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- Author or Editor: I. Jones x
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Abstract
The rate of removal and uptake of guests into layered and porous materials is important in many areas of materials chemistry. Here we report on the use of atmospheric thermogravimetry linked to a mass spectrometer (TG-MS) to investigate the thermal characteristics of three different solids. We show that (i) the desorption of cyclohexylamine from the surface of a pillared acid activated smectite clay occurs in two stages, indicating two possible acidic binding sites, (ii) TG-MS is an extremely sensitive technique for probing progressive anion exchange of lithium aluminium layered double hydroxides, (iii) on heating, the perhydrate 4Na2SO4·NH4Cl·2H2O2 releases H2O2 intact.
Possible interactions between nitric oxide donors, reactive oxygen species and anti-oxidative defence enzymes led us to determine the activities of anti-oxidative defence enzymes in isolated uterine smooth muscle before and after spontaneous rhythmic activity ex vivo. For our experiments we used isolated uteri from female Wistar rats. Our results showed an increase in total superoxide dismutase (SOD) and Mn SOD activities in uterine smooth muscle after spontaneous contractions when compared with non-exercised uterine smooth muscle. The activity of catalase (CAT) and glutathione preoxidase (GSH-Px) were also increased. No statistically significant changes in the activities of glutathione reductase (GR) and CuZn SOD were found. It is known that an organism's anti-oxidative defence system (guarding against excessive reactive oxygen species generation) requires balanced increments in its individual anti-oxidative enzyme activities rather than increases in the activity of only some enzymes without increases in others. Thus, we may conclude that some adaptive responses are found in exercised uterine smooth muscle but are not complete. Therefore, our results indicate that changes in anti-oxidative enzyme activities may influence the results of the examination of substances ex vivo.
Abstract
The conditions under which the Poisson statistical density function adequately describes the counting of a radioactive isotope are examined and found that for counting processes where λt≳1, where λ is the decay constant and t the counting period, one of the fundamental properties, namely the condition of stationarity, is violated rendering application of Poisson statistics invalid. The Ruark-Devol statistical density function, a binomial, is instead shown to be satisfactory since it is capable of describing radioactive disintegration where the only fundamental property is independence and its use is recommended in both activation analysis and medical imaging when the half-life of the isotope of interest is short compared to the period of observation. It is pointed out that no satisfactory expression incorporating the distortion produced by dead-time on the statistical density function has yet been derived but the practical implications of the adoption of the Ruark-Devol function are discussed with respect to standard deviation and precision of the measurement. It is shown how the application of the Poisson statistical density function, under conditions of tλ≳1, is not only invalid but also overestimates the standard deviation significantly.
Abstract
A method for the quantitative determination of small amounts of protein samples was developed employing neutron activation analysis. Current methods of protein concentration determination are severely limited as a result of differences in the specific characteristics of each protein. Silver binding has been used as a sensitive colorimetric method to indicate the presence of protein. However, silver-protein complexes can have a variety of absorbance spectra unique to each protein, which complicate the analysis. Various amounts of specific proteins were equilibrated in an excess of silver nitrate prior to the reduction of the silver by the addition of NaBH4, HCHO, and NaOH. The protein-silver complex was rapidly separated from the unbound silver by centrifugation chromatography and the amount of bound silver was determined by INAA. The amount of silver was proportional to the amount of protein present in each sample. When the silver was not reduced prior to removal of the unbound silver by chromatography, only negligible amounts of silver remained bound to the protein. The stoichiometry of bound silver to protein on a molar basis showed relatively small differences for the proteins that were examined. This ratio was found to depend on the conditions of the binding and reduction of the silver. The results suggest that the binding of silver is not specific to any charged or polar groups on these proteins and may, therefore, provide a means of determination of the concentration of protein that has general application for all proteins.
Abstract
The object of this paper is to give details of a production method for123I, now in routine use at Harwell. We employ the (p, 5n) reaction, irradiating a liquid target of di-iodomethane (CH2I2) spiked with additional iodine, with 58 MeV protons. A yield of ∼9 mCi/μAh is obtained; the only detectable radionuclidic impurity is125I, present to the extent of ∼0.15% by activity at the time of separation of Xe from I.
