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941.
《Current Applied Physics》2015,15(9):1036-1041
Spatial distributions of the effective electron temperature (Teff) and plasma potential were studied from the measurement of an electron energy probability function in a side type ferrite-core inductively coupled plasma with an argon–helium mixture. As the helium gas was diluted at the fixed total gas pressure of 5 mTorr in an argon discharge, the distribution of the plasma density and plasma potential changed from a concave to a flat profile, and finally became a convex profile, while all spatial profiles of Teff were hollow shapes with helium dilution in the argon discharge. This evolution of the plasma potential with helium gas could be explained by the increased energy relaxation length (λε), indicating the transition of electron kinetics from local to non-local kinetics. 相似文献
942.
Adrian Boborodea Jacques Michel André Luciani 《International Journal of Polymer Analysis and Characterization》2014,19(2):124-129
Conventional analytical temperature rising elution fractionation (ATREF) is performed using slowly crystallized polymers in about 16 h. In this work, we developed a fast ATREF method in which the polymer sample is directly injected on the column at room temperature, thus reducing the analysis time to about 1 h. The method was tested using four metallocene polyethylenes with unimodal short chain branching distributions and different densities, previously analyzed by ATREF using a cooling rate of 0.1°C/min. The obtained results demonstrate that the fast ATREF method is very effective and accurate in evaluating short chain branching distribution for polyolefins having unimodal distributions. 相似文献
943.
Hongmei Peng Bin Wang Jinggang Gai Jinyao Chen Feng Yang Ya Cao Huilin Li Jian Kang Ming Xiang 《先进技术聚合物》2014,25(12):1464-1470
Large amount of work has been published on the isotacticity–properties relationship of isotactic polypropylene (iPP). However, the stereo‐defect distribution dependence of morphology and mechanical properties of iPP injection molding samples is still not clear. In this study, two different isotactic polypropylene (iPP) resins (PP‐A and PP‐B) with similar average isotacticity but different stereo‐defect distribution were selected to investigate the morphology evolution and mechanical properties (tensile and notching) of their injection molding samples using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), 2D wide angle X‐ray diffraction (2D‐WAXD), and scanning electron microscope (SEM). The results of DMA showed that the molecular movement ability of PP‐A (with less uniform distribution of stereo‐defect) was stronger than that of PP‐B, meanwhile the analysis of DSC and SEM suggested that after injection molding, smaller spherullites, and crystals with higher perfection had formed in the specimens of PP‐A. The resulting of tensile properties of PP‐A were found to be better than that of PP‐B. The results of morphology evolution by SEM observation and 2D‐WAXD showed that PP‐A is more likely to occur interspherulite deformation and can disperse the tensile stress more efficiently, and therefore, its crystal structure can withstand a greater force when tensile stress is applied. On the other hand, PP‐B has larger spherulites and boundaries, and low perfection of lamellaes, and the intraspherulte deformation tend to take place. It is easier for the crystal of PP‐B to be broken up and reoriented along the tensile direction. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
944.
Comparison of the activation time effects and the internal energy distributions for the CID,PQD and HCD excitation modes
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Farid Ichou Adrian Schwarzenberg Denis Lesage Sandra Alves Christophe Junot Xavier Machuron‐Mandard Jean‐Claude Tabet 《Journal of mass spectrometry : JMS》2014,49(6):498-508
Reproducibility among different types of excitation modes is a major bottleneck in the field of tandem mass spectrometry library development in metabolomics. In this study, we specifically evaluated the influence of collision voltage and activation time parameters on tandem mass spectrometry spectra for various excitation modes [collision‐induced dissociation (CID), pulsed Q dissociation (PQD) and higher‐energy collision dissociation (HCD)] of Orbitrap‐based instruments. For this purpose, internal energy deposition was probed using an approach based on Rice–Rampserger–Kassel–Marcus modeling with three thermometer compounds of different degree of freedom (69, 228 and 420) and a thermal model. This model treats consecutively the activation and decomposition steps, and the survival precursor ion populations are characterized by truncated Maxwell–Boltzmann internal energy distributions. This study demonstrates that the activation time has a significant impact on MS/MS spectra using the CID and PQD modes. The proposed model seems suitable to describe the multiple collision regime in the PQD and HCD modes. Linear relationships between mean internal energy and collision voltage are shown for the latter modes and the three thermometer molecules. These results suggest that a calibration based on the collision voltage should provide reproducible for PQD, HCD to be compared with CID in tandem in space instruments. However, an important signal loss is observed in PQD excitation mode whatever the mass of the studied compounds, which may affect not only parent ions but also fragment ions depending on the fragmentation parameters. A calibration approach for the CID mode based on the variation of activation time parameter is more appropriate than one based on collision voltage. In fact, the activation time parameter in CID induces a modification of the collisional regime and thus helps control the orientation of the fragmentation pathways (competitive or consecutive dissociations). Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
945.
