Simultaneous determination of hafnium and zirconium in low grade uranium ores using INAA

A non-destructive neutron activation analysis technique has been developed for the determination of hafnium and zirconium in low grade uranium ores. In order to calculate the fission contribution of²³⁵U, thermal neutron absorption cross-section /_a/ for⁹⁴Zr has been determined. The study shows that 1 g of uranium produces the same activity as from 10.03 g of zirconium. Based on this fact, the degree of interferences have been calculated for each sample and the necessary corrections have been applied. The values have been compared with the reported IAEA and NBS values.     

BASF 13.338 INDUCED CHANGES IN STRUCTURE and FUNCTION OF THE PHOTOSYNTHETIC APPARATUS OF WHEAT SEEDLINGS

Abstract— Growing wheat seedlings in the presence of BASF 13.338 [4-chloro-5-dimethylamino-2-phenyl-3(2H)pyridazinone], a PS II inhibitor of the pyridazinone group, brought about notable changes in the structure and functioning of photosynthetic apparatus. In BASF 13.338 treated plants, there was a decrease in the ratio of Chi a/Chl b, an increase in xanthophyll/carotene ratio and an increase in the content of Cyt b 559 (HP + LP). Chl/p700 ratio increased when measured with the isolated chloroplasts but not with the isolated PS I particles of the treated plants. The SDS-PAGE pattern of chloroplast preparations showed an increase in the CPII/CP I ratio. The F685/F740 ratio in the emission spectrum of chloroplasts at -196°C increased. The difference absorption spectrum of chloroplasts between the control and the treated plants showed a relative increase of a chlorophyll component with a peak absorption at 676 nm and a relative decrease of a chlorophyll component with a peak absorption at 692 nm for the treated plants. The excitation spectra of these chloroplast preparations were similar. Chloroplasts from the treated plants exhibited a greater degree of grana stacking as measured by the chlorophyll content in the 10 K pellet. The rate of electron transfer through photosystem II at saturating light intensity in chloroplast thylakoids isolated from the treated plants increased (by 50%) optimally at treatment of 125 μM BASF 13.338 as compared to the control. This increase was accompanied by an increase in (a) I₅₀ value of DCMU inhibition of photosystem II electron transfer; (b) the relative quantum yield of photosystem II electron transfer; (c) the magnitude of C550 absorbance change; and (d) the rate of carotenoid photobleaching. These observations were interpreted in terms of preferential synthesis of photosystem II in the treated plants. The rate of electron transfer through photosystems I and through the whole chain (H₂O → methyl viologen) also increased, due to an additional effect of BASF 13.338, namely, an increase in the rate of electron transfer through the rate limiting step (between plastoquinol and cytochrome f). This was linked to an enhanced level of functional cytochrome f. The increase in the overall rate of electron transfer occurred in spite of a decrease in the content of photosystem I relative to photosystem II. Treatment with higher concentrations (> 125 μM) of BASF 13.338 caused a further increase in the level of cytochrome f, but the rate of electron transfer was no greater than in the control. This was due to an inhibition of electron transfer at several sites in the chain.     

Structure-defined c60/polymer colloids supramolecular nanocomposites in water

We report a new supramolecular method for the synthesis of well-defined pristine C 60/polymer colloid nanocomposites in water. The colloids include polymer micelles and emulsion particles. To a polymer colloid solution in water or alcohol, we introduced C 60 solution in a solvent that is miscible with water or alcohol. After the two solutions mixed, polymer colloids and C 60 spontaneously assembled into stable colloidal nanocomposites. After a dialysis process, a nanocomposite dispersion in pure water was obtained. As characterized by DLS and (Cryo-)TEM, the nanocomposites have a core-shell structure with C 60 aggregated on the surface of emulsion particles or micellar cores. The resulting nanocomposites have many potential applications such as biomedicals and photovoltaics.     

