scholarly journals Diagenetic formation of uranium-silica polymers in lake sediments over 3,300 years

2021 ◽  
Vol 118 (4) ◽  
pp. e2021844118
Author(s):  
Pierre Lefebvre ◽  
Alkiviadis Gourgiotis ◽  
Arnaud Mangeret ◽  
Pierre Sabatier ◽  
Pierre Le Pape ◽  
...  
Keyword(s):  
Contaminated Sediments ◽  
Mining Areas ◽  
Subsurface Environments ◽  
Geochemical Reactivity ◽  
High Silica ◽  
Long Term Behavior ◽  
The Impact ◽  
X Ray Absorption

The long-term fate of uranium-contaminated sediments, especially downstream former mining areas, is a widespread environmental challenge. Essential for their management is the proper understanding of uranium (U) immobilization mechanisms in reducing environments. In particular, the long-term behavior of noncrystalline U(IV) species and their possible evolution to more stable phases in subsurface conditions is poorly documented, which limits our ability to predict U long-term geochemical reactivity. Here, we report direct evidence for the evolution of U speciation over 3,300 y in naturally highly U-enriched sediments (350–760 µg ⋅ g−1 U) from Lake Nègre (Mercantour Massif, Mediterranean Alps, France) by combining U isotopic data (δ238U and (234U/238U)) with U L3-edge X-ray absorption fine structure spectroscopy. Constant isotopic ratios over the entire sediment core indicate stable U sources and accumulation modes, allowing for determination of the impact of aging on U speciation. We demonstrate that, after sediment deposition, mononuclear U(IV) species associated with organic matter transformed into authigenic polymeric U(IV)–silica species that might have partially converted to a nanocrystalline coffinite (UIVSiO4·nH2O)-like phase. This diagenetic transformation occurred in less than 700 y and is consistent with the high silica availability of sediments in which diatoms are abundant. It also yields consistency with laboratory studies that proposed the formation of colloidal polynuclear U(IV)–silica species, as precursors for coffinite formation. However, the incomplete transformation observed here only slightly reduces the potential lability of U, which could have important implications to evaluate the long-term management of U-contaminated sediments and, by extension, of U-bearing wastes in silica-rich subsurface environments.

scholarly journals Treated wastewater irrigation effects on soil hydraulic conductivity and aggregate stability of loamy soils in Israel

2015 ◽  
Vol 63 (1) ◽  
pp. 47-54 ◽  
Author(s):  
Karsten Schacht ◽  
Bernd Marschner
Keyword(s):  
Hydraulic Conductivity ◽  
Chemical Properties ◽  
Aggregate Stability ◽  
Treated Wastewater ◽  
Soil Aggregate Stability ◽  
Irrigation Effects ◽  
Physical And Chemical ◽  
The Impact

Abstract The use of treated wastewater (TWW) for agricultural irrigation becomes increasingly important in water stressed regions like the Middle East for substituting fresh water (FW) resources. Due to elevated salt concentrations and organic compounds in TWW this practice has potential adverse effects on soil quality, such as the reduction of hydraulic conductivity (HC) and soil aggregate stability (SAS). To assess the impact of TWW irrigation in comparison to FW irrigation on HC, in-situ infiltration measurements using mini disk infiltrometer were deployed in four different long-term experimental orchard test sites in Israel. Topsoil samples (0-10 cm) were collected for analyzing SAS and determination of selected soil chemical and physical characteristics. The mean HC values decreased at all TWW sites by 42.9% up to 50.8% compared to FW sites. The SAS was 11.3% to 32.4% lower at all TWW sites. Soil electrical conductivity (EC) and exchangeable sodium percentage (ESP) were generally higher at TWW sites. These results indicate the use of TWW for irrigation is a viable, but potentially deleterious option, as it influences soil physical and chemical properties.

scholarly journals The Implications of HIV Treatment on the HIV-Malaria Coinfection Dynamics: A Modeling Perspective

2015 ◽  
Vol 2015 ◽  
pp. 1-14 ◽  
Author(s):  
F. Nyabadza ◽  
B. T. Bekele ◽  
M. A. Rúa ◽  
D. M. Malonza ◽  
N. Chiduku ◽  
...  
Keyword(s):  
Hiv Treatment ◽  
Pathogen Transmission ◽  
Disease Epidemiology ◽  
Qualitative Dynamics ◽  
Potential Impact ◽  
Negative Impacts ◽  
Long Term Behavior ◽  
The Impact ◽  
Multiple Pathogens

Most hosts harbor multiple pathogens at the same time in disease epidemiology. Multiple pathogens have the potential for interaction resulting in negative impacts on host fitness or alterations in pathogen transmission dynamics. In this paper we develop a mathematical model describing the dynamics of HIV-malaria coinfection. Additionally, we extended our model to examine the role treatment (of malaria and HIV) plays in altering populations’ dynamics. Our model consists of 13 interlinked equations which allow us to explore multiple aspects of HIV-malaria transmission and treatment. We perform qualitative analysis of the model that includes positivity and boundedness of solutions. Furthermore, we evaluate the reproductive numbers corresponding to the submodels and investigate the long term behavior of the submodels. We also consider the qualitative dynamics of the full model. Sensitivity analysis is done to determine the impact of some chosen parameters on the dynamics of malaria. Finally, numerical simulations illustrate the potential impact of the treatment scenarios and confirm our analytical results.

