Synthesis and Antibacterial Activity of (AgCl, Ag)NPs/Diatomite Hybrid Composite

In the present research, hybrid (AgCl, Ag)NPs/diatomite composites were synthesized by direct impregnation with aqueous silver nitrate solutions. The silver chloride nanoparticles (AgCl-NPs) were formed as an effect of the exchange reaction when silver interacted with the diatomite mineral impurity halite. Nanoparticles of metallic silver (AgNPs) were created by the reduction of silver ions under the influence of hydrogen peroxide. The content of silver chloride nanoparticles in the (AgCl, Ag)NPs/diatomite composite was limited by the content of the halite in the used diatomite. Samples of natural diatomite and synthesized (AgCl, Ag)NPs/diatomite composites were examined by using scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction, infrared spectroscopy and thermogravimetric analysis. Moreover, the antibacterial potential of synthesized composites was also studied using the MIC (minimal inhibitory concentration) method against the most common drug-resistant microorganisms in the medical field: Gram-positive Staphylococcus aureus and Gram-negative Klebsiella pneumoniae. The obtained hybrid (AgCl, AgNPs)/diatomite composites were shown to have antimicrobial potential. However, widespread use requires further study by using various microorganisms and additional cytotoxic studies on eukaryotic systems, e.g., cell lines and animal models.

DESEMPENHO OPERACIONAL E ENERGÉTICO DE COLHEDORAS DE CANA-DE-AÇÚCAR (Saccharum spp.) PARA UMA E DUAS LINHAS DA CULTURA

O Brasil é o maior produtor de cana-de-açúcar (Saccharum spp.) do mundo, portanto, o seu cultivo é de grande importância para o agronegócio brasileiro. A mecanização da colheita da cana-de-açúcar se tornou necessária, pois a queima da cultura está, gradativamente, sendo proibida no Brasil e, sem essa prática, o corte manual se torna ineficiente e dispendioso. Com o aumento da colheita mecanizada surgiram as inovações do setor para o aumento do rendimento dessa operação e, nos últimos anos, a tentativa de se desenvolver uma colhedora especifica para duas linhas simultâneas se tornou realidade. O objetivo desse trabalho foi avaliar o desempenho operacional e energético de duas colhedoras de cana-de-açúcar para uma e duas linhas da cultura, em espaçamento convencional. Os ensaios foram conduzidos em um canavial colhido sem queima prévia, da variedade RB855156, em seu segundo corte, com espaçamento entre linhas de 1,5 m, produtividade agrícola estimada de 83,5 t ha-1 e porte ereto. As colhedoras foram avaliadas em 3 velocidades de deslocamento (2,5 km h-1, 3,5 km h-1 e 5 km h-1) para realizar avaliações do desempenho das máquinas. A média de capacidade de campo efetiva foi de 0,56 ha h-1 para a colhedora de uma linha e de 1,08 ha h-1 para a colhedora de duas linhas, o consumo de combustível por tonelada colhida foi de 0,97 L t-1 para a colhedora de uma linha contra 0,65 L t-1 para a colhedora de duas linhas. Em todos os casos a colhedora de duas linhas apresentou maior eficiência e produtividade do que a de colhedora de uma linha.PALAVRAS-CHAVES: Mecanização Agrícola; consumo de combustível; índice de impureza mineral e vegetal; eficiência; produtividade. OPERATIONAL AND ENERGETIC PERFORMANCE OF SUGARCANE (Saccharum spp.) HARVESTERS FOR ONE AND TWO ROWS OF PLANTINGABSTRACT: Brazil is the largest producer of sugarcane (Saccharum spp.) in the world, so its cultivation is of great importance for Brazilian agribusiness. The mechanized harvesting of cane sugar has become necessary because the culture of the burning is gradually being banned in Brazil and, without this practice, manual cutting becomes inefficient and costly. With increasing mechanical harvesting, emerged the sector innovations to increase the yield of this operation and, in recent years, the attempt to develop a harvester specifies for two simultaneous rows came true. The aim of this study was to evaluate the operational and energy performance of two harvesters of sugarcane, for one and two rows of planting. The tests were conducted in a sugarcane field of the variety RB855156 harvested without burning, at its second cut, with line spacing of 1.5 m, estimated agricultural productivity of 83.5 t ha-1. The harvester was evaluated in three forward speeds (2.5 km h-1, 3,5 km h-1 and 5 km h-1) to carry out evaluations of the performance of the machines. The average effective field capacity was 0.56 ha h-1 for one row harvested and 1.08 ha h-1 for two rows harvested, fuel consumption per ton of sugarcane harvested was 0.97 L t-1 for one row and 0.65 L t-1 for two rows. In all cases, the two rows showed higher efficiency and productivity against the one row.Keywords: Agricultural mechanization; fuel consumption; vegetable and mineral impurity rate; efficiency; productivity.

Clay and pyrite transformations during ignition of pulverised coal

Clay minerals are the principal reactive, non-combustible, phases present in the pulverized coal burned in power station furnace units. Despite the short heating time involved, the clay mineral impurity is wholly transformed in the ignition.Illitic clays are partially melted, fluxed by water and potash, to produce an alumino-silicate melt phase. The melt is frothed by the synchronous production of carbon dioxide in an iron oxide catalysed oxidation of associated carbonaceous matter. This produces the hollow, gasfilled, glass-walled spheres (cenospheres) characteristic of pulverized fuel ash (PFA). Partial, primary devitrification crystallization of mullite and quartz from the high-alumina glass is general and the extent of devitrification may influence the pozzolanic efficiency of the PFA cenospheres.Without the advantage of potash fluxing, the kaolinite lattices are dehydrated and transformed, without melting, to amorphous aluminosilicate and crystalline mullite.Oxidation of pyrite leads to coating of cenospheres by condensed magnetite and the emission of sulphur dioxide in the flue gases.

The influence of hydrogen ion concentration on the adsorption of weak electrolytes by pure charcoals

Recent progress in enzyme chemistry has been largely due to the use of adsorbents. In vitamin studies also, adsorbents such as Fuller's earth have been introduced with marked success. A prominent feature of such work is the influence of hydrogen ion concentration upon the efficiency of the adsorption. A technique recently introduced by Kinnersley and Peters for concentrating the antineuritic vitamin (B 1) involves at one stage the adsorption of the vitamin by acid-treated Norite charcoal. In this case also it has been found that the hydrogen ion concentration influences considerably the degree of adsorption. Adsorbents which are themselves of acidic or basic character might be expected to be influenced in their behaviour by hydrogen ion concentration, but in the case of charcoal the reason for the change in adsorptive, power is more obscure. Bartell and Miller have stressed the importance of using pure charcoals in the study of adsorption phenomena. It is probable indeed that many of the anomalous results obtained by workers in this subject have been due to the use of various impure charcoals. The acid-treated charcoal used in the vitamin work contained about 1 per cent. of mineral impurity. It was important therefore to discover whether the effect of hydrogen ion concentration on the absorption by pure charcoals was equally marked, and if so whether these effects could by correlated with the recognised chemical properties of various adsorbates.