Type 2 diabetes mellitus (T2DM) has become a prevalent health problem in China,especially in urban areas.Early prevention strategies are needed to reduce the associated mortality and morbidity.We applied the combinati...Type 2 diabetes mellitus (T2DM) has become a prevalent health problem in China,especially in urban areas.Early prevention strategies are needed to reduce the associated mortality and morbidity.We applied the combination of rules and different machine learning techniques to assess the risk of development of T2DM in an urban Chinese adult population.A retrospective analysis was performed on 8000 people with non-diabetes and 3845 people with T2DM in Nanjing.Multilayer Perceptron (MLP),AdaBoost (AD),Trees Random Forest (TRF),Support Vector Machine (SVM),and Gradient Tree Boosting (GTB) machine learning techniques with 10 cross validation methods were used with the proposed model for the prediction of the risk of development of T2DM.The performance of these models was evaluated with accuracy,precision,sensitivity,specificity,and area under receiver operating characteristic (ROC) curve (AUC).After comparison,the prediction accuracy of the different five machine models was 0.87,0.86,0.86,0.86 and 0.86 respectively.The combination model using the same voting weight of each component was built on T2DM,which was performed better than individual models.The findings indicate that,combining machine learning models could provide an accurate assessment model for T2DM risk prediction.展开更多
Although Type Ia supernovae (SNe Ia) play an important role in the study of cosmology, their progenitors are still poorly understood. Thermonuclear explosions from the helium double-detonation sub-Chandrasekhar mass...Although Type Ia supernovae (SNe Ia) play an important role in the study of cosmology, their progenitors are still poorly understood. Thermonuclear explosions from the helium double-detonation sub-Chandrasekhar mass model have been considered as an alternative method for producing SNe Ia. By adopting the assumption that a double detonation occurs when a He layer with a critical ignition mass accumulates on the surface of a carbon-oxygen white dwarf (CO WD), we perform detailed binary evolution calculations for the He double-detonation model, in which a He layer from a He star accumulates on a CO WD. According to these calculations, we obtain the initial parameter spaces for SNe Ia in the orbital period and secondary mass plane for various initial WD masses. We implement these results into a detailed binary population synthesis approach to calculate SN Ia birthrates and delay times. From this model, the SN Ia birthrate in our Galaxy is ~0.4 - 1.6 × 10^-3 yr^-1. This indicates that the double-detonation model only produces part of the SNe la. The delay times from this model are ~ 70 - 710 Myr, which contribute to the young population of SNe Ia in the observations. We found that the CO WD + sdB star system CD-30 11223 could produce an SN Ia via the double-detonation model in its future evolution.展开更多
Type Ia supernovae (SNe Ia) play an important role in studies of cosmology and galactic chemi- cal evolution. They are believed to be thermonuclear explosions of carbon-oxygen white dwarfs (CO WDs) when their mass...Type Ia supernovae (SNe Ia) play an important role in studies of cosmology and galactic chemi- cal evolution. They are believed to be thermonuclear explosions of carbon-oxygen white dwarfs (CO WDs) when their masses approach the Chandrasekar (Ch) mass limit. However, it is still not completely under- stood how a CO WD increases its mass to the Ch-mass limit in the classical single-degenerate (SD) model. In this paper, we studied the mass accretion process in the SD model to examine whether the WD can explode as an SN Ia. Employing the stellar evolution code called modules for experiments in stellar as- trophysics (MESA), we simulated the He accretion process onto CO WDs. We found that the WD can increase its mass to the Ch-mass limit through the SD model and explosive carbon ignition finally occurs in its center, which will lead to an SN Ia explosion. Our results imply that SNe Ia can be produced from the SD model through steady helium accretion. Moreover, this work can provide initial input parameters for explosion models of SNe Ia.展开更多
The core-degenerate (CD) scenario has been suggested to be a possible progenitor model of type Ia supernovae (SNe Ia), in which a carbon-oxygen white dwarf merges with the hot CO core of a massive asymptotic giant...The core-degenerate (CD) scenario has been suggested to be a possible progenitor model of type Ia supernovae (SNe Ia), in which a carbon-oxygen white dwarf merges with the hot CO core of a massive asymptotic giant branch star dur- ing their common-envelope phase. However, the SN Ia birthrates for this scenario are still uncertain. We conducted a detailed investigation into the CD scenario and then gave the birthrates for this scenario using a detailed Monte Carlo binary pop- ulation synthesis approach. We found that the delay times of SNe Ia from this sce- nario are -70 Myr- 1400 Myr, which means that the CD scenario contributes to young SN Ia populations. The Galactic SN Ia birthrates for this scenario are in the range of ~7.4×10^-5 yr^-1- 3.7 × 10^-4 yr^-1, which roughly accounts for -2%-10% of all SNe Ia. This indicates that, under the assumptions made here, the CD scenario only contributes a small portion of all SNe Ia, which is not consistent with the results of Ilkov & Soker.展开更多
