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31.
人们对化学工业可持续性关注的不断提高推动了更加高效催化反应的开发.第一代评估催化剂活性的方法基于其地壳丰度,该方法存在严重不足.本文提出了第二代评估催化剂活性的办法,该方法可以在工业应用之前预测新型催化剂的活性,从而使全球化学工业受益.采用该评估法发现,对于11个有代表性的工业催化过程,催化剂消耗与催化剂元素的年度生产或价格之间存在着关联.基于该关联,我们引入了两个新概念来描述催化剂活性:每年催化剂消耗量与可用量的比值(CCA)和每年消耗催化剂成本与产品价值的比值(CCP).将CCA和CCP评估法用于选定的工业反应,进行实例分析并根据活性将催化剂分类,根据CCA和CCP值即可确定催化剂活性的普遍极限.计算CCA和CCP,并将其与催化剂活性的普遍极限进行比较,可以为研究者提供一个新的框架,用以评估一个新催化剂的成本或物理有效率是否会成为限制因素.我们还将该方法用于计算并预测新型催化剂的可行性生产及产品成本的经济极限. 相似文献
32.
Observation of cerium isotope fractionation in ion-exchange chromatography of Ce(III)-malate complex
The cerium isotope fractionation between Ce(III)-malate complex in aqueous solution and cerium ions in a cation-exchange resin was conducted by displacement chromatography. The pH and the chemical composition of the eluent were optimized for maintaining the self-sharpening band boundaries and the 21 m chromatographic migration of the Ce band underwent. Graphite slurry was coated on the tantalum filament prior to sample loading for reducing the isobaric interferences in cerium isotopic ratio determination by mass spectrometry. From the experimental results, it was found that the heavier isotope was enriched in the front boundary part of the cerium adsorption band, which meant that the heavier isotope was preferentially fractionated into the Ce3+ malate complex rather than simply hydrated Ce3+ ions. The isotope separation coefficient for the 136Ce/140Ce and 142Ce/140Ce was 5.2 x 10(-5) and -1.9 x 10(-5), respectively, at 298 K. 相似文献
33.
《Journal of mass spectrometry : JMS》2018,53(7):560-564
Variation of the isotopic abundance of selected nutrients and molecules has been used for pharmacological and kinetics studies under the premise that the administered molecule has a different isotopic enrichment from the isotopic background of the recipient subject. The aim of this study is to test the feasibility of assessing the contribution of exogenous surfactant phospholipids to the endogenous alveolar pool in vivo after exogenous surfactant replacement therapy in rabbits. The study consisted in measuring the consistency of 13C/12C ratio of disaturated‐phosphatidylcholine palmitate (DSPC‐PA) in 7 lots of poractant alfa, produced over a year, and among bronchoalveolar lavages of 20 rabbits fed with a standard chow. A pilot study was performed in a rabbit model of lavage‐induced surfactant deficiency: 7 control rabbits and 4 treated with exogenous surfactant. The contribution of exogenous surfactant to the alveolar pool was assessed after intra‐tracheal administration of 200 mg/kg of poractant alfa. The 13C content of DSPC‐PA was measured by isotope ratio mass spectrometry. The mean DSPC‐PA 13C/12C ratio of the 7 lots of poractant alfa was −18.8‰ with a SD of 0.1‰ (range: −18.9‰; −18.6‰). The mean 13C/12C ratio of surfactant DSPC recovered from the lung lavage of 20 rabbits was −28.8 ± 1.2‰ (range: −31.7‰; −25.7‰). The contribution of exogenous surfactant to the total alveolar surfactant could be calculated in the treated rabbits, and it ranged from 83.9% to 89.6%. This pilot study describes a novel method to measure the contribution of the exogenous surfactant to the alveolar pool. This method is based on the natural variation of 13C, and therefore it does not require the use of chemically synthetized tracers. This method could be useful in human research and especially in surfactant replacement studies in preterm infants. 相似文献
34.
Federica Rossi Nghia Tuan Duong Manoj Kumar Pandey Michele R. Chierotti Roberto Gobetto Yusuke Nishiyama 《Magnetic resonance in chemistry : MRC》2019,57(6):294-303
Chemical shift anisotropy (CSA) is a sensitive probe of electronic environment at a nucleus, and thus, it offers deeper insights into detailed structural and dynamic properties of different systems, for example, chemical, biological, and materials. Over the years, massive efforts have been made to develop recoupling methods that reintroduce CSA interaction under magic angle spinning (MAS) conditions. Most of them require slow or moderate MAS (≤20 kHz) and isotopically enriched samples. On the other hand, to the best of the authors' knowledge, no 13C or 15N CSA recoupling schemes at ultrafast MAS (≥60 kHz) suitable for cost-effective natural abundant samples have been developed. We present here a proton-detected 3D 15N CS/15N CSA/1H CS correlation experiment which employs 1H indirect detection for sensitivity enhancement and a γ-encoded -symmetry-based CSA recoupling scheme. In particular, two different symmetries, that is, R837 and R1049, are first tested, in a 2D 15N CSA/1H CS version, on [U-15N]-L-histidine·HCl·H2O as a model sample under 70 kHz MAS. Then the 3D experiment is applied on glycyl-L-alanine at natural abundance, resulting in site-resolved 15N CSA lineshapes from which CSA parameters are retrieved by SIMPSON numerical fittings. We demonstrate that this 3D R-symmetry-based pulse sequence is highly robust with respect to wide-range offset mismatches and weakly dependent to rf inhomogeneity within mis-sets of ±10% from the theoretical value. 相似文献
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36.
在非局域热动力学平衡(Non-LTE)下,采用类氢近似,计算得出电子密度分别为6.0×10~(20) cm~(-3)、1.4×10~(21) cm~(-3)、1.0×10~(22) cm~(-3)和1.7×10~(22) cm~(-3)的条件下的三体复合、辐射复合、双电子复合系数随电子温度的变化,得出总的复合系数随电子温度的变化关系;结合相关的电离系数得出相应的离子占有数的比,最后,计算出一定电子密度和温度条件下Au~(48+)~Au~(52+)离子的离子丰度,从而得到金等离子体的荷态分配数与电子温度和电子密度的关系. 相似文献
37.
参加了由FAO/IAEA组合的全氮和^15N丰度检测能力验证的实验室国际间的比对两年的比对结果表明,我们实验室对3个植株样品全氮和^15N丰度的测定值与指定值十分吻合,检测结果准确,此项计划的实施,证明了本实验室的检测能力和国际实验室间的水平。 相似文献
38.
Based on the heavy element nucleosynthesis theory, with the solar heavy-nuclide abundances and the observed abundances of
three elements which are the representatives of the individul neutron-capture processes, a method to determine the relative
contributions from the individul neutron-capture processes to the abundances of heavy elements in metal-poor stars is applied.
With this method, the abundances of heavy elements in ultra-metal-poor star CS 22892-052 are calculated. It is found that
the observed abundances of heavy elements in this star are well matched by our calculations in error limits, except for thorium
Project supported by the National Natural Science Foundation of China (Grant No. 19673008).
The visiting scholar of Shijiazhuang Teacher’s College. 相似文献
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40.
指出丰度坐标系具多维性和共轭性.其坐标轴具对偶性;探讨了REE演化线、REE演化线三参数(演化强度、演化方向、演化空间位置)及其物理含义;指出REE演化线三个参数是体系的实测参数.是研究天然体系中元素质量运移的基础数据;侧重讨论了其中一个参数——REE演化方向在REE演化线类型划分上的应用、演化线类型的符号表示及其对岩石成因类型进行判别的示例。 相似文献