bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multiwavelength Ground and Space Observations of the Variable White Dwarf BOKS 53856: Nonuniform Metal Absorption in Dark Spots
Authors: Hoard D. W. , Howell Steve B. , Roettenbacher Rachael M. , Ely Justin , Debes John H. , Harmon Robert O. 
Published: August 2018

Abstract
We analyze extensive ground- and space-based ultraviolet–infrared observations of the variable white dwarf BOKS 53856. Photometry and spectroscopy were obtained from the Hubble Space Telescope, Spitzer Space Telescope, Kepler and Swift satellites, Palomar Observatory, and Kitt Peak National Observatory. Time series data spanning the entire four-year Kepler mission are used to refine the photometric rotation period of the white dwarf to 0.2557292(9) days. The associated periodic variability, with full (minimum to maximum) amplitudes of ≈5% and ≈10% in the optical and ultraviolet, respectively, is consistent with the presence of several dark spots on the white dwarf surface. A fit to the observed ultraviolet–infrared spectral energy distribution of BOKS 53856 using a grid of non-LTE synthetic spectra gives best values of effective temperature, T
WD = 31,056(19) K, surface gravity, log g = 7.913(5), mass, M
WD = 0.603(2)

, radius, R
WD = 0.0142(4)

, reddening, E

B–V
= 0.0533(1), and distance, d = 277(10) pc. The Hubble ultraviolet spectrum does not show a detectable signature of accreted metals, and the Spitzer infrared photometry does not reveal an excess attributable to a circumstellar dust disk. Nonetheless, the ground-based optical spectra show a very weak, variable Ca ii K absorption line that is phased with the Kepler light curve, being strongest at minimum brightness. We discuss BOKS 53856 and similar objects in the context of a localized enhancement of absorption from metals in dark (possibly magnetic) spots on the white dwarf surface.
Spectroscopic Orbits for Late-type Stars. II
Authors: Fekel Francis C. , Willmarth Daryl W. , Abt Helmut A. , Pourbaix Dimitri 
Published: August 2018

Abstract
We have determined spectroscopic orbital elements for 13 systems—10 single-lined binaries and three double-lined binaries. For the three binaries with previously published spectroscopic orbits, we have computed improved or comparable elements. While two systems have relatively short periods between 10 and 19 days, the remaining systems have much longer periods ranging from 604 to 9669 days. One of the single-lined systems, HD 142640, shows both short-period and long-period velocity variations and so is triple. For three systems—HD 59380, HD 160933, and HD 161163—we have combined our spectroscopic results with Hipparcos astrometric observations to obtain astrometric orbits. For HD 14802 we have determined a joint orbital solution from spectroscopic velocities and interferometric observations. The orbits given here will be useful in combination with future interferometric and Gaia satellite observations.
Different Stellar Rotations in the Two Main Sequences of the Young Globular Cluster NGC 1818: The First Direct Spectroscopic Evidence*
Authors: Marino A. F. , Przybilla N. , Milone A. P. , Costa G. Da , D’Antona F. , Dotter A. , Dupree A. 
Published: August 2018

Abstract
We present a spectroscopic analysis of main sequence (MS) stars in the young globular cluster NGC 1818 (age ∼40 Myr) in the Large Magellanic Cloud. Our photometric survey of Magellanic Clouds clusters has revealed that NGC 1818, similar to other young objects with ages ≲600 Myr, displays not only an extended MS turnoff (eMSTO), as observed in intermediate-age clusters (age ∼1–2 Gyr), but also a split MS. The most straightforward interpretation of the double MS is the presence of two stellar populations: a sequence of slowly rotating stars lying on the blue-MS (bMS) and a sequence of fast rotators, with rotation close to the breaking speed, defining a red-MS (rMS). We report the first direct spectroscopic measurements of projected rotational velocities

for the double MS, eMSTO, and Be stars of a young cluster. The analysis of line profiles includes non-local thermodynamic equilibrium effects, required for correctly deriving

