PubMed Health⌕ Search
Home/Archive/PubMed

PubMed · 9566344

Tuning fork shear-force feedback.

A G Ruiter·K O van der Werf·J A Veerman·M F Garcia-Parajo·W H Rensen·N F van Hulst
View original source ↗Export metadata ↓

Abstract

Investigations have been performed on the dynamics of a distance regulation system based on an oscillating probe at resonance. This was examined at a tuning fork shear-force feedback system, which is used as a distance control mechanism in near-field scanning optical microscopy. In this form of microscopy, a tapered optical fiber is attached to the tuning fork and scanned over the sample surface to be imaged. Experiments were performed measuring both amplitude and phase of the oscillation of the tuning fork as a function of driving frequency and tip-sample distance. These experiments reveal that the resonance frequency of the tuning fork changes upon approaching the sample. Both the amplitude and the phase of the tuning fork can be used as distance control parameter in the feedback system. Using the amplitude a second-order behavior is observed, while with phase only a first-order behavior is observed. Numerical calculations confirm these observations. This first-order behavior results in an improved stability of the feedback system. As an example, a sample consisting of DNA strands on mica was imaged which showed the height of the DNA as 1.4 +/- 0.2 nm.

Explore related subjects

Aluminum SilicatesDNAFiber Optic TechnologyMicroscopyMicroscopy, Electron, ScanningOptical FibersVibrationJournal ArticleResearch Support, Non-U.S. Gov't

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

A G Ruiter, K O van der Werf, J A Veerman, M F Garcia-Parajo, W H Rensen, N F van Hulst. 1998. Tuning fork shear-force feedback.. https://doi.org/10.1016/s0304-3991(97)00111-3

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed2000

Evidence that the reactivity of the martian soil is due to superoxide ions.

The Viking Landers were unable to detect evidence of life on Mars but, instead, found a chemically reactive soil capable of decomposing organic molecules. This reactivity was attributed to the presence of one or more as-yet-unidentified inorganic superoxides or peroxides in the martian soil. Using electron paramagnetic resonance spectroscopy, we show that superoxide radical ions (O2-) form directly on Mars-analog mineral surfaces exposed to ultraviolet radiation under a simulated martian atmosphere. These oxygen radicals can explain the reactive nature of the soil and the apparent absence of organic material at the martian surface.

Aluminum Silicates↗
PubMed2000

Clinical evaluation of paired compomer and glass ionomer restorations in primary molars: final results after 42 months.

OBJECTIVES: To undertake a clinical trial comparing the efficiency of a compomer restoration with a glass ionomer restoration in the management of caries in primary molar teeth. DESIGN: Subjects were admitted to the trial if they required at least one pair of restorations in primary molar teeth. SETTING: Department of Child Dental Health, Newcastle Dental Hospital and School. SUBJECT: Twenty nine children, aged 4-9 years, had 56 pairs of restorations placed between January 1995 and November 1997. METHOD: The durability of the restorations was assessed during a 42-month follow-up period using modified United States Public Health Service criteria. Survival analysis and the McNemar paired test were used to compare the performance of the two restorative materials. RESULTS: The compomer restorations had a higher mean survival time (42 months, SE 1.40) compared with 37 months (SE 1.90) for the glass ionomer restorations and this was significant at the 5% level. The compomer also performed significantly better in terms of anatomical form, marginal integrity, cavo surface discoloration and maintenance of interproximal contact. CONCLUSIONS: The present trial demonstrated that Dyract compomer performed significantly better than Chemfil Superior a glass ionomer cement for all modified United States Public Health Service criteria over a period of 42 months.

Aluminum Silicates↗
PubMed2000

Surface tongue-and-groove contours on lens MIP facilitate cell-to-cell adherence.

The lens major intrinsic protein (MIP, AQP0) is known to function as a water and solute channel. However, MIP has also been reported to occur in close membrane contacts between lens fiber cells, indicating that it has adhesive properties in addition to its channel function. Using atomic force and cryo-electron microscopy we document that crystalline sheets reconstituted from purified ovine lens MIP mostly consisted of two layers. MIP lattices in the apposing membranes were in precise register, and determination of the membrane sidedness demonstrated that MIP molecules bound to each other via their extracellular surfaces. The surface structure of the latter was resolved to 0.61 nm and revealed two protruding domains providing a tight "tongue-and-groove" fit between apposing MIP molecules. Cryo-electron crystallography produced a projection map at 0.69 nm resolution with a mirror symmetry axis at 45 degrees to the lattice which was consistent with the double-layered nature of the reconstituted sheets. These data strongly suggest an adhesive function of MIP, and strengthen the view that MIP serves dual roles in the lens.

Aluminum Silicates↗