Assessing Diagnostic Performance.

Assessing Diagnostic PerformanceDiagnosis is an action and a goal in medicine. This article is the introduction to a series of review articles on varying facets of diagnosis. Clinical diagnosis is an exercise in classification; that is, placing the patient's condition in the correct diagnostic category. However, consideration must also be given to the performance objective, whether it is technical performance of a test, acquiring diagnostic information with respect to clinical management for an individual or a population's health outcomes, or cost-effectiveness and equity of care.

Health professional education at global scale: The inaugural Lincoln Chen lecture.

This inaugural Lincoln Chen Lecture comments on five themes raised in the International Conference on the Future of Health Professional Education (University of Miami, November 2022), identifies challenges for the future of health professional education, and highlights the contributions and legacy of Lincoln Chen.

Color Vision in the Mountains.

This Lessons from History article uses science, aviation, medicine, and mountaineering sources to describe some of the effects of hypoxia, illumination, and other environmental conditions on the eye, the central nervous system, and light and color perception. The historical perspective is augmented by an analysis of an informal observation of the altered perception of red color on a deck of playing cards while climbing Mera Peak in the Himalaya. The appearance of a grayer red color on the cards was initially attributed to the effects of hypoxia alone. Instead, analysis of cards in combination with the low incidence of protan color vision defects at altitude indicated that glare and contrast effects in the extremely bright lighting environment combined with hypoxia likely caused the perception of a grayer red. The incident provides an educational opportunity for review, analysis, and commentary about some of the complex elements that impact color vision.

The impact of nontransparent health communication during the COVID-19 pandemic on vaccine-hesitant people's perception of vaccines.

Background: Although transparency is crucial for building public trust, public health communication during the COVID-19 pandemic was often nontransparent. Methods: In a cross-sectional online study with COVID-19 vaccine-hesitant German residents (N = 763), we explored the impact of COVID-19 public health communication on the attitudes of vaccine-hesitant individuals toward vaccines as well as their perceptions of incomprehensible and incomplete information. We also investigated whether specific formats of public health messaging were perceived as more trustworthy. Results: Of the 763 participants, 90 (11.8%) said they had become more open-minded toward vaccines in general, 408 (53.5%) reported no change, and 265 (34.7%) said they had become more skeptical as a result of public health communication on COVID-19 vaccines. These subgroups differed in how incomprehensible they found public health communication and whether they thought information had been missing. Participants' ranking of trustworthy public health messaging did not provide clear-cut results: the fully transparent message, which reported the benefit and harms in terms of absolute risk, and the nontransparent message, which reported only the benefit in terms of relative risk were both considered equally trustworthy (p = 0.848). Discussion: Increased skepticism about vaccines during the COVID-19 pandemic may have partly been fueled by subpar public health communication. Given the importance of public trust for coping with future health crises, public health communicators should ensure that their messaging is clear and transparent.

Challenges and opportunities for educating health professionals after the COVID-19 pandemic.

The education of health professionals substantially changed before, during, and after the COVID-19 pandemic. A 2010 Lancet Commission examined the 100-year history of health-professional education, beginning with the 1910 Flexner report. Since the publication of the Lancet Commission, several transformative developments have happened, including in competency-based education, interprofessional education, and the large-scale application of information technology to education. Although the COVID-19 pandemic did not initiate these developments, it increased their implementation, and they are likely to have a long-term effect on health-professional education. They converge with other societal changes, such as globalisation of health care and increasing concerns of health disparities across the world, that were exacerbated by the pandemic. In this Health Policy, we list institutional and instructional reforms to assess what has happened to health-professional education since the publication of the Lancet Commission and how the COVID-19 pandemic altered the education process.

Cooling and Contraction of the Mesosphere and Lower Thermosphere From 2002 to 2021.

We examine the thermal structure of the mesosphere and lower thermosphere (MLT) using observations from 2002 through 2021 from the SABER instrument on the NASA TIMED satellite. These observations show that the MLT has significantly cooled and contracted between the years 2002 and 2019 (the year of the most recent solar minimum) due to a combination of a decline in the intensity of the 11-year solar cycle and increasing carbon dioxide (CO2.) During this time the thickness of atmosphere between the 1  and 10-4 hPa pressure surfaces (approximately 48 and 105 km) has contracted by 1,333 m, of which 342 m is attributed to increasing CO2. All other pressure surfaces in the MLT have similarly contracted. We further postulate that the MLT in the two most recent solar minima (2008-2009 and 2019-2020) was very likely the coldest and thinnest since the beginning of the Industrial Age. The sensitivity of the MLT to a doubling of CO2 is shown to be -7.5 K based on observed trends in temperature and growth rates of CO2. Colder temperatures observed at 10-4 hPa in 2019 than in the prior solar minimum in 2009 may be due to a decrease of 5% in solar irradiance in the Schumann-Runge band spectral region (175-200 nm).

