Crossover from Endogenous to Exogenous Activity in Open-Source Software Development

We have investigated the origin of fluctuations in the aggregated behaviour of an open-source software community. In a recent series of papers, de Menezes and co-workers have shown how to separate internal dynamics from external fluctuations by capturing the simultaneous activity of many system's components. In spite of software development being a planned activity, the analysis of fluctuations reveals how external driving forces can be only observed at weekly and higher time scales. Hourly and higher change frequencies mostly relate to internal maintenance activities. There is a crossover from endogenous to exogenous activity depending on the average number of file changes. This new evidence suggests that software development is a non-homogeneous design activity where stronger efforts focus in a few project files. The crossover can be explained with a Langevin equation associated to the cascading process, where changes to any file trigger additional changes to its neighbours in the software network. In addition, analysis of fluctuations enables us to detect whether a software system can be decomposed in several subsystems with different development dynamics.Comment: 7 pages, 4 figures, submitted to Europhysics Letter

Sustainable growth in complex networks

Based on the empirical analysis of the dependency network in 18 Java projects, we develop a novel model of network growth which considers both: an attachment mechanism and the addition of new nodes with a heterogeneous distribution of their initial degree, $k_0$. Empirically we find that the cumulative degree distributions of initial degrees and of the final network, follow power-law behaviors: $P(k_{0}) \propto k_{0}^{1-\alpha}$, and $P(k)\propto k^{1-\gamma}$, respectively. For the total number of links as a function of the network size, we find empirically $K(N)\propto N^{\beta}$, where $\beta$ is (at the beginning of the network evolution) between 1.25 and 2, while converging to $\sim 1$ for large $N$. This indicates a transition from a growth regime with increasing network density towards a sustainable regime, which revents a collapse because of ever increasing dependencies. Our theoretical framework is able to predict relations between the exponents $\alpha$, $\beta$, $\gamma$, which also link issues of software engineering and developer activity. These relations are verified by means of computer simulations and empirical investigations. They indicate that the growth of real Open Source Software networks occurs on the edge between two regimes, which are either dominated by the initial degree distribution of added nodes, or by the preferential attachment mechanism. Hence, the heterogeneous degree distribution of newly added nodes, found empirically, is essential to describe the laws of sustainable growth in networks.Comment: 5 pages, 2 figures, 1 tabl

Logarithmic growth dynamics in software networks

In a recent paper, Krapivsky and Redner (Phys. Rev. E, 71 (2005) 036118) proposed a new growing network model with new nodes being attached to a randomly selected node, as well to all ancestors of the target node. The model leads to a sparse graph with an average degree growing logarithmically with the system size. Here we present compeling evidence for software networks being the result of a similar class of growing dynamics. The predicted pattern of network growth, as well as the stationary in- and out-degree distributions are consistent with the model. Our results confirm the view of large-scale software topology being generated through duplication-rewiring mechanisms. Implications of these findings are outlined.Comment: 7 pages, 3 figures, published in Europhysics Letters (2005

Controlling Excitations Inversion of a Cooper Pair Box Interacting with a Nanomechanical Resonator

We investigate the action of time dependent detunings upon the excitation inversion of a Cooper pair box interacting with a nanomechanical resonator. The method employs the Jaynes-Cummings model with damping, assuming different decay rates of the Cooper pair box and various fixed and t-dependent detunings. It is shown that while the presence of damping plus constant detunings destroy the collapse/revival effects, convenient choices of time dependent detunings allow one to reconstruct such events in a perfect way. It is also shown that the mean excitation of the nanomechanical resonator is more robust against damping of the Cooper pair box for convenient values of t-dependent detunings.Comment: 11 pages, 5 figure

La inhibición de la proteína tirosina fosfatasa 1B protege frente a la apoptosis temprana inducida por paracetamol en hepatocitos

Premio “Consejo General de Colegios Oficiales de Farmacéuticos” en el Concurso Científico 2013 de la Real Academia Nacional de Farmacia.[EN]: Acetaminophen (paracetamol, APAP) is a widely used analgesic and antipyretic drug safe at therapeutic doses but its overdose causes liver injury. Our goal was to explore whether protein tyrosine phosphatase 1B (PTP1B), a negative modulator of survival signaling pathways, plays a role in APAP-induced cell death in hepatocytes. Hepatotoxicity was evaluated in immortalized hepatocytes generated from wild-type (PTP1B+/+) and PTP1B-deficient (PTP1B-/-) mice. Apoptosis occurred as an early event only in APAP-treated PTP1B+/+ hepatocytes. PTP1B deficiency conferred protection against cell cycle arrest and loss of cellular viability. These data suggest that PTP1B as a target against APAP-induced liver failure.[ES]: El paracetamol es un analgésico/antipirético hepatotóxico a dosis altas. Investigamos el papel de la proteína tirosina fosfatasa 1B (PTP1B), un modulador negativo de señalización de supervivencia celular, en la muerte celular temprana (apoptosis) inducida por paracetamol en hepatocitos. En hepatocitos controles se inducía apoptosis en respuesta al paracetamol. Este efecto se encontraba disminuido en hepatocitos deficientes en PTP1B. La falta de PTP1B protegía a los hepatocitos de la parada del ciclo celular y la pérdida de la viabilidad celular tras el tratamiento con paracetamol. Proponemos a la PTP1B como diana terapéutica frente al fallo hepático inducido por sobredosis de paracetamol.We acknowledge the following grant support: SAF2012-33283 (MINECO, Spain), Comunidad de Madrid S2010/BMD-2423, EFSD and Amylin Paul Langerhans Grant and Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas (CIBERDEM, ISCIII, Spain).Peer Reviewe

