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Charged particles in the space environment can degrade the scientific performances of X-ray detectors in astronomical telescopes. An efficient countermeasure is to place a magnetic diverter at the exit pupil of optics to deflect charged particles away from the sensitive detection area. In this work, we have performed a preliminary design of the magnetic diverter on-board the enhanced X-ray Timing and Polarimetry (eXTP) observatory. It relies on a Monte Carlo method via the GEANT4 toolkit to simulate the mirror responses to charged particles, using the single scattering physics for electrons and the elastic Remizovich physics for protons. It also implements a numerical method to calculate magnetic fields generated by an assembly of permanent magnets and its impact on the trajectories of charged particles. The compact calculation scheme provides efficient access to the background level estimation given the certain radiation environment, which enables the verification of the diverter configuration with the scientific requirements.

A black hole X-ray binary produces hard X-ray radiation from its corona and disk when the accreting matter heats up. During an outburst, the disk and corona co-evolves with each other. However, such an evolution is still unclear in both its geometry and dynamics. Here we report the unusual decrease of the reflection fraction in MAXI J1820+070, which is the ratio of the coronal intensity illuminating the disk to the coronal intensity reaching the observer, as the corona is observed to contrast during the decay phase. We postulate a jet-like corona model, in which the corona can be understood as a standing shock where the material flowing through. In this dynamical scenario, the decrease of the reflection fraction is a signature of the corona's bulk velocity. Our findings suggest that as the corona is observed to get closer to the black hole, the coronal material might be outflowing faster., 11 pages, 5 figures; published in Nature Communications; An artist's impression of Figure 5 is updated here, and the animation is available at http://youbei.work/research/

Recently, the system parameters of Cygnus X-1, i.e., the black hole mass M, the orbital inclination i and the source distance D, have been updated. As the input constraints of the continuum-fitting method, it is necessary to refine the spin with these new parameters. The Hard X-ray Modulation Telescope (HXMT, also named Insight) was successfully launched on June 15th, 2017 in China. In this work, we analyzed spectra obtained by the Insight-HXMT during 2017-2018 and re-estimated the spin via the continuum-fitting method. We first re-estimated the spin using old parameters and found the dimensionless spin parameter to be a ⁎ > 0.934 (3σ), which is consistent with previous measurements both from the continuum-fitting and iron-line fitting methods ( Gou et al. 2011 , Gou et al. 2014 ; Fabian et al. 2012 , Walton et al. 2016 , Tomsick et al. 2018 ). Then, when the new parameters were applied, we obtained an increased spin: a ⁎ > 0.967 (3σ), which is also consistent with the recent measurement (Zhao et al. 2020, submitted to ApJ) and also confirms an extreme Kerr black hole lying in this system.

The Hard X-ray Modulation Telescope (HXMT) named Insight is China's first X-ray astronomical satellite, with the Low Energy X-ray Telescope (LE) as one of its main payloads onboard. The detectors of LE adopt swept charge device CCD236 using L-shaped transfer electrodes. To measure the time response distribution resulted from the continuous readout of charges in detection area along specific paths, a long exposure readout mode has been designed. In this mode, CCD236 firstly performs exposure without readout, then all charges generated in preceding exposure phase are read out completely. And an analysis of the photons readout time in this mode is carried out, to obtain the time response distribution.

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 $4.3\sigma$. 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., Comment: 11 pages, 13 figures, published in Phys. Rev. Lett. Add one more digit for first three columns in Table S2

The Follow-up X-ray Telescope (FXT), a key payload onboard the Einstein Probe sallite (EP), is equipped with a Wolter-I x-ray focusing mirror system. We introduce the principle of such a mirror system and analyze the influence of the mirror gap in the multishell nested mirror of the FXT on the effective area, stray-light ratio, and vignetting. To ensure that no occlusion occurs within adjacent shells and minimize stray-light ratio, the size of the gap is set to a optimized value for corresponding shell. We finished a design of a 54-shell mirror system according to these results. The optical performance of the design was then simulated using a Monte Carlo algorithm and the ray-tracing principle. The simulation shows that the effective area is 414.5 ± 0.2 cm2 at 1.25 keV (considering the spider), and the field of view is 64 arcmin in diameter. These parameters meet the optical requirements of the FXT.

The main scientific goal of the Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) is to monitor various types of Gamma-Ray Bursts (GRB) originated from merger of binary compact stars, which could also produce gravitational wave, and collapse of massive stars. In order to study the response of GECAM Gamma-Ray Detectors (GRDs) to high-energy bursts and test the in-flight trigger and localization software of GECAM before the launch, a portable GRB simulator device is designed and implemented based on grid controlled X-ray tube (GCXT) and direct digital synthesis (DDS) technologies. The design of this GRB simulator which modulates X-ray flux powered by high voltage up to 20 kV is demonstrated, and the time jitter (FWHM) of the device is about 0.9 $\mu$s. Before the launch in December, 2020, both two GECAM satellites were irradiated by different types of GRBs (including short and long bursts in duration) generated by this GRB simulator. The light curves detected with GECAM/GRDs are consistent with the programmed input functions within statistical uncertainties, indicating the good performance of both the GRDs and the GRB simulator., Comment: 15 pages, 12 figures, accepted to be published in Experimental Astronomy on 09 July 2021

