Pressure-induced strong ferroelectric polarization in tetra-phase perovskite CsPbBr3.

Ab initio simulations combined with the Berry phase method are employed to investigate ferroelectric polarization of tetragonal CsPbBr3 crystals by applying hydrostatic pressure varying from 0 to 19 GPa; we find that the object research belongs to the P4mm space group. The calculated results show that the materials undergo a paraelectric-ferroelectric phase transition when the pressure increases to a critical value 15 GPa. The polarization is strongly enhanced and attains a high value of about 23 µC cm-2, owing to the increase in the ionic and electric contributions to the polarization under compressive strain. We present a detailed theoretical investigation to analyze the origin of polarization. The ionic polarization is mainly ascribed to the central displacements of Pb2+ cations and Br- anions induced by a highly distorted octahedral PbBr6- framework. Electronic structure calculations suggest that asymmetric hopping p orbital electrons of Br(3) ions are responsible for the enhancement in electric polarization. These discoveries suggest that tetragonal CsPbBr3 has significant potential in future ferroelectric applications, and this can broaden the application field from optoelectronics to ferroelectrics.

The effect of regular aerobic exercise on renal function in patients with CKD: A systematic review and meta-analysis.

Objective: To evaluate the effect of regular aerobic exercise on the improvement of renal function in patients with chronic kidney disease through meta-analysis and to provide targeted exercise recommendations for patients with CKD. Methods: PubMed, Web of Science, EBSCO, China National Knowledge Infrastructure (CNKI), and other databases were searched, and randomized controlled trials on the effects of regular aerobic exercise on renal function-related indexes in patients with CKD were collected according to the inclusion and exclusion criteria. The methodological quality of the included literature was evaluated using the Cochrane evaluation tool second generation, and statistical analysis was performed using R analysis software. Results: A total of 12 randomized controlled trials (RCTs) with a total of patients with CKD were included, and the results of the meta-analysis showed that regular aerobic exercise significantly improved the estimated glomerular filtration rate SMD = 0.65, 95% CI [0.30, 1.00], serum creatinine SMD = -0.63, 95% CI [-0.86, -0.40], 24-h urine protein volume in patients with CKD SMD = -0.41, 95% CI [-0.70, -0.11], and serum urea nitrogen SMD = -0.66, 95% CI [-1.20, -0.12]. Single exercise session longer than 30 min significantly improved the estimated glomerular filtration rate in CKD patients (p < 0.01), and walking and running as exercise modalities significantly improved CKD patients' SCr levels were significantly improved by walking and running as exercise modalities (p < 0.05), and the improvement effect was not significant when cycling was selected as an exercise modality. Conclusion: Regular aerobic exercise has a significant effect on the estimated glomerular filtration rate, serum creatinine, 24-h urine protein amount, and blood urea nitrogen in CKD patients. Aerobic exercise with a single exercise duration longer than 30 min has a more significant effect on the estimated glomerular filtration rate, and aerobic exercise by walking or running can more effectively improve the serum creatinine in CKD patients.

Effects of exercise training in hypoxia versus normoxia on fat-reducing in overweight and/or obese adults: A systematic review and meta-analysis of randomized clinical trials.

