Modelling experimental results on radiolytic processes at the spent fuel water interface. II. Radionuclides release

2006 ◽  
Vol 932 ◽  
Author(s):  
E. Cera ◽  
M. Grivé ◽  
J. Bruno ◽  
T.E. Eriksen
Keyword(s):  
Redox State ◽  
Kinetic Modelling ◽  
Initial Increase ◽  
Spent Fuel ◽  
Work Related ◽  
Radiolysis Products ◽  
The Matrix ◽  
Anoxic Environment ◽  
Bicarbonate Solutions

ABSTRACTExperimental and modelling efforts in the last decade in the frame of nuclear waste management field have been focused on studying the role of the UO2 surfaces in poising the redox state of solid/water systems as well as the radionuclides release behaviour. For this purpose, an experimental programme was developed consisting on dissolution experiments with PWR spent fuel fragments in an anoxic environment and by using different solution compositions.Some of the collected data has been previously published [1], specifically those data concerning radiolysis products and dissolution of the matrix. The results and the modelling tasks indicated an overall balance of the generated radiolytic species and that uranium dissolution was controlled by the oxidation of the spent fuel matrix in 10mM bicarbonate solutions while in the tests carried out at lower or without carbonate concentrations uranium in the aqueous phase was governed by the precipitation of schoepite.This paper is the continuation of a series accounting for the data and modelling work related to investigating the release behaviour of minor radionuclides from the spent fuel.Uranium concentrations as a function of time showed an initial increase until reaching a steady state, indicating a matrix dissolution control. The same behaviour is observed for neptunium, caesium, strontium, technetium and molybdenum indicating a congruent release of these elements with the major component of the fuel matrix. On the other hand, no cler tendency is observed for plutonium data where additional solubility limiting mechanisms may apply.Kinetic modelling of the trace elements: caesium, strontium, technetium and molybdenum is based on the congruent release of these elements with the major component of the fuel matrix. Rate constants have been determined. Kinetic modelling of neptunium data took also into account the subsequent precipitation as Np(IV) hydroxide. Finally, measured Pu concentrations may be explained by the precipitation of Pu(IV) and/or Pu(III) solid phases.

Modelling Experimental Results on Radiolytic Processes at the Spent Fuel Water Interface. I. Radiolysis Products and U Release

2003 ◽  
Vol 807 ◽  
Author(s):  
J. Bruno ◽  
E. Cera ◽  
T. E. Eriksen ◽  
M. Grivé ◽  
S. Ripoll
Keyword(s):  
Aqueous Phase ◽  
Initial Increase ◽  
Water Interface ◽  
Spent Fuel ◽  
Constant Concentration ◽  
Radiolysis Products ◽  
Reducing Conditions ◽  
Anoxic Environment ◽  
Bicarbonate Solutions

ABSTRACTExperimental and modelling efforts in the last decade in the frame of nuclear waste management field have been focused on studying the role of the UO2 surfaces in poising the redox state of solid/water systems. For this purpose, an experimental programme was developed consisting on dissolution experiments with PWR spent fuel fragments in an anoxic environment and by using different solution compositions.The collected data so far, indicate that production and fate of radiolysis products follow the same trends independently on the solution composition used in the tests. Hydrogen and oxygen concentrations show an initial increase with time until reaching a constant concentration. The trend observed for hydrogen peroxide is a decrease at short contact times to reach again a constant concentration with time. These steady-states indicate an overall balance of the generated radiolytic species.Modelling work indicates that uranium dissolution is controlled by the oxidation of the spent fuel matrix in 10mM bicarbonate solutions while in the tests carried out at lower or without carbonate concentrations uranium in the aqueous phase is governed by the precipitation of schoepite.These results are determinant to highlight that reducing conditions are restored in the aqueous phase in relatively short periods of time and at short distances away from the dynamic redox spent fuel/water interface.

Alteration Behavior of High Burnup Spent Fuel in Salt Brine Under Hydrogen Overpressure and in Presence of Bromide

2006 ◽  
Vol 985 ◽  
Author(s):  
Andreas Loida ◽  
Volker Metz ◽  
Bernhard Kienzler
Keyword(s):  
Dissolution Rate ◽  
Spent Fuel ◽  
Radiolysis Products ◽  
The Matrix ◽  
Matrix Bound ◽  
Salt Brine ◽  
High Burnup ◽  
Geological Formations ◽  
Α Activity

AbstractRecent studies have shown that in the presence of H2 overpressure, which forms due to the corrosion of the Fe based container, the dissolution rate of the spent fuel matrix is slowed down by a factor of about 10, associated with a distinct decrease of concentrations of important ra-dionuclides. However, in a natural salt environment as well as in geological formations with chloride rich groundwater the presence of radiation chemically active impurities such as bro-mide must be taken in consideration. Bromide is known to react with β/γ radiolysis products, thus counteracting the protective H2 effect. In the present experiments using high burnup spent fuel it is observed that during 212 days the matrix dissolution rate was enhanced by a factor of about10 in the presence of up to 10-3 M bromide and 3.2 bar H2 overpressure. However, concen-trations of matrix bound actinides were found at the same level or below as found under identical conditions, but in the absence of bromide. In the long-term it is expected that the effect of bro-mide becomes less important, because the decrease of β/γ-activity results in a decrease of oxida-tive radicals, which react with bromide, while α activity will dominate the radiation field.

