Flutuações dos níveis dos carboidratos de reserva disponíveis nas raízes e no caule do marmeleiro (Croton sonderianus Muell. Arg.).

Resumo: O objetivo deste trabalho foi estudar as flutuações dos níveis dos carboidratos de reserva (Carboidratos Ácido-Digeríveis, CAD), nas raízes e no caule do marmeleiro (Croton sonderianus Muell.Arg.), durante seu ciclo fenológico. Um delineamento experimental inteiramente casualizado, com quatro repetições e distribuição fatorial de 3 x 9 (diâmetro de raiz ou caule vs estádios fenológicos), foi usado na análises estatísticas das variáveis raiz e caule. Os níveis dos CAD nas raízes apresentaram duas fases distintas: a de depleção-reposição das reservas, no período compreendido entre o intumescimento das gemas e a de frutificação, em que não ocorreram diferenças entre as classes de diâmetro nos diferentes estádios fenológicos. Houve uma fase de armazenamento, no período entre a frutificação e a queda das folhas, que variou conforme o diâmetro da raiz. Os níveis de CAD no caule mostraram o menor padrão de depleção-reposição e armazenamento, em função dos estádios fenológicos, mas não variaram em função do diâmetro do caule. [Change in the available storage carbohydrate levels on the roots and on the stems of marmeleiro (Croton sonderianus Muell. Arg.]. Abstract: The objective of this work was to study the change of the storage carbohydrate levels (Acid Digestible Carbohydrate, ADC) on the roots and on the stems of marmeleiro (Croton sonderianus Muell. Arg.), during its phenologic cycle. A complete randomized experimental design with four replicatos in a 3 × 9 factorial arrangement (roots and stems fraction x phenophase) was used in statistical analyses of the root and stems variables. The levels of the ADC in the roots showed two distinct stages, a depletion-reposition storage phase in the period between the tumescence of the aerial buds and the fruiting, when effect was found for root diameter and a storage phase, during the period between the fruiting and the falling of the leaves where differences among the smallest diameter class and the biggest diameter class were observed. The phases of depletion-reposition and storage of the ADC in the stems did not present differences among the three classes of length in each phenophase. However, the phenophase affected the depletion-reposition and the storage phases

Electrochemical properties of oxygen-enriched carbon-based nanomaterials

The introduction of oxygen moieties on a carbon-based material to enhance the electrode material activity for the oxygen reduction reaction (ORR) is a most unexplored experimental approach due to the risk of reducing the electron-transport ability of the electrode material. Herein, it is shown that carbon nanomaterials generated electrochemically from graphite can simultaneously show an anomalous high content of oxygen functionalities and a high heterogeneous electron transfer rate. This study was demonstrated with a set of four samples, prepared at different galvanostatic conditions. All the samples display a non-ordered carbon network dominated by aromatic rings, an O/C ratio greater than 0.4, but different amounts of various oxygen-containing functionalities. The electron-transport properties of the obtained films were appraised by cyclic voltammetry and electrochemical impedance spectroscopy. The application of these metal-free electrode materials to the ORR in the alkaline medium has shown a direct correlation between the materials catalytic activity (potential onset, kinetic current and number of electrons transferred) and the Cdouble bondO amount, whereas a negative correlation was found for Csingle bondO. Their excellent ability for the H2O2 reduction was also demonstrated. This work opens a new perspective on the use of highly oxidized carbon nanomaterials in electrocatalysis.publishe

Vine performance and physicochemical characteristics of berries of new wine grape cultivars in the São Francisco Valley.

This study aimed to evaluate the performance and characteristics of the grapes as subsidies to the recommendation of new wine grape cultivars for the São Francisco Valley

Intake, nutrients digestibility and nitrogen balance of elephant grass silages with mango by-product addition.

The objective of this study was to evaluate the nutritive value of elephant grass silages with increasing levels of dried mango by-product (DMB). Five addition levels were studied (0, 4, 8, 12 and 16%) using 20 rams, in a randomized complete design with five treatments (addition levels) and four replications. Dry matter (DM), organic matter (OM), crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), ether extract (EE), total carbohydrates (TC), non-fibrous carbohydrates (NFC) intake and digestibility were evaluated, as well as the total digestible nutrients (TDN) and the silage nitrogen balance (NB). Mango by-product addition did not influence the DM, CP and TC intakes, the TDN level or the OM, CT and NFC digestibilities. On the other hand, DMB addition reduced the NDF and the ADF intakes, as well as the DM, CP, NDF and ADF digestibilities, and the NB of the silages. There was also a increasing linear effect of DMB addition on the EE and NFC intakes, and on EE digestibility. The elephant grass silage with DMB by-product may not be used as a single feed to ruminants because it reduces the NDF and the ADF intakes and the DM, CP, NDF and ADF digestibilities, as well as the nitrogen balance

Efeito do manejo de rebrotas de espécies lenhosas da caatinga sobre o crescimento em altura das hastes.

