Linear energy transfer , production

Because of the high linear energy transfer (LET) of the particles produced by the 10B(n,a)7Li reaction, the production of secondary ions is not enhanced in the presence of oxygen with low-LET radiation such as external photon irradiation, tissues... 

Linear energy transfer has often been shown to be a poor parameter for characterizing product yields. Therefore in order to compare the results for the different ions the MZ jE parameter has been used. This parameter has been successfully used in the past and seems to work well for the data presented here. Note that an increase in MZ jE corresponds to an increase in LET so product trends as a function of MZ jE presented here are comparable to similar discussions in the literature using LET. Unfortunately, there is no good formalism to fit product yields as a function of MZ jE. The solid lines in Figs. 9-14... 

The methods used in the investigation of heavy-ion reactions are similar to those described in section 8.6. The high linear energy transfer (LET) and the relatively short range of heavy ions have to be taken into account. On-line separation of shortlived products is of special importance. 

The effect of Linear Energy Transfer (let) on the radiolysis of methyl iodide has been studied by Sturm and Schwarz The increase of the yields of ethane, methane, hydrogen, ethylene and acetylene with let supports the view of Gillis et that these products are formed by diffusion-controlled reactions of radicals... 

Friedland W., Jacob P., Paretzke H.G., Stork T., Monte Carlo simulation ofthe production of short DNA fragments by low-linear energy transfer radiation using higher-order DNA models, Radiat. Res., 1998,150,170-182. 

The yield of H2 in the radiolysis of polymers with y-rays is well known for several types of polymers [2], However, transuranic waste materials are a-particle emitters. The radiation chemistry induced by a-particles can be very different than that due to y-rays because of the difference in energy deposition density [13], The high linear energy transfer (LET, equal to the stopping power) of heavy particles leads to an increase in second order reactions, which may change the yields of some products. 

The application of the calculation method based on derived relationships between the yields of some radiolysis products and the amounts of linear energy transfer (LET) made it possible to determine the value of the observed yield of water decomposition in aerated solutions. The value obtained is in agreement with the quantity G(—H20)02, found by the equation of material balance. 

In radiation protection it is necessary to provide a factor that denotes the modification of the effectiveness of a given absorbed dose by LET (Linear Energy Transfer). Unlike RBE, which is always experimentally determined, this factor must be assigned on the basis of a number of considerations and it is recommended that it be termed the quality factor (QF). Provisions for other factors are also made. Thus a distribution factor (DF) may be used to express the modification of biological effect due to nonuniform distribution of internally deposited radionuclides. The product of absorbed dose and modifying factors is termed the dose equivalent, (//). 

Finally, in activated chemiluminescence, an added compound also leads to an enhancement of the emission intensity however, in contrast with the indirect CL, this compound, now called activator (ACT), is directly involved in the excitation process and not just excited by an energy transfer process from a formerly generated excited product (Scheme 5). Activated CL should be considered in two distinct cases. In the first case, it involves the reaction of an isolated HEI, such as 1,2-dioxetanone (2), and the occurrence of a direct interaction of the ACT with this peroxide can be deduced from the kinetics of the transformation. The observed rate constant (kobs) in peroxide decomposition is expected to increase in the presence of the ACT and a hnear dependence of kobs on the ACT concentration is observed experimentally. The rate constant for the interaction of ACT with peroxide ( 2) is obtained from the inclination of the linear correlation between obs and the ACT concentration and the intercept gives the rate constant for the unimolec-ular decomposition ( 1) of this peroxide (Scheme 5). The emission observed in every case is the fluorescence of the singlet excited ACT" ° . ... 

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