Transient elastography(TE)is a new non invasive tool for measuring liver stiffness,which is correlated to the histologic stage of liver fibrosis.Several studies in chronic liver disease(CLD)have determined a good accu...Transient elastography(TE)is a new non invasive tool for measuring liver stiffness,which is correlated to the histologic stage of liver fibrosis.Several studies in chronic liver disease(CLD)have determined a good accuracy of TE in predicting significant fibrosis and an optimal accuracy in predicting cirrhosis.Normal liver stiffness ranges between 3.3-7.8 KPa and using a cut off of 7.1 KPa,significant fibrosis and cirrhosis can be excluded with a very high negative predictive value(NPV).Positive predictive value(PPV)for the diagnosis of cirrhosis is lower using just a single scan but increases to 90% if high stiffness values are confirmed by a second independent scan.However the presence of fatty liver and metabolic syndrome slightly increases the readings and may reduce the accuracy of the test.It is uncertain if this increase is related to the presence of steatofibrosis or ifit is caused by steatosis itself.TE can be used in screening patients attending the liver clinics to identify those with signifi cant fi brosis or cirrhosis and may be particularly useful in discriminating HBV inactive carriers from chronic hepatitis B patients.TE,however,is not reliable in predicting the presence of esophageal varices in cirrhotics.Another potential indication for TE is the systematic screening of populations at high risk for CLD,such as intravenous drug users and alcoholics,but further studies are needed to determine its diagnostic accuracy in these settings.展开更多
Based on a three-step kinetic mechanism, a one-dimensional, time dependent, numerical model is presented for the smoldering propagation in a horizontally packed bed of cellulosic material. The kinetic processes includ...Based on a three-step kinetic mechanism, a one-dimensional, time dependent, numerical model is presented for the smoldering propagation in a horizontally packed bed of cellulosic material. The kinetic processes include pyrolysis and oxidation degradation of fuel and oxidation of char. Heat transfer between solid and gas is taken into account, and the diffusion coefficient varies with the temperature. Radiative heat transfer is included by using the diffusion approximation. The effects of airflow velocity and oxygen concentration are simulated on the smoldering velocity and the averaged maximum temperature of smoldering fuel. The results indicate that the spread rate varies linearly with increasing airflow velocity, and the inlet air velocity has little effect on the maximum temperature. The evolutions of gas species and solid compositions are predicted. The effects of frequency factors （A1, A2 and A3） are analyzed. Simulations show that the smoldering spread rate increases with increasing A2 （fuel oxidation）, but decreases with A1 （fuel pyrolysis） and A3 （char oxidation）.展开更多
Background Most incidental gastric polyps identified during upper endoscopy are considered low-risk.However,current guidelines recommend sampling all gastric polyps for histopathologic analysis.We aimed to devise a si...Background Most incidental gastric polyps identified during upper endoscopy are considered low-risk.However,current guidelines recommend sampling all gastric polyps for histopathologic analysis.We aimed to devise a simple narrow-band imaging(NBI)classification to reduce the need for routine biopsies of low-risk gastric polyps.Methods Pairs of NBI and white-light images were collected from 73 gastric polyps for which concurrent histopathologic diagnosis was available.A diagnostic accuracy cohort study was performed.Two blinded endoscopists independently analysed NBI features of each polyp for color,vessel pattern,surface pattern,and any combinations thereof to develop a classification scheme to differentiate low-risk polyps(fundic-gland or hyperplastic)from high-risk polyps(adenomatous or adenocarcinoma)and fundic-gland polyps(FGPs)from non-FGPs.Results An isolated lacy vessel pattern and a homogenous absence of surface pattern successfully differentiated low-risk from high-risk gastric polyps.Combining both descriptors into a single algorithm resulted in a negative predictive value(NPV)of 100%[95%confidence interval(CI):100%–100%],positive predictive value(PPV)of 13.7%(95%CI:2.6–24.8),sensitivity of 100%(95%CI:100%–100%),and specificity of 53.7%(95%CI:45.3%–62.0%)for high-risk polyps.This would reduce the number of polyps requiring biopsy by 50%,while still capturing all high-risk polyps.Regarding FGPs,using a rule not to biopsy polyps with isolated lacy vessels resulted in a 94.9%NPV(95%CI:89.2%–100%),63.2%PPV(95%CI:47.2%–79.2%),94.8%sensitivity(95%CI:89.5%–100%),and 63.6%specificity(95%CI:51.3%–76.0%)for non-FGPs.Conclusion In this derivation cohort study,NBI is helpful for differentiating between high-risk and low-risk gastric polyps,thereby reducing the need for routine sampling of low-risk polyps.These results need to be validated in a separate test population.展开更多
