scholarly journals Recent and Future Studies of Circumstellar Matter – A Snapshot

1999 ◽  
Vol 191 ◽  
pp. 603-610
Author(s):  
M. Jura
Keyword(s):  
Mass Loss ◽  
Theoretical Models ◽  
Circumstellar Matter ◽  
Agb Stars ◽  
Future Studies ◽  
Instruments And Techniques ◽  
Near Future ◽  
New Instruments ◽  
Loss Mechanisms

At this meeting, powerful new images and spectroscopy of AGB stars were presented. Theoretical models have advanced, and we are learning more from studies of the pre-solar grains isolated from meteorites.We suggest that several mass loss mechanisms may be operating in AGB stars: current images imply both spherical winds and highly flattened outflows. There are good arguments that in some cases, a companion may be critical in driving the final outflow. In the near future, a number of extremely powerful new instruments and techniques will be available that will lead to a much deeper understanding of these systems.

scholarly journals On Low Mass AGB Stars

1991 ◽  
Vol 145 ◽  
pp. 275-285 ◽  
Author(s):  
I.-Juliana Sackmann ◽  
Arnold I. Boothroyd
Keyword(s):  
Mass Loss ◽  
Narrow Range ◽  
Carbon Star ◽  
Theoretical Models ◽  
Initial Mass ◽  
Mixing Length ◽  
Agb Stars ◽  
Low Mass Stars ◽  
Low Mass ◽  
Thermal Pulses

Recent results on low mass AGB stars are presented. Observed amounts of AGB mass loss imply that thermal pulses will only be encountered for stars of initial mass less than about 4M⊙ for Pop I and 3 M⊙ for Pop II. Mc – L, Me – τif, and Mc – Tb relations are summarized. Carbon dredge-up has been found in low mass stars of both Pop I and Pop II; the mixing length parameter α is crucial to dredge-up, and its value must be normalized according to each author's opacities and mixing length treatment (e.g., via the Sun's Te and L). The “carbon star mystery” is nearing a solution, but a new “s-process mystery” has appeared: only in a narrow range of mass and metallicity have theoretical models been found that encounter the semiconvective 13C s-process mechanism.

scholarly journals ArcGIS Urban: an application for plan assessment

2021 ◽  
Vol 1 (1) ◽  
Author(s):  
Ellen Soward ◽  
Jianling Li
Keyword(s):  
United States ◽  
The United States ◽  
Spatial Context ◽  
Future Studies ◽  
Planning Profession ◽  
Gis Tools ◽  
Comprehensive Plans ◽  
Near Future ◽  
The City

AbstractMost cities in the United States rely on zoning to address important planning-related issues within their jurisdictions. Planners often use GIS tools to analyze these issues in a spatial context. ESRI’s ArcGIS Urban software seeks to provide the planning profession with a GIS-based solution for various challenges, including zoning’s impacts on the built environment and housing capacity.This research explores the use of ArcGIS Urban for assessing the existing zoning and comprehensive plans in meeting the projected residential growth in the near future using the City of Arlington, Texas as a case study. The exploration provides examples and lessons for how ArcGIS Urban might be used by planners to accomplish their tasks and highlights the capabilities and limitations of ArcGIS Urban in its current stand. The paper is concluded with some suggestions for future studies.

scholarly journals Discovery of Infrared Stars in Globular Clusters in the Magellanic Clouds and Their Light Variations

1998 ◽  
Vol 11 (1) ◽  
pp. 395-395
Author(s):  
S. Nishida ◽  
T. Tanabé ◽  
S. Matsumoto ◽  
T. Onaka ◽  
Y. Nakada ◽  
...  
Keyword(s):  
Mass Loss ◽  
Globular Clusters ◽  
Main Sequence ◽  
Near Infrared ◽  
Magellanic Clouds ◽  
Infrared Light ◽  
Agb Stars ◽  
Dust Shells ◽  
Infrared Stars ◽  
Infrared Survey

