Analytical Methods for the Determination of 90Sr and 239,240Pu in Environmental Samples

Artificial long-lived radionuclides such as ⁹⁰Sr and ^239,240Pu have been long released into the environment by human nuclear activities, which have a profound impact on the ecological environment. It is of great significance to monitor the concentration of these radionuclides for environmental safety. This paper summarizes and critically discusses the separation and measurement methods for ultra-trace determination of ⁹⁰Sr, ²³⁹Pu, and ²⁴⁰Pu in the environment. After selecting the measurement method, it is necessary to consider the decontamination of the interference from matrix elements and the key elements, and this involves the choice of the separation method. Measurement methods include both radiometric methods and non-radiometric methods. Radiometric methods, including alpha spectroscopy, liquid scintillation spectrometry, etc., are commonly used methods for measuring ^239+240Pu and ⁹⁰Sr. Mass spectrometry, as the representative of non-radiometric measurement methods, has been regarded as the most promising analytical method due to its high absolute sensitivity, low detection limit, and relatively short sample-analysis time. Through the comparison of various measurement methods, the future development trend of radionuclide measurement is prospected in this review. The fully automatic and rapid analysis method is a highlight. The new mass spectrometer with ultra-high sensitivity shows strong analytical capabilities for extremely low concentrations of ⁹⁰Sr, ²³⁹Pu, and ²⁴⁰Pu, and it is expected to develop determination methods with higher sensitivity and lower detection limit.     

Rational design of iridium–porphyrin conjugates for novel synergistic photodynamic and photothermal therapy anticancer agents

Near-infrared (NIR) emitters are important probes for biomedical applications. Nanoparticles (NPs) incorporating mono- and tetranuclear iridium(iii) complexes attached to a porphyrin core have been synthesized. They possess deep-red absorbance, long-wavelength excitation (635 nm) and NIR emission (720 nm). TD-DFT calculations demonstrate that the iridium–porphyrin conjugates herein combine the respective advantages of small organic molecules and transition metal complexes as photosensitizers (PSs): (i) the conjugates retain the long-wavelength excitation and NIR emission of porphyrin itself; (ii) the conjugates possess highly effective intersystem crossing (ISC) to obtain a considerably more long-lived triplet photoexcited state. These photoexcited states do not have the usual radiative behavior of phosphorescent Ir(iii) complexes, and they play a very important role in promoting the singlet oxygen (¹O₂) and heat generation required for photodynamic therapy (PDT) and photothermal therapy (PTT). The tetranuclear 4-Ir NPs exhibit high ¹O₂ generation ability, outstanding photothermal conversion efficiency (49.5%), good biocompatibility, low half-maximal inhibitory concentration (IC₅₀) (0.057 μM), excellent photothermal imaging and synergistic PDT and PTT under 635 nm laser irradiation. To our knowledge this is the first example of iridium–porphyrin conjugates as PSs for photothermal imaging-guided synergistic PDT and PTT treatment in vivo.

Iridium–porphyrin conjugates assembled in nanoparticles are photosensitizers that exhibit excellent photothermal imaging and synergistic PDT and PTT in vivo.     

Organometallic complexes as hole-transporting materials in organic light-emitting diodes

The use of metal complexes fac-tris(1-phenylpyrazolato-N,C(2)('))cobalt(III) [fac-Co(ppz)(3)], fac-tris(2-phenylpyridinato-N,C(2)(') cobalt(III) [fac-Co(ppy)(3)], and [tris[2-((pyrrole-2-ylmethylidene)amino)ethyl]amine]gallium(III) [Ga(pma)] as materials for hole-transporting layers (HTL) in organic light-emitting diodes (OLEDs) is reported. Co(ppz)(3) and Co(ppy)(3) were prepared by following literature procedures and isolated as mixtures of facial (fac) and meridional (mer) isomers. The more stable fac isomers were separated from the unstable mer forms via column chromatography and thermal gradient sublimation. Crystals of fac-Co(ppz)(3) are monoclinic, space group P2(1)/c, with a = 13.6121(12) A, b = 15.5600(12) A, c = 22.9603(17) A, beta = 100.5 degrees, V = 4781.3(7) A(3), and Z = 8. [Tris[2-((pyrrol-2-ylmethylidene)amino)ethyl]amine]gallium [Ga(pma)] was prepared by the reaction of gallium(III) nitrate with the pmaH(3) ligand precursor in methanol. Ga(pma) crystallizes in the cubic space group I3d with cell parameters a = 20.2377(4) A, b = 20.2377(4) A, c = 20.2377(4) A, beta = 90.0 degrees, V = 8288.6(3) A(3), and Z = 16. These cobalt and gallium complexes are pale colored to colorless solids, with optical energy gaps ranging 2.6-3.36 eV. A two-layer HTL/ETL (ETL = electron-transporting layer) device structure using fac-Co(ppz)(3) and fac-Co(ppy)(3) as the HTL does not give efficient electroluminescence. However, the introduction of a thin layer of a hole-transporting material (N,N'-bis(1-naphthyl)-N,N'-diphenylbenzidine, NPD) as an energy "stair-step" and electron/exciton-blocker dramatically improves the device performance. Both fac-Co(ppz)(3) and fac-Co(ppy)(3) devices give external quantum efficiencies higher than 1.0%, with brightness 5000 and 7000 Cd/m(2) at 10 V, respectively. Ga(pma) also functions as an efficient interface layer, giving device performances very similar to those of analogous devices using NPD as the interface layer. Stability tests have been carried out for Co(ppz)(3)/NPD/Alq(3) and Co(ppy)(3)/NPD/Alq(3) devices. While fac-Co(ppy)(3) gave stable OLEDs, the fac-Co(ppz)(3)-based devices had very short lifetimes. On the basis of the experimental results of chemical oxidation of fac-Co(ppz)(3), the major cause for the fast decay of the fac-Co(ppz)(3) device is proposed to be the decomposition of fac-Co(ppz)(3)(+) in the HTL layer during the device operation.     

