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Inspired by the multilayer structure of the shellfish, a novel two-dimensional (2D) composite structure consisting of graphene oxide, MoS2 and graphene oxide (G/M/G) was integrated to the flexible pressure sensing. The composite structure was prepared by the vacuum suction filtration in order to imitate the high toughness of shellfish. Based on the strategy of strain engineering, a comprehensive experimental bench capable of meeting different strain conditions was connected to a push–pull meter and an LCR digital bridge, and then a computer was used to record the changes in transducer capacitance when an external load was applied to the meter. Graphene oxide (GO) and G/M/G supercells were constructed, and density functional theory (DFT) simulations of the initial energy band structure under strain-free conditions were carried out to determine the relationship between the band gap, conductivity, capacitance, and sensitivity of the G/M/G structure based on band gap theory, and to easily understand the mechanism of the shellfish heterostructure leading to enhanced sensitivity of the sensors. Using two-point bending and axial tensile tests, a flexible pressure sensing device was designed to realize positive strains in the ranges of 0%–5 % and 5%–50 %. The results show that the sensitivity of both GO and G/M/G capacitive pressure sensors decreased with increased strain, and the sensitivity of the G/M/G sensors was significantly improved by 75%–102 % compared to the GO sensors at the same strain. The parallel-plate capacitor model and crack growth theory well explain the experimental results at small and large strains. Our results provide new concepts for the design of novel flexible sonar with high sensitivity and large strain operating range by a simple vacuum filtration method, which can be extended to the design of other high-performance 2D flexible electronic devices. Inspired by the multilayer structures of shellfish in nature, we constructed a GO/MoS2/GO heterojunction pressure sensor. The working range under strain and the pressure sensitivity of this new bio-inspired sensor were respectively improved by 25% and 102% compared to the traditional GO sensor structure. [ABSTRACT FROM AUTHOR]

Channel fracturing technology is designed to form fractures supported by non-uniform pillar proppants. Non-cured adhesive resin-coated proppant gradually becomes viscous after immersion and agglomerates during transportation. The pillars are stable after the fracture is closed. They not only maintain a certain compressive strength but also maintain long-term conductivity. Currently, there are few evaluations of coated proppant migration. Based on CFD-DEM method, a two-phase flow coupling model considering the adhesive contact force of coated proppant particles is established to study the cementation characteristics of coated proppant during transportation. The transportation mechanism of coated proppant are revealed by numerical calculation analysis. The results show that different from the conventional proppant, the migration process of the coated proppant is divided into four stages (1) the softening of the proppant contact; (2) the paving of the proppant agglomeration; (3) proppant pillars growth along fracture height; and (4) proppant pillars growth along fracture length. We have completed a preliminary geometric characteristics evaluation of sand bank formed by coated proppant by evaluating the pore volume ratio (the ratio of void volume between pillars to the sand bank volume) under various parameters. This evaluation offers some theoretical guidance for the optimization of channel fracturing proppant injection parameters. [ABSTRACT FROM AUTHOR]

Vertical drains have been widely used in soil improvement projects to accelerate consolidation and improve the strength of soft soil. Previous consolidation models are mainly based on instantaneous loading, which cannot reflect the actual time-variable loading condition. This paper presents a set of analytical solutions for consolidation with vertical drains under depth and time-dependent loading, involving one-step loading, multi-step loading, and cyclic loading. A four-element model, which is a combination of the Merchant model and Maxwell model, is introduced to consider the rheological characteristics of the soil. By simulating the results of a consolidation test, it is found that the four-element model is more accurate than the Merchant model in predicting the changes in pore pressure and settlement during the clay consolidation process. Based on the solutions obtained, several factors affecting consolidation behavior are investigated. It has been shown that the rheological behavior becomes more and more obvious at the later stage of consolidation with the decrease both in the modulus of the spring in the Kelvin body and the viscosity coefficient of the independent dashpot. With the increase in the viscosity coefficient of the dashpot in the Kelvin body, the rate of consolidation becomes faster at an initial stage but slower at a later stage. For cyclic loading, the consolidation degree in each cycle reaches a maximum at the end of unloading and reaches a minimum at the beginning of the loading. [ABSTRACT FROM AUTHOR]

Clogging of the landfill drainage layer leads to a high leachate head developing over the bottom liner, which increases the risk of leachate leakage. Estimation of the maximum leachate head in the landfill drainage layer is of great significance to the pollution control of bottom liners. In this study, a simplified model considering the development of clogging is established through assuming the spatial and temporal distributions of clogging in a drainage layer of landfill. The calculation results are compared with a previous study to verify the proposed model. Through parameter analysis, it is discovered that the larger the initial hydraulic conductivity, the less the influence of clogging on the leachate head at the beginning, but it will increase over time. Meanwhile, a longer drainage distance, a larger inflow rate, or a higher ion concentration will lead to a greater influence of clogging on the leachate head. The completion time of clogging is more sensitive to the variation of inflow rate and ion concentration. In order to effectively control the maximum leachate head, it is suggested that the drainage material with large hydraulic conductivity such as pebbles or gravel should be used, the drainage slope should be greater than 4%, the drainage distance should be controlled at 20 m, and calcium products should be removed from leachate through adsorption, precipitation, or waste reuse. [ABSTRACT FROM AUTHOR]