scholarly journals The Impact of Education and Residential Environment on Long-Term Waste Management Behavior in the Context of Sustainability

2019 ◽  
Vol 11 (14) ◽  
pp. 3775 ◽  
Author(s):  
Andreea Simona Saseanu ◽  
Rodica-Manuela Gogonea ◽  
Simona Ioana Ghita ◽  
Radu Şerban Zaharia
Keyword(s):  
Rural Areas ◽  
Academic Staff ◽  
Demographic Factors ◽  
Education Level ◽  
Waste Reduction ◽  
Long Term Effect ◽  
Long Term Behavior ◽  
The Impact ◽  
Cointegration Relationship

Currently, the problem of waste reduction is a permanent concern for all countries of the world, given the need to ensure the sustainability development. In this context, the research aims to highlight the impact of education and demographic factors by residence areas on the long-term behavior of the amount of waste generated in 29 European countries during 2013–2017. The study is based on statistical and econometric modeling aimed at identifying, testing and analyzing the existence of long-term correlation between the amount of waste per capita recorded in each country and four factors of influence considered significant for waste reduction: Pupils and students by education level and Classroom teachers and academic staff by education level, representing exogenous variables which quantify the educational outcomes, as well as The population by degree of urbanization (cities, rural areas), as demographic factors. As a result of an analysis based on correlation and regression method, a cointegration relationship between the analyzed variables was identified. Considering the amount of waste as an important component of the environmental pressure, the obtained results show the significant long-term effect that education and the demographic factor can have on its long-lasting behavior, as well as the ways through which these factors can act to strengthen sustainability.

Experimental Analysis of the Impact on the Durability of Concrete Additions

2016 ◽  
Vol 249 ◽  
pp. 73-78 ◽  
Author(s):  
Vladimír Suchánek ◽  
Kateřina Hájková
Keyword(s):  
Free Fall ◽  
Concrete Surface ◽  
Hardened Concrete ◽  
Concrete Mixer ◽  
Long Term Monitoring ◽  
The Impact ◽  
Term Monitoring ◽  
Furnace Slag

This report deals with long term monitoring of durability properties of concrete using different weight doses of various kinds of additions. Particularly limestone, silica fume as a 50% suspension and blast furnace slag were used. Even though the basic recipe is based on the designed concrete, all the fresh concrete was made with a free-fall concrete mixer in the laboratory. This report deals with long-term monitoring of cement concrete surface resistance to water and defrosting chemicals (achieved 475 cycles). The article also describes results of following tests: determination of concrete frost resistance, depth of water penetration under pressure and depth of chloride penetration. Standard tests of fresh and hardened concrete specimens complement the experiment.

scholarly journals Visibility study of Galileo satellites from a VLBI network

2021 ◽  
Author(s):  
Helene Wolf ◽  
Johannes Böhm ◽  
Matthias Schartner ◽  
Urs Hugentobler
Keyword(s):  
Reference Frames ◽  
Direct Determination ◽  
Satellite Constellation ◽  
Long Baseline ◽  
Space Geodetic Techniques ◽  
Satellite Scheduling ◽  
Observation Geometry ◽  
The Impact

<p>Over the last years, ideas have been proposed to install a Very Long Baseline Interferometry (VLBI) transmitter on one or more satellites of the Galileo constellation. Satellites transmitting signals that can be observed by VLBI telescopes provide the opportunity of extending the current VLBI research with observations to geodetic satellites. These observations offer a variety of new possibilities such as high precision tying of space geodetic techniques but also the direct determination of the absolute orientation of the satellite constellation with respect to the International Celestial Reference Frame (ICRF) and have implications on the determination of long-term reference frames. </p><p>This contribution provides a visibility study of the Galileo satellites from a VLBI network. The newly developed satellite scheduling module in VieSched++ is used to determine the time periods during which a satellite is observable from a VLBI network. The possible satellite observations are evaluated through the number of stations from which a satellite is observable. Moreover, the impact on determining the orientation of the satellite constellation, caused by the observation geometry, is investigated with using the UT1-UTC Dilution of Precision (UDOP) factor.</p>

scholarly journals Impact of quality on improvement of business performance and customer satisfaction

2021 ◽  
Vol 11 (1) ◽  
pp. 20-28
Author(s):  
Milena Cvjetković ◽  
Marko Vasiljević ◽  
Milovan Cvjetković ◽  
Milica Josimović
Keyword(s):  
Customer Satisfaction ◽  
Growth And Development ◽  
Business Performance ◽  
Consumer Confidence ◽  
Efficient Manner ◽  
Mutual Relations ◽  
High Level ◽  
The Impact

