Two and three-point functions in Liouville theory

Based on our generalization of the Goulian-Li continuation in the power of the 2D cosmological term we construct the two and three-point correlation functions for Liouville exponentials with generic real coefficients. As a strong argument in favour of the procedure we prove the Liouville equation of motion on the level of three-point functions. The analytical structure of the correlation functions as well as some of its consequences for string theory are discussed. This includes a conjecture on the mass shell condition for excitations of noncritical strings. We also make a comment concerning the correlation functions of the Liouville field itself.Comment: 15 pages, Latex, Revised version: A sign error in formula (50) is correcte

Strings, Matrix Models, and Meanders

I briefly review the present status of bosonic strings and discretized random surfaces in D>1 which seem to be in a polymer rather than stringy phase. As an explicit example of what happens, I consider the Kazakov-Migdal model with a logarithmic potential which is exactly solvable for any D (at large D for an arbitrary potential). I discuss also the meander problem and report some new results on its representation via matrix models and the relation to the Kazakov-Migdal model. A supersymmetric matrix model is especially useful for describing the principal meanders.Comment: 12 pages, 4 Latex figures, uses espcrc2.sty Talk at the 29th Ahrenshoop Symp., Buckow, Germany, Aug.29 - Sep.2, 199

Analysis of All Dimensionful Parameters Relevant in Gravitational Dressing of Conformal Theories

Starting from a covariant and background independent definition of normal ordered vertex operators we give an alternative derivation of the KPZ relation between conformal dimensions and their gravitational dressed partners. With our method we are able to study for arbitrary genus the dependence of N-point functions on all dimensionful parameters. Implications for the interpretation of gravitational dressed dimensions are discussed.Comment: 11 page

The PECACE domain: a new family of enzymes with potential peptidoglycan cleavage activity in Gram-positive bacteria

BACKGROUND: The metabolism of bacterial peptidoglycan is a dynamic process, synthases and cleavage enzymes are functionally coordinated. Lytic Transglycosylase enzymes (LT) are part of multienzyme complexes which regulate bacterial division and elongation. LTs are also involved in peptidoglycan turnover and in macromolecular transport systems. Despite their central importance, no LTs have been identified in the human pathogen Streptococcus pneumoniae. We report the identification of the first putative LT enzyme in S. pneumoniae and discuss its role in pneumococcal peptidoglycan metabolism. RESULTS: Homology searches of the pneumococcal genome allowed the identification of a new domain putatively involved in peptidoglycan cleavage (PECACE, PEptidoglycan CArbohydrate Cleavage Enzyme). This sequence has been found exclusively in Gram-positive bacteria and gene clusters containing pecace are conserved among Streptococcal species. The PECACE domain is, in some instances, found in association with other domains known to catalyze peptidoglycan hydrolysis. CONCLUSIONS: A new domain, PECACE, putatively involved in peptidoglycan hydrolysis has been identified in S. pneumoniae. The probable enzymatic activity deduced from the detailed analysis of the amino acid sequence suggests that the PECACE domain may proceed through a LT-type or goose lyzosyme-type cleavage mechanism. The PECACE function may differ largely from the other hydrolases already identified in the pneumococcus: LytA, LytB, LytC, CBPD and PcsB. The multimodular architecture of proteins containing the PECACE domain is another example of the many activities harbored by peptidoglycan hydrolases, which is probably required for the regulation of peptidoglycan metabolism. The release of new bacterial genomes sequences will probably add new members to the five groups identified so far in this work, and new groups could also emerge. Conversely, the functional characterization of the unknown domains mentioned in this work can now become easier, since bacterial peptidoglycan is proposed to be the substrate

Reversal of age-related learning deficiency by the vertebrate PACAP and IGF-1 in a novel invertebrate model of aging: the pond snail (Lymnaea Stagnalis)

With the increase of life span, nonpathological age-related memory decline is affecting an increasing number of people. However, there is evidence that age-associated memory impairment only suspends, rather than irreversibly extinguishes, the intrinsic capacity of the aging nervous system for plasticity (1). Here, using a molluscan model system, we show that the age-related decline in memory performance can be reversed by administration of the pituitary adenylate cyclase activating polypeptide (PACAP). Our earlier findings showed that a homolog of the vertebrate PACAP38 and its receptors exist in the pond snail (Lymnaea stagnalis) brain (2), and it is both necessary and instructive for memory formation after reward conditioning in young animals (3). Here we show that exogenous PACAP38 boosts memory formation in aged Lymnaea, where endogenous PACAP38 levels are low in the brain. Treatment with insulin-like growth factor-1, which in vertebrates was shown to transactivate PACAP type I (PAC1) receptors (4) also boosts memory formation in aged pond snails. Due to the evolutionarily conserved nature of these polypeptides and their established role in memory and synaptic plasticity, there is a very high probability that they could also act as “memory rejuvenating” agents in humans

