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排序方式: 共有1733条查询结果,搜索用时 15 毫秒
1.
Hongwei Hao Minsheng Wu Yifang Chen Jiaowen Tang Qingyu Wu 《Colloids and surfaces. B, Biointerfaces》2004,33(3-4):151-156
To prevent cyanobacterial bloom in eutrophic water by ultrasonic method, ultrasonic irradiations with different parameters were tested to inhibit Spirulina platensis from growth. The experimental result based on cyanobacterial growth, chlorophyll a and photosynthetic activity showed that, the ultrasonic irradiation inhibited cyanobacterial proliferation effectively, furthermore the inhibition effectiveness increased in the order: 200 kHz>1.7 MHz>20 kHz and became saturated with the increased power. The inhibition mechanism can be mainly attributed to the mechanical damage to the cell structures caused by ultrasonic cavitation, which was confirmed by light microscopy and differential interference microscopy. The optimal frequency of 200 kHz in cavition and sonochemistry was also most effective in cyanobacterial growth inhibition. The higher frequency of 1.7 MHz is weaker than 20 kHz in cavitation, but has more effective inhibition because it is nearer to the resonance frequency of gas vesicle. The inhibition saturation with ultrasonic power was due to the ultrasonic attenuation induced by the acoustic shielding of bubbles enclosing the radiate surface of transducer. 相似文献
2.
A. Pompei 《Applied Acoustics》2006,67(5):420-431
In the present paper, we simulate focused wave fields generated by a system of plane transducers used in an immersion ultrasonic technique. The ultrasonic beam penetrates into the elastic medium through the fluid-solid boundary. A real-time computer algorithm is proposed to calculate stress components in the solid medium. It is shown that a good focusing wave structure can be provided by a pair of plane rectangular transducers, inclined with respect to each other and to the beam acoustic axis. 相似文献
3.
IMPROVED PROPERTIES OF METALLOCENE-CATALYZED LINEAR LOW-DENSITY POLYETHYLENE/POLYPROPYLENE BLENDS DURING ULTRASONIC EXTRUSION 总被引:1,自引:0,他引:1
Hong Wu Shao-yun Guo 《高分子科学》2007,(4):357-364
Metallocene-catalyzed linear low-density polyethylene/polypropylene (mLLDPE/PP) blends were prepared by ultrasonic extrusion in this work. Their extrusion processing behaviors were estimated by online measured data, such as the die pressure and flow rate. Crystallization and mechanical properties of the blends were also investigated. The results show that the addition of PP improves the processing behaviors of mLLDPE, but has little effect on its mechanical properties. On the other hand, the addition of mLLDPE improves the impact strength of PP, but has little effect on its processing behavior. The processing behaviors and mechanical properties of mLLDPE/PP blends get further improved due to the presence of ultrasonic oscillation during extrusion. Compared with PP-rich blends, the apparent viscosity drop of mLLDPE-rich blends is more sensitive to ultrasonic oscillation. The ultrasonic oscillation affects the crystal nucleation, while barely the other crystalline behaviors of the blends. 相似文献
4.
GC-MS法测定焦化厂气溶胶中多环芳烃 总被引:2,自引:0,他引:2
利用气相色谱-质谱(GC-MS),电子轰击离子化(EI)法测定焦化厂气溶胶中多环芳烃的含量。超声波抽提气溶胶样品,用GC-MS的选择离子监测(SIM)方式测定EPA提出的优先监测的16种多环芳烃的含量。该法的检出限为0.167pg·m~(-3),PAHs的回收率为85.1%~110.5%,相对标准偏差为4.62%~19.4%。应用该法测定气溶胶中PAHs获得满意的结果。 相似文献
5.
Summary High-molecular-weight sodium hyaluronate isolated from rooster combs was degraded by ultrasonication. The molecular weight of hyaluronate and its polydispersity was determined by gel-permeation chromatography. During 75-min treatment the molecular weight value decreased from 1.39×106 Da to 2.25×105 Da while the polydispersity of the molecular weight increased from 1.29 to 2.36. The reciprocal value of the square of the hyaluronate's molecular weight was linearly proportional to the time of ultrasonication. 相似文献
6.
Summary A high molecular weight sodium hyaluronate isolated from rooster combs was degraded by ultrasonication. High-performance size exclusion chromatography allowed rapid and accurate determination of molecular weight parameters (Mz, Mw, Mn) and distributions. The time dependence of hyaluronan ultrasonication to the molecular characteristics of the polymer was investigated. A non-random nature of the degradation process was demonstrated and the reciprocal Mn value was found to be linearly proportional to the time of ultrasonication. 相似文献
7.
羧甲基纤维素系列高分子表面活性剂超声合成的研究 总被引:27,自引:2,他引:27
研究了在超声波作用下羧甲基纤维素的降解反应及CMC与具有不同亲水亲油比值的活性大单体「烷基醇(酚)聚氧乙烯醚丙烯酸酯及第三单体」的超声共聚反应。经萃取提纯的共聚产物用IR,^13C NMR和UV等方法进行表证,证实通过超声反应制得了二元和三元共聚物。 相似文献
8.
G.A. Groß 《Thermochimica Acta》2005,432(2):229-240
A silicon chip device with two types of integrated platinum thin film resistors was applied for microcaloric measurements. It was shown that the device is capable of fast characterization of liquid evaporation behaviour and allows the determination of evaporation enthalpies for pure liquids and mixtures. The applicability was demonstrated for a wide range of solvents from nonpolar aliphatic solvents over polar organics to protic solvents (e.g. iso-octane, toluene, acetone, ethanol, methanol and water). The sample volumes were in the range of about 2-5 μL. The determination of transient times, in case of constant power mode, or the power integral over time was used for the fast estimation of binary liquid mixtures. Thermo-resistive measurements of 5 μL droplets of solvent mixtures like methanol/iso-propanol, ethanol/water, iso-octane/iso-propanol and iso-octane/1,4-dioxane showed significant changes in temperature characteristics and evaporation enthalpies in dependence on composition. The applied heating power was about 1 W, which corresponds to measurement times between a few seconds and a minute. 相似文献
9.
10.
人参中总皂甙的超声波快速提取方法研究 总被引:7,自引:0,他引:7
建立了人参中总皂甙超声波半微量快速提取方法,与索氏提取法相比,此法提取时间由索氏法的1-2个工作日缩短到30min,节省大量试剂,综合提取效率提高数十倍,与索氏提取法对照分析表明,此法可完全满足人参中总皂甙的快速测定要求。 相似文献