The Einstein Probe (EP) is an X-ray astronomical mission mainly devoting to time-domain astronomy. There are two main scientific payloads onboard EP, the Wide Field X-ray Telescope (WXT) based on the lobster eye optics and the Follow-up X-ray Telescope (FXT). FXT contains two Wolter-1 mirrors with a pnCCD detector on each focus. The total effective area is about 600 cm2 and the energy range is 0.3-10 keV. The pnCCD detector cooled by a pulse tube cooler enables high-resolution spectroscopy and imaging combined with excellent time resolution. It will also have several working modes with time resolution ranging from tens of microseconds to 50 milliseconds. Currently, the FXT is in its qualification model phase. The mirror assemblies (STM and TCM) as well as the pnCCD EM module have been manufactured and tested.

The Spectroscopy Focusing Array (SFA) onboard the enhanced X-ray Timing and Polarimetry (eXTP) observatory consists of 9 modules, each comprising a Wolter type I telescope with a field of view (FOV) around 16 arcminutes and a focal plane silicon drift detector (SDD) with 19 hexagonal pixels. Due to the large size of each individual SDD pixel (each pixel corresponds to an area of ∼ 3.6 arcminutes in diameter) and the limited pixel number, SFA can not obtain a real image of the observed region like many other X-ray imaging telescopes. Thus, contamination from nearby bright sources needs to be considered when we study the properties of the target source. We simulate such contaminations using the SIXTE simulator. In this paper we present the results by taking observations of the millisecond pulsar PSR J0437–4715 as an example, and discuss the cases for contamination on background or target source respectively.

We present the observational results from a detailed timing analysis of the black hole candidate EXO 1846–031 during its outburst in 2019 with the observations of Insight-HXMT, NICER and MAXI. This outburst can be classified roughly into four different states. Type-C quasi-periodic oscillations (QPOs) observed by NICER (about 0.1–6 Hz) and Insight-HXMT (about 0.7–8 Hz) are also reported in this work. Meanwhile, we study various physical quantities related to QPO frequency. The QPO rms–frequency relationship in the energy band 1–10 keV indicates that there is a turning pointing in frequency around 2 Hz, which is similar to that of GRS 1915+105. A possible hypothesis for the relationship above may be related to the inclination of the source, which may require a high inclination to explain it. The relationships between QPO frequency and QPO rms, hardness, total fractional rms and count rate have also been found in other transient sources, which can indicate that the origin of type–C QPOs is non-thermal.

Low-frequency quasi-periodic oscillations (LFQPOs) are commonly found in black hole X-ray binaries, and their origin is still under debate. The properties of LFQPOs at high energies (above 30 keV) are closely related to the nature of the accretion flow in the innermost regions, and thus play a crucial role in critically testing various theoretical models. The Hard X-ray Modulation Telescope (Insight-HXMT) is capable of detecting emissions above 30 keV, and is therefore an ideal instrument to do so. Here we report the discovery of LFQPOs above 200 keV in the new black hole MAXI J1820+070 in the X-ray hard state, which allows us to understand the behaviours of LFQPOs at hundreds of kiloelectronvolts. The phase lag of the LFQPO is constant around zero below 30 keV, and becomes a soft lag (that is, the high-energy photons arrive first) above 30 keV. The soft lag gradually increases with energy and reaches ~0.9s in the 150-200 keV band. The detection at energies above 200 keV, the large soft lag and the energy-related behaviors of the LFQPO pose a great challenge for most currently existing models, but suggest that the LFQPO probably originates from the precession of a small-scale jet., 36 pages, 12 figures, 3 tables; published in Nature Astronomy

The Insight -Hard X-ray Modulation Telescope ( Insight -HXMT) is a broadband X-ray and γ-ray (1-3000 keV) astronomy satellite. One of its three main telescopes is the High Energy X-ray telescope (HE). The main detector plane of HE comprises 18 NaI(Tl)/CsI(Na) phoswich detectors, where NaI(Tl) is used as the primary detector to measure ~ 20-250 keV photons incident from the field of view (FOV) defined by collimators, and CsI(Na) is used as the active shielding detector to NaI(Tl) by pulse shape discrimination. Additionally, CsI(Na) is used as an omnidirectional γ-ray monitor. The HE collimators have a diverse FOV, i.e. 1.1°×5.7° (15 units), 5.7°×5.7° (2 units), and blocked (1 unit). Therefore, the combined FOV of HE is approximately 5.7°×5.7°. Each HE detector has a diameter of 190 mm resulting in a total geometrical area of approximately 5100 cm2, and the energy resolution is ~15% at 60 keV. For each recorded X-ray event by HE, the timing accuracy is less than 10 μs and the dead-time is less than 10 μs. HE is used for observing spectra and temporal variability of X-ray sources in the 20-250 keV band either by pointing observations for known sources or scanning observations to unveil new sources. Additionally, HE is used for monitoring the γ-ray burst in 0.2-3 MeV band. This paper not only presents the design and performance of HE instruments but also reports results of the on-ground calibration experiments.

