No abstract

We report on the dependence of the lattice parameter on thickness (t) and grain size (D) in nanogranular Nb thin films deposited on Si (100) substrates by using dc magnetron sputtering. The lattice parameter is found to exponentially increase with decreasing thickness as well as grain size. We analyze the lattice expansion in terms of the excess free volume in the grain boundaries, which is found to decrease with the grain size in large thickness limit. The thickness dependence of the lattice expansion and the grain size dependence of the excess free volume are discussed in terms of the oxygen content in the grain boundaries.

The crystal structure, magnetic and electrical transport properties of Fe 2 MnSi Heusler alloy have been investigated in the present study. It is found that the sample has been crystallized to the Fm 3m space group in the L2 1 structure. Ferromagnetic to paramagnetic phase transition (Curie temperature) has been observed at around 325 K, which is further confirmed by employing the Arrott plot technique. Critical exponent values (α, β, γ) have been obtained by employing the Kouvel-Fisher method and Widom-scaling relation; confirming the second order phase transition observance in the magnetic transition region. These values suggest that the magnetic transition follows the mean field theory. Furthermore, the electrical resistivity and spontaneous magnetization data analysis in the low-temperature region ensures the presence of magnon in the system. Detailed analysis of the resistivity data for 50 K to 400 K reveals a metal to semimetal transition at around 325 K, which is close to the Curie temperature. A correlation between electrical transport and magnetic ordering has been observed in the Fe 2 MnSi alloy.

Recent studies involving individual neurons in the seizure focal and surrounding areas have established heterogeneous firing patterns in single cells. However, the patterns become more homogeneous approaching the seizure offset. In this article, we show that similar observations are possible from intracranial recording if the right quantitative or engineering techniques are used. We have observed an increase in Hilbert transformation-based phase synchronization in the focal electrocorticoencehalogram (ECoG) in the gamma band (30-40 Hz) towards the end of the majority of focal epileptic seizures. An amplitude correlation measure shows an enhanced principal component (and hence enhanced correlation among the channels involved) approaching the offset of the large majority of seizures. Surprisingly, there are seizures which show the enhanced phase synchronization approaching offset but no enhanced amplitude correlation during the same period and vice versa. This study shows that suitable computational tools can sometimes compensate for more expensive and technologically demanding data acquisition systems. A possible neurophysiological explanation behind the observed phenomenon is also presented.

Nanocrystalline Au(x)Cu(1-x) films were synthesized by depositing Cu/Au/Cu multilayer in nanocrystalline thin film form with requisite thickness of individual layers onto fused silica substrates by high pressure sputtering technique. The absorbance spectra showed only one surface plasmon peak for all the compositions with the exception that the peak position did not indicate gradual shift as gold concentration was increased. Peak position for the two compositions corresponding to the two superlattice structures, AuCu3 and AuCu, deviated significantly from linear variation. The experimental results have been discussed in light of the existing Mie theory and the Core-shell model.