Dynamic motion of polar skyrmions in oxide heterostructures

Polar skyrmions have been widely investigated in oxide heterostructure recently, due to their exotic properties and intriguing physical insights. Meanwhile, so far, the external field-driven motion of the polar skyrmion, akin to the magnetic counterpart, has yet to be discovered. Here, using phase-field simulations, we demonstrate the dynamic motion of the polar skyrmions with integrated external thermal, electrical, and mechanical stimuli. The external heating reduces the spontaneous polarization hence the skyrmion motion barrier, while the skyrmions shrink under the electric field, which could weaken the lattice pinning and interactions between the skyrmions. The mechanical force transforms the skyrmions into c-domain in the vicinity of the indenter center under the electric field, providing the space and driving force needed for the skyrmions to move. This study confirmed that the skyrmions are quasi-particles that can move collectively, while also providing concrete guidance for the further design of polar skyrmion-based electronic devices.Comment: 17 pages, 4 figure

Hybrid composites of silica glass fibre/nano-hydroxyapatite/polylactic acid for medical application

Fibre reinforced composites (FRC) have shown great potential for the application of internal bone fixation due to mechanical properties that are similar to those of human cortical bones. Ternary composites of silica glass fibres, nano-hydroxyapatite (n-HA) and polylactic acid (PLA) were prepared by compression moulding and their mechanical properties were characterized in this study. With the volumetric content of glass fibre remained constantly at 30% and the volume fraction of n-HA increased from 0% to 5%, the flexural strengths of composites decreased from 625.68 MPa to 206.55 MPa, whereas a gradual increment of flexural modulus from 11.01 to 14.08 GPa were observed at the same time. Within a 28-day degradation period, the flexural strengths decreased by 30%, while no obvious trend of modulus variation was found. The flexural properties of all composites prepared in this study were all found to be close to the reported flexural properties. On the other hand, as more n-HA were incorporated, the water absorption percentages increased, whereas negligible mass loss were recorded. SEM images revealed that the impregnation of fibre mats was poor as loose fibres were observed, which shall be solved in future research to further improve the mechanical properties as well as endurance against degradation. © 2017 International Committee on Composite Materials. All rights reserved

Additive-manufactured gyroid scaffolds of magnesium oxide, phosphate glass fiber and polylactic acid composite for bone tissue engineering

Composites of biodegradable phosphate glass fiber and polylactic acid (PGF/PLA) show potential for bone tissue engineering scaffolds, due to their ability to release Ca, P, and Mg during degradation, thus promoting the bone repair. Nevertheless, glass degradation tends to acidify the surrounding aqueous environment, which may adversely affect the viability and bone-forming activities of osteoblasts. In this work, MgO was investigated as a neutralizing agent. Porous network-phase gyroid scaffolds were additive-manufactured using four different materials: PLA, MgO/PLA, PGF/PLA, and (MgO + PGF)/PLA. The addition of PGF enhanced compressive properties of scaffolds, and the resultant scaffolds were comparably strong and stiff with human trabecular bone. While the degradation of PGF/PLA composite induced considerable acidity in degradation media and intensified the degradation of PGF in return, the degradation media of (MgO + PGF)/PLA maintained a neutral pH close to a physiological environment. The experiment results indicated the possible mechanism of MgO as the neutralizing agent: the local acidity was buffered as the MgO reacted with the acidic degradation products thereby inhibiting the degradation of PGF from being intensified in an acidic environment. The (MgO + PGF)/PLA composite scaffold appears to be a candidate for bone tissue engineering

Recovery of carbon fibre from waste prepreg via microwave pyrolysis

Management of waste from carbon fibre composites has become a significant societal issue as the application of composite grows across many industries. In this study, carbon fibres (CF) were successfully recovered from cured carbon fibre/epoxy (CF/EP) prepreg under microwave pyrolysis at 450, 550 and 650◦ C followed by oxidation of any residual char. The recovered fibres were investigated for their tensile properties, surface morphologies and the elements/functional groups presented on the surface. The chemical compositions of gaseous and oil pyrolysis products were also analysed. The microwave pyrolysis effectively pyrolyzed the epoxy (EP) resin. Char residue remained on the fibre surface and the amount of char reduced as the pyrolysis temperature increased. Compared to virgin fibres, the recovered fibre suffered from a strength reduction by less than 20%, and this reduction could be mitigated by reducing the pyrolysis temperature. The surface of recovered fibre remained clean and smooth, while the profile of elements and functional groups at the surface were similar to those of virgin fibres. The main gaseous products were CO, H2, CO2 and CH4, whilst the liquid product stream included phenolic and aromatic compounds

