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Abstract 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.

High-temperature nanoindentation was used to reveal nano-layer size effects on the hardness of two-dimensional metallic nanocomposites. We report the existence of a critical layer thickness at which strength achieves optimal thermal stability. Transmission electron microscopy and theoretical bicrystal calculations show that this optimum arises due to a transition from thermally activated glide within the layers to dislocation transmission across the layers. We demonstrate experimentally that the atomic-scale properties of the interfaces profoundly affect this critical transition. The strong implications are that interfaces can be tuned to achieve an optimum in high temperature strength in layered nanocomposite structures.

Stainless steels are susceptible to the localized pitting corrosion that leads to a huge loss to our society. Studies in the past decades confirmed that the pitting events generally originate from the local dissolution in MnS inclusions which are more or less ubiquitous in stainless steels. Although a recent study indicated that endogenous MnCr2O4 nano-octahedra within the MnS medium give rise to local nano-galvanic cells which are responsible for the preferential dissolution of MnS, effective solutions of restraining the cells from viewpoint of electrochemistry are being tantalizingly searched. Here we report such a galvanic corrosion can be greatly resisted via bathing the steels in Cu2+-containing solutions. This chemical bath generates Cu2_δS layers on the surfaces of MnS inclusions, invalidating the nano-galvanic cells. Our study provides a low-cost approach via an atomic scale decoration to improve the pitting corrosion resistance of stainless steels in a volume-treated manner. [ABSTRACT FROM AUTHOR]

Callus induction and later plant regeneration were studied in four widely grown garlic (Allium sativum L.) cultivars from Europe. Root segments from in vitro plantlets were used as starting material. In addition to cultivar effects, the effects of auxin and cytokinin levels and the position of the segments on the root were studied. There were no statistically significant differences among cultivars for the number of root segments that induced callus in the two series of experiments. The average induction frequency was 34.7% in the first series of experiments. Callus induction on apical root segments was significantly higher compared to callus induction on non-apical root segments in the second series of experiments. Two months after callus induction, callus lines were transferred to a regeneration medium consisting of Murashige and Skoog basal medium supplemented with 30 g l-1 sucrose and 1 mg l-1 (4.6 μM) kinetin. Calluses derived from different experiments were quite uniform with respect to their regeneration potential. Also it was found that our regeneration system was cultivar-independent. The average shoot regeneration frequency was 17.9% in the first series of experiments. Highly significant differences were found in the frequency of shoot regeneration among different callus induction treatments. When the cytokinin 6-(γ,γ-dimethylallylamino)purine (0.1 mg l-1: 0.5 μM) was present during callus induction, shoot regeneration ranged from 30.10 to 47.60%. Shoot regeneration from callus induced on non-apical segments was higher, although not significant, compared to callus induction from apical root segments in the second series of experiments. All in all, an efficient callus induction and plant regeneration system was developed from both apical and non-apical segments taken along the entire length of the roots. This system has potential to be used for garlic transformation. [ABSTRACT FROM AUTHOR]

We studied the evolution of the X-ray and γ-ray spectra of the Crab pulsar utilizing the 11-year observations from the Rossi X-ray Timing Explorer (RXTE) and 9-year observations from the Fermi Gamma-ray Space Telescope (FGST). By fitting the spectrum of each observation, we obtained the corresponding flux and then analyzed the long-term evolution of the X-ray (or γ-ray) luminosities as well as their correlations with the spin-down power of the pulsar. The X-ray flux in 5–60 keV obtained by the Proportional Counter Array of RXTE decreases with a rate of (−2.4 ± 0.4) × 10−14 erg cm−2 s−1 per day. The X-ray flux in 15–250 keV obtained by the High Energy X-ray Timing Experiment of RXTE and the γ-ray flux in 0.1–300 GeV by the Large Area Telescope onboard FGST show similar decreasing trends but are insignificant statistically. The 5–60 keV X-ray luminosity LX is correlated with the spin-down power Lsd by , which is similar to the statistical results for young pulsars. [ABSTRACT FROM AUTHOR]

We study the X-ray phases of the Crab pulsar utilizing the 11-year observations from the Rossi X-ray Timing Explorer, 6-year radio observations from Nanshan Telescope, and the ephemeris from Jodrell Bank Observatory. It is found that the X-ray phases in different energy bands and the radio phases from the Nanshan Telescope show similar behaviors, including long-time evolution and short-time variations. Such strong correlations between the X-ray and radio phases imply that the radio and X-ray timing noises are both generated from the pulsar spin that cannot be well described by the the monthly ephemeris from the Jodrell Bank observatory. When using the Nanshan phases as references to study the X-ray timing noise, it has a significantly smaller variation amplitude and shows no long-time evolution, with a change rate of (−1.1 ± 1.1) × 10−7 periods per day. These results show that the distance of the X-ray and radio emission regions on the Crab pulsar has no detectable secular change, and it is unlikely that the timing noises resulted from any unique physical processes in the radio or X-ray emitting regions. The similar behaviors of the X-ray and radio timing noises also imply that the variation of the interstellar medium is not the origin of the Crab pulsar’s timing noises, which is consistent with the results obtained from the multi-frequency radio observations of PSR B1540−06. [ABSTRACT FROM AUTHOR]

Using the archival data from the Rossi X-ray Timing Explorer, we study the evolution of the Crab pulsar’s X-ray profile in a time span of 11 years. The X-ray profiles, as characterized by a few parameters, changed slightly, but with high statistical significance in these years: the separation of the two peaks increased with a rate of 0.°88 ± 0.°20 per century, the flux ratio of the second pulse to the first pulse decreased by per century, and the pulse widths of the two pulses represented by their full widths at half maxima decreased by and per century, respectively. The evolutionary trends of the X-ray profile are similar to that observed in radio, but with quantitative differences. Finally, we briefly discuss the constraints of these X-ray properties on the geometry of the emission region of this pulsar. [ABSTRACT FROM AUTHOR]

Thermal X-ray emission from young supernova remnants (SNRs) is usually dominated by the emission lines of the supernova ejecta, which are widely believed to be crossed and thus heated by the inward-propagating reverse shock (RS). Previous works using X-ray imaging data have shown that the ejecta are heated by the RS by locating the peak emission region of the most recently ionized matter, which is found to be well separated toward the inside from the outermost boundary. Here we report the discovery of a systematic increase of the Sulfur (S) to Silicon (Si) Kα line flux ratio with radius in Tycho’s SNR. This allows us, for the first time, to present continuous radial profiles of the ionization age and, furthermore, the elapsed ionization time since the onset of the ionization, which gives the history of the propagation of the ionization front into the SNR ejecta. [ABSTRACT FROM AUTHOR]