Pap test

The invention: A cytologic technique the diagnosing uterine cancer,

the second most common fatal cancer in American women.

The people behind the invention:

George N. Papanicolaou (1883-1962), a Greek-born American

physician and anatomist

Charles Stockard (1879-1939), an American anatomist

Herbert Traut (1894-1972), an American gynecologist

Cancer in History

Cancer, first named by the ancient Greek physician Hippocrates

of Cos, is one of the most painful and dreaded forms of human disease.

It occurs when body cells run wild and interfere with the normal

activities of the body. The early diagnosis of cancer is extremely

important because early detection often makes it possible to effect

successful cures. The modern detection of cancer is usually done by

the microscopic examination of the cancer cells, using the techniques

of the area of biology called “cytology, ” or cell biology.

Development of cancer cytology began in 1867, after L. S. Beale

reported tumor cells in the saliva from

a patient who was afflicted

with cancer of the pharynx. Beale recommended the use in cancer

detection of microscopic examination of cells shed or removed (exfoliated)

from organs including the digestive, the urinary, and the

reproductive tracts. Soon, other scientists identified numerous striking

differences, including cell size and shape, the size of cell nuclei,

and the complexity of cell nuclei.

Modern cytologic detection of cancer evolved from the work of

George N. Papanicolaou, a Greek physician who trained at the University

of Athens Medical School. In 1913, he emigrated to the

United States.

In 1917, he began studying sex determination of guinea pigs with

Charles Stockard at New York’s Cornell Medical College. Papanicolaou’s

efforts required him to obtain ova (egg cells) at a precise

period in their maturation cycle, a process that required an indicator

of the time at which the animals ovulated. In search of this indicator,

Papanicolaou designed a method that involved microscopic examination

of the vaginal discharges from female guinea pigs.

Initially, Papanicolaou sought traces of blood, such as those

seen in the menstrual discharges from both primates and humans.

Papanicolaou found no blood in the guinea pig vaginal discharges.

Instead, he noticed changes in the size and the shape of the uterine

cells shed in these discharges. These changes recurred in a fifteento-

sixteen-day cycle that correlated well with the guinea pig menstrual

cycle.

“New Cancer Detection Method”

Papanicolaou next extended his efforts to the study of humans.

This endeavor was designed originally to identify whether comparable

changes in the exfoliated cells of the human vagina occurred

in women. Its goal was to gain an understanding of the human menstrual

cycle. In the course of this work, Papanicolaou observed distinctive

abnormal cells in the vaginal fluid from a woman afflicted

with cancer of the cervix. This led him to begin to attempt to develop

a cytologic method for the detection of uterine cancer, the second

most common type of fatal cancer in American women of the

time.

In 1928, Papanicolaou published his cytologic method of cancer

detection in the Proceedings of the Third Race Betterment Conference,

held in Battle Creek, Michigan. The work was received well by the

news media (for example, the January 5, 1928, New YorkWorld credited

him with a “new cancer detection method”). Nevertheless, the

publication—and others he produced over the next ten years—was

not very interesting to gynecologists of the time. Rather, they preferred

use of the standard methodology of uterine cancer diagnosis

(cervical biopsy and curettage).

Consequently, in 1932, Papanicolaou turned his energy toward

studying human reproductive endocrinology problems related to

the effects of hormones on cells of the reproductive system. One example

of this work was published in a 1933 issue of The American

Journal of Anatomy, where he described “the sexual cycle in the human

female.” Other such efforts resulted in better understanding of   reproductive problems that include amenorrhea and menopause.

It was not until Papanicolaou’s collaboration with gynecologist

Herbert Traut (beginning in 1939), which led to the publication of

Diagnosis of Uterine Cancer by the Vaginal Smear (1943), that clinical

acceptance of the method began to develop. Their monograph documented

an impressive, irrefutable group of studies of both normal

and disease states that included nearly two hundred cases of cancer

of the uterus.

Soon, many other researchers began to confirm these findings;

by 1948, the newly named American Cancer Society noted that the

“Pap” smear seemed to be a very valuable tool for detecting vaginal

cancer. Wide acceptance of the Pap test followed, and, beginning

in 1947, hundreds of physicians from all over the world

flocked to Papanicolaou’s course on the subject. They learned his

smear/diagnosis techniques and disseminated them around the

world.

Impact

The Pap test has been cited by many physicians as being the most

significant and useful modern discovery in the field of cancer research.

One way of measuring its impact is the realization that the

test allows the identification of uterine cancer in the earliest stages,

long before other detection methods can be used. Moreover, because

of resultant early diagnosis, the disease can be cured in more

than 80 percent of all cases identified by the test. In addition, Pap

testing allows the identification of cancer of the uterine cervix so

early that its cure rate can be nearly 100 percent.

Papanicolaou extended the use of the smear technique from

examination of vaginal discharges to diagnosis of cancer in many

other organs from which scrapings, washings, and discharges

can be obtained. These tissues include the colon, the kidney, the

bladder, the prostate, the lung, the breast, and the sinuses. In

most cases, such examination of these tissues has made it possible

to diagnose cancer much sooner than is possible by using

other existing methods. As a result, the smear method has become

a basis of cancer control in national health programs throughout the

world

Pacemaker

The invention: A small device using transistor circuitry that regulates

the heartbeat of the patient in whom it is surgically emplaced.

The people behind the invention:

Ake Senning (1915- ), a Swedish physician

Rune Elmquist, co-inventor of the first pacemaker

Paul Maurice Zoll (1911- ), an American cardiologist

Cardiac Pacing

The fundamentals of cardiac electrophysiology (the electrical activity

of the heart) were determined during the eighteenth century;

the first successful cardiac resuscitation by electrical stimulation occurred

in 1774. The use of artificial pacemakers for resuscitation was

demonstrated in 1929 by Mark Lidwell. Lidwell and his

coworkers

developed a portable apparatus that could be connected to a power

source. The pacemaker was used successfully on several stillborn

infants after other methods of resuscitation failed. Nevertheless,

these early machines were unreliable.

Ake Senning’s first experience with the effect of electrical stimulation

on cardiac physiology was memorable; grasping a radio

ground wire, Senning felt a brief episode of ventricular arrhythmia

(irregular heartbeat). Later, he was able to apply a similar electrical

stimulation to control a heartbeat during surgery.

The principle of electrical regulation of the heart was valid. It was

shown that pacemakers introduced intravenously into the sinus

node area of a dog’s heart could be used to control the heartbeat

rate. Although Paul Maurice Zoll utilized a similar apparatus in

several patients with cardiac arrhythmia, it was not appropriate for

extensive clinical use; it was large and often caused unpleasant sensations

or burns. In 1957, however, Ake Senning observed that attaching

stainless steel electrodes to a child’s heart made it possible

to regulate the heart’s rate of contraction. Senning considered this to

represent the beginning of the era of clinical pacing.

Development of Cardiac Pacemakers

Senning’s observations of the successful use of the cardiac pacemaker

had allowed him to identify the problems inherent in the device.

He realized that the attachment of the device to the lower, ventricular

region of the heart made possible more reliable control, but

other problems remained unsolved. It was inconvenient, for example,

to carry the machine externally; a cord was wrapped around the

patient that allowed the pacemaker to be recharged, which had to be

done frequently. Also, for unknown reasons, heart resistance would

increase with use of the pacemaker, which meant that increasingly

large voltages had to be used to stimulate the heart. Levels as high

as 20 volts could cause quite a “start” in the patient. Furthermore,

there was a continuous threat of infection.

