aus benzolischer Lösung hergestellt. Die mechanischen Eigenschaften, die Gaspermeabilität sowie der Einfluß der Temperatur auf die Gasdurchlässigkeit wurden untersucht. Der höchste Pfropfgrad von 8,4% wurde bei einer Bestrahlungszeit von 15,5 herreicht. Sowohl bei kürzeren als auch längeren Bestrahlungszeiten war der Pfropfgrad  -  bedingt durch Störung durch den vorhandenen Sauerstoff  -  niedriger. Reißfestigkeit und Reißdehnung von SBS-g-VP waren vergleichbar rnit SBS. Die Spannungsrelaxation von SBS-g-VP war langsamer als bei SBS, was auf der Bildung von starren Polyvinylpyridin(DVP)-Mikrophasen beruhen könnte, die als permanente Vernetzungspunkte wirken und die Spannungsrelaxation beeinträchtigen könnten.Da SBS eine hohe Gasdurchlässigkeit und PVP eine hohe O2/N2-Selektivität aufweisen, wurde die Gasdurchlässigkeit der Pfropfmembranen untersucht. Die Selektivitat der SBS-g-VP-Membranen stieg mit steigendem Pfropfgrad, allerdings auf Kosten der Permeabilität, Bei Erhöhung der Temperatur nahm die Durchlässigkeit zu, das Verhältnis O2/N2, aber ab. Die Aktivierungsenergie (Ep) der Gasdurchlässigkeit stieg mit dem Pfropfgrad. Für eine nichtgepfropfte SBS-Membran betrug Ep 5,5 kcal/mol für Sauerstoff und 7,2 kcal/mol für Stickstoff. Für eine SBS-g-VP-Membran mit einem Pfropfgrad von 8,4% waren die Ep-Werte für Sauerstoff und Stickstoff 6,5 bzw. 8,1 kcal/mol.
    Notes: The grafting of 4-vinyl pyridine (VP) onto styrene-butadiene-styrene triblock copolymers (SBS) by homografting irradiation with dissolved oxygen was studied. Homograft membranes of various degree of grafting were prepared from a casting solution of grafted copolymer in benzene. The mechanical properties of membranes, gas permeability, and the effect of operating temperature on gas permeation were investigated.The degree of grafting of 8.4% was the largest at an irradiation time of about 15.5 h. It was smaller at both shorter and longer duration because of the interference of dissolved oxygen. It was found that the tensile strength and elongation of SBS-g-VP were similar to those of SBS. The stress relaxation of SBS-g-VP was slower than that of SBS, and this might be due to the formation of rigid microphase separation domain of poly(4-vinyl pyridine), which acted as permanent crosslinking points to reduce the stress relaxation.Using the properties of high flux of SBS and high O2/N2 selectivity of poly(4-vinyl pyridine), the performance of gas permeation of 4-vinyl pyridine homografted SBS membrane was studied. The selectivity of SBS-g-VP membrane increased with increasing degree of grafting. However, it was done at the expense of a decrease in the gas permeability.When the operating temperature of gas permeation increased, the permeability of oxygen and nitrogen increased, and the O2/N2 permeability ratio decreased. The activation energy (Ep) for gas permeation through different degree of grafting of SBS-g-VP membrane (obtained by the Arrhenius law) increased with increasing degree of grafting. For ungrafted SBS membrane, Ep was 5.5 kcal/mol for oxygen and 7.2 kcal/mol for nitrogen. For 8.4% grafting degree SBS-g-VP membrane, Ep for oxygen and nitrogen, were 6.5 and 8.1 kcal/mol, respectively.
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  • 88
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    Angewandte Makromolekulare Chemie 175 (1990), S. 13-27 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The change of molecular mass and long-term strength of high and low density polyethylene under tensile load in surface-active medium was studied. It is shown that long-term strength of polyethylene depends on the molecular mass. The influence of polydispersity on strength was investigated.
