Relative recovery rate

At typical flow rates, the concentration in the dialysate, Cout, is less than the actual concentration in the extracellular fluid, Cext (23). The ratio of Cout/Cext is defined as relative recovery, R, and must be considered for probe calibration and sampling optimization. In vitro, R is easily calculated because the dialysate and the extracellular fluid are homogenous therefore, probe calibration is easily obtained. However, in in vivo studies, calculation of R is difficult because of the active removal of neurotransmitters by uptake and tortuosity. Movement of analytes is impeded by tissue that surrounds the probe, and this movement cannot be easily accounted for with in vitro calibrations. Therefore, the most common method to determine concentrations in vivo is the zero-net flux method, in which known analyte concentrations are added to the perfusate (Cin), and then the analyte concentration is measured at the probe outlet (Cout)- The difference between analyte concentration at the inlet and outlet is used to establish the actual analyte concentration in the tissue, and the relative recovery rate can be calculated. This calibration method can be used to estimate basal levels of neurotransmitters. For example, the zero-net flux method has been used to determine that basal concentrations of dopamine are approximately 1-3.5 nM (24, 25). Although basal level concentrations... 

Therefore, the single-pump method is commonly used only for smaller spills when the gasoline-water recovery rates are relatively low (e.g., less than 1892 L/h or 500 gal/h). 

When these figures are compared to those of other major industrial countries (Figure 10.2), it is clear that the United Kingdom has a relatively good utilisation rate (57%) but its recovery rate is close to the bottom of the international league table (30%). 

If the values for all the factors are known and expressed in common units, this equation will provide a reasonable estimate of flow from recovery wells. The difficulty of actual application of this equation is the determination of the water-oil saturation in the aquifer matrix (thus, the relative permeability). The equation assumes a steady-state flow setting. In a dynamic situation where the oil reserves are being depleted and water-oil mixtures are variable, it is almost impossible (from an economic point of view) to use these equations precisely. However, inclusion of some assumptions based on results of the initial site investigation can often be of assistance in initial spacing of recovery wells and estimating recovery rates. 

Baildown tests have been used for decades during the initial or preliminary phases of LNAPL recovery system design to determine adequate locations for recovery wells and to evaluate recovery rates. Baildown tests involve the rapid removal of fluids from a well with subsequent monitoring of fluid levels, both the LNAPL-water (or oil-water) interface and LNAPL-air (or oil-air) interface, in the well with time. Hydrocarbon saturation is typically less than 1, and commonly below 0.5, due to the presence of other phases in the formation (i.e., air and water). Since the relative permeability decreases as hydrocarbon saturation decreases, the effective conductivity and mobility of the LNAPL is much less than that of water, regardless of the effects induced by increased viscosity and decreased density of the LNAPL. 

The primary disadvantage is that if these bailers are adjusted to remove only the LNAPL layer, they do not create a drawdown cone. Therefore, unless the product layer is relatively thick and quite fluid, the recovery rate tends to be slow. Also, use of bailers in deeper wells requires significant bailer travel time, which can decrease the effectiveness. 

The more water that is extracted, the smaller the volume of concentrate, but the greater the salinity of the brine. This trade off between concentration factor and recovery rate is shown in Fig. 2.1. As recovery approaches 100%, there is a sharp increase in the concentration factor, however the volume of the concentrate relative to the volume of feed, Qc/Qr is shown to decrease linearly. Figure 2.1 provides a useful comparison between the degree of concentration that may be achieved, and the volume of concentrate that must be managed. Higher recoveries are generally more desirable, as more water is recovered and less feed water is required to produce the same amount of water. 

X-/mean-charts 3 Blank value chart 3 Range chart with absolute ranges 3 Range chart with relative ranges 3 Recovery rate chart 3 Differences chart... 

