Tolerância de frutos de pessegueiro a geadas

Este trabalho teve como objetivo avaliar a tolerância de frutos de pessegueiro aos danos ocasionados pela geada. A geada ocorreu no dia 5 de setembro de 2006, sendo que a temperatura mínima, a 1,5 m do solo, foi de - 1,06ºC. Foram avaliados 28 genótipos de pessegueiro em diferentes estádios fenológicos. O delineamento experimental foi o inteiramente casualizado, com três repetições (plantas de pessegueiro), procedendo-se à avaliação em seis ramos por planta. No dia em que ocorreu a geada, foram mensurados o número de frutos por ramo, diâmetro sutural médio dos frutos, número total de gemas vegetativas, percentual de brotação e percentual de brindilas formadas a partir das gemas brotadas. Uma segunda avaliação foi realizada 15 dias após a primeira, para avaliar o percentual de queda de frutos e o diâmetro sutural médio dos frutos remanescentes. Genótipos bem enfolhados e cujos frutos apresentavam endocarpo endurecido, no momento da ocorrência da geada, foram tolerantes ao dano ocasionado pelo frio; frutos com diâmetro sutural inferior a 20 mm foram suscetíveis à geada, enquanto frutos com diâmetro sutural superior a 30 mm apresentaram boa tolerância, independentemente do genótipo avaliado.

Tolerância à dessecação e influência do tegumento na germinação de sementes de citrumelo 'swingle' (Citrus paradisi MACF X Poncirus trifoliata (L) RAF.)

O trabalho teve como objetivo estudar a tolerância à dessecação e a influência do tegumento na germinação de sementes de citrumelo 'Swingle'. As sementes foram extraídas manualmente e, em seguida, foi determinado o grau de umidade das sementes. Foi retirada uma amostra referente ao tratamento com o maior grau de umidade (48%) a ser estudado, e as demais foram submetidas à secagem em estufa com circulação forçada de ar (32±2ºC), visando à obtenção dos outros tratamentos com diferentes graus de umidade. O teste de germinação foi instalado em delineamento experimental inteiramente casualizado, num fatorial 6x2 (grau de umidade x presença ou ausência de tegumento), com quatro repetições de 25 sementes por parcela. Após a obtenção de cada tratamento as sementes foram tratadas com o fungicida Thiabendazole (0,4g.kg-1), semeadas em folhas de papel toalha umedecidas e confeccionados rolos que foram mantidos em câmara de germinação a 25ºC sob luz constante. As avaliações foram realizadas a cada sete dias até o 35º dia, sendo determinadas as porcentagens de germinação na primeira contagem, plântulas anormais, sementes mortas, sementes dormentes e germinação total. Também foram calculados o tempo médio e o índice de velocidade de germinação (IVG). Os dados foram submetidos à análise de variância, e as médias, comparadas pelo teste Tukey, a 5% de probabilidade. As sementes toleraram a dessecação até baixos níveis de umidade (16%), e a retirada do tegumento favoreceu o processo germinativo em sementes de citrumelo 'Swingle'.

Avaliação de diploides de bananeira (Musa spp.) quanto à tolerância a salinidade

A salinidade é um fator comum de estresse abiótico que afeta a produção agrícola onde ela existe. Uma das estratégias para promover a reincorporação de áreas salinizadas e o aumento da produtividade consiste no desenvolvimento e na seleção de genótipos tolerantes, o que permitirá a identificação de parentais a serem utilizados em cruzamentos. Esta pesquisa teve como objetivo identificar genótipos diploides de bananeira tolerantes à salinidade a serem utilizados em futuros trabalhos de melhoramento genético, visando à obtenção de cultivares adaptados a solos salinos. Foram avaliados nove genótipos diploides (AA) de bananeira. Para a avaliação dos parâmetros de crescimento, foram feitas medições de área foliar, altura e contagem do número de folhas. As plantas foram tratadas durante 21 dias com 0 e 100 mM de NaCl, num delineamento experimental inteiramente casualizado, com três repetições. Aos 21 dias, foi feita a determinação do peso da matéria fresca, utilizando-se balança analítica. A obtenção do peso da matéria seca das partes limbo foliar, pseudocaule e raízes+rizoma de cada planta foi feita após secagem em estufa a 60ºC até peso constante. o genótipo Tjau Lagada, que sofreu menor redução da área foliar, possivelmente apresentará uma produção relativamente superior aos genótipos avaliados neste estudo. o genótipo 0116-01, por ter apresentado maior tolerância à salinidade, poderá ser utilizado em futuros cruzamentos, disponibilizando genes a serem incorporados em cultivares produtivas utilizadas em programas de melhoramento que visem à obtenção de cultivares adaptadas às regiões de solos salinos no Nordeste brasileiro.

