Alkane-based biodiesel is considered the next generation of biodiesel owing to its potential environmental benefits and the fact that it exhibits much higher specific caloric values than traditional biodiesel.However,...Alkane-based biodiesel is considered the next generation of biodiesel owing to its potential environmental benefits and the fact that it exhibits much higher specific caloric values than traditional biodiesel.However,the formidable obstacle impeding the commercialization of this cutting-edge fuel alternative lies in the cost associated with its production.In this study,an engineered strain Escherichia coli(E.coli)showcasing harmonized coexpression of a lipase(from Thermomyces lanuginosus lipase,TLL)and a fatty acid photodecarboxylase(from Chlorella variabilis,CvFAP)was first constructed to transform triglycerides into alkanes.The potential of E.coli BL21(DE3)/pRSFDuet-1-TLL-CvFAP for alkane synthesis was evaluated with tripalmitin as a model substrate under various process conditions.Following a comprehensive examination of the reaction parameters,the scope of the biotransformation was expanded to‘real’substrates(vegetable oils).The results showed that bioderived oils can be transformed into alkanes with high yields(0.80-10.20 mmol·L^(-1))under mild conditions(35℃,pH 8.0,and 36 h)and blue light illumination.The selected processes were performed on an increased lab scale(up to 100 ml)with up to 24.77 mmol·L^(-1) tripalmitin,leading to a yield of 18.89 mmol·L^(-1) pentadecane.With the employment of a method for efficiently producing alkanes under mild conditions and a simple procedure to isolate alkanes from the reaction system,the utilization of sustainable biomass as a fundamental feedstock emerges as the primary solution to lower the cost of alkane-based biodiesel.Thus,this study proposes a readily implementable and highly effective approach for alkane-based biodiesel production.展开更多
Launch safety of explosive charges has become an urgent problem to be solved by all countries in the world aslaunch situation of ammunition becomes consistentlyworse.However, the existing numericalmodels have differen...Launch safety of explosive charges has become an urgent problem to be solved by all countries in the world aslaunch situation of ammunition becomes consistentlyworse.However, the existing numericalmodels have differentdefects. This paper formulates an efficient computational model of the combustion of an explosive charge affectedby a bottom gap in the launch environment in the context of the material point method. The current temperatureis computed accurately from the heat balance equation, and different physical states of the explosive charges areconsidered through various equations of state. Microcracks in the explosive charges are described with respectto the viscoelastic statistical crackmechanics (Visco–SCRAM) model. Themethod for calculating the temperatureat the bottomof the explosive charge with respect to the bottomgap is described. Based on this combustionmodel,the temperature history of a Composition B (COMB) explosive charge in the presence of a bottom gap is obtainedduring the launch process of a 155-mm artillery. The simulation results show that the bottom gap thickness shouldbe no greater than 0.039 cm to ensure the safety of the COM B explosive charge in the launch environment. Thisconclusion is consistent with previous results and verifies the correctness of the proposed model. Ultimately, thispaper derives amathematical expression for themaximumtemperature of the COMB explosive chargewith respectto the bottomgap thickness (over the range of 0.00–0.039 cm), and establishes a quantitative evaluationmethod forthe launch safety of explosive charges.The research results provide some guidance for the assessment and detectionof explosive charge safety in complex launch environments.展开更多
BACKGROUND Preoperative conditions in pediatric liver transplant recipients are understandably complex.Compared with adults,children have lesser compensatory abilities and demand greater precision during procedural ex...BACKGROUND Preoperative conditions in pediatric liver transplant recipients are understandably complex.Compared with adults,children have lesser compensatory abilities and demand greater precision during procedural executions.In the setting of endstage liver disease,the heightened perioperative risk of coexistent cardiovascular pathology may impact graft survival as well.Requirements for anesthesia and perioperative management are thus more rigorous,calling for individualized treatments that reflect specific cardiovascular constraints and proposed surgical plans.CASE SUMMARY Reports of perioperative anesthesia management and liver transplant prognostication in pediatric patients with concurrent atrial septal defects are scarce.Herein,we