In an immense market struggle, the only effective way to build a long-term competitive advantage is to provide a high level of quality. Offering quality to the market, the organization creates loyal consumers on the basis of which it achieves its profitability, growth and development. The research presented in this paper is aimed at determination of the impact of quality on improving business performance and customer satisfaction. Correlation analysis confirmed this influence on the basis of obtained statistically significant mutual relations between the analyzed variables. Quality was shown to have an impact on improving the business performance of the organization, primarily on profitability through the improvement of leadership and relationship management. The impact of quality on customer satisfaction was also confirmed, where the engagement of people and the management of mutual relations had the greatest impact on consumer confidence. The research confirmed that the training of employees in terms of quality had a statistically significant impact on improving customer satisfaction, if it is conducted in an efficient manner.

scholarly journals STEM education as a factor of national security

2021 ◽  
Vol 18 (2) ◽  
pp. 137-151
Author(s):  
Gulnara A. Krasnova ◽  
Alexander V. Fedotov
Keyword(s):  
National Security ◽  
Education System ◽  
Technological Development ◽  
Foreign Countries ◽  
Study Methodology ◽  
The Subject ◽  
The Impact

Problem and goal. Determination of the place and role of education in the national security system at the present stage based on the analysis of the foreign and Russian regulatory framework, as well as scientific literature on the subject of the study. Methodology. Through the analysis and parallel comparison of the main domestic and foreign regulatory legal acts in the field of security, the key transformations of the perception and vision of education as a factor of national security in foreign countries and Russia were identified, and the causal relationships between the development of the education system and national security were formulated. Results. The problems of national security in all their diversity are significantly related to the state and sustainability of the development of the educational sphere, the impact of which is long-term and has far-reaching consequences in the form of imbalances in the socio-economic, scientific and technological development of the country. Conclusion. The formalization of existing approaches to assessing threats to national security and the economic aspects of ensuring national security will allow us to propose a methodology for quantifying the costs of the education system as a whole (or only for higher education), necessary to optimize the impact of education on national security.

Rim Instant Release Radionuclide Inventory From French High Burnup Spent UOX Fuel

2009 ◽  
Vol 1193 ◽  
Author(s):  
D. Roudil ◽  
C. Jegou ◽  
V. Broudic ◽  
M. Tribet
Keyword(s):  
Small Volume ◽  
Source Term ◽  
Nuclear Waste Repository ◽  
Spent Fuel ◽  
Waste Container ◽  
High Burnup ◽  
Radionuclide Release ◽  
Long Term Behavior ◽  
The Impact

AbstractTo assess the long-term behavior of spent fuel in a nuclear waste repository, the chemical reactions between the fuel and possible intruding water must be understood and the resulting radionuclide release must be quantified. The instant release fraction (IRF) source term assumed to be instantaneously accessible to water after the failure of the waste container. Some IRF values for different kinds of spent fuel are available in the literature. However, the possible contribution the rim restructured zone for high-burnup UOX fuels, was not necessary taken into account. A specific study of the leaching behavior of the rim zone has been carried out on a UOX fuel sample with a burnup of 60 GWd·t-1 and 2.8% FGR. The 134/137Cs and 90Sr rim IRF are effectively higher than the gap and grain boundary inventories (respectively 4.4 wt% and 0.3 wt% of the total Cs and Sr inventories). Nevertheless because of the relative small volume of this zone in the pellet, the impact of the rim inventory appears to be limited and the complete Cs and Sr IRF (gap, grain boundaries and rim), were estimated at 1.85 and 0.3 wt%, respectively

Analysis of Long-Term Observation of Highway Arch Bridge Oparno

2016 ◽  
Vol 249 ◽  
pp. 209-214
Author(s):  
Vojtěch Kolínský ◽  
Jan L. Vítek
Keyword(s):  
Rheological Properties ◽  
Detailed Comparison ◽  
Bridge Construction ◽  
Final State ◽  
Arch Bridge ◽  
Arch Bridges ◽  
Long Term Observation ◽  
Long Term Behavior ◽  
The Impact

The paper deals with evaluation of experimental data collected during the Oparno arch bridge construction and with subsequent analysis of the construction process and long-term behavior with regard to rheological properties of concrete. The Oparno valley bridge is composed of two separate concrete arch structures with spans of 135 metres (this is currently the second longest span of concrete arch bridge in the Czech Republic). It was built using cantilever casting technology with temporary cable-stays and auxiliary pylons. The data recorded for this study include detailed geodetic measurement of the bridge structure during construction, along with measured strains and temperatures in the arches. Most of the data was measured during the bridge construction in 2008 and 2009. Data significant for long term behavior of structure are still being collected. Verification of different concrete material models and their suitability for design of arch bridges built by free cantilevering will be a main result of the analysis. On the basis of a detailed comparison of numerical results and measured deflections, strains and temperatures, it is possible to quantify the impact of rheological properties of the material (or their individual input parameters) on the resulting structural behavior. Unlike previous research, the examined structure is made of reinforced concrete (not prestressed) and consists of compact solid section and in the final state it is mainly in compression.

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