三种有机紫外吸收剂对菲律宾蛤仔(Ruditapes philippinarum)鳃组织抗氧化能力和细胞凋亡相关基因表达的影响

二苯甲酮-3 (BP-3)、4-甲基苄亚基樟脑(4-MBC)和4-甲氧基肉桂酸-2-乙基己酯(EHMC)是三种常用的有机紫外吸收剂, 在水环境中被频繁检出, 对水生生态系统安全构成潜在威胁。为探究三种有机紫外吸收剂对菲律宾蛤仔(Ruditapes philippinarum)鳃组织抗氧化响应和相关细胞凋亡基因的影响, 将蛤仔分别暴露于环境相关浓度的三种紫外吸收剂溶液中, 检测鳃组织抗氧化酶活性和细胞凋亡相关基因转录水平, 并通过第二代整合生物标志物响应法(IBRv2)对三种紫外吸收剂的生物毒性进行比较分析。结果显示, 三种紫外吸收剂短期暴露会诱导抗氧化响应提高抗氧化能力, 而长期高浓度暴露会导致抗氧化能力的降低。BP-3、4-MBC和EHMC可能通过启动线粒体途径和fas介导的死亡受体途径诱导菲律宾蛤仔鳃组织产生细胞凋亡。通过IBRv2分析发现, 在环境常见浓度1 μg/L的暴露水平下, 短期(1 d, 7 d)暴露时, BP-3对菲律宾蛤仔鳃组织表现出的综合毒性效应最强, 而随着暴露时间的延长(28 d), 三种紫外吸收剂表现出的综合毒性效应相近。研究结果为水环境中有机紫外吸收剂的生态风险评估提供了参考数据。     

Kalman滤波在气象数据同化中的发展与应用

气象学领域各种观测(特别是遥感遥测等非常规观测)数据的大量增多和数值天气预报模式的不断进步,推动气象数据同化技术不断发展。回顾了Kalman滤波在气象数据同化中的引入和几个发展阶段;介绍了Kalman滤波(尤其是简化Kalman滤波和总体Kalman滤波)在气象数据同化中的重要地位和应用进展。     

Lithosphere,crust and basement ridges across Ganga and Indus basins and seismicity along the Himalayan front,India and Western Fold Belt,Pakistan

Spectral analysis of the digital data of the Bouguer anomaly of North India including Ganga basin suggest a four layer model with approximate depths of 140, 38, 16 and 7 km. They apparently represent lithosphere–asthenosphere boundary (LAB), Moho, lower crust, and maximum depth to the basement in foredeeps, respectively. The Airy’s root model of Moho from the topographic data and modeling of Bouguer anomaly constrained from the available seismic information suggest changes in the lithospheric and crustal thicknesses from ∼126–134 and ∼32–35 km under the Central Ganga basin to ∼132 and ∼38 km towards the south and 163 and ∼40 km towards the north, respectively. It has clearly brought out the lithospheric flexure and related crustal bulge under the Ganga basin due to the Himalaya. Airy’s root model and modeling along a profile (SE–NW) across the Indus basin and the Western Fold Belt (WFB), (Sibi Syntaxis, Pakistan) also suggest similar crustal bulge related to lithospheric flexure due to the WFB with crustal thickness of 33 km in the central part and 38 and 56 km towards the SE and the NW, respectively. It has also shown the high density lower crust and Bela ophiolite along the Chamman fault. The two flexures interact along the Western Syntaxis and Hazara seismic zone where several large/great earthquakes including 2005 Kashmir earthquake was reported.The residual Bouguer anomaly maps of the Indus and the Ganga basins have delineated several basement ridges whose interaction with the Himalaya and the WFB, respectively have caused seismic activity including some large/great earthquakes. Some significant ridges across the Indus basin are (i) Delhi–Lahore–Sargodha, (ii) Jaisalmer–Sibi Syntaxis which is highly seismogenic. and (iii) Kachchh–Karachi arc–Kirthar thrust leading to Sibi Syntaxis. Most of the basement ridges of the Ganga basin are oriented NE–SW that are as follows (i) Jaisalmer–Ganganagar and Jodhpur–Chandigarh ridges across the Ganga basin intersect Himalaya in the Kangra reentrant where the great Kangra earthquake of 1905 was located. (ii) The Aravalli Delhi Mobile Belt (ADMB) and its margin faults extend to the Western Himalayan front via Delhi where it interacts with the Delhi–Lahore ridge and further north with the Himalayan front causing seismic activity. (iii) The Shahjahanpur and Faizabad ridges strike the Himalayan front in Central Nepal that do not show any enhanced seismicity which may be due to their being parts of the Bundelkhand craton as simple basement highs. (iv) The west and the east Patna faults are parts of transcontinental lineaments, such as Narmada–Son lineament. (v) The Munghyr–Saharsa ridge is fault controlled and interacts with the Himalayan front in the Eastern Nepal where Bihar–Nepal earthquakes of 1934 has been reported. Some of these faults/lineaments of the Indian continent find reflection in seismogenic lineaments of Himalaya like Everest, Arun, Kanchenjunga lineaments. A set of NW–SE oriented gravity highs along the Himalayan front and the Ganga and the Indus basins represents the folding of the basement due to compression as anticlines caused by collision of the Indian and the Asian plates. This study has also delineated several depressions like Saharanpur, Patna, and Purnia depressions.     

