spectrophotometry \,spek-tro-f3-'ta-m3-tre\ Branch of spectroscopy dealing with measurement of radiant energy transmitted or reflected by a body as a function of wavelength. The measurement is usually compared to that transmitted or reflected by a system that serves as a standard. In chemistry and physics, different types of spectrophotometers cover wide ranges of the electromagnetic spectrum: ultraviolet (UV), visible light, infra¬ red (IR), or microwave. UV spectrophotometry is particularly useful in detecting and quantifying colourless substances in solution. IR spectro¬ photometry is used mostly to study the molecular structures of complex organic compounds. In astronomy and astrophysics, spectrophotometric studies also include the X-ray and gamma ray ranges of the spectrum. See also COLORIMETRY.
spectroscopy \spek-'tra-sko-pe\ Branch of analysis devoted to identi¬ fying elements and compounds and elucidating atomic and molecular struc¬ ture by measuring the radiant energy absorbed or emitted by a substance at characteristic wavelengths of the electromagnetic spectrum (including
GAMMA RAY, X-RAY, ULTRAVIOLET, visible LIGHT, INFRARED, MICROWAVE, and RADIO- frequency radiation) on excitation by an external energy source. The instruments used are spectroscopes (for direct visual observation) or spec¬ trographs (for recording spectra). Experiments involve a light source, a prism or grating to form the spectrum, detectors (visual, photoelectric, radi¬ ometric, or photographic) for observing or recording its details, devices for measuring wavelengths and intensities, and interpretation of the mea¬ sured quantities to identify chemicals or give clues to the structure of atoms and molecules. Helium, cesium, and rubidium were discovered in the mid-19th century by spectroscopy of the Sun’s spectrum. Specialized techniques include Raman spectroscopy (see Chandrasekhara Venkata Raman), nuclear magnetic resonance (NMR), nuclear quadrupole reso¬ nance (NQR), dynamic reflectance spectroscopy, microwave and gamma ray spectroscopy, and electron spin resonance (ESR). Spectroscopy now also includes the study of particles (e.g., electrons, ions) that have been sorted or otherwise differentiated into a spectrum as a function of some property (such as energy or mass). See also mass spectrometry; spectrom¬ eter; SPECTROPHOTOMETRY.
spectrum Arrangement according to wavelength (or frequency) of elec¬ tromagnetic radiation. The visible, “rainbow” spectrum is the portion of the electromagnetic spectrum that is visible as light to the human eye. Some sources emit only certain wavelengths and produce an emission spectrum of bright lines with dark spaces between. Such line spectra are character¬ istic of the elements that emit the radiation. A band spectrum consists of groups of wavelengths so close together that the lines appear to form a continuous band. Atoms and molecules absorb certain wavelengths and so remove them from a complete spectrum; the resulting absorption spec¬ trum contains dark lines or bands at these wavelengths.
speech Human communication through audible language. Speech sounds are made with air exhaled from the lungs, which passes between the vocal cords in the larynx and out through the vocal tract (pharynx and oral and nasal cavities). This airstream is shaped into different sounds by the articulators, mainly the tongue, palate, and lips (see articulation). Artic¬ ulatory phonetics describes each sound in terms of the position and action of the articulators used to make it. Speech is also described in terms of syntax, lexicon (inventory of words or morphemes), and phonology (sounds).
speech, figure of See figure of speech
speech act theory Theory of meaning that holds that the meaning of linguistic expressions can be explained in terms of the rules governing their use in performing various speech acts (e.g., admonishing, asserting, commanding, exclaiming, promising, questioning, requesting, warning). In contrast to theories that maintain that linguistic expressions have mean¬
ing in virtue of their contribution to the truth conditions of sentences where they occur, it explains linguistic meaning in terms of the use of words and sentences in the performance of speech acts. Some exponents claim that the meaning of a word is nothing but its contribution to the nature of the speech acts that can be performed by using it. Ludwig Wit¬ tgenstein and J. L. Austin provided important stimuli for the theory’s devel¬ opment.
speech recognition or voice recognition Ability of computer sys¬ tems to accept speech input and act on it or transcribe it into written lan¬ guage. Current research efforts are directed toward applications of automatic speech recognition (ASR), where the goal is to transform the content of speech into knowledge that forms the basis for linguistic or cognitive tasks, such as translation into another language. Practical appli¬ cations include DATABASE-query systems, information retrieval systems, and speaker identification and verification systems, as in telebanking. Speech recognition has promising applications in robotics, particularly develop¬ ment of robots that can “hear.” See also pattern recognition.
speech synthesis Generation of speech by artificial means, usually by computer. Production of sound to simulate human speech is referred to as low-level synthesis. High-level synthesis deals with the conversion of written text or symbols into an abstract representation of the desired acoustic signal, suitable for driving a low-level synthesis system. Among other applications, this technology provides speaking aid to the speech- impaired and reading aid to the sight-impaired.
speech therapy Therapeutic treatment to correct defects in speaking. Such defects may originate in the brain, the ear (see deafness), or any¬ where along the vocal tract and may affect the voice, articulation, lan¬ guage development, or ability to speak after language is learned. Therapy begins with diagnosis of underlying physical, physiological, or emotional dysfunction. It may involve training in breathing, use of the voice, and/or speaking habits. Some abnormalities that cause speech disorders (e.g., cleft palate, stroke) can be corrected to various degrees before a speech therapist’s work begins. See also aphasia, stuttering.
speed skating Sport of racing on ice skates. The blade of the speed skate is longer and thinner than that of the hockey or figure skate. Two types of track are used in international competition. The long track is a 400-m (about one-quarter mile) flattened oval (straight sides and curved ends) on which two skaters race simultaneously. In long track the race is against the clock rather than the opponent. The short track, a more recent development, is a 111-m (364-ft) oval on which four to six skaters race during each heat. Short track is a race to the finish line. Long-track speed skating was included in the first Winter Olympics in 1924; short-track skating was added in 1992.
Speer \'shpar\, Albert (b. March 19,1905, Mannheim, Baden, Ger.—d. Sept. 1, 1981, London, Eng.) German Nazi official. He became an archi¬ tect in 1927 and an active member of the Nazi Party in 1931. He impressed Adolf Hitler with his efficiency and talent and was appointed chief archi¬ tect of the Third Reich in 1933. He designed the parade grounds and ban¬ ners of the Nazi rallies held for the party congresses, including the 1934 Numberg Rally (see NOrnberg Rallies) filmed by Leni Riefenstahl. In 1942 he became minister for armaments and war production and expanded the system of conscript and slave labour that maintained Germany’s wartime productivity. Speer confessed his guilt at the Nurnberg trials, and he served 20 years in prison. His published works include Inside the Third Reich (1969) and Spandau (1975).