Showing papers by "John Bechhoefer published in 1993"
TL;DR: In this article, the authors describe a simple, nondestructive procedure for measuring the force constant, resonant frequency, and quality factor of an AFM cantilever spring and the effective radius of curvature of an AU tip.
Abstract: Images and force measurements taken by an atomic‐force microscope (AFM) depend greatly on the properties of the spring and tip used to probe the sample’s surface. In this article, we describe a simple, nondestructive procedure for measuring the force constant, resonant frequency, and quality factor of an AFM cantilever spring and the effective radius of curvature of an AFM tip. Our procedure uses the AFM itself and does not require additional equipment.
3,975 citations
TL;DR: In this article, the frequency response of the optical-detection electronics of an atomic-force microscope cantilever was corrected for a high frequency cut-off, which, in our case, was higher than the resonant frequency of the cantilevers.
Abstract: In our calibration of atomic-force microscope cantilevers, we neglected to correct for the frequency response of the optical-detection electronics. The response to cantilever vibrations will have a high-frequency cut-off, which, in our case, was higher than the resonant frequency of the cantilever. Our results were not affected, but for higher resonant frequencies, one should calibrate the detector response. We thank V. Croquette for raising this point.
220 citations
TL;DR: In this article, the van der Waals forces can be measured using an atomic force microscope (AFM) and an appropriate fluid is immersing the tip and sample in a suitable fluid.
Abstract: Although the atomic force microscope (AFM) resembles superficially the scanning tunneling microscope (STM), its imaging resolution is in general much coarser. For the AFM, long‐range interactions—most notably the van der Waals force—imply that image resolution is set by the macroscopic tip radius rather than by a single atom, as with the STM. Experimentally, we show that van der Waals forces can be measured using an AFM. By immersing tip and sample in an appropriate fluid, we can effectively eliminate the van der Waals force, leading to a marked improvement in AFM image quality.
75 citations
TL;DR: In this article, the authors used dimensional analysis to show that although the limiting mass is finite in three spatial dimensions (d=3), it is zero in higher spatial dimensions and that any universe or part of a universe with d≥4 will be profoundly different from one with d=3.
Abstract: Chandrasekhar showed that above a limiting mass, white dwarf stars will collapse under their own gravitational force. We use dimensional analysis to show that although the limiting mass is finite in three spatial dimensions (d=3), it is zero in higher spatial dimensions. A star placed in a high‐dimensional space is unstable and will either collapse to a black hole or disperse and become unbound. Thus, any universe—or part of a universe—with d≥4 will be profoundly different from one with d=3.
3 citations
Posted Content•
TL;DR: In this article, the authors summarized a talk presented at the April NATO ASI on Spatiotemporal Chaos in Complex Fluids, in Santa Fe, NM. Much of the discussion focused on the different phenomena observed in solidification and how the increasing complexity of fluid systems decreases the velocity scale for achieving "rapid" solidification.
Abstract: This paper summarizes a talk presented at the April NATO ASI on Spatiotemporal Chaos in Complex Fluids, in Santa Fe, NM. The paper gives reasons that make complex fluids good material systems for conducting experiments on pattern formation and other nonequilibrium phenomena. Much of the discussion focuses on the different phenomena observed in solidification and how the increasing complexity of fluid systems decreases the velocity scale for achieving "rapid" solidification. Five systems are compared to illustrate this point: simple fluids, simple alloys, thermotropic liquid crystals, lyotropic liquid crystals, and diblock copolymers. Finally, an example is given of the kinds of transitions that may be observed in rapid solidification.
1 citations