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911.
Deij MA ter Horst JH Meekes H Jansens P Vlieg E 《The journal of physical chemistry. B》2007,111(7):1523-1530
Knowledge of the nucleation and growth behavior of polymorphs is vital in a variety of industrial applications. With the aid of the growth probability method the nucleus size is obtained as a function of the driving force for crystallization by simulating the growth probability of clusters of various sizes. From these values the cluster interfacial energy can be computed, allowing for the determination of the nucleation rate. The simulations show that nucleation of the metastable form of a yellow isoxazolone dye dominates at higher driving forces while below a certain driving force the stable form nucleates. Two other compounds show dominant nucleation of their stable form, even at extreme driving forces. This is in accordance with experimental findings for all these compounds. The growth probability method is therefore a promising indicator for polymorph nucleation behavior. 相似文献
912.
Vera L. M. Silva Artur M. S. Silva Diana C. G. A. Pinto José A. S. Cavaleiro Attila Vasas Tamás Patonay 《Monatshefte für Chemie / Chemical Monthly》2008,5(1):1307-1315
Several (E)- and (Z)-3-styrylchromones were prepared by two different methodologies, the Wittig reaction of chromone-3-carboxaldehyde with benzylic ylides and the Knoevenagel condensation of chromone-3-carboxaldehyde with phenylacetic acids in the presence of potassium tert-butoxide under microwave irradiation. The Knoevenagel reaction followed by a decarboxylation offered an efficient and diastereoselective method for preparing (E)-3-styrylchromones in a shorter reaction time. It was also demonstrated that phenylacetic acid can also be substituted with
success by phenylmalonic acid. The stereochemistry of all products was assigned by NMR experiments. 相似文献
913.
Luciana Vera‐Candioti María J. Culzoni Alejandro C. Olivieri Héctor C. Goicoechea 《Electrophoresis》2008,29(22):4527-4537
Drug monitoring in serum samples was performed using second‐order data generated by CE‐DAD, processed with a suitable chemometric strategy. Carbamazepine could be accurately quantitated in the presence of its main metabolite (carbamazepine epoxide), other therapeutic drugs (lamotrigine, phenobarbital, phenytoin, phenylephrine, ibuprofen, acetaminophen, theophylline, caffeine, acetyl salicylic acid), and additional serum endogenous components. The analytical strategy consisted of the following steps: (i) serum sample clean‐up to remove matrix interferences, (ii) data pre‐processing, in order to reduce the background and to correct for electrophoretic time shifts, and (iii) resolution of fully overlapped CE peaks (corresponding to carbamazepine, its metabolite, lamotrigine and unexpected serum components) by the well‐known multivariate curve resolution‐alternating least squares algorithm, which extracts quantitative information that can be uniquely ascribed to the analyte of interest. The analyte concentration in serum samples ranged from 2.00 to 8.00 mg/L. Mean recoveries were 102.6% (s=7.7) for binary samples, and 94.8% (s=13.5) for spiked serum samples, while CV (%)=4.0 was computed for five replicate, indicative of the acceptable accuracy and precision of the proposed method. 相似文献
914.
Capillary electrophoresis and liquid-phase microextraction using porous polypropylene hollow fibers were employed for the enantioselective analyses of mirtazapine and its metabolites demethylmirtazapine and 8-hydroxymirtazapine in human urine. Before the extraction, urine samples (1.0 mL) were submitted to enzymatic hydrolysis at 37 degrees C for 16 h. Then, the enzyme was precipitated with trichloroacetic acid, the pH was adjusted to 8 with 0.5 mol/L phosphate buffer solution (pH 11) and 15% sodium chloride was further added. The analytes were transferred from the aqueous donor phase, through n-hexyl ether (organic solvent immobilized in the fiber), into 0.01 moL/L acetic acid solution (acceptor phase). The electrophoretic analyses were carried out in 50 mmol/L phosphate buffer solution (pH 2.5) containing 0.55% w/v carboxymethyl-beta-cyclodextrin. The method was linear over the concentration range of 62.5-2500 ng/mL for each mirtazapine and 8-hydroxymirtazapine enantiomer and 62.5-1250 ng/mL for each demethylmirtazapine enantiomer. The quantification limit was 62.5 ng/mL for all the enantiomers. Within-day and between-day assay precision and accuracy were lower than 15% for all the enantiomers. Finally, the method proved to be suitable for pharmacokinetic studies. 相似文献
915.
Dr. Benedict J. Elvers Sebastian Pätsch Dr. Siva S. M. Bandaru Prof. Dr. Vera Krewald Prof. Dr. Carola Schulzke Dr. Christian Fischer 《Angewandte Chemie (International ed. in English)》2023,62(25):e202303151
Heteroleptic molybdenum complexes bearing 1,5-diaza-3,7-diphosphacyclooctane (P2N2) and non-innocent dithiolene ligands were synthesized and electrochemically characterized. The reduction potentials of the complexes were found to be fine-tuned by a synergistic effect identified by DFT calculations as ligand-ligand cooperativity via non-covalent interactions. This finding is supported by electrochemical studies combined with UV/Vis spectroscopy and temperature-dependent NMR spectroscopy. The observed behavior is reminiscent of enzymatic redox modulation using second ligand sphere effects. 相似文献
916.
