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Measurement of the specific surface area using the BET method is useful for comparing different cements. This may be performed using adsorption isotherms measured in different ways, including the adsorption of water vapour at temperatures near ambient, and adsorption of nitrogen at 77 K (the boiling point of liquid nitrogen).
In cardiology, aortic valve area calculation is an indirect method of determining the area of the aortic valve of the heart. The calculated aortic valve orifice area is currently one of the measures for evaluating the severity of aortic stenosis. A valve area of less than 1.0 cm 2 is considered to be severe aortic stenosis. [1] [2]
Scratches, represented by triangular-shaped grooves, make the surface area greater. Specific surface area (SSA) is a property of solids defined as the total surface area (SA) of a material per unit mass, [1] (with units of m 2 /kg or m 2 /g). Alternatively, it may be defined as SA per solid or bulk volume [2] [3] (units of m 2 /m 3 or m −1).
The D86 width is defined as the diameter of the circle that is centered at the centroid of the beam profile and contains 86% of the beam power. The solution for D86 is found by computing the area of increasingly larger circles around the centroid until the area contains 0.86 of the total power.
The cardiac index is a measure of cardiac output divided by the BSA, giving a better approximation of the effective cardiac output; Chemotherapy is often dosed according to the patient's BSA. Glucocorticoid dosing is also expressed in terms of BSA for calculating maintenance doses or to compare high dose use with maintenance requirement.
A leaf area index (LAI) expresses the leaf area per unit ground or trunk surface area of a plant and is commonly used as an indicator of the growth rate of a plant. LAI is a complex variable that relates not only to the size of the canopy, but also to its density, and the angle at which leaves are oriented in relation to one another and to ...
Measurement of air permeability can be performed very rapidly, and does not require the powder to be exposed to vacuum or to gases or vapours, as is necessary for the BET method for determination of specific surface area. This makes it both very cost-effective, and also allows it to be used for materials which may be unstable under vacuum.
Several methods can be employed to measure porosity: Direct methods (determining the bulk volume of the porous sample, and then determining the volume of the skeletal material with no pores (pore volume = total volume − material volume). Optical methods (e.g., determining the area of the material versus the area of the pores visible under the ...