Retention curve

Water-retention curve Graph showing soil-water content as a function of increasingly negative soil water potential. 

The observed calcium/phosphate ratio of 4.5 at the intercept of the calcium and phosphate retention curves that should minimize the sum of the urine calcium plus urine phosphate losses was difficult to believe in view of both the known Ca/P ratio of bone and the amounts we were adding to these solutions. This disparity between the optimal ratio determined experimentally and what we had assumed this ratio should be on the basis of known body composition is partially reconciled by the experiment of Sutton and Barltrop. They fed preterm infants stable Ca46 and observed that up to 20% of the isotope absorbed was subsequently excreted in the stool. Our infants also were undoubtedly having unmeasured calcium losses from the bile, pancreatic juice and succus entericus secreted into their intestine... 

Figure 5. The areas above the measured calcium and measured phosphate retention curves represent the percent of the intravenously administered calcium and phosphate that was lost in the urine. The combined percent losses (Ca + P) are minimized at the intercept of the curves. The dotted line represents an assumed endogenous fecal loss of 20% of the infused calcium added to the measured urinary calcium losses. The Ca/P ratio that minimizes the percent calcium and phosphate losses is then approximately 3.0. (Reproduced with permission from Ref. 4. Copyright 1983 American Society for Parenteral and Enteral Nutrition.)...

Hagenmaier (10) demonstrated that pH had little effect on water absorption of oilseed protein products, but solubility was pH dependent. He suggested that the differing degree of dependence on pH indicates that water absorption and protein solubility are not correlated. Contrastingly, Wolf and Cowan (28) reported the pH-water retention curve of soy proteins to follow the pH-solubility curve. Both solubility and water retention were minimal at the isoelectric point (4.5) and increased as the pH diverged from this point. Hutton and Campbell (20) reported that the effects of pH and temperature on water absorption of soy products paralleled those of solubility for the most part. 

Concentration of the Organic Solvent in the Eluent. As in other reversed-phase systems, the solute retention curves (log k vs. % organic modifier) on cyclodextrin-silicas are quasi-linear, at least over a limited concentration range. Such curves are shown in Figs. 2-4 for the positional isomers of nitrophenol (Fig. 2) and chloroaniline (Fig.3), and the enantiomers of Ibuprofen (Fig.4). Similar retention curves were observed and published for other positional iscmers (67), cis/trans isomers (68) and enantiomers (69). ... 

Retention curves for the nitrophenol isomers on beta-cyclodextrin-silica columns. Eluent methanol water (% v/v), column temperature 30 C, eluent flow-rate 1 mL/min. 

Fig. 3 Theoretical retention curves for catalysts noncovalently anchored to a functionalized dendritic host with various association constants concentration guest catalyst ([Guest]) in the reactor as function of the residence time (Nr). Calculation parameters [Host] = 3.60 x 10-3 M, [Guest]start = 2.80 x 1CT3 M, retention guest catalyst = 96%, retention host = 100%...

Third, picking the point on the curve of retention versus molar mass where "90 percent falls is inexact. The retention curve usually bends in a way that makes picking the "90 percent point somewhat arbitrary. 

S.4.2 Acidic Compounds. Similar retention curves can be obtained for acidic components, but obviously their retention dependence will be the mirror image of that for basic analytes (Figure 4-17). 

Fig. 9.29. (a) Retention of (S)-phenylalanine-anilide, (5)-(lK and enantioselectivity (a) for the separation of H.SX ) on a (5)-(l) imprinted polymer at different mobile pha.se pH-values. (b) Comparison of calculated (dashed lines) and experimental (solid lines) pH-retention curves for (/(,5)-(l( and benzylaminc on a benzylamine-selective polymer (reprinted with permission from Ref. 3b()l). 

Fig. 6.6. Schematic representation of a general approach that can be used to interpret the results of an in-vitro bioassay sample. The radionuclide quantities in (a) the whole body or (b) tissues or organs are expressed in logarithms because the retention curves, when expressed in such a manner, are often straight...

The primary purpose of GPC-SEC is to obtain a retention curve that represents the molecular weight (MW) distribution of the analyte. Because the retention volume is a linear function of the partition... 

Columns used in GPC-SEC are supposed to provide negligible AH regardless of MW for a given polymer. Otherwise, the dependence of AH on MW, different from that of AS, will complicate the analysis of the retention curve. Furthermore, AH would exhibit widely different characteristics determined by the interactions among the polymer, the pore surface, and the solvent, and thus negate the universality of GPC-SEC. With negligible AH, the partition coefficient is determined solely by the decrease in the conformational entropy ... 

Another mechanism that causes a change in the retention curve with concentration is intermolecular association. In a solution in which A2 is negative, such as a solution in a poor solvent, a polymer chain tends to associate with other chains at higher concentrations. In effect, the pore in the GPC-SEC column senses the presence of suspensions of a larger dimension, causing the retention curve to shift to a shorter time. 

The metabolism and tissue distribution of cesium-137 were studied in rats injected intraperitoneally and sacrificed 1-300 days postinjection. In a chronic study, rats were administered cesium-137 in their drinking water daily. In the acute study, with the exception of the brain, muscle, and total animal, all tissues showed retention curves resolvable into three exponential components with half-lives of 1.5-2, 5-8, and 15-17 days. Retention in muscles was resolvable into a two-exponential function with half-lives of 8 and 16 days. In the chronic study, the highest equilibrium cesium-137 concentrations, 10% of the average daily intake per gram, occurred in the muscle. The authors concluded that the muscle should be considered the formal critical organ for cesium-137. 

Similar to 15-bar moisture content, moisture contents at different values of suction like 0.1, 0.3, 1.0, 5.0 and 10 bars can be determined. The curve showing relationship between soil moisture content and suction is known as moisture retention curve. 

TGA behavior could be predicted from dynamic TGA behavior. Such extrapolations have, however, been found to have only very crude qualitative validity, and to fail at a quantitative level. It is possible for two polymers to have similar weight retention curves in dynamic TGA scans, but for one of them to lose weight considerably more rapidly in isothermal TGA [4,5]. 

Liquid-vapor interfacial area per pore volume (Eq. [28]) was calculated as a function of chemical potential (Fig. l-10b) using the parameters estimated from the retention curve. The resulting liquid-vapor interfacial values were then multiplied by the medium porosity to yield interfacial area per bulk sample volume as depicted in Fig. 1-1 Ob. The interfacial area Alv = 0 for p > pd (or until the largest pore is invaded by air/vapor). At the dry end of the A]v curve the interfacial area... 

Assouline S., D. Tessier, and A. Bruand. 1998. A conceptual model of the soil water retention curve. Water Resour. Res. 34 223-231. 

Comegna, V., P. Damiani, and A. Sommella. 1998. Use of a fractal model for determining soil water retention curves. Geoderma 85 307-314. 

Perfect, E. 1999. Estimating soil mass fractal dimension from water retention curves. Geoderma 88 221-232. 

Perrier, E., M. Rieu, G. Sposito, and G. de Marsily. 1996. Models of the water retention curve for soils with a fractal pore size distribution. Water Resour. Res. 32 3025-3031. 

Fig. 3-1. (A) Campbell (1974) water retention curves for different values of be, (B) Corresponding solute breakthrough curves predicted with Eq. [8].

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