Companions of Stars: From Other Stars to Brown Dwarfs to Planets: The Discovery of the First Methane Brown Dwarf

The discovery of the first methane brown dwarf provides a framework for describing the important advances in both fundamental physics and astrophysics that are due to the study of companions of stars. I present a few highlights of the history of this subject along with details of the discovery of the brown dwarf Gliese 229B. The nature of companions of stars is discussed with an attempt to avoid biases induced by anthropocentric nomenclature. With the newer types of remote reconnaissance of nearby stars and their systems of companions, an exciting and perhaps even more profound set of contributions to science is within reach in the near future. This includes an exploration of the diversity of planets in the universe and perhaps soon the first solid evidence for biological activity outside our Solar System.Comment: 31 pages, 13 figure

Big Data and Changes in Audit Technology: Contemplating a Research Agenda

This study explores the most recent episode in the evolution of audit technology, namely the incorporation of Big Data and Data Analytics (BDA) into audit firm approaches. Drawing on 22 interviews with individuals with significant experience in developing, implementing or assessing the impact of BDA in auditing, together with publicly available documents on BDA published within the audit field, the paper provides a holistic overview of BDA-related changes in audit practice. In particular, the paper focuses on three key aspects, namely the impact of BDA on the nature of the relationship between auditors and their clients; the consequences of the technology for the conduct of audit engagements and the common challenges associated with embedding BDA in the audit context. The study’s empirical findings are then used to establish an agenda of areas suitable for further research on the topic. The study is one of the first empirical accounts providing a perspective on the rise of BDA in auditing

Dust Devil Tracks

Dust devils that leave dark- or light-toned tracks are common on Mars and they can also be found on the Earth’s surface. Dust devil tracks (hereinafter DDTs) are ephemeral surface features with mostly sub-annual lifetimes. Regarding their size, DDT widths can range between ∼1 m and ∼1 km, depending on the diameter of dust devil that created the track, and DDT lengths range from a few tens of meters to several kilometers, limited by the duration and horizontal ground speed of dust devils. DDTs can be classified into three main types based on their morphology and albedo in contrast to their surroundings; all are found on both planets: (a) dark continuous DDTs, (b) dark cycloidal DDTs, and (c) bright DDTs. Dark continuous DDTs are the most common type on Mars. They are characterized by their relatively homogenous and continuous low albedo surface tracks. Based on terrestrial and martian in situ studies, these DDTs most likely form when surficial dust layers are removed to expose larger-grained substrate material (coarse sands of ≥500 μm in diameter). The exposure of larger-grained materials changes the photometric properties of the surface; hence leading to lower albedo tracks because grain size is photometrically inversely proportional to the surface reflectance. However, although not observed so far, compositional differences (i.e., color differences) might also lead to albedo contrasts when dust is removed to expose substrate materials with mineralogical differences. For dark continuous DDTs, albedo drop measurements are around 2.5 % in the wavelength range of 550–850 nm on Mars and around 0.5 % in the wavelength range from 300–1100 nm on Earth. The removal of an equivalent layer thickness around 1 μm is sufficient for the formation of visible dark continuous DDTs on Mars and Earth. The next type of DDTs, dark cycloidal DDTs, are characterized by their low albedo pattern of overlapping scallops. Terrestrial in situ studies imply that they are formed when sand-sized material that is eroded from the outer vortex area of a dust devil is redeposited in annular patterns in the central vortex region. This type of DDT can also be found in on Mars in orbital image data, and although in situ studies are lacking, terrestrial analog studies, laboratory work, and numerical modeling suggest they have the same formation mechanism as those on Earth. Finally, bright DDTs are characterized by their continuous track pattern and high albedo compared to their undisturbed surroundings. They are found on both planets, but to date they have only been analyzed in situ on Earth. Here, the destruction of aggregates of dust, silt and sand by dust devils leads to smooth surfaces in contrast to the undisturbed rough surfaces surrounding the track. The resulting change in photometric properties occurs because the smoother surfaces have a higher reflectance compared to the surrounding rough surface, leading to bright DDTs. On Mars, the destruction of surficial dust-aggregates may also lead to bright DDTs. However, higher reflective surfaces may be produced by other formation mechanisms, such as dust compaction by passing dust devils, as this may also cause changes in photometric properties. On Mars, DDTs in general are found at all elevations and on a global scale, except on the permanent polar caps. DDT maximum areal densities occur during spring and summer in both hemispheres produced by an increase in dust devil activity caused by maximum insolation. Regionally, dust devil densities vary spatially likely controlled by changes in dust cover thicknesses and substrate materials. This variability makes it difficult to infer dust devil activity from DDT frequencies. Furthermore, only a fraction of dust devils leave tracks. However, DDTs can be used as proxies for dust devil lifetimes and wind directions and speeds, and they can also be used to predict lander or rover solar panel clearing events. Overall, the high DDT frequency in many areas on Mars leads to drastic albedo changes that affect large-scale weather patterns

