Evolution of a structured cell population endowed with plasticity of traits under constraints on and between the traits.

Confronted with the biological problem of managing plasticity in cell populations, which is in particular responsible for transient and reversible drug resistance in cancer, we propose a rationale consisting of an integro-differential and a reaction-advection-diffusion equation, the properties of which are studied theoretically and numerically. By using a constructive finite volume method, we show the existence and uniqueness of a weak solution and illustrate by numerical approximations and their simulations the capacity of the model to exhibit divergence of traits. This feature may be theoretically interpreted as describing a physiological step towards multicellularity in animal evolution and, closer to present-day clinical challenges in oncology, as a possible representation of bet hedging in cancer cell populations.

Hydrodynamic limits for kinetic flocking models of Cucker-Smale type.

We analyse the asymptotic behavior for kinetic models describing the collective behavior of animal populations. We focus on models for self-propelled individuals, whose velocity relaxes toward the mean orientation of the neighbors. The self-propelling and friction forces together with the alignment and the noise are interpreted as a collision/interaction mechanism acting with equal strength. We show that the set of generalized collision invariants, introduced in [1], is equivalent in our setting to the more classical notion of collision invariants, i.e., the kernel of a suitably linearized collision operator. After identifying these collision invariants, we derive the fluid model, by appealing to the balances for the particle concentration and orientation. We investigate the main properties of the macroscopic model for a general potential with radial symmetry.

Adhesion and volume constraints via nonlocal interactions determine cell organisation and migration profiles.

The description of the cell spatial pattern and characteristic distances is fundamental in a wide range of physio-pathological biological phenomena, from morphogenesis to cancer growth. Discrete particle models are widely used in this field, since they are focused on the cell-level of abstraction and are able to preserve the identity of single individuals reproducing their behavior. In particular, a fundamental role in determining the usefulness and the realism of a particle mathematical approach is played by the choice of the intercellular pairwise interaction kernel and by the estimate of its parameters. The aim of the paper is to demonstrate how the concept of H-stability, deriving from statistical mechanics, can have important implications in this respect. For any given interaction kernel, it in fact allows to a priori predict the regions of the free parameter space that result in stable configurations of the system characterized by a finite and strictly positive minimal interparticle distance, which is fundamental when dealing with biological phenomena. The proposed analytical arguments are indeed able to restrict the range of possible variations of selected model coefficients, whose exact estimate however requires further investigations (e.g., fitting with empirical data), as illustrated in this paper by series of representative simulations dealing with cell colony reorganization, sorting phenomena and zebrafish embryonic development.

La profesionalización del community manager: claves para una formación especializada de posgrado

Introducción. La investigación que se presenta plantea una síntesis epistemológica sobre el perfil y funciones del community manager. Materiales y métodos. Se realizó desde el análisis crítico de un conjunto de opiniones valiosas de académicos, y profesionales. relacionándola con los resultados de un estudio cualitativo realizado sobre el programa académico de 19 cursos (en su mayoría conducentes a la titulación de máster) ofrecidos mayoritariamente por universidades españolas para la especialización de tales profesionales. Resultados. Este análisis comparado ha permitido establecer notables coincidencias entre los perfiles, ámbitos de trabajo y funciones asignadas a los community manager por los estudios epistemológicos existentes y las competencias que se pretenden adquirir en estas acciones formativas de posgrado. Conclusión. En esencia los cursos preparan a expertos en comunicación hipermedia y sus canales, creadores de contenidos de calidad e impacto emotivo, a profesionales, ubicuos en continuo estado de análisis de audiencias y de estudios de posicionamiento.

Introduction. This research shows an epistemological synthesis about the profile and functions of the community manager. Materials and methods. It was carried out from the critical analysis of a group of valuable opinions from academics and professionals. Relating it to the results of a qualitative study carried out on the academic program of 19 courses (mostly pursuing a master's degree) offered mainly by Spanish universities for the specialization of such professionals. Results. This comparative analysis has made it possible to establish remarkable coincidences among profiles, work areas, and functions assigned to community managers by existing epistemological studies and the competences that are intended to be acquired in these formative graduate actions. Conclusion. In essence, the courses prepare hypermedia communication experts and their channels, creators of quality content and emotional impact to professionals, ubiquitous in a continuous state of analysis of audiences and of positioning studies.

