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41.
Jien Wu Xiao-Fang Cheng Leslie J. Harrison Swee-Hock Goh Keng-Yeow Sim 《Tetrahedron letters》2004,45(52):9657-9659
Examination of the aerial parts of a Chinese herbal medicine yielded a novel metabolite, perforatumone 1, which is characterized by its unique carbon skeleton. Its structure was determined by detailed spectroscopic analysis. 相似文献
42.
The FTIR spectrum of the nu6 band of H13COOH has been collected at a resolution of 0.004 cm-1 in the frequency range of 1030-1160 cm-1. The nu6 band was analyzed to be an A-B hybrid band and perturbed by the nearby nu8 band through a-, and b-Coriolis coupling terms. Using a Watson's A-reduced Hamiltonian in the Ir representation, with the inclusion of a- and b-Coriolis resonances, a total of 3004 IR transitions of nu6 have been analyzed to provide rovibrational constants for the v6 = 1 state with a standard deviation of 0.00047 cm-1. The nu6 band was found to be centered at 1095.40365 +/- 0.00003 cm-1. Copyright 1999 Academic Press. 相似文献
43.
Predicting potential changes in groundwater salinity in low-lying coastal regions due to climate change is important, where coastal vegetation is abundant, succession competition between halophytes and glycophytes plays a significant role in the salinity budget. Sea level rise enhances salinity intrusion, contributing an additional dimension to vegetation competition. A new simulation model known as mangrove-hardwood hammock model coupled with saturated-unsaturated transport (MANTRA) has recently been developed by the authors to simulate groundwater salinity regimes in the presence of vegetation competition, subject to climate change. MANTRA is based upon linking two existing Unites States geological survey (USGS) simulation models known as mangrove-hardwood hammock model (MANHAM) and saturated-unsaturated transport (SUTRA). MANHAM simulates the evolution of vegetation succession subject to changing groundwater salinity. SUTRA simulates saturated and unsaturated transport of solutes and salinity in groundwater given sea salinity. MANTRA improves the simulation robustness to simultaneously simulate groundwater hydrology, salinity and coastal vegetation succession subject to sea level rise. Some simulation results will be presented to demonstrate the impact of sea level rise on coastal vegetation succession and groundwater salinity. 相似文献
44.
We have successfully used a commercial microfilm to produce good quality two-dimensional and three-dimensional computer-generated binary holograms. 相似文献
45.
46.
47.
B. S. Goh 《Journal of Optimization Theory and Applications》2009,142(2):275-289
We show that, for an unconstrained optimization problem, the long-term optimal trajectory consists of a sequence of greatest
descent directions and a Newton method in the final iteration. The greatest descent direction can be computed approximately
by using a Levenberg-Marquardt like formula. This implies the view that the Newton method approximates a Levenberg-Marquardt
like formula at a finite distance from the minimum point, instead of the standard view that the Levenberg-Marquadt formula
is a way to approximate the Newton method. With the insight gained from this analysis, we develop a two-dimensional version
of a Levenberg-Marquardt like formula. We make use of the two numerically largest components of the gradient vector to define
here new search directions. In this way, we avoid the need of inverting a high-dimensional matrix. This reduces also the storage
requirements for the full Hessian matrix in problems with a large number of variables.
The author thanks Mark Wu, Professors Sanyang Liu, Junmin Li, Shuisheng Zhou and Feng Ye for support and help in this research
as well as the referees for helpful comments. 相似文献
48.
Kyung Ju Lee Jung Tae Park Joo Hwan Goh Jong Hak Kim 《Journal of polymer science. Part A, Polymer chemistry》2008,46(12):3911-3918
A microphase‐separated, amphiphilic graft copolymer consisting of a poly (vinyl chloride) (PVC) backbone and poly(oxyethylene methacrylate) (POEM) side chains, (PVC‐g‐POEM at 62:38 wt %) was synthesized via atom transfer radical polymerization (ATRP). Nuclear magnetic resonance (1H NMR), FTIR spectroscopy, and transmission electron microscopy (TEM) clearly revealed that the “grafting from” method using ATRP was successful and that the graft copolymer molecularly self‐assembled into discrete nanophase domains of continuous PVC and isolated POEM regions. The self‐assembled graft copolymer film was used to template the growth of silver nanoparticles in solid state by introducing a AgCF3SO3 precursor and a UV irradiation process. The in situ formation of silver nanoparticles in the graft copolymer template film was confirmed by TEM, UV–visible spectroscopy, and wide angle X‐ray scattering. FTIR spectroscopy and X‐ray photoelectron spectroscopy also demonstrated the selective incorporation and in situ formation of silver nanoparticles within the hydrophilic POEM domains, presumably due to strong interactions between the silver and the ether oxygen in POEM. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3911–3918, 2008 相似文献
49.
Shen ZL Goh KK Cheong HL Wong CH Lai YC Yang YS Loh TP 《Journal of the American Chemical Society》2010,132(45):15852-15855
The first water-tolerant, ketone-type indium homoenolate was synthesized via the oxidative addition of In/InCl(3) to enones. The reaction proceeds exclusively in aqueous media. Both indium and indium(III) chloride are necessary for the smooth conversion of the reaction. Similar results were obtained when InCl or InCl(2) was used in place of In/InCl(3). The synthetic utility of the indium homoenolate was demonstrated through the synthesis of 1,4-dicarbonyl compounds via palladium-catalyzed coupling of indium homoenolate with acid chloride. 相似文献
50.
This article demonstrates that it is not always beneficial to exfoliate graphitic structures to single-layer graphene to achieve maximum electrochemical performance. Using electrochemical impedance spectroscopy, we show that multilayer graphene nanoribbons with cross sections of 100 × 100 nm provide larger capacitance (15.6 F/g) than do few-layer graphene nanoribbons (14.9 F/g) and far larger capacitance than single-layer graphene nanoribbons (10.9 F/g) with the same cross section. 相似文献