177 research outputs found
Surface and Grain Boundary Analysis of High Temperature Superconductors
The purpose of this paper is to survey the methods that are available for probing surfaces and grain boundaries of high temperature superconductors. Various surface-sensitive spectroscopies are applied to the analysis of YBa2Cu3O7-x and Bi2Sr2CaCu2O8+x including photoelectron spectroscopy, spatially-resolved electron energy loss spectroscopy, and scanning electron microscopy (SEM). One of the major sources of contamination at surfaces and grain boundaries is found to be BaCO3. The cleavage surface of single crystal Bi2Sr2CaCu2O8+x is inert and can be used to probe bulk properties of superconductors, even with surface-sensitive techniques. The orbital character of the superconducting oxygen 2p holes is found to be Px,y, with x,y in the a,b plane. Photoemission at the Fermi level indicates a Fermi liquid nature of these states
Behavior of Cu(P) and Oxygen Free High Conductivity Cu Anodes under Electrodeposition Conditions
Films formed on Cu(P) (with 0.1 atom percent P) and oxygen free high conductivity Cu anodes in electroplating solutions were studied by a newly developed gravimetric technique, electrochemical methods, x-ray photoelectron spectroscopy, and x-ray absorption spectroscopy. The black film formed on Cu(P) in Cl^− -containing solutions was found to resemble a porous sponge composed of CuCl but laden with concentrated CuSO_4 solution. The gravimetric experiments show that the difference between the buoyancy-corrected measured mass change and the charge-equivalent mass change has two components: a reversible part that comes and goes as the current is turned on and off, and an irreversible part that remains on the surface and increases in mass with time as dissolution proceeds. The reversible part of the mass change arises from the weight of the diffusion layer. The irreversible part results from the anodic film, which increases linearly in mass with charge density but at a rate that is independent of current density. P inhibits the disproportionation of Cu^+1 that results in the poorly adherent anodic film that forms on OFHC Cu anodes.Research was carried out in part at beamline X23A2 at the National Synchrotron Light Source, Brookhaven National Laboratory, which is supported by the U.S. Department of Energy, Division of Materials Sciences and Division of Chemical Sciences. H.S.I. was supported by the U.S. Department of Energy, Division of Materials Sciences, Office of Basic Energy Science under Contract No. DE-AC02-76CH00016
Corrosion and Passivation of Fe and FeN Films
The role of nitrogen in corrosion and passivation of thin Fe-N films was studied. Sputtered films with different levels of nitrogen were characterized for composition, conductivity, stress, and crystallinity. Corrosion and passivation of the films were evaluated by electrochemical measurements combined with in situ ellipsometry and ex situ x-ray photoelectron spectroscopy. The results indicate that in deaerated solutions the primary action of N is to reduce the catalytic activity of the surface for the hydrogen reaction and thereby reduce corrosion. In aerated solutions the corrosion rate increases with N content. Kinetics of the protective oxide formation as a function of potential, percent N, and the presence of borate buffer are discussed in detail. The work is relevant to the behavior of oxide-free Fe-N surfaces in contact with mild, nearly neutral electrolytes, such as could be used in fabrication of magnetic recording heads
X-Ray Absorption Study of Electrochemically Grown Oxide Films on Al-Cr Sputtered Alloys I. Ex situ Studies
Oxides grown electrochemically in a borate buffer solution on the surface of sputter-deposited AlCr alloy films were studied by x-ray absorption near edge structure (XANES). The measurements were made in air immediately following polarization in solution. The oxides were also examined with x-ray photoelectron spectroscopy (XPS). The effects of alloy composition and thickness as well as applied potential were studied. Cr( VI) was found in the oxides if the applied potential was sufficiently high. The Cr(VI) was enriched at the interface with the electrolyte and the proportion of Cr(VI) in the oxide was higher for alloy films containing more Cr. The Cr(VI) in the oxides could be reversibly reduced to Cr(III) and reoxidized to Cr(VI) by subsequent potentiostatic treatments in solution.Research was carried out in part at the National Synchroton Light Source, Brookhaven
National Laboratory, which is supported by the U.S. Department of Energy, Division of
Materials Sciences and Division of Chemical Sciences. A. J. D. and H. S. I. were supported by the U.S. Department of Energy, Division of Materials Sciences, Office of Basic Energy Science under Contract No. DE-AC02-76CH00016
