Background Chronic obstructive pulmonary disease （COPD） has a variable natural history and not all individuals follow the same course. This study aimed to identify the prevalence and characteristics of asymptomatic ...Background Chronic obstructive pulmonary disease （COPD） has a variable natural history and not all individuals follow the same course. This study aimed to identify the prevalence and characteristics of asymptomatic COPD patients from a population-based survey in China.Methods A multistage cluster sampling strategy was used in a population from seven different provinces/cities. All residents （over 40 years old） were interviewed with a standardized questionnaire and spirometry.Post-bronchodilator forced expiratory volume in 1 second （FEV1）/forced vital capacity （FVC） of less than 70% was defined as the diagnostic criterion of COPD. All COPD patients screened were divided into symptomatic group and asymptomatic group according to the presence or absence of chronic respiratory symptoms. Socio-demographic,personal and exposure variables were collected and analyzed.Results Among the 1668 patients who were diagnosed with COPD from the 25 627 sampling subjects, 589 （35.3%）were asymptomatic. The age, sex, body mass index （BMI）,rural and urban distributions, smoking habit and education levels were similar in the two groups. A total of 64.7% of the asymptomatic patients had no comorbidities. Cardiovascular diseases and lung cancer were more common among symptomatic COPD patients than asymptomatic group.Asymptomatic COPD group were less likely to present with poor ventilation in the kitchen, a family history of respiratory disease and recurrent childhood cough. Asymptomatic COPD patients had significantly higher FEV1 （73.1% vs. 61.0%）, FVC （91.9% vs. 82.0%）, and a higher ratio of FEV1/FVC （62.9% vs.58.7%） （all P 〈0.001） than symptomatic group. More asymptomatic patients were underdiagnosed （91.9% vs.54.3%, P〈0.001） than symptomatic patients.Conclusions This large population-based survey confirmed a high prevalence of asymptomatic COPD patients in China. More use of spirometry screening test may be important to the early detection of COPD.展开更多
The salt beds of Lower Tertiary developed in the mid-segment of Kuqa foreland fold belt, northern Tarim basin. They considerably controlled structural deformation of the belt. Ac- cording to the field observation, sei...The salt beds of Lower Tertiary developed in the mid-segment of Kuqa foreland fold belt, northern Tarim basin. They considerably controlled structural deformation of the belt. Ac- cording to the field observation, seismic profile interpretation and drilling data, three different structural styles of supra-salt, intra-salt and sub-salt occurred in the Kuqa foreland fold belt. Su- pra-salt structural styles mainly include thrust faults and fault-related sags. Intra-slat structural styles essentially are salt-pillows, intra-salt faults and folds, and salt weld structures. Sub-salt structural styles mainly consist of imbricated thrust faults, duplex structures, pop-up and fault-related folds. It is indicated that great differences exist among supra-salt, intra-salt and sub-salt structures of Kuqa foreland fold belt. The salt-related structures were formed in the same structural stress field. The dynamic mechanism of the salt-related structures is mainly associated with gravitation, compression and plastic flow of salt beds.展开更多
Background:Implementing effective interventions remain a lot of difficulties along all border regions.The emergence of artemisinin resistance of Plasmodium falciparum strains in the Greater Mekong Subregion is a matte...Background:Implementing effective interventions remain a lot of difficulties along all border regions.The emergence of artemisinin resistance of Plasmodium falciparum strains in the Greater Mekong Subregion is a matter of great concern.China has effectively controlled cross-border transmission of malaria and artemisinin resistance of P.falciparum along the China-Myanmar border.Methods:A combined quantitative and qualitative study was used to collect data,and then an integrated impact evaluation was conducted to malaria control along the China-Myanmar border during 2007-2013.Results:The parasite prevalence rate(PPR)in the five special regions of Myanmar was decreased from 13.6%in March 2008 to 1.5%in November 2013.Compared with the baseline(PPR in March 2008),the risk ratio was only 0.11[95%confidence interval(CI),0.09-0.14]in November 2013,which is equal to an 89%reduction in