Model choice is usually an inevitable source of uncertainty in model-based statistical analyses. While the focus of model choice was traditionally on methods for choosing a single model, methods to ...formally account for multiple models within a single analysis are now accessible to many researchers. The specific technique of model averaging was developed to improve predictive ability by combining predictions from a set of models. However, it is now often used to average regression coefficients across multiple models with the ultimate goal of capturing a variable's overall effect. This use of model averaging implicitly assumes the same parameter exists across models so that averaging is sensible. While this assumption may initially seem tenable, regression coefficients associated with particular explanatory variables may not hold equivalent interpretations across all of the models in which they appear, making explanatory inference about covariates challenging. Accessibility to easily implementable software, concerns about being criticized for ignoring model uncertainty, and the chance to avoid having to justify choice of a final model have all led to the increasing popularity of model averaging in practice. We see a gap between the theoretical development of model averaging and its current use in practice, potentially leaving well-intentioned researchers with unclear inferences or difficulties justifying reasons for using (or not using) model averaging. We attempt to narrow this gap by revisiting some relevant foundations of regression modeling, suggesting more explicit notation and graphical tools, and discussing how individual model results are combined to obtain a model averaged result. Our goal is to help researchers make informed decisions about model averaging and to encourage question-focused modeling over method-focused modeling.
We revisit the classical but as yet unresolved problem of predicting the breaking onset of 2D and 3D irrotational gravity water waves. Based on a fully nonlinear 3D boundary element model, our ...numerical simulations investigate geometric, kinematic and energetic differences between maximally tall non-breaking waves and marginally breaking waves in focusing wave groups. Our study focuses initially on unidirectional domains with flat bottom topography and conditions ranging from deep to intermediate depth (depth to wavelength ratio from 1 to 0.2). Maximally tall non-breaking (maximally recurrent) waves are clearly separated from marginally breaking waves by their normalised energy fluxes localised near the crest tip region. The initial breaking instability occurs within a very compact region centred on the wave crest. On the surface, this reduces to the local ratio of the energy flux velocity (here the fluid velocity) to the crest point velocity for the tallest wave in the evolving group. This provides a robust threshold parameter for breaking onset for 2D wave packets propagating in uniform water depths from deep to intermediate. Further targeted study of representative cases of the most severe laterally focused 3D wave packets in deep and intermediate depth water shows that the threshold remains robust. These numerical findings for 2D and 3D cases are closely supported by our companion observational results. Warning of imminent breaking onset is detectable up to a fifth of a carrier wave period prior to a breaking event.
Estimates of the incidence of the acute respiratory distress syndrome (ARDS) in high- and middle-income countries vary from 10.1 to 86.2 per 100,000 person-years in the general population. The ...epidemiology of ARDS has not been reported for a low-income country at the level of the population, hospital, or intensive care unit (ICU). The Berlin definition may not allow identification of ARDS in resource-constrained settings.
To estimate the incidence and outcomes of ARDS at a Rwandan referral hospital using the Kigali modification of the Berlin definition: without requirement for positive end-expiratory pressure, hypoxia cutoff of SpO2/FiO2 less than or equal to 315, and bilateral opacities on lung ultrasound or chest radiograph.
We screened every adult patient for hypoxia at a public referral hospital in Rwanda for 6 weeks. For every patient with hypoxia, we collected data on demographics and ARDS risk factors, performed lung ultrasonography, and evaluated chest radiography when available.
Forty-two (4.0%) of 1,046 hospital admissions met criteria for ARDS. Using various prespecified cutoffs for the SpO2/FiO2 ratio resulted in almost identical hospital incidence values. Median age for patients with ARDS was 37 years, and infection was the most common risk factor (44.1%). Only 30.9% of patients with ARDS were admitted to an ICU, and hospital mortality was 50.0%. Using traditional Berlin criteria, no patients would have met criteria for ARDS.
