Background and study aims: Endoscopic biliary drainage is an established mode of treatment for acute cholangitis. We compared the safety and efficacy of nasobiliary drain (NBD) placement and stent placement for biliar...Background and study aims: Endoscopic biliary drainage is an established mode of treatment for acute cholangitis. We compared the safety and efficacy of nasobiliary drain (NBD) placement and stent placement for biliary drainage in patients with acute cholangitis. Patients and methods: We recruited a total of 150 patients with severe cholangitis who required endoscopic biliary drainage. Patients were randomized to have either a 7-Fr NBD or a 7-Fr straight flap stent placed during endoscopy. Outcome measures included complications related to endoscopic retrograde cholangiopancreatography (ERCP) and the clinical outco- me. Results: Of the 150 patients, 75 were randomized to the NBD group and 75 to the stent group. The most common causes of biliary obstruction were common bile duct stones (n = 102) and biliopancreatic malignancies (n = 37). The site of the biliary obstruction was predominantly found to be the lower part of common bile duct in both the NBD group (n = 58) and the stent group (n = 59). Indications for biliary drainage were: a fever of > 100.4°F (n = 140), hypotension (n = 23), peritonism (n = 40), impaired consciousness (n = 29), and failure to improve with conservative management (n = 45). Biliary drainage was achieved in 147 patients. Abdominal pain, fever, jaundice, hypotension, peritonism and altered sensorium improved after a median period of 2 days in both groups. Leukocyte counts became normal after a median time of 7 days in the NBD group and 6 days in the stent group. There were no ERCP-related complications. There were no instances of displacement or kinking of an NBD, occlusion of an NBD or stent, or of stent migration. Four patients died (two in the NBD group and two in the stent group) as a result of uncontrolled cholangitis after 1, 2, 4, and 6 days of biliary drainage. The success rates of biliary drainage in cholangitis were not affected by the type of endoprosthesis used (72/74 for NBD patients vs. 71/73 for stent patients), the etiology of the biliary obstruction (110/112 for benign obstruction vs. 33/35 for malignant obstruction), or the site of the biliary obstruction (28/30 for upper common bile duct obstruction vs. 115/117 for obstruction at the lower end of common bile duct). Conclusions: Biliary drainage by nasobiliary drain and drainage by stent are equally safe and effective treatments for patients with severe cholangitis.展开更多
In order to select the appropriate working fluids and optimize parameters for medium-temperature geothermally-powered organic Rankine cycle(ORC), R245 fa is mixed with R601 a at geothermal water temperature of 110 ℃....In order to select the appropriate working fluids and optimize parameters for medium-temperature geothermally-powered organic Rankine cycle(ORC), R245 fa is mixed with R601 a at geothermal water temperature of 110 ℃. Based on thermodynamics, the characteristics of mixture and its influence on the performance of ORC under different evaporating temperatures and composition proportions are analyzed. Results show that the zeotropic mixture R245fa/R601a(0.4/0.6) has the highest performance. When the evaporating temperature reaches 67 ℃, the outlet temperature of geothermal water is 61 ℃, the net power output is the highest and the thermal efficiency is about 9%.展开更多
A simple and highly accurate semi-analytical method, called the differential transformation method(DTM), was used for solving the nonlinear temperature distribution equation in solid and porous longitudinal fin with t...A simple and highly accurate semi-analytical method, called the differential transformation method(DTM), was used for solving the nonlinear temperature distribution equation in solid and porous longitudinal fin with temperature dependent internal heat generation. The problem was solved for two main cases. In the first case, heat generation was assumed variable by fin temperature for a solid fin and in second heat generation varied with temperature for a porous fin. Results are presented for the temperature distribution for a range of values of parameters appearing in the mathematical formulation(e.g. N, εG, and G). Results reveal that DTM is very effective and convenient. Also, it is found that this method can achieve more suitable results in comparison to numerical methods.展开更多
Unlike other types of renewable energy resources, geothermal energy provides a stable source of energy as it can be exploited regardless of meteorological conditions. Using organic cycle, geothermal energy can be util...Unlike other types of renewable energy resources, geothermal energy provides a stable source of energy as it can be exploited regardless of meteorological conditions. Using organic cycle, geothermal energy can be utilized for power generation. In such systems, the heat is exchanged between the surrounding rock mass and transport fluid. Consequently, the temperature of extracted geofluid from the well decreases with the time in accordance with the working parameters. Those parameters includeenergy extraction rate, temperature difference between inlet and outlet of the well, and the thermal conductivity of the ground. Current work, aims to develop a reliable computer model to specify the optimal working parameters so that the geofluid temperature will not reach a low value that is not acceptable for electricity generation, and the energy availability of geothermal resource is maximized. In the current study the ground thermal properties, the geothermal gradient and well dimensions are based on realistic data in Qatar and neighboring countries. The proposed model was developed for different heat extraction rate, different ground thermal properties, and for varied temperature difference between inlet and outlet of the well. Simulation shows that selecting the optimal working parameters can increase the availability of geothermal resource significantly.展开更多
