We show that separable, locally compact spaces with property (a) necessarily have countable extent — i.e., have no uncountable
closed, discrete subspaces — if the effective weak diamond principle ⋄(ω,ω,<) holds. If the stronger, non-effective, diamond principle Φ(ω,ω,<) holds then separable, countably paracompact spaces also have countable extent. We also give a short proof that the latter
principle implies there are no small dominating families in ω1ω.
A radiochemical method to isolate99Mo from132Te, both produced in the fission of235U, has been developed. The method is based on the formation of a cationic complex of tellurium with thiourea in acid medium which is retained (98.7±0.5)% on a cation exchange resin (Dowex 50W-X8, 100–200 mesh), while (99.8±0.05)%99Mo passes through it, due to the non-formation of such complex in the same experimental conditions. The radionuclidic purity of99Mo was found to be suitable for the preparation of99Mo–99mTc generators. The retention of99Mo on an alumina column as a function of pH was investigated and the best pH range for this purpose was found to be 4.0–4.5.
Thallium-201 was obtained by irradiating natural mercury with protons from IPEN's CV-28 Cyclotron. The chemical separation process chosen to separate thallium from mercury was an extraction chromatography technique. It consists on the passage of aqueous solutions (mobile phase), containing the elements that will be separated, through a glass column packed with an inert powder (support) saturated with the extractant (stationary phase).
Ground tire rubber (GTR) was treated by microwaves
at the same power and at different times of exposure, in order to improve
their recycling characteristics. The resulting materials were characterized
by thermogravimetric analysis (TG/DTG) and differential scanning calorimetry
(DSC). DSC analysis showed that the microwaves treatment, specially for longer
exposure times, changes the thermal behavior at low temperatures, that is
to say, changing its glass transition (Tg),
probably due to the modification in the chemical structure of the rubber.
The TG/DTG analysis showed that the thermo-oxidation behavior of the sample
after the microwaves treatment is different from the sample before the treatment.
The thermo-oxidation temperature of the devulcanized rubber is shifted to
lower temperatures, even for the rubber treated in short times.
An indicator was developed to analyze the distribution of EC support to research projects in the less favoured peripheral regions of Europe, compared to support in the economically stronger core regions. For this purpose it was assumed that in theory EC research funds and contracts would tend, on average, to be allocated according to the scientific potential of each country or region. An R & D activity is considered to contribute to socio-economic cohesion if the share obtained by the less favoured regions is larger than their share of the total European scientific potential. This assessment was made both for the total of all R & D activities and for each specific research programme. It emerges that the requirement for high scientific standards is not an obstacle to the participation of less favoured regions in Community research.
The radiopharmaceutical201TlCl(thallium-201 chloride) is used in nuclear medicine for myocardial visualization. The solution of201TlCl was prepared using201Tl obtained by irradiating a natural mercury target with protons from the CV-28 cyclotron installed at IPEN-CNEN/SP. This solution was subjected to different quality control processes required for its use in medicine. Some of these controls concerned the determination of the radionuclidic impurities:200Tl,202Tl and203Hg; the chemical identification of201Tl+; the hydrazine concentration, mercury contamination and the presence of phosphate. Furthermore. the biological distribution in Wistar rats and tests for sterility, pyrogenicity and toxicity were carried out. It was verified that the solution obtained was in the form of thallous chloride. This radiopharmaceutical gave good heart images in animals but due to the high levels of200Tl and202Tl its use in humans is not possible unless enriched202Hg is used as target in the irradiation.
Authors:E. da Silva Filho, Oberto da Silva, Maria da Fonseca, Luiza Arakaki, and C. Airoldi
A series of compounds with
composition of Ca1–xCuxHPO4,
where x varied from 0.05 to 0.5 were synthesized
by precipitation method. The compounds were characterized by elemental analysis,
X-ray diffraction, infrared spectroscopy, scanning electron microscopy, and
thermogravimetry. The chemical stabilities of solids were investigated at
several pH. Elemental analysis of copper, calcium and phosphorus are in agreement
with the proposed composition. The formation of lamellar phosphates was evidenced.
The stability of the set of compounds was better for samples with high copper
Authors:C. M. Pereira da Silva and M. C. Pedroso de Lima
Calorimetric methods are becoming important analytical tools in several areas of biochemical and biological research. In this work, a flow microcalorimetric method has been applied to the determination of dihydrofolate reductase (DHFR) activities in rat and human malignant tissue homogenates. In contrast to other commonly used DHFR analytical assays, the sensitivity of flow microcalorimetry allows direct measurements of this enzyme in crude tissue preparations. Our experimental data from rat tissue homogenates show that liver has the highest level of enzyme activity, while lung and brain have lower amounts of DHFR activity. The liver enzyme has a higher activity atpH 4.5, but the optimumpH for the lung and brain enzymes is 6.8. The substrate/cofactor molar ratio which gives the highest levels of DHFR activity is 1/1.5 for the liver and lung enzymes and 1/2.5 for brain DHFR. The DHFR in these rat tissue homogenates is activated by KCl or NaCl: in the presence of these salts (0.6M), the values of enzyme activity are 1.5–3 times higher than in their absence. Using flow microcalorimetry, very low levels of DHFR activity were also measured in human bone tumour homogenates, demonstrating the potential of the technique in the analysis of this enzyme in malignant tissues.
Authors:M. Ribeiro da Silva, C. Santos, M. Monte, and C. Sousa
MPa) molar enthalpies of formation, ΔfHm0, for
crystalline phthalimides: phthalimide, N-ethylphthalimide
and N-propylphthalimide were derived from
the standard molar enthalpies of combustion, in oxygen, at the temperature
298.15 K, measured by static bomb-combustion calorimetry, as, respectively,
– (318.01.7), – (350.12.7) and – (377.32.2)
kJ mol–1. The standard molar enthalpies of
sublimation, ΔcrgHm0, at T=298.15
K were derived by the Clausius-Clapeyron equation, from the temperature dependence
of the vapour pressures for phthalimide, as (106.91.2) kJ mol–1
and from high temperature Calvet microcalorimetry for phthalimide, N-ethylphthalimide and N-propylphthalimide
as, respectively, (106.31.3), (91.01.2) and (98.21.4)
The derived standard molar enthalpies of formation,
in the gaseous state, are analysed in terms of enthalpic increments and interpreted
in terms of molecular structure.
Authors:C. Morais, E. da Silva Filho, Oberto da Silva, Maria da Fonseca, Luiza Arakaki, and J. de P. Espínola
Vermiculite with the general formula of [Si6.85Al1.15][Mg4.68Al0.51Fe0.63]O20(OH)4Ca0.128Na0.032K0.094 was made to react with heteroaromatic amines
α-, β- and γ-picolines in aqueous solution. The products were
characterized by elemental analysis, infrared spectroscopy, X-ray diffraction
and thermogravimetry. The intercalated nanocompounds maintained the crystallinity
which changed the original interlayer distance of 1422 to 1474, 1456 and 1474
pm, for the sequence of the guest picoline molecules. Thermogravimetry data
suggested the intercalation reactions were governed by basicity of amines.