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Measurements of cross section of e⁺e⁻ → pp¯π⁰ at center-of-mass energies between 4.008 and 4.600 GeV
(2017)
Based on e+e− annihilation data samples collected with the BESIII detector at the BEPCII collider at 13 center-of-mass energies from 4.008 to 4.600 GeV, measurements of the Born cross section of e+e− → pp¯π0 are performed. No significant resonant structure is observed in the measured energy dependence of the cross section. The upper limit on the Born cross section of e+e− → Y (4260) → pp¯π0 at the 90% C.L. is determined to be 0.01 pb. The upper limit on the ratio of the branching fractions B(Y (4260)→pp¯π0) B(Y (4260)→π+π− J/ψ) at the 90% C.L. is determined to be 0.02%.
We study the decays of J/ψ and ψ(3686) to the final states Σ(1385)0Σ¯(1385)0 and Ξ0Ξ¯0 based on a single baryon tag method using data samples of (1310.6±7.0)×106 J/ψ and (447.9±2.9)×106 ψ(3686) events collected with the BESIII detector at the BEPCII collider. The decays to Σ(1385)0Σ¯(1385)0 are observed for the first time. The measured branching fractions of J/ψ and ψ(3686)→Ξ0Ξ¯0 are in good agreement with, and much more precise, than the previously published results. The angular parameters for these decays are also measured for the first time. The measured angular decay parameter for J/ψ→Σ(1385)0Σ¯(1385)0, α=−0.64±0.03±0.10, is found to be negative, different to the other decay processes in this measurement. In addition, the "12\% rule" and isospin symmetry in the J/ψ and ψ(3686)→ΞΞ¯ and Σ(1385)Σ¯(1385) systems are tested.
Using a data sample of 448.1 × 106 ψ(3686) events collected with the BESIII detector at the BEPCII collider, we report the first observation of the electromagnetic Dalitz decay ψ(3686) → η e+e−, with significances of 7.0σ and 6.3σ when reconstructing the η meson via its decay modes η → γπ+π− and η → π+π−η (η → γγ ), respectively. The weighted average branching fraction is determined to be B(ψ(3686) → η e+e−) = (1.90 ± 0.25 ± 0.11) × 10−6, where the first uncertainty is statistical and the second systematic.
Relative fractions and phases of the intermediate decays are determined. With the detection efficiency estimated by the results of the amplitude analysis, the branching fraction of Dþ s → K−Kþπþπ0 decay is measured to be ð5.42 0.10stat 0.17systÞ%.
Using 2.93 fb−1 of e+e− collision data taken with the BESIII detector at a center-of-mass energy of 3.773 GeV, the observation of the D0→K1(1270)−e+νe semileptonic decay is presented. The statistical significance of the decay D0→K1(1270)−e+νe is greater than 10σ. The branching fraction of D0→K1(1270)−e+νe is measured to be (1.09±0.13+0.09−0.13±0.12)×10−3. Here, the first uncertainty is statistical, the second is systematic, and the third originates from the assumed branching fraction of K1(1270)−→K−π+π−.
Using 2.93 fb−1 of e+e− collision data taken with the BESIII detector at a center-of-mass energy of 3.773 GeV, the observation of the D0→K1(1270)−e+νe semileptonic decay is presented. The statistical significance of the decay D0→K1(1270)−e+νe is greater than 10σ. The branching fraction of D0→K1(1270)−e+νe is measured to be (1.09±0.13+0.09−0.16±0.12)×10−3. Here, the first uncertainty is statistical, the second is systematic, and the third originates from the assumed branching fraction of K1(1270)−→K−π+π−. The fraction of longitudinal polarization in D0→K1(1270)−e+νe is determined for the first time to be 0.50±0.19stat±0.08syst.
We report new measurements of the cross sections for the production of Dbar D final states at the ψ(3770) resonance. Our data sample consists of an integrated luminosity of 2.93 fb−1 of e+e− annihilation data produced by the BEPCII collider and collected and analyzed with the BESIII detector. We exclusively reconstruct three D0 and six D+ hadronic decay modes and use the ratio of the yield of fully reconstructed Dbar D events ("double tags") to the yield of all reconstructed D or bar D mesons ("single tags") to determine the number of D0bar D0 and D+D− events, benefiting from the cancellation of many systematic uncertainties. Combining these yields with an independent determination of the integrated luminosity of the data sample, we find the cross sections to be σ(e+e− → D0bar D0) nb and σ(e+e− → D+D−) = (2.830 ± 0.011 ± 0.026) nb, where the uncertainties are statistical and systematic, respectively.
