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91.
Szmytkowski C Piotrowicz M Domaracka A Kłosowski L Ptasińska-Denga E Kasperski G 《The Journal of chemical physics》2004,121(4):1790-1795
Absolute total cross sections (TCSs) for electron scattering from boron trifluoride (BF(3)) and phosphorus trifluoride (PF(3)) molecules have been measured using a linear transmission method. The electron energy ranges from 0.6 to 370 eV for BF(3) and from 0.5 to 370 eV for PF(3). The TCS energy dependence for BF(3) exhibits two very pronounced enhancements: resonantlike narrow feature located near 3.6 eV with the maximum value of 19.2 x 10(-20) m(2), and intermediate energy very broad enhancement with two humps, one centered around 21 eV (18.8 x 10(-20) m(2) in the maximum) and the other near 45 eV (19.5 x 10(-20) m(2)). For PF(3) the TCS has quite different low-energy dependence: at 0.5 eV it has a high value of 70 x 10(-20) m(2) and decreases steeply towards higher energies. Beyond the minimum near 5.5 eV, the TCS reveals two distinct humps: the resonant one centered near 11 eV with the peak value of 32.9 x 10(-20) m(2) and the second one much broader around 35 eV (27.9 x 10(-20) m(2)). The present TCSs for trifluorides are compared to each other as well as to previous TCS data for selected perfluorides and to results for their perhydrided counterparts. The differences and similarities in the shape and magnitude of TCSs are pointed out. 相似文献
92.
β-Nitro-5,10,15,20-tetraphenylporphyrin and its zinc complex, or 2,7-dinitro-5,10,15,20-tetraphenylporphyrin, react with 1,3-dihydrobenzo[c]thiophene 2,2-dioxide in refluxing 1,2,4-trichlorobenzene, giving rise to chlorins, bacteriochlorins or isobacteriochlorins. The products obtained are attractive intermediates for further functionalization of porphyrins and may be of potential use as sensitizers in photodynamic therapy. 相似文献
93.
Jacek Gruszczak Michael Heller Zdzisław Pogoda 《International Journal of Theoretical Physics》1991,30(4):555-565
It is shown that if a space-time (M, g) is time-orientable and its Levi-Civita connection [in the bundle of orthonormal frames over (M, g)] is reducible to anO(3) structure, one can naturally select a nonvanishing timelike vector field and a Riemann metricg
+ onM. The Cauchy boundary of the Riemann space (M, g
+) consists of endpoints ofb-incomplete curves in (M, g); we call it theCauchy singular boundary. We use the space-time of a cosmic string with a conic singularity to test our method. The Cauchy singular boundary of this space-time is explicitly constructed. It turns out to consist of what should be expected. 相似文献
94.
A C1-class of plane closed curves is considered, which contains all ovals and rosettes. This class is divided into some subclasses for which greatest lower bounds of numbers of antipodal and arc-antipodal sets are determined. 相似文献
95.
Adams methods for neutral functional differential equations 总被引:1,自引:0,他引:1
Zdzisław Jackiewicz 《Numerische Mathematik》1982,39(2):221-230
Summary In this paper Adams type methods for the special case of neutral functional differential equations are examined. It is shown thatk-step methods maintain orderk+1 for sufficiently small step size in a sufficiently smooth situation. However, when these methods are applied to an equation with a non-smooth solution the order of convergence is only one. Some computational considerations are given and numerical experiments are presented. 相似文献
96.
M. Malinowski S. Krzyżanowski S. Szczepańska 《Journal of Thermal Analysis and Calorimetry》1972,4(3):281-292
Thermogravimetry was applied to the investigation of the phenomena of adsorption, chemisorption, desorption and surface reactions on solid catalysts. The measurements were carried out with 13 NaX and NaY type zeolites and with silica gels treated with sodium hydroxide, in the presence of cumene and methanol. On the basis of the quantitative results it is possible to give an interpretation of surface phenomena and to establish the existence of various active centres on the surface of the catalysts.
The authors express their gratitude to Prof. S. Malinowski for help and discussion and to Mr. W. Dziklinski for his technical help. 相似文献
Zusammenfassung Adsorptions-, Chemisorptions- und Desorptionserscheinungen, sowie Oberflächenreaktionen an festen Katalysatoren wurden thermogravimetrisch untersucht. Die Messungen wurden an Zeoliten der Typen 13 NaX und NaY und an mit Natriumhydroxid behandelten Silikagelen in Gegenwart von Cumol und Methanol durchgeführt. Aufgrund der quantitativen Ergebnisse war es möglich, die Oberflächenerscheinungen zu deuten und das Vorhandensein von verschiedenen aktiven Zentren an der Katalysatoroberfläche nachzuweisen.