Weak Pion Production off the Nucleon

We develop a model for the weak pion production off the nucleon, which besides the Delta pole mechanism (weak excitation of the $\Delta(1232)$ resonance and its subsequent decay into $N\pi$), includes also some background terms required by chiral symmetry. We re-fit the $C_5^A(q^2)$ form factor to the flux averaged $\nu_\mu p \to \mu^-p\pi^+$ ANL $q^2-$differential cross section data, finding a substantially smaller contribution of the Delta pole mechanism than traditionally assumed in the literature. Within this scheme, we calculate several differential and integrated cross sections, including pion angular distributions, induced by neutrinos and antineutrinos and driven both by charged and neutral currents. In all cases we find that the background terms produce quite significant effects and that they lead to an overall improved description of the data, as compared to the case where only the Delta pole mechanism is considered. We also show that the interference between the Delta pole and the background terms produces parity-violating contributions to the pion angular differential cross section, which are intimately linked to $T-$odd correlations in the contraction between the leptonic and hadronic tensors. However, these latter correlations do not imply a genuine violation of time reversal invariance because of the existence of strong final state interaction effects.Comment: Typos corrected; comments adde

Nuclear effects in neutrino induced reactions

We discuss the relevance of nuclear medium effects in the analysis of some low and medium energy neutrino reactions of current interest. In particular, we study the Quasi-Elastic (QE) process, where RPA correlations and Final State Interactions (FSI) are shown to play a crucial role. We have also investigated the neutrino induced coherent pion production. We find a strong reduction of the cross section due to the distortion of the pion wave function and the modification of the production mechanisms in the nucleus. The sensitivity of the results to the axial $N\Delta$ coupling $C_5^A(0)$ has been also investigated.Comment: To appear in the proceedings of Chiral Symmetry in Hadron and Nuclear Physics (Chiral07), Osaka, Japan, November 13-16, 200

A Proposal for New Evaluation Metrics and Result Visualization Technique for Sentiment Analysis Tasks

Proceedings of: 4th International Conference of the CLEF Initiative (CLEF 2013). 4th International Conference of the CLEF Initiative (CLEF 2013). Valencia, Spain, September 23-26, 2013.In this paper we propound the use of a number of entropybased metrics and a visualization tool for the intrinsic evaluation of Sentiment and Reputation Analysis tasks. We provide a theoretical justification for their use and discuss how they complement other accuracybased metrics. We apply the proposed techniques to the analysis of TASS-SEPLN and RepLab 2012 results and show how the metric is effective for system comparison purposes, for system development and postmortem evaluation.FJVA and JCdA are supported by EU FP7 project LiMoSINe (contract 288024). CPM has been partially supported by the Spanish Government-Comisión Interministerial de Ciencia y Tecnología project TEC2011-26807 for this paper.Publicad

Content categories system for body constructs applied to patients with mastectomy

Body image is a predictor of psychological adjustment to cancer and a risk factor for depression. Questionnaires to assess body image in cancer patients assume a preconceived concept of body image and do not reflect the patient's subjective experience. This study aims to develop a content categories system for analyzing body constructs in breast cancer patients from their own experience. Methods The sample comprised 542 constructs, from 23 patients subjected to surgery (12 mastectomy/11 breast-conserving surgery) and 24 controls. Participants were assessed with the Body Grid. Three independent judges coded the constructs elicited following a tentative categories system. Result Six categories appeared: Objective Appearance, Esthetics, Function, Strength, Energy and Emotions, with similar distribution in the samples. Objective Appearance, Esthetics and Emotions were the most used. The inter-rater agreement was very good. Conclusions These findings highlight the importance of knowing which thematic areas concern the most to each patient and the absent ones in their constructions, in order to focus psychotherapy on the developing of new meanings that allow a more integrated body imag

Neutrino Interactions Importance for Nuclear Physics

We review the general interplay between Nuclear Physics and neutrino-nucleus cross sections at intermediate and high energies. The effects of different reaction mechanisms over the neutrino observables are illustrated with examples in calculations using several nuclear models and ingredients.Comment: To appear in the proceedings of 6th International Workshop on Neutrino-Nucleus Interactions in the Few-GeV Region (NuInt09), Sitges, Spain, 18 - 22 May 200