Search results for: N. Dehdouh

Authors: H. Amellal-Chibane, N. Dehdouh, S. Ait-Kaki, F. Halladj

Abstract:

Kefir is fermented milk that is produced by adding Kefir grains, consisting of bacteria and yeasts, to milk. The aim of this study was to investigate the antioxidant activity of the kefir supernatant and the raw milk. The Antioxidant activity assays of kefir supernatant and raw milk were evaluated by assessing the DPPH radical-scavenging activity. Kefir supernatant demonstrated high antioxidant activity (87.75%) compared to the raw milk (70.59 %). These results suggest that the Algerian kefir has interesting antioxidant activity.

Keywords: antioxidant activity, kefir, kefir supernatant, raw milk

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Authors: Ouafek Nora, Keghouche Nassira, Dehdouh Heider, Untidt Carlos

Abstract:

A lot of knowledge has been accumulated on the metal clusters supported on oxide surfaces because of their multiple applications in microelectronics, heterogeneous catalysis, and magnetic devices. In this work, the surface state of Ni / MgO has been studied by XPS (X-ray Photoemission Spectroscopy). The samples were prepared by impregnation with ion exchange Ni²⁺ / MgO, followed by either a thermal treatment in air (T = 100 -350 ° C) or a gamma irradiation (dose 100 kGy, 25 kGy dose rate h -1). The obtained samples are named after impregnation NMI, NMR after irradiation, and finally NMC(T) after calcination at the temperature T (T = 100-600 °C). A structural study by XRD and HRTEM reveals the presence of nanoscaled Ni-Mg intermetallic phases (Mg₂Ni, MgNi₂, and Mg₆Ni) and magnesium hydroxide. Mg(OH)₂ in nanometric range (2- 4 nm). Mg-Ni compounds are of great interest in energy fields (hydrogen storage…). XPS spectra show two Ni2p peaks at energies of about 856.1 and 861.9 eV, indicating that the nickel is primarily in an oxidized state on the surface. The shift of the main peak relative to the pure NiO (856.1 instead of 854.0 eV) suggests that in addition to oxygen, nickel is engaged in another link with magnesium. This is in agreement with the O1s spectra which present an overlap of peaks corresponds to NiO and MgO, at a calcination temperature T ≤ 300 °C.

Keywords: XPS, XRD, nanoparticules, Ni-MgO

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