Some Remarks on the Model Theory of Epistemic Plausibility Models

Classical logics of knowledge and belief are usually interpreted on Kripke models, for which a mathematically well-developed model theory is available. However, such models are inadequate to capture dynamic phenomena. Therefore, epistemic plausibility models have been introduced. Because these are much richer structures than Kripke models, they do not straightforwardly inherit the model-theoretical results of modal logic. Therefore, while epistemic plausibility structures are well-suited for modeling purposes, an extensive investigation of their model theory has been lacking so far. The aim of the present paper is to fill exactly this gap, by initiating a systematic exploration of the model theory of epistemic plausibility models. Like in 'ordinary' modal logic, the focus will be on the notion of bisimulation. We define various notions of bisimulations (parametrized by a language L) and show that L-bisimilarity implies L-equivalence. We prove a Hennesy-Milner type result, and also two undefinability results. However, our main point is a negative one, viz. that bisimulations cannot straightforwardly be generalized to epistemic plausibility models if conditional belief is taken into account. We present two ways of coping with this issue: (i) adding a modality to the language, and (ii) putting extra constraints on the models. Finally, we make some remarks about the interaction between bisimulation and dynamic model changes.Comment: 19 pages, 3 figure

Estabilidad genética in vitro en cultivares de caña de azúcar

Genotypic stability and uniformity of field plants from sugarcane cultivars grown in vitro (calli and cell suspensions) were evaluated by isoenzymatic peroxidase analysis after regeneration, Phenotypes of field plants exhibited uniformity within cultivars and differences among cultivars. Distribution of PRX isoenzymes was different in the constitution of the calli phenotypes, not only among cultivars but also within the same cultivar. Genotype PR980 showed a 60% heterogeneity coefficient, whereas the call of cultivars PR62258, PR641791, PR692176, V64-10 and V71-51 showed identity coefficient of 100%. The isoenzymatic pattern of PRX for the phenotypes of cell suspensions was different among the four cuitivars used, as well as within cultivars PR980 and V64-10, all of which showed heterogeneity coefficients of 50 and 22%, respectively. Nevertheless, the identity coefficient for regenerated plants of all genotypes was 100%. In sugarcane, the isoenzyme PRX1 is related to differentiated tissue, since it is present only in phenotypes from field and regenerated plants. PRX4 is induced in vitro conditions since it was observed only in callus tissue and ceil suspensions,This study detected high uniformity and genetic stability within the regenerated plants in 100% of the sugarcane cultivars used.Se evaluó la estabilidad y uniformidad de los genotipos de plantas de campo de cultivares de caña de azúcar después de haber pasado por condiciones in vitro (callos y suspensiones celulares), a través del análisis isoenzimátíco de peroxídasa en plántulas regeneradas. Los fenotipos de tas plantas de campo exhibieron uniformidad para cada cultivar y diferencias entre los distintos cultivares. La distribución de las isoenzimas de PRX en la constitución de los fenotipos de callos mostró diferencias entre cultivares así como dentro del mismo cultivar. El genotipo PR980 alcanzó un coeficiente de heterogeneidad de 60%. Para los callos de los cultivares PR62258, PR641791, PR692176, V58-4, V64-10 y V71-51 no mostró variación, señalándose un coeficiente de identidad de 100%. El patrón isoenzfmático de PRX para la conformación de los fenotipos de las suspensiones celulares fue diferente en los cuatro cultivares usados, así como también dentro de los cultivares PR980 y V64-10, los cuales exhibieron coeficientes de heterogeneidad de 50 y 22%, respectivamente. Sin embargo, los regenerantes exhibieron un coeficiente de identidad del 100%. La isoenzima PRX1 está relacionada a tejido diferenciado en caña de azúcar ya que sólo está presente en los fenotipos de plantas de campo y regenerantes. PRX4 es inducida bajo condiciones de cultivo in vitro, visualizándose exclusivamente en tejido calloso y suspensiones celulares. Este estudio detectó, en todos los cultivares de caña de azúcar usados, una alta uniformidad y estabilidad genética entre las plántulas regeneradas

Reduction of food phatogens prevalence in dietary S.cerevisiae-fed poultry orally challenged with S.enteritidis and C. jejuni.

