中国科学院机构知识库网格系统: 检索

Application of the rapid leaf A-Ci response (RACiR) technique: examples from evergreen broadleaved species 期刊论文 OAI收割
PHOTOSYNTHESIS RESEARCH, 2023, 卷号: 155, 期号: 2, 页码: 139-146
作者: Lin, Quanhong; Tian, Di; Zhao, Changti; Wang, Bin; Yan, Zhengbing

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Rapid A-C-i response (RACiR) Steady-state A-C-i CO2 response V-cmax J(max) RuBisCO Photosynthesis

Tabernaesine J, a Novel Vincamine-Type Indole Alkaloid with 6/5/6/6/6/5/5 Heptacyclic-Ring System Scaffold from Tabernaemontana pachysiphon 期刊论文 OAI收割
CHINESE JOURNAL OF CHEMISTRY, 2022, 卷号: 40, 期号: 4, 页码: 475-479
作者: Yi,Wen-Fang; Adelakun,Tiwalade A.; Bai,Xue; Zhang,Yu; Hao,Xiao-Jiang

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Natural products Alkaloids Structure elucidation Tabernaemontana pachysiphon Tabernaesine J BISINDOLE ALKALOIDS A-I ALGORITHM

Gevrey genericity of Arnold diffusion in a priori unstable Hamiltonian systems 期刊论文 OAI收割
Nonlinearity, 2021, 卷号: 34, 期号: 1
作者: Chen,Qinbo; Cheng,Chong-Qing

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收藏 | 浏览/下载：12/0 | 提交时间：2021/04/26

Arnold diffusion genericity Gevrey functions a priori unstable primary 37J40 37J50

High-content screening of diterpenoids from Isodon species as autophagy modulators and the functional study of their antiviral activities 期刊论文 OAI收割
CELL BIOLOGY AND TOXICOLOGY, 2021, 卷号: 37, 期号: 5, 页码: 695-713
作者: Huang,Lihong; Fu,Qiang; Dai,Jia-Meng; Yan,Bing-Chao; Wang,Dawei

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Diterpenoids Autophagy Lysosome Autophagosome Enanderinanin J Dengue virus (DENV) Zika virus (ZIKV) Japanese encephalitis virus (JEV) Enterovirus-A71 (EV-A71)

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

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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

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2008 1471 Astrophysics - High Energy Astrophysical Phenomena Abstract: We performed a systematic search for X-ray bursts of the SGR J1935+2154 using the Fermi Gamma-ray Burst Monitor continuous data dated from 2013 January to 2021 October. Eight bursting phases, which consist of a total of 353 individual bursts, are identified. We further analyze the periodic properties of our sample using the Lomb-Scargle periodogram. The result suggests that those bursts exhibit a period of ~238 days with a ~63.2% duty cycle. Based on our analysis, we further predict two upcoming active windows of the X-ray bursts. Since 2021 July, the beginning date of our first prediction has been confirmed by the ongoing X-ray activities of the SGR J1935+2154.

Ten picrotoxane-type sesquiterpenoids from the stems of Dendrobium wardianum Warner 期刊论文 OAI收割
PHYTOCHEMISTRY, 2021, 卷号: 190, 页码: 112858
作者: Fan,Wei-Wei; Yang,Dan; Cheng,Zhong-Quan; Xu,Feng-Qing; Dong,Fa-Wu

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Dendrobium wardianum Orchidaceae Picrotoxane-type sesquiterpenoid Dendrowardins A-J

Insight-HXMT observations of Swift J0243.6+6124: the evolution of RMS pulse fractions at super-Eddington luminosity 期刊论文 OAI收割
Monthly Notices of the Royal Astronomical Society, 2020, 卷号: 497, 页码: 5498-5506
作者: HXMT

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stars: neutron pulsars: individual: Swift J0243.6+6124 X-rays: binaries Astrophysics - High Energy Astrophysical Phenomena Abstract: Based on Insight-HXMT data, we report on the pulse fraction evolution during the 2017-2018 outburst of the newly discovered first Galactic ultraluminous X-ray (ULX) source Swift J0243.6+6124. The pulse fractions of 19 observation pairs selected in the rising and fading phases with similar luminosity are investigated. The results show a general trend of the pulse fraction increasing with luminosity and energy at supercritical luminosity. However, the relative strength of the pulsation between each pair evolves strongly with luminosity. The pulse fraction in the rising phase is larger at luminosity below 7.71 × 10³⁸ erg s^-1, but smaller at above. A transition luminosity is found to be energy independent. Such a phenomenon is first confirmed by Insight-HXMT observations and we speculate that it may have relation with the radiation-pressure-dominated accretion disc.

