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.
We report a study of the processes of e^{+}e^{-}→K^{+}D_{s}^{-}D^{*0} and K^{+}D_{s}^{*-}D^{0} based on e^{+}e^{-} annihilation samples collected with the BESIII detector operating at BEPCII at five ...center-of-mass energies ranging from 4.628 to 4.698 GeV with a total integrated luminosity of 3.7 fb^{-1}. An excess of events over the known contributions of the conventional charmed mesons is observed near the D_{s}^{-}D^{*0} and D_{s}^{*-}D^{0} mass thresholds in the K^{+} recoil-mass spectrum for events collected at sqrts=4.681 GeV. The structure matches a mass-dependent-width Breit-Wigner line shape, whose pole mass and width are determined as (3982.5_{-2.6}^{+1.8}±2.1) MeV/c^{2} and (12.8_{-4.4}^{+5.3}±3.0) MeV, respectively. The first uncertainties are statistical and the second are systematic. The significance of the resonance hypothesis is estimated to be 5.3 σ over the contributions only from the conventional charmed mesons. This is the first candidate for a charged hidden-charm tetraquark with strangeness, decaying into D_{s}^{-}D^{*0} and D_{s}^{*-}D^{0}. However, the properties of the excess need further exploration with more statistics.
The presence of water greatly influences time-dependent rock deformation. An understanding of how water can affect the time-dependent mechanical behavior of rock is important when assessing the ...long-term stability of geotechnical projects. While the previous studies have performed brittle creep experiments on oven-dry or fully-saturated rocks, we report here on a study designed to better understand brittle creep at different levels of saturation. We performed brittle creep experiments on oven-dry samples of red sandstone (Hunan province, China) and samples of the sandstone pre-immersed in water for different durations (from 2 to 8 days). These samples were deformed at a constant stress in one of either two conditions: dry or submerged in water. Before performing creep experiments, we first performed a series of water absorption and constant stress rate experiments to guide the stresses required for our creep tests and to assist with their interpretation. Our creep experiments show that immersion in water greatly increased the minimum creep strain rate and greatly shortened the time-to-failure when compared to the dry state. In detail, the minimum creep strain rate and time-to-failure increased and decreased, respectively, as pre-immersion duration increased from 4 to 6 days, but did not change as the duration was further increased to 8 days. We attribute this to the saturation of microcracks between 4 and 6 days (i.e., water imbibition was complete, or close to completion, following 6 days). We also show that oven-dry samples deformed at a constant stress underwater fail at stresses much lower than oven-dry samples deformed under dry conditions, due to the imbibition of water during deformation. Samples pre-immersed in water, but deformed in the dry condition were characterized by lower strain rates and longer time-to-failure than those pre-immersed in water and deformed underwater. Our explanation for this is that, due to the availability of water, crack tips can remain hydrated when the sample is deformed underwater, thus increasing the efficacy of stress corrosion cracking. The relationships and data provided herein inform on the long-term stability of engineering structures.
Angiogenesis and neurogenesis are crucial processes for brain tissue repair and remodeling after brain injury. Current study shows that microRNA-210 (miR-210) promotes vascular endothelial cell ...migration and tube formation under hypoxia in vitro. Whether miR-210 overexpression promotes focal angiogenesis and neurogenesis in the normal adult brain is unknown. Adult male C57BL/6 mice (n=54) underwent stereotactic injection of a lentiviral vector carrying miR-210 (LV-miR-210). Following 28 days of miR-210 gene transfer, endothelial cell and neural precursor cell proliferation, microvessel density and downstream angiogenic factor were genotyped. miR-210 was highly expressed in neurons, astrocytes and endothelial cells of the LV-miR-210-injected brain hemisphere. The endothelial cell proliferation and the number of newly formed microvessels were greatly increased in the LV-miR-210-treated mice compared with the controls (P<0.05). Neural progenitor cells in the subventricular zone were greatly increased compared with the controls (P<0.05). The data indicate that miR-210 is a key factor at the microRNA level in promoting angiogenesis and neurogenesis, which was associated with local increased vascular endothelial growth factor (VEGF) levels, suggesting that miR-210 may be a potential target for ischemic stroke therapy.
The processes X(3872) ... , and γD+D− are searched for in a 9.0 fb−1 data sample collected at center-of-mass energies between 4.178 and 4.278 GeV with the BESIII detector. We observe X(3872) ... . ...and find evidence for X (3872)→γJ/ψ with statistical significances of 7.4 σ and 3.5σ, respectively. No evident signals for X(3872)→γψ(2S) and γD+D− are found, and the upper limit on the relative branching ratio Rγψ ≡ {BX(3872)→γψ(2S)}/{BX(3872)→γJ/ψ} <0.59 is set at 90% confidence level. Measurements of branching ratios relative to decay X(3872)→π+π−J/ψ are also reported for decays ... .,γψ(2S), γJ/ψ, and γD+D−, as well as the non-... three-body decays ... .(ProQuest: ... denotes formulae omitted.)
