Chouaib Doukkali University

This study aims to evaluate, under controlled conditions, the acute toxicity of cadmium chloride (CdCl₂) in the marine gastropod Phorcus lineatus. Specimens sampled from Morocco's Atlantic coast were exposed to different concentrations of CdCl₂ for 96 h, with two replicates for each tested concentration. Survival and mobility were assessed at 24, 48, 72, and 96 h of exposure. The effect of CdCl₂ on total hemocytes number (THN) and hemocyte size were also evaluated. The results showed a significant decrease in survival and mobility with increasing CdCl₂ concentration and exposure duration. The median lethal concentration (LC₅₀) at 96 h was estimated at 6.04 mg L−1 CdCl₂ (95% confidence interval: 4.91–7.41 mg L−1), corresponding to 2.97 mg L−1 Cd. Exposure to the contaminant induced a significant reduction in the size of hyalinocytes and their nuclei in animals treated with concentrations ≥5 mg L−1, whereas granulocytes and undifferentiated cells showed no significant effects. In gastropods exposed to low CdCl₂ concentrations (≤ 5 mg L−1), THN increased significantly with exposure time. However, it decreased in individuals treated at 20 mg L−1, suggesting an immunotoxic effect of CdCl₂.

In this work, a new isatin derivative, namely 1-[2-(diethylamino)ethyl]-1H-indole-2,3-dione (5-HEI), was synthesized and its inhibitory effect on carbon steel in hydrochloric acid solution was estimated by gravimetric measurements, electrochemical impedance spectroscopy (EIS) and electrochemical potentiodynamic polarization. The steel surface was analyzed by SEM. The results obtained showed that this isatin derivative acts as an effective corrosion inhibitor for carbon steel in 1 M HCl, with an inhibition efficiency of 93.9% achieved with 1 mM after 6 hours of immersion at 303 K. Polarization curves suggested that 5-HEI acted as a mixed inhibitor. Charge transfer resistance values increased with increasing inhibitor concentration, as demonstrated by electrochemical impedance spectroscopy. The adsorption of 5-HEI onto the steel surface obeyed El-Awady's kinetic/thermodynamic model. Thermodynamic studies have indicated that the main mechanism controlling corrosion inhibition by 5-HEI involves a chemisorption process.

The development of numerical simulation software enables the modeling of complex physical phenomena that are difficult to detect in printed parts within the fused deposition modeling (FDM). However, simulating all possible combinations of process parameters, across factors and levels, remains time-consuming and computationally expensive. The use of numerical design of experiments (NDoE) is a relevant approach, as it enables the optimization and establishment of correlations between printing parameters and the associated physical phenomena. In this study, the influence of different printing temperatures (melting temperature, build-plate temperature, and ambient temperature) on polymer diffusion kinetics, filament coalescence (neck formation), and the resulting porosity is investigated numerically. The analysis is based on a two-dimensional numerical model that incorporates heat transfer and Schneider’s equations for crystallization simulation using multi-physics software. From these results, it is possible to evaluate filament coalescence, the degree of inter-filament healing, and interfacial porosity. Each parameter is analyzed separately to determine its individual influence on the phenomenon being investigated, and then the thermal interactions between these parameters are evaluated to better understand their combined effect on the physical mechanisms. The results indicate that higher build-plate temperatures, as well as prolonged exposure to processing ambient temperature, enhance inter-filament diffusion and reduce residual porosity. Moreover, changing the printing orientation from 0° to 90° leads to a significant increase in the degree of healing, rising from 0.55 to 0.71. In contrast, increasing the deposition temperature has only a limited effect on the initiation and development of these phenomena.

Mullite (Al6Si2O13), an aluminosilicate with remarkable thermal and dielectric properties, is a promising material for advanced electronic applications. This study focuses on a sintered mullite composite and examines its structural, morphological, dielectric, and electrical properties. X-ray diffraction and scanning electron microscopy analyses confirm a well-defined crystalline structure and a homogeneous microstructure. Impedance spectroscopy measurements reveal a high relative permittivity at low frequencies, dominated by interfacial and jump polarization mechanisms. Electrical conductivity follows Jonscher's double-power law, reflecting mixed ionic and electronic conduction due to contributions from grains and grain boundaries. Analysis of the Nyquist diagrams shows a marked decrease in resistances with increasing temperature: The grain resistance decreases from 21.87 M Omega to 4.85 M Omega, while that of the grain boundaries decreases from 89.44 M Omega to 5.94 M Omega between 450 degrees C and 900 degrees C. In addition, the relative permittivity increases sharply with temperature, from 25 & times; 103 to 350 & times; 103 at 1 kHz and from 200 to 1 & times; 103 at 1 MHz over the same temperature range, highlighting the dominant influence of temperature and low frequencies on polarization mechanisms. These results confirm the strong potential of sintered mullite for electronic applications. The activation energy of the grain and grain boundary were determined to be Ea,g = 0.18 eV and Ea,bg = 0.22 eV, respectively.

Drought is an increasing concern in Morocco’s semi-arid regions, where water resources are under growing pressure from climate variability and land degradation. Most previous studies on drought monitoring in Morocco have examined meteorological or hydrological dimensions separately, overlooking vegetation dynamics. This fragmented approach limits the ability to capture the full spectrum of drought impacts across natural and managed ecosystems. This study assesses drought dynamics in the Ahmed El Hansali Dam basin, located in the Upper Oum Er-Rbia watershed, during 1975–2023. The novelty of this research lies in the long-term, combined assessment of meteorological, hydrological, and remote sensing indices at the basin scale, providing one of the most comprehensive drought evaluations for Morocco’s inland watersheds. A multi-index approach combining Standardized Precipitation Index (SPI), Streamflow Drought Index (SDI), and Normalized Difference Vegetation Index (NDVI) was applied to assess meteorological, hydrological, and vegetation responses to drought. Meteorological data from five stations, hydrological inflows at the dam, and Landsat-derived NDVI composites were utilized. The SPI and SDI revealed a marked increase in drought frequency and severity beginning in the early 1990s, with the most critical period between 2020 and 2023. SPI values below − 1.5 and SDI near − 1.6 confirmed intensifying precipitation deficits and declining inflows. The NDVI showed moderate interannual variability with lower values during drought years, though weak correlation with SPI and SDI suggests that vegetation response is influenced by altitude, land cover, and soil water retention, and agricultural practices including irrigation. Spatial analyses highlighted the greater resilience of forested highlands compared to lower-elevation agricultural areas. Overall, the combined use of these three indices offers a robust picture of drought evolution in the basin. By bridging the gap between single-dimension studies and proposing a comprehensive multi-source monitoring framework, this work provides a more holistic understanding of drought impacts and delivers actionable insights for water resource managers and policymakers.