3,831 research outputs found

    Social media in qualitative research: Challenges and recommendations

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    The emergence of social media on the Internet provides an opportunity for information systems researchers to examine new phenomena in new ways. However, for various reasons qualitative researchers in IS have not fully embraced this opportunity. This paper looks at the potential use of social media in qualitative research in information systems. It discusses some of the challenges of using social media and suggests how qualitative IS researchers can design their studies to capitalize on social media data. After discussing an illustrative qualitative study, the paper makes recommendations for the use of social media in qualitative research in IS

    The Halo Occupation Distribution of Obscured Quasars: Revisiting the Unification Model

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    We model the projected angular two-point correlation function (2PCF) of obscured and unobscured quasars selected using the Wide-field Infrared Survey Explorer (WISE), at a median redshift of z1z \sim 1 using a five-parameter Halo Occupation Distribution (HOD) parameterization, derived from a cosmological hydrodynamic simulation by Chatterjee et al. The HOD parameterization was previously used to model the 2PCF of optically selected quasars and X-ray bright active galactic nuclei (AGN) at z1z \sim 1. The current work shows that a single HOD parameterization can be used to model the population of different kinds of AGN in dark matter halos suggesting the universality of the relationship between AGN and their host dark matter halos. Our results show that the median halo mass of central quasar hosts increases from optically selected (4.10.4+0.3×1012  h1  Msun4.1^{+0.3}_{-0.4} \times 10^{12} \; h^{-1} \; {M_{sun}}) and infra-red (IR) bright unobscured populations (6.32.3+6.2×1012  h1  Msun6.3^{+6.2}_{-2.3} \times 10^{12} \; h^{-1} \; {M_{sun}}) to obscured quasars (10.03.7+2.6×1012  h1  Msun10.0^{+2.6}_{-3.7} \times 10^{12} \; h^{-1} \; {M_{sun}}), signifying an increase in the degree of clustering. The projected satellite fractions also increase from optically bright to obscured quasars and tend to disfavor a simple `orientation only' theory of active galactic nuclei unification. Our results also show that future measurements of the small-scale clustering of obscured quasars can constrain current theories of galaxy evolution where quasars evolve from an IR- bright obscured phase to the optically bright unobscured phase.Comment: Accepted 2018 February 9. Received 2018 January 20; in original form 2017 June 2

    A pendant proton shuttle on [Fe4N(CO)12]- alters product selectivity in formate vs. H2 production via the hydride [H-Fe4N(CO)12].

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    Proton relays are known to increase reaction rates for H2 evolution and lower overpotentials in electrocatalytic reactions. In this report we describe two electrocatalysts, [Fe4N(CO)11(PPh3)]- (1-) which has no proton relay, and hydroxyl-containing [Fe4N(CO)11(Ph2P(CH2)2OH)]- (2-). Solid state structures indicate that these phosphine-substituted clusters are direct analogs of [Fe4N(CO)12]- where one CO ligand has been replaced by a phosphine. We show that the proton relay changes the selectivity of reactions: CO2 is reduced selectively to formate by 1- in the absence of a relay, and protons are reduced to H2 under a CO2 atmosphere by 2-. These results implicate a hydride intermediate in the mechanism of the reactions and demonstrate the importance of controlling proton delivery to control product selectivity. Thermochemical measurements performed using infrared spectroelectrochemistry provided pKa and hydricity values for [HFe4N(CO)11(PPh3)]-, which are 23.7, and 45.5 kcal mol-1, respectively. The pKa of the hydroxyl group in 2- was determined to fall between 29 and 41, and this suggests that the proximity of the proton relay to the active catalytic site plays a significant role in the product selectivity observed, since the acidity alone does not account for the observed results. More generally, this work emphasizes the importance of substrate delivery kinetics in determining the selectivity of CO2 reduction reactions that proceed through metal-hydride intermediates
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