How a well-adapting immune system remembers

An adaptive agent predicting the future state of an environment must weigh trust in new observations against prior experiences. In this light, we propose a view of the adaptive immune system as a dynamic Bayesian machinery that updates its memory repertoire by balancing evidence from new pathogen encounters against past experience of infection to predict and prepare for future threats. This framework links the observed initial rapid increase of the memory pool early in life followed by a mid-life plateau to the ease of learning salient features of sparse environments. We also derive a modulated memory pool update rule in agreement with current vaccine response experiments. Our results suggest that pathogenic environments are sparse and that memory repertoires significantly decrease infection costs even with moderate sampling. The predicted optimal update scheme maps onto commonly considered competitive dynamics for antigen receptors

At which magnetic field, exactly, does the Kondo resonance begin to split? A Fermi liquid description of the low-energy properties of the Anderson model

This paper is a corrected version of Phys. Rev. B 95, 165404 (2017), which we have retracted because it contained a trivial but fatal sign error that lead to incorrect conclusions. --- We extend a recently-eveloped Fermi-liquid (FL) theory for the asymmetric single-impurity Anderson model [C. Mora $et al.$, Phys. Rev. B, 92, 075120 (2015)] to the case of an arbitrary local magnetic field. To describe the system's low-lying quasiparticle excitations for arbitrary values of the bare Hamiltonian's model parameters, we construct an effective low-energy FL Hamiltonian whose FL parameters are expressed in terms of the local level's spin-dependent ground-state occupations and their derivatives with respect to level energy and local magnetic field. These quantities are calculable with excellent accuracy from the Bethe Ansatz solution of the Anderson model. Applying this effective model to a quantum dot in a nonequilibrium setting, we obtain exact results for the curvature of the spectral function, $c_A$, describing its leading $\sim\varepsilon^2$ term, and the transport coefficients $c_V$ and $c_T$, describing the leading $\sim V^2$ and $\sim T^2$ terms in the nonlinear differential conductance. A sign change in $c_A$ or $c_V$ is indicative of a change from a local maximum to a local minimum in the spectral function or nonlinear conductance, respectively, as is expected to occur when an increasing magnetic field causes the Kondo resonance to split into two subpeaks. We find that the fields $B_A$, $B_T$ and $B_V$ at which $c_A$, $c_T$ and $c_V$ change sign, respectively, are all of order $T_K$, as expected, with $B_A = B_T = B_V = 0.75073\,T_K$ in the Kondo limit.Comment: 21 pages, 18 figures. Version 1 of this paper, published as Phys. Rev. B 95, 165404 (2017), contained a trivial but fatal sign error that lead to incorrect physical conclusions; it has therefore been retracted. Version 3 is a corrected version with major revisions, additional NRG data and different conclusions; it has been accepted for publication in PR

Receptor crosstalk improves concentration sensing of multiple ligands

Cells need to reliably sense external ligand concentrations to achieve various biological functions such as chemotaxis or signaling. The molecular recognition of ligands by surface receptors is degenerate in many systems leading to crosstalk between different receptors. Crosstalk is often thought of as a deviation from optimal specific recognition, as the binding of non-cognate ligands can interfere with the detection of the receptor's cognate ligand, possibly leading to a false triggering of a downstream signaling pathway. Here we quantify the optimal precision of sensing the concentrations of multiple ligands by a collection of promiscuous receptors. We demonstrate that crosstalk can improve precision in concentration sensing and discrimination tasks. To achieve superior precision, the additional information about ligand concentrations contained in short binding events of the non-cognate ligand should be exploited. We present a proofreading scheme to realize an approximate estimation of multiple ligand concentrations that reaches a precision close to the derived optimal bounds. Our results help rationalize the observed ubiquity of receptor crosstalk in molecular sensing

Comparación de los estilos estructurales en la sección entre bogotá y los farallones de medina, cordillera oriental de colombia

Between the Bogotá area and the Farallones range there is a marked contrast between two structural styles of an opposed vergence. To the east, a distinct marginal high, referred to as Chingaza dome, displays by its asymmetry and its faulted eastern flank an eastern vergence. Open second-order folds, associated to an axial plane cleavage, affect this dome Ptygmatitic folds yield local shortening values of 40"10 along this structural high, but decrease notably toward the adjacent structural depressions. Deformation affects both basement and cover rocks and precludes, by its homogeneous nature, a detachment within the lower Cretaceous shales. On the western extreme of our study region, the anticlines around the Teusaca River display significant amplitudes and steeply inclined to inverted western flanks. Folding occurred by flexural slip and a layer parallel strain is here completely absent. The line-length balancing of these frontal folds yields shortening values of 17%. The geometric properties of these folds require two detachment horizons.  Between these two opposed areas, the Rio Blanco region is affected by an intermediate structural style. Folding of the frontal parts of this fold belt is viewed as a consequence of an uplift and a homogeneous shortening of the Chingaza dome, which prompted a partial detachment of the Cretaceous cover and its gravity-driven displacement toward the structural depression of the Savannah of Bogotá.En la región entre Bogotá y los Farallones de Medina se presenta un marcado contraste de estilos estructurales entre dos frentes de deformación de vergencias opuestas. Al E existe un alto asimétrico de basamento con vergencia oriental -el Domo de Chingaza- levantado a través de una falla de alto ángulo -la Falla de San Juanito- que se originó durante el Jura-Cretáceo y que se reactivó en el Terciario. El Domo de Chingaza se caracteriza por presentar plegamientos suaves asociados a un marcado clivaje transversal que buza al W y según cálculos puntuales produce un acortamiento mínimo del 41 %. Esta deformación caracteriza las principales elevaciones estructurales del Flanco Oriental de la Cordillera y se atenúa en las depresiones adyacentes. AI demostrarse una deformación homogénea del basamento y la cobertera en el alto estructural de Chingaza, se descarta un despegue de esta última originado en los niveles dúctiles basales de lodolitas que la conforman. En el otro extremo, el cinturón plegado del valle del no Teusacá, en cambio, se caracteriza por un plegamiento en rocas del Cretáceo y Terciario donde las estructuras poseen la máxima amplitud y frecuencia de toda la región de trabajo.  La presencia de estructuras con un flanco occidental muy inclinado, vertical o invertido demuestra un transporte tectónico hacia el W. Un mecanismo de deformación que ya no implica foliación tectónica sino plegamiento flexural hace que sea viable el calcular acortamientos en esta región mediante un balanceo de líneas. El valor promedio obtenido es del 17%. En esta área la geometría del plegamiento permite proponer a estos pliegues como estructuras de despegue en un modelo de plegamiento en dos pisos. Entre las dos áreas existe el cinturón plegado del Rio Blanco, una región de transición en cuanto a su estilo tectónico. En el modelo que se propone, el despegue de la cobertera en la depresión occidental ocurre como compensación al levantamiento y acortamiento homogéneo del basamento y la cobertera en el alto estructural oriental y como consecuencia de un deslizamiento por gravedad

