The Synergistic Photocatalytic Effect of H3PW12O40 and Pt Nanoparticles Comodified UiO-66-NH2 on the Reduction of Aqueous Cr(VI) under Original pH

Kinetics and Catalysis - A ternary synergistic photocatalyst H3PW12O40/Pt/UiO-66-NH2 was successfully fabricated for the first time through a simple solvothermal synthetic strategy. We found that...     

Polyvinylpyrrolidone and graphene-modified hematite nanoparticles for efficient electrocatalytic oxidation of p-nitrophenol

Journal of Solid State Electrochemistry - Polyvinylpyrrolidone (PVP) and graphene (G)-modified iron oxides (Fe2O3-PVP-G) are prepared by a simple hydrothermal reaction. Their morphology and...     

Mass and isotopic concentrations of water-insoluble refractory carbon in total suspended particulates at Mt.Waliguan Observatory(China)

Mass concentration and isotopic values δ¹³C and ¹⁴C are presented for the water-insoluble refractory carbon（WIRC） component of total suspended particulates（TSP）,collected weekly during 2003,as well as from October 2005 to May 2006 at the WMO-GAW Mt.Waliguan（WLG） site.The overall average WIRC mass concentration was（1183±120）ng/m³（n = 79）,while seasonal averages were 2081 ±1707（spring）,454±205（summer）,650±411（autumn）,and 1019±703（winter） ng/m3.Seasonal variations in WIRC mass concentrations were consistent with black carbon measurements from an aethalometer,although WIRC concentrations were typically higher,especially in winter and spring.The δ¹³C PDB value（-25.3 ± 0.8）%.determined for WIRC suggests that its sources are C₃ biomass or fossil fuel combustion.No seasonal change in δ¹³C PDB was evident.The average percent Modern Carbon（pMC） for ¹⁴C in WIRC for winter and spring was（67.2 ± 7.7）%（n = 29）.Lower pMC values were associated with air masses transported from the area east of WLG,while higher pMC values were associated with air masses from the Tibetan Plateau,southwest of WLG.Elevated pMC values with abnormally high mass concentrations of TSP and WIRC were measured during a dust storm event.     

Development of a liquid chromatography with mass spectrometry method for the determination of gelsemine in rat plasma and tissue: Application to a pharmacokinetic and tissue distribution study

Gelsemine from Gelsemium elegans Benth is a potential anesthetic and analgesic agent with no physical dependence and opiate addiction. This study was aimed at developing an ultrafast liquid chromatography coupled to tandem mass spectrometry method to quantify gelsemine in rat plasma and tissues. Plasma and tissues were processed with acetonitrile precipitation, and dendrobine was chosen as the internal standard. Sample separation was performed on an ACQUITY HSS T3 column. The mobile phase consisted of acetonitrile and 0.1% formic acid aqueous solution. Multiple reactions monitoring mode was utilized to detect the compounds of interest. The mass spectrometer was operated in the positive ion mode for detection. The MS/MS ion transitions monitored were m/z 323.2→70.5 for gelsemine and 264.2→108.05 for dendrobine, respectively. The calibration curves were linear over the range of 1–500 ng/mL in all biological matrices. The lower limit of quantification for rats plasma and tissues was 1.0 ng/mL. The values for inter‐ and intraday precision and accuracy were well within the ranges acceptable (< 15%). It was successfully applied to the pharmacokinetic and tissue distribution studies of gelsemine after intravenous doses of 5, 2, and 0.5 mg/kg in rats. These data of gelsemine would be useful for clinical application and further development.     

Simultaneous determination of three dipeptides (JBP485, Gly–Sar and JBP923) in the cell lysates by liquid chromatography‐tandem mass spectrometry: application to identify the function of the PEPT1 transfected cell

A simple and rapid liquid chromatography–tandem mass spectrometry (LC‐MS/MS) method for the simultaneous determination of JBP485, Gly–Sar and JBP923 in the cell lysates using methanol as a deproteinization solvent was developed and validated. Detection was performed by turbo ionspray ionization in multiple reaction monitoring mode using the transitions of m/z 147.1 → m/z 90.1 for Gly–Sar, m/z 201.1 → m/z 86.1 for JBP485, m/z 219.1 → m/z 86.1 for JBP923 and m/z 152.0 → m/z 110.0 for paracetamol (internal standard). The analytes were separated on a Hypersil ODS C₁₈ HPLC column using isocratic elution mode with a mobile phase containing 0.1% formic acid in water–methanol (97:3, v/v) at a flow rate of 0.2 mL/min. The calibration curves were demonstrated to be linear over the concentration range of 5.00?5000 nm with coefficient of 0.9968 for Gly–Sar, 0.9975 for JBP485 and 0.9952 for JBP923. The intra‐ and inter‐day precisions were <10.2% for each quality contro; level, and the accuracy was within ±5.6% for each analyte. The matrix effect, the extraction recovery and stabilities of LC‐MS/MS analysis were also investigated. This validated method was successfully applied to the simultaneous determination of JBP485, Gly–Sar and JBP923 in the cell lysates for identification of stably transfected HeLa cells with human PEPT1. Copyright © 2014 John Wiley & Sons, Ltd.     

