Visualization of the Malleability of the Rubber Core of Rubber Particles from Parthenium argentatum Gray and Other Rubber-Producing Species Under Extremely Cold Temperatures

Rubber particles from Parthenium argentatum Gray (guayule) were frozen in liquid nitrogen (–196°C), fractured, and visualized using cryo-scanning electron microscopy. We observed that the rubber polymer core of the rubber particles was still malleable at this extremely cold temperature, and the core stretched substantially during separation of the fracture planes. This malleability was observed in situ in tissue sections, as well as in purified rubber particles, and was found to be independent of purification procedure, guayule line, tissue age, or season. The malleability or stretching phenomenon suggests that P. argentatum rubber has some unique properties because rubber particles from Hevea brasiliensis Müll. Arg. and Ficus elastica Roxb. were brittle at this temperature, fractured cleanly, or showed only tiny threads of material pulling out of the core.     

非光合CO2同化微生物菌群的选育/优化及其群落结构分析

通过从海水及其沉积物中分离、筛选,并结合电子供体和无机碳源结构的优化以期获得不用光照与供氢的高效固碳微生物菌群;通过16S rDNA序列分析、比对等手段研究非光合固碳微生物菌群的结构,以期为优化群落配置,进一步提升固碳效率提供理论依据.结果显示,通过分离和长期驯化可从海洋中得到在普通好氧、厌氧条件下具有固碳能力的非光合微生物菌群.添加硫代硫酸钠、硫化钠和氢气作为电子供体可有效提升菌群的固碳效率,在以硫代硫酸钠为电子供体的好氧、厌氧条件下,该菌群的CO2同化效率分别可达10.44 mg/L和12.56 mg/L.该固碳菌群对混合无机碳源的同化效率显著高于单一碳源,在以CO2、碳酸氢钠及碳酸钠为混合碳源情况下,菌群好氧、厌氧固碳效率(以CO2计)分别可达110 mg.(L.d)-1,和72mg.(L.d)-1,接近氢氧化细菌的水平.微生物群落结构分析结果表明,添加不同电子供体后,固碳微生物菌群的优势种发生了显著变化,在发现的16个优势菌种中,11个是不可培养微生物,即其只能以共生方式存在.菌群混合培养时的固碳效率可能是多种菌共同作用的结果,因此优化固碳微生物菌群的结构和配比将有利于其固碳效率的进一步提升.     

供水管网不同管材内壁微生物分布的显微观察

采用扫描电镜、原子力显微镜以及激光共聚焦显微镜对不锈钢插片表面和供水管网末端PPR管内壁微生物的分布和生物膜结构进行了观察和分析.结果表明,在供水管网中,不锈钢材质表面不利于微生物附着生长,在短时间内(3个月)只有很少的微生物附着.在管网末端PPR管表面有明显的微生物附着生长,细菌容易附着在基底表面的凹穴中,细菌与基底是紧密黏附在一起的.扫描电镜和原子力显微镜结合是观察管壁非连续生长生物膜表面结构的有效手段.采用激光扫描共聚焦显微镜可同时实现管壁生物膜内部和三维结构观察.     

Fe(Ⅲ)-EDTA作为阴极电子穿梭体的微生物燃料电池持续产电机制

阴极氧还原反应（ORR）是影响微生物燃料电池（microbial fuel cell,MFC）性能的重要因素.采用双室MFC以Fe(Ⅲ)-EDTA为阴极液进行持续产电试验.结果表明,添加Fe(Ⅲ)-EDTA作为阴极液可显著加速氧还原反应速率,降低内阻,提高输出电压与功率.当阴极液中存在20.0 mmol/L的Fe(Ⅲ)-EDTA时,电池内阻仅为300　Ω,比对照降低了900　Ω,其输出电压（1 000　Ω下）与功率密度可维持在200.1 mV、 16.0 mW/m²左右,比不加的对照分别提高73.2%、 70.1%. Fe(Ⅲ)-EDTA氧化再生与持续产电试验表明,Fe(Ⅲ)-EDTA可通过曝气氧化再生、循环利用,即Fe(Ⅲ)-EDTA可作为阴极电子穿梭体加速电子至氧气的传递.Fe(Ⅲ)-EDTA首先接受阴极电子被还原成Fe(Ⅱ)-EDTA,在阴极室充分曝气条件下,Fe(Ⅱ)-EDTA将电子传递给O₂同时被氧化再生成Fe(Ⅲ)-EDTA,从而完成电子从电极传递到氧气的穿梭过程,MFC得以长期稳定运行.进一步优化试验显示,Fe(Ⅲ)-EDTA作为阴极电子穿梭体强化MFC产电的适宜条件为：浓度20.0 mmol/L、pH=5.0左右.在此条件下MFC的最大功率密度达100.9 mW/m².     