用于VLBI数字基带转换的多相滤波技术研究

该文阐述了利用低通滤波器和多相滤波器技术实现VLBI数字基带转换的原理,建立了采用多相滤波器与FFT技术的数字基带转换系统的仿真模型;然后对本模型的算法复杂度进行了分析和比较;最后对该模型的正确性进行了仿真实验验证.     

基于方向可控滤波的地震勘探随机噪声压制

针对地震勘探随机噪声的压制,本文应用拉伸厄米特高斯函数设计出方向可控滤波器.根据时空域上随机噪声的无方向性与有效信号的有向性的区别,通过局部数字特征,对数据进行选择后重组信号.方向选择性的增加,使得滤波过程能与不同方向的轴进行匹配,噪声被压制的同时保持信号的幅度;方向可调性,使得计算效率提高,且所需存储空间减少.仿真实验表明,采用此方法,信号保幅性和去噪效果均比传统的小波算法以及Curvelet变换好,在-5db信噪比下,本文方法保幅度为92.99%,信噪比提升221.774%,在实际地震信号处理中有明显的抑制噪声、保持有用信号的效果.     

Effective elimination of subharmonic ghost events from vibroseis data

Harmonic or subharmonic noise is often present in vibroseis data as reverberation‐like, laterally coherent bands occurring parallel to and before or after, the main events. Such periodic noise is typically generated during the standard correlation process when the actual source signal travelling through the subsurface is, for whatever reason, different from the desired source signal, i.e., the pilot‐sweep controlling the baseplate and used for correlation. A typical cause can be that harmonic or subharmonic frequency partials are generated in addition to the vibroseis sweep's desired fundamental frequencies. These harmonics produce strong ‘ghost events’ during correlation of the geophone trace with the pilot‐sweep, originating from additional correlations between the fundamental and harmonic frequencies. Especially subharmonic ‘ghosts’ will overlap with ‘good’ fundamental signals, since for typically used up‐sweeps they are folded to later traveltimes, where the signal/noise‐ratio is already lower, thus aggravating or preventing a reliable interpretation of possible later reflections. Here, a method is introduced to remove these unwanted noise trains (with only negligible impact on the fundamental signal) by transforming the seismogram traces into a so‐called ‘(sub)harmonic domain’. In this domain, the respective harmonic noise portions are focused and separated from the fundamental signals, enabling easier detection and appropriate suppression. After back‐transformation to the x‐T domain, the records are free from the corresponding harmonic contamination and can then be processed as usual. The method operates in a data‐driven fashion, i.e., the traces are not uniformly processed but are processed depending upon their actual (sub)harmonic content. The decontamination procedure can be applied universally, i.e., to uncorrelated/correlated and/or vertically unstacked/stacked data either in a manual, semiautomated or fully automated manner. The method works perfectly for synthetic vibroseis traces with or without harmonic/subharmonic portions. The application to real, crustal‐scale vibroseis records that were acquired in 2006 in the Dead Sea region, Israel and that were severely contaminated by subharmonic ground‐roll ghosts covering reflectivity from the basement to the Moho, shows the robustness and success of the presented method.     

一种高精度模拟振荡器

介绍一种利用32路开关芯片及电阻分压网络将直流信号直接转换为交流信号的方法,由于开关管的响应时间很短,因此,振荡器的频率能够达到100kHz以上.通过实验表明,该振荡电路正弦信号具有信号周期稳定、重复性高等特点,适合作为地学仪器的振荡源.     

Frequency‐space wavefield extrapolation using infinite impulse response digital filters: is it feasible?

The purpose of this paper is to study the possibility of performing practically stable and efficient frequency‐space (f?x) wavefield extrapolation for the application of seismic imaging and datuming via infinite impulse response (IIR) filters. The model reduction control theory was adopted to design such IIR f?x extrapolation filters. The model reduction theory reduces the order of a given order system which, in this case, involves reducing a finite impulse response (FIR) f?x extrapolation filter system into an IIR f?x extrapolation filter system. This theory relies on decomposing the states of the given filter system into strong and weakly coupled sub‐systems, and then eliminating the weakly coupled states via singular value decomposition of the Hankel and the impulse response Gramian matrices. Simulation results indicate that IIR f?x filters can be obtained, which are stable from an IIR filter design point of view. Simulations also indicate that stable seismic impulse responses and synthetics can be obtained with a reduced system model order and, hence, less computational efforts with respect to the number of complex multiplications and additions per output sample. It is hoped that this study will open new possibilities for researchers to reconsider designing IIR f?x explicit depth extrapolation filters due to their expected computational savings and wavenumber response accuracy, when compared to the FIR f?x explicit depth extrapolation filters.