Accumulation History of Uranium in Boulders - New Support for Postglacial Matrix Diffusion

1997 ◽  
Vol 506 ◽  
Author(s):  
Kari Rasilainen ◽  
Juhani Suksi ◽  
Antero Lindberg
Keyword(s):  
Time Scale ◽  
Early Stage ◽  
Matrix Diffusion ◽  
Natural Analogue ◽  
Land Uplift ◽  
Decay Stage ◽  
History Of ◽  
End Stage ◽  
Chain Decay ◽  
Accumulation History

Extended AbstractGeological formations are being considered as host media for nuclear waste disposal. The occurrence of natural U in rocks provides a possibility to test the radionuclide migration models used in safety studies of the disposal over comparable time periods. Here we study U accumulation into boulders as a process analogue for matrix diffusion; the boulders were found in glacial till in Hämeenlinna, southern Finland. Based on the glacial history of the site, matrix diffusion simulations, and independent U-series disequilibria (USD) dating, the U accumulation was interpreted to originate from the end stage of the latest glaciation, i.e. the system age is about 10 000 years1,2. The known time scale offers a rare opportunity for quantitative model testing; normally the time scale is difficult to determine for a single process in a natural analogue.The U accumulation was earlier1,2 interpreted to be due to matrix diffusion and sorption. The postulated accumulation history consists of short in-diffusion and out-diffusion stages, as well as a longer chain decay stage. The in-diffusion was caused by U-rich waters discharging on the boulders at the end stage of the glaciation. The subsequent partial out-diffusion represents the period the boulders were temporarily submerged in the Yoldia sea during the early stage of the Baltic Sea. The final isolated radioactive chain decay stage began when the boulders, and their surroundings, rose above the sea level due to land uplift.In this paper we report the first radiochemical results of a new larger boulder from the same area as the one studied earlier1; qualitatively, also the U distribution appears to be the same. Due to the larger dimensions, we can sample the inner zone of the boulder which matrix diffusion can not have reached within the postulated time, i.e. the state of the boulder before the U accumulation. The large amount of sample material containing almost only the recently accumulated U provides an opportunity to experimentally approach the kinetics of U fixation in situ. Understanding the long-term U fixation is essential in natural analogue studies, because the matrix diffusion model only has fast reversible adsorption (based on Kd) as the fixation process. Attempts to separate and quantify sorbed U in natural analogues have been reported elsewhere3.

On the Accuracy of Uranium-Series Dating: a Comparison with a Known Matrix Diffusion Case

1996 ◽  
Vol 465 ◽  
Author(s):  
K. Rasilainen ◽  
J. Suksi
Keyword(s):  
Mass Flow ◽  
Open System ◽  
Decay Chain ◽  
Matrix Diffusion ◽  
Uranium Series ◽  
Uranium Series Dating ◽  
Flow Information ◽  
History Of ◽  
Improved Accuracy ◽  
Accumulation History

ABSTRACTThe accuracy of uranium-series dating was studied quantitatively using the natural long-lived decay chains 4n+2 and 4n+3. An unusually well-bounded matrix diffusion case was used as the reference for USD simulations. The simulations applied the traditional closed and open system models, as well as detailed multistage models that incorporated the known accumulation history of the decay chain members. The results show clearly the improved accuracy and consistency in dating with detailed mass flow information.

The E-ring: interactions with plasma and implications for its evolution

1984 ◽  
Vol 75 ◽  
pp. 599-602
Author(s):  
T.V. Johnson ◽  
G.E. Morfill ◽  
E. Grun
Keyword(s):  
Time Scale ◽  
Particle Density ◽  
High Energy ◽  
Particle Removal ◽  
Density Region ◽  
Drag Forces ◽  
Orbit Evolution ◽  
History Of ◽  
Ring Particle ◽  
Ring Material

