930 research outputs found

    Effect of pyramiding Bt and CpTI genes on resistance of cotton to Helicoverpa armigera (Lepidoptera: Noctuidae) under laboratory and field conditions

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    Transgenic cotton (Gossypium hirsutum L.) varieties, adapted to China, have been bred that express two genes for resistance to insects. the Cry1Ac gene from Bacillus thuringiensis (Berliner) (Bt), and a trypsin inhibitor gene from cowpea (CpTI). Effectiveness of the double gene modification in conferring resistance to cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), was studied in laboratory and field experiments. In each experiment, performance of Bt+CpTI cotton was compared with Bt cotton and to a conventional nontransgenic variety. Larval survival was lower on both types of transgenic variety, compared with the conventional cotton. Survival of first-, second-, and third-stage larvae was lower on Bt+CpTI cotton than on Bt cotton. Plant structures differed in level of resistance, and these differences were similar on Bt and Bt+CpTI cotton. Likewise, seasonal trends in level of resistance in different plant structures were similar in Bt and Bt+CpTI cotton. Both types of transgenic cotton interfered with development of sixth-stage larvae to adults, and no offspring was produced by H. armigera that fed on Bt or Bt+CpTI cotton from the sixth stage onward. First-, second-, and third-stage larvae spent significantly less time feeding on transgenic cotton than on conventional cotton, and the reduction in feeding time was significantly greater on Bt+CpTI cotton than on Bt cotton. Food conversion efficiency was lower on transgenic varieties than on conventional cotton, but there was no significant difference between Bt and Bt+CpTI cotton. In 3-yr field experimentation, bollworm densities were greatly suppressed on transgenic as compared with conventional cotton, but no significant differences between Bt and Bt+CpTI cotton were found. Overall, the results from laboratory work indicate that introduction of the CpTI gene in Bt cotton raises some components of resistance in cotton against H. armigera, but enhanced control of H. armigera under field conditions, due to expression of the CpTI gene, was not demonstrate

    The in-plane paraconductivity in La_{2-x}Sr_xCuO_4 thin film superconductors at high reduced-temperatures: Independence of the normal-state pseudogap

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    The in-plane resistivity has been measured in La2xSrxCuO4La_{2-x}Sr_xCuO_4 (LSxCO) superconducting thin films of underdoped (x=0.10,0.12x=0.10,0.12), optimally-doped (x=0.15x=0.15) and overdoped (x=0.20,0.25x=0.20,0.25) compositions. These films were grown on (100)SrTiO3_3 substrates, and have about 150 nm thickness. The in-plane conductivity induced by superconducting fluctuations above the superconducting transition (the so-called in-plane paraconductivity, Δσab\Delta\sigma_{ab}) was extracted from these data in the reduced-temperature range 10^{-2}\lsim\epsilon\equiv\ln(T/\Tc)\lsim1. Such a Δσab(ϵ)\Delta\sigma_{ab}(\epsilon) was then analyzed in terms of the mean-field--like Gaussian-Ginzburg-Landau (GGL) approach extended to the high-ϵ\epsilon region by means of the introduction of a total-energy cutoff, which takes into account both the kinetic energy and the quantum localization energy of each fluctuating mode. Our results strongly suggest that at all temperatures above Tc, including the high reduced-temperature region, the doping mainly affects in LSxCO thin films the normal-state properties and that its influence on the superconducting fluctuations is relatively moderate: Even in the high-ϵ\epsilon region, the in-plane paraconductivity is found to be independent of the opening of a pseudogap in the normal state of the underdoped films.Comment: 35 pages including 10 figures and 1 tabl

    Measurements of Cabibbo Suppressed Hadronic Decay Fractions of Charmed D0 and D+ Mesons

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    Using data collected with the BESII detector at e+ee^{+}e^{-} storage ring Beijing Electron Positron Collider, the measurements of relative branching fractions for seven Cabibbo suppressed hadronic weak decays D0KK+D^0 \to K^- K^+, π+π\pi^+ \pi^-, KK+π+πK^- K^+ \pi^+ \pi^- and π+π+ππ\pi^+ \pi^+ \pi^- \pi^-, D+K0ˉK+D^+ \to \bar{K^0} K^+, KK+π+K^- K^+ \pi^+ and ππ+π+\pi^- \pi^+ \pi^+ are presented.Comment: 11 pages, 5 figure

    The σ\sigma pole in J/ψωπ+πJ/\psi \to \omega \pi^+ \pi^-

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    Using a sample of 58 million J/ψJ/\psi events recorded in the BESII detector, the decay J/ψωπ+πJ/\psi \to \omega \pi^+ \pi^- is studied. There are conspicuous ωf2(1270)\omega f_2(1270) and b1(1235)πb_1(1235)\pi signals. At low ππ\pi \pi mass, a large broad peak due to the σ\sigma is observed, and its pole position is determined to be (541±39)(541 \pm 39) - ii (252±42)(252 \pm 42) MeV from the mean of six analyses. The errors are dominated by the systematic errors.Comment: 15 pages, 6 figures, submitted to PL