values. Our results suggest that: (i) the mean rotation for bMS and rMS stars is

=71 ± 10 km s−1 (σ = 37 km s−1) and

= 202 ± 23 km s−1 (σ = 91 km s−1), respectively; (ii) eMSTO stars have different

, which are generally lower than those inferred for rMS stars, and (iii) as expected, Be stars display the highest

values. This analysis supports the idea that distinct rotational velocities play an important role in the appearance of multiple stellar populations in the color–magnitude diagrams of young clusters, and poses new constraints on the current scenarios.
Nucleosynthesis Constraints on the Explosion Mechanism for Type Ia Supernovae
Authors: Mori Kanji , Famiano Michael A. , Kajino Toshitaka , Suzuki Toshio , Garnavich Peter M. , Mathews Grant J. , Diehl Roland , Leung Shing-Chi , Nomoto Ken’ichi 
Published: August 2018

Abstract
Observations of type Ia supernovae (SNe Ia) include information about the characteristic nucleosynthesis associated with these thermonuclear explosions. We consider observational constraints from iron-group elemental and isotopic ratios, to compare with various models obtained with the most realistic recent treatment of electron captures (ECs). The nucleosynthesis is sensitive to the highest white-dwarf central densities. Hence, nucleosynthesis yields can distinguish high-density Chandrasekhar-mass models from lower-density burning models such as white-dwarf mergers. We discuss new results of post-processing nucleosynthesis for two spherical models (deflagration and/or delayed-detonation models) based upon new EC rates. We also consider cylindrical and 3D explosion models (including deflagration, delayed-detonation, or a violent merger model). Although there are uncertainties in the observational constraints, we identify some trends in the observations and the models. We make a new comparison of the models with elemental and isotopic ratios from five observed supernovae and three supernova remnants. We find that the models and data tend to fall into two groups. In one group, low-density cores such as in a 3D merger model are slightly more consistent with the nucleosynthesis data, while the other group is slightly better identified with higher-density cores such as in single-degenerate 1D–3D deflagration models. Hence, we postulate that both types of environments appear to contribute nearly equally to observed SN Ia. We also note that observational constraints on the yields of 54Cr and 54Fe, if available, might be used as a means to clarify the degree of geometrical symmetry of SN Ia explosions.
The Long-term Evolution of Star Clusters Formed with a Centrally Peaked Star Formation Efficiency Profile
Authors: Shukirgaliyev Bekdaulet , Parmentier Geneviève , Just Andreas , Berczik Peter 
Published: August 2018

Abstract
We have studied the long-term evolution of star clusters of the solar neighborhood, starting from their birth in gaseous clumps until their complete dissolution in the Galactic tidal field. We have combined the “local-density-driven cluster formation model” of Parmentier & Pfalzner with direct N-body simulations of clusters following instantaneous gas expulsion. We have studied the relation between cluster dissolution time, t
dis, and cluster “initial” mass, M
init, defined as the cluster mass at the end of the dynamical response to gas expulsion (i.e., violent relaxation), when the cluster age is 20–30 Myr. We consider the “initial” mass to be consistent with other works that neglect violent relaxation. The model clusters formed with a high star formation efficiency (SFE, i.e., gas mass fraction converted into stars) follow a tight mass-dependent relation, in agreement with previous theoretical studies. However, the low-SFE models present a large scatter in both the “initial” mass and the dissolution time, a shallower mass-dependent relation than high-SFE clusters, and most dissolve within 1 Gyr (cluster teenage mortality). Both groups differ in their structural properties on average. Combining two populations of clusters, high- and low-SFE ones, with domination of the latter, yields a cluster dissolution time for the solar neighborhood in agreement with that inferred from observations, without any additional destructive processes such as giant molecular cloud encounters. An apparent mass-independent relation may emerge for our low-SFE clusters when we neglect low-mass clusters (as expected for extragalactic observations), although more simulations are needed to investigate this aspect.
Comparing Redundant and Sky-model-based Interferometric Calibration: A First Look with Phase II of the MWA
Authors: Li W. , Pober J. C. , Hazelton B. J. , Barry N. , Morales M. F. , Sullivan I. , Parsons A. R. , Ali Z. S. , Dillon J. S. , Beardsley A. P. , Bowman J. D. , Briggs F. , Byrne R. , Carroll P. , Crosse B. , Emrich D. , Ewall-Wice A. , Feng L. , Franzen T. M. O. , Hewitt J. N. , Horsley L. , Jacobs D. C. , Johnston-Hollitt M. , Jordan C. , Joseph R. C. , Kaplan D. L. , Kenney D. , Kim H. , Kittiwisit P. , Lanman A. , Line J. , McKinley B. , Mitchell D. A. , Murray S. , Neben A. , Offringa A. R. , Pallot D. , Paul S. , Pindor B. , Procopio P. , Rahimi M. , Riding J. , Sethi S. K. , Udaya Shankar N. , Steele K. , Subrahmanian R. , Tegmark M. , Thyagarajan N. , Tingay S. J. , Trott C. , Walker M. , Wayth R. B. , Webster R. L. , Williams A. , Wu C. , Wyithe S. 
Published: August 2018

