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91.
Denisa Francová Petr Kaer Kvìta Jirátová Libor erveny 《Reaction Kinetics and Catalysis Letters》2004,83(1):3-9
Chromium oxides of loading ranges from 5 to 15 wt. % on γ-alumina were tested. The optimum chromium oxide loading for the
catalytic oxidation is 10 wt. %. Catalysts were investigated by BET, Raman spectroscopy and XPS. The formation of crystalline
Cr2O3 has a detrimental effect on catalysts in CH2Cl2 oxidation.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
92.
The thermally stimulated depolarization currents (TSDC) from poly(1-vinyl naphthalene) were studied over the temperature range 220–420°K. Four relaxation peaks were observed. The first three peaks (β1, β2 and β3) appeared below the glass transition temperature of the polymer. The β1 peaks seems to arise from a single dipolar relaxation process; β2, and probably β3, arise from a dipolar relaxation distributed in activation energy. The α peak could be regarded as a result of simultaneous contributions of the dipolar relaxation and conduction processes. On the basis of published work, the molecular origins of the β peaks are suggested. 相似文献
93.
F. Bunuş V. Domocoş R. Bulâceanu P. Dumitrescu G. Popescu 《Journal of Radioanalytical and Nuclear Chemistry》1976,33(2):251-262
In order to determine uranium from raw phosphoric acid solutions, resulted by the sulphuric acid attack of phosphate rocks
and the strip solutions of the solvent extraction process for uranium recovery, two classes of analytical methods were established:
one for low uranium content in phosphoric acid, and the other for higher uranium concentration in the same medium. The study
was based on specific methods, therefore interference probability with other impurities in phosphoric acid medium is low.
In the first class, X-ray fluorescence and spectrophotocolorimetric methods were used. X-ray fluorescence was applied on direct
raw phosphoric acid solution and raffinate. The last one was associated with solvent extraction [di-(2-ethylhexyl) phosphate
+ triocylphosphine oxide] on the U(IV)-Arsenazo III complex in strip. The methods of the second class, were used for strip
uranium concentrated solutions: X-ray fluorescence isotopic dilution and mass spectrometry, spectrophotocolorimetry and activation
analysis associated with gamma-spectrometry. Here spectrophotocolorimetry involves two methods. The first one is based on
the U(IV)-Arsenazo III complex and the other on direct U(IV)—phosphoric acid solutions measurements. A good agreement was
obtained in each case for all comparative measurements involving various methods. 相似文献
94.
Adrian Dumitrescu Maarten Löffler André Schulz Csaba D. Tóth 《Graphs and Combinatorics》2016,32(3):923-942
We give upper and lower bounds on the maximum and minimum number of geometric configurations of various kinds present (as subgraphs) in a triangulation of n points in the plane. Configurations of interest include convex polygons, star-shaped polygons and monotone paths. We also consider related problems for directed planar straight-line graphs. 相似文献
95.
Adrian Dumitrescu 《Periodica Mathematica Hungarica》2008,57(2):165-176
A set of points in the plane is said to be in general position if no three of them are collinear and no four of them are cocircular. If a point set determines only distinct vectors, it is called parallelogram free. We show that there exist n-element point sets in the plane in general position, and parallelogram free, that determine only O(n 2/√log n) distinct distances. This answers a question of Erd?s, Hickerson and Pach. We then revisit an old problem of Erd?s: given any n points in the plane (or in d dimensions), how many of them can one select so that the distances which are determined are all distinct? — and provide (make explicit) some new bounds in one and two dimensions. Other related distance problems are also discussed. 相似文献
96.
Adrian Dumitrescu 《Discrete and Computational Geometry》2005,33(4):687-697
We give subquadratic bounds on the maximum length of
an x-monotone path in an arrangement of n lines with at most
C log log n directions, where C is a suitable constant.
For instance, the maximum length of an x-monotone path in an
arrangement of n lines having at most ten slopes is O(n67/34).
In particular, we get tight estimates for the case of lines
having at most five directions, by showing that previous
constructions—(n3/2) for arrangements with four slopes and
(n5/3) for arrangements with five slopes—due to Sharir
and Matousek, respectively, are (asymptotically) best possible. 相似文献
97.
Adriana Ledeti Gabriela Vlase Titus Vlase Denisa Circioban Cristina Dehelean Ionut Ledeti Lenuta-Maria Suta 《Journal of Thermal Analysis and Calorimetry》2018,131(1):167-173
This paper presents the results obtained in a screening study for binary adduct formation of desipramine with three dicarboxylic acids—namely succinic, malonic and glutaric acids. Adduct formation is important because most tricyclic antidepressants show limited water solubility as free bases. Three binary adducts were prepared using a wet kneading method in non-homogenous media in presence of ethanol. Investigations of the solid state (ATR-FTIR, PXRD) and thermal analysis (TG/DTG/HF) were used for characterization of the prepared samples. The corroboration of data from employed instrumental techniques suggests that binary adducts in molar ratio 1:1 were obtained under the used experimental conditions. 相似文献
98.
Herein, we present some aspects regarding the iodination/bromination of 4-hydroxycoumarin or its O-methyl or O-acetyl derivatives with iodine monochloride or iodine monobromide as halogenation reagents. Also, the investigation of photochemical transformation of the three 3-iodocoumarins was investigated for the first time. 相似文献
99.
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. 相似文献
100.
Guangju Chen Ruozhuang Liu I. Silaghi‐Dumitrescu G. Espinosa‐Perez A. Zentella‐Dehesa F. Lara‐Ochoa 《International journal of quantum chemistry》2001,83(2):60-69
Based on the X‐ray diffraction data, electronic and magnetic properties of the (tetrakis(2‐pyridylmethyl)ethylenediamine)iron(II) perchlorate complex have been studied using three different unrestricted computational methods. The changes of energy versus temperature obtained by different computational methods are compared. The extent of spin contaminant and its influence on the energy, the spin, the charge populations, and the characteristics of molecular orbitals are analyzed in detail. Comparison of the computational results and spin‐state transition phenomena of this complex demonstrates that the B3LYP method is the most satisfactory, leading to an excellent correlation with experimental data. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 83: 60–69, 2001 相似文献