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  • 1
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 942-944 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The photochemistry of an appropriately substituted bisimide has been studied in solution by conventional means and time resolved laser techniques as a model for the behavior of inherently photosensitive solvent soluble polyimides, whose photochemistry are not well understood. A mechanism for the photochemical insolubilization of the polymer systems is suggested based on the results for the model system, which is confirmed by time resolved laser studies of polyimide solutions. Phosphorescence quenching rate constants for the model compound indicate that the triplet excited state is about one order of magnitude more reactive than triplet benzophenone, an increase most likely due to the inductive effect of the imide moieties.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0003-3146
    Keywords: polyethylene ; photo-oxidation ; weathering ; mechanism ; kinetics ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The kinetics of the natural and accelerated photo-oxidation of low-denisty polyethylene (LDPE) films have been studied; different geographical locations have been selected for the natural tests, and a range of temperatures used in the accelerated experiments in a specially built temperature-controlled ultraviolet radiation enclosure. A meaningful correlation between natural and accelerated weathering results was established, by means of an adequate superposition of the effects of UV radiation exposure and temperature. Reasonably detailed and accurate, lumped-parameter, kinetic models of the photo-oxidation process have also been developed, to interpret and predict the results of measurements of carbonyl, hydroperoxide and vinyl absorbances as functions of time and temperature; the models predict the general experimental behaviour, and also that both the formation of hydroperoxides and carbonyl Norrish-I reactions are important initiation steps. More complex models have the potential of interpreting other fine details of the degradation behaviour, namely the generation of other chemical species, and the chain scission and cross-linking process which are directly related to changes in the mechanical properties.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Publication Date: 2021-05-19
    Description: Varios individuos del pargo cunaro Rhomboplites aurorubens fueron observados formando cardúmenes heteroespecíficos entre 10 y 20 m de profundidad en un arrecife coralino en Isla Tesoro (Archipiélago del Rosario, Caribe colombiano). Uno de esos ejemplares fue colectado y examinados sus caracteres meristicos y morformétricos, así como su contenido estomacal y madurez sexual. Se compara con la literatura existente sobre la biología y ecología de este pargo para tratar de explicar su presencia en esas condiciones.
    Description: Several individuals of the vermilion snapper Rhomboplites aurorubens were observed swimming in hetero specific schools between 10 and 20 m depth in a coral reef at Isla Tesoro (Archipiélago del Rosario, Colombian Caribbean). One of those specimens was collected and its meristic and morphometric characters examined, as well as its stomach content and sexual maturity. A comparison with the literature on the biology and ecology of this snapper is made in an attempt to explain its presence on those conditions.
    Description: Published
    Description: Reefs Fishes,
    Keywords: Fish ; Fish ; Stomach content
    Repository Name: AquaDocs
    Type: Journal Contribution
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  • 4
    Publication Date: 2021-05-19
    Description: Se describen 19 especies de peces colectadas en los archipiélagos coralinos de las islas del Rosario y de San Bernardo, las cuales son nuevos registros para el Caribe continental colombiano. Tres de esas especies (Ichthyapus ophioneus, Calamopteryx goslinei y Apogon leptocaulus) no habían sido colectadas antes en el Caribe sur, por lo que estos récords son nuevos para este sector del Mar de las Antillas. Se incluye información sobre aspectos biológicos y ecológicos de las especies.
    Description: 19 species of fishes coliected in the coralline archipelagos of Islas de) Rosario and San Bernardo, which are reponed for the first time for the Colombian continental Car¡bbean, are described. Three of those species (Ichtyapus ophioncus, Calamopteryx goslmei and Apogon leptocaulus) had not been collected before in the southern Caribbean, being therefore new records for this section of the Sea. Biological and ecological information about the 19 species is given as well.
    Description: Published
    Keywords: Fish ; Ecology ; Biology ; Fish ; New records ; Biology ; Ecology
    Repository Name: AquaDocs
    Type: Journal Contribution
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  • 5
    Publication Date: 2021-05-19
    Description: Se presenta una comparación de fa ictiofauna de arrecifes coralinos de las regiones de Cartagena (Islas del Rosario e Islas de San Bernardo) y de Santa Marta (incluyendo el Parque Nacional Tayrona), Caribe colombiano, con base en los resultados de más de cinco años de muestreo en esta última y de 76 horas de observaciones y colectas subacuáticas en las islas cercanas a Cartagena. Se ha encontrado que numerosas especies que existen en la región de Cartagena no habitan o tienen poblaciones muy reducidas en los arrecifes adyacentes a Santa Marta, mientras que sí habitan en las Islas Bahamas, separadas geográficamente de Cartagena por una distancia casi 8 veces mayor. Factores como la relativa inestabilidad ambiental, la influencia de corrientes de aguas lurbias y el menor desarrollo de las formaciones coralinas estarían actuando como limitantes para el desarrollo de estos peces en el área de Santa Marta. Se analiza también la distribución en Venezuela de las especies consideradas, donde se presenta un fenómeno similar al del Caribe colombiano por la influencia de aguas turbias y aguas de surgencias sobre ciertas regiones.
    Description: A comparison of reef fish fauna frorn the Cartagena (Rosario and San Bernardo islands) and Santa Mana (including Tayrona National Park) regions, Colombian Caribbean, is presented. This comparison isbasedon more than five years of sampling in Santa Marta and on 76 hours of underwater observations and collection in the isiands around Cartagena. It has been found that manyspeciespresentin the Cartagena región do not exist or have reduced populations in the Santa Marta reefs, but are present in ihe Bahama Isiands, which are more than 8 times farther from Cartagena than Santa Marta. Such factors as the relative environmental instability. influente of turbid currents and less developed coral reefs, may be acting as limiting conditions for the development of these fishes in the Santa Marta región. The distribution in Venezuela of the species considered is also analyzed; there is a similar phenomenon to that of the Colombian Caribbean, probably produced by the influence of upwelling and turbid waters on some coastal áreas.
    Description: Published
    Keywords: Fauna ; Fish ; Sampling ; Fauna ; Fish ; Sampling
    Repository Name: AquaDocs
    Type: Journal Contribution
    Format: pp.67-77
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