22,021 research outputs found
Black Holes, Entropy Bound and Causality Violation
The gravity/gauge theory duality has provided us a way of studying QCD at
short distances from straightforward calculations in classical general
relativity. Among numerous results obtained so far, one of the most striking is
the universality of the ratio of the shear viscosity to the entropy density.
For all gauge theories with Einstein gravity dual, this ratio is \eta/s=1/4\pi.
However, in general higher-curvature gravity theories, including two concrete
models under discussion - the Gauss-Bonnet gravity and the (Riemann)^2 gravity
- the ratio \eta/s can be smaller than 1/4\pi (thus violating the conjecture
bound), equal to 1/4\pi or even larger than 1/4\pi. As we probe spacetime at
shorter distances, there arises an internal inconsistency in the theory, such
as a violation of microcausality, which is correlated with a classical limit on
black hole entropy.Comment: 8 pages, no figures; Invited contribution to appear in the
Proceedings of the 75 Years since Solvay, Singapore, Nov 2008, (World
Scientific, Singapore, 2009
Graded reflection equation algebras and integrable Kondo impurities in the one-dimensional t-J model
Integrable Kondo impurities in two cases of the one-dimensional model
are studied by means of the boundary -graded quantum inverse
scattering method. The boundary matrices depending on the local magnetic
moments of the impurities are presented as nontrivial realizations of the
reflection equation algebras in an impurity Hilbert space. Furthermore, these
models are solved by using the algebraic Bethe ansatz method and the Bethe
ansatz equations are obtained.Comment: 14 pages, RevTe
ALMA Observations of Ethyl Formate toward Orion KL
Orion KL is one of the prime templates of astrochemical and prebiotic
chemical studies. We wish to explore more organic molecules with increasing
complexity in this region. In particular, we have searched for one of the most
complex organic molecules detected in space so far, ethyl formate
(CHOCHO). This species is the next step in chemical complexity
after the simplest member of esters (methyl formate, CHOCHO). The
mechanisms leading to its formation are still poorly known. We have used high
angular resolution ( 1.5) ALMA observations covering a
large bandwidth from 214 to 247 GHz. We have detected 82 unblended lines of
CHOCHO (49 and 33 of the trans and gauche conformers,
respectively). The line images showed that CHOCHO arises mainly
from the compact ridge and the hot core-southwest regions. The derived
rotational temperatures and column densities are 122 34 K, (0.9
0.3) 10 cm for the hot core-SW, and 103 13 K, (0.6
0.3) 10 cm for the compact ridge. The comparison
of spatial distribution and abundance ratios with chemically related molecules
(methyl formate, ethanol and formic acid) indicates that CHOCHO is
likely formed on the surface of dust grains by addition of CH to
functional-group radicals (CHOCHO) derived from methyl formate
(CHOCHO)
Rhein induces apoptosis of HCT-116 human colon cancer cells via activation of the intrinsic apoptotic pathway
Rhein, a major compound in rhubarb, has been found to have anti-tumor properties in many human cancer cells. However, the details about rhein suppressing the growth of human colon cancer cells remained elusive. In this paper, we explored the potential of rhein as a chemotherapeutic agent on HCT- 116 cells and demonstrated significant inhibition of HCT-116 cells proliferation in both concentration (0, 10, 30, and 100 μM) and time (24, 48, and 72 h) dependent manners. The anti-tumor effects were associated with the introduction of cellular apoptosis, which was relative with reduction of Bcl-2, NF-κB and activation of caspase-9 and 3. In conclusion, these findings suggested that rhein inhibited the growth of HCT-116 through the intrinsic apoptotic pathway and might be a useful strategy of chemotherapeutics of colon cancers.Key words: Rhein, apoptosis, HCT-116 human colon cancer cells, anti-tumor properties, caspases, Bcl-2 family proteins, NF-κB
Holographic fermions in charged Gauss-Bonnet black hole
We study the properties of the Green's functions of the fermions in charged
Gauss-Bonnet black hole. What we want to do is to investigate how the presence
of Gauss-Bonnet coupling constant affects the dispersion relation,
which is a characteristic of Fermi or non-Fermi liquid, as well as what
properties such a system has, for instance, the Particle-hole (a)symmetry. One
important result of this research is that we find for , the behavior of
this system is different from that of the Landau Fermi liquid and so the system
can be candidates for holographic dual of generalized non-Fermi liquids. More
importantly, the behavior of this system increasingly similar to that of the
Landau Fermi liquid when is approaching its lower bound. Also we find
that this system possesses the Particle-hole asymmetry when , another
important characteristic of this system. In addition, we also investigate
briefly the cases of the charge dependence.Comment: 22 pages, 6 figures; version published in JHE
Cellulase production by Trichoderma sp. on apple pomace under solid state fermentation
The feasibility of using apple pomace for cellulase production by Trichoderma sp. under solid state fermentation was evaluated in this study. Our results indicated that initial moisture level of the medium, incubation temperature and inoculum size influenced the cellulase production greatly. The optimuminitial moisture level, incubation temperature and inoculum size were 70%, 32 and 2×108 spores/flask, respectively. The supplement of lactose and corn-steep solid to the apple pomace favored the enzyme formation markedly
- …