scholarly journals Rapid destruction of planetary debris around white dwarfs through aeolian erosion

2021 ◽  
Vol 502 (4) ◽  
pp. 5176-5184
Author(s):  
Mor Rozner ◽  
Dimitri Veras ◽  
Hagai B Perets
Keyword(s):  
White Dwarfs ◽  
Extensive Study ◽  
Destructive Process ◽  
Rapid Destruction ◽  
Aeolian Erosion ◽  
Formation And Evolution ◽  
Destructive Processes ◽  
Solid Bodies ◽  
Erosive Effect

ABSTRACT The discovery of numerous debris discs around white dwarfs (WDs) gave rise to extensive study of such discs and their role in polluting WDs, but the formation and evolution of these discs is not yet well understood. Here, we study the role of aeolian (wind) erosion in the evolution of solids in WD debris discs. Aeolian erosion is a destructive process that plays a key role in shaping the properties and size distribution of planetesimals, boulders, and pebbles in gaseous protoplanetary discs. Our analysis of aeolian erosion in WD debris discs shows that it can also play an important role in these environments. We study the effects of aeolian erosion under different conditions of the disc and its erosive effect on planetesimals and boulders of different sizes. We find that solid bodies smaller than $\sim \! 5 \, \rm {km}$ will be eroded within the short disc lifetime. We compare the role of aeolian erosion in respect to other destructive processes such as collisional fragmentation and thermal ablation. We find that aeolian erosion is the dominant destructive process for objects with radius $\lesssim \! 10^3 \, \rm {cm}$ and at distances $\lesssim \! 0.6 \, \mathrm{R}_\odot$ from the WD. Thereby, aeolian erosion constitutes the main destructive pathway linking fragmentational collisions operating on large objects with sublimation of the smallest objects and Poynting–Robertson drag, which leads to the accretion of the smallest particles on to the photosphere of WDs, and the production of polluted WDs.

scholarly journals l-Aspartate: An Essential Metabolite for Plant Growth and Stress Acclimation

Molecules ◽  
2021 ◽  
Vol 26 (7) ◽  
pp. 1887
Author(s):  
Mei Han ◽  
Can Zhang ◽  
Peter Suglo ◽  
Shuyue Sun ◽  
Mingyao Wang ◽  
...  
Keyword(s):  
Plant Growth ◽  
Physiological Role ◽  
Tca Cycle ◽  
Extensive Study ◽  
Cell Compartments ◽  
Stress Acclimation ◽  
Whole Plant ◽  
Glycolysis Pathway ◽  
Acid Pathway

L-aspartate (Asp) serves as a central building block, in addition to being a constituent of proteins, for many metabolic processes in most organisms, such as biosynthesis of other amino acids, nucleotides, nicotinamide adenine dinucleotide (NAD), the tricarboxylic acid (TCA) cycle and glycolysis pathway intermediates, and hormones, which are vital for growth and defense. In animals and humans, lines of data have proved that Asp is indispensable for cell proliferation. However, in plants, despite the extensive study of the Asp family amino acid pathway, little attention has been paid to the function of Asp through the other numerous pathways. This review aims to elucidate the most important aspects of Asp in plants, from biosynthesis to catabolism and the role of Asp and its metabolic derivatives in response to changing environmental conditions. It considers the distribution of Asp in various cell compartments and the change of Asp level, and its significance in the whole plant under various stresses. Moreover, it provides evidence of the interconnection between Asp and phytohormones, which have prominent functions in plant growth, development, and defense. The updated information will help improve our understanding of the physiological role of Asp and Asp-borne metabolic fluxes, supporting the modular operation of these networks.

scholarly journals The Role of Radio Loud Phase of Nuclear Activity in Galaxy Formation and Evolution

2013 ◽  
Vol 9 (S304) ◽  
pp. 419-420
Author(s):  
Gabriel A. Ohanian
Keyword(s):  
Galaxy Formation ◽  
Subsequent Development ◽  
Nuclear Activity ◽  
Evolution Of Galaxies ◽  
Galaxy Formation And Evolution ◽  
Formation And Evolution ◽  
Key Questions

AbstractKey questions, which arise when one tries to clear up a problem of formation and evolution of galaxies, is the question of energy: what is the energetic budget of AGN owing to form galaxies and provide its subsequent development? Hence, for understanding the formation and evolution of galaxies, it is important to estimate the energetic budget of AGN which we try to do involving radio loud phase of nuclear activity.

