OPEN SOURCE SOFTWARE PROJECTS\u27 ATTRACTIVENESS, ACTIVENESS, AND EFFICIENCY AS A PATH TO SOFTWARE QUALITY: AN EMPIRICAL EVALUATION OF THEIR RELATIONSHIPS AND CAUSES

An organizational strategy to develop software has appeared in the market. Organizations release software source code open and hope to attract volunteers to improve their software, forming what we call an open source project. Examples of organizations that have used this strategy include IBM (Eclipse), SAP (Netweaver) and Mozilla (Thunderbird). Moreover, thousands of these projects have been created as a consequence of the growing amount of software source code released by individuals. This expressive phenomenon deserves attention for its sudden appearance, newness and usefulness to public and private organizations. To explain the dynamics of open source projects, this research theoretically identified and empirically analyzed a construct – attractiveness – found crucial to them due to its influence on how they are populated and operate, subsequently impacting the qualities of the software produced and of the support provided. Both attractiveness\u27 causes and consequences were put under scrutiny, as well as its indicators. On the side of the consequences, it was theoretically proposed and empirically tested whether the attractiveness of these projects affects their levels of activeness, efficiency, likelihood of task completion, and time for task completion, though not linearly, as task complexity could moderate the relationships between them. Also, it was argued at the theoretical level that activeness, efficiency, likelihood of task completion, and time for task completion mediate the relationship between attractiveness and software/support quality. On the side of attractiveness\u27 causes, it was proposed and tested that five open software projects\u27 characteristics (license type, intended audience, type of project and project’s life-cycle stage) impact attractiveness directly. Additionally, these projects\u27 characteristics were argued to influence projects\u27 levels of activeness, efficiency, likelihood of task completion, and time for task completion (and so an empirical evaluation of their associations was performed). The empirical tests of all these relationships between constructs were carried out using Structural Equation Modeling with Maximum Likelihood on three samples of over 4,600 projects each, collected from the largest repository of open source software, Sourceforge.net (a repeated cross-sectional approach). The results confirmed the importance of attractiveness, suggesting a direct influence on projects\u27 dynamics, as opposed to the moderated-by-task complexity indirect paths first proposed. Furthermore, all four projects\u27 characteristics studied were found to significantly influence projects\u27 attractiveness, activeness, efficiency, likelihood of task completion, and time for task completion (with the exception of license type and time for task completion). Besides providing a statistical test of these propositions, this study discovered the direction of the influence of each project characteristic on projects\u27 attractiveness, activeness, efficiency, likelihood of task completion and time for task completion. Lastly, conclusions, limitations, and future directions are discussed based on these findings

Evolution of the Small Magellanic Cloud

Based on the results of N-body simulations on the last 2.5 Gyr evolution of the Large and Small Magellanic Clouds (LMC and SMC, respectively) interacting with the Galaxy, we firstly show when and where the leading arms (LAs) of the Magellanic stream (MS) can pass through the Galactic plane after the MS formation. We secondly show collisions between the outer Galactic HI disk and the LAs of the MS can create giant HI holes and chimney-like structures in the disk about 0.2 Gyr ago. We thirdly show that a large amount of metal-poor gas is stripped from the SMC and transfered to the LMC during the tidal interaction between the Clouds and the Galaxy about 0.2 and 1.3 Gyr ago. We thus propose that this metal-poor gas can closely be associated with the origin of LMC's young and intermediate-age stars and star clusters with distinctively low-metallicities with [Fe/H] < -0.6.Comment: 4 pages, 3 figures, to appear in the proceedings of ``Galaxies in the Local Volume'', Sydney, 8 to 13 July, 200

Interplay of tidal evolution and stellar wind braking in the rotation of stars hosting massive close-in planets

This paper deals with the application of the creep tide theory (Ferraz-Mello, Cel. Mech. Dyn. Astron. vol. 116, 109, 2013) to the study of the rotation of stars hosting massive close-in planets. The stars have nearly the same tidal relaxation factors as gaseous planets and the evolution of their rotation is similar to that of close-in hot Jupiters: they tidally evolve towards a stationary solution. However, stellar rotation may also be affected by stellar wind braking. Thus, while the rotation of a quiet host star evolves towards a stationary attractor with a frequency ($1+6e^2$) times the orbital mean-motion of the companion, the continuous loss of angular momentum in an active star displaces the stationary solution towards slower values: Active host stars with big close-in companions tend to have rotational periods larger than the orbital periods of their companions. The study of some hypothetical examples shows that because of tidal evolution, the rules of gyrochronology cannot be used to estimate the age of one system with a large close-in companion, no matter if the star is quiet or active, if the current semi-major axis of the companion is smaller than 0.03--0.04 AU. Details on the evolution of the systems: CoRoT LRc06E21637, CoRoT-27, Kepler-75, CoRoT-2, CoRoT-18, CoRoT-14 and on hypothetical systems with planets of mass 1--4 M_Jup in orbit around a star similar to the Sun are given.Comment: 22 pages, 8 figures; Publication in Ap