A systematic near-infrared survey was made for globular clusters in the Magellanic Clouds. Two infrared stars were discovered in NGC419 (SMC) and NGC1783 (LMC). NGC419 and NGC1783 are well-studied rich globular clusters whose turn-off masses and ages are estimated MTO ~ 2.0 Mʘ and т ~1.2 Gyr for NGC419, and MT0 ~ 2.0 Mʘ and т ʘ 0.9 Gyr for NGC1783, respectively. The periods of the infrared light variations were determined to be 540 dfor NGC419IR1 and to be 480 d for NGC1783IR1, respectively. Comparison of the measurements with the period—if magnitude relation for carbon Miras in the LMC by Groenewegen and Whitelock(1996) revealed that the Kmagnitudes of the infrared stars were fainter by about 0.3 — 0.8 magnitude than those predicted by the P — K relation. This deviation can be explained if the infrared stars are surrounded by thick dust shells and are obscured even in the K band. The positions of NGC419IR1and NGC1783IR1 on the P — K diagram suggest that AGB stars with the main sequence masses of about 2 Mʘ start their heavy mass-loss when P ʘ 500 d.

scholarly journals Blockchain Applications in Agribusiness: A Systematic Review

2021 ◽  
Vol 13 (4) ◽  
pp. 95
Author(s):  
Geneci da Silva Ribeiro Rocha ◽  
Letícia de Oliveira ◽  
Edson Talamini
Keyword(s):  
Complex System ◽  
Systematic Review ◽  
Web Of Science ◽  
Scientific Literature ◽  
Early Stage ◽  
Technological Development ◽  
Economic Sectors ◽  
Future Studies ◽  
Blockchain Technology ◽  
Near Future

Blockchain is a technology that can be applied in different sectors to solve various problems. As a complex system, agribusiness presents many possibilities to take advantage of blockchain technology. The main goal of this paper is to identify the purposes for which blockchain has been applied in the agribusiness sector, for which a PRISMA-based systematic review was carried out. The scientific literature corpus was accessed and selected from Elsevier’s Scopus and ISI of Knowledge’s Web of Science (WoS) platforms, using the PRISMA protocol procedures. Seventy-one articles were selected for analysis. Blockchain application in agribusiness is a novel topic, with the first publication dating from 2016. The technological development prevails more than blockchain applications since it has been addressed mainly in the Computer Sciences and Engineering. Blockchain applications for agribusiness management of financial, energy, logistical, environmental, agricultural, livestock, and industrial purposes have been reported in the literature. The findings suggest that blockchain brings many benefits when used in agribusiness supply chains. We concluded that the research on blockchain applications in agribusiness is only at an early stage, as many prototypes are being developed and tested in the laboratory. In the near future, blockchain will be increasingly applied across all economic sectors, including agribusiness, promoting greater reliability and agility in information with a reduced cost. Several gaps for future studies were observed, with significant value for science, industry, and society.

scholarly journals Carbon star wind models at solar and sub-solar metallicities: a comparative study

2019 ◽  
Vol 623 ◽  
pp. A119 ◽  
Author(s):  
S. Bladh ◽  
K. Eriksson ◽  
P. Marigo ◽  
S. Liljegren ◽  
B. Aringer
Keyword(s):  
Mass Loss ◽  
Agb Stars ◽  
Carbon Stars ◽  
Dust Production ◽  
Grain Sizes ◽  
Solar Metallicity ◽  
Effective Temperatures ◽  
Carbon Excess ◽  
Thermal Pulses ◽  
Loss Rates

