Geological alteration of organic macromolecules by irradiation: Implication for organic matter occurrence on Mars

Geology ◽  
2020 ◽  
Vol 48 (7) ◽  
pp. 713-717 ◽  
Author(s):  
Shengyu Yang ◽  
Hans-Martin Schulz ◽  
Brian Horsfield ◽  
Niels H. Schovsbo ◽  
Kliti Grice ◽  
...  
Keyword(s):  
Organic Matter ◽  
Uranium Content ◽  
Degradation Pathway ◽  
Radiation Environment ◽  
Martian Surface ◽  
Surface Samples ◽  
Alum Shale ◽  
Particle Irradiation ◽  
Radiation Induced ◽  
Irradiation Dosage

Abstract The harsh radiation environment on Mars is widely believed to destroy organic matter, but elucidating the systematic degradation pathway and its controlling factors has proved elusive. Here we show the alteration of macromolecular organic matter in the ∼500-m.y.-old uranium-rich Alum Shale Formation (northwestern Europe), which is suggested as a geological analogue on Earth of the Martian surface samples, in response to ⟨-particle irradiation. The composition and quantity of pyrolysates as well as the extractability of immature Alum Shale are governed by uranium content, and this has been confirmed independently using uranium-rich shales of younger geological age. During the course of irradiation, macromolecules undergo cross-linking, demethylation, and aromatization processes, which are active at different stages in the alteration of the organic matter. A comparison of the Martian surface samples with Kolm (carbonaceous nodules with very high uranium content intercalated in the Alum Shale) samples in terms of irradiation dosage and organic geochemical characteristics reveals that they have received similar levels of irradiation. A model of the radiation-induced alteration of organic matter has been developed, which opens a window for understanding the possible pristine nature and composition of the irradiated organic matter on Mars and offers arguments to qualitatively predict potential organic matter in the Martian paleo-lacustrine subsurface.

Defect Reduction and Defect Engineering in Silicon-on-Sapphire Material Using Ge Implantation

1990 ◽  
Vol 201 ◽  
Author(s):  
F. Namavar ◽  
E. Cortesi ◽  
N. M. Kalkhoran ◽  
J. M. Manke ◽  
B. L. Buchanan
Keyword(s):  
Leakage Current ◽  
Defect Density ◽  
Solid Phase ◽  
Substantial Reduction ◽  
Interface Region ◽  
Radiation Environment ◽  
Solid Phase Epitaxy ◽  
Defect Reduction ◽  
Radiation Induced

AbstractSubstantial reduction of defect density in silicon-on-sapphire (SOS) material is required to broaden its range of applications to include CMOS and bipolar devices. In recent years, solid phase epitaxy and regrowth (SPEAR) and double solid phase epitaxy (DSPE) processes were applied to SOS to reduce the density of defects in the silicon. These methods result in improved carrier mobilities, but also in increased leakage current, even before irradiation. In a radiation environment, this material has a large increase in radiation induced back channel leakage current as compared to standard wafers. In other words, the radiation hardness quality of the SOS declines when the crystalline quality of the Si near the sapphire interface is improved.In this paper, we will demonstrate that Ge implantation, rather than Si implantation normally employed in DSPE and SPEAR processes, is an efficient and more effective way to reduce the density of defects near the surface silicon region without improving the Si/sapphire interface region. Ge implantation may be used to engineer defects in the Si/sapphire interface region to eliminate back channel leakage problems.

scholarly journals Radiation-Induced Helium Bubbles in Metals

Materials ◽  
2019 ◽  
Vol 12 (7) ◽  
pp. 1036 ◽  
Author(s):  
Shi-Hao Li ◽  
Jing-Ting Li ◽  
Wei-Zhong Han
Keyword(s):  
Nuclear Reactors ◽  
Bubble Nucleation ◽  
High Dose ◽  
Metallic Multilayers ◽  
Helium Bubbles ◽  
The Past ◽  
Particle Irradiation ◽  
Radiation Induced ◽  
Radiation Tolerant ◽  
Strength And Ductility

Helium (He) bubbles are typical radiation defects in structural materials in nuclear reactors after high dose energetic particle irradiation. In the past decades, extensive studies have been conducted to explore the dynamic evolution of He bubbles under various conditions and to investigate He-induced hardening and embrittlement. In this review, we summarize the current understanding of the behavior of He bubbles in metals; overview the mechanisms of He bubble nucleation, growth, and coarsening; introduce the latest methods of He control by using interfaces in nanocrystalline metals and metallic multilayers; analyze the effects of He bubbles on strength and ductility of metals; and point out some remaining questions related to He bubbles that are crucial for design of advanced radiation-tolerant materials.

