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321.
Let ${\mathcal{S}}$ be a semigroup acting on a topological space M. We define attractors for the action of ${\mathcal{S}}$ on M. This concept depends on a family ${\mathcal{F}}$ of subsets of ${\mathcal{S}}$ . For certain semigroups and families it recovers the concept of attractors for flows or semiflows. We define and study the complementary repeller of an attractor. We also characterize the set of chain recurrent points in terms of attractors.  相似文献   
322.
Molecular Diversity - A combined organocatalytic and multicomponent synthetic approach was designed for the preparation of selenium-based peptoids and peptide–peptoid conjugates. This...  相似文献   
323.
Plant extracts are complex mixtures that are difficult to characterize, and mass spectrometry is one of the main techniques currently used in dereplication processes. Fridericia chica is a species with medicinal uses in Latin American countries, used in the treatment of inflammatory and infectious diseases. Extracts of this plant species are characterized by the presence of anthocyanidins. In this study, using high-resolution mass spectrometry coupled with liquid chromatography, it was possible to determine the molecular formula of thirty-nine flavonoids. Fragmentation analysis, ultraviolet spectrum and nuclear magnetic resonance data allowed the partial characterization of the structures of these compounds. The spectral dataset allowed the identification of a series of flavones in addition to the desoxyanthocyanidins common in extracts of the species. The occurrence of some of the proposed structures is uncommon in extracts of species of the Bignoniaceae family, and they are reported for the first time in the extract of this species. Quantitative analyses of total flavonoids confirmed the high content of these constituents in the species, with 4.09 ± 0.34 mg/g of dry plant material. The extract under study showed low in vitro cytotoxicity with CC50 ≥ 296.7 ± 1.4 µg/mL for Vero, LLC-MK2 and MRC-5 cell lines. In antiviral activity assays, inhibition of the cytopathic effects of Dengue, Zika and Mayaro viruses was observed, with EC50 values ranging between 30.1 and 40.9 µg/mL. The best result was observed against the Mayaro virus, with an EC50 of 30.1 µg/mL.  相似文献   
324.
Technical Physics - Interaction of electromagnetic radiation (250–850 nm, 2.5–15.3 μm, and 11.5–17.1 mm) with the isatin-β-anil (C14H10N2O) films deposited with the aid...  相似文献   
325.
Photodynamic therapy has been used to treat a variety of diseases, however, there is continuing search for new biocompatible photosensitizers. Herein, we demonstrate for the first time that imidazo[1,2-a]pyrimidine compounds are able to generate singlet oxygen species and can act as photosensitizers in the intracellular environment. Our results show that this class of compounds absorb and emit in the 400–500 nm region, present low cytotoxicity in the dark, are efficiently uptaken by cells, are fluorescent in intracellular medium, and generate singlet oxygen upon irradiation, killing cancer cells within 2 h at low concentration (2.0 μm ). The imidazo[1,2-a]pyrimidine compounds are a potential new tool for phototheranostics, because they can be simultaneously used for fluorescence imaging and photodynamic therapy.  相似文献   
326.
Among the decapods, the caridean Exhippolysmata oplophoroides has been described as a simultaneous protandric hermaphrodite, seeing that it presents a male initial stage followed by a hermaphrodite one in which it can function as male and as female. This work had the aims of characterizing the microscopical morphology of the male portion of the ovotestes gonads from E. oplophoroides, at the different development stages, identifying each cell from the germ lines during spermatogenesis, as well as describing the ultramorphology of spermatozoans in the terminal region of the vasa deferentia. Shrimps were collected in Ubatuba, north coast of São Paulo, and their male gonads and the ampoule were removed, fixed and processed according to histological routine and for scanning electron microscopy. The testicular portion is divided in lobes, inside which cells at the same stage of the spermatogenic cycle are observed, with prevalence of spermatogonia and spermatocytes at stages I, II and V of gonad development, whereas spermatids and spermatozoans are found at stages III and IV, respectively. Ultramorphology of the terminal portion of the vasa deferentia exhibits mature aflagellated spike-shaped spermatozoans, encased in secretion and between membrane foldings that will constitute the spermatophores. Despite presenting reproductive characteristics common to other decapods, E. oplophoroides shows spermatozoans as well as spermatophore with typical morphology, which is important for its identification and taxonomy. Further, this species showed polysaccharide secretions where the spermatozoa are immerse as far as the testicular portion, which could have a role in their transport and nutrition as well as spermatophore constitution and/or fixation; differently, other caridean species begin spermatophore formation during the passage of the gametes through the vasa deferentia.  相似文献   
327.
In this paper we develop a theory of Lyapunov stability for generalized flows on principal and associated bundles. We present a study of Lyapunov stability and attraction in the total space of a principal bundle by means of the action of the structure group.We also relate limit sets, prolongations, prolongational limit sets, attracting sets and stable sets in the total space of an associated bundle to the corresponding concepts in the fibers.  相似文献   
328.
Journal of Thermal Analysis and Calorimetry - Chitosan microspheres were used to remove emerging pollutants such as: oxycam anti-inflammatories, piroxycam, meloxycam and tenoxycam from water....  相似文献   
329.
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330.
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