The Gale Encyclopedia of Science docx

Department of Embryology, Obstetrics, andGynecology University of BolognaBologna, Italy Clayton Harris Associate ProfessorDepartment of Geography and GeologyMiddle Tennessee State Univer

The GALE ENCYCLOPEDIA

THIRD EDITION

The GALEENCYCLOPEDIA

Gale Encyclopedia of Science, Third Edition

K Lee Lerner and Brenda Wilmoth Lerner, Editors

Project Editor

Kimberley A McGrath

Editorial

Deirdre S Blanchfield, Chris Jeryan, Jacqueline

Longe, Mark Springer

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LIBRARY OF CONGRESS CATALOGING-IN-PUBLICATION DATA

Gale encyclopedia of science / K Lee Lerner & Brenda Wilmoth Lerner, editors.— 3rd ed.

p cm.

Includes index.

ISBN 0-7876-7554-7 (set) — ISBN 0-7876-7555-5 (v 1) — ISBN 0-7876-7556-3 (v 2) — ISBN 0-7876-7557-1 (v 3) — ISBN 0-7876-7558-X (v 4) — ISBN 0-7876-7559-8 (v 5) — ISBN 0-7876-7560-1 (v 6)

1 Science—Encyclopedias I Lerner, K Lee II Lerner, Brenda Wilmoth.

Topic List vii

Organization of the Encyclopedia xxvii

Advisory Board xxix

Contributors xxxi

Entries Volume 1 (Aardvark–Chaos) 1–818 Volume 2 (Charge-coupled device–Eye) 819–1572 Volume 3 (Factor–Kuru) 1573–2254 Volume 4 (Lacewings–Pharmacogenetics) 2255–3036 Volume 5 (Pheasants–Star) 3037–3800 Volume 6 (Star cluster–Zooplankton) 3801–4378

General Index 4379–4495

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AluminumAluminum hydroxideAlzheimer diseaseAmaranth family (Amaranthaceae)Amaryllis family (Amaryllidaceae)American Standard Code forInformation InterchangeAmes test

Amicable numbersAmides

Amino acidAmmoniaAmmonificationAmnesiaAmniocentesisAmoebaAmphetaminesAmphibiansAmplifierAmputationAnabolismAnaerobicAnalemmaAnalgesiaAnalog signals and digital signalsAnalytic geometry

AnaphylaxisAnatomyAnatomy, comparativeAnchovy

Anemia

AdrenalsAerobicAerodynamicsAerosolsAfricaAge of the universeAgent OrangeAging and deathAgouti

Agricultural machinesAgrochemicalsAgronomyAIDSAIDS therapies and vaccinesAir masses and frontsAir pollution

AircraftAirshipAlbatrossesAlbedoAlbinismAlchemyAlcoholAlcoholismAldehydesAlgaeAlgebraAlgorithmAlkali metalsAlkaline earth metalsAlkaloid

Alkyl groupAllelesAllergyAllotropeAlloy

TOPIC LIST

Atomic modelsAtomic numberAtomic spectroscopyAtomic theoryAtomic weightAtomsAttention-deficit/Hyperactivitydisorder (ADHD)

AuksAustraliaAutismAutoimmune disordersAutomatic pilotAutomationAutomobileAutotrophAvogadro’s numberAye-ayes

B

BabblersBaboonsBacteriaBacteriophageBadgersBall bearingBallistic missilesBallisticsBalloonBananaBandicootsBar codeBarberryBarbetsBarbituratesBariatricsBariumBarium sulfateBark

BarleyBarnaclesBarometerBarracuda

ArcARC LAMPArchaebacteriaArchaeoastronomyArchaeogeneticsArchaeologyArchaeometallurgyArchaeometryArcheological mappingArcheological sitesArithmeticArmadillosArrow wormsArrowgrassArrowrootArteriesArteriosclerosisArthritisArthropodsArthroscopic surgeryArtifacts and artifact classificationArtificial fibers

Artificial heart and heart valveArtificial intelligence

Artificial visionArum family (Araceae)Asbestos

Asexual reproductionAsia

Assembly lineAsses

Associative propertyAsteroid 2002AA29AsthenosphereAsthmaAstrobiologyAstroblemesAstrolabeAstrometryAstronomical unitAstronomyAstrophysicsAtmosphere, composition andstructure

Atmosphere observation Atmospheric circulationAtmospheric optical phenomenaAtmospheric pressure

Brown dwarfBrownian motionBrucellosisBryophyteBubonic plagueBuckminsterfullereneBuckthorn

BuckwheatBuds and buddingBuffer

Building design/architectureBulbuls

Bunsen burnerBuoyancy, principle ofBuret

BurnBustardsButtercupButterfliesButterfly fishButyl groupButylated hydroxyanisoleButylated hydroxytolueneBuzzards

C

CactusCAD/CAM/CIMCaddisfliesCaeciliansCaffeineCaissonCalciumCalcium carbonateCalcium oxideCalcium propionateCalcium sulfateCalculatorCalculusCalendars