detail the course of liver transplantation in a child with dual afflictions,focusing on perioperative anesthesia management and the important contributions of the anesthesiologist(pre-and perioperatively) to a positive therapeutic outcome,despite the clinical hurdles imposed.CONCLUSION Children with atrial septal defects bear substantially more than customary perioperative risk during orthotopic liver transplants,given their compromised cardiopulmonary reserves and functional states.Comprehensive preoperative cardiovascular assessments,including use of agitated-saline contrast echocardiography(to characterize intracardiac shunting) and multidisciplinary deliberation,may offer insights into structural cardiac pathophysiologic effects and transplantrelated hemodynamic changes that impact new grafts.At the same time,active and effective monitoring and other measures should be taken to maintain hemodynamic stability in the perioperative period,avoid entry of bubbles into the circulation,and ease congestion in newly grafted livers.Such efforts are crucial for transplantation success and graft survival.展开更多
The South Sichuan is one of the areas in China famous for Danxia Landform. Danxia Landform in the South Sichuan is characterized by wide distribution and square shaped hills. However, there is no systematic research o...The South Sichuan is one of the areas in China famous for Danxia Landform. Danxia Landform in the South Sichuan is characterized by wide distribution and square shaped hills. However, there is no systematic research on the genesis of those Danxia Landforms at present. Based on the study of spatial distribution and the genesis of the Danxia Landforms in the South Sichuan, we discovered that the lithostratigraphy, regional tectonic, crustal uplift and external forces contribute together to the formation of the Danxia Landform. On the basis of learning the development experiences from famous scenic spots and the updated national policies and regulations, proposals were made to boost the development of Danxia Landform resources in the South Sichuan by excavating its historic, cultural, natural and scientific connotation in the form of educational tourism.展开更多
目的探讨罗哌卡因腹横肌平面(TAP)阻滞对腹腔镜子宫肌瘤剔除术患者镇痛效果及应激反应的影响。方法选取2019年10月-2020年5月于该院行腹腔镜子宫肌瘤剔除术的患者90例作为研究对象,采用随机数字表法分为A组(n=45)和B组(n=45)。A组在术...目的探讨罗哌卡因腹横肌平面(TAP)阻滞对腹腔镜子宫肌瘤剔除术患者镇痛效果及应激反应的影响。方法选取2019年10月-2020年5月于该院行腹腔镜子宫肌瘤剔除术的患者90例作为研究对象,采用随机数字表法分为A组(n=45)和B组(n=45)。A组在术毕实施静脉镇痛,B组在麻醉诱导时采用罗哌卡因TAP阻滞。对比两组麻醉效果、麻醉药物用量、不良反应发生情况、围术期各时点心率(HR)、平均动脉压(MAP)、应激反应指标[血糖(Glu)、去甲肾上腺素(NE)、皮质醇(Cor)]水平以及术后各时点疼痛程度。结果 B组麻醉唤醒时间、恢复自主呼吸时间和拔管时间均明显短于A组(P<0.01)。A组和B组舒芬太尼用量分别为(31.26±6.35)和(21.18±2.54)μg,七氟醚用量分别为(35.63±7.65)和(25.33±5.06) mL,两组麻醉药物用量比较,差异有统计学意义(t=9.89和7.53,均P<0.01)。B组切皮前(T_(1))、切皮后5 min (T_(2))、切皮后10 min (T_(3)) HR和MAP均明显低于A组(P<0.01)。B组T_(1)、T_(2)、T_(3)和T_(4)时点血浆Glu、NE和Cor水平均明显低于A组(P<0.01)。B组术后2、4和12 h的视觉模拟评分(VAS)均明显低于A组(P<0.01)。A组和B组术后不良反应发生率(33.33%和13.33%)比较,差异有统计学意义(χ^(2)=5.03,P=0.025)。结论罗哌卡因TAP阻滞能够减轻腹腔镜下子宫肌瘤剔除术患者术中应激反应,提高麻醉效果,并降低术后不良反应发生率。展开更多
AIM To explore the association between Helicobacter pylori(H. pylori) infection and obesity/weight gain in a Chinese population.METHODS Our primary outcome was the change in body mass index(BMI). The generalized linea...AIM To explore the association between Helicobacter pylori(H. pylori) infection and obesity/weight gain in a Chinese population.METHODS Our primary outcome was the change in body mass index(BMI). The generalized linear models were used to explore the association between H. pylori infection and the change of BMI, and the logistic regression models were used to explore the association between H. pylori infection and obesity.RESULTS A total of 3039 subjects were recruited and analyzed, of which 12.8% were obese. The prevalence of H. pylori infection was 53.9%(1639/3039) overall and 54.6%(212/388) in the obese subjects. The change of BMI in the H. pylori(+) group was not significantly higher than that in the H. pylori(-) group after adjustment for potential confounding factors [RR = 0.988, 95%CI:0.924-1.057, P = 0.729]. The prevalence of obesity decreased 1.1% in the H. pylori(+) group and 0.5% in the H. pylori(-) group. The RR of H. pylori infection for obesity was 0.831(95%CI: 0.577-1.197, P = 0.321) after the adjustment.CONCLUSION H. pylori infection was not associated with overweight/obesity observed from the retrospective study in this Chinese population.展开更多
