scholarly journals Bubbles to Chondrites-II. Chemical fractionations in chondrites

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Akihiko Hashimoto ◽  
Yuki Nakano
Keyword(s):  
Lightning Discharge ◽  
Chemical Compositions ◽  
Vortex Center ◽  
Redox States ◽  
Current Observation ◽  
System Composition ◽  
Formation Zone ◽  
Self Gravity ◽  
Chondrule Formation ◽  
Large Charge

AbstractWe attempt to develop a possible theory of chemical fractionations in chondrites, that is consistent with various features of chondritic components and current observation of protoplanetary disks (PPD). Combining the 3+2 component fitting calculation that simulates chondrule formation process proposed in paper (I) with additional mixing procedures, we investigate essential causes that made various types of chondrites evolve from the uniform solar system composition, the CI-chondritic composition. Seven chemical types of chondrites (CM, CV, CO, E, LL, L and H) are examined, for which reliable chemical compositions for both bulk chondrites and chondrules therein are known. High vaporization degree of the primordial dust aggregates (dustons) required by the calculation vindicates that the chondrule formation was the driving force for the chemical fractionations in all chondrites examined. Various initial redox states in dustons and different timings of CAIs’ invasion to the chondrule formation zone are identified for different chondrite types. These results, together with a good correlation with the D/H ratios of chondrites measured previously, lead us to the notion that PPD evolved from reducing to oxidizing. We explore the heating mechanism for the chondrule formation and the place it occurred. Only heat source being consistent with our chondrule formation model is lightning discharge. We postulate that large vortices encompassing the snow-line are ideal places for large charge separation to occur between dustons and small ice particles, and that direct strikes on dustons should make them boil for ten seconds and longer and allow a swarm of chondrules released from their surfaces. Chemical fractionations are completed by an aerodynamic separation of dustons from chondrules inside the vortex, in such a way that the dustons fall fast into the vortex center and form a planetesimal immediately, while chondrules with dust mantles fall slow and form a thin veneer on the planetesimal surface. During collisional episodes, the veneers are preferentially fragmented and reassemble themselves by a weak self-gravity to form a rubble-piled chondritic asteroid, i.e. chondrite.

scholarly journals Thermal History of Matrix Forsterite Grains from Murchison Based on High-resolution Tomography

2021 ◽  
Vol 922 (2) ◽  
pp. 256
Author(s):  
Giulia Perotti ◽  
Henning O. Sørensen ◽  
Henning Haack ◽  
Anja C. Andersen ◽  
Dario Ferreira Sanchez ◽  
...  
Keyword(s):  
High Resolution ◽  
Electron Density ◽  
Chemical Compositions ◽  
X Ray Diffraction ◽  
X Ray ◽  
Density Maps ◽  
Thermally Processed ◽  
The Matrix ◽  
History Of ◽  
Chondrule Formation

Abstract Protoplanetary disks are dust- and gas-rich structures surrounding protostars. Depending on the distance from the protostar, this dust is thermally processed to different degrees and accreted to form bodies of varying chemical compositions. The primordial accretion processes occurring in the early protoplanetary disk such as chondrule formation and metal segregation are not well understood. One way to constrain them is to study the morphology and composition of forsteritic grains from the matrix of carbonaceous chondrites. Here, we present high-resolution ptychographic X-ray nanotomography and multimodal chemical microtomography (X-ray diffraction and X-ray fluorescence) to reveal the early history of forsteritic grains extracted from the matrix of the Murchison CM2.5 chondrite. The 3D electron density maps revealed, at unprecedented resolution (64 nm), spherical inclusions containing Fe–Ni, very little silica-rich glass and void caps (i.e., volumes where the electron density is consistent with conditions close to vacuum) trapped in forsterite. The presence of the voids along with the overall composition, petrological textures, and shrinkage calculations is consistent with the grains experiencing one or more heating events with peak temperatures close to the melting point of forsterite (∼2100 K), and subsequently cooled and contracted, in agreement with chondrule-forming conditions.

