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Introduction Focal segmental glomerulosclerosis (FSGS) is a common glomerulopathy with unclear mechanism. The demand for FSGS clinical diagnostic biomarkers has not yet been met. Circular RNA (circRNA) is a novel non-coding RNA with multiple functions, but its diagnostic value for FSGS remains unexplored. This study aimed to identify circRNAs that could aid in early clinical diagnosis and to investigate their mechanisms in podocyte injury. Methods The signature of plasma circRNAs for FSGS was identified by circRNA microarray. The existence of circRNAs was confirmed by qRT-PCR, RNase R assay, and DNA sequencing. Plasma levels of circRNAs were evaluated by qRT-PCR. The diagnostic value was appraised by receiver operating characteristic curve. The circRNA-miRNA-mRNA network was built with Cytoscape 7.3.2. Statistically significant differences were calculated by the Mann-Whitney U-test. Results A total of 493 circRNAs (165 upregulated, 328 downregulated) were differentially expressed in the plasma of FSGS patients (n = 3) and normal controls (n = 3). Eight candidate circRNAs were demonstrated to be circular and stable transcripts. Among them, hsa_circ_0001230 and hsa_circ_0023879 were significantly upregulated in FSGS patients (n = 29) compared to normal controls (n = 51). The areas under the curve value of hsa_circ_0001230 and hsa_circ_0023879 were 0.668 and 0.753, respectively, while that of two-circRNAs panel was 0.763. The RNA pull-down analysis revealed that hsa_circ_0001230 and hsa_circ_0023879 could sponge hsa-miR-106a. Additionally, hsa_circ_0001230 and hsa_circ_0023879 positively regulated hsa-miR-106a target genes phosphatase and tensin homolog (PTEN) and Bcl-2-like protein 11 (BCL2L11) in podocytes. Conclusion Hsa_circ_0001230 and hsa_circ_0023879 are novel blood biomarkers for FSGS. They may regulate podocyte apoptosis by competitively binding to hsa-miR-106a.

In order to study the creep mechanical properties of sandstone subjected to graded loading under the condition of freeze-thaw cycles, 15 freeze-thaw cycles were conducted with four groups of rock samples. The porosity variation of sandstone before and after the freeze-thaw cycles were obtained by using the nuclear magnetic resonance (NMR) technique. The results show that under the action of freeze-thaw cycles, the cohesion between particles inside the rock decreases, the pore structure deteriorates continuously, and the porosity of the rocks increases. During the graded loading creep test, the rock underwent macroscopic failure under low-level loading. Moreover, the fracture morphology showed tensile-shear failure characteristics, which caused obvious decreases in the long-term strength of the rock. The comprehensive analysis of the experimental data to establish the creep model and constitutive equation under the condition of the freeze-thaw cycle, and discuss the relationship between creep model parameters and freeze-thaw factors. The nonlinear creep mode can effectively reflect the graded loading creep law of frozen and thawed sandstone.

To study the evolutionary characteristics of mesostructural damage to saturated limestone under different loading and unloading paths, three types of loading and unloading tests involving three different loading rates and initial peak stresses were performed. Nuclear magnetic resonance technology and scanning electron microscopy were used to investigate the evolutionary characteristics of pore water during the loading and unloading of the limestone. The results indicated that, with an increase in the initial peak stress, the rock viscoplasticity gradually decreased, and the variation of pore radius and the reduction of bound water decreased. With an increasing loading rate, the mesostructure evolution law under disturbance-increasing amplitude (DIA) cycling was opposite to those under increasing amplitude (IA) and repeated-increasing amplitude (RIA) cycling. With the increasing loading stress level, the porosity decreased and then increased. Under increasing amplitude cycling, a larger initial porosity resulted in higher pore compaction and expansion limits. Reducing the initial peak stress inhibited the pore expansion, whereas it had the opposite effect under RIA and DIA cycling. During loading and unloading, bound water exists in pores of organic matter and mesopores, and free water exists in macropores of intergranular and transgranular fractures. These changes indicate certain laws under different loading and unloading paths. The results of this study indicate that the mesostructure characteristics of rock depend on the loading and unloading paths.

