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The Unequal Ocean: Living with Environmental Change Along the Peruvian Coast by Maximilian Viatori (review)
No full textExtragalactic magnetar giant flare GRB 231115A: Insights from Fermi /GBM observations
Get PDFMagnetar giant flares (MGFs) are the extremely short, energetic transients originating from highly magnetized neutron stars. When observed in nearby galaxies, these rare events are nearly indistinguishable from cosmological short gamma-ray bursts. We present the analysis of GRB 231115A, a candidate extragalactic MGF observed by Fermi/GBM and localized by INTEGRAL to the starburst galaxy M82. This burst exhibits distinctive temporal and spectral characteristics, including a short duration and a high peak energy, consistent with known MGFs. Time-resolved analysis reveals rapid spectral evolution and a clear correlation between luminosity and spectral hardness, providing robust evidence of relativistic outflows. Archival Chandra data identified point sources within the GRB 231115A localization consistent with the theoretical maximum persistent emission luminosity, though no definitive counterpart was found. Simulations indicate that any transient emission associated with GRB 231115A would require energies exceeding those of typical magnetar bursts to be detectable by current instruments. While the tail of a MGF originating from outside of the Milky Way and its satellite galaxies has never been detected, analysis suggests that such emission could be observable at M82-s distance with instruments like Swift/XRT or NICER, though no tail was identified for this event. These findings underscore the need for improved follow-up strategies and technological advancements to enhance MGF detection and characterization
Spectroscopic Modeling of Luminous Transients Powered by H-rich and He-rich Circumstellar Interaction
Get PDFIn this study, we perform detailed spectroscopic modeling to analyze the interaction of circumstellar material (CSM) with ejecta in both hydrogen-rich and hydrogen-poor superluminous supernovae (SLSNe), by systematically varying properties such as the CSM density, composition, and geometry to explore their effects on spectral lines and light-curve evolution. Using advanced radiative transfer simulations with the new, open-source SuperLite code to generate synthetic spectra, we identify key spectroscopic indicators of CSM characteristics. Our findings demonstrate that spectral lines of hydrogen and helium exhibit significant variations due to differences in CSM mass and composition. In hydrogen-rich Type II SLSNe, we observe pronounced hydrogen emission lines that correlate strongly with a dense, extended CSM, suggesting massive, eruptive mass-loss histories. Conversely, in hydrogen-poor SLSNe, we recover mostly featureless spectra at early times, with weak hydrogen lines appearing only in the very early phases of the explosion, highlighting the quick ionization of traces of hydrogen present in the CSM. We analyze the properties of the resulting emission lines, particularly Hα and Hβ , for our models using sophisticated statistical methods. This analysis reveals how variations in the SN progenitor and CSM properties can lead to distinct spectroscopic evolutions over time. These temporal changes provide crucial insights into the underlying physics driving the explosion and the subsequent interaction with the CSM. By linking these spectroscopic observations to the initial properties of the progenitor and its surrounding material, our study offers a useful tool for probing the pre-explosion histories of these explosive events
Nuclear β -decay half-life predictions and r -process nucleosynthesis using machine learning models
No full textThis study investigates the predictive capabilities of machine learning models in nuclear β-decay half-life predictions and their application to r-process nucleosynthesis. The research explores the intricacies of statistical modeling using support vector machines (SVM), focusing on understanding the learning and prediction of various nuclear configurations and features that influence β-decay half-lives. By considering a comprehensive dataset spanning from light to heavy mass nuclei, the SVM demonstrates remarkable accuracy in reproducing experimentally known half-lives across diverse nuclear structures. Evaluations reveal the effectiveness of this model across different nuclear classes, with notable improvements observed in even-even nuclei predictions. Furthermore, this study demonstrates the extrapolative capabilities of SVM predictions in solar r-process nucleosynthesis, emphasizing its ability to accurately predict r-process abundances. The SVM model, particularly when utilizing the radial basis function kernel, exhibits strong agreement with experimental data, providing valuable insights into the behavior of highly neutron-rich nuclei. These findings underscore the significance of machine learning as a powerful tool in nuclear physics research, offering promising avenues for advancing our understanding of β-decay processes and r-process nucleosynthesis
HWO Target Stars and Systems: A Prioritized Community List of Potential Stellar Targets for the Habitable Worlds Observatory’s ExoEarth Survey
No full textThe HWO Target Stars and Systems 2025 (TSS25) list is a community-developed catalog of potential stellar targets for the Habitable Worlds Observatory (HWO) in its survey to directly image Earth-sized planets in the habitable zone. The TSS25 list categorizes potential HWO targets into priority tiers based on their likelihood to be surveyed and the necessity of obtaining observations of their stellar properties prior to the launch of the mission. This target list builds upon previous efforts to identify direct imaging targets and incorporates the results of multiple yield calculations assessing the science return of current design concepts for HWO. The TSS25 list identifies a sample of target stars that have a high probability to be observed by HWO (Tiers 1 and 2), independent of assumptions about the mission’s final architecture. These stars should be the focus of community precursor science efforts in order to mitigate risks and maximize the science output of HWO. This target list is publicly available and is a living catalog that will be continually updated leading up to the mission
Navigating New Technology: A Phenomenological Study into Technology Coaches’ Experiences During AI Expansion in Schools
Get PDFArtificial intelligence (AI) is rapidly influencing instructional practices in K–12 education, yet most states have not issued clear, binding policies to guide its integration. As a result, local school systems and support staff must interpret emerging guidance and determine how AI should be used in classrooms. This study examined how system-level technology coaches in the Deep South experience and support AI adoption in contexts where state guidance is advisory rather than mandatory. This qualitative phenomenological study used questionnaires and semi-structured interviews with technology coaches, and a content analysis of AI-related state and local policy guidance. Participants included technology coaches who serve as intermediaries between evolving policy and classroom practice. Data was analyzed through multi-phase coding and thematic analysis grounded in phenomenology and the social constructivism framework.
