Results 1 - 10 of 30
Results 1 - 10 of 30. Search took: 0.017 seconds
|Sort by: date | relevance|
[en] We apply perturbative QCD to the radiative decays of charmonia J/ψ and χcJ into light mesons. We perform a complete numerical calculation for the quark-gluon loop diagrams involved in these processes. The calculated J/ψ decay branching ratios into p-wave mesons f2(127)) and f1(1285) fit the data well, while that of f0(980) (if treated as an s(s-bar) meson) is predicted to be 1.6 x 10-4, which implies that f0(1710) can not be the s(s-bar) or (uu-bar+ddbar)/√2 meson. Decays of p-wave charmonia χcJ→ρ(ω, φ)γ (J=0,1,2) are also studied, and the branching ratio of χcl→ργ is predicted to be 1.4 x 10-5, which may be tested by CLEO-c collaboration and BESIII collaboration with future experiments. (authors)
[en] We study radiative decays of Υ to light quark jets in nonrelativistic QCD by taking both the color singlet and color octet b b-bar operators into consideration. The cut for quark jet energy and cut for the angle between two quark jets are introduced. The sensitivity to the soft and collinear singularities in the loop integrals are greatly reduced by these cuts. With the jet energy cut of about 1 GeV, and the jet angle cut of about 360, the branching ratio for Υ→γq q-bar is found to be 8.2x10-4 from color singlet contributions. The color octet contributions could be much larger than that of color singlet, depending on the estimate of the color octet matrix elements. This process may provide a new test for the color octet mechanism in nonrelativistic QCD.
[en] This study examined the tissues distribution and pharmacokinetics of rhTNT-IL2, a fusion protein, in rats and macaques after iv. injection. The rhTNTIL2 was labeled with 125I. The 125I-rhTNT-IL2 was administered into rats and macaques at a dose of 250 μg x kg-1 and 125 μg x kg-1, respectively. Upon administration, rhTNT-IL2 declined in tri-exponentially with the half-lives of 1.78 h (T1/2α), 25.06 h (T1/2β), 114.19 h (T1/2γ) for rats and 1.87 h (T1/2α), 9.82 h (T1/2β), 43.17 h (T1/2γ) for macaques. The fraction of 125I-rhTNT-IL2 excreted in feces was low (about 1%), while the majority of 125I-rhTN-IL2 was excreted in urine. The tissue distributions showed that the liver, spleen and heart were major organs for deposition of the fusion protein in rats and macaques in 48-hour post-injection, and the fusion protein could not penetrate through blood brain barrier. (author)
[en] To obtain the high toughness yellow ceramic, using the Y2O3 (5%) stabilized ZrO2 as main starting material, Al2O3 as toughen reagent, NH4VO3, V2O5 as colorant, and mixed with ball mill, molded with dry press method and two times sintered. By testing the properties and structure of the ceramic, we have optimized the best technical conditions, and the mechanism of toughness and color present have been studied. The result shows that the NH4VO3 as colorant is better than V2O5, and the color is between X=0.396-0.412 and Y=0.402-0.390. The highest bending strength of toughened ZrO2 ceramics is 1138 MPa, and the fracture toughness is 14.8 MPa m1/2. The toughen mechanism is that phase transformation of ZrO2 and the dispersion of toughen reagents, and the color causing is by the colorful ion (V4+) entered into the zirconia crystals lattice of the ceramics
[ru]Получена высоко вязкая желтая керамика, где исходным матералом служил ZrO2, стабилизированный Y2O3 (5%); Al2O3 использован как вяжущий агент, NH4VO3 и V2O5 - красители. Материал проходил обработку в шаровой мельнице, просушен и дважды отожжен. Изучены свойства и структура керамики, технологический процесс оптимизирован, изучены механизмы связывания и окрашивания. Результаты показали, что NH4VO3 является лучшим окрашивающим агентом, по сравнению с V2O5, показатели цветности находятся в диапазонах X=0.396-0.412 и Y=0.402-0.390. Наибольшая прочность на изгиб упрочненных ZrO2 керамик составляет 1138 МПа, ударная вязкость - 14.8 МПа м1/2. Механизм вязкости представляет собой фазовые превращения в ZrO2 и дисперсию вяжущего агента, цветность определяется окрашивающим ионом (V4+), имплантированным в кристаллическую решетку циркониевой керамики
