Liquid carbon dioxide phase change fracturing (LCPCF) technology can effectively increase the coal permeability. In order to evaluate the influence of LCPCF on pore structure and permeability ...characteristics of coal, mercury intrusion porosimetry (MIP) analyses and permeability tests were used in this study. The experimental results show that LCPCF has less effect on transition pores, but it indeed has significant influence on pores (> 100 nm) and fracture structure of coal, further affecting the gas permeability characteristics within coal. This influence is heavily dependent on the distance from the fracturing borehole. When 1.26 L of liquid CO2 (weighing 1.25 kg–1.40 kg) was used to conduct physical blasting, according to the change trends of pore/fracture and gas permeability within coal, the influence degree of LCPCF on coal can be divided into three stages at the distance of 0.2–1.0 m, 1.0–6.0 m and > 6.0 m, respectively. For the first stage, the influence of LCPCF is strengthened, and mesopores within coal are reduced and shift to the larger pores under the effect of high-energy gas and shock wave, leading to the increase in the number of macropores and microfractures, which in turn improves the gas permeability of coal to a large degree. At the second stage, due to the energy attenuation of shock wave and high-pressure CO2 gas, the fracturing effect of LCPCF is reduced with the distance increasing from 1.0 m to 6.0 m, and the increase of coal permeability is rapidly diminished. At the third stage, both the change rates of pore structure and permeability characteristics of coal tend to be stable over 6.0 m away from the fracturing borehole, indicating that the influence scope of LCPCF is approximately 6.0 m for a single fracturing borehole.
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•The change rate of mesopore volume demonstrates a U-shape curve with distance.•The ΔP reduced rate is linearly reduced with the distance at 0.2–6.0 m.•The influence degree of LCPCF on coal was divided into three stages.•The maximum increase of coal permeability is enhanced by 1.2–1.7 times.
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•The composite was prepared by electrohydrodynamic atomization deposition, layer-by-layer stacking and hot pressing technology.•The synergistic strengthening effect of van der Waals ...forces and covalent bonds improved the tensile strength of the composite.•The composite showed outstanding resistance stability, flexibility and electromagnetic interference shielding stability.
It is a challenge to design Ti3C2Tx MXene-based electromagnetic interference (EMI) shielding composites with excellent mechanical properties. Herein, a highly robust, flexible and durable Ti3C2Tx MXene/carbon fiber fabric/thermoplastic polyurethanes (Ti3C2Tx MXene/CFf/TPU) composite was fabricated through simple electrohydrodynamic atomization deposition, layer-by-layer stacking and hot pressing technology. The synergistic strengthening effect of van der Waals forces and covalent bonds can improve the tensile strength of the composite up to170.2 MPa, which is far greater than that of other MXene-based composites previously reported. In addition, the EMI shielding performance of the Ti3C2Tx MXene/CFf/TPU composite also improved with increasing MXene mass fraction, reaching 40.4 dB, which can be attributed to the dielectric loss provided by conductive fillers and the enhanced absorption within the sandwich structure. More interestingly, the composite retained excellent resistance stability, EMI-SE stability and flexibility, even after multiple bending and releasing cycles. This work provides a facile and environmentally-friendly method for preparing composites with excellent EMI shielding properties and mechanical properties, which may provide more possibilities for applications in intelligent wear and electronic wireless communication equipment.
Understanding the mechanical properties of α-quartz is of vital importance to rock engineering because α-quartz is the main component of igneous, metamorphic and sedimentary rocks. Molecular dynamics ...simulations (MDs) of nanoindentation tests on α-quartz were performed to investigate the effects of indenter tip radius and penetration depth on the mechanical properties of α-quartz. Indentation load-penetration depth (P-h) curves were plotted, from which Reduced Young’s modulus (Er), hardness (H)were obtained and these mechanical parameters were then compared with the laboratory nanoindentation results. The mechanical results obtained from MDs are in good agreement with the experimental values. It can be found that Er and H increase with indentation depth at shallow contact depth while they decrease with indenter tip size. To the authors’ knowledge, this is the first MDs of nanoindentation test of hard rock-forming minerals reported and we believe that this study can shed light on the precise measurement of the mechanical properties of rock minerals at micro- and nano-scales.
