Lowland boreal forest ecosystems in Alaska are dominated by wetlands comprised of a complex mosaic of fens, collapse‐scar bogs, low shrub/scrub, and forests growing on elevated ice‐rich permafrost ...soils. Thermokarst has affected the lowlands of the Tanana Flats in central Alaska for centuries, as thawing permafrost collapses forests that transition to wetlands. Located within the discontinuous permafrost zone, this region has significantly warmed over the past half‐century, and much of these carbon‐rich permafrost soils are now within ~0.5 °C of thawing. Increased permafrost thaw in lowland boreal forests in response to warming may have consequences for the climate system. This study evaluates the trajectories and potential drivers of 60 years of forest change in a landscape subjected to permafrost thaw in unburned dominant forest types (paper birch and black spruce) associated with location on elevated permafrost plateau and across multiple time periods (1949, 1978, 1986, 1998, and 2009) using historical and contemporary aerial and satellite images for change detection. We developed (i) a deterministic statistical model to evaluate the potential climatic controls on forest change using gradient boosting and regression tree analysis, and (ii) a 30 × 30 m land cover map of the Tanana Flats to estimate the potential landscape‐level losses of forest area due to thermokarst from 1949 to 2009. Over the 60‐year period, we observed a nonlinear loss of birch forests and a relatively continuous gain of spruce forest associated with thermokarst and forest succession, while gradient boosting/regression tree models identify precipitation and forest fragmentation as the primary factors controlling birch and spruce forest change, respectively. Between 1950 and 2009, landscape‐level analysis estimates a transition of ~15 km² or ~7% of birch forests to wetlands, where the greatest change followed warm periods. This work highlights that the vulnerability and resilience of lowland ice‐rich permafrost ecosystems to climate changes depend on forest type.
Abstract Body size overestimation is a fundamental feature in anorexia nervosa (AN). The extent or even existence of body size overestimation in AN is controversial. The most recent review ( Farrell ...et al., 2005 ) found that only half the studies reported overestimation of body size in individuals diagnosed with AN. The remaining studies found no overestimation or in some instances underestimation. The discrepancy in these findings has been attributed to the wide variety of assessment techniques that are used, including many with questionable psychometric properties. We review all 9 contemporary studies conducted in this area since the last review in 2005. For each study we describe the number of participants, methodology, reliability/validity data, amount of whole body distortion, effect sizes, and a summary of findings. In all studies that included a healthy control group, individuals with AN overestimated their whole body size more than healthy controls did. The difference was significant in all except two studies. Based on these contemporary findings, we conclude that individuals with AN overestimate their body size and that the greater consistency of findings in the studies conducted over the last decade is attributable to the use of improved methodologies and assessment tools with documented psychometric properties.
Widespread degradation of ice wedges has been observed during the last decades in numerous areas within the continuous permafrost zone of Eurasia and North America. To study ice-wedge degradation, we ...performed field investigations at Prudhoe Bay and Barrow in northern Alaska during 2011–2016. In each study area, a 250-m transect was established with plots representing different stages of ice-wedge degradation/stabilization. Field work included surveying ground- and water-surface elevations, thaw-depth measurements, permafrost coring, vegetation sampling, and ground-based LiDAR scanning. We described cryostratigraphy of frozen soils and stable isotope composition, analyzed environmental characteristics associated with ice-wedge degradation and stabilization, evaluated the vulnerability and resilience of ice wedges to climate change and disturbances, and developed new conceptual models of ice-wedge dynamics that identify the main factors affecting ice-wedge degradation and stabilization and the main stages of this quasi-cyclic process. We found significant differences in the patterns of ice-wedge degradation and stabilization between the two areas, and the patterns were more complex than those previously described because of the interactions of changing topography, water redistribution, and vegetation/soil responses that can interrupt or reinforce degradation. Degradation of ice wedges is usually triggered by an increase in the active-layer thickness during exceptionally warm and wet summers or as a result of flooding or disturbance. Vulnerability of ice wedges to thermokarst is controlled by the thickness of the intermediate layer of the upper permafrost, which overlies ice wedges and protects them from thawing. In the continuous permafrost zone, degradation of ice wedges rarely leads to their complete melting; and in most cases wedges eventually stabilize and can then resume growing, indicating a somewhat cyclic and reversible process. Stabilization of ice wedges after their partial degradation makes them better protected than before degradation because the intermediate layer is usually 2 to 3 times thicker on top of stabilized ice wedges than on top of initial ice wedges in undisturbed conditions. As a result, the likelihood of formation of large thaw lakes in the continuous permafrost zone triggered by ice-wedge degradation alone is very low.