the malaria burden.Annual parasite incidence(API)across 19 Chinese border counties was reduced from 19.6 per 10000 person-years in 2006 to 0.9 per 10000 person-years in 2013.Compared with the baseline(API in 2006),the API rate ratio was only 0.05(95%CI,0.04-0.05)in 2013,which equates to a reduction of the malaria burden by 95.0%.Meanwhile,the health service system was strengthened and health inequity of marginalized populations reduced along the international border.Conclusion:The effective collaboration between China,Myanmar and the international non-governmental organization promptly carried out the core interventions through simplified processes.The integrated approaches dramatically decreased malaria burden of Chinese-Myanmar border.展开更多
Data-driven surrogate models that assist with efficient evolutionary algorithms to find the optimal development scheme have been widely used to solve reservoir production optimization problems.However,existing researc...Data-driven surrogate models that assist with efficient evolutionary algorithms to find the optimal development scheme have been widely used to solve reservoir production optimization problems.However,existing research suggests that the effectiveness of a surrogate model can vary depending on the complexity of the design problem.A surrogate model that has demonstrated success in one scenario may not perform as well in others.In the absence of prior knowledge,finding a promising surrogate model that performs well for an unknown reservoir is challenging.Moreover,the optimization process often relies on a single evolutionary algorithm,which can yield varying results across different cases.To address these limitations,this paper introduces a novel approach called the multi-surrogate framework with an adaptive selection mechanism(MSFASM)to tackle production optimization problems.MSFASM consists of two stages.In the first stage,a reduced-dimensional broad learning system(BLS)is used to adaptively select the evolutionary algorithm with the best performance during the current optimization period.In the second stage,the multi-objective algorithm,non-dominated sorting genetic algorithm II(NSGA-II),is used as an optimizer to find a set of Pareto solutions with good performance on multiple surrogate models.A novel optimal point criterion is utilized in this stage to select the Pareto solutions,thereby obtaining the desired development schemes without increasing the computational load of the numerical simulator.The two stages are combined using sequential transfer learning.From the two most important perspectives of an evolutionary algorithm and a surrogate model,the proposed method improves adaptability to optimization problems of various reservoir types.To verify the effectiveness of the proposed method,four 100-dimensional benchmark functions and two reservoir models are tested,and the results are compared with those obtained by six other surrogate-model-based methods.The results demonstrate that our approach can obtain th展开更多
Background： Liquid-based cytology （LBC） offers an alternative method to biopsy in screening endometrial cancer. Cell block （CB）, prepared by collecting residual cytological specimen, represents a novel method to ...Background： Liquid-based cytology （LBC） offers an alternative method to biopsy in screening endometrial cancer. Cell block （CB）, prepared by collecting residual cytological specimen, represents a novel method to supplement the diagnosis of endometrial cytology. This study aimed to compare the specimen adequacy and diagnostic accuracy of LBC and CB in the diagnosis of endometrial lesions. Methods： A total of 198 women with high risks of endometrial carcinoma （EC） from May 2014 to April 2015 were enrolled in this study. The cytological specimens were collected by the endometrial sampler （SAP-1 ） followed by histopathologic evaluation of dilatation and curettage or biopsy guided by hysteroscopy. The residual cytological specimens were processed into paraffin-embedded CB after LBC preparation. Diagnostic accuracies of LBC and CB for detecting endometrial lesions were correlated with histological diagnoses. Chi-square test was used to compare the specimen adequacies of LBC and CB. Results： The specimen inadequate rate of CB was significantly higher than that of LBC （22.2% versus 7.1%, P 〈 0.01）. There were 144 cases with adequate specimens for LBC and CB preparation. Among them, 29 cases were atypical endometrial hyperplasia （ 11 cases） or carcinoma （18 cases） confirmed by histology evaluation. Taking atypical hyperplasia and carcinoma as positive, the diagnostic accuracy of CB was 95.1% while it was 93.8% in LBC. When combined LBC with CB, the diagnostic accuracy was improved to 95.8%, with a sensitivity of 89.7% and specificity of 97.4%. Conclusions： CB is a feasible and reproducible adjuvant method for screening endometrial lesions. A combination of CB and LBC can improve the diagnostic accuracy of endometrial lesions.展开更多
