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A Dictionary of Science (Oxford Quick Reference) PDF

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A Dictionary of Science FIFTH EDITION 3 1 Great Clarendon Street, Oxford ox2 6dp Oxford University Press is a department of the University of Oxford. It furthers the University’s objective of excellence in research, scholarship, and education by publishing worldwide in Oxford New York Auckland Cape Town Dar es Salaam Hong Kong Karachi Kuala Lumpur Madrid Melbourne Mexico City Nairobi New Delhi Shanghai Taipei Toronto With offices in Argentin Austria Brazil Chile Czech Republic France Greece Guatemala Hungary Italy Japan Poland Portugal Singapore South Korea Switzerland Thailand Turkey Ukraine Vietnam Oxford is a registered trade mark of Oxford University Press in the UK and in certain other countries Published in the United States by Oxford University Press Inc., New York © Market House Books Ltd. 1984, 1991, 1996, 1999, 2005 The moral rights of the author have been asserted Database right Oxford University Press (maker) First edition, under the title Concise Science Dictionary, 1984 Second edition 1991 Third edition 1996 Fourth edition 1999 retitled A Dictionary of Science Fifth edition 2005 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, without the prior permission in writing of Oxford University Press, or as expressly permitted by law, or under terms agreed with the appropriate reprographics rights organization. Enquiries concerning reproduction outside the scope of the above should be sent to the Rights Department, Oxford University Press, at the address above You must not circulate this book in any other binding or cover and you must impose the same condition on any acquirer British Library Cataloguing in Publication Data Data available Library of Congress Cataloging in Publication Data Data available Typeset by Market House Books Ltd. Printed in Great Britain on acid-free paper by Cox & Wyman Ltd. Reading, Berkshire ISBN 0–19–280641–6 978–0–19–280641–3 10 9 8 7 6 5 4 3 2 1 Contents Preface vii Credits viii Dictionary 1 Atomic Theory Chronology 63 The Big-Bang Theory (Feature) 88 Biochemistry Chronology 92 Cell Biology Chronology 144 Cosmology Chronology 201 Crystal Defects (Feature) 212 Electronics Chronology 277 El Niño (Feature) 286 Explosives Chronology 309 Genetically Modified Organisms (Feature) 352 Learning in Animals (Feature) 470 Microscopy Chronology 527 Moon Exploration Chronology 540 Magnetic Resonance Imaging (Feature) 568 Plastics Chronology 637 Polymers (Feature) 648 Refrigeration (Feature) 700 Solar System (Feature) 762 Optical Astronomical Telescopes (Feature) 805 Vitamins Chronology 857 Appendices 881 SI units 881 Fundamental constants 883 The solar system 883 Geological time scale 884 Simplified classification of the plant kingdom 885 Simplified classification of the animal kingdom 886 The periodic table 887 Useful websites 888 Preface This fifth edition of A Dictionary of Science, like its predecessors, aims to provide school and first-year university students with accurate explanations of any unfamiliar words they might come across in the course of their studies, in their own or adjacent disciplines. For example, students of the physical sciences will find all they are likely to need to know about the life sciences, and vice versa. The dictionary is also designed to provide non-scientists with a useful reference source to explain the scientific terms that they may encounter in their work or in their general reading. At this level the dictionary provides full coverage of terms, concepts, and laws relating to physics, chemistry, biology, biochemistry, palaeontology, and the earth sciences. There is also coverage of key terms in astronomy, cosmology, mathematics, biotechnology, and computer technology. In addition, the dictionary includes: • over 160 short biographical entries on the most important scientists in the history of the subject • ten features (each of one or two pages) on concepts of special significance in modern science ` • ten chronologies showing the development of selected concepts, fields of study, and industries ` • eight Appendices, including the periodic table, tables of SI units and conversion tables to and from other systems of units, summary classifications of the plant and animal kingdoms, and useful websites. For this fifth edition over 300 new entries have been added to the text, incorporating recent advances in all the major fields and increased