Two types of poleward moving plasma concentration enhancements (PMPCEs) were observed during a sequence of pulsed reconnection events, both in the morning convection cell: Type L (low density) was ...associated with a cusp flow channel and seems likely to have been produced by ionization associated with particle precipitation, while Type H (high density) appeared to originate from the segmentation of the tongue of ionization by the processes which produced the Type L events. As a result, the Type L and Type H PMPCEs were interspersed, producing a complex density structure which underlines the importance of cusp flow channels as a mechanism for segmenting and structuring electron density in the cusp and shows the necessity of differentiating between at least two classes of electron density patches.
Key Points
First observed TOI patches in the morning cell
Differentiating between at least two classes of electron density patches
TOI patches segmented by flow channels with precipitation electrons
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Glioma is a primary intracranial tumor with an unfavorable prognosis. Evolving evidence indicates that circular RNA Tau tubulin kinase 2 (circ-TTBK2) is a cancer-associated gene. Therefore, this ...study was to explore the potential role of circ-TTBK2.
Levels of circ-TTBK2, microRNA (miR)-761, and integrin subunit beta 8 (ITGB8) were determined by adopting quantitative real-time polymerase chain reaction (qRT-PCR) or Western blot. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was performed to detect cell viability, and the invaded cells were distinguished utilizing transwell assay. Iron and lipid reactive oxygen species (ROS) assays were implemented to examine the iron (total iron and ferrous iron) and lipid-based ROS in glioma cells, respectively. Besides, dual-luciferase reporter assay was administrated to illustrate the interaction between miR-761 and circ-TTBK2 or ITGB8. The role of circ-TTBK2 was identified via xenograft tumor model.
Levels of circ-TTBK2 and ITGB8 were upregulated, whereas miR-761 level was low-expressed in glioma tissues and cells. Circ-TTBK2 was a sponge of miR-761 to modulate ITGB8. Additionally, circ-TTBK2 knockdown or miR-761 increase could retard cell proliferation, invasion, and promote ferroptosis in glioma cells. Interestingly, miR-761 inhibitor could abolish the repressive impact of circ-TTBK2 silencing on cell growth in vitro. Also, the influence of miR-761 mimic on cell phenotypes was regained after ITGB8 upregulation. Meanwhile, circ-TTBK2 deficiency caused the decrease of tumor growth.
Circ-TTBK2 regulated cell proliferation, invasion and ferroptosis via targeting ITGB8 by sponging miR-761 in glioma, providing a promising biomarker for the clinical therapy of human glioma.
The event rate, energy distribution and time-domain behaviour of repeating fast radio bursts (FRBs) contain essential information regarding their physical nature and central engine, which are as yet ...unknown
. As the first precisely localized source, FRB 121102 (refs.
) has been extensively observed and shows non-Poisson clustering of bursts over time and a power-law energy distribution
. However, the extent of the energy distribution towards the fainter end was not known. Here we report the detection of 1,652 independent bursts with a peak burst rate of 122 h
, in 59.5 hours spanning 47 days. A peak in the isotropic equivalent energy distribution is found to be approximately 4.8 × 10
erg at 1.25 GHz, below which the detection of bursts is suppressed. The burst energy distribution is bimodal, and well characterized by a combination of a log-normal function and a generalized Cauchy function. The large number of bursts in hour-long spans allows sensitive periodicity searches between 1 ms and 1,000 s. The non-detection of any periodicity or quasi-periodicity poses challenges for models involving a single rotating compact object. The high burst rate also implies that FRBs must be generated with a high radiative efficiency, disfavouring emission mechanisms with large energy requirements or contrived triggering conditions.
