Large Enhancement of the Single-Molecular Conductance of a Molecular Wire through a Radical Substituent

The single-molecular conductance between two π-conjugated wires with and without a radical substituent has been compared. Specifically, methyl- and iminonitroxide-substituted 4-(biphenyl-4-yl)pyridine wires bound onto a porphyrin template were subjected to scanning tunneling microscopy (STM) apparent-height measurement at the interface between highly oriented pyrolytic graphite (HOPG) and octan-1-oic acid. Statistical analysis of the STM images revealed that the radical-substituted wire has 3.2±1.7-fold higher conductance than the methyl-substituted reference. Although density functional theory (DFT) calculation suggests that only 17 % of the SOMO is distributed on the wire moiety, the effect was significant. This study presents the potential of radical substituents to achieve high conductivity in molecular wires.     

Mechanistic Investigation and Conductance Modulation of a Metal-Molecule-Metal Junction via Extra Acid Addition

One important prerequisite for the fabrication of molecular functional device strongly relies on the understanding the conducting behaviors of the metal-molecule-metal junction that can respond to an external stimulus. The model Lewis basic molecule 4,4′-(pyridine-3,5-diyl)dibenzonitrile (DBP), which can react with Lewis acid and protic acid, was synthesized. Then, the molecular conducting behavior of DBP, DBP-B(C₆F₅)₃, and DBP-TfOH (DBP-B(C₆F₅)₃, and DBP-TfOH were produced by Lewis acid and protonic acid treatment of DBP) was researched and compared. Given that their identical physical paths for DBP, DBP-B(C₆F₅)₃, and DBP-TfOH to sustain charge transport, our results indicate that modifying the molecular electronic structure, even not directly changing the conductive physical backbone, can tune the charge transporting ability by nearly one order of magnitude. Furthermore, the addition of another Lewis base triethylamine (of stronger alkaline than DBP), to Lewis acid-base pair reverts the electrical properties back to that of a single DBP junction, that is constructive to propose a useful but simple strategy for the design and construction of reversible and controllable molecular device based on pyridine derived molecule.     

Preparation and Characterization of Activated Carbon from Microwave and Conventional Heated Almond Shells Using Phosphoric Acid Activation

Activated carbon production from almond shells using phosphoric acid activation agent was achieved by applying both conventional heating and microwave heating in succession. The morphology and surface properties of activated carbon were studied using thermogravimetric and differential gravimetric analysis, Fourier-transform infrared spectroscopy, scanning electron microscopy, and Brunauer–Emmett–Teller analysis. A surface area of 1128 m²/g was achieved by optimizing the microwave power (500?W), microwave application time (15?minutes), conventional heating time (45?minutes), conventional heating temperature (500?°C), and the phosphoric acid:sample ratio (0.7:1). An adsorption capacity of methylene blue of 148?mg/g and an iodine value of 791?mg/g was obtained for the prepared activated carbon.     

Atomic-Scale Insights into Electrode Surface Dynamics by High-Speed Scanning Probe Microscopy

Atomic-scale processes at electrode surfaces in liquid electrolytes are central elemental steps of electrochemical reactions. Detailed insights into the structure of these interfaces can be obtained with in situ scanning tunnelling and atomic force microscopy. By increasing the time resolution of these methods into the millisecond range, highly dynamic processes at electrode surfaces become directly observable. This review gives an overview of in situ studies with video-rate scanning probe microscopy techniques. Firstly, quantitative investigations into the dynamic behaviour of individual adsorbed atoms and molecules are described. These reveal a complex dependence of adsorbate surface diffusion on potential and co-adsorbed species and provide data on adsorbate–adsorbate and adsorbate–substrate interactions in a liquid environment. Secondly, results on collective dynamic phenomena are discussed, such as molecular self-assembly, the dynamics of nanoscale structures, nucleation and growth, and surface restructuring due to phase-formation processes.     

Peculiarities of melting and crystallization of n-decane in a porous glass

Melting and crystallization of n-decane embedded into porous glass with the mean pore size of about 6.4 nm were studied using acoustic and DSC methods. Smearing of the phase transitions, decrease of melting and freezing temperatures, pronounced hysteresis between melting and crystallization were revealed by both methods. In DSC measurements for the pore filling factors 70% and higher double peaks were observed upon cooling while only single peaks were present upon heating. Also a high reduction of the corresponding phase transition heats was revealed. Melting and freezing intervals determined by acoustic and DSC methods strongly differed from each other. A model which qualitatively explains the observed anomalies is proposed. It supposes the formation of liquid layers on the surface of the pores.     