In 1957, Senning and his colleague Rune Elmquist developed a

pacemaker that was powered by rechargeable nickel-cadmium batteries,

which had to be recharged once a month. Although Senning

and Elmquist did not yet consider the pacemaker ready for human

testing, fate intervened.Aforty-three-year-old man was admitted to

the hospital suffering from an atrioventricular block, an inability of

the electrical stimulus to travel along the conductive fibers of the

“bundle of His” (a band of cardiac muscle fibers). As a result of this

condition, the patient required repeated cardiac resuscitation. Similar

types of heart block were associated with a mortality rate higher

than 50 percent per year and nearly 95 percent over five years.

Senning implanted two pacemakers (one failed) into the myocardium

of the patient’s heart, one of which provided a regulatory

rate of 64 beats per minute. Although the pacemakers required periodic

replacement, the patient remained alive and active for twenty

years. (He later became president of the Swedish Association for

Heart and Lung Disease.)

During the next five years, the development of more reliable and

more complex pacemakers continued, and implanting the pacemaker

through the vein rather than through the thorax made it simpler

to use the procedure. The first pacemakers were of the “asynchronous”

type, which generated a regular charge that overrode the

natural pacemaker in the heart. The rate could be set by the physician

but could not be altered if the need arose. In 1963, an atrialtriggered synchronous pacemaker was installed by a Swedish team.

The advantage of this apparatus lay in its ability to trigger a heart

contraction only when the normal heart rhythm was interrupted.

Most of these pacemakers contained a sensing device that detected

the atrial impulse and generated an electrical discharge only when

the heart rate fell below 68 to 72 beats per minute.

The biggest problems during this period lay in the size of the

pacemaker and the short life of the battery. The expiration of the

electrical impulse sometimes caused the death of the patient. In addition,

the most reliable method of checking the energy level of the

battery was to watch for a decreased pulse rate. As improvements

were made in electronics, the pacemaker became smaller, and in

1972, the more reliable lithium-iodine batteries were introduced.

These batteries made it possible to store more energy and to monitor

the energy level more effectively. The use of this type of power

source essentially eliminated the battery as the limiting factor in the

longevity of the pacemaker. The period of time that a pacemaker

could operate continuously in the body increased from a period of

days in 1958 to five to ten years by the 1970’s.

Consequences

The development of electronic heart pacemakers revolutionized

cardiology. Although the initial machines were used primarily to

control cardiac bradycardia, the often life-threatening slowing of

the heartbeat, a wide variety of arrhythmias and problems with cardiac

output can now be controlled through the use of these devices.

The success associated with the surgical implantation of pacemakers

is attested by the frequency of its use. Prior to 1960, only three

pacemakers had been implanted. During the 1990’s, however, some

300,000 were implanted each year throughout the world. In the

United States, the prevalence of implants is on the order of 1 per

1,000 persons in the population.

Pacemaker technology continues to improve. Newer models can

sense pH and oxygen levels in the blood, as well as respiratory rate.

They have become further sensitized to minor electrical disturbances

and can adjust accordingly. The use of easily sterilized circuitry

has eliminated the danger of infection. Once the pacemaker has been installed in the patient, the basic electronics require no additional

attention.With the use of modern pacemakers, many forms

of electrical arrhythmias need no longer be life-threatening.

Orlon

The invention: A synthetic fiber made from polyacrylonitrile that

has become widely used in textiles and in the preparation of

high-strength carbon fibers.

The people behind the invention:

Herbert Rein (1899-1955), a German chemist

Ray C. Houtz (1907- ), an American chemist

A Difficult Plastic

“Polymers” are large molecules that are made up of chains of

many smaller molecules, called “monomers.” Materials that are

made of polymers are also called polymers,

and some polymers,

such as proteins, cellulose, and starch, occur in nature. Most polymers,

however, are synthetic materials, which means that they were

created by scientists.

The twenty-year period beginning in 1930 was the age of great

discoveries in polymers by both chemists and engineers. During

this time, many of the synthetic polymers, which are also known as

plastics, were first made and their uses found. Among these polymers

were nylon, polyester, and polyacrylonitrile. The last of these

materials, polyacrylonitrile (PAN), was first synthesized by German

chemists in the late 1920’s. They linked more than one thousand

of the small, organic molecules of acrylonitrile to make a polymer.

The polymer chains of this material had the properties that

were needed to form strong fibers, but there was one problem. Instead

of melting when heated to a high temperature, PAN simply

decomposed. This made it impossible, with the technology that existed

then, to make fibers.

The best method available to industry at that time was the process

of melt spinning, in which fibers were made by forcing molten

polymer through small holes and allowing it to cool. Researchers realized

that, if PAN could be put into a solution, the same apparatus

could be used to spin PAN fibers. Scientists in Germany and the

United States tried to find a solvent or liquid that would dissolve

PAN, but they were unsuccessful until World War II began.

Fibers for War

In 1938, the German chemist Walter Reppe developed a new

class of organic solvents called “amides.” These new liquids were

able to dissolve many materials, including some of the recently discovered

polymers. WhenWorldWar II began in 1940, both the Germans

and the Allies needed to develop new materials for the war effort.

Materials such as rubber and fibers were in short supply. Thus,

there was increased governmental support for chemical and industrial

research on both sides of the war. This support was to result in

two independent solutions to the PAN problem.

In 1942, Herbert Rein, while working for I. G. Farben in Germany,

discovered that PAN fibers could be produced from a solution of

polyacrylonitrile dissolved in the newly synthesized solvent dimethylformamide.

At the same time Ray C. Houtz, who was working for E.

I. Du Pont de Nemours inWilmington, Delaware, found that the related

solvent dimethylacetamide would also form excellent PAN fibers.

His work was patented, and some fibers were produced for use

by the military during the war. In 1950, Du Pont began commercial

production of a form of polyacrylonitrile fibers called Orlon. The

Monsanto Company followed with a fiber called Acrilon in 1952, and

other companies began to make similar products in 1958.

There are two ways to produce PAN fibers. In both methods,

polyacrylonitrile is first dissolved in a suitable solvent. The solution

is next forced through small holes in a device called a “spinneret.”

The solution emerges from the spinneret as thin streams of a thick,

gooey liquid. In the “wet spinning method,” the streams then enter

another liquid (usually water or alcohol), which extracts the solvent

from the solution, leaving behind the pure PAN fiber. After air drying,

the fiber can be treated like any other fiber. The “dry spinning

method” uses no liquid. Instead, the solvent is evaporated from the

emerging streams by means of hot air, and again the PANfiber is left

behind.

In 1944, another discovery was made that is an important part of

the polyacrylonitrile fiber story. W. P. Coxe of Du Pont and L. L.

Winter at Union Carbide Corporation found that, when PAN fibers

are heated under certain conditions, the polymer decomposes and

changes into graphite (one of the elemental forms of carbon) but still

keeps its fiber form. In contrast to most forms of graphite, these fibers

were exceptionally strong. These were the first carbon fibers

ever made. Originally known as “black Orlon,” they were first produced

commercially by the Japanese in 1964, but they were too

weak to find many uses. After new methods of graphitization were

developed jointly by labs in Japan, Great Britain, and the United

States, the strength of the carbon fibers was increased, and the fibers

began to be used in many fields.

Impact

As had been predicted earlier, PAN fibers were found to have

some very useful properties. Their discovery and commercialization

helped pave the way for the acceptance and wide use of polymers.

