RESUMEN
Herein, we carefully investigated the Fe3+ doping effects on the structure and electron distribution of Cr2O3 nanoparticles using X-ray diffraction analysis (XRD), maximum entropy method (MEM), and density functional theory (DFT) calculations. We showed that increasing the Fe doping induces an enlargement in the axial ratio of c/a, which is associated with an anisotropic expansion of the unit cell. We found that as Fe3+ replaces Cr in the Cr2O3 lattice, it caused a higher interaction between the metal 3d states and the oxygen 2p states, which led to a slight increase in the Cr/Fe-O1 bond length followed by an opposite effect for the Cr/Fe-O2 bonds. Our results also suggest that the excitations characterize a well-localized bandgap region from occupied Cr d to unoccupied Fe d states. The Cr2O3 and Fe-doped Cr2O3 nanoparticles behave as Mott-Hubbard insulators due to their band gap being in the d-d gap, and Cr 3d orbitals dominate the conduction band. These findings suggest that the magnitude and the character of the electronic density near the O atom bonds in Cr2O3 nanoparticles are modulated by the Cr-Cr distances until its stabilization at the induced quasi-equilibrium of the Cr2O3 lattice when the Fe3+ doping values reaches the saturation level range.
RESUMEN
SETTING: World Health Organization advocates for integration of HIV-tuberculosis (TB) services and recommends intensive case finding (ICF), isoniazid preventive therapy (IPT), and infection control ("Three I's") for TB prevention and control among persons living with HIV. OBJECTIVE: To assess the implementation of the "Three I's" of TB-control at HIV treatment sites in lower income countries. DESIGN: Survey conducted between March-July, 2012 at 47 sites in 26 countries: 6 (13%) Asia Pacific, 7 (15%), Caribbean, Central and South America, 5 (10%) Central Africa, 8 (17%) East Africa, 14 (30%) Southern Africa, and 7 (15%) West Africa. RESULTS: ICF using symptom-based screening was performed at 38% of sites; 45% of sites used symptom-screening plus additional diagnostics. IPT at enrollment or ART initiation was implemented in only 17% of sites, with 9% of sites providing IPT to tuberculin-skin-test positive patients. Infection control measures varied: 62% of sites separated smear-positive patients, and healthcare workers used masks at 57% of sites. Only 12 (26%) sites integrated HIV-TB services. Integration was not associated with implementation of TB prevention measures except for IPT provision at enrollment (42% integrated vs. 9% non-integrated; p = 0.03). CONCLUSIONS: Implementation of TB screening, IPT provision, and infection control measures was low and variable across regional HIV treatment sites, regardless of integration status.