共查询到20条相似文献,搜索用时 31 毫秒
1.
WU Hongbo WANG Xiao & CHEN Jianmin Department of Environmental Science Engineering Fudan University Shanghai China 《中国科学B辑(英文版)》2005,48(1):31-37
Carbonyl sulfide (COS) is one of the most abun-dant sulfur containing gases in the troposphere andlower stratosphere[1,2]. It is relatively inert in the tro-posphere and can be transported into the stratosphere,where it dissociates under the solar ultravi… 相似文献
2.
《Fluid Phase Equilibria》2004,224(1):13-22
This work is related to the definition of a reduced thermal diffusion coefficient thanks to numerical microscale molecular dynamics simulations. This cross transport process, also called Soret effect, couples mass flux and thermal gradient and is still largely misunderstood. For this study, we have applied a boundary driven non-equilibrium molecular dynamics algorithm on Lennard–Jones spheres mixtures. Simulations have been performed at a constant reduced supercritical state, using a van der Waals’ one fluid approximation in order to fulfil the law of the corresponding states. In binary mixtures, we have studied the molecular parameters and the molar fraction influences on thermal diffusion separately and then combined. It is shown that, on pressure and on thermal conductivity, the corresponding states law is fulfilled for a wide range of molecular parameters ratios. In this frame, we have then constructed simple correlations which relate thermal diffusion factor to the mixture parameters. Combining the relations obtained, a reduced thermal diffusion factor taking into account all the various contributions has been defined. Finally, it is shown that this relation enables us to estimate thermal diffusion in various binary and ternary mixtures of Lennard–Jones spheres representing alkanes with a maximum deviation of 15%. 相似文献
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Vladimir D. Kiselev Alexander V. Bolotov Ilzida I. Shakirova Helen A. Kashaeva Lubov N. Potapova Alexander I. Konovalov 《Journal of solution chemistry》2012,41(3):525-535
In this article negative values of the activation volume in retro-Diels–Alder reactions are interpreted in terms of the different
possibilities of penetration of the solvent molecules into the sterically branched structures of the adduct and activated
complex. Empty spaces, inaccessible to penetration of solvent molecules, lead to increases of the molar volume of the screened
adducts in solution and, consequently, to a less negative value of the Diels–Alder reaction volume. The values of partial
molar volumes of anthracene, maleic anhydride and the adducts cyclopentadiene–maleic anhydride, anthracene–maleic anhydride
and anthracene–tetracyanoethylene, in several solvents, were calculated from the solution density data. 相似文献
5.
In recent hundred years the annual discharge variations of the Changjiang River (represented by the Yichang station) and the Huanghe River (represented by Shanxian and Tangnaihe, respectively) have closely related to the geographical distribution of the earthquakes coming about in China in the same year, Both the occurrence of the destructive seism or seismic swarm in the river basins and the disappearance of the shocks in the east and south of the basins are the conditions that the Changjiang and Huanghe Rivers are the high flow while that the strong earthquake of magnitude 7 or more occurred in North China is the condition for the Changjiang low flow year and that of 6 or more in the Qilian Mountains area is for the Huanghe River. In the latter part of this paper, a 2-year sample is given to explain that the conditions of the 2 rivers being high flow years are that the north-south seismic belt is active and in the meanwhile no seism occurred in South China, and those of the low flow year are that the 相似文献
6.
7.
The reactions of pentabromotoluene with i-PrONa or t-BuONa in pyridine give N-(pentabromobenzyl)pyridinium bromide and a mixture of isomeric tetrabromotoluenes. In the presence of bromine or carbon tetrabromide, the reductive debromination is blocked, and the reactions involve exclusively substitution of hydrogen in the methyl group of pentabromotoluene by the pyridinium residue. 相似文献
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9.
C.-L. Zhang S.-J. Cui Y. Wang 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2017,91(1):80-83
The solubilities of sulfamethoxydiazine in methanol, ethanol, 1-propanol, 2-propanol, acetone, and chloroform have been determined in the range 293.15–323.15 K by a static equilibrium method. The calculated results show that the correlation of the Apelblat equation for measured systems has less deviation than that of the λh equation. The positive Δsol H and Δsol S for each system revealed that sulfamethoxydiazine being dissolved in each solvent was an entropy-driven process. 相似文献
10.
L. N. Vakhitova K. V. Matvienko A. V. Skrypka N. V. Lakhtarenko N. A. Taran V. V. Rybak A. F. Popov 《Theoretical and Experimental Chemistry》2010,46(1):1-7
The kinetics of the reaction of the 4-nitrophenyl esters of diethylphosphoric and 4-toluenesulfonic acids with HO– and HOO– anions in microemulsions of the “oil-in-water” type was studied. It was shown that the reactivity of the HOO– anion depends on the nature of the detergent forming the microemulsion and decreases in the order cetyltrimethylammonium
bromide > Triton X-100 > sodium dodecyl sulfate. It was established that concentration of the reagents on the surface of the
microdrops leads to an increase of 2–3 orders of magnitude in the rate during the transition from aqueous solutions to the
microemulsion. 相似文献
11.
