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1.
The effect of ultrasonic irradiation (45KHz at 25°C) on the solvolysis of -butyl chloride in aqueous ethanol, -propanol and -butanol is (1) to increase the rate constants in the more alcoholic media and (2) to reduce the m values of these reactions. 相似文献
2.
The Ramsey numbers r(m1Kp, …, mcK) are calculated to within bounds which are independent of m1, …, mc when c > 2 and p1, …, pc > 2. 相似文献
3.
The generation of HO radicals by acoustic cavitation in water was monitored by their reaction with terephthalic acid (TA) anion to produce fluorescent hydroxyterephthalate ions using a cleaning bath (38kHz) and a probe system (20, 40 and 60 kHz) as different sources of ultrasound. When using the ultrasonic bath as a source of energy for sonochemical studies, the shape of the reaction vessel is important. In the case of HO production from water (50 cm3), reaction in a conical flask (100 cm3) produces 2.75 times more radicals than a round-bottomed flask of the same capacity. The fluorescence yield (fluorescence intensity/ultrasound dosage) obtained using the conical flask and ultrasonic bath was similar to that for a probe operating at 40 kHz on the same volume of solution. For a probe system operating at 20, 40 and 60 kHz the greatest sonochemical efficiency was attained at the highest of these frequencies (60 kHz). For the probe system the fluorescence yield is directly proportional to power input and the concentration of TA. The fluorescence yield decreases as the temperature is increased. 相似文献
4.
Potential for the use of ultrasound in the extraction of antioxidants from Rosmarinus officinalis for the food and pharmaceutical industry 总被引:7,自引:0,他引:7
Ultrasound was used to increase the extraction efficiency of carnosic acid from the herb Rosmarinus officinalis using butanone, ethyl acetate and ethanol as solvents. Both dried and fresh leaves of the herb were extracted and, when performed at the same temperature, sonication improved the yields of carnosic acid for all three solvents and shortened the extraction times. Sonication also reduced the solvent effect so that ethanol, which is a poor solvent under conventional conditions, reached a similar level of extraction efficiency to the other two when sonicated. The extraction of dried herb with ethanol proved to be more efficient than that of fresh material, probably due to the water present in the latter. 相似文献
5.
6.
J. P. Lorimer T. J. Mason D. Kershaw I. Livsey R. Templeton-Knight 《Colloid and polymer science》1991,269(4):392-397
In this paper we describe the effect of 20 kHz power ultrasound on the encapsulation of titanium dioxide pigment with poly (methyl methacrylate) in an otherwise conventional emulsion-polymerisation process. In all instances, sonication of the reaction during the mixing period led to an improvement in the extent and uniformity of the coverage of the pigment. Low-power ultrasound produced a more uniform coverage than high-power ultrasound, but the latter provided greater particle dispersion. 相似文献
7.
William S. Lorimer und Edgar F. Smith 《Fresenius' Journal of Analytical Chemistry》1893,32(1):127-128
Ohne Zusammenfassung 相似文献
8.
Some recent studies at Coventry University sonochemistry centre 总被引:1,自引:0,他引:1
Three main areas of research at Coventry University are discussed: the uses of power ultrasound in polymer science (for both synthesis and degradation) and its effects on catalytic reactivity and radical production in solution. 相似文献
9.
10.
Peter Lorimer 《Journal of Graph Theory》1984,8(1):55-68
Let G be a group acting symmetrically on a graph Σ, let G1 be a subgroup of G minimal among those that act symmetrically on Σ, and let G2 be a subgroup of G1 maximal among those normal subgroups of G1 which contain no member except 1 which fixes a vertex of Σ. The most precise result of this paper is that if Σ has prime valency p, then either Σ is a bipartite graph or G2 acts regularly on Σ or G1 | G2 is a simple group which acts symmetrically on a graph of valency p which can be constructed from Σ and does not have more vertices than Σ. The results on vertex-transitive groups necessary to establish results like this are also included. 相似文献