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排序方式: 共有483条查询结果,搜索用时 187 毫秒
1.
Mengjie Liu Te‐Chun Chu Agnes Jocher Mica C. Smith Istvan Lengyel William H. Green 《国际化学动力学杂志》2021,53(1):27-42
Using Reaction Mechanism Generator (RMG), we have automatically constructed a detailed mechanism for acetylene pyrolysis, which predicts formation of polycyclic aromatic hydrocarbons (PAHs) up to pyrene. To improve the data available for formation pathways from naphthalene to pyrene, new high‐pressure limit reaction rate coefficients and species thermochemistry were calculated using a combination of electronic structure data from the literature and new quantum calculations. Pressure‐dependent kinetics for the CH potential energy surface calculated by Zádor et al. were incorporated to ensure accurate pathways for acetylene initiation reactions. After adding these new data into the RMG database, a pressure‐dependent mechanism was generated in a single RMG simulation which captures chemistry from C to C. In general, the RMG‐generated model accurately predicts major species profiles in comparison to plug‐flow reactor data from the literature. The primary shortcoming of the model is that formation of anthracene, phenanthrene, and pyrene are underpredicted, and PAHs beyond pyrene are not captured. Reaction path analysis was performed for the RMG model to identify key pathways. Notable conclusions include the importance of accounting for the acetone impurity in acetylene in accurately predicting formation of odd‐carbon species, the remarkably low contribution of acetylene dimerization to vinylacetylene or diacetylene, and the dominance of the hydrogen abstraction CH addition (HACA) mechanism in the formation pathways to all PAH species in the model. This work demonstrates the improved ability of RMG to model PAH formation, while highlighting the need for more kinetics data for elementary reaction pathways to larger PAHs. 相似文献
2.
Eva Vergucht Björn De Samber Andrei Izmer Bart Vekemans Karen Appel Sergei Tolmachev Laszlo Vincze Frank Vanhaecke 《Analytical and bioanalytical chemistry》2015,407(6):1559-1566
This study aims at evaluating the capabilities of synchrotron radiation micro X-ray fluorescence spectrometry (SR micro-XRF) for qualitative and semi-quantitative elemental mapping of the distribution of actinides in human tissues originating from individuals with documented occupational exposure. The investigated lymph node tissues were provided by the United States Transuranium and Uranium Registries (USTUR) and were analyzed following appropriate sample pre-treatment. Semi-quantitative results were obtained via calibration by external standards and demonstrated that the uranium concentration level in the detected actinide hot spots reaches more than 100 μg/g. For the plutonium hot spots, concentration levels up to 31 μg/g were found. As illustrated by this case study on these unique samples, SR micro-XRF has a high potential for this type of elemental bio-imaging owing to its high sensitivity, high spatial resolution, and non-destructive character.
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相似文献
3.
Yihui Yan Lucas Schmitt Anastasiya Khramchenkova Jozef Lengyel 《Journal of mass spectrometry : JMS》2023,58(7):e4955
We present the design and performance of an in-house built electrospray ionization-mass spectrometry (ESI-MS) interface equipped with an S-lens ion guide. The ion source was designed specifically for our ion beam experiments to investigate the chemical reactivity and deposition of the clusters and nanoparticles. It includes standard ESI-MS interface components, such as nanoelectrospray, ion transfer capillary, and the S-lens. A custom design enables systematic optimization of all relevant factors influencing ion formation and transfer through the interface. By varying the ESI voltage and flow rate, we determined the optimal operating conditions for selected silica emitters. A comparison of the pulled silica emitters with different tip inner diameters reveals that the total ion current is highest for the largest tip, whereas a tip with the smallest diameter exhibited the highest transmission efficiency through the ESI-MS interface. Ion transmission through the transfer capillary is strongly limited by its length, but the loss of ions can be reduced by increasing the capillary voltage and temperature. The S-lens was characterized over a wide range of RF frequencies and amplitudes. Maximum ion current was detected at RF amplitudes greater than 50 V peak-to-peak (p/p) and frequencies above 750 kHz, with a stable ion transmission region of about 20%. A factor of 2.6 increase in total ion current is observed for 650 kHz as RF amplitudes reach 400 V p/p. Higher RF amplitudes also focus the ions into a narrow beam, which mitigates their losses when passing through the ion guide. 相似文献
4.