Introdução. A investigação que se apresenta planteia uma síntese epistemológica sobre o perfil e funções do community manager. Materiais e métodos. Se realizou desde a análise crítica de um conjunto de opiniões valiosas de acadêmicos, e profissionais. Relacionando ela com os resultados de um estudo qualitativo realizado sobre o programa acadêmico de 19 cursos (na sua maioria conducentes à titulação de Máster) oferecidos maioritariamente por universidades espanholas para a especialização de tais profissionais. Resultados. Este análise comparado há permitido estabelecer notáveis coincidências entre os perfis, âmbitos de trabalho e funções designadas aos community manager pelos estudos epistemológicos existentes e as competências que se pretendem adquirir nestas ações formativas de pós graduação. Conclusão. Em essência os cursos preparam a especialistas em comunicação hipermídia e seus canais, criadores de conteúdos de qualidade e impacto emotivo, a profissionais, ubíquos em contínuo estado de análise de audiências e de estudos de posicionamento.

Some free boundary problems involving non-local diffusion and aggregation.

We report on recent progress in the study of evolution processes involving degenerate parabolic equations which may exhibit free boundaries. The equations we have selected follow two recent trends in diffusion theory: considering anomalous diffusion with long-range effects, which leads to fractional operators or other operators involving kernels with large tails; and the combination of diffusion and aggregation effects, leading to delicate long-term equilibria whose description is still incipient.

On global minimizers of repulsive-attractive power-law interaction energies.

We consider the minimization of the repulsive-attractive power-law interaction energies that occur in many biological and physical situations. We show the existence of global minimizers in the discrete setting and obtain bounds for their supports independently of the number of Dirac deltas in a certain range of exponents. These global discrete minimizers correspond to the stable spatial profiles of flock patterns in swarming models. Global minimizers of the continuum problem are obtained by compactness. We also illustrate our results through numerical simulations.

Complexity reduction of rate-equations models for two-choice decision-making.

We are concerned with the complexity reduction of a stochastic system of differential equations governing the dynamics of a neuronal circuit describing a decision-making task. This reduction is based on the slow-fast behavior of the problem and holds on the whole phase space and not only locally around the spontaneous state. Macroscopic quantities, such as performance and reaction times, computed applying this reduction are in agreement with previous works in which the complexity reduction is locally performed at the spontaneous point by means of a Taylor expansion.

Low intrathecal immune response of anti-EBNA-1 antibodies and EBV DNA from multiple sclerosis patients.

Numerous studies have been carried out to determine whether an Epstein-Barr virus (EBV) infection can be considered a risk factor for multiple sclerosis (MS), following the evidence of an increase in IgG response to nuclear antigen-1 (EBNA-1) in both serum and cerebrospinal fluid (CSF) from MS patients. However, the possible interaction between EBV and MS has still not been well characterized, and the possible pathogenic role is yet to be determined. A case-control study (76 cases and 75 controls) was conducted to investigate anti-EBV antibodies synthesis in serum and CSF through intrathecal specific IgG synthesis to EBNA-1, as well as the presence of EBV DNA in plasma, peripheral blood mononuclear cells, and CSF from MS patients. Intrathecal EBNA-1 specific IgG synthesis was detected in 6.6% MS patients and in 17.3% controls. No EBV DNA was found in plasma or CSF, and our findings showed no evidence of high intrathecal EBNA-1 specific IgG synthesis or of significant EBV DNA in CSF in MS patients.

A decision-making Fokker-Planck model in computational neuroscience.

