褪黑素合成及环化机理研究

以邻苯二甲酰亚胺钾盐为起始原料,经五步反应合成了褪黑素,鉴定了产物结构,合成收率达35.6%,纯度99.1%。对中间产物2-羧乙酯基-3-(2-邻苯二甲酰亚胺乙基)-5-甲氧基-吲哚的环化反应过程进行了机理研究,为最佳工艺条件的确定提供了理论依据。

氧化呋咱合成策略、反应机理及其在含能材料研发中的应用

氧化呋咱是蕴含“潜硝基”片段的富氮芳环结构,其骨架致密性与突出的生成焓水平使其成为含能材料等领域的重要分子骨架。特殊的氮氧原子排布显著提升了氧化呋咱互变异构的倾向,而互变异构体的存在降低了氧化呋咱骨架的稳定性同时增加了其合成的难度。本文综述了基于不同策略的氧化呋咱的合成方法研究,以氧化呋咱骨架本身的制备反应机理为重点,分析比较了不同合成方法的优势与不足,并进一步总结了以氧化呋咱合成策略为基础的含能化合物研发进展。鉴于氧化呋咱本身的高致密性、高氧平衡、高生成焓特点,以氧化呋咱结构为基础的含能结构仍将是高能量密度材料研发的重点方向。

类胡萝卜素代谢途径中相关番茄红素环化酶的功能

番茄红素环化是其生物合成途径中的一个关键分支点。自然界存在两类氨基酸序列不相关的番茄红素环化酶,其中单体型环化酶在成环的化学机理,底物特异性和活性,蛋白特征及氨基酸序列保守性等方面的存在相似性,包括G-细菌的番茄红素环化酶CrtY,蓝藻的CrtL,以及绿藻和植物的Lyc-B/E及相关的Ccs和Nsy。另一类异二聚体型番茄红素环化酶则存在于G+细菌,古生菌和真菌中,其催化机理和需要的辅因子尚待进一步证实。

Recent Advances in Transition Metal-Based Catalysts for Electrocatalytic Nitrate Reduction Reaction

The accumulation of excessive nitrate in the atmosphere not only jeopardizes human health but also disrupts the balance of the nitrogen cycle in the ecosystem.Among various nitrate removal technologies,electrocatalytic nitrate reduction reaction(eNO_(3)RR)has been widely studied for its advantages of being eco-friendly,easy to operate,and controllable under environmental conditions with renewable energy as the driving force.Transition metal-based catalysts(TMCs)have been widely used in electrocatalysis due to their abundant reserves,low costs,easy-to-regulate electronic structure and considerable electrochemical activity.In addition,TMCs have been extensively studied in terms of the kinetics of the nitrate reduction reaction,the moderate adsorption energy of nitrogen-containing species and the active hydrogen supply capacity.Based on this,this review firstly discusses the mechanism as well as analyzes the two main reduction products(N_(2)and NH_(3))of eNO_(3)RR,and reveals the basic guidelines for the design of efficient nitrate catalysts from the perspective of the reaction mechanism.Secondly,this review mainly focuses on the recent advances in the direction of eNO_(3RR)with four types of TMCs,Fe,Co,Ni and Cu,and unveils the interfacial modulation strategies of Fe,Co,Ni and Cu catalysts for the activity,reaction pathway and stability.Finally,reasonable suggestions and opportunities are proposed for the challenges and future development of eNO_(3)RR.This review provides far-reaching implications for exploring cost-effective TMCs to replace high-cost noble metal catalysts(NMCs)for eNO_(3)RR.

1,5-二氨基四唑的异构化合成动力学

用密度泛函方法，计算研究1，5-二氨基四唑（DAT）的电子结构及异构化反应机理。在B3LYP／6—311G水平下，对涉及反应各驻点的几何结构、振动频率、自然键轨道、以及零点能（ZPE）进行了计算；用内禀反应坐标理论（IRC）获得反应的最小能量路径（MEP），在耦合簇理论的CCSD（T）方法下计算单点能得到了反应的最小势能曲线；并且用传统过渡态理论（TST）、Eckart隧道校正理论（TST／Eckart）和变分过渡态理论（CVT），计算了200～1000K的反应速率常数。计算结果表明，DAT分子中的N（4）和N（9）易参与金属原子配位，形成一系列以DAT为配体的配位化合物。异构化合成DAT反应为叠氮基关环机理，气态情况下该反应为放热且自发反应，反应活化能较低。