Context. The heavy mass loss observed in evolved stars on the asymptotic giant branch (AGB) is usually attributed to dust-driven winds, but it is still an open question how much AGB stars contribute to the dust production in the interstellar medium, especially at lower metallicities. In the case of C-type AGB stars, where the wind is thought to be driven by radiation pressure on amorphous carbon grains, there should be significant dust production even in metal-poor environments. Carbon stars can manufacture the building blocks needed to form the wind-driving dust species themselves, irrespective of the chemical composition they have, by dredging up carbon from the stellar interior during thermal pulses. Aims. We investigate how the mass loss in carbon stars is affected by a low-metallicity environment, similar to the Large and Small Magellanic Clouds (LMC and SMC). Methods. The atmospheres and winds of C-type AGB stars are modeled with the 1D spherically symmetric radiation-hydrodynamical code Dynamic Atmosphere and Radiation-driven Wind models based on Implicit Numerics (DARWIN). The models include a time-dependent description for nucleation, growth, and evaporation of amorphous carbon grains directly out of the gas phase. To explore the metallicity-dependence of mass loss we calculate model grids at three different chemical abundances (solar, LMC, and SMC). Since carbon may be dredged up during the thermal pulses as AGB stars evolve, we keep the carbon abundance as a free parameter. The models in these three different grids all have a current mass of one solar mass; effective temperatures of 2600, 2800, 3000, or 3200 K; and stellar luminosities equal to logL*∕L⊙ = 3.70, 3.85, or 4.00. Results. The DARWIN models show that mass loss in carbon stars is facilitated by high luminosities, low effective temperatures, and a high carbon excess (C–O) at both solar and subsolar metallicities. Similar combinations of effective temperature, luminosity, and carbon excess produce outflows at both solar and subsolar metallicities. There are no large systematic differences in the mass-loss rates and wind velocities produced by these wind models with respect to metallicity, nor any systematic difference concerning the distribution of grain sizes or how much carbon is condensed into dust. DARWIN models at subsolar metallicity have approximately 15% lower mass-loss rates compared to DARWIN models at solar metallicity with the same stellar parameters and carbon excess. For both solar and subsolar environments typical grain sizes range between 0.1 and 0.5 μm, the degree of condensed carbon varies between 5 and 40%, and the gas-to-dust ratios between 500 and 10 000. Conclusions. C-type AGB stars can contribute to the dust production at subsolar metallicities (down to at least [Fe∕H] = −1) as long as they dredge up sufficient amounts of carbon from the stellar interior. Furthermore, stellar evolution models can use the mass-loss rates calculated from DARWIN models at solar metallicity when modeling the AGB phase at subsolar metallicities if carbon excess is used as the critical abundance parameter instead of the C/O ratio.

scholarly journals Evolved massive stars at low-metallicity

2019 ◽  
Vol 629 ◽  
pp. A91 ◽  
Author(s):  
Ming Yang ◽  
Alceste Z. Bonanos ◽  
Bi-Wei Jiang ◽  
Jian Gao ◽  
Panagiotis Gavras ◽  
...  
Keyword(s):  
Massive Star ◽  
Far Infrared ◽  
Asymptotic Giant Branch ◽  
Initial Mass ◽  
Agb Stars ◽  
Proper Motions ◽  
Future Studies ◽  
Low Metallicity ◽  
Different Color ◽  
Yellow Supergiant

