ABSTRACT
In this paper, we presented a detailed timing analysis of a prominent outburst of 4U 0115+63 detected by Insight-HXMT in 2017 August. The spin period of the neutron star was determined to be ...3.613 98 ± 0.000 02 s at MJD 57978. We measured the period variability and extract the orbital elements of the binary system. The angle of periastron evolved with a rate of $0.048^\circ \pm 0.003^\circ \rm \, yr^{-1}$. The light curves are folded to sketch the pulse profiles in different energy ranges. A multipeak structure in 1–10 keV is clearly illustrated. We introduced wavelet analysis into our data analysis procedures to study quasi-periodic oscillation (QPO) signals and perform a detailed wavelet analysis in many different energy ranges. Through the wavelet spectra, we report the discovery of a QPO at the frequency of ∼10 mHz. In addition, the X-ray light curves showed multiple QPOs in the period of ∼16–32 and ∼67–200 s. We found that the ∼100 s QPO was significant in most of the observations and energies. There exist positive relations between X-ray luminosity and their Q-factors and S-factors, while the QPO periods have no correlation with X-ray luminosity. In wavelet phase maps, we found that the pulse phase of ∼67–200 s QPO is drifting frequently while that of ∼16–32 s QPO is scarcely drifting. The dissipation of oscillations from high energy to low energy was also observed. These features of QPOs in 4U 0115+63 provide a new challenge to our understanding of their physical origins.
Every supernova so far observed has been considered to be the terminal explosion of a star. Moreover, all supernovae with absorption lines in their spectra show those lines decreasing in velocity ...over time, as the ejecta expand and thin, revealing slower-moving material that was previously hidden. In addition, every supernova that exhibits the absorption lines of hydrogen has one main light-curve peak, or a plateau in luminosity, lasting approximately 100 days before declining. Here we report observations of iPTF14hls, an event that has spectra identical to a hydrogen-rich core-collapse supernova, but characteristics that differ extensively from those of known supernovae. The light curve has at least five peaks and remains bright for more than 600 days; the absorption lines show little to no decrease in velocity; and the radius of the line-forming region is more than an order of magnitude bigger than the radius of the photosphere derived from the continuum emission. These characteristics are consistent with a shell of several tens of solar masses ejected by the progenitor star at supernova-level energies a few hundred days before a terminal explosion. Another possible eruption was recorded at the same position in 1954. Multiple energetic pre-supernova eruptions are expected to occur in stars of 95 to 130 solar masses, which experience the pulsational pair instability. That model, however, does not account for the continued presence of hydrogen, or the energetics observed here. Another mechanism for the violent ejection of mass in massive stars may be required.
▶ The effect of Ag content on the mechanical properties of Sn–Ag–Cu lead-free solders was studied systematically and the Ag content and strain rate-dependent material constitutive models have been ...developed for the first time. The effect of Ag content on the microstructures of Sn–Ag–Cu solder was also studied. The effect of Ni doping on the mechanical properties of Sn–1.0Ag–0.5Cu solder was also investigated and the temperature and strain rate-dependent material constitutive model has been developed for Sn–1.0Ag–0.5Cu–0.02Ni solder, which is essential for finite element simulation for assessment of reliability of electronic assembly with such solder.
In this paper, the tensile tests were conducted at 25
°C to investigate the effect of Ag content and Ni doping on the microstructures and mechanical properties of Sn–3.0Ag–0.5Cu, Sn–2.0Ag–0.5Cu, Sn–1.0Ag–0.5Cu, Sn–1.0Ag–0.5Cu–0.05Ni and Sn–1.0Ag–0.5Cu–0.02Ni solders. The effect of strain rate on mechanical properties was investigated for each solder using stain rates of 10
−5
s
−1, 10
−4
s
−1, 10
−3
s
−1, 10
−2
s
−1 and 10
−1
s
−1. In addition, the effect of temperature on mechanical properties was investigated for Sn–1.0Ag–0.5Cu–0.02Ni solder by conducting tests at −35
°C, 25
°C, 75
°C and 125
°C. Test results show that the elastic modulus, yield stress and ultimate tensile strength increase with increasing strain rate and Ag content, but they decrease with increasing temperature. The elastic modulus, yield stress and ultimate tensile strength are lower and the elongation is larger for Sn–1.0Ag–0.5Cu–0.05Ni solder compared with Sn–1.0Ag–0.5Cu–0.02Ni solder. The strain rate and Ag content dependent mechanical property models have been developed for Sn–Ag–Cu solders for the first time. In addition, the temperature and rate-dependent mechanical property models have also been developed for Sn–1.0Ag–0.5Cu–0.02Ni solder. The microstructures of solders were also analyzed. The Ag content affects Ag
3Sn intermetallic compound dispersion and Sn dendrite size. The microstructures of solder have fine Sn dendrites and more dispersed IMC particles for the high Ag content solder, which makes the solder exhibit high strength and yield stress.