Objective: To investigate the effects of fluidized bed granulation with dextrin on moisture sorption and diffusion of Zexie Decoction granules.Methods: The particle characterization was studied by the particle size, s...Objective: To investigate the effects of fluidized bed granulation with dextrin on moisture sorption and diffusion of Zexie Decoction granules.Methods: The particle characterization was studied by the particle size, scanning electron microscopy(SEM), differential scanning calorimetry(DSC), and Fourier transform infrared(FTIR). The moisture sorption isotherm, equilibrium moisture content(EMC), and moisture diffusion coefficients were determined by using the saturated salt solution method.Results: The particle size increased from 6.04 μm(powder) to 1201.47 μm(granule). The glass transition temperature of dextrin, Zexie Decoction powder, and granule was 107.13 °C, 94.82 °C, and 126.25 °C. As the increase of temperature, the initial rate of moisture sorption become higher. Furthermore, the initial rate of moisture sorption of Zexie Decoction granules was lower than those of powders and dextrin. The EMC and moisture diffusion coefficients were reduced significantly after granulation(P < 0.01). Critical relative humidity and diffusion activation energy of granules were higher than powders.Conclusion: Results suggested that fluidized bed granulation with dextrin could reduce the hygroscopicity of the Zexie Decoction extract powders and inhibited moisture diffusion, which is mainly related to the microstructure reorganization by fluidized bed granulation and anti-plasticizing effects of dextrin.展开更多
Poly(glycolic acid)is a biocompatible as well as biocomposable polymer with superior mechanical and barrier properties and,consequently,has found important applications in both medical and packaging fields.However,the...Poly(glycolic acid)is a biocompatible as well as biocomposable polymer with superior mechanical and barrier properties and,consequently,has found important applications in both medical and packaging fields.However,the high hydrolysis rate in a high humidity environment restricts its application.In this work,a solid-state drawing process after melt extrusion is applied in order to produce fibrous PGA with enhanced mechanical properties and a much better resistance towards hydrolysis.The crystal structure of PGA gradually transformed from spherulites into oriented fibrous crystals in the stretching direction upon solid-state drawing.Meanwhile,both the length of microfibril and the size of lamellae increased initially with the drawing ratio(DR),while the chain-folded lamellae transformed into extended-chain fibrils at high(er)DR.The oriented structures lead to an overall improvement of the mechanical properties of PGA,e.g.,the tensile strength increased from 62.0±1.4 MPa to 910±54 MPa and the elongation at break increased from around 7%to 50%.Meanwhile,the heat capacity of totally mobile amorphous PGA(∆C_(p)^(0)=0.64 J·g^(−1)·℃^(−1))was reported for the first time,which was used to analyze the content of mobile amorphous fraction(XMAF)and rigid amorphous fraction(XRAF).Both the oriented chain-folded lamellae crystals and the tightly arranged RAF are beneficial to prevent water molecules from penetrating the matrix,thus improving the resistance towards hydrolysis.As a consequence,the fibrous PGA with a DR of 5 showed a tensile strength retention rate of 17.3%higher in comparison with the undrawn sample after 7-days accelerated hydrolysis.Therefore,this work provides a feasible method to improve the mechanical and resistance towards hydrolysis performance of PGA,which may broaden its application and prolong the shelf-life of PGA products.展开更多