The complicated structure of the neutron cannot be calculated using first-principles calculations due to the large colour charge of quarks and the self-interaction of gluons. Its simplest structure ...observables are the electromagnetic form factors1, which probe our understanding of the strong interaction. Until now, a small amount of data has been available for the determination of the neutron structure from the time-like kinematical range. Here we present measurements of the Born cross section of electron–positron annihilation reactions into a neutron and anti-neutron pair, and determine the neutron’s effective form factor. The data were recorded with the BESIII experiment at centre-of-mass energies between 2.00 and 3.08 GeV using an integrated luminosity of 647.9 pb−1. Our results improve the statistics on the neutron form factor by more than a factor of 60 over previous measurements, demonstrating that the neutron form factor data from annihilation in the time-like regime is on par with that from electron scattering experiments. The effective form factor of the neutron shows a periodic behaviour, similar to earlier observations of the proton form factor. Future works—both theoretical and experimental—will help illuminate the origin of this oscillation of the electromagnetic structure observables of the nucleon.Form factors encode the structure of nucleons. Measurements from electron–positron annihilation at BESIII reveal an oscillating behaviour of the neutron electromagnetic form factor, and clarify a long-standing photon–nucleon interaction puzzle.
An advantage of the powder-bed-based metal additive manufacturing (AM) processes is that the powder can be reused. The powder reuse or recycling times directly affect the affordability of the ...additively manufactured parts, especially for the AM of titanium parts. This study examines the influence of powder reuse times on the characteristics of Ti-6Al-4V powder, including powder composition, particle size distribution (PSD), apparent density, tap density, flowability, and particle morphology. In addition, tensile samples were manufactured and evaluated with respect to powder reuse times and sample locations in the powder bed. The following findings were made from reusing the same batch of powder 21 times for AM by selective electron beam melting: (i) the oxygen (O) content increased progressively with increasing reuse times but both the Al content and the V content remained generally stable (a small decrease only); (ii) the powder became less spherical with increasing reuse times and some particles showed noticeable distortion and rough surfaces after being reused 16 times; (iii) the PSD became narrower and few satellite particles were observed after 11 times of reuse; (iv) reused powder showed improved flowability; and (v) reused powder showed no measurable undesired influence on the AM process and the samples exhibited highly consistent tensile properties, irrespective of their locations in the powder bed. The implications of these findings were discussed.
The exclusive process e+e−→ΛΛ¯, with Λ→pπ− and Λ¯→p¯π+, has been studied at s=2.396 GeV for measurement of the timelike Λ electric and magnetic form factors, GE and GM. A data sample, corresponding ...to an integrated luminosity of 66.9 pb−1, was collected with the BESIII detector for this purpose. A multidimensional analysis with a complete decomposition of the spin structure of the reaction enables a determination of the modulus of the ratio R=|GE/GM| and, for the first time for any baryon, the relative phase ΔΦ=ΦE−ΦM. The resulting values are R=0.96±0.14(stat)±0.02(syst) and ΔΦ=37°±12°(stat)±6°(syst), respectively. These are obtained using the recently established and most precise value of the asymmetry parameter αΛ=0.750±0.010 measured by BESIII. In addition, the cross section is measured with unprecedented precision to be σ=118.7±5.3(stat)±5.1(syst) pb, which corresponds to an effective form factor of |G|=0.123±0.003(stat)±0.003(syst). The contribution from two-photon exchange is found to be negligible. Our result enables the first complete determination of baryon timelike electromagnetic form factors.
Though immensely successful, the standard model of particle physics does not offer any explanation as to why our Universe contains so much more matter than antimatter. A key to a dynamically ...generated matter-antimatter asymmetry is the existence of processes that violate the combined charge conjugation and parity (CP) symmetry
. As such, precision tests of CP symmetry may be used to search for physics beyond the standard model. However, hadrons decay through an interplay of strong and weak processes, quantified in terms of relative phases between the amplitudes. Although previous experiments constructed CP observables that depend on both strong and weak phases, we present an approach where sequential two-body decays of entangled multi-strange baryon-antibaryon pairs provide a separation between these phases. Our method, exploiting spin entanglement between the double-strange Ξ
baryon and its antiparticle
Formula: see text, has enabled a direct determination of the weak-phase difference, (ξ
- ξ
) = (1.2 ± 3.4 ± 0.8) × 10
rad. Furthermore, three independent CP observables can be constructed from our measured parameters. The precision in the estimated parameters for a given data sample size is several orders of magnitude greater than achieved with previous methods
. Finally, we provide an independent measurement of the recently debated Λ decay parameter α
(refs.
). The Formula: see text asymmetry is in agreement with and compatible in precision to the most precise previous measurement
.
We study the e^{+}e^{-}→γωJ/ψ process using 11.6 fb^{-1} e^{+}e^{-} annihilation data taken at center-of-mass energies from sqrts=4.008 GeV to 4.600 GeV with the BESIII detector at the BEPCII ...storage ring. The X(3872) resonance is observed for the first time in the ωJ/ψ system with a significance of more than 5σ. The relative decay ratio of X(3872)→ωJ/ψ and π^{+}π^{-}J/ψ is measured to be R=1.6_{-0.3}^{+0.4}±0.2, where the first uncertainty is statistical and the second systematic (the same hereafter). The sqrts-dependent cross section of e^{+}e^{-}→γX(3872) is also measured and investigated, and it can be described by a single Breit-Wigner resonance, referred to as the Y(4200), with a mass of 4200.6_{-13.3}^{+7.9}±3.0 MeV/c^{2} and a width of 115_{-26}^{+38}±12 MeV. In addition, to describe the ωJ/ψ mass distribution above 3.9 GeV/c^{2}, we need at least one additional Breit-Wigner resonance, labeled as X(3915), in the fit. The mass and width of the X(3915) are determined. The resonant parameters of the X(3915) agree with those of the Y(3940) in B→KωJ/ψ and of the X(3915) in γγ→ωJ/ψ observed by the Belle and BABAR experiments within errors.
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