Safety assessment of the film boiling chemical vapor infiltration (FB-CVI) process through a system-theoretic accident model and process (STAMP)

Film boiling chemical vapor infiltration (FB-CVI) is considered as one of the fastest process methodologies for manufacturing carbon-carbon (C–C) composite products and possesses various advantages compared to conventional methodologies. However, there are safety concerns associated with this process for large-scale manufacturing, mainly owing to the intrinsic nature of the precursor and the process conditions. Considering the multifunctional interactions of the various systems during the process, a system-theoretic process analysis (STPA)/system theoretic accident model and process (STAMP) model is used to perform a safety analysis of the hazardous states of the FB-CVI process at the system level. As a case study, the FB-CVI process equipment employed for the manufacturing of C–C composites is considered. The safety constraints present in the system are assessed for adequacy through a hazard analysis by STPA/STAMP. The analysis through STPA/STAMP demonstrated the capability to create proactive strategies for the design and realization of process equipment that can be employed to manufacture C–C composite products through the FB-CVI process.     

Review: recent advances in biogas purifying technologies

Biomethane production through biogas upgrading is a promising renewable energy for some industries which could be part of the equilibrium needed with fossil fuels consumption to achieve a sustainable society. This paper presents a comprehensive list of biogas upgrading technologies focused on carbon dioxide removal as well as recent advances reported by researcher with wide expertise in this topic. Additionally, an extensive costs–performance comparison among the technologies studied is discussed. Among the different alternatives, chemical scrubbing stood out to achieve high biomethane purities while cryogenic technologies proved to be effective against methane losses. Regarding the different costs, water scrubbing and membrane separation seem to be the most affordable techniques.     

Exoautometabolic regulation of transgenes in microorganisms

Data on the existence of a specific system regulating the growth, size, and structure of enterobacterial populations are first summarized in terms of the chemical ecology concept formulated by S.S. Shvarts. The role of this system in transgene functioning is described using the example of the lux operon integrated into Escherichia coli. A relatively simple test for estimating such interactions is proposed.Translated from Ekologiya, No. 2, 2005, pp. 91–96.Original Russian Text Copyright © 2005 by Pshenichnov, Maslennikova, Nikitina.     

Is the alkaloid in 2spot ladybirds (Adalia bipunctata) a defence against ant predation?

Garden black ants,Lasius niger L., in a laboratory colony, attacked three species of live ladybirds found near their nest, killing the smaller two species. A second colony was offered artificial diets containing crushed ladybirds of two species, and the ants' choice of feeding site noted. Both the diets were aversive compared to control, but that containing 7spot,Coccinella septempunctata L., was more aversive than the diet containing 2spot,Adalia bipunctata L. The implications of this lesser protection for 2spots in terms of the chemical defence of the species are discussed.     

基于不同废污泥源的短程反硝化快速启动及稳定性

为探究不同废污泥源快速启动短程反硝化和实现稳定NO_2~--N积累的可行性,在3个完全相同的SBR反应器(S1、S2和S3)分别接种:实验室城市污水反硝化除磷系统排泥、城市污水厂剩余污泥及河涌底泥,比较其短程反硝化启动快慢和NO_2~--N积累特性,考察系统短程反硝化活性和NO_3~--N→NO_2~--N转化性能,并从微生物学角度分析反应器功能菌群特征.结果表明,在乙酸钠为唯一碳源、高碱度和适宜COD/NO_3~--N比进水条件下,3个SBR短程反硝化反应器在短时间内均能够成功启动,系统平均NO_3~--N→NO_2~--N转化率为S1 S2 S3(75. 92% 73. 36% 69. 90%).同时发现持续低温条件下S1和S2呈现不同程度的短程反硝化性能恶化趋势,但S3能够稳定维持良好NO_2~--N积累性能.微生物高通量测序表明,变形菌门和拟杆菌门居PD系统主导地位,3个短程反硝化反应器NO_2~--N积累关键功能菌属Thauera属丰度差异明显:S3 S1 S2(25. 09% 4. 71% 3. 60%),表明S3具备稳定高效的NO_2~--N积累性能,同时高丰度Thauera属可能是维持低温短程反硝化活性的重要原因.     

