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Abstract  

This paper discusses the diffusion of Cs+ and Zn2+ ions through Nafion-117 cation exchange membrane using radiotracer technique. The validity of the Donnan's equation is checked for these ions using65Zn and137Cs radiotracers. The paper also discusses the diffusion of Cl and I anions studied by using36Cl and131I radiotracers. The probable mechanism of diffusion of these anions in the presence of Zn2+ cations is suggested.

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Abstract  

A summary of k 0-based R&D work on neutron activation analysis (NAA), internal mono standard NAA (IM-NAA) and prompt gamma-ray NAA (PGNAA) is presented. The k 0-based NAA was standardized by characterizing irradiation sites of research reactors, validated using reference materials and applied to samples of different origin. Recently IM-NAA method was developed, validated for small and large size samples and applied for the analysis of large size as well as non-standard geometry samples. Studies on PGNAA included characterization of neutron beam, determinations of detection efficiency and prompt k 0-factors, and analytical applications.

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Abstract  

A non-destructive assay technique based on prompt gamma-ray neutron activation analysis for the determination of 238U to 232Th ratio in the mixed oxide fuel materials has been established. The method uses closely spaced high energy gamma-rays in the region of 4000 keV to 4150 keV enabling it to be applied for samples of any geometry and thickness without having any correction for gamma-ray attenuations and detection efficiencies.

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Abstract  

Formation cross sections of several fission products have been determined using recoil catcher technique followed by gamma-ray spectrometry in 12C induced fission of 232Th at E lab = 72 MeV, corresponding to E cm just above the Coulomb barrier. The measured formation cross sections were used to get the mass distribution by using known charge distribution systematic. Critical data analysis was carried out to look for the signatures of transfer induced fission. However, within the experimental uncertainty of about 10%, no clear indication of transfer induced fission could be seen at this energy level. The mass distribution shows a single peaked broad Gaussian distribution with the most probable mass of 119.5±1.1 and FWHM of 40.6 mass units. The total fission cross section computed from the mass distribution curve is 771±50 mb.

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Abstract  

Using radiochemical and gamma spectrometric technique the branching fractions in the beta decay of117Cd isomers and the internal transition branching of117mIn have been established. The beta branching fraction of117gCd 117gIn was obtained as 0.86±0.06 and the value of117mCd 117gIn was found to be less than 1%. The internal transitin branching and the isomer cross-section ratio were obtained as 0.31±0.02 and 0.197±0.002, respectively. From the measured isomer cross-section ratio the spin cut-off parameter was evaluated, which agreed with the value reported in the literature.

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Abstract  

Magnesium aluminum silicate (MAS) glass samples with different concentrations of alumina (7.58 to 14.71 mol%) were prepared by melt and quench-technique. Total Mg content in the form of MgF2+MgO was kept constant at 25 mol%. MAS glass was converted into glass-ceramics by controlled heat treatment at around 950C. Crystalline phases present in different samples were identified by powder X-ray diffraction technique. Dilatometry technique was used to measure the thermal expansion coefficient and glass transition temperature. Scanning electron microscopy (SEM) was employed to study the microstructure of the glass-ceramic sample. It is seen from X-ray diffraction studies that at low Al2O3 concentrations (up to 10.5 mol%) both MgSiO3 and fluorophlogopite phases are present and at higher Al2O3 concentrations of 12.3 and 14.7 mol%, fluorophlogopite and magnesium silicate (Mg2SiO4), respectively are found as major crystalline phases. The average thermal expansion co-efficient (aavg) of the glass samples decreases systematically from 9.8 to 5.510-6C-1 and the glass transition temperature (T g) increases from 610.1 to 675C with increase in alumina content. However, in glass-ceramic samples the aavg varies in somewhat complex manner from 6.8 to 7.910-6C-1 with variation of Al2O3 content. This was thought to be due to the presence of different crystalline phases, their relative concentration and microstructure.

