Dielectric relaxation and conduction mechanism in Aurivillius ceramic Bi5Ti3FeO15

For this study, we synthesized Aurivillius Bi5Ti3FeO15 ceramic using the generic solid-state reaction route and then performed room-temperature X-ray diffraction to confirm that the compound had a single phase with no impurities. The surface morphology of the prepared sample was observed to contain microstructural grains approximately 0.2–2 μm in size. The dielectric properties of the sample were determ-ined as a function of frequency in a range of approximately 100 Hz to 1 MHz at various temperatures (303 K ≤ T ≤ 773 K). Nyquist plots of the impedance data were found to exhibit a semi-circular arc in the high-temperature region, which is explained by the equivalent electrical circuit (R1C1)(R2QC2), where R1 and R2 represent the resistances associated with the grains and grain boundaries, respectively, C1 and C2 are the re-spective capacitances, and Q is the constant phase element (CPE), which accounts for non-Debye type of behavior. Our results indicate that both the resistance and capacitance of the grain boundaries are more prominent than those of the grains. The alternating current (ac) conductiv-ity data were analyzed based on the Jonscher universal power law, which indicated that the conduction process is dominated by the hopping mechanism. The calculated activation energies of the relaxation and conduction processes were very similar (0.32 to 0.53 eV), from which we conclude that the same type of charge carriers are involved in both processes.     

G蛋白偶联受体的共同激活机制

G蛋白偶联受体(G protein-coupled receptor, GPCR)构成人体中最庞大的膜蛋白家族，也是最重要的一类药物靶 标。随着GPCR结构解析技术的突破，目前已破解八十余个受体的400多个结构，揭示出GPCR复杂多样的配体结合模式和 跨膜信号转导机制。近年来，残基相互作用计算已实现对GPCR构象变化的精细描述，揭示出A家族GPCR存在共同的激活 机制。文章简要回顾GPCR激活机制研究的方法和创新点，并对A家族GPCR共同激活机制如何推动功能研究和药物研发进行展望。     

Ultra-fine grinding and mechanical activation of mine waste rock using a high-speed stirred mill for mineral carbonation

CO2 sequestration by mineral carbonation can permanently store CO2 and mitigate climate change. However, the cost and reaction rate of mineral carbonation must be balanced to be viable for industrial applications. In this study, it was attempted to reduce the carbonation costs by using mine waste rock as a feed stock and to enhance the reaction rate using wet mechanical activation as a pre-treatment method. Slurry rheological properties, particle size distribution, specific surface area, crystallinity, and CO2 sequestration reaction efficiency of the initial and mechanically activated mine waste rock and olivine were characterized. The results show that serpentine acts as a catalyst, in-creasing the slurry yield stress, assisting new surface formation, and hindering the size reduction and structure amorphization. Mechanically activated mine waste rock exhibits a higher carbonation conversion than olivine with equal specific milling energy input. The use of a high-speed stirred mill may render the mineral carbonation suitable for mining industrial practice.     

高静态动作压力下粉尘爆炸泄放标准的可靠性

粉尘爆炸泄放设计标准的可靠性对能否实现爆炸防护尤为关键.以中径70μm石松子粉尘为介质,采用20 L球形粉尘爆炸装置进行了4种泄放口径、静态动作压力在0.12~0.6 MPa的爆炸泄放实验,对比了实验值与NFPA 68和EN 14491计算值.结果表明,NFPA 68在预测高静态动作压力下的泄放面积时,随着泄放口径的增大,预测结果由保守变为危险,但预测结果精度较好且数值稳定;EN 14491在预测高静态动作压力下的泄放面积时非常保守,预测精度较差,数据不可靠.依据两种标准推荐的经验函数关系,分析了NFPA 68和EN 14491在预测高静态动作压力时产生这种差异的原因.     

关于两种活化熵△≠rS(θ)m(c(θ))和△≠rS(θ)m(P(θ))的讨论

用热力学方法处理过渡状态理论的艾林方程,选择两种不同参考点作为标准态,得出两个不同的计算公式,两种类型的活化自由能、活化焓、活化熵意义数值不同,对于理想气体的反应,两种类型的活化焓相等,活化熵不等,但两种活化熵之间存在定量关系式:△≠rSθm(Pθ)=△≠rSθm(cθ) (n-1)Rln[Pθ/RTcθ].     