The application of the modular multilevel matrix converter in high-power wind turbines

The trend in wind turbines has shown an ongoing power rating growth, reaching sizes up to 10 MW. Multilevel converters have therefore become a favourable solution for Multi-MW Wind Energy Conversion Systems (WECSs), due to high efficiency, reliability, controllability and the ability to reach high power/voltage ratings. Moreover, stringent grid codes to regulate the connection of WECSs to the electrical networks have been developed in countries with a high penetration of wind energy. In this context, this paper introduces the novel application of the Modular Multilevel Matrix Converter for interfacing Multi-MW Wind Turbines to provide decoupled input-output regulation, variable speed operation and fulfilment of modern grid codes

What do corpus data reveal about anaphora resolution? Spanish vs. Greek and the Type of Topic Hypothesis

This research was funded by the following agencies/institutions: CEDEL2 corpus (ANACOREX R&D project no. PID2020-113818GB-I00 and ANACOR R&D project no. FFI2016-75106-P granted to the first author) funded by MINECO (Ministerio de Economía y competitividad), AEI (Agencia Estatal de Investigación), 10.13039/501100011033, Spain and ERDF (European Regional Development Fund, A way of making Europe). GLC corpus (LAL2A project no. 3161) funded by the Hellenic Foundation for Research & Innovation, Greece, granted to Alexandros Tantos, the fourth author being a member of the research project.Anaphora Resolution (AR) is a pervasive phenomenon in natural languages. AR relates to how referring expressions (REs) (e.g., null/overt subject pronouns, and NPs) corefer with their antecedents in discourse. We use corpus methods to simultaneously compare AR in two null-subject languages (Spanish vs. Greek). We analyse a Spanish-native sample (CEDEL2 corpus, N=341 REs analysed) and an equally-designed Greek-native sample (GLC corpus, N=400 REs analysed), while keeping constant the text type (Chaplin narrative task), the annotation scheme (tagset), the tagging procedure, and the profile of the natives. Our corpus results reveal similarities in the way Spanish and Greek natives construct their narratives regarding the distribution of the information status of the REs (topic continuity/shift) and the distribution of characters (main/secondary) in discourse. Crucially, our two languages differ in relation to topicality (Greek capitalises on discourse topic whereas Spanish relies more on sentential topic), which leads to a different distribution in the realization of REs in discourse. These similarities and differences are accounted for by a new theoretical proposal, the Type of Topic Hypothesis (TTH), which postulates that there is a tension between discourse-topic vs. sentential-topic oriented languages. The TTH captures the idea that, while narratives are constructed in the same way in both languages, RE realization varies as a result of the discourse-topic orientation of Greek vs. the sentential-topic orientation of Spanish.Agencia Estatal de Investigación 10.13039/501100011033European Regional Development FundHellenic Foundation for Research and Innovation LAL2A project no. 3161Ministerio de Economía y Competitividad ANACOREX R&D PID2020-113818GB-I00, ANACOR R&D FFI2016-75106-

Control of wind energy conversion systems based on the Modular Multilevel Matrix converter

The nominal power of single Wind Energy Conversion Systems (WECS) has been steadily growing, reaching power ratings close to 10MW. In the power conversion stage, medium-voltage power converters are replacing the conventional low-voltage back-to-back topology. Modular Multilevel Converters have appeared as a promising solution for Multi-MW WECSs, due to their modularity, and the capability to reach high nominal voltages. This paper discusses the application of the Modular Multilevel Matrix Converter (M3C) to drive MultiMW WECSs. The modelling and control systems required for this application are extensively analysed and discussed in this paper. The proposed control strategies enable decoupled operation of the converter, providing maximum power point tracking (MPPT) capability at the generator-side, grid code compliance at the grid-side [including Low Voltage Ride Through Control (LVRT)], and good steady state and dynamic performance for balancing the capacitor voltages in all the clusters. Finally, the effectiveness of the proposed control strategy is validated through simulations and experimental results conducted with a 27 power-cell prototype