You can order any item in this columndirect from the supplier...details below.

Metric Converter/$79In a flash make 36 dif-ferent metric to U.S.conversions: F- C, in-cm, in2 ic2in3-c3,lb-kg, qt-liter. 5 fullcalculator functions (4regular plus percen-tage). RechargeableNiCd battery with ACcharger, deluxe carry-ing pouch, 5 oz. light,handheld, wire wheels,automatic trans., AM-FM, air cond., solidstate, gee whiz' Just 79(bucks till Mar. 31. 1975)Order direct No. 8166Metric Converter. Forliterature only.

3 pH Probes Cost Less Than 2It's ouIr popular long,thin combination elec-gtrode that reaches 10inches down into testtubes and flasks. Andit's precalibrated andgel f'illed. Never needsmessy ref'illing. Orderdirect No. 808 pH elec-trode, $98.00 each.Special offer (expiresMarch 31, 1975 ):Three or more, $65.33each. Or for literatureonly. ..

Waring Blendors: 1 qt-l gal.Famous Waring Blend-ors, rugged industriallab models. Choosesingle speed, multi-speed, timer model, 1qt., 2 qt. or giant gallonsize. Accessories, too!Ordei direct No. 78821 qt., single speed,$49.95, No. 7883 1 qt.,7-speed, $88.95, No. -7888 2 qt., 2-speed, $195,No. 7887 1 gal., 3- speed,ss$399. All include glasscontainer. Optional 1Iqt. stainless steel con-tainei Nor 7873, $24.95.Fur liter'atuire on1v..

o drflfdt-ircc't tt'riotl

MARKSON SCIENCE INC.131 Oak Street, Del Mar, CA 92014Telephone (714) 755-6655

I

Liquid Dispensers

D)ispensors ,are now available in 13ne"' fiXCd-volumne miodels from 0.1 to10 milliliters. Adjustable solurne mod-els Co\ er 0.04 to 0.8 milliliter, 0.2 to 3milliliters, aind 3 to 1 0 milliliters. Thedev ices are casy to prime with smallaIouLnts of the liquid to be dispensed.1Ihe harrelS and plungers are factor\nmlatched for each instrunient. OxfordItahbrettorties Iticorporated. Circle 81 3.

Incuibator

[he laborato rv incuibator is sLitablefoi cUIltUrine coliform and other bac-tcrial. caist, and miold and for micro-hioloical alpplications in qualitv con-trol work. The ullit features three alLuiml-imILum shels es and overtill dimension of229 b' 208 bhy 3 I I millinieters. Theshelses are 279 by 140nmillinieters.TemIpeIiatuire is indicated hb an includedtherimionmeter and is thermostaticallycontrolled to a vsariation of -+ 5°C instalble anmbients. Operating temperatureis adjLlstedI bV a panel knob from roomamIllbienit to 55 C. Capacity is 37 dis-posable 47-millimeter petri dishes. Milli-pore Co rporation. Circle 811.

Digital Timers

The LT-20B series of dicital timersconsists of maorc than 30 models with achoicc of resolution in nminutes. sec-onds, milliseconids, and niicroseconds.Each model features direct-reading dig-tal displass. which, at 3½ inch high. arelegible up to 1-5 feet awav. MNodels are

asailahle with from two to five digits.Advantages include solid-state circuitryand binary-coded decimal output forprilntilng. line frequency may be fromSf) to 400) hertz for crystald oscillatormlodels ( ).005 percenit accuracvs ) and5)) or (6) hertz I-or stLindard cuLrrentm10odels ( 0.1 percenit accuracy). Dur-i&: Brow)sne. Incorporated. Circle 81-5.

562

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Photoni Counter

Vhe SCI photon counting system isdesiggned to measure light from nearinfrared to ultraviolet wavelengths in avariety of applications. It operates atuip to 100 megahertz with 10-nanosec-ond pulse-pair resolution. It can dis-pllay through an oscilloscope, the pulse-heig ht distribution with marker puIlsesthat show discriminator levels. The dis-crimiiinator levels are selected by a dual-channel pUlse-height analyzer that pro-ides first-order pile-up correction at

high coLu1nting rates and window-modediscrimination of high and low pulses.'Ihe SCI is thus able to operate within5 percen t of true linearity at countingraites whcre conventionial systems "lose"coUnts. EG & G/Ortec, Incorporated.Ci-clc 809.

