Nanoscale potassium niobate crystal structure and phase transition

Nanoscale potassium niobate (KNbO3) powders of orthorhombic structure were synthesized using the sol-gel method. The heat-treatment temperature of the gels had a pronounced effect on KNbO3 particle size and morphology. Field emission scanning electron microscopy and transmission electron microscopy were used to determine particle size and morphology. The average KNbO3 grain size was estimated to be less than 100 nm, and transmission electron microscopy images indicated that KNbO3 particles had a brick-like morphology. Synchrotron X-ray diffraction was used to identify the room-temperature structures using Rietveld refinement. The ferroelectric orthorhombic phase was retained even for particles smaller than 50 nm. The orthorhombic to tetragonal and tetragonal to cubic phase transitions of nanocrystalline KNbO3 were investigated using temperature-dependent powder X-ray diffraction. Differential scanning calorimetry was used to examine the temperature dependence of KNbO3 phase transition. The Curie temperature and phase transition were independent of particle size, and Rietveld analyses showed increasing distortions with decreasing particle size

Congenital malformation syndromes associated with peripheral neuroblastic tumors: A systematic review

Malformation syndromes with predisposition to peripheral neuroblastic tumors (pNT), including neuroblastoma, ganglioneuroblastoma, and ganglioneuroma, may provide clues to critical mutations influencing pNT development. Our objective was to identify and characterize features of pNT associated with specific malformation syndromes. A systematic review of the literature was performed using MEDLINE, Scopus, and Web of Science. We identified 154 of 1014 papers that met eligibility, comprising 207 cases. The patient's age, tumor histology, and frequency of multiple primary tumors varied by malformation syndrome. Genomic studies and systematized reporting are necessary to elucidate cancer risk and the distinct clinical and biological pNT patterns within syndromes