Biocompostable poly(glycolic acid)(PGA)crystallizes slowly under fast cooling condition,leading to poor mechanical performance of the final products.In this work,a self-nucleation(SN)route was carried out to promote t...Biocompostable poly(glycolic acid)(PGA)crystallizes slowly under fast cooling condition,leading to poor mechanical performance of the final products.In this work,a self-nucleation(SN)route was carried out to promote the crystallization of PGA by regulating only the thermal procedure without any extra nucleating agents.When self-nucleation temperature(Ts)decreased from 250℃ to 227℃,the nuclei density was increased,and the non-isothermal crystallization temperature(Tc)of PGA was increased from 156℃ to 197℃ and the half-life time(t0.5)of isothermal crystallization at 207℃ was decreased by 89%.Consequently,the tensile strength and the elongation at break of the PGA were increased by 12%and 189%,respectively.According to the change of Tc as a function of Ts,a three-stage temperature domain map(Domain I,II and III)was protracted and the viscoelastic behavior of the self-nucleation melt and the homogeneous melt was studied.The results indicated that interaction among PGA chains was remained in Domain IIb,which can act as pre-ordered structure to accelerate the overall crystallization rate.This work utilizes a simple and effective SN method to regulate the crystallization behavior and the mechanical properties of PGA,which may broaden the application range of resulting materials.展开更多
The Kela-2 gas field is located in the center ofKelasu structural belt in Kuqa Depression. This trap is oneof a series of traps in the folded belts which are distributed ina string of pearls in the dual structure. The...The Kela-2 gas field is located in the center ofKelasu structural belt in Kuqa Depression. This trap is oneof a series of traps in the folded belts which are distributed ina string of pearls in the dual structure. The primary gas-bearing layers are sandstone of Lower Cretaceous K<sub>1</sub>bswhile the secondary layers are dolomite member and gluten-ite member of Lower Tertiary E<sub>1-2</sub>km and sandstone ofLower Cretaceous K<sub>1</sub>b. The main component of natural gasis methane whose content is higher than 97%. It is charac-terized by dry gas whose source rock is Jurassic coal meas-ure. The Kela-2 structural trap was formed during the Xiyuperiod and then became a reservoir in the late time. The res-ervoir formed late and the thick seal rock of Lower Tertiarygipsmantle are the avail reason why the giant Kela-2 gasfield has been well kept. The abnormal high pressure of theKela-2 gas field results from the strong structural compres-sion in the northern part during the Xiyu period.展开更多
文摘Background Chronic obstructive pulmonary disease （COPD） has a variable natural history and not all individuals follow the same course. This study aimed to identify the prevalence and characteristics of asymptomatic COPD patients from a population-based survey in China.Methods A multistage cluster sampling strategy was used in a population from seven different provinces/cities. All residents （over 40 years old） were interviewed with a standardized questionnaire and spirometry.Post-bronchodilator forced expiratory volume in 1 second （FEV1）/forced vital capacity （FVC） of less than 70% was defined as the diagnostic criterion of COPD. All COPD patients screened were divided into symptomatic group and asymptomatic group according to the presence or absence of chronic respiratory symptoms. Socio-demographic,personal and exposure variables were collected and analyzed.Results Among the 1668 patients who were diagnosed with COPD from the 25 627 sampling subjects, 589 （35.3%）were asymptomatic. The age, sex, body mass index （BMI）,rural and urban distributions, smoking habit and education levels were similar in the two groups. A total of 64.7% of the asymptomatic patients had no comorbidities. Cardiovascular diseases and lung cancer were more common among symptomatic COPD patients than asymptomatic group.Asymptomatic COPD group were less likely to present with poor ventilation in the kitchen, a family history of respiratory disease and recurrent childhood cough. Asymptomatic COPD patients had significantly higher FEV1 （73.1% vs. 61.0%）, FVC （91.9% vs. 82.0%）, and a higher ratio of FEV1/FVC （62.9% vs.58.7%） （all P 〈0.001） than symptomatic group. More asymptomatic patients were underdiagnosed （91.9% vs.54.3%, P〈0.001） than symptomatic patients.Conclusions This large population-based survey confirmed a high prevalence of asymptomatic COPD patients in China. More use of spirometry screening test may be important to the early detection of COPD.
基金jointly supported by the National Major Fundamental Research and Development Project(Grant No.G19990433)the National Natural Science Foundation of China(Grant No.40172076)the National Key Project of the Ninth Five-Year Plan(No.99-111).