As China's first X-ray astronomical satellite, the Hard X-ray Modulation Telescope (HXMT), which was dubbed as Insight-HXMT after the launch on June 15, 2017, is a wide-band (1-250 keV) slat-collimator-based X-ray astronomy satellite with the capability of all-sky monitoring in 0.2-3 MeV. It was designed to perform pointing, scanning and gamma-ray burst (GRB) observations and, based on the Direct Demodulation Method (DDM), the image of the scanned sky region can be reconstructed. Here we give an overview of the mission and its progresses, including payload, core sciences, ground calibration/facility, ground segment, data archive, software, in-orbit performance, calibration, background model, observations and some preliminary results., 29 pages, 40 figures, 6 tables, to appear in Sci. China-Phys. Mech. Astron. arXiv admin note: text overlap with arXiv:1910.04434

LE is the low energy telescope of Insight-HXMT. It uses swept charge devices (SCDs) to detect soft X-ray photons. The time response of LE is caused by the structure of SCDs. With theoretical analysis and Monte Carlo simulations we discuss the influence of LE time response (LTR) on the timing analysis from three aspects: the power spectral density, the pulse profile and the time lag. After the LTR, the value of power spectral density monotonously decreases with the increasing frequency. The power spectral density of a sinusoidal signal reduces by a half at frequency 536 Hz. The corresponding frequency for QPO signals is 458 Hz. The Root mean square (RMS) of QPOs holds the similar behaviour. After the LTR, the centroid frequency and full width at half maxima (FWHM) of QPOs signals do not change. The LTR reduces the RMS of pulse profiles and shifts the pulse phase. In the time domain, the LTR only reduces the peak value of the crosscorrelation function while it does not change the peak position. Thus it will not affect the result of the time lag. When considering the time lag obtained from two instruments and one among them is LE, a 1.18 ms lag is expected caused by the LTR. The time lag calculated in the frequency domain is the same as that in the time domain., Comment: 11 pages, 9 figures

We present a novel photovoltaic self-powered gas sensor based on a p-type single-walled carbon nanotube (SWNT) and n-type silicon (n-Si) heterojunction. The energy from visible light suffices to drive the device owing to a built-in electric field (BEF) induced by the differences between the Fermi levels of SWNTs and n-Si.

DAMPE satellite has directly measured the cosmic ray proton spectrum from 40 GeV to 100 TeV and revealed a new feature at about 13.6 TeV., 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.

The recently discovered neutron star transient Swift J0243.6+6124 has been monitored by {\it the Hard X-ray Modulation Telescope} ({\it Insight-\rm HXMT). Based on the obtained data, we investigate the broadband spectrum of the source throughout the outburst. We estimate the broadband flux of the source and search for possible cyclotron line in the broadband spectrum. No evidence of line-like features is, however, found up to $\rm 150~keV$. In the absence of any cyclotron line in its energy spectrum, we estimate the magnetic field of the source based on the observed spin evolution of the neutron star by applying two accretion torque models. In both cases, we get consistent results with $B\rm \sim 10^{13}~G$, $D\rm \sim 6~kpc$ and peak luminosity of $\rm >10^{39}~erg~s^{-1}$ which makes the source the first Galactic ultraluminous X-ray source hosting a neutron star., published

To overcome the obstacle of triangular prism-like MoO3 nanorods (MoO3) gas sensor including low response, poor selectivity and a heavy influence of humidity to Triethylamine (TEA), heterostructured tin sulfide (SnS) composited with MoO3 hollow nanotubes (SnS@MoO3) were synthesised by a facilely hydrothermal method. Its morphology and structure were charactered through different technologies. The result indicated that the sensor based on SnS@MoO3 exhibited higher response (73.46%), shorter response/recovery time (8.1/4.5 s), excellently selectivity and anti-humidity properties than MoO3 to 50 ppm TEA at 250 °C. Thus, the SnS@MoO3 is a promising material for detecting TEA.

This paper describes a 5-bit cyclic column-parallel ADC for Monolithic Active Pixel Sensor. The column-parallel ADC combines the dedicated sample phase and the signal conversion phase into a single phase. Moreover, it has a high tolerance to the offset of the comparators in the ADC by generating 1.5 bit in every stage. Each column-parallel ADC covers a small area of 100 μm × 200 μm, consumes 4.5 mW at 3.3 V supply and provides the sampling rate of 10 MS/s with the dynamic range of 1000 mV. The results show that the ADC has a signal-to-noise and distortion ratio (SNDR) of 28.47 dB. Its DNL and INL are −0.039/0.055 LSB and −0.048/0.095 LSB, respectively.

