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The measurement of the cosmic ray energy spectrum, in particular for individual species of nuclei, is an important tool to investigate cosmic ray production and propagation mechanisms. The determination of the "knees" in the spectra of different species remains one of the main challenges in cosmic ray physics. In fact, experimental results are still conflicting. In this paper we report a measurement of the mixed proton and helium energy spectrum, obtained with the combined data of the ARGO-YBJ experiment and a wide field of view Cherenkov telescope, a prototype of the future LHAASO experiment. By means of a multiparameter technique, we have selected a high-purity proton plus helium sample. The reconstructed energy resolution is found to be about 25% throughout the investigated energy range from 100 TeV to 3 PeV, with a systematic uncertainty in the absolute energy scale of 9.7%. The found energy spectrum can be fitted with a broken power-law function, with a break at the energy E k ¼ 700 AE 230ðstatÞ AE 70ðsysÞ TeV, where the spectral * zhangss@ihep.ac.cn † caozh@ihep.ac.cn PHYSICAL REVIEW D 92, 092005 (2015) 1550-7998=2015=92(9)=092005 (12) 092005-1 © 2015 American Physical Society index changes from −2.56 AE 0.05 to −3.24 AE 0.36. The statistical significance of the observed spectral break is 4.2 standard deviations.

The Crab Nebula is a bright source of gamma-rays powered by the Crab Pulsar's rotational energy, through the formation and termination of a relativistic electron-positron wind. We report the detection of γ-rays from this source with energies from 5 × 10−4 to 1.1 petaelectronvolts (PeV), with a spectrum showing gradual steepening over three energy decades. The ultra-high-energy photons imply the presence of a PeV electron accelerator (a pevatron) in the nebula, with an acceleration rate exceeding 15% of the theoretical limit. We constrain the pevatron's size between 0.025 and 0.1 pc, and magnetic field ≈110 μG. The production rate of PeV electrons, 2.5 × 1036 erg s−1, constitutes 0.5% of the pulsar spin-down luminosity, although we cannot exclude a contribution of PeV protons to the production of the highest energy γ-rays.

A sub-array of the Large High Altitude Air Shower Observatory (LHAASO), KM2A is mainly designed to observe a large fraction of the northern sky to hunt for γ-ray sources at energies above 10 TeV. Even though the detector construction is still underway, half of the KM2A array has been operating stably since the end of 2019. In this paper, we present the KM2A data analysis pipeline and the first observation of the Crab Nebula, a standard candle in very high energy γ-ray astronomy. We detect γ-ray signals from the Crab Nebula in both energy ranges of 10 100 TeV and 100 TeV with high significance, by analyzing the KM2A data of 136 live days between December 2019 and May 2020. With the observations, we test the detector performance, including angular resolution, pointing accuracy and cosmic-ray background rejection power. The energy spectrum of the Crab Nebula in the energy range 10-250 TeV fits well with a single power-law function dN/dE = (1.13 0.05 0.08 ) 10 (E/20 TeV) cm s TeV . It is consistent with previous measurements by other experiments. This opens a new window of γ-ray astronomy above 0.1 PeV through which new ultrahigh-energy γ-ray phenomena, such as cosmic PeVatrons, might be discovered.

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Horseradish peroxidase isoenzyme C (HRP) and Engyodontium album proteinase K (proK) were immobilized inside macro- and mesoporous silica monoliths. Stable immobilization was achieved through simple noncovalent adsorption of conjugates, which were prepared from a polycationic, water-soluble second generation dendronized polymer (denpol) and the enzymes. Conjugates prepared from three denpols with the same type of repeating unit (r.u.), but different average lengths were compared. It was shown that there is no obvious advantage of using denpols with very long chains. Excellent results were achieved with denpols having on average 750 or 1000 r.u. The enzyme-loaded monoliths were tested as flow reactors. Comparison was made with microscopy glass coverslips onto which the conjugates were immobilized and with glass micropipettes containing adsorbed conjugates. High enzyme loading was achieved using the monoliths. Monoliths containing immobilized denpol–HRP conjugates exhibited good operational stability at 25 °C (for at least several hours), and good storage stability at 4 °C (at least for weeks) was demonstrated. Such HRP-containing monoliths were applied as continuous flow reactors for the quantitative determination of hydrogen peroxide in aqueous solution between 1 μM (34 ng/mL) and 50 μM (1.7 μg/mL). Although many methods for immobilizing enzymes on silica surfaces exist, there are only a few approaches with porous silica materials for the development of flow reactors. The work presented is a promising contribution to this field of research toward bioanalytical and biosynthetic applications.