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

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

Missing energies at pair creation

Wilson cloud chamber measurements of the separated spectra of positrons and electrons produced by gamma quanta of 6.14 MeV differ considerably from the theoretically predicted spectra by BETHE and HEITLER, but are in good agreement with those of a modified theory of pair creation

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

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

Semiclassical degeneracies and ordering for highly frustrated magnets in a field

We discuss ground state selection by quantum fluctuations in frustrated magnets in a strong magnetic field. We show that there exist dynamical symmetries -- one a generalisation of Henley's gauge-like symmetry for collinear spins, the other the quantum relict of non-collinear weathervane modes -- which ensure a partial survival of the classical degeneracies. We illustrate these for the case of the kagome magnet, where we find zero-point energy differences to be rather small everywhere except near the collinear `up-up-down` configurations, where there is rotational but not translational symmetry breaking. In the effective Hamiltonian, we demonstrate the presence of a term sensitive to a topological `flux'. We discuss the connection of such problems to gauge theories by casting the frustrated lattices as medial lattices of appropriately chosen simplex lattices, and in particular we show how the magnetic field can be used to tune the physical sector of the resulting gauge theories.Comment: 10 pages, 8 figure

Purification of genuine multipartite entanglement

In tasks, where multipartite entanglement plays a central role, state purification is, due to inevitable noise, a crucial part of the procedure. We consider a scenario exploiting the multipartite entanglement in a straightforward multipartite purification algorithm and compare it to bipartite purification procedures combined with state teleportation. While complete purification requires an infinite amount of input states in both cases, we show that for an imperfect output fidelity the multipartite procedure exhibits a major advantage in terms of input states used.Comment: 5 pages, 2 figure

Comparison of Ordinary Kriging and Multiple Indicator Kriging Estimates of Asuadai Deposit at Adansi Gold Ghana Limited

Adansi Gold Ghana Ltd has taken over from the then Resolute Amansie Ltd and has three main historical deposits: Nkran, Adubia, Abore, and a new deposit, Asuadai. The company now wants to evaluate the resources at Asuadai which is about 7.5 km from Nkran deposit where Ordinary Kriging (OK) method had been used for estimation. Results of the estimation showed a consistent underestimation of tonnage and grade. Linear estimation models such as OK often produce good estimates but may encounter problems estimating recoverable reserves in cases where the distribution of samples is highly skewed. Multiple Indicator Kriging (MIK) is one of the popular non-linear methods that can handle skewed distribution such as that for gold grades, and addresses some of the deficiencies of the linear methods. This paper compares the estimation results obtained by using MIK and OK for the Asuadai deposit and establishes that MIK presents a better estimate than the OK, and recommends that MIK be used to estimate the gold resources of the Asuadai deposit and other deposits with similar geological settings.Keywords: Indicator Kriging, Ordinary Kriging, Variography, Gold, Outlie

Necessary and Sufficient Condition for Oscillations of Neutral Differential Equation

2000 Mathematics Subject Classification: 34K15, 34C10.We obtain necessary and sufficient conditions for the oscillation of all solutions of neutral differential equation with mixed (delayed and advanced) arguments ..

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