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81.
In this paper, we present the results of Monte Carlo simulations for two popular techniques of long-range correlation detection — classical and modified rescaled range analyses. A focus is put on an effect of different distributional properties on an ability of the methods to efficiently distinguish between short-term memory and long-term memory. To do so, we analyze the behavior of the estimators for independent, short-range dependent, and long-range dependent processes with innovations from eight different distributions. We find that apart from a combination of very high levels of kurtosis and skewness, both estimators are quite robust to distributional properties. Importantly, we show that R/S is biased upwards (yet not strongly) for short-range dependent processes, while M-R/S is strongly biased downwards for long-range dependent processes regardless of the distribution of innovations. 相似文献
82.
Kloucek P Smid J Flesar J Havlik J Titera D Rada V Drabek O Kokoska L 《Natural product communications》2012,7(2):253-256
This work evaluates the in vitro inhibitory activity of 70 essential oils (EOs) in the vapor phase for the control of Chalkbrood disease caused by Ascosphaera apis Maassen ex Claussen (Olive et Spiltoir). Two wild strains isolated from infected honey bee colonies together with one standard collection strain were tested by the microatmosphere method. From 70 EOs, 39 exhibited an antifungal effect against A. apis standard and wild strains. The greatest antifungal action was observed for EO vapors from Armoracia rusticana, followed by Thymus vulgaris, Cymbopogon flexosus, Origanum vulgare and Allium sativum. An investigation of chemical composition by GC-MS revealed, that the most active EOs contained allyl isothiocyanate, citral, carvacrol and diallyl sulfides as the main constituents. The chemical composition plays a key role, as activities of different EOs from the same botanical species were different according to their composition. 相似文献
83.
Ladislav Ceniga 《Acta Mechanica Sinica》2010,26(1):101-106
The paper deals with analytical models of the elastic energy gradient Wsq representing an energy barrier. The energy barrier is a surface integral of the elastic energy density Wq. The elastic energy density is induced by thermal stresses acting in an isotropic spherical particle (q = p) with the radius R and in a cubic cell of an isotropic matrix (q = m). The spherical particle and the matrix are components of a multi-particle-matrix system representing a model system applicable to a real two-component material of a precipitation-matrix type. The multi-particle-matrix system thus consists of periodically distributed isotropic spherical particles and an isotropic infinite matrix. The infinite matrix is imaginarily divided into identical cubic cells with a central spherical particle in each of the cubic cells. The dimension d of the cubic cell then corresponds to an inter-particle distance. The parameters R, d along with the particle volume fraction v = v(R, d) as a function of R, d represent micro- structural characteristics of a real two-component material. The thermal stresses are investigated within the cubic cell, and accordingly are functions of the microstructural charac- teristics. The thermal stresses originate during a cooling pro- cess as a consequence of the difference am - ap in thermal expansion coefficients between the matrix and the particle, am and ap, respectively. The energy barrier Wsq is used for the determination of the thermal-stress induced strengthening aq. The strengthening represents resistance against com- pressive or tensile mechanical loading for am - ap 〉 0 or am - ap 〈 0. respectively. 相似文献
84.
Zuzana Hricovíniová Miloš Hricovíni Ladislav Petruš 《Monatshefte für Chemie / Chemical Monthly》2001,132(6):731-737
Summary. D-Glycero-D-gulo-heptose reacted with 2,2-dimethoxypropane to give its 2,3:6,7-di-O-isopropylidene derivative. Its base-catalyzed addition
to formaldehyde resulted in the formation of 2,3:6,7-di-O-isopropylidene-2-C-(hydroxymethyl)-D-glycero-D-gulo-heptofuranose. After acid hydrolysis of this aldolization product, a new branched-chain aldose, 2-C-(hydroxymethyl)-D-glycero-D-gulo-heptose, was obtained, which was stereospecifically rearranged under the catalytic action of molybdic acid to D-glycero-D-ido-oct-2-ulose.
Received October 17, 2000. Accepted December 4, 2000 相似文献
85.
