Non-alcoholic fatty liver disease (NAFLD) is commonly diagnosed in obese subjects;however,it is not rare among lean individuals.Given the absence of traditional risk factors,it tends to remain under-recognised.The met...Non-alcoholic fatty liver disease (NAFLD) is commonly diagnosed in obese subjects;however,it is not rare among lean individuals.Given the absence of traditional risk factors,it tends to remain under-recognised.The metabolic profiles of lean NAFLD patients are frequently comparable to those of obese NAFLD patients.Though results from several studies have been mixed,it has been generally revealed that lean subjects with NAFLD have minor insulin resistance compared to that in obese NAFLD.Several genetic variants are associated with NAFLD without insulin resistance.Some data suggest that the prevalence of steatohepatitis and advanced fibrosis do not differ significantly between lean and obese NAFLD;however,the former tend to have less severe disease at presentation.The underlying pathophysiology of lean NAFLD may be quite different.Genetic predispositions,fructose-and cholesterol-rich diet,visceral adiposity and dyslipidaemia have potential roles in the pathogenic underpinnings.Lean NAFLD may pose a risk for metabolic disturbances,cardiovascular morbidity or overall mortality.Secondary causes of hepatic steatosis are also needed to be ruled out in lean subjects with NAFLD.The effectiveness of various treatment modalities,such as exercise and pharmacotherapy,on lean NAFLD is not known.Weight loss is expected to help lean NAFLD patients who have visceral obesity.Further investigation is needed for many aspects of lean NAFLD,including mechanistic pathogenesis,risk assessment,natural history and therapeutic approach.展开更多
BACKGROUND Nonalcoholic fatty liver disease(NAFLD)is one of the most common chronic diseases in the world.Nowadays,the percentage of non-obese or lean patients with NAFLD is increasing.NAFLD in non-obese populations,e...BACKGROUND Nonalcoholic fatty liver disease(NAFLD)is one of the most common chronic diseases in the world.Nowadays,the percentage of non-obese or lean patients with NAFLD is increasing.NAFLD in non-obese populations,especially the lean subgroup with a normal waist circumference(WC),might lead to more problems than obese individuals,as these individuals may not visit clinics for NAFLD diagnosis or ignore the diagnosis of NAFLD.If the precise characteristics of these populations,especially the lean subgroup,are identified,the clinicians would be able to provide more appropriate advice and treatment to these populations.AIM To investigate the prevalence,clinical characteristics,risk factors,and possible indicators for NAFLD in lean Chinese adults with a normal WC.METHODS People without diabetes mellitus or significant alcohol consumption who underwent routine health examinations were included.Their fatty liver index(FLI),abdominal ultrasonography results,and controlled attenuation parameter were all assessed.Genotyping for single-nucleotide polymorphisms associated with NAFLD was performed in another small group consisting of biopsy-proven NAFLD subjects and healthy controls.RESULTS A total of 2715 subjects who underwent routine health examinations were included in the study.Among 810 lean participants with a normal WC,142(17.5%)fulfilled the diagnostic criteria for NAFLD.Waist-height ratio,hemoglobin,platelets,and triglycerides were significant factors associated with the presence of NAFLD in these participants.The appropriate cut-off value of the FLI score in screening for NAFLD in the lean subjects with a normal WC was 25.15,which had a 77.8%sensitivity and 75.9%specificity.There was no significant difference in the single-nucleotide polymorphisms in the SIRT1,APOC3,PNPLA3,AGTR1,and PPARGC1A genes between lean subjects with and without NAFLD(P<0.05).CONCLUSION NAFLD is not uncommon in lean Chinese adults even with a normal WC.Metabolic factors,rather than genetic factors,may play important roles in the developmen展开更多
