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The self-diffusion coefficients of N(CH 3 ) 4 + ions in a cation-exchange membrane, the Nafion, have been measured at different time scales. The time range extends from the picosecond with neutron quasi-elastic scattering experiments to the second with NMR experiments and tens of seconds with radiotracer experiments. At short times, the values of self-diffusion coefficient in the membrane are equal to those in nonconfined solution; the diffusion process is governed by ion-solvent collisions. The NMR results present two different time scales: for short times (<1 s), the self-diffusion coefficient depends both on time and on electrolyte concentration; for long times, these two dependencies disappear. The radiotracer method confirms the NMR results at long time scales: the diffusion does not depend on electrolyte concentration.

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We argue that the continued growth of the Internet, both as a form of mainstream media and as a tool for organizing democratic social interactions, requires that Internet politics be retheorized from a standpoint that is both critical and reconstructive. While we undertake an approach that is critical of corporate forms and hegemonic uses of the Internet, we advocate for new software developments such as blogs and trace the oppositional deployments of the Internet made by a wide variety of groups in the cause of progressive cultural and political struggle. In this regard, we describe how the Internet has facilitated the worldwide emergence of the anti-globalization, anti-war and anti-capitalism movements, even as it has coalesced local communities and groups, and so we conclude that the future of Internet politics must be thought dialectically as both global and local. We end by noting the relevance of the ideas of Guy Debord, with his focus on the construction of situations, the use of technology, media of communication and cultural forms to promote a revolution of everyday life.

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The diffusion of hydrogen in NaA zeolite was studied by incoherent neutron scattering. An experiment was carried out on samples loaded with 1.2 to 3.4 molecules per cavity and at several temperatures from 70 to 150 K. The angular (θ) dependence of the elastic and quasielastic intensities shows that the H2 molecule has a translational motion in a nonrestricted volume. A diffusion model where the molecule undergoes isotropic jumps of mean length l̄=3.9 Å independent of temperature and is at rest for a time τ0 between two jumps accounts for the width of the quasielastic scattering in the entire (θ,T) range (τ0=10.8 ps at T=100 K). This leads to a diffusion coefficient D(cm2/s)=6×10−4 exp(E/RT) with E=2 kJ/mol for the less loaded samples. The diffusion coefficient increases slightly with the loading.

This study examined the sources of job stress among 150 dentists. It was found that the ‘dentist at risk’ tends to be older, somewhat anxious, and feels he is perceived as an ‘inflictor of pain’, with pressures from his work stemming from trying to sustain and build a practice, too little work, administrative difficulties and having to cope with difficult patients.