I summarize and analyse key problems with observations of the UV bump in active galactic nuclei (AGN), and especially the accretion disc interpretation - the temperature problem, the ionization ...problem, the time-scale problem and the co-ordination problem - and suggest that all these problems can be solved if, in addition to the accretion disc, there is a population of cold, thick clouds at approximately 30R
S which reprocess the intrinsic continuum. Exploring cloud parameter space, I find that clouds with density n∼ 1012 cm−3 and column N
H > 4 × 1024 cm−2 reflect most of the intrinsic continuum, but convert a substantial fraction of the EUV luminosity into lines, dominated by Lyβ and He ii Lyα. When velocity-blurred, this makes a false continuum peak at ∼1100 Å which fits the observed spectral energy distribution (SED) well, but turns back up in the FUV to make a hard EUV SED, as required by ionization models. I argue that the observed UV variability is dominated by this component of fixed shape, possibly due to changes of covering factor. The amount of mass required is small, so it is not necessary to disrupt the disc, but only to make an unstable and inhomogeneous atmosphere. The proposed clouds may be related to those suggested by several X-ray phenomena (X-ray reflection components, high-velocity outflows, Compton thick partial covering) but are not the same, leading to a picture with a wide range of inhomogeneous structures at different radii.
Qualitative and mixed methods play a prominent role in mental health services research. However, the standards for their use are not always evident, especially for those not trained in such methods. ...This article reviews the rationale and common approaches to using qualitative and mixed methods in mental health services and implementation research based on a review of the articles included in this special series along with representative examples from the literature. Qualitative methods are used to provide a "thick description" or depth of understanding to complement breadth of understanding afforded by quantitative methods, elicit the perspective of those being studied, explore issues that have not been well studied, develop conceptual theories or test hypotheses, or evaluate the process of a phenomenon or intervention. Qualitative methods adhere to many of the same principles of scientific rigor as quantitative methods but often differ with respect to study design, data collection, and data analysis strategies. For instance, participants for qualitative studies are usually sampled purposefully rather than at random and the design usually reflects an iterative process alternating between data collection and analysis. The most common techniques for data collection are individual semistructured interviews, focus groups, document reviews, and participant observation. Strategies for analysis are usually inductive, based on principles of grounded theory or phenomenology. Qualitative methods are also used in combination with quantitative methods in mixed-method designs for convergence, complementarity, expansion, development, and sampling. Rigorously applied qualitative methods offer great potential in contributing to the scientific foundation of mental health services research.
Recent data on DNA sequencing of human tumours have established that cancer cells contain thousands of mutations. These data support the concept that cancer cells express a mutator phenotype. This ...Perspective considers the evidence supporting the mutator phenotype hypothesis, the origin and consequences of a mutator phenotype, the implications for personalized medicine and the feasibility of ablating tumours by error catastrophe.
Mutations, the fuel of evolution, are first manifested as rare DNA changes within a population of cells. Although next-generation sequencing (NGS) technologies have revolutionized the study of ...genomic variation between species and individual organisms, most have limited ability to accurately detect and quantify rare variants among the different genome copies in heterogeneous mixtures of cells or molecules. We describe the technical challenges in characterizing subclonal variants using conventional NGS protocols and the recent development of error correction strategies, both computational and experimental, including consensus sequencing of single DNA molecules. We also highlight major applications for low-frequency mutation detection in science and medicine, describe emerging methodologies and provide our vision for the future of DNA sequencing.
Purpose To review the history of indocyanine green (ICG) angiography and to present a personal perspective on its use in the clinical setting today. Design Perspective with literature review and ...opinions based on personal experience. Methods To acquire views from international retinal physicians experienced with the technique on uses in their facilities and to compare them to the author's personal standards. Results The author and contributing retinal physicians had surprisingly similar views for most, but not all, applications for ICG angiography use in the clinical setting. Conclusions ICG angiography is recommended for a few highly selective chorioretinal disorders, including certain forms of neovascularization in age-related macular degeneration, other neovascular maculopathies, chronic central serous chorioretinopathy, choroidal hemangiomas, and posterior uveitis.
After new ventures have exhausted the limited financial resources of founders, family, and friends, they often pursue initial external capital. To secure investment, entrepreneurs can signal about ...their venture's latent potential by aligning themselves with reliable third parties. Such affiliations affirm the new venture's legitimacy and provide substantive benefits in the form of mentoring, access to resources, and ongoing monitoring. However, early stage financing is an especially "noisy" signaling environment owing to the large number of startups seeking funding, many of which will not survive. The real value of third-party affiliations in this context resides in their ability to unlock the potential of other more pedestrian signals, such as the entrepreneur's characteristics and actions that might otherwise go unnoticed. We borrow from the sensemaking literature to explain how third-party affiliation signals disambiguate signals with multiple possible interpretations so that potential investors interpret them positively. Findings support our theory that a startup's characteristics and actions are signals that remain relatively unnoticed unless a startup combines them with a third-party affiliation that enhances the signal's value, thus increasing the likelihood of receiving external capital.
Lessons in corporate finance Asquith, Paul; Weiss, Lawrence A
2016, 2019/01/01, 2016, 2019, 2016-03-16, 2016-03-28, 2019-04-08, 2019-04-09
eBook
"Lessons in Corporate Finance explains the fundamentals of the field in an intuitive way, using a unique Socratic question and answer approach. Written by award-winning professors at M.I.T. and ...Tufts, this book draws on years of research and teaching to deliver a truly interactive learning experience. Each case study is designed to facilitate class discussion, based on a series of increasingly detailed questions and answers that reinforce conceptual insights with numerical examples. Complete coverage of all areas of corporate finance includes capital structure and financing needs along with project and company valuation, with specific guidance on vital topics such as ratios and pro formas, dividends, debt maturity, asymmetric information, and more. Corporate finance is a complex field composed of a broad variety of sub-disciplines, each involving a specific skill set and nuanced body of knowledge. This text is designed to give you an intuitive understanding of the fundamentals to provide a solid foundation for more advanced study"--Publisher's website.
Innovations in Mixed Methods Evaluations Palinkas, Lawrence A; Mendon, Sapna J; Hamilton, Alison B
Annual review of public health,
04/2019, Letnik:
40, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Mixed methods research-i.e., research that draws on both qualitative and quantitative methods in varying configurations-is well suited to address the increasing complexity of public health problems ...and their solutions. This review focuses specifically on innovations in mixed methods evaluations of intervention, program or policy (i.e., practice) effectiveness, and implementation. The article begins with an overview of the structure, function, and process of different mixed methods designs and then provides illustrations of their use in effectiveness studies, implementation studies, and combined effectiveness-implementation hybrid studies. The article then examines four specific innovations: procedures for transforming (or "quantitizing") qualitative data, application of rapid assessment and analysis procedures in the context of mixed methods studies, development of measures to assess implementation outcomes, and strategies for conducting both random and purposive sampling, particularly in implementation-focused evaluation research. The article concludes with an assessment of challenges to integrating qualitative and quantitative data in evaluation research.
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