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  • 1
    Keywords: Chemistry ; Food science
    ISBN: 9780387754307
    Language: English
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  • 2
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The configuration of several keto-cyclolignans related to podophyllotoxin has been reviewed. Under basic catalysis, the configuration at the C-atom in α-position to the lactone carbonyl group in podophyllotoxone is inverted instead of the C-atom in α-position to the ketone group, as it has been reported.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 56 (1995), S. 1029-1037 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    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: By employing differential scaning calorimetry, DSC, we have studied, under isothermal conditions, the kinetics of the cure reaction for a system containing a diglycidyl ether of bisphenol A (DGEBA) and 1,3-bisaminomethylcyclohexane (1,3-BAC) as a curing agent, over the temperature range of 60-110°C. We have determined the conversions reached at several cure temperatures and the reaction rates. The experimental data, showing an autocatalytic behavior, were compared with the model proposed by Kamal, which includes two rate constants, k1 and k2, and two reaction orders, m and n. This model gives a good description of cure kinetics up to the onset of vitrification. The activation energies for these rate constants were 44-57 kJ/mol. The reaction orders present a moderate change but their sum is in the range 2.5-3. Diffusion control is incorporated to describe the cure in the latter stages (postivitrification region). By combining the autocatalytic model and a diffusion factor, it was possible to predict the cure kinetics over the whole range of conversion. © 1995 John Wiley & Sons, Inc.
    Additional Material: 12 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 61 (1996), S. 1553-1559 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    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 isothermal cure of an epoxy-cycloaliphatic amine system has been studied following the evolution of both glass transition temperature and conversion. A functional relationship between Tg and conversion is established. The cure reaction is satisfactorily described by a phenomenological model with parameters determined from DSC experiments. By applying the kinetic model, gelation and vitrification curves are calculated and compared with experimental times to gelation and times to vitrification determined at temperatures between 50 and 100°C. The isothermal time-temperature-transformation (TTT) curing diagram including iso-Tg contours has been established. © 1996 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 38 (1995), S. 353-356 
    ISSN: 0959-8103
    Keywords: epoxy resin ; DSC ; vitrification ; gelation ; activation energy ; time-temperature-transformation diagram ; Chemistry ; Polymer and Materials Science
    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: Times to gelation and times to vitrification during isothermal curing for the epoxy system diglycidyl ether of bisphenol A and 1,3-bisaminomethyl-cyclohexane were measured at different curing temperatures between 50 and 100°C. Gelation occurs around 56% conversion. Vitrification was determined from data curves of glass transition temperature, Tg, versus curing time obtained from DSC experiments. The minimum and maximum Tg determined for this epoxy system were Tgo = -37°C and Tg∞ = 150°C. Values of activation energy of the epoxy/amine cure reaction of 58 kJ/mol and 49.5 kJ/mol were obtained from Tg versus time shift factors and gel time measurements respectively. The isothermal time-temperature-transformation diagram has been established.
    Additional Material: 5 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 19 (1998), S. 1826-1833 
    ISSN: 0192-8651
    Keywords: quantum-chemical computations ; β-lactams ; ester enolate-imine condensation ; solvent effect ; stepwise process ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The condensation reaction of the enolate of methyl acetate with formaldimine to afford a β-lactam was studied using the MP2-FC/6-31+G* level of theory taking into account the electrostatic effect of the solvent by means of a self-consistent reaction field continuum model. The reaction is a stepwise process with three main steps: the formation of the C3(SINGLE BOND)C4 bond, the closure of the β-lactam ring, and the elimination of the methoxide ion. The formation of the C3(SINGLE BOND)C4 bond is rate determining and according to our calculations is not a reversible step.   © 1998 John Wiley & Sons, Inc.   J Comput Chem 19: 1826-1833, 1998
    Additional Material: 4 Ill.
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  • 7
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    Facultad de Ciencias Naturales y Museo (FCNyM), Universidad Nacional de La Plata (UNLP) | La Plata, Argentina
    In:  hlopez@fcnym.unlp.edu.ar | http://aquaticcommons.org/id/eprint/16250 | 196 | 2015-02-18 17:17:32 | 16250 | Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata
    Publication Date: 2021-07-02
    Description: Esta serie tiene como propósito mostrar diferentes expresiones artísticas relacionadas con la Ictiología nacional, generadas en diferentes épocas y que surgen por diversas motivaciones personales que, en algún caso, muestran casi con exactitud a los modelos que inspiraron la obra, en otras, por lo contrario, responden a la imaginación y creatividad del autor.Nuestra primera contribución toma una imagen del artista Cándido López, quién a través de sus pinturas, de alguna manera , fuera un “corresponsal de guerra” de la fratricida Guerra de la Triple Alianza.En este caso contamos con la colaboración de la joven artista plástica Jimena López Miquelarena, quién aportó sus conocimientos sobre el tema central de esta serie.Sólo me resta invitar a quienes quieran sumarse a esta iniciativa, se acerquen con sus aportes para consolidar esta idea, ya que podría ser otro instrumento de difusión del conocimiento de nuestra disciplina a los diferentes estamentos de la sociedad.
