ATEF KORCHEF - Academia.edu (original) (raw)
Papers by ATEF KORCHEF
CRC Press eBooks, Feb 2, 2022
Crystals, Apr 21, 2023
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Annales De Chimie-science Des Materiaux, Apr 17, 2008
La diffraction des rayons X, la spectroscopie Raman et l'analyse par spectroscopie d'emis... more La diffraction des rayons X, la spectroscopie Raman et l'analyse par spectroscopie d'emission optique ont ete utilisees pour etudier l'effet des ions magnesium, calcium et sulfate sur la cinetique de precipitation et la microstructure du carbonate de calcium forme, par la methode de degazage controle, a partir des solutions synthetiques equivalentes a l'eau de mer standard. Pour toutes les experiences, la phase aragonite a ete obtenue. La presence des ions Mg 2+ et SO 4 2- dans la solution augmente le temps de germination et diminue la vitesse de croissance de l'aragonite. Les ions magnesium ont ete inseres dans la structure cristalline de l'aragonite en substituant les ions calcium. Cette substitution depend de la concentration des ions Mg2 + , Ca 2+ et SO 4 2- . L'augmentation de la concentration du calcium mene a un faible taux d'incorporation de Mg 2+ . Les ions sulfates peuvent etre adsorbes sur les surfaces de l'aragonite ou inhibent la substitution du calcium par le magnesium, suivant les concentrations ajoutees.
Crystals
In the present study, the microstructure, mechanical properties, and stored energy of an aluminum... more In the present study, the microstructure, mechanical properties, and stored energy of an aluminum alloy containing iron-rich fine precipitates, subjected to severe plastic deformation through equal-channel angular pressing (ECAP), were investigated using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. Up to four passes through ECAP resulted in significant nanometer-scale grain refinement, as well as the accumulation of lattice defects, such as dislocations and mesoscopic shear planes. This resulted in a noticeable enhancement in the Vickers microhardness and the flow stress after ECAP. Differential scanning calorimetry results showed that the ECAP’ed material exhibited two exothermal peaks at 222 ± 2 °C and 362 ± 2 °C, with total thermal effects of ΔH = 4.35 and 6.5 J/g, respectively. Slight increases in the ECAP’ed material microhardness and flow stress were observed at 200 °C. The heat release, at a relatively low tem...
Arabian Journal of Chemistry
Crystals
Phosphorus and ammonium can both be recovered in the presence of magnesium through struvite (MgNH... more Phosphorus and ammonium can both be recovered in the presence of magnesium through struvite (MgNH4PO4·6H2O) crystallization. The present work aimed to optimize struvite crystallization at turbulent solution flow. Struvite was crystallized by magnetic stirring at different initial phosphorus concentrations between 200 and 800 mg·L−1 and high stirring rates between 100 and 700 rpm. The crystals obtained were analyzed by powder X-ray diffraction, Fourier-transform infrared spectroscopy, and scanning electron microscopy. For all experiments, the only phase detected was struvite. It was shown that for an initial phosphorus concentration of 200 mg·L−1, increasing the stirring rate to 500 rpm accelerated the precipitation of struvite, improved the phosphorus removal efficiency, and obtained larger struvite crystals. A decrease in the phosphorus removal efficiency and smaller struvite crystals were obtained at higher stirring rates. This was attributed to the solution turbulence. The limiti...
CRC Press eBooks, Feb 2, 2022
physica status solidi (a), 2006
A 99.1% aluminium was deformed by Equal Channel Angular (ECA) pressing. The material contains a l... more A 99.1% aluminium was deformed by Equal Channel Angular (ECA) pressing. The material contains a low volume fraction of Al 8 Fe 2 Si precipitates located essentially at the grain boundaries. An important increase of the X-ray diffraction peak broadening was observed after ECA pressings. This is due to grain refinement and enhanced lattice distortions. This was accompanied by a lattice decrease due to compressive stresses and partial dissolution of the Al 8 Fe 2 Si precipitates. The grain refinement leads to a significant improvement of the mechanical properties in compression and tension after the first pass through the die. Thereafter, the increase was less significant. The strengthening of the material was accompanied by decreased strain hardening, due to enhanced activities in grain boundaries.
