An observation operator is a bridge linking the system state vector and observations in a data assimilation system. Despite its importance, the degree to which an observation operator influences the performance of dat...An observation operator is a bridge linking the system state vector and observations in a data assimilation system. Despite its importance, the degree to which an observation operator influences the performance of data assimilation methods is still poorly understood. This study aimed to analyze the influences of linear and nonlinear observation operators on the sequential data assimilation through soil temperature simulation using the unscented particle filter(UPF) and the common land model. The linear observation operator between unprocessed simulations and observations was first established. To improve the correlation between simulations and observations, both were processed based on a series of equations. This processing essentially resulted in a nonlinear observation operator. The linear and nonlinear observation operators were then used along with the UPF in three assimilation experiments: an hourly in situ soil surface temperature assimilation, a daily in situ soil surface temperature assimilation, and a moderate resolution imaging spectroradiometer(MODIS) land surface temperature(LST) assimilation. The results show that the filter improved the soil temperature simulation significantly with the linear and nonlinear observation operators. The nonlinear observation operator improved the UPF's performance more significantly for the hourly and daily in situ observation assimilations than the linear observation operator did, while the situation was opposite for the MODIS LST assimilation. Because of the high assimilation frequency and data quality, the simulation accuracy was significantly improved in all soil layers for hourly in situ soil surface temperature assimilation, while the significant improvements of the simulation accuracy were limited to the lower soil layers for the assimilation experiments with low assimilation frequency or low data quality.展开更多
Administration of human umbilical cord-derived mesenchymal stem cells(hUC-MSCs)is believed to be an effective method for treating neurodevelopmental disorde rs.In this study,we investigated the possibility of hUC-MSCs...Administration of human umbilical cord-derived mesenchymal stem cells(hUC-MSCs)is believed to be an effective method for treating neurodevelopmental disorde rs.In this study,we investigated the possibility of hUC-MSCs treatment of neonatal hypoxic/ischemic brain injury associated with maternal immune activation and the underlying mechanism.We established neonatal rat models of hypoxic/ischemic brain injury by exposing pregnant rats to lipopolysaccharide on day 16 or 17 of pregnancy.Rat offspring were intranasally administe red hUC-MSCs on postnatal day 14.We found that polypyrimidine tract-binding protein-1(PTBP-1)participated in the regulation of lipopolysaccharide-induced maternal immune activation,which led to neonatal hypoxic/ischemic brain injury.Intranasal delive ry of hUC-MSCs inhibited PTBP-1 expression,alleviated neonatal brain injury-related inflammation,and regulated the number and function of glial fibrillary acidic protein-positive astrocytes,there by promoting plastic regeneration of neurons and im p roving brain function.These findings suggest that hUC-MSCs can effectively promote the repair of neonatal hypoxic/ischemic brain injury related to maternal immune activation through inhibition of PTBP-1 expression and astrocyte activation.展开更多
We investigate the spatially resolved specific star formation rate (SSFR) in the inner -40 pc for a nearby Seyfert 2 galaxy, M51 (NGC 5194) by analyzing spectra obtained with the Hubble Space Telescope (HST) Spa...We investigate the spatially resolved specific star formation rate (SSFR) in the inner -40 pc for a nearby Seyfert 2 galaxy, M51 (NGC 5194) by analyzing spectra obtained with the Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS). We present 24 radial spectra measured along the STIS long slit in M51, extending - 1" from the nucleus (i.e., -41.5 pc to 39.4 pc). By simple stellar population synthesis, the stellar contributions in these radial optical spectra are modeled. It is found that the mean flux fraction of young stellar populations (younger than 24.5 Myr) is about 9%. Excluding some regions with zero young flux fraction near the center (from -6 pc to 2 pc), the mean mass fraction is about 0.09%. The young stellar populations are not required in the center inner -8 pc in M51, suggesting a possible SSFR suppression in the circumnuclear region (- 10 pc) from the feedback of active galactic nuclei (AGNs). The radial distribution of SSFR in M51 is not symmetrical with respect to the long slit in STIS. This unsymmetrical SSFR distribution is possibly due to the unsymmetrical AGN feedback in M51, which is related to its jet.展开更多
