一种计算液接电势的新方法*

依据液接电势达稳态时通过边界层的净电荷为零这一思想,提出了一种计算液接电势的新方法。对于3类液接电势的计算,特别是Lewis-Sargent公式与Henderson方程的推导,思路清晰易懂,避免了过往液接电势计算方法存在的一些问题。本文所提出的方法能够为液接电势相关内容的教学提供借鉴。     

硼膜制备工艺、微观结构及其在硼化镁超导约瑟夫森结中的应用

MgB_2材料具备临界转变温度较高、相干长度大、临界电流和临界磁场高等优点,被认为有替代Nb基超导材料的潜力.研究了不同温度下以化学气相沉积法制备的硼(B)薄膜的微观结构.实验结果表明:较低温度沉积的B先驱薄膜为无定形B膜,可以与Mg蒸气反应生成MgB_2超导薄膜;当沉积温度高于550?C时,所得硼薄膜为晶型薄膜;以晶型硼薄膜为先驱膜在镁蒸气中退火,不能生成硼化镁超导薄膜.利用晶型B膜的这一特点,成功制备了以晶型硼薄膜为介质层的硼化镁超导约瑟夫森结.     

Waiting times of entangled electrons in normal–superconducting junctions

We consider a normal–superconducting junction in order to investigate the effect of new physical ingredients on waiting times. First, we study the interplay between Andreev and specular scattering at the interface on the distribution of waiting times of electrons or holes separately. In that case the distribution is not altered dramatically compared to the case of a single quantum channel with a quantum point contact since the interface acts as an Andreev mirror for holes. We then consider a fully entangled state originating from splitting of Cooper pairs at the interface and demonstrate a significant enhancement of the probability to detect two consecutive electrons in a short time interval. Finally, we discuss the electronic waiting time distribution in the more realistic situation of partial entanglement.     

Quantification of the bisphosphonate alendronate using capillary electrophoresis mass spectrometry with dynamic pH barrage junction focusing

A quantitative method was developed for the direct identity confirmation and quantification of alendronate using CE-MS combined with a pH-assisted focusing technique, dynamic pH barrage junction focusing. A pH-induced variation in electrophoretic mobility led to online focusing of alendronate at the sample/pH barrage boundary, significantly improving the detection sensitivity. In addition, the use of a flow-through microvial CE electrospray interface and the multiple reaction monitoring mode of MS further improved the specificity and quantification capability of this technology. This quantitative method presented a wide linear dynamic range over 8–2000 ng/mL and an LOD of 2 ng/mL. A 460-fold improvement in sensitivity was obtained when pH barrage junction focusing was applied during the CE process, in comparison to when normal CE was conducted without online sample stacking. The superior detection sensitivity over previously reported methods enables direct analysis of bisphosphonate compounds, eliminating tedious pre-column sample enrichment and derivatization. Validation of alendronate content in a commercial drug tablet further proved the reliability and power of this method. This simple method with no sample derivatization, superior sensitivity, and short run time (<8 min) is a promising alternative for accurate quantification of alendronate and other types of bisphosphonate compounds in both drug formulations and plasma samples.     

Rapid and label-free classification of pathogens based on light scattering,reduced power spectral features and support vector machine

The rapid identification of pathogens is crucial in controlling the food quality and safety. The proposed system for the rapid and label-free identification of pathogens is based on the principle of laser scattering from the bacterial microbes. The clinical prototype consists of three parts: the laser beam, photodetectors, and the data acquisition system. The bacterial testing sample was mixed with 10 mL distilled water and placed inside the machine chamber. When the bacterial microbes pass by the laser beam, the scattering of light occurs due to variation in size, shape, and morphology. Due to this reason, different types of pathogens show their unique light scattering patterns. The photo-detectors were arranged at the surroundings of the sample at different angles to collect the scattered light. The photodetectors convert the scattered light intensity into a voltage waveform. The waveform features were acquired by using the power spectral characteristics, and the dimensionality of extracted features was reduced by applying minimal-redundancy-maximal-relevance criterion (mRMR). A support vector machine (SVM) classifier was developed by training the selected power spectral features for the classification of three different bacterial microbes. The resulting average identification accuracies of E. faecalis,E. coli and S. aureus were 99%, 87%, and 94%, respectively. The overall experimental results yield a higher accuracy of 93.6%, indicating that the proposed device has the potential for label-free identification of pathogens with simplicity, rapidity, and cost-effectiveness.     

