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1.
Bismuth molybdate in the alpha phase Bi2Mo3O12 behaves as an intrinsic semiconductor, whereas the gamma phase (Bi2MoO6) appears as an n-type semiconductor, whose conduction electrons originate from the formation of Bi+ interstitials in the excess Bi2O3 layer, present at the surface. The elimination of the excess of Bi2O3 could account for the synergic effect observed in the mild catalytic oxidation of propene.
- Bi2Mo3O12 , -, Bi2MoO6 n-, Bi+ Bi2O3 , . Bi2O3 , .相似文献
2.
The electrostatic interaction pressure of charged surface layers is considered qualitatively and quantitatively. In the case of mutual penetration of the surface layers in addition to Maxwell stress and osmotic resp. hydrostatic pressure an isotropic stress on the fixed charges carrying molecules of the surface layers has to be taken into account. The derivation of the pressure-distance equations is given starting from both thermodynamic/electrostatic and hydrostatic/electrostatic principles. A possible biological significance of the additional stress is discussed emphasizing its role in modifying the structure of surface layer molecules.List of symbols
e
0
elementary charge
-
k
Boltzmann constant
-
n
i
concentration of theith ionic species in the bulk solution
-
P
hydrostatic pressure
-
P
hydrostatic pressure in the bulk volume (× )
-
P
h
integration constant, independent on ×:P
h
=P(h)
-
T
absolute temperature
-
Z
i
electrovalence of theith ionic species
-
thickness of the surface layer
-
,
0
relative and absolute permittivities
-
II(×)
osmotic pressure at position ×
-
II
osmotic pressure in the bulk solution (× )
-
osmotic pressure in the symmetry plane of interacting identical surface layers (electric field strength equals zero)
-
integration constant, independent on ×:
-
e
h
electrostatic component of the disjoining pressure
e
h
=
e
(h)
-
(×)
mobile charge density profile (cations and anions of the electrolyte)
-
(×)
fixed charge density profile
-
t(x)
total charge density profile (
t
= +)
-
1(x)
fixed charge density profile of one of the two surface layers (
1(×) 0 for 0×)
-
(×)
electric potential profile 相似文献
3.
Goebbert C. Bisht H. Al-Dahoudi N. Nonninger R. Aegerter M.A. Schmidt H. 《Journal of Sol-Gel Science and Technology》2000,19(1-3):201-204
A new wet chemical concept to produce coatings by dip, spin or spray processes is presented. It is based on the preparation of solutions made of crystalline nanoparticles fully redispersable in a solvent. It is exemplified for the preparation of SnO2 : Sb (ATO) and In2O3 : Sn (ITO) transparent conducting coatings. The process combines the advantages of using particles having already a low resistivity and the possibility to sinter the coatings at low temperature. The particles are prepared using an in-situ monitoring of the surface energy to control the growth of the particles and to avoid their agglomeration. The dried powders can be fully redispersed in alcohol (ITO) or water (ATO). Single layers with thickness up to 200 nm (ATO) and 400 nm (ITO) have been fabricated. The sheet resistance of the coatings decreases with the sintering temperature. Typical values are 430 for ATO (550°C) and 380 for ITO (550°C). Sols made by redispersing the powders in organosilanes allow to produce coatings at low temperature with antistatic (R
> 100 k) and anti-glare properties (R
> 100 k, 60 to 80 gloss units). 相似文献
4.
I. A. Sukhina M. A. Agzamova B. A. Imomnazarov M. I. Isaev 《Chemistry of Natural Compounds》2000,36(4):373-376
Cyclosiversigenin 6-O--L-rhamnopyranoside and 6-O--D-glucopyranoside were isolated fromAstragalus coluteocarpusBoiss. (Leguminosae) andAstragalus dissectusB. Fedtsch. et N. Ivanova, respectively. Cyclosiversigenin 5-O--L-rhamnopyranoside was shown to be an artifact forAstragalus coluteocarpus.Thus, the cyclosiversigenin 6-O--D-glucopyranoside that was isolated from certainAstragalusspecies is hypothesized also to be an artifact. Glycosylation of the 6 -hydroxyl group of cycloartanes by D-glucose and D-xylose, in contrast with other substituents, does not change the low-field position of the PMR signal of the 4-CH
3
group (1.65 2.01 ppm) that is caused by the influence of deuteropyridine directly on the 6 -hydroxyl. Obviously one of the hydroxyls of the -D-glucopyranoside or -D-xylopyranoside residues has the same effect in this instance. 相似文献
5.