    Notes: Es wird über die Untersuchungsergebnisse von Lebensdauer und Molmassenänderung an polydispersen Proben von HDPE und HDPE in einem breiten M̄v-Bereich im Zugversuch in einem oberflächenaktiven Medium berichtet.Die Arbeit enthält auch die Darstellung der quantitativen Änderung der Molmasse von Hochdruck- und Niederdruck-Polyethylen unter Dauerbeanspruchung und die Analyse der Lebensdauer in Abhängigkeit von den unterschiedlichen Molmassen (MM) (M̄w, M̄n, M̄v); die Unterschiede in Abhängigkeit von der Lebensdauer von M̄v für Proben und polydisperse Muster sowie die Vorstellungen über den dualen Einfluß der Polydispersität auf die Lebensdauer mit einer Interpretation der auftretenden Erscheinungen werden beschrieben.
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  • 89
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: One constitutive property for the description of dyeing polyester-materials with disperse dyes is the particle size distribution in the dye bath. To measure particle sizes below one micrometer in situ, special techniques are required. One of these is the so called photon-correlation-spectroscopy, depending on the scattering of laser light by suspended small particles in a fluid. The mathematical and physical principles of the photon-correlation-technique are explained in this article.
    Notes: Eine zur Beschreibung des Färbevorganges von Polyestermaterialien mit Dispersionsfarbstoffen wesentliche Größe stellt die Partikelgrößenverteilung im Farbebad dar. Partikelgrößen unterhalb eines Mikrometers lassen sich in situ nur mit wenigen Meßtechniken bestimmen. Dazu zählt u. a. die Photonen-Korrelations-Spektroskopie, die auf Streuung von Laserlicht an kleinen, in einer Flüssigkeit suspendierten Teilchen basiert. Die mathematischen und physikalischen Grundlagen dieser Meßtechnik werden in diesem Artikel erläutert.
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  • 90
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    Angewandte Makromolekulare Chemie 175 (1990), S. 81-97 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die Kristallinität von Polyethylen, Polyethylenterephthalat und Polypropylen wurde mit Hilfe der Röntgenweitwinkel(WAXS)-und-kleinwinkel(SAXS)streuung gemessen. Die mittels der letzteren Methode erhaltenen Kristallinitätswerte sind deutlich größer als die durch WAXS. Es wird vermutet, daß die Unterschiede mit der Schicht zusammenhängen, die zwischen den amorphen und kristallinen Bereichen liegt. Daraus wurde geschlossen, daß die Röntgenkleinwinkelstreuung nicht als unabhängige Routinemethode zur Kristallinitätsbestimmung angewendet werden kann.
    Notes: The crystallinity of polyethylene, polyethyleneterephthalate, and polypropylene was measured with the aid of wide angle (WAXS) and small angle (SAXS) X-ray scattering methods. The values of crystallinity evaluated using the latter method are distinctly larger than those ones given by the WAXS method. The differences are supposed to be associated with the transition layer existing between the amorphous and crystalline regions. It was concluded that small angle X-ray scattering cannot be employed as an independent routine method of crystallinity determination.
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  • 91
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    Angewandte Makromolekulare Chemie 175 (1990), S. 117-128 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Für das System Cellulosenitrat-μ-Styragel-THF wurde die DP-Ve-Beziehung sowie die Ausarbeitung der betreffenden Eichparameter einer genaueren Betrachtung unterzogen. Die etwa dreißig Eichpräparate waren durch definierten säurekatalysierten Abbau von Baumwollcellulose und anschließende Nitrierung hergestellt worden und umfaßten einen DP-Bereich von 150 〈 DP 〈 8000. Es wird gezeigt, daß mit steigendem DP die DP-Ve-Beziehung drei verschiedene Phasen aufweist. Bei der Anwendung der SEC auf Cellulosenitrat müssen daher bezüglich der Eichung zwei Fehlerquellen in Betracht gezogen werden: eine bezieht sich auf die Methode der Ausarbeitung der Eichparameter als solche, und die andere auf die Nichtbeachtung des Vorhandenseins dreier Abschnitte in der DP-Ve-Beziehung. Die Auswirkung dieser Fehler auf die Genauigkeit der aus den Elutionsdiagrammen abgeleiteten Verteilungskurven und DP-Mittelwerte wird diskutiert.
