Search results for "Interfaces."
showing 10 items of 1252 documents
Spin relaxation in Cu and Al spin conduits
2014
We study the spin relaxation in Al and Cu spin conduits embedded in non-local spin valve nanostructures. Measuring the key spin transport properties, we determine the spin and charge diffusion constants as well as the spin flip time. By varying the temperature, we find that the maximum of the non-local spin resistance change occurs at finite temperatures with a clear difference between Al and Cu. In particular, we find that the maximum of the non-local spin signal in Al is less pronounced and occurs at lower temperatures compared to Cu suggesting that the self-passivating Al surface plays a role. Having fabricated devices with both materials in identical processes, we can attribute the diff…
First-order and tricritical wetting transitions in the two-dimensional Ising model caused by interfacial pinning at a defect line
2014
We present a study of the critical behavior of the Blume-Capel model with three spin states (S=±1,0) confined between parallel walls separated by a distance L where competitive surface magnetic fields act. By properly choosing the crystal field (D), which regulates the density of nonmagnetic species (S=0), such that those impurities are excluded from the bulk (where D=) except in the middle of the sample [where DM(L/2)≠], we are able to control the presence of a defect line in the middle of the sample and study its influence on the interface between domains of different spin orientations. So essentially we study an Ising model with a defect line but, unlike previous work where defect lines …
Atomic, electronic and thermodynamic properties of cubic and orthorhombic LaMnO3 surfaces
2009
We studied in detail the atomic and electronic structure of the LaMnO3 surfaces, in both cubic and orthorhombic phases, combining GGA-plane wave approach, as implemented into the VASP-4.6.19 computer code, with a slab model. These studies are complemented by a thermodynamic analysis of the surface stability at different gas pressures and temperatures. The obtained results are compared with similar studies for other ABO3-perovskites. 2008 Elsevier B.V. All rights reserved. The ABO3-type perovskite manganites and cobaltates (A = La, Sr, Ca; B = Mn, Co) are important functional materials with numerous high-tech applications [1]. Some of them require understanding and control surface properties…
Fabrication of Chemically Tunable, Hierarchically Branched Polymeric Nanostructures by Multi-branched Anodic Aluminum Oxide Templates
2016
In this paper, a template-assisted replication method is demonstrated for the fabrication of hierarchically branched polymeric nanostructures composed of post-modifiable poly(pentafluorophenyl acrylate). Anodic aluminum oxide templates with various shapes of hierarchically branched pores are fabricated by an asymmetric two-step anodization process. The hierarchical polymeric nanostructures are obtained by infiltration of pentafluorophenyl acrylate with a cross-linker and photoinitiator, followed by polymerization and selective removal of the template. Furthermore, the nanostructures containing reactive pentafluorophenyl ester are modified with spiropyran amine via post-polymerization modifi…
Effect of Cholesterol on Electrostatics in Lipid−Protein Films of a Pulmonary Surfactant
2010
We report the changes in the electrical properties of the lipid-protein film of pulmonary surfactant produced by excess cholesterol. Pulmonary surfactant (PS) is a complex lipid-protein mixture that forms a molecular film at the interface of the lung's epithelia. The defined molecular arrangement of the lipids and proteins of the surfactant film gives rise to the locally highly variable electrical surface potential of the interface, which becomes considerably altered in the presence of cholesterol. With frequency modulation Kelvin probe force microscopy (FM-KPFM) and force measurements, complemented by theoretical analysis, we showed that excess cholesterol significantly changes the electri…
A static SIMS study of superficial reactions (O2, (CN)2) on silver
1998
Abstract The exposure of silver surfaces to oxygen under about 10 −6 mbar at room temperature was studied mainly by secondary ion mass spectrometry (SIMS) used in a static mode. No reactivity of oxygen appeared under these exposure conditions in accordance with previous works. No modifications in the AES spectra, but an unexpected and huge increase in the intensities of secondary ions such as CN − , CNO − , Ag(CN) − 2 , Ag 2 CN + were observed. Different experiments were performed in order to specify the origin of this unexpected reaction in presence of pure oxygen. Moreover, exposures to pure (CN) 2 and to a mixture of cyanogen and oxygen were performed in order to compare the reactivity o…
Comparative optical reflection and mass spectrometry analysis of thermodesorption of Langmuir-Blodgett films
1992
Abstract Thermodesorption of cadmium arachidate multilayers is studied by optical surface analysis and by mass spectrometry measurements. The optical reflection technique has been improved to discriminate signal contributions from desorption and light scattering. The scattering arises from film heterogeneities that are also observed by Nomarsky microscopy. The assessment of these heterogeneities is important to understand mass spectrometry data. Both the optical technique and mass spectrometry are sensitive to observing the multilayer phase transition at 110 °C and the desorption near 200 °C (at the heating rate applied). The mass spectrometry analysis yields detailed information on the des…
Multivariate nonparametric estimation of the Pickands dependence function using Bernstein polynomials
2017
Abstract Many applications in risk analysis require the estimation of the dependence among multivariate maxima, especially in environmental sciences. Such dependence can be described by the Pickands dependence function of the underlying extreme-value copula. Here, a nonparametric estimator is constructed as the sample equivalent of a multivariate extension of the madogram. Shape constraints on the family of Pickands dependence functions are taken into account by means of a representation in terms of Bernstein polynomials. The large-sample theory of the estimator is developed and its finite-sample performance is evaluated with a simulation study. The approach is illustrated with a dataset of…
Fluorescence quenching by trapped charge carriers in N,N-dimethylaminobenzylidene 1,3-indandione films
2010
Effects caused by the applied voltage on the steady state and time-resolved fluorescence of vacuum evaporated N,N-dimethylaminobenzylidene 1,3-indandione films sandwiched between gold and aluminium electrodes were investigated and discussed. Fluorescence enhancement and quenching as well as the fluorescence band narrowing depending on the applied voltage have been observed. Fluorescence decay and recovery take place on a time scale of tens of seconds after voltage is switched on and off. Similar fluorescence decay also takes place after switching on the excitation light. These fluorescence changes are attributed to the exciton quenching by trapped charge carriers.
Chemically driven phase separation in black lipid membranes and its coupling to membrane functions
1992
Abstract We analysed the single-channel current fluctuations of gramicidin in bimolecular lipid membranes in order to demonstrate (i) the influence of protein binding to the lateral organisation of a mixed membrane, and (ii) how this couples to the function of the ionophore. Examples of phase separations induced by synthetic polyelectrolytes, as models for peripheral membrane proteins, and specific ligand-receptor interactions are presented and discussed in view of the important lateral order-function relationship in biomembranes.