EQCM and in-situ reflectance FTIR spectroscopic studies of adsorption and oxidation of methanol on Pt electrode in alkaline media

The adsorption and oxidation of methanol on Pt electrode in alkaline media have been investigated by using cyclic voltammetry, electrochemical quartz crystal microbalance (EQCM) and in-situ reflectance FTIR spectroscopy. The experimental results demonstrated that the electrooxidation of CH3OH was closely relative to solution acidity. Only one current peak of methanol oxidation in PGPS was detected at -0.09 V, which illustrated the disappearance of the second current peak due to Pt electrode passivation in alkaline media. The magnitude of the dissociative adsorbate of methanol in alkaline media is smaller than that in acidic media. The main product, such as CO2 and CO32-, was detected clearly and the reactive intermediates that were determined by FTIRS under experimental condition might be mainly HCOO- species. The EQCM studies provide quantitative results of surface mass changes during methanol oxidation, and have thrown new light in the elucidating methanol oxidation

碱性介质中甲醇在铂电极表面吸附和氧化的电化学原位FTIR反射光谱和EQCM研究

运用电化学循环伏安、原位FTIR反射光谱和石英晶体微天平(EQCM)等方法研究了碱性介质中甲醇在Pt电极表面吸附和氧化行为.结果表明:甲醇电氧化与溶液酸碱性有密切的关系.酸性介质中甲醇在Pt电极上的CV曲线有两个正向氧化峰,而碱性介质中只有一个正向氧化峰,第二个氧化峰的消失可能是由于碱性介质中Pt电极在高电位下形成高氧化态的氧物种毒化其表面引起的.碱性介质中甲醇解离吸附产物的数量比酸性介质的明显减少,对甲醇氧化的第一个氧化峰表现出更高的电催化活性.目前实验条件下,原位FTIR反射光谱检测到:碱性介质中甲醇电氧化的最终产物是CO_2和CO_3~(2-),反应中间体主要为HCOO~-物种.从电极表面质量定量变化的角度提供了甲醇反应机理的新数据

碱性介质中正丁醇在铂电极上吸附和氧化的电化学原位FTIR反射光谱和EQCM研究

运用电化学循环伏安(CV)、原位FTIR反射光谱和电化学石英晶体微天平(EQCM)等方法研究了碱性介质中正丁醇在Pt电极表面吸附和氧化行为。结果表明:正丁醇电氧化过程与溶液酸碱性有着密切的关系。酸性介质中正丁醇在Pt电极上的CV曲线有2个正向氧化峰,而碱性介质中只有1个正向氧化峰,第2个氧化峰的消失可能是由于碱性介质中Pt电极表面钝化引起的。原位FTIR反射光谱检测到,在实验条件下,碱性介质中正丁醇电氧化过程的最终产物只有丁酸根。EQCM研究还从电极表面质量定量变化的角度提供了正丁醇反应机理的新数据

The adsorption and oxidation of isopropanol at platinum electrode in alkaline media

The adsorption and oxidation of isopropanol in alkaline media at platinum electrode have been investigated by using electrochemical quartz crystal microbalance (EQCM) and in situ FTIR spectroscopy. The results show that there is no self-poisoning in the electrooxidation of isopropanol in alkaline media. Though no poison species, such as CO, are evidenced by in situ FTIR spectroscopy, the adsorption of isopropanol or its dissociative products on Pt surface is suggested by EQCM data. The final product of isopropanol oxidation is only acetone under experimental condition, which suggests that the oxidation of isopropanol into acetone takes place via dehydrogenation step. The EQCM studies provide quantitative results of surface mass variation and have thrown new light in the elucidating isopropanol oxidation

浦城县大口窑调查勘探报告

浦城县大口窑是宋元时期闽北地区一处著名的窑场,以烧造青白瓷为主,此外还兼烧部分酱釉瓷、少量绿釉瓷等。器型种类丰富,质量较高,窑业技术与江西景德镇窑关系密切。其产品在东亚、东南亚等地有发现,是福建一处重要的外销瓷生产地

弹道靶上的跨音速实验

本文介绍用弹道靶作跨音速试验的新方法,在二级轻气炮上采用了二个特殊的新技术:充气放炮能发射模型达到亚音速,低充填条件能发射模型达到跨、超音速。由于初始加速度较小,发射的模型外形完整,姿态稳定;加上没有支撑干扰和小洞壁效应的优点,使弹道靶设备在跨音速实验方面有特殊的优越性,用上述技术得到了圆球跨音速流场的清晰照片,其中击波脱体距离、分离点位置、颈部宽度、尾迹形状与超音速、高超音速流动比较有明显变化。文中M≈1.010和M≈0.99的二张全流场照片是十分有意义的。最后提出一个想法,用靶场加压、降温的方法可以提高雷诺数直到10~7以上

Preliminary study on PAH degradation by bacteria from contami-nated sediments in Xiamen Western Sea, Fujian, China

In order to estimate the biodegradation of three polycyclic aromatic hydrocarbons (PAHs) compounds, bacterial strains were isolated from marine sediments in three heavily contaminated sites (Yuandang Lake, Dongdu Port and Aquacultural zones in Maluan Bay) in Xiamen Western Sea. The results show three bacterial strains, which used pyrene as the sole carbon source, were identified as strains of Aureobacterium sp., Arthrobacter sp., Rhodococcus sp. The PAH-degrading bacteria isolated had a strong ability to degrade phenan-hrene, fluoranthene and pyrene at different degradation rates. The highest degradation rate was observed when three PAH compounds were mixed with an individual strain in the medium. The three PAHs were degraded after one week with a degradation rate of 89.94 % for phenanthrene and 93.4 % for both of fluoranthene and pyrene. In addition, after 25 days of incubation, the degradation rate was 99.98 % for phenanthrene and 99.97 % for both of fluoranthene and pyrene. Optical density was measured to ..

