169 research outputs found
The Dynamical Implications of Multiple Stellar Formation Events in Galactic Globular Clusters
Various galactic globular clusters display abundance anomalies that affect
the morphology of their colour-magnitude diagrams. In this paper we consider
the possibility of helium enhancement in the anomalous horizontal branch of NGC
2808. We examine the dynamics of a self-enrichment scenario in which an initial
generation of stars with a top-heavy initial mass function enriches the
interstellar medium with helium via the low-velocity ejecta of its asymptotic
giant branch stars. This enriched medium then produces a second generation of
stars which are themselves helium-enriched. We use a direct N-body approach to
perform five simulations and conclude that such two-generation clusters are
both possible and would not differ significantly from their single-generation
counterparts on the basis of dynamics. We find, however, that the stellar
populations of such clusters would differ from single-generation clusters with
a standard initial mass function and in particular would be enhanced in white
dwarf stars. We conclude, at least from the standpoint of dynamics, that
two-generation globular clusters are feasible.Comment: 24 pages, 7 figures, 3 tables. Accepted for publication in Ap
Physician Executive Leadership: Assessing a Student-Led Approach to Healthcare Leadership Education in Medical School
Poster presented at: 14th Annual AMA Research Symposium in Orlando, Fl
Objective:
To investigate the effectiveness of Physican Leadership, an open access, student-led healthcare leadership program at Sidney Kimmel Medical College, in preparing to face five key emerging topics in medical practice: healthcare economics, health policy, care and quality and safety, law and medicine, and patient experience.
The Problem: Gaps in Medical Education
Healthcare in the US continues to evolve, and topics such as health policy, health finance, and patient experience are not central to the practice of medicine.
However, the sheer volume of material students are required to learn in the preclinical years makes it challenging to introduce new subjects into traditional medical school curricula. As a result, these topics in healthcare leadership are often left out. Indeed, only 40-50% of medical student report appropriate training in the practice of medicine, including subjects as medical economics, healthcare systems, and managed care.https://jdc.jefferson.edu/pel/1002/thumbnail.jp
Contributions of Fire Refugia to Resilient Ponderosa Pine and Dry MixedâConifer Forest Landscapes
Altered fire regimes can drive major and enduring compositional shifts or losses of forest ecosystems. In western North America, ponderosa pine and dry mixedâconifer forest types appear increasingly vulnerable to uncharacteristically extensive, highâseverity wildfire. However, unburned or only lightly impacted forest stands that persist within burn mosaicsâtermed fire refugiaâmay serve as tree seed sources and promote landscape recovery. We sampled tree regeneration along gradients of fire refugia proximity and density at 686 sites within the perimeters of 12 large wildfires that occurred between 2000 and 2005 in the interior western United States. We used generalized linear mixedâeffects models to elucidate statistical relationships between tree regeneration and refugia pattern, including a new metric that incorporates patch proximity and proportional abundance. These relationships were then used to develop a spatially explicit landscape simulation model. We found that regeneration by ponderosa pine and obligateâseeding mixedâconifer tree species assemblages was strongly and positively predicted by refugia proximity and density. Simulation models revealed that for any given proportion of the landscape occupied by refugia, small patches produced greater landscape recovery than large patches. These results highlight the disproportionate importance of small, isolated islands of surviving trees, which may not be detectable with coarseâscale satellite imagery. Findings also illustrate the interplay between patchâscale resistance and landscapeâscale resilience: Disturbanceâresistant settings (fire refugia) can entrain resilience (forest regeneration) across the burn matrix. Implications and applications for land managers and conservation practitioners include strategies for the promotion and maintenance of fire refugia as components of resilient forest landscapes
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Matching scope, purpose and uses of planetary boundaries science
Background: The Planetary Boundaries concept (PBc) has emerged as a key global sustainability concept in international sustainable development arenas. Initially presented as an agenda for global sustainability research, it now shows potential for sustainability governance. We use the fact that it is widely cited in scientific literature (>3500 citations) and an extensively studied concept to analyse how it has been used and developed since its first publication. Design: From the literature that cites the PBc, we select those articles that have the terms 'planetary boundaries' or 'safe operating space' in either title, abstract or keywords. We assume that this literature substantively engages with and develops the PBc. Results: We find that 6% of the citing literature engages with the concept. Within this fraction of the literature we distinguish commentariesâthat discuss the context and challenges to implementing the PBc, articles that develop the core biogeophysical concept and articles that apply the concept by translating to sub-global scales and by adding a human component to it. Applied literature adds to the concept by explicitly including society through perspectives of impacts, needs, aspirations and behaviours. Discussion: Literature applying the concept does not yet include the more complex, diverse, cultural and behavioural facet of humanity that is implied in commentary literature. We suggest there is need for a positive framing of sustainability goalsâas a Safe Operating Space rather than boundaries. Key scientific challenges include distinguishing generalised from context-specific knowledge, clarifying which processes are generalizable and which are scalable, and explicitly applying complex systems' knowledge in the application and development of the PBc. We envisage that opportunities to address these challenges will arise when more human social dimensions are integrated, as we learn to feed the global sustainability vision with a plurality of bottom-up realisations of sustainability
Does Educator Training or Experience Affect the Quality of Multiple-Choice Questions?