基金supported by the National Key Research and Development Program of China(Grants No.2016YFC0402706 and 2016YFC0402710)the National Natural Science Foundation of China(Grants No.51709046 and41323001)the Open Foundation of the State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering,Hohai University(Grant No.2015490311)
文摘An observation operator is a bridge linking the system state vector and observations in a data assimilation system. Despite its importance, the degree to which an observation operator influences the performance of data assimilation methods is still poorly understood. This study aimed to analyze the influences of linear and nonlinear observation operators on the sequential data assimilation through soil temperature simulation using the unscented particle filter(UPF) and the common land model. The linear observation operator between unprocessed simulations and observations was first established. To improve the correlation between simulations and observations, both were processed based on a series of equations. This processing essentially resulted in a nonlinear observation operator. The linear and nonlinear observation operators were then used along with the UPF in three assimilation experiments: an hourly in situ soil surface temperature assimilation, a daily in situ soil surface temperature assimilation, and a moderate resolution imaging spectroradiometer(MODIS) land surface temperature(LST) assimilation. The results show that the filter improved the soil temperature simulation significantly with the linear and nonlinear observation operators. The nonlinear observation operator improved the UPF's performance more significantly for the hourly and daily in situ observation assimilations than the linear observation operator did, while the situation was opposite for the MODIS LST assimilation. Because of the high assimilation frequency and data quality, the simulation accuracy was significantly improved in all soil layers for hourly in situ soil surface temperature assimilation, while the significant improvements of the simulation accuracy were limited to the lower soil layers for the assimilation experiments with low assimilation frequency or low data quality.
基金the National Natural Science Foundation of China,No.81471308(to JL)Stem cell Clinical Research Registry Program,No.CMR-20161129-1003(to JL)+2 种基金Liaoning Province Excellent Talent Program Project of China,No.XLYC1902031(to JL)Dalian Innovation Fund of China,No.2018J11CY025(to JL)National Defense Science and Technology New Special Zone Contract,No.19-163-00-kx-003-001-01(to JL)。
文摘Administration of human umbilical cord-derived mesenchymal stem cells(hUC-MSCs)is believed to be an effective method for treating neurodevelopmental disorde rs.In this study,we investigated the possibility of hUC-MSCs treatment of neonatal hypoxic/ischemic brain injury associated with maternal immune activation and the underlying mechanism.We established neonatal rat models of hypoxic/ischemic brain injury by exposing pregnant rats to lipopolysaccharide on day 16 or 17 of pregnancy.Rat offspring were intranasally administe red hUC-MSCs on postnatal day 14.We found that polypyrimidine tract-binding protein-1(PTBP-1)participated in the regulation of lipopolysaccharide-induced maternal immune activation,which led to neonatal hypoxic/ischemic brain injury.Intranasal delive ry of hUC-MSCs inhibited PTBP-1 expression,alleviated neonatal brain injury-related inflammation,and regulated the number and function of glial fibrillary acidic protein-positive astrocytes,there by promoting plastic regeneration of neurons and im p roving brain function.These findings suggest that hUC-MSCs can effectively promote the repair of neonatal hypoxic/ischemic brain injury related to maternal immune activation through inhibition of PTBP-1 expression and astrocyte activation.
基金Supported by the National Natural Science Foundation of China
文摘We investigate the spatially resolved specific star formation rate (SSFR) in the inner -40 pc for a nearby Seyfert 2 galaxy, M51 (NGC 5194) by analyzing spectra obtained with the Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS). We present 24 radial spectra measured along the STIS long slit in M51, extending - 1" from the nucleus (i.e., -41.5 pc to 39.4 pc). By simple stellar population synthesis, the stellar contributions in these radial optical spectra are modeled. It is found that the mean flux fraction of young stellar populations (younger than 24.5 Myr) is about 9%. Excluding some regions with zero young flux fraction near the center (from -6 pc to 2 pc), the mean mass fraction is about 0.09%. The young stellar populations are not required in the center inner -8 pc in M51, suggesting a possible SSFR suppression in the circumnuclear region (- 10 pc) from the feedback of active galactic nuclei (AGNs). The radial distribution of SSFR in M51 is not symmetrical with respect to the long slit in STIS. This unsymmetrical SSFR distribution is possibly due to the unsymmetrical AGN feedback in M51, which is related to its jet.