Marigold (Tagetes erecta L.) as an attractive crop to natural enemies in onion fields

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

NATURAL TRIPLOIDY IN ASTYANAX-SCABRIPINNIS (PISCES, CHARACIDAE) AND SIMULTANEOUS OCCURRENCE OF MACRO B-CHROMOSOMES

The occurrence of natural triploidy in two specimens of Astyanax scabripinnis collected in the Araqua river and in the Corrego das Pedras stream, respectively, is noticed. The triploid specimen from the Araqua river presented one macro B-chromosome and the triploid specimen from Corrego das Pedras stream presented two macro B-chromosomes. The C-banding performed in the specimen from the Araqua river confirmed the triploidy and showed that the macro B-chromosome was entirely heterochromatic. Ag-NOR characterization showed two chromosomes involved in the nucleolar activity in both specimens. Some aspects related to the origin of triploid fishes are described.

Whydration effects on DNA double helix stability modulates ligand binding to natural DNA in response to changes in water activity

In this work we present evidence that water molecules are actively involved on the control of binding affinity and binding site discrimination of a drug to natural DNA. In a previous study, the effect of water activity (a(w)) on the energetic parameters of actinomycin-D intercalation to natural DNA was determined using the osmotic stress method (39). This earlier study has shown evidence that water molecules act as an allosteric regulator of ligand binding to DNA via the effect of water activity on the long-range stability of the DNA secondary structure. In this work we have carried out DNA circularization experiments using the plasmid pUC18 in the absence of drugs and in the presence of different neutral solutes to evaluate the contribution of water activity to the energetics of DNA helix unwinding. The contribution of water to these independent reactions were made explicit by the description of how the changes in the free energy of ligand binding to DNA and in the free energy associated with DNA helix torsional deformation are linked to a(w) via changes in structural hydration. Taken together, the results of these studies reveal an extensive linkage between ligand binding affinity and site binding discrimination, and long range helix conformational changes and DNA hydration, This is strong evidence that water molecules work as a classical allosteric regulator of ligand binding to the DNA via its contribution to the stability of the double helix secondary structure, suggesting a possible mechanism by which the biochemical machinery of DNA processing takes advantage of the low activity of water into the cellular milieu.

A natural triploid in Trichomycterus davisi (Siluriformes, Trichomycteridae): mitotic and meiotic characterization by chromosome banding and synaptonemal complex analyses

Within a total of 50 analyzed specimens a male individual of Trichomycterus davisi has been recorded with 81 chromosomes including 60 metacentric, 18 submetacentric and three subtelocentric chromosomes. When compared with diploid individuals (2n = 54) and the morphological standard of chromosomes, this male is a triploid with 3 = 81 chromosomes. Since staining with silver nitrate indicates three active nucleolar organizer regions (NORs), the three NOR- bearing chromosomes in this individual are genetically active. Analysis of the synaptonemal complex (SC) by electronic microscopy shows that there is an incomplete pairing of the third set of chromosomes in the triploid individual.

Purification and characterization of polygalacturonase produced by thermophilic Thermoascus aurantiacus CBMAI-756 in submerged fermentation

An extracellular polygalacturonase was isolated from 5-day culture filtrates of Thermoascus aurantiacus CBMAI-756 and purified by gel filtration and ion-exchange chromatography. The enzyme was maximally active at pH 5.5 and 60-65 degrees C. The apparent K (m) with citrus pectin was 1.46 mg/ml and the V (max) was 2433.3 mu mol/min/mg. The apparent molecular weight of the enzyme was 30 kDa. The enzyme was 100% stable at 50 degrees C for 1 h and showed a half-life of 10 min at 60 degrees C. Polygalacturonase was stable at pH 5.0-5.5 and maintained 33% of initial activity at pH 9.0. Metal ions, such as Zn+2, Mn+2, and Hg+2, inhibited 50, 75 and 100% of enzyme activity. The purified polygalacturonase was shown to be an endo/exo-enzyme, releasing mono, di and tri-galacturonic acids within 10 min of hydrolysis.

Numerical and experimental analysis of natural convection in a cavity heated from below

In this work, an analysis of the natural convection flow caused by heat sources dissipating energy at a constant rate simulating electronic components mounted at the bottom surface of a cavity symmetrically cooled from the sides and insulated at the top is performed. This problem was studied numerically and experimentally for several aspect ratios (height/width), for different levels of dissipation in the sources, and for different side wall temperatures. Temperature and velocity fields were determined as well as the temperature variation along the surface where the sources are mounted and the average Nusselt number in the source surfaces. Numerical and experimental results were found to agree.

