Formulation and characterization of alprazolam-loaded nanoliposomes: screening of process variables and optimizing characteristics using RSM

This research study aimed to develop a novel sustained release formulation of alprazolam that can also be used for transdermal delivery. This was carried out, for the first time, through encapsulation of alprazolam in nanoliposomes using ethanol injection. In order to obtain the best formulation, four process variables, including the solvent/nonsolvent volume ratio, phospholipid concentration, alprazolam concentration, and cholesterol content were considered as key factors. Response surface methodology (RSM) and a central composite design (CCD) model were used to investigate the effect of these factors on vesicle size (VS) and encapsulation efficiency (EE) as the major properties of nanoliposomes. Experimental data were statistically analyzed, and two significant quadratic models were developed to test the VS and EE responses. The findings indicate that alprazolam and phospholipid concentrations have a significant effect on the mean VS. However, EE was significantly affected by both the alprazolam and phospholipid concentrations and the cholesterol content. The optimized formulation for preparation of alprazolam-loaded nanoliposomes with appropriate VS and EE was suggested. Small unilamellar vesicles (SUVs), ranging in size from 50 to 100?nm were clearly observed in the transmission electron microscopy (TEM) images, which is appropriate for transdermal delivery of alprazolam. The study of the prepared nanoliposomes over 28 days at 4?°C confirmed the stability of the formulations containing cholesterol. The results of an in vitro release study of alprazolam-loaded nanoliposomes in phosphate buffered saline (PBS), pH 7.4 for 24?h at 37?°C using dialysis, indicated the sustained release of alprazolam due to encapsulation.     

Flow characterization in the near‐wake region of a horizontal axis wind turbine

An experimental study is conducted to investigate the flow dynamics within the near‐wake region of a horizontal axis wind turbine using particle image velocimetry (PIV). Measurements were performed in the horizontal plane in a row of four radially distributed measurement windows (tiles), which are then patched together to obtain larger measurement field. The mean and turbulent components of the flow field were measured at various blade phase angles. The mean velocity and turbulence characteristics show high dependency on the blade phase angle in the near‐wake region closer to the blade tip and become phase independent further downstream at a distance of about one rotor diameter. In the near‐wake region, both the mean and turbulent characteristics show a systemic variation with the phase angle in the blade tip region, where the highest levels of turbulence are observed. The streamlines of the instantaneous velocity field at a given phase allowed to track a tip vortex which showed wandering trend. The tip vortices are mostly formed at r/R > 1, which indicates the wake expansion. Results also show the gradual movement of the vortex region in the axial direction, which can be attributed to the dynamics of the helical tip vortices which after being generated from the tip, rotate with respect to the blade and move in the axial direction because of the axial momentum of the flow. The axial velocity deficit was compared with other laboratory and field measurements. The comparison shows qualitative similarity. Copyright © 2015 John Wiley & Sons, Ltd.     

Investigation of the effect of air turbulence intensity on NOx emission in non-premixed hydrogen and hydrogen-hydrocarbon composite fuel combustion

In this paper, the effect of air turbulence intensity on NO formation in the combustion of mixed hydrogen-hydrocarbon fuel is numerically studied. The fuels used in this study are 100% H₂, 70% H₂ + 30% CH₄, 10% H₂ + 90% CH₄ and 100% CH₄. Finite volume method is utilized to solve the governing equations. The obtained results using realizable k-ε and β-PDF models show good agreement with other numerical and experimental results. The results show that increasing air turbulence intensity decreases NO concentration in the flame zone and at the combustor outlet. With increasing air turbulence intensity, maximum decreasing of NO at the combustor outlet is for the case of pure hydrogen fuel. It is also found that adding hydrogen to methane rises the peak temperature of the flame.     

