Estrutura e dinâmica do fitoplânctone bacterioplâncton em cultivos de camarão no Rio Grande do Norte-Brasil: impacto sobre o ambiente natural

This work aimed to study the structure and dynamic of Phytoplankton and Bacterioplankton in a complete cycle of shrimp cultivation (Litopenaeus vannamei) and determine the environmental factors responsible for the structural changes of these communities. The study was realized in a saltwater shrimp farm (Macaíba, RN), between September/2005 and February/2006, and in a freshwater shrimp farm (Ceará Mirim, RN), between May/2007 and September 2007. The samplings were collected weekly in saltwater farm and every fifteen days in freshwater farm. Total phosphorus, chlorophyll a and environmental parameters (pH, dissolved oxygen, salinity, temperature, depth and water transparency) were measured. Qualitative and quantitative analysis of the phytoplankton and bacterioplankton were carried out. The Shannon-Wiener ecologic indexes of diversity and the Pielou equitability indexes were calculated to the phytoplankton. Bacterial density was determined by epifluorescence microscopy. The data were statistically analyzed by Pearson correlation and t-Test. Chlorophycea were predominat in salt water and in the captation/drainage point (24 to 99%). Diatoms had higher wealth. The species Choricystis minor had the highest occurrence (100%) and dominance (90-100%), thus showing its adaptation to the high temperatures, salinity and low water transparency conditions. Filamentous Cyanobacteria like Oscillatoria sp., Pseudoanabaena sp. and Phormidium sp. had constant levels. The negative correlation between chlorophycea and water transparency, and the positive correlation between chlorophyll a and salinity, showed that the phytoplankton was well adapted to the low transparency and to the high salinity. The bacterioplankton was negatively correlated with the total phosphorus and salinity. In freshwater, Cyanobacteria were predominant (>80%), presenting some producers of toxins species like Microcystis sp., Aphanizomenon sp., Cylindrospermopsis raciborskii e Anabaena circinalis. Cyanobacterial density and total phosphorus and chlorophyll a concentrations exceeded the maximum value allowed by legislation. The means of total phosphorus varied from 264 to 627 Wg.L-1 and the means of chlorophyll a oscillated between 22 and 182 Wg.L-1. The phytoplankton species were selected by low availability of the light, high pH, temperature and high availability of total phosphorus. The bacterioplankton showed high densities (5,13 x 107 to 8,50 x107 Bac.mL-1). The studied environments (ponds and rivers) presented a high level of trophic state based on the high concentrations of chlorophyll a and total phosphorus and cyanobacteria dominance. The composition of species in the ponds and rivers was similar, as well as high concentrations of total phosphorus and chlorophyll a, highlighting the pollution caused by the discharges of the farms in natural environment

Biologia populacional comparada de duas espécies de heliconius (Lepidoptera: Nymphalidae) em um ambiente sazonal de floresta atlântica do nordeste brasileiro

Tropical environments often face strong seasonal variations in climate, such as alternate periods of dry and rain, that may often be important influence in the annual X the organisms lives. Here we assess how population dynamics of two butterfly species (Heliconius erato and Heliconius mepomene) respond to environmental and seasonal variations. A mark-release-recapture study carried out in an Atlantic forest reserve, 15 Km from Natal, Rio Grande do Norte, Brazil, for 3 years, during the dry and rainy season, with three visits weekly done. Information such as species, wing lenght, site of capture, pollen load and phenotype (number of spots) (in H. erato only) were noted for each capture. Seasonal variation exists in capture rates of the two species, with great capture rates during the rainy season. Despite finding differences in the mean density of individuals of the two species among the different collection areas, this difference was only significant between floodplain and central areas, and no influence of seasonality was observed in the mean density between the areas. Seasonality in wing size was only observed for H. erato, with larger wings during the rainy season. Females carried larger pollen loads than males both species, but species were similar. Only males differed seasonally, with larger pollen loads during the rainy season. The distribution of the number of wing spots did not vary between the dry and rainy seasons, and the number of spots in males and females was similar. Therefore, we conclude that there was a strong influence of seasonal variation in the population dynamic of the two Heliconius species, as well as in several aspects of their biology

Cálculos AB initio de propriedades estruturais, eletrônicas e ópticas de colmpostos CaXo3 (X=Si, Ge, Sn)