We report the first results of a light weakly interacting massive particles (WIMPs) search from the CDEX-10 experiment with a 10 kg germanium detector array immersed in liquid nitrogen at the China ...Jinping Underground Laboratory with a physics data size of 102.8 kg day. At an analysis threshold of 160 eVee, improved limits of 8×10^{-42} and 3×10^{-36} cm^{2} at a 90% confidence level on spin-independent and spin-dependent WIMP-nucleon cross sections, respectively, at a WIMP mass (m_{χ}) of 5 GeV/c^{2} are achieved. The lower reach of m_{χ} is extended to 2 GeV/c^{2}.
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The design of artificial molecular machines often takes inspiration from macroscopic machines. However, the parallels between the two systems are often only superficial, because most molecular ...machines are governed by quantum processes. Previously, rotary molecular motors powered by light and chemical energy have been developed. In electrically driven motors, tunnelling electrons from the tip of a scanning tunnelling microscope have been used to drive the rotation of a simple rotor in a single direction and to move a four-wheeled molecule across a surface. Here, we show that a stand-alone molecular motor adsorbed on a gold surface can be made to rotate in a clockwise or anticlockwise direction by selective inelastic electron tunnelling through different subunits of the motor. Our motor is composed of a tripodal stator for vertical positioning, a five-arm rotor for controlled rotations, and a ruthenium atomic ball bearing connecting the static and rotational parts. The directional rotation arises from sawtooth-like rotational potentials, which are solely determined by the internal molecular structure and are independent of the surface adsorption site.
The equiatomic multicomponent CoCrFeNiTiAl high-entropy solid solution alloy was synthesized by mechanical alloying (MA). The effects of milling duration and subsequent annealing on the structure and ...morphology evolution were investigated. Supersaturated BCC and FCC solid solutions appear when the blended powder is ball milled more than 18
h. The 30
h ball milled alloy powder shows excellent chemical homogeneity and refined morphology with mean particle size of less than 5
μm. The microscaled particles are actually hard agglomerations of nanoscaled crystallines with crystal size of about 40
nm. The phase composition transforms to two BCC solid solutions when the 30
h mechanically alloyed powder was annealed at 600
°C for 1
h. The simple solid solution structure can be maintained even after the alloy was annealed at 1000
°C. The 30
h milled alloy powder was subsequently consolidated by spark plasma sintering (SPS) at 800
°C for 10
min. The sintered sample Exhibits 98% in relative density and 432 HV in Vickers hardness.
Context.
A link has finally been established between magnetars and fast radio burst (FRB) sources. Within this context, a major issue that remains unresolved pertains to whether sources of ...extragalactic FRBs exhibit X/
γ
-ray outbursts and whether this is correlated with radio activity. If so, the subsequent goal is to identify these sources.
Aims.
We aim to constrain possible X/
γ
-ray burst activity from one of the nearest extragalactic FRB sources currently known. This is to be done over a broad energy range by looking for bursts over a range of timescales and energies that are compatible with those of powerful flares from extragalactic magnetars.
Methods.
We followed up on the observation of the as-yet nearest extragalactic FRB source, located at a mere 149 Mpc distance, namely, the periodic repeater
FRB 180916.J0158+65
. This took place during the active phase between 4 and 7 February 2020, using the Insight–Hard X-ray Modulation Telescope (Insight–HXMT). By taking advantage of the combination of broad-band wavelengths, a large effective area, and several independent detectors at our disposal, we searched for bursts over a set of timescales from 1 ms to 1.024 s with a sensitive algorithm that had been previously characterised and optimised. Moreover, through simulations, we studied the sensitivity of our technique in the released energy-duration phase space for a set of synthetic flares and assuming a range of different energy spectra.
Results.
We constrain the possible occurrence of flares in the 1−100 keV energy band to
E
< 10
46
erg for durations Δ
t
< 0.1 s over several tens of ks exposure.