Extracellular matrix: the gatekeeper of tumor angiogenesis

2019 ◽  
Vol 47 (5) ◽  
pp. 1543-1555 ◽  
Author(s):  
Maurizio Mongiat ◽  
Simone Buraschi ◽  
Eva Andreuzzi ◽  
Thomas Neill ◽  
Renato V. Iozzo
Keyword(s):  
Extracellular Matrix ◽  
Tumor Angiogenesis ◽  
Signaling Cascades ◽  
Cancer Growth ◽  
Cell Behavior ◽  
Metastatic Progression ◽  
Surface Receptors ◽  
The Matrix ◽  
Multiple Signaling

Abstract The extracellular matrix is a network of secreted macromolecules that provides a harmonious meshwork for the growth and homeostatic development of organisms. It conveys multiple signaling cascades affecting specific surface receptors that impact cell behavior. During cancer growth, this bioactive meshwork is remodeled and enriched in newly formed blood vessels, which provide nutrients and oxygen to the growing tumor cells. Remodeling of the tumor microenvironment leads to the formation of bioactive fragments that may have a distinct function from their parent molecules, and the balance among these factors directly influence cell viability and metastatic progression. Indeed, the matrix acts as a gatekeeper by regulating the access of cancer cells to nutrients. Here, we will critically evaluate the role of selected matrix constituents in regulating tumor angiogenesis and provide up-to-date information concerning their primary mechanisms of action.

The Role of Positive and Negative Affectivity in Healthy and Unhealthy Work-Related Behavior and Experiences

2019 ◽  
Vol 26 (2) ◽  
pp. 56-67 ◽  
Author(s):  
Hanna Hofmann ◽  
Carl-Walter Kohlmann
Keyword(s):  
Negative Affectivity ◽  
Coping Behavior ◽  
Common Method ◽  
Positive Affectivity ◽  
Work Related ◽  
Teacher Students ◽  
And Behaviors ◽  
Main Effects ◽  
Positive And Negative Affectivity

Abstract. Positive affectivity (PA) and negative affectivity (NA) are basic traits that affect work-related perceptions and behaviors and should be considered in any assessment of these variables. A quite common method to assess healthy or unhealthy types of work-related perceptions and behaviors is the questionnaire on Work-Related Coping Behavior and Experience Patterns (WCEP). However, the association of PA and NA with WCEP remained unclear. In a sample of teachers, physiotherapists, and teacher students ( N = 745; Mage = 35.07, SD = 12.49; 78% females), we aimed to identify the relevance of these basic traits. After controlling for age, gender, and type of occupation, we found main effects of PA and NA, with the specific combination of PA and NA being decisive for predicting the assignment to a WCEP type. The results highlight the need to include PA and NA in future assessments with the WCEP questionnaire.

Redox State in Atrial Fibrillation Pathogenesis and Relevant Therapeutic Approaches

2019 ◽  
Vol 26 (5) ◽  
pp. 765-779 ◽  
Author(s):  
Alexios S. Antonopoulos ◽  
Athina Goliopoulou ◽  
Evangelos Oikonomou ◽  
Sotiris Tsalamandris ◽  
Georgios-Angelos Papamikroulis ◽  
...  
Keyword(s):  
Atrial Fibrillation ◽  
Clinical Studies ◽  
Redox State ◽  
Redox Balance ◽  
Therapeutic Approaches ◽  
Critical Determinant ◽  
Electrophysiological Properties ◽  
Antioxidant Agents ◽  
Clinical Benefits

Background: Myocardial redox state is a critical determinant of atrial biology, regulating cardiomyocyte apoptosis, ion channel function, and cardiac hypertrophy/fibrosis and function. Nevertheless, it remains unclear whether the targeting of atrial redox state is a rational therapeutic strategy for atrial fibrillation prevention. Objective: To review the role of atrial redox state and anti-oxidant therapies in atrial fibrillation. Method: Published literature in Medline was searched for experimental and clinical evidence linking myocardial redox state with atrial fibrillation pathogenesis as well as studies looking into the role of redoxtargeting therapies in the prevention of atrial fibrillation. Results: Data from animal models have shown that altered myocardial nitroso-redox balance and NADPH oxidases activity are causally involved in the pathogenesis of atrial fibrillation. Similarly experimental animal data supports that increased reactive oxygen / nitrogen species formation in the atrial tissue is associated with altered electrophysiological properties of atrial myocytes and electrical remodeling, favoring atrial fibrillation development. In humans, randomized clinical studies using redox-related therapeutic approaches (e.g. statins or antioxidant agents) have not documented any benefits in the prevention of atrial fibrillation development (mainly post-operative atrial fibrillation risk). Conclusion: Despite strong experimental and translational data supporting the role of atrial redox state in atrial fibrillation pathogenesis, such mechanistic evidence has not been translated to clinical benefits in atrial fibrillation risk in randomized clinical studies using redox-related therapies.

