Kernel representation of long-wave dynamics on a uniform slope.

Long-wave propagation on a uniformly sloping beach is formulated as a transient-response problem, with initially stationary water subjected to an incident wave. Both the water surface elevation and the horizontal flow velocity on the slope can be represented as convolutions of the rate of displacement of the water surface at the toe of the slope with a singular kernel function of time and space. The kernel, which is typically expressed in the form of an infinite series, accommodates the dynamic processes of long waves, such as shoaling, reflection, and multiple reflections over the slope and yields exact solutions of the linear shallow water equations for any smooth incident wave. The kernel convolution can be implemented numerically by using double exponential formulas to avoid the kernel singularity. The kernel formulation can be extended readily to nonlinear dynamics via the hodograph transform, which in turn enables the instantaneous prediction of nonlinear wave properties and of the occurrence of wave breaking in the near-shore area. This general description of long-wave dynamics provides new insights into the long-studied problem.

Large-Scale Channel Migration in the Sittang River Estuary.

An estuary is a dynamic environment where marine and fluvial processes meet to form complex and transient morphology. The estuary morphology is largely determined by net sediment transport by two-way tidal flows, but the hydrodynamics also depends on the morphology of the tidal channels. The estuary inherently accommodates cyclic processes that are internally generated through hydro-morphodynamic interactions. In addition, the estuary evolves in response to changes in external forces by natural and anthropogenic factors. Morphological changes under the different controls often hinder the comprehension of the evolutionary processes of estuaries. Here we explored morphological changes in the Sittang River estuary, Myanmar, which has great morphological dynamism from extreme tidal energy and large sediment inputs, through field surveys and satellite imagery analysis. We identify an autocyclic process in a sedimentary system driving large-scale channel migration in decadal to multidecadal cycles. We show that drastic changes of the estuary morphology occasionally occur with rapid bank erosion through modulation of the cyclic channel migration under conflicting tidal and fluvial forces. This extreme case with minimal human intervention highlights channel migration as a key process in morphological evolution of tide-dominated estuaries undergoing active infilling.

Duodenal ulceration into the cystic artery with massive hemorrhage.

This is a case presentation of a unique cause of intestinal bleeding. A duodenal ulcer eroded into the superficial branch of the cystic artery, causing massive intestinal hemorrhage. The patient, a 76-year-old woman, presented with left upper abdominal and left back pain secondary to cystic lesions in the pancreas body and tail. Stress after operation and complication of leakage of pancreatic juice after distal pancreatectomy with splenectomy and diclofenac sodium administration may have caused a deep peptic ulcer to erode the cystic artery. We performed a transfixing ligation of the bleeding vessel, serosal suture of ulcer of the gallbladder, and simple closure of the duodenal ulcer with covering greater omentum. There were no serious complications after the operation, and the patient made an uneventful recovery.