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.
Other types of porphyria, called acute porphyrias, primarily affect the nervous system. These disorders are described as acute because their signs and symptoms appear quickly and usually last a short time. Episodes of acute porphyria can cause abdominal pain, vomiting, constipation, and diarrhea.