The fibers derive their properties from the stiff, rodlike structure

of polyacrylonitrile. Known as acrylics, these fibers are more

durable than cotton, and they are the best alternative to wool for

sweaters. Acrylics are resistant to heat and chemicals, can be dyed

easily, resist fading or wrinkling, and are mildew-resistant. Thus, after

their introduction, PAN fibers were very quickly made into

yarns, blankets, draperies, carpets, rugs, sportswear, and various

items of clothing. Often, the fibers contain small amounts of other

polymers that give them additional useful properties.

A significant amount of PAN fiber is used in making carbon fibers.

These lightweight fibers are stronger for their weight than any

known material, and they are used to make high-strength composites

for applications in aerospace, the military, and sports. A “fiber

composite” is a material made from two parts: a fiber, such as carbon

or glass, and something to hold the fibers together, which is

usually a plastic called an “epoxy.” Fiber composites are used in

products that require great strength and light weight. Their applications

can be as ordinary as a tennis racket or fishing pole or as exotic

as an airplane tail or the body of a spacecraft.

Optical disk

The invention:Anonmagnetic storage medium for computers that

can hold much greater quantities of data than similar size magnetic

media, such as hard and floppy disks.

The people behind the invention:

Klaas Compaan, a Dutch physicist

Piet Kramer, head of Philips’ optical research laboratory

Lou F. Ottens, director of product development for Philips’

musical equipment division

George T. de Kruiff, manager of Philips’ audio-product

development department

Joop Sinjou, a Philips project leader

Holograms Can Be Copied Inexpensively

Holography is a lensless photographic method that uses laser

light to produce three-dimensional images. This is done by splitting

a laser beam into two beams. One of the beams

is aimed at the object

whose image is being reproduced so that the laser light will reflect

from the object and strike a photographic plate or film. The second

beam of light is reflected from a mirror near the object and also

strikes the photographic plate or film. The “interference pattern,”

which is simply the pattern created by the differences between the

two reflected beams of light, is recorded on the photographic surface.

The recording that is made in this way is called a “hologram.”

When laser light or white light strikes the hologram, an image is created

that appears to be a three-dimensional object.

Early in 1969, Radio Corporation of America (RCA) engineers

found a way to copy holograms inexpensively by impressing interference

patterns on a nickel sheet that then became a mold from

which copies could be made. Klaas Compaan, a Dutch physicist,

learned of this method and had the idea that images could be recorded

in a similar way and reproduced on a disk the size of a phonograph

record. Once the images were on the disk, they could be

projected onto a screen in any sequence. Compaan saw the possibilities

of such a technology in the fields of training and education.

Computer Data Storage Breakthrough

In 1969, Compaan shared his idea with Piet Kramer, who was the

head of Philips’ optical research laboratory. The idea intrigued

Kramer. Between 1969 and 1971, Compaan spent much of his time

working on the development of a prototype.

By September, 1971, Compaan and Kramer, together with a handful

of others, had assembled a prototype that could read a blackand-

white video signal from a spinning glass disk. Three months

later, they demonstrated it for senior managers at Philips. In July,

1972, a color prototype was demonstrated publicly. After the demonstration,

Philips began to consider putting sound, rather than images,

on the disks. The main attraction of that idea was that the 12-

inch (305-millimeter) disks would hold up to forty-eight hours of

music. Very quickly, however, Lou F. Ottens, director of product development

for Philips’ musical equipment division, put an end to

any talk of a long-playing audio disk.

Ottens had developed the cassette-tape cartridge in the 1960’s.

He had plenty of experience with the recording industry, and he had

no illusions that the industry would embrace that new medium. He

was convinced that the recording companies would consider fortyeight

hours of music unmarketable. He also knew that any new

medium would have to offer a dramatic improvement over existing

vinyl records.

In 1974, only three years after the first microprocessor (the basic

element of computers) was invented, designing a digital consumer

product—rather than an analog product such as those that were already

commonly accepted—was risky. (Digital technology uses

numbers to represent information, whereas analog technology represents

information by mechanical or physical means.) When

George T. de Kruiff became Ottens’s manager of audio-product

development in June, 1974, he was amazed that there were no

digital circuit specialists in the audio department. De Kruiff recruited

new digital engineers, bought computer-aided design

tools, and decided that the project should go digital.

Within a few months, Ottens’s engineers had rigged up a digital

system. They used an audio signal that was representative of an

acoustical wave, sampled it to change it to digital form,

and encoded it as a series of pulses.

On the disk itself, they varied the

length of the “dimples” that were used to represent the sound so

that the rising and falling edges of the series of pulses corresponded

to the dimples’ walls. A helium-neon laser was reflected from

the dimples to photodetectors that were connected to a digital-toanalog

converter.

In 1978, Philips demonstrated a prototype for Polygram (a West

German company) and persuaded Polygram to develop an inexpensive

disk material with the appropriate optical qualities. Most

important was that the material could not warp. Polygram spent

about $150,000 and three months to develop the disk. In addition, it

was determined that the gallium-arsenide (GaAs) laser would be

used in the project. Sharp Corporation agreed to manufacture a

long-life GaAs diode laser to Philips’ specifications.

The optical-system designers wanted to reduce the number

of parts in order to decrease manufacturing costs and improve

reliability. Therefore, the lenses were simplified and considerable

work was devoted to developing an error-correction code.

Philips and Sony engineers also worked together to create a standard

format. In 1983, Philips made almost 100,000 units of optical

disks.

Consequences

In 1983, one of the most successful consumer products of all time

was introduced: the optical-disk system. The overwhelming success

of optical-disk reproduction led to the growth of a multibillion-dollar

industry around optical information and laid the groundwork

for a whole crop of technologies that promise to revolutionize computer

data storage. Common optical-disk products are the compact

disc (CD), the compact disc read-only memory (CD-ROM), the

write-once, read-many (WORM) erasable disk, and CD-I (interactive

CD).

The CD-ROM, the WORM, and the erasable optical disk, all of

which are used in computer applications, can hold more than 550

megabytes, from 200 to 800 megabytes, and 650 megabytes of data,

respectively.

The CD-ROM is a nonerasable disc that is used to store computer

data. After the write-once operation is performed, a WORM becomes

a read-only optical disk. An erasable optical disk can be

erased and rewritten easily. CD-ROMs, coupled with expert-system

technology, are expected to make data retrieval easier. The CD-ROM,

the WORM, and the erasable optical disk may replace magnetic

hard and floppy disks as computer data storage devices.

Oil-well drill bit

The invention: Arotary cone drill bit that enabled oil-well drillers

to penetrate hard rock formations.

The people behind the invention:

Howard R. Hughes (1869-1924), an American lawyer, drilling

engineer, and inventor

Walter B. Sharp (1860-1912), an American drilling engineer,

inventor, and partner to Hughes

Digging for Oil

Arotary drill rig of the 1990’s is basically unchanged in its essential

components from its earlier versions of the 1900’s. A drill bit is

attached to a line of hollow drill pipe. The latter passes through a

hole on a rotary table, which acts essentially as a horizontal gear

wheel and is driven by an engine. As the rotary table turns, so do the

pipe and drill bit.

During drilling operations, mud-laden water is pumped under

high pressure down the sides of the drill pipe and jets out with great

force through the small holes in the rotary drill bit against the bottom

of the borehole. This fluid then returns outside the drill pipe to

the surface, carrying with it rock material cuttings from below. Circulated

rock cuttings and fluids are regularly examined at the surface

to determine the precise type and age of rock formation and for

signs of oil and gas.

Akey part of the total rotary drilling system is the drill bit, which

has sharp cutting edges that make direct contact with the geologic

formations to be drilled. The first bits used in rotary drilling were

paddlelike “fishtail” bits, fairly successful for softer formations, and

tubular coring bits for harder surfaces. In 1893, M. C. Baker and C. E.

