Species richness in an assemblage is frequently used as a measure of biological diversity. However, observed species richness is strongly dependent on sample size. If more samples are collected, then more species are observed. Non-parametric species richness estimators, such as the jackknife 1 and 2 and the Chao 1 and 2, are indicated in the literature as potential solutions to the problem of dependence of observed species richness on sampling effort. These methods are intended to estimate the total species richness in an area or assemblage with small sampling effort. Non-parametric estimators are based on the number of species observed, and the number of rare species in a sample, i.e., that occurred in one and/or two sampling units, or with one and/or two individuals. High estimates are produced when samples contain large proportions of rare species. Using a range of real datasets, I show that estimates produced by non-parametric methods are generally dependent on observed species richness. An implicit assumption of these non-parametric techniques is that the rare species curve should present high values at small sample sizes and decreasing values as sampling effort is increased. This assumption was observed in only one out of eight datasets presented. Instead, the rare species curve generally flattens off around a constant value as sampling effort increases. I conclude that non-parametric estimators are not reliable to estimate species richness in an assemblage when the rare species curve does not show a decreasing trend. Comments are made on the possibilities of using non-parametric estimators in the comparison of species assemblages.
Authors:J. Rodrigues Silva, A. de Melo Ferreira, and A. da Costa
The biosorption of uranium by the seaweed Sargassum filipendula was investigated under dynamic conditions at various bed heights. Our results indicate that a bed height of 40.0 cm (111.9
g biomass) was the most efficient for long-term operation of the continuous system. Our results also indicate that the effluent
solutions produced are in accordance with Brazilian legislation for safe discharge of uranium in aqueous streams. The efficiency
of the process increased with an increase in bed height from 5.0 to 40.0 cm due to changes in the transfer zone. In treatment
of a real effluent contaminated with uranium, stable heavy metals and essential metals, 64% of the uranium was biosorbed,
as well as the stable heavy metals chromium, lead and barium. The essential metals calcium, magnesium, iron and manganese
were not biosorbed by the seaweed, in fact, their concentrations in the solution increased due to ion-exchange mechanisms
with the constituent polysaccharides of the biomass. Another important result was the 85–87% reduction of mass obtained after
drying and calcination of the biomass. This is a relevant indication that long-term storage of biomass loaded with radionuclides
and heavy metals is possible after concentration of the contaminants. In the present work, the reduction in total mass of
the loaded biomass was considerable, thus facilitating storage of the contaminated seaweed.
Authors:M. Conceição, A. Melo, N. Narain, I. Santos, and A. Souza
The thermogravimetric procedures applied to quality control of foods attain the global analysis of quality of the product,
through the determination of quality parameters and the thermal stability of products. The kinetic parameters such as order
of reaction, apparent activation energy, pre-exponential factors and the thermal decomposition rate constant were determined
for the samples of corn and its derivatives by applying isothermal thermogravimetry, utilizing the Arrhenius law. This method
presented excellent results as verified with the coherence and data adjustment. The rate constant values showed the expected
performance from the chemical point of view.
Authors:Érika Marinho, A. Souza, Danniely de Melo, Iêda Santos, Dulce Melo, and Walquíria da Silva
of their electrical, magnetic and catalytic properties rare earth and transition
metal mixed oxides are important compounds. Lanthanum chromites have been
extensively used as solid oxide fuel cell (SOFC) interconnect materials. In
this work, lanthanum chromites partially substituted by alkaline earth metals
were synthesized by the urea combustion process. TG and DSC techniques were
used to evaluate the presence of the organic material in the powder after
reaction on the hot plate. The powders were calcinated at 900C and characterized
by XRD and SEM. The results show that the particles have nanometric dimensions
and the perovskite structure was formed.
Authors:M. Batista, M. Ginani, D. Melo, and A. Oliveira
ZnS(1-x)MSx(x=0.01 and M=Mn2+, Cu2+ and Eu2+) compounds have been obtained by precipitation from homogeneous solutions of zinc, copper, manganese and europium salts,
with S2- as the precipitating anion, formed by the decomposition of thioacetamide. The thermal study of the milled zinc acetate, thioacetamide,
copper acetate, manganese acetate and europium nitrate, respectively, was studied for thermal analyis TG/DSC. XRD respect
exhibits a zinc blend crystal structure.