Rationale and objectivesPhysicians receive little training on proper multiple-choice question (MCQ) writing methods. Well-constructed MCQs follow rules, which ensure that a question tests what it is intended to test. Questions that break these are described as "flawed." We examined whether the prevalence of flawed questions differed significantly between those with or without prior training in question writing and between those with different levels of educator experience.Materials and methodsWe assessed 200 unedited MCQs from a question bank for our senior medical student radiology elective: an equal number of questions (50) were written by faculty with previous training in MCQ writing, other faculty, residents, and medical students. Questions were scored independently by two readers for the presence of 11 distinct flaws described in the literature.ResultsQuestions written by faculty with MCQ writing training had significantly fewer errors: mean 0.4 errors per question compared to a mean of 1.5-1.7 errors per question for the other groups (P < .001). There were no significant differences in the total number of errors between the untrained faculty, residents, and students (P values .35-.91). Among trained faculty 17/50 questions (34%) were flawed, whereas other faculty wrote 38/50 (76%) flawed questions, residents 37/50 (74%), and students 44/50 (88%). Trained question writers' higher performance was mainly manifest in the reduced frequency of five specific errors.ConclusionsFaculty with training in effective MCQ writing made fewer errors in MCQ construction. Educator experience alone had no effect on the frequency of flaws; faculty without dedicated training, residents, and students performed similarly
Biodiversity change is uncoupled from species richness trends: consequences for conservation and monitoring
Global concern about human impact on biological diversity has triggered an intense research agenda on drivers and consequences of biodiversity change in parallel with international policy seeking to conserve biodiversity and associated ecosystem functions. Quantifying the trends in biodiversity is far from trivial, however, as recently documented by meta-analyses, which report little if any net change in local species richness through time.
Here, we summarise several limitations of species richness as a metric of biodiversity change and show that the expectation of directional species richness trends under changing conditions is invalid. Instead, we illustrate how a set of species turnover indices provide more information content regarding temporal trends in biodiversity, as they reflect how dominance and identity shift in communities over time.
We apply these metrics to three monitoring datasets representing different ecosystem types. In all datasets, nearly complete species turnover occurred, but this was disconnected from any species richness trends. Instead, turnover was strongly influenced by changes in species presence (identities) and dominance (abundances). We further show that these metrics can detect phases of strong compositional shifts in monitoring data and thus identify a different aspect of biodiversity change decoupled from species richness.
Synthesis and applications: Temporal trends in species richness are insufficient to capture key changes in biodiversity in changing environments. In fact, reductions in environmental quality can lead to transient increases in species richness if immigration or extinction has different temporal dynamics. Thus, biodiversity monitoring programmes need to go beyond analyses of trends in richness in favour of more meaningful assessments of biodiversity change
Utility of routine viral load, CD4 cell count, and clinical monitoring among adults with HIV receiving antiretroviral therapy in Uganda: randomised trial
Objective To evaluate the use of routine laboratory monitoring in terms of clinical outcomes among patients receiving antiretroviral therapy (ART) in Uganda
Evaluation of GPT-3.5 and GPT-4 for supporting real-world information needs in healthcare delivery
Despite growing interest in using large language models (LLMs) in healthcare,
current explorations do not assess the real-world utility and safety of LLMs in
clinical settings. Our objective was to determine whether two LLMs can serve
information needs submitted by physicians as questions to an informatics
consultation service in a safe and concordant manner. Sixty six questions from
an informatics consult service were submitted to GPT-3.5 and GPT-4 via simple
prompts. 12 physicians assessed the LLM responses' possibility of patient harm
and concordance with existing reports from an informatics consultation service.
