Characteristics and Source Analysis of Soil Heavy Metal Pollution in a Mining Area

It is of great significance to study the degree and source of soil heavy metal pollution in geological high background value area for remediation of local contaminated soil. The 0 - 20 cm topsoil was taken around the mining area, and the contents of Pb, Zn, Ni, Cd, Hg, Cu and As in the soil were measured. Single-factor pollution index, Nemeiro comprehensive pollution index and potential ecological risk index were used to evaluate the degree of heavy metal pollution and ecological risk. Finally, multivariate statistical analysis was used to analyze the sources of soil heavy metals. The results show that the measured elements are polluted to different degrees, mainly due to the ecological environment problems caused by extensive mining development methods and inefficient utilization of resources. The key link is the release of pollutants at the source. Effectively blocking the release at the source can cut off the possibility of pollutants entering the food chain and the circulation of materials in the ecosystem. The results of potential ecological risk index showed that the potential ecological damage of seven heavy metals was ranked as follows: Cd (97.67) > Hg (68.97) > As (14.29) > Pb (11.55) > Ni (4.62) > Zn (1.61) > Cu (1.45) had a high ecological risk coefficient, and the potential comprehensive ecological risk index was 200.16 and the degree was medium. Principal component analysis shows that the sources of heavy metals are divided into Pb, Cd, As, Zn and Hg mainly from human activities such As mining, while Ni and Cu mainly come from soil parent materials, mining and agricultural activities.

Layer-by-Layer Assembled Bacterial Cellulose/Graphene Oxide Hydrogels with Extremely Enhanced Mechanical Properties

Uniform dispersion of two-dimensional(2 D) graphene materials in polymer matrices remains challenging. In this work, a novel layer-by-layer assembly strategy was developed to prepare a sophisticated nanostructure with highly dispersed 2 D graphene oxide in a three-dimensional matrix consisting of onedimensional bacterial cellulose(BC) nanofibers. This method is a breakthrough, with respect to the conventional static culture method for BC that involves multiple in situ layer-by-layer assembly steps at the interface between previously grown BC and the culture medium. In the as-prepared BC/GO nanocomposites, the GO nanosheets are mechanically bundled and chemically bonded with BC nanofibers via hydrogen bonding,forming an intriguing nanostructure. The sophisticated nanostructure of the BC/GO leads to greatly enhanced mechanical properties compared to those of bare BC. This strategy is versatile, facile, scalable, and can be promising for the development of high-performance BC-based nanocomposite hydrogels.

A Novel <i>in Vitro</i>Three-Dimensional Macroporous Scaffolds from Bacterial Cellulose for Culture of Breast Cancer Cells

In this work, patterned macropores with a diameter larger than 100 μm were introduced to pristine three-dimensional (3D) nanofibrous bacterial cellulose (BC) scaffolds by using the infrared laser micromachining technique in an attempt to create an in vitro model for the culture of breast cancer cells. The morphology, pore structure, and mechanical performance of the obtained patterned macroporous BC (PM-BC) scaffolds were characterized by scanning electron microscopy (SEM), mercury intrusion porosimeter, and mechanical testing. A human breast cancer cell (MDA-MB-231) line was cultured onto the PM-BC scaffolds to investigate the role of macropores in the control of cancer cell behavior. MTT assay, SEM, and hematoxylin and eosin (H&E) staining were employed to determine cell adhesion, growth, proliferation, and infiltration. The PM-BC scaffolds were found to be able to promote cellular adhesion and proliferation on the scaffolds, and further to allow for cell infiltration into the PM-BC scaffolds. The results demonstrated that BC scaffolds with laser-patterned macropores were promising for the in vitro 3D culture of breast cancer cells.

