scholarly journals The Impact of Stellar Surface Magnetoconvection and Oscillations on the Detection of Temperate, Earth-Mass Planets Around Sun-Like Stars

Geosciences ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 114 ◽  
Author(s):  
H. Cegla
Keyword(s):  
Stellar Surface ◽  
Theoretical Understanding ◽  
Stellar Oscillations ◽  
Long Period ◽  
Habitable Zones ◽  
Reduction Strategies ◽  
Low Mass ◽  
The Impact ◽  
Host Stars ◽  
Instrumental Precision

Detecting and confirming terrestrial planets is incredibly difficult due to their tiny size and mass relative to Sun-like host stars. However, recent instrumental advancements are making the detection of Earth-like exoplanets technologically feasible. For example, Kepler and TESS photometric precision means we can identify Earth-sized candidates (and PLATO in the future will add many long-period candidates to the list), while spectrographs such as ESPRESSO and EXPRES (with an aimed radial velocity precision [RV] near 10 cm s − 1 ) mean we will soon reach the instrumental precision required to confirm Earth-mass planets in the habitable zones of Sun-like stars. However, many astrophysical phenomena on the surfaces of these host stars can imprint signatures on the stellar absorption lines used to detect the Doppler wobble induced by planetary companions. The result is stellar-induced spurious RV shifts that can mask or mimic planet signals. This review provides a brief overview of how stellar surface magnetoconvection and oscillations can impact low-mass planet confirmation and the best-tested strategies to overcome this astrophysical noise. These noise reduction strategies originate from a combination of empirical motivation and a theoretical understanding of the underlying physics. The most recent predications indicate that stellar oscillations for Sun-like stars may be averaged out with tailored exposure times, while granulation may need to be disentangled by inspecting its imprint on the stellar line profile shapes. Overall, the literature suggests that Earth-analog detection should be possible, with the correct observing strategy and sufficient data collection.

scholarly journals Asteroseismology of low-mass stars: the balance between partial ionization and Coulomb interactions

2021 ◽  
Vol 507 (4) ◽  
pp. 5747-5757
Author(s):  
Ana Brito ◽  
Ilídio Lopes
Keyword(s):  
Electrostatic Interactions ◽  
Chemical Elements ◽  
Acoustic Oscillation ◽  
Coulomb Interactions ◽  
Low Mass Stars ◽  
Stellar Oscillations ◽  
Diagnostic Potential ◽  
Low Mass ◽  
Coulomb Effects ◽  
The Impact

ABSTRACT All cool stars with outer convective zones have the potential to exhibit stochastically excited stellar oscillations. In this work, we explore the outer layers of stars less massive than the Sun. In particular, we have computed a set of stellar models ranging from 0.4 to 0.9 M⊙ with the aim at determining the impact on stellar oscillations of two physical processes occurring in the envelopes of these stars. Namely, the partial ionization of chemical elements and the electrostatic interactions between particles in the outer layers. We find that alongside with partial ionization, Coulomb effects also impact the acoustic oscillation spectrum. We confirm the well-known result that as the mass of a star decreases, the electrostatic interactions between particles become relevant. We found that their impact on stellar oscillations increases with decreasing mass, and for the stars with the lowest masses (M ≲ 0.6 M⊙), it is shown that Coulomb effects dominate over partial ionization processes producing a strong scatter on the acoustic modes. The influence of Coulomb interactions on the sound-speed gradient profile produces a strong oscillatory behaviour with diagnostic potential for the future.

scholarly journals CO in OH/IR-Stars - on Excitation and Mass Loss

1989 ◽  
Vol 106 ◽  
pp. 368-368
Author(s):  
A. Heske ◽  
H.J. Habing ◽  
W.E.C.J. van der Veen ◽  
A. Omont ◽  
T. Forveille
Keyword(s):  
Mass Loss ◽  
Agb Stars ◽  
Line Formation ◽  
Circumstellar Envelopes ◽  
Simple Method ◽  
Long Period ◽  
Ir Stars ◽  
Low Mass ◽  
The Impact ◽  
Loss Rates

