Klein–Nishina Effect and the Cosmic Ray Electron Spectrum

Radiative energy losses are very important in regulating the cosmic ray electron and/or positron(CRE) spectrum during their propagation in the Milky Way. Particularly, the Klein–Nishina(KN) effect of the inverse Compton scattering(ICS) results in less efficient energy losses of high-energy electrons, which is expected to leave imprints on the propagated electron spectrum. It has been proposed that the hardening of CRE spectra around 50 GeV observed by Fermi-LAT, AMS-02, and DAMPE could be due to the KN effect. We show in this work that the transition from the Thomson regime to the KN regime of the ICS is actually quite smooth compared with the approximate treatment adopted in some previous works. As a result, the observed spectral hardening of CREs cannot be explained by the KN effect. It means that an additional hardening of the primary electrons spectrum is needed. We also provide a parameterized form for the accurate calculation of the ICS energy-loss rate in a wide energy range.     

Synthesis of a benzoxazine with precisely two phenolic OH linkages and the properties of its high‐performance copolymers

A phenolic OH‐containing benzoxazine ( F‐ap ), which cannot be directly synthesized from the condensation of bisphenol F, aminophenol, and formaldehyde by traditional procedures, has been successfully prepared in our alternative synthetic approach. F‐ap was prepared by three steps including (a) condensation of 4‐aminophenol and 5,5'‐methylenebis(2‐hydroxybenzaldehyde) (1) , (b) reduction of the resulting imine linkage by sodium borohydride, and (c) ring closure condensation by formaldehyde. The key starting material, (1) , was prepared from 2‐hydroxybenzaldehyde and s‐trioxane in the presence of sulfuric acid. F‐ap is structurally similar to bis(3,4‐dihydro‐2H‐3‐phenyl‐1,3‐benzoxazinyl)methane ( F‐a, a commercial benzoxazine based on bisphenol F/aniline/formaldehyde) except for two phenolic OHs. The phenolic OHs can provide reaction sites with epoxy and 1,1'‐(methylenedi‐p‐phenylene)bismaleimide (BMI). The structure–property relationships between the thermosets of F‐ap /epoxy, F‐a /epoxy, F‐ap /BMI, and F‐a /BMI were discussed. Experimental data showed that thermosets based on F‐ap /epoxy and F‐ap /BMI provided much better thermal properties than those based on F‐a /epoxy and F‐a /BMI. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 2686–2694     

Coupled intramolecular/heterointerfacial electron transfer in polyelectrolyte-shielded Iso-type black phosphorus hetero-structure boosts oxygen reduction kinetics

Searching new structured black phosphorus (BP) and exploring intriguing functions and applications have become a hot topic so far.Here,we introduce a novel Iso-...     

尖晶石型LiMn2O4的低温制备

锂锰氧化物;溶胶凝胶法;尖晶石型LiMn2O4的低温制备     

Size-refinement enhanced flexibility and electrochemical performance of MXene electrodes for flexible waterproof supercapacitors

Increasing mechanical flexibility without sacrificing electrochemical performance of the electrode mate-rial is highly desired in the design of flexible electro...     

A simple and efficient method for the allylation of heteroarenes catalyzed by PdCl2

The PdCl₂-catalyzed allylation of heteroarenes is presented. Various heteroarenes including O-, N-, and S-based ones were allylated efficiently with a rich range of allylic acetates in the presence of only 2 mol % of PdCl₂, without the need of bases/acids, additives, and external supporting ligands. In addition, the reactions were carried out under mild and simple conditions just by stirring the two reactants and catalyst in CH₂Cl₂ at 60 °C. Moreover, the by-product produced was non-toxic acetic acid. Thus, the method presented in this work provides a general, clean, and operationally simple approach for the functionalization of heteroarenes. Finally, a preliminary mechanistic study suggested that the Pd(II) may be reduced in situ by the heteroarenes to Pd(0), which serves as the active metal center to catalyze the following allylations of heteroarenes via a Tsuji–Trost pathway.