ARDS seems to be a common and fatal syndrome in a hospital in Rwanda, with few patients admitted to an ICU. The Berlin definition is likely to underestimate the impact of ARDS in low-income countries, where resources to meet the definition requirements are lacking. Although the Kigali modification requires validation before widespread use, we hope this study stimulates further work in refining an ARDS definition that can be consistently used in all settings.
Observed crest speeds of maximally steep, breaking water waves are much slower than expected. Our fully nonlinear computations of unsteadily propagating deep water wave groups show that each wave ...crest approaching its maximum height slows down significantly and either breaks at this reduced speed, or accelerates forward unbroken. This previously noted crest slowdown behavior was validated as generic in our extensive laboratory and field observations. It is likely to occur in unsteady dispersive nonlinear wave groups in other natural systems.
Being a Historian Banner, Jr, James M
Being a Historian,
04/2012
eBook, Book Chapter
Based on the author's more than 50 years of experience as a professional historian in academic and other capacities, Being a Historian is addressed to both aspiring and mature historians. It offers ...an overview of the state of the discipline of history today and the problems that confront it and its practitioners in many professions. James M. Banner, Jr argues that historians remain inadequately prepared for their rapidly changing professional world and that the discipline as a whole has yet to confront many of its deficiencies. He also argues that, no longer needing to conform automatically to the academic ideal, historians can now more safely and productively than ever before adapt to their own visions, temperaments and goals as they take up their responsibilities as scholars, teachers and public practitioners. Critical while also optimistic, this work suggests many topics for further scholarly and professional exploration, research and debate.
Here we analyze hospitalized andintensive care unit coronavirus disease 2019 (COVID‐19) patient outcomes from the international VIRUS registry (https://clinicaltrials.gov/ct2/show/NCT04323787). We ...find that COVID‐19 patients administered unfractionated heparin but not enoxaparin have a higher mortality‐rate (390 of 1012 = 39%) compared to patients administered enoxaparin but not unfractionated heparin (270 of 1939 = 14%), presenting a risk ratio of 2.79 (95% confidence interval CI: 2.42, 3.16; p = 4.45e−52). This difference persists even after balancing on a number of covariates including demographics, comorbidities, admission diagnoses, and method of oxygenation, with an increased mortality rate on discharge from the hospital of 37% (268 of 733) for unfractionated heparin versus 22% (154 of 711) for enoxaparin, presenting a risk ratio of 1.69 (95% CI: 1.42, 2.00; p = 1.5e−8). In these balanced cohorts, a number of complications occurred at an elevated rate for patients administered unfractionated heparin compared to patients administered enoxaparin, including acute kidney injury, acute cardiac injury, septic shock, and anemia. Furthermore, a higher percentage of Black/African American COVID patients (414 of 1294 32%) were noted to receive unfractionated heparin compared to White/Caucasian COVID patients (671 of 2644 25%), risk ratio 1.26 (95% CI: 1.14, 1.40; p = 7.5e−5). After balancing upon available clinical covariates, this difference in anticoagulant use remained statistically significant (311 of 1047 30% for Black/African American vs. 263 of 1047 25% for White/Caucasian, p = .02, risk ratio 1.18; 95% CI: 1.03, 1.36). While retrospective studies cannot suggest any causality, these findings motivate the need for follow‐up prospective research into the observed racial disparity in anticoagulant use and outcomes for severe COVID‐19 patients.
Introduction
Coronavirus disease 2019 (COVID‐19) is associated with high rates of morbidity and mortality. Primary hypothyroidism is a common comorbid condition, but little is known about its ...association with COVID‐19 severity and outcomes. This study aims to identify the frequency of hypothyroidism in hospitalized patients with COVID‐19 as well as describe the differences in outcomes between patients with and without pre‐existing hypothyroidism using an observational, multinational registry.
Methods
In an observational cohort study we enrolled patients 18 years or older, with laboratory‐confirmed severe acute respiratory syndrome coronavirus‐2 infection between March 2020 and February 2021. The primary outcomes were (1) the disease severity defined as per the World Health Organization Scale for Clinical Improvement, which is an ordinal outcome corresponding with the highest severity level recorded during a patient's index COVID‐19 hospitalization, (2) in‐hospital mortality and (3) hospital‐free days. Secondary outcomes were the rate of intensive care unit (ICU) admission and ICU mortality.