文摘The salt beds of Lower Tertiary developed in the mid-segment of Kuqa foreland fold belt, northern Tarim basin. They considerably controlled structural deformation of the belt. Ac- cording to the field observation, seismic profile interpretation and drilling data, three different structural styles of supra-salt, intra-salt and sub-salt occurred in the Kuqa foreland fold belt. Su- pra-salt structural styles mainly include thrust faults and fault-related sags. Intra-slat structural styles essentially are salt-pillows, intra-salt faults and folds, and salt weld structures. Sub-salt structural styles mainly consist of imbricated thrust faults, duplex structures, pop-up and fault-related folds. It is indicated that great differences exist among supra-salt, intra-salt and sub-salt structures of Kuqa foreland fold belt. The salt-related structures were formed in the same structural stress field. The dynamic mechanism of the salt-related structures is mainly associated with gravitation, compression and plastic flow of salt beds.
基金supported by the sixth(CHN-607-G09-M)and the tenth(CHN-011-G15-M)grants of the Global Fund to fight AIDS,Tuberculosis and Malaria(GFATM)to Chinasupported by the tenth(CHN-011-G15-M)grants of the GFATM to Chinasupported by the National Natural Science Foundation of China(NSFC/81560543).
文摘Background:Implementing effective interventions remain a lot of difficulties along all border regions.The emergence of artemisinin resistance of Plasmodium falciparum strains in the Greater Mekong Subregion is a matter of great concern.China has effectively controlled cross-border transmission of malaria and artemisinin resistance of P.falciparum along the China-Myanmar border.Methods:A combined quantitative and qualitative study was used to collect data,and then an integrated impact evaluation was conducted to malaria control along the China-Myanmar border during 2007-2013.Results:The parasite prevalence rate(PPR)in the five special regions of Myanmar was decreased from 13.6%in March 2008 to 1.5%in November 2013.Compared with the baseline(PPR in March 2008),the risk ratio was only 0.11[95%confidence interval(CI),0.09-0.14]in November 2013,which is equal to an 89%reduction in the malaria burden.Annual parasite incidence(API)across 19 Chinese border counties was reduced from 19.6 per 10000 person-years in 2006 to 0.9 per 10000 person-years in 2013.Compared with the baseline(API in 2006),the API rate ratio was only 0.05(95%CI,0.04-0.05)in 2013,which equates to a reduction of the malaria burden by 95.0%.Meanwhile,the health service system was strengthened and health inequity of marginalized populations reduced along the international border.Conclusion:The effective collaboration between China,Myanmar and the international non-governmental organization promptly carried out the core interventions through simplified processes.The integrated approaches dramatically decreased malaria burden of Chinese-Myanmar border.
基金This work is supported by the National Natural Science Foundation of China under Grant 52274057,52074340 and 51874335the Major Scientific and Technological Projects of CNPC under Grant ZD2019-183-008+2 种基金the Major Scientific and Technological Projects of CNOOC under Grant CCL2022RCPS0397RSNthe Science and Technology Support Plan for Youth Innovation of University in Shandong Province under Grant 2019KJH002111 Project under Grant B08028.
