排序方式: 共有67条查询结果,搜索用时 31 毫秒
51.
Najah Cheriaa Rym Abidi Jacques Vicens 《Journal of inclusion phenomena and macrocyclic chemistry》2008,60(3-4):303-312
Four imidazolyl acetamido p-tert-butylcalix[4]arenes 5–8 have been prepared by reacting the corresponding methyl esters derivatives 1–4 with histamine in 1:1 mixture of methanol:toluene. The yields ranged from 56 to 68%. 5–8 have been shown to be in cone conformation. The complexation behaviour of 5–8 towards monovalent metal picrates M+Pic− with M+ = Li+, Na+, K+, Rb+ and Cs+ and divalent metal picrates M2+(Pic−)2 with M2+ = Mg2+, Ca2+, Sr2+, Ba2+, Pb2+, Cd2+, Zn2+ and Co2+ are given. Tentative localisation of the metal cations in the receptors is given. The binding properties towards these cations
have been determined along with stoichiometries of the complexes. 相似文献
52.
Najah Cheriaa Rym Abidi Jacques Vicens 《Journal of inclusion phenomena and macrocyclic chemistry》2008,62(3-4):223-229
The synthesis of a new di-imidazolyl-di-methoxy acetamido p-tert-butylcalix[4]arene 4 is reported. 4 has been prepared by reacting the corresponding di-methyl ester di-methoxy derivative with histamine in 1:1 mixture of methanol: toluene. The binding properties of 4 towards alkali, alkaline earth, transition (Zn2+, Co2+) and heavy (Pb2+, Cd2+) metals have been investigated along with the complexes stoichiometries. The 1H-NMR spectra of complexes show the location of cations in receptor 4. Partial cone conformation is observed only with strontium and calcium whereas the cone conformation is detected with most of the cations. Comparison of the complexation results with those obtained for di-imidazolyl acetamido p-tert-butylcalix[4]arene 3 missing the methyl groups is also reported. 相似文献
53.
Amel Ben Othman Young Hoon Lee Keisuke Ohto Rym Abidi Yang Kim Jacques Vicens 《Journal of inclusion phenomena and macrocyclic chemistry》2008,62(1-2):187-191
Hyperbranched molecules, 4–8, based on calixarenes attached to newly synthesised cores 2 and 3 have been prepared. Preliminary complexation studies of the complexation of Zn(Pic)2 by 8 showed that the ligand prefers to bind the picrate anions. 相似文献
54.
The main purpose of this study was to investigate the relationship between some coffee roasting variables (weight loss, density and moisture) with near infrared (NIR) spectra of original green (i.e. raw) and differently roasted coffee samples, in order to test the availability of non-destructive NIR technique to predict coffee roasting degree. Separate calibration and validation models, based on partial least square (PLS) regression, correlating NIR spectral data of 168 representatives and suitable green and roasted coffee samples with each roasting variable, were developed. Using PLS regression, a prediction of the three modelled roasting responses was performed. High accuracy results were obtained, whose root mean square errors of the residuals in prediction (RMSEP) ranged from 0.02 to 1.23%. Obtained data allowed to construct robust and reliable models for the prediction of roasting variables of unknown roasted coffee samples, considering that measured vs. predicted values showed high correlation coefficients (r from 0.92 to 0.98). Results provided by calibration models proposed were comparable in terms of accuracy to the conventional analyses, revealing a promising feasibility of NIR methodology for on-line or routine applications to predict and/or control coffee roasting degree via NIR spectra. 相似文献
55.
Rym Akkari Abdelhamid Ghorbel Nadine Essayem François Figueras 《Journal of Sol-Gel Science and Technology》2006,38(2):185-190
Sol-gel process was used to prepare silica supported sulfated zirconia catalysts. The main parameter studied in this work
was the gel drying method through four different ways of solvent evacuation. Textural, structural as well as the acidic properties
of the four samples were studied using N2 physisorption, X-ray diffraction, mass spectrometry, sulfur chemical analysis and adsorption-desorption of pyridine. The
isomerization of n-hexane was used as a catalytic test. The surface areas and the pore distributions are highly affected by
the drying mode. One of the four drying methods leads to a solid having improved textural properties and presenting both the
crystalline ZrO2 tetragonal phase and a particular type of sulfate mode bond. It seems that these three conditions are necessary for achieving
high catalytic activity. 相似文献
56.
Amel Ben Othman Najah Cheriaa Rym Abidi Jacques Vicens Pierre Thury 《Acta Crystallographica. Section C, Structural Chemistry》2004,60(12):o859-o861
The title compound, C47H60O6·3CHCl3, is the first example of a lower‐rim mono‐ester calixarene derivative to be crystallographically characterized. The cone conformation adopted by the macrocycle is stabilized by three intramolecular hydrogen bonds. Self‐inclusion of the methyl ester chain in the cavity of an adjacent molecule gives rise to infinite chains parallel to the c axis. C—H⋯π interactions involving the methyl group most imbedded in the cavity contribute to the stabilization of the system. 相似文献
57.
The Team Orienteering Problem (TOP) is a particular vehicle routing problem in which the aim is to maximize the profit gained from visiting customers without exceeding a travel cost/time limit. This paper proposes a new and fast evaluation process for TOP based on an interval graph model and a Particle Swarm Optimization inspired Algorithm (PSOiA) to solve the problem. Experiments conducted on the standard benchmark of TOP clearly show that our algorithm outperforms the existing solving methods. PSOiA reached a relative error of 0.0005% whereas the best known relative error in the literature is 0.0394%. Our algorithm detects all but one of the best known solutions. Moreover, a strict improvement was found for one instance of the benchmark and a new set of larger instances was introduced. 相似文献
58.
59.
Goong Chen Tingwen Huang Maria Christina Mariani Roza Espandeary Rym Kanes Mohammed Sheriff Srikanth Srinivasan 《Physica A》2013
The Fourier spectrum of a curve on a given interval, as represented by the Fourier series, is very reflective of the oscillatory behavior of the curve as the “weights” of the Fourier coefficients can indicate the individual prominence of frequencies of oscillations. But, unfortunately, the calculations of the Fourier coefficients can often get quite cumbersome. 相似文献
60.
Reactions of 1-Aminoalkane-1,1-diphosphonic Acids with Nitrous Acid Compounds of the structure RC(NH2)(PO3H2)2 1 give products RC(OH)(PO3H2)2 2 in high yields by the reaction with nitrous acid. In contrast, when R = Aryl the reaction of 1 often gives in concentrated hydrochloric acid RCCl(PO3H2)2 3 . Exceptions to the above reaction are described. 相似文献