A qualitatively driven approach to multimethod and mixed methods research

This chapter discusses the meaning of qualitatively -driven inquiry and what this is in the context of mixed and multi methods research. It distinguishes between qualitatively-driven mixed and multi methods approaches and considers why methods may be mixed using a qualitatively-driven approach. The chapter identifies some reasons for using qualitatively-driven mixed and multi method approaches and defines templates for their application. The chapter provides several research examples throughout to illustrate the insight gained with these approaches. It concludes with in-depth discussions of the value of these approaches and considers their contribution more widely to the field of mixed-methods researc

Enabling optimization-based localization for IoT devices

In this paper, we propose an embedded optimization approach for the localization of Internet of Things (IoT) devices making use of range measurements from ultra-wideband (UWB) signals. Low-cost, low-power UWB radios provide time-of-arrival measurements with decimeter accuracy over large distances. UWB-based localization methods have been envisioned to enable feedback control in IoT applications, particularly, in GPS-denied environments, and large wireless sensor networks. In this paper, we formulate the localization task as a nonlinear least-squares optimization problem based on two-way time-of-arrival measurements between the IoT device and several UWB radios installed in a 3-D environment. For the practical implementation of large-scale IoT deployments we further assume only approximate knowledge of the UWB radio locations. We solve the resulting optimization problem directly on IoT devices equipped with off-the-shelf microcontrollers using state-of-the-art code generation techniques for plug-and-play deployment of the nonlinear-programming algorithms. This paper further provides practical implementation details to improve the localization accuracy for feedback control in experimental IoT applications. The experimental results finally show that subdecimeter localization accuracy can be achieved using the proposed optimization-based approach, even when the majority of the UWB radio locations are unknown

Effect of the Reconnection Electric Field on Electron Distribution Functions in the Diffusion Region of Magnetotail Reconnection

Electron distribution functions in the electron diffusion region during symmetric magnetic reconnection are investigated by means of theory and fully kinetic simulations. Crescentlike striations are formed in distribution functions in the velocity plane perpendicular to the magnetic field. Using an analytical current sheet, we solve the equation of motion for electrons, and derive the shape of a crescent distribution, as a function of the distance from the neutral line, field gradients, and the reconnection electric field. Each crescent is tilted in the velocity plane because of the acceleration by the reconnection electric field, and multiple stripes appear due to multiple meandering bounces. Applying the theory to distribution functions observed in Earth's magnetotail, we deduce the amplitude of the reconnection electric field

The young stellar population of NGC 4214 as observed with HST. II. Results

We present the results of a detailed UV-optical study of the nearby dwarf starburst galaxy NGC 4214 using multifilter HST/WFPC2+STIS photometry. The stellar extinction is found to be quite patchy, with some areas having values of E(4405-5495)< 0.1 mag and others, associated with star forming regions, much more heavily obscured, a result which is consistent with previous studies of the nebular extinction. We determined the ratio of blue-to-red supergiants and found it to be consistent with theoretical models for the metallicity of the SMC. The stellar IMF of the field in the range 20-100 solar masses is found to be steeper than Salpeter. A number of massive clusters and associations with ages between a few and 200 million years are detected and their properties are discussed.Comment: 49 pages, 12 figures, 6 table

The Second INTEGRAL AGN Catalogue

The INTEGRAL mission provides a large data set for studying the hard X-ray properties of AGN and allows testing of the unified scheme for AGN. We present analysis of INTEGRAL IBIS/ISGRI, JEM-X, and OMC data for 199 AGN supposedly detected by INTEGRAL above 20 keV. The data analysed here allow a significant spectral extraction on 148 objects and an optical variability study of 57 AGN. The slopes of the hard X-ray spectra of Seyfert 1 and Seyfert~2 galaxies are found to be consistent within the uncertainties, whereas higher cut-off energies and lower luminosities are measured for the more absorbed / type 2 AGN. The intermediate Seyfert 1.5 objects exhibit hard X-ray spectra consistent with those of Seyfert 1. When applying a Compton reflection model, the underlying continua appear the same in Seyfert 1 and 2 with photon index 2, and the reflection strength is about R = 1, when assuming different inclination angles. A significant correlation is found between the hard X-ray and optical luminosity and the mass of the central black hole in the sense that the more luminous objects appear to be more massive. There is also a general trend toward the absorbed sources and type 2 AGN having lower Eddington ratios. The black holemass appears to form a fundamental plane together with the optical and X-ray luminosity of the form Lv being proportional to Lx^0.6 M^0.2, similar to that found between radio luminosity Lr, Lx, and M. The unified model for Seyfert galaxies seems to hold, showing in hard X-rays that the central engine is the same in Seyfert 1 and 2, but seen under different inclination angles and absorption. (Abridged)Comment: 26 pages, 16 figures, accepted for publication in A&A. Corrections by language editor included in version

