Study of the motion of a spheroidal drop in a linear shear flow

The motion of a spheroidal deformable drop in a simple shear flow is simulated using a finite-difference/front-tracking method. The effect of surface tension coefficient, viscosity ratio and inertia on lateral migration and deformation of the drop is investigated. It is revealed that the deformation of a spheroidal drop is directly related to the capillary and Reynolds numbers. In the limit of finite Reynolds numbers, the equilibrium position of prolate drops depends strongly on the viscosity ratio; the final position of more viscous drops is closer to the wall in contrast with the spherical ones. As the deformability of drops increases and the inertial force decreases, the rate of migration of the prolate drops increases. Although the steady-state position does not depend on the capillary and Reynolds numbers, the migration rate depends considerably on these dimensionless parameters. In addition, the rate of migration is a decreasing function of the aspect ratio due to different direction of the lift force acting on the drop.     

Solving a new fuzzy multi-objective model for a multi-skilled manpower scheduling problem by particle swarm optimization and elite tabu search

Manpower scheduling is a complicated problem to solve that strives to satisfy employers’ objectives and employees’ preferences as much as possible by generating fairly desirable schedules. But sometimes, objectives and preferences may not be determined precisely. This problem causes manpower scheduling takes the fuzzy nature. This paper presents a new fuzzy multi-objective mathematical model for a multi-skilled manpower scheduling problem considering imprecise target values of employers’ objectives and employees’ preferences. Hence, a fuzzy goal programming model is developed for the presented mathematical model and two fuzzy solution approaches are used to convert the fuzzy goal programming model to two single-objective models. Since the complexity of a manpower scheduling problem is NP-hard, the single-objective models are solved by two meta-heuristics, namely particle swarm optimization and elite tabu search. Eventually, the performance of the proposed algorithms is verified and the results are compared with each other to select the best schedules.     

Some new efficient multipoint iterative methods for solving nonlinear systems of equations

It is attempted to put forward a new multipoint iterative method of sixth-order convergence for approximating solutions of nonlinear systems of equations. It requires the evaluation of two vector-function and two Jacobian matrices per iteration. Furthermore, we use it as a predictor to derive a general multipoint method. Convergence error analysis, estimating computational complexity, numerical implementation and comparisons are given to verify applicability and validity for the proposed methods.     

Recent advances on akermanite calcium-silicate ceramic for biomedical applications

Owing to great biocompatibility and high capacity of apatite formation, bioceramics, especially calcium silicate-based compounds, were extensively employed in orthopedic and dental uses concerning biomedical applications. Lately, akermanite (AK; Ca₂MgSi₂O₇), as a bioceramic containing Ca-, Mg- and Si, has gained an increased level of attention because of its more tunable mechanical characteristics and degradation rate. All studies indicate that this magnesium incorporating Ca-silicate ceramic has a great capacity to use as a bone graft material to fulfill the necessity of bone reconstruction. Despite the rising interest in using these materials in biomedical fields, there has not yet been an extensive overview of this bioceramic property and its potential benefits. Thus, it has been speculated that this concept and the emergence of akermanite bioactive ceramics might lead to significant upcoming advancements in the field of bone tissue engineering (BTE). Definitely, the approach still requires additional advances to considerably better respond to the vital concerns regarding the clinical application. The review tackles the present research trends on akermanite ceramics for biomedical purposes such as bone scaffold, coating materials, bone cement, and treatment of osteoporotic bone defects, commencing with recent status and shifting to upcoming developments.     

Copper chloride modified copper electrode: Application to electrocatalytic oxidation of methanol

Copper chloride modified copper (CCMC) electrode was prepared as a new electrode. For the preparation of the modified electrode, the polished copper electrode was placed in 0.1 M CuCl₂ solution for 20 s. In this step, a layer of copper (I) chloride was formed at the surface of copper electrode. Then, the electrode was placed in 0.1 M NaOH and the electrode potential was cycled between −250 and 1000 mV (vs. SCE) at a scan rate of 50 mV s⁻¹ for 5 cycles in a cyclic voltammetry regime until a featureless voltammogram was obtained. Surface physical characteristics of the modified electrode were studied by scanning electron micrographs (SEM). Results showed that considerable amounts of microcrystals have been formed on the copper surface during the modification. Surface elemental analysis of electrode were performed by energy dispersive X-ray (EDX) technique. The results showed that in addition to copper and chloride elements, there is also oxygen at the surface of CCMC electrode. This indicates that a layer of (ClCu)₂O was formed at the surface of the modified electrode. The electrocatalytic activity of the modified electrode for the oxidation of methanol, in aqueous basic solution was studied by using cyclic voltammetry. Results showed that, copper chloride modified electrode can improve the activity of Cu towards the oxidation of this small organic molecule, showing the possibility of attaining good electrocatalytic anodes for fuel cells. The modified electrode shows a stable and linear response in the concentration range of 5 × 10⁻³ to 8 × 10⁻² M with a correlation coefficient of 0.9958.     