coverage of climatology, seismology, and computing. In compiling the dictionary, the contributors and editors have made every effort to make the entries as concise and comprehensible as possible, always bearing in mind the needs of the readers. Particular features of the book are its lack of unnecessary scientific jargon and its extensive network of cross-references. An asterisk placed before a word used in an entry indicates that this word can be looked up in the dictionary and will provide further explanation or clarification. However, not every word that is defined in the dictionary has an asterisk placed before it when it is used in an entry. Some entries simply refer the reader to another entry, indicating either that they are synonyms or abbreviations or that they are most conveniently explained in one of the dictionary’s longer articles. Synonyms and abbreviations are usually placed within brackets immediately after the headword. Terms that are explained within an entry are highlighted by being printed in boldface type. Where appropriate, the entries have been supplemented by fully labelled line-drawings or tables in situ. JD EM 2005 A aa See lava. position of a star as a result of the earth’s AAS See atomic absorption spec- motion round the sun. Light appears to troscopy. come from a point that is slightly dis- placed in the direction of the earth’s mo- ab- A preÜx attached to the name of a tion. The angular displacement α= v/c, practical electrical unit to provide a name where v is the earth’s orbital velocity and for a unit in the electromagnetic system c is the speed of light. of units (see electromagnetic units), e.g. abampere, abcoulomb, abvolt. The preÜx abiogenesis The origin of living from nonliving matter, as by *biopoiesis. See is an abbreviation of the word ‘absolute’ also spontaneous generation. as this system is also known as the abso- lute system. Compare stat-. In modern abiotic factor Any of the nonliving fac- practice both absolute and electrostatic tors that make up the abiotic environ- units have been replaced by *SI units. mentin which living organisms occur. They include all the aspects of climate, abdomen The posterior region of the geology, and atmosphere that may affect body trunk of animals. In vertebrates it the biotic environment. Compare biotic contains the stomach and intestines and factor. the organs of excretion and reproduction. It is particularly well deÜned in mam- abomasum The fourth andÜnal cham- mals, being separated from the *thorax ber of the stomach of ruminants. It leads by the *diaphragm. In many arthropods, from the *omasum and empties into the such as insects and spiders, it may be seg- small intestine. The abomasum is re- mented. ferred to as the ‘true stomach’ as it is in Abelian group See group. this chamber that protein digestion oc- curs, in acidic conditions. See aberration 1.(in optics) A defect in the ruminantia. image formed by a lens or curved mirror. ABO system One of the most impor- In chromatic aberration the image formed tant human *blood group systems. The by a lens (but not a mirror) has coloured system is based on the presence or ab- fringes as a result of the different extent sence of *antigens A and B on the surface to which light of different colours is re- of red blood cells and of *antibodies fracted by glass. It is corrected by using against these in blood serum. A person an *achromatic lens. In spherical aberra- whose blood contains either or both tion, the rays from the object come to a these antibodies cannot receive a transfu- focus in slightly different positions as a sion of blood containing the correspond- result of the curvature of the lens or mir- ing antigens as this would cause the red ror. For a mirror receiving light strictly cells to clump (see agglutination). The parallel with its axis, this can be cor- table illustrates the basis of the system: rected by using a parabolic surface rather people of blood group O are described as than a spherical surface. Spherical aberra- ‘universal donors’ as they can give blood tion in lenses is minimized by making to those of any of the other groups. See both surfaces contribute equally to the also immune response. ray deviations, and can (though with re- duced image brightness) be reduced by abscisic acid A naturally occurring the use of diaphragms to let light pass plant *growth substance that appears to only through the centre part of the lens. be involved primarily in seed maturation, See also astigmatism; coma. 2.