Precise electro-reduction of alkyl halides for radical defluorinative alkylation

Reported here is a precise electro-reduction strategy for radical defluorinative alkylation towards the synthesis of gem-difluoroalkenes from α-trifluoromethylstyrenes. According to the redox-potential difference of the radical precursors, direct or indirect electrolysis is respectively adopted to realize the precise reduction. An easy-to-handle, catalyst-and metal-free condition is developed for the reduction of alkyl radical precursors that are generally easier to be reduced than α-trifluorome...     

直接内重整熔融碳酸盐燃料电池中甲烷蒸汽重整催化剂探索性研究

选择甲烷蒸汽重整催化剂用于直接内重整熔融碳酸盐燃料电池(DIR-MCFC)中,并考察了DIR-MCFC的性能,讨论了电池放电量、气体压力、燃料气进料水/碳比(S/C)等因素对该催化剂性能的影响.结果表明,重整催化剂能够满足电池放电需求;放电量大小影响电池内的H2含量,但对CH4含量影响不大;当气体压力为0.36MPa时...     

侵彻弹体快速烤燃安全特性实验研究

为了考核大尺寸侵彻弹体的快速烤燃安全特性,利用自行研制的快速烤燃装置开展了实验。将质量为290 kg的侵彻弹体平吊在距航空燃油液面0.4 m的高度进行快速加热,实时采集弹体表面温度并拍摄实验过程,同时测量距弹体质心水平7 m处的反射冲击波超压,最后从加热时间、弹体表面温度、实验后现场破坏情况、反射冲击波超压峰值、反应机理及响应类型等方面对大尺寸侵彻弹体的快速烤燃安全特性进行了详细分析。实验结果表明：侵彻弹体在537 ℃高温中加热16 min 4 s后开始发生剧烈反应,且弹体内腔下方炸药最先响应形成热点,逐渐积聚的高温高压气体将壳体撕裂后快速泄压,在7 m处测量得到的反射冲击波超压峰值为33.622 kPa,远小于该弹体在空气中完全爆轰产生的冲击波超压峰值。综合判断该侵彻弹体的快速烤燃响应类型为爆燃,其安全特性满足要求。

     

硅探测器的数字化脉冲形状甄别

介绍了利用硅探测器的脉冲形状甄别进行粒子鉴别的原理。详细叙述了基于数字化方法的脉冲形状甄别的实现。采样频率和位数是数字化方法的两个重要参数。对于硅探测器信号,采用100 MS/s,12 bit的Digitizer可以满足脉冲形状甄别法对时间分辨的要求。同时对该方法粒子鉴别的特征和能量阈值做了简要的分析和对比。粒子背面入射硅探测器的所得的阈值低于正面入射的情况。例如对于氖周围的同位素,背面入射情况的阈值约为100 MeV,为正面入射情况下鉴别阈值的二分之一,相当与ΔE-E方法中ΔE探测器厚度约为60 μm情况下的阈值。最后定性讨论了硅探测器的电阻率不均匀性和沟道效应对粒子鉴别性能的影响。In this paper Pulse Shape Discrimination(PSD) for silicon detector has been briefly introduced. The emerging digital method successfully applied to detector signal processing makes digital PSD method one of the most promising particle identification methods. Sampling frequency and the number of bits are two key parameters of digital method. For silicon detector signal, adopting 100 Ms/s, 12 bit Digitizer can satisfy the time resolution requirement of PSD method. The identification characteristic and energy threshold of this method have been discussed and compared with both front injection and rear injection cases. Energy threshold with rear injection usually is much lower than that with front injection. For example, around for Neon isotope energy threshold with rear injection is about 100 MeV which is only half of the threshold with front injection, also equivalent to thickness of about 60 μm silicon detector threshold in ΔE-E method. At the end the impact of silicon detector's resistivity nonuniformity and channel effect on the identification capacity of PSD method has been discussed in detail.     

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.     

Electroreduction Enables Regioselective 1,2-Diarylation of Alkenes with Two Electrophiles

Precisely introducing two similar functional groups into bulk chemical alkenes represents a formidable route to complex molecules. Especially, the selective activation of two electrophiles is in crucial demand, yet challenging for cross-electrophile-coupling. Herein, we demonstrate a redox-mediated electrolysis, in which aryl nitriles are both aryl radical precursors and redox-mediators, enables an intermolecular alkene 1,2-diarylation with a remarkable regioselectivity, thereby avoiding the involvement of transition-metal catalysts. This transformation utilizes cyanoarene radical anions for activating various aryl halides (including iodides, bromides, and even chlorides) and affords 1,2-diarylation adducts in up to 83 % yield and >20 : 1 regioselectivity with more than 80 examples, providing a feasible approach to complex bibenzyl derivatives.     