At least six major phytotoxic air pollutants have been shown to reversibly inhibit apparent photosynthetic rates in plants (1 - ). Studies indicate that these phytotoxicants ranked in the following order according to the relative amount of inhibition effected after several hours of exposure to equal pollutant concentrations HF>Cl2-03>S02>N02>N0. A summary of the experimental results which compares measured depressions in CO2 uptake rates of barley and oat canopies after 2-hr pollutant exposures in environmental chambers appears in Figure Typical inhibition and recovery rate curves for exposures that reduced CO2 absorption rates by 20 percent at the end of the 2-hr fumigations are also shown. Similar data have been obtained for alfalfa, another important crop species which was cultured and exposed under identical conditions In contrast, equivalent... 

In another application, Esy-GC-ECD was applied to the extraction of 14 organochlorine pesticides (OCPs) in spiked and contaminated complex samples, such as raw leachate water and soil-water slurry samples.94 A downsized filtration vessel was deemed crucial for sample filtration after acidification and the addition of activated copper granules (to remove elemental sulfur) and 20% acetonitrile (to prevent adsorption and enhance enrichment). Under optimal conditions, extraction of a 3-mL leachate water sample dispensed at a flow rate of 100 pL min-1 gave Ee values between 32 and 242 and LODs between 1 and 20 ng I. It was also demonstrated that, since ESy extraction is dynamic and its extraction efficiency low, calculation of relative recovery was more relevant than extraction efficiency in all ESy applications. 

Since the first reports on microdialysis in living animals, there have been efforts to estimate true (absolute) extracellular concentrations of recovered substances (ZetterstrOm et al., 1983 Tossman et al., 1986). Microdialysis sampling, however, is a dynamic process, and because of a relatively high liquid flow and small membrane area, it does not lead to the complete equilibration of concentrations in the two compartments. Rather, under steady state conditions, only a fraction of any total concentration is recovered. This recovery is referred to as relative or concentration recovery, as opposed to the diffusion flux expressed as absolute or mass recovery. The dependence of recovery on the perfusion flow rate is illustrated in Figure 6.2. As seen, relative recovery will exponentially decrease with increasing flow as the samples become more... 

Obtaining realistic errors is one of the most difficult, yet most crucial problems in all flux estimates. Such errors can be approximated through an independent error analysis for several factors that are involved in estimating fresh and altered rock composition. There are uncertainties arising from petrographic observations, in the choices of representative samples, recovery rate biases, and analytical errors. In most cases analytical errors are a relatively minor source of uncertainty, and they are typically rather well documented. Probably the most crucial analytical uncertainty is in acurately determining the titanium concentration that is used as a normalizing factor to account for open-system behavior. This uncertainty directly relates to an error in the fluxes, and thus fluxes are difficult to constrain to better than 1 % of the whole rock abundance of a particular element. 

Recovery rate (if the recovery relative occurred as a desorption at zero analyte concentration) or recovery efficiency (if an external influence for the signal recovery is required) it was defined as signal changes during the fixed desorption time or during another defined recovery procedure (i.e., a temperature pulse)... 

Many relatively shallow reservoirs, especially those in Alaska and some in West Texas, are at temperatures below 50° C. In such reservoirs, three hydrocarbon fluid phases (L1-L2-V) form when oil and solvents mix.f Slim tube recoveries greater than 90% can be observed in such fluids with hydrocarbon solvents, even when three fluid phases form. Although true miscibility did not develop, high oil recovery rates were observed through the condensing-vaporizing mechanism. These solvents also had high coreflood recoveries. 

In middle-phase microemulsion, owing to the lowest ITT, oil and water can be solubilized in each other, and oil droplets can flow more easily through pore throats. The oil droplets move forward and merge with the oil downstream to form an oil bank. Because of the solubilization effect, water and oil volumes are expanded, leading to higher relative permeabilities and lower residual saturations. However, when kj increases faster than k with decreasing IFT, the oil saturation in the oil bank and the oil recovery rate are deterioated, if no viscosity alteration is made. 

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