A Study of Football Chants as Political Expression in the Algerian Hirak

Abstract Since the establishment of indigenous football clubs in Algeria, football supporters have used their voice to express political opinion in the form of stadium songs. This chapter examines how the chants and other kinds of football art originated in Algeria, how supporter groups formed and grew increasingly concerned with political life in Algeria and across North Africa, and how football art was adopted by protestors during the anti-regime "Hirak" protests of 2019 and 2020. The chapter relied on the works of Mahfoud Amara's work on football sub-culture in Algeria and Youcef Fates' analysis of discourse in Algerian stadia, and concludes with a lyrical analysis of football songs sung in the Algerian Hirak protests.</jats:p

Reactivity kinetics of sol-gel derived 52S4 glass versus the treatment temperature

International audienceThis work is devoted to study the reactivity of the quaternary glass 52S4 (52% SiO2–30% CaO–14% Na2O–4% P2O5 (wt%)), synthesized by sol-gel process versus the treatment temperature. The dried gel was heat treated at 600 and 650 °C and soaked in simulated body fluid (SBF). XRD results confirm the amorphous character of glass treated at 600 °C even though the heat treatment at 650 °C induces Na2Ca2Si3O9 formation. After soaking in SBF, SEM and EDS results show the formation of carbonated hydroxyapatite (CHA) at the glass surface for both temperatures. For the glasses treated at 600 and 650 °C, two phenomena were observed: the glass dissolution in SBF and the CHA precipitation, but the reactivity kinetics of glass was different when temperature changes. For SGDG600, the CHA began to crystallize after 16 h. For SGDG650, a glass ceramic made of a glassy matrix and of Na2Ca2Si3O9, the crystallized carbonated HA was observed after 2 h. In addition, a new crystallization at the glass surface of Na2Ca2Si3O9 was observed after 15 days

Grain Growth in Sintered Natural Hydroxyapatite

Hydroxyapatite $(HA: Ca_{10}(PO_4)_6(OH)_2)$ can be synthesized using several methods or manufactured from natural materials such as coral or bone after removal of the organic matter by heating (denoted as NHA). The "in vitro" and "in vivo" studies showed that the natural apatite was well tolerated and has better osteoconductive properties than synthetic HA. In addition, the exploitation of natural source represents an economical way of synthesizing NHA by means of sintering, rather than by sol-gel techniques. For these reasons, the NHA was manufactured from cortical bovine bones in all our studies. Moreover, there has been much effort to improve the mechanical properties of HA by introducing foreign oxides or finding out other alternative processes such as grain growth control. Indeed, encouraging lower AGS instead of exaggerated grain growth may be jugged useful for many applications. Since the works carried out on the correlation between AGS and physico-chemical properties of NHA were very limited, the present study was mainly focused on its grain growth. A carful combination between the main parameters controlling NHA production such as milling techniques, compacting pressure, sintering temperature and holding time may lead to an interesting NHA based bio-ceramics. In this way, a simple and energetically vibratory multidirectional milling system using bimodal distribution of highly resistant ceramics has been used for obtaining sub-micron sized NHA powders. For example, the AGS was ranged between 0.75 and 1.40 μm (using intercept method) when NHA samples were sintered at 1250°C for 15 and 480 min, respectively

IN VITRO HYDROXYAPATITE FORMING ABILITY OF DICALCIUM SILICATE PREPARED FROM LOCAL RAW MATERIALS AND SINTERED AT 1050?C

International audienceIn this study, Ca2SiO4 powders were synthesised using solid state reaction. The starting powders were sintered at 1050 ??C for 2 h. Moreover, the in vitro bioactivity of ??-Ca2SiO4 was investigated by soaking the powders in a simulated body fluid (SBF) for various time periods to analyse the growth of hydroxyapatite (HA) on the surface of these powders. The synthesised powders were characterised by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR), and Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) analysis. The simulated body fluid results showed that the ??-Ca2SiO4 powders had good bioactivity to induce hydroxyapatite formation on their surface. The results obtained showed that (HCA) can be formed on the surface of ??-Ca2SiO4 soaked in the SBF solution for 1 day, and a continuous layer of dense HCA deposits covered the surface of ??-Ca2SiO4 powders after 3 days of soaking in the SBF solution. Finally, the results obtained suggest that ??-Ca2SiO4 ceramics are promising candidates for bone regeneration

Reactivity kinetics of 52S4 glass in the quaternary system SiO2-CaO-Na2O-P2O5: Influence of the synthesis process: Melting versus sol-gel

International audienceA new composition of bioactive glass, in the quaternary system SiO2-CaO-Na2O-P2O5, was synthesized using melting and sol-gel routes. The prepared glass, 52S4: (wt.%) 52% SiO2-30% CaO-14% Na2O-4% P2O5, was soaked in Simulated Body Fluid (SBF) in order to evaluate the kinetic reactivity of this glass versus the synthesis mode. The obtained results have shown that 52S4 is a bioactive glass if it is prepared either by melting or sol-gel methods. The bone-like apatite was formed at the glass surface prepared by sol-gel route after 2 h. However, the formation of this apatite was delayed to 1 day when the glass was prepared by melting method. In addition, this apatite was crystallized, after 30 days soaking in SBF, only if the glass is prepared by melting route. The glass prepared by sol-gel method was more resorbable and leads to silica gel formation up on amorphous apatite layers at any time. So, this silica gel inhibited the crystallization of amorphous apatite

Effect of ZrO2, TiO2, and Al2O3 Additions on Process and Kinetics of Bonelike Apatite Formation on Sintered Natural Hydroxyapatite SurfaceS

International audienceIn this study, the ability to form bone-like apatite on surface of both pure natural hydroxapatite (N-HA) and natural hydroxyapatite containing 5 wt% of ZrO2 or TiO2 or Al2O3, sintered at 1300°C for 2 h and soaked in the simulated body fluid for different times, was studied. It has been found that the presence of β-tricalcium phosphate in N-HA + 5 wt% ZrO2 or TiO2 has promoted the precipitation of bone-like apatite in the Zr or Ti poorest regions. By contrast, the presence of 5 wt% of Al2O3 did not induce any apatite precipitation on N-HA sample surfaces