Randall Claywell Laszlo Nadai Imre Felde Sina Ardabili Amirhosein Mosavi 《Entropy (Basel, Switzerland)》2020,22(11)
The accurate prediction of the solar diffuse fraction (DF), sometimes called the diffuse ratio, is an important topic for solar energy research. In the present study, the current state of Diffuse irradiance research is discussed and then three robust, machine learning (ML) models are examined using a large dataset (almost eight years) of hourly readings from Almeria, Spain. The ML models used herein, are a hybrid adaptive network-based fuzzy inference system (ANFIS), a single multi-layer perceptron (MLP) and a hybrid multi-layer perceptron grey wolf optimizer (MLP-GWO). These models were evaluated for their predictive precision, using various solar and DF irradiance data, from Spain. The results were then evaluated using frequently used evaluation criteria, the mean absolute error (MAE), mean error (ME) and the root mean square error (RMSE). The results showed that the MLP-GWO model, followed by the ANFIS model, provided a higher performance in both the training and the testing procedures. 相似文献
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7.
Serena Indelicato David Bongiorno Sergio Indelicato Laszlo Drahos Vincenzo Turco Liveri Lilla Turiák Karoly Vékey Leopoldo Ceraulo 《Journal of mass spectrometry : JMS》2013,48(3):379-383
The characteristic collision energy (CCE) to obtain 50% fragmentation of positively and negatively single charged noncovalent clusters has been measured. CCE was found to increase linearly with the degrees of freedom (DoF) of the precursor ion, analogously to that observed for synthetic polymers. This suggests that fragmentation behavior (e.g. energy randomization) in covalent molecules and clusters are similar. Analysis of the slope of CCE with molecular size (DoF) indicates that activation energy of fragmentation of these clusters (loss of a monomer unit) is similar to that of the lowest energy fragmentation of protonated leucine–enkephalin. Positively and negatively charged aggregates behave similarly, but the slope of the CCE versus DoF plot is steeper for positive ions, suggesting that these are more stable than their negative counterparts. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
8.
Claude St. Thomas Hortensia Maldonado‐Textle Antal Rockenbauer Laszlo Korecz Nora Nagy Ramiro Guerrero‐Santos 《Journal of polymer science. Part A, Polymer chemistry》2012,50(14):2944-2956
Two different initiator/transfer agents (inifers) containing an alkoxyamine and a dithiobenzoate were synthetized and used to trigger out either reversible addition‐fragmentation chain transfer (RAFT) polymerization or nitroxide‐mediated polymerization (NMP). α‐Dithiobenzoate‐ω‐alkoxyamine‐difunctional polymers were produced in both cases which were subsequently used as precursors in the formation of block copolymers. This synthetic approach was applied to N‐isopropylacrylamide (NIPAM) or polyethylene oxide methacrylate (EOMA) to form α,ω‐heterodifunctional homopolymers via RAFT at 60°C which were chain extended with styrene by activating the alkoxyamine moiety at 120°C. Under such temperature conditions, it is proposed that a tandem NMP/RAFT polymerization is initiated producing a simultaneous growth of polystyrene blocks at both chain‐ends. Self‐assembled nanostructures of these amphiphilic block copolymers were evidenced by scanning electron microscopy. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
9.
Isabelle Minet Laszlo Hevesi Manuel Azenha Joseph Delhalle Zineb Mekhalif 《Journal of chromatography. A》2010,1217(17):2758-2767
We report on the fabrication and performances of a solid-phase microextraction (SPME) fiber based on a stainless steel wire coated with a covalently attached polyacrylonitrile (PAN)/multi-walled carbon nanotubes (MWCNTs) composite. This new coating is obtained by atom transfer radical polymerization (ATRP) of acrylonitrile mixed with MWCNTs. ATRP is initiated from 11-(2-bromo-2-methylpropionyloxy)-undecyl-phosphonic acid molecules grafted on the wire surface via the phosphonic acid group. The extraction performances of the fibers are assessed on different classes of compounds (polar, non-polar, aromatic, etc.) from water solutions by headspace extraction. The optimization of the parameters affecting the extraction efficiency of the target compounds was studied as well as the reproducibility and the repeatability of the fiber. The fibers sustain more than 200 extractions during which they remain chemically stable and maintain good performances (detection limits lower than 2 μg/l, repeatability, etc.). Considering their robustness together with their easy and inexpensive fabrication, these fibers could constitute promising alternatives to existing products. 相似文献
10.
Tom Schoonjans Antonio Brunetti Bruno Golosio Manuel Sanchez del Rio Vicente Armando Solé Claudio Ferrero Laszlo Vincze 《Spectrochimica Acta Part B: Atomic Spectroscopy》2011,66(11-12):776-784
This work presents the recent developments of xraylib, an ANSI C library that provides convenient access to a large number of X-ray related databases, with a focus on quantitative X-ray fluorescence applications. The enhancements include improved X-ray fluorescence production cross sections that take into account cascade effects and M-lines, as well as revised line energies, atomic level widths, Compton broadening profiles etc. A full overview of the complete application programming interface is presented. 相似文献