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1.
An efficient way of obtaining travelling waves in a periodic fluid system is described and tested. We search for steady states in a reference frame travelling at the wave phase velocity using a first‐order pseudospectral semi‐implicit time scheme adapted to carry out the Newton's iterations. The method is compared to a standard Newton–Raphson solver and is shown to be highly efficient in performing this task, even when high‐resolution grids are used. This method is well suited to three‐dimensional calculations in cylindrical or spherical geometries. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
2.
Spectrofluorimetric characteristics of pindolol have been investigated with the aim of using this technique for analytical determinations. Other monosubstituted indole derivatives, 4-methoxy and 5-methoxyindole, have been also studied for comparative purposes. Corrected excitation and emission wavelengths in different solvents are reported and the effect of solvent on the Stokes shifts of these compounds has been analysed using the Lippert equation. In addition, the Stokes shift of pindolol has been determined in dioxan-water solvent mixtures and the presence of specific solvent effects is discussed. The fluorescence of pindolol is pH dependent, the quantum yields determined in water are lower than those in other solvents. With respect to the sensitivity, it has been found that the detection limits in aqueous solutions are improved in the presence of beta and methyl-beta-cyclodextrin. Finally, a fluorimetric analysis of the interaction between pindolol and different cyclodextrins has been carried out in order to determine the apparent stability constants of the complexes and the thermodynamic parameters associated to complexation. 相似文献
3.
M. Uzqueda G. González-Gaitano D. Wouessidjewe A. Zornoza M. Sánchez C. Martín 《Supramolecular chemistry》2013,25(8):759-769
The complexation of naftifine (NF) and terbinafine (TB) with cyclodextrins (CDs) has been investigated by UV/visible and 1H NMR spectroscopy, ROESY techniques and also ESI-MS. Both drugs form 1:1 inclusion complexes with all the CDs tested except with α-CD, as deduced from the Benesi–Hildebrand plots and confirmed by ESI-MS and NMR spectroscopy (Job plot method). The K 11 values for NF decrease in the order β-CD > methylated β-CD > 2-hydroxypropyl-β-CD >γ-CD. The determination of the enthalpy and entropy provides information about the main driving forces in the process. The stability constants of the complexes NF–β-CD, TB–β-CD and TB–γ-CD determined by 1H NMR spectroscopy are in agreement with the values obtained by UV. For TB–β-CD, the value is higher, due to the fact that the length of the TB aliphatic chain allows a deeper inclusion of the naphthalene group inside the corresponding β-CD molecule, according to the 2D ROESY experiments. 相似文献
4.
Arantxa Rodriguez 《Tetrahedron letters》2009,50(27):3942-357
Sydnones have been directly functionalised with alkenyl halides and an alkynyl bromide under palladium catalysis. 相似文献
5.
Maite Uzqueda Carmen Martín Arantza Zornoza Miguel Sánchez Itziar Vélaz 《Journal of inclusion phenomena and macrocyclic chemistry》2010,66(3-4):393-402
Terbinafine (TB) is an allylamine derivative used as oral and topical antifungal agent. The physicochemical properties of the complexes between TB and different cyclodextrins (CDs): α-CD, β-CD, hydroxypropylβ-CD, methylβ-CD and γ-CD, have been studied in pH 12 aqueous solutions at 25 °C and in the solid state. Different phase solubility profiles of TB in the presence of CDs have been obtained: AL type for TB with hydroxypropylβ-CD and γ-CD, AP type for the complexes with methylβ-CD and α-CD, while a BS profile was found for TB-β-CD. The apparent stability constants of the complexes were calculated at 25 °C from the phase solubility diagrams. The higher increase of TB solubility, up to 200-fold, together with the higher value of the stability constant were found for the complex with methylβ-CD. Solid systems of 1:1 drug:CD molar ratio were prepared and characterised using X-ray diffraction patterns, thermal analysis and FTIR spectroscopy. The coevaporation method can be considered the best method in preparing these solid complexes. The complexes of TB with natural CDs, except with α-CD, were crystalline, whereas the methyl and hydroxypropyl derivatives gave rise to amorphous phases. Dissolution rate studies have been performed with TB-β-CD and TB-HPβ-CD complexes, showing a positive influence of complexation on the drug dissolution. 相似文献
6.
Mixed-matrix membranes (MMMs) were prepared by combinations of two different kinds of porous fillers [metal-organic frameworks (MOFs) HKUST-1 and ZIF-8, and zeolite silicalite-1] and polysulfone. In the search for filler synergy, the MMMs were applied to the separation of CO(2)/N(2), CO(2)/CH(4), O(2)/N(2), and H(2)/CH(4) mixtures and we found important selectivity improvements with the HKUST-1-silicalite-1 system (CO(2)/CH(4) and CO(2)/N(2) separation factors of 22.4 and 38.0 with CO(2) permeabilities of 8.9 and 8.4 Barrer, respectively). 相似文献
7.