BioremediationBiosphereBiosphere ProjectBiotechnologyBioterrorismBirch family (Betulaceae)Birds

Birds of paradiseBirds of preyBirthBirth defectsBisonBitternsBivalves

BL Lacertae objectBlack holeBlackbirdsBlackbody radiationBleach

BlenniesBlindness and visual impairmentsBlindsnakes

BloodBlood gas analysisBlood supplyBlotting analysisBlue revolution (aquaculture)Bluebirds

BoarfishBoasBohr ModelBoiling pointBond energyBony fishBoobies and gannetsBoolean algebraBoric acidBotanyBotulismBowen’s reaction seriesBowerbirds

BowfinBoxfishBrachiopodsBrackishBrainBrewingBrick

ChlorineChlorofluorocarbons (CFCs)Chloroform

ChlorophyllChloroplastCholeraCholesterolChordatesChorionic villus sampling (CVS)Chromatin

ChromatographyChromosomal abnormalitiesChromosome

Chromosome mappingCicadas

Cigarette smokeCircle

Circulatory systemCircumscribed and inscribedCirrhosis

Citric acidCitrus treesCivetsClimax (ecological)Clingfish

Clone and cloningClosed curvesClosure propertyClouds

Club mossesCoalCoast and beachCoatis

CocaCocaineCockatoosCockroachesCodeineCodfishesCodonsCoefficientCoelacanth

CatfishCathetersCathodeCathode ray tubeCation

CatsCattailsCattle family (Bovidae)Cauterization

CaveCave fishCelestial coordinatesCelestial mechanicsCelestial sphere: The apparentmotions of the Sun, Moon,planets, and stars

CellCell deathCell divisionCell, electrochemical Cell membrane transportCell staining

Cellular respirationCellular telephoneCellulose

CentipedesCentrifugeCeramicsCerenkov effectCetaceansChachalacasChameleonsChaosCharge-coupled deviceChelate

Chemical bondChemical evolutionChemical oxygen demandChemical reactionsChemical warfareChemistryChemoreceptionChestnutChi-square testChickenpoxChildhood diseasesChimaeras

Chimpanzees

CrystalCubic equationsCuckoosCurareCurlewsCurrentsCurveCushing syndromeCuttlefish

CyberneticsCycadsCyclamateCyclone and anticycloneCyclosporine

CyclotronCystic fibrosisCytochromeCytology

D

DamsDamselfliesDark matterDating techniquesDDT (Dichlorodiphenyl-trichloroacetic acid)Deafness and inherited hearing lossDecimal fraction

DecompositionDeer

Deer mouseDeforestationDegreeDehydroepiandrosterone (DHEA)Delta

DementiaDengue feverDenitrification

ConstellationConstructionsContaminated soilContaminationContinentContinental driftContinental marginContinental shelfContinuityContour plowingContraceptionConvectionCoordination compoundCopepods

CopperCoral and coral reefCoriolis effectCork

CormCormorantsCorn (maize)Coronal ejections and magneticstorms

Correlation (geology)Correlation (mathematics)Corrosion

Cosmic background radiationCosmic ray

CosmologyCotingasCottonCoulombCountableCoursers and pratincolesCourtship

CoypuCrabsCraneCranesCrayfishCrestfishCreutzfeldt-Jakob diseaseCrickets

Critical habitatCrocodilesCrop rotationCropsCross multiply

EcosystemEcotoneEcotourismEdemaEel grass

El Niño and La NiñaEland

Elapid snakesElasticityElectric arcElectric chargeElectric circuitElectric conductorElectric currentElectric motorElectric vehiclesElectrical conductivityElectrical power supplyElectrical resistanceElectricity

Electrocardiogram (ECG)Electroencephalogram (EEG)Electrolysis

ElectrolyteElectromagnetic fieldElectromagnetic inductionElectromagnetic spectrumElectromagnetismElectromotive forceElectron

Electron cloudElectronicsElectrophoresisElectrostatic devicesElement, chemicalElement, families ofElement, transuraniumElements, formation ofElephant

Elephant shrews

DobsonfliesDogwood treeDomainDonkeysDopamineDoppler effectDoriesDormouseDouble-blind studyDouble helix Down syndromeDragonfliesDrift netDrongos

Drosophila melanogaster

DroughtDucksDuckweedDuikersDuneDuplication of the cubeDust devil

DVDDwarf antelopesDyes and pigmentsDysentery

DyslexiaDysplasiaDystrophinopathies

E

e (number)EaglesEarEarthEarth scienceEarth’s interiorEarth’s magnetic fieldEarth’s rotationEarthquakeEarwigsEating disordersEbola virusEbonyEchiuroid worms

Elephant snout fish

Figurative numbersFiltration

FinchesFirsFishFlagellaFlame analysisFlamingosFlatfishFlatwormsFlaxFleasFliesFlightless birdsFloodingFloraFlowerFluid dynamicsFluid mechanicsFluorescenceFluorescence in situ hybridization(FISH)

Fluorescent lightFluoridationFlying fishFocused Ion Beam (FIB)Fog

FoldFood chain/webFood irradiationFood poisoningFood preservationFood pyramidFoot and mouth diseaseForce

