Origin of the High Permittivity and Varistor Behavior in SnO2–Zn2SnO4 Composite Ceramics

SnO₂–Zn₂SnO₄ composite ceramics with a colossal dielectric permittivity and varistor behavior are prepared by traditional ceramic processing. By increasing bias voltage from 0 to 10 V at a low frequency (~10³ Hz) and at room temperature, the relative permittivity decreased rapidly from about 20 000 to several thousand, whereas the radius of the semicircle in the complex impedance decreased and the tail gradually disappeared. However, the peak height and the position of the imaginary part of the complex modulus in the spectra were independent of the applied DC voltage. The slope deduced from the bias voltage‐dependent straight lines of the double‐logarithmic imaginary permittivity spectra were constant with a value of ?0.63 at high frequencies and they decreased to ?1 at low frequencies. The results strongly indicate that a number of weekly trapped charges existed in the ceramic bulk. From the temperature‐dependent dielectric and electric modulus spectra, the trapped charge activation energy was about 0.32 eV, which may be associated with the oxygen vacancies. Based on the results, a modified equivalent circuit related to the colossal dielectric permittivity and varistor properties was proposed, in which a Warburg impedance was added in parallel with the resistance and capacitance.     

介孔分子筛MCM-41在废水处理中的应用

介孔分子筛MCM-41具有高度有序排列的孔道结构、孔径均匀且尺寸可调、高比表面积、较大的孔体积及吸附容量,孔道表面具有易于修饰的硅羟基,在废水处理中吸附重金属离子、有机污染物等方面具有很大的应用价值。对近几年介孔分子筛MCM-41用于处理废水中污染物的应用情况进行了综述。     

The synthesis of salt-resistant emulsion and its application in ecological sand-fixing of high salt-affected sandy land

For the first time, the salt-resistant emulsion was applied as an ecological sand-fixing material to enhance the sand-fixing ability in salty desert. This study started from the synthesis of the novel salt-resistant poly(vinyl acetate-dibutyl maleate-acyclic acid-sodium p-styrene sulphonate) copolymer emulsion. Then, the structure, composition and thermal property of the emulsion were characterised. The sand-fixing properties and ecological effect of the emulsion were evaluated. The experimental results showed that the emulsion has been successful synthesised and could be used as an ecological sand-fixing material. The related reason is that, first, the emulsion could significantly visibly enhance the sand-fixing ability in high salt-affected sand land. Second, the prepared emulsion had good thermal aging resistance and freeze-thaw stabilities to withstand the changes in the temperature of salty desert, and the test of the influence of the emulsion on the growth of microbe of sand showed a favourable ecological effect.     

固定管板式换热器有限元分析及应力评定

利用有限元分析软件ANSYS,对某固定管板式换热器在机械载荷和温度载荷共同作用下的应力强度进行分析,并对其危险截面作应力评定和强度校核。指出换热器应力分析应包括不同危险工况,并对不同危险部位进行分析与评定,这样才能保证其安全可靠地运行。     

Photodynamic Therapy of Up-Conversion Nanomaterial Doped with Gold Nanoparticles

Two key concerns exist in contemporary cancer chemotherapy: limited therapeutic efficiency and substantial side effects in patients. In recent years, researchers have been investigating the revolutionary cancer treatment techniques of photodynamic therapy (PDT) and photothermal therapy (PTT) proposed by many scholars. A photothermal treatment of cancer was synthesized using the hydrothermal method which has high photothermal conversion efficiency and can generate reactive oxygen species (ROS) in cells. Photothermal treatment of tumors has a good short-term effect and photodynamic therapy lasts longer. However, both PTT and PDT have their inevitable shortcomings and it is difficult to completely eradicate a tumor using a single mode of treatment. PTT and PDT synergistic treatment not only inherits the advantages of low toxicity and side effects of phototherapy but also enables the two treatment methods to complement each other. It is an effective strategy to improve curative effects and reduce toxic and side effects. Furthermore, gold doped UCNPs have an exceptionally high target recognition for tumor cells. The gold doped UCNPs, in particular, are non-toxic to normal tissues, endowing the as-prepared medications with outstanding therapeutic efficacy and exceptionally low side effects. These findings may encourage the creation of fresh, effective imaging-guided approaches to meet the goal of photothermal cancer therapy.     

Data acquisition system for chemical kinetic studies

A microcomputer-interfaced data acquisition system for chemical kinetics (interfacing with laboratory analogue instruments) has been developed. Analogue signals from instruments used in kinetics experiments are amplifed by a wide-range adjustable high-gain operational amplifier and smoothed by an op-based filter, and then digitized at rates of up to 10⁴ samples per channel by an ADC 0816 digitizer. The ADC data transfer and manipulation routine was written in Assembler code and in high-level language; the graphics package and data treatment package is in Basic. For the various sampling speeds, all of the program can be written using Basic-Assembler or completely in Assembler if a high sampling rate is needed. Several numerical treatment methods for chemical kinetics have been utilized to smooth the data from experiments.The computer-interfaced system for second-order chemical kinetic studies was applied to the determination of the rate constant of the saponification of ethyl acetate at 35°C. For this specific problem, an averaging treatment was used which can be called an interval method. The use of this method avoids the diffcully of measuring the starting time of the reaction. Two groups of experimental data and results were used to evaluate the systems performance. All of the results obtained are in agreement with the reference value.     

5-(4-氨基)-苄叉若丹宁光度法测定烟草中的铜

研究了 5- (4氨基 ) -苄叉若丹宁 (ABR)与铜的显色反应 ,在 pH为 4.5的HAc -NaAc缓冲介质中 ,吐温 - 80存在下 ,ABR与铜反应生成 2∶1稳定络合物 ,λmax=50 0nm ,ε =1 .64× 1 0 4 L/(mol·cm)。铜含量在 0～ 50μg/2 5mL内符合比尔定律 ,方法用于烟草中铜含量的测定 ,结果令人满意。     

A new (3,4,7)-connected topology framework based on [Cd2(CO2)3O4N2] second building unit

A new 3D coordination polymer [Cd₂(L³)(BTC)(H₂O)] (1) (HL³ = 3,5-bis(pyridin-3-ylmethoxy)benzoic acid, H₃BTC = 1,3,5-benzenetricarboxylic acid), has been isolated under hydrothermal condition and characterized by single-crystal X-ray diffraction. Compound 1 is constructed from Cd₂-based second building units (SBUs) [Cd₂(CO₂)₃O₄N₂] and displays a 3D (3,4,7)-connected net with (4²·6)(4³·6³)(4⁵·6¹¹·8⁵) topology. In addition, the photoluminescent spectra indicate compound 1 may be a good candidate for blue-luminescent materials.