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I Please rush UNITRON's Microscope Catalog 4-X-5 II Name I

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1994

Toronto, Ont., Canada. (WMO, 41 AvenueGiuseppe Motta, Geneva, Switzerland)

11. Role of Hormones in Protein Syn-thesis, Assoc. of Vitamin Chemists,Chicago, Ill. (H. S. Perdue, Abbott Lab-oratories, N. Chicago)

15-17. American Pomological Soc.,Toronto, Canada. (G. M. Kessler, Dept.of Horticiulture, Michigan State Univ., E.Lansing)

17-79. Instrument Soc. of America,winter conf. and exhibit, St. Louis, Mo.(W. H. Kushnick, ISA, 313 Sixth Ave.,Pittsburgh 22, Pa.)

18-31. Tropical Cyclones, inter-regionalseminar, World Meteorological Organiza-tion, Tokyo, Japan. (WMO, 41 AvenueGiuseppe Motta, Geneva, Switzerland)

22. American Ethnological Soc., NewYork, N.Y. (N. F. S. Woodbury, ArizonaState Museum, Univ. of Arizona, Tucson)

22-23. Symposium on Perspectives inVirology 111, New York, N.Y. (M. Pollard,Univ. of Notre Dame, Notre Dame, Ind.)

22-24. Institute of-Ihe Aerospace Sci-ences, 30th annual, New York, N.Y. (lAS,2 E. 64 St., New York 21)

22-26. American Mathematical Soc.,annual, Cincinnati, Ohio. (AMS, 190 HopeSt., Providence 6, R.I.)

23. Conference on Cardiac and VascularSurgery, New York Heart Assoc., NewYork, N.Y. (R. Ober, NYHA, 10 Colum-bus Circle, New York 19)

23-25. American Soc. of Safety Engi-neers, Philadelphia, Pa. (A. C. Blackman,5 N. Wabash Ave., Chicago 2, Ill.)

23-25. Obstetrics and Gynaecology, 2ndAsiatic congr., Calcutta, India. (S. Mitra,4 Chowringhee Terrace, Calcutta 20)

24-26. Mathematical Assoc. of America,45th annual, Cincinnati, Ohio. (H. M.Gehman, Univ. of Buffalo, Buffalo, N.Y.)

24-26. Thermophysical Properties,symp., American Soc. of Mechanical Engi-neers, Princeton, N.J. (E. F. Lype, ASME,c/o Thompson Ramo Wooldridge, 23555Euclid Ave., Cleveland, Ohio)

24-27. Americanw Physical Soc., annual,New York, N.Y. (K. K. Darrow, 538 W.120 St., New York 27)25-26. Western Spectroscopy Assoc., 9th

annual, Pacific Grove, Calif. (D. G. Rea,WSA, Univ. of California Space SciencesLaboratory, Berkeley 4)

25-27. Western Soc. for Clinical Re-search, 15th annual, Carmel-by-the-Sea,Calif. (H. R. Warner, WSCR, Latter-daySaints Hospital, Dept. of Physiology, SaltLake City 3, Utah)

26-29. Man and Civilization: Control ofthe Mind-Il, San Francisco, Calif. (S. M.Farber, Univ. of California San FranciscoMedical Center, San Francisco 22)

28-3. American Inst. of Electrical Engi-neers, New York, N.Y. (R. S. Gardner,AIEE, 33 W. 39 St., New York 18)

28-3. Pan American Assoc. ofOphthalmology, interim congr., Lima,Peru. (J. M. McLean, 525 E. 68 St., NewYork 21)

29-30. Carbohydrates, Cellulose, andCellulose Industries, symp., Council ofScientific and Industrial Research,

New ProductsThe information reported here is obtainied from

manufacturers and from other sources consideredto be reliable. Neither Science nor the writer as-sumnes responzsibility for the accuracy of the in-formnationi. All inquiries concerning items listedshould be addressed to the manufacturer. In-clutde the departmenit number in your inquiry.

Microbalance (Fig. 1), manufacturedby Sartorius-Werke (Germany), is a

self-balancing instrument with electri-cal indication. The beam of the balanceconsists of two quartz arms fused ontoa quartz ring. The ring carries a wirecoil wound on its inside surface, andis suspended by platinum-iridium tor-sion wires that also serve as currentleads to the coil. The coil surrounds a

cross-magnetized ceramic magnet thatsupports another coil through which a

480-kcy/ sec current flows. When thebalance is at equilibrium, the beam coilis not exposed to the high-frequencyfield. If the beam deviates from theequilibrium position because of a weightchange, a 480-kc/sec signal is inducedin the beam coil. This is used as an

error signal to generate a counteractingcurrent that is applied to the beam coilto return the coil to its equilibrium posi-tion. The counter torque is proportionalto the current that produces it, so thatthe latter is a measure of the torqueacting on the beam. At maximum sen-

sitivity, 1 pta is equivalent to 1 lug.The object to be weighed is placed

on a small pan or suspended by wirefrom a hook on the stirrup. Preliminaryzeroing is achieved by adjusting a

counterweight that compensates for thatportion of the sample weight in excess

of the selected range. Final correctionis made by dials controlling the torsionwire.

