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catchment area

(Encyclopedia)catchment area or drainage basin, area drained by a stream or other body of water. The limits of a given catchment area are the heights of land—often called drainage divides, or watersheds—separat...

Spectral Classes for Main Sequence Stars (table)

(Encyclopedia)Characteristics of Spectral Classes for Main Sequence Stars ...

Boltzmann, Ludwig

(Encyclopedia)Boltzmann, Ludwig lo͝otˈvĭkh bôltsˈmän [key], 1844–1906, Austrian physicist, b. Vienna, educated at Univ. of Vienna. He began teaching (1869) at Graz Univ. In 1873 he became mathematics profes...

geyser

(Encyclopedia)geyser gīˈzər [key] [Icel.], hot spring from which water and steam are ejected periodically to heights ranging from a few to several hundred feet. Notable geysers are found in Iceland, New Zealand,...

ephedrine

(Encyclopedia)ephedrine ĭfĕdˈrĭn, ĕfˈĭdrēnˌ [key], drug derived from plants of the genus Ephedra (see Pinophyta), most commonly used to prevent mild or moderate attacks of bronchial asthma. Unlike epinephr...

fainting

(Encyclopedia)fainting or syncope sĭngˈkəpē [key], temporary loss of consciousness caused by an insufficient supply of oxygen to the brain. It can be concurrent with any serious disease or condition, such as he...

sap

(Encyclopedia)sap, fluid in plants consisting of water and dissolved substances. Cell sap refers to this fluid present in the large vacuole, or cell cavity, that occupies most of the central portion of mature plant...

beta-blocker

(Encyclopedia)beta-blocker or beta-adrenergic blocking agent bāˈtə ădˌrənûrˈjĭk [key], drug that reduces the symptoms connected with hypertension, cardiac arrhythmias, angina pectoris, migraine headaches, ...

sun, in astronomy

(Encyclopedia)CE5 Structure of the sun sun, intensely hot, self-luminous body of gases at the center of the solar system. Its gravitational attraction maintains the planets, comets, and other bodies of the sola...

lubrication

(Encyclopedia)lubrication, introduction of a substance between the contact surfaces of moving parts to reduce friction and to dissipate heat. A lubricant may be oil, grease, graphite, or any substance—gas, liquid...