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GEOZS, IJS, IMTLJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK, ZAGLJ
Gravitational‐wave high‐energy Electromagnetic Counterpart All‐sky Monitor (GECAM) is a space‐borne instrument dedicated to monitoring high‐energy transients, including Terrestrial Gamma‐ray Flashes ...(TGFs) and Terrestrial Electron Beams (TEBs). We implemented a TGF/TEB search algorithm for GECAM, with which 147 bright TGFs, 2 typical TEBs and 2 special TEB‐like events are identified during an effective observation time of ∼9 months. We show that, with gamma‐ray and charged particle detectors, GECAM can effectively identify and distinguish TGFs and TEBs, and measure their temporal and spectral properties in detail. A very high TGF‐lightning association rate of ∼80% is obtained between GECAM and GLD360 in east Asia region.
Plain Language Summary
Terrestrial gamma‐ray flashes (TGFs) and Terrestrial Electron Beams (TEBs) represent the most energetic radioactive phenomena in the atmosphere of the Earth. They reflect a natural particle accelerator that can boost electrons up to at least several tens of mega electron volts and produce gamma‐ray radiation. With novel detection technologies, Gravitational‐wave high‐energy Electromagnetic Counterpart All‐sky Monitor (GECAM) is a new powerful instrument to observe TGFs and TEBs, as well as study their properties. For example, it is difficult for most space‐borne high‐energy instruments to distinguish between TGFs and TEBs. However, we show here that, with the joint observation of gamma‐ray and charged particle detectors, GECAM can effectively identify TGFs and TEBs. GECAM can also reveal their fine features in the light curves and spectra.
Key Points
During 9‐month observation, Gravitational‐wave high‐energy Electromagnetic Counterpart All‐sky Monitor (GECAM) has detected 147 bright Terrestrial Gamma‐ray Flashes (TGFs), 2 typical Terrestrial Electron Beams (TEBs), and 2 special TEB‐like events
With novel detector design, GECAM can effectively classify TGFs and TEBs, and reveal their fine temporal features
We obtained a very high TGF‐lightning association rate (∼80%) between GECAM and GLD360 in east Asia region
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
The purpose of this review is to discuss the development and the state of the art in dynamic testing techniques and dynamic mechanical behaviour of rock materials. The review begins by briefly ...introducing the history of rock dynamics and explaining the significance of studying these issues. Loading techniques commonly used for both intermediate and high strain rate tests and measurement techniques for dynamic stress and deformation are critically assessed in Sects.
2
and
3
. In Sect.
4
, methods of dynamic testing and estimation to obtain stress–strain curves at high strain rate are summarized, followed by an in-depth description of various dynamic mechanical properties (e.g. uniaxial and triaxial compressive strength, tensile strength, shear strength and fracture toughness) and corresponding fracture behaviour. Some influencing rock structural features (i.e. microstructure, size and shape) and testing conditions (i.e. confining pressure, temperature and water saturation) are considered, ending with some popular semi-empirical rate-dependent equations for the enhancement of dynamic mechanical properties. Section
5
discusses physical mechanisms of strain rate effects. Section
6
describes phenomenological and mechanically based rate-dependent constitutive models established from the knowledge of the stress–strain behaviour and physical mechanisms. Section
7
presents dynamic fracture criteria for quasi-brittle materials. Finally, a brief summary and some aspects of prospective research are presented.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
We present a systematic temporal and spectral study of all Swift-X-ray Telescope observations of gamma-ray burst (GRB) afterglows discovered between 2005 January and 2007 December. After constructing ...and fitting all light curves and spectra to power-law models, we classify the components of each afterglow in terms of the canonical X-ray afterglow and test them against the closure relations of the forward shock models for a variety of parameter combinations. The closure relations are used to identify potential jet breaks with characteristics including the uniform jet model with and without lateral spreading and energy injection, and a power-law structured jet model, all with a range of parameters. With this technique, we survey the X-ray afterglows with strong evidence for jet breaks (~12% of our sample), and reveal cases of potential jet breaks that do not appear plainly from the light curve alone (another ~30%), leading to insight into the missing jet break problem. Those X-ray light curves that do not show breaks or have breaks that are not consistent with one of the jet models are explored to place limits on the times of unseen jet breaks. The distribution of jet break times ranges from a few hours to a few weeks with a median of ~1 day, similar to what was found pre-Swift. On average, Swift GRBs have lower isotropic equivalent gamma -ray energies, which in turn result in lower collimation corrected gamma -ray energies than those of pre-Swift GRBs. Finally, we explore the implications for GRB jet geometry and energetics.