Immobilization of β-D-galactosidase onto Nanofibers and Its Application

b-D-半乳糖苷酶可以催化乳糖和脂肪醇之间的转糖苷化反应合成重要的表面活性剂烷基糖苷。由于该反应通常为油水两相体系，水相中的酶分子与疏水底物不能有效接触、界面处酶分子遇有机溶剂易失活等问题限制了其工业化生产。针对该问题，本论文将b-D半乳糖苷酶固定化在苯乙烯马来酸酐共聚物（PSMA）纳米纤维膜上，并考察了纳米纤维酶膜用于催化乳糖水解以及烷基糖苷合成反应中的应用。具体研究包括如下三部分内容：（1）通过静电纺丝法制备了PSMA纳米纤维，优化PSMA电纺液浓度、电纺液流速、电场距离和外加电压等参数，结果表明以上各因素对纳米纤维形态均有显著影响。当电纺液浓度为35%（w/v）、流速为250 mL/h、距离为25 cm时，采用21 kV电压进行电纺即可得到直径在300 nm左右且分布均匀的纳米纤维；（2）以PSMA纳米纤维为载体进行固定化b-D-半乳糖苷酶的研究，经优化确定最佳固定化酶条件为pH 4.0（0.2 M醋酸-醋酸钠缓冲液）、固定化温度为15 oC、酶浓度为1 mg/mL。固定化4 h后固定化酶量可达到16.5±1.3 mg/g 膜，固定化酶催化2-硝基苯酚-b-D-半乳吡喃糖苷（ONPG）水解反应的米氏常数Km值为2.7 mM，略大于游离酶的Km值（2.2 mM）；固定化酶的Vmax为97.2 mmol/(min·mg)，为游离酶的47.8%。固定化酶在37 oC重复使用21次后活性损失仅为15%。在连续搅拌式反应器中将固定化酶用于催化乳糖的水解反应，连续使用18天仍能稳定运行；（3）利用固定化在纳米纤维上的b-D-半乳糖苷酶在己醇/水两相体系中催化己醇和乳糖之间的转糖苷化反应制备己基半乳糖苷。研究表明剧烈搅拌和高温对固定化酶的活性影响较大，在50 oC、强搅拌的条件下反应，固定化酶使用两次后仅剩余0.83%的活力。将反应温度降至37 oC，辅以温和振荡反应条件时，固定化酶的重复使用性能得到较大提升，重复使用6次仍剩余44.2%的活力。使用聚丙烯夹套可以实现负载有b-D-半乳糖苷酶的PSMA纳米纤维酶膜均匀分布于油水两相界面上，从而显著降低了乳糖水解这一副反应的发生

齿轮无摩擦接触的等几何分析研究

使用等几何分析法进行平面无摩擦接触分析,采用罚函数法将接触约束条件引入系统势能函数,采用多片NURBS曲面片缝合的方式进行渐开线齿轮建模和接触分析,将计算结果与有限元解进行了对比,结果表明等几何分析法在分析接触问题时具有计算精度高、应力场更加光滑等优势,为解决接触问题提供了一种有效的方法

Effect of Scout Bees on the Performance of Artificial Bee Colony Algorithm

人工蜂群算法(artificial bee colony algorithm,ABC)是一种模仿蜜蜂采蜜行为的新兴的群智能优化技术。侦察蜂作为人工蜂群的成员之一,进行随机搜索以找到蜜源。为了弄清楚侦察蜂在ABC中的作用,本文首先分析ABC的生物学机理和主要处理步骤,然后研究当问题维数、种群规模、limit值和最大循环次数等4个控制参数取不同值时对无侦察蜂ABC、单侦察蜂ABC与多侦察蜂ABC性能的影响。实验结果表明,在绝大多数情况下,多侦察蜂ABC求解5个著名的基准函数获得的解优于单侦察蜂ABC和无侦察蜂ABC,而单侦察蜂ABC获得的解优于无侦察蜂ABC。此外,由于这3种算法的搜索复杂度是同阶的,在相同条件下其运行时间相差不大,这充分说明了侦察蜂实施随机勘探过程确实对ABC的性能具有积极意义。Artificial Bee Colony （ABC） algorithm is a new swarm intelligence technique inspired by the foraging behavior of a honeybee swarm. As the member of the artificial bee colony,scout bees carry out random search for discovering food sources. Irt order to investigate the effect of scout bees ort the perfor-mance of ABC,the biological mechanism and main steps of ABC were analyzed,and then,different prob-lem dimensions, population sizes, limit values and maximum cycle numbers were tested on the perfor-mance of ABC under the conditions of no scout bee,single scout bee and multi-scout bees conditions. Al-most all the experimental results show that ABC with multi-scout bees outperforms ABC with single scout bee and ABC without scout bee on five well-known benchmark functions,meanwhile,ABC with single scout bee performs better than ABC without scout bee. Besides,the three algorithms have almost the same execution time under the same conditions due to the same order of their search complexity. These fully demonstrate that the random exploration process adopted by scout bees has positive effect on the performance of ABC.国家自然科学基金资助项目(70971020);广西混杂计算与集成电路设计分析重点实验室开放基金资助项目(2012HCI09);广西民族大学重点科研资助项目(2012MDZD035