Giuseppina Castronuovo Vittorio Elia Filomena Velleca 《Journal of solution chemistry》1996,25(10):971-982
Calorimetric measurements were carried out at 25°C on binary aqueous solutions containing N-acetyl derivatives of the following -amino acids: glycine, alanine, valine, leucine, norleucine, aspartic acid, glutamic acid, phenylalanine, methionine, asparagine, glutamine, cysteine, histidine, serine. The N-acetyl derivative of the -amino acid proline was also studied. The results obtained have been used to calculate the pairwise enthalpic interaction coefficients and these are compared with results reported in the literature concerning free -amino acids, and their acetylamide derivatives. The coefficients largely increase passing from free amino acids to N-acetyl derivatives. The derivatives of -amino acids bearing unsubstituted alkyl chains present an increased cooperativity of hydrophobic interactions. 相似文献
12.
The transformations of 4-tert-butyl-1,2-benzoquinone (I), 3,5-di-tert-butyl-1,2-benzoquinone (II), and 4-methoxy-5-tert-butyl-1,2-benzoquinone (III) in deaerated cyclohexane solutions under exposure to γ-radiation were studied. It was found by chromatography-mass spectrometry and 1H and 13C NMR spectroscopy that the addition of cyclohexyl radicals at the C=O bond in compounds I–III resulted in monoalkyl ethers, whereas cyclic ketal XXI was also formed in the case of compound II. Moreover, quinone I afforded mixed O-and C-alkylation products, and the adduct of cyclohexyl radicals and quinone II at the C=C bond was the source of dimeric products. 相似文献
13.
The straight-line method of Asmus was originally developed for the determination of n in mononuclear complexes of the general form ABn (n≧ 1). In the present investigation it is demonstrated that the method also can be used for determining the value of n in polynuclear complexes of the form A[mBn (m > 1). The method as suggested by Asmus, is, however, not capable of distinguishing between mono- and polynuclear species. It is further shown, that the straight-line method can be applied for the determination of the value of m. 相似文献
14.
Gamayurova V. S. Vorobiev E. S. Davletshina G. A. Rzhechitskaya L. E. 《Kinetics and Catalysis》2021,62(3):360-366
Kinetics and Catalysis - Some of the kinetic parameters of esterifications of aliphatic acids and alcohols involving biocatalysts in nonaqueous media were analyzed using mathematical modeling. The... 相似文献
15.
Using the method of solid-phase peptide synthesis, two peptides have been synthesized, one of which corresponds to the central ring structure of -bungarotoxin (-BTX), while the second has in position 28 a Gly residue in place of the Trp in the first peptide, and their interrelationship with antitoxin antibodies has been investigated. It has been shown that the amino acid residue Trp-28 of -BTX, which is the contact residue in binding with the acetylcholine receptor, also participates directly in binding with the active centers of antibodies to -BTX.Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 628–631, July–August, 1997. 相似文献
16.
The chemiluminescence (CL) kinetics in U(IV) oxidation by atmospheric oxygen in aqueous HClO4 has been investigated. The CL quantum yield (ηCL, E/(mol U(IV))) in this reaction is 1.4 × 10?8. The elementary event generating the CL emitter, which is the electronically excited uranyl ion *(UO 2 2+ ), is electron transfer from the uranyl ion UO 2 + to the oxidizer (·OH radical). The Ag+ ion quenches CL, and the Cu2+ ion enhances CL. 相似文献
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《Computational and Theoretical Polymer Science》2001,11(2):155-166
We performed molecular dynamics simulations to analyze the initial stage of the thermal degradation of polyethylene, which is dominated by the random scission reaction. The simulations were initiated from structures that were taken from previously equilibrated snapshots of the amorphous polymer and of a free-standing thin film. Isolated chains were also used for comparison. Our systems were coupled to a thermal heat bath, and the effect of different coupling constants was studied. Rate of random scission increases as the strength of the temperature coupling increases. Rates of reaction are almost similar in thin films and the bulk, whereas the rates are much faster in isolated chains. Expansion of the free-standing thin film accompanies degradation, producing fragments of various sizes. Chains of higher molecular weights than the initial chains can be produced due to recombination of fragments during the expansion of thin films. The polydispersity index of the resulting fragments is higher in thin films compared to the bulk. The bonds at the low density portion of the thin films have a higher probability of being broken. 相似文献
19.
B. L. Tumanskii N. N. Bubnov S. P. Solodovnikov V. F. Cherstkov S. R. Sterlin É. A. Avetisyan V. M. Rogovik L. S. German 《Russian Chemical Bulletin》1992,41(3):594-596
ESR spectroscopy was used to establish that the UV irradiation of -ketofluorosulfates containing an OSO
2
F group at a tertiary carbon atom gives radicals formed upon cleavage of the C-OSO
2
F bond. If the OSO
2
F group is attached to a primary or secondary carbon atom, we observe ordinary photodecomposition with cleavage of the acyl—carbon bond. The ESR spectra of the new radicals were studied. Replacement of fluorine by the OSO
2
F group in the trifluoromethyl radical leads to compression of the radical site. Branched -oxoperfluoroalkyl radicals are not heteroallylic and the unpaired electron is localized largely on the carbon atom. The [(CF
3
)
2
CF]
2
C(O)CF
3
radical is stable in the air.A. N. Nesmeyanov Institute of Heteroorganic Compounds, Russian Academy of Sciences, 117813 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 3, pp. 757–761, March, 1992. 相似文献
20.
The intensity of the 1001 keV -ray occurring in the decay of234mPa in equilibrium with natural uranium sources is found to be (0.818±0.030)%. This value is in agreement with a recent measurement employing depleted uranium sources, but does not agree with earlier reports employing radiochemically pure sources. 相似文献