A Simple Perspective on the Mass-Area Relationship in Molecular Clouds

Despite over 30 yr of study, the mass–area relationship within and among clouds is still poorly understood both observationally and theoretically. Modern extinction data sets should have sufficient resolution and dynamic range to characterize this relationship for nearby molecular clouds, although recent papers using extinction data seem to yield different interpretations regarding the nature and universality of this aspect of cloud structure. In this paper we try to unify these various results and interpretations by accounting for the different ways cloud properties are measured and analysed. We interpret the mass–area relationship in terms of the column density distribution function and its possible variation within and among clouds. We quantitatively characterize regional variations in the column density probability distribution function (PDF). We show that structures both within and among clouds possess the same degree of ‘universality’, in that their PDF means do not systematically scale with structure size. Because of this, mass scales linearly with area.Astronom

A Simple Perspective on the Mass-Area Relationship in Molecular Clouds

Despite over 30 years of study, the mass-area relationship within and among clouds is still poorly understood both observationally and theoretically. Modern extinction datasets should have sufficient resolution and dynamic range to characterize this relationship for nearby molecular clouds, although recent papers using extinction data seem to yield different interpretations regarding the nature and universality of this aspect of cloud structure. In this paper we try to unify these various results and interpretations by accounting for the different ways cloud properties are measured and analyzed. We interpret the mass-area relationship in terms of the column density distribution function and its possible variation within and among clouds. We quantitatively characterize regional variations in the column density PDF. We show that structures both within and among clouds possess the same degree of "universality", in that their PDF means do not systematically scale with structure size. Because of this, mass scales linearly with area.Comment: 10 pages, 8 figures, MNRAS in pres

The COMPLETE Survey of Star-Forming Regions: Phase I Data

We present an overview of data available for the Ophiuchus and Perseus molecular clouds from ``Phase I'' of the COMPLETE Survey of Star-Forming Regions. This survey provides a range of data complementary to the Spitzer Legacy Program ``From Molecular Cores to Planet Forming Disks.'' Phase I includes: Extinction maps derived from 2MASS near-infrared data using the NICER algorithm; extinction and temperature maps derived from IRAS 60 and 100um emission; HI maps of atomic gas; 12CO and 13CO maps of molecular gas; and submillimetre continuum images of emission from dust in dense cores. Not unexpectedly, the morphology of the regions appears quite different depending on the column-density tracer which is used, with IRAS tracing mainly warmer dust and CO being biased by chemical, excitation and optical depth effects. Histograms of column-density distribution are presented, showing that extinction as derived from 2MASS/NICER gives the closest match to a log-normal distribution as is predicted by numerical simulations. All the data presented in this paper, and links to more detailed publications on their implications are publically available at the COMPLETE website.Comment: Accepted by AJ. Full resolution version available from: http://www.cfa.harvard.edu/COMPLETE/papers/complete_phase1.pd

Mitochondrial calcium exchange links metabolism with the epigenome to control cellular differentiation.

Fibroblast to myofibroblast differentiation is crucial for the initial healing response but excessive myofibroblast activation leads to pathological fibrosis. Therefore, it is imperative to understand the mechanisms underlying myofibroblast formation. Here we report that mitochondrial calcium (mCa2+) signaling is a regulatory mechanism in myofibroblast differentiation and fibrosis. We demonstrate that fibrotic signaling alters gating of the mitochondrial calcium uniporter (mtCU) in a MICU1-dependent fashion to reduce mCa2+ uptake and induce coordinated changes in metabolism, i.e., increased glycolysis feeding anabolic pathways and glutaminolysis yielding increased α-ketoglutarate (αKG) bioavailability. mCa2+-dependent metabolic reprogramming leads to the activation of αKG-dependent histone demethylases, enhancing chromatin accessibility in loci specific to the myofibroblast gene program, resulting in differentiation. Our results uncover an important role for the mtCU beyond metabolic regulation and cell death and demonstrate that mCa2+ signaling regulates the epigenome to influence cellular differentiation