实用型三谱段太阳模拟器的设计与研制

本文设计并研制了一种实用型三谱段太阳模拟器,其光谱匹配可同时调整3个谱段(300~700 nm,700~900 nm,900~1 700 nm)范围的能量,修正后可满足三结砷化镓太阳电池的测试使用要求。本文重点阐述了三谱段太阳模拟器滤光片的设计和氙灯光谱的修正及测试,介绍了太阳模拟器的光机结构。实验表明:三谱段太阳模拟器的光谱匹配满足三结砷化镓太阳电池各子电池的响应电流值。在有效辐照面150 mm×150 mm上,平均辐照度可以达到2个太阳常数(2 730 W/m²),辐照不均匀度达到±1.77%,辐照不稳定度达到±0.83%,为太阳电池自动分拣系统提供了可靠稳定的平台。     

Meta Junction Promoting Efficient Thermally Activated Delayed Fluorescence in Donor-Acceptor Conjugated Polymers

The meta junction is proposed to realize efficient thermally activated delayed fluorescence (TADF) in donor–acceptor (D-A) conjugated polymers. Based on triphenylamine as D and dicyanobenzene as A, as a proof of concept, a series of D-A conjugated polymers has been developed by changing their connection sites. When the junction between D and A is tuned from para to meta, the singlet–triplet energy splitting (ΔE_ST) is found to be significantly decreased from 0.44 to 0.10 eV because of the increasing hole–electron separation. Unlike the para-linked analogue with no TADF, consequently, the meta-linked polymer shows a strong delayed fluorescence. Its corresponding solution-processed organic light-emitting diodes (OLEDs) achieve a promising external quantum efficiency (EQE) of 15.4 % (51.9 cd A⁻¹, 50.9 lm W⁻¹) and CIE coordinates of (0.34, 0.57). The results highlight the bright future of D-A conjugated polymers used for TADF OLEDs.     

单分子电导测量技术及其影响因素

Molecular electronics is an important field for the application of nanotechnologies with an ultimate goal of building functional devices using single molecules or molecular arrays to realize the same functionality as macroscopic devices. To attain this goal, reliable techniques for measuring and manipulating electron transfer processes through single molecules are essential. There are various techniques and many environmental factors influencing single-molecule electronic conductance measurements. In this review, we first provide a detailed introduction and classification of the current well-accepted techniques in this field for measuring single-molecule conductance. All available techniques are summarized into two categories: the fixed junction technique and break junction technique. The break junction technique involves repeatedly forming and breaking molecular junctions by mechanically controlling a pair of electrodes moving into and out of contact in the presence of target molecules. Single-molecule conductance can be determined from the conductance plateaus that appear in typical conductance decay traces when molecules bind two electrodes during their separation process. In contrast, the fixed junction technique is to fix the distance between a pair of electrodes and measure the conductance fluctuations when a single molecule binds the two electrodes stochastically. Both techniques comprise different application methods and have been employed preferentially by different groups. Specific features of both techniques and their intrinsic advantages are compared and summarized in Section 4.     

MVF Sensor Enables Analysis of Nucleic Acids with Stable Secondary Structures

One major challenge in nucleic acids analysis by hybridization probes is a compromise between the probe's tight binding and sequence‐selective recognition of nucleic acid targets folded into stable secondary structures. We have been developing a four‐way junction (4WJ)‐based sensor that consists of a universal stem‐loop (USL) probe immobilized on an electrode surface and two adaptor strands (M and F). The sensor was shown to be highly selective towards single base mismatches at room temperature, able to detect multiple targets using the same USL probe, and have improved ability to detect folded nucleic acids. However, some nucleic acid targets, including natural RNA, are folded into very stable secondary and tertiary structures, which may represent a challenge even for the 4WJ sensors. This work describes a new sensor, named MVF since it uses three probe stands M, V and F, which further improves the performance of 4WJ sensors with folded targets. The MVF sensor interrogating a 16S rRNA NASBA amplicon with calculated folding energy of ?32.82 kcal/mol has demonstrated 2.5‐fold improvement in a signal‐to‐background ratio in comparison with a 4WJ sensor lacking strand V. The proposed design can be used as a general strategy in the analysis of folded nucleic acids including natural RNA.     

A novel rigid wheel for agricultural machinery applicable to paddy field with muddy soil

The working performance of agricultural machinery is largely determined by the walking performance of the wheel when driving in complex unstructured soil. However, the driving performance of existing wheels is not satisfactory for paddy field with muddy soil. The purpose of the current study is therefore to propose a novel rigid wheel for agricultural machinery which is applicable to paddy field with muddy soil. Firstly, a novel arc edge shaped wheel was designed based on the principles of mechanics on the ground. Then the driving performance of this arc edge shaped wheel was evaluated using FE modeling of interaction between rigid wheel and soil. Finally, the structure originally designed arc edge shaped wheel was improved according to FE modeling results, and this improved design was further evaluated by both FE simulation and prototype experiments. Both FE modeling and experimental results indicate that the improved arc edge shaped wheel proposed in this study has a good driving performance with regarding to wheel sinkage and soil reaction force. The proposed arc edge shaped wheel could be used as an effective component of rice harvester for paddy field with muddy soil.