In this study, alleviation of ion suppression effect in sonic spray ionization mass spectrometry (SSI‐MS) was investigated. Ion suppression effect was firstly compared between electrospray ionization (ESI) and conventional SSI, and more severe ion suppression effect was observed with SSI. Ion suppression effect of SSI was also found difficult to be alleviated by simply optimizing major parameters. Alternatively, we found that with the assistance of an alternating current (AC) voltage with low amplitude, the ion suppression effect was greatly alleviated (comparable with conventional ESI). That AC voltage was applied outside the SSI spray tip, and no direct contact between the electrode and spray solution was necessary. Besides the alleviation of the ion suppression effect, this newly‐developed method, termed as induced electrosonic spray ionization (IESSI), appeared to preserve similar charge state distribution with SSI for protonated cytochrome c, hemoglobin, and bradykinin. IESSI could also obtain significantly improved ion intensities (~1000‐fold over conventional SSI). In addition, tolerance of concentrated salts for IESSI‐MS was investigated through the analysis of cytochrome c in the presence of concentrated sodium chloride (NaCl) or ammonium acetate (NH4OAc). Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
946.
HPLC‐MS/MS method for quantitative determination of the novel dual inhibitor of FGF and VEGF receptors E‐3810 in tumor tissues from xenograft mice and human biopsies
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Monique Zangarini Laura Ceriani Ezia Bello Giovanna Damia Roberta Cereda Maria Gabriella Camboni Massimo Zucchetti 《Journal of mass spectrometry : JMS》2014,49(1):19-26
We developed and validated a high‐performance liquid chromatography–tandem mass spectrometry analytical method to measure E‐3810, a novel dual inhibitor of fibroblast growth factor receptor 1 and vascular endothelial growth factor receptor 1–3 in tissues and determined the drug concentration in a biopsy of human breast cancer for the first time. The method is a modification of our previous one in plasma to study the clinical pharmacokinetics of the drug during the phase I/II trial. In view of the changes in matrix, we applied a partial validation protocol to determine recovery, sensitivity, range of linearity, precision, accuracy and stability of the method over three runs in a mouse tumor tissue and liver. The recovery of E‐3810 from liver or tumor homogenate was >69%, and the lower limit of quantification was 5 ng/ml. The method was linear in the concentration range 5.0–500.0 ng/ml, as demonstrated by a determination coefficient R2 ≥ 0.9955. The range of the calibration curve was appropriate for the analysis, as demonstrated by the accuracy, which was between 91.4% and 106.7%. Interday precision and accuracy on quality control samples at 9, 30 and 300 ng/ml were 3.1‐11.2% and 98.3–111.4%, respectively. The assay was applied successfully to determine the intratumor concentration of E‐3810 in different mouse xenograft tumor models and in a biopsy of a patient with breast cancer included in the phase I/II trial of the drug. In mouse tumors, the concentrations of E‐3810 were higher than necessary to exert antitumor activity in vitro (1 µM). Even more of interest was the result obtained in a human biopsy of few milligrams, where E‐3810 reached 4.9 µg/g (11 µM). Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
947.
