Factors affecting social interaction on Social Network Sites: The Facebook Case

Purpose - Our paper focuses on understanding which factors affect the social interaction in the case of Facebook. Many authors point out the great potential of these networks for social interaction and as conduits of information. However, studies show that the topology of the network is disconnected, consisting of small sub-networks that make Facebook unsuitable for disseminating information. This situation has created the need to introduce exogenous factors, aimed at boosting and providing cohesion to the network structure. In this context, we test the following question: how exogenous and endogenous factors contribute to encouraging social interaction on Facebook. Design/methodology/approach - For the analysis of social interaction on Facebook, a population consisting of all the followers of the walls of 10 corporate social networks was used. From the total 269,424 users analysed, a stratified sample of 132 followers was obtained and networks were built for each of them. We then proceeded to search for each follower's friends and friends of friends to build the social network up to the fourth level, obtaining a total of 132 subnets with 1,628,074 links between them. To determine the impact of both exogenous and endogenous factors in the interaction of the network we performed a causal analysis. Findings - The results obtained from this study provide empirical evidence on the adequacy of companies? dynamization measures used and how exogenous and endogenous factors influence the social interaction on Facebook. Thus, our results show that exogenous factors, such as the activity of the community manager and the digital marketing investment in the network, do not have a significant effect on the interaction. On the other hand, endogenous factors, such as network density and clustering, have a positive effect on the trigger of social interaction between the followers. Therefore, companies must consider the importance of the structural factors that characterize network followers, such as density or clustering coefficient, to be able to interpret and optimize them to obtain higher levels of social interaction. Originality/value - This is one of a few papers that examine interactions in social network sites, particularly in corporate network sites in Facebook. The results expose the importance for organizations to have reliable information on the patterns of interaction to properly manage the resources allocated for this purpose in SNS

The Pattern of Histologically-Proven Acute Post-infectious Glomerulonephritis in Tunisian Adults Seen in 1976 - 2004

Introduction: Acute post-infectious glomerulonephritis (APIGN) is uncommon in adults. It is widely recognized that the prognosis of APIGN is good in children. There is however little information about its long-term prognosis in adults.Methods: Between December 1976 and October 2004, 148 adult cases of APIGN were managed in our center. We retrospectively reviewed these patients’ records and evaluated their clinical course and outcome.Results: The mean age of studied patients was 36±15 years, and the male to female ratio was 2.3. The most common site of preceding infection was the respiratory tract (68.8%). At presentation, 89.2% had nephritic syndrome and 9.4% had rapidly progressive glomerulonephritis.Proteinuria was observed in 99.3%, hematuria in 95.3%, peripheral edema in 89.2% and hypertension in 81.8%. Most patients (60.7%) had acute kidney injury and four patients (2.7%) required dialysis. Renal biopsy showed diffuse endocapillary proliferative glomerulonephritis in 88.8% of patients, associated with extracapillary proliferation in 12%. After a median follow-up of 2.5 year, only two patients died and 16.12% of patients hadpersistent clinical and/or biological abnormality. Chronic kidney disease was noted in 10 patients (6.75%) including four patients (2.7%) who progressed to end-stage renal disease. Poor prognostic factors included nephrotic range proteinuria, extracapillary proliferation in renal biopsy,acute kidney injury and the need for dialysis.Conclusion: In this cohort of patients, APIGN progressed to chronic kidney disease in less than 10% of patients

How Universal are the Young Cluster Sequences? - the Cases of LMC, SMC, M83 and the Antennae

Aims.Recently a new analysis of cluster observations in the Milky Way found evidence that clustered star formation may work under tight constraints with respect to cluster size and density, implying the presence of just two sequences of young massive cluster. These two types of clusters each expand at different rates with cluster age. Methods. Here we investigate whether similar sequences exist in other nearby galaxies. Results:We find that while for the extragalactic young stellar clusters the overall trend in the cluster-density scaling is quite comparable to the relation obtained for Galactic clusters, there are also possible difference. For the LMC and SMC clusters the densities are below the Galactic data points and/or the core radii are smaller than those of data points with comparable density. For M83 and the Antenna clusters the core radii are possibly comparable to the Galactic clusters but it is not clear whether they exhibit similar expansion speeds. These findings should serve as an incentive to perform more systematic observations and analysis to answer the question of a possible similarity between young galactic and extragalactic star clusters sequences.Comment: 6 pages, 4 figures, A&A in pres