文摘Background and study aims: Endoscopic biliary drainage is an established mode of treatment for acute cholangitis. We compared the safety and efficacy of nasobiliary drain (NBD) placement and stent placement for biliary drainage in patients with acute cholangitis. Patients and methods: We recruited a total of 150 patients with severe cholangitis who required endoscopic biliary drainage. Patients were randomized to have either a 7-Fr NBD or a 7-Fr straight flap stent placed during endoscopy. Outcome measures included complications related to endoscopic retrograde cholangiopancreatography (ERCP) and the clinical outco- me. Results: Of the 150 patients, 75 were randomized to the NBD group and 75 to the stent group. The most common causes of biliary obstruction were common bile duct stones (n = 102) and biliopancreatic malignancies (n = 37). The site of the biliary obstruction was predominantly found to be the lower part of common bile duct in both the NBD group (n = 58) and the stent group (n = 59). Indications for biliary drainage were: a fever of > 100.4°F (n = 140), hypotension (n = 23), peritonism (n = 40), impaired consciousness (n = 29), and failure to improve with conservative management (n = 45). Biliary drainage was achieved in 147 patients. Abdominal pain, fever, jaundice, hypotension, peritonism and altered sensorium improved after a median period of 2 days in both groups. Leukocyte counts became normal after a median time of 7 days in the NBD group and 6 days in the stent group. There were no ERCP-related complications. There were no instances of displacement or kinking of an NBD, occlusion of an NBD or stent, or of stent migration. Four patients died (two in the NBD group and two in the stent group) as a result of uncontrolled cholangitis after 1, 2, 4, and 6 days of biliary drainage. The success rates of biliary drainage in cholangitis were not affected by the type of endoprosthesis used (72/74 for NBD patients vs. 71/73 for stent patients), the etiology of the biliary obstruction (110/112 for benign obstruction vs. 33/35 for malignant obstruction), or the site of the biliary obstruction (28/30 for upper common bile duct obstruction vs. 115/117 for obstruction at the lower end of common bile duct). Conclusions: Biliary drainage by nasobiliary drain and drainage by stent are equally safe and effective treatments for patients with severe cholangitis.
基金Supported by the National High Technology Research and Development Program of China("863" Program,No.2012AA053001)
文摘In order to select the appropriate working fluids and optimize parameters for medium-temperature geothermally-powered organic Rankine cycle(ORC), R245 fa is mixed with R601 a at geothermal water temperature of 110 ℃. Based on thermodynamics, the characteristics of mixture and its influence on the performance of ORC under different evaporating temperatures and composition proportions are analyzed. Results show that the zeotropic mixture R245fa/R601a(0.4/0.6) has the highest performance. When the evaporating temperature reaches 67 ℃, the outlet temperature of geothermal water is 61 ℃, the net power output is the highest and the thermal efficiency is about 9%.
文摘A simple and highly accurate semi-analytical method, called the differential transformation method(DTM), was used for solving the nonlinear temperature distribution equation in solid and porous longitudinal fin with temperature dependent internal heat generation. The problem was solved for two main cases. In the first case, heat generation was assumed variable by fin temperature for a solid fin and in second heat generation varied with temperature for a porous fin. Results are presented for the temperature distribution for a range of values of parameters appearing in the mathematical formulation(e.g. N, εG, and G). Results reveal that DTM is very effective and convenient. Also, it is found that this method can achieve more suitable results in comparison to numerical methods.
文摘Unlike other types of renewable energy resources, geothermal energy provides a stable source of energy as it can be exploited regardless of meteorological conditions. Using organic cycle, geothermal energy can be utilized for power generation. In such systems, the heat is exchanged between the surrounding rock mass and transport fluid. Consequently, the temperature of extracted geofluid from the well decreases with the time in accordance with the working parameters. Those parameters includeenergy extraction rate, temperature difference between inlet and outlet of the well, and the thermal conductivity of the ground. Current work, aims to develop a reliable computer model to specify the optimal working parameters so that the geofluid temperature will not reach a low value that is not acceptable for electricity generation, and the energy availability of geothermal resource is maximized. In the current study the ground thermal properties, the geothermal gradient and well dimensions are based on realistic data in Qatar and neighboring countries. The proposed model was developed for different heat extraction rate, different ground thermal properties, and for varied temperature difference between inlet and outlet of the well. Simulation shows that selecting the optimal working parameters can increase the availability of geothermal resource significantly.