    Notes: The calibration behaviour of the system cellulose nitrate-μ-Styragel-THF has been studied using about 30 different calibration samples prepared by defined acid catalyzed degradation of cotton cellulose. The samples covered a range of DP between 150 〈 DP 〈 8000. It is shown that the DP-Ve relationship is characterized by the existence of three subsequent stages. Consequently, two sources of errors in the DP-Ve calibration must be taken into consideration. One refers to the methods as such to elaborate the calibration parameters, and the other one arises by neglecting that the DP-Ve relationship involves 3 distinct stages. The extent of the two classes of errors in regard to the exactness of the determined molecular weight averages and molecular weight distributions is discussed.
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  • 92
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    Angewandte Makromolekulare Chemie 175 (1990), S. 141-156 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Bei der Polycondensation von d,l-Asparaginsäure mit Nδ-phthaloyl-L-ornithin in Phosphorsäure bei 185°C entstehen statisticsche Copolymere (Ausbeute 60  -  70%) aus Poly(d,l-succinimid-co-Nδ-phthaloyl-d,l-ornithin), Formel 6, mit inhärenten Viskositäten (DMF) von 5 bis 15 ml g-1. Copolyimide der selben Zusammensetzung 6 und vergleichbarer Kettenlänge werden aus Asparaginsäure und dem Kupferchelat des Phthaloylornithins erhalten. Die Behandlung des Copolymeren 6 mit Hydrazinhydrat fuhrt zur Öffnung der Succinimid-Kettenglieder unter Bildung von Hydrazid-Seitengruppen. Die resultierenden Polyamide sind Poly(α,β-d,l-asparaginsäurehydrazid-co-d,l-ornithin), Formel 7. Kürzere Reaktionszeiten bedingen unvollständige Ringöffnung, und die verbleibenden Succinimid-Gruppen werden bei der folgenden Aufarbeitung hydrolytisch gespalten unter Bildung von Asparaginsaüre-Gruppen; die sogebildeten Polyamide besitzen die Struktur 8. Beide Polymere, 7 und 8, sind in Wasser loslich und zeigen in Wasser inharente Viskositiiten von 5 bis 14 ml g-l. Die Fahigkeit dieser Polyamide zur Arzneimittelverankerung wird durch Ankoppeln von Carbonsau- ren als Modellsubstanzen gezeigt.
    Notes: The polycondensation of d,l-aspartic acid with Nδ-phthaloyl-l-ornithine in phosphoric acid at 185°C gives rise to the formation, in 60  -  75% yield, of random copolymers of the poly(d,l-succinimide-co-Nδ-phthaloyl-D,L-ornithine) type 6 possessing inherent viscosities (DMF) in the range of 5  -  15 ml g-1. Copolyimides of the same compositions 6 and comparable chain lengths are obtained from aspartic acid and the copper chelate of the phthaloylornithine. Treatment of copolymers 6 with hydrazine hydrate in DMF leads to N-deprotection and opening of the intrachain succinimide rings with formation of hydrazide side groups. The resultant polyamides are of the poly(α,β-d,l-asparthydrazide-co-d,l-ornithine) type 7. Shorter reaction periods give incomplete hydrazinolytic ring opening, and the remaining succinimide units are cleaved hydrolytically during the subsequent aqueous workup, thereby transforming into aspartic acid units. The polyamides so formed possess the general poly(α,β-d,l-asparthydrazide-co-α,β-d,l-aspartic acid-co-d,l-ornithine) structure 8 Both types 7 and 8 are soluble in water and, in this medium, give inherent viscosities of 5  -  14 ml g-1. The potential drug-anchoring capabilities of these amine-functionalized polyamides are demonstrated by coupling reactions with model carboxylic acids.