Forensic scienceForestryForestsFormula, chemical

EthnoarchaeologyEthnobotanyEthyl groupEthylene glycolEthylenediaminetetra-acetic acidEtiology

EubacteriaEugenicsEukaryotaeEuropeEutrophicationEvaporationEvapotranspirationEven and oddEvent horizonEvolutionEvolution, convergentEvolution, divergentEvolution, evidence ofEvolution, parallelEvolutionary change, rate ofEvolutionary mechanismsExcavation methodsExclusion principle, PauliExcretory systemExercise

Exocrine glandsExplosivesExponentExtinctionExtrasolar planetsEye

F

FactorFactorialFalconsFaraday effectFat

Fatty acidsFaultFaunaFax machineFeather starsFermentation

Grand unified theoryGrapes

Graphs and graphingGrasses

GrasshoppersGrasslandsGravitational lensGravity and gravitationGreat Barrier ReefGreatest common factorGrebes

Greenhouse effectGroundhogGroundwaterGroupGrouseGrowth and decayGrowth hormonesGuenons

Guillain-Barre syndromeGuinea fowl

Guinea pigs and caviesGulls

GuppyGutenberg discontinuityGutta percha

GymnospermGynecologyGyroscope

H

HabitatHagfishHalf-lifeHalide, organicHall effect

Genetic disordersGenetic engineeringGenetic identification ofmicroorganismsGenetic testingGenetically modified foods andorganisms

GeneticsGenetsGenomeGenomics (comparative)Genotype and phenotypeGeocentric theoryGeochemical analysisGeochemistryGeodeGeodesicGeodesic domeGeographic and magnetic polesGeologic map

Geologic timeGeologyGeometryGeomicrobiologyGeophysicsGeotropismGerbilsGerm cells and the germ cell lineGerm theory

GerminationGerontologyGesneriasGeyserGibbons and siamangsGila monster

GingerGinkgoGinsengGiraffes and okapiGIS

GlaciersGlandsGlassGlobal climateGlobal Positioning SystemGlobal warming

GlycerolGlycol

IbisesIceIce age refugesIce agesIcebergsIcemanIdentity elementIdentity propertyIgneous rocksIguanasImaginary numberImmune systemImmunologyImpact craterImprinting

In vitro fertilization (IVF)

In vitro and in vivo

Incandescent lightIncinerationIndicator, acid-base Indicator speciesIndividualIndoor air qualityIndustrial mineralsIndustrial RevolutionInequality

Inertial guidanceInfectionInfertilityInfinityInflammationInflection pointInfluenzaInfrared astronomyInherited disordersInsecticidesInsectivore

HistamineHistorical geologyHoatzin

Hodgkin’s diseaseHolly family (Aquifoliaceae)Hologram and holographyHomeostasis

HoneycreepersHoneyeatersHoopoeHorizonHormonesHornbillsHorse chestnutHorsehair wormsHorses

Horseshoe crabsHorsetailsHorticultureHot spotHovercraftHubble Space TelescopeHuman artificial chromosomesHuman chorionic gonadotropinHuman cloning

Human ecologyHuman evolutionHuman Genome ProjectHumidity

HummingbirdsHumusHuntington diseaseHybrid

HydraHydrocarbonHydrocephalusHydrochlorofluorocarbonsHydrofoil

HydrogenHydrogen chlorideHydrogen peroxideHydrogenationHydrologic cycleHydrologyHydrolysisHydroponicsHydrosphereHydrothermal vents

Internal combustion engine

International Space Station

International Ultraviolet Explorer

Internet file transfer and tracking

Internet and the World Wide Web

LEDLegionnaires’ diseaseLegumes

LemmingsLemursLensLeprosyLeukemiaLewis structureLice

LichensLife historyLigandLightLight-yearLightningLilacLily family (Liliaceae)Limit

Limiting factorLimpetsLine, equations ofLinear algebraLipid

Liquid crystalsLithiumLithographyLithosphereLithotripsyLiverwortLivestockLobstersLockLock and keyLocusLogarithmsLoonsLORAN

Jet streamJuniperJupiter

K

K-T event (Cretaceous-Tertiaryevent)

Kangaroo ratsKangaroos and wallabiesKarst topographyKaryotype and karyotype analysisKelp forests

Kepler’s lawsKeystone speciesKillifish

KingfishersKingletsKoalasKolaKorsakoff’s syndromeKrebs cycle

Kuiper belt objectsKuru

L

LacewingsLactic acidLagomorphsLakeLamarckismLampreys and hagfishesLand and sea breezesLand use

LandfillLandformLangurs and leaf monkeysLantern fish

LanthanidesLarksLaryngitisLaserLaser surgeryLatitude and longitude

MildewMilkweedsMilky WayMiller-Urey ExperimentMillipedes

MimicryMineralogyMineralsMiningMinkMinnowsMinor planetsMint familyMir Space StationMirrors

MiscibilityMistletoeMitesMitosisMixture, chemicalMöbius stripMockingbirds and thrashersMode

