Proton-exchange membrane fuel cellProton-exchange membrane fuel cells (PEMFC), also known as polymer electrolyte membrane (PEM) fuel cells, are a type of fuel cell being developed mainly for transport applications, as well as for stationary fuel-cell applications and portable fuel-cell applications. Their distinguishing features include lower temperature/pressure ranges (50 to 100 °C) and a special proton-conducting polymer electrolyte membrane. PEMFCs generate electricity and operate on the opposite principle to PEM electrolysis, which consumes electricity.
Hydrogen sulfideHydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs. The underground mine gas term for foul-smelling hydrogen sulfide-rich gas mixtures is stinkdamp. Swedish chemist Carl Wilhelm Scheele is credited with having discovered the chemical composition of purified hydrogen sulfide in 1777.
Arsenical bronzeArsenical bronze is an alloy in which arsenic, as opposed to or in addition to tin or other constituent metals, is combined with copper to make bronze. The use of arsenic with copper, either as the secondary constituent or with another component such as tin, results in a stronger final product and better casting behavior. Copper ore is often naturally contaminated with arsenic; hence, the term "arsenical bronze" when used in archaeology is typically only applied to alloys with an arsenic content higher than 1% by weight, in order to distinguish it from potentially accidental additions of arsenic.
Christian crossThe Christian cross, seen as a representation of the crucifixion of Jesus on a large wooden cross, is a renowned symbol of Christianity. It is related to the crucifix (a cross that includes a corpus, usually a three-dimensional with representation of Jesus' body) and to the more general family of cross symbols, the term cross itself being detached from the original specifically Christian meaning in modern English (as in many other western languages).
Latin crossA Latin cross or crux immissa is a type of cross in which the vertical beam sticks above the crossbeam, with the three upper arms either equally long or with the vertical topmost arm shorter than the two horizontal arms, and always with a much longer bottom arm. If displayed upside down it is called St. Peter's Cross, because he was executed on this type of cross. When displayed sideways it is called St. Philip's cross for the same reason.
