Displacement Damage and Self-Healing in High-Entropy Alloys: a TEM with in situ ion irradiation study

Recent developments in the field of materials for future nuclear fusion reactors have led to the design of innovative metallic alloys that can sustain their mechanical and structural properties under a wide variety of extreme conditions, such as fast neutrons (E <= 14 MeV) and alpha particle bombardment (4He with E up to ~ 3.5 MeV). High-Entropy Alloys (HEAs) are promising candidates for new concepts of nuclear reactors as they have mechanical properties and thermodynamic stability that is believed to be superior to conventional metallic alloys, although their radiation resistance is still a subject of intense research. The efforts to understand the behavior of HEAs under particle irradiation indicated a possible “self-healing” effect of radiation induced defects. In this report, a preliminary study using Transmission Electron Microscopy (TEM) with in situ ion irradiation was performed to investigate the formation and evolution of displacement damage in the microstructure of a FeCrMnNi HEA

To each their own! Nectar plasticity within a flower mediates distinct ecological interactions

Our results highlight the plasticity of nectar traits underlying the diversity of nectaries within a plant, which mediates distinct ecological interactions. Nuptial nectaries are exclusively visited by bees and extranuptial nectaries by ants, cockroaches, wasps and flies. Nectar from these nectaries differ in energy amount, nutritional value and neuroactive specialized metabolites. The specificity of visitors' taxa between distinct nectaries may be due to plant-driven differences in nectar chemical composition. Nevertheless, as all floral visitors exclusively consume only one of the two nectar types, they are prone to exert selective pressures upon nectar traits, selecting those that fit their specific preferences.Nuptial and extranuptial nectaries are involved in interactions with different animal functional groups. Nectar traits involved in pollination mutualisms are well known. However, we know little about those traits involved in other mutualisms, such as ant-plant interactions, especially when both types of nectaries are in the same plant organ, the flower. Here we investigated if when two types of nectaries are exploited by distinct functional groups of floral visitors, even being within the same plant organ, the nectar secreted presents distinct features that fit animal requirements. We compared nectar secretion dynamics, floral visitors and nectar chemical composition of both nuptial and extranuptial nectaries in natural populations of the liana Amphilophium mansoanum (Bignoniaceae). For that we characterized nectar sugar, amino acid and specialized metabolite composition by high-performance liquid chromatography. Nuptial nectaries were visited by three medium- and large-sized bee species and extranuptial nectaries were visited mainly by ants, but also by cockroaches, wasps and flies. Nuptial and extranuptial nectar differed regarding volume, concentration, milligrams of sugars per flower and secretion dynamics. Nuptial nectar was sucrose-dominated, with high amounts of gamma-aminobutyric acid and beta-aminobutyric acid and with theophylline-like alkaloid, which were all exclusive of nuptial nectar. Whereas extranuptial nectar was hexose-rich, had a richer and less variable amino acid chemical profile, with high amounts of serine and alanine amino acids and with higher amounts of the specialized metabolite tyramine. The nectar traits from nuptial and extranuptial nectaries differ in energy amount and nutritional value, as well as in neuroactive specialized metabolites. These differences seem to match floral visitors' requirements, since they exclusively consume one of the two nectar types and may be exerting selective pressures on the composition of the respective resources of interest

Effects of temperature on the ion-induced bending of germanium and silicon nanowires

Nanowires can be manipulated using an ion beam via a phenomenon known as ion-induced bending (IIB). While the mechanisms behind IIB are still the subject of debate, accumulation of point defects or amorphisation are often cited as possible driving mechanisms. Previous results in the literature on IIB of Ge and Si nanowires have shown that after irradiation the aligned nanowires are fully amorphous. Experiments were recently reported in which crystalline seeds were preserved in otherwise-amorphous ion-beam-bent Si nanowires which then facilitated solid-phase epitaxial growth (SPEG) during subsequent annealing. However, the ion-induced alignment of the nanowires was lost during the SPEG. In this work, in situ ion irradiations in a transmission electron microscope at 400°C and 500°C were performed on Ge and Si nanowires, respectively, to supress amorphisation and the build-up of point defects. Both the Ge and Si nanowires were found to bend during irradiation thus drawing into question the role of mechanisms based on damage accumulation under such conditions. These experiments demonstrate for the first time a simple way of realigning single-crystal Ge and Si nanowires via IIB whilst preserving their crystal structure

Preliminary assessment of the irradiation behaviour of the FeCrMnNi High-Entropy Alloy for nuclear applications

In the search for new nuclear materials with improved radiation tolerance and behavior, the high-entropy alloys (HEAs) have arisen as new candidates for structural components in nuclear reactors due to their suspected superior stability under irradiation. The metallurgical definition of HEAs is any alloy with multiple elements, five or more all in equiatomic compositions. The basic principle is the high mixing entropy of its solid solution lowers the Gibbs free energy giving a strong enhancement of the microstructural stability at low and high temperatures. The objective of this project is to assess the irradiation behaviour of the FeCrMnNi HEA system in order to investigate whether the high entropy effect is responsible for a microstructure with better radiation resistance compared to conventional alloys. In this work transmission electron microscopy (TEM) with in-situ ion irradiation has been used at the MIAMI-1 facility at the University of Huddersfield, UK: a 100 kV ion accelerator coupled with a JEOL JEM-2000FX TEM. This methodology allows the evolution of the HEA microstructure to be studied on the nanoscale during the ion irradiation

Preliminary assessment of the irradiation behaviour of the FeCrMnNi High-Entropy Alloy for nuclear applications

