Chemical composition and antimicrobial activity of essential oil of Cupressus atlantica

Cupressus atlantica Gaussen, an endemic species from Morocco, is used in traditional medicine. The chemical composition of the essential oil isolated by hydrodistillation from the leaves was investigated by capillary gas chromatography and gas chromatography/mass spectrometry, and also evaluated for in vitro antimicrobial activity. Sixty-one components, representing 98.1% of the total, were detected of which fifty-seven were identified. Germacrene D (34.8%), alpha-pinene (13.6%), delta-cadinene (6.1%), alpha-phellandrene (5.5%), gamma-cadinene (5.0%), beta-caryophyllene (4.8%) and alpha-humulene (4.4%) were the predominant compounds. The oil was characterized by a relatively high amount of oxygenated monoterpenes (66.5%). The oil, screened for antimicrobial activity against both Gram-positive and Gram-negative, showed pronounced activity against all the microbes tested, except Pseudomonas, which showed resistance.     

Role of oxygen on the optical properties of borate glass doped with ZnO

Lithium tungsten borate glass (0.56−x)B₂O₃–0.4Li₂O–xZnO–0.04WO₃ (0≤x≤0.1 mol%) is prepared by the melt quenching technique for photonic applications. Small relative values of ZnO are used to improve the glass optical dispersion and to probe as well the role of oxygen electronic polarizability on its optical characteristics. The spectroscopic properties of the glass are determined in a wide spectrum range (200–2500 nm) using a Fresnel-based spectrophotometric technique. Based on the Lorentz–Lorenz theory, as ZnO content increases on the expense of B₂O₃ the glass molar polarizability increased due to an enhanced unshared oxide ion 2p electron density, which increases ionicity of the chemical bonds of glass. The role of oxide ion polarizability is explained in accordance with advanced measures and theories such as optical basicity, O 1s binding energy, the outer most cation binding energy in Yamashita–Kurosawa's interionic interaction parameter and Sun's average single bond strength. FT-IR measurements confirm an increase in bridging oxygen bonds, as a result of replacement of ZnO by B₂O₃, which increase the UV glass transmission window and transmittance.     

Dynamic conformance and design quality in a supply chain: an assessment of contracts’ coordinating power

We consider a two-echelon supply chain involving one manufacturer and one supplier who collaborate on improving both design and conformance quality. Design quality is supposed to increase product desirability, and therefore market demand, while conformance quality should reduce the proportion of defective items, and therefore increase the manufacturer’s sales revenue. We investigate how the supply chain parties allocate effort between design and conformance quality under both cooperative and non-cooperative settings in an intertemporal framework. Furthermore, we evaluate wholesale price contracts and revenue-sharing contracts in terms of their performance and coordination power. We show that although a revenue-sharing contract enables the manufacturer to effectively involve the supplier in quality improvement, neither contract type allows for perfect coordination resulting in the quality that can be achieved by a cooperative supply chain. We thus suggest a reward-based extension to the revenue-sharing contract, to ensure system-wide optimal quality performance. Importantly, we find that the supplier would be better off adopting a reward-based revenue sharing contract and refusing a standard revenue-sharing contract, while the opposite would be true for the manufacturer.     

First-principles calculations to investigate half-metallic ferromagnetism in Zn0.50Ti0.50S alloy by using DFT + U calculations

ABSTRACT

The spin-polarized structural, electronic and magnetic properties of the Ti-doped zincblende ZnS compound at x?=?0.50 (Zn_0.50Ti_0.50S alloy) have been investigated by employing the first-principles full-potential linearised augmented plane wave with local orbitals (FP-L/APW?+?lo) method within the frame-work of spin-polarized density functional theory (spin-DFT). For the treating of the structural properties, the electronic exchange and correlation (XC) functional was defined by generalised gradient approximation (GGA), whereas both GGA and GGA?+?U approximations are applied to treat and to compare the electronic and magnetic properties (U is the Coulomb repulsion energy). It has been confirmed that the ferromagnetic (FM) state of this alloy is found the most stable phase; however, all the equilibrium lattice parameters such as; lattice constant (a₀), bulk modulus (B₀), and its first-pressure derivative (B′) are computed in all paramagnetic, ferromagnetic and anti-ferromagnetic phases. The calculations of electronic properties unveil the perfect half-metallic character in the tetragonal Zn_0.50Ti_0.50S system. The computed magnetic properties reveal that the total magnetic moment is mainly originated from the transition element (TM) of Ti. Moreover, we have found that the p-d hybridisation is the paramount responsible for the reduction of the magnetic moment of TM from its free space charge value and for the production of minor magnetic moments on the nonmagnetic Zn and S sites.     

