Synthesis of silicon-substituted hydroxyapatite by a hydrothermal method with two different phosphorous sources

Silicon-substituted hydroxyapatite (Si-HA) with up to 1.8 wt% Si content was prepared successfully by a hydrothermal method, using Ca(NO₃)₂, (NH₄)₃PO₄ or (NH₄)₂HPO₄ and Si(OCH₂CH₃)₄ (TEOS) as starting materials. Silicon has been incorporated in hydroxyapatite (HA) lattice by partially replacing phosphate (PO₄³⁻) groups with silicate (SiO₄⁴⁻) groups resulting in Si-HA described as Ca₁₀(PO₄)_6−x(SiO₄)_x(OH)_2−x. X-ray diffraction (XRD), Fourier transform IR spectroscopy (FTIR), inductively coupled plasma AES (ICP-AES) and scanning electron microscopy (SEM) techniques reveal that the substitution of phosphate groups by silicate groups causes some OH⁻ loss to maintain the charge balance and changes the lattice parameters of HA. The crystal shape of Si-HA has not altered compared to silicon-free reference hydroxyapatite but Si-incorporation reduces the size of Si-HA crystallites. Based on in vitro tests, soaking the specimens in simulated body fluid (SBF), and MTT assays by human osteoblast-like cells, Si-substituted hydroxyapatite is more bioactive than pure hydroxyapatite.     

A comparative study on the effects of Coriolus versicolor on properties of HDPE/wood flour/paper sludge composites

In this study, the effects of white-rot fungus (Coriolus versicolor) on the properties of high density polyethylene (HDPE)/wood flour/paper sludge composites were examined. In addition, the effectiveness of using coupling agent on the durability of decayed and undecayed WPCs was investigated. Two different types of sludge materials, namely paper making waste water sludge (PS) and ink-eliminated sludge (IES) were used. The mechanical properties, morphology, and water absorption of fabricated composites were investigated. At a similar wood flour loading, except for modulus of elasticity, the fungi treated composites showed lower mechanical properties (such as modulus of rupture and unnotched Izod impact strength), and higher water absorption compared to untreated composites. According to the results, addition of wood flour decreased the resistance of the composites to moisture and fungal environment. The exposure of the composites to a 4-cycle (2, 24, 48 and 72 h) water immersion caused serious damage to the interfacial adhesion between wood flour and polymer matrix due to contraction and swelling stresses developed during the cyclic exposure. The detrimental effect of fungal treatment on the water uptake of the composites could be explained by the degradation of lignin which made the cellulose content more accessible. Further, it makes chains of cavities that accelerate water absorption. However, the weight losses of all cases of treated composites were low (less than 2.5%), while PS filled composites were more susceptible to white-rot fungi. The addition of coupling agent during the compounding of wood flour and HDPE prevented the colonization and proliferation of fungus on the surface of the composites, and had an advantageous effect on the water uptake and mechanical properties of both treated and untreated composites.     

New diaminomaleonitrile-based azo-azomethine dyes; synthesis, characterization and spectral properties

New diaminomaleonitrile-based azo-azomethine dyes were synthesized via a condensation between 2,6-bis(N-(2-amino-1,2-dicyanoetheneimino))-4-methylphenol and 5-(4-substituted-phenyl)-azo-salicyladehyde. FT-IR and ¹H NMR spectroscopy and mass spectrometry studies as well as elemental analysis data revealed the symmetrical bis-iminated structures of the dyes. The electrochemical behavior of the dyes has been investigated by cyclic voltammetry. The effect of various solvents with different polarities on the UV-Vis spectra of the dyes was also studied. The thermal analysis data indicated that the framework of the dyes was stable up to 285 °C.     

Finite element modelling of field compaction of hot mix asphalt. Part I: Theory

This paper presents the theoretical background for the development of a constitutive model that is used in the simulation of the compaction of asphalt mixtures. The constitutive model is developed to comply with the principles of thermodynamics, and is derived to represent the macroscopic behaviour of an asphalt mixture as a highly compressible viscoelastic material. The paper presents the details of the mathematical formulation and the computational implementation of the model in the finite element package computer-aided pavement analysis 3D. The capabilities of the compaction model and its sensitivity to changes in model's parameters are illustrated using simple numerical applications. In a companion publication, (Masad et al., Finite element modelling of field compaction of hot mix asphalt. Part II: Application, International Journal of Pavement Engineering, Accepted, 2014), the model is verified against field compaction measurements which demonstrate the ability of the model to capture the general trends of the compaction observed in the field.     

Adaptive-Network-Based Fuzzy Inference System Analysis to Predict the Temperature and Flow Fields in a Lid-Driven Cavity

Heat transfer behavior in a 2-D square lid-driven cavity has been studied for various pertinent Reynolds and Rayleigh numbers. The lattice Boltzmann method, a numerical tool based on the particle distribution function is applied to simulate a thermal fluid flow problem. Bhatnagar-Gross-Krook (BGK) is combined with the double population thermal Lattice Boltzmann model to solve mixed convection in a square cavity. An adaptive-network-based fuzzy inference system (ANFIS) method is trained and validated using BGK Lattice Boltzmann model results. The results show that the trained ANFIS model successfully predicts the temperature and flow fields in a few seconds with acceptable accuracy.     

