A method for evaluating Ra-228 in environmental matrices and its use at Pocos de Caldas plateau, Brazil

This work describes a methodology developed for performing the extraction, detection and quantification of Ra-228 in waters, suspended solids and sediments. The technique proved to be useful for analyzing samples from the hydrological environment of Morro do Ferro, Pocos de Caldas plateau, Brazil. The 228Ra activity in underground waters of 5 boreholes drilled in the area varied from 0.02 up to 14.5 Bq/l, whereas for the surficial waters the variation was from 0.04 to 0.51 Bq/l; for the suspended solids, the values ranged from 1.5 up to 419 Bq/g, whereas it was possible to find a value of 2.04 Bq/g for the sediments. These results show the applicability of the method for characterizing different matrices of environmental interest. (C) 2002 Elsevier B.V. Ltd. All rights reserved.

Caracterização morfológica dos estádios de desenvolvimento do aparelho reprodutor masculino da rã-touro, Rana catesbeiana, no sistema anfigranja de criação intensiva

The objective of this work was to caracterize the morphological characterization of the development stages of male reproduction apparel of bullfrog Rana catesbeiana from intensive Anfigranja system. During the period of one year, 657 bullfrog males were removed from regrowing and reproduction sections in Anfigranja system to study basic aspects of the reproduction of this specie. The collections were realized monthly and, in that occasion, the body and testicles weights for each animal were recorded and their macroscopic gonadal characteristics, registred. Testicles from 274 males were removed and histologically analyzed. From the macro and microscopic gonadal characteristics, analysis set of the testicles, five stages of gonadal maturation for the male of Rana catesbeiana were determined: juvenile, beginning of maturation, intermediate maturation, advanced maturation and spent.

pH at the micellar interface: Synthesis of pH probes derived from salicylic acid, acid-base dissociation in sodium dodecyl sulfate micelles, and Poisson-Boltzmann simulation

The study of the H+ concentration at the micellar interface is a convenient system for modeling the distribution of H+ at interfaces. We have synthesized salicylic acid derivatives to analyze the proton dissociation of both the carboxylic and phenol groups of' the probes, determining spectrophotometrically the apparent pK(a)'s (pK(ap)) in sodium dodecyl Sulfate, SDS, micelles with and without added salt. The synthesized probes were 2-hydroxy-5-(2-trimethylammoniumacetyl)benzoate; 2-hydroxy-5-(2-dimethylhexadecylammoniumacetyl)benzoate- 2-hydroxy-5-(2-dimethylhexadecylammoniumhexanoyl)benzoate-, 2-hydroxy-5-(2-diniethylhexadecylammoniumundecanoyl)betizoate; 2-hydroxy-5-acetylbenzoic acids and 2-hydroxy-5-dodecanoylbenzoic acid. Upon incorporation into SDS micelles the pK(ap)'s of both carboxylic and phenol groups increased by ca. 3 pH units and NaCl addition caused a decrease in the probe-incorporated pKap. The experimental results were fitted with a cell model Poisson-Boltzmann (P-B) equation taking in consideration the effect of salt on the aggregation number of SDS and using the distance of' the dissociating group as a parameter. The conformations of the probes were analyzed theoretically using two dielectric constants, e.g., 2 and 78. Both the P-B analysis and conformation calculations can be interpreted by assuming that the acid groups dissociate very close to, or at, the interface. Our results are consistent with the assumption that the intrinsic pK(a)'s of both carboxylic and phenol groups of the salicylic acid probes used here can be taken as those in water. Using this assumption the micellar and salt effects on the pKap's of the (trialkylammonium)benzoate probes were described accurately using a cell model P-B analysis. (c) 2005 Elsevier B.V. All rights reserved.

Planar membranes interaction

The system of two parallel planar, arbitrarily charged surfaces immersed in a solution containing only one ionic species, the counterions, is completely analyzed under a mean field Poisson-Boltzmann approach. Results for the pressure, reduced potential, and counterionic concentration are graphically displayed for two dissociating membranes and for a dissociating and an adsorbing membrane. The results indicate that the system of two planar parallel dissociating membranes acts as a buffer for pressure values and for counterionic concentration values in regions interior to and far from the membranes. The results are related to properties of planar or quasiplanar structures in biological cells.

Uroflow studies in children: Correlation with age, weight and body surface area.

Peak flow rate data (Q(max)) are important for diagnosis of lower urinary tract obstruction. However, the lack of uroflowmetry studies in children, makes their interpretation difficult. With this aim, we studied 167 boys classified in four groups according to their age (G1 : n = 48, 6-7 years; G2 : n = 43, 8-9 years; G3 : n = 37, 10-11 years; G4: n = 39, 12-14 years). We studied in all children, weight, height, body surface area, peak flow rate (Q(max) and the correspondant urinary volume (Vol). Means and standard deviations of Q(max) (ml/sec) were : 15 +/- 5 (G1), 15 +/- 5 (G2), 17 +/- 5 (G3) and 22 +/- 7 (G4) respectively. Corresponding urinary volumes (Vol) (mean standard deviation - in ml) were : G1 = 123 +/- 75; G2 = 122 +/- 79; G3 = 158 +/- 96 and G4 = 162 +/- 101. We found a significant correlation (p < 0,01) between Q(max) and Vol in groups G2, G3 and G4; and between Q(max) and height in groups G1 and G4.The authors demonstrated a positive correlation between maximum flow and voided volume, and an increase of Q(max) with age.

