scholarly journals Influence of sub- and super-solar metallicities on the composition of solid planetary building blocks

2019 ◽  
Vol 633 ◽  
pp. A10 ◽  
Author(s):  
Bertram Bitsch ◽  
Chiara Battistini
Keyword(s):  
Planet Formation ◽  
Building Blocks ◽  
The Other ◽  
Chemical Model ◽  
Stellar Abundances ◽  
Water Ice ◽  
Other Hand ◽  
Iron Abundance ◽  
Ice Content ◽  
Ice Fraction

The composition of the protoplanetary disc is thought to be linked to the composition of the host star, where a higher overall metallicity provides the building blocks for planets. However, most of the planet formation simulations only link the stellar iron abundance [Fe/H] to planet formation and the iron abundance in itself is used as a proxy to scale all elements. On the other hand, large surveys of stellar abundances show that this is not true. Here we use stellar abundances from the GALAH surveys to determine the average detailed abundances of Fe, Si, Mg, O, and C for a broad range of host star metallicities with [Fe/H] spanning from −0.4 to +0.4. Using an equilibrium chemical model that features the most important rock-forming compounds as well as volatile contributions of H2O, CO2, CH4, and CO, we calculate the chemical composition of solid planetary building blocks around stars with different metallicities. Solid building blocks that are formed entirely interior to the water ice line (T > 150 K) only show an increase in Mg2SiO4 and a decrease in MgSiO3 for increasing host star metallicity, which is related to the increase of [Mg/Si] for higher [Fe/H]. Solid planetary building blocks forming exterior to the water ice line (T < 150 K), on the other hand, show dramatic changes in their composition. In particular, the water ice content decreases from around ~50% at [Fe/H] = −0.4 to ~6% at [Fe/H] = 0.4 in our chemical model. This is mainly caused by the increasing C/O ratio with increasing [Fe/H], which binds most of the oxygen in gaseous CO and CO2, resulting in a small water ice fraction. Planet formation simulations coupled with the chemical model confirm these results by showing that the water ice content of super-Earths decreases with increasing host star metallicity due to the increased C/O ratio. This decrease of the water ice fraction has important consequences for planet formation, planetary composition, and the eventual habitability of planetary systems formed around these high-metallicity stars.

scholarly journals N-body Simulations of Planet Formation

2003 ◽  
Vol 208 ◽  
pp. 25-35 ◽  
Author(s):  
Shigeru Ida ◽  
Eiichiro Kokubo ◽  
Junko Kominami
Keyword(s):  
Final Stage ◽  
Planet Formation ◽  
Planetary Systems ◽  
Terrestrial Planet ◽  
The Other ◽  
Other Hand ◽  
Giant Impacts ◽  
Gas Accretion

Accretion from many small planetesimals to planets is reviewed. Solid protoplanets accrete through runaway and oligarchic growth until they become isolated. The isolation mass of protoplanets in terrestrial planet region is about 0.1-0.2 Earth mass, which suggests giant impacts among the protoplanets in the final stage of terrestrial planet formation. On the other hand, the isolation mass in Jupiter's and Saturn's orbits is about a few to 5 Earth masses, which may be massive enough to trigger gas accretion onto the cores. The isolation mass in Uranus and Neptune's orbits is as large as their present cores. Extending the above arguments to extrasolar planetary systems that are formed from disks with various initial masses, we also discuss diversity of extrasolar planetary systems.

scholarly journals The Doctrinal Complication in Al-Ash'ari’s Doctrine and its Role in Managing the Doctrinal Disputes

2021 ◽  
Vol 32 (2) ◽  
pp. 1-15
Author(s):  
Mohamed Ararou
Keyword(s):  
Analytical Approach ◽  
Building Blocks ◽  
Research Topic ◽  
The Other ◽  
Other Hand ◽  
General Rules ◽  
The One