The effect of yeast supplementation in broiler chickens on Salmonella enteritidis and Campylobacter jejuni contamination in faeces, cecum, breast, and neck skin was evaluated. Two groups (12 replicates/group, 20 Hubbard female chickens 1d old/replicate) were fed pre-starter (0-10d), starter (11-20d) and growing (21-38d) diets, and administered (Y) or not (C) Levucell\uae SB20 (Saccharomyces cerevisiae type boulardii I-1079; 106 CFU/g feed through a 0.05% premix). Birds were orally challenged at 10 days of life (S. enteritidis, 1x105 CFU/bird, and C. jejuni, 3x105 CFU/bird). On day 10 and 28 post-infection (PI), 10 animals/replicate were slaughtered and pooled ceca content of 5 birds/replicate was analysed for Salmonella and Campylobacter detection and enumeration together with total yeast count. Neck and breast skin were tested for Salmonella and Campylobacter presence on 1 subject/replicate. Data were analysed by a GLM procedure of SAS considering two experimental periods, from 0 to 20 days and from 20 to 38 days. Growth performance and faecal coliforms content were not affected by treatment. Higher yeast and lactobacilli (P=0.01) faecal count, and a significant decreased Salmonella enumeration and frequency in neck (-41%, P=0.03) and tendency in faeces (-25%; P=0.06), cecum (-25%; P=0.06), and breast skin (-33%; P=0.08) were found in Y group on day 38. No fecal Campylobacter was detected at 10d (P<0.01) or 28d (P=0.06) PI in Y birds, while in neck skin absence of Campylobacter was only recorded on day 10 PI (P=0.01). Campylobacter was significantly lower in Y birds in cecum (-42%; P=0.01), and breast skin (-58%; P=0.04) on 10d PI, while on day 38 it was reduced in breast skin (-42%; P=0.02), and tended to decrease in faeces (-25%; P=0.06). Saccharomyces cerevisiae (CNCM I-1079) significantly controlled Campylobacter carriage in chickens with some positive results also on Salmonella contamination, thus reducing the contamination of carcasses with both food borne pathogens

First Measurement of the Tensor Structure Function b1b_1 of the Deuteron

The \Hermes experiment has investigated the tensor spin structure of the deuteron using the 27.6 GeV/c positron beam of \Hera. The use of a tensor polarized deuteron gas target with only a negligible residual vector polarization enabled the first measurement of the tensor asymmetry \At and the tensor structure function \bd for average values of the Bj{\o}rken variable $0.01<0.45$ and of the squared four-momentum transfer $0.5 {\rm GeV^2} <5 {\rm GeV^2}$. The quantities \At and \bd are found to be non-zero. The rise of \bd for decreasing values of $x$ can be interpreted to originate from the same mechanism that leads to nuclear shadowing in unpolarized scattering

Search for an exotic S=-2, Q=-2 baryon resonance at a mass near 1862 MeV in quasi-real photoproduction

A search for an exotic baryon resonance with $S=-2, Q=-2$ has been performed in quasi-real photoproduction on a deuterium target through the decay channel $\Xi^- \pi^- \to \Lambda \pi^- \pi^- \to p \pi^- \pi^- \pi^-$. No evidence for a previously reported $\Xi^{--}(1860)$ resonance is found in the $\Xi^- \pi^-$invariant mass spectrum. An upper limit for the photoproduction cross section of 2.1 nb is found at the 90% confidence level. The photoproduction cross section for the $\Xi^{0}(1530)$ is found to be between 9 and 24 nb

Double hadron leptoproduction in the nuclear medium

First measurement of double-hadron production in deep-inelastic scattering has been measured with the HERMES spectrometer at HERA using a 27.6 GeV positron beam with deuterium, nitrogen, krypton and xenon targets. The influence of the nuclear medium on the ratio of double-hadron to single-hadron yields has been investigated. Nuclear effects are clearly observed but with substantially smaller magnitude and reduced $A$-dependence compared to previously measured single-hadron multiplicity ratios. The data are in fair agreement with models based on partonic or pre-hadronic energy loss, while they seem to rule out a pure absorptive treatment of the final state interactions. Thus, the double-hadron ratio provides an additional tool for studying modifications of hadronization in nuclear matter

Single-spin asymmetries in semi-inclusive deep-inelastic scattering on a transversely polarized hydrogen target

Single-spin asymmetries for semi-inclusive electroproduction of charged pions in deep-inelastic scattering of positrons are measured for the first time with transverse target polarization. The asymmetry depends on the azimuthal angles of both the pion ($\phi$) and the target spin axis ($\phi_S$) about the virtual photon direction and relative to the lepton scattering plane. The extracted Fourier component \cmpi is a signal of the previously unmeasured quark transversity distribution, in conjunction with the so-called Collins fragmentation function, also unknown. The Fourier component \smpi of the asymmetry arises from a correlation between the transverse polarization of the target nucleon and the intrinsic transverse momentum of quarks, as represented by the previously unmeasured Sivers distribution function. Evidence for both signals is observed, but the Sivers asymmetry may be affected by exclusive vector meson productio