Carbon Isotope Ratios of Particulate Organic Matter in the Gulf of St. Lawrence

1979 ◽  
Vol 36 (6) ◽  
pp. 678-682 ◽  
Author(s):  
F. C. Tan ◽  
P. M. Strain
Keyword(s):  
Organic Matter ◽  
Surface Water ◽  
Organic Carbon ◽  
Carbon Isotope ◽  
Particulate Organic Matter ◽  
Surface Sediments ◽  
Isotope Ratios ◽  
Lawrence Estuary ◽  
Carbon Isotope Ratios ◽  
Surface Samples

Sixteen offshore surface samples within the Gulf of St. Lawrence show low δ13C values and are similar to eight offshore surface samples collected seaward of the Gulf of St. Lawrence. The δ13C surface values are consistent with δ13C values in plankton produced at the temperature found in the euphotic zone in the study area. Higher values are observed in four surface samples from the mouth of the St. Lawrence Estuary and probably result from high carbon demand during periods of high biological productivity. Lower values found in seven deep POC samples indicate changes in the nature of the POC caused by biological degradation of the organic matter. Significant differences (2–6‰) between the uniformly high δ13C values of the organic carbon in surface sediments and the low values of near-bottom water POC have been observed. The similarity between the δ13C values of surface water POC and the surface sediments suggest that surface water POC is an important source of organic carbon in surface sediments. Several observations of large vertical δ13C gradients in deep water POC suggest the presence of resuspended sediments 30–60 m above the sediment–water interface. Key words: particulate organic matter, carbon isotope ratios, isotope fractionation, sediment resuspension, sediment sources, Gulf of St. Lawrence

The Relationships between Uranium Mineralization and Organic Matter in 373 Uranium Deposit

2014 ◽  
Vol 962-965 ◽  
pp. 203-207 ◽  
Author(s):  
Ping Li ◽  
Zheng Qi Xu ◽  
Ye Wang ◽  
Peng Chong Wang
Keyword(s):  
Organic Matter ◽  
Rock Type ◽  
Uranium Deposit ◽  
Thermal Evolution ◽  
Uranium Content ◽  
Uranium Mineralization ◽  
Pelitic Rock ◽  
Organic Matter Type ◽  
Main Component ◽  
The Relationship

The 373 deposit,as a typical carbonanceous-siliceous-pelitic rock type uranium deposit,is rich in organic matter and pyrite.Close relationships exist between organic matter and uranium mineralization in a lot of uranium deposits. But few people have studied the relationship between uranium mineralization and organic matter of carbonanceous-siliceous-pelitic rock type uranium deposit.The organic matter type of 373 uranium deposit is type-II2.The sources of organic matter are mainly marine plankton,microbial and terrestrial plant. The organic maturity is relatively low,at the immature-low mature stage.Compared with the surrounding rock ,the ore has gone through higher paletemperature on account of hydrothermal and fault. The type and the maturity of organic matter result in the generation of large amount of humic acid during thermal evolution that could be preserved in strata. The contents of chloroform bitumen “A” of organic matter in the mineralized layer are 0.47—10.42ug/g .Asphaltene is the main component of chloroform bitumen “A”.The correlation between chloroform bitumen “A” and uranium content is high,as well as the correlation between the content of asphaltene and uranium content. Study shows that the functions of organic matter in 373 uranium deposit are mainly adsorption,complexation and reduction.

A calculation of the radiation environment on the Martian surface

2017 ◽  
Vol 14 ◽  
pp. 51-56 ◽  
Author(s):  
Wouter C. de Wet ◽  
Lawrence W. Townsend
Keyword(s):  
Radiation Environment ◽  
Martian Surface

In situ immobilization of metals in contaminated or naturally metal-rich soils

2001 ◽  
Vol 9 (2) ◽  
pp. 81-97 ◽  
Author(s):  
B R Singh ◽  
L Oste
Keyword(s):  
Organic Matter ◽  
Contaminated Soils ◽  
Plant Uptake ◽  
Binding Capacity ◽  
Peat Soil ◽  
Cadmium Concentration ◽  
In Situ Immobilization ◽  
Soil Matrix ◽  
Alum Shale

