3,144 research outputs found

    Natural History Analysis of 101 Severe Dysplasia and Esophageal Carcinoma Cases by Endoscopy

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    Objectives. Our research is to realize the natural history from dysplasia to carcinoma and to provide evidence for exploring proper screening intervals. Methods. After the onset endoscopy screening, 2093 of the patients participated in the endoscopic follow-up voluntarily. Totally, 101 severe dysplasia and carcinoma cases, either diagnosed in the first endoscopy without treatment or diagnosed in the second endoscopy, were included in our study. We compared the pathologic results of their two endoscopies and calculate the mean and median progression time. Results. Of the 39 severe dysplasia cases diagnosed by the onset endoscopy, only 8 progressed to carcinoma. For severe dysplasia cases diagnosed by the follow-up endoscopy, mean progression times are 55.0, 49.8, and 38.0 months and median progression times are 43, 56, and 31 months for esophagitis, mild dysplasia, and moderate dysplasia, respectively. For superficial carcinoma cases diagnosed by the second endoscopy, mean progression times are 76.0, 57.4, and 47.0 months and median progression times are 77, 63, and 35 months for mild dysplasia, moderate dysplasia, and severe dysplasia, respectively. Conclusions. Population-based severe dysplasia cases may have much lower carcinoma progression rate than specific-selected ones. The progression time for most enrolled cases seems longer than that of the recent screening protocol recommended

    A selected ion flow tube study of the ion-molecule reactions of monochloroethene, trichloroethene and tetrachloroethene

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    Data for the rate coefficients and product cations of the reactions of a large number of atomic and small molecular cations with monochloroethene, trichloroethene and tetrachloroethene in a selected ion flow tube at 298 K are reported. The recombination energy of the ions range from 6.27 eV (H3_3O+^+) through to 21.56 eV (Ne+^+). Collisional rate coefficients are calculated by modified average dipole orientation theory and compared with experimental values. Thermochemistry and mass balance predict the most feasible neutral products. Together with previously reported results for the three isomers of dichloroethene (J. Phys. Chem. A., 2006, 110, 5760), the fragment ion branching ratios have been compared with those from threshold photoelectron photoion coincidence spectroscopy over the photon energy range 9-22 eV to determine the importance or otherwise of long-range charge transfer. For ions with recombination energy in excess of the ionisation energy of the chloroethene, charge transfer is energetically allowed. The similarity of the branching ratios from the two experiments suggest that long-range charge transfer is dominant. For ions with recombination energy less than the ionisation energy, charge transfer is not allowed; chemical reaction can only occur following formation of an ion-molecule complex, where steric effects are more significant. The products that are now formed and their percentage yield is a complex interplay between the number and position of the chlorine atoms with respect to the C=C bond, where inductive and conjugation effects can be important

    A simulation study on the measurement of D0-D0bar mixing parameter y at BES-III

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    We established a method on measuring the \dzdzb mixing parameter yy for BESIII experiment at the BEPCII e+ee^+e^- collider. In this method, the doubly tagged ψ(3770)D0D0\psi(3770) \to D^0 \overline{D^0} events, with one DD decays to CP-eigenstates and the other DD decays semileptonically, are used to reconstruct the signals. Since this analysis requires good e/πe/\pi separation, a likelihood approach, which combines the dE/dxdE/dx, time of flight and the electromagnetic shower detectors information, is used for particle identification. We estimate the sensitivity of the measurement of yy to be 0.007 based on a 20fb120fb^{-1} fully simulated MC sample.Comment: 6 pages, 7 figure

    Observation of a charged charmoniumlike structure in e+e(DDˉ)±πe^+e^- \to (D^{*} \bar{D}^{*})^{\pm} \pi^\mp at s=4.26\sqrt{s}=4.26GeV

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    We study the process e+e(DDˉ)±πe^+e^- \to (D^{*} \bar{D}^{*})^{\pm} \pi^\mp at a center-of-mass energy of 4.26GeV using a 827pb1^{-1} data sample obtained with the BESIII detector at the Beijing Electron Positron Collider. Based on a partial reconstruction technique, the Born cross section is measured to be (137±9±15)(137\pm9\pm15)pb. We observe a structure near the (DDˉ)±(D^{*} \bar{D}^{*})^{\pm} threshold in the π\pi^\mp recoil mass spectrum, which we denote as the Zc±(4025)Z^{\pm}_c(4025). The measured mass and width of the structure are (4026.3±2.6±3.7)(4026.3\pm2.6\pm3.7)MeV/c2^2 and (24.8±5.6±7.7)(24.8\pm5.6\pm7.7)MeV, respectively. Its production ratio σ(e+eZc±(4025)π(DDˉ)±π)σ(e+e(DDˉ)±π)\frac{\sigma(e^+e^-\to Z^{\pm}_c(4025)\pi^\mp \to (D^{*} \bar{D}^{*})^{\pm} \pi^\mp)}{\sigma(e^+e^-\to (D^{*} \bar{D}^{*})^{\pm} \pi^\mp)} is determined to be 0.65±0.09±0.060.65\pm0.09\pm0.06. The first uncertainties are statistical and the second are systematic.Comment: 7 pages, 4 figures, 1 table; version accepted to be published in PR

