Methods to assess lactic acid bacteria diversity and compatibility in food

Food microflora is a complex and mutable ecosystem where the effects of microbial culture addition are still not entirely foreseeable due to microbial diversity. Starter, probiotic, and adjunct microorganisms are widely selected and used in food to improve quality and safety; they may be formulated as monostrain or multistrain cultures. Lactic acid bacteria are included among the main groups deemed useful for these aims. Compatibility tests can constitute an effective way to assess interactions among lactic acid bacteria. Food microflora composition is generally examined using both culture-dependent and culture-independent methods. The existing limits of each method can be overcome by combining them, so that they give more information on microbial complexity. Since mixed cultures of starter, probiotic, or adjunct lactic acid bacteria provide more beneficial effects than single cultures, future research should be guided by compatibility tests to show the most suitable and beneficial mixed cultures

Nuevos conocimientos sobre la actividad antifúngica de las bacterias del ácido láctico aisladas de diferentes matrices alimentarias

The anti-mold activity of 397 strains of lactic acid bacteria was evaluated using both the spot method in Petri plates and coculture in liquid medium. The study led to the selection of 34 strains isolated from table olives or olive brines, 15 strains from dairy products, and 10 strains from sourdoughs, all able to inhibit a strain of Penicillium crustosum and/or a strain of Aspergillus section Nidulantes, prevailing in two Calabrian olive brines. Seven representative strains were identified as Lactobacillus pentosus (four strains) and Lactobacillus sanfranciscensis (three strains) and are currently under testing for their antifungal activity during table olive fermentation. This research constitutes an initial contribution to the control of fungal growth and mycotoxin accumulation during table olive fermentation. The selected strains could be used as adjunct cultures in table olive fermentation, allowing for the biological control of table olive safety.La actividad antimoho de 397 bacterias del ácido láctico se evaluó utilizando tanto el método puntual en placas de Petri como el co-cultivo en medio líquido. El estudio condujo a la selección de 34 cepas aisladas de aceitunas de mesa o salmueras de oliva, 15 cepas de productos lácteos y 10 cepas de masa madre, todas capaces de inhibir una cepa de Penicillium crustosum y/o una cepa de Aspergillus sección Nidulantes, que prevalecen en dos salmueras de aceituna de Calabria. Se identificaron siete cepas representativas como Lactobacillus pentosus (cuatro cepas) y Lactobacillus sanfranciscensis (tres cepas) y actualmente se están probando su actividad antifúngica durante la fermentación de aceituna de mesa. Esta investigación constituye una primera contribución para controlar el crecimiento de hongos y la acumulación de micotoxinas durante la fermentación de aceitunas de mesa. Las cepas seleccionadas podrían usarse como cultivos adjuntos en la fermentación de aceitunas de mesa

A BGG-type resolution for tensor modules over general linear superalgebra

We construct a Bernstein-Gelfand-Gelfand type resolution in terms of direct sums of Kac modules for the finite-dimensional irreducible tensor representations of the general linear superalgebra. As a consequence it follows that the unique maximal submodule of a corresponding reducible Kac module is generated by its proper singular vector.Comment: 11pages, LaTeX forma

Critical Excitation Spectrum of Quantum Chain With A Local 3-Spin Coupling

This article reports a measurement of the low-energy excitation spectrum along the critical line for a quantum spin chain having a local interaction between three Ising spins and longitudinal and transverse magnetic fields. The measured excitation spectrum agrees with that predicted by the (D$_4$, A$_4$) conformal minimal model under a nontrivial correspondence between translations at the critical line and discrete lattice translations. Under this correspondence, the measurements confirm a prediction that the critical line of this quantum spin chain and the critical point of the 2D 3-state Potts model are in the same universality class.Comment: 7 pages, 2 figure