Aridity-driven shift in biodiversity–soil multifunctionality relationships

From Springer Nature via Jisc Publications RouterHistory: received 2021-01-07, accepted 2021-08-12, registration 2021-08-25, pub-electronic 2021-09-09, online 2021-09-09, collection 2021-12Publication status: PublishedFunder: National Natural Science Foundation of China (National Science Foundation of China); doi: https://doi.org/10.13039/501100001809; Grant(s): 31770430Abstract: Relationships between biodiversity and multiple ecosystem functions (that is, ecosystem multifunctionality) are context-dependent. Both plant and soil microbial diversity have been reported to regulate ecosystem multifunctionality, but how their relative importance varies along environmental gradients remains poorly understood. Here, we relate plant and microbial diversity to soil multifunctionality across 130 dryland sites along a 4,000 km aridity gradient in northern China. Our results show a strong positive association between plant species richness and soil multifunctionality in less arid regions, whereas microbial diversity, in particular of fungi, is positively associated with multifunctionality in more arid regions. This shift in the relationships between plant or microbial diversity and soil multifunctionality occur at an aridity level of ∼0.8, the boundary between semiarid and arid climates, which is predicted to advance geographically ∼28% by the end of the current century. Our study highlights that biodiversity loss of plants and soil microorganisms may have especially strong consequences under low and high aridity conditions, respectively, which calls for climate-specific biodiversity conservation strategies to mitigate the effects of aridification

Additive manufacturing of phosphate glass / polylactic acid composites for biomedical application

Phosphate glass/polylactic acid (PG/PLA) composites are prospective materials for biodegradable bone fracture fixation plates as well as bone tissue engineering scaffolds. However, the PG/PLA composites previously fabricated do not have either the geometry that precisely matches the bone anatomy or the interconnected porous structure that favours the colonisation of bone-forming cells. This work explores the additive manufacturing of PG/PLA composites via fused deposition modelling (FDM). PG in the form of particles (PGP) and milled fibres (PGF) were incorporated into PLA, and then melt-extruded into filament feedstocks for FDM. The FDM-fabricated composites were first studied for their potential for bone fracture fixation devices. Incorporation of PGP or PGF led to reduced flexural strength but increased flexural modulus of composites. Comparing to PGP, the PGF was more effective to improve the flexural modulus, and the resultant composites showed better resistance to in-vitro degradation. The PGF reinforced composites had mechanical properties comparable to biodegradable fixation devices used in clinical practice. The filament preparation process had a strong impact on the length of fibres in FDM products. The longer fibres preserved in FDM products also elicited a higher degree of alignment with the direction of material extrusion during FDM. The fibre alignment and fibre length collectively enhanced the mechanical properties of composites. The FDM-fabricated composites were also investigated as bone tissue engineering scaffolds. The incorporation of PG reinforcement led to enhanced compressive properties and increased surface roughness. However, the strong acidity due to locally accumulated acidic degradation products may result in inferior viability of osteoblast-like cells comparing to PLA-only scaffolds. MgO was added to the PGF/PLA composites as a buffering agent. Its incorporation led to slightly reduced compressive properties, but enhanced surface hydrophilicity. The resultant composite scaffolds did not induce significant acidification of the degradation environment within 14 days of degradation. MgO was extensively degraded to neutralise the acidity, meanwhile preventing the acidity-induced accelerated degradation of PGF. The current project has developed the processes including material preparation, feedstock making and configuration of the FDM process. These processes are all essential to the research of additive manufacturing of PG/PLA composites. The current research shows good prospect for the making of both patient-specific, biodegradable bone fracture fixation plates as well as bone tissue engineering scaffolds with well-defined interconnecting porosity. Further works are required to validate the performances in the context of biomechanical loading and biological testing

Additive manufacturing of phosphate glass / polylactic acid composites for biomedical application

Phosphate glass/polylactic acid (PG/PLA) composites are prospective materials for biodegradable bone fracture fixation plates as well as bone tissue engineering scaffolds. However, the PG/PLA composites previously fabricated do not have either the geometry that precisely matches the bone anatomy or the interconnected porous structure that favours the colonisation of bone-forming cells. This work explores the additive manufacturing of PG/PLA composites via fused deposition modelling (FDM). PG in the form of particles (PGP) and milled fibres (PGF) were incorporated into PLA, and then melt-extruded into filament feedstocks for FDM. The FDM-fabricated composites were first studied for their potential for bone fracture fixation devices. Incorporation of PGP or PGF led to reduced flexural strength but increased flexural modulus of composites. Comparing to PGP, the PGF was more effective to improve the flexural modulus, and the resultant composites showed better resistance to in-vitro degradation. The PGF reinforced composites had mechanical properties comparable to biodegradable fixation devices used in clinical practice. The filament preparation process had a strong impact on the length of fibres in FDM products. The longer fibres preserved in FDM products also elicited a higher degree of alignment with the direction of material extrusion during FDM. The fibre alignment and fibre length collectively enhanced the mechanical properties of composites. The FDM-fabricated composites were also investigated as bone tissue engineering scaffolds. The incorporation of PG reinforcement led to enhanced compressive properties and increased surface roughness. However, the strong acidity due to locally accumulated acidic degradation products may result in inferior viability of osteoblast-like cells comparing to PLA-only scaffolds. MgO was added to the PGF/PLA composites as a buffering agent. Its incorporation led to slightly reduced compressive properties, but enhanced surface hydrophilicity. The resultant composite scaffolds did not induce significant acidification of the degradation environment within 14 days of degradation. MgO was extensively degraded to neutralise the acidity, meanwhile preventing the acidity-induced accelerated degradation of PGF. The current project has developed the processes including material preparation, feedstock making and configuration of the FDM process. These processes are all essential to the research of additive manufacturing of PG/PLA composites. The current research shows good prospect for the making of both patient-specific, biodegradable bone fracture fixation plates as well as bone tissue engineering scaffolds with well-defined interconnecting porosity. Further works are required to validate the performances in the context of biomechanical loading and biological testing

