dust-free drilling
81Venus — This article is about the planet. For other uses, see Venus (disambiguation). Venus   …
82Chernobyl disaster — This article is about the 1986 nuclear plant accident in Ukraine. For other uses, see Chernobyl (disambiguation). Chernobyl disaster …
83History of the Panama Canal — The history of the Panama Canal goes back almost to the earliest explorers of the Americas. The narrow land bridge between North and South America offers a unique opportunity to create a water passage between the Atlantic and Pacific oceans. This …
84Chromium — This article is about the chemical element. For other uses, see Chromium (disambiguation). vanadium ← chromium → manganese ↑ Cr ↓ Mo …
85Helium — otherusesHelium (He) is a colorless, odorless, tasteless, non toxic, inert monatomic chemical element that heads the noble gas group in the periodic table and whose atomic number is 2. Its boiling and melting points are the lowest among the… …
86Compressed-air vehicle — The Victor Tatin airplane of 1879 used a compressed air engine for propulsion. Original craft, at Musée de l Air et de l Espace …
87Africa — /af ri keuh/, n. 1. a continent S of Europe and between the Atlantic and Indian oceans. 551,000,000; ab. 11,700,000 sq. mi. (30,303,000 sq. km). adj. 2. African. * * * I Second largest continent on Earth. It is bounded by the Mediterranean Sea,… …
88Cretaceous Period — Interval of geologic time from с 144 to 65 million years ago. During the Cretaceous the climate was warmer than today. In the seas, marine invertebrates flourished, and bony fishes evolved. On land, flowering plants arose, and insects, bees in… …
89Air conditioner — For general aspects of air conditioning, see Air conditioning. A typical home air conditioning unit. An air conditioner (often referred to as AC) is a home appliance, system, or mechanism designed to dehumidify and extract heat from an area. The… …
90Book — A book is a set or collection of written, printed, illustrated, or blank sheets, made of paper, parchment, or other material, usually fastened together to hinge at one side. A single sheet within a book is called a leaf, and each side of a leaf… …