Optimum design of microirrigation systems in sloping lands

When an area to be irrigated has a high slope gradient in the manifold line direction, an option is to use a tapered pipeline to economize on pipe costs and to keep pressure head variations within desired limits. The objective of this paper is to develop a linear optimization model to design a microirrigation system with tapered, downhill manifold lines, minimizing the equivalent annual cost of the hydraulic network and the annual pumping cost, and maximizing the emission uniformity previously established to the subunit. The input data are irrigation system layout, cost of all hydraulic network components, and electricity price. The output data are equivalent annual cost, pipeline diameter in each line of the system, pressure head in each node, and total operating pressure head. To illustrate its capability, the model is applied in a citrus orchard in Sao, Paulo State, Brazil, considering slopes of 3, 6, and 9%. The model proved to be efficient in the design of the irrigation system in terms of the emission uniformity desired.

Numerical and experimental analysis of natural convection in a cavity with flush mounted heat sources on a side wall

This work considers a problem of interest in several technological applications such as the thermal control of electronic equipment. It is also important to study the heat transfer performance of these components under off-normal conditions, such as during failure of cooling fans. The effect of natural convection on the flow and heat transfer in a cavity with two flush mounted heat sources on the left vertical wall, simulating electronic components, is studied numerically and experimentally. The influence of the power distribution, spacing between the heat sources and cavity aspect ratio have been investigated. An analysis of the average Nusselt number of the two heat sources was performed to investigate the behavior of the heat transfer coefficients. The results obtained numerically and experimentally, after an error analysis, showed a good agreement.

Design of microirrigation systems in sloping lands using linear programming

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Periphyton on natural substratum in jurumirim reservoir (São Paulo, Brazil): Community biomass and primary productivity

Seasonal variation in the biomass and primary productivity of the periphyton on natural substratum (internodes of Echiiwchloa polystaclya HBK Hitch.) was studied during one year (from August 1993 to July 1994) in a lagoon with permanent connection with a river. We also analysed the relationships between the hydrological regime, climatic conditions and physico-chemical variables of water with the biological compounds of the periphyton. Values of dry mass, ash-free dry mass, chlorophyll a and phaeophytin of periphyton ranged from 0.55±0.24 g m-2 to 7.86±4.93 g m-2; 0.28±0.18 g m-2 to 3.72±2.23 g m-2; 0.57±0.09 mg m-2 to 15.57±4.52 mg m-2; 0.03±0.03 mg m-2 to 4.74±3.46 mg m-2, respectively. The primary productivity of periphytic algae measured by C14 method ranged from 6.45±1.29 mg C m-2 h-1 to 52.88± 7.55 mg C m-2 h-1. The biomass showed a peak in October 1993, February and April 1994. Higher value of primary productivity was recorded in December 1993 and January 1994 and was due to the peculiar light and nutrition conditions during this period. We conclude that biomass and productivity of the community are controlled mainly by hydrological regime (fluctuations of water level). © INTERNATIONAL SCIENTIFIC PUBLICATIONS.

Puncture wounds by driftwood catfish during bucket baths: Local habits of riverside people and fish natural history in the Amazon

Objective. - To assess the prevalence of stings by small spiny driftwood catfish (carataí) of the genus Centromochlus (Auchenipteridae) accidentally caught in buckets during bucket bathing by riverside people along the Brazilian Amazon and to determine the probability of catching specimens of these fish during random throws of a bucket into the river. Methods. - We interviewed 27 adult residents living at the confluence of the Negro and Solimões rivers in Brazil regarding whether or not they had ever been stung by driftwood catfish while bucket bathing. To assess the likelihood of catching catfish in bathing buckets, we randomly threw a typical plastic bucket used for bathing in 4 series of 10 throws into the river at dusk or night around a floating house. Results. - Seventeen of the 27 subjects (63%) reported being injured by driftwood catfish during bucket bathing. Three individuals (17.6%) had been injured 2 to 3 times, totaling 23 puncture accidents. All stings occurred at dusk or early night. In the 4 series of 10 bucket throws, we caught 3 driftwood catfish (in 1 series we did not catch any fish). Thus, the chance of catching a driftwood catfish in a single bucket throw at dusk was slightly less than 10%. Conclusions. - The prevalence of stings by driftwood catfish to people bucket bathing in this section of the Brazilian Amazon is high, partly because of the relatively high chances of catching these small catfish during random throws of a bathing bucket into the river.