Abstract
Interferometric arrays seeking to measure the 21 cm signal from the epoch of reionization (EOR) must contend with overwhelmingly bright emission from foreground sources. Accurate recovery of the 21 cm signal will require precise calibration of the array, and several new avenues for calibration have been pursued in recent years, including methods using redundancy in the antenna configuration. The newly upgraded Phase II of Murchison Widefield Array (MWA) is the first interferometer that has large numbers of redundant baselines while retaining good instantaneous UV coverage. This array therefore provides a unique opportunity to compare redundant calibration with sky-model-based algorithms. In this paper, we present the first results from comparing both calibration approaches with MWA Phase II observations. For redundant calibration, we use the package OMNICAL and produce sky-based calibration solutions with the analysis package Fast Holographic Deconvolution (FHD). There are three principal results: (1) We report the success of OMNICAL on observations of ORBComm satellites, showing substantial agreement between redundant visibility measurements after calibration. (2) We directly compare OMNICAL calibration solutions with those from FHD and demonstrate that these two different calibration schemes give extremely similar results. (3) We explore improved calibration by combining OMNICAL and FHD. We evaluate these combined methods using power spectrum techniques developed for EOR analysis and find evidence for marginal improvements mitigating artifacts in the power spectrum. These results are likely limited by the signal-to-noise ratio in the 6 hr of data used, but they suggest future directions for combining these two calibration schemes.
Microphysics of KCl and ZnS Clouds on GJ 1214 b
Authors: Gao Peter , Benneke Björn 
Published: August 2018

Abstract
Clouds in the atmospheres of exoplanets confound characterization efforts by reducing, eliminating, and distorting the spectral signatures of molecular abundances. As such, interpretations of exoplanet spectra strongly depend on the choice of cloud model, many of which are highly simplified and lack predictive power. In this work, we use a cloud model that incorporates microphysical processes to simulate potassium chloride (KCl) and zinc sulfide (ZnS) clouds in the atmosphere of the super-Earth GJ 1214 b and how they vary as a function of the strength of vertical mixing and the atmospheric metallicity. Microphysical processes control the size and spatial distribution of cloud particles, allowing for the computation of more physical cloud distributions than simpler models. We find that the mass and opacity of KCl clouds increase with mixing strength and metallicity, with the particle size and spatial distribution defined by nucleation, condensation, evaporation, and transport timescales. ZnS clouds cannot form without the presence of condensation nuclei, while heterogeneous nucleation of ZnS on KCl reduces particle sizes compared to pure KCl cases. In order to explain the flat transmission spectrum of GJ 1214 b with homogeneously nucleated KCl clouds, the atmospheric metallicity must be at least 1000× solar, and the eddy diffusivity must be at least 1010 cm2 s−1. We predict that James Webb Space Telescope observations of GJ 1214 b may reveal the presence of methane, carbon monoxide, and water, allowing for constraints to be placed on atmospheric metallicity and C/O ratio.
Management of Delia (Diptera: Anthomyiidae) through selectively timed planting of Phaseolus vulgaris (Fabaceae) in Atlantic Canada
Authors: Silver Natalie , Hillier Kirk , Blatt Suzanne 
Published: August 2018

