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.

The DArk Matter Particle Explorer (DAMPE), one of the four scientific space science missions within the framework of the Strategic Pioneer Program on Space Science of the Chinese Academy of Sciences, is a general purpose high energy cosmic-ray and gamma-ray observatory, which was successfully launched on December 17th, 2015 from the Jiuquan Satellite Launch Center. The DAMPE scientific objectives include the study of galactic cosmic rays up to $\sim 10$ TeV and hundreds of TeV for electrons/gammas and nuclei respectively, and the search for dark matter signatures in their spectra. In this paper we illustrate the layout of the DAMPE instrument, and discuss the results of beam tests and calibrations performed on ground. Finally we present the expected performance in space and give an overview of the mission key scientific goals.Comment: 45 pages, including 29 figures and 6 tables. Published in Astropart. Phy

A novel pH sensitive shape‐memory polymer (SMP) is prepared by cross‐linking the β‐cyclodextrin modified alginate (β‐CD‐Alg) and diethylenetriamine modified alginate (DETA‐Alg): The pH reversible β‐CD‐DETA inclusion complexes serve as a reversible phase, and the cross‐linked alginate chains serve as a fixing phase. It is shown that this material can be processed into temporary shape as we needs at pH 11.5 and recover to its initial shape at pH 7. The recovery ratio and the fixity ratio were 95.7 ± 0.9% and 94.8 ± 1.1%, respectively. Furthermore, this material showed good degradability and biocompatibility. Because the shape transition pH value is quite close to that of our body fluid and this pH triggered shape‐memory effect is convenient and safe to use, this material has a high potential for medical application.

The precise measurement of the spectrum of protons, the most abundant component of the cosmic radiation, is necessary to understand the source and acceleration of cosmic rays in the Milky Way. This work reports the measurement of the cosmic ray proton fluxes with kinetic energies from 40 GeV to 100 TeV, with 2 1 / 2 years of data recorded by the DArk Matter Particle Explorer (DAMPE). This is the first time that an experiment directly measures the cosmic ray protons up to~100 TeV with high statistics. The measured spectrum confirms the spectral hardening at~300 GeV found by previous experiments and reveals a softening at~13.6 TeV, with the spectral index changing from~2.60 to~2.85. Our result suggests the existence of a new spectral feature of cosmic rays at energies lower than the so-called knee and sheds new light on the origin of Galactic cosmic rays.

AlF 3 -coated Li͓Li 0.2 Mn 0.54 Ni 0.13 Co 0.13 ͔O 2 materials have been synthesized as positive electrode materials for lithium-ion batteries. The pristine and AlF 3 -coated Li͓Li 0.2 Mn 0.54 Ni 0.13 Co 0.13 ͔O 2 materials were characterized by X-ray diffraction, scanning electron microscopy, differential scanning calorimetry, and charge-discharge techniques. The electrochemical studies indicated that the AlF 3 -coated Li͓Li 0.2 Mn 0.54 Ni 0.13 Co 0.13 ͔O 2 showed initial irreversible capacity loss of only 47 mA h/g compared to 75.5 mA h/g for pristine material. Meanwhile, the coated material also exhibited better rate capability and cyclic performance, which has higher capacity retention of 87.9% after 80 cycles at 0.5 C rate at room temperature in comparison with only 67.8% for the pristine one. The functional mechanism of AlF 3 coating on the performance of Li͓Li 0.2 Ni 0.13 Mn 0.54 Co 0.13 ͔O 2 was also investigated by electrochemical impedance spectroscopy ͑EIS͒ and in situ differential electrochemical mass spectrometry ͑DEMS͒. EIS analysis indicated that AlF 3 -coated Li͓Li 0.2 Mn 0.54 Ni 0.13 Co 0.13 ͔O 2 had stable charge transfer resistance ͑R ct ͒. In situ DEMS results revealed that the activity of extracted oxygen species from layered positive electrode material was greatly reduced and the decomposition of the electrolyte was significantly suppressed for AlF 3 -coated Li͓Li 0.2 Mn 0.54 Ni 0.13 Co 0.13 ͔O 2 . Therefore, more oxygen molecules rather than carbon dioxide were observed in the coated material system. It is demonstrated again that the AlF 3 coating layer played an important role in the stabilization of the electrode/electrolyte interface for the coated material.