The Trade‑Offs in the Design of Reversible Zinc Anodes for Secondary Alkaline Batteries

Zinc-based batteries have long occupied the largest share of the primary battery market,but this advantage has not continued in the secondary battery market.This is mainly because the cycling performance of secondary zinc-based batteries is significantly limited by the poor reversibility of zinc electrodes,including the formation of zinc dendrites,electrode deformation,corrosion,and hydrogen evolution.To solve the above problems,researchers have developed many novel strategies,such as surface coating,use of electrode additives,use of electrolyte additives,and electrode structure design.However,the implementation of these strategies inevitably requires consideration of trade-offs because the core factors that limit the reversibility of zinc electrodes are not isolated but intertwined.Therefore,fully understanding the trade-offs in the zinc electrode design process is necessary to fundamentally improve the cycling performance of the zinc electrode and construct a practical secondary zinc-based battery.This perspective gives an introduction to various problems that limit the cycling of zinc electrodes and discusses the theoretical causes of these problems.The trade-offs in various typical strategies are systematically analyzed,and their positive and negative effects on performance are discussed.This work aims to provide insights for the development of highly reversible zinc anodes for practical secondary zinc-based batteries.

Synthesis of ZnO by Chemical Bath Deposition in the Presence of Bacterial Cellulose

The control of the morphology of zinc oxide（ZnO） crystals is very important in science and industry.This article reports the influence of bacterial cellulose（BC） on the morphology of ZnO prepared by chemical bath deposition.ZnO nanostructures synthesized with and without adding BC to the aqueous solution of zinc acetate and ammonia were characterized by scanning electron microscopy,transmission electron microscopy,and X-ray diffraction.The results reveal that the presence of BC in the aqueous solution changes the morphology from spindle to flower,which is ascribed to the interactions between –OH on BC nanofibers and Zn2？in the solution.In addition,optical property of the two ZnO nanostructures was compared.

Bioactive glass nanotube scaffold with well-ordered mesoporous structure for improved bioactivity and controlled drug delivery

In this study, a novel mesoporous bioactive glass nanotube (MBGN) scaffold has been fabricated via template-assisted sol-gel method using bacterial cellulose (BC) as template and nonionic block copolymer (PI23) as pore-directing agent. The scaffold was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared (FTIR) spectroscopy, and N2 adsorption-desorption analysis. Furthermore, simvastatin was used to evaluate the loading efficiency and release kinetics of the scaffold. The obtained scaffold displays nanofiber-like morphology, ordered mesopores on the tube walls, and interconnected three-dimensional (3D) network structure that completely replicates the BC template. In addition, it shows dual pore sizes (16.2 and 3.3 nm), large specific surface area (537.2 m^2 g^-1) and pore volume (1.429 cm^3 g^-1). More importantly, the scaffold possesses excellent apatite-forming ability and sustainable drug release as compared to the counterpart scaffold without mesopores. This unique scaffold can be considered a promising candidate for drug delivery and bone tissue regeneration.

Hemodynamic evaluation of different stent graft schemes in aortic arch covered stent implantation

Implantation of the left subclavian artery(LSA)stent graft used in fenestration technique of the thoracic endovascular aortic repair(TEVAR)may interfere with the aortic helical blood flow that is believed to have important protective functions against atherogenesis.The present study investigated four different LSA stent graft implantation schemes for their resulted blood flow patterns in the thoracic aortic with hemodynamic computational simulation methods:the flush branch(FB),the protruding branch(PB),the straight cuff branch(SCB)and the cured cuff branch(CCB).The results showed that the PB scheme could slightly enhance helicity of the swirling flow in the aorta,but the other three schemes had less effect on blood flow helicity.The PB scheme produced lowTAWSS,high-OSI and high-RRT around the LSA root,and the FB scheme had similar TAWSS,OSI and RRT in both value and distribution to those in the aorta without LSA stent graft implantation.The SCB and CCB schemes led to less area of high-OSI and high-RRT values along the walls of the LSA branch arteries.The results also showed that the PB scheme would significantly reduce blood supply to the LSA,on the contrary,the CCB scheme enhanced LSA blood supply and less effect on the total blood supply to the three branches of the thoracic aorta.In summary,all of the four schemes have no significant effect on the aortic swirling flow,however,in the terms of TAWSS,OSI,RRT and blood supply to the LSA,the CCB model might be the best option with less area of low-WSS,high-OSI,high-RRT and well blood supply in the LSA.