Observations of CO in long period variables have been widely used to determine mass loss rates by applying models for CO line formation (e.g. Knapp and Morris, 1985) which use a simple method to take the impact from infrared radiation into account. Recent 00(2-1) and (1-0) observations of some more evolved OH/IR stars yielded much too low mass loss rates using these simple models, thus indicating that they cannot be extrapolated to far evolved AGB stars with optically thick circumstellar envelopes.

scholarly journals On Mautner-Type Probability of Capture of Intergalactic Meteor Particles by Habitable Exoplanets

Sci ◽  
2019 ◽  
Vol 1 (3) ◽  
pp. 61
Author(s):  
Andjelka B. Kovačević
Keyword(s):  
Single Molecule ◽  
Rare Events ◽  
Birth And Death Processes ◽  
Habitable Zones ◽  
Source Populations ◽  
Dynamical Description ◽  
The Impact ◽  
Near Future ◽  
Host Stars ◽  
Information Metrics

Both macro and microprojectiles (e.g., interplanetary, interstellar and even intergalactic material) are seen as important vehicles for the exchange of potential (bio)material within our solar system as well as between stellar systems in our Galaxy. Accordingly, this requires estimates of the impact probabilities for different source populations of projectiles, including for intergalactic meteor particles which have received relatively little attention since considered as rare events (discrete occurrences that are statistically improbable due to their very infrequent appearance). We employ the simple but comprehensive model of intergalactic microprojectile capture by the gravity of exoplanets which enables us to estimate the map of collisional probabilities for an available sample of exoplanets in habitable zones around host stars. The model includes a dynamical description of the capture adopted from Mautner model of interstellar exchange of microparticles and changed for our purposes. We use statistical and information metrics to calculate probability map of intergalactic meteorite particle capture. Moreover, by calculating the entropy index map we estimate the concentration of these rare events. We further adopted a model from immigration theory, to show that the time dependent distribution of single molecule immigration of material indicates high survivability of the immigrated material taking into account birth and death processes on our planet. At present immigration of material can not be observationally constrained but it seems reasonable to think that it will be possible in the near future, and to use it along other proposed parameters for life sustainability on some planet.

scholarly journals On Mautner-Type Probability of Capture of Intergalactic Meteor Particles by Habitable Exoplanets

Sci ◽  
2019 ◽  
Vol 1 (2) ◽  
pp. 40
Author(s):  
Andjelka B. Kovačević
Keyword(s):  
Rare Events ◽  
Transient Distribution ◽  
Habitable Zones ◽  
Source Populations ◽  
Dynamical Description ◽  
The Impact ◽  
Host Stars ◽  
Information Metrics ◽  
Bio Material ◽  
Probability Of Capture

Both macro and microprojectiles (e.g., interplanetary, interstellar and even intergalactic material) are seen as an important vehicle for the exchange of (bio)material within our solar system as well as between stellar systems in our Galaxy. Accordingly, this requires estimates of the impact probabilities for different source populations of projectiles, specifically for intergalactic meteor particles which have received relatively little attention since considered as rare events (discrete occurrences that are statistically improbable due to their very infrequent appearance). We employ the simple but yet comprehensive model of intergalactic microprojectile capture by the gravity of exoplanets which enables us to estimate the map of collisional probabilities for an available sample of exoplanets in habitable zones around host stars. The model includes a dynamical description of the caption adopted from Mautner model of interstellar exchange of microparticles and changed for our purposes. We use statistical and information metrics to calculate probability map of intergalactic meteorite particle capture. Moreover, by calculating the entropy index map we measure the concentration of these rare events. By adopting a model from immigration theory, we show that the transient distribution of birth/death/immigration of material for the simplest case has a high value.

