Empirical regularities of opening call auction in Chinese stock market

We study the statistical regularities of an opening call auction using the ultra-high-frequency data of 22 liquid stocks traded on the Shenzhen Stock Exchange in 2003. The distribution of the relative price, defined as the relative difference between the order price in the opening call auction and the closing price on the last trading day, is asymmetric and that the distribution displays a sharp peak at the zero relative price and a relatively wide peak at the negative relative price. The detrended fluctuation analysis (DFA) method is adopted to investigate the long-term memory of relative order prices. We further study the statistical regularities of order sizes in the opening call auction, and observe a phenomenon of number preference, known as order size clustering. The probability density function (PDF) of order sizes could be well fitted by a q-Gamma function, and the long-term memory also exists in order sizes. In addition, both the average volume and the average number of orders decrease exponentially with the price level away from the best bid or ask price level in the limit-order book (LOB) established immediately after the opening call auction, and a price clustering phenomenon is observed.     

Scaling and memory in the non-Poisson process of limit order cancelation

The order submission and cancelation processes are two crucial aspects in the price formation of stocks traded in order-driven markets. We investigate the dynamics of order cancelation by studying the statistical properties of inter-cancelation durations, defined as the waiting times between consecutive order cancelations of 22 liquid stocks traded on the Shenzhen Stock Exchange of China in year 2003. Three types of cancelations are considered, including cancelation of any limit orders, of buy limit orders and of sell limit orders. We find that the distributions of the inter-cancelation durations of individual stocks can be well modeled by Weibulls for each type of cancelation, and the distributions of rescaled durations of each type of cancelations exhibit a scaling behavior for different stocks. Complex intra-day patterns are also unveiled in the inter-cancelation durations. The detrended fluctuation analysis (DFA) and the multifractal DFA show that the inter-cancelation durations possess long-term memory and multifractal nature, which are not influenced by the intra-day patterns. No clear crossover phenomenon is observed in the detrended fluctuation functions with respect to the time scale. These findings indicate that the cancelation of limit orders is a non-Poisson process, which has potential worth in the construction of order-driven market models.     

532nm激光作用下甲基异丙基酮的电离解离研究

在532 nm激光波长下,利用时间飞行质谱(TOF-MS)对甲基异丙基酮的多光子电离解离机制进行了研究.实验结果显示,母体分子首先发生α断裂并且吸收(2+2)个光子到达离子态.主要的质谱峰C_2H_3~+,CH_3COC_3H_7~+,CH_3~+等在质谱图中清晰可见.结合Guassian03,运用HF/3-21G、CIS/3-21G对基态和激发态的构型进行了优化和频率计算,发现激发态的碳氧键变为介于碳氧单键和双键之间特殊键,并用QST2方法找到了其中的过渡态,对三个状态的几何结构参数进行了分析得出了其解离过程是α键断裂和基团构象转化协同进行的结论.     

Sensitive and Facile Determination of Catechol and Hydroquinone Simultaneously Under Coexistence of Resorcinol with a Zn/Al Layered Double Hydroxide Film Modified Glassy Carbon Electrode

A stable dihydroxybenzene sensor was fabricated by electrochemical deposition of Zn/Al layered double hydroxide film on glassy carbon electrode (LDHf/GCE). The sensitive and facile electrochemical method for the simultaneous determination of catechol (CA) and hydroquinone (HQ) under coexistence of resorcinol (RE) has been achieved at the LDHf/GCE in phosphate buffer solution (pH 6.5). Under the optimized conditions, the differential pulse voltammetry response of the modified electrode to CA (or HQ) shows a linear concentration range of 0.6 μM to 6.0 mM (or 3.2 μM to 2.4 mM) with a correlation coefficient of 0.9987 (or 0.9992) and the calculated limit of detection is 0.1 μM (or 1.0 μM) at a signal‐to‐noise ratio of 3. In the presence of 50 μM isomer, the linear concentration ranges for CA and HQ are 3.0 μM to 1.5 mM and 12.0 μM to 0.8 mM, respectively. The detection limits are 1.2 μM and 9.0 μM. Further, the proposed method has been performed to successfully detect dihydroxybenzene isomers in analysis of real samples, such as water and tea.     