For the chip integration of MEMS(micro-electromechanical system) safety and arming device, a miniature detonator needs to be developed to reduce the weight and volume of explosive train. A Si-based micro-detonator is ...For the chip integration of MEMS(micro-electromechanical system) safety and arming device, a miniature detonator needs to be developed to reduce the weight and volume of explosive train. A Si-based micro-detonator is designed and fabricated, which meets the requirement of MEMS safety and arming device. The firing sensitivity of micro-detonator is tested according to GJB/z377A-94 sensitivity test methods:Langlie. The function time of micro-detonator is measured using wire probe and photoelectric transducer. The result shows the average firing voltage is 6.4 V when the discharge capacitance of firing electro-circuit is 33 mF. And the average function time is 5.48 ms. The firing energy actually utilized by Si-based micro-detonator is explored.展开更多
Photodegradation of nonylphenol ethoxylates （NPloEO） was investigated in laboratory scale under UV irradiation. The intermediate photodegradation products were analyzed by LC-ESI-MS. Three kinds of intermediate prod...Photodegradation of nonylphenol ethoxylates （NPloEO） was investigated in laboratory scale under UV irradiation. The intermediate photodegradation products were analyzed by LC-ESI-MS. Three kinds of intermediate products including aldehydic compounds, carboxylic compounds and cyclohexanyl compounds were identified. Five main degradation routes involving the oxidation of the alkyl chain and ethoxylate unit, shortening of the alkyl chain and ethoxylate unit, hydrogenation of the benzene ring were proposed.展开更多
Despite of suitable band structures for harvesting solar light and driving water redox reactions,polymeric carbon nitride(PCN)has suffered from poor charge transfer ability and sluggish surface reaction kinetics,which...Despite of suitable band structures for harvesting solar light and driving water redox reactions,polymeric carbon nitride(PCN)has suffered from poor charge transfer ability and sluggish surface reaction kinetics,which limit its photocatalytic activity for water splitting.Herein,atomically dispersed Zn-coordinated three-dimensional(3D)sponge-like PCN(Zn-PCN)is synthesized through a novel intermediate coordination strategy.Advanced characterizations and theoretical calculations well evidence that Zn single atoms are coordinated and stabilized on PCN in the form of Zn-N_(6) configura-tion featured with an electron-deficient state.Such an electronic configuration has been demonstrated contributive to promoted electron excitation,accelerated charge separation and transfer as well as reduced water redox barriers.Further benefited from the abundant surface active sites derived from the 3D porous structure,Zn-PCN realizes visible-light photocatalysis for overall water splitting with H_(2) and O_(2) simultaneously evolved at a stoichiometric ratio of 2:1.This work brings new insights into the design of novel single-atom photocatalysts by deepening the understanding of electronic configurations and reactive sites favorable to excellent photocatalysis for water splitting and related solar energy conversion reactions.展开更多
Objective:The clinical characteristics and microbiological data of patients with K.pneumoniae bloodstream infections(BSI)from January 2018 to December 2020 were retrospectively analyzed to study the molecular epidemio...Objective:The clinical characteristics and microbiological data of patients with K.pneumoniae bloodstream infections(BSI)from January 2018 to December 2020 were retrospectively analyzed to study the molecular epidemiology of Carbapenem-resistant Klebsiella pneumoniae(CRKP).We also aimed to identify the risk factors for the development of CRKP BSI.Methods:This retrospective study was conducted at Renmin Hospital of Wuhan University from January 2018 to December 2020.The date of non-duplicate K.pneumoniae isolates isolated from blood samples was identified using the microbiology laboratory database.The data from patients diagnosed with K.pneumoniae BSI were collected and analyzed.展开更多
Reducing the radiated noise of a gearbox is a difficult problem in aviation,navigation,machinery,and other fields.Structural improvement is the main means of noise reduction for a gearbox,and it is realized primarily ...Reducing the radiated noise of a gearbox is a difficult problem in aviation,navigation,machinery,and other fields.Structural improvement is the main means of noise reduction for a gearbox,and it is realized primarily through contribution analysis and structure optimization.However,these approaches have certain limitations.In this study,a low-noise design method for a gearbox that combines the two approaches is proposed,and experimental verification is performed.First,a finite element/boundary element model is established using a single-stage herringbone gearbox.Considering the vibration excitation of the gear system,the radiation noise of a single-stage gearbox is predicted based on the modal acoustic transfer vector(MATV)method.Subsequently,the maximum field point of the radiated noise is determined,and the acoustic transfer