Improved Duncan-Chang model for reconstituted hydrate-bearing clayey silt from the South China Sea

The experimental testing and analysis of strength and deformation characteristics of hydrate reservoirs is an integral part of natural gas hydrate exploitation. However, studies so far have failed to deeply explore samples from the South China Sea. Especially, there is a lack of a simple and applicable method to estimate their mechanical behaviors. Thus, based on test data, an improved Duncan-Chang model is established in this paper to characterize the strength and deformation of reconstituted samples with various hydrate saturation and stress states from this area. This model can accurately describe the strain-hardening characteristics, and failure strength is estimated by the improved Drucker-Prager criterion with high fitting accuracy. The initial elastic modulus and failure ratio are given by the proposed empirical models, which are obtained from experimental data and fitting methods. Generally, this model has several advantages including simple structure, favorable performances, and a limited number of model parameters. Therefore, it could be widely used in strength and deformation analysis. This study can support the prevention and control of geological risks during natural gas hydrate exploitation in the South China Sea.Cited as: Dong, L., Wu, N., Zhang, Y., Liao, H., Hu, G. Li, Y. Improved Duncan-Chang model for reconstituted hydrate-bearing clayey silt from the South China Sea. Advances in Geo-Energy Research, 2023, 8(2): 136-140. https://doi.org/10.46690/ager.2023.05.0

CT-based Subchondral Bone Microstructural Analysis in Knee Osteoarthritis via MR-Guided Distillation Learning

Background: MR-based subchondral bone effectively predicts knee osteoarthritis. However, its clinical application is limited by the cost and time of MR. Purpose: We aim to develop a novel distillation-learning-based method named SRRD for subchondral bone microstructural analysis using easily-acquired CT images, which leverages paired MR images to enhance the CT-based analysis model during training. Materials and Methods: Knee joint images of both CT and MR modalities were collected from October 2020 to May 2021. Firstly, we developed a GAN-based generative model to transform MR images into CT images, which was used to establish the anatomical correspondence between the two modalities. Next, we obtained numerous patches of subchondral bone regions of MR images, together with their trabecular parameters (BV / TV, Tb. Th, Tb. Sp, Tb. N) from the corresponding CT image patches via regression. The distillation-learning technique was used to train the regression model and transfer MR structural information to the CT-based model. The regressed trabecular parameters were further used for knee osteoarthritis classification. Results: A total of 80 participants were evaluated. CT-based regression results of trabecular parameters achieved intra-class correlation coefficients (ICCs) of 0.804, 0.773, 0.711, and 0.622 for BV / TV, Tb. Th, Tb. Sp, and Tb. N, respectively. The use of distillation learning significantly improved the performance of the CT-based knee osteoarthritis classification method using the CNN approach, yielding an AUC score of 0.767 (95% CI, 0.681-0.853) instead of 0.658 (95% CI, 0.574-0.742) (p<.001). Conclusions: The proposed SRRD method showed high reliability and validity in MR-CT registration, regression, and knee osteoarthritis classification, indicating the feasibility of subchondral bone microstructural analysis based on CT images.Comment: 5 figures, 4 table

Expression of the Mxra8 receptor promotes alphavirus infection and pathogenesis in mice and Drosophila

Mxra8 is a recently described receptor for multiple alphaviruses, including Chikungunya (CHIKV), Mayaro (MAYV), Ross River (RRV), and O\u27nyong nyong (ONNV) viruses. To determine its role in pathogenesis, we generated mice with mutant Mxra8 alleles: an 8-nucleotide deletion that produces a truncated, soluble form (Mxra

Marine Gas Hydrate: Geological Characterization, Resource Potential, Exploration, and Development

Natural gas hydrate is critical for its tremendous potential to impact the energy supply field, accelerate global warming if methane reaches the atmosphere, and affect the safety of deep-sea oil and gas production [...