This research aims to clarify the concept of doctrinal rules and adjust its basic terminologies. It further aims to lay down a map for the method of rooting this science by mentioning its rooted sources, in addition to drawing a miniature picture of its history, origin, formation and development. The paper ends with practical models to highlight its importance in rooting the science of nodal rules and facilitating the mentioning of its scattered discussions in a short and comprehensive phrase. The study further illustrates the pioneering role of doctrinal rules science in managing the doctrinal disputes, combining multiple sayings, and in bringing together opposing opinions. The study follows the inductive, descriptive and analytical approach. The importance of the research topic lies in the fact that it tackles something that has not yet been widely examined. Thus, researching such a topic is considered a new thing due to the scarcity of what has been written on it, on the one hand. On the other hand, the topic is serious as it talks about the Contractual Rules, which have not gained sufficient research among the applicants. Besides, what has been so far written on the doctrinal rules is related to the chapters of the doctrine and its general discussions; a matter which is similar to Al-Ghazali’s rules of beliefs. No allocation was dedicated to its contractual aspect. Accordingly, the present research is one of the important building blocks of the doctrinal lesson, as it is related to inferencing the science of belief and collecting its dispersed discussions under general rules in an

scholarly journals Collisions of Planetesimals and Formation of Planets

2015 ◽  
Vol 10 (S314) ◽  
pp. 251-252
Author(s):  
Rudolf Dvorak ◽  
Thomas I. Maindl ◽  
Áron Süli ◽  
Christoph M. Schäfer ◽  
Roland Speith ◽  
...  
Keyword(s):  
Numerical Integration ◽  
Planet Formation ◽  
Terrestrial Planet ◽  
The Other ◽  
Smooth Particle Hydrodynamics ◽  
Small Bodies ◽  
Preliminary Results ◽  
Other Hand ◽  
Particle Hydrodynamics ◽  
The One

AbstractWe present preliminary results of models of terrestrial planet formation using on the one hand classical numerical integration of hundreds of small bodies on CPUs and on the other hand—for comparison—the results of our GPU code with thousands of small bodies which then merge to larger ones. To be able to determine the outcome of collision events we use our smooth particle hydrodynamics (SPH) code which tracks how water is lost during such events.

A two-level grammar of the reduction processes of French complex terms in discourse

Terminology ◽  
2003 ◽  
Vol 9 (1) ◽  
pp. 1-27 ◽  
Author(s):  
Tanja Collet
Keyword(s):  
Surface Structure ◽  
Building Blocks ◽  
The Other ◽  
Descriptive Grammar ◽  
Main Building ◽  
Reduction Processes ◽  
Other Hand ◽  
Semantic Properties

The aim of this paper is to offer an outline of a descriptive grammar — as yet unfinished — of two reduction processes, namely elliptic anaphor and lexical elision, which delete constituents of reiterated complex terms in French LSP texts. After an examination of these reduction processes and the term variants they generate, the paper presents the main building blocks of the grammar. The architecture of these building blocks, i.e. of the deep and surface structure rules which constitute the two levels of the grammar, is derived from the structural and semantic properties of French complex terms. The ordering of the rules in the grammar, on the other hand, is based on characteristics of elliptic anaphor and lexical elision as well as on properties of the term variants produced by these context-conditioned transformations.

scholarly journals Transition-Metal-Catalyzed Alkenyl sp2 C–H Activation: A Short Account

Synthesis ◽  
2019 ◽  
Vol 51 (05) ◽  
pp. 1049-1062 ◽  
Author(s):  
Manikantha Maraswami ◽  
Teck-Peng Loh
Keyword(s):  
Transition Metal ◽  
Scientific Community ◽  
Chemical Properties ◽  
Building Blocks ◽  
Metal Catalysts ◽  
Transition Metal Catalysts ◽  
The Other ◽  
Short Account ◽  
Other Hand ◽  
Metal Catalyzed