MnO2/Al2O3催化剂-微气泡臭氧体系催化降解喹啉及其机理

制备了纳米MnO₂,并以Al₂O₃为载体制备了掺杂型MnO₂/Al₂O₃颗粒催化剂.催化剂焙烧温度和时间分别为500℃和4 h、MnO₂质量分数为8%时,催化剂具有最高的臭氧催化氧化活性.SEM分析表明,纳米MnO₂均匀分布于Al₂O₃载体表面.MnO₂/Al₂O₃催化剂的比表面积（BET）为183.22 m²·g^-1,平均孔容为0.27 cm³·g^-1,平均孔径为4.87 nm.建立了MnO₂/Al₂O₃催化剂-微气泡臭氧催化反应体系,研究了该体系对喹啉的降解去除效果及其机理.臭氧微气泡的平均粒径为61.7 μm.微气泡臭氧投量为30 mg·L^-1时,反应60 min后喹啉去除率能达到95%以上;反应20 min后,MnO₂/Al₂O₃催化剂-微气泡臭氧体系对实际煤化工废水二级出水的TOC去除率可达到55%以上.以叔丁醇作为分子探针,证明了羟基自由基（·OH）氧化作用在臭氧微气泡催化氧化体系中对喹啉的降解起到主导作用.     

亚氧化钛膜电极电化学特性及其处理印染工业废水的效能研究

电化学氧化法具有稳定高效、操作灵活、集成度高等特点,在处理难降解有机废水领域具有独特优势.电化学废水处理过程通常受限于传质速率,而膜电极有望解决这一瓶颈问题.亚氧化钛膜电极（TiSO-ME）的化学结构与电化学性质结果显示,经过高温还原法制备的TiSO-ME电极主要由Ti₄O₇和少量Ti₅O₉组成,大孔体积占总孔体积的92.7%,平均孔径为0.508 μm.电化学测试结果表明,TiSO-ME具有良好的导电性、高析氧电位和电化学稳定性.过滤试验结果表明,在0.82×10^-3~3.14×10^-3 mL·cm^-2·s^-1范围内膜通量与传质系数成正比.在电流密度为8 mA·cm^-2,膜通量为2.31×10^-3 mL·cm^-2·s^-1的条件下,电解1.5 h即可有效处理实际印染工业废水,sCOD去除率高达96.07%,电流效率可达24.22%,电能消耗较不存在膜通量时降低了32.99%.TiSO-ME能够实现废水在膜孔结构内部的穿流式操作,有效克服旁流式操作传质受限的问题,在小规模分散式工业废水处理中有着重要的研究价值和发展潜力.     

北京地区基于化学组分的夏季气溶胶吸湿特性

利用吸湿增长光散射测量系统、黑碳仪和气相色谱质谱联用仪等仪器,于2019年7月15日~8月4日在北京地区开展了为期21d的大气气溶胶观测实验.观测期间北京市区于7月27日出现短暂的轻度污染,并在7月29日出现强降水天气.结果显示：北京市区夏季大气污染变化剧烈且短暂,大气气溶胶散射吸湿增长因子f（RH）呈现平滑连续的特点,并且降水会对f（RH）造成显著影响.7月27日PM_2.5的平均质量浓度为（92.54±47.05）μg/m³;,表现出较为剧烈的污染变化.7月28~30日平均散射吸湿增长因子f（80%±1%）分别为（1.50±0.35）,（1.43±0.36）和（1.48±0.25）,反映了降水对于大气气溶胶的湿清除作用.最后利用实验数据估算粒径吸湿增长因子gf（RH）,并建模研究f（RH）和gf（RH）的关系,模型精度R²最高可达0.698.     

电场与MnxCey催化剂在苯氧化反应中的协同效应及机理探究

挥发性有机物（VOCs）大量排放已成为日益严重的环境问题,为了实现VOCs的高效去除,本文采用自蔓延燃烧合成法制备了一系列锰铈复合氧化物催化剂,将稳恒直流电场引入典型VOCs气体苯的催化氧化过程,并基于不同电场条件下催化剂的理化性质表征结果进行机理分析.实验结果表明,Mn_xCe_y催化剂对含苯废气的去除有良好的效果,稳恒直流电场显著促进了催化剂的活性,其中Mn₁Ce₃的催化性能最佳,电流为5 mA时,Mn₁Ce₃催化剂在155℃可达到50%的苯转化率,在202.4℃可达到90%的苯转化率,对应的转化温度T₅₀和T₉₀比传统方法分别降低了62.4℃和48.3℃,且电场中的反应活化能由52.32 kJ·mol^-1降低至32.31 kJ·mol^-1.根据实验现象及表征结果,发现协同效应与活性位点的快速持续再生及活性氧物种的转化有关,由此提出苯在Mn_xCe_y催化剂上的氧化机理及电场协同催化的反应模型.