Thermorheological and mechanical behavior of polylactide and its enantiomeric diblock copolymers and blends

In this study, different compositions of nearly monodispersed diblock copolymers of dl-lactide or d-lactide and l-lactide were synthesized by living ring-opening polymerization with a dinuclear indium catalyst. The effects of molecular weight and block length ratio on the rheological behavior of dl and l-lactide diblock copolymers in the disordered state were investigated. For comparison, blends of PDLLA and PLLA homopolymers of equivalent molecular weights to the diblock copolymers were prepared. We found that the time–temperature (t–T) superposition principle is applicable to the diblock copolymers PLLA-b-PDLLA and blends in the disordered state. However, the t–T superposition failed at low temperatures close to the temperature of crystallization. In contrast, diblock copolymers PLLA-b-PDLA formed stereocomplex crystallites of high melting point (slightly above 200 °C) that causes a viscosity enhancement. The failure of t–T superposition was found due to existing of micro homo or stereocomplex crystallites. The non-isothermal crystallization behavior was investigated using differential scanning calorimetry (DSC). The DSC thermograms of blends exhibited a single glass transition at 50–60 °C followed by melting point of PLLA at 177 °C. With decreasing of the PLLA content in the blends, the intensity of the melting peak decreased. In addition, different crystallization behavior was observed for diblock copolymers compared to their equivalent blends. Specifically, low temperatures and enthalpies of melting peaks were observed for diblock copolymers. These also show improvement in elongation at break and tensile strength as compared to their counterpart homopolymer blends.     

Sugar cane juice concentration via CO2 gas hydrate formation

Sugar cane juice concentration via evaporation is the traditional method, though the downside in this technique is the product loss due to sucrose inversion. Gas hydrate separation is an emerging technology applied in desalination, carbon capture, and in this study, for concentrating fruit juice by trapping the water in the form of crystalline cages. A 750 cm³ hydrate reactor was used for hydrate formation experiments to concentrate the sugar cane juice, with a sampling of the concentrate to determine the final solids content. Hydrate formation experiments showed the successful concentration of a 0.12 mass fraction feed to approximately 0.56 mass fraction using four batchwise concentration stages. A comparison of the energy usage between the evaporation train as used in sugar factories and a single batch hydrate formation stage, to concentrate a 0.12 mass fraction feed to 0.30 mass fraction showed an energy reduction of approximately 20% for the hydrate method.     

Self‐Assembling Peptide as a Potential Carrier for Hydrophobic Anticancer Drug Ellipticine: Complexation,Release and In Vitro Delivery

The self‐assembling peptide EAK16‐II is capable of stabilizing hydrophobic compounds to form microcrystal suspensions in aqueous solution. Here, the ability of this peptide to stabilize the hydrophobic anticancer agent ellipticine is investigated. The formation of peptide‐ellipticine suspensions is monitored with time until equilibrium is reached. The equilibration time is found to be dependent on the peptide concentration. When the peptide concentration is close to its critical aggregation concentration, the equilibration time is minimal at 5 h. With different combinations of EAK16‐II and ellipticine concentrations, two molecular states (protonated or cyrstalline) of ellipticine could be stabilized. These different states of ellipticine significantly affect the release kinetics of ellipticine from the peptide‐ellipticine complex into the egg phosphatidylcholine vesicles, which are used to mimic cell membranes. The transfer rate of protonated ellipticine from the complex to the vesicles is much faster than that of crystalline ellipticine. This observation may also be related to the size of the resulting complexes as revealed from the scanning electron micrographs. In addition, the complexes with protonated ellipticine are found to have a better anticancer activity against two cancer cell lines, A549 and MCF‐7. This work forms the basis for studies of the peptide‐ellipticine suspensions in vitro and in vivo leading to future development of self‐assembling peptide‐based delivery of hydrophobic anticancer drugs.     

Extraction and Preconcentration of Some Triazole Pesticides in Grape Juice by Salting Out Homogeneous Liquid–Liquid Extraction in a Narrow-Bore Tube Prior to Their Determination by Gas Chromatography–Flame Ionization Detection

A fast and simple extraction and preconcentration method for some triazole pesticides has been developed using a homogeneous liquid–liquid extraction method performed in a narrow-bore tube. The extraction is based on phase separation of a water-miscible organic solvent from aqueous solution in the presence of a salting out agent. In this work, the homogeneous solution of water and acetonitrile (water-soluble extraction solvent) was broken by addition of 30 %, w/v, sodium chloride (salting out agent). After sonication, a small volume of acetonitrile was collected on top of the tube and the extracted analytes in the collected phase were determined by gas chromatography–flame ionization detection. The effect of various experimental parameters including kind and volume of the water-soluble organic solvent, amount of salt, length and diameter of tube, and pH of sample solution was investigated. Under the optimum conditions, calibration graphs were linear over the range of 3–5,000 μg L^?1. Relative standard deviations were less than 5.4 % for six repeated determinations (C?=?100 μg L^?1). Furthermore, the limits of detection (S/N?=?3) and quantification (S/N?=?10) were obtained in the ranges of 0.60–4.8 and 1.9–16 μg L^?1, respectively. This method is very simple and rapid, requiring less than 10 min for sample preparation. It has been successfully utilized for the analysis of triazole pesticides in the grape juice samples.