Influence of social networks on business processes’ development

2020 ◽  
Vol 19 (12) ◽  
pp. 2225-2252
Author(s):  
E.V. Popov ◽  
V.L. Simonova ◽  
O.V. Komarova ◽  
S.S. Kaigorodova
Keyword(s):  
Social Networks ◽  
Social Media ◽  
Business Models ◽  
Business Processes ◽  
Digital Economy ◽  
Theoretical Understanding ◽  
Sales Channels ◽  
A Value ◽  
The Impact

Subject. The emergence of new ways of interaction between sellers and buyers, the formation of new sales channels and product promotion based on the use of digital economy tools is at the heart of improving the business processes. Social networks became a tool for development; their rapid growth necessitates theoretical understanding and identification of potential application in enterprise's business process digitalization. Objectives. We explore the role of social media in the digitalization of business processes, systematize the impact of social networks on business processes of enterprises in the digital economy. Methods. The theoretical and methodological analysis of social networks as a tool for digitalization of company's business processes rests on the content analysis of domestic and foreign scientific studies, comparison, generalization and systematization. Results. We highlight the key effects of the impact of social networks on the business processes of the company; show that the digitalization of business processes should be considered in the context of a value-based approach, aimed at creating a value through the algorithmization of company operations. We determine that social networks are one of the most important tools for digitalization of company's business processes, as they have a high organizational and management potential. We also systematize the effects of social media on company's business processes. Conclusions. We present theoretical provisions of the impact of social networks on business processes of enterprises, which will enable to model and organize ideas about the development of digital ecosystems and the formation of business models.

Toxic Political Leadership and the Problems of Professionals in Free State Municipalities

2019 ◽  
Vol 48 (1) ◽  
Author(s):  
David Matheakuena Mohale
Keyword(s):  
Good Governance ◽  
Political Leadership ◽  
Primary Source ◽  
Free State ◽  
Audit Report ◽  
Theoretical Understanding ◽  
Number Of Factors ◽  
Auditor General ◽  
Appointed Officials ◽  
The Impact

The 2016–17 Audit Report by the Auditor General points to the deterioration in audit results of South African municipalities. This deterioration confirms the perennial dysfunctionality of municipalities, at least from the governance perspective. Corporate governance is a function of leadership. Municipal councils are, therefore, responsible for the overall performance of municipalities they lead. Sound regulatory framework, good plans, clear strategies, policies, and systems are inadequate if not supported by highly gifted and ethical leadership. The Auditor General’s Audit Report suggests that local government struggles the most in the area of ethics. The Principal-Agent Theory argues that appointed officials are more likely to subvert the interests of an organisation. However, this article argues that the primary source of problems in municipalities is a combination of ineptitude and unethical political leadership taking root. This conclusion is based on the empirical comparative cases of eight municipalities in the Free State Province.  The conduct of councillors makes it difficult to attract and retain professionals in municipalities, resulting in notable deficiencies in the delivery of services. Essentially, councillors are the root cause for governance failure in municipalities arising from a number of factors. Findings in this study contribute towards the understanding of the impact of leadership in the failure of municipalities to meet good governance and developmental objectives. Further, they deepen the theoretical understanding of the political-administrative interface.

scholarly journals Effect of Storage Conditions on Storability and Antioxidant Potential of Pears cv. ‘Conference’

Agriculture ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 545
Author(s):  
Grzegorz P. Łysiak ◽  
Krzysztof Rutkowski ◽  
Dorota Walkowiak-Tomczak
Keyword(s):  
Mass Loss ◽  
Strong Influence ◽  
Storage Conditions ◽  
Quality Parameters ◽  
Soluble Solids ◽  
Controlled Atmosphere ◽  
Postharvest Diseases ◽  
Market Prices ◽  
Long Period ◽  
The Impact