In computational neuroscience, decision-making may be explained analyzing models based on the evolution of the average firing rates of two interacting neuron populations, e.g., in bistable visual perception problems. These models typically lead to a multi-stable scenario for the concerned dynamical systems. Nevertheless, noise is an important feature of the model taking into account both the finite-size effects and the decision's robustness. These stochastic dynamical systems can be analyzed by studying carefully their associated Fokker-Planck partial differential equation. In particular, in the Fokker-Planck setting, we analytically discuss the asymptotic behavior for large times towards a unique probability distribution, and we propose a numerical scheme capturing this convergence. These simulations are used to validate deterministic moment methods recently applied to the stochastic differential system. Further, proving the existence, positivity and uniqueness of the probability density solution for the stationary equation, as well as for the time evolving problem, we show that this stabilization does happen. Finally, we discuss the convergence of the solution for large times to the stationary state. Our approach leads to a more detailed analytical and numerical study of decision-making models applied in computational neuroscience.

Development and preliminary evaluation of a rapid oligochromatographic assay for specific detection of new human influenza A H1N1 virus.

A new oligochromatographic assay, Speed-Oligo Novel Influenza A H1N1, was designed and optimized for the specific detection of the 2009 influenza A H1N1 virus. The assay is based on a PCR method coupled to detection of PCR products by means of a dipstick device. The target sequence is a 103-bp fragment within the hemagglutinin gene. The analytical sensitivity of the new assay was measured with serial dilutions of a plasmid that contained the target sequence, and we determined that down to one copy per reaction of the plasmid was reliably detected. Diagnostic performance was assessed with 103 RNAs from suspected cases (40 positive and 63 negative results) previously analyzed with a reference real-time PCR technique. All positive cases were confirmed, and no false-positive results were detected with the new assay. No cross-reactions were observed when other viral strains or clinical samples with other respiratory viruses were tested. According to these results, this new assay has 100% sensitivity and specificity. The turnaround time for the whole procedure was 140 min. The assay may be especially useful for the specific detection of 2009 H1N1 virus in laboratories not equipped with real-time PCR instruments.

Adaptive dynamics via Hamilton-Jacobi approach and entropy methods for a juvenile-adult model.

We consider a nonlinear system describing a juvenile-adult population undergoing small mutations. We analyze two aspects: from a mathematical point of view, we use an entropy method to prove that the population neither goes extinct nor blows-up; from an adaptive evolution point of view, we consider small mutations on a long time scale and study how a monomorphic or a dimorphic initial population evolves towards an Evolutionarily Stable State. Our method relies on an asymptotic analysis based on a constrained Hamilton-Jacobi equation. It allows to recover earlier predictions in Calsina and Cuadrado [A. Calsina, S. Cuadrado, Small mutation rate and evolutionarily stable strategies in infinite dimensional adaptive dynamics, J. Math. Biol. 48 (2004) 135; A. Calsina, S. Cuadrado, Stationary solutions of a selection mutation model: the pure mutation case, Math. Mod. Meth. Appl. Sci. 15(7) (2005) 1091.] that we also assert by direct numerical simulation. One of the interests here is to show that the Hamilton-Jacobi approach initiated in Diekmann et al. [O. Diekmann, P.-E. Jabin, S. Mischler, B. Perthame, The dynamics of adaptation: an illuminating example and a Hamilton-Jacobi approach, Theor. Popul. Biol. 67(4) (2005) 257.] extends to populations described by systems.

Evolutionary dynamics of satellite DNA in species of the Genus Formica (Hymenoptera, Formicidae).

The satellite DNA has been characterized in eight species of the Formica genus. This satellite DNA is organized as tandemly repeated 129-bp monomers in all species and it presents internal inverted repeats. The results of all the analyses performed in the sequences sampled from Formica cunicularia, F. fusca, F. gerardi, F. rufibarbis, F. selysi, F. frontalis, and F. sanguinea suggest interspecific conservation of satellite DNA. Nevertheless, the results from the comparative analysis of the sequences sampled from F. subrufa and the remaining species studied suggest that the mechanisms producing concerted evolution have been efficient in these taxa. A CENP-B-like motif has been found in the satellite DNA from the species analysed, including F. subrufa. This satellite DNA is located in the pericentromeric regions of all chromosomes. We suggest that, although the evolution of the DNA satellite in ants could be similar to that in other organisms, there may be some particularities as a result of a haplodiploid system.