Evidence for directed percolation universality at the onset of spatiotemporal intermittency in coupled circle maps.

We consider a lattice of coupled circle maps, a popular model for the study of mode-locked phenomena. We find that the onset of spatiotemporal intermittency (STI) in this system is analogous to directed percolation (DP), with the transition being to a unique absorbing state for low nonlinearities, and to weakly chaotic absorbing states for high nonlinearities. We find that the complete set of static exponents and spreading exponents at all critical points match those of DP very convincingly.

Connectivity strategies to enhance the capacity of weight-bearing networks.

The connectivity properties of a weight-bearing network are exploited to enhance its capacity. We study a 2D network of sites where the weight-bearing capacity of a given site depends on the capacities of the sites connected to it in the layers above. The network consists of clusters, viz.

Computation of the Lyapunov spectrum for continuous-time dynamical systems and discrete maps.

In this paper, we describe in detail a method of computing Lyapunov exponents for a continuous-time dynamical system and extend the method to discrete maps. Using this method, a partial Lyapunov spectrum can be computed using fewer equations as compared to the computation of the full spectrum, there is no difficulty in evaluating degenerate Lyapunov spectra, the equations are straightforward to generalize to higher dimensions, and the minimal set of dynamical variables is used. Explicit proofs and other details not given in previous work are included here.

[Regulation of vasopressin release in primary hypothyroidism and Addison's disease as well as in central diabetes insipidus].

The osmoregulation of arginine-8-vasopressin (AVP) was investigated in 14 patients with primary hypothyroidism, in 6 with Addison's disease, and in 21 with central diabetes insipidus (CDI). In the latter disease the effect of histamine stimulus was also evaluated. Plasma AVP was measured by radioimmunoassay (RIA).