Multifunctional WSe2/SnSe2/WSe2 van der Waals heterostructures

Journal of Materials Science: Materials in Electronics - In this study, we report the fabrication of WSe2/SnSe2/WSe2 van der Waals (vdW) heterostructures for potential applications as tunnel...     

Vitamin B12 buccoadhesive tablets: auspicious non-invasive substitute for intra muscular injection: formulation,in vitro and in vivo appraisal

Attempting to prepare a convenient bioavailable formulation of vitamin B₁₂ (cyanocobalamin), 17 tablet formulations were prepared by direct compression. Different concentrations of hydroxypropyl methyl cellulose (HPMC), carbopol 971p (CP971p), and chitosan (Cs) were used. The tablets were characterized for thickness, weight, drug content, hardness, friability, surface pH, in vitro drug release, and mucoadhesion. Kinetic analysis of the release data was conducted. Vitamin B₁₂ bioavailability from the optimized formulations was studied on rabbits by the aid of enzyme-linked immunosorbent assay. Neurotone^® I.M. injection was used for comparison. HPMC (F1-F4), CP971p (F5-F8), and HPMC/CP971p (F12-F15)-based formulations showed acceptable mechanical properties. The formulated tablets showed maximum swelling indices of 232?±?0.13. The surface pH values ranged from 5.3?±?0.03 to 6.6?±?0.02. Bioadhesive force ranged from 66?±?0.6 to 150?±?0.5?mN. Results showed that CP971p-based tablets had superior in vitro drug release, mechanical, and mucoadhesive properties. In vitro release date of selected formulations were fitted well to Peppas model. HPMC/CP971p-based formulations showed bioavailability up to 2.7-folds that of Neurotone^® I.M. injection.     

Effects of excimer laser annealing energy on the properties of thermally evaporated tin antimony sulfide thin films and TEM characterization of the powder

Tin antimony sulfide (TAS) is one of the most promising compounds for the next generation of optoelectronic and thin film photovoltaic devices. TAS material was synthesized by a solid-state reaction using earth-abundant tin, antimony and sulfur elements. The structural properties of the TAS powder were investigated by transmission electron microscopy (TEM). X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and selected electron diffraction (SAED) were employed to establish the crystalline nature of the powder. The TEM observations demonstrated that the powder was polycrystalline in nature with rod-shaped structure. The effects of excimer laser annealing (ELA) at different pulse energies on the structural, morphological and optical properties of thermally evaporated TAS films were investigated. X-ray diffraction (XRD), scanning electron microscopy (SEM) and Raman spectroscopy measurements showed that the films annealed by an excimer laser of 248 nm were amorphous for weak energy densities whereas the sample irradiated with 111 mJ/cm^??2 was polycrystalline with a preferential \({\text{(}}\overline {{\text{2}}} {\text{1}}\overline {{\text{3}}} {\text{)}}\) orientation. The ELA effects on the optical properties were also studied in the wavelength range 300–1800 nm by using UV–Vis–NIR spectroscopy. The absorption coefficient of all samples in the fundamental absorption region is higher than 10⁴ cm^?1. We also found that the optical band gap decreases from 2.04 to 1.84 eV after irradiating the thin films under different laser energy densities.     

Efficient global optimization for high-dimensional constrained problems by using the Kriging models combined with the partial least squares method

In many engineering optimization problems, the number of function evaluations is often very limited because of the computational cost to run one high-fidelity numerical simulation. Using a classic optimization algorithm, such as a derivative-based algorithm or an evolutionary algorithm, directly on a computational model is not suitable in this case. A common approach to addressing this challenge is to use black-box surrogate modelling techniques. The most popular surrogate-based optimization algorithm is the efficient global optimization (EGO) algorithm, which is an iterative sampling algorithm that adds one (or many) point(s) per iteration. This algorithm is often based on an infill sampling criterion, called expected improvement, which represents a trade-off between promising and uncertain areas. Many studies have shown the efficiency of EGO, particularly when the number of input variables is relatively low. However, its performance on high-dimensional problems is still poor since the Kriging models used are time-consuming to build. To deal with this issue, this article introduces a surrogate-based optimization method that is suited to high-dimensional problems. The method first uses the ‘locating the regional extreme’ criterion, which incorporates minimizing the surrogate model while also maximizing the expected improvement criterion. Then, it replaces the Kriging models by the KPLS(+K) models (Kriging combined with the partial least squares method), which are more suitable for high-dimensional problems. Finally, the proposed approach is validated by a comparison with alternative methods existing in the literature on some analytical functions and on 12-dimensional and 50-dimensional instances of the benchmark automotive problem ‘MOPTA08’.     

