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1. Statistics of BY Draconis chromospheric variable stars

   https://doi.org/10.1093/mnras/stac1660  

   Chahal, Deepak ; de Grijs, Richard ; Kamath, Devika ; Chen, Xiaodian ( June 2022 , Monthly Notices of the Royal Astronomical Society)

   We present an extensive catalogue of BY Draconis (BY Dra)-type variables and their stellar parameters. BY Dra are main-sequence FGKM-type stars. They exhibit inhomogeneous starspots and bright faculae in their photospheres. These features are caused by stellar magnetic fields, which are carried along with the stellar disc through rotation and which produce gradual modulations in their light curves (LCs). Our main objective is to characterize the properties of BY Dra variables over a wide range of stellar masses, temperatures, and rotation periods. A recent study categorized 84 697 BY Dra variables from Data Release 2 of the Zwicky Transient Facility based on their LCs. We have collected additional photometric data from multiple surveys and performed broad-band spectral energy distribution fits to estimate stellar parameters. We found that more than half of our sample objects are of K spectral type, covering an extensive range of stellar parameters in the low-mass regime (0.1–1.3 M⊙). Compared with previous studies, most of the sources in our catalogue are rapid rotators, and so most of them must be young stars for which a spin-down has not yet occurred. We subdivided our catalogue based on convection zone depth and found that the photospheric activity index, Sph, is lower for higher effective temperatures, i.e. for thinner convective envelopes. We observe a broad range of photospheric magnetic activity for different spectral classes owing to the presence of stellar populations of different ages. We found a higher magnetically active fraction for K- than M-type stars.

    

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2. Light Microscopy Outreach as an Introduction to Scientific Concepts for Students in Under-Resourced Schools Across the Globe

   Endow, Sharyn A. ; Paul, Umika S. ( January 2020 , Microscopy and microanalysis)

   Light microscopy provides a window into another world that is not visible to the unaided eye. Because of this and its importance in biological discoveries, the light microscope is an essential tool for scientific studies. It can also be used with a variety of easily obtained specimens to provide dramatic demonstrations of previously unknown features of common plants and animals. Thus, one way to interest young people in science is to start with an introduction to light microscopy. This is an especially effective strategy for individuals who attend less advantaged or under-resourced schools, as they may not have been previously exposed to scientific concepts in their classes. However, introducing light microscopy lessons in the classroom can be challenging because of the high cost of light microscopes, even those that are relatively basic, in addition to their usual large size. Efforts are underway by our laboratory in collaboration with the Biophysical Society (BPS) to introduce young people to light microscopy using small, easy-to-assemble wooden microscopes developed by Echo Laboratories. The microscopes are available online as low-cost kits ($10 each with shipping), each consisting of 19 parts printed onto an 81⁄2 x 11 inch sheet of light-weight wood (Fig. 1). After punching out the pieces, they can be assembled into a microscope with a moveable stage and a low-power lens, also provided in the kit (Fig. 2). Photos taken with a cell phone through the microscope lens can give magnifications of ~16-18x, or higher. At these magnifications, features of specimens that are not visible to the unaided eye can be easily observed, e.g., small hairs on the margins of leaves or lichens [1]. As a member of the BPS Education Committee, one of us (SAE) wrote a Lesson Plan on Light Microscopy specifically for use with the wooden microscopes. SAE was also able to obtain a gift of 500 wooden microscope kits for the BPS from Echo Laboratories and Chroma Technology Corp in 2016. The wooden microscope kits, together with the lesson plan, have provided the materials for our present outreach efforts. Rather than giving out the wooden microscope kits to individuals, the BPS asked the Education Committee to maximize the impact of the gift by distributing the microscopes with the Lesson Plan on Light Microscopy to teachers, e.g., through teachers’ workshops or outreach sessions. This strategy was devised to enable the Society to reach a larger number of young people than by giving the microscopes to individuals. The Education Committee first evaluated the microscopes as a tool to introduce students to scientific concepts by providing microscopes to a BPS member at the National University of Colombia who conducted a workshop on Sept 19-24, 2016 in Tumaco, Columbia. During the workshop, which involved 120 high school girls and 80 minority students, including Afro-Colombian and older students, the students built the wooden microscopes and examined specimens, and compared the microscopes to a conventional light microscope. Assembling the wooden microscopes was found to be a useful procedure that was similar to a scientific protocol, and encouraged young girls and older students to participate in science. This was especially promising in Colombia, where there are few women in science and little effort to increase women in STEM fields. Another area of outreach emerged recently when one of us, USP, an undergraduate student at Duke University, who was taught by SAE how to assemble the wooden microscopes and how to use the lesson plan, took three wooden microscopes on a visit to her family in Bangalore, India in summer 2018 [2]. There she organized and led three sessions in state run, under-resourced government schools, involving classes of ~25-40 students each. This was very successful – the students enjoyed learning about the microscopes and building them, and the science teachers were interested in expanding the sessions to other government schools. USP taught the teachers how to assemble and use the microscopes and gave the teachers the microscopes and lesson plan, which is also available to the public at the BPS web site. She also met with a founder of the organization, Whitefield Rising, which is working to improve teaching in government schools, and taught her and several volunteers how to assemble the microscopes and conduct the sessions. The Whitefield Rising members have been able to conduct nine further sessions in Bangalore over the past ~18 months (Fig. 3), using microscope kits provided to them by the BPS. USP has continued to work with members of the Whitefield Rising group during her summer and winter breaks on visits to Bangalore. Recently she has been working with another volunteer group that has expanded the outreach efforts to New Delhi. The light microscopy outreach that our laboratory is conducting in India in collaboration with the BPS is having a positive impact because we have been able to develop a partnership with volunteers in Bangalore and New Delhi. The overall goal is to enhance science education globally, especially in less advantaged schools, by providing a low-cost microscope that can be used to introduce students to scientific concepts. 