In this work we present a study of structural, electronic and optical properties, at ambient conditions, of CaSiO3, CaGeO3 and CaSnO3 crystals, all of them a member of Ca-perovskite class. To each one, we have performed density functional theory ab initio calculations within LDA and GGA approximations of the structural parameters, geometry optimization, unit cell volume, density, angles and interatomic length, band structure, carriers effective masses, total and partial density of states, dielectric function, refractive index, optical absorption, reflectivity, optical conductivity and loss function. A result comparative procedure was done between LDA and GGA calculations, a exception to CaSiO3 where only LDA calculation was performed, due high computational cost that its low symmetry crystalline structure imposed. The Ca-perovskite bibliography have shown the absence of electronic structure calculations about this materials, justifying the present work

Aprendizado espacial-temporal em um ambiente complexo sem restrição alimentar em ratos

Timeplace learning is the capacity of organisms to associate both space and time with a biological relevant stimulus such as food. Experiments are usually done with food restricted animals due to the belief that food system activation is necessary for timeplace learning. Another line of thought suggest that, in addition to food system activation, response cost should be increased to effectively allow timeplace discrimination. The purpose of this experiment was to test whether a complex environment, which presumably implied in a heightened response cost, would facilitate timeplace association in satiated rats using a highly palatable food as reward. Nine rats were trained in a timeplace task for 30 nonconsecutive days. A large experimental box (1x1m) divided in four compartments was used. To access each compartment the animal had to overcome a series of obstacles such as ramps, staircases and mazes. Two feeders localized in opposite compartments were rewarded with sunflower seeds in two daily sessions. One feeder offered the reward during the morning sessions while the second feeder in afternoon sessions. After the 15th day of training, the animals began to show a preference for the correct feeder during the correct time of day expressed by increased frequency of visits as well as lower latency to access the feeders. These results suggest that satiated animals are also capable of learning a timespace task as far as the experimental context is complex enough to result in a higher response cost

O papel das rotas e da obtenção de informações sobre a eficiência no forrageio de dinoponera quadriceps em ambiente natural

In this study, we investigated the role of routes and information attainment for the queenless ant species Dinoponera quadriceps foraging efficiency. Two queenless ant colonies were observed in an area of Atlantic secondary Forest at the FLONA-ICMBio of Nisia Floresta, in the state of Rio Grande do Norte, northeastern Brazil, at least once a week. In the first stage of the study, we observed the workers, from leaving until returning to the colony. In the second stage, we introduced a acrylic plate (100 x 30 x 0,8 cm) on a selected entrance of the nest early in the morning before the ants left the nest. All behavioral recordings were done through focal time and all occurence samplings. The recording windows were of 15 minutes with 1 minute interval, and 5 minute intervals between each observation window. Foraging was the main activity when the workers were outside the nest. There was a positive correlation between time outside the nest and distance travelled by the ants. These variables influenced the proportion of resource that was taken to the nest, that is, the bigger its proportion, the longer the time outside and distance travelled during the search. That proportion also influenced the time the worker remained in the nest before a new trip, the bigger the proportion of the item, the shorter was the time in the nest. During all the study, workers showed fidelity to the route and to the sectors in the home range, even when the screen was in the ant´s way, once they deviated and kept the route. The features of foraging concerning time, distance, route and flexibility to go astray by the workers indicate that decisions are made by each individual and are optimal in terms of a cost-benefit relation. The strategy chosen by queenless ants fits the central place foraging and marginal value theorem theories and demonstrate its flexibility to new informations. This indicates that the workers can learn new environmental landmarks to guide their routes

Caracterização estrutural de Perovskitas Lax-1AxCoO3 (x=0 e 0,2) ,dopadas com cálcio e bario, por espectroscopia de absorção de raios X (XAS).

In this work, the structures of LaCoO3, La0,8Ba0,2CoO3 and La0,8Ca0,2CoO3 perovskites were characterized as a function of temperature (LaCoO3 structure being analyzed only at room temperature). The characterization of these materials were made by X-Ray Absorption Spectroscopy (XAS), in the cobalt K-edge, taking into account the correlated Einstein model X-ray absorption fine structure (EXAFS). The first part of the absorption spectrum corresponded the X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS). These materials were prepared by the combustion method. The combustion products were calcinated at 900 0C, for 6 hours in air. Noted that the sample LaCoO3 at room temperature and samples doped with Calcium and Barium in the temperature range of 50 K to 298 K showed greater distortion to monoclinic symmetry with space group I2/a. However, the sample doped with barium at the temperatures 50 K, 220 K, and 260 K showed a slight distortion to rhombohedral symmetry with space group R-3c. The La0,8Ca0, 2CoO3 structure was few sensitive to temperature variation, showing a higher local distortion in the octahedron and a higher local thermal disorder. These interpretations were in agreement with the information electronic structural on the XANES region and geometric in the EXAFS region