vector(ATV)analysis and modal acoustic contribution(MAC)analysis are conducted to determine the region that contributes significantly to the radiated noise of the field point.The optimization region is selected through the panel acoustic contribution(PAC)analysis.Next,to reduce the normal speed in the optimization region,topology optimization is performed.According to the topology optimization results,four different noise reduction structures are added to the gearbox,and the low-noise optimization models are established respectively.Finally,by measuring the radiated noise of the gearbox before and after optimization under a given working condition,the validity of the radiated noise prediction method and the low-noise optimization design method are verified by comparing the simulation and experimental data.A comparison of the four optimization models proves that the noise reduction effect can be achieved only by adding a noise reduction structure to the center of the density nephogram.展开更多
This study focuses on the effect of lateral mass impact on ring-stiffened thin-walled cylindrical shell.Cylindrical shells were fabricated to validate the numerical modeling and analytical techniques,and drop tests we...This study focuses on the effect of lateral mass impact on ring-stiffened thin-walled cylindrical shell.Cylindrical shells were fabricated to validate the numerical modeling and analytical techniques,and drop tests were performed using a rigid spherical indenter.Next,stiffened-ring cylindrical shells with various structural size parameters were simulated using ABAQUS software.The relationships between the impact force,deformation displacement,and rebound velocity were established,on the basis of impact mechanics theory and simulation results.It derived fitting functions to analyse the relationship between the maximum load and maximum displacement of ring-stiffened cylindrical shell under dynamic mass impact.Based on the validation of the simulation model,the fitting function data were compared with the simulation results,and the functions showed a good accuracy.Besides,the parameters,mass ratio and stiffened-ring mass ratio were used to reflect the effect of the mass change in the ring-stiffened cylindrical shell.Furthermore,parametric studies on ring-stiffened cylindrical shell models were conducted to analyse the progressive impact responses.展开更多
Soot emissions (PM 2.5) from land-based sources pose a substantial health risk, and now are subject to new and tougher EPA regulations. Flaring produces significant amount of particulate matter in the form of soot, al...Soot emissions (PM 2.5) from land-based sources pose a substantial health risk, and now are subject to new and tougher EPA regulations. Flaring produces significant amount of particulate matter in the form of soot, along with other harmful gas emissions. A few experimental studies have previously been done on flames burning in a controlled condition. In these lab-experiments, great effort is needed to collect, sample, and analyze the soot so that the emission rate can be calculated. Soot prediction in flares is tricky due to variable conditions such as radiation and surrounding air available for combustion. Work presented in this paper simulates some lab-scale flares in which soot yield for methane flame mixture was measured under different conditions. The focus of this paper is on soot modeling with various flair operating conditions. The computational fluid dynamics software ANSYS Fluent 13 is used. Different soot models were explored along with other chemistry mechanisms. The effect of radiation models, quantity of air supplied, different fuel mixture and its effect over soot formations were also studied.展开更多
To timely modify breeding scheme and improve selection efficiency of Dahen broiler, genetic and breeding progress analysis on five pure lines was conducted. The results showed that the selection on breeding goal trait...To timely modify breeding scheme and improve selection efficiency of Dahen broiler, genetic and breeding progress analysis on five pure lines was conducted. The results showed that the selection on breeding goal traits of each line was effective since 14 generations, especially the selection on growth traits did not cause adverse influence on reproductive performance. After the 6^ th generation, main performances of each line maintained in higher level, but the breeding progress obviously declined. It illustrated that current breeding means was effective for maintaining and consolidating breeding goal traits of Dahen broiler, and it should timely adjust breeding scheme to obtain more genetic progress.展开更多
基金financially supported by the National Natural Science Foundation of China(42376097)Guangdong Basic and Applied Basic Research Foundation(2023A1515030226,2021A1515010829).