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3. Magmatic Response to Subduction Initiation: Part 1. Fore‐arc Basalts of the Izu‐Bonin Arc From IODP Expedition 352

   https://doi.org/10.1029/2018GC007731  

   Shervais, John W. ; Reagan, Mark ; Haugen, Emily ; Almeev, Renat R. ; Pearce, Julian A. ; Prytulak, Julie ; Ryan, Jeffrey G. ; Whattam, Scott A. ; Godard, Marguerite ; Chapman, Timothy ; et al ( January 2019 , Geochemistry, Geophysics, Geosystems)

   The Izu‐Bonin‐Mariana (IBM) fore arc preserves igneous rock assemblages that formed during subduction initiation circa 52 Ma. International Ocean Discovery Program (IODP) Expedition 352 cored four sites in the fore arc near the Ogasawara Plateau in order to document the magmatic response to subduction initiation and the physical, petrologic, and chemical stratigraphy of a nascent subduction zone. Two of these sites (U1440 and U1441) are underlain by fore‐arc basalt (FAB). FABs have mid‐ocean ridge basalt (MORB)‐like compositions, however, FAB are consistently lower in the high‐field strength elements (TiO₂, P₂O₅, Zr) and Ni compared to MORB, with Na₂O at the low end of the MORB field and FeO* at the high end. Almost all FABs are light rare earth element depleted, with low total REE, and have low ratios of highly incompatible to less incompatible elements (Ti/V, Zr/Y, Ce/Yb, and Zr/Sm) relative to MORB. Chemostratigraphic trends in Hole U1440B are consistent with the uppermost lavas forming off axis, whereas the lower lavas formed beneath a spreading center axis. Axial magma of U1440B becomes more fractionated upsection; overlying off‐axis magmas return to more primitive compositions. Melt models require a two‐stage process, with early garnet field melts extracted prior to later spinel field melts, with up to 23% melting to form the most depleted compositions. Mantle equilibration temperatures are higher than normal MORB (1,400 °C–1,480 °C) at relatively low pressures (1–2 GPa), which may reflect an influence of the Manus plume during subduction initiation. Our data support previous models of FAB origin by decompression melting but imply a source more depleted than normal MORB source mantle.

    

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4. Identifying the granitic composition water-saturated solidus

   Rufledt C, Thomas JB ( September 2023 , Xth Hutton Symposium)