Results
Among the 20,366 adult patients included in the study, pre‐existing hypothyroidism was identified in 1616 (7.9%). The median age for the Hypothyroidism group was 70 (interquartile range: 59–80) years, and 65% were female and 67% were White. The most common comorbidities were hypertension (68%), diabetes (42%), dyslipidemia (37%) and obesity (28%). After adjusting for age, body mass index, sex, admission date in the quarter year since March 2020, race, smoking history and other comorbid conditions (coronary artery disease, hypertension, diabetes and dyslipidemia), pre‐existing hypothyroidism was not associated with higher odds of severe disease using the World Health Organization disease severity index (odds ratio OR: 1.02; 95% confidence interval CI: 0.92, 1.13; p = .69), in‐hospital mortality (OR: 1.03; 95% CI: 0.92, 1.15; p = .58) or differences in hospital‐free days (estimated difference 0.01 days; 95% CI: −0.45, 0.47; p = .97). Pre‐existing hypothyroidism was not associated with ICU admission or ICU mortality in unadjusted as well as in adjusted analysis.
Conclusions
In an international registry, hypothyroidism was identified in around 1 of every 12 adult hospitalized patients with COVID‐19. Pre‐existing hypothyroidism in hospitalized patients with COVID‐19 was not associated with higher disease severity or increased risk of mortality or ICU admissions. However, more research on the possible effects of COVID‐19 on the thyroid gland and its function is needed in the future.
Strategic conservation efforts for cryptic species, especially bats, are hindered by limited understanding of distribution and population trends. Integrating long‐term encounter surveys with ...multi‐season occupancy models provides a solution whereby inferences about changing occupancy probabilities and latent changes in abundance can be supported. When harnessed to a Bayesian inferential paradigm, this modeling framework offers flexibility for conservation programs that need to update prior model‐based understanding about at‐risk species with new data. This scenario is exemplified by a bat monitoring program in the Pacific Northwestern United States in which results from 8 years of surveys from 2003 to 2010 require updating with new data from 2016 to 2018. The new data were collected after the arrival of bat white‐nose syndrome and expansion of wind power generation, stressors expected to cause population declines in at least two vulnerable species, little brown bat (Myotis lucifugus) and the hoary bat (Lasiurus cinereus). We used multi‐season occupancy models with empirically informed prior distributions drawn from previous occupancy results (2003–2010) to assess evidence of contemporary decline in these two species. Empirically informed priors provided the bridge across the two monitoring periods and increased precision of parameter posterior distributions, but did not alter inferences relative to use of vague priors. We found evidence of region‐wide summertime decline for the hoary bat (λ^ = 0.86 ± 0.10) since 2010, but no evidence of decline for the little brown bat (λ^ = 1.1 ± 0.10). White‐nose syndrome was documented in the region in 2016 and may not yet have caused regional impact to the little brown bat. However, our discovery of hoary bat decline is consistent with the hypothesis that the longer duration and greater geographic extent of the wind energy stressor (collision and barotrauma) have impacted the species. These hypotheses can be evaluated and updated over time within our framework of pre–post impact monitoring and modeling. Our approach provides the foundation for a strategic evidence‐based conservation system and contributes to a growing preponderance of evidence from multiple lines of inquiry that bat species are declining.
We evaluate evidence of region‐wide summertime bat population decline in the Pacific Northwestern United States over a 16‐year period with large‐sample acoustic monitoring survey data and Bayesian occupancy models with empirically informative parameter priors. We provide compelling evidence that the hoary bat (shown in the photo, credit Michael Durham), a species known to be at risk from collision and barotrauma at wind energy production facilities, is experiencing regional decline at a rate of approximately 2% per year since 2010. Our study outlines a hypothesis‐driven model‐based framework for linking monitoring to conservation decision‐making.