Evaluation of Polar Winter Mesopause Wind in WACCMX+DART.

This work evaluates zonal winds in both hemispheres near the polar winter mesopause in the Whole Atmosphere Community Climate Model (WACCM) with thermosphere-ionosphere eXtension combined with data assimilation using the Data Assimilation Research Testbed (DART) (WACCMX+DART). We compare 14 years (2006-2019) of WACCMX+DART zonal mean zonal winds near 90 km to zonal mean zonal winds derived from Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) geopotential height measurements during Arctic mid-winter. 10 years (2008-2017) of WACCMX+DART zonal mean zonal winds are compared to SABER in the Antarctic mid-winter. It is well known that WACCM, and WACCM-X, zonal winds at the polar winter mesopause exhibit a strong easterly (westward) bias. One explanation for this is that the models omit higher order gravity waves (GWs), and thus the eastward drag caused by these GWs. We show for the first time that the model winds near the polar winter mesopause are in closer agreement with SABER observations when the winds near the stratopause are weak or reversed. The model and observed mesosphere and lower thermosphere winds agree most during dynamically disturbed times often associated with minor or major sudden stratospheric warming events. Results show that the deceleration of the stratospheric and mesospheric polar night jet allows enough eastward GWs to propagate into the mesosphere, driving eastward zonal winds that are in agreement with the observations. Thus, in both hemispheres, the winter polar night jet speed and direction near the stratopause may be a useful proxy for model fidelity in the polar winter upper mesosphere.

Transport of Nitric Oxide Via Lagrangian Coherent Structures Into the Top of the Polar Vortex.

The energetic particle precipitation (EPP) indirect effect (IE) refers to the downward transport of reactive odd nitrogen (NOx = NO + NO2) produced by EPP (EPP-NOx) from the polar winter mesosphere and lower thermosphere to the stratosphere where it can destroy ozone. Previous studies of the EPP IE examined NOx descent averaged over the polar region, but the work presented here considers longitudinal variations. We report that the January 2009 split Arctic vortex in the stratosphere left an imprint on the distribution of NO near the mesopause, and that the magnitude of EPP-NOx descent in the upper mesosphere depends strongly on the planetary wave (PW) phase. We focus on an 11-day case study in late January immediately following the 2009 sudden stratospheric warming during which regional-scale Lagrangian coherent structures (LCSs) formed atop the strengthening mesospheric vortex. The LCSs emerged over the north Atlantic in the vicinity of the trough of a 10-day westward traveling planetary wave. Over the next week, the LCSs acted to confine NO-rich air to polar latitudes, effectively prolonging its lifetime as it descended into the top of the polar vortex. Both a whole atmosphere data assimilation model and satellite observations show that the PW trough remained coincident in space and time with the NO-rich air as both migrated westward over the Canadian Arctic. Estimates of descent rates indicate five times stronger descent inside the PW trough compared to other longitudes. This case serves to set the stage for future climatological analysis of NO transport via LCSs.

The Wind-Chill Index.

This Lessons from History article about the wind-chill index (WCI) explores the historical polar and meteorologic literature relevant to the topic and presents unpublished work from 1939. Geographer Paul Siple (1908-1968) was a 6-time Antarctic explorer and scientist who invented and named the WCI in his doctoral dissertation at Clark University. Siple and Charles Passel (1915-2002) performed studies in Antarctica in 1940 that led to publication in 1945. This paper is often credited as the beginning of the WCI. Through years of critiques and revisions by others, these efforts evolved into the wind-chill equivalent temperatures (WCTs) used today. This essay explores the history, the science, and the overlooked originality, simplicity, and details of Siple's unpublished work. The remarkable similarity of the original chart to a current chart is shown by adapting and overlaying the 1939 WCI onto a current WCT chart with its times-to-frostbite data. The writings of Siple, Passel, and others provide an evocative supporting narrative to illustrate some of the problems of living in cold environmental conditions.

How Hospitals Can Save Lives and Themselves: Lessons on Patient Flow From the COVID-19 Pandemic.

COVID-19 has strained hospital capacity, detracted from patient care, and reduced hospital income. This article lays out a tested strategy that surgical and hospital leaders can use to overcome clinical and financial strain, emphasizing the experience at 2 leading North American medical centers. By classifying the time and resource needs of surgical patients and smoothing the flow of surgical admissions over all days of the week, hospitals can dramatically improve hospital efficiency, the quality of care and timely access to care for emergent and urgent surgeries. Through and beyond the time of COVID, smoothing the flow of surgical patients is a key means to restore hospital vitality and improve the care of all patients.

Impact of September 2019 Antarctic Sudden Stratospheric Warming on Mid-Latitude Ionosphere and Thermosphere Over North America and Europe.