Alkenes are ubiquitous in Nature and their functionalization continues to attract attention from the scientific community. On the other hand, activation of alkenyl sp2 C–H bonds is challenging due to their chemical properties. In this short account, we elucidate, discuss and describe the utilization of transition-metal catalysts in alkene activation and provide useful strategies to synthesize organic building blocks in an efficient and sustainable manner.1 Introduction2 Breakthrough3 Controlling E/Z, Z/E Selectivity3.1 Esters and Amides as Directing Groups3.2 The Chelation versus Non-Chelation Concept4 Other Alkene Derivatives5 Intramolecular C–H Activation6 Conclusion and Future Projects

scholarly journals An overall picture of EMP stars using the stellar abundances for galactic archaeology (SAGA) database

2009 ◽  
Vol 5 (S265) ◽  
pp. 90-93
Author(s):  
Takuma Suda ◽  
Shimako Yamada ◽  
Yutaka Katsuta ◽  
Chikako Ishizuka ◽  
Yutaka Komiya ◽  
...  
Keyword(s):  
Early Phase ◽  
Globular Clusters ◽  
The Other ◽  
Stellar Abundances ◽  
Mixing Processes ◽  
Lithium Abundance ◽  
Other Hand ◽  
The Galaxy ◽  
Order Of Magnitude ◽  
Red Giant

AbstractWe explore the general characteristics of extremely metal-poor (EMP) stars in the Galaxy using the Stellar Abundances for Galactic Archaeology (SAGA) database (Suda et al. 2008, PASJ, 60, 1159). The overall trend of EMP stars suggests that there are at least two types of extra mixing to change the surface abundances of EMP stars. One is to deplete lithium abundance during the early phase of giant branch and another is to decrease C/N ratio by one order of magnitude during the red giant branch or AGB phase. On the other hand, these mixing processes are different from those suggested in the Galactic globular clusters because of the different relations between O, Na, Mg, and Al abundances.

Allenes: Versatile Building Blocks in cobalt-catalyzed C-H Activation

Synlett ◽  
2021 ◽  
Author(s):  
Chandra Volla ◽  
Rahul Shukla ◽  
Akshay Nair
Keyword(s):  
Transition Metal ◽  
Building Blocks ◽  
The Other ◽  
Lewis Acidity ◽  
Other Hand ◽  
Leaving Group ◽  
Widespread Interest

The unique reactivity of allenes have led to their emergence as resourceful coupling partners in transition metal mediated C-H activation reactions. On the other hand, cobalt due to its wide abundance and higher Lewis acidity is garnering widespread interest as useful catalyst for C-H activation. Summarised herein are the cobalt-catalyzed C-H activations engaging allenes as coupling partners followed by our studies on Co(III)-catalyzed C-8 dienylation of quinoline N-oxides with allenes bearing leaving group at α-position for realizing a dienylation protocol.

scholarly journals Rocky super-Earths or waterworlds: the interplay of planet migration, pebble accretion, and disc evolution

2019 ◽  
Vol 624 ◽  
pp. A109 ◽  
Author(s):  
Bertram Bitsch ◽  
Sean N. Raymond ◽  
Andre Izidoro
Keyword(s):  
Gas Phase ◽  
Source Region ◽  
The Other ◽  
Relative Speed ◽  
Water Ice ◽  
Migration History ◽  
Planet Migration ◽  
Ice Content ◽  
Outward Migration ◽  
Water Contents

Recent observations have found a valley in the size distribution of close-in super-Earths that is interpreted as a signpost that close-in super-Earths are mostly rocky in composition. However, new models predict that planetesimals should first form at the water ice line such that close-in planets are expected to have a significant water ice component. Here we investigate the water contents of super-Earths by studying the interplay between pebble accretion, planet migration and disc evolution. Planets’ compositions are determined by their position relative to different condensation fronts (ice lines) throughout their growth. Migration plays a key role. Assuming that planetesimals start at or exterior to the water ice line (r > rH2O), inward migration causes planets to leave the source region of icy pebbles and therefore to have lower final water contents than in discs with either outward migration or no migration. The water ice line itself moves inward as the disc evolves, and delivers water as it sweeps across planets that formed dry. The relative speed and direction of planet migration and inward drift of the water ice line is thus central in determining planets’ water contents. If planet formation starts at the water ice line, this implies that hot close-in super-Earths (r < 0.3 AU) with water contents of a few percent are a signpost of inward planet migration during the early gas phase. Hot super-Earths with larger water ice contents on the other hand, experienced outward migration at the water ice line and only migrated inwards after their formation was complete either because they become too massive to be contained in the region of outward migration or in chains of resonant planets. Measuring the water ice content of hot super-Earths may thus constrain their migration history.

