Corrosion behavior of iron in cementitious solution at 80°C in anoxic condition

International audienceThe Belgian reference concept for high-level radioactive waste packaging proposed by ONDRAF/NIRAS is called Supercontainer. The design of the Supercontainer includes a stainless-steel liner, a concrete buffer and a carbon steel overpack containing one or several waste canisters. An objective of the concrete buffer is to maintain high alkaline conditions on the surface of the overpack during underground disposal of these wastes. In these conditions (alkaline and anoxic conditions), a passive film forms on the surface of the steel, resulting in very low and almost negligible uniform corrosion rates (passive dissolution). This film is generally composed of a double layer an inner layer, accounting for passivity, and a more or less porous outer layer. The latter is in contact with the environment and is formed by precipitation of elements in solution. The presence of silicon and cations from the cementitious environment could lead to neo-formed phases such as ferrous-silicates or phyllosilicates possessing corrosion inhibiting properties. The aim of this work is to study the impact of the cementitious materials during the corrosion at 80DC in anoxic media by characterizing the layer formed during the corrosion process. To ensure these measurements, iron plates were corroded in solution representative of a cementitious environment (at 80DC and under anoxic conditions). Evolution of the nature and growth of the corrosion layer is studied on samples after several duration tests. Corrosion products are characterized by means of several analytical techniques such as scanning electron microscopy, Raman micro-spectroscopy, X-ray diffraction, X-ray photoelectron spectrometry and transmission electronic microscopy. Results have revealed evolution of composition as a function of time. Layers are mainly composed of magnetite and others phases containing iron, calcium and silicon

Experimental investigation of aminoacetonitrile formation through the Strecker synthesis in astrophysical-like conditions: reactivity of methanimine (CH2NH), ammonia (NH3), and hydrogen cyanide (HCN)

International audienceAstronomy & Astrophysics Experimental investigation of aminoacetonitrile formation through the Strecker synthesis in astrophysical-like conditions: reactivity of methanimine (CH 2 NH), ammonia (NH 3), and hydrogen cyanide (HCN) ABSTRACT Context. Studing chemical reactivity in astrophysical environments is an important means for improving our understanding of the origin of the organic matter in molecular clouds, in protoplanetary disks, and possibly, as a final destination, in our solar system. Laboratory simulations of the reactivity of ice analogs provide important insight into the reactivity in these environments. Here, we use these experimental simulations to investigate the Strecker synthesis leading to the formation of aminoacetonitrile in astrophysical-like conditions. The aminoacetonitrile is an interesting compound because it was detected in SgrB2, hence could be a precursor of the smallest amino acid molecule, glycine, in astrophysical environments. Aims. We present the first experimental investigation of the formation of aminoacetonitrile NH 2 CH 2 CN from the thermal processing of ices including methanimine (CH 2 NH), ammonia (NH 3), and hydrogen cyanide (HCN) in interstellar-like conditions without VUV photons or particules. Methods. We use Fourier Transform InfraRed (FTIR) spectroscopy to monitor the ice evolution during its warming. Infrared spec-troscopy and mass spectroscopy are then used to identify the aminoacetonitrile formation. Results. We demonstrate that methanimine can react with − CN during the warming of ice analogs containing at 20 K methanimine, ammonia, and [NH + 4 − CN] salt. During the ice warming, this reaction leads to the formation of poly(methylene-imine) polymers. The polymer length depend on the initial ratio of mass contained in methanimine to that in the [NH + 4 − CN] salt. In a methanimine excess, long polymers are formed. As the methanimine is progressively diluted in the [NH + 4 − CN] salt, the polymer length decreases until the aminoacetonitrile formation at 135 K. Therefore, these results demonstrate that aminoacetonitrile can be formed through the second step of the Strecker synthesis in astrophysical-like conditions

Indigenous women managing pregnancy complications in rural Ecuador

Previous research has explored the potential use of digital health to support maternal health in the Global South highlighting the importance of understanding the socio-cultural context to inform system design. However, the experiences of indigenous women managing pregnancy complications in Latin America remain underexplored in HCI. We present a qualitative study with 25 indigenous pregnant women in an Ecuadorian rural community looking at their experiences during complications, their antenatal care visits and their access and use of technologies. Our findings highlight key barriers that hinder the use of antenatal care services and influence women's experiences managing complications. Based on the findings, we present opportunities for digital health centered on indigenous women to enhance antenatal care in rural Ecuador

Analiza właściwości maszyny indukcyjnej z uzwojeniem stojana połączonym gwiazda-trójkąt

W artykule przeanalizowano właściwości maszyny z równoległym połączeniem uzwojenia stojana. Analizę prowadzono w zakresie liczby przewodów delta i połączonego w gwiazdę uzwojenia. Przedstawiono wpływ stosunku liczby przewodów tych uzwojeń do możliwości stłumienia wyższych harmonicznych przestrzennych i dotyczących sprawności urządzenia. Pochodne równania maszyny z połączonym uzwojeniem stojana opisują zachowanie maszyny, zarówno w stanie ustalonym, nieustalonym oraz podczas awarii

Nowy układ uzwojenia mieszanego gwiazda-trójkąt w stojanie zmniejszający zużycie miedzi w maszynie elektrycznej

The submitted paper deals with the increased energy efficiency of induction machines by means of the so-called combined stator winding. Two basic variants of this winding, the series and parallel ones, are shown. The suppression of higher harmonics is analysed by means of the method of space vectors and symmetrical components. It is shown that the so-called series variant of the combined winding has a better ability to suppress higher spatial harmonics. The commonly used combined winding has, however, a longer pitch and thus bigger stator resistance and greater consumption of copper. The paper presents a proposal of an adapted combined winding whose pitch is smaller than that of the used three-phase winding. This fact results in decreasing the consumption of copper conductors with preserving the energy efficiency. The results of the analysis have been verified by measurements on physical models of machines with the combined and the adapted combined windings