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"Li, Jianhua"
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Research status and development trend of ceramifiable silicone rubber composites: a brief review
Ceramifiable silicone rubber composites (CSR) are one of the most important industrially produced elastic technical materials. At present, there is a strong demand for CSR in the high-tech fields of high-speed rail, nuclear power, rocket and aerospace, which are still to be met. Many scholars have committed to the research work of improving the thermal stability, flame retardant, mechanical properties by changing the silicone rubber (SR) matrixes and filler, tremendous advances in CSR have been made for over the last decades where CSR intended for the high technology fields has evolved through different generations. In summary, the first-generation research is based on matrix reaction, the second-generation research is on reaction products, and the third-generation research is on fillers effects. In this review, the evolution of CSR and the synthesis routes, reaction mechanism, and degradation mechanism are introduced and analyzed; fillers, various types of CSR based composites as well as the flame retardancy and mechanical properties are reviewed. Finally, the problems of developing high-performance CSRs are proposed and discussed. This review provides a theoretical basis and supporting data for the application of high-performance CSR, as well as provides details on the fire prevention mechanism of CSR.
Journal Article
Improving the mechanical and ceramifiable properties of low temperature prepared silicone rubber composites
Silicone rubber has been widely used in electronic appliances, nuclear power cable, aerospace and so on, However, silicone rubber will continue to burn when exposed to flame, so flame retardant modification is required. In this work, aluminum hypophosphite (AHP) and Mica were used fluxing agent to make ceramizable silicone rubber material (CSR). The ceramization mechanism was investigated based on microstructure, mechanical and flame retardation properties. The scanning electron microscope result shows that the addition of AHP reduce the ceramization temperature effectively. AHP/Mica modified CSR have better flame retardation properties than pure silicone rubber, the addition of AHP increase LOI to 33.9%, and the LOI is 34.8% and the UL-94 is FV1 as 25 parts of Mica are added. When the 10 phr aluminum hypophosphite replaces Mica, the compression strength reach 14.46 MPa, increased by 42.5%. Moreover, the phenomenon of expansion into ceramics was founded and studied.
Journal Article
Seismic response of a mid-story isolated stilted structure in mountainous areas
Research on the SSI effect on flat sites has yielded many valuable conclusions. However, current research on the impacts of various special local terrains on structural dynamics remains limited. For mountainous areas, it is common to construct houses in a multi-step, climbing, and laterally staggered architectural form that follows the mountain terrain. Only through the analysis of the combined action of the upper and lower parts can the seismic performance of this type of structural form be better revealed; considering the influence of SSI effects will be closer to the actual seismic effects. Therefore, to identify the damage factors of the mid-story isolated stilted structures under earthquakes and provide optimized design plans for the structures, six models are established considering three slopes and two types of foundations based on the engineering case in Chongqing, China. Through the elastic-plastic time-history analysis under earthquakes in the down and transverse-slope directions, concludes, compared with not considering SSI, the seismic response of the mid-story isolated stilted structures considering SSI in mountainous areas is amplified. With the increase of the mountain slope, the seismic response of the structures considering SSI increases, and the amplification coefficients are between 1–1.8. The amplification coefficients of the structures without SSI are concentrated around 1, which is less influenced by the slope. The damage to the stilted isolated layer is mainly concentrated in the column and the beam end, and the maximum seismic response appears in the short columns. The foundation soil stress increases with the increase of the mountain slope.
Journal Article
Correction: Seismic response of a mid-story isolated stilted structure in mountainous areas
[This corrects the article DOI: 10.1371/journal.pone.0312503.].
Journal Article
Chloroplastic metabolic engineering coupled with isoprenoid pool enhancement for committed taxanes biosynthesis in Nicotiana benthamiana
Production of the anticancer drug Taxol and its precursors in heterologous hosts is more sustainable than extraction from tissues of yew trees or chemical synthesis. Although attempts to engineer the Taxol pathway in microbes have made significant progress, challenges such as functional expression of plant P450 enzymes remain to be addressed. Here, we introduce taxadiene synthase, taxadiene-5α-hydroxylase, and cytochrome P450 reductase in a high biomass plant
Nicotiana benthamiana
. Using a chloroplastic compartmentalized metabolic engineering strategy, combined with enhancement of isoprenoid precursors, we show that the engineered plants can produce taxadiene and taxadiene-5α-ol, the committed taxol intermediates, at 56.6 μg g
−1
FW and 1.3 μg g
−1
FW, respectively. In addition to the tools and strategies reported here, this study highlights the potential of
Nicotiana spp
. as an alternative platform for Taxol production.
Engineering Taxol pathway in microbes needs to overcome the difficulty of expressing plant P450 enzymes. Here, the authors use a compartmentalized metabolic engineering strategy to construct the taxanes production pathway in chloroplasts of
Nicotiana benthamiana
and realize the production of taxadience-5α-ol.