Modular arithmeticMohs’ scaleMoldMoleMole-ratsMolecular biologyMolecular formulaMolecular geometryMolecular weightMoleculeMolesMollusksMomentumMonarch flycatchersMongooses

Monitor lizardsMonkeys

MarsupialsMarten, sable, and fisherMaser

MassMass extinctionMass numberMass productionMass spectrometryMass transportationMass wastingMathematicsMatrixMatterMaunder minimumMaxima and minimaMayflies

MeanMedianMedical geneticsMeiosis

MembraneMemoryMendelian geneticsMeningitis

MenopauseMenstrual cycleMercurous chlorideMercury (element)Mercury (planet)Mesoscopic systemsMesozoa

Metabolic disordersMetabolismMetalMetal fatigueMetal productionMetallurgyMetamorphic gradeMetamorphic rockMetamorphismMetamorphosisMeteorologyMeteors and meteoritesMethyl group

Metric systemMice

Michelson-Morley experimentMicrobial genetics

Mulberry family (Moraceae)

Multiple personality disorder

Number theoryNumeration systemsNut

NuthatchesNutmegNutrient deficiency diseasesNutrients

NutritionNux vomica tree

O

OaksObesityObsessionOceanOcean basinOcean sunfishOcean zonesOceanographyOctet ruleOctopusOhm’s lawOil spillsOil well drillingOld-growth forestsOlive family (Oleaceae)Omnivore

One-to-one correspondenceOpah

Open-source softwareOpossums

Opportunistic speciesOptical data storageOptics

Orang-utanOrbitOrchid familyOrdinal numberOre

OrganOrganelles and subcellular genetics

Natural gasNatural numbersNautical archaeologyNEAR-Earth Object Hazard IndexNectar

NegativeNeptuneNerve growth factorNerve impulses and conduction ofimpulses

Nervous systemNeuromuscular diseasesNeuron

NeuroscienceNeurosurgeryNeurotransmitterNeutralizationNeutrinoNeutronNeutron activation analysisNeutron star

New World monkeysNewton’s laws of motionNewts

NicheNicotineNight vision enhancement devicesNightshade

Nitric acidNitrificationNitrogenNitrogen cycleNitrogen fixationNoise pollutionNon-Euclidean geometryNon-point sourceNonmetalNorth AmericaNova

NovocainNuclear fissionNuclear fusionNuclear magnetic resonanceNuclear medicine

Nuclear powerNuclear reactorNuclear weaponsNuclear winter

PhotochemistryPhotocopyingPhotoelectric cellPhotoelectric effectPhotographyPhotography, electronicPhoton

PhotosynthesisPhototropismPhotovoltaic cellPhylogenyPhysical therapyPhysics

PhysiologyPhysiology, comparativePhytoplankton

PiPigeons and dovesPigs

PikePiltdown hoaxPinecone fishPinesPipefishPlaceboPlanck’s constantPlane

Plane familyPlanetPlanet XPlanetary atmospheresPlanetary geologyPlanetary nebulaePlanetary ring systems

PandasPangolinsPapayaPaperParabolaParallaxParallelParallelogramParasitesParityParkinson diseaseParrots

ParthenogenesisParticle detectorsPartridgesPascal’s trianglePassion flowerPaternity and parentage testingPathogens

PathologyPCRPeafowlPeanut wormsPeccariesPedigree analysisPelicans

PenguinsPeninsulaPentyl groupPeonyPepperPeptide linkagePercentPerceptionPerchPeregrine falconPerfect numbersPeriodic functionsPeriodic tablePermafrostPerpendicularPesticidesPestsPetrels and shearwatersPetroglyphs and pictographsPetroleum

pHPhalangers

Potassium aluminum sulfate

Potassium hydrogen tartrate

Quantum numberQuarks

QuasarQuetzalQuinine

R

RabiesRaccoonsRadarRadial keratotomyRadiation

Radiation detectorsRadiation exposureRadical (atomic)Radical (math)Radio

Radio astronomyRadio wavesRadioactive datingRadioactive decayRadioactive falloutRadioactive pollutionRadioactive tracersRadioactive wasteRadioisotopes in medicineRadiology

RadonRailsRainbowsRainforestRandomRangelandRaptorsRare gasesRare genotype advantage

Prairie dogPrairie falconPraying mantisPrecession of the equinoxesPrecious metals

PrecipitationPredatorPrenatal surgeryPrescribed burnPressurePreyPrimatesPrime numbersPrimrosesPrintingPrionsPrismProbability theoryProboscis monkeyProjective geometryProkaryote

PronghornProofPropyl groupProsimiansProstheticsProteasProtected areaProteinsProteomicsProtistaProtonProtozoaPsychiatryPsychoanalysisPsychologyPsychometryPsychosisPsychosurgeryPubertyPuffbirdsPuffer fishPulsarPunctuated equilibriumPyramid

Pythagorean theoremPythons

SealsSeamountsSeasonal windsSeasonsSecondary pollutantsSecretary birdSedgesSediment and sedimentationSedimentary environmentSedimentary rockSeed fernsSeedsSegmented wormsSeismographSelectionSequencesSequencingSequoiaServomechanismsSesame

