Caracterização de nanocompósitos de poliuretano/montmorilonita organofílica por RMN de baixo campo Characterization of polyurethane/organophilic montmorilonite nanocomposites by low field NMR

Poliuretanos são materiais poliméricos importantes e versáteis, principalmente devido a algumas de suas propriedades, como alta resistência à abrasão, resistência ao rasgo, excelente absorção de choques mecânicos, boa flexibilidade e elasticidade. No entanto, existem também algumas desvantagens, como a baixa estabilidade térmica e propriedade de barreira. Para superar essas desvantagens, têm sido produzidos nanocompósitos de poliuretano/montmorilonita organofílica. A investigação da estrutura dos nanocompósitos de poliuretano/argila tem sido realizada principalmente por difração de raios X (DRX) e microscopia eletrônica de transmissão (TEM). Neste trabalho, foram estudados filmes de nanocompósitos de PU/argila organofílica obtidos por intercalação por solução. Os nanocompósitos foram caracterizados por DRX e, principalmente, por ressonância magnética nuclear de baixo campo (RMN-BC). As medidas de RMN-BC, com a determinação do tempo de relaxação spin-rede do núcleo de hidrogênio, forneceram informações ímpares e importantes sobre a dinâmica molecular desses nanocompósitos. Para validar esse estudo foram realizadas análises de difração de raios X, que confirmaram os resultados de RMN. A estabilidade térmica dos materiais também foi determinada por análise termogravimétrica em atmosfera de gás inerte, observando-se pequena melhora na estabilidade do nanocompósito quando comparado com o poliuretano.<br>Polyurethanes are important and versatile materials, mainly due to some of their properties, such as high resistance to abrasion and tearing, excellent absorption of mechanical shocks and good flexibility and elasticity. However, they have some drawbacks as well, such as low thermal stability and barrier properties. To overcome these disadvantages, various studies have been conducted involving organophilic polyurethane/montmorillonite nanocomposites. The investigation of the structure of polyurethane/clay nanocomposites has mainly been done by X-ray diffraction (XRD) and transmission electron microscopy (TEM). In this work, PU/clay nanocomposite films obtained by solution intercalation were studied. The nanocomposites were characterized by XRD and low-field nuclear magnetic resonance (LF-NMR). The LF-NMR measurements, with determination of the spin-lattice relaxation time of the hydrogen nucleus, supplied important information about the molecular dynamics of these nanocomposites. The X-ray diffraction measurements validated the results found by NMR. The thermal stability of the material was also determined by thermogravimetric analysis (TGA) under an inert atmosphere. A slight improvement in this stability was observed in the nanocomposite in comparison with polyurethane

Interhabitat variation in diplochory : seed dispersal effectiveness by birds and ants differs between tropical forest and savanna

Diversified assemblages of frugivores interact with fruits/seeds in tropical environments. Species within assemblages vary largely in body size, abundance, seed treatment and places of seed deposition, with possible delayed consequences for seed dispersal and plant regeneration. The variable outputs of the interaction may be magnified when considering different habitats and diplochoric plants that include more than one agent in subsequent steps of dispersal. Here we compared the contribution of birds and ants to the seed dispersal effectiveness (SDE) of two species of Etythroxylum shrubs that grow in Atlantic forest and Cerrado savannas in Brazil. We compared the number of seeds dispersed by each one of 16 bird and 30 ant species and their delayed consequences for seed germination and seedling survival combining experimental and modeling approaches. We observed shifts in the role of different dispersal agents between habitats, with birds being more important in the forest while ants are highlighted in the savanna. Quantity and quality components of SDE were not correlated, but large body size emerged as an important trait driving the quantity (birds) and quality (ants) components of SDE. A high diversified assemblage of dispersal agents does not always result in redundant effects for SDE, with some species consistently providing better dispersal than others and several opportunities for complementary effects. Therefore, even in diversified assemblages operating in diplochoric dispersal systems, there is the opportunity for ecological specialization384857CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESFUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO - FAPESP478938/2011-0; 302219/2017-0não tem02/12895-8; 2014/23141-1; 2017/16645-

Microcapsules of ‘jabuticaba’ byproduct: Storage stability and application in gelatin

ABSTRACT This study aimed to produce microcapsules using ‘jabuticaba’ byproduct through lyophilization, and evaluate the stability of the powder, intended for use in gelatin. Three formulations were prepared, including the pure lyophilized extract (E), capsule with maltodextrin (CapM), and capsule with maltodextrin and xanthan gum (CapMG). The storage stability was evaluated at 4 and 25 ºC, and in the presence and absence of light, regarding color parameters, phenolic compounds and monomeric anthocyanins. The microencapsulated powders were applied in gelatin and analyzed for sensorial acceptance. Following an investigation of the storage stability of the three powders at 4 °C for 60 days, the sample that presented the best result was then analyzed at 25 ºC in the presence/absence of light. Microcapsules, independent of the encapsulant agent, exhibited lower values of degradation (2.82% phenolic compounds and 14.5% monomeric anthocyanins) than extract E when exposed to light and at 25 °C. Regarding color stability, CapMG showed smaller variations in the total color difference (ΔE) than the other samples. The lowest ΔE value corresponded to the gelatin sample with CapM, stored in the absence of light. It is possible to conclude that microencapsulation is an alternative for the preservation of ‘jabuticaba’ byproduct extracts, facilitating their use, retaining some compounds and protecting them against adverse conditions

Preclinical development of kinetin as a safe error-prone SARS-CoV-2 antiviral able to attenuate virus-induced inflammation

The search for antivirals against SARS-CoV-2 continue due to the emergence of variants of concerns, able to escape the vaccinal humoral response. In this work, authors pre-clinically explore the potential of kinetin against SARS-CoV-2, which could be used alone or in combination with other antivirals