Journal Article
Land use land cover change analysis and detection of its drivers using geospatial techniques: a case of south-central Ethiopia
The rapid expansion of agriculture and human settlements has simplified natural ecosystems and harmed the earth's biodiversity. The current study was conducted in south-central Ethiopia to identify LULC change dynamics, and analysis of their driving force using geospatial technology. A supervised maximum likelihood image classification method was employed in combination with the visual interpretation of satellite images to categorise and map LULC classes of the study landscape. Semi-structured interviews, field observations, key informants, and Focus Group Discussions (FGDs) were employed to identify major driving forces, periodic LULC changes and impacts. The classification result showed a considerable decline in forestland from (43.1%) in 1973 to (13.1%) in 2000. Similarly, grasslands declined from (45.5%) in 1973 to (6.3%) in 2018. On the other hand, cropland has increased from (9.24%) in 1973 to (32.04%) in 1986 likewise between 2000 and 2018 its coverage was augmented from 45.4% to 51.1%, respectively. . Local communities perceived population growth, settlement, urbanisation, expansion of farmlands, and fuel wood collection as dominant drivers of LULC changes in the study area in thewatershed. The respondents also observed that the decline in forest LULC triggered the loss of biodiversity, soil fertility, and water availability. Hence, local and national regimes must take adequate measures to minimise the rapid shift in land use and to balance the protection of the human livelihood with the environment.
Journal Article
An in situ tissue engineering scaffold with growth factors combining angiogenesis and osteoimmunomodulatory functions for advanced periodontal bone regeneration
Background
The regeneration of periodontal bone defect remains a vital clinical challenge. To date, numerous biomaterials have been applied in this field. However, the immune response and vascularity in defect areas may be key factors that are overlooked when assessing the bone regeneration outcomes of biomaterials. Among various regenerative therapies, the up-to-date strategy of in situ tissue engineering stands out, which combined scaffold with specific growth factors that could mimic endogenous regenerative processes.
Results
Herein, we fabricated a core/shell fibrous scaffold releasing basic fibroblast growth factor (bFGF) and bone morphogenetic protein-2 (BMP-2) in a sequential manner and investigated its immunomodulatory and angiogenic properties during periodontal bone defect restoration. The in situ tissue engineering scaffold (iTE-scaffold) effectively promoted the angiogenesis of periodontal ligament stem cells (PDLSCs) and induced macrophage polarization into pro-healing M2 phenotype to modulate inflammation. The immunomodulatory effect of macrophages could further promote osteogenic differentiation of PDLSCs in vitro. After being implanted into the periodontal bone defect model, the iTE-scaffold presented an anti-inflammatory response, provided adequate blood supply, and eventually facilitated satisfactory periodontal bone regeneration.
Conclusions
Our results suggested that the iTE-scaffold exerted admirable effects on periodontal bone repair by modulating osteoimmune environment and angiogenic activity. This multifunctional scaffold holds considerable promise for periodontal regenerative medicine and offers guidance on designing functional biomaterials.
Graphic Abstract
Journal Article
Comparing the effects of highly aspherical lenslets versus defocus incorporated multiple segment spectacle lenses on myopia control
To compare spectacle lenses with highly aspherical lenslets (HAL) versus defocus incorporated multiple segments (DIMS) on myopia progression control in 1 year. This retrospective cohort study involved data from children prescribed HAL or DIMS spectacle lenses in Guangzhou Aier Eye Hospital, China. To address the discrepancy that some children followed up at less than or more than 1 year, the standardized 1-year spherical equivalent refraction (SER) and axial length (AL) changes from baseline were calculated. The mean differences in the changes between the two groups were compared with linear multivariate regression models. Age, sex, baseline SER/AL, and treatment were included in the models. A total of 257 children who qualified for the inclusion criteria were included for the analyses (193 in the HAL group and 64 in the DIMS group). After controlling baseline variates, the adjusted mean (standard error, SE) of the standardized 1-year changes in SER for HAL and DIMS spectacle lens users were − 0.34 (0.04) D and − 0.63 (0.07) D, respectively. HAL spectacle lenses reduced myopia progression by 0.29 D (95% confidence interval [CI] 0.13 to 0.44 D) at 1 year compared to DIMS lenses. Accordingly, the adjusted mean (SE) ALs increased by 0.17 (0.02) and 0.28 (0.04) mm for children wearing HAL lenses and DIMS lenses, respectively. HAL users had 0.11 mm less AL elongation (95% CI − 0.20 to − 0.02 mm) than DIMS users. Age at baseline was significantly associated with AL elongation. Chinese children wearing spectacle lenses designed with HAL had less myopia progression and axial elongation than those wearing spectacle lenses designed with DIMS.
Journal Article