Morphology and stability of aggregates of an Oxisol according to tillage system and gypsum application

Morphological characterization and aggregate stability is an important factor in evaluating management systems. The aim of this paper is to evaluate the stability and morphology of the aggregates of a dystrophic Oxisol managed with no-tillage and conventional tillage with and without the residual action of gypsum. The experimental design was randomized blocks arranged in split-split plot, where the treatments were two soil management systems (plots) with 0 and 2000 kg ha-1 of gypsum (subplots) and five depths (0-0.05, 0.05-0.10, 0.10-0.15, 0.15-0.20 and 0.20-0.30 m) as the subsubplots, with four replications. The aggregate morphology was determined through images and later evaluated by the Quantporo software. Stability was determined by the wet method. The results showed that the no-tillage system, with or without gypsum residual effect, provided the aggregates with the largest geometric diameters. The combination of no-tillage system and the gypsum residual effect provided rougher aggregates.

Lista dos gêneros incluídos na super-família Brachylaemoidea

Dans le travail présent, il est fait um groupement des trématodes considérés par les auteurs comme appartenant à la super-famille Brachylaemoidea, groupement constitué par les families suivantes; Brachylaemidae Joyeux & Foley, 1930; Leucochloridiidae Dollfus, 1934; Urorygmidae fam. n.; Leucochloridiomorphidae fam. n.; Hasstilesiidae Hall, 1916; Moreauiidae Yamaguti, 1958; Liolopidae Dollfus, 1934; Urotrematidae Poche, 1925; et Thapariellidae Srivastava, 1955. Les diagnostics des genres et les figures des tòpes sont données.

Compressibility of Oxisol aggregates under no-till in response to soil water potential

The system of no-till sowing stands out as being a technology that suits the objectives of more rational use of the soil and greater protection against the erosion. However, through till, any of it, occurs modifications of the soil's structure. This current work aims to study the influence of the energy state of the water and of the organic matter on the mechanism of compaction of Red Oxisol under no-till management system. Humid and non-deformed sample were collected in horizon AP of two agricultural areas under no-till, with and without rotation of cultures. In the laboratory, these samples were broken into fragments and sifted to obtain aggregates of 4 to 5 mm sized, which were placed in equilibrium under four matrix potentials. Thereafter, they were exposed to uni-dimensional compression with pressures varying from 32 to 1,000 kPa. The results in such a way show that the highest compressibility of aggregates both for the tilling with rotation of cultures as for the tilling without rotation of cultures, occurred for matrix potential -32 kPa (humidity of 0.29-0.32 kg kg-1, respectively), while the minor occurred for the potentials of -1 and -1,000 kPa (humidity of 0.35 and 0.27 kg kg-1, respectively), indicating that this soil should not be worked with humidity ranging around 0.29 to 0.32 kg kg-1 and the highest reduction of volume of aggregates was obtained for the mechanical pressures lower than 600 inferior kPa, indicating that these soils showed to be very influenced by compression, when exposed to mechanical work. Also, the aggregates of soil under no-till and rotation of crops presented higher sensitivity to the compression than the aggregates of soil under no-till and without rotation of crops, possibly for having better structural conditions given to a higher content of organic matter.

Improvement of a testing apparatus for dynamometry: procedures for penetrometry and influence of strain rate to quantify the tensile strength of soil aggregates

Soil penetration resistance (PR) and the tensile strength of aggregates (TS) are commonly used to characterize the physical and structural conditions of agricultural soils. This study aimed to assess the functionality of a dynamometry apparatus by linear speed and position control automation of its mobile base to measure PR and TS. The proposed equipment was used for PR measurement in undisturbed samples of a clayey "Nitossolo Vermelho eutroférrico" (Kandiudalfic Eutrudox) under rubber trees sampled in two positions (within and between rows). These samples were also used to measure the volumetric soil water content and bulk density, and determine the soil resistance to penetration curve (SRPC). The TS was measured in a sandy loam "Latossolo Vermelho distrófico" (LVd) - Typic Haplustox - and in a very clayey "Nitossolo Vermelho distroférrico" (NVdf) - Typic Paleudalf - under different uses: LVd under "annual crops" and "native forest", NVdf under "annual crops" and "eucalyptus plantation" (> 30 years old). To measure TS, different strain rates were applied using two dynamometry testing devices: a reference machine (0.03 mm s-1), which has been widely used in other studies, and the proposed equipment (1.55 mm s-1). The determination coefficient values of the SRPC were high (R² > 0.9), regardless of the sampling position. Mean TS values in LVd and NVdf obtained with the proposed equipment did not differ (p > 0.05) from those of the reference testing apparatus, regardless of land use and soil type. Results indicate that PR and TS can be measured faster and accurately by the proposed procedure.