Preparation and characterization of microencapsulated ammonium polyphosphate with polyurethane shell by in situ polymerization and its flame retardance in polyurethane

Microencapsulated ammonium polyphosphate (APP) with polyurethane (MCAPP) was prepared by in situ polymerization of pentaerythtritol (PER) and toluene‐2,4‐diisocyanate (TDI) in the presence of added APP. MCAPP was then incorporated into polyurethane (PU) to obtain flame retarded PU/MCAPP. Fourier transform infrared (FT‐IR) and X‐ray photoelectron spectroscopy (XPS) showed that APP was encapsulated by a layer of PU. It found that the optimal reaction time was 8 hr and microencapsulation led to an improvement in water leaching from scanning electron microscopy (SEM) and determination of water resistance. Thermal degradation of flame retarded PU was also investigated by thermogravimetric analysis (TGA). UL‐94 test and SEM were performed before and after water treatment at 75°C for seven days, and the results showed that PU loading of 30% MCAPP can maintain the V‐0 level, due to the shield effect of microencapsulation. Copyright © 2008 John Wiley & Sons, Ltd.     

Simultaneous processes of electricity generation and p-nitrophenol degradation in a microbial fuel cell

This study initially demonstrates that the electricity generated by a microbial fuel cell (MFC) can be used to in situ generate H₂O₂ at a carbon felt cathode. In the presence of scrap iron, H₂O₂ further reacts with Fe²⁺ to produce hydroxyl radicals. Attributed to the oxidation of H₂O₂ and hydroxyl radicals, and the oxidation–reduction of scrap iron, p-nitrophenol was significantly removed in the cathode chamber of the MFC. The p-nitrophenol was completely degraded after 12 h, and about 85% of TOC was removed after 96 h. Simultaneously, a maximum power density (143 mW m^?2) was generated by the MFC. It is concluded that a MFC not only can generate electricity and degrade biodegradable compounds, but also remove bio-refractory pollutants.     

Gold Supported on Hydroxyapatite as a Versatile Multifunctional Catalyst for the Direct Tandem Synthesis of Imines and Oximes

Two birds with one auric stone : The title system acts as a highly efficient heterogeneous catalyst for the one‐pot tandem synthesis of imines or oximes from alcohols and the corresponding amines under mild conditions (see scheme; HAP= hydroxyapatite).

     

Electrochemical Studies on the Interaction of Heparin with Phenosafranine and Its Analytical Application

The interaction of phenosafranine (PSF) with a glycosaminoglycan of heparin (Hep) in aqueous solution was characterized by cyclic voltammetry (CV) and linear sweep voltammetry (LSV) in this paper and further used for Hep detection. In pH 1.5 Britton‐Robinson (B‐R) buffer solution PSF had a well‐defined voltammetric reductive peak at ?0.256 V (vs SCE), and the electrochemical response was faded by the addition of Hep. Cyclic voltammetric experiments indicated that the electrochemical behaviors of free PSF didn't change no matter whether Hep was presented in PSF solution or not. Based on the decrease of the peak current, a second order derivative linear sweep voltammetry was used to establish a sensitive electroanalytical method for Hep. The peak current was proportional to the concentration of Hep in the range of 0.7～20.0 mg L^?1, demonstrating that this method was suitable for routine Hep detection. Under optimal conditions, the linear regression equation for the Hep determination was ΔIp”(nA) = 46.30 C (mg L^?1) + 343.31 (n = 11, γ = 0.991) with a detection limit of 0.08 mg L^?1 (3σ). The established method was further successfully applied to heparin sodium injection samples determination. The interaction mechanism was discussed based on the electrostatic attraction of the negatively charged Hep with the positively charged PSF, and the stoichiometry of Hep‐PSF was calculated by the voltammetric method.     

关于GL(3,2)的两个反例

指出GL(3,2)的两个不共轭的{2,3}-Hall子群都和S_4同构.由此,进一步给出两个不同构的S_4-模提供相同2-Brauer特征标的例子.     

求解单变量无约束优化问题的一类新割线法

本文基于分式逼近提出了一类求解单变量无约束优化问题的新割线法,给出并证明了该方法的收敛阶是(√2+1).并进一步对新方法的性能进行了分析,给出了新方法、经典的牛顿法和其他修正的割线类方法解单变量无约束优化问题的数值实验.理论和数值结果均表明新的割线法是有效的.