The Medium Energy X-ray Telescope (ME), covering 5-30 keV, is one of the three main payloads of the Hard X-ray Modulation Telescope (HXMT). ME adopts an array of Si-PIN detectors. The detection area of one pixel is 56.25 mm2 , and the total detection area is 952 cm2 . The ME has a large active area while the pixel size is smaller. So the front-end electronics and forming electronics are realized by Application Specific Integrated Circuit (ASIC) chips. In this paper, we will describe the matching design of ME Si-PIN detector and ASIC, and the performance of the design. The energy response, temperature response, and dead time of a Two-Pixels Si-PIN detectors with the simplest readout electronics which is similar with ME, were tested on the Max Planck Institute for Extraterrestrial Physics PANTER X-ray test facility at Neuried by Munchen (Germany). The overall performance is quite similar to what was expected.

Gallium-doped zinc oxide ceramics with high density were sintered by conventional solid-state reaction method. The phase, fracture morphology, conductive properties and density of the samples were tested by XRD, SEM, Hall testing and Archimedes method, respectively. Increasing of the sintering temp and sintering time does not affect the characteristic peaks belong to lead–zinc mine structure of zinc oxide polycrystal, but it has a great influence on the samples' density and the size of grains. The density first increases with heat preservation temp and hour then decreases, the maximum value obtained is 5.54 g cm−3. Micrographs clearly shown that increase the heating temp is beneficial to the growth of the grain. The measured results have shown that the optimum sintering conditions of Ga-doped zinc ceramics are a sintering temperature of 1325°C and a sintering time of 4 hours. The whole process indicates that the lowest resistivity of Ga-doped zinc samples is 2.282 × 10−3 Ω·cm.

Few studies have examined direct impacts of intensive tillage on soil structural stability in hillslope landscapes. In this experiment, we performed simulation tillage within the steep hillslope landscape of the Sichuan Basin, China, i.e., 20-time consecutive tillage by hoeing in a short time interval (3 days) under no rainfall. The Cs-137 tracing was used to demonstrate tillage erosion/deposition in soil profiles and landscape positions. A wet-sieving method was used to determine mean weight diameter (MWD) and geometric mean diameter (GMD) as indices of soil aggregate stability. Soil organic matter (SOM) was also determined just before and after hoeing tillage implementation. The greatest changes in Cs-137 inventory due to 20-operation tillage were observed at 1 and 20 m slope positions, with a decrease of 100% at the 1 m position and an increase of 50.58% at the 20 m position compared with pre-tillage. The

Cotton composite material, also called cotton cloth, is the fabric weaved with cotton yarn as raw material. Cotton fabric becomes one of the most common fabric for its excellent wearability and is widely used in garment fabric, decorative fabric and technical fabric. This paper conducts factor test in the aspects of dyeing rate and colour fastness of cotton composite material through experimental analysis and verification. Through the comprehensive analysis of various factors, influence on the dye-uptake rate varies from that on the colour fastness, therefore, in order to get a better dyeing effect, the values of the dye-uptake rate and the colour fastness need to be adjusted properly for finding out the optimal dyeing effect.

In this work, Zn particles with magnetic shell were synthesised and investigated. Zn particles with different sizes were synthesised by arc-discharge method, and then the Zn particles were put in a suitable concentration of FeSO4 solution with a surface active agent. After some time, the Zn particles with magnetic shell were produced. The particles contain oxygen shell probably in the form of FeO and ZnO, while the core material is Zn. From the saturation magnetisation at room temperature and transmission electron microscopy (TEM) images, it is noticed that the FeO was first formed on the surface of Zn and then ZnO appeared with increasing reaction time. The microwave absorption is not as good as that reported in other materials, because of the weak magnetisation and the faulty core–shell structure formed by metal core and magnetic shell.

The magneto-optical Kerr effect (MOKE) is a widely used technique in magnetic domain imaging for its high surface sensitivity and external magnetic compatibility. In this work, we use the generalized magneto-optical ellipsometry technique to study the influence of polarizer and analyzer azimuth on domain image contrast in the Kerr microscope. Results show that the image contrasts around the extinction place are larger than other area. When the polarizer and analyzer are set slightly deviated from the extinction condition (0.35°,89.7°), the maximum image contrast can be obtained. The color map of image contrast on polarizer and analyzer angle is given by measuring the MOKE response of 200 nm permalloy. Results verify the validity of the conclusion.

Duckweed is considered a promising feedstock for bioethanol production due to its high biomass and starch production. Selection of duckweed strains with high starch accumulation is essential for application of duckweeds to bioethanol production. Geographic differentiation had a large influence on genetic diversity of duckweeds. Biomass production, starch content and starch amount in geographically isolated strains of 20 Lemna aequinoctialis and Spirodela polyrhiza were calculated to evaluate their potential for bioethanol production. The influence of different collection time, culture medium and NaCl concentration on starch accumulation of the best strains were analysed. The results showed that biomass production, starch content and starch production of duckweeds demonstrated clonal dependency. The best strain was L. aequinoctialis 6000, with biomass production of 15.38 ± 1.47 g m-2 , starch content of 28.68 ± 1.10% and starch production of 4.39 ± 0.25 g m-2 . Furthermore, starch content of L. aequinoctialis 6000 was highest after 8 h of light, tap water was the best medium for starch induction, and NaCl did not induce starch accumulation. This study suggests duckweed biomass production and starch production demonstrate clonal dependency, indicating that extensive clonal comparisons will be required to identify the most suitable isolates for duckweed selective breeding for bioethanol.

