845 research outputs found
Size-dependent electronic-transport mechanism and sign reversal of magnetoresistance in Nd0.5Sr0.5CoO3
A detailed investigation of electronic-transport properties of Nd0.5Sr0.5CoO3
has been carried out as a function of grain size ranging from micrometer order
down to an average size of 28 nm. Interestingly, we observe a size induced
metal-insulator transition in the lowest grain size sample while the bulk-like
sample is metallic in the whole measured temperature regime. An analysis of the
temperature dependent resistivity in the metallic regime reveals that the
electron-electron interaction is the dominating mechanism while other processes
like electron-magnon and electron-phonon scatterings are also likely to be
present. The fascinating observation of enhanced low temperature upturn and
minimum in resistivity on reduction of grain size is found due to
electron-electron interaction (quantum interference effect). This effect is
attributed to enhanced disorder on reduction of grain size. Interestingly, we
observed a cross over from positive to negative magnetoresistance in the low
temperature regime as the grain size is reduced. This observed sign reversal is
attributed to enhanced phase separation on decreasing the grain size of the
cobaltite
Development of an Advanced Engineering Polymer from the Modification of Nylon 66 by e-Beam Irradiation
When Nylon 66 was irradiated by an optimum dose of e-beam in presence of polyurethane as impact modifierin combination with triallyl isocyanurate as cross-linker, a superior performance was observed for the irradiatednylon 66. Significant improvement of properties, such as hardness, tensile strength, flexural modulus and impactstrength was obtained on radiation processing of nylon 66 by e-beam. More interestingly, percent water absorptionof such irradiated nylon 66 was reduced substantially. Improvement of mechanical properties and reduction of waterabsorption of irradiated nylon 66 were due to the cross-linking of the polymer system. Increase of cross-linkingwith dose of e-beam was verified by the increased gel content at higher doses. Irradiated nylon 66 showed betterdimensional stability than those achieved with pristine nylon 66. The increase in dimensional stability may beattributed to reduction in crystallinity with increasing dose of e-beam as revealed by DSC studies.Defence Science Journal, Vol. 64, No. 3, May 2014, pp. 281-289, DOI:http://dx.doi.org/10.14429/dsj.64.732
The interparticle interaction and crossover in critical lines on field-temperature plane in PrSrMnO nanoparticles
The magnetic properties and the effects of interparticle interaction on it
have been studied in nanoparticles of half doped PrSrMnO.
Three samples consisting of nanoparticles of different average particle sizes
are synthesized to render the variation in interparticle interaction. Though
all the samples crystallize in the same structure to that of their bulk
compound, the low temperature ferromagnetic-antiferromagnetic transition, which
is present in bulk compound, is not evident in the nanoparticles. Linear as
well as nonlinear ac susceptibility coupled with dc magnetic measurements have
shown the superparamagnetic behavior of these nanoparticles where the blocking
temperature increases with the increasing particle size. Presence of
interparticle interaction is confirmed from the temperature variation of
coercive field and the analysis of frequency dependent ac susceptibility. We
have identified the nature of this interaction to be of dipolar type, and show
that its strength decreases with the increasing particle size. The effect of
this dipolar interaction on magnetic properties is intriguing as the compounds
exhibit crossover from de Almeida-Thouless to Gabay-Toulouse like critical
lines on field-temperature plane above their respective interaction field. In
agreement with theoretical prediction, we infer that this crossover is induced
by the unidirectional anisotropy arising from interparticle interaction, and
this is confirmed from the presence of exchange bias phenomenon.Comment: To appear in Phys. Rev.
Two photon excitable graphene quantum dots for structured illumination microscopy and imaging application: lysosome specificity and tissue-dependent imaging
Two-photon active Graphene Quantum Dots (GQDs) are obtained from extracts of the neem root. These biocompatible GQDs are found to be suitable for structured illumination microscopy. Two-photon microscopy ensured lysosome specificity of GQDs in live cells and confocal luminescence microscopic studies showed tissue-dependent localization of GQDs in Zebrafis
Sizing Of Trousers and Shirts for Indian Army Personnel : An Anthropometric Application
The paper describes how anthropometric data obtained on 4400 Indian Army personnel was utilized in evolving size rolls for the trousers and shirts. A bivariate frequency distribution of abdominal circumference and abdominal height indicated that the data could be grouped into 14 sizes and such grouping could provide good fitting trousers to 92.52 percent of the troops. For shirts, the bivariate frequency distribution of chest circumference and arm length grouped army personnel again into 14 sizes. Such grouping encompassed 84.22 percent of the personnel studied. An extra large size has been provided for those not covered by these 14 size. In this study, 95 army officers’ clothing measurements essential for their good fitting trousers and shirts were taken along with the relevant body measurements. A stepwise linear regression analysis was also carried out to predict clothing measurements from body measurements. These regression equations were used to work out the dimensions of the trousers and shirts for different sizes from the classified anthropometric data
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