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1.
Estrogen compounds may pose a serious threat to the health of humans and wildlife.The estrogen receptor (ER) exists as two subtypes,ERβ and ERβ.Compounds might have different relative affinities and binding modes for ERβ and ERβ.In this study,the heuristic method was performed on 31 compounds binding to ERβ to select 5 variances most related to the activity (LogRBA) from 1524 variances,which were then employed to develop the best model with the significant correlation and the best predictive power (r2 = 0.8...  相似文献   

2.
Ant colony optimization (ACO) is a meta-heuristic algorithm, which is derived from the observation of real ants. In this paper, ACO algorithm is proposed to feature selection in quantitative structure property relationship (QSPR) modeling and to predict λmax of 1,4-naphthoquinone derivatives. Feature selection is the most important step in classification and regression systems. The performance of the proposed algorithm (ACO) is compared with that of a stepwise regression, genetic algorithm and simulated annealing methods. The average absolute relative deviation in this QSPR study using ACO, stepwise regression, genetic algorithm and simulated annealing using multiple linear regression method for calibration and prediction sets were 5.0%, 3.4% and 6.8%, 6.1% and 5.1%, 8.6% and 6.0%, 5.7%, respectively. It has been demonstrated that the ACO is a useful tool for feature selection with nice performance.  相似文献   

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NiO-MoO3/γ-Al2O3 catalysts were prepared by the reaction of γ-Al2O3 extrudates with an aqueous slurry of MoO3, followed by the reaction of the MoO3/γ-Al2O3 catalyst with an aqueous slurry of NiO, Ni(OH)2, NiCO3·2Ni(OH)2·xH2O, or 2NiCO3·3Ni(OH)2·4H2O and by subsequent drying. The NiO deposition was examined with electron probe microanalysis. The deposited Ni efficiently increased the activity in benzothiophene hydrodesulfurization.  相似文献   

5.
ESCA studies of the state of Pd/–Al2O3 catalysts modified by potassium carbonate show that such catalysts differ from unmodified samples in much greater changes of a positive charge of palladium ions under redox conversions. This is ascribed to the lower interaction of Pd with the support in modified samples.
Pd/–Al2O3 . , -, Pd .
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6.
Methanol oxidation on V2O5 and V2O5–MoO3 catalysts supported on montmorillonite has been studied in the temperature range of 250–500°C. The V2O5–MoO3 containing sample shows higher selectivity towards formaldehyde formation than the V2O5 catalyst.  相似文献   

7.
In this comment to a recent paper [Anal. Chim. Acta 585 (2007) 241-245], we report a comparison study on Mn oxide-related compounds with different crystallographic forms, which distinguish between β-MnO2 and α-MnO2 type materials via Raman scattering (RS) spectroscopy. The tetragonal rutile-type β-MnO2 is characterized by a RS band at ∼667 cm−1 of symmetry A1g, whereas the α-MnO2 type materials feature two main RS contributions at about 574 and 634 cm−1, belonging to Ag spectroscopic species of a tetragonal hollandite-type framework. These data represent a clear signature for identifying β-MnO2 and α-MnO2 type materials via RS spectroscopy.  相似文献   

8.
SrCe0.92 Nb 0.03 Tm0.05 O 3-δ powders were synthesized by a modified sol-gel method using citrate as a chelating agent.X-ray diffraction(XRD) analysis verified SrCe 0.92 Nb 0.03 Tm 0.05 O 3-δ powders and membranes consisting of a single perovskite phase.The morphologies of the sintered membranes were investigated by using scanning electron microscopy(SEM) technique.Stability tests demonstrated that the Nb introduction into doped strontium cerate greatly enhanced the chemical stability.Electrical conductivities of SrCe 0.92 Nb 0.03 Tm 0.05 O 3-δ and SrCe 0.95 Tm 0.05 O 3-δ were measured by the four-point DC method under 10% H 2 /He atmosphere and temperatures(700-900℃).With a maximum conductivity of 0.0067 S cm-1 at 900℃,the total electrical conductivity of SrCe 0.92 Nb 0.03 Tm 0.05 O 3-δ increases with increasing temperature.The H 2 permeation flux of SrCe 0.92 Nb 0.03 Tm 0.05 O 3-δ is 0.035 mL cm-2 min-1 when 40% H 2 /He and Ar were used respectively as the feed and sweeping gases at 900℃.  相似文献   

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Ar and Kr matrix effect on the geometry and Cl–H stretching (ν s (Cl–H)) and librational (ν l (Cl–H)) frequencies of the hydrogen-bonded complex Cl–H···NH3 are simulated within the framework of polarizable continuum model with integral equation formalism (IEF-PCM) at B3LYP and MP2 levels of theory with the basis set 6-311++G(2df,2pd). Within the framework of B3LYP and IEF-PCM, the simulated gas phase, Ar, and Kr matrix ν s (Cl–H) of the complex are 2140, 1684, and 1550 cm−1, respectively, which deviate from the experimental values (~2200, 1371, and 1218 cm−1) by −60, 313, and 332 cm−1. Within the framework of MP2 and IEF-PCM, the gas phase, Ar, and Kr matrix ν s (Cl–H) are calculated as 2366, 2037, and 1957 cm−1 by the harmonic approximation, and as 2177, 1876, and 1665 cm−1 by the full-dimensional anharmonic correction. The matrix effect modeling is of greater importance than the anharmonic correction in accounting for the large experimental gas phase to Ar or Kr matrix shift of the ν s (Cl–H) (−829 or −982 cm−1). Our calculations do not support the assignment of the 733.8 and 736.9 cm−1 bands to the Ar and Kr matrix ν l (Cl–H).  相似文献   