There is a considerable deficiency in the number of known supernova remnants (SNRs) in the Galaxy compared to that expected. Searches for extended low-surface brightness radio sources may find new Galactic SNRs, but confusion with the much larger population of HII regions makes identifying such features challenging. SNRs can, however, be separated from HII regions using their significantly lower mid-infrared (MIR) to radio continuum intensity ratios. We use the combination of high-resolution 1-2 GHz continuum data from The HI, OH, Recombination line survey of the Milky Way (THOR) and lower-resolution VLA 1.4 GHz Galactic Plane Survey (VGPS) continuum data, together with MIR data from the Spitzer GLIMPSE, Spitzer MIPSGAL, and WISE surveys to identify SNR candidates. To ensure that the candidates are not being confused with HII regions, we exclude radio continuum sources from the WISE Catalog of Galactic HII Regions, which contains all known and candidate H II regions in the Galaxy. We locate 76 new Galactic SNR candidates in the THOR and VGPS combined survey area of 67.4deg>l>17.5deg, |b, Accepted for publication in A&A

Finding the electromagnetic (EM) counterpart of binary compact star merger, especially the binary neutron star (BNS) merger, is critically important for gravitational wave (GW) astronomy, cosmology and fundamental physics. On Aug. 17, 2017, Advanced LIGO and \textit{Fermi}/GBM independently triggered the first BNS merger, GW170817, and its high energy EM counterpart, GRB 170817A, respectively, resulting in a global observation campaign covering gamma-ray, X-ray, UV, optical, IR, radio as well as neutrinos. The High Energy X-ray telescope (HE) onboard \textit{Insight}-HXMT (Hard X-ray Modulation Telescope) is the unique high-energy gamma-ray telescope that monitored the entire GW localization area and especially the optical counterpart (SSS17a/AT2017gfo) with very large collection area ($\sim$1000 cm$^2$) and microsecond time resolution in 0.2-5 MeV. In addition, \textit{Insight}-HXMT quickly implemented a Target of Opportunity (ToO) observation to scan the GW localization area for potential X-ray emission from the GW source. Although it did not detect any significant high energy (0.2-5 MeV) radiation from GW170817, its observation helped to confirm the unexpected weak and soft nature of GRB 170817A. Meanwhile, \textit{Insight}-HXMT/HE provides one of the most stringent constraints (~10$^{-7}$ to 10$^{-6}$ erg/cm$^2$/s) for both GRB170817A and any other possible precursor or extended emissions in 0.2-5 MeV, which help us to better understand the properties of EM radiation from this BNS merger. Therefore the observation of \textit{Insight}-HXMT constitutes an important chapter in the full context of multi-wavelength and multi-messenger observation of this historical GW event., Comment: accepted by Science China - Physics, Mechanics & Astronomy. Planned to publish on Oct 17, but postponed due to a problem on pdf file

High energy cosmic ray electrons plus positrons (CREs), which lose energy quickly during their propagation, provide an ideal 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 directly measured up to $\sim 2$ TeV in previous balloon- or space-borne experiments, and indirectly up to $\sim 5$ TeV by ground-based Cherenkov $\gamma$-ray telescope arrays. Evidence for a spectral break in the TeV energy range has been provided by indirect measurements of H.E.S.S., although the results were qualified by sizeable systematic uncertainties. Here we report a direct measurement of CREs in the energy range $25~{\rm GeV}-4.6~{\rm TeV}$ by the DArk Matter Particle Explorer (DAMPE) with unprecedentedly high energy resolution and low background. The majority of the spectrum can be properly fitted by a smoothly broken power-law model rather than a single power-law model. The direct detection of a spectral break at $E \sim0.9$ TeV confirms the evidence found by H.E.S.S., clarifies the behavior of the CRE spectrum at energies above 1 TeV and sheds light on the physical origin of the sub-TeV CREs., Comment: 18 pages, 6 figures, Nature in press, doi:10.1038/nature24475

The soil–rock mixture (SRM) is a special inhomogeneous multiphase geomaterial, the study of the SRM’s damage characteristic is crucial to the stability of engineering. This paper explores the use of high-resolution X-ray tomography and Realistic Failure Process Analysis code (RFPA2D) to identify the damage mechanism and the cracking process of SRM during compressive loading. X-ray tomography images were used to extract defects of SRM specimen under different compressive loadings, also damage characteristics of region of interest (ROI) were analysed by X-ray tomography. Numerical simulation was conducted to describe the damage characteristics with damage element number (DEN) recorded during compression. Results show that X-ray tomography and numerical simulation based on RFPA2D are complementary good methods to research the damage evolution of SRM. Damage characteristics of SRM are progressive; cracking begins from rock–soil jointed interfaces, and then propagates into soil matrix, and the growth of crack-...

