Two-injection scenario for the hard X-ray excess observed in Mrk 421

An interesting result recently reported for Mrk 421 is the detection of a significant excess at hard X-ray energies, which could provide useful information for investigating particle acceleration and emission mechanisms in the relativistic jet. Considering a two-injection scenario, we develop a self-consistent one-zone leptonic model to understand the origin of the hard X-ray excess in Mrk 421 during the period of extremely low X-ray and very high energy (VHE) flux in 2013 January. In the model, two populations of mono-energetic ultrarelativistic electrons are injected into the emission region that is a magnetized plasmoid propagating along the blazar jet. We numerically calculate the emitting electron energy distribution by solving a kinetic equation that incorporates both shock acceleration and stochastic acceleration processes. Moreover, we infer analytic expressions relating electrons acceleration, cooling, escape and injection to the observed spectra and variability. For the injection luminosity in particular, we derive a new approximate analytical expression for the case of continual injection with a mono-energetic distribution. Based on a comparison between the theoretical predictions and the observed SED, we conclude that the hard X-ray excess observed in Mrk 421 may be due to the synchrotron radiation emitted by an additional electrons population, which is co-spatial with an electron population producing simultaneous Optical/UV, soft X-ray, and $\gamma$-ray emissions. The stochastic acceleration may play a major role in producing the observed X-ray spectrum.Comment: 12 pages, 4 figures, 2 tables, Accepted for publication in Ap

Crystal structure of (5′S,8′S)-3-(2,5-di-methylphenyl)-8-methoxy-3-nitro-1-aza-spiro[4.5]decane-2,4-dione

Peer reviewedPublisher PD

Analysis on the vibration modes of the electric vehicle motor stator

The lightweight design of the electric vehicle motor brought about more serious vibration and noise problem of the motor. An accurate modal calculation was the basis for the study of the vibration and noise characteristics of the electric vehicle motor. The finite element method was used to perform the modal simulation of the PMSM. Through the reasonable simplification and equivalence of the motor stator model, the first 7 orders natural frequencies and corresponding modes of the motor stator under the free state were calculated. After that, the accuracy of the finite element model was verified by the hammering modal experiment of the prototype. Furthermore, the above results will provide the theoretical basis for the electric vehicle motor’s vibration control and NVH improvement

The band-gap structures and recovery rules of generalized n-component Fibonacci piezoelectric superlattices

The spectral evolution from periodic structure to random structure has always been an interesting topic in solid state physics, the generalized n-component Fibonacci sequences (n- CF) provide a convenient tool to investigate such process since its randomness can be controlled via the parameter n. In this letter, the band-gap structures of n-CF piezoelectric superlattices have been calculated using the transfer-matrix-method, the self-similarity behavior and recovery rule have been systematically analyzed. Consistent with the rigorous mathematical proof by Hu et al.[A. Hu et al. Phys. Rev. B. 48, 829 (1993)], we find that the n-CF sequences with 2 \leq n \leq 4 are identified as quasiperiodic. The imaginary wave numbers are characterized by the self-similar spectrum, their major peaks can all be properly indexed. In addition, we find that the n = 5 sequence belongs to a critical case which lies at the border between quasiperiodic to aperiodic structures. The frequency range of self-similarity pattern approaches to zero and a unique indexing of imaginary wave numbers becomes impossible. Our study offers the information on the critical 5-CF superlattice which was not available before. The classification of band-gap structures and the scaling laws around fixed points are also given

Crystal Structures of the Transcriptional Repressor RolR Reveals a Novel Recognition Mechanism between Inducer and Regulator

Many members of the TetR family control the transcription of genes involved in multidrug resistance and pathogenicity. RolR (Resorcinol Regulator), the recently reported TetR-type regulator for aromatic catabolism from Corynebacterium glutamicum, distinguishes itself by low sequence similarities and different regulation from the previously known members of the TetR family. Here we report the crystal structures of RolR in its effector-bound (with resorcinol) and aop- forms at 2.5 Å and 3.6 Å, respectively. The structure of resorcinol-RolR complex reveal that the hydrogen-bonded network mediated by the four-residue motif (Asp94- Arg145- Arg148- Asp149) with two water molecules and the hydrophobic interaction via five residues (Phe107, Leu111, Leu114, Leu142, and Phe172) are the key factors for the recognition and binding between the resorcinol and RolR molecules. The center-to-center separation of the recognition helices h3-h3′ is decreased upon effector-binding from 34.9 Å to 30.4 Å. This structural change results in that RolR was unsuitable for DNA binding. Those observations are distinct from that in other TetR members. Structure-based mutagenesis on RolR was carried out and the results confirmed the critical roles of the above mentioned residues for effector-binding specificity and affinity. Similar sequence searches and sequence alignments identified 29 RolR homologues from GenBank, and all the above mentioned residues are highly conserved in the homologues. Based on these structural and other functional investigations, it is proposed that RolR may represent a new subfamily of TetR proteins that are invovled in aromatic degradation and sharing common recognition mode as for RolR

A data analysis method for isochronous mass spectrometry using two time-of-flight detectors at CSRe

The concept of isochronous mass spectrometry (IMS) applying two time-of-flight (TOF) detectors originated many years ago at GSI. However, the corresponding method for data analysis has never been discussed in detail. Recently, two TOF detectors have been installed at CSRe and the new working mode of the ring is under test. In this paper, a data analysis method for this mode is introduced and tested with a series of simulations. The results show that the new IMS method can significantly improve mass resolving power via the additional velocity information of stored ions. This improvement is especially important for nuclides with Lorentz factor $\gamma$-value far away from the transition point $\gamma _t$ of the storage ring CSRe.Comment: published in Chinese Physics C Vol. 39, No. 10 (2015) 10620