Revaluating coal permeability-gas pressure relation under various gas pressure differential conditions

Identifying changes in coal permeability with gas pressure and accurately codifying mean efective stresses in laboratory samples are crucial in predicting gas-fow behavior in coal reservoirs. Traditionally, coal permeability to gas is assessed using the steady-state method, where the equivalent gas pressure in the coal is indexed to the average of upstream and downstream pressures of the coal, while ignoring the nonlinear gas pressure gradient along the gas fow path. For the fow of a compressible gas, the traditional method consistently underestimates the length/volume-averaged pressure and overestimates mean efective stress. The higher the pressure diferential within the sample, the greater the error between the true mean pressure for a compressible fuid and that assumed as the average between upstream and downstream pressures under typical reservoir conditions. A correction coefcient for the compressible fuid pressure asymptotes to approximately 1.3%, representing that the error in mean pressure and efective stress can be on the order of approximately 30%, particularly for highly pressure-sensitive permeabilities and compressibilities, further amplifying errors in evaluated reservoir properties. We utilized this volume-averaged pressure and efective stress to correct permeability and compressibility data reported in the literature. Both the corrected initial permeability and the corrected pore compressibility were found to be smaller than the uncorrected values, due to the underestimation of the true mean fuid pressure, resulting in an overestimation of reservoir permeability if not corrected. The correction coefcient for the initial permeability ranges from 0.6 to 0.1 (reservoir values are only approximately 40% to 90% of laboratory values), while the correction coefcient for pore compressibility remains at approximately 0.75 (reservoir values are only approximately 25% of laboratory value). Errors between the uncorrected and corrected parameters are quantifed under various factors, such as confning pressure, gas sorption, and temperature. By analyzing the evolutions of the initial permeability and pore compressibility, the coupling mechanisms of mechanical compression, adsorption swelling, and thermal expansion on the pore structure of the coal can be interpreted. These fndings can provide insights that are useful for assessing the sensitivity of coal permeability to gas pressure as truly representative of reservoir conditions.

Study on the Therapeutic Effects and Mechanisms of Human Mesenchymal Stem Cell-Derived Exosomes Carrying NGF Gene in Treating Ischemic Stroke in Rats

Objective:To investigate the therapeutic effects and mechanisms of human mesenchymal stem cell-derived exosomes(hMSCs-Exo)carrying the NGF gene in treating ischemic stroke in rats,aiming to provide new insights and treatment methods for ischemic stroke therapy.Methods:After successful construction of the cerebral ischemia model in 40 male SPF-grade SD rats aged 6-8 weeks,the model rats were randomly divided into 4 groups:Sham group,PBS group,hMSCs-Exo group,and NGF-hMSCs-Exo group,with 10 rats in each group.The rat MCAO model was prepared using the classic filament method,and NGF-hMSCs-Exo were injected via the tail vein into the MCAO model rats.The expression of the NGF gene in brain ischemic tissues,neuronal regeneration,and rat neurological function recovery were observed using TTC staining,memory function evaluation,Western blot,qRT-PCR,and other methods.Results:Compared with the Sham group,neurological deficits were significant in the PBS group(P<0.01).Compared with the PBS group,neurological scores improved in the hMSCs-Exo group and NGF-hMSCs-Exo group(P<0.05).Compared with the hMSCs-Exo group,the improvement in neurological deficits was more significant in the NGF-hMSCs-Exo group(P<0.05).The infarct area after NGF-hMSCs-Exo intervention was significantly reduced(P<0.05)compared with the Sham group.Compared with the PBS group,relative expression levels of NGF mRNA and protein decreased,while Caspase-3 mRNA and protein expression significantly increased in the PBS group(P<0.01).Compared with the PBS group and hMSCs-Exo group,there were differences in NGF and Caspase-3 mRNA and protein expression in the NGF-hMSCs-Exo group rat brain tissues(P<0.05).Conclusion:Treatment with human mesenchymal stem cell-derived exosomes carrying the NGF gene improves cognitive function and exerts protective effects on SD rats while inhibiting apoptotic levels in cells.

The advantages of penehyclidine hydrochloride over atropine in acute organophosphorus pesticide poisoning:A meta-analysis

Background:Penehyclidine hydrochloride(PHC)has been used for many years as an anticholinergic drug for the treatment of acute organophosphorus pesticide poisoning(AOPP).The purpose of this meta-analysis was to explore whether PHC has advantages over atropine in the use of anticholinergic drugs in AOPP.Methods:We searched Scopus,Embase,Cochrane,PubMed,ProQuest,Ovid,Web of Science,China Science and Technology Journal Database(VIP),Duxiu,Chinese Biomedical literature(CBM),WanFang,and Chinese National Knowledge Infrastructure(CNKI),from inception to March 2022.After all qualified randomized controlled trials(RCTs)were included,we conducted quality evaluation,data extraction,and statistical analysis.Statistics using risk ratios(RR),weighted mean difference(WMD),and standard mean difference(SMD).Results:Our meta-analysis included 20,797 subjects from 240 studies across 242 different hospitals in China.Compared with the atropine group,the PHC group showed decreased mortality rate(RR=0.20,95%confidence intervals[CI]:0.16–0.25,P<0.001),hospitalization time(WMD=-3.89,95%CI:-4.37 to-3.41,P<0.001),overall incidence rate of complications(RR=0.35,95%CI:0.28–0.43,P<0.001),overall incidence of adverse reactions(RR=0.19,95%CI:0.17–0.22,P<0.001),total symptom disappearance time(SMD=-2.13,95%CI:-2.35 to-1.90,P<0.001),time for cholinesterase activity to return to normal value 50–60%(SMD=-1.87,95%CI:-2.03 to-1.70,P<0.001),coma time(WMD=-5.57,95%CI:-7.20 to-3.95,P<0.001),and mechanical ventilation time(WMD=-2.16,95%CI:-2.79 to-1.53,P<0.001).Conclusion:PHC has several advantages over atropine as an anticholinergic drug in AOPP.

Fiber-dominated Soft Actuators Inspired by Plant Cell Walls and Skeletal Muscles

Morphing botanical tissues and animal muscles are all fiber-mediated composites, in which fibers play a passive and active role, respectively. Herein, inspired by the mechanism of fibers functioning in morphing botanical tissues and animal muscles, we propose two sorts of fiber-dominated composite actuators. First, inspired by the deformation of awned seeds in response to humidity change, we fabricate passive fiber-dominated actuators using non-active aligned carbon fibers via 4D printing method. The effects of process parameters, structural parameters, and fiber angles on the deformation of the printed actuators are examined. The experimental results show that the orientation degree is enhanced, resulting in a better swelling effect as the printing speed increases. Then, motivated by the actuation mechanism of skeletal muscle, we prepare active fiber-dominated actuators using active polyurethane fibers via 4D printing and pre-stretching method. The effect of fiber angle and loading on the actuation mode is experimentally analyzed. The experimental results show that the rotation angle of the actuator gradually decreases with the angle from 45° to 60°. When the fiber angle is 0° and 90°, the driver basically stops rotating while shrinking along the loading direction. Based on the above actuation mechanisms, identical contraction behaviors are realized both in passive and active fiber-dominated soft actuators. This work provides a validation method for biologically actuation mechanisms via 4D printing technique and smart materials and adds further insights to the design of bioinspired soft actuators.