    Description: Facultad de Ciencias Naturales y Museo, UNLP
    Description: ProBiota: Programa para el estudio y uso sustentable de la biota austral
    Description: Debe citarse: López, H. L & J. López Miquelarena. 2012. Cándido López. ProBiota, FCNyM, UNLP, La Plata, Argentina, Serie Arte y Sociedad en la Ictiología Nacional 1: 1-7. ISSN 1515 9329.
    Keywords: Biology ; Sociology ; Argentina ; Ichthyology-Ictiología ; Visual arts-Artistas plásticos
    Repository Name: AquaDocs
    Type: monograph
    Format: application/pdf
    Format: application/pdf
    Format: 7
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  • 8
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 39 (1996), S. 435-444 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using the Brownian dynamics simulation technique, we studied the fracture process of DNA chains subjected to transient extensional flow, letting the solution with DNA molecules pass through a very small orifice (radius = 0.0065 cm), thus experiencing extensional flow of the convergent (sink) type. The DNA molecules were modeled as FENE bead-spring chains with the springs obeying a modified Warner force law, as proposed by Reese and Zimm. The fracture yield was strongly dependent on flow rate and molecular weight, reaching, in our setup, a level of 100% at a flow rate of around 0.001 cm3/s for DNA with molecular weight 26 × 106 (T7 DNA). There was found to exist a critical flow rate (Qcrit) below which fracture did not occur, in accordance with what was observed in studies on polystyrene in transient extensional flow. We found that for DNA, the critical flow rate depended on the molecular weight as Qcrit ∼ M-14 when the hydrodynamic interaction effect (HI) was not included in the simulations. When HI was accounted for, the relation was found to be Qcrit ∼ M-1.1, close to the theoretical prediction for fracture of partly extended chains in transient extensional flow. © 1996 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 226 (1995), S. 129-141 
    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: Der Einfluß der Verstärkung von Polyethylen niedriger Dichte (LDPE) und Polypropylen (PP) sowie deren Blends mit kurzen Polyamid-66-Fasern (PA) auf das Zug-, Biege- und Schlagzähverhalten der Matrix wurde untersucht. Die Moduli der Composite nehmen mit steigendem Faser- und PP-Gehalt zu, insbesondere bei LDPE/PP-Verhältnissen größer als 1. Der Einfluß der Fasern auf die Zug- und Biegefestigkeit hängt jedoch von der Zusammensetzung der Matrix ab. Während die Fasern bei LDPE/PP-Verhältnissen größer als 1 verstärkend wirken, zeigt sich bei Compositen mit PP als kontinuierlicher Phase eine Abnahme der Zugfestigkeit. In allen Fällen nimmt die Festigkeit der Composite, bei gleichem Faseranteil, mit steigendem PP-Gehalt zu. Das Einmischen von PA-Fasern bewirkt eine Zunahme der Zugfestigkeit bei Compositen mit einem PP-Anteil über 50% in der Matrix. Aus den Ergebnissen wird geschlossen, daß die PA-Fasern vornehmlich in der LDPE-Phase verstärkend wirken, verursacht durch eine höhere Affinität zwischen PA und LDPE.
    Notes: The effect of short polyamide 66 (PA) fibers on the tensile, flexural, and impact behaviour of low density polyethylene (LDPE), polypropylene (PP), and their blends has been investigated. The moduli of the composites increase as fiber and PP contents increase, and this effect is more noticeable at LDPE/PP ratios above 1. However, the effect of the fibers on the tensile and flexural strength of these materials depends on matrix composition. So, the polyamide fibers act as a reinforcing agent for polymer matrices with LDPE/PP ratios above 1, but with PP as the continuous phase a decrease in the tensile strength is observed. In all cases, at the same fiber content, the strength of the composites increases as PP percentage increases. On the other hand, the addition of PA fibers gives rise to an increase of the tenacity of the composites with PP percentages above 50% in the matrix composition. From the observed results a higher reinforcing effect and a better affinity between the polyamide fibers and the LDPE are suggested.
    Additional Material: 8 Ill.
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  • 10
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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