文摘Alkane-based biodiesel is considered the next generation of biodiesel owing to its potential environmental benefits and the fact that it exhibits much higher specific caloric values than traditional biodiesel.However,the formidable obstacle impeding the commercialization of this cutting-edge fuel alternative lies in the cost associated with its production.In this study,an engineered strain Escherichia coli(E.coli)showcasing harmonized coexpression of a lipase(from Thermomyces lanuginosus lipase,TLL)and a fatty acid photodecarboxylase(from Chlorella variabilis,CvFAP)was first constructed to transform triglycerides into alkanes.The potential of E.coli BL21(DE3)/pRSFDuet-1-TLL-CvFAP for alkane synthesis was evaluated with tripalmitin as a model substrate under various process conditions.Following a comprehensive examination of the reaction parameters,the scope of the biotransformation was expanded to‘real’substrates(vegetable oils).The results showed that bioderived oils can be transformed into alkanes with high yields(0.80-10.20 mmol·L^(-1))under mild conditions(35℃,pH 8.0,and 36 h)and blue light illumination.The selected processes were performed on an increased lab scale(up to 100 ml)with up to 24.77 mmol·L^(-1) tripalmitin,leading to a yield of 18.89 mmol·L^(-1) pentadecane.With the employment of a method for efficiently producing alkanes under mild conditions and a simple procedure to isolate alkanes from the reaction system,the utilization of sustainable biomass as a fundamental feedstock emerges as the primary solution to lower the cost of alkane-based biodiesel.Thus,this study proposes a readily implementable and highly effective approach for alkane-based biodiesel production.
基金the Natural Science Foundation of Heilongjiang Province,China(LH2019A008).
文摘Launch safety of explosive charges has become an urgent problem to be solved by all countries in the world aslaunch situation of ammunition becomes consistentlyworse.However, the existing numericalmodels have differentdefects. This paper formulates an efficient computational model of the combustion of an explosive charge affectedby a bottom gap in the launch environment in the context of the material point method. The current temperatureis computed accurately from the heat balance equation, and different physical states of the explosive charges areconsidered through various equations of state. Microcracks in the explosive charges are described with respectto the viscoelastic statistical crackmechanics (Visco–SCRAM) model. Themethod for calculating the temperatureat the bottomof the explosive charge with respect to the bottomgap is described. Based on this combustionmodel,the temperature history of a Composition B (COMB) explosive charge in the presence of a bottom gap is obtainedduring the launch process of a 155-mm artillery. The simulation results show that the bottom gap thickness shouldbe no greater than 0.039 cm to ensure the safety of the COM B explosive charge in the launch environment. Thisconclusion is consistent with previous results and verifies the correctness of the proposed model. Ultimately, thispaper derives amathematical expression for themaximumtemperature of the COMB explosive chargewith respectto the bottomgap thickness (over the range of 0.00–0.039 cm), and establishes a quantitative evaluationmethod forthe launch safety of explosive charges.The research results provide some guidance for the assessment and detectionof explosive charge safety in complex launch environments.
