Parity of the weak Fréedericksz transition

The European Physical Journal E - Motivated by the recent experimental findings by Kumar et al. (Phys. Rev. E., 82, 011701 (2010)) in which the inverse Fréedericksz transition is observed, we...     

Structural,luminescence and biological studies of trivalent lanthanide complexes with N,N′-bis(2-hydroxynaphthylmethylidene)-1,3-propanediamine Schiff base ligand

New eight lanthanide metal complexes were prepared. These complexes were characterized by elemental analysis, molar conductivity measurements, spectral analysis (¹H NMR, FT-IR, UV–vis), luminescence and thermal gravimetric analysis. All Ln(III) complexes were 1:1 electrolytes as established by their molar conductivities. The microanalysis and spectroscopic analysis revealed eight-coordinated environments around lanthanide ions with two nitrate ligands behaving in a bidentate manner. The other four positions were found to be occupied with tetradentate L_III ligand. Tb–L_III and Sm–L_III complexes exhibited characteristic luminescence emissions of the central metal ions and this was attributed to efficient energy transfer from the ligand to the metal center. The L_III and Ln–L_III complexes showed antibacterial activity against a number of pathogenic bacteria.     

Optimizing ICA in fMRI using information on spatial regularities of the sources

Spatial independent component analysis (ICA) is a well-established technique for multivariate analysis of functional magnetic resonance imaging (fMRI) data. It blindly extracts spatiotemporal patterns of neural activity from functional measurements by seeking for sources that are maximally independent. Additional information on one or more sources (e.g., spatial regularity) is often available; however, it is not considered while looking for independent components. In the present work, we propose a new ICA algorithm based on the optimization of an objective function that accounts for both independence and other information on the sources or on the mixing model in a very general fashion. In particular, we apply this approach to fMRI data analysis and illustrate, by means of simulations, how inclusion of a spatial regularity term helps to recover the sources more effectively than with conventional ICA. The improvement is especially evident in high noise situations. Furthermore we employ the same approach on data sets from a complex mental imagery experiment, showing that consistency and physiological plausibility of relatively weak components are improved.     

Superheating of silicon nanocrystals observed by Raman spectroscopy

In the Raman spectra of silicon nanocrystals a new anomalous component was detected. Close to the usual first order Raman peak situated for a bulk crystal at 521 cm⁻¹ at room temperature, two peaks arise shifting towards lower energy and demonstrating a huge temperature increase, as measured by the ratio of the Stokes/anti-Stokes peak intensities. This behavior is dependent on the laser power and on the morphology of the nanocrystals. We can exclude, however, confinement effects, although surface enhanced phonon modes could be responsible of such superheating. Alternative explanations are also suggested and discussed.     

Impairment of mitochondrial calcium handling in a mtSOD1 cell culture model of motoneuron disease

Background  

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized by the selective loss of motor neurons (MN) in the brain stem and spinal cord. Intracellular disruptions of cytosolic and mitochondrial calcium have been associated with selective MN degeneration, but the underlying mechanisms are not well understood. The present evidence supports a hypothesis that mitochondria are a target of mutant SOD1-mediated toxicity in familial amyotrophic lateral sclerosis (fALS) and intracellular alterations of cytosolic and mitochondrial calcium might aggravate the course of this neurodegenerative disease. In this study, we used a fluorescence charged cool device (CCD) imaging system to separate and simultaneously monitor cytosolic and mitochondrial calcium concentrations in individual cells in an established cellular model of ALS.     

Microstructural and optical properties of europium-doped zinc oxide nanowires

Single-crystal Eu³⁺-doped wurtzite ZnO micro- and nanowires were synthesized by chemical vapor deposition. The nanostructures grew via a self-catalytic mechanism on the walls of an alumina boat. The structure and properties of the doped ZnO were characterized using X-ray diffraction, energy-dispersive X-ray spectroscopy, scanning and transmission electron microscopy, and photoluminescence (PL) methods. A 10-min synthesis yielded vertically grown nanowires of 50–400 nm in diameter and several micrometers long. The nanowires grew along the ±[0001] direction. The Eu³⁺ concentration in the nanowires was 0.8 at.%. The crystal structure and microstructure of were compared for Eu³⁺-doped and undoped ZnO. PL spectra showed a red shift in emission for Eu³⁺-doped (2.02 eV) compared to undoped ZnO nanowires (2.37 eV) due to Eu³⁺ intraionic transitions. Diffuse reflectance spectra revealed widening of the optical bandgap by 0.12 eV for Eu³⁺-doped compared to undoped ZnO to yield a value of 3.31 eV. Fourier-transform infrared spectra confirmed the presence of europium in the ZnO nanowires.