Using News Abstracts to Represent News Agendas

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Aerosolized Silver Nanoparticles in the Rat Lung and Pulmonary Responses over Time

Silver nanoparticle (Ag NP) production methods are being developed and refined to produce more uniform Ag NPs through chemical reactions involving silver salt solutions, solvents, and capping agents to control particle formation. These chemical reactants are often present as contaminants and/or coatings on the Ag NPs, which could alter their interactions in vivo. To determine pulmonary effects of citrate-coated Ag NPs, Sprague-Dawley rats were exposed once nose-only to aerosolized Ag NPs (20 nm [C20] or 110 nm [C110] Ag NPs) for six hours. Bronchoalveolar lavage fluid (BALF) and lung tissues were obtained at 1, 7, 21, and 56 days post exposure for analyses. Inhalation of Ag NPs, versus citrate buffer control, produced significant inflammatory and cytotoxic responses that were measured in BALF cells and supernatant. At Day 7, total cells, protein, and lactate dehydrogenase were significantly elevated in BALF, and peak histopathology was noted after C20 or C110 exposure versus control. At Day 21, BALF PMNs and tissue inflammation was significantly greater after C20 versus C110 exposure. By Day 56, inflammation was resolved in Ag NP-exposed animals. Overall, results suggest delayed, short-lived inflammatory and cytotoxic effects following C20 or C110 inhalation and potential for greater responses following C20 exposure

Coronal Heating as Determined by the Solar Flare Frequency Distribution Obtained by Aggregating Case Studies

Flare frequency distributions represent a key approach to addressing one of the largest problems in solar and stellar physics: determining the mechanism that counter-intuitively heats coronae to temperatures that are orders of magnitude hotter than the corresponding photospheres. It is widely accepted that the magnetic field is responsible for the heating, but there are two competing mechanisms that could explain it: nanoflares or Alfv\'en waves. To date, neither can be directly observed. Nanoflares are, by definition, extremely small, but their aggregate energy release could represent a substantial heating mechanism, presuming they are sufficiently abundant. One way to test this presumption is via the flare frequency distribution, which describes how often flares of various energies occur. If the slope of the power law fitting the flare frequency distribution is above a critical threshold, $\alpha=2$ as established in prior literature, then there should be a sufficient abundance of nanoflares to explain coronal heating. We performed $>$600 case studies of solar flares, made possible by an unprecedented number of data analysts via three semesters of an undergraduate physics laboratory course. This allowed us to include two crucial, but nontrivial, analysis methods: pre-flare baseline subtraction and computation of the flare energy, which requires determining flare start and stop times. We aggregated the results of these analyses into a statistical study to determine that $\alpha = 1.63 \pm 0.03$. This is below the critical threshold, suggesting that Alfv\'en waves are an important driver of coronal heating.Comment: 1,002 authors, 14 pages, 4 figures, 3 tables, published by The Astrophysical Journal on 2023-05-09, volume 948, page 7