Morphology of single inhalable particle inside public transit biodiesel fueled bus

In an urban-transit bus,fueled by biodiesel in Toledo,Ohio,single inhalable particle samples in October 2008 were collected and detected by scanning electron microscopy and energy dispersive X-ray spectrometry(SEM/EDS).Particle size analysis found bimodal distribution at 0.2 and 0.5 μm.The particle morphology was characterized by 14 different shape clusters:square,pentagon,hexagon,heptagon,octagon,nonagon,decagon,agglomerate,sphere,triangle,oblong,strip,line or stick,and unknown,by quantitative order.The square particles were common in the samples.Round and triangle particles are more,and pentagon,hexagon,heptagon,octagon,nonagon,decagon,strip,line or sticks are less.Agglomerate particles were found in abundance.The surface of most particles was coarse with a fractal edge that can provide a suitable chemical reaction bed in the polluted atmospheric environment.The three sorts of surface patterns of squares were smooth,semi-smooth,and coarse.The three sorts of square surface patterns represented the morphological characteristics of single inhalable particles in the air inside the bus in Toledo.The size and shape distribution results were compared to those obtained for a bus using ultra low sulfur diesel.     

郑州大气PM10的形貌特征及生物活性研究

采集郑州市区和郊区秋季大气PM₁₀样品,利用场发射扫描电镜（FESEM）和图像分析技术对PM₁₀颗粒进行形貌特征和粒度分布进行分析,同时应用质粒DNA评价法研究了市区和郊区PM₁₀样品的生物活性.结果显示,在市区采集的样品中燃煤飞灰占有相当大的数量,而在郊区采集的样品中矿物质占有较大的数量,粒径分析表明,市区PM₁₀的数量-等效球直径分布较为集中,主要分布在0.1～0.4 μm范围内,郊区则相对比较分散;PM₁₀的体积-等效球直径主要分布在>1 μm范围内.结果表明,在郑州市秋季大气PM₁₀中,数量上细粒子占优势, 而在体积上(质量上)较粗颗粒占优势.质粒DNA评价结果表明,郑州市区和郊区PM₁₀颗粒对DNA的损伤程度不同,市区样品的生物活性大于郊区样品.     

Biochemical and histopathological ultrastructural changes caused by ZnO nanoparticles in mice

Five week-old mice were divided into a vehicle control group, and groups exposed to ZnO nanoparticles at low (0.5 g/kg), middle (1 g/kg), high (3 g/kg), and exceptionally high-dose (5 g/kg). After the first, second, third, and fourth weeks’ of exposure, blood biochemistry, histopathology, and electron microscopic ultrastructural changes in liver, kidney and spleen were investigated. Increased alkaline phosphatase activities were observed in all treated mice being statistically significant at higher dose. No changes were observed in the serum glutamic pyruvic transaminase, serum glutamic oxaloacetic transaminase, creatinine, blood urea nitrogen, and lipid levels. During the first and second weeks of the treatment, effects on the cytoarchitecture of liver, kidney, and spleen were not perceived while during the third and fouth weeks of treatment sporadic mild effects were seen. Ultrastructural electron microscopic changes in liver, kidney, and spleen were not observed for the low-dose group on the first, second, third, and fourth weeks, suggesting that exposure to ZnO nanoparticles at low dose is safe. Long-term (i.e., more than 28 days) exposure to the exceptionally high-dose resulted in sporadic changes in nuclear chromatin condensation, irregular nuclear membrane, polymorphic mitochondria, mitochondrial swelling, and vacuolation. ZnO nanoparticles could be well tolerated and no death occurred in any group of treated mice.     