Transient Translational and Rotational Water Defects in Gas Hydrates

We report our observations of the transient formation of the translational and rotational defects in the host lattice of methane hydrates. We perfortn molecular dynamics simulations of a fully occupied methane hydrate system and find that the hydrogen bonds of a water molecule can be thermally broken, and the water molecule can: then rotate more freely. We observe the formation of transient Bjerrum defects around, the water: molecule, and the two hydrogens of the water molecule can be interchanged when the transient defects anneal. The 95% confidence interval for the rate of the hydrogen interchange is estimated to be 1.3 X 10(5)-2.4 X 10(5) s(-1) per water molecule, and the 95% confidence interval for the associated free energy of activation is estimated to be 38.2-39.4 kJ/mol at 270 K. We also observe the transient formation of vacancy-interstitial water defects. The, formation and annealing of these vacancy-interstitial defects can result in the interchange of two or three neighboring water molecules on the gas hydrate lattices. The 95% confidence interval for the rate of the formation of transient vacaney-interstitial water defects as a result of the water interchanges is estimated to be 6.7 x 10(2)-1.6 X 10(4) s(-1) per water molecule and. the 95% confidence interval for the associated free energy of activation is estimated to be 44.1-51.3 kJ/mol at 270 K

Molecular Mechanisms of Gas Diffusion in CO2Hydrates

Gas diffusion is considered a rate-limiting step in the formation of gas hydrates, yet its molecular mechanisms remain unclear. In this work, we present the molecular mechanisms of the CO2 cage-to-cage transport in gas hydrates, as directly observed from molecular dynamics simulations performed at elevated temperatures. We found that at least one water vacancy is required for the CO2 molecules to pass through five-membered water rings, while only the distortion of the local ring structure is required for the CO2 molecules to pass through the six-membered water rings. We used the transition-state theory to estimate the relevant kinetic parameters associated with the CO2 diffusion in gas hydrates. The calculated free energy of activation is about 44 ± 6 kJ/mol, and the diffusion coefficient is in the range of 1.0 × 10–16∼2.0 × 10–14 m2/s, for the CO2 diffusion at 270 K, in close agreement with previous experiments. This work suggests that the presence of empty cages is crucial for the CO2 cage-to-cage transport in gas hydrates

Numerical simulation on gas production from inclined layered methane hydrate reservoirs in the Nankai Trough: A case study

Natural gas hydrate is generally disseminated in tilted sediments. The inclination of hydrate reservoirs significantly affects the fluid migration behaviour and production potential. However, most of the current simulations ideally assume that the hydrate reservoir is horizontally distributed; resulting in the effect of the formation dip on the well deployment and corresponding gas production remains unclear. Here, we implement a real inclined alternating sand-clay hydrate reservoir model based on geological data from the Nankai Trough, Japan, to simulate the production performance of a single horizontal well and dual horizontal wells. Results show that the gas and water productions are enhanced when a single horizontal production well is deployed in the structural low of the reservoir. The gas and water production performance in upper sandy reservoir and the water extraction in the middle muddy reservoir are sensitive to the layout of the production wells, which can cause the daily difference is over 6%. The gas-to-water ratio is independent from the structural deployment positions of the horizontal wells in the same inclined layer. Compared to the single depressurization method, placing a horizontal thermal injection well in the structural high of the upper inclined sandy reservoir and a horizontal production well in the structural low of the same formation improves the gas recovery efficiency nearly twice, which is recommended for production enhancement. Our findings are useful for achieving effective and economic gas recovery from natural inclined layered hydrate reservoirs. (C) 2021 The Authors. Published by Elsevier Ltd

Advances in the Current Understanding of the Mechanisms Governing the Acquisition of Castration-Resistant Prostate Cancer

Despite aggressive treatment and androgen-deprivation therapy, most prostate cancer patients ultimately develop castration-resistant prostate cancer (CRPC), which is associated with high mortality rates. However, the mechanisms governing the development of CRPC are poorly understood, and androgen receptor (AR) signaling has been shown to be important in CRPC through AR gene mutations, gene overexpression, co-regulatory factors, AR shear variants, and androgen resynthesis. A growing number of non-AR pathways have also been shown to influence the CRPC progression, including the Wnt and Hh pathways. Moreover, non-coding RNAs have been identified as important regulators of the CRPC pathogenesis. The present review provides an overview of the relevant literature pertaining to the mechanisms governing the molecular acquisition of castration resistance in prostate cancer, providing a foundation for future, targeted therapeutic efforts