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991.
The metal-catalyzed Baeyer-Villiger oxidation of cyclohexanone with molecular oxygen (latm) in the presence of benzaldehyde gives δ -caprolactone in high yield. The same oxidation in the absence of metal catalysts is also studied. Additives to the system can improve the reaction highly efficiently. 相似文献
992.
Quanfei Zou Yuan Gu Rong Lu Tiejun Zhang Guang‐Rong Zhao Changxiao Liu Duanyun Si 《Biomedical chromatography : BMC》2013,27(9):1123-1128
In this study, a simple and sensitive LC/MS/MS method was developed and validated for the determination of arctigenin in rat plasma. The MS detection was performed using multiple reaction monitoring at the transitions of m/z 373.2 → 137.3 for arctigenin and m/z 187.1 → 131.0 for psoralen (internal standard) with a Turbo IonSpray electrospray in positive mode. The calibration curves fitted a good linear relationship over the concentration range of 0.2–500 ng/mL. It was found that arctigenin is not stable enough at both room temperature and ?80 °C unless mixed with methanol before storage. The validated LC/MS/MS method was successfully applied for the pharmacokinetic study of arctigenin in rats. After intravenous injection of 0.3 mg/kg arctigenin injection to rats, the maximum concentration, half‐life and area under the concentration–time curve were 323 ± 65.2 ng/mL, 0.830 ± 0.166 and 81.0 ± 22.1 h ng/mL, respectively. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
993.
Ke Wang Zuyi Li Chengye Yuan 《Phosphorus, sulfur, and silicon and the related elements》2013,188(6-7):1797-1800
Bioreduction of 2-oxo-3-halo (or azido) alkanephosphonates and 4-ethoxy-4,2-dioxobutanephosphonates by baker's yeast afforded 3-substituted 2-hydroxyalkanephosphonates in moderate to good yields and ee value. Moreover, a regio- and stereoselective bioreduction of 2,3-dioxoalkanephosphonates and 2,4-dioxoalkanephosphonates by baker's yeast was studied also. The resulting chiral hydroxy compounds can be used as chirons for the stereoselective synthesis of biologically active molecules. 相似文献
994.
The watermiscible room temperature ionic liquid 1butyl3methylimidazolium tetrafluorob orate ([bmim] [BF4]) is a model system for studying the interactions between ionic liquid and water molecules. In this work the orientational structure of the low concentrated aqueous solution of [bmim] [BF4] at the air/liquid interface was investigated by sum frequency gener ation vibrational spectroscopy. It has been found that at very low concentrations, the butyl chain exhibited a significant gauche defect, indicating a disordered conformation; and the cation ring oriented with a fairly small tilting angle at the surface. When the concentration increased, the cation ring tended to lie flat at the surface, and the gauche defects of the butyl chain decreased due to the intermolecular chainchain interactions and the consequent more ordered interfacial molecular arrangement. Additionally, the antisymmetric stretching mode in the PPP and SPS spectra exhibited a peak shift, showing that there exists more than one kind of orientation or chemical environment for the butyl CH3 group. These results may shed new light on understanding the surface behavior of watermiscible ionic liquids as well as the imidazolium based surfactants. 相似文献
995.
Yong‐Kai Deng Zhi‐Hao Yan Di Sun 《Acta Crystallographica. Section C, Structural Chemistry》2013,69(10):1147-1151
An infinite one‐dimensional cadmium metal–organic chain, namely catena‐poly[aquabis(μ3‐2,2′‐{[1,2‐phenylenebis(methylene)]bis(sulfanediyl)}dibenzoato)dicadmium(II)], [Cd2(C22H16O4S2)2(H2O)]n, was synthesized by solvothermal reaction of Cd(NO3)2·4H2O and 2,2′‐{[1,2‐phenylenebis(methylene)]bis(sulfanediyl)}dibenzoic acid (H2L). The CdII centres have six‐coordinate CdS2O4 and CdSO5 geometries. Due to the flexible –CH2–S– arms, the L2− ligand adopts both syn and anti conformations. Four CdII cations are linked by two syn L2− ligands to form a centrosymmetric planar tetranuclear CdII core, which is further extended through bonding to the anti L2− ligands to form a one‐dimensional metal–organic chain. Adjacent one‐dimensional chains are connected by C—H...π interactions and nonclassical C—H...O hydrogen bonds to form the resultant three‐dimensional supramolecular framework. 相似文献
996.
Yi Yuan Zong-Lin Jiang Jia-Ming Yan Ge Gao Albert S. C. Chan Ru-Gang Xie 《合成通讯》2013,43(24):4555-4561
Two new macrobicyclic imidazolium and benzimidazolium phanes were synthesized by direct quaternization of the corresponding tripodal azacycles with tribromide under high dilution condition in excellent yields. The cyclophanes were identified by 1H-NMR, 13C-NMR, FAB-MS, IR, elemental analysis and X-ray diffraction analysis. 相似文献
997.
998.
We consider the augmented Lagrangian method (ALM) as a solver for the fused lasso signal approximator (FLSA) problem. The ALM is a dual method in which squares of the constraint functions are added as penalties to the Lagrangian. In order to apply this method to FLSA, two types of auxiliary variables are introduced to transform the original unconstrained minimization problem into a linearly constrained minimization problem. Each updating in this iterative algorithm consists of just a simple one-dimensional convex programming problem, with closed form solution in many cases. While the existing literature mostly focused on the quadratic loss function, our algorithm can be easily implemented for general convex loss. We also provide some convergence analysis of the algorithm. Finally, the method is illustrated with some simulation datasets. 相似文献
999.
This work extends our previous understanding concerning the nonlinear responses of entangled polymer solutions and melts to large external deformation in both simple shear and uniaxial extension. Many similarities have recently been identified for both step strain and startup continuous deformation, including elastic yielding, i.e., chain disentanglement after cessation of shear or extension, and emergence of a yield point during startup deformation that involves a deformation rate in excess of the dominant molecular relaxation rate. At a sufficiently high constant Hencky rate, uniaxial extension of an entangled melt is known to produce window-glass-like rupture. The present study provides evidence against the speculation that chain entanglements tie up into "dead knots" in constant-rate extension because of the exponentially growing chain stretching with time. In particular, it is shown that even Instron-style tensile stretching, i.e., extending a specimen by applying a constant velocity on both ends, results in rupture. Yet, in the same rate range, the same entangled melt only yields in simple shear, and the resulting shear banding is clearly not a characteristic of rupture. Thus, we conclude that chain entanglements respond to simple shear in the manner of yielding whereas uniaxial extension is rather effective in causing some entanglements to lock up, making it impossible for the entanglement network to yield at high rates. 相似文献
1000.
DETERMINATION OF QUADRICEPS FORCES IN SQUAT AND ITS APPLICATION IN CONTACT PRESSURE ANALYSIS OF KNEE JOINT 总被引:1,自引:0,他引:1
While the quadriceps muscles of human body are quite important to the daily activities of knee joints,the determination of quadriceps forces poses significant challenges since it cannot be measured in ... 相似文献