Magnetoresistance of metallic perovskite oxide LaNiO3−δ_{3-\delta}

We report a study of the magnetoresistance (MR) of the metallic perovskite oxide LaNiO$_{3-\delta}$ as a function of the oxygen stoichiometry $\delta$ ($\delta \leq$ 0.14), magnetic field (H $\leq 6T$) and temperature (1.5K $\leq$ T $\leq$ 25K). We find a strong dependence of the nature of MR on the oxygen stoichiometry. The MR at low temperatures change from positive to negative as the sample becomes more oxygen deficient (i.e, $\delta$ increases). Some of the samples which are more resistive, show a resistivity minima at $T_{min}$ $\approx$ 20K. We find that in these samples the MR is positive at T > $T_{min}$ and negative for T < $T_{min}$. We conclude that in the absence of strong magnetic interaction, the negative MR in these oxides can arise from weak localisation effects.Comment: 10 pages in REVTeX format, 4 eps fig

Change in the room temperature magnetic property of ZnO upon Mn doping

We present in this paper the changes in the room temperature magnetic property of ZnO on Mn doping prepared using solvo-thermal process. The zero field cooled (ZFC) and field cooled (FC) magnetisation of undoped ZnO showed bifurcation and magnetic hysteresis at room temperature. Upon Mn doping the magnetic hysteresis at room temperature and the bifurcation in ZFC-FC magnetization vanishes. The results seem to indicate that undoped ZnO is ferromagnetic while on the other hand the Mn doped ZnO is not a ferromagnetic system. We observe that on addition of Mn atoms the system shows antiferromagnetism with very giant magnetic moments.Comment: 5 figure

Phytochemical screening and antimicrobial activity of Capsicum chinense Jacq.

The present study investigated on the comparative evaluation of the extraction, quantification, phytochemical and antimicrobial activity of Capsaicin from acetone and acetonitrile extracts of Capsicum chinense Jacq. The polar aprotic solvent extracts showed high amount of Capsaicin with pungency level of 1,529,500 Scoville Heat Units. The Thin layer chromatography method is providing a fingerprint of plant extract. The Capsaicin extracted in the solvents on TLC chromatogram was viewed under UV 254 nm and UV 366 nm and documented. The extraction and estimation of chlorophyll and Carotenoids were also performed for the plant sample following standard procedure. Phytochemical analysis shows that acetone and acetonitrile extract of callus, leaf, shoot, fruit and seed which shows abundant presence of alkaloids, flavonoids, phenols, saphonins etc. The acetone and acetonitrile extract showed maximum zone of inhibition of Klebsiella pneumonia and Staphylococcus aureus against the gram positive and gram negative bacteria respectively through agar well diffusion method. The acetone and acetonitrile extract was found to be more effective at different concentration against all the tested bacteria and fungi. The results revealed that the Capsaicin and other secondary metabolites present in the acetone and acetonitrile extract of Capsicum chinense would contribute for the further extraction and purification of capsaicin as an antimicrobial agent