Showing papers by "Nankai University published in 2002"
TL;DR: This work provides mutual authentication between the user and the server and achieves more functionality and requires much less computational cost than other smart card-based schemes.
474 citations
TL;DR: In this article, a new protocol for the Biginelli reaction was proposed, which produces excellent yields, allows the recycling of catalyst with no loss in its activity, and leads to zero-discharge during the process.
325 citations
TL;DR: Receptor models infer contributions from particulate matter (PM) source types using multivariate measurements of particle chemical and physical properties, and complement source models that estimate concentrations from emissions inventories and transport meteorology.
286 citations
TL;DR: Values of R = sigma(e(+e(-)-->hadrons)/sigma( e(+)e (-)-->mu(+)mu(-)) for 85 center-of-mass energies between 2 and 5 GeV measured with the upgraded Beijing Spectrometer at the Beijing Electron-Positron Collider are reported.
Abstract: We report values of $R\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\ensuremath{\sigma}({e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}\mathrm{hadrons})/\ensuremath{\sigma}({e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}})$ for 85 center-of-mass energies between 2 and $5\mathrm{GeV}$ measured with the upgraded Beijing Spectrometer at the Beijing Electron-Positron Collider.
239 citations
TL;DR: It is demonstrated recently that the Rh complex of (S)-1a (R CH3) is a highly efficient catalyst in the asymmetric hydrogenation of dehydroamino acid and itaconic acid derivatives with up to 99.3% ee, and for the first time, monodentate phosphorus ligands can be effective in the enantiocontrol of asymmetric Hydrogenation of enamides.
Abstract: Optically active -arylalkylamines are an important class of compounds that are widely used in organic and pharmaceutical synthesis, and much effort has been made to develop efficient asymmetric synthetic methods for them.[1] Asymmetric catalytic hydrogenation of enamides, initiated by Kagan et al. ,[2] provides a direct and convenient route to chiral amine derivatives. However, many well-known chiral diphosphane ligands, such as DIOP, BINAP, and CHIRAPHOS, which are extremely successful in the asymmetric hydrogenation of dehydroamino acid derivatives, do not give high enantioselectivity in the hydrogenation of enamides.[3, 4] A breakthrough was achieved by Burk et al.[4a] with the introduction of BPE and DuPHOS ligands, which gave excellent enantioselectivity in the Rh-catalyzed asymmetric hydrogenation of enamides. Lately, some other P ligands were also reported to be efficient in the hydrogenation of enamides.[4b, 5] However, all ligands that gave a high degree of enantiocontrol are bidentate. To our knowledge, no efficient chiral monodentate ligand has been reported for the asymmetric hydrogenation of enamides, although some monodentate P ligands were successfully used in the hydrogenation of dehydroamino acid derivatives.[6] Here we describe highly efficient monodentate chiral ligands 1 containing a 1,1 -spirobiindane backbone for the Rh-catalyzed asymmetric hydrogenation of -arylethenylamine derivatives [Eq. (1)] with excellent enantioselectivities (up to 99.7% ee). The chiral monodentate phosphoramidite ligands 1 (abbreviated SIPHOS) were conveniently synthesized in good yields from enantiomerically pure 1,1 -spirobiindane-7,7 -diol, which was easily prepared from 3-methoxybenzaldehyde by using the procedure described by Birman et al.[7] We demonstrated recently that the Rh complex of (S)-1a (R CH3) is a highly efficient catalyst in the asymmetric hydrogenation of dehydroamino acid and itaconic acid derivatives with up to 99.3% ee. Therefore, we were prompted to investigate the utility of this catalyst in the asymmetric hydrogenation of -phenylenamide 4a and an excellent enantioselectivity (up to 98.8% ee) was achieved. This showed, for the first time, that monodentate phosphorus ligands can be effective in the enantiocontrol of asymmetric hydrogenation of enamides. The results in Table 1 show that the enantioselectivity of the reaction was sensitive to the solvent used, and toluene is the solvent of choice. In contrast, the hydrogen pressure has a negligible influence on the enantioselectivity. For example, in the hydrogenation of 4a with Rh/(S)-1a catalyst in toluene, the ee values of product 5a at 25 C under 10 atm and 100 atm H2 were 96% and 96.2%, respectively (Table 1, entries 1 and 2). The investigation of catalyst loading showed that 0.5 mol% catalyst was sufficient to give a high enantioselectivity, while the ee value of the product dropped drastically with 0.1 mol% catalyst.
