Microstructural investigation of magnetic CoFe2O4 nanowires inside carbon nanotubes by electron tomography

Magnetic nanowires of CoFe 2O4 were casted inside the channel of multiwall carbon nanotubes by mild chemical synthesis. A detailed investigation of these nanowires was performed using mainly the electron tomography technique; this study provides a complete characterization of their microstructure in terms of the spatial organization and the size distribution of individual particles forming the nanowire as well as its residual porosity. In particular, we have shown that the size of the CoFe 2O4 monocrystalline particles is closely dependent on the location of the particle within the nanotube, i.e., small particles close to the tube tip (5 nm) and bigger particles inside the tube channel (15 nm). As the theoretical critical size for superparamagnetic relaxation in CoFe 2O4 is estimated within the range of 4-9 nm, the size distribution obtained by 3D-TEM agrees with the Mossbauer study that suggests the presence of two different magnetic components inside the nanowire. We have shown also that, by using this preparation method and for this internal diameter of nanotube, the CoFe 2O4 nanowire exhibits a continuous structure along the tube, has a residual porosity of 38%, and can fill the tube at only 50%, parameters which influence in a significant manner the magnetic behavior of this system.     

Gender and education impact on brain aging: A general cognitive factor approach.

In cognitive aging research, the study of a general cognitive factor has been shown to have a substantial explanatory power over the study of isolated tests. The authors aimed at differentiating the impact of gender and education on global cognitive change with age from their differential impact on 4 psychometric tests using a new latent process approach, which intermediates between a single-factor longitudinal model for sum scores and an item-response theory approach for longitudinal data. The analysis was conducted on a sample of 2,228 subjects from PAQUID, a population-based cohort of older adults followed for 13 years with repeated measures of cognition. Adjusted for vascular factors, the analysis confirmed that women performed better in tests involving verbal components, while men performed better in tests involving visuospatial skills. In addition, the model suggested that women had a slightly steeper global cognitive decline with oldest age than men, even after excluding incident dementia or death. Subjects with higher education exhibited a better mean score for the 4 tests, but this difference tended to attenuate with age for tests involving a speed component. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Capillary electrophoresis as a second dimension to isoelectric focusing for peptide separation

Capillary zone electrophoresis and carrier ampholytes based capillary electrophoresis have been used as a second separation step to Off-Gel isoelectric focusing for the analysis of complex peptide mixtures. A tryptic digest of four proteins (bovine serum albumin, beta-lactoglobulin, horse myoglobin, cytochrome c) has been chosen as a peptide test mixture. After assessment of different modes of capillary electrophoresis as a second dimension to Off-Gel isoelectric focusing, the optimized two-dimensional platforms provide a degree of orthogonality comparable to state-of-the-art multidimensional liquid chromatography systems as well as a practical peak capacity above 700.     

Remote monitoring of multi-gas mixtures by passive standoff Fourier transform infrared radiometry

The passive remote monitoring of multi-gas mixtures was experimentally investigated using Fourier transform infrared (FT-IR) radiometry. The spectral radiance data were collected using a dual-port radiometrically balanced interferometer for a variety of multi-gas plumes at a standoff distance of 60 m. Two basic sets of mixtures were studied. The first set corresponded to mixtures consisting of three gases with no overlapping spectral bands (C(2)H(2), C(2)H(4), and R14). The second set corresponded to mixtures of three gases having significant spectral overlap (C(2)H(4), R114, and R134a). For each mixture the flow rates of individual constituents were adjusted to yield specific constituent optical-density (CL) ratios. These ratios were compared to the optical-density ratios retrieved from the measured infrared radiance spectra. Results of this study indicated that for both sets of multi-gas mixtures the optical-density ratios retrieved by the passive remote monitoring technique were in good agreement with those derived from the release flow rates, provided that a simple correction scheme was introduced to compensate for the limited accuracy of the fast radiance model implemented in the monitoring algorithm.     

