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Quantitative stability evaluation of multi-tunnel structure is an important issue related to the safety assessment and stable construction of geotechnical underground tunnels. In this work, the overall failure process of twin tunnels were exhibited by a physical simulation based on the 3D printing (3DP) sandstone analogues model, and a safety factor method was also presented for evaluating the general safety of multi-tunnel structure. For checking the 3DP material performance of physical model, uniaxial and triaxial compressions for the 3DP cylinder specimens were first tested and showed that their mechanical properties and failure characteristics were similar to natural rock in general. Then, the overloading tests for twin-tunnel model were carried out and have exposed the critical position of overall failure of twin-tunnel structure through visual observation and automatic measurement. Testing results and corresponding numerical back analysis indicated that the connectivity of plastic strain between tunnels can be deemed as the conservative instability criterion (i.e. yielding of material) and the inflection point of tunnels’ displacement can be deemed as overall failure criterion (i.e. structure failure) for twin-tunnel structure. The safety analysis for underground hydraulic caverns indicated that this method can provide a reference for quantitative and reasonable evaluation of the general safety of multi-tunnels or caverns and the local instability zone of surrounding rock.

Background Expression of either Cas9 or Cas12a and guide RNAs by a single Polymerase II (Pol II) promoter represents a compact CRISPR expression system and has many advantages for different applications. In order to make this system routine in plant biology, engineering efforts are needed for developing and optimizing such single transcript unit (STU) systems for plant genome editing. Results To develop novel intron-based STU (iSTU) CRISPR system (STU CRISPR 3.0), we first evaluated three introns from three plant species for carrying guide RNAs by using an enhanced green fluorescence protein (eGFP) system in rice. After validation of proper intron slicing, we inserted these gRNA-containing introns into the open reading frames (ORFs) of Cas9 and Cas12a for testing their genome editing capability. Different guide RNA processing strategies have been tested for Cas9 and Cas12a. We demonstrated singular genome editing and multiplexed genome editing with these iSTU-Cas9 and iSTU-Cas12a systems. Conclusion We developed multiple iSTU-CRISPR/Cas9 and Cas12a systems for plant genome editing. Our results shed light on potential directions for further improvement of the iSTU systems.

A variational Bayesian blind restoration reconstruction based on shear wave transform for low-dose medical computed tomography (CT) image is proposed. The proposed algorithm eliminates the effects of the point spread function in the process of low-dose medical CT image reconstruction and improves the reconstructed image quality. The shear wave transform is used to sparsely represent the CT image, which can speed up the efficiency of image processing. In the Bayesian framework, a posteriori probability objective function with unknown parameters is constructed. These unknown parameters include the shear wave coefficients, the point spread function, and the hyper parameters. It specified a Laplacian distribution model for the prior probability distribution of the shear wave coefficients. The autoregressive model is used as the prior model of the point spread function. All of hyper parameters follow the gamma distribution. The variational Bayesian method is used to estimate all of unknown parameters and solve the above posteriori probability objective function. These generalized parameter estimators are used to realize the low-dose CT image blind restoration reconstruction. Computer simulation results indicate that a good performance-reconstructed image can be obtained and some metrics such as peak signal-to-noise ratio (PSNR), universal image quality index (UIQI), structural similarity index metric (SSIM), and sum of square differences error (SSDE) are improved.