Objective: Fat loss theory under various oxygen conditions has been disputed, and relevant systematic review studies are limited. This study is a systematic review and meta-analysis to assess whether hypoxic exercise training (HET) leads to superior fat-reducing compared with normoxic exercise training (NET). Methods: We searched PubMed, Web of Science, CNKI, ProQuest, Google Scholar, Cochrane Library, and EBSCOhost from inception to June 2022 for articles comparing the effects of hypoxic and normoxic exercise on body composition indicators, glycometabolism, and lipometabolism indicators in obese and overweight adults. Only randomized controlled trials (RCTs) were included. The effect sizes were expressed as standardized mean difference (SMD) and 95% confidence intervals (CI). Between-study heterogeneity was examined using the I 2 test and evaluated publication bias via Egger's regression test. The risk of bias assessment was performed for each included trial using Cochrane Evaluation Tool second generation. The meta-analysis was performed by using R 4.1.3 and RevMan 5.3 analytic tools. Results: A total of 19 RCTs with 444 subjects were analyzed according to the inclusion and exclusion criteria. Among them, there were 14 English literature and five Chinese literature. No significant difference in body composition (SMD -0.10, 95% CI -0.20 to -0.01), glycometabolism and lipid metabolism (SMD -0.01, 95% CI -0.13 to -0.10) has been observed when comparing the HET and NET groups. We only found low heterogeneity among trials assessing glycometabolism and lipometabolism (I 2 = 20%, p = 0.09), and no publication bias was detected. Conclusion: The effects of HET and NET on fat loss in overweight or obese people are the same. The application and promotion of HET for fat reduction need further exploration.

Effect of Long-Term Exercise on Liver Lipid Metabolism in Chinese Patients With NAFLD: A Systematic Review and Meta-Analysis.

Purpose: Using meta-analysis to evaluate the effect of various long-term exercises (more than 4 weeks) on liver lipid metabolism of Chinese patients with non-alcoholic fatty liver disease (NAFLD) and provides more targeted exercise recommendations. Methods: Four databases consisting of PubMed, Web of Science, China Science and Technology Journal Database (VIP), China Knowledge Resource Integrated Database (CNKI) were searched up to May 2021. Randomized controlled trials (RCTs) were eligible, and the outcomes of body composition, lipid metabolism [including triglyceride (TG), total cholesterol (TC), low-density lipoprotein-cholesterol (LDL-C), and high-density lipoprotein-cholesterol (HDL-C)], and liver function [including alanine aminotransferase (ALT) and aspartate aminotransferase (AST)] were used to assess the effectiveness of long-term exercise on Chinese patients with NAFLD. Results: Eleven articles with a total of 13 data points (involving 1,006 participants) satisfied the inclusion criteria and were pooled in the meta-analysis. The findings demonstrated that long-term exercise decreased the level of TG [-0.50, 95%CI (-0.64, -0.36)], TC [-0.55, 95%CI (-0.92, -0.18)], LDL-C [-0.29, 95%CI (-0.43, -0.15)], ALT [-3.45, 95%CI (-6.78, -0.12)], AST [-6.91, 95%CI (-10.00, -3.81)], and body mass index (BMI) of patients who did exercise last more than 6 months [-1.55, 95%CI (-2.32, -0.79)] significantly. The effect on HDL-C was not obvious. Conclusion: Long-term exercise can improve the levels of TG, TC, LDL-C, ALT, and AST in Chinese patients with NAFLD significantly, and exercise last more than 6 months can decrease the BMI of Chinese patients with NAFLD.

Effects of Different Resistance Exercise Forms on Body Composition and Muscle Strength in Overweight and/or Obese Individuals: A Systematic Review and Meta-Analysis.

PURPOSE: This study is a systematic review and meta-analysis to determine the effects of different forms of resistance training on body composition and muscle strength in overweight and/or obese people. METHOD: Only randomized controlled trials (RCTs) were included by searching relevant databases such as a web of science, PubMed, and EBSCO, with search dates up to September 30, 2021. These trials performed resistance exercise training in overweight and/or obese people, and outcome indicators included evaluation of body composition and muscle strength, among other relevant indicators. The Cochrane evaluation tool was used to evaluate the methodological quality of the included literature, and statistical analysis was performed using the R analysis software. RESULTS: Fifteen studies, 18 trials, with a total of 669 participants meeting eligibility criteria were included in the final analysis, which included three resistance training types (own body weight, resistance bands, and free weight). The results showed that resistance bands improved body fat (BF; SMD -0.79, 95% CI -1.25 to -0.33, I 2 = 0%) in overweight or obese people better than other resistance training types. Own body weight resistance training was better for increasing skeletal muscle mass in overweight or obese people (SMD 0.48, 95% CI 0.04-0.92, I 2 = 0%). In addition, for muscle strength increase, although resistance exercise was shown to improve muscle strength, there was no significant difference between the three exercise forms compared. CONCLUSION: Resistance bands can improve body composition by reducing BF. Resistance bands can improve body composition by reducing BF, while it is more effective in increasing muscle mass and own body weight. Therefore, for overweight and obese people, resistance bands resistance exercise can be taken for fat loss, and resistance exercise for own body weight for further muscle gain and maintenance of muscle mass, so as to achieve the purpose of improving body composition.

