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AP10andECIS S/.,yOU. They're a lot fastermnio ers. EitherDisystem canperform 1024* pxfoatlgpOiltFFTs I

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;ense,

The first inverted microscopedesigned as an inverted microscope.

The new Leitz Diavertwas engineered fromthe base up to meet the special requirements ofinverted microscopy. It is exceptionally stablewith a large rectangular base area. The stand willsupport large or small vessels and photomicro-graphic equipment, including the Leitz Orthomat®fully automatic camera and the Leicina® Super 8movie camera for time lapse studies.

The large object stage is positioned low soyou can see what you are doing while manip-ulating the specimen.

The image moves in the same direction asthe specimen. Reason: image-erecting optics.The transmitted light source moves with thestage so it doesn't have to be refocused when

you change the specimen plane.Special long-working-distance, brightfield as

well as phase objectives, and also long-working-distance condensers (up to 64mm) are importantfeatures.

The Diavert is a building block system soyou can readily employ all the techniques oflight microscopy, including new interferencecontrast and incident fluorescence accessories.If you own a Leitz Ortholux 11 research microscope,you can interchange all Ortholux accessories.

For information call 201-767-1100 or writeE. Leitz, Inc., Dept. SC 29Rockleigh, N.J. 07647.

Circle No. 129 on Readers' Service CardWhere most new developments start.

SCIENCE, VOL. 203502

With some micro centrifuges,constant speed is a constant problem,but not with an Eppendorf.

Within ten seconds, the Eppendorf 5412 attains 15,000 rpm,

generating a force of 1 2,800xG, regardless of load. Performancelike this means rapid sample separation, in most cases within60 seconds or less. An angled rotor accommodates twelve dis-posable Eppendorf 1 .5ml micro test tubes, or twelve 500,uI, 400,uIor 250/hI tubes using adapters. (For higher capacity requirements,the Eppendorf Model 5413 accepts forty 1 .5ml, 400,uI or 250/,Idisposable test tubes in four carriers, but operates at lowerspeeds.) Eppendorf Micro Centrifuges are equipped with auto-matic 15 min. timer, safety switch (prevents operation with lidopen) and safety lid lock (lid stays locked while rotor is spinning).

1.5m 400A <Eppendorf Micro Test Tubes have attached caps and are

ideal for centrifuging, mixing, or storing reagents. Economicallypriced, they are available in the following sizes: polypropylene -1.5ml, 500,u1, 400,1l; polyethylene - 400,u, 250,1l.

For complete literature, write: Eppendorf Division, BrinkmannInstruments, Inc., Cantiague Road, Westbury, N.Y. 11590.In Canada: Brinkmann Instruments (Canada), Ltd.

flEppendorfZLNMicro Centrifuges

Circle No. 140 on Readers' Service Card

ouearenot dAll.And we are happy to

share the expe-rience we'veaccumulated

' over theyears.Request our

W _ helpful tech-_awo nical bulletin

on the uses of ourh-specific-activity

Bolton-Hunter Reagent.Bolton-HunterReagent [1251]-2000Ci/mmol NEX-120

Monoiodinated: Prepared weekly-4000Ci/mmol NEX-120H

Diiodinated: Prepared biweeklyNot for use in humans or clinical diagnosis.

New -Nka&49 549 Albany Street, Boston, Mass. 02118

Call toll-free: 800-225-1572(In Massachusetts and International: 617-482-9595)

JEN Chemicals GmbH, Dreieich, W. Germany; NEN Canada Ltd., Lachine, Quebec

Circle No. 164 on Readers' Service Card

ELECTRODEIMPEDANCETESTER

For EEG, EOG, EMG, EKG, evokedpotentials and wherever surfaceelectrodes are used to recordbioelectric events.

Compact, portable instrumentquickly and conveniently checks surfaceelectrode impedances. Electrodes aresimply plugged in and a buttonpushed. Color-coded meter shows at aglance whether impedance is in the"safe", "doubtful" or "unacceptable"ronge. Alternating test current preventselectrode polarization. Multiple safetyfeatures guard against test currentexceeding medical safety standards.

YLie-TechInsbtuments, In.BOX 36221- HOUSTON TEXAS 77036(7131783-6490

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Hellma-the largest assortment of highestprecision glass and quartz cells.S.tandard* Flow-through * Constant-temperatureAnaerobic* Special DesignsAlso available-ULTRAVIOLET LIGHT SOURCESDeuterium Lamps ' Mercury Vapor LampsHollow Cathode Lamps* Power Supplies

XIEIL LMA gWrite for literature=~~L.v. ~ Box 544Borough Hall Station

CEL LS, I NC. Jamaica, New York 11424C___E__L___L__S,____I__N___C__._ Phone (212) 544-9534

Circle No. 149 on Readers' Service Card

Why Sol® is theorightsmall co puterfor sciensts and engineers.

Solg small computer systems offer the flexibility you need to analyze awide range of data and solve complex problems.

* Language Flexibility. Sol small computers use Extended BASIC, FORTRAN,FOCAL, PILOT and Assembler on both disk and cassette.

* Precision Flexibility. Extended Disk BASIC is available with 6, 8, 10, 12, 14or 16 digits of precision.

* Memory Storage Flexibility. Up to 1.5 million bytes of disk and 64K bytesof onboard memory fully supported by an outstanding disk operating system.

For a full report on why Sol stands up to the minis, address Box RD,Processor Technology Corporation, 7100 Johnson Drive, Pleasanton, CA 94566, orsee your nearest dealer.

Toll-free Dealer Locator Hotline, (800) 227-1241. In Californiacall toll-free (800) 972-5951.

ProcessorTechnologyCircle No. 217 on Readers' Service Card

Circle No. 220 on Readers' Service Cardi

LI/'s new REPIPETlI1d4ispenserVirtually

unbreakable!Berthanay $8

patk dispeer! But only S rL5O!Here it is, the best value ever offered in reagent

dispensers. The tough REPIPET ii reflects more than14 years of L/1's experience in liquid dispensing-your

best assurance of quality and performance. All REPIPET IIdispensers feature the use of fluorocarbon and extra-thick

borosilicate glass for strength and durability. They'retough lab workhorses, virtually impossible to break.

Note the 100-divisiorf scales, printed where they shouldbe-on the glass barrel, not on an elastic plastic! L/1's

exclusive sturdy magnifying indicator is a further aid toprecise volume settings.

L/l guarantees accuracy of 1.5% full scale and 0.2%reproducibility for all REPIPET Ii dispensers. They are

suitable for use with all laboratory reagents (except HF).

(Although TEFZELO plastic and TEFLONO plastic are chemicallyinert to all laboratory reagents, slight distortions may occur

at autoclaving temperatures and with some strong solvents.)

*REPIPET 11 dispensers are offered in three popularsizes, 5, 10, and 20 ml. Price of 5 and 10 ml

units is $52.50; 20 ml, $64.50.To order, contact your distributor. For literature, write,

call or circle the reader service number below.

*LABINDUSTRIES620 Hearst Avenue, Berkeley, CA 94710

I Phone (415) 843-0220

Accurate settings. 100-division scalesare printed right on the rugged glassbarrel. (You can set a 10 ml instrumentaccurately to 10 microliters.)

Circle No. 119 on Readers' Service CardClrch No. 147 on Readers' Service Card