Conclusions.
We can rule out the occurrence of giant flares similar to the ones that were observed in the few cases of Galactic magnetars. The absence of reported radio activity during our observations prevents us from making any determinations regarding the possibility of simultaneous high-energy emission.
Self-DNA is present in the cytosol of many cancer cells and can promote effective immune rejection of tumor cells, but the mechanisms leading to the presence of cytosolic DNA are unknown. Here, we ...report that the cleavage of genomic DNA by DNA structure-specific endonuclease MUS81 and PARP-dependent DNA repair pathways leads to the accumulation of cytosolic DNA in prostate cancer cells. The number of nuclear MUS81 foci and the amount of cytosolic dsDNA increased in tandem from hyperplasia to clinical stage II prostate cancers and decreased at stage III. Cytosolic DNA generated by MUS81 stimulated DNA sensor STING-dependent type I interferon (IFN) expression and promoted phagocytic and T cell responses, resulting in type I and II IFN-mediated rejection of prostate tumor cells via mechanisms that partly depended on macrophages. Our results demonstrate that the tumor suppressor MUS81 alerts the immune system to the presence of transformed host cells.
•Presence of cytosolic DNA in prostate cancer cells depends on Mus81•Mus81 induces STING-dependent type I interferon expression•Immune rejection of prostate cancer cells relies on Mus81 and STING•Mus81 enhances innate and adaptive anti-cancer immune responses
The mechanisms leading to the presence of cytosolic DNA in cancer cells are unknown. Gasser and colleagues find that the DNA structure-specific endonuclease Mus81 promotes the shedding of genomic DNA into the cytosol of prostate cancer cells. Mus81 stimulates STING-dependent DNA sensor pathways and immune rejection of prostate cancer cells.
The emergence of the H7N9 influenza virus in humans in Eastern China has raised concerns that a new influenza pandemic could occur. Here, we used a ferret model to evaluate the infectivity and ...transmissibility of A/Shanghai/2/2013 (SH2), a human H7N9 virus isolate. This virus replicated in the upper and lower respiratory tracts of the ferrets and was shed at high titers for 6 to 7 days, with ferrets showing relatively mild clinical signs. SH2 was efficiently transmitted between ferrets via direct contact, but less efficiently by airborne exposure. Pigs were productively infected by SH2 and shed virus for 6 days but were unable to transmit the virus to naïve pigs or ferrets. Under appropriate conditions, human-to-human transmission of the H7N9 virus may be possible.
Electromagnetic ion cyclotron (EMIC) waves can drive precipitation of tens of keV protons and relativistic electrons, and are a potential candidate for causing radiation belt flux dropouts. In this ...study, we quantitatively analyze three cases of EMIC‐driven precipitation, which occurred near the dusk sector observed by multiple Low‐Earth‐Orbiting (LEO) Polar Operational Environmental Satellites/Meteorological Operational satellite programme (POES/MetOp) satellites. During EMIC wave activity, the proton precipitation occurred from few tens of keV up to hundreds of keV, while the electron precipitation was mainly at relativistic energies. We compare observations of electron precipitation with calculations using quasi‐linear theory. For all cases, we consider the effects of other magnetospheric waves observed simultaneously with EMIC waves, namely, plasmaspheric hiss and magnetosonic waves, and find that the electron precipitation at MeV energies was predominantly caused by EMIC‐driven pitch angle scattering. Interestingly, each precipitation event observed by a LEO satellite extended over a limited L shell region (ΔL ~ 0.3 on average), suggesting that the pitch angle scattering caused by EMIC waves occurs only when favorable conditions are met, likely in a localized region. Furthermore, we take advantage of the LEO constellation to explore the occurrence of precipitation at different L shells and magnetic local time sectors, simultaneously with EMIC wave observations near the equator (detected by Van Allen Probes) or at the ground (measured by magnetometers). Our analysis shows that although EMIC waves drove precipitation only in a narrow ΔL, electron precipitation was triggered at various locations as identified by POES/MetOp over a rather broad region (up to ~4.4 hr MLT and ~1.4 L shells) with similar patterns between satellites.
Key Points
We show three cases of proton and relativistic electron precipitation observed simultaneously with EMIC waves
EMIC‐driven precipitation was observed by POES/MetOp satellites at different locations over a broad L‐MLT region
Each precipitation event extended over ΔL ~ 0.3 on average, showing that wave‐driven pitch angle scattering is localized
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