Baker brought a rotary water-well drill rig to Corsicana, Texas, for

modification to deeper oil drilling. This rig led to the discovery of

the large Corsicana-Powell oil field in Navarro County, Texas. This

success also motivated its operators, the American Well and Prospecting

Company, to begin the first large-scale manufacture of rotary

drilling rigs for commercial sale.In the earliest rotary drilling for oil, short fishtail bits were the

tool of choice, insofar as they were at that time the best at being able

to bore through a wide range of geologic strata without needing frequent

replacement. Even so, in the course of any given oil well,

many bits were required typically in coastal drilling in the Gulf of

Mexico. Especially when encountering locally harder rock units

such as limestone, dolomite, or gravel beds, fishtail bits would typically

either curl backward or break off in the hole, requiring the

time-consuming work of pulling out all drill pipe and “fishing” to

retrieve fragments and clear the hole.

Because of the frequent bit wear and damage, numerous small

blacksmith shops established themselves near drill rigs, dressing or

sharpening bits with a hand forge and hammer. Each bit-forging

shop had its own particular way of shaping bits, producing a wide

variety of designs. Nonstandard bit designs were frequently modified

further as experiments to meet the specific requests of local drillers

encountering specific drilling difficulties in given rock layers.

Speeding the Process

In 1907 and 1908, patents were obtained in New Jersey and

Texas for steel, cone-shaped drill bits incorporating a roller-type

coring device with many serrated teeth. Later in 1908, both patents

were bought by lawyer Howard R. Hughes.

Although comparatively weak rocks such as sands, clays, and

soft shales could be drilled rapidly (at rates exceeding 30 meters per

hour), in harder shales, lime-dolostones, and gravels, drill rates of 1

meter per hour or less were not uncommon. Conventional drill bits

of the time had average operating lives of three to twelve hours.

Economic drilling mandated increases in both bit life and drilling

rate. Directly motivated by his petroleum prospecting interests,

Hughes and his partner, Walter B. Sharp, undertook what were

probably the first recorded systematic studies of drill bit performance

while matched against specific rock layers.

Although many improvements in detail and materials have been

made to the Hughes cone bit since its inception in 1908, its basic design

is still used in rotary drilling. One of Hughes’s major innovations

was the much larger size of the cutters, symmetrically distributed as a large number of small individual teeth on the outer face of

two or more cantilevered bearing pins. In addition, “hard facing”

was employed to drill bit teeth to increase usable life. Hard facing is

a metallurgical process basically consisting of wedding a thin layer

of a hard metal or alloy of special composition to a metal surface to

increase its resistance to abrasion and heat. A less noticeable but

equally essential innovation, not included in other drill bit patents,was an ingeniously designed gauge surface that provided strong

uniform support for all the drill teeth. The force-fed oil lubrication

was another new feature included in Hughes’s patent and prototypes,

reducing the power necessary to rotate the bit by 50 percent

over that of prior mud or water lubricant designs.

Impact

In 1925, the first superhard facing was used on cone drill bits. In

addition, the first so-called self-cleaning rock bits appeared from

Hughes, with significant advances in roller bearings and bit tooth

shape translating into increased drilling efficiency. The much larger

teeth were more adaptable to drilling in a wider variety of geological

formations than earlier models. In 1928, tungsten carbide was

introduced as an additional bit facing hardener by Hughes metallurgists.

This, together with other improvements, resulted in the

Hughes ACME tooth form, which has been in almost continuous

use since 1926.

Many other drilling support technologies, such as drilling mud,

mud circulation pumps, blowout detectors and preventers, and

pipe properties and connectors have enabled rotary drilling rigs to

reach new depths (exceeding 5 kilometers in 1990). The successful

experiments by Hughes in 1908 were critical initiators of these developments.

Nylon

The invention: A resilient, high-strength polymer with applications

ranging from women’s hose to safety nets used in space flights.

The people behind the invention:Wallace Hume Carothers (1896-1937),

an American organic chemist Charles M. A. Stine (1882-1954), an American chemist

and director of chemical research at Du Pont Elmer Keiser Bolton (1886-1968),

an American industrial chemist Pure Research In the twentieth century,

American corporations created industrial research laboratories.

Their directors became the organizers of inventions,

and their scientists served as the sources of creativity.

The research program of

E. I. Du Pont de Nemours and Company

(Du Pont), through its most famous invention—nylon—became the

model for scientifically based industrial research in the chemical

industry.

During World War I (1914-1918), Du Pont tried to diversify,

concerned that after the war it would not be able to expand with

only explosives as a product. Charles M. A. Stine, Du Pont’s director

of chemical research, proposed that Du Pont should move

into fundamental research by hiring first-rate academic scientists

and giving them freedom to work on important problems in

organic chemistry. He convinced company executives that a program

to explore the fundamental science underlying Du Pont’s

technology would ultimately result in discoveries of value to the

company. In 1927, Du Pont gave him a new laboratory for research.

Stine visited universities in search of brilliant, but not-yetestablished,

young scientists. He hired Wallace Hume Carothers.

Stine suggested that Carothers do fundamental research in polymer

chemistry.Before the 1920’s, polymers were a mystery to chemists. Polymeric

materials were the result of ingenious laboratory practice,

and this practice ran far ahead of theory and understanding. German

chemists debated whether polymers were aggregates of smaller

units held together by some unknown special force or genuine molecules

held together by ordinary chemical bonds.

German chemist Hermann Staudinger asserted that they were

large molecules with endlessly repeating units. Carothers shared

this view, and he devised a scheme to prove it by synthesizing very

large molecules by simple reactions in such a way as to leave no

doubt about their structure. Carothers’s synthesis of polymers revealed

that they were ordinary molecules but giant in size.

The Longest Molecule

In April, 1930, Carothers’s research group produced two major

innovations: neoprene synthetic rubber and the first laboratorysynthesized

fiber. Neither result was the goal of their research. Neoprene

was an incidental discovery during a project to study short

polymers of acetylene. During experimentation, an unexpected substance

appeared that polymerized spontaneously. Carothers studied

its chemistry and developed the process into the first successful synthetic

rubber made in the United States.

The other discovery was an unexpected outcome of the group’s

project to synthesize polyesters by the reaction of acids and alcohols.

Their goal was to create a polyester that could react indefinitely

to form a substance with high molecular weight. The scientists

encountered a molecular weight limit of about 5,000 units to the

size of the polyesters, until Carothers realized that the reaction also

produced water, which was decomposing polyesters back into acid

and alcohol. Carothers and his associate Julian Hill devised an apparatus

to remove the water as it formed. The result was a polyester

with a molecular weight of more than 12,000, far higher than any

previous polymer.

Hill, while removing a sample from the apparatus, found that he

could draw it out into filaments that on cooling could be stretched to

form very strong fibers. This procedure, called “cold-drawing,” oriented

the molecules from a random arrangement into a long, linear one of great strength. The polyester fiber, however, was unsuitable

for textiles because of its low melting point.

In June, 1930, Du Pont promoted Stine; his replacement as research

director was Elmer Keiser Bolton. Bolton wanted to control

fundamental research more closely, relating it to projects that would

pay off and not allowing the research group freedom to pursue

purely theoretical questions.

Despite their differences, Carothers and Bolton shared an interest

in fiber research. On May 24, 1934, Bolton’s assistant Donald

Coffman “drew” a strong fiber from a new polyamide. This was the

first nylon fiber, although not the one commercialized by Du Pont.