Political Commitment and Sense of Social Responsibility among Social Entrepreneurs in Davao City, Philippines

Social entrepreneurs can play a game-changing role in local and national development by introducing social innovation. Strongly committed and mission- driven, they employ entrepreneurial schemes to organize and manage resources through financially sound and economically sustainable entities in order to create social value. This study aimed to determine the levels of political commitment and sense of social responsibility among social entrepreneurs of small and medium-sized social enterprises in Davao City. Using the non-experimental descriptive correlation method to gather survey inputs from 47 respondents, the researchers found that the respondents exhibited high levels of political commitment and sense of social responsibility. Furthermore, a significant relationship existed between political commitment and sense of social responsibility. When analyzed according to sex, no significant difference was observed in the level of political commitment. However, a significant difference appeared when analyzed according to type of business venture. No significant difference was ever observed in the level of sense of social responsibility in both variables

Spectral Variations of Of?p Oblique Magnetic Rotator Candidates in the Magellanic Clouds

Optical spectroscopic monitoring has been conducted of two O stars in the Small and one in the Large Magellanic Cloud, the spectral characteristics of which place them in the Of?p category, which has been established in the Galaxy to consist of oblique magnetic rotators. All of these Magellanic stars show systematic spectral variations typical of the Of?p class, further strengthening their magnetic candidacy to the point of virtual certainty. The spectral variations are related to photometric variations derived from OGLE data by Naze et al. (2015) in a parallel study, which yields rotational periods for two of them. Now circular spectropolarimetry is required to measure their fields, and ultraviolet spectroscopy to further characterize their low-metallicity, magnetically confined winds, in support of hydrodynamical analyses.Comment: 18 pages, 6 figures, accepted for publication by A

Nucleation and Crystallization of PA6 Composites Prepared by T-RTM: Effects of Carbon and Glass Fiber Loading

Thermoplastic resin transfer molding (T-RTM) is attracting much attention due to the need for recyclable alternatives to thermoset materials. In this work, we have prepared polyamide-6 (PA6) and PA6/fiber composites by T-RTM of caprolactam. Glass and carbon fibers were employed in a fixed amount of 60 and 47 wt.%, respectively. Neat PA6 and PA6 matrices (of PA6-GF and PA6-CF) of approximately 200 kg/mol were obtained with conversion ratios exceeding 95%. Both carbon fibers (CF) and glass fibers (GF) were able to nucleate PA6, with efficiencies of 44% and 26%, respectively. The α crystal polymorph of PA6 was present in all samples. The lamellar spacing, lamellar thickness and crystallinity degree did not show significant variations in the samples with or without fibers as result of the slow cooling process applied during T-RTM. The overall isothermal crystallization rate decreased in the order: PA6-CF > PA6-GF > neat PA6, as a consequence of the different nucleation efficiencies. The overall crystallization kinetics data were successfully described by the Avrami equation. The lamellar stack morphology observed by atomic force microscopy (AFM) is consistent with 2D superstructural aggregates (n = 2) for all samples. Finally, the reinforcement effect of fibers was larger than one order of magnitude in the values of elastic modulus and tensile strength.We gratefully acknowledge the Basque Government by the funding received through the ELKARTEK 2017 Cooperative Fundamental Research project: ”Automotion Composites fabricated by RTM adapted to the 4.0 industrial philosophy (RTM4.0). The authors thank the ALBA Synchrotron Light facility for supporting the X-rays experiments at beamline BL11-NCD-SWEET and the funding by ALBA project nº 2017092338. The UPV/EHU team gratefully acknowledges the financial contribution of the Basque Government through grant IT1309-19

Metal enrichment in near-IR luminous galaxies at z~2: signatures of proto-ellipticals?

We present the analysis of the coadded rest-frame UV spectrum (1200<z<2000 A) of five K-luminous galaxies at z~2 from the K20 survey. The composite spectrum is characterized by strong absorption lines over the UV continuum from C, N, O, Al, Si, and Fe in various ionization stages. While some of these lines are interstellar, several among the strongest absorptions are identified with stellar photospheric lines. Most of the photospheric and interstellar features are stronger in the K-luminous composite spectrum than in LBGs at z~3. This suggests higher metallicity and possibly also larger interstellar velocity dispersion caused by macroscopic motions. The absorption lines and the slope of the UV continuum is well matched by the spectrum of the nearby luminous infrared galaxy NGC 6090, which is in the process of merging. A metallicity higher than solar is suggested by comparing the pure photospheric lines (SiIII, CIII, FeV) with starburst models. The evidence of high metallicity, together with the high masses, high star-formation rates, and possibly strong clustering, well qualify these galaxies as progenitors of local massive ellipticals.Comment: 4 pages, 3 figures, Accepted ApJ Letter