Wojciech Duczmal Beata Maciejewska Elżbieta Śliwińska Bogdan Marciniec 《Transition Metal Chemistry》1995,20(2):162-165
Summary Trisubstituted silanes, HSiR3–n
X
n
(R = Me, Et, Pr or Bu; X = Cl, OEt or Ph; and n = 0–3) readily undergo oxidative addition to complex [RhCl(cod)PPh3] (where cod = cycloocta-1,5-diene).The quantitative correlation between rate constants, k
1, of the reaction, followed spectrophotometrically at 20 °C in benzene solutions, and the structure of tri-substituted silanes represented by stereoelectronic parameters , and E of the substituents, was established: logk
1 = a + b + c + dE. The reaction rate is accelerated by electron-withdrawing substituents at silicon and retarded by the bulk and pd donation of nonalkyl substituents.Author to whom all correspondence should be directed. 相似文献
6.
Résumé Sous azote ou sous vide, le sulfite ferreux anhydre se décompose vers 210° en magnétite, pyrite et dioxyde de soufre. Concurremment une réaction de dismutation intervient avec formation de FeSO4, Fe3O4 et FeS2. Lorsque la température atteint 320°, la pyrite et le sulfate réagissent ensemble pour donner Fe1–xS, Fe3O4 et SO2. Au-delà de 370° le sulfure ferreux non-stchiométrique commence à réagir à son tour avec le sulfate restant pour former de la magnetite et du dioxyde de soufre.
In nitrogen or under vacuum, anhydrous iron(II) sulfite decomposes near 210° to magnetite, pyrite and sulfur dioxide. A parallel disproportionation reaction occurs with formation of FeSO4, Fe3O4 and FeS2. When the temperature reaches 320°, pyrite and sulfate react together to give Fe1–xS, Fe3O4 and SO2. Above 370° the non-stoichiometric ferrous sulfide begins to react with the remaining sulfate to give magnetite and sulfur dioxide.
Zusammenfassung Unter Stickstoff oder im Vakuum zersetzt sich das wasserfreie Eisen(II)-sulfit in der Nähe von 210 °C zu Magnetit, Pyrit und Schwefeldioxid. Parallel hierzu findet eine Disproportionierung unter Bildung von FeSO4, Fe3O4 und FeS2 statt. Wenn die Temperatur 320 °C erreicht, reagieren Pyrit und Sulfat unter Bildung von Fe1–xS, Fe3O4 und SO2 Oberhalb von 370 °C beginnt das nichtstöchiometrische Eisensulfit seinerseits mit dem restlichen Sulfat zu reagieren um Magnetit und Schwefeldioxid zu ergeben.
(II) 210° , . FeSO4, Fe3O4 FeS2. 320°, , Fe1–xS, Fe3O4 SO2. 370° .相似文献
7.
Zusammenfassung -Acyl--alkyl-methylentriphenylphosphorane, (C6H5)3P=CC(OR1)(R2), setzen sich mit Acetylazid zu 4-R1-5-R2-N-Acetyl-1,2,3-triazolen um. R1 kann auch Doppelbindungen enthalten oder Äthoxyl sein. Dieselben Triazolverbindungen erhält man auch, wenn man die genannten -Oxophosphorylene zuerst mit Acetylchlorid, und anschließend mit NaN3 umsetzt. Nur im Falle des Phosphorylens1g liefert die zuletzt genannte Führung der Reaktion ein anderes Produkt, die -Azidovinylcarbonylverbindung2g. Aus dem Phosphorylen1h entsteht auf beiden Reaktionswegen der -Azidoacrylester2d.
Reactions with phosphoroorganic compounds, XXIV: Reaction of -acyl--alkyl-methylene-triphenyl-phosphoranes with acetyl azide
-Acyl--alkylmethylenetriphenylphosphoranes (C6H5)3P=C(COR1)(R2) react with acetyl azide to give 4-R1-5-R2-N-acetyl-1,2,3-triazoles, where R1 is an unsaturated lower alkyl or an ethoxy group. The same reaction products are formed by acylation and subsequent treatment with sodium azide. Only in the case of the phosphoroylene1g the two-step modification of the reaction leads to the -azidovinylcarbonyl compound2g. The -azidoacrylester2d, however, is formed from the phosphoroylene1h in either way.相似文献
8.