Unveiling the importance of reactant mass transfer in environmental catalysis: Taking catalytic chlorobenzene oxidation as an example

To date, investigations onto the regulation of reactants mass transfer has been paid much less attention in environmental catalysis. Herein, we demonstrated that by rationally designing the adsorption sites of multi-reactants, the pollutant destruction efficiency, product selectivity, reaction stability and secondary pollution have been all affected in the catalytic chlorobenzene oxidation (CBCO). Experimental results revealed that the co-adsorption of chlorobenzene (CB) and gaseous O₂ at the oxygen vacancies of CeO₂ led to remarkably high CO₂ generation, owning to their short mass transfer distance on the catalyst surface, while their separated adsorptions at Brönsted HZSM-5 and CeO₂ vacancies resulted in a much lower CO₂ generation, and produced significant polychlorinated byproducts in the off-gas. However, this separated adsorption model yielded superior long-term stability for the CeO₂/HZSM-5 catalyst, owning to the protection of CeO₂ oxygen vacancies from Cl poisoning by the preferential adsorption of CB on the Brönsted acidic sites. This work unveils that design of environmental catalysts needs to consider both of the catalyst intrinsic property and reactant mass transfer; investigations of the latter could pave a new way for the development of highly efficient catalysts towards environmental pollution control.     

开放光程扬尘颗粒物浓度测量方法及系统

利用单波长激光通过扬尘空间发生散射消光衰减的特性,设计了开放光程的颗粒物浓度检测方法及系统。该方法利用双峰正态分布模型模拟颗粒物粒径分布,实时计算一定空间范围内的扬尘颗粒物浓度,具有响应速度快、测量动态范围宽的优点,适合浓度高、变化快、空间范围大的扬尘颗粒物浓度测量。通过水溶胶模拟实验与烟尘实验验证了该方法的可行性。实验数据表明,系统量程可达0~400mg/m3,分辨率为0.05mg/m3,响应时间小于1s。     

低β 162.5 MHz taper型HWR腔的机械性能分析（英文）

北京大学正在设计β=0.09,频率为162.5 MHz taper型的二分之一波长射频超导谐振腔(HWR腔),这种腔针对高流强质子束(约100mA)和氘束(约50mA)的加速而设计。对于这种超导腔而言机械性能分析是十分重要的,可以通过机械性能分析来估计由于腔体的形变带来的频率偏移。用ANSYS分析了由于液氦压力不稳定造成的麦克风效应以及洛伦兹力造成的腔体失谐,并且对沿腔体轴线方向的调谐进行了分析。模拟结果显示这只腔压力敏感系数为31.1 Hz/kPa,洛伦兹力系数为-0.41Hz/(MV·m~(-1))~2。腔体的调谐范围达到±177kHz,足够补偿腔体可能的频率偏移。腔体的机械性能满足腔体正常运行的要求。     

Single-Atom Iron Catalysts on Overhang-Eave Carbon Cages for High-Performance Oxygen Reduction Reaction

Single-atom catalysts have drawn great attention, especially in electrocatalysis. However, most of previous works focus on the enhanced catalytic properties via improving metal loading. Engineering morphologies of catalysts to facilitate mass transport through catalyst layers, thus increasing the utilization of each active site, is regarded as an appealing way for enhanced performance. Herein, we design an overhang-eave structure decorated with isolated single-atom iron sites via a silica-mediated MOF-templated approach for oxygen reduction reaction (ORR) catalysis. This catalyst demonstrates superior ORR performance in both alkaline and acidic electrolytes, comparable to the state-of-the-art Pt/C catalyst and superior to most precious-metal-free catalysts reported to date. This activity originates from its edge-rich structure, having more three-phase boundaries with enhanced mass transport of reactants to accessible single-atom iron sites (increasing the utilization of active sites), which verifies the practicability of such a synthetic approach.