Set theorySETISevere acute respiratory syndrome(SARS)

Sewage treatmentSewing machineSex changeSextant

Ribonucleic acid (RNA)Ribosomes

RiceRicinRickettsiaRiversRNA functionRNA splicingRobinsRoboticsRockets and missilesRocks

RodentsRollersRoot systemRose family (Rosaceae)Rotation

RoundwormsRuminationRushesRusts and smuts

S

Saiga antelopeSalamandersSalmonSalmonellaSaltSaltwaterSampleSandSand dollarsSandfishSandpipersSapodilla treeSardinesSarin gasSatelliteSaturnSavannaSavantSawfishSaxifrage familyScalar

Scale insects

StarStar clusterStar formationStarburst galaxyStarfish

StarlingsStates of matterStatistical mechanicsStatistics

Steady-state theorySteam engineSteam pressure sterilizerStearic acid

SteelStellar evolutionStellar magnetic fieldsStellar magnitudesStellar populationsStellar structureStellar windStem cellsStereochemistrySticklebacksStilts and avocetsStimulus

Stone and masonryStoneflies

StorksStormStorm surgeStrataStratigraphyStratigraphy (archeology)Stream capacity and competenceStream valleys, channels, andfloodplains

StrepsipteraStressStress, ecologicalString theory

Solar activity cycleSolar flare

Solar illumination: Seasonal anddiurnal patterns

Solar prominenceSolar systemSolar windSolder and soldering ironSolstice

SolubilitySolutionSolution of equationSonar

Song birdsSonoluminescenceSorghum

Sound wavesSouth AmericaSoybeanSpaceSpace probeSpace shuttleSpacecraft, mannedSparrows and buntingsSpecies

Spectral classification of starsSpectral lines

SpectroscopeSpectroscopySpectrumSpeechSphereSpider monkeysSpiderwort familySpin of subatomic particlesSpina bifida

SpinachSpiny anteatersSpiny eelsSpiny-headed wormsSpiral

SpirometerSplit-brain functioningSponges

Spontaneous generationSpore

SpringtailsSpruce

Swallows and martins

Swamp cypress family

TouchTowers of HanoiToxic shock syndromeToxicology

Trace elementsTragopansTrains and railroadsTranquilizersTranscendental numbersTransducer

TransformerTransgenicsTransistorTransitiveTranslationsTranspirationTransplant, surgicalTrapezoid

TreeTree shrewsTrichinosisTriggerfishTriglyceridesTrigonometryTritiumTrogonsTrophic levelsTropic birdsTropical cycloneTropical diseasesTrout-perchTrue bugs

T

T cellsTanagersTaphonomyTapirsTarponsTarsiersTartaric acidTasmanian devilTaste

TaxonomyTay-Sachs diseaseTea plant

TectonicsTelegraphTelemetryTelephoneTelescopeTelevisionTemperatureTemperature regulationTenrecs

TeratogenTermTermitesTernsTerracingTerritorialityTetanusTetrahedronTextilesThalidomideTheoremThermal expansionThermochemistryThermocoupleThermodynamicsThermometerThermostatThistleThoracic surgeryThrips

ThrombosisThrushesThunderstormTides

Weaver finchesWeevilsWeldingWest Nile virusWetlandsWheatWhisk fernWhite dwarfWhite-eyesWhooping coughWild typeWildfireWildlifeWildlife trade (illegal)Willow family (Salicaceae)Wind

Wind chillWind shearWintergreenWolverineWombatsWoodWoodpeckersWoolly mammothWork

VacuumVacuum tubeValenceVan Allen beltsVan der Waals forcesVapor pressureVariableVariable starsVarianceVaricella zoster virusVariola virusVegetablesVeinsVelocityVenusVerbena family (Verbenaceae)Vertebrates

Video recordingViolet family (Violaceae)Vipers

Viral geneticsVireosVirtual particlesVirtual realityVirus

ViscosityVisionVision disordersVitaminViviparityVivisectionVolatilityVolcanoVolesVolumeVoyager spacecraftVulcanizationVultures

VX agent

W

Wagtails and pipitsWalkingsticksWalnut familyWalruses

Y2KYakYamYeastYellow feverYewYttrium

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The Gale Encyclopedia of Science, Third Edition

has been designed with ease of use and ready reference

in mind

• Entries are alphabetically arranged across six volumes,

in a single sequence, rather than by scientific field

• Length of entries varies from short definitions of one or

two paragraphs, to longer, more detailed entries on

more complex subjects

• Longer entries are arranged so that an overview of the

subject appears first, followed by a detailed discussion

conveniently arranged under subheadings

• A list of key terms is provided where appropriate to

de-fine unfamiliar terms or concepts

• Bold-faced terms direct the reader to related articles

• Longer entries conclude with a “Resources” section,

which points readers to other helpful materials

(includ-ing books, periodicals, and Web sites)

• The author’s name appears at the end of longer entries.His or her affiliation can be found in the “Contributors”section at the front of each volume

• “See also” references appear at the end of entries topoint readers to related entries

• Cross references placed throughout the encyclopediadirect readers to where information on subjects withouttheir own entries can be found

• A comprehensive, two-level General Index guidesreaders to all topics, illustrations, tables, and personsmentioned in the book

AVAILABLE IN ELECTRONIC FORMATS

Licensing The Gale Encyclopedia of Science, Third

Edition is available for licensing The complete database

is provided in a fielded format and is deliverable on suchmedia as disk or CD-ROM For more information, con-tact Gale’s Business Development Group at 1-800-877-GALE, or visit our website at www.gale.com/bizdev

ORGANIZATION OF THE ENCYCLOPEDIA

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ACADEMIC ADVISORS

Marcelo Amar, M.D.