AbstractDelia Robineau-Desvoidy (Diptera: Anthomyiidae), including Delia platura (Meigen), are known pests of vegetable crops. Here, three studies were conducted to examine the relationship between Delia species and Phaseolus vulgaris Linnaeus (Fabaceae). Field studies documented a relationship between planting date and occurrence of Delia damage on P. vulgaris. Plantings in mid-June resulted in higher crop yields (mean bean pods per plant) and reduced damage ratings compared with earlier plantings. Late-May and early-June planting dates were not favourable, as they resulted in high damage ratings and low plant survival. Late-June and July plantings resulted in low damage ratings but low crops yields. Growth chamber experiments examined oviposition preference of D. platura females at eight phenological stages for two varieties of P. vulgaris. Results indicated significantly higher oviposition rates on bean plants at early phenological growth stages, with no significant varietal preference shown by maggots. Laboratory experiments quantified the impact of D. platura larval infestation on two P. vulgaris varieties at two growth stages. Results indicated no significant difference in variety choice. Recommendation for planting P. vulgaris to coincide with Delia phenology using a degree-day model is discussed.
The Canonical but Not the Noncanonical Wnt Pathway Inhibits the Development of Allergic Airway Disease
Authors: Beckert Hendrik , Meyer-Martin Helen , Buhl Roland , Taube Christian , Reuter Sebastian 
Published: August 2018

Abstract
Asthma is a syndrome with multifactorial causes, resulting in a variety of different phenotypes. Current treatment options are not curative and are sometimes ineffective in certain disease phenotypes. Therefore, novel therapeutic approaches are required. Recent findings have shown that activation of the canonical Wnt signaling pathway suppresses the development of allergic airway disease. In contrast, the effect of the noncanonical Wnt signaling pathway activation on allergic airway disease is not well described. The aim of this study was to validate the therapeutic effectiveness of Wnt-1–driven canonical Wnt signaling compared with Wnt-5a–driven noncanonical signaling in murine models. In vitro, both ligands were capable of attenuating allergen-specific T cell activation in a dendritic cell–dependent manner. In addition, the therapeutic effects of Wnt ligands were assessed in two different models of allergic airway disease. Application of Wnt-1 resulted in suppression of airway inflammation as well as airway hyperresponsiveness and mucus production. In contrast, administration of Wnt-5a was less effective in reducing airway inflammation or goblet cell metaplasia. These results suggest an immune modulating function for canonical as well as noncanonical Wnt signaling, but canonical Wnt pathway activation appears to be more effective in suppressing allergic airway disease than noncanonical Wnt activation.
Measurement properties of the construct of the code of ethics content: The South African experience
Authors: Mpinganjira Mercy , Roberts-Lombard Mornay , Svensson Goran , Wood Greg 
Published: August 2018

Background: Many organisations develop codes of ethics to help guide business conduct. However, not much is known about the contents of codes of ethics. Objectives: This article aims at investigating the code of ethics content construct and its measurement properties using a sample of firms from South Africa. Method: The study followed a quantitative research approach. The sampling frame consisted of the top 500 companies in South Africa. A structured questionnaire was administered using the telephone survey method. The respondents consisted of company secretaries and heads or managers responsible for ethics in the respective companies. At the end of the data collection period, a total of 222 usable responses were obtained. Results: The findings show that South African top companies have comprehensive codes of ethics as evidenced by the high mean values obtained from all of the content items under investigation. The findings also support the notion that the code of ethics content construct is multidimensional. Seven different dimensions were confirmed in the analysis. The measurement model of the ethics content construct was found to be valid as evidenced by the goodness-of-fit measure and measures of validity. Conclusion: The study shows that the code of ethics construct is multi-dimensional in nature. The framework provided in this study can also be used in developing, evaluating and strengthening existing codes where such need arises. This study contributes to theory on business ethics and presents the first tested measurement model of the code of ethics construct in South Africa.
The combined influence of self-leadership and locus of control on the job performance of engineering workforce in a power generation utility: An empirical perspective
Authors: Rambe Patient , Modise Disebo L. , Chipunza Crispen 
Published: August 2018

