Adhesion of a chemically deposited monetite coating to a Ti substrate

Monetite is a promising biomaterial for restoring the function of the compromised skeletal structures due to its superior osteoconductive and resorption properties. However, its potential as a coating for orthopaedic implants in load bearing applications has not yet been investigated. The aim of this study was to prepare monetite coating on Ti substrate in mild conditions, which may allow incorporation of protein-based drugs during the coating deposition. Coatings were prepared using chemical deposition of monetite on Ti substrate in acidic conditions at 75 °C for 24 h. Coatings were characterised by scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Adhesion of the coatings to Ti substrate was measured using tensile tests. EDS confirmed the calcium phosphate nature of the coating and XRD and FTIR confirmed the monetite phase of the coatings. SEM revealed that the coatings were formed of densely packed plate-like monetite crystals, with the crystal size approximately 20 × 10 × 5 μm. Adhesion tests showed cohesive failure of the monetite coatings and the tensile strength of the coating was in the range of 15.43 ± 0.20 MPa. Mechanical tests showed that monetite coatings were stable and could be considered for use with Ti orthopaedic implants.     

The effect of major parameters on simulation results of gas pipelines

Predictions of the gas temperature and pressure profiles are vital to the design and operation of gas transmission lines. Available analytical methods for the calculation of these profiles are evaluated and a numerical framework for the rigorous calculation has been developed. The predictions from both the analytical and numerical procedure have been compared to field data from the Iranian Gas Trunk-lines (IGAT). These comparisons showed that all the available methods were tuned using data obtained from small to medium diameter pipes extrapolated poorly to large diameter pipelines. In order to improve the predictions for large diameter pipelines, the effect of model parameters such as soil thermal conductivity, pipe relative roughness and velocity profile correction factor has been evaluated. The results show that temperature and pressure profiles at high Reynolds number are sensitive to the Fanning friction factor; however, thermal conductivity and velocity distribution correction factor have almost no effect on the temperature and pressure profiles provided these parameters were set at an average acceptable industry value. Since the pressure profile for large diameter pipes was most sensitive to the Fanning friction factor a parameter optimization method was used to fine-tune the Fanning friction factor as a function of Reynolds number at an average accepted industry relative pipe roughness.     

Regional water quality management for the Karun–Dez River basin, Iran

To achieve water quality goals in a river basin, a water quality management model (WQMM) has been developed through the geographic information system (GIS) approach and a mathematical water quality model. The developed model has been applied to the Karun and Dez Rivers, where water quality has decreased due to heavy pollutant loads from Khuzestan province cities and surrounding areas. Pollution sources, land use, geographic features and measured water quality data of the river basin were incorporated into the Arc‐View GIS database. With the database, the management model calculated management type and management cost for each management project in the river basin. Until now, river management policy for polluted rivers in Iran first penalizes pollution sources and then constructs treatment plants for the pollution sources whose wastewater is released untreated and for which the wastewater quality goal of the Iranian Department of Environment is not met. Different management projects with a time programme were proposed and they were compared with the results of the river quality without any management approach. It became clear that the results based on the management approach were much better than those for the unmanaged condition from the viewpoint of the achievement of water quality goals and cost optimization.     

Linear and nonlinear vibration analysis of sandwich cylindrical shell with constrained viscoelastic core layer

Damping characteristics of three-layered sandwich cylindrical shell for thin and thick core viscoelastic layers are studied using semi-analytical finite element method. The finite element method is developed based on the linear and nonlinear variations of the displacement distribution through the thickness of the core layer. Transient vibration has been conducted using the developed linear and nonlinear models and shown that the nonlinear formulation exhibits more damping property than the linear model. The effect of geometric nonlinearity due to the large deformation of the shell has also been considered assuming small strain and moderate rotation. Different assumptions based on the continuity and discontinuity in transverse shear stresses and slope of in-plane displacements are considered in the finite element formulation and their effects have been investigated. Considering nonlinearity of eigenvalue problem due to the frequency dependent property of viscoelastic material, an efficient algorithm has been developed to find the natural frequencies and loss factors of the viscoelastic cylindrical shell considering large deformation. The effect of imperfect bonding between the layers has also been investigated in the modeling and it is shown that slippage between layers at the interfaces leads to reduction in loss factor at the majority of modes.     

Study on automatic control of arc gap in robotic TIG welding

This paper presents a method for automatic control of arc length in tungsten inert gas (TIG) welding process using the arc voltage. By using this method, the role of operator in arc length control is played by an automatic control system based on a predefined arc voltage value for any special welding operation. A dynamic model for feed-rate mechanism and the relation between variations of arc length and voltage are described in details. Using a proportional-integral controller, variations of arc length in welding path is compensated with an automatic feed-rate mechanism in a normal direction to the welding path. By keeping the voltage constant during the process, a stable weld with higher quality and better appearance is obtained specially in welding of uneven surfaces. Theoretical and practical investigations show that the suggested method is able to control the TIG welding process successfully. Test results show that an accurate weld is obtained without the interference of the operator, and by comparing the predefined values of arc voltage with what is practically obtained, the welding gap is automatically adjusted.     