Senior Fellow, Molecular Disease Branch

National Institutes of Health (NIH)

University of South Carolina School of Medicine

Columbia, South Carolina

William J Engle P.E

Exxon-Mobil Oil Corporation (Rt.) New Orleans, Louisiana

Bill Freedman

ProfessorDepartment of Biology and School for Resource andEnvironmental Studies

Dalhousie UniversityHalifax, Nova Scotia, Canada

Antonio Farina, M.D., Ph.D

Department of Embryology, Obstetrics, andGynecology

University of BolognaBologna, Italy

Clayton Harris

Associate ProfessorDepartment of Geography and GeologyMiddle Tennessee State UniversityMurfreesboro, Tennesses

encyclo-The University of Western Australia

Molecular Oncology and Development

Program/Boyer Center for Molecular Medicine

Yale University School of Medicine

New Haven, Connecticut

William S Pretzer

Curator

Henry Ford Museum and Greenfield Village

Dearborn, Michigan

Judyth Sassoon, Ph.D., ARCS

Department of Biology and Biochemistry

Michael J Sullivan, M.D., Ph.D., FRACP

Cancer Genetics LaboratoryUniversity of Otago

Dunedin, New Zealand

Richard Addison Wood

Meteorological ConsultantTucson, Arizona

Diego F Wyszynski, M.D., Ph.D

Department of Medicine, Epidemiology &

BiostatisticsBoston University School of MedicineBoston, Massachusetts

Rashmi Venkateswaran

Undergraduate Lab CoordinatorDepartment of ChemistryUniversity of OttawaOttawa, Ontario, Canada

LIBRARIAN ADVISORS Donna Miller

DirectorCraig-Moffet County LibraryCraig, Colorado

Judy Williams

Media CenterGreenwich High SchoolGreenwich, Connecticut

Nasrine Adibe

Professor Emeritus

Department of Education

Long Island University

Westbury, New York

Georgia Southern UniversityStatesboro, Georgia

Carolyn Black

ProfessorIncarnate Word CollegeSan Antonio, Texas

Larry Blaser

Science WriterLebanon, Tennessee

Jean F Blashfield

Science WriterWalworth, Wisconsin

Richard L Branham Jr

DirectorCentro Rigional deInvestigaciones Científicas yTecnológicas

Mendoza, Argentina

Patricia Braus

EditorAmerican DemographicsRochester, New York

Dana M Barry

Editor and Technical WriterCenter for Advanced MaterialsProcessing

Clarkston UniversityPotsdam, New York

Puja Batra

Department of ZoologyMichigan State UniversityEast Lansing, Michigan

Donald Beaty

Professor EmeritusCollege of San MateoSan Mateo, California

Eugene C Beckham

Department of Mathematics andScience

Northwood InstituteMidland, Michigan

Martin Beech

Research AssociateDepartment of AstronomyUniversity of Western OntarioLondon, Ontario, Canada

Julie Berwald, Ph.D (Ocean Sciences)

Austin, Texas

Massimo D Bezoari

Associate ProfessorDepartment of ChemistryHuntingdon CollegeMontgomery, Alabama

John M Bishop III

TranslatorNew York, New York

CONTRIBUTORS

Brandon R Brown

Graduate Research Assistant

Oregon State University

Toronto, Ontario, Canada

Scott Christian Cahall

Center for Quantum Mechanics

The University of Texas at Dallas

Physician and Medical Writer

Durham, North Carolina

Mary Ann Cunningham

Environmental Writer

St Paul, Minnesota

Les C Cwynar

Associate ProfessorDepartment of BiologyUniversity of New BrunswickFredericton, New Brunswick

