Retention function

Pulmonary retention functions are given as fractions of the initial pulmonary burden and are not corrected for radioactive decay of lMCe Ti/> = 285 d). 

FIGURE 2.11 Influence of substitution on solute retention. Functional groups with phenol as base. Column Lichrosorb RP CIS 250 x4 mm mobile phase water. 

Based on data on these dial painters from the 1985 listing of radium cases studied at the Argonne National Laboratory (Gustafson and Stehney 1985) Rundo et al. (1986) have estimated that the lowest total intake level of radium associated with a malignancy was 60 pCi (2,222 kBq) or 1.03 p Ci/kg (38 kBq/kg) based on an estimated 58 kg body weight for a woman. These estimates are based on current radium body content modified by the Norris retention function (to account for the decrease in body radium content with time since exposure) and an estimate of radium-228 from measurements of radium-226 and the known or presumed ratios of these isotopes in the materials to which these persons were exposed (Rundo et al. 1986). 

Adams, N., Spoor, N.L. (1974). Kidney and bone retention functions in the human metabolism of uranium. Phys. Med. Biol 19 460-71. 

The phenomenological description of the retention mechanism discussed above is only applicable for the system with single partitioning process and well-defined stationary and mobile phases. A more general method for the derivation of retention function is based on the solution of column mass balance [17]. 

In the derivations of the retention functions so far, the adsorbed phase volume or thickness of the adsorbed layer was not introduced. The adsorbent and column parameters (surface area and void volume) independently measured are not dependent on the eluent type composition. Measurement of the void volume and adsorbent surface area is discussed in the following references 18 and 23. 

The principle involved in this type of multi-layered design is to ideally (1) impart the retention function to a layer of the separating membrane as thin as possible (so long as it... 

This method enables prediction of the quahty of a separation on the basis of a relatively hmited number of the experimental data, collected in previous experiments. According to this approach, the chromatographic results are interpreted in terms of the retention functions, valid for each individual solute separately. Some good examples of the interpretative strategy are the so-called window diagrams approach [20] and the search for the extremum of the multiparameter response function with the aid of the genetical algorithm [21],... 

Mode Type of Retention Functional Groups Column Packing... 

In practice, this local scale is considered to correspond to the size of the characterization techniques of local soil properties, let s say a small laboratory column. As such the microscopic pore scale variability is no longer explicitly modelled but encoded through effective flow and transport properties at the macroscopic level. The effective macroscopic properties contain of course the signature of the lower level microscopic variability. As such macroscopic effective moisture retention function, hydraulic conductivity or hydrodynamic dispersivity is determined by microscropic pore size distribution, connectivity and tortuosity within the macroscopic sample. 

The soil retention function of the geotextile separator can be seen as similar to the geotextile filter, in that for a suitable separator the AOS of the geotextile must be related to the particle size distribution and, as stated under the filtration function, this aspect will be considered in more detail later when describing the relationship between structure, properties, and functionalities of geotextiles. 

To measure the moisture retention function of soils, which are a required parameter for modelling unsaturated flow in soils (Stormont, Henry, Evans, 1997). 

Stormont, J. C., Henry, K. S., Evans, T. M. (1997). Water retention functions of four nonwoven polypropylene geotextiles. Geosynthetics International, 4(6), 661—672. Svedova, J. (1990). Industrial textiles. NY Elsvier Science Publishing Co. Inc. 

Direct or indirect measurements provide information about the amount(s) of radionuclides present in the body, in parts of the body such as specific organs or tissues, in a biological sample or in a sample from the working enviromnent. The first use of these data is likely to be an estimation of the intake of the radionuclide by the worker. Biokinetic models which describe body and organ contents, and activity in excreta, as a function of time following intake, and exposure models which relate intake to workplace conditions, are used for this purpose. Alternatively, measurements of activity in the body can be used to estimate dose rates directly. The calculation of committed doses from direct measurements still involves the assumption of a biokinetic model if sufficient measurements are not available to determine retention functions. 

The ICRP has pnblished generic valnes of m t) for selected radionuclides in tissnes or excreta, together with retention functions for systemic activity [8]. Further information is provided in ICRP Pnblication 78 [9] using more recent biokinetic models. 

Equation (16) defines the observed or apparent solute retention Fq as a function of the actual solute concentrations on both faces of the membrane. Unlike the true retention fimction, F, the observed or apparent retention function, Fq, can be dependent on solution pressure, recirculation speed, and/or molecular weight [134]. 

Measurements of mucociliary clearance in lungs of healthy human subjects were performed by inhaling radiolabeled aerosol particles. Retention of these particles was measured either with a gamma-camera or other gamma-ray detectors from outside the lungs. The fast-cleared fraction of the retention function was used as an indicator of mucociliary clearance. The half-time of the mucociliary clearance in healthy humans was 4(fast) = 2-4 hr, and this fast phase of clearance was flnished after about 6-12 hr. Thus, many authors have used 24-hr clearance as a measure of airway deposition or deposition in the tracheobronchial tree. However, this is true only if all particles are cleared from intrathoracic airways by mucociliary clearance within 24 hr. If particles are retained in airways after 24 hr, they carmot be distinguished from those deposited in the peripheral lungs from where particle transport is well known to be slow (see Sec. III). 

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