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81.
Mathieu Y. Laurent Vivien StockerValéry Momo Temgoua Gilles DujardinRobert Dhal 《Tetrahedron letters》2011,52(14):1608-1611
A new family of analogs of steganacin, an important antimitotic compound, was accessed. It takes advantage of a completely stereoselective sequence of two key steps. The central dihydropyrane core is built by a highly diastereoselective and facially controlled hetero-Diels-Alder reaction. It is followed by a nonphenolic biaryl oxidative coupling with a complete atropo-stereoselectivity. It leads to a quick way to form cyclic biaryl lignans. 相似文献
82.
C Alonso-Ramos R Halir A Ortega-Moñux P Cheben L Vivien I Molina-Fernández D Marris-Morini S Janz DX Xu J Schmid 《Optics letters》2012,37(17):3534-3536
Integrated polarization rotators are known to exhibit stringent fabrication tolerances, which severely handicap their practical application. Here we present a general polarization rotator scheme that enables both the compensation of fabrication errors and wavelength tunability. The scheme is described analytically, and a condition for perfect polarization conversion is established. Simulations of a silicon-on-insulator polarization rotator show polarization extinction ratios in excess of 40 dB even in the presence of large fabrication errors that in a conventional rotator configuration degrade the extinction ratio to below 5 dB. Additionally, wavelength tuning over ±30 nm is shown. 相似文献
83.
84.
85.
Multiple Timescales, Mixed Mode Oscillations and Canards in Models of Intracellular Calcium Dynamics
Emily Harvey Vivien Kirk Martin Wechselberger James Sneyd 《Journal of Nonlinear Science》2011,21(5):639-683
A range of representative models of intracellular calcium dynamics are surveyed, with the aim of determining which model characteristics
are qualitatively unchanged by changes to details of the model components. Techniques from geometric singular perturbation
theory are used to investigate the role of separation of timescales in determining model dynamics, with particular emphasis
on identifying parameter regimes in which mixed mode oscillations are present as a result of the separation of timescales.
We find that the number of distinct timescales and the number of variables evolving on each timescale varies between models
and depends on both the model assumptions and on the parameter regime of interest within the model, but in all cases, the
presence of canards and associated mixed mode oscillations provides a mechanism by which the models can robustly exhibit complex
oscillations, with the frequency of oscillation depending sensitively on parameter values. We find that analysis of the number
and nature of the distinct timescales in a model allows us to make useful predictions about the dynamics associated with the
model, and that this may give us more information about the model dynamics than a classification according to the modelling
assumptions made about different cellular mechanisms in deriving the models. 相似文献
86.
C. Finck O. Stézowski F.A. Beck D.E. Appelbe T. Byrski S. Courtin D.M. Cullen D. Curien G. de France G. Duchêne S. Ertürk B.J.P. Gall U. Garg B. Haas N. Khadiri B. Kharraja N. Kintz A. Nourreddine D. Prévost C. Rigollet H. Savajols P.J. Twin J.P. Vivien K. Zuber 《The European Physical Journal A - Hadrons and Nuclei》1998,2(2):123-127
87.
F. Mougel F. Augé G. Aka A. Kahn-Harari D. Vivien F. Balembois P. Georges A. Brun 《Applied physics. B, Lasers and optics》1998,67(5):533-535
3+ :Ca4GdO(BO3)3 (Nd:GdCOB). 21 mW of green cw laser emission for an absorbed pump power of 820 mW were achieved under laser diode-pumping.
64 mW of green cw laser output were obtained with 1 W of absorbed pump power under titanium-sapphire pumping. Its availability
in large-size crystals with good optical quality makes Nd:GdCOB a true challenger to the best SFD laser crystal reported so
far: Nd:YAl3(BO3)4 (Nd:YAB or NYAB).
Received: 2 March 1998/Revised version: 20 May 1998 相似文献
88.
We study a simple transport model driven out of equilibrium by reservoirs at the boundaries, corresponding to the hydrodynamic limit of the symmetric simple exclusion process. We show that a nonlocal transformation of densities and currents maps the large deviations of the model into those of an open, isolated chain satisfying detailed balance, where rare fluctuations are the time reversals of relaxations. We argue that the existence of such a mapping is the immediate reason why it is possible for this model to obtain an explicit solution for the large-deviation function of densities through elementary changes of variables. This approach can be generalized to the other models previously treated with the macroscopic fluctuation theory. 相似文献
89.
Chan Kiang Lim Hemaroopini Subramaniam Yee How Say Vivien Yi Mian Jong Hamid Khaledi Chin Fei Chee 《Natural product research》2015,29(21):1970-1977
A new chromanone acid, namely caloteysmannic acid (1), along with three known compounds, calolongic acid (2), isocalolongic acid (3) and stigmasterol (4) were isolated from the stem bark of Calophyllum teysmannii. All these compounds were evaluated for their cytotoxic and antioxidant activities in the MTT and DPPH assays, respectively. The structure of compound 1 was determined by means of spectroscopic methods including 1D and 2D NMR experiments as well as HR-EIMS spectrometry. The stereochemical assignment of compound 1 was done based on the NMR results and X-ray crystallographic analysis. The preliminary assay results revealed that all the test compounds displayed potent inhibitory activity against HeLa cancer cell line, in particular with compound 1 which exhibited the highest cytotoxic activity comparable to the positive control used, cisplatin. However, no significant antioxidant activity was observed for all the test compounds in the DPPH radical scavenging capacity assay. 相似文献
90.
A. Vivien 《Fresenius' Journal of Analytical Chemistry》1884,23(1):427-428
Ohne Zusammenfassung 相似文献