Affective iconic words benefit from additional sound–meaning integration in the left amygdala
Recent studies have shown that a similarity between sound and meaning of a word (i.e., iconicity) can help more readily access the meaning of that word, but the neural mechanisms underlying this beneficial role of iconicity in semantic processing remain largely unknown. In an fMRI study, we focused on the affective domain and examined whether affective iconic words (e.g., high arousal in both sound and meaning) activate additional brain regions that integrate emotional information from different domains (i.e., sound and meaning). In line with our hypothesis, affective iconic words, compared to their non‐iconic counterparts, elicited additional BOLD responses in the left amygdala known for its role in multimodal representation of emotions. Functional connectivity analyses revealed that the observed amygdalar activity was modulated by an interaction of iconic condition and activations in two hubs representative for processing sound (left superior temporal gyrus) and meaning (left inferior frontal gyrus) of words. These results provide a neural explanation for the facilitative role of iconicity in language processing and indicate that language users are sensitive to the interaction between sound and meaning aspect of words, suggesting the existence of iconicity as a general property of human language
Pathway to the PiezoElectronic Transduction Logic Device
The information age challenges computer technology to process an
exponentially increasing computational load on a limited energy budget - a
requirement that demands an exponential reduction in energy per operation. In
digital logic circuits, the switching energy of present FET devices is
intimately connected with the switching voltage, and can no longer be lowered
sufficiently, limiting the ability of current technology to address the
challenge. Quantum computing offers a leap forward in capability, but a clear
advantage requires algorithms presently developed for only a small set of
applications. Therefore, a new, general purpose, classical technology based on
a different paradigm is needed to meet the ever increasing demand for data
processing.Comment: in Nano Letters (2015
Trends in Metal Oxide Stability for Nanorods, Nanotubes, and Surfaces
The formation energies of nanostructures play an important role in
determining their properties, including the catalytic activity. For the case of
15 different rutile and 8 different perovskite metal oxides, we find that the
density functional theory (DFT) calculated formation energies of (2,2)
nanorods, (3,3) nanotubes, and the (110) and (100) surfaces may be described
semi-quantitatively by the fraction of metal--oxygen bonds broken and the
bonding band centers in the bulk metal oxide
A new tool to ensure the fluorescent dye labeling stability of nanocarriers: A real challenge for fluorescence imaging
International audienceNumerous studies on nanocarriers use fluorescent dye labeling to investigate their biodistribution or cellular trafficking. However, when the fluorescence dye is not grafted to the nanocarrier, the question of the stability of the labeling arises. How can it be validated that the fluorescence observed during an experiment corresponds to the nanocarriers, and not to the free dye released from the nanocarriers? Studying the integrity of the labeling is challenging. Therefore, an innovative approach to confirm the labeling stability was developed, based on the transfer of a fluorescent dye from its hosting nanocarrier to a lipophilic compartment. Lipid nanocapsules (LNC) and triglyceride oil were used as models. The protocol involved mixing of LNC suspension and oil, and then separation by centrifugation. The quality of the separation was controlled by light scattering, using the derived count rate tool. Dye transfer from loaded LNCs to the lipophilic compartment or from a lipophilic compartment containing dye to non-loaded LNC was investigated by varying the nature of the dye and the oil, the oil volume and the LNC dilution. Tensiometry was used to define the dye location in the nanocarrier. Results showed that when dyes such as Nile Red and Coumarin-6 are located in oily core, the transfer occurred in a partition-dependent manner. In contrast, when the dye was entrapped in the surfactant shell of LNCs such as lipophilic indocarbocyanines (i.e. DiO, DiI and DiD), no transfer was observed. Dye diffusion was also observed in cell culture, with Nile Red inside lipid bodies of HEI-OC1 cells, without uptake of LNCs. In contrast, DiO-loaded LNCs had to be internalized to observe fluorescence inside the cells, providing a further confirmation of the absence of transfer in this case, and the stability of fluorescence labeling of the LNCs
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