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Abstract  

The effects of temperature (373–1373 K) on the point of zero charge (PZC) and isoelectric point (IEP) of a red soil rich in kaolinite and iron minerals were studied. PZC values of the soil treated at 373 and 573 K indicated the presence of iron oxide. The soil calcined between 773 and 1173 K shows a PZC almost coincident with the respective values of kaolinite. At 1373 K, the PZC of the soil is nearer to the value of iron oxide. In the entire temperature range studied the PZC values were lower than the IEP values. An approach of PZC and IEP values was observed after a partial removal of iron oxide by the dithionite-citrate-bicarbonate (DCB) method. The analyses of the PZC and IEP values, of electron probe micro analysis (EPMA) data and of specific surface areas evidence a specific adsorption of iron oxide on kaolinite. Finally, the dissolution sequence of iron and aluminium contained in soil was determined using hydrochloric acid.

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Abstract  

A99Tc-ADP complex was prepared when KTcO4 was reduced in aquous medium by SnCl2, Na2S2O4, NaBH4 or Zn in the presence of ADP in excess. The resulting solution was studied by chromatography and spectrophotometry. Electrochemical reduction and substitution on [TcIII(tu)6]3+ were investigated as alternative synthetic routes. The anionic Tc-ADP complex was isolated as a solid. Cerimetric titrations confirmed the oxidation state +3 for the central atom. IR and1H-NMR data showed that the purine base is bonded to the Tc central atom but not the ribose moiety. No oxo groups seemed to be directly bonded to the Tc atom. The complex is rather stable in neutral solutions. However, it decomposes to pertechnetate and TcO2 at extreme pH values.

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Abstract  

A study of loss modulus values was conducted for three different metal alloys, in both superplastic and non-superplastic condition, using Dynamic Mechanical Analysis (DMA). Results showed a direct relationship between loss modulus values and the homologous superplastic temperature for each of the three different metal alloys that were studied.

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Abstract  

This paper summarizes the development and preparation procedures for two particulate preparations of153Sm, namely the hydroxyapatite (HA) particles and human serum albumin (HSA) microspheres. Preparation of153Sm-labeled hydroxyapatite particles and153Sm-labeled albumin microspheres were done in two steps. Radiolabeling efficiency was greater than 95% for hydroxyapatite particles and greater than 80% for albumin microspheres.

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Abstract  

This paper describes the preparation and labeling procedures of: N-(2-di-ethylaminoethyl-4-iodobenzamide), [IDAB] and (2-piperidinylaminoethyl)-4-iodobenzamide, [IPAB]. The results of biodistribution studies are presented.

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Abstract  

Divalent transition metal nitroprussides form a family of microporous materials which lose their crystallization water (coordinated and zeolitic) below 100°C and then remain stable up to above 150°C. The dehydration process of representative samples in their stable phases was studied by thermo-gravimetry (TG) and differential scanning calorimetry (DSC). The copper complex dehydrates in a single step through a practically irreversible process. For cadmium and cobalt complexes the water evolution on heating takes place in two stages. The first one, where only zeolitic waters are removed, is dominated by a diffusion mechanism while, during the loss of the strongly bonded waters (second stage) the material framework effect is added. The involved activation energy and its dependence on the conversion degree were estimated evaluating the thermo-gravimetric data according to an isoconversion model.

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Journal of Thermal Analysis and Calorimetry
Authors:
B. Zapata
,
J. Balmaseda
,
E. Fregoso-Israel
, and
E. Torres-García

Abstract  

Thermal degradation of orange peel was studied in dynamic air atmosphere by means of simultaneous TG-DSC and TG-FTIR analysis. According to the obtained thermal profiles, the orange peel degradation occurred in at least three steps associated with its three main components (hemicellulose, cellulose and lignin). The volatiles compounds evolved out at 150–400 °C and the gas products were mainly CO2, CO, and CH4. A mixture of acids, aldehydes or ketones C=O, alkanes C–C, ethers C–O–C and H2O was also detected. The E α on α dependence reveled the existence of different and simultaneous processes suggesting that the combustion reaction is controlled by oxygen accessibility, motivated by the high evolution low-molecular-mass gases and volatile organic compounds. These results could explain the non-autocatalytic character of the reactions during the decomposition process.

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The River Paraná is the second largest river of South America and its flood plain is covered by different kinds of forests and herbaceous vegetation. It is subject to an annual pulse of flooding; floods larger than the normal annual ones at irregular periods of few year and catastrophic extraordinary floods few times in a century. The last catastrophic flood was in 1983, followed by a short lived high flood in 1992. The catastrophic flood destroyed almost completely the herbaceous vegetation. Our hypotheses are, on the one hand, that the plant communities of this area will be restored rapidly, and on the other, that there will be a succession process which will produce a shift of communities so that, those on the higher part of the elevation gradient will encroach the ones at its lower part. We analyse, by means of the floristic composition, the effect of disturbance induced by catastrophic floods on the vegetation stability and dynamic processes, in an internal depression and pond of the riparian plant communities in an island of the River Paraná valley. The results strongly support the first hypothesis.

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Abstract  

The chemistry laboratory at the Peruvian Institute of Nuclear Energy (IPEN) has carried out a validation method for the samples of siliceous composition. At least seven variables affecting the robustness of the results were initially identified, which may interact simultaneously or individually. Conventional evaluation hereof would imply a massive number of analyses and a far more effective approach for assessment of the robustness for these effects was found in the Youden-Steiner test, which provides the necessary information by only eight analyses for each sample type. Three reference materials were used for evaluating the effects of variations in sample mass, irradiation duration, standard mass, neutron flux, decay time, counting time and counting distance.

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The floodplain herbaceous vegetation of the Paraná River (Argentina) was destroyed by a catastrophic extraordinary flood in 1982-83. The main communities were Panicum prionitis tall grasslands. According to a succession model, they were seral communities that would have evolved to hygrophilous forest. After the flood, the area was surveyed in 1984, 1988 and 2002 and analyzed with numerical methods. First, the area was invaded by a community of annual species, which were the sparse species of tall grasslands, but five years after the colonization this community disappeared and was replaced by the original tall grasslands and turfs. The tall grasslands rapid recovery and the absence of woody species support the hypothesis that this community is a stable community which was rejuvenated by catastrophic floods and was prevented to develop into woody species communities.

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