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排序方式: 共有87条查询结果,搜索用时 15 毫秒
1.
Roly J. Armstrong Wasim M. Akhtar Tom A. Young Fernanda Duarte Timothy J. Donohoe 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(36):12688-12692
Hydrogen borrowing catalysis serves as a powerful alternative to enolate alkylation, enabling the direct coupling of ketones with unactivated alcohols. However, to date, methods that enable control over the absolute stereochemical outcome of such a process have remained elusive. Here we report a catalytic asymmetric method for the synthesis of enantioenriched cyclohexanes from 1,5‐diols via hydrogen borrowing catalysis. This reaction is mediated by the addition of a chiral iridium(I) complex, which is able to impart high levels of enantioselectivity upon the process. A series of enantioenriched cyclohexanes have been prepared and the mode of enantioinduction has been probed by a combination of experimental and DFT studies. 相似文献
2.
Dey Chaudhuri S. Banerjee D. Bhattacharjee T. Wasim Raja Sk Acharya R. Pujari P. K. 《Journal of Radioanalytical and Nuclear Chemistry》2020,324(2):829-835
Journal of Radioanalytical and Nuclear Chemistry - Performance of 1″?×?1″ LaBr3 (5% Ce) scintillator coupled to Hamamatsu R2083 PM Tube has been investigated for the... 相似文献
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Dr. Wasim Abuillan Dr. Mariam Veschgini Salomé Mielke Dr. Akihisa Yamamoto Xianhe Liu Dr. Oleg Konovalov Prof. Dr. Marie Pierre Krafft Prof. Dr. Motomu Tanaka 《Chemphyschem》2019,20(6):898-904
The structure and lateral correlation of fluorocarbon-hydrocarbon tetrablock di(F10Hm) domains at the air/water interface have been determined by quantitative analysis of grazing incidence small-angle X-ray scattering (GISAXS) data. The measured GISAXS signals can be well represented by the full calculation of the form and structure factors. The form factor suggests that di(F10Hm) domains take a hemiellipsoid shape. Both major and minor axes of the hemiellipsoids monotonically increased in response to the elongation of the hydrocarbon blocks, which can be explained by the concominant increase in van der Waals interaction. The structure factor calculated from the GISAXS signals suggests that the domains take an orthorhombic lattice. Remarkably, the lateral correlation can reach over a distance that is more than 14 times longer than the distance to the nearest neighbors. Our data suggest that quantitative GISAXS enables the optimal design of mesoscopic self-assemblies at the air/water interface by fine-tuning of the structures of molecular building blocks. 相似文献
5.
Wang Haoran Wasim Akhtar Lalit Mohan Nainwal Sumit Kumar Kaushik Mymoona Akhter Mohammad Shaquiquzzaman Mohammad Mumtaz Alam 《Journal of heterocyclic chemistry》2020,57(9):3350-3360
Thirteen new benzimidazole pendant cyanopyrimidine derivatives were synthesized. The compounds were synthesized through multistep reaction protocol. The structures of synthesized derivatives were studied by EI-MS, 1H NMR, FT-IR and elemental analysis. All the compounds were studied for their anticancer activity at National Cancer Institute. Except compound 7j , all the compounds unveiled cytotoxicity against cancer cells. The most active compound 7a had shown highest value of growth inhibition of 88.44% and 84.19% against HOP-92 and T-47D cancer cell lines. 相似文献
6.
Nasir Khalid Mohammad Wasim Nadeem A. Lodhi Mohammad Arif 《Journal of Radioanalytical and Nuclear Chemistry》2013,297(1):153-159
Certified alloys of Ni–Cu based, Fe based and Cu–Sn based were analysed by semi-absolute, standardless k 0-instrumental neutron activation analysis (k 0-INAA) and flame atomic absorption spectrophotometry (FAAS) aiming at evaluating their comparative performances. In k 0-INAA measurements, the irradiations were performed at miniaturized neutron source reactor having thermal neutron flux of about 1 × 1012 cm?2 s?1. The experimentally optimized parameters for INAA suggested a maximum of three irradiations for the quantification of 21 elements within 5 days. The same experiments also produced quantitative results of 13 elements not reported in the certificates of the reference materials. AAS was, however, unable to determine any of those elements. Accuracy of the two techniques was assessed by comparing their average root mean squared errors. The data analysis concluded that k 0-INAA had better sensitivity and accuracy than FAAS. 相似文献
7.
Khalida Inayat Noor Mohammad Arif Wasim Ul-Haq 《Applied mathematics and computation》2009,215(2):629-635
In this paper, we define and study some subclasses of analytic functions by using fractional derivative operator. Some interesting properties, coefficients problems and inclusion results of these classes are investigated. It is also shown that these classes are closed under convolution with convex functions and some applications are given. 相似文献
8.
Farhat Waqar Saida Jan Bashir Mohammad Muhammad Hakim Shah Alam Wasim Yawar 《中国化学会会志》2009,56(2):335-340
An analytical method has been developed for the preconcentration of rare earth elements (REEs) in seawater for their determination by inductively coupled plasma optical emission spectrometry (ICP‐OES). An indigenously synthesized chelating resin was used for the preconcentration of (REEs) which was based on immobilization of fluorinated β‐diketone group on solid support styrene divinyl benzene. Sample solutions (adjusted to optimized pH) were passed through a polyethylene column packed with 250 mg of the resin. Experimental conditions consisting of pH, sample flow rate, sample volume and eluent concentration were optimized. The established method has been applied for the preconcentration of light, medium and heavy REEs in coastal sea water samples for their subsequent determination by (ICP‐OES). Percentage recoveries of La, Ce, Nd, Sm, Eu, Gd, Dy, Er, Yb and Lu were ≥ 95%, a preconcentration factor of 200 times, and relative standard deviations < 5% were achieved. 相似文献
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Continuous online monitoring of rotating machines is necessary to assess real-time health conditions so as to enable early detection of operation problems and thus reduce the possibility of downtime. Rolling element bearings are crucial parts of many machines and there has been an increasing demand to find effective and reliable health monitoring technique and advanced signal processing to detect and diagnose the size and location of incipient defects. Condition monitoring of rolling element bearings, comprises four main stages which are, statistical analysis, fault diagnostics, defect size calculation, and prognostics. In this paper the effect of defect size, operating speed, and loading conditions on statistical parameters of acoustic emission (AE) signals, using design of experiment method (DOE), have been investigated to select the most sensitive parameters for diagnosing incipient faults and defect growth on rolling element bearings. A modified and effective signal processing algorithm is designed to diagnose localized defects on rolling element bearings components under different operating speeds, loadings, and defect sizes. The algorithm is based on optimizing the ratio of Kurtosis and Shannon entropy to obtain the optimal band pass filter utilizing wavelet packet transform (WPT) and envelope detection. Results show the superiority of the developed algorithm and its effectiveness in extracting bearing characteristic frequencies from the raw acoustic emission signals masked by background noise under different operating conditions. To experimentally measure the defect size on rolling element bearings using acoustic emission technique, the proposed method along with spectrum of squared Hilbert transform are performed under different rotating speeds, loading conditions, and defect sizes to measure the time difference between the double AE impulses. Measurement results show the power of the proposed method for experimentally measuring size of different fault shapes using acoustic emission signals. 相似文献