ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Reassignment of the Configuration of Several Keto-cyclolignans Prepared from Podophyllotoxin (1995)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 78 (1995), S. 1793-1796 
    Details
    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
    URL: http://dx.doi.org/10.1002/hlca.19950780713
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Isothermal cure kinetics of a diglycidyl ether of bisphenol A/1,3-bisaminomethylcyclohexane (DGEBA/1,3-BAC) epoxy resin system (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 56 (1995), S. 1029-1037 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1995.070560902
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    TTT isothermal cure diagram of a dyglicidyl ether of bisphenol A/1,3-bisaminomethylcyclohexane (DGEBA/1,3-BAC) epoxy resin system (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 61 (1996), S. 1553-1559 
    Details
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 4
    Electronic Resource
    Electronic Resource
    Isothermal cure of an epoxy/cycloaliphatic amine system. Vitrification and gelation (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 38 (1995), S. 353-356 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pi.1995.210380406
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Theoretical study of ester enolate-imine condensation route to β-lactams (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 19 (1998), S. 1826-1833 
    Details
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 6
    Electronic Resource
    Electronic Resource
    Fracture of DNA in transient extensional flow. A numerical simulation study (1996)
    New York : Wiley-Blackwell
    Biopolymers 39 (1996), S. 435-444 
    Details
    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.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
  • 7
    Electronic Resource
    Electronic Resource
    PP/LDPE blends filled with short polyamide fibers (1995)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 226 (1995), S. 129-141 
    Details
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1995.052260112
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Dimensions of short, rodlike macromolecules from translational and rotational diffusion coefficients. Study of the gramicidin dimer (1984)
    New York : Wiley-Blackwell
    Biopolymers 23 (1984), S. 611-615 
    Details
    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
    URL: http://dx.doi.org/10.1002/bip.360230402
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Computer simulation of hydrodynamic properties of semiflexible macromolecules: Randomly broken chains, wormlike chains, and analysis of properties of DNA (1990)
    New York : Wiley-Blackwell
    Biopolymers 29 (1990), S. 883-900 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The translational and rotational diffusion coefficients and the intrinsic viscosity of semiflexible, randomly broken, and wormilike chains have been obtained by Monte Carlo simulation in the context of the rigid-body treatment. Both approximate and rigorous rigid-body hydrodynamics are used, so that the error introduced by the approximate methods can be evaluated. A randomly broken chain and a wormilike chain having the same contour length and persistence length have the same radius of gyration but different values for any of the hydrodynamic properties. The two types of chains are compared in this regard. Considering that the cross section of the chain is represented by a cylinder better than by a string of spheres, we devise a cylindrical correction to be applied to the results simulated for chains of beads. Application is made to the analysis of experimental data for the translational and rotational coefficients of DNA fragments with up to 103 base pairs, obtaining the persistence length for each model. The values for the wormlike chain agree well with model-independent values obtained from radii of gyration and with other literature data at varying ionic strength. The randomly broken chain is equally able to reproduce the experimental length dependence of the properties, but the resulting persistence length may be too high.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360290603
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Persistance of the Cyclopnane Radical Anions and its Relation to Structure (1982)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 65 (1982), S. 1391-1397 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactions of [2N]cyclophanes (N = 2,⃛6) with solvated electrons in 1,2-di-methoxyethane at 193 K have been studied by ESR. and ENDOR. spectroscopy. All but the two most highly bridged cyclophanes (N = 5 and 6) are reduced to paramagnetic species under these conditions. Whereas the radical anions of [2.2]-paracyclophane and [23](1,2,4)- and [24](l,2,4,5)cyclophanes are sufficiently persistent to be characterized by their hyperfine data, those of the remaining five cyclophanes undergo a rapid cyclization to the radical anions of 4,5,9,10-tetrahydropyrenes. These have been identified as the unsubstituted tetrahydropyrene (from [2.2]-metacyclophane and [23](l,2,3)cyclophane), the 2,7-dimethyl-derivative (from [23](1,3,5)- and [24](l,2,3,5)cyclophanes) and the 1,8-dimethyl-derivative (from (24l,2,3,4)cyclophane). The persistence of the cyclophane radical anions seems to depend on the numbers, nmeta and npara, of the meta-and para-positions of the bridging ethano groups in the two benzene rings. The prerequisite for the radical anion to be persistent is nmeta≤npara.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19820650510
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...