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11.
Ecaterina Stela Dragan Ionel Adrian Dinu Marcela Mihai 《Colloids and surfaces. A, Physicochemical and engineering aspects》2009,348(1-3):282-288
The interaction between strong polycations, which possess the ammonium quaternary centers attached to an acrylic macromolecular chain derived from poly(N,N-dimethylaminoethyl methacrylate) (polycations Qx), and divalent counterions was investigated by viscometry and turbidimetry. Conformational changes of polycations were influenced by the polycation charge density, counterion nature (SO42− or S2O82−) and concentration. The morphology of the polycation layers deposited onto silicon wafers has been studied by tapping mode atomic force microscopy, a strong influence of the polycation and ammonium persulfate concentration on the surface topography being observed. The optimum flocculation concentration of polycation decreased and the flocculation window increased in the presence of S2O82−, in the destabilization of kaolin model dispersion. Removal of Congo Red from aqueous solution by the complex system formed between polycations and divalent counterions was also investigated. The behavior of polycations Qx in separation processes was compared with that of one polycation containing 95 mol% N,N-dimethyl-2-hydroxypropyleneammonium chloride units in the backbone (PCA5). 相似文献
12.
Ionel Haiduc Gellert Mezei Rodica Micu‐Semeniuc Frank T. Edelmann Axel Fischer 《无机化学与普通化学杂志》2006,632(2):295-300
The three (O‐methyl)‐p‐ethoxyphenyldithiophosphonato triphenylphosphine complexes of copper, silver and gold, [(Ph3P)nM{S2P(OMe)C6H4OEt‐p}] (M = Cu, n = 2; M = Ag, Au, n = 1) investigated structurally by X‐ray diffraction exhibit remarkable structural differences. The copper compound is a four‐coordinate chelate monomer with Cu–S 2.4417(6) and 2.5048(6) Å; P–Cu–S 104.24(2)–114.01(2)°; Cu–S–P 82.49(3)° and 80.85(2)°. The silver compound is a cyclic dimer with bridging dithiophosphonato ligands and three‐coordinate silver atoms [Ag–S 2.5371(5) and 2.6867(5) Å; P–Ag–S 122.88(2)° and 122.17(2)°; Ag–S–P 89.32(2)° and 103.56(2)°]. The gold compound is monomeric with linear dicoordinate gold [Au–S 2.3218(6) Å; P–Au–S 177.72(2)°, Au–S–P 100.97(3)°]. 相似文献
13.
Ciucanu I Kaykhaii M Montero L Pawliszyn J Szubra J 《Journal of chromatographic science》2002,40(6):350-354
A novel method for the continuous monitoring of thermooxidative degradation products of polystyrene by membrane extraction with sorbent interface (MESI) and gas chromatography (GC) is developed. The results are compared with solid-phase microextraction-GC, which can extract gases, vapors, and aerosols. The volatile and semivolatile degradation products are identified by mass spectrometry. The membrane used in the MESI-GC analysis shows a high permeation for volatile aromatic hydrocarbons; a low permeation for corresponding volatile aldehydes; and no permeation for less volatile alcohols, acids, and degradation products with a high molecular weight, thus reducing significantly the number of compounds detected from MESI-GC. Sensitivity of the method depends on the time of trapping, which is limited by the breakthrough of the trap. By heating the trap at fixed intervals of time, consecutive gas chromatograms are obtained. 相似文献
14.
For the first time in the cycloimminium ylide series, we present a theoretical and experimental study concerning the correlation between structure, stability, reactivity, and biological activity of 4‐(R)‐pyrimidinium (4‐halobenzoyl)methylides (R = Me and 4‐chlorophenyl; hal = X = F, Cl, Br, I; see 5 and 6 in Scheme 1). The 4‐methylpyrimidinium (4‐halobenzoyl)methylides 5 are relatively stable compounds, while the (4‐chlorophenyl)pyrimidinium (4‐halobenzoyl)methylides 6 are more unstable. Their stability varies with the nature of the substituents at the ylide carbanion and pyrimidinium cation moieties as confirmed by quantum‐chemical calculations. The latter also disclose the possibility to use pyrimidinium ylides as nucleophilic reagents as well as 1,3‐dipoles in reactions with appropriate reagents. The experimental data obtained confirm the calculations concerning the nucleophilicity and reactivity of the ylides 5 and 6 . Moreover, the influence of microwave irradiation on the synthesis of the pyrimidinium salts 3 and 4 from pyrimidine and an organic halide is studied and reveals a remarkable reaction‐rate increase under microwave irradiation as compared to classical conditions; this allows the general and facile synthesis of the salts 3 and 4 (Scheme 1, Table 1). The in vitro biological activity of the newly obtained 4‐methylpyrimidine compounds is also tested. Some of them exhibit a remarkable activity against different microorganisms (germs and fungi) which allows to establish structure–activity correlations. 相似文献
15.
Claudio A. Téllez S. Sergio G. de la Riva Eduardo Hollauer Ionel Haiduc Cristian S. Silvestru 《光谱学快报》2013,46(7):1469-1483
Abstract The infrared and Raman spectra of dimethyldithiophosphinate anion (CH3)2PS2 were measured and the vibrational modes for the anion complex were assigned. A Normal Coordinate Analysis in the Modified General Valence Force Field (MGVFF) approximation was carried out assuming C2v symmetry. Ab Initio Calculations at RHF and MP2 level were also carried out for the anion geometry as well as for its frequencies, intensities and force constants. 相似文献
16.
An efficient and straightforward method for the preparation of spirodiazine derivatives is reported which involves mild reaction conditions and easily accessible reactants. A new class of spiroazaheterocycles, spiro[pyrrolidine-pyrrolo[3,4-c]pyrroles], is obtained. A feasible explanation is given for the unexpected results obtained at high energy (high temperatures, MW and ultrasound irradiation). 相似文献
17.
Aequationes mathematicae - The Hardy–Littlewood–Pólya inequality of majorization is extended for $$\mathbf {\omega }$$ – $$\textbf{m}$$ –star-convex functions to the... 相似文献
18.
Ionel Sorinel Ciuperca 《Journal of Dynamics and Differential Equations》1998,10(1):73-108
We consider the Schrödinger operator on two types of domains depending on a small parameter : dumbbell domains and thin domains with varying orders of thinness. In both situations we compare the eigenvalues and eigenvectors of the Schrödinger operator with the corresponding eigenvalues and eigenvectors of a limit operator defined on the limit domain. 相似文献
19.
Ionel Popescu 《Journal of Functional Analysis》2006,235(1):1-68
In this paper we prove the Morse inequalities in the non-degenerate and degenerate cases. Like the approach of J.-M. Bismut, ours is based on the idea suggested by Witten. In fact, if anything, our approach is closer to Witten's original idea than Bismut's. 相似文献
20.
Varga Zsolt Wallenius Maria Nicholl Adrian Mayer Klaus Balan Ionel Benea Vasile 《Journal of Radioanalytical and Nuclear Chemistry》2019,322(3):1585-1591
JRC-Karlsruhe obtained a swipe sample from a highly enriched uranium seizure, which had taken place in 2011. Due to the very low amount of uranium (nanograms) a new method needed to be developed to determine the U production date (age). The particles on the swipe were collected on a pyrolytic graphite planchet using a vacuum impactor and they were subsequently leached with ccHNO3. The “bulk” U isotopic composition (235U: 72.51?±?0.03 wt%) and the production date (December 1992?±?1 year) determined by MC-ICP-MS indicated that the material showed similarity with two other HEU cases seized earlier in Europe.
相似文献