A novel design of RF MEMS dual band phase shifter

In this paper a novel design of RF MEMS dual band phase shifter is presented. The new design is switched-line type phase shifter which has been constructed by distributed MEMS transmission line (DMTL). Since the constant phase of DMTL can be changed, the proposed design has capability for working at two or more frequencies. The performances of the new design are compared with conventional switched-line design that has been constructed by transmission line of coplanar waveguide. The results show the feasibility of the new design and also show the new design reduces the size and loss of the structure compared with conventional switched-line design. The proposed design is unique approach to achieve a dual band phase shifter using MEMS technology which has low loss and weight with high linearity respect to the other technologies. This dual band phase shifter has very small size than the other passive dual band phase shifters.     

Throughput optimization using simultaneous sensing and transmission in energy harvesting cognitive radio networks

A three‐dimensional continuous‐time Markov model is proposed for an energy harvesting cognitive radio system, where each secondary user (SU) harvests energy from the ambient environment and attempts to transmit data packets on spectrum holes in an infinite queuing buffer. Unlike most previous works, the SU can perform spectrum sensing, data transmission, and energy harvesting simultaneously. We determine active probability of the SU transmitter, where the average energy consumption for both spectrum sensing and data transmission should not exceed the amount of harvested energy. Then, we formulate achievable throughput of secondary network as a convex optimization problem under average transmit and interference energy constraints. The optimal pair of controlled energy harvesting rate and data packet rate is derived for proposed model. Results indicate that no trade‐off is available among harvesting, sensing/receiving, and transmitting. The SU capability for self‐interference cancelation affects the maximum throughput. We develop this work under hybrid channels including overlay and underlay cases and propose a hybrid solution to achieve the maximum throughput. Simulation results verify that our proposed strategy outperforms the efficiency of the secondary network compared to the previous works.     

Polycaprolactone/gelatin electrospun nanofibres containing biologically produced tellurium nanoparticles as a potential wound dressing scaffold: Physicochemical,mechanical, and biological characterisation

The biologically synthesised tellurium nanoparticles (Te NPs) were applied in the fabrication of Te NP‐embedded polycaprolactone/gelatin (PCL/GEL) electrospun nanofibres and their antioxidant and in vivo wound healing properties were determined. The as‐synthesised nanofibres were characterised using scanning electron microscopy (SEM), energy‐dispersive X‐ray (EDX) spectroscopy and elemental mapping, thermogravimetric analysis (TGA), and Fourier‐transform infrared (FTIR) spectroscopy. The mechanical properties and surface hydrophobicity of scaffolds were investigated using tensile analysis and contact angle tests, respectively. The biocompatibility of the produced scaffolds on mouse embryonic fibroblast cells (3T3) was evaluated using MTT assay. The highest wound healing activity (score 15/19) was achieved for scaffolds containing Te NPs. The wounds treated with PCL/GEL/Te NPs had inflammation state equal to the positive control. Also, the mentioned scaffold represented positive effects on collagen formation and collagen fibre''s horizontalisation in a dose‐dependent manner. The antioxidative potency of Te NP‐containing scaffolds was demonstrated with lower levels of malondialdehyde (MDA) and catalase (∼3 times) and a higher level of glutathione (GSH) (∼2 times) in PCL/GEL/Te NP‐treated samples than the negative control. The obtained results strongly demonstrated the healing activity of the produced nanofibres, and it can be inferred that scaffolds containing Te NPs are suitable for wound dressing.     

Simultaneous separation/preconcentration of ultra trace heavy metals in industrial wastewaters by dispersive liquid-liquid microextraction based on solidification of floating organic drop prior to determination by graphite furnace atomic absorption spectrometry

In the present work, an efficient microextraction method was applied to separation and preconcentration of Ni(II), Co(II), Pb(II) and Cr(III). This method is dispersive liquid-liquid microextraction based on solidification of floating organic drop, which overcomes the most important problems of each aforementioned technique. The influences of analytical parameters, including pH, extraction solvent volume, disperser solvent type and its volume, concentration of chelating agent, salt effect and extraction time on the quantitative recoveries of nickel, cobalt, lead and chromium ions were investigated. Under the optimized conditions, the limits of detection were 0.2 ng L(-1) for Cr and 1.3 ng L(-1) for Co, Ni and Pb, with a preconcentration factor of 800 times. The relative standard deviations of 6.2% at 6.0 ng L(-1) of Cr and 7.2% at 10 ng L(-1) of Co, Ni and Pb were obtained (n=7). The proposed method was successfully applied for the analysis of ultra trace metals in water and wastewater samples.     

Green Synthesis of Chitosan-Coated Silver Nanoparticle,Characterization, Antimicrobial Activities,and Cytotoxicity Analysis in Cancerous and Normal Cell Lines

Journal of Inorganic and Organometallic Polymers and Materials - The production of silver nanoparticles (AgNPs) using chemical synthesis routes require hazardous and toxic solvents. Nowadays, there...