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71.
M. B. Rane K. Kondaiah A. R. Middleton G. T. Wernimont S. L. Archangelowa M. Stschigol N. Dubinski L. W. N. Godward A. M. Ward A. D. Worobjewa P. Wukolow A. Reich N. A. Tananajew F. P. Dwyer R. H. Bullard J. S. Knapper K. A. Craig G. C. Chandlee W. I. Kosakow L. Szebellédy M. Ajtai M. Uljanitschew M. S. Platonow N. F. Kriwoschlykow A. A. Marakajew M. J. Petrow K. M. Rauner 《Analytical and bioanalytical chemistry》1939,117(3-4):118-132
72.
In line with current efforts to understand the piece-by-piece structure and articulation of children’s mathematical concepts, this case study compares the reversibility schemes of two eighth-grade students. The aim of the study was to identify the mechanism through which students reverse their thought processes in a multiplicative situation. Data collected through clinical interviews depict the precise strategies that the participants used to work back to find the missing values in an inverse proportional task. This study also illustrates how a conceptual template generated by one of the participants afforded him considerable flexibility in the multiplicative task. Another outcome of the study is that it shows how the numerical characteristics of the parameters in the problem affected the students’ ability to reverse their thought processes. We infer that there is a need for further research on how students might represent their reversibility schemes in the form of algebraic equations. 相似文献
73.
74.
Vikas Kumar Mehak Gupta Sumit G. Gandhi Sonali S. Bharate Ajay Kumar Ram A. Vishwakarma Sandip B. Bharate 《Tetrahedron letters》2017,58(42):3974-3978
Herein we report isolation of a new chromone alkaloid chrotacumine K (12) from fruits and a chromone glycoside schumaniofioside A (13) from leaves of Dysoxylum binectariferum Hook f. Schumaniofioside A is reported for the first time from Meliaceae family. Other known alkaloids isolated include rohitukine (1) and chrotacumine E (6). The structure of new alkaloid 12 was elucidated on the basis of extensive 1D and 2D NMR analysis, synthesis and chemical hydrolysis. Chemically, chrotacumine K (12) is a 3′-O-acetyl rohitukine which on chemical or enzymatic hydrolysis produces rohitukine. The new alkaloid 12 is also present in seeds and stem-barks of this plant. The glycoside schumaniofioside A (13) is present only in leaves, and in abundance (~1% w/w of dried leaves). The isolated compounds and extracts were evaluated for in vitro effect on the proinflammatory cytokines (TNF-α and IL-6) in human monocytic THP-1 cells. The alkaloid 12 displayed potent inhibition (57%) of TNF-α at 0.3 µM, and was non-toxic to THP-1 cells up to 40 µM, indicating its excellent therapeutic window. Furthermore, a nitrobenzoyl ester analog 15e showed better inhibition of IL-6 than parent natural product chrotacumine K. 相似文献
75.
Palladium catalyzed intramolecular aminoacetoxylation of d-ribose derived alkenyl tosylsulfonamide to deliver l-deoxyallonojirimycin in an overall yield of 19%. The preliminary screening of l-deoxyallonojirimycin against carbohydrate processing enzymes showed moderate inhibitory activity against α-glucosidase (yeast) and α-mannosidases. 相似文献
76.
Nitin Wadnerkar Vijayanand Kalamse Ajay Chaudhari 《Theoretical chemistry accounts》2010,127(4):285-292
Using density functionals theory, we show that gravimetric hydrogen uptake of C2H4Ti complex and its cation, C2H4Ti+, differ by about 2 wt%. Six and five hydrogen molecules are found to be adsorbed on C2H4Ti+ and C2H4Ti complexes thereby showing a hydrogen-uptake capacity of 13.74 and 11.72 wt%, respectively. All hydrogen molecules are adsorbed
in molecular form on C2H4Ti+ ion with an increase in metal bond strength, whereas in some cases, the hydrogen molecules are found to be dissociated on
C2H4Ti neutral complex. The uptake capacity of neutral C2H4Ti complex shown in this work is in excellent agreement with that reported experimentally, Phillips and Shivaram (Phys Rev
Lett 100:105505, 2008). The H2 adsorption energy and its dependence on exchange and correlation functions in density functionals method were illustrated.
Even after the adsorption of maximum number of hydrogen molecules on C2H4Ti and C2H4Ti+ complexes, Ti and Ti+ remain strongly bound to C2H4 substrate. 相似文献
77.
Since the introduction of erbium-doped fiber amplifier (EDFA) in optical fiber communication systems at 1550 nm, the fiber loss is no longer considered as the limiting factor but the fiber dispersion and chirp parameters play an important role in degrading the performance of optical communication systems. Further, the invention of external modulators of Mach-Zehnder (MS) type minimizes the transmission power penalty due to fiber chromatic dispersion as these modulators are consider almost chirp-free modulators. Also, better suppression of nonlinear distortions consists of harmonic distortions (HDs) and intermodulation distortions (IMDs) were achieved by using Mach-Zehnder external modulator [8]. In this work, a simulation comparison of external- and direct-modulation schemes using different optical amplifiers; SOA and EDFA in single-tone RoF system is reported. A single-tone channel of 20 GHz is transmitted over single-mode fiber (SMF) either externally modulated by using single-electrode (SEMZM) - and dual-electrode (DEMZM) - Mach-Zehnder modulator or by direct-modulation scheme. Better improvements in the measurement of received RF power of a 20 km linked single-tone RoF system are achieved by using SEMZM with EDFA, which means maximum optical link is achieved between Central Office (CO) and Base Station (BS). Further, this scheme provides better BER as compare to other schemes discussed in this paper. 相似文献
78.
Santanu Pyne Priyanka Sarkar Samita Basu Gobinda Prasad Sahoo Dipak Kumar Bhui Harekrishna Bar Ajay Misra 《Journal of nanoparticle research》2011,13(4):1759-1767
Synthesis of core @ shell (Au @ Ag) nanoparticle with varying silver composition has been carried out in aqueous poly vinyl
alcohol (PVA) matrix. Core gold nanoparticle (~15 nm) has been synthesized through seed-mediated growth process. Synthesis
of silver shell with increasing thickness (~1–5 nm) has been done by reducing Ag+ over the gold sol in the presence of mild reducing ascorbic acid. Characterization of Au @ Ag nanoparticles has been done
by UV–Vis, High resolution transmission electron microscope (HRTEM) and energy dispersive X-ray (EDX) spectroscopic study.
The blue shift of surface plasmon resonance (SPR) band with increasing mole fraction of silver has been interpreted due to
dampening of core, i.e. Au SPR by Ag. The dependence of nonlinear optical response of spherical core @ shell nanoparticles
has been investigated as a function of relative composition of each metal. Simulation of SPR extinction spectra based on quasi-static
theory is done. A comparison of our experimental and the simulated extinction spectra using quasi-static theory of nanoshell
suggests that our synthesized bimetallic particles have core @ shell structure rather than bimetallic alloy particles. 相似文献
79.
80.
Novel arylamino alcohols were synthesized and these alcohols were used to prepare 12 novel N-(2-hydroxy-ethyl)-2,3-didehydroazapodophyllotoxins, in one step, by simple reflux in ethanol. Isolated yields in the range of 50-70% were obtained. 相似文献