2,689 research outputs found

    The Clean Air Act\u27s Accidental Release Program: An Overview

    Get PDF

    An Overview of Missouri\u27s Air Permit Laws

    Get PDF

    Amfibieën

    Get PDF

    Données sur les transferts du 137Cs et du 60Co dans un écosystème fluvial : le Rhône

    Get PDF
    L'étude radioécologique du Rhône permet d'évaluer qualitativement et quantitativement les radionucléides présents dans le fleuve. Les études menées in situ posent des questions concernant les modalités de transfert des radionucléides. Dans ce travail des expériences sont mises au point, afin d'analyser les mécanismes de bioconcentration dans les écosystèmes aquatiques. Pour le césium-137 les échanges entre l'eau, le sédiment et divers organismes aquatiques ont permis d'élaborer un modèle mathématique que l'on peut confronter aux valeurs mesurées sur le terrain. En ce qui concerne le Cobalt-60 les auteurs décrivent des expériences permettant l'évaluation de la contribution relative de l'eau et de la nourriture dans l'accumulation du radionucléide par un poisson.The radioecology of the Rhone Basin has been studied for the last 15 years. This has been an opportunity to make a quantitative and qualitative evaluation of radionuclides as a function of their different sources. Special attention is given to 137Cs (present both in fallout and liquid wastes) and 60Co, which characterize the liquid wastes of pressurised water reactors. In order to assess the transfer and bioconcentration of these two radionuclides in freshwater ecosystems, several experimental studies were undertaken.The 137Cs transfer studies were carried out with a 5-component experimental ecosystem and the data were included in a mathematical model. For 60Co, the experimental study concerns the relative contribution of water and food in the accumulation of the radionuclide by Cyprinus carpio.Water, sediment, plants and fishes were taken from 60 sampling stations set up along the river (figure 1). Water was filtrated, then percolated on resin columns. Sediment, plants and fishes were dried and burnt to ashes in an oven at 500° C. Radioactivity was measured by gamma spectrometry and radiochemistry.137Cs experimental transfers were studied between water, sediment, midge larvae, daphnid and carp. These components were taken in pairs in order to estimate the radionuclide transfer from one to the other. Thus ten experiments were carried out (figure 2). In order to study the relative importance of food and water as 60Co sources for the carp, an experiment was carried out simultaneously on three homogeneous groups of ten juvenile fishes. The individuals of the first group were maintained in separate aquaria and offered 45 daily rations of labelled food over a 63-day period. Bach carp of the other two groups was placed in a compartment of a large tank with contaminated water. One group was fed with radioactive food, the other with non-radioactive food (table 1).Natural radioactivity remained steady all along the river. It ranged around 1 Bq.l-1 in water, 2250 Bq.kg-1 DW in sediment, 1700 Bq.kg-1 DW in aquatic plants, 110 Bq.kg-1 WW in fish. The fallout impact was characterized by 137Cs presence. PWR liquid wastes contained mainly, 58Co, 60Co, 134 Cs, 137Cs. The Chernobyl fallout gave an increase of Cs and the presence of 103Ru and 106RU+Rh specially during May and June 1986 which later decreased (tables 2, 3 and 4).137Cs transfer between water and sediment was very fast and important. Less than 2 % of the radionuclide was released from sediment into a non-radioactive water. During the transfer from water to chironomids the larvae radioactivity increased steadily (figure 3). Conversely, the transfer from the sediment to larvae did not seem to depend on the contact time. The transfer from water to carp was regular without any steady state during the 63 days of the experiment (figure 3). Then the fish concentration factor was less than 5. For 42 days, the transfer factor from sediment to carp was 3.6.10-3. The retention factor from food to carp was 0.03 when fishes were fed with daphnids and 0.13 with chironomids. An experiment showed that the various ways of 137Cs transfer could have an added impact. Thus the carp radioactivity was the sum of the separate transfers. Water was responsible for 4 % of the fish 137 Cs concentration, sediment for 45 % and chironomids for 51 %.It is possible to include the different kinetic equations in a mathematical model. If the radioactivity of one of the components is known, the nuclide concentration can be computed in others, as a relation of the contact time, the quantity and quality of ingested food, etc... This model gives a concentration factor for juvenile carp of 1000 in 180 days and 500 for 3-year old fish. Considering the field conditions (e.g. seasonal nutritive cycles) the computed concentration factor in fish was between 200 and 350. For a 1 mBq.l-1 137Cs concentration in water, the model gave a concentration of 0.2 to 0.35 Bq.kg-1 WW in carp, which was the 137Cs radioactivity level measured in the Rhone fish before the Chernobyl accident.During the 60Co accumulation phase, the mean weight of the fish in the three groups increased exponentially and the resultant relative weight gain was 52-59 % after 63 days (table 5).The 60Co accumulation kinetics showed that the steady state should be reached after 165 days for fish exposed to 60Co in food, 92 days for fish exposed to radiocobalt in water and 120 days for fish exposed to 60Co in both sources (figure 4). According to the 60Co concentration in the fish in the three treated groups, the accumulation from water accounted for 75 % of the total radioactivity and the accumulation of the radionuclide from both water and food was in addition.Depuration of 60Co from carp was a relatively intensive process reflecting a high Co turnover. Biological half-lives for loss from the long-lived compartment ranged from 35d in fish previously contaminated by food, to 87d in fish previously contaminated by food, to 87d in fish previously contaminated by water (figure 5).137Cs and 60Co are the most concentrated radionuclides in liquid wastes of the pressurised water reactors, and they are often measured in the aquatic ecosystem components. Though it accounts for the highest fraction of total radioactivity in the liquid wastes, 60Co cobalt is not the most concentrated radionuclide in fish. Experimental studies show that it is primarily transferred from the water so it is logical that its concentration in fish remains at a low level. Conversely the 137Cs has a low concentration in water but as it is transferred simultaneously from water, sediment and food, its concentration in fish is still important. Moreover its 30 years half-life means that the cesium contamination of fish is a long and important process, all the more so as the source terms can add their own effects during time and space