    Precision measurement of the branching fractions of J/psi -> pi+pi-pi0 and psi' -> pi+pi-pi0

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    We study the decays of the J/psi and psi' mesons to pi+pi-pi0 using data samples at both resonances collected with the BES III detector in 2009. We measure the corresponding branching fractions with unprecedented precision and provide mass spectra and Dalitz plots. The branching fraction for J/psi -> pi+pi-pi0 is determined to be (2.137 +- 0.004 (stat.) +0.058-0.056 (syst.) +0.027-0.026 (norm.))*10-2, and the branching fraction for psi' -> pi+pi-pi0 is measured as (2.14 +- 0.03 (stat.) +0.08-0.07 (syst.) +0.09-0.08 (norm.))*10-4. The J/psi decay is found to be dominated by an intermediate rho(770) state, whereas the psi' decay is dominated by di-pion masses around 2.2 GeV/c2, leading to strikingly different Dalitz distributions.Comment: 15 pages, 2 figure

    Measurement of azimuthal asymmetries in inclusive charged dipion production in e+ee^+e^- annihilations at s\sqrt{s} = 3.65 GeV

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    We present a measurement of the azimuthal asymmetries of two charged pions in the inclusive process e+eππXe^+e^-\rightarrow \pi\pi X based on a data set of 62 pb1\rm{pb}^{-1} at the center-of-mass energy s=3.65\sqrt{s}=3.65 GeV collected with the BESIII detector. These asymmetries can be attributed to the Collins fragmentation function. We observe a nonzero asymmetry, which increases with increasing pion momentum. As our energy scale is close to that of the existing semi-inclusive deep inelastic scattering experimental data, the measured asymmetries are important inputs for the global analysis of extracting the quark transversity distribution inside the nucleon and are valuable to explore the energy evolution of the spin-dependent fragmentation function.Comment: 7 pages, 5 figure

    Observation of χc1\chi_{c1} decays into vector meson pairs ϕϕ\phi\phi, ωω\omega\omega, and ωϕ\omega\phi

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    Decays of χc1\chi_{c1} to vector meson pairs ϕϕ\phi\phi, ωω\omega\omega and ωϕ\omega\phi are observed for the first time using (106±4)×106(106\pm4)\times 10^6 \psip events accumulated at the BESIII detector at the BEPCII e+ee^+e^- collider. The branching fractions are measured to be (4.4±0.3±0.5)×104(4.4\pm 0.3\pm 0.5)\times 10^{-4}, (6.0±0.3±0.7)×104(6.0\pm 0.3\pm 0.7)\times 10^{-4}, and (2.2±0.6±0.2)×105(2.2\pm 0.6\pm 0.2)\times 10^{-5}, for χc1ϕϕ\chi_{c1}\to \phi\phi, ωω\omega\omega, and ωϕ\omega\phi, respectively. The observation of χc1\chi_{c1} decays into a pair of vector mesons ϕϕ\phi\phi, ωω\omega\omega and ωϕ\omega\phi indicates that the hadron helicity selection rule is significantly violated in χcJ\chi_{cJ} decays. In addition, the measurement of χcJωϕ\chi_{cJ}\to \omega\phi gives the rate of doubly OZI-suppressed decay. Branching fractions for χc0\chi_{c0} and χc2\chi_{c2} decays into other vector meson pairs are also measured with improved precision.Comment: 4 pages, 2 figure

    Study of J/ψppˉJ/\psi\to p\bar{p} and J/ψnnˉJ/\psi\to n\bar{n}

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    The decays J/ψppˉJ/\psi\to p\bar{p} and J/ψnnˉJ/\psi\to n\bar{n} have been investigated with a sample of 225.2 million J/ψJ/\psi events collected with the BESIII detector at the BEPCII e+ee^+e^- collider. The branching fractions are determined to be B(J/ψppˉ)=(2.112±0.004±0.031)×103\mathcal{B}(J/\psi\to p\bar{p})=(2.112\pm0.004\pm0.031)\times10^{-3} and B(J/ψnnˉ)=(2.07±0.01±0.17)×103\mathcal{B}(J/\psi\to n\bar{n})=(2.07\pm0.01\pm0.17)\times10^{-3}. Distributions of the angle θ\theta between the proton or anti-neutron and the beam direction are well described by the form 1+αcos2θ1+\alpha\cos^2\theta, and we find α=0.595±0.012±0.015\alpha=0.595\pm0.012\pm0.015 for J/ψppˉJ/\psi\to p\bar{p} and α=0.50±0.04±0.21\alpha=0.50\pm0.04\pm0.21 for J/ψnnˉJ/\psi\to n\bar{n}. Our branching-fraction results suggest a large phase angle between the strong and electromagnetic amplitudes describing the J/ψNNˉJ/\psi\to N\bar{N} decay.Comment: 16 pages, 13 figures, the 2nd version, submitted to PR
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