Effect of preservation on the δ13C value of dissolved inorganic carbon in different types of water samples

Recent studies have shown that the stable carbon isotope compositions of dissolved inorganic carbon (δ¹³C_DIC) of water samples preserved with HgCl₂ and CuSO₄ vary. Furthermore, mercury and cuprum compounds are toxic to the human or biological system and require proper waste disposal. To test the effect of preservation on the δ¹³C value of DIC in different types of water samples, a set of water samples with different DIC concentrations was preserved using different methods, including preserving with inhibitors (CuSO₄ or HgCl₂), preserving under frozen conditions, filtering through a 0.4 μ m paper filter, and the DIC species precipitated in the form of solid BaCO₃. Our results show that δ¹³C_DIC values of the samples preserved with CuSO₄ and HgCl₂ become more positive with increased storage time. The δ¹³C_DIC of the water samples preserved under frozen conditions and the precipitated DIC as BaCO₃ are also more positive than original water samples. However, the δ¹³C values were relatively stable for up to 90 days in all water samples filtered through the 0.4 μ m paper filter and stored under cool conditions (0–4 °C). Therefore, we suggest that the better method for the storage of water samples is to filter the samples through a 0.4 μ m paper filter while out in the field and preserve them under cool conditions, thereby avoiding the use of preservatives.     

ICP-MS determination of lead isotope ratios in legal and counterfeit cigarette tobacco samples

A method for the determination of Pb isotope ratios (IR) in cigarette tobacco by quadrupole inductively coupled plasma mass spectrometry (Q-ICP-MS) has been developed and applied to tobacco samples from genuine and counterfeit cigarettes obtained in the USA. The IR ²⁰⁷Pb/²⁰⁶Pb, ²⁰⁸Pb/²⁰⁶Pb, ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb were measured using a Q-ICP-MS instrument. Two certified reference materials, grown in the USA and Bulgaria, were also analysed for comparison with the tobacco samples, as were tobacco samples from cigarettes obtained in Pakistan and China. The precision of the results was sufficient to distinguish between the counterfeit and genuine USA cigarettes. All of the genuine cigarettes and both reference materials, grown in different regions, were statistically distinct based on the measured ratios. The counterfeit cigarettes were indistinguishable from the reference material grown in Bulgaria. The technique shows promise as a method for identifying counterfeit cigarettes, possibly determining the source region.     

Comparison of sample preparation methods for stable isotope analysis of dissolved sulphate in forested watersheds

Pretreatment methods for measuring stable sulphur (δ³⁴S) and oxygen (δ¹⁸O) isotope ratios of dissolved sulphate from watersheds have evolved throughout the last few decades. The current study evaluated if there are differences in the measured stable S and O isotope values of dissolved sulphate from forested watersheds when pretreated using three different methods: Method 1 (M1): adsorb sulphate on anion exchange resins and send directly to isotope facility; Method 2 (M2): adsorb sulphate on anion exchange resins, extract sulphate from anion exchange resins, and send the produced BaSO₄ to the isotope facility; and Method 3 (M3): directly precipitate BaSO₄ without anion exchange resins with the precipitates being sent to the isotope facility. We found an excellent agreement of the δ³⁴S_sulphate values among all the three methods. However, some differences were observed in the δ¹⁸O_sulphate values (M1 versus M2:?1.5 ‰; M1 versus M3:?1.2 ‰) associated with possible O contamination before isotope measurement. Several approaches are recommended to improve the pretreatment procedures for δ¹⁸O_sulphate analysis.     

High hydrostatic pressure equipment for neutron scattering studies of samples in solutions

The design of new high pressure equipment for structural and dynamical studies on samples in solution is described. We present two sample cells for applying pressures up to 150 and 700 MPa (i.e. 1.5 and 7 kbar), respectively. These cells are mounted on special sticks and inserted into the calorimeter of a cryostat to regulate the temperature. Different parts of the equipment – the pressure controller, the sticks and the cells – are described. In addition, radiography tests which were performed with neutrons in situ at the Institut Laue Langevin to verify the tightness of the cells and the hydrostatic transmission of the pressure to the sample are presented. First results on model lipids are in agreement with former results by R. Winter et al. [Towards an understanding of the temperature/pressure configurational and free-energy landscape of biomolecules, J. Non-Equilib. Thermodyn. 32 (2007), pp. 41–97].     

