Super-resolution reconstruction of digital rock CT images based on residual attention mechanism

Computer tomography technology is widely used in geological exploration because it is a nondestructive and three-dimensional imaging method that can be integrated with computer simulation. However, the large-scale application of the computer tomography technique is limited by economic costs and time consumption. Therefore, it is challenging and intractable to indicate the pore structure characteristics of rock. To address this issue, a super-resolution reconstruction algorithm based on convolutional neural networks, residual learning, and attention mechanism was proposed to generate super-resolution images in this study. This algorithm was applied to the reconstruction of carbonate rock and sandstone. The performance of two-dimensional image reconstruction was evaluated by quantitative extraction and qualitative visualization. The results from experiments indicate that the built model performs well on different upscaling factors and is superior to the existing super-resolution approaches based on convolutional neural network.Cited as: Shan, L., Bai, X., Liu, C., Feng, Y., Liu, Y., Qi, Y. Super-resolution reconstruction of digital rock CT images based on residual attention mechanism. Advances in Geo-Energy Research, 2022, 6(2): 157-168. https://doi.org/10.46690/ager.2022.02.0

The G Protein Coupled Receptor 3 Is Involved in cAMP and cGMP Signaling and Maintenance of Meiotic Arrest in Porcine Oocytes

The arrest of meiotic prophase in mammalian oocytes within fully grown follicles is dependent on cyclic adenosine monophosphate (cAMP) regulation. A large part of cAMP is produced by the Gs-linked G-protein-coupled receptor (GPR) pathway. In the present study, we examined whether GPR3 is involved in the maintenance of meiotic arrest in porcine oocytes. Expression and distribution of GPR3 were examined by western blot and immunofluorescence microscopy, respectively. The results showed that GPR3 was expressed at various stages during porcine oocyte maturation. At the germinal vesicle (GV) stage, GPR3 displayed a maximal expression level, and its expression remained stable from pro-metaphase I (MI) to metaphase II (MII). Immunofluorescence staining showed that GPR3 was mainly distributed at the nuclear envelope during the GV stage and localized to the plasma membrane at pro-MI, MI and MII stages. RNA interference (RNAi) was used to knock down the GPR3 expression within oocytes. Injection of small interfering double-stranded RNA (siRNA) targeting GPR3 stimulated meiotic resumption of oocytes. On the other hand, overexpression of GPR3 inhibited meiotic maturation of porcine oocytes, which was caused by increase of cGMP and cAMP levels and inhibition of cyclin B accumulation. Furthermore, incubation of porcine oocytes with the GPR3 ligand sphingosylphosphorylcholine (SPC) inhibited oocyte maturation. We propose that GPR3 is required for maintenance of meiotic arrest in porcine oocytes through pathways involved in the regulation of cAMP and cGMP

Effect of Mo/Nb ratio variations on the microstructure and cryogenic impact toughness of NiCrMo deposited metals

Effects of varying the Mo/Nb (in weight percent) ratio in ENiCrMo-6-deposited metals on the microstructure and cryogenic impact toughness of the metals were investigated. When the Mo/Nb ratio decreased from 6.09 to 3.28, the Nb-rich phase on the grain boundaries was transformed from un-continuous precipitation to continuous precipitation, the area fraction and average size of the precipitates within the grains were significantly increased, and a eutectic-type Laves phase appeared. Although the austenitic matrix of the deposited metals indicated a ductile fracture mode, the precipitates significantly deteriorated the cryogenic impact toughness. As the average size and area fraction of the precipitates increased, the cryogenic impact value decreased significantly

The effect of SPC on distribution of GPR3 in porcine oocytes.

<p>Distribution of GPR3 in oocytes after treatment with SPC was revealed by immunofluorescent staining. In the GV stage, GPR3 was mainly distributed at the nuclear membrane and plasma membrane. GPR3 accumulated in the inner cytoplasm and plasma at the pro-MI stage. From MI to MII stages, GPR3 aggregated at the plasma membrane. Green, GPR3; Blue, chromatin. Bar = 40 µm.</p

The effect of GPR3 RNAi on meiotic resumption in porcine oocytes.

<p>(A) Samples from control and RNAi groups were collected to test the efficiency of GPR3-RNAi. Control: 150 oocytes injected with 25 µM control siRNA; RNAi: 150 oocytes injected with 25 µM GPR3 siRNA. Oocytes were then incubated for 24 h or 30 h in the TCM-199 medium with or without 4 mM HX before collection for western blotting. (B) Oocytes cultured with normal medium without HX were injected with 25 µM GPR3 siRNA or control siRNA and then cultured for 24 h or 30 h. The GVBD rates of the injected oocytes are shown along with non-injected oocytes. (C) Oocytes treated with 4 mM HX were injected with the GPR3 siRNA or control siRNA and then cultured in the presence of HX for 24 h or 30 h. The GVBD rates of the injected oocytes are shown along with non-injected oocytes. (D) Cyclin B (upper panel) and CDC2 (middle panel) levels were detected after siRNA injection by western blot using 150 oocytes in each sample. The results are shown along with those of non-injected oocytes cultured without HX. Samples were collected from culture medium with or without HX at 0 h, 24 h and 30 h. (E) cAMP levels of porcine oocytes in the GPR3 siRNA injection group and control siRNA group after culture with HX at 24 h or 30 h. Dotted line represents cAMP level at time 0. (F) cGMP levels of porcine oocytes in the GPR3 siRNA injection group and control siRNA group after culture with HX at 24 h or 30 h. Dotted line represents cGMP level at time 0. The number “n” on top of the bars indicates the total number of treated oocytes in each group. Data are shown as mean ± SEM of at least three repeated experiments and letters ‘a’ and ‘b’ indicate statistically significant difference (p<0.05).</p

The efficiency of GPR3 overexpression.

<p>(A) Immunofluorescence detection of GPR3 overexpression. Control: oocytes were injected with 2.5 mg/ml Myc₆ mRNA solution; Overexpression: oocyets were injected with 2.5 mg/ml Myc₆-GPR3 mRNA solution. Green, Myc₆-GPR3; Blue, chromatin. Bar = 40 µm. (B) Samples from control and overexpression groups were collected to test the expression of Myc₆-GPR3. Control: 150 oocytes injected with 2.5 mg/ml Myc₆ mRNA solution; Overexpression: 150 oocytes injected with 2.5 mg/ml Myc₆- GPR3 mRNA solution. Oocytes were then incubated for 15 h in TCM-199 medium containing 2.5 µM Milrinone before collection or culture for western blotting.</p

Expression and subcellular localization of GPR3 during porcine oocyte meiotic maturation.

<p>(A) Subcellular localization of GPR3 as revealed by immunofluorescent staining. In the GV stage, GPR3 was mainly distributed at the nuclear membrane and plasma membrane. GPR3 accumulated at the inner cytoplasm and plasma membrane at the pro-MI stage. From MI to MII, GPR3 aggregated at the plasma membrane. (B) Expression of GPR3 protein was measured by western blotting. Samples were collected at 0 h, 24 h, 30 h, and 44 h of culture which were the time points when most oocytes had reached the GV, GVBD, MI and MII stages, respectively. Each sample was derived from 150 oocytes. Green, GPR3; Blue, chromatin. Bar = 40 µm.</p