Model Selection in Overlapping Stochastic Block Models

Networks are a commonly used mathematical model to describe the rich set of interactions between objects of interest. Many clustering methods have been developed in order to partition such structures, among which several rely on underlying probabilistic models, typically mixture models. The relevant hidden structure may however show overlapping groups in several applications. The Overlapping Stochastic Block Model (2011) has been developed to take this phenomenon into account. Nevertheless, the problem of the choice of the number of classes in the inference step is still open. To tackle this issue, we consider the proposed model in a Bayesian framework and develop a new criterion based on a non asymptotic approximation of the marginal log-likelihood. We describe how the criterion can be computed through a variational Bayes EM algorithm, and demonstrate its efficiency by running it on both simulated and real data.Comment: articl

L'evolution du cortege des mineraux argileux dans la sedimentation marine neogene du bassin occidental du Guadalquivir (Espagne du s.o.)

La depresión neógena de sedimentación marina del Bajo Guadalquivir resulta del hundimiento del zócalo durante el Mioceno final. En cuanto se asienta dicha depresión, está ocupada en su mayor parte por el manto de corrimiento submarino de Carmona, que la parte en tres "subestructuras": una depresión S. en el área subbética, una cúpula central al S y al SE de Sevilla, un surco N en el borde del Paleozoicode la Meseta ibérica.En las dos primeras, la sedimentación arcillosa se caracteriza por la abundancia de la montmorillonita. En la última, los minerales arcillosos predominantes siguen una evolución cíclica vertical : Montmorillonita - Illita - Kaolinita + Chlorita - Illita - Montmorillonita, interpretada mediante el acarreo de dos clases de materiales detríticos finos: - procedentes directamente de los continentes limítrofes de clima caluroso y de estaciones contrastadas, en cuanto a la abundancia de la Montmorillonita; - procedentes del mar, desde regiones más o menos próximas, de clima caluroso más húmedo, en cuanto a los sedimentos,entre los cuales predominan Iillita, Kaolinita y Chlorita.Por otra parte, los valores elevados de dichos minerales muestran que a fines del Mioceno superior II y a principios del Plioceno, el surco norte bético se abre a las influencias marinas, quedándose fuera del control continental de sedimentación durante ese corto período

L'evolution du cortege des mineraux argileux dans la sedimentation marine neogene du bassin occidental du Guadalquivir (Espagne du s.o.)

La depresión neógena de sedimentación marina del Bajo Guadalquivir resulta del hundimiento del zócalo durante el Mioceno final. En cuanto se asienta dicha depresión, está ocupada en su mayor parte por el manto de corrimiento submarino de Carmona, que la parte en tres "subestructuras": una depresión S. en el área subbética, una cúpula central al S y al SE de Sevilla, un surco N en el borde del Paleozoicode la Meseta ibérica.En las dos primeras, la sedimentación arcillosa se caracteriza por la abundancia de la montmorillonita. En la última, los minerales arcillosos predominantes siguen una evolución cíclica vertical : Montmorillonita - Illita - Kaolinita + Chlorita - Illita - Montmorillonita, interpretada mediante el acarreo de dos clases de materiales detríticos finos: - procedentes directamente de los continentes limítrofes de clima caluroso y de estaciones contrastadas, en cuanto a la abundancia de la Montmorillonita; - procedentes del mar, desde regiones más o menos próximas, de clima caluroso más húmedo, en cuanto a los sedimentos,entre los cuales predominan Iillita, Kaolinita y Chlorita.Por otra parte, los valores elevados de dichos minerales muestran que a fines del Mioceno superior II y a principios del Plioceno, el surco norte bético se abre a las influencias marinas, quedándose fuera del control continental de sedimentación durante ese corto período

Gas phase formation of the prebiotic molecule formamide: insights from new quantum computations

New insights into the formation of interstellar formamide, a species of great relevance in prebiotic chemistry, are provided by electronic structure and kinetic calculations for the reaction NH2 + H2CO -> NH2CHO + H. Contrarily to what previously suggested, this reaction is essentially barrierless and can, therefore, occur under the low temperature conditions of interstellar objects thus providing a facile formation route of formamide. The rate coefficient parameters for the reaction channel leading to NH2CHO + H have been calculated to be A = 2.6x10^{-12} cm^3 s^{-1}, beta = -2.1 and gamma = 26.9 K in the range of temperatures 10-300 K. Including these new kinetic data in a refined astrochemical model, we show that the proposed mechanism can well reproduce the abundances of formamide observed in two very different interstellar objects: the cold envelope of the Sun-like protostar IRAS16293-2422 and the molecular shock L1157-B2. Therefore, the major conclusion of this Letter is that there is no need to invoke grain-surface chemistry to explain the presence of formamide provided that its precursors, NH2 and H2CO, are available in the gas-phase.Comment: MNRAS Letters, in pres

In vivo localization at the cellular level of stilbene fluorescence induced by Plasmopara viticola in grapevine leaves