Crystal Research and Technology, 2009
In the present work, investigations on the microstructure of a commercial purity 1100 aluminum th... more In the present work, investigations on the microstructure of a commercial purity 1100 aluminum that had been subjected to moderate to strong deformation (strains of 1 to 4) by equal channel angular pressing (ECAP) were carried out using X-ray diffraction (XRD) and scanning electron microcopy (SEM). A significant grain refinement and development of heterogeneous microstructure after ECAP were observed. High precision XRD and SEM investigations provided useful results on the dissolution of coherent iron rich precipitates, previously formed in the aluminium matrix, by ECAP deformation process.
Crystal Research and Technology
Understanding General Chemistry, 2022
Saudi Pharmaceutical Journal, 2022
The rapid transmission of the pneumonia (COVID-19) emerged as an entire worldwide health concern ... more The rapid transmission of the pneumonia (COVID-19) emerged as an entire worldwide health concern and it was declared as pandemic by the World Health Organization (WHO) as a consequence of the increasing reported infections number. COVID-19 disease is caused by the novel SARS-CoV-2 virus, and unfortunatly no drugs are currently approved against this desease. Accordingly, it is of outmost importance to review the possible therapeutic effects of naturally-occuring compounds that showed approved antiviral activities. The molecular docking approach offers a rapid prediction of a possible inhibition of the main enzymes Mpro and RdRp that play crucial role in the SARS-CoV-2 replication and transcription. In the present work, we review the anti-viral activities of polyphenol compounds (phenolic acids, flavonoids and stilbene) derived from the traditional Chinese medicinal Vitis amurensis. Recent molecular docking studies reported the possible binding of these polyphenols on SARS-CoV-2 enzymes Mpro and RdRp active sites and showed interesting inhibitory effects. This antiviral activity was explained by the structure-activity relationships of the studied compounds. Also, pharmacokinetic analysis of the studied molecules is simulated in the present work. Among the studied polyphenol compounds, only five, namely caffeic acid, ferulic acid, quercetin, naringenin and catechin have drug-likeness characteristics. These five polyphenols derived from Vitis amurensis are promising drug candidates for the COVID-19 treatment.
Understanding General Chemistry, 2022
Understanding General Chemistry, 2022
Understanding General Chemistry, 2022
Understanding General Chemistry, 2022
Understanding General Chemistry, 2022
CRC Press eBooks, Feb 2, 2022
Crystals, Apr 21, 2023
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Annales De Chimie-science Des Materiaux, Apr 17, 2008
La diffraction des rayons X, la spectroscopie Raman et l'analyse par spectroscopie d'emis... more La diffraction des rayons X, la spectroscopie Raman et l'analyse par spectroscopie d'emission optique ont ete utilisees pour etudier l'effet des ions magnesium, calcium et sulfate sur la cinetique de precipitation et la microstructure du carbonate de calcium forme, par la methode de degazage controle, a partir des solutions synthetiques equivalentes a l'eau de mer standard. Pour toutes les experiences, la phase aragonite a ete obtenue. La presence des ions Mg 2+ et SO 4 2- dans la solution augmente le temps de germination et diminue la vitesse de croissance de l'aragonite. Les ions magnesium ont ete inseres dans la structure cristalline de l'aragonite en substituant les ions calcium. Cette substitution depend de la concentration des ions Mg2 + , Ca 2+ et SO 4 2- . L'augmentation de la concentration du calcium mene a un faible taux d'incorporation de Mg 2+ . Les ions sulfates peuvent etre adsorbes sur les surfaces de l'aragonite ou inhibent la substitution du calcium par le magnesium, suivant les concentrations ajoutees.
Crystals
In the present study, the microstructure, mechanical properties, and stored energy of an aluminum... more In the present study, the microstructure, mechanical properties, and stored energy of an aluminum alloy containing iron-rich fine precipitates, subjected to severe plastic deformation through equal-channel angular pressing (ECAP), were investigated using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and atomic force microscopy. Up to four passes through ECAP resulted in significant nanometer-scale grain refinement, as well as the accumulation of lattice defects, such as dislocations and mesoscopic shear planes. This resulted in a noticeable enhancement in the Vickers microhardness and the flow stress after ECAP. Differential scanning calorimetry results showed that the ECAP’ed material exhibited two exothermal peaks at 222 ± 2 °C and 362 ± 2 °C, with total thermal effects of ΔH = 4.35 and 6.5 J/g, respectively. Slight increases in the ECAP’ed material microhardness and flow stress were observed at 200 °C. The heat release, at a relatively low tem...