The nylon fiber was high-melting and tough, and it seemed that a

practical synthetic fiber might be feasible.

By summer of 1934, the fiber project was the heart of the research

group’s activity. The one that had the best fiber properties was nylon

5-10, the number referring to the number of carbon atoms in the

amine and acid chains. Yet the nylon 6-6 prepared on February 28,

1935, became Du Pont’s nylon. Nylon 5-10 had some advantages,

but Bolton realized that its components would be unsuitable for

commercial production, whereas those of nylon 6-6 could be obtained

from chemicals in coal.

A determined Bolton pursued nylon’s practical development,

a process that required nearly four years. Finally, in April, 1937,

Du Pont filed a patent for synthetic fibers, which included a statement

by Carothers that there was no previous work on polyamides;

this was a major breakthrough. After Carothers’s death

on April 29, 1937, the patent was issued posthumously and assigned

to Du Pont. Du Pont made the first public announcement

of nylon on October 27, 1938.

Impact

Nylon was a generic term for polyamides, and several types of

nylon became commercially important in addition to nylon 6-6.

These nylons found widespread use as both a fiber and a moldable

plastic. Since it resisted abrasion and crushing, was nonabsorbent,

was stronger than steel on a weight-for-weight basis, and was almost

nonflammable, it embraced an astonishing range of uses: in laces, screens, surgical sutures, paint, toothbrushes, violin strings,

coatings for electrical wires, lingerie, evening gowns, leotards, athletic

equipment, outdoor furniture, shower curtains, handbags, sails,

luggage, fish nets, carpets, slip covers, bus seats, and even safety

nets on the space shuttle.

The invention of nylon stimulated notable advances in the chemistry

and technology of polymers. Some historians of technology

have even dubbed the postwar period as the “age of plastics,” the

age of synthetic products based on the chemistry of giant molecules

made by ingenious chemists and engineers.

The success of nylon and other synthetics, however, has come at

a cost. Several environmental problems have surfaced, such as those

created by the nondegradable feature of some plastics, and there is

the problem of the increasing utilization of valuable, vanishing resources,

such as petroleum, which contains the essential chemicals

needed to make polymers. The challenge to reuse and recycle these

polymers is being addressed by both scientists and policymakers.

Nuclear reactor

The invention: 



The first nuclear reactor to produce substantial

quantities of plutonium, making it practical to produce usable

amounts of energy from a chain reaction.



The people behind the invention:



Enrico Fermi (1901-1954), an American physicist

Martin D. Whitaker (1902-1960), the first director of Oak Ridge

National Laboratory

Eugene Paul Wigner (1902-1995), the director of research and

development at Oak Ridge









The Technology to End a War



The construction of the nuclear reactor at Oak Ridge National

Laboratory in 1943 was a vital part of the Manhattan Project, the effort

by the United States during World War II (1939-1945) to develop

an atomic bomb. The successful operation of that reactor

was a major achievement not only for the project itself but also for

the general development and application of nuclear technology.

The first director of the Oak Ridge National Laboratory was Martin

D. Whitaker; the director of research and development was Eugene

Paul Wigner.

The nucleus of an atom is made up of protons and neutrons. “Fission”

is the process by which the nucleus of certain elements is split

in two by a neutron from some material that emits an occasional

neutron naturally. When an atom splits, two things happen: A tremendous

amount of thermal energy is released, and two or three

neutrons, on the average, escape from the nucleus. If all the atoms in

a kilogram of “uranium 235” were to fission, they would produce as

much heat energy as the burning of 3 million kilograms of coal. The

neutrons that are released are important, because if at least one of

them hits another atom and causes it to fission (and thus to release

more energy and more neutrons), the process will continue. It will

become a self-sustaining chain reaction that will produce a continuing

supply of heat.

Inside a reactor, a nuclear chain reaction is controlled so that it

proceeds relatively slowly. The most familiar use for the heat thus

released is to boil water and make steam to turn the turbine generators

that produce electricity to serve industrial, commercial, and

residential needs. The fissioning process in a weapon, however, proceeds

very rapidly, so that all the energy in the atoms is produced

and released virtually at once. The first application of nuclear technology,

which used a rapid chain reaction, was to produce the two

atomic bombs that ended World War II.





Breeding Bomb Fuel



The work that began at Oak Ridge in 1943 was made possible by a

major event that took place in 1942. At the University of Chicago,

Enrico Fermi had demonstrated for the first time that it was possible to

achieve a self-sustaining atomic chain reaction. More important, the reaction

could be controlled: It could be started up, it could generate heat

and sufficient neutrons to keep itself going, and it could be turned off.

That first chain reaction was very slow, and it generated very little heat;

but it demonstrated that controlled fission was possible.

Any heat-producing nuclear reaction is an energy conversion

process that requires fuel. There is only one readily fissionable element

that occurs naturally and can be used as fuel. It is a form of

uranium called uranium 235. It makes up less than 1 percent of all

naturally occurring uranium. The remainder is uranium 238, which

does not fission readily. Even uranium 235, however, must be enriched

before it can be used as fuel.

The process of enrichment increases the concentration of uranium

235 sufficiently for a chain reaction to occur. Enriched uranium is used

to fuel the reactors used by electric utilities. Also, the much more plentiful

uranium 238 can be converted into plutonium 239, a form of the

human-made element plutonium, which does fission readily. That

conversion process is the way fuel is produced for a nuclear weapon.

Therefore, the major objective of the Oak Ridge effort was to develop a

pilot operation for separating plutonium from the uranium in which it

was produced. Large-scale plutonium production, which had never

been attempted before, eventually would be done at the Hanford Engineer

Works in Washington. First, however, plutonium had to be pro-

duced successfully on a small scale at Oak Ridge.

The reactor was started up on November 4, 1943. By March 1,

1944, the Oak Ridge laboratory had produced several grams of plutonium.

The material was sent to the Los Alamos laboratory in New

Mexico for testing. By July, 1944, the reactor operated at four times

its original power level. By the end of that year, however, plutonium

production at Oak Ridge had ceased, and the reactor thereafter was

used principally to produce radioisotopes for physical and biological

research and for medical treatment. Ultimately, the Hanford Engineer

Works’ reactors produced the plutonium for the bomb that

was dropped on Nagasaki, Japan, on August 9, 1945.

The original objectives for which Oak Ridge had been built had

been achieved, and subsequent activity at the facility was directed

toward peacetime missions that included basic studies of the structure

of matter.



Impact



The most immediate impact of the work done at Oak Ridge was

its contribution to ending World War II. When the atomic bombs

were dropped, the war ended, and the United States emerged intact.

The immediate and long-range devastation to the people of Japan,

however, opened the public’s eyes to the almost unimaginable

death and destruction that could be caused by a nuclear war. Fears

of such a war remain to this day, especially as more and more nations

develop the technology to build nuclear weapons.

On the other hand, great contributions to human civilization

have resulted from the development of nuclear energy. Electric

power generation, nuclear medicine, spacecraft power, and ship

propulsion have all profited from the pioneering efforts at the Oak

Ridge National Laboratory. Currently, the primary use of nuclear

energy is to produce electric power. Handled properly, nuclear energy

may help to solve the pollution problems caused by the burning

of fossil fuels.



See also Breeder reactor; Compressed-air-accumulating powerplant; Fuel cell;

Geothermal power; Heat pump; Nuclear power plant; Solar thermal engine; Nuclear reactor

Nuclear power plant

The invention: 



The first full-scale commercial nuclear power plant,
which gave birth to the nuclear power industry.

