Inhibition of corrosion of carbon steel 1018 in acid medium with ethoxylated aliphatic alcohols

The effectiveness of inhibition of carbon steel 1018 in 1 M solution of HCl by three ethoxylated aliphatic alcohols with a different number of ethylene oxide units was investigated by measuring the weight loss of the steel and galvanostatic polarization. An increase in the effectiveness of inhibition with an increase in the concentration of the inhibitor, number of ethylene oxide units in its molecule, and decrease in the temperature was found. Inhibition of corrosion is due to adsorption of ethylene oxide groups in the inhibitors on the metal surface. Adsorption is described by a Langmuir isotherm. The effect of the temperature on the corrosion rate in the presence and absence of inhibitors was investigated. Some thermodynamic parameters of corrosion were calculated.     

Calculations of Thermal Expansivity and Lattice Constant of GaN Using Integer and Noninteger n-Dimensional Debye Functions

A theoretical model to calculate the thermal expansivity and lattice constant are described and used to evaluate the GaN semiconductor. This method is based on the use of integer and noninteger n-dimensional Debye functions for analytical evaluation of the thermal expansivity and lattice constant. The agreement between calculated and experimental values for GaN is generally satisfactory.     

A novel noncooperative game competing model using generalized simple additive weighting method to perform network selection in heterogeneous wireless networks

Network selection mechanisms have a significant role in guaranteeing the QoS for users in a heterogeneous wireless networks environment. These mechanisms allow the selection of an optimal wireless network to satisfy the needs of users. Users are provided with the opportunity to select from multiple connectivity opportunities available all over various wireless networks. Furthermore, the network operators themselves can execute active selection strategies that facilitate proper decision making, in which user preferences are considered. This study proposes a new noncooperative competing game‐theoretic model and strategy space based on user preference. This model can solve network selection problems and capture the inter‐linkages of decisions taken by various networks. A generalized simple additive weighting method is incorporated into the framework of noncooperative game theory. In addition, the utility function is employed to assess the usefulness of the system. Simulation results and analysis illustrate the efficacy of the suggested model in attaining optimum network utility for heterogeneous wireless networks while optimizing user satisfaction. Copyright © 2014 John Wiley & Sons, Ltd.     

Evaluation of sericin/collagen membranes as prospective wound dressing biomaterial

Sericin, a silk protein, has high potential for use in biomedical applications. In this study, wound dressing membranes of Sericin (S) and Collagen (C) were prepared by glutaraldehyde cross-linking at S/C; 2:1, 1:1, 1:2, and 0:1 weight ratios. They were stable in water for 4 weeks. However, increasing the proportion of sericin had decreasing effect on the membrane stability. Water swelling property of membranes was enhanced with sericin. The highest water swelling was obtained in 1:1 group (9.06 g/g), but increasing collagen or sericin content in the membranes had a diminishing effect. Highest water vapor transmission rate was obtained with 1:2 group (1013.80 g/m²/day). Oxygen permeability results showed that 1:2 (7.67 mg/L) and 2:1 (7.85 mg/L) S/C groups were better than the other groups. While sericin decreased the tensile strength and elongation of membranes, it increased modulus. Sericin also increased brittleness of membranes, but their UTS range (24.93–44.92 MPa) was still suitable for a wound dressing. Membranes were not penetrable to microorganisms. Cytotoxicity studies showed that fibroblasts and keratinocytes attached and gained their characteristic morphologies. They also proliferated on membranes significantly. After 1 week of subcutaneous implantation, a fibrous capsule formed around all membranes with an acute inflammation. Sericin containing membranes showed signs of degradation (at 2nd week), while collagen only membranes remained largely intact. Eventually, sericin containing membranes degraded in 3 weeks with moderate inflammatory response. Overall results suggest that sericin/collagen membranes would be favorable as wound dressing material when sericin ratio is less than or equal to the collagen component.     

