顶空气相色谱法测定杏脯中二氧化硫

建立顶空气相色谱测定杏脯中二氧化硫残留的方法,探讨了气液体积比、加酸量、平衡温度和平衡时间对检测结果的影响。向450 mL顶空瓶内加入5 g样品、10 g石蜡、200 mL水及25 mL盐酸溶液,于75℃平衡20 min后放至室温,抽取0.5 mL顶空气体进行定性定量分析检测。该方法标准工作曲线线性相关系数r~2为0.992,检出限和定量限分别为0.1,1.0 mg/kg,测定结果的相对标准偏差为1.9%~3.2%(n=6),样品加标回收率为89.4%~94.3%。该法操作简便、快捷,灵敏度高,人为误差小,满足杏脯中二氧化硫残留的批量检测要求。     

Flexural,impact, rheological and physical characterizations of POM reinforced by carbon nanotubes and paraffin oil

The paraffin oil dispersion technique innovated in the recent years to synthesize bulk polymer nanocomposite materials has a uniform dispersion. This research work aims to study the effect of added carbon nanotubes (CNTs) on flexural, impact and rheology behaviors of polyoxymethylene (POM) reinforced by 0–0.03 wt% of CNT using paraffin oil dispersion technique. The wettability and lamellar thickness were measured and rheological performance investigated using a parallel plate rheometer. The flexural and impact mechanical properties were also evaluated. The fracture surfaces were then examined by microscopy. The results showed that the energy to break, flexural strength and modulus increased proportionally with the addition of the amount of CNT in the matrix. For the rheology behavior, the viscosity decreased at the low percentage of CNT and then increased with increase in the percentage weight ratio of CNT in the POM matrix. It was also noted that the water contact angle rose with the increase the CNT percentages. Copyright © 2016 John Wiley & Sons, Ltd.     

多级孔HZSM-5分子筛催化剂的制备及低碳烃芳构化应用

采用0.2 mol/L的NaOH溶液对HZSM-5分子筛进行了不同时间的碱改性处理, 并对分子筛的结构和酸性进行表征, 考察了碱改性对HZSM-5催化剂的低碳烃芳构化活性的影响. 结果表明, HZSM-5分子筛经碱改性后会产生少量介孔, 且随改性时间延长, 介孔数量增加, 平均孔径增大, 总酸量降低, B酸/L酸比值降低. 120 min碱改性HZSM-5催化剂的活性、 稳定性以及目标产物苯、 甲苯、 乙苯和二甲苯(统称BTEX)的选择性最高.     

Beyond labels: A review of the application of quantum dots as integrated components of assays, bioprobes, and biosensors utilizing optical transduction

A comprehensive review of the development of assays, bioprobes, and biosensors using quantum dots (QDs) as integrated components is presented. In contrast to a QD that is selectively introduced as a label, an integrated QD is one that is present in a system throughout a bioanalysis, and simultaneously has a role in transduction and as a scaffold for biorecognition. Through a diverse array of coatings and bioconjugation strategies, it is possible to use QDs as a scaffold for biorecognition events. The modulation of QD luminescence provides the opportunity for the transduction of these events via fluorescence resonance energy transfer (FRET), bioluminescence resonance energy transfer (BRET), charge transfer quenching, and electrochemiluminescence (ECL). An overview of the basic concepts and principles underlying the use of QDs with each of these transduction methods is provided, along with many examples of their application in biological sensing. The latter include: the detection of small molecules using enzyme-linked methods, or using aptamers as affinity probes; the detection of proteins via immunoassays or aptamers; nucleic acid hybridization assays; and assays for protease or nuclease activity. Strategies for multiplexed detection are highlighted among these examples. Although the majority of developments to date have been in vitro, QD-based methods for ex vivo biological sensing are emerging. Some special attention is given to the development of solid-phase assays, which offer certain advantages over their solution-phase counterparts.     

Influence of sample preparation on thermal decomposition of wasted polyolefins-oil mixtures

Significant influence of sample preparation on thermal decomposition of polyolefin-technological oil mixtures was proved during tests. Samples of polymer-oil mixtures were prepared with two methods: reducing size and components mixing and soaking in temperature 170°C. Soaking causes decreasing thermal stability of the charge. This fact manifests itself in decreasing of thermal decomposition temperature in laboratory scale, as well as in change of characteristic decomposition temperatures during thermogravimetric analyses. Data analysis was performed with the use of classic method based on Arrhenius kinetic equation and three-parameter model. The influence of sample composition and preparation method on values of three-parameter equation coefficients was observed.     

纳米ZnO／石蜡复合相变材料的热物理性质研究

本文通过将纳米氧化锌（ZnO）颗粒加入熔融的石蜡（PW）并进行搅拌和超声制备了一种纳米ZnO／PW复合相变储能材料。为使纳米氧化锌在基体物质中分散均匀,在制备过程中使用了搅拌和超声以制备均匀的复合材料。使用扫描电镜观察其微观结构表明氧化锌在石蜡中分散良好。对所得ZnO／PW复合相变材料的相变温度、相变焓及导热系数等热物...     

解析法确定含蜡原油热质耦合的蜡分子扩散速率

蜡分子扩散过程是在热和质的广义热力学"力"耦合驱动下产生广义热力学"流"的结果,其实质是传热和传质同时存在的复杂耦合不可逆过程.基于非平衡态热力学的基本原理,推导出含蜡原油管输过程蜡分子扩散热质传递的线性唯象方程组;依据质量和能量的守恒关系,得到蜡分子扩散的传热一传质微分方程组,利用拉普拉斯变换求解到其解析解,探讨促使蜡分子扩散的动力学原因,分析输量和季节变化的不同工况对扩散速率的影响.     

Experimental Study of Oil Deposition Through a Flow Loop

In this article, the effect of temperature, pressure, and flow rate on deposition rate has been investigated by using chemical analysis method for calculating the deposit thickness and comparing to heat transfer and pressure drop methods. To do so, an experimental high pressure flow loop setup was designed and constructed to conduct various experiments. Caliper readings at the end of each test showed the chemical analysis method in comparison to the heat transfer and pressure drop methods is superior for deposit thickness calculation.     

用固体石蜡山梨酸碳糊电极电位法测定食品中山梨酸

制备了一种以山梨酸根与乙基紫形成的缔合物为电活性物的固体石蜡山梨酸碳糊电极,并对其性能做了测定。结果显示该电极对山梨酸有较好的能斯特响应。山梨酸的线性范围为2.2×10-5～1.0×10-1mol.L-1,检出限为1.6×10-5mol.L-1。该电极用于食品中山梨酸根的测定,结果与分光光度法结果相符。     

Thermal Behavior of Hexogen Phlegmatized with Montan Waxes

Hexogen can be used pressed only if its crystals are covered by some polymeric material [1], either natural or artificial. Montan waxes, as natural polymeric materials, were used for the phlegmatization. The melting process of seven types of waxes was analyzed by differential scanning calorimetry. The thermal decomposition processes of hexogens and phlegmatized hexogens were investigated by dynamic differential scanning calorimetry and dynamic thermogravimetric analyses. Kinetic parameters of the decomposition processes of hexogens were evaluated by using data obtained from differential scanning calorimetric curves. This revised version was published online in August 2006 with corrections to the Cover Date.