Paul Cypher

Provisional InterpreterLake Erie MetroparkTrenton, Michigan

Stanley J Czyzak

Professor EmeritusOhio State UniversityColumbus, Ohio

Rosi Dagit

Conservation BiologistTopanga-Las Virgenes ResourceConservation District

Topanga, California

David Dalby

PresidentBruce Tool Company, Inc.Taylors, South Carolina

Lou D’Amore

Chemistry TeacherFather Redmund High SchoolToronto, Ontario, Canada

Douglas Darnowski

Postdoctoral FellowDepartment of Plant BiologyCornell University

Ithaca, New York

Sreela Datta

Associate WriterAztec PublicationsNorthville, Michigan

Sarah K Dean

Science WriterPhiladelphia, Pennsylvania

Kenneth B Chiacchia

Medical EditorUniversity of Pittsburgh MedicalCenter

Pittsburgh, Pennsylvania

M L Cohen

Science WriterChicago, Illinois

Robert Cohen

ReporterKPFA Radio NewsBerkeley, California

Sally Cole-Misch

Assistant DirectorInternational Joint CommissionDetroit, Michigan

George W Collins II

Professor EmeritusCase Western ReserveChesterland, Ohio

Jeffrey R Corney

Science WriterThermopolis, Wyoming

Tom Crawford

Assistant DirectorDivision of Publication andDevelopment

University of Pittsburgh MedicalCenter

Edward Cruetz

PhysicistRancho Santa Fe, California

Frederick Culp

ChairmanDepartment of PhysicsTennessee TechnicalCookeville, Tennessee

New York University

New York, New York

New York University

New York, New York

Bill Freedman

ProfessorDepartment of Biology andSchool for Resource andEnvironmental StudiesDalhousie UniversityHalifax, Nova Scotia

T A Freeman

Consulting ArchaeologistQuail Valley, California

Elaine Friebele

Science WriterCheverly, Maryland

Randall Frost

Documentation EngineeringPleasanton, California

Agnes Galambosi, M.S.

ClimatologistEotvos Lorand UniversityBudapest, Hungary

Larry Gilman, Ph.D (Electrical Engineering)

EngineerSharon, Vermont

Kathryn Glynn

AudiologistPortland, Oregon

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Charge-coupled device

Charge-coupled devices (CCDs) have made possible

a revolution in image processing They consist of a series

of light-sensitive elements, called pixels, arranged in a

square or rectangular array When CCDs are exposed to

light, an image of the object being observed is formed;

this image can be extracted from the CCD and stored on

a computer for later analysis CCDs are used in a variety

of modern instruments, ranging from scanners and

pho-tocopiers to video cameras and digital still cameras

They have transformed the way scientists measure and

chart the universe Because CCDs are available in a wide

price range, they are accessible to amateurs as well as

professionals, and enable both to make significant

con-tributions to modern astronomy.

How the devices work

All CCDs work on the same principle The CCD

sur-face is a grid of pixels (pixel is a contraction for “picture

element”) Small CCDs may have a grid of 256 x 256

pixels, while large CCDs may have 4,096 x 4,096 pixel

grids Although many CCD pixel grids are square, this is

not always the case; scanners and photocopiers, for

ex-ample, have a single line of pixels that passes over the

picture or page of text being imaged The pixels are tiny;

some CCDs have pixels only 9 microns across, while

oth-ers may have 27-micron pixels The scale and resolution

of the image a camera is able to form on the CCD

de-pends both on the pixel size and the grid size Regardless

of the pixel or grid size, however, each pixel on the CCD

has the ability to convert the light striking it into an

elec-tric signal The voltage accumulated by each pixel during

an exposure is directly proportional to the amount of light

striking it When the CCD is exposed to light for a length

of time, an image of whatever is being observed—

whether a distant galaxy or cars in a parking lot—forms

on the CCD as an array of differing electric voltages

After an image has been recorded on the CCD, the

device can be “read out,” meaning that the voltages are

extracted from the CCD for storage on a computer The

analogy that is almost universally used to describe this

process is the “bucket brigade” analogy Picture each

pixel on the CCD as a bucket with a certain amount of

water in it When the CCD is read out, the water in each

row of buckets is emptied into the adjacent row The

water in the first row goes into a special row of storage

buckets, the water in each bucket in the second row goes

into its neighbor bucket in the first row, and so on across

the whole CCD Then, the amount of water in each of

these buckets is emptied, measured, and stored in a

com-puter’s memory This process is repeated until all of the

rows have been shifted into the storage buckets, emptied,and measured If you now replace the water with electricvoltages, and replace the measurement of water with thedigital measurement of the analog electric signal, youhave the basic process by which an image is extractedfrom the CCD The actual process of reading out theCCD is performed by fairly complicated and exquisitely

synchronized electronics that move all the electric

charges between the “buckets,” convert the analog ages into digital numbers, and make the data availablefor storage on a computer

volt-Once the pixel outputs have been measured andstored on a computer, they can be used in a variety ofways For simple line drawings, the image processingsoftware may render the data from the CCD in black andwhite For pictures, a 256-level grayscale may be appro-priate In either case, a grid of numbers, corresponding

to the original light intensity, is present and can be lyzed in any way the person studying the image desires.From the description above, it may seem that CCDs

ana-cannot be used for color imaging, since they respond

only to light intensity In fact, color CCDs are available,although they are used in video equipment such as cam-corders and almost never in astronomy If an astronomerwanted to create a color image using a CCD, the oldpractice of taking three images through three differentcolor filters is still the usual way to go True color CCDshave pixels with built-in filters, alternating red, green,and blue They can produce real-time color images, butthey are undesirable for scientific work because they in-troduce significant difficulties into the data analysisprocess, as well as reducing the effective resolution ofthe CCD by a factor of three

