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81.
This work demonstrates resolution enhancement of a quadrupole mass filter (QMF) under the influence of a static magnetic field. Generally, QMF resolution can be improved by increasing the number of rf cycles an ion experiences when passing through the mass filter. In order to improve the resolution, the dimensions of the QMF or the operating parameters need to be changed. However, geometric modifications to improve performance increase the manufacturing cost and usually the size of the instrument. By applying a magnetic field, a low‐cost, small footprint instrument with reduced power requirements can be realized. Significant improvement in QMF resolution was observed experimentally for certain magnetic field conditions, and these have been explained in terms of our theoretical model developed at the University of Liverpool. This model is capable of accurate simulation of spectra allowing the user to specify different values of mass spectrometer dimensions and applied input signals. The model predicts enhanced instrument resolution R>26 000 for a CO2 and N2 mixture with a 200‐mm long mass filter operating in stability zone 3 via application of an axial magnetic field. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
82.
我们用X射线荧光光谱滤纸片法分析了古今13铜矿石样品中的铜含量,测量结果与化学法一致。此法不需要铜矿石的标样,而且手续简单,方便,检出限低,灵敏度高,测量结果正确可靠,是分析矿石中单一或几个元素的含量较好的方法之一。 相似文献
83.
Spatial,Hysteretic, and Adaptive Host–Guest Chemistry in a Metal–Organic Framework with Open Watson–Crick Sites 下载免费PDF全文
Xiao‐Rong Lin Wei Chen Prof. Guang‐Hui Chen Prof. Xiao‐Chun Huang Prof. Dan Li 《Angewandte Chemie (International ed. in English)》2015,54(36):10454-10459
Biological and artificial molecules and assemblies capable of supramolecular recognition, especially those with nucleobase pairing, usually rely on autonomous or collective binding to function. Advanced site‐specific recognition takes advantage of cooperative spatial effects, as in local folding in protein–DNA binding. Herein, we report a new nucleobase‐tagged metal–organic framework (MOF), namely ZnBTCA (BTC=benzene‐1,3,5‐tricarboxyl, A=adenine), in which the exposed Watson–Crick faces of adenine residues are immobilized periodically on the interior crystalline surface. Systematic control experiments demonstrated the cooperation of the open Watson–Crick sites and spatial effects within the nanopores, and thermodynamic and kinetic studies revealed a hysteretic host–guest interaction attributed to mild chemisorption. We further exploited this behavior for adenine–thymine binding within the constrained pores, and a globally adaptive response of the MOF host was observed. 相似文献
84.
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86.
We present a unified approach for linear and nonlinear sensitivity analysis for models of reaction kinetics that are stated in terms of systems of ordinary differential equations (ODEs). The approach is based on the reformulation of the ODE problem as a density transport problem described by a Fokker-Planck equation. The resulting multidimensional partial differential equation is herein solved by extending the TRAIL algorithm originally introduced by Horenko and Weiser in the context of molecular dynamics (J. Comp. Chem. 2003, 24, 1921) and discussed it in comparison with Monte Carlo techniques. The extended TRAIL approach is fully adaptive and easily allows to study the influence of nonlinear dynamical effects. We illustrate the scheme in application to an enzyme-substrate model problem for sensitivity analysis w.r.t. to initial concentrations and parameter values. 相似文献
87.
Detect early stage lung cancer by a LAMP microfluidic chip system with a real-time fluorescent filter processor 总被引:1,自引:0,他引:1
TongZhou Wang Ye Zhang GuoLiang Huang Can Wang Lan Xie Li Ma ZhiYong Li XianBo Luo Hao Tian Qiang Li Xin Li ZhouYan Lv XiaoFan Bao 《中国科学:化学(英文版)》2012,55(4):508-514
This work presents a promising clinical molecular diagnostics for early stage lung cancer. This novel diagnostic method utilized the loop-mediated isothermal amplification (LAMP), microfluidic chips and a confocal optical detector with a non-linear fluorescent filter processor. An isothermal amplification based microfluidic chip for the early diagnostics of lung cancer was developed and a confocal optical detector was improved by a novel real-time fluorescent filter to sensitively monitor the DNA amplification procedure with high signal to noise ratio and fluorescence collecting ability. Experiment showed that a rapid diagnostic of lung cancer by detecting the existence of the CEA mRNA could be performed in only 5 μL of reaction assay in less than 45 min. While the traditional in-tube RT-PCR set consumed more than 25 μL of the assay and took more than 90 min. 相似文献
88.