 







The people behind the invention:



Enrico Fermi (1901-1954), an Italian American physicist who

won the 1938 Nobel Prize in Physics

Otto Hahn (1879-1968), a German physical chemist who won the

1944 Nobel Prize in Chemistry

Lise Meitner (1878-1968), an Austrian Swedish physicist

Hyman G. Rickover (1898-1986), a Polish American naval officer









Discovering Fission



Nuclear fission involves the splitting of an atomic nucleus, leading

to the release of large amounts of energy. Nuclear fission was

discovered in Germany in 1938 by Otto Hahn after he had bombarded

uranium with neutrons and observed traces of radioactive

barium. When Hahn’s former associate, Lise Meitner, heard of this,

she realized that the neutrons may have split the uranium nuclei

(each of which holds 92 protons) into two smaller nuclei to produce

barium (56 protons) and krypton (36 protons). Meitner and her

nephew, Otto Robert Frisch, were able to calculate the enormous energy

that would be released in this type of reaction. They published

their results early in 1939.

Nuclear fission was quickly verified in several laboratories, and

the Danish physicist Niels Bohr soon demonstrated that the rare uranium

235 (U-235) isotope is much more likely to fission than the common

uranium 238 (U-238) isotope, which makes up 99.3 percent of

natural uranium. It was also recognized that fission would produce

additional neutrons that could cause new fissions, producing even

more neutrons and thus creating a self-sustaining chain reaction. In

this process, the fissioning of one gram of U-235 would release about

as much energy as the burning of three million tons of coal.

The first controlled chain reaction was demonstrated on December

2, 1942, in a nuclear reactor at the University of Chicago, under

 the leadership of Enrico Fermi. He used a graphite moderator to

slow the neutrons by collisions with carbon atoms. “Critical mass”

was achieved when the mass of graphite and uranium assembled

was large enough that the number of neutrons not escaping from

the pile would be sufficient to sustain a U-235 chain reaction. Cadmium

control rods could be inserted to absorb neutrons and slow

the reaction.

It was also recognized that the U-238 in the reactor would absorb

accelerated neutrons to produce the new element plutonium, which

is also fissionable. During World War II (1939-1945), large reactors

were built to “breed” plutonium, which was easier to separate than

U-235. An experimental breeder reactor at Arco, Idaho, was the first

to use the energy of nuclear fission to produce a small amount of

electricity (about 100 watts) on December 20, 1951.





Nuclear Electricity



Power reactors designed to produce substantial amounts of

electricity use the heat generated by fission to produce steam or

hot gas to drive a turbine connected to an ordinary electric generator.

The first power reactor design to be developed in the United

States was the pressurized water reactor (PWR). In the PWR, water

under high pressure is used both as the moderator and as the coolant.

After circulating through the reactor core, the hot pressurized

water flows through a heat exchanger to produce steam. Reactors

moderated by “heavy water” (in which the hydrogen in the water

is replaced with deuterium, which contains an extra neutron) can

operate with natural uranium.

The pressurized water system was used in the first reactor to

produce substantial amounts of power, the experimental Mark I

reactor. It was started up on May 31, 1953, at the Idaho National

Engineering Laboratory. The Mark I became the prototype for the

reactor used in the first nuclear-powered submarine. Under the

leadership of Hyman G. Rickover, who was head of the Division of

Naval Reactors of the Atomic Energy Commission (AEC), Westinghouse

Electric Corporation was engaged to build a PWR system

to power the submarine USS Nautilus. It began sea trials in January

of 1955 and ran for two years before refueling.

In the meantime, the first experimental nuclear power plant for

generating electricity was completed in the Soviet Union in June of

1954, under the direction of the Soviet physicist Igor Kurchatov. It

produced 5 megawatts of electric power. The first full-scale nuclear

power plant was built in England under the direction of the British

nuclear engineer Sir Christopher Hinton. It began producing about

90 megawatts of electric power in October, 1956.

 On December 2, 1957, on the fifteenth anniversary of the first controlled

nuclear chain reaction, the Shippingport Atomic Power Station

in Shippingport, Pennsylvania, became the first full-scale commercial

nuclear power plant in the United States. It produced about

60 megawatts of electric power for the Duquesne Light Company until

1964, when its reactor core was replaced, increasing its power to

100 megawatts with a maximum capacity of 150 megawatts.





Consequences



The opening of the Shippingport Atomic Power Station marked

the beginning of the nuclear power industry in the United States,

with all of its glowing promise and eventual problems. It was predicted

that electrical energy would become too cheap to meter. The

AEC hoped to encourage the participation of industry, with government

support limited to research and development. They encouraged

a variety of reactor types in the hope of extending technical

knowledge.

The Dresden Nuclear Power Station, completed by Commonwealth

Edison in September, 1959, at Morris, Illinois, near Chicago,

was the first full-scale privately financed nuclear power station in

the United States. By 1973, forty-two plants were in operation producing

26,000 megawatts, fifty more were under construction, and

about one hundred were on order. Industry officials predicted that

50 percent of the nation’s electric power would be nuclear by the

end of the twentieth century.

The promise of nuclear energy has not been completely fulfilled.

Growing concerns about safety and waste disposal have led to increased

efforts to delay or block the construction of new plants. The

cost of nuclear plants rose as legal delays and inflation pushed costs

higher, so that many in the planning stages could no longer be competitive.

The 1979 Three Mile Island accident in Pennsylvania and

the much more serious 1986 Chernobyl accident in the Soviet Union

increased concerns about the safety of nuclear power. Nevertheless,

by 1986, more than one hundred nuclear power plants were operating

in the United States, producing about 60,000 megawatts of

power. More than three hundred reactors in twenty-five countries

provide about 200,000 megawatts of electric power worldwide.

 Many believe that, properly controlled, nuclear energy offers a

clean-energy solution to the problem of environmental pollution.





See also : Breeder reactor; Compressed-air-accumulating power

plant; Fuel cell; Geothermal power; Nuclear reactor; Solar thermal

engine; Nuclear power plant




 Further Reading :

Nuclear magnetic resonance

The invention: Procedure that uses hydrogen atoms in the human body, strong electromagnets, radio waves, and detection equipment to produce images of sections of the brain. The people behind the invention: Raymond Damadian (1936- ), an American physicist and inventor Paul C. Lauterbur (1929- ), an American chemist Peter Mansfield (1933- ), a scientist at the University of Nottingham, England Peering into the Brain Doctors have always wanted the ability to look into the skull and see the human