[en] The impact of the three state-of-the-art germanium (Ge) profiles (box, trapezoid and triangular) across the base of SiGe heterojunction bipolar transistors (HBTs) under the condition of the same total amount of Ge on the temperature dependence of current gain β and cut-off frequency fT, as well as the temperature profile, are investigated. It can be found that although the β of HBT with a box Ge profile is larger than that of the others, it decreases the fastest as the temperature increases, while the β of HBT with a triangular Ge profile is smaller than that of the others, but decreases the slowest as the temperature increases. On the other hand, the fT of HBT with a trapezoid Ge profile is larger than that of the others, but decreases the fastest as the temperature increases, and the fT of HBT with a box Ge profile is smaller than that of the others, but decreases the slowest as temperature increases. Furthermore, the peak and surface temperature difference between the emitter fingers of the HBT with a triangular Ge profile is higher than that of the others. Based on these results, a novel segmented step box Ge profile is proposed, which has modest β and fT, and trades off the temperature sensitivity of current gain and cut-off frequency, and the temperature profile of the device. (semiconductor devices)
[en] The inclusive J/ψ production in e+e-→J/ψcc at B factories is one of the most challenging open problems in heavy quarkonium physics. The observed cross section of this double-charm production process is larger than existing leading order (LO) QCD predictions by a factor of 5. In the nonrelativistic QCD (NRQCD) factorization formalism, we calculate the next-to-leading order (NLO) QCD virtual and real corrections to this process, and find that these corrections can substantially enhance the cross section with a K factor of about 1.8. We further take into account the feeddown contributions from higher charmonium states [mainly the ψ(2S) as well as χcJ] and the two-photon contributions, and find that the discrepancy between theory and experiment can be largely removed
[en] Polyvinylpyrrolidone-protected (PVP-protected) graphene was synthesized by refluxing graphene oxide (GO) in dimethylformamide (DMF), using PVP as the dispersant. The structure and stability of this composite (DMF-rGO) were characterized using UV-vis spectroscopy, atomic force microscopy (AFM), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD) and thermogravimetric analysis (TGA). The results confirm the presence of a single sheet of DMF-rGO with PVP of 42%. This kind of chemically reduced GO has a greater solubility in water and also is more biocompatible than rGO reduced by hydrazine hydrate. This method is simple, environmentally friendly and the composite has potential applications in biology and polymer nanocomposites.
[en] A movie encryption scheme is proposed using a discrete multiple-parameter fractional Fourier transform and theta modulation. After being modulated by sinusoidal amplitude grating, each frame of the movie is transformed by a filtering procedure and then multiplexed into a complex signal. The complex signal is multiplied by a pixel scrambling operation and random phase mask, and then encrypted by a discrete multiple-parameter fractional Fourier transform. The movie can be retrieved by using the correct keys, such as a random phase mask, a pixel scrambling operation, the parameters in a discrete multiple-parameter fractional Fourier transform and a time sequence. Numerical simulations have been performed to demonstrate the validity and the security of the proposed method. (paper)
[en] One of the most challenging open problems in heavy quarkonium physics is the double charm production in e+e- annihilation at B factories. The measured cross section of e+e-→J/ψ+ηc is much larger than leading order (LO) theoretical predictions. With the nonrelativistic QCD factorization formalism, we calculate the next-to-leading order (NLO) QCD correction to this process. Taking all one-loop self-energy, triangle, box, and pentagon diagrams into account, and factoring the Coulomb-singular term into the cc bound state wave function, we get an ultraviolet and infrared finite correction to the cross section of e+e-→J/ψ+ηc at √(s)=10.6 GeV. We find that the NLO QCD correction can substantially enhance the cross section with a K factor (the ratio of NLO to LO) of about 1.8-2.1; hence, it greatly reduces the large discrepancy between theory and experiment
[en] Quantum channels that break CHSH nonlocality on all input states are known as CHSH-breaking channels. In quantum networks, such channels are useless for distributing correlations that can violate the CHSH Inequality. Motivated by previous work on activation of nonlocality in quantum states, here we demonstrate an analogous activation of CHSH-breaking channels. That is, we show that certain pairs of CHSH-breaking channels are no longer CHSH-breaking when used in combination. We find that this type of activation can emerge in both uni-directional and bi-directional communication scenarios. (paper)