On the nature of Lithium-rich giant stars: constraints from Beryllium abundances

We have derived beryllium abundances for 7 Li-rich giant (A(Li) > 1.5) stars and 10 other Li-normal giants, with the aim of investigating the origin of the Lithium in the Li-rich giants. In particular, we test the predictions of the engulfment scenario proposed by Siess & Livio (1999), where the engulfment of a brown dwarf or one or more giant planets would lead to a simultaneous enrichment of 7Li and 9Be. We show that regardless their nature, none of the stars studied in this paper were found to have detectable beryllium. Using simple dilution arguments we show that the engulfment of an external object as the sole source of Li enrichment is ruled out by the Li and Be abundance data. The present results favor the idea that Li has been produced in the interior of the stars by a Cameron-Fowler process and brought up to the surface by an extra mixing mechanism.Comment: Accepted in A&

A New Giant Branch Clump Structure In the Large Magellanic Cloud

We present Washington C, T1 CCD photometry of 21 fields located in the northern part of the Large Magellanic Cloud (LMC), and spread over a region of more than 2.52 degrees approximately 6 degrees from the bar. The surveyed areas were chosen on the basis of their proximity to SL 388 and SL 509, whose fields showed the presence of a secondary giant clump, observationally detected by Bica et al. (1998, AJ, 116, 723). From the collected data we found that most of the observed field CMDs do not show a separate secondary clump, but rather a continuous vertical structure (VS), which is clearly seen for the first time. Its position and size are nearly the same throughout the surveyed regions: it lies below the Red Giant Clump (RGC) and extends from the bottom of the RGC to approximately 0.45 mag fainter, spanning the bluest color range of the RGC. The more numerous the VS stars in a field, the larger the number of LMC giants in the same zone. Our analysis demonstrate that VS stars belong to the LMC and are most likely the consequence of some kind of evolutionary process in the LMC, particularly in those LMC regions with a noticeable large giant population. Our results suggest that in order to trigger the formation of VS stars, there should be other conditions besides the appropriate age, metallicity, and the necessary red giant star density. Indeed, stars satisfying the requisites mentioned above are commonly found throughout the LMC, but the VS phenomenon is only clearly seen in some isolated regions. Finally, the fact that clump stars have an intrinsic luminosity dispersion further constrains the use of the clump magnitude as a reliable distance indicator.Comment: 25 pages, 9 figures, 3 tables; to be published in AJ, Dec. issu

Herbage and Livestock Responses for N-Fertilized and Grass-Legume Grazing Systems

Forage legumes provide an alternative N source in grazing systems. The objective was to evaluate plant and animal responses in N-fertilized or grass-legume-based systems under continuous stocking during winter and summer, from 2016-2019. The three treatments consisted of year-round forage systems including winter and summer forage components. The first system (Grass+N) included N-fertilized (112 kg N ha-1 yr-1) ‘Argentine’ bahiagrass (Paspalum notatum) pastures during the summer, overseeded with a mixture (56 kg ha-1 of each) of ‘FL 401’ cereal rye (Secale cereale) and ‘RAM’ oat (Avena sativa) during winter with a second application of 112 kg N ha-1 yr-1. Total annual fertilization for this treatment was 224 kg N ha-1 yr-1. System 2 (Grass + clover) included unfertilized Argentine bahiagrass during summer, overseeded with a similar rye-oat mixture, plus a mixture of clovers [17 kg ha-1 of ‘Dixie’ crimson (Trifolium incarnatum), 6.7 kg ha-1 of ‘Southern Belle’ red clover (Trifolium pratense), and 3.4 kg ha-1 ball clover (Trifolium nigrescens), fertilized with 34 kg N ha-1 during winter. System 3 (Grass+CL+RP) included the germplasm Ecoturf rhizoma peanut (Arachis glabrata; RP) and Argentine bahiagrass during the summer, overseeded with the same a similar rye-oat-clover mixture used in System 2 and fertilized with 34 kg N ha-1 during winter. Pastures were continuously stocked using variable stocking rates. Results indicate that clover inclusion during winter improved herbage distribution along the grazing season. Integrating RP during summer increased steer ADG by nearly 80% compared with Grass+N or Grass+Clover (bahiagrass monocultures during summer). While N fertilizer allowed for greater stocking rates, it did not improve animal performance throughout the year. Overall, similar gain per area was achieved in Grass+CL+RP than Grass+N, with lesser N-fertilizer inputs