文摘Transient elastography(TE)is a new non invasive tool for measuring liver stiffness,which is correlated to the histologic stage of liver fibrosis.Several studies in chronic liver disease(CLD)have determined a good accuracy of TE in predicting significant fibrosis and an optimal accuracy in predicting cirrhosis.Normal liver stiffness ranges between 3.3-7.8 KPa and using a cut off of 7.1 KPa,significant fibrosis and cirrhosis can be excluded with a very high negative predictive value(NPV).Positive predictive value(PPV)for the diagnosis of cirrhosis is lower using just a single scan but increases to 90% if high stiffness values are confirmed by a second independent scan.However the presence of fatty liver and metabolic syndrome slightly increases the readings and may reduce the accuracy of the test.It is uncertain if this increase is related to the presence of steatofibrosis or ifit is caused by steatosis itself.TE can be used in screening patients attending the liver clinics to identify those with signifi cant fi brosis or cirrhosis and may be particularly useful in discriminating HBV inactive carriers from chronic hepatitis B patients.TE,however,is not reliable in predicting the presence of esophageal varices in cirrhotics.Another potential indication for TE is the systematic screening of populations at high risk for CLD,such as intravenous drug users and alcoholics,but further studies are needed to determine its diagnostic accuracy in these settings.
基金Project supported by the National Natural Science Foundation of China (Grant No.50476073)
文摘Based on a three-step kinetic mechanism, a one-dimensional, time dependent, numerical model is presented for the smoldering propagation in a horizontally packed bed of cellulosic material. The kinetic processes include pyrolysis and oxidation degradation of fuel and oxidation of char. Heat transfer between solid and gas is taken into account, and the diffusion coefficient varies with the temperature. Radiative heat transfer is included by using the diffusion approximation. The effects of airflow velocity and oxygen concentration are simulated on the smoldering velocity and the averaged maximum temperature of smoldering fuel. The results indicate that the spread rate varies linearly with increasing airflow velocity, and the inlet air velocity has little effect on the maximum temperature. The evolutions of gas species and solid compositions are predicted. The effects of frequency factors （A1, A2 and A3） are analyzed. Simulations show that the smoldering spread rate increases with increasing A2 （fuel oxidation）, but decreases with A1 （fuel pyrolysis） and A3 （char oxidation）.
文摘Background Most incidental gastric polyps identified during upper endoscopy are considered low-risk.However,current guidelines recommend sampling all gastric polyps for histopathologic analysis.We aimed to devise a simple narrow-band imaging(NBI)classification to reduce the need for routine biopsies of low-risk gastric polyps.Methods Pairs of NBI and white-light images were collected from 73 gastric polyps for which concurrent histopathologic diagnosis was available.A diagnostic accuracy cohort study was performed.Two blinded endoscopists independently analysed NBI features of each polyp for color,vessel pattern,surface pattern,and any combinations thereof to develop a classification scheme to differentiate low-risk polyps(fundic-gland or hyperplastic)from high-risk polyps(adenomatous or adenocarcinoma)and fundic-gland polyps(FGPs)from non-FGPs.Results An isolated lacy vessel pattern and a homogenous absence of surface pattern successfully differentiated low-risk from high-risk gastric polyps.Combining both descriptors into a single algorithm resulted in a negative predictive value(NPV)of 100%[95%confidence interval(CI):100%–100%],positive predictive value(PPV)of 13.7%(95%CI:2.6–24.8),sensitivity of 100%(95%CI:100%–100%),and specificity of 53.7%(95%CI:45.3%–62.0%)for high-risk polyps.This would reduce the number of polyps requiring biopsy by 50%,while still capturing all high-risk polyps.Regarding FGPs,using a rule not to biopsy polyps with isolated lacy vessels resulted in a 94.9%NPV(95%CI:89.2%–100%),63.2%PPV(95%CI:47.2%–79.2%),94.8%sensitivity(95%CI:89.5%–100%),and 63.6%specificity(95%CI:51.3%–76.0%)for non-FGPs.Conclusion In this derivation cohort study,NBI is helpful for differentiating between high-risk and low-risk gastric polyps,thereby reducing the need for routine sampling of low-risk polyps.These results need to be validated in a separate test population.
