Chung-Ang University

About: Chung-Ang University is a education organization based out in Seoul, South Korea. It is known for research contribution in the topics: Population & Thin film. The organization has 13381 authors who have published 26978 publications receiving 416735 citations. The organization is also known as: CAU & Chung.

Enhanced Triterpene and Phytosterol Biosynthesis in Panax ginseng Overexpressing Squalene Synthase Gene

Abstract: ;Roots of Panax ginseng, one of the most famous medicinal plants, contain various phytosterols and bioactive triterpene saponins (ginsenosides). In P. ginseng, phytosterols and triterpenes share the common biosynthetic intermediate, squalene. Here, we investigate the regulatory role of Panax ginseng squalene synthase (PgSS1) on the biosynthesis of phytosterols and triterpene saponins. PgSS1 transcripts are expressed ubiquitously in the various plant tissues, but higher in shoot apex and root. The transcript levels of PgSS1 increased markedly in the adventitious roots during 12- to 96-h period after metyl jasmonate (MeJA) treatment; MeJA treatment induced the activation of the transcripts of squalene epoxidase (SE), β-amyrin synthase (bAS), but not cycloartenol synthase (CAS). Unlike MeJA treatment, overexpression of PgSS1 in adventitious roots of transgenic P. ginseng was followed by the up-regulation of all the downstream genes tested, such as SE, bAS, and CAS. The enhanced activity of PgSS1 enzyme resulted in remarkable increase of phytosterols as well as ginsenoside contents. These results demonstrate that PgSS1 is a key regulatory enzyme not only for phytosterol but also for triterpene biosynthesis and overexpressing of PgSS1 confers the hyperproduction of triterpene saponins to P. ginseng.

Majorana fermions in the Kitaev quantum spin system α-RuCl 3

Abstract: α-RuCl3 has recently attracted great interest as a possible experimental realization of the Kitaev model. Neutron scattering measurements of a single crystal of this material reveal signatures of Majorana excitations, consistent with Kitaev’s predictions. Geometrical constraints to the electronic degrees of freedom within condensed-matter systems often give rise to topological quantum states of matter such as fractional quantum Hall states, topological insulators, and Weyl semimetals1,2,3. In magnetism, theoretical studies predict an entangled magnetic quantum state with topological ordering and fractionalized spin excitations, the quantum spin liquid4. In particular, the so-called Kitaev spin model5, consisting of a network of spins on a honeycomb lattice, is predicted to host Majorana fermions as its excitations. By means of a combination of specific heat measurements and inelastic neutron scattering experiments, we demonstrate the emergence of Majorana fermions in single crystals of α-RuCl3, an experimental realization of the Kitaev spin lattice. The specific heat data unveils a two-stage release of magnetic entropy that is characteristic of localized and itinerant Majorana fermions. The neutron scattering results corroborate this picture by revealing quasielastic excitations at low energies around the Brillouin zone centre and an hour-glass-like magnetic continuum at high energies. Our results confirm the presence of Majorana fermions in the Kitaev quantum spin liquid and provide an opportunity to build a unified conceptual framework for investigating fractionalized excitations in condensed matter1,6,7,8.

Sterile Neutrino Search at the NEOS Experiment.

Abstract: An experiment to search for light sterile neutrinos is conducted at a reactor with a thermal power of 2.8 GW located at the Hanbit nuclear power complex. The search is done with a detector consisting of a ton of Gd-loaded liquid scintillator in a tendon gallery approximately 24 m from the reactor core. The measured antineutrino event rate is 1976 per day with a signal to background ratio of about 22. The shape of the antineutrino energy spectrum obtained from the eight-month data-taking period is compared with a hypothesis of oscillations due to active-sterile antineutrino mixing. No strong evidence of $3+1$ neutrino oscillation is found. An excess around the 5 MeV prompt energy range is observed as seen in existing longer-baseline experiments. The mixing parameter ${\mathrm{sin}}^{2}2{\ensuremath{\theta}}_{14}$ is limited up to less than 0.1 for $\mathrm{\ensuremath{\Delta}}{m}_{41}^{2}$ ranging from 0.2 to $2.3\text{ }{\mathrm{eV}}^{2}$ with a 90% confidence level.