HD 49798(a hydrogen depleted subdwarf O6 star) with its massive white dwarf(WD) companion has been suggested to be a progenitor candidate of a type Ia supernova(SN Ia). However, it is still uncertain whether the...HD 49798(a hydrogen depleted subdwarf O6 star) with its massive white dwarf(WD) companion has been suggested to be a progenitor candidate of a type Ia supernova(SN Ia). However, it is still uncertain whether the companion of HD 49798 is a carbon-oxygen(CO) WD or an oxygen-neon(ONe) WD. A CO WD will explode as an SN Ia when its mass grows and approaches the Chandrasekhar limit, but the outcome of an accreting ONe WD is likely to be a neutron star. We generated a series of Monte Carlo calculations that incorperate binary population synthesis to simulate the formation of ONe WD + He star systems. We found that there is almost no orbital period as large as HD 49798 with its WD companion in these ONe WD + He star systems based on our simulations, which means that the companion of HD 49798 might not be an ONe WD. We suggest that the companion of HD 49798 is most likely a CO WD, which can be expected to increase its mass to the Chandrasekhar limit by accreting He-rich material from HD 49798. Thus, HD 49798 and its companion may produce an SN Ia as a result of its future evolution.展开更多
基金This work was supported by grants from the National Natural Science Foundation of China (No.81570737, No.81370947, No.81570736, No.81770819, No.81500612, No.81400832, No.81600637, No.81600632, and No.81703294)the National Key Research and Development Program of China (No.2016YFC1304804 and No.2017YFC1309605)+4 种基金the Jiangsu Provincial Key Medical Discipline (No.ZDXKB2016012)the Key Project of Nanjing Clinical Medical Sciencethe Key Research and Development Program of Jiangsu Province of China (No.BE2015604 and No.BE2016606)the Jiangsu Provincial Medical Talent (No.ZDRCA2016062)the Nanjing Science and Technology Development Project (No.201605019).
文摘Type 2 diabetes mellitus (T2DM) has become a prevalent health problem in China,especially in urban areas.Early prevention strategies are needed to reduce the associated mortality and morbidity.We applied the combination of rules and different machine learning techniques to assess the risk of development of T2DM in an urban Chinese adult population.A retrospective analysis was performed on 8000 people with non-diabetes and 3845 people with T2DM in Nanjing.Multilayer Perceptron (MLP),AdaBoost (AD),Trees Random Forest (TRF),Support Vector Machine (SVM),and Gradient Tree Boosting (GTB) machine learning techniques with 10 cross validation methods were used with the proposed model for the prediction of the risk of development of T2DM.The performance of these models was evaluated with accuracy,precision,sensitivity,specificity,and area under receiver operating characteristic (ROC) curve (AUC).After comparison,the prediction accuracy of the different five machine models was 0.87,0.86,0.86,0.86 and 0.86 respectively.The combination model using the same voting weight of each component was built on T2DM,which was performed better than individual models.The findings indicate that,combining machine learning models could provide an accurate assessment model for T2DM risk prediction.
基金Supported by the National Natural Science Foundation of China
文摘Although Type Ia supernovae (SNe Ia) play an important role in the study of cosmology, their progenitors are still poorly understood. Thermonuclear explosions from the helium double-detonation sub-Chandrasekhar mass model have been considered as an alternative method for producing SNe Ia. By adopting the assumption that a double detonation occurs when a He layer with a critical ignition mass accumulates on the surface of a carbon-oxygen white dwarf (CO WD), we perform detailed binary evolution calculations for the He double-detonation model, in which a He layer from a He star accumulates on a CO WD. According to these calculations, we obtain the initial parameter spaces for SNe Ia in the orbital period and secondary mass plane for various initial WD masses. We implement these results into a detailed binary population synthesis approach to calculate SN Ia birthrates and delay times. From this model, the SN Ia birthrate in our Galaxy is ~0.4 - 1.6 × 10^-3 yr^-1. This indicates that the double-detonation model only produces part of the SNe la. The delay times from this model are ~ 70 - 710 Myr, which contribute to the young population of SNe Ia in the observations. We found that the CO WD + sdB star system CD-30 11223 could produce an SN Ia via the double-detonation model in its future evolution.