Magnetic layer formation on plasma nitrided CoCrMo alloy

In this study structural and magnetic character of the expanded austenite phase (γ_N) layer formed on a medical grade CoCrMo alloy by a low-pressure Radio-Frequency plasma nitriding process was investigated. The formation of the expanded austenite phase is facilitated at a substrate temperature near 400 °C for 1, 2, 4, 6 and 20 h under a gas mixture of 60% N₂–40% H₂. The magnetic state of the γ_N layers was determined by a surface sensitive technique, magneto-optic Kerr effect (MOKE), and with a scanning probe microscope in magnetic force mode (MFM). Strong evidence for the ferromagnetic nature of the γ_N-(Co,Cr,Mo) phase is provided by the observation of stripe domain structures and the hysteresis loops. The ferromagnetic state for the γ_N phase observed here is mainly linked to large lattice expansions (~ 10%) due to high N contents (~ 30 at.%). As an interstitial impurity, nitrogen dilates the host lattice i.e. the Co–Co (or Fe–Fe) distance is increased, which strongly influences the magnetic interactions. An analogy between the magnetic properties of the expanded phases, γ_N-(Fe,Cr,Ni) and γ_N-(Co,Cr,Mo), formed in austenitic stainless steel alloys and the CoCrMo alloy of this study is made, and it is suggested that the ferromagnetic states for the γ_N-(Co,Cr,Mo) and γ_N-(Fe,Cr,Ni) phases may be correlated with the volume dependence of the magnetic properties of fcc-Co/Co₄N and fcc-Fe/Fe₄N, respectively.     

Study of Influence of Annealing Time on Some Physical Properties of ZnO:Cu Nanorods Grown by a Simple Chemical Bath Deposition Method

A simple chemical bath deposition method was used to prepare high density ZnO nanorods on ZnO seeded Si substrates. Upon the nanorods growth, Cu-doping was achieved by diffusion process at 500 ^°C for different times in vacuum ambient. The structural, optical, and magnetic properties of the obtained ZnO:Cu nanorods were then examined. XRD analysis showed that undoped and ZnO:Cu samples were highly c-axis oriented with a hexagonal wurtzite structure. SEM analysis indicated that ZnO:Cu nanorods had diameters of ～200 nm and lengths of ～1.5 μm. X-ray photoemission spectroscopy demonstrated that Cu was successfully doped into ZnO in a divalent state. Photoluminescence results showed that Cu-doping caused a decrease in the green band intensity of nanorods compared to undoped ZnO. Room temperature magnetic measurements showed that pure ZnO nanorods exhibited ferromagnetism that might be ascribed to defect-induced d⁰ ferromagnetism. All the ZnO:Cu nanorods also showed the room temperature ferromagnetism that was attributed to the bound magnetic polarons (BMPs).     

Mineral content of milk, colostrum, and serum as affected by physiological state and mineral supplementation

A 22-mo experiment was conducted to determine effects of mineral supplementation of cows on mineral elements in milk, colostrum, and blood serum. Purebred Brahman beef cows grazing pastures grown on sandy and well-drained soils were allotted to three treatments of 12 cows each as follows: control, a complete commercial mineral mixture, control plus dietary and injected Se, and control plus fortified mineral mixture. Milk and serum were analyzed for minerals 2 consecutive yr at parturition and 3 mo postpartum. Mean cow serum, Ca, Mg, P, and packed cell volume values were higher at parturition than 3 mo later, whereas serum Cu was highest at 3 mo. Mean serum concentrations were affected by year with higher Ca and hemoglobin and lower Cu concentrations in 1982 than in 1981. Increasing dietary Se resulted in higher serum Se. Colostrum was higher in Mg, P, Cu, Fe, Se, and Zn than milk, whereas milk was higher than colostrum in Mn. Means for treatment X time showed cows fed dietary and dietary plus injected Se and vitamin E had more Se in milk than milk from cows fed no supplemental Se.