Transparent all oxide pn junction film diode consisting of p-type NiO:Na and n-type ZnO was fabricated by magnetron sputtering method on Si substrate. These films were characterised by diffraction (XRD), atomic force microscopy (AFM) and UV-visible spectroscopy. XRD results show that NiO:Na film had a preferred orientation along the (111) direction while ZnO film was highly oriented along the (002) direction. The optical transmittance of NiO:Na and ZnO films were 60 and 80% respectively. I-V characteristic of NiO:Na/ZnO junction showed rectification. The junction parameters such as ideality factor, barrier height and series resistance were determined using conventional forward bias I-V characteristics and the Cheung method.

Three-dimensional mullite fibre reinforced silica rich mullite matrix (Muf/S-Mu) composites were fabricated by sol–gel process employing silica rich mullite sols. The structural evolution of the mullite precursors and effects of sintering temperature on the mechanical and dielectric properties and microstructure of the composites were investigated. The results showed that the long club shaped orthorhombic mullite grains embedded in amorphous SiO2 were obtained for the gels sintered at 1200°C. The composite fabricated at 1200°C shows an obvious brittle failure behaviour, and the flexural strength of which is 54·2 MPa. The permittivity of the composites fabricated at 1200°C is 5·41–i0·11 at 8·2 GHz, and almost constant within measured frequency between 8·2 and 12·4 GHz. Because of the enhancement of the matrix densification, the real part of permittivity of all composites increases as fabrication cycle increases from 8 to 13.

Nanocrystals of up-conversion (UC) phosphor Yb 3+ /Tm 3+ co-doped NaYF 4 are prepared by a facile hydrothermal method using oleic acid as a stabilizing agent. The as-prepared nanocrystals are of hexagonal phase, and have tube-like morphology and strong ultraviolet (UV) and blue UC fluorescence intensity, which have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and luminescence spectroscopy. The effect of Yb 3+ concentration on the UC emission properties is also analyzed. Our results reveal that the intensity of emission peaks can be controlled by varying the Yb 3+ concentration and these NaYF 4 nanotubes are highly efficient host material. The as-prepared NaYF 4 nanotubes show potential applications in UV compact solid state lasers and multi-channel fluorescent label.

Context. Radio continuum surveys of the Galactic plane are an excellent way to identify different source populations such as planetary nebulae, H IIregions, and radio stars and characterize their statistical properties. The Global View of Star Formation in the Milky Way (GLOSTAR) survey will study the star formation in the Galactic plane between −2° < ℓ < 85° and |b| < 1° with unprecedented sensitivity in both flux density (∼40μJy beam−1) and range ofangular scales (∼1".5 to the largest radio structures in the Galaxy).Aims. In this paper we present the first results obtained from a radio continuum map of a 16-square-degree-sized region of the Galactic plane centered on ℓ = 32° andb = 0° (28° < ℓ < 36° and |b| < 1°). This map has a resolution of 18″ and a sensitivity of ∼60−150μJy beam−1.Methods. We present data acquired in 40 h of observations with the VLA in D-configuration. Two 1 GHz wide sub-bands were observed simultaneously and they were centered at 4.7 and 6.9 GHz. These data were calibrated and imaged using theObitsoftware package. The source extraction was performed using theBLOBCATsoftware package and verified through a combination of visual inspection and cross-matching with other radio and mid-infrared surveys.Results. The final catalog consists of 1575 discrete radio sources and 27 large scale structures (including W43 and W44). By cross-matching with other catalogs and calculating the spectral indices (S(ν) ∝ να), we have classified 231 continuum sources as H IIregions, 37 as ionization fronts, and 46 as planetary nebulae. The longitude and latitude distribution and negative spectral indices are all consistent with the vast majority of the unclassified sources being extragalactic background sources.Conclusions. We present a catalog of 1575 radio continuum sources and discuss their physical properties, emission nature, and relation to previously reported data. These first GLOSTAR results have increased the number of reliable H IIregions in this part of the Galaxy by a factor of four.

The La doped Ba2FeReO6 has been investigated by using the first-principles. Our calculations indicated that with the increase of La doping, half metallic to insulating transition is observed from Ba2FeReO6, Ba1.5La0.5FeReO6 to BaLaFeReO6. The injection of electron mainly goes to Re t(2g) orbitals, while Fe 3d orbitals are nearly unchanged with the increase of La doping. The valence state of Fe is 3 + for doped and undoped cases. For Re, the valence state is 5+ in Ba2FeReO6, 4.5+ in Ba1.5La0.5FeReO6 and 4+ in BaLaFeReO6. The net magnetic moment decreases with the increase of La doping. (C) 2013 Elsevier B.V. All rights reserved.

We present the fabrication of submicron polyimide film sandwiched by Al film. The preparation in two-step method and spin-coating parameters of submicron polyimide film are described. To achieve self-supported structure, thick nickel mesh (ca. 200 μm) was introduced by micro-electroforming. Using negative tone photoresist SU-8 2150, the nickel grid width was demonstrated in good agreement with its original design value with optical microscopy.