(in astron- stress responses (e.g. to heat and water- omy) The apparent displacement in the logging), and in regulating closure of leaf abscissa 2 a Group Antigens on red Antibodies Blood group of Blood group of cell surface in serum people donor can people donor can receive blood from give blood to A A anti-B A, O A, AB B B anti-A B, O B, AB AB A and B none A, B, AB, O AB O neither A nor B anti-A and O A, B, AB, O anti-B The ABO blood group system pores (stomata). In seeds, it promotes the lates the structure of the molecule to synthesis of storage protein and prevents some reference molecule. In the case of premature germination. In leaves, abscisic sugars and similar compounds, the acid is produced in large amounts when dextrorotatory form of glyceraldehyde the plant lacks sufÜcient water, promot- (HOCHCH(OH)CHO), 2,3-dihydroxy- 2 ing closure of stomata and hence reduc- propanal) was used. The rule is as fol- ing further water losses. It was formerly lows. Write the structure of this molecule believed to play a role in *abscission, down with the asymmetric carbon in the hence the name. centre, the –CHO group at the top, the abscissa See cartesian coordinates. –OH on the right, the –CH2OH at the bot- tom, and the –H on the left. Now imagine abscission The separation of a leaf, that the central carbon atom is at the cen- fruit, or other part from the body of a tre of a tetrahedron with the four groups plant. It involves the formation of an ab- at the corners and that the –H and –OH scission zone, at the base of the part, come out of the paper and the –CHO and within which a layer of cells (abscission –CHOH groups go into the paper. The re- 2 layer) breaks down. This process is sup- sulting three-dimensional structure was pressed so long as sufÜcient amounts of taken to be that of d-glyceraldehyde and *auxin, a plant growth substance,Ûow called d-glyceraldehyde. Any compound from the part through the abscission that contains an asymmetric carbon atom zone. However, if the auxinÛow declines, having this conÜguration belongs to the for example due to injury or ageing, ab- d-series. One having the opposite conÜgu- scission is activated and the part becomes ration belongs to the l-series. It is impor- separated. tant to note that the preÜxes d- and l- do absolute 1.Not dependent on or rela- not stand for dextrorotatory and laevoro- tive to anything else, e.g. *absolute zero. tatory (they are not the same as d- and l-). 2.Denoting a temperature measured on In fact the arbitrary conÜguration as- an absolute scale, a scale of temperature signed to d-glyceraldehyde is now known based on absolute zero. The usual abso- to be the correct one for the dextrorota- lute scale now is that of thermodynamic tory form, although this was not known *temperature; its unit, the kelvin, was for- at the time. However, all d-compounds merly called the degree absolute (°A) and are not dextrorotatory. For instance, the is the same size as the degree Celsius. In acid obtained by oxidizing the –CHO British engineering practice an absolute group of glyceraldehyde is glyceric acid scale with Fahrenheit-size degrees has (1,2-dihydroxypropanoic acid). By conven- been used: this is the Rankine scale. tion, this belongs to the d-series, but it is in fact laevorotatory; i.e. its name can be absolute alcohol See ethanol. written as d-glyceric acid or l-glyceric acid. absolute conÜguration A way of de- To avoid confusion it is better to use + (for noting the absolute structure of an optical dextrorotatory) and – (for laevorotatory), isomer (see optical activity). Two conven- as in d-(+)-glyceraldehyde and d-(–)- tions are in use: The d–l convention re- glyceric acid. 3 absolute value CHO CHO CHO a H C OH C HCOH H OH CHOH CHOH CHOH 2 2 2 planar formula structure in 3 Fischer projection dimensions D–Lconvention: D-(+)-glyceraldehyde (2,3-dihydroxypropanal) H COOH C H CH3 COOH CH3 NH2 NH 2 D–Lconvention: D-alanine (R is CH2in the CORN rule); the molecule is viewed with H on top 1 1 C C 3 2 2 3 R–configuration S–configuration R–S system: the lowest priority group is behind the chiral carbon atom The d–l convention can also be used to the r-series; if the descending order is with alpha amino acids (compounds with anticlockwise it is in the s-series. d-(+)- the –NH group on the same carbon as the glyceraldehyde is r-(+)-glyceraldehyde. See 2 –COOH group). In this case the molecule illustration. is imagined as being viewed along the absolute expansivity See expansivity. H–C bond between the hydrogen and the asymmetric carbon atom. If the clockwise absolute humidity See humidity. order of the other three groups is –COOH, absolute permittivity See permittiv- s–eRr, i–eNs;H o2t,h tehrew aisme iint ob aecloidn gbse ltoon tghse t lo- stehreie ds.