The role of surface chemical reactivity in the stability of electronic nanodevices based on two-dimensional materials "beyond graphene" and topological insulators

Here, we examine the influence of surface chemical reactivity toward ambient gases on the performance of nanodevices based on two-dimensional materials "beyond graphene" and novel topological phases of matter. While surface oxidation in ambient conditions was observed for silicene and phosphorene with subsequent reduction of the mobility of charge carriers, nanodevices with active channels of indium selenide, bismuth chalcogenides and transition-metal dichalcogenides are stable in air. However, air-exposed indium selenide suffers of p-type doping due to water decomposition on Se vacancies, whereas the low mobility of charge carriers in transition-metal dichalcogenides increases the response time of nanodevices. Conversely, bismuth chalcogenides require a control of crystalline quality, which could represent a serious hurdle for up scaling

Flame-spray pyrolysis preparation of perovskites for methane catalytic combustion

A flame spray pyrolysis apparatus was set-up and optimised for the preparation of perovskitic mixed metal oxides in nanoparticle-size powder form. LaCoO3 was chosen as test catalyst, aiming at correlating crystallinity, surface area, particle size, catalytic activity and durability with some fundamental operating parameters of the apparatus. In particular, feeding rate of precursors solution, flow rate of the O2/CH4 mixture for the igniter and flow rate and linear velocity of the main dispersing-oxidising oxygen have been thoroughly analysed. The activity of the prepared samples was tested for the catalytic flameless combustion of methane, a reaction requiring a proper combination of activity and thermal stability of the catalyst. Provided a crystalline perovskitic phase forms, activity increases with increasing surface area of the powder. By contrast, the higher the initial sintering of catalyst particles within the flame, the higher is thermal stability. Tuning up of operating parameters allows to properly address the desired catalyst properties

Microwave-induced thermal escape in Josephson junctions

We investigate, by experiments and numerical simulations, thermal activation processes of Josephson tunnel junctions in the presence of microwave radiation. When the applied signal resonates with the Josephson plasma frequency oscillations, the switching current may become multi-valued in a temperature range far exceeding the classical to quantum crossover temperature. Plots of the switching currents traced as a function of the applied signal frequency show very good agreement with the functional forms expected from Josephson plasma frequency dependencies on the bias current. Throughout, numerical simulations of the corresponding thermally driven classical Josephson junction model show very good agreement with the experimental data.Comment: 10 pages and 4 figure

Avaliação dos danos de Sibinia spp. (Coleoptera: Curculionidae) em sementes de Bracatinga (Mimosa scabrella Benth.) de três procedências.

bitstream/item/101248/1/PA-1983-Iede-AvaliacaoDanos.pd

Pré-otimização do pré-tratamento por explosão a vapor de Eucalyptus urograndis visando maior susceptibilidade na hidrólise enzimática.

21-SBQSul. Poster

Gut microbiomes of freshwater mussels (Unionidae) are taxonomically and phylogenetically variable across years but remain functionally stable

Freshwater mussels perform essential ecosystem functions, yet we have no information on how their microbiomes fluctuate over time. In this study, we examined temporal variation in the microbiome of six mussel species (Lampsilis ornata, Obovaria unicolor, Elliptio arca, Fusconaia cerina, Cyclonaias asperata, and Tritogonia verrucosa) sampled from the same river in 2016 and 2019. We examined the taxonomic, phylogenetic, and inferred functional (from 16S rRNA sequences) facets of their microbiome diversity. Significant differences between the two years were identified in five of the six species sampled. However, not all species that exhibited a temporally variable microbiome were functionally distinct across years, indicating functional redundancy within the mussel gut mi-crobiome. Inferred biosynthesis pathways showed temporal variation in pathways involved in deg-radation, while pathways involved in cellular metabolism were stable. There was no evidence for phylosymbiosis across any facet of microbiome biodiversity. These results indicate that temporal variation is an important factor in the assembly of the gut microbiomes of freshwater mussels and provides further support that the mussel gut microbiome is involved in host development and ac-tivity

Solvent nature effect in preparation of perovskites by flame pyrolysis: 2 : Alcohols and alcohols plus propionic acid mixtures

The effect of either pure alcohols or alcohols + propionic acid mixtures as solvents for the preparation by flame pyrolysis of a standard LaCoO3 catalyst, to be employed for the catalytic flameless combustion of methane, has been investigated. All the catalysts proved very active for the mentioned reaction. Low-MW pure alcohols showed however less suitable than alcohols-propionic acid mixtures, leading to lower perovskite phase purity, less particle size homogeneity and lower specific surface area. The high volatility of the solvent seems to be the major cause, together with the improper behaviour of nitrates (forced by solubility reasons) as perovskite metals precursors. However, the addition of propionic acid to the alcohols allowed to use the acetates as precursors and hence to obtain high perovskitic phase purity, high SSA and Uniform particle size. Moreover, the increase of combustion enthalpy of the solvent, through the addition of higher-MW alcohols, leading to progressively higher flame temperature, strongly improved the thermal resistance of the catalyst, without lowering catalytic performance

Contribuição à biologia larval de Hylesia sp. (Lepidoptera: Hemileucidae) em Bracatinga (Mimosa scabrella Benth.).

bitstream/item/101249/1/PA-1983-Iede-ContribuicaoBiologia.pd