ABSTRACT
Supratentorial extraventricular anaplastic ependymoma (SEAE) in adults is a relatively rare intracranial tumor. Because of the very low prevalence, only a few cases have been reported. According to a recent study, SEAE is associated with a poor prognosis and there is no definite consensus on optimal treatment. We report a case of an adult SEAE patient who had no recurrence until seven years after a gross total resection (GTR) followed by conventional radiotherapy. A 42-year-old male had a persistent mild headache, left facial palsy, dysarthria, and left hemiparesis. Preoperative neuroimaging revealed an anaplastic astrocytoma or supratentorial ependymoma in the right frontal lobe. A GTR was performed, followed by adjuvant radiotherapy. Histologic and immunohistochemical results revealed anaplastic ependymoma. After seven years of initial therapy, a regular follow-up MRI showed a 3-cm-sized partially cystic mass in the same area as the initial tumor. The patient underwent a craniotomy, and a GTR was performed. Histopathologic examination revealed recurrence of the SEAE. External radiotherapy was performed. The patient has been stable without any disease progression or complications for 12 months since the surgery for recurrent SEAE.
ABSTRACT
Ultrathin black phosphorus (BP) is one of the promising two-dimensional (2D) materials for future optoelectronic devices. Its chemical instability in ambient conditions and lack of a bottom-up approach for its synthesis necessitate efficient etching methods that generate BP films of designed thickness with stable and high-quality surfaces. Herein, reporting a photochemical etching method, we demonstrate a controlled layer-by-layer thinning of thick BP films down to a few layers or a single layer and confirm their Raman and photoluminescence characteristics. Ozone molecules generated by O2 photolysis oxidize BP, forming P2O5-like oxides. When the resulting phosphorus oxides are removed by water, the surface of BP with preset thickness is highly flat and self-protective by surface oxygen functional groups. This method provides a fabrication strategy of BP and possibly other 2D semiconductors with band gaps tuned by their thickness.
ABSTRACT
We fabricate mixed halide perovskite films through dual-source vacuum deposition of PbX2 (X = Cl, Br, and I) and methyl ammonium iodide (MAI) precursors with various deposition ratios. Vacuum deposition is an optimal way for film fabrication because it gives a uniform perovskite film which is free from contamination such as metallic phase lead, residual solvent, and moisture. The ionization potential and bandgap of MAPb(I1-yBry)3 film are controlled by changing the halide composition and lattice constant. In contrast, MAPb(I1-yCly)3 film shows negligible difference from MAPbI3 in terms of structural and electronic properties, which is due to poor Cl incorporation in the film from the MACl removal during crystal formation. An excess supply of MAI is necessary to form a perovskite crystal structure. Based on the elemental stoichiometry analysis, the additional methyl ammonium cation with respect to Pb in the film plays a critical role in changing the electron affinity and energy level alignment.