190 citations
TL;DR: In this paper properties and construction of designs under a centered version of the L2-discrepancy are analyzed and optimization is performed using the threshold accepting heuristic which produces low discrepancy designs compared to theoretic expectation and variance.
Abstract: In this paper properties and construction of designs under a centered version of the L2-discrepancy are analyzed. The theoretic expectation and variance of this discrepancy are derived for random designs and Latin hypercube designs. The expectation and variance of Latin hypercube designs are significantly lower than that of random designs. While in dimension one the unique uniform design is also a set of equidistant points, low-discrepancy designs in higher dimension have to be generated by explicit optimization. Optimization is performed using the threshold accepting heuristic which produces low discrepancy designs compared to theoretic expectation and variance.
186 citations
TL;DR: The synthesis of open-ended MoS2 nanotubes and their application as the catalyst for methanation of carbon monoxide with hydrogen are reported and may provide new solutions toward harnessing the environmental load caused by CO emission.
160 citations
TL;DR: The synthesis and crystal structure of the three-dimensional coordination polymer of an angular dipyridyl ligand 2,5-bis(4-pyridol)-1,3,4-oxadiazole (L) and Cu(ClO(4))(2), exhibiting the first Cu(II) diamondoid network with 2-fold interpenetration, are reported.
Abstract: The synthesis and crystal structure of the three-dimensional coordination polymer of an angular dipyridyl ligand 2,5-bis(4-pyridyl)-1,3,4-oxadiazole (L) and Cu(ClO4)2, exhibiting the first CuII diamondoid network with 2-fold interpenetration, {[Cu(L)2(H2O)2](ClO4)(OH)(H2O)2.5}n (1), together with the Cu(OAc)2 complex of L, [Cu(L)2(OAc)2(H2O)](H2O)2(CH3OH) (2), with an unexpected mononuclear structure, are reported. Crystal data for 1: tetragonal, space group I41/a, a = b = 13.477(3) A, c = 46.167(13) A, Z = 8. Crystal data for 2: triclinic, space group P1, a = 7.847(2) A, b = 13.189(4) A, c = 15.948(5) A, α = 75.225(7)°, β = 79.945(6)°, γ = 77.540(5)°, Z = 2. The magnetic properties and anion effect are also discussed.
157 citations
TL;DR: In this paper, the inclusion complexation behavior of some dye guest molecules with two kinds of molecular receptors, i.e., native α-, β-, and γ-cyclodextrins, and chemically modified β-cyclodesxtrin, and water-soluble calix[n]arenesulfonates (n = 4, 6, 8) and their lower rim alkylated derivatives, was investigated.
Abstract: The inclusion complexation behavior of some dye guest molecules with two kinds of molecular receptors, i.e., native α-, β-, and γ-cyclodextrins, and chemically modified β-cyclodextrins, and water-soluble calix[n]arenesulfonates (n = 4, 6, 8) and their lower rim alkylated derivatives, has been investigated. It was found that the fluorescence intensity of guest molecules evidently changes upon the addition of molecular receptors. The calix[n]arenesulfonates (n = 4, 6, 8) cause gradual decreases in the fluorescence intensity, whereas native α-, β-, and γ-cyclodextrins cause gradual increases in the fluorescence intensity. Interestingly, the fluorescence intensity of dye guest molecules gradually increases upon the addition of the lower rim alkylated calix[n]arenesulfonate derivatives (n = 4, 6, 8), in contrast to their parent calix[n]arenesulfonates (n = 4, 6, 8). Meanwhile, chemically modified cyclodextrins still show the same effect on the fluorescence intensity of dye guest molecules; however, the hydroph...
144 citations
TL;DR: In homogeneous H(2)O/solvent medium, the reaction rate of aromatic aldehydes and acrylonitrile or acrylate was greatly accelerated, which led to shorter reaction time, lower reaction temperature, and higher yield.
144 citations
TL;DR: In this paper, a method to determine the focal length of a thermal lens and the beam waist in the gain medium in laser-diode-pumped solid-state lasers is presented.
