Collisionless shocks are ubiquitous in the Universe as a consequence of supersonic plasma flows sweeping through interstellar and intergalactic media. These shocks are the cause of many observed ...astrophysical phenomena, but details of shock structure and behavior remain controversial because of the lack of ways to study them experimentally. Laboratory experiments reported here, with astrophysically relevant plasma parameters, demonstrate for the first time the formation of a quasiperpendicular magnetized collisionless shock. In the upstream it is fringed by a filamented turbulent region, a rudiment for a secondary Weibel-driven shock. This turbulent structure is found responsible for electron acceleration to energies exceeding the average energy by two orders of magnitude.
Full text
Available for:
CMK, CTK, FMFMET, NUK, UL
FeSiAl/hBN soft magnetic composites were prepared by mixing gas atomized FeSiAl powder and hexagonal BN by ball milling at a certain mass ratio and then compacted and annealed. The microstructure of ...the composites was characterized by XRD, SEM and EDS. It was found that ball milling can destroy the weaker interlayer bond of hexagonal BN and turn it into nanoflakes attached to the surface of FeSiAl particles. The magnetic properties of the composites were measured by SQUID and B-H analyzer. It was found that the nanoflakes on the surface of FeSiAl particles effectively blocked the eddy current among different metallic particles and largely reduced eddy current loss. The permeability analysis showed that the composites had a relative lower magnetic loss at f = 30 MHz, which indicated that the FeSiAl/hBN composites can be used in a frequency higher than other FeSiAl composites. However, the saturation magnetization and permeability of the composites decreased with the increase of BN content. The experimental results show that the magnetic loss value of FeSiAl/1 wt% hBN soft magnetic composites is about 392 kW m−3 at f= 100 kHz and Bm= 100mT, which is just about 2/3 of commercial FeSiAl soft magnetic composites.
•The magnetic loss value of FeSiAl/1wt% hBN SMCs is about 392kW.m-3 at f=100kHz and Bm=100mT, which have low power losses.•The composites had a relative lower magnetic loss at f =1MHz, which indicated that the FeSiAl/hBN composite material can be applied to high frequency.•Hysteresis loss is below the commercial value, which have commercial application value in high-power electrical systems.
Sodium–sulfur batteries (NaSBs) have emerged as a promising energy storage technology for large-scale stationary applications such as smart electrical grids due to their exceptionally high energy ...density and cost-effectiveness. However, one of the challenging problems impeding their practical applications is the sulfur shuttle effect by which the active redox intermediates are gradually dissolved in electrolytes. In this work, we have employed first-principles density functional theory (DFT) calculations to unravel the suppression of the shuttle effect in NaSBs with a two-dimensional (2D) As2S3 monolayer as the anchoring material. We show that semiconducting As2S3 is a suitable anchoring layer to inhibit the dissolution of the polysulfide intermediates in common electrolytes because of its stronger chemical binding with sodium polysulfides than with the electrolytes. The immense adsorption is attributed to the electron donation from the unfilled S-3p states of the polysulfides to As2S3. These mechanisms increase the carrier population and consequently improve the electrical conductivity of As2S3. Hence, the use of As2S3 can both reduce the shuttle effect and enhance the cathode electron conductivity to enable improved cycling stability and coulombic efficiency of the battery.
► SiCp/AZ91 nanocomposite was subjected to extrusion. ► Grains of matrix in the SiCp/AZ91 nanocomposites are greatly refined. ► Distribution of SiC nanoparticles is improved due to the extrusion ...process. ► Tensile strength of nanocomposite conducted at various temperatures is enhanced.
Particulate reinforced magnesium matrix nanocomposite prepared with semisolid stirring assisted ultrasonic vibration was subjected to extrusion at 350°C with an extrusion ratio of 12:1. Extrusion of the SiCp/AZ91 nanocomposite induced large scale dynamic recrystallization resulting in a fine matrix microstructure. There were two kinds of zones in the extruded nanocomposite: SiC nanoparticle bands parallel to the extrusion direction and refined-grain zones between the SiC nanoparticle bands. In the SiC nanoparticle bands, there were SiC nanoparticles along the boundaries of refined grains. The distribution of SiC nanoparticles was uniform although some agglomerates of SiC nanoparticles still existed in the SiC nanoparticle bands. The ultimate tensile strength, yield strength and elongation to fracture of the SiCp/AZ91 nanocomposite were simultaneously improved by extrusion. Results from the extruded SiCp/AZ91 nanocomposite tensile testing at different temperatures (75, 125, 175 and 225°C) revealed an increase of the tensile strength and ductility values compared with the unreinforced and extruded AZ91 alloy.