';A whole book devoted exclusively to the misconduct of American presidents and their responses to charges of misconduct is without precedent.' from the introduction to the 1974 edition by C. Vann ...Woodward, Pulitzer Prizewinning Yale historianThe historic 1974 report for the House Committee on the Judiciary, updated for today by leading presidential historiansIn May 1974, as President Richard Nixon faced impeachment following the Watergate scandal, the House Judiciary Committee commissioned a historical account of the misdeeds of past presidents. The account, compiled by leading presidential historians of the day, reached back to George Washington's administration and was designed to provide a benchmark against which Nixon's misdeeds could be measured.What the report found was that, with the exception of William Henry Harrison (who served less than a month), every American president has been accused of misconduct: James Buchanan was charged with rigging the election of 1856; Ulysses S. Grant was reprimanded for not firing his corrupt staffer, Orville Babcock, in the ';Whiskey Ring' bribery scandal; and Franklin D. Roosevelt's administration faced repeated charges of malfeasance in the Works Progress Administration.Now, as another president and his subordinates face an array of charges on a wide range of legal and constitutional offenses, a group of presidential historians has come together under the leadership of James M. Banner, Jr.one of the historians who contributed to the original reportto bring the 1974 account up to date through Barack Obama's presidency. Based on current scholarship, this new material covers such well-known episodes as Nixon's Watergate crisis, Reagan's Iran-Contra scandal, Clinton's impeachment, and George W. Bush's connection to the exposure of intelligence secrets. But oft-forgotten events also take the stage: Carter's troubles with advisor Bert Lance, Reagan's savings and loan crisis, George H.W. Bush's nomination of Clarence Thomas to the Supreme Court, and Obama's Solyndra loan controversy.The only comprehensive study of American presidents' misconduct and the ways in which chief executives and members of their official families have responded to the charges brought against them, this new edition is designed to serve the same purpose as the original 1974 report: to provide the historical context and metric against which the actions of the current administration may be assessed.
Intensive Care Unit (ICU) risk prediction models are used to compare outcomes for quality improvement initiatives, benchmarking, and research. While such models provide robust tools in high-income ...countries, an ICU risk prediction model has not been validated in a low-income country where ICU population characteristics are different from those in high-income countries, and where laboratory-based patient data are often unavailable. We sought to validate the Mortality Probability Admission Model, version III (MPM0-III) in two public ICUs in Rwanda and to develop a new Rwanda Mortality Probability Model (R-MPM) for use in low-income countries.
We prospectively collected data on all adult patients admitted to Rwanda's two public ICUs between August 19, 2013 and October 6, 2014. We described demographic and presenting characteristics and outcomes. We assessed the discrimination and calibration of the MPM0-III model. Using stepwise selection, we developed a new logistic model for risk prediction, the R-MPM, and used bootstrapping techniques to test for optimism in the model.
Among 427 consecutive adults, the median age was 34 (IQR 25-47) years and mortality was 48.7%. Mechanical ventilation was initiated for 85.3%, and 41.9% received vasopressors. The MPM0-III predicted mortality with area under the receiver operating characteristic curve of 0.72 and Hosmer-Lemeshow chi-square statistic p = 0.024. We developed a new model using five variables: age, suspected or confirmed infection within 24 hours of ICU admission, hypotension or shock as a reason for ICU admission, Glasgow Coma Scale score at ICU admission, and heart rate at ICU admission. Using these five variables, the R-MPM predicted outcomes with area under the ROC curve of 0.81 with 95% confidence interval of (0.77, 0.86), and Hosmer-Lemeshow chi-square statistic p = 0.154.
The MPM0-III has modest ability to predict mortality in a population of Rwandan ICU patients. The R-MPM is an alternative risk prediction model with fewer variables and better predictive power. If validated in other critically ill patients in a broad range of settings, the model has the potential to improve the reliability of comparisons used for critical care research and quality improvement initiatives in low-income countries.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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