scholarly journals Abundances in Diffuse Interstellar Clouds

1980 ◽  
Vol 5 ◽  
pp. 293-300 ◽  
Author(s):  
M. Jura
Keyword(s):  
Interstellar Extinction ◽  
Future Research ◽  
Chemical Compositions ◽  
Interstellar Clouds ◽  
Dark Clouds ◽  
Neutral Gas ◽  
Self Gravity ◽  
Ultraviolet Observations ◽  
Diffuse Clouds ◽  
Intercloud Medium

Interstellar clouds are concentrations of cold (T ≲ 100 K) neutral gas (cf. Spitzer 1978) which are immersed within an intercloud medium. It is worthwhile to distinguish between diffuse clouds (roughly those with E[B-V] ≳ 0.5) and dark clouds (those with E[B-V] ≳ 0.5). This distinction is useful in the sense that diffuse clouds are relatively warm (T ∼ 100 K), they are composed mostly of atomic species except for hydrogen which can be appreciably molecular, and they are dynamically controlled by their interaction with the intercloud medium. Dark clouds are relatively cold (T ∼ 10 K), they contain a rich variety of molecules, and self-gravity is important in their evolution. Because the interstellar extinction is a rapid function of wavelength, most ultraviolet observations have been of diffuse clouds. The IUE satellite is sufficiently powerful that observations of some dark clouds are possible, and an important area of future research will be to delineate more quantitatively the similarities and differences between diffuse clouds and dark clouds.With ultraviolet observations, considerable progress has been made in understanding the physical characteristics of clouds including determinations of their densities, temperatures, chemical compositions and dynamics (cf. Spitzer and Jenkins 1976). Because particular progress has been made on understanding the abundances within diffuse clouds and because of the limitations of space, we restrict this review to a discussion of abundances within diffuse clouds. These abundance measurements provide a set of fundamental astrophysical data.

scholarly journals Nitro-graphene oxide in iridium oxide hybrids: electrochemical modulation of N-graphene redox states and charge capacities

2020 ◽  
Vol 4 (5) ◽  
pp. 1421-1433
Author(s):  
E. Pérez ◽  
N. M. Carretero ◽  
S. Sandoval ◽  
A. Fuertes ◽  
G. Tobias ◽  
...  
Keyword(s):  
Graphene Oxide ◽  
Iridium Oxide ◽  
Redox States ◽  
Large Charge

Electrochemical modulation of N-graphene oxide in IrOx hybrids results in an oxidizing range of graphenes and large charge capacities.

Analytical Electron Microscopy of Ion-Implanted Metals

1985 ◽  
Vol 43 ◽  
pp. 282-285
Author(s):  
D.I. Potter ◽  
M. Ahmed ◽  
K. Ruffing
Keyword(s):  
Electron Microscopy ◽  
Ion Implantation ◽  
Friction And Wear ◽  
Analytical Electron Microscopy ◽  
Chemical Compositions ◽  
Surface Chemical ◽  
Near Surface ◽  
The Past ◽  
Analytical Electron ◽  
Property Changes

Ion implantation, used extensively for the past decade in fabricating semiconductor devices, now provides a unique means for altering the near-surface chemical compositions and microstructures of metals. These alterations often significantly improve physical properties that depend on the surface of the material; for example, catalysis, corrosion, oxidation, hardness, friction and wear. Frequently the mechanisms causing these beneficial alterations and property changes remain obscure and much of the current research in the area of ion implantation metallurgy is aimed at identifying such mechanisms. Investigators thus confront two immediate questions: To what extent is the chemical composition changed by implantation? What is the resulting microstructure? These two questions can be investigated very fruitfully with analytical electron microscopy (AEM), as described below.

TEM/AEM characterization of fine-grained clay minerals in very-low-grade rocks: Evaluation of contamination by empa involving celadonite family minerals

1996 ◽  
Vol 54 ◽  
pp. 694-695
Author(s):  
Gejing Li ◽  
D. R. Peacor ◽  
D. S. Coombs ◽  
Y. Kawachi
Keyword(s):  
Electron Microscopy ◽  
Volcanic Rocks ◽  
Analytical Electron Microscopy ◽  
Metamorphic Rocks ◽  
New Mineral ◽  
Chemical Compositions ◽  
Low Grade ◽  
Fine Grained ◽  
Depth Analysis ◽  
Mineral Aggregates

