A fluorescent glucose bioassay based on the hydrogen peroxide-induced decomposition of a quencher system composed of MnO<Subscript>2</Subscript> nanosheets and copper nanoclusters

The authors describe a fluorometric glucose assay that is based on the use of MnO₂ nanosheets and copper nanoclusters (CuNCs) acting as nanoprobes. The CuNCs were synthesized by using bovine serum albumin as a template by chemical reduction of copper(II) sulfate. On addition of MnO₂ nanosheets to a colloidal solution of CuNCs, the fluorescence of CuNCs (measured at excitation/emission wavelengths of 335/410 nm) is quenched. However, in the presence of enzymatically generated H₂O₂, the MnO₂ nanosheets are reduced to form Mn(II) ions. As a result, fluorescence intensity recovers. The glucose assay is based on the enzymatic conversion of glucose by glucose oxidase to generate H₂O₂ and glucuronic acid. The calibration plot is linear in the 1 μM to 200 μM glucose concentration range, and the detection limit is 100 nM. The method was successfully applied to the determination of glucose in spiked human serum samples.

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Graphical abstract A sensitive fluorescent bioassay is reported for the detection of glucose based on the hydrogen peroxide-induced decomposition of a quencher system composed of MnO₂ nanosheets and copper nanoclusters (CuNCs).

     

同步辐射计算机断层技术光源误差机理分析

基于同步辐射X射线的优越特性及计算机断层重建技术对材料无损检测等优点,同步辐射计算机断层重建技术被广泛应用于很多领域.本文对光源非均匀、过饱和以及过穿透的三种情形所引起同步辐射计算机断层技术重建误差的形成机理进行了分析研究,给出了三种情形所引起误差的基本形式.在此基础上,对这三种误差进行了数值模拟,模拟结果证实了分析的正确性. 关键词： 同步辐射 计算机断层 光源 误差     

DNS study of swirling intensity effect on flow pattern of a circular jet

Abstract  

The figures show the 3D flow pattern of a circular jet with different swirling intensity. Reynolds number is approximately 4300 computed based on the nozzle diameter (d), jet velocity (U), and air fluid property at 1 atm and 300 K. The overall computational domain is set to be 4 × 4 × 12 d in spanwise, height, and streamwise direction. The governing equations are the fully compressible Navier–Stokes equations, firstly differenced by eighth-order explicit scheme and then advanced temporarily by using the fourth-order explicit Runge–Kutta method. 3D characteristics non-reflecting boundary condition including transverse source contribution is imposed on all other boundaries except the inflow boundary handled by assigning fixed profiles of temperature and velocity. To ensure the simulation resolution, here over 16 million grids are employed in sum, combined with a handful of grids located at buffer zones of outflow boundaries. To correctly represent the vortex in the flow field, velocity gradient tensor invariant Q is used here. And ψ refers to the swirling intensity defined as the ratio of tangential momentum to axis momentum. As shown in velocity profile, the flow pattern of the jet changes from a close mode to a totally open mode as ψ increases from 0.4 to 1.5. Accordingly, the recirculation zone gradually moves upstream and backflow velocity is enlarged as well. It is inteseting to found that the obvious drops of the momentums in two shown directions always occur at the same position downstream, no matter how large the ψ value is. Therefore, a momentum compensatory mechanism is expected to exist in the vortex-abundant zone. With the increase of ψ value, the increased strain rate in tangential direction can induce vortex more quickly, intensifying the entrainment and velocity-attenuation, which can be observed in Q value profile.     

藏药珠西的化学成分与结构分析

采用X射线荧光(XRF)、电感耦合等离子体发射光谱(ICP-OES)和X射线衍射(XRD)对不同来源藏药珠西中的元素成分和结构组成进行测定,以期揭示其药理作用的物质基础。XRF和ICP-OES分析结果表明,藏药珠西中主要元素为Fe,S和O,及少量的Si,Na,Mg,Al,K,Ni,Ca,Ti等元素。XRD分析表明,藏药珠西中主要存在立方晶系FeS2,此外还含有少量的斜方晶系Fe+3O(OH)等。通过XRF,ICP-OES和XRD分析,获得了藏药珠西的化学成分和结构组成基本数据,为其药理作用物质基础的揭示和质量标准的制定提供了科学依据。     

一种新的液晶高分子——丁酸壳聚糖的合成与表征

甲壳素几乎不溶于任何溶剂,由于其脱乙酰化产物壳聚糖含自由氨基,能被酸质子化而溶解,所以壳聚糖的应用领域远多于甲壳素.但是壳聚糖也仅能溶于酸性介质中,并不能溶于纯水和普通有机溶剂,因而人们对甲壳素或壳聚糖进行各种化学改性[1,2],寻求溶解性更好尤其能溶于水的衍生物,以扩大其应用范围.本文按文献[2～4]方法合成了O-丁酰化壳聚糖(简称丁酸壳聚糖),首次报道它具有溶致液晶性.     

N-烷基壳聚糖玻璃化转变温度的研究

采用差示扫描量热(DSC)法和热释电流(TSC)法研究了N-烷基壳聚糖的玻璃化转变行为. DSC法中采用二次扫描以消除溶剂和热历史的影响, 并利用物理老化方法来增强N-烷基壳聚糖在DSC曲线上的玻璃化转变区域的热焓吸热峰, 以克服DSC法的不灵敏性. 两种研究方法的结果一致表明, 三种N-烷基壳聚糖的玻璃化转变均发生在110～150 ℃温区内；取代的柔性烷基越大, 玻璃化转变温度(Tg)越低；但N-甲基壳聚糖例外, 其Tg略高于壳聚糖, 空间阻碍在这里起决定的作用.     

左右手系材料界面处全反射行为的特性

基于电磁场理论，推导了左右手系材料界面处发生全反射时的物理特性，分析了相位变化情况.提出利用左右手系材料构成周期性结构，观测全反射时介质中隐失波干涉的实验设想，并从理论上计算了干涉条纹的分布. 关键词： 左手材料 负折射率 全反射 隐失波     

Mn替代对Dy2AlFe16-xMnx化合物的结构和磁性的影响

通过X射线衍射及磁测量手段研究了Dy2AlFe16-xMnx化合物的结构和磁性.研究结果表明Dy2AlFe16-xMnx化合物具有六角相的Th2Ni17型结构.对x=1,2的样品采用X射线热膨胀测定法在104-647K的温度范围内测量了其热膨胀性质,发现这些化合物在低温下存在热膨胀反常现象,在居里点附近出现负膨胀性质.对自发磁致伸缩的研究结果表明Dy2AlFe16-xMnx化合物中存在着较强的各向异性的自发磁致伸缩,随着Mn含量的增加,其低温下的自发体磁致伸缩减弱.磁测量结果表明Mn的替代导致Dy2AlFe16-xMnx化合物的居里温度及自发磁化强度急剧下降.