11.
Summary The effect of Mo loadings and preparation methods, slurry and conventional impregnation, on the performances of alumina-supported MoO3 catalysts in transesterification of dimethyl oxalate (DMO) with phenol was investigated. Slurry prepared MoO3/-Al2O3 catalyst exhibited higher activity and dispersion capacity than conventional one. Slurry MoO3/water was used instead of an ammonium heptamolybdate solution. Highly dispersed amorphous Mo catalysts were obtained, closely related to the catalytic activities without calcination, waste solutions, and calcining nitrogenous gases.  相似文献   

12.
Traditional urea synthesis under harsh conditions is usually associated with high energy input and has aroused severe environmental concerns.Electrocatalytic C-N coupling by converting nitrate and CO2 into urea under ambient conditions represents a promising alternative process.But it was still limited by the strong competition between nitrate electrochemical reduction(NO3ER) and CO2 electrochemical reduction(CO2ER).Here,Fe-FeOO...  相似文献   

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By static magnetic measurements it was found that the ability to reduction of an amorphous NiO–Al2O3/SiO2 catalyst decreases in the order: but-2-eneshydrogen isobutene>but-1-ene>propeneethene. The reduction temperatures are significantly higher than the dimerization reaction temperatures.
, NiO–Al2O3/SiO2 : -2>-1> . .
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16.
The Michael addition of nitromethane to 3-buten-2-one has been carried out in the absence of solvent, using potassium fluoride supported on Al2O3, ZnO, SnO2, sepiolite, AlPO4, AlPO4–Al2O3 and AlPO4–ZnO catalysts. We found that KF/ZnO easily performed the Michael addition and thus, ZnO is a better support for the basic reagent than Al2O3. Besides, the Michael addition was not successful with AlPO4 or AlPO4-metal oxide acidic supports.
3--2- , , Al2O3, ZnO, SnO2, , AlPO4, AlPO4–Al2O3 AlPO4–ZnO. , KF/ZnO .. ZnO, , , Al2O3. , , AlPO4 AlPO4- .
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17.
Atmospheric Pressure Dielectric Barrier Discharge (APDBD) initiated decomposition of CO2 and C6–C9 alkanes (in Ar carrier) with uncoated and TiO2/ZnO coated glass surfaces, and under molecular sieve 10 X packing are presented in this study. Alkanes employed include 2-methylpentane, cyclohexane, n-hexane, n-heptane, n-octane, n-nonane and their decomposition products studied include C1–C3 hydrocarbons viz. CH4, C2H4, C2H6 and C3H8. Generally the yields of all these C1–C3 products increased with discharge energy, however to a major extent the parent alkane structure controlled the relative concentration profiles of the individual products. Typically the slopes of the increase in various products yield varied from 0.025 to 0.25 ppm (v/v) mm V−1. However, in the case of cyclohexane the total yield of methane, ethane and propane were only ∼20% of ethylene yield. Use of TiO2 as well as TiO2/ZnO coated central glass electrode in the APDBD apparatus showed ∼11% enhancement in degradation efficiency. However, while overall 2-methylpentane decomposition reduced significantly to ∼30%, in case of n-octane its decomposition to the C1–C3 products remained unaffected. On the other hand under molecular sieve 10X packing, yield of CH4 and C2H4 increased significantly in both cases.  相似文献   

18.
In this work, titanium dioxide (TiO2) nanowires were synthesized by the sol–gel method, without using any kind of templates, instead of that acetic acid was used as morphological modifier. In order to control crystalline phases and crystal size, TiO2 was calcinated at 400, 500 and 600 °C during 1 h. The resulting morphology was nanowires, which diameter was maintained constant after calcination at different temperature (about 76 nm). Moreover, crystalline phases in order of predominance were anatase, anatase–rutile and rutile–anatase at 400, 500 and 600 °C, respectively. Additionally, the crystallite size increases with respect to temperature from 13 to 75 nm.  相似文献   

19.

Abstract  

Thermolysis of cis-Fe(CO)4(SiCl3)2 results in the formation of the novel compound Fe2(CO)62-SiCl2)3, which was characterized by single crystal X-ray diffraction. Density functional theory calculations were carried out to elucidate possible reaction steps leading to the formation of Fe2(CO)6(SiCl2)3, including CO dissociation and chlorine abstraction by a SiCl3 radical generated from homolytic Fe–Si bond cleavage involving a singlet–triplet intersystem crossing.  相似文献   

20.
Relativistic scalar and spin-orbit density functional calculations of the electronic structure, Nucleus-Independent Chemical Shift (NICS) index and ELF function of the [Re2(CO)8(μ-BiPh)2] and [Re2(CO)8(μ-BiPh2)2] clusters are reported. We show here that the [Re2(CO)8(μ-BiPh)2] cluster has large negative NICS values in the region defined by the Re-Bi-Re-Bi four-membered ring and the ELF function shows significant electron delocalization density in the center of the metallic ring, thus indicating an aromatic cluster. In contrast the Re-Bi-Re-Bi four-membered ring in the [Re2(CO)8(μ-BiPh2)2] cluster has negligible paratropic ring currents and the ELF function shows a low-density region within the metallic ring indicating that aromaticity is switched off. However, the phenyl ligands in both clusters show the expected aromatic character.  相似文献   

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