Antibacterial and Antifungal Activities of the Essential Oils of Two Saltcedar Species from Tunisia

The chemical composition of the volatile constituents from the flowering parts of Suaeda fructicosa and Limonium echioides were analysed by GC-FID and GC-MS. Sixty-five compounds were identified in L. echioides aerial parts. 48 out of 65 were found common to the aerial part of S. fructicosa. Palmitic acid was found as a predominant compound in both tested halophytic oils. Furthermore, the essential oil was tested against six bacteria and four fungi at different concentrations. Both oils, tested at 0.5 and 0.8 mg ml⁻¹, inhibited the visible growth of Staphylococcus aureus, Staphylococcus epidermidis, Micrococcus luteus, Escherichia coli and Salmonella typhimurium, but no antibacterial effect was detected against Pseudomonas aeruginosa. Additionally, both halophytic oils failed to show antifungal activity against all the test fungi when applied at 80, 200 and 500 μg/disc.     

Photoelectrochemical (PEC) etching of Ga2O3

In recent years, interest in the use of gallium oxide (Ga₂O₃) in semiconductor devices has increased due to its wide bandgap that permits device operation at high temperatures and high voltages. As the size of these devices decrease, it becomes more important to be able to produce features on the micro and nanoscale. Traditional etching (both wet and dry) have several limitations which either are unable to produce nano-features at the required scale or degrade device quality. Consequently, photoelectrochemical etching of Ga₂O₃ is of interest to researchers for its potential to produce features on the order of magnitude required while also causing minimal device degradation. Photoelectrochemical etching introduces a number of parameters that can be adjusted to control the etching process. In this work, we demonstrated photoelectrochemical etching of Ga₂O₃ by showing the effect of changing electrolyte concentration, anodic voltage, and etching time on the etching process. This etching method could be useful for a variety of applications which require complex patterning of Ga₂O₃ with high degrees of control compared to simple wet or dry etching processes.     

Phase Transitions in the BiVO<Subscript>4</Subscript>-<Emphasis Type="Italic">n</Emphasis>PbO (<Emphasis Type="Italic">n</Emphasis> = 1, 2) System: Structural–Electrical Properties Relationships

In a general survey of nPbO-BiVO₄ compounds, interesting phases corresponding to n = 1: PbBiVO₅, and n = 2: Pb₂BiVO₆ are described. A phase transition has been unambiguously characterized for PbBiVO₅. The crystal structures were solved from twinned crystals at room temperature (α phase, triclinic, S.G. P-1) and at 530°C (β phase, monoclinic, C2/m). Powder neutron diffraction experiments confirmed these settings and both room-temperature (RT) and high-temperature (HT) refinements corroborated space group choices, clearing up a literature controversy about the centrosymmetry of the α phase, and identifying structural modifications occurring under the α → β transition. Cationic substitutions for V were tested and PbBi(V_1−x M _x )O₅ (M = P) solid solutions identified. Pb₂BiVO₆ (n = 2) is a compound showing several successive structural transitions, i.e., α → β → δ. Structures of α and δ forms have been previously described from powder diffraction data (x-ray and neutron). In this work, we have refined these structures from single-crystal data, and the resolution of the intermediate β form, so far unsolved, was possible through a stabilization thermal cycle; its complete structural understanding required a 4D formalism. Two new polymorphic phases, α′ and δ′, were obtained by substituting Mn or P for V; their structures are closely related to, respectively, the α phase at room temperature, and the δ phase at 680°C. Electrical conductivities of all structurally characterized compositions were investigated, and correlations were drawn between their conduction properties and structural characteristics. Conductivity properties measured under variable O₂ partial pressures for Pb₂Bi(V_0.75P_0.25)O₆ were interpreted as a mixed ionic–electronic (p-type) conduction mechanism.     

Decision support tool for used oil regeneration technologies assessment and selection

Regeneration is the most efficient way of managing used oil. It saves money by preventing costly cleanups and liabilities that are associated with mismanagement of used oil, it helps to protect the environment and it produces a technically renewable resource by enabling an indefinite recycling potential. There are a variety of processes and licensors currently offering ways to deal with used oils. Selecting a regeneration technology for used oil involves "cross-matching" key criteria. Therefore, the first prototype of spent oil regeneration (SPORE), a decision support tool, has been developed to help decision-makers to assess the available technologies and select the preferred used oil regeneration options. The analysis is based on technical, economical and environmental criteria. These criteria are ranked to determine their relative importance for a particular used oil regeneration project. The multi-criteria decision analysis (MCDA) is the core of the SPORE using the PROMETHEE II algorithm.     

On SISO and MIMO variable structure control of non linear distributed parameter systems: application to fixed bed reactors

This paper deals with the design of variable structure control of distributed parameter systems. The control problem is discussed in relation to a model consisting of a set of non-linear, time varying partial differential equations of hyperbolic type. A formulation of a Single Input–Single Output (SISO) variable structure controller based on the distributed parameter model (late lumping control) is given. An extension to the Multiple Input–Multiple Output (MIMO) case is derived when the control variables are coupled and located on boundary conditions. A theoretical proof of DPS convergence in sliding mode is given. A fixed bed bioreactor in which drinkable water is treated, was used as a simulated example to prove the effectiveness of the control design. The bioreactor must control the harmful component concentrations in such a way that the quality of water fulfils international standards.     

Evaluation of the effect of fennel (Foeniculum vulgare Mill) essential oil addition on the quality parameters and shelf‐life prediction of yoghurt

Yoghurt was prepared by adding three concentrations of fennel essential oil (FEO) (2.5, 5 and 7.5 µL) in 100 mL of pasteurised milk. Fennel essential oil did not affect the viability of yoghurt starters during fermentation. Based on sensory analysis, only the 5‐µL FEO concentration was incorporated in order to investigate the physicochemical and microbiological properties of enriched yoghurt during storage. Results showed that FEO in yoghurt did not significantly affect the quality after acidification (P > 0.05). However, total solid content, syneresis and lightness (L*) differed significantly (P < 0.05). Bacterial counts indicated that the control yoghurt had the highest values. Fortified yoghurt had an increased shelf life of 29 days.     

Chemical composition and oxidative stability of Tunisian monovarietal virgin olive oils with regard to fruit ripening

The chemical composition of virgin olive oil may be influenced by genotype and different agronomic (i.e. fruit ripeness degree, water supply) and technological factors. This article reports the evaluation of the influence of the olive ripening stage on the quality indices, the major and the minor components and the oxidative stability of the two main monovarietal Tunisian cultivars (cvv. Chétoui and Chemlali) virgin olive oils. Moreover, the olives cv. Chétoui were tested in a rain-fed control and an irrigation regime. The oils sampled at five different ripeness stages were submitted to liquid chromatographic determination (HPLC-DAD/MSD) of their quali-quantitative phenolic and tocopherolic profiles. Moreover, the triacylglycerol and fatty acid compositions, and minor components such as squalene, pigments and their relation with the oil oxidative stability were evaluated. The tested oils showed very good correlation between the oxidative stability and the concentrations of total phenols, practically secoiridoids and α-tocopherol.     

Heat Capacity Calculation of Some Semiconductor Compounds Using Lambert W Function

Silicon - Based on the Lambert-Boltzmann distribution, a simple and efficient expression for the determination of the heat capacity of some semiconductor compounds is proposed. The new expression...