Abstract: A method to determine the focal length of a thermal lens and pumping laser beam waist in the gain medium in laser-diode-pumped solid-state lasers is presented. This method, using resonator transform circle theory, is both simple and reliable. The measured focal length of the thermal lens is used to calculate the beam waist of pumping laser inside the gain medium. The effect of the thermal lens on the output power is also measured and analyzed.
TL;DR: The crystal structure of a 3D coordination polymer of AgI and a simple bisthioether ligand, [Ag2(L)3(ClO4)2]n, exhibiting a chiral and noninterpenetrated (10,3)-a net is reported.
Abstract: The crystal structure of a 3D coordination polymer of AgI and a simple bisthioether ligand, [Ag2(L)3(ClO4)2]n, exhibiting a chiral and noninterpenetrated (10,3)-a net is reported.
TL;DR: Histological and histomorphological studies proved that P-chitosan containing cements are biocompatible, bioabsorbable and osteoinductive and could be used as bone substitutes in clinic.
TL;DR: Novel monodentate phosphorus ligands containing the 1,1'-spirobiindane backbone have been synthesized and applied in the asymmetric rhodium-catalyzed hydrogenation of functionalized olefins, providing excellent enantioselectivities.
TL;DR: Volatiles from A. conyzoides plants infected with E. cichoracearum or exposed to A. gossypii feeding inhibited or killed fungi and insects, and phytoinhibitory effects decreased under fungal infection and aphid feeding.
Abstract: The allelopathic potential of Ageratum conyzoides was investigated under different environmental stress conditions, including nutrient deficiency, physical damage, 2,4-D treatment, competition with Bidens pilosa, infection with Erysiphe cichoracearum, and feeding by Aphiids gossypii. The inhibitory effects of A. conyzoides volatiles on peanut (Arachis hypogaea), redroot amaranth (Amaranthus retroflexus), cucumber (Cucumis sativus), and ryegrass (Lolium multiforum) increased when plants were grown under nutrient-deficient conditions or in competition with B. pilosa; however, there was no difference with physical damage or 2,4-D treatment. Phytoinhibitory effects decreased under fungal infection and aphid feeding. Volatiles from A. conyzoides plants infected with E. cichoracearum or exposed to A. gossypii feeding inhibited or killed fungi and insects. Precocenes and their derivatives, monoterpenes, and sesquiterpenes were the major volatile components of A. conyzoides.
TL;DR: It is proved that regular graphs with order more than 5 have at least one 3-RC, and it is shown that vertex-and edge-transitive graphs other than cycles are super-λ(3).
TL;DR: Outdoor human exposure assessment requires measurements taken continuously throughout the day, preferably over durations of 1 h or less, and more detailed particle size and chemistry data are also desirable, as smaller size fractions and specific chemicals may be better indicators of adverse health effects than total mass samples.
TL;DR: In this article, the difference of surface acidic features between tetragonal and monoclinic nanostructured zirconia was analyzed and a parallel relationship between Zr 4þ density and the surface acid-site density was established.
TL;DR: The analytical results obtained by the present method for total arsenic in the certified reference materials, SLRS-4 (river water) and NASS-5 (seawater), agreed well with the certified values.
Abstract: A flow injection on-line sorption preconcentration and separation in a knotted reactor (KR) was coupled to hydride generation atomic fluorescence spectrometry (HG-AFS) for speciation of inorganic arsenic in natural water samples. The method involved on-line formation of the As(III)−pyrrolidinedithiocarbamate (PDC) complex over a sample acidity of 0.001−0.1 mol L-1 HCl, its adsorption onto the inner walls of the KR made from 150-cm long × 0.5-mm i.d. PTFE tubing, elution with 1 mol L-1 HCl, and detection by HG-AFS. Total inorganic arsenic was determined after prereduction of As(V) to As(III) with 1% m/v L-cysteine. The concentration of As(V) was calculated by the difference of the total inorganic arsenic and As(III). A 1 mol L-1 concentration of HCl was employed not only as the efficient eluent but also as the required medium for subsequent hydride generation. Potential factors that affect adsorption, rinsing, elution, and hydride generation were investigated in detail. The low cost, easy operation, and hi...
TL;DR: In this paper, the structures of complexes 1 and 3 were determined by single crystal X-ray analysis, which indicated that complex 1 exists in a square planar configuration, while complex 3 is dimeric square pyramidal.