Late pear cultivars, such as ‘Conference’, can be stored for a long period if kept in good storage conditions. A three-year study (2011–2013) compared the impact of six-month storage using four technologies—normal atmosphere, normal atmosphere + 1-methylcyclopropene (1-MCP), controlled atmosphere, and controlled atmosphere + 1-MCP—on the quality parameters of ‘Conference’ pears, such as mass loss, firmness, total soluble solids, acidity, antioxidant capacity, and the incidence of diseases and disorders. Additionally, the study analysed different storage conditions in terms of profitability, based on the market prices for pears in the seasons during which the pears were stored. The storage conditions had a very strong influence on the fruit quality parameters, and were found to affect most visibly the mass loss and the incidence of postharvest diseases and disorders. The storage of ‘Conference’ pears for 180 days in normal atmosphere is not economically viable, even if the fruit is subjected to 1-MCP treatment; at the same time, it is profitable to store ‘Conference’ pears in controlled atmosphere for the same period, no matter whether 1-MCP was applied or not.

PODC 2020 Review

2021 ◽  
Vol 51 (4) ◽  
pp. 75-81
Author(s):  
Ahad Mirza Baig ◽  
Alkida Balliu ◽  
Peter Davies ◽  
Michal Dory
Keyword(s):  
Machine Learning ◽  
Distributed Computing ◽  
Keynote Speaker ◽  
Lively Discussion ◽  
Theoretical Understanding ◽  
New Directions ◽  
New Ideas ◽  
New Challenges ◽  
The Impact ◽  
Distributed Machine Learning

Rachid Guerraoui was the rst keynote speaker, and he got things o to a great start by discussing the broad relevance of the research done in our community relative to both industry and academia. He rst argued that, in some sense, the fact that distributed computing is so pervasive nowadays could end up sti ing progress in our community by inducing people to work on marginal problems, and becoming isolated. His rst suggestion was to try to understand and incorporate new ideas coming from applied elds into our research, and argued that this has been historically very successful. He illustrated this point via the distributed payment problem, which appears in the context of blockchains, in particular Bitcoin, but then turned out to be very theoretically interesting; furthermore, the theoretical understanding of the problem inspired new practical protocols. He then went further to discuss new directions in distributed computing, such as the COVID tracing problem, and new challenges in Byzantine-resilient distributed machine learning. Another source of innovation Rachid suggested was hardware innovations, which he illustrated with work studying the impact of RDMA-based primitives on fundamental problems in distributed computing. The talk concluded with a very lively discussion.

scholarly journals Collaborative Learning in Makerspaces: A Grounded Theory of the Role of Collaborative Learning in Makerspaces

SAGE Open ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 215824402110207
Author(s):  
Kolja Oswald ◽  
Xiaokang Zhao
Keyword(s):  
Grounded Theory ◽  
Collaborative Learning ◽  
Venture Creation ◽  
Theoretical Understanding ◽  
Innovative Environment ◽  
Open Coding ◽  
Axial Coding ◽  
The Impact ◽  
Emergent Theory

Makerspaces are a relatively new phenomenon that seem to create an innovative environment for individuals to work on projects and learn about technology. This article presents a grounded theory study, which investigates the impact that makerspaces have on innovation. Strauss and Corbin’s grounded theory methodology is used to research this exploratory topic. The data sample consists of 16 interviews of members of a makerspace in Shanghai, China. Data analysis was conducted abiding by Strauss and Corbin’s coding framework, entailing open coding, axial coding, and selective coding as well as coding tools, such as the coding paradigm and the conditional matrix. Collaborative learning was identified as the core phenomenon of this research, and The Collaborative Learning and its Outcomes Theory was created. The emergent theory contributes to the understanding of how makerspaces impact outcomes, such as innovation and venture creation, as well as explain how collaborative learning in conjunction with other modes of learning can facilitate learning at various complexities. As such, this study’s contributions are in developing the theoretical understanding of makerspaces as well as collaborative learning. It offers managerial and pedagogical implications that can help create learning environments where collaborative learning is fostered.

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