The fundamental aspects of charging in electrospray ionization (ESI) are hotly debated. In the present study, ESI charging of DNA oligonucleotides was explored in both positive (ESI+) and negative (ESI?) polarity using mass spectrometry detection. Single‐stranded 12‐mer CCCCAATTCCCC in buffer solution (aqueous NH4Ac, 100 mM) produced similar charge state distribution (CSD) in either ESI+ or ESI?. Similarity of CSD in ESI+ and ESI? was also observed for the double‐stranded 12‐mer CGCGAATTCGCG. By adding typical low‐vapor reagents (e.g. m‐nitro benzyl alcohol, m‐NBA; sulfolane) into the same buffer solution (<0.5% w/v), both CCCCAATTCCCC and CGCGAATTCGCG revealed strong supercharging (SC) effect in ESI?, while very little or no SC effect was observed in ESI+. With either sulfolane or m‐NBA, the CGCGAATTCGCG duplex dissociated into single strands in ESI?. No SC was observed in both ESI+ and ESI? for thermally denatured CGCGAATTCGCG duplex in NH4Ac buffer without the reagents. These findings are difficult to reconcile with the earlier model, which attributes SC in aqueous buffer solution to the conformational changes of analytes. Our observations suggest that the ionic strength of ESI droplets strongly affects the CSD of biopolymers such as DNA oligonucleotides and that SC effect is related to the depletion of ionic strength during the ESI process. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
948.
Dr. Masaki Yoshida Dr. Mio Kondo Prof. Toshikazu Nakamura Prof. Ken Sakai Prof. Shigeyuki Masaoka 《Angewandte Chemie (International ed. in English)》2014,53(43):11519-11523
A series of [{(terpy)(bpy)Ru}(μ‐O){Ru(bpy)(terpy)}]n+ ( [RuORu]n+ , terpy=2,2′;6′,2′′‐terpyridine, bpy=2,2′‐bipyridine) was systematically synthesized and characterized in three distinct redox states (n=3, 4, and 5 for RuII,III2 , RuIII,III2 , and RuIII,IV2 , respectively). The crystal structures of [RuORu]n+ (n=3, 4, 5) in all three redox states were successfully determined. X‐ray crystallography showed that the Ru? O distances and the Ru‐O‐Ru angles are mainly regulated by the oxidation states of the ruthenium centers. X‐ray crystallography and ESR spectra clearly revealed the detailed electronic structures of two mixed‐valence complexes, [RuIIIORuIV]5+ and [RuIIORuIII]3+ , in which each unpaired electron is completely delocalized across the oxo‐bridged dinuclear core. These findings allow us to understand the systematic changes in structure and electronic state that accompany the changes in the redox state. 相似文献
949.
Zhen Gu Yi-Lun Ying Bing-Yong Yan Hui-Feng Wang Pin-Gang He Yi-Tao Long 《中国化学快报》2014,25(7):1029-1032
Nanopore technique plays an important role in single molecule detection, which illuminates the properties of an individual molecule by analyzing the blockage durations and currents. However, the traditional exponential function is lack of efficiency to describe the distributions of blockage durations in nanopore experiments. Herein, we introduced an exponentially modified Gaussian (EMG) function to fit the duration histograms of both simulated events and experimental events. In comparison with the traditional exponential function, our results demonstrated that the EMG provides a better fit while covers the entire range of the distributions. In particular, the fitted parameters of EMG could be directly used to discriminate the sequence length of the oligonucleotides at single molecule level. 相似文献
950.
Unfilled natural rubber compounds composed of conventional (CV), semi-efficient (SEV), efficient (EV) and sulfur donor (SD) vulcanization systems were heat aged to promote sulfur reversion. Rheometry, hardness, strain-strain characteristics including Mooney-Rivlin analysis, equilibrium solvent swell and Double Quantum (DQ) Nuclear Magnetic Resonance (NMR) were used to monitor crosslink density changes. A loss of crosslink density was observed by rheometry, C1, equilibrium swelling and by DQ NMR as a function of cure extent. No chain scission reactions were operating in the time/temperature conditions used. All crosslink distributions were unimodal and the network homogeneity followed the order of EV > SD > SEV > CV. The crosslink distribution narrowed during the curing process for the CV and SEV systems. Non-oxidative maturation reactions were advantageous in promoting a more random distribution of crosslinks in the polymer matrix. 相似文献