Jan Lokaj Jan Moncol Monika Polakova Ladislav Petru? 《Journal of chemical crystallography》2012,42(1):89-92
Abstract
The crystal structure of 2-cyclohexylethyl α-d-mannopyranoside (C14H26O6, Mr = 290.35) has been determined by single crystal X-ray diffraction analysis. The compound crystallizes in the monoclinic crystal system with space group C2 and unit cell parameters: a = 14.2420(2), b = 6.0320(1), c = 17.8065(3) ?, β = 102.131(2)° and Z = 4. The final reliability index is 0.0256 for 2,654 observed reflections. The one molecule of 2-cyclohexylethyl α-d-mannopyranoside is localized in independent part of unit cell. The molecules of 2-cyclohexylethyl α-d-mannopyranoside are linked through O–H···O hydrogen bond into bilayer. 相似文献86.
Ladislav Novotny 《Fresenius' Journal of Analytical Chemistry》1999,363(1):55-58
The adsorption of the polyether-antibiotic monensin from an aqueous solution on mercury was used to investigate the effect
of the decreasing size of a stationary mercury drop electrode on the shape of the voltammetric desorption peak of the surfactant.
The change of the i-E curve indicated an acceleration of the transport of the surfactant to the electrode as well as of time-dependent
changes in the adsorption layer. A decrease of the radius of the hanging mercury drop electrode from 220 μm to 80 μm at a
constant accumulation time of tac = 70 s resulted in an about 4-fold increase of the evaluated signal (i-E pre-wave) of monensin. A 7-fold increase of the
voltammetric desorption peak of monensin at conc. 5 · 10–7 mol/L was observed as result of a compressive accumulation of the surfactant due to a contraction of the mercury drop electrode.
A scheme of an apparatus for voltammetric/polarographic measurements by means of the contractible (compressible) mercury drop
electrode is described. The controlled contraction of the electrode surface is presented together with preliminary results
covering a new way of accumulation of surfactants, new accumulation effects, effective in adsorptive voltammetry, and other
electroanalytical techniques.
Received: 26 March 1998 / Revised: 14 July 1998 / Accepted: 15 July 1998 相似文献
87.
Julien Antih Marketa Houdkova Klara Urbanova Ladislav Kokoska 《Molecules (Basel, Switzerland)》2021,26(21)
While the inhalation of Thymus vulgaris L. essential oil (EO) is commonly approved for the treatment of mild respiratory infections, there is still a lack of data regarding the antimicrobial activity and chemical composition of its vapours. The antibacterial activity of the three T. vulgaris EOs against respiratory pathogens, including Haemophilus influenzae, Staphylococcus aureus, and Streptococcus pyogenes, was assessed in both liquid and vapour phases using the broth microdilution volatilisation (BMV) method. With the aim of optimising a protocol for the characterisation of EO vapours, their chemical profiles were determined using two headspace sampling techniques coupled with GC/MS: solid-phase microextraction (HS-SPME) and syringe headspace sampling technique (HS-GTS). All EO sample vapours exhibited antibacterial activity with minimum inhibitory concentrations (MIC) ranging from 512 to 1024 μg/mL. According to the sampling technique used, results showed a different distribution of volatile compounds. Notably, thymol was found in lower amounts in the headspace—peak percentage areas below 5.27% (HS-SPME) and 0.60% (HS-GTS)—than in EOs (max. 48.65%), suggesting that its antimicrobial effect is higher in vapour. Furthermore, both headspace sampling techniques were proved to be complementary for the analysis of EO vapours, whereas HS-SPME yielded more accurate qualitative results and HS-GTS proved a better technique for quantitative analysis. 相似文献
88.
Ladislav Stacho 《Journal of Graph Theory》2001,36(2):117-120
We show that for any graph G, the chromatic number χ(G) ≤ Δ2(G) + 1, where Δ2(G) is the largest degree that a vertex ν can have subject to the condition that ν is adjacent to a vertex whose degree is at least as big as its own. Moreover, we show that the upper bound is best possible in the the following sense: If Δ2(G) ≥ 3, then to determine whether χ(G) ≤ Δ2(G) is an NP‐complete problem. © 2001 John Wiley & Sons, Inc. J Graph Theory 36: 117–120, 2001 相似文献
89.
90.
Chitosan, industrially acquired by the alkaline N-deacetylation of chitin, belongs to β-N-acetyl-glucosamine polymers. Another β-polymer is hyaluronan. Chitosan, a biodegradable, non-toxic, bacteriostatic, and fungistatic biopolymer, has numerous applications in medicine. Hyaluronan, one of the major structural components of the extracellular matrix in vertebrate tissues, is broadly exploited in medicine as well. This review summarizes that these two biopolymers have a mutual impact on skin wound healing as skin wound dressings and carriers of remedies. 相似文献