The equiatomic multiprincipal CoCrFeNiCuAl high-entropy alloy was prepared using a vacuum arc melt casting method. The as-cast alloy was subsequently annealed at 1000
°C for 2
h and the annealing ...effects on the structure and properties evolution were investigated. The as-cast alloy is composed of simple BCC and FCC solid solutions. The “2” FCC phase precipitates from the ordered BCC matrix and the FCC phases become dominated after the alloy was annealed. Both alloys show typical cast-dendrite morphology and similar elemental segregation. The as-annealed alloy exhibits high strength and excellent ductility of 1.63
GPa and 34%, respectively. Both alloys possess high saturated magnetization and undergo a ferromagnetic transition.
The dipole approximation is usually employed to describe light-matter interactions under ordinary conditions. With the development of artificial atomic systems, 'giant atom' physics is possible, ...where the scale of atoms is comparable to or even greater than the wavelength of the light they interact with, and the dipole approximation is no longer valid. It reveals interesting physics impossible in small atoms and may offer useful applications. Here, we experimentally demonstrate the giant spin ensemble (GSE), where a ferromagnetic spin ensemble interacts twice with the meandering waveguide, and the coupling strength between them can be continuously tuned from finite (coupled) to zero (decoupled) by varying the frequency. In the nested configuration, we investigate the collective behavior of two GSEs and find extraordinary phenomena that cannot be observed in conventional systems. Our experiment offers a new platform for 'giant atom' physics.
ABSTRACT
We present timing solutions and analyses of 11 pulsars discovered by the Five-hundred-meter Aperture Spherical radio Telescope (FAST). These pulsars were discovered using an ultrawide ...bandwidth receiver in drift-scan observations made during the commissioning phase of FAST, and were then confirmed and timed using the 64-m Parkes Radio Telescope. Each pulsar has been observed over a span of at least one year. Highlighted discoveries include PSR J0344−0901, which displays mode-changing behaviour and may belong to the class of so-called swooshing pulsars (alongside PSRs B0919+06 and B1859+07); PSR J0803−0942, whose emission is almost completely linearly polarized; and PSRs J1900−0134 and J1945+1211, whose well-defined polarization angle curves place stringent constraints on their emission geometry. We further discuss the detectability of these pulsars by earlier surveys, and highlight lessons learned from our work in carrying out confirmation and monitoring observations of pulsars discovered by a highly sensitive telescope, many of which may be applicable to next-generation pulsar surveys. This paper marks one of the first major releases of FAST-discovered pulsars, and paves the way for future discoveries anticipated from the Commensal Radio Astronomy FAST Survey.
Abstract
Ultrafast control of material physical properties represents a rapidly developing field in condensed matter physics. Yet, accessing the long-lived photoinduced electronic states is still in ...its early stages, especially with respect to an insulator to metal phase transition. Here, by combining transport measurement with ultrashort photoexcitation and coherent phonon spectroscopy, we report on photoinduced multistage phase transitions in Ta
2
NiSe
5
. Upon excitation by weak pulse intensity, the system is triggered to a short-lived state accompanied by a structural change. Further increasing the excitation intensity beyond a threshold, a photoinduced steady new state is achieved where the resistivity drops by more than four orders at temperature 50 K. This new state is thermally stable up to at least 350 K and exhibits a lattice structure different from any of the thermally accessible equilibrium states. Transmission electron microscopy reveals an in-chain Ta atom displacement in the photoinduced new structure phase. We also found that nano-sheet samples with the thickness less than the optical penetration depth are required for attaining a complete transition.
Summary
Background
The short‐term effect of ambient air pollution on atopic dermatitis (AD), along with its effect modifiers, has not been fully addressed.
Objectives
To examine the short‐term ...associations between air pollution and AD, and to identify effect modifications by age and season.
Methods
We used the generalized additive model to evaluate the short‐term effect of ambient air pollution on daily hospital visits for AD, adjusting for potential confounders. Subgroup analyses were performed to identify potential effect modifications by season and age (< 18 years and ≥ 18 years).