An experimental setup in dark condition was established to investigate the temperature and bias voltage dependence of the Multi-Pixel Photon Counter (MPPC), one type of the SiPM developed by Hamamatsu. The dark current of an MPPC near room temperature at a given gain can be approximated by an exponential function of temperature which is similar to the behavior of a negative temperature coefficient (NTC) thermistor. According to these facts, a gain control and stabilization circuit for MPPC is developed by using a programmable current sink with temperature compensation. Detailed design and performance analysis results of the circuit in the temperature range from 5.1 degrees C to 33.3 degrees C will be discussed in this paper. (C) 2011 Elsevier B.V. All rights reserved.

The effects of molybdenum (Mo), manganese (Mn) and tungsten (W) on the corrosion behavior and hardness of iron-based metallic glasses (MG) were investigated by using electrochemical measurements, X-ray photoelectron spectroscopy, and micro-hardness tester. The results showed that the alloying elements (Mo, Mn, and W) have great influence on the corrosion behavior and hardness. Corrosion resistance of the MG increased with Mo and W content to a critical value (9.4 and 3.2 at%, respectively) and then decreased, while kept increasing with Mn. The corrosion behavior is dependent on the composition of the passive film. The protective Mo(IV), Mn(IV), and W(VI) oxide film on the surface attributes to the enhanced stability of the film. The hardness of the MG is not sensitive to the Mn content, but increased with the Mo and W content. Little influence on the hardness is found when the Mo content is higher than 9.4 at%. Based on the above mentioned influence of alloying elements, corrosion, and wear resistance can be balanced to meet the service of marine pump that served in both corrosive and erosive environments.

Results of the growth and annealing processes of Ho3+:CaNb2O6 crystal with high oxygen defects were reported. The spectroscopic properties of Ho3+:CaNb2O6 were also analysed, and the decay curves of the bulk and powder samples in correspondence with the emission 5I7→5I8 at 2·0 μm were recorded. The effects of radiative trapping on the final results were also indicated, and the final value of the fluorescence lifetimes of 5I7→5I8 transition is calculated to be 5·19 ms. CaNb2O6 crystal was shown to be a prospective material for an infrared laser medium at 2·0 μm.

The corrosion corrosion behaviour and passive films of the FeCrMnMoWBCSi metallic glasses were investigated in acidic and neutral solutions using electrochemical measurements, AFM, and XPS. The alloys exhibit high corrosion resistance in H2SO4 and NaCl solutions in contrast with Na2SO4 and HCl solutions, respectively. In sulphate solutions, the film composition plays a key role in corrosion resistance and the films in H2SO4 solutions enrich low-valence Cr(III) and Mo(IV) species on the surface. In chloride solutions, the stability of the films depends on their structural properties. Possible mechanisms related to HSO4-/SO42- ions adsorption and Cl- ions penetration are also proposed. (C) 2012 Elsevier Ltd. All rights reserved.

A FeCrMoMnWBCSi amorphous metallic coating was prepared by using high-velocity oxy-fuel spray. The influence of processing parameters on microstructure, porosity level, amorphous phase fraction and corrosion behaviour of the coatings was characterised by scanning electron microscopy, X-ray diffraction, differential scanning calorimeter and electrochemical methods. The results indicated that the microstructures of the coatings were sensitive to the spray parameters considerably. Porosity and unmelted particle proportion decreased with the oxygen/fuel (O/F) ratio and increased with the powder feed rate. The trend of oxides content was opposite to the porosity and unmelted particle proportion. The coatings obtained with higher O/F ratio and lower powder feed rate exhibited higher hardness. The low coating hardness was mainly due to the high porosity especially when the porosity was higher than 1.21%. The spraying parameters strongly affected the amorphous phase fraction. There was a critical passive current density for balancing the porosity and the amorphous phase fraction. Corrosion resistance is dominant by the amorphous phase fraction when the porosity is less than 1.21%, while by porosity when it is higher than that. Open-circuit potential, potentiodynamic polarisation and electrochemical impedance spectroscopy results showed that the coatings obtained with the O/F ratio of 4.2 and the powder feed rate of 40 g/min exhibiting the best corrosion resistance in 1 wt% sodium chloride solution.

High-velocity oxy-fuel-sprayed FeCrMoMnWBCSi amorphous metallic coatings were sealed with sodium orthosilicate (Na(3)SiO(4)), aluminium phosphate (AlPO(4)), and cerium salt sealants. The microstructure of the sealed coatings was characterised by scanning electron microscopy, energy dispersive spectrometer, and X-ray diffraction. Corrosion behaviour was examined using electrochemical methods of potentiodynamic polarisation, cyclic polarisation, electrochemical impedance spectroscopy, and Mott-Schottky tests. The results indicated that the uniform corrosion resistance of the three sealed coatings was enhanced greatly, and the passive current densities were decreased by one order of magnitude after the sealing treatments. The AlPO(4) sealant can penetrate the coatings by no less than 50 mu m and enhance their hardness, which exhibited a more uniform corrosion resistance, fairly good pitting corrosion resistance, and can be applied in long-term corrosive and/or abrasive environments. The cerium salt-sealed coating showed better pitting corrosion resistance but inferior corrosion resistance in the local regions of micro-cracks, which was practically used for temporary corrosion protection. The Na(3)SiO(4)-sealed coating showed better uniform corrosion resistance and inferior pitting corrosion resistance, which can be applied in short-term corrosion environments. The stability of the passive film affected the corrosion behaviour of the sealed coatings. The AlPO(4)-sealed coating performed better as a protective passive film during the long-term immersion test for a lower defect concentration and a more protective passive film. (C) 2011 Elsevier B.V. All rights reserved.