Structural modifications induced in Bayfol polycarbonate due to heavy highly energetic ions irradiations

The effects of 28 GeV ⁵⁶Fe and 13.72 GeV ²⁸Si ion irradiation on the structural properties of two types of Bayfol, namely DPF 5023 and CR 1–4 polycarbonates, have been investigated. It is worth mentioning that this report is almost the first one dealing with the topic of material changes in such a high energy range. Samples from each type of Bayfol were classified into two groups. The first group has been exposed to Fe ion fluences at levels between 2000 and 8000 ion/cm². The second group has been exposed to Si ions with similar fluences. The total energy deposited is between 27.44 and 224 E12 eV. The modifications induced in Bayfol samples due to ion irradiation have been studied using X-ray diffraction (XRD) and Fourier Transform Infrared spectroscopy. The results indicate that the Fe ion irradiation causes crosslinking in Bayfol DPF 5023, reflected as a decrease in the ordering character. Also, the tendency of Bayfol CR 1–4 to crosslinking due to Fe ion irradiation is lower than that of Bayfol DPF 5023. On the other hand, the Si ion irradiation causes mainly chain scission at the carbonate site of both types of Bayfol associated with the formation of hydroxyl group.     

Variational Approach to the Orbital Stability of Standing Waves of the Gross-Pitaevskii Equation

This paper is concerned with the mathematical analysis of a masssubcritical nonlinear Schrödinger equation arising from fiber optic applications. We show the existence and symmetry of minimizers of the associated constrained variational problem. We also prove the orbital stability of such solutions referred to as standing waves and characterize the associated orbit. In the last section, we illustrate our results with few numerical simulations.     

Structural and catalytic properties of ZnO and Al<Subscript>2</Subscript>O<Subscript>3</Subscript> nanostructures loaded with metal nanoparticles

Nanostructured zinc oxide (ZnO) nanobelts and aluminum oxide (Al₂O₃) nanoribbons have been grown successfully from the vapor phase. XRD results confirmed the purity and the high quality of the formed crystalline materials. TEM images showed that ZnO nanostructures grew in the commonly known tetrapod structure with nanobelts separated from the tetrapods with an average width range of 10–30 nm and a length of about 500 nm. Al₂O₃ nanostructures grew in the form of nanoribbons with an average width range of 20–30 nm and a length of up to 1 μm. The catalytic oxidation of CO gas into CO₂ gas over the synthesized nanostructures is also reported. Higher catalytic activity was observed for Pd nanoparticles loaded on the ZnO nanobelts (100% conversion at 270 °C) and Al₂O₃ nanoribbons (100% conversion at 250 °C). The catalytic activity increased in the order Cu < Co < Au < Pd for the metal-loaded nanostructures. The preparation methods could be applied for the synthesis of novel nanostructures of various materials with novel properties resulting from the different shapes and morphologies.     

Impact of the Structural Changes on the Fracture Behavior of Naturally Weathered Low-Density Polyethylene (LDPE) Films

Weathering of LDPE films was performed in a sub-Saharan facility in Laghouat, Algeria. Ageing led to a rapid change of the physicochemical properties resulting from the alteration of the material's microstructure. XRD revealed the progressive increase of the crystallinity ratio and the thickness of the crystalline lamellae as well. SEM revealed the presence of white particles, which look like crystalline phase emerging from the surface of the film. The oxidation and crystallinity varied according to a concentration gradient across the thickness. The impact of the microstructural changes on the mechanical properties was highlighted based on the essential work of fracture (EWF) method. There was a progressive decrease of the total energy of fracture and a lowering of the net stress (σ_net) and the (β_wp) term. Nevertheless, this loss of the mechanical properties was characterized by a rapid transition from a ductile mode of failure to a very brittle mode.