The Study to Improve Oil Recovery through the Clay State Change during Low Salinity Water Flooding in Sandstones.

Low salinity water flooding is a low-cost enhanced oil recovery (EOR) technology. The mechanism of EOR in a sandstone reservoir is still controversial, and there are many influencing factors. In this study, the effects of salinity (2000, 4000, 8000, and 100,000 ppm), pH (5.5 acidic, 7.0 neutral, and 8.0 alkaline), cation type (Na+ and Ca2+), and clay content (A rock 6.04%, B rock 11.94%) on zeta potential and recovery related to clay swelling were studied. The results showed that the absolute value of zeta potential increased with the decrease of salinity, cation changes from divalent to monovalent, and an increase of the pH value or clay content. The results of the SEM test before and after displacement and the continuous increase of displacement pressure after low salinity water injection show that low salinity water will cause clay swelling and the absolute value of zeta potential increased. The extreme value of recovery appears in the rocks with a high clay content: In neutral and alkaline NaCl solutions, RI and PEOR of rock B first increase and then decrease with the decrease of salinity. When the salinity is 4000 ppm, RI and PEOR were 8.16 and 34.13% in the neutral state, and 8.50 and 25.00% in the alkaline state, respectively. RI and PEOR of other experimental groups increased with the decrease of salinity. The study showed that the displacement pressure increases with the decrease of salinity, which indicates that the proper expansion of clay can improve the recovery of a sandstone reservoir, while the excessive expansion of clay will damage the reservoir and reduce the recovery. Based on the experimental results, the factors and indexes involved in the experiment were analyzed by multiple variance analysis. The result showed that the salinity, cationic type, and pH value have a significant effect on the zeta potential. All factors in the experiment have a significant effect on RI , salinity, and cationic type, and the clay content have a significant effect on PEOR. The conclusion of this study could guide the design of low-salinity water flooding technology in oil fields.

Layer-dependent transport and optoelectronic property in two-dimensional perovskite: (PEA)2PbI4.

Recently, two-dimensional (2D) layered organic-inorganic hybrid perovskites have attracted a huge amount of interest due to their unique layered structure, and potential optical properties. However, amongst researchers it has long been disputed as to whether it is suitable for use as a photovoltaic material or light-emitting device. Here, we present a detailed theoretical investigation to discuss the photovoltaic and optoelectronic properties of a novel synthetic 2D layered perovskite (PEA)2PbI4. Based on the calculated geometric and electronic structure, charge carrier mobilities of the 2D layered (PEA)2PbI4 are predicted theoretically. In addition, the linear dichroism and exciton binding energies are also calculated. We found that the carrier mobilities of the 2D layered (PEA)2PbI4 reach the same order of magnitude as those of the optoelectronic material MoS2, but smaller than those of the photovoltaic material MAPbI3 and Si crystal, whereas exciton binding energies (Eb) enlarge with the thinning layers, being obviously higher than MAPbI3 and Si crystal. Moreover, the system exhibits a strong linear dichroism, suggesting weak absorption along the c axis in the visible spectrum, which is detrimental to photovoltaics. Our work provides a theoretical basis to prove that ultrathin two-dimensional (2D) materials may be potential candidates for optoelectronic detection devices, rather than solar absorbers.