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961.
The influence of the pump pulse, group-velocity mismatch, dispersion and self-phase modulation & cross phase modulation on the phase transfer in the OPA process were analyzed. The results show that very sharp phase modulation can be maintained in mid infrared range by optical parametric amplifier. The period and depth of the periodic modulation can also be maintained due to small group-velocity mismatching in the calculated wavelength range.  相似文献   
962.
Four ofloxacin derivatives 3, 5, 6 , and 11 were found to exhibit > 90% inhibition on the growth of M. tuberculosis at a concentration of 6.25 μg/mL. Compounds 3, 5 and 11 have also exhibited a broad spectrum of antibacterial activities while 8‐fluoro‐3‐methyl‐9‐[4‐(4‐nitrophenylsulfonyl)piperazin‐1‐yl)‐6‐oxo‐2,3‐dihydro‐6H‐1‐oxo‐3a‐azaphenalene‐5‐carboxylic acid ( 6 ), which exhibited potent activity against the growth of TB with the MIC of 2.23 μg/mL and a selectivity index (SI) of > 14.80, was inactive against the growth of G(+)‐ and G(‐)‐bacteria. Selective anti‐TB activity was achieved by the introduction of an arylsulfonyl group at C‐7 piperazin‐4‐yl of N‐demethyl ofloxacin. Compound 6 is species‐specific, exhibiting no significant activity against the growth of bacterial species other than M. tuberculosis, which implied the possibility of developing new specific anti‐TB drug candidates without inducing cross resistance with other currently used antibacterial drugs. Structural optimization of 6 is on‐going.  相似文献   
963.
The formation and growth of δ' particles in an alloy of Al-7.87at% Li have been investigated using the small angle x-ray scattering technique. It has been shown that a transition zone, which exists between the δ' phase and the matrix after ageing for 16 h, disappears after ageing for 32 h. The existence of a transition zone indicates that the δ' phase is precipitated in the process of spinodal decomposition. This result also indicates that the growth of δ' particles should be divided into two stages. During the first stage, the δ' phase increases eating up the transition zone before ageing for 32 h, and in the second stage it grows by swallowing up each other after ageing for 32 h. In the latter stage, the larger and smaller δ' particles can coexist in the alloy.  相似文献   
964.
李希曾  苏保霞  柴路 《中国物理》2004,13(12):2058-2063
It is found that the two-mode output quantum electromagnetic field in two-mode squeezed states exhibits higherorder squeezing to all even orders, and the degree of higher-order squeezing is greater than that of the second-order.The higher-order squeezed parameter and squeezed limit due to the modulation frequency are investigated. The smaller the modulation frequency is, the stronger the degree of higher-order squeezing becomes. Furthermore, the higher-order uncertainty relations in two-mode squeezed states are presented for the first time. The product of higher-order noise moments is related to even order number N and the squeeze factor r.  相似文献   
965.
31P nuclear magnetic resonance (NMR) spectroscopy was used to determine the structure of the intermediate species of sol derived from triethyl phosphite, calcium diethoxide and acetic acid. NMR spectral data revealed that the reaction proceeds via a dialkyl phosphite intermediate. The use of a dialkyl phosphite precursor (diethyl phosphite) with calcium diethoxide eliminated the aging time required in triethylphosphite method and offered an effective sol-gel procedure for monophasic hydroxyapatite.  相似文献   
966.
慈薇  柴逸峰  刘荔荔  尹茶  吴玉田 《分析化学》2001,29(10):1144-1146
研究了机体组织中三磷酸腺苷、二磷酸腺苷、一磷酸腺苷及磷酸肌酸的毛细管区带电泳分离条件;12min内完成上述4组分分离;其检出限分别为 3.5、3.6、2.4、5.1mg/L;迁移时间及校正峰面积的定量精度分别低于0.17%和3.8%。方法已用于猫心肌中上述4组分的定量分析。  相似文献   
967.
建立了两种以火试金预浓集为基础的、可用于准确测定铂族元素的方法;中子活化法和电感耦合等离子体质谱法。讨论了它们的分析检出限、准确度及其适应性。并用这两种方法测定了5种候选地质参考物质中铂族元素的含量。  相似文献   
968.
 基于密度泛函理论的第一性原理方法,计算了硅铍石型和尖晶石型结构BeP2N4的总能量随体积的变化关系。利用Brich-Murnaghan状态方程,通过能量和体积拟合,得到了2种结构的体变模量及其对压强的一阶导数。在压力作用下,BeP2N4的相变是从硅铍石型结构(空间群R-3,No.148)转变到尖晶石型结构(空间群Fd-3m,No.227),计算出的相变点与其它理论值符合得非常好。同时计算了BeP2N4的相对晶格常数a/a0和相对体积V/V0的压缩率,在低压下发现,尖晶石结构BeP2N4的压缩率接近金刚石,进一步计算了不同压力下的体弹模量BH、剪切模量GH、BH/GH和杨氏模量E。此外,对两种结构的BeP2N4的电子态密度和带隙随压强的变化关系进行了计算和分析。结果表明:在压力作用下,上价带顶向费米能级移动,并有一定的展宽。Be—N、P—N键缩短,电子转移增加,导致电荷发生重新分布。  相似文献   
969.
Dynamic process of self-started self-mode-locked Ti : sapphire laser with a semiconductor saturable absorber mirror (SESAM) was investigated and two mode-locking starting processes were found in which one is fast and the other is slow. In the fast starting process, a mode-locking build-up time of about 400 μs was needed during which pure passive mode-locking process was caused by the SESAM and Kerr-lens mode-locking process arose from the nonlinearity of the Ti : sapphire gain medium. In the slow starting process, a build-up time of about several minutes was found in which temperature effect of the SESAM dominates the dynamic process.  相似文献   
970.
半导体可饱和吸收镜启动的高功率飞秒掺钛蓝宝石激光器   总被引:2,自引:0,他引:2  
半导体可饱和吸收镜(SESAM)启动的高功率飞秒掺钛蓝宝石激光器,在Ar^ 激光器10W全线抽运下,其平均输出功率达到1.7W,脉冲宽度小于16fs,斜率效率为22%。文中对半导体可饱和吸收镜自启动的动力学过程进行了实验研究。这种自启动、高功率、窄脉宽的飞秒激光器将具广泛的应用前景。  相似文献   
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