brain without harming the patient who is being examined. Over the years, various attempts were made to achieve this ability. At one time, the use of X rays, which were first used byWilhelm Conrad Röntgen in 1895, seemed to be an option, but it was found that X rays are absorbed by bone, so the skull made it impossible to use X-ray technology to view the brain. The relatively recent use of computed tomography (CT) scanning, a computer-assisted imaging technology, made it possible to view sections of the head and other areas of the body, but the technique requires that the part of the body being “imaged,” or viewed, be subjected to a small amount of radiation, thereby putting the patient at risk. Positron emission tomography (PET) could also be used, but it requires that small amounts of radiation be injected into the patient, which also puts the patient at risk. Since the early 1940’s, however, a new technology had been developing. This technology, which appears to pose no risk to patients, is called “nuclear magnetic resonance spectroscopy.” It was first used to study the molecular structures of pure samples of chemicals. This method developed until it could be used to follow one chemical as it changed into another, and then another, in a living cell. By 1971, Raymond Damadian had proposed that body images that were more vivid and more useful than X rays could be produced by means of nuclear magnetic resonance spectroscopy. In 1978, he founded his own company, FONAR, which manufactured the scanners that are necessary for the technique. Magnetic Resonance Images The first nuclear magnetic resonance images (MRIs) were published by Paul Lauterbur in 1973. Although there seemed to be no possibility that MRI could be harmful to patients, everyone involved in MRI research was very cautious. In 1976, Peter Mansfield, at the University of Nottingham, England, obtained an MRI of his partner’s finger. The next year, Paul Bottomley, a member ofWaldo Hinshaw’s research group at the same university, put his left wrist into an experimental machine that the group had developed. A vivid cross section that showed layers of skin, muscle, bone, muscle, and skin, in that order, appeared on the machine’s monitor. Studies with animals showed no apparent memory or other brain problems. In 1978, Electrical and Musical Industries (EMI), a British corporate pioneer in electronics that merged with Thorn in 1980, obtained the first MRI of the human head. It took six minutes. An MRI of the brain, or any other part of the body, is made possible by the water content of the body. The gray matter of the brain contains more water than the white matter does. The blood vessels and the blood itself also have water contents that are different from those of other parts of the brain. Therefore, the different structures and areas of the brain can be seen clearly in an MRI. Bone contains very little water, so it does not appear on the monitor. This is why the skull and the backbone cause no interference when the brain or the spinal cord is viewed. Every water molecule contains two hydrogen atoms and one oxygen atom. A strong electromagnetic field causes the hydrogen molecules to line up like marchers in a parade. Radio waves can be used to change the position of these parallel hydrogen molecules. When the radio waves are discontinued, a small radio signal is produced as the molecules return to their marching position. This distinct radio signal is the basis for the production of the image on a computer screen.Hydrogen was selected for use in MRI work because it is very abundant in the human body, it is part of the water molecule, and it has the proper magnetic qualities. The nucleus of the hydrogen atom consists of a single proton, a particle with a positive charge. The signal from the hydrogen’s proton is comparatively strong. There are several methods by which the radio signal from the hydrogen atom can be converted into an image. Each method uses a computer to create first a two-dimensional, then a threedimensional, image. Peter Mansfield’s team at the University of Nottingham holds the patent for the slice-selection technique that makes it possible to excite and image selectively a specific cross section of the brain or any other part of the body. This is the key patent in MRI technology. Damadian was granted a patent that described the use of two coils, one to drive and one to pick up signals across selected portions of the human body. EMI, the company that introduced the X-ray scanner for CT images, developed a commercial prototype for the MRI. The British Technology Group, a state-owned company that helps to bring innovations to the marketplace, has sixteen separate MRIrelated patents. Ten years after EMI produced the first image of the human brain, patents and royalties were still being sorted out. Consequences MRI technology has revolutionized medical diagnosis, especially in regard to the brain and the spinal cord. For example, in multiple sclerosis, the loss of the covering on nerve cells can be detected. Tumors can be identified accurately. The painless and noninvasive use of MRI has almost completely replaced the myelogram, which involves using a needle to inject dye into the spine. Although there is every indication that the use of MRI is very safe, there are some people who cannot benefit from this valuable tool. Those whose bodies contain metal cannot be placed into the MRI machine. No one instrument can meet everyone’s needs. The development of MRI stands as an example of the interaction of achievements in various fields of science. Fundamental physics, biochemistry, physiology, electronic image reconstruction, advances in superconducting wires, the development of computers, and advancements in anatomy all contributed to the development of MRI. Its development is also the result of international efforts. Scientists and laboratories in England and the United States pioneered the technology, but contributions were also made by scientists in France, Switzerland, and Scotland. This kind of interaction and cooperation can only lead to greater understanding of the human brain.

Neutrino detector

The invention:Adevice that provided the first direct evidence that the Sun runs on thermonuclear power and challenged existing models of the Sun. The people behind the invention: Raymond Davis, Jr. (1914- ), an American chemist John Norris Bahcall (1934- ), an American astrophysicist Missing Energy In 1871, Hermann von Helmholtz, the German physicist, anatomist, and physiologist, suggested that no ordinary chemical reaction could be responsible for the enormous energy output of the Sun. By the 1920’s, astrophysicists had realized that the energy radiated by the Sun must come from nuclear fusion, in which protons or nuclei combine to form larger nuclei and release energy.

These reactions were assumed to be taking place deep in the interior of the Sun, in an immense thermonuclear furnace, where the pressures and temperatures were high enough to allow fusion to proceed. Conventional astronomical observations could record only the particles of light emitted by the much cooler outer layers of the Sun and could not provide evidence for the existence of a thermonuclear furnace in the interior. Then scientists realized that the neutrino might be used to prove that this huge furnace existed. Of all the particles released in the fusion process, only one type—the neutrino— interacts so infrequently with matter that it can pass through the Sun and reach the earth. These neutrinos provide a way to verify directly the hypothesis of thermonuclear energy generated in stars. The neutrino was “invented” in 1930 by the American physicist Wolfgang Pauli to account for the apparent missing energy in the beta decay, or emission of an electron, from radioactive nuclei. He proposed that an unseen nuclear particle, which he called a neutrino, was also emitted in beta decay, and that it carried off the “missing” energy. To balance the energy but not be observed in the decay process, Pauli’s hypothetical particle had to have no electrical charge, have little or no mass, and interact only very weakly with ordinary matter. Typical neutrinos would have to be able to pass through millions of miles of ordinary matter in order to reach the earth. Scientists’ detectors, and even the whole earth or Sun, were essentially transparent as far as Pauli’s neutrinos were concerned. Because the neutrino is so difficult to detect, it took more than twenty-five years to confirm its existence. In 1956, Clyde Cowan and Frederick Reines, both physicists at the Los Alamos National Laboratory, built the world’s largest scintillation counter, a device to detect the small flash of light given off when the neutrino strikes (“interacts” with) a certain substance in the apparatus. They placed this scintillation counter near the Savannah River Nuclear Reactor, which was producing about 1 trillion neutrinos every second. Although only one neutrino interaction was observed in their detector every twenty minutes, Cowan and Reines were able to confirm the existence of Pauli’s elusive particle. The task of detecting the solar neutrinos was even more formidable. If an apparatus similar to the Cowan and Reines detector were employed to search for the neutrinos from the Sun, only one interaction could be expected every few thousand years. Missing Neutrinos At about the same time that Cowan and Reines performed their experiment, another type of neutrino detector was under development by Raymond Davis, Jr., a chemist at the Brookhaven National Laboratory. Davis employed an idea, originally suggested in 1948 by the nuclear physicist Bruno Pontecorvo, that when a neutrino interacts with a chlorine-37 nucleus, it produces a nucleus of argon 37. Any argon so produced could then be extracted from large volumes of chlorine-rich liquid by passing helium gas through the liquid. Since argon 37 is radioactive, it is relatively easy to detect. Davis tested a version of this neutrino detector, containing about 3,785 liters of carbon tetrachloride liquid, near a nuclear reactor at the Brookhaven National Laboratory from 1954 to 1956. In the scientific paper describing his results, Davis suggested that this type of neutrino detector could be made large enough to permit detection of solar neutrinos.Although Davis’s first attempt to detect solar neutrinos from a limestone mine at Barberton, Ohio, failed, he continued his search with a much larger detector 1,478 meters underground in the Homestake Gold Mine in Lead, South Dakota. The cylindrical tank (6.1 meters in diameter, 16 meters long, and containing 378,540 liters of perchloroethylene) was surrounded by water to shield the detector from neutrons emitted by trace quantities of uranium and thorium in the walls of the mine. The experiment was conducted underground to shield it from cosmic radiation. To describe his results, Davis coined a new unit, the “solar neutrino unit” (SNU), with 1 SNU indicating the production of one atom of argon 37 every six days. Astrophysicist John Norris Bahcall, using the best available astronomical models of the nuclear reactions going on in the sun’s interior, as well as the physical properties of the neutrinos, had predicted a capture rate of 50 SNUs in 1963. The 1967 results from Davis’s detector, however, had an upper limit of only 3 SNUs.The main significance of the detection of solar neutrinos by Davis was the direct confirmation that thermonuclear fusion must be occurring at the center of the Sun. The low number of solar neutrinos Davis detected, however, has called into question some of the fundamental beliefs of astrophysics. As Bahcall explained: “We know more about the Sun than about any other star. . . . The Sun is also in what is believed to be the best-understood stage of stellar evolution. . . . If we are to have confidence in the many astronomical and cosmological applications of the theory of stellar evolution, it ought at least to give the right answers about the Sun.” Many solutions to the problem of the “missing” solar neutrinos have been proposed. Most of these solutions can be divided into two broad classes: those that challenge the model of the sun’s interior and those that challenge the understanding of the behavior of the neutrino. Since the number of neutrinos produced is very sensitive to the temperature of the sun’s interior, some astrophysicists have suggested that the true solar temperature may be lower than expected. Others suggest that the sun’s outer layer may absorb more neutrinos than expected. Some physicists, however, believe neutrinos may occur in several different forms, only one of which can be detected by the chlorine detectors.Davis’s discovery of the low number of neutrinos reaching Earth has focused years of attention on a better understanding of how the Sun generates its energy and how the neutrino behaves. New and more elaborate solar neutrino detectors have been built with the aim of understanding stars, including the Sun, as well as the physics and behavior of the elusive neutrino.

