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It is defined as the time needed for water to flow from the most remote point in a watershed to the watershed outlet. [1] It is a function of the topography, geology, and land use within the watershed. A number of methods can be used to calculate time of concentration, including the Kirpich (1940) [2] and NRCS (1997) [3] methods.
For example, gentamicin is an antibiotic that can be nephrotoxic (kidney damaging) and ototoxic (hearing damaging); measurement of gentamicin through concentrations in a patient's plasma and calculation of the AUC is used to guide the dosage of this drug. [3] AUC becomes useful for knowing the average concentration over a time interval, AUC/t.
Fick's first law relates the diffusive flux to the gradient of the concentration. It postulates that the flux goes from regions of high concentration to regions of low concentration, with a magnitude that is proportional to the concentration gradient (spatial derivative), or in simplistic terms the concept that a solute will move from a region of high concentration to a region of low ...
There are various competing calculation methods for the drug accumulation ratio, yielding somewhat different results. A commonly used formula defines R ac as the ratio of the area under the curve (AUC) during a single dosing interval under steady state conditions to the AUC during a dosing interval after one single dose: [1]
From the above definitions it follows that is the first derivative of concentration with respect to time, i.e. the change in concentration with time. It is derived from a mass balance. Clearance of a substance is sometimes expressed as the inverse of the time constant that describes its removal rate from the body divided by its volume of ...
The residence time of a fluid parcel is the total time that the parcel has spent inside a control volume (e.g.: a chemical reactor, a lake, a human body).The residence time of a set of parcels is quantified in terms of the frequency distribution of the residence time in the set, which is known as residence time distribution (RTD), or in terms of its average, known as mean residence time.
D t = time required; the unit of time used is the same as is used for Q; V = air or gas volume of the closed space or room in cubic feet, cubic metres or litres; Q = ventilation rate into or out of the room in cubic feet per minute, cubic metres per hour or litres per second; C initial = initial concentration of a vapor inside the room measured ...
Not to be confused with lag time. Lag time the time interval from the maximum rainfall to the peak discharge. Time to peak time interval from the start of rainfall to the peak discharge. Time of concentration Time of concentration is the time from the end of the precipitation period to the end of the quick–response runoff in the hydrograph. [3]