Form factors of descendant operators in the massive Lee-Yang model

The form factors of the descendant operators in the massive Lee-Yang model are determined up to level 7. This is first done by exploiting the conserved quantities of the integrable theory to generate the solutions for the descendants starting from the lowest non-trivial solutions in each operator family. We then show that the operator space generated in this way, which is isomorphic to the conformal one, coincides, level by level, with that implied by the $S$-matrix through the form factor bootstrap. The solutions we determine satisfy asymptotic conditions carrying the information about the level that we conjecture to hold for all the operators of the model.Comment: 23 page

Tof ion spectra de convolution for lasergenerated plasmas

EnA study of different targets (Fe, Ti, Ni, Al2O3) ablation, in vacuum, by using a ns Nd:YAG laser radiation, 1064 nm and 532 nm (second harmonic) wavelengths, is reported. Laser pulse with high intensity generates a plasma at the target surface, with high non-isotropic emission of neutral and ion species, mainly emitted along the normal to the target surface. Time of flight (TOF) measurements are performed by using an ion collector consisting of a collimated Faraday cup placed along the normal to the target surface and an Ion Energy Analyzer (IEA) detector. The TOF spectra are converted as a function of the ions velocity and they are deconvolved for the various ion charge states by using the “Coulomb-Boltzmann shifted” function approach through the “Peakfit” mathematical code. The fit of the experimental distribution data permits to estimate the equivalent plasma temperature and the average energy shift of the distributions as a function of the ion charge state. This energy shift leads to the evaluation of the electric field producing the ion acceleration inside the plasma

Homogeneous components in the moduli space of sheaves and Virasoro characters

The moduli space $\mathcal M(r,n)$ of framed torsion free sheaves on the projective plane with rank $r$ and second Chern class equal to $n$ has the natural action of the $(r+2)$-dimensional torus. In this paper, we look at the fixed point set of different one-dimensional subtori in this torus. We prove that in the homogeneous case the generating series of the numbers of the irreducible components has a beautiful decomposition into an infinite product. In the case of odd $r$ these infinite products coincide with certain Virasoro characters. We also propose a conjecture in a general quasihomogeneous case.Comment: Published version, 19 page

Exceptional structure of the dilute A3_3 model: E8_8 and E7_7 Rogers--Ramanujan identities

The dilute A$_3$ lattice model in regime 2 is in the universality class of the Ising model in a magnetic field. Here we establish directly the existence of an E$_8$ structure in the dilute A$_3$ model in this regime by expressing the 1-dimensional configuration sums in terms of fermionic sums which explicitly involve the E$_8$ root system. In the thermodynamic limit, these polynomial identities yield a proof of the E$_8$ Rogers--Ramanujan identity recently conjectured by Kedem {\em et al}. The polynomial identities also apply to regime 3, which is obtained by transforming the modular parameter by $q\to 1/q$. In this case we find an A_1\times\mbox{E}_7 structure and prove a Rogers--Ramanujan identity of A_1\times\mbox{E}_7 type. Finally, in the critical $q\to 1$ limit, we give some intriguing expressions for the number of $L$-step paths on the A$_3$ Dynkin diagram with tadpoles in terms of the E$_8$ Cartan matrix. All our findings confirm the E$_8$ and E$_7$ structure of the dilute A$_3$ model found recently by means of the thermodynamic Bethe Ansatz.Comment: 9 pages, 1 postscript figur

Local height probabilities in a composite Andrews-Baxter-Forrester model

We study the local height probabilities in a composite height model, derived from the restricted solid-on-solid model introduced by Andrews, Baxter and Forrester, and their connection with conformal field theory characters. The obtained conformal field theories also describe the critical behavior of the model at two different critical points. In addition, at criticality, the model is equivalent to a one-dimensional chain of anyons, subject to competing two- and three-body interactions. The anyonic-chain interpretation provided the original motivation to introduce the composite height model, and by obtaining the critical behaviour of the composite height model, the critical behaviour of the anyonic chains is established as well. Depending on the overall sign of the hamiltonian, this critical behaviour is described by a diagonal coset-model, generalizing the minimal models for one sign, and by Fateev-Zamolodchikov parafermions for the other.Comment: 34 pages, 5 figures; v2: expanded introduction, references added and other minor change