Programmable Pocket Calculator

The HP-55 features simplified key-strioke programming with 49 steps ofprogr,am memory plus branching, test-ing, aind editing capability. It has 20 ad-diressable memories and full registerarithmetic may be performed on andwith the data in ten of the memories.It has 86 keyIboard fuinctions and a dig-ital tinmer with 100-hour capacity andthe ahility to store and recall uip to ten

splits (elapsed time readings within an

esent). In addition to standard arith-mietic. trigonometric, and logarithmicfuinctions, the HP-55 will work in anyof three trigonometric modes: degrees,radians, and grads. Statistical applica-tions are possible with the memory reg-isters. A storage register permits correc-

Ness is offered itistruLmilentation. apparatus, andlaboratorv iriateiilals of intercst to researchers iniil disciplines in academic, indtistrial, and gov-erniricti organizations are feattured in this space.Frphlsis is riven to purt-pose, chief characteristics.,tni navaiabitits of prodtucts and materials. En-6I Sniiient bs Science or AAAS is not implied.\dditatnal infor-mation miiay be obtained from theimiantifacturers or suippliers named by circling theappropriate number on the Readers' Service Card.c gpages 496A nd 576C ;ind plicing it in the.lilhox. 'ostije is frlee.-R( iiiRi (J. SONVOER

S(1 [-N(FE \ 01 7187

Mr Z ;P Z oF Z r /r / ;/ r i! / / ZZ Z // / / / / /-,/,/Z.I/I/111,1:LLz I

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newsuperduper

It's a technical wizard. It's the quickest, sim-plest and most economical way to make thefinest quality dupes, filmstrips, internegs,sectional blowups and superimpositions with-out guesswork.

The new Bowens lllumitran 3, with its built-in.automatically controlled electronic flash,provides a repeatable, continuously variablelighting range of 5:1 in each of two intensityranges: one for regular daylight films, theother for the new duping films.

A direct reading exposure meter, coupled tothe light output, indicates the correct expo-sure and compensates when originals ofvarying density are being copied or whencolor compensating filters are being used.

You can copy original transparencies from35mm to 4x5", make enlargements up to 1oXand reductions to filmstrip format with thenew Illumitran 3.

i--I

Ask your dealer or write for free literature on

the new, more versatileBOWENS ILLUMITRAN 3

- eS.

-

U

tion of an error in arithmetic ornumber entry in the midst of any calcu-lation. The HP-55 displays uLp to tensignificant digits with a two-digit expo-nent and appropriate signs. Hewlett-Packard Company. Circle 810.

Miagnetic Fluid I)esign Kit

The K-102 Special Kit provides twolow-viscosity ferrofluids thaLt will per-form in damping, sealinr. luLbrication,levitation, and other applications. Eachk}it includes 30 cubic cclltimeters of adiester-hase 20O-gaussLand 7 ctubic cen-timeters ot' a hydrocarbon-base 400--uLss ferrofluid along with mlagnets.accessories, and detailed instruLctions.Ferrofluiclics Corporation. Circle 819.

Flutorescenice Spectrophotonieter

The SPF-1000 CS is a corrected in-|strmLnent that offers quLantulm etficiencies|inmd corrected phosphorescenlt spectra.It rccords corrected excitation and emis-sioin ,,pcctra in quantum or energV uinits.It corrects Ceimissionl spectra for the valri-able wla e-number handwidth of theemission nionochromiiator. It ofters adfditferctntial fllorescence mode of opera-tioIn which contilnLuously stUbtracts theblank or amplifies sIm1all differenices inthe corrected cmissioni spectra of tworel.ated compounds. When a polarizeraiccessory is tised, it aUtomatically cor-rects pol,arization data for artifacts ofthe (rating. The SPF-1 00') CS willrecordl spectra on an X-Y recordler- withwas elenigth and wave-nurmber uinits onthe X-axis. American InStrunment Coinp.linx. Circle 812.

EMI GENCOM PMTHOUSINGS FORBroadband Photon CountingGeneral Lab Use

O.E.M. ApplicationsEMI Gencom PMT Housings are

unsurpassed for flexibility, ease ofuse, litetite construction, and RFIshielding. They are designed by en-gineers with years of PhotomultiplierApplication experience.The "B" type shown above uses the

unique Bayonet Lock, is available inSTD and RFI versions, with and with-out flange and provides space forAC-DC Power Supply if required. It ac-commodates all EMI 2" tubes andsome competitive types.

I.- .------

The QL-30 is similar in design andfits all EMI 1-1/8" tubes. When sup-plied less flange, the slim line designallows compact packaging for OEMuse. RFI shielded version available.

