ABSTRACT
The megajansky radio burst, FRB 20200428, and other bright radio bursts detected from the Galactic source SGR J1935+2154 suggest that magnetars can make fast radio bursts (FRBs), but the emission site and mechanism of FRB-like bursts are still unidentified. Here, we report the emergence of a radio pulsar phase of the magnetar 5 months after FRB 20200428. Pulses were detected in 16.5 hours over 13 days using the Five-hundred-meter Aperture Spherical radio Telescope, with luminosities of about eight decades fainter than FRB 20200428. The pulses were emitted in a narrow phase window anti-aligned with the x-ray pulsation profile observed using the x-ray telescopes. The bursts, conversely, appear in random phases. This dichotomy suggests that radio pulses originate from a fixed region within the magnetosphere, but bursts occur in random locations and are possibly associated with explosive events in a dynamically evolving magnetosphere. This picture reconciles the lack of periodicity in cosmological repeating FRBs within the magnetar engine model.
ABSTRACT
Carbonaceous-magnetic composites are the most appealing candidates for electromagnetic wave absorption, and creating hollow interiors and nanopores in the composites is commonly recognized as an essential strategy to reinforce their overall performances. Herein, we propose a spatial confinement strategy mediated by Co2(OH)2CO3 nanosheet assemblies for achieving highly dispersed Co nanoparticles into hollow porous N-doped carbon shells (HP-Co@NCS). Systematic multi-technique characterizations indicate that the Co2(OH)2CO3 nanosheet assemblies simultaneously play a trifunctional role during the synthesis, including Co source, template of the hollow interior cavities, and micro-/mesopore porogen. The chemical composition can be modulated by simply varying the ratio of Co2(OH)2CO3 and carbon source (dopamine). The optimized HP-Co@NCS absorber exhibits a well-defined hollow structure and unprecedented high porosity (specific surface area of 742 m2 g-1) even with a high metallic Co content of 35.8 wt%. These profitable structural characteristics can facilitate incident EM waves penetrating the absorber's interior and promoting multiple reflections and scattering. Therefore, the HP-Co@NCS absorber exhibits efficient microwave absorption ability with a minimum reflection loss of -39.0 dB at a thin thickness of 2.5 mm and an effective absorption bandwidth up to 5.5 GHz (12.5-18.0 GHz) at a thin thickness of 2.0 mm. This work provides a new methodology to design advanced carbonaceous-magnetic composite materials with hollow porous structures for microwave absorption.
ABSTRACT
Overall foraging success and ultimate fitness of an individual animal is highly dependent on their food-searching strategies, which are the focus of foraging theory. Considering the consistent inter-individual behavioural differences, personality may have a fundamental impact on animal food-scratching behaviour, which remains largely unknown. In this study, we aimed to investigate how personality traits (i.e., boldness and exploration) affect the food-scratching behaviour and food intake of the domestic Japanese quail Coturnix japonica during the foraging process. The quails exhibited significant repeatability in boldness and exploration, which also constituted a behavioural syndrome. More proactive, that is, bolder and more explorative, individuals scratched the ground more frequently for food and began scratching earlier in a patch. Individuals that scratched more frequently had a longer foraging time and a higher food intake. The correlation between personality traits and temporary food intake during every 2 min varied over time and was sex dependent, with females exhibiting a positive correlation during the first half of the foraging stage and males after the initial stage. These findings suggest that personality traits affect the food-scratching behaviour and, thus, the food intake of quails. Our study provides insights into the impact of personality traits on animal's foraging behaviour by influencing their food-searching strategies.
ABSTRACT
The shallow lake wetlands in the middle and lower Yangtze River floodplain are important wintering and stopover habitats for migratory waterbirds on the East Asia-Australia Flyway. With increasing fishery practices in recent years, however, the wetlands have deteriorated significantly and now threaten wintering waterbirds. To gain insight into the influence of deteriorating wetlands on waterbirds, we conducted a survey of wintering waterbird species, population size, and distribution across 11 belt transects in Caizi Lake and Shengjin Lake, two shallow lakes along the Yangtze River in Anhui Province from November 2007-April 2008 and from November 2008-April 2009, respectively. The impacts of different fishery patterns on the distribution of waterbirds were also analyzed. A total of 43 waterbirds species belong to 7 orders of 12 families were counted during the surveys, of which 38 were found in Caizi Lake with a density of 8.2 ind./hm(2), and 42 in Shengjin Lake with a density of 3.5 ind./hm(2). Geese (Anser cygnoides), bean geese (Anser fabalis), tundra swan (Cygnus columbianus), and dunlin (Calidris alpina) were the dominant species in the two shallow lakes. Species number and individual assemble reached maximum at the end of December and in early January of the following year, without coincidence of the largest flock for different ecological groups. Based on waterbird diversity across the 11 belt transects and the fishery patterns, habitats could be divided into three groups. Gruiformes, Anseriformes and Charadriiformes had relatively higher densities in the natural fishery zones and lower densities in the cage fishery zones; whereas, the density of Ardeidae showed little change across all lake zones. It is important to develop sustainable fishery patterns in shallow lakes along the middle and lower Yangtze River floodplain to better protect resources of wintering waterbirds.