Accurate localization of phytoalexins is a key for better understanding their role. This work aims to localize stilbenes, the main phytoalexins of grapevine. The cellular localization of stilbene fluorescence induced by Plasmopara viticola, the agent of downy mildew, was determined in grapevine leaves of very susceptible, susceptible, and partially resistant genotypes during infection. Laser scanning confocal microscopy and microspectrofluorimetry were used to acquire UV-excited autofluorescence three-dimensional images and spectra of grapevine leaves 5–6 days after inoculation. This noninvasive technique of investigation in vivo was completed with in vitro spectrofluorimetric studies on pure stilbenes as their fluorescence is largely affected by the physicochemical environment in various leaf compartments. Viscosity was the major physicochemical factor influencing stilbene fluorescence intensity, modifying fluorescence yield by more than two orders of magnitude. Striking differences in the localization of stilbene fluorescence induced by P. viticola were observed between the different genotypes. All inoculated genotypes displayed stilbene fluorescence in cell walls of guard cells and periclinal cell walls of epidermal cells. Higher fluorescence intensity was observed in guard-cell walls than in any other compartment due to increased local viscosity. In addition stilbene fluorescence was found in epidermal cell vacuoles of the susceptible genotype and in the infected spongy parenchyma of the partially resistant genotype. The very susceptible genotype was devoid of fluorescence both in the epidermal vacuoles and the mesophyll. This strongly suggests that the resistance of grapevine leaves to P. viticola is correlated with the pattern of localization of induced stilbenes in host tissues

Cancer Patient T Cells Genetically Targeted to Prostate-Specific Membrane Antigen Specifically Lyse Prostate Cancer Cells and Release Cytokines in Response to Prostate-Specific Membrane Antigen

AbstractThe expression of immunoglobulin-based artificial receptors in normal T lymphocytes provides a means to target lymphocytes to cell surface antigens independently of major histocompatibility complex restriction. Such artificial receptors have been previously shown to confer antigen-specific tumoricidal properties in murine T cells. We constructed a novel ζ chain fusion receptor specific for prostate-specific membrane antigen (PSMA) termed Pz-1. PSMA is a cell-surface glycoprotein expressed on prostate cancer cells and the neovascular endothelium of multiple carcinomas. We show that primary T cells harvested from five of five patients with different stages of prostate cancer and transduced with the Pz-1 receptor readily lyse prostate cancer cells. Having established a culture system using fibroblasts that express PSMA, we next show that T cells expressing the Pz-1 receptor release cytokines in response to cell-bound PSMA. Furthermore, we show that the cytokine release is greatly augmented by B7.1-mediated costimulation. Thus, our findings support the feasibility of adoptive cell therapy by using genetically engineered T cells in prostate cancer patients and suggest that both CD4+ and CD8+ T lymphocyte functions can be synergistically targeted against tumor cells

Minimising pain in farm animals: the 3S approach - ‘Suppress, Substitute, Soothe'

Recently, the French National Institute for Agricultural Research appointed an expert committee to review the issue of pain in food-producing farm animals. To minimise pain, the authors developed a ‘3S' approach accounting for ‘Suppress, Substitute and Soothe' by analogy with the ‘3Rs' approach of ‘Reduction, Refinement and Replacement' applied in the context of animal experimentation. Thus, when addressing the matter of pain, the following steps and solutions could be assessed, in the light of their feasibility (technical constraints, logistics and regulations), acceptability (societal and financial aspects) and availability. The first solution is to suppress any source of pain that brings no obvious advantage to the animals or the producers, as well as sources of pain for which potential benefits are largely exceeded by the negative effects. For instance, tail docking of cattle has recently been eliminated. Genetic selection on the basis of resistance criteria (as e.g. for lameness in cattle and poultry) or reduction of undesirable traits (e.g. boar taint in pigs) may also reduce painful conditions or procedures. The second solution is to substitute a technique causing pain by another less-painful method. For example, if dehorning cattle is unavoidable, it is preferable to perform it at a very young age, cauterising the horn bud. Animal management and constraint systems should be designed to reduce the risk for injury and bruising. Lastly, in situations where pain is known to be present, because of animal management procedures such as dehorning or castration, or because of pathology, for example lameness, systemic or local pharmacological treatments should be used to soothe pain. These treatments should take into account the duration of pain, which, in the case of some management procedures or diseases, may persist for longer periods. The administration of pain medication may require the intervention of veterinarians, but exemptions exist where breeders are allowed to use local anaesthesia (e.g. castration and dehorning in Switzerland). Extension of such exemptions, national or European legislation on pain management, or the introduction of animal welfare codes by retailers into their meat products may help further developments. In addition, veterinarians and farmers should be given the necessary tools and information to take into account animal pain in their management decision

Mukaiyama addition of (trimethylsilyl) acetonitrile to dimethyl acetals mediated by trimethylsilyl trifluoromethanesulfonate

(Trimethylsilyl) acetonitrile reacts smoothly with dimethyl acetals in the presence of stoichiometric trimethylsilyl trifluoromethanesulfonate (TMSOTf) to yield β-methoxynitriles. The ideal substrates for this reaction are acetals derived from aromatic aldehydes. Elimination to the corresponding α,β-unsaturated nitriles is observed as the major product in the case of electron-rich acetals. A mechanistic hypothesis that includes isomerization of the silylnitrile to a nucleophilic N-silyl ketene imine is presented