Gas Chromatography–Mass Spectrometry Determination of Pregabalin in Human Plasma Using Derivatization Method

A gas chromatography–mass spectrometry method for the determination of pregabalin in human plasma is described. The procedure involves precipitation of protein, liquid–liquid extraction with ethylene glycol monomethyl ether, and derivatization with 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide in the presence of N-hydroxysuccinimide as additive. Separation was attained on HP column (30 m × 0. 25 mm ID, 0.25 μm) coupled with mass spectrometric detector using electron impact selected ion monitoring. The assay showed an excellent linearity in the concentration range of 0.36–10 μg mL^?1 with correlation coefficient (r²) values of 0.999. The intra- and inter-day assay variations for three different concentration levels were less than 10%. The limit of quantification was detected at 0.36 μg mL^?1. The method is highly specific, precise, accurate, and reproducible and could also be applied for the determination of pregabalin in human plasma.     

Thermoanalytical investigations on the sol-gel synthesis of YBa2Cu3O72212;δ

The high temperature superconducting compound YBa₂Cu₃O_72212; (Y-123) is synthesised by sol-gel process using various precursors viz., acetate, acetate-citrate, nitrate-citrate and acrylamide. The phase purity of the final product depends on the homogeneity of the gels which intern depends on the bonding of the metal ions in the gels. The samples prepared by acrylamide and nitrate-citrate gel routes yielded phase pure Y-123 compound with better superconducting properties. The mechanism of formation of Y-123 in all these four gel routes is established by characterising the gels and intermediate phases using TG, DTA and XRD techniques. Kinetic analysis is carried out on the mass loss data using the method proposed by Phadni's and Deshpande. Avrami-Erofeev nuclei growth in case of acrylamide, diffusion controlled process in nitrate-citrate and phase boundary reaction mechanisms in case of acetate-citrate gels are found to be responsible for the formation of Y-123 phase.The authors are grateful to Dr. Baldev Raj, Director, Metals and Materials Group, for his constant encouragement and support. We thank Prof. G. V. Subba Rao, Director, Central Electrochemical Research Institute, Karaikudi for his keen interest in this work. Thanks are also due to Dr. Sundaram, CECRI, Karaikudi for his help in thermal analysis experiments.     

Determination of Trace Elements in Integrated Human Diet for Dietary Assessment

Abstract

Neutron activation analysis in combination with atomic absorption spectrometry was utilized for the determination of 21 elements in integrated diet samples of the inhabitants of the Rawalpindi/Islamabad area. The study was carried out to determine prevailing concentration levels of trace elements nutrition, inadequacy, imbalances and toxicity. This data will serve as baseline values and will be helpful to monitor the degree of future contamination from foreign chemicals. The dietary intake values were also estimated and compared with the reported daily intake values. In general, the diets studied are adequate source of nutrient elements. The toxic elements intake through all the diet samples are within the safety limits.     

Rogue waves in multi‐pair plasma medium

The non‐linear propagation of ion acoustic (IA) waves, which is governed by the non‐linear Schrödinger equation, in multi‐pair plasmas (MPPs) containing adiabatic positive and negative ion fluids as well as non‐extensive (q‐distributed) electrons and positrons is theoretically investigated. It is observed that the MPP under consideration supports two types of modes, namely fast and slow IA modes, and the modulationally stable and unstable parametric regimes for the fast and slow IA modes are determined by the sign of the ratio of the dispersive coefficient to the non‐linear one. It is also found that the modulationally unstable regime generates highly energetic IA rogue waves (IARWs), and the amplitude as well as the width of the IARWs decreases with increase in the value of q (for both q > 0 and q < 0 limits). These new striking features of the IARWs are found to be applicable in the space (i.e., D‐region [], and F‐region [H⁺, H^?] of the Earth's ionosphere) and laboratory MPPs (i.e., fullerene [C⁺, C^?]).     

Fe(II)LSCo(III)LS]2 ⇔ [Fe(III)LSCo(II)HS]2 photoinduced conversion in a cyanide-bridged heterobimetallic molecular square

The self-assembly of [Fe(III){B(pz)(4)}(CN)(3)](-) and [Co(II)(bik)(2)(S)(2)](2+) affords the diamagnetic cyanide-bridged [Fe(II)(LS)Co(III)(LS)](2) molecular square which is converted into the corresponding magnetic [Fe(III)(LS)Co(II)(HS)](2) species under light irradiation at relatively low temperatures.