- ity. This is known as the CORN rule. absolute pitch (perfect pitch) The abil- The r–s convention is a convention ity of a person to identify and reproduce a based on priority of groups attached to note without reference to a tuned musical the chiral carbon atom. The order of pri- instrument. ority is I, Br, Cl, SO3H, OCOCH3, OCH3, absolute temperature See absolute; OH, NO2, NH2, COOCH3, CONH2, COCH3, temperature. CHO, CHOH, CH, CH, CH, H, with hy- 2 6 5 2 5 3 drogen lowest. The molecule is viewed absolute value (modulus) The square with the group of lowest priority behind root of the sum of the squares of the real the chiral atom. If the clockwise arrange- numbers in a *complex number, i.e. the ment of the other three groups is in de- absolute value of the complex number scending priority, the compound belongs z = x + iy is |z| = √(x2+ y2). absolute zero 4 a absolute zero Zero of thermodynamic mass of a speciÜed element in the earth’s *temperature (0 kelvin) and the lowest crust to the total mass of the earth’s crust, temperature theoretically attainable. It is often expressed as a percentage. For ex- the temperature at which the kinetic en- ample, the abundance of aluminium in ergy of atoms and molecules is minimal. the earth’s crust is about 8%. 2.The ratio It is equivalent to –273.15°C or –459.67°F. of the number of atoms of a particular iso- See also zero-point energy; cryogenics. tope of an element to the total number of absorbed dose See dose. atoms of all the isotopes present, often ex- pressed as a percentage. For example, the absorptance Symbol α. The ratio of the abundance of uranium–235 in natural ura- radiant or luminousÛux absorbed by a nium is 0.71%. This is the natural abun- body to theÛux falling on it. Formerly dance, i.e. the abundance as found in called absorptivity, the absorptance of a nature before any enrichment has taken *black body is by deÜnition 1. place. absorption 1.(in chemistry) The take abyssal zone The lower depths of the up of a gas by a solid or liquid, or the take ocean (below approximately 2000 metres), up of a liquid by a solid. Absorption dif- where there is effectively no light pene- fers from *adsorption in that the ab- tration. Abyssal organisms are adapted for sorbed substance permeates the bulk of living under high pressures in cold dark the absorbing substance. 2.(in physics) conditions. See also aphotic zone. The conversion of the energy of electro- magnetic radiation, sound, streams of par- a.c. See alternating current. ticles, etc., into other forms of energy on acceleration Symbol a. The rate of in- passing through a medium. A beam of crease of speed or velocity. It is measured light, for instance, passing through a in ms–2. For a body moving linearly with medium, may lose intensity because of constant acceleration a from a speed u to two effects: *scattering of light out of the a speed v, beam, and absorption of photons by atoms or molecules in the medium. When a=(v–u)/t=(v2–u2)/2s a photon is absorbed, there is a transition where t is the time taken and s the dis- to an excited state. 3.(in biology) The tance covered. movement ofÛuid or a dissolved sub- If the acceleration is not constant it is stance across a plasma membrane. In given by dv/dt = d2s/dt2. If the motion is many animals, for example, soluble food not linear the vector character of displace- material is absorbed into cells lining the ment, velocity, and acceleration must be alimentary canal and thence into the considered. See also rotational motion. blood. In plants, water and mineral salts are absorbed from the soil by the *roots. acceleration of free fall Symbol g. See osmosis; transport protein. The acceleration experienced by any mas- sive object falling freely in the earth’s absorption coefÜcient 1.(in physics) gravitationalÜeld. Experimentally this is See lambert’s laws. 2.