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Vegetables are the most important source of nitrate in the human diet. The nitrate content is not the same in the plant. Depending on the amount of nitrites, plant organs can be classified as follows: leaf (the largest amount) stem, inflorescence root, tuber, fruit. One of the most important factors in determining the quality of vegetable products is the content of nitrates and nitrites and the maximum permitted limits play an important role in human health. It is well known that a high dietary intake of nitrates and nitrites may increase the risk of gastrointestinal cancer due to the formation of carcinogenic chemicals known as N-nitroso compounds and the appearance in newborns of blue child syndrome. This study assessed the concentrations of nitrates and nitrates in 5 varieties of tomatoes from organic and the same 5 varieties from classical crops. The study showed that the amount of nitrates and nitrites in the tomato varieties taken in the studio was within the limits according to the legislation in force.

For the past three years we have been teaching a course titled Experimental History of Science as part of the Social and Human Sciences program at EPFL. Following the teaching method of “learning by doing,” the course is aimed at master students in engineering, physics, architecture, chemistry, mathematics, life sciences, or computer science, who have almost no background in history or history of science and technology. The first semester introduces the essential questions and insights in our...

This contribution argues that a particular scientific context made summits a place of interest for eighteenth-century travelers. This development is connected to two particular scientific practices. First, the challenges raised by making the barometer into an instrument capable of measuring the altitude of mountains transformed the summit into a privileged experimental site. Second, the scientific publications which described these experiments acted as guides to the summit for its readers, as shown by the example of the first ascents of Mont Buet by Jean-André Deluc, Marc-Théodore Bourrit, and Horace Bénédict de Saussure. Those who ascended on summits not only followed in the footsteps of Deluc and Saussure, but also imitated some of their scientific practices and observations, though not always with a clear scientific goal of their own. We suggest that these travelers engaged in science not so much because they needed a justification for their ascents, but rather because their experience of the mountain came to be mediated through such instruments, observations and publications. The ambiguity behind these scientific practices lacking a clear scientific purpose draws an interesting parallel between this historical study and the contemporary phenomenon of scientific tourism. Our historical case study indicates how contemporary scientific tourism could rely on a model of public engagement with science informed by the history of science and technology. Cet article avance qu’un contexte scientifique particulier a fait des sommets alpins un lieu d’intérêt pour les voyageurs du xviiie siècle. Ce développement est lié à deux pratiques scientifiques spécifiques. Premièrement, les défis soulevés par l’utilisation du baromètre comme instrument capable de mesurer l’altitude des montagnes ont transformé le sommet en un site privilégié pour l’expérimentation. D’autre part, les publications scientifiques qui décrivirent ces expériences servirent de guides jusqu’au sommet pour leurs lecteurs, comme le montre l’exemple des premières ascensions du Mont Buet par Jean-André Deluc, Marc-Théodore Bourrit et Horace Bénédict de Saussure. Les voyageurs qui ont réalisé l’ascension des sommets ont non seulement suivi les traces de Deluc et de Saussure, mais ont également imité certaines de leurs pratiques et observations savantes, parfois sans objectif scientifique clair et précis. Nous suggérons que ces voyageurs se sont adonnés à de telles activités non pas tant parce qu’ils avaient besoin de justifier leurs ascensions par la science, mais plutôt parce que leur expérience même de la montagne a été médiatisée par ces instruments, observations et publications scientifiques. L’ambiguïté de ces pratiques scientifiques dépourvues d’objectif scientifique clair ouvre un parallèle intéressant entre cette étude de cas historique et le phénomène contemporain du tourisme scientifique, suggérant comment le tourisme scientifique contemporain pourrait s’appuyer sur un modèle de médiation scientifique informé par l’histoire des sciences et des techniques.

In this paper, static mechanical characteristics for some epoxy/hemp composites are studied. By using the tensile test, the static mechanical characteristics are determined, such as: breaking strength, yield stress, Young modulus and breaking elongation. There is also determined the standard deviation. Then, by using some known theories, there is validated the static Young modulus.