To study the acoustic emission evolution characteristics of saturated limestone under different loading and unloading paths, three cyclic loading and unloading tests were conducted with different loading rates and initial cyclic peak stresses, and acoustic emission monitoring was performed simultaneously. The results indicate that, during loading and unloading, the intermediate-frequency signals of saturated rock exhibit a variation trend of sparse–dense–sparse signals, whereas the low-frequency signals are continuously and massively produced. With the increase in the loading rate, the development trends of cumulative hits and energy become closer, and the development form of ringing count changes from N-type to U-type and then to N-type. The slight increase period and attenuation period are extended, whereas the intense growth period and postpeak calm period are shortened. With an increase in the initial cyclic peak stress, the change in cumulative energy is more obvious than that in cumulative hits near the rock failure. The development form of the ringing count changes from U-type to W-type and then to N-type, and each period is first shortened and then extended. With the increase in loading rate, the increase in the slow-change period tends to change from gradually increasing to increasing and then decreasing. By contrast, the increase in the step tends to change to a gradual increase. With the increase in the initial cyclic peak stress, the duration of and increase in the energy in the step and the slow-change period tend to decrease and then increase.

The issue of rock deterioration in chemical environments has drawn much attention in recent years in the rock engineering community. In this study, a series of 30 freeze-thaw cycling tests are conducted on sandstone samples soaked in H2SO4 solution and in pure water, prior to the application of nuclear magnetic resonance (NMR) on the rock specimens. The porosity of the sandstone, the distribution of transverse relaxation time T2, and the NMR images are acquired after each freeze-thaw cycle. The pore size distribution curves of the sandstone after freeze-thaw cycles, four categories of pore scale, and the features of freeze-thaw deterioration for pores of different sizes in H2SO4 solution and pure water are established. The result shows that, with the influence of the acid environment and the freeze-thaw cycles, the mass of the samples largely deteriorates. As the freeze-thaw cycles increase, the porosity of rocks increases approximately linearly. The distribution of the NMR T2 develops gradually from 4 peaks to 5 or even to 6. Magnetic resonance imaging (MRI) dynamically displays the process of the freeze-thaw deterioration of the microstructure inside the sandstones under acid conditions. The results also show pore expansion in rocks under the coupling effects of chemistry and the freeze-thaw cycles, which differ largely from the freeze-thaw deterioration of the rock specimens placed in pure water.

To analyse the effect of loading rate on the energy evolution of rocks under cyclic loading and unloading, tests on saturated limestone were conducted at loading rates of 0.15, 0.2, and 0.3 mm/min, and the evolution characteristics of plastic, elastic, dissipation, and input energies were examined under different loading rates. The results indicated that the plastic strain in the entire test was directly proportional to the loading rate. In addition, strength, residual stress, plastic energy, and dissipation energy under residual resistance were inversely proportional to the loading rate. The plastic strain exhibited a decreasing–stabilising–increasing trend, and the smaller loading rate delayed the “increasing” trend. The increasing extent of each energy exhibited the following trend: input > elastic > plastic > dissipation energy. Furthermore, the first three types of energy exhibited a slow–fast–slow–fast increase trend. The dissipation energy exhibited a fast–steady–fast–slow–fast increase trend. Additionally, the elastic energy index exhibited a large increase–steady increase–decrease trend, which was proportional to the loading rate. The damping ratio exhibited a decrease–increase–decrease–increase–decrease trend which was proportional to the loading rate in the compaction stage and inversely proportional to the plastic stage.

To study the evolution of porosity in the process of filling slurry hydration, samples of tailing filling with different mixing ratios and different curing ages were prepared, and the pore structure was tested by low-field nuclear magnetic resonance (LF-NMR). According to the T2 spectrum distribution curve and T2 spectrum area of the filling slurry hydration process, the porosity and the evolution of the pore distribution features of the filling samples were analysed. The results showed that the higher the mass concentration of the filling slurry, the slower the hydration reaction, the smaller the average size of the pores, the higher the proportion occupied by harmful pores, and the lower the proportion occupied by multiharmful pores. The smaller the cement-sand ratio of the slurry, the higher the proportion occupied by harmful pores and the larger the aperture of the pores. The porosity of the filling slurry with the cement-sand ratio of 1 : 8 is the highest, and the hydration velocity of the filling slurry with the cement-sand ratio of 1 : 3 is the fastest.