Search for: All records

The evolution of protoplanetary disks in regions with massive OB stars is influenced by externally driven winds that deplete the outer parts of these disks. The winds have previously been studied via forbidden oxygen emission lines, which also arise in isolated disks in low-mass star-forming regions (SFRs) with weak external UV fields in photoevaporative or magnetic (internal) disk winds. It is crucial to determine how to disentangle external winds from internal ones. Here, we report a proxy for unambiguously identifying externally driven winds with a forbidden line of neutral atomic carbon, [CI] 8727 Å. We compare for the first time the spatial location of the emission in the [OI] 5577 Å, [OI] 6300 Å, and [CI] 8727 Å lines traced by VLT/MUSE-NFM with the ALMA Band 7 continuum disk emission in a sample of 12 proplyds in the Orion Nebula Cluster (ONC). We confirm that the [OI] 5577 Å emission is co-spatial with the disk emission, whereas that of [OI] 6300 Å is emitted both on the disk surface and on the ionization front of the proplyds. We show for the first time that the [CI] 8727 Å line is also co-spatial with the disk surface in proplyds, as seen in the MUSE and ALMA data comparison. The peak emission is compatible with the stellar location in all cases, apart from one target with high relative inclination with respect to the ionizing radiation, where the peak emission is located at the disk edge in the direction of the ionizing radiation. To verify whether the [CI] 8727 Å line is detected in regions where external photoevaporation is not expected, we examined VLT/X-Shooter spectra for young stars in low-mass SFRs. Although the [OI] 5577 Å and 6300 Å lines are well detected in all these targets, the total detection rate is ≪10% in the case of the [CI] 8727 Å line. This number increases substantially to a ∼40% detection rate inσ-Orionis, a region with higher UV radiation than in low-mass SFRs, but lower than in the ONC. The spatial location of the [CI] 8727 Å line emission and the lack of its detection in isolated disks in low-mass SFRs strongly suggest that this line is a tell-tale tracer of externally driven photoevaporative winds, which agrees with recent excitation models. 

Illicit gold flows constitute a major development challenge for governments and a social responsibility challenge for the jewellery industry, which accounts for the majority of global gold demand. This paper highlights aspects of gold supply chains that lack transparency and may indicate junctures where illicit activities are taking place, resulting in a loss of tax and customs revenues. Using Peru and Kenya as case study countries, we draw from United Nations Comtrade data and qualitative data from field research to examine the magnitude of the gold trade, the forms in which gold is traded, and key trade partners for each country. We suggest that midstream portions of gold supply chains should be given more attention, certain types of gold exports and imports present greater traceability challenges than others, and some countries play a much more significant role in the global jewellery trade. We propose areas where further investigations may be warranted to ensure more transparent and responsible gold supply chains. 

Abstract Entender las respuestas de la población a perturbaciones ambientales, específicamente a pulsadas individuales, es esencial para la conservación y la gestión adaptativa. Las poblaciones de interés pueden reducirse a niveles bajas debido a la perturbación, y es necesario entender las diferencias interespecíficas en las trayectorias de recuperación para evaluar las opciones de gestión. Analizamos modelos para especies individuales para investigar los factores demográficos y de gestión que determinan los dos componentes de la ‘resiliencia’ de la población: la magnitud del impacto inicial sobre la abundancia de la población y la duración del tiempo de recuperación. Simulamos poblaciones estructuradas por edad con reclutamiento que depende de la densidad, las sometimos a una perturbación pulsada que consiste en un período de mayor mortalidad del grupo etário juvenil o de todos los grupos etários, y calculamos tanto el impacto como el tiempo de retorno. A modo de ilustración, utilizamos parámetros demográficos de un conjunto de 16 especies de peces. Formulamos el modelo como una ecuación de renovación, lo que nos permite describir matemáticamente los impactos de las perturbaciones como una convolución. También incluimos dinámicas no lineales que representan poblaciones que se recuperan hacia un estado estable; esto es más realista (en la mayoría de los casos) que los análisis previos de resiliencia en modelos lineales sin la dependencia de la densidad. Cuando la perturbación ha afectado a uno o a algunos pocos grupos etários jóvenes, la longevidad fue el principal determinante de la historia de vida del impacto y el tiempo de recuperación. Las especies de vida más corta sufrieron mayores impactos cuando fueron perturbadas porque cada grupo etáreo representa una mayor proporción de la población. Sin embargo, las especies con vidas más cortas también tuvieron tiempos de recuperación más rápidos, por la misma razón. Cuando la perturbación afectó a los grupos etários adultos, el impacto fue más inmediato y ya no se vio afectado por la longevidad de las especies, aunque se mantuvo el efecto de la longevidad sobre el tiempo de recuperación. Estos resultados mejoran nuestra comprensión de las diferencias interespecíficas de la resiliencia y aumentan nuestra capacidad para hacer predicciones con fin a la gestión adaptativa. Además, formular el problema como una ecuación de renovación y usar convoluciones matemáticas nos permite cuantificar cómo las perturbaciones con distintos lapsos de tiempo (no solo un nivel de perturbación constante e inmediato, sino niveles de perturbación que aumentan o disminuyen gradualmente) tendrían diferentes efectos sobre la resiliencia de la población: respuestas tardías para especies en las que la biomasa se concentra en grupos etários de mayor edad y para perturbaciones que se vuelven progresivamente más severas. 