A key issue in the commercial aircraft engine design is environmental acceptability, and designers are continually challenged to reduce emissions. In this paper, an experimental investigation is performed to evaluate ...A key issue in the commercial aircraft engine design is environmental acceptability, and designers are continually challenged to reduce emissions. In this paper, an experimental investigation is performed to evaluate the emission performance of a liquid-fueled trapped vortex combustor （TVC） under lean premixed prevaporized （LPP） mode. When operating as an LPP system, a TVC is fueled both in the cavities and in the main stream. The correlations between the emission performance and the total ex- cess air ratio, the positions （4 positions） of the fuel injectors in the main stream, and the inlet temperature are obtained. Experimental results show that both the volume concentrations of unburnt hydrocarbon （UHC） and NOv （NO, NOxusually grouped together as NOx） increase with the increase of total excess air ratio from 1.5 to 3.0; the emission performance relies heavily on the position of the main stream injector, and the best perfomlance is achieved at Position 4 in the experiments, the increase of the inlet temperature impacts on the emission performance positively： the smallest volume concentrations of UHC and NO,. obtained in the experiment are 94×10^-6 and 2.3× 10 ^-6 respectively. This paper validates the feasibility of low emissions for an LPP/TVC and provides a reference for further optimization of TVCs.展开更多
Air worthiness requirements of the aircraft engine emission bring new challenges to the combustor research and design. With the motivation to design high performance and clean combustor, computational fluid dynamics ...Air worthiness requirements of the aircraft engine emission bring new challenges to the combustor research and design. With the motivation to design high performance and clean combustor, computational fluid dynamics （CFD） is utilized as the powerful design approach. In this paper, Reynolds averaged Navier-Stokes （RANS） equations of reactive two-phase flow in an experimental low emission combustor is performed. The numerical approach uses an implicit compressible gas solver together with a Lagrangian liquid-phase tracking method and the extended coherent flamelet model for turbulence-combustion interaction. The NOx formation is modeled by the concept of post-processing, which resolves the NOx transport equation with the assumption of frozen temperature distribution. Both turbulence-combustion interaction model and NOx formation model are firstly evaluated by the comparison of experimental data published in open literature of a lean direct injection （LDI） combustor. The test rig studied in this paper is called low emission stirred swirl （LESS） combustor, which is a two-stage model combustor, fueled with liquid kerosene （RP-3） and designed by Beihang University （BUAA）. The main stage of LESS combustor employs the principle of lean prevaporized and premixed （LPP） concept to reduce pollutant, and the pilot stage depends on a diffusion flame for flame stabili-zation. Detailed numerical results including species distribution, turbulence performance and burning performance are qualita-tively and quantitatively evaluated. Numerical prediction of NOx emission shows a good agreement with test data at both idle condition and full power condition of LESS combustor. Preliminary results of the flame structure are shown in this paper. The flame stabilization mechanism and NOx reduction effort are also discussed with in-depth analysis.展开更多
文摘Non-alcoholic fatty liver disease (NAFLD) is commonly diagnosed in obese subjects;however,it is not rare among lean individuals.Given the absence of traditional risk factors,it tends to remain under-recognised.The metabolic profiles of lean NAFLD patients are frequently comparable to those of obese NAFLD patients.Though results from several studies have been mixed,it has been generally revealed that lean subjects with NAFLD have minor insulin resistance compared to that in obese NAFLD.Several genetic variants are associated with NAFLD without insulin resistance.Some data suggest that the prevalence of steatohepatitis and advanced fibrosis do not differ significantly between lean and obese NAFLD;however,the former tend to have less severe disease at presentation.The underlying pathophysiology of lean NAFLD may be quite different.Genetic predispositions,fructose-and cholesterol-rich diet,visceral adiposity and dyslipidaemia have potential roles in the pathogenic underpinnings.Lean NAFLD may pose a risk for metabolic disturbances,cardiovascular morbidity or overall mortality.Secondary causes of hepatic steatosis are also needed to be ruled out in lean subjects with NAFLD.The effectiveness of various treatment modalities,such as exercise and pharmacotherapy,on lean NAFLD is not known.Weight loss is expected to help lean NAFLD patients who have visceral obesity.Further investigation is needed for many aspects of lean NAFLD,including mechanistic pathogenesis,risk assessment,natural history and therapeutic approach.
基金National Key R&D Program of China,No.2017YFC0908900National Natural Science Foundation of China,No.81873565 and No.81900507Hospital Funded Clinical Research,Xinhua Hospital Affiliated to Shanghai Jiao Tong University School of Medicine,No.17CSK04 and No.15LC06.