基金supported by the National Basic Research Program of China(973 program,2014CB845700)the National Natural Science Foundation of China(Nos.11322327,11390374,11521303 and 61561053)+2 种基金the Chinese Academy of Sciences(Nos.KJZD-EW-M06-01 and XDB09010202)the Natural Science Foundation of Yunnan Province(Nos.2013HB097 and 2013FB083)the Youth Innovation Promotion Association,CAS
文摘Type Ia supernovae (SNe Ia) play an important role in studies of cosmology and galactic chemi- cal evolution. They are believed to be thermonuclear explosions of carbon-oxygen white dwarfs (CO WDs) when their masses approach the Chandrasekar (Ch) mass limit. However, it is still not completely under- stood how a CO WD increases its mass to the Ch-mass limit in the classical single-degenerate (SD) model. In this paper, we studied the mass accretion process in the SD model to examine whether the WD can explode as an SN Ia. Employing the stellar evolution code called modules for experiments in stellar as- trophysics (MESA), we simulated the He accretion process onto CO WDs. We found that the WD can increase its mass to the Ch-mass limit through the SD model and explosive carbon ignition finally occurs in its center, which will lead to an SN Ia explosion. Our results imply that SNe Ia can be produced from the SD model through steady helium accretion. Moreover, this work can provide initial input parameters for explosion models of SNe Ia.
基金supported by the National Basic Research Program of China(973 program,2014CB845700)the National Natural Science Foundation of China(Grant Nos.11322327,11390371,11473063,11033008 and 61561053)+2 种基金the Foundation of State Ethnic Affairs Commission(Grant No.12YNZ008)the Science Foundation of Key Laboratory in Software Engineering(Grant No.2012SE402)the Natural Science Foundation of Yunnan Province(Grant Nos.2013FB083 and 2013HB097)
文摘The core-degenerate (CD) scenario has been suggested to be a possible progenitor model of type Ia supernovae (SNe Ia), in which a carbon-oxygen white dwarf merges with the hot CO core of a massive asymptotic giant branch star dur- ing their common-envelope phase. However, the SN Ia birthrates for this scenario are still uncertain. We conducted a detailed investigation into the CD scenario and then gave the birthrates for this scenario using a detailed Monte Carlo binary pop- ulation synthesis approach. We found that the delay times of SNe Ia from this sce- nario are -70 Myr- 1400 Myr, which means that the CD scenario contributes to young SN Ia populations. The Galactic SN Ia birthrates for this scenario are in the range of ~7.4×10^-5 yr^-1- 3.7 × 10^-4 yr^-1, which roughly accounts for -2%-10% of all SNe Ia. This indicates that, under the assumptions made here, the CD scenario only contributes a small portion of all SNe Ia, which is not consistent with the results of Ilkov & Soker.
基金supported by the National Basic Research Program of China (973 program, 2014CB845700)the National Natural Science Foundation of China (Grant Nos. 11322327, 11390374 and 61561053)the Natural Science Foundation of Yunnan Province (Grant Nos. 2013FB083 and 2013HB097)
文摘HD 49798(a hydrogen depleted subdwarf O6 star) with its massive white dwarf(WD) companion has been suggested to be a progenitor candidate of a type Ia supernova(SN Ia). However, it is still uncertain whether the companion of HD 49798 is a carbon-oxygen(CO) WD or an oxygen-neon(ONe) WD. A CO WD will explode as an SN Ia when its mass grows and approaches the Chandrasekhar limit, but the outcome of an accreting ONe WD is likely to be a neutron star. We generated a series of Monte Carlo calculations that incorperate binary population synthesis to simulate the formation of ONe WD + He star systems. We found that there is almost no orbital period as large as HD 49798 with its WD companion in these ONe WD + He star systems based on our simulations, which means that the companion of HD 49798 might not be an ONe WD. We suggest that the companion of HD 49798 is most likely a CO WD, which can be expected to increase its mass to the Chandrasekhar limit by accreting He-rich material from HD 49798. Thus, HD 49798 and its companion may produce an SN Ia as a result of its future evolution.