Pressure-swing distillation is essentially the same as the unidirectional distillation used to break azeotropic mixtures, but here both positive and negative pressures may be employed.
This improves the selectivity of the distillation and allows a chemist to optimize distillation by avoiding extremes of pressure and temperature that waste energy. This is particularly important in commercial applications.
One example of the application of pressure-swing distillation is during the industrial purification of ethyl acetate after its catalytic synthesis from ethanol.
Problems of the thyroid gland occur in 2050% of individuals with Down syndrome. Low thyroid is the most common form, occurring in almost half of all individuals. Thyroid problems can be due to a poorly or nonfunctioning thyroid at birth (known as congenital hypothyroidism) which occurs in 1% or can develop later due to an attack on the thyroid by the immune system resulting in Graves' disease or autoimmune hypothyroidism. Type 1 diabetes mellitus is also more common.
The diagnosis can often be suspected based on the child's physical appearance at birth. An analysis of the child's chromosomes is needed to confirm the diagnosis, and to determine if a translocation is present, as this may help determine the risk of the child's parents having further children with Down syndrome. Parents generally wish to know the possible diagnosis once it is suspected and do not wish pity.
Efforts are underway to determine how the extra chromosome 21 material causes Down syndrome, as currently this is unknown, and to develop treatments to improve intelligence in those with the syndrome. One hope is to use stem cells. Other methods being studied include the use of antioxidants, gamma secretase inhibition, adrenergic agonists, and memantine. Research is often carried out on an animal model, the Ts65Dn mouse.
The taxon Dinosauria was formally named in 1842 by paleontologist Sir Richard Owen, who used it to refer to the "distinct tribe or sub-order of Saurian Reptiles" that were then being recognized in England and around the world. The term is derived from the Greek words (deinos, meaning "terrible", "potent", or "fearfully great") and (sauros, meaning "lizard" or "reptile"). Though the taxonomic name has often been interpreted as a reference to dinosaurs' teeth, claws, and other fearsome characteristics, Owen intended it merely to evoke their size and majesty.
Other prehistoric animals, including mosasaurs, ichthyosaurs, pterosaurs, plesiosaurs, and Dimetrodon, while often popularly conceived of as dinosaurs, are not taxonomically classified as dinosaurs.