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81.
Irving M Krueger CA Wade JV Hodges JC Leopold K Collins N Chan C Shaqair S Shornikov A Yan B 《Journal of combinatorial chemistry》2004,6(4):478-486
A 4-amido-pyrrolidone library that was intentionally synthesized as pairs of diastereomers was produced by solution-phase parallel syntheses and purified by an automated high-throughput purification system. A total of 2592 4-amido-pyrrolidinones were ultimately isolated as single diastereomers from a matrix of 1920 syntheses. After the four-step synthesis and HPLC purification, the average yield of a single diastereomer was 36.6%. The average chemical purity was >90%, and the average diastereomeric purity was >87%. The choice of chiral amines used to make amides with heterocyclic acid chlorides had a dramatic effect on success. Analysis of the relationship between amines used for synthesis and the diastereomeric separation showed that amides made from chiral 1,2-amino alcohols gave superior separation to amides from chiral morpholines. The presence of a hydrogen bond donor on the amide side chain seems to be required for a better diastereomeric separation. 相似文献
82.
83.
An asymptotically correct beam model is obtained for a long, thin-walled, circular tube with circumferentially uniform stiffness (CUS) and made of generally anisotropic materials. By virtue of its special geometry certain small parameters cause unusual non-linear phenomena, such as the Brazier effect, to be exhibited. The model is constructed without ad hoc approximations from 3D elasticity by deriving its strain energy functional in terms of generalized 1D strains corresponding to extension, bending, and torsion. Large displacement and rotation are allowed but strain is assumed to be small. Closed-form expressions are provided for the 3D non-linear warping and stress fields, the 1D non-linear stiffness matrix and the bending moment–curvature relationship. In bending, failure could be caused by limit-moment instability, local buckling or material failure of a ply. A procedure to determine the failure load is provided based on the non-linear response, neglecting micro-mechanical failure modes, post-failure behavior, and hygrothermal effects. Asymptotic considerations lead to the neglect of local shell interlaminar and transverse shear stresses for the thin-walled configuration. Results of the theory are illustrated for a few symmetric, antisymmetric angle-ply and unsymmetric layups and show that some previously published theories are not asymptotically correct. 相似文献
84.
G. Le Bras P. Bonville J. A. Hodges P. Imbert G. PolatsekP. Fischer L. KellerA. Dnni M. Kohgi T. Suzuki 《Physica B: Condensed Matter》1993,190(4):333-346
The Kondo lattices YbP and YbN (nonstoichiometric samples) have been investigated by 170Yb Mössbauer spectroscopy, in the temperature range 0.085 K to 80 K in zero magnetic field in YbN and with an applied magnetic field at T=0.045 K in YbP and YbN, and by neutron diffraction in YbN. In both compounds, the antiferromagnetic transition at TN0.7 K is first order and occurs through a progressive growth of paramagnetic domains as the temperature increases. The measured exchange interaction is much larger than kBTN in both compounds and it is found to be isotropic in YbP and anisotropic in YbN. The saturated magnetic moment in both compounds is reduced by 50% with respect to the value calculated from the crystal field and exchange interactions. These properties are interpreted in terms of the competition between the Kondo effect and the RKKY exchange interaction; using a model mean field NCA calculation to describe the magnetic phase, the Kondo temperatures TK are found to be near 5–10 K. 相似文献
85.
J. P. Hodges P. R. Slater P. P. Edwards C. Greaves M. Slaski G. Van Tendeloo S. Amelinckx 《Physica C: Superconductivity and its Applications》1996,260(3-4):249-256
The ambient-pressure synthesis of a new tetragonal alkaline-earth superconducting cuprate, Sr0.8Ba1.2CuO3+δ, from a cupro-oxycarbonate is reported. Magnetic-susceptibility measurements show the presence of a superconducting transition 50 K in a post-annealed sample. The crystal structure, refined from time-of-flight powder neutron-diffraction data was found to have an oxygen-deficient La2CuO4-type tetragonal T structure (a = 3.8988(3) Å and C = 12.815(3) Å) with oxygen vacancies located within the CuO2 planes. Ordering of these oxygen vacancies is responsible for the observation of a superlattice in both neutron- and electron-diffraction measurements. An interpretation of the electron-diffraction patterns suggests that the superlattice in Sr0.8Ba1.2CuO3+δ and also in the isostructural superconductor Sr2CuO3+δ are of an identical nature. 相似文献
86.
87.
John H. Hodges 《Annali di Matematica Pura ed Applicata》1969,82(1):135-142
Summary Analogs are proved for sequences in Φ=GF[q, x], the ring of polynomials in x over a finite field of q elements, of results
of Niven, Zane, and Cavior concerning uniform distribution of sequences of integers generated by polynomials with integer
coefficients. The uniform distribution (mod m), m an integer, in these papers is replaced here by a concept called weak uniform
distribution (mod M), M ε Φ.
Supported byNSF Research GrantGP 6515.
Entrata in Redazione il 21 settembre 1968. 相似文献
88.
89.