基金Supported by Natural Science Foundation of Zhejiang Province,No. LQ19C090006。
文摘BACKGROUND Preoperative conditions in pediatric liver transplant recipients are understandably complex.Compared with adults,children have lesser compensatory abilities and demand greater precision during procedural executions.In the setting of endstage liver disease,the heightened perioperative risk of coexistent cardiovascular pathology may impact graft survival as well.Requirements for anesthesia and perioperative management are thus more rigorous,calling for individualized treatments that reflect specific cardiovascular constraints and proposed surgical plans.CASE SUMMARY Reports of perioperative anesthesia management and liver transplant prognostication in pediatric patients with concurrent atrial septal defects are scarce.Herein,we detail the course of liver transplantation in a child with dual afflictions,focusing on perioperative anesthesia management and the important contributions of the anesthesiologist(pre-and perioperatively) to a positive therapeutic outcome,despite the clinical hurdles imposed.CONCLUSION Children with atrial septal defects bear substantially more than customary perioperative risk during orthotopic liver transplants,given their compromised cardiopulmonary reserves and functional states.Comprehensive preoperative cardiovascular assessments,including use of agitated-saline contrast echocardiography(to characterize intracardiac shunting) and multidisciplinary deliberation,may offer insights into structural cardiac pathophysiologic effects and transplantrelated hemodynamic changes that impact new grafts.At the same time,active and effective monitoring and other measures should be taken to maintain hemodynamic stability in the perioperative period,avoid entry of bubbles into the circulation,and ease congestion in newly grafted livers.Such efforts are crucial for transplantation success and graft survival.
文摘The South Sichuan is one of the areas in China famous for Danxia Landform. Danxia Landform in the South Sichuan is characterized by wide distribution and square shaped hills. However, there is no systematic research on the genesis of those Danxia Landforms at present. Based on the study of spatial distribution and the genesis of the Danxia Landforms in the South Sichuan, we discovered that the lithostratigraphy, regional tectonic, crustal uplift and external forces contribute together to the formation of the Danxia Landform. On the basis of learning the development experiences from famous scenic spots and the updated national policies and regulations, proposals were made to boost the development of Danxia Landform resources in the South Sichuan by excavating its historic, cultural, natural and scientific connotation in the form of educational tourism.
文摘目的探讨罗哌卡因腹横肌平面(TAP)阻滞对腹腔镜子宫肌瘤剔除术患者镇痛效果及应激反应的影响。方法选取2019年10月-2020年5月于该院行腹腔镜子宫肌瘤剔除术的患者90例作为研究对象,采用随机数字表法分为A组(n=45)和B组(n=45)。A组在术毕实施静脉镇痛,B组在麻醉诱导时采用罗哌卡因TAP阻滞。对比两组麻醉效果、麻醉药物用量、不良反应发生情况、围术期各时点心率(HR)、平均动脉压(MAP)、应激反应指标[血糖(Glu)、去甲肾上腺素(NE)、皮质醇(Cor)]水平以及术后各时点疼痛程度。结果 B组麻醉唤醒时间、恢复自主呼吸时间和拔管时间均明显短于A组(P<0.01)。A组和B组舒芬太尼用量分别为(31.26±6.35)和(21.18±2.54)μg,七氟醚用量分别为(35.63±7.65)和(25.33±5.06) mL,两组麻醉药物用量比较,差异有统计学意义(t=9.89和7.53,均P<0.01)。B组切皮前(T_(1))、切皮后5 min (T_(2))、切皮后10 min (T_(3)) HR和MAP均明显低于A组(P<0.01)。B组T_(1)、T_(2)、T_(3)和T_(4)时点血浆Glu、NE和Cor水平均明显低于A组(P<0.01)。B组术后2、4和12 h的视觉模拟评分(VAS)均明显低于A组(P<0.01)。A组和B组术后不良反应发生率(33.33%和13.33%)比较,差异有统计学意义(χ^(2)=5.03,P=0.025)。结论罗哌卡因TAP阻滞能够减轻腹腔镜下子宫肌瘤剔除术患者术中应激反应,提高麻醉效果,并降低术后不良反应发生率。
基金Supported by the State Key Laboratory of Pathogen and Biosecurity(Academy of Military Medical Science)No.SKLPBS1442the Youth Talent Support Program of the School of Public Health,Peking University
文摘AIM To explore the association between Helicobacter pylori(H. pylori) infection and obesity/weight gain in a Chinese population.METHODS Our primary outcome was the change in body mass index(BMI). The generalized linear models were used to explore the association between H. pylori infection and the change of BMI, and the logistic regression models were used to explore the association between H. pylori infection and obesity.RESULTS A total of 3039 subjects were recruited and analyzed, of which 12.8% were obese. The prevalence of H. pylori infection was 53.9%(1639/3039) overall and 54.6%(212/388) in the obese subjects. The change of BMI in the H. pylori(+) group was not significantly higher than that in the H. pylori(-) group after adjustment for potential confounding factors [RR = 0.988, 95%CI:0.924-1.057, P = 0.729]. The prevalence of obesity decreased 1.1% in the H. pylori(+) group and 0.5% in the H. pylori(-) group. The RR of H. pylori infection for obesity was 0.831(95%CI: 0.577-1.197, P = 0.321) after the adjustment.CONCLUSION H. pylori infection was not associated with overweight/obesity observed from the retrospective study in this Chinese population.
