The effect of increasing state anxiety on autobiographical memory specificity and future thinking.

BACKGROUND AND OBJECTIVES: Impairments in the specificity of autobiographical memory (AM) and future thinking are associated with a range of affective and psychopathological states, however, whether these deficits also occur in the context of state anxiety is not well known. We examined the effects of increasing state anxiety on the specificity of AM and future thoughts, as well as whether changes in rumination and executive functioning mediate any observed effects. METHODS: Sixty-four participants (M age = 29.1, SD = 11.5) were randomized to either an anxiety or neutral mood induction and completed pre and post-measures of the constructs of interest. RESULTS: There were significant decreases observed in AM specificity in the anxiety induction group, relative to the neutral group. No changes were observed for future thinking specificity. Rumination was increased as a result of the anxiety induction, but only a non-significant trend was observed with respect to its association with changes in AM and future thinking specificity. Verbal fluency and working memory were not affected by the induction. LIMITATIONS: Physiological measures of anxiety were not used. State anxiety, although increased, was not high in severity. Future research might use a clinical sample to assess generalizability of these findings. CONCLUSIONS: Although preliminary, these findings provide first evidence of the causal impact of an anxiety induction on the ability to retrieve specific AM.

Geometrical properties of turbulent dispersion.

It is shown that the shape statistics of four correlated particles, known as a tetrad, in a direct numerical simulation of three-dimensional homogeneous isotropic turbulence agree very well with a simple diffusion equation with a separation-dependent eddy diffusivity. The latter is essentially an extension of Richardson's model for particle-pair dispersion to tetrads. It is also shown that the degree of elongation of the tetrad in the inertial subrange of a turbulentlike flow is controlled by the exponent, m, in an eddy diffusivity of the form K(r)[proportionality]r(m) where r is the interparticle separation, becoming more elongated as m increases in the range 0≤m<2.

Comment on "Fundamentals of pair diffusion in kinematic simulations of turbulence".

Osborne et al [Phys. Rev. E 74, 036309 (2006)] suggested that our conclusions on the ability of kinematic simulation to represent the t(3) Richardson law [Thomson and Devenish, J. Fluid Mech. 526, 277 (2005)] were an artifact of our choice of time step. Here we repeat some of the simulations with a small fixed time step, enabling us to confirm that our previous study was not compromised by the variable time step used.

Multifractal statistics of Lagrangian velocity and acceleration in turbulence.

The statistical properties of velocity and acceleration fields along the trajectories of fluid particles transported by a fully developed turbulent flow are investigated by means of high resolution direct numerical simulations. We present results for Lagrangian velocity structure functions, the acceleration probability density function, and the acceleration variance conditioned on the instantaneous velocity. These are compared with predictions of the multifractal formalism, and its merits and limitations are discussed.