Extrinsic mode

Extrinsic. Many of the traditional bioassays are based on optical measurements, but these are solution assays without immobilised reagents. Optical biosensors are concerned with interrogation of reactions at surfaces, but often the reagents are the same the optical fibres acting, in the extrinsic mode as light guides to transmit information to and from a remote target reaction at its terminus. 

FIGURE 7 Photoconductor. Intrinsic operation shown. In extrinsic mode, mobile electrons are photoexcited from fixed positive donor impurities, or holes from negative acceptors. 

Fig. 1. Photoexcitation modes iu a semiconductor having band gap energy, E, and impurity states, E. The photon energy must be sufficient to release an electron (° ) iato the conduction band (CB) or a hole (o) iato the valence band (VB) (a) an intrinsic detector (b) and (c) extrinsic donor and acceptor...

INTRINSIC AND EXTRINSIC FLUORESCENCE. Intrinsic fluorescence refers to the fluorescence of the macromolecule itself, and in the case of proteins this typically involves emission from tyrosinyl and tryptopha-nyl residues, with the latter dominating if excitation is carried out at 280 nm. The distance for tyrosine-to-tryp-tophan resonance energy transfer is approximately 14 A, suggesting that this mode of tyrosine fluorescence quenching should occur efficiently in most proteins. Moreover, tyrosine fluorescence is quenched whenever nearby bases (such as carboxylate anions) accept the phenolic proton of tyrosine during the excited state lifetime. To examine tryptophan fluorescence only, one typically excites at 295 nm, where tyrosine weakly absorbs. [Note While the phenolate ion of tyrosine absorbs around 293 nm, its high pXa of 10-11 in proteins typically renders its concentration too low to be of practical concern.] The tryptophan emission is maximal at 340-350 nm, depending on the local environment around this intrinsic fluorophore. 

KhisinaN. R., Wirth R., Andrut M., and Ukhanov A. V. (2001) Extrinsic and intrinsic mode of hydrogen occurrence in natural olivines FTIR and TEM investigation. Phys. Chem. Mineral. 28, 291-301. 

Far-IR reflectivity spectra of the (Pbo 5Cao 5)(Eeo 5Tao 5)03 specimens sintered at 1250°C for 30 min were taken to calculate the intrinsic dielectric loss at microwave frequencies. The spectra of the specimens were fitted by 10 resonant modes. The calculated reflectivity spectra are well fitted with the measured ones, as shown in Figure 22.4 and Table 22.2. The dispersion parameters of the specimens in Table 22.2 were determined by the Kramers-Kronig analysis and the classical oscillator model. The calculated values were higher than the measured ones by Hakki and Coleman s method, which is due to extrinsic effects such as grain size and porosity. Assuming the mixture of dielectrics and spherical pore with 3-0 connectivity, the measured loss quality also depends on the porosity as well as the intrinsic loss of materials, and Equation 22.24 may be modified for the loss quality, as in Equation 22.25 ... 

The crystallization of constituent OLED materials is likely to facilitate most of the extrinsic failure modes. If the cathode conforms to the volume shrinkage in the film that occurs with aging and/or crystallization, uneven charge injection... 

Fig. 13.10 Caspase activation by extrinsic and intrinsic apoptotic pathways, (a) Extrinsic path. This path is mediated by members of the tumor necrosis factor (TNF) superfamily (see text), (b) Intrinsic pathway. This path may be mediated by various physiological or pathological changes, but only the modes of induction of this path in periodontitis are discussed (see text). Details of cytochrome c release and caspase activation are shown in Fig. 13.11 (This figure is modified from Fig. 1 in Schimmer AD (2004 Oct 15) Inhibitor of Apoptosis Proteins Translating Basic Knowledge into Clinical Practice. Cancer Research, 64 7183-7190)...

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