Results
A total of 29 972 hospital visits for AD were recorded in Guangzhou, China, from 19 January 2013 to 31 December 2017. Among them, 72·8% were visits by children and 51·4% occurred in the cool season. Acute and delayed effects on AD hospital visits were significant for all air pollutants. Stronger effects were seen in the cool season (approximately 1·7–3·0 times higher than effects in the warm season). Stronger effects were also observed in children (approximately 1·3–1·8 times higher than effects in adults). Sensitivity analyses indicated the results were robust.
Conclusions
Air pollution might be an important trigger for AD in subtropical Guangzhou, China. Children are more vulnerable than adults, and the effects are stronger in the cool season.
What is already known about this topic?
Atopic dermatitis (AD) has the highest number of disability‐adjusted life‐years among skin disorders.
The acute effect of air pollution on AD has not been well studied in China.
What does this study add?
We found that air pollution (including ambient fine particulate matter, inhalable particles, sulfur dioxide, nitrogen dioxide and ozone) acutely triggers AD, and that children are more sensitive to this effect.
The cool season is the vulnerable exposure window for these acute effects.
The event rate, energy distribution and time-domain behaviour of repeating fast radio bursts (FRBs) contain essential information regarding their physical nature and central engine, which are as yet ...unknown
. As the first precisely localized source, FRB 121102 (refs.
) has been extensively observed and shows non-Poisson clustering of bursts over time and a power-law energy distribution
. However, the extent of the energy distribution towards the fainter end was not known. Here we report the detection of 1,652 independent bursts with a peak burst rate of 122 h
, in 59.5 hours spanning 47 days. A peak in the isotropic equivalent energy distribution is found to be approximately 4.8 × 10
erg at 1.25 GHz, below which the detection of bursts is suppressed. The burst energy distribution is bimodal, and well characterized by a combination of a log-normal function and a generalized Cauchy function. The large number of bursts in hour-long spans allows sensitive periodicity searches between 1 ms and 1,000 s. The non-detection of any periodicity or quasi-periodicity poses challenges for models involving a single rotating compact object. The high burst rate also implies that FRBs must be generated with a high radiative efficiency, disfavouring emission mechanisms with large energy requirements or contrived triggering conditions.
Understanding the corrosion behavior of Fe-based amorphous coatings under wet-dry cyclic conditions is of pretty importance for coating applications in marine environments. In this paper, the ...corrosion evolutions of the coatings under wet-dry cyclic conditions were investigated by electrochemical impedance spectroscopy (EIS), scanning electron microscope (SEM) and transmission electron microscopy (TEM). Accurate charge transfer resistance (Rt) was obtained through fitting EIS results using a modified transmission line equivalent circuit model and a landscape map of Rt was constructed for a panoramic investigation on coating corrosion. The results show that the corrosion rate of the coating changes cyclically under wet-dry cyclic conditions. Corrosion within a single wet-dry cycle can be presented as four stages: an initial decrease of corrosion rate due to passivation or repassivation when the coating is wetted, then a slow increase due to concentrated aggressive ions with solution evaporation, followed by a rapid increment associated with fast oxygen transport under ultrathin solution film and finally a stable stage as solution dries out. It is deduced that an oxygen concentration gradient can form between the inside and the outside of coating pores when the solution film over the coating is very thin, which further promotes the localized corrosion in the pores. According to the landscape map of Rt, the coating maintains its high corrosion resistance for the initial 33 wet-dry cycles. But its corrosion resistance decreases significantly in the 35th wet-dry cycle accompanied by the attack of localized corrosion. After 65 wet dry cycles, the coating fails due to the penetration of localized corrosion. The interparticle oxide layers are defective, which enhances the localized corrosion process.
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•Accurate charge transfer resistance has been obtained for wet-dry corrosion of coatings.•Corrosion rate of coatings changes cyclically under wet-dry cyclic conditions.•Oxygen concentration gradient under thin solution film promotes localized corrosion in pores.
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