A. S. Stolyarenko V. I. Grishkovets A. S. Shashkov V. Ya. Chirva 《Chemistry of Natural Compounds》2000,36(3):295-298
The structures of four triterpene glycosides from leaves ofScheffleropsis angkae (Araliaceae) are established using chemical and NMR methods. The structures 3-O--D-glucopyranosyl-(1-3)-O--L-arabinopyranosides of oleanic and ursolic acids and their 28-O--L-rhamnopyranosyl-(1-4)-O--gentiobiosyl ethers are proposed for L-E1, L-E2, L-K1, and L-K2, respectively. L-K1 and L-K2 are new triterpene glycosides.Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 239–241, May–June, 2000. 相似文献
9.
L. I. Vereshchagin L. D. Gavrilov E. I. Titova L. G. Tikhonova S. R. Buzilova 《Chemistry of Heterocyclic Compounds》1976,12(11):1212-1214
Acetylenic - and -keto alcohols and acetals of acetylenic - and -keto alcohols and acetals of acetylenic - and -formyl alcohols undergo cyclization to -dihydropyrones and -dihydrofuranones under the influence of acids.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1471–1473, November, 1976. 相似文献
10.
The reaction of phenylacetylene with CO and n-butanol in toluene (363 K) catalyzed by the Pd(dba)2/m(CF3COOH)/n(Ph3P) system (dba is dibenzylideneacetone; 2 m 8; 10 n 30) is studied. The initial rate of the main product (butyl 2-phenylpropenoate) buildup is found to depend on the pressure of CO and the concentrations of reactants and system components. The state of the catalyst under reaction conditions is studied in situby IR spectroscopy. A kinetic model is developed based on the experimental results. This model corresponds to the mechanism that resembles the hydride mechanism in the type of main intermediates in the catalytic cycle. 相似文献
11.
Y. Kitazawa Y. Kunimoto M. Wakihara M. Taniguchi 《Journal of Thermal Analysis and Calorimetry》1982,25(2):279-290
The phase diagram of the La-S-O system at 1073 K was established with the vacuum seal technique. Six phases exist at this temperature: La2O3 (B-type), LaS2, La2S3, La2O2SO4, La2O2S and La2O2S2. The thermodynamic functions for the reaction La2O2SO4=La2O3+SO2+1/2 O2 were determined by using the emf method at temperatures from 1123 to 1373 K. The mechanisms of the oxidation reactions in the La-S-O system under different partial pressures of oxygen (–4.4 < log
<–0.7) were also investigated by means of DTA, TG and powder X-ray diffractometry.
Zusammenfassung Das Phasendiagramm des La-S-O-Systems bei 1073 K wurde bestimmt. Bei dieser Temperatur liegen 6 Phasen vor, und zwar La2O3 (B-Typ), LaS2, La2S3, La2O2SO4, La2O2S und La2O2S2. Für die Reaktion La2O2SO4=La2O3+SO2+1/2 O2 wurden die thermodynamischen Funktionen im Temperaturbereich von 1123–1373 K nach der EMF-Methode bestimmt. DTA, TG und Pulver-Röntgendiffraktometrie wurden zur Untersuchung der Mechanismen der im La-S-O-System verlaufenden Oxydationsreaktionen herangezogen, wobei der Sauerstoffpartialdruck in den Grenzen von – 4.4 < log < <-0.7 variiert wurde.
La-S-O 1073 . : La2O3 (-), LaS2, La2S3, La2O2SO4, La2O2S La2O2S2. . . ., La2O2SO4=La2O3+ SO2+1/2 2 1123–1373. , La-S-O –4.4 < log < –0.7.相似文献
12.
A. A. Kicha A. I. Kalinovskii N. I. Ivanchina Yu. N. El'kin V. A. Stonik 《Russian Chemical Bulletin》1994,43(10):1726-1730
Four new polyhydroxysteroids, 5-cholesta-3,5,6,15,16,25,26-heptaol, 24-ethyl-5-cholesta-3,5,6,15,28,29-heptaol-29-sulfate, (22E)-24-methyl-5-cholest-22-ene-3,5,6,15,25,26-hexaol-26-sulfate, 24-propyl-5-cholesta-3,5,6,8,15,28,29-heptaol, and the known 5-cholesta-3,5,6,15,16,26-hexaol, have been isolated from the starfishCtenodiscus crispatus.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1821–1825, October, 1994. 相似文献
13.
