scholarly journals Links between surface magnetic fields, abundances, and surface rotation in clusters and in the field

2014 ◽  
Vol 9 (S307) ◽  
pp. 404-413
Author(s):  
Norbert Przybilla
Keyword(s):  
Magnetic Fields ◽  
Massive Stars ◽  
Chemical Elements ◽  
Relevant Information ◽  
Transport Processes ◽  
Observational Constraints ◽  
Comprehensive Description ◽  
Surface Rotation ◽  
The Many ◽  
Further Development

AbstractTheory predicts that hydrodynamical instabilities transport angular momentum and chemical elements in rotating massive stars. An interplay of rotation and a magnetic field affects these transport processes. The complexity of the problem imposes that a comprehensive description cannot be developed on theoretical grounds alone, progress in the understanding of the evolution of massive stars has to be guided by observations. The challenge lies both in the derivation of accurate and precise observational constraints as well as in the extraction of the relevant information for identifying possible correlations – like between surface magnetic fields, abundances, and surface rotation – from a multivariate function of the many parameters involved. I review the most important steps recently made based on detailed studies of massive stars both in the field and in clusters towards finding such links that ultimately may guide the further development of the models.

scholarly journals The effects of surface fossil magnetic fields on massive star evolution – II. Implementation of magnetic braking in mesa and implications for the evolution of surface rotation in OB stars

2020 ◽  
Vol 493 (1) ◽  
pp. 518-535 ◽  
Author(s):  
Z Keszthelyi ◽  
G Meynet ◽  
M E Shultz ◽  
A David-Uraz ◽  
A ud-Doula ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Magnetic Fields ◽  
Massive Star ◽  
Massive Stars ◽  
Rotation Rates ◽  
Momentum Loss ◽  
Star Models ◽  
Surface Rotation ◽  
Angular Momentum Loss ◽  
Magnetic Braking

ABSTRACT The time evolution of angular momentum and surface rotation of massive stars are strongly influenced by fossil magnetic fields via magnetic braking. We present a new module containing a simple, comprehensive implementation of such a field at the surface of a massive star within the Modules for Experiments in Stellar Astrophysics (mesa) software instrument. We test two limiting scenarios for magnetic braking: distributing the angular momentum loss throughout the star in the first case, and restricting the angular momentum loss to a surface reservoir in the second case. We perform a systematic investigation of the rotational evolution using a grid of OB star models with surface magnetic fields (M⋆ = 5–60 M⊙, Ω/Ωcrit = 0.2–1.0, Bp = 1–20 kG). We then employ a representative grid of B-type star models (M⋆ = 5, 10, 15 M⊙, Ω/Ωcrit = 0.2, 0.5, 0.8, Bp = 1, 3, 10, 30 kG) to compare to the results of a recent self-consistent analysis of the sample of known magnetic B-type stars. We infer that magnetic massive stars arrive at the zero-age main sequence (ZAMS) with a range of rotation rates, rather than with one common value. In particular, some stars are required to have close-to-critical rotation at the ZAMS. However, magnetic braking yields surface rotation rates converging to a common low value, making it difficult to infer the initial rotation rates of evolved, slowly rotating stars.

scholarly journals The MiMeS project: first results

2008 ◽  
Vol 4 (S259) ◽  
pp. 387-388
Author(s):  
Jason H. Grunhut ◽  
E. Alecian ◽  
D. A. Bohlender ◽  
J.-C. Bouret ◽  
H. Henrichs ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Massive Star ◽  
Massive Stars ◽  
Chemical Elements ◽  
Statistical Properties ◽  
The Sun ◽  
Large Program ◽  
Stellar Component ◽  
First Results ◽  
The Universe

AbstractMassive stars are those stars with initial masses above about 8 times that of the sun, eventually leading to catastrophic explosions in the form of supernovae. These represent the most massive and luminous stellar component of the Universe, and are the crucibles in which the lion's share of the chemical elements are forged. These rapidly-evolving stars drive the chemistry, structure and evolution of galaxies, dominating the ecology of the Universe - not only as supernovae, but also during their entire lifetimes - with far-reaching consequences. Although the existence of magnetic fields in massive stars is no longer in question, our knowledge of the basic statistical properties of massive star magnetic fields is seriously incomplete. The Magnetism in Massive Stars (MiMeS) Project represents a comprehensive, multidisciplinary strategy by an international team of recognized researchers to address the “big questions” related to the complex and puzzling magnetism of massive stars. This paper present the first results of the MiMeS Large Program at the Canada-France-Hawaii Telescope.