Inkless Chart Recorder

IThe Speed Serio 11 recorder thermal-l1 hbrands analog data from 4, 6, 8, 12or 24 chaninels on a 10-inch calibratedheat-sensitive chart. Data format is pro-r nmmable as a dot with channlel ntunm-

her, a series of dots, or a combinationof both. Data are easily readable atchart speeds as slow as '/4 inch perhour. A uni ersal input panel acceptsmillixrolt/volt or thermocouple inputs.Options include ch.annel print/skipswitches, duLal range control, alarms,and time or data identification nuLmberrecording. Full-scale response is as rap-id as I second per point and accuracyis 0.25 percent of span or +- 5 mi-crovolts. FoLur chart drives are avail-

The new "S" Housing for side look-ing (squirrel cage) PMTs fits all tubesof this type, EMI or others. STD orRFIshielded versions available.

All of these new designs give im-proved performance at lower cost.Available from Stock.

~ Detaileddatafrom:

EMI GENCOM INC.80 Express St

Plainview, New York 1.1803Tel (516) 433-5900TWX 510-221-1889

Circle No. 413 on Readers Service Car4

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able, including a stepper motor drivewith fixed and variable speed controlfrom 1/4 inch per hour to 1 inch perminute. Esterline Angus InstrumentCorporation. Circle 814.

Video Disk Recording System

The model 80-0002 features high-resolution and the ability to stop andhold a single picture indefinitely. Theheart of this modular system is a 12-inch magnetic, coated aluminum diskthat revolves at 3600 revolutions perminute and records up to 60 imagesper second. With adequate light, thecamera can be used with its own varia-ble shutter to photograph fast-movingobjects. Where more light is required,the unit may be operated with a high-frequency strobe light for stoppingmoving objects. Pictures may bestopped at any point during playback.Up to 1 hour of information may bestored and played back at variablespeeds or in stopped-action. RedlakeCorporation. Circle 820.

Cartridge Tape System

DataPacer can read or write on tapeat speeds of 30 inches per second witha transfer rate of 48,000 bits per sec-ond. It comes complete with single ca-ble, single card interfacing, and DEC-compatible software. For file operationsit is bidirectional with 90-inch-per-sec-ond speed for rewinding and searching.It can store 2.8 million bytes on up tofour selectable tracks per cartridgemodule. Up to three modules fit acrossa 19-inch rack. There are switch panelsbelow each transport module for trackselection, on-line or local selection, andoff-line rewind. Tape position indicatorsshow mode and position of each mod-ule at any time. Tennecomp Systems,Incorporated. Circle 817.

Scanning Polarograph

The Digi-Scan analyzer features apeak-capture capability which displaysmaximum current on a digital readout.Visual scanning eliminates meter read-ing. Applications include rapid repeti-tive analysis of metals and organic com-pounds such as detecting formaldehydein air, acetaldehyde in acetic acid, cor-rosion inhibitors in generator-coolingwater, iodides and bromates in aqueoussystems, and others. Sensitivity is in14 FEBRUARY 1975

ENVIRONATORis Growth Chambers

* Hinged lift top* Close tolerance temperature

control R.50C*Modular design for low cost

maintenance and accessi-bility

* Barrier System: UVT Plexi-glass

* Covered observation window* Non-cycling reverse heat!

cool system* Most capacity per floorA

space requirement

Key to research with Super cold freezers *Growth Chambers *ProgrammedIncubators * Environmental Rooms*

6200 Main Streeti/~' N Columbia, South Carolina 29203

803-754-8990formerly

Key to Research Environmental Equipment, IncorporatedCircle No. 290 on Readers' Service Card

r -- ---i

FREE.1975CatalogofTubes,BoUtlesandiAdlapters.

Listings include plastic, glass and stainlessl steel tubes and bottles for Du Pont Instruments/

I ;SORVALL and other centrifuge rotors. Chartsand tables contain useful data on rotorapplications, characteristics of various tube Imaterials, and chemical resistance properties of Iplastic tubes. I

For a free copy, send coupon to Du PontI - Instruments, Room 23704B, Newtown, CT 06470. l

PNIInstruments SO)RXAL |ODR.l

| DMR. INAME D MS.

DEPT.

I INS I ITUTION

I ADDRESS

I CITY

LCircle No. 468 on Readers'

II

-STATE ZIPI

Serv -iceCord565Service Card 565

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parts per million for many applications.The device is simple to operate; a singleswitch initiates a scan. The unit is com-pact and weighs less than 10 pounds.Heath International, Instrument Divi-sion. Circle 816.

Holography System

H-LAB-1 is a self-contained holo-camera with an integral helium-neonlaser and reconstruction system. Itweighs less than 60 pounds and willtake reflection holograms of objects upto 60 cubic inches. Also included areall required reflecting mirrors, diverg-ing optics, beam splitters, shutters, var-iable density filters, and plate holders.External controls allow adjustment oflaser intensity, the reconstruction de-vice, and the shutter. Panel lamps indi-cate the status of the laser source,alignment, shutter, and reconstructionsystem. Apollo Lasers. Circle 818.