A. I. Shushin 《Theoretical and Experimental Chemistry》1981,17(1):1-6
Conclusions The investigation carried out has shown that in the diffusion approximation, which is valid when the effective length of the free path =vov is much smaller than the dimension of the nonadiabatic region, an adiabatic limit is achieved only under the condition vv 1. This case cannot be described when (4) is assumed to be valid for , since this equation is fulfilled only when vv 1. It is perfectly natural that the use of Eq. (4) produces a strong interaction between the terms of the quantum subsystem, i.e., we do not attain an adiabatic limit. In the work it was shown that at the adiabatic limit the rate of transitions between the terms decreases rapidly with increasing vv.The condition vv 1 strongly restricts the region for the applicability of (4) and, therefore, of (12). In this sense, expression (21) is a significant generalization of (14), since it was obtained only under the. assumption and VD 1. However, the range of parameters which satisfy these inequalities corresponds to a fairly narrow group of processes; therefore, it would be of interest to also investigate the region of a. This question will be the subject of the next report.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 17, No. 1, pp.3–9, January–February, 1981.In conclusion, we express our sincerest thanks to I. V. Aleksandrov, S. Ya. Umanskii, and M. Ya. Ovchinnikova for numerous and useful discussions. 相似文献
14.
Activities of catalysts obtained in the reaction of [MCl(C8H14)2]2, (M=Rh, Ir) with amines NH2(CH2)nNH2, (N=2–5), (CH3)2NC2H4(CH3)2 and 1.8=diaminonaphthalene have been examined. The most efficient catalyst was obtained with 1.3-diaminopropane.
, [MCl(C8H14)2]2. (M=Rh, Ir) NH2(CH2)nNH2, (n=2–5). (CH3)2NC2H4(CH3)2 1,8-. , 1,3-.相似文献
15.
D. W. Davidson J. E. D. Davies S. R. Gough D. Leaist J. A. Ripmeester 《Journal of inclusion phenomena and macrocyclic chemistry》1990,8(1-2):187-197
Dielectric measurements of SO2 quinol clathrates show that the reorientation of encaged SO2 molecules is very rapid and depends greatly on the degree of cage occupancy. For a-quinol sample of cage occupancy = 0.57, the reorientation rate was 1 MHz at 6 K, with a reorientational activation energy of 673 J/mol. For a sample identified by13C NMR as-quinol, and for a-quinol sample with most cages filled with Xe, SO2 reorientation rates are even greater, with activation energies of only some tens of J/mol. The low temperature dielectric studies show that some ethanol may be enclathrated in-quinol recrystallized from this solvent. The13C NMR spectra confirm the X-ray results that the lattice becomes distorted with increased SO2 content.Dedicated to Dr D. W. Davidson in honor of his great contributions to the sciences of inclusion phenomena. 相似文献
16.
Multiphoton IR dissociation of SF6 (in a mixture with CH4) under nonequilibrium conditions of a compression shock formed by an intense, gas dynamically cooled, pulsed molecular beam impacting a solid surface was studied using the HF* luminescence detection ( 2.5 m) technique. The dependences of the HF* luminescence intensity on the distance x between the region in which molecules were excited and the surface and on the laser radiation frequency at different values of x were obtained. It was shown that, as the distance x decreased from 4 to 1.5 mm, the HF* luminescence intensity increased by more than an order of magnitude as compared to the case of excitation of molecules in an undisturbed flow, whereas the frequency dependences of luminescence intensity (SF6 dissociation yield) were broadened only insignificantly. 相似文献
17.
Ligand exchange between the compounds Co(AA)2Py2 and Co(AA)Clpyx (x=1 or 3) formed in the, system, CO(AA)2–SnR2Cl2(R=Ph, Et) in chloroform with pyridine has been established to be catalyzed by SnR2Cl2. An interpretation of the catalytic action of SnR2Cl2 is suggested.