Estudo da deposição de filmes finos de BaTi(1-X)Zr(X)O3 por meio de planejamento Box-Behnken

Ferroelectric ceramics with perovskite structure (ABO3) are widely used in solid state memories (FeRAM’s and DRAM's) as well as multilayered capacitors, especially as a thin films. When doped with zirconium ions, BaTiO3-based materials form a solid solution known as barium zirconate titanate (BaTi1-xZrxO3). Also called BZT, this material can undergo significant changes in their electrical properties for a small variation of zirconium content in the crystal lattice. The present work is the study of the effects of deposition parameters of BaTi0,75Zr0,25O3 thin films by spin-coating method on their morphology and physical properties, through an experimental design of the Box-Behnken type. The resin used in the process has been synthesized by the polymeric precursor method (Pechini) and subsequently split into three portions each of which has its viscosity adjusted to 10, 20 and 30 mPa∙s by means of a rotary viscometer. The resins were then deposited on Pt/Ti/SiO2/Si substrates by spin-coating method on 15 different combinations of viscosity, spin speed (3000, 5500 and 8000 rpm) and the number of deposited layers (5, 8 and 11 layers) and then calcined at 800 ° C for 1 h. The phase composition of the films was analyzed by X-ray diffraction (XRD) and indexed with the JCPDS 36-0019. Surface morphology and grain size were observed by atomic force microscopy (AFM) indicating uniform films and average grain size around 40 nm. Images of the cross section of the films were obtained by scanning electron microscopy field emission (SEM-FEG), indicating very uniform thicknesses ranging from 140-700 nm between samples. Capacitance measurements were performed at room temperature using an impedance analyzer. The films presented dielectric constant values of 55-305 at 100kHz and low dielectric loss. The design indicated no significant interaction effects between the deposition parameters on the thickness of the films. The response surface methodology enabled better observes the simultaneous effect of variables.

Estrutura e dinâmica do fitoplânctone bacterioplâncton em cultivos de camarão no Rio Grande do Norte-Brasil: impacto sobre o ambiente natural

This work aimed to study the structure and dynamic of Phytoplankton and Bacterioplankton in a complete cycle of shrimp cultivation (Litopenaeus vannamei) and determine the environmental factors responsible for the structural changes of these communities. The study was realized in a saltwater shrimp farm (Macaíba, RN), between September/2005 and February/2006, and in a freshwater shrimp farm (Ceará Mirim, RN), between May/2007 and September 2007. The samplings were collected weekly in saltwater farm and every fifteen days in freshwater farm. Total phosphorus, chlorophyll a and environmental parameters (pH, dissolved oxygen, salinity, temperature, depth and water transparency) were measured. Qualitative and quantitative analysis of the phytoplankton and bacterioplankton were carried out. The Shannon-Wiener ecologic indexes of diversity and the Pielou equitability indexes were calculated to the phytoplankton. Bacterial density was determined by epifluorescence microscopy. The data were statistically analyzed by Pearson correlation and t-Test. Chlorophycea were predominat in salt water and in the captation/drainage point (24 to 99%). Diatoms had higher wealth. The species Choricystis minor had the highest occurrence (100%) and dominance (90-100%), thus showing its adaptation to the high temperatures, salinity and low water transparency conditions. Filamentous Cyanobacteria like Oscillatoria sp., Pseudoanabaena sp. and Phormidium sp. had constant levels. The negative correlation between chlorophycea and water transparency, and the positive correlation between chlorophyll a and salinity, showed that the phytoplankton was well adapted to the low transparency and to the high salinity. The bacterioplankton was negatively correlated with the total phosphorus and salinity. In freshwater, Cyanobacteria were predominant (>80%), presenting some producers of toxins species like Microcystis sp., Aphanizomenon sp., Cylindrospermopsis raciborskii e Anabaena circinalis. Cyanobacterial density and total phosphorus and chlorophyll a concentrations exceeded the maximum value allowed by legislation. The means of total phosphorus varied from 264 to 627 Wg.L-1 and the means of chlorophyll a oscillated between 22 and 182 Wg.L-1. The phytoplankton species were selected by low availability of the light, high pH, temperature and high availability of total phosphorus. The bacterioplankton showed high densities (5,13 x 107 to 8,50 x107 Bac.mL-1). The studied environments (ponds and rivers) presented a high level of trophic state based on the high concentrations of chlorophyll a and total phosphorus and cyanobacteria dominance. The composition of species in the ponds and rivers was similar, as well as high concentrations of total phosphorus and chlorophyll a, highlighting the pollution caused by the discharges of the farms in natural environment