EPL

Hinrichsen, E. L.; Hansen, A.; Roux, S.

doi: 10.1209/0295-5075/8/1/001pmid: N/A

We study numerically a model for localized growth of a rupture in an elastic network. The model studied is the vector equivalent of the dielectric breakdown model (analogous to DLA). We find that the clusters of broken bonds are self-affine, and can be characterized by a fractal dimension of D = 1.25, even though we argue that the full inertia tensor must be used to understand the anisotropy of the structures. We have also studied the elastic properties of the samples as the cluster grows, and we find a power-law behaviour in the deviation of the elastic constant from its initial value with respect to the number of broken bonds. A corresponding power-law is also found in the scalar model.

Garel, T.; Huse, D. A.; Leibler, S.; Orland, H.

doi: 10.1209/0295-5075/8/1/002pmid: N/A

We consider a simple model of a random chain at an interface between two fluids, and suppose that its monomers have random affinities with both fluids (e.g., a Gaussian distribution with mean value 0). Simple statistical arguments and replica theory lead to the prediction of a localization transition of the chain (for the generic case of nonzero 0). This transition separates a low-temperature phase, in which the random chain is localized at the interface, from a high-temperature phase in which it is delocalized in one solvent. This physical picture is qualitatively confirmed by numerical studies.

Sengupta, K.; Singh, G.; Ritter, T.; Jain, P. L.

doi: 10.1209/0295-5075/8/1/003pmid: N/A

By using the along-the-track scanning technique, 505 primary peripheral events with one or more He fragments are observed in a total track of 78 meters of the 16O beam at 60 GeV/n. By following 831 relativistic He fragments from peripheral events, 362 secondary inelastic interactions have been observed. The interaction mean free paths of the He fragments have been found to be independent of the distances from their production points.

Cue, N.; Poizat, J.-C.; Remillieux, J.

doi: 10.1209/0295-5075/8/1/004pmid: N/A

A new mechanism by which the resonant capture of a target electron by a swiftly moving heavy ion is translated in one step into nuclear excitation is identified. It is in fact the inverse of internal conversion. Predicted resonances have energies   10 MeV/u, widths specified by the target electrons' momentum distribution, and cross-sections approaching tens of millibarns for some, and appear to be observable under channelling condition.

Weaire, D.; O'Carroll, C.; Wickham, C.

doi: 10.1209/0295-5075/8/1/005pmid: N/A

Using elementary finite difference methods the response of a Fabry-Perot cavity is investigated for the case of dispersive nonlinearity, with diffusion of the carriers responsible for the nonlinearity. Results are consistent with those of other workers in this field and are extended over a wider range, exposing a simple scaling law for the switch-up power.

Grynberg, G.; Paye, J.

doi: 10.1209/0295-5075/8/1/006pmid: N/A

A nonlinear medium interacting with a standing wave can become unstable for a sufficiently large value of the nonlinearity. The instability appears as a coherent emission in an off-axis direction. We study the instability threshold as a function of the angle of emission.

Loeff, P. I.; Bakker, H.

doi: 10.1209/0295-5075/8/1/007pmid: N/A

We report the results of the ball milling of several La-TM alloys (TM = Ag, Ni, Co). In contrast to the La-Au system the grinding of the intermetallic compounds does not result in the expected amorphous phase, but appears to decompose the alloys into the elemental constituents. A tentative explanation of the phenomenon is given in terms of energy absorption and the thermodynamics of the various systems.

Schöpf, W.; Zimmermann, W.

doi: 10.1209/0295-5075/8/1/008pmid: N/A

The nonlinear coefficients of the amplitude equations for the stationary pattern, the travelling waves, and the standing waves are calculated for the first time rigorously for binary fluid mixtures with realistic boundary conditions. We find that the travelling-wave pattern bifurcates subcritically except in the immediate vicinity of the codimension-2 point and has a larger amplitude than standing waves. The tricritical points for the stationary pattern and the travelling waves lie always at negative values for the separation ratio with the codimension-2 point between them. In the limit of small Lewis numbers both tricritical points and the codimension-2 point converge to the interesting, highly degenerate point  = 0.

Silva, L. R. da; Hansen, A.; Roux, S.

doi: 10.1209/0295-5075/8/1/009pmid: N/A

We show that damage spreading in a wide class of deterministic cellular automata (i.e. legal ones) can be seen as a growth phenomenon on a network of elements constructed from the rule of the original cellular automation. The chaotic state of the automation is related to a percolating state of this network. Numerical studies of several different cellular automata show that the percolation threshold of this network, as determined by a burning algorithm, coincides with the onset of chaos.

Lereah, Y.; Deutscher, G.; Kofman, R.

doi: 10.1209/0295-5075/8/1/010pmid: N/A

We have studied, by dark-field electron microscopy, the melting of lead clusters of about 200 Å in size embedded in a SiO matrix. Structural changes are observed before the melting temperature Tm is reached. At low temperatures (T < 290 °C) their frequency is temperature independent and seems to be dominated by the intensity of the electron beam. Close to Tm the frequency becomes strongly temperature dependent. The data suggest that it diverges at Tm. This behaviour is interpreted as indicative of activated rotation of the clusters in the SiO host matrix prior to bulk melting.