RESUMO
Nanostructuring followed by incorporation of defect induced non-stoichiometry is an emerging field of prominence due to its capacity to introduce unprecedented properties in materials with potential applications. In this work, crystalline α-MnO2 nanorods are synthesised using a facile co-precipitation method to exhibit ferroelectric behaviour for the first time. The evolution mechanism of the nanorods is investigated using XRD, HRTEM and FTIR spectra, while their thermal stability is probed using TGA/DTA. The novel properties observed are the result of structural rearrangements sparked by electrons in mixed valence cations (Mn3+/Mn4+). The high density of Jahn-Teller active Mn3+ cations breaks the inversion symmetry in α-MnO2, thereby altering the atomic environment inducing distortion in the basic MnO6 octahedra. Since variable temperature XRD analysis confirms the phase stability of the crystal structure up to very high temperatures, the ferroelectric phase exhibited by the material below Tc is an outcome of the combined effects of orbital ordering (OO) of the eg electron in Mn3+ and charge ordering (CO) of Mn3+ and Mn4+ cations. This is confirmed by DSC analysis. The breakdown of the ferroelectric nature is identified to originate as a result of octahedral tilting as suggested by temperature-dependent Raman studies. Magnetic and electrical transport studies provide additional evidence of a CO ferroelectric phase as they predict the existence of double-exchange hopping conduction and surface ferromagnetism in the sample.
RESUMO
PURPOSE: To assess the safety and feasibility of laparoscopic donor nephrectomy with transvaginal extraction and impact of body mass index (BMI), menopausal status, previous surgery, and uterine fibroids. PATIENTS AND METHODS: Five-port conventional laparoscopic donor nephrectomy with successful transvaginal extraction of the kidney was performed in 30 donors. The parameters assessed included age, BMI, operative time, estimated blood loss, warm ischemia time, postoperative pain score, preoperative and postoperative sexual function, wound complications, hospital stay, return to normal activities, recipient creatinine level, and other recipient-related complications. The data were compared with 30 female donors who had laparoscopic donor nephrectomy and transabdominal extraction. RESULTS: The total number of patients who consented for the study was 38. In seven patients, an intraoperative decision to abort the transvaginal extraction was made because of obesity, pelvic adhesions, large uterine fibroids, and uterine artery injury. When compared with transabdominal extraction, there was no significant difference in warm ischemia time, mean operative time, estimated blood loss, hospital stay, recipient creatinine level, and complications. The mean pain score was significantly less on postoperative day 3 and day 4. There was also an earlier return to normal activities in the transvaginal group. There was no increase in infectious complication in both donors and recipient. CONCLUSION: Based on our initial experience with laparoscopic donor nephrectomy with transvaginal extraction, we recommend this procedure for a premenopausal donor, with a BMI <30. Our initial cases demonstrate that transvaginal extraction is feasible and safe for the donors.