Using a data sample of 𝑒+𝑒− collisions corresponding to an integrated luminosity of 567 pb−1 collected at a center-of-mass energy of √𝑠=4.6 GeV with the BESIII detector, we measure the absolute branching fraction of the inclusive semileptonic Λ+𝑐 decay with a double-tag method. We obtain ℬ(Λ+𝑐→𝑋𝑒+𝜈𝑒)=(3.95±0.34±0.09)%, where the first uncertainty is statistical and the second systematic. Using the known Λ+𝑐 lifetime and the charge-averaged semileptonic decay width of nonstrange charmed mesons (𝐷0 and 𝐷+), we obtain the ratio of the inclusive semileptonic decay widths Γ(Λ+𝑐→𝑋𝑒+𝜈𝑒)/¯Γ(𝐷→𝑋𝑒+𝜈𝑒)=1.26±0.12.
We study the electromagnetic Dalitz decay 𝐽/𝜓→𝑒+𝑒−𝜂 and search for dielectron decays of a dark gauge boson (𝛾′) in 𝐽/𝜓→𝛾′𝜂 with the two 𝜂 decay modes 𝜂→𝛾𝛾 and 𝜂→𝜋+𝜋−𝜋0 using (1310.6±7.0)×106 𝐽/𝜓 events collected with the BESIII detector. The branching fraction of 𝐽/𝜓→𝑒+𝑒−𝜂 is measured to be (1.43±0.04(stat)±0.06(syst))×10−5, with a precision that is improved by a factor of 1.5 over the previous BESIII measurement. The corresponding dielectron invariant mass dependent modulus square of the transition form factor is explored for the first time, and the pole mass is determined to be Λ=2.84±0.11(stat)±0.08(syst) GeV/𝑐2. We find no evidence of 𝛾′ production and set 90% confidence level upper limits on the product branching fraction ℬ(𝐽/𝜓→𝛾′𝜂)×ℬ(𝛾′→𝑒+𝑒−) as well as the kinetic mixing strength between the standard model photon and 𝛾′ in the mass range of 0.01≤𝑚𝛾′≤2.4 GeV/𝑐2.
The decays of χc2→K+K−π0, KSK±π∓ and π+π−π0 are studied with the ψ(3686) data samples collected with the Beijing Spectrometer (BESIII). For the first time, the branching fractions of χc2→K∗K¯¯¯¯¯, χc2→a±2(1320)π∓/a02(1320)π0 and χc2→ρ(770)±π∓ are measured. Here K∗K¯¯¯¯¯ denotes both K∗±K∓ and K∗0K¯¯¯¯¯0+c.c., and K∗ denotes the resonances K∗(892), K∗2(1430) and K∗3(1780). The observations indicate a strong violation of the helicity selection rule in χc2 decays into vector and pseudoscalar meson pairs. The measured branching fractions of χc2→K∗(892)K¯¯¯¯¯ are more than 20 times larger than that of χc2→ρ(770)±π∓, which implies the effects are largely due to U-spin symmetry breaking, rather than just isospin symmetry breaking in charmonium decays.
The decays of χc2→K+K−π0, KSK±π∓ and π+π−π0 are studied with the ψ(3686) data samples collected with the Beijing Spectrometer (BESIII). For the first time, the branching fractions of χc2→K∗K¯¯¯¯¯, χc2→a±2(1320)π∓/a02(1320)π0 and χc2→ρ(770)±π∓ are measured. Here K∗K¯¯¯¯¯ denotes both K∗±K∓ and K∗0K¯¯¯¯¯0+c.c., and K∗ denotes the resonances K∗(892), K∗2(1430) and K∗3(1780). The observations indicate a strong violation of the helicity selection rule in χc2 decays into vector and pseudoscalar meson pairs. The measured branching fractions of χc2→K∗(892)K¯¯¯¯¯ are more than 10 times larger than the upper limit of χc2→ρ(770)±π∓, which is so far the first direct observation of a significant U-spin symmetry breaking effect in charmonium decays.
The decays of χc2→K+K−π0, KSK±π∓ and π+π−π0 are studied with the ψ(3686) data samples collected with the Beijing Spectrometer (BESIII). For the first time, the branching fractions of χc2→K∗K¯¯¯¯¯, χc2→a±2(1320)π∓/a02(1320)π0 and χc2→ρ(770)±π∓ are measured. Here K∗K¯¯¯¯¯ denotes both K∗±K∓ and K∗0K¯¯¯¯¯0+c.c., and K∗ denotes the resonances K∗(892), K∗2(1430) and K∗3(1780). The observations indicate a strong violation of the helicity selection rule in χc2 decays into vector and pseudoscalar meson pairs. The measured branching fractions of χc2→K∗(892)K¯¯¯¯¯ are more than 20 times larger than that of χc2→ρ(770)±π∓, which implies the effects are largely due to U-spin symmetry breaking, rather than just isospin symmetry breaking in charmonium decays.
