Linear cascades

The simplest but most valuable cascades are the linear cascades. For example, Herter and coworkers [41] report an excellent example of a linear cascade using galactose oxidase mutants to oxidize amino alcohols and amino diols to aldehydes, which are 

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The sputtering yield is proportional to the number of displaced atoms. In the linear cascade regime that is appUcable for medium mass ions (such as argon), the number of displaced atoms, E (E, is proportional to the energy deposited per unit depth as a result of nuclear energy loss. The sputtering yield Y for particles incident normal to the surface can be expressed as foUows (31). 

Fig. 29. Product kinetic energy distributions for E[ = 25, 50, 100, and 200 eV. The solid line is a best fit to the total distribution using linear cascade theory (Sigmund, 1969). (From Abrams and Graves, 2000c.)...

Time-resolved fluorescence spectra clearly indicate a linear cascade of excitation-energy transfer from BChl c in the chlorosome rods, through the BChl a-containing baseplate, to the core-antenna BChl a in the membrane, and finally to the reaction center. Overall excitation transfer efficiency from BChl c to the core antenna (B806-866) in Cf. aurantiacus cells has been reported to be 69 13% at 50 °C, but only -15% at 4 K. Excitation transfer from B806 to B866 within the core antenna is 100%. When the reaction center is closed, the 883-nm fluorescence decays less rapidly in -250 ps. 

Erythropoiesis Erythropoiesis is the development of mature red blood cells containing hemoglobin (erythrocytes) from pluripotential stem cells via a linear cascade. 

Figure 1. Three types of ion/solid interactions that can lead to sputtering. A) Knock-off, B) Linear Cascade, C) Spike.

It is implied that reflected primary ions (such as those used in ISS) are not counted in determining S. The reflected primary ion fraction is usually very small unless light (HT or He" ") ions are used with massive targets. The fundamental equation for S derived by Sigmund (15) for a linear cascade is... 

The angular and energy distribution of the sputtered atoms have also been extensively studied (10). The linear cascade theory predicts an isotropic angular distri-... 

It is useful to summarize the linear cascade theory of ion/solid interactions in the energy regime typical for surface analysis. The main ion effect is the production of the linear cascade of recoiled target atoms whose number distribution with depth depends on the ion energy, ion mass and target mass with typical values from 10 to 200A for 0.5 to 5 keV for Ar and Xe ions. 

If the primary collision density is low, the cascade is linear. Linear cascades occur when the primary collision atoms do not displace a large number of atoms per unit volume. In implanted materials, where the linear cascade is the predominant feature of the ion interaction, accurate predictions of the positions of the vacancies and ions can be made. In these materials, the presence of the ions in the structure is the largest change in the material, particularly if the material is post-annealed. Thus, for linear cascades, the ion doping effect is much more important than the ion damage effect. 

Linear Cascade Reactions Involving (a-Trantam mases I 75... 

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