494 research outputs found
The arrow of time, black holes, and quantum mixing of large N Yang-Mills theories
Quantum gravity in an AdS spacetime is described by an SU(N) Yang-Mills
theory on a sphere, a bounded many-body system. We argue that in the high
temperature phase the theory is intrinsically non-perturbative in the large N
limit. At any nonzero value of the 't Hooft coupling , an
exponentially large (in N^2) number of free theory states of wide energy range
(of order N) mix under the interaction. As a result the planar perturbation
theory breaks down. We argue that an arrow of time emerges and the dual string
configuration should be interpreted as a stringy black hole.Comment: 50 pages 3 figures uses harvma
On a modular property of N=2 superconformal theories in four dimensions
In this note we discuss several properties of the Schur index of N=2
superconformal theories in four dimensions. In particular, we study modular
properties of this index under SL(2,Z) transformations of its parameters.Comment: 23 page, 2 figure
Sulodexide counteracts endothelial dysfunction induced by metabolic or non-metabolic stresses through activation of the autophagic program
OBJECTIVE: Endothelial dysfunction (ED) predisposes to venous thrombosis (VT) and post-thrombotic syndrome (PTS), a long-term VT-related complication. Sulodexide (SDX) is a highly purified glycosaminoglycan with antithrombotic, pro-fibrinolytic and anti-inflammatory activity used in the treatment of chronic venous disease (CVD), including patients with PTS. SDX has recently obtained clinical evidence in the “extension therapy” after initial-standard anticoagulant treatment for the secondary prevention of recurrent deep vein thrombosis (DVT). Herein, we investigated how SDX counteracts ED. MATERIALS AND METHODS: Human umbilical vein endothelial cells (HUVEC) were used. Metabolic and non metabolic-induced ED was induced by treating with methylglyoxal (MGO) or irradiation (IR), respectively. Bafilomycin A1 was used to inhibit autophagy. The production of reactive oxygen species (ROS), tetrazolium bromide (MTT) assay for cell viability, terminal de-oxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay for cell apoptosis, Real-time PCR and Western blot analysis for gene and protein expression were used. RESULTS: SDX protected HUVEC from MGO- or IR-induced apoptosis by counteracting the activation of the intrinsic and extrinsic caspase cascades. The cytoprotective effects of SDX resulted from a reduction in a) ROS production, b) neo-synthesis and release of pro-inflammatory cytokines (TNFα, IL1, IL6, IL8), c) DNA damage induced by MGO or IR. These effects were reduced when autophagy was inhibited. CONCLUSIONS: Data herein collected indicate the ability of SDX to counteract ED induced by metabolic or non-metabolic stresses by involving the intracellular autophagy pathway. Our experience significantly increases the knowledge of the mechanisms of action of SDX against ED and supports the use of SDX in the treatment of CVD, PTS and in the secondary prevention of recurrent DVT
Gravitational quasinormal modes of AdS black branes in d spacetime dimensions
The AdS/CFT duality has established a mapping between quantities in the bulk
AdS black-hole physics and observables in a boundary finite-temperature field
theory. Such a relationship appears to be valid for an arbitrary number of
spacetime dimensions, extrapolating the original formulations of Maldacena's
correspondence. In the same sense properties like the hydrodynamic behavior of
AdS black-hole fluctuations have been proved to be universal. We investigate in
this work the complete quasinormal spectra of gravitational perturbations of
-dimensional plane-symmetric AdS black holes (black branes). Holographically
the frequencies of the quasinormal modes correspond to the poles of two-point
correlation functions of the field-theory stress-energy tensor. The important
issue of the correct boundary condition to be imposed on the gauge-invariant
perturbation fields at the AdS boundary is studied and elucidated in a fully
-dimensional context. We obtain the dispersion relations of the first few
modes in the low-, intermediate- and high-wavenumber regimes. The sound-wave
(shear-mode) behavior of scalar (vector)-type low-frequency quasinormal mode is
analytically and numerically confirmed. These results are found employing both
a power series method and a direct numerical integration scheme.Comment: added references, typos corrected, minor changes, final version for
JHE
Real time response on dS_3: the Topological AdS Black Hole and the Bubble
We study real time correlators in strongly coupled N=4 supersymmetric
Yang-Mills theory on dS_3 x S^1, with antiperiodic boundary conditions for
fermions on the circle. When the circle radius is larger than a critical value,
the dual geometry is the so-called "topological AdS_5 black hole". Applying the
Son- Starinets recipe in this background we compute retarded glueball
propagators which exhibit an infinite set of poles yielding the quasinormal
frequencies of the topological black hole. The imaginary parts of the
propagators exhibit thermal effects associated with the Gibbons-Hawking
temperature due to the cosmological horizon of the de Sitter boundary. We also
obtain R-current correlators and find that after accounting for a small
subtlety, the Son-Starinets prescription yields the retarded Green's functions.
The correlators do not display diffusive behaviour at late times. Below the
critical value of the circle radius, the topological black hole decays to the
AdS_5 "bubble of nothing". Using a high frequency WKB approximation, we show
that glueball correlators in this phase exhibit poles on the real axis. The
tunnelling from the black hole to the bubble is interpreted as a hadronization
transition.Comment: 52 pages, 11 figures, typos corrected, references adde
Biological rationale for the use of DNA methyltransferase inhibitors as new strategy for modulation of tumor response to chemotherapy and radiation
Epigenetic modifications play a key role in the patho-physiology of many tumors and the current use of agents targeting epigenetic changes has become a topic of intense interest in cancer research. DNA methyltransferase (DNMT) inhibitors represent a promising class of epigenetic modulators. Research performed yielded promising anti-tumorigenic activity for these agents in vitro and in vivo against a variety of hematologic and solid tumors. These epigenetic modulators cause cell cycle and growth arrest, differentiation and apoptosis. Rationale for combining these agents with cytotoxic therapy or radiation is straightforward since the use of DNMT inhibitor offers greatly improved access for cytotoxic agents or radiation for targeting DNA-protein complex. The positive results obtained with these combined approaches in preclinical cancer models demonstrate the potential impact DNMT inhibitors may have in treatments of different cancer types. Therefore, as the emerging interest in use of DNMT inhibitors as a potential chemo- or radiation sensitizers is constantly increasing, further clinical investigations are inevitable in order to finalize and confirm the consistency of current observations
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