湿有效能量预报暴雨的动力分析

根据7个例子的对比分析表明:湿有效能量对预报暴雨具有较好的指示性,但在某些条件下湿有效能量在有无暴雨发生两者上并无明显差别。对暴雨和无暴雨个例的动力条件分析表明:(1)有暴雨时,在杭州地区为一个相对辐散区(300—900百帕),并伴有较强的上升运动,无暴雨时则为相对辐合区;(2)暴雨时高空有一支强的急流,暴雨区位于高空发散流场和急流中心的入口区右侧。(3)稳定度大小两者也有明显差异。分析结果对业务预报有一定参考价值。     

广义弱群像代数

本文首先介绍了广义弱群像代数的概念, 并构造了一系列具体的例子, 通过例子可以看出有限群胚代数和群像代数都可以看作是广义弱群像代数; 接着本文证明了广义弱群像代数也可以看作是一类广义弱双Frobenius代数, 并探讨了广义弱双Frobenius代数成为有限群胚代数的条件; 最后本文给出了低维广义弱群像代数的具体结构.     

聚乙二醇介质中纳米铁基催化剂上的费托合成

 采用化学还原法在纯水中制备了纳米铁基催化剂, 将其直接分散到液态聚乙二醇 (PEG) 中进行费托合成 (FTS) 反应. 透射电子显微镜、X 射线衍射、穆斯堡尔谱和 X 射线光电子能谱等结果表明, 还原态催化剂粒径在 30~65 nm, 主要由无定形的 Fe-B 和α-Fe 组成, 其中 B 部分电子向 Fe 转移. 反应过程中, 无定形的 Fe-B 首先快速转变为 α-Fe, 而 α-Fe 很容易发生碳化或氧化, 最终转变为 Fe3O4 和碳化铁. PEG 能有效抑制纳米粒子的聚集长大, 反应后催化剂粒径减小为 20~55 nm. 在 3.0 MPa, V( H2)/V(CO) = 2 和 200 oC 的反应条件下, 该催化剂表现出优异的 FTS 低温活性和较高的稳定性, 反应后产物和催化体系很容易实现分离.     

Fabrication of ZnSe/C Hollow Polyhedrons for Lithium Storage

ZnSe has got extensive attention for high-performance LIBs anode due to its remarkable theoretical capacity and environmental friendliness. Nevertheless, the large volume variation for the ZnSe in the discharge/charge processes brings about rapid capacity fading and poor rate performance. Herein, ZnSe/C hollow polyhedrons are successfully synthesized by selenization of zeolitic imidazolate framework-8 (ZIF-8) with resorcinol-formaldehyde (RF) coating. The protection of C layer derived from RF coating layer and Ostwald ripening during the process of selenization play important roles in promoting formation of ZnSe/C hollow polyhedrons. The ZnSe/C hollow polyhedrons exhibit good rate performance and long-term cycle stability (345 mAh g⁻¹ up to 1000 cycles at 1 A g⁻¹) for lithium ion batteries (LIBs) anode. The improved electrochemical performance is benefit from the unique ZnSe/C hollow structure, in which the hollow structure can effectively avoid terrible volume expansion, and the thin ZnSe/C shell can not only provide adequate diffusion paths of lithium ions and but also enhance the electronic conductivity.     

A TRANSPLANTABLE COMPENSATION SCHEME FOR THE EFFECT OF THE RADIANCE FROM THE INTERIOR OF A CAMERA ON THE ACCURACY OF TEMPERATURE MEASUREMENT

Radiance coming from the interior of an uncooled infrared camera has a significant effect on the measured value of the temperature of the object. This paper presents a three-phase compensation scheme for coping with this effect. The first phase acquires the calibration data and forms the calibration function by least square fitting. Likewise, the second phase obtains the compensation data and builds the compensation function by fitting. With the aid of these functions, the third phase determines the temperature of the object in concern from any given ambient temperature. It is known that acquiring the compensation data of a camera is very time-consuming. For the purpose of getting the compensation data at a reasonable time cost, we propose a transplantable scheme. The idea of this scheme is to calculate the ratio between the central pixel’s responsivity of the child camera to the radiance from the interior and that of the mother camera, followed by determining the compensation data of the child camera using this ratio and the compensation data of the mother camera Experimental results show that either of the child camera and the mother camera can measure the temperature of the object with an error of no more than 2°C.     

自组装短肽GFS-2构建新型三维细胞培养支架材料

典型的自组装短肽在水中可形成稳定的β-sheet二级结构,在生理性环境下则能够形成稳定的纳米纤维,可进一步形成含水量达99%的水凝胶,具有高纯度、可降解及无免疫反应等突出优点,能模拟生物体内的三维基质环境而作为细胞三维培养的新型生物材料。本文主要采用了圆二色谱仪、原子力显微镜、倒置显微镜等探究新型短肽GFS-2的自组装性能及其在细胞三维培养中的应用。此研究可能会启发设计更多的新型自组装短肽服务于化学、生物材料、医学工程等领域。