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Comparison of photometric and radiometric quantities. Radiometry is a set of techniques for measuring electromagnetic radiation, including visible light.Radiometric techniques in optics characterize the distribution of the radiation's power in space, as opposed to photometric techniques, which characterize the light's interaction with the human eye.
In photometric quantities every wavelength is weighted according to how sensitive the human eye is to it, while radiometric quantities use unweighted absolute power. For example, the eye responds much more strongly to green light than to red, so a green source will have greater luminous flux than a red source with the same radiant flux would.
Spectrophotometry is a tool that hinges on the quantitative analysis of molecules depending on how much light is absorbed by colored compounds. Important features of spectrophotometers are spectral bandwidth (the range of colors it can transmit through the test sample), the percentage of sample transmission, the logarithmic range of sample ...
Mathematically, for the spectral power distribution of a radiant exitance or irradiance one may write: =where M(λ) is the spectral irradiance (or exitance) of the light (SI units: W/m 2 = kg·m −1 ·s −3); Φ is the radiant flux of the source (SI unit: watt, W); A is the area over which the radiant flux is integrated (SI unit: square meter, m 2); and λ is the wavelength (SI unit: meter, m).
Protein methods are the techniques used to study proteins. There are experimental methods for studying proteins (e.g., for detecting proteins, for isolating and purifying proteins, and for characterizing the structure and function of proteins, [1] often requiring that the protein first be purified). Computational methods typically use computer ...
cd/m 2 (= lm/(sr⋅m 2)) L −2 ⋅J: Luminous flux per unit solid angle per unit projected source area. The candela per square metre is sometimes called the nit. Illuminance: E v: lux (= lumen per square metre) lx (= lm/m 2) L −2 ⋅J: Luminous flux incident on a surface Luminous exitance, luminous emittance M v: lumen per square metre lm/m ...
This is the activity of an enzyme per milligram of total protein (expressed in μmol min −1 mg −1). Specific activity gives a measurement of enzyme purity in the mixture. It is the micro moles of product formed by an enzyme in a given amount of time (minutes) under given conditions per milligram of total proteins. Specific activity is equal ...
Protein–protein docking, the prediction of protein–protein interactions based only on the three-dimensional protein structures from X-ray diffraction of protein crystals might not be satisfactory. [44] [45] Network analysis includes the analysis of interaction networks using methods of graph theory or statistical methods.