Authors:M. Santos, A. Azeredo, D. Melo, and L. Julião
The decay products of uranium and thorium natural series are widely distributed in all the terrestrial crust. Their concentrations are considerable in the phosphates utilized as fertilizer in the Brazilian agriculture. In this work analysis was performed on238U,234U,232Th,238Th,226Ra and210Po in 22 Brazilian tobacco samples. The results showed238U and234U are in isotopic activity equilibrium (0.5±0.2 mBq/g). The equilibrium was not reached in the case of thorium isotopes: the228/232Th ratio was about 6.4. The average values obtained were 34.3 mBq/g for228Th and 5.4 mBq/g for232Th. The226Ra values were higher than its radioactive precursor,238U. This can be explained by the high affinity of radium to tobacco plant and the uranium removal during physical and chemical processes. The high concentration of210Po (20 mBq/g) in tobacco samples may be due to radon daughter products being electrically charged and then attaching themselves to inert dusts, which then become attached to tiny hairs on tobacco leaves. The results of this work are consistent with values presented in specialized literature.
Authors:A. Azeredo, L. Julião, M. Santos, D. Melo, and J. Lipsztein
Internal contamination with radioactive materials of mining workers is a common problem in Brazil. This is caused by the presence of uranium, thorium, and their natural decay series associated with the mined ore. The clear examples are the workers at the niobium mine located in the state of Goiás. The niobium is associated with considerable quantities of uranium and thorium, but the mine is not legally subject to radiation protection requirements.Twenty mine workers were evaluated using in vitro bioassay techniques (urine and feces). The fecal samples were analyzed by alpha spectrometry using the method developed in the Bioassay Laboratory of the Instituto de Radioproteção e Dosimetria/CNEN which evaluates thorium and uranium isotopes simultaneously. Minor modifications were introduced to measure a higher level of activity, around 1 Bq of uranium per sample. The urine samples were analyzed by alpha spectrometry for thorium and by fluorimetry for uranium. The results obtained show that a control of the occupationally-exposed workers is necessary.
Authors:G. Melo, J. Sponchiado, A. Machado, and N. Cáceres
We investigated how the small-mammal community is structured in a deciduous forest in southern Brazil, analysing the patterns of vertical and horizontal distribution. We used 12 transect lines, with 180 live-traps distributed on the ground and in the understory, and 12 pitfall traps in total. During six field sessions, we captured 510 individuals belonging to 12 small-mammal species. The combination of different methods of capture resulted in a relative high species richness for the area, although the presence of additional species cannot be ruled out. The forest complexity plays an important role allowing the coexistence of cursorial, scansorial and some arboreal species in this community. The structural variables, liana and bamboo, were the most important ones for species richness. However, the dominant species, Akodon montensis was associated to sites with dense vegetation at ground level such as ferns, bamboos, and shrubs.
Authors:C. C. Dantas, R. Narain, V. A. dos Santos, and A. C. B. A. Melo
The axial and radial distribution of the catalyst concentration, in the riser of an EMC - experimental cold model of a fluid
catalytic cracking type unit, was measured by gamma-absorption. The solid concentration in the circulating fluidized bed was
determined by measurements with a 241Am gamma-source and a NaI(Tl) detector. The operation, instrumental measurements and data acquisition system of the cold unit
were automated. The catalyst concentration measurements were carried out in static experiments and in the circulating fluidized
bed. A calibration of the distribution concentration was made with experimental data from gas velocity and pressure drop along
the riser that gave the best multi-regression model. A spatial resolution of 5.0 . 10-3 m by scanning the riser and a catalyst density resolution of 5.0±0.8 kg/m3 were obtained. The axial catalyst concentration distribution, in the 5-13 kg/m 3 interval, showed a predicted pattern according to the literature. The radial distribution was in an annular configuration
for this diluted catalyst concentration.
Authors:A. Garrido Pedrosa, M. Souza, S. Lima, Dulce Melo, A. Souza, and A. Araújo
bifunctional catalysts were synthesized using impregnation and polymeric precursor
methods. After the synthesis process the samples were calcined at 600, 700
and 800C and characterized by X-ray diffraction, nitrogen adsorption
and temperature programmed reduction study by thermogravimetry. DTG-TPR profiles
showed between three and five reduction events at different temperatures attributed
to platinum reduction and to different stages of tungsten species reduction.
A comparative study of the synthesis method influence on the DTG-TPR curves