元宵节期间北京PM_(2.5)单颗粒的物理化学特征

采集2014年元宵节期间北京PM2.5样品,使用场发射扫锚电镜-能谱仪观察北京PM2.5单颗粒的显微形貌和元素组成,并利用图像分析系统对PM2.5的粒径进行分析.结果表明:PM2.5的单颗粒类型以烟尘集合体、矿物颗粒和飞灰为主;烟花爆竹燃放产生的PM2.5是造成元宵节期间北京PM2.5浓度升高的主要原因;PM2.5中总颗粒物个数呈现先升高后降低的趋势;元宵节期间北京PM2.5中大部分颗粒物的粒径小于0.7μm;然而,重污染天气PM2.5中粒径大于0.7μm颗粒物的数量明显高于轻污染天气.     

反硝化耐冷菌Acinetobacter johnonii DBP-3的低温除磷特性

通过批实验技术研究了不同条件下一株反硝化耐冷菌Acinetobacter johnonii DBP-3(Genbank登录号JN314436,保藏号CGMCC4753)的低温除磷特性.结果表明,菌株可分别利用氧气(O2)、硝酸根(NO3-)和亚硝酸根(NO2-)为电子受体吸收溶液中的磷酸盐,不同电子受体条件下吸磷效能的大小顺序为:氧气>硝酸根>亚硝酸根.NO3-的浓度为0～150mg·L-1时,菌株对磷酸盐的吸收能力随着NO3-浓度的增加而增加.亚硝酸盐浓度为0～20mg·L-1时菌株对磷酸盐的吸收能力随NO2-浓度的增加而明显增加;浓度为20～60mg·L-1时,菌株对磷酸盐的吸收能力受NO2-浓度的影响较小;浓度达80mg·L-1时,菌株的除磷能力明显下降.不同碳源条件下厌氧培养的菌体细胞在缺氧条件下培养时对磷酸盐的去除能力大小顺序为:乙酸钠>柠檬酸钠>葡萄糖.菌株除磷的适宜pH值范围为7～9.温度为5℃时,菌株仍保持一定的除磷能力,随着温度的升高除磷能力逐渐增加,当温度达35℃时,除磷能力开始下降.菌株对盐度的耐受性在好氧培养时大于缺氧培养.缺氧培养48h,菌体细胞中磷的平均含量可达5.7%,而厌氧培养的菌体细胞中磷的最低含量为2.6%,表现出了明显的聚磷和释磷特性.研究结果可为低温富营养化水体或富氮磷污水的生物处理提供理论依据.     

Photocatalytic degradation of perfluorooctanoic acid with β-Ga2O3 in anoxic aqueous solution

Perfluorooctanoic acid (PFOA) is a new-found hazardous persistent organic pollutant, and it is resistant to decomposition by hydroxyl radical (HO·) due to its stable chemical structure and the high electronegativity of fluorine. Photocatalytic reduction of PFOA with β-Ga₂O₃ in anoxic aqueous solution was investigated for the first time, and the results showed that the photoinduced electron (e_cb^-) coming from the β-Ga₂O₃ conduction band was the major degradation substance for PFOA, and shorter-chain perfluorinated carboxylic acids (PFCAs, C_nF_2n+1COOH, 1 ≤ n ≤ 6) were the dominant products. Furthermore, the concentration of F^- was measured by the IC technique and defluorination efficiency was calculated. After 3 hr, the photocatalytic degradation efficiency was 98.8% and defluorination efficiency was 31.6% in the presence of thiosulfate and bubbling N₂. The degradation reaction followed first-order kinetics (k = 0.0239 min^-1, t_1/2 = 0.48 hr). PFCAs (C_nF_2n+1COOH, 1 ≤ n ≤ 7) were detected and measured by LC-MS and LC-MS/MS methods. It was deduced that the probable photocatalytic degradation mechanism involves e_cb^- attacking the carboxyl of C_nF_2n+1COOH, resulting in decarboxylation and the generation of C_nF_2n+1·. The produced C_nF_2n+1· reacted with H2O, forming C_nF_2n+1OH, then C_nF_2n+1OH underwent HF loss and hydrolysis to form C_nF_2n+1COOH.