Neoprene

The invention: The first commercially practical synthetic rubber, Neoprene gave a boost to polymer chemistry and the search for new materials. The people behind the invention: Wallace Hume Carothers (1896-1937), an American chemist Arnold Miller Collins (1899- ), an American chemist Elmer Keiser Bolton (1886-1968), an American chemist Julius Arthur Nieuwland (1879-1936), a Belgian American priest, botanist, and chemist Synthetic Rubber: A Mirage? The growing dependence of the industrialized nations upon elastomers (elastic substances) and the shortcomings of natural rubber motivated the twentieth century quest for rubber substitutes. By 1914

, rubber had become nearly as indispensable as coal or iron. The rise of the automobile industry, in particular, had created a strong demand for rubber. Unfortunately, the availability of rubber was limited by periodic shortages and spiraling prices. Furthermore, the particular properties of natural rubber, such as its lack of resistance to oxygen, oils, and extreme temperatures, restrict its usefulness in certain applications. These limitations stimulated a search for special-purpose rubber substitutes. Interest in synthetic rubber dates back to the 1860 discovery by the English chemist Greville Williams that the main constituent of rubber is isoprene, a liquid hydrocarbon. Nineteenth century chemists attempted unsuccessfully to transform isoprene into rubber. The first large-scale production of a rubber substitute occurred duringWorldWar I. ABritish blockade forced Germany to begin to manufacture methyl rubber in 1916, but methyl rubber turned out to be a poor substitute for natural rubber. When the war ended in 1918, a practical synthetic rubber was still only a mirage. Nevertheless, a breakthrough was on the horizon.Mirage Becomes Reality In 1930, chemists at E. I. Du Pont de Nemours discovered the elastomer known as neoprene. Of the more than twenty chemists who helped to make this discovery possible, four stand out: Elmer Bolton, Julius Nieuwland, Wallace Carothers, and Arnold Collins. Bolton directed Du Pont’s drystuffs department in the mid- 1920’s. Largely because of the rapidly increasing price of rubber, he initiated a project to synthesize an elastomer from acetylene, a gaseous hydrocarbon. In December, 1925, Bolton attended the American Chemical Society’s convention in Rochester, New York, and heard a presentation dealing with acetylene reactions. The presenter was Julius Nieuwland, the foremost authority on the chemistry of acetylene. Nieuwland was a professor of organic chemistry at the University of Notre Dame. (One of his students was the legendary football coach Knute Rockne.) The priest-scientist had been investigating acetylene reactions for more than twenty years. Using a copper chloride catalyst he had discovered, he isolated a new compound, divinylacetylene (DVA). He later treated DVA with a vulcanizing (hardening) agent and succeeded in producing a rubberlike substance, but the substance proved to be too soft for practical use. Bolton immediately recognized the importance of Nieuwland’s discoveries and discussed with him the possibility of using DVAas a raw material for a synthetic rubber. Seven months later, an alliance was formed that permitted Du Pont researchers to use Nieuwland’s copper catalyst. Bolton hoped that the catalyst would be the key to making an elastomer from acetylene. As it turned out, Nieuwland’s catalyst was indispensable for manufacturing neoprene. Over the next several years, Du Pont scientists tried unsuccessfully to produce rubberlike materials. Using Nieuwland’s catalyst, they managed to prepare DVA and also to isolate monovinylacetylene (MVA), a new compound that eventually proved to be the vital intermediate chemical in the making of neoprene. Reactions of MVA and DVA, however, produced only hard, brittle materials. In 1928, Du Pont hired a thirty-one-year-old Harvard instructor, Wallace Carothers, to direct the organic chemicals group. He began a systematic exploration of polymers (complex molecules). In early 1930, he accepted an assignment to investigate the chemistry of DVA. He appointed one of his assistants, Arnold Collins, to conduct the laboratory experiments. Carothers suggested that Collins should explore the reaction between MVA and hydrogen chloride. His suggestion would lead to the discovery of neoprene. One of Collins’s experiments yielded a new liquid, and on April 17, 1930, he recorded in his laboratory notebook that the liquid had solidified into a rubbery substance. When he dropped it on a bench, it bounced. This was the first batch of neoprene. Carothers named Collins’s liquid “chloroprene.” Chloroprene is analogous structurally to isoprene, but it polymerizes much more rapidly. Carothers conducted extensive investigations of the chemistry of chloroprene and related compounds. His studies were the foundation for Du Pont’s development of an elastomer that was superior to all previously known synthetic rubbers. Du Pont chemists, including Carothers and Collins, formally introduced neoprene—originally called “DuPrene”—on November 3, 1931, at the meeting of the American Chemical Society in Akron, Ohio. Nine months later, the new elastomer began to be sold. Impact The introduction of neoprene was a milestone in humankind’s development of new materials. It was the first synthetic rubber worthy of the name. Neoprene possessed higher tensile strength than rubber and much better resistance to abrasion, oxygen, heat, oils, and chemicals. Its main applications included jacketing for electric wires and cables, work-shoe soles, gasoline hoses, and conveyor and powertransmission belting. By 1939, when Adolf Hitler’s troops invaded Poland, nearly every major industry in America was using neoprene. After the Japanese bombing of Pearl Harbor, in 1941, the elastomer became even more valuable to the United States. It helped the United States and its allies survive the critical shortage of natural rubber that resulted when Japan seized Malayan rubber plantations. A scientifically and technologically significant side effect of the introduction of neoprene was the stimulus that the breakthrough gave to polymer research. Chemists had long debated whether polymers were mysterious aggregates of smaller units or were genuine molecules. Carothers ended the debate by demonstrating in a series of now-classic papers that polymers were indeed ordinary— but very large—molecules. In the 1930’s, he put polymer studies on a firm footing. The advance of polymer science led, in turn, to the development of additional elastomers and synthetic fibers, including nylon, which was invented by Carothers himself in 1935.