O problema da contaminação na determinação de traços de alumínio

The most common difficulties which occur in trace analysis are those which involve contamination, mainly when the measurement is at very low concentration of ubiquitous elements as aluminium. The worst situation is when a separation step is necessary, because it requires extra-manipulations of the sample. This article describes the degree of contamination and its control for the aluminium trace analysis in dialysis solutions, when aluminium content of about 15 µg/l must be determinated.

Uso do violeta de alizarina N (AVN) como reagente espectrofotométrico na determinação de alumínio

The present work proposes the application of the 4-Hidroxy-3-(2-hydroxynaphtylazo)-benzenesulphonic acid (C.I. 15670), Alizarine Violet N (AVN), as a reagent for direct aluminium determination using molecular absorption spectrophotometry in the presence of tensoatives. Al(III) cation reacts with AVN in pH 9.4, forming a red complex, stable for at least 24 hours, with absorption minimum at 607nm and, against a reagent blank, (epsiloncomplex - epsilonreagent) = -2.71x10(4) L.mol-1.cm-1. The reaction occurs in the presence of a Triton-X100 and CTAB tensoatives mixture, in the presence of EDTA. Al(III) determination is possible in the linear range of 50 up to 400ng.mL-1, with a detection limit of 41 ng.mL-1.

Efeito da temperatura no desempenho catalítico de óxidos de ferro contendo cobre e alumínio

Aluminum and copper doped hematite was evaluated in the high temperature shift (HTS) reaction at several temperatures in order to find catalysts that can work in different operational conditions. It was found that the catalysts work in kinetic regime in the range of 300-400 ºC. Both copper and aluminum increases the activity and selectivity. Aluminum acts as textural promoter whereas copper acts as structural one. The most promising catalyst is that with both copper and aluminum which showed higher activity and selectivity than a commercial sample. This catalyst has the advantages of being non toxic and can work at low temperatures.

Preparação de compostos de alumínio a partir da bauxita: considerações sobre alguns aspectos envolvidos em um experimento didático

Aluminum metal and aluminum compounds have many applications in several branches of the industry and in our daily lives. The most important raw material for aluminum and its manufactured compounds is bauxite, a rock constituted mainly by aluminum hydroxides minerals. In this work, a didactic experiment aiming the preparation of alumina and potassium alum starting from bauxite is proposed for undergraduate students. Both compounds are of great commercial, scientific and historical interest. The experiment involves applications of important chemical principles such as acid-base and precipitation. Some chemical properties and uses of aluminum compounds are also illustrated.

Determinação de cobre, alumínio e ferro em solos derivados do basalto através de extrações seqüenciais

Copper, aluminum and iron concentrations were determined in four geochemical fractions of three different basaltic soils from the northwest region of the Parana State, Brazil. The fractions examined were the reducible manganese dioxide and amorphous iron oxide, crystaline iron oxide, organic and residual. Metal concentrations were determined in the extracts by flame atomic absorption spectrophotometry. High Fe concentrations were extracted from the crystalline iron oxide (>20%), as well as the amorphous iron oxide (>12%). Copper was extracted from the amorphous and crystalline iron oxides in the range 5 to 12%, but low concentrations were bound to organic matter. Low concentrations of aluminum were extracted (<8%) from the amorphous and crystaline iron oxides, and organic matter. High concentrations of aluminum were found in the residual fraction.

Determinação espectrofotométrica de alumínio em concentrados salinos utilizados em hemodiálise empregando pré-concentração em fluxo

An automatic flow injection procedure for spectrophotometric aluminium determination in purified water and solutions containing high salts concentrations used for hemodyalisis treatment was developed. The method was base on reaction of Al3+ with cianine eriochrome R (ECR) after preconcentration using the AG50W-X8 cationic-exchange resin. Elution was carried out using a 1 % (m/v) calcium chloride solution. The manifold comprised an automatic proporcional injector controlled by a computer equipped with an eletronic interface and software written in QuicBASIC 4.5 with facilities to control the injector and perform data acquisition. Samples with concentration ranging from 4.96 to 19.90 µg L-1 Al were analyzed and recoveries between 88 and 113% were obtained by using the standard addition method. Other profitable analytical characteristics such as a relative standard deviation 1.3 % (n = 10) for a typical sample 14.5 µg L-1 Al, a linear response ranging up to 60.0 µg L-1Al, and a sampling throughput of 10 determinations per hour were achieved. A detection limit of 4.2 µg L-1 Al was estimated as suggested by IUPAC.