    A study of charged kappa in J/ψK±Ksππ0J/\psi \to K^{\pm} K_s \pi^{\mp} \pi^0

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    Based on 58×10658 \times 10^6 J/ψJ/\psi events collected by BESII, the decay J/ψK±Ksππ0J/\psi \to K^{\pm} K_s \pi^{\mp} \pi^0 is studied. In the invariant mass spectrum recoiling against the charged K(892)±K^*(892)^{\pm}, the charged κ\kappa particle is found as a low mass enhancement. If a Breit-Wigner function of constant width is used to parameterize the kappa, its pole locates at (849±7714+18)i(256±4022+46)(849 \pm 77 ^{+18}_{-14}) -i (256 \pm 40 ^{+46}_{-22}) MeV/c2c^2. Also in this channel, the decay J/ψK(892)+K(892)J/\psi \to K^*(892)^+ K^*(892)^- is observed for the first time. Its branching ratio is (1.00±0.190.32+0.11)×103(1.00 \pm 0.19 ^{+0.11}_{-0.32}) \times 10^{-3}.Comment: 14 pages, 4 figure

    Measurements of the observed cross sections for exclusive light hadron production in e^+e^- annihilation at \sqrt{s}= 3.773 and 3.650 GeV

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    By analyzing the data sets of 17.3 pb1^{-1} taken at s=3.773\sqrt{s}=3.773 GeV and 6.5 pb1^{-1} taken at s=3.650\sqrt{s}=3.650 GeV with the BESII detector at the BEPC collider, we have measured the observed cross sections for 12 exclusive light hadron final states produced in e+ee^+e^- annihilation at the two energy points. We have also set the upper limits on the observed cross sections and the branching fractions for ψ(3770)\psi(3770) decay to these final states at 90% C.L.Comment: 8 pages, 5 figur

    Direct Measurements of Absolute Branching Fractions for D0 and D+ Inclusive Semimuonic Decays

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    By analyzing about 33 pb1\rm pb^{-1} data sample collected at and around 3.773 GeV with the BES-II detector at the BEPC collider, we directly measure the branching fractions for the neutral and charged DD inclusive semimuonic decays to be BF(D0μ+X)=(6.8±1.5±0.7)BF(D^0 \to \mu^+ X) =(6.8\pm 1.5\pm 0.7)% and BF(D+μ+X)=(17.6±2.7±1.8)BF(D^+ \to \mu^+ X) =(17.6 \pm 2.7 \pm 1.8)%, and determine the ratio of the two branching fractions to be BF(D+μ+X)BF(D0μ+X)=2.59±0.70±0.25\frac{BF(D^+ \to \mu^+ X)}{BF(D^0 \to \mu^+ X)}=2.59\pm 0.70 \pm 0.25

    Measurement of the Bottom contribution to non-photonic electron production in p+pp+p collisions at s\sqrt{s} =200 GeV

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    The contribution of BB meson decays to non-photonic electrons, which are mainly produced by the semi-leptonic decays of heavy flavor mesons, in p+pp+p collisions at s=\sqrt{s} = 200 GeV has been measured using azimuthal correlations between non-photonic electrons and hadrons. The extracted BB decay contribution is approximately 50% at a transverse momentum of pT5p_{T} \geq 5 GeV/cc. These measurements constrain the nuclear modification factor for electrons from BB and DD meson decays. The result indicates that BB meson production in heavy ion collisions is also suppressed at high pTp_{T}.Comment: 6 pages, 4 figures, accepted by PR

    Measurements of J/psi Decays into 2(pi+pi-)eta and 3(pi+pi-)eta

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    Based on a sample of 5.8X 10^7 J/psi events taken with the BESII detector, the branching fractions of J/psi--> 2(pi+pi-)eta and J/psi-->3(pi+pi-)eta are measured for the first time to be (2.26+-0.08+-0.27)X10^{-3} and (7.24+-0.96+-1.11)X10^{-4}, respectively.Comment: 11 pages, 6 figure

    Search for the Rare Decays J/Psi --> Ds- e+ nu_e, J/Psi --> D- e+ nu_e, and J/Psi --> D0bar e+ e-

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    We report on a search for the decays J/Psi --> Ds- e+ nu_e + c.c., J/Psi --> D- e+ nu_e + c.c., and J/Psi --> D0bar e+ e- + c.c. in a sample of 5.8 * 10^7 J/Psi events collected with the BESII detector at the BEPC. No excess of signal above background is observed, and 90% confidence level upper limits on the branching fractions are set: B(J/Psi --> Ds- e+ nu_e + c.c.)<4.8*10^-5, B(J/Psi --> D- e+ nu_e + c.c.) D0bar e+ e- + c.c.)<1.1*10^-5Comment: 10 pages, 4 figure
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