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101.
Pyrolysis-capillary gas chromatography (Py-cGC) represents important method to identify the analytes in the mixture after thermal degradation. This combines high effective analyte separation on-line coupled with thermal degradation process that depends on analyte structure. System of retention indices has been used for identification of the analytes after on-line pyrolysis and chromatographic separation. The pyrolysate composition has been studied during thermal degradation of polymethylmethacrylate (PMMA) at different pyrolysis temperatures and chromatographic column conditions. Homologues series of n-alkanes have been used for calculation of pyrolysate Kováts retention indices (I) and compared with mass spectrometric (MS) data of pyrolysate model mixture. To identify PMMA thermal degradation products the high density polyethylene (HDPE) as additive standard producing triplets of the olefin homologous series during co-pyrolysis has been used. These homologous series enable to calculate programmed temperature retention indices (ITPGC) to identify the analytes present in the pyrolysate. Calculated I values were compared with published I values databases to identify analytes yielded at different pyrolysis temperatures. 相似文献
102.
Kalenda Petr Koudelka Ladislav Mošner Petr Beneš Ludvík Černošek Zdeněk 《Journal of Thermal Analysis and Calorimetry》2018,131(3):2303-2310
Journal of Thermal Analysis and Calorimetry - The thermal behavior and crystallization of barium molybdate-phosphate glasses were studied in two compositional series, namely A:... 相似文献
103.
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106.
Zuzana Bujdošová Katarína Györyová Daniela Hudecová Jana Kovářová Ladislav Halás 《Chemical Papers》2010,64(5):584-591
New zinc(II) 4-chloro- and 5-chlorosalicylate complex compounds of the general formula ((4- or 5-Cl)C6H3(2-OH)COO)2Zn · L
n
(where L = methyl 3-pyridylcarbamate, phenazone; n = 2, 4) were prepared and characterized by elemental analysis, thermal analysis (TG/DTG, DTA), and IR spectroscopy. During
thermal decomposition, mpc, phen, chlorosalicylic acid, chlorophenol, carbon dioxide, and carbon monoxide were released. Volatile
products of the thermal decomposition were confirmed by mass spectrometry. The final solid product of the thermal decomposition
up to 700°C was zinc oxide or metallic zinc. Antimicrobial activity of the compounds prepared was tested against various strains
of bacteria, yeasts and filamentous fungi. The highest antimicrobial effect was determined against the G+ bacteria S. aureus. 相似文献
107.
On Hurst exponent estimation under heavy-tailed distributions 总被引:1,自引:0,他引:1
In this paper, we show how the sampling properties of the Hurst exponent methods of estimation change with the presence of heavy tails. We run extensive Monte Carlo simulations to find out how rescaled range analysis (R/S), multifractal detrended fluctuation analysis (MF-DFA), detrending moving average (DMA) and generalized Hurst exponent approach (GHE) estimate Hurst exponent on independent series with different heavy tails. For this purpose, we generate independent random series from stable distribution with stability exponent α changing from 1.1 (heaviest tails) to 2 (Gaussian normal distribution) and we estimate the Hurst exponent using the different methods. R/S and GHE prove to be robust to heavy tails in the underlying process. GHE provides the lowest variance and bias in comparison to the other methods regardless the presence of heavy tails in data and sample size. Utilizing this result, we apply a novel approach of the intraday time-dependent Hurst exponent and we estimate the Hurst exponent on high frequency data for each trading day separately. We obtain Hurst exponents for S&P500 index for the period beginning with year 1983 and ending by November 2009 and we discuss the surprising result which uncovers how the market’s behavior changed over this long period. 相似文献
108.
Zuzana Bujdošová Katarína Győryová Jana Kovářová Daniela Hudecová Ladislav Halás 《Journal of Thermal Analysis and Calorimetry》2009,98(1):151-159
New zinc(II) salicylate complex compounds of general formula (X-C6H3-2-(OH)COO)2Zn · Ln · xH2O (where X = H, 5-Cl; L = theophylline, urea; n = 2, 4; x = 1, 2, 4) were prepared and their thermal, spectral and biological properties were studied. It was found that the thermal
decomposition of hydrated compounds starts with the release of water. During the thermal decomposition of anhydrous compounds,
the release of salicylic acid, theophylline, urea, CO2, H2O and C6H5Cl takes place. Zinc oxide was found as the final product of the thermal decomposition heated up to 900 °C. The complexes
were tested against bacteria, yeasts and filamentous fungi. The highest biological activity show 5-chlorosalicylate compounds. 相似文献
109.
Ladislav Skula 《Czechoslovak Mathematical Journal》2009,59(3):759-771
On the ring R = F[x 1,..., x n ] of polynomials in n variables over a field F special isomorphisms A’s of R into R are defined which preserve the greatest common divisor of two polynomials. The ring R is extended to the ring S: = F[[x 1,..., x n ]]+ and the ring T: = F[[x 1,..., x n ]] of generalized polynomials in such a way that the exponents of the variables are non-negative rational numbers and rational numbers, respectively. The isomorphisms A’s are extended to automorphisms B’s of the ring S. Using the property that the isomorphisms A’s preserve GCD it is shown that any pair of generalized polynomials from S has the greatest common divisor and the automorphisms B’s preserve GCD. On the basis of this Theorem it is proved that any pair of generalized polynomials from the ring T = F[[x 1,..., x n ]] has a greatest common divisor. 相似文献
110.
Petrásková L Charvátová A Prikrylová V Kristová V Rauvolfová J Martínková L Jiménez-Barbero J Aboitiz N Petrus L Kren V 《Journal of chromatography. A》2006,1127(1-2):126-136
A new separation method based on the combination of exclusion and ion exchange chromatography in borate buffer was developed. It allows semi-preparatory and preparatory separation of isobaric N-acylhexosamines (C-2 epimers) and corresponding methyl glycosides (anomers and tautomers). Three types of polyolic gels were tested for these separations. Ion-exchange HPLC was used as a rapid and reliable method for the quantification of the respective analytes. NMR studies of the interactions of N-acetylhexosamines with borate confirmed the importance of a proper stereochemical arrangement of acetamido sugars for their interactions with borate anions. 相似文献