Constraining the X-Ray-Infrared Spectral Index of Second-timescale Flares from SGR 1935+2154 with Palomar Gattini-IR 期刊论文 OAI收割
The Astrophysical Journal, 2020, 卷号: 901, 页码: L7
作者: HXMT

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Radio transient sources Magnetars Soft gamma-ray repeaters 2008 992 1471 Astrophysics - High Energy Astrophysical Phenomena Astrophysics - Instrumentation and Methods for Astrophysics Abstract: The Galactic magnetar SGR 1935+2154 has been reported to produce the first example of a bright millisecond-duration radio burst (FRB 200428) similar to the cosmological population of fast radio bursts (FRBs). The detection of a coincident bright X-ray burst represents the first observed multiwavelength counterpart of an FRB. However, the search for similar emission at optical wavelengths has been hampered by the high inferred extinction on the line of sight. Here, we present results from the first search for second-timescale emission from the source at near-infrared (NIR) wavelengths using the Palomar Gattini-IR observing system in the J band, enabled by a novel detector readout mode that allows short exposure times of ?0.84 s with 99.9% observing efficiency. With a total observing time of ?12 hr (?47,728 images) during its 2020 outburst, we place median 3Ҡlimits on the second-timescale NIR fluence of ?18 Jy ms (13.1 AB mag). The corresponding extinction-corrected limit is ?125 Jy ms for an estimated extinction of A_J = 2.0 mag. Our observations were sensitive enough to easily detect an NIR counterpart of FRB 200428 if the NIR emission falls on the same power law as observed across its radio to X-ray spectrum. We report nondetection limits from epochs of four simultaneous X-ray bursts detected by the Insight-HXMT and NuSTAR telescopes during our observations. These limits provide the most stringent constraints to date on fluence of flares at 10¹⁴ Hz, and constrain the fluence ratio of the NIR emission to coincident X-ray bursts to R_NIR ? 0.025 (fluence index ?0.35).

An underlying clock in the extreme flip-flop state transitions of the black hole transient Swift J1658.2-4242 期刊论文 OAI收割
Astronomy and Astrophysics, 2020, 卷号: 641, 页码: A101
作者: HXMT

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accretion accretion disks black hole physics X-rays: binaries time Astrophysics - High Energy Astrophysical Phenomena Abstract:
Aims: Flip-flops are top-hat-like X-ray flux variations, which have been observed in some transient accreting black hole binary systems, and feature simultaneous changes in the spectral hardness and the power density spectrum (PDS). They occur at a crucial time in the evolution of these systems, when the accretion disc emission starts to dominate over coronal emission. Flip-flops remain a poorly understood phenomenon, so we aim to thoroughly investigate them in a system featuring several such transitions.
Methods: Within the multitude of observations of Swift J1658.2-4242 during its outburst in early 2018, we detected 15 flip-flops, enabling a detailed analysis of their individual properties and the differences between them. We present observations by XMM-Newton, NuSTAR, Astrosat, Swift, Insight-HXMT, INTEGRAL, and ATCA. We analysed their light curves, searched for periodicities, computed their PDSs, and fitted their X-ray spectra, to investigate the source behaviour during flip-flop transitions and how the interval featuring flip-flops differs from the rest of the outburst.
Results: The flip-flops of Swift J1658.2-4242 are of an extreme variety, exhibiting flux differences of up to 77% within 100 s, which is much larger than what has been seen previously. We observed radical changes in the PDS simultaneous with the sharp flux variations, featuring transitions between the quasi-periodic oscillation types C and A, which have never been observed before. Changes in the PDS are delayed, but more rapid than changes in the light curve. Flip-flops occur in two intervals within the outburst, separated by about two weeks in which these phenomena were not seen. Transitions between the two flip-flop states occurred at random integer multiples of a fundamental period of 2.761 ks in the first interval and 2.61 ks in the second. Spectral analysis reveals the high and low flux flip-flop states to be very similar, but distinct from intervals lacking flip-flops. A change of the inner temperature of the accretion disc is responsible for most of the flux difference in the flip-flops. We also highlight the importance of correcting for the influence of the dust scattering halo on the X-ray spectra.