Stability of the balance depends on

Ahmedabad, India. (Director, AhmedabadTextile Industry Research Assoc.,Ahmedabad-9)(See issue of I December for comprehensive list)

SCIENCE, VOL. 134

GERM PLASMRESOURCESAAAS SymposiumVolume No. 66

Edited by Ralph E. Hodgson

394 pages, 59 illustrationsIndex, Cloth, April 1961.

PRICE: $9.75. For AAAS members,Only $8.50, prepoid.

Origin of Germ Plasm-4 chaptersNeed For and Utilization ofAdditional Sources of Germ Plasm

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Developmental Programs in Cropsand Livestock -5 chaptersNew Approaches in the Use ofPlant and Animal Germ Plasm

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the temperature constancy of the coremagnet. The latter has a temperaturecoefficient of 10' per degree Centi-grade, so the temperature of the beamhousing must be kept constant. Othertemperature effects occur in both thestandard and the vacuum models. Thelatter permits operation under vacuumor controlled atmospheric conditions. Inthis model, the entire mechanism iscontained inside a glass body that willhold a vacuum of 10- to 10'0 mm-Hg.Eight ranges are provided from 0-100jug (smallest division 0.001 mg) to 0-20mg (smallest division 0.2 mg). An indi-vidual balance covers seven of the eightranges. Load capacity is 1 g. (BrinkmanInstruments, Inc., Dept. Sci498, 115Cutter Mill Rd., Great Neck, N.Y.)

Dielectric constant and dissipationfactor of solids or liquids are measuredby this instrument. A probe, essentiallya guarded capacitor, forms one leg of abridge; a variable capacitor forms thecomplementary leg. In operation, adielectric material is placed in the fieldof the probe. If the bridge is not bal-anced, a signal appears at the input ofthe instrument's amplifier. The signalpath is split in the amplifier so that twophase discriminators may be driven. A90-deg lag is introduced into the di-electric-constant discriminator. By re-solving the unbalance signal into twocomponents, one in phase and one inquadrature with the reference signal, itis possible to indicate, on separate nullmeters, which control the operator mustadjust to obtain bridge balance. Thedielectric constant and dissipation fac-tor are read directly from the controls.A flat probe for solid samples and

a corrosion-resistant probe for liquidsamples are available. Dielectric-con-stant range is 1.0 to 12.0 with accuracysaid to be ±5 percent. Dissipation-factor range is 0 to 0.15 and accuracy+(5 percent + 0.001). (Delsen Corp.,Dept. Sci500, 719 West Broadway,Glendale, Calif.)

Calorimeter controller is a thermistor-actuated system consisting of the neces-sary power supply, bridge circuit, am-plifiers, relays, electric water heater,and valves for the automatic additionof hot and cold water to adjust andcontrol calorimeter jacket temperatures.It can be used with old or new modelsof the manufacturer's adiabatic calorim-eters if minor changes are made in thewater connections. Temperature is saidto be maintained to within +0.01°C ofthe bucket temperature throughout the

15 DECEMBER 1961

It's easier, safer to buy reagents in Fisher PolyPacs. You just storea PolyPac until needed, then quickly convert it into a sealed, on-the-shelf dispenser using special pour-spout cap. No need totransfer reagents; no chance for contamination; no deposits, noreturns. Fisher's PolyPac is a five-gallon polyethylene bottle insturdy, ICC-approved cardboard carton-pounds lighterthan bulky,expensive carboy it replaces. Among the many liquid reagentsavailable in PolyPacs are formaldehydes, hydrochloric acids, sul-furic acids, buffer solutions. Obtain all the facts from your Fisherbranch, and ask about getting other reagents in PolyPacs. J-189

F FISHER SCIENTIFICWorld's Largest Manufacturer-Distributor ofLaboratory Appliances& Reagent ChemicalsBoston . Chicago . Fort Worth . Houston . New York . Odessa, TexasPhiladelphia . Pittsburgh . St. Louis * Washington * Montreal . Toronto

1995

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test period except for momentary vari-ations of not more than 0.10C duringperiods of rapid temperature rise. Astainless-steel thermistor probe in thecalorimeter jacket and another in thebucket are held adjacent to the cus-tomary mercurial thermometer to sensetemperature equality.

