Chonbuk National University

About: Chonbuk National University is a education organization based out in Jeonju, South Korea. It is known for research contribution in the topics: Apoptosis & Graphene. The organization has 14820 authors who have published 28884 publications receiving 554131 citations.

Precision measurement of the X(3872) mass in J/ψπ+π- decays

Abstract: We present an analysis of the mass of the X(3872) reconstructed via its decay to J/psi pi(+)pi(-) using 2.4 fb(-1) of integrated luminosity from p (p) over bar collisions at root s = 1.96 TeV, collected with the CDF II detector at the Fermilab Tevatron. The possible existence of two nearby mass states is investigated. Within the limits of our experimental resolution the data are consistent with a single state, and having no evidence for two states we set upper limits on the mass difference between two hypothetical states for different assumed ratios of contributions to the observed peak. For equal contributions, the 95% confidence level upper limit on the mass difference is 3.6 MeV/c(2). Under the single-state model the X(3872) mass is measured to be 3871.61 +/- 0.16(stat) +/- 0.19(syst) MeV/c(2), which is the most precise determination to date.

Facile synthesis of 3D hierarchical N-doped graphene nanosheet/cobalt encapsulated carbon nanotubes for high energy density asymmetric supercapacitors

Abstract: A novel three-dimensional (3D) hierarchical hybrid architecture, consisting of in situ designed cobalt-encapsulated nitrogen doped carbon nanotubes (Co–NCNTs) grown on nitrogen doped graphene (NG), is fabricated for asymmetric supercapacitors. When evaluated as an electrode material for supercapacitors, the 3D hybrid has an excellent energy density, outstanding rate capability and long-cycle life compared with commercial electrode materials. The decent electrochemical performance is comparable to most of the earlier reported results and the synergistic effect boosts the pseudocapacitive performance. The constructed hybrid exhibits excellent energy storage characteristics, which result in an ultra-high specific capacitance of 2568 F g−1 at 2 A g−1 and excellent rate capability with an extraordinary capacitance of 1594 F g−1 at 100 A g−1 (96.64% capacitance retention after 20000 cycles). The improvement in the outstanding electrochemical performance can be attributed to the unique morphology, extraordinary porosity, excellent conductive networks, and the intense networking of Co–NCNT and NG nanosheets in the 3D hybrid. An asymmetric supercapacitor fabricated using the 3D NG/Co–NCNT hybrid as the positive electrode and NG as the negative electrode demonstrates exceptional performance for practical energy storage devices. The assembled asymmetric supercapacitors provide a greater energy density (∼88.44 W h kg−1), an ultra-high power density (∼17991 W kg−1 at 56.97 W h kg−1), and outstanding cyclability (∼10000 times).

Nitrogen doping and chirality of carbon nanotubes

Abstract: We have theoretically studied nitrogen doping of carbon nanotubes in a periodic supercell using density functional theory. We find that the most stable isomer is different for different chiralities of the tube. In the (10,0) tube, N atoms tend to be uniformly distributed, while they prefer to be adjacent to each other in (5,5) tube. As more nitrogen atoms are introduced in (5,5) tube, they are aligned parallel to the tube axis in two rows, breaking the $\mathrm{N}\mathrm{N}$ single bonds and forming aromatic $(4n+2)\ensuremath{\pi}$ systems. This leads us to conjecture that the armchair tubes are more easily subject to the opening of the tubular sheets than the zigzag tubes under the existence of a nitrogen source. The hole formation recently proposed by Czerw et al. [Nano Lett. 1, 457 (2001)] is also shown to be energetically favorable. Calculation of the electronic density of states shows that the doping-induced electronic states near the Fermi energy are sensitive to the chirality.