this study investigates the influence of some chemical additives such as methanol, ethanol, sodium oleat, chloroform and sodium hexametaphosphate (shmp) on the dry fine grinding of calcite (x50= 33 µm) using a stirred media mill. the experiments were carried out by a batch operation, and the change in colour properties (ry, whiteness and yellowness) of calcite powder. the results showed that th...

This study examined the effect of 10% and 16% carbamide peroxide bleaching agents on the surface microhardness of micro-particulate feldspathic ceramics (VM7 and VM13, Vita Zahnfabrik). Forty specimens (8-mm diameter, 2-mm thickness) were divided into four groups (n=10): GI-VM7 + 10% Whiteness, G2-VM7 + 16% Whiteness, G3-VM13 + 10% and G4-VM13 + 16% Whiteness. The home-use bleaching agents were...

In this article, I reflect on Signithia Fordham and John Ogbu’s classic research on the “burden of ‘acting White’ ” to develop a long overdue dialogue between Africana studies and critical white studies. It highlights the dialectical nature of Fordham and Ogbu’s philosophy of race and critical race theory by locating the origins of the “burden of ‘acting White’ ” in the work of W.E.B. Du Bois, ...

Recent observation of 850μm sub-mm polarization from T Tauri disks opens up the possibility of studying magnetic field structure within protostellar disks. The degree of polarization is around 3 % and the direction of polarization is perpendicular to the disk. Since thermal emission from dust grains dominates the spectral energy distribution at the sub-mm/FIR regime, dust grains are thought to ...

OBJECTIVES The aim of this study was to investigate the superficial texture of composite restorations after different bleaching protocols. METHODS Filtek Supreme (S), Filtek Z350 (F), and Grandio (G) were compared to Opallis (O) and Filtek Z250 (Z) (control microhybrid composites) and to bovine enamel using three different bleaching agents: 35% hydrogen peroxide Whiteness HP (WHP), 35% Whiten...

nine organic substrates viz., rice grains, sorghum grains, wheat grains, millet grains, wheat straw, rice husk, cow dung, sawdust, and poultry manure were used for mass multiplication of trichoderma harzianum. of these,sorghum grains followed by millet grains were the best substrates. the poultry manure appeared to be the most unsuitable substrate, whereas rice grains, wheat grains, wheat straw...