A number of lines of evidence suggest that the particles making up the E-ring are small, on the order of a few microns or less in size (Terrile and Tokunaga, 1980, BAAS; Pang et al., 1982 Saturn meeting; Tucson, AZ). This suggests that a variety of electromagnetic and plasma affects may be important in considering the history of such particles. We have shown (Morfill et al., 1982, J. Geophys. Res., in press) that plasma drags forces from the corotating plasma will rapidly evolve E-ring particle orbits to increasing distance from Saturn until a point is reached where radiation drag forces acting to decrease orbital radius balance this outward acceleration. This occurs at approximately Rhea's orbit, although the exact value is subject to many uncertainties. The time scale for plasma drag to move particles from Enceladus' orbit to the outer E-ring is ~104yr. A variety of effects also act to remove particles, primarily sputtering by both high energy charged particles (Cheng et al., 1982, J. Geophys. Res., in press) and corotating plasma (Morfill et al., 1982). The time scale for sputtering away one micron particles is also short, 102 - 10 yrs. Thus the detailed particle density profile in the E-ring is set by a competition between orbit evolution and particle removal. The high density region near Enceladus' orbit may result from the sputtering yeild of corotating ions being less than unity at this radius (e.g. Eviatar et al., 1982, Saturn meeting). In any case, an active source of E-ring material is required if the feature is not very ephemeral - Enceladus itself, with its geologically recent surface, appears still to be the best candidate for the ultimate source of E-ring material.

Phanerozoic Oxygen

2017 ◽  
Author(s):  
Donald Eugene Canfield
Keyword(s):  
Oxygen Consumption ◽  
Organic Carbon ◽  
Sea Level ◽  
Time Scale ◽  
Atmospheric Oxygen ◽  
Sea Level Change ◽  
Oxygen Production ◽  
Level Change ◽  
History Of ◽  
Geologic Processes

This chapter discusses the modeling of the history of atmospheric oxygen. The most recently deposited sediments will also be the most prone to weathering through processes like sea-level change or uplift of the land. Thus, through rapid recycling, high rates of oxygen production through the burial of organic-rich sediments will quickly lead to high rates of oxygen consumption through the exposure of these organic-rich sediments to weathering. From a modeling perspective, rapid recycling helps to dampen oxygen changes. This is important because the fluxes of oxygen through the atmosphere during organic carbon and pyrite burial, and by weathering, are huge compared to the relatively small amounts of oxygen in the atmosphere. Thus, all of the oxygen in the present atmosphere is cycled through geologic processes of oxygen liberation (organic carbon and pyrite burial) and consumption (weathering) on a time scale of about 2 to 3 million years.

ABOUT THE PERIODIZATION AND CHRONOLOGY OF THE HISTORY OF TAURIC CHERSONESUS IN THE PRE-ROMAN AND THE LATE ANTIQUE PERIODS

2020 ◽  
Vol 6 (72) (3) ◽  
pp. 127-148
Author(s):  
S. V. Ushakov
Keyword(s):  
Scientific Literature ◽  
Early Stage ◽  
Late Antique ◽  
Ancient History ◽  
History Of ◽  
Transitional Time ◽  
Early Byzantine

Hundreds of scientific works are devoted to the study of the Tauric Chersonesus, but the problem of chronology and periodization of its ancient history is not sufficiently developed in historiography. Analysis of scientific literature and a number of sources concerning this subject allows to define the chronological framework and to reveal 10 stages of the history of ancient Chersonesos (as a preliminary definition). The early stage, the Foundation and formation of the Polis, is defined from the middle/last third of the VI century (or the first half of the V century BC) to the end of the V century BC. The end of the late-Antique − early-Byzantine (transitional) time in Chersonesos can be attributed to the second half of the VI – first third of the VII centuries ad).

HIGHER EDUCATION IN ANCIENT INDIA

2018 ◽  
Vol 6 (26) ◽  
Author(s):  
Satyendra Singh Chahar ◽  
Nirmal Singh
Keyword(s):  
Cultural History ◽  
Early Stage ◽  
University Education ◽  
Educational Institutions ◽  
Educational Method ◽  
Men And Women ◽  
Ancient India ◽  
Herbert Spencer ◽  
History Of ◽  
The Ideal

University education -on almost modern lines existed in India as early as 800 B.C. or even earlier. The learning or culture of ancient India was chiefly the product of her hermitages in the solitude of the forests. It was not of the cities. The learning of the forests was embodied in the books specially designated as Aranyakas "belonging to the forests." The ideal of education has been very grand, noble and high in ancient India. Its aimaccording to Herbert Spencer is the 'training for completeness of life' and ‘the molding o character of men and women for the battle of life’. The history of the educational institutions in ancient India shows a glorious dateline of her cultural history. It points to a long history altogether. In the early stage it was rural, not urban. British Sanskrit scholar Arthur Anthony Macdonell says "Some hundreds of years must have been needed for all that is found" in her culture. The aim of education was at the manifestation of the divinity in men, it touches the highest point of knowledge. In order to attain the goal the whole educational method is based on plain living and high thinking pursued through eternity.

