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浏览/检索结果: 共402条，第1-10条 帮助

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Lower Devonian conodonts from the Xainza area, central Tibet and the Lower Devonian stage boundaries in China 期刊论文  OAI收割
PALAEOWORLD, 2024, 卷号: 33, 期号: 3, 页码: 584-597
作者:  Guo, Wen;  Song, Jun -Jun;  Lu, Jian-Feng;  Huang, Jia-Yuan;  Wang, Yu-Jue
  |  收藏  |  浏览/下载：131/0  |  提交时间：2024/08/28
Two anachoropterid fern rachises from the in situ volcanic ash of the Whetstone Horizon (Kladno Formation, Pennsylvanian), Radnice Basin, Czech 期刊论文  OAI收割
PALAEOWORLD, 2024, 卷号: 33, 期号: 2, 页码: 341-362
作者:  Zhou, Wei -Ming;  Psenicka, Josef;  Frojdova, Jana Votockova;  Wang, Jun;  Wan, Ming -Li
  |  收藏  |  浏览/下载：13/0  |  提交时间：2024/08/28
Low-Dose Ketamine-Induced Deficits in Arbitrary Visuomotor Mapping in Monkeys 期刊论文  OAI收割
ENEURO, 2023, 卷号: 10, 期号: 6, 页码: 13
作者:  Zhao, Zhi-Ping;  Nie, Chuang;  Jiang, Cheng-Teng;  Cao, Sheng-Hao;  Tian, Kai-Xi
  |  收藏  |  浏览/下载：25/0  |  提交时间：2023/12/21
A Dual Simple Recurrent Network Model for Chunking and Abstract Processes in Sequence Learning 期刊论文  OAI收割
FRONTIERS IN PSYCHOLOGY, 2021, 卷号: 12, 页码: 17
作者:  Wang, Lituan;  Feng, Yangqin;  Fu, Qiufang;  Wang, Jianyong;  Sun, Xunwei
  |  收藏  |  浏览/下载：44/0  |  提交时间：2021/06/09
Synchronous X-ray/Optical QPOs from the Black Hole LMXB MAXI J1820+070 期刊论文  OAI收割
Monthly Notices of the Royal Astronomical Society, 2021
作者:  HXMT
  |  收藏  |  浏览/下载：53/0  |  提交时间：2022/02/08
black hole physics  Low Mass X-ray Binaries  accretion  accretion  discs  stars: individual (MAXI J1820+070)  Astrophysics - High Energy  Astrophysical Phenomena  Abstract: We present high-speed optical photometry from SAAO and SALT on the black hole LMXB MAXI J1820+070 (ASSASN-18ey), some of it simultaneous with NICER, Swift and Insight-HXMT X-ray coverage. We detect optical Quasi-Periodic Oscillations (QPOs) that move to higher frequencies as the outburst progresses, tracking both the frequency and evolution of similar X-ray QPOs previously reported. Correlated X-ray/optical data reveal a complex pattern of lags, including an anti-correlation and a sub-second lag that evolve over the first few weeks of outburst. They also show correlated components separated by a lag equal to the QPO period roughly centered on zero lag, implying that the inter-band variability is strongly and consistently affected by these QPOs at a constant phase lag of roughly ±Ю The synchronisation of X-ray and optical QPOs indicates that they must be produced in regions physically very close to each other  we thus propose that they can be explained by a precessing jet model, based on analogies with V404 Cyg and MAXI J1348-630.  
Periodicity Search on X-Ray Bursts of SGR J1935+2154 Using 8.5 yr of Fermi/GBM Data 期刊论文  OAI收割
The Astrophysical Journal, 2021, 卷号: 923, 页码: L30
作者:  HXMT
  |  收藏  |  浏览/下载：22/0  |  提交时间：2022/02/08
On the Terrestrial Gamma Ray Flashes Preceding Narrow Bipolar Events 期刊论文  OAI收割
Geophysical Research Letters, 2021, 卷号: 48, 页码: e92160
作者:  HXMT
  |  收藏  |  浏览/下载：28/0  |  提交时间：2022/02/08
low frequency magnetic sferics  narrow bipolar events (NBEs)  relativistic feedback mechanism  Terrestrial Gamma ray Flashes (TGFs)  Abstract: Narrow bipolar events (NBEs) are occasionally reported to occur within a few ms after Terrestrial Gamma ray Flashes (TGFs), while the formation mechanism remains mysterious partially due to the lack of sufficient observations. Here, nine more TGFs of this scenario are reported with concurrent LF sferics and lightning location data. The gamma ray production in these TGFs preceded the occurrence of NBEs by a minimum of 60 µs up to 13.5 ms, and no other fast leader discharge was found within 20 ms before the TGF. The TGF preceded positive NBEs occurred at altitudes of 8.6-11 km in thunderstorms, likely in the high electric field (E field) region of lightning initiation. The analyses show that the NBE preceding TGFs bear harder energy spectrum with larger proportion of high energy photons than EIP related TGFs produced in association with lightning leader. Our findings support the relativistic feedback mechanism of gamma ray generation in the large scale thunderstorm E field.  
