A Stable Q Compensated Reverse Time Migration Method Based on Excitation Amplitude Imaging Condition

The stability and efficiency, especially the stability, are generally concerned issues in Q compensated reverse time migration (Q-RTM). The instability occurs because of the exponentially boosted high frequency ambient noise during the forward or backward seismic wavefield propagation. The regularization and low-pass filtering methods are two effective strategies to control the instability of the wave propagation in Q-RTM. However, the regularization parameters are determined experimentally, and the wavefield cannot be recovered accurately. The low-pass filtering method cannot balance the selection of cutoff frequency for varying Q values, and may damage the effective signals, especially when the signal-to-noise ratio (SNR) of the seismic data is low, the Q-RTM will be a highly unstable process. In order to achieve the purpose of stability, the selection of cutoff frequency will be small enough, which can cause great damage to the effective high frequency signals. In this paper, we present a stable Q-RTM algorithm based on the excitation amplitude imaging condition, which can compensate both the amplitude attenuation and phase dispersion. Unlike the existing Q-RTM algorithms enlarging the amplitude, the exponentially attenuated seismic wavefield will be used during both the forward and backward wavefield propagation of Q-RTM. Therefore, the new Q-RTM algorithm is relative stable, even for the low SNR seismic data. In order to show the accuracy and stability of our stable Q-RTM algorithm clearly, an example based on Graben model will be illustrated. Then, a realistic BP gas chimney model further demonstrates that the proposed method enjoys good stability and anti-noise performance compared with the traditional Q-RTM with amplitude amplification. Compare the Q-RTM images of these two models to the reference images obtained by the acoustic RTM with acoustic seismic data, the new Q-RTM results match the reference images quite well. The proposed method is also tested using a field seismic data, the result shows the effectiveness of our proposed method.     

KIF20A对胶质瘤细胞增殖、迁移和侵袭、凋亡及细胞周期分布的影响

目的:研究KIF20A对胶质瘤U87细胞系增殖、侵袭、迁移、凋亡及细胞周期分布的影响。方法:利用 RNA干扰技术下调胶质瘤细胞系 U87中 KIF20A 的表达。RT-qPCR 和 Western blot 分别检测 KIF20A 在mRNA 和蛋白水平上的表达。CCK-8 实验检测 U87细胞增殖能力的变化，Transwell 实验检测U87细胞迁移及侵袭能力的变化，流式细胞术检测 U87细胞凋亡及细胞周期的变化。结果:RT-qPCR和Western blot 结果显示 siRNA-KIF20A显著下调 KIF20A 的表达，CCK-8和Transwell 实验显示下调 KIF20A 的表达显著抑制了U87细胞的增殖、迁移及侵袭能力，流式细胞术结果显示下调 KIF20A 的表达显著促进了U87细胞的凋亡，诱导细胞周期阻滞在G0/G1期。结论:下调KIF20A的表达抑制胶质母细胞瘤细胞的增殖、迁移及侵袭，促进胶质母细胞瘤细胞的凋亡并诱导细胞周期G0/G1期阻滞。     

高压氧综合治疗糖尿病性胃轻瘫患者的疗效观察

目的观察高压氧（HBO）联合吗丁啉综合治疗对糖尿病性胃轻瘫患者胃动素及胃排空时间的影响。方法采用随机数字表法将2000年10月至2004年10月间连续人院的糖尿病性胃轻瘫患者112例随机分为高压氧组和对照组各46例，HBO组在给予吗丁啉（每次10mg，每天3次，连用4周）的基础上加用HBO治疗，HBO采用多人氧舱，在舱内停留120min，压力为0．25MPa（2．5ATA），戴面罩吸人纯氧60min（30min各2次，中间休息10min吸人舱内空气），10次为1个疗程，共3个疗程，每疗程间隔3～5d（排除HBO治疗禁忌证）。对照组为单纯吗丁啉，每次10mg，每天3次，连用4周。45d分别对两组患者治疗前后胃动素、空腹血糖、胃排空时间及症状的改善各项指标进行研究对比。结果HBO组和对照组总有效率分别为92．9％和76．8％，症状的改善、胃动素及胃排空时间治疗组均优于对照组，差异有显著性（P〈0．05）。结论糖尿病性胃轻瘫患者在服用吗丁啉的基础上应用HBO可降低胃动素、加速胃排空时间，对临床症状的改善具有积极作用。     

谷氨酸对腺苷A2A受体调节一氧化氮合酶活力的影响

目的探讨谷氨酸是否能够影响腺苷A2A受体对一氧化氮合酶（NOS）活力的调节。方法用1000ng／ml脂多糖（LPS）刺激小胶质细胞，分别加入100nmol／L A2A受体激动剂CGS21680以及不同浓度的谷氨酸（0，1，0，25，0，5mmol／L）干预，观察NOS活力变化。结果LPS诱导NOS活力增高，激活A2A受体可以产生抑制作用；0，25及0．5mmoL／L谷氨酸和A2A受体激动剂同时存在时，NOS活力进一步增高。结论高浓度谷氨酸可逆转腺苷A2A受体激动剂抑制升高NOS活力的作用。     

实时三维超声对室间隔缺损的直视效果及影响因素分析

目的探讨实时三维超声（RT3DE）对室间隔缺损（VSD）全貌的直视效果及其影响因素。 方法应用RT3DE对238例VSD患者进行检查，其中包括法洛四联症（TOF）36例、完全型心内膜垫缺损（TECD）2例和十字交叉心2例。获取并切割“全容积三维”图像，寻找最佳视角显示病变结构全貌。 结果RT3DE对中型和大型VSD（直径≥5mm）的直视效果优于小型VSD（〈5mm）。可显示缺损的形状、部位及毗邻结构。胸骨旁四腔位和心底短轴位RT3DE图像效果最佳，胸骨旁长轴位及心尖五腔位次之。 结论VSD的大小、部位及三维图像质量是决定RT3DE观察效果的主要因素。RT3DE可清晰直视中型及大型VSD的全貌。     

Characterizing luminous efficiency functions for a simulated mesopic night driving task based on reaction time

The objective of this study is to test the luminous efficiency functions V(lambda), V'(lambda), V(10)(lambda) and their linear combinations on the basis of a data set gained from a simulated mesopic night-time driving experiment. Another aim is to provide 'real-world' data for the 'X framework' or 'linear combination model', and to find out its limits in a practical situation. Human performance was measured by the reaction time method. Results show that the single parameter of the linear combination of photopic and scotopic luminous efficiency functions can be determined analytically with little variation for a given mesopic background luminance level and a given visual target colour, but the computation leads to considerable deviations comparing all three target colours (red, green and blue) used in the experiment. The conclusion for the given experimental conditions is that the single parameter of the linear combination model has an increasing deviation for lower background luminance levels.     

腰椎穿刺术后头痛与卧床时间的关系

目的探讨腰椎穿刺术后平卧时间30min、2h对头痛的影响。方法对794例具有腰椎穿刺术适应证而无禁忌证并排除有关因素的患者，随机分为30min组、2h组。分别观察术后头痛发生率。结果30min组头痛发生率为（8／460）1．74％，2h组为（7／334）2.10％，两组组间比较均无显著性差异（P〉0．05）。结论本研究说明腰穿后卧床时间长短（30min～2h），对腰穿后头痛的发生率无影响，可缩短至30min，没有必要卧床2h，更没有必要卧床4～6h。