•Novel stir casting assisted by ultrasonic treatment was developed.•Ultrasonic treatment significantly improved the stir casting.•Ultrasonic treatment improved the mechanical properties.
The novel ...stir casting assisted by ultrasonic treatment processing was studied. Unlike traditional stir casting, short semi-solid stir time was needed for addition and pre-dispersion of the particles in the novel processing. For ultrasonic treatment, there existed an optimal time. Both too short and too long time for the treatment resulted in nonhomogeneous particle distribution. Furthermore, the liquid stirring after ultrasonic treatment was proved to be necessary to further improve particle distribution. The mechanical properties of the composites fabricated by different parameters indicated that ultrasonic treatment evidently improved the mechanical properties compared with traditional stir casting. 5–20% SiCp/AZ91 composites were fabricated by the novel processing. The particle distribution was uniform in these composites. The grains were refined by addition of SiC particles. Grain sizes of composites decreased with the increases of particle contents. The ultimate tensile strength, yield strength and elastic modulus were enhanced as the particle contents increased.
The hepatic activities of uridine diphosphate glucuronosyltransferase (UGT) and sulfotransferase (SULT) of male Ross 708 broiler chickens at the age of 1, 7, 14, 28, and 56 days and male ...Camborough‐29 pigs at the age of 1 day and 2, 5, 10, and 20 weeks were investigated. Glucuronidation and sulfation of 4‐nitrophenol were used to evaluate the activities. Porcine hepatic UGT and SULT activities were low at birth, peaked at around 5–10 weeks, and then declined. Both hepatic UGT and SULT activities of chickens were high at hatch and declined. Chicken hepatic UGT activity had a peak at the age of 28 days. Affinity of hepatic SULT to 4‐nitrophenol is similar in chickens and pigs, but the affinity of hepatic UGT in pigs was about 10 times higher than that in chickens. 4‐nitrophenol was predominantly conjugated by SULT instead of UGT in chicken livers from hatch to day 56. Conversely, hepatic UGT contributed predominantly in 4‐nitrophenol conjugation than the SULT in pigs from birth to 20 weeks. Therefore, age has significant impact on hepatic activities of UGT and SULT, and the importance of UGT and SULT on conjugation is different in chickens and pigs.
► The grain size of the as-extruded Mg–Zn–Ca alloy was refined by trace Mn addition. ► The basal texture was enhanced in the as-extruded Mg–Zn–Ca–Mn alloy due to the lower volume fraction of ...recrystallized grains. ► The tensile yield strength (TYS) of Mg–Zn–Ca alloy was improved through trace Mn addition, a good balance of strength and ductility was achieved.
The effect of trace Mn addition on the microstructure, texture and mechanical properties of the as-cast and as-extruded Mg–5.25
wt.% Zn–0.6
wt.% Ca (ZX51) alloys was investigated in this study. Mn addition had a negligible effect on the grain size of the as-cast ZX51 alloy. However, the addition of Mn led to the obvious decrease of grain size in the as-extruded Mg–5.25
wt.% Zn–0.6
wt.% Ca–0.3
wt.% Mn (ZXM510) alloy, because the Mn addition restricted the grain growth during the hot extrusion process. After the addition of Mn, the basal fiber texture with most of {0
0
0
2} planes parallel to the extrusion direction (ED) was significantly enhanced in the as-extruded ZXM510 alloy. Both tensile yield strength (TYS) and ultimate tensile strength (UTS) were increased in the as-extruded ZXM510 alloy, while the ductility was slightly decreased, which was ascribed to the grain refinement and texture strengthening.
Exceptional fossil specimens with preserved soft parts from the Maotianshan Shale (ca 520 Myr ago) and the Burgess Shale (505 Myr ago) biotas indicate that the worldwide distributed bivalved ...arthropod Isoxys was probably a non-benthic visual predator. New lines of evidence come from the functional morphology of its powerful prehensile frontal appendages that, combined with large spherical eyes, are thought to have played a key role in the recognition and capture of swimming or epibenthic prey. The swimming and steering of this arthropod was achieved by the beating of multiple setose exopods and a flap-like telson. The appendage morphology of Isoxys indicates possible phylogenetical relationships with the megacheirans, a widespread group of assumed predator arthropods characterized by a pre-oral 'great appendage'. Evidence from functional morphology and taphonomy suggests that Isoxys was able to migrate through the water column and was possibly exploiting hyperbenthic niches for food. Although certainly not unique, the case of Isoxys supports the idea that off-bottom animal interactions such as predation, associated with complex feeding strategies and behaviours (e.g. vertical migration and hunting) were established by the Early Cambrian. It also suggests that a prototype of a pelagic food chain had already started to build-up at least in the lower levels of the water column.
PDF
