Index of absorption

The cell is fitted with windows, and the concentration of polymer along its length is determined by optical methods which are based on measurements of refractive index of absorption solvents to be used for ultracentrifugation experiments must be chosen for difference from the polymer in both density and refractive index. An effort be made to avoid mixed solvents. Low solvent viscosity is also desirable. 

The complex index of refraction ii = n — k has a real part n, called the index of refraction, and an imaginary part k, called the index of absorption, related to the absorption coefficient a by k = a /2n. For the important case where medium 1 is air with hi = 1, the reflectivity from the surface of medium 2 is... 

The absorption of vitamin B12 can be determined by the Schilling test. An oral dose of [ Co] or [ Co]vitamin B12 is given with a parenteral flushing dose of 1 mg of nonradioactive vitamin, and the urinary excretion of radioactivity is followed as an index of absorption of the oral material. Normal subjects excrete 16% to 45% of the radioactivity over 24 hours, whereas patients lacking intrinsic factor or with antiintrinsic factor antibodies excrete less than 5%. 

Solubility parameters of dmgs (d2) have also been correlated with membrane absorption rates in model systems. A reasonable relationship was obtained between d2 and a logarithmic absorption term, thus providing one predictive index of absorption. Scott has said of solubility parameters and equations employing them that the theory offers a useful initial approach to a very wide area of solutions. Like a small-scale map for a very broad long-distance view of a sub-continent they are unlikely to prove highly accurate when a small area is examined carefully, but they are equally unlikely to prove completely absurd. ... 

Some authors have stated that human hair can be employed as an index for an excess, or a deficiency, of specific nutrients in the diet or as an index of absorption of contaminants from the environment [39]. Analysis of hair is considered to give an indication of the integrated dose of elements ingested by a person over some months. In addition, it is easier to collect hair than blood or urine. Therefore, analysis of human hair is performed by a number of organisations to monitor the level of exposure to heavy metals of a population or an individual [40]. However, this monitoring is often hampered by an insufficient reliability of the measurements. The BCR has thus decided to provide laboratories with a mean of checking their analytical performance by... 

The value of the index of absorption (a = AttR /1) in thin solid films for PIC2-18 is in the... 

Absorption, Lambert s law n. If is the original intensity, I the intensity after passing through a thickness x of a material whose absorption coefficient isk, I = loC. The index of absorption k is given by the relation k = Ank nIX j where n is the index of refraction and X the wavelength in vacuo. The mass absorption is given by k/d when d is the density. The transmission factor is given by l/lo- Barton AFM (1983) Handbook of solubihty parameters and other cohesion parameters. Chemical Rubber Company Press, Boca Raton, FL. 

The absorption coefficient, a, is related to a unitless parameter that is also used as a measure of the absorption, known as the index of absorption, k. The absorption coefficient can be derived in terms of k as... 

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