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  • Author or Editor: A.J. Das x
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Abstract  

Accuracy and precision of instrumental neutron activation analysis, based on short-lived radionuclides, are considered. Equations are derived for both quantitives as a function of concentration and features of the γ-ray spectrum. The determination of vanadium by way of52V(T=3.75 min) is used as an example.

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Abstract  

The detection of “plated” specimens (ancient falsifications consisting of a copper core with a silver outer layer) amidst a great collection of silver coins was performed by non-destructive neutron analysis. The “plating” can be detected by measuring the Ag/Cu ratio. In practice it is more convenient to determine the Au/Cu ratio which is proportional to it, A short activation in a low thermal neutron flux is sufficient for this purpose. Consequently the induced activity of the long-lived110mAg is small. The necessary correction for self-absorption on the measured ratio is small. A series of 2000 coins was analysed in this way.

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Abstract  

The applicability of a 400 kV neutron generator in the elemental analysis of dry biological material is considered. Data for the specific count-rates of 66 elements are given. A procedure for the determination of N, Mg, Si, P, K and Ca is described. The results for three Standard Reference Materials and some samples are given.

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Abstract  

A simple procedure for the correction of residual dead-time losses in γ-ray spectrometry of mixtures of short-lived radionuclides is given. It is based on the value of the total deadtime at the beginning of the measurement and three constants which are characteristics for a given matrix. The application to the instrumental neutron activation analysis of fluorine and sodium in bone is given as an exaple.

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Abstract  

Two single doses of X-ray radiation, i.e., 75 cGy and 4.0 Gy were applied on male Swiss albino mice. Quantitative changes in concentrations of trace metals like copper, zinc, cadmium and chromium in the whole body irradiated mice skin at several post-irradiated time intervals were studied in comparison to that of control animals. Observations indicate that irradiation induce redistribution of trace metals studied in skin at different post-irradiation time intervals.

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Abstract  

The synthesis of hydrotalcite-like compounds (HTlcs) containing Mg, Al and Ti using titanium-rich bauxite as one of the starting materials was described. The HT precursors and their calcined products were characterized by powder X-ray diffraction, TG-TDA, FT-IR and surface area measurements. Although the above characterization indicated the formation of hydrotalcite-like structure with good crystallinity, the presence of Ti4+ in the brucite layer was not confirmed. Calcination at 450 °C gave rise mainly to poorly crystalline MgO and amorphous mixed oxides, which can be reconstructed to their original structure by exposure to an aqueous solution. The calcined sample containing titanium showed relatively high adsorption capacity for fluoride and

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as compared to that without titanium.

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Abstract  

A neutron activation analysis method for the determination of Se(IV) in natural waters is described. It is based on the coprecipitation of the metal dibenzyldithiocarbamate with phenolphthalein. The precipitate is collected on 0.45 m membrane filters and selenium is determined by instrumental neutron activation. A Se(IV) radiotracer (75Se, T=120 d) was used to establish optimum conditions and to evaluate the chemical yield. Samples of sea and canal water were analyzed.

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Abstract  

An attempt is made to quantify the influence of wall-adsorption in trace analysis. The retention of the aqueous phase is defined in terms of three dimensionless parameters: surface capacity/total amount in the solution, concentration of adsorbable species/total concentration, ratio of adsorption parameters. Based on the measurement of the adsorption parameters by radiotracer experiments and the initial conditions the final retention may be calculated. Time dependence may be included.

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Lactic acid bacteria were isolated from tungrymbai, a traditional fermented soybean product of Meghalaya, India and assessed for their probiotic properties. Survival under simulated gastric conditions was tested and five acid tolerant strains were selected. By using 16S rDNA sequencing, these isolates were confirmed to be Enterococcus species. The strains exhibited good survivability in high concentrations of bile salts. The strains were susceptible to antibiotics and they were also found to inhibit growth of Staphylococcus aureus and Escherichia coli. The strains were gelatinase negative and non-haemolytic. The strains also assimilated cholesterol up to a certain level. The study confirmed that all identified five strains have in vitro probiotic properties.

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Abstract  

The interferences by uranium fission on the determination by neutron activation analysis of Zr, Mo, Ru, La, Ce, Nd and Sm are investigated for the Argonaut-type Low Flux Reactor at ECN, Petten, The Netherlands. In addition, the spectral interference of the determination of Sm by239Np is considered. The experimental values for fission yields are found to be in good agreement with calculated values based on recent cross-section compilations.

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