Bisabocurcumin, a new skeleton curcuminoid from the rhizomes of Curcuma longa L.

A new skeleton bisabolane-type sesquiterpene curcuminoid,bisabocurcumin(1),along with 5 known compounds,curcumin(2), demethoxycurcumin(3),bidemethoxycurcumin(4),(1E,4E)-1,5-bis(4-hydroxy-3-methoxyphenyl)-penta-1,4-dien-3-one(5),and (1E,4E)-1-(4-hydroxy-3-methoxyphenyl)-5-(4-hydroxy phenyl-)-penta-1,4-dien-3-one(6)were isolated from the rhizomes of Curcuma longa L.Their structures were determined on the basis of spectroscopic analysis.Bisabocurcumin(1) is firstly obtained from nature with a new skeleton combined by a bisabolane-type sesquiterpene and a 1,7-diphenylheptanoid through a C-C bond.     

DFT study on the selective oxidation of vinyl chloride on different metal surfaces

Selective epoxidation of vinyl chloride on Ag(111), Pt(111) and Rh(111) with pre-adsorbed atomic oxygen has been studied by density functional theory (DFT) calculation with the periodic slab model. The reaction energies and activation energies of the epoxidation reaction are determined. Because of the asymmetry of vinyl chloride, three competitive reaction pathways are investigated. The results indicate that the most possible reaction pathway is pathway III. Compared the activation energies of the epoxidation reaction on Ag(111), Pt(111) and Rh(111), it is obvious that the reaction via OMMC(3) on Ag(111) is the most possible process. However, the selectivity to the target product over Ag(111) is the lowest among the three metals. The results also indicate that the formation of chloroacetaldehyde is more favorable than that of chloroepoxide.     

介质阻挡放电诱导化学蒸气发生-ICP-OES测定痕量Se(IV)

本文将介质阻挡放电诱导化学蒸气发生与电感耦合等离子体原子发射光谱分析法联用,用于痕量Se(IV)的选择性测定.考察了介质阻挡放电诱导化学蒸气发生的主要影响因素.在最优的实验条件下,甲酸浓度为15%时,本方法对Se(IV)的检出限(3σ)为6μg·L-1,测定100μg·L-1 Se(IV)溶液的相对标准偏差(n=11)...     

新型多氧取代环己烯酮的合成

以莽草酸为起始原料,经酯化、丙酮叉保护顺式邻二羟基、叔丁基二甲硅烷保护羟基、还原、羟基酯化、脱保护基、保护反式邻二羟基、烯丙醇氧化,脱保护基共9步反应,合成了新型(5R,6S)-3-苯甲酰氧基亚甲基-5,6-二羟基-2-环己烯-1-酮,总产率19.3％,其结构经1H NMR,IR和HR-MS表征.     

3,4‐Dihydroxy‐L‐phenylalanine for Preparation of Gold Nanoparticles and as Electron Transfer Promoter in H2O2 Biosensor

3,4‐Dihydroxy‐L ‐phenylalanine (dopa) and 2‐(3,4‐dihydroxyphenyl)ethylamine (dopamine) were investigated as reducing agent and stabilizer for synthesis of gold nanoparticles (AuNPs) by one‐pot heating of a solution of HAuCl₄/dopa or dopamine. AuNPs with different sizes were obtained by controlling the mass ratios of HAuCl₄/dopa or dopamine. The formation mechanism for AuNPs was also proposed. Immobilization of horseradish peroxidase (HRP) and promotion of its electron transfer by polydopa film were investigated for preparation of H₂O₂ biosensor. Alkaline dopa solution was dropped onto a gold electrode for the formation of polydopa film. HRP was immobilized on the polydopa film through interactions between heme centre of HRP and the amine and carboxyl groups in polydopa. The AuNPs embedded in the polydopa film improved the electron transfer efficiency. These two factors allowed successful development of a H₂O₂ sensor with HRP@polydopa‐AuNPs electrode. Due to its biocompatibility, the polydopa‐AuNPs film provided good retention of enzyme activity and long‐term stability of the sensor. A rapid catalytic response (3 s) and a linear range from 0.006 to 5.0 mmol L^?1 were obtained for H₂O₂. This facile preparation strategy can be extended to other enzyme‐based biosensors.     

Heterogeneous reaction of suspended phosmet particles with NO3 radicals

As an organophosphorous insecticide, phosmet is widely used for plant protection as well as against the ectoparasites on productive livestock. It emits into the atmosphere in both gas and particulate phases via spray drift from treatments and postapplication emissions, but its degradation in the atmosphere is not well-known up to now. In this study, the heterogeneous reaction of phosmet absorbed on the azelaic acid particles with NO(3) radicals is investigated in real-time using a vacuum ultraviolet photoionization aerosol time-of-flight mass spectrometer (VUV-ATOFMS). Two primary products and their nitro-substituted derivates are observed. The apparent reaction rate of phosmet particles with NO(3) radicals is also obtained by a relative rate method with isoprene and 1,4-cyclohexadiene as the reference compounds. The concentrations of the reference substance and phosmet particles are synchronously detected with an atmospheric gas analysis mass spectrometer and the VUV-ATOFMS. Under the experimental conditions, the average apparent reaction rate obtained is (1.92 ± 0.09) × 10(-12) cm(3) molecule(-1) s(-1), and the corresponding atmospheric lifetime toward NO(3) radicals is roughly estimated to be ~0.3 h.     

Erratum to: “On the HSS iteration methods for positive definite Toeplitz linear systems” [J. Comput. Appl. Math. 224 (2009) 709-718]

In [1], Gu and Tian [Chuanqing Gu, Zhaolu Tian, On the HSS iteration methods for positive definite Toeplitz linear systems, J. Comput. Appl. Math. 224 (2009) 709-718] proposed the special HSS iteration methods for positive definite linear systems Ax=b with A∈C^n×n a complex Toeplitz matrix. But we find that the special HSS iteration methods are incorrect. Some examples are given in our paper.     

Dynamic lot-sizing in sequential online retail auctions

Retailers often conduct non-overlapping sequential online auctions as a revenue generation and inventory clearing tool. We build a stochastic dynamic programming model for the seller’s lot-size decision problem in these auctions. The model incorporates a random number of participating bidders in each auction, allows for any bid distribution, and is not restricted to any specific price-determination mechanism. Using stochastic monotonicity/stochastic concavity and supermodularity arguments, we present a complete structural characterization of optimal lot-sizing policies under a second order condition on the single-auction expected revenue function. We show that a monotone staircase with unit jumps policy is optimal and provide a simple inequality to determine the locations of these staircase jumps. Our analytical examples demonstrate that the second order condition is met in common online auction mechanisms. We also present numerical experiments and sensitivity analyses using real online auction data.     

Comments on “Competitive analysis of a better on-line algorithm to minimize total completion time on a single-machine”

For the single machine scheduling problem of minimizing the total completion time, Montoya Torres (J Glob Opt 27:97–103, 2003) presented a semi-online algorithm under the assumption that release dates are known in advance, and showed that it was \({\sqrt{3}}\)-competitive. However, there are flaws in the proof, and the conclusion about the competitive ratio is not correct. In this note, we show that the semi-online algorithm cannot perform better than the best non-clairvoyant online algorithm with a competitive ratio of 2.