文摘Data-driven surrogate models that assist with efficient evolutionary algorithms to find the optimal development scheme have been widely used to solve reservoir production optimization problems.However,existing research suggests that the effectiveness of a surrogate model can vary depending on the complexity of the design problem.A surrogate model that has demonstrated success in one scenario may not perform as well in others.In the absence of prior knowledge,finding a promising surrogate model that performs well for an unknown reservoir is challenging.Moreover,the optimization process often relies on a single evolutionary algorithm,which can yield varying results across different cases.To address these limitations,this paper introduces a novel approach called the multi-surrogate framework with an adaptive selection mechanism(MSFASM)to tackle production optimization problems.MSFASM consists of two stages.In the first stage,a reduced-dimensional broad learning system(BLS)is used to adaptively select the evolutionary algorithm with the best performance during the current optimization period.In the second stage,the multi-objective algorithm,non-dominated sorting genetic algorithm II(NSGA-II),is used as an optimizer to find a set of Pareto solutions with good performance on multiple surrogate models.A novel optimal point criterion is utilized in this stage to select the Pareto solutions,thereby obtaining the desired development schemes without increasing the computational load of the numerical simulator.The two stages are combined using sequential transfer learning.From the two most important perspectives of an evolutionary algorithm and a surrogate model,the proposed method improves adaptability to optimization problems of various reservoir types.To verify the effectiveness of the proposed method,four 100-dimensional benchmark functions and two reservoir models are tested,and the results are compared with those obtained by six other surrogate-model-based methods.The results demonstrate that our approach can obtain th
文摘Background： Liquid-based cytology （LBC） offers an alternative method to biopsy in screening endometrial cancer. Cell block （CB）, prepared by collecting residual cytological specimen, represents a novel method to supplement the diagnosis of endometrial cytology. This study aimed to compare the specimen adequacy and diagnostic accuracy of LBC and CB in the diagnosis of endometrial lesions. Methods： A total of 198 women with high risks of endometrial carcinoma （EC） from May 2014 to April 2015 were enrolled in this study. The cytological specimens were collected by the endometrial sampler （SAP-1 ） followed by histopathologic evaluation of dilatation and curettage or biopsy guided by hysteroscopy. The residual cytological specimens were processed into paraffin-embedded CB after LBC preparation. Diagnostic accuracies of LBC and CB for detecting endometrial lesions were correlated with histological diagnoses. Chi-square test was used to compare the specimen adequacies of LBC and CB. Results： The specimen inadequate rate of CB was significantly higher than that of LBC （22.2% versus 7.1%, P 〈 0.01）. There were 144 cases with adequate specimens for LBC and CB preparation. Among them, 29 cases were atypical endometrial hyperplasia （ 11 cases） or carcinoma （18 cases） confirmed by histology evaluation. Taking atypical hyperplasia and carcinoma as positive, the diagnostic accuracy of CB was 95.1% while it was 93.8% in LBC. When combined LBC with CB, the diagnostic accuracy was improved to 95.8%, with a sensitivity of 89.7% and specificity of 97.4%. Conclusions： CB is a feasible and reproducible adjuvant method for screening endometrial lesions. A combination of CB and LBC can improve the diagnostic accuracy of endometrial lesions.
基金financial support provided for this research by Tianjin Municipal Education Commission Research Project(Grant No.2017KJ134)
文摘Objective: To investigate the effects of fluidized bed granulation with dextrin on moisture sorption and diffusion of Zexie Decoction granules.Methods: The particle characterization was studied by the particle size, scanning electron microscopy(SEM), differential scanning calorimetry(DSC), and Fourier transform infrared(FTIR). The moisture sorption isotherm, equilibrium moisture content(EMC), and moisture diffusion coefficients were determined by using the saturated salt solution method.Results: The particle size increased from 6.04 μm(powder) to 1201.47 μm(granule). The glass transition temperature of dextrin, Zexie Decoction powder, and granule was 107.13 °C, 94.82 °C, and 126.25 °C. As the increase of temperature, the initial rate of moisture sorption become higher. Furthermore, the initial rate of moisture sorption of Zexie Decoction granules was lower than those of powders and dextrin. The EMC and moisture diffusion coefficients were reduced significantly after granulation(P < 0.01). Critical relative humidity and diffusion activation energy of granules were higher than powders.Conclusion: Results suggested that fluidized bed granulation with dextrin could reduce the hygroscopicity of the Zexie Decoction extract powders and inhibited moisture diffusion, which is mainly related to the microstructure reorganization by fluidized bed granulation and anti-plasticizing effects of dextrin.