Findings revealed four major themes shaping AI integration in schools. First, a gap persists between policy visions of personalization and innovation and teachers’ practical use of AI, which primarily focuses on efficiency tasks such as lesson planning and email communication. Second, governance and data security dominate policy guidance, but teachers receive limited training in privacy and ethical use of data. Third, capacity building is strained as the demand for AI-related professional development outpaces available resources and the technology coaches’ ability to stay current. Finally, concerns about academic integrity and inconsistent local policies create uneven implementation and confusion for teachers and students. Overall, the study illuminates the central role of technology coaches in bridging the gap between policy and practice, while underscoring the need for more transparent governance, stronger professional development, and consistent expectations for AI use in K–12 schools
Energy-Efficient Photocatalysis: Toward Practical Degradation of Waterborne Pollutants
No full textFreshwater scarcity poses a growing threat to human welfare and society, with 4 billion people experiencing severe shortages at least one month of the year and half a billion affected year-round. Rising demand from population growth and development combined with the impacts of climate change on water supplies further intensifies this crisis, underscoring the need for improved water reclamation and treatment technologies. Photocatalytic advanced oxidation processes have great potential for chemical-free, energy-efficient degradation of waterborne pollutants, provided long-standing issues including poor light management, mass transfer limitations, and high charge carrier recombination rates are addressed.
Here, we report the development of a dual-porous titanium dioxide photocatalyst designed to overcome these challenges. The immobilized catalyst achieves a surface area-to-volume ratio of 940,000 m2/m3—surpassing even suspension-based systems—which enhances mass transport while eliminating the need for a filtration step. The use of a UV-transparent quartz fiber support further improves performance by preventing parasitic photon absorption.
This photocatalytic system enables efficient degradation of diverse pollutant classes, including dyes, chlorohydrocarbons, alcohols, viral contaminants, and hydrogen sulfide (H2S). For organic pollutants, electrical energy per order (EEO) values remain within the practical benchmark of less than 10 kWh/m3. Viral contamination undergoes a 2-log reduction in a single pass with an EEO of 0.1 kWh/m3. H2S removal is particularly efficient due to the autocatalytic effect of the oxidation product, sulfate. The presence of sulfate improves charge carrier separation, giving an EEO for H2S oxidation of 0.1 kWh/m3 and a photonic efficiency of over 30% under kinetically-limited conditions. Finally, we present preliminary in situ XANES spectroscopic evidence of the photocatalytic reduction of hexavalent chromium to trivalent chromium, highlighting the system’s versatility for treating a broad range of contaminants
Macroevolutionary Insights into Plant Radiations in the Tropical Andes from the High-Elevation Genus Brachyotum
No full textBiodiversity on Earth is unevenly distributed, where mountains sustain most plant and animal life. The fauna and flora in these regions comprise a combination of ancient lineages and recently diverged species, with specific mountains having different amounts of each. With a high concentration of vascular plants in a small area, the Tropical Andes is the most biodiverse region globally. Similarly, its flora is the most species- rich, with about half of the species restricted to these mountains. The origin of this plant community has several components of in situ evolutionary radiations, which also happen to be recent. With the advance of high-throughput DNA sequencing technologies, and computational tools to process large data sets, it opens a new avenue to understanding the origin of this rich flora. By integrating molecular, phenotypic and distributional data with model-based inference, this dissertation aims to understand what has driven the geographically uneven, rapid and recent radiation of plants—particularly at higher elevations. I used the genus Brachyotum, whose 55 species only occur along the Tropical Andes, and are distinguished by their tubular-shaped flowers that produce nectar. In addition, I compared patterns of conflicting evolutionary histories across different plant taxa in the Tropical Andes along an elevational gradient. This study heavily relied on fieldwork, scientific collections, publicly available data, and collaborations to investigate the origin of species in the core of the Neotropics
The Impact of Outdoor Youth Education: An Examination of the Social, Personal, and Environmental Developmental Outcomes Experienced by Youth at a Residential 4-H Summer Camp
Get PDFOne of the most innovative ways that 4-H has fostered agricultural innovation and hands-on, experiential education has been through the development of youth outdoor education programs, more commonly known as 4-H Camp. State 4-H Camps and national camping events, including the inaugural National 4-H Conference, emerged following the establishment of localized county club camps. Three years after establishing the first 4-H Camp, more than 1,700 had emerged across the U.S., with early attendance exceeding 100,000 youth participants.
