Biogéochimie du fer et des éléments associés : exemple de l'arsenic (V)

Iron, a major element of the Earth's crust, has a very strong reactivity through its redox sensitive nature, its ability to be used by living organisms as well as sorption abilities of a number of trace elements. The objective of this study is to assess the role of biological activity and non-metabolic reactions in controlling kinetic mineralogical transformations and transfers of iron and associated contaminants. The main targets of this study are iron oxides, more or less crystallized, but ubiquitous in soils and waters. They behave like sinks or sources of trace elements depending on the environmental redox conditions. This work is focused on wetlands, fragile, but of major environmental interest. These are real biogeochemical reactors, the seat of alternating redox conditions likely to stabilize or destabilize the iron oxides and where bacterial activities are catalyzed by the presence of large quantities of organic matter and nutrients. This study is divided into two parts (bio-oxidation and bio-reduction). The first part concerns therefore the oxidation of Fe(II) in the presence of bacteria and biomineralization. The results showed that bacteria delayed the oxidation of Fe(II) rather than catalyse the process by passive (non metabolic reactions). Microscopic observations coupled with chemical analyses have shown the ability of bacteria to adsorb ions Fe2+, Fe3+ and Fe(III) oligomers, but also to inhibit the oxidation of Fe2+ ions by blocking them at their surfaces, which then oxidize over time. This oxidation of iron adsorbed onto the surface is heavily dependent on pH, and the process of absorption or desorption if oxidation occurs in solution. The mineralogical analyses have shown the formation of amorphous iron oxides in biotic environments, while crystallised iron oxides were formed in abiotic systems. The second part concerns the in situ study of bio-reduction of iron oxyhydroxydes (ferrihydrite and lepidocrocite) doped or not with As(V). The study has helped develop an original methodology for both in situ qualitative and quantitative monitoring (in wetland from the experimental Kervidy-Naizin catchment, Brittany), and ex situ (soil column) of reductive dissolution of ferrihydrite and lepidocrocite, doped or not with As(V). In situ monitoring showed dissolution rates of pure or As-doped ferrihydrite and lepidocrocite close to those that have been measured in laboratory studies with reducing biological or chemical agents. On the otherhand, the dissolution rates observed ex situ showed higher values than those reported in the literature for laboratory and field data. Most secondary phases are composed of iron sulphides, which are formed late on the slides during the reductive dissolution. The As release is more important for lepidocrocite dissolution than for ferrihydrite because of the unavailability or destuction of surface sites, while part of arsenic is readsorb onto the surface of reduced ferrihydrite. In all cases, the key role played by the bacterial colonization was established.Le fer, élément majeur de la croûte terrestre, présente une très forte réactivité grâce à son caractère rédox sensible, sa capacité à être utilisé par les organismes vivants et ses capacités de sorption d'un certain nombre d'éléments traces. L'objectif de cette étude est d'évaluer le rôle de l'activité biologique et des réactions non métaboliques dans le contrôle cinétique des transformations minéralogiques et des transferts de fer et des contaminants associés. Les cibles principales de cette étude sont les oxydes de fer ubiquistes dans les sols et les eaux. Ils se comportent comme des puits ou des sources d'éléments traces en fonction des conditions rédox du milieu. Ce travail est centré sur les zones humides, fragiles mais d'intérêt environnemental majeur. Ces dernières sont de véritables réacteurs biogéochimiques, siège d'alternances rédox susceptibles de stabiliser ou déstabiliser les oxydes de fer et où les activités bactériennes sont catalysées par la présence de quantités importantes de matière organique et de nutriments. Cette étude est divisée en deux volets (bio-oxydation et bio-réduction). Le premier volet concerne donc l'oxydation du Fe(II) en présence des bactéries et la biominéralisation. Les résultats obtenus ont montré que les bactéries retardaient l'oxydation du Fe(II) plutôt que de la catalyser par des processus passifs (réactions non métaboliques). Les observations microscopiques couplées avec des analyses chimiques ont montré la capacité des bactéries à adsorber les ions Fe2+, Fe3+ et oligomères de Fe(III), mais aussi à inhiber l'oxydation des ions Fe2+ en les bloquant à leurs surfaces, qui s'oxydent ensuite avec le temps. Cette oxydation du fer adsorbé à la surface est fortement dépendante de pH, et donc du processus d'adsorption ou de désorption si l'oxydation a lieu en solution. Les analyses minéralogiques ont montré une formation en présence des bactéries d'oxydes de fer amorphes et des oxydes de fer cristallisés dans les systèmes abiotiques. Le deuxième volet concerne l'étude in situ de la bio-réduction d'oxyhydroxydes de fer synthétiques (ferrihydrite et lépidocrocite) dopés ou non en As(V). L'étude a permis de développer une méthodologie originale de suivi qualitatif et quantitatif in situ (zone humide du bassin versant expérimental de Kervidy-Naizin, Bretagne) et ex situ (colonne du sol) de la dissolution réductrice de ferrihydrite et lépidocrocite dopées ou non en arsenic. Les résultats du suivi in situ de la dissolution de la ferrihydrite et la lépidocrocite pures et dopées en arsenic ont montré des taux de dissolution proches de ceux qui ont été mesurés dans des études de laboratoire avec des réducteurs biologiques ou chimiques. Par contre, les taux de dissolution observés ex situ ont montré des valeurs plus élevées que ceux reportés dans la littérature pour des données de laboratoire et de terrain. La majeure partie des phases néoformées est composée de sulfures de fer qui sont formés tardivement sur les plaquettes dans la dissolution réductrice. La libération de l'arsenic est plus importante dans le cas de la dissolution de la lépidocrocite que dans celle de la ferrihydrite, à cause de l'indisponibilité ou de la destruction des sites à la surface de la lépidocrocite réduite, alors qu'une partie de l'arsenic se réadsorbe à la surface de la ferrihydrite réduite. Dans tous les cas, le rôle majeur de la colonisation bactérienne a été montré