Limited observational evidence indicates that ionospheric changes caused by Arctic sudden stratospheric warmings (SSWs) occur at middle latitudes in the Southern Hemisphere. However, it is not known if a similar interhemispheric linkage is produced by Antarctic SSWs. Here we examine thermospheric and ionospheric anomalies observed in September 2019 at middle latitudes in the Northern Hemisphere. We report persistent (at least 30 days) and strong (up to 80%-100%) positive anomalies in the daytime total electron content (TEC) and increases in the thermospheric O/N2 ratio in the western region of North America. However, central and eastern regions of North America experience moderate suppression of TEC reaching 20%-40% of the baseline. Different positive and negative anomalies are observed over the European sector. We hypothesize that regional differences in the TEC response could be related to modulation of thermospheric winds during SSWs, changes in thermospheric composition, and differences in declination angle.

A New MEPED-Based Precipitating Electron Data Set.

The work presented here introduces a new data set for inclusion of energetic electron precipitation (EEP) in climate model simulations. Measurements made by the medium energy proton and electron detector (MEPED) instruments onboard both the Polar Orbiting Environmental Satellites and the European Space Agency Meteorological Operational satellites are used to create global maps of precipitating electron fluxes. Unlike most previous data sets, the electron fluxes are computed using both the 0° and 90° MEPED detectors. Conversion of observed, broadband electron count rates to differential spectral fluxes uses a linear combination of analytical functions instead of a single function. Two dimensional maps of electron spectral flux are created using Delaunay triangulation to account for the relatively sparse nature of the MEPED sampling. This improves on previous studies that use a 1D interpolation over magnetic local time or L-shell zonal averaging of the MEPED data. A Whole Atmosphere Community Climate Model (WACCM) simulation of the southern hemisphere 2003 winter using the new precipitating electron data set is shown to agree more closely with observations of odd nitrogen than WACCM simulations using other MEPED-based electron data sets. Simulated EEP-induced odd nitrogen increases led to ozone losses of more than 15% in the polar stratosphere near 10 hPa in September of 2003.

Lower Thermospheric Material Transport via Lagrangian Coherent Structures.

We show that inter-model variation due to under-constraint by observations impacts the ability to predict material transport in the lower thermosphere. Lagrangian coherent structures (LCSs), indicating regions of maximal separation (or convergence) in a time-varying flow, are derived in the lower thermosphere from models for several space shuttle water vapor plume events. We find that inter-model differences in thermospheric transport manifest in LCSs in a way that is more stringent than mean wind analyses. LCSs defined using horizontal flow fields from the Specified Dynamics version of the Whole Atmosphere Community Climate Model with thermosphere-ionosphere eXtension (SD-WACCMX) at 109 km altitude are compared to Global Ultraviolet Imager (GUVI) observations of the space shuttle main engine plume. In one case, SD-WACCMX predicts an LCS ridge to produce spreading not found in the observations. LCSs and tracer transport from SD-WACCMX and from data assimilative WACCMX (WACCMX + DART) are compared to each other and to GUVI observations. Differences in the modeled LCSs and tracer positions appear between SD-WACCMX and WACCMX + DART despite the similarity of mean winds. WACCMX + DART produces better tracer transport results for a July 2006 event, but it is unclear which model performs better in terms of LCS ridges. For a February 2010 event, when mean winds differ by up to 50 m/s between the models, differences in LCSs and tracer trajectories are even more severe. Low-pass filtering the winds up to zonal wavenumber 6 reduces but does not eliminate inter-model LCS differences. Inter-model alignment of LCSs improves at a lower 60 km altitude.

The Death Zone: Lessons from History.

This Lessons from History article about the naming of the extreme altitude "Death Zone" explores the historical mountaineering and medical literature relevant to the topic. Swiss alpinist and radiologist Edouard Wyss-Dunant (1897-1983) authored several reports and books about expeditions to arctic regions, deserts, and the Himalaya. Encouraged by the success of a Swiss expedition to the Garhwal Himalaya in 1947, Wyss-Dunant joined his fellow climbers from Geneva on a 1949 expedition to several peaks in the Kanchenjunga region. Wyss-Dunant was then invited to lead the spring 1952 Swiss Everest expedition. Despite this being the first Swiss attempt on Everest and on an untried route, Raymond Lambert and Tenzing Norgay nearly summitted Everest from the Nepal side. Wyss-Dunant earned mountaineering immortality by coining the phrase the Death Zone during the expedition's foray into the upper regions of Everest. Wyss-Dunant went on to become a president of the Swiss Alpine Club and the International Climbing and Mountaineering Federation. His writings and that of others provide an evocative supporting narrative to illustrate some of the problems of living (or dying) at extreme altitude.