Application of SSA thermal fractionation and X‐ray diffraction to elucidate comonomer inclusion or exclusion from the crystalline phases in poly(butylene succinate‐ran‐butylene azelate) random copolymers
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Idoia Arandia Agurtzane Mugica Manuela Zubitur Amaia Iturrospe Arantxa Arbe Guoming Liu Dujin Wang Rosica Mincheva Philippe Dubois Alejandro J. Müller 《Journal of Polymer Science.Polymer Physics》2016,54(22):2346-2358
Poly(butylene succinate‐ran‐butylene azelate) random copolyesters were thermally fractionated by successive self‐nucleation and annealing (SSA). The samples before and after SSA were analyzed by differential scanning calorimetry (DSC) and X‐ray diffraction (WAXS and SAXS). WAXS results indicate that a small degree of comonomer inclusion is present in the crystalline phases that are formed in the copolymers depending on composition: a PBS‐like unit cell or/and a PBAz‐like unit cell, thus confirming the isodimorphic behavior of the samples. SSA on the other hand demonstrated that the degree of comonomer exclusion during crystallization is far larger than comonomer inclusion, as judged by the increase in fractionation degree with compositions leading to the pseudo‐eutectic point. Furthermore, WAXS, SAXS, and SSA results show that the isodimorphic behavior is not highly dependent on kinetic factors, as the degree of comonomer inclusion or exclusion in the samples was not significantly altered by SSA thermal fractionation, a thermal treatment that promotes annealing and molecular segregation of defects to the amorphous regions of the material. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 2346–2358 相似文献
8.
Dr. Sabina Rodríguez‐Hermida Dr. Ana Belén Lago Arantxa Pino‐Cuevas Dr. Adelheid Hagenbach Dr. Laura Cañadillas‐Delgado Prof. Rosa Carballo Prof. Ulrich Abram Prof. Ezequiel M. Vázquez‐López 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(5):1847-1853
Materials based on the cationic copper(II) hexanuclear 18‐membered metallacrown [18‐MC ‐6]6+ (2phH=2‐piconyl hydrazide) and tetrafluoroborate, perchlorate, nitrate, sulfate, and perrhenate anions were prepared by an easy method in aqueous medium. Single‐crystal X‐ray characterization of six members of this new family of complexes showed that the anions are attached to the metallacrown by direct coordination to a copper cation or by hydrogen‐bonding interaction with the center of the hexamer. The stable cationic nature of the complexes and their ability to bind different anions allows them to adsorb and immobilize environmentally relevant anions such as MO4? (M=Tc, Re). The MO4? trapping capacities suggest that these materials would be useful in the treatment of oxoanionic contaminants in water. 相似文献
9.
Victoria García Sakai Arantxa Arbe 《Current Opinion in Colloid & Interface Science》2009,14(6):381-390
The general trend in soft matter is to study systems of increasing complexity which are more technologically and biologically relevant. This is facilitated by the capability of quasielastic neutron scattering (QENS) to selectively probe spatially resolved dynamical modes at a molecular level. The large number of recent publications using QENS for investigating complex and multi-component soft matter systems, serves as recognition of the suitability of this technique by the scientific community. Exploiting its complementarity with molecular dynamics (MD) simulations and other experimental techniques is the basis of a successful methodology for this scientific challenge. We illustrate the potential of QENS with three kinds of soft materials whose structural units increase in size/complexity: lipids, polymers and biomolecules. 相似文献
10.
Pedro Carmona Arantxa Rodríguez-Casado Marina Molina 《Analytical and bioanalytical chemistry》2009,393(4):1289-1295
We describe the improvement of a novel approach to investigating hydrogen/deuterium (H/D) exchange kinetics in biomolecules
using transmission infrared spectroscopy. The method makes use of a Fourier transform infrared spectrometer coupled with a
microdialysis flow cell to determine exchange rates of labile hydrogens. With this cell system, the monitoring of exchange
reactions has been studied here as a function of some cell characteristics such as: (a) dialysis membrane surface contacting
both the H2O and D2O compartments; (b) molecular cutoff of dialysis membrane; and (c) distance between the cell-filling holes. The best improvement
has been obtained by increasing the dialysis membrane surface followed by increase of molecular cutoff. However, not significant
differences were found using various distances between filling holes. The fastest exchange rate which can be measured with
the cell system used here is found to be k = 0.41 ± 0.02 min−1, that is, about threefold greater than the one got in a previous work. This microdialysis flow cell has been used here for
the study of H/D exchange in nucleic acids with subsequent structural analysis by 2D correlation spectroscopy. 相似文献