Unitarity and Interfering Resonances in pipi Scattering and in Pion Production piN->pipiN

Additivity of Breit-Wigner phases has been proposed to describe interfering resonances in partial waves in $\pi\pi$ scattering. This assumption leads to an expression for partial wave amplitudes that involves products of Breit-Wigner amplitudes. We show that this expression is equivalent to a coherent sum of Breit-Wigner amplitudes with specific complex coefficients which depend on the resonance parameters of all contributing resonances. We use analyticity of $\pi\pi$ partial wave amplitudes to show that they must have the form of a coherent sum of Breit-Wigner amplitudes with complex coefficients and a complex coherent background. The assumption of additivity of Breit-Wigner phases restricts the partial waves to analytical functions with very specific form of residues of Breit-Wigner poles. We argue that the general form provided by the analyticity is more appropriate in fits to data to determine resonance parameters. The partial wave unitarity can be imposed using the modern methods of constrained optimization. We discuss unitarity and the production amplitudes in $\pi N\to\pi\pi N$ and use analyticity in the dipion mass variable to justify the common practice of writing the production amplitudes as a coherent sum of Breit-Wigner amplitudes with free complex coefficients and a complex coherent background in fits to mass spectra with interfering resonances.Comment: 31 page

Management of acute hypercortisolism

An occasional patient with Cushing's syndrome may require urgent management primarily because the chronic ravages of hypercortisolism have caused the patient to be in a precarious metabolic condition. The side effects of prolonged excess corticosteroids increase the risk of operations in such patients and must be considered in overall management. Among the many effects of hypercortisolism to be considered are hypertension, diabetes, ocular hypertension, myopathies, dermatologic changes including skin infection, pancreatitis, osteoporosis, pathological fractures, peptic ulcers, renal calculi, coagulopathies, hypokalemia, poor wound healing, and increased susceptibility to infection. The most effective way to avert these complications is by earlier diagnosis and definitive treatment of Cushing's syndrome. The present report includes a review of the etiology and diagnosis of Cushing's syndrome and the management of problems associated with hypercortisolism . Il est possible qu'un malade atteint de maladie de Cushing ait besoin d'être traité sans attente en raisons de troubles métaboliques sévères dus aux effets nocifs de l'hypercortisolisme chronique qui augmentent les risques opératoires et doivent être pris en considération avant tout traitement. Il en est ainsi de l'hypertension, du diabète, de l'hypertension intra-oculaire, des lésions dermiques comprenant l'infection cutanée, la pancréatite, l'ostéoporose, les fractures pathologiques, l'ulcère peptique, les calculs rénaux, les coagulopathies, l'hypokaliémie, la lenteur du processus de cicatrisation et l'augmentation de la suceptibilité à l'infection.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/41309/1/268_2005_Article_BF01655367.pd

Long-Baseline Neutrino Facility (LBNF) and Deep Underground Neutrino Experiment (DUNE) Conceptual Design Report Volume 2: The Physics Program for DUNE at LBNF

The Physics Program for the Deep Underground Neutrino Experiment (DUNE) at the Fermilab Long-Baseline Neutrino Facility (LBNF) is described

An Improved Near-infrared Spectrum of the Archetype y Dwarf WISEP J182831.08+265037.8

We present a Hubble Space Telescope/Wide-Field Camera 3 near-infrared spectrum of the archetype Y dwarf WISEP 182831.08+265037.8. The spectrum covers the 0.9-1.7 μm wavelength range at a resolving power of λ/Δλ ≈ 180 and is a significant improvement over the previously published spectrum because it covers a broader wavelength range and is uncontaminated by light from a background star. The spectrum is unique for a cool brown dwarf in that the flux peaks in the Y, J, and H bands are of near equal intensity in units of f λ . We fail to detect any absorption bands of NH3 in the spectrum, in contrast to the predictions of chemical equilibrium models, but tentatively identify CH4 as the carrier of an unknown absorption feature centered at 1.015 μm. Using previously published ground- and spaced-based photometry, and using a Rayleigh-Jeans tail to account for flux emerging longward of 4.5 μm, we compute a bolometric luminosity of, which is significantly lower than previously published results. Finally, we compare the spectrum and photometry to two sets of atmospheric models and find that the best overall match to the observed properties of WISE 1828+2650 is a ∼1 Gyr old binary composed of two T eff ∼ 325 K, ∼5 M Jup brown dwarfs with subsolar [C/O] ratios. © 2021. The American Astronomical Society. All rights reserved..Immediate accessThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]