Arabian Journal of Chemistry
Crystals
Phosphorus and ammonium can both be recovered in the presence of magnesium through struvite (MgNH... more Phosphorus and ammonium can both be recovered in the presence of magnesium through struvite (MgNH4PO4·6H2O) crystallization. The present work aimed to optimize struvite crystallization at turbulent solution flow. Struvite was crystallized by magnetic stirring at different initial phosphorus concentrations between 200 and 800 mg·L−1 and high stirring rates between 100 and 700 rpm. The crystals obtained were analyzed by powder X-ray diffraction, Fourier-transform infrared spectroscopy, and scanning electron microscopy. For all experiments, the only phase detected was struvite. It was shown that for an initial phosphorus concentration of 200 mg·L−1, increasing the stirring rate to 500 rpm accelerated the precipitation of struvite, improved the phosphorus removal efficiency, and obtained larger struvite crystals. A decrease in the phosphorus removal efficiency and smaller struvite crystals were obtained at higher stirring rates. This was attributed to the solution turbulence. The limiti...
CRC Press eBooks, Feb 2, 2022
physica status solidi (a), 2006
A 99.1% aluminium was deformed by Equal Channel Angular (ECA) pressing. The material contains a l... more A 99.1% aluminium was deformed by Equal Channel Angular (ECA) pressing. The material contains a low volume fraction of Al 8 Fe 2 Si precipitates located essentially at the grain boundaries. An important increase of the X-ray diffraction peak broadening was observed after ECA pressings. This is due to grain refinement and enhanced lattice distortions. This was accompanied by a lattice decrease due to compressive stresses and partial dissolution of the Al 8 Fe 2 Si precipitates. The grain refinement leads to a significant improvement of the mechanical properties in compression and tension after the first pass through the die. Thereafter, the increase was less significant. The strengthening of the material was accompanied by decreased strain hardening, due to enhanced activities in grain boundaries.
Crystal Research and Technology, 2009
In the present work, investigations on the microstructure of a commercial purity 1100 aluminum th... more In the present work, investigations on the microstructure of a commercial purity 1100 aluminum that had been subjected to moderate to strong deformation (strains of 1 to 4) by equal channel angular pressing (ECAP) were carried out using X-ray diffraction (XRD) and scanning electron microcopy (SEM). A significant grain refinement and development of heterogeneous microstructure after ECAP were observed. High precision XRD and SEM investigations provided useful results on the dissolution of coherent iron rich precipitates, previously formed in the aluminium matrix, by ECAP deformation process.
Crystal Research and Technology
Understanding General Chemistry, 2022
Saudi Pharmaceutical Journal, 2022
The rapid transmission of the pneumonia (COVID-19) emerged as an entire worldwide health concern ... more The rapid transmission of the pneumonia (COVID-19) emerged as an entire worldwide health concern and it was declared as pandemic by the World Health Organization (WHO) as a consequence of the increasing reported infections number. COVID-19 disease is caused by the novel SARS-CoV-2 virus, and unfortunatly no drugs are currently approved against this desease. Accordingly, it is of outmost importance to review the possible therapeutic effects of naturally-occuring compounds that showed approved antiviral activities. The molecular docking approach offers a rapid prediction of a possible inhibition of the main enzymes Mpro and RdRp that play crucial role in the SARS-CoV-2 replication and transcription. In the present work, we review the anti-viral activities of polyphenol compounds (phenolic acids, flavonoids and stilbene) derived from the traditional Chinese medicinal Vitis amurensis. Recent molecular docking studies reported the possible binding of these polyphenols on SARS-CoV-2 enzymes Mpro and RdRp active sites and showed interesting inhibitory effects. This antiviral activity was explained by the structure-activity relationships of the studied compounds. Also, pharmacokinetic analysis of the studied molecules is simulated in the present work. Among the studied polyphenol compounds, only five, namely caffeic acid, ferulic acid, quercetin, naringenin and catechin have drug-likeness characteristics. These five polyphenols derived from Vitis amurensis are promising drug candidates for the COVID-19 treatment.
Understanding General Chemistry, 2022
Understanding General Chemistry, 2022
Understanding General Chemistry, 2022
Understanding General Chemistry, 2022
Understanding General Chemistry, 2022