Pengantar dan Survey Tentang Optical Music Recognition

2014 ◽  
Vol 6 (1) ◽  
pp. 36-39
Author(s):  
Kevin Purwito
Keyword(s):  
Character Recognition ◽  
Optical Character Recognition ◽  
Optical Music Recognition ◽  
Optical Character ◽  
Digital Format ◽  
Music Recognition ◽  
Index Terms ◽  
The Many ◽  
Further Development ◽  
Music Symbol

This paper describes about one of the many extension of Optical Character Recognition (OCR), that is Optical Music Recognition (OMR). OMR is used to recognize musical sheets into digital format, such as MIDI or MusicXML. There are many musical symbols that usually used in musical sheets and therefore needs to be recognized by OMR, such as staff; treble, bass, alto and tenor clef; sharp, flat and natural; beams, staccato, staccatissimo, dynamic, tenuto, marcato, stopped note, harmonic and fermata; notes; rests; ties and slurs; and also mordent and turn. OMR usually has four main processes, namely Preprocessing, Music Symbol Recognition, Musical Notation Reconstruction and Final Representation Construction. Each of those four main processes uses different methods and algorithms and each of those processes still needs further development and research. There are already many application that uses OMR to date, but none gives the perfect result. Therefore, besides the development and research for each OMR process, there is also a need to a development and research for combined recognizer, that combines the results from different OMR application to increase the final result’s accuracy. Index Terms—Music, optical character recognition, optical music recognition, musical symbol, image processing, combined recognizer  

scholarly journals The Formation of Massive Stars

2010 ◽  
Vol 6 (S270) ◽  
pp. 57-64
Author(s):  
Ian A. Bonnell ◽  
Rowan J Smith
Keyword(s):  
Star Formation ◽  
Magnetic Fields ◽  
Massive Star ◽  
Massive Stars ◽  
Cluster Formation ◽  
High Mass ◽  
Prestellar Cores ◽  
Stellar Mergers ◽  
Massive Clusters ◽  
Viable Mechanism

AbstractThere has been considerable progress in our understanding of how massive stars form but still much confusion as to why they form. Recent work from several sources has shown that the formation of massive stars through disc accretion, possibly aided by gravitational and Rayleigh-Taylor instabilities is a viable mechanism. Stellar mergers, on the other hand, are unlikely to occur in any but the most massive clusters and hence should not be a primary avenue for massive star formation. In contrast to this success, we are still uncertain as to how the mass that forms a massive star is accumulated. there are two possible mechanisms including the collapse of massive prestellar cores and competitive accretion in clusters. At present, there are theoretical and observational question marks as to the existence of high-mass prestellar cores. theoretically, such objects should fragment before they can attain a relaxed, centrally condensed and high-mass state necessary to form massive stars. Numerical simulations including cluster formation, feedback and magnetic fields have not found such objects but instead point to the continued accretion in a cluster potential as the primary mechanism to form high-mass stars. Feedback and magnetic fields act to slow the star formation process and will reduce the efficiencies from a purely dynamical collapse but otherwise appear to not significantly alter the process.

The Ecclesial Notions of the Apocalypse in Recent Studies

2002 ◽  
Vol 1 (1) ◽  
pp. 112-136
Author(s):  
Felise Tavo
Keyword(s):  
People Of God ◽  
Historical View ◽  
The Cross ◽  
The 1950S ◽  
The Many ◽  
Further Development ◽  
The Church

Images of the church are found scattered throughout the Apocalypse. These have thus been the focus of recent studies in the ecclesial notions of the seer of Patmos. But as this article illustrates, these studies vary to some extent in their principal focus while the methods of approach have been remarkably 'selective' in their treatment of the many church images of the book. As a way of bringing together these disparate methods and focus, this article discusses seven key thematic emphases in the recent studies of the seer's ecclesial notions since the 1950s, which could perhaps serve as 'rallying points' for further development of a more comprehensive portrait of the church in the Apocalypse: the 'cross-event' as underpinning; the eschatologi cal people of God; a community of equality; corporate in nature; non-addi tive in character; a community seeking repentance; and a trans-historical view of reality.

scholarly journals Modeling Changes in the Composition of River Water with Discharged Wastewater: A Case Study in NW Russia

Water ◽  
2022 ◽  
Vol 14 (2) ◽  
pp. 165
Author(s):  
Alexander I. Malov ◽  
Evgeniya S. Sidkina ◽  
Mikhail V. Mironenko ◽  
Alexey S. Tyshov ◽  
Elena V. Cherkasova
Keyword(s):  
Surface Water ◽  
Chemical Elements ◽  
Conservation Status ◽  
Simplex Algorithm ◽  
Drainage Water ◽  
Discharge Zone ◽  
Mining Operations ◽  
Diamond Deposit ◽  
Further Development

