用^60Co放射源检测油垢厚度的初步实验研究

本文用石蜡模拟油垢，用^60Co放射源的1．25MeV平均能量的γ射线垂直入射，以一定的散射角和不同的探测立体角接收散射γ光子敫．发现散射γ计数与被测石蜡厚度之间存在不同的线性关系．结果发现，放射源与探测器之间屏蔽的好坏和合理的探测距离对提高线性度有很大关系．本实验测得最佳线性相关系数平方值为0．9981，平均测量精度为1．26mm．这对研究散射法检测油垢厚度和选择合适的探测距离提供了实验基础．     

Regioselective Synthesis of Trichloromethyl‐Substituted Salicylates and Cyclohexenones by One‐Pot Cyclizations of 1,3‐Bis(trimethylsilyloxy)buta‐1,3‐dienes

A variety of 6‐(trichloromethyl)salicylates (=2‐hydroxy‐6‐(trichloromethyl)benzoates) were prepared by TiCl₄‐mediated cyclization of 1,3‐bis(trimethylsilyloxy)buta‐1,3‐dienes with 1,1,1‐trichloro‐4,4‐dimethoxybut‐3‐en‐2‐one. The employment of trimethylsilyl trifluoromethanesulfonate (Me₃SiOTf) as Lewis acid resulted in the formation of trichloromethyl‐substituted cyclohexenones. The cyclizations proceeded with good‐to‐very‐good regioselectivities.     

Strained Ammonium Precursors for Radiofluorinations

The increasing application of positron emission tomography (PET) in nuclear medicine has stimulated the extensive development of a multitude of novel and versatile techniques to introduce fluorine-18, especially for the radiolabelling of biologically or pharmacologically active molecules. Taking into consideration that the introduction of fluorine-18 (t_1/2=109.8 min) mostly proceeds under harsh conditions, radiolabelling of such molecules represents a challenge and is of enormous interest. Ideally, it should proceed in a regioselective manner under mild physiological conditions, in an acceptable time span, with high yields and high specific activities. Special attention has been drawn to 2-fluoroethyl and 3-fluoropropyl groups, which are often the active sites of radiofluorinated compounds. Precursors containing an ammonium leaving group – such as a strained azetidinium or aziridinium moiety – can help to overcome these obstacles leading to a convenient and mild introduction of [¹⁸F]fluoride with high radiochemical yields.     

Hierarchically Ordered Porous Carbon with Atomically Dispersed FeN4 for Ultraefficient Oxygen Reduction Reaction in Proton-Exchange Membrane Fuel Cells

The low catalytic activity and poor mass transport capacity of platinum group metal free (PGM-free) catalysts seriously restrict the application of proton-exchange membrane fuel cells (PEMFCs). Catalysts derived from Fe-doped ZIF-8 could in theory be as active as Pt/C thanks to the high intrinsic activity of FeN₄; however, the micropores fail to meet rapid mass transfer. Herein, an ordered hierarchical porous structure is introduced into Fe-doped ZIF-8 single crystals, which were subsequently carbonized to obtain an FeN₄-doped hierarchical ordered porous carbon (FeN₄/HOPC) skeleton. The optimal catalyst FeN₄/HOPC-c-1000 shows excellent performance with a half-wave potential of 0.80 V in 0.5 m H₂SO₄ solution, only 20 mV lower than that of commercial Pt/C (0.82 V). In a real PEMFC, FeN₄/HOPC-c-1000 exhibits significantly enhanced current density and power density relative to FeN₄/C, which does not have an optimized pore structure, implying an efficient utilization of the active sites and enhanced mass transfer to promote the oxygen reduction reaction (ORR).     

