A Systematic Study of the Temperature Dependence of the Dielectric Function of GaSe Uniaxial Crystals from 27 to 300 K.

We report the temperature dependences of the dielectric function ε = ε1 + iε2 and critical point (CP) energies of the uniaxial crystal GaSe in the spectral energy region from 0.74 to 6.42 eV and at temperatures from 27 to 300 K using spectroscopic ellipsometry. The fundamental bandgap and strong exciton effect near 2.1 eV are detected only in the c-direction, which is perpendicular to the cleavage plane of the crystal. The temperature dependences of the CP energies were determined by fitting the data to the phenomenological expression that incorporates the Bose-Einstein statistical factor and the temperature coefficient to describe the electron-phonon interaction. To determine the origin of this anisotropy, we perform first-principles calculations using the mBJ method for bandgap correction. The results clearly demonstrate that the anisotropic dielectric characteristics can be directly attributed to the inherent anisotropy of p orbitals. More specifically, this prominent excitonic feature and fundamental bandgap are derived from the band-to-band transition between s and pz orbitals at the Γ-point.

A large lipoma of the descending colon: A rare case report.

Colon lipoma is a rare benign disease in the gastrointestinal tract with an incidence rate of approximately 0.035%-4.4%. The disease is often asymptomatic, so it is frequently discovered incidentally through endoscopy, computed tomography , or autopsy. When the tumor is over 2 cm in size, symptoms such as abdominal pain, bowel disorders, and bowel obstruction are common. Surgery is considered the mainstay of treatment for colonic lipomas. Furthermore, surgical (rather than endoscopic) resection is preferred for lipomas >2 cm to avoid complications such as bleeding and perforation. We report on a 61-year-old female patient who was diagnosed with a 4-cm descending colonic fat tumor detected by endoscopy and computed tomography and confirmed by pathology.

Oxygen vacancy clustering and electron localization in oxygen-deficient SrTiO(3): LDA + U study.

We find, using a local density approximation +Hubbard U method, that oxygen vacancies tend to cluster in a linear way in SrTiO(3), a prototypical perovskite oxide, accompanied by strong electron localization at the 3d state of the nearby Ti transition metal ion. The vacancy clustering and the associated electron localization lead to a profound impact on materials properties, e.g., the reduction in free-carrier densities, the appearance of characteristic optical spectra, and the decrease in vacancy mobility. The high stability against the vacancy migration also suggests the physical reality of the vacancy cluster.