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排序方式: 共有512条查询结果,搜索用时 609 毫秒
91.
Hanisch M Mačković M Taccardi N Spiecker E Klupp Taylor RN 《Chemical communications (Cambridge, England)》2012,48(36):4287-4289
Here we report that silver nanoparticle necklaces can be readily formed by treatment of colloidal silica with ammoniacal silver complex solution followed by washing, deposition and ageing. We investigate the morphology of the produced materials and elucidate the key variables that influence this promising new approach to one-dimensional nanostructuring. 相似文献
92.
Eleonora Erdmann Marcos L. Dias Victor J. R. R. Pita Hugo Destéfanis Fernanda Monasterio Delicia Acosta 《Macromolecular Symposia》2007,258(1):82-89
Summary: Preparation and morphology of high density polyethylene (HDPE)/ polyamide 6 (PA 6)/modified clay nanocomposites were studied. The ability of PA 6 in dispersing clays was used to prepare modified delaminated clays, which were then mixed with HDPE. Mixing was performed using melt processing in a torque rheometer equipped with roller rotors. After etching the materials with boiling toluene and formic acid at room temperature, the morphology was examined by SEM analyses, showing that the PA 6 formed the continuous phase and HDPE the dispersed phase. X-ray diffraction patterns show that the (001) peak of the clay is dramatically decreased and shifted to lower angles, indicating that intercalated/exfoliated nanocomposites are obtained. TEM analyses confirmed the typical structure of exfoliated nanocomposites. A scheme for the mechanism of exfoliation and/or intercalation of these HDPE /PA 6/ /organoclay nanocomposites is proposed. 相似文献
93.
Melanie Egli Alicia Hartmann Helena Rapp Wright Keng Tiong Ng Frdric B. Piel Leon P. Barron 《Molecules (Basel, Switzerland)》2021,26(18)
The rapid source identification and environmental risk assessment (ERA) of hundreds of chemicals of emerging concern (CECs) in river water represent a significant analytical challenge. Herein, a potential solution involving a rapid direct-injection liquid chromatography–tandem mass spectrometry method for the quantitative determination of 102 CECs (151 qualitatively) in river water is presented and applied across six rivers in Germany and Switzerland at high spatial resolution. The method required an injection volume of only 10 µL of filtered sample, with a runtime of 5.5 min including re-equilibration with >10 datapoints per peak per transition (mostly 2 per compound), and 36 stable isotope-labelled standards. Performance was excellent from the low ng/L to µg/L concentration level, with 260 injections possible in any 24 h period. The method was applied in three separate campaigns focusing on the ERA of rivers impacted by wastewater effluent discharges (1 urban area in the Basel city region with 4 rivers, as well as 1 semi-rural and 1 rural area, each focusing on 1 river). Between 25 and 40 compounds were quantified directly in each campaign, and in all cases small tributary rivers showed higher CEC concentrations (e.g., up to ~4000 ng/L in total in the R. Schwarzach, Bavaria, Germany). The source of selected CECs could also be identified and differentiated from other sources at pre- and post- wastewater treatment plant effluent discharge points, as well as the effect of dilution downstream, which occurred over very short distances in all cases. Lastly, ERA for 41 CECs was performed at specific impacted sites, with risk quotients (RQs) at 1 or more sites estimated as high risk (RQ > 10) for 1 pharmaceutical (diclofenac), medium risk (RQ of 1–10) for 3 CECs (carbamazepine, venlafaxine, and sulfamethoxazole), and low risk (RQ = 0.1–1.0) for 7 CECs (i.e., RQ > 0.1 for 11 CECs in total). The application of high-throughput methods like this could enable a better understanding of the risks of CECs, especially in low flow/volume tributary rivers at scale and with high resolution. 相似文献
94.
Tobias Weissenberger Rainer Leonhardt Dr. Benjamin Apeleo Zubiri Dr. Martina Pitínová-Štekrová Dr. Thomas L. Sheppard Bastian Reiprich Dr. Jürgen Bauer Dr. Ralf Dotzel Maik Kahnt Dr. Andreas Schropp Prof. Christian G. Schroer Prof. Jan-Dierk Grunwaldt Dr. John L. Casci Prof. Jiří Čejka Prof. Erdmann Spiecker Prof. Wilhelm Schwieger 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(63):14430-14440
The successful synthesis of hierarchically structured titanium silicalite-1 (TS-1) with large intracrystalline macropores by steam-assisted crystallisation of mesoporous silica particles is reported. The macropore topology was imaged in 3D by using electron tomography and synchrotron radiation-based ptychographic X-ray computed tomography, revealing interconnected macropores within the crystals accounting for about 30 % of the particle volume. The study of the macropore formation mechanism revealed that the mesoporous silica particles act as a sacrificial macropore template during the synthesis. Silicon-to-titanium ratio of the macroporous TS-1 samples was successfully tuned from 100 to 44. The hierarchically structured TS-1 exhibited high activity in the liquid phase epoxidation of 2-octene with hydrogen peroxide. The hierarchically structured TS-1 surpassed a conventional nano-sized TS-1 sample in terms of alkene conversion and showed comparable selectivity to the epoxide. The flexible synthesis route described here can be used to prepare hierarchical zeolites with improved mass transport properties for other selective oxidation reactions. 相似文献
95.
H. Erdmann und P. Köthner 《Fresenius' Journal of Analytical Chemistry》1905,44(10):632-633
Ohne Zusammenfassung 相似文献
96.
97.
Karin Erdmann 《manuscripta mathematica》1995,88(1):357-386
LetK be an algebraically closed field of characteristic,p>0 and letD
λ be the simple modules of the symmetric groupS
r
overK where λ is a p-regular partition ofr. The dimensions ofD
λ for λ with at mostn parts are the same as the multiplicities of direct summands ofD
⊗r
whereE is the natural module for the groupGL
n
(K). Whenn=2 we determine generating functions for these multiplicities and hence for the dimensions ofD
λ for all partitions λ with two parts. These can be expressed as rational functions of Chebyshev polynomials; and we obtain
explicit formulae for the coefficients. 相似文献
98.
99.
100.
H. Erdmann 《Fresenius' Journal of Analytical Chemistry》1905,44(2):139-140
Ohne Zusammenfassung 相似文献