We report an efficient inkjet printing of water-based pristine GNPs graphene ink and a facile aqueous halogen doping process that provides significant and thermally stable conductivity enhancement of ...printed patterns. Highly concentrated aqueous graphene ink populated by few-layer pristine graphene flakes is obtained by means of scalable shear exfoliation process with the aid of bromine intercalation. The as-printed GNP films which has been merely treated by drying at 100 °C exhibits DC conductivity (σDC) of ∼1400 S/m likely due to bromine doping effect. This value is significantly increased to ∼3 × 104 S/m when an additional treatment by means of dipping in aqueous iodine solution is applied prior to the drying. As contrast, σDC is increased to ∼2.4 × 104 S/m when a mere annealing at elevated temperature in air is employed. When the aqueous iodine doping process and annealing at elevated temperature is combined, an unprecedented value of σDC ∼105 S/m is achieved. The availability of water-based GNPs inks and low-temperature doping scheme for efficient and reliable conductivity enhancement has offered a pathway for the application of GNPs in different printed electronics devices.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
We present a detailed experimental procedure for the quantitative determination of mechanical properties and full-field strain measurement of rock material under dynamic loads. Three kinds of testing ...methods, i.e., notched semi-circular bending, Brazilian disc, and uniaxial compression, were conducted using a split Hopkinson pressure bar (SHPB) system. Experimental setup, data acquisition and interpretation were described in detail. The digital image correlation (DIC) technique in conjunction with high-speed (HS) photography was adopted for the measurement of surface deformation characteristics (e.g., strain localization and evolution, and onset of fracture) of rock specimens. To verify the accuracy of this technique, comparative tests were performed in which the strains in the specimens were simultaneously determined using on-specimen strain gauges. Strain gauges were also used to determine the time-to-fracture and crack propagation velocity. Specifically, the scanning electron microscope (SEM) imaging technique was used to investigate the brittle failure micromechanisms of white belt initiated and developed prior to observable cracks in specimens. Experimental results show that dynamic crack initiation toughness, dynamic tensile strength and dynamic uniaxial compressive strength can be well determined, and the HS-DIC technique provides reliable full-field strain fields in the specimens under dynamic loads.
► A detailed experimental procedure is presented for determining dynamic mechanical properties. ► The DIC technique in conjunction with high-speed camera provides full-field strain fields. ► Dynamic mechanical properties of the Fangshan marble increase with increasing strain rate. ► Failure mechanisms of strain rate are mostly induced by fracture mode transitions in the marble.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Recent observations with the Chandra X-ray telescope continue to detect X-ray emission from the transient GW170817. In a total exposure of 96.6 ks, performed between 2020 March 9 and 16 (935–942 d ...after the merger), a total of 8 photons are measured at the source position, corresponding to a significance of ≈5σ. Radio monitoring with the Australian Telescope Compact Array (ATCA) shows instead that the source has faded below our detection threshold (<33 μJy, 3σ). By assuming a constant spectral index of β = 0.585, we derive an unabsorbed X-ray flux of ≈1.4 × 10−15 erg cm−2 s−1, higher than earlier predictions, yet still consistent with a simple structured jet model. We discuss possible scenarios that could account for prolonged emission in X-rays. The current data set appears consistent both with energy injection by a long-lived central engine and with the onset of a kilonova afterglow, arising from the interaction of the sub-relativistic merger ejecta with the surrounding medium. Long-term monitoring of this source will be essential to test these different models.
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