FeCrMoMnWBCSi amorphous metallic coatings (AMCs) were deposited onto the 304 stainless steel (base material of pump impeller operated in sand-containing seawater) by high-velocity oxygen-fuel (HVOF) thermal spray. The preparation, microstructural characteristics, and static corrosion behavior of the AMCs were presented. The microstructure and corrosion behavior of the AMCs were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and electrochemical methods. Melt-spun ribbon and 304 stainless steel were also used for comparison purposes. The results indicated that the AMCs can spontaneously passivate with a wide passive region, and much higher ability to withstand pitting corrosion than that of the 304 stainless steel for the high pitting resistance equivalent value. The passive current density of the AMCs was at least two orders of magnitude higher than the counterpart ribbon, which showed a slightly decreased uniform corrosion resistance of the AMCs due to the incompact structure and porosity. The corrosion resistance of the AMCs increased with the coating thickness and decreased with the concentration of NaCl solution. A stable passivation ability held in the AMCs endowed them suitably used in marine environments.

Using the Tibet-III air shower array, we search for steady TeV -rays from 18 pulsars in the Fermi Large Area Telescope pulsar catalog. Among them, we ob- serve 8 sources including the Crab instead of the expected

Five Chinese species of Epimedium (Berberidaceae), E. simplicifolium T. S. Ying, E. baojingensis Q. L. Chen & B. M. Yang, E. zhushanense K. F. Wu & S. X. Qian, E. glandulosopilosum H. R. Liang and E. elachyphyllum Stearn are the only species of the genus previously described with unifoliolate leaves. Here, the authors review these five species based on extensive examination of specimens in herbaria and careful observation in the field and garden. E. simplicifolium is treated as a synonym of E. acuminatum Franch., and with the exception of E. elachyphyllum, the taxa are found to have predominantly trifoliolate and only occasionally unifoliolate leaves. Neotypes for E. zhushanense and E. glandulosopilosum are designated. In addition, we describe some characters of E. baojingensis, E. zhushanense, E. glandulosopilosum and E. elachyphyllum.

An efficient laser diode end-pumped continuous-wave (CW) and AO Q-switched laser of Nd:LiLuF4 crystal with dual central wavelengths of 1053.1 and 1054.7 nm is reported for the first time. The maximum CW output power of 6.22 W was obtained at absorbed pump power of ∼14.6 W with the output transmission of 2%. The optical conversion efficiency is ∼43%, corresponding to a slope efficiency of about 48% with respect to the absorbed pump. For the Q-switched operation, the shortest pulse width of 17 ns was obtained at the pulse repetition frequency (PRF) of 0.5 kHz, resulting in a pulse energy of 2.24 mJ and peak power of 131.8 kW.

The observation of the extensive air showers has been carried out since 1990 by Tibet air-shower array to study the origin of the cosmic-rays. In order to investigate the chemical composition around the knee, air-shower core detector was used in two experimental phases aiming to separate light primary elements (proton and helium). In a first phase experiment made in 1996-1999, primary proton and helium spectra were measured using a hybrid detector consisted of Tibet II air-shower array, emulsion chambers, and burst detectors. The result indicated that the fraction of light elements among the all particle spectrum is less than 30%. We performed the second phase experiment in 2002-2005 to measure proton + helium together to confirm the previous result with higher statistics by improving the detection efficiency for the air-shower cores. The P + He spectrum was obtained in a good agreement with previous result by several times higher statistics. The flux of the light elements, together with the all-particle energy spectrum, indicates the dominance of nuclei heavier than helium in the energy range around the knee. We also present the outline of the next phase experiment, which is to measure the heavy elements around the knee, using low threshold air-shower core detector named YAC. (C) 2010 COSPAR. Published by Elsevier Ltd. All rights reserved.

The effect of electric field enhancement on damage growth of flat bottom pit and nodule-ejected pit was studied based on the finite difference time domain method and temperature field theory. The electric field enhancement around the edge of damage pits indeed exists and varies from 1.2 to 2.0 times. It is found that damage growth not only depends on the electric field enhancement but also the local absorptive coefficient by temperature field calculation. The results also meet the reported damage growth behavior very well. A conclusion can be drawn that field enhancement and potential defects or new generated defects during former pulses are jointly responsible for the damage growth. In addition, an inference can be drawn from theoretical analysis that the flat bottom pit has been initiated by absorbing defect located at the H–L interfaces, which the peaks of electrical field happen to.