Uniform large-area surface patterning achieved by metal dewetting for the top-down fabrication of GaN nanowire ensembles.

The dewetting of thin Pt films on different surfaces is investigated as a means to provide the patterning for the top-down fabrication of GaN nanowire ensembles. The transformation from a thin film to an ensemble of nanoislands upon annealing proceeds in good agreement with the void growth model. With increasing annealing duration, the size and shape uniformity of the nanoislands improves. This improvement speeds up for higher annealing temperature. After an optimum annealing duration, the size uniformity deteriorates due to the coalescence of neighboring islands. By changing the Pt film thickness, the nanoisland diameter and density can be quantitatively controlled in a way predicted by a simple thermodynamic model. We demonstrate the uniformity of the nanoisland ensembles for an area larger than 1 cm2. GaN nanowires are fabricated by a sequence of dry and wet etching steps, and these nanowires inherit the diameters and density of the Pt nanoisland ensemble used as a mask. Our study achieves advancements in size uniformity and range of obtainable diameters compared to previous works. This simple, economical, and scalable approach to the top-down fabrication of nanowires is useful for applications requiring large and uniform nanowire ensembles with controllable dimensions.

Urinary trypsinogen activation peptide is more accurate than hematocrit in determining severity in patients with acute pancreatitis: a prospective study.

OBJECTIVE: The management of patients with acute pancreatitis is complicated by the inability to distinguish mild from severe disease during the early stages. It has been previously shown that urinary trypsinogen activation peptide (TAP) and hematocrit (Hct) may serve as early predictors of severity in patients with acute pancreatitis. To establish which marker is more accurate in the determination of severity in patients with acute pancreatitis, a prospective study was performed. METHODS: A consecutive series of patients admitted with pain consistent with acute pancreatitis and an amylase of three times the upper limit of normal were included. The admission and 24-h Hct was obtained. A urine sample was obtained within 12 h of admission. Urinary TAP was determined using a modified solid phase ELISA. Severity was defined by the Atlanta Symposium, as the presence of organ failure and/or pancreatic necrosis. RESULTS: Fifty-eight consecutive patients with acute pancreatitis participated. There were 33 men and 25 women with a mean age of 60 +/- 19. Thirty-nine patients had mild disease; 19 had severe disease. Urinary TAP was elevated in 26 patients. All patients with severe pancreatitis were correctly identified as having severe disease by an elevated urinary TAP (sensitivity 100%, specificity 77%). The admission Hct was higher than 47 in only three patients, all with mild disease. Of the patients with a rise in Hct, eight had mild disease, and only one had severe disease. Using a Hct of 44 as a cutoff did not affect the accuracy. There was no association between a rise in Hct and failure of Hct to decrease in the determination of severity. CONCLUSIONS: In comparison to admission Hct, urinary TAP was more accurate in determining severity in patients with acute pancreatitis by Atlanta, APACHE II, and Ranson criteria. We conclude that urinary TAP is a more accurate predictor of severity in patients with acute pancreatitis compared with Hct. Urinary TAP should be used to determine severity in patients early in the course of acute pancreatitis.