    Recurrent difficulties: solving quantitative problems

    Get PDF
    Investigating the process students use to solve quantitative problems using a think aloud strategy

    The implementation of the Isiseko Sokomoleza HIV/aids programme in the diocese of false bay: a critical theological investigation

    Get PDF
    Philosophiae Doctor - PhDThe multidimensional nature of the AIDS pandemic continues to pose challenges within all spheres of society, for example health and religion, human rights, social development politics, economics, human sexuality, and Christian theologies - in particular, the pastoral and caring ministries, as well as the educational ministries. Its multidimensional nature is further exacerbated by factors of, stigma, gender power-relations, poverty, and violence against women and children. The Anglican Church of Southern Africa, in particular the Diocese of False Bay, has responded to the challenges relating to stigma reduction through many programmes, campaigns and workshops. Despite the implementation of the Isiseko Sokomoleza HIV/AIDS Programme in the Diocese of False Bay, it has had a limited impact on reducing the stigma associated with HIV/AIDS. As such, stigma remains a critical challenge in the pastoral response of the Church. In light of this observation, the question pertinent to this research project is; “What are the most significant reasons for the limited impact of the Isiseko Sokomoleza HIV/AIDS Programme in the Diocese of False Bay?” The framework of Practical Theology, with special emphasis on pastoral care and counselling, will be used as the theological framework to explore the reasons for the limited impact. In order to achieve this goal, the Primary Healthcare Model (2012) introduced in Brazil and Cuba was utilised. This does not imply that HIV/AIDS is only a medical problem, on the contrary, this medical model of implementation assists the pastoral model of the Church to analyse the reasons for the limited impact of the Isiseko Sokomoleza programme

    A Synthesis and Optimization of Patented Direct Air Capture Technology

    Get PDF
    Title from PDF of title page, viewed November 10, 2023Dissertation advisor: John KevernVitaIncludes bibliographical references (pages 142-157)Dissertation (Ph.D.)--Department of Civil and Mechanical Engineering, Department of Geosciences. University of Missouri--Kansas City, 2023An engineering method termed direct air capture is used to take CO₂, the predominant global warming greenhouse gas, out of the atmosphere directly. Given that CO₂ levels in the air are only 0.04%, it presents a technical challenge. Ambient air has a concentration that is 2-4 orders of magnitude lower than other typically targeted sources for CO₂ capture, like flue gases from energy production and industrial activities. Nevertheless, direct air capture has drawn more attention recently, partly because of the creation and implementation by a small number of start-ups. An increasing quantity of research is being done on novel direct air capture materials and methods, and it’s important to comprehend the costs and environmental effects of direct air capture. The author believes that this engineering tool should be one of many tools utilized in the fight against climate change. This dissertation seeks to gather and analyze critical information on fifteen recently issued United States patents and then synthesize the findings from those fifteen patents and then to optimize the critical components of the patented direct air capture technology to advance the state of the art in carbon removal to ameliorate the impacts of increasing carbon concentrations in the atmosphere.Introduction -- Non-profits and climate change -- The role of the Securities and Exchange Commission in addressing climate change -- The role of patents in advancing the state of the art in direct air capture -- Conclusio
    • …
    corecore