Adsorption of argon on carbon nanotube bundles and its influence on the bundle lattice parameter

We report experimental studies of the adsorption characteristics and structure of both 36Ar and 40Ar on single-wall carbon nanotube bundles. The structural studies make use of the large difference in coherent neutron scattering cross section for the two Ar isotopes to explore the influence of the adsorbate on the nanotube lattice parameter. We observe no dilation of the nanotube lattice with 40Ar, and explain the apparent expansion of this lattice upon 36Ar adsorption by the location of the adsorbed Ar atoms on the outer bundle surface.     

Minimal spanning tree analysis of regular,random and cluster structures

It is shown that a graph called the minimal spanning tree (MST) is capable of detecting several kinds of cluster structure in arbitrary points set. From a MST it is possible to deduce the average edge lengthm and the standard deviationσ, which are characteristics for the corresponding distribution. The use of a diagram involving bothm andσ makes it possible to determine the degree of order by taking a simple reading in the (m,σ) plane. It is also possible, through angular diagrams retrieved from the MST, to bring out directional properties. The method is applied to the study of the growth of granular thin films.     

Phénomène de croissance apparaissant sur les dépôts de lithium préparés sous ultra vide statique,et soumis à l'action de l'air

The action of air on thin layers of lithium prepared under a static ultrahigh vacuum is investigated. It is shown, during the degradation, that small grains develop at the metal surface. The growth of these small grains, whose contours are regular, takes place in an orderly manner. The presence of LiOH and LiNO₃ in degraded films are shown, using electron diffraction patterns.     

Study of structural and electronic transport properties of Ce-doped LaMnO3

The structural and electronic transport properties of La_1−x Ce _x MnO₃ (x=0.0–1.0) have been studied. All the samples exhibit orthorhombic crystal symmetry and the unit cell volume decreases with Ce doping. They also make a metal-insulator transition (MIT) and transition temperature increases with increase in Ce concentration up to 50% doping. The system La_0.5Ce_0.5MnO₃ also exhibits MIT instead of charge-ordered state as observed in the hole doped systems of the same composition.     

Roughness spectrum for surfaces of silver deposits

The roughness spectrum g(k) (or spectral density function) for surfaces of silver deposits is deduced from surface profiles determined by using microdensitometer analysis of micrographs of surface shadowed carbon replicas. We used a process based on the computation of autocovariance function (ACF) via the fast Fourier transform (FFT) algorithm. Results are compared with those provided by attenuated total reflexion (ATR) method. It is shown that the g(k) function is not perfectly gaussian as it is usually assumed.     

Two connected inverse spectral transforms

We establish a transformation which connects the potentials of the one-dimensional Dirac and Klein-Gordon operators. This transformation links the solutions of the nonlinear evolution equations solvable by means of the two inverse spectral transforms which use the Dirac and Klein-Gordon direct and inverse spectral problems.