Investigation of the role of anxiety and depression on the formation of phantom vibration and ringing syndrome induced by working stress during medical internship (Preprint)

2019 ◽  
Author(s):  
Yu-Hsuan Lin ◽  
Kuan-I Lin ◽  
Yuan-Chien Pan ◽  
Sheng-Hsuan Lin
Keyword(s):  
Anxiety And Depression ◽  
Depression And Anxiety ◽  
Prospective Longitudinal Study ◽  
Work Related ◽  
Working Stress ◽  
Causal Mediation Analysis ◽  
Accompanying Symptoms ◽  
Prospective Longitudinal ◽  
The Relationship

BACKGROUND Phantom vibrations syndrome (PVS) and phantom ringing syndrome (PRS) are prevalent hallucinations during medical internship. Depression and anxiety are probably understudied risk factors of PVS and PRS. OBJECTIVE The aim of this study was to investigate the role of anxiety and depression on the relationship between working stress during medical internship and PVS and PRS. METHODS A prospective longitudinal study of 74 medical interns was carried out using repeated investigations of the severity of phantom vibrations and ringing, as well as accompanying symptoms of anxiety and depression as measured by Beck Anxiety Inventory and the Beck Depression Inventory before, at the 3rd, 6th, and 12th month during internship, and 2 weeks after internship. We conducted a causal mediation analysis to investigate the role of depression and anxiety in the mechanism of working stress during medical internship inducing PVS and PRS. RESULTS The results showed that depression explained 21.9% and 8.4% for stress-induced PRS and PVS, respectively. In addition, anxiety explained 15.0% and 7.8% for stress-induced PRS and PVS, respectively. CONCLUSIONS Our findings showed both depression and anxiety can explain a portion of stress-induced PVS and PRS during medical internship and might be more important in clinical practice and benefit to prevention of work-related burnout.

scholarly journals Biogeochemical Controls on the Redox Evolution of Earth’s Oceans and Atmosphere

Elements ◽  
2020 ◽  
Vol 16 (3) ◽  
pp. 191-196 ◽  
Author(s):  
Christopher T. Reinhard ◽  
Noah J. Planavsky
Keyword(s):  
Redox State ◽  
Modeling Tools ◽  
Evolutionary Trajectory ◽  
Geochemical Tracers ◽  
Atmosphere System ◽  
Ocean Atmosphere ◽  
Dramatic Shift ◽  
Redox Evolution

The redox state of Earth’s atmosphere has undergone a dramatic shift over geologic time from reducing to strongly oxidizing, and this shift has been coupled with changes in ocean redox structure and the size and activity of Earth’s biosphere. Delineating this evolutionary trajectory remains a major problem in Earth system science. Significant insights have emerged through the application of redox-sensitive geochemical systems. Existing and emerging biogeochemical modeling tools are pushing the limits of the quantitative constraints on ocean–atmosphere redox that can be extracted from geochemical tracers. This work is honing our understanding of the central role of Earth’s biosphere in shaping the long-term redox evolution of the ocean–atmosphere system.

scholarly journals The Interactions between Polyphenols and Microorganisms, Especially Gut Microbiota

Antioxidants ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 188
Author(s):  
Małgorzata Makarewicz ◽  
Iwona Drożdż ◽  
Tomasz Tarko ◽  
Aleksandra Duda-Chodak
Keyword(s):  
Intestinal Bacteria ◽  
Research Data ◽  
Bioactive Metabolites ◽  
Human Organism ◽  
Comprehensive Knowledge ◽  
Bidirectional Relationship ◽  
The Matrix ◽  
Intestinal Pathogens ◽  
The Impact

This review presents the comprehensive knowledge about the bidirectional relationship between polyphenols and the gut microbiome. The first part is related to polyphenols’ impacts on various microorganisms, especially bacteria, and their influence on intestinal pathogens. The research data on the mechanisms of polyphenol action were collected together and organized. The impact of various polyphenols groups on intestinal bacteria both on the whole “microbiota” and on particular species, including probiotics, are presented. Moreover, the impact of polyphenols present in food (bound to the matrix) was compared with the purified polyphenols (such as in dietary supplements) as well as polyphenols in the form of derivatives (such as glycosides) with those in the form of aglycones. The second part of the paper discusses in detail the mechanisms (pathways) and the role of bacterial biotransformation of the most important groups of polyphenols, including the production of bioactive metabolites with a significant impact on the human organism (both positive and negative).

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