9,258 research outputs found
Dynamics of Gravity as Thermodynamics on the Spherical Holographic Screen
The dynamics of general Lovelock gravity, viewed on an arbitrary spherically
symmetric surface as a holographic screen, is recast as the form of some
generalized first law of thermodynamics on the screen. From this observation
together with other two distinct aspects, where exactly the same temperature
and entropy on the screen arise, it is argued that the thermodynamic
interpretation of gravity is physically meaningful not only on the horizon, but
also on a general spherically symmetric screen.Comment: 10 pages, revtex4; v2: minor corrections, references added? v3: the
summary paragraph replaced by the discussion of the general static case,
minor corrections/clarifications/modifications, references added, match the
published versio
Bulk Viscosity of dual Fluid at Finite Cutoff Surface via Gravity/Fluid correspondence in Einstein-Maxwell Gravity
Based on the previous paper arXiv:1207.5309, we investigate the possibility
to find out the bulk viscosity of dual fluid at the finite cutoff surface via
gravity/fluid correspondence in Einstein-Maxwell gravity. We find that if we
adopt new conditions to fix the undetermined parameters contained in the stress
tensor and charged current of the dual fluid, two new terms appear in the
stress tensor of the dual fluid. One new term is related to the bulk viscosity
term, while the other can be related to the perturbation of energy density. In
addition, since the parameters contained in the charged current are the same,
the charged current is not changed.Comment: 15 pages, no figure, typos corrected, new references and comments
added, version accepted by PL
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Use of a Purple Non-Sulphur Bacterium, Rhodopseudomonas palustris, as a Biocatalyst for Hydrogen Production from Glycerol
This project was aimed to use a purple non-sulphur bacterium, Rhodopseudomonas palustris, as a biocatalyst for hydrogen production, from the waste of biodiesel manufacturing, crude glycerol. The goal of this project was to understand the fundamentals relevant to scaling up the process and developing an off the shelf product.
The first objective was to determine the ability of R. palustris to generate hydrogen by non-growing cells in comparison to that by growing cells. Similar average hydrogen production rates and energy conversion were found for both processes but a significant difference in the hydrogen yield was observed. Hydrogen production reached ~ 80 % of the theoretical maximum hydrogen yield by non-growing R. palustris, about eight-fold of that reached by growing R. palustris.
The high yield suggested that it is economically appealing to use non-growing R. palustris as the biocatalyst for continuous hydrogen production. To accomplish the proposed scale-up systems, understanding its product formation kinetics is the key. It was found that the hydrogen production rate is not growth-associated and depends solely on the dry cell mass with a non-growth associated coefficient of 2.52 (Leudeking–Piret model dP/dt=2.52 X).
Light is vital for hydrogen production by non-growing R. palustris, in terms of light intensity and wavelength range. It was found that excessive or insufficient light intensity may constrain the performance. Only photons of light with appropriate wavelengths can excite cytochrome bacteriochlorophyll complexes II in R. palustris to generate hydrogen. Among white LEDs, infrared LEDs, and incandescent light bulbs, at the same light intensity, infrared LEDs gave the best results in the H2 production rate and energy conversion by non-growing cells, 22.0 % ± 1.5 % higher than that with white LEDs and around 25-30 times of that by incandescent light bulbs.
It was found that non-growing R. palustris can be immobilised in alginate beads to give similar H2 production rates as that by cells suspended in media. This preliminary result pointed the direction of developing an off the shelf product of immobilised non-growing R. palustris as a biocatalyst for continuous hydrogen production.Cambridge – KACST Joint Research Programm
From Petrov-Einstein-Dilaton-Axion to Navier-Stokes equation in anisotropic model
In this paper we generalize the previous works to the case that the
near-horizon dynamics of the Einstein-Dilaton-Axion theory can be governed by
the incompressible Navier-Stokes equation via imposing the Petrov-like boundary
condition on hypersurfaces in the non-relativistic and near-horizon limit. The
dynamical shear viscosity of such dual horizon fluid in our scenario,
which isotropically saturates the Kovtun-Son-Starinet (KSS) bound, is
independent of both the dilaton field and axion field in that limit.Comment: 13 pages,no figures; v2: 15 page, Equation.(33), some discussions and
references added, minor corrections , Version accepted for publication in
Physics Letters
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