, Co(AA2py2 Co(AA)Clpyx (x=1 3) (Co(AA)2–SnR2Cl2 (R=Ph, Et) , SnR2Cl2. SnR2Cl2.相似文献
18.
M. I. Krivopustov J. Adam V. Bradnova R. Brandt V. S. Butsev P. I. Golubev V. G. Kalinnikov J. Karachuk B. A. Kulakov E.-J. Langrock G. Modolo M. Ochs R. Odoj A. N. Premyshev V. S. Pronskich Th. Schmidt V. I. Stegailov J. S. Wan V. M. Zupko-Sitnikov 《Journal of Radioanalytical and Nuclear Chemistry》1997,222(1-2):267-270
First experiments on the transmutation of long-lived129I and237Np using relativistic protons of 3.7 GeV are described. Relativistic protons generate in extended Pb-targets substancial neutron fluences. These neutrons get moderated in paraffin and are used for transmutation as follows:129I(n,)130I and237Np(n,)238Np. The isotopes130I (T
1/2-12.36 h) and238Np (T
1/2=2.117 d) were identified radiochemically. One can estimate the transmutation cross-section (n,) in the given neutron field as (129I(n,))=(10±2)b and (237Np(n,))=(140±30)b The experiments were carried out in November 1996 at the Synchrophasotron, LHE, Dubna, Russia. The investigation has been performed at the Laboratory of High Energies, JINR, Dubna. 相似文献
19.
J. C. Ménézo L. C. Hoang C. Montassier J. Barbier 《Reaction Kinetics and Catalysis Letters》1992,46(1):1-6
Decomposition of Mn3Mo2TeO12 during oxidation of toluene to benzaldehyde was observed. Depending on the surface composition of the initial catalyst, the decomposition leads to less active but highly selective MnMoTeO6 or to MnMoO4 which is not selective in toluene oxidation.
Mn3Mo2TeO12 . , MnMoTeO6, MnMoO6.相似文献
20.
J. G. H. du Preez A. Litthauer C. P. J. van Vuuren 《Journal of Thermal Analysis and Calorimetry》1980,19(2):305-311
The thermal decomposition reactions of various hexanitrato uranium(IV) species, M2U(NO3)6 where M=Cs+, NEt
4
+
, AsPh
4
+
and PPh
4
+
have been studied.The overall decomposition reaction can be described in terms of an oxidation-reduction reaction in which the nitrate oxidizes the uranium. The enthalpies of decomposition were found to be very similar, approximately 55 kJ mole–1 except for the PPh
4
+
-salt which was only 27 kJ mole–1.The decomposition kinetics of all the compounds were studied and found to be complex — especially during the initial stages of the reaction.
Zusammenfassung Die thermischen Zersetzungsreaktionen verschiedener Hexanitratouran (IV)-Arten der Formel M2U(NO3)6 (M=Cs+, NEt 4 + , AsPh 4 + und PPh 4 + ) wurden untersucht.Die allgemeine Zersetzungsreaktion kann durch eine Oxidations-Reduktionsreaktion beschrieben werden, in der Uran durch Nitrat oxidiert wird. Die Zersetzungsenthalpien erwiesen sich als sehr ähnlich, annähernd 55 kJ. mol–1 mit Ausnahme des PPh 4 + -Salzes, dessen Wert nur 27 kJ. mol–1 betrug.Die Zersetzungskinetik sämtlicher Verbindungen wurde studiert und für komplex gefunden, besonders in den Anfangsstadien der Reaktion.
Résumé On a étudié la décomposition thermique des diverses espèces d'hexanitrate d'uranium IV de formule: M2U(NO3)6 (M=Cs+, NEt 4 + , AsPh 4 + et PPh 4 + ).La réaction générale de la décomposition peut être décrite par une réaction d'oxydo-réduction, dans laquelle le nitrate oxyde l'uranium. On a trouvé que les enthalpies de décomposition étaient très similaires, environ 55 kJ. mole–1, à l'exception du se! de PPh 4 + dont la valeur n'était que 27 kJ. mole–1.On a étudié la cinétique de décomposition de tous les composés. Elle est complexe, spécialement pendant les étapes initiales de la réaction.
oypaa(IV) M2U(NO3)6, M=Cs+, Et4N+, Ph4As+ Ph4P+. - , . , 55 .–1, Ph4P+ — , 27 .–1. , .相似文献