Behavior and process of background signal formation of hydrogen,carbon, nitrogen,and oxygen in silicon wafers during depth profiling using dual-beam TOF-SIMS

The behavior and mechanism of background signals during depth profiling of atmospheric elements using dual-beam time-of-flight secondary ion mass spectrometry (TOF-SIMS) have been experimentally investigated for silicon wafers. The background signals of atmospheric elements were found to be inversely proportional to the sputtering rate. Most of the background signals are largely attributable to the accumulation of components through adsorption and ion bombardment in the pre-equilibrium state. On the other hand, the contribution of real-time adsorption during the instant after the last sputtering in the equilibrium state is negligible under the present experimental conditions. H₂O is dominant in the background formation process of hydrogen and oxygen, which is supported by the higher adsorption coefficients. The background levels of carbon and nitrogen are lower than those of hydrogen and oxygen. Furthermore, the background signal of carbon with respect to the sputtering rate shows a different trend than the other elements. This could be attributed to accumulation in the pre-equilibrium state. These results indicate that the background levels can be lowered close to those of dynamic-SIMS by using an extremely high sputtering rate in dual-beam TOF-SIMS.     

A review of recent advances in catalytic combustion of VOCs on perovskite-type catalysts

Along with the rapid development of industry, VOCs gradually move into the spotlight, and now become a kind of harmful environmental pollutants that cannot be overlooked. This paper introduces the hazards of VOCs and the common catalytic combustion catalysts, noble metal catalysts and non-noble metal catalysts, for the elimination of VOCs. Perovskite catalysts, as one of the non-noble catalysts, play an important role in the field of catalytic combustion in recent years. According to the classification of elements doping in perovskites, the research achievements in the past five years were analyzed and reviewed. In addition, this paper also analyzes and elaborates the reaction kinetics and QSAR/QSPR models for the introduction of structural properties and reaction mechanisms.     

Development and validation of a liquid chromatography–tandem mass spectrometry method for the simultaneous analysis of androgens,estrogens, glucocorticoids and progestagens in human serum

We present a liquid chromatography tandem mass spectrometry method for the simultaneous analysis of 16 endogenous steroids (androgens, estrogens, glucocorticoids and progestogens) in human serum. Samples (250 μl of matrix) were extracted with t-butylmethyl ether prior to LC–MS/MS analysis. The chromatographic separation was achieved on a reversed-phase column using a methanol–water gradient. The HPLC was coupled to a triple quadrupole mass spectrometer equipped with an electrospray ionization source with acquisition in multiple reaction monitoring mode. The method was validated using surrogate matrices and human serum samples. The specificity of the method was confirmed for all of the considered steroids; linearity was also assessed (R² > 0.99, lack-of-fit test) in the ranges of concentrations investigated. The lower limits of quantification were in the range 10–400 pg/ml depending on the target steroid. Accuracy was in the range 85–115% for all target steroids except for the lower limit of quantitation levels where it was 80–120%. The extraction recovery was always >65%. No significant matrix effects were observed. To test the reliability of the method, the analysis of serum samples collected from 10 healthy subjects (5 M/5F) was performed. The present method can be used to identify the trajectories of deviation from the concentration normality ranges applied to disorders of the gonadal and adrenal axes.     

Synthesis of 3-aminoindan-1-one derivatives from 2-acetylbenzaldehydes and secondary amines by Mannich annulation

An acid-promoted 2-component Mannich annulation reaction of readily available acetylbenzaldehydes and secondary amines has been reported. The approach provides a simple and efficient method under mild conditions to synthesize 3-aminoindan-1-one derivatives in moderate to good yields.     

SIMS of organic layers with unknown matrix parameters: Locating the interface in dual beam argon gas cluster depth profiles

Four simple methods are evaluated to determine their accuracies for establishing the interface location in secondary ion mass spectrometry intensity depth profiles of organic layers where matrix effects have not been measured. Accurate location requires the separate measurement of each ion's matrix factor. This is often not possible, and so estimates using matrix-less methods are required. Six pure organic material interfaces are measured using many secondary ions to compare their locations from the four methods with those from full evaluation with matrix terms. For different secondary ions, matrix effects cause the apparent interface positions to vary over 20 nm. The shifts in the intensity profiles on going from a layer of P into a layer of Q are in the opposite direction to that for going from Q into P, so doubling layer thickness errors. The four methods are as follows: M1, use of the median interface position in the intensity profiles for the five lightest ions for 15 ≤ m/z ≤ 150; M2, extrapolation of the position for each ion to m/z = 0 for ions with m/z ≤ 150; M3, as M2 but for m/z ≤ 300; and M4, the extreme positions for all m/z ≤ 100. Comparison with the location using matrix terms shows their ranking, from best to worst, to be M4, M3, M1, and M2 with average errors of 10%, 12%, 14%, and 17%, respectively, of the profile interface full widths at half maximum. Use of pseudo-molecular ions is very much poorer, exceeding 50%, and should be avoided.     

