Uptake calculated

Figure 6.8 The time-course of (a) N uptake, (b) soil solution NH4, and (c) and (d) root length density in pots of flooded soil planted with rice with (O) and without ( ) added N. In (a), lines are fitted logistic curves, slopes of which give values of dU/dt in Equation (6.10). In (b), solid horizontal lines are Cl broken lines Cls calculated with Equation (6.11). In (c) and (d), the lines indicate the minimum root length densities required to explain uptake calculated with the measured Cl values se (full lines) and Cl derived from exchangeable NH4+ values se (Kirk and Solivas, 1997). Reproduced by permission of Blackwell Publishing...

Total partial pressure range (sum of the partial pressures of aU three MoOs vapor polymers) covered in these measurements is from about 9 X 10 to 4 X 10 s atm. Average particle diameters were 0.22 0.02 cm. Rates of uptake on the clay loam particles are shown at 0,10, and SO minutes. Dashed line indicates the rate of uptake calculated by Maxwell s equation... 

By expanding the study to include Ga [Co (CN)g], as well as additional PBs constructed from the [Fe(CN)g] building blocks, Kaye and Long (42) examined the role of framework vacancies in hydrogen sorption. The maximum amount (saturation) of hydrogen uptake, calculated from gas sorption isotherms, was found to correlate with the concentration of vacancies in the framework, but the effect is weak. The Ga [Co (CN)e] complex is free of framework vacancies and has a calculated maximum H2 sorption of 1.4 wt%, while Cu " "3[Co " "(CN)6]2 complex, which has 33% vacancy at the Co + (CN)g sites, has a calculated maximum H2 sorption of 2.1%. The authors conclude that, at least with respect to hydrogen uptake, open metal coordination sites in the framework may be more important than the increased volume that results from framework vacancies. 

In addition to isotope dilution of the DIN pools, DON can be released during the course of the experiment. The DON pool can be isolated so that the amount of N released to the pool can be quantified. This recently released N was taken up by the cells and so should be included in the uptake calculation. This rate is referred to as a gross uptake rate, Pq, and is the sum of measured uptake plus any N that was taken up and released as DON. The difference between gross and the traditionally measured net uptake rates results from the release of N-label to the DON pool. When N-labeled DON is released to the extra cellular DON pool, it is no longer in the pool and so is not included in the traditional calculation of N uptake (Bronk and Ward, 2000 Bronk et al., 1994). The following equation is used to calculate a gross N uptake rate p(Pc) ... 

A 0.5 wt. % Pt on silica catalyst gave the data listed below for the sorption of H2. Upon completion of Run 1, the system was evacuated and then Run 2 was performed. Find the dispersion and average particle size of the Pt particles. Hint. Run 1 measures the total sorption of hydrogen (reversible + irreversible) while Run 2 gives only the reversible hydrogen uptake. Calculate the dispersion based on the chemisorbed (irreversible) hydrogen. 

Transient moisture contents were measured by psychrometers within the buffer. These measurements have been converted into a water uptake calculation. Chandler (2000), based on a simplifying assumption of constant dry density. The results obtained are presented in Figure 3. 

Figure 18.4 Plot of uptake measured versus the uptake calculated the retention parameters.

Fig. 7.6 Amount of lead in long-term storage as a function of lead uptake. Based on data of Kehoe, cited in [10], with uptake calculated from gut absorption = 0.15 X intake.

The data show that the water uptakes, calculated on the assumption of liquid density in the pores, tend to be slightly lower than the micropore volumes determined from nitrogen adsorption. However it has been reported that the density of water adsorbed in microporous carbons is less than the liquid value [5]. Taking this into account suggests that for dynamic testing of carbons pre-equilibrated to a relative humidity of 80%, the micropores will be filled with water. Study of the filling of the mesoporosity by water is limited by the experimental... 

Effects of moderate doses of iodide are essentially the same as in rat thyroids. Fig.4 shows the results on 15 euthyroid J q>anese subjects whose dietary iodide intake averaged 3 mg/day Thyroid I uptake and thyroid clearance of decreased as the serum inorganic iodide concentrations increased. However, the absolute iodide uptake calculated from thyroid clearance and serum inorganic iodide concentrations clearly increased as serum iodide increased. 

Uptake at saturation by a ferric oxide gel at 25°C, calculated as a volume of liquid (v,)... 

Fig. 3.2 Adsorption isotherms for argon and nitrogen at 78 K and for n-butane at 273 K on porous glass No. 3. Open symbols, adsorption solid symbols, desorption (courtesy Emmett and Cines). The uptake at saturation (calculate as volume of liquid) was as follows argon at 78 K, 00452 nitrogen at 78 K, 00455 butane at 273 K, 00434cm g .

In calculations of pore size from the Type IV isotherm by use of the Kelvin equation, the region of the isotherm involved is the hysteresis loop, since it is here that capillary condensation is occurring. Consequently there are two values of relative pressure for a given uptake, and the question presents itself as to what is the significance of each of the two values of r which would result from insertion of the two different values of relative pressure into Equation (3.20). Any answer to this question calls for a discussion of the origin of hysteresis, and this must be based on actual models of pore shape, since a purely thermodynamic approach cannot account for two positions of apparent equilibrium. 

