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  • 81.20.Lb  (2)
  • Camptothecin  (2)
  • Springer  (4)
  • 1
    Electronic Resource
    Electronic Resource
    Effects of particle packing on the sintered microstructure (1988)
    Springer
    Applied physics 45 (1988), S. 271-275 
    Details
    ISSN: 1432-0630
    Keywords: 81.20.Ev ; 81.20.Lb
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The sintering process is shown to be critically dependent on particle-packing density and porosity uniformity. Sintering experiments were conducted on compacts consisting of monodisperse, spherical TiO2 particles. Densification kinetics and microstructure evolution for two initial packing densities, 55% and 69% of theoretical, were investigated. The lower-density compacts sintered rapidly to theoretical density, yet improved particle-packing density and uniformity significantly enhanced densification.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00617931
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  • 2
    Electronic Resource
    Electronic Resource
    MM3(96) parameterization for camptothecin analogs: An ab initio and molecular mechanics study (1997)
    Springer
    Journal of computer aided molecular design 11 (1997), S. 61-70 
    Details
    ISSN: 1573-4951
    Keywords: Molecular mechanics ; MM3 ; Dihedral driver ; Camptothecin ; α-Hydroxy lactone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Torsional parameters for MM3(96) were derived for the missing atom types present in thenatural product camptothecin (CPT). Potential energy curves were calculated via ab initiocalculations on representative compounds for dihedral angles containing these missingparameters. Gaussian 92 at the restricted Hartree–Fock level of theory using thestandard 6-31G** and 4-31G** basis sets, was used for all the quantum-mechanicscalculations. Missing MM3 torsional terms were obtained by optimizing the V1, V2 and V3parameters such that MM3 could reproduce the ab initio torsional profile. MM3 calculatedmolecular structures that compare well with the ab initio results. Using the newly developedparameters, conformational analyses and QSAR studies of camptothecin analogs wereundertaken. MM3 predicts two distinct ‘boatlike’ conformations for the α-hydroxy lactonemoiety. The low-energy lactone conformation predicted by MM3 is in general agreement withreported X-ray crystal structures of CPT iodoacetate and 7-ethyl-10-(4-piperidino)piperidinylcarbonyloxy CPT HCl as well as the ab initio structure of a CPT-likeα-hydroxy lactone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008075411380
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  • 3
    Electronic Resource
    Electronic Resource
    Comparative molecular field analysis and molecular modeling studies of 20-(S)- camptothecin analogs as inhibitors of DNA topoisomerase I and anticancer/antitumor agents (1997)
    Springer
    Journal of computer aided molecular design 11 (1997), S. 71-78 
    Details
    ISSN: 1573-4951
    Keywords: CoMFA ; Camptothecin ; MM3
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Conformational studies and comparative molecular field analysis (CoMFA) were undertakenfor a series of camptothecin (CPT) analogs to correlate topoisomerase I inhibition with thesteric and electrostatic properties of 32 known compounds. The resulting CoMFA modelshave been used to make predictions on novel CPT derivatives. Using the newly derived MM3parameters, a molecular database of the 32 CPT analogs was created. Various point atomiccharges were generated and assigned to the MM3 minimized structures, which were used inpartial least-squares analyses. Overall, CoMFA models with the greatest predictive validitywere obtained when both the R- and S-isomers were included in the data set, andsemiempirical charges were calculated for MM3 minimized low-energy lactone structures. Across-validated R2 of 0.758 and a non-cross-validated R2 of 0.916 were obtained for MM3minimized structures with PM3 ESP charges for the 32 CPT analogs. The derived QSARequations were used to assign topoisomerase I inhibition values for compounds in this studyand compounds not included in the original data set. Prior to its appearance in the literature,an IC50 of 103 nM was predicted for the 10,11-oxazole derivative. This CoMFA predictedvalue compared favorably with the recently reported value of 150 nM. The CoMFA modelwas also evaluated by predicting the activities of recently reported 11-aza CPT and trionederivatives. The predicted activity (IC50 = 249 nM) for 11-aza CPT compared well with thereported value of 383 nM.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008027528218
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  • 4
    Electronic Resource
    Electronic Resource
    An investigation of catalytic activity in mixed metal oxide nanophase materials (1993)
    Springer
    The European physical journal 26 (1993), S. 46-50 
    Details
    ISSN: 1434-6079
    Keywords: 82.65.Jv ; 81.20.Lb
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present preliminary evidence for catalytic activity by unsupported mixed metal oxide nanocrystalline materials. The results of this study show that a nanophase form of Li-MgO has begun to exhibit catalytic activity by 300 °C. This is at least 200 degrees below the temperature at which conventional Li-MgO catalysts exhibit comparable activity. Furthermore, at higher temperatures, the same nanophase composition shows enhanced activities and somewhat improved hydrocarbon selectivities over conventional Li-MgO catalysts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01429104
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