Summary
Porcine reproductive and respiratory syndrome virus (PRRSV) is a major economically significant pathogen that has adversely affected China's swine industry. Currently, a novel type 2 PRRSV, ...called the NADC30‐like strain, is epidemic in numerous provinces of China, and commercial vaccines provide limited protection for infected animals. The extensive recombination phenomenon among NADC30‐like PRRSVs is identified as a unique molecular characteristic of the virus. However, our understanding of how recombination influences NADC30‐like PRRSVs is largely inadequate. In this study, we analysed the genetic characteristics of a recombinant NADC30‐like PRRSV (SC‐d) and examined its pathogenicity compared with a non‐recombinant NADC30‐like PRRSV (SD‐A19) and a highly pathogenic PRRSV (HuN4). SC‐d has three discontinuous deletions in nsp2, consistent with NADC30 isolated from the United States in 2008. Furthermore, we identified four recombination breakpoints in the SC‐d genome, which separated the SC‐d genome into four regions (regions A, B, C and D). Regions A and C are closely related to the JXA1‐like strain, one of the earliest Chinese HP‐PRRSV strains, and regions B and D are closely related to the NADC30 strain. Moreover, SC‐d inoculated piglets exhibited a persistent fever, moderate weight loss, mild thymus atrophy and obvious microscopic lung lesions. In summary, the recombinant NADC30‐like PRRSV SC‐d strain displayed a higher pathogenicity than the non‐recombinant NADC30‐like PRRSV SD‐A19 strain; however, the pathogenicity of the NADC30‐like PRRSV SC‐d was lower compared with the HP‐PRRSV HuN4 strain in piglets. Our findings demonstrate that recombination is responsible for the enormous genetic diversity and pathogenicity variance of the NADC30‐like PRRSV in China. This study provides a theoretical basis for developing a more reasonable PRRSV control and prevention strategy.
Near the boundary between ordered and disordered quantum phases, several experiments have demonstrated metallic behaviour that defies the Landau Fermi paradigm.sup.1-5. In moiré heterostructures, ...gate-tuneable insulating phases driven by electronic correlations have been recently discovered.sup.6-23. Here, we use transport measurements to characterize metal-insulator transitions (MITs) in twisted WSe.sub.2 near half filling of the first moiré subband. We find that the MIT as a function of both density and displacement field is continuous. At the metal-insulator boundary, the resistivity displays strange metal behaviour at low temperatures, with dissipation comparable to that at the Planckian limit. Further into the metallic phase, Fermi liquid behaviour is recovered at low temperature, and this evolves into a quantum critical fan at intermediate temperatures, before eventually reaching an anomalous saturated regime near room temperature. An analysis of the residual resistivity indicates the presence of strong quantum fluctuations in the insulating phase. These results establish twisted WSe.sub.2 as a new platform to study doping and bandwidth-controlled metal-insulator quantum phase transitions on the triangular lattice.
Fast radio bursts (FRBs) are highly dispersed, millisecond-duration radio bursts1-3. Recent observations of a Galactic FRB4-8 suggest that at least some FRBs originate from magnetars, but the origin ...of cosmological FRBs is still not settled. Here we report the detection of1,863 bursts in 82 h over 54 days from the repeating source FRB 20201124A (ref.9). These observations show irregular short-time variation ofthe Faraday rotation measure (RM), which scrutinizes the density-weighted line-of-sight magnetic field strength, of individual bursts during the first 36 days, followed by a constant RM. We detected circular polarization in more than half of the burst sample, including one burst reaching a high fractional circular polarization of 75%. Oscillations in fractional linear and circular polarizations, as well as polarization angle as a function of wavelength, were detected. All of these features provide evidence for a complicated, dynamically evolving, magnetized immediate environment within about an astronomical unit (au; Earth-Sun distance) ofthe source. Our optical observations of its Milky-Way-sized, metal-rich host galaxy10-12 show a barred spiral, with the FRB source residing in a low-stellar-density interarm region at an intermediate galactocentric distance. This environment is inconsistent with a young magnetar engine formed during an extreme explosion of a massive star that resulted in a long gamma-ray burst or superluminous supernova.