Using a sample of 4.48×108 ψ(3686) events collected with the BESIII detector at the BEPCII collider, we study the two-photon decays of the pseudoscalar mesons π0, η, η′, η(1405), η(1475), η(1760), and X(1835) in J/ψ radiative decays using ψ(3686)→π+π−J/ψ events. The π0, η and η′ mesons are clearly observed in the two-photon mass spectra, and the branching fractions are determined to be B(J/ψ→γπ0→3γ)=(3.57±0.12±0.16)×10−5, B(J/ψ→γη→3γ)=(4.42±0.04±0.18)×10−4, and B(J/ψ→γη′→3γ)=(1.26±0.02±0.05)×10−4, where the first errors are statistical and the second systematic. No clear signal for η(1405), η(1475), η(1760) or X(1835) is observed in the two-photon mass spectra, and upper limits at the 90% confidence level on the product branching fractions are obtained.
We provide a review of the enoplid suborder Trefusiina Siddiqi, 1983, based on morphological considerations and analyses of new and published 18S rDNA sequences. We also describe Halanonchus scintillatulus Leduc sp. nov. from the Hauraki Gulf, northern New Zealand, as well as females of Trefusialaimus idrisi Leduc, 2013 from the continental slope of New Zealand. We show for the first time that the structure of the female reproductive system of Trefusialaimus Riemann, 1974 consists of two opposed and outstretched ovaries, an unusual feature for the Enoplida. The Trefusiina did not form a monophyletic group in the 18S rDNA phylogeny due to the placement of Lauratonema Gerlach, 1953 and Trefusialaimus sequences well away from the main Trefusiina clade. However, due to generally weak Maximum Likelihood support values, we refrain from changing the classification of these taxa until more comprehensive analyses can be conducted. Our phylogenetic analysis supports the inclusion of the Trischistomatidae Andrássy, 2007 within the Trefusiina, meaning that all of the enoplid suborders now include at least some terrestrial/freshwater representatives. The Trefusiina currently comprises five families, 14 genera and 92 valid species.
Background: Transient elastography (TE) has been validated as an effective noninvasive tool for the assessment of liver fibrosis. The XL probe is a new probe that was initially designed for use in patients with obesity. A meta-analysis was performed to assess the feasibility and efficacy of TE using the XL probe.
Methods: In September 2016, we systematically searched the PubMed and Science Direct search engines. The feasibility of TE was evaluated based on the failure rate and the results of the unreliable liver stiffness measurement (LSM). The efficacy of TE was measured using sensitivity, specificity, and summary receiver-operating characteristic as measures/indices assessed in different stages of fibrosis. Heterogeneity was measured using the chi-squared test and the Q-statistic. We used the 95% confidence interval (95% CI) as an effect measure.
Results: We included 8 studies in the meta-analysis. When the XL was compared to the M probe, the former showed a lower risk of failure rate [relative risk (RR) 0.24, 95% CI 0.14–0.38]. In patients with a body mass index ≥30 kg/m2, the XL probe showed a statistically significantly lower risk of failure rate (RR 0.16, 95% CI 0.08–0.32) but no significant improvement (RR 0.76, 95% CI 0.50–1.16) in the unreliable LSM result. In patients showing liver fibrosis stage ≥F2, the XL probe showed a sensitivity of 0.56 (95% CI 0.39–0.72), specificity of 0.71 (95% CI 0.61–0.79), and an area under the curve (AUC) of 0.71. The results observed in patients with liver fibrosis stage F4 were more promising with a sensitivity of 0.84 (95% CI 0.76–0.90), specificity of 0.78 (95% CI 0.70–0.84), and an AUC of 0.88.
Conclusion: TE using the XL probe demonstrates significant diagnostic utility in patients with liver fibrosis and is likely to be more reliable than the M probe in patients with obesity. Large prospective multicenter studies are, however, necessary to establish the new cut-off values to be used for the XL probe in patients with obesity.