As a direct result of these early successes, the 4-H Camping movement has become celebrated as a novel technique to motivate youth to engage in agrarian concepts. Twenty first century demands, combined with the modernization of 4-H, has now evolved the outdoor education learning model to incorporate many additional concepts including a focus on STEM education, fostering creative arts among participants, and often integrating a robust environmental educational component. Although the 4-H camping program is now over 100 years old, little evidence has been documented regarding the educational value of learning experiences in the unique residential summer camp context. Therefore, a need emerged to describe the unique factors that contribute to the learning outcomes of participating youth campers.
The primary purpose of this ex post-facto quasi-experimental study was to examine the outcomes experienced by Louisiana 4-H youth, grades four to six, regarding their experience after attending a four-day residential summer camp program. Through our analysis of post-program survey data, this study supported previous findings that campers attending an overnight youth summer camp program experience significant social and personal developmental outcomes, with female campers reporting significantly higher scores on the American Camp Association’s Camper Learning Scale (CLS) than male campers. Additionally, campers participating in an environmental education (EE) based youth outdoor education program during camp reported significant pro-environmental orientations following their camp experience, with male campers reporting significantly higher scores on the post-program Children’s Environmental Perceptions Scale (CEPS) when compared to female campers participating in the same program.
A key implication from this investigation was the need for intentionally designed socialization, reflection, and team-building activities during camp to improve camp-related youth outcomes. Future research should focus on further analyzing factors influencing camp-related social, personal, and environmental outcomes among youth participants, especially in terms of seeking a deeper understanding of gender-based differences explored in this study
Thermal Noise Measurement Below the Standard Quantum Limit
Get PDFQuantum mechanics places sensitivity restrictions on physical measurements. These limitations manifest themselves in interferometric force and displacement measurements as uncertainty both in the photon number measured at a photodetector (shot noise), and in the quantum radiation pressure applied to the interferometer (quantum back action noise manifested as quantum radiation pressure noise). The balance between shot noise and quantum radiation pressure noise imposes the Standard Quantum Limit (SQL). A large body of work has been dedicated to measuring these quantum effects and mitigating them. Owing to the inherently small scale at which quantum effects are visible, classical effects must be subverted before these quantum effects are studied. One formidable source of noise, present in any system, is thermal noise.
The central goal of the work presented in this thesis is to measure the thermal noise contribution from a GaAs/AlGaAs micro-mirror suspended on a GaAs cantilever microresonator when brought to a cryogenic temperature ∼ 25 K. These materials exhibit an intrinsically low mechanical loss which results in a small contribution of thermal noise and high reflectivity allowing for a high finesse when used to form one end of an op tomechanical Fabry–Pérot cavity. In this configuration, the cantilever mirror enabled the observation of optomechanically generated squeezed light at room temperature [1], the observation of quantum back-action (QBA) in the audio band [2], a demonstration that this QBA noise is reduced via squeezed light injection [3] and that it can be suppressed when operating a detuned optomechanical (OM) cavity [4]. Finally, the low thermal noise allowed for a measurement of sensitivities falling below the free mass SQL [5]. All these demonstrations were aimed towards improving ground based interferometric gravitational wave detectors (LIGO, Virgo, KAGRA). Our motivation to study the thermal noise produced by the GaAs/AlGaAs cantilever mirror is also, in part, to improve gravitational wave detectors. Because of the low mechanical loss, and corresponding low thermal noise contribution of the coating, combined with its high reflectivity, an effort to implement GaAs/AlGaAs crystalline mirror coatings into gravitational wave detectors is currently underway [6].
While reducing thermal noise to a level that allows these measurements is a noteworthy accomplishment, it produces an interesting quandary: how to characterize the thermal noise at this level while removing the contribution from quantum noise. This thesis explores a quantum correlation measurement which removes shot noise, and a backaction evasion technique which utilizes the optical spring effect to mitigate quantum radiation pressure noise, comparing this technique to more conventional approaches to limiting quantum back-action noise. The result of this investigation is twofold: a measurement of thermal noise falling 5 dB below the SQL, and in turn a measurement of quantum noise, free from thermal noise, which falls 10 dB below the SQL