RESUMO
Herein we report the studies of different physical properties (structural, magnetic, thermal, morphologic, electrical, and electrochemical) of two new allotropic ß-Na2Ni2M(PO4)3 (NNMP) phosphates, with M = Fe and Al. Pure orthorhombic single-phase powders were prepared under air, using an autocombustion synthesis method. They crystallize in the orthorhombic Imma space group with similar unit cell parameters [a = 10.1592(2), b = 13.0321(3), c = 6.4864(2) Å] and [a = 10.3993(1), b = 13.1966(1), c = 6.4955(1) Å] for ß-Na2Ni2M(PO4)3 (NNAP) and ß-Na2Ni2Fe(PO4)3 (NNFP), respectively. Crystal structures of both compounds were determined using X-ray powder diffraction and Rietveld method refinements, which indicate the occurrence of Ni2+ in the 8g site, and of M3+ in the 4a site of the structure. The structure consists of a three-dimensional anionic framework obtained by the association on MO6, NiO6, and PO4 polyhedra, sharing edges and corners. The resulting three-dimensional structure creates monodimensional channels along the [100] and [010] directions formed by face-shared oxygen polyhedra and occupied by Na+ cations. This nondisordered cationic distribution is confirmed by a significant change of magnetic properties. Thus, both NNAP and NNFP samples show paramagnetic to ferromagnetic transition at 14 and 19 K, respectively. For the two compounds, thermal stability, electrical conductivity, and electrochemical properties have been also investigated. The intercalation/desintercalation properties of NNMP compounds as positive electrode were tested in sodium-ion batteries. The first cycling curves exhibit a significant polarization for both prepared samples.
RESUMO
This study compared the pre-emptive and the prophylactic strategies used to prevent cytomegalovirus (CMV) infection and disease in CMV-seropositive orthotopic liver-transplant recipients and searched for associated predictive factors. Seventy-three orthotopic liver-transplant recipients who had received a transplant before November 2005 were given ganciclovir IV pre-emptively (group I) and 56 recipients who had received a transplant after November 2005 were given prophylactic valganciclovir for 3 months (group II). Demographic and biochemical parameters did not statistically vary between the groups at baseline. Monitoring of CMV DNAemia was similar in both groups. Forty-two (57.5%) patients presented with CMV infection in group I and 18 (32.1%) in group II (P < 0.004). CMV DNAemia was first detected at a median of 33 days post-transplant in group I and at 98.5 days in group II (P < 0.003), but viral loads were not significantly different. The overall incidence of CMV disease was 9.6% in group I versus 7.1% in group II (ns). Thirty-five (47.9%) patients presented with biopsy-proven acute rejection in group I and 13 (23.2%) in group II (P = 0.004). Forty (55%) patients in group I and 25 (44.6%) in group II presented with de novo post-transplant diabetes (P = 0.057). At 1-year post-transplant, global survival curves were not significantly different. Independent factors associated with CMV reactivation were an absence of CMV prophylaxis, CMV serological status of the donor, cold ischemia time, and HLA A + B + DR compatibility. CMV prophylaxis is efficacious and can prevent safely the direct and indirect effects of CMV infection in CMV-seropositive orthotopic liver-transplant recipients.