Surface characterization and biological properties of regular dentin,demineralized dentin,and deproteinized dentin

Bone autografts are often used for reconstruction of bone defects; however, due to the limitations of autografts, researchers have been in search of bone substitutes. Dentin is of particular interest for this purpose due to high similarity to bone. This in vitro study sought to assess the surface characteristics and biological properties of dentin samples prepared with different treatments. This study was conducted on regular (RD), demineralized (DemD), and deproteinized (DepD) dentin samples. X-ray diffraction and Fourier transform infrared spectroscopy were used for surface characterization. Samples were immersed in simulated body fluid, and their bioactivity was evaluated under a scanning electron microscope. The methyl thiazol tetrazolium assay, scanning electron microscope analysis and quantitative real-time polymerase chain reaction were performed, respectively to assess viability/proliferation, adhesion/morphology and osteoblast differentiation of cultured human dental pulp stem cells on dentin powders. Of the three dentin samples, DepD showed the highest and RD showed the lowest rate of formation and deposition of hydroxyapatite crystals. Although, the difference in superficial apatite was not significant among samples, functional groups on the surface, however, were more distinct on DepD. At four weeks, hydroxyapatite deposits were noted as needle-shaped accumulations on DemD sample and numerous hexagonal HA deposit masses were seen, covering the surface of DepD. The methyl thiazol tetrazolium, scanning electron microscope, and quantitative real-time polymerase chain reaction analyses during the 10-day cell culture on dentin powders showed the highest cell adhesion and viability and rapid differentiation in DepD. Based on the parameters evaluated in this in vitro study, DepD showed high rate of formation/deposition of hydroxyapatite crystals and adhesion/viability/osteogenic differentiation of human dental pulp stem cells, which may support its osteoinductive/osteoconductive potential for bone regeneration.     

Hydrocracking and hydrodesulfurization of diesel over zeolite beta-containing NiMo supported on activated red mud

NiMo nanocatalysts supported on activated red mud with different zeolite beta contents were successfully prepared by impregnation technique. Their hydrocracking and hydrodesulfurization activities were evaluated with two different kinds of diesel feed (iso diesel and heavy diesel) in a fixed bed reactor at ambient pressure and 500 °C. Physico-chemical properties of synthesized samples were characterized using the methods of XRF, XRD, FESEM, BET, FTIR and NH₃-TPD. The results indicated that zeolite incorporation resulted in a significant increase in specific surface area (BET result) and acidic strength (TPD result) of nanocatalysts. FESEM analysis confirmed that the particles size of zeolite-containing NiMo/ARM was less than 100 nm and the average size of particles was about 30 nm. Hydrocracking results illustrated that incorporation of zeolite beta improved cracking activity considerably. In addition, NiMo nanocatalyst containing 37.5 wt% of zeolite had the highest yields of desirable products (naphtha, kerosene and diesel) and the highest conversion. Moreover, the flash point and viscosity of the liquid product decreased notably the nanocatalysts with 37.5 wt% and 12.5 wt% of zeolite were able to remove approximately 96% and 72% of the sulfur content of iso diesel and heavy diesel, respectively.     

Modulating protein adsorption onto hydroxyapatite particles using different amino acid treatments

Hydroxyapatite (HA) is a material of choice for bone grafts owing to its chemical and structural similarities to the mineral phase of hard tissues. The combination of osteogenic proteins with HA materials that carry and deliver the proteins to the bone-defective areas will accelerate bone regeneration. The study investigated the treatment of HA particles with different amino acids such as serine (Ser), asparagine (Asn), aspartic acid (Asp) and arginine (Arg) to enhance the adsorption ability of HA carrier for delivering therapeutic proteins to the body. The crystallinity of HA reduced when amino acids were added during HA preparation. Depending on the types of amino acid, the specific surface area of the amino acid-functionalized HA particles varied from 105 to 149 m² g^–1. Bovine serum albumin (BSA) and lysozyme were used as model proteins for adsorption study. The protein adsorption onto the surface of amino acid-functionalized HA depended on the polarities of HA particles, whereby, compared with lysozyme, BSA demonstrated higher affinity towards positively charged Arg-HA. Alternatively, the binding affinity of lysozyme onto the negatively charged Asp-HA was higher when compared with BSA. The BSA and lysozyme adsorptions onto the amino acid-functionalized HA fitted better into the Freundlich than Langmuir model. The amino acid-functionalized HA particles that had higher protein adsorption demonstrated a lower protein-release rate.