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  • 93
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Im Zusammenhang mit Arbeiten über den Wirkungsmechanismus von Antioxidantien in Kohlenwasserstoffpolymeren unter Sauerstoffmangel wurde die Abfangreaktion des Modellradikals 1-Cyano-1-methylethyl (R°) mit N-Isopropyl-N′-phenyl-1,4-phenylendiamin (Ia) und seinem Oxidationsprodukt IIa untersucht. Reines Ia und IIa reagieren kaum mit R′, eine Mischung aus beiden ist jedoch ein effektiver Fänger fur R′, wobei R′ entweder am Stickstoffatom zwischen den aromatischen Ringen unter Bildung von VIa gebunden wird, oder unter Substitution mit dem Phenylenring reagiert, wobei VIIIa entsteht. Verbindung VIa ist labil, bei Vulkanisationstemperatur spaltet sie im neutralen Medium Olefin unter Regenerierung von Ia ab. In Gegenwart von Säuren lauft diese Reaktion auch bei niedrigerer Temperatur ab. Im Produkt VIIIa ist R′ fest gebunden, durch die Nitrilgruppe tritt jedoch eine säurekatalysierte Cyclisierung zum Indolinderivat X ein. Die Bildung von VIIIa ist ein Modell für die Entstehung einer „nichtextrahierbaren Fraktion“ des Antioxidants Ia bei der Stabilisierung von Kohlenwasserstoffpolymeren.
    Notes: In connection with the investigation of the mechanism of antioxidant action of antidegradants in hydrocarbon polymers under the conditions of a relative deficiency of oxygen, scavenging of a model alkyl (1-cyano-1-methylethyl,R°) was studied with Nisopropyl-N′-phenyl-1,4-phenylenediamine (Ia)For abbreviations see p. 11. and its oxidation product, i.e. Nisopropyl-N′-phenyl-1,4-benzoquinonediimine (IIa). While pure Ia and IIa do not react with the radical R° almost at all, their mixture is able to scavenge R° effectively. The reaction is further accelerated with acids. The alkyl R° combines with the antidegradant molecule in two ways, one of which leads to the substitution at the nitrogen atom between the aromatic rings, giving rise to VIa, while the other consists in the substitution of phenylene, leading to VIIIa. The product VIa is labile, and at vulcanization temperatures it readily splits off olefin in a neutral medium, being regenerated to Ia. In the presence of acids this reaction proceeds even at lower temperatures. In the other product, i.e. in VIIIa, the alkyl R° is bound firmly, but due to the presence of the nitrile group, VIIIa is readily cyclized by the effect of acids, and an indoline derivative X is formed. The formation of VIIIa is a model of the formation of an “unextractable fraction” of antidegradant Ia in the stabilization of hydrocarbon polymers. Investigations based on the isolation of reaction products bear at the same time evidence of the possibility of regeneration of an effective antioxidant in the stabilized substrate.
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  • 94
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The photochemical degradation of polymers (commonly known as UV degradation) takes place in two stages: First, there is the primary process comprising the rapid formation of radicals caused by quanta of visible light; this involves the dissociation of polymer chain molecules and/or the activation of polymer chain molecules respectively of additives, colorants and impurities contained in the polymer. The secondary process consists in oxidation reactions with singulett-oxygen generated by energy-transfer and/or between the polymer radicals thus formed and adsorbed oxygen, as a result of which gradual degradation of the polymer takes place.An investigation of these individual reactions using a combination of selected physical test methods leads to an unterstanding of the entire reaction sequence involved in photo-oxidative degradation. This knowledge provides a basis for systematically improving the weather-resistance of polymers by modifying their basic polymeric structure or through the controlled use of UV absorbers, quenchers, radical interceptors and antioxidants.The physical test methods themselves are divided into two categories: techniques used for investigating the primary processes (ultra short-time spectroscopy, ESR) and those used to investigate the secondary processes (XPS, FT-IR, UV/VIS et al.).With pigmented polymers, attention is focussed on borderline cases in the use of photoactive and photoinactive pigments: as a result of “photocatalytic oxidation”, photoactive pigments (e.g. TiO2 anatase) lead to additional degradation reactions which take place at the same time as the UV degradation reaction. Photoinactive pigments (e.g. high-grade TiO2-rutile and iron oxide pigments), on the other hand, exhibit negligible or no photocatalytic oxidation and, by absorbing UV radiation, provides better protection for the polymer against UV degradation.This paper gives an overview of the above-mentioned physical methods of investigating primary and secondary photochemical processes, taking a thermoplastic material (Polycarbonate) as an example. A description is also given of the photocatalytic oxidation reations which can take place if pigmented polymers are used, and there is a discussion of the degradation-inhibiting effects of inorganic pigments.