Several methods of extraction were optimized to extract polycyclic aromatic hydrocarbons (PAHs), their nitrated derivatives and heavy n-alkanes from a highly adsorptive particulate matter resulting from the combustion of diesel fuel in a diesel engine. This particular carbonaceous particulate matter, collected at high temperatures in cordierite diesel particulate filters (DPF), which are optimized for removing diesel particles from diesel engine exhaust emissions, appeared extremely refractory to extractions using the classical extracting conditions for these pollutants. In particular, the method of accelerated solvent extraction (ASE) is described in detail here. Optimization was performed through experimental design to understand the impact of each factor studied and the factors’ possible interactions on the recovery yields. The conventional extraction technique, i.e., Soxhlet extraction, was also carried out, but the lack of quantitative extractions led us to use a more effective approach: hot Soxhlet. It appeared that the extraction of the heaviest PAHs and nitroPAHs by either the optimized ASE or hot Soxhlet processes was far from complete. To enhance recovery yields, we tested original solvent mixtures of aromatic and heteroaromatic solvents. Thereafter, these two extraction techniques were compared to microwave-assisted extraction (MAE) and supercritical fluid extraction (SFE). In every case, the only solvent mixture that permitted quantitative extraction of the heaviest PAHs from the diesel soot was composed of pyridine and diethylamine, which has a strong electron-donor character. Conversely, the extraction of the nitrated PAHs was significantly improved by the use of an electron-acceptor solvent or by introducing a small amount of acetic acid into the pyridine. It was demonstrated that, for many desirable features, no single extraction technique stound out as the best: ASE, MAE or SFE could all challenge hot Soxhlet for favourable extractions. Consequently, the four optimized extraction techniques were performed to extract the naturally polluted diesel soot collected inside the DPF. Comparisons with the NIST standard reference material SRM 1650b showed that the soot collected from the DPF contained 50% fewer n-alkanes, and also markedly lower levels of PAHs (44 less concentrated) than SRM 1650b, and that the ratio of nitroPAHs to PAHs was increased. These results were attributed to the high temperatures reached inside the particulate filter during sampling runs and to the contribution of the catalytic DPF to aromatic and aliphatic hydrocarbons abatement. 相似文献
89.
Despite biological variability the spectral characteristics of undiluted human urine show relatively low autofluorescence at short UV (250-300 nm) excitation. However with dilution the fluorescence intensity remarkably increases. This paper examines the mechanisms behind this effect, by using excitation-emission matrices. Corrections for the inner filter effect were made for improved understanding of the spectral patterns. We focused on three major fluorophores (tryptophan, indoxyl sulfate and 5-hydroxyindole-3-acetate) that are excited at these wavelengths, and whose content in urine is strongly linked with various health conditions. Their fluorescence was studied both individually and in combinations. We also examined the effect of ammonium on the fluorescence of these major fluorophores individually and in combinations. Through these studies we have identified the leading effects that reduce the UV fluorescence, namely higher concentration of indoxyl sulfate producing the inner filter effect and concentration quenching and quenching of fluorophores by ammonium. This result will assist in broader utilisation of UV fluorescence in medical diagnostics. 相似文献
90.
燃煤电站布袋除尘器和静电除尘器脱汞性能比较 总被引:8,自引:0,他引:8
采用国际上通用的Ontario Hydro方法(OHM)对中国五个燃煤电站布袋除尘器(FF)/静电除尘器(ESP)前、后的烟气进行采样,应用美国EPA标准方法测定了烟气中Hg0、Hg2+和HgP的浓度。应用DMA80测定固体样品(煤、底灰、ESP飞灰)中的汞浓度。由汞平衡得出各个环节中汞所占的份额。由此得到FF和ESP脱除烟气中汞的性能。安装FF的电站1和2的综合脱除效率约为80%和20%,安装ESP的电站3、4和5的综合脱除效率分别为6%、20%和4%左右。这说明FF比ESP有更加优良的脱汞性能,而且FF/ESP脱除烟气中的汞受到很多因素的影响。 相似文献