Influence of Fine Sediment on the Fluidity of Debris Flows

Debris flows include a great diversity of grain sizes with inherent features such as inverse grading,particle size segregation,and liquefaction of fine sediment.The liquefaction of fine sediment affects the fluidity of debris flows,although the behavior and influence of fine sediment in debris flows have not been examined sufficiently.This study used flume tests to detect the effect of fine sediment on the fluidity of laboratory debris flows consisting of particles with various diameters.From the experiments,the greatest sediment concentration and flow depth were observed in the debris flows mixed with fine sediment indicating increased flow resistance.The experimental friction coefficient was then compared with the theoretical friction coefficient derived by substituting the experimental values into the constitutive equations for debris flow.The theoretical friction coefficient was obtained from two models with different fine-sediment treatments:assuming that all of the fine sediments were solid particles or that the particles consisted of a fluid phase involving pore water liquefaction.From the comparison of the friction coefficients,a fully liquefaction state was detected for the fine particle mixture.When the mixing ratio and particle size of the fine sediment were different,some other cases were considered to be in a partially liquefied transition state.These results imply that the liquefaction of fine sediment in debris flows was induced not only by the geometric conditions such as particle sizes,but also by the flow conditions.

0.025-inch vs 0.035-inch guide wires for wire-guided cannulation during endoscopic retrograde cholangio pancreatography:A randomized study

AIM:To compare the clinical outcomes between 0.025-inch and 0.035-inch guide wires(GWs) when used in wire-guided cannulation(WGC).METHODS:A single center,randomized study was conducted between April 2011 and March 2013. This study was approved by the Medical Ethics Committee at our hospital. Informed,written consent was obtained from each patient prior to study enrollment. Three hundred and twenty-two patients with a na?ve papilla of Vater who underwent endoscopic retrograde cholangiopancreatography(ERCP) for the purpose of selective bile duct cannulation with WGC were enrolled in this study. Fifty-three patients were excluded based on the exclusion criteria,and 269 patients were randomly allocated to two groups by a computer and analyzed:the 0.025-inch GW group(n = 109) and the 0.035-inch GW group(n = 160). The primary endpoint was the success rate of selective bile duct cannulation with WGC. Secondary endpoints were the success rates of the pancreatic GW technique and precutting,selective bile duct cannulation time,ERCP procedure time,the rate of pancreatic duct stent placement,the final success rate of selective bile duct cannulation,andthe incidence of post-ERCP pancreatitis(PEP).RESULTS:The primary success rates of selective bile duct cannulation with WGC were 80.7%(88/109) and 86.3%(138/160) for the 0.025-inch and the 0.035-inch groups,respectively(P = 0.226). There were no statistically significant differences in the success rates of selective bile duct cannulation using the pancreatic duct GW technique(46.7% vs 52.4% for the 0.025-inch and 0.035-inch groups,respectively; P = 0.884) or in the success rates of selective bile duct cannulation using precutting(66.7% vs 63.6% for the 0.025-inch and 0.035-inch groups,respectively; P = 0.893). The final success rates for selective bile duct cannulation using these procedures were 92.7%(101/109) and 97.5%(156/160) for the 0.025-inch and 0.035-inch groups,respectively(P = 0.113). There were no significant differences in selective bile duct cannulation time(median ± interquartile range:3.7 ± 13.9 min vs 4.0 ± 11.2 min for the 0.025-inch and 0.035-inch groups,respectively; P = 0.851),ERCP procedure time(median ± interquartile range:32 ± 29 min vs 30 ± 25 min for the 0.025-inch and 0.035-inch groups,respectively; P = 0.184) or in the rate of pancreatic duct stent placement(14.7% vs 15.6% for the 0.025-inch and 0.035-inch groups,respectively; P = 0.832). The incidence of PEP was 2.8%(3/109) and 2.5%(4/160) for the 0.025-inch and 0.035-inch groups,respectively(P = 0.793).CONCLUSION:The thickness of the GW for WGC does not appear to affect either the success rate of selective bile duct cannulation or the incidence of PEP.

Evaluation of diagnostic cytology via endoscopic naso-pancreatic drainage for pancreatic tumor

AIM: To evaluate the usefulness of cytology of the pancreatic juice obtained via the endoscopic naso-pancreatic drainage tube(ENPD-C).METHODS: ENPD was performed in cases where a diagnosis could not be made other than by using en-doscopic retrograde cholangiopancreatography and in cases of pancreatic neoplasms or cystic tumors, includ-ing intraductal papillary mucinous neoplasm(IPMN) suspected to have malignant potential. 35 patients(21 males and 14 females) underwent ENPD between January 2007 and June 2013. The pancreatic duct was imaged and the procedure continued in one of ENPD-C or ENPD-C plus brush cytology(ENPD-BC). We checked the cytology result and the final diagnosis.RESULTS: The mean patient age was 69 years(range, 48-86 years). ENPD-C was performed in 24 cases andENPD-C plus brush cytology(ENPD-BC) in 11 cases. The ENPD tube was inserted for an average of 3.5 d. The final diagnosis was confirmed on the basis of the resected specimen in 18 cases and of follow-up findings at least 6 mo after ENPD in the 18 inoperable cases. Malignancy was diagnosed in 21 cases and 14 patients were diagnosed as having a benign condition. The ratios of class Ⅴ/Ⅳ:Ⅲ:Ⅱ/Ⅰ?findings were 7:7:7 in malignant cases and 0:3:11 in benign cases. The sensitivity and specificity for all patients were 33.3% and 100%, re-spectively. The cytology-positive rate was 37.5%(6/16) for pancreatic cancer. For IPMN cases, the sensitivity and specificity were 33% and 100%, respectively.CONCLUSION: Sensitivity may be further increased by adding brush cytology. Although we can diagnosis cancer in cases of a positive result, the accuracy of ENPD-C remains unsatisfactory.

Right colon cancer presenting as hemorrhagic shock

A 67-year-old man visited our hospital with a history of continuous hematochezia leading to hemorrhagic shock.An abdominal computed tomography scan re-vealed a large mass in the ascending colon invading the duodenum and pancreatic head as well as extra-vasation of blood from the gastroduodenal artery(GDA) into the colon.Colonoscopy revealed an irregular ulcerative lesion and stenosis in the ascending colon.Therefore,right hemicolectomy combined with pylorus-preser ving pancreaticoduodenectomy was performed.Histologically,the tumor was classified as a moderately differentiated adenocarcinoma.Moreover,cancer cells were mainly located in the colon but had also invaded the duode-num and pancreas and involved the GDA.Immunohistochemically,the tumor cells were positive for cytokeratin(CK)20 and carcinoembryonic antigen(CEA)but not forCK7 and carbohydrate antigen(CA)19-9.The patient died 23 d after the surgery because he had another episode of arterial bleeding from the anastomosis site.Although En bloc resection of the tumor with pancreatico duodenectomy and colectomy performed for locally advanced colon cancer can ensure long-term survival,patients undergoing these procedures should be carefully monitored,particularly when the tumor involves the main artery.