5,638 research outputs found
Comment on "Vortex Liquid Crystal in Anisotropic Type II Superconductors"
This is a Comment on "Vortex Liquid Crystal in Anisotropic Type II
Superconductors" by E. W. Carlson et al. in PRL, vol.90, 087001 (2003)
[cond-mat/0209175].Comment: 2 pages, 1 figure, revised versio
Determining layer number of two dimensional flakes of transition-metal dichalcogenides by the Raman intensity from substrate
Transition-metal dichalcogenide (TMD) semiconductors have been widely studied
due to their distinctive electronic and optical properties. The property of TMD
flakes is a function of its thickness, or layer number (N). How to determine N
of ultrathin TMDs materials is of primary importance for fundamental study and
practical applications. Raman mode intensity from substrates has been used to
identify N of intrinsic and defective multilayer graphenes up to N=100.
However, such analysis is not applicable for ultrathin TMD flakes due to the
lack of a unified complex refractive index () from monolayer to bulk
TMDs. Here, we discuss the N identification of TMD flakes on the SiO/Si
substrate by the intensity ratio between the Si peak from 100-nm (or 89-nm)
SiO/Si substrates underneath TMD flakes and that from bare SiO/Si
substrates. We assume the real part of of TMD flakes as that of
monolayer TMD and treat the imaginary part of as a fitting
parameter to fit the experimental intensity ratio. An empirical ,
namely, , of ultrathin MoS, WS and WSe
flakes from monolayer to multilayer is obtained for typical laser excitations
(2.54 eV, 2.34 eV, or 2.09 eV). The fitted of MoS has
been used to identify N of MoS flakes deposited on 302-nm SiO/Si
substrate, which agrees well with that determined from their shear and
layer-breathing modes. This technique by measuring Raman intensity from the
substrate can be extended to identify N of ultrathin 2D flakes with N-dependent
. For the application purpose, the intensity ratio excited by
specific laser excitations has been provided for MoS, WS and
WSe flakes and multilayer graphene flakes deposited on Si substrates
covered by 80-110 nm or 280-310 nm SiO layer.Comment: 10 pages, 4 figures. Accepted by Nanotechnolog
Probing nuclear symmetry energy at high densities using pion, kaon, eta and photon productions in heavy-ion collisions
The high-density behavior of nuclear symmetry energy is among the most
uncertain properties of dense neutron-rich matter. Its accurate determination
has significant ramifications in understanding not only the reaction dynamics
of heavy-ion reactions especially those induced by radioactive beams but also
many interesting phenomena in astrophysics, such as the explosion mechanism of
supernova and the properties of neutron stars. The heavy-ion physics community
has devoted much effort during the last few years to constrain the high-density
symmetry using various probes. In particular, the pion-/pion+ ratio has been
most extensively studied both theoretically and experimentally. All models have
consistently predicted qualitatively that the pion-/pion+ ratio is a sensitive
probe of the high-density symmetry energy especially with beam energies near
the pion production threshold. However, the predicted values of the pion-/pion+
ratio are still quite model dependent mostly because of the complexity of
modeling pion production and reabsorption dynamics in heavy-ion collisions,
leading to currently still controversial conclusions regarding the high-density
behavior of nuclear symmetry energy from comparing various model calculations
with available experimental data. As more pion-/pion+ data become available and
a deeper understanding about the pion dynamics in heavy-ion reactions is
obtained, more penetrating probes, such as the kaon+/kaon0 ratio, eta meson and
high energy photons are also being investigated or planned at several
facilities. Here, we review some of our recent contributions to the community
effort of constraining the high-density behavior of nuclear symmetry energy in
heavy-ion collisions. In addition, the status of some worldwide experiments for
studying the high-density symmetry energy, including the HIRFL-CSR external
target experiment (CEE) are briefly introduced.Comment: 10 pages, 10 figures, Contribution to the Topical Issue on Nuclear
Symmetry Energy in EPJA Special Volum
Gene-to-metabolite network for biosynthesis of lignans in MeJA-elicited Isatis indigotica hairy root cultures.
Root and leaf tissue of Isatis indigotica shows notable anti-viral efficacy, and are widely used as "Banlangen" and "Daqingye" in traditional Chinese medicine. The plants' pharmacological activity is attributed to phenylpropanoids, especially a group of lignan metabolites. However, the biosynthesis of lignans in I. indigotica remains opaque. This study describes the discovery and analysis of biosynthetic genes and AP2/ERF-type transcription factors involved in lignan biosynthesis in I. indigotica. MeJA treatment revealed differential expression of three genes involved in phenylpropanoid backbone biosynthesis (IiPAL, IiC4H, Ii4CL), five genes involved in lignan biosynthesis (IiCAD, IiC3H, IiCCR, IiDIR, and IiPLR), and 112 putative AP2/ERF transcription factors. In addition, four intermediates of lariciresinol biosynthesis were found to be induced. Based on these results, a canonical correlation analysis using Pearson's correlation coefficient was performed to construct gene-to-metabolite networks and identify putative key genes and rate-limiting reactions in lignan biosynthesis. Over-expression of IiC3H, identified as a key pathway gene, was used for metabolic engineering of I. indigotica hairy roots, and resulted in an increase in lariciresinol production. These findings illustrate the utility of canonical correlation analysis for the discovery and metabolic engineering of key metabolic genes in plants
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