AudioFool: Fast, Universal and synchronization-free Cross-Domain Attack on Speech Recognition

Automatic Speech Recognition systems have been shown to be vulnerable to adversarial attacks that manipulate the command executed on the device. Recent research has focused on exploring methods to create such attacks, however, some issues relating to Over-The-Air (OTA) attacks have not been properly addressed. In our work, we examine the needed properties of robust attacks compatible with the OTA model, and we design a method of generating attacks with arbitrary such desired properties, namely the invariance to synchronization, and the robustness to filtering: this allows a Denial-of-Service (DoS) attack against ASR systems. We achieve these characteristics by constructing attacks in a modified frequency domain through an inverse Fourier transform. We evaluate our method on standard keyword classification tasks and analyze it in OTA, and we analyze the properties of the cross-domain attacks to explain the efficiency of the approach.Comment: 10 pages, 11 Figure

Metal concentrations in river water and bed sediments of the Lower Litani River Bassin, Lebanon

The distribution of pollutants in the Litani River is almost severe. It resulted from domestic, sewage, agricultural and industrial sources. In this study, the distribution of metals (Cu, Fe, Cd, Mg, Zn, Pb , Al, Ba, Ni, Mn, Ag and Cr) were measured in river water and the bed sediments of the Lower Litani River Basin (LLRB). The impacts of metals on the water quality were monitored during the rainy, mid rainy and dry season in the year 2012. The objectives of this study were first to identify possible sources of metals (i.e. geological and/or anthropogenic) and then to characterize the chemical behavior of these metals in water and bed sediments. Water and bed load sediments were sampled at six sites along the LLRB main watercourse, The metal concentrations in the river sediments were remarkably high, but varied between different sampling sites, and the concentrations in water were mainly within the permissible limits. The metal contents in bed sediment were highest during closure of summer period. By applying the principal component analysis applied to total and extractable metal contents as a tool for studying metal pollution in the LLRB, it was useful to distinguish between anthropogenic and natural sources

Physiochemical and Microbial Assessment of Water Quality in the Upper Litani River Basin, Lebanon