Ultrafast all-optical order-to-chaos transition in silicon photonic crystal chips

ADF acknowledges support from EPSRC (EP/L017008/1).The interaction of light with nanostructured materials provides exciting new opportunities for investigating classical wave analogies of quantum phenomena. A topic of particular interest forms the interplay between wave physics and chaos in systems where a small perturbation can drive the behavior from the classical to chaotic regime. Here, we report an all-optical laser-driven transition from order to chaos in integrated chips on a silicon photonics platform. A square photonic crystal microcavity at telecom wavelengths is tuned from an ordered into a chaotic regime through a perturbation induced by ultrafast laser pulses in the ultraviolet range. The chaotic dynamics of weak probe pulses in the near infrared is characterized for different pump-probe delay times and at various positions in the cavity, with high spatial accuracy. Our experimental analysis, confirmed by numerical modelling based on random matrices, demonstrates that nonlinear optics can be used to control reversibly the chaotic behavior of light in optical resonators.PostprintPeer reviewe

Chemically-specific dual/differential CARS micro-spectroscopy of saturated and unsaturated lipid droplets

We have investigated the ability of dual-frequency Coherent Antistokes Raman Scattering (D-CARS) micro-spectroscopy, based on femtosecond pulses (100 fs or 5 fs) spectrally focussed by glass dispersion, to distinguish the chemical composition of micron-sized lipid droplets consisting of different triglycerides types (poly-unsaturated glyceryl trilinolenate, mono-unsaturated glyceryl trioleate and saturated glyceryl tricaprylate and glyceryl tristearate) in a rapid and label-free way. A systematic comparison of Raman spectra with CARS and D-CARS spectra was used to identify D-CARS spectral signatures which distinguish the disordered poly-unsaturated lipids from the more ordered saturated ones both in the CH-stretch vibration region and in the fingerprint region, without the need for lengthy CARS multiplex acquisition and analysis. D-CARS images of the lipid droplets at few selected wavenumbers clearly resolved the lipid composition differences, and exemplify the potential of this technique for label-free chemically selective rapid imaging of cytosolic lipid droplets in living cell

Efectos del establecimiento de las áreas marinas protegidas en la pesquería argentina de la merluza negra (Dissostichus eleginoides)

At the beginning of the 1990s, the Argentine toothfish fishery gained prominence as a consequence of the rapid expansion of trawler and longliner fleets targeting this species. This fishing area covers the slope and shelf from 60° S to 37° S in the Argentine Exclusive Economic Zone. The main fishing ground is located in the southern area, bordering Namuncurá-Burdwood Bank II (NBBII) and Yaganes (Y) marine protected areas (MPA) established in 2018. In order to determine the impact generated by MPAs on effort distribution, 308 fishing trips carried out between 2010 and 2020, which reported 82% of the total fishing effort of Argentine toothfish declared in that period, were spatially analyzed. The Y-MPA sector categorized as National Marine Reserve and located to the south of Tierra del Fuego reported more than half (58%) of the toothfish catch recorded throughout that period, while the NBBII-MPA located to the east of Tierra del Fuego and south of De los Estados Island represented 17%. The NBBII-MPA sector established as a Strict National Marine Reserve and located to the south of the Burdwood Bank represented 25%. With the establishment of the MPAs, 7.11% of the international requirement has been met. At the moment, effects resulting from the creation of MPAs can only be speculated upon qualitatively, but should be quantified in the near future.A principios de la década de 1990, la pesquería de merluza negra argentina ganó protagonismo gracias a la rápida expansión de las flotas de arrastre y palangre que se dirigían a esta especie. Esta zona de pesca cubre el talud y plataforma desde los 60° S hasta los 37° S en la Zona Económica Exclusiva argentina. El principal caladero se encuentra en la zona sur, colindando con las áreas marinas protegidas (AMP) Banco Namuncurá-Burdwood II (NBBII) y Yaganes (Y), establecidas en 2018. Para determinar el impacto que generan las AMP en la distribución del esfuerzo, se analizaron espacialmente 308 viajes de pesca realizados entre 2010 y 2020, que reportaron 82% del total del esfuerzo pesquero declarado de merluza negra argentina en ese período. El sector Y-AMP categorizado como Reserva Nacional Marina y ubicado al sur de Tierra del Fuego, reportó más de la mitad (58%) de la captura de merluza negra registrada durante ese período, mientras que el NBBII-AMP ubicado al este de Tierra del Fuego y sur de la Isla de los Estados representaron 17%. El sector NBBII-AMP establecido como Reserva Nacional Marina Estricta y ubicado al sur del Banco Burdwood representó el 25%. Con el establecimiento de las AMP se ha cumplido 7,11% del requerimiento internacional. En la actualidad, los efectos resultantes de la creación de AMP solo pueden especularse cualitativamente, pero deberían cuantificarse en un futuro próximo.