Mortality response of folate receptor-activated,PEG–functionalized TiO2 nanoparticles for doxorubicin loading with and without ultraviolet irradiation

TiO₂ nanoparticles (NPs) were synthesized by hydrothermal assisted sol–gel technique. In the next step, as-synthesized NPs were modified by poly ethylene glycol (PEG). Then, folic acid (FA) was conjugated to TiO₂–PEG. Finally, Doxorubicin (Dox) as an anticancer drug was loaded on as-prepared TiO₂–PEG–FA nanocarrier. The optimization of TiO₂ and FA concentration and the influence of ultraviolet (UV) irradiation on photocatalytic activity of nanocarrier and Dox loaded carrier were assessed by utilizing the 3-(4,5-dimethylthiazol-2yl)-2,5-diphenyltetrazolium bromide (MTT)-assay method.     

Interfacial energy for solutions of nanoparticles,surfactants, and electrolytes

The addition of surfactants to modify the surface property of nanoparticles (NPs) from hydrophilic to hydrophobic also enhances their interfacial properties. Several approaches were previously proposed to calculate the surface tension/interfacial tension (IFT) for different systems in the presence of NPs, surfactants, and electrolytes. However, most of these approaches are indirect and require several measured parameters. Therefore, a mathematical model is developed here to calculate the surface tension/IFT for these systems. The developed model takes into account the cohesive energy due to the interaction of the surfactant CH₂ groups, the electric double layer effect due to the interaction among the ions of NPs, surfactants, and electrolytes, and the dipole–dipole interaction of NPs and electrolytes. The developed model is compared and validated with the laboratory experimental data in literature. The results reveal further understanding of the mechanisms involved in stabilization of oil/water emulsion in the presence of NPs, surfactants, and electrolytes.     

Dynamically vulcanized thermoplastic elastomer nanocomposites based on linear low-density polyethylene/styrene-butadiene rubber/nanoclay/bitumen: morphology and rheological behavior

Dynamically crosslinked thermoplastic elastomer nanocomposites were synthesized as modifier for the bitumen binder-based asphalts. Linear low-density polyethylene (LLDPE) and styrene-butadiene rubber (SBR), with the ratio of 80/20, bitumen, and organically modified clay (OC) were all melt mixed in the presence of the sulfur curing system. The proposed mixing was carried out in an internal mixer at 160 °C with a rotor speed of 120 rpm. To enhance the molecular interactions between the polymer phases and the clay silicate layers, maleic anhydride-grafted LLDPE (PE-g-MA) with the maleiation degree of 50% was also incorporated into the mixture. Observation of the composite samples, using the scanning electron microscopy (SEM), revealed the matrix dispersed type of morphology for all dynamically vulcanized samples. X-ray diffraction (XRD) and transmission electron microscopy (TEM) examinations evidenced the exfoliation of the clay silicate layers with good dispersion. Rheomechanical spectrometry (RMS) was performed on the prepared nanocomposites. All dynamically vulcanized nanocomposites comprising 2.5% of OC exhibited shear-thinning behavior and non-terminal characteristics with a low frequency range. These indicate the formation of three-dimensional physical networks by the clay nanolayers throughout the LLDPE matrix. The presence of the bitumen in the composition of the prepared nanocomposites improved the flowability of the samples. This is a promising feature of the prepared nanocomposites to be used as an elastic and resistant modifier in the composition of the bitumen-based asphalts.

     

Investigation of miscibility and phase structure of a novel blend of poly(lactic acid) (PLA)/acrylic rubber (ACM) and its nanocomposite with nanosilica

In this work, a novel polymer blend containing poly(lactic acid) (PLA) as a biocompatible and biodegradable thermoplastic and acrylic rubber (ACM) is prepared and the miscibility and phase structure of the blend and its nanocomposite (PLA/ACM/nanosilica) are investigated through theoretical and experimental methods. To predict the phase diagram of the blend, a compressible regular solution model was employed, in which an upper critical solution temperature was observed. The model predicted that PLA/ACM blends are immiscible over the whole composition range at temperatures below 260 °C. Performing scanning force microscopy on the blend showed phase separated structures for the blends containing different amounts of the PLA and ACM. This was in accordance with the results of dynamic mechanical analysis, which revealed two distinct glass transition temperatures for the studied blends. The effect of nanometer sized silica particle on morphology and rheological properties of these blends was also investigated. Scanning force microscopy results showed much reduction of droplet size in the blends containing 2 wt % nanosilica. This was attributed to the suppression effect of nanosilica on the droplets coalescences. Rheological measurements confirmed the interaction of both components with the silica nanofiller. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45499.     

The influence of depth of cut on the machinability of an alloyed austempered ductile iron

The volume fraction of high carbon austenite present in the microstructure of austempered ductile iron (ADI) is one of the important factors that influence the mechanical and physical properties of the alloy. Formation of martensite by TRIP (transformation induced plasticity) mechanism during the machining operation in which a large amount of stress is applied to the microstructure results in a decrease in machinability of austempered ductile iron which has affected the expansion of ADI in industry. In this article, the effect of depth of cut as a machining variable is assessed in an alloyed austempered ductile iron containing Cu, Ni and Mo. The measurements of mechanical properties including impact energy, tensile strength, hardness and microhardness along the cross-section of samples are reported for samples austenitized at 870 °C followed by austempering at 375, 340 and 300 °C. Results indicate that contrary to the behavior of many alloys, in austempered ductile iron, reducing the depth of cut will not improve the machinability. In the case of studied composition, cutting with depths of 0.5 and 0.1 mm had the best and worst results, respectively.     

Mesoscale finite element prediction of concrete failure

The present paper studies the failure of concrete from the mesoscopic point of view. Biphasic cubic concrete samples containing spherical aggregates embedded in a homogenized mortar have been simulated using standard finite element method. Linear elasticity and damage-plasticity hypotheses are considered for the aggregates and mortar, respectively. Various triaxial loading conditions are assumed for each sample to generate adequate discrete failure points within the stress space. In the next step, the approximated failure surfaces of specimens are constructed using the Delaunay triangulation technique. The effects of mesostructural features such as aggregate grading curve, aggregate volumetric share, and more importantly the controlling parameters of mortar’s damage-plasticity constitutive model have been investigated. Finally, the failure modes of some selected samples have been reported and discussed.