As a typical plasma-based optical element that can sustain ultra-high light intensity,plasma density gratings driven by intense laser pulses have been extensively studied for wide applications.Here,we show that the pl...As a typical plasma-based optical element that can sustain ultra-high light intensity,plasma density gratings driven by intense laser pulses have been extensively studied for wide applications.Here,we show that the plasma density grating driven by two intersecting driver laser pulses is not only nonuniform in space but also varies over time.Consequently,the probe laser pulse that passes through such a dynamic plasma density grating will be depolarized,that is,its polarization becomes spatially and temporally variable.More importantly,the laser depolarization may spontaneously take place for crossed laser beams if their polarization angles are arranged properly.The laser depolarization by a dynamic plasma density grating may find application in mitigating parametric instabilities in laser-driven inertial confinement fusion.展开更多
Introduction The main physical objective of the GECAM satellite is to detect gamma-ray bursts,which is related to gravitational waves of double compact object mergers.The GECAM satellite also detects and investigates ...Introduction The main physical objective of the GECAM satellite is to detect gamma-ray bursts,which is related to gravitational waves of double compact object mergers.The GECAM satellite also detects and investigates various bursts of high-energy celestial bodies.Purposes and methods In this study,we designed,developed and calibrated the payload and launched it into orbit with GECAM satellite.The payload consists of the gamma ray detector(GRD,for detecting 4 keV–4 MeV X/γray),the charged particle detector(CPD,for detecting 150 keV–5 MeV charged particle),and the electronic box(EBOX).The all-sky field coverage is achieved via two 229-degree large-area satellites positioned 180 degrees apart and are on opposite sides of the geo-center.Each satellite is equipped with 25 GRDs and 8 CPDs;thus,the satellite can identify charged particle bursts in space.Gamma-ray detectors adopt lanthanum bromide crystal technology combined with silicon photomultipliers.This is the first time that this technology was used massively in space detectors.Conclusions The GECAM satellite can quickly determine the direction of gamma-ray bursts(positioning)via indexing and fitting method,while the transmit variability,energy spectrum and direction of the gamma-ray bursts guide subsequent observations through the Beidou-3 RDSS in quasi-real time.It will play an important role in the study of high energy celestial bursts.展开更多
To investigate the association of specific ultrasonography features identified during the diagnosis of early pregnancy loss(EPL)and abnormal karyotype.This was a systematic review and meta-analysis conducted in accord...To investigate the association of specific ultrasonography features identified during the diagnosis of early pregnancy loss(EPL)and abnormal karyotype.This was a systematic review and meta-analysis conducted in accordance with PRISMA criteria.We searched PubMed,Cochrane and Ovid MEDLINE from 1977 to Jan 2017 to identify the articles that described EPL with karyotype and ultrasonography features.Risk differences were pooled to estimate the chromosomal abnormality rates in ultrasonography features,including pre-embryonic,enlarged yolk sac(YS),short crown rump length(CRL),small gestational sac(GS),symmetrical arrested growth embryo,or gestational sac with only a YS.Quality assessment of included studies was performed using Strengthening the Reporting of Observational Studies in Epidemiology(STROBE)checklists for Observational Studies(2007 version).Thirteen studies were included in the meta-analysis.Chromosomal abnormality was more likely to occur in embryonic EPL and enlarged YS.On the other hand,short CRL,small GS,symmetrical arrested growth embryo,or gestational sac with only a YS,were not associated with an increased risk of fetal chromosomal abnormality.Ultrasonography features at the time of diagnosis of EPL have limited predictive value of fetal chromosomal abnormality.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.11975154,11991074,12005287 and 12135009)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant Nos.XDA25050100 and XDA25010100)+1 种基金the Presidential Foundation of the China Academy of Engineering Physics(Grant No.YZJJLX2016008)the Science Challenge Project(Grant No.TZ2018005).
文摘As a typical plasma-based optical element that can sustain ultra-high light intensity,plasma density gratings driven by intense laser pulses have been extensively studied for wide applications.Here,we show that the plasma density grating driven by two intersecting driver laser pulses is not only nonuniform in space but also varies over time.Consequently,the probe laser pulse that passes through such a dynamic plasma density grating will be depolarized,that is,its polarization becomes spatially and temporally variable.More importantly,the laser depolarization may spontaneously take place for crossed laser beams if their polarization angles are arranged properly.The laser depolarization by a dynamic plasma density grating may find application in mitigating parametric instabilities in laser-driven inertial confinement fusion.
基金This project is supported by National Natural Science Foundation of China(12173038)the strategic leading science and technology program(XDA 15360100,XDA 15360102)of the Chinese Academy of Sciences.
文摘Introduction The main physical objective of the GECAM satellite is to detect gamma-ray bursts,which is related to gravitational waves of double compact object mergers.The GECAM satellite also detects and investigates various bursts of high-energy celestial bodies.Purposes and methods In this study,we designed,developed and calibrated the payload and launched it into orbit with GECAM satellite.The payload consists of the gamma ray detector(GRD,for detecting 4 keV–4 MeV X/γray),the charged particle detector(CPD,for detecting 150 keV–5 MeV charged particle),and the electronic box(EBOX).The all-sky field coverage is achieved via two 229-degree large-area satellites positioned 180 degrees apart and are on opposite sides of the geo-center.Each satellite is equipped with 25 GRDs and 8 CPDs;thus,the satellite can identify charged particle bursts in space.Gamma-ray detectors adopt lanthanum bromide crystal technology combined with silicon photomultipliers.This is the first time that this technology was used massively in space detectors.Conclusions The GECAM satellite can quickly determine the direction of gamma-ray bursts(positioning)via indexing and fitting method,while the transmit variability,energy spectrum and direction of the gamma-ray bursts guide subsequent observations through the Beidou-3 RDSS in quasi-real time.It will play an important role in the study of high energy celestial bursts.
文摘To investigate the association of specific ultrasonography features identified during the diagnosis of early pregnancy loss(EPL)and abnormal karyotype.This was a systematic review and meta-analysis conducted in accordance with PRISMA criteria.We searched PubMed,Cochrane and Ovid MEDLINE from 1977 to Jan 2017 to identify the articles that described EPL with karyotype and ultrasonography features.Risk differences were pooled to estimate the chromosomal abnormality rates in ultrasonography features,including pre-embryonic,enlarged yolk sac(YS),short crown rump length(CRL),small gestational sac(GS),symmetrical arrested growth embryo,or gestational sac with only a YS.Quality assessment of included studies was performed using Strengthening the Reporting of Observational Studies in Epidemiology(STROBE)checklists for Observational Studies(2007 version).Thirteen studies were included in the meta-analysis.Chromosomal abnormality was more likely to occur in embryonic EPL and enlarged YS.On the other hand,short CRL,small GS,symmetrical arrested growth embryo,or gestational sac with only a YS,were not associated with an increased risk of fetal chromosomal abnormality.Ultrasonography features at the time of diagnosis of EPL have limited predictive value of fetal chromosomal abnormality.
