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991.
Two bacteria exhibiting resistance to toxic arsenic were isolated. These had been contaminated with arsenic in a Chlorella sp. culture medium containing arsenic. The two bacteria were identified as Klebsiella oxytoca and Xanthomonas sp., and grew well in a peptone medium at neutral pH at 30°C, reaching the stationary phase in ca 100h and 70h, respectively. The growth of the bacteria was not affected by arsenic(V) concentrations in the medium as high as 1000mg dm?3. The bacteria bioaccumulated arsenic, a part of the arsenic being methylated. The bioaccumulation exhibited its peak around the turing point from the log phase to the stationary phase. The relative content of methylated arsenic in the excrement was greater than that in the bacterial cells. Adaptation treatment of inorganic arsenic caused an increase in the bioaccumulation of inorganic arsenic by K. oxytoca. Such a situation was not observed in the case of Xanthomonas sp. The bacteria also bioaccumulated methylated arsenic compounds, and demethylation of these species was observed. When the bacteria were killed by ethanol, arsenic was not taken up by the cells. 相似文献
992.
993.
由于超导薄膜的表面阻抗Rs这一参量对超导微波元件的设计和开发有很重要意义,测量超导薄膜的表面阻抗Rs也就非常重要.目前国际上制定了高温超导薄膜在微波波段上表面阻抗Rs电特性的标准测量方案:IEC/TC90.此方案采用介质杆谐振器法测量表面阻抗的原理,使用蓝宝石介质杆和超导膜组成的谐振器法测量超导膜的Rs.本文分析了各个测量量对标准测量方案的测量精度,分析了在12GHz微波频率下,系统的各个实际部件的加工误差.认为频谱曲线的测量误差,即背景误差对最终测量结果Rs的影响是主要的. 相似文献
994.
Laser alloying was carried out on the surface of pure titanium substrate with TiN–B–Si–Ni mixed powders. The result of X-ray diffraction (XRD) analysis shows that the alloyed layer consists of many kinds of intermetallic compounds. The test results show that the alloyed layers have high microhardness (1500–1600 HV0.1), low friction coefficient (about 0.4), and are more resistant to oxidation than untreated substrate. 相似文献
995.
Yu Li Hui Bin Zhang Wen Long Huang Xia Zhen Yun Man Li 《中国化学快报》2008,19(2):169-171
Tetrahydroisoquinoline derivatives were synthesized and their multidrug resistance reversal activities were evaluated in vitro. The results showed that some of the synthetic compounds had higher multidrug resistance (MDR) reversal activities than verapamil. 相似文献
996.
997.
在分析传统的压控振荡器的基础上,针对微机电系统(microelectromechanical systems,MEMS)可变电容小尺寸、低功耗、高Q值等特点,设计了一种新型的基于高Q值的MEMS可变电容的压控振荡器.通过标准对称式的负阻抗LC振荡电路验证:当调谐电压从0~5V变化时,振荡器频率在2.320~2.430GHz之间呈均匀变化,提高了测量精确性;同时,其宽频带调谐范围从传统的振荡器的2%~3%提高到了4.58%,扩大了使用范围. 相似文献
998.
999.
粒径为0.02~10μm的半导体氧化锡粉末在真空中充分脱气和施加高于40MPa压力可获得重现性较好的直流电阻。无锑掺杂氧化锡粉末的直流电阻随试样冷却吸附的温度而异,讨论了多晶氧化锡粉末的结构对电阻测定的影响。 相似文献
1000.
By considering the now in a slider bearing to be a nearly viscometric flow we have examined the effects of variation in viscosity,
and normal stress differences on the total resistance and total normal force. We have found that under certain conditions
the normal stress differences may be neglected compared with the variation in viscosity. We have found that the effects of
variation in viscosity are to reduce the total resistance, and to increase or decrease the total normal force depending on
the ratio of the thickness of the liquid at the entry and exit. 相似文献