The technogenic impact of the development of the Lomonosov diamond deposit is associated with the discharge of quarry and drainage water into the river, which has a special conservation status. Earlier studies on the composition of bottom sediments showed that there are signs of increased accumulation of heavy metals and radionuclides at wastewater discharge sites. The purpose of this work was to predict changes in the composition of surface water and bottom sediment in the river during the further development of mining operations with brackish and salty water captured by drainage systems, the presence of which was established in the zone of their future influence. For this, a simulation of changes in the composition of the water in the river was carried out using the GEOCHEQ software package by minimizing the free energy of the system using a convex simplex algorithm. It was found that the maximum salinity of surface water can reach 1.51 g/L. In this case, the MPC of Cl−, Na+, SO42−, Mg2+, Sr, V, and U can be exceeded for fishery watercourses. The genetic basis of the accumulation of these components in solutions for mixing was considered. According to the calculations, when about 5000 m3/h of drainage water is discharge d into the river, the mass of precipitated chemical elements will be 56–191 t/h, including up to 2.1 t/h of iron; therefore, accumulation in the discharge zone must be controlled.

60Fe and 244Pu deposited on Earth constrain the r-process yields of recent nearby supernovae

Science ◽  
2021 ◽  
Vol 372 (6543) ◽  
pp. 742-745
Author(s):  
A. Wallner ◽  
M. B. Froehlich ◽  
M. A. C. Hotchkis ◽  
N. Kinoshita ◽  
M. Paul ◽  
...  
Keyword(s):  
Pacific Ocean ◽  
Neutron Stars ◽  
Neutron Capture ◽  
Half Life ◽  
Massive Stars ◽  
Chemical Elements ◽  
Capture Process ◽  
Isotopic Signatures ◽  
Supernova Explosions ◽  
R Process

Half of the chemical elements heavier than iron are produced by the rapid neutron capture process (r-process). The sites and yields of this process are disputed, with candidates including some types of supernovae (SNe) and mergers of neutron stars. We search for two isotopic signatures in a sample of Pacific Ocean crust—iron-60 (60Fe) (half-life, 2.6 million years), which is predominantly produced in massive stars and ejected in supernova explosions, and plutonium-244 (244Pu) (half-life, 80.6 million years), which is produced solely in r-process events. We detect two distinct influxes of 60Fe to Earth in the last 10 million years and accompanying lower quantities of 244Pu. The 244Pu/60Fe influx ratios are similar for both events. The 244Pu influx is lower than expected if SNe dominate r-process nucleosynthesis, which implies some contribution from other sources.

Computer Gaming Scenarios for Product Development Teams

2014 ◽  
pp. 216-233
Author(s):  
Andrew J. Wodehouse ◽  
William J. Ion
Keyword(s):  
Product Development ◽  
Computer Games ◽  
Digital Technologies ◽  
Relevant Information ◽  
Concept Design ◽  
Concept Generation ◽  
Computer Gaming ◽  
Development Teams ◽  
New Ideas ◽  
Further Development

In this paper, computer gaming approaches are introduced as a viable means to structure the interaction of a product development team during concept generation. During concept generation, teams gather large amounts of information before generating new ideas and concepts. Digital technologies mean that relevant information can be sourced faster than ever, but this does not necessarily migrate into the activity of concept creation. It is suggested that cues from computer games can help integrate information as well as individuals more effectively, resulting in better conceptual output. A range of game types are evaluated with a view to their possible utilization in support of concept design. Two scenarios for the implementation of gaming methods are proposed, and one refined scenario identified as having potential for further development.

scholarly journals Sun-like Stars: magnetic fields, cycles and exoplanets

2015 ◽  
Vol 11 (A29A) ◽  
pp. 360-364
Author(s):  
Rim Fares
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Large Scale ◽  
Observational Constraints ◽  
The Sun ◽  
Field Generation ◽  
Large Scale Magnetic Field ◽  
Planetary Orbits ◽  
Activity Cycles ◽  
Magnetic Cycles

AbstractIn Sun-like stars, magnetic fields are generated in the outer convective layers. They shape the stellar environment, from the photosphere to planetary orbits. Studying the large-scale magnetic field of those stars enlightens our understanding of the field properties and gives us observational constraints for field generation dynamo models. It also sheds light on how “normal” the Sun is among Sun-like stars. In this contribution, I will review the field properties of Sun-like stars, focusing on solar twins and planet hosting stars. I will discuss the observed large-scale magnetic cycles, compare them to stellar activity cycles, and link that to what we know about the Sun. I will also discuss the effect of large-scale stellar fields on exoplanets, exoplanetary emissions (e.g. radio), and habitability.

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