scholarly journals Sequential fate-switches in stem-like cells drive the tumorigenic trajectory from human neural stem cells to malignant glioma

Cell Research ◽  
2021 ◽  
Author(s):  
Xiaofei Wang ◽  
Ran Zhou ◽  
Yanzhen Xiong ◽  
Lingling Zhou ◽  
Xiang Yan ◽  
...  
Keyword(s):  
Malignant Glioma ◽  
Single Cell ◽  
De Novo ◽  
Early Stage ◽  
Lineage Tracing ◽  
Human Neural Stem Cells ◽  
Transcriptional Reprogramming ◽  
Neural Stem Progenitor Cells ◽  
Human Gbm ◽  
End Stage

AbstractGlioblastoma (GBM) is an incurable and highly heterogeneous brain tumor, originating from human neural stem/progenitor cells (hNSCs/hNPCs) years ahead of diagnosis. Despite extensive efforts to characterize hNSCs and end-stage GBM at bulk and single-cell levels, the de novo gliomagenic path from hNSCs is largely unknown due to technical difficulties in early-stage sampling and preclinical modeling. Here, we established two highly penetrant hNSC-derived malignant glioma models, which resemble the histopathology and transcriptional heterogeneity of human GBM. Integrating time-series analyses of whole-exome sequencing, bulk and single-cell RNA-seq, we reconstructed gliomagenic trajectories, and identified a persistent NSC-like population at all stages of tumorigenesis. Through trajectory analyses and lineage tracing, we showed that tumor progression is primarily driven by multi-step transcriptional reprogramming and fate-switches in the NSC-like cells, which sequentially generate malignant heterogeneity and induce tumor phenotype transitions. We further uncovered stage-specific oncogenic cascades, and among the candidate genes we functionally validated C1QL1 as a new glioma-promoting factor. Importantly, the neurogenic-to-gliogenic switch in NSC-like cells marks an early stage characterized by a burst of oncogenic alterations, during which transient AP-1 inhibition is sufficient to inhibit gliomagenesis. Together, our results reveal previously undercharacterized molecular dynamics and fate choices driving de novo gliomagenesis from hNSCs, and provide a blueprint for potential early-stage treatment/diagnosis for GBM.

The diagnosis of early pneumoconiosis in dust-exposed workers: comparison of chest radiography and computed tomography

2021 ◽  
pp. 028418512110225
Author(s):  
Hideyuki Hayashi ◽  
Kazuto Ashizawa ◽  
Masashi Takahashi ◽  
Katsuya Kato ◽  
Hiroaki Arakawa ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Chest Radiography ◽  
Pulmonary Emphysema ◽  
Early Stage ◽  
Pathological Changes ◽  
Occupational History ◽  
Exposed Workers ◽  
History Of ◽  
Ct Data ◽  
Positive Results

Background Chest radiography (CR) is employed as the evaluation of pneumoconiosis; however, we sometimes encounter cases in which computed tomography (CT) is more effective in detecting subtle pathological changes or cases in which CR yields false-positive results. Purpose To compare CR to CT in the diagnosis of early-stage pneumoconiosis. Material and Methods CR and CT were performed for 132 workers with an occupational history of mining. We excluded 23 cases of arc-welder’s lung. Five readers who were experienced chest radiologists or pulmonologists independently graded the pulmonary small opacities on CR of the remaining 109 cases. We then excluded 37 cases in which the CT data were not sufficient for grading. CT images of the remaining 72 cases were graded by the five readers. We also assessed the degree of pulmonary emphysema in those cases. Results The grade of profusion on CR (CR score) of all five readers was identical in only 5 of 109 cases (4.6%). The CR score coincided with that on CT in 40 of 72 cases (56%). The CT score was higher than that on CR in 13 cases (18%). On the other hand, the CT score was lower than that on CR in 19 cases (26%). The incidence of pulmonary emphysema was significantly higher in patients whose CR score was higher than their CT score. Conclusion CT is more sensitive than CR in the evaluation of early-stage pneumoconiosis. In cases with emphysema, the CR score tends to be higher in comparison to that on CT.

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