scholarly journals 1. Interstellar Material in Meteorites: Implications for the Origin and Evolution of the Solar Nebula

1977 ◽  
Vol 39 ◽  
pp. 335-341
Author(s):  
R. N. Clayton
Keyword(s):  
High Temperature ◽  
Solar Nebula ◽  
Decay Product ◽  
Solid Particles ◽  
Carbonaceous Chondrites ◽  
Origin And Evolution ◽  
Interstellar Material ◽  
Nuclear Processes ◽  
Identification And Characterization

Several isotopie anomalies, unexplained by known nuclear or non-nuclear processes within the solar system have been attributed to the preservation of pre-solar variations. The largest of these (in number of atoms) in an 16O-excess (up to 5%) in “high-temperature condensate” minerals in primitive meteorites. Some of these same minerals have an excess of 26Mg, probably a decay product of 26Al, that could have been a major source of heat for melting and metamorphosing planetesimals. Excesses of 22Ne and of isotopes of Xe, found in carbonaceous chondrites, may have origins in presolar solid particles. Large variation in the isotopie abundances of nitrogen and carbon in meteorites may also represent isotopie heterogeneity in the solar nebula. Most of these “Isotopically anomalous” elements are found to be highly concentrated in minute phases within the meteorites, rather than being uniformly distributed. The identification and characterization of these carriers of presolar materials constitutes the principal thrust of current research in this area.

Magnetotactic bacteria in Tengchong hot springs, China

2020 ◽  
Author(s):  
Jia Liu ◽  
Wensi Zhang ◽  
Fang Yuan ◽  
Yongxin Pan ◽  
Wei Lin
Keyword(s):  
Hot Springs ◽  
Hot Spring ◽  
Extreme Environments ◽  
Magnetotactic Bacteria ◽  
Origin And Evolution ◽  
Water Columns ◽  
Genomic Analyses ◽  
Ph Range ◽  
Identification And Characterization

<p>Magnetotactic bacteria (MTB) biomineralize intracellular magnetic nanocrystals and can use the geomagnetic field to navigate towards specific microenvironments in water columns and sediments. MTB are a model system to study the mechanisms of microbial magnetoreception and biomineralization. The majority of MTB identified so far are from environments with pH values near neutral and at the normal range of temperature. MTB from extreme environments, such as hot springs, has not been observed and described until recently. However, our knowledge on extremophilic MTB is still very limited. Here we report the identification and characterization of various MTB in Tengchong hot springs, China, with a temperature range of 41.3-69.5 °C and a pH range of 7.1-8.6. Although MTB are diverse in cell morphology, they all form bullet-shaped magnetite magnetosomes organized into either one chain or multiple bundles of chains. Through genome-resolved metagenomics, we have reconstructed five genome bins of hot spring MTB that are all affiliated within the <em>Nitrspirae</em> phylum. Genomic analyses and metabolic reconstructions are now in progress. These results will help to better understand the extremophilic MTB and may shed new lights on the origin and evolution of microbial magnetoreception and biomineralization.</p>

scholarly journals 1. High-Temperature Condensates in Carbonaceous Chondrites

1977 ◽  
Vol 39 ◽  
pp. 507-516
Author(s):  
L. Grossman
Keyword(s):  
High Temperature ◽  
Trace Element ◽  
Solar Nebula ◽  
Trace Element Content ◽  
Group Iv ◽  
Carbonaceous Chondrites ◽  
Equilibrium Thermodynamic ◽  
Iron Meteorites ◽  
Solar Composition ◽  
Different Types

Equilibrium thermodynamic calculations of the sequence of condensation of minerals from a cooling gas of solar composition play an important role in explaining the mineralogy and trace element content of different types of inclusions in carbonaceous chondrites. Group IV B iron meteorites and enstatite chondrites may also be direct condensates from the solar nebula. Condensation theory provides a framework within which chemical fractionations between different classes of chondrites may be understood.

scholarly journals Functional Proteomics of Nuclear Proteins in Tetrahymena thermophila: A Review

Genes ◽  
2019 ◽  
Vol 10 (5) ◽  
pp. 333 ◽  
Author(s):  
Alejandro Saettone ◽  
Syed Nabeel-Shah ◽  
Jyoti Garg ◽  
Jean-Philippe Lambert ◽  
Ronald E. Pearlman ◽  
...  
Keyword(s):  
Genome Stability ◽  
Tetrahymena Thermophila ◽  
Protein Complexes ◽  
Significant Progress ◽  
Unique Biology ◽  
Chromatin Biology ◽  
Nuclear Processes ◽  
Identification And Characterization ◽  
Ciliate Protozoa

Identification and characterization of protein complexes and interactomes has been essential to the understanding of fundamental nuclear processes including transcription, replication, recombination, and maintenance of genome stability. Despite significant progress in elucidation of nuclear proteomes and interactomes of organisms such as yeast and mammalian systems, progress in other models has lagged. Protists, including the alveolate ciliate protozoa with Tetrahymena thermophila as one of the most studied members of this group, have a unique nuclear biology, and nuclear dimorphism, with structurally and functionally distinct nuclei in a common cytoplasm. These features have been important in providing important insights about numerous fundamental nuclear processes. Here, we review the proteomic approaches that were historically used as well as those currently employed to take advantage of the unique biology of the ciliates, focusing on Tetrahymena, to address important questions and better understand nuclear processes including chromatin biology of eukaryotes.

scholarly journals Rapid condensation of the first Solar System solids

2019 ◽  
Vol 116 (47) ◽  
pp. 23461-23466 ◽  
Author(s):  
Yves Marrocchi ◽  
Johan Villeneuve ◽  
Emmanuel Jacquet ◽  
Maxime Piralla ◽  
Marc Chaussidon
Keyword(s):  
High Temperature ◽  
Thermal Annealing ◽  
Large Mass ◽  
Protoplanetary Disk ◽  
Carbonaceous Chondrites ◽  
Si Isotopes ◽  
Si Isotope ◽  
Mass Dependent ◽  
Isotopic Measurements

Chondritic meteorites are composed of primitive components formed during the evolution of the Solar protoplanetary disk. The oldest of these components formed by condensation, yet little is known about their formation mechanism because of secondary heating processes that erased their primordial signature. Amoeboid Olivine Aggregates (AOAs) have never been melted and underwent minimal thermal annealing, implying they might have retained the conditions under which they condensed. We performed a multiisotope (O, Si, Mg) characterization of AOAs to constrain the conditions under which they condensed and the information they bear on the structure and evolution of the Solar protoplanetary disk. High-precision silicon isotopic measurements of 7 AOAs from weakly metamorphosed carbonaceous chondrites show large, mass-dependent, light Si isotope enrichments (–9‰ < δ30Si < –1‰). Based on physical modeling of condensation within the protoplanetary disk, we attribute these isotopic compositions to the rapid condensation of AOAs over timescales of days to weeks. The same AOAs show slightly positive δ25Mg that suggest that Mg isotopic homogenization occurred during thermal annealing without affecting Si isotopes. Such short condensation times for AOAs are inconsistent with disk transport timescales, indicating that AOAs, and likely other high-temperature condensates, formed during brief localized high-temperature events.

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