Optical and electrical properties of a new polymer

Thin film of poly (5-isopropylidenecyclo-1,4-vinylene-2,3-dicarboxylicacidamide-s-methyl hydrazinecarbodithioate) (II) (Scheme 1) of 5 μm thickness was prepared. The dielectric properties of the prepared sample were studied as a function of frequency and temperature, and the results were analyzed by the Cole–Cole method. The optical permittivity and the dc-conductivity have been deduced, and the activation energy has been calculated and found to be 0.023 eV. Also, a detailed study of optical absorption is presented. The optical absorption spectra were measured in the wavelength range from 200–600 nm. The calculated absorption coefficient, absorption index, and determined values of energy gaps ( and ΔE) are presented. The results indicate that both mechanisms of direct and indirect transitions exist. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1653–1657, 1997     

Use and recycling of Ca-alginate biocatalyst for removal of phenol from wastewater

The objective of the current work is the exhaustive study of the phenol degradation potential in both free cell and immobilized bacterium (Pseudomonas aeruginosa) in calcium alginate beads (biocatalyst) was investigated for its ability to grow and degrade phenol as its sole source of carbon and energy.The biodegradation assays were performed in liquid medium with phenol being the only substrate. It was found that P. aeruginosa is able to degrade phenol up to 500 mg L^?1 in 50 h as free cell and 900 mg L^?1 in 80 h when immobilized in the calcium alginate beads. However, for 1200 mg L^?1 concentration, the immobilized cells took much more time (290 h) for a complete degradation.The reuse of these beads in different concentrations of phenol (100–900 mg L^?1) showed that the cells keep their phenol degradation ability up to 900 mg L^?1in 78.5 h with 99% removal efficiency.Similarly, the reuse of the biocatalyst in the same initial phenol concentration (500 mg L^?1), allows us to get 9 cycles.     

Hot compression and fracture toughness of HSS composed hot strip work rolls

The rolls in the finishing stands must have good resistance to both wear and fire cracks. The use of high-speed steel at the finishing stands has shown satisfactory results. The composition of this high-alloyed steel is an important parameter as the most significant change lays on the type, morphology, and volume fraction of the eutectics carbides. The heat treatment of these products consists of high temperature austenization followed by quenching and two temperings, as required in order to increase their overall hardness and to completely eliminate residual austenite. The influence of tempering temperatures on the mechanical properties of these products, determined using tensile, hot compression and fracture toughness tests, was studied in this research work. Their corresponding failure micromechanisms were defined by means of the analysis of fracture surfaces.     

Curing characteristics and internal stresses in epoxy coatings: Effect of crosslinking agent

The development of internal stresses in a series of epoxy coatings prepared using five different crosslinking agents have been studied. The crosslinking agents were: H1, 4,4 methylenedianiline (DDM); H2, diethylentriamine (DETA); H3, cycloaliphatic polyamine; H4, polyaminoimidazoline; and H5, polyamidoamine adduct. Four different post-cure treatments were applied and the dependence of internal stress on crosslinking agent and post-cure treatment was determined. Curing was followed by monitoring the FTIR epoxy band at 916 cm^{– 1} and the glass transition temperature was determined using DSC to assist interpretation of the measured values of internal stress. The internal stress was tensile in all of the materials at the end of each post-cure treatment. The stress magnitudes increased monotonically with post-cure temperature. The largest stresses were recorded with H1, H2 and H3 whereas the lowest stresses were recorded with H4 and H5, which both included a flexible aliphatic chain. The effects of ageing for extended periods in dry air and in humid air (52%RH and 97%RH) were also examined. Exposure to humid air almost always caused a reduction in the tensile stress and often produced compressive stresses, attributed to swelling due to water absorption. A comparison was made of the stresses formed in coatings applied to a thin substrate that was (i) free to bend during curing, post-curing and ageing, and (ii) prevented from bending (restrained substrate). The general trends in behaviour were in agreement but no simple relationship could be found between the stress magnitudes obtained by the two different test configurations.     

Etude de diverses roches au laboratoire par ondes ultrasonores

The wave propagation velocity in the rocks is a well known tool with many applications in their structure and conditions studies (porosity, microcracks, saturation) or for the relationship with their mechanical properties (R_c, dynamic modulus, ...). In this paper, the interest of the signal shape study is pointed out for a better characterization of the porous medium. An examination of the transmitted frequencies looks particularly promising for materials quality determination.     

Forced transverse vibration of composite sandwich beam with magnetorheological elastomer core

We studied, experimentally and numerically, the vibrational response of a magnetorheological elastomer sandwich beam, clampedfree, delimited by two skins aluminum 7075T6, first subjected to a variable magnetic field perpendicular to the skin of the beam, and second to a harmonic excitation by magnetic force applied at the free end. Our main objective was to predict the effect of the intensity of the current flowing through a coil on several dynamic factors. The maximum amplitude of resonance and the variation of the loss factor as a function of structural stiffness are adjusted simultaneously by the application of different magnetic fields. The results of both methods are compared.