A Method of Determining Selectivity Coefficients Based on the Practical Slope of Ion Selective Electrodes

It is a problem to be solved that the experimental selectivity coefficients of ion selective electrodes (ISEs) depend on the activity. This paper studied the new method of determining selectivity coefficients. A mixed ion response equation, which was similar to Nicolsky-Eisenman (N-E) equation recommended by IUPAC, was proposed. The equation includes the practical response slope of ISEs to the primary ion and the interfering ion. The selectivity coefficient was defined by the equation instead of the N-E equation. The experimental part of the method is similar to that based on the N-E equation. The values of selectivity coefficients obtained with this method do not depend on the activity whether the electrodes exhibit the Nernst response or non-Nernst response. The feasibility of the new method is illustrated experimentally.

分子点群的判别

分子点群是结构化学课程中分子对称性章节中的核心内容,是学生深入学习、认识和理解分子结构对称性以及结构与分子性质之间关系的理论基础。其中,分子点群的判别是分子点群的重要知识点之一。本文回顾了国内外不同结构化学教材中分子点群的判别流程,讨论了现有分子点群判别流程在判断分子所属点群中可能出现的问题以及不足之处,并提出了分子点群判别中部分流程的改进方案,有助于学生更加深刻理解分子点群的内涵。

Energy-level dependent H_2_O_2 production on metal-free,carbon-content tunable carbon nitride photocatalysts

Light-driven production of H2O2 from water and molecular oxygen could be a promising way for obtaining both solar fuels and fundamental chemicals. During that process, the H2O2 yield is strongly dependent on the reaction pathway associated with two-electron reduction of dioxygen by the photo-generated electrons. Herein, we synthesized a series of metal-free, carbon-content tunable carbon nitride photocatalysts（named C3N4-Carbon） by a facile hydrothermal reaction and subsequent thermal treatment at appropriate temperatures. The energy levels of the C3N4-Carbon catalysts vary with the carbon doping level, which is conveniently tuned by changing the initial glucose concentration during the hydrothermal reaction. The surface carbon species evolve with the carbon content and the nitrogen atoms in the structure of carbon nitride are partially substituted by foreign carbon atoms based on XPS measurements. The optimal catalyst leads to the highest H2O2 yield of 1271 μmol L-1 in an acidic aqueous solution（pH 3） after a reaction period of 4 h, twice higher than the pristine C3N4. In addition, the largest formation rate constant and the smallest decomposition rate constant of H2O2 are obtained on the optimal one according to the kinetics analyses. The decomposition tests of H2O2 indicate that the formation rate could be a dominant factor impacting the H2O2 yield. The conduction band position of the optimal catalyst is positively shifted to 0.06 V versus RHE, which is more favorable to the reduction of dioxygen to H2O2（O2/H2O2 at 0.69 V versus RHE）. The positive shift of valence band also improves hole collection and leads to enhanced formation of H2O2.

Effects of Different Flue-curing Technologies on Submicroscopic Structure of Flue-cured Tobacco Leaves