Detection of Flare Multiperiodic Pulsations in Mid-ultraviolet Balmer Continuum, Lyl Hard X-Ray, and Radio Emissions Simultaneously 期刊论文  OAI收割
The Astrophysical Journal, 2021, 卷号: 921, 页码: 179
作者:  HXMT
  |  收藏  |  浏览/下载：27/0  |  提交时间：2022/02/08
Solar flares  Solar oscillations  Solar ultraviolet emission  Solar  x-ray emission  Solar radio emission  1496  1515  1533  1536  1522  Astrophysics - Solar and Stellar Astrophysics  Abstract: Quasi-periodic pulsations (QPPs), which usually appear as temporal pulsations of the total flux, are frequently detected in the light curves of solar/stellar flares. In this study, we present the investigation of nonstationary QPPs with multiple periods during the impulsive phase of a powerful flare on 2017 September 6, which were simultaneously measured by the Hard X-ray Modulation Telescope (Insight-HXMT), as well as the ground-based BLENSW. The multiple periods, detected by applying a wavelet transform and Lomb-Scargle periodogram to the detrended light curves, are found to be ~20-55 s in the Ly`and mid-ultraviolet Balmer continuum emissions during the flare impulsive phase. Similar QPPs with multiple periods are also found in the hard X-ray emission and low-frequency radio emission. Our observations suggest that the flare QPPs could be related to nonthermal electrons accelerated by the repeated energy release process, i.e., triggering of repetitive magnetic reconnection, while the multiple periods might be modulated by the sausage oscillation of hot plasma loops. For the multiperiodic pulsations, other generation mechanisms could not be completely ruled out.  
GDAL/OGR and Geospatial Data IO Libraries 专著章节  OAI收割
出自: Geographic Information Science & Technology Body of Knowledge, Online:John P. Wilson, 2020
作者:  Qin, Cheng-Zhi;  Zhu, Liang-Jun
  |  收藏  |  浏览/下载：22/0  |  提交时间：2022/10/21
No pulsed radio emission during a bursting phase of a Galactic magnetar 期刊论文  OAI收割
Nature, 2020, 卷号: 587, 页码: 63-65
作者:  HXMT
  |  收藏  |  浏览/下载：44/0  |  提交时间：2022/02/08
Astrophysics - High Energy Astrophysical Phenomena  Abstract: Fast radio bursts (FRBs) are millisecond-duration radio transients of unknown physical origin observed at extragalactic distances1-3. It has long been speculated that magnetars are the engine powering repeating bursts from FRB sources4-13, but no convincing evidence has been collected so far14. Recently, the Galactic magnetar SRG 1935+2154 entered an active phase by emitting intense soft íray bursts15. One FRB-like event with two peaks (FRB 200428) and a luminosity slightly lower than the faintest extragalactic FRBs was detected from the source, in association with a soft íray/hard-X-ray flare18-21. Here we report an eight-hour targeted radio observational campaign comprising four sessions and assisted by multi-wavelength (optical and hard-X-ray) data. During the third session, 29 soft-íray repeater (SGR) bursts were detected in íray energies. Throughout the observing period, we detected no single dispersed pulsed emission coincident with the arrivals of SGR bursts, but unfortunately we were not observing when the FRB was detected. The non-detection places a fluence upper limit that is eight orders of magnitude lower than the fluence of FRB 200428. Our results suggest that FRB-SGR burst associations are rare. FRBs may be highly relativistic and geometrically beamed, or FRB-like events associated with SGR bursts may have narrow spectra and characteristic frequencies outside the observed band. It is also possible that the physical conditions required to achieve coherent radiation in SGR bursts are difficult to satisfy, and that only under extreme conditions could an FRB be associated with an SGR burst.