Nanoindentation has become an increasingly popular method to determine the mechanical properties of both homogeneous and heterogeneous materials. Rocks are inherently heterogeneous and understanding ...their mechanical properties is of vital importance for relevant engineering applications. Due to its high precision and resolution in both force and displacement, nanoindentation can be utilized to extract the localized mechanical properties of individual grains. This review paper presents an overview of applications of nanoindentation techniques in various rocks, such as shale, coal, limestone, marble, sandstone and claystone. Apart from the conventional mechanical parameters, i.e., Young’s modulus and hardness, other parameters, such as fracture toughness, time-dependent creep and tensile strength can also be obtained using nanoindentation methods. Basic equations and parameters employed to obtain the above mechanical parameters are clearly explained. In addition, merits and demerits of previous nanoindentation studies are summarised and roadmap for future trends of nanoindentation in geomaterials are suggested.
Although researchers have extensively investigated the dynamic mechanical properties of metallic materials at the macro-scale in terms of deformation mechanisms, strain rate strengthening and ...fracture mechanisms, they have rarely investigated the dynamic mechanical properties affected by size effects at the micro-/meso-scales. In this study, experiments on quasi-static compression and the split-Hopkinson pressure bar (SHPB) were conducted using oxygen-free high-conductivity (OFHC) copper with different geometrical and grain sizes to explore the size effects on various dynamic mechanical properties at the micro-/meso-scales. The experimental results showed that the quasi-static and dynamic mechanical properties of OFHC copper are affected by size effects at the micro-/meso-scales. In particular, OFHC copper was found to exhibit strain rate strengthening effects at the micro-/meso-scales, and the presence of micro-cracks was observed in the SHPB experimental specimens. In this study, after proposing a modified Johnson-Cook (J-C) constitutive model based on the surface layer model, we analysed the average relative error of the modified model and the original constitutive model. The influence of the size effect on the mechanical properties of materials is taken into account in the new modified constitutive model. The results of relative error analysis showed that the average relative errors for the original J-C model ranged from 3.2% to 18%, while the modified J-C model’s results ranged from 2.2% to 11%. The accuracy of the modified model is greatly improved. Following finite element analysis based on the modified J-C model and the original model, the results showed that the modified J-C model agreed well with the experimental results.
Reconstruction of historical cropland cover is not only essential for studying agricultural development in historical periods, but also provides the basic data for long-term global and climatic ...change simulations. However, reconstructing the amount and spatial distribution of cropland prior to the past millennium remains challenging because of incomplete data and the suitability of the allocation method. Based on the household census and cropland demand per household data, which was calculated from grain consumption per household and crop yield per unit area, this study estimated the prefecture-level cropland area in northern China in AD 609 during the Sui dynasty. Then, a cropland allocation model based on natural land suitability for cultivation was used to reconstruct the spatial distribution of cropland in 5′ × 5′ grid cells. The results were as follows: (1) the cropland area in northern China in AD 609 was 1.77 × 105 km2, with an average cropland area fraction of 10.04%. (2) The cropland was continuously distributed in the North China Plain, Guanzhong Plain, Fenhe Valley and central Shangdang and Changping on the Loess Plateau, resulting in a high cropland agglomeration area appearing in those regions. While it is scattered in the northern Loess Plateau and the Hexi Corridor. (3) Compared with our reconstruction, the HYDE dataset underestimated the cropland area in plains except for riverine areas and overestimated the cropland area in the hills and mountainous areas along the border. (4) This discrepancy was primarily derived from population differences and the divergent cropland allocation methods between the two datasets.
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•Exosomes are nanoscale membrane vesicles formed by dynamic multistep endocytosis processes, about 30–150 nm in diameter.•The crosstalk of exosomes between lung cancer cells and ...healthy cells accelerates the malignant process of lung cancer.•Exosomes play essential roles in the regulation of lung cancer immune suppression.•Exosomes can be used as a diagnostic and the prognostic biomarker for lung cancer.
The incidence and mortality of lung cancer account for first place all over the world. Lung cancer lacks early diagnostic biomarkers; lung cancer patients are usually diagnosed in both middle and advanced stages and have poor treatment outcomes. It is more important to find the first diagnostic tools for lung cancer with high specificity and sensitivity. Besides, exosomes are usually nanometer-sized bi-layered lipid vesicles formed and produced by various types of cells. As one of the main modes of intercellular communication, they can deliver multiple functional biomolecules, such as DNA, microRNAs, messenger RNA (mRNA), long non-coding RNA, and proteins, and the events as mentioned above affects different physiological processes of recipient cells. It has been reported that exosomes are involved in different types of cancer, including lung cancer. Various studies proved that exosomes are involved in multiple cancer processes such as cell proliferation, metastasis, epithelial-mesenchymal transition (EMT), angiogenesis, and the tumor microenvironment in lung cancer. Tumor-derived exosomes (TEX) contain a variety of stimulatory and inhibitory factors involved in regulating immune response, which can affect the tumor microenvironment (TME) and thus participate in the formation and progression of lung cancer. This review's primary purpose to review the latest research progress of exosomes in diagnosing and treating lung cancer.