文摘BACKGROUND Nonalcoholic fatty liver disease(NAFLD)is one of the most common chronic diseases in the world.Nowadays,the percentage of non-obese or lean patients with NAFLD is increasing.NAFLD in non-obese populations,especially the lean subgroup with a normal waist circumference(WC),might lead to more problems than obese individuals,as these individuals may not visit clinics for NAFLD diagnosis or ignore the diagnosis of NAFLD.If the precise characteristics of these populations,especially the lean subgroup,are identified,the clinicians would be able to provide more appropriate advice and treatment to these populations.AIM To investigate the prevalence,clinical characteristics,risk factors,and possible indicators for NAFLD in lean Chinese adults with a normal WC.METHODS People without diabetes mellitus or significant alcohol consumption who underwent routine health examinations were included.Their fatty liver index(FLI),abdominal ultrasonography results,and controlled attenuation parameter were all assessed.Genotyping for single-nucleotide polymorphisms associated with NAFLD was performed in another small group consisting of biopsy-proven NAFLD subjects and healthy controls.RESULTS A total of 2715 subjects who underwent routine health examinations were included in the study.Among 810 lean participants with a normal WC,142(17.5%)fulfilled the diagnostic criteria for NAFLD.Waist-height ratio,hemoglobin,platelets,and triglycerides were significant factors associated with the presence of NAFLD in these participants.The appropriate cut-off value of the FLI score in screening for NAFLD in the lean subjects with a normal WC was 25.15,which had a 77.8%sensitivity and 75.9%specificity.There was no significant difference in the single-nucleotide polymorphisms in the SIRT1,APOC3,PNPLA3,AGTR1,and PPARGC1A genes between lean subjects with and without NAFLD(P<0.05).CONCLUSION NAFLD is not uncommon in lean Chinese adults even with a normal WC.Metabolic factors,rather than genetic factors,may play important roles in the developmen
基金Aeronautical Science Foundation of China(2008ZB52013)Funding of Jiangsu Innovation Program for Graduate Education(CXLX11_0211)
文摘A key issue in the commercial aircraft engine design is environmental acceptability, and designers are continually challenged to reduce emissions. In this paper, an experimental investigation is performed to evaluate the emission performance of a liquid-fueled trapped vortex combustor （TVC） under lean premixed prevaporized （LPP） mode. When operating as an LPP system, a TVC is fueled both in the cavities and in the main stream. The correlations between the emission performance and the total ex- cess air ratio, the positions （4 positions） of the fuel injectors in the main stream, and the inlet temperature are obtained. Experimental results show that both the volume concentrations of unburnt hydrocarbon （UHC） and NOv （NO, NOxusually grouped together as NOx） increase with the increase of total excess air ratio from 1.5 to 3.0; the emission performance relies heavily on the position of the main stream injector, and the best perfomlance is achieved at Position 4 in the experiments, the increase of the inlet temperature impacts on the emission performance positively： the smallest volume concentrations of UHC and NO,. obtained in the experiment are 94×10^-6 and 2.3× 10 ^-6 respectively. This paper validates the feasibility of low emissions for an LPP/TVC and provides a reference for further optimization of TVCs.
文摘Air worthiness requirements of the aircraft engine emission bring new challenges to the combustor research and design. With the motivation to design high performance and clean combustor, computational fluid dynamics （CFD） is utilized as the powerful design approach. In this paper, Reynolds averaged Navier-Stokes （RANS） equations of reactive two-phase flow in an experimental low emission combustor is performed. The numerical approach uses an implicit compressible gas solver together with a Lagrangian liquid-phase tracking method and the extended coherent flamelet model for turbulence-combustion interaction. The NOx formation is modeled by the concept of post-processing, which resolves the NOx transport equation with the assumption of frozen temperature distribution. Both turbulence-combustion interaction model and NOx formation model are firstly evaluated by the comparison of experimental data published in open literature of a lean direct injection （LDI） combustor. The test rig studied in this paper is called low emission stirred swirl （LESS） combustor, which is a two-stage model combustor, fueled with liquid kerosene （RP-3） and designed by Beihang University （BUAA）. The main stage of LESS combustor employs the principle of lean prevaporized and premixed （LPP） concept to reduce pollutant, and the pilot stage depends on a diffusion flame for flame stabili-zation. Detailed numerical results including species distribution, turbulence performance and burning performance are qualita-tively and quantitatively evaluated. Numerical prediction of NOx emission shows a good agreement with test data at both idle condition and full power condition of LESS combustor. Preliminary results of the flame structure are shown in this paper. The flame stabilization mechanism and NOx reduction effort are also discussed with in-depth analysis.
