With more education and experience, accountants can become certified. Some financial documents, such as those submitted to the Securities and Exchange Commission, must be signed by a Certified Public Accountant.
Hyperchromicity is the increase of absorbance (optical density) of a material. The most famous example is the hyperchromicity of DNA that occurs when the DNA duplex is denatured. The UV absorption is increased when the two single DNA strands are being separated, either by heat or by addition of denaturant or by increasing the pH level.
On mixing at ambient temperature the two strands of DNA spontaneously form a duplex (C ds) (i.e. Î± = 1) (this is true for DNA strands of any reasonable length). Each sample is heated in a UV spectrometer from 20 ÂºC to (say) 80 ÂºC at a rate of one degree per minute and the absorbance is monitored as shown in Figure 2. The melting temperature, T m, is the temperature at the maximum absorbance gradient (d A /d T) and corresponds to 50% association (Î± = Â½).