新型染料敏化剂三苯基咪唑丙烯酸的合成及其光电性能

以苯偶姻、苯甲醛和丙二酸为原料经3步反应合成了新型三苯基咪唑系染料敏化剂(TPIA),其结构经1H NMR,13C NMR,IR和MS表征,并分析了咪唑的环化反应机理。将TPIA用于染料敏化太阳能电池染料敏化剂,表明TPIA具有良好的光电转换性能,TPIA的乙醇饱和溶液吸附敏化光阳极24 h的DSSC光电转换效率为1.90%,填充因子为74.5%。

Xanthophyll Cycle and Its Molecular Mechanism in Photoprotection

When plants absorb more light than that can be used for photosynthesis, the excessive energy can cause photoinhibition and even photooxidation of photosynthetic apparatus. Xanthophyll cycle-dependent photo-protection is believed to be the main mechanism for plants to deal with excessive light energy. This review focuses on molecular biological aspects and regulations of violaxanthin de-epoxidase and zeaxanthin epoxidase involved in xanthophyll cycle. We will summarize the functions of xanthophyll cycle, especially recent advances in its thermal dissipation mechanism of photoprotection. Some interesting issues deserving further study will be discussed.

2-硫代-3-芳基-5-苯基亚甲基-4-咪唑啉二酮衍生物的有效合成新方法

研究了应用烯基膦亚胺与二硫化碳、芳伯胺的串联aza Wittig反应 ,来合成 2 硫代 3 芳基 5 苯基亚甲基 4 咪唑啉二酮衍生物的有效新方法。提出了可能的环化反应机理 ,探讨了所合成化合物的成环反应条件和波谱性质。生成的环化产物均为新的化合物 ,其结构经元素分析、IR、1HNMR和MS确证。

1,2-双(5,5′-二硝胺基-1,3,4-噁二唑-2-)乙烷的合成与性能

为了得到钝感的1,3,4-噁二唑类含能化合物,以丁二酸二甲酯和溴化氰为起始原料,通过肼解、环化、硝化反应合成了1,2-双(5,5'-二硝胺基-1,3,4-噁二唑-2-)乙烷(BNOE),总收率为49.93%。采用元素分析、傅里叶变化红外光谱和核磁对其结构进行了表征。用热重-差示扫量热仪研究了其热稳定性,依据GJB5891-2006方法测试了感度,采用密度瓶法测试了密度,用量子化学软件Gaussian 09计算了固相生成焓,采用EXPLO 5 V6.02程序预估了其爆轰性能。结果表明,BNOE的起始分解温度为202.2℃,热分解峰温为208.6℃,撞击感度为8.6 J,摩擦感度为88%,静电感度为108.1 mJ,实测密度为1.714 g·cm-3,固相生成焓为48.25 kJ·mol^-1,计算爆压为22.6 GPa,计算爆速为7663 m·s^-1。采用Gaussian 09分析了5-甲基-2-氨基-1,3,4-噁二唑(NAOz)的环化反应机理,认为其反应分为肼解反应和成环反应两个阶段。

In-situ polymerization for PPy/g-C_3N_4 composites with enhanced visible light photocatalytic performance

Polypyrrole‐modified graphitic carbon nitride composites(PPy/g‐C3N4)are fabricated using an in‐situ polymerization method to improve the visible light photocatalytic activity of g‐C3N4.The PPy/g‐C3N4 is applied to the photocatalytic degradation of methylene blue(MB)under visible light irradiation.Various characterization techniques are employed to investigate the relationship between the structural properties and photoactivities of the as‐prepared composites.Results show that the specific surface area of the PPy/g‐C3N4 composites increases upon assembly of the amorphous PPy nanoparticles on the g‐C3N4 surface.Owing to the strong conductivity,the PPy can be used as a transition channel for electrons to move onto the g‐C3N4 surface,thus inhibiting the recombination of photogenerated carriers of g‐C3N4 and improving the photocatalytic performance.The elevated light adsorption of PPy/g‐C3N4 composites is attributed to the strong absorption coefficient of PPy.The composite containing 0.75 wt%PPy exhibits a photocatalytic efficiency that is 3 times higher than that of g‐C3N4 in 2 h.Moreover,the degradation kinetics follow a pseudo‐first‐order model.A detailed photocatalytic mechanism is proposed with·OH and·O2-radicals as the main reactive species.The present work provides new insights into the mechanistic understanding of PPy in PPy/g‐C3N4 composites for environmental applications.