Recent advances in transmission electron microscopy (TEM) and analytical electron microscopy (AEM) have led to many new insights into the structural and chemical characteristics of very finegrained, optically homogeneous mineral aggregates in sedimentary and very low-grade metamorphic rocks. Chemical compositions obtained by electron microprobe analysis (EMPA) on such materials have been shown by TEM/AEM to result from beam overlap on contaminant phases on a scale below resolution of EMPA, which in turn can lead to errors in interpretation and determination of formation conditions. Here we present an in-depth analysis of the relation between AEM and EMPA data, which leads also to the definition of new mineral phases, and demonstrate the resolution power of AEM relative to EMPA in investigations of very fine-grained mineral aggregates in sedimentary and very low-grade metamorphic rocks.Celadonite, having end-member composition KMgFe3+Si4O10(OH)2, and with minor substitution of Fe2+ for Mg and Al for Fe3+ on octahedral sites, is a fine-grained mica widespread in volcanic rocks and volcaniclastic sediments which have undergone low-temperature alteration in the oceanic crust and in burial metamorphic sequences.

Repulsion effect in orientation of “lightning” discharge

1992 ◽  
Vol 2 (7) ◽  
pp. 1359-1365 ◽  
Author(s):  
E. N. Chernov ◽  
A. V. Lupeiko ◽  
N. I. Petrov
Keyword(s):  
Lightning Discharge ◽  
Repulsion Effect

Chemical compositions from Biscogniauxia sp. PK15-040 fungus

2019 ◽  
Author(s):  
A Churat ◽  
W Mongkolthanaruk ◽  
N Suwannasai ◽  
N Wangsawat ◽  
S McCloskey
Keyword(s):  
Chemical Compositions

Chemical, anatomical, and technology aspects of Eucalyptus benthamii and Eucalyptus dunii for use in an integrated pulp and paper mill

TAPPI Journal ◽  
2015 ◽  
Vol 14 (2) ◽  
pp. 73-81 ◽  
Author(s):  
GISELY SAMISTRARO ◽  
PETER W. HART ◽  
JORGE LUIZ COLODETTE ◽  
RICARDO PAIM
Keyword(s):  
Energy Levels ◽  
Black Liquor ◽  
Basic Density ◽  
Paper Mill ◽  
Frost Tolerance ◽  
Strength Properties ◽  
Kappa Number ◽  
Pulp Yield ◽  
Chemical Compositions ◽  
Physical Strength

Eucalyptus dunii has been commercially used in southern Brazil because of its relatively good frost tolerance and adequate productivity in the winter months. More recently, interest has grown in cultivating Eucalyptus benthamii Maiden & Cambage, which presents even superior frost tolerance compared to E. dunii and is highly productive as well. The quality of E. benthamii for pulp production is not yet proven. Thus, the chemical, anatomical, and technological aspects of pulp made from E. benthamii were compared with those of E. dunii for unbleached paper production. Samples of E. benthamii chips were obtained and analyzed for their basic density, chemical composition, higher heating value, trace elemental analysis, and chip size distribution. The chips were kraft cooked using conditions that produced a 74 ± 6 kappa number. The pulps were characterized for kappa number, yield, viscosity, and morphologic characteristics (e.g., length, wall thickness, and coarseness). Black liquor was analyzed for total solids, organics, inorganics, sodium sulfide, sodium hydroxide, and sodium carbonate. Brownstocks were beaten at five different energy levels in a Valley beater, and the physical strength properties of 120 g/m² handsheets were measured to develop a beater curve. The results of this study showed differences in delignification between the two woods and lower pulp yield for E. benthamii , which are related to their chemical compositions and basic densities. The E. benthamii studied in this work exhibited higher amounts of lignin and extractives, lower carbohydrate content, and lower basic density. However, cooking a blend of the two woods afforded good results in pulping and in physical pulp properties.

Isolated Large Bipolar Pulse (ILBP) Produced by Lightning Discharge in Winter Thunderstorm

2013 ◽  
Vol 133 (9) ◽  
pp. 451-457
Author(s):  
Ting Wu ◽  
Yuji Takayanagi ◽  
Tsuyoshi Funaki ◽  
Satoru Yoshida ◽  
Tomoo Ushio ◽  
...  
Keyword(s):  
Lightning Discharge ◽  
Bipolar Pulse
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