Geomorphic processes of a dammed palaeo-lake in the middle Yarlung Tsangpo River, Tibet.

The failure of a natural dam is an extreme geological event. Palaeo-lake sediments were discovered in the broad Xigazê valley and Dazhuka-Yueju gorge in the middle reach of the Yarlung Tsangpo River in Tibet. However, the sedimentary processes, dam failure, and peak flood of the Xigazê dammed palaeo-lake are poorly understood. Hence, we conducted a field survey of eight lacustrine sedimentary terraces in the area. We divided the sedimentary processes of the palaeo-lake into five stages and deposit types: pre-palaeo-lake sediments (fluvial or aeolian deposits); early stage sediments of the palaeo-lake (coarse sand); main stage palaeo-lake sediments (clayey silt and sand), sediments following the discharge of the palaeo-lake (sand and gravel-cobbles); and cover deposits (aeolian sediments and colluvium). Additionally, the water level along the palaeo-lake was almost constant (3811 m a.s.l.). The dam was likely located at the eastern end of the Dazhuka-Yueju gorge. Based on the water level, dam location and 30-m ASTER GDEM2 data, the capacity of the palaeo-lake was estimated as 22.55 km3. To separate the water volume and sediment volume, the sediment surface elevation along the palaeo-lake was simulated based on the elevations of the six lacustrine sedimentary terraces. The volume of the sediment was ~11.56 km3, which was calculated from the dam location, sediment surface elevation, and the ASTER GDEM2 data. Finally, subtraction of the sediment volume from the capacity of the palaeo-lake gave a backwater volume of 10.99 km3. The peak flood possibly exceeded 3.4 × 105 m3/s as a moraine dam joined the discharge during the dam failure. However, the dammed event probably had a limited effect on the landforms at downstream because of the presence of another dammed palaeo-lake in the broad Zetang valley; moreover, the bedrock upstream of the dam was protected from erosion.

Giant Pelvic Adenoma Originating from Ectopic Prostatic Tissue.

Ectopic prostatic tissue detected outside the genitourinary system has been rarely reported. A case with a giant pelvic adenoma that originated from ectopic prostatic tissue is presented. A 71-year male was detected with lower abdominal mass for eight months and recurrent acute urinary retention for one week. This patient already had mild lower urinary tract symptoms for three years. The physical examination, laboratory tests, ultrasonography, and MRI of this patient were analysed, and the pathological diagnosis was ectopic prostatic adenoma. The suprapubic incision for pelvic exploration and tumorectomy was chosen. The recognition and awareness of this unusual lesion is important, in order not to confuse this particular lesion with other pelvic tumors.

Rare presentation of a right retroperitoneal accessory spleen: A case report.

An accessory spleen is a congenital malformation, which is defined as ectopic splenic parenchyma. Here, an extremely rare case of a right retroperitoneal accessory spleen, mimicking a retroperitoneal neoplasm, is reported. A 40-year-old woman was referred following the incidental detection of a retroperitoneal neoplasm. Computed tomography and magnetic resonance imaging scans confirmed the presence of a retroperitoneal neoplasm at the hepatorenal recess. Retroperitoneoscopic excision was conducted, with excellent results. Pathological examination of the resected specimen revealed splenic tissue. In conjunction with a review of the literature and a discussion of the salient radiological features, the present case highlights the requirement for accurate preoperative diagnosis of an accessory spleen in the right retroperitoneal space, in order to avoid unnecessary surgical intervention.

Topological incommensurate magnetization plateaus in quasi-periodic quantum spin chains.

Uncovering topologically nontrivial states in nature is an intriguing and important issue in recent years. While most studies are based on the topological band insulators, the topological state in strongly correlated low-dimensional systems has not been extensively explored due to the failure of direct explanation from the topological band insulator theory on such systems and the origin of the topological property is unclear. Here we report the theoretical discovery of strongly correlated topological states in quasi-periodic Heisenberg spin chain systems corresponding to a series of incommensurate magnetization plateaus under the presence of the magnetic field, which are uniquely determined by the quasi-periodic structure of exchange couplings. The topological features of plateau states are demonstrated by the existence of non-trivial spin-flip edge excitations, which can be well characterized by nonzero topological invariants defined in a two-dimensional parameter space. Furthermore, we demonstrate that the topological invariant of the plateau state can be read out from a generalized Streda formula and the spin-flip excitation spectrum exhibits a similar structure of the Hofstadter's butterfly spectrum for the two-dimensional quantum Hall system on a lattice.