Additive Manufacturing of Bioactive Glass and Its Polymer Composites as Bone Tissue Engineering Scaffolds: A Review

Bioactive glass (BG) and its polymer composites have demonstrated great potential as scaffolds for bone defect healing. Nonetheless, processing these materials into complex geometry to achieve either anatomy-fitting designs or the desired degradation behavior remains challenging. Additive manufacturing (AM) enables the fabrication of BG and BG/polymer objects with well-defined shapes and intricate porous structures. This work reviewed the recent advancements made in the AM of BG and BG/polymer composite scaffolds intended for bone tissue engineering. A literature search was performed using the Scopus database to include publications relevant to this topic. The properties of BG based on different inorganic glass formers, as well as BG/polymer composites, are first introduced. Melt extrusion, direct ink writing, powder bed fusion, and vat photopolymerization are AM technologies that are compatible with BG or BG/polymer processing and were reviewed in terms of their recent advances. The value of AM in the fabrication of BG or BG/polymer composites lies in its ability to produce scaffolds with patient-specific designs and the on-demand spatial distribution of biomaterials, both contributing to effective bone defect healing, as demonstrated by in vivo studies. Based on the relationships among structure, physiochemical properties, and biological function, AM-fabricated BG or BG/polymer composite scaffolds are valuable for achieving safer and more efficient bone defect healing in the future

Direct tangible damage assessment for regional snowmelt flood disasters with HJ-1 and HR satellite images: a case study of the Altay region, northern Xinjiang, China

Regional snowmelt flood disasters (RSFDs) can cause significant direct tangible damage which generally refers to the physical destruction due to direct contact with the flood water, such as damage to buildings, croplands, livestock, and infrastructure. Information about people, habitations, and infrastructure affected by the flood is essential for disaster responders and the humanitarian community to plan and coordinate emergency response activities. However, this direct tangible damage information obtained in the ground is limited, incomplete, contradictory, and sometimes impossible to obtain in a short time. Earth observation satellites help overcome operational uncertainties after the RSFDs. Here, we present an improved rapid direct tangible damage assessment model using HJ-1 and GF-1/2 satellite images. We selected the Altay region in northern Xinjiang, China, as the study area, and investigated a RSFD occurring in spring 2017. A series of HJ-1 and GF-1 images were used to track the flood extent over the duration of the disaster, and the maximum affected flood area was assigned as the area in which direct tangible damage occurred. Pre-disaster GF-2 images were then used to estimate direct tangible damage to habitations (2375 households and 6388 rooms), infrastructure (102 km of roads), and affected population (7125) in the flood area, which covered an area of 185,240 m2. Our method is an effective approach for the design of rescue plans and disaster subsidy programs

A Review of Fine-Scale Land Use and Land Cover Classification in Open-Pit Mining Areas by Remote Sensing Techniques

Over recent decades, fine-scale land use and land cover classification in open-pit mine areas (LCCMA) has become very important for understanding the influence of mining activities on the regional geo-environment, and for environmental impact assessment procedure. This research reviews advances in fine-scale LCCMA from the following aspects. Firstly, it analyzes and proposes classification thematic resolution for LCCMA. Secondly, remote sensing data sources, features, feature selection methods, and classification algorithms for LCCMA are summarized. Thirdly, three major factors that affect LCCMA are discussed: significant three-dimensional terrain features, strong LCCMA feature variability, and homogeneity of spectral-spatial features. Correspondingly, three key scientific issues that limit the accuracy of LCCMA are presented. Finally, several future research directions are discussed: (1) unitization of new sensors, particularly those with stereo survey ability; (2) procurement of sensitive features by new sensors and combinations of sensitive features using novel feature selection methods; (3) development of robust and self-adjusted classification algorithms, such as ensemble learning and deep learning for LCCMA; and (4) application of fine-scale mining information for regularity and management of mines