Convolution-based multi-scale envelope inversion

Envelope inversion(El)is an efficient tool to mitigate the nonlinearity of conventional full waveform inversion(FWI)by utilizing the ultralow-frequency component in the seismic data.However,the performance of envelope inversion depends on the frequency component and initial model to some extent.To improve the convergence ability and avoid the local minima issue,we propose a convolution-based envelope inversion method to update the low-wavenumber component of the velocity model.Besides,the multi-scale inversion strategy(MCEI)is also incorporated to improve the inversion accuracy while guaranteeing the global convergence.The success of this method relies on modifying the original envelope data to expand the overlap region between observed and modeled envelope data,which in turn expands the global minimum basin of misfit function.The accurate low-wavenumber component of the velocity model provided by MCEI can be used as the migration model or an initial model for conventional FWI.The numerical tests on simple layer model and complex BP 2004 model verify that the proposed method is more robust than El even when the initial model is coarse and the frequency component of data is high.

3D variable-grid full-waveform inversion on GPU

Full-waveform inversion(FWI)is a powerful tool to reconstruct subsurface geophysical parameters with high resolution.As3 D surveys become widely implemented,corresponding 3 D processing techniques are required to solve complex geological cases,while a large amount of computation is the most challenging problem.We propose an adaptive variable-grid 3 D FWI on graphics processing unit devices to improve computational efficiency without losing accuracy.The irregular-grid discretization strategy is based on a dispersion relation,and the grid size adapts to depth,velocity,and frequency automatically.According to the transformed grid coordinates,we derive a modified acoustic wave equation and apply it to full wavefield simulation.The 3 D variable-grid modeling is conducted on several 3 D models to validate its feasibility,accuracy and efficiency.Then we apply the proposed modeling method to full-waveform inversion for source and residual wavefield propagation.It is demonstrated that the adaptive variable-grid FWI is capable of decreasing computing time and memory requirements.From the inversion results of the 3 D SEG/EAGE overthrust model,our method retains inversion accuracy when recovering both thrust and channels.

Malignant melanoma resection and reconstruction with the first manifestation of lumbar metastasis:A case report

BACKGROUND Malignant melanoma(MM)has shown an increasing incidence worldwide,and a potential to metastasize to almost any part of the body.Clinically,MM with bone metastasis as the initial manifestation is extremely rare.Spinal metastatic MM can cause spinal cord or nerve root compression,resulting in severe pain and paralysis.Currently,the primary clinical treatments for MM are surgical resection in conjunction with chemotherapy,radiotherapy,and immunotherapy.CASE SUMMARY Here,we report the case of a 52-year-old male who presented to the clinic with progressive low back pain and limited nerve function.No primary lesion or spinal cord compression was detected from computed tomography and magnetic resonance imaging of the lumbar vertebrae and positron emission tomography scan.A lumbar puncture biopsy confirmed the diagnosis of lumbar spine metastatic MM.Following surgical resection,the patient’s quality of life improved,symptoms were relieved,and comprehensive treatment was initiated,which prevented recurrence.CONCLUSION Spinal metastatic MM is clinically rare,and may cause neurological symptoms,including paraplegia.Currently,the clinical treatment plan consists of surgical resection in combination with chemotherapy,radiotherapy,and immunotherapy.

Four new feather mite species of the genus Proctophyllodes Robin(Astigmata:Proctophyllodidae) from China

Four new species of the feather mite genus Proctophyllodes are described from the birds of the order Passeriformes in China： P. flexuosa sp. nov. from Eophona migratoria Hartert （Chongqing）, P. brevis sp. nov. from Passer montanus （Linnaeus） （Anhui and Chongqing）, P. garrula sp. nov. from Garrulaxpoecilorhynchus Gould （Anhui）, P. canora sp. nov. from Garrulax canorus （Linnaeus） （Guizhou）.