Fretting description

Chapter 8 written by Steve Vogel et al. also deals with sensitized emission based FRET methodology, but now using a spectral imaging detector device. Because a spectral detector and spectral unmixing software nowadays are standard options on the major commercial confocal microscopes, here a complete description is given how to quantify FRET from unmixed spectral components. 

There are numerous excellent reviews and original literature about Forster resonance energy transfer (FRET) where one can read detailed descriptions and get lists of earlier references [1-11]. This chapter is neither a review of the literature, nor a detailed account... 

Summary of the basic equations of FRET Equations (1.1)—(1.3) are the quintessential theoretical descriptions of FRET. These equations, together with the well-known theoretical descriptions of spectroscopic transitions (see below) are the basics from which all the experimental acquisition and analysis methods are derived. 

Fig. 5 Schematic description of the contact conditions encountered under small amplitude cyclic lateral micro-motions (fretting). S is the applied lateral displacement, Q is the lateral force and P is the applied constant normal load. The elliptic and trapezoidal Q(S) loops correspond to partial slip and gross slip condition respectively...

Fig. 1 Schematic description of the fretting device. (1) spherical glass counterface, (2) epoxy specimen, (3) tangential load transducer, (4,5) normal load transducers, (6) extensometer, (7) microscope and CCD camera.

Strain rate of 5x10" s , while the strain rates within the epoxy surface layer are in the order of 10 s under fretting conditions. Accordingly, the values of the octahedral shear stress at the onset of yield are probably underestimated. In addition to the limited viscoelastic response of the epoxy material at the considered frequency and temperature (tan 8 = 0.005 at 25°C and 1 Hz, table I), this analysis supports the validity of a global elastic description of the contact stress environment. 

The potential of fluorescence cross correlation (FXS) has been outlined by Eigen and Rigler [54]. Compared to FRET which gives information about the vicinity of fluorescent centers FXS gives Information about their connectivity in the dynamic sense independent of how close or far away the fluorescent centers are positioned. A detailed theoretical description has been provided [55,56[ and FXS has been used successfully in a variety of applications both in solution as well as at the cellular level. C. Zeiss with his Confocor 2 (for solution measurements) and Confocor 3 (for cellular measurements) has provided instruments of highest sensitivity. 

A detailed description of a TCSPC-FLIM-FRET system is given in [147]. The system is used for FRET between ECPF-EYFP and FMl-43 - FM4-64 in cultured neurones. FRET between ECFP and EYFP in plant cells was demonstrated in [68]. FRET measurements in plant cells are difficult because of the strong autofluorescence of the plant tissue. It is possible to show that two-photon excitation can be used to keep the autofluorescence signal at a tolerable level. 

Again, wear is the removal of material. The idea that friction causes wear and therefore, low friction means low wear, is a common mistake. Brief descriptions of five types of wear abrasive, adhesive, fatigue, chemical or corrosive, and fretting — may be found in Reference 2 as well as in other references in this article. Next, it maybe useful to consider some of the major concepts of lubrication. 

In this description the FRET rate is therefore a fimction of the refractive index of the medium between the two molecules n, the fluorescence lifetime Tp[s] and quantum efficiency Qd of the donor in the absence of FRET, Avogadro s number N, the separation of the two molecules R[cm], the normalized spectral overlap integral / [ cm j and the so-called orientation factor k. Note that different forms of equa-... 

Description of problem Fretting and pitting on the raceway of the ball bearing is shown in Fig. 4.78. The inner and outer rings were made of cold drawn 52100 steel tubing. 

General Description. Fretting corrosion is a combined wear and corrosion process in which material is removed from contacting surfaces when motion between the surfaces is restricted to very small amplitude oscillations (often, the relative movement is barely discernible). Usually, the condition exists in machine components that are considered fixed and not expected to wear. Pressed-on wheels can often fret at the shaft/wheel hole interface. 

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