Water-Stable Aggregates and Associated Carbon in a Subtropical Rice Soil Under Variable Tillage

ABSTRACT Tillage systems can influence C sequestration by changing aggregate formation and C distribution within the aggregate. This study was undertaken to explore the impact of no-tillage without straw (NT-S) and with straw (NT+S), and moldboard plow without straw (MP-S) and with straw (MP+S), on soil aggregation and aggregate-associated C after six years of double rice planting in a Hydragric Anthrosol in Guangxi, southwest of China. Soil samples of 0.00-0.05, 0.05-0.20 and 0.20-0.30 m layers were wet-sieved and divided into four aggregate-size classes, >2 mm, 2.00-0.25 mm, 0.25-0.053 and <0.053 mm, respectively, for measuring aggregate associated C and humic and fulvic acids. Results showed that the soil organic carbon (SOC) stock in bulk soil was 40.2-51.1 % higher in the 0.00-0.05 m layer and 11.3-17.0 % lower in the 0.05-0.20 m layer in NT system (NT+S and NT-S) compared to the MP system (MP+S and MP-S), respectively. However, no statistical difference was found across the whole 0.00-0.30 m layer. The NT system increased the proportion of >2 mm aggregate fraction and reduced the proportion of <0.053 mm aggregates in both 0.00-0.05 and 0.05-0.20 m layers. The SOC concentration, SOC stock and humic and fulvic acids within the >0.25 mm macroaggregate fraction also significantly increased in the 0.00-0.5 m layer in NT system. However, those within the 2.00-0.25 mm aggregate fraction were significantly reduced in the 0.05-0.200 m layer under NT system. Straw incorporation increased not only the SOC stock in bulk soil, but also the proportion of macroaggregate, aggregate associated with SOC and humic and fulvic acids concentration within the aggregate. The effect of straw on C sequestration might be dependent on the location of straw incorporation. In conclusion, the NT system increased the total SOC accumulation and humic and fulvic acids within macroaggregates, thus contributing to C sequestration in the 0.00-0.05 m layer.

Arbuscular mycorrhizal fungi in soil aggregates from fields of "murundus" converted to agriculture

The objective of this work was to evaluate the spore density and diversity of arbuscular mycorrhizal fungi (AMF) in soil aggregates from fields of "murundus" (large mounds of soil) in areas converted and not converted to agriculture. The experiment was conducted in a completely randomized design with five replicates, in a 5x3 factorial arrangement: five areas and three aggregate classes (macro-, meso-, and microaggregates). The evaluated variables were: spore density and diversity of AMF, total glomalin, total organic carbon (TOC), total extraradical mycelium (TEM), and geometric mean diameter (GMD) of soil aggregates. A total of 21 AMF species was identified. Spore density varied from 29 to 606 spores per 50 mL of soil and was higher in microaggregates and in the area with 6 years of conversion to agriculture. Total glomalin was higher between murundus in all studied aggregate classes. The area with 6 years showed lower concentration of TOC in macroaggregates (8.6 g kg-1) and in microaggregates (10.1 g kg-1). TEM was greater at the top of the murundus in all aggregate classes. GMD increased with the conversion time to agriculture. The density and diversity of arbuscular mycorrhizal spores change with the conversion of fields of murundus into agriculture.

Super/subcritical fluid chromatography with packed columns: state of the art and applications

Separations using supercritical fluid chromatography (SFC) with packed columns have been re-discovered and explored in recent years. SFC enables fast and efficient separations and, in some cases, gives better results than high performance liquid chromatography (HPLC). This paper provides an overview of recent advances in SFC separations using packed columns for both achiral and chiral separations. The most important types of stationary phases used in SFC are discussed as well as the most critical parameters involved in the separations and some recent applications.