Applications in astronomy

Astronomers began using charge-coupled devices intheir work in the early 1980s, when the increasing powerand clock speed of semiconductors, and the computersneeded to drive the hardware and analyze the data be-came both fast and affordable Almost every field of as-tronomy was directly impacted by CCDs: for observa-tions of asteroids, galaxies, stars, and planets, whether

by direct imaging or the recording of spectra, the CCDrapidly became the detector of choice

CCDs are also useful to astronomers because an erage, CCDs are about ten times more light-sensitivethan film Astronomers are notorious for finding desper-ately faint objects to observe, so the CCD gave them theability not only to see fainter objects than they could be-fore, but to reduce the amount of time spent tracking andobserving a given object A CCD camera can record in a

av-15 minute exposure the same information that would

take a standard camera loaded with film two hours or

more While film typically records only 2–3% of the

light that strikes it, charge-coupled device cameras can

record between 50–80% of the light they detect

Further-more, CCDs can capture light outside the visible

spec-trum, which film cannot do The devices operate

with-out darkrooms or chemicals, and the results can be

re-constructed as soon as the information is loaded into an

image processing program

However, CCD cameras do have some drawbacks

The small size of the most affordable arrays results in a

much smaller field of view Large celestial bodies such as

the moon, which are easily photographed with a 35mm

camera, become very difficult to reproduce as a single

image with a CCD camera Although larger arrays are

coming to the market, they remain pricy and beyond the

resources of the amateur astronomer They require

com-plicated systems to operate, any many of them have to be

cooled to typical temperatures of -112°F (-80°C) to

re-duce their background electronic noise to an acceptable

level Finally, color images for astronomical CCD

cam-eras (unlike commercially-available video and digital still

cameras) require three separate exposures for each filter

used The final image has to be created by combining the

data from each exposure within the computer

CCDs, professionals, and amateurs

With web-based star catalogues and other Internet

and electronic resources, such as the Hubble Guide Star

Catalog and the Lowell Observatory Asteroid Database,

professional and amateur astronomers have begun

shar-ing resources and comparshar-ing data in hopes of creatshar-ing a

more accurate and complete picture of the heavens

Or-ganizations such as the Amateur Sky Survey help

indi-viduals coordinate and share data with others Thanks to

CCDs, amateurs have often contributed as significantly

to these projects as professional astronomers have Paul

Comba, an amateur based in Arizona, discovered and

registered some 300 previously unknown asteroids in

1996–97, after adding a digital camera to his telescope.

In 1998, astrophysics student Gianluca Masi recorded

the existence of an unknown variable star, discovered

with the use of his Kodak KAF-0400 CCD, mounted in a

Santa Barbara Instrument Group ST-7 camera CCDs

help level the playing field in the science of astrometry,

drastically reducing the equipment barrier between the

amateur and the professional

Resources

Periodicals

di Cicco, Dennis “Measuring the Sky with CCDs.”Sky &

Tele-scope 94 (December 1997): 115-18.

Gombert, Glenn, and Tom Droege “Boldness: The Amateur

Sky Survey.” Sky & Telescope 95 (February 1998): 42- 45 Hannon, James “Warming Up to Digital Imaging.” Sky & Tele- scope 97 (March 1999): 129.

Masi, Gianluca “CCDs, Small Scopes, and the Urban

Ama-teur.” Sky & Telescope 95 (February 1998): 109-12.

Terrance, Gregory “Capture the Sky on a CCD: Digital ing with a CCD Camera Is Revolutionizing the Way Ama-

Imag-teur Astronomers Record Planets and Galaxies.”

A chelate is a type of coordination compound in

which a single metallic ion is attached by coordinate

co-valent bonds to a molecule or an ion called a ligand The

term chelate comes from the Greek word chela, meaning

“crab’s claw.” The term clearly describes the appearance

of many kinds of chelates, in which the ligand surroundsthe central atom in a way that can be compared to thegrasping of food by a crab’s claw

Bonding in a chelate occurs because the ligand has

at least two pairs of unshared electrons These unshared

pairs of electrons are regions of negative electrical

charge to which are attracted cations such as the

cop-per(I) and copper(II), silver, nickel, platinum, and

alu-minum ions A ligand with only two pairs of unshared

electrons is known as a bidentate (“two-toothed”) ligand;one with three pairs of unshared electrons, a tridentate(“three-toothed”) ligand, and so on

The geometric shape of a chelate depends on thenumber of ligands involved Those with bidentate lig-ands form linear molecules, those with four ligands formplanar or tetrahedral molecules, and those with six lig-ands form octahedral molecules

One of the most familiar examples of a chelate is

hemoglobin, the molecule that transports oxygen through the blood The “working part” of a hemoglobin

molecule is heme, a complex molecule at whose core is

an iron(II) ion bonded to four nitrogen atoms with

coor-dinate covalent bonds

Among the most common applications of chelates is

in water softening and treatment of poisoning In the

former instance, a compound such as sodium

tripolyphosphate is added to water That compound

forms chelates with calcium and magnesium ions, ions