We present a clean, magnitude-limited (IRAC1 or WISE1 ≤ 15.0 mag) multiwavelength source catalog for the Small Magellanic Cloud (SMC) with 45 466 targets in total, with the purpose of building an anchor for future studies, especially for the massive star populations at low-metallicity. The catalog contains data in 50 different bands including 21 optical and 29 infrared bands, retrieved from SEIP, VMC, IRSF, AKARI, HERITAGE, Gaia, SkyMapper, NSC, Massey (2002, ApJS, 141, 81), and GALEX, ranging from the ultraviolet to the far-infrared. Additionally, radial velocities and spectral classifications were collected from the literature, and infrared and optical variability statistics were retrieved from WISE, SAGE-Var, VMC, IRSF, Gaia, NSC, and OGLE. The catalog was essentially built upon a 1″ crossmatching and a 3″ deblending between the Spitzer Enhanced Imaging Products (SEIP) source list and Gaia Data Release 2 (DR2) photometric data. Further constraints on the proper motions and parallaxes from Gaia DR2 allowed us to remove the foreground contamination. We estimate that about 99.5% of the targets in our catalog are most likely genuine members of the SMC. Using the evolutionary tracks and synthetic photometry from MESA Isochrones & Stellar Tracks and the theoretical J − KS color cuts, we identified 1405 red supergiant (RSG), 217 yellow supergiant, and 1369 blue supergiant candidates in the SMC in five different color-magnitude diagrams (CMDs), where attention should also be paid to the incompleteness of our sample. We ranked the candidates based on the intersection of different CMDs. A comparison between the models and observational data shows that the lower limit of initial mass for the RSG population may be as low as 7 or even 6 M⊙ and that the RSG is well separated from the asymptotic giant branch (AGB) population even at faint magnitude, making RSGs a unique population connecting the evolved massive and intermediate stars, since stars with initial mass around 6 to 8 M⊙ are thought to go through a second dredge-up to become AGB stars. We encourage the interested reader to further exploit the potential of our catalog.

scholarly journals Observing compact disks inside pre-PNe with the VLTI

2011 ◽  
Vol 7 (S283) ◽  
pp. 115-118
Author(s):  
Stacey N. Bright ◽  
Orsola De Marco ◽  
Olivier Chesneau ◽  
Eric Lagadec ◽  
Hans Van Winckel ◽  
...  
Keyword(s):  
Mass Loss ◽  
Agb Stars ◽  
Reflected Light ◽  
Shaping Process ◽  
Show Evidence ◽  
Compact Disks

AbstractAGB stars appear to lose mass spherically, but many PNe resulting from the AGB mass-loss have non-spherical morphologies. Compact disks have been found in some bipolar PNe, but their role in the shaping process remains unknown. Compact Keplerian disks are found to be common around post-AGB binaries, however, these objects may never develop into PNe. Another group of post-AGB stars, known as pre-PNe, are surrounded by collimated nebulae shining by reflected light or shock ionisation. We are observing the inner circumstellar regions of pre-PNe at high angular resolutions with the VLTI. We seek to compare pre-PNe disks to those around other post-AGB stars and PNe. New observations of the pre-PN, IRAS 16279-4757, show evidence for a disk similar to those seen in young PNe.

Metallicity, pulsation and mass loss in globular cluster low-mass AGB stars

2009 ◽  
Author(s):  
Iain McDonald ◽  
Jacco Th. van Loon ◽  
Martha L. Boyer ◽  
Eric Stempels
Keyword(s):  
Mass Loss ◽  
Globular Cluster ◽  
Agb Stars ◽  
Low Mass

Two decades of business negotiation research: an overview and suggestions for future studies

2017 ◽  
Vol 32 (4) ◽  
pp. 487-504 ◽  
Author(s):  
Henrik Agndal ◽  
Lars-Johan Åge ◽  
Jens Eklinder-Frick
Keyword(s):  
Literature Review ◽  
Design Methodology ◽  
Theoretical Models ◽  
Research Field ◽  
Statistical Testing ◽  
Content Type ◽  
Business Negotiation ◽  
Future Studies ◽  
Negotiation Research ◽  
Practical Implications

Purpose This paper aims to present a review of articles on business negotiation published between 1995 and 2015. Design/methodology/approach This literature review is based on 490 articles on business negotiation. Findings When analyzing the conceptual underpinnings of this field, two paradigms emerge as dominant. The most prominent paradigm is a cognitive, psychological approach, typically relying on experiments and statistical testing of findings. The second dominating paradigm is a behavioral one, largely concerned with mathematical modeling and game-theoretical models. Practical implications Besides offering a description of the characteristics adhered to the business negotiation field, this paper will also suggest recommendations for further research and specify areas in which the research field needs further conceptual and empirical development. Originality/value This literature review serves to be the first representation of the characteristics adhered to the budding research field of business negotiation.

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