Orientation: The joint effects of self-leadership and locus of control within an engineering context have been under-explored because much research focused on self-leadership and locus of control as independent concepts, and studies on their combined effects on organisational performance remain hard to encounter in emerging economies.Research purpose: The aim of the study was to develop deeper empirical knowledge of the combined effects of self-leadership and locus of control on job performance of engineering workforce in Eskom Free State.Motivation for the study: The originality of the study lies in the reconstitution of individual self-leadership and locus of control concepts as they relate to job performance and its impact on prospective engineers who work at Eskom in Bloemfontein.Research approach/design and method: Drawing on a quantitative approach, a survey was conducted on 134 engineering personnel (comprising engineers, technologists and technicians). Of this workforce, a total of 107 engineers participated in the study representing a response rate of 79.8%. Correlation and multiple regression analysis were used to analyse the corpus of quantitative data.Main findings: The results demonstrate that self-leadership and locus of control are significant independent variables and when considered jointly, they have a positive significant impact on job performance of the Eskom engineering workforce.Practical/managerial implications: Implications for the initiation and fostering of self-leadership and locus of control to improve the job performance of Eskom Bloemfontein engineering workforce are discussed.Contribution/value-add: The study contributes to engineers’ task-focused behaviour through its expectations for the engineering workforce to be self-leaders who exercise internal locus of control in the execution of their jobs. This study also contributes to engineers’ work-related personality dimensions and sense of self-awareness through an exposition of individual personalities they were not conscious of.
Amanita dulciodora (Amanitaceae, Basidiomycota), a striking new species of Amanita section Lepidella from Northeast Brazil
Authors: Nascimento Cristiano C. , Sá Mariana C.A. , Bezerra José Luiz , Wartchow Felipe 
Published: August 2018

Background – Amanita Pers. has a worldwide distribution and is one of the most well-known fungal genera in terms of both morphotaxonomy and molecular phylogenetics, consisting of many edible, as well as poisonous, even lethal, mushrooms. The genus is also known to form ectomycorrhizal associations with angiosperms and gymnosperms and play an important role in ecosystems. Although previous studies have already pointed out the high diversity of the genus Amanita in tropical areas, only a few recent studies continue to record and/or describe new species of Amanita from Brazilian territory. Herein, an additional, morphologically striking new species of Amanita sect. Lepidella is described from Northeast Brazil.Methods – The new species was collected at ‘Parque Estadual Serra do Conduru’ (PESC), located in the municipalities of Uruçuca, Itacaré e Ilhéus, Bahia state. The park is an Atlantic Forest protected area with about 7000 ha in a region with a high degree of endemism. For morphological analysis, standard methods for Amanita were followed.Key results – Amanita dulciodora is described as new species from Atlantic Forest remnants in southeast Bahia. It is assignable to Amanita stirps Crassiconus within Amanita subsect. Solitariae and is mainly characterized by its (1) medium-size basidiomata with cap colour and appearance dominated by universal veil at first; (2) distinctly coloured acute-pyramidal, truncate-pyramydal to verrucose warts which are mainly composed of irregularly disposed, ovoid to subglobose to clavate cells intermixed with very abundant filamentous hyphae; (3) mostly ellipsoid to elongate amyloid basidiospores and (4) the common presence of clamps at the basal septa of basidia. It was compared with its similar species, A. crassiconus and illustrated with line drawings and photographs.