Previous studies have demonstrated the protective effect of hypoxic preconditioning on acute cerebral infarction, but the mechanisms underlying this protection remain unclear. To investigate the protective mechanisms ...Previous studies have demonstrated the protective effect of hypoxic preconditioning on acute cerebral infarction, but the mechanisms underlying this protection remain unclear. To investigate the protective mechanisms of hypoxic preconditioning in relation to its effects on angiogenesis, we in- duced a photochemical model of cerebral infarction in an inbred line of mice （BALB/c）. Mice were then exposed to hypoxic preconditioning 30 minutes prior to model establishment. Results showed significantly increased vascular endothelial growth factor and CD31 expression in the ischemic penumbra at 24 and 72 hours post infarction, mainly in neurons and vascular endothelial cells. Hypoxic preconditioning increased vascular endothelial growth factor and CD31 expression in the ischemic penumbra and the expression of vascular endothelial growth factor was positively related to that of CD31. Moreover, hypoxic preconditioning reduced the infarct volume and improved neu- rological function in mice. These findings indicate that the protective role of hypoxic preconditioning in acute cerebral infarction may possibly be due to an increase in expression of vascular endothelial growth factor and CD31 in the ischemic penumbra, which promoted angiogenesis.展开更多
Chip-scale integration of optical frequency combs,particularly soliton microcombs,enables miniaturized instrumentation for timekeeping,ranging,and spectroscopy.Although soliton microcombs have been demonstrated on var...Chip-scale integration of optical frequency combs,particularly soliton microcombs,enables miniaturized instrumentation for timekeeping,ranging,and spectroscopy.Although soliton microcombs have been demonstrated on various material platforms,realizing complete comb functionality on photonic chips requires the co-integration of highspeed modulators and efficient frequency doublers,features that are available in a monolithic form on X-cut thin-film lithium niobate(TFLN).However,the pronounced Raman nonlinearity associated with extraordinary light in this platform has so far precluded soliton microcomb generation.Here,we report the generation of transverse-electric-polarized soliton microcombs with a 25 GHz repetition rate in high-Q microresonators on X-cut TFLN chips.By precisely orienting the racetrack microresonator relative to the optical axis,we mitigate Raman nonlinearity and enable soliton formation under continuous-wave laser pumping.Moreover,the soliton microcomb spectra are extended to 350 nm with pulsed laser pumping.This work expands the capabilities of TFLN photonics and paves the way for the monolithic integration of fast-tunable,self-referenced microcombs.展开更多
基金supported by the National Natural Science Foundation of China,No.30870854the Natural Science Foundation of Beijing,No.7111003the Natural Science Foundation of Shandong Province,No.ZR2010HM029
文摘Previous studies have demonstrated the protective effect of hypoxic preconditioning on acute cerebral infarction, but the mechanisms underlying this protection remain unclear. To investigate the protective mechanisms of hypoxic preconditioning in relation to its effects on angiogenesis, we in- duced a photochemical model of cerebral infarction in an inbred line of mice （BALB/c）. Mice were then exposed to hypoxic preconditioning 30 minutes prior to model establishment. Results showed significantly increased vascular endothelial growth factor and CD31 expression in the ischemic penumbra at 24 and 72 hours post infarction, mainly in neurons and vascular endothelial cells. Hypoxic preconditioning increased vascular endothelial growth factor and CD31 expression in the ischemic penumbra and the expression of vascular endothelial growth factor was positively related to that of CD31. Moreover, hypoxic preconditioning reduced the infarct volume and improved neu- rological function in mice. These findings indicate that the protective role of hypoxic preconditioning in acute cerebral infarction may possibly be due to an increase in expression of vascular endothelial growth factor and CD31 in the ischemic penumbra, which promoted angiogenesis.
基金supported by Beijing Natural Science Foundation(Z210004)National Key R&D Plan of China(Grant No.2021ZD0301500)+2 种基金National Natural Science Foundation of China(92150108,12293050,12304412)the highperformance computing Platform of Peking Universitythe Advanced Photonic Integrated Center(APIC)of State Key Laboratory of Advanced Optical Communication System and Networks.
文摘Chip-scale integration of optical frequency combs,particularly soliton microcombs,enables miniaturized instrumentation for timekeeping,ranging,and spectroscopy.Although soliton microcombs have been demonstrated on various material platforms,realizing complete comb functionality on photonic chips requires the co-integration of highspeed modulators and efficient frequency doublers,features that are available in a monolithic form on X-cut thin-film lithium niobate(TFLN).However,the pronounced Raman nonlinearity associated with extraordinary light in this platform has so far precluded soliton microcomb generation.Here,we report the generation of transverse-electric-polarized soliton microcombs with a 25 GHz repetition rate in high-Q microresonators on X-cut TFLN chips.By precisely orienting the racetrack microresonator relative to the optical axis,we mitigate Raman nonlinearity and enable soliton formation under continuous-wave laser pumping.Moreover,the soliton microcomb spectra are extended to 350 nm with pulsed laser pumping.This work expands the capabilities of TFLN photonics and paves the way for the monolithic integration of fast-tunable,self-referenced microcombs.