Estimativa do Tamanho da Primeira Maturação Sexual da Rã - Touro, Rana catesbeiana, no Sistema Anfigranja de Criação Intensiva

The objective of this research was to study the basic aspects of bullfrog reproduction in Anfigranja system from June 1989 to July 1990. For the 1493 animals involved in this experiment (657 males and 836 females) biometrical data were obtained (weight, length and tympanum diameter) and developmental stages of gonads were determined. Female sizes at first maturation were 10,33 cm and 109,78 g and for males it was around 8,09 cm; all males above 45 g were already in the maturation process. The relationship between tympanum diameter and body length (RTC) was considered a good index for male maturation.

Caracterização morfológica dos estádios de desenvolvimento do aparelho reprodutor feminino da rã-touro, Rana catesbeiana, no sistema anfigranja de criação intensiva

The objective of this work was to caracterize the morphological characterization of the development stages of female reproduction apparel of bullfrog Rana catesbeiana from intensive Anfigranja system. During the period of one year, 836 bullfrog females were removed from regrowing and reproduction sections of the Anfigranja system to study the basic aspects of the reproduction of this specie. The collections were realized monthly and, in that occasion, the body and ovary weights for each animal were recorded and their macroscopic gonadal characteristics, registred. The ovaries from 303 females were removed and histologically examined. From the macro and microscopic characteristics analysis set of the ovary, five stages of gonadal maturation for the female of Rana catesbeiana were determined: juvenile, beginning of maturation, intermediate maturation, advance maturation and spent.

Leishmania spp. in Didelphis albiventris and Micoureus paraguayanus (Didelphimorphia: Didelphidae) of Brazil

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

The characterisation of the protective film formed by benzotriazole on the 90/10 copper-nickel alloy surface in H2SO4 media

The nature of the protective film formed by benzotriazole (BTAH) on the surface of the 90/10 CuNi alloy in deaerated 0.5 mol L-1 H2SO4 solution containing Fe(III) ions as oxidant was investigated by weight-loss, calorimetric measurements, and by surface-enhanced Raman spectroscopy (SERS). The SERS measurements show that the protective film is composed by the [Cu(I)BTA](n), polymeric complex and that the BTAH molecules are also adsorbed on the electrode surface. A modification of the BET isotherm for adsorption of gases ill solids is proposed to describe the experimental results obtained from weight-loss experiments that suggest an adsorption in multilayers. Electrochemical studies of copper and nickel in 0.5 mol L-1 H2SO4 in presence and absence of BTAH have also been made as an aid to interpret the results. The calculated adsorption free energy of the cuprous benzotriazolate on the surface of the alloy is in accordance with the value for pure copper. (C) 2007 Elsevier Ltd. All rights reserved.

Fish Migration, Dams, and Loss of Ecosystem Services in the Mekong Basin

The past decade has seen increased international recognition of the importance of the services provided by natural ecosystems. It is unclear however whether such international awareness will lead to improved environmental management in many regions. We explore this issue by examining the specific case of fish migration and dams on the Mekong river. We determine that dams on the Mekong mainstem and major tributaries will have a major impact on the basin's fisheries and the people who depend upon them for food and income. We find no evidence that current moves towards dam construction will stop, and consider two scenarios for the future of the fisheries and other ecosystems of the basin. We conclude that major investment is required in innovative technology to reduce the loss of ecosystem services, and alternative livelihood strategies to cope with the losses that do occur.

Spikes em espectrometria alfa para analise de amostras geologicas

The technique of isotope dilution has been extensively utilized for determining the content of trace elements in geological samples; it has been especially useful for the determination of 238U and 234U contents in crustal materials with measurements made by alpha spectrometry. 232U-228Th has usually been used as diluent (spike) during the application of this analytical technique. More recently, 236U and 229Th have been used. Some methodological problems concerning the utilization of these spikes are presented with examples of experimental data obtained in analyses of groundwater and borehole spoil samples from Morro do Ferro, Pocos de Caldas (MG). -from English summary

Supersymmetric quantum mechanics and the equivalent classical transformation

In the usual supersymmetric quantum mechanics, the supercharges change the eigenfunction from the bosonic to fermionic sector and conversely. The classical correspondent of this transformation is shown to be the addition of a total time derivative of a purely imaginary function to the Lagrangian function of the system.

Polyacids self-dissociation model

This work deals with a model to interpret pH measurements of solutions of weak rodlike polyacids, in the absence of added salts or titrating base. The polyacid is modeled as a series of point charges discretely distributod in a straight line with a distance of closest approach for the protons and an average distance between dissociable monomers, projected in the polymer chain axis. Aside from these two geometrical parameters, the dissociation constant for the isolated monomer that describes the proton dissociated monomer interaction forms the basis of the model. The assumption of cylindrical symmetry and the adoption of the cell model lead to a form written in terms of elementary functions for the mean electrostatic potential. Values of pH (related to the proton concentration in a region beyond the influence of the polyacid) as a function of polymer concentration are displayed graphically for some values of the geometrical parameters and of the dissociation, constant. Theoretical predictions of pH values as a function of polymeric concentration are compared with measured values for poly-L-glutamic and polygalacturonic acids, and a good agreement is found. Theoretical values for the dissociation degree in terms of polymeric concentration are shown for the two experimentally investigated systems. These values are in a range appreciably smaller than what is usually studied as a result of titration.