A simple miniaturised photometrical method for rapid determination of nitrate and nitrite in freshwater

A rapid, simple miniaturised photometrical method was developed for the determination of nitrate and/or nitrite in freshwater samples. All procedures, including sample buffering, reduction by copperised cadmium granules, colour development and absorbance determination, were completed in a 96-well microplate. The factors governing the nitrate reduction and its recovery were investigated in detail, and the optimised analysing conditions were established. Nitrate was quantitatively reduced by copperised cadmium granules with a high reduction efficiency (96.59 ± 0.96%). The proposed method gave a linear calibration ranging from 0.01 to 1.50 mg L⁻¹ for NO₂⁻-N and 0.02 to 1.50 mg L⁻¹ for NO₃⁻-N. The detection limits for nitrite and nitrate were 2 and 4 μg L⁻¹, respectively. The proposed method allowed at least 48 samples to be simultaneously analysed in duplicate, with good precision, within 90 min for nitrate and 30 min for nitrite, and was successfully applied to actual freshwater sample analysis with a recovery of 98.02 ± 1.04% for nitrite and 99.72 ± 1.39% for nitrate. This method produced accurate results comparable to standard methods, provided a much higher sample throughput than conventional methods and could be routinely used in actual freshwater sample monitoring.     

端三吡啶基聚异丙基丙烯酰胺的合成及其金属配合物

合成出三吡啶官能化的二硫代酯并以其作为链转移剂进行了异丙基丙烯酰胺(NIPAAm)的可逆加成断裂链转移(RAFT)聚合,得到分子量可控和窄分子量分布的端三吡啶基聚异丙基丙烯酰胺(tpy-PNIPAAm),聚合反应为对单体浓度的一级动力学关系.Tpy-PNIPAAm在水中既保持了与聚异丙基丙烯酰胺类似的相转变行为,又拥有三吡啶(tpy)的强络合能力.将tpy-PNIPAAm与金属核素模型进行络合得到金属配合物,所得金属配合物在水中拥有与PNIPAAm类似的相转变行为,同时tpy-PNIPAAm的金属配合物由于其两亲性,在水中可以形成纳米粒子,由于纳米粒子间的静电排斥作用,这种纳米粒子即使在高于相转变温度时,仍能稳定于水中.     

Non-zero-sum stochastic differential reinsurance and investment games with default risk

This paper investigates the implications of strategic interaction (i.e., competition) between two CARA insurers on their reinsurance-investment policies. The two insurers are concerned about their terminal wealth and the relative performance measured by the difference in their terminal wealth. The problem of finding optimal policies for both insurers is modelled as a non-zero-sum stochastic differential game. The reinsurance premium is calculated using the variance premium principle and the insurers can invest in a risk-free asset, a risky asset with Heston’s stochastic volatility and a defaultable corporate bond. We derive the Nash equilibrium reinsurance policy and investment policy explicitly for the game and prove the corresponding verification theorem. The equilibrium strategy indicates that the best response of each insurer to the competition is to mimic the strategy of its opponent. Consequently, either the reinsurance strategy or the investment strategy of an insurer with the relative performance concern is riskier than that without the concern. Numerical examples are provided to demonstrate the findings of this study.     

High power diode-pumped 914-nm Nd：YVO_4 laser

<正>A high power continuous-wave(CW) 914-nm Nd:YVO_4 laser at room temperature is presented.Using an end-pumped structure and employing an 808-nm diode-laser as the pump source,the maximum output power of 15.5 W of the 914-nm laser is achieved at the absorbed pump power of 40.2 W,with a corresponding average slope efficiencyη_s=65.6%.To the best of our knowledge,this is the highest output power of diode-pumped 914-nm laser.A beam quality factor M~2=2.8 at the output power of 15 W is measured by using the traveling knife-edge method.     