一带一路背景下企业地域影响力发展的规划研究

面对一个分布在新地理区域的新市场,合理规划区域服务影响力的发展战略对企业至关重要。本文假设企业的服务影响力在地理区域上的发展可以用其地理上分布的立足点来表示。单个立足点覆盖有限范围内的地理区域,并且在一个特定时刻用所有立足点所覆盖地理区域的总和来表示企业该时刻的发展状态。由于资源限制,企业对经济发展迅速的区域的覆盖必须在一定时间内逐步完成。因此,在发展时期内如何确定立足点的位置并使其位于知名城市中,是企业管理者亟待解决的问题。针对这个问题,本文首先基于时间序列预测方法建立了区域经济指标评估模型;然后使用集合覆盖理论提出了以成本和满意度为目标的选址优化模型并使用分支定界算法求解该模型;最后,使用从“一带一路”地区收集的数据对模型进行了检验。结果表明,该方法对有相关问题的企业具有较大的参考价值。     

An effect of residual gas component on detected secondary ions during TOF‐SIMS depth profiling and a method to estimate contained component

With regard to Secondary Ion Mass Spectroscopy (SIMS) measurement of atmospheric gas elements, a problem occurs that the detected signal includes background components caused by residual gas along with contained components. Relating to this issue, an available method to quantify the contained components by separating the background ones had been established for Dynamic SIMS. Time‐of‐Flight SIMS with sputtering ion gun has also applied for depth profiling as well as Dynamic SIMS. However, few studies have attempted to investigate the secondary ion behavior of the atmospheric gas elements for depth profiling by Time‐of‐flight SIMS, especially for low concentration levels. In this study, experimental examinations of the secondary ions of the atmospheric gas elements, such as oxygen, hydrogen, and carbon in the silicon substrate, has been conducted in various analytical conditions of TOF‐SIMS depth profiling mode. Under the analytical conditions of our study, it has been proved that the background intensity of these elements was correlated to the sputtering rate. For the analysis of Floating Zone Silicon substrate, the oxygen intensity of the background component was proportional to the inverse number of the sputtering rate. Based on these facts, the total detected intensity of the atmospheric gas elements was able to be separated into the contained components and background ones by changing the sputtering rate during TOF‐SIMS measurement. An experimental result has shown that the contained oxygen concentration in the Czochralsk Silicon substrate estimated by the “TOF‐SIMS Raster Change Method” has successfully agreed with the result by the Dynamic SIMS.     

Comparative metabolic profiling of Costus speciosus leaves and rhizomes using NMR,GC-MS and UPLC/ESI-MS/MS

Costus speciosus had been used in oriental systems of medicines, to treat diverse ailments. The present study was focused on NMR, GC-MS and UPLC/ESI-MS/MS-based metabolic profiling of C. speciosus. This metabolic study resulted in the identification of 91 and quantification of 69 metabolites. Caffeic acid derivatives previously unreported in C. speciosus were also identified. High quantity of steroidal saponins namely methyl protogracillin (297.97 ± 0.07 mg/g dried wt.) and dioscin (158.72 ± 0.27 mg/g dried wt.) were observed in butanol fraction of rhizomes. Health care metabolites including caffeic acid (37.88 ± 0.04 mg/g dried wt.) and trehalose (75.12 ± 0.08 mg/g dried wt.) were also detected in ethyl acetate and aqueous fractions of rhizomes, respectively. Metabolites of nutraceutical and biological significance including eremanthine (5.14 ± 0.68%, peak area), tocopherols (~22%), sterols (~25%) were also identified from hexane fractions of rhizomes and leaves using GC-MS. The analytical techniques used had successfully differentiated metabolites composition among leaves and rhizomes.     

Application of pathways activity profiling to urine metabolomics for screening Qi‐tonifying biomarkers and metabolic pathways of honey‐processed Astragalus

Honey‐processed Astragalus, a widely used Qi‐tonifying and immunomodulating herb in traditional Chinese medicine, has strengthened the tonic effects and achieved fewer side effects compared with astragali radix in clinical application. Here, we focus on Qi‐tonifying biomarkers and pathways of honey‐processed Astragalus using urine metabolomics that provide the basis for building the linkage between metabolites in rat urine and its symptoms. The spleen Qi deficiency model group, normal group, astragali radix group, and honey‐processed Astragalus group were implemented to evaluate Qi‐tonifying effects. Twelve potential biomarkers were screened by multivariate statistical analysis by using ultra high performance liquid chromatography with quadrupole time‐of‐flight mass spectrometry. Furthermore, pathways activity profiling showed unique pathways that are primarily involved in tryptophan metabolism, tricarboxylic acids cycle, and methionine metabolism. The results demonstrated that metabolomics coupled with pathway activity profiling were promising tools. It might serve as a novel methodological clue to systematically dissect the underlying Qi‐tonifying mechanism of honey‐processed Astragalus.     

GC-MS with ethyl chloroformate derivatization for comprehensive analysis of metabolites in serum and its application to human uremia

An optimized method based on GC-MS with ethyl chloroformate derivatization has been developed for the comprehensive analysis of endogenous metabolites in serum. Twenty-two reference standards and serum samples were used to validate the proposed method. The correlation coefficient was higher than 0.9900 for each of the standards, and the LOD varied from 125 to 300 pg on-column. The analytical equipment exhibited good repeatability (RSD<10%) for all of the standards. Both the repeatability and the within-48-h stability of the analytical method were satisfactory (RSD<10%) for the 18 metabolites identified in the serum samples. Mean recovery was acceptable for the 18 metabolites, ranging from 70% to 120% with RSDs of less than 10%. Using the optimized protocol and a subsequent multivariate statistical technique, complete differentiation was achieved between the metabolic profile of uremic patients and that of age- and sex-matched normal subjects. Significantly decreased levels of valine, leucine, and isoleucine and increased levels of myristic acid and linoleic acid were observed in the patient group. This work demonstrated that this method is suitable for serum-based metabolic profiling studies.