Subleading-twist effects in single-spin asymmetries in semi-inclusive deep-inelastic scattering on a longitudinally polarized hydrogen target

Single-spin asymmetries in the semi-inclusive production of charged pions in deep-inelastic scattering from transversely and longitudinally polarized proton targets are combined to evaluate the subleading-twist contribution to the longitudinal case. This contribution is significantly positive for (\pi^+) mesons and dominates the asymmetries on a longitudinally polarized target previously measured by \hermes. The subleading-twist contribution for (\pi^-) mesons is found to be small

The HERMES Polarized Hydrogen and Deuterium Gas Target in the HERA Electron Storage Ring

The HERMES hydrogen and deuterium nuclear-polarized gas targets have been in use since 1996 with the polarized electron beam of HERA at DESY to study the spin structure of the nucleon. Polarized atoms from a Stern-Gerlach Atomic Beam Source are injected into a storage cell internal to the HERA electron ring. Atoms diffusing from the center of the storage cell into a side tube are analyzed to determine the atomic fraction and the atomic polarizations. The atoms have a nuclear polarization, the axis of which is defined by an external magnetic holding field. The holding field was longitudinal during 1996-2000, and was changed to transverse in 2001. The design of the target is described, the method for analyzing the target polarization is outlined, and the performance of the target in the various running periods is presented

Alzheimer's disease: Clinical practice guideline

El Grupo de Trabajo de Neurología de la Conducta y Neurociencias Cognitivas de la Sociedad Neurológica Argentina publicó en 2006 la primera Guía de práctica clínica sobre la enfermedad de Alzheimer para su aplicación en nuestro medio y, eventualmente, en el resto de los países hispanoparlantes del Cono Sur. La Guía que hoy publicamos, mediante la revisión y actualización del estado actual del conocimiento sobre la enfermedad de Alzheimer y su manejo clínico y neurológico, provee a los profesionales los estándares surgidos de la medicina basada en la evidencia para una adecuada implementación de las conductas diagnósticas y terapéuticas a su alcance en nuestro medio.In 2006, the Argentine Neurological Society Research Group on Behavioral Neurology and Cognitive Neurosciences published the first Clinical Practice Guideline on Alzheimer's Disease to be consulted in Argentina and eventually in other countries in Latin America. The present Guideline is a review of the state of the art concerning the 2010 knowledge on the management of this disease. It provides physicians with the usual standards provided by evidence based medicine in order to reach the most adequate diagnostic and therapeutic measures at hand in our countries.Fil: Allegri, Ricardo Francisco. Sociedad Neurológica Argentina; Argentina. Fundación para la Lucha contra las Enfermedades Neurológicas de la Infancia. Instituto de Neurociencias - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Neurociencias; ArgentinaFil: Arizaga, Raúl Luciano. Sociedad Neurológica Argentina; ArgentinaFil: Bavec, Claudia V.. Sociedad Neurológica Argentina; ArgentinaFil: Colli, Liliana P.. Sociedad Neurológica Argentina; ArgentinaFil: Demey, Ignacio. Sociedad Neurológica Argentina; ArgentinaFil: Fernández, María C.. Sociedad Neurológica Argentina; ArgentinaFil: Frontera, Silvina A.. Sociedad Neurológica Argentina; ArgentinaFil: Garau, María L.. Sociedad Neurológica Argentina; ArgentinaFil: Jiménez, Julio J.. Sociedad Neurológica Argentina; ArgentinaFil: Golimstok, Angel. Sociedad Neurológica Argentina; ArgentinaFil: Kremer, Janus. Sociedad Neurológica Argentina; ArgentinaFil: Labos, Edith. Sociedad Neurológica Argentina; ArgentinaFil: Mangone, Carlos Antonio. Sociedad Neurológica Argentina; ArgentinaFil: Ollari, Juan A.. Sociedad Neurológica Argentina; ArgentinaFil: Rojas, Zenón Galeno. Centro de Educación Médica e Investigaciones Clínicas "Norberto Quirno"; Argentina. Sociedad Neurológica Argentina; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Salmini, Omar. Sociedad Neurológica Argentina; ArgentinaFil: Ure, Jorge A.. Sociedad Neurológica Argentina; ArgentinaFil: Zuin, Daniel R.. Sociedad Neurológica Argentina; Argentin