Leibniz's theory of bodies: monadic aggregates, phenomena, or both?

Leibniz's conception of bodies seems to be a puzzling theory. Bodies are seen as aggregates of monads and as wellfounded phenomena. This has initiated controversy and unending discussions. The paper attempts to resolve the apparent inconsistencies by a new and formally spirited reconstruction of Leibniz's theory of monads and perception, on the one hand, and a (re-)formulation and precisation of his concept of preestablished harmony, on the other hand. Preestablished harmony is modelled basically as a covariation between the monadic and the ideal realm.

Super especialização na cirurgia geral : problema ou solução?

A cirurgia geral atualmente é considerada, por alguns, como uma especialidade cansativa, desinteressante. Acredita-se que o aparecimento de novas tecnologias, a internet, a videocirurgia, a robótica, a telemedicina, a especialização e o desinteresse, dos recém formados, pela cirurgia geral são fatores que contribuem para esta mudança. Neste artigo são discutidas as mudanças no exercício da cirurgia geral que ocorrem no Brasil, no mundo, as suas consequencias na formação do Cirurgião Geral e o reflexo no atendimento à população.

Effect of urea on biomimetic aggregates

The effect of urea on biomimetic aggregates (aqueous and reversed micelles, vesicles and monolayers) was investigated to obtain insights into the effect of the denaturant on structured macromolecules. Direct evidence obtained from light scattering (static and dynamic), monolayer maximum isothermal compression and ionic conductivity measurements, together with indirect evidence from fluorescence photodissociation, fluorescence suppression, and thermal reactions, strongly indicates the direct interaction mechanism of urea with the aggregates. Preferential solvation of the surfactant headgroups by urea results in an increase in the monomer dissociation degree (when applied), which leads to an increase in the area per headgroup and also in the loss of counterion affinities

Resistance of multicellular aggregates to pharmorubicin observed in human hepatocarcinoma cells

The objective of the present study was to investigate the multicellular resistance of human hepatocarcinoma cells BEL-7402 to pharmorubicin. Cells (1 x 10(4)) and 200 microcarrier Cytodex-3 beads were seeded onto a 24-well plate and cultured in RPMI 1640 medium. After the formation of multicellular aggregates, morphology and cell viability were analyzed by scanning electron microscopy, transmission electron microscopy and flow cytometry, respectively. The IC50 was determined by flow cytometry and MTT assay after the cells cultured in aggregates and monolayers were treated with pharmorubicin. The culture products exhibited structural characteristics somewhat similar to those of trabecular hepatocarcinoma in vivo. Among the microcarriers, cells were organized into several layers. Intercellular spaces were 0.5-2.0 µm wide and filled with many microvilli. The percent of viable cells was 87%. The cells cultured as multicellular aggregates were resistant to pharmorubicin with IC50 4.5-fold and 7.7-fold that of monolayer culture as determined by flow cytometry and MTT assay, respectively. This three-dimensional culture model may be used to investigate the mechanisms of multicellular drug resistance of hepatocarcinoma and to screen new anticancer drugs.

Mathematical modeling of electro-rotation spectra of small particles in liquid solutions: Application to human erythrocyte aggregates

Electro-rotation can be used to determine the dielectric properties of cells, as well as to observe dynamic changes in both dielectric and morphological properties. Suspended biological cells and particles respond to alternating-field polarization by moving, deforming or rotating. While in linearly polarized alternating fields the particles are oriented along their axis of highest polarizability, in circularly polarized fields the axis of lowest polarizability aligns perpendicular to the plane of field rotation. Ellipsoidal models for cells are frequently applied, which include, beside sphere-shaped cells, also the limiting cases of rods and disks. Human erythrocyte cells, due to their particular shape, hardly resemble an ellipsoid. The additional effect of rouleaux formation with different numbers of aggregations suggests a model of circular cylinders of variable length. In the present study, the induced dipole moment of short cylinders was calculated and applied to rouleaux of human erythrocytes, which move freely in a suspending conductive medium under the effect of a rotating external field. Electro-rotation torque spectra are calculated for such aggregations of different length. Both the maximum rotation speeds and the peak frequencies of the torque are found to depend clearly on the size of the rouleaux. While the rotation speed grows with rouleaux length, the field frequency nup is lowest for the largest cell aggregations where the torque shows a maximum.