Light-Activated Carbon Monoxide Prodrugs Based on Bipyridyl Dicarbonyl Ruthenium(II) Complexes

Two photoactivatable dicarbonyl ruthenium(II) complexes based on an amide-functionalised bipyridine scaffold (4-position) equipped with an alkyne functionality or a green-fluorescent BODIPY (boron-dipyrromethene) dye have been prepared and used to investigate their light-induced decarbonylation. UV/Vis, FTIR and ¹³C NMR spectroscopies as well as gas chromatography and multivariate curve resolution alternating least-squares analysis (MCR-ALS) were used to elucidate the mechanism of the decarbonylation process. Release of the first CO molecule occurs very quickly, while release of the second CO molecule proceeds more slowly. In vitro studies using two cell lines A431 (human squamous carcinoma) and HEK293 (human embryonic kidney cells) have been carried out in order to characterise the anti-proliferative and anti-apoptotic activities. The BODIPY-labelled compound allows for monitoring the cellular uptake, showing fast internalisation kinetics and accumulation at the endoplasmic reticulum and mitochondria.     

简谈空气中的声速与温度关系

讨论了驻波法测空气中声速的实验,分别用相位比较法和李萨如图法来确定超声波波长.在不同温度条件下测量了声速并与理论值进行比较,实验结果显示测量温度接近室温时实验值与理论值基本一致,测量温度与室温相差较大时实验值与理论值偏差较大.     

激光尾场第一周期加速带电粒子模拟

在关于激光尾场加速(LWFA)的很多文献中,都暗示了尾场有周期性结构.可是激光驱动尾场可以不是周期性的,尾场第一周期可以捕获和加速外来电子束.Esirkepov和Bulanov等人提出了带电粒子在激光高斯脉冲驱动尾场第一周期加速的处理方法.本文在此理论基础上进一步讨论电子在尾场第一周期中能获得的最大能量与激光脉冲的强度和脉冲的波长之间的关系.结果显示,捕获电子最大能量与脉冲激光强度成正比.适当的选择脉冲激光波长也直接影响到捕获电子的最大能量值.     

Synthesis, structure determination, and (radio-)fluorination of novel functionalized phosphanes suitable for the traceless Staudinger ligation

An elegant and efficient synthesis approach for the preparation of novel benzoate and nicotinate containing phosphanes is presented. This reaction path has a broad substrate scope. Thus, various functionalized phosphanes were obtained in high yields using an esterification procedure under Steglich conditions. A facile blocking of the phosphorus atom with BH₃ was carried out. BH₃ as easily insertable and removable protecting group enables a further derivatization of the benzoate residue. The prepared phosphane derivatives proved to be valuable labeling building blocks for the implementation of a bioorthogonal (radio-)fluorination strategy and were applied for labeling purposes using the traceless Staudinger ligation. For this purpose, a selection of azide-functionalized small organic and bioactive sample molecules was prepared. Furthermore, a mild and selective (radio-)fluorination of these derivatives is demonstrated adopting this bioorthogonal ligation method.     

大学物理基础实验的拓展应用:探讨牛奶的光学性质

牛奶是生活中重要的饮料之一,牛奶光学性质的研究具有重要意义。本文采用紫外-可见吸收光谱法、掠面入射法及法拉第磁光效应原理,分别测出五种不同浓度牛奶的吸光度、折射率、旋光度等光学参数。实验结果显示,随着牛奶样品稀释倍数的增加,吸光度下降。新鲜牛奶的折射率小于四种袋装牛奶的折射率。随着稀释倍数的增加,折射率和旋光度均减小。结果表明,随着牛奶酪蛋白含量的增加,吸光度、折射率和旋光度均增加。     

沙疗对骨关节炎兔子股骨骨质影响的对比研究

目的:试验研究维医沙疗对骨关节炎动物模型骨质层转移的影响.方法:采用CT扫描的手段分别四次(建立实验对象OA模型前后各一次、进沙疗第14天和第28天各一次)采集两个实验对象股骨数据.将数据导入MIMICS软件分离实验对象股骨,根据CT值范围不同把股骨分为六个骨质层并读取各层体积.分析了各骨质层的体积在股骨总骨量中所占比例的变化和股骨平均CT值的变化.结果:分析四次CT数据的变化,发现沙疗对象股骨总骨量增长,而对照对象之下降.与此同时沙疗对象股骨平均CT值上升,相比之下对照对象平均CT值下降.结论:沙疗对关节炎对象有促进骨代谢作用,使骨质从低CT值的骨质层转移至高CT值骨质层.