In the absence of an active prophylactic vaccine against HIV-1, passively administered, broadly neutralizing antibodies (bnAbs) identified in some chronically infected persons were shown to prevent HIV-1 infection in animal models. However, passive administration of bnAbs may not be suited to prevent sexual HIV-1 transmission in high-risk cohorts, as a continuous high level of active bnAbs may be difficult to achieve at the primary site of sexual transmission, the human vagina with its acidic pH. Therefore, we used Lactobacillus, a natural commensal in the healthy vaginal microbiome, to express bn nanobodies (VHH) against HIV-1 that we reported previously. After demonstrating that recombinant VHHA6 expressed in E. coli was able to protect humanized mice from mucosal infection by HIV-1Bal, we expressed VHHA6 in a soluble or in a cell-wall-anchored form in Lactobacillus rhamnosus DSM14870. This strain is already clinically applied for treatment of bacterial vaginosis. Both forms of VHHA6 neutralized a set of primary epidemiologically relevant HIV-1 strains in vitro. Furthermore, VHHA6 was still active at an acidic pH. Thus, lactobacilli expressing bn VHH potentially represent an attractive vector for the passive immunization of women in cohorts at high risk of HIV-1 transmission.
Spermatogonial stem cells (SSCs) are adult stem cells that are slowly cycling and self-renewing. The pool of SSCs generates very large numbers of male gametes throughout the life of the individual. SSCs can be cultured in vitro for long periods of time, and established SSC lines can be manipulated genetically. Upon transplantation into the testes of infertile mice, long-term cultured mouse SSCs can differentiate into fertile spermatozoa, which can give rise to live offspring. Here, we show that the testicular soma of mice with a conditional knockout (conKO) in the X-linked gene Tsc22d3 supports spermatogenesis and germline transmission from cultured mouse SSCs upon transplantation. Infertile males were produced by crossing homozygous Tsc22d3 floxed females with homozygous ROSA26-Cre males. We obtained 96 live offspring from six long-term cultured SSC lines with the aid of intracytoplasmic sperm injection. We advocate the further optimization of Tsc22d3-conKO males as recipients for testis transplantation of SSC lines.
Litinium gludi sp. nov. (Nematoda, Oxystominidae) from Kermadec Trench, Southwest Pacific Ocean
(2021)
Recent work on the taxonomy of nematodes in Southwest Pacific Ocean trenches has led to the discovery of taxa which so far appear to be restricted to the oceans’ deepest environments. Here, Litinium gludi sp. nov. is described based on specimens obtained from a deep basin within the Kermadec Trench at 9540 m water depth. The new species differs from other species of the genus in having a conico-cylindrical tail, papillose labial sensilla, and heart- or leaf-shaped amphideal fovea. Both SSU and LSU phylogenetic analyses provide strong support for the placement of the new species within a clade containing both Thalassoalaimus and Litinum, and within Oxystomininae, which is consistent with the structure of the female reproductive system with only one posterior ovary in this subfamily. Our molecular analyses also indicate that the new species is most closely related to Thalassoalaimus despite lacking a caudal capsule, the main trait characterizing the latter genus, and despite being most morphologically similar to Litinium, particularly in the unusual shape of the amphideal fovea. However, given the changing definitions of the closely-related genera Thalassoalaimus and Litinium in recent years, available GenBank sequences may have been misidentified, which makes the interpretation of molecular phylogenetic analyses problematic. Given the current morphological definitions of Litinium and Thalassoalaimus, we choose to place the new species within Litinium, despite the apparently contradictory findings of molecular phylogenetic analyses. The placement of Cricohalalaimus in a clade with Thalassoalaimus and Litinium in both SSU and LSU analyses indicates that this genus should be placed within the Oxystomininae and not the Halalaiminae as in the current classification. This new proposed grouping is consistent with variation in the structure of the female reproductive system, a feature which appears more taxonomically informative than amphid shape for subfamily-level classification.
Gram-negative bacteria maintain an intrinsic resistance mechanism against entry of noxious compounds by utilizing highly efficient efflux pumps. The E. coli AcrAB-TolC drug efflux pump contains the inner membrane H+/drug antiporter AcrB comprising three functionally interdependent protomers, cycling consecutively through the loose (L), tight (T) and open (O) state during cooperative catalysis. Here, we present 13 X-ray structures of AcrB in intermediate states of the transport cycle. Structure-based mutational analysis combined with drug susceptibility assays indicate that drugs are guided through dedicated transport channels toward the drug binding pockets. A co-structure obtained in the combined presence of erythromycin, linezolid, oxacillin and fusidic acid shows binding of fusidic acid deeply inside the T protomer transmembrane domain. Thiol cross-link substrate protection assays indicate that this transmembrane domain-binding site can also accommodate oxacillin or novobiocin but not erythromycin or linezolid. AcrB-mediated drug transport is suggested to be allosterically modulated in presence of multiple drugs.