Water resources in Lebanon are witnessing serious challenges and reached depletion. One of the major challenges is the quality deterioration, which is accompanied with uncontrolled resources management, and thus the increasing demand. There are several consumption aspects, mainly the domestic, industrial and irrigation. Yet, exploitation of water resources in Lebanon implies both the surface and groundwater. However, surface water resources are most used due to the ease of exploitation processes, and more certainly water from rivers. Typically, the Litani River is the largest one in Lebanon. The river has been lately subjected to several aspects of deterioration in its quality. This includes the major physiochemical characteristics. This study aims to assess the seasonal variations in water quality in the Upper Litani River Basin, including the Qaraaoun Lake. Samples were collected from particular sites along the river, and at several dates during the years of 2010 and 2011. The carried analysis implies the physical (pH, T°, TDS, Ec), chemicals (Na+, Ca2+, Mg2+, Cl?, SO42?, NH3+, NO3?, PO42?, K+, BOD5 and COD, Heavy metals (Fe, Ni, Zn, Cu, Cr, Al, Ba, Pb, Mn) and microbiological parameters. This resulted numeric data are being compared with WHO guidelines. In addition, PCA was applied to evaluate the data accuracy. We can conclude that the variables used are very efficient and the dry season shows the worst water quality with nitrate, metal and microbial enrichments. Keywords: Water Contamination, Human Interference, Litani River, Principal Component Analysis

Recommendations for change in infection prevention programs and practice

Fifty years of evolution in infection prevention and control programs have involved significant accomplishments related to clinical practices, methodologies, and technology. However, regulatory mandates, and resource and research limitations, coupled with emerging infection threats such as the COVID-19 pandemic, present considerable challenges for infection preventionists. This article provides guidance and recommendations in 14 key areas. These interventions should be considered for implementation by United States health care facilities in the near future

Adherence to the United States Department of Agriculture Dietary Recommendations Pre- and During the Coronavirus Disease-19 Pandemic Among Pregnant Women in Arab Countries

During pregnancy, woman’s diet is one of the most preeminent factors affecting mother and child’s health. Prior to the coronavirus disease-19 (COVID-19) pandemic, inadequate maternal diet and low adherence to dietary guidelines was reported among pregnant women in the Arab countries. Nowadays, COVID-19 infection during pregnancy is widely discussed among literature. However, there is limited data on the health impacts of the COVID-19 pandemic on non-infected pregnant women. This substantially larger group also suffered significant lifestyle changes during the lockdown period. The aim of the study is to characterize dietary patterns, intake and adherence to the United States Department of Agriculture (USDA) pregnancy guidelines before and during the COVID-19 pandemic in Arab pregnant women. Using a specially designed questionnaire and using the snowball sampling method, the survey was carried out among a convenient sample of 1,939 pregnant women from five Arab countries. Our study found an increment in the consumption of cereals, fruits, vegetables, dairy products, meats, and nuts that occurred during the pandemic compared to the preceding period. Despite this noticeable increase during the pandemic, the Arab pregnant women in this study had significantly lower adherence to the USDA pregnancy guidelines. The daily consumption of almost all food groups was lower than the USDA’s daily recommendations, except for fruits intake, which was higher than the daily standard. Demonstrated poor adherence to prenatal USDA dietary guidelines by Arab pregnant women can lead to numerous deficiencies and health risks among their offspring. In conclusion, our study showed that before and during the COVID-19 pandemic, poor adherence to dietary recommendations occurred in a considerable number of Arab pregnant women. The findings emphasize the need for nutritional education and intervention during prenatal visits

Multisociety statement on coronavirus disease 2019 (COVID-19) vaccination as a condition of employment for healthcare personnel

This consensus statement by the Society for Healthcare Epidemiology of America (SHEA) and the Society for Post-Acute and Long-Term Care Medicine (AMDA), the Association for Professionals in Epidemiology and Infection Control (APIC), the HIV Medicine Association (HIVMA), the Infectious Diseases Society of America (IDSA), the Pediatric Infectious Diseases Society (PIDS), and the Society of Infectious Diseases Pharmacists (SIDP) recommends that coronavirus disease 2019 (COVID-19) vaccination should be a condition of employment for all healthcare personnel in facilities in the United States. Exemptions from this policy apply to those with medical contraindications to all COVID-19 vaccines available in the United States and other exemptions as specified by federal or state law. The consensus statement also supports COVID-19 vaccination of nonemployees functioning at a healthcare facility (eg, students, contract workers, volunteers, etc)