Abstract: The novel chloro(1-naphthyl)[8-(diphenylphosphino)quinoline]nickel(II)
(1), chloro(1-naphthyl)[2-methyl-8-(diphenylphosphino)quinoline]nickel(II)
(2), and [2-methyl-8-(diphenylphosphino)quinoline]nickel(II) dichloride (3) complexes were synthesized in satisfactory yield and fully characterized. The structures of complexes 1 and 3 were determined by single crystal X-ray analysis, which indicated that complex 1 exists in a square planar configuration, while complex 3 is dimeric square pyramidal. In the presence of MAO cocatalyst, complexes 1–3 displayed good catalytic activities for ethylene oligomerization in toluene, up to 2.45 × 105 g ethylene (mol Ni·h·atm)−1 by complex 3.
TL;DR: In this article, the authors used solvated metal atom impregnation (SMAI) and conventional impregnation (CI) for carbon monoxide oxidation in CO and air.
Abstract: Cu/CeO2 and CuO/CeO2 catalysts were prepared by solvated metal atom impregnation (SMAI) and conventional impregnation (CI) and used for carbon monoxide oxidation in CO and air. The catalysts were characterized by means of XRD, XPS, AES and H2-TPR techniques. The Cu/CeO2 catalyst prepared via SMAI exhibits higher catalytic activity in CO oxidation than that prepared via CI with the same Cu content due to the smaller Cu particles. The CuO/CeO2 catalyst prepared via SMAI also shows higher catalytic activity than that prepared via CI because the CuO particles of the former are smaller than the latter and can be reduced by CO more easily. The Cu/CeO2 catalysts display higher catalytic activities than CuO/CeO2 catalysts with the same Cu content and prepared by the same method. The TPR profile for CuO/CeO2 catalyst prepared via SMAI has a single peak, indicating a one-step reduction, whereas the TPR profile for CuO/CeO2 catalyst prepared via CI has two peaks, indicating a two-step reduction due to the existence of two kinds of CuO species.
TL;DR: In this paper, the authors considered a risk model with two dependent classes of insurance business and derived explicit expressions for the ultimate survival probabilities under the assumed model when the claim sizes are exponentially distributed.
Abstract: In this paper we consider a risk model with two dependent classes of insurance business In this model the two claim number processes are correlated Claim occurrences of both classes relate to Poisson and Erlang processes We derive explicit expressions for the ultimate survival probabilities under the assumed model when the claim sizes are exponentially distributed We also examine the asymptotic property of the ruin probability for this special risk process with general claim size distributions
TL;DR: This article extends the new strategy to map quantitative trait loci (QTL), using molecular markers within the EM-implemented maximum-likelihood framework, so increasing the efficiency and effectiveness of genome mapping for recalcitrant outcrossing species.
Abstract: Linkage analysis and allelic association (also referred to as linkage disequilibrium) studies are two major approaches for mapping genes that control simple or complex traits in plants, animals, and humans. But these two approaches have limited utility when used alone, because they use only part of the information that is available for a mapping population. More recently, a new mapping strategy has been designed to integrate the advantages of linkage analysis and linkage disequilibrium analysis for genome mapping in outcrossing populations. The new strategy makes use of a random sample from a panmictic population and the open-pollinated progeny of the sample. In this article, we extend the new strategy to map quantitative trait loci (QTL), using molecular markers within the EM-implemented maximum-likelihood framework. The most significant advantage of this extension is that both linkage and linkage disequilibrium between a marker and QTL can be estimated simultaneously, thus increasing the efficiency and effectiveness of genome mapping for recalcitrant outcrossing species. Simulation studies are performed to test the statistical properties of the MLEs of genetic and genomic parameters including QTL allele frequency, QTL effects, QTL position, and the linkage disequilibrium of the QTL and a marker. The potential utility of our mapping strategy is discussed.
TL;DR: The experiments showed that the dosage of oxidant H2O2, experimental temperature, pressure, reaction residence time and even initial concentration of the aniline in wastewater have a significant affect on the TOC removal.
TL;DR: The reactions of 3,6-di-2-pyridyl-1,2,4,5-tetrazine (DPTZ) with different Cu(II) salts generate two new ligands that form three new complexes, a mononuclear complex, a linear coordination polymer, and a cyclic tetranuclear complex.
