Large full band gaps for photonic crystals in two dimensions computed by an inverse method with multigrid acceleration.

In this study, two fast and accurate methods of inverse iteration with multigrid acceleration are developed to compute band structures of photonic crystals of general shape. In particular, we report two-dimensional photonic crystals of silicon air with an optimal full band gap of gap-midgap ratio Deltaomega/omega(mid)=0.2421, which is 30% larger than ever reported in the literature. The crystals consist of a hexagonal array of circular columns, each connected to its nearest neighbors by slender rectangular rods. A systematic study with respect to the geometric parameters of the photonic crystals was made possible with the present method in drawing a three-dimensional band-gap diagram with reasonable computing time.

Multistability and symmetry breaking in the two-dimensional flow around a square cylinder.

We use numerical methods to study two-dimensional flow passing a square cylinder at low Reynolds numbers, and observe period-1 and -3 vortices behind the cylinder at the same Reynolds number Re. When Re increases from a small number to a critical value Re(c) approximately equal to 320, the system could change from bistability, which maintains the spatial symmetry, to tristability, which breaks the spatial symmetry. Our results suggest many interesting problems for further studies.

Eccrine porocarcinoma.

Eccrine porocarcinoma is a malignant tumor of eccrine sweat glands. It is a very rare, slow growing tumor and clinically resembles other skin cancers. We report a case and review its clinical and pathological features. These tumors have a propensity for local recurrence, and wide excision with negative margins is recommended.

A new liver perfusion and preservation system for transplantation research in large animals.

A kidney perfusion machine, model MOX-100 (Waters Instruments, Ltd, Rochester, MN) was modified to allow continuous perfusion of the portal vein and pulsatile perfusion of the hepatic artery of the liver. Additional apparatus consists of a cooling system, a membrane oxygenator, a filter for foreign bodies, and bubble traps. This system not only allows hypothermic perfusion preservation of the liver graft, but furthermore enables investigation of ex vivo simulation of various circulatory circumstances in which physiological perfusion of the liver is studied. We have used this system to evaluate the viability of liver allografts preserved by cold storage. The liver was placed on the perfusion system and perfused with blood with a hematocrit of approximately 20%, and maintained at 37 degrees C for 3 h. The flows of the hepatic artery and portal vein were adjusted to 0.33 mL and 0.67 mL/g of liver tissue, respectively. Parameters of viability consisted of hourly bile output, oxygen consumption, liver enzymes, electrolytes, vascular resistance, and liver histology. This method of liver assessment in large animals will allow the objective evaluation of organ viability for transplantation and thereby improve the outcome of organ transplantation. Furthermore, this pump enables investigation into the pathophysiology of liver ischemia and preservation.

Cholangiocarcinoma in hepatolithiasis.

During the period of 1979-1982, 10 cases of cholangiocarcinoma associated with hepatolithiasis were seen. We report the clinical features of 10 cases of cholangiocarcinoma in association with hepatolithiasis, along with detailed histopathology from the four resected specimens. Our observations suggest that whenever intrahepatic stones are encountered in patients over 50 years of age with a long history of recurrent cholangitis and intractable pain, further examination including echo-guided aspiration cytology, liver scanning, and peritoneoscopy should be performed to rule out a coexisting cholangiocarcinoma.