Anais da Academia Brasileira de Ciencias最新文献

Latency in flux observation has an adverse effect on the performance of observer-based field-oriented speed control for three-phase induction motor (IM). The reduction of the convergent rate of estimation errors could improve the performance of speed-controlled IM based on flux observers. The main contribution is to design a fast convergent flux observer, which provides bounded estimation error immediately after one instant of motor startup. The proposed flux observer fused barrier function adaptive mechanism with integral sliding mode control principle to yield BFISMO. Rigorous stability analysis has been conducted to achieve global flux estimation error ultimate boundedness. Moreover, three controllers have been designed. The first control design is devoted to flux control based on a backstepping controller, while the other two controllers' design is dedicated to rotor speed control of the motor. The speed controller is developed by combining the backstepping control with disturbance observers to estimate the unmatched load torque named quasi-sliding mode observer (QSMDO), and nonlinear disturbance observer (NLDO). Based on numerical simulations, the performance and efficacy of the proposed BFISMO have been assessed by conducting a comparison study to other observer techniques. The results showed the superiority of the proposed observer over the conventional versions.

The exploration of extraterrestrial environments has become a focal point of scientific inquiry, driven by advancements in technology and a growing interest in the potential for life beyond Earth. This study investigates the adaptability of Antarctic nematodes, known for thriving in extreme cold and isolation, to simulated Martian (MGS-1) and Lunar (LMS-1) soils. The experiment revealed differential responses in nematode survivability to the two simulants, with Lunar soil demonstrating better adaptability compared to Martian soil. Our study provides valuable insights into the potential survivability of Antarctic nematodes on real Martian and Lunar substrates with the use of the MGS-1 and the LMS-1 under terrestrial conditions. The observed results suggest differential survival responses to Lunar (6.92 ± 0.74) and Martian (5.58 ± 1.91) regolith simulants and highlight the complexity of factors influencing organismal survival. Considering their crucial role in soil food webs, and their relation with nutrient cycling and carbon dioxide emissions, the observed capacity of nematodes to thrive in Martian and Lunar regoliths positions them as potential candidates to sustain human habitats, helping on the development of in-situ resource utilization (ISRU) systems, and forming the basis for a biological life-support system to facilitate human survival in extraterrestrial environments.

The region of the Maritime Antarctic suffers significantly from climate change, resulting in regional warming and consequently affecting coverage. This study characterized three surface zones of Collins Glacier and three other zones in ice-free areas on the Fildes Peninsula, which has an area of 29.6 km². We used TerraSAR-X satellite images from 2014 to 2016 and analyzed the influence of meteorological and environmental conditions on these surface zones. We used five images from the TerraSAR-X satellite, three of these data were obtained during the same period of fieldwork. The classification considered three classes on the glacier (higher moisture, transition in moisture, and lower moisture) and three on the ice-free areas (wet snow, transition wet snow-bare ice, and bare ice), using Maximum Likelihood and ISODATA methods. In low-altitude glaciers with maritime influence, such as Collins, monitoring variations in surface zones is essential because the continuous increase in exposed ice may indicate potential retreat. The TerraSAR-X images enabled the classification of land features, highlighting the potential for continuous monitoring in the Maritime Antarctic, regardless of weather conditions and solar illumination.

The whole plant Saccocalyx satureioides, an endemic medicinal plant in Algeria, was evaluated for its polyphenolic contents, antioxidant and antimicrobial activities. The polyphenolic contents of the plant methanolic extracts ranged from 170.47 to 285.56 (µg GAEs/mg extract) and from 25.39 to 82.68 (µg QEs/mg extract), respectively. High antioxidant activity was registered: DPPH average IC50 = 14.68 µg/mL, and β-carotene average IC50 = 21.08 µg/mL. The essential oil and methanolic extracts from the aerial parts and roots were tested against bacteria and molds. Different methods, including disk diffusion, well diffusion, and microdilution tests for bacteria, were used. The essential oil (February and June harvest periods) value 1.25 µL/mL was the MIC and the MBC for all bacterial strains, except E. coli, K. pneumonia and Ps. aeruginosa. The average fungal inhibition of the methanol extracts ranged from 5.10 to 71.25%, except for F. oxysporum. The essential oil effect was 6.67-83.53% and 17.01-90.57% by the food poisoned and fumigation methods, respectively. The preliminary phytochemical evaluation demonstrated the high polyphenolic contents and effective antioxidant power of the plant extracts. This may have an essential role in the antimicrobial effectiveness and indicate that the plant contains high-quality bioactive molecules in addition to the essential oil.

