Electrical conduction in some gamma irradiated and unirradiated two-dimensional compounds, (CH2)8(NH3)2Co1−x Zn x Cl4

The electrical conductivity of -irradiated and unirradiated complexes of (CH₂)₈(NH₃)₂Co_1–x Zn _x Cl₄ (x=0, 0.2, 0.4, 0.6, 0.8 and 1) was measured in the temperature range from 300 K to a temperature near the melting points of the samples. The results showed an increase in the conductivity values with increasing concentration of zinc ions in the samples. Both differential scanning calorimeter (DSC) and conductivity measurements showed the presence of many phase transitions in each of the complexes investigated. The results of irradiated compounds with a composition of 0x0.8 showed an increase in the conductivity values, at lower temperatures, compared with the values of unirradiated ones. For compositionx=1 no change in the conductivity data has been observed after irradiation. The effect of change in the chemical composition and irradiation on the conductivity data are discussed.     

Electrical conduction in γ-irradiated and unirradiated Fe3O4, CdFe2O4 and Co x ZN1−x Fe2O4 (0 ⩽x ⩽ 1) ferrites

The electrical conductivity of -irradiated and unirradiated finely divided ferrites of composition Fe₃O₄, CdFe₂O₄ and Co _x Fn_1–x Fe₂O₄(0 x 1) was studied in a nitrogen atmosphere as a function of temperature. Fe₃O₄, ZnFe₂O₄ and CdFe₂O₄ showed n-type conduction, whereas CoFe₂O₄ showed p-type conduction. For Co _x Zn_1-x Fe₂O₄ it was found that the type of conduction varies with the composition of ferrites. The electrical conduction in Fe₃O₄, and Co _x Zn_1–x Fe₂O₄(0 x 1) was explained by a hopping mechanism, whereas the conduction in ZnFe₂O₄ and in CdFe₂O₄ is interpreted on the basis of the transfer of charge carriers through cation vacancies present on octahedral sites. The effect of -irradiation on the conductivity, activation energy, charge carriers and the conduction mechanism is discussed.     

Aflatoxins in composite spices collected from local markets of Karachi,Pakistan

This survey was carried out to evaluate the occurrence of total aflatoxins (AFs; B₁+B₂+G₁+G₂) in unpacked composite spices. A total of 75 samples of composite spices such as biryani, karhai, tikka, nihari and korma masalas were collected from local markets of Karachi, Pakistan, and analysed using HPLC technique. The results indicated that AFs were detected in 77% (n = 58) samples ranging from 0.68 to 25.74 µg kg^?1 with a mean of 4.63 ± 0.95 µg kg^?1. In 88% (n = 66) samples, AFs level was below the maximum limits (ML = 10 µg kg^?1) as imposed by EU. Furthermore, 61% (n = 46) tested samples contained AFs level between 1 and 10 µg kg^?1, 9% (n = 7) exhibited AFs contamination ranged 10?20 µg kg^?1 and only 3% (n = 2) of the investigated samples contained AFs levels higher than the ML of 20 µg kg^?1 for total aflatoxins as set by the USA. It was concluded that there is need to establish a strict and continuous national monitoring plan to improve safety and quality of spices in Pakistan.