Atividade amilolítica e qualidade fisiológica de sementes armazenadas de milho super doce tratadas com ácido giberélico

O uso de reguladores de crescimento na fase de germinação melhora o desempenho das plântulas, acelerando a velocidade de emergência e realçando o potencial das sementes de várias espécies, mesmo sob condições adversas. Este trabalho teve como objetivo avaliar a influência do ácido giberélico na atividade amilolítica e no vigor de sementes armazenadas de milho super doce. O experimento foi conduzido nos Laboratórios de Análise de Sementes do Departamento de Produção Vegetal/FCA e no Laboratório de Bioquímica de Plantas do Departamento de Química e Bioquímica/IB da Universidade Estadual Paulista (UNESP/Botucatu), entre os meses de julho e setembro de 2001, onde foram feitas as avaliações da qualidade fisiológica, através dos testes de germinação, vigor e bioquímicos. Sementes de milho super doce da cultivar DO-04, foram acondicionadas em sacos de papel e armazenadas por oito meses em câmara seca (40% UR). Após este período, foram colocadas para germinar em rolos de papel toalha, embebidos com GA3 nas concentrações zero; 50; 100; 150 e 200mg.L-1. Foram avaliadas a germinação, vigor e atividade amilolítica das sementes. As sementes submetidas à pré-embebição em solução de 50mg.L-1 de ácido giberélico, apresentaram maior germinação e vigor, menor teor de proteínas totais e maior atividade amilolítica.

Maturação de sementes de milho-doce: grupo Super Doce

O experimento teve como objetivo estudar o processo de maturação de sementes de milho doce da cultivar BR 400 (Super Doce). A primeira colheita das sementes foi realizada 27 dias após a floração (DAF), a qual foi considerada quando aproximadamente 50% das plantas apresentavam florescimento feminino. As demais colheitas foram realizadas em intervalos de sete dias, até 90 DAF. Imediatamente após a colheita, procedeu-se à debulha manual das sementes, determinando-se o grau de umidade e o peso da matéria seca; avaliou se também, visualmente, a presença da camada negra. Após a última colheita, foi determinada a qualidade fisiológica das sementes por meio dos testes de germinação, frio modificado, envelhecimento acelerado e condutividade elétrica. As sementes de milho-doce atingiram o máximo de matéria seca (maturidade de massa) aproximadamente aos 41 DAF, sendo que o máximo de germinação e vigor (maturidade fisiológica) ocorreu no período compreendido entre 48 e 76 DAF. Todas as sementes apresentaram camada negra aos 55 DAF, sendo esta uma característica visual eficiente para a identificação da maturidade fisiológica das sementes.

Tratamento fungicida em semente de milho super-doce

Neste trabalho, procurou-se avaliar a influência do tratamento fungicida no potencial fisiológico e na sanidade de sementes de milho híbrido super-doce DO-04, separadas por diferenças quanto ao formato. Foi utilizado delineamento inteiramente casualizado, em esquema fatorial 2 x 3 x 4, compreendendo dois formatos de semente (retidas em peneira 15 x ¾", representando as sementes arredondadas, e em peneira 20, representando as achatadas), três lotes e quatro tratamentos fungicidas (testemunha, Fludioxonil, Captan TS + Thiabendazol e Captan TS + Thiram PS). Avaliaram-se a germinação, o vigor (velocidade de germinação, teste de frio e envelhecimento acelerado) e a sanidade de semente. Foi verificado que as sementes arredondadas de milho híbrido super-doce DO-04 apresentam germinação e vigor mais elevados, em comparação às achatadas; os tratamentos fungicidas favorecem o vigor, sendo as combinações Captan + Thiabendazol e Captan + Thiram eficientes para o controle de F. moniliforme, Cephalosporium sp. e Penicillium sp..