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Zubia A Cossío FP Morao I Rieumont M Lopez X 《Journal of the American Chemical Society》2004,126(16):5243-5252
One reference tertiary amine and three families of structurally related trialkylamines and dendrimers have been synthesized, characterized, and studied by molecular dynamics simulations. The catalytic activity of these amines in the nitroaldol (Henry) reaction between 2-nitroethanol and benzaldehyde has been measured by FT-IR spectroscopy. It is found that, in this kind of molecule with only one catalytic center at the core, the efficiency of the catalytic process decreases with the size and/or the degree of ramification of the dendrimer. According to these results, there is a linear departure from the behavior predicted by the hard sphere collision theory (HSCT) as the size of the dendrimer increases. Therefore, the behavior of structurally related dendrimers can be quantified in terms of their molecular weight and reagent accessible surfaces. 相似文献
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The temperature dependence of the nematic electroclinic effect has been studied in binary mixtures prepared from two chiral compounds with nematic-smectic A-smectic C and nematic-smectic C phase sequences. The data obtained show a substantial difference in the magnitude of the effect, not only with the type of phase sequence, but also with the temperature range of the subsequent smectic A phase. These results suggest that short-range smectic fluctuations can play an important role in the nematic electroclinic effect at least when a smectic C phase is close to the nematic. In addition, the dynamic behaviour of the electroclinic effect has been investigated in the compound with the nematic-smectic A transition. As in previous work, an anomaly in the electroclinic response time has been found around the nematic-smectic A transition. This fact is analysed qualitatively assuming two different mechanisms contributing to the electroclinic effect. 相似文献
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Development and validation of a LC‐MS assay for the quantification of ikh12 a novel anti‐tumor candidate in rat plasma and tissues and its application in a pharmacokinetic study
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Dorleta Otaegui Carme Masdeu Eneko Aldaba Yosu Vara Aizpea Zubia Eider San Sebastian Maria Alcalá Sergio Villafruela Fernando P. Cossío Alicia Rodriguez‐Gascón 《Biomedical chromatography : BMC》2015,29(8):1249-1258
IKH12 is a novel histone deacetylase 6 selective inhibitor. A rapid and sensitive liquid chromatography tandem mass spectrometry method was developed and validated for the quantification of IKH12 in rat plasma and tissue with kendine 91 as internal standard (IS). The samples were prepared by liquid–liquid extraction with tert‐butyl methyl ether. The chromatographic separation was accomplished by using a Zorbax Extend C18 4.6 × 150 mm, 5 µm column, with a mobile phase consisting of methanol and 0.1% formic acid (75:25 v/v). Multiple reaction monitoring, using electrospray ionization in positive ion mode, was employed to quantitatively detect IKH12 and IS. The monitored transitions were set at m/z 418 → 252 and 444 → 169 for IKH12 and kendine 91, respectively. The calibration curve was linear over the concentration range 2–1000 ng mL?1. The intra‐ and inter‐assay precision and accuracy of the quality controls and the limit of quantification were satisfactory in all cases (according to European Medicines Agency guidelines). Stability studies showed that plasma samples were stable in the chromatography rack for 24 h and at ?80 °C for 2 months and also after three freeze–thaw cycles. This method was successfully applied to a pharmacokinetic study of IKH12 in rat. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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Low and high frequency dielectric spectroscopy on a liquid crystal with the phase sequence N*-SA-S*c
M. R. De La Fuente M. A. Pérez Jubindo J. Zubia T. Pérez Iglesias A. Seoane 《Liquid crystals》2013,40(6):1051-1063
Abstract Broadband dielectric measurements on a multicomponent ferroelectric liquid crystal mixture have been performed. The alignment was homeotropic and the cell and sample holder were the same in the whole frequency range. Two relaxation processes have been observed in all liquid crystal phases with shapes given by the Havriliak-Negami and inverted Havriliak-Negami functions. Strengths and frequencies of both modes have been obtained for the different phases. The values of the latter and their activation energies allowed us to assign the low and high frequency mechanism to the molecular reorientation around the transversal axis and around the longitudinal axis, respectively. The behaviour of this high frequency mode does not show any jump in the SA-S*c phase transition, neither in the amplitude nor in the frequency, indicating that the appearance of the spontaneous polarization in the S*c phase is not the consequence of the freezing of this mode. 相似文献
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An analysis of an experimental technique which allows for a simultaneous determination of several parameters with special interest for ferroelectric liquid crystals is presented. These parameters are the spontaneous polarization, the rotational viscosity and the switching time. In addition, the susceptibility associated with the soft mode free of contributions related to the helicoidal structure can also be obtained. The experimental results for these parameters for the ferroelectric liquid crystal HDOBACEEC are reported. A comparison between the switching time values deduced from the rotational viscosity and those obtained by optical measurements is performed. 相似文献
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Arrieta A Otaegui D Zubia A Cossío FP Díaz-Ortiz A de la Hoz A Herrero MA Prieto P Foces-Foces C Pizarro JL Arriortua MI 《The Journal of organic chemistry》2007,72(12):4313-4322
The stereochemical outcomes observed in the thermal and microwave-assisted [3 + 2] cycloaddition between stabilized azomethine ylides and nitrostyrenes have been analyzed using experimental and computational approaches. It has been observed that, in the absence of solvent, three stereoisomers are formed, both under classical heating conditions and under microwave irradiation. This result contrasts with that observed in solution under classical thermal conditions. The 4-nitropyrrolidines obtained in this way can be aromatized under further microwave irradiation to yield mixtures of pyrroles and 4-nitropyrroles. It is found that ground state cycloadditions between imines and nitrostyrenes take place by three-step mechanisms. The first step involves enolization of the starting imine, and this is followed by a pseudopericyclic 10-electron [1.4]-hydrogen shift. Finally, the cycloaddition takes place by a relatively asynchronous aromatic six-electron supra-supra thermal mechanism. 相似文献
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J. Zubia G. Aldabaldetreku G. Durana J. Arrue F. Jimnez 《Laser \u0026amp; Photonics Reviews》2008,2(3):182-202
This paper reviews the theoretical analysis of light propagation we have carried out on multimode multi‐step index (MSI) optical fibres. Starting from the Eikonal equation, we derive the analytical expressions that allow calculating the ray trajectories inside these fibres. We also analyse the effects of leaky rays on the transmission properties of MSI fibres. For this purpose, a single analytical expression for the evaluation of the ray power transmission coefficient is calculated. Afterwards, we investigate the effects of extrinsic and intrinsic coupling losses on the performance of MSI fibres, providing analytical expressions to calculate the coupling loss and, also, determining the most critical parameters. Finally, we carry out a comprehensive numerical analysis of the fibre bandwidth under different source configurations. 相似文献
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