Cellulose-reinforced bioglass composite as flexible bioactive bandage to enhance bone healing

Low mechanical strength of cellulose nanofiber (CNF) and its lack of osseoconductivity in physiological media limit its application for bone tissue regeneration. To resolve these limitations, the densely packed cellulosic layers with thickness of ~50 μm impregnated by 58S bioglass (BG) nanoparticles was made-up (via the simple method of vacuum filtration) in this study. The developed fabrics showed uniform distribution of BG nanoparticles and effectively wrapped between CNF layers which caused sustained ion release into the SBF × 5 solution. The FTIR spectrum of the fabric after the SBF test was illustrated the presence of newly formed HA on the fabric. Also, no significant difference in the hydrophilicity of pure CNF and the developed fabric was presented by AFM results. Alkaline phosphatase activity (ALP) and cytotoxicity evaluation were performed to investigate cell treatment of the fabric which indicated its superior osteogenic potential of developed fabric compared with pure CNF. The increase in osseoconductivity of the developed fabric caused better cell attachment thanks to the interconnected CNFs network. Effective integration of BG nanoparticles between CNF interlayers increased Young's modulus of the developed fabric by 50% that mitigated swelling and enhanced structural stability of CNFs in the SBF × 5 solution. Thus, developed fabric could be considered as an appropriate biomaterial such as a bandage around cracked bone before metallic implantation with good mechanical integrity of the layered constructs obtained as well as strength and swelling.     

The effect of surface modification on the corrosion protection ability of the passive films of sensitized UNS S31803 duplex stainless steel

ABSTRACT

The influence of sensitisation heat treatment, surface roughness and repetitive cyclic voltammetry (RCV) procedure (that was used to create passive films on the surface of sensitised samples) on the corrosion behaviour of UNS S31803 duplex stainless steel was evaluated using sodium hydroxide etching, double-loop electrochemical potentiodynamic reactivation (DLEPR), potentiodynamic polarisation, Mott–Schottky analysis, X-ray diffraction and optical microscopy techniques. The results showed that prolonged sensitisation time leads to the formation of defective passive films on the surface. In addition, as the substrate surface roughness decreases, the defect concentration in the resulting passive film decreases. Moreover, thick passive films that were created at a high number of RCV cycles contain fewer defects than the thin ones. Finally, the specimens with smooth surfaces, thick passive films and low degree of sensitisation exhibit high corrosion resistance due to their intact passive layers formed on their surfaces.     

Markovian jump guaranteed cost congestion control strategies for large scale mobile networks with differentiated services traffic

In this paper, two novel congestion control strategies for mobile networks with differentiated services (Diff-Serv) traffic are presented, namely (i) a Markovian jump decentralized guaranteed cost congestion control strategy, and (ii) a Markovian jump distributed guaranteed cost congestion control strategy. The switchings or changes in the network topology are modeled by a Markovian jump process. By utilizing guaranteed cost control principles, the proposed congestion control schemes do indeed take into account the associated physical network resource constraints and are shown to be robust to unknown and time-varying network latencies and time delays. A set of Linear Matrix Inequality (LMI) conditions are obtained to guarantee the QoS of the Diff-Serv traffic with a guaranteed upper bound cost. Simulation results are presented to illustrate the effectiveness and capabilities of our proposed strategies. Comparisons with centralized and other relevant works in the literature focused on Diff-Serv traffic and mobile networks are also provided to demonstrate the advantages of our proposed solutions.     

Storing water in powder form by self-assembling hydrophobic silica nanoparticles

Water-rich powder containing up to 98% (by weight) of water and characterized by the same flow properties as dry powder was prepared by a simple mixing process. Each particulate consists of a microscopic water droplet surrounded by a network of self-associated hydrophobic fumed silica particles. The cohesion of the silica network, attributed to the van der Waals interactions, is reinforced by particle entanglements and is probably further enhanced by the fractal structure of the network. Once the network is created, the formed shells are strong enough to withstand gravity forces and external stresses. High hydrophobicity and micrometer-sized thickness of the shells ensure that the water phase is kept within the boundaries of the particulates, thus preventing water droplet coalescence. The conditions leading to the formation of water-rich powders strongly depend on the silica particle hydrophobicity.     

A new experimental investigation on upgrading of waxy crude oils by methacrylate polymers

Several methods have been used to reduce problems caused by wax precipitation during the production and/or transportation of waxy crude oil. Polymers are used to improve pour point and rheological behavior of waxy crude oils. In this work, the influence of the polymer inhibitors such as methacrylate polymers, as wax inhibitor, with different range of molecular weight and alkyl side chain carbons on the rheological behavior and pour point of two Iranian waxy crude oils were evaluated. Two Iranian waxy crude oils were selected on the basis of wax and asphaltene contents. The rheological behavior of these crude oils in absence and in presence of methacrylate polymer was studied. The rheological data cover the temperature range of–1 to 12°C. The results indicated that the performance of methacrylate polymer was dependent on the molecular weight, alkyl side chain carbons and the asphaltene content of crude oil. Methacrylate polymers with longer alkyl side chains than 18 carbons would perform best as wax inhibitors in two cases. Also, for crude oil with low asphaltene, higher molecular weight methacrylate polymer is the best flow improver and lower molecular weight methacrylate polymer showed good efficiency for crude oil with high asphaltene content.     

Electrochemical Insight into the Role of H2O2 in Galvanostatic Passivation of AISI 316L Austenitic Stainless Steel in Citric Acid Electrolyte

Metallurgical and Materials Transactions A - In this study, AISI 316L stainless steel was passivated under galvanostatic conditions in citric acid solutions in the absence and presence of hydrogen...