基金the National Natural Science Foundation of China(Nos.52073123 and 51873082)the Distinguished Young Natural Science Foundation of Jiangsu Province(No.BK20200027)。
文摘Poly(glycolic acid)is a biocompatible as well as biocomposable polymer with superior mechanical and barrier properties and,consequently,has found important applications in both medical and packaging fields.However,the high hydrolysis rate in a high humidity environment restricts its application.In this work,a solid-state drawing process after melt extrusion is applied in order to produce fibrous PGA with enhanced mechanical properties and a much better resistance towards hydrolysis.The crystal structure of PGA gradually transformed from spherulites into oriented fibrous crystals in the stretching direction upon solid-state drawing.Meanwhile,both the length of microfibril and the size of lamellae increased initially with the drawing ratio(DR),while the chain-folded lamellae transformed into extended-chain fibrils at high(er)DR.The oriented structures lead to an overall improvement of the mechanical properties of PGA,e.g.,the tensile strength increased from 62.0±1.4 MPa to 910±54 MPa and the elongation at break increased from around 7%to 50%.Meanwhile,the heat capacity of totally mobile amorphous PGA(∆C_(p)^(0)=0.64 J·g^(−1)·℃^(−1))was reported for the first time,which was used to analyze the content of mobile amorphous fraction(XMAF)and rigid amorphous fraction(XRAF).Both the oriented chain-folded lamellae crystals and the tightly arranged RAF are beneficial to prevent water molecules from penetrating the matrix,thus improving the resistance towards hydrolysis.As a consequence,the fibrous PGA with a DR of 5 showed a tensile strength retention rate of 17.3%higher in comparison with the undrawn sample after 7-days accelerated hydrolysis.Therefore,this work provides a feasible method to improve the mechanical and resistance towards hydrolysis performance of PGA,which may broaden its application and prolong the shelf-life of PGA products.
基金the National Natural Science Foundation of China(Nos.51873082,52073123 and 52103032)the Distinguished Young Natural Science Foundation of Jiangsu Province(No.BK20200027)the Natural Science Foundation of Jiangsu Province(No.BK20200606).
文摘Biocompostable poly(glycolic acid)(PGA)crystallizes slowly under fast cooling condition,leading to poor mechanical performance of the final products.In this work,a self-nucleation(SN)route was carried out to promote the crystallization of PGA by regulating only the thermal procedure without any extra nucleating agents.When self-nucleation temperature(Ts)decreased from 250℃ to 227℃,the nuclei density was increased,and the non-isothermal crystallization temperature(Tc)of PGA was increased from 156℃ to 197℃ and the half-life time(t0.5)of isothermal crystallization at 207℃ was decreased by 89%.Consequently,the tensile strength and the elongation at break of the PGA were increased by 12%and 189%,respectively.According to the change of Tc as a function of Ts,a three-stage temperature domain map(Domain I,II and III)was protracted and the viscoelastic behavior of the self-nucleation melt and the homogeneous melt was studied.The results indicated that interaction among PGA chains was remained in Domain IIb,which can act as pre-ordered structure to accelerate the overall crystallization rate.This work utilizes a simple and effective SN method to regulate the crystallization behavior and the mechanical properties of PGA,which may broaden the application range of resulting materials.
文摘The Kela-2 gas field is located in the center ofKelasu structural belt in Kuqa Depression. This trap is oneof a series of traps in the folded belts which are distributed ina string of pearls in the dual structure. The primary gas-bearing layers are sandstone of Lower Cretaceous K<sub>1</sub>bswhile the secondary layers are dolomite member and gluten-ite member of Lower Tertiary E<sub>1-2</sub>km and sandstone ofLower Cretaceous K<sub>1</sub>b. The main component of natural gasis methane whose content is higher than 97%. It is charac-terized by dry gas whose source rock is Jurassic coal meas-ure. The Kela-2 structural trap was formed during the Xiyuperiod and then became a reservoir in the late time. The res-ervoir formed late and the thick seal rock of Lower Tertiarygipsmantle are the avail reason why the giant Kela-2 gasfield has been well kept. The abnormal high pressure of theKela-2 gas field results from the strong structural compres-sion in the northern part during the Xiyu period.