(in chemistry) The almost constant for all positions near the volume of a given gas, measured at stan- earth’s surface, independent of the nature dard temperature and pressure, that will of the falling body (provided air resistance dissolve in unit volume of a given liquid. is eliminated). This is taken to indicate absorption indicator See adsorption the strict proportionality of *weight (the indicator. force causing the acceleration) and *iner- tial mass, on the basis of *Newton’s sec- absorption spectrum See spectrum. ond law of motion. There is some absorptivity See absorptance. variation of g with latitude, because of the earth’s rotation and because the earth is ABS plastic Any of a class of plastics not completely spherical. The standard based on acrylonitrile–butadiene–styrene value is taken as 9.80665ms–2. The accel- copolymers. eration of free fall is also called the accel- abundance 1.The ratio of the total eration due to gravity. 5 acetals accelerator 1.(in physics) An apparatus retina. In humans and some other mam- a for increasing the kinetic energies of mals accommodation is achieved by reÛex charged particles, used for research in nu- adjustments in the shape of the lens clear and particle physics. See cyclotron; brought about by relaxation and contrac- linear accelerator; synchrocyclotron; tion of muscles within the *ciliary body. synchrotron. 2.(in chemistry) A sub- 2.(in animal behaviour) Adjustments stance that increases the rate of a chemi- made by an animal’s nervous or sensory cal reaction, i.e. a catalyst. systems in response to continuously changing environmental conditions. acceptor 1.(in chemistry and biochem- istry) A compound, molecule, ion, etc., to accretion The way in which collisions which electrons are donated in the forma- with relatively slow-moving smaller ob- tion of a coordinate bond. 2.(in biochem- jects add to the mass of a larger celestial istry) A *receptor that binds a hormone object. The process accelerates as the in- without any apparent biological response. creased mass strengthens the gravita- 3.(in physics) A substance that is added as tionalÜeld of the larger object. For an impurity to a *semiconductor because example, the planets are thought to have of its ability to accept electrons from the formed by the accretion of dust particles valence bands, causing p-type conduction onto *planetesimals. Other accreting ob- by the mobile positive holes left. Compare jects probably include black holes and donor. protostars. acceptor levels Energy levels of an ac- accretion disc A disc-shaped rotating ceptor atom in a *semiconductor, such as mass formed by gravitational attraction. aluminium, in silicon. These energy levels See black hole; neutron star; white are very near the top of the valence band, dwarf. and therefore cause p-type conduction. See accumulator(secondary cell; storage also energy band. battery)A type of *voltaic cell or battery acclimation The physiological changes that can be recharged by passing a cur- occurring in an organism in response to a rent through it from an external d.c. sup- change in a particular environmental fac- ply. The charging current, which is passed tor (e.g. temperature), especially under in the opposite direction to that in which laboratory conditions. Thermal acclima- the cell supplies current, reverses the tion studies reveal how such properties as chemical reactions in the cell. The com- metabolic rate, muscle contractility, nerve mon types are the *lead–acid accumulator conduction, and heart rate differ between and the *nickel–iron and nickel–cadmium cold- and warm-acclimated members of accumulators. See also sodium–sulphur the same species. These changes occur cell. naturally during *acclimatization and acellular Describing tissues or organ- equip the organism for living in, say, cold isms that are not made up of separate or warm conditions. cells but often have more than one nu- acclimatization 1.The progressive cleus (see syncytium). Examples of acellu- adaptation of an organism to any change lar structures are muscleÜbres. Compare in its natural environment that subjects it unicellular. to physiological stress. 2.The overall sum acentric Describing an aberrant chro- of processes by which an organism at- mosome fragment that lacks a cen- tempts to compensate for conditions that tromere. Such fragments are normally would substantially reduce the amount of lost because they are unable to orientate oxygen delivered to its cells. Compare ac- properly during cell division. climation. acetaldehyde See ethanal. accommodation 1.(in animal physiol- acetaldol See aldol reaction. ogy) Focusing: the process by which the focal length of the *lens of the eye is acetals Organic compounds formed by changed so that clear images of objects at addition of alcohol molecules to aldehyde a range of distances are displayed on the molecules. If one molecule of aldehyde

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