Multi-Server Multi-User Multi-Task Computation Offloading for Mobile Edge Computing Networks

This paper studies mobile edge computing (MEC) networks where multiple wireless devices (WDs) offload their computation tasks to multiple edge servers and one cloud server. Considering different real-time computation tasks at different WDs, every task is decided to be processed locally at its WD or to be offloaded to and processed at one of the edge servers or the cloud server. In this paper, we investigate low-complexity computation offloading policies to guarantee quality of service of the MEC network and to minimize WDs’ energy consumption. Specifically, both a linear programing relaxation-based (LR-based) algorithm and a distributed deep learning-based offloading (DDLO) algorithm are independently studied for MEC networks. We further propose a heterogeneous DDLO to achieve better convergence performance than DDLO. Extensive numerical results show that the DDLO algorithms guarantee better performance than the LR-based algorithm. Furthermore, the DDLO algorithm generates an offloading decision in less than 1 millisecond, which is several orders faster than the LR-based algorithm

Sequential activation of M1 and M2 phenotypes in macrophages by Mg degradation from Ti-Mg alloy for enhanced osteogenesis

Background Even though the modulatory effects of Magnisum (Mg) and its alloys on bone-healing cells have been widely investigated during the last two decades, relatively limited attention has been paid on their inflammation-modulatory properties. Understanding the activation process of macrophages in response to the dynamic degradation process of Mg as well as the relationship between macrophage phenotypes and their osteogenic potential is critical for the design and development of advanced Mg-based or Mg-incorporated biomaterials. Methods In this work, a Ti-0.625 Mg (wt.%) alloy fabricated by mechanical alloying (MA) and subsequent spark plasma sintering (SPS) was employed as a material model to explore the inflammatory response and osteogenic performance in vitro and in vivo by taking pure Ti as the control. The data analysis was performed following Student’s t-test. Results The results revealed that the macrophages grown on the Ti-0.625 Mg alloy underwent sequential activation of M1 and M2 phenotypes during a culture period of 5 days. The initially increased environmental pH (~ 8.03) was responsible for the activation of M1 macrophages, while accumulated Mg2+ within cells contributed to the lateral M2 phenotype activation. Both M1 and M2 macrophages promoted osteoblast-like SaOS-2 cell maturation. In vivo experiment further showed the better anti-inflammatory response, regenerative potentiality and thinner fibrous tissue layer for the Ti-0.625 Mg alloy than pure Ti. Conclusion The results highlighted the roles of Mg degradation in the Ti-0.625 Mg alloy on the sequential activation of macrophage phenotypes and the importance of modulating M1-to-M2 transition in macrophage phenotypes for the design and development of inflammation-modulatory biomaterials

Preparing Sr-containing nano-structures on micro-structured titanium alloy surface fabricated by additively manufacturing to enhance the anti-inflammation and osteogenesis

The development of additive manufacturing technology has made it possible to customize joint implants. However, the fibrous tissue caused by long-term chronic inflammation delays bone regeneration. Moreover, the discovery of micro/nano-structure on the natural bone makes the study of implant surface morphology meaningful. In this study, a Sr-containing nano-structure on micro-structured titanium alloy surface was fabricated to enhanced the anti-inflammatory and osteogenic properties of implants. Ti6Al4V (TC4) alloys with micro-structured surface prepared by additive manufacturing were used as the material base model. Subsequently, spherical SrTiO3 particles were fabricated on the TC4 surfaces by hydrothermal treatment. The anti-inflammatory and osteogenic performance of smooth surface, micro-structured surface, Sr-containing nano-structured surface and Sr-containing micro/nano-structured surface were investigated. In vitro results exhibited that the macrophages cultured on micro/nano-structured surface were polarized to anti-inflammatory M2 phenotype and enhanced the expression of osteogenic growth factors. The Sr-containing micro/nano-structured surface effectively upgraded the proliferation and differentiation of SaOS-2 cells compared with other surfaces. Sr2+ and micro/nano-structure effectively enhanced the anti-inflammatory and osteogenic properties of titanium alloys. This finding suggested that the micro/nano-structured surface doped with bioactive elements is expected to broaden the horizons of biomedical materials. Data availability The raw/processed data required to reproduce these findings cannot be shared at this time as the data also forms part of an ongoing study

Simultaneously stimulated osteogenesis and anti-bacteria of physically cross-linked double-network hydrogel loaded with MgO-Ag 2O nanocomposites.