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  • 95
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The aim of the present work is to predict the warehouse storage life of polyethylene low-density, polyethylene high-density and polystyrene impact-resistent, using the method of temperature-time superposition. The properties, most representative for thermal ageing, are the relative elongation at break for polyethylene and the impact resistance for polystyrene. The validity of the predicted shelf-life is verified by estimating the change of these properties under real conditions of warehouse storage.
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  • 96
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A commercial type of impact-resistant polystyrene was investigated. Two types of antioxidants, Irganox 245 and Irganox PS-800 were added to polystyrene in ammounts of 0,05 to 0.20%. Films, dumbbells and straight test pieces were subjected to thermal and u.v. ageing. Films of 250 μ thickness were thermally treated at 100°C and separately u.v. irradiated at 360 nm for 24, 72, 120 and 168 hours. Dumbbells and straight test pieces were only thermally aged at 100°C for 7, 14, 21, 28 and 35 days. Mechanical properties were determined. The spectra of samples were recorded using Perkin-Elmer, model 1750 FTIR and Perkin-Elmer data station 7700. Colour changes of all dumbbells were measured using Elrepho apparatus in u.v.-visible region. (Changes of the content of carbonyl and hydroxyl groups, as well as of polybutadiene (PB) unsaturation in films were recorded on i.r. spektrophotometer Perkin-Elmer 257 between 4000 and 625 cm-1 and were published in the first part of this study1).
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  • 97
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    Angewandte Makromolekulare Chemie 181 (1990), S. 85-91 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Formstoffe aus aromatischen Polyepoxiden, aromatischen Polyaminen mit hochtemperaturbeständigen Strukturelementen sowie pulverförmigen Füllstoffen besitzen hervorragende Eigenschaften, wie hohe Glasübergangstemperatur, hohemechanische Festigkeit, kleinen thermischen Ausdehnungskoeffizienten und Schwerbrennbarkeit ohne Zugabe von Flammschutzmitteln. Über die Synthese dieser aromatischen Polyamine, die Herstellung und Verarbeitung der Niederdruckpreßmassen sowie die Eigenschaften der Formstoffe wird berichtet.
    Notes: Moulded materials produced from aromatic epoxide resins, aromatic polyamines with high-temperature-resistant structure units and powdered mineral fillers possess outstanding properties like high glass transition temperatures, high mechanical strength, low linear thermal expansion coefficient, and reduced flammability without the addition of flame retardants. An account is given of the synthesis of aromatic polyamines, the preparation and working of moulding materials and the properties of the finished products.
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  • 98
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    Angewandte Makromolekulare Chemie 190 (1991), S. 1-14 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Durch gemeinsame Reaktion von Benzophenontetracarbonsäuredianhydrid, Maleinsäureanhydrid und Diaminen mit 1,3,5-Triazingruppen wurden niedermolekulare Prepolymere mit Amin-Endgruppen erhalten, die sowohl 1,3,5-Triazingruppen als auch Etherbindungen enthalten. Diese reaktiven Prepolymeren sind in niedrigsiedenden Lösemitteln wie z. B. Chloroform und Tetrahydrofuran löslich. Sie wurden durch Elementaranalyse, IR- und NMR-Spektroskopie, Dampfdruckosmometrie und Viskosimetrie charakterisiert. Beim Erhitzen der Prepolymeren auf Temperaturen zwischen 180 und 190°C tritt Kettenverlängerung durch Michael-Addition auf; gleichzeitig vernetzen sie durch Reaktion der Amin- mit den Maleimid-Endgruppen. Die vernetzten Polymeren sind thermisch stabil; ihr thermisches Verhalten wurde durch TGA, DTA und isotherme Alterung untersucht. Die Biegefestigkeit und interlaminare Scherfestigkeit von aus den Prepolymeren und Carbonfasergeweben hergestellten Laminaten wurden gemessen.