Synthesis of novel p-n heterojunction m-Bi_2O_4/BiOCl nanocomposite with excellent photocatalytic activity through ion-etching method

A novel p‐n heterostructure photocatalyst m‐Bi2O4/BiOCl was successfully synthetized through a facile ion‐etching method.Via adjusting the added volume of HCl solution,a series of different ratios of composite photocatalysts were obtained.The as‐prepared samples of physical,chemical and optical characteristics were examined by X‐ray diffraction,scanning electron microscope,transmission electron microscope,energy dispersive X‐ray spectroscopy,selected‐area electron diffraction,Fourier transform infrared absorption,Raman microscope,N2 adsorption‐desorption,X‐ray photoelectron spectroscopy and UV‐vis spectrum technologies.The photocatalysts showed high degradation rate and complete mineralization ability for methyl orange and tetracycline solution under visible light.The reaction rate constant of m‐Bi2O4/BiOCl for methyl orange was 52.28 times higher than that of BiOCl.The characterization presented a good stability of materials.Furthermore,the photocurrent response test certified that the heterostructure effectively accelerated the separation and migration of photo‐generated carries.The scavenger experiments evidenced that hole(h+)and superoxide radical(?O2?)were the primary active radicals.A possible photocatalytic mechanism was proposed.This work provided an alternative photocatalyst applied to water environmental remediation.

Significant role of carbonate radicals in tetracycline hydrochloride degradation based on solar light-driven TiO2-seashell composites:Removal and transformation pathways

TiO2-seashell composites prepared via a sol-gel method were used to generate carbonate radicals(·CO3–) under solar light irradiation. ·CO3–, a selective radical, was employed to degrade the target tetracycline hydrochloride contaminant. A series of characterizations was carried out to study the structure and composition of the synthesized TiO2-seashell composite. This material exhibits excellent solar light-driven photochemical activity in the decomposition of tetracycline hydrochloride. The possible pathway and mechanism for the photodegradation process were proposed on the basis of high-resolution electrospray ionization time-of-flight mass spectrometry experiments. Finally, we investigated the reusability of the TiO2-seashell composite. This study is expected to provide a new facile pathway for the application of ·CO3– radicals to degrade special organic pollutants in water.

Local regulator adrenomedullin contributes to the circulatory disturbance in cirrhotic rats

AIM： To investigate whether adrenomedullin, a potent vasodilator peptide, plays a role in the circulatory disturbance in cirrhosis. METHODS： Cirrhosis was induced in rats by weekly gavage of carbon tetrachloride. Hemodynamic studies were performed in vivo using radioactive microspheres and in vitro using isolated aortic rings. The adrenomedullin concentrations were measured by radioimmunoassay. RESULTS： Acute administration of adrenomedullin to the control rats reduced the systemic arterial pressure along with an increase of serum levels of the stable metabolite of nitric oxide （NOx）, in a dose-dependent manner. Chronic infusion of adrenomedullin reduced the vascular resistance and increased the blood flow in the systemic and splanchnic circulation. Intravenous administration of anti-adrenomedullin antibody did not affect any hemodynamic parameters in the cirrhotic rats, whereas this antibody ameliorated the blunted contractile response to phenylephrine, o-adrenergic receptor agonist, in the aortic rings of the cirrhotic rats. The adrenomedullin concentrations in the aorta were higher in the cirrhotic rats than in the controls, and correlated with the mean arterial pressure in the cirrhotic rats. Moreover, adrenomedullin blunted the contractile response to phenylephrine in both of the control aorta and cirrhotic aorta, but not in the presence of NG-nitro L-arginine methyl ester, an NO synthase inhibitor. CONCLUSION： Adrenomedullin overproduced in the vascular wall may contribute to the circulatory disturbance in cirrhosis as a local regulator of the vascular tonus rather than a circulating hormone.

Microemulsion synthesis of ZnMn2O4/Mn3O4 sub-microrods for Li-ion batteries and their conversion reaction mechanism

The hierarchical ZnMn2O4/Mn3O4 composite sub-microrods were synthesized via a water-in-oil microemulsion method followed by calcination.The ZnMn2O4/Mn3O4 electrode displays an intriguing capacity increasing from 440 to 910 mA·h/g at 500 mA/g during 550 consecutive discharge/charge cycles,and delivers an ultrahigh capacity of 1276 mA·h/g at 100 mA/g,which is much greater than the theoretical capacity of either ZnMn2O4 or Mn3O4 electrode.To investigate the underlying mechanism of this phenomenon,cyclic voltammetry and differential capacity analysis were applied,both of which reveal the emergence and the growth of new reversible redox reactions upon charge/discharge cycling.The new reversible conversions are probably the results of an activation process of the electrode material during the cycling process,leading to the climbing charge storage.However,the capacity exceeding the theoretical value indicates that there are still other factors contributing to the increasing capacity.