Thus, as pointed out by Cohan who first suggested this model, condensation and evaporation occur at difi erent relative pressures and there is hysteresis. The value of r calculated by the standard Kelvin equation (3.20) for a given uptake, will be equal to the core radius r,. if the desorption branch of the hysteresis loop is used, but equal to twice the core radius if the adsorption branch is used. The two values of should, of course, be the same in practice this is rarely found to be so. 

When the relative pressure falls to pj/p", the second group of pores loses its capillary condensate, but in addition the film on the walls of the first group of pores yields up some adsorbate, owing to the decrease in its thickness from t, to t. Similarly, when the relative pressure is further reduced to pj/p°, the decrement (nj-Wj) in the uptake will include contributions from the walls of both groups 1 and 2 (as the film thins down from tj to fj), in addition to the amount of capillary condensate lost from the cores of group 3. It is this composite nature of the amount given up at each step which complicates the calculation of the pore size distribution. 

In using the table for pore size calculations, it is necessary to read off the values of the uptake from the experimental isotherm for the values of p/p° corresponding to the different r values given in the table. Unfortunately, these values of relative pressure do not correspond to division marks on the scale of abscissae, so that care is needed if inaccuracy is to be avoided. This difficulty can be circumvented by basing the standard table on even intervals of relative pressure rather than of r but this then leads to uneven spacings of r . Table 3.6 illustrates the application of the standard table to a specific example—the desorption branch of the silica isotherm already referred to. The resultant distribution curve appears as Curve C in Fig. 3.18. 

That the uptake n, at saturation does indeed approximate to the pore volume of the adsorbent is confirmed by the agreement, frequently obtained, between the quantity and the pore volume calculated from the... 

Wynne-Jones and Marshfound somewhat similar results with a number of carbons made by pyrolysis of eight organic polymers at a series of temperatures. The isotherms of Nj at 77 K and of COj at 195 K were measured, and the apparent surface area calculated by the usual BET procedure. (Owing to the microporous nature of the solids, these figures for area will be roughly proportional to the uptake at saturation and therefore... 

In Fig. 5.21, from Dawson s paper, the uptake at X for the 250°C-outgassed sample is dose to the calculated value for a monolayer of water with a (H20) = 101 A. Point X has therefore been ascribed to a close-packed monolayer of water on a hydroxylated surface of rutile. The fact that the differential entropy of adsorption relative to the liquid state (calculated from the isosteric heat of adsorption) changes sharply from negative to positive values in this region with A s 0 at X was regarded as supporting evidence. ... 

Models for transport distinguish between the unsaturated zone and the saturated zone, that below the water table. There the underground water moves slowly through the sod or rock according to porosity and gradient, or the extent of fractures. A retardation effect slows the motion of contaminant by large factors in the case of heavy metals. For low level waste, a variety of dose calculations are made for direct and indirect human body uptake of water. Performance assessment methodology is described in Reference 22. 

As the oxygen transfer rate under steady-state conditions must equal oxygen uptake, K a may be calculated ... 

A tracing of the electrode signal during a cycle of turning aeration off and on is shown in Fig. 24-15. The rate of supply is zero (after bubbles have escaped) in the first portion of the response curve thus, the slope equals the uptake rate by the organisms. When aeration is resumed, both the supply rate and uptake rate terms apply. The values for C — C can be calculated from the data, the slope of the response curve at a given point is measured to get dC/dt, and the equation can be solved for K a because all the other values are known. 

A useful index of process performance is the oxygen uptake rate, OUR, that is calculated from the difference in oxygen concentration of the inlet air and the exiting gas. Also important is the respiration ratio defined as the carbon dioxide evolved divided by the oxygen consumed. 

The choice of die transporting reagent for a given material is made so diat die reaction is as complete as possible in one direction, in die uptake, and die reverse reaction in die opposite direction at die deposition site. This requires diat not only die choice of die reagent, but also die pressure and temperature ranges under which die reaction is most effectively, or quantitatively, performed, must be calculated (Alcock and Jeffes, 1967 1968). There will always be limitations placed on diis choice by die demands of die chemical ineruiess and temperature stability of die containing materials in which die reaction is canied out. 

The issue of the theoretical maximum storage capacity has been the subject of much debate. Parkyns and Quinn [20] concluded that for active carbons the maximum uptake at 3.5 MPa and 298 K would be 237 V/V. This was estimated from a large number of experimental methane isotherms measured on different carbons, and the relationship of these isotherms to the micropore volume of the corresponding adsorbent. Based on Lennard-Jones parameters [21], Dignum [5] calculated the maximum methane density in a pore at 298 K to be 270 mg/ml. Thus an adsorbent with 0.50 ml of micropore per ml could potentially adsorb 135 mg methane per ml, equivalent to about 205 V/ V, while a microporc volume of 0.60 mEml might store 243 V/V. Using sophisticated parallel slit... 

The dried polyoxazoline-modified silica gel was immersed into distilled water. The adsorption property of the resulting gel was estimated by the water content. The water uptake was calculated from an expression of (W -W)jW, where Wis the weight of dried gel and W is the weight of water-absorbed gel. The modified gel showed a higher water-adsorption property than that of untreated silica gel, which absorbed 10.8 multiples of water. The water uptake of modified gel was up to 13.7 multiples of the weight of dried gel. Thus, silica gel has been made more hydrophilic by a polyoxazoline segment. 

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