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201.
p-Chlorothiophenol reacts with 1-methyl-1,2,5,6-tetrahydropyridine-X-carbonitriles ( 1 , X = 4, 6 , X = 3) and with 1-methyl-1,Y-dihydropyridine-3-carbonitrile (7, Y = 6, 8 , Y = 4) to give the anticipated addition products. Geometric isomers were formed from 6 , but not from 1 , and the stereochemistry of the products has been determined. The chemistry of the reactions with p-cresol was quite different. No reaction occurred with 6 or 7 , while 8 gave a 6-(2-hydroxy-5-methylphenyl)- derivative, analogous to the unexpected product obtained previously from 1 . 相似文献
202.
The surface structure of latex dispersion films was examined with an atomic force microscope. All measurements were done in air on latex films having a minimum film formation temperature of 12°C and a glass transition temperature of 18°C. One aim of this study was to follow structural changes during film formation. Three minutes after spreading the film, its surface layer dried. Afterwards, the structure of the film did not change anymore. Only after 4 months could structural changes be observed: Though individual latex particles could be identified, the particles partly melted into one another.After annealing films at 50° or 60°C for 4 h, the latex particles partly melted into one another, but individual particles could still be identified. When annealing at or above 80°C, no individual latex particles were visible anymore. With increasing temperature the film roughness decreased from 3 nm without annealing to 0.8 nm at 100°C annealing temperature. In addition, islands of 2–4 nm thickness appeared on the film surface. These islands could be scraped off the film by increasing the force between tip and sample, indicating that they are composed of surfactant which was squeezed out of the film. 相似文献
203.
Suzanne Butt H.Geoff Davies Michael J. Dawson Gordon C. Lawrence Jeff Leaver Stanley M. Roberts Michael K. Turner Basil J. Wakefield Wilfred F. Wall John A. Winders 《Tetrahedron letters》1985,26(41):5077-5080
Bicyclo[3.2.0]hept-2-en-6-one (1) was reduced with an alcohol dehydrogenase from and a whole cell system () with excellent substrate enantioselectivity: 7,7-dimethylbicyclo[3.2.0]hept-2-en-6-one (2) was similarly reduced using the 3α,20β-hydroxysteroid dehydrogenase from Streptomyces while furnished both 6S-alcohols (4a), (6b) with high optical purity. 相似文献
204.
Effect of Dielectric Constant of Solvents on the Particle Size and Bandgap of La/SnO2‐TiO2 Nanoparticles and Their Catalytic Properties 下载免费PDF全文
Muhammad Akhyar Farrukh Iqra Muneer Komal Mehmood Butt Sadaf Batool Nazia Fakhar 《中国化学会会志》2016,63(12):952-959
Lanthanum (La) supported on tin oxide‐titanium oxide (SnO2‐TiO2 ) nanoparticles were prepared by a sol–gel method followed by a hydrothermal method. Effect of different solvents (ethyl acetate, benzyl alcohol, ethylene glycol) on the particle size and catalytic activity was investigated. The nanomaterial was characterized by transmission electron microscopy, powder X‐ray diffraction, scanning electron microscopy, fourier transform infrared spectroscopy, and energy dispersive X‐ray. The catalytic and optical properties were studied using solid‐phase spectrophotometry and ultraviolet–visible spectroscopy, respectively. Gas chromatography‐mass spectrometry (GC‐MS) was used to detect the intermediates during the catalytic degradation of methylene blue. It was observed that with decrease in the dielectric constant (ε) of the solvent, the bandgap and particle size decrease and catalytic efficiency increases. Hence, the highest catalytic activity was observed with the solvent having the least dielectric constant. 相似文献
205.
Naeem Nida Khoja Asif Hussain Butt Faaz Ahmed Arfan Muhammad Liaquat Rabia Hasnat Amin Ul 《Research on Chemical Intermediates》2022,48(5):2007-2034
Research on Chemical Intermediates - In this study, biomass fly ash (BFA)-supported Ni/CaO catalyst was synthesized, characterized and evaluated for partial oxidation of methane (POM) in a fixed... 相似文献
206.
In this work, the adsorption of a polyclonal antibody (IgG) on a preparative strong cation exchanger is described in detail. In a first stage, the polyclonal mixture is characterized using both chromatographic and non-chromatography methods. This analysis suggested that the mixture can be simplified by lumping the different components of the IgG into two "macro-components", referred to as pseudo-variants in the following. An analytical method for the determination of the concentrations of the two pseudo-variants is developed. Based on this, the mass transport and the adsorption isotherm parameters are determined experimentally using only well known sort-cut methods. This analysis is evidencing the complexity of the characterization when operating in the presence of slow diffusing mixtures of components. Even in the presence of strong competition, mass transport plays a major role in determining the peak shape. In frontal analysis, competition is still operative after full saturation of the column. 相似文献
207.
Aadil Raza Kangping Zhong Salman Ghafoor Saeed Iqbal Muhammad Adeel Shahid Habib Muhammad Fasih Uddin Butt Chao Lu 《中国光学快报(英文版)》2018,(4)
In this Letter, we have proposed a generalized Gaussian probability density function(GGPDF)-based method to estimate the symbol error ratio(SER) for pulse amplitude modulation(PAM-4) in an intensity modulation/direct detection(IM/DD) system. Furthermore, a closed form expression of SERGGDfor PAM-4 has been derived. The performance of the proposed method is evaluated through simulation as well as experimental work.The fitting of probability density functions of the received signal is applied via GGPDF and shape parameters P1 and P2 associated with different PAM-4 levels are determined. The optimum single value of shape parameter P is then calculated to estimate the SER. The mathematical relationship of P with different received optical powers and receiver bandwidths has been determined and verified. The proposed method is a fast and accurate method to estimate SER of a PAM-4 system, which is more reliable and in agreement with the error counting method. 相似文献
208.
Correlation between the activation energyQ of high-temperature creep and the Debye-Waller thermal parameterB, which is proportional to the mean-square amplitude of atomic vibrations, has been examined in the case of 17 faced-centred
cubic, body-centred cubic and diamond-structure cubic elements. It is observed thatQ is a function ofB, irrespective of the crystal structure;Q decreases asB increases. The correlation is governed by the power-lawQ=Q
0(B/B
0)
M0
, whereQ
0=0.095eV andM
0=−0.62 are numerical constants determined by least-squares fit method, and the constantB
0=1 nm2. 相似文献
209.
In the framework of relativistic harmonic confinement model for quarks and antiquarks, the masses of S- and P-wave mesons and pseudoscalar decay constants from light flavour to heavy flavour sectors are computed. The residual two-body
Coulomb interaction and the spin-dependent interaction of the confined one gluon exchange effects (COGEP) such as spin-spin
and spin-orbit interactions are perturbatively incorporated with the confinement energy to get the respective vector-pseudoscalar
meson mass differences. Here we employ the same parametrization and model parameters as used in a recent study of low-lying
hadron masses and leptonic decay widths. The results are being compared with the values obtained from other theoretical models
and the experimental values. 相似文献
210.
Chen Jianzhong Butt Nicholas A. Zhang Wanbin 《Research on Chemical Intermediates》2019,45(12):5959-5974
Research on Chemical Intermediates - This paper summarizes the application of the chiral ligand DTBM-SegPHOS in asymmetric catalytic hydrogenation reactions. DTBM-SegPHOS exhibits pronounced... 相似文献