•Ice-wedge degradation in the continuous permafrost zone is a reversible process.•Degradation and stabilization patterns are more complex than previously described.•Vulnerability of ice wedges is controlled by thickness of the intermediate layer.•Stabilization of ice wedges after partial degradation lowers risk of thermokarst.•Likelihood of formation of large thaw lakes due to ice-wedge degradation is low.
The facial feedback hypothesis suggests that an individual's facial expressions can influence their emotional experience (e.g., that smiling can make one feel happier). However, a reoccurring concern ...is that supposed facial feedback effects are merely methodological artifacts. Six experiments conducted across 29 countries (N = 995) examined the extent to which the effects of posed facial expressions on emotion reports were moderated by (a) the hypothesis communicated to participants (i.e., demand characteristics) and (b) participants' beliefs about facial feedback effects. Results indicated that these methodological artifacts moderated, but did not fully account for, the effects of posed facial expressions on emotion reports. Even when participants were explicitly told or personally believed that facial poses do not influence emotions, they still exhibited facial feedback effects. These results indicate that facial feedback effects are not solely driven by demand or placebo effects.
People who travel on ice-covered rivers to access traditional lands and resources can be profoundly impacted by effects of climate change on river ice seasonality. We used remote sensing, bolstered ...by citizen science, to assess trends and geospatial patterns of the ice cover in the Copper River Basin of Southcentral Alaska. Our analysis of Landsat imagery from water years (WYs) 1973 to 2021 suggests a severely diminishing season of river ice travel (delayed or incomplete freezeup, early breakup) due to increasing air temperatures. The weekly probability of an adequate ice cover for river crossings declined by an average of 53 percentage points. Ice extent was closely related to accumulated freezing degree days (AFDD). AFDDOct-Apr decreased by 15% since WY 1943, a significant warming trend. We mapped the spatiotemporal variation of ice and open water extent with multispectral and synthetic aperture radar (SAR) imagery (Sentinel-2, Sentinel-1). We identified reaches with more reliable opportunities for winter access and others susceptible to extensive open water, differences related to flow energy and channel form. The results of this study can support local decision making and adaptation in response to rapidly changing river ice conditions, and our approach can be applied elsewhere to document change and improve travel safety.
Remediation is a required component of pharmacy programs. In a pharmacy calculations course, two student-centered models of remediation have been utilized. These models were a shift from an ...intensive, hands-on infrastructure of faculty and student engagement to a more student self-directed process. The models utilized development of an individualized plan for each student, clearly outlined expectations, faculty availability for consultation, as well as flexibility in remote completion of the assigned activities. Both models resulted in student success.
Article Type: Note
Concussion literature and treatment guidelines are inconclusive regarding the role of sex in symptom reporting at baseline and post-concussion. Although empirical evidence is lacking, it is generally ...regarded that females have a more severe symptomatic presentation than males at all time-points on the concussion spectrum.
Our objective was to determine whether differences exist between males and females at baseline (pre-season/before concussion) or post-concussion for self-reported (1) prevalence of individual symptoms and (2) total symptom scores in high school and college athletes.
Systematic review and meta-analysis of observational cohort studies; level of evidence, 1.
A computerized search of the PubMed, SPORTDiscus, CINAHL, and Scopus databases was performed. Meta-analysis Of Observational Studies in Epidemiology (MOOSE) guidelines were followed. Criteria for inclusion were (1) self-report of symptoms at any time within the concussion spectrum, including baseline and after concussion, (2) study sample included high school and/or collegiate athletes aged 12-26 years, (3) concussions occurred during participation in sport, and (4) symptom reporting was separated by sex. The Quality Assessment Tool for Cohort Studies, Q-Coh, was utilized for quality assessment.
Twenty-one studies met the criteria for inclusion: seventeen had good quality and four, acceptable quality. At baseline, females had significantly higher odds than males of reporting the individual symptoms of vision/hearing problems, headache/migraine, difficulty concentrating, energy/sleep disturbances, and emotional disturbances. Post-concussion, only one symptom demonstrated significant differences between males and females, with females demonstrating lower odds of reporting confusion than males. Statistically, at baseline and post-concussion, females had significantly higher total symptom scores on the Post-Concussion Scale (PCS) and the Sport Concussion Assessment Tool 2 (SCAT2), but when the standard mean difference was interpreted after back-transformation, these results were clinically insignificant.
The symptomatic presentation of males and females, most notably the prevalence of specific symptoms, is very divergent. Females had higher total symptom scores at baseline and post-concussion, however, clinically this cannot be interpreted as a meaningful difference. It is possible that these differences can be explained by normal hormonal changes associated with the menstrual cycle. The implications of these findings are that symptomatic presentation during an individual female's menstrual cycle needs to be taken into consideration post-concussion when making return-to-play decisions, as returning to a completely asymptomatic level may not be a reasonable expectation.
PDF