基于灰色关联分析的航空装备技术保障能力评价模型

航空装备技术保障能力是组成航空兵战斗力的基本要素之一,其能力的高低直接影响到航空装备保障任务完成质量的优劣,因此对航空装备技术保障能力进行科学评价具有重要意义.在现有研究的基础上建立了航空装备技术保障能力评价指标体系,基于灰色关联分析方法提出了指标权重的确定方法,并利用灰色关联分析思想构建出航空装备技术保障能力评价模型,为航空装备技术保障能力评价提供量化分析模型,拓展了航空装备技术保障能力评价模型体系.     

导弹数字舵机多通道信号转换及传输系统设计

针对全数字电动舵机无法直接使用传统的模拟信号及数据传输过程中丢帧、串帧、等待时间过长等问题,设计了一种基于DSP的多通道信号转换及传输系统,该系统采用片外AD及DA转换器实现信号转换,并针对传统通信算法存在的弊端,提出新的方法,实时配置FIFO中断等级,实现存在扰动情况下的无丢帧、无串帧通信,且执行时间37 μs,提高了系统的稳定性、实时性。     

分析化学整体式电位滴定仪的自制研究

研制了整体式电位滴定仪,该滴定仪综合了加热、搅拌、酸度值测定、电位测定等功能,具有简便易操作、测试稳定、精准性和重复性高等优点,同时该仪器还可进一步应用于酸碱滴定、氧化还原滴定、络合滴定、沉淀反应、非水滴定等电位滴定的分析。从而增加了实验手段的多样化,提高了实验的趣味性和学生的积极性。     

Die Anlage K-1 zur Sauerstoffbestimmung

Die Methode der Neutronenaktivierungsanalyse mit Hilfe von transportablen Neutronengeneratoren hat in den letzten Jahren über den Rahmen von Forschungslaboratorien hinaus Anwendung unter industriellen Bedingungen gefunden. Die Robustheit und Zuverlässigkeit solcher Apparaturen für die Aktivierungsanalyse ermöglichten ihren Einsatz nicht nur in analytischen Laboratorien von Industriebetrieben, sondern auch zur Kontrolle in der Produktion selbst unmittelbar an technologischen Linien.     

浮动冲击平台冲击环境对设备响应的影响

对浮动冲击平台提供给设备的冲击环境及舰载设备在不同冲击环境下的响应进行了数值模拟和理论分析。以美国中型浮动冲击平台为计算模型,将设备基座的冲击环境与德国规范BV 043-85进行了比较,为分析两个体系在设备抗冲击要求中谱加速度的差异,对不同舰载设备进行数值模拟计算,并通过虚拟约束边界模态方法,提出不同冲击环境下基础激励的多自由度系统响应的计算方法。数值分析及理论计算结果表明:冲击谱中谱加速度对舰载设备响应影响较小,而谱位移和谱速度对设备响应有较大影响,理论计算得到的多自由度系统响应与数值模拟结果较一致,同时在进行浮动冲击平台设计时可不考虑谱加速度对设备响应的影响。     

装备制造业环境技术创新效率及其影响因素研究——基于DEA-Malmquist和Tobit的实证分析

运用2005~2011年中国装备制造业的面板数据,采用熵值法测度中国装备制造业的环境污染指数,应用DEA-Malmquist方法在考虑环境污染和能源消耗问题的基础上测度中国各类装备制造业环境技术创新效率,应用Tobit回归分析法对影响中国装备制造业环境技术创新效率的因素进行分析。研究结果表明:中国装备制造业的环境污染指数呈现下降—上升—下降的趋势;中国装备制造业的总体环境技术创新效率呈现先上升再下降的趋势,技术效率持续上升,技术退步是导致环境技术创新效率后期下降的原因;市场竞争、资本深化和外资引进对环境技术创新效率的提升具有显著的推动作用。