Sedimentation coefficient, segment

Fig. 15. Diagrammatic representation of the several forms of polyoma DNA. The duplex segment shown contains 12 turns, about one-fortieth of the total number. The twisted circular duplex shown contains one left-hand tertiary turn. 8 o of the right-hand duplex turns in the model are unwound to form I. The dashed circles around the denatured forms indicate the relative hydrodynamic diameters. Sedimentation coefficients (S) are given under each f

Fig. 12.4 Effects of the depth resolution in pore water concentration profiles on calculating the rates of diffusive transport. Three samples drawn from surface sediments are shown to possess different resolutions (intervals 0.5 cm - dots, 1.0 cm diamonds, 2.0 cm - squares). All values are sufficient to plot the idealized concentration profile within the hounds of analytical error, yet very different flux rates are calculated in dependence on the depth resolution values. In the demonstrated example, the smallest sample distance indicates the highest diffusion (2.98 mmol cmA f ). As soon as the vertical distance between single values increases, or, when the sediment segments under study grows in thickness, the calculated export across the sediment-water boundary diminishes (2.34-t.64mmol cm yr ). In our example, this error which is due to the coarse depth resolution can be reduced by applying a mathematical Fit-function. A truncation of 0.05 cm yields a flux rate of 2.84 mmol cm yr. (The indicated values were calculated under the assumption of the presented porosity profile according to Pick s first law of diffusion - see Chapter 3. A diffusion coefficient of 1 cmA f was assumed. Adaptation to the resolution interval of 2.0 cm was accomplished by using a simple exponential equation).

The dispersion term is absent since dividing the reach into Ax completely mixed segments accomplishes dispersion numerically. In equation 1 t is time (t), Ct is soluble, particulate, and colloidal, concentration (M/L ), U is average water velocity (M/t), Ds is particle deposition flux (M/L t), h is water column depth (L), m v is suspended solids concentration (M/L ), fp and fd are fractions chemical on particles and in solution, kf is the soluble fraction bed release mass-transfer coefficient (L/t), Cs is the total, soluble and colloidal, concentration at the sediment-water interface (M/L ), Rs is particle resuspension flux (M/L t), ms is the particulate chemical concentration in the surface sediment (M/L ), fps Cts is the fraction on particles and total chemical concentration in the surface sediment (M/L ), Kl is the evaporation mass-transfer coefficient (L/t), Ca is chemical vapor concentration in air (M/L ), H is Henry s constant (L / L ) and Sx is the chemical lost by reaction (M/L t). It is conventional to use the local or instantaneous equilibrium theory to quantify the dissolved fraction, fd, particulate fraction, fp, and colloidal fraction, fooM in both the water column and bed. The equations needed to quantify these fractions appear elsewhere (4, 5, 6) and are omitted here for brevity. 

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