Desidrogenação do etilbenzeno sobre compostos de ferro e alumínio

Chromium and potassium-doped iron oxides are widely used as industrial catalysts in the dehydrogenation of ethylbenzene to produce styrene. They have several advantages but deactivate with time, because of the loss of potassium. Also, they are toxic due to chromium compounds. Therefore there is a need for developing alternative non toxic catalysts without potassium. Then, iron and aluminum compounds were prepared by different methods in this work. Different phases were produced depending on the preparation method. Aluminum-doped hematite was more active and selective to styrene than the aluminum ferrite. Aluminum acts both as textural and structural promoter in the catalysts.

Coagulação/floculação de suspensões ricas em óxidos de ferro por sulfato de alumínio

The destabilization mechanism of suspensions of positively charged iron oxide particles by aluminum sulphate was investigated, aiming to evaluate the efficiency of the latter as a coagulant for natural surface waters from iron ore mining plants. Synthetic waters that simulate natural suspensions were used. The best coagulant dosage was found to be 100 mg/L at pH 4. The specific adsorption of hydrolysis products of aluminum salts on iron oxide particles and heterocoagulation processes involving differently charged substrates are proposed to explain the turbidity reduction of the suspensions.

Eletrodo íon-seletivo para determinação potenciométrica de alumínio(III) em meio de fluoreto

The construction and analytical evaluation of a coated graphite Al(III) ion-selective electrode, based on the ionic pair formed between the Al(F)n3-n anion and tricaprylylmethylammonium cation (Aliquat 336S) incorporated on a poly(vinylchloride) (PVC) matrix membrane are described. A thin membrane film of this ionic pair and dibutylphthalate (DBPh) in PVC was deposited directly on a cylindric graphite rod (2 cm length x 0.5 cm diameter) attached to the end of a glass tube using epoxy resin. The membrane solution was prepared by dissolving 40% (m/m) of PVC in 10 mL of tetrahydrofuran following addition of 45% (m/m) of DBPh and 15% (m/m) of the ionic pair. The effect of membrane composition, fluoride concentration, and several concomitants as potential interferences on the electrode response were investigated. The aluminium(III) ion-selective electrode showed a linear response ranging from 1.4 x 10-4 to 1.0 x 10-2 mol L-1, a detection limit of 4.0 x 10-5 mol L-1, aslope of -54.3±0.2mV dec-1 and a lifetime of more than 1 year (over 3000 determinations for each membrane). The slope indicates that the ion-selective electrode responds preferentially to the Al(F)4- species. Application of this electrode for the aluminium(III) determination in stomach anti-acid samples is reported.

Óxido misto de ítrio-alumínio dopado com Eu(III)

In this work, we report the synthesis and the photoluminescence features of Eu(III)-doped yttrium-aluminium oxide obtained by non-hydrolytic sol-gel routes. After heating the powders above 600 ºC the XRD patterns show the presence of the Y4Al2O9 (YAM) and Y3Al5O12 (YAG) phases. At 800 and at 1500 ºC the PL spectra display the Eu(III) lines characteristic of the YAM monoclinic phase. The 5D0->7F2 transition is favored relatively to the 5D0->7F1 lines. However, at 1100 ºC the cubic YAG is the preferential phase and the 5D0->7F1 transition dominates the spectrum. The Eu(III) ions lie in a centrosymmetrical site. The different solvents used in the sol-gel synthesis also change the relative proportion between these two phases. This is monitored analyzing the modifications in the relative intensity between the 5D0->7F2 and the 5D0->7F1 transitions.

Evidências da formação de monocamada de óxido de alumínio sobre sílica, através de reações de enxerto

Aluminum oxide was dispersed on a commercial silica gel surface, using successive grafting reactions. The reaction products were characterized by N2 adsorption-desorption isotherms, scanning electron microscopy and infrared spectroscopy. The progressive incorporation of aluminum, up to 5.5% (w/w), does not produce agglomeration of alumina, since changes in the original pore size distribution of the silica matrix were not observed. The aluminum oxide covers homogeneously the silica surface.

Pilarização de uma argila brasileira com poliidroxications de alumínio: preparação, caracterização e propriedades catalíticas

Montmorillonite clay from Brazil was pillared with aluminium polyhydroxications. The influence of aging of the pillaring solution and the concentration of the clay suspension on the properties of the prepared materials was studied. The materials were characterized by chemical analysis, XRD and pore analysis by N2 adsorption. The catalytic properties were evaluated in the cumene cracking reaction. Results showed that the pillarization process increases the basal spaces of natural clay from 9.7 to 18.5 Å and the surface area from 41 to 300 m²/g.