Measurement of the Cosmic Ray Helium Energy Spectrum from 70 GeV to 80 TeV with the DAMPE Space Mission

The measurement of the energy spectrum of cosmic ray helium nuclei from 70 GeV to 80 TeV using 4.5 years of data recorded by the Dark Matter Particle Explorer (DAMPE) is reported in this work. A hardening of the spectrum is observed at an energy of about 1.3 TeV, similar to previous observations. In addition, a spectral softening at about 34 TeV is revealed for the first time with large statistics and well controlled systematic uncertainties, with an overall significance of 4.3σ. The DAMPE spectral measurements of both cosmic protons and helium nuclei suggest a particle charge dependent softening energy, although with current uncertainties a dependence on the number of nucleons cannot be ruled out.

Measurement of the cosmic ray proton spectrum from 40 GeV to 100 TeV with the DAMPE satellite

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.

Diallel analysis of tiller number at different growth stages in rice (Oryza sativa L.)

The genetics of tiller number at different development stages in rice was studied in a 6 x 6 diallel cross set involving six indica rice varieties in which a large difference of phenotypes existed. Estimates of genetic parameters following Hayman's method showed significant additive and nonadditive gene action, and the latter appeared to be solely due to dominance. High tillering ability was inherited as a partial dominant character conditioned by two or more blocks of genes, and var 'H1459' had more dominant genes, whereas 'Zhu-Yun-Luo' had more recessive ones. Combining ability analysis by Griffing's method also indicated significance of both additive and nonadditive effects, but the former was more important than the latter. 'H1459' and 'Bi-Yu-Zao-Luo' were good general combiners, and their hybrids 'H1459' x 'Le-Yi' and 'Zhu-Yun-Luo' x 'Bi-Yu-Zao-Luo' were better crosses for combining an optimum tiller number with high percentage of productive tiller. An identical polygenic system appeared to be responsible for the genetic control of both tiller number at the different growth stages and the terminal character, productive tiller number. However, with growth of the plant, relative contributions of nonadditive gene action and environmental factors to the variation decreased, while those of additive gene action increased. Selection for high tillering ability, therefore, should be exercised at peak tillering or later stages.