The chemical behaviour of metals is primarily governed by their retention and release reactions of solute with the soil matrix. Liming increased the soil pH, resulting in increased adsorption of Zn, Cu, and Cd in soils, which in consequence decreased the concentration of easily soluble Cd fraction in the soils and the uptake of this metal by wheat (Triticum aestivum) and carrots (Daucus carota). Metal adsorption also depended on the presence of clay and organic matter, and thus the soils having highest amounts of clay (e.g., alum shale) and (or) organic matter (e.g., peat soil) showed the highest adsorption for these metals. Among the materials (Fe and Mn oxides and aluminosilicates) having high binding capacity for metals, the immobilizing capacity of birnessite (MnO2) was higher than that of other materials. Addition of synthetic zeolites significantly reduced the metal uptake by plants. Application of zeolite to a soil resulted in increased dissolved organic carbon (DOC) concentration in the leachate, which in consequence increased the leaching of Cd and Zn. Addition of beringite (an aluminosilicate) to a Zn-contaminated soil resulted in increased shoot length and leaf area of bean (Phaseolus vulgaris) and a significant reduction in Zn concentration in leaves (from 350 to 146 mg kg-1). Cadmium concentration in ryegrass and the concentrations of diethylenetriaminepentaacetic acid (DTPA)- extractable Cd, Cu, Ni, and Zn in the soil decreased significantly (P < 0.05) with increasing amounts of organic matter (peat soil and cow manure) added to soils. These effects were assumed to be related to immobilization of metals due to formation of insoluble metal--organic complexes and increased cation exchange capacity (CEC). An overview of the results showed that the products tested (lime, Fe/Mn-containing compounds, aluminosilicates, and organic matter products) can reduce the solubility and the plant uptake of metals but their immobilizing capacity is limited (sometimes through their side effects). Key words: aluminosilicates, contaminated soils, in situ immobilization, leaching, metal oxides, organic matter, plant uptake.

Insights into the nature of cometary organic matter from terrestrial analogues

2012 ◽  
Vol 11 (2) ◽  
pp. 83-92 ◽  
Author(s):  
Richard W. Court ◽  
Mark A. Sephton
Keyword(s):  
Organic Matter ◽  
Cometary Nucleus ◽  
Cometary Nuclei ◽  
Naturally Occurring ◽  
Polycyclic Aromatic ◽  
Radiation Induced ◽  
Remote Observation ◽  
Complex Organic ◽  
Cometary Comae

AbstractThe nature of cometary organic matter is of great interest to investigations involving the formation and distribution of organic matter relevant to the origin of life. We have used pyrolysis–Fourier transform infrared (FTIR) spectroscopy to investigate the chemical effects of the irradiation of naturally occurring bitumens, and to relate their products of pyrolysis to their parent assemblages. The information acquired has then been applied to the complex organic matter present in cometary nuclei and comae. Amalgamating the FTIR data presented here with data from published studies enables the inference of other comprehensive trends within hydrocarbon mixtures as they are progressively irradiated in a cometary environment, namely the polymerization of lower molecular weight compounds; an increased abundance of polycyclic aromatic hydrocarbon structures; enrichment in 13C; reduction in atomic H/C ratio; elevation of atomic O/C ratio and increase in the temperature required for thermal degradation. The dark carbonaceous surface of a cometary nucleus will display extreme levels of these features, relative to the nucleus interior, while material in the coma will reflect the degree of irradiation experienced by its source location in the nucleus. Cometary comae with high methane/water ratios indicate a nucleus enriched in methane, favouring the formation of complex organic matter via radiation-induced polymerization of simple precursors. In contrast, production of complex organic matter is hindered in a nucleus possessing a low methane/water ration, with the complex organic matter that does form possessing more oxygen-containing species, such as alcohol, carbonyl and carboxylic acid functional groups, resulting from reactions with hydroxyl radicals formed by the radiolysis of the more abundant water. These insights into the properties of complex cometary organic matter should be of particular interest to both remote observation and space missions involving in situ analyses and sample return of cometary materials.

scholarly journals Active Compensation of Radiation Effects on Optical Fibers for Sensing Applications

Sensors ◽  
2021 ◽  
Vol 21 (24) ◽  
pp. 8193
Author(s):  
Sohel Rana ◽  
Austin Fleming ◽  
Nirmala Kandadai ◽  
Harish Subbaraman
Keyword(s):  
Optical Fibers ◽  
Radiation Effects ◽  
Accurate Determination ◽  
Radiation Environment ◽  
Physical Parameters ◽  
Air Cavity ◽  
Sensing Applications ◽  
Fabry Perot ◽  
Radiation Induced

Neutron and gamma irradiation is known to compact silica, resulting in macroscopic changes in refractive index (RI) and geometric structure. The change in RI and linear compaction in a radiation environment is caused by three well-known mechanisms: (i) radiation-induced attenuation (RIA), (ii) radiation-induced compaction (RIC), and (iii) radiation-induced emission (RIE). These macroscopic changes induce errors in monitoring physical parameters such as temperature, pressure, and strain in optical fiber-based sensors, which limit their application in radiation environments. We present a cascaded Fabry–Perot interferometer (FPI) technique to measure macroscopic properties, such as radiation-induced change in RI and length compaction in real time to actively account for sensor drift. The proposed cascaded FPI consists of two cavities: the first cavity is an air cavity, and the second is a silica cavity. The length compaction from the air cavity is used to deduce the RI change within the silica cavity. We utilize fast Fourier transform (FFT) algorithm and two bandpass filters for the signal extraction of each cavity. Inclusion of such a simple cascaded FPI structure will enable accurate determination of physical parameters under the test.

Sign in / Sign up

Export Citation Format

Share Document