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221.
Rose Mary Michell Alejandro J. Müller Mariya Spasova Philippe Dubois Stefano Burattini Barnaby W. Greenland Ian W. Hamley Daniel Hermida‐Merino Nicolas Cheval Amir Fahmi 《Journal of Polymer Science.Polymer Physics》2011,49(19):1397-1409
The thermal properties, crystallization, and morphology of amphiphilic poly(D ‐lactide)‐b‐poly(N,N‐dimethylamino‐2‐ethyl methacrylate) (PDLA‐b‐PDMAEMA) and poly (L ‐lactide)‐b‐poly(N,N‐dimethylamino‐2‐ethyl methacrylate) (PLLA‐b‐PDMAEMA) copolymers were studied and compared to those of the corresponding poly(lactide) homopolymers. Additionally, stereocomplexation of these copolymers was studied. The crystallization kinetics of the PLA blocks was retarded by the presence of the PDMAEMA block. The studied copolymers were found to be miscible in the melt and the glassy state. The Avrami theory was able to predict the entire crystallization range of the PLA isothermal overall crystallization. The melting points of PLDA/PLLA and PLA/PLA‐b‐PDMAEMA stereocomplexes were higher than those formed by copolymer mixtures. This indicates that the PDMAEMA block is influencing the stability of the stereocomplex structures. For the low molecular weight samples, the stereocomplexes particles exhibited a conventional disk‐shape structure and, for high molecular weight samples, the particles displayed unusual star‐like shape morphology. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 1397–1409, 2011 相似文献
222.
Germain ObameHélène Pellissier Nicolas VanthuyneJean-Bernard Bongui Gérard Audran 《Tetrahedron letters》2011,52(10):1082-1085
The enzymatic desymmetrization of methylenecyclopropane diol or its corresponding diacetate derivative, generated from a [2+1] cycloaddition between dioxepin and methylchlorocarbene, is described. After screening five commercial lipases, the two enantiomers of acetic acid 2-hydroxymethyl-3-methylene-cyclopropylmethyl ester are obtained in high yields and excellent enantioselectivities by using PFL or LPP in organic solvent. The stereostructure of the desymmetrization products was established by X-ray analysis. We also reported a new example with this non racemic chiral building block where the sign of optical rotation is dramatically solvent dependent and inverted. Using these enantiopure building blocks, a synthesis of novel nucleoside analogs is also presented. 相似文献
223.
Nicolas De Rycke 《Tetrahedron letters》2010,51(50):6521-6525
Using an imine condensation strategy, hexaazacryptands were prepared from an aromatic triamine and various dialdehydes. The global shape of these cages can be modified by simple alkylation of the six nitrogen atoms. The cavity is thus elongated and rendered hydrophobic. 相似文献
224.
We describe and to some extent characterize a new family of Kähler spin manifolds admitting non-trivial imaginary Kählerian Killing spinors. 相似文献
225.
226.
Jonathan Levine Michael R. Savina Thomas Stephan Nicolas Dauphas Andrew M. Davis Kim B. Knight Michael J. Pellin 《International journal of mass spectrometry》2009,288(1-3):36-43
Resonance ionization mass spectrometry offers extremely high sensitivity and elemental selectivity in microanalysis, but the isotopic precision attainable by this technique has been limited. Measured isotope ratios are sensitive to small fluctuations in the pointing, pulse timing, and wavelength of the resonance lasers. We show that, by minimizing these fluctuations using feedback controls and by power-broadening the optical transitions, we are able to measure chromium isotope ratios with statistics-limited precision better than 1%. Small additional improvements in reproducibility come from careful shaping of the electric field in the region where atoms are photoionized and from minimizing pulse-to-pulse variations in the time-of-flight mass spectrometer through which the photoions travel. The increased reproducibility of isotopic measurements on standard materials has enabled us to detect anomalous chromium isotopic abundances in presolar SiC grains extracted from primitive meteorites. 相似文献
227.
Corentin Boilleau Nicolas Suaud Roland Bastardis Nathalie Guihéry Jean Paul Malrieu 《Theoretical chemistry accounts》2010,126(3-4):231-241
DFT calculations are performed on a model mixed-valence system presenting a double exchange phenomenon. Due to the intrinsic multireference character of the lowest Ms components of the spin states, it is shown that the interactions involved in the double-exchange model cannot be simply extracted from the DFT energies as it is sometimes done. It is, however, possible to extract from different DFT single determinant energies the interactions of a generalized Hubbard Hamiltonian, from which, in a second step, the double-exchange spectrum may be evaluated. The problems generated by the charge and spin polarization are discussed in both symmetric and non symmetric geometries, and the sensitivity of the results to the choice of the density functional is illustrated. 相似文献
228.
Rajamalleswaramma Jogireddy Pierre‐Yves Dakas Gaëlle Valot Sofia Barluenga Nicolas Winssinger 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(43):11498-11506
A library of resorcylic acid lactones (RAL) containing a cis‐enone moiety targeting kinases bearing a cysteine residue within the ATP‐binding pocket was prepared using a fluorous‐mixture synthesis and evaluated against a panel of 19 kinases thus providing important structure–activity trends. Two new analogues were then profiled for their selectivity against a panel of 402 kinases providing the broadest evaluation of this pharmacophores’ selectivity. 相似文献
229.
We apply algebraic and vertex operator techniques to solve two dimensional reduced vacuum Einstein's equations. This leads to explicit expressions for the coefficients of metrics solutions of the vacuum equations as ratios of determinants. No quadratures are left. These formulas rely on the identification of dual pairs of vertex operators corresponding to dual metrics related by the Kramer-Neugebauer symmetry. 相似文献
230.
Daniel Schäpper Muhd Nazrul Hisham Zainal Alam Nicolas Szita Anna Eliasson Lantz Krist V. Gernaey 《Analytical and bioanalytical chemistry》2009,395(3):679-695
Biotechnology process development involves strain testing and improvement steps aimed at increasing yields and productivity. This necessitates the high-throughput screening of many potential strain candidates, a task currently mainly performed in shake flasks or microtiter plates. However, these methods have some drawbacks, such as the low data density (usually only end-point measurements) and the lack of control over cultivation conditions in standard shake flasks. Microbioreactors can offer the flexibility and controllability of bench-scale reactors and thus deliver results that are more comparable to large-scale fermentations, but with the additional advantages of small size, availability of online cultivation data and the potential for automation. Current microbioreactor technology is analyzed in this review paper, focusing on its industrial applicability, and directions for future research are presented. 相似文献