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91.
Mihaela Frunza Gabriela Lisa M. I. Popa N. D. Miron Denisa Ileana Nistor 《Journal of Thermal Analysis and Calorimetry》2008,93(2):373-379
The thermal behavior of the new inorganic-organic nanohybrid materials obtained by intercalation of chloramphenicol and salicylate
into layered double hydroxides (LDHs) by direct synthesis method, anion exchange reaction and the reconstruction method was
evaluated by dynamic thermogravimetric analysis in air, at heating rates of 5°C min−1. The XRD patterns of the samples are characteristic for those of well crystallized solids with layered double hydroxide structures.
The FTIR spectroscopy results show the presence of the organic compound within the network structure of the synthesized LDHs.
The kinetic parameters (reaction order (n) apparent activation energy (E
a) and pre-exponential factor (lnA) were calculated by the Coats-Redfern method. The compensation effects were determined. 相似文献
92.
S. Dumitriu M. I. Popa I. Hăulică A. Crîngu A. Stratone 《Colloid and polymer science》1989,267(7):595-599
Ampicillin and chloramphenicol were coupled on xanthan by activation by dicyclohexyl-carbodiimide. Drug release from the support was studied in vitro for ampicillin, and in vitro and in vivo conditions for chloramphenicol. 相似文献
93.
This Article reveals a rare synthesis of pure Pr(2)O(2)CO(3) (POC) nanopowder by thermolysis (700 °C) of a single chemical precursor in an autogenic reaction. The autogenic thermolysis of praseodymium acetate is a solvent-free, efficient, and straightforward approach yielding luminescent POC nanoparticles. The as-prepared POC nanopowder converted to PrO(1.833) (PO) powder via combustion. Methodical morphological, structural, and compositional characterizations of POC and PO powders are carried out, supported by mechanistic elucidation and the photoluminescent properties. 相似文献
94.
Zdeněk Trávníček Prof. Dr. Richard Pastorek Pavel Štarha Igor Popa Václav Slovák 《无机化学与普通化学杂志》2010,636(8):1557-1564
The nickel(II) N‐benzyl‐N‐methyldithiocarbamato (BzMedtc) complexes [Ni(BzMedtc)(PPh3)Cl] ( 1 ), [Ni(BzMedtc)(PPh3)Br] ( 2 ), [Ni(BzMedtc)(PPh3)I] ( 3 ), and [Ni(BzMedtc)(PPh3)(NCS)] ( 4 ) were synthesized using the reaction of [Ni(BzMedtc)2] and [NiX2(PPh3)2] (X = Cl, Br, I and NCS). Subsequently, complex 1 was used for the preparation of [Ni(BzMedtc)(PPh3)2]ClO4 ( 5 ), [Ni(BzMedtc)(PPh3)2]BPh4 ( 6 ), and [Ni(BzMedtc)(PPh3)2]PF6 ( 7 ). The obtained complexes 1 – 7 were characterized by elemental analysis, thermal analysis and spectroscopic methods (IR, UV/Vis, 31P{1H} NMR). The results of the magnetochemical and molar conductivity measurements proved the complexes as diamagnetic non‐electrolytes ( 1 – 4 ) or 1:1 electrolytes ( 5 – 7 ). The molecular structures of 4 and 5· H2O were determined by a single‐crystal X‐ray analysis. In all cases, the NiII atom is tetracoordinated in a distorted square‐planar arrangement with the S2PX, and S2P2 donor set, respectively. The catalytic influence of selected complexes 1 , 3 , 5 , and 6 on graphite oxidation was studied. The results clearly indicated that the presence of the products of thermal degradation processes of the mentioned complexes has impact on the course of graphite oxidation. A decrease in the oxidation start temperatures by about 60–100 °C was observed in the cases of all the tested complexes in comparison with pure graphite. 相似文献
95.
Silica-based monolithic capillary columns—Effect of preparation temperature on separation efficiency
Josef Planeta Dana MoravcováMichal Roth Pavel KarásekVladislav Kahle 《Journal of chromatography. A》2010,1217(36):5737-5740
The temperature effects during the sol–gel process and ageing of the silica-based monolith on the structure and separation efficiency of the capillary columns (100 μm i.d., 150 mm) for HPLC separations were studied. The tested columns were synthesized from a mixture of tetramethoxysilane, polyethylene glycol and urea under the acidic conditions. The temperature was varied from 40 °C to 44 °C and formation of bypass channels between the silica mold and the capillary wall was examined. The temperature of 43 °C was estimated as optimal for preparation of efficient silica capillary columns which were subsequently modified by octadecyldimethyl-N,N-diethylaminosilane or covered by poly(octadecyl methacrylate) and tested using standard mixture of alkylbenzenes under the isocratic conditions. 相似文献
96.
We report a method of engineering generalized synchronization (GS) in chaotic oscillators using an open-plus-closed-loop coupling strategy. The coupling is defined in terms of a transformation matrix that maps a chaotic driver onto a response oscillator where the elements of the matrix can be arbitrarily chosen, and thereby allows a precise control of the GS state. We elaborate the scheme with several examples of transformation matrices. The elements of the transformation matrix are chosen as constants, time varying function, state variables of the driver, and state variables of another chaotic oscillator. Numerical results of GS in mismatched Ro?ssler oscillators as well as nonidentical oscillators such as Ro?ssler and Chen oscillators are presented. 相似文献
97.
We obtain the infimum of the Hyers–Ulam stability constants for Stancu, Bernstein and Kantorovich operators and prove that in a class of certain positive linear operators this infimum for Bernstein operator has a minimality property. 相似文献
98.
In this note we are concerned with numerical solutions to Dirichlet problem $$[\phi(u')]' =f(x) \quad \mbox{in} [\alpha, \beta]; \quad u(\alpha)=A, \; u(\beta)=B, $$ where \(\phi :(-\eta , \eta ) \to \mathbb {R}\) \((\eta <+ \infty )\) is an increasing diffeomorphism with \(\phi '(y)\geq d >0\) for all \(y\in (-\eta , \eta )\) . The obtained algorithm combines the shooting method with Euler’s method and it is convergent whenever the problem is solvable. We provide numerical experiments confirming the theoretical aspects. 相似文献
99.
In constraining iterative processes, the algorithmic operator of the iterative process is pre-multiplied by a constraining operator at each iterative step. This enables the constrained algorithm, besides solving the original problem, also to find a solution that incorporates some prior knowledge about the solution. This approach has been useful in image restoration and other image processing situations when a single constraining operator was used. In the field of image reconstruction from projections a priori information about the original image, such as smoothness or that it belongs to a certain closed convex set, may be used to improve the reconstruction quality. We study here constraining of iterative processes by a family of operators rather than by a single operator. 相似文献
100.
In this paper we obtain a result on Hyers–Ulam stability of the linear functional equation in a single variable $f(\varphi (x)) = g(x) \cdot f(x)$ on a complete metric group. 相似文献