Literature

Liquid Chromatograph Model 80-500is described in a four-page bulletin thatincludes accessories, design specifica-tions, and suggested experiments. Gow-Mac Instrument Company. Circle 821.

Ani Introduiction to Time and Fre-quency Domain Modulation and Wave-formn Analysis deals with the superhet-erodyne spectrum analyzer and its uses.Tektronix, Incorporated. Circle 822.

Hi-Low Temperature and Tempera-ture Humnidity Test Chambers arecompared and illustrated in a productbulletin. Tenney Engineering, Incorpor-ated. Circle 832.

Biology Equipment for Classroomand Laboratory is devoted to aquariumsand caging equipment for studies ofmarine and terrestrial animals andplants. Jewel Industries, Incorporated.Circle 823.

Index to Scientific Reviews will iden-tify more than 20,000 review articlesfrom over 2,700 scientific journals eachyear. Institute for Scientific Informa-tion. Circle 824.Model 1230 Test System for Frac-

tutre Mechanics Studies is a six-pagebrochure that illustrates a system formaterials investigations. Instron Cor-poration. Circle 825.How to Buy an Atomic Absorption

Spectrophotometer details features andrelative advantages for systems for var-ious applications. Instrumentation Lab-oratory, Incorporated. Circle 826.

14 FEBRUARY 1975

Biochemnicals for Scientific Research-Master Catalog II lists more than4000 products with emphasis on thosefor life science studies. Research PlusLaboratories. Circle 827.

1550 Series Broadcast Color FilmCamera is an eight-page brochure de-voted to a color television camera andoptical multiplexer system. Cohu, Elec-tronics Division. Circle 828.

Quartz Multicomponent MeasuringPlatform measures forces exerted by asubject's feet in three orthogonal direc-

tions. Kristal Instrument Corporation.Circle 829.

Polarizing Mounts and Optics de-scribes components and features a tech-nical introduction to the polarizationphenomenon. Oriel Corporation ofAmerica. Circle 830.

Universal Versaplot Software is a six-page pamphlet about a FORTRANelectrostatic plotting software packagedesigned for virtually any computer, op-erating system, or plotting application.Versatec. Circle 831.

I-NOW! Greater Capacity atNo Extra Cost with the NewLab-Line Orbit Environ-Shaker 18...

ORBIT

E-Z-OPEN "Cleer-Vue" hood allowsfor unobstructed observation of thechamber contents and thermometer.

Iyr

New! LAB-LINE ORBIT ENVIRON-SHAKER 18

Provides up to Twice the Ideal for general incubations, tissue cultures,Capacity of Competitive assays, fermentation studies, enzyme reactions,controlled purification tests, aging tests, andShakers at No Extra Cost .. . growth studies at both static and agitatedThe Lab-Line Orbit Environ-Shaker 18 combines conditions.greater capacity with accurate temperature con- Get more facts about this Shaker and ourtrol from ambient to 650C, +0.50C, and as low complete line of quality ergineered Orbit Shak-as 50C above coolant temperature with optional ers. Write for Cat. No. 274 or circle numbercooling coil. High temperature safety thermostat below on readers service card.is automatically set when temperature is se-lected, for over-temperature protection. Unitoperates at variable speeds from 10 to 500orbits per minute, with solid state speed con- Iiitrol. Requires only 20 inches of bench spaceand features 29 interchangeable platforms avail-able for holding all sizes of flasks, beakers, testtubes, etc. Specially designed 150, 300, or 450 LAB-LINE INSTRUMENTS, Inc.angle flask plafforms increases aeration without Designers and Manufacturerschanging the agitation. Optional gassing mani- Lab-Line Plaza S-2fold and optional light bank also available. Melrose Park, Illinois 60160FIRST IN INSTRUMENTS SERVING SCIENCE, INDUSTRY, AND EDUCATION SINCE 1908

Circle No. 134 on Readers' Service Card

567

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PRODUCTS and MATERIALS

DOI: 10.1126/science.187.4176.562 (4176), 562-567.187Science 

ARTICLE TOOLS http://science.sciencemag.org/content/187/4176/562.citation

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is a registered trademark of AAAS.ScienceGovernment Works. The title reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S.Advancement of Science, 1200 New York Avenue NW, Washington, DC 20005. 2017 © The Authors, some rights

(print ISSN 0036-8075; online ISSN 1095-9203) is published by the American Association for theScience

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