3D Weak-Dispersion Reverse-Time Migration with a StereoModeling Method

The finite difference method has been widely used in seismic modeling and reverse time migration. However, it generally has two issues: large computational cost and numerical dispersion. Recently, a nearly-analytic discrete operator was developed to approximate the partial differential operators. Based on this spatial discretization, many weak-dispersion and efficient StereoModeling methods have been developed, which are found to be superior to conventional algorithms in suppressing numerical dispersion. In this paper, we generalize one StereoModeling method, the nearly-analytic central difference method (NACD), from 2D to 3D and apply it to 3D reverse-time migration. Numerical results show that the NACD can be used effectively as a new tool for seismic modeling and migration. The reverse time migration (RTM) results for the 3D SEG/EAGE Phase A classic dataset 1 show that the NACD can get a much better image than the Lax-Wendroff correction (LWC) method particularly when using a coarse grid size.Massachusetts Institute of Technology. Earth Resources Laboratory (Founding Members Consortium

3D weak-dispersion reverse time migration using a stereo-modeling operator

Reliable 3D imaging is a required tool for developing models of complex geologic structures. Reverse time migration (RTM), as the most powerful depth imaging method, has become the preferred imaging tool because of its ability to handle complex velocity models including steeply dipping interfaces and large velocity contrasts. Finite-difference methods are among the most popular numerical approaches used for RTM. However, these methods often encounter a serious issue of numerical dispersion, which is typically suppressed by reducing the grid interval of the propagation model, resulting in large computation and memory requirements. In addition, even with small grid spacing, numerical anisotropy may degrade images or, worse, provide images that appear to be focused but position events incorrectly. Recently, stereo-operators have been developed to approximate the partial differential operator in space. These operators have been used to develop several weak-dispersion and efficient stereo-modeling methods that have been found to be superior to conventional algorithms in suppressing numerical dispersion and numerical anisotropy. We generalized one stereo-modeling method, fourth-order nearly analytic central difference (NACD), from 2D to 3D and applied it to 3D RTM. The RTM results for the 3D SEG/EAGE phase A classic data set 1 and the SEG Advanced Modeling project model demonstrated that, even when using a large grid size, the NACD method can handle very complex velocity models and produced better images than can be obtained using the fourth-order and eighth-order Lax-Wendroff correction (LWC) schemes. We also applied 3D NACD and fourth-order LWC to a field data set and illustrated significant improvements in terms of structure imaging, horizon/layer continuity and positioning. We also investigated numerical dispersion and found that not only does the NACD method have superior dispersion characteristics but also that the angular variation of dispersion is significantly less than for LWC. Read More: http://library.seg.org/doi/abs/10.1190/geo2013-0472.1National Natural Science Foundation (China) (Grant 41230210)Massachusetts Institute of Technology. Earth Resources Laboratory (Founding Members Consortium

Slab Morphology Beneath Northern Sumatra Revealed by Regional and Teleseismic Traveltime Tomography

An eikonal equation-based tomography method is used to invert the high-quality regional and teleseismic traveltime data recorded by 26 broadband seismic stations in northern Sumatra, following which we obtain the P and S wave velocity structures of the crust and mantle down to a depth of 800 km. The results of both P and S wave tomography clearly show that the Indo-Australian oceanic plate continuously penetrates downward beneath northern Sumatra and the maximum penetration depth varies approximately from 400 km at the northern tip of Sumatra to about 800 km around the southern boundary of our study area. Significant slab folding or bending reported in the literature as the main feature of the subducted slab beneath northern Sumatra is not found in our results. Instead, our tomographic images demonstrate only a less curved slab that mimics the shape of the Sunda Trench and volcanic arc and generally extends over depths from 120 to 450 km. P wave tomography shows broad and pronounced low-velocity anomalies beneath the island of Sumatra in the lower crust and uppermost mantle. Our model also reveals a slab tear approximately at 120-km depth, which has been documented in previous studies and considered to be related to the eruption of the Toba supervolcano.Ministry of Education (MOE)National Research Foundation (NRF)Published versio

Ferrostatin-1 post-treatment attenuates acute kidney injury in mice by inhibiting ferritin production and regulating iron uptake-related proteins

Background Acute kidney injury (AKI) is a common and serious medical condition with high morbidity and mortality. Recent research has highlighted ferroptosis, a novel form of programmed cell death, as a potential therapeutic target in mitigating renal tubular injury in AKI. Ferrostatin-1, a specific ferroptosis inhibitor, has been demonstrated to prevent renal injury through ferroptosis inhibition. Methods Utilizing a murine AKI model, we investigated the effects of Ferrostatin-1 by administering it post-injury. Through high-throughput sequencing and pathological analysis, we focused on the critical role of ferroptosis-related pathways in the treatment. Results Ferrostatin-1 post-conditioning effectively mitigated oxidative damage and reduced iron content associated with AKI. Additionally, critical ferroptosis-related proteins, such as GPX4, SLC7A11, NRF2, and FTH1, exhibited increased expression levels. In vitro, Ferrostatin-1 treatment of HK-2 cells significantly diminished lipid peroxidation and iron accumulation. Furthermore, Ferrostatin-1 was found to downregulate the PI3K signalling pathway. Conclusion Ferrostatin-1 acted as a potential ferroptosis inhibitor with the capacity to enhance antioxidant defences. This study suggests that Ferrostatin-1 could serve as a promising novel strategy for improving the treatment of AKI and promoting recovery from the condition

mGluR5 ablation in cortical glutamatergic neurons increases novelty-induced locomotion.

The group I metabotropic glutamate receptor 5 (mGluR5) has been implicated in the pathology of various neurological disorders including schizophrenia, ADHD, and autism. mGluR5-dependent synaptic plasticity has been described at a variety of neural connections and its signaling has been implicated in several behaviors. These behaviors include locomotor reactivity to novel environment, sensorimotor gating, anxiety, and cognition. mGluR5 is expressed in glutamatergic neurons, inhibitory neurons, and glia in various brain regions. In this study, we show that deleting mGluR5 expression only in principal cortical neurons leads to defective cannabinoid receptor 1 (CB1R) dependent synaptic plasticity in the prefrontal cortex. These cortical glutamatergic mGluR5 knockout mice exhibit increased novelty-induced locomotion, and their locomotion can be further enhanced by treatment with the psychostimulant methylphenidate. Despite a modest reduction in repetitive behaviors, cortical glutamatergic mGluR5 knockout mice are normal in sensorimotor gating, anxiety, motor balance/learning and fear conditioning behaviors. These results show that mGluR5 signaling in cortical glutamatergic neurons is required for precisely modulating locomotor reactivity to a novel environment but not for sensorimotor gating, anxiety, motor coordination, several forms of learning or social interactions

Cx-mGlu5 mice exhibit normal sensorimotor gating and a slight reduction in repetitive behaviors.

<p>(<b>A,B</b>) Sensorimotor gating was measured by prepulse inhibition (PPI) of the acoustic startle response in Cx-mGlu5 KO mice in C57/129 mixed (<b>A</b>) or in C57BL/6 background (<b>B</b>) and their littermate controls. Summaries of the maximum startle response to a 120 dB white noise sound burst are shown in the left panel. Summaries for the inhibition of the acoustic startle response by either one of three prepulse levels (74, 78 and 82 dB) are shown on the right. (<b>C</b>) Summaries for the number of marbles buried by Cx-mGlu5 KO and control mice in C57BL6 background.</p

Behavior data summary for Cx-mGluR5 in C57 background.

<p>Values are listed as mean ± SEM (animals number). Abbreviations: A.U., arbitrary unit;</p>*<p>, p<0.05.</p