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101.
N-Iodosaccharin (NISac): a new reusable catalyst for formal [2+4] cycloaddition of imines and enones
Ankita Rai 《Tetrahedron letters》2010,51(31):4045-3936
The first example of N-iodosaccharin (NISac)-catalyzed step, pot and atom economic synthesis of 1,3-oxazines via formal [2+4] cycloaddition of imines and enones has been reported. No by-product formation, operational simplicity, ambient temperature and high yields (85-95%) are the salient features of the present synthetic protocol. After isolation of the product, the catalyst NISac can be easily recovered and reused without any loss of efficiency. 相似文献
102.
Rotation structure of (0,0) bands of the (C-X)3/2 and (G-X)3/2 systems of SnF molecule has been photographed in the third order of a 10.6 meter concave grating spectrograph. The rotation constants, as determined from the analysis, have been reported to be:- 相似文献
103.
Prabhakar Rai Yun-Su Kim Sang-Ki Kang Yeon-Tae Yu 《Plasma Chemistry and Plasma Processing》2012,32(2):211-218
A thermal plasma system was used for the preparation of nanosized SiC powder. First SiC was synthesized by solid-state reaction
using waste silicon and activated carbon powders and then plasma processing was carried out to form nanosized SiC. Phase and
structural analysis was carried out by X-ray diffraction which confirmed the formation of SiC in both cases. Plasma treatment
did not show any kind of change in structure and phase of SiC; except little free silicon. Morphological investigation showed
the formation of 20–30 nm spherical SiC particles after plasma treatment which was initially 1–5 μm. It was found that DC
current played an important role in the reduction of particle size. It was proposed that nanosized SiC was formed due to the
dissociation of grains from their grain boundary due to strong plasma gas stream. 相似文献
104.
105.
We have described here the physical basis for lasing without population inversion (LWOPI). This type of amplification is obtained
basically by two mechanisms: (i) one is based on atomic interference and (ii) the other is based on Fano-type interference.
We have shown here, in H2 molecules, amplification without population inversion is feasible by considering both the mechanisms. 相似文献
106.
Parametric study of optical emission from two successive laser pulses produced chromium and magnesium plasma is presented.
The line emission from chromium and magnesium plasma showed an increase by more than six times for double laser pulse excitation
than for single-pulse excitation. An optimum increase in emission intensity was noted for inter-pulse delay of ∼2–3 μs for
all the elements. The experimental observations were qualitatively explained on the basis of absorption of second laser pulse
in the pre-formed (by first laser) coronal plasma by inverse Bremsstrahlung process, which were found responsible for the
excitation of more ions and atoms in the plasma. This process starts as the plasma scale length becomes greater than the laser
wavelength. This study further indicated the suitability of this technique in the field of elemental analysis 相似文献
107.
Fluorescence spectrum of Dy3+, Dy3+-Ho3+, Tb3+ and Tb3+-Er3+ doped in calibo glass have been studied using Ar+ and excimer lasers. Non-radiative energy transfer from trivalent dysprosium and terbium (donors) to holmium and erbium (acceptors)
respectively has been observed on the basis of decrease in the life time of the levels and reduction in fluorescence intensity
of Dy3+ and Tb3+ on increasing Ho and Er concentrations. The interaction mechanism of donor and acceptor ions is found to be dipole-dipole
in both cases. Various parameters such as donor-acceptor distances, non-radiative energy transfer efficiency (η) and energy transfer probability (P
da) have been computed. Stark splitting have also been marked in several intense transition of the two. 相似文献
108.
Mahesh Kumar Yadav Anju Rai Anirudh Pradhan 《International Journal of Theoretical Physics》2007,46(11):2677-2687
We investigate the integrability of cosmic strings in Bianchi III space-time in presence of a bulk viscous fluid by applying
a new technique. The behavior of the model is reduced to the solution of a single second order nonlinear differential equation.
We show that this equation admits an infinite family of solutions. Some physical consequences from these results are also
discussed. 相似文献
109.
Transition Metal Chemistry - Cyclopentadienylzirconium(IV) complexes of N-phthaloyl amino acids of general formulae Cp2Zr(L)nCl2?n (n = 1 or 2) and CpZrCl(L)2 (LH = N-phthaloyl derivatives of... 相似文献
110.
Quantitative determination of isoquinoline alkaloids and chlorogenic acid in Berberis species using ultra high performance liquid chromatography with hybrid triple quadrupole linear ion trap mass spectrometry
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Awantika Singh Vikas Bajpai Sunil Kumar Kamal Ram Arya Kulwant Rai Sharma Brijesh Kumar 《Journal of separation science》2015,38(12):2007-2013
Berberis species are well known and used extensively as medicinal plants in traditional medicine. They have many medicinal values attributable to the presence of alkaloids having different pharmacological activities. In this study, a method was developed and validated as per international conference on harmonization guidelines using ultra high performance liquid chromatography with hybrid triple quadrupole‐linear ion trap mass spectrometry operated in the multiple reaction monitoring mode for nine bioactive compounds, including protoberberine alkaloids, aporphine alkaloids and chlorogenic acid. This method was applied in different plant parts of eight Berberis species to determine variations in content of nine bioactive compounds. The separation was achieved on an ACQUITY UPLC CSH? C18 column using a gradient mobile phase at flow rate 0.3 mL/min. Calibration curves for all the nine analytes provided optimum linear detector response (with R2 ≥0.9989) over the concentration range of 0.5–1000 ng/mL. The precision and accuracy were within RSDs ≤2.4 and ≤2.3%, respectively. The results indicated significant variation in the total contents of the nine compounds in Berberis species. 相似文献