Hydrogels, with a three-dimensional network of water-soluble polymer and water, could simulate the critical properties of extracellular matrix, which has been widely used in bone tissue engineering. However, most of conventional hydrogels for bone regeneration are fragile and have poor osteogenic activity, which restricts their applications. In this work, a novel nanoparticle-hydrogel composite consisting of physically cross-linked double-network loaded with MgO-Ag 2O nanocomposites was developed by the sol-gel method. The Mg 2+ released from MgO-Ag 2O nanocomposites was used as an ionic cross-linking site of sodium alginate (SA), while the hydrophobic micelles in the polyacrylamide (PAAM) network is acted as another crosslinking point. The results indicated that the novel nanoparticle-hydrogel composites had good self-recovery ability and excellent mechanical properties compared with the conventional sodium alginate (SA)/polyacrylamide (PAAM) hydrogels. Additionally, it showed a slow release of Mg and Ag ions due to the dual function of the embedding effect of hydrogels and the increasing pH of the solution induced by the hydrolysis of sodium alginate. In terms of in vitro tests, the nanoparticle-hydrogel composites showed significantly stimulatory effects on the proliferation and differentiation of SaOS-2 cells. In addition, the antibacterial effects of the nanoparticle-hydrogel composites were gradually enhanced with the increase of MgO-Ag 2O content

Identification of a specific surface epitope of OmpC for Escherichia coli O157:H7 with protein topology facilitated affinity mass spectrometry

The goal of this work was to identify the target protein and epitope of a previously reported Escherichia coli O157:H7 (ECO157)-specific monoclonal antibody (mAb) 2G12. mAb 2G12 has shown high specificity for the recovery and detection of ECO157. To achieve this goal, the target protein was first separated by two-dimensional gel electrophoresis (2-DE) and located by Western blot (WB). The protein spots were identified to be the outer membrane protein (Omp) C by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). After that, the target protein was purified by immunoaffinity chromatography (IAC) and subjected to in situ enzymatic cleavage of the vulnerable peptides. Eight eluted peptides of OmpC identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS) were further mapped onto the homologous protein structure of E. coli OmpC (2IXX). The topology of OmpC showed that three peptides had extracellular loops. Epitope mapping with overlapping peptide library and sequence homology analysis revealed that the epitope consisted of a specific peptide, "LGVING," and an adjacent conservative peptide, "TQTYNATRVGSLG." Both peptides loop around the overall structure of the epitope. To test the availability of the epitope when ECO157 was grown under different osmolarity, pH, and nutrition levels, the binding efficacy of mAb 2G12 with ECO157 grown in these conditions was evaluated. Results further demonstrated the good stability of this epitope under potential stressful environmental conditions. In summary, this study revealed that mAb 2G12 targeted one specific and one conservative extracellular loop (peptide) of the OmpC present on ECO157, and the epitope was stable and accessible on ECO157 cells grown in different environment. KEY POINTS: • OmpC is the target of a recently identified ECO157-specific mAb 2G12. • Eight peptides were identified from the OmpC by using LC-MS/MS. • The specificity of mAb 2G12 is mainly determined by the "LGVING" peptide

Microstructure and Corrosion Behavior of Ti-Nb Coatings on NiTi Substrate Fabricated by Laser Cladding

Ti-23Nb (at.%) coatings on an NiTi alloy with metallurgical bonding were prepared by laser cladding (LC) technology using Ti-Nb mixture powders. The effects of laser processing parameters on the microstructure and mechanical properties of the coatings were systematically investigated and the corrosion resistance of the coatings was assessed. The coatings were composed of TiNb, (Ti, Nb)2Ni, and β-Nb phases. The coatings increased the hardness of the NiTi alloy by a combined strengthening effect of the eutectics and fine microstructure. The corrosion resistance of the coated part was improved. The coatings with great corrosion resistance could keep the coated parts inert in an aggressive environment, and effectively restrain the release of toxic Ni ions, which means that the Ti-Nb alloy coatings are likely to be used as a biomaterial for medical applications