Characterization of fungal and bacterial communities associated with mat-forming ectomycorrhizal fungi from old-growth stands in the H.J. Andrews Experimental Forest

Mat-forming ectomycorrhizal (EcM) fungi represent a prevalent constituent of many temperate forest ecosystems and create dramatic changes in soil structure and chemistry. EcM mat soil have been shown to have increased microbial respiration rates and have been hypothesized to harbor unique assemblages of fungi and bacteria. The objectives of this dissertation were to characterize and examine the fungal and bacterial communities associated with EcM mats in old-growth forests of the H.J. Andrews Experimental Forest located in the Oregon Cascades. Additionally, this work assessed the application of traditional, emerging, and novel molecular sampling techniques for determining microbial communities of environmental samples. This research investigated the microbial communities associated with two common EcM mat genera found in old-growth Douglas fir stands in the Pacific Northwest; Piloderma (Atheliales, Basidiomycota) and Ramaria (Gomphales, Basidiomycota). Soil samples were collected from Piloderma and Ramaria mats and surrounding non- mat soil for molecular analysis of nucleic acids. First, a comparative study was conducted to determine the most appropriate rDNA molecular sampling technique for microbial community characterization. Two next-generation sequencing methods, Roche 454 pyrosequencing and Illumina-based environmental sequencing, the latter developed by the author, were compared to a more traditional sequencing approach, i.e., Sanger sequencing of clone libraries. These findings informed the subsequent sampling of the fungal ITS and bacterial 16S rDNA fragment with 454 pyrosequencing to determine the microbial communities within mat and non-mat soils. Second, this work utilized a pyrosequencing approach to explore fungal community structure in EcM mat and non-mat soils. This work concluded that differences in microbial communities do exist between Piloderma mat, Ramaria mat, and non-mat soils, but the differences are largely quantitative with relatively few distinct taxonomic shifts in microbial constituents. Piloderma, Ramaria and Russula, in addition to being the dominant taxa found on mycorrhizal root tips, were found to be the most abundant taxa in bulk soils within their respective mat types or non-mat sample. The background fungal communities within the EcM mats in this study exhibited considerable taxonomic overlap with the exception of Piloderma vs. non-mat comparisons; Russula species dominated nonmat soils but tended to be excluded or significantly underrepresented in Piloderma mats. Lastly, this study explored the bacterial communities associated with Piloderma and Ramaria mats using lower- coverage 454-Jr pyrosequencing. Bacterial communities exhibited significant structure as a function of mat-type, soil horizon and pH, but this finding should be interpreted with respect to the nonrandom distribution of Piloderma-mats in the O- horizon and the Ramaria-mats in the A-horizon, and the tendancy for EcM mats to be more acidic than surrounding soils. Nonetheless, the total microbial (bacterial and fungal) community was typically dominated by the mat-forming taxa, or Russula, in the case of non-mat soils. While the presence of Piloderma mats did enrich or restrict some bacterial groups, soil pH was also found to be a significant driver of bacterial richness and taxonomic diversity. Fungal and bacterial richness were also found to be positively related to one another, regardless of soil horizon or EcM mat type. This work, taken together, contributes to the understanding of hyperdiversity and heterogeneity of microbial communities of temperate forest soils and highlights the potential for fungal and bacterial communities to be influenced by the presence of EcM mats

Resonant Absorption in the AGN spectra emerging from photoionized gas: differences between steep and flat ionizing continua

We present photoionization models accounting for both photoelectric and resonant absorption. Resonance absorption lines from C, O, Ne, Mg, Si S and Fe between 0.1 and 10 keV are treated. In particular we consider the complex of almost 60 strong Fe L absorption lines around 1 keV. We calculate profiles, intensities and equivalent widths of each line, considering both Doppler and natural broadening mechanisms. Doppler broadening includes a term accounting for turbulence of the gas along the line of sight. We computed spectra transmitted by gas illuminated by drastically different ionizing continua and compared them to spectra observed in flat X-ray spectrum, broad optical emission line type 1 AGN, and steep X-ray spectrum, narrow optical emission line type 1 AGN. We show that the $\sim 1$ keV absorption feature observed in moderate resolution X-ray spectra of several Narrow Line Seyfert 1 galaxies can be explained by photoionization models, taking into account for resonance absorption, without requiring relativistic outflowing velocities of the gas, if the physical properties of these absorbers are close to those found in flat X-ray spectrum Seyfert 1 galaxies.Comment: 22 pages, 10 figures. Accepted for publication on Ap