Complete oxidation of 1,4-dioxane over zeolite-13X-supported Fe catalysts in the presence of air

Zeolite-13X-supported Fe（Fe/zeolite-13X） catalysts with various Fe contents were prepared by the wet impregnation method.The catalysts were characterized by N2 adsorption-desorption isotherms to estimate the Brunauer-Emmett-Teller surface areas and Barrett-Joyner-Hanlenda pore size distributions.X-ray diffraction,scanning electron microscopy,temperature-programmed reduction,and temperature-programmed desorption of NH3 were used to investigate the textural properties of the Fe/zeolite-13 X catalysts.Their catalytic activities were determined for the complete oxidation of1,4-dioxane using air as the oxidant in a fixed-bed flow reactor in the temperature range 100-400℃.The influences of various process parameters,such as reaction temperature,metal loading,and gas hourly space velocity（GHSV）,on the dioxane removal efficiency by catalytic oxidation were investigated.The stability of the catalyst was tested at 400℃ by performing time-on-stream analysis for 50 h.The Fe/zeolite-13 X catalyst with 6 wt%Fe exhibited the best catalytic activity among the Fe/zeolite-13 X catalysts at 400℃ and a GHSV of 24000 h^（-1）,with 97%dioxane conversion and95%selectivity for the formation of carbon oxides（CO and CO2）.Trace amounts（ 3%） of acetaldehyde,ethylene glycol monoformate,ethylene glycol diformate,1,4-dioxane-2-ol,1,4-dioxane-2-one,and 2-methoxy-1,3-dioxalane were also formed as degradation products.A plausible degradation mechanism is proposed based on the products identified by GC-MS analysis.

Curing Mechanism of Condensed Polynuclear Aromatic Resin and Thermal Stability of Cured Resin

In order to improve the thermal stability of condensed polynuclear aromatic(COPNA) resin synthesized from vacuum residue, 1,4-benzenedimethanol was added to cure COPNA resin. The curing mechanism was investigated by proton nuclear magnetic resonance spectrometry, solid carbon-13 nuclear magnetic resonance spectrometry and Fourier transform infrared spectroscopy. Microstructures of the uncured and the cured COPNA resins were studied by scanning electron microscopy and X-ray diffractometry. The thermal stability of COPNA resins before and after curing was tested by thermogravimetric analysis. The element composition of the cured COPNA resin heated at different temperatures was analyzed by an element analyzer. The results showed that the uncured COPNA resin reacted with the cross-linking agent during the curing process, and the curing mechanism was confirmed to be the electrophilic substitution reaction. Compared with the uncured COPNA resin, the cured COPNA resin had a smooth surface, well-ordered and streamlined sheet structure with more crystalline solids, better molecular arrangement and orientation. The weight loss process of the uncured and cured COPNA resins was divided into three stages. Carbon residue of the cured COPNA resin was 41.65% at 600 ℃, which was much higher than 25.02% of the uncured COPNA resin, which indicated that the cured COPNA resin had higher thermal stability.

Research on the development and countermeasures for circular economy

Ecological economics and sustainable development economics are the basic theories to research on circulareconomy. Through the systemically research on the relationship of the three above, this paper thinks that the reuse andrecycle of circular economy is a way that the stall is mended after a sheep is lost. Although the reduction technicallycontrols the production process, it cannot solve the waste caused by blind production and excess competition. We haveexperienced variety obstacles when implementing the circular economy, whose main reason is the conflict between theindividual ration and the social ration. Therefore, only when the individual ration and social ration incline to conformity,the cooperating Nash equilibrium will be appeared. In order to realize the harmony of ecology, economy and society, wehave to explore effective evaluation theory. This paper cites the "five flows of wealth operation theory" from professorMa Chuandong to search operation mechanism of circular economy, makes clear the developing thoughts of circulareconomy based on the realities, and brings forward some countermeasures to develop circular economy based on theabove theoretical analysis.

