High-energy cosmic-ray electrons and positrons (CREs), which lose energy quickly during their propagation, provide a probe of Galactic high-energy processes and may enable the observation of phenomena such as dark-matter particle annihilation or decay. The CRE spectrum has been measured directly up to approximately 2 teraelectronvolts in previous balloon- or space-borne experiments, and indirectly up to approximately 5 teraelectronvolts using ground-based Cherenkov γ-ray telescope arrays. Evidence for a spectral break in the teraelectronvolt energy range has been provided by indirect measurements, although the results were qualified by sizeable systematic uncertainties. Here we report a direct measurement of CREs in the energy range 25 gigaelectronvolts to 4.6 teraelectronvolts by the Dark Matter Particle Explorer (DAMPE) with unprecedentedly high energy resolution and low background. The largest part of the spectrum can be well fitted by a 'smoothly broken power-law' model rather than a single power-law model. The direct detection of a spectral break at about 0.9 teraelectronvolts confirms the evidence found by previous indirect measurements, clarifies the behaviour of the CRE spectrum at energies above 1 teraelectronvolt and sheds light on the physical origin of the sub-teraelectronvolt CREs.
We cloned an AP2/EREBP gene by dot blotting and named it OsDREBL. Analysis of its deduced amino-acid sequence indicated that this protein had a potential nuclear-localization signal, a possible acidic-activation domain and an AP2 DNA binding domain. Northern analysis showed that the transcripts of OsDREBL accumulated rapidly (within 30 min) in response to low temperature, but not in response to ABA, NaCl and dehydration treatments. Southern analysis indicated the presence of a single-copy of the OsDREBL gene in the Oryza sativa genome. Our research also demonstrated that OsDREBL was localized to the nucleus but did not bind effectively to the C-repeat/dehydration responsive element (CRT/DRE). These results suggested that OsDREBL may function as a transcription factor in the cold-stress response, independent of the DREB signal-transduction pathway.
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