A Novel Chitosan/Polyvinyl Pyrrolidone (CS/PVP) Three-Dimensional Composite and Its Mechanism of Strength Improvement

Novel biodegradable three-dimensional (3D) composites with good mechanical properties have been prepared by coagulation of a chitosan/polyvinyl pyrrolidone (CS/PVP) solution in NaOH. For example, the strength and modulus of CS/PVP (1/1) were 82.5 MPa and 1.86 GPa, increasing 237% and 644% compared with CS, respectively. Scanning electron microscopy and Fourier transform infrared analysis suggest that the PVP component did not dissolve during the preparation process. The nonsolution of the composites is attributed to the extremely strong hydrogen bonding formed between the CS and PVP macromolecules. It was also found that there are synergistic effects between the formation of hydrogen bonding with PVP and cross-linking with glutaraldehyde (GA) for the improvement in the mechanical properties of CS. The mechanism of strength improvement has been discussed thoroughly from the aspects of free volume.     

无规聚丙烯接枝甲基丙烯酸的合成

采用溶液聚合的方法将无规聚丙烯 (APP)与甲基丙烯酸 (MAA)接枝共聚制得接枝共聚物APP -g -MAA。讨论了反应温度、反应时间、引发剂BPO浓度、单体MAA浓度对接枝率的影响。结果表明 :当聚合反应温度低于是 12 0℃时 ,接枝率随温度升高而降低。延长反应时间有利于提高接枝率。最适宜的引发剂浓度为 1% ,MAA/APP配比为 0 .2 5/1。利用红外光谱证实了接枝物APP-g -MAA的存在。     

支载型分子印迹聚合物膜的制备及其透过选择性研究

以2-氨基吡啶为模板,采用聚四氟乙烯微孔膜为支载膜,甲基丙烯酸为功能单体,偶氮二异丁腈为引发剂,紫外光引发聚合,制备出支载型分子印迹膜,并研究了分子印迹膜对2-氨基吡啶及其结构类似物的透过选择性,并对甲基丙烯酸与2-氨基吡啶之间的相互作用和膜的形貌进行了表征。结果表明,甲基丙烯酸对模板分子能够形成摩尔比为1∶2的配合物,分子印迹膜能够实现2-氨基吡啶与其类似物的分离。     

Synthesis, basicity, and dynamics of a perfluorocyclohexenyl anion

Electron transfer to perfluoro-1,3-dimethylcyclohexane in moist THF has yielded two quite different products. Tetrabutylammonium iodide irradiated with ultraviolet light gives a tetrabutylammonium enolate, but potassium fluorenone ketyl affords a cyclohexenyl anion. This allylic anion was isolated as its conjugate acid, a rather strong carbon acid. Ring inversion in the anion, measured by (19)F NMR line shape analysis, is characterized by these activation parameter values: DeltaH(++) = 8.84 +/-0.14 kcal/mol and DeltaS(++) = 0.81 +/- 0.6 cal mol(-1) K(-1).     

折射法与定时进样气相色谱法快速测定丙烯酰胺和丙烯腈

为了满足游离细胞催化、多级膜生物反应器连续转化生产丙烯酰胺的新工艺对丙烯酰胺和丙烯腈浓度进行监控的需要，分别提出了采用阿贝折射仪快速分析丙烯酰胺和定时进样气相色谱外标法快速分析丙烯腈浓度的新方法。与传统的丙烯酰胺和丙烯腈的气相色谱内标方法相比，新方法在保持原有气相色谱分析精度的基础上，显著提高了分析的时效性，可以对各级成分变化做准确及时的分析和监控，从而保证了多级膜反应器连续转化过程的操作稳定性。     

冠醚配合物热力学性质的研究(Ⅶ)-碱金属与2,3-苯并-6-甲基-15-冠-5配位反应的量热滴定研究

用自制跟踪绝热式滴定量热计研究了新合成的2,3-苯并-6-甲基-15-冠-5在无水甲醇介质中与碱金属的配位反应。