Clinical evidence regarding the value of
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F-FDG PET for therapy responses assessment in breast cancer is increasing. The objective of this study is to evaluate the accuracy of
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F-FDG PET in ...predicting responses to neoadjuvant therapies with meta-analysis and explore its optimal regimen for clinical use. Articles in English language relating to the accuracy of
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F-FDG PET for this utility were retrieved. Methodological quality was assessed by QUADAS tool. Pooled estimation and subgroup analysis data were obtained by statistical analysis. Nineteen studies met the inclusion criteria and involved 920 pathologically confirmed patients in total (mean age 49.8 years, all female). Methodological quality was relatively high. To predict histopathological response in primary breast lesions by PET, the pooled sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and diagnostic odds ratio were 84% (95% CI, 78–88%), 66% (95% CI, 62–70%), 50% (95% CI, 44–55%), 91% (95% CI, 87–94%), and 11.90 (95% CI, 6.33–22.36), respectively. In regional lymph nodes, sensitivity and NPV of PET were 92% (95% CI, 83–97%) and 88% (95% CI, 76–95%), respectively. Subgroup analysis showed that performing a post-therapy
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F-FDG PET early (after the 1st or 2nd cycle of chemotherapy) was significantly better than later (accuracy 76% vs. 65%,
P
= 0.001). Furthermore, the best correlation with pathology was yielded by employing a reduction rate (RR) cutoff value of standardized uptake value between 55 and 65%.
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F-FDG PET is useful to predict neoadjuvant therapy response in breast cancer. However, the relatively low specificity and PPV still call for caution. It is suggested to perform PET in an earlier course of therapy and use RR cutoff value between 55 and 65%, which might potentially identify non-responders early. However, further prospective studies are warranted to assess this regimen and adequately position PET in treatment management.
Surface-enhanced Raman spectroscopy (SERS) has been a powerful tool for applications including single molecule detection, analytical chemistry, electrochemistry, medical diagnostics and bio-sensing. ...Especially, flexible SERS substrates are highly desirable for daily-life applications, such as real-time and in situ Raman detection of chemical and biological targets, which can be used onto irregular surfaces. However, it is still a major challenge to fabricate the flexible SERS substrate on large-area substrates using a facile and cost-effective technique. The roll-to-roll ultraviolet nanoimprint lithography (R2R UV-NIL) technique provides a solution for the continuous fabrication of flexible SERS substrate due to its high-speed, large-area, high-resolution and high-throughput. In this paper, we presented a facile and cost-effective method to fabricate flexible SERS substrate including the fabrication of polymer nanostructure arrays and the metallization of the polymer nanostructure arrays. The polymer nanostructure arrays were obtained by using R2R UV-NIL technique and anodic aluminum oxide (AAO) mold. The functional SERS substrates were then obtained with Au sputtering on the surface of the polymer nanostructure arrays. The obtained SERS substrates exhibit excellent SERS and flexibility performance. This research can provide a beneficial direction for the continuous production of the flexible SERS substrates.
Land use-induced land cover change (LUCC) is an important anthropogenic driving force of global change that has influenced, and is still influencing, many aspects of regional and global environments. ...Accurate historical global land use/cover datasets are essential for a better understanding of the impacts of LUCC on global change. However, there are not only evident inconsistencies in current historical global land use/cover datasets, but inaccuracies in the data in these global dataset revealed by historical record-based reconstructed regional data throughout the world. A focus in historical LUCC and global change research relates to how the accuracy of historical global land cover datasets can be improved. A methodology for assessing the credibility of existing historical global land cover datasets that addresses temporal as well as spatial changes in the amount and distribution of land cover is therefore needed. Theoretically, the credibility of a global land cover dataset could be assessed by comparing similarities or differences in the data according to actual land cover data (the “true value”). However, it is extremely difficult to obtain historical evidence for assessing the credibility of historical global land cover datasets, which cannot be verified through field sampling like contemporary global land cover datasets. We proposed a methodological framework for assessing the credibility of global land cover datasets. Considering the types and characteristics of the available evidence used for assessments, we outlined four methodological approaches: (1) accuracy assessment based on regional quantitative reconstructed land cover data, (2) rationality assessment based on regional historical facts, (3) rationality assessment based on expertise, and (4) likelihood assessment based on the consistency of multiple datasets. These methods were illustrated through five case studies of credibility assessments of historical cropland cover data. This framework can also be applied in assessments of other land cover types, such as forest and grassland.
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