Temperature differences are utilizedthrough a Wheatstone-bridge circuitand a photoelectric galvanometer toactuate solenoid valves that add hotand cold water in variable amounts. Hotand cold water are added alternatelyin small amounts when the galvanom-eter beam moves on and off the photocell. When a rapid rhange in tempera-ture occurs, as in a bomb calorimeterimmediately after firing, the wide swingof the light beam strikes a second photo-cell and actuates full flow of hot water.The equipment permits manual controlat any time. The hot water reservoir ismade an integral part of the con-troller system, and flow lines are keptas short as possible to keep lags small.(Parr Instrument Co., Dept. Sci487,211 53 St., Moline, Ill.)

Time-lapse cinemicrography appara-tus is built into and on a steel desk. Itincludes the following major compo-nents: camera with drive, timing unit,and observation eyepiece; light source;antivibration mount. The 16-mm cam-era is equipped with a 400-ft magazine.The light source combines a tungsten-filament source for viewing with avariable-intensity xenon flash lamp forexposures of less than 10-' sec. Thecamera is driven through a quick-change gear box that provides eightrates from 1/4 to 32 frames per minute.The intensity of the xenon flash can bevaried over a range of about 600 with-out alteration of its color value. Alarge incubator enclosure providedwith a thermostatically controlled heatsource maintains materials under ob-servation at constant temperaturesfrom ambient to 40°C. (Sage Instru-ments, Inc., Dept. Sci488, 9 Bank St.,White Plains, N.Y.)

Calibration-transfer standard is anac-dc voltage and current measuringinstrument containing a three-dial po-tentiometer, light beam galvanometer,volt box, hermetically sealed oil-filledshunt box, standard cell, ac-dc trans-fer element, and switching circuits.Direct-reading limit of error is said tobe ±0.06 percent for ac and ±0.05percent for dc. Application of correc-tion factors permits increased accuracy.

1996

Voltage range is up to 1500 v, currentis 15 amp, and ac frequency is 20 cyto 50 kcy/sec. Adapters permit fre-quency range increase to 50 Mcy/sec.(Radio Frequency Laboratories, Inc.,Dept. Sci480, Powerville Rd., Boon-ton, N.J.)

Instrument heating units are designedto maintain exact temperatures forvarious electronic control devices. Per-formance and control characteristicsdepend upon the desired operationalfunctions. Controlled temperatures upto 500°F are available with power re-quirements ranging from 1/5 to 3watt/ in2 of exposed oven surface.(Spec-Heating, Inc., Dept. Sci478,13942 Saticoy St., Van Nuys, Calif.)

Signal-actuated voice recorder is de-signed to record a message and at thesame time maintain an automatic logof the time and date that the messageoriginated. The recording medium is¼/4-in. magnetic tape operating at aspeed of 5/8 in./sec to provide con-tinuous operation for 251/2 hours with-out changing reels. At this speed, re-sponse within 6 db is obtained over thefrequency range 300 to 2600 cy/sec.Recording begins within 10 msec aftera voice signal is detected. (Litton In-dustries, Dept. Sci438, 6601 RomaineSt., Hollywood 38, Calif.)

Low-power microscope features zoomoptics to provide continuous magnifica-tion from 10 to 30x. The instrumentmaintains constant focus throughoutpower change adjustments. Field ofview is 0.420 in. at lOX and 0.240 in.at 30X. A cross-line reticle is supplied,and a choice of two measuring reticlesis available. Direct readings are possibleat all magnifications without need forinterpolation. Folding tripod legs areprovided for convenient transport andstorage. (Bausch & Lomb, Inc., Dept.Sci447, Rochester 2, N.Y.)

Ruby rods for optional-maser appli-cations are available in sizes that willyield cylinders 1/2 in. in diameter and8 in. long, or 3/8 in. in diameter and12-in long. The boules are 0.04-percentchrome doped and oriented with C-axis perpendicular to the cylinder axis.Growing cycle is 42 hr, and annealingcycle 120 hr. (Adolph Meller Co.,Dept. Sci479, P.O. Box 6001, Provi-dence, R.I.)

JOSHUA STERNNational Bureau of Standards,Washington, D.C.

SCIENCE, VOL. 134

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New ProductsJoshua Stern

DOI: 10.1126/science.134.3494.1994 (3494), 1994-1996.134Science 

ARTICLE TOOLS http://science.sciencemag.org/content/134/3494/1994.citation

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trademark of AAAS. is a registeredScienceAdvancement of Science, 1200 New York Avenue NW, Washington, DC 20005. The title

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

1961 by the American Association for the Advancement of Science

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