Estimation of parameters in nonlinear problems

In this paper, we describe two efficient methods to estimate parameters in nonlinear least squares problems: continuation and sentinels methods. When the studied system is modeled by differential equations, we have to identify both unknown parameters and initial conditions. For that, we propose to process in two steps: first identify the unknown parameters, then identify again using the found results, considering now both the parameters and the initial conditions as unknown. This revised version was published online in June 2006 with corrections to the Cover Date.     

An extension of Cartan's method of equivalence to immersions: I. Necessary conditions

In this paper, we show that the existence of immersions preserving given geometric structures between manifolds can be expressed in terms of a relation between suitably constructed moving coframes on the manifolds, and we show that the key steps in Cartan's method of equivalence can be extended to yield necessary conditions for the existence of such immersions.     

Haloxylines A and B, antifungal and cholinesterase inhibiting piperidine alkaloids from Haloxylon salicornicum

Haloxylines A (1) and B (2), new piperidine alkaloids, have been isolated from the chloroform soluble fraction of Haloxylon salicornicum and their structures elucidated by spectroscopic techniques including 2D-NMR. Both the compounds displayed antifungal and cholinesterase enzymes inhibitory potentials.     

A relativistic quantum dynamical model based on the classical string

Motivated by geometrical considerations of the string model, we construct a dynamical theory of composite particles that is Poincaré invariant in four dimensions, with no tachyons and no ghosts. The resulting physical states lie on indefinitely rising trajectories.     

A test theory of special relativity: II. First order tests

First-order tests of special relativity are based on a comparison of clocks synchronized with the help of slow clock transport with those synchronized by the Einstein procedure. This comparison enables the measurement of the one-way velocity of light and is equivalent to a measurement of the time dilatation factor. The accuracy of present measurements is of the order 10^–7, yielding an upper limit of 3 cm/sec for the ether drift.     

Examining interaction techniques in data visualization authoring tools from the perspective of goals and human cognition: a survey

Journal of Visualization - We review the state-of-the-art interaction techniques of visualization authoring tools. The visualization tools tend to help users in the creation, exploration, or...