基于超高效液相色谱-四极杆飞行时间质谱联用技术的血瘀模型大鼠血浆代谢组学分析

采用盐酸肾上腺素加冰水浴建立急性血瘀大鼠模型，使用超高效液相色谱-四极杆飞行时间质谱（UPLC-Q-TOF/MS）检测空白对照组与血瘀模型组中血浆代谢物，用主成分分析（PCA）、有监督偏最小二乘法判别分析（PLS-DA）及正交偏最小二乘法判别分析（OPLS-DA）对代谢组学数据进行多维统计分析，筛选潜在生物标志物。与对照组相比，在血瘀模型组大鼠血浆中检测出46个差异代谢物，血瘀模型组中乙酰胆碱、N6，N6，N6-三甲基-L-赖氨酸、胞嘧啶、乙酰肉碱等21个代谢物显著上调，吲哚丙酸、LysoPC（14：0）等25个代谢物显著下调，可能与脂质代谢、半乳糖代谢、亚油酸代谢、不饱和脂肪酸生物合成、糖酵解、花生四烯酸代谢等通路有关。代谢产物可作为血瘀证研究中的重要标记物，该研究结果有助于揭示血瘀证的发病机制，可为临床血瘀疾病的诊断及选用药物治疗提供思路，为后续治疗手段提供参考依据。     

A Novel Method for Stabilizing Zein Gel Particles to Salt Ion-Induced Aggregation

The destabilization of zein gel particles by salt ions seriously limits their practical application. In this study, zein gel particles exhibiting excellent stability to salt ions were developed by grafting gum arabic with tannic acid. Gum arabic (GA) was first coated onto the surface of zein gel particles, followed by addition of tannic acid to further reinforce non-covalent cross-linking between GA and the zein gel particle surface. The stability of the gel particle dispersions was characterized by Turbiscan analysis, gel particle diameter changes and visual inspection of phase separation. The tannic acid-treated zein–GA gel particles were highly protected from precipitation or aggregation in the presence of NaCl (0–3 mol/L) at different pH values (4.0, 7.0 or 8.5). The gel particles prepared in this study will therefore have broader applicability in different pH and salt ions ion environments.     

Separation and purification of both tea seed polysaccharide and saponin from camellia cake extract using macroporous resin

A novel method to separate and purify tea seed polysaccharide and tea seed saponin from camellia cake extract by macroporous resin was developed. Among four kinds of resins (AB‐8, NKA‐9, XDA‐6, and D4020) tested, AB‐8 macroporous resin possessed optimal separating capacity for the two substances and thus was selected for the separation, in which deionized water was used to elute tea seed polysaccharide, 0.25% NaOH solution to remove the undesired pigments, and 90% ethanol to elute tea seed saponin. Further dynamic adsorption/desorption experiments on AB‐8 resin‐based column chromatography were conducted to obtain the optimal parameters. Under optimal dynamic adsorption and desorption conditions, 18.7 and 11.8% yield of tea seed polysaccharide and tea seed saponin were obtained with purities of 89.2 and 96.0%, respectively. The developed method provides a potential approach for the large‐scale production of tea seed polysaccharide and tea seed saponin from camellia cake.     

Water‐compatible halloysite‐imprinted polymer by Pickering emulsion polymerization for the selective recognition of herbicides

A water‐compatible molecularly imprinted polymer was prepared by Pickering emulsion polymerization using halloysite nanotubes as stabilized solid particles. During polymerization, we used 4‐vinylpyridine as monomer, divinylbenzene as cross‐linking agent, toluene as porogen, 2,2‐azobisisobutyronitrile as initiator, 2,4‐dichlorophenoxyacetic acid as template to form the oil phase, and Triton X‐100 aqueous solution to form the water phase. The halloysite nanotubes molecularly imprinted polymer was characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. Kinetic and equilibrium bindings were also employed to evaluate the adsorption properties of the imprinted polymer. The imprinted polymer showed better selectivity, more rapid kinetic binding (60 min) for 2,4‐dichlorophenoxyacetic acid in pure water compared with rebinding in toluene. The imprinted polymer was used as a sorbent to enrich and separate 2,4‐dichlorophenoxyacetic acid from water, and was detected by high‐performance liquid chromatography with UV detection.