[ Objective] This study aimed to compare the effects of low-temperature low-humidity tobacco flue-curing technology, moderate-temperature moderate- humidity tobacco flue-curing technology and moderate-temperature high-humidity tobacco flue-curing technology on submicroscopic structure of flue-cured tobacco leaves to provide theoretical basis for tobacco flue-curing. [ Method] Middle leaves of tobacco cuhivar K326 were collected in Pengshui County of Chongqing City for flue-curing experiment using three flue-curing technologies. Leaf samples were collected regularly in the flue-curing process, to investigate the submicroscopic structure of flue-cured tobacco leaves. [ Result] Morphology changes and structural rupture of chloroplasts occurred at different time during three flue-curing proces- ses. In low-temperature low-humidity flue-curing process, morphology changes and structural rupture of chloroplasts occurred late but rapidly; in moderate-tempera- ture moderate-humidity flue-curing process and moderate-temperature high-humidity flue-curing process, morphology changes and structural rupture of chloroplasts occurred early but slowly. Among these three flue-curing processes, the speed of changes in mitochondria morphology, cristae number and membrane rupture pres- ented an upward order of low-temperature low-humidity flue-curing process 〈 moderate-temperature high-humidity flue-curlng process 〈 moderate-temperature moderate-humidity flue-curing process. In low-temperature low-humldity flue-curing process, starch granules in chloroplasts ruptured after flue-curing for 36 -48 h ; in moderate-temperature moderate-humidity flue-curing process, starch granules in chloroplasts ruptured after flue-curing for 24 - 36 h; in moderate-temperature high-humidity flue-curing process, starch granules in chloroplasts ruptured after flue-curing for 12 - 24 h. [ Conclusion ] Using low-temperature low-humidity flue- curing technology could prolong the maintenance duration of the submicroscopic structure integrity of flue-cured tobacco leaves, which was conducive to fully decom- posing and transforming substances in tobacco leaves and obtaining high-quality flue-cured tobacco leaves.

Effects of Different Flue-curing Technologies on Microscopic Structure of Flue-cured Tobacco Leaves

[Objective] This study aimed to compare the effects of Chinese quality-improving fragrunce-increasing tobacco flue-curing technology, Chinese three- stage tobaeeo flue-curing technology and Zimbabwean tobaceo flue-euring technology on microscopie structure of flue-cured tobacco leaves to provide theoretical basis for tobacco flue-curing. [ Method ] Middle leaves of tobacco cultivar K326 were collected in Pengshui County of Chongqing City for flue-curing experiment using three flue-curing technologies. Leaf samples were collected regularly in the flue-curing process, to investigate the microscopic structure of flue-cured tobaceo leaves. [ Result] During three flue-curing processes, leaves, palisade tissues and sponge tissues shrank gradually. Three flue-euring processes exhibited significant differ- ences in the peak of tissue shrinkage ： microscopic structure of flue-cured tobacco leaves in Chinese three-stage tobacco flue-curing process shrank earliest, follower by Chinese quality-improving fragrance-increasing tobacco flue-curing process; flue-eured tobacco leaves in Zimbabwean tobacco flue-curing process presented the latest shrinkage. At 84 h post-curing, leaf thickness in three flue-curing processes showed a descend order of Chinese three-stage tobacco flue-curing process 〉 Chinese quality-improving fragrance-increasing tobacco flue-curing process 〉 Zimbabwean tobacco flue-curing process. Upper and lower epidermal cells in Zimb- abwean tobacco flue-curing process ruptured earlier than other two flue-curing processes; eventually, the majority of cells ruptured and mixed with palisade tissues and sponge tissues. In Chinese quality-improving fragranee-increasing tobacco flue-curing process, only a small number of epidermal cells in dried leaves ruptured. Among three flue-curing technologies, Zimbabwean tobacco flue-curing technology exhibited the greatest damage to epidermal cells, followed by Chinese three-stage tobaceo flue-curing technology; Chinese quality-improving fragrance-increasing tobacco flue-curing technology had the minimum damage to epidermal cells. Mese- phyll cross-section exhibited significant morphological changes in stomata. To be specific, at 0 - 12 h post-curing, stomata of tobacco leaves closed with slightly prominent stamatal apparatuses on upper and lower epidermis; at 24 -72 h post-curing, stomata of tobaceo leaves changed gradually from opening to closure with significantly prominent stomatal apparatuses on upper and lower epidermis; at 84 h post-curing, stomata of tobacco leaves closed, and the majority of stomatal appa- ratuses were significantly prominent. In Chinese quality-improving fragrance-increasing tobacco flue-curing process, only a small number of epidermal ceils ruptured at 84 h pest-flue-curing; palisade tissues and sponge tissues shrank almost simultaneously. Significant gaps were observed between palisade tissues and between pal- isade tissues and sponge tissues. Chinese quality-improving fragrance-increasing tobacco flue-curing technology exhibited lower disorder level compared with other two flue-curing technologies. [ Conclusion] Chinese quality-improving fragrance-increasing tobacco flue-curlng technology was conducive to maintaining the micro- scopic structure integrity of flue-cured tobacco leaves and obtaining high-quality flue-cured tobacco leaves.