Resumo: O experimento foi conduzido para avaliar o efeito do manejo de rebrotas de cinco espécies lenhosas da caatinga sobre o crescimento em altura das hastes. As espécies lenhosas foram submetidas aos seguintes tratamentos no delineamento inteiramente casualizado: 1 - preservação de uma haste; 2 - preservação de duas hastes; 3 - preservação de três hastes; 4 - preservação de todas as hastes. As plantas submetidas ao manejo de preservação de uma haste apresentaram maior crescimento de haste e o menor crescimento de haste foi observado para plantas submetidas ao tratamento de preservação de todas as hastes. Dentre as espécies lenhosas estudadas, a jurema preta (Mimosa hostilis) apresentou maior crescimento das hastes e a catingueira (Caesalpinia bracteosa), o menor crescimento de hastes sendo recomendada a sua preservação e uso como recurso forrageiro. A preservação de uma haste por planta propicia o maior crescimento em altura de hastes de espécies lenhosas da caatinga e, a exceção da catingueira, as demais espécies apresentam potencial para produção simultânea de lenha e forragem. [Effect of the management of the sprouts of the tree species of caating on the growth in the height of the stems]. Abstract - The experiment was carried to evaluate the effect of the management of sprouts of five woody species of caatinga on the growth in height of the stems. The woody species were assigned to a completely randomized design to the following treatments: 1-preservation of one stem; 2-preservation of two stems; 3-preservation of three stems; 4-preservation of all of the stems. Plants submitted to the management of preservation of one stem presented larger stem growth and the smallest stem growth was observed for plants submitted to the treatment of preservation of all of the stems. Among the studied woody species, the Mimosa hostilis presented larger growth of the stems and Caesalpinia bracteosa, the smallest growth of stems being recommended to preservation and use as resource forage. The preservation of one stem for plant propitiates the largest growth in height of stems of woody species of caatinga and, the exception of the Caesalpinia bracteosa, the other species present potential for simultaneous production of firewood and forage

Electrostatic interactions between graphene layers and their environment

We analyze the electrostatic interactions between a single graphene layer and a SiO$_2$ susbtrate, and other materials which may exist in its environment. We obtain that the leading effects arise from the polar modes at the SiO$_2$ surface, and water molecules, which may form layers between the graphene sheet and the substrate. The strength of the interactions implies that graphene is pinned to the substrate at distances greater than a few lattice spacings. The implications for graphene nanoelectromechanical systems, and for the interaction between graphene and a STM tip are also considered.Comment: improved introduction, section on suspended graphene correcte

Novel organotin-PTA complexes supported on mesoporous carbon materials as recyclable catalysts for solvent-free cyanosilylation of aldehydes

The work was also funded by national funds through FCT, under the Scientific Employment Stimulus-Institutional Call (CEEC-INST/00102/2018). AGM is grateful to Associação do Instituto Superior Técnico para a Investigação e Desenvolvimento ( IST-ID ) for his post-doctoral fellowship through grant no. BL133/2021-IST-ID . AP and AMF are grateful to FCT and Instituto Superior Técnico (IST), Portugal through DL/57/2017 (Contract no. IST-ID/197/2019 and IST-ID/131/2018). This publication is also supported by the RUDN University Strategic Academic Leadership Program (recipient AJLP, preparation). The authors also acknowledge the Portuguese NMR Network (IST-UL Centre) for access to the NMR facility. Publisher Copyright: © 2023 Elsevier B.V.New organotin compounds with general formula [(PTA-CH2-C6H4-p-COO)SnR3]Br (where R is Me for 3 and Ph for 4; PTA = 1,3,5-triaza-7-phosphaadamantane), bearing the methylene benzoate PTA derivative, were synthesized through a mild two-step process. The compounds were characterized by Fourier transform infrared spectroscopy, electrospray ionization mass spectrometry, elemental analysis and nuclear magnetic resonance spectroscopy (NMR). They were heterogenized on commercially available activated carbon (AC) and multi-walled carbon nanotubes (CNT), as well as on their chemically modified analogues. The obtained materials were characterized by scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. Complex 3 supported on activated carbon (3-AC) was found to be an active and recyclable catalyst for the cyanosilylation of several aromatic and aliphatic aldehydes. Using 3-AC with a low loading of 0.1 mol% several substrates were quantitatively converted, within just 5 min at 50 °C and under microwave irradiation in solvent-free conditions. Multinuclear NMR analysis suggested a mechanism that potentially involves a double activation process, where the nucleophilic phosphorus at the PTA derivative acts as a Lewis base and the Sn(IV) metal centre as a Lewis acid.publishersversionpublishe

Análise micromorfológica de horizontes coeso e fragipan em solos dos tabuleiros costeiros do extremo sul da Bahia.

Objetivando-se avaliar micromorfologicamente solos de tabuleiro costeiro, originados do Grupo Barreiras, quanto aos aspectos de coesão e a presença de fragipan, coletou-se amostras indeformadas de solos de duas toposseqüências, no extremo sul da Bahia