   The granitic water-saturated solidus (G-WSS) is the lower temperature limit of magmatic mineral crystallization. The accepted water-saturated solidus for granitic compositions was largely determined >60 years ago1. More recent advances in experimental petrology, improved analytical techniques, and recent observations that granitic systems can remain active or spend a significant proportion of their lives at conditions below the traditional G-WSS2–5 necessitate a careful experimental investigation of the near-solidus regions of granitic systems. Natural and synthetic starting materials were melted at 10 kbar and 900°C with 48 wt% H2O to produce hydrous glasses for subsequent experiments at lower PT conditions used to locate the G-WSS. We performed crystallization experiments and melting experiments at temperatures ranging from 575 to 800°C and 1, 6, 8, and 10 kbar on 12 granitoid compositions. First, we ran a series of isothermal crystallization experiments along each isobar at progressively lower temperatures until runs completely crystallized to identify apparent solidus temperatures. Geochemical analyses of quenched glass compositions demonstrate that progressive crystallization drives all starting compositions towards silica-rich, water-saturated rhyolitic/granitic melts (e.g., ~7578 wt% SiO2). After identifying the apparent solidus temperatures at which the various compositions crystallized, we then ran series of reversal-type melting experiments. With the goal of producing rocks with hydrous equilibrium microstructures, we crystallized compositions at temperatures ~10°C below the apparent solidus identified in crystallization experiments, and then heated isobarically to conditions that produced ~20% melt during the crystallization experiments. Importantly, crystallization experiments and heating experiments at the same PT conditions produced similar proportions of melt, crystals, and vapor. A time-series of experiments 230 days at PT conditions previously identified to produce ~10% to 20% melt did not reveal any kinetic effects on melt crystallization. Experiments at 6 to 10 kbar crystallized/melted at temperatures close to the published G-WSS. However, at lower pressures where the published G-WSS is strongly curved in PT space, all compositions investigated contained melt to temperatures ~75 to 100°C below the accepted G-WSS. The similarity of crystallization temperatures for the higher-pressure experiments to previously published results, similar phase proportions in melting and crystallization experiments, and the lack of kinetic effects on crystallization collectively suggest that our lower pressure constraints on the G-WSS are accurate. The new experimental results demonstrating that the lower-pressure G-WSS is significantly lower than unanimously accepted estimates will help us to better understand the storage conditions, evolution, and potential for eruption in mid- to upper-crustal silicic magmatic systems. (1) Tuttle, O.; Bowen, N. Origin of Granite in the Light of Experimental Studies in the System NaAlSi3O8–KAlSi3O8–SiO2–H2O; Geological Society of America Memoirs; Geological Society of America, 1958; Vol. 74. https://doi.org/10.1130/MEM74. (2) Rubin, A. E.; Cooper, K. M.; Till, C. B.; Kent, A. J. R.; Costa, F.; Bose, M.; Gravley, D.; Deering, C.; Cole, J. Rapid Cooling and Cold Storage in a Silicic Magma Reservoir Recorded in Individual Crystals. Science 2017, 356 (6343), 1154–1156. https://doi.org/10.1126/science.aam8720. (3) Andersen, N. L.; Jicha, B. R.; Singer, B. S.; Hildreth, W. Incremental Heating of Bishop Tuff Sanidine Reveals Preeruptive Radiogenic Ar and Rapid Remobilization from Cold Storage. Proceedings of the National Academy of Sciences 2017, 114 (47), 12407–12412. https://doi.org/10.1073/pnas.1709581114. (4) Ackerson, M. R.; Mysen, B. O.; Tailby, N. D.; Watson, E. B. Low-Temperature Crystallization of Granites and the Implications for Crustal Magmatism. Nature 2018, 559 (7712), 94–97. https://doi.org/10.1038/s41586-018-0264-2. (5) Glazner, A. F.; Bartley, J. M.; Coleman, D. S.; Lindgren, K. Aplite Diking and Infiltration: A Differentiation Mechanism Restricted to Plutonic Rocks. Contributions to Mineralogy and Petrology 2020, 175 (4). https://doi.org/10.1007/s00410-020-01677-1. 

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5. Environmental, evolutionary, and ecological drivers of slow growth in deep-sea demersal teleosts

   https://doi.org/10.3354/meps13591  

   Black, JA ; Neuheimer, AB ; Horn, PL ; Tracey, DM ; Drazen, JC ( January 2021 , Marine Ecology Progress Series)

   null (Ed.)

   The deep sea (>500 m ocean depth) is the largest global habitat, characterized by cool temperatures, low ambient light, and food-poor conditions relative to shallower waters. Deep-sea teleosts generally grow more slowly than those inhabiting shallow water. However, this is a generalization, and even amongst deep-sea teleosts, there is a broad continuum of growth rates. The importance of potential drivers of growth rate variability amongst deep-sea species, such as temperature, food availability, oxygen concentration, metabolic rate, and phylogeny, have yet to be fully evaluated. We present a meta-analysis in which age and size data were collected for 53 species of teleosts whose collective depth ranges span from surface waters to 4000 m. We calculated growth metrics using both calendar and thermal age, and compared them with environmental, ecological, and phylogenetic variables. Temperature alone explained up to 30% of variation in the von Bertalanffy growth coefficient ( K , yr -1 ), and 21% of the variation in the average annual increase in mass (AIM, %), a metric of growth prior to maturity. After correcting for temperature effects, depth was still a significant driver of growth, explaining up to 20 and 10% of the remaining variation in K and AIM, respectively. Oxygen concentration also explained ~11% of remaining variation in AIM following temperature correction. Relatively minor amounts of variation may be explained by food availability, phylogeny, and the locomotory mode of the teleosts. We also found strong correlation between growth and metabolic rate, which may be an underlying driver also related to temperature, depth, and other factors, or the 2 parameters may simply covary as a result of being linked by evolutionary pressures. Evaluating the influence of ecological and/or environmental drivers of growth is a vital step in understanding both the evolution of life history parameters across the depth continuum as well as their implications for species’ resilience to increasing anthropogenic stressors. 

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