High-energy cosmic-ray electrons and positrons (CREs), which lose energy quickly during their propagation, provide a 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 measured directly up to approximately 2 teraelectronvolts in previous balloon- or space-borne experiments, and indirectly up to approximately 5 teraelectronvolts using ground-based Cherenkov γ-ray telescope arrays. Evidence for a spectral break in the teraelectronvolt energy range has been provided by indirect measurements, although the results were qualified by sizeable systematic uncertainties. Here we report a direct measurement of CREs in the energy range 25 gigaelectronvolts to 4.6 teraelectronvolts by the Dark Matter Particle Explorer (DAMPE) with unprecedentedly high energy resolution and low background. The largest part of the spectrum can be well fitted by a 'smoothly broken power-law' model rather than a single power-law model. The direct detection of a spectral break at about 0.9 teraelectronvolts confirms the evidence found by previous indirect measurements, clarifies the behaviour of the CRE spectrum at energies above 1 teraelectronvolt and sheds light on the physical origin of the sub-teraelectronvolt CREs.
We demonstrate that magnetic properties of ultrathin Co films adjacent to Gd2O3 gate oxides can be directly manipulated by voltage. The Co films can be reversibly changed from an optimally oxidized ...state with a strong perpendicular magnetic anisotropy to a metallic state with an in-plane magnetic anisotropy or to an oxidized state with nearly zero magnetization, depending on the polarity and time duration of the applied electric fields. Consequently, an unprecedentedly large change of magnetic anisotropy energy up to 0.73 erg/cm(2) has been realized in a nonvolatile manner using gate voltages of only a few volts. These results open a new route to achieve ultralow energy magnetization manipulation in spintronic devices.
Merons which are topologically equivalent to one-half of skyrmions can exist only in pairs or groups in two-dimensional (2D) ferromagnetic (FM) systems. The recent discovery of meron lattice in ...chiral magnet Co
Zn
Mn
raises the immediate challenging question that whether a single meron pair, which is the most fundamental topological structure in any 2D meron systems, can be created and stabilized in a continuous FM film? Utilizing winding number conservation, we develop a new method to create and stabilize a single pair of merons in a continuous Py film by local vortex imprinting from a Co disk. By observing the created meron pair directly within a magnetic field, we determine its topological structure unambiguously and explore the topological effect in its creation and annihilation processes. Our work opens a pathway towards developing and controlling topological structures in general magnetic systems without the restriction of perpendicular anisotropy and Dzyaloshinskii-Moriya interaction.
Superelastic conducting fibers with improved properties and functionalities are needed for diverse applications. Here we report the fabrication of highly stretchable (up to 1320%) sheath-core ...conducting fibers created by wrapping carbon nanotube sheets oriented in the fiber direction on stretched rubber fiber cores. The resulting structure exhibited distinct short- and long-period sheath buckling that occurred reversibly out of phase in the axial and belt directions, enabling a resistance change of less than 5% for a 1000% stretch. By including other rubber and carbon nanotube sheath layers, we demonstrated strain sensors generating an 860% capacitance change and electrically powered torsional muscles operating reversibly by a coupled tension-to-torsion actuation mechanism. Using theory, we quantitatively explain the complementary effects of an increase in muscle length and a large positive Poisson's ratio on torsional actuation and electronic properties.
A new alpha-emitting isotope U-214, produced by the fusion-evaporation reaction W-182(Ar-36,4n) U-214, was identified by employing the gas-filled recoil separator SHANS and the recoil-a correlation ...technique. More precise a-decay properties of even-even nuclei U-216,U-218 were also measured in the reactions of Ar-40, Ca-40 beams with W-180,W-182,W- 184 targets. By combining the experimental data, improved alpha-decay reduced widths delta(2) for the even-even Po-Pu nuclei in the vicinity of the magic neutron number N = 126 are deduced. Their systematic trends are discussed in terms of the N-p N-n scheme in order to study the influence of protonneutron interaction on a decay in this region of nuclei. It is strikingly found that the reduced widths of( 214,216)U are significantly enhanced by a factor of two as compared with the NpNn systematics for the 84 <= Z <= 90 and N < 126 even-even nuclei. The abnormal enhancement is interpreted by the strong monopole interaction between the valence protons and neutrons occupying the pi 1f (7/2) and nu 1f(5/2) spin-orbit partner orbits, which is supported by the large-scale shell model calculation.
