Strings in Horizons, Dissipation and a Possible Interpretation of the Hagedorn Temperature

We consider the entanglement of closed bosonic strings intersecting the event horizon of a Rindler spacetime and, by using some simplified (rather semiclassical) arguments and some elements of the string field theory, we show the existence of a critical temperature beyond which closed strings \emph{cannot be in thermal equilibrium}. The order of magnitude of this critical value coincides with the Hagedorn temperature, which suggests an interpretation consistent with the fact of having a partition function which is bad defined for temperatures higher than it. Possible implications of the present approach on the microscopical structure of stretched horizons are also pointed out.Comment: A detailed description of string boundary states in a Rindler horizon was added, and their relation with the stretched horizon microscopic structure was emphasized. References added. To appear in Eur. Phys. J.

Bipyridinium Ligands: Highly Luminescent Bismuth Complexes

International audienc

Photochromism and Solid State Photoluminescence of Bi and Pb Complexes and Coordination Polymers based on N-R-4,4’-bipyridinium entities (R= O-, CH3, CH2CN)

Date du colloque : 05/2013</p

N-Methyl-4,4-bipyridinium and N-Methyl-N -oxide-4,4 -bipyridinium Bismuth Complexes - Photochromism and Photoluminescence in the Solid State

Three bismuth complexes based on N-methyl-4,4-bipyridinium (hMV(+)), (hMV)[Bi(hMV)Cl-5] (1), and N-methyl-N-oxide-4,4-bipyridinium (MVO+), [Bi(MVO)X-4(dmso)]center dot dmso [X = Cl (2), Br (3)], are reported. All three compounds show luminescence in the solid state with maxima at 545 nm (yellow for 1) and 560 nm (orange for 2 and 3) with quantum yields up to 10 %. Upon UV irradiation, 1 undergoes a color change from white to blue accompanied by a reduction of the photoluminescence intensity. The analysis of the crystal structure of the three complexes points to a photoinduced charge-transfer (PICT) process at the origin of the photochromism in 1

Photochromic and Photluminescence Properties of N-substituted-4,4’-Bipyridinium based Complexes

Date du colloque : 10/2012International audienc

Synthesis, in vitro, and in vivo biological evaluation and molecular docking simulations of chiral alcohol and ether derivatives of the 1,5-diarylpyrrole scaffold as novel anti-inflammatory and analgesic agents.

Following our previous research on anti-inflammatory drugs (NSAIDs), we report here the synthesis of chiral 1,5-diarylpyrroles derivatives that were characterized for their in vitro inhibitory effects toward cyclooxygenase (COX) isozymes. Analysis of enzymatic affinity and COX-2 selectivity led us to the selection of one compound (+/-)-10b that was further tested in vitro in the human whole blood (HWB) and in vivo for its anti-inflammatory activity in mice. The affinity data have been rationalized through docking simulations

Aggregation induced phosphorescent N-oxyde-2,2′-bipyridine bismuth complexes and polymorphism-dependent emission

Unprecedented bismuth complexes, based on the rarely used ditopic ligand N-oxide-2,2′-bipyridine (bp2mo), crystallizing as three polymorphs, α- (1), β- (2) and γ-[BiBr3(bp2mo)2] (3), exhibit phosphorescence with a quantum yield up to 17% for the crystal phase (1), while the complex displays a weak fluorescence in solution. A study of the luminescence properties combined with DFT/TDDFT calculations reveals that the lighting phenomenon originated by aggregation induced phosphorescence correlated with the weak intermolecular interactions present in the different crystal phases

Cyclooxygenase-2 inhibitors. 1,5-diarylpyrrol-3-acetic esters with enhanced inhibitory activity toward cyclooxygenase-2 and improved cyclooxygenase-2/cyclooxygenase-1 selectivity.

he important role of cyclooxygenase-2 (COX-2) in the pathogenesis of inflammation and side effect limitations of current COX-2 inhibitor drugs illustrates a need for the design of new compounds based on alternative structural templates. We previously reported a set of substituted 1,5-diarylpyrrole derivatives, along with their inhibitory activity toward COX enzymes. Several compounds proved to be highly selective COX-2 inhibitors and their affinity data were rationalized through docking simulations. In this paper, we describe the synthesis of new 1,5-diarylpyrrole derivatives that were assayed for their in vitro inhibitory effects toward COX isozymes. Among them, the ethyl-2-methyl-5-[4-(methylsulfonyl)phenyl]-1-[3-fluorophenyl]-1H-pyrrol-3- acetate (1d), which was the most potent and COX-2 selective compound, also showed a very interesting in vivo anti-inflammatory and analgesic activity, laying the foundations for developing new lead compounds that could be effective agents in the armamentarium for the management of inflammation and pain