Didymium

Didymium (Greek: twin element) is a mixture of the elements praseodymium and neodymium. It is used in safety glasses for glassblowing and blacksmithing, especially when a gas (propane) powered forge is used, where it provides a filter which selectively blocks the yellowish light at 589 nm emitted by the hot sodium in the glass, without having a detrimental effect on general vision, unlike dark welder's glasses. The strong ultraviolet light emitted by the superheated forge gases and insulation lining the forge walls is also blocked thereby saving the crafters' eyes from serious cumulative damage. (See also arc eye, also known as welder's flash or photokeratitis.) The usefulness of didymium glass for eye protection of this sort was discovered by Sir William Crookes.

Didymium photographic filters are often used to enhance autumn scenery by making leaves appear more vibrant. It does this by removing part of the orange region of the color spectrum, acting as an optical band-stop filter. Unfiltered, this group of colors tends to make certain elements of a picture appear "muddy". The "Sodium Vapor Process" used in motion picture matte work included a didymium filtering prism in the camera.

Didymium wildpretii

Didymium wildpretii is a species of slime mold which feeds on the decaying remains of various species of cacti. It was first described in 2007 and has been found across Mexico and the Canary Islands, but may be present where other cacti grow. Its sporocarps are short (0.1–0.7 mm tall); their sporotheca is pale yellow with an orange stalk and their spores have a diameter of 7.5 μm. When grown on agar, it completes its life cycle in 28–56 days. It grows on basic media with a pH of 7.8–10.0, with optimum growth occurring at 8.5–9.4. The species was named after Wolfredo Wildpret de la Torre, an expert in the flora of the Canary Islands.

Hosts

D. wildpretii is known to grow on species of the globose cacti Echinocactus platyacanthus, Mammillaria carnea and Ferocactus latispinus; the opuntioid cacti Opuntia depressa, O. maxima, O. pilifera and O. tomentosa) and the columnar cacti (Myrtillocactus geometrizans, Pachycereus hollianus, P. weberi, Stenocereus and Neobuxbaumia.

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