Selestina Gorgieva Vera Vivod Uroš Maver Lidija Gradišnik Jurij Dolenšek Vanja Kokol 《Cellulose (London, England)》2017,24(10):4235-4252
Covalent conjugation of (bis)phosphonate group-containing molecules, sodium Alendronate (Aln) and 3-AminoropylPhosphoric Acid (ApA), to Cellulose nanocrystals (CNCs) was performed via oxidation/Shiff-base reaction. Further fluorescent labelling with Rhodamine B Iso ThioCyanate (RBITC) was performed to follow CNCs interaction and potential internalization with/in human osteoblasts by confocal microscopy. Complementary analyses were applied to identify the conjugation (Atenuated Total Reflectance–Fourier Transform Infrared and UV–VIS spectroscopies), physico-chemical (Dynamic Light Scattering and Nanoparticle Tracking Analysis) and morphological (Transmission Electron Microscopy) features of native and ApA/Aln-modified CNCs in physiologically relevant environments (Phosphate Buffer Saline, Advanced Dulbecco’s Modified Eagle Medium). While conjugation did not affect the CNCs` size, the RBITC-labelling promotes their aggregation. Faster (1 h vs. 2 h) uptake by osteoblasts of RBITC-CNCoxAln, compared to RBITC-CNCoxApA, and no-internalization (in 24 h) of native RBITTC-CNC, indicate a higher affinity of Aln-modified CNCs to the cells, while all CNCs (in 0.25–0.06 wt%) promote the cell growth. Aln/Apa-modified CNCs shows high potential in drug-delivery for bone therapies, and theranostics. 相似文献
917.
We consider the approximate minimization of a given polynomial on the standard simplex, obtained by taking the minimum value over all rational grid points with given denominator \({r} \in \mathbb {N}\). It was shown in De Klerk et al. (SIAM J Optim 25(3):1498–1514, 2015) that the accuracy of this approximation depends on r as \(O(1/r^2)\) if there exists a rational global minimizer. In this note we show that the rational minimizer condition is not necessary to obtain the \(O(1/r^2)\) bound. 相似文献
918.
Permeability up-scaling using Haar Wavelets 总被引:1,自引:0,他引:1
In the context of flow in porous media, up-scaling is the coarsening of a geological model and it is at the core of water
resources research and reservoir simulation. An ideal up-scaling procedure preserves heterogeneities at different length-scales
but reduces the computational costs required by dynamic simulations. A number of up-scaling procedures have been proposed.
We present a block renormalization algorithm using Haar wavelets which provide a representation of data based on averages
and fluctuations.
In this work, absolute permeability will be discussed for single-phase incompressible creeping flow in the Darcy regime, leading
to a finite difference diffusion type equation for pressure. By transforming the terms in the flow equation, given by Darcy’s
law, and assuming that the change in scale does not imply a change in governing physical principles, a new equation is obtained,
identical in form to the original. Haar wavelets allow us to relate the pressures to their averages and apply the transformation
to the entire equation, exploiting their orthonormal property, thus providing values for the coarse permeabilities.
Focusing on the mean-field approximation leads to an up-scaling where the solution to the coarse scale problem well approximates
the averaged fine scale pressure profile. 相似文献
919.
The rheological properties of PA-6/EPM polymer blends, non-compatibilized and compatibilized with grafted ethylene propylene
rubber (EPM-g-MA), have been investigated. Linear and non-linear (relaxation both in shear and extension) experiments were
realized. Stress relaxation experiments coupled with scanning electron microscopy (SEM) analysis showed the existence of one
relaxation time and non-deformed droplets for the immiscible blend, and two relaxation times and deformed droplets for the
compatibilized ones, the second relaxation being more pronounced for higher compatibilizer contents. These results clearly
indicate that, despite the high viscosity and elasticity ratios, if high amounts of compatibilizer are added to the blend,
interfacial slip is suppressed and a high-enough adhesion between the phases is achieved for the high-viscosity dispersed
phase to be deformed.
Paper presented at the 3rd Annual European Rheology Conference, April 27–29, 2006, Crete, Greece 相似文献
920.
Lewis acidic properties of transition aluminas whose surfaces have been doped with alkaline-earth metal cations (Ca2+ and Ba2+) were studied by means of the room temperature adsorption of carbon monoxide. The vibrational features of CO adsorbed at
the surface of doped aluminas were investigated by IR spectroscopy in comparison with pure parent aluminas, while the quantitative
and energetic features were studied by adsorption microcalorimetry. Various CO adspecies were found to form at the surface
of both pure and doped-alumina, owing to the structural heterogeneity of the Al2O3 surface and to the presence of alkaline-earth metal cations. The surface heterogeneity was revealed by different vco stretching frequencies, namely vco≈2230, 2218 and 2205 cm−1 for coordinatively unsaturated tetrahedral Al3+ cations in different crystallographic configurations, and vco≈2186 and 2172 cm−1 for coordinatively unsaturated Ca2+ and Ba2+ cations, respectively. Heats of adsorption of ≈80, 70 and 55 kJ/mol were assigned to the formation of Al3+/CO complexes, ≈45 kJ/mol for Ca2+/CO and ≈30 kJ/mol for Ba2+/CO complexes. The latter value was estimated through a correlation curve existing between vco stretching frequencies and adsorption enthalpies. This correlation, already proposed in the past for CO adsorbed on non-d/d0/d10 metal cations, has been revisited and confirmed here, by including Al2O3 data for which an apparent lack of correlation between the two parameters was first observed. With respect to pure alumina,
the population of Lewis acidic sites was found to be significantly depressed by the presence of alkaline-earth cus metal cations.
These acidic sites are intrinsically weaker than tetrahedral cus Al3+ cations, as witnessed by smaller upward shifts of the vco stretching frequencies with respect to CO gas and lower heats of adsorption, in accordance with expectations from the charge/ionic
radius ratios. Ca2+ cations were found to compete in adsorbing CO with Al3+ cations more efficiently than the larger Ba2+ cations. In the case of CaO/Al2O3 systems outgassed at 1023 K, a thin surface layer of calcium aluminate, not detected by XRD or HRTEM, was suggested to form. 相似文献