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61.
利用原子力显微镜技术(AFM),系统地研究了由乙醇与多价离子(hexammine cobalt(Ⅲ)[Co(NH3)36+])协同作用导致的λ-DNA凝聚现象.单独测得3价Co(NH3)36+的临界凝聚浓度大约是10μmol·L-1,乙醇的临界凝聚体积分数大约是15%.若3价离子[Co(NH3)36+]的浓度大于400μmol·L-1时,可以观察到DNA的解凝聚现象.在DNA溶液中同时加入乙醇(体积分数12%)与Co(NH3)36+(8μmol.L-1),当其浓度各低于其临界值,也可观察到凝聚现象,说明乙醇与Co(NH3)36+对DNA的凝聚有协同作用,而且在协同作用下,可以观察到典型的圆环结构(toroids).利用电荷逆转与离子释放机制分析了观察到的解凝聚现象. 相似文献
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64.
We report the preparation of Pt–CeO2 nanoparticles on the multi-walled carbon nanotubes (MWNTs) by a reverse micellar method. Transmission electron microscopy
(TEM) analysis indicated that well-dispersed small Pt–CeO2 nanoparticles were formed on the MWCNTs. X-ray diffraction (XRD) analysis confirmed the formation of the Pt–CeO2 nanoparticles on the MWNTs. Cyclic voltammetry (CV) results demonstrated that the Pt–CeO2/MWNT exhibited a higher methanol oxidation than did the Pt/MWNT catalyst. The CO stripping test showed that CeO2 can make CO stripped at a lower potential, which is helpful for CO and methanol electro-oxidation. 相似文献
65.
采用分子动力学方法系统地研究了从常温常压到超临界状态乙醇的热力学性质、结构性质和动力学性质.模拟发现随着温度的升高,体系焓值增大,乙醇分子间的氢键作用减弱,自扩散系数增大;随着压强的增大,乙醇分子间的氢键作用增强,自扩散系数减小;乙醇自扩散系数在液相区随温度变化不明显,在气相区随压强增大很快减小,超临界区乙醇的自扩散系数比液相区大十几倍.温度和压强对乙醇自扩散系数的影响可通过密度来体现.与常温常压相比,超临界条件下的乙醇体系因密度涨落存在分子聚集现象,且在低密度区域更显著;乙醇分子间的氢键作用明显减弱,结 相似文献
66.
One step NaBH reduction of Pt-Ru-Ni catalysts on different types of carbon supports for direct ethanol fuel cells: Synthesis characterization 《燃料化学学报》2017,45(5):596-607
The ternary catalyst Pt75Ru5Ni20 was conducted on various types of carbon supports including functionalized Vulcan XC-72R (f-CB), functionalized multi-walled carbon nanotubes (f-MWCNT), and mesoporous carbon (PC-Zn-succinic) by sodium borohydride chemical reduction method to improve the ethanol electrooxidation reaction (EOR) for direct ethanol fuel cell (DEFC). It was found that the particle size of the metals on f-MWCNT was 5.20 nm with good particle dispersion. The alloy formation of ternary catalyst was confirmed by XRD and more clearly described by SEM element mapping, which was relevant to the efficiency of the catalysts. Moreover, the mechanism of ethanol electrooxidation reaction based on the surface reaction was more understanding. The activity and stability for ethanol electrooxidation reaction (EOR) were investigated using cyclic voltammetry and chronoamperometry, respectively. The highest activity and stability for EOR were observed from Pt75Ru5Ni20/f-MWCNT due to a good metal-carbon interaction. Ru and Ni presented in Pt-Ru-Ni alloy improved the activity and stability of ternary catalysts for EOR. Moreover, the reduction of Pt content in ternary catalyst led to the catalyst cost deduction in DEFC. 相似文献
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68.
Ngoc Q. Bui Pascal Fongarland Franck Rataboul Cyril Dartiguelongue Nadège Charon Christophe Vallee Nadine Essayem 《Comptes Rendus Chimie》2018,21(6):555-562
The objective of this work was to investigate the ability of supercritical (SC) ethanol conditions to attack preferentially the lignin fraction against the carbohydrate fraction and their effects on the product distribution among gases, light products, bio-oils, and chars. In this study, the conversion of each pinewood component was determined by the analysis of solid residues to quantify cellulose, hemicellulose, lignin, and char contents. It is shown that, by tuning the temperature, hemicellulose and lignin are already transformed in subcritical ethanol conditions, lignin being more reactive than hemicellulose. In contrast, native wood cellulose is recalcitrant to liquefaction in SC ethanol near the critical point (Tc = 241 °C and Pc = 61 bar), but 20% of native wood cellulose is converted in SC ethanol at 280 °C. Besides, the severity of the conditions, in terms of temperature and treatment time, does not significantly influence the yields of gases, light products, and bio-oils but strongly enhances char formation. Interestingly, the increase in SC ethanol density does not change the conversion of biomass components but has a marked effect on bio-oil yield and prevents char formation. The optimum fractionation conditions to convert the lignin component, while keeping unattacked the cellulose fraction with a minimum formation of char, are dense SC ethanol, at 250 °C for 1 h, in batch conditions. However, although lignin is more reactive than hemicellulose under these conditions, these fractions are converted, in a parallel way, to around 50% and 60%, respectively. 相似文献
69.
The catalytic role of various inert solid supports on acceleration of alcohol fermentation by Saccharomyces cerevisiae was investigated. The enhanced rate of alcohol production was dependent on the nature of the support as well as on the amount
used. Among all the tested supports, chitosan flakes showed the maximum yield of alcohol (93% of theoretical yield). This
higher rate of alcohol production was associated with the twofold increase in the activity of alcohol dehydrogenase over control.
Our results suggest that the addition of a small fraction of solids in submerged fermentations to facilitate cell anchorage
for enhanced metabolic activity is easier and more economical compared to cell immobilization processes.
IICT Communication No. 4266. Some of the results in this article are covered under a patent. 相似文献
70.
A.P. Farkas 《Surface science》2007,601(1):193-200
The adsorption, desorption and dissociation of ethanol have been investigated by work function, thermal desorption (TPD) and high resolution electron energy loss (HREELS) spectroscopic measurements on Mo2C/Mo(1 0 0). Adsorption of ethanol on this sample at 100 K led to a work function decrease suggesting that the adsorbed layer has a positive outward dipole moment By means of TPD we distinguished three adsorption states, condensed layer with a Tp = 162 K, chemisorbed ethanol with Tp = 346 K and irreversibly bonded species which decomposes to different compounds. These are hydrogen, acetaldehyde, methane, ethylene and CO. From the comparison of the Tp values with those obtained following their adsorption on Mo2C it was inferred that the desorption of methane and ethylene is reaction limited, while that of hydrogen is desorption limited process. HREEL spectra obtained at 100 K indicated that at lower exposure ethanol undergoes dissociation to give ethoxy species, whereas at high exposure molecularly adsorbed ethanol also exists on the surface. Analysis of the spectral changes in HREELS observed for annealed surface assisted to ascertain the reaction pathways of the decomposition of adsorbed ethanol. 相似文献