Real-time spatial processing of sounds for music, multimedia and interactive human-computer interfaces

This paper gives an overview of the principles and methods for synthesizing complex 3D sound scenes by processing multiple individual source signals. Signal-processing techniques for directional sound encoding and rendering over loudspeakers or headphones are reviewed, as well as algorithms and interface models for synthesizing and dynamically controling room reverberation and distance effects. A real-time modular spatial-sound-processing software system, called Spat, is presented. It allows reproducing and controling the localization of sound sources in three dimensions and the reverberation of sounds in an existing or virtual space. A particular aim of the Spatialisateur project is to provide direct and computationally efficient control over perceptually relevant parameters describing the interaction of each sound source with the virtual space, irrespective of the chosen reproduction format over loudspeakers or headphones. The advantages of this approach are illustrated in practical contexts, including professional audio, computer music, multimodal immersive simulation systems, and architectural acoustics.     

A Practical Analysis of Clustering Strategies for Hierarchical Radiosity

The calculation of radiant energy balance in complex scenes has been made possible by hierarchical radiosity methods based on clustering mechanisms. Although clustering offers an elegant theoretical solution by reducing the asymptotic complexity of the algorithm, its practical use raises many difficulties, and may result in image artifacts or unexpected behavior. This paper proposes a detailed analysis of the expectations placed on clustering and compares the relative merits of existing, as well as newly introduced, clustering algorithms. This comparison starts from the precise definition of various clustering strategies based on a taxonomy of data structures and construction algorithms, and proceeds to an experimental study of the clustering behavior for real-world scenes. Interestingly, we observe that for some scenes light is difficult to simulate even with clustering. Our results lead to a series of observations characterizing the adequacy of clustering methods for meeting such diverse goals as progressive solution improvement, efficient ray casting acceleration, and faithful representation of object density for approximate visibility calculations.     

Transport Properties and Fluctuations in Underdoped GdBa2Cu3O x Thin Films

We have investigated the transport properties, resistivity and Hall effect, in a series of underdoped GdBa ₂ Cu ₃ O _x thin films grown by off-axis magnetron sputtering. We find a systematic correlation between the critical temperature T _c and the inverse Hall constant R _H ^-1 , related, in simple models, to the carrier concentration n. Our experimental thin film T _c (n) data are in good agreement with the temperature-doping phase diagram obtained for YBa ₂ Cu ₃ O _x single crystals. By measuring the activation energies in the liquid vortex phase, and by using a 2-dimensional model for vortex dynamics, we have extracted the penetration depth of these samples, and studied the relation between the carrier concentration and the superfluid density to probe the role of phase fluctuations on superconductivity.     

Effects of the surface boundary on the determination of the optical properties of a turbid medium with time-resolved reflectance

Solutions of the time-dependent diffusion equation were developed to take into account the depth of the source and the detector inside a semi-infinite medium. These solutions permitted an evaluation of optical properties at different depths below the surface by fitting time-resolved data. Measurements were performed on liquid optical phantoms with optical fibers for delivering and collecting light. A time-correlated single-photon-counting chain was used for electronic detection. The determination of optical properties underlines the continuity between the surface model and the infinite model and shows the depth at which the derived solutions can be applied.     

Study of ethanol-induced conformational changes of holo and apo alpha-lactalbumin by spectroscopy and limited proteolysis

This study was performed to contribute to the analysis of alpha-lactalbumin "molten globule" state by using spectral and proteolysis techniques. Samples of holo and apo alpha-lactalbumin in the presence of different concentrations of ethanol were analyzed. Results of fluorescence spectroscopy of both forms showed that as ethanol concentration increased, the tryptophanyl residues became more accessible to the solvent. Near circular dichroism spectra of holo alpha-lactalbumin indicated that its tertiary structure was maintained in 20% ethanol whereas it was altered in 30 and 40% ethanol. For apo alpha-lactalbumin, spectra were similar in all samples studied. Holo alpha-lactalbumin was resistant to trypsinolysis in 0% ethanol, whereas it was easily hydrolyzed in 20 and 30% ethanol. In the case of the apo form and in the absence of ethanol, 70% of the protein was degraded after 1 h. However, in the presence of 20 and 30% ethanol, the overall reaction rate was lowered. Peptides obtained after tryptic hydrolysis were identified by reversed-phase high-performance liquid chromatography coupled to mass spectrometry. Differences in population of produced peptides indicate the changes of folding intermediates present in the studied alpha-lactalbumin solutions. This study demonstrated that proteolytic enzymes are suitable tools to determine protein structure complementing physico-chemical studies.