In the search for new nuclear materials with improved radiation tolerance and behavior, the high-entropy alloys (HEAs) have arisen as new candidates for structural components in nuclear reactors due to their suspected superior stability under irradiation. The metallurgical definition of HEAs is any alloy with multiple elements, five or more all in equiatomic compositions. The basic principle is the high mixing entropy of its solid solution lowers the Gibbs free energy giving a strong enhancement of the microstructural stability at low and high temperatures. The objective of this project is to assess the irradiation behaviour of the FeCrMnNi HEA system in order to investigate whether the high entropy effect is responsible for a microstructure with better radiation resistance compared to conventional alloys. In this work transmission electron microscopy (TEM) with in-situ ion irradiation has been used at the MIAMI-1 facility at the University of Huddersfield, UK: a 100 kV ion accelerator coupled with a JEOL JEM-2000FX TEM. This methodology allows the evolution of the HEA microstructure to be studied on the nanoscale during the ion irradiation

Estudos sobre a perspectiva histórico-cultural de Vigotski

Veresk é uma publicação internacional de Psicologia que se propõe a divulgar trabalhos que examinam e aprofundam o estudo do legado da teoria de Lev Semionovitch Vigotski. Os autores são especialmente convidados a apresentarem seus textos pelos Editores Associados ou pelo Conselho Editorial. Veresk é apresentada tanto no formato impresso, quanto no eletrônico, nas versões em russo, português e inglês. Sua publicação é patrocinada pelo Instituto de Psicologia L. S. Vigotski, da Universidade Estatal de Humanidades da Rússia, pela Faculdade de Educação da Universidade Federal Fluminense, Brasil e pela Faculdade de Ciências da Saúde, do Centro Universitário de Brasília, Brasil

Detección de Chlamydophila spp. en gatos con problemas oculares y respiratorios

En los últimos años se ha avanzado en el conocimiento de los integrantes del orden Chlamydiales y Chlamydophila felis es uno de los miembros del orden y forma parte de la familia Chlamydiaceae. Este microorganismo, tiene un rol patógeno importante en los felinos domésticos. Produce enfermedad endémica en los criaderos de gatos y podría afectar a otros felinos. Nuestro propósito fue detectar Chlamydophila spp en gatos domésticos con sintomatología respiratoria y ocular en la ciudad de La Plata, Argentina. Se tomaron muestras de animales enfermos, las que se analizaron utilizando la detección de Lipopolisacárido Clamidial común (LPS) por la técnica de Elisa y la inoculación en huevos embrionados libres de patógenos específicos( SPF ) para propagación de Chlamydophila felis. La detección y aislamiento de Chlamydophila spp fue elevada en los animales investigados. Los más jóvenes fueron lo mas afectados, no obstante todos los felinos fueron susceptibles, sin importar la edad. Se pudo verificar el rol endémico de Chlamydophila spp en los gatos domésticos de nuestro medio. Se sugiere un posible rol zoonótico de este microorganismos en personas que interactúan con estos animales. Se requiere de técnicas especiales para determinar con certeza al agente infeccioso en gatos domésticos.Facultad de Ciencias Veterinaria

Detección de Chlamydophila spp. en gatos con problemas oculares y respiratorios

En los últimos años se ha avanzado en el conocimiento de los integrantes del orden Chlamydiales y Chlamydophila felis es uno de los miembros del orden y forma parte de la familia Chlamydiaceae. Este microorganismo, tiene un rol patógeno importante en los felinos domésticos. Produce enfermedad endémica en los criaderos de gatos y podría afectar a otros felinos. Nuestro propósito fue detectar Chlamydophila spp en gatos domésticos con sintomatología respiratoria y ocular en la ciudad de La Plata, Argentina. Se tomaron muestras de animales enfermos, las que se analizaron utilizando la detección de Lipopolisacárido Clamidial común (LPS) por la técnica de Elisa y la inoculación en huevos embrionados libres de patógenos específicos( SPF ) para propagación de Chlamydophila felis. La detección y aislamiento de Chlamydophila spp fue elevada en los animales investigados. Los más jóvenes fueron lo mas afectados, no obstante todos los felinos fueron susceptibles, sin importar la edad. Se pudo verificar el rol endémico de Chlamydophila spp en los gatos domésticos de nuestro medio. Se sugiere un posible rol zoonótico de este microorganismos en personas que interactúan con estos animales. Se requiere de técnicas especiales para determinar con certeza al agente infeccioso en gatos domésticos.Facultad de Ciencias Veterinaria

Detección de Chlamydophila spp. en gatos con problemas oculares y respiratorios

En los últimos años se ha avanzado en el conocimiento de los integrantes del orden Chlamydiales y Chlamydophila felis es uno de los miembros del orden y forma parte de la familia Chlamydiaceae. Este microorganismo, tiene un rol patógeno importante en los felinos domésticos. Produce enfermedad endémica en los criaderos de gatos y podría afectar a otros felinos. Nuestro propósito fue detectar Chlamydophila spp en gatos domésticos con sintomatología respiratoria y ocular en la ciudad de La Plata, Argentina. Se tomaron muestras de animales enfermos, las que se analizaron utilizando la detección de Lipopolisacárido Clamidial común (LPS) por la técnica de Elisa y la inoculación en huevos embrionados libres de patógenos específicos( SPF ) para propagación de Chlamydophila felis. La detección y aislamiento de Chlamydophila spp fue elevada en los animales investigados. Los más jóvenes fueron lo mas afectados, no obstante todos los felinos fueron susceptibles, sin importar la edad. Se pudo verificar el rol endémico de Chlamydophila spp en los gatos domésticos de nuestro medio. Se sugiere un posible rol zoonótico de este microorganismos en personas que interactúan con estos animales. Se requiere de técnicas especiales para determinar con certeza al agente infeccioso en gatos domésticos.Facultad de Ciencias Veterinaria