Dither is an intentionally applied form of noise used to randomize quantization error, preventing large-scale patterns such as color banding in images. Dither is routinely used in processing of both digital audio and digital video data, and is often one of the last stages of audio production to compact disc.
Hepatic porphyria. Hepatic porphyrias is a form of porphyria in which the enzyme deficiency occurs in the liver. Examples include (in order of synthesis pathway): Acute intermittent porphyria. Porphyria cutanea tarda and Hepatoerythropoietic porphyria.
Points to Remember. 1  Porphyrias are rare disorders that affect mainly the skin or nervous system and may cause abdominal pain. 2  Each of the eight types of porphyria corresponds to low levels of a specific enzyme in the heme biosynthetic pathway. 3  The exact rates of porphyria are unknown and vary around the world. For example, porphyria cutanea tarda is most common in the United States, and variegate porphyria is most common in South America. 1. What causes porphyria? Most porphyrias are inherited disorders. Scientists have identified genes for all eight enzymes in the heme biosynthetic pathway.