72 research outputs found
Comment on the feasibility of carbon burning in Betelgeuse: a response to "The evolutionary stage of Betelgeuse inferred from its pulsation periods," arXiv:2306.00287
No full textThe recent pre-print by Saio et al. 2023 argues that the supergiant
Betelgeuse is already undergoing carbon burning, based on the assumption that
all of its light variations are caused by radial pulsations. However, the
angular diameter measurements of the star are in conflict with the stellar
radius required by their models, as we show in this note. We discuss the
feasibility that the Great Dimming was caused by constructive mode interference
using long-term brightness measurements and comment on differences in modeling
frameworks adopted in Saio et al. 2023 vs Joyce et al. 2020.Comment: This note is a response to the pre-print arXiv:2306.00287. We present
it in the spirit of community discourse. 3 pages, 1 figure, accepted to
RNAAS. Feedback welcom
Unknown to Meridith (4 October 1962)
No full texthttps://egrove.olemiss.edu/mercorr_anti/1221/thumbnail.jp
Unknown to James Meridith (2 October 1962)
No full texthttps://egrove.olemiss.edu/mercorr_anti/1227/thumbnail.jp
A Review of the Mixing Length Theory of Convection in 1D Stellar Modeling
No full textWe review the application of the one-dimensional Mixing Length Theory (MLT) model of convection in stellar interiors and low-mass stellar evolution. We summarize the history of MLT, present a derivation of MLT in the context of 1D stellar structure equations, and discuss the physical regimes in which MLT is relevant. We review attempts to improve and extend the formalism, including to higher dimensions. We discuss the interactions of MLT with other modeling physics, and demonstrate the impact of introducing variations in the convective mixing length, αMLT, on stellar tracks and isochrones. We summarize the process of performing a solar calibration of αMLT and state-of-the-art on calibrations to non-solar targets. We discuss the scientific implications of changing the mixing length, using recent analyses for demonstration. We review the most prominent successes of MLT, and the remaining challenges, and we conclude by speculating on the future of this treatment of convection
Star-crossed Clusters: Asteroseismic Ages for Individual Stars Are in Tension with the Ages of Their Host Clusters
No full textA meta-analysis of seismic ages determined for individual stars in the well-studied open and globular clusters NGC 6819, NGC 6791, M67, M4, M19, M80, and M9 reveals both high variance across measurements and a possible discrepancy with independent, isochrone-based age determinations for the clusters in which these stars reside. The scatter among asteroseismic ages for individual stars in any one of these clusters far surpasses both the absolute age uncertainty computed for reference cluster M92 (5.4%) and the model-to-model systematic uncertainties in isochrones (roughly 10%). This suggests that either binary processes are significantly altering the masses of stars in these clusters, or some additional corrections, perhaps as a function of mass, metallicity, or surface gravity, are required to bring the asteroseismic age scale into concordance with ages inferred from isochrone or similar model fitting
Constructivist grounded theory or interpretive phenomenology?: Methodological choices within specific study contexts
No full textConstructivist research methodologies are useful in discerning meanings of experience to subsequently inform and improve
healthcare practice. For researchers who philosophically align with the constructivist paradigm, numerous methodologies are
available from which to choose to address research questions. However, it can be challenging for researchers, especially novice
ones, to choose the most appropriate methodology that aligns with the current state of knowledge of the identified topic,
proposed research question, and the study purpose. To reduce the confusion faced by health researchers when choosing an
appropriate methodology for a specific study, this paper compares two popular qualitative health research approaches:
constructivist grounded theory and interpretive phenomenology. Philosophical underpinnings and the epistemological and ontological evolution of each methodology are explored with similarities and differences highlighted. Manifestation of the philosophical
foundations of constructivist grounded theory and interpretive phenomenology are described in relation to data collection, analysis,
and the research findings. To illustrate distinctions of each approach and support researchers in the navigation of methodological
decision-making, a specific healthcare study context is presented: the rural family members’ experiences of a relative’s interhospital
transfer for advanced critical care services. This study context is increasingly being recognized as an important area of healthcare
research and practice. However, gaps in knowledge persist, specifically in relation to the experiences of rural family members when a
critically ill relative requires an interhospital transfer to a distant urban center for advanced critical care services. Improved understanding of such experiences is necessary to inform the care provided to rural family members, potentially mitigating short and
long-term negative consequences for these individuals. Within this example, the importance of the research purpose and research
question within a specific study context is underscored as central to appropriate methodological decision-making
Unknown to Mr. James Meridith (2 October 1962)
No full texthttps://egrove.olemiss.edu/mercorr_anti/1224/thumbnail.jp
Influences of the culture of science on nursing knowledge development: Using conceptual frameworks as nursing philosophy in critical care nursing
No full textNursing knowledge development and application are influenced by numerous factors within the context of science and practice. The prevailing culture of science along with an evolving context of increasingly technological environments and rationalization within health care impacts both the generation of nursing knowledge and the practice of nursing. The effects of the culture of science and the context of nursing practice may negatively impact the structure and application of nursing knowledge, how nurses practice, and how nurses understand the patients and families for whom they care. Specifically, the nature of critical care and its highly technical environment make critical care nursing especially vulnerable to these potentially negative influences. The influences of the culture of science and the increasingly technical practice context may result in an overreliance on the natural sciences to guide critical care nursing actions and an associated marginalization of the caring relationship in critical care nursing practice. Within this environment, nursing philosophy may not be foundational to nursing actions; rather, the dominant culture of science and the rationalization of health care may be informing nursing practice. As such, the ideology and goals of nursing may not be central to the practice of critical care nursing. The purpose of this paper is to explore the influence of the culture of science on the development of nursing knowledge and theory. Further, we aim to describe the value of using conceptual frameworks, such as Roy's Adaptation Model, as a nursing philosophy to influence the development of person‐centred nursing knowledge and theory to inform critical care nursing practice as it related to the care of patients and families. In doing so, nursing philosophy is situated as foundational for nursing actions
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