塔河油田超埋深碳酸盐岩油藏基质的力学试验研究

碳酸盐岩油气藏在全球范围内分布广泛,其中30%以上为缝洞型碳酸盐岩油气藏。在我国缝洞型油藏占已探明的碳酸盐岩油藏储量的2/3,是今后增储的主要领域。为准确揭示碳酸盐岩油藏基质的力学特性,本文以塔河油田奥陶系油藏地层为研究背景,通过现场深孔钻井取样得到埋深达5300~6200m的碳酸盐岩油藏基质岩样,并通过力学试验首次获得超埋深碳酸盐岩油藏基质的弹模、泊松比、抗压强度、抗拉强度、粘聚力、内摩擦角等力学参数,借助电镜扫描试验揭示出超埋深碳酸盐岩的微细观破裂机制。该项研究成果可为分析碳酸盐岩油藏溶洞的垮塌破坏机理提供有效的试验参数。     

Crosslinked poly(ethylene oxide) containing siloxanes fabricated through thiol‐ene photochemistry

Homogenous amphiphilic crosslinked polymer films comprising of poly(ethylene oxide) and polysiloxane were synthesized utilizing thiol‐ene “ click ” photochemistry. A systematic variation in polymer composition was Carried out to obtain high quality films with varied amount of siloxane and poly(ethylene oxide). These films showed improved gas separation performance with high gas permeabilities with good CO₂/N₂ selectivity. Furthermore, the resulting films were also tested for its biocompatibility, as a carrier media which allow human adult mesenchymal stem cells to retain their capacity for osteoblastic differentiation after transplantation. The obtained crosslinked films were characterized using differential scanning calorimetry, dynamic mechanical analysis, thermogravimetric analysis, FTIR, Raman‐IR , and small angle X‐ray scattering. The synthesis ease and commercial availability of the starting materials suggests that these new crosslinked polymer networks could find applications in wide range of applications. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1548–1557     

Entropic effect implication for change in polymer coils swelling state in the demixing enthalpy recovery of aqueous poly(vinyl methyl ether) solutions

Time‐dependent demixing enthalpy recovery behavior of aqueous poly(vinyl methyl ether) (PVME) solutions exhibits distinct recovery characteristics in three concentration regions. The absence of recovery behavior below a water concentration of 38.3 wt % indicates that the PVME coil is in a globular state. The typically sigmoidal recovery behavior of demixing enthalpy above 38.3 wt % is ascribed to the reswelling of the collapsed polymer coils induced by the entropic effect. The increase in difference between the upper and lower limits indicates the continued swelling of the PVME coils. Above 65 wt %, a dominant diluting effect can be observed, and a much longer phase separation time is needed to reach the expected lower limit. In contrast, the recovery of demixing enthalpy in a wide range of water concentration (from 38.3 to 90 wt %) exhibits the same feature. The infrared spectroscopy results are in agreement with the above macroscopic differential scanning calorimetry results. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 142–151     

多层螺旋CT诊断甲状腺癌中的辐射和对比剂剂量选择

本文对多层螺旋CT（MSCT）诊断甲状腺癌中的辐射和对比剂剂量选择进行了分析。选取2016年12月～2018年12月本院行MSCT检查的甲状腺癌、甲状腺良性结节患者各200例，依据随机数字表分为A组、B组、C组、D组，每组50例，A组参数为对比剂1.2 mL/kg、120 kV、180 mA，B组为对比剂1.0 mL/kg、120 kV、180 mA，C组为对比剂1.2 mL/kg、100 kV、100 mA，D组为对比剂1.0 mL/kg、100 kV、100 mA。结果显示，A组和B组CT容积剂量指数（CTDIvol）、剂量长度乘积（DLP）、有效辐射剂量（ED）明显低于C组和D组，A组和B组甲状腺CT值、背景信号、背景噪声明显高于C组和D组，差异有统计学意义（P<0.05），A组、B组、C组、D组信噪比（SNR）、对比信噪比（CNR）、图像质量评分比较，差异无统计学意义（P>0.05）；A组、B组、C组、D组诊断甲状腺癌的敏感度、特异度、准确度比较，差异无统计学意义（P>0.05）。本文证实，对于MSCT诊断甲状腺癌中的辐射和对比剂剂量，选择1.0 mL/kg、100 kV、100 mA可在不严重影响图像质量及检查结果下有效减少患者的CT辐射，值得临床推广。