In this work, we perform Bayesian inference tasks for the chemical master equation in the tensor-train format. The tensor-train approximation has been proven to be very efficient in representing high dimensional data arising from the explicit representation of the chemical master equation solution. An additional advantage of representing the probability mass function in the tensor train format is that parametric dependency can be easily incorporated by introducing a tensor product basis expansion in the parameter space. Time is treated as an additional dimension of the tensor and a linear system is derived to solve the chemical master equation in time. We exemplify the tensor-train method by performing inference tasks such as smoothing and parameter inference using the tensor-train framework. A very high compression ratio is observed for storing the probability mass function of the solution. Since all linear algebra operations are performed in the tensor-train format, a significant reduction of the computational time is observed as well.

This paper developes a data-driven magnetostatic finite-element (FE) solver which directly exploits measured material data instead of a material curve constructed from it. The distances between the field solution and the measurement points are minimized while enforcing Maxwell's equations. The minimization problem is solved by employing the Lagrange multiplier approach. The procedure wraps the FE method within an outer data-driven iteration. The method is capable of considering anisotropic materials and is adapted to deal with models featuring a combination of exact material knowledge and measured material data. Thereto, three approaches with an increasing level of intrusivity according to the FE formulation are proposed. The numerical results for a quadrupole-magnet model show that data-driven field simulation is feasible and affordable and overcomes the need of modeling the material law., 6 pages, 5 figures

Large national programs in the United States and several Asian countries have defined and characterised their marine methane hydrate occurrences in some detail, but European hydrate occurrence has received less attention. The European Union-funded project “Marine gas hydrate – an indigenous resource of natural gas for Europe” (MIGRATE) aimed to determine the European potential inventory of exploitable gas hydrate, to assess current technologies for their production, and to evaluate the associated risks. We present a synthesis of results from a MIGRATE working group that focused on the definition and assessment of hydrate in Europe. Our review includes the western and eastern margins of Greenland, the Barents Sea and onshore and offshore Svalbard, the Atlantic margin of Europe, extending south to the northwestern margin of Morocco, the Mediterranean Sea, the Sea of Marmara, and the western and southern margins of the Black Sea. We have not attempted to cover the high Arctic, the Russian, Ukrainian and Georgian sectors of the Black Sea, or overseas territories of European nations. Following a formalised process, we defined a range of indicators of hydrate presence based on geophysical, geochemical and geological data. Our study was framed by the constraint of the hydrate stability field in European seas. Direct hydrate indicators included sampling of hydrate; the presence of bottom simulating reflectors in seismic reflection profiles; gas seepage into the ocean; and chlorinity anomalies in sediment cores. Indirect indicators included geophysical survey evidence for seismic velocity and/or resistivity anomalies, seismic reflectivity anomalies or subsurface gas escape structures; various seabed features associated with gas escape, and the presence of an underlying conventional petroleum system. We used these indicators to develop a database of hydrate occurrence across Europe. We identified a series of regions where there is substantial evidence for hydrate occurrence (some areas offshore Greenland, offshore west Svalbard, the Barents Sea, the mid-Norwegian margin, the Gulf of Cadiz, parts of the eastern Mediterranean, the Sea of Marmara and the Black Sea) and regions where the evidence is more tenuous (other areas offshore Greenland and of the eastern Mediterranean, onshore Svalbard, offshore Ireland and offshore northwest Iberia). We provide an overview of the evidence for hydrate occurrence in each of these regions. We conclude that around Europe, areas with strong evidence for the presence of hydrate commonly coincide with conventional thermogenic hydrocarbon provinces.

Gas hydrates, a solid established by water and gas molecules, are widespread along the continental margins of the world. Their dynamics have mainly been regarded through the lens of temperature-pressure conditions. A fluctuation in one of these parameters may cause destabilization of gas hydrate-bearing sediments below the seafloor with implications in ocean acidification and eventually in global warming. Here we show throughout an example of the Black Sea, the world’s most isolated sea, evidence that extensive gas hydrate dissociation may occur in the future due to recent salinity changes of the sea water. Recent and forthcoming salt diffusion within the sediment will destabilize gas hydrates by reducing the extension and thickness of their thermodynamic stability zone in a region covering at least 2800 square kilometers which focus seepages at the observed sites. We suspect this process to occur in other world regions (e.g., Caspian Sea, Sea of Marmara)., Gas hydrates are maintained via a balance of temperature and pressure, if this changes then destabilization may occur. Here, the authors show instead that due to recent changes in the salinity of the sea water of the Black Sea, gas hydrates may become destabilized with widespread methane seepage.