Integrating sustainability into supplier selection with analytical hierarchy process and improved grey relational analysis: a case of telecom industry

Supplier selection is one of the critical problems in supply chain systems. Within the last decades, by the emergence of sustainability concept, companies have been motivated to enhance their supplier’s sustainability and move toward sustainable development. This paper proposes a structured and integrated decision model for evaluating sustainable suppliers in the context of telecom industry by combining analytical hierarchy process (AHP) and improved grey relational analysis (IGRA) approaches. The proposed model employs AHP for calculating sustainability criteria weights and IGRA for ranking suppliers. Moreover, a sensitivity analysis is also performed to demonstrate the robustness of the model. In this research, the sustainable supplier selection problem of the telecom industry in the southern part of Iran was investigated, showing the effectiveness and applicability of this proposed integrated approach.     

Adhesion performance of an epoxy clear coat on aluminum alloy in the presence of vinyl and amino-silane primers

The influence of amino and vinyl-silane-based treatments on the performance of an epoxy coated AA 1050 aluminum has been studied. The surface energy of the silane treated samples was determined using static contact angle measurement. Chemical interactions between the silane layer and aluminum substrates were also examined using FTIR-ATR spectroscopy. Pull-off adhesion was used under wet, dry and recovery conditions. The contact angle measurements showed a relative increase in the surface free energy of the silane treated specimens. For specimens treated with silane solutions below the IEP of aluminum, adhesion strengths were higher than those for pHs higher than IEP. This may suggest that an acid–base interaction occurs between the negatively charged silanol species and the positively charged AA surface. FTIR revealed two modes of interaction, one between silane and Al³⁺ (Si–O–Al), and the other indicative of a siloxane network (Si–O–Si). Thickness measurement showed that the silane layer is 100–200 nm thick indicating that the silane formed at the surface is not a monomolecular layer. Direct pull-off adhesion measurements of silane treated samples showed a significant improvement in initial bond strength compared with degreased aluminum substrates. However, those silane solutions having pHs higher than 8.4 showed inferior adhesion in comparison to those having lower pHs. The adhesion improvement was maintained, to some extent, after exposure to salt spray cabinet. In spite of good dry, wet and recovery adhesion, silane treated surfaces are not comparable with chromated AA aluminum in terms corrosion resistance.     

Designing a hand rest tremor dynamic vibration absorber using H 2 optimization method

An optimal single DOF dynamic absorber is presented. A tremor has a random nature and then the system is subjected to a random excitation instead of a sinusoidal one; so the H ₂ optimization criterion is probably more desirable than the popular H _∞ optimization method and was implemented in this research. The objective of H ₂ optimization criterion is to reduce the total vibration energy of the system for overall frequencies. An objective function, considering the elbow joint angle, θ ₂, tremor suppression as the main goal, was selected. The optimization was done by minimization of this objective function. The optimal system, including the absorber, performance was analyzed in both time and frequency domains. Implementing the optimal absorber, the frequency response amplitude of θ ₂ was reduced by more than 98% and 80% at the first and second natural frequencies of the primary system, respectively. A reduction of more than 94% and 78%, was observed for the shoulder joint angle, θ ₁. The objective function also decreased by more than 46%. Then, two types of random inputs were considered. For the first type, θ ₁ and θ ₂ revealed 60% and 39% reduction in their rms values, whereas for the second type, 33% and 50% decrease was observed.     

Effects of the preparation conditions on ethylene/vinyl acetate membrane morphology with the use of scanning electron microscopy

In this research, the effects of preparation conditions, including the coagulation bath temperature, polymer solution composition, preliminary drying time, and thickness of cast polymeric films, on the morphology of ethylene/vinyl acetate copolymer membranes were investigated with scanning electron microscopy and nitrogen gas permeability tests. Flat sheet membranes were prepared through a thermal–wet phase‐inversion method. Scanning electron microscopy pictures showed asymmetric structures for some of the membranes. It was also observed that the porosity of the membranes decreased with an increase in the temperature of the coagulation bath and the solvent evaporation period. When the concentration of the polymer solution was increased from 5 to 12 wt %, the nucleation and growth of the solvent‐rich phase replaced the nucleation and growth of the polymer‐rich phase. With an increase in the thickness of the cast polymeric films, the number of macrovoids increased in the membranes. The nitrogen gas permeability of the developed membranes was in good agreement with the scanning electron microscopy results. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007