Résumé On a appliqué la méthode thermogravimétrique à l'étude des phénomènes d'adsorption, de chemisorption et de désorption ainsi qu'aux réactions de surface sur des catalyseurs solides. Les mesures ont été effectuées sur zéolites de type 13 NaX et NaY et sur des silicagels traités par la soude en présence de cumène et de méthanol. Des résultats quantitatifs permettent de donner une interprétation des phénomènes de surface et d'établir l'existence de divers centres actifs à la surface des catalyseurs.
, , , . , , , , . 13 NaX NaY , . .
The authors express their gratitude to Prof. S. Malinowski for help and discussion and to Mr. W. Dziklinski for his technical help. 相似文献
97.
Anna Katafias Olga Impert Przemysław Kita Grzegorz Wrzeszcz 《Transition Metal Chemistry》2004,29(8):855-860
Oxidation of the trans-[Cr(cyca)(OH)2]+ complex, where cyca = meso-5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane, by [Fe(CN)6 ]3- ion in strongly alkaline media, leading to [CrV O(cycaox )]3+ ion, has been studied using electronic and e.p.r. spectroscopy. The kinetics of the CrIII → CrIV transformation have been studied using a large excess of the reductant and OH- ion over the oxidant. The reaction is a second order process: first order in [CrIII] and [FeIII] at constant [OH-]. The second order rate constant is higher than linearly dependent on the OH- concentration. The mechanism of the reaction has been discussed. A relatively inert intermediate chromium(V) species was detected based on characteristic bands in the visible region and the e.p.r. signal at giso = 1.987 for the systems where an excess of oxidant was used. The hyperfine structure of the main e.p.r. signal is consistent with the d1 -electron interactions with four equivalent nitrogen nuclei and [CrV = O(cycaox)]3+ formula, where cycaox = oxidized cyca, can be postulated for the intermediate CrV complex. 相似文献
98.
Vila-Romeu N Nieto-Suarez M Dynarowicz-Łatka P 《The journal of physical chemistry. B》2005,109(31):14965-14970
The behavior of binary mixed Langmuir monolayers from gramicidin A (GA) and ethyl nonadecanoate (EN), spread on aqueous subphases containing NaCl and CaCl2, was investigated on the basis of the analysis of surface pressure-average area per molecule (pi-A) isotherms complemented with Brewster angle microscopy (BAM) images. Compression modulus versus surface pressure (C(S-1)-pi) curves indicate the existence of interactions in the GA-EN mixed monolayers at low surface pressures (below 5 mN m(-1)). However, for mixtures in which the ester is the predominant component, both GA and EN are miscible within regions from fully expanded to collapse. To examine the interactions between both components in the studied system, values of the mean molecular area per molecule (A12) were plotted as a function of molar fraction of gramicidin A (X(GA)). A12-X(GA) plots exhibit negative deviations from ideality at high surface pressures, wherein beta-helices of GA are vertically oriented in respect to the interface. However, at surface pressures below the plateau transition, which is due to reorientation of GA, the binary system obeys the additive rule. Brewster angle microscopy (BAM) was applied for a direct visualization of the monolayers morphologies. The obtained images prove that for molar ratios of GA > or = 0.3 and at surface pressures above 5 mN m(-1), both components are immiscible at the interface. The observed negative deviations from the additively rule were attributed to the formation of a three-dimensional phase in the mixed film, which provokes its contraction at the interface. 相似文献
99.
Czesław Wyganowski 《Microchemical Journal》1982,27(1):13-17
Gallium in the presence of surfactants (NTGE and CTA) forms with BPR a violet ternary complexes with λmax at 615 and 625 nm, respectively, with molar absorptivities of 7.0 × 104 and 1.3 × 105 liters mol?1 cm?1. These complexes can be advantageously used for the determination of gallium. The molar ratio of gallium to BPR, which is 1:1 in the binary complex, increases to 1:3 in the ternary complex. The presence of surfactants changes the number of BPR molecules bonded to gallium. This is the main factor in the increase in color intensity. Numerous metals interfere. Gallium can be separated by extraction of gallium from 7 M hydrochloric acid with diisopropyl ether. 相似文献
100.
Magdalena Kloskowska Jarosaw Chojnacki Wiesaw Wojnowski Barbara Becker 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(11):m541-m544
The title complex, [Li2(D2O)6][Li(C9H27SSiO3)2]2·2D2O, is the first compound with an S—M bond (M = alkali metal) within an unusual type of lithate anion, [Li(SR)2]− {where R is Si[OC(CH3)3]3}. There is a centre of symmetry located in the middle of the Li2O2 ring of the cation. All Li atoms are four‐coordinate, with LiO4 (cations) and LiO2S2 (anions) cores. The singly charged [Li(SR)2]− anions are well separated from the doubly charged [Li2(D2O)6]2+ cations; the distance between Li atoms from differently charged ions is greater than 5 Å. Both ion types are held within an extended network of O—D⋯O and O—D⋯S hydrogen bonds. 相似文献