Overall, existing models do not account for the force curves presented below. Yet, the data provide indispensable information about a truly generic phenomenon, correlation induced attraction between identically charged bodies.Attraction between macroscopically similar surfaces has been reported in the literature. For instance, the long range attraction between hydrophobic surfactantcoated surfaces 7 has recently been attributed to charge inhomogeneity 8 . Charge inversion due to over-screening by high valence ions may also lead to attraction between dissimilar surfaces. As the large Z-ion concentration is increased, one of the surfaces reverses its polarity before the other surface does, leading to "conventional" attraction between two oppositely charged objects. An AFM study of the force in the latter case has been published recently 9 . We emphasize that the attraction reported here is different than either phenomena. Unlike the first one, it takes place between two bare surfaces and unlike the latter it occurs also between identical surfaces. The resulting force is of a fundamentally shorter range compared with either phenomenon.The force between a m µ 5 silica bead 10 glued to an AFM tip and an oxidized silicon wafer or the tip-mounted silica bead and an identical bead glued to a silicon wafer was measured using a commercial AFM 11 . The microscope was placed in an acoustic hood and the AFM's piezoelectric crystal was driven by a low noise synthesizer

We present a study of finger instability observed in a propagating front resulting from dewetting of a thin water film on a mica substrate. The phenomenon results from a longitudinal instability in a thick cylindrical rim along the front, whose unusual properties are determined by domination of long-range van der Waals interaction between the film and the substrate over the effect of curvature. The interpretation is borne out by quantitative measurements and supported by computer simulations.

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The spatial resolution of the phase image derived from the interferogram by Fourier fringe analysis is limited by the necessity to isolate a first order in the Fourier plane. By use of the two complementary outputs of the interferometer, it is possible to eliminate the zero order and thus to improve the spatial resolution by a factor of approximately 2. The theory of this improvement is presented and confirmed experimentally.