Polar marine macroalgae thrive in extreme conditions, often displaying geographic isolation and high degree of endemism. The "phycosphere" refers to the zone around the algae inhabited by microrganisms. Our study used DNA metabarcoding to survey the eukaryotic communities associated with seven seaweed species obtained at King George Island (South Shetland Islands, maritime Antarctic), including two Rhodophyta, two Chlorophyta and three Phaeophyceae. The ITS2 region was used as a barcode and our analysis yielded 77 eukaryotic ASVs spanning five Kingdoms (Fungi, Metazoa, Chromista, Protozoa, and Viridiplantae) and ten phyla (Ascomycota, Basidiomycota, Cercozoa, Ciliophora, Ochrophyta, Amebozoa, Chlorophyta, Rhodophyta, Bryophyta and Cnidaria). Additionally, we identified 14 potential new occurrence records for Antarctica. Ciliates and green algae were the most species-rich groups. The most abundant assigned associated species was Monostroma angicava (Chrorophyta). Within the macroalgal, the Chlorophyceans Ulothrix sp. hosted the greatest number of taxa, followed by Monostroma hariotii. Our data suggested that Antarctic macroalgae host a rich diversity of associated organisms and the biodiversity associated with the phycosphere remains underestimated.

The Byers Peninsula, the largest ice-free area in Maritime Antarctica, is vital for studying landscape-scale natural processes due to its diverse periglacial landforms. This study aim to characterize the soils and environments of its southern sector, focusing on soil-landform-lithology interactions. Thirty-seven soil profiles were classified, collected, and chemically and physically analyzed. Principal component analysis explored relationships among variables in these profiles and 36 others from the Peninsula project database. The soils are generally shallow, with lithic or paralithic contact within the first meter. Four main soil groups were identified: patterned-ground soils on plateaus, ornithogenic soils, non-ornithogenic soils, and non-ornithogenic sodic and sandy soils on beaches and marine terraces. The Peninsula, divided into six geological units, represents a diverse periglacial morphogenetic system. Sixteen landform types were identified, each associated with different processes, topographies, lithologies, altitudes, and orientations, highlighting the importance of periglacial morphogenesis. Stable soilscapes, such as upper cryoplanation platforms, raised beaches, volcanic plugs, and ornithogenically influenced areas, show greater soil development and weathering. In contrast, dynamic periglacial landforms like scree stony slopes and talus exhibit minimal soil development and instability. The Byers Peninsula's pedodiversity is due to its varied lithologies, landforms, extensive ornithogenic influences from seabirds, and long-term vegetation establishment.

In the present study, 5-Hydroxy-2-(Oleoyloxymethyl) -4H-pyran-4-one (KMO 3), and their chelated with Cu(II) and Fe(III) ions were synthesized to explore their inhibitory activity against tyrosinase and cytotoxicity. To this end, the structures of the obtained compounds were confirmed by ATR/FT-IR, 13C and 1H-NMR, and UV-vis techniques. The results show that chelating fatty ester presents the bands at 1567m, 1511w cm-1 attributed to the coordinated carbonyl (Cu(II)←[O=C]2), and the bands at 1540m, 1519m cm-1 which were attributed to the coordinated carbonyl (Fe(III)←[O=C]3). The inhibitory effect of chelating Oleic acid 2 (inhibition 68.3% ± 4.5) showed a factor of 19 times higher than free fatty acid (3.6% ± 3.2). IC50 Anti-tyrosinase activity of the Kojic acid 1 and KMO 3 compounds were 62.8 ± 6.6 µM and 77.6 ± 4.3 µM. The IC50 and IC90 values for tyrosinase inhibitory activity for chelating fatty ester and their complexes are values > 400 µM. Finally, the assay with the series showed no hemolytic activity (EC50> 250 μg mL-1), and not cytotoxic to B16F10, ACP-02, and human dermal fibroblast cells at 100 µM and showed no hemolytic potential at the concentration of IC50 250 µM.

Lipases are enzymes that have an important role in the industry for their wide use, giving rise to a great interest in industrial bioprocesses due to their versatility. One of the applications is the enzymatic hydrolysis of waste oils. This work consists of evaluating the production of lipases using several concentrations of residual frying oil (RFO) and different pHs, through ANOVA analysis. The production of free fatty acids was carried out by hydrolysis of RFO using noncommercial lipases produced in the previous step. The production of lipase enzymes was favored at pH 2.0, with an oil concentration of 1.5% (v/v) for a period of 24 hours, resulting in an enzyme activity of 141.90 U. mL-1 . The highest result of enzymatic hydrolysis of RFO was 20.70% in 40 minutes. This conversion was favored by increasing the concentration of the enzymatic extract. In this study, it was possible to obtain free fatty acids (FFAs) using a noncommercial enzyme and waste oil as an environmentally correct and low-cost alternative.

Regional sea level rise varies from the global average and is influenced by climate variability. We studied sea level anomalies in southern Brazil from 1993 to 2022, finding increasing trend from 1993 to 2022. We used oceanic and atmospheric dynamics to understand the rapid sea level rise. Positive trends in the Southern Annular Mode and the South Atlantic Ocean subtropical gyre intensified wind stress curl and Ekman transport. If global warming continues and the Southern Annular Mode remains in a positive trend, sea level rise in southern Brazil is likely to persist and increase risks for the population in this low-lying coastal area.