油田注水诱发应力场演化及地层活动机制研究

基于多孔介质理论建立注水诱发应力场变化定量评价的力学模型,利用有限元方法对耦合模型进行求解,分析注水过程中超孔隙压力与应力场演化规律,揭示注水诱发地层活动的力学机制。计算结果表明:注水形成的超孔隙压力控制局部应力场分布,一方面导致垂向、水平有效应力减小,Mohr应力圆左移,地层活动趋势增加;另一方面削弱注水层段水平地应力的作用效果,导致主应力差值减小、Mohr应力圆直径缩小,易于地层稳定。注水诱发地层活动与岩层渗透性能、吸水软化与构造应力环境等组合因素密切相关。     

2-羟基喹啉合成新方法研究

本研究利用简单的乙酰苯胺和丙烯酸酯作为起始原料,在过硫酸钾做氧化剂,水合对甲苯磺酸做添加剂的条件下,通过钯催化的C-H键活化/C-C键生成/环化串联反应以46%~95%收率合成了一系列2-羟基喹啉衍生物.本研究为2-羟基喹啉衍生物的合成提供了实用的合成方法.     

生物质棉纤维再生纤维素膜的制备与性能分析

以天然生物质棉纤维为原料,采用氯化锂/N,N-二甲基乙酰胺(Li Cl/DMAC)溶解体系对其进行活化处理,配置不同质量分数的纤维素有机溶液系列,在不同凝固浴条件下,采用KW-4A匀胶机高速旋涂成膜和AFA-Ⅱ自动涂膜器低速平推成膜2种工艺,制备再生纤维素薄膜系列。通过运用扫描电镜(SEM)、傅里叶变换红外光谱(FT-IR)、X射线衍射仪(XRD)和表面接触角测试仪等分析设备对再生纤维素膜的大分子结构、力学性能、结晶度、热稳定性和表面浸润性进行各项性能的系列化表征,研究纤维素质量分数、凝固浴种类、制膜工艺对膜性能的影响。实验结果表明:采用KW-4A匀胶机高速成膜工艺、凝固浴为水浴、纤维素质量分数为3.5%时,制备的再生纤维素膜的各项性能最佳;与天然生物质棉纤维相比,再生纤维素膜结晶度变化很大,热稳定性与棉纤维变化趋势一致但有一定程度下降,表面浸润性良好。     

氯化钙水型油藏内源微生物激活剂研究

应用最大可能数法(MPN)和高通量测序分析新疆油田氯化钙水型油藏产出液中微生物群落结构。应用离子色谱分析了油藏地层水的离子组成,确定了激活内源微生物的基础及目标。确立以原油乳化效果、激活后烃氧化菌浓度为筛选激活剂的主要指标,进行了内源微生物激活剂的筛选。在单因素实验筛选最佳碳源、氮源和磷源后,采用均匀设计优化了激活剂组分含量,并进行了激活效果评价实验。实验结果表明:优化的激活剂激活地层水中内源微生物后,原油乳化效果明显,提高功能菌群烃氧化菌等菌浓5~6数量级,而硫酸盐还原菌被明显抑制;同时微生物群落结构发生明显改变,细菌生物多样性有所降低,实现了对Pseudomonas、Bacillus、Stenotrophomonas、Pusillimonas和Acinetobacter等常见采油功能菌的高效激活。     

赞比亚卢安西亚矿区复杂铜矿孔雀石的机械活化及浸出研究

Mechanical activation(MA) of malachite was carried out by dry planetary grinding(DPG) and wet Isa grinding(WIG) methods. When the rotational speed was increased to 400 r/min in DPG, the specific surface area of malachite reached the maximum and the particle size reached the minimum of 0.7–100 μm. Agglomeration occurred between mineral particles when the rotational speed was increased to 580 r/min in DPG.However, no agglomeration was observed among particles with sizes 0.4–3 μm in WIG. X-ray diffraction analysis showed that, at a 580 r/min rotational speed in DPG, the amorphization degree of malachite was 53.12%, whereas that in WIG was 71.40%, indicating that MA led to amorphization and distortion of crystal structures. In addition, in the Fourier transform infrared(FT-IR) spectra of activated malachite, the bands associated with –OH, CO_3^2-and metal lattice vibrations of Cu–O and Cu–OH were weakened, and a new H–O–H bending mode and peaks of gaseous CO_2 appeared, indicating that MA decreased the band energy, enhanced dihydroxylation, and increased the chemical reactivity of the malachite.Furthermore, the leaching behavior of copper ore was greatly improved by MA.