47 research outputs found
Quark number Susceptibility and Phase Transition in hQCD Models
We study the quark number susceptibility, an indicator of QCD phase
transition, in the hard wall and soft wall models of hQCD. We find that the
susceptibilities in both models are the same, jumping up at the deconfinement
phase transition temperature. We also find that the diffusion constant in the
soft wall model is enhanced compared to the one in the hard wall model.Comment: 14 pages, 2 figure
Photo-emission rate of sQGP at finite density
We calculate the thermal spectral function of SYM plasma with finite density
using holographic technique. We take the RN-AdS black hole as the dual gravity
theory. In the presence of charge, vector modes of gravitational and
electromagnetic perturbation are coupled with each other. By introducing master
variables for these modes, we solve the coupled system and calculate spectral
function. We also calculated photoemission rate of SYM plasma from spectral
function for light like momentum, AC conductivity and their density dependence.
The suppression of the conductivity in high density is noticed, which might be
yet another mechanism for the Jet quenching phenomena in RHIC experiment.Comment: 27 pages, 10 figure
The Dropping of In-Medium Hadron Mass in Holographic QCD
We study the baryon density dependence of the vector meson spectrum using the
D4/D6 system together with the compact D4 baryon vertex. We find that the
vector meson mass decreases almost linearly in density at low density for small
quark mass, but saturates to a finite non-zero value for large density. We also
compute the density dependence of the mass and the
velocity. We find that in medium, our model is consistent with the GMOR
relation up to a few times the normal nuclear density. We compare our hQCD
predictions with predictions made based on hidden local gauge theory that is
constructed to model QCD.Comment: 20 pages, 7 figure
Enhancing anaerobic digestion of vegetable waste and cellulose by bioaugmentation with rumen culture
Anaerobic digestion (AD) has been widely used to valorize food waste (FW) because of its ability to convert organic carbon into CH4 and CO2. Korean FW has a high content of fruits and vegetables, and efficient hydrolysis of less biodegradable fibers is critical for its complete stabilization by AD. This study examined the digestates from different anaerobic digesters, namely Rs, Rr, and Rm, as the inocula for the AD of vegetable waste (VW) and cellulose (CL): Rs inoculated with anaerobic sludge from an AD plant, Rr inoculated with rumen fluid, and Rm inoculated with anaerobic sludge and augmented with rumen fluid. A total of six conditions (3 inocula x 2 substrates) were tested in serial subcultures. Biogas yield was higher in the runs inoculated with Rm than in the other runs for both VW (up to 1.10 L/g VS added) and CL (up to 1.05 L/g VS added), and so was biogas production rate. The inocula had different microbial community structures, and both substrate type and inoculum source had a significant effect on the formation and development of microbial community structures in the subcultures. The overall results suggest that the bioaugmentation with rumen microbial consortium has good potential to enhance the anaerobic biodegradability of VW, and thereby can help more efficiently digest high fiber-content Korean FW
A comparative study of single- and two-phase anaerobic digestion of food waste under uncontrolled pH conditions
This study compared single- versus two-phase systems for semi-continuous anaerobic digestion of food waste without pH control at varying organic loading rates (OLRs). The methanogenic reactors of both systems required trace element supplementation for stable operation at 3.0 g VS (volatile solids)/L.d or higher OLRs. Under trace-element supplemented conditions, both systems achieved stable and efficient performance at OLRs up to 4.0 g VS/L.d. The two-phase system outperformed the single-phase system at 1.0-4.0 g VS/L.d OLRs, but it failed at an OLR of 5.0 g VS/L.d. Meanwhile, the single-phase system maintained the stable performance and reached its maximum methane production at this OLR. These results suggest that a single-phase configuration is more advantageous for robust treatment of food waste without pH control at high organic and hydraulic loads. Hydrogenotrophic methanogens dominated the methanogen community throughout the experiment in both systems. Microbial community structure shifts correlated with reactor operation and performance characteristics