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51.
M S Roos R E Apfel S C Wardlaw 《The Journal of the Acoustical Society of America》1988,83(4):1639-1644
A technique for simultaneously measuring the scattering amplitude of individual particles at two angles is applied to human red blood cells. Using a Rayleigh scattering model, the density and compressibility of the cells may be determined given a priori knowledge of their volume. A calibration method relying on measurements of the bulk properties of particle suspensions is described. Red cell properties in hypotonic and hypertonic hosts are compared with a homogeneous mixture model, and a linear relation between hemoglobin content and scattering amplitude at a 90 deg scattering angle is established. 相似文献
52.
Thresholds for cavitation produced in water by pulsed ultrasound 总被引:1,自引:0,他引:1
A A Atchley L A Frizzell R E Apfel C K Holland S Madanshetty R A Roy 《Ultrasonics》1988,26(5):280-285
The threshold for transient cavitation produced in water by pulsed ultrasound was measured as a function of pulse duration and pulse repetition frequency at both 0.98 and 2.30 MHz. The cavitation events were detected with a passive acoustic technique which relies upon the scattering of the irradiation field by the bubble clouds associated with the events. The results indicate that the threshold is independent of pulse duration and acoustic frequency for pulses longer than approximately 10 acoustic cycles. The threshold increases for shorter pulses. The cavitation events are likely to be associated with bubble clouds rather than single bubbles. 相似文献
53.
Xiaojun Guo Ni Wang Xialiang Li Zongyao Zhang Jianping Zhao Wanjie Ren Shuping Ding Gelun Xu Jianfeng Li Ulf‐Peter Apfel Wei Zhang Rui Cao 《Angewandte Chemie (International ed. in English)》2020,59(23):8941-8946
Several H?H bond forming pathways have been proposed for the hydrogen evolution reaction (HER). Revealing these HER mechanisms is of fundamental importance for the rational design of catalysts and is also extremely challenging. Now, an unparalleled example of switching between homolytic and heterolytic HER mechanisms is reported. Three nickel(II) porphyrins were designed and synthesized with distinct steric effects by introducing bulky amido moieties to ortho‐ or para‐positions of the meso‐phenyl groups. These porphyrins exhibited different catalytic HER behaviors. For these Ni porphyrins, although their 1e‐reduced forms are active to reduce trifluoroacetic acid, the resulting Ni hydrides (depending on the steric effects of porphyrin rings) have different pathways to make H2. Understanding HER processes, especially controllable switching between homolytic and heterolytic H?H bond formation pathways through molecular engineering, is unprecedented in electrocatalysis. 相似文献
54.
Ratnadip De Sabrina Gonglach Shounik Paul Michael Haas S. S. Sreejith Philipp Gerschel Ulf‐Peter Apfel Thanh Huyen Vuong Jabor Rabeah Soumyajit Roy Wolfgang Schfberger 《Angewandte Chemie (International ed. in English)》2020,59(26):10527-10534
The controlled electrochemical reduction of carbon dioxide to value added chemicals is an important strategy in terms of renewable energy technologies. Therefore, the development of efficient and stable catalysts in an aqueous environment is of great importance. In this context, we focused on synthesizing and studying a molecular MnIII‐corrole complex, which is modified on the three meso‐positions with polyethylene glycol moieties for direct and selective production of acetic acid from CO2. Electrochemical reduction of MnIII leads to an electroactive MnII species, which binds CO2 and stabilizes the reduced intermediates. This catalyst allows to electrochemically reduce CO2 to acetic acid in a moderate acidic aqueous medium (pH 6) with a selectivity of 63 % and a turn over frequency (TOF) of 8.25 h?1, when immobilized on a carbon paper (CP) electrode. In terms of high selectivity towards acetate, we propose the formation and reduction of an oxalate type intermediate, stabilized at the MnIII‐corrole center. 相似文献