VISIONS: The VISTA Star Formation Atlas -- I. Survey overview

© The Authors 2023. Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0).VISIONS is an ESO public survey of five nearby (d < 500 pc) star-forming molecular cloud complexes that are canonically associated with the constellations of Chamaeleon, Corona Australis, Lupus, Ophiuchus, and Orion. The survey was carried out with VISTA, using VIRCAM, and collected data in the near-infrared passbands J, H, and Ks. With a total on-sky exposure time of 49.4 h VISIONS covers an area of 650 deg$^2$, and it was designed to build an infrared legacy archive similar to that of 2MASS. Taking place between April 2017 and March 2022, the observations yielded approximately 1.15 million images, which comprise 19 TB of raw data. The observations are grouped into three different subsurveys: The wide subsurvey comprises shallow, large-scale observations and has visited the star-forming complexes six times over the course of its execution. The deep subsurvey of dedicated high-sensitivity observations has collected data on the areas with the largest amounts of dust extinction. The control subsurvey includes observations of areas of low-to-negligible dust extinction. Using this strategy, the VISIONS survey offers multi-epoch position measurements, is able to access deeply embedded objects, and provides a baseline for statistical comparisons and sample completeness. In particular, VISIONS is designed to measure the proper motions of point sources with a precision of 1 mas/yr or better, when complemented with data from VHS. Hence, VISIONS can provide proper motions for sources inaccessible to Gaia. VISIONS will enable addressing a range of topics, including the 3D distribution and motion of embedded stars and the nearby interstellar medium, the identification and characterization of young stellar objects, the formation and evolution of embedded stellar clusters and their initial mass function, as well as the characteristics of interstellar dust and the reddening law.Peer reviewe

Vitamin C and D Deficiency in Urban America: A Case Report

Introduction: Scurvy is caused by vitamin C deficiency and manifests with a variety of symptoms including generalized fatigue, apathy, anemia, myalgias, easy bruising, and poor wound healing. It is generally thought of as a disease of the past, especially in developed countries. However, vitamin C deficiency still occurs, especially in patients with lack of access to fruits and vegetables. Other micronutrient deficiencies, including vitamin D deficiency, are also prevalent and can cause a multitude of signs and symptoms including osteomalacia, muscle weakness, and increased risk of many chronic illnesses.Case Report: Here we present a case of vitamin C and D deficiency in a previously healthy 26-year-old man during the coronavirus disease 2019 pandemic in urban America.Conclusion: Severe nutritional deficiencies still exist today. Emergency clinicians should be aware of the signs and symptoms to promptly diagnose and initiate treatment

Reflections on the Undergraduate Research Experience of Three Former NCAA Division I Athletes

Undergraduate research (UR) opportunities are important for college students to engage in areas of interest, gain valuable skills, and contribute to their learning outside of the classroom (Mahatmya et al., 2017). There have been a few studies on college athletes engaged in high impact practices (HIPs) like study abroad programs (Navarro et al., 2020), first-year seminars (Grafnetterova et al., 2020), and learning communities (Mamerow & Navarro, 2014). However, little has been studied on athletes’ engagement in UR (also a HIP). While athletes may not be a large percentage of an institution’s student population, they are more visible in the campus community. College athletes face time constraints, balancing two full-time roles of student and athlete, often with limited time remaining to devote to extracurricular activities (Ishaq & Bass, 2019; Rubin & Moses, 2017). They also endure negative stereotypes, seen as outsiders by the student body and faculty, isolating themselves from campus involvement (Rubin & Moses, 2017; Simons et al., 2020). These stereotypes include the idea of the “dumb jock,” in which athletes are incapable of handling collegelevel work and require additional support to pass classes (Simons et al., 2007). Many campuses offer academic support in facilities designated specifically for athletes, beyond the typically weekday work hours (Rubin & Moses, 2017). Besides attending classes on campus, athletes spend most of their time in athletic facilities for meals, workouts, tutoring, and practices. In classes, they are more likely to sit with other athletes who understand their schedule and lifestyle (Rubin & Moses, 2017). Their rigid schedules might prohibit them from exploring student organizations or UR. Because of this, engaging athletes in UR is not as easy or obvious for faculty as it may be with other students. Yet, Gaston-Gayles and Hu (2009) discovered that athletes who engage in educationally purposeful activities, including faculty interaction and collaborative learning, improve in cognitive and academic outcomes. Since athletes’ college experience may differ significantly from that of other students, it is important to learn from former athletes’ participation in UR

Effects of cell doubling time on the apparent t_1/2 value of a study mRNA.

<p>(A) Hypothetical mRNA decay. Cell aliquots, each originally containing 1.0×10⁶ cells, are incubated for defined intervals between 0 and 24 hours. Cells in each aliquot double every 6 hours, in parallel with the total amount of β-actin mRNA. At T = 0, each aliquot contains an equal quantity [1 arbitrary unit (au)] of an infinitely stable β-globin mRNA, encoded by a gene that has been transcriptionally silenced. The decline in the ratio of the globin:actin mRNAs, which erroneously indicates a half-life value of 6 hours for the globin mRNA, fails to account for interval expansion in cell number. These same principles apply to mRNAs with finite stabilities (panel B). (B) True and uncorrected t_1/2 values in cells with different doubling times. Curves illustrate the uncorrected half-life for a test mRNA, following transcriptional silencing of its encoding gene, if the interval expansion in cell number is not considered. The examples utilize an mRNA with a true t_1/2 = 6 h, expressed in cells that are growth arrested (curve <i>a</i>) or display doubling times of 24, 8, 6, or 4 hours (curves <i>b</i> through <i>e</i>, respectively).</p