Although the magnetoelectric effects - the mutual control of electric polarization by magnetic fields and magnetism by electric fields, have been intensively studied in a large number of inorganic ...compounds and heterostructures, they have been rarely observed in organic materials. Here we demonstrate magnetoelectric coupling in a metal-organic framework (CH3)2NH2Mn(HCOO)3 which exhibits an order-disorder type of ferroelectricity below 185 K. The magnetic susceptibility starts to deviate from the Curie-Weiss law at the paraelectric-ferroelectric transition temperature, suggesting an enhancement of short-range magnetic correlation in the ferroelectric state. Electron spin resonance study further confirms that the magnetic state indeed changes following the ferroelectric phase transition. Inversely, the ferroelectric polarization can be improved by applying high magnetic fields. We interpret the magnetoelectric coupling in the paramagnetic state in the metal-organic framework as a consequence of the magnetoelastic effect that modifies both the superexchange interaction and the hydrogen bonding.
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•A total of 17 antibiotics were detected in water, sediment (biofilm), organism and feed samples.•Greenhouse ponds were more likely to accumulate antibiotics compared to outdoor ...ponds.•Zn as the coexisting contaminant was significantly correlated with antibiotic concentrations.•Aquaculture wastewater and domestic sewage were potential sources of antibiotics.•Ciprofloxacin and enrofloxacin may present high ecological and resistance risks.
This study focused on the distribution, combined pollution, potential source and risk assessment of 17 antibiotics in an aquaculture ecosystem surrounding the Yellow sea, North China. Antibiotics were detected in various matrices (seawater, sediment/biofilm, organism and feed) in different aquaculture modes (greenhouse and outdoor aquaculture) during the wet and dry seasons in coastal areas of Shandong province. The innovation points of the study were as follows: (1) To the best of our knowledge, this study was one of the few to investigate the occurrence and distribution of antibiotics in mariculture environments along the Yellow Sea coast; (2) Biofilms, a focus of the study, might act as a sink for antibiotics in the aquaculture ecosystem; and (3) The correlation of heavy metals and antibiotic concentrations was proved, which could correspondingly be used as an indicator for antibiotic concentrations in the studied area.
The levels of antibiotics in water were observed to be relatively low, at the ng/L level. Trimethoprim was the most prevalent antibiotic, and was detected in all water samples. Oxytetracycline was detected at high concentrations in biofilms (up to 1478.29 ng/g). Moreover, biofilms exhibited a higher antibiotic accumulation capacity compared to sediments. Concentrations of oxytetracycline and doxycycline were high in feed, while other antibiotics were almost undetected. Tetracycline was widely detected and the concentration of enrofloxacin was highest in organisms.
Correlation analysis demonstrated that environmental parameters and other coexisting contaminants (e.g. heavy metals) significantly affected antibiotic concentrations. In addition, the concentration of Zn was significantly correlated with the total antibiotic concentration and was proportional to several antibiotics in water and sediment (biofilm) samples (p < 0.01). High Mn concentrations were closely related to total and individual (e.g. sulfadiazine, sulfamethazine and enrofloxacin) antibiotic levels, which may result in the combined contamination of the environment. Antibiotics in estuaries and groundwater generally originated from aquaculture wastewater and untreated/treated domestic sewage. Most of the detected antibiotics posed no risk to the environment. Ciprofloxacin and enrofloxacin found in water may present high ecological and resistance risks, while the two antibiotics observed to accumulate in fish may pose a considerable risk to human health through diet consumption. All antibiotics detected in seafood were lower than the respective maximum residue limits. This study can act as a reference for the government for the determination of antibiotic discharge standards in aquaculture wastewater and the establishment of a standardized antibiotic monitoring and management system.
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