scholarly journals Entropy of Mixing of Cadmium-based Liquid Alloys

1970 ◽  
Vol 26 ◽  
pp. 40-45
Author(s):  
S. K. Chakrabarti ◽  
B. K. Jha ◽  
I. S. Jha
Keyword(s):  
Thermodynamic Properties ◽  
Binary Alloys ◽  
The Other ◽  
Chemical Model ◽  
Liquid Alloys ◽  
Atomic Composition ◽  
Reactive Metal ◽  
Entropy Of Mixing ◽  
Binary Liquid ◽  
Other Hand

Cadmium is a highly reactive metal. At the time of formation of binary alloys in liquidphase it often forms complexes. In the present work we have considered two such complexforming binary liquid alloys of cadmium e.g. Cd-Na and Cd-Mg. The former alloy showsanomaly in its thermodynamic properties of mixing. On the other hand, the alloyingbehavior of the latter one is symmetric around the equi-atomic composition. We havecomputed their entropy of mixing (SM) for different concentrations of the ingredients byusing the quasi-lattice chemical model. The results explain the observed anomaly as well assymmetry in SM of the present alloys.Keywords: Binary liquid alloys of cadmium; Quasi-lattice chemical model; Entropy of mixingDOI: 10.3126/jncs.v26i0.3629Journal of Nepal Chemical SocietyVol. 26, 2010Page:40-45

Propositional logic

2004 ◽  
Author(s):  
Shawn Hedman
Keyword(s):  
Fuzzy Logic ◽  
Propositional Logic ◽  
Building Blocks ◽  
English Word ◽  
The Other ◽  
American Women ◽  
Truth Values ◽  
Other Hand ◽  
Truth Value ◽  
The Relationship

In propositional logic, atomic formulas are propositions. Any assertion will do. For example, . . . A = “Aristotle is dead,” B = “Barcelona is on the Seine,” and C = “Courtney Love is tall” . . . are atomic formulas. Atomic formulas are the building blocks used to construct sentences. In any logic, a sentence is regarded as a particular type of formula. In propositional logic, there is no distinction between these two terms. We use “formula” and “sentence” interchangeably. In propositional logic, as with all logics we study, each sentence is either true or false. A truth value of 1 or 0 is assigned to the sentence accordingly. In the above example, we may assign truth value 1 to formula A and truth value 0 to formula B. If we take proposition C literally, then its truth is debatable. Perhaps it would make more sense to allow truth values between 0 and 1. We could assign 0.75 to statement C if Miss Love is taller than 75% of American women. Fuzzy logic allows such truth values, but the classical logics we study do not. In fact, the content of the propositions is not relevant to propositional logic. Henceforth, atomic formulas are denoted only by the capital letters A, B, C,. . . (possibly with subscripts) without referring to what these propositions actually say. The veracity of these formulas does not concern us. Propositional logic is not the study of truth, but of the relationship between the truth of one statement and that of another. The language of propositional logic contains words for “not,” “and,” “or,” “implies,” and “if and only if.” These words are represented by symbols: . . . ￢ for “not,” ∧ for “and,” ∨ for “or,” → for “implies,” and ↔ for “if and only if.” . . . As is always the case when translating one language into another, this correspondence is not exact. Unlike their English counterparts, these symbols represent concepts that are precise and invariable. The meaning of an English word, on the other hand, always depends on the context.

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