The role of ions in the formation and evolution of particles in aircraft plumes

1997 ◽  
Vol 24 (15) ◽  
pp. 1927-1930 ◽  
Author(s):  
Fangqun Yu ◽  
Richard P. Turco
Keyword(s):  
Formation And Evolution

Role of macronutrient intake in the epigenetics of obesity

2022 ◽  
Author(s):  
Priyadarshni Patel ◽  
Jeganathan Ramesh Babu ◽  
Xu Wang ◽  
Thangiah Geetha
Keyword(s):  
Gene Expression ◽  
Animal Studies ◽  
Extensive Study ◽  
Epigenetic Alterations ◽  
Lifestyle Choices ◽  
Obesity Genes ◽  
The Relationship ◽  
Diet And Lifestyle

Obesity is caused by a combination of hereditary and environmental factors. Despite extensive study, contemporary through diet, exercise, education, surgery, and pharmacological treatments, no effective long-term solution has been found to this epidemic. Over the last decade, there has been a tremendous advancement in understanding the science of epigenetics, as well as a rise in public interest in learning more about the influence of diet and lifestyle choices on the health of an individual. Without affecting the underlying DNA sequence, epigenetic alterations impact gene expression. Previous animal studies have shown a link between the type of diet and expression or suppression of obesity genes, but there are very few human studies that demonstrate the relationship between dietary intake and obesity gene expression. This review highlights the effects of carbohydrates, lipids, and protein intake from the diet on obesity-related genes.

Liverpool Shipowners, the Mediterranean, and the Transition from Sail to Steam During the Mid-Nineteenth Century

1992 ◽  
pp. 153-202 ◽  
Author(s):  
P.L. Cottrell
Keyword(s):  
Nineteenth Century ◽  
Extensive Study ◽  
Maritime History ◽  
Nautical Archaeology ◽  
History Of ◽  
The Mediterranean

This section of the journal is comprised of essays exploring the local maritime history of Liverpool and Merseyside. P.L. Cottrell studies Merseyside trade with the Mediterranean; Frank Neal considers the organisation of Liverpudlian ship carpenters and their impact on shipbuilding; Adrian Jarvis examines the role of Alfred Jones in Liverpool's maritime history; and Michael Stammers discusses Professor Davies' extensive study of Liverpool's nautical archaeology.

The presence of helium in hot DA white dwarfs - The role of radiative levitation and the case for stratifies atmospheres

1988 ◽  
Vol 331 ◽  
pp. 876 ◽  
Author(s):  
S. Vennes ◽  
C. Pelletier ◽  
G. Fontaine ◽  
F. Wesemael
Keyword(s):  
White Dwarfs

scholarly journals Flare Stars Database

1994 ◽  
Vol 161 ◽  
pp. 380-382
Author(s):  
M. Tsvetkov ◽  
M. Chukova ◽  
K. Tsvetkova
Keyword(s):  
Wide Field ◽  
Flare Activity ◽  
The Galaxy ◽  
Statistical Regularities ◽  
Ceti Type ◽  
Formation And Evolution ◽  
Flare Stars ◽  
Machine Readable

The important role of flare stars (UV Ceti type variables) in astrophysics is due to the fact that the flare activity is not only typical for red stars with small masses but is a necessary stage during their evolution. The flare star search in stellar aggregates has led to the accumulation of rich observational material allowing us to look for statistical regularities in star formation and evolution. At present, there are more than 1500 known flare stars in the Galaxy; these were discovered mainly during the last 30 years. Most results of the long term monitoring with wide-field telescopes are listed in existing catalogues of flare stars in stellar aggregates and in the solar neighbourhood. These catalogues and their machine-readable versions were the basis for the present database of flare stars in the Galaxy.

scholarly journals Genetic evidence further elucidates the history and extent of badger introductions from Great Britain into Ireland

2020 ◽  
Vol 7 (4) ◽  
pp. 200288 ◽  
Author(s):  
Adrian Allen ◽  
Jimena Guerrero ◽  
Andrew Byrne ◽  
John Lavery ◽  
Eleanor Presho ◽  
...  
Keyword(s):  
Great Britain ◽  
Meles Meles ◽  
Extensive Study ◽  
Colonization History ◽  
Dna Evidence ◽  
History Of ◽  
Admixed Population ◽  
The Subject ◽  
The Last Glacial

The colonization of Ireland by mammals has been the subject of extensive study using genetic methods and forms a central problem in understanding the phylogeography of European mammals after the Last Glacial Maximum. Ireland exhibits a depauperate mammal fauna relative to Great Britain and continental Europe, and a range of natural and anthropogenic processes have given rise to its modern fauna. Previous Europe-wide surveys of the European badger ( Meles meles ) have found conflicting microsatellite and mitochondrial DNA evidence in Irish populations, suggesting Irish badgers have arisen from admixture between human imported British and Scandinavian animals. The extent and history of contact between British and Irish badger populations remains unclear. We use comprehensive genetic data from Great Britain and Ireland to demonstrate that badgers in Ireland's northeastern and southeastern counties are genetically similar to contemporary British populations. Simulation analyses suggest this admixed population arose in Ireland 600–700 (CI 100–2600) years before present most likely through introduction of British badgers by people. These findings add to our knowledge of the complex colonization history of Ireland by mammals and the central role of humans in facilitating it.

scholarly journals The Role of Magnetic Field in Molecular Cloud Formation and Evolution

2019 ◽  
Vol 6 ◽  
Author(s):  
Patrick Hennebelle ◽  
Shu-ichiro Inutsuka
Keyword(s):  
Magnetic Field ◽  
Molecular Cloud ◽  
Cloud Formation ◽  
Formation And Evolution
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