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排序方式: 共有698条查询结果,搜索用时 15 毫秒
691.
This work addresses the issue of radiation chemical synthesis of MnO2 nanoparticles and also illustrates the ease of formation of nanorods and sheets by adroit manipulation of experimental conditions. The radiation chemical yield (G-value) for reduction of Mn (VII) by the hydrated electron was found to be 0.27 μmol J−1 and 0.17 μmol J−1 respectively, when tert. butanol and isopropanol were used as scavengers in nitrogen-saturated solutions. The colloids formed upon irradiation of air-saturated solution and N2-purged solution with tert. butanol as scavenger were found to be most stable. Irradiation of air-saturated solution containing 4×10−4 M KMnO4 at a dose of 1692 Gy resulted in the formation of nanorods of the dimension 100–150 nm and nanospheres in the range 10–20 nm. Irradiation of N2-purged solution containing tert. butanol as scavenger for OH-produced reticulated structure of nanorods with length varying from 50 to 100 nm at a dose of 1692 Gy. Elemental analysis was performed using scanning electron microscope on MnO2 formed by reduction and oxidation and the purity was found to be 98% of elemental Mn content. 相似文献
692.
C. J. Kliewer A. Bohlin E. Nordström B. D. Patterson P.-E. Bengtsson T. B. Settersten 《Applied physics. B, Lasers and optics》2012,108(2):419-426
Time-resolved dual-broadband picosecond pure rotational CARS has been applied to measure self-broadened S-branch N2–N2 Raman linewidths in the temperature range 294–1466 K. The coherence decays were detected directly in the time domain by following the J-dependent CARS signal decay as a function of probe delay. The rotational Raman N2–N2 linewidths were derived from these time-dependent decays and evaluated for thermometric accuracy. Comparisons were made to the energy-corrected sudden (ECS) and modified exponential gap (MEG) dynamical scaling laws, and the results were used to quantify the sensitivity of nanosecond rotational CARS thermometry to the linewidth model employed. The uncertainty based on the linewidth model used in pure N2 was found to be 2 %. The merits and limitations of this rapid method for the determination of accurate Raman linewidths are discussed. 相似文献
693.
694.
El-Sayed M. Abdel-Aal Iwona Rabalski Lili Mats Ishan Rai 《Molecules (Basel, Switzerland)》2022,27(19)
Tea is the first most popular beverage worldwide and is available in several selections such as black (fully oxidized), Oolong (partially oxidized) and green (non-oxidized), in addition to purple tea, an emerging variety derived from the same tea plant (Camellia sinensis). This study investigated purple tea leaves (non-oxidized) and flakes (water extractable) to thoroughly identify their composition of anthocyanins and catechins and to study the effect of a water extraction process on their compositional properties in comparison with green tea. Anthocyanin and catechin compounds were separated and quantified using UPLC, and their identity was confirmed using LC-MS/MS in positive and negative ionization modes. Delphinidin was the principal anthocyaninidin in purple tea, while cyanidin came in second. The major anthocyanin pigments in purple tea were delphinidin-coumaroyl-hexoside followed by delphinidin-3-galactoside and cyanidin-coumaroyl-hexoside. The water extraction process resulted in substantial reductions in anthocyanins in purple tea flakes. There were no anthocyanin compounds detected in green tea samples. Both purple and green tea types were rich in catechins, with green tea containing higher concentrations than purple tea. The main catechin in purple or green tea was epigallocatechin gallate (EGCG) followed by either epicatechin gallate (ECG) or epigallocatechin (EGC), subject to tea type. The extraction process increased the concentration of catechins in both purple and green tea flakes. The results suggest that purple tea holds promise in making healthy brews, natural colorants and antioxidants and/or functional ingredients for beverages, cosmetics and healthcare industries due to its high content of anthocyanins and catechins. 相似文献
695.
696.
Nechepurenko I. V. Mainagashev I. Ya. Barabanov A. A. Sergeev S. A. Bukatov G. D. Zakharov V. A. Mats’ko M. A. Volcho K. P. Salakhutdinov N. F. 《Russian Journal of Applied Chemistry》2021,94(6):715-725
Russian Journal of Applied Chemistry - A procedure was developed for preparing 2,3-dialkyl-substituted succinates by condensation of a succinic acid diester with two isobutyraldehyde molecules,... 相似文献
697.
The microstructure and rheological behaviour of inhomogeneous biopolymer gels was studied using a model system of β-lactoglobulin. It can form both fine-stranded and particulate gels which can be homogeneous or inhomogeneous depending on pH and heating rate. The dense and loose regions of the fine-stranded gels had different relaxation times which significantly influenced the mechanical spectrum. The particulate gels showed coarser inhomogeneities influencing the fracture properties of the gels. 相似文献
698.