Aims: Paroxysmal atrial fibrillation (PAF) commonly recurs after radiofrequency catheter ablation (RFCA). This study aimed to assess left atrial appendage (LAA) volume and function by transesophageal echocardiography (TEE) and to explore its value in predicting PAF recurrence after RFCA. Methods: Eighty patients with PAF were recruited. The left atrial (LA) and LAA volume and function were measured by transthoracic echocardiography (TTE) and TEE before ablation. Patients were followed up for 12 months after RFCA, and recurrence was recorded. Odds ratios of candidate risk indicators were determined by logistic regression analysis. Prediction model was constructed using logistic regression with backward selection. Receiver operating characteristic (ROC) curve with area under curve (AUC) was performed to evaluate the prediction efficiency. Results: Twenty‐four (30%) PAF patients had recurrence (R group), and 56 (70%) patients had no recurrence (NR group). Compared to NR group, LA dimension (LAD), LA volume index (LAVI), LAA maximum volume (LAAVmax), and LAA minimum volume (LAAVmin) were significantly higher in R group, while LAA peak emptying flow velocity (LAAeV), LAA peak filling flow velocity (LAAfV), and LAA ejection fraction (LAAEF) significantly declined in R group. According to multivariate analysis and backward selection, LAVI, LAAEF, and LAAeV were significant risk factors for PAF recurrence. The LAVI + LAAEF + LAAeV joint model could effectively predict PAF recurrence with AUC of 0.893 (95% confidence interval = 0.816, 0.970), sensitivity of 0.75, and specificity of 0.929. Conclusions: This study demonstrated that LAVI, LAAEF, and LAAeV were significant predictors of PAF recurrence after RFCA. [ABSTRACT FROM AUTHOR]

Background: There is ongoing debate about surgery of primary site in nasopharyngeal carcinoma patients.Methods: 3919 patients with nasopharyngeal carcinoma identified in the SEER registry between 2004 and 2013. The benefit of surgery of primary nasopharynx tumor site on overall and cancer-specific survival was assessed by risk-adjusted multivariate Cox proportional hazard regression and propensity score matching modeling.Results: Surgery was marginally associated with better overall survival (hazard ratio (HR) = 0.816, 95% CI 0.656-1.015, p = 0.07) and cancer-specific survival (HR = 0.749, 95% CI 0.552-1.018, p = 0.06) in the propensity score model. Among 398 cases who underwent primary site surgery, 282 (70.85%) received local tumor excision and 79 (20.31%) received pharyngectomy. Local tumor excision and pharyngectomy had almost the same effect on survival in propensity score matching analysis. The benefit was significant in subgroups of white, age <60 year, and patients with T3, N1, M0, AJCC stage III, or moderately differentiated tumors. Further survival analysis showed surgery to promote survival in both radiotherapy and non-radiotherapy patients.Conclusion: This is the first population-based analysis using propensity score model to provide evidence of a positive impact of surgery on survival in nasopharyngeal carcinoma. Moreover, surgery demonstrated the significant benefit in subgroups of patients with specific clinical characteristics. [ABSTRACT FROM AUTHOR]

Background: Long intergenic noncoding RNAs (lincRNAs) are a series of novel transcribed regions expressed in cancers that may represent candidate biomarkers for lung squamous cell carcinoma (LSqCC) treatment. In this study, we evaluated the lincRNA profile in LSqCC patients and screened valuable lincRNAs for diagnosis and prognosis. Methods: Transcriptome profiling of 549 samples derived from 501 LSqCC patients were identified in TCGA database. 48 patients had paired primary tumor (PT) and solid normal (SN) tissue samples, while 453 patients had only PT samples. 1,771 lincRNA candidates were evaluated. Paired test (Wilcoxon two‐sample paired signed rank tests) was performed in paired PT and SN samples. Logistic regression analysis were performed in independent 453 PT samples and 48 SN samples to screen the significant lincRNAs candidates for malignances. Independent 501 PT samples were further used to screen the significant lincRNAs candidates for prognosis. Results: Among 1,771 lincRNAs, 10 lincRNAs were significant highly‐expressed risk candidates in PT samples, and 10 protective lincRNAs candidates were significant lowly‐expressed in PT samples. Among 10 highly‐expressed risk lincRNAs, a small panel of LINC00487, LINC01927, and C10orf143 (LINC00959) could effectively predict malignancies in paired samples (AUC = 0.7274, 95%CI = (0.6264, 0.8285)). When combined with protective lincRNA candidates LINC02315, LINC00491, and LINC01697, the predictive efficiency was greatly improved in both paired samples (AUC = 0.8030, 95%CI = (0.7250, 0.8810)) and independent samples (AUC = 0.7481, 95%CI= (0.6642, 0.8320)). Additionally, three highly‐expressed risk lincRNAs, LINC01031, LINC01088, and LINC01931, were significantly associated with poor prognosis in PT samples, suggesting potential targets for anti‐LSqCC treatment. Conclusion: Therefore, lincRNAs could be promising biomarkers for predicting malignancies and potential anti‐LSqCC targets for drug development. [ABSTRACT FROM AUTHOR]