A Galactic O-Star Catalog

We have produced a catalog of 378 Galactic O stars with accurate spectral classifications which is complete for V<8 but includes many fainter stars. The catalog provides cross-identifications with other sources; coordinates (obtained in most cases from Tycho-2 data); astrometric distances for 24 of the nearest stars; optical (Tycho-2, Johnson, and Stromgren) and NIR photometry; group membership, runaway character, and multiplicity information; and a web-based version with links to online services.Comment: 76 pages, 13 tables, and 3 figures. Accepted for publication in Astrophysical Journal. Online version of the catalog available at http://www.stsci.edu/~jmaiz/GOSmain.htm

The Interaction between the ISM and Star Formation in the Dwarf Starburst Galaxy NGC 4214

We present the first interferometric study of the molecular gas in the metal-poor dwarf starburst galaxy NGC 4214. Our map of the 12CO(1-0) emission, obtained at the OVRO millimeter array, reveals an unexpected structural wealth. We detected three regions of molecular emission in the north-west (NW), south-east (SE) and centre of NGC 4214 which are in very different and distinct evolutionary stages (total molecular mass: 5.1 x 10^6 M_sun). These differences are apparent most dramatically when the CO morphologies are compared to optical ground based and HST imaging: massive star formation has not started yet in the NW region; the well-known starburst in the centre is the most evolved and star formation in the SE complex started more recently. We derive a star formation efficiency of 8% for the SE complex. Using high--resolution VLA observations of neutral hydrogen HI and our CO data we generated a total gas column density map for NGC 4214 (HI + H_2). No clear correlation is seen between the peaks of HI, CO and the sites of ongoing star formation. This emphasizes the irregular nature of dwarf galaxies. The HI and CO velocities agree well, so do the H-alpha velocities. In total, we cataloged 14 molecular clumps in NGC 4214. Our results from a virial mass analysis are compatible with a Galactic CO-to-H_2 conversion factor for NGC 4214 (lower than what is usually found in metal-poor dwarf galaxies).Comment: accepted for publication in the AJ (February 2001), full ps file at: ftp://ftp.astro.caltech.edu/users/fw/ngc4214/walter_prep.p

The R136 star cluster dissected with Hubble Space Telescope/STIS. I. Far-ultraviolet spectroscopic census and the origin of HeII 1640 in young star clusters

We introduce a HST/STIS stellar census of R136a, the central ionizing star cluster of 30 Doradus. We present low resolution far-ultraviolet STIS/MAMA spectroscopy of R136 using 17 contiguous 52x0.2 arcsec slits which together provide complete coverage of the central 0.85 parsec (3.4 arcsec). We provide spectral types of 90% of the 57 sources brighter than m_F555W = 16.0 mag within a radius of 0.5 parsec of R136a1, plus 8 additional nearby sources including R136b (O4\,If/WN8). We measure wind velocities for 52 early-type stars from CIV 1548-51, including 16 O2-3 stars. For the first time we spectroscopically classify all Weigelt & Baier members of R136a, which comprise three WN5 stars (a1-a3), two O supergiants (a5-a6) and three early O dwarfs (a4, a7, a8). A complete Hertzsprung-Russell diagram for the most massive O stars in R136 is provided, from which we obtain a cluster age of 1.5+0.3_-0.7 Myr. In addition, we discuss the integrated ultraviolet spectrum of R136, and highlight the central role played by the most luminous stars in producing the prominent HeII 1640 emission line. This emission is totally dominated by very massive stars with initial masses above ~100 Msun. The presence of strong HeII 1640 emission in the integrated light of very young star clusters (e.g A1 in NGC 3125) favours an initial mass function extending well beyond a conventional upper limit of 100 Msun. We include montages of ultraviolet spectroscopy for LMC O stars in the Appendix. Future studies in this series will focus on optical STIS/CCD medium resolution observations.Comment: 20 pages plus four Appendices providing LMC UV O spectral templates, UV spectral atlas in R136, wind velocities of LMC O stars and photometry of additional R136 source