文摘For the chip integration of MEMS(micro-electromechanical system) safety and arming device, a miniature detonator needs to be developed to reduce the weight and volume of explosive train. A Si-based micro-detonator is designed and fabricated, which meets the requirement of MEMS safety and arming device. The firing sensitivity of micro-detonator is tested according to GJB/z377A-94 sensitivity test methods:Langlie. The function time of micro-detonator is measured using wire probe and photoelectric transducer. The result shows the average firing voltage is 6.4 V when the discharge capacitance of firing electro-circuit is 33 mF. And the average function time is 5.48 ms. The firing energy actually utilized by Si-based micro-detonator is explored.
文摘Photodegradation of nonylphenol ethoxylates （NPloEO） was investigated in laboratory scale under UV irradiation. The intermediate photodegradation products were analyzed by LC-ESI-MS. Three kinds of intermediate products including aldehydic compounds, carboxylic compounds and cyclohexanyl compounds were identified. Five main degradation routes involving the oxidation of the alkyl chain and ethoxylate unit, shortening of the alkyl chain and ethoxylate unit, hydrogenation of the benzene ring were proposed.
基金This work was supported by the National Key Research and Development Program of China(2018YFB1502003)the National Natural Science Foundation of China(52225606,21875183,52172248)+2 种基金the“Fundamental Research Funds for the Central Universities”the Natural Science Basic Research Program of Shaanxi Province(2019JCW-10)“The Youth Innovation Team of Shaanxi Universities”.
文摘Despite of suitable band structures for harvesting solar light and driving water redox reactions,polymeric carbon nitride(PCN)has suffered from poor charge transfer ability and sluggish surface reaction kinetics,which limit its photocatalytic activity for water splitting.Herein,atomically dispersed Zn-coordinated three-dimensional(3D)sponge-like PCN(Zn-PCN)is synthesized through a novel intermediate coordination strategy.Advanced characterizations and theoretical calculations well evidence that Zn single atoms are coordinated and stabilized on PCN in the form of Zn-N_(6) configura-tion featured with an electron-deficient state.Such an electronic configuration has been demonstrated contributive to promoted electron excitation,accelerated charge separation and transfer as well as reduced water redox barriers.Further benefited from the abundant surface active sites derived from the 3D porous structure,Zn-PCN realizes visible-light photocatalysis for overall water splitting with H_(2) and O_(2) simultaneously evolved at a stoichiometric ratio of 2:1.This work brings new insights into the design of novel single-atom photocatalysts by deepening the understanding of electronic configurations and reactive sites favorable to excellent photocatalysis for water splitting and related solar energy conversion reactions.
文摘Objective:The clinical characteristics and microbiological data of patients with K.pneumoniae bloodstream infections(BSI)from January 2018 to December 2020 were retrospectively analyzed to study the molecular epidemiology of Carbapenem-resistant Klebsiella pneumoniae(CRKP).We also aimed to identify the risk factors for the development of CRKP BSI.Methods:This retrospective study was conducted at Renmin Hospital of Wuhan University from January 2018 to December 2020.The date of non-duplicate K.pneumoniae isolates isolated from blood samples was identified using the microbiology laboratory database.The data from patients diagnosed with K.pneumoniae BSI were collected and analyzed.
基金National Key R&D Program of China(Grant No.2018YFB2001501)Key Program of National Natural Science Foundation of China(Grant No.51535009).