Pathogenesis of NSAID-induced gastric damage:Importance of cyclooxygenase inhibition and gastric hypermotility

This article reviews the pathogenic mechanism of nonsteroidal anti-inflammatory drug(NSAID)-induced gastric damage,focusing on the relation between cyclooxygenase(COX) inhibition and various functional events.NSAIDs,such as indomethacin,at a dose that inhibits prostaglandin(PG) production,enhance gastric motility,resulting in an increase in mucosal permeability,neutrophil infiltration and oxyradical production,and eventually producing gastric lesions.These lesions are prevented by pretreatment with PGE 2 and antisecretory drugs,and also via an atropine-sensitive mechanism,not related to antisecretory action.Although neither rofecoxib(a selective COX-2 inhibitor) nor SC-560(a selective COX-1 inhibitor) alone damages the stomach,the combined administration of these drugs provokes gastric lesions.SC-560,but not rofecoxib,decreases prostaglandin E 2(PGE 2) production and causes gastric hypermotility and an increase in mucosal permeability.COX-2 mRNA is expressed in the stomach after administration of indomethacin and SC-560 but not rofecoxib.The up-regulation of indomethacin-induced COX-2 expression is prevented by atropine at a dose that inhibits gastric hypermotility.In addition,selective COX-2 inhibitors have deleterious influences on the stomach when COX-2 is overexpressed under various conditions,including adrenalectomy,arthritis,and Helicobacter pylori-infection.In summary,gastric hypermotility plays a primary role in the pathogenesis of NSAID-induced gastric damage,and the response,causally related with PG deficiency due to COX-1 inhibition,occurs prior to other pathogenic events such as increased mucosal permeability;and the ulcerogenic properties of NSAIDs require the inhibition of both COX-1 and COX-2,the inhibition of COX-1 upregulates COX-2 expression in association with gastric hypermotility,and PGs produced by COX-2 counteract the deleterious effect of COX-1 inhibition.

Condensation heat transfer enhancement mechanism for vertical upflows by the phase separation concept at small gravity

In the field of aerospace, minimum and seal of equipments cause the increase in the thermal loading sharply. Due to the lack of driving force, the performance of conventional condenser deteriorates greatly under the small gravity environment, which leads to reduction in the service life of equipments. In this study, a passive condenser, developed on basis of the phase separation concept,is utilized to improve the performance of the condensation heat transfer under the small gravity environment. As a result of the limitation of experiments, the mechanisms of heat transfer enhancement of the phase separation condenser tube are revealed through numerical simulation based on the volume-of-fluid(VOF) method. The following conclusions could be obtained:(1) A novel phase distribution of ‘‘gas near the tube wall and liquid in the tube core'' is formed. The thin liquid film is indeed created after the flow pattern modulation by inserting mesh cylinder.(2)The condensation quantity for single bubble in the annular region increases about 16 times greater than that in the bare tube region in the case of Jl= 0.0574 m/s and Jg= 0.0229 m/s.(3) Gas volume fraction affects the parameters of liquid film thickness, bubble length and liquid bridge length. The increase in the gas volume fraction results in the decrease in the evaluation index from21.56 to 12.82. The evaluation index is defined as the ratio of the condensation quantities per unit tube length of the annular region and the bare tube region.

Mechanistic study of copper-catalyzed intramolecular ortho-C-H activation/carbon-nitrogen and carbon-oxygen cyclizations

Intramolecular ortho-C-H activation and C-N/C-O cyclizations of phenyl amidines and amides have recently been achieved under Cu catalysis. These reactions provide important examples of Cu-catalyzed functionalization of inert C-H bonds, but their mechanisms remain poorly understood. In the present study the several possible mechanisms including electrophilic aro- matic substitution, concerted metalation-deprotonation （CMD）, Friedel-Crafts mechanism, radical mechanism, and proton- coupled electron transfer have been theoretically examined. Cu（II）-assisted CMD mechanism is found to be the most feasible for both C-O and C-N cyclizations. This mechanism includes three steps, i.e. CMD with Cu（II）, oxidation of the Cu（II） inter- mediate, and reductive elimination from Cu（III）. Our calculations show that Cu（II） mediates the C-H activation through an six-membered ring CMD transition state similar to that proposed for many Pd-catalyzed C-H activation reactions. It is also in- teresting to find that the rate-limiting steps are different for C-N and C-O cyclizations： for the former it is concerted metalation-deprotonation with Cu（II）, whereas for the latter it is reductive elimination from Cu（III）. The above conclusions are consistent with the experimental kinetic isotope effects （1.0 and 2.1 for C-O and C-N cyclizations, respectively）, substituent effects, and the reactions under O2-free conditions.