Giant magneto resistance and temperature coefficient of resistance in Sm0.55Sr0.30Ag0.15MnO3 perovskite

Silver ions substituted samarium strontium manganite (Sm0.55Sr0.30Ag0.15MnO3) pervoskite was synthesized by using respective oxides in stoichiometric ratio through solid state reaction. The as-prepared sample was characterized by various analytical techniques to confirm its formation and understand the effect of monovalent silver ions in pervoskite lattice. X-ray diffraction pattern confirms the single phase formation while grain morphology in SEM image indicates good connectivity among the grains. The enhancement in metal to insulator transition temperature shows quenched disorder and magnetoresistance phenomena. The magnetoresistance (MR) and temperature coefficient of resistance (TCR) emerge from grain growth factor and homogeneity induced by Ag+ ions in the lattice. The reduction in hysteresis loss resulted from antiferromagnetic - ferromagnetic (TN) and ferromagnetic - paramagnetic (Tc) transitions reveals the removal of disorder in perovskite lattice by Ag+ ions substitution. This increases the magnetic moment across distinct ions on the applying magnetic field. The rise in MR% (~99%) with silver doping emerging from smooth spin tunneling of the grains across the boundary and suppression of the disordered magnetic fluctuations with increase in magnetic field has been reported. The present compound exhibits the first order nature of magnetism and observed first time the highest value of TCR ~ 95%.     

Regulation of ammonia uptake inAspergillus nidulans

Summary The ammonia uptake inA. nidulans was found to be linear for about 20 min, and was proportional up to 1.5 mg/ml dry cell density. The transport of ammonia does not involve energy. Normal and biotin deficientA. nidulans showed an identical K_m-values of 10.26×10^–5 M ammonia for uptake. The uptake of ammonium ion has been shown to be regulated by the intracellular concentration of ammonia.Acknowledgment. The award of research fellowship by the Govt of India, Department of Atomic Energy, Bombay, to JDD is acknowledged.     

Riboflavin in human milk

Zusammenfassung Riboflavin ist in der Muttermilch in Form von Flavin-adenin-dinucleotid anwesend, was für eine Komplexform spricht. Ferner wurden in der Milch zwei Flavoproteine, die DPN-Cytochrom C-Reduktase und DPN-Diaphorase reduzierten, gefunden.     

Carotenogenesis: Possible mechanism of action of trisporic acid in Blakeslea trispora

Summary Stimulatory effect of trisporic acid and -ionone on carotenogenesis seems to be of a competitive nature in the minus strain of Blakeslea trispora, which suggests the same site of action. Trisporic acid may be derepressing the enzyme(s) involved in the conversion of 5-phosphomevalonate to dimethyl allyl pyrophosphate.Acknowledgment. The investigation was supported by a PL-480/FG-IN-509 grant from the Agricultural Research Service of the United States Department of Agriculture.     

Synthesis and characterization of copper foams through a powder metallurgy route using a compressible and lubricant space-holder material

In the present work, a compressible and lubricating space-holder material commonly known as “acrawax” was used to process Cu foams with various pore sizes and various porosities. The foams were processed without using binders to avoid contamination of their metal matrices. The lubricant space-holder material was found to facilitate more uniform flow and distribution of metal powder around the surface of the space holder. In addition, the use of acrawax as a space-holder material yielded considerably dense cell walls, which are an essential prerequisite for better material properties. The foams processed with a smaller-sized space holder were found to exhibit better electrical and mechanical properties than those processed with a coarser-sized space holder. The isotropic pore shape, uniform pore distribution throughout the metal matrix, and uniform cell wall thickness were found to enhance the properties pertaining to fine-pore foam samples. The processed foams exhibit properties similar to those of the foams processed through the lost-carbonate sintering process.     

Effect of ammonium ions on the growth ofAspergillus nidulans

Zusammenfassung In einer Biotin-Mangelmutante vonAspergillus nidulans wurde, verglichen mit dem der Normalkultur, ein grösserer Ammonium-Verbrauch gefunden. Dies scheint seine Ursache in der Veränderung der Permeabilität der Zellwand zu haben, deren Lipoidgehalt um 40% niedriger ist. Eine Zunahme der Transaminasen (GOT, GPT) und Glutamindehydrogenase könnte für eine höhere Proteinsynthese in Mangelstamm verantwortlich sein.

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This study was supported by a financial grant from the Council of Scientific and Industrial Research, India.     

Regulation of glucose transport in Aspergillus nidulans

Summary Pyruvate and acetate inhibited the uptake of glucose by Aspergillus nidulans; although there were significant variations in glucose uptake rate, the intracellular concentration of acetate was almost identical in biotin-supplemented, normal and deficient cells. The in vitro activity of glucose-binding protein was not affected by biotin, avidin, acetate or acetyl-CoA.J. D. Desai gratefullt acknowledges the receipt of Research Fellowship from the Govt. of India, Department of Atomic Energy, Bombay.