A Computational Study on Iridium-Catalyzed Production of Acetic Acid from Ethanol and Water Solution

The mechanism for the production of acetic acid from ethanol and water mixture catalyzed by iridium catalyst has been theoretically investigated.The cooperation of the iridium center and bpyO ligand is highlighted,which plays an important role in the catalytic activity.The hydrogen release from the iridium center is the rate-determining step,with an energy barrier of 22.5 kcal/mol.The electronic structure analysis suggests electron-donating substituents could decrease the energy barrier.

Short-term and oncological outcomes of natural orifice specimen extraction surgery(NOSES)for colorectal cancer in China:a national database study of 5055 patients

经自然腔道取标本手术(NOSES)通过无切口理念与常规手术器械的结合,表现出极佳的微创效果,并带给患者全新的就医感受.目前,尽管NOSES已广泛用于结直肠肿瘤治疗,大量研究也表明相比常规腹腔镜手术,NOSES具有恢复快、创伤小、疼痛轻等优势,但绝大多数研究均为小样本、单中心回顾性研究.本研究旨在通过分析我国5055例结直肠肿瘤NOSES患者数据,进一步探讨NOSES的短期疗效与预后.研究对象中,经直肠NOSES占整体比例的90.3%,经阴道NOSES占9.7%.NOSES术后短期并发症发生率为14.1%,吻合口瘘发生率为4.9%,腹盆腔感染率为1.9%.患者3年总生存率为93.2%,无病生存率为82.2%,局部复发率为3.6%.研究结果提示NOSES具有较好的安全性与可行性,为其应用于结直肠肿瘤治疗提供了证据.

Transcriptional and translational responses of rapeseed leaves to red and blue lights at the rosette stage

Under different red （R）：blue （B） photon flux ratios, the growth performance of rapeseed （Brassica napus L.） is significantly different. Rapeseed under high R ratios shows shade response, while under high B ratios it shows sun-type morphology. Rapeseed under monochromatic red or blue light is seriously stressed. Transcriptomic and proteomic methods were used to analyze the metabolic pathway change of rapeseed （cv. ＂Zhongshuang 11＂） leaves under different R：B photon flux ratios （including 100R：0B%, 75R：25B%, 25R：75B%, and 0R：100B%）, based on digital gene expression （DGE） and two-dimensional gel electrophoresis （2-DE）. For DGE analysis, 2054 differentially expressed transcripts （llog2（fold change）l〉1, q〈0.005） were detected among the treatments. High R ratios （100R：0B% and 75R：25B%） enhanced the expression of cellular structural components, mainly the cell wall and cell membrane. These components participated in plant epidermis development and anatomical structure morphogenesis. This might be related to the shade response induced by red light. High B ratios （25R：75B% and 0R：100B%） promoted the expression of chloroplast-related components, which might be involved in the formation of sun-type chloroplast induced by blue light. For 2-DE analysis, 37 protein spots showed more than a 2-fold difference in expression among the treatments. Monochromatic light （ML; 100R：0B% and OR： 100B%） stimulated accumulation of proteins associated with antioxidation, photosystem II （PSII）, DNA and ribosome repairs, while compound light （CL; 75R：25B% and 25R：75B%） accelerated accumulation of proteins associated with carbohydrate, nucleic acid, amino acid, vitamin, and xanthophyll metabolisms. These findings can be useful in understanding the response mechanisms of rapeseed leaves to different R：B photon flux ratios.