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

Cosmological solutions of massive gravity on de Sitter

In the framework of the recently proposed models of massive gravity, defined with respect to a de Sitter reference metric, we obtain new homogeneous and isotropic solutions for arbitrary cosmological matter and arbitrary spatial curvature. These solutions can be classified into three branches. In the first two, the massive gravity terms behave like a cosmological constant. In the third branch, the massive gravity effects can be described by a time evolving effective fluid with rather remarkable features, including the property to behave as a cosmological constant at late time.Comment: 6 pages, 1 figure; discussion extended, a few references added, improved analysis in Section

Non-Linear Massive Gravity with Additional Primary Constraint and Absence of Ghosts

We complete the Hamiltonian analysis of specific model of non-linear massive gravity that was started in arXiv:1112.5267. We identify the primary constraint and corresponding secondary constraint. We show that they are the second class constraints and hence they lead to the elimination of the additional scalar mode. We also find that the remaining constraints are the first class constraints with the structure that corresponds to the manifestly diffeomorphism invariant theory. Finally we determine the number of physical degrees of freedom and we show that it corresponds to the number of physical modes of massive gravity.Comment: 13 page

Is Low Alveolar Type II Cell SOD3 in the Lungs of Elderly Linked to the Observed Severity of COVID-19?

Human lungs single cell RNA sequencing data from healthy donors (elderly and young; GEO accession number GSE122960) were analyzed to isolate and specifically study gene expression in alveolar type II cells. Co-localization of ACE2 and TMPRSS2 enables SARS-CoV 2 to enter the cells. Expression of these genes in the alveolar type II cells of elderly and young patients were comparable and therefore do not seem to be responsible for worse outcomes observed in COVID-19 affected elderly. In cells from the elderly, 263 genes were downregulated and 95 upregulated. SOD3 was identified as the top-ranked gene that was most down-regulated in the elderly. Other redox-active genes that were also downregulated in cells from the elderly included ATF4 and M2TA. ATF4, an ER stress sensor that defends lungs via induction of heme oxygenase 1. The study of downstream factors known to be induced by ATF4, according to Ingenuity Pathway AnalysisTM, identified 24 candidates. Twenty-one of these were significantly downregulated in the cells from the elderly. These downregulated candidates were subjected to enrichment using the Reactome Database identifying that in the elderly, the ability to respond to heme deficiency and the ATF4-dependent ability to respond to endoplasmic reticulum stress is significantly compromised. SOD3-based therapeutic strategies have provided beneficial results in treating lung disorders including fibrosis. The findings of this work propose the hypotheses that lung-specific delivery of SOD3/ATF4 related antioxidants may work in synergy with promising anti-viral drugs such as remdesivir to further improve COVID-19 outcomes in the elderly

Oscillation of Nonlinear Neutral Delay Differential Equations

2000 Mathematics Subject Classification: 34K15, 34C10.In this paper, we study the oscillatory behavior of first order nonlinear neutral delay differential equation (x(t) − q(t) x(t − σ(t))) ′ +f(t,x( t − τ(t))) = 0, where σ, τ ∈ C([t0,∞),(0,∞)), q О C([t0,∞), [0,∞)) and f ∈ C([t0,∞) ×R,R). The obtained results extended and improve several of the well known previously results in the literature. Our results are illustrated with an example

Statistical Evaluation of Geochemical Au Sample Quality

Exploration and mining activities are based on anomalous occurrence of minerals. The basic concept governing this high risk venture is ‘no ore, no mining’. Hence, the quality of anomalous sample or its accurate determination is of great concern to exploration and mining operations. Regarding erratic mineralisation such as gold (Au), anomalous pattern of no significance whatsoever may appear in geochemical sample data as a result of poor sampling, improper sample handling or error in analytical techniques among other causes. To prevent the frequency of these occurrences, quality control checks coupled with classical statistical probe can form an integral part of the checklist to eliminate these errors. Although duplicate results have often accompanied original Au assays in most analytical reports submitted by laboratories, it is not immediately known upon what b asis the results need to be accepted or rejected. Often, some geologists accept results upon quick sight comparison. A total of three hundred and ninety (390) geochemical soil samples from the Sefwi-Bibiani belt of Ghana together with some blanks and standards were subjected to statistical analysis after following rigorous quality control sampling protocols. The statistical models employed include outlier test, distribution and correlation analysis. The original and duplicate samples were then statistically compared using simple nested One –Way Analysis of Variance (ANOVA), the Chi Square Test and the Student’s t –Test.The ANOVA and the t–Tests revealed no significant analytical error. However, the other tests indicated multimodality of the populations as well as batch effect which culminates into significant procedural error. The investigation concludes that these systematic procedural errors if unchecked could mask true geochemical distribution

Hadron Production in Neutrino-Nucleon Interactions at High Energies

The multi-particle production at high energy neutrino- nucleon collisions are investigated through the analysis of the data of the experiment CERN-WA-025 at neutrino energy less than 260GeV and the experiments FNAL-616 and FNAL-701 at energy range 120-250 GeV. The general features of these experiments are used as base to build a hypothetical model that views the reaction by a Feynman diagram of two vertices. The first of which concerns the weak interaction between the neutrino and the quark constituents of the nucleon. At the second vertex, a strong color field is assumed to play the role of particle production, which depend on the momentum transferred from the first vertex. The wave function of the nucleon quarks are determined using the variation method and relevant boundary conditions are applied to calculate the deep inelastic cross sections of the virtual diagram.Comment: 6 pages PDF forma

On linearization of super sine-Gordon equation

Two sets of super Riccati equations are presented which result in two linear problems of super sine-Gordon equation. The linear problems are then shown to be related to each other by a super gauge transformation and to the super B\"{a}cklund transformation of the equation.Comment: 9 Page

Molecular Dynamics Simulation of Solvent-Polymer Interdiffusion. I. Fickian diffusion

The interdiffusion of a solvent into a polymer melt has been studied using large scale molecular dynamics and Monte Carlo simulation techniques. The solvent concentration profile and weight gain by the polymer have been measured as a function of time. The weight gain is found to scale as t^{1/2}, which is expected for Fickian type of diffusion. The concentration profiles are fit very well assuming Fick's second law with a constant diffusivity. The diffusivity found from fitting Fick's second law is found to be independent of time and equal to the self diffusion constant in the dilute solvent limit. We separately calculated the diffusivity as a function of concentration using the Darken equation and found that the diffusivity is essentially constant for the concentration range relevant for interdiffusion.Comment: 17 pages and 7 figure