Physician assessments were summarized based on majority vote. For no questions
did a majority of physicians deem either LLM response as harmful. For GPT-3.5,
responses to 8 questions were concordant with the informatics consult report,
20 discordant, and 9 were unable to be assessed. There were 29 responses with
no majority on "Agree", "Disagree", and "Unable to assess". For GPT-4,
responses to 13 questions were concordant, 15 discordant, and 3 were unable to
be assessed. There were 35 responses with no majority. Responses from both LLMs
were largely devoid of overt harm, but less than 20% of the responses agreed
with an answer from an informatics consultation service, responses contained
hallucinated references, and physicians were divided on what constitutes harm.
These results suggest that while general purpose LLMs are able to provide safe
and credible responses, they often do not meet the specific information need of
a given question. A definitive evaluation of the usefulness of LLMs in
healthcare settings will likely require additional research on prompt
engineering, calibration, and custom-tailoring of general purpose models.Comment: 27 pages including supplemental informatio
The science of clinical practice: disease diagnosis or patient prognosis? Evidence about "what is likely to happen" should shape clinical practice.
BACKGROUND: Diagnosis is the traditional basis for decision-making in clinical practice. Evidence is often lacking about future benefits and harms of these decisions for patients diagnosed with and without disease. We propose that a model of clinical practice focused on patient prognosis and predicting the likelihood of future outcomes may be more useful. DISCUSSION: Disease diagnosis can provide crucial information for clinical decisions that influence outcome in serious acute illness. However, the central role of diagnosis in clinical practice is challenged by evidence that it does not always benefit patients and that factors other than disease are important in determining patient outcome. The concept of disease as a dichotomous 'yes' or 'no' is challenged by the frequent use of diagnostic indicators with continuous distributions, such as blood sugar, which are better understood as contributing information about the probability of a patient's future outcome. Moreover, many illnesses, such as chronic fatigue, cannot usefully be labelled from a disease-diagnosis perspective. In such cases, a prognostic model provides an alternative framework for clinical practice that extends beyond disease and diagnosis and incorporates a wide range of information to predict future patient outcomes and to guide decisions to improve them. Such information embraces non-disease factors and genetic and other biomarkers which influence outcome. SUMMARY: Patient prognosis can provide the framework for modern clinical practice to integrate information from the expanding biological, social, and clinical database for more effective and efficient care
Improving the diagnosis and treatment of urinary tract infection in young children in primary care:results from the âDUTYâ prospective diagnostic cohort study
PURPOSE Up to 50% of urinary tract infections (UTIs) in young children are missed in primary care. Urine culture is essential for diagnosis, but urine collection is often difficult. Our aim was to derive and internally validate a 2-step clinical rule using (1) symptoms and signs to select children for urine collection; and (2) symptoms, signs, and dipstick testing to guide antibiotic treatment. METHODS We recruited acutely unwell children aged under 5 years from 233 primary care sites across England and Wales. Index tests were parent-reported symptoms, clinician-reported signs, urine dipstick results, and clinician opinion of UTI likelihood (clinical diagnosis before dipstick and culture). The reference standard was microbiologically confirmed UTI cultured from a clean-catch urine sample. We calculated sensitivity, specificity, and area under the receiver operator characteristic (AUROC) curve of coefficient-based (graded severity) and points-based (dichotomized) symptom/sign logistic regression models, and we then internally validated the AUROC using bootstrapping. RESULTS Three thousand thirty-six children provided urine samples, and culture results were available for 2,740 (90%). Of these results, 60 (2.2%) were positive: the clinical diagnosis was 46.6% sensitive, with an AUROC of 0.77. Previous UTI, increasing pain/crying on passing urine, increasingly smelly urine, absence of severe cough, increasing clinician impression of severe illness, abdominal tenderness on examination, and normal findings on ear examination were associated with UTI. The validated coefficient- and points-based model AUROCs were 0.87 and 0.86, respectively, increasing to 0.90 and 0.90, respectively, by adding dipstick nitrites, leukocytes, and blood. CONCLUSIONS A clinical rule based on symptoms and signs is superior to clinician diagnosis and performs well for identifying young children for noninvasive urine sampling. Dipstick results add further diagnostic value for empiric antibiotic treatment
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