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排序方式: 共有822条查询结果,搜索用时 15 毫秒
141.
在考虑了泵浦损耗及激光损耗的情况下,解析求解了阈值泵浦下的三能级光纤激光器速率方程组,获得了泵浦功率阈值的显函数解析表达式,泵浦功率沿光纤变化的隐函数表达式,以及用功率变化表示的各个能级的粒子数密度随位置变化的显函数表达式。并利用这些表达式对光纤激光器的阈值特性进行了研究,研究表明:泵浦功率阈值随泵浦损耗系数增大而增大;激光上能级粒子数密度随归一化位置呈下降趋势,而下能级粒子数密度的变化与此相反;泵浦功率阈值越大(光纤长度越长),净增益系数随归一位置下降就越快。所获得的结果适用于单包层和双包层光纤激光器。 相似文献
142.
Jacques-Aurlien Sergent Hilarion Mathouet Christian Hulen Pedro Lameiras Marc Feuilloley Abdelhakim Elomri Nour-Eddine Lomri 《Molecules (Basel, Switzerland)》2022,27(9)
To develop new therapeutic molecules, it is essential to understand the biological effects and targets of clinically relevant compounds. In this article, we describe the extraction and characterization of two alkaloids from the roots of Isolona hexaloba—curine and guattegaumerine. The effect of these alkaloids on the multidrug efflux pump ABCB1 (MDR1/P-Glycoprotein) and their antiproliferative properties were studied. Compared to verapamil, a widely used inhibitor of P-gp, curine and guattegaumerine were found to be weak inhibitors of MDR1/P-Glycoprotein. The highest inhibition of efflux produced by verapamil disappeared in the presence of curine or guattegaumerine as competitors, and the most pronounced effect was achieved with curine. Altogether, this work has provided new insights into the biological effects of these alkaloids on the rat Mdr1b P-gp efflux mechanism and would be beneficial in the design of potent P-gp inhibitors. 相似文献
143.
本文选择RANS方程和RNG k-ε湍流模型,采用有限体积法,在假定流动定常的前提下对离心泵中叶片与蜗舌不同相对位置时的流场进行数值模拟,总结分析了各性能参数的计算误差在不同的相对位置时的变化规律.通过叶片与蜗舌不同相对位置时对各性能参数计算误差的均方差进行比较,认为存在一个合适的相对位置使得对各性能参数的总体预测精度保持最高,为数值方法分析离心泵的性能提供了指导. 相似文献
144.
The energy loss of the multi-stage centrifugal pump was investigated by numerical analysis using the entropy generation method with the RNG k-ε turbulence model. Entropy generation due to time-averaged motion and velocity fluctuation was mainly considered. It was found that the entropy generation of guide vanes and impellers account for 71.2% and 23.3% of the total entropy generation under the designed flow condition. The guide vanes are the main hydraulic loss domains and their entropy generation is about 9 W/K, followed by impellers. There are vortices at the tongue of the guide vane inlet as well as flow separations in the impellers, which lead to entropy generation. The fluid impacts the outer surface of the guide vanes, resulting in the increase in entropy generation. There are refluxes near the guide vane tongues which also increase the entropy generation of this part. The entropy generation distribution of the guide vanes and impellers was investigated, which found that the positive guide vane has more entropy generation compared with the reverse guide. The entropy generation of the blade suction surface is higher compared with the pressure surface. This study indicated that the entropy generation method has distinct advantages in the assessment of hydraulic loss. 相似文献
145.
基于对电渗泵中压强产生原理的讨论, 对新兴的复杂串、并联电渗泵系统的流体输液特征加以研究. 在多级串联电渗泵系统中, 可以通过增加电渗泵的级数或操作电压来提高泵系统产生的压强, 但是单一流路的输液能力有限. 而在多级并联电渗泵系统中, 输液量也可以通过增加电渗泵的级数或操作电压得到提高. 在这一体系中, 尽管输液量的叠加有利于其在更为广泛的领域中应用, 但是因Joule热产生的电场强度与电渗流速度线性关系的偏离也使得其线性范围变小, 不利于操作条件的控制. 相似文献
146.
采用流动控制沉积法,通过调控泵速和聚甲基丙烯酸甲酯(PMMA)胶体微球溶液的浓度,制备出微球排列高度有序且薄膜紧密附着于基底的高质量光子晶体薄膜。获得了制备高质量PMMA光子晶体薄膜的组装条件范围,发现在该条件范围内,当泵速或胶体微球溶液浓度一定时,PMMA光子晶体薄膜的厚度随胶体微球溶液浓度的增加或泵速的降低而增加。研究了组装条件对PMMA光子晶体薄膜光学性能的影响,发现光子禁带位置随光子晶体薄膜厚度增加或减少而红移或蓝移。在此基础上,控制组装条件得到了不同尺寸微球堆叠而成的叠层光子晶体薄膜,并研究了其光学性能的变化规律。结果显示,叠层光子晶体薄膜的光子禁带峰为各层叠层光子晶体禁带峰的简单叠加,且峰强度受光入射角方向影响。 相似文献
147.
Dedieu Luc Brunel Jean Michel Lorenzi Vanina Muselli Alain Berti Liliane Bolla Jean Michel 《Molecules (Basel, Switzerland)》2020,25(22)
Today, an alarming rise of bacterial gastroenteritis in humans resulting from consuming Campylobacter-tainted foods is being observed. One of the solutions for mitigating this issue may be the antibacterial activity of essential oils. In the present research, we propose to study the antibacterial activity against Campylobacter and other Gram-negative bacteria of Daucus carota essential oil and its active molecules. In addition, a few chemically synthesized molecules such as (E)-methylisoeugenol, Elemicin, and eugenol were also studied. The results showed that the essential oil itself and its most active component, (E)-methylisoeugenol, exhibited bactericidal effects. Similar effects were detected using purified and chemically synthesized molecules. Also, it was observed that the Daucus carota essential oil and its active molecules affected intracellular potassium and intracellular ATP contents in Campylobacter cells. Inhibition of the membrane bound FOF1-ATPase was also observed. Eventually, for the first time, the efflux mechanism of active molecules of Daucus carota essential oil was also identified in gamma proteobacteria and its specific antibacterial activity against Campylobacter jejuni was associated with the lack of this efflux mechanism in this species. 相似文献
148.
用染料激光和氙灯泵浦实现了NdS-FAP晶体低阈值、高效率的1.328μmm激光运转。在透过率7%的平-平腔情况下,染料激光泵浦斜效率为38%,阈值4.5mJ,倍频红光波长为0.664μm,线宽1.3nm;采用氙灯泵浦(4×30mm),实现了1.328μm自由运转,阈值为240mJ,斜效率为0.85%。测量了不同腔长,不同透过率情况的输出能量、光束发散角和偏振特性等。 相似文献
149.
150.
报道有一个3W激光二极管端面泵浦Nd:LMA激光器,实验采用三镜折迭像散补偿腔。在1054nm波长,激光器连续输出功率达620mW,斜率效率为50%,光-光转换效率20%,在1083nm波长处,激光器连续输出功率为64mW,斜率效率为6%,光转换效率2.1%。 相似文献