文摘Reducing the radiated noise of a gearbox is a difficult problem in aviation,navigation,machinery,and other fields.Structural improvement is the main means of noise reduction for a gearbox,and it is realized primarily through contribution analysis and structure optimization.However,these approaches have certain limitations.In this study,a low-noise design method for a gearbox that combines the two approaches is proposed,and experimental verification is performed.First,a finite element/boundary element model is established using a single-stage herringbone gearbox.Considering the vibration excitation of the gear system,the radiation noise of a single-stage gearbox is predicted based on the modal acoustic transfer vector(MATV)method.Subsequently,the maximum field point of the radiated noise is determined,and the acoustic transfer vector(ATV)analysis and modal acoustic contribution(MAC)analysis are conducted to determine the region that contributes significantly to the radiated noise of the field point.The optimization region is selected through the panel acoustic contribution(PAC)analysis.Next,to reduce the normal speed in the optimization region,topology optimization is performed.According to the topology optimization results,four different noise reduction structures are added to the gearbox,and the low-noise optimization models are established respectively.Finally,by measuring the radiated noise of the gearbox before and after optimization under a given working condition,the validity of the radiated noise prediction method and the low-noise optimization design method are verified by comparing the simulation and experimental data.A comparison of the four optimization models proves that the noise reduction effect can be achieved only by adding a noise reduction structure to the center of the density nephogram.
基金supported by the National Natural Science Foundation of China(Grant No.51508123,named“Study on blast response of floating roof storage tank in material point method”)Natural Science Foundation of Heilongjiang Province,China(LH2019A008)to provide fund for conducting experiments and research.The authors would like to acknowledge Professor Wei Wang in Harbin Institute of Technology for instructions and help in experiment design.
文摘This study focuses on the effect of lateral mass impact on ring-stiffened thin-walled cylindrical shell.Cylindrical shells were fabricated to validate the numerical modeling and analytical techniques,and drop tests were performed using a rigid spherical indenter.Next,stiffened-ring cylindrical shells with various structural size parameters were simulated using ABAQUS software.The relationships between the impact force,deformation displacement,and rebound velocity were established,on the basis of impact mechanics theory and simulation results.It derived fitting functions to analyse the relationship between the maximum load and maximum displacement of ring-stiffened cylindrical shell under dynamic mass impact.Based on the validation of the simulation model,the fitting function data were compared with the simulation results,and the functions showed a good accuracy.Besides,the parameters,mass ratio and stiffened-ring mass ratio were used to reflect the effect of the mass change in the ring-stiffened cylindrical shell.Furthermore,parametric studies on ring-stiffened cylindrical shell models were conducted to analyse the progressive impact responses.
文摘Soot emissions (PM 2.5) from land-based sources pose a substantial health risk, and now are subject to new and tougher EPA regulations. Flaring produces significant amount of particulate matter in the form of soot, along with other harmful gas emissions. A few experimental studies have previously been done on flames burning in a controlled condition. In these lab-experiments, great effort is needed to collect, sample, and analyze the soot so that the emission rate can be calculated. Soot prediction in flares is tricky due to variable conditions such as radiation and surrounding air available for combustion. Work presented in this paper simulates some lab-scale flares in which soot yield for methane flame mixture was measured under different conditions. The focus of this paper is on soot modeling with various flair operating conditions. The computational fluid dynamics software ANSYS Fluent 13 is used. Different soot models were explored along with other chemistry mechanisms. The effect of radiation models, quantity of air supplied, different fuel mixture and its effect over soot formations were also studied.
基金Supported by"13~(th)Five-year"Broiler Breeding Project of Sichuan Province(2016NYZ0025,2016NYZ0043)Sichuan Science and Technology Support Plan project(2016NZ0003,2016NZ0104)
文摘To timely modify breeding scheme and improve selection efficiency of Dahen broiler, genetic and breeding progress analysis on five pure lines was conducted. The results showed that the selection on breeding goal traits of each line was effective since 14 generations, especially the selection on growth traits did not cause adverse influence on reproductive performance. After the 6^ th generation, main performances of each line maintained in higher level, but the breeding progress obviously declined. It illustrated that current breeding means was effective for maintaining and consolidating breeding goal traits of Dahen broiler, and it should timely adjust breeding scheme to obtain more genetic progress.