Coherent Fe-rich nano-scale perovskite oxide phase in epitaxial Sr2FeMoO6 films grown on cubic and scandate substrates

We report the growth of high-quality epitaxial Sr2FeMoO6 (SFMO) thin films on various unconventional oxide substrates, such as TbScO3, DyScO3, and Sr2Al0.3Ga0.7TaO6 (SAGT) as well as on the most commonly used one, SrTiO3 (STO), by pulsed laser deposition. The films were found to contain a foreign nano-scale phase coherently embedded inside the SFMO film matrix. Through energy dispersive X-ray spectroscopy and scanning transmission electron microscopy, we identified the foreign phase to be Sr2−xFe1+yMo1−yO6, an off-stoichiometric derivative of the SFMO compound with Fe rich content (y ≈ 0.6) and a fairly identical crystal structure to SFMO. The films on STO and SAGT exhibited very good magnetic properties with high Curie temperature values. All the samples have fairly good conducting behavior albeit the presence of a foreign phase. Despite the relatively large number of items of the foreign phase, there is no significant deterioration in the properties of the SFMO films. We discuss in detail how magneto-transport properties are affected by the foreign phase. INT

Combining Performance with Thermal Stability: Synthesis and Characterization of 5‐(3,5‐Dinitro‐1H‐pyrazol‐4‐yl)‐1H‐tetrazole and its Energetic Derivatives

In this study, we present the synthesis of 5‐(3,5‐dinitro‐1H‐pyrazol‐4‐yl)‐1H‐tetrazole and its energetic derivatives starting from 4‐amino‐3,5‐dinitropyrazole, which was diazotized and cyanide substituted. A subsequent cycloaddition reaction with sodium azide led to 5‐(3,5‐dinitro‐1H‐pyrazol‐4‐yl)‐1H‐tetrazole (3). Several alkaline metal and nitrogen‐rich salts were prepared and characterized by low‐temperature X‐ray diffraction. Additionally, all compounds were analyzed by vibrational spectroscopy (IR), 1H, 13C and 14N NMR spectroscopy, elemental analysis and differential thermal analysis (DTA). Additionally, the heats of formation for selected compounds were calculated using the atomization method based on CBS‐4M enthalpies as well as important detonation parameters by using the EXPLO5 code (V6.05). Furthermore, the sensitivities of 3 and all synthesized salts toward friction, impact and electrostatic discharge according to BAM (Bundesamt für Materialforschung) were determined and compared to RDX

Long term monitoring of mode switching for PSR B0329+54

The mode switching phenomenon of PSR B0329+54 is investigated based on the long-term monitoring from September 2003 to April 2009 made with the Urumqi 25m radio telescope at 1540 MHz. At that frequency, the change of relative intensity between the leading and trailing components is the predominant feature of mode switching. The intensity ratios between the leading and trailing components are measured for the individual profiles averaged over a few minutes. It is found that the ratios follow normal distributions, where the abnormal mode has a wider typical width than the normal mode, indicating that the abnormal mode is less stable than the normal mode. Our data show that 84.9% of the time for PSR B0329+54 was in the normal mode and 15.1% was in the abnormal mode. From the two passages of eight-day quasi-continuous observations in 2004, and supplemented by the daily data observed with 15 m telescope at 610 MHz at Jodrell Bank Observatory, the intrinsic distributions of mode timescales are constrained with the Bayesian inference method. It is found that the gamma distribution with the shape parameter slightly smaller than 1 is favored over the normal, lognormal and Pareto distributions. The optimal scale parameters of the gamma distribution is 31.5 minutes for the abnormal mode and 154 minutes for the normal mode. The shape parameters have very similar values, i.e. 0.75^{+0.22}_{-0.17} for the normal mode and 0.84^{+0.28}_{-0.22} for the abnormal mode, indicating the physical mechanisms in both modes may be the same. No long-term modulation of the relative intensity ratios was found for both the modes, suggesting that the mode switching was stable. The intrinsic timescale distributions, for the first time constrained for this pulsar, provide valuable information to understand the physics of mode switching.Comment: 31 pages,12 figures, Accepted by the Ap