Abstract Environmental pathogen reservoirs exist for many globally important diseases and can fuel epidemics, influence pathogen evolution, and increase the threat of host extinction. Species composition can be an important factor that shapes reservoir dynamics and ultimately determines the outcome of a disease outbreak. However, disease‐induced mortality can change species communities, indicating that species responsible for environmental reservoir maintenance may change over time. Here we examine the reservoir dynamics ofPseudogymnoascus destructans, the fungal pathogen that causes white‐nose syndrome in bats. We quantified changes in pathogen shedding, infection prevalence and intensity, host abundance, and the subsequent propagule pressure imposed by each species over time. We find that highly shedding species are important during pathogen invasion, but contribute less over time to environmental contamination as they also suffer the greatest declines. Less infected species remain more abundant, resulting in equivalent or higher propagule pressure. More broadly, we demonstrate that high infection intensity and subsequent mortality during disease progression can reduce the contributions of high‐shedding species to long‐term pathogen maintenance. 

Understanding host persistence with emerging pathogens is essential for conserving populations. Hosts may initially survive pathogen invasions through pre-adaptive mechanisms. However, whether pre-adaptive traits are directionally selected to increase in frequency depends on the heritability and environmental dependence of the trait and the costs of trait maintenance. Body condition is likely an important pre-adaptive mechanism aiding in host survival, although can be seasonally variable in wildlife hosts. We used data collected over 7 years on bat body mass, infection and survival to determine the role of host body condition during the invasion and establishment of the emerging disease, white-nose syndrome. We found that when the pathogen first invaded, bats with higher body mass were more likely to survive, but this effect dissipated following the initial epizootic. We also found that heavier bats lost more weight overwinter, but fat loss depended on infection severity. Lastly, we found mixed support that bat mass increased in the population after pathogen arrival; high annual plasticity in individual bat masses may have reduced the potential for directional selection. Overall, our results suggest that some factors that contribute to host survival during pathogen invasion may diminish over time and are potentially replaced by other host adaptations. 

This paper details a poster presented in the National Science Foundation (NSF) Grantees Poster Session for the 2022 ASEE Annual Conference. The study, aptly titled, aims to examine the ‘Long-Term Effect of Involvement in Humanitarian Engineering Projects on Student Professional Formation and Views of Diversity, Equity, and Inclusion (DEI).’ As part of the larger study, this poster details the results from alumni (n=19) of the Lipscomb University engineering program collected through an open-ended questionnaire. The research team performed an inductive coding analysis of the qualitative data to understand the connections between humanitarian engineering projects, professional formation, and views of DEI. Quantitative results as well as data from other participant groups, including current students and non-alumni engineering professionals, will be presented elsewhere. Emergent codes showed that participants found both outward and inward value in serving others. Outward value reflected a better quality of life for the person benefiting from service while inward value provided personal satisfaction, learning, or growth for the participant. This inward value was also evident with respect to views of DEI where participants mentioned learning or growing from past events. Two participants directly mentioned a connection between their experiences with humanitarian engineering projects and their views of DEI. Additionally, the codes connected to existing literature in engineering education as well as theories like empathy, identity development, and emotional intelligence. These results are promising for this study and will be expanded upon through interviews where these connections will be examined at a deeper level.