Shallowness factor values

The EU TGD (EC 2003) recognized that the NOAEL is not very accurate with respect to the degree to which it corresponds with the (unknown) true NAEL. In the case of a steep curve the derived NOAEL can be considered as more reliable (the greater the slope, the greater the reduction in response to reduced doses) in the case of a shallow curve, the uncertainty in the derived NOAEL may be higher and this has to be taken into account in the assessment. If a LOAEL has to be used in the assessment, then this value can only be considered reliable in the case of a very steep curve. According to KEMI (2003), extrapolation factors of between 3-5 are used for LOAEL-to-NOAEL extrapolation without any scientific basis in risk assessment reports of existing substances within the European Union. 

The extraction of toluene and 1,2 dichlorobenzene from shallow packed beds of porous particles was studied both experimentally and theoretically at various operating conditions. Mathematical extraction models, based on the shrinking core concept, were developed for three different particle geometries. These models contain three adjustable parameters an effective diffusivity, a volumetric fluid-to-particle mass transfer coefficient, and an equilibrium solubility or partition coefficient. K as well as Kq were first determined from initial extraction rates. Then, by fitting experimental extraction data, values of the effective diffusivity were obtained. Model predictions compare well with experimental data and the respective value of the tortuosity factor around 2.5 is in excellent agreement with related literature data. 

In this work extraction models are developed for three different particle geometries using the shrinking core concept. Model calculations will be compared and fitted to extraction data of toluene and 1,2 dichlorobenzene (DCB) from shallow packed beds in order to obtain values of the efective diffusivity (De) and the tortuosity factor. 

Depth can be an indicator of interactions between LSPs and bulk SPs. In thick nanowires, an LSP is well isolated from bulk SPs, while LSPs interact with and are affected from bulk SPs significantly in shallow nanowires. It was shown that penetration depth was calculated to be smaller for thicker nanowires, as a result of increased field localization [17]. In fact, a nanowire period A) and a fill factor (/) should also be considered in this picture, in the sense that LSPs tend to be coupled to each other at appropriate values of A and/. On the one hand, if LSPs perturb SPs weakly, i.e., LSPs are dominated by SPs, local field enhancement and sensitivity improvement over conventional SPR structure are rather weak. On the other hand, if LSPs dominate SPs, resonance characteristics become so broad that resonance effectively disappears. In short, an optimum nanowire depth exists, although the optimum may depend on other parameters. 

Figure 14 Isotopic composition of shallow groundwater (solid circles) and formation waters from Jurassic (open circles with +) and Cretaceous (open circles) rocks from the central Mississippi Salt Dome Basin. S D values (squares) were computed from 5D values and a correction factor AS from Sofer and Gat (1972). Lines originating from SMOW are the range of trajectories for seawater undergoing evaporation, with line B being from Holser s (1979) estimate of evaporating seawater in the Gulf Coast. The least-squares line for the SD and 6 °0 values is also...

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