Highly water-stable bimetallic organic framework MgCu-MOF74 for inhibiting bacterial infection and promoting bone regeneration

As a typical metal-organic framework (MOF), Mg-MOF74 can release biocompatible Mg 2+when the framework is degraded, and it has the potential to be used as filler in the field of bone tissue engineering. However, Mg-MOF74 has poor stability in aqueous environment and limited antibacterial ability, which limit its further development and applications. In this work, MgCu-MOF74 particles with different Cu content were synthesized through a facile one-step hydrothermal method. The physicochemical properties and water stability of the synthesized powders were characterized. The osteogenic potential of the MgCu-MOF74 particles on human osteogenic sarcoma cells (SaOS-2) was evaluated. The hybrid MgCu-MOF74 exhibited favorable water stability. These results indicated that MgCu-MOF74 enhanced cellular viability, alkaline phosphatase levels, collagen (COL) synthesis and osteogenesis-related gene expression. Moreover, the samples doped with Cu 2+were more sensitive to the acidic microenvironment produced by bacteria, and exhibited stronger antibacterial ability than Mg-MOF74. In conclusion, MgCu-MOF-74 with good water stability, osteogenic ability and antibacterial ability, which could be attributed to the doping of Cu 2+. Hence, MgCu-MOF74 shows great potential as a novel medical bio-functional fillers for the treatment of bone defects

Sequential activation of M1 and M2 phenotypes in macrophages by Mg degradation from Ti-Mg alloy for enhanced osteogenesis

Abstract Background Even though the modulatory effects of Magnisum (Mg) and its alloys on bone-healing cells have been widely investigated during the last two decades, relatively limited attention has been paid on their inflammation-modulatory properties. Understanding the activation process of macrophages in response to the dynamic degradation process of Mg as well as the relationship between macrophage phenotypes and their osteogenic potential is critical for the design and development of advanced Mg-based or Mg-incorporated biomaterials. Methods In this work, a Ti-0.625 Mg (wt.%) alloy fabricated by mechanical alloying (MA) and subsequent spark plasma sintering (SPS) was employed as a material model to explore the inflammatory response and osteogenic performance in vitro and in vivo by taking pure Ti as the control. The data analysis was performed following Student’s t-test. Results The results revealed that the macrophages grown on the Ti-0.625 Mg alloy underwent sequential activation of M1 and M2 phenotypes during a culture period of 5 days. The initially increased environmental pH (~ 8.03) was responsible for the activation of M1 macrophages, while accumulated Mg2+ within cells contributed to the lateral M2 phenotype activation. Both M1 and M2 macrophages promoted osteoblast-like SaOS-2 cell maturation. In vivo experiment further showed the better anti-inflammatory response, regenerative potentiality and thinner fibrous tissue layer for the Ti-0.625 Mg alloy than pure Ti. Conclusion The results highlighted the roles of Mg degradation in the Ti-0.625 Mg alloy on the sequential activation of macrophage phenotypes and the importance of modulating M1-to-M2 transition in macrophage phenotypes for the design and development of inflammation-modulatory biomaterials

Tensile strength and wear resistance of glass-reinforced PA1212 fabricated by selective laser sintering

Glass fibre (GF) and glass bead (GB)–reinforced polyamide1212 (PA1212) was additively manufactured by selective laser sintering. The effects of laser power and GF content on the tensile and tribological properties of the printed specimens with a base GB weight fraction of 40 wt.% were investigated. The strengthening mechanism of GFs/GBs was illustrated by analyzing the interfacial adhesion between the fillers and the PA1212 matrix. The specimens with 40 wt.% GBs and 10 wt.% GFs fabricated at a laser power of 30 W exhibited a strength of 52 MPa, a friction coefficient of 0.23, and a wear rate of 0.0011 mm3/N·m. The selected optimal laser power and GF addition contributed to the strong interfacial adhesion, which realised flat surface morphology and an adequate encapsulation of fillers in the specimen. The reinforcement of GBs/GFs in PA1212 can serve as a reference for a deeper understanding of the strengthening mechanisms for other additively manufactured engineering plastics