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The interaction between salinity (8 and 12 dS m −1 ) and three levels (40, 80 and 120 kg ha −1 ) of different forms of nitrogen (NO 3 , NH 4 + and NO 3 + NH 4 + ) were studied in Brassica juncea cv. RH-30. The plants were salinized with 8 and 12 dS m −1 at 35 and 55 days after sowing. The relative water content (RWC), water potential (Ψ w ) and osmotic potential (Ψ s ) exhibited a marked decline under salinity stress. The application of the combined form (NO 3 + NH 4 + ) of nitrogen (120 kg ha −1 ) considerably improved the water status and mitigated the adverse effect of salinity on growth. The salinity-induced osmotic effect led to stomatal closure and caused a substantial reduction in net photosynthetic rate (P N ), stomatal conductance (g s ) and transpiration rate (E) at the pre-flowering and flowering stages (45 and 65 DAS). Salinity effects were considerably moderated by additional nitrogen supply, which varied with the source of nitrogen, the level of salinity/fertilizer and the stage of plant growth. The inhibition in photosynthesis was relatively greater in ammonium-fed (NH 4 + ) than in nitrate-fed (NO 3 ) plants, while the transpiration rate was relatively lower in nitrate-fed plants grown either with or without saline water irrigation. The nitrate form of nitrogen @ 120 kg ha −1 proved best in alleviating the adverse effect of salinity on photosynthesis and transpiration at both the growth stages.

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Background

Premenopausal women show a higher incidence of orthostatic hypotension than age-matched men, but there are limited data available on sex differences in cardiovascular responses to orthostatic challenge in healthy older persons. We investigated sex differences in hemodynamic and autonomic responses to orthostatic challenge in healthy older males and females.

Materials and methods

Fourteen older healthy women and 10 age-matched men performed a sit-to-stand test (5 min of sitting followed by 5 min of standing). A Task Force® Monitor continuously measured the following beat-to-beat hemodynamic parameters: heart rate, systolic blood pressure, diastolic blood pressure, mean blood pressure, stroke index, cardiac index, and total peripheral resistance index. Cardiac autonomic activity, low-frequency (LF: 0.04–0.15 Hz) normalized (LFnuRRI) and high-frequency (HF: 0.15–0.4 Hz) normalized (HFnuRRI) components, and the ratio between LF and HF power (LF/HF) were calculated using power spectral analysis of heart rate variability.

Results

Across all hemodynamic parameters, there were no significant differences between the sexes at baseline and during standing. LFnuRRI (median: 70.2 vs. 52.3, p < 0.05) and LF/HF ratio (median: 2.4 vs. 1.1, p < 0.05) were significantly higher, whereas HFnuRRI (median: 29.8 vs. 47.7, p < 0.05) was lower among women at baseline. All other heart rate variability measures did not differ between the sexes.

Conclusions

The data indicate that older women showed higher sympathetic and lower parasympathetic activity at rest compared to age-matched men. These results are contradictory to the observations from previous studies, which showed a reduced sympathetic and enhanced parasympathetic activity in women in all ages. Further studies are required to determine the underlying mechanisms contributing to higher incidence of orthostatic hypotension in older females.

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Journal of Radioanalytical and Nuclear Chemistry
Authors:
C. Agarwal
,
A. Goswami
,
P. Kalsi
,
S. Singh
,
A. Mhatre
, and
A. Ramaswami

Abstract  

Cumulative yields of 27 fission products have been determined in 229Th(n,f) by recoil catcher technique followed by gamma-ray spectrometry. Absolute fission yields were arrived at from the fission rate measured by track etch counting method. Mass yields were obtained from the cumulative yields using the charge distribution parameters reported in the literature. The values agree well with the reported values obtained both by physical and radiochemical methods. The resulting asymmetric mass distribution shows strong fluctuation in the yields in the light and heavy wings with a periodicity of five mass units.

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Abstract  

CdZnTe detector was used to monitor the radioactivity at several locations of primary heat transport (PHT) system of the Tarapur Atomic Power Station-III & IV reactor during shut down as well as operating condition of the reactor. Dose measurements at the same locations were also carried out using a teletector. MCNP code was used to simulate the detector efficiency for the required counting geometry. The efficiencies were then used to convert the experimental count rates (cps) to corresponding activity concentration (Bq/mL) of different radionuclides in coolant water. The total dose rates in these locations were also calculated by summing up the simulated dose rates of individual γ ray energy. The simulated and the measured total dose rates were found to be in reasonably good agreement.

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