    Notes: Low molecular weight amine-terminated monomaleimide prepolymers containing 1,3,5-triazine groups as well as ether linkages were synthesized by reacting benzophenone tetracarboxylic dianhydride, diamines having 1,3,5-triazine group and maleic anhydride. These reactive prepolymers are soluble in low boiling solvents such as chloroform, tetrahydrofuran etc. They were characterized by elemental analyses, IR and NMR spectroscopy, vapour pressure osmometry, and viscosity. On heating at 180-190°C these prepolymers undergo simultaneous chain extension by Michael addition reaction and crosslinking by mutual reaction between their amine-terminated and maleimide-terminated ends. The cured polymers are thermostable and the thermal behaviour was studied by TGA, DTA, and isothermal aging. Laminates fabricated using these prepolymers and carbon fiber as reinforcing agent were evaluated by their flexural strength and interlaminar shear strength.
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  • 99
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    Angewandte Makromolekulare Chemie 190 (1991), S. 15-32 
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Ein Epoxidharz wurde durch Reaktion mit Anilin bzw. Benzylamin in unterschiedlichen molaren Verhältnissen modifiziert. Die modifizierten Harze wurden dann mit Diethylamin und anschließend mit teilblockiertem Toluylendiisocyanat umgesetzt, wobei thermisch vernetzbare Harze mit tertiären Aminen in und am Ende der Polymerkette erhalten wurden. Die partielle Ansäuerung mit Essigsäure lieferte thermisch vernetzbare kationische Harze, aus denen durch Lösen in geeigneten Lösungsmitteln und Zugabe von entionisiertem Wasser Emulsionen hergestellt wurden. Diese wurden hinsichtlich ihrer Eignung zur elektrolytischen Abscheidung untersucht und verglichen. Die Ergebnisse zeigen, daß die Abscheidungsausbeute und das Streuvermögen der Emulsionen aus Benzylamin-modifizierten Epoxidharzen besser sind als die der Anilin-modifizierten Epoxidemulsionen. Ein hohes, vom pH-Wert der Emulsion abhängiges Streuvermögen ist für diese kationischen Harze charakteristisch.
    Notes: Aniline/benzylamine-modified epoxy resins with different molecular weights, which contain tertiary amines in the middle of the polymer chain, were synthesized by the reaction of aniline/benzylamine with epoxy resin at various molar ratios. The resulting aniline/benzylamine-modified epoxy resins were reacted with diethylamine and subsequently reacted with 2-ethylhexanol-blocked toluene diisocyanate to obtain thermally crosslinkable resins which contain tertiary amines at the end and in the middle of the polymer chain. These resins were partially neutralixed with acetic acid to give thermally crosslinkable cationic resins. The resulting cationic resins were dissolved in suitable solvents and mixed with deionized water to form various emulsions. The emulsion and electrodeposition properties of these resins were studied in some detail to compare the properties of these cationic resins. The results show that the deposition yields and throwing power of the emulsions prepared from benzylaminemodified epoxy resins are higher than those of the emulsions prepared from anilinemodified epoxy resins. The emulsion having proper pH values can give a high throwing power. High throwing power is the characteristic property of these modified cationic resins. Factors determining the throwing power and deposition yield of the emulsions were also investigated.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 100
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Arylacrylsäuren, wie Furylacrylsäure und Thienylacrylsäure können durch Knoevenagel-Reaktion der Arylcarbaldehyde mit Malonsäure in Pyridin dargestellt werden. Durch einfache Veresterung der Arylacrylsäuren in Methanol/Schwefelsäure werden die entsprechenden Arylacrylsäuremethylester mit guten Ausbeuten erhalten. Diese isomerisieren bei Bestrahlung mit UV-Licht (λ ≥ 280 nm) in methanolischer Lösung. Bei der Photoreaktion in Lösung wurde keine Photodimerisierung beobachtet. Die Reaktionskinetik der Photoreaktionen wurde untersucht.
    Notes: Aryl acrylic acids, e. g. furyl acrylic acid or thienyl acrylic acid are readily formed by the Knoevenagel condensation reaction of arylcarbaldehydes and malonic acid in pyridine. Esterification of these acids with methanol/sulfuric acid gives the corresponding aryl acrylic acid methyl esters in good yields. In methanolic solution these methyl esters isomerize upon irradiation (λ 280 nm). No photodimerization was observed. Kinetic data are given.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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