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81.
A facile way has been developed to provide a series of novel chiral N-(4-(piperidin-1-yl)pyridin-2-yl)amide derivatives as potential stereoselective catalysts. The key intermediate, 2-amino-4-piperidinyl pyridine, was obtained by nucleophilic substitution of 2-amino-4-chloropyridine with piperidine in good yields (up to 96%). The total control of enantioselectivity was obtained for the synthesis of L-proline and (R)-1,1′-bi(2-naphthol) derivatives. 相似文献
82.
83.
In this paper, the Gibbs-Appell' s equations of the nonholonomic controllable mechanical systems with variable mass in terms of quasi-velocities and quasi-accelerations are obtained, and the application of the new equation is illustrated by an example.The project was Supported by the Heilongjiang Natural Science Foundation 相似文献
84.
Yong-Ming Zhao Yu-jin Wang Mei Dong Man-Li Zhang Chang-Hong Huo Yu-Cheng Gu Qing-Wen Shi 《Chemistry of Natural Compounds》2010,46(3):373-376
Two new eudesmanes, 1α-hydroxy-11,13-dihydroisoalantolactone (1), 3α-hydroxy-11,13dihydroalantolactone (2), and one known compound were isolated from the roots of Inula helenium. Their structures were established on the basis of
spectral evidence. 相似文献
85.
86.
Let H be the real quaternion algebra and Hn×m denote the set of all n×m matrices over H. Let P∈Hn×n and Q∈Hm×m be involutions, i.e., P2=I,Q2=I. A matrix A∈Hn×m is said to be (P,Q)-symmetric if A=PAQ. This paper studies the system of linear real quaternion matrix equations
87.
The effective separation of dimethyl carbonate (DMC) from its methanol mixture through simple, inexpensive and low energy-input method is a promising and challenging field in the process of organic synthesis. Herein, a reversible adsorption strategy through the assistance of superbase and CO2 for DMC/methanol separation at ambient condition was described. The process was demonstrated effectively via the excellent CO2 adsorption efficiency. Notably, the protocol was also suitable to other alcohol (i.e., monohydric alcohol, dihydric alcohol, trihydric alcohol) mixtures. The study provided guidance for potential separation of DMC/alcohol mixture in the scale-up production. 相似文献
88.
Preparing a polylactide (PLA)/plasticizer system has been regarded as an effective solution to improve the ductility of brittle PLA. In this reach, a novel type of alkyl phosphine oxides consisting of three aliphatic ester substituents was prepared from PH3 tail gas, and its potential to be employed as a PLA plasticizer was studied. Differential scanning calorimeter tests confirmed that the newly-prepared plasticizer decreased the Tg of PLA (28 wt% plasticizer) from 52°C (neat PLA) to 11°C, and increased the elongation at break from 11% (neat PLA) to 271% (plasticized PLA). X-ray diffraction results showed that the crystallization degree of PLA (28 wt% plasticizer) increased from 0.12% of neat PLA to 14.04%, while Young's modulus of PLA remained as high as 121.3 MPa, which was much higher than that of the PLA/citrate ester systems with same plasticizer content. These novel phosphorus-containing plasticizers exhibited excellent thermal stability and a weight-loss of the system no more than 2.5% at 180°C; therefore, no unpleasant volatiles were released during processing. In contrast, the weight loss of the PLA/citrate system was as high as 10.8% at 180°C, forming heavy fog with an unpleasant smell during thermal mixing. Scanning electron microscopy was employed to observe the microstructure of the PLA/plasticizer systems, which indicated that the carboxylic butyl ester-containing phosphine oxides was compatible with PLA matrix. 相似文献
89.
A new analytical model for reverse characteristics of
4H--SiC merged PN--Schottky diodes (MPS or JBS) is developed. To
accurately calculate the reverse characteristics of the 4H--SiC MPS
diode, the relationship between the electric field at the Schottky
contact and the reverse bias is analytically established by solving
the cylindrical Poisson equation after the channel has pinched off.
The reverse current density calculated from the
Wentzel--Kramers--Brillouin (WKB) theory is verified by comparing it
with the experimental result, showing that they are in good
agreement with each other. Moreover, the effects of P-region spacing
(S) and P-junction depth (Xj) on the characteristics of 4H--SiC MPS
are analysed, and are particularly useful for optimizing the
design of the high voltage MPS diodes. 相似文献
90.
In this paper, the authors derive the existence criteria and the formulae of the weighted Moore-Penrose inverse, the e-core inverse and the f-dual core inverse in rings. Also, new characterizations between weighted Moore-Penrose inverses and one-sided inverses along an element are given. 相似文献