Abstract: The reactions of 3,6-di-2-pyridyl-1,2,4,5-tetrazine (DPTZ) with different Cu(II) salts generate two new ligands, 2,5-bis(2-pyridyl)-1,3,4-oxodiazole (L(1)) and N,N'-bis(alpha-hydroxyl-2-pyridyl)ketazine (H(2)L(2)), from the metal-assisted hydrolysis of DPTZ, and form three new complexes: a mononuclear complex [Cu(L(1))(2)(H(2)O)(2)] .2ClO(4) (1), a linear coordination polymer [Cu(L(1))(NO(3))(2)](8) (2), and a cyclic tetranuclear complex [Cu(4)(L(2))(2)(Im)(2)(NO(3))(4)(H(2)O)(2)] (3) (Im = imidazole). Crystal data for 1: space group P2(1)/n with a = 10.339(3) A, b = 10.974(2) A, c = 13.618(4) A, beta = 103.24(1) degrees, and Z = 2. Crystal data for 2: space group C2/c with a = 13.9299(14) A, b = 9.2275(9) A, c = 12.1865(13) A, beta = 111.248(2) degrees, and Z = 4. Crystal data for 3: space group P2(1)/n with a = 9.3422(14) A, b = 15.987(2) A, c = 13.963(2) A, beta = 108.587(3) degrees, and Z = 2. L(1) acts as a bidentate chelating ligand in 1 and as a bis-bidentate chelating ligand in 2 with the shortest intramolecular Cu...Cu distance of 6.093 A. L(2) is a hexadentate ligand to bridge four Cu(II) ions, forming an interesting neutral cyclic tetranuclear complex 3 with Cu...Cu distances varying from 4.484 to 9.370 A. The mechanism of the metal assisted hydrolysis of DPTZ is discussed in detail. Magnetic susceptibility measurements indicate that 2 shows weak ferromagnetic interaction (J = 2.85 cm(-1)) along the 1-D helical chain, and that 3 displays weak antiferromagnetic interaction (J = -1.19 cm(-1) for the N-N bridge) and ferromagnetic interaction (j = 0.11 cm(-1) for the O-C=N bridge) between the adjacent Cu(II) ions.
TL;DR: It is shown that every function in a spline subspace is uniquely determined and can be reconstructed by its local averages near certain points.
TL;DR: The proposed HG-NDAFS method was successfully applied to the simultaneous determination of Cd and As in a variety of biological samples and the recoveries of spike analytes in the biological samples studied ranged from 94 to 109%.
Abstract: Hydride generation atomic fluorescence spectrometry (HG-AFS) has been used for determination of hydride-forming elements because of its high sensitivity, simplicity, and low costs, but most of such work has been concentrated on single element analysis, and reports dealing with multielement determination by HG-nondispersive (ND)AFS are rare. In this work, a sensitive HG-NDAFS method was developed for simultaneous determination of trace cadmium and arsenic in biological materials. The conditions for the generation of volatile cadmium and arsenic species from the reaction with KBH4 in aqueous solution were investigated using a double-channel AFS integrated with an intermittent flow reactor. Like thiourea and Co(II), ascorbic acid was found to significantly enhance the generation efficiency of volatile Cd and As species. The interferences of coexisting ions were evaluated. Under optimal conditions, the detection limits for Cd and As were determined to be 10 and 150 ng L(-1), respectively. The precision for 11 replicate determinations at the 1 microg L(-1) Cd level and the 10 microg L(-1) As level were 3.5 and 2.7% (RSD), respectively. The recoveries of spike analytes in the biological samples studied ranged from 94 to 109%. The proposed method was successfully applied to the simultaneous determination of Cd and As in a variety of biological samples.
TL;DR: A review with 136 references covers the literature from July 2000 to June 2001 on the isolation, bioactivities, and synthetic highlights of complex natural products including muscarine, imidazole, oxazoles, thiazole, Amaryllidaceae and Sceletium alkaloids.
TL;DR: The first tetranuclear NiII cluster showing triangle planar geometry, formed with a new carboxylic-functionalized 1,5-diazacyclooctane bridging ligand has been presented; the global magnetic coupling is ferromagnetic and anisotropic calculations have been made.
TL;DR: In aqueous media, imidazole was found to catalyse Baylis-Hillman reactions of cyclopent-2-enone with various aldehydes to afford the desired adducts with high yields as mentioned in this paper.